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Channel estimation in CDMA systems
Kadlec, Petr ; Prokopec, Jan (referee) ; Kejík, Petr (advisor)
The subject of this work deals with the problem of channel estimation for CDMA systems. This method of multiple access when individual users share the same full bandwidth simultaneously and are differentiated with any of pseudorandom sequences, is now the most perspective method. That is proved by its wide implementation in mobile networks of the third generation and higher systems. This work describes basic theory principles of spread spectrum, above all DS-CDMA (Direct Sequence-CDMA) and furthermore some phenomena of radio wireless channel that affect changes in transmitted signal in its way from transmitter to receiver. Terms of fading, multipath propagation, loss, refraction, scattering of the wave and Rice and Rayleigh probability density functions are mentioned. The third chapter deals with yet known and used capabilities of channel estimation. Differences, advantages and disadvantages of so-called blind estimation or training-based estimation are discussed. Two algorithms: LS method and sliding correlator are analyzed in more detail. There is also description of their simulations in Matlab and some results of these simulations are discussed. The last chapter deals with comparison of main characteristics and achievable accuracy of wireless channel impulse response estimation by both methods, and their possible utilization in real live.
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Modelling of Network Coding in Wireless Networks
Svobodník, Petr ; Miloš, Jiří (referee) ; Kuder, Zenon (advisor)
During data exchange in the Point-to-Point wireless topology, in case where end nodes aren’t accessible directly, a relay is deployed. However, the basic approach to relays – Store-and-Forward – isn’t the way to reach the maximum throughput. Network Coding operation is performed by combining data words (packets) travelling through the network in opposite directions into one packet. End nodes, with knowledge of the data sent, can decode received packet. Packet exchange is then finished in shorter time which results in an increase of network throughput. There are more methods of Network Coding which differ from each other in the time requirements or the ability to work in a noisy channel. In this paper they will be described and compared.
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Modelling of Network Coding in Wireless Networks
Svobodník, Petr ; Miloš, Jiří (referee) ; Kuder, Zenon (advisor)
During data exchange in the Point-to-Point wireless topology, in case where end nodes aren’t accessible directly, a relay is deployed. However, the basic approach to relays – Store-and-Forward – isn’t the way to reach the maximum throughput. Network Coding operation is performed by combining data words (packets) travelling through the network in opposite directions into one packet. End nodes, with knowledge of the data sent, can decode received packet. Packet exchange is then finished in shorter time which results in an increase of network throughput. There are more methods of Network Coding which differ from each other in the time requirements or the ability to work in a noisy channel. In this paper they will be described and compared.
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Channel estimation in CDMA systems
Kadlec, Petr ; Prokopec, Jan (referee) ; Kejík, Petr (advisor)
The subject of this work deals with the problem of channel estimation for CDMA systems. This method of multiple access when individual users share the same full bandwidth simultaneously and are differentiated with any of pseudorandom sequences, is now the most perspective method. That is proved by its wide implementation in mobile networks of the third generation and higher systems. This work describes basic theory principles of spread spectrum, above all DS-CDMA (Direct Sequence-CDMA) and furthermore some phenomena of radio wireless channel that affect changes in transmitted signal in its way from transmitter to receiver. Terms of fading, multipath propagation, loss, refraction, scattering of the wave and Rice and Rayleigh probability density functions are mentioned. The third chapter deals with yet known and used capabilities of channel estimation. Differences, advantages and disadvantages of so-called blind estimation or training-based estimation are discussed. Two algorithms: LS method and sliding correlator are analyzed in more detail. There is also description of their simulations in Matlab and some results of these simulations are discussed. The last chapter deals with comparison of main characteristics and achievable accuracy of wireless channel impulse response estimation by both methods, and their possible utilization in real live.
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