碩士 / 淡江大學 / 電機工程學系碩士班 / 100 / Orthogonal frequency division multiplexing (OFDM) due to the robustness to the effect of multipath fading and having high spectral efficiency, it has become a good candidate of wireless communications systems. The block transmission of signal-blocks through the channel will suffer from the inter-block interference (IBI) and inter-symbol interference (ISI). Usually in the transmitter of the OFDM systems, redundancy (or guard interval), such cyclic prefix (CP) or zero padding (ZP), with sufficient length, is inserted in the transmitted block to avoid the IBI. In this thesis, we propose a novel pseudo random cyclic postfix (PRCP-) OFDM system configuration, which adopts the PRCP as redundancy and combines with multiple antennas. In fact, the multiple transmit antenna and multiple receive antenna, which exploits the spatial diversity, can be used to further enhance the channel capacity and achieve high data-rate. The main property of PRCP-OFDM modulation is that it exploits the cyclic-postfix sequences to estimate channel information with a low complexity method. Compared with CP-OFDM, it overcomes the channel null problem. For ZP-OFDM, it uses the additional information to estimate channel which is replaced by zero samples in ZP-OFDM. Moreover, PRCP-OFDM avoids the interference of signals to the desired postfix when we estimate channel impulse response (CIR) and which is different from pseudo random postfix (PRP-) OFDM [8]. Thus, as SNR grows, PRCP-OFDM can have better performance than PRP-OFDM. With the help of [9], [12] and [13], we extend the PRCP-OFDM to the MIMO case with space-time block coding.
In addition, the so-called MSSNR (Maximum Shortening Signal-to-noise Ratio) algorithm, which is a kind of Blind Channel Shortening method, is employed to alleviate the effect of IBI when the length of PRP or PRCP sequences is shorter than the order of channel impulse response.
To fair compare the system performance among the existing MIMO OFDM methods, we consider the channels which are modeled as the random time-invariant Rayleigh model and the slow random time-varying channel modeled by the Jake’s model.
Via computer simulation, we verify that the performance is improved, in terms of the accuracy of channel estimation and symbol error rate (SER).
| Identifer | oai:union.ndltd.org:TW/100TKU05442065 |
| Date | January 2012 |
| Creators | Yu-Siou Huang, 黃鈺修 |
| Contributors | Yih-Guang Jan, 詹益光 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | en_US |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 81 |
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