Ad Hoc Networks
Cheikh Sarr, Claude Chaudet, Guillaume Chelius, and Isabelle Gue´ rin Lassous Abstract—Since 2005, IEEE 802.11-based networks have been able to provide a certain level of quality of service (QoS) by the means of service differentiation, due to the IEEE 802.11e amendment. However, no mechanism or method has been standardized to accurately evaluate the amount of resources remaining on a given channel. Such an evaluation would, however, be a good asset for bandwidth-constrained applications. In multihop ad hoc networks, such evaluation becomes even more difficult. Consequently, despite the various contributions around this research topic, the estimation of the available bandwidth still represents one of the main issues in this field. In this paper, we propose an improved mechanism to estimate the available bandwidth in IEEE 802.11-based ad hoc networks. Through simulations, we compare the accuracy of the estimation we propose to the estimation performed by other state-of-the-art QoS protocols, BRuIT, AAC, and QoS-AODV.
Index Terms—Wireless communications, IEEE 802.11, ad hoc networks, quality of service, available bandwidth estimation. Ç
AD hoc networks are autonomous, self-organized, wireless,
and mobile networks. They do not require setting
up any fixed infrastructure such as access points, as the
nodes organize themselves automatically to transfer data
packets and manage topology changes due to mobility.
Many of the current contributions in the ad hoc networking
community assume that the underlying wireless technology
is the IEEE 802.11 standard due to the broad availability of interface cards and simulation models. This standard
provides an ad hoc mode, allowing mobiles to communicate
directly. As the communication range is limited by
regulations, a distributed routing protocol is required to
allow long distance communications. However, this standard
has not been targeted especially for multihop ad hoc
operation, and it is therefore not perfectly suited to this type of networks.
Nowadays, several applications generate multimedia
data flows or rely on the proper and efficient transmission
of sensitive control traffic. These applications may benefit from a quality of service (QoS) support in the network. That is why this domain has been extensively studied and more
and more QoS solutions are proposed for ad hoc networks.
However, the term QoS is vague and gathers several
concepts. Some protocols intend to offer strong guarantees
to the applications on the transmission characteristics, for instance bandwidth, delay, packet loss, or network load.
Other solutions, which seem more suited to a mobile
environment, only select the best route among all possible
choices regarding the same criteria. In both cases, an
accurate evaluation of the capabilities of the routes is
necessary. Most of the current QoS proposals leave this
problem aside, relying on the assumption that the link layer protocols are able to perform such an evaluation. However,
they are not. The resource evaluation problem is far from
being trivial as it must take into account several phenomena related to the wireless environment but also dependent on
less measurable parameters such as the node mobility.
Throughout this paper, we will focus on one of the
fundamental resources: throughput. Estimating the remaining
bandwidth at a given time and in a given part of the
network is tricky because, in a wireless network, the
medium is shared between close nodes. Consequently,
computing the available bandwidth between two neighbor
nodes necessitates an accurate identification of all potential contenders at the emitter’s side, of all potential scramblers at the receiver’s side, and a proper evaluation of their
impact. Information about nodes’ utilization of the shared resource should, therefore, be gathered and composed to
derive the amount of free resources....