A-GPS technology: what is it and how does it work? GPS satellite navigation system - principle, diagram, application.

A-GPS (English: Assisted GPS) - technology that allows you to speed up the so-called “cold start” of the GPS signal receiver. Acceleration of the provision of the required location information is achieved through the use of other communication channels. This system is often used in smartphones and cell phones that have a built-in GPS signal receiver chip.

Modern smartphones have large displays that allow you to display any graphic information, and in particular geographical maps, V excellent quality. This allows the user to easily solve both business problems and obtain information for personal needs or see entertainment information.

In Europe, users of the GPS system often confuse it with LBS service. LBS is a range of entertainment and information services, which are based on the location of the network subscriber cellular communications. To provide such services, the use of GPS or A-GPS technology is not necessary. The subscriber's location is calculated with an accuracy of 50 - 100 meters by measuring the signal level from base stations GSM plus via signals from Internet access points Wi-Fi technology, to which the subscriber’s gadget is connected.

How A-GPS works:

For the A-GPS system to function, you must have additional channel connection through which information from a remote server can quickly reach the receiver’s input. Mobile devices (smartphones, phones) most often use cellular communication channels for this. If the phone is within range cellular network and has Internet access - A-GPS system is activated automatically.

Approximate location:

To speed up the processing of location data, the system A-GPS limits the search area for satellite signals by first determining the approximate location. Mobile phones allow you to calculate it using GSM operator base stations. The accuracy of the calculations depends on how many signals the phone picks up from different base stations. The highest density of base stations is usually found in city centers. In these places, the accuracy of location measurement reaches 200 - 500 meters. On the outskirts of cities and in sparsely populated areas, the measurement accuracy is only 1500 - 2000 meters.

GPS technology is used not only by car enthusiasts and taxi drivers. It is also popular among lovers of outdoor travel, fishermen and simply people leading an active lifestyle and constantly walking/driving back and forth. If someone needs to know where he is, where the location he needs is located, how fast he is moving and how soon he will reach his goal, GPS will come to the rescue.

The reason for the widespread popularity of this technology lies in the following:

coverage area covers the entire globe;
the technology is used not only in expensive secure GPS trackers, but also in relatively cheap GPS navigators for cars and even in smartphones;
There is no need to pay for using GPS.

About the history of GPS and navigation satellites

The idea of creating a system satellite navigation Americans caught fire back in the 1950s, when the first artificial satellite Earth. In 1973, the DNSS program was launched, which was later renamed Navstar-GPS, and then simply GPS. The first satellite (test) was launched into orbit in 1974.

After the first Soviet navigation satellite GLONASS (Global Navigation System) was launched into orbit satellite system) in 1982, the US Congress allocated funds to the US military to speed up work. First worker GPS satellite was launched in February 1978 and operates in full force the system began at the end of 1993, when all 24 satellites took their places in Earth orbit.

Each navigation satellite weighs about 900-1000 kg, and in length with open solar panels reaches 5 meters. The average service life of a satellite is 10 years. After this period, a new satellite is launched to replace the exhausted satellite.

About GPS receivers

The speed of calculating coordinates when the receiver is turned on, its sensitivity and positioning accuracy are determined by the chipset with which it is equipped. Chipsets for GPS devices are made by several manufacturers, but the most common is SiRFstarIII from SiRf Technology.

Receivers with the SiRfstarIII chipset have a short cold start time (several seconds) and can simultaneously receive signals from 20 satellites. They are very sensitive and allow you to determine coordinates with high accuracy.

What is the difference between GPS and A-GPS

The list of characteristics of some smartphones indicates the presence of a GPS module, others - A-GPS. How are these modules different?

During a cold start (when the navigation system has not been used for a long time), a device with a conventional GPS receiver can search for satellites for a long time - the waiting time sometimes reaches 10 minutes or more. This is because the GPS receiver searches for satellites without knowing their location.

When using A-GPS device immediately receives part of the necessary information using the GPRS/3G network (traffic no more than 10 KB). Thus, A-GPS is a software add-on over the GPS receiver, which significantly reduces the time it takes to search for satellites during a cold start. In addition, this add-on allows you to increase location accuracy in areas with weak satellite signals.

