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Abstract: This paper investigates computationally efficient methods for blind decision feedback equalization (DFE) that reduce the complexity and power requirements of blind equalization algorithms while maintaining their steady-state characteristics for quadrature amplitude modulation (QAM) signals. These include the power-of-two error (POT), selective coefficient update (SCU), and frequency-domain block (FDB) methods. A novel radius-directed stop-and-go (RSG) method is introduced, which selectively adjusts the equalizer tap coefficients based on the equalizer output radius. In addition, a new activation/de-activation method based on the equalizer output radius is utilized to control the feedback equalizer (FBE) of the DFEs. Simulation studies and analysis are provided for empirically derived cable and microwave channels and Ricean fading channels. [Copyright &y& Elsevier]

Bus-Invert ( BI ) coding schemes have been used in the circuit design to save power usage by minimizing the number of transitions between successive words. With an increased number of bits for bus width, many other coding schemes like Bus-Shift ( BS ) and Shift-Invert ( SINV ) have been proposed for better power saving. In this paper, we are proposing a new Successive Shift-Invert ( SSINV ) coding scheme where the transmitting data will first be inverted. Then both the original and the inverted word will be shifted circularly for each bit and compared with the data just sent for least hamming distance. Thus, the combination having the least hamming distance with the last sent data will be selected and sent. The proposed method exhibits better power saving compared to other reported methods, but needs one extra control bit than BS ; which add to the computation time. Simulation results show a saving margin of 5–15% in average cases in comparison with BI , BS , and SINV for higher bus width. A VerilogA implementation of SSINV using TSMC 65 nm technology is also presented as a proof of concept. [ABSTRACT FROM AUTHOR]

Abstract: This paper proposes the use of equalization concepts in frequency domain that exploit the frequency domain channel matrix to combat inter-carrier interference (ICI) instead of inter-symbol interference (ISI) in 5.9GHz Dedicated Short Range Communications (DSRC) systems. The physical layer (PHY) of DSRC is currently being developed by work group of IEEE 802.11p. The conventional system currently assumes static channel characteristics. Channel tracking schemes were investigated and the Viterbi-aided channel estimation scheme was proposed for DSRC systems that did not explicitly exploit the ICI components caused by the time-varying channels. The performance of the DSRC system is investigated for a time-varying channel using a conventional DSRC model, a decision-directed (Viterbi-aided) channel estimation model, and the frequency-domain equalization design. It is shown that the DSRC system with the frequency-domain equalization achieves a considerable performance enhancement compared to both the conventional and the Viterbi-aided channel estimation schemes in terms of both packet error rate (PER) and bit error rate (BER) at relatively high and low velocities. [Copyright &y& Elsevier]

Abstract: In this paper, we present a study of the dedicated short range communications (DSRC) receiver performance under varying signal to noise ratio, velocity, symbol durations and packet lengths. Conventional channel estimation, which is used in IEEE 802.11a, assumes static channel characteristics for the entire packet duration. That is found to be infeasible for high velocity DSRC applications. Simulation results show that the packet-error-rate increases with the increase in relative velocity. Viterbi decoding substantially improves the performance, but the sensitivity to Doppler shift still exists. Analysis and simulation results show that extending the symbol duration or increasing packet length results in an increase of the packet-error-rate. These results may serve as benchmarks for future DSRC channel estimation methods. [Copyright &y& Elsevier]