QPSK mod- 200 Mbps ulation. Allowing for a couple of decibels of "imple- TX power -10 dBm mentation loss" (antenna limitations, cable losses, etc.) Path loss 56 dB (4m) RX power -66 dBm Noise/bit -91 dBm RX noise figure 6.6 dB Total noise -84.4 dBm Required Eg/No 6.8 dB Implementation loss 2.5 dB Link margin 8.7 dB RX sensitivity -75 dBm Figure 5.1-31 4-Ary biorthogonal symbols. CHAPTER 5.1 Wireless local area networks Group 1 Group 2 Group 3 Group 4 Group 5 Band #: frequency (GHz) Figure 5.1-32 Band definitions for OFDM UWB proposal. positive frequency (relative to the carrier) is the complex the signal, giving rise to spectral lines which reduce the conjugate of the nth subcarrier at negative frequency. A amount of power that can be transmitted. Instead, an signal composed of complex conjugate frequencies pro- equivalent amount of zero padding is added in fre- duces a pure real voltage (this is just a fancy way of quency space (zero-padded OFDM). Each data symbol reminding us that eiwt + e-iwt = 2cos(wt)). This means is spread by being sent twice, in separate frequency that the transmitter and receiver don't need separate subbands. A brief guard interval is provided between branches to keep track of the in-phase and quadrature (I symbols to allow the radio to change subbands. The use and Q) components of the signal and can be simplified. of separate subbands allows multiple collocated Successive OFDM symbols are sent on different piconets. bands within a band group. Within each band group 1-4 In Table 5.1-6 we compare link performance for the there are four hopping patterns, each six symbols long, two proposals for a data rate of 200 Mbps at 4 m. OFDM allowing for four collocated piconets. (Group 5 supports has a slight advantage in noise tolerance, giving it mod- only two hopping patterns.) Thus, a total of 18 collocated estly improved sensitivity. However, as we noted in piconets is possible. connection with the 802.11b PHY, small distinctions in The implementation parameters for the 200 Mbps radio performanc