Abstract
This thesis investigates the performance of the distributed antenna system (DAS) radio architecture and also two more flexible implementations of this, namely Zoning and Switching, in order to provide coverage and capacity for in-building hot spot areas. The research is first focused on the theoretical analysis of DAS and their impact on the propagation channel. Fading analysis and the impact of multiple antennas on the radio channel are discussed by using available measured data. Analytical techniques for outage probability calculations are investigated and compared with Monte Carlo simulations to verify the applicability of the methods. Shadowing correlations are considered and the regions of good consistency are identified. However, during outage probability calculations in the presence of multiple wanted and interfering lognormal components, it is observed that inaccuracies are present, and a new method is proposed to maintain the consistency of the analytical techniques. The modelling approach and the characterisation of the investigated DAS architectures in terms of coverage and capacity are discussed. It is found that the conventional DAS architecture is very efficient in meeting the high coverage and capacity requirements of the W-CDMA system as well as minimising the transmit power levels in both the uplink and the downlink. Capacity limitations, however, are present as this is limited by the pole capacity of the W-CMDA system. In order to overcome these limitations the deployment of Zoning and Switching are investigated. Zoning performs a similar function to sectorisation in outdoor systems but is achieved by selecting appropriate antenna elements (AE's) rather than by shaping antenna radiation patterns. Switching, on the other hand, uses only one AE to communicate with the user that is in a nearby location. It is observed that the capacity with Zoning is doubled compared with the conventional DAS implementation. However, it is seen that additional antenna elements do not result in significantly higher number of users, due to the fact that pole capacity limitations are again present in a common 3-sector Node B system. Implementing Switching to the closest antenna element, overcomes these limitations and a linear increase of capacity with the number of AE's is obtained.