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So I have little to nothing experience with anything wireless related. the WiFi modem I have in my house is far from my room and the signal is weak, so it reduces the communication rate. my first question is this:

A) Isn't the information transmitted encoded in ASK or FSK, if this is, then why would the reduction in the amplitude of the signal reduce the speed of communication? I can see how the reduction would introduce errors into the system, but not how the system can still maintain functionality but at a lower rate and the only thing I can think of is frequency attenuation, but it does not make sense to me. I remember reading somewhere that the telephone lines are analog coded signals (However, my common sense tells me fiber optics are digital because of the way they work!), as in FM or something similar, and the WiFi modem basically changes that to a digital signal (ASK, FSK or PSK)

As a solution, I was thinking i could make a PCB to:

  1. receive the signal from the modem
  2. amplify it and transmit it again
  3. my PC receives the signal
  4. my PC transmits it's signal
  5. PCB recievs PC's signal and amplifies it, and transmits it

B) Would this system work? is this something that can be implemented? I think I have sufficient knowledge in designing suitable amplifiers for this purpose. one other thing that comes to mind, is that would this receiving/amplifying/transmitting procedure introduce any interference? Say my PC receives both the original signal and the amplified one at the same time, can it differentiate between the 2? is this going to cause problems?

PS: I know EMI could cause me legal problems (EMI/EMC standards in the UK), but I have dealt with it before (in terms of standards they have to pass) so I think I am fine at that front :)

NeuroEng
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  • The modulation used is likely [QAM](https://en.wikipedia.org/wiki/Quadrature_amplitude_modulation) which is much more complicated. Any PCB you create will create delays, and this has already been done - it is called a [WiFi Extender](https://en.wikipedia.org/wiki/Wireless_repeater) or repeater. Long story short, only thing you can do is use a lower frequency, different channel, move the items closer, or run a wire (at least some distance.) – rdtsc Aug 25 '20 at 13:27
  • If it is a PC with a separate antenna connection and not a laptop, then you could experiment with using a directional antenna, aimed at the router. Inside a house this will be complicated by all the things the signal could bounce off of. I'd start by seeing if I could run a wire, though, or relocate the router. – TimWescott Aug 25 '20 at 16:22
  • For more information on how this would actually work, please see my answer to a previous question here: https://electronics.stackexchange.com/questions/440930/what-does-the-wifi-amplifier-exactly-amplify/441259#441259 – Hitek Aug 28 '20 at 07:51

1 Answers1

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Regarding the first part of your question, as to how a bad signal causes slower speeds: The TCP protocol used for most internet traffic has error detection. Basically, each packet has a checksum so the receiver can know whether it is correct. The receiver then sends an acknowledgement back to the transmitter that the packet was received. The transmitter will stop and re-send any packets that are not received, possibly more than once. This can significantly lower communication speed. See the Reliable Transmission section on the TCP Wikipedia page for more information.

As to your second question about whether this will work: In theory, yes, such a system can work. However, in practice, neither you nor I have enough knowledge or experience to do so correctly. Fortunately, WiFi extenders are available for sale, so you may be able to use those. I've used them before myself, but kept having to restart them and disconnect/reconnect so often (maybe hourly) that I found them very frustrating. Probably if you spend enough money you can get a reliable one.

What I ended up doing in my house, since the modem connection from outside was at a far corner, was running an ethernet cable from the modem through the walls into a closet located near the middle of the house, and connecting a dedicated WiFi router from there so the entire house had a good signal.

Justin
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    The IEEE 802.11 (wireless) layer has its own acknowledgement and retransmission scheme. Every time a packet doesn't make it through the air whole (which happens staggeringly often, with microwave ovens and other wireless devices all competing for the same band), the sender will retransmit it. Only after the allowed number of retransmission is exhausted, the WLAN card will give up, causing an IP packet drop (which is then compensated for by TCP retransmit). Also, the sender adjusts the bitrate (symbol rate) dynamically to optimize throughput and limit retries. – TooTea Aug 25 '20 at 15:35
  • Just a note: I also have had the same experience with older Wifi repeaters. Those broadcast to the client and connect to the access point on the same frequency. They tend to be very problematic, and significantly reduce data rates. Newer repeaters use different frequencies to connect to the client and access point using different radios, and work much better... – Hitek Aug 28 '20 at 05:17
  • @Hitek - That makes sense, my experience with them was before 5 GHz was common. – Justin Aug 28 '20 at 17:30