What does GPRS in mobile phones mean?

gprs

1. The meaning of GPRS

GPRS is the abbreviation of General Packet Radio Service. It breaks through the GSM network and can only provide The circuit switching way of thinking only realizes packet switching by adding corresponding functional entities and partially transforming the existing base station system. The investment in this transformation is relatively small, but the user data rate obtained is considerable. GPRS (General Packet Radio Service) is a data transmission technology based on the Global Mobile Phone System (GSM), which can be said to be the continuation of GSM. GPRS is different from the previous continuous channel transmission method. It is transmitted in packet (Packet) mode. Therefore, the cost borne by the user is calculated based on the unit of transmitted data, rather than using the entire channel. In theory, it is cheaper.

Another feature of GPRS is that its transmission rate can be increased to 56 or even 114Kbps. Moreover, since the intermediary converters required for current wireless applications are no longer needed, connection and transmission will be more convenient and easier. In this way, users can connect to the Internet and participate in interactive communication such as video conferencing, and users on the same video network (VRN) can even continue to connect to the Internet without dialing up.

2. Characteristics of GPRS:

1. Application characteristics

At present, using mobile phones to access the Internet is still somewhat unsatisfactory. Therefore, the comprehensive solution GPRS came into being. This new technology allows you to connect quickly and conveniently at any time and anywhere, and at a very reasonable cost. Simply put: the speed has increased, the content has become richer, the applications have increased, and the cost has become more reasonable.

(1) High-speed data transmission

The speed is 10 times that of GSM, which can meet your ideal needs and can also stably transmit large-capacity high-quality audio and video files. Extraordinary and huge progress.

(2) Always online

Since it takes almost no time to establish a new connection (that is, there is no need to establish a call connection for each data access), you can stay connected to the network at any time For example, if there is no GPRS support, when you are roaming online and there is a call coming in at this time, in most cases you have to disconnect and then answer the call, and then dial back to the Internet after the call is completed. This is indeed very annoying for most people. With GPRS, you can easily resolve this conflict.

(3) Billing is based on data traffic only

That is, billing is based on the amount of data you transmit (such as when downloading information online), not based on the time you spend online. That is to say, as long as no data is transferred, you do not need to pay even if you are always "online". To use an analogy of "making a phone call", when using a GSM WAP mobile phone to access the Internet, it is like charging starts when the phone is connected; while using GPRE WAP to access the Internet is much more reasonable, just like there is no charge when the phone is connected, only when the conversation is connected. Just calculate the cost. In short, it truly embodies the principle of using less and paying less 2.

2. Technical characteristics

Data can be sent and received in groups, and billed according to traffic; 56~115Kbps Transmission speed.

Due to the use of "packet" technology, users can avoid the pain of disconnection when surfing the Internet (the situation is probably similar to using the download software NetAnts). In addition, the method of using GPRS to access the Internet is different from that of WAP. Using WAP to access the Internet is like surfing the Internet at home. You need to "dial-up" first, and then you cannot use the phone line at the same time after accessing the Internet. However, GPRS is superior. You can download data and make calls. performed at the same time. Technically speaking, voice transmission (i.e., calls) continues to use GSM, while data transmission can use GPRS. In this case, the application of mobile phones is raised to a higher level.

Moreover, the development of GPRS technology is also very "economical" because it only needs to use the existing GSM network for development. GPRS is used for a wide range of purposes, including sending and receiving emails through mobile phones, browsing on the Internet, etc.

Nowadays, the slogans for mobile Internet access are "always online" and "IP in hand". After using GPRS, data can be sent and received in groups, which also means that users are always online and billed according to traffic. Rapidly reduces service costs. For China Mobile/China Unicom's WAP tariff policy, which continues to be in a state of difficulty, if the CSD (circuit switched data, commonly known as dial-up data, the bearer method used for Eurasian WAP services) is changed to be implemented on GPRS, it means Dozens of people are forced to bear the cost of one person.

The biggest advantage of GPRS is that its data transmission speed is not comparable to that of WAP. The current transmission speed of the GSM mobile communication network is 9.6K bytes per second. When the GPRS mobile phone was launched at the beginning of this year, it had reached a transmission speed of 56Kbps, and now it has reached 115Kbps (this speed is twice the ideal speed of the commonly used 56Kmodem) . So please cherish the Nokia7110 and Motorola L2000 in your hands. I believe that when GPRS mobile phones are launched, they will all give way.

