13,511 research outputs found
Performance Analysis for Multichannel Reception of OOFSK Signaling
In this paper, the error performance of on-off frequency shift keying (OOFSK)
modulation over fading channels is analyzed when the receiver is equipped with
multiple antennas. The analysis is conducted in two cases: the coherent
scenario where the fading is perfectly known at the receiver, and the
noncoherent scenario where neither the receiver nor the transmitter knows the
fading coefficients. For both cases, the maximum a posteriori probability (MAP)
detection rule is derived and analytical probability of error expressions are
obtained. The effect of fading correlation among the receiver antennas is also
studied. Simulation results indicate that for sufficiently low duty cycle
values, lower probability of error values with respect to FSK signaling are
achieved. Equivalently, when compared to FSK modulation, OOFSK with low duty
cycle requires less energy to achieve the same probability of error, which
renders this modulation a more energy efficient transmission technique.Comment: Proc. of the 2007 IEEE Wireless Communications and Networking
Conferenc
Max-Min SNR Signal Energy based Spectrum Sensing Algorithms for Cognitive Radio Networks with Noise Variance Uncertainty
This paper proposes novel spectrum sensing algorithms for cognitive radio
networks. By assuming known transmitter pulse shaping filter, synchronous and
asynchronous receiver scenarios have been considered. For each of these
scenarios, the proposed algorithm is explained as follows: First, by
introducing a combiner vector, an over-sampled signal of total duration equal
to the symbol period is combined linearly. Second, for this combined signal,
the Signal-to-Noise ratio (SNR) maximization and minimization problems are
formulated as Rayleigh quotient optimization problems. Third, by using the
solutions of these problems, the ratio of the signal energy corresponding to
the maximum and minimum SNRs are proposed as a test statistics. For this test
statistics, analytical probability of false alarm () and detection ()
expressions are derived for additive white Gaussian noise (AWGN) channel. The
proposed algorithms are robust against noise variance uncertainty. The
generalization of the proposed algorithms for unknown transmitter pulse shaping
filter has also been discussed. Simulation results demonstrate that the
proposed algorithms achieve better than that of the Eigenvalue
decomposition and energy detection algorithms in AWGN and Rayleigh fading
channels with noise variance uncertainty. The proposed algorithms also
guarantee the desired in the presence of adjacent channel
interference signals
Analytic solutions to a Marcum Q-function-based integral and application in energy detection of unknown signals over multipath fading channels
This work presents analytic solutions for a useful integral in wireless
communications, which involves the Marcum function in combination with an
exponential function and arbitrary power terms. The derived expressions have a
rather simple algebraic representation which renders them convenient both
analytically and computationally. Furthermore, they can be useful in wireless
communications and particularly in the context of cognitive radio
communications and radar systems, where this integral is often encountered. To
this end, we derive novel expressions for the probability of detection in
energy detection based spectrum sensing over fading channels.
These expressions are given in closed-form and are subsequently employed in
analyzing the effects of generalised multipath fading conditions in cognitive
radio systems. As expected, it is shown that the detector is highly dependent
upon the severity of fading conditions as even slight variation of the fading
parameters affect the corresponding performance significantly.Comment: Latest/Preprint Versio
Energy Detection of Unknown Signals over Cascaded Fading Channels
Energy detection is a favorable mechanism in several applications relating to
the identification of deterministic unknown signals such as in radar systems
and cognitive radio communications. The present work quantifies the detrimental
effects of cascaded multipath fading on energy detection and investigates the
corresponding performance capability. A novel analytic solution is firstly
derived for a generic integral that involves a product of the Meijer
function, the Marcum function and arbitrary power terms. This solution
is subsequently employed in the derivation of an exact closed-form expression
for the average probability of detection of unknown signals over *Rayleigh
channels. The offered results are also extended to the case of square-law
selection, which is a relatively simple and effective diversity method. It is
shown that the detection performance is considerably degraded by the number of
cascaded channels and that these effects can be effectively mitigated by a
non-substantial increase of diversity branches.Comment: 12 page
EM-Based iterative channel estimation and sequence detection for space-time coded modulation
Reliable detection of signals transmitted over a wireless communication channel requires knowledge of the channel estimate. In this work, the application of expectationmaximization (EM) algorithm to estimation of unknown channel and detection of space-time coded modulation (STCM) signals is investigated. An STCM communication system is presented which includes symbol interleaving at the transmitter and iterative EM-based soft-output decoding at the receiver. The channel and signal model are introduced with a quasi-static and time-varying Rayleigh fading channels considered to evaluate the performance of the communication system. Performance of the system employing Kalman filter with per-survivor processing to do the channel estimation and Viterbi algorithm for sequence detection is used as a reference.
The first approach to apply the EM algorithm to channel estimation presents a design of an online receiver with sliding data window. Next, a block-processing EM-based iterative receiver is presented which utilizes soft values of a posteriori probabilities (APP) with maximum a posteriori probability (MAP) as the criterion of optimality in both: detection and channel estimation stages (APP-EM receiver). In addition, a symbol interleaver is introduced at the transmitter which has a great desirable impact on system performance. First, it eliminates error propagation between the detection and channel estimation stages in the receiver EM loop. Second, the interleaver increases the diversity advantage to combat deep fades of a fast fading channel.
In the first basic version of the APP-EM iterative receiver, it is assumed that noise variance at the receiver input is known. Then a modified version of the receiver is presented where such assumption is not made. In addition to sequence detection and channel estimation, the EM iteration loop includes the estimation of unknown additive white Gaussian noise variance.
Finally, different properties of the APP-EM iterative receiver are investigated including the effects of training sequence length on system performance, interleaver and channel correlation length effects and the performance of the system at different Rayleigh channel fading rates
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