A Comparison of Three Equalization Techniques for iNET-formatted SOQPSK-TG

Abstract

This paper demonstrates the effectiveness of the zero-forcing, minimum mean-squared error, and constant-modulus equalizers in improving the BER performance of iNET-formatted SOQPSK-TG. The equalization algorithms leverage the existence of known bit sequences in the preamble and ASM fields of the iNET packet to realize data-aided equalizers. The effectiveness of these equalization techniques over ten test channels, derived from channel sounding experiments at Edwards AFB, was evaluated. The BER curves for nine out of the ten test channels display the desirable "waterfall" shape. The BER curve for the remaining test channel displays a "BER floor." Fortunately, the "BER floor" is low enough to allow error correcting codes, such as the iNET LDPC code, to correct the errors and provide virtually error-free performance.