引領無線通訊進入第三代行動系統的無線電技術是“分碼多工存取”，所謂的分碼多工存取是指於相同的頻率上，透過分配不同的編碼給不同的使用者來與系統中的其他使用者做區別。由於編碼的種類眾多，而造就分碼多工存取系統的容量能優於其它多工技術。但也因為分碼多工存取系統是在相同頻率上同時提供服務給所有使用者，因而造成干擾量隨著系統負載的增加而升高，使得系統在容量上受限於干擾，也就是說干擾會造成系統容量的降低。所以對於干擾的產生，需要特別注意。干擾源主要來自於系統內其他使用者所造成的同頻干擾，但是透過良好的細胞規劃可以有效地消除此項干擾。而另一值得注意的干擾源為鄰頻干擾，它是因不同的業者於相同的地理區域使用相鄰的頻段所造成的干擾，而且這樣的干擾是無法事先被預知的。又由於無線電頻譜資源是很珍貴的，且可利用的土地資源是有限的，所以電信業者應該致力於規劃適宜的基地台位置來降低干擾以提供最佳的電信服務。

當分時雙工與分頻雙工技術同時被利用於多變的環境下來擴大覆蓋率及提昇系統容量之際，隨之衍生出一個有趣的議題。當兩個不同系統同時被利用於相同的地理區域，無論是單一或多個電信業者同時使用這兩個系統的情況下，此時的網路規劃議題都是需要費心思考的。因此，在相同的地理區域使用兩種不同的系統但相鄰頻率所造成的鄰頻干擾是值得探討的。

本文主要在探討鄰頻干擾對同時使用分時雙工與分頻雙工技術的寬頻分碼多工存取系統的上鏈容量之影響。文中提出一個簡易的模型來估算鄰頻干擾及系統容量的衰減，而此干擾分析方法是基於考量遮蔽效應所造成信號在路徑傳播時的能量損失以及使用者於系統覆蓋範圍是隨機分佈的。模擬結果指出鄰頻干擾可能造成系統容量高達30%的衰減。但是，透過適當的基地台位置架設，能夠有效降低鄰頻干擾對系統容量的影響。本文所提出的方法對於在相鄰頻率同時採用分時雙工與分頻雙工系統之電信業者的網路規劃是非常實用的。

It is well known that code division multiple access (CDMA) is an interference-limited system. The sources of the interference mainly came from the co-channel interference and noise. The co-channel interference is caused by the same operator using the same frequency in the nearby area and it could be avoided by cell planning. As for the adjacent channel interference (ACI), it is caused by different operators using adjacent frequencies in the vicinity, and this phenomenon can’t be identified in advance. ACI doesn’t severely damage the system capacity as co-channel interference do. Since the resources of radio spectrums and the lands are limited, telecomm operators should endeavor to suppress the undesired interference to provide the optimal telecomm services. For this reason, the impact of ACI on system performance still can’t be ignored.

An interesting issue emerges from the circumstances that both frequency division duplex (FDD) and time division duplex (TDD) are used as coverage and capacity increasing systems in various environments. When both system modes are deployed in the same geographical area or, for indoor systems, in the same building, care needs to be taken in network planning. This statement is valid regardless of whether one or several operators are running the two modes. Consequently, the interference caused by two different systems due to using the adjacent channel in the same geographical area is worthy to discuss.

This thesis studies the impacts of ACI on uplink capacity in a wide-band code division multiple access (W-CDMA) system using both FDD mode and TDD mode. A simple model is proposed to estimate ACI and capacity loss. This method is based on an interference analysis that considers propagation loss with shadow fading and random distribution of mobile users. Simulation results indicate that ACI may cause up to 30% capacity reduction. However, with suitable arrangement for the location of base stations, the impacts of ACI on capacity can be reduced. The proposed method is useful for mobile operators to plan their radio networks when both FDD mode and TDD mode need to be deployed at adjacent channel frequencies.

