Journal articles on the topic 'Code-division multiplexed (CDM) system'

Expanding the functionality of LED indoor lighting with visible light communication (VLC) allows an additional communication channel beside wireless radio in buildings. This service may be based on various channel access methods and modulation types. Code division multiplexing (CDM) is a suitable method to such an application, but it is complicated to measure the signal quality which is essential to compare different codes and settings, and necessary for some applications like position-dependent information services. Computing crest factor is a suitable method to estimate quality, but it may be inaccurate in some cases. This paper presents novel methods to approximate the quality of received CDM signals along with the crest factor, aiding the more accurate investigation of the VLC CDM technique.

Abstract Future air traffic control will be based on the distributed processing environment. This leads to the use of high-speed optical fibre networks and systems to connect many processors (for both general and specific purposes) and workstations in the air traffic control centres. To efficiently support such applications, communication systems should be capable of multirate operations. To achieve this aim, we propose an efficient optical fibre code-division multiplexing (OF-CDM) technique that can support multirate data communications without any increase of system complexity when compared with the equal-rate operation case. Unlike conventional optical orthogonal codes (OOCs), the use of our proposed unequal-length OOCs can eliminate any possible violation of the minimum cross-and auto-correlation constraint (i.e. ‘1’) in multirate OF-CDM systems. Thus, using unequal-length OOCs can achieve a better bandwidth efficiency and a lower bit error rate for multirate transmissions than employing conventional OOCs. Moreover, we present the design of cost-effective OF-CDM transmitters for multirate data transmissions. The proposed systems can be also employed to support future airborne real-time data distributions and computer interconnects.

For decoding the asynchronous superposition of response signals from different sensors, it is a challenge to achieve correlation in a code division multiplexing (CDM) based passive wireless surface acoustic wave (SAW) multisensor system. Therefore, an on-chip correlator scheme is developed in this paper. In contrast to conventional CDM-based systems, this novel scheme enables the correlations to be operated at the SAW sensors, instead of the reader. Thus, the response signals arriving at the reader are the result of cross-correlation on the chips. It is then easy for the reader to distinguish the sensor that is matched with the interrogating signal. The operation principle, signal analysis, and simulation of the novel scheme are described in the paper. The simulation results show the response signals from the correlations of the sensors. A clear spike pulse is presented in the response signals, when a sensor code is matched with the interrogating code. Simulations verify the feasibility of the on-chip correlator concept.

In this paper spread spectrum transmission system of multiplex detecting signal is studied. The method of transmission after multiplex detecting based on signal spread spectrum and code division multiplexing is mentioned. The system realization for the transmission of multiplexed testing signals using spread spectrum technology based on DSP is discussed. The circuit system is devised and testing conclusion is normal.

Abstract In advanced optical communication systems, a photonic crystal (PC) based channel drop filter (CDF) and dense wavelength division multiplexer (DWDM) demultiplexer are essential components in the design of a complete DWDM system, which offers a high transmission data rate. In the present work, a novel PC, CDF filter and demultiplexer based on a ring resonator with a super ellipse shape is designed and analyzed. To design a high-performance device, the performance parameters of the proposed components, such as transmission efficiency, spectral line width, channel spacing, Q-factor and crosstalk, are investigated. The proposed CDF is designed to drop a resonant wavelength with a high quality factor of 3955, and the ring resonator design is extended to the demultiplexer. The demultiplexer is designed to drop the four resonant wavelengths of 1579.8 nm, 1582 nm, 1583.6 nm and 1574.9 nm, respectively. The observed high quality factor (3955), bandwidth (0.4 nm) and transmission efficiency (90%) of the proposed demultiplexer will support high-performance DWDM systems

