Critical Role of Microwave in LTE and Small Cell Backhaul

Mobile backhaul has become one of hottest and most contentious subjects in telecommunications ever since LTE cellular phone technology started to ramp up. One much overlooked aspect of deploying LTE lies not in the capacity required to backhaul cell site traffic but the effort required to build out the required sites. It is really about site surveys, frequency coordination, engineering, planning and installation. Aviat Networks’ chief technology officer (CTO), Paul Kennard, addressed this dichotomy and others related to LTE in his presentation to the IEEE’s Communications Society.

Although, Paul did have plenty to present regarding capacity. For example, with proper use of rings, overbooking, QoS, XPIC and other techniques and technologies, microwave backhaul can provide 400 Mbps-plus throughput. Compare this to the realistic throughput demands of a typical LTE site that max out at about 100 Mbps.

He also delved into the emerging backhaul category for Small Cells—designed to supplement traditional cellular infrastructure. The fact is that traditional techniques of deploying cellular macrocell basestations will be insufficient to provide broad enough coverage for this LTE wireless technology. To augment macrocell coverage for LTE mobile telecommunications providers have been investigating, trialing and, in some cases, deploying one or more of several small cell technologies (e.g., picocell, microcell, femtocell). Consequently, new methods will be needed to backhaul traffic from Small Cell sites.

Fiber backhaul may not be available at all small cell sites and when it is it could be very expensive to trench long distances. Regular line-of-sight (LOS) microwave with its parabolic dishes could prove aesthetically unsuitable for many Small Cell locations and/or difficult to install. Non-line-of-sight (NLOS) microwave and millimeter-wave point-to-point and point-to-multi-point wireless may have their applications, but their latency of 5-10 ms may be too much for real-time applications and voice—not to mention licensed spectrum is costly and unlicensed spectrum is very risky due to interference issues.

 

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