Melida

Since the development of GPS receivers, GPS technology has continued to evolve in order to receive the best satellite transmissions in the shortest amounts of time. As a result there are a number of GPS devices using various technologies to triangulate, transmit, and correct signals. Assisted GPS is a technology that applies the use of another server to help determine a location via GPS. For this reason, A-GPS is quite effective in areas which satellite transmission is more difficult, such as urban areas or places with heavy foliage. Over cellular networks, A-GPS is frequently utilized in Location Based Services (LBS), making the location of cell phones available to emergency dispatchers as well as allowing high quality civilian GPS calculation.

An Assistance Server is the only thing separating A-GPS from standard GPS. GPS networks usually operate using GPS receivers and satellites to calculate a specific location on the Earth. The Assistance Server allows devices with less processing power to utilize the high processing power and reference network of the server. Because an A-GPS receiver has the assistance of another server, it can produce results more efficiently and quickly, however, the connection to that server is necessary for A-GPS to give any benefit. In most cases, this is a cellular signal. Without this signal, an A-GPS receiver will not have the help of the server to calculate a location.

So what are the advantages of A-GPS?

As you may know, GPS signals shift in frequency because of the motion of the satellite relative to the receiver. For the receiver to lock onto a signal, it has to find the frequency bin. Any outside knowledge of the satellite position will increase the speed at which a receiving device can accomplish this. With an assistance server, a receiver can retrieve the orbit and clock data in order to narrow the possible frequencies, lowering the TTFF, or Time To First Fix. Due to this shorter TTFF, a receiver can find a location more quickly (saving time and energy) because it does not have to decode the navigational data, and it also has greater sensitivity. Since the better "time to first fix" narrows the frequency bins for the GPS receiver to search, the receiver can dwell longer on specific bins to produce more accurate results. Simply put, A-GPS allows receivers to retrieve location information accurately, quickly, and more energy efficiently by deferring most of the work on to the assistance server.

Due to its simple infrastructural connection to cell towers and cellular networks, A-GPS is becoming the most reliable and common strategy for determining a location through GPS. GPS cell phones, watches, cars, and other devices utilize A-GPS to provide the government and consumers alike with quick and accurate location results, making Assisted GPS the best strategy for using GPS with small, low powered receivers.

About the Author: Jon Werner is the Founder and Evangelist for Bones In Motion, a leading provider of GPS cell phone and Garmin GPS compatible software. For more information, please visit www.bonesinmotion.com.