Title page
Abstract
Contents
1. Introduction 14
1.1 Background 14
1.2 Previous Work 16
1.2.1 Existing Channel Estimation Schemes 16
1.2.2 Problems of Existing Schemes 17
1.3 Proposed Technique 19
1.4 Thesis Organization 20
2. OFDM Systems 21
2.1 SISO OFDM Systems 21
2.1.1 CP-OFDM 21
2.1.2 ZP-OFDM 24
2.2 Space-Time Coded OFDM Systems 27
2.2.1 STBC-OFDM 28
2.2.2 SFBC-OFDM 31
3. Channel Estimation in OFDM Systems 34
3.1 Basic Procedure 34
3.2 Existing Schemes 35
3.2.1 Pilot Symbols in Time Slots 35
3.2.2 Pilot Symbol in Subcarriers 36
3.3 Proposed Scheme 38
4. Simulation Model 40
4.1 SISO OFDM 40
4.2 Space-Time Coded OFDM 44
5. Simulation Results 48
5.1 SISO OFDM 48
5.2 Space-Time Coded OFDM 53
6. Conclusions 58
국문요약 60
References 62
감사의 글 65
Table 2.1 : Space-time block code for two transmit antennas 29
Table 2.2 : Space-frequency block code for two transmit antennas 31
Table 4.1 : Main parameters 40
Table 4.2 : Channel types in SISO OFDM systems 43
Figure 1.1 : Pilot patterns in OFDM systems 16
Figure 2.1 : Block diagram of CP-OFDM system 21
Figure 2.2 : Block diagram of ZP-OFDM system 25
Figure 2.3 : Block diagram of the two transmit diversity OFDM system 27
Figure 2.4 : Encoding scheme of the STBC-OFDM system 30
Figure 2.5 : Encoding scheme of the SFBC OFDM system 32
Figure 3.1 : Channel frequency response and channel impulse response estimated by using the pilot symbols in time slots 35
Figure 3.2 : Channel frequency response and channel impulse response estimated by using the pilot symbols in subcarriers 37
Figure 3.3 : Transmitted sequence and received sequence when using the impulse symbol in the time domain 38
Figure 4.1 : Structure of the OFDM symbol block for each channel estimation scheme 42
Figure 4.2 : Structure of the OFDM symbol block in space-time coded OFDM systems 45
Figure 4.3 : Modified structure of the OFDM symbol block to increase the date rate 47
Figure 5.1 : BER versus SNR/bit of SISO OFDM systems in the channel with ΔfD = 0.05 and тrms = 2цs 50
Figure 5.2 : MSE versus SNR/bit of SISO OFDM systems in the channel with ΔfD = 0.05 and тrms = 2цs 50
Figure 5.3 : BER versus SNR/bit of SISO OFDM systems in the channel with ΔfD = 0.1 and тrms = 2цs 51
Figure 5.4 : MSE versus SNR/bit of SISO OFDM systems in the channel with ΔfD = 0.1 and тrms = 2цs 51
Figure 5.5 : BER versus SNR/bit of SISO OFDM systems in the channel with ΔfD = 0.05 and тrms = 10цs 52
Figure 5.6 : MSE versus SNR/bit of SISO OFDM systems in the channel with ΔfD = 0.05 and тrms = 10цs 52
Figure 5.7 : BER versus SNR/bit of STBC-OFDM systems in the channel with ΔfD = 0.02 and тrms = 4цs 54
Figure 5.8 : MSE versus SNR/bit of STBC-OFDM systems in the channel with ΔfD = 0.02 and тrms = 4цs 54
Figure 5.9 : BER versus SNR/bit of SFBC-OFDM systems in the channel with ΔfD = 0.02 and тrms = 4цs 55
Figure 5.10 : MSE versus SNR/bit of SFBC-OFDM systems in the channel with ΔfD = 0.02 and тrms = 4цs 55
Figure 5.11 : BER versus SNR/bit of STBC-OFDM systems in the channel with ΔfD = 0.02 and тrms = 4цs 56
Figure 5.12 : MSE versus SNR/bit of STBC-OFDM systems in the channel with ΔfD = 0.02 and тrms = 4цs 56
Figure 5.13 : BER versus SNR/bit of SFBC-OFDM systems in the channel with ΔfD = 0.02 and тrms = 4цs 57
Figure 5.14 : MSE versus SNR/bit of SFBC-OFDM systems in the channel with ΔfD = 0.02 and тrms = 4цs 57