Abstract By virtue of their direct cytotoxicity to transformed and virus infected cells, Natural Killer (NK) cells play crucial roles in immunity. NK cells modulate and coordinate innate and adaptive responses through the release of chemokines and cytokines. Although NK cells are endowed only with germ-line encoded receptors, evidence has been accumulating, that subsets of NK cells can bestow adoptively transferable, long-lasting and antigen-specific immune responses to certain haptens and viruses. Growing evidence suggests that adaptive immune responses lie on a spectrum. Rechallenge of cells, canonically belonging to the innate immune system, can result in enhanced responsiveness - a process termed 'trained immunity' and thought to be maintained by epigenetic and metabolic reprogramming. In previous work, our lab studied the role of NK cell responses to rhesus cytomegalovirus (rhCMV) in a genetic barcoding model. We found that new clones arose in the CD16 + NK compartment after primary rhCMV infection. There was rapid clearance without the emergence of new clones in subsequent rechallenge with rhCMV. In this study we used 3'-end single cell RNA-seq (3'-scRNA-seq) with CITE-seq to profile NK and T cells from an initially CMV-naïve rhesus macaque (RM) at four time points before and after primary and secondary infections with rhCMV. We immunophenotypically sorted NK and T cells from peripheral Blood (PB) samples at 'baseline', 30 days after initial rhCMV infection ('primary infection'), ca. 500 days after initial rhCMV infection ('steady state') and 10 days after rmCMV reinfection ('secondary infection'). Alongside the PB samples at 'steady state' and after 'secondary infection', we also sorted NK and T cells from lymph nodes (LN). We applied CD16 and CD56 CITE-seq antibodies to NK cells from all samples; NK cells from the 'steady state' and 'secondary infection' samples were also labeled with CX3CL1 CITE-seq antibodies. We multiplexed NK and T cells from each time point in 4:1 ratios before preparing 3'-scRNA-seq libraries. We used scanpy and scvi-tools as well as custom python code to demultiplex NK from T cells, harmonize 3'-scRNA-seq with CITE-seq data and integrate the 6 different samples. We used scvelo and cellrank to compute RNA velocities and infer trajectories, respectively. We obtained a total of 35,523 high-quality cells. We identified 20 clusters of NK and T cells, on the basis of community detection via the Leiden algorithm. All clusters contained cells from both tissue sources. The 4 clusters characterized by expression of CD56 exhibit higher expression of KLRC1 (protein: NKG2A), IL7R and the transcription factors LEF1 and MYC. The 8 clusters of CD16 + cells are distinguished by high expression of the transcription factors ZEB2 and TBX21/T-BET, cytotoxicity markers, GZMB and PRF1, and activating receptors, KLRC2 (protein: NKG2C), KLRC3 (protein: NKG2E) and NCR3 (protein: NKp30). An adaptive population of NK cells is identified on the basis of high KLRC2 and low FCER1G expression. We analyzed changes in the proportions of cells in each cluster of the time course of CMV infection using a binomial generalized linear model. Clusters associated with proliferation and acute inflammation were increased in proportion after primary rhCMV infection; the proportion of the adaptive population did not significantly change during the acute phase of primary infection but increased markedly by the later 'steady state' samples. RNA velocity and inferred developmental trajectories suggest transitions between the adaptive, proliferating CD16 + and mature effector subsets; the predominant path into the adaptive population occurring from the proliferating CD16 + subset after primary infection. There is a notable paucity of inferred transitions between the CD56 + and CD16 +subpopulations under all the experimental conditions we observed. We have characterized the single cell transcriptional states and dynamics of RM NK cells in response to rhCMV infection. We focus on a subset transcriptionally resembling a previously identified subset with adaptive function and find it arises from a proliferating population of effector cells after primary infection. This may be analogous to the dedifferentiation of effector CD8 T cells into memory T cells proposed by Youngblood et al. Confirmatory experiments to analyze the reconstitution of the CD16 + compartment after treatment with a depleting antibody are on-going. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

The evaporation duct is an effective means for realizing non-line-of-sight (NLOS) wireless transmission over the sea. However, the effects of marine weather conditions on electromagnetic propagation have rarely been studied. In this study, the influence of the marine atmospheric environment on electromagnetic propagation was analyzed through numerical simulation. Additionally, the impacts of antenna height, transmission distance, and electromagnetic wave frequency on path loss were studied. Finally, the link capacity of the code division multiplexing (CDM) communication system in the evaporation duct environment was studied via numerical analysis and simulations. Simulation results demonstrated that CDM communication technology can improve the link capacity under an evaporation duct compared with that of the spread-spectrum communication technology.

