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Indoor Building Distributed Antenna System (DAS)

1 Aug

Introduction & Objectives:

Indoor sites are built to cater capacity and coverage issues in indoor compounds where outdoor macro site can’t be a good solution.

In dense urban clutter where buildings structures and indoor environment losses are quite large for macro site which makes it‘s an inappropriate solution. Generally floors underground (basements and lower ground) have poor RSSI. Major part of reflections takes place from ground and because of this portion below ground have poor signal coverage.

On the other hand floors above third have quality and DCR issues. Due to fewer obstacles in the LOS path, path losses are less compared to ground floors. So there is a multiservers environment due to less path losses and cells overshooting which leads to ping pong handovers and interference issues inside the compound.

In urban areas there are buildings that generate high traffic loads like commercial buildings, offices; shopping malls may need indoor systems to take care of the traffic demands. For such areas indoor is the efficient solution regarding cost, coverage and capacity.

In indoors downlink is
the critical link in the air interface. There is no need to use the uplink diversity in an indoor system or use amplifiers like TMA for improving the uplink signal .Multi-antenna indoor system is providing diversity as uplink signals received by several antennas.

In-building solutions DAS-IBS technology is one of the fastest changes in mobile network rollouts. It has been estimated that 70-90% of all mobile calls are made inside the buildings; therefore to improve the QOS, operators today have started concentrating more on this aspect of network rollouts.

The most efficient way to achieve optimal quality, coverage & capacity result inside the building is to use Microcell with Distributed Antennae System (DAS)

Hayat Telecom LCC has set up support to Venders in rolling out IBS network & gathered both planning tools and professionals for attaining quality rollouts with utmost levels of customer satisfaction.

Indoor Building Systems Solution, Specifically the Solutions of Radio Network Design is needed to enhance QOS and Capacity of the network. Most of calls are generated from inside of buildings so it ‘does require special attention for enhancing the network performance’.

The key essentials for a potential IBS system for planning are:-

  • Identification of potential buildings for IBS.Design Distributed Antenna system using passive & active elements and, Prepare complete Link engineering diagram with each antenna’s EIRP proposal report.
  • Implementation of IBS solution with best professional way without disturbing aesthetic of building.
  • LOS & Link Planning to connect site.
  • RF parameter planning, RF walk test and call quality testing.

As moving ahead details of key part explain in detail.

Types of indoor cells:

There are mainly three types of indoor cell.

1-Micro Cells

2-Pico cells

3-Femto Cells

 

Micro cells constitute most of the indoors deployed for BTS coverage. They are more costly and also on large scale with respect to Femto or Pico cells. They consist of indoor micro /metro BTS and distributed antenna system for signal propagation in indoor environment .Usually they have passive components but where large distance to be required amplifiers especially optical amplifiers are deployed called active components.

A Pico cell is wireless communication system typically covering a small area, such as in-building (offices, shopping malls, train stations, etc.), or more recently in-aircraft. A Pico cell is analogous to a WIFI access point. In cellular wireless networks, such as GSM, the Pico cell base station is typically a low cost, small (typically the size of a sheet of A4 paper and about 2-3cm thick), reasonably simple unit that connects to a Base Station Controller (BSC). Multiple Pico cell ‘heads’ connect to each BSC: the BSC performs radio resource management and hand-over functions, and aggregates data to be passed to the Mobile Switching Centre (MSC) and/or the GPRS Support Node (GSN).

In telecommunications, a Femto cell—originally known as an Access Point Base Station—is a small cellular base station, typically designed for use in residential or small business environments. It connects to the service provider’s network via broadband (such as DSL or cable); current designs typically support 5 to 100 mobile phones in a residential setting. A Femto cell allows service providers to extend service coverage indoors, especially where access would otherwise be limited or unavailable. The Femto cell incorporates the functionality of a typical base station but extends it to allow a simpler, self contained deployment; an example is a UMTS Femto cell containing a Node B, RNC and GPRS Support Node (SGSN) with Ethernet for backhaul. Although much attention is focused on UMTS, the concept is applicable to all standards, including GSM, CDMA2000, TD-SCDMA and WiMax solutions.

Objective of IBS design:

The basic aim of indoor building solution is increasing the quality of indoor signal at different public and business locations. The Public locations are such as said before Shopping Malls, Airport terminals, Hospitals, Residential flats and business exhibition centers, Govt and private offices etc

The fig shown the obligation of IBS .With BTS site deep indoor signal penetration is not good in dense urban areas specially in high rise Building Areas.IBS cover this obligation .

IBS Design solution Scenarios:

There are various solutions that can be implemented for a particular site. For a design approach, we will select the most cost-effective solution to meet the performance criteria.

Distributed antenna network:

The useful application of antennas in indoor systems is the idea of distributed antennas.  The philosophy behind this approach is to split the transmitted power among several antenna elements, separated in space so as to provide coverage over the same area as a single antenna, but with reduced total power and improved reliability.  The smaller coverage footprint of each antenna element provides for controlled coverage and reduces excessive interference and spillage effects.

A distributed antenna system can be implemented in several ways, a number of which are listed below.

DAS-1-Passive coaxial network design:

The network is made up of passive components such as coaxial cable, combiners, splitters, directional couplers, etc. Antennas that are utilized can be of wide-bandwidth to support multi-band and/or multi-system requirements. The advantage of this approach is that the network is simple and requires minimal maintenance.

DAS -2-Leaky feeder system:

The ultimate form of a passive distributed antenna system is a radiating cable (leaky feeder) that is a special type of coaxial cable where the screen is slotted to allow radiation along the cable length. With careful design, such cables can produce virtually uniform coverage. This type of system is best suited for applications requiring in-tunnel coverage (such as in subways). The radiating cable in this case is run along the entire length of the tunnel. The cable is either a radiating coaxial cable or radiating wire.

 DAS-3-Fiber Optic Solution:

In this method, RF signals are converted to optical signals before being transmitted to distribution units via optical fibers. Single-mode and multi-mode fibers can be used but multi-mode fiber requires frequency conversion before RF- to-optic conversion. The fiber optic solution is ideal for wide-area deployments such as in buildings with extensive floor areas and high-rise office buildings. The installation cost can be well contained if the existing optical fiber infrastructure within a building can be re-used. This solution is also useful for expanding on an existing distributed antenna system that is operating on coaxial solutions.

DAS-4-Repeater Solution:

This solution is implemented to expand the coverage of an indoor or outdoor cell. If coverage is to be expanded to an isolated place, a repeater solution can be used. This input signal to the repeater can be sourced either from an existing off-the-air RF signal or fiber-fed from a remote location. In large buildings, where coaxial cable network is required to use, EBTS power will not be enough to power all the antennas. In this instance, in-line repeaters are used to boost up RF signal.

DAS-IBS Deployment Design:

Passive IBS

Mostly passive IBS is deployed as an indoor solution. Passive IBS contains splitters, couplers, attenuators, combiners, coaxial cable, DAS but there is no active element involved.

Active IBS

Active IBS is generally used when the EIRP required is more than the available. Usually this happen when distance involve are large and antenna elements are more as well. Active IBS is actually a hybrid IBS as it contains an active component (repeater) and passive IBS.

DAS-IBS-Design Entities:

Antenna:

Mostly antennas used in IBS design are Omni directional and flat panel directional antennas.The selection of antenna types is based on the availability, feasibility. Retain ability, compatibility and performance with selected solution .The usage of different type of antennas varies for different physical atmosphere. The antennas are connected with coax feeders inside the building. The antenna selection depends upon the general Product Description and specification shared by venders.

The Primary Antenna types in IBS design are:

1-Omni directional antenna

2-Directional antenna

3-Leaky cable

1-Omni Directional Antennas

It transmits signal in all direction .it contain Low gain. Horizontal direction pattern all over the place but vertical direction concentrated. General specifications of Omni Antenna as below:

Gain   2-3 dbi

Beam width 360

Polarized Vertical

VSWR  less than 1

2-Directional Antennas:

It transmits signal in a specified direction. It Contain high gain.

3-Leaky Coaxial Cable:

It transmits signal along path of the coaxial cable .Contains closely spaced slots in the outer conductor of the cable to transmit/Receive signals. There atre Two types of losses in leaky cable.

I-Feeder loss- cable attenuation loss

II-Coupling loss-Average signal level difference between the cable and dipole antenna at distance of 6m approx.

Some of the general feature reviews of antennas are given below:

Application:

-WiFi System, ISM application

 

-Indoor/in-building Coverage

 

-WLAN Communication Application

 

-CDMA, GSM, DCS, 3G/4GUMTS Application

 

-Next Gen Mobile-LTE

 

Features:

-Low return loss

-Wide beanwidth

 

-Suitable for wall mounting

 

-Low, aestheticall pleasing profile

 

Model: XXXXXXXX (Any )

 

RF Parameters:

 

-Frequency: In MHz (its selection depend upon spectrum allocation)

-Polarization: Vertical, Linear

 

-Horizontal Beam Width: 360 deg

 

-Vertical Beam Width: 90 deg (698-960MHz band (its selection depend upon spectrum allocation))

 

50 deg (1710-2700MHz band (its selection depend upon spectrum allocation))

 

-Gain: in dBi

 

-VSWR ≤ 1.5

 

-F/B >in dB

 

-Max Power: in  “W”

 

-Impedance: in Ω

 

Mechanical Specification:

 

-Radome Material ABS with UV Protection

 

-Lightning Protection Direct Ground

 

-Connector N-female

 

-Weight in  kg

 

-Size in mm

 

-Operating Temperature Range in degrees

 

-Storage Temperature in degrees

 

Different technologies antennas are available in market. Customer selects it as per need, services and requirement. i.e dual band antennas supports two band signal, quad band antennas suppots threes different band signals etc .

In addition of antennas detail as mentioned above in Passive Coaxial Cable design Distributed antennas connected with couplers, Power splitters, Jumpers and feeder cable Link Budget calculations based on how many couplers and Splitters are we used & Losses of coupler, splitters and feeder cable length in design. In the marker 20db, 15db, 10db and 6db couplers  2way, 3way and 4 way splitters  ½” inch Jumpers, ½”,7/8”,11/4” inch  feeders cables are using. Below Figures indicates how we cater losses of these coupler, splitter and cable.

Power Splitters

Splitters are used to split antenna feeder network power equally over the output ports.Two way, three way and four way splitters are generally used.

Splitters Loss:

2-Way Splitter Loss – around 3 db

3-Way Splitter Loss- around 5db

4-Way Splitter Loss- around 6db

Insertion loss for these splitters is 0 .2db.

