Advice needed concerning choice of radio module

Wireless & IoT
1

hi my name is mile,

i’m doing a research for my masters and seeing i have no experience with radios, i need an advice on what kind of radio modules to use for my project.

NOTE:

-i didn’t just opened this thread blindly, as first I took a look around the web manufacturers web site, the forum and plenty other sites as well. however when a know little about a certain topic, i always ask help from people who are more competent than me and whose knowledge in this ‘unknown area’ is greater than mine.

GOAL:

-to find a wireless radio with 400m range for the sensor nodes that i’m going to use for the fire detection system.

USE CASE:

-the sensor nodes will be placed inside the forest and they will have smoke sensors attached to them in order to detect potential fire.

-once smoke is detected, the sensor node will generate a warning and he will pass it to his neighbor, who will pass it on to the next sensor node, and it will go all the way to the base station. the signal from the base station will go throgh wireless backhaul, but that’s another topic that currently doesn’t need to be discussed

REQUIREMENTS:

-the maximum distance between two sensor nodes will be 400m at most

-the sensor nodes will be put in a pinetree forest where the trees grow upto 40m

-the sensor nodes should be able to communicate with all of their neighbor-sensor nodes that are within the 400m radio range

-the sensor node is actually a microcontroler development board with ARM7 LPC2368 processor and the radio should be able to communicate with it. here’s the board’s specifications >> http://www.micro4you.com/files/lpc2368/ARM7_LPC2368.pdf

SOLUTION:

-tell me i’m doing overkill with the 400m reqirement. can i use certain antenna to get to the 400m mark? what if there’s a sensor node that will be even further away, let’s say 1.5km

-i’m inclining towards this choice, but i have no idea how will the forest trees affect the radio transmission >> http://www.digi.com/products/wireless-w … -900#specs

FINAL NOTE:

if you have better ideas please share.

if you know other place where i can ask for help, let me know in your replies

if you have other more appropriate manufactures in mind, please share. what are some other companies that are xbee’s competitors on the market (i’m not sure if i’m allowed to ask this, but i hope it won’t get someone mad)

P.S. i do most of my shopping on ebay, but i think other specialized web sites would have better prices than ebay in this case. Please recommend me some websites that sell radio equipment and have low prices as well.

thanks. mile

2

Full disclaimer: I work for Digi so I am inclined to recommend our radio modules. The module you identified, the XBee DigiMesh 900MHz DishMesh radio, is the perfect choice according to your specs as long as you are in a country where you can use the 900MHz band legally. You should be able to easily reach 400m with these modules using even the wire antenna, even in a forest.

I don’t believe that SparkFun carries the modules. You can contact us if you want a full list of the people who stock the part.

Where will you be deploying your project?

3

I have a few of clarifying questions:

Do you know the deployment environment from the standpoint of height of all nodes, tree density, tree species, density and composition of understory (if within the line of sight of nodes) and maximum topography changes within any 400m? Heavy foliage, earthen features and high density of trees will impair your line of sight from node to node. If the node cannot see the other node, it cannot communication with it. In urban environments, everything is a reflector and line of sight is less critical. However, in non-urban environments, there are few natural reflectors and line of sight becomes critical. Also, remember the environment changes. This is Spring and understory and canopy grow more dense throughout the season. What works today may not work in August.

What is the minimum number of nodes any node will need to communicate with? This will effect antenna deployment which will depend on the question above. If you only need to connect each node to 2 other nodes(upstream and downstream) then each gets a yagi antenna aligned with each node and 400m is not a problem even with a low power transmitter. Yagi’s are easy to make with various materials. Waveguide antennas (think cantenna) are also a good option for point to point and the signal gains are unbelievable. However, antenna alignment is critical. If each node communicates with 3 or more, the number of yagis/cans grows unmanageable very quickly. Finding a spot where an omni antenna will have line of sight with all other nodes will be difficult or impossible with even modest tree density.

At this point in your project, I would be more concerned about the physical propagation of the signal (line of sight from node to node) and the minimum number of nodes any node needs to communicate with than selecting your transmitter.

