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1. Photonic Networks-on-Chip Employing Multilevel Signaling: A Cross-Layer Comparative Study

   https://doi.org/10.1145/3487365  

   Karempudi, Venkata Sai ; Sunny, Febin ; Thakkar, Ishan G. ; Chittamuru, Sai Vineel ; Nikdast, Mahdi ; Pasricha, Sudeep ( July 2022 , ACM Journal on Emerging Technologies in Computing Systems)

   Photonic network-on-chip (PNoC) architectures employ photonic links with dense wavelength-division multiplexing (DWDM) to enable high throughput on-chip transfers. Unfortunately, increasing the DWDM degree (i.e., using a larger number of wavelengths) to achieve a higher aggregated data rate in photonic links and, hence, higher throughput in PNoCs, requires sophisticated and costly laser sources along with extra photonic hardware. This extra hardware can introduce undesired noise to the photonic link and increase the bit error rate (BER), power, and area consumption of PNoCs. To mitigate these issues, the use of 4-pulse amplitude modulation (4-PAM) signaling, instead of the conventional on-off keying (OOK) signaling, can halve the wavelength signals utilized in photonic links for achieving the target aggregate data rate while reducing the overhead of crosstalk noise, BER, and photonic hardware. There are various designs of 4-PAM modulators reported in the literature. For example, the signal superposition (SS)–, electrical digital-to-analog converter (EDAC)–, and optical digital-to-analog converter (ODAC)–based designs of 4-PAM modulators have been reported. However, it is yet to be explored how these SS-, EDAC-, and ODAC-based 4-PAM modulators can be utilized to design DWDM-based photonic links and PNoC architectures. In this article, we provide a systematic analysis of the SS, EDAC, andmore »ODAC types of 4-PAM modulators from prior work with regards to their applicability and utilization overheads. We then present a heuristic-based search method to employ these 4-PAM modulators for designing DWDM-based SS, EDAC, and ODAC types of 4-PAM photonic links with two different design goals: (i) to attain the desired BER of 10 -9 at the expense of higher optical power and lower aggregate data rate and (ii) to attain maximum aggregate data rate with the desired BER of 10 -9 at the expense of longer packet transfer latency. We then employ our designed 4-PAM SS–, 4-PAM EDAC–, 4-PAM ODAC–, and conventional OOK modulator–based photonic links to constitute corresponding variants of the well-known CLOS and SWIFT PNoC architectures. We eventually compare our designed SS-, EDAC-, and ODAC-based variants of 4-PAM links and PNoCs with the conventional OOK links and PNoCs in terms of performance and energy efficiency in the presence of inter-channel crosstalk. From our link-level and PNoC-level evaluation, we have observed that the 4-PAM EDAC–based variants of photonic links and PNoCs exhibit better performance and energy efficiency compared with the OOK-, 4-PAM SS–, and 4-PAM ODAC–based links and PNoCs.« less
2. A Comparison of Hybrid Beamforming and Digital Beamforming with Low-Resolution ADCs for Multiple Users and Imperfect CSI

   https://doi.org/10.1109/JSTSP.2018.2813973  

   Roth, Kilian ; Pirzadeh, Hessam ; Swindlehurst, A. Lee ; Nossek, Josef A. ( March 2018 , IEEE Journal of Selected Topics in Signal Processing)

   For 5G it will be important to leverage the available millimeter wave spectrum. To achieve an approximately omni- directional coverage with a similar effective antenna aperture compared to state-of-the-art cellular systems, an antenna array is required at both the mobile and basestation. Due to the large bandwidth and inefficient amplifiers available in CMOS for mmWave, the analog front-end of the receiver with a large number of antennas becomes especially power hungry. Two main solutions exist to reduce the power consumption: hybrid beam forming and digital beam forming with low resolution Analog to Digital Converters (ADCs). In this work we compare the spectral and energy efficiency of both systems under practical system constraints. We consider the effects of channel estimation, transmitter impairments and multiple simultaneous users for a wideband multipath model. Our power consumption model considers components reported in literature at 60 GHz. In contrast to many other works we also consider the correlation of the quantization error, and generalize the modeling of it to non- uniform quantizers and different quantizers at each antenna. The result shows that as the Signal to Noise Ratio (SNR) gets larger the ADC resolution achieving the optimal energy efficiency gets also larger. The energy efficiencymore »peaks for 5 bit resolution at high SNR, since due to other limiting factors the achievable rate almost saturates at this resolution. We also show that in the multi- user scenario digital beamforming is in any case more energy efficient than hybrid beamforming. In addition we show that if mixed ADC resolutions are used we can achieve any desired trade-off between power consumption and rate close to those achieved with only one ADC resolution.« less
3. Towards Programming the Radio Environment with Large Arrays of Inexpensive Antennas

