Pub Date : 2002-08-07DOI: 10.1109/VTC.2002.1002641
Chunlong Bai, Jun Jiang, Ping Zhang
For the efficient implementation of a turbo decoder with Log-MAP (logarithm-maximum a posteriori) algorithm, we propose in this paper a solution with three highlights: the general core for forward and backward recursions, the simple branch metric calculation and a simplified rescaling of the path metrics. An FPGA (field programmable gate array) implementation with the proposed solution reduces area consumption to half and shows favorable performance.
{"title":"Simplified recursive structure for turbo decoder with Log-MAP algorithm","authors":"Chunlong Bai, Jun Jiang, Ping Zhang","doi":"10.1109/VTC.2002.1002641","DOIUrl":"https://doi.org/10.1109/VTC.2002.1002641","url":null,"abstract":"For the efficient implementation of a turbo decoder with Log-MAP (logarithm-maximum a posteriori) algorithm, we propose in this paper a solution with three highlights: the general core for forward and backward recursions, the simple branch metric calculation and a simplified rescaling of the path metrics. An FPGA (field programmable gate array) implementation with the proposed solution reduces area consumption to half and shows favorable performance.","PeriodicalId":159750,"journal":{"name":"Vehicular Technology Conference. IEEE 55th Vehicular Technology Conference. VTC Spring 2002 (Cat. No.02CH37367)","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116116613","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 : 2002-08-07DOI: 10.1109/VTC.2002.1002796
A. Roy, N. Banerjee, Sajal K. Das
The increasing demand of real-time wireless communication has led to the development of quality-of-service (QoS) based routing. Most of the wireless multimedia applications require strict QoS guarantee (e.g. delay, bandwidth) during the communication between a single source and multiple destinations. This gives rise to the need for an efficient multicast QoS-routing strategy. Determination of such QoS-based optimal multicast routes boils down to a multi-objective optimization problem, which is computationally intractable in polynomial time. We propose a new multicast tree selection algorithm based on non-dominated sorting technique of the genetic algorithm to simultaneously optimize multiple QoS parameters. Simulation results demonstrate that the proposed algorithm is capable of discovering a set of QoS-based near optimal, non-dominated multicast routes within a few iterations. From this set the user can choose desirably favorite solution depending on specific QoS requirements. The scalability and the performance of the algorithm with increasing number of network nodes is also presented.
{"title":"An efficient multi-objective QoS-routing algorithm for wireless multicasting","authors":"A. Roy, N. Banerjee, Sajal K. Das","doi":"10.1109/VTC.2002.1002796","DOIUrl":"https://doi.org/10.1109/VTC.2002.1002796","url":null,"abstract":"The increasing demand of real-time wireless communication has led to the development of quality-of-service (QoS) based routing. Most of the wireless multimedia applications require strict QoS guarantee (e.g. delay, bandwidth) during the communication between a single source and multiple destinations. This gives rise to the need for an efficient multicast QoS-routing strategy. Determination of such QoS-based optimal multicast routes boils down to a multi-objective optimization problem, which is computationally intractable in polynomial time. We propose a new multicast tree selection algorithm based on non-dominated sorting technique of the genetic algorithm to simultaneously optimize multiple QoS parameters. Simulation results demonstrate that the proposed algorithm is capable of discovering a set of QoS-based near optimal, non-dominated multicast routes within a few iterations. From this set the user can choose desirably favorite solution depending on specific QoS requirements. The scalability and the performance of the algorithm with increasing number of network nodes is also presented.","PeriodicalId":159750,"journal":{"name":"Vehicular Technology Conference. IEEE 55th Vehicular Technology Conference. VTC Spring 2002 (Cat. No.02CH37367)","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115254454","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 : 2002-08-07DOI: 10.1109/VTC.2002.1002805
T. Hasegawa, M. Shimizu
A new signal reception method, multipath interference exchange reduction (MIXR), that reduces multipath interference in direct-sequence code division multiple access (DS-CDMA) systems is described. This method uses a despread signal at a timing correlated with the interference in the conventional despread signal before RAKE combining. It is especially effective in the downlink receiver of DS-CDMA systems in which the downlink signals of all users are received with the same fading channels. One computer simulation showed that the BER of the proposed method is 1-2 dB better than that of a conventional RAKE receiver. Other simulations showed that the MIXR receiver is more sensitive than conventional RAKE receivers.
