In this thesis, we design a high capacity system for wireless multi-hop Ad Hoc Networks, utilizing multiple orthogonal channels and multiple transceivers. Our Design mainly consists of two parts. One is Multi-Channel Medium Access Control (MC-MAC) protocol design, and the other is the dual stack link controller on top of existing logical link controller (LLC). For the design of MC-MAC protocol, we utilize orthogonal transmission resources, and for the design of dual stack link controller, we deploy separate wireless protocol stacks having common routing protocol and let dual stack link controller choose proper wireless interface depending on its needs. Finally, we try multi-band environment using our proposed dual stack architecture. Our design allows concurrent multiple packet transmissions, so that network capacity increases dramatically.
For this work, we assume that multiple orthogonal channels by orthogonal transmission resources like Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), etc, are available, and further assume that co-channel, co-antenna interferences can be compensated for in physical layer, that is, we treat channels at a logical level, not at a physical level [1].
Our basic idea is as follows. First, in a chosen single frequency band, Bandwidth (BW) is divided into the number of orthogonal multiple channels which are assumed to be available by orthogonal transmission resources, as usual as in previously proposed Multi-Channel MAC (MC-MAC) protocols [1, 2, 3]. If N+1 orthogonal channels are available, we assign one channel to Common Control Channel (CCCH) and N channels to each Data Channels (DCH) respectively. The Separation of Control Channel and Data Channel guarantees that the number of collisions between control message and data message can be reduced, so more channel access can be made and can be successful in the existence of hidden nodes which are very common in wireless multiple Ad Hoc Networks. Similar approach has been attempted in [2], but we modify Network Allocation Vector (NAV), so that we give fair access right to nodes in sensing range of transmit node, nodes getting RTS messages and nodes getting CTS messages. We observe more than 10% performance improvement, compared to system with NAV mechanism like previously proposed MC-MAC protocols [1, 2, 3].
The capacity of wireless multi-hop Ad Hoc Networks with our proposed MC-MAC can be further increased by deploying dual protocol stack in parallel having common routing protocol, so Second part of our basic idea is architecture with dual protocol stack and dual stack controller on top of existing link controller. The main function of this controller is to choose wireless interface depending on predetermined network policy. In order to make simulation simple, our policy is just to separate traffic coming from routing protocol, but we consider that this controller may find its usage further depending on predetermined network policy.
The simulation results show that proposed dual stack architecture with MC-MAC outperforms single channel CSMA/CA protocol and single stack MC-MAC architecture.
