Radiating cables - are they any good?
Last Post: August 15, 2006:
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Exactly. While a data client can be functional with as many as 20 retries, a phone will have serious problems after 3. Plus, if you have a data client running along with a phone, it's possible that the AP will "fixate" on retrying the data packets to the detriment of the delay-sensitive voice packets. Or for that matter even fixating on one phone which will kill every other phone in the giant cell that you've created.
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I have found leaky coax to be useful in very specific situations, but in the majority of cases, regular omni and directional antennas are preferable. As others have pointed out, one problem with leaky coax is hidden node problems. If the cable runs around a corner or corners, as is probably the case if you're considering leaky coax, you can get a situation where clients in one part of the coverage area can't hear clients in another part of the coverage area. Now, of course, this can also happen with omni antennas, and 802.11 has built-in mechanisms to compensate for it, but it seems much more likely with leaky coax.
Line loss on leaky coax can be another factor, but in my opinion, the places where you're using leaky coax typically have two characteristics that make this not as much of a factor. First, you're more concerned about getting coverage around obstacles, corners, or into a specific area than you are about absolute range. Second, the clients will be located relatively close to the cable. An example of this would be a long, twisty hallway or tunnel. To cover it with regular antennas might require one antenna per straight length of tunnel, which would be a lot of antennas and APs. So maybe you run leaky coax. Yeah, the attenuation of the cable means that range of a single AP is less than it would be with unobstructed free space, but you don't have unobstructed free space in the hallway anyway, so what are you going to do? Yeah, the signal strength coming out of the cable is pitiful, but since the clients are never more than three feet from the antenna, it doesn't matter.
That being said, I have almost never come across a situation where I felt that leaky coax was the best solution for the job. When I first heard about it, I thought that it must be the most awesome thing since sliced bread, but further examination (and explanation from more experienced engineers) showed me its faults. -
What about implementing the leaky coax at home? Runing it into every room of the house...
Cheaper to use the Wireless AP versus this idea?
Thoughts...thanks! -
What about implementing the leaky coax at home? Runing it into every room of the house...
Cheaper to use the Wireless AP versus this idea?
Thoughts...thanks!
I think that it's highly unlikely that leaky coax would be a cheaper option than just using omni antennas in this case. -
Leaky coax...I think... fits the bill here....
D.C. Transit Police Carry Two Radios for Safety
By Glenn Fleishman
The transit police can?¡é?€??t ditch their old system because new $60m network doesn?¡é?€??t work reliably in tunnels: The Washington Post reports that the Metro Transit Police force cannot rely on the new radio system underground, despite the Motorola system being required to cover 95 percent of the area with 95 percent reliability of voices being understand. The old system has a single channel shared across the network; the new one has 255 channels. Officers must carry two radios for safety.
The Post quotes Motorola as stating they don?¡é?€??t have an ETA for the six-year-old system achieving the required level of availability. The current Metro chief sounds aggravated. It?¡é?€??s only part of the subway network that?¡é?€??s a real problem: four tunnel segments and seven underground stations. An officer was attacked in March and had just a radio from the new system. She was forced to track and arrest the attacker while trying futilely to get a signal?¡é?€?¡±she eventually got one word to pass through the network, enough to get her location.
Radios have been installed 1,500 buses and 55 police cruisers where they apparently work just fine, as well as working as expected for two aboveground transit police units.
Motorola is testing a cable replacement which, if successful, might lead to them replacing 100 miles of antenna cable. Metro and Motorola haven?¡é?€??t agreed on which party would pay for any of this.
Go figure? -
If you can run leaky coax around your house, why don't you just run CAT-5?
In my opinion, the number 1 reason for a home wireless network is that you don't have to run wires anywhere. Wait... that's the only reason. :)