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The processing gain of a spread-spectrum (SS) system is generally defined as the ratio between the transmission bandwidth and data bandwidth, and is a measure of its interference rejection capability. Due to limited spectrum, most licence-free commercial ISM-band direct sequence (DS) SS modems suffer from insufficient processing gain if they are to support a reasonably high data rate. This paper presents a novel parallel DS-SS signaling system designed to increase the processing gain without reducing the aggregate data rate. The performance against single tone jammers is analyzed. Theoretical and simulation results show that the proposed scheme is able to increase immunity against jamming by increasing the number of parallel signaling stream, while maintaining a high data rate.