I have been following a tutorial that enables you to play around with the TXPOWER parameter of your wifi card / wifi adapter:
http://null-byte.wonderhowto.com/how-to/set-your-wi-fi-cards-tx-power-higher-than-30-dbm-0149606/
You can easily boost up your wifi range when increasing the TXPOWER.
Now, most people want to improve their wifi signal strength of their home router, right. But in my case, I would like my home router (which runs on a raspberry pi) to have a relative small wifi signal radius (say, a radius of 2 meters), so that you actually need to physically look for the pi home router when trying to connect to it.
I have learned that this tutorial does not do a thing with the wifi link quality and/or the wifi signal level and thus does not influence the wifi radius of my pi home router.
link quality & signal level
Do you guys have any ideas/thoughts about how to decrease link quality and/or wifi signal level (e.g Link Quality = 12/70 and Signal level =-10dBm) ? Is this even possible ?
I am using a Tp-Link TL-WN722N IEEE 802.11n USB - Wi-Fi Adapter.
WIRELESS LITE N ADAPTER 150M USB HIGH GAIN 1DETACHABLE ANTENNA WL-AP.
150 Mbps - External
First, I recommend reviewing this section from your link:
QUICK DECIBEL UNDERSTANDING:
Every 10 decibels is a 10X increase in power starting from 1 dBm equal
to 1mW... 10 dBm equals 10 mW, 20 dBm equals 100 mW, 30 dBm equals
1000 mW, and so on. Every 3 decibels is approximately double that of
the prior power, so 30 dBm is 1000 mW, if we add 3 dBm, then we can
double the power such that 33 dBm is about equal to 2000 mW.
It appears to me that you are able to modify the transmit power of your adapter as the tutorial states. Are you saying this is not working? If you set your transmit power to something extremely low (-30dBm, for example) you would effectively be turning off the transmitter. Keep increasing that value until you get your desired coverage radius.
If the transmit power parameter is not functioning as per the tutorial, then there are other means to achieve reduced coverage. The model you specified has a detachable antenna....so detach it. This would definitely reduce your coverage. However, if it reduces coverage too much, you could simply add an inline attenuator. Fortunately, your antenna uses an SMA connector which is very common. You can find many SMA attenuators on ebay with different attenuation values. Experiment with different values until you get the desired coverage.
And if that doesn't work, just wrap a bunch of aluminum foil around the thing lol.
Related
I got a question about the data rate of the ethernet interface and hope someone can give me some hints on that.
I know the calculation method of the PCIe interface, for example, PCIe Gen3 X1 lane:
The data rate of single-lane should be
8 Gb/s (Gen3 line rate) * 2 (TX/RX, full-duplex) / 8 (to Byte) = 2 GB/s
(128/130 encoding is ignored)
So, how do we calculate the data rate of an ethernet interface?
Take 1000base-T for example, we have 4 twisted pairs, to sum up to 1Gb data rate.
So one pair should provide a 250Mb data rate. It’s full-duplex so TX/RX provides 125Mb each at the same time. With that being said, the “line rate” of a 1000base-T interface is 125MHz (125Mb).
Do I understand it correctly about the speedrunning on the ethernet interface?
how do we calculate the data rate of an ethernet interface?
Ethernet's nominal bit rate is generally defined at the top of the physical layer (L1). It includes preamble, SOF and IPG, but excludes all PHY-specific line encoding (PCS and PMA).
This is done to make all PHY variants of the same speed 100% compatible with each other. You can convert 1000BASE-T to 1000BASE-LX to 1000BASE-SX and back to 1000BASE-T without any buffer drops.
It’s full-duplex so TX/RX provides 125Mb each at the same time.
No - the nominal bitrate runs each direction, simultaneously for full duplex links. Each 1000BASE-T lane transports 250 Mbit/s worth of "user" data.
With that being said, the “line rate” of a 1000base-T interface is 125MHz (125Mb).
Since the line rate is (usually) the PHY rate it's 1000 MBit/s, four lanes of 250 Mbit/s each.
1000BASE-T does use a symbol rate of 125 MBaud since its PAM-5 modulation transports more than two bits per symbol. You might think that PAM-4 with exactly two bits would be sufficient, but the line code overhead eats up the rest. 1000BASE-T is already quite complex, it uses two-dimensional Trellis modulation plus scrambling to get across the wire (to produce a self-clocking signal, improve the signal/noise ratio and eliminate excess DC).
The 1000BASE-X PHYs for fiber are much simpler. The PCS uses 8b10b to produce a binary stream of 1.25 GBd that can be directly used to modulate the laser.
I want to set up a point-to-point communication link between two Raspberry Pi using LoRa.
I know for lorawan there is (at least in Europe, where I live) a duty cycle limitation so the nodes can transmit only for an average of 30 seconds uplink time on air, per day, per device.
Is this valid also for point-to-point lora communications? Because my sender keeps on sending.
I am using the code provided here.
Yes, this is also valid for your LoRa application, since it is emitting radio waves. You can look up limits for europe for specific frequency bands in the ERC Recommendation 70-03 (page 7). In the ERC Recommendation 70-03 on page 42 you can then look up which of the frequecny bands are allowed for each country.
