對一個無線通訊系統來說，設計一個適合的換手機制不但可以改善使用者的通道容量還可以改善提供給使用者的服務品質。在同通道蜂巢網路系統中，以接收到之訊號強度為指標的換手機制有時可能無法滿足預期的服務品質，其表現也會被干擾嚴重影響。以所得總資料傳輸速率的換手機制太過複雜以致很難實際應用在多天線輸出輸入系統上。在這篇論文中，我們評估一個以自由度為基準的換手機制在同通道多輸入多輸出上行傳輸兩細胞網路系統的表現。當應用干擾對齊的技術於提出的換手機制上時，能夠達到一個較好的個體及網路系統表現。此外，當結合交接收到之訊號強度指標至自由度換手機制的標準中時可以使提出的換手機制更加實際。我們也為自由度換手機制提出一個以換手矩陣組成的樹狀圖，此樹狀圖可以為整體系統的換手提供所需的資訊。在模擬結果中證明提出的換手機制和其他傳統的換手機制做比較後，提出的換手機制在高訊雜比的區域表現良好，而且對位於細胞邊緣的使用者有助益。

In a wireless communication system, designing a proper handover scheme can improve not only capacity but also quality of service (QoS) for users. In cellular co-channel networks, received signal strength indicator (RSSI) based handover scheme does not necessarily satisfy the promised QoS sometimes. Also, the performance is seriously affected by interference. Sum rate based handover scheme is too complicate to apply to a multiple-input multiple-output (MIMO) system. In this thesis, the performance of a proposed handover scheme based on the degrees of freedom (DoF) in a two-cell uplink co-channel MIMO network is evaluated. By adopting interference alignment technique in our proposed scheme, a better individual and network performance can be accomplished. Furthermore, combine received signal strength indicator with DoF handover criterion make proposed scheme more practical. We develope a handover-matrix tree structure for DoF-based handover scheme, which carries information for system-wide handover. The proposed scheme is compared with traditional handover schemes, the simulation results show that the proposed scheme performs well in high SNR regimes and is advantageous to cell-edge users.

hinese Abstract i
English Abstract ii
Contents iii
1 Introduction 1
2 Background 3
2.1 Handover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1.1 RSSI-based Handover [1] . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1.2 Sum-rate-based Handover . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 Degree of Freedom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2.1 Concept of Degree of Freedom . . . . . . . . . . . . . . . . . . . . . . 5
2.2.2 Degree of Freedom based Base Station Selection [2] . . . . . . . . . . 6
2.3 Interference Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.3.1 System Model of Two-Cell MIMO Interference Networks . . . . . . . 7
2.3.2 Design of Precoding Matrix for Aligning ICI . . . . . . . . . . . . . 9
iii
3 Proposed DoF-Based Handover Scheme 11
3.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.2 System Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.3 Handover Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.3.1 RSSI-based Handover Scheme . . . . . . . . . . . . . . . . . . . . . . 14
3.3.2 Sum rate-based Handover Scheme . . . . . . . . . . . . . . . . . . . . 16
3.3.3 DoF-based Handover Scheme . . . . . . . . . . . . . . . . . . . . . . 17
3.3.4 Joint DoF-RSSI-based Handover Scheme . . . . . . . . . . . . . . . . 21
3.4 Two Illustrative Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.4.1 Example with (M;N[1];N[2]) = (2; 3; 5) . . . . . . . . . . . . . . . . . 23
3.4.2 Example with (M;N[1];N[2]) = (4; 10; 10) . . . . . . . . . . . . . . . . 25
4 Simulations 28
4.1 The Comparison of Sum Rate vs. SNR Performance with Different Handover
Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4.2 The Comparison of Sum Rate vs. Channel Power Gain Ratio Performance
with Different Handover Scheme . . . . . . . . . . . . . . . . . . . . . . . . . 31
5 Conclusions 35
Bibliography 36

[1] K. I. Itoh, S. Watanabe, J. S. Shih, and T. Sato, “Performance of handoff algorithm
based on distance and rssi measurements,” IEEE Transactions on Vehicular Technology,
vol. 51, no. 6, pp. 1460–1468, Nov 2002.
[2] H. J. Chou, R. Y. Chang, and J. M. Wu, “Degrees-of-freedom-based sequential basestation
selection in cochannel mimo networks,” IEEE Transactions on Vehicular Technology,
vol. 65, no. 2, pp. 953–959, Feb 2016.
[3] H. J. Chou, C. C. Chou, J. M. Wu, and R. Y. Chang, “On the achievable degrees
of freedom of two-cell multiuser mimo interference networks,” IEEE Transactions on
Communications, vol. 62, no. 8, pp. 2880–2893, Aug 2014.
[4] N. D. Tripathi, J. H. Reed, and H. F. VanLandingham, Radio resource management in
cellular systems. Springer Science & Business Media, 2006, vol. 618.
[5] N. Zhang and J. M. Holtzman, “Analysis of handoff algorithms using both absolute and
relative measurements,” IEEE Transactions on Vehicular Technology, vol. 45, no. 1, pp.
174–179, Feb 1996.
[6] Q. Shi, M. Razaviyayn, Z. Q. Luo, and C. He, “An iteratively weighted mmse approach
to distributed sum-utility maximization for a mimo interfering broadcast channel,”
IEEE Transactions on Signal Processing, vol. 59, no. 9, pp. 4331–4340, Sept 2011.
36
[7] J. Kim, S. H. Park, H. Sung, and I. Lee, “Spatial multiplexing gain for two interfering
mimo broadcast channels based on linear transceiver,” IEEE Transactions on Wireless
Communications, vol. 9, no. 10, pp. 3012–3017, October 2010.
[8] C. M. Yetis, T. Gou, S. A. Jafar, and A. H. Kayran, “On feasibility of interference
alignment in mimo interference networks,” IEEE Transactions on Signal Processing,
vol. 58, no. 9, pp. 4771–4782, Sept 2010.
[9] T. Gou and S. A. Jafar, “Degrees of freedom of the k user m n mimo interference
channel,” IEEE Transactions on Information Theory, vol. 56, no. 12, pp. 6040–6057,
Dec 2010.
[10] S. A. Jafar and M. J. Fakhereddin, “Degrees of freedom for the mimo interference
channel,” IEEE Transactions on Information Theory, vol. 53, no. 7, pp. 2637–2642,
July 2007.
[11] C. Suh and D. Tse, “Interference alignment for cellular networks,” in Communication,
Control, and Computing, 2008 46th Annual Allerton Conference on, Sept 2008, pp.
1037–1044.
[12] V. R. Cadambe and S. A. Jafar, “Interference alignment and degrees of freedom of the
k -user interference channel,” IEEE Transactions on Information Theory, vol. 54, no. 8,
pp. 3425–3441, Aug 2008.
[13] M. Amir, A. El-Keyi, and M. Nafie, “Constrained interference alignment and the spatial
degrees of freedom of mimo cognitive networks,” IEEE Transactions on Information
Theory, vol. 57, no. 5, pp. 2994–3004, May 2011.
37
[14] Y. Chen and A. Terzis, “On the implications of the log-normal path loss model: an
efficient method to deploy and move sensor motes,” in Proceedings of the 9th ACM
Conference on Embedded Networked Sensor Systems. ACM, 2011, pp. 26–39.
[15] D. Tse and P. Viswanath, Fundamentals of wireless communication. Cambridge university
press, 2005.