The biggest advantage of GPRS is that its data transmission speed is not comparable to that of WAP. The current transmission speed of the GSM mobile communication network is 9.6K bytes per second. When the GPRS mobile phone was launched at the beginning of this year, it had reached a transmission speed of 56Kbps, and now it has reached 115Kbps (this speed is twice the ideal speed of the commonly used 56Kmodem) .

GPRS uses packet switching for data transmission. Because it is packet switching, the utilization of network resources is greatly improved compared to circuit switching, and GPRS can transmit voice and data at the same time. Delivery, and billing can be calculated entirely based on the traffic generated. The existing WAP is carried by circuit switching (CSD). In the circuit switching mode, data and voice cannot be carried out at the same time, and the charging mode is also charged according to the time.

In fact, WAP itself is not comparable to GPRS in nature. The content on existing WAP can also be browsed and applied on GPRS, but GPRS makes the existing CSD WAP faster and more efficient. Convenient and more reasonable charges, the service content of WAP will also be greatly promoted and improved due to the technological progress of the network.

In the long run, WAP currently uses the GSM data service of CSD (Circuit Switched Data). In the future, WAP can also switch to using GPRS, a new GSM network, as the bearer method.

Therefore, GPRS will not replace WAP. To give a vivid example: GPRS and the current CSD GSM data service are both roads, while WAP is a car on the road. WAP is now driving on two lanes. , GPRS has improved the data transmission speed and is 8 lanes. It can be said that GPRS has enhanced the WAP business. The content on the existing WAP can also be browsed and applied through GPRS.

The application of GPRS will later cooperate with the development of Bluetooth (Bluetooth technology). By then, if a digital camera is equipped with bluetooth, it will be possible to immediately send photos to a distant place through a mobile phone. It only takes a quarter of an hour. It is cool enough. This day will not be far away from us.

3. Characteristics shown in the comparison between GPRS and GSM

Compared with GSM’s access speed of 9.6kbps, GPRS has an access speed of 171.2kbps; in terms of connection establishment time , GSM takes 10-30 seconds, while GPRS only takes a very short time to access the relevant requests; as for fees, GSM is billed by connection time, while GPRS only needs to be billed by data traffic; GPRS is The utilization rate of network resources is relatively much higher than that of GSM.

4. Scope corresponding to GPRS service characteristics

1. Mobile commerce

2. Mobile information service

3. Mobile Internet

4. Multimedia services

5. Technical advantages of GPRS

(1) Relatively low connection fees

High resource utilization In the GSM network, GPRS first introduced the packet-switched transmission mode, which fundamentally changed the GSM data transmission method that originally used the circuit-switched mode. This is particularly important when wireless resources are scarce. According to the circuit switching mode, during the entire connection period, the user will exclusively occupy the wireless channel regardless of whether to transmit data or not. During a session, many applications often have a lot of idle time, such as Internet browsing, sending and receiving emails, and so on. For packet switching mode, users only occupy resources during the period of sending or receiving data, which means that multiple users can efficiently share the same wireless channel, thereby improving resource utilization. The billing of GPRS users is mainly based on the amount of communication data, which embodies the principle of "pay what you get". In fact, GPRS users may have connection times of up to several hours while paying relatively low connection fees.

(2) High transmission rate

GPRS can provide a transmission rate of up to 115kbit/s (the highest value is 171.2kbit/s, excluding FEC). This means that within a few years, through portable computers, GPRS users will be able to browse the Internet as quickly as ISDN users, and it will also make some mobile multimedia applications that are sensitive to transmission rates possible.

(3) Short access time. Packet switching access time is shortened to less than 1. GPRS is a new GSM data service, which can provide wireless packet data access services to mobile users. GPRS mainly provides a connection between mobile users and remote data networks (such as supporting TCP/IP, X.25 and other networks), thereby providing mobile users with high-speed wireless IP and wireless X.25 services.