4

WethaGuy:
I have a few of clarifying questions:

Do you know the deployment environment from the standpoint of height of all nodes, tree density, tree species, density and composition of understory (if within the line of sight of nodes) and maximum topography changes within any 400m? Heavy foliage, earthen features and high density of trees will impair your line of sight from node to node. If the node cannot see the other node, it cannot communication with it. In urban environments, everything is a reflector and line of sight is less critical. However, in non-urban environments, there are few natural reflectors and line of sight becomes critical. Also, remember the environment changes. This is Spring and understory and canopy grow more dense throughout the season. What works today may not work in August.

the nodes will be in a housing, that will be either put on a pole with legs (like tripod) or attached to a tree. but i guess i’ll go with the tripod to get as much as elevation as i can, and try to put them in open places whenever possible.

it will be pine forest with trees that grow 35-40m, (http://www.nppelister.org.mk/DesktopDef … 4&tabid=24) hey, message to all when i’ll have some question i’ll number it, so someone wants to five me answer answer he can refer to the number when he’s giving me an answer

i guess what the real question is how much the radio range will be decreased…

  1. lets say that i’m using the http://www.digi.com/products/wireless-w … -900#specs radio as i think this one is the one that has the strongest Tx range.

  2. do you think you can give me an approximate evaluation, what kind of range should expect if i use High-Gain Antenna (http://tinyurl.com/cehrgzz) with this radio?

  3. asgeneral rule of thumb can i think for the radios transmission as if the radio decreases its frequency, it will increase its range but lower its bandwidth? am i getting this right?

What is the minimum number of nodes any node will need to communicate with? This will effect antenna deployment which will depend on the question above. If you only need to connect each node to 2 other nodes(upstream and downstream) then each gets a yagi antenna aligned with each node and 400m is not a problem even with a low power transmitter. Yagi’s are easy to make with various materials. Waveguide antennas (think cantenna) are also a good option for point to point and the signal gains are unbelievable. However, antenna alignment is critical. If each node communicates with 3 or more, the number of yagis/cans grows unmanageable very quickly. Finding a spot where an omni antenna will have line of sight with all other nodes will be difficult or impossible with even modest tree density.

for now because it is a pilot project there will be only 5 nodes, and they will have to be deployed around the base station within at least 400m. ideally i would like to have range as much as possible, but without having to complicate things , like adding other components besides the antenna, such as amplifiers etc. i am looking for a straightforward solution from just a radio + antenna.

if the pilot goes through good, and some one likes to invest in the whole system for the whole forest, the number of the nodes will be greater but they will have to communicate in a mesh topology. (http://tinyurl.com/c5l2obf) but i don’t know what the distance between them will have to be. for this i have to consult experienced firefighter so i can find out what kind of resolution HE would like to have. since firefighters will be using this system

At this point in your project, I would be more concerned about the physical propagation of the signal (line of sight from node to node) and the minimum number of nodes any node needs to communicate with than selecting your transmitter.

for now i think i will make the system work just with the 5 nodes ignoring terrain and topology, and once i have the pilot system up and running i will then went on to designing efficient topology, making a balanced workload on the nodes, antennas, protocols etc.

thanks for the help. let me know if you think i should do something different based on what i just wrote.

5

midzata:
it will be pine forest with trees that grow 35-40m, (http://www.nppelister.org.mk/DesktopDef … 4&tabid=24) hey, message to all when i’ll have some question i’ll number it, so someone wants to five me answer answer he can refer to the number when he’s giving me an answer

That is a dense forest :o . Getting 400m range through that will be very difficult or impossible as I see large rocks and steep elevation changes. You will probably need to get all antennas up to 2/3 or more the height of the trees to get any kind of range. Tree diameter decreases with height and there will be less trees blocking your antenna’s “view” at greater heights. In that dense forest environment, everything will be line of sight limited. If you are standing at one node and can’t see the antenna of the other node with your eyes, there will be no communication with that node unless you are really close.

midzata:
2. do you think you can give me an approximate evaluation, what kind of range should expect if i use High-Gain Antenna (http://tinyurl.com/cehrgzz) with this radio?

I would SWAG the range of an omni antenna (like that ducky in your link) in that environment to be less than 30m on average. “Range” varies tremendously. You might get that transmitter and antenna to communicate reliably at 400m from the nearest node. Then, you move the transmitter 2 feet to the left and get nothing. Line of sight distance is your effective range at that low of transmitting power.

To estimate your range, tie some bright surveyor’s tape (ribbon) around a tree trunk about the same height as your node antenna will be. Then, walk out away from the tree until you can’t see it anymore. Move left/right until you can see it, back up, repeat. When you get to where you can’t see the marker no matter how much you move left/right, that is a good estimate for your maximum range. You will be underwhelmed by how far you can transmit. Line of sight is everything.

