Comparison between digital radio and GPRS

1、 Overview

With the development of network technology, private network has also attracted more and more attention. But what kind of method should be adopted when setting up a private network! Now let's make a comparison between digital radio and GPRS.

1.GPRS

GPRS is the English abbreviation of general packet radio service. It is a new bearer service developed from the existing GSM system. Its purpose is to provide GSM users with packet data service. GPRS adopts the same wireless modulation standard, the same frequency band, the same burst structure, the same frequency hopping rules and the same TDMA frame structure as GSM. This new packet data channel is very similar to the current circuit switched voice service channel. Therefore, the existing base station subsystem (BSS) can provide comprehensive GPRS coverage from the beginning. GPRS allows users to send and receive data in end-to-end packet transfer mode without using the network resources of circuit switching mode. Thus, an efficient and low-cost wireless packet data service is provided. It is especially suitable for intermittent, sudden, frequent and small amount of data transmission, as well as occasional large amount of data transmission. The theoretical bandwidth of GPRS can reach 171.2kb/s, and the actual application bandwidth is about 0 ~ 70kb / s. TCP / IP connection is provided on this channel, which can be used for Internet connection, data transmission and other applications. GPRS is a new mobile data communication service, which provides a connection between mobile users and data network and provides high-speed wireless IP for mobile users.

GPRS adopts packet switching technology. Each user can occupy multiple wireless channels at the same time, and the same wireless channel can be shared by multiple users. Resources are effectively utilized, and the data transmission rate is as high as 160kbps. GPRS technology is used to send and receive data packets. Users are always online and charged according to traffic, which quickly reduces the service cost. GPRS mobile data transmission system has a wide range of applications, and almost all low and medium speed data transmission services can be applied, such as urban distribution network automation, tap water, gas pipeline automation, commercial POS machine, Internet access, personal information, stock information, finance, transportation, public security and so on. In addition to supporting traditional Internet applications, GPRS can also enable wireless terminals to support B2B and B2C e-commerce and e-payment, stock trading, bank transfer and other applications.

GPRS can also be applied to the company's intranet. The remote LAN access based on IP makes the wireless terminal an extension of LAN. GPRS technology can be applied to provide a virtual private data communication network with high-speed, always online and transparent data transmission. Mainly for the applications of power system automation, industrial monitoring, traffic management, environmental protection, finance, securities and other departments, the GPRS network platform is used to realize the transparent transmission of data information. At the same time, considering the networking needs of various application departments, the virtual data private network is realized in the network structure.

2. Digital radio

Computer automation SCADA (supervisory control and data acquisition) technology, also known as computer four remote (telemetry, remote signaling, remote control and remote adjustment) technology, is a computer-based production process control and dispatching automation system. It can monitor and control the remote field operation equipment to realize the functions of remote data acquisition, equipment control, measurement, parameter adjustment and various signal alarms. Digital radio station adopts digital signal processing, error correction coding, software radio, digital modulation and demodulation, surface mount integrated design and other technologies, which has the characteristics of high performance, high reliability and strong anti-interference ability. The radio station provides standard 232 data port, which can be directly connected with computer, RTU, PLC, GPS receiver, digital camera and data terminal, with a transmission rate of 19200bps, The bit error is lower than 10e-6 (when the receiving level is - 110dbm), the transmission power is adjustable from 0.5 to 25 watts, any type of radio station can be set as the master station or remote station, and the non transfer communication distance is more than 50km, which can adapt to the harsh indoor or outdoor working environment. The radio station is compatible with data and voice. It can work in simplex, half duplex, time division duplex TDD and full duplex mode, transmit and receive the same frequency or different frequency transfer network, and has the functions of remote diagnosis, testing and supervision, so as to meet the data collection and control between the dispatching or control center of various industries and many remote stations.

2、 Performance characteristics

1.GPRS

The main functions of GPRS DTU are easy to use, flexible and reliable. It supports dual band GSM / GPRS. It complies with ETSI GSM phase 2 + standard. The data terminal is always online. The real-time clock supports A5 / 1 & A5 / 5 encryption algorithm enhancement. It supports transparent data transmission and protocol conversion. It supports virtual data private network. It supports point-to-point, point to multipoint The center supports RS-232 / 485 interface for multi-point peer-to-peer data transmission, short message data standby channel (option), audio interface, convenient maintenance, operating system configuration and maintenance interface, air software upgrade and remote maintenance (option) self diagnosis and alarm output anti-interference design, moisture-proof design for application requirements in harsh electromagnetic environment, and outdoor application

2. Digital radio

Performance features: 9600 / 19200bps data throughput, temperature and power supply | voltage regulator are widely used in common frequency bands all over the world. The radio station software can be upgraded to directly start the transmission of data. Transparent data transmission outputs the external device control signal tail noise pulse suppression carrier detection signal for carrier wave collision detection. Frequency synthesis and simplex half duplex mode are used, The bandwidth occupied by the channel is 12.5/25khz, the same frequency and different frequency transmission is transparent RS-232, the port rate of db-25 hole is 1200 ~ 38400bps, the air rate is 9600bps, and the data delay is < 2S

3、 Application field.

