Abstract
We investigate two important aspects in sensor network
design—the throughput and the energy efficiency. We consider
the uplink reachback problem where the receiver is equipped with
multiple antennas and linear multiuser detectors. We first assume
Rayleigh flat-fading, and analyze two MAC schemes: round-robin
and slotted-ALOHA. We optimize the average number of
transmissions per slot and the transmission power for two
purposes: maximizing the throughput, or minimizing the effective
energy (defined as the average energy consumption per
successfully received packet) subject to a throughput constraint.
For each MAC scheme with a given linear detector, we derive the
maximum asymptotic throughput as the signal-to-noise ratio goes
to infinity. It is shown that the minimum effective energy grows
rapidly as the throughput constraint approaches the maximum
asymptotic throughput. By comparing the optimal performance of
different MAC schemes equipped with different detectors, we draw
important tradeoffs involved in the sensor network design.
Finally, we show that multiuser scheduling greatly enhances
system performance in a shadow fading environment.