GPRS uses packet switching technology, which allows multiple users to share certain fixed channel resources. If all 8 time slots in the TDMA frame on the air interface are used to transmit data, the data rate can reach up to 164kb/8. The channel resources of the GSM air interface can be occupied by voice or GPRS data services. Of course, if there are sufficient channels, some channels can be defined as GPRS dedicated channels. To implement GPRS network, new network interfaces and communication protocols need to be introduced into the traditional GSM network. Currently, the GPRS network introduces GSN (GPRS Surporting Node) nodes. The mobile station must be a GPRS mobile station or a GPRS/GSM dual-mode mobile station.

According to the European ETSI's GSM Phase 2+ recommendations, GPRS is divided into two development stages (Phase 1 and Phase 2). The Phase l phase of GPRS will be able to support the following functions and services:

1.TCP/IP and X.25 services

2.New GPRS air interface encryption technology

3.GPRS additional services

4. Enhanced SMS services (E-SMs)

GPRS packet data charging function, that is, the above-mentioned charging is based on the amount of data. The most significant functional services are TCP/IP and X.25 functions. The GSM network can provide users with e-mail, WWW browsing, dedicated data, LAN access and other services through TCP/IP and X.25. The specifications of GPRS Phase 2 are still being formulated and will provide more new functions and services.

3. Application of GPRS

1. WAP application in GPRS

The combination of GPRS and WAP is currently the best way to take "mobile Internet access" to a new level. Best implementation plan: GPRS is a powerful bottom layer transmission, and WAP is a high-level application. If WAP is compared to a speeding vehicle, then GPRS is a wide and smooth highway, allowing you to roam freely in the wireless information world.

2. Applications on devices

GPRS can be implemented in a variety of devices besides cellular phones, including PCMCIA modems for laptops and extensions for personal digital assistants modules and laptops. Research in Motion (RIM), the manufacturer of the popular handheld e-mail device BlackBerry, is working with a GSM supplier called Microcell Telecommunications to study how to use GPRS for message transmission in other wireless systems.

3.GPRS business application

Since the first realization of text information transmission, wireless data applications have experienced leaps and bounds. Just look at the publicity of general packet wireless by well-known European and American manufacturers. The momentum of GPRS services seems to make people feel that the next generation of mobile data application era is coming. The general packet radio service GPRS, which will be launched at the end of 1999 or early 2000, is an important milestone towards the third generation of personal multimedia services. It will integrate mobile communications and data networks into one, allowing IP services to be introduced into the vast mobile market. . Although mobile data usage is currently relatively low, in some markets different user groups are growing rapidly, driven primarily by commercial markets adopting data services in the mobile space. Whether it is Ericsson, Nokia or Alcatel, almost all manufacturers promoting GPRS use the rapid growth of the commercial user market to lobby operators.

GSM system's packet mobile data communication (i.e. GPRS) is a basic packet wireless service. It adopts packet switching and has a data rate up to 164kb/. It can provide GSM users with high-speed data in a mobile environment. Business, it can also provide functions such as sending and receiving Email1 and Internet browsing.

(1) Business applications corresponding to the GPRS function

GPRS is a new GSM data service that can provide wireless packet data access services to mobile users. GPRS mainly provides a connection between mobile users and remote data networks (such as supporting TCP/IP, X.25 and other networks), thereby providing mobile users with high-speed wireless IP and wireless X.25 services.

GPRS uses packet switching technology, which allows multiple users to share certain fixed channel resources. If all 8 time slots in the TDMA frame on the air interface are used to transmit data, the data rate can reach up to 164kb/8. The channel resources of the GSM air interface can be occupied by voice or GPRS data services. Of course, if there are sufficient channels, some channels can be defined as GPRS dedicated channels.

To implement GPRS network, new network interfaces and communication protocols need to be introduced into the traditional GSM network. Currently, the GPRS network introduces GSN (GPRS SurportingNode) nodes. The mobile station must be a GPRS mobile station or a GPRS/GSM dual-mode mobile station.

According to the European ETSI's GSM Phase 2+ recommendations, GPRS is divided into two development stages (Phase 1 and Phase 2).

