Error correction for asynchronous communication

We propose a forward error correction scheme for asynchronous sensor communication where the dominant errors consist of pulse deletions and insertions, and where encoding is required to take place in an instantaneous fashion. The presented scheme consists of a combination of a systematic convolutional code, an embedded marker code, and power-efficient frequency-shift keying (FSK) modulation at the sensor node. Decoding is first obtained via a maximum a-posteriori (MAP) decoder for the marker code which achieves synchronization for the insertion and deletion channel, followed by MAP decoding for the convolutional code. Besides investigating the rate trade-off between marker and convolutional codes, we also show that residual redundancy in the asynchronously sampled and quantized source signal can be successfully exploited in combination with redundancy only from a marker code. This provides a low complexity alternative for deletion and insertion error correction compared to using explicit redundancy.