Piggybacking lightweight control messages on physical layer for multicarrier wireless LANs

Abstract

Piggyback is an effective scheme to transmit control messages in wireless local area networks (WLANs). In traditional approaches, the piggyback scheme is achieved by redefining or adding control fields in the MAC frame header, i.e., MAC layer piggyback scheme. However, this method has shortcomings. In this paper, we design and present PhyPig (Physical Piggyback), a cross-layer design for lightweight control channel. In the newly proposed communication strategy, the control messages are piggybacked on OFDM-based physical layer so that PhyPig does not consume extra channel resources, and does not harm the normal data throughput. Specifically, PhyPig modulates control messages (or sequences of binary bits) into null or non-null (i.e., normal) data symbols, the minimum 2-D time-frequency resource unit in OFDM. The thus-transmitted messages can be interpreted by checking the patterns of data symbols on OFDM subcarriers. Our extensive results validate the feasibility of PhyPig and show that PhyPig delivers control messages with close to 100% accuracy on a channel with practical SNR regions. Further, based on our simulation results, we demonstrate that PhyPig outperforms traditional piggyback scheme with significant performance improvements in different scenarios.