416 research outputs found
A Coded Bit-Loading Linear Precoded Discrete Multitone Solution for Power Line Communication
Linear precoded discrete multitone modulation (LP-DMT) system has been
already proved advantageous with adaptive resource allocation algorithm in a
power line communication (PLC) context. In this paper, we investigate the bit
and energy allocation algorithm of an adaptive LP-DMT system taking into
account the channel coding scheme. A coded adaptive LP-DMT system is presented
in the PLC context with a loading algorithm which ccommodates the channel
coding gains in bit and energy calculations. The performance of a concatenated
channel coding scheme, consisting of an inner Wei's 4-dimensional 16-states
trellis code and an outer Reed-Solomon code, in combination with the roposed
algorithm is analyzed. Simulation results are presented for a fixed target bit
error rate in a multicarrier scenario under power spectral density constraint.
Using a multipath model of PLC channel, it is shown that the proposed coded
adaptive LP-DMT system performs better than classical coded discrete multitone
Optimal Linear Precoding Strategies for Wideband Non-Cooperative Systems based on Game Theory-Part I: Nash Equilibria
In this two-parts paper we propose a decentralized strategy, based on a
game-theoretic formulation, to find out the optimal precoding/multiplexing
matrices for a multipoint-to-multipoint communication system composed of a set
of wideband links sharing the same physical resources, i.e., time and
bandwidth. We assume, as optimality criterion, the achievement of a Nash
equilibrium and consider two alternative optimization problems: 1) the
competitive maximization of mutual information on each link, given constraints
on the transmit power and on the spectral mask imposed by the radio spectrum
regulatory bodies; and 2) the competitive maximization of the transmission
rate, using finite order constellations, under the same constraints as above,
plus a constraint on the average error probability. In Part I of the paper, we
start by showing that the solution set of both noncooperative games is always
nonempty and contains only pure strategies. Then, we prove that the optimal
precoding/multiplexing scheme for both games leads to a channel diagonalizing
structure, so that both matrix-valued problems can be recast in a simpler
unified vector power control game, with no performance penalty. Thus, we study
this simpler game and derive sufficient conditions ensuring the uniqueness of
the Nash equilibrium. Interestingly, although derived under stronger
constraints, incorporating for example spectral mask constraints, our
uniqueness conditions have broader validity than previously known conditions.
Finally, we assess the goodness of the proposed decentralized strategy by
comparing its performance with the performance of a Pareto-optimal centralized
scheme. To reach the Nash equilibria of the game, in Part II, we propose
alternative distributed algorithms, along with their convergence conditions.Comment: Paper submitted to IEEE Transactions on Signal Processing, September
22, 2005. Revised March 14, 2007. Accepted June 5, 2007. To be published on
IEEE Transactions on Signal Processing, 2007. To appear on IEEE Transactions
on Signal Processing, 200
On the Transport Capability of LAN Cables in All-Analog MIMO-RoC Fronthaul
Centralized Radio Access Network (C-RAN) architecture is the only viable
solution to handle the complex interference scenario generated by massive
antennas and small cells deployment as required by next generation (5G) mobile
networks. In conventional C-RAN, the fronthaul links used to exchange the
signal between Base Band Units (BBUs) and Remote Antenna Units (RAUs) are based
on digital baseband (BB) signals over optical fibers due to the huge bandwidth
required. In this paper we evaluate the transport capability of copper-based
all-analog fronthaul architecture called Radio over Copper (RoC) that leverages
on the pre-existing LAN cables that are already deployed in buildings and
enterprises. In particular, the main contribution of the paper is to evaluate
the number of independent BB signals for multiple antennas system that can be
transported over multi-pair Cat-5/6/7 cables under a predefined fronthauling
transparency condition in terms of maximum BB signal degradation. The MIMO-RoC
proves to be a complementary solution to optical fiber for the last 200m toward
the RAUs, mostly to reuse the existing LAN cables and to power-supply the RAUs
over the same cable
A near-optimal linear crosstalk precoder for downstream VDSL
This paper presents a linear crosstalk precoder for VDSL that has a low run-time complexity. A lower bound on the data-rate of the precoder is developed and guarantees that the precoder achieves near-optimal performance in 99% of VDSL channels
A Near-Optimal Linear Crosstalk Precoder for VDSL
Crosstalk is the major source of performance degradation in VDSL. In downstream transmission crosstalk precoding can be applied. The transmitted signal is predistorted, such that the predistortion annihilates with the crosstalk introduced in the binder. Several crosstalk precoders have been proposed. Unfortunately they either give poor performance or require non-linear operations, which results in a high complexity. In this paper we present a simple, linear diagonalizing crosstalk precoder with low run-time complexity. A lower bound on the performance of the DP is derived. This allows performance to be predicted without explicit knowledge of the crosstalk channels, which simplies service provisioning considerably. This bound shows that the DP operates close to the single-user bound. So the DP is a low complexity design with predictable, near-optimal performance. The combination of spectra optimization and crosstalk precoding is also considered. Spectra optimization in a broadcast channel generally involves a highly complex optimization problem. Since the DP decouples transmission on each line, the spectrum on each modem can be optimized through a dual decomposition, leading to a significant reduction in complexity
Ordered Tomlinson-Harashima Precoding in G.fast Downstream
G.fast is an upcoming next generation DSL standard envisioned to use
bandwidth up to 212 MHz. Far-end crosstalk (FEXT) at these frequencies greatly
overcomes direct links. Its cancellation based on non-linear
Tomlinson-Harashima Precoding (THP) proved to show significant advantage over
standard linear precoding. This paper proposes a novel THP structure in which
ordering of successive interference pre-cancellation can be optimized for
downstream with non-cooperating receivers. The optimized scheme is compared to
existing THP structure denoted as equal-rate THP which is widely adopted in
wireless downlink. Structure and performance of both methods differ
significantly favoring the proposed scheme. The ordering that maximizes the
minimum rate (max-min fairness) for each tone of the discrete multi-tone
modulation is the familiar V-BLAST ordering. However, V-BLAST does not lead to
the global maximum when applied independently on each tone. The proposed novel
Dynamic Ordering (DO) strategy takes into account asymmetric channel statistics
to yield the highest minimum aggregated rate.Comment: 7 pages, 11 figures, Accepted at the 2015 IEEE Globecom 2015,
Selected Areas in Communications: Access Networks and Systems, 6-10 December,
201
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