Location Location Location
January 2004 The future use of location information to enhance the handling of emergency mobile phone calls
PO Box 13112 Law Courts MELBOURNE VIC 8010 Telephone (03) 9963 6800 Facsimile (03) 9963 6899 TTY (03) 9963 6948 www.aca.gov.au ABN 78334953951
Table of Contents 1.
PURPOSE OF THIS PAPER ....................................................................................................... 3
2.
INTRODUCTION ......................................................................................................................... 4
3.
THE NEED FOR MORE ACCURATE MOBILE LOCATION INFORMATION ................ 5
4.
LOCATION TECHNIQUES AND TECHNOLOGIES ............................................................. 6
5.
REGULATING THE INTRODUCTION OF LOCATION TECHNOLOGIES ..................... 7
6.
COMMERCIAL DRIVERS ......................................................................................................... 7
7.
THE NEXT STEPS........................................................................................................................ 9
8.
LIST OF ACRONYMS ............................................................................................................... 13
ATTACHMENT A—BACKGROUND TO THE EMERGENCY CALL SERVICE.................... 14 ATTACHMENT B—THE EMERGENCY CALL PROCESS AND THE USE OF MOLI .......... 17 ATTACHMENT C—AN OVERVIEW OF THE REGULATION OF HIGH ACCURACY MOLI IN THE USA AND THE EUROPEAN UNION............................................ 19 ATTACHMENT D—OVERVIEW OF MOBILE LOCATION TECHNIQUES .......................... 27
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1.
Purpose of this paper
1.1 The potential use of highly accurate location information to enhance the emergency call service poses a complex challenge to both the telecommunications industry and the emergency services community. In an effort to engage stakeholders and interested parties in this challenge, the ACA has prepared this paper to: •
inform readers about some of the relevant issues;
•
document some of the key regulatory considerations;
•
seek input from stakeholders;
•
provide industry with an early indication of the likely level of regulation in this area; and
•
outline the initiatives that the ACA, in consultation, may pursue in the short-tomedium term.
1.2 To generate further discussion and enable ongoing consideration of the associated issues, written submissions are invited in response this paper. To aid in the provision of feedback, discussion questions are included throughout the paper. However, broader comments on any relevant issues are also welcomed. 1.3 All submissions received will be made available for public inspection on the ACA website. Any information that submitters wish kept in-confidence should be clearly identified as such and, if possible, provided by way of a separate attachment to enable the non-confidential material to be published. 1.4
Submissions should be addressed to: The Manager Licensing and National Interests Australian Communications Authority PO Box 13112 Law Courts MELBOURNE VIC 8010
1.5 Electronic documents may be emailed to
[email protected]. Written queries about the discussion paper can also be emailed to that address. 1.6 The closing date for submissions in response to this paper is Friday 30 April 2004. All submissions received will be taken into consideration by the ACA. This consultation is part of the ACA’s efforts to ensure that the emergency call service benefits from future developments in location techniques and the availability of more accurate location information for mobile users.
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2.
Introduction
2.1 To facilitate timely and accurate responses to calls for emergency assistance, emergency service organisations (ESOs) require information about the name and location of callers at the time the calls are made. Unlike emergency calls made using a fixed line telephone, the precise location of emergency callers who use mobile phones is not as readily known by either the emergency call person receiving the calls or the ESO responding to them. 2.2 The ESO currently has to ask mobile callers to specifically identify where they are calling from or where the emergency is—a process that may be frustrating for the caller and which can add to the time taken to dispatch emergency assistance. It is now possible to address this situation through the implementation of techniques that can identify the whereabouts of a mobile phone and its user with a higher degree of accuracy. 2.3 At present, a mobile call to the emergency call service is accompanied by very broad mobile location information (MoLI) relating to what is called a standardised mobile service area (SMSA). These SMSAs can range in size from 2,000 to 500,000 square kilometres and are thus too broad to assist ESOs to find someone in an emergency. Rather, the SMSAs are used by the emergency call person to identify the requested ESO answering point that is closest to the caller—a process known as jurisdiction determination—and to ensure that emergency calls are routed to ESOs that are in the same state or territory as the caller. 2.4 In the future, the use of higher accuracy location techniques to provide highly accurate MoLI—say, within 50 to 500 metres—has the potential to enhance the emergency call process in a number of ways by: •
enabling the emergency call person to perform jurisdiction determination quicker and more accurately;
•
limiting multiple reports of the same emergency incident through, for example, location-based routing to an interactive voice response (IVR);
•
reducing the time spent by ESOs in determining the whereabouts of a caller;
•
assisting an ESO with its fleet management and enabling almost instantaneous identification of the closest available unit and its dispatch;
•
locating and apprehending hoax and malicious callers to the emergency services;
•
locating lost or missing persons;
•
assisting in the planning of resource distribution through, for example, the collection of historical data to identify particular areas prone to emergency incidents;
•
complementing computer-assisted navigation and route mapping technologies to reduce the travelling time of ESO vehicles; and
•
reducing the time spent by ESO units in trying to locate the caller or emergency.
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2.5 High accuracy location techniques are yet to be implemented in Australia and are still relatively uncommon outside the USA. Other location methods that can identify the particular mobile base station being used to carry a mobile call (and thus provide MoLI generally within 500 metres to 30 kilometres accuracy) are more readily available, but have still not yet been widely deployed within Australian networks.
3.
The need for more accurate mobile location information
3.1 Mobile phone calls accounted for 51 per cent (or almost 5.8 million) of the 11.3 million calls to the emergency call service during 2002–03.1 However, the overwhelming majority of those mobile calls were non-genuine, with only 1.1 million (or 19 per cent) progressing to an ESO. Based on information recently provided by ESOs, it is estimated that only about 36 per cent (or approximately 396,000 calls) of those 1.1 million mobile calls related to a genuine life-threatening or time-critical emergency, with the remainder being non-genuine or relating to non-emergency situations. These statistics are reflected in Figure A. 3.2 By comparison, 2.8 million (or 51 per cent) of the 5.5 million fixed line calls to the emergency call service during 2003–03 were connected to an ESO, of which an estimated 30 per cent (or approximately 843,000 calls) related to a genuine lifethreatening or time-critical emergency.
Mobile phone calls to the emergency call service in 2002-03
8% 81%
4%
19%
7%
Proportion of non-genuine calls terminated by the ECP Estimated proportion of life-threatening or time-critical emergency calls transferred to an ESO Estimated proportion of non-emergency calls transferred to an ESO Estimated proportion of non-genuine calls transferred to an ESO
Figure A: Mobile phone calls to the emergency call service during 2002–03
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Further emergency call statistics are available in the ACA’s Telecommunications Performance Report 2002–03.
