CDMA Positioning Method

Positioning Methods

Through CDMA, carriers can provide the following positioning methods:

1. Cell-ID: it obtains the cell information of the current base station on the network side to obtain the current location of the user. Its accuracy depends on the distribution and coverage of the mobile base station. That is, determine the base station where the mobile phone is located, and the user's location is within the coverage of the base station, which is a crude positioning.

Ii. Positioning Technology of aflt, aflt (Advanced forward link trilateration ). During the positioning operation, the mobile phone/terminal monitors the pilot information of multiple base stations at the same time, uses the bitwise delay to determine the distance to the nearby base station, and finally calculates the specific location using the triangular Positioning method. The principle is similar to that of satellite positioning. Locate multiple base stations.

For the self-positioning function, other mobile networks, such as GSM and GPRS, are also supported. However, because CDMA is the same throughout the network, the precision is the highest. If the density of base stations is high in the city, it will be better for underground parking lots, under the viaduct, and where there are many tall buildings.

Iii. GPS: Because traditional GPS technology relies too much on terminal performance, satellite scanning, capturing, pseudo-range signal receiving, and positioning operations are applied to terminals, as a result, the positioning sensitivity is low and the terminal power consumption is large.

• Consists of 24 communication satellites, a ground control platform, and a GPS terminal.
• The Ground Control Platform broadcasts calendars and other information to satellites.
• The terminal performs satellite scanning, capturing, receiving pseudo-distance signals, and locating operations to calculate the longitude and latitude. The disadvantages are as follows:
  • Power consumption;

  • It takes a long time to obtain location information for the first time
  • In poor environments, such as city centers, underground parking lots cannot be located or the error is large.
    

Iv. agps (Wireless Network-assisted GPS Positioning Technology): agps simplifies terminal work, and the locating server on the network side works with the terminal to complete location work, it is to transfer the most heavy work such as satellite scanning and positioning operations from the terminal side to the locating server on the network side. The terminal informs the positioning platform of the approximate position (which base station) through the wireless network only when positioning is required, and then obtains GPS satellite information through the positioning platform, which greatly shortens the satellite capture time, greatly reduce power consumption. With the powerful computing capability of the locating server, you can use complex locating algorithms to reduce the impact of unfavorable factors such as weak reception signals, thus improving positioning accuracy and sensitivity. The positioning platform sends the longitude and latitude information to the application service platform, or sends the information back to the terminal through a wireless network to locate the application. A server is required on the network side.

• Devices with the AGPS function transmit their base station addresses to the location server through a mobile network, based on the approximate location of the device, the location server obtains the GPS auxiliary information (including the GPS calendar and azimuth angle) related to the location and sends the information to the device with the AGPS function. Using the A-GPS, the receiver does not have to download and decode the navigation data from the GPS satellite, so it can have more time and processing capabilities to track the GPS signal, which can reduce the first positioning time, increase sensitivity and maximum availability.
• The AGPS module of the device receives the original GPS signal based on the received auxiliary information (to improve the first lock time TTFF capability of the GPS signal; the mobile network transmits the auxiliary data generated by the GPS reference network, such as the differential correction data and satellite operation status to the mobile phone, and find the approximate location of the mobile phone and the location information of the residential area from the database to the mobile phone, then the mobile phone can quickly capture the GPS signal, this first capture time will be greatly reduced, generally, it takes only a few seconds. The first capture time that does not need to be like GPS may be 2 ~ 3 minutes, and the precision is only a few meters, higher than the precision of GPS.
• After the device receives the original GPS signal, it parses the data to calculate the pseudo-distance from the device to the satellite, that is, the distance affected by various GPS errors. There are two calculation methods: MS-Based: There is a terminal for calculation. This step is the same as standalone GPS below,

  MS-encoded ed: transmits the information to the location server through the mobile network.
  

• The location server processes the GPS information based on the sent GPS pseudo-distance information and auxiliary information from other positioning devices (such as the differential GPS reference station), and estimates the location of the device;
• The location server transmits the device's location over the network to the location gateway or application platform.

Agps/GpsOne

GpsOne is actually no different from agps. It is a solution provided by Qualcomm and integrates the triangular positioning of base stations, gpsOne and agps are not two different positioning methods.Gpsone is just a general term of Qualcomm's software and hardware technical solutions for its own chip to implement GPS functions, including standalone, MS-based, Ms-powered ed | ms ted three methods, the technical implementation of StandaloneGPS, AGPS, and AFLT has been covered.

