WIRELESS NETWORKS
Ensuring QoE with end-to-end network visibility Deploying LTE By Vikas Arora, Chief Technical Offi cer, EXFO
Long-term evolution (LTE) promises a range of benefi ts to cellular networks, including increased fl exibility, effi ciency and cost savings. However, to reach these benefi ts, operators must overcome a series of potential challenges, including ensuring performance, service delivery, and ultimately, providing the quality of experience (QoE) that today’s consumers expect. There is also the need to support older 2G and 3G networks alongside LTE as consumers gradually migrate to new technologies. Ericsson estimates that by 2015 there
Long-term evolution could be the solution to expanding users, devices and packet user-plane traffi c on mobile networks. Vikas Arora considers quality of experience when deploying LTE.
will be 3.5 billion mobile broadband users, a growth which operators must meet. However, with intense competition and rising customer expectations, operators must also deliver wireless services that rival the fi xed-line experience. To ensure that migration to LTE takes place without disrupting QoE, operators need to adopt more granular test and measurement processes.
LTE Network Challenges There are a number of key challenges that operators have to overcome: All-IP networks require new interfaces and protocols; delivering a fi xed-like experience runs the risk of impacting QoE; there is a lack of radio network controls; and they must work alongside and interoperate with 2G and 3G networks. Let’s examine each challenge in more detail:
• All-IP networks require new interfaces and protocols. AII-IP networks are a different undertaking for mobile operators. While with ‘circuit-switched’ universal mobile telecommunication system (UMTS) networks they could both test and ensure performance with a simple bit-error-rate test (BERT) across the network, this approach has become redundant now as operators are turning to packet-switched architectures.
• The challenge of delivering a fi xed-like experience has high stakes as any drop in quality of service (QoS) or experience (QoE) could result in customer churn. Today’s consumers are more willing to change providers than they once were with QoE often being primary driver
20 NETCOMMS europe Volume II Issue 3 2012
for this churn. However, delivering service levels required for seamless provision of applications is complex, with application usage displaying peaks and troughs over time as well as across the network. For example, requests for the latest YouTube video might be higher in the evening, and Skype requests might peak during the working day, meaning that testing needs to be at a very granular level.
• One of the most striking features of the new architecture is the shift of radio network controls in the LTE network. Radio link control (RLC) and radio resource control (RRC) messages traditionally provide information relating to specifi c network operations.
• Another aspect of LTE deployments is the need for smaller cell sizes. One approach to build smaller cells is to centralise baseband units (BBU) while distributing radio units (RU) that are closer to antenna masts.
• Although rollouts are happening fast and in large numbers, LTE networks are still relatively rare, so in reality, they must work alongside and interoperate with 2G and 3G networks. Ensuring that the interoperability issues are minimized requires comprehensive end-to-end testing across the frequency bands used in the different regions.
• There are four main stages to identify what is really happening across the network: R&D and systems testing, rollout of LTE, LTE service assurance, and maintenance and troubleshooting.
R&D and Systems Testing The R&D and systems testing phases require a variety fl ows and sessions, and this data allows for more checks to ensure that the infrastructure is fi t for the purpose. For example, vendors and operators must verify functionality, run load tests and confi rm interoperability capabilities before rollout. When next- generation, high-capacity switches, routers, security gateways, session border controls and radio access nodes are launched, simulators and load generators will need to have been in action in order to fully exercise them with more capacity than they can handle.
LTE Service Assurance LTE service assurance relies on systems that can measure the QoS parameters for specifi c applications from any LTE interface. By holding and analysing this data, operators can be proactive in dealing with ever-changing network demands, enabling more effi cient allocation of resources. LTE user- plane sessions and fl ow analysis are essential for exploring the network traffi c in converged IP-based networks. Individual IP fl ows must be assessed to fi nd source and destination IP addresses, ports, protocols, locations and origins, throughput and the amount of transferred data values also in tunneled fl ows. Producing charts for top talkers, transmission and application protocols assist in the identifi cation of events across the network.
Maintenance Maintenance and troubleshooting occurs as and when anomalies are detected during monitoring. The real- time actionable information provided by an end-to-end, applications-focused approach allows performance metrics tests to be launched from a centralised test device to the performance endpoint, allowing for quicker isolation of potential problems and improving the mean time-to-repair (MTTR) via network segmentation. If monitoring is unable to identify the
fault, the portable test equipment used in earlier stages of the LTE lifecycle can fi nd hard-to-diagnose problems. To succeed at this stage, operators should have the ability to troubleshoot without affecting service and perform maintenance, while minimising truck rolls.
Conclusion With LTE network rollout beginning to gather momentum, effectively testing and measuring the network is critical. It is the only way that network operators can remain competitive. With customer expectations always on the increase, operators must ensure a problem-free rollout of new mobile technologies. By doing so, they can expect to reduce churn and increase their revenues.
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