毕业论文外文翻译---第三代cdma系统的仿真(编辑修改稿)

毕业论文外文翻译---第三代cdma系统的仿真(编辑修改稿)内容摘要：

Terrestrial Radio Access (UTRA) [1]. The access scheme for UTRA is Direct Sequence Code Division Multiple Access (DSCDMA). The information is spread over a band of approximately 5 MHz. This wide bandwidth has given rise to the name Wideband CDMA or WCDMA. There are two different modes namely Frequency Division Duplex (FDD) Time Division Duplex (TDD) Since different regions have different frequency allocation schemes, the capability to operate in either FDD or TDD mode allows for efficient utilization of the available spectrum. A brief definition of FDD and TDD modes is given next. FDD: The uplink and downlink transmissions employ two separated frequency bands for this duplex method. A pair of frequency bands with specified separation is assigned for a connection. TDD: In this duplex method, uplink and downlink transmissions are carried over the same frequency band by using synchronized time intervals Thus time slots in a physical channel are divided into transmission and reception part. We developed the simulator for a WCDMA system operating in the FDD mode. So all the system description provided in chapter 2 holds for the FDD mode only. WCDMA Key Features The key operational features of the WCDMA radio interface are listed below [3], [4]: Support of high data rate transmission: 384 kbps with wide area coverage, 2 Mbps with local coverage. High service flexibility: support of multiple parallel variable rate services on each connection. Both Frequency Division Duplex (FDD) and Time Division Duplex (TDD). Built in support for future capacity and coverage enhancing technologies like adaptive antennas, advanced receiver structures and transmitter diversity. Support of inter frequency hand over and hand over to other systems, including hand over to GSM. Efficient packet access. WCDMA Key Technical Characteristics The following table shows the key technical features of the WCDMA radio interface: Table : WCDMA Key Technical Characteristics Multiple Access Scheme DSCDMA Duplex Scheme FDD/TDD Packet Access Dual mode (Combined and dedicated channel) Multirate/Variable rate scheme Variable spreading factor and multicode Chip Rate Mcps Carrier Spacing MHz (200 kHz carrier raster) Frame Length 10 ms Inter Base Station synchronization FDD: No accurate synchronization needed TDD: Synchronization required Channel Coding Scheme Convolutional Code (rate 1/2 and 1/3) Turbo code The chip rate may be extended to two or three times the standard Mcps to acmodate for data rates higher than 2 Mbps. The 200 kHz carrier raster has been chosen to facilitate coexistence and interoperability with GSM. Chapter 5 Conclusion and Future Work We implemented a signal simulator according to the physical layer specification of the IMT2020 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. The signal is further corrupted by AWGN at the front end of the receiver. Simple rake diversity bining is employed at the receiver. We investigated the bit error rate at both uplink and downlink for two differ。