Dynamic partial reconfigurable Viterbi decoder for wireless standards

This paper presents a high throughput (1Gbps) and moderate area for constraint length K=3, code rate R=1/2 and four states (N=4) hard decision state parallel Viterbi decoder. The Add Compare Select (ACS) unit in path metric unit is designed to reduce the latency of ACS loop delay by using Modified Carry Look Ahead Adder and Digital Comparator. We also consider the design of Survivor Memory Unit (SMU) which combines the advantages of both Register Exchange method and Trace Back method, to reduce the decoding latency and total area of the Viterbi decoder. The proposed Viterbi decoder design is described using Verilog HDL and implemented in standard cell ASIC flow using Synopsys EDA tool. The design operation is verified by decoding the one million bits. The behavior of the decoder is verified by using Synopsys simulator and synthesized using Synopsys Design Compiler in 65nm CMOS technology library. The proposed decoder operates at 250MHz, supply voltage 1.32V and operating temperature range -40°C to 125°C. The ACS architecture achieves 67.07% improvement in reduction of latency compared to the conventional ACS architecture and achieves 1.235 Gbps throughput. The results show that, the Viterbi decoder architecture achieves 73.03% to 92.46% improvement in area as compared to the other architectures. This reduction in latency and area finds application in high data rate communication.

In this paper, a novel attempt is made to design a reconfigurable coder system which can be reconfigured on-the-fly to work either as an encoder, or decoder, or both encoder and decoder depending on the user requirements. In order to build the proposed reconfigurable system, Convolutional encoder, Viterbi decoder, Golay encoder and Golay decoder are employed in different combinations for the proposed design. The proposed system is implemented on a Virtex-5 FPGA and the performance of the system with and without reconfigurable architecture are reported. It is observed that 56.36% of hardware resources and 72.21% of power are saved on using reconfigurable architecture over non-reconfigurable architecture. The proposed system can be easily extended to include various other encoding and decoding schemes.

This paper describes the hardware design of a high speed Viterbi decoder for the IEEE 802.11a Wireless Local Area Networks (WLAN) application. A fully parallel Add-Compare-Select (ACS) and trace-back architecture is presented to achieve the decoding rate up to 54Mbps. Modulation scheme and coding rate dependent quntaization accuracy for soft decision Viterbi decoding is explored and a hardware implementation scheme with run-time configurable bit-length for soft decision is then proposed to reduce the system power consumption.

Convolutional coding and Viterbi decoding, along with binary phase-shift keyed modulation, is presented as an efficient system for reliable communication on power limited satellite and space channels. Performance results, obtained theoretically and through computer simulation, are given for optimum short constraint length codes for a range of code constraint lengths and code rates. System efficiency is compared for hard receiver quantization and 4 and 8 level soft quantization. The effects on performance of varying of certain parameters relevant to decoder complexity and cost is examined. Quantitative performance degradation due to imperfect carrier phase coherence is evaluated and compared to that of an uncoded system. As an example of decoder performance versus complexity, a recently implemented 2-Mbit/s constraint length 7 Viterbi decoder is discussed. Finally a comparison is made between Viterbi and sequential decoding in terms of suitability to various system requirements.

Application specific integrated circuits are used to provide real-time performance of handheld devices within the compact physical size and low energy dissipation. However, these circuits are inflexible for any modification like redesign and refabrication. Reconfigurable architectures are promising alternative for conventional computing devices such as application-specific integrated circuits. It provides high-level flexibility to adapt the applications through dynamic hardware customization even after fabrication. A reconfigurable computing system design considers the peculiarities of the targeted application domain along with architectural issues like dynamic reconfiguration, partial reconfiguration, hardware/software co-design and context management. A brief survey has been carried out to understand the concepts and applications of CGRA, FPGA, SoC, NoC, MPSoC, dynamic partial reconfiguration, hardware/software co-design, design-space exploration, multi-objective optimization, genetic algorithm and reconfigurable computing on wireless communications. This paper deals with the survey on modeling, design, implementation and evaluation of coarse-grained dynamically reconfigurable processor architectures targeting the real-time embedded computing domain.

