Real-time applications are sensitive to conditions such as transmission delay and jittering. To cut down on the influence generated by the WLAN handoff process, three parts of WLAN （wireless local area networks） han...Real-time applications are sensitive to conditions such as transmission delay and jittering. To cut down on the influence generated by the WLAN handoff process, three parts of WLAN （wireless local area networks） handoff： handoff triggering, access point selection and the fast handoff algorithm are investigated. A fast handoff solution totally based on the station is proposed and it is composed of three parts： a handoff triggering mechanism based on dynamic threshold adjustment; an AP selection criterion based on probe delay; a fast handoff algorithm with differentiated channel selection and a dynamic cache. The station based solution is independent with AP＇s collaboration and avoids any changes in the IEEE 802. l l protocol. It is robust and has very good extensibility. Through tests and evaluation in a hotspot WLAN, the solution effectively reduces handoff latency and user experience of real-time applications is enhanced.展开更多
The new IEEE 802.11 standard, IEEE 802.11ax, has the challenging goal of serving more Uplink (UL) traffic and users as compared with his predecessor IEEE 802.11ac, enabling consistent and reliable streams of data (ave...The new IEEE 802.11 standard, IEEE 802.11ax, has the challenging goal of serving more Uplink (UL) traffic and users as compared with his predecessor IEEE 802.11ac, enabling consistent and reliable streams of data (average throughput) per station. In this paper we explore several new IEEE 802.11ax UL scheduling mechanisms and compare between the maximum throughputs of unidirectional UDP Multi Users (MU) triadic. The evaluation is conducted based on Multiple-Input-Multiple-Output (MIMO) and Orthogonal Frequency Division Multiple Access (OFDMA) transmission multiplexing format in IEEE 802.11ax vs. the CSMA/CA MAC in IEEE 802.11ac in the Single User (SU) and MU modes for 1, 4, 8, 16, 32 and 64 stations scenario in reliable and unreliable channels. The comparison is conducted as a function of the Modulation and Coding Schemes (MCS) in use. In IEEE 802.11ax we consider two new flavors of acknowledgment operation settings, where the maximum acknowledgment windows are 64 or 256 respectively. In SU scenario the throughputs of IEEE 802.11ax are larger than those of IEEE 802.11ac by 64% and 85% in reliable and unreliable channels respectively. In MU-MIMO scenario the throughputs of IEEE 802.11ax are larger than those of IEEE 802.11ac by 263% and 270% in reliable and unreliable channels respectively. Also, as the number of stations increases, the advantage of IEEE 802.11ax in terms of the access delay also increases.展开更多
The IEEE 802.15.4a standard provides a framework for low-data-rate communication systems,typically sensor networks.In this paper,we established a realistic environment for the time delay characteristic of industrial n...The IEEE 802.15.4a standard provides a framework for low-data-rate communication systems,typically sensor networks.In this paper,we established a realistic environment for the time delay characteristic of industrial network based on IEEE 802.15.4a.Several sets of practical experiments are conducted to study its various features,including the effects of 1） numeral wireless nodes,2） numeral data packets,3） data transmissions with different upper-layer protocols,4） physical distance between nodes,and 5） adding and reducing the number of the wireless nodes.The results show that IEEE 802.15.4a is suitable for some industrial applications that have more relaxed throughput requirements and time-delay.Some issues that could degrade the network performance are also discussed.展开更多
IEEE 802.11ax,which is an emerging WLAN standard,aims at providing highly efficient communication in ultra-dense wireless networks.However,due to a large number of stations(STAs)in the ultra-dense device deployment sc...IEEE 802.11ax,which is an emerging WLAN standard,aims at providing highly efficient communication in ultra-dense wireless networks.However,due to a large number of stations(STAs)in the ultra-dense device deployment scenarios,the potentially high packet collision rate significantly decreases the communication efficiency of WLAN.In this paper,we propose an adaptive STA grouping scheme to overcome this dense network challenge in IEEE 802.11ax by using Buffer State Report(BSR)based Two-stage Mechanism(BTM).In order to achieve the optimal efficiency of BSR delivery,we analyze the functional relationship between STA number in group and Resource Unit(RU)efficiency.Based on this analysis results,an adaptive STA grouping algorithm with variable group size is proposed to achieve efficient grouping in BTM.The numerical results demonstrate that the proposed adaptive BTM grouping algorithm significantly improves the BSR delivery efficiency and the throughput of overall system and each STA in the ultra-dense wireless network.展开更多
