79,529 research outputs found
Energy Efficient Adaptive Network Coding Schemes for Satellite Communications
In this paper, we propose novel energy efficient adaptive network coding and
modulation schemes for time variant channels. We evaluate such schemes under a
realistic channel model for open area environments and Geostationary Earth
Orbit (GEO) satellites. Compared to non-adaptive network coding and adaptive
rate efficient network-coded schemes for time variant channels, we show that
our proposed schemes, through physical layer awareness can be designed to
transmit only if a target quality of service (QoS) is achieved. As a result,
such schemes can provide remarkable energy savings.Comment: Lecture Notes of the Institute for Computer Sciences, Social
Informatics and Telecommunications Engineering, 24 March 201
Adaptive Network Coding Schemes for Satellite Communications
In this paper, we propose two novel physical layer aware adaptive network
coding and coded modulation schemes for time variant channels. The proposed
schemes have been applied to different satellite communications scenarios with
different Round Trip Times (RTT). Compared to adaptive network coding, and
classical non-adaptive network coding schemes for time variant channels, as
benchmarks, the proposed schemes demonstrate that adaptation of packet
transmission based on the channel variation and corresponding erasures allows
for significant gains in terms of throughput, delay and energy efficiency. We
shed light on the trade-off between energy efficiency and delay-throughput
gains, demonstrating that conservative adaptive approaches that favors less
transmission under high erasures, might cause higher delay and less throughput
gains in comparison to non-conservative approaches that favor more transmission
to account for high erasures.Comment: IEEE Advanced Satellite Multimedia Systems Conference and the 14th
Signal Processing for Space Communications Workshop (ASMS/SPSC), 201
Performance Analysis of Adaptive Physical Layer Network Coding for Wireless Two-way Relaying
The analysis of modulation schemes for the physical layer network-coded two
way relaying scenario is presented which employs two phases: Multiple access
(MA) phase and Broadcast (BC) phase. It was shown by Koike-Akino et. al. that
adaptively changing the network coding map used at the relay according to the
channel conditions greatly reduces the impact of multiple access interference
which occurs at the relay during the MA phase. Depending on the signal set used
at the end nodes, deep fades occur for a finite number of channel fade states
referred as the singular fade states. The singular fade states fall into the
following two classes: The ones which are caused due to channel outage and
whose harmful effect cannot be mitigated by adaptive network coding are
referred as the \textit{non-removable singular fade states}. The ones which
occur due to the choice of the signal set and whose harmful effects can be
removed by a proper choice of the adaptive network coding map are referred as
the \textit{removable} singular fade states. In this paper, we derive an upper
bound on the average end-to-end Symbol Error Rate (SER), with and without
adaptive network coding at the relay, for a Rician fading scenario. It is shown
that without adaptive network coding, at high Signal to Noise Ratio (SNR), the
contribution to the end-to-end SER comes from the following error events which
fall as : the error events associated with the removable
singular fade states, the error events associated with the non-removable
singular fade states and the error event during the BC phase. In contrast, for
the adaptive network coding scheme, the error events associated with the
removable singular fade states contributing to the average end-to-end SER fall
as and as a result the adaptive network coding scheme
provides a coding gain over the case when adaptive network coding is not used.Comment: 10 pages, 5 figure
Pairwise Check Decoding for LDPC Coded Two-Way Relay Block Fading Channels
Partial decoding has the potential to achieve a larger capacity region than
full decoding in two-way relay (TWR) channels. Existing partial decoding
realizations are however designed for Gaussian channels and with a static
physical layer network coding (PLNC). In this paper, we propose a new solution
for joint network coding and channel decoding at the relay, called pairwise
check decoding (PCD), for low-density parity-check (LDPC) coded TWR system over
block fading channels. The main idea is to form a check relationship table
(check-relation-tab) for the superimposed LDPC coded packet pair in the
multiple access (MA) phase in conjunction with an adaptive PLNC mapping in the
