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UPPCL JE EC Official Paper (Held on 25 March 2021: Shift 2)

Option 2 : Number of times a cluster is replicated

__Concept:__

To understand the frequency reuse concept, consider a cellular system which has a total of S duplex channels available for use.

If each cell is allocated a group of **k channels (k < S)**, and if the S channels are divided among **N cells** into unique and disjoint channel groups which each have the same number of channels, the** total **number of available radio channels can be expressed as

**S = kN**

The N cells which collectively use the complete set of available frequencies is called a **cluster**.

If a cluster is **replicated M times** within the system, the total number of duplex channels, C, can be used as a measure of **capacity **and is given by

**C = MkN = MS**

If the cluster size N is reduced while the cell size is kept constant, more clusters are required to cover a given area, and hence more capacity is achieved.

__Conclusion:__

The capacity of a cellular system is directly proportional to the number of times a cluster is replicated in a fixed area.