Evaluating the performance of genomic selection on purebred population by incorporating crossbred data in pigs

Genomic selection(GS)has been widely used in livestock,which greatly accelerated the genetic progress of complex traits.The population size was one of the significant factors affecting the prediction accuracy,while it was limited by the purebred population.Compared to directly combining two uncorrelated purebred populations to extend the reference population size,it might be more meaningful to incorporate the correlated crossbreds into reference population for genomic prediction.In this study,we simulated purebred offspring(PAS and PBS)and crossbred offspring(CAB)base on real genotype data of two base purebred populations(PA and PB),to evaluate the performance of genomic selection on purebred while incorporating crossbred information.The results showed that selecting key crossbred individuals via maximizing the expected genetic relationship(REL)was better than the other methods(individuals closet or farthest to the purebred population,CP/FP)in term of the prediction accuracy.Furthermore,the prediction accuracy of reference populations combining PA and CAB was significantly better only based on PA,which was similar to combine PA and PAS.Moreover,the rank correlation between the multiple of the increased relationship(MIR)and reliability improvement was 0.60-0.70.But for individuals with low correlation(Cor(Pi,PA or B),the reliability improvement was significantly lower than other individuals.Our findings suggested that incorporating crossbred into purebred population could improve the performance of genetic prediction compared with using the purebred population only.The genetic relationship between purebred and crossbred population is a key factor determining the increased reliability while incorporating crossbred population in the genomic prediction on pure bred individuals.

Absolute copy number differences of Y chromosomal genes between crossbred (Bos taurus×Bos indicus) and Indicine bulls

Background： The Y chromosome in mammal is paternally inherited and harbors genes related to male fertility and spermatogenesis. The unique intra-chromosomal recombination pattern of Y chromosome and morphological difference of this chromosome between Bos taurus and Bos indicus make it an ideal model for studying structural variation, especially in crossbred （Bos taurus x Bos indicus） bulls. Copy Number Variation （CNV） is a type of genomic structural variation that gives information complementary to SNP data. The purpose of this study was to find out copy number differences of four Y chromosomal spermatogenesis-related candidate genes in genomic DNA of crossbred and purebred Indicine bulls. Result： Four Y chromosomal candidate genes of spermatogenesis namely, sex determining gene on Ychromosome （SRY）, DEAD box po/ypeptide 3-Y chromosome （DDX3 Y）, Ubiquidn specific peptidase 9, Y-linked （ usPgY）, testis-specific protein on Y chromosome （TSPY） were evaluated. Absolute copy numbers of Y chromosomal genes were determined by standard curve-based quantitative real time PCR. Copy numbers of SRYand TSPYgenes per unit amount of genomic DNA are higher in crossbred than Indicine bulls. However, no difference was observed in DDX3Yand usPgYgene copy numbers between two groups. Conclusion： The present study demonstrates that the structural organization of Y chromosomes differs between crossbred and Indicine bulls which are reproductively healthy as observed from analysis of semen attributes. The absolute copy numbers of SRY and TSPY genes in unit mass of genomic DNA of crossbred bulls are significantly higher than Indicine bulls. No alteration in absolute copies ofDDX3Yand usPgYgene was found between the genome of crossbred and Indicine bulls. This study suggests that the DDX3Yand USPgYare likely to be single copy genes in the genome of crossbred and Indicine bulls and variation in Y chromosome length between crossbred and Indicine bulls may be due to the copy number variation of SRY gene and TSPYarray.

Factors affectingin-vivo fertility of crossbred Egyptian - Italian buffalo semen

Objective:To assess the effect of region, season and year of insemination onin-vivo fertility of Italian-Egyptian crossbred buffalo semen.Methods: A total number of 4799 female buffaloes were inseminated by frozen semen with at least 50% post-thaw motility of Egyptian-Italian crossbred bulls in three localities in Delta, lower Egypt (El-Behira, El-Sharkia and Damietta) during the period of 2013, 2014 and 2015. The pregnancy rate after two months was evaluated during the four seasons.Results:The rate of pregnancy was significantly (P<0.0001) differ among the three localities. The effect of year of insemination on pregnancy rate was significantly higher during 2014 and 2015 than 2013 in El-Sharkia and El-Behira. But in Damietta, the rate of pregnancy was significantly higher in 2014 than 2013 and 2015. There were no significant differences among seasons in El-Behira and Damietta governorates but there was significant (P<0.05) differences in pregnancy rate in El-Sharkia. It was higher in summer, spring and autumn than in winter.Conclusions:Localities, year of insemination and season of the year have effects on fertility of crossbred Egyptian-Italian buffalo semen.