However, A-GPS has one small disadvantage. Unlike GPS, which is completely free to use, A-GPS has to be paid according to the tariff set by your provider, since it consumes Internet traffic (however small).

While looking through various types of GPS equipment, you have probably come across the abbreviation A-GPS (most often found on smartphones). What is A-GPS and why would it be good to have this feature?
It should be noted that since 2012, all GPS trackers Intel companies have this function.

A-GPS stands for Assisted GPS (accompanied by GPS), the function helps GPS module install a satellite signal. The so-called “cold start time” is the time required to determine coordinates from the moment the GPS is turned on with the device completely turned off. There is a so-called TTFF parameter (time to determine coordinates), this period increases significantly in difficult conditions when there is no direct visibility of all satellites. Most often, this happens in dense urban areas, when satellite signals are reflected from all nearby buildings.

It must be said that the AGPS function only works when connected to mobile internet. This can be GPRS data transmission or WCDMA (3g mobile internet). By transmitting and receiving location-related data from the Internet, the technology allows you to speed up the process of determining your coordinates. What data is transmitted via the Internet will be discussed below.

First start GPS devices- called a cold start or factory start. At this time, three types of data are loaded into the device: satellite signals, almanac data and ephemeris data) to determine its location. A cold start occurs after a prolonged shutdown, moving over long distances, or when resetting the cache data (saved data about the last location of the module.

For standalone GPS receivers, a cold start can take up to 10 minutes. However, if the signal is uncertain and is interrupted during the start of coordinate determination, (due to low level signal, weather conditions, buildings, etc.), a cold start may take longer.

A-GPS helps speed up coordinate determination by connecting via the Internet to a web server (called an Assisted Server) that already contains up-to-date information about all satellites. This information is transmitted via GPRS to the phone.

In addition, it has been shown that even a warm start is faster using A-GPS, by an average of a minute.

What A-GPS technology doesn't do

Despite the fact that the described function remarkably improves the performance of the satellite module, there are certain limitations. Satellite signal will not be detected inside large and reinforced concrete buildings (far from windows). Also, GPS signal will not work underwater or even underground. By the way, in the absence mobile communications(Internet), this function doesn't work either.

In addition, do not confuse the A-GPS function with Wi-Fi positioning or the “triangulation” method for cell phones, when determining coordinates using GPS is impossible.

Some devices combine these positioning methods. Such location determination methods are called: hybrid positioning systems.

Where is Intelli LLC heading with its developments? First of all, these are integrated positioning systems.

IN ideal conditions GPS or Glonass is the fastest and in an exact way determining the location of the object. At the same time, there are certain positioning restrictions: inside buildings, underground (underground parking, for example), under water, etc. The positioning technology we have come to is to provide our clients with a comprehensive solution.

At the 2010 FIG Congress, the main trend was universal positioning using all available technologies: GPS/Glonass, WI-Fi positioning and triangulation method for cell phones.

Combining the advantages of these technologies will improve not only the accuracy and stability of GPS monitoring systems, but will also be used universally in all popular mobile devices.

Back

Let's start with the fact that GPS or Global Positioning System is global system positioning. To put it quite simply, then this system represents virtual card, with which the user can determine his location. It is worth noting that the above system has nothing to do with GPRS (General Packet Radio Service), since the latter is a so-called GSM add-on for packet data transmission for accessing the mobile Internet.

If we return to GPS technology, it is not only used by motorists, as many people think. The scope of use of the GPS system is much wider. For example, it is very popular among travelers, hunters, fishermen and other people who prefer an active pastime and who from time to time need information about their own location or the location of a particular location. In addition, if information on movement speed is needed vehicle and estimated time of arrival at your destination - GPS can become an indispensable tool.

Note that GPS receivers differ in the speed with which they can calculate coordinates from the moment they are turned on, as well as in the sensitivity and accuracy of positioning. All these parameters depend on the chipset that the GPS receiver is equipped with. There are chipsets for GPS devices from a number of manufacturers on the market, however, the most popular are the SiRfstarIII chipsets, produced by SiRf Technology. Receivers equipped with the SiRfstarIII chipset demonstrate a short so-called cold start time when the navigation system was not used for a long time, it lasts a couple of seconds. In addition, these chipsets make it possible to receive signals from 20 satellites at once. Moreover, GPS receivers with SiRfstarIII chipsets are considered the most sensitive and have highly accurate position determination capabilities.

