Extending LTE networks the easy way

We’ve often stated that YateUCN, our unified 2G/4G core network solution, can be used to extend existing LTE networks or upgrade GSM deployments to 4G LTE. And that’s correct. In this post we will take a closer look at how that happens and why YateUCN is more profitable than current solutions for operators moving towards LTE networks.

YateUCN is designed as a unified equipment that replaces all the functions performed by separate hardware components with one software application running on commodity hardware. This has the advantages of reducing the infrastructure costs, minimizing the equipment’s time to market, and increasing network resiliency due to a simplified management of software.

Let’s look at two scenarios where YateUCN can be integrated in existing networks.

Extend 4G LTE networks

For operators looking to increase access to 4G services YateUCN is a flexible, cost-effective solution. It drastically reduces initial equipment investment, allowing them to roll out more networks in a shorter time, to better serve growing consumer needs.

This can be done easily because YateUCN integrates all the LTE-specific functions and protocols, so that it interconnects with any existing operator setup. Every hardware component in the EPC – the MME, SGW, PGW, PCRF, and PCEF – is replaced with software running on a single piece of equipment.

The MME function handles UEs trying to connect to the network. It is responsible for subscriber authentication and uses S6a interface (Diameter) to connect to the operator’s HSS. The MME is also in charge of mobility management, allowing UEs continuous connectivity and active sessions as they move through the network.

YateUCN is fully compatible with any eNodeB, using S1-AP interface to manage inter-MME handover.

The SGW function allows YateUCN to manage data traffic routing over S1-U interface, ensuring communication between the eNodeB and the PGW, which establishes and maintains the IP session. The PGW interconnects with the charging solution of the operator using Diameter and Radius interface, allowing AAA management for wireless access.

The PCRF in YateUCN maintains QoS levels and charging policies, enabling mobile operators to control bandwidth usage while their subscribers are roaming. The Policy and Control Enforcement Function, PCEF, performs policy enforcement and service data flow detection, making sure the data flow through from the PGW is accessible.

The unified nature of YateUCN leads to large equipment savings, and makes it easy to manage the network capacities with a software upgrade.

Upgrade networks to 4G LTE

2G/3G networks can be upgraded to 4G LTE using YateUCN core network and SatSite for the radio network. A new LTE network with YateUCN and YateENB SatSite significantly reduces overall network roll-out costs. SatSite operating on YateENB is an eNodeB communicating with the MME in YateUCN over S1 interface and with any other eNodeB over X2 interface.

Since YateUCN also unifies all the layers of the GSM/GPRS core alongside the EPC, it also acts as an extension of existing 2G networks, achieved at no costs for additional 2G core equipment.

SatSite can run on YateBTS and YateENB at the same time, so each cell will act as a mixed 2G/4G site. As a result, operators can choose to use SatSite in mixed 2G/4G networks, without needing a new 2G core. What’s more, since in 2G mode YateBTS SatSite unifies both the BTS and the BSC layer, it communicates directly with YateUCN core network, using the SIP/GTP protocols.

The MSC contained in YateUCN allows subscribers to be handed over from the YateUCN – SatSite network to the operator’s current 2G deployment in the case of CS services mobility. Subscribers can roam from the YateUCN/SatSite network to any existing MSC serving the roaming area to ensure voice services continuity.

YateUCN can be integrated in any system already deployed by the operator. Used together with SatSite, it serves to build complete 4G LTE or mixed 2G/LTE networks with a low infrastructure and operations investment, ensuring consumers consistent access to both voice and data services.

Rethinking redundancy: a new approach to core networks

Mobile communications must provide uninterrupted mobile service at all times, but the costs to create network redundancy with current conventional equipment are restrictive. YateUCN unified core is a profitable and flexible solution for redundancy in 2G and 4G mobile networks.

Network redundancy ensures that as technology advances, the capacity of network infrastructures to support more subscribers without blackouts adapts accordingly. YateUCN is a unified core network allowing resiliency in 2G/LTE mobile networks using YateBTS and YateENB SatSite. SatSite acts as a BTS/BSC communicating directly with the MSC/VLR/SGSN/GGSN and EPC in YateUCN.

As a software-defined core solution, YateUCN replaces the heavy, expensive core equipment used in conventional networks with smaller, affordable, and easy-to-manage equipment. It is a software implementation of 2G and LTE core network layers, operating on commodity hardware.

yucn_redund_2015-7-16_draft4.2_pic2

In typical networks, redundancy is achieved by supplying an additional core server for any given core server, causing costs to more than double, since supplementary costs for the configuration of back-up servers add up to the capital expenses.

