Difference between Fixed and Dynamic Channel Allocations.

Fixed Channel Allocation (FCA):
Fixed Channel Allocation is a strategy in which fixed number of channels or voice channels are allocated to the cells. Once the channels are allocated to the specific cells then they cannot be changed. In FCA channels are allocated in a manner that maximize Frequency reuse.
If all channels are occupied and user make a call then the call is blocked. Borrowing Channels handles this type of problem. In this cell borrow channels from other cells.

Dynamic Channel Allocation (DCA):
Dynamic Channel Allocation is a strategy in which channels are not permanently allocated to the cells. When a User makes a call request then Base Station(BS) send that request to the Mobile Station Center(MSC) for the allocation of channels or voice channels. This way the likelihood of blocking calls is reduced. As traffic increases more channels are assigned and vice-versa.

Difference between Fixed Channel Allocation(FCA) and Dynamic Channel Allocation(DCA):

FIXED CHANNEL ALLOCATION(FCA)	DYNAMIC CHANNEL ALLOCATION(DCA)
Fixed number of channels or voice channels are allocated to cells.	Fixed number of channels are not allocated to cells.
If all the channels are occupied and user make a call then the call will be blocked in FCA.	If all the channels are occupied and user make a call then Base Station(BS) request more channel to the Mobile Station Center(MSC).
Frequency reuse is maximum because cells channels are separated by minimum reuse distance.	Frequency reuse is not that maximum in DCA because of channel randomness allocation.
In FCA no such complex algorithms are used.	In DCA complex algorithms are used to decide which available channel is most efficient.
Fixed Channel Allocation Strategy is less costly than the DCA	Dynamic Channel Allocation Strategy is costly because lot of computation is required in real-time.
In FCA allocated channels remains to the cell, once the call is completed	In DCA once the call is completed then the channel or the voice channel return to the MSC.
Mobile Station Center(MSC) has less responsibilities.	Mobile Station Center(MSC) has more signalling load and responsibilities.