NG9-1-1 for Managed VoIP Services
Team Members: Aditya Ramadurgam, Ashish Raj, Vishal Pratap Singh, Upasana Dangi
“A Capstone paper submitted as partial fulfilment for the Degree of Masters in
Telecommunications at the University of Colorado at Boulder”
Faculty Advisor: Dr. Dale N. Hatfield
Abstract
Response to emergency calls can be most effective if the correct location of the caller is
known to the responder. The current E9-1-1 architecture poses challenges for location
tracking for E9-1-1 callers from managed Voice over Internet Protocol (VoIP). In order to
provide efficient emergency response, 9-1-1 location identification capabilities for managed
VoIP networks must be improved. This capstone paper focuses on determining the
limitations of managed VoIP environments for E9-1-1 calls and provides a high level
framework for dynamic location determination of a VoIP E9-1-1 caller to relay it to the
Public Safety Answering Point (PSAP).
In order to understand the limitations, the network faces due to the use of legacy
technologies such as Time Division Multiplexing (TDM); we implemented a managed VoIP
network and documented the issues we observed. We also analyzed various VoIP E9-1-1
software available in the industry that provide the location of a VoIP caller to the PSAPs. As
a resolution/addition, we studied the possibility of the Global Positioning System (GPS)
integration with managed VoIP services to improve location tracking and addressed the
challenges associated with the integration.
Based on the results from our capstone, we conclude that GPS, with its significant
progress, can be used to provide dynamic location of a VoIP caller to the PSAP responder in
an end-to-end IP environment.
I.
Table of Contents
Introduction ............................................................................................................... 1
i.
Introduction and Background ............................................................................................. 1
ii.
Research Problem ............................................................................................................... 2
iii.
Research-Sub Problems ...................................................................................................... 2
iv.
Scope of the Study .............................................................................................................. 2
II.
Literature Review ....................................................................................................... 3
III.
Research Methodology ............................................................................................... 6
IV.
Research Results ......................................................................................................... 8
i.
CAMA and PRI Lines......................................................................................................... 8
ii.
Single routable DID and shared phone lines....................................................................... 9
iii.
9-1-1 VoIP Software – CER and RedSky ........................................................................... 9
1. Cisco Emergency Responder .........................................Error! Bookmark not defined.
2. RedSky ...........................................................................Error! Bookmark not defined.
iv.
Concerns raised during Interviews.................................................................................... 11
v.
GPS vendors – NextNav and iPosi ................................................................................... 12
vi.
New Architecture for dynamic location tracking............................................................ 166
V.
Discussion of Results ............................................................................................... 199
VI.
Conclusion and Future Research ............................................................................ 20
VII.
References ................................................................................................................ 211
Index of Figures
Figure 1: VoIP call signaling message has no location information field ...................................... 9 Figure 2: Proposed Architecture for VoIP and GPS Integration .Error! Bookmark not defined.8 I.
i.
Introduction
Introduction and Background
Enterprise VoIP services are unlike traditional wireline and wireless phones, as VoIP
phones inside a managed environment are Internet Protocol (IP) based solutions and offer
mobility to the end users. Traditionally, an E9-1-1 call originated from a VoIP endpoint is
directed through analog lines or Primary Rate Interfaces (PRIs) to the Public Safety Answer
Points (PSAPs) and these PSAPs look through their databases to determine the location of
the 9-1-1 caller based on the calling number. The continued use of analog platforms implies
the failure of 9-1-1 services to keep on par with emerging communication technologies, as IP
solutions allow for greater mobility than the fixed landline phones and, therefore, should not
rely on fixed databases anymore. This research paper proposes to address the limitations of
the use of analog line solutions for E9-1-1 calls for managed VoIP endpoints and suggests
measures to improve the framework for location tracking services of the E9-1-1 calls for
enterprise managed VoIP deployments.
