1,996 research outputs found
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Novel digital radio over fibre for 4G-LTE
Digital radio over fibre (RoF) technology has been
suggested as a promising solution to replace conventional
analogue RoF technology for multi-service in-building wireless
coverage. However in conventional digital RoF, digitisation leads
to high data rates which in turn results in high capital
expenditure (CAPEX) and operational expenditure (OPEX). This
paper investigates a novel methodology to transmit efficiently a
digitised radio service over an optical link to provide wireless
coverage. We demonstrate a digital processing technique that is
able to compress the digitised 20MHz bandwidth Long Term
Evolution (LTE) data stream to a much lower level than in a
conventional link without impairing its radio performance.This work is supported by Engineering and Physical Sciences Research Council (EPSRC) via the Digital Distributed Antenna System (DDAS) project and Beijing Institute of Aerospace Control Devices (BIACD), a subsidiary institute of China Academy of Aerospace Electronics Technology (CAAET) via the Smart In-building Wireless System using Flexible Transmission Technology (SWIFT) project.This is the author accepted manuscript. The final version is available from IEEE via http://dx.doi.org/10.1109/ICCW.2015.724719
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Bandwidth studies on multimode polymer waveguides for ≥ 25 Gb/s optical interconnects
Multimode polymer waveguides constitute a promising technology for use in board-level optical interconnects. However, the continuous improvements in high-speed performance of VCSELs raise important questions about their ability to support such high data rates due to their inherent highly-multimoded nature. Thorough experimental studies on the bandwidth of a 1.4 m long multimode spiral waveguide are presented in this paper, indicating a bandwidth-length product of at least 35 GHz×m even in the case of an overfilled launch. No significant transmission impairments are observed for spatial input offsets, while error-free (BER<10⁻¹²) data transmission over the 1.4 m long spiral waveguide is demonstrated at 25 Gb/s.This is the final version of the article. It first appeared from IEEE Photonics Technology Letters via http://dx.doi.org/10.1109/LPT.2014.2342881. © © 2014 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works
Reduction of Proximity Effects on UHF Passive RFID Systems by Using Tags with Polarization Diversity
A new technique that enables passive ultra high fre-
quency (UHF) radio frequency identification (RFID) tags to be
read when they are placed in close proximity in an array is pre-
sented. This paper demonstrates that, in a linear tag array with
a tag separation of 1 cm, the interaction between the backscat-
tered waves and incident wave causes a significant degradation in
tag sensitivity. It is found that the use of tags that have polariza-
tion diversity can improve the read performance when they are
placed in close proximity to one another compared with conven-
tional linear tags. Two ways of achieving polarization diversity are
studied in this paper, namely: 1) using a circularly polarized tag
and 2) using a cross-polarized tag pair. Both methods show an
improvement in close proximity read performance and it is exper-
imentally demonstrated that by using cross-polarized tag pairs in
an array, one achieves on average a 2.6-dB increase in read power
margin for a 57-tag array with 1 cm separation compared with
using conventional linearly polarized tags.This work has been supported by UK Engineering and
Physical Science Research Council
via the COPOSII project.This is the final published version. It first appeared at http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7042269
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High-bandwidth and low-loss multimode polymer waveguides and waveguide components for high-speed board-level optical interconnects
Multimode polymer waveguides are being increasingly considered for use in short-reach board-level optical interconnects as they exhibit favourable optical properties and allow direct integration onto standard PCBs with conventional methods of the electronics industry. Siloxane-based multimode waveguides have been demonstrated with excellent optical transmission performance, while a wide range of passive waveguide components that offer routing flexibility and enable the implementation of complex on-board interconnection architectures has been reported. In recent work, we have demonstrated that these polymer waveguides can exhibit very high bandwidth-length products in excess of 30 GHz×m despite their highly-multimoded nature, while it has been shown that even larger values of > 60 GHz×m can be achieved by adjusting their refractive index profile. Furthermore, the combination of