• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Sum Rate Maximization-based Fair Power Allocation in Downlink NOMA Networks

    2022-08-23 02:18:20MohammedAbdElnaby
    Computers Materials&Continua 2022年6期

    Mohammed Abd-Elnaby

    Department of Computer Engineering,College of Computers and Information Technology,Taif University,Taif,21944,Saudi Arabia

    Abstract: Non-orthogonal multiple access (NOMA) has been seen as a promising technology for 5G communication.The performance optimization of NOMA systems depends on both power allocation(PA)and user pairing(UP).Most existing researches provide sub-optimal solutions with high computational complexity for PA problem and mainly focuses on maximizing the sum rate (capacity) without considering the fairness performance.Also,the joint optimization of PA and UP needs an exhaustive search.The main contribution of this paper is the proposing of a novel capacity maximizationbased fair power allocation (CMFPA) with low-complexity in downlink NOMA.Extensive investigation and analysis of the joint impact of signal to noise ratio (SNR) per subcarrier and the channel gains of the paired users on the performance of NOMA in terms of the capacity and the user fairness is presented.Next, a closed-form equation for the power allocation coefficient of CMFPA as a function of SNR, and the channel gains of the paired users is provided.In addition,to jointly optimize UP and PA in NOMA systems an efficient low-complexity UP(ELCUP)method is proposed to be incorporated with the proposed CMFPA to compromise the proposed joint resource allocation(JRA).Simulation results demonstrate that the proposed CMFPA can improve the capacity and fairness performance of existing UP methods, such as conventional UP, and random UP methods.Furthermore,the simulation results show that the proposed JRA significantly outperforms the existing schemes and gives a near-optimal performance.

    Keywords:5G;NOMA;UP;PA;capacity;fairness

    1 Introduction

    Non-orthogonal multiple access(NOMA)arises as the reliable multiple access technique for the fifth-generation (5G) communication systems to provide the required high data rates and massive connectivity[1,2].Successive interference cancelation(SIC)enables NOMA to remove the co-channel interference among the users and to efficiently exploit the channel diversity.In NOMA,multiple users can use the same spectrum resources, which leads to achieve higher spectral efficiency and provide higher data rate and latency to a massive number of users compared to conventional orthogonal multiple access(OMA)techniques[3].

    The conventional OMA techniques such as orthogonal frequency division multiple access,which are categorized cannot support massive connectivity since each subcarrier can be allocated to a single user to avoid multiple access interference[4].On the contrary,NOMA allows multiple user equipment(UE)to simultaneously utilize the same frequency by using the SIC technique at the receiver[5],which leads to increase the spectral efficiency [6].NOMA can also be used to enhance the performance of other communication technologies, such as visible light communication [7], MIMO [8,9], and millimeter-wave communication[10].

    Resource allocation represented in power allocation(PA)and channel assignment or user pairing(UP)are the keys to optimize the performance of NOMA systems.The optimal PA was only existed for users on a single channel and only for the maximization of the sum rate.Furthermore,in most of the existing works,the fairness performance was not taken into account,and the PA only depends on the channel gain of the paired users[11–13].Unfortunately,the joint optimization of PA and UP in NOMA systems requires exhaustive search,which is not applicable or practical solution[14].In this paper,the resource allocation for downlink NOMA systems is investigated with a focus on PA which is based on SNR per subcarrier and the channel gains of the paired users for optimization of both the sum rate and fairness performance.

    The main contributions of this paper are as follows:

    1) Extensive investigation and analysis of the joint impact of SNR per subcarrier and the paired users’channel gains on the performance of NOMA is presented.

    2) A novel capacity maximization-based fair power allocation (CMFPA) with low-complexity in downlink NOMA is proposed, which represents the main contribution of this paper.In CMFPA,a closed-form equation is proposed for the power allocation coefficient as a function of SNR per subcarrier and the channel gains of the paired users.

    3) In addition, efficient low-complexity UP (ELCUP) method is proposed to be incorporated with the proposed CMFPA to compromise the proposed joint resource allocation (JRA) for the optimization of capacity and fairness performance of NOMA systems with a significantly low computational complexity.

    4) Compared to the existing schemes,CMFPA can significantly improve the capacity and fairness performance of existing UP methods such as conventional UP,and random UP methods.

    5) Finally,simulation results show that the proposed JRA outperforms the existing schemes and gives a near-optimal performance.

    The rest of the paper is organized as follows.A discussion of related work is presented in Section 2.Section 3 presents the system model.In Section 4,the investigation and analysis of the joint impact of SNR per subcarrier and the paired users’channel gains on the performance of NOMA and the proposed CMFPA are provided.The ELCUP method is given in Section 5.The simulation results and discussion are introduced in Section 6.Finally,the conclusion is given in Section 7.

    2 Related Work

    PA in NOMA depends on several aspects such as the channel conditions and signal-to-noise ratio (SNR), which is related to the total power restriction.The main aim of PA in NOMA is the maximization of the sum-rate(capacity),and there are many related works[14–18].

    In[14],the authors develop an optimal joint PA and subcarrier assignment policy using monotonic optimization to maximize the weighted sum rate, which, however, has exponential computational complexity.In [15], a suboptimal PA solution for sum-rate maximization was presented where the nonconvex PA problem was solved using DC programming.Game theory was applied in PA for NOMA systems in several researches for sum-rate maximization [16,17].The optimal PA is investigated in[18]under QoS constraints for the maximization of the weighted sum rate.

    In[19],and[20],sub-optimal solutions for sub-channel and power allocation in multi-user NOMA systems are proposed to enhance energy efficiency.The authors derived a closed form expression to solve the non-convex problem, followed by KKT conditions.An iterative approach is adopted to obtain a solution for the joint problem of power and user allocation to increase the energy efficiency was investigated in[21].In[22],Lagrangian optimization was used for efficient power allocation,and two-sided matching technique was used for sub-channel assignment to improve the energy efficiency.Besides this, optimal power management and user clustering were performed in [23] to reduce the power consumption in multi-cell NOMA networks.