Power Couplers:

Couplers are used to split antenna feeder power unequally among output ports.Couplers have tap/coupling loss and through loss e.g 10/0.5 coupler means its coupling loss is 10 while through loss is 5.Couplers generally are available in ratings of 3, 6, 7, 10, 15 & 20 db.

Attenuators:

Attenuators are used to reduce EIRP at antennas where less EIRP   required but the other antennas required high EIRP.

Attenuators are of values 3, 5, 7, 10 etc.

 

BTS:

The Base station capacity specification varies in Vander to Vander. The General specification of base station   is same as off Outdoor Base station or normal Base station.

Building Specifications and Coverage and Capacity Demands (Expansions): The capacity requirement enhances and fulfilled by adding extra Transceivers card into the cabinet of IBS_BTS. You can add as many card as IBS-base station supports.

For DAS-IBS coverage design regardless any type of DAS accurate building sketch and dimensions of building are very important .Designer should must required sketch map of building because defining he marked the route of cable and plan the coupler and splitter at right place without effecting KPI of deployment and coverage. For sacking this many tools in the markets are available .Mostly recommended by Vander.

Initial RF Survey:

Following are the things which are taken under consideration during initial RF Survey:

  • Site(Indoor Building) coordinates
  • Site Rough Layout sketch
  • RSSI and C/I of strong servers in different location of indoor site using TEMS pocket view mode.
  • No. of subscribers’ estimation/ floor or as the building architectural division.
  • Marking of the different areas what they are specified for.
  • Snaps of different floors
  • Building structure observation.

Initial RF survey report:

After the survey report is made in which all the above inputs are put.

 

Indoor Site Evaluation:

After the survey it is checkout if any modifications (Hard / Soft Changes) can be done to the existing neighboring site to improve the condition at the affected area. Otherwise Site is evaluated as to be an indoor Micro or wall mounted metro according to the location, requirements and conditions.

DAS-IBS Designing Tools:

iBwave Design radio planning software automates the design in-building wireless networks for optimal voice coverage and data capacity. It eliminates guesswork, to bring strong, reliable wireless communications indoors. iBwave Design is an integrated solution that takes RF designers through network planning, design, costing, validation, documentation and reporting. iBwave Design makes it easy for RF engineers to test scenarios for optimizing network coverage for 2G, 3G and 4G cellular technologies, as well as WiFi, public safety bands and femtocell.
Networks

  • RF System Design and Calculations.
  • Components Database to manage DAS equipment
  • Display DAS equipment position on floor plans
  • Create professional project documentation
  • Create automated reports on IBS project performance and cost
  • Standardize IBS design format
  • Propagation Module- Simulate indoor and outdoor propagation prediction in your building
  • Optimization module – Extrapolate outdoor wireless signals inside the building to analyze signal quality and data throughput before design phase
  • Collection module- import survey data and trace routes from collection devices, and overlaying survey data onto wireless indoor network design.
  • RF professionals to manage complex in-building network projects, generating cost efficiency, increasing productivity and delivering a larger return on investment.
  • Below address may help us to review and finalize designing tools. We can ask the IBS design module quotations to all RF Tools Venders after mailing info@ to all link presents..


Planning Tools for Wide Area Wireless Systems

Radio Planning Tools
Mentum Planet ™
Mentum CellPlanner ™
Forsk Atoll
ASSET
Broadband Planner
CelPlan 
WinProp
V-Soft Probe
EDXWireless
x-Wizard

Overture

iBwave

CRC-COVLAB

FUN

Hi-Res

MbP

RedPredict

TAP

RFCAD

Astrix

ComSite

 

RF Survey with floor Plan:

Once the indoor site is finalized, floor Architectural Plans are requested from building Authorities.

RF survey with Floor Plans is carried, RSSI is checked & recorded at each and every part of the indoor environment and C/I is checked at worst.

Drive test tool idle mode log files for different floors are made using floor plans provided.

During the RF survey Detailed Analysis/Observations of the building/environment is carried out as well as what is the ceiling thickness, floor heights, thickness of the walls in between floors, thin walls and their thickness.

Antenna locations are finalized using traditional Ray tracing techniques(By simply analyzing how reflections and propagation going to occur)

Fig  RSSI of different servers with floor plans

Marking of Priority Area:

In indoor areas like offices and meeting rooms etc have usually high priority. On the other hand areas like mosques, gyms etc have low priorities. Similarly area in which outdoor macro coverage and quality is satisfactory should not be included in intended coverage area for indoor site. For high priority area coverage should be around -75 dbm at each point while for low priority area levels should be around -85 dbm. These values vary according to KPI’s doc of the network.

Fig : Priority area marking for an indoor site location

Indoor Antenna Placement:

Antenna placement is the most crucial step in indoor planning. Following observations should   be considered during antenna placement:

  • Antennas especially Omni-directional antennas should be placed at centralized locations.
  • Panels should be placed in the corners of corridors or where design demands while keeping in view the spillage of indoor signals.
  • Antennas should be placed at high elevations where people can’t touch them as it will affect the performance.
  • Obstacle free path should be provided for antennas otherwise coverage in indoor will suffer a lot.
  • Antennas should be placed away from conductive objects.
  • Exposure levels of the indoor RF signals are below RF safety standard of WHO, IRPA, IEEE and FCC. However discretely placed antenna will reduce the unnecessary public concerns about RF exposure.
  • If the building with low traffic capacity is to be planned antennas should be placed in zigzag manner such to get an even distribution of signals as depicted in fig. below

Fig :  Improvement in indoor coverage

Link Budget:

Link Budget calculations are used to calculate the output power (db) at each antenna element. Passive component (coupler, splitter and attenuator losses) and feeder cable losses are subtracted from BTS output power. Link budget calculations are made for band to be used for indoor GSM/DCS/UMTS.

EIRP= Pout BTS + Ga – Lf – Lc- Ls – La

Pout BTS= BTS output power at antenna connector

Ga= Antenna gain (db)

Lf= Feeder loss

Lc= Coupler loss

Ls= Splitter loss

La= Attenuator loss

With standard parameters we can calculate link budget of the access site shared by Vander side

RF Indoor Plan:

After the path loss and link budget calculations RF plan is made floor by floor on the autocad layout of the building. Care should be taken while adjusting the AutoCAD scale. Also antenna, cable lengths and passive elements should be drawn accurately according to the plan.

Fig : RF indoor Plan for a floor

Antenna tree diagram:

Antenna tree diagram is made to have a quick overview of the IBS design. Care should be taken while calculating the lengths.

 

Fig 5.18: Antenna Tree diagram

Fig : Measurements for Cable lengths

Indoor Equipment List:

Detailed and complete BoQ list essential at site.

Fig: Indoor Equipment List

Indoor Site frequency planning:

Frequency planning is performed manually selecting suitable frequencies by carefully analyzing the neighboring frequencies.Exclude the co-channel and adjacent frequencies which will likely to interfere.From the remaining set choose the frequency that most likely to cause interference. BCCH frequency should be the least disturbed. Hopping on several frequencies will smooth out the interference.

Following need to be considered if two much clean frequency options exist:

  • Increase signal strength of indoor cell.
  • Allocate dedicated 3-5 frequencies for indoor cells.
  • Redesign the frequency plan.
  • (Indoor sites in our network are single cell; single band sites, so no frequency reuse is done in indoor)

IBS System Deployment Recommendations:

Traditional IBS deployment as said before Passive and active DAS –IBS.
Operators deploy solutions as per regulatory requirements (e.g. GSM or UMTS license) Recently operators deployed their own systems, single users DAS in a buildings. This resulted in multiple DAS in the same building, one for each operator (2-4) cause of

  • Multiple cable runs
  • Multiple Antennas
  • Multiple Maintenance organizations

So now a day’s regulatory authorities, building developers/owners and operators are

More operators are in force of sharing the IBS DAS. As illustrated before, all operators can share one DAS which cause of less cables and antennas and Shared maintenance efforts which helps controlling apex of IBS-DAS. This equals less negative impact on the esthetics of the building, less maintenance activities and lower cost for DAS.

The Third party installs the DAS most of the times. Generic Multi Operator DAS implemented by developer/owner in a building. DAS connected with Coaxial cables  with star configuration, Antennas (location based on generic guidelines, cables routed back to the nearest technical room e.g. maximum 90 meter cable run.

Wireless Design Simplicity

Goal – Provide a “-75dBm Coverage Blanket”for meeting coverage ,QOS KPI’s.

The Antenna Location Design Rules:

  • Outside antennas within 20ft of the edge of the building
  • Antennas spaced at 100 ft apart
  • One antenna per floor within 20 ft of the elevator core
  • One back-to-back antenna every 6 floors in the elevator shaft starting on floor 3
  • Cable: Star configuration

Following rules of thumb Maximum flexibility for the future RF planning

  • Omni antennas on a basic 100ft (30m) grid
  • Perimeter antennas < 20ft (6m) from walls
  • If on external wall, utilize directional antenna
  • One antenna < 20ft (6m) from elevator core

  

 

Stairwells:

  • If open, Omni antenna every 6th floor,
  • If closed, Omni antenna every 2nd floor

Installation & Certification:

  • Each cable run directly to TR < 300ft (90m)
  • Install connectors on both ends
  • Sweep-test for integrity and loss
  • Attach antennas & document cable paths
  • Extended warranty

Site Acceptance:

Once the indoor site is implemented site acceptance request is made by vendors/sub cons. Implementation team will take care of VSWR calculations, antenna grounding etc. Following is required from RF Team for acceptance of the indoor site:

  1. On site Audit
  2. Walk test
  3. Spillage check

1-On Site Audit:

On site verification of the indoor is performed to check the antenna location as well as the equipment count.

2-WALK TEST:

Walk test summarizing the coverage actual manners. It will be tested at two  types of  drive test mode

I-Idle Mode:

Walk test in idle mode for the indoor site is performed to check the RSSI and C/I of indoor site. Logfiles are made on the floor plans provided. (In case of vendor planning walk test  report is to be provided by them).

Fig : Rx-Level Idle mode

II-Dedicated mode:

Dedicated mode walk test is performed to check the quality and RSSI of indoor after call setup. Qualities of different TRX are also checked at RF end by locking the call on different TRX’s. Also handovers with other neighboring sites is tested.

Fig : Rx-Qual Dedicated mode

III-Spillage Check:

Spillage is spill of indoor signal outside the indoor location. Spillage is generally checked 20m away from the periphery of indoor compound. Generally -85dbm is set as a threshold and levels below it are problematic   as they will cause unnecessary handovers on the indoor site. However using Cell Reselection Offset parameters and handover control parameters, the unnecessary reselections and handovers can be avoided.

