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Opensource Small Cells for the lab and unserved rural communities

30 Jan

 What exactly is Opensource?

The Opensource concept has been highly successful in many areas of software. This website, as do the majority of the web, runs on MySQL and Linux – both developed by volunteers from around the world. Source code is published and can be used by anyone, on the basis that any improvements made are also shared with the community. Most of the successful projects have a commercial business co-ordinator that is funded by providing support and/or more robust/complete for those organisations that want to pay for it. Well supported crowd-sourced developments can achieve high levels of functionality, security and maturity because they’ve been stretched, scrutinised and tested in many different ways. Smaller projects that haven’t attracted critical mass can fall by the wayside leaving poor quality or incomplete designs.

Opensource also applies to other fields, and includes hardware, media (photos, videos etc.). Popular opensource licence agreements, such as GNU and Creative Commons encourage sharing by making it clear what the author intends.

This doesn’t avoid the issue of patents and Intellectual Property Rights – there are many involved in all aspects of mobile networks, embedded in the standards. Many of the original GSM patents have expired since the system was originally developed more than 20 years ago. Others still apply.

Opensource for Mobile

There are several Opensource projects working towards a complete mobile network, including both the hardware and software, compatible with today’s standard mobile phones.

OpenBTS is the most successful, with quite a mature and stable solution for GSM with 3G UMTS released in October 2014. It builds on Asterisk, an opensource voice switch used in many PBX and Internet VoIP services, extending it with the GSM protocols. It’s managed by Range Networks who own the trademark and strongly supported by others including Fairwaves.

Osmocom appears to be more research lab oriented including GSM alongside other radio technologies, such as DECT and TETRA. Core network is GPRS but there is no voice switch in scope.

YateBTS was recently started by one of the founders of OpenBTS. It has a long term vision to create a unified core network using VoLTE for calls for both 2G and 4G, and substantially reducing bandwidth for voice over satellite links compared to traditional SIP. The project is co-ordinated by Romanian company Legba.

OpenLTE is relatively new project to implement the core 3GPP LTE specifications. Today, code is available for test and simulation of downlink transmit and receive functionality and uplink PRACH transmit and receive functionality. This is very much research lab oriented and nowhere near ready for field use. Three other LTE opensource projects are also at early stages as described here.

These projects all benefit from and build on other Opensource projects, such as OpenSS7, Asterisk, GNURadio etc.

Limited capabilities

Although not nearly as extensive as a standard commercial product, these can be feasible for basic use with isolated service. Mobility, handover and roaming capabilities are included as are voice, SMS and data services. Looking a bit deeper, each cell/sector is configured as a completely separate Location Area so a full location area update is used to handover between cells. GPRS supports only two of the four coding schemes; manual configuration is required of many parameters, such as neighbour lists, timeslot allocation, RF power levels. In my view, this would hamper anything other than a small scale deployment.

The system can be connected to wholesale VoIP, SMS and Internet connections to provide inbound and outbound voice and data. One complication is that because different suppliers are typically used to provide wholesale voice and text services, each would require a different MSISDN (phone number) – definitely confusing for end users.

GPRS data does work but isn’t as fast or mature as a commercial EDGE implementation. One company doesn’t recommend using it at all, reasoning that Wi-Fi is cheaper/better in such low price markets for data only. However VoIP over Wi-Fi is considered far less attractive than GSM for voice.

SIM Cards

The system can use existing SIM cards from an existing network, assigning a local number and automatically registering them for use. The full GSM security can’t be used in this case (because the encryption key is hidden inside the SIM card), but a simpler form of encryption is offered.

Today, it’s possible to program your own SIM cards manually. For larger quantities, a full production run can be bought with your own logo design using your own specified parameters.

Off the shelf hardware

Several vendors offer all you need to run a basic GSM service, including the core network, with off-the-shelf hardware for use in the lab or outdoors.

Just don’t expect a fully automated SON solution that sits comfortably with any existing network on the same frequencies – you’d still need a commercially mature small cell solution for that. You’ll also need some spectrum to use this legally, either a test licence for your lab or a fully blown one from the regulator. In a few countries, low power GSM is legally permitted in certain guard bands (eg at 1800MHz) without a licence.

