Integrated resource allocation and adaptive antennas in mobile cellular systems.

摘要

Thirst for higher capacity in mobile cellular communication systems has fueled an interest in finding more efficient ways of allocating limited resources and incorporating adaptive antenna techniques in order to enhance capacity on a per-channel-per-base-station basis. Over the last several years, different resource allocation schemes—including dynamic channel allocation, power control—and adaptive antenna techniques have been proposed and intensively studied. Separately, they have been shown to increase system capacity. However, little research has been done to quantify the capacity gain of their integration and to investigate their interactions in realistic mobile environments. The high complexity of the interactions renders analytical solutions to these problems intractable. A large-scale computer simulation is created to investigate this integrated performance.; We show that more than 20 times capacity gain, compared to a conventional fixed-power fixed channel allocation system, can be achieved by integrating resource allocation schemes and adaptive antennas. With the help of directed retry, “integrated” systems using efficient interference cancellation in the adaptive antennas can achieve an effective channel reuse smaller than one. In addition, we discover that the separate capacity gains achieved by power control and adaptive antennas are not directly additive due to the significant overlap in their ability to reduce interference. Furthermore, the relative effectiveness of different channel allocation schemes depends on whether or not adaptive antennas are included.; When evaluating the performance of systems with adaptive antennas, it is important to include certain spatial information about the propagation channel. Unfortunately, most commonly used angular spread models cannot be used here due to the large computation burden incurred on our already computation intensive large-scale computer simulation. We propose a simplified channel model to characterize the angular spread and evaluate its impact on performance. Under this model, we show that the impact on capacity is minimal unless the angular spread is large with respect to antenna beamwidth. Nevertheless, the angular spread does cause an increase in the required transmit power. A system with optimal interference cancellation achieves the highest capacity gain, but it also suffers the largest power increase when angular spread is taken into consideration.