What is the difference between GPS and A-GPS?

To begin with, it is worth mentioning that in technical specifications smartphones contains information about different modules. If in some we are talking about a GPS module, then in others we are talking about A-GPS. So what is their difference? If the device is equipped with a regular GPS receiver, then during a cold start (read what this is - read above), the search may take longer because the navigator cannot quickly find the satellite, and this can last for more than one minute. The reason for the long search for a satellite by a GPS navigator is simple - the lack of information about the actual location of the satellite.

If your device uses A-GPS technology, then necessary information V operational mode arrives using a GPRS, 3G or LTE (4G) network (traffic does not exceed 12 KB). At its core, A-GPS is a software add-on for a GPS receiver, with the help of which the satellite search time during a cold start can be significantly reduced. As already noted, acceleration is achieved mainly through alternative communication channels. By and large, for A-GPS technology to function, it requires a communication channel with remote server, from which the information necessary for the GPS receiver comes. If we go back to mobile devices, then in their case it is an Internet connection via cellular or Wi-Fi.

Note that the A-GPS add-on has both advantages and disadvantages. If we start with the advantages, it is worth noting the very fast determination of coordinates immediately after switching on. In addition, the technology enhances reception sensitivity weak signal in so-called dead zones - tunnels, indoors, in valleys, etc. However, a significant disadvantage of A-GPS is the inability to work where there is no cellular network coverage. In addition, the use of A-GPS cannot be absolutely free, like, for example, GPS. This is due to the consumption of Internet traffic by the A-GPS add-on, which must be paid depending on the tariffs of a particular Internet provider.

Let's start, perhaps, with an explanation of what it is A-GPS and how is it different from GPS. In most cases cell phones do not have a good enough receiver that could provide reliable signal reception indoors or between high-rise buildings. This is where the so-called A-GPS, which in most others mobile phones called simply GPS.

A-GPS(eng. Assisted GPS) system that speeds up coordinate determination GPS receiver

Most big problem For GPS The receiver is a so-called “cold start”. It is at this moment that the search for satellites occurs. Depending on external factors, the starting process may be delayed, which not only causes discomfort, but also leads to increased energy consumption. Technology A-GPS helps to cope not only with this problem, but to make life a little easier GPS to the receiver.

In the case of iPhone this means that the current position will be determined using GPS, Wi-Fi and stations mobile operators(craftsmen from Apple For all this, we managed to use only 2 antennas, which are located in unexpected places - a ring around the camera, an audio jack, a metal rim around the screen, etc. All this data will be processed by the auxiliary server. This is precisely the advantage A-GPS before GPS: the first one works much faster, but the second one “slows down” during a “cold start” when searching for satellites. With regular GPS receiver for positioning you need several strong signals and a certain amount of time to obtain coordinates. At A-GPS The secondary server itself tells your phone where the nearest satellites are, thereby reducing search time. In addition, this approach also saves battery.

Unlike many other phones, A-GPS V iPhone will work without connection to the network, which will allow you to use it outdoors, and indeed anywhere in the world where a satellite signal is received (however, do not forget that you will need Google Maps , you will have to download it in advance).

It is currently not known how quickly A-GPS will drain the battery: iPhone will automatically turn the positioning system on and off as needed, which will save charge. It is expected that during active operation (constant position tracking, etc.) it will still consume quite a lot.

Realizing how good he really is GPS will be in iPhone, we move on to the most interesting part - navigation. Here it is Apple as always in my repertoire. Current version SDK prohibits its use for navigation in real time (“Real-Time Route Guidance”). But it's not all bad, giant GPS industry TomTom stated that they are already working on a navigator for the iPhone. Apparently, large companies have to somehow obtain permission to use SDK on an individual basis. Thus, additional expenses await us in order to turn iPhone acceptable for use navigator. But we are apparently no strangers :-).