 to each other via Ethernet (802.3) bus. The devices first access the WLAN network which is connected to 802.20 clients via a router. The client connects the end users to 802.20 base stations which in turn connects them to the Internet via Home Agent. The client together with the WLAN network and base stations, jointly offer the transparent services on the physical layer and data link layer between the Internet and the devices. With the help of NAT (network address translate) technology the whole network may only need a single IP address. A server can automatically assign each device a dynamic IP address [6]. 6.8 Performance A high level performance analysis via simulations and field trial of the IEEE 802.20 Wideband mode technology is presented in this section. 6.8.1 Lab Simulations The simulation results of IEEE 802.20 technology has been published in [7, 8]. In these papers au- thors simulated the physical layer via SIMULINK and subsystems in MATLAB S-function files. ITU IEEE 802.20 Mobile-Fi Home Agent Internet IEEE 802.20 client IEEE 802.20 client Ethernet (802.3) ((0)) ((o)) ((o)) Figure 6.12 IEEE 802.20 network architecture Vehicular-A and Vehicular-B models were used to measure the performance under various speeds. The two models differ via different delay spread values and both were encountered for some percentage of time in a given test environment. Simulations were performed at 3 GHz carrier frequency and with 6-MHz channel bandwidth. The key results are as follows: QPSK and 8-PSK modulations have good performance at all speeds (0-250 km/h) whereas perfor- mance of 16-QAM and 64-QAM schemes is not acceptable at 250 km/h: Lower modulation techniques (QPSK and 8-PSK) can be used at such high speeds (120 km/h and 250 km/h) to avoid high BER (bit error rate) values and the loss of data. Higher modulation schemes could be used at lower speeds (30 km/h) to provide higher data throughputs. In the stationary position and at 20 dB SNR, 64-QAM can provide around 5.5 Mbps data throughput whereas at 250 km/h the t