the terminal 325 wakes up to receive data in the downlink only every two beacons its downlink latency is double that of its uplink latency and is double that of the terminal 320 stated another way the uplink latency of terminal 325 is half its downlink latency it will also be noted that although the terminal 325 has the same duty cycle as the terminals in group b the terminals in group b have an uplink latency that is twice that of the terminal 325 of course different relationships can be chosen that accommodate different latency differences between terminals in a group or between uplink and downlink latencies in a terminal fig4 depicts an exemplary beacon message packet 400 transmitted by a network controller or master that enables terminal grouping as described above the packet 400 advantageously starts with a preamble 410 that may be used by a terminal to train its radio i e carry out frequency tuning bit synchronization etc after the preamble 410 there may be one or more fields for administrative information such as a packet type field 420 that indicates that this is a beacon packet and possibly a packet length field 430 that indicates the length of the packet in bits bytes time or other suitable measure the administrative fields may include information indicating the beacon group for which this particular packet 400 is intended if the beacon structure is fixed this is not required but including such information in either.