qifei zhang - Academia.edu (original) (raw)
Papers by qifei zhang
Due to the ignorance of the relation between different collisions, traditional medium access cont... more Due to the ignorance of the relation between different collisions, traditional medium access control protocols cant
achieve their anticipated collision resolution results. This paper
proposes a novel way to distribute MAC accesses in MANETs
based on collision classification approach and modified backoff
schemes. The idea is to avoid cross collisions through dynamically allocated elementary windows which prevent intersection of spaces in which the backoff counters are decremented. It develops a policy to select an appropriate backoff value as a function of retransmission attempts, observed number of collisions etc. to minimize repeated collisions, and thus improves throughput, delay jitter, as well as fairness. The performance improvement is demonstrated convincingly using a wide range of simulations.
Due to the ignorance of the relation between different collisions, traditional medium access cont... more Due to the ignorance of the relation between different collisions, traditional medium access control protocols cant achieve their anticipated collision resolution results. This paper proposes a novel way to distribute MAC accesses in MANETs based on collision classification approach and modified backoff schemes. The idea is to avoid cross collisions through dynamically allocated elementary windows which prevent intersection of spaces in which the backoff counters are decremented. It develops a policy to select an appropriate backoff value as a function of retransmission attempts, observed number of collisions etc. to minimize repeated collisions, and thus improves throughput, delay jitter, as well as fairness. The performance improvement is demonstrated convincingly using a wide range of simulations.
ABSTRACT Traditional backoff algorithms in distributed contention-based MAC protocols adopt conte... more ABSTRACT Traditional backoff algorithms in distributed contention-based MAC protocols adopt contention window scheme for collision resolution. Collided nodes are redistributed in extended windows to avoid further collision. However, collision may still occur due to intersecting window ranges. In this paper, we propose an effective backoff algorithm featuring collision-free collision classification resolution (CF-CCR) based on collision classification model to resolve different collisions with different manners. Under the schedule of CF-CCR, the network will ultimately converges to a collision free state, in which nodes access channel sequentially with no collision occurred. The simulation results show that CF-CCR outperforms IEEE 802.11 DCF in collision times, throughput, delay and fairness.
Backoff algorithms in traditional distributed contention-based MAC protocols concentrate on adjus... more Backoff algorithms in traditional distributed contention-based MAC protocols concentrate on adjusting contention window size to resolve collision. However, collision may still occur as long as these windows intersect with each other. In order to solve this problem, we put forward a collision classification model to classify collisions into cross collision and intra collision and suggest to solve them with different manners. Based on this model, we propose collision classification resolution (CCR) algorithm to dynamically allocate discrete distribution windows for collided nodes to avoid cross collision, and the intra collision is resolved with an appropriate distribution window size to achieve a tradeoff between delay and collision probability. The extensive simulations performed demonstrate that compared to IEEE 802.11 DCF, CCR algorithm consistently excels, in terms of collision times, throughput, delay and fairness.
Traditional backoff algorithms in WLAN extend their contention windows to resolve collisions. How... more Traditional backoff algorithms in WLAN extend their contention windows to resolve collisions. However, collisions may still occur due to intersecting windows among contending stations. Based on such observation, this paper puts forward a collision classification model to classify collisions into two categories and proposes an algorithm featuring collision classification resolution (CCR) to resolve different collisions with different manners. The simulation results demonstrate that compared to IEEE 802.11 DCF, CCR algorithm achieves improvement in collision times, throughput, delay and fairness.
Traditional backoff algorithms in WLAN adopt contention window scheme for collision resolution. C... more Traditional backoff algorithms in WLAN adopt contention window scheme for collision resolution. Collided stations are redistributed in extended contention window ranges to avoid further collisions. However, due to the existence of intersection among these ranges, collision can still occur. This paper proposes Collision Sequential Resolution (CSR) algorithm to address the problem, which is compatible with IEEE 802.11. CSR allocates discrete contention windows for active stations, therefore the stations can be deployed in a series of separated distribution windows sequentially to eliminate collisions. The simulation results demonstrate that CSR algorithm provides significant comprehensive improvement to IEEE 802.11 protocol.