    However, the objective of these researches is the maximization of the sum rate and energy efficiency, where fairness among users is not considered, which is an important issue for NOMA networks.Several works considered the fairness issue in NOMA,e.g.,[24–27].In[24]and[25],optimal PA based on the maximin fairness (MMF) as a fairness indicator was investigated.A proportional fairness scheme for the maximization of the weighted MMF was investigated in [26], for a single channel and two users.The main feature of the suboptimal fractional transmit power control(FTPC)proposed in[27]is that the target performance metric(fairness or sum rate)needs to be determined a priori.In FTPC,the user transmits power depends on the channel gains of the multiplexed users and the decay factor.As the value of decay factor (0 ≤decay factor ≤1) increases, the allocated power to the user with lower channel gain increases,and fairness improves while the sum rate decreases,and vice versa.

    Joint sub-channel and power management for downlink heterogeneous NOMA networks were investigated in[28–30].In addition,the problems of resources in cognitive NOMA networks to increase the spectral efficiency in NOMA were investigated recently in[31–33].

    3 System Model

    A single-cell based downlink NOMA system scenario is considered, where a base station (BS)simultaneously transmits information to K users(i.e.,users’equipment(UEs))over M subcarriers,as illustrated in Fig.1[34].Let m={1,...,M}be the set of subcarriers,and k={1...K}denotes the set of UEs.In the considered NOMA network system,two users are assigned per subcarrier to reduce the complexity of SIC.

    For a subcarrier m,the channel gain of the user1(UE-1)which is called strong UE is assumed to be larger than the channel gain of the user2(UE-2),which is called weak UE(|hm,1|2>|hm,2|2).So,the receiver of UE-1 can perform SIC by treating its signal as noise and decoding the signal of UE-2 first.The ratio of weak UE’channel gain(hm,2)to the strong UE’s channel gain(hm,1)issuch thathm,2=μhm,1and henceμis always<1.The power allocation coefficient for strong UE is denoted byαand must be lower than 0.5(i.e.,α <0.5).So,1-αof the subcarrier transmitted power is allocated to weak UE.

    Figure 1:System model for downlink NOMA system[34]

    On a subcarrier m,the superimposed signal transmitted from BS to the paired UEs is

    wherePmis the subcarrier allocated power andsm,1andsm,2are the transmitted signal to UE-1 and UE-2.

    The received signals of the paired UEs are

    wherehm,idenotes the channel gain of the subcarrier m between the BS and UE-i,andnm,irefers to the additive white Gaussian noise(AWGN)with zero mean and varianceσ2.

    Since|hm,1|2>|hm,2|2,UE-1’s receiver can execute SIC and eliminate the interference from UE-2’s signal.Assuming that the transmission bandwidth per subcarrier is normalized to 1 Hz,the data rates of the paired UEs will be as follows[35].

    where()represents the SNR per subcarrier.

    So,the sum-rate over a subcarrier m(i.e.,the subcarrier capacity)for NOMA system isRm,1+Rm,2.

    The achievable rate of the UE-iover a subcarrier m for OMA system is

    So,the sum-rate over a subcarrier m for OMA system iswhere the factoris since the OMA system produces a multiplexing loss of[35].

    4 The Proposed Capacity Maximization Based Fair Power Allocation(CMFPA)

    In this section,extensive investigation and analysis of the joint impact of SNR per subcarrier and the channel gains of the paired users on the performance of NOMA with respect to the capacity and the user fairness are firstly introduced in Section 4.1.After that,the proposed CMFPA,which is based on this investigation,will be presented in Section 4.2 as a function of the following three parameters:

    2.The channel gain of strong UE(hm,1)

    3.The ratio of the channel gain of weak UE to the channel gain of strong UE(μ=

    Wherehm,1and μ represent the channel gain parameters of the paired users.

    4.1 The Joint Impact of Subcarrier’s SNR and Channel Gains of the Paired UEs with α on the Performance of NOMA

    In this section, the joint impact of subcarrier’s SNR and the channel gains of the paired UEs with the power allocation coefficientαon the subcarrier capacity (i.e., the sum-rate per subcarrier)and the fairness between the paired UEs will be investigated.The main target of these investigations is to specify the best choices of the power allocation coefficient to optimize the capacity and fairness performance according to the values of subcarrier’s SNR and the channel gains of the paired UEs.

    The subcarrier capacity(i.e.,Rm,1+Rm,2)can be computed using Eqs.(3)and(4)which presented in the previous section.On the other hand,the well-known Jain’s fairness index(FI)which measures the fairness among the achieved data rates of UEs [36] is used for fairness performance evaluation according to the following equation.

    where Rkis the achieved data rate of the kthUE and K is the number of UEs.

    During the analysis and discussion of results,we will refer tohm,1by h1for simplicity.The impact of channel gains on NOMA performance is represented in term of the impact of both h1and μ(i.e.,).The discussion of results concentrates on clarifying the best choices for the value ofαfor capacity maximization with highest achievable FI values.The investigation results are organized as follows:

    §To show the joint impact of both SNR and h1 withαat a fixed value ofμ,the investigation results are presented as a function of SNR andαat h1=1 and then as a function of h1 andαat SNR=0 dB

    §To show the impact of μ,the investigation results are taken at a large value of μ(μ=0.9),a medium value of μ(μ=0.5),and a small value of μ(μ=0.1).

