Cross-Layer Signaling and Interface Design for OFDM Systems Using Overlay Watermarks

A new cross-layer signaling interface using overlay watermarks for orthogonal frequency division multiplexing (OFDM) system is proposed in this paper. The major advantage of the new proposal is the multiple functionalities the overlay watermark provides, which includes a cross-layer signaling interface, a transceiver identification for position-aware cross-layer design, as well as its basic role as a training sequence for channel estimation. Location information of a mobile can be easily derived for efficient routing when a unique watermark is associated with each individual mobile transceiver. In addition, a new data pipe can be created by modulating the overlay watermarks for the transmission of cross-layer signaling and other interlayer interactive information. We also study the channel estimation and watermark removal techniques at the physical layer for the proposed overlay OFDM. Our channel estimator iteratively estimates the channel impulse response and the combined signal vector from the overlay OFDM signal. Cross-layer design that leads to low power consumption and more efficient routing are investigated.