A more efficient way of channel allocation would be Dynamic Channel Allocation or Dynamic Channel Assignment (DCA) in which voice channel are not allocated to cell permanently, instead for every call request base station request channel from MSC. The channel is allocated following an algorithm which accounts the following criteria:
Future blocking probability in neighboring cells and Reuse distance
Usage frequency of the candidate channel
Average blocking probability of the overall system
Instantaneous channel occupancy distribution
It requires the MSC to collect real time data on channel occupancy, traffic distribution and Received Signal Strength Indications (RSSI). DCA schemes are suggested for TDMA/FDMA based cellular systems such as GSM, but are currently not used in any products. OFDMA systems, such as the downlink of 4G cellular systems, can be considered as carrying out DCA for each individual sub-carrier as well as each timeslot.
DCA can be further classified into centralized and distributed. Some of the centralized DCA schemes are:
First available (FA): the first available channel satisfying reuse distance requirement is assigned to the call
Locally optimized dynamic assignment (LODA): cost function is based on the future blocking probability in the neighboring cells
Selection with maximum usage on the reuse ring (RING): a candidate channel is selected which is in use in the most cells in the co-channel set
DCA and DFS eliminate the tedious manual frequency planning work. DCA also handles bursty cell traffic and utilizes the cellular radio resources more efficiently. DCA allows the number of channels in a cell to vary with the traffic load, hence increasing channel capacity with little costs.