06-03-2013, 09:50 AM
Bandwidth Estimation for IEEE 802.11 Based Ad Hoc Networks
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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.
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.
EXISTING SYSTEM:
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. 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 rely on the assumption that the link layer protocols are able to perform such an evaluation. 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.
PROPOSED SYSTEM:
Here, we present a new method to evaluate the available bandwidth in ad hoc networks based on the IEEE 802.11 MAC layer. This method uses the nodes’ carrier sense capability combined to other techniques such as collision prediction to perform this estimation. It provides upper layers with an evaluation that represents an acceptable compromise between accuracy and measurement cost. Finally, even though it is closely linked to a particular technology, it may easily be adapted to similar random medium access protocols. In wireless ad hoc networks, a flow could easily take over the whole capacity of the network due to the strong interdependency between wireless links. Therefore, it is necessary to take into account the disruption that may be introduced in the network by the addition of a new flow and to distinguish between the raw throughput that may be transferred along a path and the maximum data rate that may be transferred without any noticeable interference.
We define the available bandwidth between two neighbor nodes as the maximum throughput that can be transmitted between these two peers without disrupting any already ongoing flow in the network. We will denote by link capacity the maximum throughput a flow can achieve between two neighbor nodes regardless of other flows present in the network.
MODULES:
Packet Creation
In this module we split the Data in to N number of Fixed size packet with Maximum length of 48 Characters.
Apply the RREQ and get RREP
The aim of the RREQ is to find a route between the sender and the receiver that meets the constraints specified by the application level in terms of Bandwidth.
Therefore, two flows with the same source and destination can follow different routes depending on the network state.
When a source node has data to send, it broadcasts a route request (RREQ) to its neighbors. The RREQ packet contains the address of the sender, and the requirements at the application level, the destination address, and a sequence number. The Intermediate Node or Destination Node sends RREP if it is free, otherwise, it silently discards the message.
Admission Control Mechanism
The Admission Control Mechanism is done in the receiver side. The Admission Control Mechanism has the all status of the node so if the nodes want to send RREP or discard the message, the particular node check the status by using the Admission Control Mechanism.
Bandwidth Utilized
After the source nodes send the total message to the Destination Node finally we calculate the end to end delivery of the Bandwidth and Time delay.
The implementation requires following resources: