OPNET WORK'0303 Powerpoint format (662KB)
This s paper develops a novel slotted ALOHA protocol (Direction-Of-Arrival ALOHA) for use in ad hoc networks where nodes are equipped with smart antennas. The protocol relies on the ability of the antenna and DOA algorithms to identify the direction of the desired signal and the direction of the interferers to maximize SINR (Signal to Interference and Noise Ratio) at the receiver. The performance of the protocol is evaluated using joint simulation in OPNET and Matlab. We show that DOA-ALOHA achieves significantly higher throughput than 802.11 protocol. The impact of using different number of antenna elements is also studied for this environment.
VTC'03 Powerpoint format (221KB)
Transport connections set up in wireless ad hoc networks are plagued by problems such as high bit error rate (BER), frequent route changes and partitions. If we run TCP over such connections, the throughput of the connection is observed to be extremly poor because TCP treates lost or delayed ACK's as congestion. In this paper authors present an approach where they implement a thin layer between IP and standard TCP that corrects these problems and maintains high end-to-end TCP throughput.
Powerpoint format (213KB), PDF format (331KB) (Winter 2001)
Wireless nodes loose considerable amount of power in overhearing the network which is known as listening problem. A New power-aware metrics for determining routes in wireless ad hoc networks is propossed. A significant amount of power can be reduced by using theses metrics in shortest-cost routing algorithms. It also ensures that the mean time to node failure is increased significantly.
Powerpoint format (214KB), PDF format (77KB) (Fall 2000)
In this paper we compare the energy consumption behavior of three versions of TCP -- Reno, Newreno, and SACK. The experiments were performed on a wireless testbed where we measured the energy consumed at the sender node. Our results indicate that, in most cases, using total energy consumed as the metric, SACK outperforms Newreno and Reno while Newreno performs better than Reno. The experiments emulated a large set of network conditions including variable round trip times, random loss, bursty loss, and packet reordering. We also estimated the idealized energy for each of the three implementations (i.e., we subtract out the energy consumed when the sender is idle) and here, surprisingly, we find that in many instances SACK performs poorly compared to the other two implementations. We conclude that if the mobile device has a very low idle power consumption then SACK is not the best implementation to use for bursty or random loss. On the other hand, if the idle power consumption is significant, then SACK is the best choice since it has the lowest overall energy consumption.
Powerpoint format (1235KB)