隨著網路資訊的蓬勃發展與各種有線及無線通訊技術成熟的今日，人們對於網路的依賴與需求也日益劇增，網路通訊技術正在改變人們的溝通、生活及工作模式，WiMAX (IEEE 802.16e) 與LTE (Long Term Evolution)等規約的相繼定訂，都是為了能提供使用者更多且更快的網路服務的。
本論文針對次世代行動通訊系統中提供更好的效能來討論，並分為三部份，其中第一個部份與第二個部份針對骨幹網路 (Backbone) 作討論，第三個部份針對無線網路 (Wireless) 的部份作討論。
第一個部份，第三代和第四代移動通信中，分碼多工存取 (Code-Division Multiple Access , CDMA) 技術為其重要的技術基礎。CDMA技術具有許多優於其它技術的特點，如在提高系統的容量方面具有顯著的優勢，能夠有效解決移動通信系統之中的抗干擾和抗多徑衰落的問題， CDMA技術與光纖通信能充分發揮其技術本身的優點。
由於傳統發射同步型光分碼多工存取(Optical Code-Division Multiple Access, OCDMA) 同步訊框的設計中，在接收端所收到的功率均假設為同等的大小，也就是在彼此各使用者之間所產生的相互干擾量的能量為相同，但在實際的傳輸情況下，由於在距離的遠近影響了耦合器所接收信號的大小，因此在實際的系統中，必須加入接收端所收信號強弱的變異來考量設計出符合現況的架構。針對此一情形第一部份提出接收同步型訊框格式設計來提升OCDMA 系統的效能。
第二個部份，由於光纖具有頻寬大、損耗小等優點，所以為了在未來能提供更快的頻寬與更有彈性的服務，利用光纖作為傳輸介質網路將為必要的選擇，光纖網路技術的成熟促使其他光纖網路元件的推陳出新，光放大器和雷射等相關元件的降價，使得目前光纖網路的使用劇增，但是在光纖網路中要有快速及穩定的資料傳輸，雷射元件能提供更穩定及快速的波長是一個重要的課題，因為穩定的波長能夠提供更多波長給使用者與提升網路或系統的效率與穩定性，所以在第二個部份中我們針對雷射穩定性做研究，能更符合高速移動與高資料傳輸率之網路需求。
第三個部份，次世代行動通訊系統中，要讓使用者在戶外及移動下，能夠提供用戶與室內相同甚至更好的網路品質，但在移動及戶外的環境下，訊號經過通道時會受到衰減及雜訊等影響，包括障礙物阻擋所產生之遮蔽衰落(Shadow Fading)、高速移動所產生的都普勒位移和多重路徑所產生之快速衰落(Fast Fading)，以及基地台及移動台所產生之同頻道間干擾問題 (Co-channel Interference, CCI) 與（Other-cell Interference, OCI），這些都會影響到訊號的接收品質，為了能在上述的通道中能得到更好的效能我們在第三個部份提出幾種Pilot與干擾的解決方法。

With the emerging and prosperous development of network information and various communication technology developments in wire and wireless systems, people are increasingly demanding for more network application services and the network service becomes an indispensable service in human’s daily life. With the consecutive introduction of the standards of WiMAX (IEEE 802.16e) and Long Term Evolution (LTE) systems, they will provide the users with higher speed, better service quality.
In this dissertation it will study and discuss the next generation mobile communication systems and their capabilities of providing better system efficiency. It consists of three parts in this dissertation, in the first and second parts we will study the optical fiber networks in backbone and then in part 3 we will discuss pilot design in the mobile wireless communications.
In Part one, Code-division multiple access (CDMA) technology plays an important role in the development of backbone. It possess in CDMA the characteristic better than other techniques such as it has the advantages of providing wide transmission bandwidth, effectively solving the interference and multipath fading problems in mobile wireless communications. The combination of CDMA and the fiber optical communication can enhance the advantages of both techniques.
In the synchronous frame design of the conventional synchronous transmission system, it always assumes that at the receiver end it will receive the same amount of powers from all users, i.e. it assumes that the interference powers of mutual interferences among users are constant, however in actual communication environment, the distance between each user and the receiver is different and this distance difference affects the signal strength received at the optical coupler, it needs in the design of system structure to consider the actual variation in the receiving signal strength so as to have the system structure to meet the actual communication environment. We introduce in the first part the design of a system structure to generate synchronous frames at the receiving end so as to increase the system efficiency.
