In an industry obsessed with increasing average revenue per user (ARPU), delivering a quality customer experience - in terms of the availability, variety and performance of the myriad services available to subscribers - is becoming a critical competitive advantage for mobile operators. 

Eileen Haggarty

In fact, differentiation can often be found in simple things - such as how fast the mail indicator shows up on a customer's handset or keeping WAP browsers authorization failures to a minimum. With so many subscribers and services running across their networks, mobile operators need to migrate from the traditional focus on voice quality assessment to a new world of comprehensive, real-time visibility of all IP-based voice, video and data services so they know what's working, what isn't and why.

Key Performance Questions
There are the obvious ways a mobile operator knows if there is a problem occurring in the network - customer complaints and calls to customer service - but that means subscribers are already experiencing a level of poor service - and quite possibly have been for an extended period of time before reaching the point when they actually report their frustrations. A more proactive approach begins with answering some key performance questions on an ongoing basis:

• How fast is each service running? 
• Is that response time acceptable? 
• Are there any errors? 
• What is the success rate?

For virtually any service element, whether it is an enabling service like AAA Radius or Diameter or a revenue-generating service such as SMS or ringtone downloads, key performance indicators (KPIs) can be derived to monitor how fast the service is operating.  Passive response time analysis that records, in milliseconds, the actual time it takes to traverse key points in the network is one way to gain valuable insight.  This KPI can be monitored for values that fall out of acceptable ranges, and then additional analysis engaged as needed. 

As an example, monitoring AAA Radius for acceptable response times and errors will help identify when individuals or groups of subscribers are having trouble gaining access to the mobile network and are thus unable to complete revenue-generating voice calls or initiate Internet sessions. 

Analyzing IP Traffic Flows
Invariably, there needs to be an evaluation of how the IP-based traffic behaves and/or traverses the mobile operator network.  Questions that this analysis should answer on an ongoing and proactive basis include:

• Which resources are being used?
• How much?
• By who?
• How are multiple services traversing a shared infrastructure affecting one another?

Consistent, real-time monitoring and analysis needs to be performed across multiple points in the service delivery infrastructure in order to proactively identify and troubleshoot service-affecting problems.  Interfaces operating in either GSM/GPRS/UMTS (e.g.: Gn, Gi, Gp, etc.) or CDMA2000  (e.g.: A10/A11, Pi, Xd, etc.) networks as well as in the MPLS / VRF core backbones should be monitored in order to identify and track both overall traffic volume statistics (e.g. bytes, packets, utilization) as well as details on what comprises that volume to reveal how these resources are being utilized. 

For example, if an operator is rolling out a new DNS server in one part of the network, it will need to analyze the actual DNS traffic flows side by side with other services in that area of the network to determine the performance, traffic volume and responsiveness of all services and service elements, including DNS. 

Leveraging the IP Packet
For many situations, traditional monitoring approaches provide excellent analysis of networks, services, conversations, response times and trending.   However, at times, packet-level details are necessary to troubleshoot and identify the more complicated network problems.  Key questions that packet-level analysis can answer include:

• What exactly was the conversation exchange for a specific service?
• How can we reconstruct a session from the recent past to see what happened?
• Is there a poorly designed application service causing the degradation?

By continuously recording packet flows from target interfaces in the mobile network, the operator can analyze complete trace files with both header and payload information for in-depth, post-event forensic data mining with microsecond granularity.  In diagnosing the most challenging packet-level problems, trace-based tools like session bounce charts for each enabling and revenue-generating service monitored become an essential asset. 

Summary
Mobile operators urgently need enhanced visibility into performance of IP-based services throughout the network to protect and enhance customers' experience, which will reduce churn and protect ARPU.

Network and service performance monitoring with real-time and historical reporting is an effective tool to answer proactive questions related to capacity planning and optimization, service monitoring and subscriber profiling, and for real-time troubleshooting and rapid service restoration.

Haggerty is director of Solutions Marketing for NetScout Systems