Fig Spillage

4-Coverage Acceptance:

Coverage is checked at each part of the indoor compound and should be within the range.

5-VSWR:

To be checked by implementation.

6-Parameters fine tuning:

Before site is accepted by the planning team Fine tuning of parameters is performed to achieve the below mentioned KPI’s. After achieving the KPI targets planning will accept this and handed over to optimization team for further fine tuning

KPIs
1 RX Level for 2G for 95% of the Covered Area=-75dBm
2 RSCP for 95% of the Covered Area=-80dBm
3 DL Rx Quality for 2G for 95% area of the covered Area less than 2

 

Pilot power  of 3G common area  less than -75 dBm

Pilot Ec/Io of common area  less than -7 dBm

Spillage Test (On the surrounding main street nearby the building)

1

Signal from indoor system not higher than -95dBm

 

Frequency Planning for Indoor Systems Conclusion:

For improve coverage and Capacity inside building using IBS solution and it shows an increase of the cellular traffic with up to 70% for larger buildings. For good coverage we have to assign frequencies manually by excluding the frequencies of the Surrounding cells and the adjacent frequencies. For avoiding interference it is good to apply Frequency Hooping to smooth out the interference. It is good for coverage if we are increasing the BTS power if the available frequencies are few in numbers.

h

IBS Planning & Implementation:

To starting planning process of IBS DAS Statically review of the network is very important and essential .The identification of the right area or building for IBS DAS design very critical .Once the Area identified with help of stats of the network, field visits and complains.

Once location identified standardized planning ladder followed till all entity of DAS IBS design practical implemented.

Conclusion:

In-building Solutions as defined in this document is a way to enable efficient usage of wireless mobile applications inside different kinds of buildings. This requires that sufficient coverage and capacity with good radio quality is available inside the buildings. Although the mobile operators will cover most buildings from outdoor sites in their macro network, there is a need to provide many buildings with extended radio coverage and capacity. In-building solutions are well-proven methods for an operator to capture new traffic and new revenue streams.

One can provide enhanced in-building solutions to off-load the macro network, thus increasing mobile traffic, and attract additional subscribers due to the enhanced mobile network quality and accessibility to mobile Internet applications and other services that require high data-rates and capacity. There are several different ways to implement in-building solutions. Dedicated Radio Base Stations, RBSs, that are connected to Distributed Antenna Systems, DASs, are commonly implemented solutions. These solutions provide additional capacity as well as covers “black holes” inside different kinds of buildings. A number of different types of both RBSs and DASs are available and the solutions can be customized for different buildings and needs. Repeaters are often used for buildings with a limited need for capacity, but where additional coverage is needed, like road tunnels and smaller buildings or parts of buildings.

Indoor systems can be solution if the coverage is weak from outdoor cells or causing to bad quality To build indoor systems into the buildings, which are generating high traffic, can reduce the network load by handling that traffic In developed business centers, indoor system can replace the fixed network.

Indoor systems are sometimes the complements that can provide a good image.

Source: http://telecom-knowledge.blogspot.nl/2014/09/indoor-building-distributed-antenna.html

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LTE Femto Gateway with X2 Broker

14 Mar
 An LTE femtocell* (HeNB) is an ultra-small cellular base station that connects to a mobile operator’s LTE core network via broadband Internet. Using this femtocell, a mobile operator can eliminate indoor shadowing areas, thereby extending LTE service coverage and improving call quality.

* Femtocell and HeNB are interchangeable, and so are Femtocell Gateway and HeNB Gateway in this document.

The mobile operator can benefit from the femtocell as it allows LTE traffic to be distributed between macro eNB and femtocells at home and also at indoor and outdoor hotspots in crowded places like coffee shops, restaurants, bus stop, malls, schools, and so on. This helps the operator to effectively reduce loads at macro cells and in the backhaul, and provide its users with better QoE.

The beauty of LTE femtocell is that, as all it takes is simply connecting existing broadband Internet to an ultra-small base station, it gives the advantage of quick deployment. It also minimizes additional costs and burdens that may be imposed in case of building macro cells, in relation to installation site acquisition, site rental, power supply, construction of backhaul network, etc. Such benefits make it one of the most cost-effective ways to expand coverage and capacity in an LTE network.


Figure 1-1. Key values provided by femtocell in 4G era

Years ago, mobile operators started building macro LTE networks, and have always been in the quest for solutions to shadowing areas and high costs of operating multiple networks (2G, 3G and 4G) since then. Recently, operators are pursuing a strategy to i) provide uninterrupted voice coverage without relying on legacy networks like 2G or 3G by introducing small cells in shadowing areas and supporting seamless handover between them and macro cells, and ii) ultimately migrate into an all LTE network through gradual replacement of legacy networks.

That is, many operators are pushing forward with this strategy to minimize the total OPEX of the entire network by operating only one LTE network instead of multiple mobile networks. Femtocells are considered the most likely candidate to serve this purpose.

Meanwhile, operators without 2G or 3G, but with LTE macro network, are also active in introducing LTE femtocells in their networks as a cost-effective solution to enhance LTE coverage and capacity.

Here, what concerns the operators most is “uncertainty that can be caused while these femtocells (HeNB). Unlike existing macro cells, if deployed in a large scale – in tens or hundreds of thousands, these cells can cause unpredictable, operational risk while interworking with legacy LTE systems (EPC, eNB, etc.).”

SMEC’s Femto GW (HeNB-GW), designed to work as a sponge to absorb such uncertainty and risk, helps to operate the femto network just as stably as macro networks.

Chapter 2 will look into the benefits and issues of HeNB-GW, and chapter 3 will introduce HeNB-GW solution of SMEC, specifically X2 broker feature in details. Chapter 4 will summarize the benefits of the SMEC solution.

 


2. HeNB-GW: Benefit and Issues

2.1 Benefits

Table 2-1 summarizes issues in connecting HeNBs directly to MME, without HeNB-GW, as compared to the benefits of deploying HeNB-GW.

Table 2-1. Benefits of deploying HeNB-GW

2.2 Issues – X2 Handover Support

Mobile operators prefer X2 handover that uses just X2 interface between eNBs to more complicated S1 handover that increases loads at MME. As seen in Figure 2-1(a), the more HeNBs are deployed, the more hand-in and hand-out activities are performed between macro eNBs and HeNBs (particularly outdoors).

This means even more loads are caused at MME and S-GW by S1 handover, affecting the reliability of the LTE network. For more reliable, secured operation of the LTE core network, X2 handover without MME’s intervention is essential in a femto network (Figure 2-1(b)).


Figure 2-1. Handover options between macro eNB and HeNBs: S1 vs. X2

 


Figure 2-2. Issues: scalability and uncertainty

But in reality, supporting X2 handover in a femtocell environment is not easy because of possible scalability and instability issues. If existing macro eNBs establish X2 connections directly with a large number of HeNBs, scalability can be compromised due to the limit in the number of X2 connections that can be managed (Figure 2-2(a)).

For X2 handover, existing MME and eNB must interact directly with HeNBs (S1-MME, X2), and this process can bring about instability between the two (Figure 2-2(b)). Also, configuring X2 GW requires upgrade of eNBs and HeNBs all to R-12, consequently aggravating the complexity of the network even further.

These issues have been an obstacle standing in the way of applying X2 handover between macro eNB and HeNB in the commercial network. The HeNB-GW solution by SMEC is designed to address these issues. We will learn how in chapter 3.

 

3. SMEC HeNB-GW Solution

3.1 SMEC HeNB-GW

The Figure 3-1 describes a high level view of LTE network with femtocell and SMEC HeNB-GW. SMEC HeNB-GW can provide:

  • Virtual eNB (eNB ID based HeNB grouping)
  • X2 service broker (X2 proxy between eNB and HeNB)
  • S1 and X2 handover between eNB and HeNB
  • S1 signaling and bearer aggregation with SeGW functionality


Figure 3-1. SMEC HeNB-GW architecture

SMEC HeNB-GW, technologically based on virtual eNB concept, can group a number of HeNBs for management by group. Each virtual eNB, capable of aggregating 256 HeNBs, functions as a logical HeNB GW, providing S1 interface to EPC and HeNBs, and X2 interface to macro eNB and HeNB. From a S1 interface point of view, MME and S-GW see virtual eNB as ‘one macro eNB’, and HeNB sees it as ‘MME and S-GW’. Virtual eNB provides the following functionalities in respect of S1 interfaces:

  • Relaying UE-associated S1AP messages between MME and HeNB
  • Terminating non-UE associated S1AP procedures towards HeNB and towards MME
  • Terminating S1-U interfaces with HeNB and with S-GW

Virtual eNB, as a logical macro eNB, provides X2 interfaces. From X2 interface point of view, the macro eNB sees virtual eNB as an eNB with 256 cells that offers following functionalities:

  • Providing X2 interfaces between macro eNB and HeNBs
  • Terminating non-UE associated X2AP messages between eNB and HeNB
  • Converting UE-X2AP-ID between eNB and HeNB
  • Routing UE-associated X2AP messages between eNB and HeNB

3.2 X2 Service Broker

SMEC HeNB-GW features X2 service broker for complexity and stability issues as seen in Figure 2-2. As shown in Figure 3-2(b), each HeNB establishes X2 connection with virtual eNB (acting as a ‘X2 service broker’) at SMEC HeNB-GW, and macro eNB establishes only one X2 connection with the virtual eNB.

This X2 aggregation function provided by X2 broker drastically reduces the number of X2 connections needed between macro eNB and  HeNBs (256 X2 connections to only one X2 connection). SMEC HeNB-GW makes existing macro eNBs recognize it as another regular macro eNB, by hiding all the HeNBs behind its back.

Existing MME and eNB must interact directly with HeNBs (S1-MME, X2) for X2 handover, etc., and this can bring about instability between the two. X2 broker, upon receiving S1 and X2 messages from HeNB, modifies  the messages as if it is eNB itself, and sends them to MME and eNB. This ensures the stability of the LTE core network and eNB remains unaffected.

As a result, network complexity and unstability anticipated by deployment of HeNB can be significantly decreased, and kept as low as in existing macro eNB network. LG U+, a South Korean LTE network operator, has already deployed SMEC’s HeNB-GW, applying X2 handover between macro eNB and HeNBs in its commercial network. The company has been able to keep the load level at MME at a minimum and provide uninterrupted VoLTE service across femto hotspots in macro cells.

