Bluetooth Low Energy data throughput

This chapter outlines achievable Bluetooth® Low Energy connection throughput for Generic Attribute Protocol (GATT) procedures used to send and receive data in stated SoftDevice configurations.

The throughput numbers listed in this chapter are based on measurements in an interference-free radio environment. Maximum throughput is only achievable if the application, without delay, reads data packets as they are received and provides new data as packets are transmitted. The connection event length should be set to such a value that the entire connection event can be filled with packets. The SoftDevice may transfer as many packets as can fit within the connection event as specified by the event length for the connection. For example, in simplex communication, where data is transmitted in only one direction, more time will be available for sending packets. Therefore, there may be extra TX-RX packet pairs in connection events. Additionally, more time can be made available for a connection by extending the connection events beyond their reserved time. See Connection timing with Connection Event Length Extension for more information.

The maximum data throughput numbers given in this chapter represent the maximum amount of data that can be transferred between two applications in a given time. The maximum throughput depends on the mechanism used to transfer data. When the application utilizes ATT Handle Value Notification or ATT Write Command, the transactions are one direction only. When the application utilizes ATT Write Request, it is assumed that the peer responds with an ATT Write Response in the next connection interval. The throughput will in this case be limited to one packet every second connection interval. The amount of data in each packet is the MTU size subtracted by the ATT header size. Therefore, the throughput can be expressed as follows:

Throughput_bps = num_packets * (ATT_MTU - 3) * 8 / seconds

All data throughput values apply to packet transfers over an encrypted connection using maximum payload sizes.

The following table shows maximum data throughput at a connection interval of 7.5 ms for a single peripheral connection.