Top 5 ways to resolve RAN issues

Improving RAN performance is critical given that over 50% of Net Promoter Score, a leading indicator of customer satisfaction and propensity to churn, is driven by network performance. Yet, results from a survey of RAN operations specialists at communication service provider (CSP) organizations, reveal significant challenges associated with RAN performance management.

Such as:

• 74% of CSPs require 3 or more tools to analyze complex RAN issues
• 59% of RAN specialists lack subscriber and handset analytics
• 5G visibility is less than half of what it was for 4G
• 48% of operators lack the end-to-end visibility to optimize VoLTE

These realities put many CSPs in the hot seat when it comes to investigating and resolving RAN issues. Performance degradations are not addressed promptly, and customer satisfaction suffers as a result, with its inevitable effects on churn.

Top 5 ways to resolve RAN issues

EXFO’s Nova RAN professional services team, which works with CSPs around the world to resolve RAN performance troubles, identified the top 5 ways to resolve RAN issues: improve RAN coverage, reduce interference, expand capacity or implement load balancing, correct configuration inconsistencies and manage handset incompatibilities.

Let’s explore each of these in turn, keeping in mind that the magnitude of the problem varies based on the CSP, the technology, and the maturity of a given network.

1. Improve RAN coverage

The RAN is a complex multi-faceted entity. It becomes more so with initial 5G rollouts and their accompanying plethora of small cells combined with concurrent use of multiple radio access technologies (RATs). These technologies enable capabilities such as dual connectivity, dynamic spectrum sharing and 4G power reduction to improve 5G capacity. Notwithstanding the explosion of base stations and cell sites due to 5G, coverage remains an issue for many operators. Improving RAN coverage is a surefire way to improve the quality of service for subscribers.

Improving RAN coverage can take multiple forms:

• Add new cells to address physical coverage gaps
• Densify the network to address hot spots
• Address black spots due to radio conditions and configuration
• Improve RF weaknesses (cells with bad radio health scores)
• Replace underperforming network equipment

EXFO’s Nova RAN simplifies the diagnosis and resolution of RAN coverage issues in several ways.

a) Gathering crucial performance data from the RAN and the core is much easier. Nova RAN features massive, precise color-coded maps, with resolution down to 50m x 50m, to show actual coverage, coverage quality, best-serving sites, and gaps. It can geolocate calls to assess cell and location radio conditions and follow subscriber behavior. It also retrieves and analyzes impacted calls, with the ability to see call flow and protocol decoding.

b) Implementing fixes is easier and more effective. Nova RAN makes it possible to ensure that the proper configurations are in place or that there are no discrepancies in configurations. Before pushing out configuration changes, it simulates their impact with real-world subscriber data. Later, KPI trends validate that the improvements were real.

c) Validating fixes is fast and efficient. Nova RAN uses real-world performance data to prove that the fixes took effect. This is akin to a ‘virtual’ drive test.

Radio coverage was mentioned by 84.4% of CSPs when asked their top three sources of performance impairment CSPs (EXFO 2020). This makes it the number one source of performance impairments, ahead of cell capacity and customer devices.

None of this is to discount interference as a significant contributor to RAN performance. Let’s explore that next.

2. Reduce interference

Second in our top 5 ways to resolve RAN issues is reducing interference. The components that make up increasingly complex RAN architecture create a recipe for ongoing RF interference issues. Signal collisions, cell non-dominance, eNodeBs with crossed sectors, misconfigured neighbor relations (ANR), PCI clashes that lead to handset confusion and handover failures, and overshooting cells are just some of the RF interference problems that RAN operators face daily. Changes to network topology, power control and handset configuration are typical steps that operators take to resolve these issues.

EXFO’s Nova RAN provides geo-located cell and subscriber data based on signal strength and other variables, displayed in a color-coded map to facilitate analysis. To aid CSPs in reducing RF interference, Nova RAN measures network coverage and quality, analyses hotspots, identifies contributing cells to poor quality and drills down to location and Layer 3 analysis.

These are important capabilities given that 52% of CSPs say RF capacity or interference stops them from fully optimizing VoLTE calling.

Next up: what can CSPs do to maximize capacity on their RAN networks?

3. Expand capacity or implement load balancing

Effective planning of capacity improvements and load balancing across sites are two additional challenges facing RAN specialists in our top 5 ways to resolve RAN issues. Whether it’s new site placement, network densification, small cell planning, the designation of nearest neighbors, or even de-commissioning sites, the opportunities to get it wrong abound. Forecasting traffic patterns and network dimensioning are particularly challenging without access to real-world subscriber data and measures of actual network performance. Additional concerns include traffic management and inter-RAT load sharing.

