GSM and LTE, 2 technologies in 1 base station

LTE for bandwidth and GSM for voice are a match made in heaven for subscribers. The roll-out however, not so much. Running them both from the same radio equipment (BTS) can be the answer. SatSite can run both YateBTS (GSM) and YateENB (LTE) at the same time, in the same spectrum, using the same radio hardware.

Software-defined BTS

This is made possible by replacing commonly used FPGA and DSP boards with one Intel Atom chipset. Both the GSM YateBTS and the LTE YateENB are modules implemented in software, allowing the base station to be reprogrammed or reconfigured to support new protocols. A base station can run GSM at first, and can be later software-upgradeable to LTE, running multiple air interface protocols using the same radio, at the same time.

Mixed 2G/4G spectrum allocation

From a spectrum point of view, as seen in the image below, the mixed GSM/LTE technology enables a base station to be software-configurable for up to 4-TRX/ARFCN. A base station can use the 850, 900, 1800, and 1900 MhZ bands for both GSM and LTE, meaning that it will allocate two ARFCN to GSM and will use the remaining spectrum for LTE.

ss_mix_spectr_2015-10-6_pic1_version1.1Based on the subscribers’ activity (data vs. voice), operators can assign in software the spectrum priority for either LTE or GSM, so LTE gets a higher priority if there is a lower use of voice services. This optimizes the resources allocation in the network and supplies better access to users.

YateBTS and YateENB – Yate modules

Yate is an underlying part of the software architecture of our mixed 2G/4G RAN. It has a highly expandable architecture that provides unified management and monitoring. Both YateBTS and YateENB are software modules based on Yate. Yate’s SDR architecture enables the LTE and the GSM modules to use the same radio hardware. You can find out more about Yate’s multiple modules here.

ss_mix_spectr_2015-10-6_pic2_version1.1Yate’s SDR architecture also enabled us to replace the conventional, special purpose equipment combination of a baseband unit (BBU) + a remote radio unit (RRU), with a single unit. With this technology we implemented all the functions of both a conventional base station and a base station controller, eliminating the costly Abis interface for traffic and signaling, as well as partial functions of an Mobile Switching Center (MSC), in terms of mobility, power and frequency management and handover.

The mixed 2G/4G RAN technology is embodied in our SatSite base station. SatSite acts more like a conventional eNodeB, even when running on GSM, because it uses IP backhaul for both 2G and 4G. It also contains the IP list of all neighboring SatSite units.

Using off-the-shelf hardware and a generic operating system, SatSite embraces everything SDR stands for, and is the solution for an easy adoption of new standards or technologies, even 5G in the future.

A forecast on the evolution of radio access networks

This month we participated at an active antenna workshop in Warsaw. The event was well attended by many RAN managers, strategists and planners from various mobile operators around the world. There were also a large number of radio head and eNodeB, antenna, semiconductors and materials and test equipment vendors.

Crowded towers

There was a lot of talk about crowded towers. The majority of towers are already very crowded and at their mechanical limits. Because new equipment cannot be added, often times the only solution is that of replacing existing equipment with new antennas and radios. Since everyone in the industry wants ‘cleaner’, less crowded towers, the experts found that radio equipment capable of running on both GSM and LTE would help reduce the overall load on cell site towers.


3G sunset

Within this workshop quite a few of our beliefs regarding the future of the UMTS have been confirmed:

  • In a number of markets UMTS 3G will be discontinued, while 2G will continue to stay, allowing for 2G/4G mixed networks to flourish.
  • While 2G spectrum allocation will diminish in time, GSM will still be alive and well for a while.
  • In many markets, UMTS 3G spectrum is already re-farmed for 4G LTE.

Massive MIMO?

