An End-to-End Technique to Estimate the Transmission Rate of an IEEE 802.11 WLAN

Abstract

Abstract-The deployment of wireless LANs (WLANs) has been steadily increasing over the years and estimating the actual bit rate of a WLAN device is important for management and applications such as those that can adapt their transmission rates according to the network characteristics. We propose a simple and accurate active measurement technique to infer the bit rate of an IEEE802.11 device. The proposed method is based both on a recently proposed technique to infer the type of access network and on the packet pair approach, but adapted to take into account the overhead caused by the IEEE802.11 control and the existence of concurrent WLAN traffic. Furthermore, the technique does not require the WLAN to be the bottleneck link in the path from the measuring point to the end computer. Results from simulation and from measurements show that the approach is accurate to infer WLAN access point rates both in scenarios where the WLAN devices can adapt their rates as well as WLANs with fixed transmission rates. I. INTRODUCTIONWireless local area networks (WLANs) based on the IEEE 802.11 standards [1] have become one of the most popular access networks. The high transmission rates offered by the current standards (802.11a/b/g) and the significant reduction in the costs of the equipment have greatly eased the deployment of this technology on public locations (e.g. airports, universities, libraries, cafes, shopping centers) and residences.Access networks consist of the links between end systems and edge Internet routers. Examples of such links are dial-up lines, ADSL, Cable Modem, Ethernet and WLAN. The various types of access networks have different characteristics in terms of transmissions speeds, physical media, and capacity in the reverse and forward links.Identifying the connection type of the last hop of an Internet path can be very useful for several applications, such as video streaming, overlay networks and peer to peer. For example, in order to improve performance, it may be advantageous to peerto-peer applications to know the type of access network (as suggested in [2]) and the transmission rates of the clients, in order to choose the best peer to connect. As another example, there are proposals to improve TCP performance when the last hop is a WLAN [3] or a cable modem [4].These examples explain why recent research was devoted to characterizing the type of connection available to an end user. The work of [5] was the first aiming at differentiating between wireless and wired network access. It is based on the observation of round trip times (RTT's) of TCP connections. In [2] the authors proposed a method to identify the type of an access network (Ethernet, WLAN, or low bandwidth).