For testing, take a look at the [RF12 and [RF22 radio modules at Sparkfun. They are cheap ($7-13 for bare transmitters) but require some soldering and hardware skills. The RF22 has a [breakout board version too if you are a little lacking in soldering skills for $23. You can use a non-impedence-matched, bare wire, 1/4 wavelength antenna without that being the limiting factor in transmission range. If you want plug-and-play and network protocol already implemented for you, go for the xbee. But, you could use the jeelabs library for communication and deploy 20 RF12 modules for the cost of the 4 xbees in that dev kit.](SparkFun RF Transceiver Breakout - RFM22B-S2 (434 MHz) - WRL-10154 - SparkFun Electronics)](RFM22B-S2 SMD Wireless Transceiver - 434MHz - WRL-10153 - SparkFun Electronics)](http://www.sparkfun.com/products/9582)

6

WethaGuy:

midzata:
it will be pine forest with trees that grow 35-40m, (http://www.nppelister.org.mk/DesktopDef … 4&tabid=24) hey, message to all when i’ll have some question i’ll number it, so someone wants to five me answer answer he can refer to the number when he’s giving me an answer

That is a dense forest :o . Getting 400m range through that will be very difficult or impossible as I see large rocks and steep elevation changes. You will probably need to get all antennas up to 2/3 or more the height of the trees to get any kind of range. Tree diameter decreases with height and there will be less trees blocking your antenna’s “view” at greater heights. In that dense forest environment, everything will be line of sight limited. If you are standing at one node and can’t see the antenna of the other node with your eyes, there will be no communication with that node unless you are really close.

midzata:
2. do you think you can give me an approximate evaluation, what kind of range should expect if i use High-Gain Antenna (http://tinyurl.com/cehrgzz) with this radio?

I would SWAG the range of an omni antenna (like that ducky in your link) in that environment to be less than 30m on average. “Range” varies tremendously. You might get that transmitter and antenna to communicate reliably at 400m from the nearest node. Then, you move the transmitter 2 feet to the left and get nothing. Line of sight distance is your effective range at that low of transmitting power.

To estimate your range, tie some bright surveyor’s tape (ribbon) around a tree trunk about the same height as your node antenna will be. Then, walk out away from the tree until you can’t see it anymore. Move left/right until you can see it, back up, repeat. When you get to where you can’t see the marker no matter how much you move left/right, that is a good estimate for your maximum range. You will be underwhelmed by how far you can transmit. Line of sight is everything.

For testing, take a look at the [RF12 and [RF22 radio modules at Sparkfun. They are cheap ($7-13 for bare transmitters) but require some soldering and hardware skills. The RF22 has a [breakout board version too if you are a little lacking in soldering skills for $23. You can use a non-impedence-matched, bare wire, 1/4 wavelength antenna without that being the limiting factor in transmission range. If you want plug-and-play and network protocol already implemented for you, go for the xbee. But, you could use the jeelabs library for communication and deploy 20 RF12 modules for the cost of the 4 xbees in that dev kit.[/quote]
thanks for the tips for the range estimation. i think i’m going to go with the xbee since it seems as it is more user friendly and i am pretty new to this stuff. however there’s been a change in planes, the 900mhz area is reserved for telecommunication in macedonia, so i’ll go with 2.4Ghz

i am planing to use these radios now >> http://www.digi.com/products/wireless-w … -2-4#specs

XBee-PRO® DigiMesh® 2.4

after i have the system up and running in a lab environment i will start thinking about antennas and range. i will come back here and ask for advice when i need some help, if that is ok with you. than you very much for your time and interest. best, mile](SparkFun RF Transceiver Breakout - RFM22B-S2 (434 MHz) - WRL-10154 - SparkFun Electronics)](RFM22B-S2 SMD Wireless Transceiver - 434MHz - WRL-10153 - SparkFun Electronics)](http://www.sparkfun.com/products/9582)

7

Please do keep us posted. I’m very curious to know what your results are!

8

JordanHusney:
Please do keep us posted. I’m very curious to know what your results are!

my mentor is reviewing the paper that i submitted. he said that it is interesting and we should talk soon, you never know however. i'll remember to post when there will be something new with the project
9

Can you update us on your project? There were lots of good questions and answers and others would benefit from seeing the final results :slight_smile:

10

my proposal was accepted, however before i start working on the project i have to finish the two more exams that i have left.

afterwards i will be able to continue along and i’ve kept all threads i’ve opened around the forums and i will update my progress. thanks for the help i will return it back. mile

11

Hi Mile,

Now a days I am seeing [WhizNets posted on some forums. You can check with them as well.](http://www.whiznets.com/wifi-modules.html)

12

thanks. i’m currently working on other exams but i’ll check this later once i get back to work on my project. thanks again