SRVCC made easy

As promised in our last LTE technology post,  we want to tackle a new technology used in voice in 4G: Single Radio Voice Call Continuity. We’ll explain what SRVCC entails and give you an insight into our own approach towards this technology: inter-MSC SRVCC from 4G to 2G.

While most voice traffic in LTE  is provided with CSFB, today the next stage involves using VoLTE and a technology called SRVCC for providing seamless voice continuity from LTE to other 2G/3G networks in areas not covered by LTE.

One of the main issues for LTE for operators is that deployment is spotty and incomplete. Once the big challenge of deploying VoLTE has been achieved, operators have to use SRVCC to offer subscribers continuous voice traffic when they reach an area without LTE coverage.

SRVCC allows for inter-Radio Access Technology handover, while also providing handover between a packet data-only network to a CS network. As the name suggests, SRVCC removes the need for two simultaneous active radios in devices, as required by CSFB, preserving the battery life, and manages to maintain continuous QoS during voice calls which are in progress. SRVCC is also a mandatory technology for maintaining continuity during emergency calls.

Typically, SRVCC enables voice and data handover from LTE to legacy networks and viceversa. To enable SRVCC, operators need to upgrade their legacy MSCs, the LTE RAN and EPC and the IMS network for VoLTE.

We have a different, simpler approach to offer operators: our YateUCNserver handles SRVCC by performing and inter-MSC handover from 4G to 2G. Built to simultaneously be an MME/MSC and the IMS network for VoLTE, YateUCN performs SRVCC without the additional network upgrades (in LTE and 2G) mentioned above.


With YateUCN, the SRVCC handover will be performed as simple as an inter-MSC handover, without the additional investments normally required.

We are committed to innovation and believe in providing software-defined mobile network equipment, designed to cater to both 4G and 2G, while relieving operators from the huge costs of upgrade, maintenance and service. Our resilient and scalable YateUCN embodies this philosophy entirely.

Voice in LTE – CSFB trials and tribulations

As LTE is a packet data-only network, operators use two main solutions to provide voice to their subscribers with LTE devices: VoLTE, which we previously discussed in our blog posts, and Circuit Switched Fallback (CSFB).

CSFB is often seen as a “temporary” solution, until there are enough VoLTE devices on the market, and consists of 4G users being handed over to legacy 2G/3G networks to use voice services. However, CSFB also has major challenges, such as the fact that subscribers can lose their 4G data connectivity after their CSFB call ended. This is also a troublesome aspect for operators with LTE-only networks, as they have roaming agreements with MNOs for voice services over 2G or 3G, and will be forced to pay higher fees once their subscribers don’t return to their 4G networks.

CSFB allows operators with newly created LTE networks to exploit their legacy networks or to use MVNO agreements, and provide voice capabilities without major investments or fundamental changes to their circuit switched (CS) core networks. CSFB moves a subscriber from the LTE core network to the CS core network through the SGs interface during call setup (the SGs interface is added to the LTE architecture and allows mobility management and paging procedures between the MME and the MSC). Normally, one would expect the subscriber will return to the LTE network once the call has ended. The reality, however, is otherwise.

Circuit Switched Fallback

Among CSFB’s main issues, we can name:

  • data traffic suspends during the handover between networks
  • data rates decrease dramatically during the CSFB call’s answer and hang-up moments
  • mobile apps terminate during the CSFB voice call
  • data transfer is suspended during the call if the 2G/3G networks don’t support dual transfer mode
  • most importantly, once the voice call has ended, the subscriber cannot return to the home LTE network, especially in the case of MVNO agreements and not when the operator has both the LTE and CS networks

Studies have shown that behavior patterns such as those listed above depend on the data packet size and the running data packet interval.

Operators with LTE-only networks need to use roaming agreements with other MNOs to enable CSFB. Therefore, they are the ones who will bare the data traffic costs when their subscribers remain stuck in 2G/3G networks, sometimes even for hours.

The main impediment in proposing a solution that will work for all operators and will prevent such problems is that CSFB standards don’t give any insight into how devices are supposed to return to the LTE home network. One solution non-MVNOs typically adopt is to set up rules for the handover back to 4G or for the cell reselection procedure.