Typically, an E9-1-1 call made from an enterprise VoIP phone, goes through a
Centralized Automatic Message Accounting (CAMA) trunk to the PSAPs, which is
essentially an analog line, not an IP solution. The PSAPs then map the Caller ID with an
associated address in a database to determine the location of the caller. Historically and till
date, the E9-1-1 services are primarily dependent upon manual databases to provide location
information of the 9-1-1 caller.
In this paper, we introduce a solution to avoid the dependency of analog lines to track the
location of a 9-1-1 call from a managed enterprise VoIP endpoint, and rather use an end-toend IP solution. In addition, we propose few methods to perform dynamic location tracking
1
of the calling endpoint from an enterprise VoIP solution, which will present an alternative
against a manual database lookup for location services for a 9-1-1 call from a physical VoIP
endpoint inside a managed VoIP enterprise solution.
ii.
Research Problem
To improve the location tracking capabilities of an E9-1-1 caller from an enterprise
managed VoIP service by avoiding dependency on analog lines and incorporating next-gen
features such as GPS to dynamically locate an E9-1-1 caller from managed VoIP services.
iii.
Research-Sub Problems
In an attempt to propose a solution to improve location tracking services for E9-1-1 calls
from managed enterprise VoIP solutions, following sub-problems have been identified:
a. Issues with location tracking for calls originating from managed VoIP endpoints
when placed through CAMA/PRI lines.
b. Limitations due to single routable Direct Inward Dial (DID) number and shared VoIP
phone lines when integrating with CAMA/PRI lines or newer software such as Cisco
Emergency Responder (CER) and RedSky.
c. Location tracking features of VoIP software applications such as RedSky and CER
and their limitations.
d. Research the possibility of using existing or advanced GPS solutions for location
identification of a 9-1-1 call from a VoIP endpoint and determine the possibility for
integration of the same with the managed VoIP architecture.
2
e. Propose a high level framework to merge the GPS solution with managed VoIP
services for E9-1-1.
iv.
Scope of the Study
The research is limited to the limitations of E9-1-1 calls originated from VoIP soft and
hard endpoints inside a managed VoIP network. In addition, the research is limited to the 91-1 architecture of the United States.
II.
Literature Review
Telecommunications is no longer based on fixed locations [1], rather the location of the
user is mobile, which is evident with the demise of analog landline phones and increase in
the usage of cellular and IP phones. With fixed landline architectures, the caller’s location is
easily determined by referring to the user database of all the landline numbers and their
billing address. However, for VoIP phone users there is no accurate method available to
determine their location. Federal Communications Commission (FCC) states that 72.7
percent of 9-1-1 calls are made from wireless phones and an average of 56 percent of
wireless calls [2] are made from indoor locations. Also, with a wide spread usage of
smartphones and VoIP phones the statistics mentioned above are predicted to go higher in the
near future and location tracking in those particularly challenged area need to be accurate to
track the exact/precise location of 9-1-1 callers [2].
The National Emergency Number Association (NENA) VoIP Deployment and
Operational Guidelines relies on the usage of location databases for translating a VoIP call
3
into an address for the location determination of an E9-1-1 call [3]. However, the dependency
on a database is not always reliable as the VoIP networks lack physical mapping of caller ID
to a fixed location; and database might not have the latest mapping of the network. In the
FCC Notice of Proposed Rulemaking 2005, the FCC realized that there are VoIP services
that pose a significant challenge for E9-1-1 implementation as compared to landline or
cellular devices [4]. FCC cited the limitation as, “IP communications are routed to devices
and not geographic locations” [4].
In this research paper, we want to propose a new architecture to remove the dependency
on legacy technologies such as analog lines and the user database of all the landline numbers
and their billing address. We wish to explore new possibilities of incorporating technologies
such as GPS in the 9-1-1 architecture for managed VoIP services to provide dynamic location
tracking capabilities.
