Performance Study of OFDM and SC-CP Systems in Nonideal Transmission Environment
Date Issued
2005
Date
2005
Author(s)
Lee, Li-Hsiang
DOI
en-US
Abstract
The OFDM system has been a widely adopted technique for both wired and wireless transmission. It is well-known that OFDM systems suffer from the noise enhancement problem due to channel spectral nulls and the PAPR problem. Recently, another new system called SC-CP (single carrier with cyclic prefix) system is receiving growing attention as another wireless transmission technique. This is because the SC-CP system can mitigate the noise enhancement problem and it does not suffer from PAPR problem.
Both of OFDM and SC-CP systems are ISI- and IBI-free if the following two conditions hold. First, the channel is quasi-static, which means the channel does not change during a data block transmission. Second, the length of cyclic prefix (CP) is larger than the channel order. When any of these two conditions is violated, the BER performance will degrade significantly.
In the first part of this thesis, we will consider a special doubly selective channel model. This type of channel is time-varying and hence no longer satisfies the quasi-static condition. We will analyze ISI effect and BER performance of the OFDM and SC-CP systems for conventional ZF FEQ and conventional MMSE FEQ respectively. Then, we derive the exact MMSE FEQ for given channel model and analyze the BER performance.
In the second part of this thesis, we will study the effect of the OFDM and SC-CP system when the CP length is smaller than the channel order. We will derive new MMSE receivers for both systems to improve the BER performance.
The simulation results will validate our performance analysis and we can find that new MMSE FEQ will outperform conventional ZF FEQ and conventional MMSE FEQ.
Subjects
正交分頻多工系統
前置迴旋碼
單載波系統
OFDM
SC-CP
doubly selective channel
cyclic prefix
Type
thesis
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