    4.1.1 Performance Investigation Results at a Large Value of μ(μ=0.9)

    Concerning the capacity,Figs.2 and 3 demonstrate that there is no significant loss in the capacity asαdecreases and it increases as the values of SNR and h1 increase.Concerning the fairness performance, Figs.4 and 5 show that at h1=1 and SNR=0 dB, the FI values are nearly optimum asα >0.25 and as the values of SNR and h1 increase,αshould be gradually decreased to maximize the FI.

    Figure 2:Capacity as a function of SNR and α(at h1=1 and μ=0.9)

    Figure 3:Capacity as a function of h1 and α(at SNR=0 dB and μ=0.9)

    Figure 4:Fairness Index(FI)as a function of SNR and α(at h1=1 and μ=0.9)

    Figure 5:Fairness Index(FI)as a function of h1 and α(at SNR=0 dB and μ=0.9)

    4.1.2 Performance Investigation Results at a Medium Value of μ(μ=0.5)

    Concerning the capacity, Figs.6 and 7 show that it slightly decreases asαdecreases and the decrement is significant at small values of SNR and h1.Concerning the fairness performance,Figs.8 and 9 show that at h1=1 and SNR=0 dB,the FI values are nearly optimum as 0.35 ≥α≥0.15 and,as the values of SNR and h1 increase,αshould be gradually decreased to maximize the FI.

    Figure 6:Capacity as a function of SNR and α(at h1=1 and μ=0.5)

    4.1.3 Performance Investigation Results at a Small Value of μ(μ=0.1)

    Concerning the capacity, Figs.10 and 11 show that the capacity significantly reduces asαdecreases,specifically at small values ofα.Also,it is clear that increasing the SNR is more effective in improving the capacity rather than increasing h1.Concerning the fairness performance,Figs.12 and 13 demonstrates that the worst fairness performance occurs at a small value of μ (μ=0.1), and the FI sharply decreases asαand becomes greater than 0.05.Also,it is shown that fairness performance improves as the SNR and h1 increase and the highest achieved values of FI are obtained at the lowest value ofα(α=0.05).

    Figure 7:Capacity as a function of h1 and α(at SNR=0 dB and μ=0.5)

    Figure 8:Fairness Index(FI)as a function of SNR and α(at h1=1 and μ=0.5)

    Figure 9:Fairness Index(FI)as a function of h1 and α(at SNR=0 dB and μ=0.5)

    Figure 10:Capacity as a function of SNR and α(at h1=1 and μ=0.1)

    Figure 11:Capacity as a function of h1 and α(at SNR=0 dB and μ=0.1)

    Figure 12:Fairness Index(FI)as a function of SNR and α(at h1=1 and μ=0.1)

    Figure 13:Fairness Index(FI)as a function of h1 and α(at SNR=0 dB and μ=0.1)

    It is worth mentioning that in case of small values of μ,the optimization of both the capacity and the fairness performance cannot be achieved.Therefore,it is better to maximize the capacity and avoid a large loss in the achieved capacity at the expense of the degradation of the fairness performance by settingαclose as possible to its highest possible value(α=0.5).

    4.2 The Proposed CMFPA

    Based on the extensive investigation results in previous section, the following concepts can be concluded:

    1) In the case of a large value of μ,no capacity loss occurs asαdecreases,while to optimize the fairness performance(maximize the FI),αshould be greater than 0.25 at h1=1 and SNR=0 dB,and gradually decreased as the values of SNR and h1 increase.

    2) In the case of a medium value of μ (i.e., μ=0.5), no significant capacity loss occurs asαdecreases except at low values of SNR and h1, while to optimize the fairness performance,αshould be in the range from 0.15 to 0.35 (0.35 ≥α≥0.15) at h1=1 and SNR=0 dB, and gradually decreases as the values of SNR and h1 increase.

    3) In the case of a small value of μ(i.e.,μ=0.1),the best choice is settingαclose as possible to its highest possible value(α=0.5)to maximize the capacity and avoid a large loss in the achieved capacity at the expense of the degradation of the fairness performance.

    Since the proposed CMFPA targets to maximize the capacity and to achieve the highest possible FI values without capacity loss,αshould be adjusted as follows:

    §As the value of μ decreases,αshould be increased and be closer to its maximum valueαmax.

    §As the values of SNR and h1 increase,αshould be monotonically decreased to optimize the fairness performance.

    Based on the concluded concepts from the extensive investigation results in the previous section,the following closed-form equations for the adjustment ofαaccording to the values of μ,SNR,and h1 are proposed:

    where

    Eq.(9)forαmaxis derived from the following equation for the needed gap between the paired UEs’received powers to perform SIC successfully,whereθis its minimum value[34].

    During simulation value ofθis set to be 1 Watt.

    The proposed equation guarantees that the value ofαbe in the range required to optimize both the capacity and fairness performance in case of large and medium values of μ and maximize the capacity at the expense of some loss in the fairness performance in case of small values of μ.For example, ifαmaxis assumed to be 0.5.So,at large values of μ(i.e.,μ close to 1),αinitially starting at 0.25 at h1=1 and SNR=0 dB since 10log10(h1SNR)=0.Then,αgradually decreases as the values of h1 and SNR increase to reach its minimum valueαminas 10log10(h1SNR)becomes greater than 20 dB.On the other hand,at small values of μ(i.e.,μ close to zero),αinitially starting atαmaxat h1=1 and SNR=0 dB,and gradually decreases as the values of SNR and h1 increase.