In Part two, due to it provides the advantages of wide bandwidth and low loss in the fiber optical, the utilization of optical fiber will be the choice for the future transmission medium to provide wide transmission bandwidth and various kinds of services. The maturity of the optical fiber network technology has increased the developments of various optical fiber devices, the prices reduction in the optical amplifiers and laser sources etc. have promoted the wide usage of optical fiber networks. In the laser devices development it is an important issue to have the laser device to provide a stable and wideband wavelength because a stable wavelength can provide more wavelengths to users and enables the increase in the network or system efficiency, stability so that it can meet the requirements of providing high mobility and high data transmission rate in the network. In the Part two of this dissertation we will study the stability of laser sources so as to meet the network requirements of high mobility and high data transmission rate in the network.
In Part three, in the Next Generation mobile communication system, it will provide the users in outdoor and moving environment with the same or better service qualities as the indoor users. When a user is in the moving and outdoor environment, his signal will suffer the fading and noise effects when it transmits through the channel, these effects including the Shadowing Fading as the signal encounters the blocking obstructions, the Doppler Effect due to fast moving and the Fast Fading due to the multipath effect, the Co-channel Interference (CCI) and the Other-cell Interference (OCI) generating from using the same channel frequency in the transmission between the base station and the mobile station, and consequently the receiving signal quality will be affected by these adverse effects. We will in Part three recommends the design of several pilot signals and measures to solve interference issue so as to provide better system performance when signal passes through the channel suffering the above-mentioned fading and noise effects.

TABLE OF CONTENTS
CHINESE ABSTRACT..........................................I
ENGLISH ABSTRACT........................................III
TABLE OF CONTENTS........................................VI
LIST OF FIGURES..........................................IX
LIST OF TABLES...........................................XI
CHAPTER 1	 INTRODUCTION....................................1
1.1 Study Motivation......................................1
1.1.1 Review of OCDMA Synchronous Technology for Global Switch....................................................4
1.1.2 Review of Laser Wavelength Stability Technology for Local Switch..............................................5
1.1.2.1 PID Controller for Stabilizing Laser Wavelength...6
1.1.2.2 Optimum Driving Current Combinations for Tunable Laser.....................................................6
1.1.3 Review of OFDM Techniques for Wireless Part.........7
1.1.3.1 Orthogonal Pilots for OFDM System.................8
1.1.3.2 Dynamic Pilots for OFDM System....................8
1.1.3.3 Pilot Design for Interference Mitigation..........9
1.2 Organization..........................................9
CHAPTER 2	 AN OPTICAL CDMA SYSTEM IMPLEMENTED WITH SYNCHRONOUS RECEIVER.....................................13
2.1 Introduction.........................................13
2.2 System Architecture of Balanced Coding...............14
2.2.1 Balanced Encoder...................................14
2.2.2 Decoder............................................16
2.3 Synchronous OCDMA Receiver...........................16
2.3.1 Synchronization Design for Synchronous Receiver....17
2.3.2 Frame Format.......................................19
2.4 Simulation Results and Discussions...................21
2.4.1 Simulation Architecture............................21
2.4.2 Threshold Current..................................23
2.4.3 BER vs. Power......................................23
2.5 Summary..............................................24
CHAPTER 3	 PID CONTROLLER FOR STABILIZING LASER WAVELENGTH...............................................26
3.1 Introduction.........................................26
3.2 System Description...................................27
3.3 System Steady State and Transient Analysis...........29
3.4 Algorithm for PID Controller.........................30
3.5 Performance Analysis.................................33
3.6 Summary..............................................34
CHAPTER 4	 ANALYSIS AND SELECTION OF OPTIMUM DRIVING CURRENT COMBINATIONS FOR TUNABLE WAVELENGTH LASER........36