   Li, Zhuqi ; Xie, Yaxiong ; Shangguan, Longfei ; Zelaya, R. Ivan ; Gummeson, Jeremy ; Hu, Wenjun ; Jamieson, Kyle ( January 2019 , NSDI)

   Conventional thinking treats the wireless channel as a constraint, so wireless network designs to date target endpoint designs that best utilize the channel. Examples include rate and power control at the transmitter, sophisticated receiver decoder designs, and high-performance forward error correction for the data itself. We instead explore whether it is possible to reconfigure the environment itself to facilitate wireless communication. In this work, we instrument the environment with a large array of inexpensive antenna (LAIA) elements, and design algorithms to configure LAIA elements in real time. Our system achieves a high level of programmability through rapid adjustments of an on-board phase shifter in each LAIA element. We design a channel decomposition algorithm to quickly estimate the wireless channel due to the environment alone, which leads us to a process to align the phases of the LAIA elements. Variations of our core algorithm then improve wireless channels on the fly for singleand multi-antenna links, as well as nearby networks operating on adjacent frequency bands. We implement and deploy a 36-element LAIA array in a real indoor home environment. Experiments in this setting show that, by reconfiguring the wireless environment, we can achieve a 24% TCP throughput improvement on average andmore »a median improvement of 51.4% in Shannon capacity over baseline single-antenna links. Over baseline multi-antenna links, LAIA achieves an improvement of 12.23% to 18.95% in Shannon capacity.« less
4. Experimentation Framework for Wireless Communication Systems under Jamming Scenarios Dataset

   https://doi.org/10.5281/zenodo.4749668  

   Jacovic, Marko ( January 2021 )

