Research On The Paired Carrier Multiple Access Technique In Satellite Communication Systems

Paired Carrier Multiple Access (PCMA) is a new technique which can be applied in two-way satellite communication systems. It is used in addition to various multiple access techniques, and allows two earth stations to communicate using the same frequency, time slots and CDMA code. In this way, available bandwidth may be effectively increased, as well as the system capacity. PCMA takes better advantage of the on-board resource, so that it can keep the balance of system bandwidth and power. With the rapid development of telecommunication technology and users'demands, system capacity has gradually become the key factor of service expansion in satellite communications. Therefore, it becomes quite meaningful to carry out research on PCMA systems.This dissertation studied on the key techniques in PCMA systems: parameter estimation, reconfiguration and suppression of the self-interference signal. First, the dissertation analyzed the essential principle and scheme of the PCMA technique. Both symmetric and asymmetric modes were discussed in PCMA applications with different multiple access techniques, and some basic concepts such as parameter estimation, self-interference, signal reconfiguration and suppression were illustrated. Also, specific examples were given to analyze the overall system performance influenced by PCMA technique. Second, this paper built the base band transmission model of PCMA system, and a new parameter estimation algorithm was proposed on the basis of correlation function fitting. Here the dissertation only focused on frequency and time delay estimation of the self-interference signal. Without sending any training sequences, the proposed algorithm can accurately estimate the frequency and time delay of self-interference signal through three phases: frequency pre-search, correlation function fitting and peak acquisition. Simulations under different SNR conditions have shown that the limitations of traditional algorithms were all overcome, with less calculation complexity and more robust estimation performance. Based on the estimation algorithm proposed above, this dissertation then reconfigured and suppressed the self-interference in the software environment, and analyzed the influences of PCMA applications on bottom-layer performance through BER experiments. What's more, implementations of PCMA technique in current TDMA and CDMA systems were further discussed using relevant simulation results. Conditions and cost of PCMA applications were analyzed by deriving and calculating the bandwidth and power used in the systems, and on the other hand, the algorithm proposed by this paper was proved again to enlarge the capacity of satellite communication systems effectively, especially the bandwidth limited ones.