Revisiting partial packet recovery in 802.11 wireless LANs

Abstract

In wireless LANs, partial packets are often received which usually contain only a few errors. According to the current 802.11 standard, such packets have to be retransmitted. Much effort has been invested recently in repairing such packets without retransmitting the entire packet, e.g., by using error correction (EC) code or retransmitting only the corrupted blocks. In this paper, we revisit this problem, and propose Unite, a framework for more efficient partial packet recovery. Unite is motivated by two key observations. First, the two repair methods, i.e., the EC-based and block-based, are not mutually exclusive and can be combined to achieve higher performance. Second, the recently introduced error estimators can be utilized to determine the optimal repair method depending on the condition of each partial packet. The combined method should achieve better performance than each individual method; in addition, it should remain low in complexity because the EC-based and block-based method are both simple in nature. Unite uses AMPS, a recently proposed estimator, for error estimation. We implement Unite on the Madwifi open source driver, and our experiments show that Unite outperforms other recovery schemes.

Augmenting wide-band 802.11 transmissions via unequal packet bit protection

“…UnPKT adopts the RS(255, w) where each symbol consists of eight bits. This type of RS code has efficient software implementation and is widely used as 802.11 MAClayer FEC [19], [18], [20], [27]. Figure 8 depicts bit error burst statistics from the corrupted packets measured in Section III.…”

“…However, retransmission causes nonnegligible overhead, e.g., transmission delay and MAC-layer overhead. A variety of partial packet retransmission schemes [18], [19], [20] have been proposed to improve the retransmission efficiency, which reduce the transmission delay of each retransmission, but still suffer from the MAC-layer overhead. Different from those approaches, UnPKT predictively protects the packet bits of each transmission and completely eliminates most retransmission overhead.…”

Green partial packet recovery in wireless sensor networks

“…Several other techniques [17], [18], [19] used the concept of Forward Error Correction (FEC) for error recovery. In fact, FEC requires a knowledge of the channel BER.…”

PRAC: Exploiting partial packets without cross-layer or feedback information

“…pilot bits), modifying the feedback mechanism to include detailed information in the acknowledgment frames (e.g. multiple CRCs), using cross-packet coding methods on top of PHY FEC codes, such as packet erasure codes, or a combination of them [7], [10], [8], [9], [11].…”

“…Cross-layer information (e.g. PHY soft information [5] and confidence hints [6]), multiple CRCs [10], pilot bits within a packet [8], detailed feedback information [9] and redundancy enabling error estimation codes [11] have been proposed as potential solutions. PRAC does not use any of these methods.…”