Microwave Engineering Europe - January/February 2009 - (Page 19)

4G TECHNOLOGY FOCUS 19 Table: Characteristics of cells from macro to femto. Pico base stations The indoor pico base station is a small device that can be mounted on a wall or ceiling to support users in airports, shopping malls, ofﬁce buildings and other large enterprises. In these areas, the pico station can provide better coverage at a signiﬁcantly lower capital investment than a macro base station. Multiple pico base stations can be distributed throughout a large building, all connecting back to a centralized device that communicates with the carrier’s network. The carrier typically works closely with the owner of the building to install these devices. Outdoor units are weatherized and mounted on poles or buildings. They help cover shadow areas behind large obstructions such as tall buildings, hills and trees. Pico base stations usually integrate the baseband equipment and radios into a single unit, which sometimes includes the antennas. This unit generally uses a single Ethernet connection for backhaul and sometimes a wireless connection. The unit’s integration coupled with lower RF power outputs results in lower cost than even the micro base stations. For pico base stations, the typical power range is between 23 and 30 dBm, and some will be slightly higher. Femto base stations Taking the pico concept a step further, the femto base station operates at even lower power levels. The typical power level for a femto will be on the order of 17-20 dBm. Providing coverage within an individual home, it is similar in size to a home Wi-Fi router or access point. The connection to the carriers’ network is through the customer’s DSL, cable or even the wireless broadband connection to the macro base station. The latter method increases overall network capacity because the femto station off-loads trafﬁc from the carrier’s wireless network. Large service providers such as Sprint and Comcast have said that WiMAX femto base stations will play an important role in deployments for homes now and into the future. The usage model is similar to that of a 3G femto where users connect to the network via an existing broadband connection, and the femto station provides wireless coverage to a few WiMAX mobile stations inside a home. ABI Research recently forecast that there will be 102 million femtocell users in 2011. This forecast covers all femto base stations, regardless of technology. Wireless broadband roadmap Although no single technology has been selected for 4G broadband wireless technology, several options provide similar capabilities. All these technologies support an all-IP packet network with the ability to run multiple services simultaneously, including high quality streaming video. The top candidates include WiMAX, based on IEEE 802.16 standards, and Long Term Evolution (LTE), the next standard beyond 3G developed by the 3rd Generation Partnership Project (3GPP). Both technologies use Orthogonal Frequency Division Multiple Access (OFDMA) on the downlink to provide high peak data rates — up to 100 Mbps in a 20 MHz channel with good spectral efﬁciency. Regulatory bodies of various countries are already looking to license spectrum for these technologies. In early 2008, the European Commission opened spectrum in the 2.6 GHz band to allow regulatory groups within each European Union country to make decisions regarding technology that can be utilized within this band. This approach represents a change from the past and allows technologies such as WiMAX or LTE to be deployed as long as service providers meet the technical requirements for the band. This band is already open in countries such as the US and Japan, and it is expected that more countries will license this spectrum for broadband wireless. Femto reference design kit To accelerate product development, reference design kits (RDK) currently exist that incorporate all the resources necessary to develop a cost-effective femto base station that is ready for mass production. The kits contain a femto base station unit along with radio and antennas supporting Mobile WiMAX Wave 2 MIMO (2X/2X) operating in the 2.5 to 2.7 GHz band and support for Gigabit Ethernet as well as GPS/IEEE 1588 for network synchronization. About the author Dean Chang is Senior Manager, Application Speciﬁc Standard Products Group at Fujitsu Microelectronics America. Prior to joining FMA he was employed at Aperto Systems as director of product management. (Reprinted courtesy of CommsDesign) Microwave Engineering Europe ● January/February 2009 ● www.mwee.com http://www.mwee.com

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Microwave Engineering Europe - January 2009 News Contents Comment Using KPIs to Ensure Quality in a Converging Network Amplifier Error Vector Magnitude Characterisation Using High-Speed Modular PXI Instruments GPS: Making a Play for Femtocells Accelerating Global WiMAX Adoption: The Move to Picocell and Femtocell Base Stations Addressing PA Efficiency for Multi-Mode Wideband Handset Applications Wi-Fi: Mobile Feature or Fundamental RAN? Products Calendar

Microwave Engineering Europe - January/February 2009

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