Wireless extender vs. router

I am contemplating whether to use wifi range extender or router (many have extender function) to extend the range of my wifi coverage. My project involves logging data in the field and uploading them to a server. I would like to use one mobile hot spot to access the internet and extend its range to cover several loggers. Right now I am using Arduino with wifi shield but the shield has an antenna that is rather small. I want to extend the mobile hot spot with an extender so it may reach the loggers, around 1,000 ft or hundreds of meters.

So does anyone have some experience with a range extender and how does it compare with a router with extender function, in terms of extended range? Thank you!

Antenna, give me an antenna, I will give you the world.

Friis Transmission Equation for free space loss:

R is the range and ? is the wavelength.

modification of Friis Transmission Equation:

Frequency f
Tx power p_t
Tx antenna gain g_t
Rx antenna gain g_r
Rx sensitivity p_r

10^(6/20)=2

Every 6 dBi antenna gain will be double the distance, rest is so simple and calculate it yourself.

On average, Wifi only reaches about 100 ft in GOOD conditions, now you need 1000 ft.

10^(X/20)=1000/100
10^(X/20)=10
10^(X/20)=10^1
X/20=1
......

Base on Friis Transmission Equation, for sub Ghz chipset, if we select 300 Mhz v.s 900 Mhz band, the distance will be 3 times more. same thing if we select 300 Mhz v.s. 2400 Mhz, the distance will be 8 times more.

In case you don't want the world I give, Here is the Plan B;-

sonnyyu:

Riva:
Could you use a couple of powerline network nodes http://www.amazon.co.uk/Netgear-200Mbps-Powerline-Ethernet-Adapter/dp/B007JD6LBS/ref=pd_sim_sbs_computers_3/278-4290633-8656936

Good move!
However 2 conditions have to meet;-

1. The powerline networks won't work across power transformers, i.e. greenhouse and office have to be under same transformer.
2. Since most of Powerline-Ethernet-Adapter use Qualcomm Atheros chipset, if not all. It has maximum distance 300 m between nodes.

The powerline networks will be extended 300 m/984 ft distance.

Thanks sonnyyu. I will not be able to use any wires. It's a field (i.e. grows plants). I could have shacks with car batteries inside to power these logger units but that's it! Since wifi is 2.4GHz I won't be able to extend a few hundred feet without huge antennas I guess? That's too bad. I'll give some extender some tests. Worst case: every logger gets a mobile hotspot.

At base;-

2.4GHz premium quality 10dB gain omni-directional antenna 30", 76.2 cm

Each arduino;-

25 Dbi 2.4 Ghz 802.11b/g Wifi Yagi Antenna Rp-sma Wlan 23.6 x 3 x 1.2 inch, 60cm x 7.5cm x 3cm

Yagi Antenna,$12.60

Now we have 25+10=35 dbi, will give you 56*100= 5600 ft. You could use 10 dbi antenna at Arduino, the size could go down a lot.

Thank you sonnyyu! I once watched a thread where OP asked about external antenna on arduino wifi shield. I guess it's probably time to try it.

Here we go;-

sonnyyu:
...

1. What is the maximum current usage on the WIFI-shield?

WIFI-shield has two big power hungry devices;

HDG104 WIFI chip

Current - Receiving 60mA
Current - Transmitting 15mA

AT32UC3A 32 bits CPU

Current - 37mA

maximum current usage on the WIFI-shield is ~100mA (at least).

2. Can i use it in Ad-hoc or Wifi-direct/p2p mode? I need to connect it to a PC without a Wireless-router.

I doubt it support Ad-hoc or Wifi-direct/p2p mode. Here is the link of firmware;-

GitHub - arduino/wifishield: Arduino Wifi Shield

3. Can i attach an external antenna to it?

at least from diagram it support.

...

I could have shacks with car batteries inside to power these logger units but that's it!

I want to extend the mobile hot spot with an extender so it may reach the loggers, around 1,000 ft or hundreds of meters.

move car batteries to each shack could be good exercise, do you need a hand?

