Troubleshoot LTE & VoLTE service issues - Mobile Operators

White Paper: Troubleshooting LTE and VoLTE service issues for Mobile Operators

Mobile Operators worldwide are rushing to migrate from 2G and 3G services to 4G technologies. Deployment or migration to Evolved Packet Core (EPC) high-speed data service over 3G and 4G LTE posts big challenges to the network operations team. With today’s LTE networks, traffic volume is higher and if there is a problem it will require troubleshooting IP and application performance across control plane as well as user plane.

This white paper will discuss changing requirements for network troubleshooting equipment and the new capabilities network engineers need to resolve data and voice problems fast.

  • Introduction
  • The Numbers
  • Increasing Market Demand
  • LTE Mobile Broadband Regional Growth and Penetration
  • LTE Optimized Network Financials
  • LTE Presents New Network Challenges
  • The 360° Solution to Troubleshooting LTE and VoLTE
  • End-to-End Subscriber Session Analysis
  • Empowering Network Engineers
  • Summary


Mobile Operators worldwide are rushing to migrate from 2G and 3G services to 4G technologies. Once deployed, operators must optimize their LTE mobile broadband network. No sooner is LTE deployed than operators initiate network engineering plans for the integration and overlay of VoLTE (voice over LTE) functionality to free up their valuable spectrum still consumed by 2G and 3G voice services and redeploy it for LTE.

The process is complicated and creates new testing and troubleshooting challenges for operators’ engineering teams. Prior to LTE and VoLTE, troubleshooting via signaling tests was the standard mode of operation. The advent of true mobile broadband services has raised the bar for network engineers, especially those whose experience has primarily been within the mobile communications silo. New knowledge, skillsets and equipment are vital to quickly and effectively mitigate service issues.

The Numbers

The explosion of mobile broadband devices looks like a hockey stick on every graph you look at. Mobile broadband growth is fueled by the rapidly approaching ubiquity of smartphones in both developed and developing markets, PC modems, next generation tablets, phablets, machine-to-machine devices and as yet to be conceived mobile data devices. Global consumers’ appetites to communicate and be connected are exponentially increasing demands on wireless operators.

Mobile devices outnumber planet’s humans by 2017 = 10.3 billion

Global Mobile Broadband Projections and Stats:

  • Mobile devices outnumber planet’s humans by 2014.
  • 1.4 devices per person by 2017. Simply put: 10.3 billion.
  • 12 percent LTE global penetration by 2017.
  • 1 billion (15 percent) mobile devices/connections IPv6-capable today
  • 4.2 billion (41 percent) IPv6-capabile by 2017.
  • 2.1 billion mobile broadband subscriptions start of 2014.
  • 8 billion mobile broadband subscriptions by the end of 2017.
  • 70% per year increases in data consumption.
  • 13-fold data traffic increase by 2017.

Increasing Market Demands

LTE and VoLTE provide customers with a quantum leap in their user experience. Wireless customers are experiencing better service levels and broader coverage as networks are deployed. The data rates of LTE are far superior to 3G rates and this translates into customers utilizing more applications and services that depend on the higher speeds.

Competition among service providers is extreme. Customer loyalty is a thing of the past. As prepaid services become the new reality in many markets, customers are free to move to a competitor. To meet this continually increasing demand for mobile data bandwidth and retain their customers, operators are rushing to deploy LTE networks that will sustain 4G devices and connections currently generating 20Xs the data traffic of non-4G products.

Mobile data and voice communications customers are dependent upon the flexibility wireless devices provide to both the enterprise and personal use sectors. Major international corporations rely on quick, accurate distribution of critical information just to maintain a competitive position. Small business entrepreneurs in emerging markets embrace smartphones and mobile computing devices to run their businesses. SOHO, the acronym coined in the 1980s for Small Office/Home Office, might be redefined as Sole Owner/Handheld Office in many places in the world today. Personal data use continues to skyrocket due to increased LTE coverage, capacity, device upgrading, and new-user entrants. Mobile broadband users continue to demonstrate an ever expanding appetite for more interactive connectivity – whether streaming video, online gaming, opting in for push notifications or any of the myriad applications encouraging them to keep their devices “always on.”

Always On has become the gold standard service mode for enterprise and personal users of mobile broadband

Always on has become the gold standard service mode for enterprise and personal users of mobile broadband. They expect full accessibility to their corporate intranet, push content, subscription services, business associates, and their friends 24/7/365. Consumers of mobile data are much like the majority of automobile owners. They do not care how their mobile service or auto works, they just want it to work seamlessly wherever and whenever. They want it fast. They want it perfect. They want it now.

LTE Mobile Broadband Regional Growth and Penetration

The global mobile broadband statistics presented (in Chart 2) demonstrate the necessity for operators to prepare for the challenges they will face as their broadband systems sustain such rapid user demands. The Global Mobile Suppliers Association recently reported 260 commercially operating LTE networks in 93 countries by the end of 2013 and an additional 200 networks planned.

More than 80 percent of the estimated 100 million LTE subscriber connections are found in the US, Canada, South Korea, Japan and Australia. Given the vast geographic areas of the US, Canada and Australia it is noteworthy that 80 percent of the population has LTE coverage.

