A-GPS

How is your mobile navigation works  

A GPS navigation device is a device that receives Global Positioning System (GPS) signals to determine the device's location on Earth. GPS devices provide latitude and longitude information, and some may also calculate altitude, although this is not considered sufficiently accurate or continuously available enough (due to the possibility of signal blockage and other factors) to rely on exclusively to pilot aircraft. GPS devices are used by the military, by aircraft pilots, by sailors, and for recreational purposes by the public.

GPS devices may have capabilities such as

• maps, including streets maps, displayed in human readable format via text or in a graphical format,
• turn-by-turn navigation directions to a human in charge of a vehicle or vessel via text or speech,
• directions fed directly to an autonomous vehicle such as a robotic probe,
• traffic congestion maps (depicting either historical or real time data) and suggested alternative directions,
• information on nearby amenities such as restaurants, fueling stations, and tourist attractions.

GPS may be able to answer:

• roads or paths available,
• roads or paths that might be taken to get to the destination,
• if some roads are busy (now or historically) the best route to take,
• The location of food, fuel or other needs,
• the shortest route between the two locations.

  

  Bicycle navigation on a personal navigation assistant

  
  

  Mobile phones with GPS capability

Due in part to regulations encouraging mobile phone tracking, including E911, the majority of GPS receivers are built into mobile telephones, with varying degrees of coverage and user accessibility. Commercial navigation software is available for most 21st-century smartphones as well as someJava-enabled phones that allows them to use an internal or external GPS receiver (in the latter case, connecting via serial or Bluetooth). Some phones using assisted GPS (A-GPS) function poorly when out of range of their carrier's cell towers. Others can navigate worldwide with satellite GPS signals as well as a dedicated portable GPS receiver does, upgrading their operation to A-GPS mode when in range. Still others have a hybrid positioning system that can use other signals when GPS signals are inadequate.

More bespoke solutions also exist for smartphones with inbuilt GPS capabilities. Some such phones can use tethering to double as a wireless modem for a laptop, while allowing GPS-navigation/localisation as well.^[1] One such example is marketed by Verizon Wireless in the United States, and is called VZ Navigator. The system uses gpsOne technology to determine the location, and then uses the mobile phone's data connection to download maps and calculate navigational routes. Other products including iPhone are used to provide similar services. Nokia givesOvi Maps free on its smart phones and maps can be preloaded.

According to market research from the independent analyst firm Berg Insight, the sales of GPS-enabled GSM/WCDMA handsets was 150 million units in 2009, while only 40 million separate GPS receivers were sold. GPS navigation applications for mobile phones include on-line (e.g. Waze, Google Maps Navigation) and off-line (e.g. iGo for Android, Maverick) navigation applications. Google Maps Navigation, which is included with Android, means most smart phone users only need their phone to have a personal navigation assistant.

Many Android smart phones have an additional GPS feature, called EPO (Extended Prediction Orbit). The phone downloads a file to help it locate GPS satellites more quickly and reduce the Time To First Fix.

The mobile phone navigation system works on concept of A-GPS that is nothing but  assisted GPS system 

now we are going to see how this stuff works in our hand held mobile devices.

with the help of A-GPS, the GPS (Global Positioning System) technology has been brought to your cell phones too. Let us understand what it is and how it works. A-GPS topology  A-GPS is an acronym for Assisted Global Positioning System. It addresses signal and network problems by using assistance from other services. Such technology in your cell phone can help you in various ways like tracking your current location, receiving turn-by-turn direction instructions, location based tracking, etc. The working of a GPS and an AGPS is similar apart from this minor detail. Let us first understand how GPS signals are received and monitored. GPS devices can plot absolute directions based on your current position or they can give you directions through a map device irrespective of your current position. Thus a good GPS system with high-sensors can cost you quite a lot.  As a step further, A-GPS technology helps to overcome these glitches. Suited for mobile devices, A-GPS takes assistance from GPRS and at times, the service provider network information, to pin-point the current location accurately. Moreover the amount of CPU and programming required for a GPS phone is reduced by diverting most of the work to the assistance server instead.  A typical A-GPS enabled Cell phone uses a GPRS or other such Internet based data connection to build a contact with the assistance server for A-GPS. This exercise usually is a bit slow if you are connecting with the server for the first time. As this technique does not take into account the cell phone service provider network completely, you only pay the GPRS usage charges and nothing else. The only down-side to this technology is that an A-GPS server cannot utilize any of the three standby satellites available for GPS connections.