MIMO-OFDM系統下使用ML接收機之鏈路淬取演算法

Link Level Abstraction for MIMO-OFDM Systems with Maximum Likelihood Receiver

張景涵(Ching-Han Chang)

指導教授 ： 邱茂清

國立中正大學/工學院/通訊工程學系/碩士(2015年)

摘要

為了降低系統模擬的複雜度，鏈路至系統的映射(limk-to-system mapping)被廣泛的運用以便估計系統的效能，同此模型更可進一步應用在實際的系統上，例如：用以改善適應性鏈路(link adaptation)的正確性以及更有效地做無線資源管理(radio-resource-management)。傳統上所使用的訊雜比(Signal to Noise Ratio, SNR)平均已不足以用來描述衰退通道(fading channel)的特性。因為在變動衰退通到下，一樣的訊雜比平均值可能會導致錯誤率的表現有很大的差異。
本文主要探討一個以互消息量為基準的映射模型，其中包含了可以被分離的兩個模型，調變模型及編碼模型。調變模型針對每個接收到的符號將訊雜比轉換為互消息；而編碼模型則將每個編碼方塊的平均互消息量轉換為錯誤率。與現行的模型相比，以互消息量為基準的模型在計算上較為簡單且在預估系統效能方便更為準確，並且更容易應用在混合式的調變系統下。最後透過驗證比較實際模擬的區塊錯誤率以及利用鏈路淬取所預測的區塊錯誤率。結果顯示兩者SNR的差距能夠被壓抑在0.4dB之內。

關鍵字

多輸入多輸出 ； 鏈路淬取 ； 最大相似接收機 ； 正交分頻多工

並列摘要

Link-to-system mapping is widely used in system evaluations to reduce the simulation complexity. It is also important in practical systems for improving the accuracy of the link adaptation and the efficiency of radio-resource-management. Conventional methods using linear average of signal-to-noise-ratios (SNR) may not work well over fading channels, since the same SNR may lead to drastic error rate due to different fading characteristics.
This paper studies a mutual-information-based (MI-based) link-to-system mapping method, which contains separate modulation and coding models. The modulation model maps the symbol-by-symbol received SNR to the mutual information and take the arithmetic average of mutual information. The coding model maps the averaged mutual information to decoding performance for each coding block. Compared with the existing methods, the MI-model is more accurate and easier to apply to mixed-modulation cases. Finally, we use simulation and to verify the accuracy of the low-complexity link abstraction algorithm by comparing BLERs from simulation and those predicted by the link abstraction. The results show that the SNR gaps between the predicted BLERs and simulated BLERs are within 0.4dB.

並列關鍵字

Link level abstraction ； Maximum Likelihood receiver ； MIMO ； OFDM

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