In this paper we investigate the distance properties of orthogonal codes and evaluate its error control properties. We examine this by noting that an n-bit orthogonal code has n/2 1's and n/2 0's; i.e., there are n/2 positions where 1 's and 0 's differ. Therefore, the distance between two orthogonal codes is also n/2. By exploiting this distance property, we show that a code rate r = k/n, where n is the code length and k is the data length, is available out of orthogonal codes with error control capabilities. We then develop a method of coded modulation with bandwidth efficiency. The proposed technique offers a simpler solution to error control coding with bandwidth efficiency. Finally, the construction of an orthogonal coded modulation scheme is presented to illustrate the concept.
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