Comparison of Cdmais95a/b and cdma20001x

CDMA was proposed by Qualcomm in the early 90, and IS-95 is the first standard to be released in the Cdmaone series, and the first CDMA standard that is really widely used globally is is-95a, on the basis of is-95a, Also published separately to support the 13K Voice Encoder TSB74 Standard, support 1.9GHz CDMA PCs system STD-008 standard, support 64kbit/s data service is-95b.

When the ITU solicited the third generation mobile communication wireless candidate technology, IS-95 due to commercial success, the United States TR45 Standards Committee did not devote much effort to the study of the three-generation standards, but was trying to complete the is-95b standards, at the request of the ITU, Hastily in the year put forward the third generation standard of cdma2000, namely cdma2000 1X and 3X (1 x represents its carrier one times the bandwidth of is-95a, 3X represents its carrier three times times the bandwidth of is-95a), 3 x is divided into downlink direct spread spectrum and three carrier two ways, Later, the direct spread spectrum CDMA2000 part and WCDMA Fusion, so in fact the current cdma2000 only includes CDMA2000 1X and three carrier mode 3X.

Since 1X uses exactly the same technology as 3X, the volume of voice or data traffic per MHz is basically the same, and 1X backlinks are fully compatible with is-95a and is-95b. At present, Qualcomm Company has made the is-95a, is-95b, cdma2000 1X fully compatible cell phone and base station dedicated chip, and the chip's PIN definition and the previous chip is fully consistent, in this case, is-95a operators are currently very optimistic about CDMA2000 1X, because cdma2000 3X and cdma2000 1X, the only advantage is the increase in data capabilities, so the IS-95 operator organization is now working to promote the CDMA2000 1X continue to improve, It is hoped that with the continued use of 1.25 MHz bandwidth to enable the data business capacity to meet the ITU-mandated third-generation business rate standard of 2 mbit/s or more, the United States Standardization Committee is called the CDMA2000 1X Enhanced Technology Unified CDMA2000 1X EV. Once the CDMA2000 1X EV technology achieves the desired results in practical applications (that is, the ITU requirements for third-generation business), the operator will not consider CDMA2000 3X for a long time. The evolution direction of the CDMA2000 1X EV currently consists of two branches: branches that support data services only and branches that support both data and voice, and only the technology that supports data services is single, and currently only HDR presented by Qualcomm, There are several existing proposals for supporting both data and voice branches, including a technical LAS-CDMA currently submitted by our country, which are currently in the process of being reviewed. The comparison of is-95a and CDMA2000 1X is shown in table 1. (Computer science)

I. Evolution of IS-95 to CDMA2000 1X

The difference between is-95b and is-95a is that multiple channels can be bundled. When the secondary business channel is not used, is-95b and is-95a are basically the same and can coexist in the same carrier. CDMA2000 1X has improved significantly, CDMA2000 and IS-95 are distinguished by different wireless configurations (RC). The CDMA2000 1X system device can be installed with RC, while supporting both 1X terminals and is-95a/b terminals. Therefore, is-95a/b/1x can exist in the same carrier simultaneously. For CDMA2000 systems, the transition from 2G to 3G can take the form of gradual substitution. That is, the compression of a 2G system of a carrier, converted to 3G carrier, began to provide users with the high rate of business. This operation is completely transparent to the user, because the IS-95 user can still work in 3G carrier, so the number of users in the 2G carrier has not increased, and will not increase the loss. With the increase in the number of users in 3G system, we can gradually reduce the carrier used by 2G system and increase the carrier of 3G system. In this way, can solve the problem of network upgrade, network operators through this smooth upgrade, not only to provide users with a variety of the latest business, but also a good protection of existing equipment investment.

In the process of evolution to the third generation, the problems needing attention are the evolution of wireless devices such as BTS and BSC. In the development of CDMA2000 standards, has been fully considered to protect the operator's investment, many wireless indicators in the 2G and 3G are the same. For BTS, RF parts such as antennas, RF filters and power amplifiers can be the same, while baseband signal processing must be replaced.

Second, the main characteristics of CDMA2000 1X

The main difference between the CDMA2000 and the IS-95 system is that the channel type and the modulation of the physical channel are enhanced to adapt to more and more complex third-generation business. The following is mainly about the channel type and modulation technology of CDMA2000 1X.

(i) CDMA2000 1X channel type

CDMA2000 1X System, although due to IS-95, but performance than IS-95 enhanced a lot of cdma2000 1X main channel types include:

1. Reverse Channel

(1) Reverse-guided channel

The Anti-guide channel is an not modulated spread spectrum signal transmitted by a mobile station, and its main function is to assist the base station to carry on the correlation detection. The wireless configuration of the reverse guidance channel in the enhanced access channel, the reverse public control channel and the reverse service channel is launched from 3 to 6 o'clock. The reverse-guided channel is also launched in the enhanced access channel prefix, the reverse public control channel prefix, and the reverse service channel prefix.