How to reduce the energy consumption powered mainly by battery to prolong the standby time is one of the crucial issues for IEEE 802.16e wireless MANs.By predicting the next downlink inter-packet arrival time,three tr...How to reduce the energy consumption powered mainly by battery to prolong the standby time is one of the crucial issues for IEEE 802.16e wireless MANs.By predicting the next downlink inter-packet arrival time,three traffic-prediction-assisted power saving mechanisms based on P-PSCI,i.e.,PSCI-PFD,PSCI-ED and PSCI-LD,were proposed.In addition,the corresponding adjustment strategies for P-PSCI were also presented when there were uplink packets to be transmitted during sleep mode.Simulation results reveal that compared with the sleep mode algorithm recommended by IEEE 802.16e,the proposed mechanism P-PSCI can improve both energy efficiency and packet delay for IEEE 802.16e due to the consideration of the traffic characteristics and rate changes.Moreover,the results also demonstrate that PSCI-PFD (a=-2) significantly outperforms PSCI-ED,PSCI-LD,and the standard sleep mode in IEEE 802.16e is in terms of energy efficiency and packet delay.展开更多
Due to their easy-to-deploy and self-healing features, WMNs (Wireless Mesh Networks) are emerging as a new promising technology with a rich set of applications. While the IEEE standardization of this new technology is...Due to their easy-to-deploy and self-healing features, WMNs (Wireless Mesh Networks) are emerging as a new promising technology with a rich set of applications. While the IEEE standardization of this new technology is still in progress, its main traits are already set, e.g., architecture and MAC routing. WMNs are attracting considerable research in academia and industry as well, but the lack of open-source testbeds is restricting such a research to simulation tools. The main problem with simulation tools is that they do not reflect the complexity of RF propagation, especially in indoor environments, of which IEEE 802.11s WMNs are an example. This paper presents an open-source implementation of an indoor IEEE 802.11s WMN testbed. The implementation is transparent, easy-to-deploy, and both the source code and deployment instructions are available online. The implementation can serve as a blueprint for the WMN research community to deploy their own testbeds, negating the shortcomings of using simulation tools. By delving into the testbed implementation subtleties, this paper is shedding further light on the details of the ongoing IEEE 802.11s standard. Major encountered implementation problems (e.g., clients association, Internetworking, and supporting multiple gateways) are identified and addressed. To ascertain the functionality of the testbed, both UDP and TCP traffic are supported and operational. The testbed uses the default IEEE 802.11s HWMP (Hybrid Wireless Mesh Protocol) routing protocol along with the default IEEE 802.11s Airtime routing metric.展开更多
The sub-6 G band is too crowded to accommodate higher data rate, while the millimeter wave(mmWave) bands have abundant spectrum resources and massive MIMO can provide high spectral and energy efficiency. Therefore, th...The sub-6 G band is too crowded to accommodate higher data rate, while the millimeter wave(mmWave) bands have abundant spectrum resources and massive MIMO can provide high spectral and energy efficiency. Therefore, the combination of the two,namely mmWave-MIMO system, has attracted intensive research interests. In this paper, we develop a high-speed mmWave-MIMO communication system and conduct exhaustive field tests. The detail of the system design is provided and the key modules of the testbed are analyzed. The testbed exploits high gain of mmWave RF and flexible configuration of embedded system. The validation and field tests show that the developed testbed can provide up to 2.3 Gbps network layer data rate in single channel with low latency and support point-to-multi-point(PtMP) transmission aided by relay. The testbed can be used in future B5 G and 6 G systems to provide high reliability and low latency wireless coverage.展开更多
