4 research outputs found
Full-Duplex Cognitive Radio: A New Design Paradigm for Enhancing Spectrum Usage
With the rapid growth of demand for ever-increasing data rate, spectrum
resources have become more and more scarce. As a promising technique to
increase the efficiency of the spectrum utilization, cognitive radio (CR)
technique has the great potential to meet such a requirement by allowing
un-licensed users to coexist in licensed bands. In conventional CR systems, the
spectrum sensing is performed at the beginning of each time slot before the
data transmission. This unfortunately results in two major problems: 1)
transmission time reduction due to sensing, and 2) sensing accuracy impairment
due to data transmission. To tackle these problems, in this paper we present a
new design paradigm for future CR by exploring the full-duplex (FD) techniques
to achieve the simultaneous spectrum sensing and data transmission. With FD
radios equipped at the secondary users (SUs), SUs can simultaneously sense and
access the vacant spectrum, and thus, significantly improve sensing
performances and meanwhile increase data transmission efficiency. The aim of
this article is to transform the promising conceptual framework into the
practical wireless network design by addressing a diverse set of challenges
such as protocol design and theoretical analysis. Several application scenarios
with FD enabled CR are elaborated, and key open research directions and novel
algorithms in these systems are discussed
Simultaneous Bidirectional Link Selection in Full Duplex MIMO Systems
In this paper, we consider a point to point full duplex (FD) MIMO
communication system. We assume that each node is equipped with an arbitrary
number of antennas which can be used for transmission or reception. With FD
radios, bidirectional information exchange between two nodes can be achieved at
the same time. In this paper we design bidirectional link selection schemes by
selecting a pair of transmit and receive antenna at both ends for
communications in each direction to maximize the weighted sum rate or minimize
the weighted sum symbol error rate (SER). The optimal selection schemes require
exhaustive search, so they are highly complex. To tackle this problem, we
propose a Serial-Max selection algorithm, which approaches the exhaustive
search methods with much lower complexity. In the Serial-Max method, the
antenna pairs with maximum "obtainable SINR" at both ends are selected in a
two-step serial way. The performance of the proposed Serial-Max method is
analyzed, and the closed-form expressions of the average weighted sum rate and
the weighted sum SER are derived. The analysis is validated by simulations.
Both analytical and simulation results show that as the number of antennas
increases, the Serial-Max method approaches the performance of the
exhaustive-search schemes in terms of sum rate and sum SER
How to Split UL/DL Antennas in Full-Duplex Cellular Networks
To further improve the potential of full-duplex communications, networks may
employ multiple antennas at the base station or user equipment. To this end,
networks that employ current radios usually deal with self-interference and
multi-user interference by beamforming techniques. Although previous works
investigated beamforming design to improve spectral efficiency, the fundamental
question of how to split the antennas at a base station between uplink and
downlink in full-duplex networks has not been investigated rigorously. This
paper addresses this question by posing antenna splitting as a binary nonlinear
optimization problem to minimize the sum mean squared error of the received
data symbols. It is shown that this is an NP-hard problem. This combinatorial
problem is dealt with by equivalent formulations, iterative convex
approximations, and a binary relaxation. The proposed algorithm is guaranteed
to converge to a stationary solution of the relaxed problem with much smaller
complexity than exhaustive search. Numerical results indicate that the proposed
solution is close to the optimal in both high and low self-interference capable
scenarios, while the usually assumed antenna splitting is far from optimal. For
large number of antennas, a simple antenna splitting is close to the proposed
solution. This reveals that the importance of antenna splitting is inversely
proportional with the number of antennas.Comment: 7 pages, 4 figures. Accepted to IEEE ICC 2018 Workshop on Full-Duplex
Communications for Future Wireless Network