## 2 Background and Related Work  
### ECG Algorithm Review  
There are currently no ECG studies which include research on both watermarks and compression. However, there are some studies looking at compression or watermarking individually, so based on existing research, we surveyed watermarking and compression as two separate aspects. At present, from the watermark point of view, research on the protection of ECG information is still in its infancy, although there are some research studies, shown in Figure 1, related to the watermarkingof ECG signals, and with the use of wavelet transform based digital watermarking encryption technology [5]. Therefore, research in this field has great potential for the researcher. The existing research may be divided several categories. The first application is the digital watermark technology used in medical images. This application proposes a novel blind watermarking method, by embedding a secret key into the medical image of ECG signals. The second is a sensor network-based ECG monitoring system. ECG signals are watermarked with patient biomedical information to confirm patient/ECG linkage integrity [6]. The third application is wavelet transform-based ECG digital watermarking technology. In ECG signals, the energy is concentrated in QRS complex waves [7], so the selection of wavelet coefficients for concealment should avoid causing the QRS complex waves to distort obviously. The last application is ECG transmission in a wireless network. This paper proposes the use of digital watermarking to ensure the safe transmission of ECG signals in a wireless network [8]. A low frequency chirp signal is used to embed the watermark, which is a 15-bit digital code assigned to the patient. The characteristic of the proposed watermarking scheme is that the embedded watermark can be fully removed by the receiver due to the blind recovery feature of the watermark [9]. [PERSON] _et al_. [10] proposed a novel session based blind watermarking method with a secret key by embedding a binary watermark image into the ECG signal. In addition, the \"P Q R S T\"-peaks are marked and stored over the entire ECG signal and the time interval between two consecutive 'R'-peaks, and intervals between other peaks, are measured to detect anomalies in the behavior of the heart. However, these two methods are non-blind. [PERSON] and [PERSON] proposed a wavelet-based steganography technique which combines encryption and scrambling technique to protect patient confidential data. The proposed method allows the ECG signal to hide its corresponding patient confidential data and other physiological information [11]. In the aspect of ECG compression, the ECG is a dynamic signal. It will continue to produce new signals. For example, Holter monitoring technology has been applied more and more, and there are patients for whom more than 24 h of ECG data has to be collected, which greatly increases the amount of data you need to record. With the advent of an aging society, the number of patients with heart disease will grow, and cardiac care will become a social problem. Remote transmission of ECGs can allow real-time monitoring; it is conducive to diagnosis and first aid instructions. Therefore, the remote transmission of  
Figure 1: Related works. ECGs has a good economic and market outlook [12]. ECG signal compression is a key technology for remote ECG transmission. It directly determines the practicality and effectiveness of the system. For example, in a wireless communication network which is employed for data transmission, long term ECG guardianship generates a huge amount of data that will make wireless communication costs unacceptable, and raise issues of transmission speed and bandwidth. ECG signal compression technology will guarantee that none of the information of the ECG signal is lost and will minimize the amount of data that needs to be transmitted, reduce transmission costs, and increase transmission speed.