Improvement of the orthogonal code convolution capabilities using FPGA implementation

Abstract

When data is stored, compressed, or communicated through a media such as cable or air, sources of noise and other parameters such as EMI, crosstalk, and distance can considerably affect the reliability of these data. Error detection and correction techniques are therefore required. Orthogonal Code is one of the codes that can detect errors and correct corrupted data. An n-bit orthogonal code has n/2 1s and n/2 0s. In a previous work these properties have been exploited to detect and correct errors. In this paper we present a new methodology to enhance error detection capabilities of the orthogonal code. The technique was implemented experimentally using Field Programmable Gate Arrays (FPGA). The results show that the proposed technique improves the detection capabilities of the orthogonal code by approximately 50%, resulting in 99.9% error detection, and corrects as predicted up to (n/4-1) bits of error in the received impaired code with bandwidth efficiency.

Error Detection using Orthogonal Code

“…Hence the detection percentage for 8-bit orthogonal code is given by (28 -24)/28 = 93.57% and also able to correct single bit error. Similarly, the percentage of detection for 16-bit orthogonal code is 99.95% and gives 3-bit of error correction [1]. Following table-3 shows the data detection capacity of orthogonal code.…”

“…Therefore all orthogonal codes will generate zero parity bits. The main reason for using orthogonal scheme is that they are not sensitive to the near-far effects and as cross correlation of each generated orthogonal code is zero, detection of corrupted code sequence is easy [1]. The concept is illustrated by means of an 8-bit orthogonal code as shown in table-1.…”

“…Where n is the code length and dth is the threshold midway between two orthogonal codes [1]. For 8-bit orthogonal code we have dth=8/4=2.For reliable detection extra 1-bit offset is added to eq.…”

“…In the first case, the received code has a match in the lookup table.In the second case, the received code has no match in the lookup table.In this case the single bit error is detected and corrected by the receiver. In the third case, there is more than one possibility of closest match in the lookup table.The value of minimum count is associated with more than one orthogonal code and thus it is not possible to determine the closest match in the lookup table for the received code [1]. Then the signal labelled "REQ" goes high, which is a request for a retransmission.…”

“…Some of the error detection techniques can only detect errors,such as cyclic redundancy check;other are designed to detect and correct errors, such as salomon codes [5].however the existing techniques are not able to achieve high efficiency and to meet bandwidth requirements, especially with the increase in the quantity of data transmitted. orthogonal code is one of the code that can detect errors and correct corrupted data [1].…”