極化碼可將實體獨立的二元通道化為同樣數量的等效位元通道; 在碼長趨近無窮大時，所有位元通道可區分為通道容量趨近1的完美通道與通道容量趨近0的純雜訊通道。於傳輸時只使用接近完美的極化通道，使其傳輸率達通道容量。另一方面，相差空間調變是一種一次只使用一根天線傳送訊號的多天線技術，藉由選擇傳送天線可以多傳額外的資料位元，並避免前導(pilot)訊號的浪費。
在本論文中，我們將極化碼應用於相差空間調變，針對相差空間調變中天線位元以及訊息位元分別使用不同組極化碼編碼，由模擬結果可以證實此方法有更好的錯誤率，我們也提出用於相差空間調變的低複度調變軟式輸出方法，雖錯誤率略差於原先作法，但大幅降低執行時間。

Polar code converts the physical independent binary channels into the same number of equivalent bit channels; when the code length approaches infinity, all bit channels can be distinguished into perfect channels with channel capacity approaching 1, and pure noise channels with channel capacity approaching 0. Polar codes only use nearly perfect polarized channels during transmission, so that the transmission rate reaches the channel capacity. On the other hand, differential spatial modulation is a multi-antenna technique that uses only one antenna to transmit signals at a time and avoids pilot overhead. By selecting the transmitting antenna, additional data bits can be transmitted.
In this paper, we apply polar code to differential spatial modulation. Different sets of polarization codes are used for the antenna bits and message bits in differential spatial modulation. The simulation results prove that this method has better error rate. We also propose a low-complexity soft-output decoding differential spatial modulation. Although the error rate is slightly worse than the original method, the execution time is greatly reduced.

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