How Do Wireless Digital Transmissions Work and What Affects Their Quality?

[jaydnul]

For some reason I can't find any satisfying answers to my questions on the internet.

1. Are mostly all remotes, phones, wifi, etc. using wireless digital transmission? If so, why does a wifi signal get weaker when you move further away? The inverse square law shouldn't apply to a digital signal as long as it makes it to the receiver, right?

2. Do digital transmissions only require one specific frequency rather than a range of frequencies like analog? For example, you could just send pulses at 800Mhz exactly and have your receiver set to the same frequency.

3. Are wireless digital transmissions always encrypted in some way? If so, is there anyway to get the codes? For example, if i wanted to build a receiver (other than the TV) for my Samsung TV remote, could I? Or would Samsung keep that info secret?

4. What is the best way to read a wireless signal? Say i wanted to know the binary signal sent from my remote when I press a specific button, how could I read out the binary digits?

Thanks a bunch!

 

[russ_watters]

1. Are mostly all remotes, phones, wifi, etc. using wireless digital transmission? If so, why does a wifi signal get weaker when you move further away? The inverse square law shouldn't apply to a digital signal as long as it makes it to the receiver, right?

Most remotes use IR: that's what the little lens on the end of the remote is for. The others are radio/microwave frequency. They are very different from each other.

The signal in wifi/cell phones is weaker with distance because of the inverse square law, but the quality doesn't suffer until it gets so weak that it can't be reliably detected.

2. Do digital transmissions only require one specific frequency rather than a range of frequencies like analog? For example, you could just send pulses at 800Mhz exactly and have your receiver set to the same frequency.

Digital signals are modulated in ways somewhat similar to the way analog signals are:
http://en.wikipedia.org/wiki/Direct-sequence_spread_spectrum

3. Are wireless digital transmissions always encrypted in some way? If so, is there anyway to get the codes? For example, if i wanted to build a receiver (other than the TV) for my Samsung TV remote, could I? Or would Samsung keep that info secret?

Some are, some aren't. A remote's codes are not encrypted, otherwise universal remotes couldn't be made.

4. What is the best way to read a wireless signal? Say i wanted to know the binary signal sent from my remote when I press a specific button, how could I read out the binary digits?

Again, most remotes are infrared. You could probably record them with an infrared camera or other IR receiver. They also tend to be analog:
http://en.wikipedia.org/wiki/Remote_control#Technique

 

[Jon B]

For some reason I can't find any satisfying answers to my questions on the internet.

1. Are mostly all remotes, phones, wifi, etc. using wireless digital transmission? If so, why does a wifi signal get weaker when you move further away? The inverse square law shouldn't apply to a digital signal as long as it makes it to the receiver, right?

It is still a signal carried by radio waves. The original name for radio was "wireless." As you know radio waves get weaker with distance and the modulation dies with it.

2. Do digital transmissions only require one specific frequency rather than a range of frequencies like analog? For example, you could just send pulses at 800Mhz exactly and have your receiver set to the same frequency.

Digital transmissions can be a single frequency that is turned on and off (like morse code) or frequency shifted to provide pulse code modulated (digital) data. The High priority encrypted communication across the pacific used time division Frequency Shift Keyed (FSK) transmissions at around 50 mHz. Other data systems used AM Frequency Division Modulation for data transmissions.

3. Are wireless digital transmissions always encrypted in some way? If so, is there anyway to get the codes? For example, if i wanted to build a receiver (other than the TV) for my Samsung TV remote, could I? Or would Samsung keep that info secret?

Most Remote controls are optical. No WIFI. Different codes can be used on specific units to keep optical TV remotes from triggering the wrong functions or other devices. There are universal remotes that are programmable. Most remote controlled devices come with a specific remote for the device. It is conceivable that you could make an optical receiver that can be programmed to respond to the codes from a remote and do whatever you want it to do.

4. What is the best way to read a wireless signal? Say i wanted to know the binary signal sent from my remote when I press a specific button, how could I read out the binary digits?

The Wireless and Bluetooth signals are radio frequency. The signal for most remotes are light outside of our vision range. You can use a storage oscilloscope and a photo sensor to see the data patterns of an optical remote. I use a cell phone camera to check optical controllers. Thanks a bunch!

 

[jim hardy]

There are plenty of hobbyist "IR Remote Control Hackers"

try searching on that phrase, both with and without IR.

http://www.interlockroc.org/2012/07/20/remote-control-hacking/