Microwave Engineering Europe - March 2009 - (Page 18) 18 WIRELESS INFRASTRUCTURE Networks need femtocells and femtocells need SoCs By Rupert Baines, Vice President Marketing, PicoChip emtocells — compact cellular base stations designed to support small numbers of users — have emerged over recent months as vital enablers for wireless data services. Indeed, Dr Alastair Brydon of Analysys has stated: “Femtocells have the potential to transform the telecoms industry.” Femtocells were originally conceived as purely home-based products, akin to WiFi access points. The energizing force behind their development was the need to improve coverage indoors, to offload 3G data traffic from increasingly congested macrocell networks and to provide wireless network operators with a way of combating the threat of Voice-over-IP and Wi-Fi. But it is becoming increasingly clear that the potential of femtocells goes much further than this: they can deliver the converged services required by enterprises; with increased use of mobile broadband and 4G they can act as metropolitan ‘hot zones’ that allow operators to target coverage and capacity exactly where it is needed; they may even prove key to the costeffective provision of mobile coverage in sparsely populated rural areas. In some respects these new roles for femtocells replace the traditional picocell applications. Operators such as Vodafone, Comcast , Sprint and Softbank have backed this vision and are making it clear that for them, the day of the femtocell cannot come soon enough. This presents a headache for some OEMs, because manufacturing a femtocell — wherever it is to be used — presents a dramatically different set of design requirements and constraints than those traditionally encountered by network infrastructure makers. For the first time, the industry needs to think seriously about provisioning and ease of use in infrastructure equipment. This is a ‘make or break’ issue for products aimed at the residential market, where users will perform their own installation. But it is just as important in operator-led applications such as metropolitan hot zones and enterprise service provision. Deploying thousands or millions of femtocells is a Microwave Engineering Europe ● March 2009 ● F Figure 1: FAP stack software. devastatingly costly business if their configuration requires skilled technicians to spend a substantial amount of time on each installation (as was the case for traditional picocells). Similarly, operators need to know that reliability will be high, and on-going costs low. All femtocells must therefore include selfoptimizing network (SON) features that cut the cost of maintaining a network of huge volumes of basestations. Critically, features are required to ensure that each femtocell interacts smoothly in the radio spectrum with its neighbors without causing interference which would affect the macrocell network. Similarly, femtocells must connect to the core (wired) operator network seamlessly and scalably; and the core network itself must evolve to integrate effectively with so many individual access points. Femtocells will also need to contain security features. This is absolutely critical. Protecting against theft of service and securing users’ data seem obvious, but the real issue is more powerful. The femtocell connects directly into the heart of the mobile operator’s network so without the most stringent security measures a malicious user could access it and launch an attack that compromises the whole cellular network. www.mwee.com As well as including new features, OEMs need to break new ground in terms of capital cost. The price of a macrocell basestation is typically in excess of $10,000; the total bill of materials for a femtocell (though itself currently a matter of debate) must certainly be below $150 — substantially less for a mass market residential product. Last but not least, in addition to ease of use, femtocells share many of the design features associated with consumer products: primarily small size and low power consumption. Gigahertz DSP-based solutions requiring square centimeters of silicon real estate and more than 10 W of power simply will not measure up. This pressure to deliver new features, aggressive pricing and low power consumption can only be delivered via silicon integration. To satisfy these needs wireless baseband chip makers are already beginning to deliver a new category of semiconductor device — the single-chip femtocell. Products are most advanced in the WCDMA arena, with devices such as picoChip’s PC302. Developments in China Because both cdma2000 and WCDMA are already widely deployed, most femtocell http://www.mwee.com
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