A New Rate Adaptation Algorithm over Block-ACK of 802.11 Protocol

Abstract

INSTRUCTIONAs wireless LANs become increasingly popular, people have produced higher requirements to the throughput. According to the IEEE 802.11n standardization [1], the rate of the physical layer can reach at most 600Mbps due to that the physical layer have introduced the OFDM and MIMO technologies. The MAC layer also have introduced frame aggregation and Block ACK mechanism to reduce the MAC overhead. For the physical layer rate, the range of selectable rates in 802.11n are larger than any prior 802.11 standard. So studying how to dynamically select transmission rate accordance with channel quality has more particular significance in the 802.11n.Since These algorithms are all based on the basic ACK statistics. But Block ACK mechanism returns a Block ACK that includes a lot of MPDUs' transmission information after sending a number of MPDUs, the response time of Block ACK is longer than the basic ACK and one time statistics numbers are more than the basic ACK. So these algorithms are no longer suitable for Block ACK mechanism. The literature [13] proposed an algorithm for Block ACK mechanism, but it uses the SNR of BA frame to conduct rate selection and has no in-depth analysis on the problems exist when the original algorithms are used under the Block ACK mechanism. We assess ARF under Block ACK mechanism and the results show that these classical algorithms exist serious problems about rate change. We analyze the cause of each problem and propose a new algorithm B-ARF to achieve higher throughput.The contents of this article are organized as follows: Section 1 briefly introduces the Block ACK mechanism and the existing classical algorithms ARF, AARF; Section 2 assesses these classic algorithms under Block ACK mechanism; Section 3 analyzes simulation results of ARF in BA case; Section 4 proposes a new B-ARF algorithm and simulates it; and Section 5 summarizes this article. RELATED WORKS Block ACK mechanismBlock-ACK mechanism was firstly used in the IEEE 802.11e [2] and has been expanded in the IEEE 802.11n that put forward the compressed Block-ACK mechanism. When sender and receiver intend to use the Block-ACK mechanism, sender sends an add Block-ACK request frame (add BA-REQ) to the receiver, receiver which support Block-ACK mechanism will respond an add Block-ACK response frame (add BA-RSP), then they will begin to use Block-ACK mechanism for data transmission. A New Rate Adaptation Algorithm over Block-ACK of 802.11 ProtocolXueping Chen, Wenda Li, Hongyuan Chen School of Electronic and Optical Engineering, Nanjing University of Science and Technology, Nanjing, Jiangsu, ChinaABSTRACT: Rate Adaptation is one important way to improve the throughput in the 802.11 networks. However, the previously proposed rate adaptation algorithms were based on the Basic-ACK mechanism. In IEEE 802.11e and 802.11n protocols, the Block-ACK was introduced to reduce the overhead caused by the ACKs so as to improve the system throughput. In this paper, we focus on the rate adaptation under the Block-ACK. Through a lot of simulation...