    5 The Proposed Efficient Low Complexity User Pairing(ELCUP)Algorithm

    The UP algorithm is responsible for the selection of the paired UEs according to their channel gains and consequently the selection ofh1,andh2(i.e.,the selection ofh1,and μ since μ=h2/h1).The impact ofh1, and μ on the capacity and user fairness is presented in Figs.14 and 15, respectively at SNR=10 dB andα=0.2.It is clear that the capacity increases ash1increases and decreases as the values of μ become significantly small.With respect to the fairness between the paired users,it is mainly affected by the value of μ and significantly deteriorates as the values of μ become significantly small as shown in Fig.15.Therefore,the objectives of the proposed Efficient Low Complexity User Pairing(ELCUP)Algorithm are as follows:

    · Maximizing the capacity by increasing the values ofh1.Thiscan be achieved by making the order of the UP process bases on the best subcarrier first and selecting the user with the highest channel gain to be the strong user.

    · Improving the fairness among the paired user by avoiding small values of μ.

    · Minimizing the computational complexity of the UP process.

    The steps of the user pairing process are proceeded as follows:

    · The average value of the channel gains of all users over each subcarrier is computed to be used as a simple measure of the channel quality per subcarrier, such that, the subcarrier with the highest average value of the channel gains is considered as the best subcarrier.

    · The order of subcarriers during the UP process is the highest channel quality subcarrier(i.e.,the best subcarrier)first.

    · UP process is performed on two sequential stages;the first stage is the assignment of the strong user for each subcarrier followed by the second stage in which the assignment of the weak user for each subcarrier is performed.

    · During the strong user assignment stage,the user with the largest channel gain over each ordered subcarrier is assigned as the strong user.The selected user is discarded from the subsequent assignment process.

    · During the weak user assignment stage,the user with the most convergent channel gain to the strong user’s channel gain is assigned as the weak user to avoid small values of μ.The selected user is discarded from the subsequent assignment process.

    The pseudo-code of ELCUP is presented in Algorithm 1.

    Figure 14:Capacity as a function of h1(at SNR=10 dB and α=0.2)

    Figure 15:Fairness Index(FI)as a function of h1(at SNR=10 dB and α=0.2)

    6 Simulation Results

    In this section,the performance of the proposed CMFPA and the performance of the proposed joint resource allocation (JRA), which consists of the proposed ELCUP incorporated with the proposed CMFPA are evaluated via simulations.During the simulation,a frequency selective fading channel with six independent multipath is considered with Rayleigh distributed fading parameters.Link level simulations are performed in MATLAB,and 5000 realizations of channel gains are taken to generate each data point on the forthcoming figures.

    The simulation results investigate the performance of the proposed CMFPA compared with that of Fractional Transmit Power Allocation(FTPA)[27]with the conventional user pairing(conventional UP)[37],and random user pairing(random UP)[38].Also,the performance of the proposed JRA is compared with that of OMA system,and that of conventional UP and random UP NOMA schemes where FTPA and proposed CMFPA are used for power allocation.

    Algorithm 1:ELCUP Algorithm 1: Initialization:Construct channel gain matrix H =|hm,k|2 ?m ∈M subcarriers &k ∈K users z.2: for m=1 to M do 3: Compute the average value of the channel gains of all users over each subcarrier to be used as a simple measure of the channel quality per subcarrier:hm Average = 1 K K∑k=1|hm,k|2?m.4: end for 5: Sort the M subcarriers in descending order according to hm Average 6: Start strong user assignment stage 7: for the ordered M subcarrier do 8: Assign the user with the largest channel gain for each ordered subcarrier as the strong user.9: Remove the assigned user from the subsequent assignment processes.10: end for 11: Start weak user assignment stage 12: for the sorted M subcarrier do 13: Assign the available user with the most convergent channel gain to the strong user’s channel gain as the weak user.14: Remove the assigned user from the subsequent assignment processes.15: end for 16:End of the Algorithm.

    Random UP is the easiest method for user pairing,in which the users are randomly selected and allocated into a random empty subcarrier.On the other hand,in conventional UP,the user with the best channel gain is paired with the user with the worst channel gain,which needs exhaustive search to assure that the capacity of the NOMA system is larger than that of OMA system.So,the impact of pairing users whose channel gains are more divergent(i.e.,small values of μ)can be investigated in case of conventional UP.

    The decay factor of FTPA is chosen to be 0.4 to make a compromise between the capacity and the fairness performance.The minimum power gapθis set to be 1 W for the proposed CMFPA.The following simulation results are presented as a function of SNR at the number of subcarriersMequals to 32 subcarriers(i.e.,K=64 UEs).

    Fig.16 presents the obtained capacity in bps/Hz and shows that the proposed CMFPA increases the capacity of conventional UP especially as SNR decreases,and makes it outperform random UP for all SNR values.It is also shown that the proposed JRA achieves the highest capacity with a significant capacity gain compared to other NOMA schemes (i.e., conventional UP and random UP NOMA schemes).

    Figure 16:The capacity vs.SNR

    Fig.17 presents the fairness performance and shows that the proposed JRA provides the best fairness performance with FI higher than 0.95 for most of the SNR values.Also, it is clear that the proposed CMFPA significantly improves the fairness performance of random UP especially as SNR increases.For example,at 20 dB,using CMFPA the obtained FI is higher than 0.9,while using FTPA the obtained FI equals to 0.65.On the other hand,for conventional UP,the proposed CMFPA improves its fairness performance as SNR increases and makes its fairness performance better than that with FTPA at high SNR values,while FTPA provides slightly better fairness performance at low SNR values at the expense of the loss in capacity as previously shown in Fig.16.

    Figure 17:Fairness Index(FI)vs.SNR

    One of the important performance metrics is the outage probability which is defined as the probability that the data rate of UE is lower than a certain minimum rate R0.The outage probability for R0=1 bps/Hz and R0=2 bps/Hz is presented in Figs.18 and 19, respectively.It is clear that the proposed JRA achieves the lowest outage probability,and its outage probability significantly decreases as SNR increases and it is lower by a factor less than 0.1 than the outage probability of OMA,conventional UP, and random UP for R0=1 bps/Hz and R0=2 bps/Hz.Also, it is shown that the outage probability of the random UP using the proposed CMFPA is better than that using FTPA especially at R0=2 bps/Hz and is always lower than that of OMA.For conventional UP,it provides the worst(i.e.,highest)outage probability at R0=1 bps/Hz and the proposed CMFPA can improve its outage probability for R0=2 bps/Hz at high SNR’values to outperform random UP using FTPA.