Here is some thing for your version II logger;-

sonnyyu:
Tech background;-

Gas Law

PV = nRT

• P is pressure
• V is volume
• n is the number of moles
• R is the universal gas constant
• T is temperature (K)

Gas laws - Wikipedia

The sensors are in a Tire Pressure Monitoring System (TPMS)

• Pressure, gas law
• Acceleration, car speed
• Temperature, gas law
• Battery Voltage, battery management

The requirement of system;-

• -40°C ~ +125°C full specified operation
• Battery have to last longer than 5 years

Atmel solution;-

A low-power low frequency wake-up receiver for Tire Pressure sensor of battery power management.
315/434 MHz ASK/FSK UHF Transmitter.
125 KHz LF Receiver.

Infineon solution;-

Since 2003, more than 150 million TPMS sensors of Infineon continuously improved product generations were sold worldwide.

SP37 1300kPa Tire Pressure Sensor

SP37 1300kPa Tire Pressure Sensor

SP37 Development RF Kit is Available in two “flavors”

• Operating frequency of 315 MHz or 433.92 MHz
• Output power of 8dBm

Infineon only draws 4 sensors per car so do I, but my Lexus SUV's spare tire has one of those which make me lost a big face when light lit and I send it to dealer repair.

In your case, no 125 KHz LF wake up, but same 315/434 MHz frequency wake up (battery power management). One tiny battery last 5 years.
315 MHz will give you 8 time longer distance than wifi.

liudr:
So does anyone have some experience with a range extender and how does it compare with a router with extender function, in terms of extended range? Thank you!

Yes I have some experience creating WiFi networks over longer distances. However you go about it, it can be a bit of a nightmare. A fixed installation is more straightforward than a roaming one but ultimately, WiFi was designed for short spans, under 75m LoS. Much less in noisy RF environments.

My gut feeling is WiFi is the wrong technology for the application. Unless WiFi's ubiquity is essential to the application, I see little reason to bother with it's drawbacks.

Have you thought about using XBee for the loggers?
Low power, spans measured in Kilometers, mesh-able networks. Seems to fit the bill.
I have no idea how XBee fits into the Arduino ecosystem though.

Thanks Matt. I should definitely try Xbee. I have no experience with Xbee. The reason I chose wifi was first to replace a cell modem and slow upload speed and bandwidth/month. WIth wifi and a mobile hotspot, I can get 5GB/month for 50USD so data and image uploads will be possible. The arduino wifi shield also provides an easy way to make connections to the server I'm using for data upload. So if I switch to Xbee, I wonder what would be the best way to keep this project working. Will I need to make a master module that collects things from slave modules (loggers) and relay to internet? I have no idea. Will the mesh network also extend the range that signal can travel?

I've used this extender
http://www.trait-tech.com/product/T-NB-1001__wireless-n-wifi-repeater-router-range-expander-for-wlan-network.html

I got ok results, but have to say this extender could be better (for example does not have connection for external / proper antenna).. So I can not recommend it...

I've currently Asus router as wireless router + extender + TP Link 703 (external antenna mod) and Arduino connected to rj45 of 703 with 5100 shield..
Maybe I should connect yagi-antenna to tp-link 703 and try directly to Asus..

Some time nothing is needed;-

from Friis Transmission Equation,

Every 6 dBm Transmitter power gain will be double the distance. Here is gui of my Asus RT-N16 router which I flash with DD-WRT.

Default setting = 17 mW = 12 dBm

Maximum setting = 251 mW = 24 dBm

if I select 251 mW, The distance will be 4 times longer. I use this method to control my kids Internet access and keep it top secret, but now my last one is going to college soon.

Two rules to convert dBm to mW

Rule 1: The Rule of 3

If you raise the dBm value by 3 you double the mW value:

0dBm = 1mW
3dBm = 2mW
6dBm = 4mW
9dBm = 8mW
12dBm = 16mW
15dBm = 32mW
18dBm = 64mW
21dBm = 128mW
24dBm = 256mW
27dBm = 512mW
30dBm = 1024mW (5GHz Band B legal limit)
33dBm = 2048mW
36dBm = 4096mW (5GHz Band C legal limit)

This also mean that if you lower the dBm value by 3 you halve the mW value.

Rule 2: The Rule of 10

If you raise the dBm value by 10 you multiply the mW value by 10:

0dBm = 1mW
10dBm = 10mW
20dBm = 100mW
30dBm = 1000mW (5GHz Band B legal limit)
40dBm = 10000mW (Over the 5GHz Band C legal limit)