AbstractIn an incoherent optical code division multiple access (OCDMA) system using amplitude spectral coding (SAC), which exceeds 1.5 Gbps, it is difficult or impossible to make a transmission with a bit error rate better than 10–9. For this, it is necessary to associate an error correction code (ECC) to the SAC-OCDMA system. In this paper, we proposed an architecture of a two-dimensional SAC-OCDMA system (spectral (w) and spatial (s)) using multi-diagonal code (MD) as spreading code and low-density parity check code (LDPC) as ECC. According to the properties of the MD code and the proposed architecture, the phase induced intensity noise is eliminated, which has improved the performance of the system. The theoretically results shows that LDPC/2D-SAC-OCDMA allowing more than 40 users to be multiplexed compared to a non-coded 2D SAC-OCDMA system. This combination allowed us to increase the cardinality of the LDPC/SAC-OCDMA (W/S) system without using an optical hard limiter.

Abstract Security postulates of visible light communication (VLC) is a paramount area of consideration due to its deployment in military, businesses, and residential establishments. Optical code division multiplexing (OCDMA) is prominent multiples access technique to serve multiple users and offer better security as compared to other available techniques such as wavelength and time division multiplexing (TDM). Wavelength conversion, multicode keying, optical logic gates, and quantum key distribution are some of the widely used security enhancement techniques but come at high cost and greater complexity. Zero cross correlation codes (ZCC) with integration of time dimension is an ultimate solution to the complex security improvement techniques but conventional two dimensional (2D) ZCC codes has an utmost issue of adjacent weights (W) and time (t) in the code which can be easily decoded by eavesdropper. Therefore, in this work, a novel weight managed ZCC (WMZCC) OCDMA code is presented with the non-adjacent W and t in the code matrix for making authentic information decoding difficult. Proposed 2D-WMZCC codes are investigated for 5 users at 100 Gbps over VLC link length of 5 m using polarization division multiplexed (PDM) quadrature phase shift keying (QPSK) and digital signal processing in terms of log symbol error rate (log SER), Q factor and bit error rate (BER). Further, a detailed comparison of 2D-WMZCC codes is performed with existing 2D diagonal identity matrix (DIM) codes and results revealed that former one exhibits better security than later OCDMA code.

Abstract Transmission of acoustic signals between distributed sensor nodes may be useful for status monitoring of elongated structures such as pipelines. In principle, coded signals can be used in an asynchronous multiplexed system, provided the signals are distinguishable. However, multimode effects complicate signal propagation, so any such codes should be short. A search for polyphase code families with properties suitable for acoustic code division multiple access (CDMA) is presented. Algorithms for reduction of search space to allow use of a laptop for code discovery are described. Short codes of base 6 are shown to outperform codes of bases 2, 3, 4 and sets suitable for systems with 2 and 3 users are identified. The codes have similar properties to Barker codes but larger sidelobes. Their use is demonstrated by simulation and experiment at kHz frequencies using an air-filled copper pipe, an electromagnetic acoustic transducer (EMAT) and a microphone designed to excite and detect the L(0,1) mode. Low loss propagation over 25 m is achieved with a 20 kHz carrier. Excellent agreement between experiment and theory is demonstrated, with performance limited by transducer bandwidth.

