116 research outputs found
EBG enhanced broadband dual antenna configuration for passive self-interference suppression in full-duplex communications
A full-duplex system is realised using dual EBG isolated rectangular spiral antennas and its performance is compared with the same full-duplex system using a circulator and a single spiral antenna element. The new antenna system consists of two antennas one with RHCP and the another one with LHCP implemented on a single substrate. Two columns of EBG is placed between the two antennas to improve the isolation. At the operating frequency of 3.2 GHz, the antenna configuration has nearly 31 dB isolation. For the identical baseband input power, the full-duplex system utilising dual spiral antenna configuration exhibits 9 dB higher isolation than the circulator based full-duplex system
AirSync: Enabling Distributed Multiuser MIMO with Full Spatial Multiplexing
The enormous success of advanced wireless devices is pushing the demand for
higher wireless data rates. Denser spectrum reuse through the deployment of
more access points per square mile has the potential to successfully meet the
increasing demand for more bandwidth. In theory, the best approach to density
increase is via distributed multiuser MIMO, where several access points are
connected to a central server and operate as a large distributed multi-antenna
access point, ensuring that all transmitted signal power serves the purpose of
data transmission, rather than creating "interference." In practice, while
enterprise networks offer a natural setup in which distributed MIMO might be
possible, there are serious implementation difficulties, the primary one being
the need to eliminate phase and timing offsets between the jointly coordinated
access points.
In this paper we propose AirSync, a novel scheme which provides not only time
but also phase synchronization, thus enabling distributed MIMO with full
spatial multiplexing gains. AirSync locks the phase of all access points using
a common reference broadcasted over the air in conjunction with a Kalman filter
which closely tracks the phase drift. We have implemented AirSync as a digital
circuit in the FPGA of the WARP radio platform. Our experimental testbed,
comprised of two access points and two clients, shows that AirSync is able to
achieve phase synchronization within a few degrees, and allows the system to
nearly achieve the theoretical optimal multiplexing gain. We also discuss MAC
and higher layer aspects of a practical deployment. To the best of our
knowledge, AirSync offers the first ever realization of the full multiuser MIMO
gain, namely the ability to increase the number of wireless clients linearly
with the number of jointly coordinated access points, without reducing the per
client rate.Comment: Submitted to Transactions on Networkin
Transmission Capacity of Full-Duplex MIMO Ad-Hoc Network with Limited Self-Interference Cancellation
In this paper, we propose a joint transceiver beamforming design to
simultaneously mitigate self-interference (SI) and partial inter-node
interference for full-duplex multiple-input and multiple-output ad-hoc network,
and then derive the transmission capacity upper bound (TC-UB) for the
corresponding network. Condition on a specified transceiver antenna's
configuration, we allow the SI effect to be cancelled at transmitter side, and
offer an additional degree-of-freedom at receiver side for more inter-node
interference cancellation. In addition, due to the proposed beamforming design
and imperfect SI channel estimation, the conventional method to obtain the
TC-UB is not applicable. This motivates us to exploit the dominating interferer
region plus Newton-Raphson method to iteratively formulate the TC-UB. The
results show that the derived TC-UB is quite close to the actual one especially
when the number of receive-antenna is small. Moreover, our proposed beamforming
design outperforms the existing beamforming strategies, and FD mode works
better than HD mode in low signal-to-noise ratio region.Comment: 7 pages, 4 figures, accepted by Globecom 201
Full-Duplex Cloud Radio Access Network: Stochastic Design and Analysis
Full-duplex (FD) has emerged as a disruptive communications paradigm for
enhancing the achievable spectral efficiency (SE), thanks to the recent major
breakthroughs in self-interference (SI) mitigation. The FD versus half-duplex
(HD) SE gain, in cellular networks, is however largely limited by the
mutual-interference (MI) between the downlink (DL) and the uplink (UL). A
potential remedy for tackling the MI bottleneck is through cooperative
communications. This paper provides a stochastic design and analysis of FD
enabled cloud radio access network (C-RAN) under the Poisson point process
(PPP)-based abstraction model of multi-antenna radio units (RUs) and user
equipments (UEs). We consider different disjoint and user-centric approaches
towards the formation of finite clusters in the C-RAN. Contrary to most
existing studies, we explicitly take into consideration non-isotropic fading
channel conditions and finite-capacity fronthaul links. Accordingly,
upper-bound expressions for the C-RAN DL and UL SEs, involving the statistics
of all intended and interfering signals, are derived. The performance of the FD
C-RAN is investigated through the proposed theoretical framework and
Monte-Carlo (MC) simulations. The results indicate that significant FD versus
HD C-RAN SE gains can be achieved, particularly in the presence of
sufficient-capacity fronthaul links and advanced interference cancellation
capabilities
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