Hi all,
I was wondering if anyone could help me out with a deployment situation? I am looking to use 450m for distribution in a couple small towns that only have DSL copper and 10-15mbps speeds, on a rare day one would maybe get 8mbps.
So I have never deployed in a town situation and was wondering if centralizing a tower right in town with 360 coverage is more ideal than setting up tower on one end of town and covering it with 120 coverage? If right in town then will houses closer to the tower have issues connecting due to angle from AP? Should one have APs well above tree line and then tilt for appropriate coverage?
Again, my 3 current tower deployments are in rural pasture/farmland with closest SM at half a mile away so I am green with this type deployment.
Is this for 5GHz or 3GHz? Are these clients LOS of nNLOS?
LinkPlanner is excellent for modeling situations where you’re trying to find out if a spread of clients in one direction or another will result in optimal MU-MIMO groupings.
depending on town size, foilage density and what you are expecting to offer for speeds.
IF there is a structure tall enough to act as a good tower site, the owners are amenable and you can convince town council to approve your use and setup. Then go for it. You may wan to look at a 3Ghz 450m and use connectorized APs ( think dual frequency sectors, yes more money but also gives you options). Having both 3 and 5Ghz options will mitigate most issues you would come across.
If you have large structures on the outside of town, they can also be used in both single and multiple tower setups. You would have to model this in Linkplaner to know what your facing.
Spend some time with linkplaner and google earth. Add your sectors and at least 30 SM locations per sector, the more you add the better picture you will get. This will give you a good idea of the local feasibility. Then upload to cnHeat to see what the line of sight issues would be. Depending on your location cnHeat has some good LIDAR maps of tree and building heights.
Your concern for close to tower SMs is not really a big issue. Just because you set the max range to a large number (this is used for colocation timing) doesnt mean the down tilt of the antenna is suitable for that range. Every antenna has both a physical and electrical down tilt. Linkplaner can help you set this if it knows about the antenna pattern. This allows you to keep timing uniform and shrink a service zone to only cover a wanted area. This is a very valuable but overlooked tool that I wish was better understood and taught, especially in the introductory courses.
Appreciate the reply! I will dive into link planner and see what it looks like. Just out of curiosity, what issues is one mitigating using the connectorized dual frequency sectors?
Not all frequency bands act the same. Having 3ghz is nice but it has its limits too. You mitigate RF issues by having a second band and fewer antennas. If you have a client that you can not get with 3ghz, you can always try a 5ghz solution (epmp is a good companion for this).
You dont have to do this, but always planning ahead will save you $$$ in the long run. The price difference is actually small in comparison to adding a second antenna later. By that is a business decision.
covering a town from the sides with good line of sight is usually a good option to optimize coverage with fewer APs (Two to 3 APs). Note that the PMP 450m AP has 90 degree beamwidth instead of 120 degrees.
If you select the down town location, usually 4 APs are required to have an optimized coverage. This increase throughput as links are short and also allows you a better frequency reuse if needed. And make sure you selected tower has good line of sight to every corner of town.
You know your place, it is up to you to choose the rigt topology.
Thank you so much for your reply! I really appreciate your time and insight! If I have an average tree height in town of 40-50ft, how much higher should the AP be?
This is a hard one as there are factors to consider such as how far from the tower are you considering. The amount of down tilt you can achieve. cnHeat is a good tool for this.
We use a rule of three times the average foilage height to start, but also considering the terrain and structures available you may need to go higher. If you go too high then your blind zone beneath the tower increases. If you go too high you will need to determine your points of compromise, higher is good for distance until you down tilt the antenna to minimize the blind zone. Linkplanner with lots of SMs will give you a good idea. Push that to cnHeat to get a very detailed RF map.
Thank you for your reply, we were going to do 100ft AP height. I will load up the AP on link planner with different SM distances and see what I see. We are talking a .5-.8km distance around the tower for SM distance… would 3GHz push through trees fine at that distance? This isnt a deciduous forest or dense trees situation… funny thing is in link planner it keeps plotting and using deciduous forest for the trees in town… definitely not lol
Link planner uses the worst type of tree to shoot through.
If your only concerned about the town itself and not for any of the rural space then 100ft may be too low, but model it in linkplaner.
An average house is 35ft tall, 50ft trees means your height above average install is only 65ft. This would mean that you would need to add some height to the houses farther out to minimize the effects of the trees. Some simple math will give you a downtilt (and uptilt) angle for the required distance. Your main issue is the look angle from the farthest clients, 100ft (30m) is probably too low, it would work with some annoyances. If you can get another 50ft (15m) you will change the scenario quite a bit and improve your serviceability. If you cant or its not feasible then work with what you have.
3ghz does polk through light trees but its really the worst of 2.4ghz and 5ghz issues. It has a high absorbtion in water rate which means even pine needles are more sponges than mirrors.
Once you have it modeled in Linkplaner, use cnheat to give you everything you need to know.
The default heights for trees may not be appropriate for region, so you should modify them as required. The default clutter types for a region can also cause problems, although this is more of an issue in other parts of the world where the clutter resolution is only 1 pixel every 300 m.
You may want to edit the individual profiles if you know that they don’t reflect the terrain/clutter in that area.
cnHeat uses data that is higher resolution and also captured more recently, so it eliminates some of these issues.
Thank you for your reply and your info/advice, it is greatly appreciated! Unfortunately for me there is no LiDAR data available for my sites in my region so I cannot use cnHeat, but I was really looking forward in using it!
If you have height for your towers (mountain located), I would recommend choosing alternative sides of town over centrally located. Even a 300’ tower can be pushing through a mile of trees once you get 3-5 miles away from it, so centrally located can leave the majority of people unserviceable in my experience. Mountain top towers on the sides of town leave a lot more options for LOS and for breaking through tree tops to get signal. But if they are all within a short distance (<2 miles), then centrally located would be best for budget reasons and the fact that you can likely push through trees on 3ghz at those distances.
On another note, if you go for 360-degree coverage with a 450m on 3ghz, I recommend no more than 3 AP’s. Consider each 120 degrees each rather than 90 degrees, because I’ve had a lot of backsplash noise on the 3ghz 450m when using 3-4 units, where I simply don’t have enough spectrum to separate them out. Having back-to-back units (with GPS sync enabled) dropped my modulation rates from 8 to 4x on my 7-10 mile links, which was rather disappointing.
Appreciate your info/advice, greatly appreciated. My centrally located spot would only be servicing clients in a 1 mile radius, 1 mile being the furthest clients. No mountains where I am from lol!