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Description
This thesis describes the design of a Medium Access Control (MAC) layer, to employ Multi-Beam Smart Antennas in Wireless LAN communications. The multi-beam smart antennas can transmit data concurrently in multiple directions, thereby increasing the speed of wireless communication and the spectral bandwidth of the devices. The thesis discusses the implementation of a new MAC scheme for multi-beam smart antennas in a Wireless LAN, on the Riverbed modeler (formerly known as Opnet). The use of multiple beam smart antennas enables the concurrent packet transmission and reception on a node. This MAC layer essentially uses multiple transmitter and receiver ports which connect packet streams to a single MAC processor, to support the multiple beams. Riverbed Modeler is a network simulator that provides a hierarchical construction of a network. The modeler proposes the use of the IEEE 802.11n protocol for packet processing, for omni-directional antennas with collision avoidance mechanism. For multi-beam antennas, the node model in Riverbed, has been constructed to contain as many ports as beams for the antenna. As compared to the standard node model with just one port for transmission and reception, the inclusion of multiple ports allows the transmission and reception of multiple packets concurrently, thus significantly increasing the throughput of a given node. The inclusion of multiple ports in the MAC layer requires modifications in the pipeline stages for a Wireless LAN node in Riverbed modeler. The pipeline stages, originally designed to accept only a single packet at a time has been modified to accept multiple packets. This imposes on the fact that the pipeline stages should not accept noise or interference packets, but packets that are valid and meant for that particular node. These stages have thus been modified to segregate the valid and invalid packets and convey this information down to the MAC processor, before the packets are passed to it, for further processing. Introduction of multiple nodes receiving packets concurrently also required a change in the design of the network attributes so that packets from multiple destination/arrival addresses could be accepted. The information about these addresses are passed to the Wireless LAN MAC interface.
