Double Parity Checking Technique

1.1.1 Parity Checking

The parity checking is generally used for single bit error detection. Either even parity or odd parity checking is generally used for single bit error detection. The sending code word is N+R bits, where R and N is the parity bit and main data bits respectively. On the receiver side accept the data bits if the parity bit is valid otherwise rejected.

Suppose k data bits of a message are D1, D2 ……. appended a parity bit p and n=k+1 is the length of a codeword. Parallel XOR operations generate parity P =D₁ D₂ ….... [19]_.

1.1.2 Two-dimensional Parity Checking

Parity check bits are calculated to generate single bit for each row and each column as shown in Figure 2.6. Parity is created for each row and each column. The row wise streams are appended and sent to receiver. After receiving, these data are compared using two-dimension parity [19]. The limitation of it is given below:

Ø When two bits in one data are occurred error and same position in another data unit of two bits are also occurred, this parity checker is unable to detect the error.

Ø It is unable to detect the four bits errors or more.

Figure 2.6: Two-dimensional parity checking.