الفهرس Only 14 pages are availabe for public view
 |  | from | 83 |  |  |
| | | from | 83 | | |
Abstract
The main aim of this thesis is to study the different methods for coding and modulation techniques used for high rate users and for multiuser communication systems. The main problem in the next mobile generations is high bit rates used for multimedia. We present the Wavelet Packet Division Multiplexing and the Wavelet Modulation as methods for increasing the number of users.
The main problem in wireless communication systems is the fading channels which causes errors at the receiver. Using diversity techniques improves the performance and overcome fading errors. Among all kinds of diversity space diversity or transmit diversity as Space Time Block Coding is suitable for mobile systems due to the simplicity at the receiver. We can enhance Space Time Coding with the wavelet modulation and hence can be used for multiuser systems. Different techniques are used for multiuser space time coding systems.
Multirate is one of the advantages of Wavelet Modulation. Multirate systems are required for multimedia communication systems to send different forms of data (voice, images, video....). Multirate systems can also be used as a diversity technique. We can send replicas of the data on the same rate or different rate, by joining them at the receiver, we get a better performance. Ons can use the multirate system as an adaptive transmission depending on how fast is the time varying flat fading channel. We can combine all these useful techniques to build a Multiuser-Multirate Adaptive Space Time Coding.