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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:


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:


-WiFi System, ISM application


-Indoor/in-building Coverage


-WLAN Communication Application


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


-Next Gen Mobile-LTE



-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 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.



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.

  • 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
Broadband Planner
V-Soft Probe













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




  • 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.


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.


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

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)


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.


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.


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.


Beam forming for 5G communication systems

7 Mar

Technology and methods for providing beam-forming antennas for 5G mobile communications systems

5G communications standards promise to enable a thousand-fold increase in wireless data capacity over the next ten years.

But with the amount of data that can be coded onto a single channel approaching theoretical limits, it will take a combination of frequency, time and spatial multiplexing to create the multiple channels necessary to get data from sender to receiver at such high aggregate rates for 5G mobile communications systems as well as other wireless systems.

What are our options? We can borrow from the MIMO (multiple input, multiple output) techniques used in WLAN. We can take advantage of new frequency bands, including some at millimeter wavelengths, that regulators will make available.

And we can develop techniques to steer mm-wave signals to create a more direct link from sender to receiver, to counter their strong attenuation in free space.

Tackling path loss with more antennas

Why is there such an attenuation problem at millimeter wavelengths? Consider a communication link between a base-station and a smartphone, operating at mm-wave frequencies, in which the smartphone has an isotropic antenna (that is, one which radiates and receives equally in all directions). The path loss between the transmit and receive antennas is given as in [1]:

Radio propagation path loss between two antennas

&nbps;   where PRX and PTX are the received and transmitted powers, and GRX and GTX are the receive and transmit antenna gains, respectively. The path loss is partly due to the attenuation caused by the signal’s energy spreading into an increasing volume as the distance R between transmitter and receiver grows, and is defined by 1/4πR2. The other key factor in path loss is the amount of energy that the receive antenna can capture, which is controlled by its effective aperture (defined by the λ2/4π term) and shrinks with the square of the wavelength.

This means that, for example, changing the signal frequency from 3GHz to 30GHz (and therefore shortening the signal’s wavelength) increases the path loss by 20dB. To compensate, we can increase the number of receive antennas, but it takes 100 antenna elements receiving a 30GHz signal to achieve the same total array aperture and therefore received power as the original antenna at 3GHz.

Beam forming in antenna arrays for 5G communications

How do you build such an antenna array? The simplest form consists of N elements spaced closely together at regular intervals, a distance d apart (Figure 1).

One-dimensional antenna array for possible 5G use

Figure 1: A one-dimensional antenna array, in which all elements have identical phase, points its beam towards θ = 0 degrees

If all the elements in such an array are isotropic, have the same gain, and are driven with a signal at the same phase and power, the resultant beam will point straight out of the plane on which they are mounted (i.e. in the z direction). The resultant field is shown in Figure 2 as a function of θ, the angle between the z-axis and the observation direction, when the distance between the array elements d is λ/2 (half the wavelength).

One dimensional antenna array side lobe patterns

Figure 2: Side-lobe patterns for a one-dimensional antenna array in which all elements have identical phase, creating a beam at θ = 0 degrees. The array consists of 64 elements.

If we apply a phase difference between adjacent array elements, the beam can be directed towards another angle, for example 20 degrees, as shown in Figure 3.

One dimensional antenna array side lobe patterns with elements phase shifted

Figure 3: The same array, but with all elements shifted in phase to create a beam at θ = 20 degrees

In both cases, unwanted side-lobe signals form alongside the main beam. If the array elements are spaced more widely, the strength of the side lobes increases until, when the separation distance d matches the signal wavelength λ, unwanted beams with the same power level as the main beam appear at +90 and -90 degrees. In Figure 4, the separation distance d is twice the signal wavelength, and unwanted lobes have been created at ± 30 degrees and ± 90 degrees. These lobes are usually unwanted, since they increase the likelihood of one antenna array interfering with another.

Grating lobes of antenna array radiation pattern

Figure 4: Grating lobes appear in the array radiation pattern when the inter-antenna distances exceed the wavelength, in this case d = 2λ

In practice it is not possible to make an isotropic antenna, since all physical antennas have a certain antenna pattern, and so the ability to steer them electrically is limited.

Analogue and digital beam forming

How do we create the phase shifts necessary to steer the beam? Analog beam forming can be done in the RF domain by using phase shifters in front of each antenna, as in Figure 5.

Antenna analogue beam forming

Figure 5: In analogue beam forming, the beam is steered using phase shifters. Only one data stream and one beam can be generated

A single data stream is handled by a set of data converters and a transceiver. After the transceiver, the transmit data stream is split as many ways as there are array elements. The signal in each branch passes through a phase shifter, is amplified and then fed into the array element.

Analogue beam forming in the RF path is simple and uses a minimal amount of hardware, making it the most cost-effective way to build a beam-forming array. The drawback is that the system can only handle one data stream and generate one signal beam.

Digital beam forming, in which each antenna has its own transceiver and data converters, can handle multiple data streams and generate multiple beams simultaneously from one array, as shown in Figure 6.

Antenna digital beam forming for 5g mobile communications

Figure 6: In digital beam forming, the beam is steered by baseband processing. Multiple data streams and beams can be generated simultaneously

The phase differences needed to generate a signal beam are created in the baseband, which can also create several sets and superimpose them on the array elements. This enables one antenna to generate multiple beams, each with its own signal and serving multiple users, with one array and one set of spectrum resources. This approach needs more hardware and puts a greater burden on the signal processing in the digital domain than the analog approach.

Beam forming, massive MIMO and channel state information for 5G

Digital beam forming can be used for 5G mobile communications and can point a signal from a sender to a receiver when they are in line of sight. When they aren’t, users are only reached by beams that have been scattered by buildings, trees and other features of the environment.

Scattered beams suffer 20 to 30dB more path losses than line-of-sight beams, so it makes sense to use many of them to ensure that the sum of their scattered signals at the receiver provides enough energy to correctly interpret the communication they are carrying.

Such low-power, scattered beams only interfere constructively at the user’s location, with other users nearby only experiencing their signals as a slight increase in background noise. This means that an antenna array can serve several users, each with a multitude of beams that are being scattered, so long as the number of elements in the array exceeds the number of users. This is known as massive MIMO.

It is possible to take massive MIMO a step further for 5G mobile communications by replacing an antenna array of N elements with N individual antennas distributed widely through the environment on separate buildings, lamp posts, etc. Applying time delays to the distributed antennas ensures that signals for each user only interfere positively at their location.

As seen above, an antenna array with element spacings less than the signal wave length only radiates very little energy in unwanted directions. This isn’t so for a set of widely distributed antennas, whose signals can be configured to interfere constructively at the user’s location, but which do not interfere destructively in other directions and so may cause interference and power loss.

The information necessary to work out the phase shifts needed to form beams can be derived from the channel state information. One way to obtain this is by having the user equipment transmit a pilot tone and then setting the bases-station to measure the phase shifts between the various paths that the signal follows between the user equipment and the base-station’s antenna elements.

