VoLTE Optimization Challenges

MNOs need to monitor QoE and make network adjustments in real-time

Today’s smartphones are incredible feats of engineering. Packing the processing power of a mid-1980s supercomputer into a sleek, pocket-size slab, they can take photographs, play music and videos, and stream tens of megabits of data to the palm of your hand every second.

But try ringing your boss in rush-hour traffic to say you’re running late, and there’s a good chance your call won’t get through. “Mobile companies have rather lost the focus on a smartphone also being a telephone,” says Jeremy Green, a tech-industry analyst at Machina Research, in Reading, England.

Laboratory tests by Broadcom confirm that even in the best conditions, with a low signal to interference and noise ratio (SINR), users consistently rate voice quality lower on a cellphone than on a landline. Weaken the cellular link or increase interference or noise, and callers’ opinions of the experience drop dramatically because of garbled voice, dropped words, silence and dropped calls.

Interference and noise at the cell edge of the Radio Access Network (RAN) causes service quality degradation and significantly affects VoLTE quality. Noise, interference and network coverage are the leading causes of the following VoLTE quality errors:

  • Packet error – When a packet is lost or incorrectly received, it needs to be retransmitted causing delay, transmission speed reduction and may severely degrade voice quality.
  • Packet delay (latency) – The round trip time (RTT) of a packet can be delayed from network queuing, retransmission, or other issues that delay packet delivery to levels which VoLTE cannot tolerate as the quality of calls become unacceptable.
  • Jitter – Packets which experience a variation in delay of transmission over time due to network queuing, etc., causing timing gaps that result in call quality degradation when the variation is too wide.

The above errors, occurring predominately at the cell edge of the eNodeB, are the root cause of a significant number of VoLTE quality issues.

LTE incorporates end-to-end Quality of Service (QoS) that defines priorities for different services, ensuring appropriate bandwidth for different QoS Class Identifier (QCI) bearers. QoS tries to provide optimal voice quality by guaranteeing bandwidth and if required, reduces network admissions if packet errors or packet delay exceed the thresholds for the bearer.

While QoS is effective in ensuring bandwidth, it doesn’t solve the cell edge noise, interference and coverage problems, which require real-time detection and network adjustments. Mobile Network Operators (MNOs) need a centralized VoLTE optimization platform which has the ability to monitor Quality of Experience (QoE) affecting cell edge performance issues in real-time and to make network changes which result in an enhanced VoLTE service. VoLTE optimization resolves the cell edge quality errors that negatively affect voice quality, the most valuable service offering for MNOs.

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