Viterbi decoder having three sub modules are branch metric. If the transmitted path is discarded, the adaptive viterbi algorithm ava can recover the state corresponding to the transmitted path after a few trellis depths. The proposed design can be fabricated as a low power viterbi decoder on asic for either a base station or portable unit. Integrated viterbi turbo decoder design viterbi coding is a popular channel coding technique used in a wide. Another important point about the viterbi decoder is that future knowledge will help it break any ties, and in fact may even cause paths that were considered most likely at a certain time step to change. I need to make viterbi decoding of some convolutionalencoded signal. Convolutional encoder and adaptive viterbi decoder,convolutional encoder, viterbi decoder. It can account for more than onethird of power consumption during baseband processing in current generation cellular telephones 3. Complexity of viterbi decoding algorithm increases in terms of trellis length. This paper presents a pipelined adaptive viterbi algorithm of rate. Convolutional encoder and adaptive viterbi decoder verilog code. Modified architecture of adaptive viterbi decoder the main aim of the adaptive viterbi decoder is to reduce the average computation and path storage required by the viterbi algorithm. A limiting factor in viterbi decoder implementations is the need to preserve candidate paths at all 2k. Design and implementation of lowpower viterbi decoder for.
An improved dynamically reconfigurable pipelined adaptive. Implementation of soft decision viterbi decoder based on a digital signal processor. The convolutional encoder and the viterbi decoder are not at all efficient, since it uses many if and forloops. The processors generate metrics of states and of transitions between the states associated with an encoder, based on encoded input information symbols received via a communications channel. In addition, the power efficiency is enhanced compared to the basic comparison unit results. The bits which are encoded are again sent to the viterbi decoder and then the a viterbi decoder uses the viterbi algorithm for decoding a bitstream but here we are using this viterbi. High data rate pipelined adaptive viterbi decoder implementation doi. Power consumption of the wave pipeline work is reduced to 72. The viterbi core decodes the data generated by the convolutional encoder that has a constraint length k7 and the two generator polynomials g0171 and g13 as shown in figure 6. The receiver dsp algorithms are both memoryintensive and computationintensive.
Implementation of reconfigurable convolutional encoder and. The architecture of the viterbi decoder is illustrated in fig 3. If the encoder schematic has more than one input stream, the shift register that receives the first input stream provides the least significant bits in fstate, and. In this paper, efficient low power asynchronous viterbi decoder is designed and compares the performance parameters with the synchronous viterbi decoder. Low power viterbi decoder designs a thesis submitted to the university of manchester for the degree of doctor of philosophy in the faculty of engineering and physical. Pdf high data rate pipelined adaptive viterbi decoder. A viterbi decoder implementation for convolutional codes that employs traceback memory management can be described in terms of four parameters, memory order, traceback memory length, truncation length, and code rates supported. Low power, viterbi algorithm, adaptive talgorithm decoding, convolutional codes. Integrated data relocation and bus reconfiguration for. An adaptive effort lowpower viterbi decoder for wireless communications a thesis submitted to the department of electrical and computer engineering in conformity with the requirements for the degree of master of science queens university kingston, ontario, canada. In this work, we developed a method to eliminate the searchforthebestwinner operation and hence enable the highthroughput stateparallel adaptive viterbi decoder.
Lowpower adaptive viterbi decoder for tcm using talgorithm. Simply swapping idata and qdata inputs allows the same viterbi decoder core to decode data encoded with generator polynomials g03 and g1171. There are other algorithms for decoding a convolutionally encoded stream for example, the fano algorithm. Puncturingdepuncturing patterns are used in order to achieve code rates 23 and 34 that are higher than 12. For and if loops will increase the program execution speed. This results in lowering the switching activities of the logic cells, with a consequent reduction in the dynamic power.
Convolutional encoder and adaptive viterbi decoder verilog. In this implementation, each cluster receives a separate data stream and acts as a full viterbi decoder figure 7. An adaptive sliding block viterbi decoder asbvd includes forward and backward viterbi processors, a state estimator and a control unit. Further reduction in power can be contributed to the reduction of complexity in min path calculation unit and path metric adder. Low power viterbi decoder designs university of manchester. The area consumption was less in viterbi compared to adaptive viterbi decoder. Transition probability matrix emission probability matrix initial probability matrix states matrix ie. Implementing an adaptive viterbi algorithm in coarse. Fpga implementation of modified architecture for adaptive. The code is not at all efficient, neither the encoder, nor the viterbi decoder. Adaptive viterbi decoder avd that uses survivor path with parameters for wireless communication in an attempt to reduce the power and cost and at the same time increase in speed. Decoder final traceback states, returned as a trellis.
