Possible to transmit digital signals by a wireless transmitter universally? - Page 1
Forum section: electronics / beginners

author: sam1275
author_rank: Frequent Contributor
timestamp: March 29, 2015, 10:03:12 am
content: Hello.I used to looking for a "KVM over IP" to let me use my computer remotely, but those things are very expensive and some even cause lag or compatibility issue. Then just an unusual thought pops up... All digital signals are 0 or 1, so why have we consider the protocol? If we just transmit the RAW data over-the-air and reproduce it on the receiver, then there will be no lag, no compatibility issue, and real universal on all port types. But there are some thing to consider, first, the bandwidth of the transmitter must higher than the port, second, there might be security issues if we really transmit the RAW data, but is a encryption that difficult?Thank you.

author: nitro2k01
author_rank: Frequent Contributor
timestamp: March 29, 2015, 11:05:14 am
content: To name a few problems:You need enough bandwidth to faithfully reproduce the signal on the receiving end, including preventing edge jitter/phase distortion.Many protocols have multiple digital channels. DVI starts out at a minimum of 4 channels, if you count each differential pair (red, green, blue, clock) as one digital channel and ignore the DDC channel used by the monitor to signal which resolutions it can handle.Some protocols, notably USB, is using a bi-directional differential pair. Without being aware of the protocol, you can't know whether the host is currently transmitting or receiving over this channel.You need to deal with interference. Without being aware of the protocol, it would be very difficult to reproduce any data lost, since you don't know where a packet starts or ends, etc. With knowledge of the protocol, the KVM can for example acknowledge that a USB packet was received, one side, and the transmitting side at the time could resend it if no ack comes back as expected. Likewise, the KVM could repeat the previous display frame if it detects interference, instead of showing a blank screen or whatever noise it picks up as interference.Likewise, you need to deal with not creating interference. The unlicensed bands are very crowded with things like wi-fi and bluetooth, and you need to keep within the legal transmission power limit. You could ignore that and wait until your neighbors come knocking on your door wondering why their wi-fi stopped working all of a sudden.

author: sam1275
author_rank: Frequent Contributor
timestamp: March 30, 2015, 05:35:51 pm
content: Quote from: nitro2k01 on March 29, 2015, 11:05:14 amThank you.

author: electr_peter
author_rank: Unknown
timestamp: March 30, 2015, 09:07:43 pm
content: Wireless protocols are much harder to implement than wired protocols. With wired protocol, you at least know that there is something specific at the other end. With wireless protocol it is like being blind in a big room and shouting to get information across to none, 1 or many more recipients which you have no idea even exist. Wireless protocol is a very difficult subject.Have a look at simple protocols to get an idea or get cheap ISM band transmitter/receiver pair and try to implement simple protocol yourself.Quote from: sam1275 on March 29, 2015, 10:03:12 amOne huge problem with wireless communication - BW available can increase/decrease any time (may things influence this). This means that if actual BW is pushed to the limit it may become less than available BW and data will be lost. For digital data signals this generally means irrecoverably lost data/signal/connection. Only way around this problem is underutilise available BW or make robust connection BW adjuster (with bidirectional communication) - not easy at all.Such problem is most obvious in TV transmission and with wireless cameras in RC aircraft. Almost all RC aircraft use only analog video transmitters. If signal is weakened on analog transmission, receiver at least sees picture with noise (digital signal simply drops).Lag is another issue. HDMI like transmission is almost impossible to do reliably because of lag, BW limitations, digital coding and compression.Also, for live transmission and minimal lag such systems are essentially unidirectional. That is, it sends data at max possible power at defined BW with a hope it is enough for a receiver to understand. Transmitter does not know how good/bad signal is at receiver end and cannot adjust or limit data rate in any way. Wired systems on the other hand at least have defined BW limitations one can rely on.

author: Whales
author_rank: Super Contributor
timestamp: March 30, 2015, 09:24:16 pm
content: Sidenote: if you are still looking for solutions similar to KVM, tryVNC. Lots of free client and server software exists.

author: Michaela Joy
author_rank: Contributor
timestamp: March 31, 2015, 01:07:26 am
content: Take a look here.http://www.codeproject.com/Articles/565/Remote-Control-PCsI haven't looked at the code, but it looks like He did most of the groundwork already.:MJ