TeleCommunication Systems
PDF of this tutorialIn their simplest form, location services depend on three basic components: a positioning technology, a location services platform, and applications. Each of these components is described in detail in the sections that follow.
Positioning Technologies
Positioning technologies calculate the physical location of the user and communicate this to the location services platform. They range in type from purely handset-based approaches to those that only utilize information from the network. Currently most positioning technologies use some portion of the network, which allows service providers to own the data and to ensure that its use generates revenue for them. A key benefit of network-centric solutions is that all handsets can utilize the positioning technology without modification. But network solutions are more expensive than handset-centric solutions, since each base station must be upgraded-and they are less accurate in rural areas, where base stations are situated further apart. Alternatively, handset-centric solutions are more accurate and less expensive to deploy than network-centric solutions, since the handset expense is passed on to the subscriber as a one-time charge. However, handset-centric solutions are only available to subscribers who purchase the new handsets.
The choice of positioning technologies also involves evaluating a number of complex factors such as the signaling load on the network, the impact of the technology on handset performance, and issues of privacy and ownership of location data. Descriptions of some of the key network and handset technologies-either in active use or awaiting wide-scale deployment-are described below.
Network-Centric Solutions
Cell-ID/Cell Site Sector - Currently the most widely deployed solution, this network-based technology uses existing data from the network to identify which radio cell site and sector a user is in. As a result, location accuracy is dependent on cell size. While this solution works well in dense, urban areas-enabling positioning down to a city block or so-it is far less accurate in country areas where a cell might cover many square miles. Its main advantage is that it requires no new functionality to be added to handsets.
Enhanced Cell-ID - Enhanced Cell-ID is a network technology that combines Cell ID (CI) with one or more additional technologies. The level of accuracy is increased over basic Cell ID, ranging from 75 - 500 meters. In GSM networks, CI can be combined with Timing Advance (which measures handset range from the base station, including whether or not the handset is connected to the nearest cell) and/or Received Signal Level (which measures average signal strength). In W-CDMA networks, CI can be combined with Round-Trip-Time (W-CDMA version of Timing Advance) to improve accuracy.
Enhanced Observed Time Difference (E-OTD) - E-OTD is a network technology that requires additional software on the mobile device and the addition of GPS receivers to base stations.
The mobile device calculates a user's position by triangulating the differing arrival times of network synchronization data regularly transmitted between handset and base station; it can provide accuracy to tens of meters.
Time Difference of Arrival (TDOA) - TDOA is similar in concept to E-OTD in that it also uses triangulation and time delay, but the processing is carried on the network side. While this has the advantage that older, legacy handsets can be supported, such a strategy does involve the installation of GPS receivers at all base stations.
Handset-Centric Solutions
Global Positioning Systems (GPS) - Using GPS satellites, this handset-based technology provides high accuracy, but has poor in-building coverage and either draws heavily on battery life if position is determined regularly, or delays results by tens of seconds (or even minutes) if the handset calculates position on-demand.
Assisted-GPS (A-GPS) - A-GPS is primarily a handset-based technology that uses enhancements to the network to provide additional accuracy and speed of location fix. GPS receivers are connected to the network at various known geographic points to provide additional data to the handset, greatly reducing the time needed to get positioning information and thereby allowing longer battery life. Certain A-GPS variants can provide better in-building location coverage and accuracy as well.
There are a number of additional technologies that use similar concepts to analyze the radio behaviors involved in cellular communications, to position the handset, and to calculate distances, angles of reception and signal strengths. These technologies are often combined to create hybrid approaches by incorporating the strengths of each technology.
Irrespective of which systems are adopted by service providers, it is likely that a mix of hybrid technologies will be used to meet the very different demands for accuracy and performance required by the different location service market sectors. As a result, flexibility will become an increasingly vital attribute of the supporting location platforms. In this context, it should also be remembered that the radio infrastructure of mobile service providers is constantly changing, and the effects of this on positioning performance must be easily manageable.