4.1 Introduction.........................................36
4.2 Problems Identification for DBR Laser................37
4.3 Simulation Structure for DBR Laser System............40
4.4 Simulation Method....................................41
4.5 Simulation Result....................................47
4.6 The Optimization of Wavelength Switching.............49
4.7 The Optimal Control Method in the Wavelength Switching between Two Channels.....................................49
4.8 The Optimal Control Method in the Wavelength Switching in Four Channels.........................................52
CHAPTER 5	 PILOT DESIGN FOR 4G SYSTEM.....................56
5.1 The Design of Low Interference Orthogonal Pilots for OFDM System..............................................56
5.1.1 Introduction.......................................56
5.1.2 Orthogonal Pilots for OFDM System..................57
5.1.3 Simulation Result..................................61
5.1.4 Summary............................................61
5.2 The Design of Dynamic Pilots for OFDM System.........63
5.2.1 Introduction	.......................................63
5.2.2 Design Considerations of Pilot Structure...........65
5.2.3 Simulation Results.................................68
5.2.4 MB-Zone for DL/UL Pilot Design.....................71
5.2.5 Summary............................................76
CHAPTER 6 CONCLUSIONS AND FUTURE WORK....................77
Reference                                                 81

                   LIST OF FIGURES
Figure 1.1 A demonstration pilot to illustrate the system operations of the next generation network system that complies with the IMT-Advance specifications..............3
Figure 1.2 The organization of this dissertation.........12
Figure 2.1 Principle of balanced encoder.................14
Figure 2.2 Block diagram of spread spectrum balanced encoding system..........................................15
Figure 2.3 Block diagram of Balanced-encoded receiver....16
Figure 2.4 (a) Illustration of users connecting to a start coupler; (b) Illustration of various users arrival times....................................................17
Figure 2.5 (a) Frame format for synchronous transmitting scheme; (b) Frame format for synchronous receiving scheme...................................................20
Figure 2.6 (a) OCDMA transmitter architecture; (b) OCDMA receiver architecture....................................22
Figure 2.7 BER vs. receiver power........................24
Figure 3.1 The block diagram for laser model.............28
Figure 3.2 The block diagram for laser model using for PID controller analysis......................................29
Figure 4.1 Basic architecture in DBR laser. From right to left is the grating zone, the phase zone and the active zone.....................................................38
Figure 4.2 Ia is fixed at 40 mA, Ig varies from 2 mA to 15 mA with a step size of 0.2 mA. Ip varies from 0 mA to 15 mA with a step size of 0.2 mA...............................39
Figure 4.3 Simulation functional block diagram for sweeping channels.................................................41
Figure 4.4 Simulation functional block diagram for chirping and switching time	.......................................42
Figure 4.5 Input laser signals for measuring chirping and switching time...........................................45
Figure 4.6 Method for measuring chirping.................46
Figure 4.7 Method for measuring switching time...........46
Figure 4.8 Switching time due to different current combinations in Ch 1~ Ch 4...............................47
Figure 4.9 Chirping due to different current combinations between Ch 1and Ch 3.....................................48
Figure 4.10 The illustration of the selection of current combinations in wavelength switching in the conventional method...................................................50
Figure 4.11 (a) The control process in wavelength switching in conventional method ; (b)The optimal control method in the wavelength switching.................................51
Figure 4.12 The possible problem when it increase two channels to three channels...............................53
Figure 4.13 Current combinations for the shortest time switching................................................54
Figure 5.1 Different pilot types in a typical 18 x 6 resource block in the IEEE802.16m........................58
Figure 5.2 Simulated system performance when different pilot types are implemented in a typical 18 x 6 resource block when a mobile moves at 120 km/hr...................59
