YateUCN – the redundant MSC/VLR

Traditionally, the redundancy of the Mobile Switching Center / Visitor Location Register (MSC/VLR) is obtained through redundant dedicated hardware and software. The problem lies in the Abis + A interfaces (BSSAP protocol) which do not allow a base station to move easily to another MSC/VLR. To overcome this problem, we decided to use the SIP protocol (with enhanced features for GSM operations), which allows a YateBTS SatSite base station to move to another YateUCN (MSC/VLR) automatically and quickly.

Redundant GSM MSC/VLR

In a GSM network deployed with YateBTS-based SatSite base stations and YateUCN core network servers, each subscriber is randomly assigned to a YateUCN from a pool of core network servers. Operators can increase the redundancy of the pool by simply adding additional YateUCN servers for excess capacity in case a unit malfunctions. Therefore, handsets connected to a single SatSite can be served by multiple identical YateUCNs, while, at the same time, a single YateUCN serves multiple SatSite units. If a YateUCN server fails, all the mobile devices served by it are automatically moved to the other available YateUCN servers. When the subscriber is registered to the new YateUCN, its location is updated in the HLR.

In short, YateUCN and the GSM YateBTS SatSite base stations form a many-to-many relationship, and this was made possible though a number of characteristics.

  • The GSM YateBTS SatSite implements all the functions of a conventional Base Station Controller (BSC).
  • The A interface (between the BSC and the MSC/VLR) was replaced with SIP (between YateBTS and YateUCN), making it possible to quickly re-associate handsets with different YateUCN servers.
  • All YateUCN servers are identical units that support many core network functions. Operators will only have to duplicate one component, as opposed to multiple in conventional networks.
  • YateUCN is implemented in commodity hardware (off-the-shelf servers) and software (Linux), delivering a shorter lead time, more servicing options and faster replacement time.

The diagram below illustrates the technology perfectly.


Integration in an LTE core network

The SatSite and the YateUCN components are easy to integrate into existing LTE networks because 2G services are delivered in SIP. These GSM services are integrated into a 4G network by employing the same GTP and IMS interfaces that are typically used in conventional EPC/IMS core networks.

YateUCN implements the same SIP switch to both provide GSM services and connect to an existing IMS network. Thus, with both the SIP-powered RAN and core network products, operators’ migration from GSM to LTE turns into a much simpler process.

Integration in a GSM core network

As an MSC/VLR, YateUCN performs all the functions of other MSC/VLRs: mobility, authentication, speech call and SMS routing. The server supports authentication of handsets using the SIM/USIM (EAP-SIM/EAP-AKA) and SIP AKAv1-MD5 algorithms.

YateUCN can connect to any standard HLR via the SS7 MAP protocol, and to other MSCs and GMSCs through the MAP-E protocol, allowing it to be in any conventional GSM network.

A few final words

YateUCN brings something new to GSM equipment: affordable redundancy, scalability, and uncomplicated management into a single core network server. It is easy to integrate to existing GSM and LTE networks and can be easily upgraded with new features within the same hardware and allows operators a seamless network extension.

Modernizing GSM networks – an ever difficult feat

GSM has turned 24 this year and throughout this time showed that it is invaluable for telephone calls and M2M applications. Many industry observers estimate that 2G will continue to be in use even after 3G is discontinued. But GSM networks are confronted with the difficult task of adapting to the new operating environments.

The modernization of GSM is particularly arduous when considering that equipment vendors and solutions providers have concentrated on developing components for newer networks (3G, 4G, even 5G) and less on innovating GSM network components. The SatSite is designed to serve either GSM, LTE, or mixed GSM/LTE networks working directly with the unified core YateUCN, proving that there’s still plenty of room for innovative results for GSM deployments.

The technology behind our GSM network equipment allows new techniques like radio resource sharing with LTE, running GSM from a remote radio head, applying SON or beamforming technologies, which are typical for LTE, to be applied to 2G networks. The result is a simplified and flexible network architecture, better management and reduced costs.

Spectrum sharing
The SatSite base station is based on commodity, off-the shelf,-hardware and can be software-‘switched’ to provide either GSM, LTE, or both. When running YateBTS for GSM, it communicates directly with the unified core network, eliminating the base station controller (BSC). This architecture, where the BTS connects straight to the core network and communicates to other BTS in the network over peering protocols is very similar to the architecture of LTE.

This is also what makes it possible to support multiple technologies in the same equipment. If one BTS uses the same frequency bands to provide both GSM and LTE access, operators may choose freely on how to allocate spectrum between them. Depending on the service use at a given time, operators can assign prioritize voice over data services and vice versa. We’ve detailed spectrum sharing between GSM and LTE in the SatSite here.

Self-Organizing Network
SON techniques feature dynamic self-configuration, self-optimization, and self-healing functions, which can be achieved due to the eNodeB not being controlled by a distinct BSC component as in the typical case of GSM. Without a BSC, SatSite base stations are able to connect to each other over peering protocols, allowing an exchange of neighbor information between units. This presentation offers more details on SON technology for mixed 2G/4G networks.

Beamforming relies on grouping the signals of multiple antennas and into one beam sent to a desired direction. It aims to reduce interference and obtain a better quality of a service for a certain user. Unlike MIMO, where the network sends different parts of the data stream on different antennas, beamforming combines the signals from the different antennas and sends them to one device. What’s more, as opposed to MIMO, beamforming does not require any support from the handset, making it suitable for use in any mobile network technology, be it 2G, 3G, 4G or even 5G, in the future.