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3.3 Given such a low volume of genuine emergency calls by mobile phone users, it may be difficult to justify the cost-benefit of implementing more accurate location techniques specifically for emergency call purposes. 3.4 The need for more accurate MoLI is not determined by call volumes alone, but by the nature of the individual emergency and the particular environment surrounding the emergency. MoLI is not necessary in the majority of emergency situations, because callers are generally able to identify their whereabouts or are in environments where there are sufficient landmarks and points of reference. This is reflected in the effectiveness with which ESOs are currently able to respond to genuine emergency calls from mobile phones. 3.5 In the USA, Dispatch Monthly—an American magazine containing news and information for America’s public safety dispatchers—calculated that only one per cent of callers to a typical American public safety answering point were likely to benefit from the high accuracy MoLI capabilities being implemented in the USA.2 In the European Union, where emergency calls may need to cross national borders and language barriers, it was estimated that only about six per cent of all the emergency mobile calls made across Europe each year would benefit from location information.3 3.6 While the availability of more accurate MoLI would undoubtedly enhance the call handling capabilities of ESOs, the current need for more accurate MoLI is not so apparent. In the absence of such a prerequisite, it would seem premature for the ACA to consider regulatory intervention to require the implementation of more accurate location techniques, particularly given the costs to ESOs that would be involved in upgrading their systems.
4.
Location techniques and technologies
4.1 There is a number of different techniques and technologies that could potentially be employed by carriers to provide emergency services with more accurate MoLI. The different solutions range in cost and complexity and have different performance characteristics and accuracy capabilities, making some techniques more suitable than others within certain environments. 4.2 Location technology may be primarily handset-based, primarily network-based, or a combination of the two. Handset-based solutions will generally provide more accurate MoLI than a network-based solution, but they are more expensive to implement and require handsets to be modified or replaced. 4.3 An example of a network-based solution is cell identification, which essentially estimates the general location of a handset based upon the location of the serving base station. It can be used to locate existing ‘legacy’ handsets without their modification. By comparison, a handset-based solution such as the satellite-based Global Positioning
2
www.911dispatch.com/911_file/phaseII_chart.html Anderson, Tatum; European Commission set to release E112 draft paper, in Mobile Communications, Issue #335, 23 July, 2002, p.1 3
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System (GPS) requires dedicated GPS chips to be added to handsets before they can be located by the GPS satellite system. 4.4 An explanation of these and other mobile location techniques is provided in Attachment D.
5.
Regulating the introduction of location technologies
5.1 In the USA, the Federal Communications Commission (FCC) has made a requirement for mobile carriers to implement high accuracy location techniques and provide ESOs with location information within specific levels of accuracy. At this stage, the ACA does not intend to pursue a similar regulatory approach in Australia and mandate the implementation of high accuracy location techniques. The question of necessity aside, to do so would impose undue costs on the industry at a time when much of the industry is still not financially buoyant. Further, the success of any such regulatory intervention would require complementary action and investment to be undertaken by all ESOs in all states and territories—activities which go beyond the ACA’s regulatory jurisdiction. 5.2 There also remains a degree of uncertainty about the effectiveness and appropriateness of some high accuracy location techniques. Experience in the USA is helping to resolve such issues, but it appears that no particular high accuracy location method, or even a particular combination, would perform consistently and satisfactorily in all Australian environments—in urban, regional or rural areas and indoors. Accordingly, it would appear that Australia’s interests would be well served by waiting for the global debate on the most suitable solutions to be settled, and allowing market forces and the industry to determine when and how location techniques are introduced in Australia for commercial purposes. 5.3 However, this is not to suggest that MoLI will be left entirely unregulated. Once a carrier has introduced a location technique for its own commercial purposes, it is reasonable to expect that the capability will then be used in conjunction with emergency calls and, as currently exists, carriers will be required to provide emergency services with any available means or information about the location of mobile callers. 5.4 Rather than focusing regulatory attention on the suitability of various methods or on appropriate levels of accuracy, it would be valuable to first ensure that the emergency call services will be ready and able to exploit more accurate MoLI once it becomes available. This would involve, among other things, establishing a delivery mechanism to enable MoLI, whatever its level of accuracy, to be made available to ESOs in a consistent, cost-effective and useable manner.
6.
Commercial drivers
6.1 As there are sufficient commercial incentives for carriers to consider deploying location techniques to support location based services (LBS), regulatory intervention may not be necessary to ensure that location techniques are introduced. Estimates of the potential commercial benefits of LBS globally range between US$10 billion and US$40 7
billion by 2005. The commercial applications of MoLI that can be expected in the future include: •
roadside assistance;
•
navigation assistance and route mapping;
•
traffic and locality maps;
•
location-based billing;
•
personalised and locality-based information, for example, weather or traffic reports;
•
entertainment and interactive games; and
•
directory services, for example, “where’s my nearest…?”.
6.2 Although the use of location techniques for asset tracking and fleet management is becoming increasingly common, very few LBS are currently available to Australian mobile phone users. 6.3 As is occurring overseas, it is likely that in the near future carriers will want to begin experimenting with LBS offerings and will consider introducing a basic and costeffective location capability such as cell identification within their existing networks. This would provide an opportunity for the enhancement of the emergency call service to ‘piggy-back’ on commercially motivated technological developments and allow for the cost-effective introduction of an improved MoLI accuracy. 6.4 Looking further forward, it is expected that higher accuracy location solutions will begin to be widely deployed in an IMT-20004 environment where the significantly greater data transfer rates and enhanced handsets will support a wider array of applications that can utilise location information. The further enhancement of the emergency call service could therefore continue to piggy-back on such commercial developments and exploit any progressive improvements in MoLI accuracy introduced by industry. 6.5 The cultivation of a robust and viable Australian market for LBS is therefore in the interests of the emergency call service and its users. The ACA may be able to facilitate and encourage the commercial introduction of location solutions and LBS by addressing any regulatory uncertainties that may otherwise impede or delay their introduction. Such issues may relate to the maintenance of end-user privacy in the provision of commercial LBS, the ‘ownership’ of customer location information when collected to provide commercial services, or legal liabilities if, for instance, location information happened to be inaccurate. 6.6 The resolution of such concerns is principally a responsibility of the telecommunications industry itself. However, in the interests of ensuring the early resolution of such issues, the ACA is well placed to undertake some preparatory work
4
IMT-2000—or International Mobile Telecommunications 2000—is an International Telecommunication Union (ITU) initiative for mobile network architecture and encompasses what is commonly called the third generation (3G) of mobile communications.
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with appropriate stakeholders to scope these and related issues to establish how they might best be addressed. 6.7 In the main though, it would seem necessary to focus regulatory efforts on ensuring the necessary preparations are made to enable the emergency call service and ESOs to exploit more accurate MoLI once it becomes available. To that end, a number of initiatives have been proposed.
Comment is invited on: (a) the way in which the market for location-based services is likely to develop in Australia, including the expected timing and type of applications to be made available; and (b) any key regulatory issues that may need to be addressed prior to the introduction of location based services or location techniques in Australia and how they could be resolved.
7.
The next steps
7.1 At this time, the ACA proposes to focus on four key areas of activity in the short-to-medium term. They are the: •
identification of the technological implications of more accurate MoLI on the emergency call process and the functions of the emergency call persons;
•
identification of a common delivery infrastructure for more accurate MoLI;
•
monitoring of overseas developments in the use of location information for emergency call purposes; and
•
harmonisation of MoLI specifications for third generation mobile systems.