    Figure 18:Outage probability at R0=1 bps/Hz vs.SNR

    Figure 19:Outage probability at R0=2 bps/Hz vs.SNR

    7 Conclusion

    In this paper, a novel low complexity PA called CMFPA in downlink NOMA is proposed to maximize the capacity while nearly optimize the fairness performance.Extensive investigation and analysis of the joint impact of SNR and paired users’channel gains on the performance of NOMA is presented.Next,in CMFPA,a closed-form equation is proposed for the power allocation coefficient as a function of SNR and the channel gains of the paired users.In addition, an efficient lowcomplexity UP (ELCUP) method is proposed to be incorporated with the proposed CMFPA to compromise the proposed joint resource allocation(JRA)for the optimization of capacity and fairness performance of NOMA systems.Compared to FTPC,the proposed CMFPA can significantly improve the capacity and the fairness performance of existing UP methods such as conventional UP, and random UP methods.Also, the proposed JRA outperforms the existing schemes and gives a nearoptimal performance.

    Acknowledgement:The authors would like to acknowledge the support received from Taif University Researchers Supporting Project Number(TURSP-2020/147),Taif University,Taif,Saudi Arabia.

    Funding Statement:This research was supported by Taif University Researchers Supporting Project Number(TURSP-2020/147),Taif University,Taif,Saudi Arabia.

    Conflicts of Interest:The author declares that he has no conflicts of interest to report regarding the present study.