Although, time and again GPS solutions have been put forward to alleviate the situation
[5], challenges continue to remain in this implementation such as indoor signal for GPS,
number of satellites to get a true fix of the location, and time to get the first fix [6]. The
Communications Security, Reliability and Interoperability Council III (CSRIC) recently
determined that although indoors location tracking has shown significant improvements, the
results obtained lead to a requirement of additional development [7]. In March 2013, the
CSRIC Working Group 3 (WG3) issued a report discussing the results of the CSRIC test bed
involving three GPS vendors Qualcomm, Polaris, and NextNav. Testing was carried out in
four different environments such as Dense Urban, Urban, Suburban and Rural environments
and the WG3 reports that “all technologies tested demonstrated relatively high yield and
various levels of accuracy in indoor environments” [5]. This report also consists of
4
recommendations put forth by WG3 on how best to tackle the improvements for indoor
location accuracy.
This report stated that the beacon technology used by NextNav is novel and had the
capability to provide vertical location information. The technology enables the first
responders to approximate the floor-level accuracy while the two other technologies,
Assisted GPS/Advanced Forward Link Trilateration (AGPS/AFLT) and RF Fingerprinting
adopted by Polaris and Qualcomm, are already in commonplace for emergency services [5].
In addition, the CSRIC Indoor Location Test Bed Report also stated that the participating
vendors are currently working towards improvement on their location technology and that the
vendors are considering advancements to improve location tracking. Taking the efforts of
CSRIC and the GPS vendors in consideration, the FCC issued a Notice of Proposed
Rulemaking on February 21, 2014 that sets the standards for indoor location tracking
requirements. The Notice of Proposed Rulemaking summarized the following points: [2].
a. Horizontal location (x and y axis) within of 50 meters of the caller for 67 percent of
the 9-1-1 calls placed from indoor environments within two years, and 80 percent of
indoor 9-1-1 calls within five years [2].
b. Vertical location (z-axis) within 3 meters of the caller for 67 percent of the 9-1-1 calls
placed from indoor environments within two years, and 80 percent of indoor 9-1-1
calls within five years [2].
c. Vendors would demonstrate compliance with the above set standards by participating
in an independently administered test bed program modeled by CSRIC [2].
5
d. PSAPs can seek Commission enforcement of these requirements within their
jurisdiction, but only as long as they have implemented location bid/rebid policies
that are designed to obtain all 9-1-1 location information [2].
During our research, we found that two vendors, iPosi and NextNav have claimed to
produce promising results in terms of horizontal and vertical location accuracy in different
environments. iPosi is a company based in Denver and Boulder, Colorado that focuses on
developing accurate mobile and fixed indoor positioning via Assisted GPS (AGPS). NextNav
is a company based in Sunnyvale, California that focuses to solve the indoor positioning
problems by creating a nation-wide footprint of beacons that assist in location tracking.
Based on our interview with the senior management at iPosi (see page 22: List of
Interviewees from iPosi Management) and an analysis of WG3 report on CSRIC test bed for
NextNav, we have evaluated the viability of using these positioning solutions for VoIP
endpoints. We have discussed our findings in the “Research Results” section below.
The hypothesis made by us is that, in spite of the challenges traditional GPS poses for
location determination in dense indoor environment, there are some solutions in the market
that make GPS a better candidate for a long term solution for tracking E9-1-1 calls made
from VoIP endpoints. In this capstone paper, we have put forth a framework that possibly
extends GPS technologies to VoIP endpoints to provide dynamic locations of E9-1-1 calls to
the PSAPs, thus removing dependencies on manual databases for accurate location
identification of the emergency callers.
III.
Research Methodology
6
To resolve the first sub-problem as described in bullet “a” on page 2, we studied the
signaling standards of CAMA trunks and PRI lines. We replicated an enterprise VoIP setup
in the lab with Cisco Unified Communications Manager (PBX), and routed the calls through
PRI lines to PSTN, and studied the various fields in ISDN signaling standard to check the
viability to include location information. The aim of the implementation was to observe the
limitations due to the use of CAMA trunk lines to deliver the E9-1-1 calls to the PSAPs from
managed VoIP networks.
