Time hopping direct-sequence CDMA for asynchronous transmitter-only sensors

This paper investigates transmission schemes for asynchronous transmitter-only wireless sensor nodes. We propose a time hopping DS-CDMA scheme by utilizing time hopping code design. Each sensor transmits only in pre-assigned active time slots and switches to sleep mode in idle time slots. By utilizing the proposed scheme, each sensor can always have several collision-free time slots. We also propose a new detector that has better BER performance than conventional matched filter (MF) detector by utilizing channel energy capturing and multipath diversity. We compare BER performance, power consumptions, and computational complexities of the proposed transmission scheme with conventional DS-CDMA scheme. The proposed scheme achieves significant energy and complexity savings while keeping similar BER performance with conventional DS-CDMA scheme.