• Wiki describes GPSOne as follows: gpsOne is the brand name for a cellphone chipset manufactured by Qualcomm that allows cell phones to more accurately plot a user's position, using a technology referred to as a A-GPS or your ed-GPS.
• The wireless auxiliary AGPS and Advanced forward link AFLT triangle Positioning method are combined to achieve high precision, high availability and high speed positioning. GPSONE automatically switches to the Cell ID sector positioning mode to ensure the positioning success rate. GSPOne can be understood as the first use of AGPS, the second use of AFLT, and finally the use of Cell-ID, as much as possible to provide more accurate location information, and can not be used to scan the satellite. A server is required on the network side.

AGPS/GPSONE technology simplifies the work of the terminal, and transfers the most heavy work such as satellite scanning and positioning operations from the terminal side to the locating server on the network side. The positioning accuracy, sensitivity, and cold start speed of the terminal are improved to reduce the power consumption of the terminal. When GPS satellite signals and wireless network signals cannot be located independently, the GPSONE system combines these two types of information sources. As long as one satellite and one regional site can be located, it solves the problem that traditional GPS cannot solve. The infrastructure Auxiliary Equipment of the GPSONE System also provides a sensitivity of 20 dB higher than that of conventional GPS positioning, the performance improvement allows GPSONE hybrid positioning to work normally in the depths of modern buildings or between buildings in urban areas.

"Standalone" or "Autonomous" GPS devices use radio signals from satellites alone. a-GPS additionally uses network resources to locate and utilize the satellites faster as well as better in poor signal conditions. in very poor signal conditions, for example in a city, these signals may suffer multipath propagation (propagation) where signals bounce off buildings, or be weakened by passing through atmospheric conditions, wils or tree cover. when first turned on in these conditions, some standalone GPS navigation devices may not be able to work out a position due to the fragmentary signal, rendering them unable to function until a clear signal can be attached ed continuously for up to 12.5 minutes, (the time needed to download the GPS almanac and ephemeris ).

An existing ed GPS system can address these problems by using data available from a network. Balance ance falls into two categories:

1. Using information known to the specified ance server but not the GPS receiver er

O It can supply orbital data or almanac () for the GPS satellites to the GPS receiver, enabling the GPS receiver to lock to the satellites more rapidly in some cases.

O The network can provide precise time.

O The device captures a snapshot of the GPS signal, with approximate time, for the server to later process into a position.

O Accurate, surveyed coordinates for the cell site towers allow better knowledge of local ionospheric () conditions and other conditions affecting the GPS signal than the GPS generator er alone, enabling more precise calculation of position. (See also Wide Area Augmentation System and CellHunter .)

2. Calculation of position by the server using information from the GPS receiver

O The balance server has a good satellite signal, and plentiful computation power, so it can compare fragmentary signals relayed to it by GPS receivers, with the satellite signal it records es directly, and then inform the GPS generator er or emergency services of the GPS generator er's position.

As an additional benefit, in some A-GPS device implementations, known as "MS-received, "the amount of CPU and programming required for a GPS generator er is already ced by offloading most of the work onto the balance server.

A typical A-GPS-enabled authentication er will use a data connection (Internet or other) to contact the specified ance server for aGPS information. if it also has functioning autonomous GPS, it may use standalone GPS, which is sometimes slower on time to first fix, but does not depend on the network, and therefore can work beyond network range. some aGPS devices do not have the option of falling back to standalone or autonomous GPS.

Mobile phones combine A-GPS and other location services including Wi-Fi Positioning System and cell-site triangulation and sometimes a hybrid positioning system.

High Sensitivity GPS is an allied technology that addresses some of these issues in a way that does not require additional infrastructure. however, unlike some forms of A-GPS, high-sensitivity GPS cannot provide a fix instantaneously when the GPS generator er has been off for some time. (This indicates that high-precision GPS does not adopt the AGPS method)

The above describes the excellent parts of AGPS/GPSOne, but in terms of continuous positioning, the traditional GPS performance is better, the MSA takes more than 10 seconds, MSB takes 2-3 seconds, and standalone takes 1 second.

Source:

1. http://www.pcjx.com/GPS/ying/174570.html

2. http://hi.baidu.com/428501/blog/item/8db95b5487528b143a29359a.html

Http://en.wikipedia.org/wiki/GpsOne

4. http://en.wikipedia.org/wiki/Assisted_GPS

5. http://www.s128.com/view/13897589

6. http://www.docin.com/p-51164475.html