Use your frequency wisely: Explore frequency domain for channel contention and ACK

Abstract

Abstract-The promise of high speed (over 1Gbps) wireless transmission rate at the physical layer can be significantly compromised with the current design of 802.11 DCF. There are three overheads in the 802.11 MAC that contribute to the performance degradation: DIFS, random backoff and ACK. Motivated by the recent progress in OFDM and self-interference cancellation technologies, in this paper, we propose a novel MAC design called REPICK (REversed contention and PIggy-backed ACK) to collectively address all the three overheads. The key idea in our proposal is to take advantage of OFDM subcarriers in the frequency domain to enhance the MAC efficiency. In REPICK, we propose a novel reverse contention algorithm, which enables and facilitates receivers to contend channel in the frequency domain (reversed contention). We also design an efficient mechanism which allows ACKs from receivers to be piggy-backed through subcarriers together with the contention information (piggy-backed ACK). We prove through rigorous analysis that the proposed scheme can substantially reduce the overheads associated with 802.11 DCF and a guaranteed throughput gain can be obtained. In addition, results from extensive simulations demonstrate that REPICK can improve the throughput by up to 170%.

SMCSS: A Quick and Reliable Cooperative Spectrum Sensing Scheme for Cognitive Industrial Wireless Networks

“…Compared with works [38]- [40], both Wang et al [41] and this paper improve the sensing performance of CSS schemes by OFDM subcarrier modulation rather than reducing the overhead of IEEE 802.11 MAC. However, Wang et al [41] suffered limitations on accurate synchronization due to the distributed nature of CRAHNs, as well as hardware limitation on one extra half-duplex antenna with self-cancelation technique for each SU, whereas all of these limitations can be avoided in this paper.…”

“…On the other hand, aiming to improve the efficiency of IEEE 802.11 MAC, recent works [38]- [41] took advantage of OFDM subcarrier modulation to reduce the communication overhead of coordinating multiple stations. Feng et al [38] extended the use of OFDM subcarriers to reduce all three overheads (including DIFS, random backoff and ACK) in IEEE 802.11 DCF. Sen et al [39] reduced the backoff overhead by counting contention using subcarriers.…”

“…Motivated by recent works leveraging Orthogonal Frequency Division Multiplexing (OFDM) modulation to resolve channel contention of IEEE 802.11 MAC in the frequency domain [38]- [41], this paper proposes a novel Subcarrier Modulation-based Cooperative Spectrum Sensing (SMCSS) scheme, in which each SU sends one Binary Amplitude Shift Keying (BASK) symbol carrying its local decision (BASK modulates local decisions ''1'' and ''0'' using on-off keying) over the allocated subcarriers and the fusion center then could easily demodulate BASK symbols over all allocated subcarriers. In contrast to conventional CSS schemes, the proposed SMCSS scheme allows the fusion center to collect multiple local decisions in one reporting time unit.…”

Distributed Collision-Resolvable Medium Access Control for Wireless LANs with Interference Cancellation Support

“…In [10], Tan et al employed a physical-layer RTS/CTS signaling frequency-domain backoff for the channel contention. In [11] and [12], the authors also performed backoff in frequency domain, and time-domain counting down is emulated with OFDM subcarrier counting down. However, the above backoff optimization work [7][8][9][10][11][12] just relieved but do not solved the inefficiency problem, as they still shared the traditional idea of collision avoidance.…”