Service Management is not a new concept in the Operation Support System (OSS) world and indeed the category has been recognized for several decades by standard bodies such as the ITU-T. The emergence of wireless data technology such as GPRS which provides a reasonably fast and ‘always on’ bearer over which a multitude of wireless data services can be offered from Internet access and email through to corporate VPN and consumer-focused location-enabled games is one of the key factors that has led Mobile telecom operators to look again at Service Management with a renewed urgency. What is significant is not the bearer itself, nor specifically the services, but the customer experience gap between the bearer and the services, as illustrated below;
The QoS experienced by the user of, say, a multimedia football final score service is dominated by the timeliness of delivery, the quality of the content and other factors not always simply related to the performance of the underlying bearer.
In truth, this gap has always been present even for basic voice services but in this case it is so much smaller that the difference between managing the quality of the bearer and managing the QoS has not been significant. This has now clearly changed. While assuring the basic availability and retainability of the GPRS network is still essential, management systems that focus on the network provide extremely limited visibility of the actual services that are really being experienced by their. It is this gap that has led to a new focus on Service Management for GPRS and 3G.
Customers buy services, not networks or technologies, and therefore operators now fundamentally must shift to managing the product they actually sell, i.e. the service, rather than the technology that delivers it, i.e. the network. Service Management solutions potentially fulfill that need. Such factors are principally drivers of Service Management for GPRS and 3G.
Three distinct but complementary approaches have emerged to provide Service Management
Systems to wireless operators, namely; ‘Classic’ or Synthesized Service Management,
Active Service Management and CEM. In this article I discuss the CEM approach.
CEM is a new category of Service Management, which attempts to directly measure the customers’ experience of the quality and performance of services in real time. By customer experience we mean the throughput, delay or error conditions that were actually experienced by a single subscriber – factors that are likely to directly impact their perception on the quality of service.
It directly measures real-time performance on a per customer or per customer group basis rather than attempting to infer it from network-based measurements.
In this approach near end-to-end measurements can be made at the application layer and also retaining the ability to drill down into the underlying protocols, for example BSSGP, GTP, to support accurate fault diagnosis. For example, CEM uses probing technology to monitor in real time the Gb, Gn and A interfaces and collect the actual customer experience of GPRS and GSM services as illustrated below.
Monitoring around the SGSN gives a good compromise between seeing a full end-to-end view of performance and scaling to a pervasive solution for the entire network. However, the CEM vision is that ultimately the handset itself will evolve to become the ideal point for passive monitoring of the customer experience. The handset is as close to the customer as possible and is able to directly measure accessibility indicators, such as holes in RF coverage or accessibility of GPRS, which simply cannot be seen by the network itself. While some agent-based solutions exist today, they are generally limited to the user layer and so are unable to link problems here with the underlying mobility management, session management and RF measurements. Trials of handset-based customer data collection technology in an existing GSM network have already been conducted, and, as the application environment in the handsets evolve, will continue to develop solutions in this area. A key feature of passive monitoring, unlike an active test solution, is that it is able to see down through all the protocol layers thus providing visibility of not only the user layer data such as the HTTP or WML application requests, but also the BSSGP signalling in the control plane or PDP context information carried over GTP. Consequently, when a KQI does indicate a service problem, additional information can be provided in the form of low-level signaling error codes and related network data such as current cell or link information. This allows the operator to drill down using existing network performance systems to understand what is causing the service problem, combining the direct measurement advantage of the active approach with the fault diagnosis capability of the synthesized approach.
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