Cellular Systems Cellular Concepts The cellular concept was a ...

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EE5401 Cellular Mobile Communications EE5401 Cellular Mobile Communications R R R 2 2 2 Atri = 1.3R Asq = 2.0R Ahex = 2.6R • Interference tier : A set of co-channel cells at the same distance from the reference cell is called an interference tier. The set of closest co-channel cells is call the first tier. There is always 6 co-channel cells in the first tier. • Hence, a conventional cellular layout is often defined by a uniform grid of regular hexagons. Frequency reuse : • A cellular system which has a total of S duplex channels. • S channels are divided among N cells, with each cell uses unique and disjoint channels. • If each cell is allocated a group of k channels, then S = kN . Co-ordinates for hexagonal cellular geometry • With these co-ordinates, an array of cells can be laid out so that the center of every cell falls on a point specified by a pair of integer co-ordinates. Terminology • Cluster size : The N cells which collectively use the complete set of available frequency is called the cluster size. • Co-channel cell : The set of cells using the same set of frequencies as the target cell. If ( ∆ u , ∆v) = ( i, j) , i,j are known as the shift parameters, then the distance between the two cell centres is given by 2 2 D = i + j + ij ⋅ 3R (Cosine’s Rule) Institute for Infocomm Research 45 National University of Singapore Institute for Infocomm Research 46 National University of Singapore
EE5401 Cellular Mobile Communications EE5401 Cellular Mobile Communications Designing a cellular system Examples: N=3,4,7,9,12,13 Proof : to obtain the area of the cluster and compare with the area of a single cell. The cluster size must satisfy 2 2 N = i + ij + j where i, j str non-negative integers. Can also verify that D Q = = 3N where Q is the co-channel reuse ratio. R Institute for Infocomm Research 47 National University of Singapore Institute for Infocomm Research 48 National University of Singapore
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Cellular Systems Cellular Concepts The cellular concept was a ...

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