4 research outputs found
Bits Through Bufferless Queues
This paper investigates the capacity of a channel in which information is
conveyed by the timing of consecutive packets passing through a queue with
independent and identically distributed service times. Such timing channels are
commonly studied under the assumption of a work-conserving queue. In contrast,
this paper studies the case of a bufferless queue that drops arriving packets
while a packet is in service. Under this bufferless model, the paper provides
upper bounds on the capacity of timing channels and establishes achievable
rates for the case of bufferless M/M/1 and M/G/1 queues. In particular, it is
shown that a bufferless M/M/1 queue at worst suffers less than 10% reduction in
capacity when compared to an M/M/1 work-conserving queue.Comment: 8 pages, 3 figures, accepted in 51st Annual Allerton Conference on
Communication, Control, and Computing, University of Illinois, Monticello,
Illinois, Oct 2-4, 201
Strictly Bandlimited ISI-Free Transmission Over Intensity-Modulated Channels
In this paper, the design and analysis of a new bandwidth-efficient signalling method over the bandlimited intensity-modulated direct-detection (IM/DD) channel is pro- posed. The channel can be modeled as a bandlimited channel with nonnegative input and additive white Gaussian noise. Due to the nonnegativity constraint, the methods previously proposed for conventional bandlimited channels cannot be applied here. We propose a method to transmit without intersymbol interference in a narrower bandwidth compared to previous works, by combining Nyquist pulses with a constant bias. In fact, we can transmit with a bandwidth equal to that of coherent transmission. A trade-off between the required average optical power and the bandwidth is investigated. At low bandwidths, the most power- efficient transmission is obtained by either the parametric linear pulse or the so-called “better than Nyquist” pulse, depending on the exact bandwidth
Bandlimited Intensity Modulation
In this paper, the design and analysis of a new bandwidth-efficient signaling
method over the bandlimited intensity-modulated direct-detection (IM/DD)
channel is presented. The channel can be modeled as a bandlimited channel with
nonnegative input and additive white Gaussian noise (AWGN). Due to the
nonnegativity constraint, standard methods for coherent bandlimited channels
cannot be applied here. Previously established techniques for the IM/DD channel
require bandwidth twice the required bandwidth over the conventional coherent
channel. We propose a method to transmit without intersymbol interference in a
bandwidth no larger than the bit rate. This is done by combining Nyquist or
root-Nyquist pulses with a constant bias and using higher-order modulation
formats. In fact, we can transmit with a bandwidth equal to that of coherent
transmission. A trade-off between the required average optical power and the
bandwidth is investigated. Depending on the bandwidth required, the most
power-efficient transmission is obtained by the parametric linear pulse, the
so-called "better than Nyquist" pulse, or the root-raised cosine pulse.Comment: 28 pages 10 Figure
The Impact of Polarization-Dependent Loss on the Constant Modulus Algorithm for Varying Number of Fiber Spans Based on an Outage Criterion
We investigate the effect of polarization-dependent loss (PDL) on the constant modulus algorithm (CMA) in 4-QAM and 16-QAM polarization multiplexed (PolMux) systems with varying number of fiber spans and different PDL values. To quantify this effect, outage probability is introduced as the probability of having a signal-to-noise ratio (SNR) degradation smaller than 1 dB 99% of the time. We observe that by increasing the number of fiber spans, the SNR penalty for CMA reaches a limiting value. Moreover, in the 16-QAM multi-span case, the effect of PDL on CMA depends on the amount of PDL, while for 4-QAM, the effect of PDL on CMA is insensitive to the amount of PDL. These results will provide guidelines for designing systems and adjusting transmission power