Trans-10,cis-12 conjugated linoleic acid reduces neutral lipid content and may affect cryotolerance of in vitro-produced crossbred bovine embryos

Background：Due to high neutral lipids accumulation in the cytoplasm,in vitro-produced embryos from Bos primigenius indicus and their crosses are more sensitive to chilling and cryopreservation than those from Bos primigenius taurus.The objective of the present study was to evaluate the effects of trans-10,cis-12 conjugated linoleic acid（CLA） on the development and cryotolerance of crossbred Bos primigenius taurus x Bos primigenius indicus embryos produced in vitro,and cultured in the presence of fetal calf serum.Bovine zygotes（n = 1,692）were randomly assigned to one of the following treatment groups：1） Control,zygotes cultured in Charles Rosenkrans 2 amino acid（CR2aa） medium（n = 815） or 2） CLA,zygotes cultured in CR2 aa medium supplemented with 100 μmol/L of trans-10,cis-12 CLA（n =877）.Embryo development（cleavage and blastocyst rates evaluated at days 3 and 8 of culture,respectively）,lipid content at morula stage（day 5） and blastocyst cryotolerance（re-expansion and hatching rates,evaluated 24 and 72 h post-thawing,respectively） were compared between groups.Additionally,selected mRNA transcripts were measured by Real-Time PCR in blastocyst stage.Results：The CLA treatment had no effect on cleavage and blastocyst rates,or on mRNA levels for genes related to cellular stress and apoptosis.On the other hand,abundance of mRNA for the 1-acylglycerol-3-phosphate0-acyltransferase-encoding gene（AGPAT）,which is involved in triglycerides synthesis,and consequently neutral lipid content,were reduced by CLA treatment.A significant increase was observed in the re-expansion rate of embryos cultured with trans-10,cis-12 CLA when compared to control（56.3 vs.34.4%,respectively,P = 0.002）.However,this difference was not observed in the hatching rate（16.5 vs.14.0%,respectively,P=0.62）.Conclusions：The supplementation with trans-10,ds-12 CLA isomer in culture medium reduced the lipid content of in vitro produced bovine embryos by reducing the gene expression of 1-acylglycerol 3-phosphate 0-acyltransferase（AGPAT） enzyme.However,a possible improvement in embryo cryotolerance in response to CLA,as suggested by increased blastocyst re-expansion rate,was not confirmed by hatching rates.

Meat Production Performances of Geese in Different Crossbred Combinations

[ Objective] To study the meat production performance of geese in different crossbred combination, and provide a reference for cultivating new multiplication strains of meat geese. [Method] A total of five goose breeds including Taihu goose （T）, Wulong goose （WL）, Wanxi white goose （WX）, Sichuan white goose （SC） and Sanhua goose （SH） were used as research objects, and eight crossbred combinations were designed. The body measurements, slaughter performance, conventional meat quality and muscle composition of 90-day-old geese in eight crossbred combinations were determined and comparatively analyzed. [ Result] All the body measurement indexes except thud width of WXSC combination were the biggest in the eight crossbred combinations. Contrarily, the body measurement indexes of SHSC combination, including average body weight, body slope length, breast depth, breast width, shank length, neck length and half-diving depth were the lowest in the eight crossbred combinations. The live weight, slaughter weight and abdomen fat weight of WXSC combinations ware 3 291.36, 2 956.46 and 77.84 g, respectively, which were the biggest in eight crossbred combinations. The slaughter rate of SHWL combinations was 92.96%, and more than other crossbred combinations. The shear force of SHT and WXWL combinations were the lowest （3.09 kg） and the highest （3.78 kg）, respectively. The water holding capacities of SCWL and WXSC combinations were the highest （66.46%） and the lowest （61.48%）, respectively. The percentage of moisture content of SHWL and SCT combinations were the highest （73.05%） and the lowest （66.77%）, respectively. The crude protein content of SHT and SHWL combinations were the highest （23.32%） and the lowest （21.94%）, respectively. The percentage of crude fat content of SHT and SCWL combinations were the highest （3.06%） and the lowest （1.67%）, respectively. [ Concusion] The growth rate of WXSC combination is the fastest, and the meat performance of SHT combination is the best.