For this to work, the path from the sender to the receiver must be the same as the path from the receiver to the sender, which means that they must be at the same frequency and hence that the overall system must use time-division duplexing. And phase shifting the signals between antennas can only compensate for the different path lengths at one frequency. For large signal bandwidths, the number of pilot frequencies should increase to map the channel behaviour properly.

We can conclude that digital beam forming offers the most versatile solution for future 5G communication systems, but is also the most expensive and complex implementation. It can therefore be expected that the first 5G mobile systems will use some kind of combination of analogue and digital beam forming, such that proper trade-offs can be made between system performance and cost.


[1] C.A. Balanis, Antenna Theory, Analysis and Design, 3rd ed. 2005, John Wiley & Sons, ISBN: 0-471-66782-X


Wireless Routers 101

14 Feb

A wireless router is the central piece of gear for a residential network. It manages network traffic between the Internet (via the modem) and a wide variety of client devices, both wired and wireless. Many of today’s consumer routers are loaded with features, incorporating wireless connectivity, switching, I/O for external storage devices as well as comprehensive security functionality. A wired switch, often taking the form of four gigabit Ethernet ports on the back of most routers, is largely standard these days. A network switch negotiates network traffic, sending data to a specific device, whereas network hubs simply retransmit data to all of the recipients. Although dedicated switches can be added to your network, most home networks don’t incorporate them as standalone appliances. Then there’s the wireless access point capability. Most wireless router models support dual bands, communicating over 2.4 and 5GHz and many are also able to connect to several networks simultaneously.

Part of trusting our always-on Internet connections is the belief that private information is protected at the router, which incorporates features to limit home network access. These security features can include a firewall, parental controls, access scheduling, guest networks and even a demilitarized zone (DMZ), referring to the military concept of a buffer zone between neighboring countries). The DMZ, also called a perimeter network, is a subnetwork where vulnerable processes like mail, Web and FTP servers can be placed so that, if it is breached, the rest of the network isn’t compromised. The firewall is a core component in today’s story. In fact, what differentiates a wireless router from a dedicated switch or wireless access point is the firewall. Although Windows has its own software-based firewall, the router’s hardware firewall forms the first line of defense in keeping malicious content off the home network. The router’s firewall works by making sure packets were actually requested by the user before allowing them to pass through to the local network.

Finally, you have peripheral connectivity like USB and eSATA. These ports make it possible to share external hard drives or even printers. They offer a convenient way to access networked storage without the need for a dedicated PC with a shared disk or NAS running 24/7.

Some Internet service providers (ISPs) integrate routers into their modems, yielding an “all-in-one” device. This is done to simplify setup, so the ISP has less hardware to support. It can also be advantageous to space-constrained customers. However, in general, these integrated routers do not get firmware updates as frequently, and they’re often not as robust as stand-alone routers. An example of a combo modem/router is Netgear’s Nighthawk AC1900 Wi-Fi cable modem router. In addition to its 802.11ac wireless connectivity, it offers a DOCSIS 3.0 24 x 8 broadband cable modem.

DOCSIS stands for “data over cable service interface specifications,” and version 3.0 is the current cable modem spec. DOCSIS 1.0 and 2.0 defines a single channel for data transfers, while DOCSIS 3.0 specifies the use of multiple channels to allow for faster speeds. Current DOCSIS 3.0 modems commonly use 8, 12 or 16 channels, with 24-channel modems also available. Each channel offers a theoretical maximum download speed of 38 Mb/s and a maximum upload speed of 27 Mb/s. The standard’s next update, DOCSIS 3.1, promises to offer download speeds of up to 10 Gb/s and upload speeds of up to 1 Gb/s.

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Wi-Fi Standards

The oldest wireless routers supported 802.11b, which worked on the 2.4GHz band and topped out at 11 Mb/s. This original Wi-Fi standard was approved in 1999, hence the name 802.11b-1999 (later it was shortened to 802.11b).

Another early Wi-Fi standard was 802.11a, also ratified by the IEEE in 1999. It operated on the less congested 5GHz band and maxed out at 54 Mb/s, although real-world throughput was closer to half that number. Given a shorter wavelength than 2.4GHz, the range of 802.11a was shorter, which may have contributed to less uptake. While 802.11a enjoyed popularity in some enterprise applications, it was largely eclipsed by the more pervasive 802.11b in homes and small businesses. Notably, 802.11a’s 5GHz band became part of later standards.

Eventually, 802.11b was replaced by 802.11g on the 2.4GHz band, upping throughput to 54 Mb/s. It all makes for an interesting history lesson, but if your wireless equipment is old enough for that information to be relevant, it’s time to consider an upgrade.


In the fall of 2009, 802.11n was ratified, paving the way for one device to operate on both the 2.4GHz and 5GHz bands. Speeds topped out at 600 Mb/s. With N600 and N900 gear, two separate service set identifiers (SSIDs) were transmitted—one on 2.4GHz and the other on 5GHz—while less expensive N150 and N300 routers cut costs by transmitting only on the 2.4GHz band.

Wireless N networking introduced an important advancement called MIMO, an acronym for “multiple input/multiple output.” This technology divides the data stream between multiple antennas. We’ll go into more depth on MIMO shortly.

If you’re satisfied with the performance of your N wireless gear, then hold onto it for now. After all, it does still exceed the maximum throughput offered by most ISPs. Here are some examples of available 802.11n product speeds:

Type 2.4GHz (Mb/s) 5GHz (Mb/s)
N150 150 N/A
N300 300 N/A
N600 300 300
N900 450 450


The 802.11ac standard, also known as Wireless AC, was released in January 2014. It broadcasts and receives on both the 2.4GHz and 5GHz bands, but the 2.4GHz frequency on an 802.11ac router is really a carryover of 802.11n. That older standard maxed out at 150 Mb/s on each spatial stream, with up to four simultaneous streams, for a total throughput of 600 Mb/s.

In 802.11ac MIMO was also refined with increased channel bandwidth and support for up to eight spatial streams. Beamforming was introduced with Wireless N gear, but it was proprietary, and with AC, it was standardized to work across different manufacturers’ products. Beamforming is a technology designed to optimize the transmission of Wi-Fi around obstacles by using the antennas to direct and focus the transmission to where it is needed.

With 802.11ac firmly established as the current Wi-Fi standard, enthusiasts shopping for routers should consider one of these devices, as they offer a host of improvements over N gear. Here are some examples of available 802.11ac product speeds:

Type 2.4GHz (Mb/s) 5GHz (Mb/s)
AC600 150 433
AC750 300 433
AC1000 300 650
AC1200 300 867
AC1600 300 1300
AC1750 450 1300
AC1900 600 1300
AC3200 600 1300, 1300

The maximum throughput achieved is the same on AC1900 and AC3200 for both the 2.4GHz and 5GHz bands. The difference is that AC3200 can transmit two simultaneous 5GHz networks to achieve such a high total throughput.

The latest wireless standard with products currently hitting the market is 802.11ac Wave 2. It implements multiple-user, multiple-input, multiple-output, popularly referred to as MU-MIMO. In broad terms, this technology provides dedicated bandwidth to more devices than was previously possible.

