Taking 2.5G Network Optimization to the Next Level
Mobile networks around the world have finally achieved effective integration of voice and packet services. Just 18 months ago, data access via mobile networks seemed a distant promise. But today millions of mobile subscribers rely on email-push services and access to the worldwide web via mobile phones.
What made this rapid transition possible? In part it is the initial implementation of 3G networks in some regions. But more prominently the transition stems from upgrading 2G networks to 2.5G protocols, particularly EDGE. This proven technology complements emerging 3G networks in suburban and remote areas.
EDGE remains a core transport infrastructure for mobile operators worldwide, even as 3G gets the lion's share of the publicity. Of the 290 GPRS networks around the globe, 120 have already upgraded to EDGE, offering data throughput rates exceeding 150 kb/s.
Triple play services-voice, video and data from the same provider-are the new ideal, and EDGE technology enables distribution on a large scale beyond metropolitan areas. Triple play services are regarded as the path to profits for network service providers. That makes optimization of EDGE-based network services a critical activity for every operator striving to compete in the wireless marketplace. An investment in EDGE optimization is likely to pay off for years to come.
A Brave New Multi-Technology World
In the near future, mobile network operators may support three, four, five or more access technologies. These include GSM, GPRS/EDGE, and UMTS as well as the emerging Unlicensed Media Access (UMA) and WiMAX (802.16e, 802.16-2005 mobile) technologies.
This development will impact network optimization practices. Gone are the days of supporting single technology (GSM/EDGE) or single service (voice/minimal data) environments. Dual/triple technologies and multi-service environments are part of the triple-play infrastructure. To meet these challenges without a huge expansion in maintenance resources, operators may make some deliberate compromises in their services, such as:
- Trading off UMTS or HSDPA coverage along highways in favor of EDGE, which is considered superior for high-speed mobility applications.
- Handing over pure voice calls from UMTS to GSM to free up capacity for high-speed HSDPA data services.
Until now, optimization has not needed to deal with such complex and potentially far-reaching strategies and approaches. The policies, procedures, and tools of optimization must evolve in concert with their target applications.
2.5G Networks Help Carry the 3G Load
The steep increase in traffic levels for mobile packet services is driving a significant effort in planning and optimization of 2.5G networks. After an admittedly slow start, new data-related service offerings are gaining momentum in the 2.5G network environment. Simultaneous voice and data calls (dual-mode operation) and presence services (which provide a single, shared voice mailbox for both fixed and mobile phones as well as services dealing with location, advertising and approvals), exemplify some of the new products currently being deployed.
In 2G-based networks (including 2.5G), capacity is increased by adding base stations while minimizing interference through astute frequency distribution. Each GSM/GPRS/EDGE operator owns a set of frequencies that must be assigned to transmitting base stations in such a way that any two base stations using the same frequency are spaced as far apart as possible.
With the advent of 2.5G EDGE networks and their mobile data features, the demand for capacity is accelerating. The number of call attempts for data services has already overtaken voice services in some regions. Once connected, many data services update the content automatically and frequently, creating a large volume of "calls." Thus the sheer number of calls is increasing dramatically for technical reasons associated with mobile data applications.
Moreover, the number of data service roamers has gone up significantly. Internet and email access are a critical part of conducting business these days, and businesspersons are nothing if not "roamers." One side effect is that more and more 3G users are being handed over to 2.5G networks due to coverage, quality or capacity reasons.
All of these trends add up to a substantial new capacity burden on EDGE networks. Emerging services can tax network capacity beyond its limits unless the network is rigorously optimized.
New Tools and Methods Take Optimization to the Next Level
Due to the market pressure for data services and the competitive pressure to earn and retain triple-play subscribers, network operators are learning that EDGE optimization needs to reach far beyond basic frequency and base station density management.
In addition to exacting base station placement, a quality of service (QoS) assessment of the service mix in the user plane is now essential. Because the sending and receiving equipment is constantly moving, the QoS information must be correlated with location data. The same is true for network performance parameters such as successful and unsuccessful handovers or dropped calls.
These may sound like complex procedures, but a new generation of tools has emerged to simplify today's optimization challenges. Foremost among these is Tektronix' Optimization Expert, a powerful software toolset that runs on either a K12/K15 Series protocol analyzer or a notebook PC.
Optimization Expert delivers statistics on network users' call behaviors, in roaming and quality delivered to roamers, and more. There is also a tool that tracks radio measurements: radio channel management, handovers, coverage, etc. The result is a panoramic view of network performance and QoS; plenty of information to guide pragmatic optimization of the network. Figures 1, 2, and 3 illustrate some Optimization Expert capabilities. With this information in hand, a K15 protocol analyzer can be used to track down faults in the access portion of the network.
If an RF problem is observed, what's the next step? Often the problem has its origins in interference of one kind or another. Here, the Tektronix RF Scout Interference Hunter is the right tool. This portable instrument combines a hand-held spectrum analyzer with built-in carrier scanners that quickly locate coverage gaps or overlaps, whether indoors or out, and actually maps the measurements.
2.5G: May It Live Long And Prosper
The growth in demand for data services c0ntinues unabated, but 3G infrastructure and spectrum are costly. Ironically these trends point toward a long and prosperous future for the 2.5G EDGE technologies carrying much of the data traffic in the world today. Network optimization is the key to delivering 3G-caliber data services with 2.5G equipment.
Now is the time to take a fresh look at optimization strategies for 2G and 2.5G networks. New tools and procedures are in place to take network planning, tuning and optimization to the next level.
Figure 1: Assessing eMail QoE (Quality of Experience) of 2.5G eMail services
Figure 2: Correlating network data and geographic location information in a
2.5G network using the Tektronix 2.5G Optimization Expert
Figure 3: Using Abis data to assess Radio Network Performance in 2.5G Networks