6,266 research outputs found
Maximum Euclidean distance network coded modulation for asymmetric decode-and-forward two-way relaying
Network coding (NC) compresses two traffic flows with the aid of low-complexity algebraic operations, hence holds the potential of significantly improving both the efficiency of wireless two-way relaying, where each receiver is collocated with a transmitter and hence has prior knowledge of the message intended for the distant receiver. In this contribution, network coded modulation (NCM) is proposed for jointly performing NC and modulation. As in classic coded modulation, the Euclidean distance between the symbols is maximised, hence the symbol error probability is minimised. Specifically, the authors first propose set-partitioning-based NCM as an universal concept which can be combined with arbitrary constellations. Then the authors conceive practical phase-shift keying/quadrature amplitude modulation (PSK/QAM) NCM schemes, referred to as network coded PSK/QAM, based on modulo addition of the normalised phase/amplitude. To achieve a spatial diversity gain at a low complexity, a NC oriented maximum ratio combining scheme is proposed for combining the network coded signal and the original signal of the source. An adaptive NCM is also proposed to maximise the throughput while guaranteeing a target bit error probability (BEP). Both theoretical performance analysis and simulations demonstrate that the proposed NCM can achieve at least 3 dB signal-to-noise ratio gain and two times diversity gain
Source and Physical-Layer Network Coding for Correlated Two-Way Relaying
In this paper, we study a half-duplex two-way relay channel (TWRC) with
correlated sources exchanging bidirectional information. In the case, when both
sources have the knowledge of correlation statistics, a source compression with
physical-layer network coding (SCPNC) scheme is proposed to perform the
distributed compression at each source node. When only the relay has the
knowledge of correlation statistics, we propose a relay compression with
physical-layer network coding (RCPNC) scheme to compress the bidirectional
messages at the relay. The closed-form block error rate (BLER) expressions of
both schemes are derived and verified through simulations. It is shown that the
proposed schemes achieve considerable improvements in both error performance
and throughput compared with the conventional non-compression scheme in
correlated two-way relay networks (CTWRNs).Comment: 15 pages, 6 figures. IET Communications, 201
Achieving full diversity in multi-antenna two-way relay networks via symbol-based physical-layer network coding
This paper considers physical-layer network coding (PNC) with M-ary phase-shift keying (MPSK) modulation in two-way relay channel (TWRC). A low complexity detection technique, termed symbol-based PNC (SPNC), is proposed for the relay. In particular, attributing to the outer product operation imposed on the superposed MPSK signals at the relay, SPNC obtains the network-coded symbol (NCS) straightforwardly without having to detect individual symbols separately. Unlike the optimal multi-user detector (MUD) which searches over the combinations of all usersâ modulation constellations, SPNC searches over only one modulation constellation, thus simplifies the NCS detection. Despite the reduced complexity, SPNC achieves full diversity in multi-antenna relay as the optimal MUD does. Specifically, antenna selection based SPNC (AS-SPNC) scheme and signal combining based SPNC (SC-SPNC) scheme are proposed. Our analysis of these two schemes not only confirms their full diversity performance, but also implies when SPNC is applied in multi-antenna relay, TWRC can be viewed as an effective single-input multiple-output (SIMO) system, in which AS-PNC and SC-PNC are equivalent to the general AS scheme and the maximal-ratio combining (MRC) scheme. Moreover, an asymptotic analysis of symbol error rate (SER) is provided for SC-PNC considering the case that the number of relay antennas is sufficiently large
STiCMAC: A MAC Protocol for Robust Space-Time Coding in Cooperative Wireless LANs
Relay-assisted cooperative wireless communication has been shown to have
significant performance gains over the legacy direct transmission scheme.
Compared with single relay based cooperation schemes, utilizing multiple relays
further improves the reliability and rate of transmissions. Distributed
space-time coding (DSTC), as one of the schemes to utilize multiple relays,
requires tight coordination between relays and does not perform well in a
distributed environment with mobility. In this paper, a cooperative medium
access control (MAC) layer protocol, called \emph{STiCMAC}, is designed to
allow multiple relays to transmit at the same time in an IEEE 802.11 network.
The transmission is based on a novel DSTC scheme called \emph{randomized
distributed space-time coding} (\emph{R-DSTC}), which requires minimum
coordination. Unlike conventional cooperation schemes that pick nodes with good
links, \emph{STiCMAC} picks a \emph{transmission mode} that could most improve
the end-to-end data rate. Any station that correctly receives from the source
can act as a relay and participate in forwarding. The MAC protocol is
implemented in a fully decentralized manner and is able to opportunistically
recruit relays on the fly, thus making it \emph{robust} to channel variations
and user mobility. Simulation results show that the network capacity and delay
performance are greatly improved, especially in a mobile environment.Comment: This paper is a revised version of a paper with the same name
submitted to IEEE Transaction on Wireless Communications. STiCMAC protocol
with RTS/CTS turned off is presented in the appendix of this draf
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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