Cross-Layer Optimal Congestion Control Scheme in Mobile Ad Hoc Networks
Xu Wei · 2010
This paper identifies all factors impairing TCP performance based on network protocol hierarchy:Lossy wireless channel at the physical layer;excessive contention and unfair access at the MAC layer;frequent routing changes due to node mobility at the network layer;the fundamentally inappropriate mechanisms of TCP at the transport layer,including window-based congestion control,loss-based congestion detection,slow-start and AIMD(additive increase/multiplicative-decrease) of congestion window;reliance on ACK-clocked characteristics.Then,it designs a novel cross-layer optimal congestion control(CCOC) protocol tailored toward the characteristics of ad hoc networks.Cross-Layer design framework is applied in CCOC to improve fair access at MAC layer,to detect false link failure,to reduce the number of route failures,to quick-start during route changes,to transmit reliably based on SACK,and to implement the adaptive optimization strategy guided by the nonlinear optimization theory.Then,this paper outlines the protocol framework of CCOC.Finally,the extensive packet-level simulations is implemented in NS2 environment.The simulation results show that CCOC significantly outperforms TCP and ATCP in many important performances such as throughput and fairness,under a variety of scenario and mobility conditions.