Example products include:

  • Range Networks products based on OpenBTS include a standalone GSM development kit for $2,300 and a full size outdoor basestation.
  • Fairwaves offer solutions based on OpenBTS and Osmocom hardware with their development board for just $850 and a packaged lab system for $2,500
  • Sysmocom in Germany use Oscocom; products include a 200mW small cell and larger 10W outdoor product.
  • Legba, the new company behind YateBTS, currently offer a GSM lab radio kit for about $2000 and an outdoor model for $12,000. Licences for their HLR/HSS and other modules run from $12,000.

Case study deployments

An example installation described here is of a remote Mexican village of 700 inhabitants 5 hour away from the nearest city. It has a simple network with two GSM transceivers that handle around 1000 voice calls and 4000 texts in a typical day. The antenna mast is constructed from a 6 metre bamboo pole. Another Mexican village of 500, San Juan Yaee, was connected for just $8,000 – about 15% of the cost quoted by the national operator – with ongoing monthly rates of $2. At those prices, nobody’s going to get rich.

Other applications

Software definable radio hardware can be used for a wide variety of different applications, ranging from detecting/decoding shipping and aircraft location beacons. This article outlines 10 different possibilities.

One application which I though remarkably innovative was used to locate stranded hillwalkers from a helicopter. The GSM basestation onboard takes several measurements of the walker’s phone signal from different positions and triangulates to find where they are. Using simple GSM time-advance measurements, the results are displayed on an iPad inside the helicopter. It’s not dependent on mobile data or the victim being conscious, as is needed for a similar app called SARLOC.


I’m enthusiastic about the use of Opensource projects to stimulate research and development into new pioneering new ways and means of improving and extending mobile technology. It should enable our academic institutions to demonstrate and prove their theories with limited budgets.

There may also be an opportunity to connect some of the most remote and unserved communities which commercial organisations haven’t been able to reach. The scale of this would be limited by spectrum licences and IPR. The recent proposal by Mexican regulators to allocate some 850MHz spectrum for community use by unserved areas Mexico sends a signal to commercial operators that they can’t simply ignore this demand.

In most cases, I believe it would be better to use commercially mature, mass market solutions managed by professional organisations. Only where those needs are not being served, and regulators support and encourage it, would we see this self-driven community driven approach adopted more widely. The lack of scalability and management features of these solutions limits their scope to very small and simple deployments. Commercial ventures could either develop their own products using proven software from companies such as Radisys or NodeH, or adapt and extend many of the existing proven small cell products already on the market (look in our vendor section for plenty of ideas!)



GSM Terminating SMS Call

3 Feb

SMS terminating call flow

In this call flow we will look at how a terminating SMS is handled in GSM. Setting up a terminating
SMS session is a multi-step process.

  1. Interrogate the MSC to locate the subscriber
  2. Setting SMS session setup and acquiring radio resources
  3. Sending the SMS.
  4. Releasing the session and associated radio resources.

GSM Mobile Terminated SMS Sequence Diagram


LTE Migration strategies pose challenges for CDMA Operators

21 May

Commercial, market, spectrum and regulatory factors will define the strategy that CDMA operators adopt to migrate to LTE.

CDMA is arguably superior to GSM in radio technology terms, but CDMA ultimately failed to achieve the same level of success as GSM mainly because of limited international roaming and handset variety. In most developed telecoms markets, CDMA operators have gradually migrated their networks to GSM (for example, Telstra in Australia, Hutchison Telecommunications in Hong Kong and M1 in Singapore). CDMA operators have enjoyed prolonged success in a limited number of countries – for example, Japan, South Korea and the USA.

CDMA operators have many options for migrating to LTE

Outside these countries, most CDMA operators have a small market share, limited network coverage and generally remain niche propositions. CDMA has dwindling vendor support and operators are now faced with an existential question: where do we go from here?

Several migration options are available (see Figure 1), but voice provision will be the key factor defining the strategy.