Effect of Concentrate to Roughage Ratio on Cost Effective Growth Performance of Brahman Crossbred Calves

An experiment was conducted to evaluate the growth performance and cost per gain of Brahman × local crossbred bull calves receiving three diets with varying concentrate to roughage ratio （C：R） of 75：25, 65：35 and 55：45 on dry matter （DM） basis. Twelve bull calves （aging 11.5 ±1.2 months and 170.8 ± 13.0 kg live weight） divided into three equal groups were fed on three diets. The diets were balanced to 14.5% crude protein （CP） level and 10.5 MJ metabolizable energy （ME） per kg DM, formulating different concentrate mixtures. German grass （Echinoclora grousgali） and paddy straw were offered at 2：1 ratio on DM basis as roughages. The results revealed that C：R ratio did not affect （P 〉 0.05） the intake of feed and nutrients, feed efficiency （7.04, 6.94 and 6.76） and average daily gain （981,958 and 976 g）. Digestibility of nutrients was not affected （P 〉 0.05） by C：R. Animals fed diet with C：R = 55：45 had the lowest feed cost （Bangladeshi Taka 136.8 BDT/kg live weight gain）, which was increased （147.5 B DT and 153.8 BDT） non-significantly （P 〉 0.05） with the increasing level of concentrate. The diet consisting of 55% concentrate mixture showed similar results with the diet consisting of 75% concentrate mixture, but was comparatively economic. Therefore, considering the growth performance and cost per kg gain of Brahman crossbred growing calves, it may be concluded that the diet consisting of 55：45 C：R may be used for economic beef production.

A Retrodirective Array Enabled by CMOS Chips for Two-Way Wireless Communication with Automatic Beam Tracking

This article proposes and demonstrates a retrodirective array(RDA)for two-way wireless communication with automatic beam tracking.The proposed RDA is enabled by specifically designed chips made using a domestic complementary metal-oxide semiconductor(CMOS)process.The highly integrated CMOS chip includes a receiving(Rx)chain,a transmitting(Tx)chain,and a unique tracking phaselocked loop(PLL)for the crucial conjugated phase recovery in the RDA.This article also proposes a method to reduce the beam pointing error(BPE)in a conventional RDA.To validate the above ideas simply yet without loss of generality,a 2.4 GHz RDA is demonstrated through two-way communication links between the Rx and Tx chains,and an on-chip quadrature coupler is designed to achieve a nonretrodirective signal suppression of 23 dBc.The experimental results demonstrate that the proposed RDA,which incorporates domestically manufactured low-cost 0.18 lm CMOS chips,is capable of automatically tracking beams covering±40with a reduced BPE.Each CMOS chip in the RDA has a compact size of 4.62 mm^(2) and a low power consumption of 0.15 W.To the best of the authors’knowledge,this is the first research to demonstrate an RDA with a fully customized CMOS chip for wireless communication with automatic beam tracking。

Reference-frame-independent quantum key distribution with two-way classical communication

The data post-processing scheme based on two-way classical communication(TWCC)can improve the tolerable bit error rate and extend the maximal transmission distance when used in a quantum key distribution(QKD)system.In this study,we apply the TWCC method to improve the performance of reference-frame-independent quantum key distribution(RFI-QKD),and analyze the influence of the TWCC method on the performance of decoy-state RFI-QKD in both asymptotic and non-asymptotic cases.Our numerical simulation results show that the TWCC method is able to extend the maximal transmission distance from 175 km to 198 km and improve the tolerable bit error rate from 10.48%to 16.75%.At the same time,the performance of RFI-QKD in terms of the secret key rate and maximum transmission distance are still greatly improved when statistical fluctuations are considered.We conclude that RFI-QKD with the TWCC method is of practical interest.

Beamforming Design for IRS-and-UAV-Aided Two-Way Amplify-and-Forward Relay Networks in Maritime IoT

In this paper,an intelligent reflecting surface(IRS)-and-unmanned aerial vehicle(UAV)-assisted two-way amplify-and-forward(AF)relay network in maritime Internet of Things(IoT)is proposed,where ship1(S1)and ship2(S2)can be viewed as data collecting centers.To enhance the message exchange rate between S1 and S2,a problem of maximizing minimum rate is cast,where the variables,namely AF relay beamforming matrix and IRS phase shifts of two time slots,need to be optimized.To achieve a maximum rate,a low-complexity alternately iterative(AI)scheme based on zero forcing and successive convex approximation(LC-ZF-SCA)algorithm is presented.To obtain a significant rate enhancement,a high-performance AI method based on one step,semidefinite programming and penalty SCA(ONSSDP-PSCA)is proposed.Simulation results show that by the proposed LC-ZF-SCA and ONS-SDP-PSCA methods,the rate of the IRS-and-UAV-assisted AF relay network surpass those of with random phase and only AF relay networks.Moreover,ONS-SDP-PSCA perform better than LC-ZF-SCA in aspect of rate.

