EVDO (EV-DO) is actually the abbreviation of three words: Evolution and DataOnlyFull nameCDMA20001xEV DO is a stage of a path of CDMA20001x evolution (3G).This path has two stages of development. The first stage is called 1xEV DO, or "DataOnly", which enablesOperatorUsing a CDMA carrier with the same bandwidth as IS-95 or CDMA2000, the forward direction of up to 2.4Mbps can be achievedData transmission rate, which has been accepted as the international 3G standard by ITU of ITU, and is ready for commercialization.The second stage is called 1xEV-DV.1xEV DV means "Data and Voice". It can support voice and data on one CDMA carrier.
EV-DO is the abbreviation of Evolution Data Optimized or Evolution Data only, sometimes it is also written as EVDO or EV.One of EVDO application technologies, which supports the conversion from Wifi connection to 3G connection.(See the extension at the end of this article. See page 24 of VPNGuide.pdf)
Technical Introduction
CDMA2000 1xEV DO is a technology that can meet the requirements of mobile high-speed data services.The bandwidth of one EV-DO channel is 1.25 MHz.Two differentcarrierIt supports voice and data services, which reduces frequency utilization, but in terms of spectral efficiency, CDMA2000 1X+CDMA2000 1xEV DO's data transmission capacity has greatly exceededWCDMA(WCDMA can achieve an air interface rate of 2.4Mbps/5Mhz for R4, 2.4Mbps for CDMA2000 1xEV DO Release 0, and 3.1Mbps for CDMA2000 1xEV DO Revision A,CDMA2000 1xEV DO Revision B rate is 9.3Mbps）。And from the perspective of technical implementation, the separation of voice service and data service not only maintains high quality voice, but also achieves higherData transmission rate。Network planningIn terms of optimization, CDMA2000 1X and CDMA2000 1xEV DO are the same. The systems of all major equipment manufacturers can support the smooth upgrade from CDMA2000 1X to CDMA2000 1xEV DOTelecom operatorsThe choice of technology and investment is ideal, which is conducive to the promotion of CDMA2000 1xEV DO.
Development overview
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Background
The CDMA20001xEV DO standard originated from Qualcomm's HDR technology. As early as 1997, Qualcomm proposed the concept of HDR (high-speed data) to CDG. After continuous improvement and experiments, in March 2000, the CDMA20001xEV DO standard submitted a formal technical scheme to 3GPP2 under the name of CDMA20001xEV DO.1xEV means''''Evolution '' '', also means the development of standards, and DO means DataOnly (later, in order to better express the meaning of this technology, DataOnly was changed to DataOptimized, indicating that EV-DO technology is an effective means of enhancing CDMA20001X network in providing data services).October of the same year3GPP2The voting defines the standard as CS0024,In the United StatesTIA/EIAIt is called IS-856.At the ITU meeting in December 2001, CDMA20001xEV-DO technology, as a branch of CDMA2000 family, was absorbed asIMT-2000One of the standards.
With the development of standards and the support of technical implementation means, the technology can be applied to the market as quickly as possible. Since EV-DO technology is actually derived from Qualcomm's HDR technology, Qualcomm can also launch the corresponding technology in a timely mannerMODEMIn the second quarter of 2001, Qualcomm announced that it could mass produce CSM5500 and MSM5500 chips for EV-DO network side and terminals. In fact, the competition between technology standards and chips is ultimately to gain a leading position in the market. As we all know, Qualcomm has made huge profits relying on CDMA technology patents and chip manufacturing capabilities.Other companies can't touch the profits of CDMA technology patents, but many powerful chip manufacturers and communication equipment manufacturers have coveted the profits of CDMA chips for a long time. There are SamsungTexas Instruments, Nokia and other companies are capable of manufacturingCDMA2000Series MODEM chips, actuallySamsungSince 1999, CDMA20001X chip has been used in its base station, and EV-DO chip is still used in its EV-DO base station."We welcome competition, but we don't want to lose market share." This is Qualcomm's view. Some table tennis sports like these, but in the long run, the emergence of competition does have more advantages than disadvantages.
From the perspective of system equipment manufacturers, the equipment manufacturers that have announced their support for EV-DO include Hitachi, Samsung, Lucent, LGIC, Nortel, Ericsson, Airvana, ComDev, Motorola, ZTE, Huawei, etc.In addition, almost all manufacturers of CDMA20001X equipment claim that their equipment can be "smoothly upgraded to EV-DO".Indeed, South Korea's SKT and KTFreetel use Samsung's BTSs, and upgrade from 1X to 1X+EV-DO at a small cost. Therefore, the network runs well.
