Several space-time coding based transmit diversity techniques for wideband code division multiple access (WCDMA) systems with four transmitter antennas are investigated. Performances of the rake receivers are analyzed...Several space-time coding based transmit diversity techniques for wideband code division multiple access (WCDMA) systems with four transmitter antennas are investigated. Performances of the rake receivers are analyzed and compared with those of the multi-antenna receive diversity techniques. Theoretical analysis shows that the multi-antenna transmit diversity techniques provide considerable performance gain at the mobile receiver in the wireless channel with less inherent multipath diversity, especially the G4 coding based scheme. Compared with the multi-antenna receive diversity techniques with the same diversity order, the transmit diversity techniques introduce much more multi-access plus multipath interference and require measures of interference suppression in the multi-user environments.展开更多
Space-time spreading (STS) and orthogonal transmit diversity (OTD) are towtransmit diversity schemes proposed by cdma2000 standard. In this paper, performance comparisonanalysis of the two transmits diversity schemes ...Space-time spreading (STS) and orthogonal transmit diversity (OTD) are towtransmit diversity schemes proposed by cdma2000 standard. In this paper, performance comparisonanalysis of the two transmits diversity schemes in multipath channel under multiuser situation arecarried out. Link level simulation in forward link cdma2000 is performed in IMT-2000 channel.Performance analysis and simulation results show that the performance improvement provided STS overOTD decreases as the increase of propagation path number and decrease of the user number.展开更多
Space time coding can provide high data rate and performance gain for wireless communication system. Performance comparison of space time trellis codes and space time transmit diversity is carried out under the sam...Space time coding can provide high data rate and performance gain for wireless communication system. Performance comparison of space time trellis codes and space time transmit diversity is carried out under the same bandwidth efficiency in this paper. We also propose some optimum low rate space time trellis codes in quasi static Rayleigh fading chan￣nel. Performance analysis and simulation show that the low rate space time trellis codes outperform space time transmit diversity at the same bandwidth efficiency, and are more suitable for the power limited wireless communication system which has no strict requirement on bandwidth efficiency.展开更多
Many common multimedia signal processing,including cropping,filtering,and perceptual coding,make watermark signal fading-like modification.A scheme that applies transmit diversity technique to improve robustness of di...Many common multimedia signal processing,including cropping,filtering,and perceptual coding,make watermark signal fading-like modification.A scheme that applies transmit diversity technique to improve robustness of digital watermarking is presented.First,the scheme decomposes the original image using wavelet pyramid algorithm and chooses the middle-frequency band for transmission channel that the watermark will be embedded into.Then the watermark is pseudo-randomly permuted.The scheme makes use of space-time coding and differential detection technique to embed and extract watermark.The extracting process has access to neither the original image nor channel state information.Experimental results demonstrate that the scheme improves the performance of robust watermarking.展开更多
The paper investigates closed-loop transmit diversity （CLTD） systems with antenna selection technique. The expected received signal-noise-ratio （RxSNR） of the proposed systems is analyzed and compared with CLTD sy...The paper investigates closed-loop transmit diversity （CLTD） systems with antenna selection technique. The expected received signal-noise-ratio （RxSNR） of the proposed systems is analyzed and compared with CLTD systems. An algorithm is proposed for determining the number of increased transmit antennas in terms of a reduced RF chains without performance degradation. Since a feedback channel is bandwidth-limited, we present a method of quantizing transmit-weight vectors. Simulation results demonstrate advantage of the proposed systems with full and quantized feedback information. Quantized feedback has less effect on the proposed systems than CLTD systems.展开更多
This paper deals with channel estimation for orthogonal frequency-division multiplexing (OFDM) systems with transmit diversity. Space time coded OFDM systems, which can provide transmit diversity, require perfect chan...This paper deals with channel estimation for orthogonal frequency-division multiplexing (OFDM) systems with transmit diversity. Space time coded OFDM systems, which can provide transmit diversity, require perfect channel estimation to improve communication quality. In actual OFDM systems, training sequences are usually used for channel estimation. The authors propose a training based channel estimation strategy suitable for space time coded OFDM systems. This novel strategy provides enhanced performance, high spectrum efficiency and relatively low computation complexity.展开更多
Transmit diversity has been recently proposed to reduce the effects of fading channels in various wireless applications. Orthogonal transmit diersity (OTD) is one of the standardized techniques in 3G systems. In this ...Transmit diversity has been recently proposed to reduce the effects of fading channels in various wireless applications. Orthogonal transmit diersity (OTD) is one of the standardized techniques in 3G systems. In this paper, we apply orthogonal transmit diversity technique to multicarrier CDMA systems. Andlysis and simulation results show that performance benefits can be achieved compared with conventioal MC-CDMA systems in multipath fading channels.展开更多
This paper investigates the transmission scheme of the orthogonal time frequency space(OTFS)system with multiple antennas.Previous works have studied the multi-antenna transmitter diversity scheme with the ideal pulse...This paper investigates the transmission scheme of the orthogonal time frequency space(OTFS)system with multiple antennas.Previous works have studied the multi-antenna transmitter diversity scheme with the ideal pulse shaping in OTFS systems assuming the wireless channels of two consecutive frames duration are invariant.However,the ideal pulse shaping can not be realized in practice and the channel varies rapidly in two consecutive frames in the high-speed mobility scenarios.To this end,we redesign the multi-antenna transmitter diversity scheme to ensure its practicability in the rectangular-pulsebased OTFS systems.At first,the information symbols of each antenna are divided into two half frames along the Doppler domain.Then,the guard symbols are carefully arranged to eliminate the interference between two half frames,and to ensure the equivalent channels of two half frames being identical.By considering the positions of the guard symbols,the transmission codeword is designed and a low complexity linear detection is proposed.Finally,simulation results validate that the bit error rate performance of the proposed scheme has the superiority over the existing works.展开更多
