Network-Supported TCP Rate Control for High-Speed Power Line Communications

The high-speed power line communications (PLC) technology has great potential to serve as an infrastructure for home networking because every home electric device must be connected to a power line network. However, various special environmental factors, such as power level attenuation, divergence between different voltage lines (100/200 V), and fluctuations of source impedance and noise by other equipment, often severely degrade the communication performance. In the present paper, we focus on the flow-level performance of end-to-end data transmission (i.e., TCP) over PLC line with various negative environmental factors, which has not been well investigated so far. We first develop a new module on the NS-2 network simulator, which is driven by the information on time-varying packet error rate over PLC line prepared beforehand, to simulate the High Definition (HD)-PLC's data transmission including some dedicated mechanisms against degradation caused by the environmental factors. The simulator is validated by comparing the TCP performance obtained from experiments on a real HD-PLC network and that from simulations using the packet error rate information measured in the real environments. Next, we address a problem on co-existing multiple TCP flows over PLC line and then, as a solution, propose a new and practical network-supported TCP rate control scheme in which the sender-side PLC modem modifies the advertised window (awnd) in TCP ACK packets for controlling the TCP's sending rate in response to the PLC line condition. The simulation results demonstrate the effectiveness of the proposed scheme.