As the workshop’s theme was the evolution of active antennas, a lot of the conversation revolved around MIMO technology and MIMO antennas. The 2×2 MIMO configuration is becoming a standard for mobile networks, and 4×2 MIMO is expected to become the standard in two to three years. There is little prospect in the industry for LTE devices to support more than 2 MIMO channels, meaning that the most practical MIMO configuration is the Nx2 variety. One of the most important current issues is that many LTE devices still don’t support MIMO.

Vertical sectorization

In terms of vertical sectorization, the consensus is that it can be useful only when combined with fast-responding self-organizing networks (SON). Vertical sectorization is only efficient when used throughout the whole network, and no just in a few cell sites. However, vertical sectorization will be obsolete once most LTE devices will support MIMO.

VoLTE perspectives from the RAN side

RAN experts present at the workshop discussed VoLTE’s slow adoption. One reason for this is that for any given cell site, the service range for VoLTE is typically smaller than that for UMTS’ or GSM’s circuit-switched service. It’s range is also limited by the overall uplink performance. However, MIMO antennas are expected to improve VoLTE’s uplink performance.


It was a pleasure to meet with so many representatives from both operators and vendors and hear their insights. To answer to the current needs of the industry, we developed combined 2G/4G software-defined radio systems. Our SatSite macro base station will support GSM and LTE independently, as well as at the same time, using a common radio access. This event was a confirmation that we are on the right track, as mixed 2G/4G networks are the future of mobile networks.

SDN and beyond

Software-defined networking (SDN) and network function virtualization (NFV) are new approaches to designing and operating mobile networks, granting operators better management possibilities and better use of the network capabilities.

NFV represents the virtualization of network nodes roles, which culminates in separate software implementations performing the functions typically executed by hardware components. At the other end, SDN uses the virtualisation technology to split the control plane (where you need flexibility) from the data plane (where you need speed/performance). However, the price for this is complexity which translates into high operation costs.

Operators benefit from such frameworks because they increase the network capacity and performance, and allow for better manageability.

The YateUCN approach recognizes the usefulness of separating the user plane and the data plane, but it implements both of them in software. The control plane is implemented in the user space for flexibility while the user plane in the kernel space for speed.

As a result, operators who deploy YateUCN networks will gain from considerably scaling down equipment, and will have better control over the network scalability and performance requirements. The image below shows the YateUCN implementation and a common SDN deployment using an OpenFlow switch.

Unified Core Network vs. Common SDN deployment

Common NFV/SDN implementations rely on virtualizing the EPC, so that the functions of the MME (Mobility Management Entity), the SGW (Serving Gateway), and the PGW (Packet Data Network Gateway) are each implemented in software and run on the same hardware. Drawbacks of this approach include:

  • the separation between the control and user plane is achieved by means of a switch, usually hardware-based and external to the network. This is a limitation of software-defined network functions;
  • the switch is designed to replace the PGW and obtain the IP connection which it sends to the eNodeB over the user plane. This means that it must support both GTP protocol for the user plane and IP which determines the high costs for such equipment.
  • the complexity of NFV requires additional effort from the network to accommodate it, which increases the overall cost of the solution.

The implementation of YateUCN differs significantly from the above.

First, it uses commodity hardware, so no special-purpose equipment needs is needed. Simply put, YateUCN is a COTS server, which completely diminishes investment, staff, space, and power requirements.

Secondly, YateUCN differs from virtualized EPC because it implements a unique software, based on Yate, that performs all functions of the MME, SGW, and PGW. All-software implementation also means that multiple protocols (Diameter, SS7) are equally implemented in YateUCN, and no additional implementations are required for the core to connect to the Home Subscriber Server or IMS. This helps operators cut down on highly specialized staff needs and facilitates inter-working with legacy networks.

Thirdly, instead of using a hardware switch, YateUCN implements it in the Yate kernel. Because the Unified Core Network is based on Yate, an expandable Linux-based telephony engine, it was possible to integrate a software switch in the core software, allowing for much faster data processing and eliminating the need to work with multiple vendors.

YateUCN core network solution removes the barriers of entering the market due to simplicity, scalability and low cost. YateUCN specifications features and specifications list can be accessed here.

