We have noted throughout this book, in discussing cellular systems, that the radio channel used for communication between mobile stations and a base station limits the communication possible. In particular, whether using TDMA or CDMA as the underlying multiple access technique, only a limited number of users may be accommodated in a given frequency band. Users must thus be given permission to transmit, using a given frequency and a specified number of time slots or codes, as the case may be. To obtain permission to transmit, a user must first access the base station indicating a desire to use the system. The availability, in turn, of only a limited number of access channels, whether ...
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