Pub Date : 2015-04-27DOI: 10.1109/ICT.2015.7124652
Mengyu Huang, Jinhong Yuan
In this paper, lattice network coding (LNC) is studied in the multiple-antenna (MA) two-way relay channel (TWRC), where each user has a single antenna and the relay has multiple antennas. We propose two relay computation schemes for the MA TWRC with nested lattice codes, namely the receive antenna selection (RAS) scheme and the receive antenna combining (RAC) scheme. In the RAS scheme, the relay calculates the computation rates of all the relay antennas with different channel conditions and then selects a single antenna with the highest computation rate to recover a linear combination of transmitted messages. In the RAC scheme, the signals from all the relay antennas are combined with a scaling factor vector, from which a linear combination of the transmitted messages is recovered. We derive the achievable rate and analyze the error performance of the two scheme. The simulation result shows that the RAC scheme outperforms the RAS scheme significantly.
{"title":"Lattice network coding in multiple-antenna two-way relay channels","authors":"Mengyu Huang, Jinhong Yuan","doi":"10.1109/ICT.2015.7124652","DOIUrl":"https://doi.org/10.1109/ICT.2015.7124652","url":null,"abstract":"In this paper, lattice network coding (LNC) is studied in the multiple-antenna (MA) two-way relay channel (TWRC), where each user has a single antenna and the relay has multiple antennas. We propose two relay computation schemes for the MA TWRC with nested lattice codes, namely the receive antenna selection (RAS) scheme and the receive antenna combining (RAC) scheme. In the RAS scheme, the relay calculates the computation rates of all the relay antennas with different channel conditions and then selects a single antenna with the highest computation rate to recover a linear combination of transmitted messages. In the RAC scheme, the signals from all the relay antennas are combined with a scaling factor vector, from which a linear combination of the transmitted messages is recovered. We derive the achievable rate and analyze the error performance of the two scheme. The simulation result shows that the RAC scheme outperforms the RAS scheme significantly.","PeriodicalId":375669,"journal":{"name":"2015 22nd International Conference on Telecommunications (ICT)","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114984767","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-04-27DOI: 10.1109/ICT.2015.7124680
S. Hanly, Chunshan Liu, P. Whiting
Heterogeneous wireless networks (HetNets) provide a means to increase network capacity by introducing small cells and adopting a layered architecture. HetNets can allocate resources flexibly through time sharing, on-off scheduling and cell range expansion/contraction. As shown in [1] such networks are constrained to a capacity limit in terms of the maximum number of downloads per second which can be achieved for a given offered traffic density. This capacity can be obtained as the solution to a continuous linear program (LP) (see [1]). Using the above results we investigate the scope for capacity extension in a single macro cell network. In particular it is shown that multiple pico cells per hot spot can significantly extend capacity but the gains can only be realized in conjunction with on-off scheduling of the picocells. We further show that scheduling according to a small number of on-off modes is sufficient to realise this gain. We also develop tight capacity bounds which can be used to investigate larger networks in cases where the size of the LP is too large for direct solution.
{"title":"Joint user association and BS on-off scheduling in heterogeneous networks","authors":"S. Hanly, Chunshan Liu, P. Whiting","doi":"10.1109/ICT.2015.7124680","DOIUrl":"https://doi.org/10.1109/ICT.2015.7124680","url":null,"abstract":"Heterogeneous wireless networks (HetNets) provide a means to increase network capacity by introducing small cells and adopting a layered architecture. HetNets can allocate resources flexibly through time sharing, on-off scheduling and cell range expansion/contraction. As shown in [1] such networks are constrained to a capacity limit in terms of the maximum number of downloads per second which can be achieved for a given offered traffic density. This capacity can be obtained as the solution to a continuous linear program (LP) (see [1]). Using the above results we investigate the scope for capacity extension in a single macro cell network. In particular it is shown that multiple pico cells per hot spot can significantly extend capacity but the gains can only be realized in conjunction with on-off scheduling of the picocells. We further show that scheduling according to a small number of on-off modes is sufficient to realise this gain. We also develop tight capacity bounds which can be used to investigate larger networks in cases where the size of the LP is too large for direct solution.","PeriodicalId":375669,"journal":{"name":"2015 22nd International Conference on Telecommunications (ICT)","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129787428","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-04-27DOI: 10.1109/ICT.2015.7124664
Ashraf Awadelkarim Widaa Ahmed, J. Markendahl
Nowadays the spectrum regulations landscape is changing towards more flexible spectrum management schemes, such trends are expected to make additional spectrum resources available and lowers the spectrum access hurdles. In this paper, different spectrum aggregation scenarios have been compared focusing on the tradeoff between the total cost of ownership and the targeted QoS under different market conditions. The main finding in this study thereof indicates that the addition of more spectrum resources will lead to an overall reduction in the total cost of ownership (TCO) as long as the spectrum price remains small compared to the cost of the network infrastructure. Moreover, schemes such as LSA and secondary access will enable operators who have insufficient licensed spectrum resource to expand their mobile network infrastructure especially in hotspots with high subscribers demand in a cost-effective way. In this regard, the harmonization of spectrum use for LSA and TVWS across multiple countries stands as a key requirement for the reduction of the production cost of equipment and hence, the creation of an economy of scale considering both of the network equipment (i.e. radio base station) and end-subscriber devices.