Example
Let's say you live in Germany and you want to use frequency 869,400 MHz to 869,650 MHz (this frequency band is called h1.6):
A quick lookup in the ERC Recommendation 70-03 page 39 shows that this band is allowed to be used in Germany:
Further this specific band allows you to use 10% time-on-air (duty-cycle) for your transmitter. This basically means you are allowed to transmit 1 second and are obligated to pause 9 seconds after that.
Which cables are best for gaming, cat5 e or cat7? I have top tier internet connection. So im just looking for latency to the minimum
As long as the cable is working correctly it has zero impact* on whatever workload you put on it. Gigabit is as fine over Cat.5e as over Cat.6 or Cat.7 or Cat.8.
*Not true with absolute precision: Cat.7 has a velocity factor (VF) of .79, so with a 100 m cable run it would actually save you 90 nanoseconds in comparison to Cat.5e (VF .66) each direction - or 9 ns for a 10 m cable. You might well round that off to zero though.
I have a project that consisted of transmitting data wirelessly from 15 tractors to a station, the maximum distance between tractor and station is 13 miles. I used a raspberry pi 3 to collect data from tractors. with some research I found that there is no wifi or GSM coverage so the only solution is to use RF communication using VHF. so is that possible with raspberry pi or I must add a modem? if yes, what is the criterion for choosing a modem? and please if you have any other information tell me?
and thank you for your time.
I had a similar issue but possibly a little more complex. I needed to cover a maximum distance of 22 kilometres and I wanted to monitor over 100 resources ranging from breeding stock to fences and gates etc. I too had no GSM access plus no direct line of sight access as the area is hilly and the breeders like the deep valleys. The solution I used was to make my own radio network using cheap radio repeaters. Everything was battery operated and was driven by the receivers powering up the transmitters. This means that the units consume only 40 micro amps on standby and when the transmitters transmit, in my case they consume around 100 to 200 milliamps.
In the house I have a little program that transmits a poll to the receivers every so often and waits for the units to reply. This gives me a big advantage because I can, via the repeater trail (as each repeater, the signal goes through, adds its code to the returning message) actually determine were my stock are.
Now for the big issue, how long do the batteries last? Well each unit has a 18650 battery. For the fence and gate controls this is charged by a small 5 volt solar panel and after 2 years running time I have not changed any of them. For the cattle units the length of time between charges depends solely on how often you poll the units (note each unit has its own code) with one exception (a bull who wants to roam and is a real escape artist) I only poll them once or twice a day and I swap the battery every two weeks.
The frequency I use is 433Mhz and the radio transmitters and receivers are very cheap ( less then 10 cents a pair if you by them in Australia) with a very small Attiny (I think) arduino per unit (around 30 cents each) and a length on wire (34.6cm long as an aerial) for the cattle and 69.2cm for the repeaters. Note these calculations are based on the frequency used i.e. 433Mhz.
As I had to install lots of the repeaters I contacted an organisation in China (sorry they no longer exist) and they created a tiny waterproof and rugged capsule that contained everything, while also improving on the design (range wise while reducing power) at a cost of $220 for 100 units not including batterys. I bought one lot as a test and now between myself and my neighbours we bought another 2000 units for only $2750.
In my case this was paid for in less then three months when during calving season I knew exactly were they were calving and was on site to assist. The first time I used it we saved a mother who was having a real issue.
To end this long message I am not an expert but I had an idea and hired people who were and the repeater approach certainly works over long distances and large areas (42 square kilometres).
Following on from the comments above, I'm not sure where you are located but spectrum around the 400mhz range is licensed in many countries so it would be worth checking exactly what you can use.
If this is your target then this is UHF rather than VHF so if you search for 'Raspberry PI UHF shield' or 'Raspberry PI UHF module' you will find some examples of cheap hardware you can add to your raspberry pi to support communication over these frequencies. Most of the results should include some software examples also.
There are also articles on using the pins on the PI to transmit directly by modulating the voltage them - this is almost certainly going to interfere with other communications so I doubt it would meet your needs.
Hi,
In the CDMA cellular networks when MS (Mobile Station) need to change a BS(Base Station), exactly necessary for hand-off, i know that is soft hand-off (make a connection with a target BS before leaving current BS-s). But i want to know, because connection of MS remaining within a time with more than one BS, MS use the same code in CDMA to communicate with all BS-s or different code for different BS-s ?
Thanks in advance
For the benefit of everyone, i have touched upon few points before coming to the main point.
Soft Handoff is also termed as "make-before-break" handoff. This technique falls under the category of MAHO (Mobile Assisted Handover). The key theme behind this is having the MS to maintain a simultaneous communication link with two or more BS for ensuring a un-interrupted call.
In DL direction, it is achieved using different transmission codes(transmit same bit stream) on different physical channels in the same frequency by two or more BTS wherein the CDMA phone simultaneously receives the signals from these two or more BTS. In the active set, there can be more than one pilot as there could be three carriers involved in soft hand off. Also, there shall also be a rake receiver that shall do maximal combining of received signals.
In UL direction, MS shall operate on a candidate set where there could be more than 1 pilot that have sufficient signal strength for usage as reported by MS. The BTS shall tag each of the user's data with Frame reliability indicator that can provide details about the transmission quality to BSC. So, even though the signals(MS code channel) are received by both base stations, it is achieved by routing the signals to the BSC along with information of quality of received signals, which shall examine the quality based on the Frame reliability indicator and choose the best quality stream or the best candidate.