室內(nèi)無線局域網(wǎng)定位研究多普勒頻移對OFDMA性能的影響.pdf

1、Wireless communication fast development and accessibility to an increasing number of users in the recent years have placed much demand on broadband wireless access(BWA) technology that has attracted much attention. As a

2、BWA solution，Worldwide Interoperability for Microwave Access(WIMAX) is accepted by carriers of worldwide for broadband wireless service. It can be classified as fixed WIMAX(IEEE 802.16d version) using OFDM transmitting t

3、echnique and mobile WIMAX(IEEE 802.16e version) using OFDMA transmitting technique. One of the main benefits of those transmitting techniques in wireless communication is that the receiver does not need to constantly ada

4、pt an equalizer as a single carrier system would. They also show much favorable properties such as high spectral efficiency，robustness to channel fading，immunity to impulse interference，capability of handling very strong

5、 echoes(multipath fading). But one of their main drawbacks is the sensitivity to frequency errors caused by the frequency differences between the local oscillators in the transmitter and the receiver.
　　 In mobile ra

6、dio environment these frequency errors are due to the relative movement between transmitter and receiver. It is known as the Doppler frequency shifts phenomenon which causes a broadening of the signal spectrum.
　　 Th

7、e main purpose of this thesis is to study the effect of Doppler Shift on OFDMA modulation technique conducting to orthogonality destruction which in its turn leads to ICI. The method of Frequency Bank Signal(FBS) based o

8、n Walsh functions is described in order to combat high Doppler Shift impairment suffered by mobile wireless communication system like Mobile WiMax. FBS is a hybrid of CDMA and OFDMA but without pilots signals(used for es

9、timation) whose effect becomes negative in signal reception in a high Doppler shift environment.
　　 Simulations are conducted by using MATLAB codes to evaluate the different performances of BER between OFDMA with and