To resolve the second and third sub-problems as described in bullet “b” and “c” on page
2, we studied the current state-of-the-art solutions for managed VoIP environments namely
Cisco Emergency Responder and RedSky. The study was done to recognize the software
functionality, implementation, and requirements in real-world scenarios for identifying the
location of E9-1-1 calls. The study focused on three aspects for the software:
a. Features provided.
b. Solution offered for a single Automatic Number Identification (ANI)
representation for the whole company to PSAP, irrespective of location.
c. Location determination method to track soft VoIP endpoints.
In order to validate our findings, we interviewed eminent personalities from the E9-1-1
and public safety community. The scope of the interview was to primarily address VoIP
deployments and its challenges for E9-1-1 calls with regards to mobility and dynamic
location.
To deal with the fourth sub-problem as described in bullet “d” on page 2, the research
paper identifies two companies namely, NextNav and iPosi which claim to provide better
7
GPS accuracy with proven reliability either in lab experiments or test environments. These
GPS solutions claim to provide sufficient 2D and 3D accuracy indoors, as well. The technical
viability of these vendors has been studied and identified with respect to FCC regulations for
9-1-1 and challenges associated to GPS indoors.
To deal with the fifth sub-problem as described in bullet “e” on page 3, we have proposed
a technical frame-work for integrating GPS technologies with existing software VoIP
solutions. The new frame-work will help supply real-time location tracking information to
the PSAPs on an IP backbone. We evaluated technologies that may enable us to deliver the
location through IP backbone, and designed a high-level architecture proposing a complete
end-to-end integration to relay the E9-1-1 call to the correct PSAP.
IV.
i.
Research Results
CAMA and PRI Lines
Currently, CAMA/PRI trunk lines are widely used in telephony backbone for 9-1-1 calls.
CAMA trunk lines provide the location information of the E9-1-1 caller through the DID
number or the Caller-ID number, which is essentially a publically routable number. The
CAMA trunk lines search against a database to identify the billing location and identify the
caller’s address through the Calling number received. This approach does not serve the VoIP
phones efficiently as a VoIP endpoint mostly identifies a person, not the device itself [6]. The
implication is that the location of an individual is no more limited to a single station. He /
She can login into any VoIP device within an organization and be able use the same DID
number from any part of the U.S. or the world. In our PRI based enterprise VoIP lab
8
simulation, we did not find any header in the signaling message that can be used to provide
location information. Figure 1 contains the header information fields.
Figure 1: VoIP call signaling message has no location information field
ii.
Single Routable DID and Shared Phone Lines
The traditional E9-1-1 solution using CAMA lines does not help if a 9-1-1 call is made
from a shared line number from a VoIP phone. A shared line implies two or more physical
devices or VoIP phones sharing a single DID number. Two or more VoIP shared line phones
can reside in the same building, different buildings or even different cities. The location
tracking for these endpoints renders the old system of finding location useless. It is because it
is not possible anymore to lookup for the caller’s address in the database against the Caller
ID number.
iii.
9-1-1 VoIP Software – CER and RedSky
Software such as Cisco Emergency Responder (CER) and RedSky are extensively used in
enterprise VoIP environment to manage E9-1-1 calls
1. Cisco Emergency Responder:
9
In its current architecture, CER is integrated with Enterprise Call manager, through Java
Telephony API. When a user dials 9-1-1, the call is first routed to the CER software, where it
finds corresponding Emergency Location Identifier Number (ELIN). After which the CER
replaces the calling number (ANI) by ELIN and sends it to the service providers. The service
providers provide the ELIN to the PSAPs and the PSAPs look through Automatic Location
Information (ALI) database for the correct Emergency Response Location (ERL) and call
back number. CER tracks users based on IP subnets and switchport for on-premise users. A
network administrator typically maps various parts of the building to different DID numbers,
which are mapped to the ALI database [7].