Identifying the technical implications for the emergency call persons 7.2 The use of accurate MoLI to enhance emergency calls would have considerable technical implications for the emergency call persons and on the emergency call service more broadly. There may also be additional issues relating specifically to the handling of calls to the text-based emergency call service. The complexity of these implications and issues needs to be closely examined. 7.3 To gain a better understanding of these and related implications, the ACA, in conjunction with its Emergency Services Advisory Committee, will identify the implications for the emergency call persons and the emergency call process, and how such changes could be achieved successfully and cost-effectively in the future.
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Comment is invited on: (c) the extent to which the emergency call persons may be required to facilitate access by ESOs to higher accuracy mobile location information and what additional functions the emergency call persons may need to fulfil. Identifying a common delivery infrastructure 7.4 It is unlikely that the existing delivery mechanism for MoLI could continue to be used to deliver more accurate MoLI. Currently, a three-digit SMSA code is appended to the call routing information by the carrier before the call is presented to the emergency call person. However, a latitude–longitude reference, or a similar type of location indicator, would be considerably longer than three digits and may not be able to be similarly appended. 7.5 Further, as the calculation of a caller’s location would most likely take a short time to complete, the MoLI would probably not be available at the time of call set-up but would become available some seconds after the call had been connected. As it may not be feasible or appropriate for the carrier or the emergency call person to delay call connection until accurate MoLI is available, ESOs may no longer be able to rely on MoLI being ‘pushed’ to them by the emergency call person (as currently occurs with the SMSA). Instead, ESOs may have to have the capacity to independently ‘pull’ the MoLI from the relevant carrier’s location server while connected to the emergency caller. 7.6 This is the technique employed in the USA, where the public safety answering points have a data connection to the carrier’s network via a Gateway Mobile Location Centre (GMLC) and submit a request for MoLI after answering the call. For this same purpose, the European Commission requested the European Telecommunications Standards Institute (ETSI) to consider standardisation issues for emergency call services and to develop a specification for a common interface between European carriers and Europe’s ESOs.5 In the United Kingdom, the Office of Communications (then OFTEL) has prescribed the interconnect protocol to be used by ESOs.6 7.7 To ensure that more accurate MoLI—once available—can be delivered to ESOs consistently and cost-effectively, it is necessary to further explore the issue of a simple and low-cost interface between carriers and ESOs (or the emergency call persons). Such work would utilise and integrate relevant international standards and practice to the fullest extent possible.
5
Refer ETSI TR 102 197 v1.1.1 (2003-10) Services and Protocols for Advanced Networks (SPAN); Preliminary analysis of EMTEL and Local Emergency Service requirements for IP networks and Next Generation Networks, http://portal.etsi.org/STFs/documents/draft%20tr%20130%20318.doc
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ND1013:2002/11 PNO-ISC/SPEC/013: Emergency Location Information Interface (www.oftel.gov.uk/ind_groups/nicc), developed by the then OFTEL Network Interoperability Consultative Committee, identifies the sections of the Location Inter-operability Forum (LIF) specification TS101 v3.0.0 (www1.cs.columbia.edu/sip/drafts/LIF_TS_101_v3.0.0.pdf) that are applicable to the emergency location information services.
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Comment is invited on: (d) the potential mechanisms to deliver higher accuracy mobile location information to ESOs in the future and how each will alter: (i) the functions of the emergency call persons; and (ii) the handling of emergency calls by ESOs. (e) whether action similar to that taken by OFTEL with its Emergency Location Information Interface (described in paragraph 6.6) should be considered for Australian purposes. Monitoring overseas developments 7.8 The ACA will continue to maintain a watching brief on international developments in the use of various types of high accuracy location techniques and technologies for emergency service purposes. The USA and the European Union have adopted contrasting regulatory approaches in this area and Australia will therefore be able to benefit greatly from their experiences. Comment in invited on: (f) what lessons can be learnt from the approaches adopted in the USA or in the European Union in relation to the regulation of mobile location information for emergency service purposes? Harmonising MoLI specifications for third generation mobile systems 7.9 The technical requirements for MoLI in third generation mobile systems are specified by two international 3G ‘partnership projects’—3GPP (based on the use of a GSM core network) and 3GPP2—based on an IS95 (CDMA) core network.7 For countries like Australia that will permit both 3GPP and 3GPP2 mobile systems, any differences in the format and content of the MoLI technical requirements developed by 3GPP and 3GPP2 could result in higher costs for: •
ESOs in acquiring different equipment to receive and utilise MoLI relating to the different systems; and
•
manufacturers and carriers to provide for interoperability between IMT-2000 systems and legacy systems.
7
3GPP (see www.3gpp.org) principally comprises of China Wireless Telecommunication Standard Group (CWTS); the Association of Radio Industries and Business (ARIB)(Japan); the Telecommunications Technology Committee (TTC)(Japan); the Telecommunications Technology Association (TTA)(Republic of Korea); the Standards Committee T1 (USA); and the European Telecommunications Standards Committee (ETSI)(EU). 3GPP2 (see www.3gpp2.org) is made up principally of CWTS, ARIB, TTC, TTA, T1 and the Telecommunications Industry Association (TIA) of the USA.
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7.10 Australia therefore has a strong interest in the harmonisation of MoLI technical standards to:8 •
realise significant cost reductions for carriers and ESOs through the establishment of economies of scope and scale;
•
reconcile differences between different mobile technologies, including legacy systems; and
•
help resolve complex technical issues associated with roaming, interoperability, privacy, security, and billing.
7.11 The term harmonisation is used in this context to refer to the establishment of common technical capabilities, specifications and physical interfaces in third generation mobile systems to support the application of technology-neutral regulatory requirements and promote public interest benefits for all types of users. 7.12 The ACA intends to continue working closely with Australian-based equipment vendors and mobile carriers to promote harmonisation activity within the appropriate International Telecommunication Union (ITU) and regional activity in an effort to ensure that Australia’s MoLI and emergency service needs are reflected (or at least not compromised) in the evolving third generation mobile standards. Australia, through its involvement in relevant ITU and regional activities, may also contribute to efforts that encourage 3GPP and 3GPP2 to work towards harmonised network interfaces and other related technical standards for commercial LBS. Comment in invited on: (g) the extent to which Australian-specific requirements for mobile location information needs to be, and can be, incorporated into third generation mobile technical standards developed by 3GPP and 3GPP2.
8
Refer to the presentation made by Dr Bob Horton, then ACA Deputy Chairman, at the ITU IMT-2000 Seminar, Ottawa, May 2002, available at www.itu.int/osg/imt-project/Subdirectories_links/Seminar.html.
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8.