Definition: MIMO

LTE brought forth a variety of equipment and technologies. One of these new technologies is Multiple Input Multiple Output, also known as MIMO. It allows the use of use of multiple antennas in wireless communications is one of the main reasons why LTE has such high bandwidth rates.

It all started with the V-BLAST (Vertical-Bell Laboratories Layered Space-Time) project, in 1996, which is, in fact, at the basis of MIMO systems. V-BLAST was a detection algorithm of multiple signals whose main purpose was to reconstruct the multiple received signals into a single, faster stream of transmitted data. This, of course, is precisely why MIMO does.

The principal application of this technology is embodied in MIMO antennas, particularly used in LTE mobile networks. As opposed to SISO (Single Input and Single Output) – an antenna system with one transmitter and one receiver – two 2×2 MIMO antenna systems will use 2 transmitters and 2 receivers to generate 4 paths for transmitting and receiving different data at the same time. The two transmitters send different parts of the same data stream simultaneously, while the receivers have to piece them back together. MIMO increases overall performance and range and is able to send more data without additional power or added bandwidth requirements.

mimo_antenna_2015-9-3_version1.2Typically, radio signals traveling through the air are prone to being affected by various phenomena such as: fading, interference, path loss and more. What’s special about MIMO is that it does wonders in multipath environments, increasing the data throughput and lowering the bit error rate. MIMO is able to identify one signal from another at the receiver side because they have been altered differently by multipath. The receivers can spot the ‘clues’ that multipath left behind to correctly decode the received signals into a single faster data stream. As opposed to MIMO, SISO systems perform poorly in multipath conditions. Considering that LTE has gained such momentum in urban ares, the home ground of multipath, it’s easy to understand why 4G uses MIMO antennas.

As mentioned above, a 2×2 MIMO antenna will send each data stream through two independent channels to overcome fading. This is a concept called ‘diversity’ and it ensures that at least one data stream will be less affected by fading, increasing the chances of the receiver to decode more data correctly. ‘Polarization diversity’ is a ‘diversity flavor and is also used in MIMO systems. To give a simple example, polarization diversity would translate in using antenna pairs polarized orthogonally, either in a vertical/horizontal position or slanted at ± 45º. 

To sum up, the MIMO technology used in LTE antenna systems increases overall data throughput, reduces co-channel interference and multipath propagation effects, improves the signal to noise ratio and reduces the bit error rate.

2G networks, to sunset or not to sunset

In recent years, network operators have faced an impressive rise in smartphone numbers, which, in turn, lead to a higher demand of packet-data. A 2015 Cisco report indicated that in 2014 alone mobile data traffic increased with 69% from the previous year. Many mobile carriers have already devised what they call ‘sunset plans’. While things might be a bit easier for subscribers, the situation is more urgent and concerning for M2M and IoT devices. The same Cisco report showed that in 2014 62% of all these intelligent devices were connected to 2G networks.

This is precisely the circumstance in which, in 2012, AT&T announced its decision to discontinue its 2G network to reuse the 850 MHz and 1900MHz spectrum for its 3G and 4G deployments.

However, AT&T is not the only operator in this situation. In Singapore, for example, all the nation’s operators (M1, SingTel  and StarHub)  will no longer provide 2G services by the end of 2016. From the 15 of September 2015 mobile dealers will stop registering 2G-only mobile devices. Similarly, the 2G spectrum will be reused for 3G and 4G services.

Telstra, the Australian carrier, has the same 2G decommissioning deadline as the operators mentioned above, since sales on 2G devices have dropped dramatically and 2G data traffic represents less than 1% of the network’s whole traffic.

It’s easy to see why some operators chose to discontinue their 2G deployments, yet these are still the best networks to provide for low-power IoT devices. To them it is old, very few subscribers are based solely in these networks and current data traffic rates demand for spectrum reuse. However, 2G is far from being obsolete. Telematics applications, smart meters, sensors, credit card transaction processors and the IoT lot demand low-bandwidth connectivity.  IoT needs an inexpensive, ubiquitous and consistent network and 2G is still the most suited technology for it.

