I. INTRODUCTION
In Direct-Sequence Code Division Multiple Access (DS-CDMA) due to practical conditions it is desirable to use binary antipodal signatures (spreading codes) in conjunction with BPSK modulation. In these systems we can obtain errorless transmission using orthogonal codes (e.g. Hadamard codes) under the assumption of noiseless channel. This is only true if the number of users does not exceed the spreading factor (under-loaded or fully-loaded CDMA). When the number of users exceeds the spreading factor, such orthogonal codes do not exist. Also, using Pseudo-Noise (PN) spreading signatures creates interference that cannot be completely removed and results in errors in the Multi-User Detection (MUD) receiver [1]–[3]. There are papers that discuss double orthogonal codes for increasing capacity [4]–[5]. These codes are non-binary complex codes (equivalent to phases for MC-OFDM) and thus are not a fair comparison to binary codes.