China Telecom
China Telecom builds the world's second largest EV-DO network
Here we can talk a little about EV-DV.After the CDMA20001X phase, EV-DV is technically the subsequent evolution phase of 1X, and EV-DV is also compatible with CDMA20001X.Therefore, some people once wanted to skip DO and directly reach the DV stage. In previous communication exhibitions, companies have also demonstrated EV-DV.But EV-DV is to put voice and data services in the same placecarrierIt transmits data at a higher speed. Therefore, it is very difficult to implement the technology itself and the actual network. There are still many problems that need to be analyzed and solved through experiments and simulations.From the perspective of the most basic and critical chip manufacturing, manufacturing EV-DO chips requires CDMA20001X chip manufacturing experience. Only Qualcomm and Samsung have their own CDMA20001X chips, while Qualcomm has been vigorously promoting EV-DO from its HDR, and South Korea and Japan have also used EV-DO base stations provided by Samsung for networking business,So although the standard of CDMA20001xEV DV was determined by 3GPP2 in May 2012, it is still a long time before the actual commercial equipment appears.
Technical characteristics
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The front and reverse peak speed is greatly improved
Compared with EV-DORev0, in EV-DORevA, the peak rate of the forward link is raised from 2.4Mbps to 3.1Mbps, and more importantly, the reverse link is improved qualitatively.With the combination of the application of incremental transmission and flexible packet length, as well as the introduction of HybridARQ and higher-order modulation technologies in the reverse link, DORevA has achieved a leap in the peak rate of the reverse link from 153.6Kbps to 1.8Mbps of DORev0.
Cell front reverse capacity equalization
By using dual antenna receive diversity technology and equalization technology in mobile phones, the average capacity of EV DORevA's forward sector can reach 1500Kbps, which is 75% higher than EV-DORev0 (average cell capacity 850Kbps).The reverse average cell capacity of EV-DORevA has also been greatly improved, from 300Kbps of EV-DORev0 to 600Kbps.If 4-branch receive diversity technology is adopted in the BTS, the reverse average cell capacity can be further increased to 1200Kbps.
Fully support QoS
Compared with EV-DORev0, EV-DORevA has optimized QoS support and achieved significant improvement.
Flexible and effective QoS control mechanism
EV DORevA introduces a multi stream mechanism to enable systems and terminals to allocate resources and schedule each high-level data stream based on different QoS requirements of applications.At the same time, EV DORevA also improves the transmission rate of the reverse activity indication channel, so that the terminal can track the network load in real time, and ensure the data transmission of data streams with low transmission delay when the system is under high load.In addition, EV DORevA also introduces more data transmission rates and packet formats, so that the system can schedule more flexibly.In a word, EV DORevA can flexibly and effectively meet the transmission requirements of different data streams on the premise of ensuring the stability of the system, so that it can simultaneously support real-time and non real-time services on one terminal.
Low access delay
EV DORevA optimizes both the access channel and the control channel.First, the access channel can support higher transmission rate and shorter access prefix, so that users can access the network faster when they initiate service requests;Secondly, shorter paging cycles can be supported on the control channel, so that users can quickly respond to service requests from the network;In addition, EV DORevA high-level protocol introduces a three-level paging cycle mechanism, which enables the terminal to adapt to the network service conditions while reducing power consumption and improving standby time.This is very important for supporting services that need to establish and release channels frequently, such as push to talk (PTT) and instant messaging (IMM).
In data transmission, EV DORevA introduces high-capacity mode and low delay mode.Low delay mode can be used to transmit adata packetEach sub packet of.High power transmission is adopted for the sub packet transmitted first, so that the probability of the packet terminating transmission in advance is increased and the average is reducedTransmission delay。This pair supportsVoIPAnd video phone and other real-time services are very important.
Low handover delay
The DSC channel is introduced into EV DORevA, so that when the terminal selects other service cells based on the channel situation, it can give advance instructions to the network, synchronize the data transmission queue in advance, and greatly reduce the forward handover delay.This is very important and effective for supporting real-time services such as VoIP and videophone.
New business supported by EV DORevA
Benefiting from the significantly improved forward and backward peak rate, average cell capacity and QoS support, the EV DORevA system can not only significantly improve users' experience of services already carried out on CDMA1X and EV-DORev0 networks, but also support many new services with high QoS requirements.
Videophone
As a representative 3G service, videophone service has beenOperatorSpecial attention.Videophone serviceIt can provide real-time two-way communication of voice and video.Mobile users can share important moments and feelings with their relatives and friends through video phones.Operators can also develop other value-added services on top of videophones, such asvideo conference , multiplayer interactive games, insurance claimsTelemedicine, Visualsafety systemwait.
Video phone has the requirements of high bandwidth and high real-time, so it should be carried out on EV DORevA network that can guarantee QoS.The reverse rate and reverse spectrum efficiency greatly improved in EV DORevA areVideophone serviceGuarantee of smooth development.The QoS mechanism of EV DORevA can support fast call establishment, low-end to end delay and fast handover required by videophone.In addition, the use of receive diversity technology will be able to better improve the quality of service of videophones.
