 reply to Jafster
Re: How can i use single Freq. in 4 Canopy AP's in one tower? Its hard to remember who understands canopy and not with the flood of the UBNT noobs.
That being said, I stand behind your diagram being incorrect for the application. 

lutful... of ideasPremium join:20050616 Ottawa, ON kudos:1  said by wirelessdog:I stand behind your diagram being incorrect for the application. You could draw a correct diagram for this application? If it uses same frequency in same direction, you will have to consider the scenario shown above. said by wirelessdog:Its hard to remember who understands canopy and not with the flood of the UBNT noobs. Some Canopy fans are worse than Ubiquity fans because of their "blind faith" in GPS synced TDMA. P.S. If you search my old posts for TDMA and FPGA, you will see references to a radio platform (my company) designed in 2004 before Canopy added FPGA and a Canopy clone with better spectrum sharing features in 2006. I disclosed recently that (my new company) has developed a TDMA system designed from scratch for HD IPTV delivery. 

LLigetfa join:20060515 Fort Frances, ON kudos:1  That diagram does not describe what the OP said. For the OP the problem is one SM sitting out on the edge between two APs on the same tower.
The multiple tower scenarios are all conjecture since the OP did not say where they are situated relative to each other.
I think the other SMs and other towers are not contributors to the problem. The SM sees two APs on the same tower, both with about the same signal strength, both on the same frequency and polarity.
Instead of trying to get four APs on a tower, all on the same frequency, he should try only using the same frequency on backtoback APs, so two frequencies per tower. Of course then the two other towers come into play so he needs to plan his frequency reuse between towers as well.  Strange as it seems, no amount of learning can cure stupidity, and formal education positively fortifies it.  Stephen Vizinczey 

 If you post a sketch of you towers locations we might find a good freq plan for all 3 towers using the 3 channels. also inlcude the 3 exact channels 

lutful... of ideasPremium join:20050616 Ottawa, ON kudos:1  reply to LLigetfa
said by LLigetfa:The multiple tower scenarios are all conjecture since the OP did not say where they are situated relative to each other. The exact distances between towers (AB/BC/CA) will not make much of a difference since the 3 towers are located 12km from each other. He really wants to run 4 sectors on each tower and he wants to use all 3 frequencies available to him. My suggestion on previous page is a good setup considering all known factors. If you disagree, post a sketch showing what sector/frequency allocation may work better. 

LLigetfa join:20060515 Fort Frances, ON kudos:1  said by lutful:He really wants to run 4 sectors on each tower and he wants to use all 3 frequencies available to him. Not quite. Yes, he wants to run four sectors but he wants to run all four sectors on the same frequency. He wants each tower to have its own frequency. As for the distances between the towers, they are not a factor under his current config since each tower has a unique frequency. It only becomes relevant if he decides to use the same frequency on more than one tower. Then the placement must take into consideration all factors. There are so many permutations possible that it is senseless for me to post sketches based on conjecture. Maybe the towers are all on the periphery and no SMs would see two or more towers? J/K  Strange as it seems, no amount of learning can cure stupidity, and formal education positively fortifies it.  Stephen Vizinczey 

lutful... of ideasPremium join:20050616 Ottawa, ON kudos:1  said by LLigetfa:he wants to run four sectors but he wants to run all four sectors on the same frequency. Yes, he wanted to do that but obviously that won't work very well even with GPS sync and excellent fronttoback ratio sector antennas. There would be interference contribution from 3 SMs (belonging to the other 3 APs) in every time slot. When some or all of those SMs are located at shorter distance from the tower than the target SM, noise may rise above expected RSSI. People already suggested using a single omni antenna or 2x 180 degree sectors or a 1:4 splitter at each tower to meet his original desire to run one frequency per tower. Using all three available frequencies at each tower to maximize his total wireless network capacity is just another option. 

LLigetfa join:20060515 Fort Frances, ON kudos:1  said by lutful:Using all three available frequencies at each tower to maximize his total wireless network capacity is just another option. Yes but using only two frequencies per tower might also be an option and may in fact make channel reuse easier. Until such time that the OP gives us more details, it is mostly conjecture.  Strange as it seems, no amount of learning can cure stupidity, and formal education positively fortifies it.  Stephen Vizinczey 
