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H.323 video conf. on 350 repeaters

Here's the situation: My client has asked us to install a wireless network between a courthouse and the correction center to provide datacommunications and video conferencing capabilities. The Corrections facility and courthouse are 3 km apart however they do not have line of sight. We have installed the wireless network using a repeater at our local radio tower to relay between the two sites. We are configured to use 11Mbps.

This unfortunately enphasises the half duplex attributes of the network by requiring two wireless hops between locations.

The highest speed settings we can obtain using a pair of Polycom units is 256Kbps (peeking at about 400K) stably.

We are going to try installing a H.323 gateway at our repeater location to help buffer and perform call handling. Don't know how well this will work out.

Does any one have any suggestions or has anyone been able to get a reliable (highspeed) video link working using the 350's?

Our next step if the h.323 gateway doesn't improve performance is to install a second repeater at the relay site to segment the two links.?

3 REPLIES

Re: H.323 video conf. on 350 repeaters

Since there has been no response to your post, it appears to be either too complex or too rare an issue for other forum members to assist you, or there is no public information available at this time. If you don't get a suitable response to your post, you may wish to review our resources at the online http://www.cisco.com/go/solutions. You may also contact our product information line at 1-800-553-NETS or a Cisco Systems Engineer at your local Cisco office or reseller. To locate your local Cisco representative, visit http://www.cisco.com/warp/public/687/Directory.shtml

If anyone else in the forum has some advice, please reply to this thread.

Thank you for posting.

Cisco Employee

Re: H.323 video conf. on 350 repeaters

You can dramatically improve your throughput by using back-to-back bridges at the intermediate site instead of a single repeater.

With a repeater the bridge in the middle can only be receiving or transmitting at any one point in time; thus halving throughput. I will try to illustrate below (simple illustration - no acks shown);

Bridge1...............bridge2............Bridge3

..............----1----->

...........................................-----1--->

.............------2---->

...........................................------2---->

With two bridges back-to-back in the middle (on seperate non-overlapping 802.11 channels), on bridge can be receiving packets while the other bridge can be transmitting at the same time; thus throughput is no longer halved by the repeating function.

Bridge1..................Bridge2/3................Bridge4

..............------1----->

..............-------2----->...............------1----->

..............--------3----->..............-----2------>

Not sure if this will make the video application work acceptably, but it shouldhelp. be nice if you could bench-test it :)

New Member

Re: H.323 video conf. on 350 repeaters

Have you looked at how tall a mast you would have to put at each end to get line of sight?

Even if the expense of roof-top towers is higher than an additional bridge at the repeater point, you will get more long term. If the height requirements are too extreme, circular polarization may help you cheat a little with the Fresnel zone clearance.

BTW - if you are using APs instead of bridges to bounce through your repeater site, a second unit there won't help you. Bridges would be an improvement over an AP-Repeater-client link from day 1.

And if you are considering .11a with the new Aironet 1200 - forget it. You can't go far enough to get the job done because of the FCC power limit at 5.2GHz.

Matthew Wheeler

Blue Modal

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