Location Based Services (LBS)


Location Based Services offer a unique opportunity to mobile service providers to differentiate their brand, retain existing customers, induce a positive churn and increase vertical penetration. Choosing the right position determination technology and evolving a clear migration path to future technologies that improve accuracy and consistency will be the key for successfully tapping this opportunity. Also critical will be the choice and design of innovative services and applications that fit into the accuracy profile of the positioning technology chosen.Services that exploit information of the physical location of a subscriber to add value can be defined as Location Based Services. This information about the physical location of subscribers is a very valuable asset for mobile service providers and can be leveraged to offer a plethora of value added services.
Such business and consumer Location Based Services or LBS for short will enable users or machines to find other people, vehicles, resources, services or machines. They will also enable users to identify their own location and access information pertinent to their environment or vicinity.
Location Based Services can provide a key differentiator to mobile operators to retain existing customers and also induce a positive churn. According to some research analysts, global wireless LBS revenues will increase from US $1 billion in 2000 to over US $25 billion in 2006, representing a CAGR of 81%. This presents a huge opportunity to mobile operators - one that cannot be missed. Another study predicts that 40% of operator mobile data services revenues worldwide in 2007 will be location-based. Thus it would be disastrous for an operator to ignore LBS in its overall data services offering.
However, many challenges need to be overcome before LBS can be implemented successfully. The most important of these will be the choice of the position determination technology that is used to calculate (make a ‘fix’) the location of the mobiles. There are several technology options that are available to operators to do this. Each option has a different accuracy and consistency profile. Each option will be more suited to a particular set of applications than others. Or in other words different applications will have varying accuracy and consistency requirements and hence will work better with a certain position determination technology than others. Also important to consider will be the impact of the technology on existing infrastructure and the support for legacy mobiles (those that do not support any handset based position determination technology). Apart from the position determination technology, the choice of the services and applications, the delivery mechanisms and the content provided by those applications will also be critical.Merely knowing the location of a subscriber does not add any value. Location or position information is only an enabler, which makes possible a whole host of applications. To be able to make an impact on the customer with such applications or value added services, the position information must be combined with rich content (such as maps, city guides, event information etc.), innovative delivery mechanisms (such as push a mobile discount coupon whenever the subscriber is in the vicinity of a certain mall)
LBS will account for up to 40% of data services revenue of mobile operators. In this context it will be important to note the breakup of LBS revenue for different services to enable operators to position their offerings appropriately.Although LBS got a push in the US due to the FCC E-911 mandate, the positioning infrastructure thus deployed is now being leveraged to offer various value added services.
The number of location-enabled subscribers in the US is fast approaching the entire customer base. This capability which is now available thanks to the FCC mandate cannot be left for just emergency use and must be leveraged to create additional revenues (and also recover the costs of the FCC mandate as it is entirely unfunded). These developments are now getting translated into location-based value added services, not just in the US but around the world.Forecasts by the Strategis Group predict that a major chunk of worldwide LBS subscribers will be for location-based information services. by 2005 there will be more than 200 million subscribers for the various location-based information services worldwide.
The next major category in terms of subscribers will be location-based billing which will account for close to 100 million subscribers by 2005. Traffic & navigation and roadside assistance will form the other major categories. It may be noted that each of these categories will consist of a number of different services catering to different consumer segments and different usage scenarios.
Location-based information and location-based billing emerge as the top two categories. Location-based billing will account for more than US$ 15 billion in revenues worldwide by 2005. Location-based information services will create close to US$ 12 billion in revenues. These revenue forecasts and subscriber figures will make LBS an indispensable part of the data service offering of mobile operators in the near future.
Mobile Positioning:
Position determination technologies can be broadly categorized as network based and mobile based. Network based options require minimal or no changes on the handsets and thus are suited to support legacy mobiles also. Mobile based technologies rely on the mobile for taking measurements (time, angle, time difference etc.) or making the calculations for the fix or both. Mobile-based methods may require software or hardware upgrades on the handsets.Conceptually, all the positioning techniques are based on calculating the distance of the mobile from the location of a known radio source (e.g. base stations and satellites) by measuring the angle, time of arrival or time difference of arrival of the radio signals from the base station to the mobile or from the mobile to the base station. Usually such measurements need to be made with one or more pairs of base stations to get an unambiguous fix. If these measurements are made at the base station, the actual calculations are performed in the network and if they are made at the mobile, the calculations may be performed either by the mobile itself or by the network.A hybrid method involving two or more techniques is also conceivable to provide greater consistency in scenarios where one technique fails to provide an acceptable fix. For example one technique that works only in the “conversation” mode of the mobile but provides greater accuracy can be combined with another technique which works in the “idle” mode also but perhaps is able to provide a limited accuracy.The various positioning techniques can be characterized and compared based on the following major attributes:
Accuracy:The error margin within which the positioning technology is able to provide a fix. It is the most important attribute of a positioning technology. The crudest technology provides around 500m of accuracy, while the most advanced technology is able to provide an accuracy of up to 5m.Parameter:The parameter that is measured to calculate the location. Some of the commonly used parameters are time of arrival, angle of arrival, time difference of arrival and signal strength.Measuring NE:The network element (or elements) that makes the measurement. This is usually the handset or the base station.Calculating NE:The network element that performs the calculations to make the fix.Consistency (Topographical):The consistency of the technology in providing a fix in different topographies such as rural areas, sub-urban areas and in-building support.Number of BTS:The minimum number of base stations that need to be involved in a measurement to provide an unambiguous fix.Network Impact:The impact on existing infrastructure (base stations, BSC, MSC etc.) in implementing this technology.Mobile Impact:The impact on handsets in implementing this technology. Whether it supports legacy handsets or not.