Wi-Fi Features


Multiple-input and multiple-output (MIMO), first seen on 802.11n devices, takes advantage of a radio phenomenon known as multipath propagation, which increases the range and speed of Wi-Fi. Multipath propagation is based on the ability of a radio signal to take slightly different pathways between the router and client, including bouncing off intervening objects as well as floors and ceilings. With multiple antennas on both the router as well as the client—and provided they both support MIMO—then using antenna diversity can combine simultaneous data streams to increase throughput.

When MIMO was originally implemented, it was SU-MIMO, designed for a Single User. In SU-MIMO, all of the router’s bandwidth is devoted to a single client, maximizing throughput to that one device. While this is certainly useful, today’s routers communicate with multiple clients at one time, limiting the SU-MIMO’s technology’s utility.

The next step in MIMO’s evolution is MU-MIMO, which stands for Multiple User-MIMO. Whereas SU-MIMO was restricted to a single client, MU-MIMO can now extend the benefit to up to four. The first MU-MIMO router released, the Linksys EA8500, features four external antennas that facilitate MU-MIMO technology allowing the router to provide four simultaneous continuous data streams to clients.

Before MU-MIMO, a Wi-Fi network was the equivalent of a wired network connected through a hub. This was inefficient; a lot of bandwidth is wasted when data is sent to clients that don’t need it. With MU-MIMO, the wireless network becomes the equivalent of a wired network controlled by a switch. With data transmission able to occur simultaneously across multiple channels, it is significantly faster, and the next client can “talk” sooner. Therefore, just as the transition from hub to switch was a huge leap forward for wired networks, so will MU-MIMO be for wireless technology.


Beamforming was originally implemented in 802.11n, but was not standardized between routers and clients; it essentially did not work between different manufacturers’ products. This was rectified with 802.11ac, and now beamforming works across different manufacturers’ gear.

What beamforming does is, rather than have the router transmit its Wi-Fi signal in all directions, it allows the router to focus the signal to where it is needed to increase its strength. Using light as an analogy, beamforming takes the camping lantern and turns it into a flashlight that focuses its beam. In some cases, the Wi-Fi client can also support beamforming to focus the signal of the client back to the router.

While beamforming is implemented in 802.11ac, manufacturers are still allowed to innovate in their own way. For example, Netgear offers Beamforming+ in some of its devices, which enhances throughput and range between the router and client when they are both Netgear products and support Beamforming+.

Other Wi-Fi Features

When folks visit your house, they often want to jump on your wireless network, whether to save on cellular data costs or to connect a notebook/tablet. Rather than hand out your Wi-Fi password, try configuring a Guest Network. This facilitates access to network bandwidth, while keeping guests off of other networked resources. In a way, the Guest Network is a security feature, and feature-rich routers offer this option.

Another feature to look for is QoS, which stands for Quality of Service. This capability serves to prioritize network traffic from the router to a client. It’s particularly useful in situations where a continuous data stream is required; for example, with services like Netflix or multi-player games. In fact, routers advertised as gaming-optimized typically include provisions for QoS, though you can find the functionality on non-gaming routers as well.

Another option is Parental Control, which allows you to act as an administrator for the network, controlling your child’s Internet access. The limits can include blocking certain websites, as well as shutting down network access at bedtime.

Wireless Router Security

There are two types of firewalls: hardware and software. Microsoft’s Windows operating system has a software firewall built into it. Third-party firewalls can be installed as well. Unfortunately, these only protect the device they’re installed on. While they’re an essential part of a Windows-based PC, the rest of your network is otherwise exposed.

An essential function of the router is its hardware firewall, known as a network perimeter firewall. The router serves to block incoming traffic that was not requested, thereby operating as an initial line of defense. In an enterprise setup, the hardware firewall is a dedicated box; in a residential router, it’s integrated.

A router is also designed to look for the address source in packets traveling over the network, relating them to address requests. When the packets aren’t requested, the firewall rejects them. In addition, a router can apply filtering policies, using rules to allow and restrict packets before they traverse the home network. The rules consider the source of a packet’s IP address and its destination. Moreover, packets are matched to the port they should be on. This is all done at the router to keep unwanted data off the home network.

The wireless router is responsible for the Wi-Fi signal’s security, too. There are various protocols for this, including WEP, WPA and WPA2. WEP, which stands for Wired Equivalent Privacy, is the oldest standard, dating back to 1999. It uses 64-bit, and subsequently 128-bit encryption. As a result of its fixed key, WEP is widely considered quite insecure. Back in 2005, the FBI showed how WEP could be broken in minutes using publicly available software.

WEP was supplanted by WPA (Wi-Fi Protected Access) featuring 256-bit encryption. Addressing the significant shortcoming of WEP, a fixed key, WPA’s improvement was based on the Temporal Key Integrity Program (TKIP). This security protocol uses a per-packet key system that offers a significant upgrade over WEP. WPA for home routers is implemented as WPA-PSK, which uses a pre-shared key (PSK, better known as the Wi-Fi password that folks tend to lose and forget). While the security of WPA-PSK via TKIP was definitely better than WEP, it also proved vulnerable to attack and is not considered secure.

Introduced in 2006, WPA2 (Wi-Fi Protected Access 2) is the more robust security specification. Like its predecessor, WPA2 uses a pre-shared key. However, unlike WPA’s TKIP, WPA2 utilizes AES (Advanced Encryption Standard), a standard approved by the NSA for use with top secret information.

Any modern router will support all of these security standards for the purpose of compatibility, as none of them are new, but ideally, you want to configure your router to employ WPA2/AES. There is no WPA3 on the horizon because WPA2 is still considered secure. However, there are published methods for compromising it, so accept that no network is impenetrable.

All of these Wi-Fi security standards rely on your choice of a strong password. It used to be that an eight-character sequence was considered sufficient. But given the compute power available today (particularly from GPUs), even longer passwords are sometimes recommended. Use a combination of numbers, uppercase and lowercase letters, and special characters. The password should also avoid dictionary words or easy substitutions, such as “p@$$word,” or simple additions—for example, “password123” or “passwordabc.”

While most enthusiasts know to change the router’s Wi-Fi password from its factory default, not everyone knows to change the router’s admin password, thus inviting anyone to come along and manipulate the router’s settings. Use a different password for the Wi-Fi network and router log-in page.

In the event that you lose your password, don’t fret. Simply reset the router to its factory state, reverting the log-in information to its default. Manufacturers have different methods for doing this, but many routers have a physical reset button, usually located on the rear of the device. After resetting, all custom settings are lost, and you’ll need to set a new password.

Wi-Fi Protected Setup (WPS) is another popular feature on higher-end routers. Rather than manually typing in a password, WPS lets you press a button on the router and adapter, triggering a brief discovery period. Another approach is the WPS PIN method, which facilitates discovery through the entry of a short code on either the router or client. It’s vulnerable to brute-force attack, though, so many enthusiasts recommend simply disabling WPS altogether.


Web And Mobile Interfaces

Wireless routers are typically controlled through a software interface built into their firmware, which can be accessed through the router’s network address. Through this interface you can enable the router’s features, define the parameters and configure security settings. Routers employ a variety of custom operating environments, though most are Web-based. Some manufacturers do offer smartphone-enabled apps for iOS and Android, too. Here’s is an example of a software interface for the Netis WF2780, seen on a Windows desktop. While not easy to use for amateurs, it does allow for control over all the settings. Here we can see the Bandwidth Control Configuration in the Advanced Settings.