Location tracking mechanism for an off-premise user, such as an employee using
softphone on his desktop is different. Off-premise users need to enter location information
manually before the phone registration. However, it is not mandatory, and the phone can
work even without this information entered [7]. If a user enters his information, it seems like
an efficient method for location tracking but it has the following drawbacks:
a. CER cannot support multi-vendor switching platforms; it works only with Cisco
switches to do MAC based tracking to determine the change in location of the device.
b. Soft-phone clients cannot do accurate call routing for off-premise users.
c. In the case of a shared line phone calling 9-1-1 center, the ELIN number sent out will
ring back all the devices of a shared line in case of a call back.
d. In case of soft-phone clients, the E9-1-1 caller/user is responsible for reporting his/her
own location, which may be prone to errors.
2. RedSky:
10
RedSky is another leading organization that provides software solutions for managed
enterprise VoIP environment. Its initial implementation like the CER, is based on dividing a
building logically into multiple network regions or groups, each with a different set of IP
addresses for location determination of a VoIP endpoint. Based upon the caller’s IP address,
call servers determine the network region of the VoIP endpoint and associate that network
region with an ELIN which triggers the correct ALI record at the PSAP. In large multistory
buildings where network region planning is not feasible a layer 2 port level discovery method
is used, known as Network Discovery. With Network Discovery, each port on a switch is
assigned an ERL and an ELIN and exact location of an IP phone can be found by identifying
the port and network device that the phone is plugged into [8]. Off-Premise users need to
provide manual self-location information whenever they register their VoIP endpoint to the
E9-1-1 manager [8].
The RedSky approach for location tracking is not vendor-specific, but like CER it has
some inherent drawbacks.
a. A Network Administrator needs to make many crucial decisions and understand
network complexity in order to provide location information. The Network
Administrator needs to reserve the IP Pool and keep the records for each region and
needs to have granular information of the network topology.
b. Network Discovery and IP addressing are not effective if VoIP endpoints are latched
to the network wirelessly.
iv.
Concerns Raised During Interviews
11
During our research, we interviewed people from the 9-1-1 community and the VoIP
industry. A complete list of interviewees is mentioned in the Reference section (see page 22:
List of Interviewees). We found that the concerns raised were aligned with our research subproblems and are as follows:
a. Shortcomings of CAMA / PRI lines:
Most people think that when they call 9-1-1, their location information is being
relayed to the appropriate PSAPs but in reality the only data is the Caller ID. The
Caller ID field only contains static mapping and in many cases, the number is mapped
to a single DID number representing the whole enterprise and typically spanning
multiple buildings or locations. The Caller ID or the ANI field does not prove to be
efficient in that case.
b. Technical challenges associated to mobility/nomadic VoIP users:
To address the challenge related to mobility, the interviewees had a common view
that most of the VoIP software require manual address entry. The challenge with this
approach is that often it is not practical for users to update the location changes every
time upon movement. Some software applications also mention the limitation for 9-11 calling in their disclaimer statements, but almost all of the time a user ignores the
disclaimer.
c. Limitations of available 9-1-1 software:
The panel almost unanimously stated that, “If the VoIP 9-1-1 software is
configured correctly, the proper location can be determined from CallerID.” But they
also asserted that it requires very detailed and careful planning by the Network
Administrator designing the 9-1-1 system for the managed VoIP services. One more
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common issue that came out during the interviews was that many managed VoIP
Network Administrators configure 9-1-1 calling as 9-9-1-1 or 8-9-1-1 calling, which
may cause confusion among callers. The extra prefix of “9” or “8” is configured for
calls out of the enterprise intranet.
d. GPS technologies and challenges:
The major challenges put forward in regards to GPS were time to fix, signal
fading inside dense urban indoors, and accuracy levels of the current GPS technology.