 


Figure 3-2. Benefits of X2 broker: scalability and stability

3.3 X2 Service Broker Operation

In order for X2 service broker to work, HeMS allocates HeNB IDs to HeNBs as seen in Figure 3-3. An HeNB ID is 28 bits long, and consists of i) an eNB ID (20 bits long), identical for all HeNBs (up to 256) that belong to the same virtual eNB, and ii) a cell ID (8 bits long), unique for all the HeNBs (up to 256). This HeNB ID plaNning scheme lets a macro eNB recognize a virtual eNB as just another macro eNB, and all the HeNBs belonging to it as its cells.

 


Figure 3-3. SMEC X2 service broker: HeNB ID planning

Detailed call flow for X2 broker operation is as follows:

❶ HeNB1 initiates TNL address discovery procedure towards an MeNB: HeNB1 detects a new cell (cell A of macro eNB) and decides to setup X2 towards Macro eNB (MeNB). It initiates an TNL address discovery procedure by sending eNB Configuration Transfer message indicating its own HeNB ID (HeNB1, 28 bits long) and MeNB ID (20 bits long) as neighbor information to virtual eNB through S1 interface.

The virtual eNB does not have any information on the MeNB’s X2 IP address, and it must forward the message to MME to find the X2 IP address of MeNB. Before forwarding the message, virtual eNB (X2 broker) replaces the 28-bit HeNB ID with its own ID (virtual eNB, 20 bit long) in the message and forwards it to MME. MME knows the MeNB and so sends an MME Configuration Transfer message to it (note that virtual eNB does not disclose 28-bit-long HeNB ID to MME and MeNB).

 


Figure 3-4. SMEC X2 service broker: HeNB1 initiates TNL address discovery procedure towards an MeNB

MeNB returns its X2 IP address, and MME sends it to virtual eNB (now, virtual eNB obtains MeNB’s X2 IP address). Virtual eNB replaces the MeNB’s X2 IP address in SeNB Information with its own IP address, and sends MME Configuration Transfer message to HeNB1. Then, this leads HeNB1 to recognize the virtual eNB IP address as MeNB’s X2 IP address.

❷ X2 setup between HeNB1 and MeNB: HeNB1 starts X2 setup towards MeNB, indicating its HeNB ID (virtual eNB (20b) + cell 1 (8b)) and MeNB as neighbor information. Since HeNB1 knows virtual eNB’s IP address as MeNB’s X2 IP address, this message is actually forwarded to virtual eNB. Virtual eNB starts another X2 setup procedure to continue the setup of X2-connectivity towards MeNB, indicating its own eNB ID (virtual eNB) and cell information (cell 1) and MeNB ID as neighbor information. When MeNB and virtual eNB responds, a single X2 connection is set up between HeNB1 and virtual eNB, and also between virtual eNB and MeNB.
This process lets MeNB add the cell information of HeNB1 (virtual eNB/cell1) to its X2 neighbor list and also lets HeNB1 add the cell information of MeNB (MeNB/cell A) to its X2 neighbor list.

Figure 3-5. SMEC X2 service broker: X2 setup between HeNB1 and MeNB

❸ Subsequent X2 connection setups: As X2 connection between virtual eNB and MeNB has already been setup, any further X2-address request from other HeNBs for X2-connectivity towards MeNB will be responded by the virtual eNB without forwarding the request via the MME towards the MeNB. Virtual eNB sends its own IP address in response to other HeNB’s X2-address request to the MeNB.

For any further X2 setup request to the MeNB, virtual eNB, through the already-established X2 connection, sends an X2 message (eNB Configuration Update) containing HeNB2 cell information to inform MeNB of the updated cell information.

Virtual eNB sends X2 Setup Response to HeNB2 if the X2 Configuration Update between the virtual eNB and MeNB is performed successfully.

Figure 3-6. SMEC X2 service broker: Subsequent X2 connection setups

Once the above process is completed, an X2 connection is set up between each HeNB and virtual eNB (HeNB-GW), and also between virtual eNB and macro eNB. Logically, existing macro eNB recognizes HeNB-GW as a new macro eNB, and all HeNBs belonging to it as cells in the macro eNB as shown in Figure 3-7.

 

Figure 3-7. SMEC X2 service broker: Logical configuration

This means, the legacy LTE network (eNB and EPC) will see even a large-scale deployment of HeNBs as a small-scale deployment of additional macro eNBs. This completely eliminates any chance of uncertainty, complexity, or risk factors that would otherwise be caused by a large-scale deployment of HeNB in the legacy LTE network. For example, because the 28-bit HeNB IDs are not exposed to MME or eNB, there is no potential issue in interworking between HeNBs and MME/eNBs, which makes the network architecture even more stable and reliable.

As the X2 service broker feature by SMEC is implemented using S1 interface (eNB n MME) and X2 interface (eNB n eNB) defined in Rel. 8, no change or modification is needed in the EPC core or eNBs already deployed in the legacy LTE network. This makes the feature readily applicable to any LTE commercial network where Rel. 8 or higher is implemented (i.e., in any LTE network).

 

4. Benefits of SMEC HeNB-GW

SMEC’s HeNB-GW helps to keep the impact of introducing LTE femtocell – even when massively deployed – in the legacy LTE network low, as low as that of small scale addition of macro eNB. This ensures the stability of the LTE core network remains unaffected and the additional investment costs resulting from such deployment are kept to a minimum.

  • SMEC’s HeNB-GW delivers both SeGW feature and aggregation feature (for control plane, S1-MME and user plane, S1-U) at a single point, proactively preventing overload at existing MME and S-GW, and also easing potential uncertainty in the legacy LTE network to be caused by tens of thousands of newly deployed femtocells. Also, it helps to bring down the costs for additional installation of MME resulting from the large scale deployment of femtocells (e.g. purchasing additional equipment and license).
  • SMEC’s HeNB-GW supports S1 and X2 handover between macro eNB and femtocell, which ensures uninterrupted, reliable call quality, even during switches between the two cells – all just through 4G network (i.e. just through VoLTE) without 2G or 3G.
  • SMEC’s HeNB-GW offers X2 service broker feature that provides X2 handover between macro eNB and HeNB without having to modify X2 interface used between the macro eNBs.
  1. Traditional HeNB-GW can only support S1 handover, and thus heavy overloads are inevitably passed on to MME during handover. SMEC HeNB GW, however, supports X2 handover where no MME involvement during handover process is needed, drastically reducing overload at MME.
  2. It significantly reduces the number of X2 interfaces needed through aggregation of X2 interfaces between macro eNB and femtocells, thereby decreasing network complexity to be caused by X2 interface used in small cell environment.
  3. The X2 service broker feature by SMEC, implementable through S1 and X2 interfaces defined in 3GPP Rel. 8., is readily deployable in any LTE system regardless of its release version. Without additional installation of X2 GW nodes defined in R-12 or upgrade of R-12 X2 GW feature license of MME, eNB and HeNB, or of LTE network, X2 handover between macro eNB and HeNB can be readily supported.

Acronyms

 

3GPP 3rd Generation Partnership Project
eNB Evolved Node B
EPC Evolved Packet Core
GTP GPRS Tunneling Protocol
GW Gateway
HeMS HeNB Management System
HeNB Home eNodeB (Femtocell)
HeNB-GW Home eNodeB Gateway (Femto Gateway)
ID Identifier
IMS IP Multimedia Subsystem
ISP Internet Service Provider
LTE Long Term Evolution
MeNB Macro eNB
MME Mobility Management Entity
PGW Packet Data Network Gateway
QoE Quality of Experience
RAN Radio Access Network
SCTP Stream Control Transmission Protocol
SeGW Security Gateway
SeNB Source eNB
SOHO Small Office Home Office
S-GW Serving Gateway
TNL Transport Network Layer
UE User Equipment
VoLTE Voice over LTE
X2 AP X2 Application Protocol
X2 GW X2 Gateway

 

SMEC’s LTE Femto Gateway with X2 Broker – Facilitating instant mass deployment of LTE femtocells in existing LTE infrastructure
March 14, 2016 | By Y.C. Lee (www.esmec.com), Dr. Harrison Jangwoo Son (tech@netmanias.com)

 

Source: http://www.netmanias.com/en/?m=view&id=reports&no=8493

Parallel Wireless breaks lines with new radio architecture

28 Jan
Parallel Wireless takes wraps off reference femtocell and function-packed gateway product with aim of realigning costs of enterprise wireless.

The US start-up that is trying to reimagine the cost structures of building has released details of two new products designed to drive an entirely new cost structure for major enterprise wireless deployments.

Parallel Wireless has announced a reference design (white label) Cellular Access Point femtocell built on an Intel chipset. Alongside the ODM-able femto it has released its upgraded HetNet Gateway Orchestrator – a solution that integrates several network gateway elements (HeNB,FemtoGS, Security GW, ePDG, TWAG), plus SON capability, as Virtual Network Functions on standard Intel hardware, enabled by Intel Open Network Platform Server and DPDK accelerators.

Showing the functions absorbed as VNFs into the HetNet Gateway

Showing the functions absorbed as VNFs into the HetNet Gateway

The net result, Parallel Wireless claims, is an architecture that can enable much cheaper deployments than current large scale wireless competitors. More cost-stripping comes with the femto reference design which is intended to be extremely low cost to manufacture.

parallel price compare

The company claimed that comparable system costs place it far below the likes of SpiderCloud’s E-RAN, Ericsson’s Radio Dot and Huawei’s LampSite solutions.

The brains of the piece is the HetNet Gateway, which provides X2, Iuh, Iur and S1 interface support, thereby providing unified mobility management across WCDMA, LTE and WiFi access. As an NFV-enabled element it also fits in with MEC architectures and can also deployed at different points in the network, dependent on where the operator deems fit.

parallel wireless architecture

Parallel Wireless vision of the overall architecture

One challenge for Parallel will be to convince operators that the HetNet Gateway is the element they need in their network to provide the SON, orchestration, X2 brokering and so on of the RAN. Not only is it challenging them to move to an Intel-based virtualised architecture for key gateway and security functions, but also given the “open” nature of NFV, in theory there is no particular need for operators to move to Parallel’s implementation as the host of these VNFs.

Additionally, it’s a major structural change to make just to be able to address the enterprise market, attractive as it is. Of course, you wouldn’t expect Parallel’s ambitions to stop at the enterprise use case – this is likely it biting off the first chunk of the market it thinks best suits its Intel-based vRAN capabilities.

And Parallel would no doubt also point out that the HNG is not solely integrated with Parallel access points, and could be used to manage other vendors’ equipment, giving operators a multi-vendor, cross-mode control point in the network.

