超高密度網路下干擾感知接收機之設計與實作

隨著行動通訊的快速發展，5G對於傳輸流量的要求提高，高密度網路(Ultra Dense Network)成為未來發展的重要技術之一。高密度網路即是新增小型基地台在大型基地台用戶負載較重或是覆蓋不及的地方，用以分擔大型基地台的負載，但是也造成基地台與基地台之間的訊號干擾。因此本論文針對超高密度網路的情境，設計並實做干擾感知接收機。在通道估測的部分，UDN干擾感知接收機與一般接收機有很大的不同，我們需要估計出干擾訊號以及目標訊號的通道。為了節省參考訊號擺放的位置以及有良好的通道估測結果，我們提出新式小型基地台參考訊號樣式(pattern)與序列，設計小型基地台參考訊號序列為大型基地台之角度旋轉，在接收端設計相對應的通道估測方式，最後我們可以同時估計多個傳送端到接收端的通道且通道估測結果如同干擾源不存在。超高密度網路實作展示中，我們實作LTE下行軟體定義無線電(SDR)實收實解系統。SDR平台結合了CPU、GPU與USRP，在傳送端以三台不同傳送功率的USRP模擬大型基地台造成的強干擾(interfering MBS)、服務小型基地台(serving PBS)的目標訊號以及鄰近小型基地台(interfering PBS)造成的弱干擾。接收端以GPU為主要運算裝置實作干擾感知接收機，利用GPU優越的平行處理能力壓縮執行時間，進而讓系統運作在更高的取樣率。這篇論文完成LTE 10 MHz頻寬的UDN即時解調系統，並測試傳送端同步不匹配以及不同能量組合下，接收端的通道估測結果與解碼情況。

關鍵字

高密度異質網路；參考訊號設計；通道估測；干擾感知接收機；軟體定義無線電

並列摘要

To meet the requirement of 5G to deliver 1000 times higher data throughput, ultra-dense network (UDN) has become one of the important technologies for the future. The UDN architecture employs a large number of small pico base stations (PBS) whose service regions are embedded within that of a larger macro base station (MBS). UDN has the advantages of good coverage, higher spectrum utilization and low cost. However, increasing BS density inevitably induces inter-cell interference (ICI). In this paper, we redesign interference-aware receiver and present a real-time software defined radio (SDR) demonstration for an LTE downlink transceiver in UDN. For interference-aware receiver, we need to estimate channel of the target signal and the interference signal. In order to avoid throughput degradation and have good channel estimation results, we redesign PBS reference signal. The new PBS reference signal sequence is the phase rotation of MBS reference signal sequence. At the receiver, the corresponding channel estimation method can estimate the channels from multiple transmitters to the receiver simultaneously and perform as well as single cell scenario. In the over-the-air UDN demonstration, we present a real-time software-defined radio (SDR) solution for an LTE downlink transceiver in UDN. This SDR platform integrated the processing power of CPU, GPU, and commercial RF transmitting and receiving front-end instruments. At the transmitting end, we emulated three 4G LTE base stations: one strong interference from MBS and another weaker interference from a neighboring PBS, plus the serving PBS. At the receiving end, we used the GPU as the main computing device to implement the interference-aware receiver. Powerful parallel processing on GPU can compress the execution time and thereby enable the system to operate at a higher sampling rate. Finally, the prototype successfully demonstrated real-time reception of 10-MHz two-stream LTE signal under two interference sources.

並列關鍵字

ultra-dense network ； reference signal design ； channel estimation ； interference aware receiver ； software-defined radio

參考文獻

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超高密度網路下干擾感知接收機之設計與實作

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