Routers offer a wide range of features, and each vendor has its own set of unique capabilities. Overall, though, they do share generally similar feature sets, including:

  • Quick Setup: For the less experienced user, Quick Setup is quite useful. This gets the device up and running with pre-configured settings, and does not require advanced networking knowledge. Of course, experienced users will want more control.
  • Wireless Configuration: This setting allows channel configuration. In some cases, the router’s power can be adjusted, depending on the application. Finally, the RF bandwidth can be selected as well. Analogous settings for 5GHz are available on a separate page.
  • Guest Network: The router software will provide the option to set up a separate Guest Network. This has the advantage of allowing visitors to use your Internet, without getting access to the entire network.
  • Security: This is where the SSIDs for each of the configured networks, as well as their passwords, can be configured.
  • Bandwidth Control: Since there is limited bandwidth, it can be controlled to provide the best experience for all (or at least the one who pays the bills). The amount of bandwidth that any user has, both on the download and upload sides, can be limited so one user does not monopolize all the bandwidth.
  • System Tools: Using this collection of tools, the router’s firmware can be upgraded and the time settings specified. This also provides a log of sites visited and stats on bandwidth used.

Here is a screenshot of a mobile app called QRSMobile for Android, which can simplify the setup of a wireless router, in this case the D-Link 820L.

This screenshot shows the smartphone app for the Google OnHub.



Open-Source Firmware

Historically, some of these vendor-provided software interfaces did not allow full control of all possible settings. Out of frustration, a community for open source router firmware development took shape. One popular example of its work is DD-WRT, which can be applied to a significant number of routers, letting you tinker with options in a granular fashion. In fact, some manufacturers even sell routers with DD-WRT installed. The AirStation Extreme AC 1750 is one such model.

Another advantage of open firmware is that you’re not at the mercy of a vendor in between updates. Older products don’t receive much attention, but DD-WRT is a constant work in progress. Other open source firmware projects in this space include OpenWRT and Tomato, but be mindful that not all routers support open firmware.


System Board Components

Inside a wireless router is a purpose-built system, complete with a processor, memory, power circuitry and a printed circuit board. These are all proprietary components, with closed specifications, and are not upgradeable.

The above image shows the internals of Netis’ N300 Gaming Router (WF2631). We see the following components:

  1. Status LEDs that indicate network/router activity
  2. Heat sink for the processor—these CPUs don’t use much power, and are cooled without a fan
  3. Antenna leads for the three external antennas to connect to the PCB
  4. Four Ethernet LAN ports for the home network
  5. WPS Button
  6. Ethernet WAN port that connects to a provider’s modem
  7. Power jack
  8. Factory reset button
  9. 10/100BASE-TX transformer modules — these support the RJ45 connectors, which are the Ethernet ports.
  10. 100 Base-T dual-port through-hole magnetics. These are designed for IEEE802.3u (Ethernet ports).
  11. Memory chip (DRAM)

Antenna Types

As routers send and receive data across the 2.4 and 5GHz bands, they need antennas. There are multiple antenna choices: external versus internal designs, routers with one antenna and others with several. If a single antenna is good, then more must be better, right? And this is the current trend, with flagship routers like the Nighthawk X6 Tri-Band Wi-Fi Router featuring as many as six antennas, which can each be fine-tuned in terms of positioning to optimize performance. A setup like that facilitates three simultaneous network signals: one 2.4GHz and two 5GHz.

While a router with an internal antenna might look sleeker, these designs are built to blend into a living area. The range and throughput of external antennas are typically superior. They also have the advantages of reaching up to a higher position, operating at a greater distance from the router’s electronics, reducing interference, and offering some degree of configurability to tune signal transmission. This makes a better argument for function over form.

The more antennas you see on a router, the more transmit and receive radios there are, corresponding to the number of supported spatial streams. For example, a 3×3 router employs three antennas and handles three simultaneous spatial streams. Using current standards, these additional spatial streams account for much of how performance is multiplied. The Netis N300 router, pictured on the left, features three external antennae for better signal strength.

Ethernet Ports

While the wireless aspect of a wireless router gets most of the attention, a majority also enable wired connectivity. A popular configuration is one WAN port for connecting to an externally-facing modem and four LAN ports for attaching local devices.

The LAN ports top out at either 100 Mb/s or 1 Gb/s, also referred to as gigabit Ethernet or GbE. While older hardware can still be found with 10/100 ports, the faster 10/100/1000 ports are preferred to avoid bottlenecking wired transfer speeds over category 5e or 6 cables. If you have the choice between a physical or wireless connection, go the wired route. It’s more secure and frees up wireless bandwidth for other devices.

While four Ethernet ports on consumer-oriented routers is standard, certain manufacturers are changing things up. For example, the TP-Link/Google OnHub router only has one Ethernet port. This could be the start of a trend toward slimmer profiles at the expense of expansion. The OnHub router, pictured on the right, features a profile designed to be displayed, and not hidden in a closet, but this comes at the expense of external antennas, and the router has only a single Ethernet port. Asus’ RT-AC88U goes the other direction,incorporating eight Ethernet ports.

USB Ports

Some routers come with one or two USB ports. It is still common to find second-gen ports capable of speeds of up to 480 Mb/s (60 MB/s). Higher-end models implement USB 3.0, though. Though they cost more, the third-gen spec is capable 5 Gb/s (640 MB/s). The D-Link DIR-820L features a rear-mounted USB port. Also seen are the four LAN ports, as well as the Internet connection input (WAN).

One intended use of USB ports is to connect storage. All of them support flash drives; however, some routers output enough current for external enclosures with mechanical disks. If you don’t need a ton of capacity, you can use a feature like that to create an integrated NAS appliance. In some models, the storage is only accessible over a home network. In other cases, you can reach it remotely.

The other application of USB on a router is shared printing. Networked printers make it easy to consolidate to just one peripheral. Many new printers do come with Wi-Fi controllers built-in. But for those that don’t, it’s easy to run a USB cable from the device to your router and share it across the network. Just keep in mind that you might lose certain features if you hook your printer up to a router. For instance, you might not see warnings about low ink levels or paper jams.


The Future Of Wi-Fi

Wireless routers continue to evolve as Wi-Fi standards get ratified and implemented. One rapidly expanding area is the Connected Home space, with devices like thermostats, fire alarms, front door locks, lights and security cameras all piping in to the Internet. Some of these devices connect directly to the router, while others connect to a hub device—for example, the SmartThings Hub, which then connects to the router.

One upcoming standard is known as 802.11ad, also referred to as WiGig. Actual products based on the technology are just starting to appear. It operates on the 60GHz spectrum, which promises high bandwidth across short distances. Think of it akin to Bluetooth with a roughly 10 meter range, but performance on steroids. Look for docking stations without wires and 802.11ad as a protocol for linking our smartphones and desktops.