The mobility of the targets asks for high requirements of the locating speed in indoor positioning systems.The standard medium access control(MAC)algorithm will often cause lots of packet conflicts and high transmissi...The mobility of the targets asks for high requirements of the locating speed in indoor positioning systems.The standard medium access control(MAC)algorithm will often cause lots of packet conflicts and high transmission delay if multiple users communicate with one beacon at the same time,which will severely limit the speed of the system.Therefore,an optimized MAC algorithm is proposed based on channel reservation to enable users to reserve beacons.A frame threshold is set to ensure the users with shorter data frames do not depend on the reservation mechanism,and multiple users can achieve packets switching with relative beacon in a fixed sequence by using frequency division multiplexing technology.The simulation results show that the optimized MAC algorithm proposed in this paper can improve the positioning speed significantly while maintaining the positioning accuracy.Moreover,the positioning accuracy can be increased to a certain extent if more channel resources can be obtained,so as to provide effective technical support for the location and tracking applications of indoor moving targets.展开更多
Over the past years, wireless sensor systems have picked up a global consideration from both the researchers and the genuine clients. It includes a large number of sensing devices, some computing techniques and commun...Over the past years, wireless sensor systems have picked up a global consideration from both the researchers and the genuine clients. It includes a large number of sensing devices, some computing techniques and communication with limited power supplies and processing abilities which collectively work to fulfill a large sensing task. IEEE 802.15.4/ZigBee based Wireless Sensor Networks raise a few issues like Energy Scavenging for the limited power supply. Accordingly good functioning of such system relies upon energies of the wireless motes. This paper presents two analytical models which demonstrate and predict the QoS in terms of throughput, jitter, average end-to-end delay and energy consumption. These two distinct network models based on IEEE 802.15.4 are cluster-based and grid-based, and are simulated using QualNet v 6.1 Simulator.展开更多
IEEE 802.11ah brings in Restricted Access Window （RAW） to decrease contention, which is the grouping-based MAC protocol. The way to group a large number of devices and application of RAW size would have influence on...IEEE 802.11ah brings in Restricted Access Window （RAW） to decrease contention, which is the grouping-based MAC protocol. The way to group a large number of devices and application of RAW size would have influence on the energy efficiency in the process of medium access and communications. In this paper, we study an efficient window control algorithm to improve the uplink energy efficiency with a novel retransmission scheme that utilises the next empty slot for retransmission in the uplink. The grouping scheme is based on the college admission game. The problem is formulated based on energy efficiency by probability theory and Marker chain. To optimise energy efficiency, a window control scheme is proposed to group the devices and set the adaptive window size （number of slots per RAW and internal slot interval） based on the number of groups, applications and the distance between devices and Access Point （AP）. The optimal solution is derived by Gradient Descent approach. Simulation results show that our proposed algorithm outperforms existing one on uplink energy efficiency and fairness.展开更多
One main issue of degrading IEEE 802.15.4performance is the beacon conflict which increases the energy consumption.However,IEEE 802.15.4does not address a solution to avoid the beacon conflict.In order to reduce this ...One main issue of degrading IEEE 802.15.4performance is the beacon conflict which increases the energy consumption.However,IEEE 802.15.4does not address a solution to avoid the beacon conflict.In order to reduce this beacon conflict,an individual time division(ITD)algorithm based on IEEE 802.15.4is proposed.In this algorithm,a coordinator assigns the time division(TD)for each associated coordinator so that different coordinators transmit a beacon frame at different time slice.In this way,the beacon conflict is decreased substantially.The experimental results show that ITD reduces both the beacon conflict and the network energy consumption,and improves the network performance.展开更多