List of Acronyms
3GPP
3rd Generation Partnership Project
3GPP2
3rd Generation Partnership Project 2
ACE
Australian Communication Exchange Limited
AOA
Angle of Arrival
CDMA
code division multiple access
CGALIES
(EU’s) Coordination Group on Access to Location Information for Emergency Services
CLI
calling line identification
E-OTD
enhanced observed time difference
ECLIPS
enhanced calling line identification presentation system
ESAC
(ACA’s) Emergency Services Advisory Committee
ESO
emergency service organisation
ETSI
European Telecommunications Standards Institute
EU
European Union
FCC
(USA’s) Federal Communications Commission
GPS
global positioning system
GMLC
Gateway Mobile Location Centre
GSM
global system for mobile communications
IMT-2000
International Mobile Telecommunications 2000
IP
Internet protocol
IPND
Integrated Public Number Database
ITU
International Telecommunication Union
IVR
interactive voice response
LBS
location-based service
LOCUS
(EU’s) Location of Cellular Users for Emergency Services Group
MoLI
mobile location information
PSAP
public safety answering point
SIM
subscriber identity module
SMSA
standardised mobile service area
TA
timing advance
TDOA
time difference of arrival
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Attachment A—Background to the Emergency Call Service The emergency call service is an operator-assisted service that connects callers to an ESO in a life-threatening or time-critical situation. The emergency call service is provided free of charge to all callers from any fixed or mobile phone. Regulatory environment The Australian telecommunications regulatory regime is principally focused on facilitating a competitive and increasingly self-regulated industry to meet the needs of the Australian community. Section 4 of the Telecommunications Act 1997 states that it is Parliament’s intention: that telecommunications be regulated in a manner that: (a) promotes the greatest practicable use of industry self-regulation; and (b) does not impose undue financial and administrative burdens on participants in the Australian telecommunications industry; but does not compromise the effectiveness of regulation in achieving the objects [of the Telecommunications Act]. The objects of the Telecommunications Act are identified in section 3 of the Act and include, inter alia, the intention to: •
ensure that standard telephone services, payphones and other carriage services of social importance are supplied as efficiently and economically as practicable;
•
promote the supply of diverse and innovative carriage services and content services;
•
promote the development of an Australian telecommunications industry that is efficient, competitive and responsive to the needs of the Australian community; and
•
promote research and development that contributes to the growth of the Australian telecommunication industry.
The role of the ACA The ACA regulates and monitors certain aspects of the emergency call service under primary legislation—namely the Telecommunications (Consumer Protection and Service Standards) Act 1999 and Telecommunications Act 1997—and through two subordinate legislative instruments: •
Telecommunications (Emergency Call Service) Determination 2002; and
•
Telecommunications (Emergency Call Persons) Determination 1999.
The Emergency Call Service Determination places emergency call related obligations on carriers, carriage service providers, and emergency call persons. The Emergency Call Persons Determination specifies the emergency call persons as Telstra and the National Relay Service provider (currently Australian Communication Exchange Ltd (ACE)). As ESOs are not considered a part of the telecommunications industry, there are no obligations on them under any of the primary or secondary legislation mentioned above.
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Emergency service numbers The Telecommunications Numbering Plan 1997 specifies that the primary emergency service number is 000, and that the secondary emergency service numbers are 106 and 112. There are no other emergency service numbers. The 106 emergency call service number is for the exclusive use of text-based telecommunications users and allows people who are deaf or have a hearing or speech impairment to call directly the text emergency call service and request assistance from an ESO. The ACE relay officer will then relay the call directly to the appropriate ESO. In addition to 000, mobile users with a GSM mobile phone can also dial the emergency call service using 112. The number 112 is the emergency service number developed through the European Telecommunications Standards Institute and, consequently, is becoming the European Union standard emergency service number. When a caller dials 112 using a GSM mobile phone, their call will be transferred to the emergency call person for 000 and 112. Dialling 112 on a fixed network will not result in connection to the emergency call person. The emergency number 112 is incorporated in international GSM standards and it can be dialled: •
from anywhere in the world where there is GSM coverage, with the call automatically being transferred to that country’s primary emergency call service number—that is, within Australia, 112 calls are treated as calls to 000;
•
in any area covered by GSM—for example, when you are out of your carrier’s GSM coverage area but in another carrier’s GSM coverage area, your 112 call will be carried on that other carrier’s network; and
•
without necessarily having to key in a security-protection personal identification number.
Efforts are being made in Australia to provide similar access capabilities for 000. While access to 112 is only mandatory for GSM mobile phones, both Telstra and Hutchison CDMA mobile phones are also able to successfully dial 112, although without the above-mentioned special access capabilities. Emergency call persons The emergency call person is responsible for receiving calls made to the emergency service numbers and, if appropriate, transferring the calls to the appropriate ESO. Telstra is the emergency call person for calls to 000 and 112. ACE is the emergency call person for calls to 106. The role of the emergency call person is to connect callers to the nearest and most appropriate ESO, as per the ESO contact list provided by ESOs, as quickly as possible. The emergency call person for calls to 106 also relays the call to the appropriate ESO. Thus, the emergency call person is essentially a call centre that acts as an important
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national stepping stone to those responsible for providing the real help in an emergency situation—the ESOs. Emergency service organisations An ESO refers only to a police force, a fire brigade, or an ambulance service (or a service for dispatching a police, fire or ambulance service). No other organisation can be accessed through the emergency call service. ESOs come under the jurisdiction of the individual states and territories. Within a state or territory, ESOs may be managed under a single state government department or under a number of departments. For example, in Victoria, all the ESOs are the responsibility of the Department of Justice. By contrast, in New South Wales the responsibility for the various ESOs is spread across the Department of Police, the Department of Emergency Services and the Department of Health. ESOs—particularly ambulance services—may also be operated by independent organisations, such as St John Ambulance Australia in Western Australia and the Northern Territory; and SA Ambulance Service in South Australia.9 However, even if operated by an independent organisation, they are still responsible to the relevant state government.
9
SA Ambulance Service is an independently operated division of SA St John Ambulance Service Inc.
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Attachment B—The emergency call process and the use of MoLI All calls to 000 or 112 are routed with priority to one of two Telstra emergency call service answering points where they are typically answered within five seconds. Calls to 106 are routed with priority to one of the two answering points operated by ACE where they are typically answered within one second. The computer systems used by the emergency call persons use the calling line identification (CLI) data that is provided with all emergency calls to interrogate a special emergency call service database called ECLIPS, which receives the content of the Integrated Public Number Database (IPND) on regular intervals. The IPND contains the subscriber details, that is, name and address, associated with the telephone number from which the emergency call has been made. For the majority of fixed line callers, the information obtained from ECLIPS is sufficient to determine in which ESO’s jurisdiction the caller is in. Once the caller advises which emergency service is required, the emergency call person uses the caller’s postcode to determine the closest ESO answering point. The emergency call person will then transfer the call to the appropriate ESO answering point, forwarding the data from ECLIPS via a separate X25 data link. Once the ESO answering point begins talking directly with the caller, the emergency call person will disconnect itself from the conversation and prepare to answer another emergency call. The entire process up to this point, outlined in Figure B below, is so quick that the caller will usually not even realise that it has occurred at all. The process for emergency calls to 106 is slightly different, because it involves the emergency call person facilitating the call by relaying the conversation between the caller and the ESO until the completion of the call.
