Building a CDMA2000 1x EV-DO test network is an important way to master and implement this technology. The article describes and analyzes various problems that need to be considered and paid attention to during the planning and construction of the test network, and proposes a corresponding solution.
1 IntroductionCDMA2000 1x EV-DO technology is one of the popular standards for the evolution of the 1X live network to the 3G phase. In China, the technical standard has not yet been put into commercial use, and its technical characteristics and network characteristics have yet to be further mastered and deepened. In order to achieve this goal, in addition to learning from the theory, it is also a more objective and direct way to build a trial network of a certain scale.
In the planning and construction process of the CDMA2000 1x EV-DO test network, various problems will inevitably be encountered. This paper introduces the problems that need to be considered and paid attention to during the networking of the EV-DO test network, and proposes a Set the corresponding solution, I hope to play a role in attracting jade.
2. Selection of technical standard versionFirst, a brief introduction to the development process of CDMA technology standards is given.
Figure 1 CDMA technology development process
As shown in Figure 1, in the development of CDMA technology, the second generation mobile communication technologies including IS-95, IS-95A, and IS-95B are collectively referred to as CDMAOne. The technology mainly supports voice services, China. China Unicom's CDMA network also sailed from here.
In the subsequent development, CDMA2000 1X technology was introduced. In addition to increasing voice capacity and introducing various new features, it is also capable of supporting high-speed data services such as 153.6 kb/s and 307.2 kb/s.
Since then, the CDMA2000 spread spectrum system has evolved further in versions C and D, the CDMA2000 1x EV-DV technology we often refer to. In addition to inheriting the voice function of CDMA2000 1X technology, the data throughput has been greatly improved. The pre-reverse peak rate of the EV-DO in the D version has reached 3.1Mb/s and 1.8Mb/s respectively.
At the same time as the development of CDMA2000 spread spectrum system, the CDMA2000 HRPD (High Rate Packet Data) standard system is introduced in the 3GPP2 standard system, which is the CDMA2000 1x EV-DO technology we usually talk about. The technical standard currently has two versions, 0 and A. At present, the 0 version of EV-DO technology is relatively mature, and has already been put into commercial use in countries such as Korea and Japan. The A version of EV-DO technology has also entered a substantial commercial development, and a series of excellent performances such as 3.1Mb/s and 1.8Mb/s front reverse peak rate and QoS improvement are its biggest highlights. Although there is news that the A version of the EV-DO network will officially enter commercial operation in 2006, no manufacturer has been able to provide trial network equipment.
Therefore, if the CDMA2000 1X EV-DO test network is currently being built, the version that can be selected is still version 0. Although it can only support data services and does not guarantee QoS for real-time data services like video telephony, its pre-reverse peak rate of 2.4 Mb/s and 153.6 kb/s is still an epoch-making advance.
3. Selection of test frequency bandsAs one of the most important telecommunications resources, spectrum resources are fully controlled by the government. Therefore, the selection of the test network frequency band must comply with the relevant national laws and regulations.
In 1992, the ITU allocated core frequency bands for third-generation mobile communications, including 1885MHz to 2025MHz and 2110MHz to 2200MHz, for a total of 230MHz. In conjunction with China's national conditions, the Ministry of Information Industry promulgated the "No [2002] No. 479" document in October 2002 to determine China's 3G wireless spectrum planning program. In this scheme, in addition to the main working frequency band of the IMT-2000 FDD mode is 1920MHz ~ 1980MHz / 2110MHz ~ 2170MHz, the supplementary working frequency band is 1755MHz ~ 1785MHz / 1850MHz ~ 1880MHz, the current network 825MHz ~ 835MHz / 870MHz ~ 880MHz frequency band also It is planned to be an extended frequency band of the FDD mode.
At present, the main working frequency band and the supplementary working frequency band are not open to operators. Therefore, from a legal point of view, 800M is the EV-DO test network frequency band that can be legally used at present. Among the 7 frequency points that can be used in China Unicom's 800M frequency band, 283, 242 and 201 frequency points are already occupied. According to relevant regulations, the recommended frequency of the current EV-DO test network is 37.
4, networking mode4.1 Wireless side
On the wireless side, the networking mode of the EV-DO test network can be divided into two types: upgrade networking and overlay networking. Upgrading the network refers to adding the corresponding EV-DO card to the existing 1X base station and supplementing it with software upgrade. Overlay networking is not done by adding a board, but by adding a new EV-DO base station.
