基于循环延迟分集的空时频编码策略

结合空时编码和正交频分复用(OFDM)技术，将循环延迟分集引入到传统的空时OFDM编码系统中，提出了一种新的空时频编码策略．在该策略中，对OFDM帧间相同载波上的符号进行空时编码，实现空时分集；OFDM帧内各子载波上的符号则使用循环延迟引入频率分集，实现空频编码．接收端综合利用空时、空频编码的结构信息实现联合译码，获得空时频分集增益．仿真结果表明，该策略具有结构简单、差错性能改善明显等优势．在频率选择性信道中，新编码策略可以获得空时频全分集增益．在相同信干比条件下，差错性能明显优于传统空时或空频OFDM系统的差错性能．

A New Space-Time-Frequency Coded Strategy Based on Cyclic Delay Diversity

While integrating with space-time code and orthogonal frequency division multiplexing (OFDM), putting cyclic delay diversity into the traditional space time OFDM coded system, a new space time frequency coded strategy was proposed. In the new coded strategy, symbols on the same sub-carriers between different OFDM frames are to be space-time coded and then transmit diversity could be achieved; proper cyclic delay is used to implement frequency diversity and then those symbols on all sub-carriers in one OFDM frame would be space frequency coded. The tests show that the new strategy has obvious advantages on its simple structure and great improvement on error performance. The new coded strategy can achieve full space-time-frequency diversity over frequency selective fading channel. At the same signal to interference ratio (SIR) level, the error performance of the new coded strategy is better than that of the traditional space time OFDM or space frequency OFDM system.