110 research outputs found
A study of major coding techniques for digital communication Final report
Coding techniques for digital communication channel
Analysis and construction of full-diversity joint network-LDPC codes for cooperative communications
Cooperative communication is a well known technique to yield transmit diversity and network coding can increase the spectral efficiency. These two techniques can be combined to achieve a double diversity order for a maximum coding rate Rc = 2/3 on the Multiple Access Relay Channel (MARC); Transmit diversity is necessary in harsh environments to reduce the required transmit power for achieving a given error performance at a certain transmission rate. In networks; where two sources share a common relay in their transmission to the destination. However; codes have to be carefully designed to obtain the intrinsic diversity offered by the MARC. This paper presents the principles to design a family of full-diversity LDPC codes with maximum rate. Simulation of the word error rate performance of the new proposed family of LDPC codes for the MARC confirms the full-diversity
Advanced Statistical Signal Processing Methods in Sensing, Detection, and Estimation for Communication Applications
The applications of wireless communications and digital signal processing have dramatically changed the way we live, work, and learn over decades. The requirement of higher throughput and ubiquitous connectivity for wireless communication systems has become prevalent nowadays. Signal sensing, detection and estimation have been prevalent in signal processing and communications for many years. The relevant studies deal with the processing of information-bearing signals for the purpose of information extraction. Nevertheless, new robust and efficient signal sensing, detection and estimation techniques are still in demand since there emerge more and more practical applications which rely on them. In this dissertation work, we proposed several novel signal sensing, detection and estimation schemes for wireless communications applications, such as spectrum sensing, symbol-detection/channel-estimation, and encoder identification. The associated theories and practice in robustness, computational complexity, and overall system performance evaluation are also provided
Iterative multiuser receivers for coded DS-CDMA systems
The introduction of cellular wireless systems in the 1980s has resulted in a continuous and
growing demand for personal communication services. This demand has made larger capacity
systems necessary. With the interest from both the research community and industry in wireless
code-division multiple-access (CDMA) systems, the application of multiuser detection (MUD)
techniques to wireless systems is becoming increasingly important. MUD is an important area
of interest to help obtain the significant increase in capacity needed for future wireless services.
The standardisation of direct-sequence CDMA (DS-CDMA) systems in the third generation of
mobile communication systems has raised even more interest in exploiting the capabilities and
capacity of this type of technology. However, the conventional DS-CDMA system has the major
problem of multiple-access interference (MAI). The MAI is unavoidable because receivers
deal with information which is transmitted not by a single source but by several uncoordinated
and geographically separated sources. As a result, the capacity of these systems is inherently interference
limited by other users. To overcome these limitations, MUD emerges as a promising
approach to increase the system capacity.
This thesis addresses the problem of improving the downlink capacity of a coded DS-CDMA
system with the use of MUD techniques at the mobile terminal receiver. The optimum multiuser
receiver scheme is far too computational intensive for practical use. Therefore, the aim of this
thesis is to investigate sub-optimal multiuser receiver schemes that can exploit the advantages
of MUD but also simplify its implementation. The attention is primarily focused on iterative
MUD receiver schemes which apply the turbo multiuser detection principle. Essentially this
principle consists of an iterative exchange of extrinsic information among the receiver modules
to achieve improved performance.
In this thesis, the implementation of an iterative receiver based on a linear MUD technique and
a cancellation scheme over an additive white Gaussian noise (AWGN) channel is first proposed
and analysed. The interference analysis shows that good performance is achieved using a lowcomplexity
receiver structure. In more realistic mobile channels, however, this type of receiver
suffers from the presence of higher levels of interference resulting in poor receiver performance.
The reason for this is that in such scenarios the desired signals are no longer linearly separable.
Therefore, non-linear detection techniques are required to provide better performance. With
this purpose, a hybrid iterative multiuser receiver is investigated for the case of a stationary
multipath channel. The incorporation of antenna arrays is an effective and practical technique to
provide a significant capacity gain over conventional single-antenna systems. In this context, a
novel space-time iterative multiuser receiver is proposed which achieves a large improvement in
spectral efficiency and performance over multipath fading channels. In addition, it is shown that
this architecture can be implemented without a prohibitive complexity cost. The exploitation
of the iterative principle can be used to approach the capacity bounds of a coded DS-CDMA
system. Using the Shannon’s sphere packing bound, a comparison is presented to illustrate how
closely a practical system can approach the theoretical limits of system performance
Tracking and data relay satellite system configuration and tradeoff study. Volume 4: TDRS system operation and control and telecommunications service system, part 1
Major study areas treated in this volume are: 1) operations and control and 2) the telecommunication service system. The TDRS orbit selection, orbital deployment, ground station visibility, sequence of events from launch to final orbit position, and TDRS control center functions required for stationkeeping, repositioning, attitude control, and antenna pointing are briefly treated as part of the operations and control section. The last topic of this section concerns the operations required for efficiently providing the TDRSS user telecommunication services. The discussion treats functions of the GSFC control and data processing facility, ground station, and TDRS control center. The second major portion of this volume deals with the Telecommunication Service System (TSS) which consists of the ground station, TDRS communication equipment and the user transceiver. A summary of the requirements and objectives for the telecommunication services and a brief summary of the TSS capabilities is followed by communication system analysis, signal design, and equipment design. Finally, descriptions of the three TSS elements are presented
Development And Implementation Of Improved Coded OFDM System Using SDR Platform
he increasing demand for high speed wireless connectivity at low cost poses new
challenges for communication system designers, to implement solutions that increase
the data rate by utilizing the limited radio resources more efficiently at a low
additional complexity. Adaptive Coding and Modulation (ACM) exploits the
flexibility of channel coding and constellation in Orthogonal Frequency Division
Multiplexing (OFDM) to obtain higher data rates. This technique employs multiple
modulation and coding schemes to instantaneously adapt to the variations in the
channel Signal to Noise Ratio (SNR), thus maximizing the system throughput and
improving Bit Error Rate (BER) performance. On the other hand, OFDM system
suffers from inter-symbol interference (ISI), especially in mobile communication
environments. This problem may be tackled by increasing the individual symbol
duration for each subcarrier together with the use of guard time. Nevertheless, this
does not solve the problem completely in multipath fading channel, because all
subcarriers will arrive at the receiver with different amplitudes. Unfortunately, some
subcarriers may be completely lost because of deep fades. Hence even though most
subcarriers may be detected without errors, the overall BER will be largely
dominated by a few subcarriers with bad SNR. To eliminate this problem, OFDM
based systems usually employ a special technique like error correction coding
(ECC). Various coding methods are adopted by many standards to mitigate the
effects of frequency selective channel which causes bit errors to occur in bur
Investigation of coding and equalization for the digital HDTV terrestrial broadcast channel
Includes bibliographical references (p. 241-248).Supported by the Advanced Telecommunications Research Program.Julien J. Nicolas
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