Used in the enterprise segment, 802.11k and 802.11r are being developed for the consumer market. The home networking industry plans to address the problem of using multiple access points to deal with Wi-Fi dead spots, and the trouble client devices have with hand-offs between multiple APs. 802.11k allows client devices to track APs for where they weaken, and 802.11r brings Fast Basic Service Set Transition (F-BSST) to facilitate authentication with APs. When 802.11k and 802.11r are combined, they will enable a technology known as Seamless Roaming. Seamless Roaming will facilitate client handoffs between routers and access points.

Beyond that will be 802.11ah, which is being developed to use on the 900MHz band. It is a low-bandwidth frequency, but is expected to double the range of 2.4GHz transmissions with the added benefit of low power. The envisioned application of it is connecting Internet of Things (IoT) devices.

Out on the distant horizon is 802.11ax, which is tentatively expected to roll out in 2019 (although remember that 802.11n and 802.11ac were years late). While the standard is still being worked on, its goal is 10 Gb/s throughput. The 802.11ax standard will focus on increasing speeds to individual devices by slicing up the frequency into smaller segments. This will be done via MIMO-OFDA, which stands for multiple-input, multiple-output orthogonal frequency division multiplexing, which will incorporate new standards to pack additional data into the 5GHz data stream.

What To Look For In A Router

Choosing a router can get complicated. You have tons of choices across a range of price points. You’ll want to evaluate your needs and consider variables like the speed of your Internet connection, the devices you intend to connect and the features you anticipate using. My own personal recommendation would be to look for a minimum wireless rating of AC1200, USB connectivity and management through a smartphone app.

Netis’ WF2780 Wireless AC1200 offers an inexpensive way to get plenty of wireless performance at an extremely low price. While it lacks USB, you do get four external antennas (two for 2.4GHz and two for 5GHz), four gigabit Ethernet ports and the flexibility to use this device as a router, access point or repeater. Certain features are notably missing, but at under $60, this is an entry-level upgrade that most can afford.

Moving up to the mid-range, we find the TP-Link Archer C9. It features AC1900 wireless capable of 600 Mb/s on the 2.4GHz band and 1300 Mb/s on the 5GHz band. It has three antennas and a pair of USB ports, one of which is USB 3.0. There’s a 1GHz dual-core processor at the router’s heart and a TP-Link Tether smartphone app to ease setup and management. You’ll find the device for $130.

At the top end of the market is AC3200 wireless. There are several routers in this tier, including D-Link’s AC3200 Ultra Wi-Fi Router (DIR-890L/R). It features Tri-Band technology, which supports a 2.4GHz network at 600 Mb/s and two 5GHz networks at 1300 Mb/s. To accomplish this, it has a dual-core processor and no less than six antennas. There’s also an available app for network management, dual USB ports and GbE wired connectivity. The Smart Connect feature can dynamically balance the wireless clients among the available bands to optimize performance and prevent older devices from slowing down the rest of the network. Plus, this router has the aesthetics of a stealth destroyer and the red metallic paint job of a sports car! Such specs do not come cheap; expect to pay $300.


Wireless routers are assuming an ever-important role as the centerpiece of a residential home network. With the increasing need for multiple, simultaneous continuous data streams, robust throughput is no longer a nice feature, but rather a necessity. This becomes even more imperative as streaming 4K video moves from a high-end niche into the mainstream. By taking into consideration such factors as the data load as well as the number of simultaneous users, enthusiasts shopping for wireless routers will get the help they need to choose the router that best fits their needs and budget.

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Smart Antennae: Critical for 5G

14 Jan

The 5G Network of Tomorrow is coming to mobile broadband, and like SDN/NFV, it will generate new network operating models.While avant-garde operators will quickly adopt, further cementing their market leading positions, 5G will open the door to non-traditional network operators and infrastructure vendors for networks in unlicensed and shared licensed spectrum. Notably, the Radio Access Network will experience a major change, as the nature of 5G frequencies will change the design and operation of cellular networks.Knowing that 5G is a major change for operators with a legacy mindset, the development community is trying to deliver the maximum utility and longevity with a platform that should last for 10 years and avoid operators’ buyer remorse of “I wish we had known…”

What are the differences with 5G frequencies, and what can we expect from them? Today’s cellular frequencies range from 450 MHz to more than 3000 MHz—technical terms that have important physical and economic implications, and traditionally licensed spectrum. With 5G multi-connectivity, operators can use unlicensed spectrum for added capacity or develop isolated networks for enterprise and industrial applications.Because of the physics of electromagnetic radio waves, the lower numbered frequencies are able to reach farther and cover more area for less cost than the higher numbered frequencies. However, it is not a free lunch, because as more subscribers sign up, cell sites using the lower numbered frequencies will have too many subscribers for each base station, causing slow data rates and delivering a poor user experience. Operators can buy more radio spectrum (if available) and/or put up more cell sites, including small cells, to meet wireless broadband data demand. Smarter antenna systems will also improve network performance and capacity beyond what is capable with today’s standard 2×2 and 4×4 MIMO deployments in 4G LTE.

For cellular networks, the signal quality matters most for the user experience, and as a simple rule of thumb, a stronger signal (relative to the surrounding electronic noise) leads to a better user experience withfaster data rates.In the digital realm, blazing speed correlates with mass-market capacity, as all subscribers in a cell share the total data rate. Obtaining stronger signals with 5G involves smarter antenna technology, more radio spectrum, and smaller cells. The physics of 5G spectrum changes the economics for antenna solutions, as the higher frequencies equate to packing more antennae into a smaller space and remaining cost effective. The higher numbered frequencies are promising, because there is a lot of radio space available, which will help support a 1000x increase in traffic. Smaller cells and smart antennae offset the propagation physics that would otherwise mean a very short range and poor user experience.

5G will encompass a wide range of spectrum, but my primary interest is new frequencies above 6 GHz.At 28 GHz, for example, a single antenna, called a “half wavelength dipole,” is about 0.2 inches—not big at all.The small size spurs creative engineers to do many clever things, like beamforming.An array of antennae, say 128 elements, is still very small, but the right digital signal processing can generate a very focused beam from the base station to the mobile.This is necessary for the cellular signals to overcome the energy losses due to distance, buildings, trees, rain, or people.

At a recent 5G workshop, Qualcomm demonstrated a 28 GHz test setup with a 128 element antenna representing a base station, and a mock-up mobile with a smaller set of selectable antennae (read about the demo).The 128 element base station antenna was about 6”x8” and the ability to focus a radio beam was demonstrated under a variety of orientations. An antenna designed the same way for today’s LTE frequencies at 700 MHz would be about 20’x30’ and not feasible. An operator can hang an abundance of 6”x8” antennae in a place like Times Square, which leads back to another aspect of 5G—Massive MIMO (Multiple-Input, Multiple Output – who thinks up these names?). Massive MIMO essentially means that the network uses multiple antenna beams from multiple base stations to deliver the fastest data to your mobile.

