[vimal2007]

i need to know what are the available location based services?need to do a comparison with respect to the architecture.pls send me some details/thesis reports.pls help me as am new to this area.

[mobileraj]

The following sections explain the most common positioning methods in more detail. Figure 1 provides an overview of the described methods.

Handset-Based Methods
# Global Positioning System (GPS): This system was developed by the U.S. Department of Defense and is still maintained by them. Originally developed only for the military, today this positioning system is widely used by civilians. The system is based on signals that are transmitted from 24 satellites that GPS receivers on earth use to calculate the current location. Each GPS receiver needs to be in contact with four satellites at the same time to be able to determine the user's longitude, latitude, and altitude. Among the advantages are the relatively exact positioning result (close to 10-30 meters) as well as the possibility of determining the altitude at which the terminal is located. A serious disadvantage is the lack of reception of GPS signals within buildings, which can make the positioning process impossible.
# Enhanced Observed Time Difference (E-OTD): This method is often referred to as the opposite of the TOA (Time of Arrival) method. Instead of measuring the time differences of signals that are transmitted from the terminal to the base station, the terminal calculates the location. Therefore, special software has to be installed in the mobile terminal. In addition, so-called "Location Measurement Units" have to be installed at each base station. The accuracy of E-OTD is relatively high, although the best results that are close to GPS can only be expected in urban areas, where many GSM cells are available.
# Subscriber Identity Module Toolkit (SIM): Another handset-based positioning method is via the SIM Toolkit. The STK is an API that allows communication with the SIM smart card, which many mobile phones have from applications that were installed on the handset. The quality can be as bad as the COO method, but can also be improved by some algorithms that are stored on the SIM and by some extra features that are provided by the network.

Network-Based Methods
# Cell of Origin (COO): COO is the easiest and most common method, but also the most inaccurate one. The network determines only the cell from which the user is placing a call or initiating a data transfer and can determine the location based on the known locations for the base stations of the network. Interestingly, this method is already sufficient for most location-based services, and additional calculations like Timing Advance (TA) can further enhance the quality of positioning.
# Angle of Arrival (AOA): This method uses special equipment that has to be installed at the base stations to determine the angle of arrival for the radio signals. With some basic geometric calculations, you can then determine the location of the user with only two base stations receiving its signal.
# Time Difference of Arrival (TDOA): This method uses the differences of arrival for the radio signals at the base stations (from the mobile terminal). A minimum of three receiving base stations is required to calculate the location of the user.
# Location Pattern Matching (LPM): This complex method analyzes the radio signals and compares them to patterns saved in a database. These patterns include signal reflections and echoes. When a pattern is recognized, the location of the user can be identified. This method can be used only in urban areas, where these signals often occur. In these areas the quality might be better than using other methods; unfortunately this method is not suitable as a general method for rural areas.

Hybrid Methods
# Assisted GPS (AGPS): AGPS uses information from the network to more quickly determine the position of the four satellites that it needs to listen to. The network cell distributes the locations of those satellites and can drastically reduce the initialization time that a normal GPS receiver needs. In addition, this method saves battery power as the GPS receiver is only activated on a usage basis.

Other methods of mobile positioning include short-range beacon methods such as Bluetooth or IrDA. Those methods can be used to locate users indoors and the quality of service is good. On the other hand, the setup of those networks is a highly complex task as a new infrastructure is needed and mobile terminals have to be updated as well.

[Nokia Ron]

I encourage you to post this on the Wiki

Ron

[petrib]

Maybe not without rewriting or verifying the original source (if it has been copied from someplace else, like the phrase "Figure 1 provides an overview of the described methods" leads at least me to suspect).

[hartti]

Looks like this
http://goliath.ecnext.com/coms2/gi_0...fy-access.html

Hartti