Feature Article

Test and Measurement Key to LTE Deployment and Operations Success

This article originally appeared in the March 2011 issue of INTERNET TELEPHONY.

Carriers are deploying LTE (News - Alert) to meet the fast-growing demand for always on, always available mobile services.But the introduction of LTE substantially increases the complexity of monitoring and troubleshooting mobile data services.

LTE introduces many new end user devices capable of delivering high-bandwidth services supported by a much more complicated radio and core network in terms of service delivery despite the simplification in structure. Service providers must successfully plan and execute LTE trials and solve the problems that will inevitably occur during deployment. After deployment, service providers must troubleshoot and manage quality of service issues to avoid costly outages while dealing with the high number of test points and large volumes of data that need to be correlated across the LTE network. Efficient LTE test solutions will help service providers manage these issues and meet customer demands in 2011 and beyond.

LTE provides a single global standard that secures and drives higher economies of scale. With the HSPA mobile broadband eco-system in place, LTE is the natural migration choice for GSM/HSPA operators. As a result of collaboration between 3GPP, 3GPP2 and IEEE (News - Alert), there is a roadmap for CDMA operators to evolve to LTE as their clear mobile broadband system of choice. The majority of LTE commitments and deployments are for the paired spectrum (FDD) mode. The LTE TDD mode for unpaired spectrum is complementary and key for several markets. LTE TDD also provides a future-proof evolutionary path for TD-SCDMA, another 3GPP standard. According to a Global mobile Suppliers Association (GSA (News - Alert)) report, 132 operators in 56 countries are investing in LTE and 113 LTE network commitments already have been made in 46 countries. GSA expects that at least 55 LTE networks will be in service by the end of 2012.

Well planned and executed LTE trials are critical to service providers because they help develop the knowledge and experience needed for successful deployment. LTE base stations and core network equipment are deployed as part of these trials to verify functions that are critical for future LTE services. Trials enable service providers to anticipate problems and develop effective coping strategies for issues that do arise. Trials also provide the potential to compare different equipment with the goal of reducing operating costs – a critical consideration when revenue per bit is falling. LTE testing is technically and logistically complex, and incomplete or inaccurate results can mislead as much as inform. Extra preparation during trials can prevent huge headaches and save millions once the network becomes operational.

Fully integrated test platforms that provide on-the-fly measurements from the radio access network to the network core are needed to provide measurements during LTE trials. These tools enable trial teams to replicate services in as many different scenarios and environments as are practical for all relevant standards and on different frequency bands. Testing can verify all functions critical to future LTE services, including data capacity and throughput, network coverage, end-to-end network latency, seamless handover with legacy networks, interoperability of multi-vendor devices and QoS. The latest testing tools support LSTI Field Trial Test Cases, flexible key performance indicators, correlation of user plane and control plane data, interactive measurements with preferred user equipment devices and the latest permutations of LTE standards. The tools need to work for all vendors’ equipment and enable apple-to-apple comparisons. The result is that operators are able to make LTE equipment purchasing decisions on objective criteria.

Centralized data and payload management cut costs and accelerate analysis by providing multiple users with simultaneous access to the same probes from less expensive PC/server systems. Multi-user access increases the productivity of the trial team. With centralized management, one user can make configuration changes while other users need only copy the changes for testing to proceed. Hardware processing that separates control and signaling plane traffic from user payload traffic reduces storage requirements and speeds analysis of the relevant data. Special purpose hardware maximizes efficiency by allocating much of the processing to hardware probes and by removing inessential user plane data while keeping what is important.

The latest generation of tools offers access to multiple air interface data sources as well as air-probe devices. Real-time traffic flow statistics correlate network performance and utilization with the control plane, enabling multi-gbps per user and per service analysis. Carriers can install a 10gbps Ethernet blade that delivers real-time data without packet loss to improve data throughput and take advantage of 10gbps Ethernet deployments. This approach enables real-time delivery of all control plane data in high volume environments and significantly reduces storage requirements.

Leading edge testing tools deliver a comprehensive range of intelligent measurement and analysis applications such as a robust decoding engine that provides bit-level detail to full multi-interface performance and optimization analysis. Call tracing capabilities correlate and track all procedures and functions across each involved interface, enabling full end-to-end analysis that is essential to root cause isolation. Real-time measurements are provided against KPIs defined by LTE standards, enabling organizations to see at a glance that something has gone wrong and then quickly drill down to the root cause. Results can be collected over extended test times, enabling system regression and historic analysis. The same toolset can be used for network trials, load and stress testing, optimization and deployment.

The rise in complexity of 4G services is matched by more exacting user demands. Customers expect a seamless, robust service and are quick to migrate to other providers if they perceive any drop in standards or performance. Yet the complexity of LTE technology increases the risk of QoS issues compared with 3G networks. These challenges are complicated by the high number of test points that must be managed and large volumes of data that need to be correlated across the network. LTE’s complexity means there are far more interfaces need to be tapped for the relevant data and the signaling that goes with service delivery is much more complex. As service providers try to be first to market with high-quality service and understand how customers would use 4G services in 2011, they must troubleshoot and manage issues to avoid costly outages. Service providers must ensure that they can identify and troubleshoot any user, service or network problem in a very short period of time to deliver the highest possible standard of customer care.

Efficient LTE test solutions can play an important role in resolving these issues. Composite KPIs can reduce the number of KPIs without losing detail while providing flexibility about what sequence of messages a KPI relates to. Operators will most likely need to capture all of the control plane data but can be more flexible about the user plane. An intuitive interface makes it easy to understand signaling messages and clearly highlights failures. On-line real-time filtering allows users to narrow investigations to focus on events related to a cause and provides a sequence diagram for each failure, enabling faster diagnosis.

Newer assurance tools go one step further by analyzing subscribers’ networks and service interactions, correlating these transactions into a single context and tracing them from real time to several weeks in the past. For example, successfully setting up a call requires that many different individual transactions be completed across the entire network. Effective troubleshooting demands that this series of inter-related transactions be presented in a single end-to-end view of the complete LTE network. This view enables the operations team to diagnose complex issues quickly and reliably to ensure customer satisfaction and protect revenues. For example, a pictorial sequence diagram of a user’s session provides a detailed analysis of signaling procedures. This approach moves troubleshooting from a domain occupied by a handful of specialists to one in which a much broader group of users can effectively diagnose problems.

Because of its technical benefits and the enormous revenues that are at stake, service providers are moving to rapidly deploy LTE networks. The move to LTE greatly increases the complexity of the task of monitoring and troubleshooting mobile data services. Service providers need to develop, deploy and manage the technology in a way that ensures a high QoS while minimizing capital expenditures and operations costs. The latest generation of test and measurement equipment helps evaluate and deploy equipment that meets specifications and quality standards, verifies new services, and accelerates problem resolution cycle time. Carriers that get test and measurement right will have many highly profitable customers loyal to their network and brand for the long term.

Paul Gowans is global marketing manager for LTE test solutions at JDSU (News - Alert)