A multi-rate modulation scheme suitable for code-division multiple-access (CDMA) communications systems is introduced. Balanced incomplete block designs (BIBD) are used to control the peak-to-average power (PAV) ratio and produce a signal whose amplitude is within the linear region of a power amplifier a larger proportion of the time than is the amplitude of a signal without a controlled PAV ratio. The PAV ratio and its effects on the power amplifier behavior are examined. The performances of the proposed scheme in the additive white Gaussian noise (AWGN) channel and in a multi-user environment are investigated.

A multirate modulation scheme with controlled peak-to-average power (PAV) ratio and suitable for code division multiple access techniques is introduced. The scheme utilizes codes drawn from a fixed set of Walsh-Hadamard codes but other code families can also be used. The strategy employs balanced incomplete block designs to define the multirate data symbols, with the objective being to reduce depletion of the code pool while controlling the PAV ratio. Existing multirate schemes are reviewed. Code depletion and PAV ratio characteristics of the proposed scheme are compared to existing schemes. Symbol error performance of the proposed scheme in an additive white Gaussian noise channel is examined. It is concluded that the proposed scheme, unlike the two other existing schemes that are examined, strikes a good balance between PAV ratio, code depletion, and error performance.