74 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
On Non-coherent MIMO Channels in the Wideband Regime: Capacity and Reliability
We consider a multiple-input, multiple-output (MIMO) wideband Rayleigh block
fading channel where the channel state is unknown to both the transmitter and
the receiver and there is only an average power constraint on the input. We
compute the capacity and analyze its dependence on coherence length, number of
antennas and receive signal-to-noise ratio (SNR) per degree of freedom. We
establish conditions on the coherence length and number of antennas for the
non-coherent channel to have a "near coherent" performance in the wideband
regime. We also propose a signaling scheme that is near-capacity achieving in
this regime.
We compute the error probability for this wideband non-coherent MIMO channel
and study its dependence on SNR, number of transmit and receive antennas and
coherence length. We show that error probability decays inversely with
coherence length and exponentially with the product of the number of transmit
and receive antennas. Moreover, channel outage dominates error probability in
the wideband regime. We also show that the critical as well as cut-off rates
are much smaller than channel capacity in this regime
Unified Capacity Limit of Non-coherent Wideband Fading Channels
In non-coherent wideband fading channels where energy rather than spectrum is
the limiting resource, peaky and non-peaky signaling schemes have long been
considered species apart, as the first approaches asymptotically the capacity
of a wideband AWGN channel with the same average SNR, whereas the second
reaches a peak rate at some finite critical bandwidth and then falls to zero as
bandwidth grows to infinity. In this paper it is shown that this distinction is
in fact an artifact of the limited attention paid in the past to the product
between the bandwidth and the fraction of time it is in use. This fundamental
quantity, called bandwidth occupancy, measures average bandwidth usage over
time. For all signaling schemes with the same bandwidth occupancy, achievable
rates approach to the wideband AWGN capacity within the same gap as the
bandwidth occupancy approaches its critical value, and decrease to zero as the
occupancy goes to infinity. This unified analysis produces quantitative
closed-form expressions for the ideal bandwidth occupancy, recovers the
existing capacity results for (non-)peaky signaling schemes, and unveils a
trade-off between the accuracy of approximating capacity with a generalized
Taylor polynomial and the accuracy with which the optimal bandwidth occupancy
can be bounded.Comment: Accepted for publication in IEEE Transactions on Wireless
Communications. Copyright may be transferred without notic
Error exponents for multipath fading channels : a strong coding theorem
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.Includes bibliographical references (leaves 43-45).This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.We derive upper and lower bounds on the probability of error (the exponents of which are the error exponents) with "peaky" signaling -- the signaling strategy that achieves the capacity of the multipath fading channel under an average power constraint in the limit of infinite bandwidth. These bounds constitute a strong coding theorem for the channel as they not only delimit the range of achievable rates, but also give us a relationship among the error probability, data rate, bandwidth, "peakiness", and fading parameters such as the coherence time. They can be used to compare peaky signaling to other large bandwidth systems over fading channels, such as ultrawide band (UWB) radio and wideband CDMA. We first derive an upper bound for general fading, then specialize to the case of Rayleigh fading where we obtain upper and lower bounds that are exponentially tight and therefore yield the reliability function. We study the behavior of the reliability function and the upper and lower error probability bounds numerically.by Desmond S. Lun.S.M
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