9 research outputs found
A Unified Framework for Multi-Hop Wireless Relaying with Hardware Impairments
Relaying increases the coverage area and reliability of wireless
communications systems by mitigating the fading effect on the received signal.
Most technical contributions in the context of these systems assume ideal
hardware (ID) by neglecting the non-idealities of the transceivers, which
include phase noise, in-phase/quadrature mismatch and high power amplifier
nonlinearities. These non-idealities create distortion on the received signal
by causing variations in the phase and attenuating the amplitude. The resulting
deterioration of the performance of wireless communication systems is further
magnified as the frequency of transmission increases. In this paper, we
investigate the aggregate impact of hardware impairments (HI) on the general
multi-hop relay system using amplify-and-forward (AF) and decode-and-forward
(DF) relaying techniques over a general H-fading model. H-fading model includes
free space optics, radio frequency, millimeter wave, Terahertz, and underwater
fading models. Closed-form expressions of outage probability, bit error
probability and ergodic capacity are derived in terms of H-functions. Following
an asymptotic analysis at high signal-to-noise ratio (SNR), practical
optimization problems have been formulated with the objective of finding the
optimal level of HI subject to the limitation on the total HI level. The
analytical solution has been derived for the Nakagami-m fading channel which is
a special case of H-fading for AF and DF relaying techniques. The overall
instantaneous signal-to-noise-plus-distortion ratio has been demonstrated to
reach a ceiling at high SNRs which has a reciprocal proportion to the HI level
of all hops transceivers on the contrary to the ID.Comment: 16 pages, 10 figures, journal pape
Performance Analysis of Mixed FSO/RF System for Satellite-Terrestrial Relay Network
This paper analyzes the performance of a satellite-terrestrial free-space optical (FSO)/millimeter wave (MMW) radio frequency (RF) relaying system with amplify-and-forward (AF) and decode-and-forward (DF) relaying. The Málaga () distribution with pointing error impairments and the multi-cluster fluctuating two-ray (MFTR) fading model are introduced to characterize the FSO link for both heterodyne detection (HD) and indirect modulation/direct detection (IM/DD) and MMW link, respectively. Therefore, the precise closed-form expression of end-to-end signal-to-noise ratio (SNR) for the outage probability (OP), average bit error rate (BER), ergodic capacity (EC) and effective capacity (EFC) is derived. In addition, we present an asymptotical result analysis for the OP and average BER at high SNR in terms of simple functions. Finally, we employ Monte-Carlo (MC) simulation results to verify all our analytical results
1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface
A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance
Beam scanning by liquid-crystal biasing in a modified SIW structure
A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium