8.2 SPACE DIVISION MULTIPLE ACCESS

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8.2 SPACE DIVISION MULTIPLE ACCESS

Because radio spectrum is a natural resource, we have to make best use of it. When a set of frequencies is reused in another location, it is called space division multiple access (SDMA). Again, consider a mobile communication system. A base station will be allocated a few frequencies. The same set of frequencies can be allocated to another region, provided there is sufficient distance between the two regions.

As shown in Figure 8.2, the area covered by a mobile communication system can be divided into small regions called cells. A cell is represented as a hexagon. In each cell, there will be a base station that will be given a pool of frequencies. The frequencies of cell A (1) can be reused in cell A(2). We will study the detail of SDMA in more detail when we discuss cellular mobile communications in the chapter "Cellular Mobile Communication Systems."

Figure 8.2: Space division multiple access.

In SDMA, a service area is divided into small regions called cells and each cell is allocated certain frequencies. Two cells can make use of the same set of frequencies, provided these two cells are separated by a distance called reuse distance. SDMA is used in mobile communication systems.

Note 

The main attraction of SDMA is frequency reuse. Frequencies allocated to one cell can be allocated to another cell, provided there is sufficient distance between the two cells to avoid interference. This minimum distance is called reuse distance.

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