With the emerging awareness of health care, this paper addresses the challenging research issue o... more With the emerging awareness of health care, this paper addresses the challenging research issue of healthcare sensor decision. On light of the technology combination of WSN, MAS and RST, and its contribution to the framework of healthcare sensor decision network, this work further studies the multiplicity of intelligent agent based healthcare sensor decision network, and proposes the hierarchical model DHMASDN and its corresponding agent layer built healthcare sensor decision network, attribute layer built healthcare sensor decision network and rule layer built healthcare sensor decision network. Furthermore, the tutorial algorithm and results are also given based on rule layer built healthcare sensor decision network. And as expected, the presented model, algorithm and illustrative results are demonstrated to be more helpful to enhance the integrality and reliability of healthcare sensor decision network than those of previous related works.
A Mobile Ad Hoc Network (MANET) is a dynamic wireless network that can be formed without the need... more A Mobile Ad Hoc Network (MANET) is a dynamic wireless network that can be formed without the need for any pre-existing infrastructure in which each node can act as a router. Due to energy constraint and dynamic topology of mobile ad hoc networks, multicast supported routing is a very important research issue. MAODV (Multicast Ad hoc On-demand Distance Vector) routing protocol provides fast and efficient route establishment between mobile nodes that need to communicate with each other in MANET. By analyzing the operation mechanism of MAODV, this paper presents an Energy Entropy-based multicast routing protocol in MAODV (EEMAODV). The key idea of the protocol is to find the minimal nodal residual energy of each route in the process of selecting path by descending nodal residual energy. It can balance individual nodes battery power utilization and hence prolong the entire networks lifetime. Simulation results show that the proposed EEMAODV routing protocol performed better than MAODV.
Most routing protocols for sensor networks try to extend network lifetime by minimizing the energ... more Most routing protocols for sensor networks try to extend network lifetime by minimizing the energy consumption, but have not taken the network reliability into account. To be adaptive to the harsh environment, we propose an energy-aware, load-balancing and fault-tolerant routing scheme, termed as ELFR. We first present a network robustness model. Based on this model, we design the route discovery phase to make the sensors to construct into a hop-leveled network which is mesh structure. We adopt a cross-layer design to measure the transmission delay so as to detect the failed nodes. The routing scheme works with ACK feedback mechanism to transfer control messages to avoid producing extra control overhead messages. When nodes fail, the new healthy paths will be selected locally without rerouting. Simulation results show that our scheme is much robust, and it achieves better energy efficiency, load balancing and maintains good end-to-end delay.
An ad hoc network is a collection of wireless mobile nodes dynamically forming a temporary networ... more An ad hoc network is a collection of wireless mobile nodes dynamically forming a temporary network without the use of any existing network infrastructure or centralized administration. The multipath routing in mobile ad hoc networks is difficult because the network topology may change constantly, and the available alternative path is inherently unreliable. A number of routing protocols like ad hoc on demand distance vector routing (AODV), on-demand multipath distance vector protocol (AOMDV), AODVM (AODV multipath) have been implemented. In this paper an attempt has been made to compare the performance of three prominent on demand routing protocols for mobile ad hoc networks. An on demand node disjointed multipath routing protocol with low broadcast redundancy is proposed. Multipath routing allows the establishment of multiple paths between a single source and single destination node. The solution is based on lower layer specifics. Simulation results show that, with the proposed multipath routing protocol, packet delivery ratio, end-to-end delay, and routing overhead ratio can be improved in most of cases. It is an available approach to multipath routing decision.
IEEE 802.11 MAC standard and model are well researched. Although it supports multiple channels in... more IEEE 802.11 MAC standard and model are well researched. Although it supports multiple channels in physical layer, how to provide multi-channel support in MAC layer is still challenging. Most of current work on multi-channel MAC only evaluate by simulations. In this paper, we propose a simple but general scheme to describe channel switching process. With its help, we extend the IEEE 802.11 MAC into a multi-channel MAC, and present a three-dimensional Markov chain to model it. This analytical model supports both access methods: basic and RTS/CTS. Simulation results show that our model can predict saturation throughput well. We also investigate the effect of two major parameters, namely the number of retransmission and the number of switching channel, on the performance of multichannel MAC.