The Phase l phase of GPRS will be able to support the following functions and services:

TCP/IP and X.25 services

New GPRS air interface encryption technology

(2)GPRS additional services

Enhanced short message service (E-SMs)

GPRS packet data charging function, that is, based on the amount of data The most significant of the above functional services are TCP/IP and X.25 functions. The GSM network can provide users with e-mail, WWW browsing, dedicated data, LAN access and other services through TCP/IP and X.25.

The specifications of GPRS Phase 2 are still being formulated, and it will provide more new functions and services.

4. GPRS related technologies

1. GPRS technology embodiment

GPRS general wireless packet service is a wireless packet switching technology based on the GSM system, providing End-to-end, wide-area wireless IP connectivity. In layman's terms, GPRS is a high-speed data processing technology that transmits data to users in the form of "packets". Although GPRS is a transitional technology for the evolution of existing GSM networks to third-generation mobile communications, it has significant advantages in many aspects. At present, Hong Kong, as the first region to conduct GPRS field testing, has achieved good results.

Due to the use of "grouping" technology, users can avoid the pain of disconnection when surfing the Internet (the situation is probably similar to using the download software NetAnts). In addition, the method of using GPRS to access the Internet is different from that of WAP. Using WAP to access the Internet is like surfing the Internet at home. You need to "dial up" first, and then you cannot use the phone line at the same time. However, GPRS is superior. You can download data and make calls. performed at the same time. Technically speaking, voice transmission (i.e. calls) continues to use GSM, while data transmission can use GPRS. In this case, the application of mobile phones is raised to a higher level. Moreover, the development of GPRS technology is also very "economical" because it only needs to use the existing GSM network for development. GPRS is used for a wide range of purposes, including sending and receiving emails through mobile phones, browsing on the Internet, etc.

Nowadays, the slogans for mobile Internet access are "always online" and "IP in hand". After using GPRS, data can be sent and received in groups, which also means that users are always online and billed according to traffic. Rapidly reduces service costs. For China Mobile/China Unicom's WAP tariff policy, which continues to be in a state of difficulty, if the CSD (circuit switched data, commonly known as dial-up data, the bearer method used for Eurasian WAP services) is changed to be implemented on GPRS, it means Dozens of people are forced to bear the cost of one person.

The biggest advantage of GPRS is that its data transmission speed is not comparable to WAP. The current transmission speed of the GSM mobile communication network is 9.6K bytes per second. When the GPRS mobile phone was launched at the beginning of this year, it had reached a transmission speed of 56Kbps, and now it has reached 115Kbps (this speed is twice the ideal speed of the commonly used 56Kmodem) . So please cherish the Nokia7110 and Motorola L2000 in your hands. I believe that when GPRS mobile phones are launched, they will all give way.

2. Packet technology

The so-called Packet is to encapsulate Date into many independent packets, and then transmit these packets one by one. The form is somewhat similar. When sending packages, the advantage of using packet switching is that the bandwidth will only be occupied when there is data that needs to be transmitted, and the price can be calculated based on the amount of data transmitted. This is a more reasonable billing method for users, because things like the Internet Most of the time bandwidth for data transmission is indirect.

In addition, in the GSM phase 2 standard, GPRS can provide four different encoding methods, and these encoding methods also provide different error protection capabilities. The transmission rates provided by each time slot using four different encoding methods are CS-1 (9.05K), CS-2 (13.4K), CS-3 (15.6K) and CS-4 (21.4K), among which CS-1 is the most heavily protected, while CS-4 is completely unprotected. Each user can use up to eight time slots at the same time, so GPRS claims a maximum transmission rate of 171.2K.

3. GPRS network structure

The GPRS network is implemented based on the existing GSM network. Some nodes need to be added to the existing GSM network, such as GGSN (Gateway GPRS Supporting Node) and SGSN (Serving GSN).

The GPRS network reference model is shown in Figure 1. GSN is the most important network node in the GPRS network. GSN has a mobile routing management function, which can connect to various types of data networks and can be connected to GPRS registers. GSN can complete data transmission and format conversion between mobile stations and various data networks. GSN can be an independent device similar to a router, or it can be integrated with the MSC in GSM.

