The world over, mobile network operators and solutions providers have carried on an active discussion of small cell networking, an architectural paradigm shift intended to boost network capacity and coverage, says Siphiwe Nelwamondo, Technical Marketing for Aviat Networks, South Africa.
Also known as network “densification”, small cell networks will mandate a toolkit of wireless backhaul technologies that promise to be simpler, less costly and, of course, smaller than existing radio access and backhaul devices.
These new technologies include higher frequency, smaller form-factor, millimetre wave radios and low frequency, non-line-of-sight (NLOS) radios. In addition, a core tenet of distributed and ubiquitous small cell networks is that they offer self-organising, advanced networking features.
But is it all necessary? What’s the big deal!? Isn’t this whole scenario overly complicated, courtesy of an eager commercial ecosystem that has yet to fully understand the purpose and value of small cell in the telecommunications universe? The complexity is enough to give operators a headache.
Many mobile operators have had strategy swings concerning small cells between doing everything new and doing absolutely nothing. In today’s 3G and LTE networks, traditional microwave (that is, Packet Ethernet, 6-42GHs) backhaul technology has served the macro cell network quite well.
The details must be considered in any solution to the small cell network densification problem, because users tend to overlook seemingly little matters. 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. 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-6GHs frequencies is appealing, but undoubtedly, they will be required for 3GPP, WiFi and other future radio access methods to meet the overwhelming demand for data.
Millimetre wave frequencies in the unlicensed 60GHs and licensed 70-80GHs bands are easier and less costly to attain, although this varies by country. This trade off is shorter paths.
Performance for traditional microwave systems is very reliable and deterministic. Network availability has been proven to match or exceed that of fibre, meeting five nines (that is, 99,999% availability) requirements, which equates to less than five minutes downtime per year.
Transmission latency is also very low for microwave transmission, typically 150µs – ensuring that strict latency requirements of LTE and LTE-A are met. This cannot be said about sub-6G NLOS radios.
Deployment logistics for microwave backhaul are 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. While we talk about street-level small cell designs, operators question their deployability. This kind of design could be an exception rather than a typical use.
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. But operators expect that microwave providers will continue to cost-reduce, shrink and enrich their product offerings.
New backhaul architectures should not force us to fix what is not 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. Does traditional microwave need to evolve? Yes.
From a cost and form-factor perspective, macro cell microwave backhaul solutions are not yet fully optimised 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 many people anticipate. As a result, microwave for small cells should be a top priority for carriers as they leverage best practices to evolve mobile networks profitably while maintaining an optimal user experience.
