為滿足用戶對資訊傳輸量的大量要求，預期後4代或第5代行動通訊系統將佈建密集的小細胞，與原有之大細胞形成所謂的異質網路。然而，伴隨小細胞密度的提升，用戶將頻繁地執行細胞間交接(handover)程序，而嚴重增加的互干擾也將導致服務中斷的機率提升。因此，本論文延續[10]成果(利用模糊Q學習(fuzzy Q-learning)架構以達到細胞間的負載平衡)外，提出一套應用於LTE系統下，採用多點協調技術(Coordinated Multi-Point, CoMP)之交接程序，包括透過細胞間的合作，執行多點協調之動態資源調整(CoMP-Dynamic Resource Scheduling, CoMP-DRS)及多點協調之聯合傳輸(CoMP-Joint Transmission, CoMP-JT)兩種功能，以降低用戶受到的干擾，並避免用戶服務被中斷。從系統模擬結果顯示，本論文提出之交接程序能有效降低通話中斷率(call drop rate, CDR)，並且提高系統可以服務的用戶人數。

To address the explosive growth of data-communication demands, the ultra-dense small cell deployment is a key technique in Beyond 4G or 5G mobile networks. The co-existence of small cells and macro cells forms a so-called heterogeneous network. However, due to the increase of small-cell density, users will experience much handover process and the probability of service interruption will increase with the dramatic rise of inter-cell interference. This thesis extends the proposed algorithm of [10] which adopts the fuzzy Q-learning to achieve loading balancing among cells, and proposes a handover process with the Coordinated Multi-Point (CoMP) technique in the LTE heterogeneous networks. To mitigate the inter-cell interference and reduce user’s drop rate, the CoMP technique adopted in the proposed handover process includes the functions of dynamic resource scheduling (DRS) and joint transmission (JT). Simulation results show that the proposed handover process with CoMP can effectively reduce the call drop rate (CDR) and serve more number of users.

[1] 3GPP TR 36.839, “Mobility enhancements in heterogeneous networks” V11.1.0
[2] 3GPP TS 36.331, “Radio Resource Control (RRC); Protocol specification” V14.3.0
[3] 3GPP TS 36.133, “Requirements for support of radio resource management” V14.4.0
[4] 3GPP TR36.819, “Coordinated multi-point operation for LTE physical layer aspects” V11.2.0
[5] 3GPP TR 36.814 V9.2.0, “Further advancements for E-UTRA physical layer aspects”
[6] A. Nakano, T. Saba, "A handover scheme based on signal power of coordinated base stations for comp joint processing systems", Proc. 8th International Conference on Signal Processing and Communication Systems (ICSPCS), 2014.
[7] L. Zhang, Y. Nagai, T. Okamawari, T. Fujii, "Field experiment of network control architecture for CoMP JT in LTE-advanced over asynchronous X2 interface", Proc. IEEE 77th VTC—Spring, pp. 1-5, Jun. 2013.
[8] T. Okamawari, H. Hayashi, T. Fujii, "A Proposal on Network Control Architecture for CoMP JT with IP Network between eNBs", IEE Vehicaular Technology Conference, 2012.
[9] A. Nagate, S. Nabatame, D. Ogata, K. Hoshino, T. Fujii, "Field experiment of CoMP joint transmission over X2 interface for LTE-Advanced", Proc. IEEE VTC, pp. 1-5, 2013.
[10] Yang-Bang Li, “A Fuzzy Q-learning Approach for Load Balancing in LTE Systems,” National Cheng Kung University Thesis for Master of Science, July, 2015
[11] 3GPP TS 36.214, “E-UTRA Physical layer Measurements ” V14.2.0
[12] 3GPP TR 36.942, “E-UTRA Radio Frequency (RF) system scenarios” V14.0.0