    特级一级黄色大片| 日本黄色视频三级网站网址| 内射极品少妇av片p| 成年版毛片免费区| 你懂的网址亚洲精品在线观看 | 看免费成人av毛片| 人人妻人人看人人澡| 精品久久久噜噜| 国产av麻豆久久久久久久| 欧美日本视频| 一个人看视频在线观看www免费| 久久久久久久久久成人| 国产探花极品一区二区| 看十八女毛片水多多多| h日本视频在线播放| 成人特级黄色片久久久久久久| 日本-黄色视频高清免费观看| 日韩一本色道免费dvd| 亚洲精品日韩av片在线观看| 亚洲18禁久久av| av在线播放精品| 日韩av在线大香蕉| 男人的好看免费观看在线视频| 男女边吃奶边做爰视频| 久久99热这里只有精品18| 亚洲内射少妇av| 一本久久精品| 国产又黄又爽又无遮挡在线| 九九在线视频观看精品| 国产不卡一卡二| 欧美日韩乱码在线| 女的被弄到高潮叫床怎么办| 国产伦在线观看视频一区| 91午夜精品亚洲一区二区三区| 亚洲精品色激情综合| 天天躁日日操中文字幕| 午夜福利成人在线免费观看| 婷婷亚洲欧美| 草草在线视频免费看| av视频在线观看入口| 麻豆精品久久久久久蜜桃| 国产精品野战在线观看| 男女啪啪激烈高潮av片| 综合色av麻豆| 少妇人妻精品综合一区二区 | 午夜a级毛片| а√天堂www在线а√下载| 久久99热6这里只有精品| 少妇的逼水好多| 亚洲精品日韩在线中文字幕 | 婷婷亚洲欧美| 亚洲欧美成人综合另类久久久 | 亚洲美女搞黄在线观看| 在线观看66精品国产| 搡女人真爽免费视频火全软件| 精品免费久久久久久久清纯| 亚洲av电影不卡..在线观看| 人妻制服诱惑在线中文字幕| 国产一区二区三区av在线 | 国产精品1区2区在线观看.| 国产一区二区在线观看日韩| 毛片一级片免费看久久久久| 中文字幕免费在线视频6| 两性午夜刺激爽爽歪歪视频在线观看| 久久精品国产自在天天线| 嫩草影院新地址| 国产精品伦人一区二区| 国产精品国产高清国产av| 久久99精品国语久久久| 91麻豆精品激情在线观看国产| 中国国产av一级| 欧美性猛交╳xxx乱大交人| 国产成人a∨麻豆精品| 亚洲国产色片| 国产精品久久久久久久久免| 真实男女啪啪啪动态图| 欧美日本视频| av.在线天堂| 久久国产乱子免费精品| 亚洲国产欧美在线一区| 欧美激情在线99| 人妻少妇偷人精品九色| 国产又黄又爽又无遮挡在线| 亚洲国产精品合色在线| 男的添女的下面高潮视频| 久久精品久久久久久噜噜老黄 | 久久久成人免费电影| 色哟哟·www| 毛片一级片免费看久久久久| 久久精品夜色国产| 国产综合懂色| 国产伦一二天堂av在线观看| 你懂的网址亚洲精品在线观看 | 久久精品国产清高在天天线| 免费看美女性在线毛片视频| 一本一本综合久久| 国产精品伦人一区二区| 赤兔流量卡办理| av福利片在线观看| 99热只有精品国产| 精品人妻熟女av久视频| 亚洲性久久影院| 免费观看a级毛片全部| 狠狠狠狠99中文字幕| 成熟少妇高潮喷水视频| 女同久久另类99精品国产91| 久久久久久久久久黄片| 欧美xxxx性猛交bbbb| 欧美潮喷喷水| 你懂的网址亚洲精品在线观看 | 久久精品国产清高在天天线| 亚洲aⅴ乱码一区二区在线播放| 九九爱精品视频在线观看| 精品不卡国产一区二区三区| 国产精品av视频在线免费观看| 偷拍熟女少妇极品色| 1024手机看黄色片| 精品久久久久久成人av| 亚洲国产日韩欧美精品在线观看| 少妇丰满av| 亚洲五月天丁香| 国产在视频线在精品| 日本-黄色视频高清免费观看| 色哟哟·www| 色视频www国产| 色综合色国产| 国产精品一及| 日韩一区二区三区影片| 亚洲在久久综合| 少妇丰满av| 久久久久九九精品影院| 国产视频内射| 美女被艹到高潮喷水动态| 精品久久久噜噜| 久久久久国产网址| 国产老妇女一区| 国产成人精品婷婷| 成人av在线播放网站| 日韩欧美在线乱码| 久久久成人免费电影| 欧美色视频一区免费| 97超碰精品成人国产| 日韩中字成人| 日本欧美国产在线视频| 在线播放无遮挡| 五月伊人婷婷丁香| 日本欧美国产在线视频| av在线亚洲专区| 搡女人真爽免费视频火全软件| 亚洲最大成人手机在线| 国产免费男女视频| 97超视频在线观看视频| 麻豆精品久久久久久蜜桃| 少妇高潮的动态图| 丰满人妻一区二区三区视频av| 可以在线观看的亚洲视频| 小蜜桃在线观看免费完整版高清| 中文字幕av成人在线电影| 国国产精品蜜臀av免费| 好男人在线观看高清免费视频| 久久这里有精品视频免费| 久久人人精品亚洲av| 好男人视频免费观看在线| 99热这里只有是精品50| 久久人人精品亚洲av| 18禁在线无遮挡免费观看视频| 精品久久久久久久久久免费视频| 村上凉子中文字幕在线| 亚洲欧美清纯卡通| 少妇的逼水好多| 久久精品久久久久久噜噜老黄 | 久久久久久久亚洲中文字幕| 男人舔奶头视频| 亚洲无线在线观看| 久久久久性生活片| 波多野结衣巨乳人妻| 国产亚洲精品久久久久久毛片| www日本黄色视频网| 青青草视频在线视频观看| 99热全是精品| 免费一级毛片在线播放高清视频| 国产精品久久久久久久电影| 九九久久精品国产亚洲av麻豆| 岛国在线免费视频观看| 一本久久中文字幕| 久久久久久久久久久丰满| 国产精品乱码一区二三区的特点| 欧美+亚洲+日韩+国产| 九九热线精品视视频播放| 国产成人aa在线观看| 美女被艹到高潮喷水动态| 人人妻人人澡人人爽人人夜夜 | 六月丁香七月| 男人狂女人下面高潮的视频| 中文字幕av在线有码专区| 国产高潮美女av| 国产成人福利小说| 国产人妻一区二区三区在| 国内精品久久久久精免费| 国产黄片美女视频| 久久精品久久久久久噜噜老黄 | 99久久精品国产国产毛片| 一本精品99久久精品77| 亚洲av二区三区四区| 最新中文字幕久久久久| 天美传媒精品一区二区| 欧美色欧美亚洲另类二区| 中文资源天堂在线| 