Fractional-bit detection with advanced sampling to combat multipath-induced error floor

In digital mobile communications, the error floor caused by time dispersion of the channel limits data rate even in low delay spread situations. The errors originate in the transition regions between adjacent symbols when deep fades occur. A detection method to reduce these errors, i.e., fractional bit differential detection with sample timing which is advanced from the average mean excess delay, avoiding the transition regions, is analyzed. Assuming a minimum shift keying (MSK) modulation format, the error probability is calculated and verified by a Monte Carlo software simulation. The approach increases the tolerable delay spread in an unequalized receiver, depending on the details of the delay power profile. These are accounted for by introducing an effective delay spread. Limiting the bandwidth tends to smear the transition regions over the entire bit duration, thus offsetting part of the method's benefit.