The tiny smart antennae demonstrated by Qualcomm had about 27 db gain, about 10–12 more db than a typical cellular base station antenna. 10 db more means that antenna could put 10x more signal power on a mobile than a legacy cellular antenna. An analogy to this effect is like using a candle to light up a dark room versus using a flashlight. This focused approach also extends to the many antennae that might be deployed, that is several base stations with lots of antennae may deliver the signal to your mobile, hence Massive.The net effect is to provide you a stronger signal with less interference, or noise, from all the other mobiles nearby. The relative signal-to-noise ratio (SNR) limits how fast the network can deliver the data, and a bigger ratio is better. Beam Forming Smart Antennae makes for a larger signal value at the top of the ratio fraction, and smaller noise value at the bottom for a double boost to SNR.

A second aspect, and just as critical as the base station antenna, are mobile antennae. Qualcomm demonstrated a facsimile of a mobile, a Form Factor Accurate device, with antenna in the case edges, front and back, top and bottom.Many antennae are needed to make sure that at least some are unobstructed by your hand or other body parts. I expect that there are best practices in mobile antenna design that will come from this, so that 5G handset vendors will not have Antennagate déjà vu all over again.

A third critical aspect of a 5G cellular network will be multi-connectivity. 5G multi-connectivity means that while your network is delivering an outstanding data experience in the uber-fast 6 GHz (and higher) frequencies, it maintains additional connections with 4G LTE (Long Term Evolution – seriously, where do they get these names?). In spite of the multiple beam forming antennae that puts your device in the spotlight, there will be occasional times where the 28 GHz signal is blocked. Rather than drop off the network, the network maintains the connection through the wider coverage of 4G LTE until the 28 GHz signal returns.

The bigger picture of 5G is more than just the spectrum, antennae, anda faster-better-cheaper mobile broadband. The 5G Network of Tomorrow is about designing and operating the networks with the forethought and flexibility to last through 2030. The 5G network will bring to fruition the aspirations of the connected society, that is the Internet of Everything. Of course, none of this is simple to implement, but by connecting the dots among 4G, 5G, and millimeter wave smart antennae research, we have a good idea for key components of a 5G network. The creative geniuses at companies like Qualcomm are working diligently to make this happen.




Embedded LTE antenna in detail

1 May

This LTE antenna with is very detailed documentation is a good example to explain the working of ceramic antennas on a PCB with different size of ground plane.

LTE antenna embedded efficiency 400x173 Embedded LTE antenna in detail

I. Embedded LTE antenna efficiency

The antenna is resonating in all major LTE, GSM and HSPA bands and on Wi-Fi 2400 MHz and 5 GHz as well. The mentioned parameters are valid on a ground plane with size of 50 mm x 120 mm. The antenna efficiency was measured on a common PCB based on FR4 with a thickness of 1.6 mm.

LTE antenna embedded size 400x196 Embedded LTE antenna in detail

II. Embedded LTE antenna dimensions

With 34 x 8.5 x 3.2 mm³ the antenna is already very small. The free space area is 50 mm x 20 mm on top of the PCB only.

LTE antenna embedded vswr 400x260 Embedded LTE antenna in detail

III. Embedded LTE antenna performance on smaller ground plane

Most embedded antenna documentation does not tell, what will happen by changing of the recommended size of the ground plane. This embedded LTE antenna is telling the true on one few. In the lower bands it will lose performance as usual. The resonate frequency will shift in most of the mentioned frequency bands as well. With a matching circuit it is possible to reduce the detuning by the enclosure. Based on its high bandwidth in the lower bands, the antenna will be perfect for IoT / M2M applications on 2G or 3G modules. As told in the chapter for the self-made GSM Quad band Antenna – as bigger the bandwidth is as lower will be the effort for the tuning.

LTE antenna embedded eval board 400x311 Embedded LTE antenna in detail

IV. Cupper nose close to the embedded LTE antenna

The cupper nose is already a part of the LTE antenna. The strip line at the cupper free area is a part of the antenna as well. Do change the width of the strip line, because malfunction will occur.

Summary of embedded LTE antenna

If there is a budget then the antenna structure can be changed. Even the design of an own customised LTE antenna is possible on small to medium quantities. The antenna is always the key to success in any wireless application. They selection of the right antenna in an early stage will decide between success and failure.

If you still not sure which antenna to select and why, then do not hesitate to drop an email to harald.naumann (at)


For A Better Signal You Need Nicer Base Station Antennas

10 Apr

Base Station Antennas


For best signals you will have to use the special devices that will ensure that you can hear what is being said on the radio from anywhere in the country. The signals that are being transmitted are known as radio waves, and are sent from the base station antennas to the exact spot you are listening to on your own radio. These are useful for getting a variety of stations. 

You will find that there are a lot of different types of antennas out there, and you will have to decide which one will work the best for your own radio. Just like the radio stations have to decide which radio antennas work for them. These produce signal that can either allow you to hear clearly, or can cause the signal to make a funny noise.

Having a radio is super exciting when you are young, this is so helpful and all children will want one at some stage. Radios are made to produce a different stimulation like sound, and helps with your imagination. Children who have radios will find it easier to use their imagination then those who don’t.

You get aerials that are made from Aluminium which is used as a good conductor. These are used for all weather conditions and are also easy to put up. These are used to enhance all signals, and are not just for radio use. When you get your very first radio, you can enjoy hours of fun with it.

Signals need to be transmitted for everything these days. So they can either be done using a cable or even be a wireless system. This will depends on the company and what they are trying to achieve. As a family or a company you will need to be able to receive and send information, and the best way is to either tell someone what’s on your heart or to write them a letter. This could take forever to get to them so instead send them an email.

Where you place the aerial will also play a big part on the area you stay, your type of home and what the purpose of it will be for. These decisions will play a role in your decision, and will either give you great reception or will cause your picture or sound to come out fuzzy. You will also have to consider if you want it inside your house or outside your house.

Televisions, computers, laptops or even your radios work directly from a signal which connects them to a bigger unit. This is how you will receive all your important information. To make sure that you can get all your information that you have required, you will need a good signal.

There are always new things out there that allow you to not need to use any cables. This will only affect you if you live in an area that has poor signal. Your only concern will be is how far these are from where you live.

For A Better Signal You Need Nicer Base Station Antennas

Station Antennas, Base Station, Base Station Antennas

via Top5Stars


Intel Touts New Ultra-High-Speed Wireless Data Technology

27 Feb

Small base stations could achieve huge data capacity increases using Intel’s modular antenna arrays.

Intel says it has prototyped a chip-based antenna array that can sit in a milk-carton-sized cellular base station. The technology could turbocharge future wireless networks by using ultrahigh frequencies.

Intel’s technology, known as a millimeter wave modular antenna array, is expected to be demonstrated today at the Mobile World Congress conference in Barcelona, Spain, says Ali Sadri, director of the millimeter wave standards and advanced technology group at Intel.

Any one such cell could send and receive data at speeds of more than a gigabit per second over up to few hundred meters—and far more at shorter distances—compared to about 75 megabits per second for the latest standard, known as 4G LTE.

For mobile cellular communications, both the Intel and Samsung technologies could eventually use frequencies of 28 or 39 gigahertz or higher. These frequencies are known as millimeter wave and carry far more data than those used in cellular networks today. But they are easily blocked by objects in the environment—and even water droplets in the air. So they’ve traditionally been seen as impractical for mobile devices.

