Forward Error Correction (FEC) is one of the mostcommon means of performing packet error recovery in data trans-missions. FEC schemes typicallytune the FEC rate in accordancewith feedback information provided by the receiver. However, thefeedback and FEC rate calculation processes inevitably have afinite duration, and thus the FEC rate implemented at the sendermay not accurately reflect the current state of the network. Thus,this paper proposes an Enhanced Random Early Detection For-ward Error Correction (ERED-FEC) mechanism to improve thequality of video transmissions over Wireless Local Area Networks(WLANs). In contrast to most FEC schemes, the FEC redundancyrate is calculated directly at the Access Point (AP). Moreover, theredundancy rate is tuned in accordancewithboththewirelesschannel condition (as indicatedby the number of packet retrans-missions) and the network traffic load (as indicated by the APqueue length). The experimental results show that the proposedERED-FEC mechanism achieves a significant improvement inthe video quality compared to existing FEC schemes withoutintroducing an excessive numberof redundant packets into thenetwork An Access Point-Based FEC Mechanism for Video Transmission Over Wireless LANs
THE use of wireless devices such as laptop computers andPDAs to connect to Internet services is becoming increas-ingly common nowadays. However, wireless communicationchannels are prone to serious transmission errors due to atten-uation, fading, scattering or interference [1]–[4]. Packet lossesin wireless environments are generally recovered using eitherAutomatic Repeat reQuest (ARQ)or Forward Error Correction(FEC) methods [5]–[8]. ARQ schemes automatically retransmitthe lost packets during timeouts,or in response to explicit re-ceiver requests. By contrast, in FEC schemes, the effects of po-tential packet losses are mitigated in advance by transmittingredundant packets together with the source packets such that a block of packets can be successfully reconstructed at there-ceiver end even if some of the packets within the block are lostduring transmission. Of the two approaches, FEC schemesre-sult in a lower retransmission latency, and are therefore widelypreferred for the delivery of video streams overwireless net-works