management & optimisation
It is 2.5G EDGE, as much as UMTS and 3G, which has been responsible for the surge in data usage, and now operators need advanced optimisation techniques to take their networks to the next level, argues Othmar Kyas.
Triple play voice, video and data services are the new market imperative for service providers and require optimisation of the mobile network infrastructure to be successful. EDGE has become universal over the past few years, complementing 3G networks in suburban and remote areas and serving as the core transport infrastructure for the vast majority of the mobile operators worldwide. Now, with a rapidly growing customer base, advanced 2.5G network optimisation has become a critical activity for every operator.
During the past few years, the mobile network world has finally achieved the large scale integration of voice and packet services. Only 18 months ago, data access via a mobile network was left to corner cases – viewed more or less as a theoretical feature. Today, however, millions rely on email-push services and the usage of the worldwide web via mobile phones. While much of the hype around triple play networks has focused on UMTS (3G), the above explosion in mobile data usage has been triggered by upgrading 2G networks to 2.5G networks. Of the 290 GPRS networks worldwide, 120 have already upgraded to EDGE, offering data throughputs well above 150kBit/s.
The steep increase in traffic levels for mobile packet services such as email, MMS and HTTP has put networks under considerable stress and is requiring significant effort in network planning and optimisation of 2.5G networks. However, with data finally going mobile, planning and optimisation tasks are rapidly changing.
Traditional optimisation of a mobile 2G network meant increasing the capacity by adding base stations where needed, while minimising interference through clever frequency distribution. (In GSM/GPRS/EDGE networks, each operator owns a set of frequencies, which need to be assigned to the transmitting base stations such that two base stations using the same frequency are as far apart as possible.)
Today, some of the data services are much less response-time-delay sensitive than others. In some areas, the number of call attempts for data services has already overtaken that for voice services (many data services frequently update content automatically, which can lead to a large call volume). Along the same lines, the share of data service roamers has gone up significantly. Internet and email access have become critical for businesses worldwide. In addition, the increasing number of 3G users, which are handed over to 2.5G networks due to coverage, quality or capacity reasons puts an additional burden on the 2G networks. Finally the evolution of the GSM standards for 2.5G networks has once again gained momentum. Simultaneous voice and data calls (dual mode operation), presence services or a single, shared voice mailbox for fixed and mobile phone service are just a few of the recent new services in deployment.
Tools and Methods
iven the above market dynamics, the optimisation in a state-of-the-art mobile network has gone far beyond smart frequency and base station density management. A quality of service (QoS) assessment of the service mix in the user plane has become imperative. And since the equipment sending and receiving traffic is moving, the QoS information needs to be correlated with location information. The same is the case for network performance parameters such as successful and unsuccessful hand-overs or dropped calls. The correlation of data and geographic location using technologies such as the Tektronix Optimisation Expert creates the type of information that allows operators to tune the network to cope with the increased complexity of the service mix.
With mobile WiMAX (802.16e, 802.16-2005 mobile) and UMA (Unlicensed Media Access) in early stages of deployment, it becomes clear that in the near future, many mobile network operators will operate a minimum of three of the five access technologies – GSM, GPRS/EDGE, UMTS, UMA and WiMAX. This will clearly add complexity and further change the approaches to network optimisation. Optimisation strategies will need to evolve from single technology (GSM/EDGE) and single service (voice/little or no data) environments to dual/triple technology and multi-service environments.
Current complexity
In the later environment, it might be acceptable or even desired to degrade the performance of one technology or one service if a better suited technology or service can cover. For example, limited UMTS or HSDPA coverage along highways might be acceptable, since the performance of EDGE in high-speed mobility applications is considered superior. In addition, the hand-over of pure voice calls from UMTS to GSM might be encouraged through appropriate parameter settings in order to free up capacity for high-speed HSDPA data services. Past optimisation strategies did not have to deal with such complex and potentially far-reaching strategies and approaches.
While the above discussion suggests that in the near term, things are not going to become easier or less complex, the scenario does provide additional options for operators. Being able to pick the right combination for customers from a variety of choices will enable operators to provide more features and better quality at lower costs. However, getting it right will be key to success. This is why the planning, tuning and optimisation of networks needs to be lifted to the next level. The time is critical to take a second look at existing optimisation strategies for 2G and 2.5G networks to ensure these strategies are still appropriate. Where they are found lacking, it will be important to implement new strategies, based on new and emerging optimisation solutions and technologies that can address the changing and more complex needs of today’s mobile networks.