In wireless multicast, some users may fail to receive data as a result of bad channel con-ditions. The throughput of traditional multicast strategy is constrained by the node with the worst channel condition. In this ...In wireless multicast, some users may fail to receive data as a result of bad channel con-ditions. The throughput of traditional multicast strategy is constrained by the node with the worst channel condition. In this paper, we propose a distributed cooperative multicast scheduling strategy, in which, every user which has successfully received data can decide whether to retransmit data by sensing MNACK packets. The proposed scheme can achieve good throughput by exploiting multi-channel diversity across multiple users' cooperation. In addition, the constraint of power consumption is also considered. Simulation results show that our scheme can provide good throughput and fairness per-formance with the constraint of average system power consumption.展开更多
Abstract： In this paper, we propose a mecha- nism for multicast data transmission in IEEE 802.16 mesh networks aimed at increasing the throughput by incorporating mini-slot spatial reuse. The proposed mechanism inclu...Abstract： In this paper, we propose a mecha- nism for multicast data transmission in IEEE 802.16 mesh networks aimed at increasing the throughput by incorporating mini-slot spatial reuse. The proposed mechanism includes two novel algorithms： a source-based multicast tree topology construction algorithm followed by an interference-aware multieast scheduling algorithm. The proposed multicast interfer- ence-aware scheduling algorithm can be ap- plied to both source-based and rendez- vous-based multicast tree topologies. Results of our simulation study show that in compari- son to the mechanism used for the IEEE 802.16＇s standard, the proposed multicast tree generation algorithm reduces the number of consumed mini-slots by 64% on average. Moreover, using the proposed interfer- ence-aware scheduling algorithm decreases the number of required mini-slots by a further 22% on average. Therefore, the proposed mul- ticast scheduling mechanism shows a higher throughput than the previous approaches and it is more scalable with respect to increasing the number of multicast groups as well as in- creasing the number of members inside each multicast group.展开更多
IEEE 802.16 mesh mode defines routing tree for transmitting data in centralized scheduling but it does not define any explicit proposal for combining uplink and downlink subframes. Deploying combined uplink and downli...IEEE 802.16 mesh mode defines routing tree for transmitting data in centralized scheduling but it does not define any explicit proposal for combining uplink and downlink subframes. Deploying combined uplink and downlink subframes on the centralized scheduling scheme can be more flexible and utilization is improved. However, existing interferences among the transmission of neighboring nodes lead to performance reduction of the network. In this paper, an efficient routing tree algorithm is proposed with combined uplink and downlink slot allocation on the centralized scheduling scheme which can abate interferences in the network. This algorithm allows more subscriber stations to transmit concurrently and so improves spatial reuse in the network. Also, the algorithm uses multi-channel and single channel systems and considers relay model, smoothing switching frequently between transmitting and receiving in successive time slots and fairness in the network. Extensive simulation results demonstrate the effectiveness of the proposed method in terms of scheduling length, link concurrency ratio, network throughput and Channel Utilization Ratio (CUR).展开更多
基金The National Natural Science Foundation of China(No.90604003,60603067)
文摘Real-time applications are sensitive to conditions such as transmission delay and jittering. To cut down on the influence generated by the WLAN handoff process, three parts of WLAN （wireless local area networks） handoff： handoff triggering, access point selection and the fast handoff algorithm are investigated. A fast handoff solution totally based on the station is proposed and it is composed of three parts： a handoff triggering mechanism based on dynamic threshold adjustment; an AP selection criterion based on probe delay; a fast handoff algorithm with differentiated channel selection and a dynamic cache. The station based solution is independent with AP＇s collaboration and avoids any changes in the IEEE 802. l l protocol. It is robust and has very good extensibility. Through tests and evaluation in a hotspot WLAN, the solution effectively reduces handoff latency and user experience of real-time applications is enhanced.
