Hidden node questions

[accessonline]

Been reading about "hidden node" issues on the ISP-Wireless lists.

Someone said using Star-OS for the AP will overcome these problems, is that true? Does it require special configuration, or does it set for optimum hidden node rejection by default?

Also, I had considered for some very small POPs using a standard client connection to the AP as the backhaul, but those on the list said hidden node would kill it, since the one client link would then carry all traffic for the other clients. If Star-OS overcomes hidden node as above, would it then allow a client connection backhaul for small numbers of clients on one AP? Looking at less than 20 very limited-bandwidth clients on one Star-OS AP, and use one client link to back haul it to the bandwidth LAN.

Let me know if I did not explain myself very well!

Thanks.

[lonnie]

StarOS does not overcome the problem entirely. By limiting user bandwidth you avoid most of the problems.

When you add in the use of RTS, set low at about 300, you will avoid even more of the issue. RTS is a reservation system of controlled access. It is not quite as efficient as true polling, but it is very effective and free.

Our own backhaul to repeaters at 52 miles, 32 miles, 18 miles, and a customer unit at 8 miles shows full throughut when we enable RTS. It varies all over the place with it is disabled. These units obviously cannot hear each other, but they all hear the AP.

[accessonline]

Your backhauls are connected to the AP as a client station?

Thats the ultimate goal here, is to install just one AP at a site and no other equipment, the client stations connect to it like normal and one of them IS the backhaul... is that the same as your setup you commented about above?

In other words, will this work for a small POP with RTS and some bandwidth limitation turned on?

[lonnie]

Yes it works great. There is nothing special about a repeater site. The radio on the backhaul is merely a client and uses the AP to access the Internet.

[accessonline]

Awesome. Thats exactly what we wanted to do. Thanks!

[bairdc]

Your backhauls are connected to the AP as a client station?

Thats the ultimate goal here, is to install just one AP at a site and no other equipment, the client stations connect to it like normal and one of them IS the backhaul... is that the same as your setup you commented about above?

Wait Wait Wait!!!!

Lonnie, I think you may have misunderstood what he is trying to do (or maybe I did). Here's what I'm getting from this:

He wants to set up a StarOS box as an AP with only one radio. He then wants to connect clients to that radio, and one of those clients connected to that same radio will be the backhaul link.

If this is what you're wanting to do, this is a bad idea. What you need to do is put two radio cards into the StarOS box. You put them on different channels and use two separate antennas (sector or omni for the clients and directional for the backhaul). You set up the radio that will service clients as an AP (obviously), and you set up the backhaul radio as a client. Then the StarOS box on the other side of the backhaul link is set as an AP.

Anyway, maybe this isn't what was meant in the post, but it sort of sounded like it, so I thought I should jump in and clarify a bit.

Craig

[accessonline]

Yes, that is exactly right. One radio with clients and one of the clients is also the backhaul.

Lonnie is that the way you took it?

The whole point being limited cost for a very small POP, only need one radio and one antenna.

[accessonline]

Lonnie, is my thinking right on this, or am I all wrong?

Let me know if I havent explained myself well...

:~)

[dkii]

I think it's a bad idea, just for the fact that you will spend twice as much time on-air, effectively cutting your available bandwidth in half. Your backhaul will need air access to send and recieve a packet, and each client will need air access to send and recieve a packet. That would compound the hidden node problem as a collision will be more likely to occur when the backhaul has the air, since it will occupy most of the AP's time. With only 20 clients, it may not be much of a problem though, depending on what kind of throughput you are wanting. I would spend the extra cash now and use a second radio, antenna, and channel for the backhaul. It will be worth it later. On the flip side of it, if you get a box capable of accepting a second radio later, it would not be much trouble to add it later if you begin experiencing trouble, assuming your antennas are fairly accessible.

[lonnie]

I did misunderstand. That sort of use can be done but it is a real bad thing to do. If you have just a few users (less than 5) with small bandwidth needs it will be OK. Rarely will it work as hoped for and you will spend so much time trying to tweak things to make it work.

It does use twice as much air time and it means that the backhaul link is only given the status of an ordinary user.

I did say the radio on the backhaul is merely a client, but it still talks to another remote AP, and it feeds its data to an AP on site to rebroadcast.

My simple view would be to have an AP feeding clients. Any one of those clients can be a card that feeds another AP to extend the reach.

The AP is at an end but not the middle like you are hoping for. I guess I better read more carefully. Sorry for the confusion.

[dkii]

hmm... real bad huh? is it worse than bridging instead of routing?? :twisted:

[lonnie]

:D You went right to the perfect analogy. :D I would design with everything bridged before I would use repeating. Perfect, thanks.

[bairdc]

The whole point being limited cost for a very small POP, only need one radio and one antenna.

For around $150 you can have a 24dB grid and another card in the StarOS box. A small price to pay to do it right.

Craig

[redfeaag]

Being in the UK adds 50% to the price of everything, that is before the import duty. :(

My idea on this subject is to use a soekris unit with two orinoco cards and staros router. we have got these running in project cases with POE and a variety of antennas. A neat (ie. cheap) solution seems to be a couple of 15db planar's or one planar and an omni.

The 'cheap' bit is as follow: We intend to use the single soekris radio with a small 8db as the CPE. Where we need to relay just that little bit extra we will swap the CPE unit for the dual card unit. ie. The customer is paying for the CPE anyway so our net cost is another $60 for the card plus the cost of the antenna. We can extend wherever we like and the customer effectively pays for it.

The set up is an extended star network. The great benefit that I see is that the radio bandwidth is used far more effectively and we can make a fair sized IP network. We have a single backhaul on 11mps to the ISP but by keeping this on a seperate radio we are able to grow.

Consider this: dedicated radio = dedicated 11 meg backhaul. For ease of use, call it 10 meg. This means I can run from my distribution AP at the end remote to the ISP to another 5 AP's running at 2meg AP to AP. I have seen AP's with 100+ users on a T1 with no issues. The backhaul can handle this and I can get 500 paying customers on my network with no significant performance issues.

My advice: buy the extra card and antenna. The first extra customer you sign will have paid for it.