Method of operating a communications system, a communications system and a secondary station for use in the system

Claim 3

A cellular communications system which comprises a plurality of primary stations and a plurality of secondary stations, the respective primary stations having respective carrier channels, communication between a primary station and secondary stations being in accordance with a time division multiplex protocol such that the relevant carrier channel is divided into successive time frames each of which is further divided into successive physical channels, an idle physical channel of a carrier channel being so identified by a beacon signal transmitted therein by the relevant primary station; and wherein to select a physical channel an out-of-lock secondary station is periodically actuated to sequentially scan the physical channels of the carrier channels to detect beacon signals therein, the scanning including detection of the transmission characteristics of such carrier channels; characterized in that: each secondary station comprises receiving means and control means for periodically actuating the receiving means to perform the following scanning sequence when the secondary station is out-of-lock in order to select an idle physical channel of a carrier channel with which to lock-in: (i) scan successive physical channels of one of a selected series of non-adjacent carrier channels; (ii) during step (i) identify, by detecting beacon signals therein, any idle physical channels in said one carrier channel as well as in a carrier channel adjacent thereto; (iii) consecutively repeat steps (i) and (ii) for consecutive non-adjacent carrier channels in said selected series; and (iv) cease further scanning after having identified an idle physical channel in a carrier channel having transmission characteristics which are acceptable to the secondary station, and lock-in to such carrier channel.

Claim 4

A cellular communications system which comprises a plurality of primary stations and a plurality of secondary stations, the respective primary stations having respective carrier channels, communication between a primary station and secondary stations being in accordance with a time division multiplex protocol such that the relevant carrier channel is divided into successive time frames each of which is further divided into successive physical channels, an idle physical channel of a carrier channel being so identified by a beacon signal transmitted therein by the relevant primary station; and wherein to select a physical channel an out-of-lock secondary station is periodically actuated to sequentially scan the physical channels of the carrier channels to detect beacon signals therein, the scanning including detection of the transmission characteristics of such carrier channels; characterized in that: each secondary station comprises receiving means and control means for periodically actuating the receiving means to perform the following scanning sequence when the secondary station is out-of-lock in order to select an idle physical channel of a carrier channel with which to lock-in: (i) scan successive physical channels of one of a selected series of non-adjacent carrier channels; (ii) during step (i) identify, by detecting beacon signals therein, any idle physical channels in said one carrier channel as well as in a carrier channel adjacent thereto; (iii) consecutively repeat steps (i) and (ii) for consecutive non-adjacent carrier channels in said selected series; and (iv) cease further scanning after having identified an idle physical channel in a carrier channel having transmission characteristics which are acceptable to the secondary station, and lock-in to such carrier channel.

Claim 5

A secondary station for use in a cellular communications system which comprises a plurality of primary stations and a plurality of said secondary stations, the respective primary stations having respective carrier channels, communication between a primary station and secondary stations being in accordance with a time division multiplex protocol such that the relevant carrier channel is divided into successive time frames each of which is further divided into successive physical channels, an idle physical channel of a carrier channel being so identified by a beacon signal transmitted therein by the relevant primary station; characterized in that each said secondary station comprises: receiving means and control means for periodically actuating the receiving means to perform the following scanning sequence when the secondary station is out-of-lock in order to select an idle physical channel of a carrier channel with which to lock-in: (i) scan successive physical channels of one of a selected series of non-adjacent carrier channels; (ii) during step (i) detect beacon signals which identify any idle physical channels in said one carrier channel as well as in a carrier channel adjacent thereto, and evaluate the transmission characteristics of such carrier channels; (iii) consecutively repeat steps (i) and (ii) for consecutive non-adjacent carrier channels in said selected series; and (iv) cease further scanning after having identified an idle physical channel in a carrier channel having acceptable transmission characteristics, and lock-in to such carrier channel.

Claim 6

A secondary station for use in a cellular communications system which comprises a plurality of primary stations and a plurality of said secondary stations, the respective primary stations having respective carrier channels, communication between a primary station and secondary stations being in accordance with a time division multiplex protocol such that the relevant carrier channel is divided into successive time frames each of which is further divided into successive physical channels, an idle physical channel of a carrier channel being so identified by a beacon signal transmitted therein by the relevant primary station; characterized in that each said secondary station comprises: receiving means and control means for periodically actuating the receiving means to perform the following scanning sequence when the secondary station is out-of-lock in order to select an idle physical channel of a carrier channel with which to lock-in: (i) scan successive physical channels of one of a selected series of non-adjacent carrier channels; (ii) during step (i) detect beacon signals which identify any idle physical channels in said one carrier channel as well as in a carrier channel adjacent thereto, and evaluate the transmission characteristics of such carrier channels; (iii) consecutively repeat steps (i) and (ii) for consecutive non-adjacent carrier channels in said selected series; and (iv) cease further scanning after having identified an idle physical channel in a carrier channel having acceptable transmission characteristics, and lock-in to such carrier channel.

Claim 7

A secondary station as claimed in claim 3 wherein each primary station has a respective coverage area, the beacon signal transmitted by each primary station includes a system identification code, and the secondary station has a home primary station; characterized in that said secondary station further comprises means for storing the system identification codes of the home primary station and of primary stations having coverage areas neighboring that of the home primary station; and said control means is adapted to increase the rate of scanning of physical channels of non-adjacent carrier channels when the system identification codes of the beacon signals detected by the secondary station signify that the secondary station is passing through neighboring coverage areas in a direction toward the coverage area of said home primary station.

Claim 8

A secondary station as claimed in claim 3, wherein scanning of successive physical channels of a carrier channel comprises all physical channels in a frame of such carrier channel.

Claim 9

A secondary station as claimed in claim 3, wherein the physical channels of a carrier channel comprise a series of consecutive forward physical channels and a series of consecutive reverse physical channels, and scanning of successive physical channels of a carrier channel comprises only the physical channels in one of said two series.

Claim 10

A secondary station as claimed in claim 3, wherein scanning of a physical channel includes monitoring thereof all during such scanning in order to detect any signals present therein.

Claim 11

A secondary station as claimed in claim 3, wherein scanning of a physical channel includes monitoring thereof during only a fraction of the scanning period in order to detect the strength of any signals present therein.