毕业论文外文翻译---第三代CDMA系统的仿真

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1、Simulation of Third Generation CDMA Systems By Fakhrul Alam ABSTRACT The goal for the next generation of mobile communications system is to seamlessly integrate a wide variety of communication services such as high speed data, video and multimedia traffic as well as voice signals. The technology nee

2、ded to tackle the challenges to make these services available is popularly known as the Third Generation (3G) Cellular Systems. One of the most promising approaches to 3G is to combine a Wideband Code Division Multiple Access (WCDMA) air interface with the fixed network of Global System for Mobile c

3、ommunications (GSM). In this thesis a signal simulator was implemented according to the physical layer specification of the IMT-2000 WCDMA system. The data is transmitted in a frame by frame basis through a time varying channel. The transmitted signal is corrupted by multiple access interference whi

4、ch is generated in a structured way rather than treating it as Additive White Gaussian Noise (AWGN). The signal is further corrupted by AWGN at the front end of the receiver. Simple rake diversity combining is employed at the receiver. We investigate the bit error rate at both uplink and downlink fo

5、r different channel conditions. Performance improvement due to error correction coding scheme is shown. The simulator developed can be an invaluable tool for investigating the design and implementation of WCDMA systems. Chapter 1 Introduction The goal for the next generation of mobile communications

6、 system is to seamlessly provide a wide variety of communication services to anybody, anywhere, anytime. The intended service for next generation mobile phone users include services like transmitting high speed data, video and multimedia traffic as well as voice signals. The technology needed to tac

7、kle the challenges to make these services available is popularly known as the Third Generation (3G) Cellular Systems. The first generation systems are represented by the analog mobile systems designed to carry the voice application traffic. Their subsequent digital counterparts are known as second g

8、eneration cellular systems. Third generation systems mark a significant leap, both in applications and capacity, from the current second generation standards. Whereas the current digital mobile phone systems are optimized for voice communications, 3G communicators are oriented towards multimedia mes

9、sage capability. 1.1 First Generation Cellular Systems The first generation cellular systems generally employ analog Frequency Modulation (FM) techniques. The Advanced Mobile Phone System (AMPS) is the most notable of the first generation systems. AMPS was developed by the Bell Telephone System. It

10、uses FM technology for voice transmission and digital signaling for control information. Other first generation systems include: Narrowband AMPS (NAMPS) Total Access Cellular System (TACS) Nordic Mobile Telephone System (NMT-900) All the first generation cellular systems employ Frequency Division Mu

11、ltiple Access (FDMA) with each channel assigned to a unique frequency band within a cluster of cells. 1.2 Second Generation Cellular Systems The rapid growth in the number of subscribers and the proliferation of many incompatible first generation systems were the main reason behind the evolution tow

12、ards second generation cellular systems. Second generation systems take the advantage of compression and coding techniques associated with digital technology. All the second generation systems employ digital modulation schemes. Multiple access techniques like Time Division Multiple Access (TDMA) and

13、 Code Division Multiple Access (CDMA) are used along with FDMA in the second generation systems. Second generation cellular systems include: United States Digital Cellular (USDC) standards IS-54 and IS-136 Global System for Mobile communications (GSM) Pacific Digital Cellular (PDC) cdmaOne 1.3 Third

14、 Generation Cellular Systems Third generation cellular systems are being designed to support wideband services like high speed Internet access, video and high quality image transmission with the same quality as the fixed networks. The primary requirements of the next generation cellular systems are:

15、 Voice quality comparable to Public Switched Telephone Network (PSTN). Support of high data rate. The following table shows the data rate requirement of the 3G systems Table 1.1: 3G Data Rate Requirements Mobility Needs Minimum Data Rate Vehicular 144 kbps Outdoor to indoor and pedestrian 384 kbps I

16、ndoor Office 2 Mbps Support of both packet-switched and circuit-switched data services. More efficient usage of the available radio spectrum Support of a wide variety of mobile equipment Backward Compatibility with pre-existing networks and flexible introduction of new services and technology An ada

17、ptive radio interface suited to the highly asymmetric nature of most Internet communications: a much greater bandwidth for the downlink than the uplink. Research efforts have been underway for more than a decade to introduce multimedia capabilities into mobile communications. Different standard agen

18、cies and governing bodies are trying to integrate a wide variety of proposals for third generation cellular systems. The following figure, adopted from 1, shows the evolution of third generation cellular systems: Figure 1.1: Evolution of 3G References 2 and 3 provide further discussion on the evolut

19、ion of third generation cellular Systems. 1.4. WCDMA: Air Interface for 3G One of the most promising approaches to 3G is to combine a Wideband CDMA (WCDMA) air interface with the fixed network of GSM. Several proposal supporting WCDMA were submitted to the International Telecommunication Union (ITU)

20、 and its International Mobile Telecommunications for the year 2000 (IMT2000) initiative for 3G. Among several organizations trying to merge their various WCDMA proposals are Japans Association of Radio Industry and Business (ARIB) Alliance for Telecommunications Industry Solutions (ATIS) T1P1 European Telecommunications Standards Institute (ETSI) through its Special Mobile Group (SMG)