Tactical Wireless Communications and Networks: Design Concepts and Challenges

4.3 Concluding Remarks

This chapter emphasized queue modeling in order to give you an understanding of how tactical networks get congested at the IP layer or at the MAC layer. Other books, covering the network layer, may focus on protocols such as IP or OSPF (open shortest path first). However, in tactical wireless networks, we not only have connectivity at layers 2 and 3 (which cause us to look at routing differently from wired and point-to-point networks), but we also face specific challenges with fluctuation of bandwidth that can cause queue build-up. This can lead to packet drops, excessive delays, and delay variation (jitter). For the purpose of addressing tactical wireless network challenges, we would rather you acquire a firm grip on the causes of degradation of service, and the recommended design concepts, instead of explaining basic protocols that can be found in other books.

4.3.1 How Congestion Happens in Tactical Wireless Networks

The M/M/1 queue model, which we discussed in detail, albeit the simplest queue model, can provide us with a good sense of some of the challenges that we are facing with tactical wireless networks. Let us look at a common dangerous engineering practice that correlates percentage utilization to congestion in a linear fashion. Going through the M/M/1 queue model you can see that if we correlate congestion to: (i) the expected number of packets waiting in the queue (which can cause packet drop, since we have a limited queue size and cannot tolerate ...