Here, the two wireless side networking methods are compared and analyzed:
(1) The upgrade networking method actually utilizes resources such as racks, power modules, and clock boards of the existing network base stations, and the construction is relatively simple. The overlay networking method requires the addition of new equipment, which is easily limited by the objective conditions such as the space and load-bearing of the existing equipment room. However, since the 1X network equipment single cabinet can only support 3 4 carriers, for the 3 carrier base station of the existing network, after upgrading the DO carrier, it has actually reached the full capacity of the single cabinet. If a new carrier is added later, the same Will face the problem of adding new cabinets. From this perspective, upgrading the networking mode can only alleviate the construction difficulties of the new cabinet.
(2) The upgrade networking mode is limited to the DO products of the existing network 1X equipment provider. The overlay networking mode can select the same manufacturer equipment as the 1X existing network, or select the DO equipment from different manufacturers. This is beneficial for operators to introduce competition and increase the number of chips in possible commercial negotiations in the future.
(3) Technically, since there is no compatibility between 1X and EV-DO technologies, there is no fundamental difference between the two networking modes for network performance.
(4) In the actual networking process, the two networking modes can be flexibly combined. In addition, some EV-DO sites can be built in a location independent of the existing network room according to the actual situation. Although the cost of the test network will be increased, the flexibility of planning and networking can be increased.
4.2 Data core network side
On the data core network side, the problem to be considered is the PDSN sharing problem. Since the CDMA2000 1X and CDMA2000 1X EV-DO technologies are only different in the air interface standard, the data core network can be shared. In fact, when the EV-DO enters the commercial phase, the 1X and DO systems necessarily need to share the PDSN, but in the trial network phase, in order to avoid the impact on the live network PDSN, a separate PDSN may be considered.
If the EV-DO test network uses a separate PDSN, then when the mobile phone moves from the DO network coverage area to the area with only 1X network coverage, the data switch under the PPP connection unchanged state cannot be completed. If the PDSN of the 1X system is shared, the PPP connection and IP address can be kept unchanged during the handover process.
From a technical point of view, we still hope that the trial network can share the PDX of the 1X live network to support the DO to 1X handover test. Then, there are two common ways to share:
(1) Upgrade all the boards of the live network PDSN to the software and hardware versions that can support the EV-DO technology, and then access the test network. Although this method can be used in one step, it has the greatest impact on the existing network and the construction risk is also large.
(2) Add a new board to the existing network PDSN, and bind the EV-DO terminal in the trial network to the board to achieve the purpose of sharing the PDSN with the existing network. This approach poses less risk to the existing network, but it may still need to be re-engineered when it evolves to the commercial network stage in the future.
Both methods have their own advantages and disadvantages, but for the trial network, the impact on the live network should be minimized on the premise of meeting the test requirements. Therefore, the personal recommendation is to adopt the second method in the trial network phase. It should be noted that, due to the different performance of the PDSN manufacturers, the above two methods may not be fully supported, and there may be other special methods. It is recommended to make detailed decisions before communicating with the PDSN manufacturers before setting up the test network.
If the PDSN of the live network is shared, the CDRs generated by the EV-DO test terminal will be sent to the billing system of the live network. This requires consultation with the billing department to process these bills. A feasible method is that the EV-DO test terminal uses a user name and a password different from the existing network to log in to the network for data service, and performs special processing on the bill generated by the user name and password on the billing side to avoid charging.
In addition, if the PDSN sharing the existing network is used, it is necessary to pay attention to the capacity and load of the current Internet access bandwidth of the PDSN. The data throughput of CDMA2000 1X technology is small, and the outgoing bandwidth of the existing network PDSN connected to the external Internet is not large, and it is likely that it cannot withstand the impact of high data traffic generated by the EV-DO test network. If it is not urgently expanded, it will seriously affect the use of existing data services.
5. Selection of test area and siteThe dense urban area is the primary area to be laid by commercial EV-DO networks in the future. The urban-rural integration and important expressways are also possible coverage targets for EV-DO networks. One of the important goals of building a trial network is to enable the network to cover areas with the above geographical features as much as possible, and to accumulate experience in the actual networking and testing process to provide a basis for future planning.
However, since the number of test site points is unlikely to be excessive, how to use the least number of sites to achieve the best test results is the desired result in the test network planning phase. The choice of test sites and areas needs to consider the following aspects:
(1) Several base stations need to be selected to form the main test area. The test area should contain as many of the topographical features as possible in the dense urban area and represent the typical geographical features of the bustling area of ​​the city. Because dense urban areas characterized by large traffic volume will become the primary and key coverage areas for commercial 3G networks.