Security-Reliability Analysis and Optimization for Cognitive Two-Way Relay Network with Energy Harvesting

This paper investigates the security and reliability of information transmission within an underlay wiretap energy harvesting cognitive two-way relay network.In the network,energy-constrained secondary network(SN)nodes harvest energy from radio frequency signals of a multi-antenna power beacon.Two SN sources exchange their messages via a SN decode-and-forward relay in the presence of a multiantenna eavesdropper by using a four-phase time division broadcast protocol,and the hardware impairments of SN nodes and eavesdropper are modeled.To alleviate eavesdropping attacks,the artificial noise is applied by SN nodes.The physical layer security performance of SN is analyzed and evaluated by the exact closed-form expressions of outage probability(OP),intercept probability(IP),and OP+IP over quasistatic Rayleigh fading channel.Additionally,due to the complexity of OP+IP expression,a self-adaptive chaotic quantum particle swarm optimization-based resource allocation algorithm is proposed to jointly optimize energy harvesting ratio and power allocation factor,which can achieve security-reliability tradeoff for SN.Extensive simulations demonstrate the correctness of theoretical analysis and the effectiveness of the proposed optimization algorithm.

Two-way中继系统中的双向中继选择及功率分配策略

通过中继选择和功率分配,可以达到提高two-way中继系统总速率的目的。综合考虑中继节点处的接收信噪比和中继节点到目的节点间的信道增益,提出了two-way AF中继系统中的双向中继选择策略(BRS);同时,在总功率受限的条件下,建立了two-way AF中继系统中的优化功率分配模型,通过对模型进行数学分析求解,提出了一种自适应的最优功率分配策略(OPA)。仿真结果证明两种策略均能提高系统总速率。

Two-way中继系统中基于最小化中断概率的功率分配策略

为了降低Two-way中继系统中断概率,提出了一种Two-way中继系统中基于最小化中断概率的功率分配策略。首先推导了Two-way中继系统中断概率的闭合表达式,然后在总功率受限的条件下,提出了一种最小化中断概率的最优功率分配策略(OPA),通过拉格朗日乘数法对该优化模型进行了求解。仿真结果证明了该策略能够有效降低系统的中断概率,提高系统性能。

Characteristics of Deposition of Inosine Monophosphate(IMP) and Intramuscular Fat(IMF) in Muscles of Jinghai Yellow Chicken and Its Crossbreeds

[Objective] This study aimed to investigate the characteristics of deposition of inosine monophosphate （IMP） and intramuscular fat （IMF） in muscles of Jinghai yellow chickens and its crossbred.[Method] The characteristics of IMP and IMF deposition of 112-day-old Jinghai yellow chickens （J×J） and its two different 70-day- old crossbreeds （J×B and B×B） were analyzed. The IMP content in breast muscle and leg muscle were determined by HPLC. [Result] The contents of IMP and cor- rected inosine monophosphate （IMPc） in breast muscle were significantly or ex- tremely significantly higher than that in leg muscle of the chickens in the three groups whether in male or female chickens （P〈0.05 or P〈0.01）. There were no sig- nificant difference in the contents of IMP and IMPc between hens and roosters （P〉 0.05）. The fresh degree of breast muscle and leg muscle was 96,11%-98.16% and 87.22%-93.07%, respectively. And the fresh degree of breast muscle was higher than that of leg muscle. In the three groups, the IMF content in leg muscle was significantly higher than that in breast muscle whether in male or female chickens （P〈0.05）. The contents of IMF in breast muscle and leg muscle were 0.36%-0.75% and 1.84%-2.38%, respectively. The iMP content in breast muscle of chickens in Bx J group was extremely significantly higher than that in breast muscle of chickens in JxJ group （P〈0.01）, but the contents of IMPc and iMF of breast muscle and leg muscle of the chickens in the three groups had no significant difference （P〉0.05）. [Conclusion] To sum up, the freshness and flavor significantly differ between the breast muscle and leg muscle of chickens, but show no significant difference among the three groups.

