Enhancing throughput over wireless LANs using channel state dependent packet scheduling

Abstract

Unlike wired networks, packets transmitted on wireless channels are often subject to burst errors which cause back to back packet losses. Most wireless LAN link layer protocols recover from retransmitting lost segments. channel is in a burst error state, most retransmission attempts fail, thereb causing poor utilization of the wireless channel Furthermore, in the event of multiple sessions sharing a wireless link, FIFO packet scheduling can cause the HOL blocking effect, resulting in unfair sharing of the bandwidth. This observation leads to a new class of acket dispatchne ! characteristics into consideration in making packet dispatching decisions. We compare a variety of channel state dependent packet (CSDP) scheduling methods with a view towards enhancing the performance of transport layer sessions. Our results indicate that by employing a CSDP scheduler at the wireless LAN device driver level, significant improvement in channel utilization can be achieved in typical wireless LAN configurations.acket losses b b h e n the wireess P in methods which explicitly ta f e wireless chan-

Providing quality of service guarantees in wireless LANs compliant with 802.11e

“…1. In this field the QoS frame indicates its Traffic Category (0-7) or Traffic Stream (8)(9)(10)(11)(12)(13)(14)(15) and the size (in terms of number of bytes) of the corresponding queue in the QSTA. A QSTA which needs to request a new TXOP can transmit a Null QoS data frame, just to inform HC about the request.…”

“…802.11 MAC AND CHANNEL CONDITION As many studies describe, the error characteristics of the wireless medium differ significantly from that of the wired medium [12,13]. Packet losses in the wire-line medium are very rare and random.…”

“…Several methods of scheduling in a wireless environment have been proposed recently. Reference [12] proposes a scheduling procedure which depends on channel state. Through this procedure, the link quality of different users is tracked to avoid transmission during fades.…”

“…Channel model Many studies [11,12,13] have proposed the use of finite state Markovian models to characterize the error behavior of wireless links. In [12] the authors propose the use of a two-state Markov model (Good -Bad) to model the wireless channel.…”

“…In [12] the authors propose the use of a two-state Markov model (Good -Bad) to model the wireless channel. We have adopted a similar model in our simulations.…”