(2) In the actual test, most performance tests are single station tests. Therefore, it is necessary to select a main test base station in the main test area, and all single station tests are completed on the base station as much as possible. The main test base station has a radial test road starting from the base station in at least one sector direction, and has a certain length (at least 2 to 3 kilometers), so that the test conditions such as coverage test and fixed point throughput test can be satisfied. If possible, there should be a fan and a fan at a point near the main test base station (C/I>10), midpoint (C/I=5) and far point (C/I=0). The radius of the radius of the zone is tangent to meet the test conditions of the sector throughput test under mobile conditions.
(3) A certain length of urban trunk line or expressway that can guarantee a higher speed should be covered to conduct a comparative test of data throughput at different speeds.
(4) In the test area, a PCF boundary should be set, and there is at least one test route tangent to the PCF boundary to meet the conditions for cross-PCF handover test.
(5) If there is more than one EV-DO base station equipment provider, the test areas of each manufacturer should be connected, and the test roads are tangent to the manufacturer boundary for cross-factory handover testing.
(6) In non-traffic hotspots, EV-DO base stations can be deployed at twice or even three times the current site to verify the possibility of building an overlay EV-DO network in low traffic areas.
(7) Construction of individual indoor EV-DO coverage systems to examine the impact of EV-DO networks on dry and distributed systems.
(8) It is possible to upgrade individual macro base stations with repeaters to investigate the impact of EV-DO networks on repeaters.
6, TianzhuIf the test network is deployed in the 2.1G frequency band, due to the limitation of the working frequency band, most of the antenna feeder systems on the live network cannot be used up, and new antennas need to be added. However, as mentioned earlier in this paper, the current trial network can only be deployed in the 800M band for the time being, so there is the possibility of sharing the live network. However, the EV-DO test network is built on the 800M frequency band. In some cases, independent antenna feed is also a good choice.
Table 1 compares the two methods of shared antenna feed and independent antenna feed.
It can be seen from Table 1 that the two ways of using the antenna have their own advantages and disadvantages, and should be selected and used in combination with the actual situation. For example, when DO coverage network planning is performed in a manner larger than the current website distance, independent antenna feed can be considered, and by adjusting the azimuth and downtilt angle of the DO base station antenna, the number of base stations is reduced to obtain a better coverage effect. .
When it comes to the specific implementation of shared antenna feed, the most easy way to think of is the combiner mode. The existing network signal and the DO signal are combined and transmitted through the live network antenna. This method will bring about 3dB signal attenuation. In addition, combined with the equipment characteristics of some equipment manufacturers, there are also some common antenna feeders that do not use combiners, which can reduce the attenuation caused by the combined signals. Figure 2 is a schematic diagram of a shared antenna feed without a combiner.
Figure 2 Schematic diagram of a common antenna feeder without a combiner
7, transmission and other supportingCompared with the 1X carrier-to-transmission requirements, the transmission resources occupied by the EV-DO carrier are relatively large. For a three-sector EV-DO test station in a high traffic load area, two to three E1 transmissions need to be configured per carrier; if the traffic load is low, only one E1 transmission may be configured, but it may be due to transmission resources. The tension caused a drop in sector throughput. For omnidirectional stations and micro cells, one or two E1 transmissions can be configured per carrier.
As a new carrier or base station is added to the base station, the DC power load increases. The DC power module needs to be added according to the actual equipment. In addition, for the part of the mains introduction line, the original wire diameter may not meet the current demand, and the power line transformation is required. These require professional planning units to assist in the exploration and determination.
In addition, the air conditioner in the base station room is also a place that may need to be expanded, and needs to be determined according to specific conditions.
8. ConclusionOn the eve of the third-generation mobile communication technology really landing in the commercial market, the test network is undoubtedly an indispensable test field. Regardless of the equipment provider or the operator, the trial network is a great opportunity for military training and competition. It also provides a good place for competition and innovation. In the test, not only can we master the new technology, but also train and train a group of outstanding technical teams.
This paper analyzes some problems encountered in the EV-DO test network networking and planning process, and proposes corresponding solutions. Since it is a trial network, all kinds of new networking ideas, methods and design schemes can be fully utilized and analyzed in the experiment, in order to find an optimal combination in practice, in the best state, the best The hand is welcoming the upcoming 3G tide.
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