A new algorithm for reducing peak-to-average power ratio (PAPR) of multicode code division multiple access (MC-CDMA) systems under binary PSK modulation is presented. The algorithm is based on Reed-Muller (RM) codes that are modified by finding a suitable binary sequence that minimises the PAPR of the MC-CDMA. Three types of RM codes are investigated: namely, zero order, first order and second order. Simulation studies conducted show that the proposed algorithm achieves transmitter power savings of up to 6 dB. Zero-order and first-order codes exhibit 0 dB PAPR, while several others maintain a constant and low PAPR as compared with the original MC-CDMA systems.Introduction: Multicode code division multiple access (MC-CDMA) is based on summation of n channels or signals of basic data rates from an orthogonal set called Walsh-Hadamard transform (WHT) sequences. This summation of n signals results in high peaks (present at the forward link of transmitter), which can be as large as n times the average signal power. Typically, n = 2 m where m lies between 2 and 6 [1-3]. Therefore, to transmit MC-CDMA signals without distortion we need an expensive power amplifier (PA) that operates in its linear region [1,2,4]. Since these peaks occur only occasionally, using a PA that does not distort the high peak signals would be expensive, unrealistic and highly inefficient.The high peaks of the signal are usually measured by a well-known parameter called peak-to-average power ratio (PAPR) [5]. The objective then is to reduce PAPR that reduces the high signal peaks.Paterson [1] has developed constant-amplitude codes for MC-CDMA from bent function, Kerdock and Delsarte-Goethals codes. While Schmidt [6] has designed quaternary constant-amplitude codes for MC-CDMA. Both of them have reduced the PAPR in MC-CDMA to the value of 1. Their construction of codes is based on complex mathematics. Several other methods have been proposed to reduce the PAPR. Some of these are reported in, for example, [3,7] where they have used partial transmit sequence (PTS) and selected mapping (SLM) to reduce PAPR, at the expense of complexity [2,8]. A consolidated comparison table showing other algorithms can be found in [9].In this Letter, we propose a new and simple approach to reduce PAPR of MC-CDMA using Reed-Muller (RM) codes. These RM codes are one of the oldest and well understood families of codes. The great merit of RM codes is that they are relatively easy to decode using majority logic circuits [10].Binary RM code may be defined as RM(r, m) of order r, r = 0, 1, …, m [9, Chapter 3, p.57] has the triplets (n, k, d ) as follows: