Superposed Signaling Option for Bandwidth Efficient Wireless LANs

One key challenge for increasing the throughput of future wireless local area networks at higher layers is matching the capabilities of the physical (PHY) layer with the need of exchanging small control messages at these higher layers. The bottleneck in this regard lies at the medium access control (MAC) layer that may waste considerable channel resources in the transmission of these small packets. In this contribution we introduce superposed signaling, a PHY layer extension that opens up a new way to map small packets to the channel while reducing inefficient use of the medium. This scheme provides a low-rate signaling sublayer at the PHY level in addition to a high-rate data sublayer. These sublayers share the channel by a variant of multi-carrier code-division multiple access (MC-CDMA). We investigate the design of receivers that are capable of detecting the signals of both sublayers, and focus on a structure employing successive interference cancellation (SIC). Our main interest is in identifying the operation modes in terms of per-user powers in which it is possible to use these receivers. Furthermore, it will be shown that the scheme is appropriate for sublayer-synchronous as well as asynchronous scenarios. Keywords— Superposed signaling, multi-carrier spread spectrum, OFDM, successive interference cancellation.