In this paper, a time-switched space-time （TSST） coded orthogonal frequency division nmltiplexing （OFDM） scheme against the time-varying channels is proposed. In the TSST-OFDM scheme, it is equipped with four tran...In this paper, a time-switched space-time （TSST） coded orthogonal frequency division nmltiplexing （OFDM） scheme against the time-varying channels is proposed. In the TSST-OFDM scheme, it is equipped with four transmit antennas, but only double of them are used for coding in every time slot. It is shown that the signal to inter-antenna interference ratio is a function of Doppler frequency in time-varying channels for a given space-time code. The analyses and simulations results validate that the proposed scheme not only gets time- switched diversity and lower decoding complexity, but also suffers less time-varying impairments. Hence, it ex- hibits better performance than quasi-orthogonal space-time coded scheme.展开更多
In this paper, the closed loop transmit diversity technology for the Wideband Code Division Multiple Access(WCDMA) systems is investigated in a multipath Rayleigh fading channel. The RAKE receiver model and the weighi...In this paper, the closed loop transmit diversity technology for the Wideband Code Division Multiple Access(WCDMA) systems is investigated in a multipath Rayleigh fading channel. The RAKE receiver model and the weighing vector algorithm are presented. The performance is theoretically analyzed in terms of the average maximal Signal-to-Noise Ratio(SNR) gain available over the Space-Time block coding based Transmit Diversity(STTD) technology. Theoretic analysis and simulation results show that the closed loop transmit diversity can provide a 3dB performance gain over the open loop scheme in a single path fading channel, while the performance gain decreases dramatically with the increasing inherent multipath diversity of the wireless channel.展开更多
In this paper, we introduce a novel merger of antenna arrays with scanning beam patterns, and Orthogonal Frequency Division Multiplexing (OFDM) systems. Controlled time varying phase shifts are applied to the antenna ...In this paper, we introduce a novel merger of antenna arrays with scanning beam patterns, and Orthogonal Frequency Division Multiplexing (OFDM) systems. Controlled time varying phase shifts are applied to the antenna array elements mounted at the base station with beam patterns directed toward the desired user. This creates a small beam pattern movement called Beam Pattern Scanning (BPS). In rich scattering environments BPS creates a time varying environment leading to time diversity exploitable at the receiver enhances its probability-of-error performance. Here, we apply OFDM signals to BPS antenna arrays, and we achieve: (1) directionality, which supports Space Division Multiple Access (SDMA);and (2) a time diversity gain, which leads to high performance. We discuss the structure of the base station antenna array and the OFDM receiver that exploits time diversity. We also introduce the merger of BPS and multi-carrier OFDM (MC-OFDM) systems. In MC-OFDM each bit is transmitted over all sub-carriers after serial to parallel conversion. BPS/ MC-OFDM receiver exploits both time diversity inherent in BPS, and frequency diversity inherent in MC-OFDM transmission technique. Simulation results show high Probability-of-error performance is achie- vable via BPS/OFDM and BPS/MC-OFDM schemes comparing to the traditional OFDM and MC-OFDM, respectively. Simulations also reveal that MC-OFDM system as well as its merger with BPS is capable of mitigating large Peak-to-Average Ratio (PAPR) problem in traditional OFDM system. In addition, performance simulations with coded OFDM (COFDM) and coded MC-OFDM (MC-COFDM) and their merger with BPS are studied.展开更多
The performance analysis, using outage capacity for a forward link cellular communications system is presented. The effects of correlated fading, the distribution of angle of arrivals, and the array configurations are...The performance analysis, using outage capacity for a forward link cellular communications system is presented. The effects of correlated fading, the distribution of angle of arrivals, and the array configurations are considered. The objective is to examine the effect of angle of arrival (AOA) energy distributions on two systems (transmit diversity and beamforming) with angle spread. We do so by comparing the performance of transmit diversity with a system that uses beamforming to point a relatively narrow beam at the mobile station. Analytical results show that the transmit diversity system using uniform linear arrays (ULA) and uniform circular arrays (UCA) with truncated Laplacian AOA, performs better even at smaller angle spreads as compared to other energy distributions. The ULA geometry is a preferable configuration for transmit diversity system as compared to UCA.展开更多
The next generation of High Throughput Satellite(HTS)will exploit Q/V band for the feeder link and Ka band for the user link.The exploitation of multiple gateways(GWs)is a transmit diversity measure to compensate seve...The next generation of High Throughput Satellite(HTS)will exploit Q/V band for the feeder link and Ka band for the user link.The exploitation of multiple gateways(GWs)is a transmit diversity measure to compensate severe rain attenuation of Q/V band feeder links.This paper introduces a new smart gateway diversity combination scheme that combinates N-active(K=2)and N+1 diversity method in detail from the working principle,gateway switching strategy,evaluation of system availability and implementation complexity.In addition,a feeder link outage event prediction algorithm featuring combination scheme is given detailly based on modified time-adaptive linear regression.Compared with the existing N+P scheme,the proposed scheme can provide higher system availability and more stable user’s experience under the condition of properly increasing the complexity of payload design.Compared with Nactive scheme that has been reported,it is much easier to implement in engineering and more cost-effective.As a result,the combination scheme is a realistic solution based on a trade-off between performance improvement and implementation complexity.展开更多
