3,910 research outputs found
On the Maximum Achievable Sum-Rate of Interfering Two-Way Relay Channels
Hierarchical networks can provide very high data rates to multiple mobile stations (MSs) through a dense network of fixed relay nodes (RNs) fed by few hub base stations (HBSs). In order to achieve high spectral efficiencies RNs can act as two-way RNs. However the dense RN deployment gives rise to high co-channel interference (CCI) that limits sum-rate performance. In this letter we consider a simple hierarchical network consisting of an HBS with two highly directional antennas communicating with two MSs via two interfering two-way RNs. To mitigate CCI and boost sum-rates we propose a two-way relaying strategy based on AF combined with Network MIMO processing which is applied over the concatenation of the backhaul and access network channels. We compare our proposed strategy with a baseline DF approach and we show that it performs significantly better when CCI is dominant
Interference Alignment for Cognitive Radio Communications and Networks: A Survey
© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).Interference alignment (IA) is an innovative wireless transmission strategy that has shown to be a promising technique for achieving optimal capacity scaling of a multiuser interference channel at asymptotically high-signal-to-noise ratio (SNR). Transmitters exploit the availability of multiple signaling dimensions in order to align their mutual interference at the receivers. Most of the research has focused on developing algorithms for determining alignment solutions as well as proving interference alignment’s theoretical ability to achieve the maximum degrees of freedom in a wireless network. Cognitive radio, on the other hand, is a technique used to improve the utilization of the radio spectrum by opportunistically sensing and accessing unused licensed frequency spectrum, without causing harmful interference to the licensed users. With the increased deployment of wireless services, the possibility of detecting unused frequency spectrum becomes diminished. Thus, the concept of introducing interference alignment in cognitive radio has become a very attractive proposition. This paper provides a survey of the implementation of IA in cognitive radio under the main research paradigms, along with a summary and analysis of results under each system model.Peer reviewe
Interference Channel with a Half-Duplex Out-of-Band Relay
A Gaussian interference channel (IC) aided by a half-duplex relay is
considered, in which the relay receives and transmits in an orthogonal band
with respect to the IC. The system thus consists of two parallel channels, the
IC and the channel over which the relay is active, which is referred to as
Out-of-Band Relay Channel (OBRC). The OBRC is operated by separating a multiple
access phase from the sources to the relay and a broadcast phase from the relay
to the destinations. Conditions under which the optimal operation, in terms of
the sum-capacity, entails either signal relaying and/or interference forwarding
by the relay are identified. These conditions also assess the optimality of
either separable or non-separable transmission over the IC and OBRC.
Specifically, the optimality of signal relaying and separable coding is
established for scenarios where the relay-to-destination channels set the
performance bottleneck with respect to the source-to-relay channels on the
OBRC. Optimality of interference forwarding and non-separable operation is also
established in special cases.Comment: 5 pages, 5 figures, to appear in Proceedings of IEEE ISIT 201
Relays for Interference Mitigation in Wireless Networks
Wireless links play an important role in the last mile network connectivity. In contrast to the strictly centralized approach of today's wireless systems, the future promises decentralization of network management. Nodes potentially engage in localized grouping and organization based on their neighborhood to carry out complex goals such as end-to-end communication. The quadratic energy dissipation of the wireless medium necessitates the presence of certain relay nodes in the network. Conventionally, the role of such relays is limited to passing messages in a chain in a point-point hopping architecture. With the decentralization, multiple nodes could potentially interfere with each other. This work proposes a technique to exploit the presence of relays in a way that mitigates interference between the network nodes. Optimal spatial locations and transmission schemes which enhance this gain are identified
On the Capacity Region of the Two-user Interference Channel with a Cognitive Relay
This paper considers a variation of the classical two-user interference
channel where the communication of two interfering source-destination pairs is
aided by an additional node that has a priori knowledge of the messages to be
transmitted, which is referred to as the it cognitive relay. For this
Interference Channel with a Cognitive Relay (ICCR) In particular, for the class
of injective semi-deterministic ICCRs, a sum-rate upper bound is derived for
the general memoryless ICCR and further tightened for the Linear Deterministic
Approximation (LDA) of the Gaussian noise channel at high SNR, which disregards
the noise and focuses on the interaction among the users' signals. The capacity
region of the symmetric LDA is completely characterized except for the regime
of moderately weak interference and weak links from the CR to the destinations.
The insights gained from the analysis of the LDA are then translated back to
the symmetric Gaussian noise channel (GICCR). For the symmetric GICCR, an
approximate characterization (to within a constant gap) of the capacity region
is provided for a parameter regime where capacity was previously unknown. The
approximately optimal scheme suggests that message cognition at a relay is
beneficial for interference management as it enables simultaneous over the air
neutralization of the interference at both destinations
Distributed Full-duplex via Wireless Side Channels: Bounds and Protocols
In this paper, we study a three-node full-duplex network, where a base
station is engaged in simultaneous up- and downlink communication in the same
frequency band with two half-duplex mobile nodes. To reduce the impact of
inter- node interference between the two mobile nodes on the system capacity,
we study how an orthogonal side-channel between the two mobile nodes can be
leveraged to achieve full-duplex-like multiplexing gains. We propose and
characterize the achievable rates of four distributed full-duplex schemes,
labeled bin-and- cancel, compress-and-cancel, estimate-and-cancel and decode-
and-cancel. Of the four, bin-and-cancel is shown to achieve within 1 bit/s/Hz
of the capacity region for all values of channel parameters. In contrast, the
other three schemes achieve the near-optimal performance only in certain
regimes of channel values. Asymptotic multiplexing gains of all proposed
schemes are derived to show that the side-channel is extremely effective in
regimes where inter-node interference has the highest impact.Comment: Published in IEEE Transactions on Wireless Communications, August
201
Resource Allocation for Energy-Efficient 3-Way Relay Channels
Throughput and energy efficiency in 3-way relay channels are studied in this
paper. Unlike previous contributions, we consider a circular message exchange.
First, an outer bound and achievable sum rate expressions for different
relaying protocols are derived for 3-way relay channels. The sum capacity is
characterized for certain SNR regimes. Next, leveraging the derived achievable
sum rate expressions, cooperative and competitive maximization of the energy
efficiency are considered. For the cooperative case, both low-complexity and
globally optimal algorithms for joint power allocation at the users and at the
relay are designed so as to maximize the system global energy efficiency. For
the competitive case, a game theoretic approach is taken, and it is shown that
the best response dynamics is guaranteed to converge to a Nash equilibrium. A
power consumption model for mmWave board-to-board communications is developed,
and numerical results are provided to corroborate and provide insight on the
theoretical findings.Comment: Submitted to IEEE Transactions on Wireless Communication
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