Wireless coherent OFDM modem 2001/2002
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Table of contents
1 Introduction................................................................................................................. 4
1.1 Hardware description.......................................................................................... 4
1.2 Software description ........................................................................................... 5
1.3 Channel assumptions and properties................................................................... 5
2 Background and multi-carrier transmission................................................................ 7
2.1 PSK..................................................................................................................... 8
2.2 QAM ................................................................................................................... 9
2.3 FFT-based OFDM system................................................................................... 9
2.4 Making a real signal.......................................................................................... 13
2.5 The incoherent scheme ..................................................................................... 16
3 Transmitter................................................................................................................ 17
3.1 Block Diagram of the Transmitter.................................................................... 17
3.2 Transmitter functionalities................................................................................ 17
3.3 Gray Coding- .................................................................................................... 18
3.3.1 Pseudo code for gray encoding-................................................................ 18
3.3.2 Advantages of Gray perm-........................................................................ 19
4 Receiver .................................................................................................................... 20
4.1 The synchronization.......................................................................................... 21
4.2 The header specification and information......................................................... 25
4.3 The demodulation ............................................................................................. 26
4.3.1 Received signal......................................................................................... 26
4.3.2 Channel estimation.................................................................................... 28
4.4 Optimum detection and performance of the systems........................................ 35
4.4.1 Pair wise error probability ........................................................................ 37
4.4.2 Performance of PSK ................................................................................. 38
4.4.3 Performance of QAM ............................................................................... 41
4.4.4 Incoherent detection.................................................................................. 45
5 Further improvements and applications.................................................................... 47
6 References................................................................................................................. 48
7 Appendix- ................................................................................................................. 49
7.1 List of MATLAB functions used in the code ................................................... 49
7.2 A list of functions and their pseudo code written by us.................................... 50
7.3 Pseudo code: Incoherent and Coherent modems .............................................. 52
7.3.1 Transmitter................................................................................................ 52
7.3.2 Receiver .................................................................................................... 52
7.4 Actual code ....................................................................................................... 53
7.4.1 Common functions.................................................................................... 53
7.5 Incoherent modem ............................................................................................ 57
7.5.1 Globals text file......................................................................................... 57
7.5.2 Transmitter................................................................................................ 58
7.5.3 Receiver .................................................................................................... 59
7.6 Coherent modem............................................................................................... 60
7.6.1 Globals text file......................................................................................... 60
7.6.2 Transmitter................................................................................................ 60
7.6.3 Receiver .................................................................................................... 62
