Metrics measurement

Capacity estimation:

In multi-hop wireless networks, flows that traverse the same geographical vicinity contend for the same wireless channel capacity. This is in sharp contrast with wireline networks, where the network resource is modeled as a set of links (or edges in the topological graph) connecting nodes and only flows that traverse the same link contend for the capacity of this link.

Determining the capacity of an arbitrary ad hoc network is difficult because neighboring links using the same channel interfere, and the interference relationships between all of the links in a network can be quite complex. Several researchers interested in the capacity of ad hoc networks have modeled the ad-hoc network using randomized models, and evaluated asymptotic bounds on the capacity. Other work has addressed the question of whether a given flow vector is feasible on a particular ad hoc network, where "feasible" means that a global scheduler with access to all the information in the network could find a link scheduling policy that would achieve the desired rates.

In this project, we are also interested in methods for determining whether a flow vector is feasible, but we are particularly interested in methods that are suitable for distributed control in an ad hoc network.

We have developed 3 methods:

  • Clique constraints, based on graph theory;
  • Analytical models, based on probability model and mathematical analyses;
  • Real measurements, based on information given by wireless card driver.

Delay estimation:

With the QOLSR protocol, QoS information required for route calculation is immediately available when needed. So, before sending data traffic we must inform each node about the delay information between any node and its MPRs. The only way to calculate the delay is to use the control messages. Each node periodically broadcasts locally its HELLO messages. These control messages are transmitted in broadcast mode without acknowledgements in response.

The received HELLO messages are used by each node to estimate the Expected Total Time Transmission (ETTT). The Expected Total Time Transmission is a function of Mac queuing time, loss rate and bandwidth of the link.

We have developed 2 methods:

  • Analytical models, based on probability model and mathematical analyses;
  • Real measurements, based on information given by wireless card driver.

Other metrics

Methods fot metrics like jitter, data loss probability, security, power consumption and others are currently being worked on.

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