Figure B: Emergency call schematic10 10
Diagram from ACIF G530 1999
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An additional step is involved in jurisdiction determination for calls made to the emergency call service from mobile phones. The CLI data will only indicate the subscriber’s billing address, which cannot be used to determine the ESO answering point nearest to the caller at the time of the call. Accordingly, the originating mobile carrier will append a three-digit location indicator (LI) code to the digits/data string that it routes to the emergency call person. The LI code corresponds to a standardised mobile service area (SMSA), which represents a grouping of mobile cells that broadly reflects the mobile coverage areas of all mobile carriers combined. Figure C below shows this call process. Prior to the adoption of the SMSA-level of MoLI, the identification of the state or territory in which the call originated had overcome the problems caused by different locations sharing the same name.
Figure C: SMSA MoLI Schematic11 The emergency call person manually enters the LI code into a database of SMSA localities to bring up an alphabetical listing of the towns or suburbs corresponding to that SMSA. This information, of itself, is still not sufficient for the purposes of jurisdiction determination, because an SMSA can range in area from approximately 2,000 to 500,000 square kilometres. By way of example, the LI code 211 corresponds to the Bendigo, Victoria SMSA which, in addition to the city of Bendigo, also comprises the ‘adjoining zones’ of Bridgewater, Goornong, Harcourt, Maldon, Marong, Raywood, Strathfieldsaye, Castlemaine and Rushworth. An emergency caller displaying the LI code ‘221’ could be anywhere in any one of these towns. To further narrow the caller’s likely location, the emergency call person will verbally query the caller about his or her location until enough environmental information is obtained to allow the emergency call person to determine the ESO answering point nearest the caller. Having done so, the emergency call person then routes the call to the appropriate ESO answering point. 11
Diagram from ACIF G530 September 1999 Specification Mobile Location indicator for emergency services Stage 1 Service Description Interim Mobile Location Indicator
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Attachment C—An overview of the regulation of high accuracy MoLI in the USA and the European Union United States of America Since 1996, the US Federal Communications Commission (FCC) sought to enhance the quality and reliability of the American 911 emergency call service by requiring mobile carriers to provide high accuracy MoLI to public safety answering points (PSAPs)—the answering points for calls to 911 that originate within specific geographic areas. The FCC’s enhanced 911—or E911—mandate has proven to be the international catalyst for the development of high accuracy location technologies and their commercial application. Recognising that the implementation of E911 would require coordination among public safety agencies, mobile carriers, technology vendors, equipment manufacturers and local exchange carriers, the FCC adopted a phased approach to implementation. The four-year rollout schedule is to be completed by 31 December 2005 Phase I Phase I of the E911 mandate commenced in April 1998 and required mobile carriers to provide to the PSAP the telephone number of the calling party and the location of the cell site used to originate the call. That requirement was subject to three prerequisites: •
that the PSAP had requested the provision of E911 information;
•
that the PSAP was capable of receiving and utilising the E911 information; and
•
that the PSAP had a means of recovering its costs incurred as a result of deploying systems to receive and utilise the E911 information.
The FCC’s rules did not mandate any specific action nor specify any particular mechanism for funding the technology and service capability necessary to enable the PSAPs to make a valid service request. However, for a PSAP’s request to be valid, the PSAP had to show that: •
a mechanism was in place by which the PSAP would recover its implementation costs;
•
the PSAP had ordered the equipment necessary to receive and utilise the Phase I data to be installed and would be capable of receiving and utilising that data within six months of its request to a carrier; and
•
the PSAP has made a timely request to the appropriate local exchange carrier (LEC) for the necessary trunking and other facilities—including any necessary database upgrades—to enable the Phase 1 data to be transmitted to the PSAP.
Phase II Phase II of the E911 mandate commenced in October 2001. It required mobile carriers to provide PSAPs with the location of all 911 callers by longitude and latitude to conform with specified accuracy requirements, depending on whether the carrier chose to use network-based or handset-based solutions. In instances where Phase II MoLI
19
cannot be provided, Phase I information must be provided. The same prerequisites that applied to the Phase I requirement applied to Phase II. The FCC set different accuracy standards and deployment schedules for carriers depending on whether they were employing a handset-based solution or a networkbased solution. Approximately 60 per cent of carriers initially chose a handset-based solution, with 20 per cent opting for a network-based solution, and the remaining 20 per cent preferring a hybrid solution. Handset-based solutions Carriers deploying handset-based technology (which required new or modified handsets) were required to: •
begin selling and activating Phase II capable handsets by 1 October 2001;
•
ensure that by 31 December 2001, at least 25 per cent of all new handsets activated were Phase II capable;
•
ensure that by 30 June 2002, at least 50 per cent of all new handsets activated were Phase II capable;
•
ensure that by 31 December 2002, 100 per cent of all new handsets activated are Phase II capable; and
•
achieve a 95 per cent penetration rate of Phase II capable handsets among its subscribers by 31 December 2005.
Within six months of a valid request being lodged by a PSAP, or by 1 October 2001 (whichever was later), carriers were required to have installed all the necessary hardware and software, and commence providing PSAPs with Phase 2 MoLI for all mobile calls originating in the area served by the PSAP. For handset based solutions, the accuracy requirements are within: •
50 metres for 67 per cent of calls; and
•
150 metres for 95 per cent of calls.
Network-based solutions From 1 October 2001, following a valid request from a PSAP for Phase II MoLI, carriers deploying a network based solution are required to: •
provide Phase II MoLI for at least 50 per cent of the PSAP’s coverage area or population within six months; and
•
provide Phase II MoLI for 100 per cent of the PSAP’s coverage area or population within 18 months.
For network based solutions, the accuracy requirements are within: •
100 metres for 67 per cent of calls; and
•
300 metres for 95 per cent of calls.
20
PSAP preparedness As of January 2003, two-thirds of the USA’s PSAPs were still yet to implement Phase I arrangements.12 From September 2003, less than 10 per cent of the approximately 4,300 PSAPs across the USA were capable of receiving Phase II MoLI. Meeting the mandate The vast majority of carriers failed to meet the requirements of Phase II by the required date of 1 October 2001. In total, the FCC granted 70 separate requests from mobile carriers seeking variations to the deployment schedule, the accuracy standard, or both. In seeking extensions, applicants claimed a lack of handsets and infrastructure affected their ability to comply with the E911 mandate. The FCC adopted a quarterly monitoring arrangement to track the compliance of carriers with their revised implementation schedules. In October 2001, the FCC granted delays to six major carriers, extending the deadline to December 2005. On 20 October 2001, St Clair County (Illinois) became the first PSAP jurisdiction with operational Phase II capability. The mobile carrier Verizon used a network-based solution to provide Phase II MoLI to the St Clair County PSAP for all Verizon customers calling 911 from within the county. On 26 October 2001, Sprint PCS used assisted GPS technology to provide Phase II MoLI to PSAPs in the state of Rhode Island, becoming the first carrier to use a handsetbased solution. E911 is now operational in Rhode Island and some counties in Illinois, Indiana, North Carolina and Pennsylvania. In July 2002, the FCC further extended (by seven months and 13 months respectively) the E911 Phase II deadlines for so called Tier II and Tier III carriers—medium and small sized carriers. However, that ruling did not extend the ultimate implementation deadline of December 31 2005, which remains applicable to all carriers.13 In October 2002, the FCC released A Report on Technical and Operational Issues Impacting the Provision of Wireless Enhanced 911 Services (known as the Hatfield Report).14 It was the result of a six-month inquiry by Dale Hatfield, which evaluated information from technology vendors, network equipment and handset manufacturers, carriers and the public safety community about issues of technology standards, the development of hardware and software, and supply conditions. The inquiry also examined the provisioning by incumbent local exchange carriers of the facilities and equipment necessary to receive and utilise the Phase II data. The report made recommendations to the FCC, including the following15:
12
Consumer Reports.org Inching towards Wireless E911, February 2003, www.consumerreports.org Pulver.com’s location based services report, August 2002, www.pulver.com 14 Available at http://gullfoss2.fcc.gov/prod/ecfs/retrieve.cgi?native_or_pdf=pdf&id_document=6513296239 15 Pulver.com’s location based services report, December 2002, www.pulver.com 13
21
•
form an advisory committee to further the development and evolution of E911 systems and services including technical standards;
•
encourage the creation of a national level clearing house to collect, store and disseminate status information on the rollout of E911 services;
•
coordinate efforts to educate state and local governments and PSAPs on the benefits of wireless E911 services; and
•
urge the various parties to develop industry-wide procedures for the testing and certification of wireless E911 to ensure that they meet accuracy requirements.