Network Based Technologies:
This section discusses the positioning technologies that do not require any kind of assistance from the mobile. The technologies discussed in this section are listed below:· Cell Identification (Cell ID)· Enhanced Cell ID (Network Based)· Angle of Arrival (AOA)· Time of Arrival (TOA)
Cell ID:
Cell ID technique is the most straightforward to understand and implement. Any terrestrial cellular network consists of a number of cell sites (or base stations) to provide coverage to any given area. At any given time the mobile is in the coverage area of (or is being “served by”) a single cell site (except in the case of soft handoffs). The information about which cell site is serving a particular mobile is readily available to the network as and when the mobile registers (power-up registration, timer based registration etc.) or originates/terminates a call.Even if this information is not available or is not recent enough for the requirements of a particular application, it can be obtained by paging the mobile.In order to be able to query the Cell ID of a mobile, support for WIN Phase 2 (IS-848) is required at the VLR, MSC, HLR and SCP.The accuracy provided by this technique is substantially low as a given base station covers a large area. This problem is further aggravated in sub-urban and rural areas where the base station densities are very low. The area covered per sector in big cities is significantly large. This will be even larger for other cities as the base station densities will be much lower. But even this much accuracy is sufficient for a large number of services that require only a broad area of the mobile’s location and not a precise position.The biggest advantage is that Cell ID supports all handsets, as it is a completely network-based solution. It can be used to offer location-based services that do not require a high accuracy to legacy mobiles. It can also be used as a backup positioning technology for the cases when a high accuracy technique fails to provide a fix.
Enhanced Cell ID:
Enhanced Cell ID is a technique, which uses signal strength measurements to supplement Cell ID information for estimating the location of a mobile. Enhanced Cell ID provides an accuracy that is better than Cell ID alone.Signal strength of the signal received from MS (at BTS) or from BTS (at MS) is measured. This measurement is compared to a database of RF signatures of different locations, which may be based on a signal attenuation model or actual measurements to get a position estimate. A cell coverage area can be split into 50m x 50m (for example) blocks for which signal strengths can be measured and stored in a database beforehand. The position of a mobile can be estimated by comparing the actual measured signal strength to those stored in the database.The signal strength measurement can be for the forward link or the reverse link. This section covers the network-based Enhanced Cell ID technique in which the reverse link signal strengths are measured by the BTS.
This technology will not give very good results when a subscriber is indoors as the signal strength will decrease in comparison to the outdoor strength (the RF signatures that are generated are generally for outdoors). Moreover the signal strength can change with environment and man-made structures.
The network directs the mobile to transmit a Power Up Function message (PUF) starting at a predetermined time and at a predetermined power level. Mobile transmits a PUF on the reverse traffic channel, which is received by the base station. The PUF is transmitted at a high power to enable multiple base stations to listen to it. These multiple measurements, though not mandatory, improve the accuracy of the technique.There is currently no standardization in this area. It is not very clear how the signal strength measured by the BTS will be transmitted to the PDE and how the network (MPC) will initiate the position determination procedure.
Angle of Arrival (AOA):
In the AOA technique, the angle of arrival of a signal from a mobile is measured at several BTS through the use of antenna arrays. Using the angle of arrival at these BTS the location of the mobile can be calculated. To pinpoint the location of a mobile, at least two BTS with a known separation between them are required.
This technique assumes that the signals coming from the mobile are Line of Sight (LOS) transmissions. However, in most practical scenarios the LOS component is not present.As all Non-LOS (NLOS) components of a signal arrive after scattering, in the absence of a LOS component, the antenna array will lock onto a signal coming from a wrong direction. Also the accuracy of this technique decreases with distance due to the scattering characteristics.For Macrocells, scattering objects are primarily within a small distance of the mobile, since the BTSs are well elevated above the local terrain. Researchers have modeled this situation by assuming a ring of scatterers around the MS with the BTS situated well outside the ring.For Microcells, BTSs may be placed below roof top levels. Consequently the signals received at the BTS can suffer from scattering near the BTS as well. Thus, AOA may not be useful for Microcells.
There is currently no standardization in this area. It is not very clear how the angle measurements made by the BTSs will be transmitted to the PDE and how the network (MPC) will initiate the position determination procedure.
Time of Arrival (TOA):
In the TOA technique, several base stations measure the propagation delay of the signal received from a mobile. The propagation delay gives a distance circle with the base station at the center on which the mobile should lie. Theoretically using three or more BTS the location of a mobile can be calculated precisely by finding the intersection of these distance circles.However in real life scenarios the signal received at BTS will be delayed due to scattering.
A similar approach involves measuring the time difference of the arrival of the signal from a mobile at three or more BTS. This approach is known as Time Difference of Arrival (TDOA). Here instead of getting distance circles, we get constant distance hyperbolas, which intersect to give the location of the mobile.
Time Difference of Arrival is also referred to as U-TDOA (Uplink Time difference of Arrival) as the measurements are done on the reverse link or uplink.
Both in TOA and TDOA, presence of the LOS component is important. In absence of the LOS component the calculations will give a region instead of a precise location.At least three BTS are required to listen to the mobile. However an estimated location of the mobile can be found by using two BTS as well at the cost of accuracy.Since at least 3 BTS have to listen to the mobile for this technology, every time location has to be ascertained the mobile will have to be assigned a traffic channel.There is currently no standardization in this area. It is not very clear how the measurements made by the BTSs will be transmitted to the PDE and how the network (MPC) will initiate the position determination procedure.
Posted by Aayush Bhatnagar at Thursday, March 22, 2007
Labels: Location Based Services (LBS)