Another challenge for the startup will be that it is introducing its concept at a time when the likes of Altiostar with its virtualised RAN, and Artemis (now in an MoU with Nokia) with its pCell are introducing new concepts to outdoor radio. Indoors  the likes of SpiderCloud and Airvana(Commscope) market themselves along broadly similar lines. For instance Airvana already tags its OneCell as providing LTE at the economics of WiFi. Another example: SpiderCloud‘s Intel-based services control node is positioned by the vendor as fitting into the virtualised edge vision, and SpiderCloud was a founder member of the ETSI MEC SIG.

In other words, it is going to take some time for all of this to shake out. There can be little doubt, however, that the direction of travel is NFV marching further towards the edge, on standard hardware. Parallel, then, is positioning itself on that road. Can it hitch a ride?

Femtocell Opinion, comment and reviews

26 Sep
5G
There’s been a lot of media hype around the term 5G in the past year. Is this groundless  and just another excuse for more conference events, or is there some substance to it? Setting some constraints

Telecoms professionals have a pretty poor track record of predicting what applications and services will be most popular. For example, 3G had plenty of hype around personal videocalls and M-commerce which have still to come to fruition. 4G certainly provides faster data speeds (especially uplink), but we seem to have forgotten about voice.

Moray Rumney of Agilent (soon to be rebranded Keysight) spoke of the tradeoffs when designing any new generation. Do we want high speed, long battery life, reachability or resilience. It’s tempting to say we want all of those. For sure, the focus in recent releases seems to be mostly around peak data rates and many other benefits have gone out the window. I still find many buildings or locations where I can’t be connected or have poor quality voice/slow or unusable data service. The conference venue itself was a relevant example. Further confirmation can be found in a recent UK OFCOM report based on RootMetrics data which established that 30% of consumers find themselves outside coverage at least once a week.

Looking at it from a performance perspective, you might think:

Features we’d all like Consequences
(in no particular order)
Higher bit rates
Lower latency
Higher capacity density
Higher spectral efficiency
Higher connection density
Terminal and Network Cost
Terminal battery life
Energy efficiency
Reliability
Mobility

Where others might prefer to focus more on availability and efficiency:

Features we’d all like Consequences
(in no particular order)
High service availability
Lower terminal and network cost
Higher energy efficiency
Lower mobility
Longer Batter Life
Lower or sufficient bit rates
Higher latency
Lower spectral efficiency
Lower capacity density
Lower connection density

The tradeoffs are perhaps best illustrated using a Spider Chart:

5G-requirement-spider-chart

 

Surely 5G won’t be just a single technology

This leads to the view that 5G will become more than one technology to serve our needs – perhaps amalgamating one or two that go really fast with one or two that reach the most remote regions. Perhaps it could focus on one (sub)set of requirements and rely on existing technologies to cater for others.

Indeed, as with 3G and 4G before it, we would expect 5G to be able to interwork with previous generations rather than replace them. With Carrier Wi-Fi also emerging strongly, including the new Gigabit 802.11ad short range technology, 5G will have to deliver significant additional benefits to justify heavy further investment and shouldn’t be considered a never-ending gravy train.

Finding customers across different verticals

One theme we heard many times throughout the event was the need to develop and extend telecoms services into the many vertical market sectors. Perhaps 5G could look to build on and extend the value of fully mobile wireless service differently for each sector.

The theme of M2M (Machine to Machine) comes up a lot in this context, but again it seemed to be all encompassing and widespread. We’re not talking about a specific radio technology here – any and every technology available would be considered. Low power Bluetooth was mentioned more than once.

As an example of one vertical (energy retailers), what I learnt was that (here in the UK) we’re implementing two somewhat contradictory approaches. Our first responders and emergency services, who today use the expensive and outdated European TETRA radio system, will find it replaced by standardised LTE – possibly using different frequencies with a few extra standardised features added in. This will save huge amounts of money and benefit from the mass market of LTE.

At the same time, the UK is installing a completely separate national radio network to communicate with smart energy meters. In the north of the country, Arquiva has a contract to do so and uses their own proprietary system. In the middle and south, Telefonica will simply reuse their existing 2G/3G/4G mobile network which seems to be a lot more practical to me. Extending coverage of the cellular network where needed to reach outlying meters would bring wider benefits of cellular connectivity to those areas overall.

Timescales

The headline timeframe for 5G is really quite short. Japan (DoCoMo) have made bold assertions that they would have it available for the 2020 Summer Olympics. They’ve even announced their six suppliers for 5G trials. Meanwhile the South Koreans have announced trials in 2018 and commercial service in 2020, perhaps aiming to showcase it during the 2018 Winter Olympics.

Given the uncertainty of what 5G requirements are, I think it could easily take much longer. We’ll need some clear agreements of what the goals are (probably from the ITU) before the industry can make real progress.

Perhaps the UK should rebrand its smart meter project as 5G, which will be delivered in a similar timescale.

The current reality

While we discussed the finer points of multi-gigabit, low latency wireless service that 5G could offer, a reality check was the poor (i.e. non-existant 3G) cellular service at the conference venue. This isn’t unusual at conferences and no specific to any particular network operator. We already have plenty of in-building small cell technology to fix these issues today without needing 5G, but seem to lack the commercial and operational focus to make it happen.

There has been a gap of about 10 years between each new generation of radio technology, during which time the previous one matures and develops considerably. Even 2G GSM continues to evolve and remains present in almost every phone. We can expect to see substantial development for both 3G and LTE over the next 10 years, so I wouldn’t wait for 5G to come along and solve all our problems quite yet.

Moray Rumney’s 5G presentation can be found on the Cambridge Wireless event website here

Source: http://www.thinksmallcell.com/Opinion/how-will-the-indeterminate-shape-of-5g-encompass-small-cells.html

IMSI Catchers

21 Nov

Tapped_620x258

An IMSI catcher is essentially a false mobile tower acting between the target mobile phone(s) and the service providers real towers. As such it is considered a Man-in-The-Middle (MiTM) attack. It is used as an eavesdropping device used for interception and tracking of cellular phones and usually is undetectable for the users of mobile phones.

With the recent wave of femto cell technology  available to the general public; Hackers are turning these useful devices into devious wire-tapping machines.

What is an IMSI?

A unique  International Mobile Subscriber Identity (IMSI) is issued to every user of the GSM/UMTS/LTE System.

Composition of IMSI

Global-IMSI-Numbers-and-Networks
IMSI is composed of three parts:

  1. Mobile Country Code (MCC)consisting of 3 digits. The MCC identifies uniquely the country of domicile of the mobile subscriber;
  2. National Mobile Station Identity (NMSI):
    • MobileNetworkCode (MNC)consisting of 2 or 3 digits for GSM/UMTS applications. The MNC identifies the home PLMN of the mobile subscriber. The length of the MNC (two or three digits) depends on the value of the MCC. A mixture of two and three digit MNC codes within a single MCC area is not recommended and is outside the scope of this specification.
    • Mobile Subscriber Identification Number (MSIN) identifying the mobile subscriber within a PLMN.

Example IMSI:

234150999999999

  • MCC = 234 (UK)
  • MNC = 15 (02 UK)
  • MSIN = 0999999999

For a full list of MCCs and MNCs visit: http://en.wikipedia.org/wiki/Mobile_country_code

The National Mobile Subscriber Identity (NMSI) consists of the Mobile Network Code and the Mobile Subscriber Identification Number.

In order to support the subscriber identity confidentiality service the VLRs, SGSNs and MME may allocate Temporary Mobile Subscriber Identities (TMSI) to visiting mobile subscribers. The VLR, SGSN and MME must be capable of correlating an allocated TMSI with the IMSI of the MS (Mobile Subscriber or your physical phone ;))to which it is allocated.

VLRs, SGSNs, MME and more will be covered later….

IMSI Catcher

An IMSI catcher is essentially a false mobile tower acting between the target mobile phone(s) and the service providers real towers. As such it is considered a Man-in-The-Middle (MiTM) attack. It is used as an eavesdropping device used for interception and tracking of cellular phones and usually is undetectable for the users of mobile phones.

With the recent wave of femto cell technology  available to the general public; Hackers are turning these useful devices into devious wire-tapping machines.

How?

The GSM specification requires the handset to authenticate to the network, butdoes not require the network to authenticate to the handset. This well-known security hole can be exploited by an IMSI catcher.

The IMSI catcher masquerades as a base station and logs the IMSI numbers of all the mobile stations in the area, as they attempt to attach to the IMSI-catcher. It allows forcing the mobile phone connected to it to use no call encryption (i.e., it is forced into A5/0 mode), making the call data easy to intercept and convert to audio.

IMSI catchers are used in some countries by law enforcement and intelligence agencies, but based upon civil liberty and privacy concerns, their use is illegal in others. Some countries do not even have encrypted phone data traffic (or very weak encryption) rendering an IMSI catcher unnecessary.

Source: http://penturalabs.wordpress.com/2013/11/20/imsi-catchers/

Handover in LTE Femtocell

16 Nov

Femtocell is a small base station designed for home and small business environment. It connects the mobile device to cellular operator network using xDSL, cable, or optical connection. But, there were a problem for handover femtocell in cellular network. This is because the new architecture of femtocell technology, we didn’t know how is the right procedure for this process. So what’s the solution of this issue?

As we know from 3GPP specifications, femtocell architecture in LTE is a little different. In E-UTRAN, there is a interface between eNB and each eNB connects to the Core Network (MME/SGW). But, in femtocell there is no interface between each HeNB (femtocell eNodeB). And all HeNBs connect to the MME/SGW via HeNB GW (Home eNodeB Gateway). HeNB GW works as virtual CN to the HeNBs, and as a virtual eNB to the real CN. Because there is no RNC in LTE, most of RNC functions are shifted to eNB. So, mobility management function function by HeNB GW will be a interesting issue to be discussed.

With a new architecture, E-UTRAN of femtocell has different handover procedure compared to common E-UTRAN’s. There are three kinds of handover in femtocell deployment. They are hand-in (handover from macrocell to femtocell), hand-out (handover from femtocell to macrocell), and femto-to-femto handover.

The HeNB GW is assigned with a normal eNB ID so MME will see it as usual eNB. HeNB GW could allocate private ID for eache HeNB within its coverage, and it also maintain this list of HeNB IDs. A unique Tracking Area Code (TAC) is assigned to HeNB GW and HeNBs in the list.  MME associates the TAC and the eNB ID for the HeNB GW and notify the surrounding eNBs.

For hand-in, the source eNB knows that the potential target cell is a HeNB cell from the TAC and the HeNB ID reporting from the UE. It identifies its HeNB GW and sends handover required message to MME. MME then routes the message to the HeNB GW. Then HeNB GW delivers the message to the right HeNB.

