ENC3250 Solutions pg 55

ENC3250 Solutions pg 55 - 11.8(1 MMDS signals have larger...

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Unformatted text preview: 11.8 (1) MMDS signals have larger wavelengths (greater than 10 cm) and can travel farther without losing significant power. Hence MMDS can operate in considerably larger cells, thereby lowering base station equipment costs. (2) Equipment at lower frequencies is less expensive, yielding cost savings at both the subscriber and base station. (3) MMDS signals don't get blocked as easily by objects and are less susceptible to rain absorption. 11.9 802.16.1 is targeted at the 10 to 66 GHz spectrum and is considered a millimeter wave system. It is designed to support data rates above 2 Mbps. The target market is small and medium size businesses. 802.16.2 is concerned with coexistence of multiple systems in the same area. 802.16.3 is targeted at the 2 to 11 GHz spectrum and is a microwave system. It is designed for data rates below 2 Mbps. The target market is residential and small business. A N SWERS NSWERS TO PROBLEMS 11.1 A straightforward way to do this is to double the bandwidth of each individual channel (using half as many channels), double the data rate, and use TDD on each channel. So, the channel bandwidth becomes 400 kHz with a bit rate of 541.6 kbps. Total number of TDD channels = 125. 11.2 a. First, we need the attenuation from rain. We use Equation 11.3, namely A = aRb. From Table 11.8, we get R = 32 mm/hr. For the parameters a and b, we use Table 11.7 and interpolate for ah and bh at 38 GHz, yielding a = 0.3152 and b = 0.955. With these parameters A = 0.3152 x (32)0.955 = 8.63 dB/km. Total attenuation = 8.63 x 12 = 103.56 dB b. At 99.9%, R = 10 mm/hr. A = 0.3152 x (10) 0.955 = 2.84 dB/km Total attenuation = 2.84 x 12 = 34.08 dB At 99%, R = 2 mm/hr. A = 0.3152 x (2) 0.955 = 0.61 dB/km Total attenuation = 0.61 x 12 = 7.32 dB The 99.99% requirement would be difficult to meet. Source: [FREE98] -55- ...
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