This blog post is two days late because things like shopping and catching up on sleep take a stupidly long time. (As you can see, I gave up on one of these tonight.)
The last long-range tests went well.
The Tang, where resides the amazingly wonderful Tetazoan cruft Chris Calabrese who let us use his apartment many times when it wasn't actually convenient for him, is just under 1.5 kilometers away from the New Media Lab. Cbreezy's 12th floor apartment is actually just a bit below the treeline in front of the E15 roof deck where we had our receiving antenna set up; we didn't quite have line of sight there. But the signal strength was -76 dBm (to out of four power bars- not bad). The Internet speed test on the receiving end didn't work because it was too slow, but google search was decently fast and the HTML version of gmail loaded fine. At the Tang, the speed was around 7-8 Mbps. I think at this point that one of the toughest things about implementing in Tanzania will be that the Internet speed at the source will already be quite slow- less than 4 Mbps for sure. Not sure whether we'll be able to do anything about that.
The second test was almost as long a distance: 1.12 km from the 14th floor of MacGregor to the Media Lab roof deck. This time, we had perfectly clear line of sight, and a high elevation off the ground. The signal strength was -47 dBm (without the 100 ft Ethernet cable in the system), and the speed on the Media Lab end was around 8-10 Mbps (the wireless speed in the same room as the Netgear router). The speed at MacGregor was around 60 Mbps, so there was a loss of about a factor of six. Assuming the loss in speed is directly proportional to the loss in received power (which might not be true), I think that's about 8 dB of loss (10*log(6)). Dunno what that tells me, though.
In the second test, we used our 100 ft Ethernet cable and discovered that the the signal strength seemed to fluctuate between -47 and -61 dBm; we aren't sure why that would be happening, but the speed test didn't reveal any speed difference with the cable so it did not seem to matter.
J (at the receiving end) also moved the computer around to different places to test the range of the Netgear router. There was no difference in speed 25 feet away from the router with only space or a glass wall in between. With a wall between, there was almost a tenfold decrease in speed.
One really troubling/puzzling thing happened: even with the Bullets configured correctly using static IP addresses, when J plugged the Bullet directly into her computer, there was a DNS lookup error. I'm not sure why that would happen, especially because it never happened before when we were testing the same setup at a shorter distance (across East Campus courtyard). This is another question for Ubiquiti tech support.
The promised update having to do with the GPS coordinates of the staff houses and school:
We got them. And then we used Google Earth's Path tool to find the elevation profile along the line of sight paths between the school and the various staff houses and offices that could be our Internet source. The results were amazing.
Kudos again to Google Earth, and satellite imaging.
We are hoping that the little hill on the Orkeeswa side of the path (on the right side of the elevation profile, since the path started in Monduli) is right underneath the school rather than behind it. Apparently this isn't just wishful thinking; the coordinates we were given for the staff house was exact, but the coordinates given for the school were actually the coordinates of a girls' school close to Orkeeswa, a little bit further from Monduli. Our IEFT contact tells us that Orkeeswa is likely on that little hill, which would be really awesome, to say the least.
The profiles between the other possible Internet sources and the school were also decent, but not as good.
The last thing left to test is whether or not the relay connection will work. The two Bullets at the midpoint (if we use one, which may happily not be the case) are connected via an Ethernet cable between the two LAN ports in both of their POE injectors. We'll do a short-range test on Monday.
I promised the schematic sketches I did. Here is a very drafty and messy second draft that should really be copied over at least once more:
Miscellany:
Things bought/obtained yesterday:
3 pairs of thin long pants
1 floppy-brimmed hat
1 mosquito net for sleeping in
1 huge, garishly pink hard suitcase
Things to buy today:
Lots of bug spray
Granola bars
Travel-size stove/water boiler?
Reading Flashlight (because I dumbly sent all of mine over already)
Blooming teas (gift for host family)
Things to buy at MIT:
Another MIT t-shirt (lost mine)
Screw-cap water bottle
Things to do today:
Go to Apple store, get computer fixed(?)
