2.7.2 Sample Link Budgets and Coverage Range

Table 2.8 shows a sample link budget for a WiMAX system for two deployment scenarios. In the first scenario, the mobile WiMAX case, service is provided to a portable mobile handset located outdoors; in the second case, service is provided to a fixed desktop subscriber station placed indoors. The fixed desktop subscriber is assumed to have a switched directional antenna that provides 6 dBi gain. For both cases, MIMO spatial multiplexing is not assumed; only diversity reception and transmission are assumed at the base station. The numbers shown are therefore for a basic WiMAX system.

The link budget assumes a QPSK rate 1/2 modulation and coding operating at a 10 percent block error rate (BLER) for subscribers at the edge of the cell. This corresponds to a cell edge physical-layer throughput of about 150kbps in the downlink and 35kbps on the uplink, assuming a 3:1 downlink-to-uplink ratio. Table 2.8 shows that the system offers a link margin in excess of 140 dB at this data rate. Assuming 2,300MHz carrier frequency, a base station antenna height of 30 m, and a mobile station height of 1 m, this translates to a coverage range of about 1 km using the COST-231 Hata model discussed in Chapter 12. Table 2.8 shows results for both the urban and suburban models. The pathloss for the urban model is 3 dB higher than for the suburban model.

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Saturday, September 22, 2007  | Permalink |  Comments (1)