干擾消除與通道估測錯誤對於結合塊狀時空碼與VBLAST系統之影響

Vertical Bell Labs Layered Space-Time (VBLAST) 是一種藉由使用多根天線傳送來得到高速傳輸速率的空間多工架構。在其接收端，信號的偵測需要一連串的處理程序，包括nulling和干擾消除，這會花費很大的運算量。所以在本論文中，我們提出一個降低複雜度的方法叫做部分干擾消除。首先一個系統中需要做幾次干擾消除將先被分析，接著針對分析結果做部份干擾消除。經過此方法後，系統效能仍然接近使用完全消除之VBLAST的效能；也因為少做了幾次信號消除，系統複雜度降低了。另一方面，VBLAST之錯誤率還不夠好。雖然可以利用增加接收端天線個數使其接收分集增加，進而使錯誤率降低，但是接收端往往會因為資源有限而無法增加天線個數(例如裝置大小及功率因素)，所以在傳送端增加分集是最好的選擇。因此我們在傳送端加入塊狀時空碼以增加傳送端之分集來達到降低錯誤率的目的，此新的系統稱作STBC-VBLAST。 STBC-VBLAST跟傳統的並聯型塊狀時空碼並不ㄧ樣。傳統的並聯型塊狀時空碼是由多個塊狀時空碼所組成的系統。而STBC-VBLAST則是只在較容易影響系統效能的層(layer)上加入塊狀時空碼(即加入STBC於較先偵測的層)，也由於這些層會主導整個系統的錯誤率，所以在這些層上加入塊狀時空碼將會有效率的改善系統的效能。另外，由於此系統在接收端需要有通道的資訊，所以在本論文中，我們也加入通道估測技術來討論通道估測錯誤對系統的影響。最後，我們提出一個估算STBC-VBLAST錯誤率的方法，藉由這個方法得到了STBC-VBLAST在有干擾消除錯誤和通道估測錯誤之情況下的錯誤率計算公式，這對於系統的設計將是非常有幫助的。

關鍵字

多輸入多輸出； VBLAST ；塊狀時空碼；通道估測；瞬間訊雜比

並列摘要

Vertical Bell Labs Layered Space-Time (VBLAST) is a spatial multiplexing scheme and can provide huge data rate by using multiple antennas. At the receiver of VBLAST, a successive processing, nulling and interference cancellation, which consumes high computation to reconstruct the information, is required. Therefore, we propose a method, partial interference cancellation (PIC), to reduce the complexity. By this way, the number of the layers required to be cancelled are evaluated first. After canceling only these layers, the performance will still be close to that of the original VBLAST, and the computation can be reduced. On the other hand, the BER of VBLAST is not good enough. Although increasing the number of receive antenna N can enlarges the diversity order and improves the performance, it is not suitable for downlink transmission where the receiver has limited resource (e.g. power and size). As a result, the space-time block coding (STBC), an effective transmit diversity scheme, can be utilized on the first detected layers to provide the diversity gain. This system incorporating the STBC and VBLAST schemes is called STBC-VBLAST. Different form the traditional combination of STBC and VBLAST (parallel STBC), the STBC encoders are applied into only a few layers of VBLAST in STBC-VBLAST, which are detected first, and dominates the system performance. Thus, the system performance can be improved by the increased diversity. Additionally, in order to make our analysis be close to the real environment, the channel state information (CSI) is assumed non-perfect in STBC-VBLAST scheme. We apply training sequence to estimated CSI. Finally, the derivation of BER for STBC-VBLAST with interference cancellation and channel estimation errors is proposed. It is helpful for the system design.

並列關鍵字

MIMO ； VBLAST ； STBC ； Channel Estimation ； Effective SINR

參考文獻

[12] P. H. Chuang, Transmit Diversity Block Coding for OFDM System, Master Thesis, National Taipei University of Technology, Taipei, Taiwan, 2002.

[3] G. J. Foschini, “Layered space-time architecture for wireless communication in a fading environment using multi-element antennas,” Bell Labs Tech. J., vol. 1, no. 2, pp. 41-59, 1996.

[4] P. W. Wolniansky, G. J. Foschini, G. D. Golden, and R. A. Valenzuela, “V-BLAST: An Architecture for Realizing Very High Data Rates Over the Rich-Scattering Wireless Channel,” in Proc. International Symposium on Signals, Systems, and Electronics, pp.295-300, Sept. 29-Oct. 2, 1998.

[6] T. Mao, and M. Motani, “STBC-VBLAST for MIMO Wireless Communication Systems,” in Proc. IEEE International Conference on Communications, vol. 4, pp.2266-2270, May 16-20, 2005.

[10] S. Al-Ghandhban, R.M. Buehrer, and B.D. Woerner, “ Outage Capacity Comparison of Multi-Layered STBC and V-BLAST Systems,” in Proc. IEEE Vehicular Technology Conference, vol. 1, pp.24-27, Sept. 25-28, 2005.

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干擾消除與通道估測錯誤對於結合塊狀時空碼與VBLAST系統之影響

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