Outdoor Mesh Throughput and Hops

Question

Hi guys, it ́s a good to be here again,
i would like to know how the throughput is calculated by hop in a mesh network, for example let ́s imagine that we have:

Example 1:
root ap (t300) ------link------map(t300) -----link------map(t300)-----link----map(t300)----link---laptop

Question 1
In a best practice design guide from ruckus i read that the throughput is approximately
1/N where N is the hop number......is this real??? for the first link root----map what is the throughput???

Question 2
In other topics about Mesh in this forum i read that it lose 50% by hop.

which one is real??? (question 1 or 2)

Question 3
The throughput for the wireless devices (laptop) in the example 1 is share between all the devices connected to it???

Question 4
Is there any way to measure the speed about how an ap process a packet from user device to wired network?? some clients usually say that they connections is slow and the guilty is the ap.

Thanks guys for your help!!!

Golbert

unknown · Answer

In response your questions:Question 1
In a best practice design guide from ruckus i read that the throughput is approximately
1/N where N is the hop number......is this real??? for the first link root----map what is the throughput???

I would never believe anything from a manufacturer when it come to performance without backing it up by testing it myself.Question 2
In other topics about Mesh in this forum i read that it lose 50% by hop

As above.Question 3
The throughput for the wireless devices (laptop) in the example 1 is share between all the devices connected to it???

If the AP has 100Mbps TCP capacity between itself and the Root AP, then this value is shared between the devices connected i.e. if you have 10 clients they should each be able to draw approx 10Mbps concurrently (based on clients not connecting to the 5GHz which is used for MESH layer connectivity).

Note: as you client numbers increase you will start to see an overhead curve in terms of AP to client capacityQuestion 4
Is there any way to measure the speed about how an ap 
process a packet from user device to wired network?? some clients 
usually say that they connections is slow and the guilty is the ap.

Use ZAP:

http://www.ruckuswireless.com/press/releases/20100104-zap-wireless-tool

Link to Code and User Guide:

https://app.box.com/s/w6akdafikmh3pi46qvk171m26vl4vtok

Note: There is also a good paper on Wireless Nework Performance in there too.

Alternatively you can use SpeedFlex which is more or less the same, but more GUI based and has client support for Android and iOS.

http://www.ruckuswireless.com/products/mobile-apps/speedflex

You can either use ZAP as the server on the PC or you can download SpeedFlex for the PC from the ZD/SZ: you are given a download option when you ryr and run a test between the ZD/SZ/AP and yourself.

john_d · Answer

These are excellent questions, and after spending almost a year now perfecting meshed parts of my network in two home/pro-consumer deployments, here's my observations:

As far as "what's the mesh throughput at hop N", if you're talking about getting out to the internet, it's approximately 1/2^n, where N is the number of hops to the root AP. The reason is simple, at each hop, airtime must be distributed between listening to a client, and transmitting that data up to the next mesh link. So, at hop 1, you approximately split 1/2 your time listening/talking to the client and 1/2 the time listening and talking to the mesh root. So at hop 2, you only have 1/2 of the bandwidth of hop 1, and you must split your time talking to the client and talking back to hop #1.

Ruckus's mesh implementation has two nice things about it:

(1) Unlike a lot of consumer WDS systems, if you are doing LAN communication, the mesh will find the shortest mesh path between two peers. For example, if you are transferring files between laptops on the same mesh AP, you get 100% of the bandwidth and none of the other mesh links are involved.

(2) Ruckus supports the concept of an "eMesh AP", where two mesh APs are wired together via ethernet. They will self-arrange into a backhaul arrangement where one AP serves as the mesh uplink, and the second AP will broadcast a new network on a new channel. This in effect gets rid of the 1/2 bandwidth loss per mesh hop, of course at the cost of adding another AP.

If you need to deploy a mesh topology that involves more than ~2 hops on N or 3-4 hops on AC, you almost certainly will benefit from using eMesh AP topologies. So, if you can run ethernet between some of the mesh nodes, or afford to add some additional APs to form mesh-eMesh pairs, you'll greatly improve the bandwidth.

At my parents place over Christmas, I noticed that they currently have a mesh topology using 7982's of Basement -> Kitchen -> Bedrooms. At the bedrooms, despite all the mesh links having 80%+ signal, there's only 30-40mbit/s of throughput. They complained the internet felt slow. I added a second 7982 to the kitchen, and wired the two APs together just a few feet from each other. So now it's Basement -> Kitchen1/Kitchen2 -> Bedrooms. This change alone boosted their bandwidth to 80mbit/s in the bedrooms.