This study primarily aimed to investigate the prevalence of human papillomavirus(HPV)and other common pathogens of sexually transmitted infections(STIs)in spermatozoa of infertile men and their effects on semen parame...This study primarily aimed to investigate the prevalence of human papillomavirus(HPV)and other common pathogens of sexually transmitted infections(STIs)in spermatozoa of infertile men and their effects on semen parameters.These pathogens included Ureaplasma urealyticum,Ureaplasma parvum,Chlamydia trachomatis,Mycoplasma genitalium,herpes simplex virus 2,Neisseria gonorrhoeae,Enterococcus faecalis,Streptococcus agalactiae,Pseudomonas aeruginosa,and Staphylococcus aureus.A total of 1951 men of infertile couples were recruited between 23 March 2023,and 17 May 2023,at the Department of Reproductive Medicine of The First People’s Hospital of Yunnan Province(Kunming,China).Multiplex polymerase chain reaction and capillary electrophoresis were used for HPV genotyping.Polymerase chain reaction and electrophoresis were also used to detect the presence of other STIs.The overall prevalence of HPV infection was 12.4%.The top five prevalent HPV subtypes were types 56,52,43,16,and 53 among those tested positive for HPV.Other common infections with high prevalence rates were Ureaplasma urealyticum(28.3%),Ureaplasma parvum(20.4%),and Enterococcus faecalis(9.5%).The prevalence rates of HPV coinfection with Ureaplasma urealyticum,Ureaplasma parvum,Chlamydia trachomatis,Mycoplasma genitalium,herpes simplex virus 2,Neisseria gonorrhoeae,Enterococcus faecalis,Streptococcus agalactiae,and Staphylococcus aureus were 24.8%,25.4%,10.6%,6.4%,2.4%,7.9%,5.9%,0.9%,and 1.3%,respectively.The semen volume and total sperm count were greatly decreased by HPV infection alone.Coinfection with HPV and Ureaplasma urealyticum significantly reduced sperm motility and viability.Our study shows that coinfection with STIs is highly prevalent in the semen of infertile men and that coinfection with pathogens can seriously affect semen parameters,emphasizing the necessity of semen screening for STIs.展开更多
Paeonia suffruticosa Andr.is an endemic shrub flower in China with 2n=10.This study used 228 cultivars from four populations,i.e.,Jiangnan,Japan,Northwest,and Zhongyuan,as materials to explore the genetic diversity le...Paeonia suffruticosa Andr.is an endemic shrub flower in China with 2n=10.This study used 228 cultivars from four populations,i.e.,Jiangnan,Japan,Northwest,and Zhongyuan,as materials to explore the genetic diversity levels among different populations of tree peony varieties.The results showed that 34 bands were amplified using five pairs of cp SSR primers,with an average of 6.8 bands per primer pair.The average number of different alleles(N_(a)),effective alleles(N_(e)),Shannon's information index(I),diversity(H),and polymorphic information content(PIC)were 3.600,2.053,0.708,0.433,and 0.388,respectively.The PIC value was between 0.250 and 0.500,indicating a moderate level of polymorphism for the five cp SSR primer pairs.The genetic diversity levels of peony cultivars varied among different populations,with the Northwest population showing relatively lower levels(I=0.590,H=0.289,and PIC=0.263).A total of 52 haplotypes were identified in the four examined populations,and the number of haplotypes per population ranged from 11 to 22.Forty-four private haplotypes were detected across populations,and the Northwest population exhibiting the highest count of private haplotypes with 17.The mean number of effective number of haplotypes(N_(eh)),haplotypic richness(R_(h)),and diversity(H)were 8.351,6.824,and 0.893,respectively.Analysis of molecular variance indicated that genetic variation within tree peony germplasm was greater than that between germplasm resources,and the main variation was found within individuals of peony germplasm.Cluster analysis,principal coordinate analysis,and genetic structure analysis classified tree peonies from different origins into two groups,indicating a certain degree of genetic differentiation among these four tree peony cultivation groups.This study provides a theoretical basis for the exploration,utilization,and conservation of peony germplasm resources,as well as for research on the breeding of excellent varieties.展开更多
Wetland degradation is an escalating global challenge with profound impacts on animal diversity,particularly during successional processes.Birds,as highly mobile and environmentally sensitive organisms,serve as effect...Wetland degradation is an escalating global challenge with profound impacts on animal diversity,particularly during successional processes.Birds,as highly mobile and environmentally sensitive organisms,serve as effective indicators of ecological change.While previous studies have primarily focused on local community structures and species diversity during a specific season,there is a need to extend the research timeframe and explore broader spatial variations.Additionally,expanding from simple species diversity indices to more multidimensional diversity indices would provide a more comprehensive understanding of wetland health and resilience.To address these gaps,we investigated the effects of wetland degradation on bird diversity across taxonomic,phylogenetic,and functional dimensions in the Zoige Wetland,a plateau meadow wetland biodiversity hotspot.Surveys were conducted during both breeding(summer)and overwintering(winter)seasons across 20 transects in 5 sampling areas,representing 4 degradation levels(pristine,low,medium,and high).Our study recorded a total of 106 bird species from 32 families and 14 orders,revealing distinct seasonal patterns in bird community composition and diversity.Biodiversity indices were significantly higher in pristine and low-degraded wetlands,particularly benefiting waterfowl(Anseriformes,Ciconiiformes)and wading birds(Charadriiformes)in winter,when these areas provided superior food resources and habitat conditions.In contrast,medium and highly degraded wetlands supported increased numbers of terrestrial birds(Passeriformes)and raptors(Accipitriformes,Falconiformes).Seasonal differences in taxonomic,phylogenetic,and functional diversity indices highlighted the contrasting ecological roles of wetlands during breeding and overwintering periods.Furthermore,indicator species analysis revealed key species associated with specific degradation levels and seasons,providing valuable insights into wetland health.This study underscores the importance of spatiotemporal dynamics in understanding avian responses to wetland degradation.By linking seasonal patterns of bird diversity to habitat conditions,our findings contribute to conservation efforts and provide a framework for assessing wetland degradation and its ecological impacts.展开更多
Marine fish diversity in the Beibu Gulf from 2014 to 2022 was analyzed,using various methods including at-sea fisheries resource surveys,fishing port surveys,underwater survey techniques,and data from literature,books...Marine fish diversity in the Beibu Gulf from 2014 to 2022 was analyzed,using various methods including at-sea fisheries resource surveys,fishing port surveys,underwater survey techniques,and data from literature,books,and databases,from which 1059 fish species across 40 orders,166 families,and 503 genera were identified.Among them,Acanthuriformes displayed the highest diversity,followed by Carangiformes and Perciformes.Notably,eight alien species were found in the Beibu Gulf.The International Union for Conservation of Nature(IUCN)Red List assessment revealed 51threatened species,primarily cartilaginous fish.Taxonomic changes affected 88.70%of species due to classification adjustments,misidentifications,and junior synonymy.This study contributed new data of the gulf,including one additional order,six new families,34 new genera,and 81 new species,emphasizing the dynamic nature of marine ecosystems.Fish diversity in the gulf was relatively lower than the broader South China Sea,attributed to limited habitats and survey methods.Different survey methods,such as gill nets,trap nets,and underwater cameras,yielded varying results.Ocean currents may have transported deep-sea species into the Beibu Gulf,leading to accidental records.Research gaps exist in unexplored areas,warranting further investigation.Therefore,the Beibu Gulf hosts significant marine biodiversity,but taxonomic challenges and undiscovered species require new research and conservation efforts.展开更多
