T S Bindiya

Modified Metaheuristic Algorithms for the Optimal Design of Multiplier-Less Non-uniform Channel Filters

Reconfigurable non-uniform channel filters are now being widely used in software define radio (SDR). The hardware implementation of these filters requires low complexity, low chip area and low power consumption. The frequency response masking (FRM) approach is proved to be a good candidate for the realization of a sharp digital finite impulse response (FIR) filter with low complexity. To reduce the complexity further, this paper gives an optimal design method which makes the channel filters totally multiplier-less. This is done in two steps. The channel filters are designed using the FRM approach with continuous filter coefficients. To obtain multiplier-less design, these filter coefficients are converted to finite-precision coefficients using signed power of two (SPT) space and the filter coefficients are synthesized in the canonic signed-digit (CSD) format. But this may lead to degradation of the filter performance. Hence the filter coefficients synthesis in the CSD format is formulated as an optimization problem. Several meta-heuristic algorithms like Differential Evolution (DE), Artificial Bee Colony (ABC), Harmony Search Algorithm (HSA) and Gravitational Search Algorithm (GSA) are modified and deployed and the best one is selected.

Design of Multiplier-less Reconfigurable Non-uniform Channel Filters using Meta-heuristic Algorithms

Low complexity and reconfigurability are reported to be the key features in a software defined radio (SDR). To obtain these features, a reconfigurable architecture based on frequency response masking (FRM) technique can be used for the implementation of the channel filters in the SDR. The frequency response masking approach is proved to be a good candidate for the realization of a sharp digital finite impulse response (FIR) filter with low complexity. To reduce the complexity and power consumption for hardware realization, a design method which makes the channel filters totally multiplierless is proposed in this paper. Continuous filter coefficients are first converted to finite precision coefficients using signed power of two (SPT) space to obtain a multiplier-less filter. The representation of the FRM filter coefficients in the SPT space can degrade the filter performance. This calls for the use of a suitable optimization technique. The classical gradient based optimization techniques cannot be deployed here, because the search space consists of integers. In this context, meta-heuristic algorithm is a good choice as it can be tailor made to suit the problem under consideration. They are especially useful in finding near optimal solutions in multimodal, multidimensional space. Several meta-heuristic algorithms are modified in this paper to be used for the discrete optimization.

Design of multiplier-less sharp transition width non-uniform filter banks using gravitational search algorithm

In this paper, multiplier-less near-perfect reconstruction tree-structured filter banks are proposed. Filters with sharp transition width are preferred in filter banks in order to reduce the aliasing between adjacent channels. When sharp transition width filters are designed as conventional finite impulse response filters, the order of the filters will become very high leading to increased complexity. The frequency response masking (FRM) method is known to result in linear-phase sharp transition width filters with low complexity. It is found that the proposed design method, which is based on FRM, gives better results compared to the earlier reported results, in terms of the number of multipliers when sharp transition width filter banks are needed. To further reduce the complexity and power consumption, the tree-structured filter bank is made totally multiplier-less by converting the continuous filter bank coefficients to finite precision coefficients in the signed power of two space. This may lead to performance degradation and calls for the use of a suitable optimisation technique. In this paper, gravitational search algorithm is proposed to be used in the design of the multiplier-less tree-structured uniform as well as non-uniform filter banks. This design method results in uniform and non-uniform filter banks which are simple, alias-free, linear phase and multiplier-less and have sharp transition width.

Meta-heuristic evolutionary algorithms for the design of optimal multiplier-less recombination filter banks