{"title":"Multipath interference reduction method using multipath interference correlative timing for DS-CDMA systems","authors":"T. Hasegawa, M. Shimizu","doi":"10.1109/VTC.2002.1002805","DOIUrl":"https://doi.org/10.1109/VTC.2002.1002805","url":null,"abstract":"A new signal reception method, multipath interference exchange reduction (MIXR), that reduces multipath interference in direct-sequence code division multiple access (DS-CDMA) systems is described. This method uses a despread signal at a timing correlated with the interference in the conventional despread signal before RAKE combining. It is especially effective in the downlink receiver of DS-CDMA systems in which the downlink signals of all users are received with the same fading channels. One computer simulation showed that the BER of the proposed method is 1-2 dB better than that of a conventional RAKE receiver. Other simulations showed that the MIXR receiver is more sensitive than conventional RAKE receivers.","PeriodicalId":159750,"journal":{"name":"Vehicular Technology Conference. IEEE 55th Vehicular Technology Conference. VTC Spring 2002 (Cat. No.02CH37367)","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121841528","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 : 2002-08-07DOI: 10.1109/VTC.2002.1002576
Wang Ying, Gong Fei, Zhang Ping, W. Hae
This paper compares two different handover criteria in WCDMA through simulations. The simulations are carried out in a WCDMA HCS system where the hexagonal macro and the Manhattan-like micro layer use different frequencies. Two possible handover triggering schemes i.e. CPICH RSCP and CPICH Ec/No, are compared under the same simulation environments and various cell loads. The handover performance is observed in terms of system efficiency including signalling and QoS such as call dropping probability and call blocking probability.
{"title":"Performance of RSCP-triggered and Ec/No-triggered inter-frequency handover criteria for UTRA","authors":"Wang Ying, Gong Fei, Zhang Ping, W. Hae","doi":"10.1109/VTC.2002.1002576","DOIUrl":"https://doi.org/10.1109/VTC.2002.1002576","url":null,"abstract":"This paper compares two different handover criteria in WCDMA through simulations. The simulations are carried out in a WCDMA HCS system where the hexagonal macro and the Manhattan-like micro layer use different frequencies. Two possible handover triggering schemes i.e. CPICH RSCP and CPICH Ec/No, are compared under the same simulation environments and various cell loads. The handover performance is observed in terms of system efficiency including signalling and QoS such as call dropping probability and call blocking probability.","PeriodicalId":159750,"journal":{"name":"Vehicular Technology Conference. IEEE 55th Vehicular Technology Conference. VTC Spring 2002 (Cat. No.02CH37367)","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123884567","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 : 2002-08-07DOI: 10.1109/VTC.2002.1002899
Ki-Wan Kim, D. Kim
We propose both the simulation model and the queuing network model for the performance evaluation of mobile IP. The performance models include the registration process of a mobile host from which a previous foreign agent receives a binding update message. When the previous foreign agent receives the binding information, it transmits the buffered packets to new care-of address of a mobile host. The two stages queuing network model is suggested. The first stage models a queue at the new foreign agent that represents the traffic for the request of the registration process generating during handoffs from mobile hosts. In the second stage a queue at the previous foreign agent represents the traffic for binding update messages and also represents the traffic destined to mobile hosts at the previous foreign agent. Therefore, in the second stage it is modeled with a queue having 2 priorities. It is shown that the queuing network model is compatible with the simulation model. Finally, it is shown that at the foreign agent traffic characteristics, host mobility, registration process time and buffer management scheme have a critical impact on the performance of mobile IP.
{"title":"Performance models for mobile IP in a cellular environment","authors":"Ki-Wan Kim, D. Kim","doi":"10.1109/VTC.2002.1002899","DOIUrl":"https://doi.org/10.1109/VTC.2002.1002899","url":null,"abstract":"We propose both the simulation model and the queuing network model for the performance evaluation of mobile IP. The performance models include the registration process of a mobile host from which a previous foreign agent receives a binding update message. When the previous foreign agent receives the binding information, it transmits the buffered packets to new care-of address of a mobile host. The two stages queuing network model is suggested. The first stage models a queue at the new foreign agent that represents the traffic for the request of the registration process generating during handoffs from mobile hosts. In the second stage a queue at the previous foreign agent represents the traffic for binding update messages and also represents the traffic destined to mobile hosts at the previous foreign agent. Therefore, in the second stage it is modeled with a queue having 2 priorities. It is shown that the queuing network model is compatible with the simulation model. Finally, it is shown that at the foreign agent traffic characteristics, host mobility, registration process time and buffer management scheme have a critical impact on the performance of mobile IP.","PeriodicalId":159750,"journal":{"name":"Vehicular Technology Conference. IEEE 55th Vehicular Technology Conference. VTC Spring 2002 (Cat. No.02CH37367)","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130158514","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 : 2002-08-07DOI: 10.1109/VTC.2002.1002630
D. Fernández, H. Montes
The goal of this paper is to present a complete quality of service (QoS) framework for the radio resource management (RRM) able to provide guaranteed bitrate (GBR) services, when they are transmitted over shared channels in a Enhanced General Packet Radio Service (EGPRS) network. This QoS scheme is composed by an admission control (AC) and a channel allocation (CA) functionality, which are taking part in the connection establishment phase, as well as a QoS aware packet scheduler (PS) acting along the connection duration. The scheme is rounded off by the use of a quality control (QC) function, in charge of checking that the provided QoS by the system is in line with the negotiated QoS with the mobile station (MS). The performance of the proposed QoS framework has been evaluated by means of dynamic simulations.