[1]Sergio Barberis1 and Ermanno Berruto1, “A CDMA based radio interface for third generation mobile systems”, Mobile Networks and Applications 2 p.p. 19–29, 1997
[2]H. Haas, S. McLaughlin and G.J.R. Povey, “Capacity-coverage analysis of TDD and FDD mode in UMTS at 1920MHz”, IEE Proc Communication., Vol. 149, No. 1 , February 2002
[3]Deepak Ayyagari and Anthony Ephremides, ‘‘Cellular multi-code CDMA capacity for integrated (voice and data) services”, IEEE J.Select. Areas. Communication ,Vol. 17,No.5, p.p. 928-938, May 1999
[4]Sumit Kundu and Saswat Chakrabarti,” Outage Analysis of Cellular CDMA for Integrated Voice and Data Services with Correlated Signal and Interference, ”Personal Wireless Communications, 2000 IEEE International Conference on 17-20 Page(s):249 – 253, Dec 2000
[5]Josefina Castañeda-Camacho, Carlos Eduardo Uc-Rios, Domingo Lara-Rodríguez, “Reverse Link Erlang Capacity of Multi-class CDMA Cellular System Considering Non-ideal Antenna Sectorization”, IEEE Transactions on Vehicular. Technology, Vol. 52, No. 6, Nov 2003
[6]Duk Kyung Kim, Dan Keun Sung,” Capacity Estimation for an SIR-Base Power-Controlled CDMA System Supporting ON–OFF Traffic”, IEEE Transactions on Vehicular. Technology. Vol. 49, No.4, July 2000
[7]Gilhousen, K.S., Jacobs, I.M., Padovani, R., Viterbi,A.J., Weaver, LA. JR, and Wheatly III, C.E.: ‘On the capacity of a cellular CDMA system’, IEEE Transactions. Vehicular. Technology ,40, pp.303-312, 1991
[8]Chae Y. Lee, Member, IEEE, and Hyon G. Kang, “Cell Planning with Capacity Expansion in Mobile Communications: A Tabu Search Approach”, IEEE Transactions on Vehicular. Technology, Vol. 49, No.5, September 2000
[9]Alexander M. Wyglinski, and Steven D. Blostein,” On Uplink CDMA Cell Capacity: Mutual Coupling and Scattering Effects on Beamforming, IEEE Transactions on Vehicular. Technology, Vol. 52, No. 2, MARCH 2003
[10]Hyoung-Goo Jeon; Sung-Moon Shin; Taewon Hwang; Chang Eon Kang “Reverse link capacity analysis of a CDMA cellular system with mixed cell sizes”, Vehicular Technology, IEEE Transactions on Volume 49, Issue 6 Page(s):2158 – 2163, Nov 2000
[11]Tao Shu; Zhisheng Niu;,” Uplink capacity optimization by power allocation for multimedia CDMA networks with imperfect power control”, Selected Areas in Communications, IEEE Journal on Volume 21, Issue 10 Page(s):1585 – 1594, Dec 2003
[12]Jaana Laiho ; Achim Wacker ; Tomas Novosad; “Radio Network Planning and Optimization for UMTS”, John Wiley & Sons, LTD, 2002
[13]Wyglinski, A.M.; Blostein, S.D.;” On uplink CDMA cell capacity: mutual coupling and scattering effects on beam-forming”, Vehicular Technology, IEEE Transactions on Volume 52, Issue 2 Page(s):289 – 304, March 2003
[14]S. M. Heikkinen, H. Haas and G. J. R. Povey; “Investigation of Adjacent Channel Interference in UTRA-TDD System ”, Page(s):13/1 - 13/6, 26 April 1999
[15]3rd Generation Partnership Project; Technical Specification Group Radio Access Networks; Radio Frequency (RF) system scenarios. TR 25.942 V.6.3.0
[16]Universal Mobile Telecommunications System (UMTS);Selection procedures for the choice of radio transmission technologies of the UMTS, UMTS 30.03 version 3.2.0
[17]Dieter J. Cichon, Thomas Kürner, Chapter 4 : Propagation Prediction Models, COST 231
[18]D E Thompson, “Modelling Adjacent Channel Interference in 3G Networks”, Multiple Access Communications Ltd, UK, The Institution of Electric Engineers. Printed and Published by the IEE, 2003