VoIP and concurrent services of VoIP and data
In line with the trend of the evolution of networks and services to all IP, EV DORevA can also support VoIP services on packet networks.Like video phones, VoIP has high real-time requirements, which can be guaranteed through the unique QoS mechanism of EV DORevA.On the other hand, compared with the videophone service, VoIP requires lower bandwidth, but it is more effective in packaging and antiDelay jitterThere are higher requirements.In EV DORevA, VoIP willdata packetThe format is optimized.At the same time, 3GPP2 has also formulatedC.S0063Specification, which definessegmentOfFramingTechnology and Headcompression technique 。
EV DORevA pera sectorIt can support up to 44 VoIP calls, which has exceeded the capacity of circuit voice on CDMA1X network.If technologies such as reception diversity and interference cancellation are adopted, the capacity can be further increased.
When VoIP services are carried out on the EV DORevA network, users can not only obtain the same voice quality as circuit based voice services, but also conduct concurrent communication of voice and data through one terminal.For example, sending and receiving email and browsing on the Internet during a call, or transmitting multimedia content such as text, pictures, audio, video, etc. to the other party during a call.It can even initiate and answer voice calls while data applications are in progress (such as downloading or mobile games).
Push to Connect and instant multimedia communication
Push-to-Connect(PTC) service is a one-to-one or half duplex push to talk service between groups.Instant multimedia communication also extends PTC to include multimedia such as text, pictures and videos.
In addition to the same requirements as video phone and VoIP, such as fast call establishment, low-end to end delay and fast handover, PTC and IMM also require the network to be able to support frequent and fast call establishment and release.EV DORevA introduces higher transmission rate and shorter access prefix on the access channel, and introduces three-level paging cycle mechanism in the high-level protocol, which can enable the terminal to meet the above requirements while reducing power consumption and improving standby time.
Mobile Games
Online mobile games can be single player (interaction between people and servers) or multi player interactive games.With mobile interactive games, users can continue to play games at home on the road.
Different interactive gamesbandwidthThe requirements of are quite different.For example, some scenario games need higher bandwidth to transmit scene maps in real time, while some games need to transmit less when the player presses the key to controldata packet。EV DORevA can support high data rate in both front and back directions, which can meet the requirements of real-time scene games.At the same time, EV DORevA also designed a very flexible packaging method for game applications with less data but frequent data packets.If several small user data packets can be combined into a larger data packet for transmission, it will ensure thattransmission efficiency And reduces the waiting delay of data packet transmission.
Multicast service based on BCMCS
EV-DO provides higherFront reverse sector capacityandPeak rate, enabling users to quickly download or upload large amounts of data.But EV-DO network providesunicastTechnology, that is, the data transmitted on the network can only be received by one user.When many users in the cell need to receive the same content at the same time, such as many users watching the sameStreaming MediaContent, unicast mode will occupy a lot of network resources, making the networkHigh load state。In this case, the unicast scheme is a very uneconomical transmission mode.
Global EVDO commercial situation
In order to transmit multimedia content to a large number of users simultaneously in a more economical way, 3GPP2 first completed the gold medal multicast standard based on DORev0 in March 2004, and then completed its adoption in August 2005OFDMModulatedPlatinum Multicast Standard, relevant BCMCS groundNetwork StandardsIt was also completed in 2005.By using OFDM modulation on the broadcast timeslot, platinumMulticastMore based onDORev0Golden Multicast can achieve a capacity increase of about three times, and a data rate of 1.2Mbps can be achieved within 98% coverage (DORev0 is 409.6Kbps in the case of dual antenna reception).Gold medal multicast and platinum multicast can share one with DOcarrierSo that the DO carrier can be fully used in both busy and idle time of the network.OperatorCan be deployed inEV-DORevAAt the same time, the system allocates some timeslots on the same carrier to deploy BCMCS and gradually develops some distinctive services on the BCMCS platform, such as mobile TV and DOunicastBundled integrated multimedia delivery services;It can also integrate the widely concerned and recognizedStreaming MediaThe business is transitioned to the BCMCS platform to improve the capacity of network transmission of video streaming media to reduce business costs.
EV DORevA system can support many new services with high QoS requirements.
Mechanism mode
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Rate control mechanism
China Telecom builds the world's second largest EV-DO network
According to relevant theoretical research, the following conclusions have been drawn: "Increase the data transmission volume when SNR is high andSNRWhen it is bad, reduce the amount of data transmission. Such a transmission mechanism can obtain a larger system capacity than using variable power to transmit constant rate data "(Goldsmith and Varaiya,IEEETrans.OnInformationTheory,Nov.1997)。Therefore, power control is beneficial for circuit type connections, but it will reduce system throughput when packet data services are performed.Therefore, rate control mechanism is adopted in EV-DO system for packet data service.
