Asynchronous Random Access Data Compression

This work introduces a framework for an asynchronous random access source code (ARASC) and bounds the achievable performance under this framework. Like prior multiple access (or Slepian-Wolf) source codes, the ARASC enables multiple transmitters to efficiently, reliably, and independently describe dependent sources to a common receiver. As in prior "random access" codes, the number of active encoders is unknown a priori to both the transmitters and the receiver and single-bit stop-feedback from the receivers to the transmitters enables variable-rate coding. Unlike prior works, the proposed system eliminates all forms of block synchronization. The main result is a two-transmitter achievability bound demonstrating the achievability of a first-order average rate across blocks equal to the weighted average of the point-to-point source coding rate and multiple access achievable sum rate. The weights observed approach the fractions of time that separate and simultaneous observations are encoded. The result's second order term bounds the speed at which the average rate approaches this weighted average.