Stay tuned for our next blog post in which we’ll cover more on voice solutions for 4G, namely inter-MSC SRVCC from LTE to 2G.

Roaming in LTE – facing challenges with new opportunities

With LTE, operators are now able to offer their subscribers huge bandwidths and significantly improved quality of service, but they also have to face new challenges. LTE drastically changed the mobility architecture and led to the adoption of new interfaces, frequencies, protocols, which ultimately impacted on the state of roaming.

A 2013 Informa report on the market status of LTE Roaming found that most operators hadn’t even finished their roaming strategy. By 2015, operators who deployed LTE networks had data roaming only in a few countries.

Our answer to the LTE roaming dilemma is YateUCN.

So what’s different?

Roaming allows subscribers to use voice and data services when they are abroad. There are two main aspects to keep in mind when discussing roaming:

  • commercial  roaming agreements between operators
  • technical implementation SS7 (Camel/MAP) protocol in the case of 2.5G and 3G networks, and Diameter in 4G networks

Each roaming protocol requires new roaming and interconnect agreements, even with existing partners. Therefore, once an operator deploys a 4G network, it will need new roaming agreements for their LTE subscribers.

Operators who want to add an LTE network will have to face two challenges related to:

  • deploying a network with a radically different infrastructure, including new interfaces and protocols
  • setting up new roaming agreements for Diameter, since LTE roaming requires it

Our solution

YateUCN, our core network solution, allows 4G devices to authenticate to foreign partners over SS7 roaming agreements, to an HLR.

YateUCN is a mixed 2.5G/4G core network server, capable of replacing all the core network equipments associated to both networks, while also using both Camel/MAP and Diameter for roaming.



YateUCN also makes it possible for 4G devices to be registered to a 2.5G network and a 4G network at the same time, if necessary.

With the innovative YateUCN, MNOs will tap the great opportunity LTE roaming is, while also using the standing roaming agreements with their partners. Operators will gain time to set up the right agreements, and at the same time will garner new revenues by encouraging their customers to use data roaming.

Off to greener networks

Going green is not just good for the environment, it’s also good for mobile operators.

It is common knowledge that the share of energy drives the largest costs in mobile network deployments – about 50% of the total OPEX in emerging markets. While diesel power systems play a large part in the high level of expenditure, according to a 2014 GSMA Green Power for Mobile report, they account today for nearly 90% of power solutions used in off-grid and unreliable grid sites.

Operational fuel costs, logistics (transportation, depositing), diesel pilferage – which alone increases costs with about 15%-20%, the need for continual service in areas where power outages are frequent, all add up to operators’ investment and operational expenditure, reflecting eventually in a higher service cost for users and therefore in a drop in use of mobile services.

green power SatSite

60% of the overall network infrastructure costs is attributable to building and powering cell towers [1], so saving on energy requires the choice of equipment that uses makes a more efficient use of power resources.

Deploying cell sites using green energy is easy when using a base station like SatSite, which requires a low power input (45W) and is ideal for installing in remote areas with unstable or no electrical grids. Cell towers using SatSite in either single or 3-sector configuration are a lightweight deployment which allows it to serve isolated or remote locations, relying only on the existing natural resources.

SatSite’s design differentiates from that of traditional base station by integrating a passive cooling system that makes its use independent from air conditioning or ventilation units. The power required for air conditioning makes up for a large part of the overall input needed to run operate a site. Eliminating air conditioning also frees up space to make cell towers more resilient.

Over diesel power systems, solar panels and wind turbines, for example, have a much longer life expectancy, that can range to 20-25 years. Combined with diesel power in hybrid energy systems, operators can achieve a longer and more reliable operation of cell towers, driving down fuel costs to save more than $10 billion annually.

Shifting to green towers has major implications. First, it reduces operators’ costs and allows them to extend mobile networks in places in areas that are completely deprived of coverage due to the lack of an adequate infrastructure. Then, it reduces the negative effects on environment; GSMA reports that an off-grid site in Africa has an average annual consumption of 13,000 litres of diesel, adding as much as 35 tons of CO2 emissions to the environment.

