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Studies on Trade-off Between Throughput and Reliability in Wireless SystemsAnsari Sadrabadi, Mehdi January 2007 (has links)
In the first part of the thesis, we study the trade-off between the transmission reliability and data
rate in high signal-to-noise ratio regime in ad-hoc wireless
networks. Bandwidth allocation plays a significant role in this
trade-off, since dividing bandwidth reduces the number of users on
each band and consequently decreases the interference level, however
it also decreases the data rate. Noting that the interference power
is substantially influenced by the network density, this trade-off
introduces a measure for appropriate bandwidth allocation among
users considering the network density. The diversity-multiplexing trade-off
is derived for a one-dimensional regular ad-hoc
network.
In the second part of the thesis, we study the performance of point-to-point and broadcast systems
with partial channel state information at the transmitter in a time-varying environment.
First, the capacity of time-varying channels with
periodic feedback at the transmitter is evaluated. It is assumed that the
channel state information is perfectly known at the receiver
and is fed back to the transmitter at the regular time-intervals. The system capacity is investigated in two cases: i) finite state Markov channel, and
ii) additive white Gaussian noise channel with time-correlated fading. In a multiuser scenario, we consider a downlink system in which a single-antenna base
station communicates with single antenna users, over a
time-correlated fading channel. It is assumed that
channel state information is perfectly known at each receiver, while
the rate of channel variations and the fading
gain at the beginning of each frame are known to the transmitter. The asymptotic throughput of the
scheduling that transmits to the user with the maximum signal to
noise ratio is examined applying variable code rate and/or variable
codeword length signaling. It is shown that by selecting a fixed codeword
length for all users, the order of the maximum possible throughput (corresponding to quasi-static fading) is achieved.
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FPGA-design av en STDM-baserad multiplexer för seriell multiprotokollskommunikation / A FPGA design of a STDM-based multiplexer for serial multi protocol communicationJanson, Robert, Mottaghi, Amir January 2012 (has links)
The remotely operated underwater vehicles that the client develops have needs of different kinds of data channels. In order to minimize the need of physical cable between the control unit and a ROV, a multiplex protocol has been developed. The protocol has been designed with the aim of using the bandwidth of the transferring link as efficient as possible. The different kinds of data channels used during this thesis project is; RS232, RS485 and CAN. ROM and FIFO-memories have been used to be able to effectively manage the different data channels. All the reading and sending of these channels have been implemented in FPGA-technology, the coding is made generic so that it will be easier to add more channels to the system in the future. The multiplex protocol is a modified version of the method STDM and it is a proprietary protocol. Calculations has been made in MatLab to ensure that the protocol does not exceed the maximal bandwidth that is available. The protocol utilizes the error-detecting technique CRC for the purpose of error detection. A PCB has been developed during this thesis project, the PCB is made so that the different data channels have connection with the FPGA circuit.
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Studies on Trade-off Between Throughput and Reliability in Wireless SystemsAnsari Sadrabadi, Mehdi January 2007 (has links)
In the first part of the thesis, we study the trade-off between the transmission reliability and data
rate in high signal-to-noise ratio regime in ad-hoc wireless
networks. Bandwidth allocation plays a significant role in this
trade-off, since dividing bandwidth reduces the number of users on
each band and consequently decreases the interference level, however
it also decreases the data rate. Noting that the interference power
is substantially influenced by the network density, this trade-off
introduces a measure for appropriate bandwidth allocation among
users considering the network density. The diversity-multiplexing trade-off
is derived for a one-dimensional regular ad-hoc
network.
In the second part of the thesis, we study the performance of point-to-point and broadcast systems
with partial channel state information at the transmitter in a time-varying environment.
First, the capacity of time-varying channels with
periodic feedback at the transmitter is evaluated. It is assumed that the
channel state information is perfectly known at the receiver
and is fed back to the transmitter at the regular time-intervals. The system capacity is investigated in two cases: i) finite state Markov channel, and
ii) additive white Gaussian noise channel with time-correlated fading. In a multiuser scenario, we consider a downlink system in which a single-antenna base
station communicates with single antenna users, over a
time-correlated fading channel. It is assumed that
channel state information is perfectly known at each receiver, while
the rate of channel variations and the fading
gain at the beginning of each frame are known to the transmitter. The asymptotic throughput of the
scheduling that transmits to the user with the maximum signal to
noise ratio is examined applying variable code rate and/or variable
codeword length signaling. It is shown that by selecting a fixed codeword
length for all users, the order of the maximum possible throughput (corresponding to quasi-static fading) is achieved.