文摘The new IEEE 802.11 standard, IEEE 802.11ax, has the challenging goal of serving more Uplink (UL) traffic and users as compared with his predecessor IEEE 802.11ac, enabling consistent and reliable streams of data (average throughput) per station. In this paper we explore several new IEEE 802.11ax UL scheduling mechanisms and compare between the maximum throughputs of unidirectional UDP Multi Users (MU) triadic. The evaluation is conducted based on Multiple-Input-Multiple-Output (MIMO) and Orthogonal Frequency Division Multiple Access (OFDMA) transmission multiplexing format in IEEE 802.11ax vs. the CSMA/CA MAC in IEEE 802.11ac in the Single User (SU) and MU modes for 1, 4, 8, 16, 32 and 64 stations scenario in reliable and unreliable channels. The comparison is conducted as a function of the Modulation and Coding Schemes (MCS) in use. In IEEE 802.11ax we consider two new flavors of acknowledgment operation settings, where the maximum acknowledgment windows are 64 or 256 respectively. In SU scenario the throughputs of IEEE 802.11ax are larger than those of IEEE 802.11ac by 64% and 85% in reliable and unreliable channels respectively. In MU-MIMO scenario the throughputs of IEEE 802.11ax are larger than those of IEEE 802.11ac by 263% and 270% in reliable and unreliable channels respectively. Also, as the number of stations increases, the advantage of IEEE 802.11ax in terms of the access delay also increases.
基金supported by National High Technology Research and Development Program of China (863 Program)(No. 2007AA04Z174,No. 2006AA04030405)National Natural Science Foundation of China (No. 61074032,No. 60834002)
文摘The IEEE 802.15.4a standard provides a framework for low-data-rate communication systems,typically sensor networks.In this paper,we established a realistic environment for the time delay characteristic of industrial network based on IEEE 802.15.4a.Several sets of practical experiments are conducted to study its various features,including the effects of 1） numeral wireless nodes,2） numeral data packets,3） data transmissions with different upper-layer protocols,4） physical distance between nodes,and 5） adding and reducing the number of the wireless nodes.The results show that IEEE 802.15.4a is suitable for some industrial applications that have more relaxed throughput requirements and time-delay.Some issues that could degrade the network performance are also discussed.
文摘IEEE 802.11ax,which is an emerging WLAN standard,aims at providing highly efficient communication in ultra-dense wireless networks.However,due to a large number of stations(STAs)in the ultra-dense device deployment scenarios,the potentially high packet collision rate significantly decreases the communication efficiency of WLAN.In this paper,we propose an adaptive STA grouping scheme to overcome this dense network challenge in IEEE 802.11ax by using Buffer State Report(BSR)based Two-stage Mechanism(BTM).In order to achieve the optimal efficiency of BSR delivery,we analyze the functional relationship between STA number in group and Resource Unit(RU)efficiency.Based on this analysis results,an adaptive STA grouping algorithm with variable group size is proposed to achieve efficient grouping in BTM.The numerical results demonstrate that the proposed adaptive BTM grouping algorithm significantly improves the BSR delivery efficiency and the throughput of overall system and each STA in the ultra-dense wireless network.
基金Projects(60873265,61070194)supported by the National Natural Science Foundation of ChinaProject(2009AA112205)supported by the National High Technology Research and Development Program of China+1 种基金Project(2011FJ2003)supported by Science and Technology Key Projects of Hunan Province,ChinaProject(531107040201)supported by Chinese Universities Scientific Fund
文摘How to reduce the energy consumption powered mainly by battery to prolong the standby time is one of the crucial issues for IEEE 802.16e wireless MANs.By predicting the next downlink inter-packet arrival time,three traffic-prediction-assisted power saving mechanisms based on P-PSCI,i.e.,PSCI-PFD,PSCI-ED and PSCI-LD,were proposed.In addition,the corresponding adjustment strategies for P-PSCI were also presented when there were uplink packets to be transmitted during sleep mode.Simulation results reveal that compared with the sleep mode algorithm recommended by IEEE 802.16e,the proposed mechanism P-PSCI can improve both energy efficiency and packet delay for IEEE 802.16e due to the consideration of the traffic characteristics and rate changes.Moreover,the results also demonstrate that PSCI-PFD (a=-2) significantly outperforms PSCI-ED,PSCI-LD,and the standard sleep mode in IEEE 802.16e is in terms of energy efficiency and packet delay.
