While we hear a lot of marketing hype about Smart Cities, with various interpretations of what that might mean, several are taking serious steps towards becoming Connected Cities – building out infrastructure to support the data super-highways of the future. This won’t be exclusively wireless or wired but a combination of both.
Small Cell Backhaul
Small Cell backhaul is the transmission link between the small cell and the mobile network operator's core network. This can take many forms:
For residential and many enterprise small cells, this can be almost any broadband internet service, including DSL and Cable. Sometimes mobile operators mandate that only their own fixed broadband service can be used with their residential small cells, but at least 50% don't. The performance of the broadband link can affect the quality of service, but residential femtocells have been found to work with as little as 256kb/s broadband throughput. Sometimes, a benchmarking performance test is conducted during the online sale of a residential small cell, to ensure this will be adequate. In live operation, small cells monitor the bandwidth available and restrict their own capacity to handle calls where there is insufficient available - for example, limiting to one or two concurrent calls rather than multiple.
For metrocells, deployed in streets and other public areas, a combination of wireless (for the last few hundred metres) and fibre seems ideal. A wide variety of technologies are being considered or adapted for this purpose, and we explain how a toolkit approach to metrocell backhaul is most likely. In particular, the last few hundred metres from a remote metrocell to the nearby hub will be a wireless link, and this (dubbed "fronthaul" or "streethaul") has attracted the most attention.
For rural small cells, an existing broadband wireline service can also be used. However, for the more remote locations, satellite backhaul is now a cost effective option. A related use case involves dealing with natural disasters, where satellite connected small cells can quickly restore service.
ThinkSmallCell resources for Small Cell Backhaul:
In addition to the articles outlined further below, you may find some of these specific links worthwhile:
- Small Cell Wireless Backhaul Vendor Landscape for Metrocells
- List of Wireless Backhaul Vendors
- NGMN white paper outlining small cell backhaul requirements
- Small Cell Forum white paper discussing backhaul technologies (approx 80 pages)
Enterprise small cells require some form of IP broadband connection back into the mobile operator core. But what if it fails? The consequences to ongoing business activity could be significant. Several options are available, depending on the level of protection against outage required.
While take-up is slower than originally forecast, the cellular industry is beginning to show signs of densification through urban small cells. One of the constraints has been suitable backhaul, with fibre being strongly preferred but not universally available. Several wireless backhaul vendors have recently launched higher speed products. We ask if throughput is the most critical factor for adaptable and rapid urban small cell roll out, or more relevant for adjacent markets.
I’ve heard from several sources the idea that when building out LTE Urban Small Cells, the backhaul design should be adequate to cope with future demands of 5G. For some that means dark fibre, for most it means high cost, delay and even makes it impractical. It can involve heavy machinery, trenching and even road closure for even the smallest of sites. Is this a sensible strategy to take from the outset?
We’ve heard of how the cellular industry plans to invade unlicensed spectrum by adapting LTE for the purpose. Mimosa is a Wi-Fi vendor choosing to modify that technology for best effect in both unlicensed and licensed bands. Jaime Fink, their CTO, explains their chosen market segment and why he thinks their technical approach will win out financially in the long run.
When we last looked at the landscape for urban small cell backhaul, we found some 20 or more companies touting a range of solutions. These congregated into four or five clear market segments based on technology. We spoke to a number of different vendors to gain their perspective and understand how technology and the market have progressed.
Data rates are getting faster all the time. Enterprise Wi-Fi and Small Cells typically use 1Gbps Ethernet backhaul over standard Cat5e cable, but that's insufficient for the latest 802.11ac Wi-Fi and LTE-U small cells. Aquantia has designed chips that achieve up to 5Gbps over existing cable, using a new technology called NBASE-T which should be more than enough to meet demand. Commercial products are already available although standards have still to catch up.
How do you introduce really innovative new wireless technology into a well-established ecosystem without needing to rip-and-replace billions of dollars of infrastructure? KUMU Networks reckon they have come up not only a radical method to double network capacity, but also a novel approach on how to introduce it efficiently.
There's a huge choice of urban small cell backhaul technologies on offer today – and that's even before considering C-RAN fronthaul alternatives. We spoke with Greg Friesen, VP Products at Dragonwave, to get the perspective of a major established player in the microwave backhaul business.
In this second of two articles, Andy Sutton, Principal Network Architect at EE, walked around central London with me. He pointed out the practicalities of Small Cell backhaul for our urban streets. As the network densifies, more street-level small cell sites will be needed. Andy explains how these will be connected back into the network, and clarifies the technical requirements for this rollout.