Microwave Engineering Europe - November 2008 - (Page 32) 32 RADIO — E-BAND Millimetre wave radio technology By Frans Versluis, program manager, Network Solutions Business, ADC, www.adc.com he 71-76 and 81-86 GHz bands (widely known as e-band) are permitted worldwide for ultra high capacity point-to-point communications. Millimetre Wave wireless (MMW) systems based on e-band frequencies offer fullduplex Gigabit Ethernet connectivity at data rates of 1 Gbps and higher in cost effective radio architectures, with carrier class availability at distances of a mile (1.6 km) and beyond. The significance of the e-band frequencies cannot be overstated. The 10 GHz of spectrum available represents by far the most ever allocated by the FCC at any one time, representing 50-times the bandwidth of the entire cellular spectrum. With 5 GHz of bandwidth available per channel, gigabit and greater data rates can easily be accommodated with reasonably simple radio architectures. E-band has propagation characteristics comparable to those at the widely used microwave bands, so its weather characteristics are well understood, allowing rain fade to be understood and for link distances of several miles/km to be confidently realized. This article explores the technology behind e-band, and demonstrates how it enables the fastest commercial radios available today. A brief history of E-band The 71-76 GHz and 81-86 GHz MMW allocations for fixed services were established by the International Telecommunication Union (ITU) almost 30 years ago at the 1979 WARC-79 World Radiocommunication Conference. However not much commercial interest was shown in the bands until the late 1990s, when the United States FCC’s Office of Engineering and Technology published a study on the use of the millimetre-wave bands [1]. This report concluded that “System designers can take advantage of the propagation properties manifested at millimetre wave frequencies to develop radio service applications. The windows in the spectrum are particularly applicable for systems requiring all-weather operation … or for short range point-to-point systems.” At the 2000 WRC-00 World Radiocommunication Conference, ITU T Figure 1: Significant USA frequency allocations. Figure 2: Atmospheric and molecular absorption. Figure 3: Rain attenuation at microwave and millimetre-wave frequencies. delegates discussed enabling high density fixed services at high frequencies. Around this time, several events were converging that caused interest in e-band wireless: • Device technology had advanced to the point where components operating in the millimetre-wave frequencies could be commercially fabricated. • Congestion in the widely used microwave bands (6 to 38 GHz) meant designers had to start considering alterative frequency bands. • With a vision for multi-megabit and even gigabit per second speeds required by newer generation communication and multimedia services, new paradigms for wireless transmission were needed. Following petition by the wireless industry, the FCC released a Notice of Proposed Rulemaking in 2002 [2] that resulted in the opening of the bands under existing Part 101 fixed service point-to-point rules in 2003 [3]. A novel “light licensing” scheme was Microwave Engineering Europe ● November 2008 ● www.mwee.com http://www.adc.com http://www.mwee.com
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