Limitations of equation-based congestion control in mobile ad hoc networks

Equation-based congestion control has been a promising alternative to TCP for real-time multimedia streaming over the Internet. However, its behavior remains unknown in the mobile ad hoc wireless network (MANET) domain. We study the behavior of TFRC (TCP Friendly Rate Control (S. Floyd et al., 2000; M. Handley et al., 2003) over a wide range of MANET scenarios, in terms of throughput fairness and smoothness. Our result shows that while TFRC is able to maintain throughput smoothness in MANET, it obtains less throughput than the competing TCP flows (i.e., being conservative). We analyze several factors contributing to TFRC's conservative behavior in MANET, many of which are inherent to the MANET network. We also show that TFRC's conservative behavior cannot be completely corrected by tuning its loss event interval estimator. Our study shows the limitations of applying TFRC to the MANET domain, and reveals some fundamental difficulties in doing so.