文摘Due to their easy-to-deploy and self-healing features, WMNs (Wireless Mesh Networks) are emerging as a new promising technology with a rich set of applications. While the IEEE standardization of this new technology is still in progress, its main traits are already set, e.g., architecture and MAC routing. WMNs are attracting considerable research in academia and industry as well, but the lack of open-source testbeds is restricting such a research to simulation tools. The main problem with simulation tools is that they do not reflect the complexity of RF propagation, especially in indoor environments, of which IEEE 802.11s WMNs are an example. This paper presents an open-source implementation of an indoor IEEE 802.11s WMN testbed. The implementation is transparent, easy-to-deploy, and both the source code and deployment instructions are available online. The implementation can serve as a blueprint for the WMN research community to deploy their own testbeds, negating the shortcomings of using simulation tools. By delving into the testbed implementation subtleties, this paper is shedding further light on the details of the ongoing IEEE 802.11s standard. Major encountered implementation problems (e.g., clients association, Internetworking, and supporting multiple gateways) are identified and addressed. To ascertain the functionality of the testbed, both UDP and TCP traffic are supported and operational. The testbed uses the default IEEE 802.11s HWMP (Hybrid Wireless Mesh Protocol) routing protocol along with the default IEEE 802.11s Airtime routing metric.
基金supported by National Key R&D Program of China ( 2020YFB1807204)。
文摘The sub-6 G band is too crowded to accommodate higher data rate, while the millimeter wave(mmWave) bands have abundant spectrum resources and massive MIMO can provide high spectral and energy efficiency. Therefore, the combination of the two,namely mmWave-MIMO system, has attracted intensive research interests. In this paper, we develop a high-speed mmWave-MIMO communication system and conduct exhaustive field tests. The detail of the system design is provided and the key modules of the testbed are analyzed. The testbed exploits high gain of mmWave RF and flexible configuration of embedded system. The validation and field tests show that the developed testbed can provide up to 2.3 Gbps network layer data rate in single channel with low latency and support point-to-multi-point(PtMP) transmission aided by relay. The testbed can be used in future B5 G and 6 G systems to provide high reliability and low latency wireless coverage.
基金Supported by the National Natural Science Foundation of China(No.61771186)Outstanding Youth Project of Heilongjiang Natural Science Foundation(No.YQ2020F012)Undergraduate University Project of Young Scientist Creative Talent of Heilongjiang Province(No.UNPYSCT-2017125)。
文摘The mobility of the targets asks for high requirements of the locating speed in indoor positioning systems.The standard medium access control(MAC)algorithm will often cause lots of packet conflicts and high transmission delay if multiple users communicate with one beacon at the same time,which will severely limit the speed of the system.Therefore,an optimized MAC algorithm is proposed based on channel reservation to enable users to reserve beacons.A frame threshold is set to ensure the users with shorter data frames do not depend on the reservation mechanism,and multiple users can achieve packets switching with relative beacon in a fixed sequence by using frequency division multiplexing technology.The simulation results show that the optimized MAC algorithm proposed in this paper can improve the positioning speed significantly while maintaining the positioning accuracy.Moreover,the positioning accuracy can be increased to a certain extent if more channel resources can be obtained,so as to provide effective technical support for the location and tracking applications of indoor moving targets.
文摘Over the past years, wireless sensor systems have picked up a global consideration from both the researchers and the genuine clients. It includes a large number of sensing devices, some computing techniques and communication with limited power supplies and processing abilities which collectively work to fulfill a large sensing task. IEEE 802.15.4/ZigBee based Wireless Sensor Networks raise a few issues like Energy Scavenging for the limited power supply. Accordingly good functioning of such system relies upon energies of the wireless motes. This paper presents two analytical models which demonstrate and predict the QoS in terms of throughput, jitter, average end-to-end delay and energy consumption. These two distinct network models based on IEEE 802.15.4 are cluster-based and grid-based, and are simulated using QualNet v 6.1 Simulator.