Viral infectious diseases,characterized by their intricate nature and wide-ranging diversity,pose substantial challenges in the domain of data management.The vast volume of data generated by these diseases,spanning fr...Viral infectious diseases,characterized by their intricate nature and wide-ranging diversity,pose substantial challenges in the domain of data management.The vast volume of data generated by these diseases,spanning from the molecular mechanisms within cells to large-scale epidemiological patterns,has surpassed the capabilities of traditional analytical methods.In the era of artificial intelligence(AI)and big data,there is an urgent necessity for the optimization of these analytical methods to more effectively handle and utilize the information.Despite the rapid accumulation of data associated with viral infections,the lack of a comprehensive framework for integrating,selecting,and analyzing these datasets has left numerous researchers uncertain about which data to select,how to access it,and how to utilize it most effectively in their research.This review endeavors to fill these gaps by exploring the multifaceted nature of viral infectious diseases and summarizing relevant data across multiple levels,from the molecular details of pathogens to broad epidemiological trends.The scope extends from the micro-scale to the macro-scale,encompassing pathogens,hosts,and vectors.In addition to data summarization,this review thoroughly investigates various dataset sources.It also traces the historical evolution of data collection in the field of viral infectious diseases,highlighting the progress achieved over time.Simultaneously,it evaluates the current limitations that impede data utilization.Furthermore,we propose strategies to surmount these challenges,focusing on the development and application of advanced computational techniques,AI-driven models,and enhanced data integration practices.By providing a comprehensive synthesis of existing knowledge,this review is designed to guide future research and contribute to more informed approaches in the surveillance,prevention,and control of viral infectious diseases,particularly within the context of the expanding big-data landscape.展开更多
Sexually transmitted infections (STIs) represent a public health problem due to their high prevalence worldwide and the emergence of multidrug resistance of responsible microorganisms. Medical laboratory diagnosis of ...Sexually transmitted infections (STIs) represent a public health problem due to their high prevalence worldwide and the emergence of multidrug resistance of responsible microorganisms. Medical laboratory diagnosis of sexually transmitted genital infections by traditional methods as culture remains extremely delicate, difficult or impossible (to find extremely fragile organisms that can be cultured). Thus, molecular techniques constitute an alternative to improve accurate diagnostic, personalized patient treatment, and public health. A total of 83 clinical samples including urethral discharge and urine samples from individual patients with symptoms of urethritis received were analyzed using traditional methods and a commercial real-time PCR (qPCR) method. Out of 83 urethritis patients, n = 55 (66.26%) were positive for at least one of the STI pathogens detected by qPCR. qPCR assay was more sensitive (50/83, positive cases) compared to culture (15/83, positive cases) and light microscopy (28/83, positive cases). The most prevalent NTD pathogen in the suspected patients was N. gonorrhoeae with 60.24% (50/83) based on real-time PCR diagnosis. Among the positive cases of STI pathogens, Neisseria gonorrhoeae had the highest frequency 49/55 (89.01%) followed by low frequencies of Trichomonas vaginalis 4/55 (7.27%) and Chlamydia trachomatis 1/55 (1.82%). This highlights the high prevalence of N. gonorrhoeae infection in male urethritis patients and a very important misdiagnosis using traditional routine methods in Burkina Faso by medical laboratories. Thus, this situation may negatively impact patients’ personalized treatment and care and public health with the possible rapid emergence of multidrug-resistant strains. This study also highlights the urgent need to optimize culture for the diagnosis of NTD pathogens in Burkina Faso and the usefulness and the need for the introduction of molecular diagnostic methods in routine diagnosis for the detection of NTD pathogens in the medical laboratories in Burkina Faso.展开更多
The mussel is one of the main cultivated species in the world.A significant challenge faced by suspension-cultured mussels is the high incidence of mussel fall-off from cultivation ropes,adversely impacting harvest yi...The mussel is one of the main cultivated species in the world.A significant challenge faced by suspension-cultured mussels is the high incidence of mussel fall-off from cultivation ropes,adversely impacting harvest yields,which have been documented at commercial mussel farms in the United Kingdom,the United States of America,Canada,Spain,New Zealand and China.Byssus is an important attachment structure for marine mussels,and weakness in byssal thread attachment is a major factor leading to mussel detachment from ropes.To investigate the relationship between genetic variability and byssal thread phenotypic characteristics in the hard-shelled mussel(Mytilus coruscus),we collected three wild populations of M.coruscus from different latitudes in the East China Sea,including the Shengsi(SS),Jiaojiang(JJ),and Fuding(FD)populations.The genetic diversity and structure of these populations were investigated using 10 microsatellite loci.The mean observed heterozygosity(Ho)in the SS population was 0.44,higher than the mean Ho values of the JJ(0.40)and FD(0.39)populations.The mean inbreeding coefficients(F_(is))in the SS population was 0.20,lower than the mean F_(is)values of the JJ(0.33)and FD populations(0.40).These results revealed that the SS population exhibited higher genetic diversity compared to the other two populations.The different numbers of private alleles(P_(a))in the three populations,ranging from 10 to 17,suggest that these populations have experienced selective pressures from various environments.Moreover,genetic differentiation was observed in the genetic distance between the SS population and the other two populations.We also examined the phenotypic characteristics of their byssal threads.There were significant differences in byssus attachment strength among the three populations,with the SS population located at the highest latitude secreting more byssal threads and exhibiting greater byssal breaking force and plaque adhesion strength,while the Fuding(FD)population located at the lowest latitude had the weakest byssal attachment.The observed differentiation in private alleles and byssus phenotypes might suggest that the three wild populations have experienced different environmental selective pressures.This study provides insight for future genetic enhancement programs aimed at improving byssus attachment in M.coruscus.展开更多
基金TheNationalNaturalScienceFoundationofChina (No .60 3 90 5 40 ) .
