A communicator for wirelessly transmitting frames to and receiving frames from a least one additional communicator in accordance with a predetermined medium access control protocol, the communicators which transmit and receive the frames constituting a Group, each communicator including a transmitter and a receiver for transmitting and receiving the frames respectively, the medium access control protocol controlling each communicator of the Group to effect predetermined functions comprising: designating one of the communicators of the Group as a hub and the remaining the communicators of the Group as remotes; the hub establishing repeating communication cycles, each of which has intervals during which the hub and the remotes transmit and receive frames; the hub transmitting information to the remotes to establish the communication cycle and a plurality of predeterminable intervals during each communication cycle, the intervals being ones when the hub is allowed to transmit frames to the remotes, when the remotes are allowed to transmit frames to the hub, and when each remote is expected to receive a frame from the hub; the remotes powering off their transmitters during times other than those intervals when the remote is allowed to transmit frames to the hub, by using the information transmitted from the hub; the remotes powering off their receivers during times other than those intervals when the remote is expected to receive a frame from the hub, by using the information transmitted from the hub; the hub assigning transmission opportunities to the remotes, each transmission opportunity being an interval for a remote to transmit frames to the hub; the hub transmitting transmission opportunity allocation information in a frame transmitted by the hub; and the hub allocating a number of transmission opportunities during at least one communication cycle which is at least one less in number than the number of remotes in the Group. view more

A communicator for wirelessly transmitting frames to and receiving frames from a least one additional communicator in accordance with a predetermined medium access control protocol, the communicators which transmit and receive the frames constituting a Group, each communicator including a transmitter and a receiver for transmitting and receiving the frames respectively, the medium access control protocol controlling each communicator of the Group to effect predetermined functions comprising: designating one of the communicators Of the Group as a hub and the remaining the communicators of the Group as remotes; the hub establishing repeating communication cycles, each of which has intervals during which the hub and the remotes transmit and receive frames; the hub transmitting information to the remotes to establish the communication cycle and a plurality of predeterminable intervals during each communication cycle, the intervals being ones when the hub is allowed to transmit frames to the remotes, when the remotes are allowed to transmit frames to the hub, and when each remote is expected to receive a frame from the hub; the remotes powering off their transmitters during times other than those intervals when the remote is allowed to transmit frames to the hub, by using the information transmitted from the hub; the remotes powering off their receivers during times other than those intervals when the remote is expected to receive a frame from the hub, by using the information transmitted from the hub; the hub transmitting two frames containing information to establish the plurality of predeterminable intervals during each communication cycle, the second frame containing the information to established the plurality of predeterminable intervals occurring before the intervals in which the remotes are allowed to transmit frames to the hub. view more