Abstract A new architecture for increasing the number of simultaneous users in a hybrid system and providing a solution for the channel bottleneck problem has been designed and simulated. The 10G-TDM-OCDMA-PON system combines optical code division multiple access (OCDMA) and time-division multiplexed passive optical network (TDM-PON) techniques. The high bit rate TDM-PON system is based on a bit interleaving that uses noncontiguous order for data arranging manner, this system used to obtain ultra-high-speed data rate of 40 Gbps based on four TDM channels of 10 Gbps. The OCDMA system is based on two-dimensional single weight zero cross-correlation (2D-SWZCC) employing polarization and wavelength scheme with two orthogonal polarization angles (vertical and horizontal states). The proposed hybrid system increases the scalability by multiplexing M OCDMA codes in the same time slot of the TDM system that has N time slots. The results show that the proposed system with 2D-SWZCC has better performance with a high number of users and higher scalability than the system with 1D-SWZCC.

Abstract Reach enhancement in inter-satellite optical wireless communication systems (IsOWC) is an utmost requirement due to ever-increasing internet usage all over the globe. Optical code division multiplexing is prominently incorporated for security enhancement in IsOWC systems, however, limited in terms of total reach. Therefore, in this work, a 120 Gbps capacity-based hybrid OCDMA and mode division multiplexed (MDM) IsOWC is presented using different optical amplifiers such as semiconductor optical amplifier (SOA), erbium-doped fiber amplifier (EDFA), and Raman fiber amplifier (RFA). Moreover, the combined effects of Laguerre–Gaussian (LG) with EDFA/SOA/RFA and Hermite–Gaussian (HG) modes with EDFA/SOA/RFA amplifiers are investigated. Results revealed that the proposed system can cover 5000 km IsOWC link within acceptable BER limits and EDFA with LG modes is found to be the best technique.