In the Asia/Pac region, South Korea, an early adopter of LTE, is expected to reach 50 percent broadband user penetration in 2014. Japan is on course to achieve 20 percent LTE penetration by the end of 2013, similar to the US adoption rate. China is scheduled to allocate 4G spectrum licenses in 2014 and appears to be favoring TD-LTE (a time division variant). Once launched, China’s mobile broadband service is destined to rapidly become an enormous market. Network operators must prepare to service these new customers.

LTE Optimized Network Financials

Meeting customer demands is the cornerstone of a financially sustainable mobile broadband business. Optimization of an LTE network results in an immediate and positive financial impact to the operator, both directly and indirectly. An optimized network reduces capital expenditures for both network infrastructure and operations center hardware and support. Significant additional savings in operating expenses are achieved by allocating skilled resources to focus on creating and supporting new services.Fully optimized LTE networks afford operators the ability to migrate data intensive traffic from 2G and 3G platforms freeing that spectrum for 4G services resulting in better utilization of costly and difficult to obtain spectrum.

Operators realize increased ARPU from satisfied mobile broadband users. These customers use more billable data; purchase operator offered apps and content, strengthen subscriber retention metrics and are more likely to refer associates, friends and relatives as new subscribers to the operator. LTE and VoLTE networks help operators to effectively meet their customers’ demands and benefit from enhanced revenue stream only if there is sufficient network coverage within the service market and if the network operator is capable of quickly resolving user experience issues and to restore optimum service.

Failing to meet customer requirements of LTE-based service is often a reality for operators whose networks are experiencing stress. Unhappy and dissatisfied customers result in decreased revenue, increased churn and negative publicity. Per capita churn losses vary depending on global region, what subsidies operators offer to acquire and load them and whether they are on prepaid or post-paid plans. Regardless, a lost subscriber requires a new add of equal or better value just to stay even.

Let’s look at some of the primary causes of poor QoS (Quality of Service) once the network is operational and what can be done to quickly remedy the problem(s) and maintain high-level user experiences. As mentioned earlier, LTE is a more sophisticated and complicated technology. The addition of the IPv6 network and its providers increases the level of complications.

Degradation of mobile broadband service generally comes in two forms:

  1. Network service troubles: Either localized or system wide it affects multiple broadband devices and connectors and can occur on either LTE or VoLTE service.
  2. Device-centric troubles: Isolated to the user it may manifest as inability to make a data connection, poor voice quality, dropped calls or at times result in no service connection.

LTE Presents New Network Challenges
Backhaul Field Engineers LTE Core Operations/ Performance Engineers Carrier IMS/Data Center Network Engineers
  • High growth in all-IP based traffic
  • Roll-out of VoLTE with QoS
  • Problems not solved by adding bandwidth anymore
  • New user experience expectations e.g. VoLTE, Video Streaming
  • IMS expansion for LTE growth
  • Roll out new revenue generating services
Visibility needs
  • Bandwidth, Packet Loss and Latency
  • Transport demarcation points
  • Packet Loss and Latency
  • User and control plane analysis (LTE, VoLTE)
  • Network element impairments
  • IMS performance metrics
  • Internet traffic profiling
  • Business application performance

In the first instance of network-based troubles, there are dozens of possible causes. The sources of these issues are frequently difficult to overcome because there are so many possible components and transactions where issues may be hiding. Some of the possible sources: the eNodeB (Radio Transceiver), the LTE Evolved Packet Core, the IMS (Internet Multimedia Services platform) or even upstream to the ISP (Internet Service Provider). Is the issue caused by the eNodeB or the backhaul? Is the network losing packets due to issues with the bearers? Or is the trouble rooted in the user plane? It could be a case of the control signal not functioning properly and compromising the ability to set up an end-to-end link with Google or a corporate intranet.

At the subscriber device level VoLTE presents another set of challenges. The migration of voice from 3G to LTE must be seamless. Operators must be able to troubleshoot problems associated with individual customers and be able to escalate the issues through progressive support tiers. Any degradation is immediately obvious to the user. The user is paying for this service and consequently it must not only meet, but beat “over the top applications” such as Skype in ease of use and quality of service.

With more than 500 different 4G devices available in the market - handsets, tablets, modems, M2M, and other connectors and another estimated 1,000 LTE devices that have been announced by one hundred manufacturers, the challenges of troubleshooting individual users issues is increasingly complex. Discovering the sources of device-centric problems are a huge concern of operator’s engineering teams and often quite difficult to ascertain and fix. The cause may be improper algorithm coding within the device itself, or that the CRM (customer relationship management) department incorrectly programmed the customer’s plan. Perhaps the device was brought to market before all the software bugs were corrected. Maybe the case shields the antenna or there is a propensity to be unusually effected by interference. The trouble can also be related to the HSS (home subscriber service) not being able to authenticate the user because certain user data isn’t correct.