{"title":"Impact of the flexible spectrum aggregation schemes on the cost of future mobile network","authors":"Ashraf Awadelkarim Widaa Ahmed, J. Markendahl","doi":"10.1109/ICT.2015.7124664","DOIUrl":"https://doi.org/10.1109/ICT.2015.7124664","url":null,"abstract":"Nowadays the spectrum regulations landscape is changing towards more flexible spectrum management schemes, such trends are expected to make additional spectrum resources available and lowers the spectrum access hurdles. In this paper, different spectrum aggregation scenarios have been compared focusing on the tradeoff between the total cost of ownership and the targeted QoS under different market conditions. The main finding in this study thereof indicates that the addition of more spectrum resources will lead to an overall reduction in the total cost of ownership (TCO) as long as the spectrum price remains small compared to the cost of the network infrastructure. Moreover, schemes such as LSA and secondary access will enable operators who have insufficient licensed spectrum resource to expand their mobile network infrastructure especially in hotspots with high subscribers demand in a cost-effective way. In this regard, the harmonization of spectrum use for LSA and TVWS across multiple countries stands as a key requirement for the reduction of the production cost of equipment and hence, the creation of an economy of scale considering both of the network equipment (i.e. radio base station) and end-subscriber devices.","PeriodicalId":375669,"journal":{"name":"2015 22nd International Conference on Telecommunications (ICT)","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128291996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-04-27DOI: 10.1109/ICT.2015.7124713
Jiawei Hao, Li Guo, Ranjie Hu, Jiaru Lin
Distributed beamforming is an energy-efficient wireless communication technique that allows cooperative nodes to transmit a common message to a receiver. This paper investigates carrier synchronization for distributed beamforming in large-scale wireless networks. In order to pursue less timeslots for synchronization, we present a time-slotted round-trip carrier synchronization protocol exploiting the broadcast nature of the wireless links with master-slave architecture among transmitters. Numerical simulations are presented and the results indicate that this protocol can achieve longer valid communication time for beamforming.
{"title":"Round-trip carrier synchronization exploiting the broadcast nature for distributed beamforming","authors":"Jiawei Hao, Li Guo, Ranjie Hu, Jiaru Lin","doi":"10.1109/ICT.2015.7124713","DOIUrl":"https://doi.org/10.1109/ICT.2015.7124713","url":null,"abstract":"Distributed beamforming is an energy-efficient wireless communication technique that allows cooperative nodes to transmit a common message to a receiver. This paper investigates carrier synchronization for distributed beamforming in large-scale wireless networks. In order to pursue less timeslots for synchronization, we present a time-slotted round-trip carrier synchronization protocol exploiting the broadcast nature of the wireless links with master-slave architecture among transmitters. Numerical simulations are presented and the results indicate that this protocol can achieve longer valid communication time for beamforming.","PeriodicalId":375669,"journal":{"name":"2015 22nd International Conference on Telecommunications (ICT)","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128430704","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-04-27DOI: 10.1109/ICT.2015.7124655
S. Islam, S. Durrani
In this paper, we propose a signal transmission model for multi-group multi-way (MGMW) relaying which allows complete information exchange among users belonging to different user groups, with applications such as file sharing among users separated by large distances. We achieve this through the use of multi-stage non-regenerative relay stations (RSs). The groups of multiple users are connected to the nearest RS stages which are again connected via RSs at the next nearest stage and so on. The RSs at each stage obtain messages from user groups connected through the next RS stage by subtracting information extracted from the previous RS stage. We formulate the achievable sum rate of such a network and investigate the impact of system parameters on it. We show that increasing the number of users per group, while keeping a smaller number of user groups, improves the sum rate.