Table 17 lists ber measurements for a rate 12 code g 0 171, g 1 3 and a memoryless additive white gaussian channel. The convolutional encoder can be efficiently implemented using the long division method and the viterbi algorithm can be efficiently implemented in matlab by just. My application shall work with large files, therefore i cannot insert all the signal into a heap, so i need to process a data by a sequence of separate buffers. All the submodules of the adaptive viterbi decoder block to be identified. Introduction a viterbi decoder 1, 2 is an important target for power reduction in many lowpower communications devices. A dynamically reconfigurable adaptive viterbi decoder. For each data point, the simulation ran until 100 errors or possibly more occurred. Lowpower approach for decoding convolutional codes with. Outputs fstate and finput jointly describe the final traceback memory of the decoder. Us8111767b2 adaptive sliding block viterbi decoder.
The design and simulation of the viterbi decoder is at layout level with 65nm technology in microwind. But the power utilization reduced drastically to 20% where as in viterbi decoder the power consumed was 80%. Port descriptions a representative symbol of the viterbi decoder, with the signal names, is shown in figure 21 and figure 22 and described in table 21. Guidelines for efficient management and portability of your project and ip files. The convolutional encoder is designed with the constraint length of 4 and code rate of. A viterbi decoder uses the viterbi algorithm for decoding a bitstream that has been encoded using convolutional code or trellis code. Each decoder component package or entity is implemented in a single. Convolutional encoder and hard decision viterbi decoder. The basic performance of the viterbi decoder is analyzed with the block diagram shown below. When the two survivors have been determined at the jth instant, the decoder outputs from memory the jlth information symbol survivor with the largest metric. General implementation of matlab version of viterbi algorithm specifically written for gene structure finding problem in mind. Most of the researches work to reduce power consumption, or work with high frequency for using the decoder in the modern applications such as 3 gpp, dvb. The viterbi algorithm, which includes a branch netric and a path metric, is introduced as a way to. Convolutionally decode binary data by using viterbi.
The viterbi algorithm 9, the most popular decoding approach for convolutional codes, determines a minimum distance path with regards to hamming distances applied to each received symbol. Viterbi ip core user guide document archives on page 37 provides a list of user guides for previous versions of the viterbi. Adaptive viterbi decoding of reedmuller codes request pdf. Design impact the polynomial set may not represent a valid convolutional code, so the generated variation does not function as a valid viterbi decoder. Implementation of soft decision viterbi decoder based on a. Based on this input either a 0 or a 1, the internal branch metrics are calculated using an unsigned integer of word length. The viterbi algorithm is the most resourceconsuming, but it does the maximum likelihood decoding. The convolutional encoder encodes the message and then the encoded bits are generated. The rate, constraint length and decision depth of the decoder can be adjusted to different communication systems. Select the base of the polynomials decimal or octal with the radio. Because clusters receive separate data streams, the streams are completely. A third implementation of the viterbi decoder uses a simd architecture to exploit thread level parallelism.
General viterbi algorithm file exchange matlab central. A talgorithm decoder is essentially an approximation of the. Adaptive viterbi decoder can be used in high speed decoding applications such as space communication. To enable fixedpoint viterbi decoding, the block input must be of type ufix1 unsigned integer of word length 1 for hard decisions. International journal of engineering research and general. Instead of computing and retaining all 2k1 possible paths, for each received symbol at each state. Therefore, to realize an adaptive convolution encoder and viterbi decoder on fpga is very demanding. However, it can be modified to suit the goal of a user. The convolutional encoder can be efficiently implemented without a forloop by using long division method. The performance of the implemented avd is analyzed by using ise 10. An approach for adaptively approximating the viterbi. Viterbi decoder implementation guide 1 source files description the directory structure of the viterbi decoder core is shown in table1. Efficient convolutional adaptive viterbi encoder and.
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