Traditional troubleshooting tools including many well-known test equipment products, while useful, fail to achieve the results LTE demands. Stories of core engineers spending weeks searching for a problem using some of these tools are legend in the industry. These tools do not provide core engineers with the detailed information they need to quickly and efficiently fix the problem. LTE networks experience more than signaling issues. Traditional tools focus on signaling analysis and do not provide the engineers with the application analysis essential to persuasively validate the problem lies with the application and not the network.

Furthermore, these lower functioning tools lack the ability to manage high data rates on backhaul/EPC leading to dropped packets and missing payloads. They are not designed to set up complex filters to avoid overflowing capture buffers. Synchronization of multiple capture points is time consuming. Many existing testing tools are poorly designed for discovering and correlating packets from multiple sources. They are generally poor at capturing control plane intelligence and transferring it to the operations center. Due to their essential sophisticated design and functionality these testing devices are often too complicated for field technicians to properly employ. Sending specialized, highly skilled engineers to the trouble site to operate these devices is cost prohibitive. And how many network operation centers have enough senior-level engineers experienced in IPV6, LTE and application analyses that they could even consider sending one on a troubleshooting mission?

The 360° Solution to Troubleshooting LTE and VoLTE

Network operators must constantly keep in mind they are in business to satisfy customer expectations that their devices are “always on.” To achieve this goal the network must also be “always on,” operating without any degradation in performance. To maintain the network at this optimum standard, operators must have the sophisticated, high-performing tools to diagnose the root causes of any problems.

If we accept that “time is money” and lost customer use, or actual lost customers, equates to lost money, then prompt and successful trouble resolution is imperative. The critical traits required of troubleshooting equipment that handles problems and accomplishes the goal of “always on” are: connect, capture, identify and solve. The traits can be identified by four functional capabilities:

  1. Performance: The troubleshooting equipment must be scalable to effectively handle the operator’s load requirements.
  2. Visibility: Network engineers must be able to immediately and clearly see packet-level metrics when problems arise and be able to know exactly where in the communications channel the gaps are.
  3. Portability: The equipment must be constructed to quickly and also cost-effectively be transported to the specified location no matter what the conditions and when it is needed.
  4. Usability: Operation of the gear must be easy be pretty much plug-and-play for field technicians to operate, yet provide the comprehensive capture and analysis required by more skilled engineering personnel usually located far from the testing site.

Effective Troubleshooting requires visibility to:

  • Troubleshoot issues back in time by "capturing and store all the packets and events".
  • Analyze voice/video/data applications for a subscriber/coverage area
  • Identify the root cause of slow applications and poor voice QOS
  • Correlate video/voice/data from multiple locations to identify root cause

End-to-End Subscriber Session Analysis

Collectively, the ideal troubleshooting tool will provide the ability to correlate control signals, control traffic, user signals and user traffic. The result is a clear picture of the user experience.

In LTE the quality of the user traffic is grounded in the “bearer,” the envelope or tunnel that transports the data packets across the network. Each user can have multiple bearers simultaneously if they are conducting a voice call, viewing an email, or surfing the Web. Each bearer is set up with different quality control indices for various data services such as voice, streaming video, SMS, etc. The network performance engineering team must have clear visibility of the bearer status and the user plane traffic performance to determine how it correlates with user traffic. The quality of real-time voice calls is the most obvious to subscribers. They will not tolerate any level of degradation or latency.

The increase in much richer IP data traffic must be easily visible to engineers when the traffic becomes overwhelming. The troubleshooting tool must deliver the highest quality tracking of varied IP traffic sources such as Web-based HDTV, video streams, as well as the Internet carrier on which the mobile operator’s traffic may be running and experiencing interference from competitive mobile operators’ traffic. It must be able to rapidly capture each IP based flow and provide the necessary information when service is degraded or interrupted. The better and faster the data is captured and presented, the faster the cure for the mishap can be addressed and quality user experience restored.

Empowering Network Engineers

Prior to the advent of LTE and today’s IPv6, IP traffic and network IP issues were much lower. Network operations and maintenance groups could get by with lower level performing packet capture devices and did not need as many engineers proficient in advanced IP skills. With today’s LTE networks, traffic volume is higher and if there is a problem it will require troubleshooting IP and application performance across control plane as well as user plane. As it takes time for field engineers to gain experience with troubleshooting IP based LTE issues, today’s tool must be very easy to setup and empower the field technician to gain visibility of the event on the network and collaborate with more skilled engineers in the core to resolve issues while building their experience. The tool must empower the performance engineering team to become a more effective collaborative team and enhances their overall performance.


As LTE broadband networks are deployed, expanded and present core engineers with ever mounting challenges, it is critical operators be equipped with an all-in-one troubleshooting tool that can discover, analyze and determine the trouble in minutes rather than hours or days. Accomplishing this goal requires tools that deliver maximum visibility of both signaling and applications data.

LTE network operators’ core engineers and C-level execs will immediately recognize the benefits of an all-in-one portable troubleshooting device. Core engineers will appreciate the ease of use that delivers superior performance and presents transparent visibility. CFOs and CMOs will realize quantifiable ROI via increased market share, data use, and enhanced ARPU and net capital and operation savings.