(2) Access channel

The Access channel transmits a coded, interlaced and modulated spread spectrum signal. The main function of the mobile station is to initiate communication with the base station or to respond to the paging channel message from the base station. The access channel is uniquely identified by its common long code mask. The access channel consists of an access test, and an access test consists of an access prefix and a series of access channel frames.

(3) Strong access channel

The enhanced access channel is used for mobile station initial access base station or response Mobile station instruction message, which may be used in the following three kinds of access modes: Basic access mode, power Control access mode and standby access mode. The power Control access mode and standby access mode can work in the same enhanced access channel, while the basic access mode needs to work in a separate access channel. Compared with the access channel, the enhanced access channel has the parallel reverse guide channel in the data part after the access prefix, and can carry on the correlation demodulation, making the reverse access channel data demodulation easier.

When working in basic access mode, the mobile station does not launch the enhanced access header on the enhanced Access channel, and the enhanced access test will consist of the access channel prefix and the enhanced access data; When working in the power Control access mode, the enhanced access test of Mobile station is composed of access channel prefix, enhanced access header and enhanced access data. When working in standby access mode, the enhanced access test launched by mobile station is composed of access channel prefix and enhanced access header. Once the base station is received, the enhanced access data is sent on the reverse public control channel.

(4) to the public control channel

This channel is when a reverse business channel is not used, and the mobile station launches user control information and signaling information to the base station at a time period specified by the base station. The reverse public control channel may be used in two kinds of access modes: Standby access mode and finger-fit access mode. The reverse public control channel transmits a coded, interlaced and modulated spread spectrum signal. The channel is uniquely identified by a long code.

(5) to the dedicated control channel

This channel is used for a mobile station to transmit the user's specific user information and signaling information to the base station during the call process. A reverse-specific control channel can be included in the reverse traffic channel.

(6) to the basic channel

The reverse basic channel is used for mobile station to transmit user information and signaling information to the base station during the call process, and the reverse service channel can contain a basic channel.

(7) Reverse Auxiliary Code Division channel

The Reverse Auxiliary Code Division channel is used for the mobile station to transmit user information and signaling information to the base station during the call process, which may be provided only when the wireless configuration RC is 1 and 2 o'clock. The channel is only established when the amount of data in the reverse packet burst increases, and exists in the time period specified by the base station. A reverse business channel can contain up to 7 reverse auxiliary code-channels.

(8) Reverse auxiliary channel

The reverse auxiliary channel is used for the mobile station to transmit user and signaling information to the base station during the call process, which may be provided only when the wireless configuration RC is 3 to 6 o'clock. The channel is only established when the amount of data in the reverse packet burst increases, and exists in the time period specified by the base station. A reverse business channel can contain 2 secondary channels.

2. Forward Channel

(1) Guiding channel

The forward guidance channel is the same as the Seeker channel in the IS-95 system, and it is fired continuously in the forward channel of CDMA.

The guidance channel includes a forward guidance channel, a transmit diversity guidance channel, an auxiliary guidance channel and an auxiliary transmit diversity guidance channel, all of which are not modulated spread spectrum signals and are used for capturing, synchronizing and detecting all mobile stations working in the base station coverage area. The Walsh code used in the forward guidance channel is W064, and the base station can add a transmit diversity guidance channel to enhance the reception effect of the pilot channel when it needs the diversity receiving. The Walsh code used in the transmit Diversity guidance channel (which does not necessarily exist) is W16128.

In order to use more flexible antenna and beam-shaping techniques, there will be 0 to multiple auxiliary guidance channels in an active CDMA channel to be launched by the base station. The base station will add an auxiliary transmit diversity guidance channel in case the auxiliary guidance channel needs to transmit diversity. If both the auxiliary guidance channel and the auxiliary transmit diversity guidance channel exist, the Walsh code used by the auxiliary guidance Channel is WNN, and the Walsh code used in the auxiliary transmit diversity guidance channel is wn+n/2n, of which n≤512 and 1≤N≤N/2-1. The Walsh code used in the auxiliary guidance Channel is WNN, which is n≤512 and 1≤n≤n-1 when the auxiliary transmit diversity guidance channel does not exist. The values of N and n are specified by the base station.

When launching a diversity-guided channel, the base station should make the forward guidance channel have continuous and sufficient power to ensure that the mobile station can capture and estimate the forward CDMA channel characteristic without using the energy of the guidance channel from the transmit diversity.

(2) Synchronous channel

The synchronization channel in the base station coverage area enables the boot state of the mobile station to obtain the initial time synchronization. The synchronous channel should be processed by convolution coding, code symbol repetition, interleaving, spread spectrum and modulation before launching.

(3) Paging channel