An optimum Frequency Reuse scheme helps in increasing Capacity and reducing interference. The Radio Spectrum has to be efficiently utilized. To meet these objectives, a number of channel assignment strategies have been suggested. They are: Fixed Channel and Dynamic Channel assignment strategies.

1. Fixed Channel Assignment Strategies:

• In the fixed channel assignment method, each cell is assigned a predetermined set of voice channels.
• Any call attempt can only be served by the unused channels within the same cell.
• If all the channels in the cell are occupied, the call is blocked and the subscriber does not receive any service.
• However, in a particular version of fixed channel assignment strategy, called as the borrowing strategy, a cell is allowed to borrow channels from its neighbouring cells in case of scarcity of the channels.
• The MSC supervises such borrowing procedures and ensures that this procedure does not interfere with any of the calls in progress.

2. Dynamic Channel Assignment Strategies:

• In this strategy, permanent allocation of voice channels to individual cells are not done.

  The entire pool of channels is in the MSC’s control.

• Whenever there is a call request, the base station requests a channel from the MSC.

• A channel is allotted after monitoring the following:

$\quad$ $\quad$ - Likelihood of future blocking within the cell.

$\quad$ $\quad$ - The reuse distance of the channel

$\quad$ $\quad$ - Rate at which the channel is being allotted and other cost functions.

• The MSC only allocates a given frequency if that frequency is not presently in use in the cell or any other cell which falls within the minimum restricted distance of frequency reuse to avoid co-channel interference.
• Thus this channel assignment strategy reduces the likelihood of blocking.
• Dynamic channel assignment strategies require the MSC to collect real-time data on channel occupancy, traffic distribution, and Radio Signal Strength Indications (RSSI) of all channels on a continuous basis. As number of subscribers increases, the storage and computational load on the system also increases. However, it provides the advantage of increased channel utilization and decreased probability of a blocked call. Most of the 1G cellular operators, opt for a static channel assignment scheme with channel borrowing provisions.