精品人妻视频免费看| 亚洲七黄色美女视频| 99久久人妻综合| 1000部很黄的大片| 性插视频无遮挡在线免费观看| 中文字幕久久专区| 在线观看一区二区三区| 亚洲成人久久爱视频| 一个人看视频在线观看www免费| 久久久久久久久久黄片| 精品久久久久久成人av| 国产一级毛片七仙女欲春2| 91久久精品国产一区二区三区| 晚上一个人看的免费电影| 天堂中文最新版在线下载 | 欧美变态另类bdsm刘玥| 免费不卡的大黄色大毛片视频在线观看 | 午夜福利在线观看免费完整高清在 | 熟女人妻精品中文字幕| 在线播放无遮挡| 国产一区二区三区av在线 | 看黄色毛片网站| 蜜臀久久99精品久久宅男| 国产精品,欧美在线| 岛国毛片在线播放| 黄色一级大片看看| 在线观看av片永久免费下载| 国产成人91sexporn| 国产一区二区三区在线臀色熟女| 精品欧美国产一区二区三| 久久久精品大字幕| 天天躁夜夜躁狠狠久久av| 国产一区二区在线av高清观看| 国模一区二区三区四区视频| 日本三级黄在线观看| 久久久久久久久久久免费av| 草草在线视频免费看| av视频在线观看入口| 精品99又大又爽又粗少妇毛片| 国产成人freesex在线| 3wmmmm亚洲av在线观看| 免费观看人在逋| 亚洲一区高清亚洲精品| 久久久久久久久久成人| 国产不卡一卡二| 在线观看午夜福利视频| 久久人妻av系列| 12—13女人毛片做爰片一| 麻豆国产97在线/欧美| 狂野欧美白嫩少妇大欣赏| 一级毛片aaaaaa免费看小| 天堂中文最新版在线下载 | 色5月婷婷丁香| 久久久精品大字幕| 亚洲精品乱码久久久久久按摩| 深夜精品福利| 在现免费观看毛片| 中文字幕久久专区| 亚洲精品日韩在线中文字幕 | 国产久久久一区二区三区| 白带黄色成豆腐渣| 美女大奶头视频| av视频在线观看入口| 国产乱人偷精品视频| 精品熟女少妇av免费看| 97在线视频观看| 99热这里只有是精品在线观看| 少妇熟女aⅴ在线视频| 日日撸夜夜添| 亚洲成人久久爱视频| 国产精品乱码一区二三区的特点| 国产精品免费一区二区三区在线| 欧美bdsm另类| 国产精品女同一区二区软件| 国产综合懂色| 日本与韩国留学比较| 精品久久国产蜜桃| 老司机福利观看| 熟女电影av网| 久久亚洲精品不卡| 久久韩国三级中文字幕| 十八禁国产超污无遮挡网站| 我的老师免费观看完整版| 黄色视频,在线免费观看| 国产在视频线在精品| 国产爱豆传媒在线观看| a级毛片免费高清观看在线播放| 青春草国产在线视频 | 你懂的网址亚洲精品在线观看 | 91久久精品国产一区二区三区| 免费在线观看成人毛片| 国产精品99久久久久久久久| 黄片wwwwww| 一本久久中文字幕| 可以在线观看毛片的网站| 久久久久久九九精品二区国产| www.色视频.com| 欧美色欧美亚洲另类二区| 欧美一区二区精品小视频在线| 亚洲精品久久国产高清桃花| av天堂中文字幕网| 毛片一级片免费看久久久久| 成年版毛片免费区| 久久韩国三级中文字幕| 色5月婷婷丁香| 国产精品一及| 久久久国产成人免费| 免费观看精品视频网站| 久久久久久九九精品二区国产| 偷拍熟女少妇极品色| 欧美高清性xxxxhd video| 日本黄色视频三级网站网址| 国产一区二区激情短视频| 国产日本99.免费观看| 九草在线视频观看| 国产精品国产三级国产av玫瑰| 亚洲国产色片| 亚洲,欧美,日韩| 久久99热这里只有精品18| 在线免费十八禁| 搞女人的毛片| 久久久久久久久大av| 99热全是精品| 女同久久另类99精品国产91| a级毛片a级免费在线| 午夜福利成人在线免费观看| 精品人妻视频免费看| 亚洲成a人片在线一区二区| 91久久精品电影网| 国产精品久久久久久精品电影小说 | 国产精品美女特级片免费视频播放器| 国产成人a区在线观看| 亚洲成人精品中文字幕电影| a级毛色黄片| 日韩一本色道免费dvd| 欧美色视频一区免费| 亚洲第一区二区三区不卡| 精品久久久久久久末码| 欧美最新免费一区二区三区| 六月丁香七月| 小说图片视频综合网站| 高清毛片免费观看视频网站| 在线天堂最新版资源| 久久久久九九精品影院| 亚洲中文字幕一区二区三区有码在线看| 国模一区二区三区四区视频| 成人特级黄色片久久久久久久| 日韩欧美精品免费久久| 欧美日韩综合久久久久久| 免费搜索国产男女视频| 欧美人与善性xxx| 乱人视频在线观看| 国产免费男女视频| 欧美在线一区亚洲| 欧美不卡视频在线免费观看| 欧美xxxx黑人xx丫x性爽| 夫妻性生交免费视频一级片| 最近手机中文字幕大全| 欧美最新免费一区二区三区| 国产精品人妻久久久影院| 99国产极品粉嫩在线观看| 一个人观看的视频www高清免费观看| 精品国内亚洲2022精品成人| 日日撸夜夜添| 日本黄色片子视频| 国产精品国产高清国产av| 婷婷色综合大香蕉| av女优亚洲男人天堂| 亚洲色图av天堂| a级毛片免费高清观看在线播放| 中文字幕人妻熟人妻熟丝袜美| 久久久午夜欧美精品| 国产成人影院久久av| 成人一区二区视频在线观看| 亚洲自拍偷在线| 春色校园在线视频观看| 午夜免费男女啪啪视频观看| 少妇被粗大猛烈的视频| 最近手机中文字幕大全| 91精品一卡2卡3卡4卡| 亚州av有码| 精品日产1卡2卡| 日韩一本色道免费dvd| 亚洲精品影视一区二区三区av| 国产成人午夜福利电影在线观看| 99久久中文字幕三级久久日本| 国产精品一二三区在线看| 三级男女做爰猛烈吃奶摸视频| 色哟哟·www| 亚洲精品乱码久久久v下载方式| 12—13女人毛片做爰片一| 美女内射精品一级片tv| 亚洲国产日韩欧美精品在线观看| 精品午夜福利在线看| 精品99又大又爽又粗少妇毛片| 国产极品天堂在线| 观看美女的网站| 亚洲av成人av| 婷婷色av中文字幕| 精品一区二区三区人妻视频| 一个人免费在线观看电影| 国产乱人偷精品视频| 亚洲av中文av极速乱| 