This study discusses the results of the experimental application of high-content screening (HCS) techniques in evaluating the induction of cell-cycle arrest and apoptosis on human liver cancer cell line, Hep-G2. Accordingly, the bisbenzimide-stained cells (Hoechst 33342; 350 to 500 nM) were analyzed by using an Olympus scanˆR HCS-system to determine the cell-cycle phases (G1, S, and G2/M) and apoptosis as well. As a result, the cell-cycle arrest could be indicated by an increase in G2/M population of Hep-G2 cells after 24h exposure to zerumbone (Zer4; 9 µg/mL) and a similar observation could be made for paclitaxel (Pac; 4 µg/mL) as a reference substance. Keywords Apoptosis, cell-cycle arrest, high-content screening, human liver cancer cell line Hep-G2. References [1] D. Hanahan, R.A. Weinberg, Hallmarks of cancer: the next generation, Cell 144 (2011) 646–674.[2] M. Malumbres, M. Barbacid, Cell cycle, CDKs and cancer: a changing paradigm, Nat. Rev. Cancer 9 (2009) 153–166.[3] S. Diermeier-Daucher, et al., Cell type specific applicability of 5-ethynyl-2'-deoxyuridine (EdU) for dynamic proliferation assessment in flow cytometry, Cytometry A 75 (2009) 535-546.[4] J. Essers, et al., Nuclear dynamics of PCNA in DNA replication and repair, Mol. Cell Biol 25 (2005) 9350- 9359. [5] V. Roukos, et al., Dynamic recruitment of licensing factor Cdt1 to sites of DNA damage. J. Cell Sci. 124 (2011) 422-434.[6] M. Hesse, et al., Direct visualization of cell division using high-resolution imaging of M-phase of the cell cycle, Nat. Commun 3 (2012) 1076. doi: 10.1038/ncomms2089.[7] P. Cappella, F. Gasparri, M. Pulici, J. Moll, A novel method based on click chemistry, which overcomes limitations of cell cycle analysis by classical determination of BrdU incorporation, allowing multiplex antibody staining, Cytometry A 73 (2008) 626–636. [8] S. Diermeier-Daucher, et al., Cell type specific applicability of 5-ethynyl-2’-deoxyundine (EdU) for dynamic proliferation assessment in flow cytometry, Cytometry A 75 (2009) 535–546.[9] T. Yokochi, D.M. Gilbert, Replication labeling with halogenated thymidine analogs, Curr. Protoc. Cell Biol, 35 (2007) 22.10.1–22.10.14. [10] T.J. McGarry, M.W. Kirschner, Geminin, an inhibitor of DNA replication, is degraded during mitosis, Cell 93 (1998) 1043–1053. [11] H. Nishitani, S. Taraviras, Z. Lygerou, T. Nishimoto, The human licensing factor for DNA replication Cdt1 accumulates in G1 and is destabilized after initiation of S-phase. J. Biol. Chem 276 (2001) 44905–44911.[12] J. Pines, T. Hunter, Human cyclin A is adenovirus E1A-associated protein p60 and behaves differently from cyclin B, Nature 346 (1990) 760–763. [13] A. Stathopoulou, et al., Cdt1 is differentially targeted for degradation by anticancer chemotherapeutic drugs. PLoS ONE 7, e34621 (2012). [14] M. Hesse, A. Raulf, G.A. Pilz, C. Haberlandt, A.M. Klein, R. Jabs, H. Zaehres, C.J. Fügemann, K. Zimmermann, J. Trebicka, A. Welz, A. Pfeifer, W. Röll, M.I. Kotlikoff, C. Steinhäuser, M. Götz, H.R. Schöler, B.K. Fleischmann, Direct visualization of cell division using high-resolution imaging of M-phase of the cell cycle, Nat. Commun 3 (2012): 1076.[15] D.A. Ridenour, M.C. McKinney, C.M. Bailey, P.M. Kulesa, CycleTrak: a novel system for the semiautomated analysis of cell cycle dynamics. Dev. Biol 365 (2012) 189–195. [16] A. Roukos, et al., Cell cycle staging of individual cells by fluorescence microscopy, Nat. Protoc 10 (2015) 334-348.[17] E. Harlow, D. Lane, Fixing attached cells in paraformaldehyde, CSH Protoc 3 (2006) doi: 10.1101/pdb.prot4294.[18] G. Mazzini, M. Danova, Fluorochromes for DNA staining and quantitation, Method. Mol. Biol 1560 (2017) 239-259.[19] A. Gottfried, E. Weinhold, Sequence-specific covalent labelling of DNA, Biochem. Soc. Trans 39 (2011) 623-628.[20] J. Bucevičius, G. Lukinavičius, R. Gerasimaitė, The use of Hoechst dyes for DNA staining and beyond, Chemosensor 6 (2018) 1-18.[21] V. Kumar, A.K. Abbas, J.C. Aster, Robbins and Cotran Pathologic Basis of Disease, Ninth ed., Elsevier/Saunders, Philadelphia (2015).[22] N.A. Jensen et al., Establishment of a high content assay for the identification and characterisation of bioactivities in crude bacterial extracts that interfere with the eukaryotic cell cycle, J. Biotechnol 140 (2009) 124-134.[23] H.S. Rahman, et al., Zerumbone induces G2/M cell cycle arrest and apoptosis via mitochondrial pathway in Jurkat cell line, Nat. Prod. Commun 9 (2014) 1237-1242.[24] S.I. Abdelwahab, et al., Zerumbone inhibits interleukin-6 and induces apoptosis and cell cycle arrest in ovarian and cervical cancer cells, Intern. Immunopharm 12 (2012) 594-602.[25] M. Xian, et al., Zerumbone, A bioactive sesquiterpene, induces G2/M cell cycle arrest and apoptosis in leukemia cells via a Fas- and mitochondria-mediated pathway, Cancer Sci 98 (2007) 118-126.[26] A. Sehrawat, et al., Zerumbone causes Bax-and Bak-mediated apoptosis in human breast cancer cells and inhibits orthotopic xenograft growth in vivo, Breast Cancer Res. Treat. 136 (2012) 429-441.[27] Y.Z. Zhou, et al., Zerumbone induces G1 cell cycle arrest and apoptosis in cervical carcinoma cells, Int. J. Clin. Exp. Med. 10 (2017) 6640-6647.