dc.description.abstract | The advancement in wireless communication and economical, portable computing devices have made mobile computing possible. One research issue that has attracted a lot of attention recently is the design of mobile ad hoc network (MANET). A MANET is one consisting of a set of mobile hosts which can communicate with one another and roam around at their will. No base stations are supported in such an environment. Due to considerations such as radio power limitation, power consumption, and channel utilization, a mobile host may not be able to communicate directly with other hosts in a single-hop fashion. In this case, a multi-hop scenario occurs, where the packets sent by the source host are relayed by several intermediate hosts before reaching the destination host. Applications of MANETs occur in situations like
battlefields or major disaster areas, where networks need to be deployed immediately but
base stations or fixed network infrastructures are not available. Multi-hop poses several new
challenges in the design of MANET.
This dissertation mainly covers four areas: (1) GRID: a fully location-aware routing protocol; (2) GeoGRID: a geocasting protocol based on GRID; (3) A multi-path QoS routing protocol; (4) A TDMA-based bandwidth reservation protocol for QoS routing.
First, we propose a routing protocol called“GRID”, which tries to exploit location Information in route discovery, packet relay, and route maintenance. Existing protocols, as
compared to ours, are either not location-aware or partially location-aware in that location
knowledge is not fully exploited in all these three aspects. One attractive feature of our
protocol is its strong route maintenance capability — the intermediate hosts of a route can perform a “handoff” operation similar to that in cellular systems when it roams away to keep a route alive. This makes routes in the MANET more stable and insensitive to host mobility. Second, we propose a “GeoGRID”geocast protocol. The GeoGRID protocol, a modification of the GRID protocol, does not try to establish a spanning tree or routing path
prior to geocasting. Instead, the protocol adopts a connectionless mode. GeoGRID uses
two methods for distributing geocast messages. Flooding-based geocasting allows any grid
leader in the forwarding zone to rebroadcast the messages. Ticket-based geocasting allows
only ticket-holding grid leaders to rebroadcast. Issuing tickets avoids blind flooding.
Third, we propose a multi-path QoS routing protocol that is an on-demand protocol for
searching for a multi-path QoS route from a source host to a destination host in a MANET,
where a multi-path is a network with a source and a sink satisfying certain bandwidth requirement. Existing works all try to find a uni-path to the destination. The basic idea is to
distribute a number of tickets from the source, which can be further partitioned into subtickets
to search for a satisfactory multi-path. Through simulations, we justify that the value of our multi-path protocol is on its flexibility: (i) when the network bandwidth is very limited,
it can offer a higher success rate to find a satisfactory QoS route than those protocols
which try to find a uni-path, and (ii) when the network bandwidth is suffcient, it can perform
almost the same as those protocols which try to find a uni-path (in both routing overhead and success rate). Finally, we propose a TDMA-based bandwidth reservation protocol. This protocol considers the bandwidth reservation problem in a MANET to support QoS routing. We approach this problem by assuming a common channel shared by all hosts under a TDMA (Time Division Multiple Access) channel model. Existing solutions have addressed this problem by assuming a stronger multi-antenna model, where the bandwidth of a link is independent of the transmitting/receiving activities of its neighboring links, or a less stronger CDMA-over-
TDMA channel model, where the use of a time slot on a link is only dependent of the status of its one-hop neighboring links. While more practical and less costly, using a TDMA model needs to face the challenge of radio interference problems. Our protocol can reserve routes by addressing both the hidden-terminal and exposed-terminal problems. The protocol can conduct accurate bandwidth calculation while performing route discovery. | en_US |