next up previous
Next: MYCALL Timer Up: Emulation Results Previous: Emulation Results

Effect of Scale on NCP

The emulation was run to determine the effect on the NCP as the number of ES and RN nodes increased. The dominate component of the configuration time is the topology calculation run by the ES which is designated as the master. Topology calculation involves searching through the problem space of constraints on the directional beams for all feasible topologies and choosing an optimal topology from that set as described in [15]. The units on all values should be consistent with the GPS coordinate units, and all angles are assumed to be degrees. The beam constraint values are Maximum link distance 1000.0, Maximum Frequencies 3, Interference Multiplier 1.0, Transmit Beam Width 10.0, Receive Beam Width 10.0.

The topology calculation is performed in MatLab and uses the MatLab provided external C interface. Passing information through this interface is clearly slow, therefore these results do not represent the exact execution times of the prototype system. However, they do provide a worse case test for the protocol.

A possible speedup may arise through the use of Virtual Network Configuration, which will provide a mechanism for predicting values in advance and also allows processing to be distributed. Another improvement which may be considered is to implement a hierarchical configuration. The network is partitioned into a small number of clusters of nodes in such a way that nodes in each group are as close together as possible. The topology code is run as though these were individual nodes located at the center of each group. This inter-group connection will be added as constraints to the topology computation for the intra-group connections. In this way the topology program only needs to calculate small numbers of nodes which it does relatively quickly.



Steve Bush
Tue Nov 12 11:48:31 CST 1996