For hand-out, HeNB GW gets the handover required message from source HeNB and forwards the message to MME.

For femto-to-femto (inter-HeNB) handover, we need to know who will make the final handover decisions and how is the handover procedure. Unlike the inter-eNB handover for LTE, where control plane messages and user plane packets are relocated from source to target eNB via X2 interface (without the involvement of the EPC), the inter-HeNB handover has to be supported by upper nodes due to the lack of X2 interface. Therefore, two  mobility management methods for femto-to-femto handover type is suggested.

Method 1 is to move the mobility anchor for user plane from the S-GW to the HeNB GW and let the HeNB GW make the handover decisions. This method implies a micro-mobility anchor at the HeNB GW for both control plane and user plane because the MME and the S-GW are not involved during inter-HeNB handover. It also implies that the S-GW does not need to be updated for the path switch after handover. When the HeNB GW receives a HO Required Message from the source HeNB, it will check the Target ID IE in the message: if the target cell is under its control, HeNB GW handles the handover.

Method 2 is similar to the S1-based handover in LTE: the MME confirms the handover request and makes sources
release decision. The S-GW still remains as the anchor for the data. Therefore, HeNB GW simply
forwards handover messages between HeNB and MME, working more like a transparent node or relay in terms of
mobility management at RNL. Since the HeNB GW acts as a relay, it forwards handover messages either from the source HeNB or from the MME instead of local processing. Thus, more control signaling messages are exchanged between radio access network and core network. The S-GW also has to be notified with the change of end point of GTP tunnel after a successful handover. The benefit for method 2 is that it has low impact on LTE standards.

Reference :

  • 3GPPP Technical Specifications Documents
  • Lan Wang, Yongsheng Zhang, Zhenrong Wei. “Mobility Management Schemes at Radio
    Network Layer for LTE Femtocells”. DOCOMO Beijing Communications Laboratories
    Co. Ltd., Beijing, China.
  • IEEE Communication Magazine. Januari 2010 and Sepember 2009

Source: http://drsaufi.wordpress.com/2010/03/18/handover-in-femtocell-technology-on-lte-network/#!

3g And 4g Cellular Technologies Computer Science Essay

6 Nov

The current 3G and 4G cellular technologies cant support high data rate demands of the voice and video applications and end up providing poor coverage indoor. Customer dissatisfaction due to dropped calls and time-consuming downloads in high density metropolitan hubs were the major concerns of the service providers. A low cost solution for this problem is deployment of Femtocells in bandwidth demanding areas. The system capacity and network coverage can be increased with the use of Femtocells , which are small base stations connected to DSL or internet cable and are installed in residential or business environments. These Femtocells provide high-quality network access to indoor users, while simultaneously reducing the load of the whole system. In this seminar, architecture of Femtocells , the basic working, and its applications will be covered. The advantages of Femtocells over other networks and the technical issues in implementation of Femtocells will be discussed.

Introduction

Femtocells are small devices that can be installed in home or premises to increase the coverage capacity indoors. These femtocells are deployed in the area of very low coverage to provide the high voice and data services to the mobile devices that are assigned to femtocells initially. These femtocells are connected to mobile operator’s core network through Internet via DSL or broadband modem. Femtocells which include both a DSL router and femtocells are called . Once plugged in, the femtocell connects to the MNO’s mobile network, and provides extra coverage. From a user’s perspective, it is plug and play, there is no specific installation or technical knowledge required—anyone can install a femtocell at home.

These are also called small cells, as their coverage is very less compared to microcells (200 Km), picocells (200m), whereas Femtocells limits themselves to the range of (10m). As shown in the below figure, the femtocell deployed in home can support from 3 to 16 mobile devices. These mobile devices are operated by femtocells. The voice and data of these mobile devices is transmitted through the Femtocells network to the Mobile operators Network. As the backhauling is carried out through internet, which in turn reduces the data load from macrocell and hence increases its efficiency

Source: EMF Series Projects with Collaborations of WHO

Femtocells provide all the services such as circuit switched and packet switched services by using different architectural models. The one model is based on 3GGP standard called SIP/IMS model and the other legacy network model is based on 3GPP2 Standard. These two models are described further in more detail. Inspite of many advantages of femtocells, there are several technical issues in implementation of femtocell like handover of device, interference of cells in network and synchronization of femtocells with the network which will be dealed with in more details.

Basic Working of Femtocells: While deploying Femtocell, User declares the mobile devices that will be using the coverage area of Femtocell which is mostly done through web interface of Mobile Network operator. These defined mobile devices are when outside the coverage area of femtocell, they use the coverage of Macrocell, but as soon as the mobile device comes in the coverage are of Femtocell, the overall control of mobile device will be transferred to femtocell. The voice and data of this mobile device will be backhauled through internet to mobile operator network. The overall communication will be carried out by femtocell., and hence providing better coverage area indoors. This process of transferring the control of device from macrocell to femtocell is known as handover.

Basic Working of Femtocell

These Femtocells uses different architectures based on the Technological standards followed by Femtocells. The WCDMA uses Iuh Architecture while CDMA2000 uses SIP/IMS architecture. This network architecture share common network components.

Network Architecture Components:

Femtocell Access Point (FAP)

Security Gateway (SeGW)

Femtocell Device Management System (FMS)

Femtocell Access Point: Femtocell Access Point is a key component of femtocell architecture. These are small access points that are deployed in user location. There functions are similar to that of base station and base station controller of macrocell network. These femtocells provide connection between user equipment and mobile operator’s network. There are different types of FAP’s available some FAP’s are plug and play devices, which can be connected to the broadband routers directly. These FAP’s are also useful for prioritizing the mobile devices depending on the data being transferred by them.

Femtocell Access Points

For example, if the call is being made by any user equipment and simultaneously the song is being uploaded by any other user equipment under the same femtocell coverage area. The Mobile device with voice data will have higher priority over the device where song uploading is taking place.

Security Gateway: As the whole backhauling of data is carried over Internet, it becomes necessary to transfer the encrypted data over a secured connection to mobile operator’s network and protect the mobile devices from security breach. These security Gateway is also used to authenticate all the mobile devices that are allowed to use femtocell services. When any initially defined mobile device comes under the coverage of femtocell network it is first authenticated before allowing it to use femtocell services. The encryption of data and signaling is carried out using standard Internet protocol such as IPSEC and IKEv2.

The security gateway is a network node that secures the Internet connection between femtocell users and the mobile operator core network.  It uses standard Internet security protocols such as IPSec and IKEv2 to authenticate and authorize femtocells and provide encryption support for all signaling and user traffic.

Femtocell Device Management System: As there is large number of femtocells, it is necessary to manage the devices and operation of all the femtocells, this is done by femtocell device management system. It is resides in operator’s network. The FDMS is use to configure the different devices available and manage the operation of each device with respect to other from the operator’s core network. This plays a key role in initiatilisation and activation of femtocells when deployed for the first time and continues providing it services of updating and configuring newly available services. For managing such large number of femtocells specific architecture called clustering and load balancing is used. The basic standard used by femtocell network management system is TR-069.

As shown in below figure, depending on the functionality, the FSM is classified further in two parts.

1. Automatic Network Planner: It is use to plan the allocation of carrier frequency for femtocell. It executes the Frequency Reuse algorithm, RF Planning algorithms and configures the best RF to the femtocell avoiding the interference with neighbouring femtocell.

2. Device Manager: Unlike Automatic Network Planner, it is associated with femtocell devices at user end. Its basic functions are error detection and management in femtocells devices, remote configuration and diagnostic, upgrading the software versions on the devices, collecting the performance information in particular.

Femtocell Service Management System

Architectural Models:

SIP/IMS Network Model

Legacy Network Model

1. SIP/IMS Network Model: In SIP/IMS model, when the call is made from the mobile devices, the signaling and encrypted data is carried out from femtocell to the IMS network architecture via security gateway and then forwarded to PSTN network. The following are the important components of architecture.

Femtocell Access Point (IMS Client)

SIP/IMS Core Network

Femtocell Convergence Server (FCS)

Legacy Network Model

This network does all the call routing and signaling functions. The Voice data from the femtocell access point is converted over RTP and then transmitted to femtocell convergence server. The 3G signaling is converted to IMS signaling. The nodes of SIP/IMS network consist of Home subscriber subsystem which provides the information of subscriber, Call signaling control function, manages all the signaling functions, Media gateway controller which connects to Legacy Network. The other most important component is femtocell convergence server which is an application server and it connects to MSC(mobile switching center) in legacy network using an IS-41 network interface and is connected to CSCF using standard ISC interface.

Femtocell Convergence Server also acts as MSC for mobile core network. It also conducts handover between femtocell and macrocell. When a mobile device moves from femtocell coverage to macrocell network coverage, macrocell to macrocell hand off mechanism is used and hence femtocells receive messages same as they are received when macrocell to macrocell handoffs takes place.

Below is the complete description of network blocks in SIP/IMS Architecture.

SIP/IMS Network Model

2. Legacy Network Model: This is the simple network model compared to SIP/IMS model as it allows the use of already existing mobile operators network.

The three important components of Legacy network model are

Femtocell Access Point

Femtocell Network Gateway (FNG)

Security Gateway

This model connects to mobile operator’s network directly through FNG (femto network gateway). These femto network gateway connects the actual FAP’s using standardize 3GPP Iuh interface to the Legacy network. FNG acts as a mobile radio network controller for femtocells. In this model the handoff is carried out by MSC of core network. In this model support of active handoff is given through the legacy MSC. When the femtocell moves from femtocell coverage to macrocell network the handoff mechanism is carried in the way similar to that between radio network controller and MSC, using the Iu interface. The legacy network model is used by 3GPPstandards for UMTS femtocells.

Legacy Network Model

The FCS and FMS mentioned above plays a very important role in setting up a call as act as mediator between the femtocell and mobile operator core network. The packet data services are provided by network components such as SGGSN/GGSN in UMTS and PDSN in CDMA femtocells. Femtocells are connected directly to SGGSN while for connecting to PDSN, FNG acts as bridge between them.

Advantages:

1. Good Coverage and increased data capacity: For the good coverage and data transfer capacity, the ratio of signal to Noise should be high enough to sustain the attenuation that occurs when a signal is transmitted from macrocell to the receiver. As the data rate of voice signal is 10kb/s compared to that of data traffic which is in Mbps, the requirement of signal strength for voice traffic is also less compared to data traffic. As the use of Smart phones is substantially increase from last few years, these high data rates could not be gained due to high attenuation that takes place during transmission of signal between transmitter and receiver. As the signal attenuation is caused mainly due to shadowing, interference from other transmitters and path loss causing the decaying of signal. The signal decay is given as D=A.d-α A is the constant loss, d is distance between transmitter and receiver and α is the decay constant. So in order to minimize the path loss d should be decreased.

