Abstract
Applying the relaying concept to a Code Division Multiple Access (CDMA) mobile network is not a new idea, and many such systems employing relaying capabilities have been suggested. An obstacle to their evaluation with respect to capacity and coverage gains over the conventional non-relaying networks has been the inapplicability of the existent path loss models for low height terminal communications. Herein, empirical propagation models for relaying systems with low height terminals are proposed. The new models consist of line-of-sight and non-line-of-sight branches, and they take into account the effect of transmitter and receiver height, citing and environmental parameters. They are also complemented by shadowing and fast-fading distribution and correlation statistics. The models are evaluated by their performance in accurate estimations of other sets of measurement data. Before the derived models are applied in an analytical and a simulation model, the thesis continues with a discussion on the distributed power control function and frequency allocation schemes in a multihop Universal Mobile Telecommunications System (UMTS), deployed in a Manhattan grid. This is in order to derive closed-form expressions, for selected frequency schemes, for the minimum transmit powers which satisfy the link quality criteria. The propagation models are then employed in these expressions to evaluate the system performance by both simulation and analysis and improvement by employing relays is shown. A dynamic system-level simulation, which was utilised to perform further analysis, is then presented. The measurement-based path loss, fading and shadowing models, derived from the previous chapters are employed. Both uplink and downlink operations of the cellular system are considered at the same time. The simulation outcomes showed that the transmit power savings and coverage and capacity gains are in agreement with the expected analytical results, but dependent on the frequency scheme, relaying, antenna directivity gains and other assumed parameters.