In this paper, we present an experimental evaluation of the performance benefits provided by flexible duplexing, an access technique that allows uplink and downlink cells to coexist within the same time-frequency resource blocks. In order to replicate a wireless multi-tier network composed of 1 macro-cell and 2 small cells, a measurement campaign has been conducted using an indoor wireless testbed comprised of a total of 6 multiple-input multiple-output (MIMO) software-defined radio (SDR) devices. Since each cell has a single active user, each uplink/downlink configuration can be identified with a different interference channel, over which interference alignment (IA) is used as an inter-cell interference management technique and compared to other existing methods. The obtained results show that flexible duplexing clearly outperforms the conventional time-division duplex (TDD) access approach, where all cells operate synchronized either in uplink or dowlink mode. Additionally, interference alignment consistently provides better results in most of the interference regimes when compared to minimum mean square error (MMSE)-based schemes. The impact of channel estimate quality on the different communication strategies is also studied. It is worth highlighting that the presented over-the-air (OTA) experiments represent the first implementation of IA with real-time precoding and decoding.

在本文中，我们对可变双工提供的性能优势进行了实验评估，这种灵活的双工是一种允许上行链路和下行链路小区共存于同一时频资源块中的访问技术。为了复制由1个宏小区和2个小小区组成的无线多层网络，使用室内无线测试台进行了测量活动，该室内测试台总共定义了6个多输入多输出（MIMO）软件，无线电（SDR）设备。由于每个小区只有一个活动用户，因此每个上行链路/下行链路配置都可以通过不同的干扰信道来识别，在该信道上，干扰对齐（IA）被用作小区间干扰管理技术，并与其他现有方法进行比较。获得的结果表明，灵活的双工明显优于传统的时分双工（TDD）接入方法，在该方法中，所有小区都以上行链路或下行链路模式同步运行。此外，与基于最小均方误差（MMSE）的方案相比，干扰对齐在大多数干扰方案中始终可以提供更好的结果。还研究了信道估计质量对不同通信策略的影响。值得强调的是，目前的空中（OTA）实验代表了具有实时预编码和解码的IA的第一个实现。与基于最小均方误差（MMSE）的方案相比，在大多数干扰方案中，干扰对准始终可以提供更好的结果。还研究了信道估计质量对不同通信策略的影响。值得强调的是，目前的空中（OTA）实验代表了具有实时预编码和解码的IA的第一个实现。与基于最小均方误差（MMSE）的方案相比，在大多数干扰方案中，干扰对准始终可以提供更好的结果。还研究了信道估计质量对不同通信策略的影响。值得强调的是，目前的空中（OTA）实验代表了具有实时预编码和解码的IA的第一个实现。