Comparison between CDMA and GPRS

The development of mobile communication technology has gone through three stages, that is, the industry called Three generations, the first generation is analog wireless network such as amps, TACs, the second generation is digital communication, including GSM, CDMA, the third generation is the packet-type mobile service, referred to as 3G. As mankind entered the 20th century, the third generation of mobile communication technology and users will be a rapid development. According to the industry, users of the wireless network in 5 years will exceed the number of people using fixed-line internet.

The third generation mobile communication currently has two main mainstream technology directions. One of them is the CDMA2000 technology evolved from the second-generation Cdmaone, Cdmaone Mobile communication network has been widely used in North America, South Korea and Hongkong. May 2001 China Unicom adopted the enhanced Cdmaone technology in China to build a comprehensive mobile communication network. CDMA2000 and Cdmaone air channels have the same chip rate, backward compatible cdmaone systems that can be upgraded from cdmaone to smooth. The route of its evolution is Cdmaone--cdma20001x--cdma20001xev. Another mainstream of the third generation of communication technology is the second generation of GSM standard developed by the WCDMA technology, because GSM uses TDMA (time division Multiple Access) modulation mode, and WCDMA uses CDMA (Code Division Multiple Access) modulation, its air channel is not compatible, Using the machine station stacking and the way of using multimode mobile phone to be backward compatible with GSM system, the route of its evolution is GSM--GPRS--EDGE--WCDMA. At present, mobile communication technology is basically mature cdma20001x and GPRS system, both can achieve high-speed packet 3G data service, but from the air channel modulation, core access network and end users and other aspects of comparison, there is a fundamental difference between the two.

GPRS (General Packet Radio System), a generic wireless packet service, is a technology between the second and third generations, often called 2.5G, which is currently implemented by upgrading the GSM network. Called 2.5G is also more appropriate, because it is a hybrid, the use of TDMA transmission of voice, the use of packet transmission data. GPRS uses the channel bundle and enhances the data rate improvement realizes the high speed access, the Air channel encoding technology which uses in the GPRS basically resembles the second generation GSM, for the service channel may choose different coding scheme according to the channel quality (CS-1 to CS-4), Each time slot can reach a data rate of one of these four types. By calculation, in the case of a very good channel environment, if the 8-time channel bundle is used to transmit a user's business data, the highest physical frame data rate in the air is 21.4 * 8 = 171.2Kbps, which is the theoretical transmission of the highest value, when the air does not use error-correcting code, at this time almost no anti-interference ability. Because there are some overhead bits in the aerial data frame, the GPRS design can increase the transmission rate of each channel to 14.4Kbps, so the maximum rate of GPRS is 8x14.4=115.2kbps. Because of the channel bundle modulation mode, the equivalent of a maximum rate of GPRS data user is equivalent to occupy 8 voice users of the air channel capacity. The second step of GPRS development is to increase the rate of each channel to 48Kbps by enhancing the data rate improvement (EDGE), so the second generation Gprs--edge design rate is 384Kbps. (Learn computer)

Cdma20001x is the first phase of CDMA2000, fully compatible with the IS-95 of the third generation mobile communication system, its air interface standards in accordance with the EIA/TIA/IS-2000 protocol, using Code Division and Frequency Division combination of multiple access technology. The modulation mode supported by the CDMA2000 1x Air channel is greatly enhanced on the basis of compatible cdmaone, and the wireless Configuration 1 and 2 (RC1 and RC2) are corresponding to the Cdmaone channel respectively, and have complete backward compatibility. For different environments, different high-speed air channel rates can be used for data transmission. The maximum transmission rate of a single aerial channel used to transmit packet data can reach 307.2Kbps. For the forward channel aerial theory the highest rate of 9.6k + 307.2k = 316.8Kbps, the reverse air theory highest rate of 9.6k + 153.6k = 163.2Kbps, fully reached the IMT-2000 data standard, is the real meaning of the third generation mobile communication system. Due to the current wireless chip processing capacity limitations, the actual use of the front reverse transmission maximum rate of 163.2Kbps, excluding the overhead bit, the actual air traffic measured in the highest transmission rate of about 150Kbps. And because of the wide use of cdma20001x, efficient aerial coding method, diversity receiving technology and fast power control technology, the modulation and demodulation gain of the channel is increased while the interference to other users is reduced. The spectrum utilization of CDMA2000 is increased by one times on the basis of IS-95, which guarantees the support of many high-speed data users without reducing the number of the original voice users, and because the CDMA has soft switching function, it can ensure the data service more stable transmission.