Privacy The FCC did not specifically address the issue of privacy as part of its E911 mandate. In November 2000, the Cellular Telecommunications Industry Association (CTIA) recommended that the FCC adopt privacy guidelines to govern the industry’s collection and use of location information (for commercial purposes). The proposed guidelines would have required carriers and location-based service providers to: •
inform customers about the collection and use of location information;
•
provide customers with a ‘meaningful opportunity’ to consent to the collection of location information before its use;
•
ensure the security and integrity of any location information collected; and
•
provide uniform rules and privacy expectations that would be consistent regardless of the underlying location technology or (if roaming) the carrier.
In July 2002, the FCC concluded that the proposed privacy principles, although reasonable, were neither necessary nor appropriate. The FCC did not want to inadvertently constrain technology or consumer choice through the introduction of regulation while the LBS market was in a nascent state.16 Furthermore, the FCC did not believe that it needed to promulgate guidelines because, by that time, Congress had introduced the Location Privacy Protection Bill (section 1164) which formally recognised the right to privacy of location information by classifying location information as ‘customer proprietary network information’ pursuant to section 222 of the Communications Act of 1934, thereby preventing use or disclosure of that information without a customer’s express prior authorisation. As at December 2003, the Bill was still under consideration by the Senate Committee on Commerce, Science and Transportation. Other relevant (draft) legislation is the Wireless Privacy Protection Bill of 2001 (H. R. 260), which was introduced into the House of Representative in January 2001 and at December 2003 was still with the House Subcommittee on Commerce, Trade and Consumer Protection.
16
Pulver.com’s location based services report, August 2002, www.pulver.com
22
European Union Whereas regulation is driving the introduction of high accuracy location technologies in the USA, the EU is leaving the deployment of such technologies to commercial forces. Following its 1999 review of telecommunications regulation, the EU has been working to develop a quality pan-European emergency call service using the emergency number 112 (in addition to the national emergency numbers). To that end, the 1999 review recommended that the location of (both fixed and mobile) callers to the emergency call service should be made available to emergency authorities from 1 January 2003. It estimated that European ESOs were unable to respond to six per cent (or 2.4 million) of the emergency mobile calls made in Europe each year due to a lack of suitable MoLI.17 CGALIES In May 2000, the European Commission established Coordination Group on Access to Location Information for Emergency Services (CGALIES) as a public service–private sector partnership tasked with finding harmonised, timely and financial sound solutions achievable by January 2003.18 The work of CGALIES focused on three work packages covering: •
identification of minimum standards for the accuracy and reliability of location data, and a location mechanism;
•
identification of minimum standards for networks, databases and PSAPs; and
•
analysis of financing and costs issues.
In January 2002, CGALIES released its final report, concluding that that none of the location technologies presently available satisfy all the necessary requirements to achieve an enhanced emergency call service by 2003. It found that: •
cell-ID technology should be available in all EU-based mobile networks by 2004 and will not require new handsets;
•
other more accurate location technologies will have significantly longer lead times;
•
European PSAPs are unlikely to have completed the necessary technical upgrades to utilise location information before 2007; and
•
the timescales of when high accuracy location technologies will be available and cost-effective, and when it is feasible to have all PSAPs in the EU able to use that information, appear to match well.
17
Anderson, Tatum; European Commission set to release E112 draft paper, in Mobile Communications, Issue #335, 23 July, 2002, p.1 18 All CGAILES reports are available at www.telematica.de/cgalies
23
LOCUS Working closely with CGAILES was a research and development committee established by the European Commission in 2000 called the Location of Cellular Users for Emergency Services (LOCUS) project.19 LOCUS was focused more on users’ needs for location information, the associated technology issues, the future commercial applications and foreseeable markets for location technologies, and various implementation options. The two principal implementation options that LOCUS considered were hard regulation and soft regulation. The hard regulation approach was akin to the USA model and would have involved defining accuracy requirements for different environments, setting dates for mandatory implementation, and developing general principles for financing. The soft regulation alternative was reliant on market forces bringing about the implementation of high accuracy location technologies (for commercial purposes) and subsequently also being used to enhance the emergency call service. Under this approach, only those carriers that had implemented location technologies would be required to provide MoLI to the PSAP. Minimum standards governing data quality and location accuracy would not be defined. Rather, carriers would be obliged to provide PSAPs with location information that was of the same quality and accuracy as that which the carriers used to support their commercial location based services. LOCUS evaluated the pros and cons of these two implementation options in terms of their: •
potential macro-economic benefits;
•
impact on the development of commercial assistance service and mobile valueadded service, and the market for such services;
•
reliance on (currently non-existent) viable business models and business plans for the commercial offering of location based services; and
•
implications for carriers if a return on investment could not be achieved.
LOCUS also conducted a cost analysis of the various location technologies to estimate the likelihood of carriers achieving a return on their investment through commercial LBS. The potential implementation costs were estimated for a theoretical ‘average European network’ that has 10 million subscribers, 2,400 base stations and 30 mobile switching centres. LOCUS concluded that a return on investment of €40 million for a Cell-ID based location platform could be achieved if subsidised through the development of a portfolio of value added services. However, ‘the business model for an investment of about €100 million corresponding to the deployment and maintenances of an E-OTD based location platform may also be attractive BUT cannot be taken for granted AND must be refined taking into account the individual operator’s business and customer segments.’ 19
All LOCUS reports are available at www.telematica.de/locus
24
It also concluded that ‘the risk for an investment of €140 million corresponding to the deployment and maintenance of an A-GPS based platform is very high and the return on the investment is only possible for a very optimistic market development and extreme assumptions for the average money spent by end users.’20 LOCUS concluded that the soft regulation was the more appropriate approach for the EU to adopt, because it did not place pressure on carriers to implement expensive technologies for which no widely applicable and working business models and cost recovery mechanisms were available at that time. It expects that European carriers will commence offering various types of location based services during the period 2003–2005 (primarily using cell-ID technology). As cell-ID is unlikely to satisfy all the needs of the emergency authorities, LOCUS suggested that a further coordination group be established in late 2003 to determine the best way for their requirements to be met throughout the EU. In 2005, a decision can be made on whether it is necessary to strength the regulatory framework towards a harder regulatory approach. The LOCUS recommendations also included: •
• •
•
•
•
devising a roadmap for the enhancement of the 112 emergency call service, for example, covering the main milestones and the decision making process; adoption of a unique interface between carriers and PSAPs; only implementing standardised and interoperable location technologies to provide location-based services; raising awareness among the civil protection community of the need for PSAPs to upgrade their facilities; counterbalancing any obligation placed on carriers with an obligation on PSAPs to upgrade their facilities in an appropriate manner; and quantifying the expected socio-economic benefits of providing high accuracy MoLI to PSAPs.
