Merging DS-CDMA (with CI chip shapes) and oscillating-beam smart antenna arrays: exploiting transmit diversity, frequency diversity and directionality

We merge a smart antenna array with CI/DS-CDMA, a novel implementation of DS-CDMA where chips have a shape referred to as the CI (carrier interferometry) chip shape and are decomposable into N narrowband frequency components. In the antenna array, by applying suitable time-varying phases to the elements, we create small movement (oscillation) in the antenna array's pattern, while steering the main lobe to the position of the intended user. The oscillating antenna pattern creates a time-varying channel with a controllable coherence time. This, in turn, provides transmit diversity in the form of a time diversity gain at the mobile receiver side. Thus, at the receiver, three stages of combining are available: 1) combining time components of the received signal within symbol duration T/sub S/ (each experiencing a different fade) to enhance performance via time diversity; 2) combining frequency components which make up the CI/DS-CDMA chip to enhance the performance via frequency diversity; 3) combining across chips to eliminate interfering users. Employing CI/DS-CDMA with the proposed smart antenna at the base station, we achieve: 1) very high capacity via the merger of SDMA (directionality of antenna array) and CDMA; 2) very high performance via the construction of receivers that exploit both transmit diversity and frequency diversity. We focus on the performance benefits of the proposed system.