文摘Several space-time coding based transmit diversity techniques for wideband code division multiple access (WCDMA) systems with four transmitter antennas are investigated. Performances of the rake receivers are analyzed and compared with those of the multi-antenna receive diversity techniques. Theoretical analysis shows that the multi-antenna transmit diversity techniques provide considerable performance gain at the mobile receiver in the wireless channel with less inherent multipath diversity, especially the G4 coding based scheme. Compared with the multi-antenna receive diversity techniques with the same diversity order, the transmit diversity techniques introduce much more multi-access plus multipath interference and require measures of interference suppression in the multi-user environments.
文摘Space-time spreading (STS) and orthogonal transmit diversity (OTD) are towtransmit diversity schemes proposed by cdma2000 standard. In this paper, performance comparisonanalysis of the two transmits diversity schemes in multipath channel under multiuser situation arecarried out. Link level simulation in forward link cdma2000 is performed in IMT-2000 channel.Performance analysis and simulation results show that the performance improvement provided STS overOTD decreases as the increase of propagation path number and decrease of the user number.
文摘Space time coding can provide high data rate and performance gain for wireless communication system. Performance comparison of space time trellis codes and space time transmit diversity is carried out under the same bandwidth efficiency in this paper. We also propose some optimum low rate space time trellis codes in quasi static Rayleigh fading chan￣nel. Performance analysis and simulation show that the low rate space time trellis codes outperform space time transmit diversity at the same bandwidth efficiency, and are more suitable for the power limited wireless communication system which has no strict requirement on bandwidth efficiency.
基金supported by the National Natural Science Foundation of China(60072041).
文摘Many common multimedia signal processing,including cropping,filtering,and perceptual coding,make watermark signal fading-like modification.A scheme that applies transmit diversity technique to improve robustness of digital watermarking is presented.First,the scheme decomposes the original image using wavelet pyramid algorithm and chooses the middle-frequency band for transmission channel that the watermark will be embedded into.Then the watermark is pseudo-randomly permuted.The scheme makes use of space-time coding and differential detection technique to embed and extract watermark.The extracting process has access to neither the original image nor channel state information.Experimental results demonstrate that the scheme improves the performance of robust watermarking.
基金Project supported by the National Natural Science Foundation of China （Grant No.60472103）, the Shanghai Excellent Academic Leader Project （Grant No.05XP14027）, and the Shanghai Leading Academic Discipline Project （Grant No.T0102）.
文摘The paper investigates closed-loop transmit diversity （CLTD） systems with antenna selection technique. The expected received signal-noise-ratio （RxSNR） of the proposed systems is analyzed and compared with CLTD systems. An algorithm is proposed for determining the number of increased transmit antennas in terms of a reduced RF chains without performance degradation. Since a feedback channel is bandwidth-limited, we present a method of quantizing transmit-weight vectors. Simulation results demonstrate advantage of the proposed systems with full and quantized feedback information. Quantized feedback has less effect on the proposed systems than CLTD systems.
基金Project supported by the Hi-Tech Research and Development Pro-gram (863) of China (No. 2003AA123310) and the National Natural Science Foundation of China (No. 60332030)
文摘This paper deals with channel estimation for orthogonal frequency-division multiplexing (OFDM) systems with transmit diversity. Space time coded OFDM systems, which can provide transmit diversity, require perfect channel estimation to improve communication quality. In actual OFDM systems, training sequences are usually used for channel estimation. The authors propose a training based channel estimation strategy suitable for space time coded OFDM systems. This novel strategy provides enhanced performance, high spectrum efficiency and relatively low computation complexity.
文摘Transmit diversity has been recently proposed to reduce the effects of fading channels in various wireless applications. Orthogonal transmit diersity (OTD) is one of the standardized techniques in 3G systems. In this paper, we apply orthogonal transmit diversity technique to multicarrier CDMA systems. Andlysis and simulation results show that performance benefits can be achieved compared with conventioal MC-CDMA systems in multipath fading channels.
基金supported in part by the Fundamental Research Funds for the Central Universities under Grants 2020JBM081 and 2020JBZD005in part by the National Key R&D Program of China under Grant 2020YFB1806903in part by the National Natural Science Foundation under Grant U1834210。
文摘This paper investigates the transmission scheme of the orthogonal time frequency space(OTFS)system with multiple antennas.Previous works have studied the multi-antenna transmitter diversity scheme with the ideal pulse shaping in OTFS systems assuming the wireless channels of two consecutive frames duration are invariant.However,the ideal pulse shaping can not be realized in practice and the channel varies rapidly in two consecutive frames in the high-speed mobility scenarios.To this end,we redesign the multi-antenna transmitter diversity scheme to ensure its practicability in the rectangular-pulsebased OTFS systems.At first,the information symbols of each antenna are divided into two half frames along the Doppler domain.Then,the guard symbols are carefully arranged to eliminate the interference between two half frames,and to ensure the equivalent channels of two half frames being identical.By considering the positions of the guard symbols,the transmission codeword is designed and a low complexity linear detection is proposed.Finally,simulation results validate that the bit error rate performance of the proposed scheme has the superiority over the existing works.