The interviewees recognized that using GPS for any communication technology
either VoIP or wireless, present the same set of challenges. Although much work has
been done and is still going on in that direction, there is no reliable and proven
technology that is currently available in the market that they are aware of.
e. TDM to IP transition:
Although the FCC has taken a positive step in the direction of TDM to IP
transition, yet most of the efforts are in the planning stages, and less has been done to
implement those transitions. There is a lack of funding and incentives for the state 91-1 agencies, the service providers, and the technology manufacturers to implement
the transition. The interviewees also stated that though the transition needs to be
encouraged, maintaining support to existing 9-1-1 services is critical during this
transition period.
v.
GPS vendors – NextNav and iPosi
13
NextNav uses a terrestrial positioning constellation with a nation-wide footprint of
beacons that provide highly accurate horizontal and vertical positions of the 9-1-1 caller [9].
NextNav beacon signals synchronize themselves at a coarse level using GPS [9]. The
receivers use a chipset that is responsible for locking onto the best receiving beacon and
calculate the horizontal position taking the beacons as a reference point [9]. Also, these
receivers compute vertical position based on barometer sensors and NextNav encodes real
time environmental reference information in position data payload [9].
On the other hand, iPosi claims to have a reference design featuring a software designed
Global Navigation Satellite System (GNSS) radio the host processor processes the location
data.
Given a good operational environment and calibration, both the vendors claim to provide
location positioning systems for wireless users and small cells, but we feel that VoIP services
can integrate with the embedded chips, as well. Since NextNav uses a receiver that is
integrated with the device, VoIP phone providers will need to embed these receivers within
the device to provision the software needed for calculations. NextNav uses its own
receivers/software integrated with the device, and the location information processed by the
chipset will be relayed to the concerned destination as an overlay service on NextNav’s
standalone network. Whereas, iPosi claims that if the VoIP handset is installed with their
proprietary embedded chip / software, the handset could be located three-dimensionally (3D)
within minutes, and it continues to survey so that the software can achieve optimal accuracy
and improves with time. The incremental cost of the handset is claimed to be less than the
cost of standalone GPS that is otherwise not designed to overcome deep signal fading inside
most buildings.
14
According to the WG3 report, NextNav in dense urban environment has a horizontal
accuracy ranging between 57 meters for 67 percent of calls to 102 meters for 90 percent of
calls and in a rural environment NextNav has a horizontal accuracy ranging between 28
meters for 67 percent of calls to 45 meters for 90 percent of calls [10]. In addition to the
horizontal accuracy, NextNav claims to have a vertical accuracy of 1-3 meters that are well
within standards expected by the FCC [9]. iPosi uses an augmented GPS assistance along
with the computation resource of the handset to achieve indoor location in areas where the
GNSS signal strength is -175dBm, and it claims to have an accuracy of 25 meters for 67
percent of calls [11]. In terms of vertical accuracy, iPosi has claimed an accuracy of 10
meters. During our interview iPosi has stated that it plans to exploit a joint GNSS-barometric
sensor measurement method that incorporates indoor air pressure sensing with 3D GNSS
measurements to improve the vertical position accuracy. The mobile small cell (or VoIP
endpoint) device pressure can, therefore, be referenced to gauge its pressure relative to a
static indoor point with a conjoined GNSS 3D/pressure reference. Both vendors have claimed
to achieve the optimal accuracy levels after extensive testing in various types of
environments. For NextNav, testing has been performed by TechnoCom according to the
CSRIC test plan in Dense Urban, Urban, Sub-urban, and Rural environments. iPosi has
conducted their tests in Dense Urban, Urban, Sub-urban and Rural areas in locations such as
basements, mid and higher floors in urban areas, old and new construction, though it has not
yet been tested by CSRIC.
Both the vendors use a standalone chip that processes the location information, and for
that reason each VoIP endpoint needs to have its own receiver to relay location information.
The method outlined above may also work well in the case of remote users logging into a
15
soft VoIP endpoint from home and the remote endpoint in this case needs to have the
receiver housed on it.
