Tactical Wireless Communications and Networks: Design Concepts and Challenges

4.2 Queuing Theory

Queuing theory is an essential concept to review in light of tactical wireless communications and networks. Understanding queuing theory will help you address some of the challenges facing the optimization of tactical networks performance. Understanding queuing theory will help you address critical areas of networking, such as packet delay, packet loss due to queue overflow, and the advantages of statistical multiplexing. As we have done with the physical layer and DLL analysis, we will use simplified assumptions regarding queuing theory to conduct meaningful analysis,⁴ since realistic assumptions inhibit clear theoretical analysis.

When a packet traverses a network hop, it can experience the following delays:

• Processing delay—the time from the packet's arrival at the network layer of the node until it is assigned to an outgoing queue (if routed at the IP layer). If the packet is transmitted over the air, we must add processing delay at the MAC, DLL, and physical layers.
• Queuing delay—the time from when the packet arrives to the queue until it is transmitted. Other packets waiting in the queue ahead of this packet can cause it to wait until they are transmitted.
• Transmission delay—the time between the transmission of the first and last bits of the packet (the capacity of the physical media is a decisive factor in this delay).
• Propagation delay—the time from when the last bit is transmitted until the last bit is received at the destination node. In satellite ...