Since 2011, mobile network operators and solutions providers have carried on the frenzied discussion of small cell networking, an architectural paradigm shift intended to boost network capacity and coverage. Lately termed network “densification,” small cell or micro cell networks are expected to mandate an extended toolkit of wireless backhaul technologies that promise to be simpler, less costly and, of course, comparatively diminutive versus existing radio access and backhaul devices. These neo-technologies include higher frequency, smaller form-factor millimeter wave radios and low frequency, non-line-of-sight (NLOS) radios. In addition, a core tenet of a distributed and ubiquitous small cell networks is that they offer self-organizing, advanced networking features—this in particular makes a lot of sense.
However, is it all necessary? Or is it an over-complication, courtesy of an eager commercial ecosystem yet to fully understand its purpose and value in the telecommunications universe? The complexity of it all is enough to give operators a migraine. In fact, many mobile operators have vacillated in their small cell strategy between doing everything new and doing nothing at all. In today’s modern 3G and LTE (News - Alert) networks, traditional microwave (i.e., packet Ethernet, 6-42GHz) backhaul technology has served the macro cell network quite well in terms of fit, form, function and cost. As we search for the perfect backhaul solution to the small cell network densification problem, we sometimes fail to see the forest for the trees. Traditional microwave networking may very well be the most effective solution for small cell backhaul. Specifically, operators should consider the following four points.
- Exceptional RF performance and output power of traditional microwave allows it to operate in both LOS and NLOS small cell backhaul scenarios.
It’s true that obstructions might impede LOS signals for outdoor, public access small cells. But for the short distances between rooftops and light poles—as well as lower capacity requirements of small cells—traditional LOS microwave is able to operate in NLOS conditions and still far exceed their capacity requirements, in many cases.
- Frequency spectrum for traditional microwave bands is plentiful on a global basis.
The option of sub-6GHz frequencies is appealing, but undoubtedly, they will be required for 3GPP, WiFi (News - Alert) and other future radio access methods in order to meet the overwhelming demand for data. Millimeter wave frequencies in the unlicensed 60GHz and licensed 70-80GHz bands are perhaps easier and cheaper to attain, although this varies by country. This tradeoff is shorter paths.
- Performance for traditional microwave systems is very reliable and deterministic.
Network availability has been proven to match or exceed that of fiber, meeting five nines (i.e., 99.999 percent availability) requirements, which equates to less than five minutes downtime per year. Transmission latency is also very low for microwave transmission, typically on the order of 150μs—ensuring that strict latency requirements of LTE and, especially, LTE-A are met—unfortunately, the same cannot be said for sub-6G NLOS radios.
- Deployment logistics for microwave backhaul are well understood, thanks to worldwide adoption of macro cell backhaul.
The shift to smaller, lower power small cells does not necessarily require a drastic shift in backhaul operations. As we continue to talk of street level designs for small cell, operators continue to question its deployability. Such a design could be an exception rather than a typical use case. Even with ultra-dense, urban coverage from small cell radios, usage of traditional microwave on rooftops, sides of buildings and street furniture is still very feasible, with the expectation that microwave vendors will continue to cost-reduce, shrink and enrich their product offering.
New backhaul architectures should not force us to fix what is not at all broken. Traditional microwave has been a top choice for macro backhaul worldwide and will continue to be the trusted tool for operators as they phase-in small cell networks in the coming years. Does traditional microwave need to evolve? Yes. From a cost and form factor perspective, macrocell microwave backhaul solutions are not yet fully optimized for to meet the nuances and varying deployment scenarios of small cell backhaul. However, the technology is rapidly evolving, and ultimately we are going to see more traditional microwave in small cell backhaul than most people anticipate. As a result, microwave for microcell should be a top priority for carriers as they leverage best practices to evolve mobile networks profitably while maintaining an optimal customer experience.
Edited by Jamie Epstein