Forward scheduling mechanism
The system throughput is also closely related to the scheduling algorithm.The 1xEV DO system adopts the Fair scheduling method. The DRC application of each user who wants to be served will be saved in the BTS system, and the average DRC value of a single user over a period of time will be calculated. When the current DRC application rate of this user is greater than the above averageDRCWhen the rate is high, the user gets the service, otherwise the service will not be given.In this way, the probability of each user getting the service is the same, and the system always provides business services under the best wireless environment of the current user.The system capacity is increased while ensuring the equality between users.
Mixed operation mode
On Rate Control in CDMA 1x EV-DO System
There is no clear definition and specification for the operation mode of dual-mode hybrid terminal. GenerallyOperatorTo determine how a dual-mode mobile phone selects a network and switches between states in its own network.Qualcomm has proposedDual mode terminalOfState Migration Diagram: Generally speaking, when the mobile phone successfully logs in to both networks, the mobile phone will work in theTime slot mode(slotted), which can be a timeslot mode that monitors only 1X networks or a timeslot mode that monitors both 1X and EV-DO networks. In short, you should always monitor 1X networks, because voice services have priority over data services.However, the experiment shows that the dual mode terminal will consume a lot of power when it monitors 1X and EV-DO networks at the same time, so it should set a duration, and when the duration exceeds this, it will switch to monitor only1X networkTime slot mode of.
Protocol design
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Delay structure
EV-DOair interface The layered structure is adopted, which is divided into seven layers. The advantage of this is that each layer of the protocol is independent, signaling is simplified, and maintenance is easy.Each agreement can be negotiated separately. During system development, the modular design allows a certain agreement/software to be updated separately.The air interface protocol layering will not affect the data service throughput.From the overall network protocol stack of EV-DO, only the physical layer, RLP layer, and related signaling are defined by the 1xEV-DO standard. PPP and upper layer protocols are based onIETFStandards.
network structure
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Cdma20001x ev do rev. a mobile broadband
EV-DO standard defines two network structures, called Phase1 and Phase2 respectively. In fact, these two network structures have no evolutionary relationship, and can be said to be two different ways to implement EV-DO network.From the figure above, we can see that the Phase1 structure has little change to the original 1X network. Two interfaces, A12 and A13, have been added to the interface, both of which are newly added from the ANSC/MM(Session Control/Mobility Management）It is sent from the module and connected with AN_AAA and other ANs respectively for authentication and handover of EV-DO terminal.Therefore, to upgrade from the existing 1X network to EV-DO, you only need to add the SC/MM module to the original BSC. In order to minimize the changes to the original equipment and the impact on the existing network, some manufacturers take out the SC/MM module separately to form a new network element device, and provide the public A12 and A13 interfaces.The public A13 interface is more important. It can support AT switching and roaming between different equipment manufacturers, such as JapanKDDIEV-DO network of Samsung andHitachiThe network equipment provided by both companies provides the public A13 interface, so the interconnection between ANs can be achieved.If there is no A13 interface, when the AT switches from one AN to another, it will need to renegotiate and register (that is, re-establish the session). This will not only slow the AT's response speed, but also increase the system load.The Phase2 structure separates the SC/MM function module from the AN and moves it to the PCF.Thus, new interfaces such asA14, A15, Ax. interface。In fact, the SC/MM function module is closely connected with the call processing module in the AN. It is a reasonable structure to place it in the AN, but it is not meaningful to place it in the PCF. Moreover, most manufacturers' equipment integrate the PCF into the BSC. If you pressPhaseIIThe standardization of architecture requires changes in both AN and PCF, which cannot achieve a smooth transition on 1x systems.
Commercial situation
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CDMA2000 1xEV DO has been commercially available on a large scale,OperatorIt has launched a variety of mobile data application services suitable for high speed.
Asia:
January 2002 SK Telecom, South Korea
May 2002 KT Freetel, South Korea
network structure
November 2003 KDDI Japan
November 2004 New Zealand Telecom
September 2007, Macao, ChinaChina Unicom(Since October 1, 2008, the business has been transferred to China Telecom)
In February 2009, ZTE announced that it had opened the world's first EV-DOB version (Rev. B) VoIP phone on its CDMA2000 commercial system, and took the lead in realizing 9.3MbpsDownload rateAnd 5.4MbpsUpload rate。
March 2009 China Telecom, Mainland China
In May 2009,HuaweiThe EM660 module has won the first built-in 3G module model approval certificate and network access license issued by the Ministry of Industry and Information Technology of the People's Republic of China, becoming the first EV-DO module in China to obtain a 3G network access license.In June 2009, ZTE, Qualcomm andMoroccoCDMAOperatorWana three parties jointly announced that the world's first EV DORevB The Commercial Experiment Bureau was established in Morocco.
