Channel Allocation Schemes - DCA and DFS

DCA and DFS

Dynamic Frequency Selection (DFS) may be applied in wireless networks with several adjacent non-centrally controlled access-points. The access-points automatically selects a frequency channel with low interference level. DFS is supported by the novel IEEE 802.11h wireless local area network standard. DFS is also mandated in the 5470-5725 MHz U-NII band for radar avoidance.

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 likelihood of future blocking within the cell. It requires the MSC to collect real time data on channel occupancy, traffic distribution and Radio Signal StrengthIndications (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 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.