Radio local loop based on DECT, enhancements to increase capacity

The usage of the DECT as a RLL application has many advantages such as high quality voice encoding (ADPCM at 32 kbps), full ISDN compatibility when assigning double slot to the connection, and no need of frequency planning. DECT was first designed as an indoor system with low spectral efficiency. Although it has only 120 different channels, it is capable of a high quality in the environment it has been designed for. When trying to apply it outdoors, it will be necessary to reuse those few frequencies many times, resulting in a system that is limited mainly by co-channel interference. We have studied several ways to increase the system capacity by limiting the co-channel interference and we have evaluated the impact on the system performance by simulation. Among the most significant improvements studied are the the use of directive and adaptive antennas.