Traffic Signals - polling and video

Anyone have experience with using Traffic Signals in your broadband networks?

I am finding it challenging to balance the very different requirements our traffic signals customers require. Each intersection controller is polled once per second for status information. This provides info back to a central control system indicating the status of each signal, light status, etc. Polling is done from a central server via UDP. Now each intersection also has video cameras (often quad) that allows for streaming video from the site on demand.

So 2 very different types of data traffic and characteristics (ie. low bandwidth low latency vs high bandwidth high latency).

I also have customer building sites in some of the sectors that would be similar to any office environment traffic. No VOIP. Some performance challenges from the streaming video are emerging that I would think should not be a problem at this time, with some periodic warnings about AP exceeding preset discard percentage and sluggishness.

Anyone with any QoS tips that might bear fruit to better fine tune my AP’s and SM’s to facilitate the differing traffic loads would be appreciated. We are exclusively 5.4GHz equipment in this zone built last year. 4 AP’s on tower, very clean RF environment, 20MHz channels. About 40 total SM’s.


Which gear are you looking at deploying? My experience with PMP100 is related only to VoIP. The PMP100 gear only has two queues which can be summed up as “Best Effort” and “Priority”, where you can assign a CIR to Priority traffic.

PMP320 is much more versatile and has management mechanisms appropriate to video and several other types of traffic on the same sector. Not sure how support on the other platforms work.

We deployed PTP800 for backhaul, 5480 AP’s for tower, 5491 SM’s.

Is that Canopy gear? I’m not very familiar with the part numbers.

If it is you’re looking at doing QoS based on DSCP (newer firmwares) and you only get a single queue. It will effect upstream and downstream for the whole AP. So you’ll need to decide which flow needs to be serviced first. I’m going to assume that the control data for the signals should be high priority and video doesn’t matter as much. Note that CIR between SMs can have an impact on the AP’s performance, so say you have a single SM doing the traffic light control and assign it High Priority QoS with a CIR, it will reserve that bandwidth exclusively for the signals on the AP. You could have cameras hanging off of another SM with high priority, but no CIR, and these will be prioritized over any remaining traffic on the AP. You can also play with this via the bandwidth settings to control maximum speeds.