99riav亚洲国产免费| 午夜免费男女啪啪视频观看| 免费不卡的大黄色大毛片视频在线观看 | 黄片无遮挡物在线观看| 如何舔出高潮| 菩萨蛮人人尽说江南好唐韦庄 | 国产午夜精品一二区理论片| 日韩强制内射视频| 欧美激情国产日韩精品一区| 丝袜美腿在线中文| 国产亚洲精品av在线| 亚洲国产欧洲综合997久久,| 免费在线观看成人毛片| 麻豆精品久久久久久蜜桃| 国产高清不卡午夜福利| 日韩欧美精品v在线| 免费观看的影片在线观看| 欧美日韩国产亚洲二区| 中文精品一卡2卡3卡4更新| 国产精品久久久久久久久免| 国产精品一区二区性色av| а√天堂www在线а√下载| 可以在线观看毛片的网站| 91麻豆精品激情在线观看国产| 成人鲁丝片一二三区免费| 看非洲黑人一级黄片| 亚洲精品乱码久久久v下载方式| 国产精品,欧美在线| 一级毛片aaaaaa免费看小| 青春草亚洲视频在线观看| 看免费成人av毛片| 日韩欧美精品免费久久| 日本免费一区二区三区高清不卡| 免费看日本二区| 国产伦精品一区二区三区视频9| 日本一本二区三区精品| 噜噜噜噜噜久久久久久91| 日韩,欧美,国产一区二区三区 | 成年免费大片在线观看| 久久精品人妻少妇| 午夜激情福利司机影院| 亚洲精品日韩av片在线观看| 美女 人体艺术 gogo| 日本免费一区二区三区高清不卡| 中文字幕av成人在线电影| 欧美日韩乱码在线| 久久亚洲国产成人精品v| 国产精品,欧美在线| 男人狂女人下面高潮的视频| 午夜福利在线观看免费完整高清在 | 国产成人a∨麻豆精品| 欧美变态另类bdsm刘玥| 国产成年人精品一区二区| 老司机福利观看| 亚洲精品乱码久久久久久按摩| 欧美成人一区二区免费高清观看| 在线播放无遮挡| 有码 亚洲区| 国内精品久久久久精免费| av又黄又爽大尺度在线免费看 | h日本视频在线播放| 在现免费观看毛片| 亚洲自拍偷在线| 国内久久婷婷六月综合欲色啪| 爱豆传媒免费全集在线观看| 欧美变态另类bdsm刘玥| 卡戴珊不雅视频在线播放| 午夜福利在线观看免费完整高清在 | 中文亚洲av片在线观看爽| 国产成人aa在线观看| 亚洲成人中文字幕在线播放| 国产又黄又爽又无遮挡在线| 国产一区二区三区在线臀色熟女| h日本视频在线播放| 国产片特级美女逼逼视频| 国产亚洲5aaaaa淫片| 国产久久久一区二区三区| АⅤ资源中文在线天堂| 日本熟妇午夜| 久久午夜亚洲精品久久| 国产爱豆传媒在线观看| 51国产日韩欧美| 日日啪夜夜撸| 蜜桃久久精品国产亚洲av| 高清日韩中文字幕在线| 中文在线观看免费www的网站| 国产伦精品一区二区三区视频9| 99热精品在线国产| av视频在线观看入口| 亚洲中文字幕一区二区三区有码在线看| 人妻系列 视频| 国产蜜桃级精品一区二区三区| 一级毛片aaaaaa免费看小| 亚洲av第一区精品v没综合| 美女脱内裤让男人舔精品视频 | 亚洲第一区二区三区不卡| 99热这里只有是精品在线观看| 国产蜜桃级精品一区二区三区| 国产伦精品一区二区三区四那| av在线播放精品| 不卡一级毛片| 如何舔出高潮| 亚洲av成人av| 看免费成人av毛片| 成人av在线播放网站| 日韩中字成人| 欧美潮喷喷水| 日韩av在线大香蕉| 精品人妻偷拍中文字幕| 亚洲精品乱码久久久v下载方式| 精品久久国产蜜桃| 免费无遮挡裸体视频| 国产人妻一区二区三区在| 3wmmmm亚洲av在线观看| 欧美潮喷喷水| 一个人观看的视频www高清免费观看| 欧美精品一区二区大全| 亚洲欧美精品综合久久99| 中文精品一卡2卡3卡4更新| 两性午夜刺激爽爽歪歪视频在线观看| 在现免费观看毛片| 日韩中字成人| 国产精品野战在线观看| 欧美激情在线99| 麻豆久久精品国产亚洲av| 亚洲一区高清亚洲精品| 五月玫瑰六月丁香| 欧美激情久久久久久爽电影| 久久久国产成人免费| 男人舔女人下体高潮全视频| 看片在线看免费视频| 日韩av在线大香蕉| 亚洲精品亚洲一区二区| 级片在线观看| 欧美日韩乱码在线| 两个人的视频大全免费| 人妻久久中文字幕网| 麻豆国产97在线/欧美| 国产白丝娇喘喷水9色精品| 成人av在线播放网站| 一区福利在线观看| 国产伦精品一区二区三区四那| 国产精品久久久久久av不卡| 久久久午夜欧美精品| 国产 一区 欧美 日韩| 免费观看人在逋| 色哟哟哟哟哟哟| 校园春色视频在线观看| 亚洲精品国产成人久久av| 美女脱内裤让男人舔精品视频 | 欧美+亚洲+日韩+国产| 尤物成人国产欧美一区二区三区| 欧美性感艳星| 免费观看在线日韩| 成熟少妇高潮喷水视频| 色综合站精品国产| 欧美区成人在线视频| 免费看av在线观看网站| 99在线人妻在线中文字幕| 看十八女毛片水多多多| 热99re8久久精品国产| 国产私拍福利视频在线观看| 久久精品国产亚洲av涩爱 | 亚洲成人中文字幕在线播放| 欧美潮喷喷水| 成人无遮挡网站| 深夜a级毛片| 国产精品电影一区二区三区| 亚洲精品影视一区二区三区av| 国产亚洲5aaaaa淫片| 成人美女网站在线观看视频| 欧美在线一区亚洲| 2022亚洲国产成人精品| 国产成人a区在线观看| 久久6这里有精品| 日韩精品青青久久久久久| 久久久a久久爽久久v久久| 岛国在线免费视频观看| 一区二区三区高清视频在线| 一级黄片播放器| 色噜噜av男人的天堂激情| 亚洲欧美精品综合久久99| 午夜视频国产福利| 欧美性猛交╳xxx乱大交人| 久久久久国产网址| videossex国产| 国产高潮美女av| 久久精品久久久久久久性| 亚州av有码| 成年版毛片免费区| 人妻系列 视频| 哪里可以看免费的av片| 网址你懂的国产日韩在线| 日本黄色片子视频| 有码 亚洲区| 全区人妻精品视频| 欧美另类亚洲清纯唯美| 国产精品精品国产色婷婷| 国产女主播在线喷水免费视频网站 | 波多野结衣高清作品| 亚洲av二区三区四区| 成人二区视频| 亚洲精品国产成人久久av| 日本黄大片高清|