Based on our analysis and interviews with these GPS vendors, we have identified three
major challenges: Time to First Fix (TTFF), 2D or 3D positioning, and Multipath problem.
Both the vendors have tackled these challenges in the following ways. Time to first fix is an
important criterion in determining the efficiency of the positioning system because it
determines the time it takes for the system to fix on a particular location signal. NextNav
claims a fast TTFF of 6 seconds, but in the CSRIC test bed NextNav has achieved a TTFF
between 27 to 28 seconds [5]. iPosi claims a TTFF of a couple of minutes. Further, 3D
positioning plays a major role as it gives the first responders better chance of attending the
caller because they can identify the approximate location of the caller and both vendors claim
to provide both 2D and 3D positioning location information [12] [11]. Multipath can cause
erroneous results if the distance between the receiver and location infrastructure is long.
NextNav dealt with this problem in the CSRIC test bed by placing the location infrastructure
close to the receiver [5]. iPosi deals with this challenge by averaging over time and using
additional methods to mitigate diffraction.
vi.
New Architecture for Dynamic Location Tracking
Considering the shortcomings of the current 9-1-1 system for managed VoIP services in
regards to shared lines, single DID, mobility, etc., we propose a new architecture which may
help to overcome the challenges associated with 9-1-1 calls from Managed VoIP
environments. With the current advancements in the GPS industry as outlined in the
preceding sections, we believe that it is possible to integrate GPS into the enterprise VoIP
16
architecture to provide real-time and absolute location of E9-1-1 calls to the PSAPs. The
advantages will be three-fold:
a. It will help to remove the dependence on manual database entries to map location
to numbers.
b. It will help to resolve issues with shared phone lines or a single DID number for a
branch office by delivering real-time location.
c. For off-premise users, we will not need a manual entry from the user to identify
their location.
Figure 2 outlines a high-level overview of the proposed architecture.
Explanation of Architecture:
Figure 2 assumes that the telephony backbone is IP/SIP enabled. The IP phone is
embedded with GPS/AGPS enabled chip, which can provide location information in the form
of 2D/3D GPS co-ordinates even in dense urban environments. This location information can
be embedded with the Call signaling information and can be incorporated in the Geolocation
header of SIP signaling protocol. It is proposed that the Geolocation header information be
included every time in call signaling parameters. The Internet Engineering Task Force
(IETF) draft for SIP Geolocation header defines location information in two ways, location
by Reference (LbyR) and Location by Value (LbyV) [13]. The NENA i3 recommendations
for Next Generation 9-1-1 systems also discuss the same in their draft as well [14]. GPS
technologies such as NextNav or iPosi will enable an IP endpoint to send the location by
LbyV in the SIP SDP Geolocation header, which we believe is much more ideal as compared
to LbyR. Typically the location value will be there in the "locationURI, cid-url field" [13].
17
The GPS co-ordinate thus obtained will be delivered to the Internet Telephony Service
Providers (ITSP), who can then provide this co-ordinate to either the PSAP points or any
Geographic Information Systems (GIS) company which may provide an address in a readable
format.
GPS / A-­‐GPS
Users Logged to company network through V PN
Soft C lients
Company’s
Exit Gateway
S IP/IP C onnection
To ITSP
Voice P BX inside an Enterprise
GPS Mapped MSAG Database
INTERNET / ITSP
GPS / A-­‐GPS
P SAP Selective router
IP P hones inside high-­‐rise buildings with G PS embedded chips
PSAP Operator
Figure 2: Proposed Architecture for VoIP and GPS Integration
We realize that it will be ideal if we can do location-based call routing, i.e. routing the
call to the nearest PSAP, based on the location provided in the Geolocation header. The IETF
draft defines parameters in the Geolocation header such as "used for routing" and "routing
allowed" to help route the call to the correct PSAPs. But even if the call is not routed to the
correct location, the remote PSAPs will still get the location information and route the call to
the correct PSAP, if needed.
