1,870 research outputs found
Simultaneous Transmission and Reception: Algorithm, Design and System Level Performance
Full Duplex or Simultaneous transmission and reception (STR) in the same
frequency at the same time can potentially double the physical layer capacity.
However, high power transmit signal will appear at receive chain as echoes with
powers much higher than the desired received signal. Therefore, in order to
achieve the potential gain, it is imperative to cancel these echoes. As these
high power echoes can saturate low noise amplifier (LNA) and also digital
domain echo cancellation requires unrealistically high resolution
analog-to-digital converter (ADC), the echoes should be cancelled or suppressed
sufficiently before LNA. In this paper we present a closed-loop echo
cancellation technique which can be implemented purely in analogue domain. The
advantages of our method are multiple-fold: it is robust to phase noise, does
not require additional set of antennas, can be applied to wideband signals and
the performance is irrelevant to radio frequency (RF) impairments in transmit
chain. Next, we study a few protocols for STR systems in carrier sense multiple
access (CSMA) network and investigate MAC level throughput with realistic
assumptions in both single cell and multiple cells. We show that STR can reduce
hidden node problem in CSMA network and produce gains of up to 279% in maximum
throughput in such networks. Finally, we investigate the application of STR in
cellular systems and study two new unique interferences introduced to the
system due to STR, namely BS-BS interference and UE-UE interference. We show
that these two new interferences will hugely degrade system performance if not
treated appropriately. We propose novel methods to reduce both interferences
and investigate the performances in system level.Comment: 20 pages. This manuscript will appear in the IEEE Transactions on
Wireless Communication
Joint Design of Multi-Tap Analog Cancellation and Digital Beamforming for Reduced Complexity Full Duplex MIMO Systems
Incorporating full duplex operation in Multiple Input Multiple Output (MIMO)
systems provides the potential of boosting throughput performance. However, the
hardware complexity of the analog self-interference canceller scales with the
number of transmit and receive antennas, thus exploiting the benefits of analog
cancellation becomes impractical for full duplex MIMO transceivers. In this
paper, we present a novel architecture for the analog canceller comprising of
reduced number of taps (tap refers to a line of fixed delay and variable phase
shifter and attenuator) and simple multiplexers for efficient signal routing
among the transmit and receive radio frequency chains. In contrast to the
available analog cancellation architectures, the values for each tap and the
configuration of the multiplexers are jointly designed with the digital
beamforming filters according to certain performance objectives. Focusing on a
narrowband flat fading channel model as an example, we present a general
optimization framework for the joint design of analog cancellation and digital
beamforming. We also detail a particular optimization objective together with
its derived solution for the latter architectural components. Representative
computer simulation results demonstrate the superiority of the proposed low
complexity full duplex MIMO system over lately available ones.Comment: 8 pages, 4 figures, IEEE ICC 201
An Analog Baseband Approach for Designing Full-Duplex Radios
Recent wireless testbed implementations have proven that full-duplex
communication is in fact possible and can outperform half-duplex systems. Many
of these implementations modify existing half-duplex systems to operate in
full-duplex. To realize the full potential of full-duplex, radios need to be
designed with self-interference in mind. In our work, we use an experimental
setup with a patch antenna prototype to characterize the self-interference
channel between two radios. In doing so, we form an analytical model to design
analog baseband cancellation techniques. We show that our cancellation scheme
can provide up to 10 dB improved signal strength, 2.5 bps/Hz increase in rate,
and a 10,000 improvement in BER as compared to the RF only cancellation
provided by the patch antenna.Comment: 5 pages, 8 figures, to appear in 2013 Asilomar Conference proceeding
Wideband Self-Adaptive RF Cancellation Circuit for Full-Duplex Radio: Operating Principle and Measurements
This paper presents a novel RF circuit architecture for self-interference
cancellation in inband full-duplex radio transceivers. The developed canceller
is able to provide wideband cancellation with waveform bandwidths in the order
of 100 MHz or beyond and contains also self-adaptive or self-healing features
enabling automatic tracking of time-varying self-interference channel
characteristics. In addition to architecture and operating principle
descriptions, we also provide actual RF measurements at 2.4 GHz ISM band
demonstrating the achievable cancellation levels with different bandwidths and
when operating in different antenna configurations and under low-cost highly
nonlinear power amplifier. In a very challenging example with a 100 MHz
waveform bandwidth, around 41 dB total cancellation is obtained while the
corresponding cancellation figure is close to 60 dB with the more conventional
20 MHz carrier bandwidth. Also, efficient tracking in time-varying reflection
scenarios is demonstrated.Comment: 7 pages, to be presented in 2015 IEEE 81st Vehicular Technology
Conferenc
Half-Duplex or Full-Duplex Relaying: A Capacity Analysis under Self-Interference
In this paper multi-antenna half-duplex and full-duplex relaying are compared
from the perspective of achievable rates. Full-duplexing operation requires
additional resources at the relay such as antennas and RF chains for
self-interference cancellation. Using a practical model for the residual
self-interference, full-duplex achievable rates and degrees of freedom are
computed for the cases for which the relay has the same number of antennas or
the same number of RF chains as in the half-duplex case, and compared with
their half-duplex counterparts. It is shown that power scaling at the relay is
necessary to maximize the the degrees of freedom in the full-duplex mode.Comment: New references added and some typos have been corrected. 6 Pages, 5
Figures. Accepted for publication in the CISS-201
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