Metro Rail Communication Network

To simulate the communication network of a metro railway line and develop a detailed traffic model to meet the system design of all of the sub-systems to make an assessment of

Traffic patterns and the required minimum circuit capacity
Resulting bandwidth to satisfy the communication needs of each site covering the requirements for each sub-system
Minimum 25% spare capacity, available at each site, for future expansion

The overall railway communication network is composed of four rings, which was simulated and analyzed.Traffic models were created for:

CCTV
Radio Communication
PA
Telephone
EPAX
Fare Collection
Supervisory Control

Simulation Assumptions

The link error rate assumed is Bit Error Rate (BER) of 10^-6 which is higher than the typical rate of 10^-9 thereby giving us a more conservative estimate of throughput
The propagation delay in the links is 5 micro seconds and the packet size is 1500 bytes
All traffic modeled was unicast traffic flowing from control centre to stations

Conclusions

NetSim simulation was run during about 2 million packets and 22 million events were processed

Increase link capacity: The result of the performed simulation showed that the worst case scenario caused traffic loaded to cross 1 Gbps and hence the original link dimensioning had to increase to factor this in
Use multicast where possible: These results were based on simulation of unicast traffic. If the path between server and client traverses h3 router hops and h2 switch hops, the "unicast" video would consume 1.5 x n x h3 Mbps of router bandwidth, plus 1.5 x n x h2 Mbps of switch bandwidth, where n is the number of unicast clients. However in a multi cast environment, a single video stream is replicated as required by the network's multi cast routers and switches to allow an arbitrary number of clients to subscribe to the multi cast address and receive the broadcast. Within the network, the multi cast transmission would consume only 1/nth of the bandwidth of the unicast solution