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3.5g/hsdpa technical architecture and key points of development

from voice communication to data communication, the honeycomb type is undoubtedly in a major revolutionary period in the transformation of the technical architecture. In the digital era, wireless communication, like wired communication, continues to improve the transmission rate: from GSM to GPRS with a transmission rate of about 40kbps, and from GPRS with a transmission rate of about 130kbps edge to 384kbps of UMTS of 3G generation, Up to now, the 3.5 generation HSDPA to be produced

HSDPA, which is known as 3.5G, is a new term that is threatening the market. It will become a topic of concern in the market and has the significance of the times. First, because CDMA2000 has achieved a leading advantage in the 3G market, WCDMA camp feels great pressure; In addition, WiMAX promoted by the non line camp is of great momentum, which also makes the WCDMA camp urgently need to launch a new generation of technology to consolidate the existing territory

let's take a look at the current situation of 3G market promotion. According to the statistics of GSA and CDG, in mid-2004, there were only 37, 87 and 10 commercial roads for WCDMA, CDMA2000 1x and CDMA2000 1xEV-DO respectively. As of June 2005, 223 3G commercial roads had been opened worldwide, including 123 CDMA2000 1x roads and 22 CDMA2000 1x EV-DO roads, compared with 78 WCDMA roads; It is expected that 22 CDMA2000 1x EV-DO lines will be opened next year, and seven telecom companies will be ready to enter the commercial phase for WCDMA lines. Please refer to figure 1

Figure 1 global 3G commercial road growth trend

if compared in terms of the number of users, the difference between the two camps is even more obvious. According to the data released by the Telecommunications Research Institute of the Ministry of information industry of China, by the end of June 2005, there were 191.9 million 3G users worldwide, including 143.7 million CDMA2000 1x users, 17.8 million EV-DO users and only 30.4 million WCDMA users

for countries with two concurrent specifications at the same time, this situation makes the telecom operators using WCDMA worried that the number of users who have managed to increase will be lost to another camp. The representative countries are Japan, the United States and China. Since 2004, Japan NTT DoCoMo has planned to invest 350million US dollars in two years to support six terminal manufacturers (Fujitsu, Mitsubishi electronics, Motorola, NEC, Panasonic and sharp) to accelerate the research and development of HSPDA terminals to combat KDDI's wireless high-speed data service. KDDI recently announced that it would open CDMA2000 1x EV-DO rev. at the end of 2006 Channel a, which increases the uplink/downlink rate to 1.8/3.1mbps

in the United States, the EV-DO system built by Verizon Wireless has covered 32 cities, with a population coverage rate of more than 30%, and plans to exceed 40% by the end of 2005. In order to cope with the competition, cigular, the largest mobile communication service provider in the United States, announced the upgrade of WCDMA system at the end of 2004 and planned to take the lead in deploying HSDPA roads in urban areas and campuses of several major cities in the United States at the end of 2005. In China, China Unicom has begun to vigorously promote the CDMA2000 1x EV-DO system, which will undoubtedly cause competitive pressure on China Mobile. To this end, China Mobile said that after the issuance of 3G licenses, China Mobile will first deploy HSDPA roads in developed coastal and important cities

comparison of two 3.5G standards

reviewing the development of two competitive specifications, the international organization for standardization 3gpp/3gpp2 launched these two technologies respectively in 2000. In terms of 1xEV do, 3GPP2 has completed the standardization of Rev0 and Reva (reverse enhancement), is developing the revb standard, and is expected to complete the standardization of the revb version in early 2006

3gpp divides the evolution of HSDPA into three stages. The first stage was started in 2000. The basic HSDPA was defined in R5 version. At present, this stage has been completed. After introducing HS-DSCH channel, AMC and HARQ technologies, the ideal peak rate can reach 14.4mbps; The second stage is the enhanced HSDPA defined in the R6 version, which increases the peak rate to 30mbps by using MIMO technology; In the third stage, OFDM and 64QAM modulation technologies will be used together to make the peak rate reach more than 50Mbps. Please refer to (Table 1), (Figure 2) and (Figure 3)

table I HSDPA development stages and key technologies

due to the strain of elastic elements in direct proportion to the size of external force P

figure II HSDPA and CDMA 1xEV do standard evolution

figure III honeycomb technology performance evolution

in order to ensure the investment of operators, both standards carry out evolution design based on the principle of minimum changes to existing roads, that is, try not to change the road architecture and core roads, and use existing spectrum resources. In this case, innovation must be carried out through advanced technology, and the two standards use AMC, HARQ and other technical practices, which will be compared and explained below

■ 1xEV do

1xev do (evolution data optimized) is a commercialized and feasible 3G technology, which can improve the data transmission rate to 2Mbps. The bandwidth used is 1.25mhz, which is 3-4 times faster than cdma2000 1xRTT and WCDMA, two voice service center technologies

