e are likely to be less important than are summarized in Table 5.1-5. A convolutional code cost and ease of use in determining commercial viability. with rate 5/8 (8 output bits for 5 input bits) is used. Of Recent modifications (March 2004) to the direct-se- the 128 subcarriers, 22 are used as pilot tones and guard quence proposal have changed the MBOK signaling and tones and 6 are not used at all. The resulting symbol is proposed a common signaling mechanism between the about 1/4 of a microsecond long. The cyclic prefix is no multiband OFDM and direct sequence approaches. The longer included, because this prefix adds a periodicity to Table 5.1-5 Wideband OFDM parameters, 200 Mbps rate. Table 5.1-6 Link performance, 200 Mbps. Parameter Value Parameter Wideband OFDM DS-CDMA Data rate 200 Mbps Information data rate 200 Mbps 200 Mbps Modulation constellation OFDM/QPSK Average TX power -10 dBm -10 dBm FFT size 128 tones Total path loss 56 dB (4m) 56 dB(4m) Coding rate R = 5/8 Average RX power -66 dBm -66 dBm Spreading rate Noise power per bit -91.0 dBm -91 dBm Pilot/guard tones Complementary metal-oxide 6.6 dB 6.6 dB semiconductor RX noise Data tones figure Information length 242.4 nsec Total noise power -84.4 dBm -84.4 dBm Padded prefix 60.6 nsec Required Eb/No 4.7 dB 6.8 dB Guard interval 9.5 nsec Implementation loss 2.5 dB 2.5 dB Symbol length 312.5 ns Link margin 10.7 dB 8.7 dB Channel bit rate 640 Mbps RX sensitivity level -77.2 dBm -75 dBm Wireless local area networks CHAPTER 5.1 selection process appears to be favoring the multiband interoperability between vendors. These factors made OFDM proposal, but it has not yet been approved. At the 802.111 Wi-Fi networks popular despite limited support time of this writing, it is not known whether either of for time-sensitive traffic and porous link security. En- these proposals will be approved by the IEEE as standards hancements of the 802.11b standard to higher data rates or whether the resulting standard will enjoy any success in (802.11g) and different bands (802