Figure 1: Migration options for CDMA operators [Source: Analysys Mason, 2013]


Option Voice Data Comments
1 None LTE
  • Data-centric strategy
  • Raises the question of where to migrate existing voice subscribers.
  • Could potentially launch VoLTE when the market is conducive.
  • Lack of spectrum.
  • Need to invest in a GSM network.
  • 2G handset availability is not an issue, but it will not be possible to target 3G handset users.
  • Lack of spectrum.
  • Need to invest in a UMTS network.
  • 3G handset availability is not an issue, but with GSM-only networks it is not possible to target 2G-only handset users.
  • Handset availability is not an issue.
  • Lack of spectrum.
  • Need to invest in a GSM/UMTS network.
5 National roaming (GMS/UMTS) LTE
  • Handset availability is not an issue.
  • Low margins on voice.
  • It is likely that the strategy will be to focus on data.
  • Data-centric strategy.
  • Installed base of VoLTE handsets is limited.
  • VoLTE is yet to reach technological maturity.
  • International roaming issues are yet to be resolved.
  • It may not make commercial sense to migrate established voice subscribers to VoLTE.

However, the choice of LTE migration strategy is not straightforward

Replacing a CDMA network with GSM and/or UMTS networks (Options 2–5) will require significant investment and can be problematic because of limited available spectrum in standard GSM/UMTS bands. The operators may avoid network investments by signing a national roaming agreement with a GSM/UMTS operator for voice services (Option 5) but, because of low margins on voice services, CDMA operators are likely to evolve into data-centric operators, based on mobile broadband (closer towards Option 1).

Deploying VoLTE (Option 6) is a challenging and risky strategy. VoLTE-enabled devices are expensive and limited in variety, and it will take time, particularly in countries where handset subsidies are not prevalent, for such handsets to become widespread. Other challenges exist such as international roaming and general technological immaturity. MetroPCS Wireless, a CDMA operator in the USA, opted for the VoLTE route relying on handset subsidies and launched VoLTE in selected regions in 2012. However, the operator announced a merger with T-Mobile (USA) less than 3 months later. As a result, MetroPCS’s voice subscribers are being migrated to T-Mobile’s GSM network and MetroPCS’s CDMA spectrum is being used to support LTE.

So far, many CDMA operators have been consolidating their positions with an intention to focus on data. In Ukraine during October–November 2012, one small CDMA operator exited the market, and Intertelecom, a CDMA operator, and Astelit, a GSM operator with a CDMA licence, announced a network-sharing agreement. The operators are focusing on mobile broadband and plan to launch LTE when the regulator introduces technology-neutral licensing. In Nigeria, MTS, Multi-Links and Starcomms (all use 1900MHz spectrum) and were merged into Capcom, a new entity that plans to launch LTE focusing on data. It is not clear what will happen to Capcom’s voice subscribers (750 000 as of December 2012 according to the regulator, the Nigerian Communications Commission (NCC)). The NCC is working with the CDMA operators to get them either to upgrade to LTE or vacate the valuable 850MHz spectrum for future LTE deployments.

LTE offers an opportunity for CDMA operators to upgrade networks but also poses challenging questions. Commercial, market, spectrum and regulatory factors will define their migration strategy. Failure to migrate to LTE might mean that CDMA operators in countries other than Japan, South Korea and the USA are forced to exit the market and consolidate.

Source: Analysys Mason –

Pico-cellen krijgen meer ruimte

31 Jan

Bedrijven en particulieren met een eigen klein gsm-netwerk (private GSM) kunnen dit blijven gebruiken. Dat heeft Agentschap Telecom besloten. Er komt ook vanaf 26 februari meer frequentieruimte voor deze netwerken beschikbaar.

Sinds 2009 kan iedereen zonder vergunning een eigen laagvermogen basisstation voor mobiele telefonie gebruiken in de 1800 MHz-band. Dit werkt via GSM-picocellen, kleine zenders met een bereik van enkele tientallen meters. Picocellen kunnen bijvoorbeeld gekoppeld worden aan de vaste bedrijfstelefooncentrale. Voordeel is dat medewerkers op eigen terrein zonder kosten met hun GSM kunnen bellen via de vaste telefooncentrale.

Eén van de voorwaarden was dat het gebruik gemeld werd bij Agentschap Telecom. In drie jaar tijd zijn er ruim 3.000 van deze GSM-basisstations geregistreerd, onder meer bij grote bedrijven, in ziekenhuizen en in verzorgingstehuizen. De regeling was bij wijze van proef ingesteld tot 26 februari 2013. Vanwege het grote succes heeft het ministerie van Economische Zaken besloten het vergunningsvrije gebruik voort te zetten. De registratie was ook bedoeld om te peilen of er behoefte aan was.