1xev do is a part of the CDMA2000 standard, but it does not rely on any component in the CDMA voice path to provide services, mobility or roaming. System operators do not need mobile switching center (MSc) or path components such as home and visitor location registers (hlr/vlr). Therefore, no matter what kind of voice technology the system operator currently uses, 1xEV do can be built as long as it has a 1.25mhz paired spectrum

there are three main units in the 1xEV do path, as shown in Figure 4:

● radio nodes (RNs)

● radio network controller (RNC)

● packet data serving node (PDSN)

Figure 4 1xEV do path architecture

each wireless node generally supports three sectors and serves a cellular system, There is an exclusive transmitter in each area, which is used to save the air connection between the user's modem and the wireless node. The higher layer protocols in 1xEV do will be processed in RNC, which is also responsible for transferring user data between Rn and PDSN. PDSN is a wireless edge router used to connect non line and inter line. This architecture is different from some other 3G wireless technologies in that it does not need to rely on mobile switching centers (MSc)

in addition to RNC and PDSN, the 1xEV do data center also has an aggregation router, an element management system (EMS) and several ISP servers. The aggregation router extracts the IP information from the RN and transmits it to the RNC; EMS is responsible for managing wireless access. The commonly used ISP servers include standard IP servers such as domain name system (DNS), Dynamic Host Configuration Protocol (DHCP) and authentication, authorization, and accounting (AAA)

on the whole, 1xEV Technology (also known as high data rate; HDR) is an efficient and cost-effective international solution. This high-speed technology is compatible with CDMA and provides optimized packet data services. More specifically, it achieves its performance with the minimum path and spectrum resources. It is a high-frequency spectral efficiency technology

■ hsdpa

hsdpa (high speed downlink packet access) is an additional scheme based on 3GPP r99/r4 architecture, that is, an air interface of UMTS. Its architecture mainly includes three components, namely user equipment (UE), node B and RNC, as shown in Figure 5. Under the standard of basic model, the peak data transmission rate of category 6 mobile users with rake receiver can reach 3.6mbps; Category 10 mobile users with advanced receiver scheme can be upgraded to 14.4mbps

Figure 5 HSDPA protocol architecture

hsdpa is based on the evolution of existing WCDMA routes. Its route construction cost is mainly used for the software/hardware upgrade of node B (base station) and RNC. It transfers the key data processing from RNC to node B, making the data processing closer to the air interface, so as to achieve higher system transmission volume and improve service quality. Moreover, HSDPA can also expand the system capacity. Compared with the existing WCDMA technology, HSDPA can provide services for more high-speed users on the same wireless carrier frequency

basically, HSDPA is a packet data service of WCDMA downlink link, and its data transmission rate can reach 8 ~ 10Mbps (20MBps with MIMO system) under 5MHz bandwidth. It adds a new high speed downlink shared channel (HS-DSCH), which divides the main channel into 15 sub channels by code splitting, and allocates channel time to different users within 2ms in combination with the shortened TTI (transmission time interval). In this way, multiple users can share the bandwidth at the same time, thus improving the spectrum utilization

in addition, it also introduces shorter TTI (2ms) in the physical layer (PHY), adopts adaptive modulation and coding and HARQ fast retransmission technologies, so that high-speed transmission can be realized. Its technical features are as follows:

adaptive modulation and coding (AMC)

in order to provide the best data rate for each user, an adaptive modulation and channel coding scheme is adopted in HSDPA to meet the current channel conditions

fast scheduling

in WCDMA, RNC is responsible for packet scheduling. In HSDPA, packet scheduling is transferred to node B itself, so the delay caused by condition change can be greatly reduced. In order to obtain the maximum efficiency of the inspectable right side oil buoy for scheduling data packet transmission, HSDPA uses channel quality information, mobile terminal capacity, QoS and available power/code

fast retransmission

data retransmission is required when a link error occurs. The current WCDMA system must wait for 100ms or more before the RNC reacts. When this function is introduced into node B, the delay will be reduced by one order of magnitude to about 10ms. This method uses the hybrid ARQ (HARQ) technology, in which the previously transmitted data and retransmitted data are combined in a special way to improve the decoding efficiency and dispersion gain

Table II comparison of technical characteristics between 1xev/do and HSDPA

comprehensive comparison

as mentioned above, the two standards are similar or the same in terms of technical purpose or means. Both demand to meet the needs of asymmetric data services, that is, to provide high-speed downlink transmission speed so that operators can promote mobile value-added services such as video entertainment. However, in order to reduce the cost and impact of the road upgrade, in addition to considering the compatibility with the existing version, it is also required that the software and hardware can be adjusted with a minimum range to improve the spectrum utilization

at present, 1xEV do has a fast pace of commercialization, which is closely related to the high compatibility of a series of CDMA standards. Unlike upgrading from gsm/gprs to WCDMA, the infrastructure needs to be significantly changed. However, the slow pace of development also means that there is more experience for reference. Therefore, the technical version of HSDPA has a high data transmission rate and can fully use the remaining voice bandwidth. In addition, HSDPA can support voice and data services at the same time

however, the evolution of these two standards has just started, and it can be predicted that

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