r time; in frequency hopping, errors are distributed in clusters. For packetized data systems such as wireless LAN applications, fre- quency-hopping radios have an advantage. During a hop, frequency-hop- ping radios may transmit one or more packets. The higher-layer LAN protocol typically checks for errors in a packet, and if they exist, requests retransmission of the packet. In this type of system, the number of errors in a packet is not important-only the fact that an error has occurred is important. Thus, if the average number of packets with errors is the main performance criterion, it is preferable to have errors arrive in clusters, as in frequency-hopping radios. The receiving slow frequency-hopping radio, however, generally takes longer to synchronize to the transmitting radio than corresponding direct- sequence radios with matched filters. For packetized data, this can be a major problem owing to the time needed for resynchronization for each packet or group of packets. For all practical purposes, the FCC rules limit frequency-hopping radios to a maximum data rate of 1 Mbps since their instantaneous bandwidth is a The FCC Part 15 Rules maximum of 1 MHz. Direct-sequence radios can have higher data rates when sufficient bandwidth is available. For the 5.7-GHz band, several manufac- turers offer commercial direct-sequence spread-spectrum radios capable of a wireless LAN burst rate of at least 5 Mbps and full-duplex operation of 2 Mbps. Voice applications are more tolerant of errors but require full-duplex operation. In voice applications, the acquisition time is not as critical, but unlike applications with packetized data, strong bursts of errors are more bothersome. In addition, owing to lower data rates (typically 32 kbps or less) for voice than for most data applications, each direct-sequence radio channel requires less bandwidth. For cordless telephones, e.g., each voice channel typically requires 2 MHz of bandwidth. For the 902-928 MHz ISM band, this means that 13 non-overlapping direct-sequence voice 