   Abstract

   <p>Data files were used in support of the research paper titled &#34;“Experimentation Framework for Wireless<br /> Communication Systems under Jamming Scenarios&#34; which has been submitted to the IET Cyber-Physical Systems: Theory &amp; Applications journal. </p> <p>Authors: Marko Jacovic, Michael J. Liston, Vasil Pano, Geoffrey Mainland, Kapil R. Dandekar<br /> Contact: krd26&#64;drexel.edu</p> <p>---------------------------------------------------------------------------------------------</p> <p>Top-level directories correspond to the case studies discussed in the paper. Each includes the sub-directories: logs, parsers, rayTracingEmulation, results. </p> <p>--------------------------------</p> <p>logs:    - data logs collected from devices under test<br />     - &#39;defenseInfrastucture&#39; contains console output from a WARP 802.11 reference design network. Filename structure follows &#39;*x*dB_*y*.txt&#39; in which *x* is the reactive jamming power level and *y* is the jaming duration in samples (100k samples &#61; 1 ms). &#39;noJammer.txt&#39; does not include the jammer and is a base-line case. &#39;outMedian.txt&#39; contains the median statistics for log files collected prior to the inclusion of the calculation in the processing script. <br />     - &#39;uavCommunication&#39; contains MGEN logs at each receiver for cases using omni-directional and RALA antennas with a 10 dB constant jammer and without the jammer. Omni-directional folder contains multiple repeated experiments to provide reliable results during each calculation window. RALA directories use s*N* folders in which *N* represents each antenna state. <br />     - &#39;vehicularTechnologies&#39; contains MGEN logs at the car receiver for different scenarios. &#39;rxNj_5rep.drc&#39; does not consider jammers present, &#39;rx33J_5rep.drc&#39; introduces the periodic jammer, in &#39;rx33jSched_5rep.drc&#39; the device under test uses time scheduling around the periodic jammer, in &#39;rx33JSchedRandom_5rep.drc&#39; the same modified time schedule is used with a random jammer. </p> <p>--------------------------------</p> <p>parsers:    - scripts used to collect or process the log files used in the study<br />         - &#39;defenseInfrastructure&#39; contains the &#39;xputFiveNodes.py&#39; script which is used to control and log the throughput of a 5-node WARP 802.11 reference design network. Log files are manually inspected to generate results (end of log file provides a summary). <br />         - &#39;uavCommunication&#39; contains a &#39;readMe.txt&#39; file which describes the parsing of the MGEN logs using TRPR. TRPR must be installed to run the scripts and directory locations must be updated. <br />         - &#39;vehicularTechnologies&#39; contains the &#39;mgenParser.py&#39; script and supporting &#39;bfb.json&#39; configuration file which also require TRPR to be installed and directories to be updated. </p> <p>--------------------------------</p> <p>rayTracingEmulation:    - &#39;wirelessInsiteImages&#39;: images of model used in Wireless Insite<br />             - &#39;channelSummary.pdf&#39;: summary of channel statistics from ray-tracing study<br />             - &#39;rawScenario&#39;: scenario files resulting from code base directly from ray-tracing output based on configuration defined by &#39;*WI.json&#39; file <br />             - &#39;processedScenario&#39;: pre-processed scenario file to be used by DYSE channel emulator based on configuration defined by &#39;*DYSE.json&#39; file, applies fixed attenuation measured externally by spectrum analyzer and additional transmit power per node if desired<br />             - DYSE scenario file format: time stamp (milli seconds), receiver ID, transmitter ID, main path gain (dB), main path phase (radians), main path delay (micro seconds), Doppler shift (Hz), multipath 1 gain (dB), multipath 1 phase (radians), multipath 1 delay relative to main path delay (micro seconds), multipath 2 gain (dB), multipath 2 phase (radians), multipath 2 delay relative to main path delay (micro seconds)<br />             - &#39;nodeMapping.txt&#39;: mapping of Wireless Insite transceivers to DYSE channel emulator physical connections required<br />             - &#39;uavCommunication&#39; directory additionally includes &#39;antennaPattern&#39; which contains the RALA pattern data for the omni-directional mode (&#39;omni.csv&#39;) and directional state (&#39;90.csv&#39;)</p> <p>--------------------------------</p> <p>results:    - contains performance results used in paper based on parsing of aforementioned log files<br />  </p>
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5. Demonstration of using two aperture pairs combined with multiple-mode receivers and MIMO signal processing for enhanced tolerance to turbulence and misalignment in a 10  Gbit/s QPSK FSO link

   https://doi.org/10.1364/OL.391120  

   Song, Haoqian ; Li, Long ; Pang, Kai ; Zhang, Runzhou ; Zou, Kaiheng ; Zhao, Zhe ; Du, Jing ; Song, Hao ; Liu, Cong ; Cao, Yinwen ; et al ( May 2020 , Optics Letters)

   We utilize aperture diversity combined with multiple-mode receivers and multiple-input-multiple-output (MIMO) digital signal processing (DSP) to demonstrate enhanced tolerance to atmospheric turbulence and spatial misalignment in a 10 Gbit/s quadrature-phase-shift-keyed (QPSK) free-space optical (FSO) link. Turbulence and misalignment could cause power coupling from the fundamental Gaussian mode into higher-order modes. Therefore, we detect power from multiple modes and use MIMO DSP to enhance the recovery of the original data. In our approach, (a) each of multiple transmitter apertures transmits a single fundamental Gaussian beam carrying the same data stream, (b) each of multiple receiver apertures detects the signals that are coupled from the fundamental Gaussian beams to multiple orbital angular momentum (OAM) modes, and (c) MIMO DSP is used to recover the data over multiple modes and receivers. Our simulation shows that the outage probability could be reduced from$><\#comment/>0.1$to$<<\#comment/>0.01$. Moreover, we experimentally demonstrate the scheme by transmitting two fundamental Gaussian beams carrying the same data stream and recovering the signals on OAM modes 0 and$+1$at each receiver aperture. We measure an up to$\sim <\#comment/>10\mathrm{d}\mathrm{B}$power-penalty reduction for a bit error rate (BER) at the 7% forward error correction limit formore »a 10 Gbit/s QPSK signal.

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