文摘IEEE 802.11ah brings in Restricted Access Window （RAW） to decrease contention, which is the grouping-based MAC protocol. The way to group a large number of devices and application of RAW size would have influence on the energy efficiency in the process of medium access and communications. In this paper, we study an efficient window control algorithm to improve the uplink energy efficiency with a novel retransmission scheme that utilises the next empty slot for retransmission in the uplink. The grouping scheme is based on the college admission game. The problem is formulated based on energy efficiency by probability theory and Marker chain. To optimise energy efficiency, a window control scheme is proposed to group the devices and set the adaptive window size （number of slots per RAW and internal slot interval） based on the number of groups, applications and the distance between devices and Access Point （AP）. The optimal solution is derived by Gradient Descent approach. Simulation results show that our proposed algorithm outperforms existing one on uplink energy efficiency and fairness.
基金supported by the National Natural Science Foundation of China(61202440)the Natural Science Foundation of Jiangsu Province(BK20141230)
文摘One main issue of degrading IEEE 802.15.4performance is the beacon conflict which increases the energy consumption.However,IEEE 802.15.4does not address a solution to avoid the beacon conflict.In order to reduce this beacon conflict,an individual time division(ITD)algorithm based on IEEE 802.15.4is proposed.In this algorithm,a coordinator assigns the time division(TD)for each associated coordinator so that different coordinators transmit a beacon frame at different time slice.In this way,the beacon conflict is decreased substantially.The experimental results show that ITD reduces both the beacon conflict and the network energy consumption,and improves the network performance.
基金Supported by the National High Technology Research and Development Program of China(863 Program,No.2009-AAZ249)the Major Special Project of China(2010ZX03003-003-01)
文摘In wireless multicast, some users may fail to receive data as a result of bad channel con-ditions. The throughput of traditional multicast strategy is constrained by the node with the worst channel condition. In this paper, we propose a distributed cooperative multicast scheduling strategy, in which, every user which has successfully received data can decide whether to retransmit data by sensing MNACK packets. The proposed scheme can achieve good throughput by exploiting multi-channel diversity across multiple users' cooperation. In addition, the constraint of power consumption is also considered. Simulation results show that our scheme can provide good throughput and fairness per-formance with the constraint of average system power consumption.
文摘Abstract： In this paper, we propose a mecha- nism for multicast data transmission in IEEE 802.16 mesh networks aimed at increasing the throughput by incorporating mini-slot spatial reuse. The proposed mechanism includes two novel algorithms： a source-based multicast tree topology construction algorithm followed by an interference-aware multieast scheduling algorithm. The proposed multicast interfer- ence-aware scheduling algorithm can be ap- plied to both source-based and rendez- vous-based multicast tree topologies. Results of our simulation study show that in compari- son to the mechanism used for the IEEE 802.16＇s standard, the proposed multicast tree generation algorithm reduces the number of consumed mini-slots by 64% on average. Moreover, using the proposed interfer- ence-aware scheduling algorithm decreases the number of required mini-slots by a further 22% on average. Therefore, the proposed mul- ticast scheduling mechanism shows a higher throughput than the previous approaches and it is more scalable with respect to increasing the number of multicast groups as well as in- creasing the number of members inside each multicast group.
文摘IEEE 802.16 mesh mode defines routing tree for transmitting data in centralized scheduling but it does not define any explicit proposal for combining uplink and downlink subframes. Deploying combined uplink and downlink subframes on the centralized scheduling scheme can be more flexible and utilization is improved. However, existing interferences among the transmission of neighboring nodes lead to performance reduction of the network. In this paper, an efficient routing tree algorithm is proposed with combined uplink and downlink slot allocation on the centralized scheduling scheme which can abate interferences in the network. This algorithm allows more subscriber stations to transmit concurrently and so improves spatial reuse in the network. Also, the algorithm uses multi-channel and single channel systems and considers relay model, smoothing switching frequently between transmitting and receiving in successive time slots and fairness in the network. Extensive simulation results demonstrate the effectiveness of the proposed method in terms of scheduling length, link concurrency ratio, network throughput and Channel Utilization Ratio (CUR).
