CODEWITHSUNDEEP
androidbluetooth
Laxman Ch
Laxman Ch

Reputation: 1

Bluetooth device data transfer issues

  1. How can a device identify the other devices to whom we need to send data and transfer the data to other device.

  2. If the device1 send the data to device2, will other device say device3 near to them will receive same data?

Upvotes: 0

Views: 254

Answers (2)

takrishna
takrishna

Reputation: 5002

Bluetooth can connect up to eight devices simultaneously. With all of those devices in the same 10-meter (32-foot) radius, you might think they'd interfere with one another, but it's unlikely. Bluetooth uses a technique called spread-spectrum frequency hopping that makes it rare for more than one device to be transmitting on the same frequency at the same time. In this technique, a device will use 79 individual, randomly chosen frequencies within a designated range, changing from one to another on a regular basis. In the case of Bluetooth, the transmitters change frequencies 1,600 times every second, meaning that more devices can make full use of a limited slice of the radio spectrum. Since every Bluetooth transmitter uses spread-spectrum transmitting automatically, it’s unlikely that two transmitters will be on the same frequency at the same time. This same technique minimizes the risk that portable phones or baby monitors will disrupt Bluetooth devices, since any interference on a particular frequency will last only a tiny fraction of a second.

So what if they interfere and there is a erroneous data, the receiving system simply discards it based on correcting bits of the packets transffered.

  1. Bluetooth devices have a parameter or option called visibility. When you enable visibility, then the bluetooth device starts publishing its presence within the bluetooth frequency range. This presence can then be detected by any other bluetooth device which can connect to this device when it scans the above bluetooth frequency range.

  2. As they use spread-spectrum frequency hopping described above they publish data to all receivers but only the intended receiver with whom the sender is connected will have the key to unlock the data.

Upvotes: 0

ppeterka
ppeterka

Reputation: 20726

Please read up on the whole Bluetooth story. You seem to have problems with basic concepts. Also, it would probably help to be a bit more specific in your questions for example specifying which BT version are you referring to.

For identifying the devices, each of them has a separate address. They even have human readable names. (Look at the Wiki page linked above Connection and communication) Also, during the pairing process, you should have to get to know and explicitly allow the devices which you really want to communicate with, the goal of the process is exactly to make sure to have an explicit authorization between the devices for communication.

Yes, device3 will receive the radio signals, but if not authorized, it won't be able to tell what is going on - unless it is a misbehaving device cracking the encryption... (Given the communication is actually encrypted, that is.) Reading the Security Concerns part is also useful.

Upvotes: 1

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