Node position information in ad hoc networks will soon be obsolete due to its frequent movement. ... more Node position information in ad hoc networks will soon be obsolete due to its frequent movement. The traditional location-based algorithms that assume the position of destination is reasonably accurate are not able to deal with eventual position deviation and impose high mobility tracking overhead. Moreover, once source node is ignorant of position of destination node, flooding scheme is used instead, which increases control overhead. This paper proposed a novel routing scheme named location-based adaptive ad hoc routing (LAAR). LAAR adopts hierarchical architecture to achieve a network-wide consistent location database to eliminate inaccuracy that may be introduced by distributed prediction mechanism and implements adaptive adjustment mechanism to combine node movement with route discovery, which can dynamically track mobility of destination node. Control overhead thus can be reduced and destination location information is guaranteed to be up-to-date and accurate enough to enhance the possibility of finding a feasible route. Simulation performed demonstrates that our LAAR scheme outperforms LAR over a large density of nodes.
Comparing with the flat architecture in the design of sensor networks, the hierarchical architect... more Comparing with the flat architecture in the design of sensor networks, the hierarchical architecture is much attractive for the reason of scalability, management and energy efficiency. In order to distribute the energy evenly, nodes act the cluster head in some orders. The existing approaches don't pay critical attention to the overhead during the role rotations. And the duration of a round is a priori, which is very application-specific. An energy-aware hierarchical architecture design scheme is put forward in this paper, namely, adaptive minimum rotational cost (AMRC) cluster formation scheme. The decision of beginning a new round is made adaptively by the cluster head itself. It combines the dynamic and static advantages in the clustering architecture. The simulation results demonstrate AMRC outperforms some other clustering protocols in many aspects
Hidden receiver problem remains a primary concern in wireless ad hoc networks. Due to its ignoran... more Hidden receiver problem remains a primary concern in wireless ad hoc networks. Due to its ignorance of the state of the hidden terminal, the potential sender, which is a neighbor of the hidden node, enters into an unnecessary backoff and retransmission circle, incurring serious unfairness between competing traffics and exhausting scarce energy. A novel explicit blocking notification (EBN) scheme is proposed here to solve this problem, in which handshake sequence RTS/CTS/BN/DATA/ACK is adopted to notify the potential sender in advance to avoid blind backoff. The simulation results show that our EBN scheme not only achieves better fairness between competing traffics in addition to stabilizing the throughput but also refrains unnecessary control packet transmission to conserve energy with only a negligible additional latency.
Due to the ignorance of the relation between different collisions, traditional medium access cont... more Due to the ignorance of the relation between different collisions, traditional medium access control protocols cant
achieve their anticipated collision resolution results. This paper
proposes a novel way to distribute MAC accesses in MANETs
based on collision classification approach and modified backoff
schemes. The idea is to avoid cross collisions through dynamically allocated elementary windows which prevent intersection of spaces in which the backoff counters are decremented. It develops a policy to select an appropriate backoff value as a function of retransmission attempts, observed number of collisions etc. to minimize repeated collisions, and thus improves throughput, delay jitter, as well as fairness. The performance improvement is demonstrated convincingly using a wide range of simulations.
Due to the ignorance of the relation between different collisions, traditional medium access cont... more Due to the ignorance of the relation between different collisions, traditional medium access control protocols cant achieve their anticipated collision resolution results. This paper proposes a novel way to distribute MAC accesses in MANETs based on collision classification approach and modified backoff schemes. The idea is to avoid cross collisions through dynamically allocated elementary windows which prevent intersection of spaces in which the backoff counters are decremented. It develops a policy to select an appropriate backoff value as a function of retransmission attempts, observed number of collisions etc. to minimize repeated collisions, and thus improves throughput, delay jitter, as well as fairness. The performance improvement is demonstrated convincingly using a wide range of simulations.
ABSTRACT Traditional backoff algorithms in distributed contention-based MAC protocols adopt conte... more ABSTRACT Traditional backoff algorithms in distributed contention-based MAC protocols adopt contention window scheme for collision resolution. Collided nodes are redistributed in extended windows to avoid further collision. However, collision may still occur due to intersecting window ranges. In this paper, we propose an effective backoff algorithm featuring collision-free collision classification resolution (CF-CCR) based on collision classification model to resolve different collisions with different manners. Under the schedule of CF-CCR, the network will ultimately converges to a collision free state, in which nodes access channel sequentially with no collision occurred. The simulation results show that CF-CCR outperforms IEEE 802.11 DCF in collision times, throughput, delay and fairness.