broadcast (BC) phase. Using PCD, we then present a partial decoding method,
two-stage closest-neighbor clustering with PCD (TS-CNC-PCD), with the aim of
minimizing the worst pairwise error probability. Moreover, we propose the
minimum correlation optimization (MCO) for selecting the better
check-relation-tabs. Simulation results confirm that the proposed TS-CNC-PCD
offers a sizable gain over the conventional XOR with belief propagation (BP) in
fading channels.Comment: to appear in IEEE Trans. on Communications, 201
Truncated-ARQ aided adaptive network coding for cooperative two-way relaying networks: cross-layer design and analysis
Network Coding (NC) constitutes a promising technique of improving the throughput of relay-aided networks. In this context, we propose a cross-layer design for both amplifyand- forward (AF-) and decode-and-forward two-way relaying (DF-TWR) based on the NC technique invoked for improving the achievable throughput under specific Quality of Service (QoS) requirements, such as the maximum affordable delay and error rate.We intrinsically amalgamate adaptive Analog Network Coding (ANC) and Network Coded Modulation (NCM) with truncated Automatic Repeat reQuest (ARQ) operating at the different OSI layers. At the data-link layer, we design a pair of improved NC-based ARQ strategies based on the Stop-andwait and the Selective-repeat ARQ protocols. At the physical layer, adaptive ANC/NCM are invoked based on our approximate packet error ratio (PER). We demonstrate that the adaptive ANC design can be readily amalgamated with the proposed protocols. However, adaptive NC-QAM suffers from an SNR-loss, when the transmit rates of the pair of downlink (DL) channels spanning from the relay to the pair of destinations are different. Therefore we develop a novel transmission strategy for jointly selecting the optimal constellation sizes for both of the relay-to-destination links that have to be adapted to both pair of channel conditions. Finally, we analyze the attainable throughput, demonstrating that our truncated ARQ-aided adaptive ANC/NCM schemes attain considerable throughput gains over the schemes dispensing with ARQ, whilst our proposed scheme is capable of supporting bidirectional NC scenarios
Constellation Mapping for Physical-Layer Network Coding with M-QAM Modulation
The denoise-and-forward (DNF) method of physical-layer network coding (PNC)
is a promising approach for wireless relaying networks. In this paper, we
consider DNF-based PNC with M-ary quadrature amplitude modulation (M-QAM) and
propose a mapping scheme that maps the superposed M-QAM signal to coded
symbols. The mapping scheme supports both square and non-square M-QAM
modulations, with various original constellation mappings (e.g. binary-coded or
Gray-coded). Subsequently, we evaluate the symbol error rate and bit error rate
(BER) of M-QAM modulated PNC that uses the proposed mapping scheme. Afterwards,
as an application, a rate adaptation scheme for the DNF method of PNC is
proposed. Simulation results show that the rate-adaptive PNC is advantageous in
various scenarios.Comment: Final version at IEEE GLOBECOM 201
Space-Time Coded Spatial Modulated Physical Layer Network Coding for Two-Way Relaying
Using the spatial modulation approach, where only one transmit antenna is
active at a time, we propose two transmission schemes for two-way relay channel
using physical layer network coding with space time coding using Coordinate
Interleaved Orthogonal Designs (CIOD's). It is shown that using two
uncorrelated transmit antennas at the nodes, but using only one RF transmit
chain and space-time coding across these antennas can give a better performance
without using any extra resources and without increasing the hardware
implementation cost and complexity. In the first transmission scheme, two
antennas are used only at the relay, Adaptive Network Coding (ANC) is employed
at the relay and the relay transmits a CIOD Space Time Block Code (STBC). This
gives a better performance compared to an existing ANC scheme for two-way relay
channel which uses one antenna each at all the three nodes. It is shown that
for this scheme at high SNR the average end-to-end symbol error probability
(SEP) is upper bounded by twice the SEP of a point-to-point fading channel. In
the second transmission scheme, two transmit antennas are used at all the three
nodes, CIOD STBC's are transmitted in multiple access and broadcast phases.
This scheme provides a diversity order of two for the average end-to-end SEP
with an increased decoding complexity of for an arbitrary
signal set and for square QAM signal set.Comment: 9 pages, 7 figure
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