Design and Implementation of Encoder for (15, k) Binary BCH Code Using VHDL and eliminating the fan-out

Abstract

In this paper we have designed and implemented(15, k) a BCH Encoder on FPGA using VHDL for reliable data transfers in AWGN channel with multiple error correction control. The digital logic implementation of binary encoding of multiple error correcting BCH code (15, k) of length n=15 over GF (2 4 ) with irreducible primitive polynomial x 4 +x+1 is organized into shift register circuits. Using the cyclic codes, the reminder b(x) can be obtained in a linear (15-k) stage shift register with feedback connections corresponding to the coefficients of the generated polynomial. Three encoder are designed using VHDL to encode the single, double and triple error correcting BCH code (15, k) corresponding to the coefficient of generated polynomial. Information bit is transmitted in unchanged form up to k clock cycles and during this period parity bits are calculated in the LFSR then the parity bits are transmitted from k+1 to 15 clock cycles. Total 15-k numbers of parity bits with k information bits are transmitted in 15 code word. Here we have implemented (15, 5, 3), (15, 7, 2) and (15, 11, 1) BCH code encoder on Xilinx Spartan 3 FPGA using VHDL and the simulation & synthesis are done using Xilinx ISE 13.3. BCH encoders are conventionally implemented by linear feedback shift register architecture. Encoders of long BCH codes may suffer from the effect of large fan out, which may reduce the achievable clock speed. The data rate requirement of optical applications require parallel implementations of the BCH encoders. Also a comparative performance based on synthesis & simulation on FPGA is presented. Keywords: BCH, BCH Encoder, FPGA, VHDL, Error Correction, AWGN, LFSR cyclic redundancy checking, fan out .