RF Traffic  - Page 1
Forum section: electronics / rf-microwave

author: time_remnant
author_rank: Newbie
timestamp: July 13, 2019, 07:30:44 am
content: Hey, I'm a Programmer. So, I've working on a new project in which I need to detect an intruder other than some particular people. Assuming no Wifi and Bluetooth is active. Only Mobile Networks. So i thought of two ways, 1) Network Traffic Monitoring 2) Signal Strength MonitoringNow, I need a help with how mobile Networks work. So they operate in RF.1. Traffic MonitoringSuppose there are 4 people in the room so there must be some kind of signal or RF traffic. Now If a 5th person (intruder) enters the room with his phone, the traffic would change,wouldn't it? Can this be a valid and possible way to detect intruder?Is the change in traffic significant and reliable to detect intrusion?2. Signal StrengthCan this be a reliable way?Signal Strength are displayed in Phone Settings but they keep fluctuating a bit. Now when two or more phones come together does signal strength reduces? For this to reduce do they have to be of same SIM (or using same tower). If possible, I can keep the 4 phones together and see the signal strength and can keeping in mind the fluctuation can set a strength value. If intruder enters signal strength would drop and i can alert.IDK if any of these is practical or not ,these are just ideas.If i'm wrong in interpreting the working of signals and traffic correct me. If there is any other way around, help me out.Thank You.

author: radiolistener
author_rank: Super Contributor
timestamp: July 13, 2019, 09:05:27 am
content: Quote from: time_remnant on July 13, 2019, 07:30:44 amYes, you can detect intruder by RF radiation from his mobile phone and automatically enable alarm system, so the security team will come into game and intruder will be eliminatedBut it's more easy and more reliable way to use classic IR or ultrasonic sensors and video cameras, because intruder may leave his mobile phone at homeQuote from: time_remnant on July 13, 2019, 07:30:44 amno, it won't work

author: time_remnant
author_rank: Newbie
timestamp: July 13, 2019, 01:31:25 pm
content: QuoteBy this you mean there will be a increase in RF traffic and it can be measured. IS there any app or some IC that can help in achieving monitoring RF Traffic.So what i'll basically do is measure the traffic when four persons are in the room. Now if there is a considerable(relibable )increase in traffic I can alert.Is there an option to check traffic within certain proximity?QuoteYeahI know that i just want to create this as a small project.(Assuming intruder doesn't know about my alarm system. Hope he brings his phone

author: radiolistener
author_rank: Super Contributor
timestamp: July 13, 2019, 03:22:33 pm
content: Quote from: time_remnant on July 13, 2019, 01:31:25 pmFirst, you're needs to ban the use of a mobile phone by authorized personnel.After that you can detect intruders by RF radiation from their mobile phone.It's easy, since mobile phone use at protected area is banned for authorized personnel, then those who are using mobile phone are unauthorized intruders and should be eliminated by trained security team.You can use this AD8318 module from aliexpress in order to measure RF radiation in the protected room:https://www.aliexpress.com/item/32956897680.htmlYou will also need an antenna for GSM band. Connect antenna to AD8318 module, also connect power supply to AD8318 module. You can use any DC 7-15V power supply or battery for that. Be careful not to confuse the polarity.The output of AD8318 will correspond with RF radiation level in the room where you placed antenna. This is just DC voltage. The lower voltage means the higher RF level. You can use simple multimeter in order to mesure AD8318 output, or just connect it to some arduino board.After power on, just remove any mobile phone from a room and measure normal RF level. And write it down.Now you're ready to catch unauthorized intruders with mobile phone.When RF level will raise above normal level (it happens when voltage level from AD8318 output is drops down), then intruder with mobile phone is entered the room. In such case you will need to enable alarm system and call security team or whatever you need.Quote from: time_remnant on July 13, 2019, 01:31:25 pmit's hard to measure exact proximity by RF radiation level, because it depends on different factors and mobile phone can vary it's transmitter output power. But you can evaluate the distance by RF radiation level. When antenna of your detector is more close to mobile phone, the detector will show more high RF level.But note, mobile phone transmits very rarely. So, the chance that you can catch that moment is minimal. There is need to make phone call in order to catch it's transmission. When phone is in idle mode it doesn't use transmit mode, so RF radiation level will be normal and you cannot detect itSo, practically it won't works, but you can learn many things by experimenting with AD8318 module

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: July 19, 2019, 08:25:30 am
content: If the room is a faraday cage, I believe the mobile phones will start blasting at full power trying to hunt for a tower.

author: Bicurico
author_rank: Super Contributor
timestamp: July 19, 2019, 08:49:09 am
content: IMHO it will not work at all.Different cell phones share the same channels. Unless you are the cell antenna you won't know how many phones are around. The communication is done by encrypted packets which you cannot assign to each cell phone present.Same with signal strength. The cell phones adjust their signal power as required and not by a simple distance/power ratio. A further away phone may be transmitting with less power than a phone closer to your system.Plus you may be in conflict with data protection laws and you definitely may not broadcast any signal at those reserved frequencies - i.e. to set up a fake cell to attract and count the phones in vicinity.This would be the only feasible way I could think of: a fake powerful cell that attracts the phones and matches them with authorised list. Then it releases them so that they connect to the real cell. Highly illegal but you can do experiments with GNURadio and SDR dongles using the GSM implementation.RegardsVitor

author: radiolistener
author_rank: Super Contributor
timestamp: July 19, 2019, 08:57:42 am
content: Quote from: Bicurico on July 19, 2019, 08:49:09 amTechincally it is possible, you can install your own cell base station which will emulate real base station. In such way you can identify mobile device, request it for desired transmitter power, and other things. But using such equipment with no license is illegal, you're needs government license for such technology.

author: Bicurico
author_rank: Super Contributor
timestamp: July 19, 2019, 09:01:01 am
content: Read my last paragraph...

author: CJay
author_rank: Super Contributor
timestamp: July 19, 2019, 09:29:54 am
content: Actually, I wonder if this could be achieved with one of the Femtocells that providers supply as weak signal area boosters, sure you'd need to see if you could somehow access information about the connected devices and of course there's no guarantee the devices will register with it but...IMHO, a CCTV system with people tracking/object counting would be a far better option