In this thesis the communication range of packet based broadband radio access systems with access to fixed networks is improved by using a relay concept. This newly developed concept is presented and evaluated. Using the concept user terminals (Mobile Terminal (MT)), that are outside the range of a central base station (Access Point (AP)) are supported by relay stations (Forwarding Mobile Terminal (FMT)), that connect MT and AP. At the same time the relay concept is able to support Quality of Service (QoS) aspects like throughput and end-to-end delay. HIPERLAN/2 was chosen as example supporting QoS in the broadband world. The modifications to the different layers of the protocol stack were formally specified and implemented on a prototype basis. For the relay concept a so-called sub frame is introduced to the medium access control layer. The sub frame divides the different hops of a relay connection in the time domain, without the necessity to use new frequency channels. MTs and APs conforming to the HIPERLAN/2 standard can also be used in conjunction with the FMT. The concept has been submitted for patent [119,120]. Besides a theoretical analysis of the extension of the communication range the throughput and the end-to-end delay are investigated analytically and proved by extensive simulations. Additionally the parameter setting for the link adaptation and the procedures and criteria for a handover of an MT from AP to FMT are developed. In buildings the FMT shows much benefit, if there are non line of sight conditions. In these areas the service for the users can be improved significantly. In further investigations different cellular scenarios, i.e. open space and urban scenarios, were analysed analytically and by simulation. As results the throughput and the spectrum efficiency were determined. In these scenarios the relay concept proves to be a cost efficient solution to support wireless users.
Ein Relaiskonzept für das hochbitratige drahtlose lokale Netz HIPERLAN/2
Reihe : ABMT
Bandnummer : 42
ISBN : 978-3-86130-169-1