To get around the blockage problem, processors dynamically shape how a signal is combined among 64, 128, or even more antenna elements, controlling the direction in which a beam is sent from each antenna array, making changes on the fly in response to changing conditions.

Several groups are working on such antenna arrays, but Intel says its version is more efficient. “We can scale up the number of modular arrays as high as practical to increase transmission and reception sensitivity. The barrier is only regulatory issues, not technological ones,” Sadri says.

A major problem is finding a way to get so many antennas into a mobile device. The NYU technology used a benchtop gadget hauled around the sidewalks of Manhattan for testing. It steers beams mechanically toward intended users. The Intel chip does the same thing by shaping the direction of the signal electronically, and is now packaged in a gadget smaller than a shoebox.

A number of companies are betting next-generation wireless technologies will need to use millimeter wave links to deliver all the data people want. The European Commission, for example, last year launched a $1.8 billion 5G research effort to help develop this and other technologies.



Energy Consumption in Wireless Networks: The Big Picture

7 Nov

Green Energy

I recently came across a presentation on advanced antenna systems with the statement: “advanced antenna systems for power consumption savings not for capacity.” I was very intrigued for a couple of reasons. The first is how much of a problem is power consumption in wireless networks is. The second is that I recalled a conversation I had over 14 years ago with a colleague at Metawave prior to joining them. He said that they were approaching smart antenna systems from the perspective of capacity and not coverage. Back then, the nascent technology was traditionally targeted at improving coverage which was the reason why these systems failed to get traction in the market. So, today, we are changing the pitch for these systems from a capacity focus to a power savings focus. But will that make them more attractive? How much of a problem power consumption is?


Let’s look at some back of the envelop numbers to frame the issue. A base station site consumes between 1000 – 2000 W (and often more), depending on a number of factors such as the number of radios, frequency channels, and traffic load.  For a typical US operator with about 50,000 sites, that over $60mil a year in operational expenses just to power the radio access network (RAN). The RAN accounts for about 70% – 80% of the total power, the rest is consumed by the core network. The total is then over $90mil – and I think this is a conservative number.

Cost of powering the RAN
BTS Power consumption


Number of sites


Energy consumed


Price of electricity





Taking a macro view for a top-bottom approach, the telecom industry accounts for over 1% of the total world energy consumption. I found the table below shows the energy consumption of some leading telecom companies in the world from 2008. Today, Verizon’s total energy consumption is on the order of 10.5 TWh up from 8.9 TWh in 2008 – of course, this is an entire company’s power consumption, wireless and wireline businesses included. Verizon’s annual operating budget is on the order of $46bil. So power consumption in the RAN accounts for about a fraction of 1% of the total operating budget. The question is then: is power consumption a significant issue to sway operator’s technology roadmap?


Source: Emerson Network Power

Source: Emerson Network Power

Verizon Electricity Consumption (Source: Verizon)
Year 2009 2010 2011 2012 % change
Electricity (TWh) 10.27 10.24 10 10.47 1.90%

There are a few favorite topics in the wireless industry that everyone likes to talk about such as capacity and stale ARPUs. But green energy in wireless networks is a much less ‘sexy’ topic that is only discussed in few focused forums without much media attention and it has not been one of the top priorities for CTOs despite limited projects to use renewable energy to power base stations.

As we move to LTE, we can expect an increase in energy consumption because LTE radios are less efficient than 3G radios due to the OFDM physical layer and requires more radios for MIMO. Radios account for anywhere between 40-80% of the base station total power consumption.  For this reason there has been a fair bit of work on improving the efficiency of power amplifiers. There are other techniques also used to reduce overall power consumption like the adoption of remote radios. So while demand on energy increases, there are new techniques being introduced to keep energy consumption in check.

Going back to advanced antenna systems, this is a further evolution where the remote radio is distributed across the antenna elements to create beams that can be changed in orientation and focus to meet base station performance requirements and optimize for energy consumption. But will the operators adopt such solution? Should investors invest in companies targeting green products for wireless networks? I think framing the question simply based on power consumption will not be enough to sway operators, but there has to be a real value in cost-performance trade off compelling enough for their adoption.



Antenna Ports and Transmit-Receive Paths (LTE)

22 Oct

The purpose of this topic is to give an overview and explanation of the relationships between antenna ports, physical transmit antennas, and receive channels. Included in this discussion is information about reference signals, PDSCH, usage of antenna ports, and beamforming. Also, this discussion is not an exhaustive listing of all the variations supported by the LTE standard, but is focused around the analysis capabilities of the 89600 VSA.

For exact information about what is possible in LTE, see 3GPP TS 36.211 and 36.213. Also, see App Note 5990-9997: Verify and Visualize Your TD-LTE Beamforming Signals.

Antenna Ports

The LTE standard defines what are known as antenna ports. These antenna ports do not correspond to physical antennas, but rather are logical entities distinguished by their reference signal sequences. Multiple antenna port signals can be transmitted on a single transmit antenna (C-RS port 0 and UE-RS port 5, for example). Correspondingly, a single antenna port can be spread across multiple transmit antennas (UE-RS port 5, for example).

Let us consider antenna ports used for PDSCH allocations since they probably have the most variations. Initially, the 89600 VSA’s LTE demodulator supported only analysis of PDSCH transmitted on Antenna Ports 0, (0 and 1), (0, 1, 2), or (0, 1, 2, 3). These ports are considered C-RS antenna ports, and each port has a different arrangement of C-RS resource elements. Various configurations are defined that use these C-RS antenna ports, including 2- or 4-port Tx Diversity and 2-, 3-, or 4-port Spatial Multiplexing.

Then beamforming support was added and single-layer PDSCH allocations transmitted on Port 5 could be analyzed. The LTE demodulator has since been enhanced to support the LTE Release 9 which added Transmission Mode 8–Dual-Layer Beamforming (i.e. beamforming + spatial multiplexing)–where PDSCH is transmitted on Antenna Ports 7 and 8 (note that single-layer beamforming in Rel 9 can also use port 7 or port 8 in addition to port 5). In Rel 10 of the standard, the new transmission mode 9 (TM9) added up to 8-layer transmissions using Ports 7-14. TM9 is supported by the LTE-Advanced demodulator.

As Ports 0-3 are indicated by the existence of C-RS, so Ports 5 and 7-14 are indicated by the UE-specific Reference Signal (UE-RS). The following is a table that summarizes the various PDSCH mappings that can be used along with the corresponding reference signal and antenna ports.

Reference Signal PDSCH Mapping # layers # physical antennas Antenna Ports LTE Release
C-RS Single-layer 1 1 0 8
Tx Diversity 2 or 4 2 or 4 0-1 or 0-3 8
Sp Multiplexing 2, 3, or 4 2, 3, or 4 0-1, 0-2, or 0-3 8
UE-RS Single-layer 1 >= 2 5 8
5, 7, 8 9
Dual-layer 2 >= 2 7-8 9
N-layer, N <=8 N >= N 7-(6+N) 10

In a MIMO or Tx Diversity configuration, each C-RS antenna port must be transmitted on a separate physical antenna to create spatial diversity between the paths. Single-layer beamforming, on the other hand, is accomplished by sending the same signal to each antenna but changing the phase of the each antenna’s signal relative to the others. Since the same UE-RS sequence is sent from each antenna, the 89600 VSA can compare the received UE-RS sequence with the reference sequence and calculate the weights that were applied to the antennas to accomplish the beamforming.