基金Sponsored by the Science and Technology Project of Dalian,China (Grant No. 2011J21DW009)
文摘In this paper, a time-switched space-time （TSST） coded orthogonal frequency division nmltiplexing （OFDM） scheme against the time-varying channels is proposed. In the TSST-OFDM scheme, it is equipped with four transmit antennas, but only double of them are used for coding in every time slot. It is shown that the signal to inter-antenna interference ratio is a function of Doppler frequency in time-varying channels for a given space-time code. The analyses and simulations results validate that the proposed scheme not only gets time- switched diversity and lower decoding complexity, but also suffers less time-varying impairments. Hence, it ex- hibits better performance than quasi-orthogonal space-time coded scheme.
基金Supported by the National Natural Science Foundation of China (No. 60496311)
文摘In this paper, the closed loop transmit diversity technology for the Wideband Code Division Multiple Access(WCDMA) systems is investigated in a multipath Rayleigh fading channel. The RAKE receiver model and the weighing vector algorithm are presented. The performance is theoretically analyzed in terms of the average maximal Signal-to-Noise Ratio(SNR) gain available over the Space-Time block coding based Transmit Diversity(STTD) technology. Theoretic analysis and simulation results show that the closed loop transmit diversity can provide a 3dB performance gain over the open loop scheme in a single path fading channel, while the performance gain decreases dramatically with the increasing inherent multipath diversity of the wireless channel.
文摘In this paper, we introduce a novel merger of antenna arrays with scanning beam patterns, and Orthogonal Frequency Division Multiplexing (OFDM) systems. Controlled time varying phase shifts are applied to the antenna array elements mounted at the base station with beam patterns directed toward the desired user. This creates a small beam pattern movement called Beam Pattern Scanning (BPS). In rich scattering environments BPS creates a time varying environment leading to time diversity exploitable at the receiver enhances its probability-of-error performance. Here, we apply OFDM signals to BPS antenna arrays, and we achieve: (1) directionality, which supports Space Division Multiple Access (SDMA);and (2) a time diversity gain, which leads to high performance. We discuss the structure of the base station antenna array and the OFDM receiver that exploits time diversity. We also introduce the merger of BPS and multi-carrier OFDM (MC-OFDM) systems. In MC-OFDM each bit is transmitted over all sub-carriers after serial to parallel conversion. BPS/ MC-OFDM receiver exploits both time diversity inherent in BPS, and frequency diversity inherent in MC-OFDM transmission technique. Simulation results show high Probability-of-error performance is achie- vable via BPS/OFDM and BPS/MC-OFDM schemes comparing to the traditional OFDM and MC-OFDM, respectively. Simulations also reveal that MC-OFDM system as well as its merger with BPS is capable of mitigating large Peak-to-Average Ratio (PAPR) problem in traditional OFDM system. In addition, performance simulations with coded OFDM (COFDM) and coded MC-OFDM (MC-COFDM) and their merger with BPS are studied.
文摘The performance analysis, using outage capacity for a forward link cellular communications system is presented. The effects of correlated fading, the distribution of angle of arrivals, and the array configurations are considered. The objective is to examine the effect of angle of arrival (AOA) energy distributions on two systems (transmit diversity and beamforming) with angle spread. We do so by comparing the performance of transmit diversity with a system that uses beamforming to point a relatively narrow beam at the mobile station. Analytical results show that the transmit diversity system using uniform linear arrays (ULA) and uniform circular arrays (UCA) with truncated Laplacian AOA, performs better even at smaller angle spreads as compared to other energy distributions. The ULA geometry is a preferable configuration for transmit diversity system as compared to UCA.
基金supported by the Key Pre-Research Project for Civil Space Technology(No.B0106).
文摘The next generation of High Throughput Satellite(HTS)will exploit Q/V band for the feeder link and Ka band for the user link.The exploitation of multiple gateways(GWs)is a transmit diversity measure to compensate severe rain attenuation of Q/V band feeder links.This paper introduces a new smart gateway diversity combination scheme that combinates N-active(K=2)and N+1 diversity method in detail from the working principle,gateway switching strategy,evaluation of system availability and implementation complexity.In addition,a feeder link outage event prediction algorithm featuring combination scheme is given detailly based on modified time-adaptive linear regression.Compared with the existing N+P scheme,the proposed scheme can provide higher system availability and more stable user’s experience under the condition of properly increasing the complexity of payload design.Compared with Nactive scheme that has been reported,it is much easier to implement in engineering and more cost-effective.As a result,the combination scheme is a realistic solution based on a trade-off between performance improvement and implementation complexity.
基金supported by the Yunnan Provincial Key Laboratory of Clinical Virology(No.202002AG070062)the Key Projects of Yunnan Province Science and Technology Department(No.202302AA310044)the National Natural Science Foundation of China(No.82060664).
文摘This study primarily aimed to investigate the prevalence of human papillomavirus(HPV)and other common pathogens of sexually transmitted infections(STIs)in spermatozoa of infertile men and their effects on semen parameters.These pathogens included Ureaplasma urealyticum,Ureaplasma parvum,Chlamydia trachomatis,Mycoplasma genitalium,herpes simplex virus 2,Neisseria gonorrhoeae,Enterococcus faecalis,Streptococcus agalactiae,Pseudomonas aeruginosa,and Staphylococcus aureus.A total of 1951 men of infertile couples were recruited between 23 March 2023,and 17 May 2023,at the Department of Reproductive Medicine of The First People’s Hospital of Yunnan Province(Kunming,China).Multiplex polymerase chain reaction and capillary electrophoresis were used for HPV genotyping.Polymerase chain reaction and electrophoresis were also used to detect the presence of other STIs.The overall prevalence of HPV infection was 12.4%.The top five prevalent HPV subtypes were types 56,52,43,16,and 53 among those tested positive for HPV.Other common infections with high prevalence rates were Ureaplasma urealyticum(28.3%),Ureaplasma parvum(20.4%),and Enterococcus faecalis(9.5%).The prevalence rates of HPV coinfection with Ureaplasma urealyticum,Ureaplasma parvum,Chlamydia trachomatis,Mycoplasma genitalium,herpes simplex virus 2,Neisseria gonorrhoeae,Enterococcus faecalis,Streptococcus agalactiae,and Staphylococcus aureus were 24.8%,25.4%,10.6%,6.4%,2.4%,7.9%,5.9%,0.9%,and 1.3%,respectively.The semen volume and total sperm count were greatly decreased by HPV infection alone.Coinfection with HPV and Ureaplasma urealyticum significantly reduced sperm motility and viability.Our study shows that coinfection with STIs is highly prevalent in the semen of infertile men and that coinfection with pathogens can seriously affect semen parameters,emphasizing the necessity of semen screening for STIs.
