GPS positioning technology can provide users with accurate location information service anytime and anywhere. After the signal received by GPS receiver is processed by error, the location information is calculated, and then transmitted to the connected equipment. After the connected equipment calculates and transforms the information, it is transmitted to the mobile terminal.
GPS positioning technology can provide users with accurate location information service anytime, anywhere. Its basic principle is to get the position information from the signal received by the GPS receiver after the error processing, and then transmit the position information to the connected equipment. The connected equipment calculates and transforms the information (such as map projection transformation, coordinate system transformation, etc.) and then transmits it to the mobile terminal.
GPS 全球卫星定位导航系统，开始时只用于军事目的，后转为民用被广泛应用于商业和科学研究上。GPS 空间部分使用了二十四颗卫星组成的星座，卫星高度约 20200 公里，分布在六条升交点互隔 60 度的轨道面上，每条轨道上均匀分布四颗卫星，相邻两轨道上的卫星相隔 40 度，使得地球任何地方至少同时可看到四颗卫星。传统的 GPS 定位技术在户外运转良好，但在室内或卫星信号无法覆盖的地方效果较差，而且如果所在位置上空没有 3 颗以上的卫星，那么系统就无法从冷启动状态实现定位。
GPS global positioning and navigation system was only used for military purposes at the beginning, and then it was widely used in commercial and scientific research. In the space part of GPS, a constellation composed of 24 satellites is used. The satellite height is about 20200 km, and it is distributed on the orbit surface with six ascending intersections separated by 60 degrees. Four satellites are evenly distributed in each orbit, and the satellites in two adjacent orbits are separated by 40 degrees, so that at least four satellites can be seen at any place on the earth at the same time. The traditional GPS positioning technology works well in the outdoor, but the effect is poor in the indoor or where the satellite signal can’t cover, and if there are no more than three satellites above the location, then the system can’t realize the positioning from the cold start state.
在移动通信网络中，通常有以下几种定位技术: 一是基于 Cell ID 的定位技术，它由网络侧获取用户当前所在的基站 Cell 信息以获取用户当前位置，其精度取决于移动基站的分布及覆盖范围的大小; 二是基于 AFLT 的定位技术，AFLT（Advanced Forward Link Trilateration）是 CDMA 独有的技术，在定位操作时，手机/终端同时监听多个基站的导频信息，利用码片时延来确定到附近基站的距离，最后用三角定位法算出具体位置; 三是基于 AGPS（无线网络辅助 GPS 定位技术）的定位技术，AGPS 将终端的工作简化，由网络侧的定位服务器与终端相互配合完成定位工作，就是将卫星扫描及定位运算等最为繁重的工作从终端一侧转移到网络一侧的定位服务器完成。
In the mobile communication network, there are usually the following positioning technologies: first, cell ID based positioning technology, which obtains the cell information of the user’s current base station from the network side to obtain the user’s current location, and its accuracy depends on the distribution and coverage of the mobile base station; Second, based on the location technology of AFLT, AFLT (advanced forward link trilateration) is a unique technology of CDMA. During the location operation, the mobile phone / terminal simultaneously monitors the pilot information of multiple base stations, uses chip delay to determine the distance to the nearby base station, and finally calculates the specific location with triangle location method; Third, based on the positioning technology of AGPs (wireless network assisted GPS positioning technology), AGPs simplifies the work of the terminal, and completes the positioning work by the cooperation between the positioning server on the network side and the terminal, which is to transfer the most heavy work such as satellite scanning and positioning operation from the terminal side to the positioning server on the network side.
而 CDMA 定位技术是美国高通公司为基于位置业务开发的定位技术，采用 Client/Server 方式。它将无线辅助 AGPS 和高级前向链路 AFLT 三角定位法两种定位技术有机结合，实现高精度、高可用性和较高速度定位。在这两种定位技术均无法使用的环境中，CDMA 定位技术会自动切换到 Cell ID 扇区定位方式，确保定位成功率。广域 GPS 卫星参考网络由多个高灵敏度 GPS 接收机组成，负责全天候监测覆盖区域上空所有 GPS 卫星的星历数据、多普乐频移等定位所需信息，动态刷新存储于定位平台中的 GPS 卫星数据库（卫星数据与地理位置对应关系）。终端只有在需要定位时才通过无线网络向定位平台通报大概位置（属于哪个基站），然后通过定位平台获得 GPS 卫星信息，从而大大缩短卫星捕获时间，大幅度降低耗电。
CDMA positioning technology is a positioning technology developed by Qualcomm for location-based services, which adopts client / server mode. It combines wireless assisted AGPs and advanced forward link AFLT triangulation to achieve high accuracy, high availability and high speed positioning. In the environment where neither of the two positioning technologies can be used, CDMA positioning technology will automatically switch to cell ID sector positioning mode to ensure the success rate of positioning. The wide area GPS satellite reference network consists of multiple high-sensitivity GPS receivers, which are responsible for monitoring the ephemeris data, Doppler frequency shift and other positioning information of all GPS satellites over the coverage area all day long, and dynamically refreshing the GPS satellite database stored in the positioning platform (corresponding relationship between satellite data and geographical location). The terminal only informs the positioning platform about the location (which base station it belongs to) through the wireless network when it needs positioning, and then obtains GPS satellite information through the positioning platform, so as to greatly shorten the satellite acquisition time and greatly reduce the power consumption.
