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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It’s a Whole New World at 4G World

4G World October 29, 2012, ChicagoThe 4G World show is in 10 days in Chicago, Ill. Speaking of 4G, those of us at Aviat Networks are excited to see what LTE technology will be on display and its promise of 4G speeds for our mobile networks. Confusion will mount as vendors address the myriad capabilities of LTE and the challenges of implementing such an amazing network. Small cell access will be a key topic. Mobile operators need these outdoor-mounted, street-level smaller versions of their LTE basestations to offload some of the overwhelming demand for capacity in metro areas.

One of the critical small cell challenges is backhaul. Imagine the complexity of aggregating traffic from the numerous small cells deployed at key intersections in a big city. Fiber cannot be everywhere and is not economical to operate in most metro locations. There is a lot of buzz around unlicensed Non-Line-of-Sight (NLOS) Point-to-Multipoint (PMP) radios that take advantage of fewer installations than traditional Point-to-Point (PTP) microwave. But be careful of comparisons between PMP and PTP microwave…we hear a lot of hype, promulgated by confusion and relying on fear!

Unlicensed spectrum sounds good but suffers from serious interference issues. NLOS radio capacity drops significantly when trying to transmit around a building. You have to ask: Is the resultant capacity sufficient to serve this specific small cell backhaul need? There are also concerns over latency because LTE has strict delay requirements, and Voice over LTE (VoLTE) will really struggle if latency is not within specification. What about spectrum…is it actually available? Is there only 20 MHz of spectrum available when 40 MHz of capacity is needed?

What about good ol’ reliable and proven Line of Sight (LOS) PTP microwave? With the emergence of millimeter wave PTP radios, capacities up to 1Gbps can be achieved easily over 1-2 kilometers—certainly sufficient for metro small cell distances!

If you have a chance to attend the show, please take the time to ask some of these questions…or else you may be victimized by hype, confusion or fear.

If you would like to hear straight talk on this topic, tune into Aviat’s Small Cell Backhaul webinar. Stay tuned for future blog posts to read about spectrum, capacity, latency, FCC rule changes and technology evolution as the search for viable solutions to the small cell backhaul challenge continues!

Randy Jenkins
Director Business Development
Aviat Networks

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