23,678 research outputs found
A Tight Lower Bound to the Outage Probability of Discrete-Input Block-Fading Channels
In this correspondence, we propose a tight lower bound to the outage
probability of discrete-input Nakagami-m block-fading channels. The approach
permits an efficient method for numerical evaluation of the bound, providing an
additional tool for system design. The optimal rate-diversity trade-off for the
Nakagami-m block-fading channel is also derived and a tight upper bound is
obtained for the optimal coding gain constant.Comment: 22 pages, 4 figures. This work has been accepted for IEEE
Transactions on Information Theory and has been presented in part at the 2007
IEEE International Symposium on Information Theory, Nice, France, June 200
Polar Coding for Secure Transmission and Key Agreement
Wyner's work on wiretap channels and the recent works on information
theoretic security are based on random codes. Achieving information theoretical
security with practical coding schemes is of definite interest. In this note,
the attempt is to overcome this elusive task by employing the polar coding
technique of Ar{\i}kan. It is shown that polar codes achieve non-trivial
perfect secrecy rates for binary-input degraded wiretap channels while enjoying
their low encoding-decoding complexity. In the special case of symmetric main
and eavesdropper channels, this coding technique achieves the secrecy capacity.
Next, fading erasure wiretap channels are considered and a secret key agreement
scheme is proposed, which requires only the statistical knowledge of the
eavesdropper channel state information (CSI). The enabling factor is the
creation of advantage over Eve, by blindly using the proposed scheme over each
fading block, which is then exploited with privacy amplification techniques to
generate secret keys.Comment: Proceedings of the 21st Annual IEEE International Symposium on
Personal, Indoor, and Mobile Radio Communications (PIMRC 2010), Sept. 2010,
Istanbul, Turke
Block QPSK modulation codes with two levels of error protection
A class of block QPSK modulation codes for unequal error protection (UEP) is presented. These codes are particularly suitable either for broadcast channels or for communication systems where parts of the information messages are more important than others. An example of the latter is coded speech transmission. Not much is known on the application of block UEP codes in combined coding and modulation schemes. We exhibit a method to combine binary linear UEP (LUEP) block codes of even length, using a Gray mapping, with a QPSK signal set to construct efficient block QPSK modulation codes with nonuniform error protection capabilities for bandwidth efficient transmission over AWGN (additive white Gaussian noise) and Rayleigh fading channels
Multilevel Block Coded 8-PSK Modulations Using Unequal Error Protection Codes for the Rayleigh Fading Channel
This paper introduces new block coded 8-PSK modulations with unequal error protection (UEP) capabilities for Rayleigh fading channels. The design of efficient block coded modulations (BCM) over 8-PSK signal sets, for the specific purpose of UEP, over Rayleigh fading channels is considered. UEP is desirable in communications systems where part of the source information is more important, or error sensitive, such as the transmission of coded speech and data broadcasting. The proposed block modulation codes are based on the multilevel construction of Imai and Hirakawa (1977). It is shown that the use of binary linear UEP (LUEP) codes as component codes in one or two of the encoding levels provides, in addition to superior UEP capabilities, a higher error performance, at the expense of a very modest reduction in bandwidth efficiency, with respect to conventional multilevel codes. Computer simulation results show that, over a Rayleigh fading channel, a significant improvement in the coding gain is obtained by the use of binary LUEP codes as constituent codes in the multilevel construction
Full-Rate, Full-Diversity Adaptive Space Time Block Coding for Transmission over Rayleigh Fading Channels
A full-rate, full-diversity Adaptive Space Time Block Coding (ASTBC) scheme based on Singular Value Decomposition (SVD) is proposed for transmission over Rayleigh fading channels. The ASTBC-SVD scheme advocated is capable of providing both full-rate and full-diversity for any number of transmit antennas, Nt, provided that the number of receive antennas, Nr, equals to Nt. Furthermore, the ASTBC-SVD scheme may achieve an additional coding gain due to its higher product distance with the aid of the block code employed. In conjunction with SVD, the “water-filling” approach can be employed for adaptively distributing the transmitted power to the various antennas transmit according to the channel conditions, in order to further enhance the attainable performance. Since a codeword constituted by Nt symbols is transmitted in a single time slot by mapping the Nt symbols to the Nt transmit antennas in the spatial domain, the attainable performance of the ASTBC-SVD scheme does not degrade, when the channel impulse response values vary from one time slot to the next. Hence, the proposed ASTBC-SVD scheme is attractive in the context of both uncorrelated and correlated Rayleigh fading channels. The performance of the proposed scheme was evaluated, when communicating over uncorrelated Rayleigh fading channels. Explicitly, an Eb/N0 gain of 2.5 dB was achieved by the proposed ASTBC-SVD scheme against Alamouti’s scheme [1], when employing Nt = Nr = 2 in conjunction with 8PSK
A Low-Complexity Semi-Analytical Approximation to the Block Error Rate in Nakagami-m Block Fading Channels
<p>There are few analytical formulas that can be used
for calculating the block error rate (BLER) in block fading
channels. Thus, an estimate of the BLER is often obtained using
numerical methods. One such method is the threshold method
which assigns 0 or 1 to the instantaneous BLER given the signal
to noise ratio (SNR) level. It has been shown that utilizing such
a method results in an accurate approximation of the BLER in
Nakagami-m block fading channels for a wide range of m.</p>
<p>In this work, we consider a recently proposed simple method of
obtaining the threshold and study the effect of adopting different
physical layer and channel parameters on that threshold. We
show that, while the value of this threshold depends on the
modulation, coding, and block size, it is almost unaffected by
the m parameter of Nakagami-m channels for a wide range of
practical values. In addition, for a given modulation and coding
method, the threshold is shown to be a simple function of block
size. As a result, the computational complexity required to obtain
the threshold can be significantly reduced.</p
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