基金supported by Innovation Scientists and Technicians Troop Construction Projects of Henan Province(Grant No.212101510003)the Central Plains Scholar Workstation Project(Grant No.224400510002)+1 种基金the Youth Science Foundation of Henan Province(Grant No.202300410136)the Experimental Development Foundation of Henan University of Science and Technology(Grant No.SY2324004)。
文摘Paeonia suffruticosa Andr.is an endemic shrub flower in China with 2n=10.This study used 228 cultivars from four populations,i.e.,Jiangnan,Japan,Northwest,and Zhongyuan,as materials to explore the genetic diversity levels among different populations of tree peony varieties.The results showed that 34 bands were amplified using five pairs of cp SSR primers,with an average of 6.8 bands per primer pair.The average number of different alleles(N_(a)),effective alleles(N_(e)),Shannon's information index(I),diversity(H),and polymorphic information content(PIC)were 3.600,2.053,0.708,0.433,and 0.388,respectively.The PIC value was between 0.250 and 0.500,indicating a moderate level of polymorphism for the five cp SSR primer pairs.The genetic diversity levels of peony cultivars varied among different populations,with the Northwest population showing relatively lower levels(I=0.590,H=0.289,and PIC=0.263).A total of 52 haplotypes were identified in the four examined populations,and the number of haplotypes per population ranged from 11 to 22.Forty-four private haplotypes were detected across populations,and the Northwest population exhibiting the highest count of private haplotypes with 17.The mean number of effective number of haplotypes(N_(eh)),haplotypic richness(R_(h)),and diversity(H)were 8.351,6.824,and 0.893,respectively.Analysis of molecular variance indicated that genetic variation within tree peony germplasm was greater than that between germplasm resources,and the main variation was found within individuals of peony germplasm.Cluster analysis,principal coordinate analysis,and genetic structure analysis classified tree peonies from different origins into two groups,indicating a certain degree of genetic differentiation among these four tree peony cultivation groups.This study provides a theoretical basis for the exploration,utilization,and conservation of peony germplasm resources,as well as for research on the breeding of excellent varieties.
基金supported by the Southwest Minzu University Research Startup Funds (No.16011221038,RQD2022021)Double World-Class Project (No.CX2023010)。
文摘Wetland degradation is an escalating global challenge with profound impacts on animal diversity,particularly during successional processes.Birds,as highly mobile and environmentally sensitive organisms,serve as effective indicators of ecological change.While previous studies have primarily focused on local community structures and species diversity during a specific season,there is a need to extend the research timeframe and explore broader spatial variations.Additionally,expanding from simple species diversity indices to more multidimensional diversity indices would provide a more comprehensive understanding of wetland health and resilience.To address these gaps,we investigated the effects of wetland degradation on bird diversity across taxonomic,phylogenetic,and functional dimensions in the Zoige Wetland,a plateau meadow wetland biodiversity hotspot.Surveys were conducted during both breeding(summer)and overwintering(winter)seasons across 20 transects in 5 sampling areas,representing 4 degradation levels(pristine,low,medium,and high).Our study recorded a total of 106 bird species from 32 families and 14 orders,revealing distinct seasonal patterns in bird community composition and diversity.Biodiversity indices were significantly higher in pristine and low-degraded wetlands,particularly benefiting waterfowl(Anseriformes,Ciconiiformes)and wading birds(Charadriiformes)in winter,when these areas provided superior food resources and habitat conditions.In contrast,medium and highly degraded wetlands supported increased numbers of terrestrial birds(Passeriformes)and raptors(Accipitriformes,Falconiformes).Seasonal differences in taxonomic,phylogenetic,and functional diversity indices highlighted the contrasting ecological roles of wetlands during breeding and overwintering periods.Furthermore,indicator species analysis revealed key species associated with specific degradation levels and seasons,providing valuable insights into wetland health.This study underscores the importance of spatiotemporal dynamics in understanding avian responses to wetland degradation.By linking seasonal patterns of bird diversity to habitat conditions,our findings contribute to conservation efforts and provide a framework for assessing wetland degradation and its ecological impacts.
基金Supported by the Regional Innovation Development Joint Fund Project of the National Natural Science Foundation of China(No.U20A2087)the Shiptime Sharing Project of National Natural Science Foundation of China(No.42249911)。
文摘Marine fish diversity in the Beibu Gulf from 2014 to 2022 was analyzed,using various methods including at-sea fisheries resource surveys,fishing port surveys,underwater survey techniques,and data from literature,books,and databases,from which 1059 fish species across 40 orders,166 families,and 503 genera were identified.Among them,Acanthuriformes displayed the highest diversity,followed by Carangiformes and Perciformes.Notably,eight alien species were found in the Beibu Gulf.The International Union for Conservation of Nature(IUCN)Red List assessment revealed 51threatened species,primarily cartilaginous fish.Taxonomic changes affected 88.70%of species due to classification adjustments,misidentifications,and junior synonymy.This study contributed new data of the gulf,including one additional order,six new families,34 new genera,and 81 new species,emphasizing the dynamic nature of marine ecosystems.Fish diversity in the gulf was relatively lower than the broader South China Sea,attributed to limited habitats and survey methods.Different survey methods,such as gill nets,trap nets,and underwater cameras,yielded varying results.Ocean currents may have transported deep-sea species into the Beibu Gulf,leading to accidental records.Research gaps exist in unexplored areas,warranting further investigation.Therefore,the Beibu Gulf hosts significant marine biodiversity,but taxonomic challenges and undiscovered species require new research and conservation efforts.
