Mobile station access to a base station on a digital multiple access control channel

DETAILED DESCRIPTION It is an object of the present invention to provide a procedure usable by a mobile station to access the land system via a digital control channel, taking into consideration that existing EIA/TIA-54 formats for digital traffic channels shall be used with minimum modification for the digital control channel in order to achieve low hardware complexity in the mobile station.
This is accomplished by using the same format for both the traffic channels and the control channels except that the CDVCC and SACCH fields of the traffic channel are used on the control channel to perform the function of structuring the access to the land system from a mobile.
It is a further object of the invention to avoid access burst collision in very large cells.
This is accomplished by defining two separate access methods, one to be used in very large cells and the other to be used in smaller cells.
According to an access method to be used in very large cells, a mobile station transmits two access bursts, a first shortened access burst containing mainly synchronization information and enabling time-alignment information for the mobile station to be derived and a second normal-length access burst containing the usual access information.
It is a further object of the invention to provide sufficient synchronization information in an access burst to ensure good reception.
This is achieved by using the CDVCC and SACCH fields defined in existing EIA/TIA-54 formats to transmit additional synchronization information.
It is a further object of the invention to provide an access method with a low probability of causing multiple accesses, i.
e.
an access method not making more than one base station believe that it has been granted access.
This is achieved by using the digital verification color code DVCC when coding/decoding the cyclic redundancy check CRC the same way as for the traffic channels.
In other words, the "implicit" DVCC is still used whereas the "explicit" DVCC (the CDVCC field in the message) is used for the access procedure