2,847 research outputs found
Joint Relay Selection and Analog Network Coding using Differential Modulation in Two-Way Relay Channels
In this paper, we consider a general bi-directional relay network with two
sources and N relays when neither the source nodes nor the relays know the
channel state information (CSI). A joint relay selection and analog network
coding using differential modulation (RS-ANC-DM) is proposed. In the proposed
scheme, the two sources employ differential modulations and transmit the
differential modulated symbols to all relays at the same time. The signals
received at the relay is a superposition of two transmitted symbols, which we
call the analog network coded symbols. Then a single relay which has minimum
sum SER is selected out of N relays to forward the ANC signals to both sources.
To facilitate the selection process, in this paper we also propose a simple
sub-optimal Min-Max criterion for relay selection, where a single relay which
minimizes the maximum SER of two source nodes is selected. Simulation results
show that the proposed Min-Max selection has almost the same performance as the
optimal selection, but is much simpler. The performance of the proposed
RS-ANC-DM scheme is analyzed, and a simple asymptotic SER expression is
derived. The analytical results are verified through simulations.Comment: 20 pages, 7 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
Dispensing with channel estimation: differentially modulated cooperative wireless communications
As a benefit of bypassing the potentially excessive complexity and yet inaccurate channel estimation, differentially encoded modulation in conjunction with low-complexity noncoherent detection constitutes a viable candidate for user-cooperative systems, where estimating all the links by the relays is unrealistic. In order to stimulate further research on differentially modulated cooperative systems, a number of fundamental challenges encountered in their practical implementations are addressed, including the time-variant-channel-induced performance erosion, flexible cooperative protocol designs, resource allocation as well as its high-spectral-efficiency transceiver design. Our investigations demonstrate the quantitative benefits of cooperative wireless networks both from a pure capacity perspective as well as from a practical system design perspective
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 users’ 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
Relay Selection for Two-way Relaying with Amplify-and-Forward Protocols
In this paper, we propose a relay selection amplify-and-forward (RS-AF)
protocol in general bi-directional relay networks with two sources and
relays. In the proposed scheme, the two sources first transmit to all the
relays simultaneously, and then a single relay with a minimum sum symbol error
rate (SER) will be selected to broadcast the received signals back to both
sources. To facilitate the selection process, we propose a simple sub-optimal
Min-Max criterion for relay selection, where a single relay which minimizes the
maximum SER of two source nodes will be selected. Simulation results show that
the proposed Min-Max selection has almost the same performance as the optimal
selection with lower complexity. We also present a simple asymptotic SER
expression and make comparison with the conventional all-participate
amplify-and-forward (AP-AF) relaying scheme. The analytical results are
verified through simulations. To improve the system performance, optimum power
allocation (OPA) between the sources and the relay is determined based on the
asymptotic SER. Simulation results indicate that the proposed RS-AF scheme with
OPA yields considerable performance improvement over an equal power allocation
(EPA) scheme, specially with large number of relay nodes.Comment: 19 pages, 6 figure
- …