Backoff algorithms in traditional distributed contention-based MAC protocols concentrate on adjus... more Backoff algorithms in traditional distributed contention-based MAC protocols concentrate on adjusting contention window size to resolve collision. However, collision may still occur as long as these windows intersect with each other. In order to solve this problem, we put forward a collision classification model to classify collisions into cross collision and intra collision and suggest to solve them with different manners. Based on this model, we propose collision classification resolution (CCR) algorithm to dynamically allocate discrete distribution windows for collided nodes to avoid cross collision, and the intra collision is resolved with an appropriate distribution window size to achieve a tradeoff between delay and collision probability. The extensive simulations performed demonstrate that compared to IEEE 802.11 DCF, CCR algorithm consistently excels, in terms of collision times, throughput, delay and fairness.
Traditional backoff algorithms in WLAN extend their contention windows to resolve collisions. How... more Traditional backoff algorithms in WLAN extend their contention windows to resolve collisions. However, collisions may still occur due to intersecting windows among contending stations. Based on such observation, this paper puts forward a collision classification model to classify collisions into two categories and proposes an algorithm featuring collision classification resolution (CCR) to resolve different collisions with different manners. The simulation results demonstrate that compared to IEEE 802.11 DCF, CCR algorithm achieves improvement in collision times, throughput, delay and fairness.
Traditional backoff algorithms in WLAN adopt contention window scheme for collision resolution. C... more Traditional backoff algorithms in WLAN adopt contention window scheme for collision resolution. Collided stations are redistributed in extended contention window ranges to avoid further collisions. However, due to the existence of intersection among these ranges, collision can still occur. This paper proposes Collision Sequential Resolution (CSR) algorithm to address the problem, which is compatible with IEEE 802.11. CSR allocates discrete contention windows for active stations, therefore the stations can be deployed in a series of separated distribution windows sequentially to eliminate collisions. The simulation results demonstrate that CSR algorithm provides significant comprehensive improvement to IEEE 802.11 protocol.
With the emerging awareness of health care, this paper addresses the challenging research issue o... more With the emerging awareness of health care, this paper addresses the challenging research issue of healthcare sensor decision. On light of the technology combination of WSN, MAS and RST, and its contribution to the framework of healthcare sensor decision network, this work further studies the multiplicity of intelligent agent based healthcare sensor decision network, and proposes the hierarchical model DHMASDN and its corresponding agent layer built healthcare sensor decision network, attribute layer built healthcare sensor decision network and rule layer built healthcare sensor decision network. Furthermore, the tutorial algorithm and results are also given based on rule layer built healthcare sensor decision network. And as expected, the presented model, algorithm and illustrative results are demonstrated to be more helpful to enhance the integrality and reliability of healthcare sensor decision network than those of previous related works.
A Mobile Ad Hoc Network (MANET) is a dynamic wireless network that can be formed without the need... more A Mobile Ad Hoc Network (MANET) is a dynamic wireless network that can be formed without the need for any pre-existing infrastructure in which each node can act as a router. Due to energy constraint and dynamic topology of mobile ad hoc networks, multicast supported routing is a very important research issue. MAODV (Multicast Ad hoc On-demand Distance Vector) routing protocol provides fast and efficient route establishment between mobile nodes that need to communicate with each other in MANET. By analyzing the operation mechanism of MAODV, this paper presents an Energy Entropy-based multicast routing protocol in MAODV (EEMAODV). The key idea of the protocol is to find the minimal nodal residual energy of each route in the process of selecting path by descending nodal residual energy. It can balance individual nodes battery power utilization and hence prolong the entire networks lifetime. Simulation results show that the proposed EEMAODV routing protocol performed better than MAODV.
Most routing protocols for sensor networks try to extend network lifetime by minimizing the energ... more Most routing protocols for sensor networks try to extend network lifetime by minimizing the energy consumption, but have not taken the network reliability into account. To be adaptive to the harsh environment, we propose an energy-aware, load-balancing and fault-tolerant routing scheme, termed as ELFR. We first present a network robustness model. Based on this model, we design the route discovery phase to make the sensors to construct into a hop-leveled network which is mesh structure. We adopt a cross-layer design to measure the transmission delay so as to detect the failed nodes. The routing scheme works with ACK feedback mechanism to transfer control messages to avoid producing extra control overhead messages. When nodes fail, the new healthy paths will be selected locally without rerouting. Simulation results show that our scheme is much robust, and it achieves better energy efficiency, load balancing and maintains good end-to-end delay.