{"title":"An enhanced quality of service method for guaranteed bitrate services over shared channels in EGPRS systems","authors":"D. Fernández, H. Montes","doi":"10.1109/VTC.2002.1002630","DOIUrl":"https://doi.org/10.1109/VTC.2002.1002630","url":null,"abstract":"The goal of this paper is to present a complete quality of service (QoS) framework for the radio resource management (RRM) able to provide guaranteed bitrate (GBR) services, when they are transmitted over shared channels in a Enhanced General Packet Radio Service (EGPRS) network. This QoS scheme is composed by an admission control (AC) and a channel allocation (CA) functionality, which are taking part in the connection establishment phase, as well as a QoS aware packet scheduler (PS) acting along the connection duration. The scheme is rounded off by the use of a quality control (QC) function, in charge of checking that the provided QoS by the system is in line with the negotiated QoS with the mobile station (MS). The performance of the proposed QoS framework has been evaluated by means of dynamic simulations.","PeriodicalId":159750,"journal":{"name":"Vehicular Technology Conference. IEEE 55th Vehicular Technology Conference. VTC Spring 2002 (Cat. No.02CH37367)","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131505898","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 : 2002-08-07DOI: 10.1109/VTC.2002.1002893
Lei-yang Fu, A. Fapojuwo
This paper proposes a new soft handoff-like rerouting (SHLR) scheme for handoff of quality of service (QoS) based multimedia connections in wireless asynchronous transfer mode (ATM) networks and evaluates its performance. The main idea behind the SHLR scheme is the use of a make-before-break concept at the radio and network links to minimize latency and cell loss ratio during the handoff process. Performance of the SHLR scheme is evaluated using a discrete-event simulation technique to determine cell queueing delay and cell loss ratio. Results from simulation indicate that the cell queueing delay obtained for the SHLR scheme is better than that of existing schemes in the literature by a factor of at least 2. Further, the SHLR scheme provides up to two orders of magnitude improvement in cell loss ratio performance over that of the existing schemes. The results presented in the paper are useful for dimensioning buffer size as a function of QoS requirements and handoff traffic. The results also provide insights on the underlying causes of cell loss in wireless ATM networks.
{"title":"Performance of a soft handoff-like rerouting scheme for wireless ATM networks","authors":"Lei-yang Fu, A. Fapojuwo","doi":"10.1109/VTC.2002.1002893","DOIUrl":"https://doi.org/10.1109/VTC.2002.1002893","url":null,"abstract":"This paper proposes a new soft handoff-like rerouting (SHLR) scheme for handoff of quality of service (QoS) based multimedia connections in wireless asynchronous transfer mode (ATM) networks and evaluates its performance. The main idea behind the SHLR scheme is the use of a make-before-break concept at the radio and network links to minimize latency and cell loss ratio during the handoff process. Performance of the SHLR scheme is evaluated using a discrete-event simulation technique to determine cell queueing delay and cell loss ratio. Results from simulation indicate that the cell queueing delay obtained for the SHLR scheme is better than that of existing schemes in the literature by a factor of at least 2. Further, the SHLR scheme provides up to two orders of magnitude improvement in cell loss ratio performance over that of the existing schemes. The results presented in the paper are useful for dimensioning buffer size as a function of QoS requirements and handoff traffic. The results also provide insights on the underlying causes of cell loss in wireless ATM networks.","PeriodicalId":159750,"journal":{"name":"Vehicular Technology Conference. IEEE 55th Vehicular Technology Conference. VTC Spring 2002 (Cat. No.02CH37367)","volume":"891 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131610664","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 : 2002-08-07DOI: 10.1109/VTC.2002.1002789
W. Jeon, D. Jeong, Bonghoe Kim
This paper proposes a packet scheduler for high speed downlink packet access (HSDPA) systems. In designing the scheduler, we consider the delay constraint of packets from the user's point of view and throughput performance in whole systems, as well as the throughput fairness between mobiles. The performance of the proposed scheme is evaluated by simulation.
