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R. David Koilpillai

Bio: R. David Koilpillai is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Phase noise & Orthogonal frequency-division multiplexing. The author has an hindex of 6, co-authored 30 publications receiving 126 citations. Previous affiliations of R. David Koilpillai include Dublin City University & Indian Institutes of Technology.

Papers
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Proceedings ArticleDOI
01 Dec 2019
TL;DR: The worst-case interference scenario between Mobile Base Station (BS) and Satellite Earth Station (ES) is evaluated and recommendation for path loss for 3.4 GHz operations is given based on ITU-R P.1546-5.4GHz.
Abstract: Spectrum for satellite services are likely to overlap with the ITU 5G spectrum Critical satellite services may be impacted due to interference between various communication links working in the same frequency band The worst-case interference scenario between Mobile Base Station (BS) and Satellite Earth Station (ES) is evaluated Recommendation for path loss for 34 GHz operations are given based on ITU-R P1546-5 Simulations are parameterized by ES height, BS height, terrain, time-variability and location-variability

2 citations

Proceedings ArticleDOI
05 Jan 2021
TL;DR: In this article, the advantages of using HARQ over ARQ and how HARQ outperforms ARQ across the SNR range are discussed and a breakpoint model is introduced to decide the set of rates to be chosen given the current SNR value.
Abstract: We present and discuss the applications of Hybrid Automatic Repeat Request Protocol (HARQ) in Wi-Fi systems. There has been rapid development in the next generation WiFi systems (IEEE 802.11be and beyond). However, unlike cellular, Wi-Fi systems don’t have optimized link-level protocols. One of the main reasons for this is to maintain minimal complexity and buffering requirements at user side (STA). In this paper we show the advantages of using HARQ over ARQ and how HARQ outperforms ARQ across the SNR range. We also introduce the use of a breakpoint model to decide the set of rates to be chosen given the current SNR value. Next, we explore the advantages of Short Term SNR estimation using Auto-Regressive models to further improve HARQ performance. Finally, this paper is concluded with a quick summary of the advantages of HARQ and a discussion on possible future work in this area.

2 citations

Journal ArticleDOI
TL;DR: The effectiveness of the SOA-based phase conjugator to improve the link budget with a 100 km standard single mode fiber link for 20 GHz coherent OFDM signals, with QPSK and 16QAM modulations and a corresponding net bit-rate of 40 Gbps and 80 Gbps respectively is experimentally demonstrated.
Abstract: We study the use of nonlinear semiconductor optical amplifier (SOA) for generating optical phase conjugate towards compensation of distortions in short distance optical fiber transmission due to Kerr nonlinearity and chromatic dispersion in coherent multi-carrier lightwave signals. We experimentally demonstrate the effectiveness of the SOA-based phase conjugator to improve the link budget with a 100 km standard single mode fiber link for 20 GHz coherent OFDM signals, with QPSK and 16QAM modulations and a corresponding net bit-rate of 40 Gbps and 80 Gbps respectively. Mid-span spectral inversion scheme is employed where the optical phase conjugate is generated through a partially degenerate four-wave mixing process in a nonlinear SOA. We demonstrate a bit error rate performance within $2\times 10^{-2}$ for an average launched power of up to 12 dBm (9 dBm) for QPSK (16QAM) coherent OFDM signals, in a 100 km fiber link. We also investigate the possible improvement in link budget using numerical simulation for 16QAM and 64QAM CO-OFDM signals with the proposed scheme.

2 citations

Proceedings ArticleDOI
03 Aug 2020
TL;DR: In this article, the authors presented validation study of modal decomposition methodology based on SPGD algorithm, composite beams of multiple modes with known proportions are generated using SLM and their weights and phases are determined iteratively using SPGD method.
Abstract: We present validation study of modal decomposition methodology based on SPGD algorithm. Composite beams of multiple modes with known proportions are generated using SLM and their weights and phases are determined iteratively using SPGD method.

1 citations

Proceedings ArticleDOI
TL;DR: 80 × 100 Gbit/s coherent PDM-QPSK transmission of WDM channels spaced 50 GHz apart is experimentally demonstrated over 1840 Km of Sterlite OH-LITE G652.D fiber using Kalman filtering of timing error estimates obtained from the Oerder & Meyer algorithm.
Abstract: We experimentally demonstrate 80 × 100 Gbit/s coherent PDM-QPSK transmission of WDM channels spaced 50 GHz apart, over 1840 Km of Sterlite OH-LITE G652.D fiber using Kalman filtering of timing error estimates obtained from the Oerder & Meyer algorithm.

