本論文旨在提出一個循序最小均方誤差群組解碼機制與合作式功率控制演算法來減少在上行非正交多重接取系統之多細胞干擾與領航訊號干擾。循序解碼是一個關鍵科技用於非正交多重接取系統並可以用來達到容量區域的某個邊界點在沒有多細胞干擾與通道估測錯誤。然而在現實情況中,多細胞干擾可能發生不只於資料傳輸階段,也會以因為在通道估計階段時領航訊號被其他細胞使用者使用而造成的領航訊號干擾形式出現。此論文中,循序最小均方誤差群組解碼機制先被提出來限制這些影響並且利用線性最小均方誤差濾波器繼並行單使用者解碼器之後在每個循序群組解碼的階段來避免最大概似解碼的複雜度。一個可達到的閉合遍歷容量近似式被導出並且被用來決定所有使用者中領航訊號與數據訊號的最佳功率分配。合作式功率控制問題被包裝成所有功率最小化並受限於每個使用者的容量限制,它被外圈的領航訊號與數據訊號功率的最佳化疊代搭配內圈使用 Yates' 的演算法來解標準函數形式的子問題,並藉由模擬結果來展現我們提出方法的效果。

This work proposes a successive minimum mean square error (MMSE) group decoding scheme and a coordinated power control algorithm to reduce the impact of multicell interference and pilot contamination in an uplink non-orthogonal multiple access (NOMA) system. Succes- sive decoding is a key enabling technology in NOMA systems and can be used to achieve certain boundary points of the multiple access capacity region in the absence of multicell interference and channel estimation errors. However, in practice, multicell interference may occur not only in the data transmission phase, but also in the form of pilot contamination in the training phase due to redundant pilot assignment among users in different cells. In this work, a successive MMSE group decoding scheme is first proposed to limit these effects and also to avoid the complexity of maximum likehood decoding by utilizing a linear MMSE fil- tering followed by parallel single-user decoders in each stage of the successive group decoding process. A closed-form approximation of the achievable ergodic rate is derived and utilized to determine the optimal power allocation among the pilot and data symbols of all users. The coordinated power control problem is formulated as a total power minimization problem subject to individual rate constraints for all users’, and is solved using an outer iteration that alternates between the optimization of pilot and data powers, and an inner iteration that utilizes Yate’s algorithm to compute the solutions of the subproblems, which are in the form of standard functions. The effectiveness of the proposed schemes are demonstrated through computer simulations.

Chapter 1: Introduction 1
Chapter 2: System Model 6
Chapter 3: Successive MMSE Group Decoding and its Approximate Achievable Ergodic Rate 10
3. 1: SuccessiveMMSEGroupDecoding(SMGD) 10
3. 2: Approximate Achievable Ergodic Rate under Channel Estimation Errors 12
Chapter 4: Power Control for Uplink NOMA Systems under Pilot Contamination 15
4.1: Subproblem I: Data Transmit Power Control with Fixed Pilot Power 16
4.2: Subproblem II (for Group Gb,l): Pilot Power Control with Fixed Data Transmit Power 18
4.3: Joint Pilot and Data Transmit Power Control 22
4.4: Feasibility 22
4.5: UserGrouping 23
Chapter 5: Simulations and Performance Comparisons 25
Chapter 6: Conclusion 32
Chapter 7: Appendix 33
7.1: ProofofMMSEEstimatehˆb,b′,k 33

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