2g_iotTherefore, the accelerated growth of intelligent connected devices will bring all the more revenues to mobile operators in the future. Early adopters of M2M and IoT technologies represent the group who will be affect the most by a potential sunset of 2G networks. Migrating their devices to 3G or 4G will be costly and time consuming. What’s more, the IoT business operating in rural areas will scramble to find viable connectivity solutions because 2G is still the most reliable technology in isolated and remote areas.

Furthermore, there are still mobile operators in the Western countries who can’t seem to get enough of their 2G networks. Take operators like EE, Vodafone, O2 and 3 in the UK; these carries are set to keep their 2G deployments up and running as long as there are still plenty of isolated areas which are solely covered by the reliable second generation technology. Ensuring an almost total coverage in the British Isles is only possible with 2G networks. Not to mention the cases in urban areas in which subscribers performing voice calls are moved to 2G when 3G data traffic is more demanding.

An Ovum 2015 report states that in some markets 3G networks are in fact more likely to shut down before 2G ones. Nicole McCormick, a senior analyst at Ovum concluded that: “2G is still an important source of revenue. LTE provides a better mobile broadband experience than 3G, and with VoLTE, LTE can handle the voice responsibilities of 3G. This points to the possibility that operators opt to close their 3G networks before they close 2G.” A relevant example pointing to this line of reasoning is Telenor Norway who decided to safeguard its 2G network for their M2M market and who will discontinue its 3G network by 2020.

It’s safe to assume 2G is here to stay because the world still needs it. From communities in developing countries to the whole IoT and M2M market, there isn’t quite any other communications technology like it.

Connecting public transport to the Internet of Things

Matched with contextual traffic data, information about the route and changing traffic conditions can be supplied in real time, so that both passengers and companies improve their planning efficiency.

Offering seamless and highly mobile IoT requires high bandwidth and thus only makes few applications practical.

Real-time location tracking is probably among the most common. Companies already use GPS to track their assets, but the data could also be used to offer riders accurate information about the time to destination, estimated arrival times, or traffic events.

On board entertainment systems offer a more personalized travel experience; location information combined with events information can drive travellers to activities or sites relevant to their itinerary and preferences.

In terms of planning, cameras and sensors installed in public transportation means and in their surrounding premises can collect information to estimate traffic flows and better plan and allocate their resources.

Safety can be improved with live video streaming, allowing a more rapid intervention and enabling the prevention of misconduct.

To make these solutions possible, it is essential to provide high bandwidth connectivity, and that is in itself a challenge. Even with Access Points installed in vehicles, resources from the mobile network still need to be accessed. Technology try-outs in this sense include LTE-A carrier aggregation to increase the bandwidth (as discussed here), MIMO systems to enhance spectral efficiency, or small cell technology to bring the radio cell closer to the device.

Alongside, connectivity on-the-go needs to be managed at carrier level in the sense of providing seamless coverage irrespective of the mobile operator. As this 2014 EU report underlines, ubiquitous connectivity for public transport requires ‘terminals to get connected regardless of the operator exploiting the access network’, and ‘avoid services cut-offs’. Tower infrastructure sharing is the solution adopted today, and it is particularly viable because it also allows to reduce their operating costs and provide additional capacity, reports the GSMA.

Internet of Things applications have already started to enable some of these trends in large metropolitan areas all over the world. Transport companies, mobile operators, and platform providers can leverage IoT solutions for real-time tracking and monitoring, improved efficiency and safety, and a better travel experience.

Predictions about numbers of IoT/M2M connected devices that we’re supposed to be seeing in the very near future are astounding. So we can only imagine what the huge amounts of data collected will lead to once it’s analyzed and turned into ‘actionable’ information.

