Energy Efficient Scalable Sub-band based Ultra-Wideband System

In this paper, a scalable sub-band ultra-wideband (S-SUWB) system is proposed. The technique provides scope for using the ultra-wideband bandwidth efficiently by exploiting the available link margin for short range communications with medium data rates. The bandwidth of 500 MHz or more is divided into a fixed number of sub-bands. The data transmission scheme over multiple sub-bands can be designed to achieve higher data rate or higher reliability while providing multiuser support in both uplink and downlink communications. The proposed system provides enhanced scalability by the efficient utilization of the code-frequency dimensions. Sub-banding in conjunction with orthogonal spreading code facilitates transmission of plurality of data streams within a sub-band and along sub-bands for each user. Very importantly, the proposed system incorporates methods at the receiver facilitating low power receiver designs. Primarily, S-SUWB enables reduced sampling rate receiver designs significantly reducing the power consumption. Also, the spreading code based sub-band selection method obviates the need for individual down-conversion and filtering of the sub-bands thus reducing the complexity. Moreover, an interference rejection filtering (IRF) method incorporated into the despreading process is proposed to improve the performance without significantly increasing the receiver complexity. The simulation results in terms of the bit error rate performance of the scalable multiuser S-SUWB transceiver for the IEEE 802.15.4a channel models are presented demonstrating the usefulness of the proposed scheme. Performance improvements with the use of the IRF and also multi-user results are presented. The results indicate the desirable performance is obtained using the energy efficient techniques for low and medium delay spread channels even without the use of any equalization method.