From GSM to LTE: An Introduction to Mobile Networks and Mobile Broadband

7.2 Physical Properties

Up to version 1.2 of the standard, the maximum datarate of a Bluetooth transmission channel is 780 kbit/s. All devices that communicate directly with each other have to share this datarate. The maximum datarate for a single user thus depends on the following factors:

• the number of users that exchange data with each other at the same time;
• activity of the other users.

The highest transmission speed can be achieved if only two devices communicate with each other and only one of them has a large amount of data to transmit. In this case, the highest datarate that can be achieved is 723 kbit/s. After removing the overhead, the resulting datarate is about 650 kbit/s. The bandwidth remaining for the other device to send data in the reverse direction is about 57 kbit/s. This scenario occurs quite often, for example, during web surfing or when transferring a file. In these cases, one of the two devices sends the bulk of the data while the other device sends only small amounts of data for requests or acknowledgment. The left-hand side of Figure 7.1 shows the achievable speeds for this scenario.

Figure 7.1 Three examples of achievable Bluetooth datarates depending on the number of users and their activity.

If both ends of the connection need to send data as quickly as possible, the speed that can be achieved at each side is about 390 kbit/s. The middle section of ...