refractive index engineering and launch conditioning schemes can ensure high bandwidth (> 100 GHz×m) and high coupling efficiency (< 1 dB) with standard multimode fibre inputs with relatively large alignment tolerances (~17×15 μm^2 ). In the work presented here, we investigate the effects of refractive index engineering on the performance of passive waveguide components (crossings, bends) and provide suitable design rules for their on-board use. It is shown that, depending on the interconnection layout and link requirements, appropriate choice of refractive index profile can provide enhanced component performance, ensuring low loss interconnection and adequate link bandwidth. The results highlight the strong potential of this versatile optical technology for the formation of high-performance board-level optical interconnects with high routing flexibility.The authors would like to acknowledge Dow Corning for the provision of the polymer samples and the UK EPSRC for supporting this work . Additional data related to this publication is available at the University of Cambridge data repository ( https://www.repository.cam.ac.uk/handle/1810/253542).This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by SPIE
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Low-Cost MIMO radio over fiber system for multiservice das using double sideband frequency translation
In this paper, a novel low-cost DSB frequency translation system is experimentally demonstrated and its theory is mathematically proved. The new system is capable of transmitting wideband LTE MIMO signals and supporting multiple services. Experimentally, 2×2 LTE MIMO channels with 20MHz bandwidth, and a 700MHz carrier frequency, are transmitted simultaneously along with an IEEE 802.11g signal (54Mbps) over a 300m length of multi-mode fiber (MMF). The MIMO channel matrix of the system is retrieved and the condition number is calculated. It can be seen in the experimental results that the system is well conditioned, has a low error vector magnitude (EVM) and the transmission of the MIMO signals has negligible effect on the IEEE 802.11g signal. The use of a preamplifier minimizes the non-linearity introduced by the frequency mixers, resulting in a high spurious-free dynamic range (SFDR). Compared to a single sideband (SSB) system, where multiple filters are used and two channels encounter different EVMs, the new DSB system avoids unnecessary filtering and the impairments introduced will be the same for both channels. Therefore it can be concluded that the improved MIMO over fiber system using DSB frequency translation technology is a potential low-cost solution for multiservice MIMO-enabled distributed antenna systems (DAS).This work was supported in part of the UK Engineering and Physical Sciences Research Council via the COPOS II grant and the European Community via the FP7 programme Quaternian project.This is the author accepted manuscript. The final version is available from IEEE via http://dx.doi.org/10.1109/JLT.2016.258208
Power margin reduction in linear passive UHF RFID tag arrays
This paper studies the power margin reduction
in linear passive UHF RFID tag arrays due to proximity effects.
It is shown experimentally that a 40% reduction in tag power
margin occurs when two tags are placed with a separation of
less than 2cm. Major causes of tag sensitivity degradation due
to proximity in arrays are analyzed by experiment and
simulation, including tag detuning, shadowing and re-emission
cancellation. It is shown that tag detuning has a significant
effect when tags are separated by less than 7mm. At larger
separations in excess of 1cm, the tag shadowing effect and
interactions between the backscattered waves cause more
significant degradation for large tag arrays.This work has been supported by UK Engineering and
Physical Science Research Council via the COPOSII project.This is the author accepted manuscript. The final version is available at http://ieeexplore.ieee.org/xpl/articleDetails.jsp?reload=true&arnumber=6934248
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Experimental comparison of antenna clustering strategies in MIMO distributed antenna systems
