Multi-bit System Research Articles

Performance Improvement of Secret Key Generation Scheme in Wireless Indoor Environment

The Secret Key Generation (SKG) scheme that exploits the reciprocity and uniqueness of wireless channel between two users plays a significant part in a new increasing distributed security system. The scheme performance can be distinguished based on the low value of Key disagreement Rate (KDR), the high value of Key Generation Rate (KGR), as well as the fulfillment of the NIST randomness standard. The previous SKG scheme has a high KDR due to a direct quantization of a measurement result of the Received Signal Strength (RSS). To overcome the above issue, we conduct a pre-processing of measurement result before quantization with the Kalman method. The pre-process is carried out to improve the channel reciprocity between two legitimate users with the objective to reduce the bit mismatch. Through an experiment, we propose a new quantization scheme called a Modified Multi-Bit (MMB) that uses a multi-bit system on every level of quantization. The test results show that the proposed combination of preprocessing and the MMB scheme has a better performance compared to the existing schemes in terms of KDR and KGR. The Secret Key generated by our scheme also fulfills the NIST randomness standard.

Sigma-Delta Modulation Based Adaptive Channel Equalizer Based on Wiener–Hopf Equations

Recenlty, short word length DSP systems are proposed and reported that they outperform compared to their counterpart multi-bit systems in the sense of area-performance-power analysis. In this continuation, this paper presents the application of sigma-delta modulation (SDM) in the design of adaptive channel equalizer using the Wiener filter for wireless and underwater acoustic communication (UWA). To validate the application, various aspects of design are taken into consideration and comparison is carried out with contemporary (i.e., multi-bit) approach. Besides, FPGA based implementation of SDM based design and conventional approach is also carried out to endorse the proposed algorithm to be used in hardware based implementation. The results given in terms of area -perfromance analysis show that proposed algorithm works as desired and it opens the way of using the sigma-delta modulation in adaptive signal processing domain for UWA that has remained a quite challenging task ever before.

Sigma-Delta Modulation Based Digital Filter Design Techniques in FPGA

In this paper efficient digital filter design techniques categorized as sigma-delta modulation based short word length (SWL) and multibit (or contemporary) techniques are reviewed in terms of hardware complexity, area, performance and power tradeoffs, synthesis issues, and algorithm versatility. More recent, general purpose DSP applications including classical LMS algorithms reported using sigma-delta modulation encoding are reviewed thoroughly. A small number of basic arithmetic circuits designed using sigma-delta modulation encoding and synthesized by using FPGAs are also described. Finally, recent FPGA based area-performance-power analysis of single-bit ternary FIR filtering is discussed and compared to its corresponding multi-bit system. This work shows that in most cases single-bit ternary FIR-like filters are able to outperform their equivalent multi-bit filters in terms of area, power, and performance.

Resolution of a digital servo control system using single-bit digital signal processing

The application of single-bit digital signal processing to mechanical control systems has already been proposed by the authors. Multibit A/D converters have been improved to a high level. But it is difficult to improve high-resolution A/D by the latest semiconductor technologies. A single-bit digital signal can be generated by a delta-sigma modulator. Single-bit digital signal has a small quantized error at low frequency. Then with this single-bit digital signal processing, high resolution on controlling such a narrow-bandwidth mechanical system will be realized. In this paper, resolution of analog, multibit, and single-bit control systems is estimated via simulation. According to the results of simulations, a single-bit control system has a higher resolution than a multibit system under conditions of equal bit rates. © 1999 Scripta Technica, Electr Eng Jpn, 128(4): 94–101, 1999

Quantisation noise reduction in multibit oversampling Σ-Δ A/D convertors

It is well known that when expanding the internal quantiser of a high-order single-path oversampling Σ-Δ A/D convertor from 1 bit to n bits, the improvement of baseband quantisation noise is (n − 1) bits [1]. This result, however, ignores the enhanced stability characteristics of multibit systems. When full advantage is taken of multibit Σ-Δ modulation, baseband quantisation noise reduction much greater than 1 bit per additional quantiser bit can be achieved. To realise this in a practical system, the feedback multibit D/A must exhibit sufficiently high linearity.