There are two types of GSN: one is SGSN (Serving GSN, serving GSN), and the other is GGSN (GatewayGSN, gateway GSN). The main function of SGSN is to record the current location information of the mobile station. And complete the sending and receiving of mobile packet data between the mobile station and GGSN. GGSN mainly functions as a gateway. It can connect to a variety of different data networks, such as ISDN, PSPDN and LAN. In some literature, GGSN is called GPRS router. GGSN can perform protocol conversion on GPRS packet data packets in the GSM network, so that these packet data packets can be transmitted to the remote TCP/IP or X.25 network.

In addition, some manufacturers have proposed the concept of GR (GSMRegister, GPRS database). GR is similar to HLR in GSM and is a GPRS business database. It can exist independently or coexist with HLR, and is implemented by a server or program-controlled switch. The name GR is not specifically mentioned in ETSI's recommendations.

The following new network interfaces have also been introduced in the GPRS network structure:

Gn, GSN backbone network interface, used between various GSNs

Gb, Interface between BSS and sGsN.

Gr, the interface between SGSN and HLR.

Gp, the interface between different GSM networks (different PLMNs).

Gs, the interface between SGSN and MSC.

4.GPRS protocol model

The Um interface is the air interface of GSM. The communication protocol on the Um interface has five layers, from bottom to top: physical layer, MAC (Mdium AccessControl) layer, LLC (Logical Link Control) layer, SNDC (Subnetwork Dependant Convergence) layer and network layer.

The physical layer of the Um interface is the radio frequency interface part, and the physical link layer is responsible for providing various logical channels of the air interface. The carrier frequency bandwidth of the GSM air interface is 20OkHz, and one carrier frequency is divided into 8 physical channels.

If all 8 physical channels are allocated to transmit GPRS data, the original data rate can reach 20Okb/s. Considering the overhead of the forward error correction code, the final data rate can reach about 164kb/s.

MAC is the media access control layer. The main function of MAC is to define and allocate GPRS logical channels on the air interface so that these channels can be shared by different mobile stations. There are three types of logical channels in GPRS, namely public control channels, packet service channels and GPRS broadcast channels. The public control channel is used to transmit control signaling for data communication, and is specifically divided into paging and response channels. Packet traffic channels are used to transmit packet data. The broadcast channel is used to send network information to mobile stations.

The LLC layer is the logical link control layer. It is a wireless link protocol based on the high-speed data link protocol HDLC. The LLC layer is responsible for forming the LLC address and frame fields on the SNDC data unit of the high-level SNDC layer to generate a complete LLC frame. In addition, LLC can realize point-to-multipoint addressing and data frame retransmission control.

The LLR layer in BSS is the logical link delivery layer. This layer is responsible for transmitting LLC frames between the MS and SGSN. The LLR layer is transparent to the SNDC data unit, that is, it is not responsible for processing SNDC data.

SNDC is called the subnet dependency binding layer. Its main function is to complete the grouping and packaging of transmitted data, and to determine the TCP/IP address and encryption method. At the SNDC layer, the data transmitted between the mobile station and the SGSN is divided into one or more SNDC data packet units. The SNDC data packet unit is generated and placed into the LLC frame.

The network layer protocols are currently mainly TCP/IP and L25 protocols provided in Phase

Phase l. TCP/IP and X.25 protocols are transparent to traditional GSM network equipment (such as BSS and NSS equipment).

5. GPRS routing management

GPRS routing management refers to how the GPRS network addresses and establishes data transmission routes. The routing management of GPRS is reflected in the following three aspects: the establishment of routes for the mobile station to send data; the establishment of routes for the mobile station to receive data; and the establishment of data routes when the mobile station is roaming.

For the first case, path 1 in Figure 3 is shown. When the mobile station generates a PDU (packet data unit), this PDU is processed by the SNDC layer and is called an SNDC data unit. It is then processed by the LLC layer and sent to the SGSN where the mobile station is located in the GSM network through the air interface. SGSN sends the data to GGSN. GGSN deassembles the received messages, converts them into a format that can be transmitted in the public data network (such as PDU of PSPDN), and finally sends them to users of the public data network. In order to improve transmission efficiency and ensure data transmission security, data on the air interface can be compressed and encrypted.

