|
I do love a good semantic argument. When you're talking about re-transmission sites there are a few different ways people tend to implement them; relay sites, repeater sites and point-multipoint hubs.
I'll go through the fundamentals of each type of implementation and the pros and the respective pros and cons.
Relay Site / Active Repeater Site
A relay site is usually used where you do not want to half your throughput and can afford to have two RF links instead of one.
Link 1: Central Node -> New Site
Link 2: New Site -> Storage Silo
At the relay site you would have two Cisco 340 or 350 series bridges (using the assumption that you're staying with Cisco) and a switch. This way you reduce the RF path loss by shortening each link and gain a much higher possibility of success.
The current dialup client could be patched into the switch that sat between the 2 Cisco Bridge Units and operate as part of the network.
However, as you're now managing two different links using different frequencies, you don't lose any throughput – however you may add about 2-4 ms worth of delay to your network link.
Passive Repeater Site
A passive repeater site is one where you place two directional antennae at the new site with a single cable between the two.
Central Site -> New Site Antennae A (cable) New Site Antennae B -> Silo
In this circumstance there is no Cisco units placed at the bottom of the new site and the dialup client would have to remain dialup. The advantage of this is the lack of hardware at the central site.
The beautiful thing about this solution is the simplicity of its design. Be aware that you loose about 3-6 dB using a passive repeater but you do not lose any throughput. You may also experience an additional delay of up to 2 ms on your network link but I really wouldn't imagine it to be that high.
This solution is usually used when you have excellent signal strength but no line of sight between the two end-points.
Point-Multipoint
A point to multipoint solution could be a possibility for this scenario however this is the case where you would reduce your throughput by (more than) 50% due to rebroadcasts.
A single Cisco bridge would be placed at the new site (to which the existing user could be attached via the Ethernet port) and an omni-directional antenna could be placed atop the new site.
The layout for this would look something like:
Central Site -> Omni Antenna -> Storage Silo
The advantage of this solution is that it allows you to use minimal hardware whilst breaking the long link into two shorter links. The shorter links will help to reduce your path loss but it would take a site survey and some calculations to determine whether the 10 db omni-directional antenna would be enough for a successful link.
Personally I think your best option would be an Active Repeater site if you have the budget but I also believe that a point-multipoint configuration with the Cisco Bridge Units would also work.
Unfortunately for you, whilst I have done some preliminary calculations using the information that you gave me, I'm not going to give you any hard numbers or a definite answer. This is primarily due to that fact that even if there was nothing between the two sites, I have no way of knowing what types of EMI and other RF Interference exist on each site, tree levels, etc etc etc.
However, feel free to tell your co-workers that you were right – as I believe you probably are – but without a proper site survey I can't give you a definite yes.
|