不同胎次、泌乳阶段及体细胞水平的蒙荷杂交牛泌乳性能变化规律研究

[目的]本文旨在通过比较不同胎次、泌乳阶段和体细胞水平的蒙荷杂交牛泌乳性能差异,分析其相关性和变化规律,为蒙荷杂交牛的精细化管理和乳品质提升提供理论依据。[方法]以蒙贝利亚为父本、自繁荷斯坦牛为母本的杂交一代泌乳牛为研究对象,提取其生产性能测定(dairy herd improvement,DHI)数据,分别按胎次(1 胎次、2 胎次)、泌乳阶段(0~99 d、100~199 d、200~299 d和≥300 d)、体细胞数(somatic cell count,SCC)(低SCC,0~1×10^(5) mL^(-1);中SCC,>1×10^(5)~2×10^(5) mL^(-1);高SCC,>2×10^(5) mL^(-1))进行分类和分组,采用Duncan's多重比较和Pearson相关性分析等方法进行比较研究。[结果]不同胎次蒙荷杂交牛产奶量存在极显著差异(P<0.01),第1胎次的产奶量显著低于第2胎次;产奶量与乳脂率呈显著负相关(P<0.05),脂蛋比与乳脂率呈极显著正相关(P<0.01)。不同泌乳阶段蒙荷杂交牛产奶量、乳脂率、乳蛋白率、脂蛋比、尿素氮、体细胞数和体细胞评分均存在显著差异(P<0.05),泌乳阶段在0~99 d时产奶量最高、体细胞数最低。不同SCC水平蒙荷杂交牛泌乳天数、产奶量、乳脂率和脂蛋比存在显著差异(P<0.05),产奶量在低SCC时最高。在不同的SCC水平,总乳脂量和总乳蛋白量呈极显著正相关(P<0.01),在低、中SCC水平,乳脂率与脂蛋比呈显著正相关(P<0.05);在高SCC水平,乳脂率与乳蛋白率、脂蛋比呈显著正相关(P<0.05)。[结论]不同胎次、泌乳阶段和SCC水平的蒙荷杂交牛产奶量和乳成分存在显著差异,随着泌乳天数的增加,产奶量呈现先上升后下降的变化规律,第2胎次、泌乳早期和低SCC水平时的产奶量最高,并随着泌乳天数的增加产奶量呈现先上升后下降的变化规律,乳脂率、乳蛋白率和脂蛋比呈现先下降后上升的变化趋势。因此,针对不同胎次、泌乳阶段和体细胞水平制定相应的饲养管理方案,以充分发挥蒙荷杂交牛的生产潜力及杂种优势,提高经济效益。

Buckling-controlled two-way shape memory effect in a ring-shaped bilayer

Shape memory polymers(SMPs)usually have a one-way shape memory effect.In this paper,an easy-operating method to realize a two-way shape memory effect was demonstrated in a ring-shaped bilayer structure where the two layers are SMPs with different thermal transition temperatures.By designing specific thermomechanical processes,the mismatched deformation between the two layers leads to a morphology change of ring-shaped bilayer structures from a smooth ring to a gear-like buckling shape under cooling and a reversible recovery to the smooth shape under heating.Such a morphology change is ascribed to occurrence and recovery of thermoelastic buckling.This method was validated by finite element simulation.We experimentally investigated the influence of pre-strain on buckling,and it was found that both the buckling occurrence and recovery temperature vary with pre-strain.Furthermore,considering a ring-shaped SMP-SMP bilayer structure,finite element analysis was conducted to study the influence of film thickness and modulus ratio of two layers on buckling behavior.The results showed that the critical buckling wavelength was greatly influenced by film thickness and modulus ratio.W e made a theoretical analysis that accorded well with the numerical results.

3D Two-way Coupled TEHD Analysis on the Lubricating Characteristics of Thrust Bearings in Pump-turbine Units by Combining CFD and FEA

The thermal elastic hydro dynamic （TEHD） lubrication analysis for the thrust bearing is usually conducted by combining Reynolds equation with finite element analysis （FEA）. But it is still a problem to conduct the computation by combining computational fluid dynamics （CFD） and FEA which can simulate the TEHD more accurately. In this paper, by using both direct and separate coupled solutions together, steady TEHD lubrication considering the viscosity-temperature effect for a bidirectional thrust bearing in a pump-turbine unit is simulated combining a 3D CFD model for the oil film with a 3D FEA model for the pad and mirror plate. Cyclic symmetry condition is used in the oil film flow as more reasonable boundary conditions which avoids the oil temperature assumption at the leading and trailing edge. Deformations of the pad and mirror plate are predicted and discussed as well as the distributions of oil film thickness, pressure, temperature. The predicted temperature shows good agreement with measurements, while the pressure shows a reasonable distribution comparing with previous studies. Further analysis of the three-coupled-field reveals the reason of the high pressure and high temperature generated in the film. Finally, the influence of rotational speed of the mirror plate on the lubrication characteristics is illustrated which shows the thrust load should be balanced against the oil film temperature and pressure in optimized designs. This research proposes a thrust bearing computation method by combining CFD and FEA which can do the TEHD analysis more accurately.