A snapshot of SS7ware at IoT Evolution Expo in Las Vegas

SS7ware was at IoT Evolution Expo in Las Vegas last week – if you haven’t been around to see us, here’s a recap of the most important events.

It was great to see so many companies, including manufacturers, mobile operators, M2M platform companies, developers, service providers, gathered to discuss innovation, management, and security in the M2M and IoT ecosystem.

Through 4 days of keynote presentations, panel discussions, exhibitor booths, live demos, and case studies, we also had a lot on our plates, as you can see in the gallery below.

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CEO Diana Cionoiu was invited to take part in the ‘Carrier Aggregation for Public Transport’ panel which took place Wednesday, discussing the possibilities to create a new experience for public transportation using the bandwidth capabilities in LTE and LTE-Advanced.

SS7ware also made it to the AT&T Fast Pitch finals, where we could talk about our software-defined mobile network solution among a variety of other innovative ideas bringing IoT to both businesses and individuals. Two interviews for the TMC team for their website, and a live SatSite demo were also on our list. Everyone around the Exhibit Hall on Tuesday had the chance to watch devices connected to SatSite work seamlessly. We simply plugged it in to make a GSM phone call between the two registered devices; all in the blink of an eye.

To wrap up, thanks to the TMC team for doing an amazing job organizing the event! Here are some take-aways to keep us focused on IoT/M2M developments in the near future:

  • when it comes to connecting the home, security is of utmost importance
  • connecting ‘everything’ comes with increased responsibility and safety challenges
  • new players like Google, Amazon, or Facebook are reshaping the ecosystem
  • who does what in the new business environment

For more content, don’t forget to follow us on Twitter, Facebook, and LinkedIn.

Driving the Internet of Things with carrier aggregation

Internet of Things connectivity must reach a middle ground between coverage and bandwidth to provide for applications with very different requirements.

While it’s true that tracking, measurement, control, or monitoring systems in rural or remote areas have lower traffic and rely on low-bandwidth technologies such as GSM, a different trend is growing. A whole range of M2M and IoT applications using live video, rich media, on-the-go content, multi-user sharing, demand a high network capacity that can be provided today with LTE.

Carrier aggregation (CA), the key concept in LTE-Advanced, allows operators to supply even higher bandwidth than LTE, to support such connected devices. As its name suggests, carrier aggregation combines two or more carriers in order to offer a greater throughput.

Using CA, new transmission channels can be created using the operators’ existing frequency spectrum. It is available in both TDD and FDD systems, and can be achieved by combining carriers from the same frequency band or from different frequency bands, as shown below.

Capacity is essential for IoT, as hundreds of devices are in constant communication with the network. In CA systems, up to 100 MHz bandwidth can be reached, as each component carrier can have a maximum bandwidth of 20 MHz, and a maximum of 5 carriers could be aggregated. In practice though only two carriers have been used so far.

Operators may also opt to combine carriers from different spectrum bands, as some are already reported to be doing, and this can be very practical given that LTE networks are currently being deployed on distinct frequency bands.

For carrier aggregation to work on both ends, devices must be able to detect and read the multiple frequencies sent by the radio network. In theory, a peak speed of 500Mbps for uplink and 1Gbps for downlink could be achieved with carrier aggregation.

In commercial deployments so far, as reported recently by the GSA, a maximum downlink 300Mbps has been achieved on a number of devices including smartphones and mobile hotspots. According to the same report, only 88 commercial implementations of carrier aggregation systems have been launched so far in 45 countries, but others are underway.

Carrier aggregation can be used to offer increased bandwidth for IoT, and it can also improve coverage by combining low frequency carriers with high frequency ones. Trade-offs of this system include battery life, but we’ll talk more about LTE for IoT next week during IoT Evolution Expo.

Meet us at IoT Evolution Expo!