European policy and implementation plan In late 2002, the European Commission announced its proposed policy and implementation plan for the location enhancement of emergency calls based on recommendations prepared by consultants Helios Technologies Ltd. The report on the study was entitled Caller Location in Telecommunication Networks in view of enhancing 112 Emergency Services—Recommendations towards European policy and implementation plan. It recommended, inter alia: •
20
a ‘best effort’ approach whereby carriers provide ESOs with the best location information available to the carrier, with further performance improvements dependent on commercial development;
IST-1999-14093 LOCUS Deliverable 4: Recommandations (2002), Chapter 4
25
that carriers provide location information to ESOs free of charge, with ESOs paying for the systems and technology to receive and exploit that the location information; and • transparent procedures be established to govern the availability of location information and protect users’ privacy. Privacy •
In contrast to the USA, privacy issues have been at the forefront of the EU’s deliberations on issues relating to high accuracy location technologies. The EU believes privacy concerns will be substantially addressed if all location information is maintained and used in a completely anonymous manner. Article 9 of the European Union’s Direction on Privacy in the Electronic Communications Sector states that: Where electronic communications networks are capable of processing location data other than traffic data, relating to users or subscribers of their services, these data may only be processed when they are made anonymous, or with the consent of the users of subscribers to the extent and for the duration necessary for the provision of a value addressed service.21 That principle has been reflected in the development of standards22 and increasingly in the legislation of member states.
21
Article 9 (Location Data) of Directive of the European Parliament and of the Council on the processing of personal data and the protection of privacy in the electronic communications sector. 22 See 3rd Generation Partnership Project; Technical Report Enhanced support for User Privacy on location services (Release 5); 3GPP TR 23.871 V2.0.0 (2002–03).
26
Attachment D—Overview of mobile location techniques The following overview of mobile location techniques is a summary of various research and assessments that have been carried out internationally and provided here for information purposes.23 This section aims to describe the main technologies and is not an exhaustive list of all techniques currently available. Network-based versus handset-based Location techniques may be primarily handset-based, network-based, or a combination of the two. As a general rule-of-thumb handset-based techniques provide more accurate location information, but are more expensive to implement than network-based techniques (ie. there is a price/accuracy trade off). Handset-based techniques enable each individual handset to perform its own position calculation, which is then sent to the network. The techniques require additional hardware or software be added to each handset. The modification or replacement of handsets en masse is a costly exercise for carriers of pre-existing networks, with success ultimately dependent upon the willingness of consumers to upgrade or replace their handsets. Network-based techniques calculate mobile location from network available information. They can locate legacy handsets without any modifications being made to the handset itself. They potentially require every base station to be upgraded in addition to other (more centralised) upgrades to network hardware and software. The cost of implementation of these techniques is unique to individual networks. Issues such as network topology and pre-existing capacity to accommodate the extra signalling and processing loads required to calculate the position of handsets are relevant in determining overall cost of implementation. Cell ID Cell Identification (Cell ID) is the simplest method of mobile location. It uses the coordinates of the servicing base station and the particular serving cell to estimate the handset’s general location. Information about the serving cell is generally available in mobile networks. In Figure D below, the known x,y coordinates (for example latitude and longitude) of the base station, as well as the serving cell of the particular base station, are used to calculate the location of the mobile phone.
23
The principle information sources were VTT Information Technology, Location methods, available at http://location.vtt.fi; CGALIES Final Report on implementation issues related to access to location information by emergency services (E112) in the European Union, available at http://www.telematica.de/cgalies/main.html; and LOCUS, Overview of Location Based Services as of 4th quarter 2000, available at http://www.telematica.de/locus/reports.html
27
Figure D: Cell ID24 The main advantage of this technique is that handsets do not need to be upgraded, calculations do not need to be performed, and minimal network and systems changes are necessary. The main limitation of Cell ID is its accuracy, which is dependant on cell density and the size of the individual cells (which can be particularly large in rural areas). It provides poor accuracy in rural areas, and moderate to poor accuracy in urban areas. In addition, due to the nature of radiocommunication propagation, the serving cell may not always be the cell closest to the caller, further decreasing the accuracy of the location information. A number of variations of the Cell ID method exist, though not all are presently standardised. Given its lack of complexity (in comparison to other solutions) and its ubiquity, Cell ID has been suggested as an appropriate starting point and may be considered to be an appropriate fall-back for other more accurate location technologies. Signal Strength The routine signal strength measurements made at the handset from a number of base stations can be used to estimate its location. If signal levels from three different base stations are known, the location of the handset can be determined as the unique intersection point of the three circles. This method is also known as triangulation.
24
Diagram sourced from VTT Information Technology, Location methods; op. cit.
28
Base Station A
Handset
Base Station B
Base Station C
Figure E: Signal Strength The main advantage of this technique is that it is easily implemented in GSM networks, as measurement reports (i.e. signal strength measurements) are continuously transmitted from the handset to the network whilst a call is in progress. It is an easy and low-cost method to enhance the accuracy of pure Cell ID base location. The main limitation of the signal strength technique is that it has some strong theoretical assumptions, which do not always hold, especially in urban areas. Multipath fading (caused by obstructions and reflections between the handset and the base station) and attenuation (caused by signal strength loss from obstacles) can cause large errors in location calculations. The accuracy of these calculations is moderate to poor in urban areas and good in rural areas (provided the handset can ‘see’ three or more base stations). Angle of Arrival The Angle of Arrival (AOA) method uses the angle at which the radio signals from a handset arrive at two different base stations to calculate the approximate location of a handset. This technique requires the installation of numerous arrays of smart antennas—which are yet to be commercially available—at each base station to measure the angle of the incoming signals. It is possible that AOA techniques may be more appropriate for future IMT-2000 (3G) systems, which may use some degree of smart antennas at base stations.
29
Figure F: Angle of Arrival25 The advantage of this technique is that its accuracy is better in urban areas than cell ID; however its accuracy is diminished in the absence of clear line of sight between the base station antenna and the handset. Its accuracy is further limited by the beam width of the antenna array. Its main limitation is that it is not currently commercially available. For these reasons, AOA is not considered a feasible option at this stage. Timing Advance Timing Advance (TA) is not a pure mobile location technique, as it cannot be used to provide a mobile location on its own. Rather it is an aid to enhance the accuracy of other techniques. TA is a GSM specific parameter26 which roughly measures the time taken for a signal to make the round trip from the base station to the handset and back again. Its formal function is to synchronise the arrival of signals from individual handsets into their allocated time slots within the Time Division Multiple Access (TDMA) scheme used in the GSM standard. TA can only be used to estimate location if the cell radius is greater than 500m. This is generally only the case in rural and suburban areas. ETSI have incorporated the TA positioning method into its GSM standards (GSM 03.71), which specifies that both the Cell ID and the TA measurement are used by the network to estimate handset location.
