多輸入多輸出天線廣播通道中降低迴授量

在多使用者多傳輸天線傳輸多輸入天線下行廣播通道中，資料的傳輸速率可以透過基地台的增加天線數量與排程機制來大量的增加。當使用者落在基地台的廣播範圍，所有的使用者都收到來自於基地台的相同的資料。針對於多使用者多傳輸天線與多接收天線系統，基地台具有Mt 根傳輸天線，K 總共有K 個使用者在此基地台涵蓋範圍內且每個使用者具有Mr 根接收天線，所有的多工增益Mt 可以透過空間多重存取技術或是迫零束波成形技術來達到。此外，當使用者數目遠超過傳送天線數目 K>>Mt，由於多使用者分散增益，速率總和會呈現MtloglogK 的成長趨勢。然而，上述的結果都來自於傳輸端具有所有的通道消息，因此，通道迴授量會隨著使用者與天線數量線性的增加。另一方面，透過選擇適當的調變與編碼來達到可靠的傳輸，通道消息是非常重要的，因此，對網路系統而言，迴授量是非常大的。此論文主要的貢獻在於考慮不同的系統應用，例如，多使用者多傳輸天線多接收天線廣播通道，與多點廣播通道，與不同系統的排程演算法，提出降低迴授量的策略來降低無線資源的浪費。透過分析，降低迴授量的方法，透過推導的多個閥值來執行，數個閥值是藉由序量統計的觀念配合排成演算法來得到。模擬結果可知，在廣播通道中，迴授量可以大量的被降低並且幾乎完美的速率總和都可以被達到。對於多點廣播通道，迴授量也可以大量的被降低並且解碼成功的使用者的數量幾乎與傳輸端具有完美的通道消息的情況是一樣的。此外，新的排程方法配合多閥值技術也被提出，在異直性質瑞雷衰減通道中，不同使用者被基地台挑選到的的公平性，迴授的量，與系統的速率和的關係也被討論。

關鍵字

降低迴授；多用戶分散增益；束波形成技術

並列摘要

In multiuser multiple-input multiple-output (MIMO) downlink broadcast channel, data rate can be tremendously increased by adding antennas and by scheduling algorithm at the base station (BS). When users are located in the broadcast area, the users receive the same data which is broadcasted from the BS. For the multiuser MIMO system with Mt transmit antennas and K users equipped with Mr antennas, the full multiplexing gain Mt can be achieved by using space-division multiple access schemes or zero-forcing beamforming. Moreover, in a large user regime K >> Mt, the sum rate grows like Mt log logK due to multiuser diversity. However, all these results are based on the assumptions of full channel state information (CSI) at the transmitter, thus, the feedback load linearly increases with number of users and number of antennas. On the other hand, CSI feedback is also very important in terms of proper selection of modulation and coding for achieving reliable transmission. Thus the aggregate feedback load in a network is large. The main contributions of thesis are proposing feedback reduction strategies considering different applications, such as multiuser MIMO broadcast channel and multicast channel, and scheduling algorithms to avoid waste of radio resource used for CSI feedback. Through analysis, we derive the feedback reduction methods which use multiple thresholds which are obtained through the concept of order statistics to exploit the scheduling mechanism. Simulations show that the feedback load can be reduced dramatically and almost full sum rate performance can be achieved in broadcast channel. For multicast scenario, the feedback load can be reduced dramatically and number of decoded user is almost the same as the full CSI case. Moreover, a new scheduling method with multi-threshold model is proposed and the relations among the fairness across users, the feedback load and the sum rate in heterogeneous Rayleigh fading channel are also investigated.

並列關鍵字

Feedback reduction ； Multi-user diversity ； Beamforming.

參考文獻

[1] R. Knopp and P. Humblet, “Information capacity and power control in single cell multiuser communications,” IEEE Int. Conf. on Commun., June 1995.

[3] Air Interface for Fixed Broadband Wireless Access Systems. IEEE Std. 802.16-2004, 2004.

[4] M. Costa, “Writing on dirty paper,” IEEE Trans. on Inf. Theory, vol. 29, no. 3, pp. 439–441, May 1983.

[5] H. Weingarten, Y. Steinberg, and S. Shamai, “The capacity region of the Gaussian multiple-input multiple-output broadcast channel,” IEEE Trans. on Inf. Theory, vol. 52, no. 9, pp. 3936–3964, Sept. 2006.

[6] T. Yoo and A. Goldsmith, “On the optimality of multiantenna broadcast scheduling using zero-forcing beamforming,” IEEE J. Select. Areas Commun., vol. 24, no. 3, pp. 528–541, Mar. 2006.

國際替代計量

多輸入多輸出天線廣播通道中降低迴授量

全文下載

主題瀏覽