Location Service Platforms
The location services platform is the heart of the location offer, providing the essential functionality needed to link the user's location information with all the other services and systems involved in delivering location-based services and applications. The location services platform acts as a central nervous system by gathering, integrating and transmitting data between a variety of different components, including the actual positioning technologies, the network, MMS and SMS servers, billing and service management systems, Geographic Information Systems (GIS), the end user's handset and the actual location applications. All of this is accomplished while implementing privacy rules that insure proper and authorized use of the end user's location information.
The technical environment in which location platforms operate has grown considerably more complex, with new standards bodies and new application areas continuing to appear. For the industry to fully exploit the revenue potential of location services as well as provide all the related management and support functions, a wide range of APIs and features must be supported in as seamless a way as possible.
Examples of these interfaces include APIs, defined by the Open Mobile Alliance (OMA) which now includes the Location Interoperability Forum (LIF), and through the 3GPP's Open Service
Access initiative; old and new telecommunications signaling and messaging protocols, such as SS7 and SIGTRAN, as well as those supporting applications and services using Java; security and tools involving Public Key Infrastructure (PKI) certification; emerging open Geographic Information System (GIS) standards; as well as all the other interfaces to Operation Support Systems (OSS), billing and m-commerce systems required to properly integrate operations with the back office and with related payment mechanisms. New radio environments such as Wireless Local Area Networks (WLANs) and Bluetooth must also now be considered.
In addition, platform choices are heavily affected by a variety of business-related issues. While the multi-vendor network has become an industry cliché, continued industry consolidation combined with increasingly mobile and demanding customers has created a requirement for successful inter-working between different systems with minimal systems integration overhead. Additional issues must be factored in, such as content and applications that come from third party environments over which the service provider has little or no control, and Quality of Service performance issues.
Further challenges lie in the near future. In the area of Presence and Availability Management (PAM), a company's enterprise IT system will need to interact with a service provider's location data to provide useful corporate applications that use end-user's location information. As well, the enormous potential that location services have in supporting personal safety and asset tracking also must ensure information privacy, security and reliability. Both of these scenarios emphasize the need for ease of use by the end-users in setting up and controlling their own location services in both pre-packaged and custom-built offerings. Early adopters of technology will feel more comfortable if they can directly interact with their service profiles through fixed Internet portals or "on the fly" via their handsets, and these control mechanisms must be built into the management systems from the start.
Beyond fulfilling the perennial system requirements of stability, scalability and performance, location platforms will often be employed to support experimental services, as service providers and their partners explore this new market sector. In order to gain recognition for the revenue potentials of new services, platform vendors must show flexibility in the billing models that they offer their clients.
Location-Based Service (LBS) Applications
Applications drive the usage of the location offer and range from simple push services, such as weather and traffic alerts, to more complex or interactive services, such as location-based personal safety, dating, and gaming applications.
While the potential breadth of location-based services is enormous, finding business cases to support these original visions can be challenging. As with so many other mobile services, it is unlikely that there will be one true killer application. Instead, service providers must understand how different applications can be mixed and matched to suit specific market niches as they emerge and are recognized. It should also be noted that the benefits and revenue that location services offer can flow in both directions. Many business sectors, from entertainment to tourism, are coming to understand that location information can become an invaluable tool in their marketing armory, and therefore they will pay to attract new customers.
Whether the application area is personal safety, one of the main drivers behind the purchase of mobile services for many users, or lifestyle support involving gaming, dating and entertainment or travel resources, many mobile service providers will be reluctant to commit significant internal resources to build their own application solutions from the ground up. Technical issues, market understanding, and legal and financial value chain complexities will continue to encourage them to rely on vendors with experience and existing links to the content and applications community.
This issue is particularly important, given the experimentation and flexibility that happens during the initial stages of location services rollout. The members of both the service and the content chain will be concerned with the success of the new services, as well as the assignment of benefits and revenues generated. For some participants, there will be direct cash flows, while for others, location services may translate into branding opportunities that will generate money further down the transaction line, or service stickiness that reduces churn and attracts more premium customers.
