[e2e] Throughput and delay in a theoretical model of network system

CaiShun vitacaishun at gmail.com
Tue Feb 24 19:38:00 PST 2009

Hello, everyone

I have a problem on the" throughput and delay " when view ing a network in a theoretical way, e.g. multi-commodity  flow model, or  Queueing Network(Stochastic Optimization) . 

Suppose a simple  wirless network with 6 nodes. A traffic flow from node 1 to node 6, and the rate of each link is shown in the  following Fig.

Intuitively, the throughput is  6 = 4+2.  Although the last hop  link(4,6) and link(5,6) can not be active simultaneously, the rate of the two links is much higher than link24,and link 35. 

But we observe that each node can not receive and transmit simultaneously. So it takes 3 slots for a packet to travel from node 1 to node 6. Suppose at some  slot 6 packets arrives  at node 1, then the throughput is 6/3 = 2 packets per slot, right?

I believe  there's something wrong to define throughput and delay in the way above. But I am really getting confused . why most theoretical models concern on the throughput of the system without taking DEDLAY into account? Maybe it is  about different layers -Network layer and MAC layer£¿



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