110,696 research outputs found
Signal Codes
Motivated by signal processing, we present a new class of channel codes,
called signal codes, for continuous-alphabet channels. Signal codes are lattice
codes whose encoding is done by convolving an integer information sequence with
a fixed filter pattern. Decoding is based on the bidirectional sequential stack
decoder, which can be implemented efficiently using the heap data structure.
Error analysis and simulation results indicate that signal codes can achieve
low error rate at approximately 1dB from channel capacity.Comment: Submitted to IEEE Transactions on Information Theor
Beamforming and Power Splitting Designs for AN-aided Secure Multi-user MIMO SWIPT Systems
In this paper, an energy harvesting scheme for a multi-user
multiple-input-multiple-output (MIMO) secrecy channel with artificial noise
(AN) transmission is investigated. Joint optimization of the transmit
beamforming matrix, the AN covariance matrix, and the power splitting ratio is
conducted to minimize the transmit power under the target secrecy rate, the
total transmit power, and the harvested energy constraints. The original
problem is shown to be non-convex, which is tackled by a two-layer
decomposition approach. The inner layer problem is solved through semi-definite
relaxation, and the outer problem, on the other hand, is shown to be a single-
variable optimization that can be solved by one-dimensional (1- D) line search.
To reduce computational complexity, a sequential parametric convex
approximation (SPCA) method is proposed to find a near-optimal solution. The
work is then extended to the imperfect channel state information case with
norm-bounded channel errors. Furthermore, tightness of the relaxation for the
proposed schemes are validated by showing that the optimal solution of the
relaxed problem is rank-one. Simulation results demonstrate that the proposed
SPCA method achieves the same performance as the scheme based on 1-D but with
much lower complexity.Comment: 12 pages, 6 figures, submitted for possible publicatio
Tracking A Dynamic Sparse Channel Via Differential Orthogonal Matching Pursuit
This paper considers the problem of tracking a dynamic sparse channel in a
broadband wireless communication system. A probabilistic signal model is
firstly proposed to describe the special features of temporal correlations of
dynamic sparse channels: path delays change slowly over time, while path gains
evolve faster. Based on such temporal correlations, we then propose the
differential orthogonal matching pursuit (D-OMP) algorithm to track a dynamic
sparse channel in a sequential way by updating the small channel variation over
time. Compared with other channel tracking algorithms, simulation results
demonstrate that the proposed D-OMP algorithm can track dynamic sparse channels
faster with improved accuracy.Comment: Conference: Milcom 2015 Track 1 - Waveforms and Signal Processing -
IEEE Military Communications Conference 201
A cross-uncorrelator-initializer for the super-exponential algorithms in multi-user environment
The super-exponential algorithms (SEAs) have potential to equalize a communication channel and to mitigate interference in a multi-user environment, and possess very fast (exponential) convergence rate. By considering the basic principle behind the development of SEA, we propose a novel initialization scheme based upon the null space of a cross-correlation matrix to prevent repeated retrieval of identical sources. A sequential signal-canceler based cascaded-equalizer structure is therefore not required. Simulation results support the proposed metho
Entanglement cost and quantum channel simulation
This paper proposes a revised definition for the entanglement cost of a
quantum channel . In particular, it is defined here to be the
smallest rate at which entanglement is required, in addition to free classical
communication, in order to simulate calls to , such that the
most general discriminator cannot distinguish the calls to
from the simulation. The most general discriminator is one who tests the
channels in a sequential manner, one after the other, and this discriminator is
known as a quantum tester [Chiribella et al., Phys. Rev. Lett., 101, 060401
(2008)] or one who is implementing a quantum co-strategy [Gutoski et al., Symp.
Th. Comp., 565 (2007)]. As such, the proposed revised definition of
entanglement cost of a quantum channel leads to a rate that cannot be smaller
than the previous notion of a channel's entanglement cost [Berta et al., IEEE
Trans. Inf. Theory, 59, 6779 (2013)], in which the discriminator is limited to
distinguishing parallel uses of the channel from the simulation. Under this
revised notion, I prove that the entanglement cost of certain
teleportation-simulable channels is equal to the entanglement cost of their
underlying resource states. Then I find single-letter formulas for the
entanglement cost of some fundamental channel models, including dephasing,
erasure, three-dimensional Werner--Holevo channels, epolarizing channels
(complements of depolarizing channels), as well as single-mode pure-loss and
pure-amplifier bosonic Gaussian channels. These examples demonstrate that the
resource theory of entanglement for quantum channels is not reversible.
Finally, I discuss how to generalize the basic notions to arbitrary resource
theories.Comment: 28 pages, 7 figure
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