In the second case, a public data network user transmits data to a mobile station. First, the route between the data network and the GGSN is established through the standard protocol of the data network. The data unit (such as PDU in PSPDN) sent by the data network user is sent to the GGSN through the established route. The GGSN then sends the PDU to the SGSN where the mobile station is located. The GSN encapsulates the PDU into an SNDC data unit, and then processes it into an LLC frame unit through the LLC layer, and finally sends it to the mobile station through the air interface.

The third situation is that a data network user transmits data to a roaming mobile user. The data must pass through the home GGSN and then be sent to mobile user A. Channel composition of air interface The channel composition of GPRS air interface is as follows:

PDTCH (Pachet Data Traffic Channel 1), packet data service channel. This channel is used to transmit GPRS packet data on the air interface.

PPCH (Packet Paging Channel1), the packet paging channel PPCH is used to page GPRS called users.

PRACH (Packet Randem Access Channel), packet random access channel. GPRS users send channel requests to the base station through PRACH.

PAGCH (Packet Access Grant Channel), packet access response channel. PAGCH is a response channel that responds to PRACH.

PACCH (Packet Asscrchted ControlChannel), packet associated control channel. This channel is used to transmit signaling to implement GPRS data services.

According to the European ETSI's GSM2 phase recommendations, GPRS can be divided into two development stages (Phase1 and Phase2).

The Phase1 phase of GPRS can support the following functions and services:

TCP/IP and X.25 services;

New GPRS air interface encryption technology;

GPRS additional services;

Enhanced SMS service (E-SMS);

GPRS packet data charging function, that is, charging is based on the amount of data.

The most significant of the above functions are the TCP/IP and X.25 functions. The main application of GPRS is concentrated in the field of "mobile office". The mobile office should be able to support any traditional Internet-based applications, such as file transfer, personal organizer, sending and receiving emails, and surfing the Internet using the World Wide Web.

6. GPRS service technology

According to the European ETSI's GSM2 phase recommendations, GPRS can be divided into two development stages (i.e. Phase1 and Phase2).

The Phase1 phase of GPRS can support the following functions and services:

TCP/IP and X.25 services;

New GPRS air interface encryption technology;

GPRS additional services;

Enhanced SMS service (E-SMS);

GPRS packet data charging function, that is, charging is based on the amount of data.

7. GPRS and IP

The introduction of GPRS technology organically connects telecommunications networks and computer networks and develops towards the future all-IP network platform.

It can be seen from the GPRS structure that the connection between the base station and the SGSN equipment is generally connected through frame relay, and the connection between the SGSN and GGSN equipment is through the IP network.

GGSN can use a router with NAT (Network Address Translation) function to perform the conversion between internal IP address and external network IP address. MS can access the internal GPRS network or through APN (external network access point name). ) to access external PDN/Internet networks.

In identifying GPRS devices, such as mobile phones, the MS identification needs to be assigned an IP address in addition to the IMSI, MSISDN and other numbers used in GSM. The identification of network element equipment SGSN and GGSN has both the No. 7 signaling address and the IP address of the data GGSN. The communication between GSNs (SGSN or GGSN) uses IP addresses, while the communication between GSN and MSC, HLR and other entities uses 7 Signaling address. In the GPRS system, there are two important databases to record information. One is the user mobility management context, which is used to manage the location information of the mobile user. The other is the user's PDP context (packet data protocol context), which is used to manage the communication from the mobile phone MS to the gateway GGSN and to the ISP (Internet service provider). data routing information between

When the MS accesses the GPRS internal network or the external PDN/Internet network, the MS sends an activation PDP context request message to the SGSN. The MS can contract with the operator to select the GGSN for fixed services. Or according to the APN selection rules, the SGSN selects the GGSN to serve, and the SGSN sends a PDP context establishment request message to the GGSN. The GGSN allocates an IP address (static or dynamic, public or private) to the MS. During the process of establishing the PDP context, the user's identity and required service quality need to be authenticated and demonstrated. After the PDP context is successfully established and activated, the MS , SGSN and GGSN all store the user's PDP context information. With the user's location information and data routing information, the MS can access the resources of the network. With the advent of the second-generation semi-product GPRS, some new concepts will be encountered when developing and deploying GPRS services.