Simulation and Analysis of China Climate Using Two-Way Interactive Atmosphere-Vegetation Model (RIEMS-AVIM)

In this paper, an Atmosphere-Vegetation Interaction Model （AVIM） is coupled to the Regional Integrated Environment Model System （RIEMS）, and a 10-year integration for China is performed using the RIEMS-AVIM. The analysis of the results of the 10-year integration shows that the characters of the spatial distributions of temperature and precipitation over China are well simulated. The patterns of simulated surface sensible and latent heat fluxes match well with the spatial climatological atlas： the values of winter surface sensible and latent heat fluxes are both lower than climatological values over the whole country. Summer surface sensible heat flux is higher than climatological values in western China and lower in eastern China, while summer surface latent heat flux is higher than climatological values in the eastern and lower in the western. Seasonal variations of simulated temperature and precipitation of RIMES-AVIM agree with those of the observed. Simulated temperature is lower than the observed in the Tibetan Plateau and Northwest China for the whole year, slightly lower in the remaining regions in winter, but consistent with the observed in summer. The simulated temperature of RIEMS-AVIM is higher in winter and lower in summer than that of RIEMS, which shows that the simulated temperature of RIEMS-AVIM is closer to the observed value. Simulated precipitation is excessive in the first half of the year, but consistent with the observed in the second half of the year. The simulated summer precipitation of RIEMS-AVIM has significant improvement compared to that of RIEMS, which is less and closer to the observed value. The interannual variations of temperature and precipitation are also fairly well simulated, with temperature simulation being superior to precipitation simulation. The interannual variation of simulated temperature is significantly correlated with the observed in Northeast China, the Transition Region, South China, and the Tibetan Plateau, but the correlation between precipitation simulation and observation is only significant in Northwest China.

A Novel Forwarding Method for Full-Duplex Two-Way Relay Networks

An estimate-and-forward(EF) scheme for single-input single-output(SISO) and multiple-input multiple-output(MIMO) full-duplex two-way relay networks is proposed and analyzed. The relay estimates the received signal from two terminal nodes by a minimum mean squared error(MMSE) estimation and forwards a scaled version of the MMSE estimate to the destination. The proposed EF outperforms conventional amplify-and-forward(AF) and decode-and-forward(DF) across all signal-to-noise ratio(SNR) region. Because its computational complexity is high for relays with a large number of antennas(large MIMO) and/or high order constellations, an approximate EF scheme, called list EF, are thus proposed to reduce the computational complexity. The proposed list EF computes a candidate list for the MMSE estimate by using a sphere decoder, and it approaches the performance of the exact EF relay at a negligible performance loss. The proposed forwarding approach also could be used to other relay networks, such as half-duplex, one-way or massive MIMO relay networks.

Performance of Physical-Layer Network Coding in Asymmetric Two-Way Relay Channels

In this paper, we study the performance of physical-layer network coding in asymmetric two-way relay channels using four different cases having different poor channels:phase asymmetry, downlink asymmetry, uplink asymmetry and node asymmetry. The decision and mapping rule for symmetric and asymmetric cases are studied. The performance in terms of bit error rate for each case will be studied and analysed by computer simulation. Analytical and simulation results show that uplink asymmetry is the worst case;intra-phase asymmetry and unreliable uplink channels will more severely affect the performance degradation, which is caused by channel asymmetry.

Numerical Prediction Methods for Clock Deviation Based on Two-Way Satellite Time and Frequency Transfer Data

Three functional models, polynomial, spectral analysis, and modified AR model, are studied and compared in fitting and predicting clock deviation based on the data sequence derived from two-way satellite time and frequency transfer. A robust equivalent weight is applied, which controls the significant influence of outlying observations. Some conclusions show that the prediction precision of robust estimation is better than that of LS. The prediction precision calculated from smoothed observations is higher than that calculated from sampling observations. As a count of the obvious period variations in the clock deviation sequence, the predicted values of polynomial model are implausible. The prediction precision of spectral analysis model is very low, but the principal periods can be determined. The prediction RMS of 6-hour extrapolation interval is Ins or so, when modified AR model is used.