FEATURE MOBILE FRONTHAUL
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Mobile fronthaul: a new optical opportunity
Pauline Rigby investigates the increasing use of optical transceivers in modern wireless base stations
Tis will create a market opportunity for optical transceiver vendors that could be worth nearly a billion dollars over the next five years, according to research from analyst firm LightCounting. ‘Our research shows that fronthaul
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networks will consume more than 14 million optical transceivers in 2014, with a market value of $530 million [€375 million], roughly on par with the FTTx application segment. Unlike the FTTx segment, however, we believe annual sales of fronthaul transceivers will grow to more than $900 million over the next five years’, said John Lively, principal analyst at LightCounting, who carried out the study. But what is mobile fronthaul anyway?
Optics has a very clear place in modern mobile networks
22 FIBRE SYSTEMS Issue 6 • Winter 2015
Simply put, a mobile base station consists of a baseband unit (BBU), which processes user and control data, and a radio unit (RU), which generates the radio signal that is transmitted by the antenna. About a decade ago mobile operators realised that if they could separate these functions, they could move the radio unit onto the tower to save space and power in the hut below. Te radio unit then becomes a remote radio head (RRH) and the equipment a distributed base station. Te resulting link between the two units is called fronthaul. Recently, mobile operators have latched
onto the idea of a centralised or cloud-based radio access network or C-RAN. Now they can pick up the BBU and move it a couple of kilometres away to a secure and central
s mobile carriers upgrade their networks to Long Term Evolution (LTE) 4G, they will have to embrace a new concept known as fronthaul.
location, allowing them to share data processing resources across multiple cell sites. ‘Tis architecture has gone from an idea to a real business in the last two to three years,’ said Lively. I think it’s safe to say that anyone who is doing LTE is using fronthaul in some shape or form because that’s the way it’s been designed.’ Explaining why fibre is the best choice in
this application, Lively said: ‘It’s partly capacity, partly the physical part of running up the tower, and partly because it offers longer reach – and I think this is why the optical market has taken off in the last few years. If you’re doing more than [running cable] down the tower you have to go for something other than copper. But even going just down the tower, optics has considerable advantages in terms of weight, ice loading, wind resistance and things like that. So it has a very clear place in modern mobile networks.’ As part of the development of distributed
base station equipment, the mobile vendors established the Common Public Radio Interface (CPRI) standard in 2003. Tis protocol, which is used to communicate between BBU and RRH, requires significantly higher data transmission rates than the payload that it is carrying. Lively explained: ‘Connecting between the
baseband unit and the remote radio head is very different to backhaul in terms of the traffic. Te data coming out of the baseband unit and towards the backhaul side is digitally processed. Te fronthaul carries uncompressed digital data.’ Te analogue radio signal has been digitally sampled and has error correction and encapsulation on top.
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