Small is beautiful
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Femtocells are set to expand 3G communications. But what are the silicon implications?
Femtocells – basestations for use in the home – have been an afterthought as far as 3G wireless is concerned. But, given how poor indoors signal coverage is curbing broadband wireless’ potential, femtocells are now central to operators’ thinking.
With an output of around 10mW, a femtocell typically serves four users. It ‘talks’ to handsets using the 3G air interface, but routes data and voice traffic through the home’s fixed broadband line instead of the mobile network. Femtocells thus promise to save money for mobile operators by accommodating traffic growth via the fixed network, instead of requiring the mobile network to be upgraded with costly macro cells.
The merits of greater network capacity and signal coverage explain why industry analysts believe femtocell deployments will rise to 70million by 2012. It also explains why femtocell baseband chip designs are coming to market from firms such as picoChip, Percello, Texas Instruments and RadioFrame Networks, which is developing its own silicon.
“The real big [chip] volumes will come in 2010,” said Mark Keenan, managing director, EMEA, for RadioFrame Networks. That’s because work on femtocell standards is incomplete and operators and vendors have still to undertake interoperability tests and femtocell trials, he said.
In a 3G network, a wireless base station – or Node B – connects to a radio network controller. Typically, the controller serves 50 to 100 Node Bs. A femtocell can be viewed as a simple Node B that supports four or eight 3G users instead of 1000 users for a cellular base station. Femtocells allow thousands – even tens of thousands – of Node Bs to be deployed within a radio cell.
Each femtocell must also be made as cheaply as possible to strengthen the business case. Indeed, the target price has dropped to $100 for 2009.
This rapid decline in selling price is why RadioFrame decided to design its own silicon. When it first spoke to merchant chipmakers, they were either unconvinced by the prospects of femtocells or had cost points that the femtocell maker deemed too high. “Our cost requirement is less than half what these guys are offering,” said Keenan.
