Performance Evaluation of the UMTS Terrestrial Radio Access Modes

UMTS is currently emerging as a global 3rd generation mobile communications standard. For the first time, a global international consortium has agreed on a common technology for the use in this generation mobile cellular
networks. However, since several national and international standardization bodies, industrial companies and research facilities have been involved in the development of UMTS, the standard contains quite a lot of different specialties, especially concerning the access to the radio air interface. Although the main focus for the radio access is set on WCDMA, the air interface in UMTS is divided into three elementary sub-standards. One of
them is based on FDD, the two others consider TDD in order to distinguish downlink and uplink transmission. Whereas the FDD mode in its basic version is solely based on WCDMA as multiple access technique, the TDD
modes also offer TDMA to separate the different subscribers. Moreover, the two TDD modes are based on different chip rates applied to the radio interface. Whereas the TDD 3.84Mcps option was developed in parallel to the FDD mode and considers the same bandwidth and chip rate, the TDD 1.28Mcps option is based on the Chinese TD-SCDMA standard with a lower chip rate and a slightly modified radio frame structure. This thesis gives a comprehensive survey of the three access modes within UMTS and their integration into the UTRA protocol stack. Furthermore, a performance comparison of all access technologies is presented considering realistic scenarios as well as different types of services including voice, video and Internet applications. An analytical estimate on the capacity of these networks is derived and compared to the results obtained by means
of dynamic simulations. In addition, also the enhancing techniques which are currently under study are presented, like e.g. link adaptation within the HSDPA option. Their impact on network capacity and radio coverage is evaluated and novel protocol aspects are proposed.