Design and Implementation of High Throughput and Area Efficient Hard Decision Viterbi Decoder in 65nm Technology

Abstract

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.