Why Latency Matters to Mobile Backhaul - O3b Networks

Why Latency Matters to Mobile BackhaulData services are projected to grow by a staggering 78% annually over justthe next four years. It is also clear that the mix of applications is changing,particularly with the shift towards mobile video.While the increasing data rates and the changing application mix are easilyunderstood, the impact of latency on performance requires a closer look.How does latency affect application quality and the end user experience?We will explain the significant difference lower latency can make in thedelivery of voice, video and data services. We will strive to answer thequestion: Why does latency matter to mobile backhaul?QoE is the new challengeFierce market competition is driving network operators to identify truedifferentiators capable of separating them from the rest. The innovators, inturn, are intensifying efforts to boost the Quality of Experience for theirsubscribers. As a result, QoE is now one of the latest buzzwords in themobile industry.The QoE experienced by a mobile subscriber for a voice call is influenced bya number of factors, including mouth-to-ear delay, voice call set-up delayand audio quality/noise. The QoE for data services is influenced by webpage response time and download speeds.Network segment QoS indicatorsFor mobile network elements, such as components of the access, backhauland core networks, several indicators are used to define and monitor thetarget performance.− Latency - Latency is the duration of time for information to transit fromone point to another point of the network. Depending on the type ofservice, it can be measured either in one direction (Ear-to-mouth orOne-way latency) or as a round trip time (RTT or Two-way latency).− Jitter - Jitter is the variation of the measured latency. It is generated bythe variation of the load on the network due to usage levels.− Packet loss - Packet loss is the ratio of packets being lost during transitfrom one point to another point of the network. It is generally causedby transmission errors, congestion of links, faults or the routing process.In modern IP based networks jitter is easily compensated for byimplementing buffers in the endpoints. Likewise packet loss is very low ontoday’s networks, which employ high performance error correction codessuch as LDPC which is used in DVB-S2. Latency, however, is more difficult toavoid. The root cause is linked to long distances and the speed of light.Once present in a system, latency cannot be removed. This is exactly whythe mobile industry has consistently engineered each new technologygeneration with lower latency, as seen in Figure 2.www.o3bnetworks.com 4