Increased Spectral efficiency

Femtocell overcomes this issue as the transmitter is installed in the home/premises and the receiver that will be the mobile devices will also reside at very short distance from the transmitter. Hence decreasing the distance between transmitter and receiver, will decrease the attenuation of signal and hence will avoid the signal to noise ratio to degrade. As low power is required by femtocells to operate, which eventually increase the battery life of mobile device. Mobile device will require very less power to be transmitted and hence more number of mobile devices can be used in small coverage area of femtocell. This increase in the number of mobile devices increases the overall spectral efficiency.

2. Offloading Macrocell: As the back hauling of data is carried out by femtocell the load on the macrocell is comparatively reduce. The whole control of data and all the data transfer of a mobile device take place through the femtocell. The backhauling data through Internet provides better capacity to mobile device, simultaneously reducing the data uploaded directly to Macrocell radio network. Hence the mobile base station can provide god coverage and capacity to other mobile devices that are not under the coverage area of Femtocell. The mobile base station can provide coverage to more number of mobile users in its cell area. This will be advantageous to service provider as well as subscriber. Subscriber can enjoy high data capacity and coverage area and simultaneously reducing the overall burden on the macrocell and hence improving macrocell reliability.

3. Self Organising: The Femtocell can be easily installed by non technical user. It has to be ‘plug and play’. Femtocells automatically get configured to available network environment. Any operational changes even after installation are detected and the femtocell device gets updated. Femtocell are capable of detecting and managing fault during operation. It is self configuring, self optimizing, error detecting and rectifying device. They basically work on self organizing algorithms which are executed by device manager.

4. Cost effective: It has been observed that 70% of total data transfers take place indoors. In order to provide good coverage indoor it is necessary for service providers to install more base station as the number of mobile users is increasing. Installing the macrocell basestaton is very costly and requires huge infrastructure. Installing macrocell will not be efficient way to increase the coverage indoors, as there is 20db loss of signal due to the infrastructure, fading etc. Femtocell deployments will costs above $1000/month in site lease, and additional costs for electricity and backhaul. Hence installing femtocell will reduce the operating and maintaining cost, providing the good coverage capacity indoors.

5. Win-Win Model: Due to poor coverage indoor, causing interruption in services results in customer churn and hence customers look forward to different service providers. Implementing femtocell will be beneficial to providers as it offloads the data traffic from macrocell and user can get added services provided by its provider when in the coverage area of femtocell, hence creating win-win situation for both the providers and subscribers.

Challenges:

As there are many advantages and used of femtocells there have also been some technical challenges faced while deployment of femtocellls.

1. Synchronization: Femtocell synchronization is very important in accurate implementation of femtocells. In order to provide uninterrupted service to subscriber the basestation and femtocells should be very accurately synchronized.

Handsets should be accurately synchronized with the frequency of basestation.

To provide reliable handover it is necessary that femtocell should be synchronized with the basestation network, otherwise the difference in frequency can cause handover failure.

Sychronization reduces the interference which can in turn increase the quality of service.

There are different ways of synchronizing the femtocell to the network, they are described in detail as follows:

1. Femtocell Synchronization from Internet: Femtocells can be synchronized by using the internet connection with network operator. The network operator’s clock servers send the timing information to the FAP via internet in the form of packets. The protocols such as precision time protocol, network time protocol and IEEE1588 is used. The operation is Master slave based model, in which master is the network operator’s clock which sends the timing details to the slave (Access points). The main issue with this type of synchronization is that the packets can get delayed depending on the traffic on the channel. As the timing information would be transmitted frequently and need to be highly precise, this may lead to increase in bandwidth consumption.

2. Femtocell synchronization via GPS: Collecting timing information from GPS receivers which can be embedded in femtocells. It is the low cost way of synchronization. The assistance data is sent from the macrocell of the adjacent cell to femtocell which helps to provide the sufficient timing information. The problem with this way of Synchronization is the attenuation factor. The attenuation will increase in case of femtocells as it resides inside the building.

3.Using Adjacent macrocell for Synchronization: The synchronization information can be obtain by the macrocell, as the femtocells have to always exchange information for handover. This could only pose problem when the coverage of macrocell is less and signal could not be reach the femtocell network.

2. Femtocell Security: Security plays a key role in femtocell management system, as whole data is carried over the Internet. The femtocell security have been classified in two types as-

1. User Privacy- As the complete transfer of subscriber information(voice and data) is carried out over internet while backhauling, the transmitted data should be protected against security breach. Some denial of service attacks that increase the burden on the system by creating dummy and fake user s can caused the authorized users to be deprived of services and coverage.

2. Fraud users: Some unauthorized users can enjoy the facility of femtocell services by hacking the femtocell and leading to customer dissatisfaction due to unusual bills. Also they can misuse the available customer information. Hence in order to avoid these scenarios following measures were taken.

Protocols such as IPSec and extensible authentication protocol were used. Security can also be provided by continuously authenticating the femtocell service users and always ensuring that femtocell area does not increase the physical coverage area.

3. Interference: The major challenge in femtocell deployment is interference due to the same use of frequency by neighboring femtocell or the macrocell of the area.

Causes of Interference in Femtocells:

1. Random deployment of femtocells: Unlike antennas the femtocells are installed randomly without any central controlling unit that will govern the deployment of femtocells in the specific area. Femtocells can be easily installed by anyone, which can cause the ad hoc installation of femtocells ultimately increasing the probability of interference between the femtocells and base station. As the Device manager will not know the frequency allotted to the basestation in which the femtocell will be deployed.

2. Reuse of Cellular spectrum: As the bandwidth of spectrum available is less, some frequencies are reused by other cell which is not adjacent to the current cell in order to increase the spectral effeciency. This is other main cause for interference.

3. Restricted Users: In order to allow the femtocell coverage to limited number of mobile devices, the other mobile devices of same providers face coverage issues in the area near to femtocells.

Types of Interference:

Femtocell to Macro cell Interference: The interference which takes place between the femtocell and its base station is called femto-macro interference. This is caused due to restriction on number of users in one femtocell. It causes interference while uplink as well as downlink of the mobile device that are not authorized to femtocell.

Femtocell-Macrocell Interference

For example consider a femtocell using frequency f1 which is the same frequency that of macrocell network. Hence this will cause interference leading to more consumption of signal power by the femtocell and hence giving better coverage to femtocell authorized devices and causing macrocell to give poor coverage poor coverage to the mobile devices not under femtocell coverage area. Hence due to interference the non femtocells authorized user will be deprived of the services provided by the service provider. The decrease in coverage area and data capacity is directly proportional to distance between the macrocell and the mobile devices, hence the devices near to edge of the cells will suffer maximum from problems such as call disconnection, no coverage etc. Also if number of mobile devices increases in that area can lead to severe coverage issues due to already existing femtocell and increase in number of user equipments which require high coverage.

Macrocell-Femtocell Interfernce

Downlink Interference: Consider the femtocell deployed in home. Any active femtocell handset at the edge of femtocell coverage area will also start receiving the signal power from macrocell which will result in overloading of macrocell and hence less signal power will be received by the macrocell handsets.

Uplink Interference: Now the macocell handset which doesnot have access to the femtocell is in the coverage area of femtocell. The handset is calling and hence receiving the full signal power. This may affect the femtocells mobile devices which are also on call and on edge of femtocell coverge area causing the call dropping.

Femtocell-Femtocell Interference: Due to increase in number of femtocells and its deployment in random fashion can cause two neighboring femtocells to interfere with each other. The femtocell which has maximum signal power reception cannot act as the only femtocell in the area due to limited user access.

Femtocell Femtocell Interference

Mitigation of Interference:

Adaptive power control: In this mitigation way the femtocells have added feature in which they continuously monitor the received signal power from the macrocell and compares it against the total power spectral density of the macro and femto cell downlink channel. If the power received is much higher compared to that received by macro cell handsets then it automatically lower down the signal power consumption.

Intelligent Carrier Frequency Allocation: Avoid the use of same frequency within the area of adjacent cells. The better way to use this is spectrum division. The spectrum is divided and classified based on the frequencies that will be used by femocell and the other that would be used by macrocell in particular area in order to avoid the interference between the cells and femtocells. As shown in figure the spectrum is divided into free available frequency bands and that used for femtocells and also includes frequency spectra for macrocell. Also frequency convergence server use some frequency reuse algorithm in order to avoid the allocation of same frequency in nearby cells.

Mobile Phone Uplink Power Limits: When the macrocell handset makes a call in femtocell coverage the signal transmitted from the handset is sensed continuosly, if the transmitted signal strength exceeds the threshold value the handset is assigned to macrocell network hence avoiding the interference of femtocell and macrocell handsets.

Fixed Spectrum Allocation for femtocells

4. Handover: Handover is the process of transferring the control of mobile device when it moves from one cell coverage to other seamlessly. Here when the mobile device moves from femtocell to macrocell or between two femtocell, the provider needs to provide uninterrupted services to the mobile device. This mechanisim of successful transferring control of mobile device is called handover. There are three types of handover explained below.

Inbound Handover

Inbound Handover: This type of handover takes place when the mobile device is moving from the external macrocell network to the femtocell coverage area. The user equipment (mobile device) continuously measures the signal strength of all the neighboring cells. Whenever the signal strength received by the device exceeds the threshold level the device gets ready for handover. It will then get authenticated by the femtocell which transfers maximum signal power to the device. The femtocell then authenticates the mobile device. The hand over is same as that of handover between two macrocell except the signaling connection between the two cells is through internet. Each femtocells has its unique identifier number which helps the successful handover of device to the corresponding femtocell.

The figure explains the handover procedure of inbound handover.

Outbound Handover: When the mobile device moves from femtocell to macrocell then its called outbound handover. When the transmitted signal from the femtocell handset exceeds the threshold level it is handoverd to macrocell network.

Outbound Handover

Femto-Femto Handover: when mobile device moves from one femto network to other. The signaling is carried through backhauling. The whole of handover is carried out by femtocell themselves.