Figure G: Timing Advance27 25
Ibid. Refer ETSI GSM 03.71 27 Diagram sourced from LOCUS Deliverable 1: Overview of Location Services, op. cit. 26
30
The main advantage of this technique is that it is easily implemented in GSM networks. It is an easy and low-cost method to enhance the accuracy of pure Cell ID base location. The main disadvantages are that it cannot be used on its own and cannot be used networks that are not based on the GSM standard. The accuracy of this method is poor in both urban and rural areas. Hyperbolic Triangulation Techniques Hyperbolic triangulation techniques theoretically use the signals sent to (or from) four different cell sites to mathematically calculate three distinct hyperbolas that share a unique intersection point (representing the position of the handset). As shown in Figure H below, in practice, generally two hyperbolas are sufficient to establish a unique intersection point, thus only three base stations are required to accurately locate a handset. The hyperbolas are established by calculating the time differential of the three different signals (requiring careful synchronisation), which can be done by using either the Time Difference of Arrival (TDOA) or the Enhanced Observed Time Difference (EOTD) method.
Figure H: Hyperbolic Triangulation28 Time Difference of Arrival (TDOA) In the TDOA technique (also known as Time of Arrival (TOA) in ETSI parlance), the difference in time of arrival of a known signal sent by the handset and received at three or more base stations are measured. This method works without any modifications being made to existing handsets. Location Measurement Units (LMUs)—which provide synchronisation essential to this technique—need to be deployed in the network (essentially into every base station) and position calculation functionality must be added to the core network. Enhanced Observed Time Difference (E-OTD) The E-OTD technique is slightly different to TDOA in that the handset measures the time difference between the signals from several synchronised base stations. As it is 28
Diagram sourced from VTT Information Technology, Location methods; op. cit.
31
known how far the base stations are from one another, the network is able to establish how far the handset is from the each of the base stations. The advantage of E-OTD is that it requires significantly fewer LMUs than TDOA and does not need the LMU internal clocks to be synchronised. The disadvantage is that EOTD is not supported by existing handsets and would require each subscriber to purchase a new handset. The main advantage of hyperbolic triangulation techniques is that they are more accurate than other techniques. The main limitation is that they require visibility of at least three cell sites. This can be a problem in rural areas where connection to three base stations simultaneously might not be possible, and in some urban areas where line of sight may be hindered by infrastructure. The accuracy of this method is moderate in both urban and rural areas, but poor in rural areas when few base stations can be ‘seen’ by the handset. NetworkTDOA Based (TOA)
E-OTD (E-OTD) Handset Assisted LMU LMU
Neighbour Neighbor Cell # 1
Neighbour Neighbor Cell # 1
Location Capable Handset Neighbour Neighbor Cell # 2
Serving Cell
LMU
Legacy Handset
Serving Cell
LMU Neighbour Neighbor Cell # 2 LMU: Location Measurement Unit
Figure I: Time Difference of Arrival and Enhanced Observed Time Difference29 Global Positioning System (GPS) Global Positioning System (GPS) is the common name of Navstar, a constellation of 26 satellites owned and operated by the United States Government (in practice, the Department of Defence). At any one time, a minimum of four GPS satellites are ‘viewable’ (by special GPS receivers) from anywhere on the Earth’s surface. This enables the position of users with handsets equipped with GPS receivers to be calculated—with very high accuracy—as shown in Figure J.
29
Diagram sourced from Nokia, as used in Leite, Fabio S. op. cit.
32
Figure J: Global Positioning System30 1
2
3
A GPS enabled handset measures the amount of time it takes for a radio signal from a satellite to reach the handset. As the speed at which radio signals travel is known, the distance of the handset from the satellite can be calculated.
The handset then measures the time taken for a signal from a second satellite to reach the handset. The handset is at one of the two points where the first and second circles overlap.
When the handset can receive a signal from three or more satellites, the location of the handset can be calculated precisely.
There is no limit to the number of users that may be using GPS at any one time. The handsets do not transmit anything to the satellites and the satellites are not aware of individual receivers or that a user’s location is being calculated. The main disadvantage of GPS is that it may be less effective in dense urban environments where handsets cannot see an adequate number of satellites. It is particularly limited indoors. In addition, the use of a GPS location system requires new handsets, increased power (and therefore battery) consumption, and the time taken to ‘power up’ and establish a location fix when the handset is first switched on. The main advantage of GPS is its accuracy. It provides global coverage, accuracy potentially within 20 metres, and minimal impact to existing network infrastructure. The accuracy of this method is moderate in urban areas and high rural areas. Assisted Global Positioning System (A-GPS) To address some of the deficiencies of pure GPS, an enhanced version of it called Assisted GPS (A-GPS) involves the terrestrial cellular network providing assisting data—on request—directly to the GPS-enabled handset to assist in establishing a location fix (see Figure K). The assisting data indicates where the appropriate satellites are and allows the network to assume much of the calculation role that would otherwise be performed by the handset. The main disadvantages of A-GPS are its increased complexity and reduced accuracy indoors. However, in general terms, A-GPS will perform well outdoors, in cars, in
30
Diagram and accompanying description sourced from the Alabama Chapter of the National Emergency Number Association (of America), available at http://www.al911.org/wireless/gps_location.htm
33
wooden buildings, two-storey buildings, and in steel and concrete buildings when 1–3 metres from a window. The main advantage of A-GPS is that it provides even better accuracy than GPS. The accuracy of this method is moderate to high in urban areas and high in rural areas. Assisted-GPS
+ GPS
Assistance Assistance Dat DATA a
Receiver
Figure K: Assisted GPS31 Summary of the attributes of location technologies The performance of the different location technologies in urban and rural environments, and the nature of the modifications that would be involved in their implementation, are summarised in the following table. PERFORMANCE
MODIFICATIONS
LOCATION TECHNIQUE
Urban
Rural
Handset
Network
Cell ID
Poor/Moderate
Poor
N/A
Software
Signal strength
Moderate/Poor
Good
N/A
Software
AOA
Moderate/Poor
Poor
Software
Software
Timing Advance
Poor
Poor
N/A
Software
Hyperbolic Triangulation
Moderate
Moderate/Poor
Software
Hardware & Software
GPS
Moderate
Very Good
Hardware & Software
Software
Table 1: Summary of attributes of location technologies32 It is possible to combine a handset-based technique with a network-based technique into a hybrid solution. With this option the strengths of both technologies—such as improved accuracy and greater coverage—can be maximised, whilst their weaknesses— such as reliance upon handset penetration or coverage deficiencies—can be minimised. 31 32
Diagram sourced from Nokia, as used in Leite, Fabio S. op. cit. Diagram sourced from VTT Information Technology, Location methods; op. cit.
34
