Space-division multiple access
From Free net encyclopedia
In traditional mobile cellular network systems the base station has no information on the position of the mobile units within the cell and radiates the signal in all directions within the cell in order to provide radio coverage.
This results in “wasted” power and transmission where there are no mobile units to reach as well as interference to adjacent cells using the same frequency, so called co-channel cells. Likewise, in reception, the antenna receives signals coming from all directions including noise and interference signals.
By using smart antenna technology and exploiting spatial information of the location of mobile units within the cell have led to the development of space-division multiple access (SDMA) techniques. The radiation pattern of the base station, both in transmission and reception is adapted to each user to obtain highest gain in the direction of the mobile user. This is often done using phased array techniques.