1 citations


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Journal ArticleDOI
TL;DR: In this article, a review of underwater routing protocols for UWSNs is presented, which classify the existing protocols into three categories: energy-based, data-based and geographic information-based protocols.
Abstract: Underwater wireless sensor network (UWSN) is currently a hot research field in academia and industry with many underwater applications, such as ocean monitoring, seismic monitoring, environment monitoring, and seabed exploration. However, UWSNs suffer from various limitations and challenges: high ocean interference and noise, high propagation delay, narrow bandwidth, dynamic network topology, and limited battery energy of sensor nodes. The design of routing protocols is one of the solutions to address these issues. A routing protocol can efficiently transfer the data from the source node to the destination node in the network. This article presents a review of underwater routing protocols for UWSNs. We classify the existing underwater routing protocols into three categories: energy-based, data-based, and geographic information-based protocols. In this article, we summarize the underwater routing protocols proposed in recent years. The proposed protocols are described in detail and give advantages and disadvantages. Meanwhile, the performance of different underwater routing protocols is analyzed in detail. Besides, we also present the research challenges and future directions of underwater routing protocols, which can help the researcher better explore in the future.

70 citations

Journal ArticleDOI
TL;DR: It is shown that by replacing the stand-alone optical modulator with an InP-based externally modulated laser chip for the implementation of the IFoF transmitter, a 16-Gb/s aggregate capacity was showcased on a 7-km fiber link and 5-m wireless channel with a 4-band 16-QAM encoded at 1 Gbaud.
Abstract: We experimentally demonstrate a multiband intermediate frequency-over-fiber/mmWave (IFoF/mmWave) fiber/wireless mobile fronthaul link for gigabit capacity over the unlicensed V-band (57–64 GHz). Digital synthesis of the multiband radio waveforms is performed at the baseband unit using digital subcarrier multiplexing technique, whereas digital predistortion is exploited to cope with the analog IFoF channel impairments without any further baseband processing at the digital-free remote radio head. Commercial optoelectronic components and analog V-band radio and antenna equipment for 7-km fiber and 5-m wireless transmission are employed to successfully demonstrate both uplink and downlink connectivity. An aggregate capacity up to 24 Gb/s was demonstrated with a 6-band 1 Gbaud 16-QAM on a 7.2-GHz analog bandwidth over the combined fiber/wireless channel showing error vector magnitude (EVM) values below the 3GPP requirements (<12.5%) for 5G systems. Multiformat assignment on each subcarrier was also realized by using M-PSK and 16-QAM schemes to achieve 18-Gb/s connectivity for both uplink and downlink, while demonstrating flexible resource allocation capabilities. By replacing the stand-alone optical modulator with an InP-based externally modulated laser chip for the implementation of the IFoF transmitter, a 16-Gb/s aggregate capacity was showcased on a 7-km fiber link and 5-m wireless channel with a 4-band 16-QAM encoded at 1 Gbaud. Successful operation with robust EVM performance was demonstrated using also the 6-band scheme of 1 Gbaud QPSK bands.

65 citations

Journal ArticleDOI
TL;DR: The use of analog radio-over-fiber (ARoF) is proposed and demonstrated as a viable alternative which, combined with space division multiplexing in the optical distribution network as well as photonic integration of the required transceivers, shows a path to a scaleable fronthaul solution for 5G.
Abstract: The introduction of millimeter wave (mm-wave) frequency bands for cellular communications with significantly larger bandwidths compared to their sub-6 GHz counterparts, the resulting densification of network deployments and the introduction of antenna arrays with beamforming result in major increases in fronthaul capacity required for 5G networks As a result, a radical re-design of the radio access network is required since traditional fronthaul technologies are not scaleable In this article the use of analog radio-over-fiber (ARoF) is proposed and demonstrated as a viable alternative which, combined with space division multiplexing in the optical distribution network as well as photonic integration of the required transceivers, shows a path to a scaleable fronthaul solution for 5G The trade-off between digitized and analog fronthaul is discussed and the ARoF architecture proposed by blueSPACE is introduced Two options for the generation of ARoF two-tone signals for mm-wave generation via optical heterodyning are discussed in detail, including designs for the implementation in photonic integrated circuits as well as measurements of their phase noise performance The proposed photonic integrated circuit designs include the use of both InP and SiN platforms for ARoF signal generation and optical beamforming respectively, proposing a joint design that allows for true multi-beam transmission from a single antenna array Phase noise measurements based on laboratory implementations of ARoF generation based on a Mach–Zehnder modulator with suppressed carrier and with an optical phase-locked loop are presented and the suitability of these transmitters is evaluated though phase noise simulations Finally, the viability of the proposed ARoF fronthaul architecture for the transport of high-bandwidth mm-wave 5G signals is proven with the successful implementation of a real-time transmission link based on an ARoF baseband unit with full real-time processing of extended 5G new radio signals with 800 MHz bandwidth, achieving transmission over 10 km of 7-core single-mode multi-core fiber and 9 m mm-wave wireless at 255 GHz with bit error rates below the limit for a 7% overhead hard decision forward error correction