Benefits of optimizing GSM networks include a better management of the network resources, reduced infrastructure costs and maintenance efforts, and the flexibility to upgrade or reprogram network functions.

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.

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.

The Case for the Unconnected Billions

Sending text messages, going on hour-long calls, or live-streaming videos are such an integral part of our lives that most of us take them for granted. And yet around 3 billion people live, today, in areas without access to basic infrastructure – be it remote islands in the Pacific, developing extra-urban areas, or isolated rural areas everywhere around the world.

Mobile communication can connect these people with one another and with technologies that can prove to be vital. Mobile data enables job seeking in wider area ranges, instantly accessing health care information in case of emergency or risk, or keeping farmers in line with market prices and trends.

In remote, unconnected markets, bringing voice and data coverage can be best achieved using GPRS, which provides wider coverage than 3G, and is easier to adapt to rural, remote, or low density areas. In such places, traditional cellular networks have the disadvantage of being economically counterproductive to deploy, and operators are unlikely to invest in hefty infrastructures that generate relatively little revenue from usage compared to the networks’ lifespan maintenance costs.

The YateBTS technology addresses these issues differently than most other approaches to mobile networks. 2.5G networks using SatSite and YateUCN are a simplified, flexible, and low-cost solution that can be adopted anywhere in the world.

Lightweight, low-power sites

SatSite is smaller than typical base stations which makes it easy to build lightweight cell sites that are especially profitable in higher density networks. SatSite’s low power requirements allow operators to plan self-sustaining mobile networks running on solar or wind energy, avoiding the use of costly power grids or diesel systems.

Bandwidth-efficient backhaul

Unlike traditional networks, a YateBTS/YateUCN mobile network allows bandwidth savings of up to 60%, by using the GTP protocol across the entire network.

bring_cov_2015-6-4_version1.2SatSite acts as a BTS/BSC communicating with the YateUCN core network over GTP, without using any additional network nodes, to simplify the network architecture and minimize the backhaul load. Data sessions in networks using YateBTS SatSite can be established either locally, by assigning the IP directly in the SatSite, or in the YateUCN core network, adapting to the constraints of each location.

SatSite unifies the BTS and the BSC from traditional radio access networks architecture, to eliminate the Abis radio interface used to direct traffic between the BTS and the BSC. In conventional cellular networks, the BSC handling all the communication between the core network and the devices leads to high costs and a substantial load on the network. SatSite base station can communicate with YateUCN over satellite, using GTP to replace the signalling interfaces normally used inside the radio access network and to/from the core network.

A satellite backhaul architecture is adapted particularly to sparse networks in areas with a low density populations, where cell sites are far from the core network; satellite allows operators to serve any location, and improve bandwidth performance for both voice and data services. Combined with the light design and an autonomous operation of the SatSite base station, backhaul over satellite makes YateBTS/YateUCN networks ideal for extending connectivity to uncovered areas.

YateBTS in the age of IoT

These days, everybody’s talking about the Internet of Things. And it’s no surprise that everybody loves it; from operators, who see a chance to attack new markets and better retain customers, to urban consumers who can connect a whole range of devices to an app on their smartphones, and farmers who can use technology to optimize their activities and maximize production.

Bringing IoT to such different audiences while maintaining a high quality of service and an efficient use of network resources is a challenge for most carriers’ current infrastructure capabilities and cost strategies. In fact, a critical concern when it comes to creating IoT infrastructure for new areas is laying the ground for that infrastructure – that is, mobile network coverage.

The number of IoT applications designed for farming and livestock breeding is on the rise, but their actual penetration in rural areas is limited to regions with existing GSM/GPRS infrastructure. Remote and rural areas offer mobile operators enticing prospects not only in terms of IoT coverage, but also in terms of connecting these new customers to their entire range of services such as voice, SMS, or data. But due to the high investment requirements for equipment, civil infrastructure, or maintenance, operators are still reluctant in building mobile networks in there areas.

The success of carriers setting up new networks in remote locations depends greatly on keeping investment and operational costs down, as well as on basing their network equipment choices on redundancy, power efficiency, and flexibility. A reliable IoT infrastructure amounts to operators providing continual service, seamlessly, and in very variable weather and terrain conditions. The geography of each area and the specific needs of communities influence every decision going from civil infrastructure to power supplying and equipment maintenance. In areas with low infrastructure where grid power isn’t available, for instance, carriers must rely on alternative power sources to successfully deploy new networks.


YateBTS-powered IoT applications

A base station like the YateBTS SatSite offers a reliable and flexible solution for carriers to bring mobile coverage to remote rural areas. SatSite is a 2.5G low-power, lightweight base station that allows it to be easily installed anywhere from hill tops to outlying crop fields. Practical for lightweight cell sites, it can be operated in single or three-sector sites using a single solar panel. This generates a substantial reduction in operators’ initial investment costs but also in operating cell sites in the long-run.

SatSite’s low operating costs make it a particularly suitable solution for small farms and rural households, where resources are more scarce and used less efficiently. Access to IoT applications can support these communities in rendering farming activities more productive and sustainable. The flexibility of SatSite’s architecture suits the requirements of specific IoT solutions. Used for any range of applications and devices, from water pumps and soil measurement sensors, to herd tracking and monitoring, SatSite optimizes resource allocation to allow carriers to efficiently adapt their networks to the specific demands of each location.

In rural areas, access to IoT infrastructure can make it possible to attain better farming results, optimize productivity, and increase the overall quality of life. Basic mobile services can create new standards for health care, education, as well as social and economic development of these areas. Operators can play the leading role in this process, provided that their decisions successfully combine cost effectiveness for themselves, and service quality for consumers.