基金supported by the National Natural Science Foundation of China(32370703)the CAMS Innovation Fund for Medical Sciences(CIFMS)(2022-I2M-1-021,2021-I2M-1-061)the Major Project of Guangzhou National Labora-tory(GZNL2024A01015).
文摘Viral infectious diseases,characterized by their intricate nature and wide-ranging diversity,pose substantial challenges in the domain of data management.The vast volume of data generated by these diseases,spanning from the molecular mechanisms within cells to large-scale epidemiological patterns,has surpassed the capabilities of traditional analytical methods.In the era of artificial intelligence(AI)and big data,there is an urgent necessity for the optimization of these analytical methods to more effectively handle and utilize the information.Despite the rapid accumulation of data associated with viral infections,the lack of a comprehensive framework for integrating,selecting,and analyzing these datasets has left numerous researchers uncertain about which data to select,how to access it,and how to utilize it most effectively in their research.This review endeavors to fill these gaps by exploring the multifaceted nature of viral infectious diseases and summarizing relevant data across multiple levels,from the molecular details of pathogens to broad epidemiological trends.The scope extends from the micro-scale to the macro-scale,encompassing pathogens,hosts,and vectors.In addition to data summarization,this review thoroughly investigates various dataset sources.It also traces the historical evolution of data collection in the field of viral infectious diseases,highlighting the progress achieved over time.Simultaneously,it evaluates the current limitations that impede data utilization.Furthermore,we propose strategies to surmount these challenges,focusing on the development and application of advanced computational techniques,AI-driven models,and enhanced data integration practices.By providing a comprehensive synthesis of existing knowledge,this review is designed to guide future research and contribute to more informed approaches in the surveillance,prevention,and control of viral infectious diseases,particularly within the context of the expanding big-data landscape.
文摘Sexually transmitted infections (STIs) represent a public health problem due to their high prevalence worldwide and the emergence of multidrug resistance of responsible microorganisms. Medical laboratory diagnosis of sexually transmitted genital infections by traditional methods as culture remains extremely delicate, difficult or impossible (to find extremely fragile organisms that can be cultured). Thus, molecular techniques constitute an alternative to improve accurate diagnostic, personalized patient treatment, and public health. A total of 83 clinical samples including urethral discharge and urine samples from individual patients with symptoms of urethritis received were analyzed using traditional methods and a commercial real-time PCR (qPCR) method. Out of 83 urethritis patients, n = 55 (66.26%) were positive for at least one of the STI pathogens detected by qPCR. qPCR assay was more sensitive (50/83, positive cases) compared to culture (15/83, positive cases) and light microscopy (28/83, positive cases). The most prevalent NTD pathogen in the suspected patients was N. gonorrhoeae with 60.24% (50/83) based on real-time PCR diagnosis. Among the positive cases of STI pathogens, Neisseria gonorrhoeae had the highest frequency 49/55 (89.01%) followed by low frequencies of Trichomonas vaginalis 4/55 (7.27%) and Chlamydia trachomatis 1/55 (1.82%). This highlights the high prevalence of N. gonorrhoeae infection in male urethritis patients and a very important misdiagnosis using traditional routine methods in Burkina Faso by medical laboratories. Thus, this situation may negatively impact patients’ personalized treatment and care and public health with the possible rapid emergence of multidrug-resistant strains. This study also highlights the urgent need to optimize culture for the diagnosis of NTD pathogens in Burkina Faso and the usefulness and the need for the introduction of molecular diagnostic methods in routine diagnosis for the detection of NTD pathogens in the medical laboratories in Burkina Faso.
文摘The mussel is one of the main cultivated species in the world.A significant challenge faced by suspension-cultured mussels is the high incidence of mussel fall-off from cultivation ropes,adversely impacting harvest yields,which have been documented at commercial mussel farms in the United Kingdom,the United States of America,Canada,Spain,New Zealand and China.Byssus is an important attachment structure for marine mussels,and weakness in byssal thread attachment is a major factor leading to mussel detachment from ropes.To investigate the relationship between genetic variability and byssal thread phenotypic characteristics in the hard-shelled mussel(Mytilus coruscus),we collected three wild populations of M.coruscus from different latitudes in the East China Sea,including the Shengsi(SS),Jiaojiang(JJ),and Fuding(FD)populations.The genetic diversity and structure of these populations were investigated using 10 microsatellite loci.The mean observed heterozygosity(Ho)in the SS population was 0.44,higher than the mean Ho values of the JJ(0.40)and FD(0.39)populations.The mean inbreeding coefficients(F_(is))in the SS population was 0.20,lower than the mean F_(is)values of the JJ(0.33)and FD populations(0.40).These results revealed that the SS population exhibited higher genetic diversity compared to the other two populations.The different numbers of private alleles(P_(a))in the three populations,ranging from 10 to 17,suggest that these populations have experienced selective pressures from various environments.Moreover,genetic differentiation was observed in the genetic distance between the SS population and the other two populations.We also examined the phenotypic characteristics of their byssal threads.There were significant differences in byssus attachment strength among the three populations,with the SS population located at the highest latitude secreting more byssal threads and exhibiting greater byssal breaking force and plaque adhesion strength,while the Fuding(FD)population located at the lowest latitude had the weakest byssal attachment.The observed differentiation in private alleles and byssus phenotypes might suggest that the three wild populations have experienced different environmental selective pressures.This study provides insight for future genetic enhancement programs aimed at improving byssus attachment in M.coruscus.
