Pushing the Throughput Limit of Low-Complexity Wireless Embedded Sensing Systems

To maximize the communication throughput for wireless sensing systems, designers have attempted various combinations of protocol design and manual code optimization. Although the theoretical bandwidth limit is easy to determine loosely, there have been no systematic ways to arrive at a tight upper-bound. One contribution of this paper is a formula for deriving a tight upper-bound on the throughput of low-complexity wireless interfaces transmitting packets of a fixed size. It takes into account not only the software execution times on the nodes but also other communication protocols that must be bridged by the base station. The proposed upper-bound, which we believe is the tightest, represents the maximum amount of bandwidth utilization that can be achieved in practice. It can also serve as a means of comparing protocols built on different platforms. Another contribution is a streamlined schedule-based protocol, called RIPE-MAC, which achieves at least 83% of the upper-bound, significantly higher than previously achieved throughput. The proposed protocol needs no clock synchronization and incurs no further complexity on sensor nodes. In the proposed protocol, synchronization and schedule updates are reduced to a single pull message.