Email Ubiquiti
Things to do in the future:
Send a postcard to Bello Opticians (348 Shrewsbury Street, Worcester, MA 01604)
Email that random research scientist who asked us about our project in the elevator
Write a post about science lab testing at Hunter
The last long-range tests went well.
The Tang, where resides the amazingly wonderful Tetazoan cruft Chris Calabrese who let us use his apartment many times when it wasn't actually convenient for him, is just under 1.5 kilometers away from the New Media Lab. Cbreezy's 12th floor apartment is actually just a bit below the treeline in front of the E15 roof deck where we had our receiving antenna set up; we didn't quite have line of sight there. But the signal strength was -76 dBm (to out of four power bars- not bad). The Internet speed test on the receiving end didn't work because it was too slow, but google search was decently fast and the HTML version of gmail loaded fine. At the Tang, the speed was around 7-8 Mbps. I think at this point that one of the toughest things about implementing in Tanzania will be that the Internet speed at the source will already be quite slow- less than 4 Mbps for sure. Not sure whether we'll be able to do anything about that.
The second test was almost as long a distance: 1.12 km from the 14th floor of MacGregor to the Media Lab roof deck. This time, we had perfectly clear line of sight, and a high elevation off the ground. The signal strength was -47 dBm (without the 100 ft Ethernet cable in the system), and the speed on the Media Lab end was around 8-10 Mbps (the wireless speed in the same room as the Netgear router). The speed at MacGregor was around 60 Mbps, so there was a loss of about a factor of six. Assuming the loss in speed is directly proportional to the loss in received power (which might not be true), I think that's about 8 dB of loss (10*log(6)). Dunno what that tells me, though.
In the second test, we used our 100 ft Ethernet cable and discovered that the the signal strength seemed to fluctuate between -47 and -61 dBm; we aren't sure why that would be happening, but the speed test didn't reveal any speed difference with the cable so it did not seem to matter.
J (at the receiving end) also moved the computer around to different places to test the range of the Netgear router. There was no difference in speed 25 feet away from the router with only space or a glass wall in between. With a wall between, there was almost a tenfold decrease in speed.
One really troubling/puzzling thing happened: even with the Bullets configured correctly using static IP addresses, when J plugged the Bullet directly into her computer, there was a DNS lookup error. I'm not sure why that would happen, especially because it never happened before when we were testing the same setup at a shorter distance (across East Campus courtyard). This is another question for Ubiquiti tech support.
The promised update having to do with the GPS coordinates of the staff houses and school:
We got them. And then we used Google Earth's Path tool to find the elevation profile along the line of sight paths between the school and the various staff houses and offices that could be our Internet source. The results were amazing.
 | |
| Elevation profile from Staff House 1 to Orkeeswa along the line of sight path- our best elevation profile |
We are hoping that the little hill on the Orkeeswa side of the path (on the right side of the elevation profile, since the path started in Monduli) is right underneath the school rather than behind it. Apparently this isn't just wishful thinking; the coordinates we were given for the staff house was exact, but the coordinates given for the school were actually the coordinates of a girls' school close to Orkeeswa, a little bit further from Monduli. Our IEFT contact tells us that Orkeeswa is likely on that little hill, which would be really awesome, to say the least.
The profiles between the other possible Internet sources and the school were also decent, but not as good.
 |
| Elevation profile between the Monduli office and Orkeeswa- not as good |
I promised the schematic sketches I did. Here is a very drafty and messy second draft that should really be copied over at least once more:
Miscellany:
Things bought/obtained yesterday:
3 pairs of thin long pants
1 floppy-brimmed hat
1 mosquito net for sleeping in
1 huge, garishly pink hard suitcase
Things to buy today:
Lots of bug spray
Granola bars
Travel-size stove/water boiler?
Reading Flashlight (because I dumbly sent all of mine over already)
Blooming teas (gift for host family)
Things to buy at MIT:
Another MIT t-shirt (lost mine)
Screw-cap water bottle
Things to do today:
Go to Apple store, get computer fixed(?)
Email Ubiquiti
Things to do in the future:
Send a postcard to Bello Opticians (348 Shrewsbury Street, Worcester, MA 01604)
Email that random research scientist who asked us about our project in the elevator
Write a post about science lab testing at Hunter
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