Comparisons of adaptive threshold control algorithms for unslotted common-spreading-code packet-radio networks

The authors describe adaptive threshold control algorithms for the detection of a header in an unslotted centralized packet radio system with common direct-sequence spread-spectrum modulation. Two threshold control strategies, namely, the fixed-maximum-delay (FMD) strategy and the fixed-sample-size (FSS) strategy, are analyzed for two distinct types of false-alarm events, namely, false-alarm on multiple access noise and false-alarm on a header prefix. These strategies are based on an estimate of the total noise power in the receiver. The FSS strategy achieves constant false-alarm rate on sidelobes without prior knowledge of the number of active transmitting radios. The FMD strategy achieves nearly constant false-alarm rate on sidelobes with derived knowledge of the average number of active transmitting radios. Both strategies reduce the dynamic range of the false-alarm rate on a header prefix considerably