If they choose green energy for telecom towers in remote areas, operators must move to smaller, more autonomous cell sites; profitability will come not only from power savings and a rise in service use, but also from reshaping the overall network infrastructure to better manage power factors.


[1] Telecom infrastructure sharing, (last visited June 10, 2015).

Off-grid technologies for sustainable mobile network deployments

Energy costs amount to 15% up to 50% of the total OPEX of deploying mobile networks in areas without power grid. Operators in developing countries, as those in the Sub-Saharan Africa region, need cost-effective solutions to face this issue, otherwise they will find it impossible to install new networks.

When we first heard about Tesla’s latest innovation we were impressed. It seemed the perfect solution for what households need right now. But then we gave it more thought and realized that Powerwall batteries are also an answer for mobile operators. We now know they would make a great match with our SatSite base stations.

Depending on the type of deployment, cell sites equipped with SatSite units have the following average consumption levels:

  • lightweight site, with omni antenna – approximately 45 Watts
  • three-sector site – less than 150 Watts
  • three-sector site with tower mounted booster – approximately 350 Watts


A Tesla Powerwall battery offers either 7 or 10 kWh power output, is rechargeable with aid from solar panels and can be mounted indoors and outdoors. It also has a 10 years warranty and requires no additional maintenance costs. A single 7 kWh battery is enough for running 3 SatSite units.

Recent initiatives, like GSMA’s Green Power for Mobile, have stressed the importance of deploying network infrastructures powered by green energy (in most cases solar) in developing areas and regions beyond the electrical grid.

Since both equipments can be powered by solar panels we consider this pairing an easy and seamless solution, particularly in areas where connection to the electricity grid is an issue. It can also successfully replace diesel-powered telecom towers, reducing costs and environmental pollution.

Not only does this solution work well in rural or isolated areas, but it would be a great fit for urban areas in developing nations that have an unreliable power grid. Cell towers equipped with SatSite base stations could use Powerwall batteries as a dependable and renewable backup plan in case of power outage. National blackouts affecting hundreds of millions of people, like those in India (2012), Turkey (2015) or United States (2003), will no longer restrict vital mobile communications if operators choose self-sustaining power alternatives.

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.

What we talk about when we talk about coverage

There are a multitude of factors operators take into account before deploying their networks in order to provide us with the best possible coverage. Since the radio communication of mobile networks is peer-to-peer, the most significant aspect of coverage is that the device sees the mobile mast. To bring some clarity to what coverage means, and how to calculate it, we will introduce: the elements that influence coverage for both operators and their subscribers, coverage planning and our coverage and range estimation tool.

Coverage varies from cell site to cell site, and depends on the type of terrain, the equipment used, the type of buildings around the site, the radio frequency but also, very importantly, on the sensitivity and transmit efficiency of the subscriber’s equipment.

The coverage level also relies heavily on the antenna type or the amplifier power levels. The further you get from the cell site, the weaker the signal gets, as the ground clutter standing in the signal’s way increases. This makes coverage drop exponentially. ground_clutter_2015-3-5_draft1.2.1

Operators can increase the strength of the signal and the coverage, through higher power transmissions, taller antenna masts, a higher antenna gain etc. Antenna gain is, in fact, a crucial factor in getting a broader coverage, as it accounts for the losses and the directivity of an antenna. The relation between the antenna gain and the coverage is directly proportional, i.e. the higher the antenna gain, the more coverage the cell site will deliver.

Network planners use propagation models like Hata, Cost231 or Walfisch-Ikegami, to roughly calculate, in a quantitative manner, what can be expected in a specific environment. They also utilize more accurate tools that take into account the exact type of environment where their cell sites will be deployed, as the Radio Mobile RF propagation simulation software.

We created a tool that uses a very specific coverage propagation model, so do check out how it works with our SatSite. For more information on SatSite’s coverage area, click here.

For mobile subscribers, coverage depends on their devices’ capabilities, since they are not all the same. Also, the coverage level will not be the same if they use their device attached to a car kit, handheld or with an external antenna.

As an important note, always keep in mind that most times, coverage depends on both the device’s ability to “see” the antenna and the antenna’s capability to reach the device.