In a heterogeneous wireless network environment, the network nodes are equipped with both wireless local area network (WLAN) and cellular interfaces. It is desirable to combine the higher bandwidth of a WLAN and the ubiquitous nature of cellular networks to provide the transport service for QoS demanding applications, such as remote sensing and control systems. Common solutions exploit the diversity of cellular channels by recruiting multiple WLAN peers to work as proxies for a MANET node that needs to communicate through the cellular network. One important problem when utilizing channel diversity in a heterogeneous wireless network environment is to balance the trade-off of channel diversity gains with MANET peer contentions. A greater number of proxies will inevitably increase the MANET contention and possibly QoS degrading of the cell, and fewer proxies may not be able to provide sufficient diversity. This paper aims to build a dynamic mechanism to determine the appropriate number of proxies to use. The mechanism uses the MAC layer retransmission rate as an indicator of the contention level in MANET. Simulation using cellular channel fading models and prevalent cell scheduling policies indicate the scheme can provide better QoS through channel diversity by using the appropriate number of proxies.
['Zhiwei Cen', 'Matt W. Mutka']
QoS Provision for Remote Sensing and Control in Heterogeneous Environments