Microwave Engineering Europe - May 2008 - (Page 14)

14 WIRELESS NETWORKING — INDOOR SOLUTIONS Wireless coverage where everybody WINS Whether standing on the thirtieth ﬂoor of a skyscraper or seated in a subway, today’s consumers want wireless phone and data access whenever and wherever they are. Peter Raabe, Director Global Product Management and Support for Wireless Indoor Solutions at Radio Frequency Systems, explores the new generation of wireless indoor infrastructure. By Peter Raabe, Radio Frequency Systems, www.rfsworld.com E scalating consumer demand for ‘wireless coverage where needed’ has led to the emergence of a new breed of mobile communications solutions. Such solutions provide mobile connectivity within environments not traditionally serviced by outdoor base transceiver stations (BTS) — for example, tunnels and metros, and large complexes such as airports and shopping centres. In order to meet this demand for ‘continuous coverageat-call’, there is a clear need for a range of mobile connectivity infrastructures, adaptive to each unique environment. Wireless Indoor Solutions (WINS) encompass infrastructure for services — such as global system for mobile communications (GSM), universal mobile telecommunications system (UMTS), code division multiple access (CDMA), advanced wireless services (AWS), wireless ﬁdelity (WiFi), personal mobile radio (PMR), and terrestrial enhanced trunk radio (TETRA — inside buildings and throughout structures where coverage is usually difﬁcult. With the ultimate objective of high-quality, continuous coverage, the technology allows end-users to receive signals in indoor or underground areas where the carrier’s network or WiFi signal is either weak, or not properly managed. Importantly, WINS systems need to meet certain speciﬁc criteria: they must support the new high data-rate applications that will be important sources of revenue for carriers in the future; they must prevent interference between competing networks and technologies; they should succeed against physical and aesthetic constraints; they need to reduce costs for infrastructure owners in the deployment of second-generation (2G), 3G, or WiFi; and they must be future-proof for a range of technologies including UMTS, worldwide interoperability for microwave access (WiMAX), WiFi and even mobile TV. Figure 1: Signal booster installed at building’s gate to ﬁll ‘nulls and voids’. Scaling barriers The case for WINS is demonstrated by examining the scenario of coverage inside a building (or tunnel) that does not incorporate dedicated wireless infrastructure. Provided a signal is in direct line-of-sight from a carrier’s base station, 2G and 3G signals coming from outside a building can generally cross simple obstructions such as windows and walls. However, the higher the frequency, the more difﬁcult it is for that signal to penetrate barriers. Typically, a 900 MHz GSM signal will lose 5 dB each time it passes through a partially metallic structure. Even more problematic, a 2500 MHz WiMAX signal will lose 10 dB in those circumstances. To put these ﬁgures in perspective, a loss of 3 dB equates to a 50 per cent loss in the quality of a received signal; a loss of 10 dB is equivalent to a tenfold decrease. Several types of solutions are available that resolve these coverage issues. In the most basic solution scenario (Figure 1), operator base stations can be extended with signal ‘boosters’— off-air repeaters installed at ‘building’s gate’. This technology is particularly appropriate to ﬁll ‘nulls and voids’ for wireless services of a speciﬁc carrier and ensure homogeneous coverage in areas such as large lobbies, halls and small buildings. However, a more satisfactory solution is provided by dedicated wireless infrastructure installed within the building or complex to provide premium wireless coverage. In support of this need, RFS has developed the comprehensive ClearFill suite of indoor coverage solutions. Such solutions can be either entirely passive in nature, or incorporate a hybrid topology where the signal undergoes ampliﬁcation to cover larger areas. Passive WINS Passive solutions, also known as distributed antenna systems (DAS), involve distributing an RF signal using cables and antennas, without ampliﬁcation (Figure 2). This solution is ideally suited to small buildings (typically from 5000 to 50,000 square metres) and tunnels less than 500 metres. Passive DAS can be used either in single or multi-carrier conﬁgurations. In a single carrier conﬁguration, cables are connected directly to the operator BTS or to an offair repeater. For multi-carrier solutions, different carriers’ BTSs are combined to a Microwave Engineering Europe ● May 2008 ● www.mwee.com http://www.rfsworld.com http://www.mwee.com

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Microwave Engineering Europe - May 2008 News Contents Comment Cover Feature: How to Succeed as a GaAs Foundry Wireless Networking: Wireless Coverage Where Everybody WINS Wireless Networking: Achieving Good Coexistence in the 2.4 GHz ISM Band GPS and Satellite: GPS developments: Galileo Moves Forward with Successful Giove-B Satellite Launch — Broadcom Targets AGPS in Mobile Phones and Devices Raising the Bar for the Radio: Making 802.11n Work Reducing Power Consumption in Ultrawideband Chips WiMax Catches Second Test Wave Products Calendar

Microwave Engineering Europe - May 2008

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