Multi-layer beamforming adds some complexity to beamforming by transmitting as many UE-RS sequences as there are layers to allow demodulation of each layer’s PDSCH data. The UE-RS sequence for each antenna port is orthogonal to the others, either in time/frequency domain or in the code domain. This can be thought of as beamforming of each layer independently. N-layer beamforming is an extension of dual-layer beamforming and supports up to 8 data layers with the ability to beamform each layer separately.

For reference, the following table lists the different LTE downlink reference signals and the antenna ports they use.

Reference Signal Antenna Ports LTE Release
C-RS 0-3 8
UE-RS 5 8
5, 7, 8 9
5, 7-14 10
P-RS 6 9
CSI-RS 15-22 10

Transmit-Receive Paths

In the case of a single-layer, single-antenna LTE signal (using only C-RS), there would only be one antenna port signal that could be received over the air, but in general, the reception of an LTE signal will contain a combination of multiple transmit antennas, each of which may be transmitting a combination of multiple antenna ports. The LTE standard does not specify any particular setup for transmit antennas, but since the C-RS antenna ports are used for most control channels and PDSCH, the 89600 VSA LTE demodulator uses Cell-specific RS antenna ports instead of transmit antennas when indicating transmit paths between transmitter and receiver.

The VSA denotes C-RS antenna ports by the mnemonic C-RSn on the user interface and in the documentation, where n is the antenna port number. Correspondingly, the receive channel is denoted by Rxm, where m is the measurement channel number – 1.

Together, these two endpoints constitute an transmit-receive path from transmitter to the receiver (ultimately the 89600 VSA). A transmit-receive path is denoted by C-RSn/Rxm, so for example, C-RS2/Rx1 on the MIMO Info Table shows metrics calculated from the (C-RS) antenna port 2 signal received on VSA measurement channel 2.

See Also

Layer Traces and Resource Element Distribution

LTE Physical Layer Overview


Sculpting your way to minimal interference

30 Aug

LTE rollouts are now happening all across Asia and have the potential to completely reshape how networks perform. Many LTE networks incorporate a technology called multiple-input multiple-output (MIMO), which splits data transmission into multiple streams and sends them at the same time on the same frequency using multiple antennas. The expression 2×2 MIMO means that there are two antennas transmitting in the downlink to two antennas receiving in the handset.

What makes this development so exciting is that MIMO offers a way around a classic limiting factor of RF communications known as Shannon’s Law, which dictates how much throughput can be delivered down a given amount of bandwidth. As Figure 1 shows, you can only expect to get to within 3dB of a bandwidth’s theoretical maximum in a practical application. With 2×2 MIMO you can potentially double the capacity over a traditional 3G implementation, which otherwise would be bound by Shannon’s law.


For LTE systems to maximise the potential of MIMO, interference must be minimised, making sector sculpting even more important for new 4G, LTE networks. Today, wireless consumers demand faster speeds and uninterrupted calls. In order to achieve a robust network that provides prompt, reliable data transmission with seamless voice capabilities now and well into the future, these networks will need to utilise the right antenna and sector sculpting techniques.

Shannon’s Law dictates that you can only expect to get to within 3dB of a bandwidth’s theoretical maximum in a practical application.

Shannon’s Law dictates that you can only expect to get to within 3dB of a bandwidth’s theoretical maximum in a practical application.

The Antenna

Let’s start with the basics of the antenna and why it is so important. The antenna is one of the most critical parts of a wireless system and is often the most visible. Antennas come in all shapes and sizes, because each one is built for a specific purpose but they share a common link: they are the key to how well – and how far – communications can be shared.

What makes cellular networks different from other types of communications is the principle of cell reuse. Cell reuse is a way of increasing network capacity by “reusing,” or reassigning, individual frequencies on the fly, within a particular cell.

Consider the shape of cells and how they fit together. Typically, cells are represented as interlocking hexagons. Depending on the density of the area served, these hexagons can be miles across or cover just a few hundred feet.

Sector Sculpting

Because of this incredible flexibility of distance, channel sensitivity is limited by external interference rather than noise issues, as older radio communications have traditionally been. The specialised pattern shaping of sector sculpting, available with directional antennas, both in azimuth (horizontal direction) and elevation (vertical space), enables precise coverage with minimal interference with neighboring cells.

A critical performance metric considers the relationship from one cell to its neighboring cell. This metric defines the overlap of energy between the cells and between the sectors that make up the cells. Known as sector power ratio, this is a comparison of signal power registered outside and inside a desired receiving area as a consequence of an antenna’s radiation pattern. The lower the ratio, the better the antenna’s interference performance.

Higher sector power ratios indicate a higher amount of interference between antennas in adjacent coverage areas. When competing signals overlap, interference can increase and reduce performance – such as dropping a cell phone call while moving from one cell to another. Cellular networks require precise sectorised planning to prevent this kind of problem.

The cellular network concept requires either frequencies or codes to be re-used over and over again throughout the network in order to support the massive amount of voice and data traffic. Operators use sector sculpting techniques to minimise interference between cells operating on the same frequencies or codes. Low levels of interference containment result in long distances between cells using the same frequency resources. By containing interference with sector sculpting, frequency resources can be reused closer to each other, whilst increasing spectrum efficiency, capacity and network performance.

As the cell sites become denser, the coverage area from each cell is typically decreased to reduce cell to cell interference. One way of decreasing the coverage area from a cell site is to lower the antenna radiation center. However, this is often undesirable since it could place the antenna below many surrounding obstacles such as buildings or foliage. Since most cellular networks now use sector antennas, a second option is beam tilting. This is done by tilting the vertical pattern of the antenna downwards, reducing the coverage on the horizon—where interference to neighboring cell sites takes place.

The easiest way to accomplish this is to mechanically tilt the entire sector antenna using adjustable brackets available from most antenna suppliers. However, a major drawback is that it does not reduce coverage consistently on the horizon over the sector. It reduces it more in the boresite direction and less at other angles away from the boresite, so the result is not a consistent reduction of the cell coverage. A quantifiable term for this phenomenon is known as “pattern blooming.”

Advanced networks typically deploy a more elegant method of tilting the sector antenna’s vertical pattern using electrical downtilt. This method keeps the antenna mounted upright and accomplishes the beam tilting by changing the electrical phase delivered to each element. The resulting pattern is tilted consistently over the entire 360 degrees yielding consistent reduction of the cell coverage. For electrically downtilted antennas, there is no increase in pattern blooming regardless of the amount of tilt.

Another benefit of electrical downtilt is that it can be accomplished remotely in advanced antenna systems. This feature will become even more important as more sophisticated technologies, such as LTE, mature.

One option associated with LTE is called self-organizing network (SON) where the network will continually re-optimise itself based on demand. The dynamic coverage adjustment associated with electrical downtilt is a key feature in the deployment of the SON concept.


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