An ad hoc network is a collection of wireless mobile nodes dynamically forming a temporary networ... more An ad hoc network is a collection of wireless mobile nodes dynamically forming a temporary network without the use of any existing network infrastructure or centralized administration. The multipath routing in mobile ad hoc networks is difficult because the network topology may change constantly, and the available alternative path is inherently unreliable. A number of routing protocols like ad hoc on demand distance vector routing (AODV), on-demand multipath distance vector protocol (AOMDV), AODVM (AODV multipath) have been implemented. In this paper an attempt has been made to compare the performance of three prominent on demand routing protocols for mobile ad hoc networks. An on demand node disjointed multipath routing protocol with low broadcast redundancy is proposed. Multipath routing allows the establishment of multiple paths between a single source and single destination node. The solution is based on lower layer specifics. Simulation results show that, with the proposed multipath routing protocol, packet delivery ratio, end-to-end delay, and routing overhead ratio can be improved in most of cases. It is an available approach to multipath routing decision.
IEEE 802.11 MAC standard and model are well researched. Although it supports multiple channels in... more IEEE 802.11 MAC standard and model are well researched. Although it supports multiple channels in physical layer, how to provide multi-channel support in MAC layer is still challenging. Most of current work on multi-channel MAC only evaluate by simulations. In this paper, we propose a simple but general scheme to describe channel switching process. With its help, we extend the IEEE 802.11 MAC into a multi-channel MAC, and present a three-dimensional Markov chain to model it. This analytical model supports both access methods: basic and RTS/CTS. Simulation results show that our model can predict saturation throughput well. We also investigate the effect of two major parameters, namely the number of retransmission and the number of switching channel, on the performance of multichannel MAC.
Node position information in ad hoc networks will soon be obsolete due to its frequent movement. ... more Node position information in ad hoc networks will soon be obsolete due to its frequent movement. The traditional location-based algorithms that assume the position of destination is reasonably accurate are not able to deal with eventual position deviation and impose high mobility tracking overhead. Moreover, once source node is ignorant of position of destination node, flooding scheme is used instead, which increases control overhead. This paper proposed a novel routing scheme named location-based adaptive ad hoc routing (LAAR). LAAR adopts hierarchical architecture to achieve a network-wide consistent location database to eliminate inaccuracy that may be introduced by distributed prediction mechanism and implements adaptive adjustment mechanism to combine node movement with route discovery, which can dynamically track mobility of destination node. Control overhead thus can be reduced and destination location information is guaranteed to be up-to-date and accurate enough to enhance the possibility of finding a feasible route. Simulation performed demonstrates that our LAAR scheme outperforms LAR over a large density of nodes.
Comparing with the flat architecture in the design of sensor networks, the hierarchical architect... more Comparing with the flat architecture in the design of sensor networks, the hierarchical architecture is much attractive for the reason of scalability, management and energy efficiency. In order to distribute the energy evenly, nodes act the cluster head in some orders. The existing approaches don't pay critical attention to the overhead during the role rotations. And the duration of a round is a priori, which is very application-specific. An energy-aware hierarchical architecture design scheme is put forward in this paper, namely, adaptive minimum rotational cost (AMRC) cluster formation scheme. The decision of beginning a new round is made adaptively by the cluster head itself. It combines the dynamic and static advantages in the clustering architecture. The simulation results demonstrate AMRC outperforms some other clustering protocols in many aspects
Hidden receiver problem remains a primary concern in wireless ad hoc networks. Due to its ignoran... more Hidden receiver problem remains a primary concern in wireless ad hoc networks. Due to its ignorance of the state of the hidden terminal, the potential sender, which is a neighbor of the hidden node, enters into an unnecessary backoff and retransmission circle, incurring serious unfairness between competing traffics and exhausting scarce energy. A novel explicit blocking notification (EBN) scheme is proposed here to solve this problem, in which handshake sequence RTS/CTS/BN/DATA/ACK is adopted to notify the potential sender in advance to avoid blind backoff. The simulation results show that our EBN scheme not only achieves better fairness between competing traffics in addition to stabilizing the throughput but also refrains unnecessary control packet transmission to conserve energy with only a negligible additional latency.