A radio communication system has a random access channel for the transmission
of
data from a secondary station to a primary station while the secondary station
is not engaged in a call. A secondary station wishing to use a random access channel
resource transmits a preamble encoded with a signature corresponding to the required
resource. In response the primary station can transmit a positive acknowledgement
(ACK) corresponding to the received preamble, indicating that a channel is available,
or a negative acknowledgement (NACK), indicating that the resource is not available.
A first set of signatures are used to encode ACKs and a second set of signatures
are used to encode NACKs. The two sets of signatures have the property that no
signature in one set is the inverse of a signature in the other set, thereby avoiding
the possibility of simultaneously transmitting an ACK and a NACK with signatures
that are the inverse of one another.
