Saturation throughput analysis of error-prone 802.11 wireless networks

It is well known that the medium access control (MAC) layer is the main bottleneck for the IEEE 802.11 wireless LANs. Much work has been done on performance analysis of the 802.11 MAC. However, most of them assume that the wireless channel is error free. In this paper, we investigate the saturation throughput performance achieved at the MAC layer, in both congested and error-prone channels. We provide a simple and accurate analytical model to calculate the MAC throughput. The model is validated through extensive simulation results. Our results show that channel errors have a significant impact on the system performance. Copyright (c) 2005 John Wiley & Sons, Ltd

Investigation of the block ACK scheme in wireless ad hoc networks

A Block Transmission and Acknowledgement (BTA) scheme, also called Block ACK, has been proposed in the IEEE 802.11e wireless local area networks (WLAN) specification to improve efficiency of the medium access control layer. The idea of the BTA scheme is to transmit multiple data frames followed by only one acknowledgement frame in a transmission block. In this paper, we present a theoretical model to evaluate the saturation throughput for the BTA scheme under error channel conditions in the ad hoc mode, validated with simulations. We show some advantages of BTA over the legacy MAC, and analyze how to select a proper number of frames for each transmission block. Results show that BTA is particularly effective in very high-speed wireless networks, and it is important that the number of frames in each block is negotiated before transmissions to provide better efficiency

A modular framework for implementing joint wireless network coding and scheduling algorithms

Intersession network coding (NC) can provide significant performance benefits via mixing packets at wireless routers; these benefits are especially pronounced when NC is applied in conjunction with intelligent scheduling. NC, however, imposes certain processing operations, such as encoding, decoding, copying, and storage. When not utilized carefully, all these operations can induce tremendous processing overheads in practical settings. Our testbed measurements suggest that such processing operations can severely degrade the router throughput, especially at high bit rates. Motivated by this, we design network coding framework for rate adaptive wireless links (NCRAWL). The design of NCRAWL facilitates low overhead NC operations, thereby effectively approaching the theoretically expected throughput benefits of joint NC and scheduling. We implement and evaluate NCRAWL on a wireless testbed. Our experiments demonstrate that NCRAWL meets the theoretical predicted throughput gain while requiring much less CPU processing, compared to related frameworks.WiN