48 citations

Journal ArticleDOI
TL;DR: In this article, the authors experimentally evaluate two distinct hybrid architectures applied to 5G New Radio (NR) FiWi-Fi systems based on different optical fronthaul approaches, which operate in non-standalone (NSA) mode, defined by the 3rd generation partnership project (3GPP), for simultaneously transmitting 4G and 5G technologies through an unique FiWi system.
Abstract: The fifth-generation of mobile networks (5G) claims for a radio access network (RAN) update in order to support the enormous incoming wireless data traffic. In this context, we experimentally evaluate two distinct hybrid architectures applied to 5G New Radio (NR) FiWi systems based on different optical fronthaul approaches. The first architecture operates in non-standalone (NSA) mode, defined by the 3rd generation partnership project (3GPP), for simultaneously transmitting 4G and 5G technologies through an unique FiWi system. The three considered waveforms are as follows: a filtered orthogonal frequency division multiplexing (F-OFDM) signal at 778 MHz with 10 MHz bandwidth from our 5G flexible-waveform transceiver; a long-term evolution-advanced (LTE-A) signal with five 20 MHz sub-bands centralized at 2.24 GHz; a 5G NR signal at 2.35 GHz with 100 MHz bandwidth. On the other side, the second architecture employs radio over fiber (RoF), free space optics (FSO), and wireless technologies converged into a heterogeneous network (HetNet). The additional multi-standard and multiband optical-wireless network is based on a 10-MHz bandwidth F-OFDM signal at 788 MHz, a 100-MHz bandwidth 5G NR signal at 3.5 GHz, and a 400-MHz bandwidth M -QAM signal at 26 GHz. Throughput up to 3 and 1.4 Gbps are demonstrated for RoF/FSO and RoF/FSO/Wireless transmission, respectively.

35 citations

Journal ArticleDOI
TL;DR: A high capacity multiple-input-multiple-output (MIMO) enabled all-optical analog-millimeter-wave-over fiber (A-MMWoF) fronthaul architecture is proposed for 5G and beyond of wireless networks and a comprehensive state-of-the-art literature review on the recent research works in high capacity A-RoF fr onthaul systems and related transport technologies is presented.
Abstract: The ever-increasing proliferation of mobile users and new technologies, and the demands for ubiquitous connectivity, high data capacity, faster data speed, low latency, and reliable services have been driven the quest for the next generation, fifth generation (5G), of the wireless networks. Cloud radio access network (C-RAN) has been identified as a promising architecture for addressing 5G requirements. However, C-RAN enforces stringent requirements on the fronthaul capacity and latency. To this end, several fronthaul solutions have been proposed in the literature, ranging from transporting digitized radio signals over fiber and functional splits to an entirely analog-radio-over fiber (A-RoF) based fronthual. A-RoF is a highly appealing transport solution for fronthual of 5G and beyond owing to its high bandwidth and energy efficiency, low system complexity, small footprint, cost-effectiveness, and low latency. In this paper, a high capacity multiple-input-multiple-output (MIMO) enabled all-optical analog-millimeter-wave-over fiber (A-MMWoF) fronthaul architecture is proposed for 5G and beyond of wireless networks. The proposed architecture employs photonic MMW signals generation and mode division multiplexing (MDM) along with wavelength division multiplexing (WDM) for transporting MMW MIMO signals in the optical domain. In support of the proposed architecture design, a comprehensive state-of-the-art literature review on the recent research works in high capacity A-RoF fronthaul systems and related transport technologies is presented. In addition, the corresponding potential challenges and solutions along with potential future directions are highlighted. The proposed design is flexible and scalable for achieving high capacity, high speed, and low latency fronthaul links.

33 citations