{"title":"Multi-group multi-way relaying with multi-stage non-regenerative relay stations","authors":"S. Islam, S. Durrani","doi":"10.1109/ICT.2015.7124655","DOIUrl":"https://doi.org/10.1109/ICT.2015.7124655","url":null,"abstract":"In this paper, we propose a signal transmission model for multi-group multi-way (MGMW) relaying which allows complete information exchange among users belonging to different user groups, with applications such as file sharing among users separated by large distances. We achieve this through the use of multi-stage non-regenerative relay stations (RSs). The groups of multiple users are connected to the nearest RS stages which are again connected via RSs at the next nearest stage and so on. The RSs at each stage obtain messages from user groups connected through the next RS stage by subtracting information extracted from the previous RS stage. We formulate the achievable sum rate of such a network and investigate the impact of system parameters on it. We show that increasing the number of users per group, while keeping a smaller number of user groups, improves the sum rate.","PeriodicalId":375669,"journal":{"name":"2015 22nd International Conference on Telecommunications (ICT)","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126559637","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-04-27DOI: 10.1109/ICT.2015.7124687
A. Omri, M. Hasna
In this paper, a cooperative communications scheme with interference management is proposed for wireless multi-user multi-relay networks. The scheme is using on demand decode and forward (DF) half-duplex (HD) relaying protocol, a relay selection method which maximizes the signal-to-noise ratio (SNR) of the second hop, and the maximum ratio combining (MRC) technique to combine the direct and best relay links. To avoid the interference problem and enhance the spectral efficiency, the proposed scheme uses a new relaying protocol based on the constellation real parts of the modulated signals. We derive closed form expressions of the power density function (PDF), the average outage probability, and the average bit error rate (BER) for the proposed scheme, and simulations are used to validate the analytical expressions. The results confirm the advantage of the proposed scheme in enhancing interference management and link reliability.
{"title":"Interference avoidance scheme for wireless multi-user multi-relay networks","authors":"A. Omri, M. Hasna","doi":"10.1109/ICT.2015.7124687","DOIUrl":"https://doi.org/10.1109/ICT.2015.7124687","url":null,"abstract":"In this paper, a cooperative communications scheme with interference management is proposed for wireless multi-user multi-relay networks. The scheme is using on demand decode and forward (DF) half-duplex (HD) relaying protocol, a relay selection method which maximizes the signal-to-noise ratio (SNR) of the second hop, and the maximum ratio combining (MRC) technique to combine the direct and best relay links. To avoid the interference problem and enhance the spectral efficiency, the proposed scheme uses a new relaying protocol based on the constellation real parts of the modulated signals. We derive closed form expressions of the power density function (PDF), the average outage probability, and the average bit error rate (BER) for the proposed scheme, and simulations are used to validate the analytical expressions. The results confirm the advantage of the proposed scheme in enhancing interference management and link reliability.","PeriodicalId":375669,"journal":{"name":"2015 22nd International Conference on Telecommunications (ICT)","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134131219","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-04-27DOI: 10.1109/ICT.2015.7124694
Jinhong Yuan, Lei Yang, Tao Yang, Jianping An
This paper investigates the design of practical non-binary irregular repeat-accumulate (IRA) codes for reliable physical-layer network coding. In the scheme, a same random-coset IRA code over Galois field GF(q) is employed at the two users. The relay computes the network coded message sequence directly from the superimposed signal using an iterative belief propagation algorithm. We explore the symmetry and permutation-invariant properties of the decoder's soft information distribution and adopt a two-dimension extrinsic information transfer chart to analyze and optimize the coding scheme. Numerical results demonstrate that our developed scheme achieves near-capacity performance in Gaussian two-way relay channels.
{"title":"Design of non-binary irregular repeat-accumulate codes for reliable physical-layer network coding","authors":"Jinhong Yuan, Lei Yang, Tao Yang, Jianping An","doi":"10.1109/ICT.2015.7124694","DOIUrl":"https://doi.org/10.1109/ICT.2015.7124694","url":null,"abstract":"This paper investigates the design of practical non-binary irregular repeat-accumulate (IRA) codes for reliable physical-layer network coding. In the scheme, a same random-coset IRA code over Galois field GF(q) is employed at the two users. The relay computes the network coded message sequence directly from the superimposed signal using an iterative belief propagation algorithm. We explore the symmetry and permutation-invariant properties of the decoder's soft information distribution and adopt a two-dimension extrinsic information transfer chart to analyze and optimize the coding scheme. Numerical results demonstrate that our developed scheme achieves near-capacity performance in Gaussian two-way relay channels.","PeriodicalId":375669,"journal":{"name":"2015 22nd International Conference on Telecommunications (ICT)","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123002784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-04-27DOI: 10.1109/ICT.2015.7124679
Shahriar Etemadi Tajbakhsh, T. Ray, M. Reed, Yuan Liu
The optimization problem of joint resource allocation and user association in wireless heterogeneous with the assumption of fixed transmission power by the base station has been studied in the literature. In this paper, we let the transmitted power by each base station on each resource be an optimization variable as well. The resulting optimization problem is NP-hard and non-convex. We provide a greedy algorithm to solve the optimization problem. Our numerical results shows a considerable improvement over the fixed power assumption in terms of average achievable rate by the users as well as the entire network utility measured based on proportional fairness criterion.