Here’s your chance to meet us – we’ll be at IoT Evolution Expo in Las Vegas, August 17 to 20! We’ll be there throughout the event showcasing a live product demo and we’re participating in the ‘Carrier Aggregation for Public Transport’ panel on Wednesday, August 19, starting at 2:30 pm.

Complete software-defined network for IoT coverage

During the panel, we’ll talk more about SatSite as an IoT solution for public transport. In cities, LTE is an exciting opportunity for connecting new business sectors and new activities. Devices and sensors using real-time data can provide more relevant contextual information to help make faster, better decisions. LTE IoT coverage can reshape the way we think and act towards our homes, healthcare, transportation, or security.

Our solution for connected transportation, LTE SatSite, enables deployments with lower costs, resilient infrastructure, and high capacity.

The lightweight, low-power base station can be easily installed in public access areas (such as buses or crossroads), allowing:

  • seamless 4G customer experience anytime
  • smart traffic and passenger management
  • emergency management and transport security

Join us at IoT Evolution Expo, tune in to our Youtube channel, and follow us on Twitter and Facebook. More about the speaker: follow Diana Cionoiu on LinkedIn.

The challenges behind VoLTE

In previous blog posts and demos we showed that a simplified approach is the way to obtain clear results in deploying VoLTE and 2G/4G mixed networks. We performed the industry’s first VoLTE call from a GSM mobile phone to an iPhone 6, through a single unified core network, the YateUCN, and we presented our solution for handling SRVCC (Single Radio Voice Call Continuity) as an inter-MSC (Mobile Switching Center) handover from 4G to 2G in the same YateUCN. Follow our take on why VoLTE hasn’t developed as rapidly as we all expected it would. We’ll give our insight and what we’ve learned from the many discussion we’ve had with mobile operators and smartphone producers alike.

Sure, VoLTE is great! Combining the powers of IMS and LTE, VoLTE offers excellent high-definition voice calls. It also guarantees a Quality of Service component, ensuring that customers get an unprecedented quality of voice services. However, VoLTE depends on far too many aspects to be fully functional and widely deployed, contrary to what optimistic reports have predicted in the past.


One of the main issues operators and customers alike are facing is the fact that there’s still a shortage of VoLTE capable smartphones. By April 2015 Verizon offered around 15 devices supporting VoLTE, while AT&T’s smartphone selection included around 19 devices capable of HD voice, in July 2015, as seen on their online shop. iPhone6 is still the only device capable of supporting VoLTE for all the operators that offer it. What’s more, most of these devices came from about 5 smartphone vendors, giving customers a limited choice when they buy a new phone.

Approximately 97% of VoLTE capable smartphones have their LTE chipset from the same vendor. According to reports from smartphone producers and operators alike, the VoLTE client is not stable enough, this being the reason why some vendors don’t even activate VoLTE in the baseband, and also why operators implement VoLTE in both the smartphones and the IMS network itself differently.

This also leads to the lack of interoperability between mobile carriers. Currently, VoLTE works only between devices belonging to the same network: for example, a T-Mobile customer using a VoLTE capable handset cannot roam in the AT&T VoLTE network of a called party. However, this was one of the main goals when VoLTE specifications were developed and we should still expect it to happen at some point.

Lastly, and perhaps most importantly, VoLTE deployments are scarce. A GSA report from July 2015 showed that only 25 operators have commercially launched VoLTE networks in 16 countries, while there are around 103 operators in 49 countries who are planning, trialling or deploying VoLTE. Compared with the total of 422 LTE networks commercially launched in 143 countries, VoLTE deployments are dramatically lower. This is the result of mobile carriers having a difficult time planing and building functional LTE and VoLTE networks, while also developing the essential Single Radio Voice Call Continuity (SRVCC) technology in an effective and performable way.

VoLTE still needs to leap over many hurdles until it becomes a technology used world wide. Operators, network equipment vendors, smartphones and chipset producers need to cooperate and jointly find technical solutions that will allow for a more swift VoLTE roll-out in most LTE networks.