Figure 5.3 Interference weighting levels for various pilot types....................................................60
Figure 5.4 (a)An MS locates at the cell edge and it’s interfering sources.(b)Received Interference levels when orthogonal pilot types are implemented for base stations when an MS is located at the cell edge...................62
Figure 5.5 Allocation of Pilots..........................66
Figure 5.6 Slot for 2-antenna 3x3 tile for IEEE802.16m...67
Figure 5.7 Slot for 2-antenna 4x3 tile for 802.16m.......68
Figure 5.8 BER vs. SNR with various tile size when the MS is moving at velocity 3 km/hr............................68
Figure 5.9 BER vs. SNR with various tile size when the MS is moving at velocity 120 km/hr..........................69
Figure 5.10 BER vs. SNR with various tile size when the MS is moving at velocity 250 km/hr..........................69
Figure 5.11 BER vs. SNR with various tile size when the MS is moving at velocity 350 km/hr..........................70
Figure 5.12 BER vs. SNR with various slot size when the MS moves at velocity 3 km/hr, 120 km/hr, 250 km/hr and 350 km/hr....................................................72
Figure 5.13 Various radio environments in an exemplified base station.............................................73
Figure 5.14 Design example for the DL/UL pilot structure by using MB-Zone............................................74
Figure 5.15 Simulation result for proposed DL/UL pilot format...................................................75

                   LIST OF TABLES
Table 2.1  Code word combinations with p = 3.............15
Table 2.2  Link parameters...............................21
Table 3.1 With and without PID controller the variation of △λoffset when outside supply voltage varies 1% ~ 10% from its nominal value (V=-4.9359550 mV, λ0 =1548.4483 nm)...33
Table 3.2 With and without controller when the device aging included in the system the variation of △λoffset has 0.0005% ~ 0.0013 % variation (V=-4.9359550 mV,λ0 =1548.4483nm)............................................34
Table 4.1 Basic physical parameters of DBR laser.........40
Table 4.2 The set up of simulation parameters for generating DBR laser.....................................43
Table 4.3 Current combinations in DBR laser to generate lasers in ITU-Band.......................................43
Table 4.4 The current combinations generating ITU-Band channels.................................................50
Table 4.5 The round trip switching time between two channels.................................................53
Table 5.1 System parameters used in the simulation.......58
Table 5.2 Simulation parameters..........................65
Table 5.3 18x3 and 24x3 pattern..........................72
Table 5.4 Ranges of subcarriers and symbols between pilot spacing in MB-Zone.......................................74

REFERENCE
[1].M.-H. Chuang, H.-W. Tseng, L.-P. Chin, L.-L. Jau, Y.-H. Lee, Y.-G. Jan, “Analysis of System Performance for an Optical CDMA System Implemented with Synchronous Receiver,” J. of the Chinese Institute of Engineers, (Accepted on February 09, 2009)
[2].Y.-H. Lee, Y.-S. Chou, M.-H. Chuang, C.-L. Yang, and H.-W. Tseng “PID Controller for Stabilizing Laser Wavelength,” J. of Optical Communications, vol. 28, no. 3, Nov. 2007, pp. 168-171
[3].Y.-H. Lee, C.-L. Yang, M.-H. Chuang, H.-W. Tseng, Y.-S. Chou, H.-W. Tsao, and S.-L. Lee, “Analysis and Selection of Optimum Driving Current Combinations for Tunable Wavelength Laser,” Microwave and Optical Technology Letters. vol. 48, no. 7, July 2006, pp. 1417-1423.
[4].Y.-H. Lee, Y.-G. Jan, M.-H. Chuang, H.-W. Tseng, etc. “Proposed SDD text for Interference Mitigation,” IEEE C80216m-Link-08_053 #57, IEEE 802.16 Broadband Wireless Access Working Group
[5].Y.-G. Jan, Y.-H. Lee, M.-H. Chuang, H.-W. Tseng, etc.“ SDD Text Proposal for UL PHY Structure, “IEEE C80216m-UL_PHY-08_031 #56, IEEE 802.16 Broadband Wireless Access Working Group.
[6].P. R. Prucnal, M. A. Santoro, and T. R. Fan, “Spread spectrum fiber-optic local area network using optical processing,” J. Lightwave Technology, vol. LT-4, May 1986, pp. 547−554.
[7].J. A. Salehi, “Code division multiple-access techniques in optical fiber networks－Part I: Fundamental principles,” IEEE Trans. Communication, vol. 37, Aug. 1989, pp. 824−833.
[8].L.-L. Jau and Y.-H. Lee, “Optical code-division multiplexing systems using Manchester Coded Walsh Codes,” IEE Proc.-Optoelectron., vol. 151, Apr. 2004, pp. 81–86.
[9].P. R. Prucnal, M. A. Santoro, and S. K. Sehgal, “Ultrafast all-optical synchronous multiple access fiber networks,” IEEE J. Select. Areas Communication, vol. SAC-4, Dec. 1986, pp. 1484−1492. 