In this paper the effect of partitioning arrays of transmitting antennas into spatially separated clusters on the condition number and capacity of MIMO wireless systems is examined using experimental channel measurements of an indoor MIMO-enabled distributed antenna system (DAS). It is first shown for a 3 _ 2 MIMO system that distributing the transmit antennas into spatially separated clusters provides an improvement in channel conditioning (_1dB) and hence capacity, in line with previous findings. Next, a configuration with 6 transmit antennas and 2 receive antennas is examined and it is found that when it is operated as a 6 _ 2 MIMO system, it makes negligible difference to the conditioning of the channel whether the transmit antennas are grouped into 3 clusters of 2 antennas or 2 clusters of 3 antennas. The capacity varies by only a small amount (_%1) between the two clustering schemes, which can be accounted for by environment-specific signal-tonoise ratio (SNR) effects. It is then concluded that for the two typical indoor DAS scenarios tested here, if sufficient transmit diversity is provided (i.e. there are a relatively large number of transmit antennas compared to receive antennas), greater spatial distribution through increased clustering provides diminishing performance improvements. Given the typically lower installation cost of less distributed arrangements, they may then be a preferred option in commercial DAS deployments.This is the author accepted manuscript. The final version is available from IEEE via http://dx.doi.org/10.1109/VTCFall.2014.696597
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SPAD-Array Contention Signal and Noise Model Suitable for Multilevel Modulation Schemes with Signal Processing
The first signal model for a single photon avalanche diode (SPAD)-array communication receiver for multilevel modulation schemes is reported. This paper proposes a novel, generalised SPAD array signal and noise model for both digital and analogue, synchronous and asynchronous SPAD readout arrays, which includes the competition between the input photons, dark counts and after-pulsing counts. With this contention signal and noise model, multilevel signals including the signal variation after distortion or equalisation can be evaluated. Also, we report the first numerical investigation for SPAD-based, high data rate, free space, visible light communication using higher order pulse amplitude modulation (PAM) with matched filter, linear and non-linear Volterra post-equalization. Simulations have been carried out to analyze and compare the bit error rate (BER) performances under a variety of conditions. The model is
verified by comparison with published experimental results.UK EPSRC via the TOWS project (EP/S016570/1
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RFID Enabled Health Monitoring System for Aircraft Landing Gear
RFID has been used in the aviation industry to track and identify emergency equipment and other in-cabin assets on commercial aircraft for some time. Recently, the industry is looking to expand the use of RFID to more demanding parts and surfaces both inside and outside of an aircraft’s cabin, where RFID tags face much harsher conditions. The lLanding gear (LG) is one of the critical subsystems of an aircraft that plays an essential role in dispersing the energy of landing events and taxiing. Health monitoring of the LG has been suggested to help reduce both operational and maintenance costs, and extend the life of the LG beyond its current, fixed, designed service life. In this paper, we propose such a health monitoring system using a combination of active wired sensors and passive RFID tags. We present the measurement of UHF RFID tags on an aircraft landing gear using an aircraft-mounted fixed RFID reader. The results indicate that all major landing gear components and assemblies are shown to be identifiable by their EPC, and a 7 dB system margin has been achieved using 2 RFID reader antennas. Such a margin will tolerate degradations caused by harsh environments (e.g. low temperatures and high humidity) and enable update of information (e.g. flight count) to be stored on the RFID tags
Advanced photonic routing sub-systems with efficient routing control
In recent years, there has been much interest in the development of optical switches which can route optical signals from different input guides to different outputs based on thermo-optic and electro-optic technologies. Such switches, which can be reconfigured on millisecond and microsecond timescales, have already attracted commercial interest. However switches which are able to reconfigure on the nanosecond timescales required for packet switching have been more challenging and only in recent years, have router concepts been devised to allow lossless routers to be constructed able to switch on nanosecond timescales with more than 16×16 ports. This paper will therefore review the advances that have occurred to allow such operation and then describe recent studies that have begun to determine the electronic control and functionality required to enable full and practical operation of such switches in high performance networks.This research has received funding from the UK Engineering and Physical Sciences Research Council through the INTERNET Project, STAR and COPOS II grants and the European Commission under FP7 grant agreement ICT 257210 PARADIGM.This is the author accepted manuscript. The final version is available from IEEE via http://dx.doi.org/10.1109/ICTON.2015.719339
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