Unattended ward monitoring system based on wireless radio frequency technology

Body temperature, heart rate and respiratory rate are the three most important and basic vital signs of the human body. Monitoring multiple vital signs of the injured and sick is conducive to timely and effective treatment. However, most of the monitoring systems in my country are manual bedside monitoring and wired bedside monitoring. The former wastes manpower and has low reliability; the latter is costly and difficult to wire. This urgently requires a monitoring method that can both reliably monitor patients and save manpower and material resources. The unattended ward monitoring system introduced in this article is designed to meet such needs. The system uses biomedical sensors to detect the patient's body temperature, heart rate (pulse), respiratory rate and other physiological parameters in real time, and sends the detection data to the monitoring center through a wireless radio frequency module to monitor the patient's physical condition in real time. It not only saves manpower and material resources, but also improves the quality of medical services and hospital management level of the hospital. It is also easy to install, low cost and simple to use.

 

1 System composition and working principle
 

The unattended ward monitoring system is mainly composed of a data collector, a wireless radio frequency module SRWF-106, a monitoring computer and other parts. The structural diagram is shown in Figure 1.
 

 

The digital temperature sensor DS18B20, HK-2000A integrated pulse sensor and HXB-2 piezoelectric respiratory sensor connected to the data collector are installed on the relevant parts of the patient's body as required, and then the data collector is turned on to start collecting the patient's vital signs and parameters, and the data are stored in the ferroelectric memory FM31256 together with the data collection time. At the same time, the wireless radio frequency module SRWF-106 is started to send out the bed number, collection time and monitoring data in real time. The red indicator D3 flashes to indicate successful data transmission. When the power supply battery voltage is insufficient, the single-chip microcomputer LPC932 will be interrupted. At this time, the yellow indicator D4 will flash to remind the staff to replace the battery, which improves the working reliability of the data collector.
 

2.2 Use of wireless RF module SRWF-106
 

The SRWF-106 module provides two serial ports, COM1 (Pin3 and Pin4 of CON1) is fixed as a UART serial port with TLL level; COM2 (Pin6 and Pin7 of CON1) can select the interface mode through the D position of jumper J1, including RS 485 and RS 232. In this design, the data acquisition device and SRWF-106 are connected at TTL level, while the monitoring computer and SRWF-106 are connected at RS 232. The SRWF-106 module provides interface baud rates of 1 200 b/s, 2 400 b/s, 4 800 b/s, 9 600 b/s, 14 400 b/s, and 19 200 b/s. The baud rate setting can be determined by changing the state of the pad jumper (J2~J4) on the back of the module. The module operating voltage is +4.5~+5.5 V. In order to effectively save power consumption, the module can be set to sleep mode.
 

3 Design of Communication Protocol
 

In wireless communication systems, due to the influence of power supply, spatial noise and transmission path, data transmission is easily disturbed, resulting in communication failure. Therefore, it is necessary to design a transmission protocol to ensure a reliable data connection on this unreliable physical link. In this system, the data collector and the monitoring computer are a simple multi-point to point communication.
 

3.1 Baud rate setting and communication method selection
 

Considering the characteristics of the wireless RF module SRWF-106 and the speed and stability of data communication, this design uses 9600 b/s. Since the communication is a many-to-one relationship, the serial port selects working mode 3.
 

3.2 Determination of data verification method
 

When using wireless communication technology to transmit data, it is easy to encounter interference, which will change the transmitted data and cause transmission errors. Considering the actual requirements of the system, this design adopts an 8-bit CRC (cyclic redundancy check) check method.
 

The calculation of CRC checksum is a cyclic calculation. From a mathematical point of view, CRC checksum is the remainder obtained by dividing a polynomial (represented by a data block) by a generating polynomial (algorithm rules). CRC checksum is to add some check bits to a data block to be transmitted. These check bits (CRC check bits) are calculated from the data block and transmitted together with the data block. At the receiving end, the CRC checksum is recalculated for the received data block according to the specified algorithm, so as to determine whether there is an error in the data transmission process.
 

The CRC check subroutine in this system is as follows:
 

 

4 Computer software system design
 

The system's Database Server is designed using the visual programming language Visual Basic on the Windows operating platform. Visual Basic is an object-oriented visual rapid application development tool with the advantages of powerful functions, friendly interface, ease of use, and fast code execution. The system has functions such as data indexing, system settings, and reports. Depending on the patient's condition, the doctor can formulate different monitoring standards. Figure 3 is a screenshot of the system operation interface (including some experimental data).
 

 

5 Conclusion
 

The unattended ward monitoring system based on wireless radio frequency technology omits complex wiring and is easy to install, simple to operate, reliable in operation, with a low failure rate and easy to maintain. Once it enters the practical stage, it will save operating costs for hospitals, improve the quality of medical services and management level, and ultimately benefit patients and medical staff. This is of great significance for accelerating the process of intelligent construction of hospitals in my country.