[10].C.-S. Weng and J. Wu, “Perfect difference codes for synchronous fiber-optic CDMA communication systems,” J. Lightwave Technology, vol.19, Feb. 2001, pp. 186−194.
[11].L.-L. Jau and Y.-H. Lee, “A synchronous optical CDMA system with constant multi-user interference,” Proceedings of the 2004 National Symposium on Telecommunications (NST 2004), Keelung, Taiwan, Dec. 3-4, 2004, pp. 120-125.
[12].L.-L. Jau and Y.-H. Lee, “Synchronous optical-CDMA systems using tunable hard limiters,” J. of Optical Communications. vol. 24, Dec. 2003, pp. 217–222.
[13].L.-L. Jau and Y.-H. Lee, “Optical code-division multiplexing systems using common zero codes,” Microwave and Optical Techn. Lett., vol. 39-2, Oct. 2003, pp. 165–167.
[14].Y. Sakai, S. Sudo and T. Ikegami, “Frequency stabilization of laser diodes using 1.51-1.55 μm absorption line of 12C2H2 and 13C2H2,” IEEE J. Quantum Electron., vol.28, 1992, pp.75-81.
[15].Y. C. Chung and L. W. Stulz, “Synchronized etalon filters for standardizing WDM transmitter laser wavelengths,” IEEE Photon Technology Letter, vol.5, 1993, pp.186-189.
[16].J. C. Braasch and W. Holzapfel, “Frequency stabilization of monomode semiconductor laser to birefringent resonators,” Electron. Letter, vol.28, 1992, pp.849-851.
[17].S. T. Winnall and A. C. Lindsay, “DFB semiconductor diode laser frequency stabilization employing electronic feedback and Bragg grating Fabry-Perot interferometer,” IEEE Photon Technology Letter, vol.11, 1999, pp.1357-1359.
[18].L. Colace, G. Masini, and G. Assanto, “Wavelength Stabilizer for Telecommunication Lasers: Design and Optimization,” IEEE J. of Lightwave Technol., vol.21, 2003, pp.1749-1757.
[19].S. V. Kartalopoulos, Introduction to DWDM technology, New Jersey: IEEE Press, 2000.
[20].K. Kudo, “Narrow-stripe selective MOVPE technique and its application to WDM devices,” Optical Fiber Communication Conf. and Exhibit (OFC 2002), Mar. 17-22, 2002, pp. 208-209.
[21].L. Coldren and S. Corzine, “Continuously-tunable single-frequency semiconductor lasers,” IEEE J. Quantum Electronics, vol. 23, Issue 6, June 1987, pp. 903-908 .
[22].P. Xing, H. Olesen and B. Tromborg, “A theoretical model of multielectrode DBR lasers,” IEEE J. Quantum Electronics, vol. 24, Issue 12, Dec. 1988, pp. 2423-2432. 
[23].Y. Kotaki, M. Matsuda, H. Ishikawa and H. Imai, “Tunable DBR laser with wide tuning range,” Electronics Letters, vol. 24, Issue 8, April 14, 1988, pp. 503-505. 
[24].S. Murata, I. Mito and Kobayashi, K., “Tuning ranges for 1.5 μm wavelength tunable DBR lasers,” Electronics Letters, vol. 24, Issue 10, May 12, 1988, pp.577-579
[25].N.P. Caponio, M. Goano, I. Maio, M. Meliga, G.P. Bava, G. Destefanis and I. Montrosset, “Analysis and design criteria of three-section DBR tunable lasers,” IEEE J. Selected Areas in Communications, vol. 8, Issue 6, Aug. 1990, pp. 1203-1213. 
[26].B. Stoltz, M. Dasler and O. Sahlen, “Low threshold-current, wide tuning-range, butt-joint DBR laser grown with four MOVPE steps,” Electronics Letters, vol. 29, Issue 8, April 15, 1993, pp. 700-702. 
[27].T. Sasaki, M. Yamaguchi and M. Kitamura, “10 wavelength MQW-DBR lasers fabricated by selective MOVPE growth,” Electronics Letters, vol. 30, Issue 10, May 12, 1994, pp. 785 – 786. 