Conclusions

Femtocell is very effective low power and short range device that is deployed in home for increasing the coverage area for defined number of mobile devices indoors. It allows users to enjoy services similar to wi-fi under license spectrum. They also help in reducing the overall traffic on the macrocell hence increasing the reliability and efficiency of service provider network. The femtocells are user handy devices which can be deployed easily. Femtocells system has complex architecture that differ based on the type of services that will be provided by femtocells. The SIP/IMs model and Legacy network model are the two widely use architectures in femtocells system. Femtocell Network Gateway /Femtocell convergence server bridges between the femtocell aceess points and mobile operators core network. Exponential increase in use of smart phones and hence in mobile data traffic has resulted in need development of femtocell. Though there are some technical issues in femtocell implementation various strategies have also been developed to mitigate each one of them. The research is ongoing to completely overcome the present challenges of Interference and handover.
Source: http://www.ukessays.com/essays/computer-science/3g-and-4g-cellular-technologies-computer-science-essay.php

What is a Small Cell?

22 Oct
What is a Small Cell or Femtocell?

Small cells are fully featured, short range mobile phone basestations used to complement mobile phone service from larger macrocell towers. These range from very compact residential femtocells, the size of a paperback book and connected using standard domestic internet broadband through to larger equipment used inside commercial offices or outdoor public spaces. They offer excellent mobile phone coverage and data speeds at home, in the office and public areas for both voice and data. Small cells have been developed for both 3G and the newer 4G/LTE radio technologies.

The term femtocell was originally used to describe residential products, with picocell being used for enterprise/business premises and metrocell for public/outdoor spaces. As the underlying femtocell technology expanded to address this wider scope, the term small cell was adopted to cover all aspects.

Standalone or integrated femtocells

Early residential femtocell products look very much like WiFi broadband modems, needing only two cables – one for power and one internet connection.

Several vendors such as Thomson, Netgear, Pirelli, Cisco and others integrated the femtocell with other features such as DSL modem, WiFi and even IPTV into a single box. The vast majority of residential femtocells sold to date are standalone.

Larger enterprise and metrocells are also standalone, having sturdy casing and better protection against weather and operating in unsupervised areas.

Locked to a single mobile phone network

Unlike WiFi, these devices use licenced radio spectrum, so must be operated and controlled by a mobile phone company. Thus it will work with only one mobile phone operator, and thus encourages all users in a household or business enterprise to switch to the same network operator.

When in range of the small cell, the mobile phone will automatically detect it and use it in preference to the outdoor cellsites. Calls are made and received in exactly the same way as before, except that the signals are sent encrypted from the small cell via the public or private broadband IP network to one of the mobile operators main switching centres. Making and receiving calls uses the same procedures and telephone numbers, and all the standard features (call divert, text messaging, web browsing) are available in the same way – indeed data services should operate more quickly and efficiently due to the short range involved.

Low power but high quality

Small cells operate at very low radio power levels – less than cordless phones, WiFi or some other household equipment. This substantially increases the battery life, both on standby and talktime. Since they are so much closer to the handset or mobile device, call quality is excellent and data devices can operate at full speed. The smallest femtocells can handle up to 4 simultaneous active calls from different users, with many having a standard capacity of 8. Larger small cell designs for business (enterprise) or public area use can handle 16, 32 or more concurrent calls. These numbers are in addition to passive users not actively making or receiving voice or data calls.

Open or restricted access

Restrictions can be applied on who can access a small cell. Residential femtocell owners may be concerned about paying additional charges for DSL broadband supplier where a quota applies – even though this would equate to many long voice calls or heavy data service use. For this reason, many residential femtocells include a facility to restrict service to a whitelist of up to 30 specified telephone numbers. Enterprise use is more commonly open to all, including visitors, but may prioritise phones belonging to the business itself. Metrocells are always fully open access.

Secure and self-managing

Small cells encrypt all voice and data sent and received, ensuring a high level of protection from sniffing or snooping.

In order to reduce operational and installation costs, these units are self installing and use a variety of clever tricks to sense which frequency to transmit on and power level to use.

Unlike large outdoor mobile phone basestations (masts), femtocells don’t require specialist RF planning engineers to design, calibrate or configure themselves – minimising the ongoing cost of maintaining them. They do have remote management from the network operator, who can upgrade the configuration and software as required.

Doesn’t require special phones

They are compatible with existing standard 3G mobile phones and are not restricted to any specific models. No additional software is required to enable the phone to work with a small cell.

Technology

Most of the excitement is based around the 3G UMTS/HSPA mobile phone technology, deployed in almost every country worldwide today and which includes the ability for high speed data services. There are products available for other technologies, including 2G GSM, CDMA and more recently LTE.

So if anyone asks you what a small cell or femtocell is, you can now confidently reply. Read more about the various small cell system architectures, vendors and operators on the rest of this site: http://www.thinksmallcell.com/

 

Source: http://smallcellsboothbay.wordpress.com/2013/10/19/what-is-a-small-cell/

Centralized SON

26 Aug

I was going through the presentation by SKT that I blogged about here and came across this slide above. SKT is clearly promoting the benefits of their C-SON (centralized SON) here.

The old 4G Americas whitepaper (here) explained the differences between the three approaches; Centralized (C-SON), Distributed (D-SON) and Hybrid (H-SON). An extract from that paper here:

In a centralized architecture, SON algorithms for one or more use cases reside on the Element Management System (EMS) or a separate SON server that manages the eNB’s. The output of the SON algorithms namely, the values of specific parameters, are then passed to the eNB’s either on a periodic basis or when needed. A centralized approach allows for more manageable implementation of the SON algorithms. It allows for use case interactions between SON algorithms to be considered before modifying SON parameters. However, active updates to the use case parameters are delayed since KPIs and UE measurement information must be forwarded to a centralized location for processing. Filtered and condensed information are passed from the eNB to the centralized SON server to preserve the scalability of the solution in terms of the volume of information transported. Less information is available at the SON server compared to that which would be available at the eNB. Higher latency due to the time taken to collect UE information restricts the applicability of a purely centralized SON architecture to those algorithmsthat require slower response time. Furthermore, since the centralized SON server presents a single point of failure, an outage in the centralized server or backhaul could result in stale andoutdated parameters being used at the eNB due to likely less frequent updates of SON parameters at the eNB compared to that is possible in a distributed solution.

In a distributed approach, SON algorithms reside within the eNB’s, thus allowing autonomous decision making at the eNB’s based on UE measurements received on the eNB’s and additional information from other eNB’s being received via the X2 interface. A distributed architecture allows for ease of deployment in multi-vendor networks and optimization on faster time scales. Optimization could be done for different times of the day. However, due to the inability to ensure standard and identical implementation of algorithms in a multi-vendor network, careful monitoring of KPIs is needed to minimize potential network instabilities and ensure overall optimal operation.

In practical deployments, these architecture alternatives are not mutually exclusive and could coexist for different purposes, as is realized in a hybrid SON approach. In a hybrid approach, part of a given SON optimization algorithm are executed in the NMS while another part of the same SON algorithm could be executed in the eNB. For example, the values of the initial parameters could be done in a centralized server and updates and refinement to those parameters in response to the actual UE measurements could be done on the eNB’s. Each implementation has its own advantages and disadvantages. The choice of centralized, distributed or hybrid architecture needs to be decided on a use-case by use case basis depending on the information availability, processing and speed of response requirements of that use case. In the case of a hybrid or centralized solution, a practical deployment would require specific partnership between the infrastructure vendor, the operator and possibly a third party tool company. Operators can choose the most suitable approach depending upon the current infrastructure deployment.

Finally, Celcite CMO recently recently gave an interview on this topic on Thinksmallcell here. An extract below:

SON software tunes and optimises mobile network performance by setting configuration parameters in cellsites (both large and small), such as the maximum RF power levels, neighbour lists and frequency allocation. In some cases, even the antenna tilt angles are updated to adjust the coverage of individual cells.
Centralised SON (C-SON) software co-ordinates all the small and macrocells, across multiple radio technologies and multiple vendors in a geographic region – autonomously updating parameters via closed loop algorithms. Changes can be as frequent as every 15 minutes– this is partly limited by the bottlenecks of how rapidly measurement data is reported by RAN equipment and also the capacity to handle large numbers of parameter changes. Different RAN vendor equipment is driven from the same SON software. A variety of data feeds from the live network are continuously monitored and used to update system performance, allowing it to adapt automatically to changes throughout the day including outages, population movement and changes in services being used.
Distributed SON (D-SON) software is autonomous within each small cell (or macrocell) determining for itself the RF power level, neighbour lists etc. based on signals it can detect itself (RF sniffing) or by communicating directly with other small cells.
LTE has many SON features already designed in from the outset, with the X.2 interface specifically used to co-ordinate between small and macrocell layers whereas 3G lacks SON standards and requires proprietary solutions.
C-SON software is available from a relatively small number of mostly independent software vendors, while D-SON is built-in to each small cell or macro node provided by the vendor. Both C-SON and D-SON will be needed if network operators are to roll out substantial numbers of small cells quickly and efficiently, especially when more tightly integrated into the network with residential femtocells.
Celcite is one of the handful of C-SON software solution vendors. Founded some 10 years ago, it has grown organically by 35% annually to 450 employees. With major customers in both North and South America, the company is expanding from 3G UMTS SON technology and is actively running trials with LTE C-SON.
Quite a few companies are claiming to be in the SON space, but Celcite would argue that there are perhaps only half a dozen with the capabilities for credible C-SON solutions today. Few companies can point to live deployments. As with most software systems, 90% of the issues arise when something goes wrong and it’s those “corner cases” which take time to learn about and deal with from real-world deployment experience.
A major concern is termed “Runaway SON” where the system goes out of control and causes tremendous negative impact on the network. It’s important to understand when to trigger SON command and when not to. This ability to orchestrate and issue configuration commands is critical for a safe, secure and effective solution.\

Hacked Verizon Femtocell allows hackers to spy on Phone calls made with iPhone & Android

6 Aug

Cyber world news


Two Security experts from iSEC Partners have found a way to spy on Verizon wireless mobile phone customers by hacking into devices the U.S. Carrier sells to boos Wireless signals indoors.

In a demonstration for Reuters, researchers Ritter and Doug DePerry show how they are able to spy on phone calls, messages and photos made with iPhone and Android phones by using a Verizon femtocell that they had previously hacked.

“This is not about how the NSA would attack ordinary people. This is about how ordinary people would attack ordinary people,” Reuters quoted a senior consultant with the security firm iSEC Partners , Tom Ritter as saying.

Verizon reportedly updated the software on its signal-boosting devices, known as femtocells or network extenders,to thwart hackers from copying the technique of the two experts.

“The Verizon Wireless Network Extender remains a very secure and effective solution for our customers” Verizon spokesperson said…

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