Data transmission radio is widely used in the construction of special network in the field of industrial control. At present, it is still the main transmission means in the field of industrial control. The National Radio Regulatory Commission has defined the 223.025 ~ 235.000mhz frequency band as the special frequency band for telemetry, remote control, data transmission and other services. As the special equipment of this special frequency band, data transmission radio has experienced decades of tests in the application of private network. The difference between digital radio and conventional transmission equipment is that it has been unattended for a long time, and the working environment is very complex. Many equipment are placed in the field, the power supply is unstable, and the temperature difference changes greatly. Therefore, the requirements for product structure, technical indicators and environmental indicators of data transmission radio station are much higher than those of conventional data transmission equipment. It is mainly reflected in the following aspects:

1. The data transmission station has high reliability and high frequency stability, and the transmission bit error rate (BER) should be low. Bit error rate is an important index for calculating reliability. The bit error rate of data transmission radio communication system is 0.0000001;

2. The equipment has strong anti-interference ability and good heat dissipation, can adapt to long-term work in harsh environment and electromagnetic environment, and its working temperature range is wide;

3. During operation, the waiting current is small, the power consumption is low, the power consumption is low, the working voltage range is wide, and there is reverse connection protection of power supply. It can adapt to AC, DC, battery, solar cell and other power supply modes;

4. The transmitting and receiving conversion time of data transmission station is generally less than 40 ms.

With the continuous progress of GPRS technology, the technical indicators of data transmission radio will also be improved, the volume of equipment will become smaller, the stability and reliability will be higher, the working range will be wider, the waiting current will be lower, and the transceiver conversion time will be shorter.

It uses GSM technology and hardware facilities to access the Internet for network transmission. It is mainly used in public network users with small amount of data and low real-time requirements, such as browsing web pages with laptops. To carry out data transmission service, GPRS must first make a signal in line with GSM network protocol, and then access the Internet through modulation. Of course, the data also needs two demodulations at the other end to reach the terminal. As we all know, GSM network and Internet network are relatively large public transmission networks. GPRS data will inevitably cause high bit error rate after two complex modulation and demodulation. Moreover, due to the uncontrollability of the public network, GPRS has a very large data delay, and there are frequent drops, long dialing time and even inability to dial up.

3、 Operating costs

1. GPRS GPRS charges according to data flow. The charging policies of different places may be different. Please contact the local mobile communication department. At present, the charging methods of communication expenses in Hebei Province include:

1.1. The slave station will charge 20 yuan / 50m per point and the master station will charge 100 yuan / 800m per month.

1.2. The communication bandwidth provided shall not be less than 30kbit / s.

1.3. The excess part of each site shall be charged at 0.03 yuan / KB.

2. Digital radio

2.1 wireless data frequency band 1000 yuan / frequency point / base station (unified standard of the national non Commission)

4、 Equipment cost

The cost of digital radio equipment is about 3000-5000 yuan, and the cost of GPRS equipment is about 1000-1500 yuan.

GPRS advantages

1. Good real-time response and processing ability. Compared with short message service, GPRS has real-time online characteristics and the system has no time delay. The system can receive and process various data of multiple / all monitoring points in real time at the same time. It can synchronize the clock of monitoring points without round robin, which can well meet the requirements of the system for real-time data acquisition and transmission.

2. Remote instrument and equipment control: due to the use of GPRS two-way transmission system, the monitoring center can reverse the time correction, status report, switch and other monitoring and control functions of instruments and equipment;

3. Low construction cost: the existing GSM network can be fully utilized, and the equipment can be connected immediately after installation. When using ultrashort wave communication, the on-site environment needs to be fully considered, and auxiliary equipment such as antenna iron frame needs to be equipped.

4. Simple installation and commissioning, short construction period: using the existing mature GSM network, the system basically does not need debugging when it is put into operation, and the installation is simple. When using ultrashort wave communication, the installation and commissioning workload is large. First, carry out on-site signal test, antenna iron frame erection, antenna direction and angle commissioning, etc.

5. Wide coverage. The construction of dispatching monitoring system requires wide data communication coverage, unlimited capacity expansion and unlimited access location, which can meet the access needs of mountainous areas, towns and cross regions. Due to the large number of monitoring points, they are distributed throughout the city, and some pipe network monitoring points are located in remote areas with scattered geographical locations. Ultrashort wave communication mode is adopted, and the coverage is only more than 30 kilometers; Using GPRS, in theory, monitoring can be realized within the coverage of wireless GSM / GPRS network.

6. High data transmission rate. In theory, the transmission rate of GPRS network can reach 171.2kbit/s. In practical application, the data transmission rate is about 40kbps. At present, the transmission rate of general ultrashort wave data transmission stations is mostly 2.4kbit/s or lower.

7. The transmission capacity of the system is large. The monitoring center station shall be connected with each monitoring point in real time. Due to the large number of monitoring points, the system is required to meet the needs of sudden data transmission, and GPRS technology can well meet the needs of sudden data transmission.

8. Low communication cost. Since GPRS adopts monthly billing, the operation and maintenance cost is low.