[28].H. Debregeas-Sillard, A. Vuong, F. Delorme, J. David, V. Allard, A. Bodere, O. LeGouezigou, F. Gaborit, J. Rotte, M. Goix, V. Voiriot and J. Jacquet, “DBR module with 20-mW constant coupled output power, over 16 nm (40×50-GHz spaced channels),” IEEE Photonics Technology Letters, vol. 13, Issue 1, Jan. 2001, pp. 4 – 6.
[29].IEEE 802.16m-07/002r6, “IEEE 802.16m system requirements,”
[30].IEEE 802.16m-08/004r4, “Draft IEEE 802.16m evaluation methodology,”
[31].IEEE 802.16m-08/003r2, “Draft IEEE 802.16m System Description Document,”
[32].Y.-G. Jan, Y.-H. Lee, M.-H. Chuang, H.-W. Tseng, W.-C. Lee and W.-C. Tseng, “Inter-Cell Interference Management in DL/UL Control,” IEEE C802.16m-08/443r3.
[33].Y.-G. Jan, Y.-H. Lee, M.-H. Chuang, H.-W. Tseng, J.-Y. Lin, H.-C. Tseng, P.-J. Lin and T.-C. Wang, “Propose for Uplink Pilot Design in IEEE 802.16m,” IEEE C802.16m-08/444r2.
[34].Y.-G. Jan, Y.-H. Lee, M.-H. Chuang, H.-W. Tseng, J.-Y. Lin, H.-C. Tseng, P.-J. Lin, and T.-C. Wang, “Propose for Uplink Pilot Design in IEEE 802.16m,” IEEE C802.16m-08/444r2.
[35].Y. Lomnitz, H. Niu, J.-k. Fwu, S. Ahmadi and H. Yin “UL symbol structure design for 802.16m - symbol structure and pilot design,” IEEE C802.16m-08_266r1.
[36].C.-Y. Lin, P.-K. Liao, C.-P. Wu, and P. Cheng, “Design Considerations of Pilot Structures for Uplink MIMO Transmission,” IEEE C802.16m-08_325.
[37].J. Kang, C. Wei, X. Qi et. al., “NSN & Nokia, “Uplink Physical Resource Allocation Unit (Resource blocks and Symbol Structures),” IEEE C802.16m-08_396r1.
[38].H. Si, X. Chang, Q. Li and J. Lu, “Uplink Pilot Structures,”  IEEE C802.16m-08_472.
[39].D. Lee, Z. Li, J. Yun and J. Kim, “Pilot Structures as relevant to Uplink MIMO,” IEEE C802.16m-08_378r3.
[40].J. Kang, C. Wei, X. Qi et. al., “NSN & Nokia, “Uplink Physical Resource Allocation Unit (Resource blocks and Symbol Structures),” IEEE C802.16m-08_396r1.
[41].P. Komulainen, and M. Latva-aho, “Multiuser MIMO transceiver strategy for TDD Uplink and downlink in time-varying channel,” IEEE International Conf. on Acoustics, Speech and Signal Processing (ICASSP 2008), Las Vegas, Nevada, U.S.A , March 31 2008-April 4 2008, pp. 3141 – 3144.
[42].S. Zhihua, H. Sun, C. Zhao, and Z. Ding, “Linear precoder optimization for ARQ packet retransmissions in centralized multiuser MIMO uplinks,” IEEE Trans. on Wireless Communications, vol. 7, issue 2, 2008, pp. 736 – 745. 
[43].S.P. Alex, and L.M.A. Jalloul, “Performance Evaluation of MIMO in IEEE802.16e/WiMAX,” IEEE J. of Selected Topics in Signal Processing, vol. 2, no. 2, 2008, pp. 181-190.
[44].D.-S. Han, J.-H. Lee, Y.-M. Seung, and S.-J. Cho, “Performance Analysis of System Architecture using Wireless Relay Station and Virtual MIMO in WiBro Uplink,” International Conf. on Advanced Communication Technology (ICACT 2008.), Hyderabad, India, Feb. 2008, pp. 1935-1939. 
[45].P. Komulainen, M. Latva-aho and M. Juntti, “Block diagonalization for multiuser MIMO TDD downlink and uplink in time-varying channel,” International ITG Workshop on Smart Antennas (WSA 2008), Darmstadt, Germany, Feb. 2008, pp. 74-81.