In de eind vorig jaar geveilde 1800 MHz-band is 5 MHz aan ruimte vrij gehouden voor kleine GSM-netwerken. Deze frequentieband is geschikt voor alle mobiele GSM-telefoons. Tot nu toe was hier nog 2,5 MHz voor beschikbaar. Vanaf 26 februari 2013 hoeft het gebruik van deze basisstations ook niet meer gemeld te worden. Door de extra ruimte die beschikbaar is gekomen, wordt het waarschijnlijk in de loop van 2013 ook mogelijk om 3G en 4G (mobiel breedband internet) toe te passen.

Nederland is volgens het AT een van de weinige landen ter wereld waar kleine GSM-netwerken gratis en zonder vergunning gebruikt mogen worden. Het gebruik kan alleen binnen een gebouw, eenmaal buiten het eigen gsm-netwerk kan de telefoon automatisch overschakelen op de eigen mobiele-telefonieprovider

Door het vergunningsvrij maken van een deel van de 1800 MHz-band ontstaat er volgens AT ruimte voor nieuwe toepassingen voor mobiele communicatie. Partijen kunnen hiervoor innovatieve diensten ontwikkelen. In Nederland is al zichtbaar dat er niet alleen veel kleine gsm-netwerken ontstaan, maar dat er ook bedrijven zijn of komen die voor deze nichemarkt netwerken ontwikkelen.

De voorwaarden voor het vergunningsvrij gebruik van een deel van de 1800 MHz-band zijn te vinden op de website van Agentschap Telecom, onder het onderwerp GSM-picocellen.


Western Europe: Base station deployments and forecast 2012-2017

5 Jan


According to their research, the need for additional GSM base stations will be limited in Western Europe during 2012–2017. About 22 000 units will be shipped in 2012, but this figure will decline to 13 000 in 2013. The number of new GSM base station shipments will be negligible during the remainder of the forecast period, although a substantial increase in shipments will occur in the form of RAN refresh deployments.

In addition, the constant growth in traffic per connection and the number of smart devices in use will drive demand for UMTS base stations in Western Europe during the forecast period. More than 140 000 UMTS base stations will be required in 2012, followed by an additional 140 000 in 2013. However, capacity upgrades (such as HSPA+, dual-cell and MIMO) between 2013 to 2016 will reduce demand for new base stations.

Finally, LTE capacity will largely replace UMTS capacity between 2015 and 2017. The demand for LTE in the region will remain fairly constant throughout the forecast period. The introduction of capacity enhancements will do little to offset the impact of traffic growth. LTE base station shipments will grow at an annual rate of 145% between 2012 and 2017. Slightly less than 280 000 additional LTE base stations will be required in Western Europe between 2012 and 2017.

PDF downloadAnalysys_Mason_Base_station_deployments_forecast_May2012_SAMPLES


Call Setup and Call Handling in GSM

12 Dec

Call Setup

Different procedures are necessary depending on the initiating and terminating party:

  • Mobile Originating Call MOC: Call setup, which are initiated by an MS
  • Mobile Terminating Call MTC: Call setup, where an MS is the called party
  • Mobile Mobile Call MMC: Call setup between two mobile subscribers; MMC thus consists of the execution of a MOC and a MTC one after the other.
  • Mobile Internal Call MIC: a special case of MMC; both MSs are in the same MSC area, possibly even in the same cell.


 Mobile Originating Call MOC

1. Channel Request: The MS requests for the allocation of a dedicated signaling channel to perform the call setup.

2. After allocation of a signaling channel the request for MOC call setup, included the TMSI (IMSI) and the last LAI, is forwarded to the VLR

3. The VLR requests the AC via HLR for Triples (if necessary).

4. The VLR initiates Authentication, Cipher start, IMEI check (optional) and TMSI Re-allocation (optional).

5. If all this procedures have been successful, MS sends the Setup information (number of requested subscriber and detailed service description) to the MSC.

