Abstract: A method of operating a communications system, particularly a FDM-TDD cordless telephony system, in which, in order to expedite handover, a portable secondary station builds up a record of the status and quality of the other FDM channels in the system by every 1 in n (where n is an integer greater than one) TDD frames monitoring another FDM channel. The value of n is adaptive in that, as the quality of its existing channel deteriorates, the value of n decreases, thereby updating its record more rapidly. At handover, the secondary station is able to choose immediately an acceptable alternative channel, thereby avoiding the time overhead of scanning all the other FDM channels.

Abstract: A communications system, such as the DECT, comprises a plurality of geographically separate primary stations and a plurality of secondary stations which are able to roam relative to the primary stations. Communication between a primary and a secondary station is by way of any of a plurality of time division duplex radio channels. An idle primary station transmits an idle beacon signal. When a secondary station roams out of the coverage area of a primary station and so can longer lock to that primary station, it scans all of the radio channels for an idle beacon signal. To conserve battery power, instead of continuously rescanning all channels, the successive rescans are made less frequently as the time interval from when the secondary station was last in lock increases, until a predetermined maximum interval has been reached between successive rescans.

Abstract: A time division communications system for radio communication between primary stations and a plurality of secondary stations, having a normal idle beacon message transmitted by the primary station when it has an otherwise idle period. To reduce interference with stations in adjacent areas, and power consumption, during long idle periods the primary station ascertains whether secondary stations which are in range are experiencing sufficiently low interference that the primary station can switch to a low duty cycle link mode. In the low duty cycle mode paging messages are transmitted as required, and low duty link reassurance messages are transmitted at relatively long intervals. If either the primary or secondary stations detect sufficient increase in interference, the system reverts to the normal idle state.

Abstract: A communication system such as a digital cordless telephone system comprises primary (or base) stations (PS) and secondary stations (SS). The primary stations over a local area are coupled to a system controller (14 or 15) which interfaces with the PSTN. A TDMA method is used for forward and reverse transmissions between a primary and a secondary station. For digitized speech transmission normally one duplex voice channel formed by one forward time slot (or physical channel) and one reverse time slot (or physical channel) in each frame is allocated for the transaction. For fast data rates it is desirable that additional duplex voice channels be made available quickly for the transmission of a fast data message, after which the additional duplex voice channels can be relinquished. In order to facilitate the rapid set-up of a data transaction, a map store in each data secondary station lists the usage and quality of all the duplex voice channels.

Abstract: A method of, and system for, data transmission over a time division duplex channel in which at least one duplex voice channel constituted by a pair of non-adjacent time slots (or physical channels) in a succession of time frames is allocated for effecting a data transaction between a first and a second station, one of said pair of time slots (or physical channels) being normally designated for unidirectional transmission of data in a first direction between the first and second stations and the other of the pair of time slots (or physical channels) being normally designated for unidirectional transmission of data in a second direction, opposite to the first direction.