In this thesis, a new spreading code -- complete offset-stacked spreading code (OSC) is designed and discussed. OSC has a orthogonal complementary property of auto-correlation and cross-correlation. According to the interference-free windows of cross-correlation (CC_IFW) of OSC, the proposed CDMA architecture can offer an MAI-free operation in both down-link (synchronous channel) and up-link (asynchronous channel) transmission under the AWGN channel. According to the interference-free windows of auto-correlation (AC_IFW) of OSC, the proposed CDMA architecture can also offer a part of MI-free operation in both downlink (synchronous channel) and uplink (asynchronous channel). Furthermore, the range of AC_IFW is restricted by the number of offset chips.