{"title":"Joint power control and resource scheduling in wireless heterogeneous networks","authors":"Shahriar Etemadi Tajbakhsh, T. Ray, M. Reed, Yuan Liu","doi":"10.1109/ICT.2015.7124679","DOIUrl":"https://doi.org/10.1109/ICT.2015.7124679","url":null,"abstract":"The optimization problem of joint resource allocation and user association in wireless heterogeneous with the assumption of fixed transmission power by the base station has been studied in the literature. In this paper, we let the transmitted power by each base station on each resource be an optimization variable as well. The resulting optimization problem is NP-hard and non-convex. We provide a greedy algorithm to solve the optimization problem. Our numerical results shows a considerable improvement over the fixed power assumption in terms of average achievable rate by the users as well as the entire network utility measured based on proportional fairness criterion.","PeriodicalId":375669,"journal":{"name":"2015 22nd International Conference on Telecommunications (ICT)","volume":"86 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122436467","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-04-27DOI: 10.1109/ICT.2015.7124718
Di Zhai, Zihuai Lin
Considering the instability of received signal strength (RSS) in the indoor environment, this paper presents a feasible RSS based indoor positioning method by introducing a biased but optimized distance estimator, which is transformed from the Log-Normal (LN) fading model. On the other hand, the existed positioning methods, like maximum likelihood estimation (MLE) and least square estimation (LSE), always require at least three reference distances, which sometimes cannot be met in practice due to the situation that some nodes may be too far from one or multiple reference nodes. This paper proposes a positioning method considering the situation that one of three reference nodes receiving abnormal or no RSS value from a mobile node. The motivation of using RSS as the reference information is that compared with methods with other metrics like time of flight (TOF) or angle of arrival (AOA), RSS based method has the advantages of low complexity, low device requirement and low cost. The experiment results show that the proposed method has better performance than the MLE algorithm for a common LN model.
{"title":"RSS-based indoor positioning with biased estimator and local geographical factor","authors":"Di Zhai, Zihuai Lin","doi":"10.1109/ICT.2015.7124718","DOIUrl":"https://doi.org/10.1109/ICT.2015.7124718","url":null,"abstract":"Considering the instability of received signal strength (RSS) in the indoor environment, this paper presents a feasible RSS based indoor positioning method by introducing a biased but optimized distance estimator, which is transformed from the Log-Normal (LN) fading model. On the other hand, the existed positioning methods, like maximum likelihood estimation (MLE) and least square estimation (LSE), always require at least three reference distances, which sometimes cannot be met in practice due to the situation that some nodes may be too far from one or multiple reference nodes. This paper proposes a positioning method considering the situation that one of three reference nodes receiving abnormal or no RSS value from a mobile node. The motivation of using RSS as the reference information is that compared with methods with other metrics like time of flight (TOF) or angle of arrival (AOA), RSS based method has the advantages of low complexity, low device requirement and low cost. The experiment results show that the proposed method has better performance than the MLE algorithm for a common LN model.","PeriodicalId":375669,"journal":{"name":"2015 22nd International Conference on Telecommunications (ICT)","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121255148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-04-27DOI: 10.1109/ICT.2015.7124700
Mengmeng Liu, Jianhua Zhang, Ping Zhang
This paper analyzes the performance of a large-scale multiuser multiple-input multiple-output (MU-MIMO) system with amplify-and-forward (AF) relaying in the presence of co-channel interference. Each user terminal (UT) has a single antenna while the relay is equipped with very large antenna arrays. To evaluate the impact of large number of relay antennas on the performance of the considered system, we derive a lower bound on the achievable rate. We also perform a large system analysis in the regimes of high signal-to-noise ratio (SNR), large number of relay antennas and large number of UTs. Numerical results are presented to verify the theoretical analysis.
{"title":"Performance analysis of large-scale MU-MIMO with AF relaying in the presence of interference","authors":"Mengmeng Liu, Jianhua Zhang, Ping Zhang","doi":"10.1109/ICT.2015.7124700","DOIUrl":"https://doi.org/10.1109/ICT.2015.7124700","url":null,"abstract":"This paper analyzes the performance of a large-scale multiuser multiple-input multiple-output (MU-MIMO) system with amplify-and-forward (AF) relaying in the presence of co-channel interference. Each user terminal (UT) has a single antenna while the relay is equipped with very large antenna arrays. To evaluate the impact of large number of relay antennas on the performance of the considered system, we derive a lower bound on the achievable rate. We also perform a large system analysis in the regimes of high signal-to-noise ratio (SNR), large number of relay antennas and large number of UTs. Numerical results are presented to verify the theoretical analysis.","PeriodicalId":375669,"journal":{"name":"2015 22nd International Conference on Telecommunications (ICT)","volume":"80 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134375351","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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