From the contrast of air channel, it can be found that the GPRS system realizes the transmission of high speed Channel only through the way of channel bundle, and does not improve the capacity of the system fundamentally. The CDMA2000 system is based on the IS-95 to achieve a higher than the GPRS packet data Services, and the capacity of the system has been further increased, which actually fundamentally guarantees the upgrade from the IS-95 system to the CDMA2000 system while reducing the cost of the channel, At the same time, you can support more mobile users within a limited frequency range to achieve a higher return on investment. Some professionals have done the calculation, in the same environment for data communication, per megabyte information if the cost of using CDM a20001x is less than 6 cents renminbi, and the cost of using GPRS is about 3. 5 Yuan. That is, if a consumer uses 200 megabits of information for one months, the cost of the CDM A2000 1X carrier 96?12 Yuan will be consumed, while GPRS operators will spend 670 yuan. Cost to a certain extent determines the price, the cost of operators will eventually be passed on to consumers.

At present, GPRS's core network is to introduce two new network nodes in GSM network structure, they are GPRS Gateway support node GGSN (Gateway GPRS supporting node) and GPRS service support nodes SGSN (service GPRS Supporting Node), there is also a need to increase the Group control Unit (PCU) at the machine station side (Packet). GPRS system adopts the Protocol of Special development, which realizes Internet network access and support mobile station mobility.

The same cdma20001x core network enables high-speed Internet access and supports mobility of mobile stations by increasing the packet Data Service node PDSN (Packet data serving nodes) and the home agent ha (native agent). The advantage of GPRS is that CDMA2000 adopts the IETF standard IS-835 wireless IP network, which is the same as the standard of the existing Internet, so the interface is open, it can make the transition to the whole IP network more convenient and guarantee the investment of the operators. and can provide mobile IP, simple IP, VPN, data bursts and many other data services, and can be more convenient to connect with the Internet.

In the system commercialization aspect, because cdma20001x is based on the commercial mature Cdmaone technology, the system evolution upgrades the technical risk is small, the cost is low. October 2000, fresh Beijing Telecom (SKT) launched the world's first commercial CDMA 20001X service system, transmission rate of up to 150kbps, exceeding the IMT-2000 specified 144kbps transmission standards. April 2001, LG Telecom also launched the CDMA20001X service. Meanwhile, operators in Asia, Latin America and North America have also indicated plans to launch cdma20001x business services by the end of this year. Compared with the GPRS because of the immature technology, the lack of ancillary business, many operators in the busy network upgrade at the same time, had to delay the launch of GPRS business service schedule. Vodafone's planned launch of the GPRS business service This April has been postponed. In addition, GPRS service and the existing GSM services share the same bandwidth. According to estimates, China Mobile GSM network bandwidth can only support 100 million users, if again with GPRS points and use, already congested GSM network can be overwhelmed?

For the majority of mobile users are of course the most concerned about the use of the terminal, because the cdma20001x air channel capacity is superior to GPRS, and improve the capacity of the system, but also determines the cdma20001x mobile users can get faster Internet access speed, And in the peak of traffic can also be a faster rate of browsing the network. Because the CDMA20001X system is compatible with the Cdmaone system, it means that cdma20001x users can make voice calls in the Cdmaone system without an upgrade, and Cdmaone users can roam through the upgraded CDMA system without hindrance. For GPRS users, the need to support the GPRS and GSM dual-mode terminals in the GPRS and GSM network roaming.

In short, cdma20001x in the Air channel and core network technology than GPRS has a greater advantage, to maximize the use of sophisticated technology, relatively low technical complexity, small risk, System evolution and upgrade the cost is lower, with a complete system forward and backward compatibility, This brings more convenience to the end user. Currently, the CDMA20001X system has been successfully applied commercially in many countries. Therefore, the cdma20001x is an important step in the smooth transition of the second generation to the third generation mobile communication system, and it is the inevitable trend of 3G construction.