6. The MSC requests the VLR to check from the subscriber data whether the requested service an number can be handled (or if there are restrictions which do not allow further proceeding of the call setup)

7. If the VLR indicates that the call should be proceeded, the MSC commands the BSC to assign a Traffic Channel (i.e. resources for speech data transmission) to the MS

8. The BSC assigns a Traffic Channel TCH to the MS

9. The MSC sets up the connection to requested number (called party).

Remark: This MOC as well as the MTC described in the following describes only the principles of an MOC / MTC, not the detailed signaling flow.




HSPA, UMTS, GSM, LTE and Other Acronyms Demystified

22 Aug

Femto-cells for everyone

21 Aug

We live in a country where we have almost 100% GSM coverage, outside. Because our houses are so good isolated sometimes that it can be hard to get those GSM signals inside the house. That’s why I love Vodafone’s initiative to sell tiny femto-cells in the Netherlands. A Femto-cell is kind of putting your own GMS-transmitter inside your house. But this time it does not connect you to Vodafone through the GSM-network, but through you broadband connection. I can’t wait for the other providers to supply these femto-cells.

It is hard for a lot of people to understand the working of these things as you can read in the forums of my sourced websites. The difference between WiFi, GSM, 3G, internet, broadband and other terms is sometimes hard to get. Simply put: you get a broadband connection from your ISP that provides you internet access. In order to use that on a laptop in the house you either connect that laptop Wired or Wireless (WiFi) to your broadband router. You than have a Smartphone, or other phone. This one connect via GSM (2G) or 3G to your telephony provider. But sometimes it is hard to get a good signal in the house. That is where this Femto-cell comes in. You connect it via your broadband connection to Vodafone and from that moment your GSM/3G coverage is great. You can use that connection for voice call, sms, but also internet over GSM/3G. For companies that use their own APN on Vodafone’s network this is great. Employees can get business email and other data at home again, where this was not possible when there was almost no coverage in the house.

Can this be used to avoid roaming costs outside the Netherlands? In theory yes, but I expect some technical limitations to block it and there sure will be problems with foreign telecoms laws. Because you will be transmitting GSM without a license and you are providing a network that (should) not exist in that country.

This Vodafone clip in Dutch explains it all:

Sources: Iphoneclub, Webwereld – 20 August 2012 –

Report: LTE Equipment Market to Grow Eightfold by 2016

10 Aug

The global market for Mobile Radio Access Network (RAN) LTE equipment is set to grow at an explosive 50% compound annual growth rate (CAGR) over the next five years, according to a forecast from Dell’Oro Group. Mobile broadband growth will eventually be enough to offset declining investment in CDMA, GSM and WiMAX, Dell’Oro says.

“The success with early adopters in North America, Japan, and South Korea is driving operators around the world to commit to LTE and reap the benefits of improved efficiencies, latencies, throughputs, and to ensure a future-proof roadmap,” Dell’Oro analyst Stefan Pongratz elaborated. “It has been only 18 months since the first large scale commercial deployment of LTE and it is already generating more than 15 percent of total RAN revenues.”

Overall the Mobile RAN market, macro and public access small cells, is forecast to grow at a 2% CAGR between 2011 and 2016, according to Dell’Oro. Growth in the public access small cell market is expected to accelerate in the later years of the forecast period, accounting for 9% of total RAN revenues in 2016.

Source: – 8/9/12 at 12:28 PM

Huawei, Qualcomm complete LTE voice tests

9 Aug

Huawei and Qualcomm have completed an LTE voice call to UMTS during a series of optimization tests.

The tests used R9 protocol and Qualcomm’s latest Snapdragon S4 processor, the MSM8960.

The vendors claim that the tests, based on the flash CSFB voice solution for the R9 protocol, resulted in lower call setup latency than that of the R8 protocol, and very close to that of a native UMTS voice call. 

During the CSFB testing, which also included LTE TDD calls, good call setup times were seen for both UMTS and GSM, the companies claimed.

LTE networks already meets the need for higher speed mobile broadband data services and the introduction of R9 CSFB is expected to further enhance users’ experiences and enable high quality voice services on their LTE-based smart phones, through CSFB to GSM and UMTS.

The joint CSFB testing was part of an ongoing cooperation between Huawei and Qualcomm on interoperability testing and optimization involving GSM/UMTS/LTE TDD/FDD technologies.

Source:  August 06, 2012


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