Multi-Carrier and Spread Spectrum Systems: From OFDM and MC ...

272 ApplicationsTable 5-35 Peak data rate for the OFDM mode versus modulation (7 MHz, 256sub-carriers, no diversity)T g /T s QPSK 1/2 QPSK 3/4 16-QAM 1/2 16-QAM 3/4 64-QAM 2/3 64-QAM 3/41/32 5.94 8.91 11.88 17.82 23.76 26.731/4 4.9 7.35 9.80 14.70 19.60 22.05Table 5-36 Peak data rate for the OFDMA mode versus modulation (7 MHz, 2048sub-carrier, no diversity)T g /T s QPSK 1/2 QPSK 3/4 16-QAM 1/2 16-QAM 3/4 64-QAM 2/3 64-QAM 3/41/32 5.82 8.73 11.64 17.45 23.27 26.181/4 4.8 7.2 9.6 14.40 19.20 21.6the maximum achievable data rate for the OFDM and OFDMA mode for different PHYmodes in a 7 MHz ETSI channelization raster is given. Both systems provide similarperformance. All MAC overheads are included in the tables.The achievable peak rates versus M-QAM modulation for S-OFDMA are given inTable 5-37 for both 5 and 10 MHz FDD channel bandwidths by considering a frameduration of 5 ms. In this table the parameters for the uplink and downlink are given. Inthe case of the 10 MHz channel bandwidth, data rates up to 32 Mbps and 23 Mbps fordownlink and uplink can be achieved respectively. The penalty in data rate for the uplinkis due to the large amount of overhead spent for pilots and guard times. The repetitioncode is used only in the case of QPSK.The peak data rates found by employing the most efficient mandatory modulationschemes (64-QAM for DL and 16-QAM for UL) with MIMO for S-OFDMA are givenin Table 5-38 for 10 MHz TDD channel bandwidths by considering a frame duration of5 ms. The DL/UL ratio defines the ratio between the DL and the UL allocated time framefor each direction.5.3.7.2 Link Budget, Data Rate, and CoverageFor the link budget evaluation the thresholds for a bit error rate of BER = 10 −6 are considered.The receiver power thresholds are taken from Table 5-31 and 5-32. The receiverE s /N 0 values are listed in Table 5-39.Fixed Positioned Terminal SationThe real WiMAX coverage and capacity performance for a fixed positioned terminalstation depend strongly on the terminal equipment configuration: indoor or outdoor, useof directional antenna or not, use of transmit diversity, etc. The use of a short framelength and long guard time has a negative impact on the total data rate efficiency. InTable 5-40 the link budget for a 7 MHz FDD channel allocation is given. Note that thesystem gain for the uplink is lower than the downlink. This is due to the higher BS