Low-power microarchitecture designs of Viterbi decoder are considered one of the on-demanding issues in Very Large-Scale Integration (VLSI). Viterbi decoders consume 35% of the power and 76% of the complexity in digital communication schemes, e.g., IEEE 802.11 a/g WLAN schemes. Development of Viterbi decoder itself reduces dramatically system complexity; the decoder has a source of power sink unit which rises in Add Compare-Select (ACS) unit. Various levels of development exist in VLSI such as architecture, microarchitecture, circuit, and transistor. ACS is structured of adder, comparator, and selector, so microarchitecture development of ACS unit intends one of these superior blocks. Adders in VLSI designs have a tremendous interest as they are the kernel of any digital system so enhancing this basic building block, which is used over and over, influences system specification. This paper targets different microarchitectural approaches to shrink the power of this unit which enhances overall system specification. Microarchitecture development encompasses using another block instead of the existing one or repositioning current blocks. In this review paper, comparisons of different parallel adders are presented to achieve low consumption power while obtaining high-speed operation of the addition, and an arrangement of ACS blocks to reduce the complexity of the decoder is also provided.

Convolutional or trellis codes are today widely used in digital communication networks and multimedia broadcasting systems. TheViterbi decoder is commonly used for decoding trellis codes due to its excellent forward error correction performance. High-performance and low-power Viterbi decoders are in great demand in the communication industry. Despite several significant developments in decoder design and architecture in the past decade, the issue of latency and power dissipation still remains a challenge requiring further investigation and innovation. This paper proposes arobust deep-pipelined Add-Compare-Select (ACS) Unit, based on a hybrid logic asynchronous pipeline design method. The ACS operation forms the primary deadlock on the performance of the decoder hardware. With the proposed structure, the ACS units and hence Viterbi Decoder operate at a 323.3% higher throughput with 76.4% reduced latency and 86.6% reduced power consumption, when compared with QDI based realization of the ACS unit.

A novel asynchronous data-path design is described. Circuits for the asynchronous adder unit, asynchronous comparator unit, and asynchronous selector unit are proposed. An asynchronous data-path ACS (add-compare-select) for a Viterbi decoder is formed. The performance of the 4-bit ACS is analyzed with a novel method based on a multi-delay model. The results of performance analysis of the asynchronous 4-bit ACS show that the average case response time of 6.81 ns is only 84% of the worst-case response time, 8.08 ns. It reveals that the asynchronous data-path has some performance advantages over the synchronous one.

This paper presents a new self-resetting CMOS design for an add-compare-select (ACS) unit, which is a key building block in a Viterbi decoder. Static CMOS and two-phase domino CMOS designs have also been implemented for comparison purposes. The simulation results show that, with the SRCMOS technique, the ACS units operate at a data rate of 568 Mbps in a 0.25 micron CMOS technology, as compared to 357 Mbps and 485 Mbps for static and domino CMOS implementations, respectively.

A runtime reconfigurable architecture for high speed Viterbi and turbo decoding is designed and implemented on an FPGA. The architecture can be reconfigured to decode a range of convolutionally coded data with constraint lengths varying from 3 to 9, rates 1/2 and 1/3, and various generator polynomials. It can also be reconfigured to decode turbo coded data with constraint length 4 and rate 1/3. Reconfiguration of the architecture requires a single clock cycle and does not require FPGA reprogramming. The proposed architecture can deliver data rates up to 60.5 Mbit/s for Viterbi decoding and 3.54 Mbit/s for turbo decoding, making it suitable for a range of wireless communication standards like IEEE 802.11a, 3GPP, GSM, GPRS, and many others.

At present, the Viterbi algorithm (VA) is widely used in communication systems for decoding and equalization. The achievable speed of conventional Viterbi decoders (VD's) is limited by the inherent nonlinear add-compare-select (ACS) recursion. The aim of this paper is to describe system design and VLSI implementation of a complex system of fabricated ASIC's for high speed Viterbi decoding using the minimized method (MM) parallelized VA. We particularly emphasize the interaction between system design, architecture and VLSI implementation as well as system partitioning issues and the resulting requirements for the system design flow. Our design objectives were 1) to achieve the same decoding performance as a conventional VD using the parallelized algorithm, 2) to achieve a speed of more than 1 Gb/s, and 3) to realize a system for this task using a single cascadable ASIC. With a minimum system configuration of four identical ASIC's produced by using 1.0 /spl mu/ CMOS technology, the design objective of a decoding speed of 1.2 Gb/s is achieved. This means, compared to previous implementations of Viterbi decoders, the speed is increased by an order of magnitude.