EXFO’s Nova RAN offers several capabilities that contribute to the success of capacity expansion and load balancing efforts. In addition to real-time geolocation of subscribers and their devices, these include the ability to view network coverage end-to-end (down to 50m x 50m tile resolution), benchmark performance and traffic on a per carrier layer and cell basis, to simulate coverage impacts before deploying new sites, and the ability to simulate drive tests.

The majority (62%) of RAN specialists at CSP organizations say they lack subscriber and handset analytics. This lack of contextual data makes it very difficult to solve the challenges of capacity expansion or load balancing.

Of course, making sure there are not configuration inconsistencies is also an important aspect of RAN performance management. Let’s explore that next.

4. Fix configuration inconsistencies

Inconsistent base station configurations are the bane of RAN specialists. This essentially avoidable problem is likely to get worse as 5G—with its call for small cells to ensure coverage in urban locales and requirement to support up to 100 times the number of mobile devices—creates an explosion in base station numbers. Specific challenges with configurations include general performance thresholds, ANR, physical cell ID (PCI) clashes/collisions (that lead to handset confusion and handover failures), and the performance of handovers from site to site.

Nova RAN offers several capabilities—including RF sanity checks and identifying missing neighbors not added by ANR, and multi-interface call tracing—that enable RAN specialists to successfully manage inconsistent configurations. Nova RAN is capable of troubleshooting 5G and 4G RANs with detailed support for CDR and level 3 messaging.

Clearly, these capabilities and others built into Nova RAN are needed to address configuration inconsistencies, since almost half (45%) of CSPs indicated that they must use three or more tools to troubleshoot multi-layer, multi-domain issues from core to RAN to subscriber. That is a lot of manual reconciliation of data from one tool to the next.

And, speaking of technologies not necessarily playing nicely together, let’s examine the issue of handset incompatibilities and how that affects RAN optimization.

5. Manage handset incompatibilities

Finally, in our list of Top 5 ways to resolve RAN issues, is managing handset incompatibilities. Bring your own device (BYOD) monthly service plans and other competitive pressures to introduce new devices faster also create RAN issues for operators. Often, handsets are deployed on networks before their capabilities are fully understood and accounted for, leading to performance issues for both the subscriber (incompatibility between the handset and a given network feature) and the network operator (excess signaling and data traffic leading to overwhelmed cells). Handset interactions with cell site configurations are often problematic, due to uneven implementation of industry standards by handset and network equipment vendors.

Not all handsets have out-of-the-box compatibility with VoLTE calling, to take just one example. Some handsets have issues with robust header compression (RoHC), requiring changes on the network end to compensate. And then there is the 40 ms vs. 20ms TTI identified on a leading handset provider, resulting in issues with packet loss during VoLTE calls. Other issues concern handset support for TTI bundling, which is specifically used by VoLTE calling, and circuit switch fallback (CSFB) and single radio voice call continuity (SRVCC), the hand-over between VoLTE and CS.

Finally, and this specifically affects 5G, some handsets are configured to seek out 4G even if 5G service is available, which leads to customer complaints about not receiving 5G service. EXFO helped to troubleshoot such a case in the Middle East where 5G fixed wireless access subscribers’ equipment was configured to seek out 4G connections by default. Customers had been complaining that they weren’t receiving the speeds promised by 5G.

Several aspects of Nova RAN can help operators solve their handset compatibility issues. First, it offers handset profiling and benchmarking by manufacturer and type, with the ability to drill down to KPIs and handset capabilities. Second, it offers passive crowdsourcing of handset data with no application download required. This data is geolocated down to the cell to identify if there are site-specific configuration issues. Finally, Nova RAN offers message flow data analysis for identifying handset/manufacturer compatibilities.

In the previously mentioned survey of RAN specialists at CSP organizations, customer devices were cited as a top factor in performance impairments. Specifically, over half of the respondents highlighted the lack of subscriber and handset-level analytics as an impediment to optimizing RAN performance.

Conclusion

Keeping the RAN operating at peak performance is a significant struggle for many CSPs, as we have shown with these Top 5 ways to resolve RAN issues. Whether they are striving to improve RAN coverage, reduce interference, expand capacity, fix configuration inconsistencies or manage handset incompatibilities, RAN specialists require a feature-rich toolset to quickly troubleshoot their networks, apply changes and, ideally, validate those changes without having to drive out to the cell site.