This paper proposes a design for multiplier-less recombination non-uniform filter banks (RNUFBs) optimized using meta-heuristic algorithms. The structure consists of an M-channel uniform filter bank, with some channels combined by the synthesis filters of a transmultiplexer (TMUX), yielding non-uniform sub-bands. When any structure is realized in hardware, it is necessary to have low power consumption and a small chip area. These can be achieved by replacing the multipliers with shifters and adders. Once the continuous coefficient recombination non-uniform filter bank is designed, the coefficients are converted to the canonic-signed-digit (CSD) space to make the design multiplier-less, so as to reduce the complexity of the hardware implementation. To reduce the number of adders and shifters in the multiplier-less implementation, the filter coefficients are rounded with a restricted number of signed power-of-two (SPT) terms, which may cause degradation in the performance of the RNUFBs. To improve the performance of the CSD rounded filters and filter bank, meta-heuristic algorithms such as the artificial bee colony (ABC) algorithm, harmony search algorithm (HSA) and gravitational search algorithm (GSA) are deployed. Of these meta-heuristic algorithms, GSA is found to give the best performance. The method proposed in this paper results in non-uniform filter banks with rational sampling factors which are multiplier-less and have linear-phase and near-perfect-reconstruction.

Metaheuristic algorithms for the design of multiplier-less non-uniform filter banks based on frequency response masking

In this paper, multiplier-less nearly perfect reconstruction tree structured non-uniform filter banks (NUFB) are proposed. When sharp transition width filter banks are to be implemented, the order of the filters and hence the complexity will become very high. The filter banks employ an iterative algorithm which adjusts the cut off frequencies of the prototype filter, to reduce the amplitude distortion. It is found that the proposed design method, in which the prototype filter is designed by the frequency response masking method, gives better results when compared to the earlier reported results, in terms of the number of multipliers when sharp transition width filter banks are needed. To reduce the complexity and power consumption for hardware realization, a design method which makes the NUFB totally multiplier-less is also proposed in this paper. The NUFB is made multiplier-less by converting the continuous filter bank coefficients to finite precision coefficients in the signed power of two space. The filter bank with finite precision coefficients may lead to performance degradation. This calls for the use of suitable optimization techniques. The classical gradient based optimization techniques cannot be deployed here, because the search space consists of only integers. In this context, meta-heuristic algorithm is a good choice as it can be tailor made to suit the problem under consideration. Thus, this design method results in near perfect NUFBs which are simple and multiplier-less and have linear phase and sharp transition width with very low aliasing. Also, different non-uniform bands can be obtained from the tree structured filter bank by rearranging the branches.

Design of Multiplier-less Sharp Transition Width MDFT Filter Banks using Modified Metaheuristic Algorithms

The significant advantage of modified discrete Fourier transform (MDFT) filter banks over the conventional discrete Fourier transform (DFT) filter banks is the structure inherent alias cancellation in the former. When the number of channels is increased, the filters in the filter bank need to be of sharp transition width. This increases the complexity of the filters and hence that of the filter bank. Frequency Response Masking (FRM) approach is known to reduce the complexity of sharp transition width filters. This paper proposes a method to realize MDFT filter banks using FRM with much lesser complexity. To further reduce the complexity, the filter banks are made totally multiplier-less. This is done by converting the coefficients to the canonic signed digit (CSD) representation. Metaheuristic algorithms are used to improve the performance of the CSD represented filter banks. Modified integer coded genetic algorithm, differential evolution, artificial bee colony, harmony search and gravitational search algorithms are proposed to be used for the optimization of the proposed multiplier-less MDFT filter banks. This design method reduces the complexity, power consumption and chip area for the implementation of the uniform filter banks.

Design and implementation of reconfigurable filter bank structure for low complexity hearing aids using 2-level sound wave decomposition

Abstract This paper proposes a reconfigurable digital filter bank structure, which is suitable for designing hearing aids for most types of hearing losses. The proposed structure exploits the fractional interpolation and symmetry property of linear phase filters. The structure has two stages; the first one is called masking stage and the second one is called multiple passbands generation stage. The second stage i.e., multiple passband generation stage has 2 levels. By adjusting a 7-bit control signal, different sub-bands generated by the two stages can be obtained for audiogram matching. The number of sub-bands can be increased by increasing the number of fractional interpolated filters in level 2 of the multiple passbands generation block. Using the proposed structure, various types of audiograms can be matched with acceptable delay and matching error. The merits of the proposed structure are low hardware complexity and good audiogram matching with tolerable matching error and acceptable delay, when compared to the state of the art techniques for audiogram matching. Moreover, it is a reconfigurable structure. FPGA implementation of the proposed structure is also done to supplement the theoretical claim for low hardware complexity and power.