In this paper, based on the inherent characteristic of the contention relation between flows in ad hoc networks, we introduce the notion of the link＇s interference set, extend the utility maximization problem represe...In this paper, based on the inherent characteristic of the contention relation between flows in ad hoc networks, we introduce the notion of the link＇s interference set, extend the utility maximization problem representing congestion control in wireline networks to ad hoc networks, apply the penalty function approach and the subgradient method to solve this problem, and propose the congestion control algorithm Penalty function-based Optical Congestion Control （POCC） which is implemented in NS2- simulator. Specifically, each link transmits periodically the information on its congestion state to its interference set; the set ; the sermon at each source adjusts the transmission rate based on the optimal tradeoffbetween the utility value and the congestion level which the interference set of the links that this session goes though suffers from. MATLAB-based simulation results showed that POCC can approach the globally optimal solution. The NS2-based simulation results showed that POCC outperforms default TCP and ATCP to achieve efficient and fair resource allocation in ad hoc networks.展开更多
The congestion control mechanisms of the current standard TCP constrain the congestion windows that can be achieved by TCP in high-speed networks, which leads to low link utilization. HSTCP is one solution to solve th...The congestion control mechanisms of the current standard TCP constrain the congestion windows that can be achieved by TCP in high-speed networks, which leads to low link utilization. HSTCP is one solution to solve this problem by modifying the congestion control mechanism to have the characteristics of TCP friendliness in high loss rate environment and high scalability in low loss rate environment. However, experiments revealed that HSTCP has severe RTT unfairness. After analyzing the RTT unfairness in HSTCP with a model, we proposed CW-HSTCP, which added a fair factor to decrease the difference of congestion window caused by different RTT. Fair factor of long RTT flows can cause a sharp window increment that is easy to cause a bursty traffic, so a method called block-pacing was adopted. Simulation results showed that our new proposal could alleviate the RTT unfairness while keeping advantages of HSTCP.展开更多
文摘In this paper, based on the inherent characteristic of the contention relation between flows in ad hoc networks, we introduce the notion of the link＇s interference set, extend the utility maximization problem representing congestion control in wireline networks to ad hoc networks, apply the penalty function approach and the subgradient method to solve this problem, and propose the congestion control algorithm Penalty function-based Optical Congestion Control （POCC） which is implemented in NS2- simulator. Specifically, each link transmits periodically the information on its congestion state to its interference set; the set ; the sermon at each source adjusts the transmission rate based on the optimal tradeoffbetween the utility value and the congestion level which the interference set of the links that this session goes though suffers from. MATLAB-based simulation results showed that POCC can approach the globally optimal solution. The NS2-based simulation results showed that POCC outperforms default TCP and ATCP to achieve efficient and fair resource allocation in ad hoc networks.
文摘The congestion control mechanisms of the current standard TCP constrain the congestion windows that can be achieved by TCP in high-speed networks, which leads to low link utilization. HSTCP is one solution to solve this problem by modifying the congestion control mechanism to have the characteristics of TCP friendliness in high loss rate environment and high scalability in low loss rate environment. However, experiments revealed that HSTCP has severe RTT unfairness. After analyzing the RTT unfairness in HSTCP with a model, we proposed CW-HSTCP, which added a fair factor to decrease the difference of congestion window caused by different RTT. Fair factor of long RTT flows can cause a sharp window increment that is easy to cause a bursty traffic, so a method called block-pacing was adopted. Simulation results showed that our new proposal could alleviate the RTT unfairness while keeping advantages of HSTCP.