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High-rate, short-pulse sources:jitter and pedestal level in optical time-division multiplexingGross, Michael Charles 01 December 2003 (has links)
No description available.
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A theoretical study of OFDM system performance with respect to subcarrier numbers and repeater output powerChang, Jui-Ta 09 June 2011 (has links)
Recent years, Orthogonal Frequency Division Multiplexing (OFDM) system gets more and more attentions for its great benefit to the optical fiber communication system for improving the transmission performance. Not only better performance in long distance transmission but also high bit-rate is attractive feature of the OFDM system. The OFDM technology has been developed for the wireless communication system, and is now used in Asymmetric Digital Subscriber Line (ADSL), ETSI Digital Audio Broadcasting (DAB), Digital Video Broadcasting (DVB), High Definition Television (HDTV), Wireless Local Area Network (WLAN) and so on.
The OFDM is extensively used in broadband wired and wireless communication systems, and it solves the problem of intersymbol interference (ISI) effectively. Actually, the OFDM is a kind of Multi-Carrier Modulation (MCM), and it is not a brand-new technology. The history of the OFDM can be traced back to 1966 when Chang of Bell Labs introduced the concept of the OFDM.
In this thesis, I will briefly introduce the background of optical fiber communication system, then, explain my motivation and the structure of this thesis.
Next, theoretical study has been conducted. For the simulation, I discuss the performance of the OFDM system related to the number of subcarriers and the erbium-doped fiber amplifier (EDFA) repeater output power. It revealed that small number of subcarriers had better transmission performance. In my study case, repeater output power of 0dBm was the optimum condition.
In addition, experimental study has been conducted. For the experiment, the waveform required for the OFDM signal generation was calculated offline, and it was realized by the Arbitrary Waveform Generator (AWG).
Finally, this thesis is concluded.
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Time and Frequency Synchronization and Cell Search in 3GPP LTEKe, Hung-Shiun 05 August 2011 (has links)
Long Term Evolution (LTE) developed by Third Generation Partnership Project (3GPP) is expected to be the standard of the Fourth-Generation (4G) of wireless communication system. LTE supports Frequency Division Duplex (FDD) and Time Division Duplex (TDD), and both of them are based on Orthogonal Frequency Division Multiplexing (OFDM) system in downlink. OFDM systems are sensitive to timing and frequency offset. Therefore, synchronization plays an important role in OFDM systems.
In this thesis, we study synchronization problems of a LTE FDD baseband receiver. Particularly, we develop a complete procedure to deal with the synchronization problems. The basic design concept and procedure are as follows: The receiver estimates and compensates the timing and frequency offset by using the repetition property of the cyclic prefix. In the meanwhile, the receiver also detects cyclic prefix mode (or the length of the cyclic prefix). After the frequency offset has been compensated, the receiver then processes cell search. To this end, we multiply each subcarrier by the synchronization sequence provided by LTE specification and transform them into time domain. We then estimate the channel energy in time domain to detect the Cell Identity (Cell ID). Using computer simulations, we verify that the designed receiver performs well.
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Blind SNR and Channel Length Estimation in OFDM SystemsYeh, Ying-mao 11 August 2009 (has links)
In many algorithms for Orthogonal Frequency Division Multiplexing (OFDM) systems, the channel estimation is one of the most essential factors. In wireless environment, channel is change very fast, and the channel has multipath effect, the channel length is obtained by channel estimation. In this paper, we estimation the channel length and the SNR by virtual carriers (VC) and Singular value decomposition, when channel estimator known the information for channel length, then calculate complicated can be reduced. Besides, we proposed the estimated method at carriers frequency offset effect.
Noise variance (or noise power) can improve performance of channel estimator, e.g. MMSE channel estimator, turbo code or power allocation. In this paper, we were estimate noise variance by using the blind method of property of orthogonality of matrix, which is differed from the traditional method of Pilots.
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High-rate, short-pulse sources jitter and pedestal level in optical time-division multiplexing /Gross, Michael Charles, January 2003 (has links) (PDF)
Thesis (Ph. D.)--School of Electrical and Computer Engineering, Georgia Institute of Technology, 2004. Directed by Stephen E. Ralph. / Vita. Includes bibliographical references (leaves 281-296).
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Adaptive interleaving for orthogonal frequency division multiplexing systems /Lei, Sai-weng. January 2000 (has links)
Thesis (M. Phil.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 74-78).
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A study of channel estimation for OFDM systems and system capacity forMIMO-OFDM systemsZhou, Wen, 周雯 January 2010 (has links)
published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy
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