Broadband Multi-Hop Communication in Homogeneous and Heterogeneous Wireless LAN Networks

New multimedia services accessible via the Internet are strongly driving the demand for residential and commercial broadband wireless networks. IEEE 802.11, a Wireless LAN (WLAN) system, has gained immense popularity since years back. Wi-Fi, a sort of WLAN systems, is mostly used in the hot spots such as universities, exhibition centers, airports etc. However, the coverage area of the Wi-Fi is limited to a couple of hundred meters in open-space areas but to a round one hundred meters in indoor environment. In this thesis, the author proposes multi-hop concepts for WLANs system such as IEEE 802.11e and HIPERLAN/2. Multi-hop technology enlarges the coverage area of a Base Station (BS) or an Access Point (AP). It also enables the communicating stations to minimize the battery consumption. Under multi-hop operation, the data packet from the BS or AP is transmitted to a forwarding station. The forwarding station will then forward the packet to another forwarding station or to the destination. The suggested multi-hop concepts rely on the centralized operation. Under this operation, a base station or an access point is responsible for the resource allocation. The AP assigns the resource by polling the forwarding station that is positioned on the perimeter of the radio coverage of the AP so that it can activate the sub-cell it hosts and forward the packet it receives from the AP to the destination. The centralized operation refrains forwarding stations from accessing the medium in distributed manner. So collisions can be prevented or even avoided. One of the objectives of this thesis is to present the multi-hop concepts for the IEEE 802.11 and HIPERLAN/2 systems as well as the interworking concept for both systems. The multi-hop concepts are easy to be implemented and standard compliant. The multi-hop concepts are evaluated through mathematical analysis and simulations. The author also presents the development of a multi-hop prototype which is used to evaluate the performance and the correctness of one of the multi-hop concepts. This thesis also presents a mathematical approach to model the interference situation in the multi-hop cellular network. Using the interference model, one can evaluate the effectiveness of multi-hop operation compared to that of the single-hop operation.