Distributed Antenna Systems

Intelligent distributed antenna systems (IDAS) can be considered an adaptation technology for the air interface aiming to increase the system capacity, and system robustness, be it the number of users who can be serviced or their transmission bit rates. As such, it was applied to GSM and WCDMA indoor systems to simulate performance against a conventional multi-cell system design. The simulations were based on a site-specific propagation model developed from the distributed antenna measurement campaigns in 2000 and include both deterministic and random long-term shadowing variations to model the subtle signal dynamics and correlation related to propagation in the indoor environment. The measurements show that these long-term variations tend to be correlated between distributed antennas and hence the gain from macro-diversity within the configuration of antennas correspondingly less beneficial. A simple Windows based tool was developed to ease the application of the model in DAS. For the GSM system the IDAS was applied to increase the frequency reuse of a minimum frequency allocation system, while for WCDMA the purpose was to control interference for the introduction of higher order modulation techniques. From a simulation framework with joint downlink power and distributed antenna assignment results show that the introduction of an IDAS to GSM can increase the number of users by up to 55 % compared to a more conventional multi-cell (frequency reuse) system design. Similarly, the IDAS allows a throughput increase of 79 % in the WCDMA system by facilitating the use of higher order modulation. The work has been supported by Nokia, Sonofon, and LGP Telecom. (Troels B. Sørensen, Preben E. Mogensen)