Circuit Switched Data
The data connection is established from the mobile phone to any remote station. This connection can be compared to a simple telephone call. In contrast to this, however, data is transmitted at a speed of 14.4 kbit / s (per channel). Due to the error protection of the transmission, only 9.6 kbit / s remain for the user data. This corresponds to a throughput of 1.2 kByte / s. Current frequency modulation methods can use the 14.4 kbit / s completely for data transmission. However, this is done at the expense of error correction. CSD can handle any mobile phone that has an internal GSM modem.
HSCSD is an extension of CSD by bundling several GSM data channels .
CSD is a very inefficient data service. When using CSD, the radio channel is reserved even if no data is being sent or received. For this reason, CSD is only offered to business customers for older machine-to-machine (M2M) applications by most European mobile phone providers . New machine-to-machine (M2M) applications can be implemented using the packet-oriented data service (PSD).