Medium access control layer analysis of the DVB-RCT system

The thesis investigates the performance of the medium access control (MAC) layer of the digital video broadcasting return channel terrestrial (DVB-RCT) standard. It explains the working mechanism of the MAC layer and calculates the number of return channel terrestrial users that can access the system at any given time. A MAC procedure is used, which is similar to a hybrid protocol, combining time division multiple access (TDMA) and carrier sense multiple access (CSMA) schemes to assign slot times to every user and then computing the bit-rate for every contending user by assigning sub-carriers within the sub-channel until the required bit-rate threshold is reached for a particular bit-error-rate (BER).;Quality of service (QoS) is an important parameter in connectionless networks, and is a vital element in the design on this system. QoS challenges are brought about by the vast needs of applications such as real time multimedia streaming, video conferencing etc. The proposed design tries to enhance the QoS parameter by weighting all users equally to access the system, while striving hard to accommodate the maximum number of users in the allocated bandwidth. To achieve our goal and to make our system robust, orthogonal frequency division multiplexing is used in conjunction with different quadrature amplitude modulation schemes to increase the spectral efficiency and to avoid multipath propagation effects.;The goal of providing dedicated time slots for return channel users is achieved where every user transmits at a minimum bit-rate threshold of 50 Mbps. A bit-error-rate in the vicinity of 10-6 is also maintained for every user. Finally a cross layer design is presented where MAC algorithms work jointly with the physical layer to achieve a complete non-line-of-sight communication system.;The system is intended for the residential user where the subscriber premises would be equipped with a 'Set-Top-Unit' (STU) that would communicate directly with the base station within a 5 km radius. The aim is to implement a design where the complexity is kept at the base station, and the MAC process handled by the Network User Interface assigns individual slot times to return channel stations.