YateUCN implements the core network functions and protocols in software, enabling any other YateUCN node to take over extra-traffic in case of failure of a node, or if the network capacity needs to be increased.

While conventional MSC/VLR in data centers are limited to serving a given number of BSCs in a defined geographical area, in a YateUCN – SatSite network the base station allows a device to connect to any YateUCN node in the network, irrespectively of the geographical location of the device/BTS and of whether the network is 2G or 4G. A list of available YateUCN units is configured in each YateBTS/YateENB SatSite.

Core equipment is usually designed to allocate specific core network functions (authentication, mobility, call setup, data routing) to separate nodes. Such equipment is heavy due to the large number of components, increases lead time, and requires separate back-up equipment for each node.

YateUCN unifies both GSM and LTE core layers, meaning that a single alternate YateUCN server provides full redundancy for any other server in the network. If a failover should occur in a YateUCN node, a device can register to a different YateUCN, remaining attached to the same base station, as shown below.

yucn_redund_2015-7-15_draft4.1

A new YateUCN is chosen from the list of YateUCN units held in the base station. If a mobile device remains connected to the same BTS, registration to the MSC/VLR in the new YateUCN is performed whenever the device communicates with the network to perform an action. Registration to the new YateUCN is updated in the HSS/HLR.

If the device roams to an area served by a different BTS, they will connect to the new SatSite, but will remain connected to the YateUCN currently serving it, and a new query in the HLR is not required. This reduces the load on the HLR and allows it to support a higher subscriber capacity. This can be seen below:

MS connecting to a new YateUCN

MS connecting to a new YateUCN

Increasing traffic to a YateUCN core server is easily performed because YateUCN communicates with 2G base stations using SIP and GTP, and with eNodeBs over SIP/S1AP/GTP. SIP and GTP signalling protocols have the advantage of scalability and interoperability, allowing different service requirements to be served at the same time and with the same quality standards.

Because YateUCN uses commodity hardware, operation and servicing can be managed remotely, with minimal external support, significantly driving operational costs down. YateUCN provides simplicity and cost-effectiveness to building redundancy in mobile networks so that operators can provide high-quality service at all times.

Software-defined radio for frequency reuse in LTE

The expansion of 4G LTE challenges operators who have limited spectrum; as some decide to take down existing 2G (and even 3G) deployments in favor of 4G, bandwidth allocation in an area must be carefully planned to match the quality requirements of LTE.

In 4G LTE, spectrum is a crucial resource. Performance is dependent on the proximity between the radio network and the devices. The closer the radio tower, the higher the data throughput. This means that the more cell towers operators build, the better they can cover the area.

Frequency reuse is a widely adopted solution for LTE; essentially, a given area is served by more cell towers using the same frequency. An easier and more efficient approach to this is software-defined radio.

Cell edge interference management using YateENB

Cell edge interference management using YateENB

Frequency reuse means splitting an area in several new, smaller cells. In LTE, to maintain a high throughput, the same frequency is allocated to all the new cells, at the expense of higher interference at the cell edges. Since all the new cells have equal power, two or more cells meeting causes interference around the cells edges.

Apart from that, building and maintaining additional infrastructure required by frequency reuse results in high capital and operational expenses.

SDR in the LTE base station (eNodeB) can be a solution to these limitations. The fact that SDR implements the communication protocols in software and uses general-purpose hardware has several benefits.

The most important one is the effect on infrastructure costs. Base stations built on special-purpose hardware need heavier equipment and hence larger towers, which are expensive to install and operate. An eNodeB using general purpose hardware relies on more lightweight equipment, meaning that smaller towers can be deployed more densely in an area and provide better coverage. A lower power consumption associated with SDR-based BTS equipment also contributes to reducing the overall RAN costs.

Another major benefit of SDR is flexibility. SDR-based eNodeBs can be configured more easily to manage spectrum use at the edges of the cells, and thus minimize interference. Frequency sub-carriers can be selected at two cell edges in such a way that they do not overlap as in the case of conventional systems.

What’s more, SDR permits an adaptable power management so that different services can be assigned optimal QoS depending on the context.

Another aspect of SDR is the ability to build mixed networks. Base station equipment can be programmed to support different technologies at the same time and using the same hardware, serving more users with virtually no infrastructure investment. You can read more about this topic in this previous blog post.