時間延遲下區塊衰減X通道之干擾對齊設計方法

Abstract

在[1]所舉的例子中，其考慮兩個傳輸端、兩個接收端的單天線X通道，在傳輸端與接收端具備特定時間延遲的情形下，透過干擾對齊方法的設計，此網路系統可達到4/3的自由度。在此篇論文中，我們考慮兩個傳輸端、兩個接收端的單天線類衰減X通道，首先將[1]所舉的例子推廣至廣義時間延遲的情形，我們提供了一個簡易的演算法來設計干擾對齊的結構，以使之達成目標的自由度。繼之，在M個傳輸端與N個接收端的時間衰減X通道系統下，我們提供了一個更為高階的演算法使此系統與考量無時間延遲的X通道情形能達成同樣的自由度。然而，我們也描述了在某些時間延遲的組合案例下，干擾方法的設計將無法達到上述的結果，因此，我們也提供了相關的分析詳述時間延遲的條件使得各個演算法得以順利運作。

In [1], a toy example was constructed to achieve the 4/3 sum degrees of freedom for the 2 × 2 user X channel using an interference alignment scheme, where each user is equipped with single antenna, and each link contains a specific propagation delay. In this thesis, we first generalize the example to the case of general propagation delays and assume the links are quasi-static faded. We provided a simple algorithm to design the interference alignment scheme for such 2 × 2 user X channel with faded links. A much more advanced algorithm for interference alignment for the general M × N user delayed X channel is also provided and is shown to achieve the same sum degrees of freedom as the non-delayed X channel. We report that there are some cases of propagation delays for which interference alignment is not possible. Analyses for the conditions of propagation delays for each algorithm to work are also given.