{"title":"Design of packet transmission scheduler for high speed downlink packet access systems","authors":"W. Jeon, D. Jeong, Bonghoe Kim","doi":"10.1109/VTC.2002.1002789","DOIUrl":"https://doi.org/10.1109/VTC.2002.1002789","url":null,"abstract":"This paper proposes a packet scheduler for high speed downlink packet access (HSDPA) systems. In designing the scheduler, we consider the delay constraint of packets from the user's point of view and throughput performance in whole systems, as well as the throughput fairness between mobiles. The performance of the proposed scheme is evaluated by simulation.","PeriodicalId":159750,"journal":{"name":"Vehicular Technology Conference. IEEE 55th Vehicular Technology Conference. VTC Spring 2002 (Cat. No.02CH37367)","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133584192","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 : 2002-08-07DOI: 10.1109/VTC.2002.1002913
P. Kafle, A. Sesay
A low-complexity iterative multiuser receiver is proposed using groupwise maximum likelihood sequence estimation (MLSE) combined with a modified interference cancellation scheme in a turbo coded MC-CDMA system. It is based on grouping the active users according to their signal strengths and computing the log-likelihood ratios by MLSE among each group of users at the first iteration. For subsequent iterations, a modified interference cancellation scheme that can benefit from code extrinsic information available through decoding is used, for lower complexity. Simulation results are presented in a Rayleigh multipath fading environment for a typical data transmission scheme. Comparisons are made with iterative receivers using the maximum a posteriori (MAP) criterion and soft interference cancellation. Performance very close to that of a MAP based iterative receiver is achieved by this novel scheme within a few iterations, with much lower computational cost. This approach also performs significantly well under near-far conditions.
{"title":"A low-complexity iterative multiuser receiver for turbo-coded MC-CDMA system","authors":"P. Kafle, A. Sesay","doi":"10.1109/VTC.2002.1002913","DOIUrl":"https://doi.org/10.1109/VTC.2002.1002913","url":null,"abstract":"A low-complexity iterative multiuser receiver is proposed using groupwise maximum likelihood sequence estimation (MLSE) combined with a modified interference cancellation scheme in a turbo coded MC-CDMA system. It is based on grouping the active users according to their signal strengths and computing the log-likelihood ratios by MLSE among each group of users at the first iteration. For subsequent iterations, a modified interference cancellation scheme that can benefit from code extrinsic information available through decoding is used, for lower complexity. Simulation results are presented in a Rayleigh multipath fading environment for a typical data transmission scheme. Comparisons are made with iterative receivers using the maximum a posteriori (MAP) criterion and soft interference cancellation. Performance very close to that of a MAP based iterative receiver is achieved by this novel scheme within a few iterations, with much lower computational cost. This approach also performs significantly well under near-far conditions.","PeriodicalId":159750,"journal":{"name":"Vehicular Technology Conference. IEEE 55th Vehicular Technology Conference. VTC Spring 2002 (Cat. No.02CH37367)","volume":"295 8","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132605794","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 : 2002-08-07DOI: 10.1109/VTC.2002.1002736
Chao-ming Teng, Kwang-Cheng Chen
Being confronted with numerous MAC protocols designed under a variety of networking considerations, we envision a software-defined MAC controller that can be "re-configured" to different MAC protocols. This paper presents a unified algorithm for wireless MAC protocols - a pioneer trial of this vision that benefits future wireless networks. This unified algorithm is based on the concept of MULCAR, a generalized model for MAC protocols proposed by Chen and Sun. We observed that most protocols operate in a cycling fashion and identified major differences between each algorithm. Combining this with the concept of MULCAR, we unified several representative wireless MAC protocols into one parameterized algorithm. Among them are ALOHA with geometric backoff, binary exponential backoff and Q-ary collision resolution algorithm, p-persistent CSMA, CSMA/CA, and GRAP. One can thus have the unified algorithm operate as different MAC algorithms with proper parameter setting, which enables the development of the software-defined MAC controller.
{"title":"A unified algorithm for wireless MAC protocols","authors":"Chao-ming Teng, Kwang-Cheng Chen","doi":"10.1109/VTC.2002.1002736","DOIUrl":"https://doi.org/10.1109/VTC.2002.1002736","url":null,"abstract":"Being confronted with numerous MAC protocols designed under a variety of networking considerations, we envision a software-defined MAC controller that can be \"re-configured\" to different MAC protocols. This paper presents a unified algorithm for wireless MAC protocols - a pioneer trial of this vision that benefits future wireless networks. This unified algorithm is based on the concept of MULCAR, a generalized model for MAC protocols proposed by Chen and Sun. We observed that most protocols operate in a cycling fashion and identified major differences between each algorithm. Combining this with the concept of MULCAR, we unified several representative wireless MAC protocols into one parameterized algorithm. Among them are ALOHA with geometric backoff, binary exponential backoff and Q-ary collision resolution algorithm, p-persistent CSMA, CSMA/CA, and GRAP. One can thus have the unified algorithm operate as different MAC algorithms with proper parameter setting, which enables the development of the software-defined MAC controller.","PeriodicalId":159750,"journal":{"name":"Vehicular Technology Conference. IEEE 55th Vehicular Technology Conference. VTC Spring 2002 (Cat. No.02CH37367)","volume":"54 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133423368","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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