Adaptive pilot pattern for multi-carrier spread-spectrum (MC-SS) transmission systems

In this paper, we address the issue of the design of link adaptation mechanisms in the context of multi-carrier spread-spectrum (MC-SS) transmission systems. By optimally varying the frequency pilot pattern, we present two original adaptation strategies that manage to preserve the requested QoS parameter, in our case the minimum BER target. The dynamic sub-carrier allocation policy is first detailed and then adaptive pilot pattern results are presented for different channel conditions and QoS. Moreover, an original geometric interpretation of the theoretical BER expression in terms of Bezier curves allows complexity reduction of the overall adaptation scheme. Based on the metric of the ratio between pilot and data subcarriers (pilot overhead), we thus propose a generalizing adaptive scheme, taking into account this loss of bandwidth parameter, and varying both the spreading factor and the pilot tone pattern. Allocation results of such an optimal adaptation policy are finally presented.