11,141 research outputs found
Increasing Achievable Information Rates via Geometric Shaping
Achievable information rates are used as a metric to design novel modulation
formats via geometric shaping. The proposed geometrically shaped 256-ary
constellation achieves SNR gains of up to 1.18 dB.Comment: Additional references have been adde
Probabilistic Eigenvalue Shaping for Nonlinear Fourier Transform Transmission
We consider a nonlinear Fourier transform (NFT)-based transmission scheme,
where data is embedded into the imaginary part of the nonlinear discrete
spectrum. Inspired by probabilistic amplitude shaping, we propose a
probabilistic eigenvalue shaping (PES) scheme as a means to increase the data
rate of the system. We exploit the fact that for an NFT-based transmission
scheme the pulses in the time domain are of unequal duration by transmitting
them with a dynamic symbol interval and find a capacity-achieving distribution.
The PES scheme shapes the information symbols according to the
capacity-achieving distribution and transmits them together with the parity
symbols at the output of a low-density parity-check encoder, suitably
modulated, via time-sharing. We furthermore derive an achievable rate for the
proposed PES scheme. We verify our results with simulations of the
discrete-time model as well as with split-step Fourier simulations.Comment: Published in IEEE/OSA Journal of Lightwave Technology, 201
Constellation Shaping for WDM systems using 256QAM/1024QAM with Probabilistic Optimization
In this paper, probabilistic shaping is numerically and experimentally
investigated for increasing the transmission reach of wavelength division
multiplexed (WDM) optical communication system employing quadrature amplitude
modulation (QAM). An optimized probability mass function (PMF) of the QAM
symbols is first found from a modified Blahut-Arimoto algorithm for the optical
channel. A turbo coded bit interleaved coded modulation system is then applied,
which relies on many-to-one labeling to achieve the desired PMF, thereby
achieving shaping gain. Pilot symbols at rate at most 2% are used for
synchronization and equalization, making it possible to receive input
constellations as large as 1024QAM. The system is evaluated experimentally on a
10 GBaud, 5 channels WDM setup. The maximum system reach is increased w.r.t.
standard 1024QAM by 20% at input data rate of 4.65 bits/symbol and up to 75% at
5.46 bits/symbol. It is shown that rate adaptation does not require changing of
the modulation format. The performance of the proposed 1024QAM shaped system is
validated on all 5 channels of the WDM signal for selected distances and rates.
Finally, it was shown via EXIT charts and BER analysis that iterative
demapping, while generally beneficial to the system, is not a requirement for
achieving the shaping gain.Comment: 10 pages, 12 figures, Journal of Lightwave Technology, 201
Nomographic Functions: Efficient Computation in Clustered Gaussian Sensor Networks
In this paper, a clustered wireless sensor network is considered that is
modeled as a set of coupled Gaussian multiple-access channels. The objective of
the network is not to reconstruct individual sensor readings at designated
fusion centers but rather to reliably compute some functions thereof. Our
particular attention is on real-valued functions that can be represented as a
post-processed sum of pre-processed sensor readings. Such functions are called
nomographic functions and their special structure permits the utilization of
the interference property of the Gaussian multiple-access channel to reliably
compute many linear and nonlinear functions at significantly higher rates than
those achievable with standard schemes that combat interference. Motivated by
this observation, a computation scheme is proposed that combines a suitable
data pre- and post-processing strategy with a nested lattice code designed to
protect the sum of pre-processed sensor readings against the channel noise.
After analyzing its computation rate performance, it is shown that at the cost
of a reduced rate, the scheme can be extended to compute every continuous
function of the sensor readings in a finite succession of steps, where in each
step a different nomographic function is computed. This demonstrates the
fundamental role of nomographic representations.Comment: to appear in IEEE Transactions on Wireless Communication
LANDSAT D local user terminal study
The effect of the changes incorporated in the LANDSAT D system on the ability of a local user terminal to receive, record and process data in real time was studied. Alternate solutions to the problems raised by these changes were evaluated. A loading analysis was performed in order to determine the quantities of data that a local user terminal (LUT) would be interested in receiving and processing. The number of bits in an MSS and a TM scene were calculated along with the number of scenes per day that an LUT might require for processing. These then combined to a total number of processed bits/day for an LUT as a function of sensor and coverage circle radius
Probabilistic Shaping for Finite Blocklengths: Distribution Matching and Sphere Shaping
In this paper, we provide for the first time a systematic comparison of
distribution matching (DM) and sphere shaping (SpSh) algorithms for short
blocklength probabilistic amplitude shaping. For asymptotically large
blocklengths, constant composition distribution matching (CCDM) is known to
generate the target capacity-achieving distribution. As the blocklength
decreases, however, the resulting rate loss diminishes the efficiency of CCDM.
We claim that for such short blocklengths and over the additive white Gaussian
channel (AWGN), the objective of shaping should be reformulated as obtaining
the most energy-efficient signal space for a given rate (rather than matching
distributions). In light of this interpretation, multiset-partition DM (MPDM),
enumerative sphere shaping (ESS) and shell mapping (SM), are reviewed as
energy-efficient shaping techniques. Numerical results show that MPDM and SpSh
have smaller rate losses than CCDM. SpSh--whose sole objective is to maximize
the energy efficiency--is shown to have the minimum rate loss amongst all. We
provide simulation results of the end-to-end decoding performance showing that
up to 1 dB improvement in power efficiency over uniform signaling can be
obtained with MPDM and SpSh at blocklengths around 200. Finally, we present a
discussion on the complexity of these algorithms from the perspective of
latency, storage and computations.Comment: 18 pages, 10 figure
Eight-dimensional Polarization-ring-switching Modulation Formats
We propose two 8-dimensional (8D) modulation formats (8D-2048PRS-T1 and
8D-2048PRS-T2) with a spectral efficiency of 5.5 bit/4D-sym, where the 8
dimensions are obtained from two time slots and two polarizations. Both formats
provide a higher tolerance to nonlinearity by selecting symbols with
nonidentical states of polarization (SOPs) in two time slots. The performance
of these novel 8D modulation formats is assessed in terms of the effective
signal-to-noise ratio (SNR) and normalized generalized mutual information.
8D-2048PRS-T1 is more suitable for high SNRs, while 8D-2048PRS-T2 is shown to
be more tolerant to nonlinearities. A sensitivity improvement of at least 0.25
dB is demonstrated by maximizing normalized generalized mutual information
(NGMI). For a long-haul nonlinear optical fiber transmission system, the
benefit of mitigating the nonlinearity is demonstrated and a reach increase of
6.7% (560 km) over time-domain hybrid four-dimensional two-amplitude
eight-phase shift keying (TDH-4D-2A8PSK) is observed
- …