A 140-Mb/s, 32-state, radix-4, R=1/2, eight-level soft-decision Viterbi decoder has been designed and fabricated using 1.2- mu m double-metal CMOS. The architecture of the add-compare-select (ACS) array is based on a restructuring of the conventional radix-2 trellis into a radix-4 trellis. Radix-4 units, consisting of four 4-way ACS units, process two stages of the constituent radix-2 trellis per iteration. A four-way ACS circuit achieves an iteration delay 17% longer than comparable two-way ACS circuits, resulting in a factor of 1.7 increase in throughput. A ring-based ACS placement and state metric routing topology achieves an area efficiency comparable to radix-2 designs. In a process referred to as pretrace-back, one stage of lookahead is applied to the trace-back recursion, combining two radix-4 trace-back iterations into a single radix-16 iteration based on 4-b decisions. This allows implementation of trace-back using one compact, single-ported decision memory, organized as a cyclic buffer. A 7.30-mm*8.49-mm chip containing 146000 transistors achieves a radix-4 iteration rate of 70 MHz. >

An efficient and hardware economic channel coding technique is essential in high-speed mobile communication systems. The channel coding parameters will have a large impact on the system performance (data rate and bit error rate) and also on the hardware development in terms of area consumption and timing behaviour. Therefore, important system parameters like code rate, constraint length and Viterbi decoding strategy (single state or best state and the resulting truncation depth for both strategies) have to be decided early in the design flow. The objective of this paper is to discuss the technical tradeoff (system performance and hardware cost) when choosing the channel coding parameters for a system with convolutional encoding and Viterbi decoding. For a wide range of possible channel coding parameters the impact on the system performance and on hardware consumptions, which have been acquired from field programmable gate array (FPGA) implementations, are discussed and compared.

In this paper, we concern with designing and implementing a convolutional encoder and Viterbi decoder which are the essential block in digital communication systems using FPGA technology. Convolutional coding is a coding scheme used in communication systems including deep space communications and wireless communications. It provides an alternative approach to block codes for transmission over a noisy channel. The block codes can be applied only for the block of data. The convolutional coding has an advantage over the block codes in that it can be applied to a continuous data stream as well as to blocks of data.The motivation of this paper is to realize a Viterbi decoder having Constraint length 9 and code rate 1/2 by Xilinx 12.4i tools.

Convolutional code is a coding scheme used in communication systems including deep space communications and wireless communications.It provides an alternative approach to block codes for transmission over a noisy channel.The block codes can be applied only for the block of data.The Convolutional coding has an advantage over the block codes in that it can be applied to a continuous data stream as well as to blocks of data.Viterbi decoder employed in digital wireless communication plays a rife role in the overall power consumption of trellis coded modulation decoder.Power reduction in Viterbi decoder could be achieved by reducing the number of states.A pre-computation architecture with T-algorithm was implemented for this purpose, and when we compare this result with full Trellis Viterbi decoder, this approach significantly reduces power consumption without degrading decoding speed.Convolutional encoding with viterbi decoding is a powerful FEC technique that is particularly suited to a channel in which the transmitted signal is corrupted mainly by Additive White Gaussian Noise (AWGN).It operates on data stream and has memory that uses previous bits to encode.The Viterbi Algorithm (VA) is proposed, used for decoding a bit stream that has been encoded using FEC code.The Convolutional encoder adds redundancy to a continuous stream of input data by using a linear shift register.A pre-computation architecture with Viterbi algorithm is implemented for this purpose, Viterbi (Convolutional) encoder and Viterbi decoder are designed and implemented using FPGA technology, which are the essential blocks in digital communication systems.It is particularly suited to a channel in which the transmitted signal is corrupted mainly by AWGN.The Viterbi decoder of Constraint length 7 and code rate ½ is considered.The design is implemented using verilog on Xilinx Spartan 3E and advanced Spartan 6 board and the results and Comparisons are presented.