Trunking radio system with frequency diversity

In a trunking radio system comprising a central station and at least one remote unit for communication with the central station over a plural number of frequency-divided radio channels, the central station comprising:

• a transmitter for transmitting a plurality of signals to different remote units on different channels;
• a trunking controller for allocating channels to different remote units and for signalling to a remote unit via the transmitter to access a channel to the remote unit, said trunking controller having traffic monitoring means for monitoring at a given time the number of channels allocated;
• said trunking controller being responsive to the traffic monitoring means to signal to the remote unit via the transmitter to access at least two channels when the number of channels allocated is less than the plural number of frequency-divided radio channels;
• and
• diversity means responsive to the traffic monitoring means, for receiving signals from the remote unit over said at least two channels.

In a trunking radio system comprising a central station and at least one remote unit for communication with the central station over a plurality of frequency-divided radio channels, a remote unit comprising:

• processing means for signalling to the central station a request for allocation of at least two channels for transmission, for receiving a channel grant command arranged as one of a first format and a second format, the first format containing one channel identifier and the second format containing two channel identifiers, and for decoding the channel grant command and determining in which of the two formats the command is arranged;
• and
• transmit means responsive to the processing means for transmitting on a single channel if the channel grant command contains only one channel identifier;
• and said transmitting means including a diversity transmitting means for transmitting the same signal on two channels if the channel grant command contains two channel identifiers.

A method of operating a trunking radio system having a central station and at least one remote unit for communication with the central station over a plural number of frequency-divided radio channels, the method comprising the steps of:

• at the central station:
• transmitting a plurality of signals to different remote units on different channels;
• allocating channels to said different remote units;
• monitoring at a given time the number of channels allocated;
• identifying that the number of channels allocated is less than the plural number of radio channels;
• signalling to a remote unit to access at least two channels when the number of channels allocated is less than the plural number of radio channels;
• receiving signals from the remote unit over said at least two channels;
• and
• diversity combining the signals received over the at least two channels;
• and at the remote unit:
• receiving signalling from the central station to access at least two channels;
• and
• transmitting a signal over said at least two channels.

A method of operation of a central station of a trunking radio system having a central station and at least one remote unit for communication with the central station over a plural number of frequency-divided radio channels, the method comprising the steps of:

• transmitting a plurality of signals to different remote units on different channels;
• allocating channels to different remote units;
• monitoring at a given time the number of channels allocated;
• identifying when there is no available channel;
• and
• when there are at least two channels available:
• signalling to a remote unit to access at least two channels;
• receiving signals from the remote unit over said at least two channels;
• and
• diversity combining the signals received over the at least two channels.

In a trunking radio system having a central station and at least one remote unit for communication with the central station over a plurality of frequency-divided radio channels, a method of operation of a remote unit comprising the steps of:

• signalling to the central station a request for allocation of at least two channels for transmission;
• receiving a channel grant command arranged as one of first and second formats, the first format containing one channel identifier and the second format containing two channel identifiers;
• decoding the channel grant command and determining in which of the two formats the command is arranged;
• transmitting a signal intended for the central station on a single channel if the channel grant command contains only the one channel identifier;
• and
• transmitting the signal intended for the central station on two channels if the channel grant command contains the two channel identifiers.