ECG Compression - ECG Acquisition and Automated Remote Processing - page 116

Fig. 5.13 Sequence of
sending short messages

Number
of packets

Packet 1 Packet 2 Packet 3 Packet 4

Frame 1 Frame 2 Frame 3 Frame 4 Frame 5

The mobile number of the remote cardiologist is inserted in the GUI front panel
directly through keyboard. To account for lost packets (short messages) and their
easy concatenation, a message serial number is included at the end (i.e., 160th
position) of each data packet (vide Fig. 5.11 ). The number of total messages can
be found out as:

Number of messages ¼ number of characters in ASCII file 2
159

þ 1 ð 5 : 15 Þ

The entire compressed data are transmitted in the sequence as shown in the
Fig. 5.13 .
The first frame only includes total number of packets being sent. This helps to
check whether all message packets are received. The algorithm for sending the
data packets through the GSM modem is given in End of Chapter Appendix VII .

5.4.2 Receive-End Functions

The receive-end configuration is shown in Fig. 5.10 b. The receive-end application
software functions are as follows:

1. Identification and sequencing of the arrived messages based on message serial
number.
2. Concatenation of messages by discarding fixed prefixed and suffixed infor-
mation like senders (Modem's) SIM number, time of generation, receiver's
SIM number, etc.
3. Conversion of 7-bit ASCII characters to 8-bit ACII to generate the decoded
ECG file,
4. Decompression of the ECG data and generation of graphical plot for visual or
software-based analysis.

The cardiologist can send back his comment after his analysis and sending back
to the transmit-end PC.

5.5 Conclusion

Compression of medical signals is an essential part of data archival and com-
munication applications. Telecardiology applications require compression of ECG
data prior to transmission. This chapter described the different techniques for