With the powerful computing power of the positioning server, complex positioning algorithm can be used to reduce the influence of the weak received signal and other adverse factors, so as to improve the positioning accuracy and sensitivity. The positioning platform sends the longitude and latitude information to the application service platform, or sends it back to the terminal through the wireless network to meet the positioning application.
Analysis of advantages and disadvantages
传统 GPS 技术由于过于依赖终端性能，即将卫星扫描、捕获、伪距信号接收及定位运算等工作集于终端一身，从而造成定位灵敏度低及终端耗电量大等方面缺陷。CDMA 定位技术将终端的工作简化，将卫星扫描及定位运算等最为繁重的工作从终端一侧转移到网络一侧的定位服务器完成。提高了终端的定位精度、灵敏度和冷启动速度、降低终端耗电。
Traditional GPS technology relies too much on terminal performance, that is, satellite scanning, acquisition, pseudo range signal receiving and positioning operation are integrated in the terminal, which results in low positioning sensitivity and large power consumption of the terminal. CDMA positioning technology simplifies the work of the terminal, and transfers the most heavy work such as satellite scanning and positioning operation from the terminal side to the positioning server on the network side. The positioning accuracy, sensitivity and cold start speed of the terminal are improved, and the power consumption of the terminal is reduced.
在 GPS 卫星信号和无线网络信号都无法单独完成定位的情形下，CDMA 定位系统会组合这两种信息源，只要有一颗卫星和一个小区站点就可以完成定位，解决了传统 GPS 无法解决的问题。CDMA 定位系统的基础设施辅助设备还提供了比常规 GPS 定位高出 20dB 的灵敏度，性能的改善使 GPSONE 混合式定位方式可以在现代建筑物的内部深处或市区的楼群间正常工作，而两种传统方案在这些地方通常是无法正常工作的。CDMA 定位技术结合了无线网络辅助 GPS 定位和 CDMA 三角运算定位，改善了室内定位效果。CDMA 三角运算定位弥补无卫星信号下也能完成定位，其他蜂窝电话网络如 GSM/GPRS 也有类似自定位技术，但由于 CDMA 是惟一全网同步（通过 GPS）网络，因此定位精度不高。
In the case that GPS satellite signal and wireless network signal are unable to complete the positioning alone, CDMA positioning system will combine these two information sources. As long as there is a satellite and a small area site, the positioning can be completed, which solves the problem that traditional GPS cannot solve. The infrastructure auxiliary equipment of CDMA positioning system also provides a sensitivity of 20dB higher than that of conventional GPS positioning. The improvement of performance enables the gpsOne hybrid positioning mode to work normally in the interior of modern buildings or between buildings in the urban area, while the two traditional schemes are usually unable to work normally in these places. CDMA positioning technology combines wireless network assisted GPS positioning and CDMA triangulation operation positioning to improve the indoor positioning effect. CDMA triangulation operation positioning can also complete positioning without satellite signal. Other cellular telephone networks such as GSM / GPRS have similar self positioning technology, but because CDMA is the only whole network synchronous (through GPS) network, the positioning accuracy is not high.
1. Calculation error caused by the lack of client computing power;
2. GPS 定位卫星的标准钟时间不统一，致使在计算客户端到相应卫星的距离时有误差；
2. The standard clock time of GPS positioning satellite is not uniform, resulting in errors in calculating the distance between the client and the corresponding satellite;
3. The transmission time error caused by the change of atmospheric density caused by the change of temperature and the fact that the atmospheric correction index cannot change;
4. 美国对 GPS 信号进行的模糊化处理；
4. Fuzziness of GPS signal in the United States;
5. The number of acquired satellites is small, so it is impossible to apply a good error reduction algorithm;.