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Possibilities of Error Controls in Frequency hopping Stations
Pust, Radim ; Kovář, Pavel (referee) ; Wieser,, Vladimír (referee) ; Burda, Karel (advisor)
The doctoral thesis deals with design of coding for frequency hopping stations in band with intensive jamming. In digital modulations erroneous determination of the modulation state occurs due to jam at the receiver side. The result is erroneously transferred symbols of the message. Errors created during the transmission can be eliminated by using error control systems. It is also possible to prevent these errors by using algorithms (techniques) of frequency hopping which select the appropriate channel. Appropriate communication channel is a channel with a lower probability of erroneous symbol in the message. The main contribution of this thesis is to design a new frequency hopping technique with collision avoidance (FH/CA). The station with FH/CA technique measures signal levels in the considered several channels before every jump. Based on the measurements the most appropriate channel with the lowest value of measured signal level is selected. Therefore, it is more probable that a jump to an unoccupied channel with a transmission will occur. Using a mathematical model, the performance of the newly proposed FH/CA technique is compared with the currently used techniques FH and AFH. Comparison criteria are the probability of a collision between an FH/CA communication system and a static (device transmitting continuously at a fixed frequency) or dynamic jammer (i.e. other FH or AFH systems). By comparing the values of the probability of jammed transmission, indisputable theoretical advantages of the new FH/CA technique were found, compared to the currently used FH and AFH techniques. The FH/CA technique always has better or equal results compared with the FH technique in the case of interference by static and dynamic jammers. The FH/CA technique in a band with static and dynamic jammers usually has better results than the AFH technique. A significant contribution of the FH/CA technique can be seen in the case of dynamic jammers. On the other hand, in the case of static jammers the FH/CA technique is in certain situations worse than the AFH technique. The accuracy of the mathematical models were successfully verified on a simulation model that was created as a part of this thesis in the MATLAB environment. Based on the obtained data from the model there was designed coding for frequency hopping stations with the new technique of frequency hopping FH/CA which is designed for small-volume data transfer in a band with intensive jamming.
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Systems with frequency hopping
Jelínek, Martin ; Říha, Kamil (referee) ; Pust, Radim (advisor)
This bachelor´s thesis deals the systems, which use the Frequency Hopping (FH). The brief history of frequency hopping and its development together with Adaptive Frequency Hopping technology (AFH) is introduced. The general function principle of AFH, which differs AFH from FH, is described. Advantages and disadvantages of frequency hopping and its division into fast (FFH) and slow (SFH) are described next. Some of military communication systems (e.g. SINCGARS, Eritac, MRR, Panther V-EDR and next) as well as some of commercial systems (e.g. worldwide-spread Bluetooth system) are introduced. Mentioned systems use digital modulations, three of basic digital modulations are demonstrated (ASK - Amplitude Shift Keying, FSK - Frequency Shift Keying and PSK - Phase Shift Keying). Basic types of used spectrum spreading (FHSS, DSSS, OFDM) are mentioned next. The FHSS type of spectrum spreading is described in more detail, because the spectrum spreading is done by frequency hopping. Particular systems contain error control of radio transmission of information, which is realized by FEC (Forward Error Correction) and ARQ (Automatic Repeat Query) techniques. Practical part of the bachelor´s thesis demonstrates, with usage of Matlab programme, adaptive frequency hopping function (AFH) during communication of Master-Slave devices, where more systems are active. This causes the interference of the communication. This interference is caused by static and dynamic jammers, that work in the same band as the Master-Slave devices.
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Possibilities of Error Controls in Frequency hopping Stations
Pust, Radim ; Kovář, Pavel (referee) ; Wieser,, Vladimír (referee) ; Burda, Karel (advisor)
The doctoral thesis deals with design of coding for frequency hopping stations in band with intensive jamming. In digital modulations erroneous determination of the modulation state occurs due to jam at the receiver side. The result is erroneously transferred symbols of the message. Errors created during the transmission can be eliminated by using error control systems. It is also possible to prevent these errors by using algorithms (techniques) of frequency hopping which select the appropriate channel. Appropriate communication channel is a channel with a lower probability of erroneous symbol in the message. The main contribution of this thesis is to design a new frequency hopping technique with collision avoidance (FH/CA). The station with FH/CA technique measures signal levels in the considered several channels before every jump. Based on the measurements the most appropriate channel with the lowest value of measured signal level is selected. Therefore, it is more probable that a jump to an unoccupied channel with a transmission will occur. Using a mathematical model, the performance of the newly proposed FH/CA technique is compared with the currently used techniques FH and AFH. Comparison criteria are the probability of a collision between an FH/CA communication system and a static (device transmitting continuously at a fixed frequency) or dynamic jammer (i.e. other FH or AFH systems). By comparing the values of the probability of jammed transmission, indisputable theoretical advantages of the new FH/CA technique were found, compared to the currently used FH and AFH techniques. The FH/CA technique always has better or equal results compared with the FH technique in the case of interference by static and dynamic jammers. The FH/CA technique in a band with static and dynamic jammers usually has better results than the AFH technique. A significant contribution of the FH/CA technique can be seen in the case of dynamic jammers. On the other hand, in the case of static jammers the FH/CA technique is in certain situations worse than the AFH technique. The accuracy of the mathematical models were successfully verified on a simulation model that was created as a part of this thesis in the MATLAB environment. Based on the obtained data from the model there was designed coding for frequency hopping stations with the new technique of frequency hopping FH/CA which is designed for small-volume data transfer in a band with intensive jamming.
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Systems with frequency hopping
Jelínek, Martin ; Říha, Kamil (referee) ; Pust, Radim (advisor)
This bachelor´s thesis deals the systems, which use the Frequency Hopping (FH). The brief history of frequency hopping and its development together with Adaptive Frequency Hopping technology (AFH) is introduced. The general function principle of AFH, which differs AFH from FH, is described. Advantages and disadvantages of frequency hopping and its division into fast (FFH) and slow (SFH) are described next. Some of military communication systems (e.g. SINCGARS, Eritac, MRR, Panther V-EDR and next) as well as some of commercial systems (e.g. worldwide-spread Bluetooth system) are introduced. Mentioned systems use digital modulations, three of basic digital modulations are demonstrated (ASK - Amplitude Shift Keying, FSK - Frequency Shift Keying and PSK - Phase Shift Keying). Basic types of used spectrum spreading (FHSS, DSSS, OFDM) are mentioned next. The FHSS type of spectrum spreading is described in more detail, because the spectrum spreading is done by frequency hopping. Particular systems contain error control of radio transmission of information, which is realized by FEC (Forward Error Correction) and ARQ (Automatic Repeat Query) techniques. Practical part of the bachelor´s thesis demonstrates, with usage of Matlab programme, adaptive frequency hopping function (AFH) during communication of Master-Slave devices, where more systems are active. This causes the interference of the communication. This interference is caused by static and dynamic jammers, that work in the same band as the Master-Slave devices.
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