18
The readable text information for the location of the caller can be provided by converting
those GPS signals in a regular Master Street Address Guide (MSAG) format. The readable
address can be facilitated by either vendors such as Intrado, who have a nation-wide footprint
or by the PSAPs themselves who can build up such a database by themselves in the near
future. Intrado has a facility already in place that does Geolocation lookup based on its
database and maps the GPS co-ordinates to the PSAPs in a readable format. This way we can
remove the dependency for location determination on legacy technologies based on Caller ID
or ANI and databases.
V.
Discussion of Results
The proposed architecture not only helps remove dependency on databases, but also helps
to alleviate any errors that may be present due to erroneous design of the 9-1-1 call validation
through software such as CER or RedSky. The most important benefit being, that it will be
now possible to provide location information for the nomadic users as the embedded chips
can be installed on the user’s laptops or tablets. It will not depend upon manual entry for
location identification anymore.
The architecture proposed as a result of our research is built in anticipation of the growth
and maturity of the GPS technology, as well as requirement of full transition to an end-to-end
IP infrastructure for call routing, which can support the SIP headers for location conveyance.
It also must be recognized that the PBX vendors and the ITSPs need to support the
Geolocation header in SIP signaling and should use compatible devices. Once companies
such as NextNav or iPosi have a nation-wide presence to provide GPS signals in challenging
environments such as dense urban and indoor environments and the VoIP hard / soft
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endpoints are embedded with their solutions, the migration to a new architecture will be
feasible. We also recognize the fact that the FCC has already extended support to TDM to IP
migration, but more needs to do be done in that regards in the form of stringent policies and
deadlines for IP adoption by ITSP.
VI.
Conclusion and Future Research
Based on our research we conclude that given the advancements in the dynamic location
tracking services, it is possible to integrate GPS solutions with managed VoIP environments
to provide location information to the PSAPs. The location tracking capabilities, with the
help of embedded GPS/AGPS solutions, can now be hosted by the VoIP hard
endpoints/softphones on laptop and relayed to the PSAPs directly over an IP backbone. The
solution presented for NG9-1-1 for Managed VoIP Services requires a collaborative effort of
VoIP PBX companies, GPS/A-GPS companies, ITSPs, FCC, standards development
association such as NENA, and PSAPs to ensure a successful migration to this next
generation technology.
Based on the proposed architecture and some of the technical advancements in the GPS
arena, there is a great scope for integration with mobile handsets for location conveyance for
9-1-1 calling to deliver exact location of 9-1-1 wireless callers. Also, there is yet to be a GPS
vendor which can provide dynamic location tracking for legacy VoIP infrastructure. Further
research can also be carried out to make general VoIP software such as Skype, Google
Hangouts, and Facebook 9-1-1 enabled.
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VII.
References
[1] Dorothy Spears-Dean, M. McGrady, P. Eggimann, and D. Wells, “NENA. National
Emergency Number Association, VoIP Operations Funding Work Group of the VoIP
Operations Committee (2006).,” in NENA VoIP Funding and Regulatory Issues Operational
Information Document (OID).
[2] Wireless E9-1-1 Location Accuracy Requirements. 2014.
[3] NENA Standard Operating Procedures Committe and VoIP OPerations Committee, “NENA
VoIP E9-1-1 Deployment and Operational Guidelines Operational Information Document
(OID).” NENA.
[4] Martin and Abernathy, “Notice of Proposed Rulemaking,” FCC Docket No 04-36 Docket No
05-196, May 2005.
[5] CSRIC Working Group III, “Indoor Location Test Bed Report,” 14-Mar-2013. [Online].
Available:
http://transition.fcc.gov/bureaus/pshs/advisory/csric3/CSRIC_III_WG3_Report_March_%20
2013_ILTestBedReport.pdf. [Accessed: 17-Apr-2014].
[6] H. Schulzrinne, “9-1-1 services: wireline, wireless and VoIP,” Columbia Univ. March, vol.
18, p. 2004, 2004.
[7] “Cisco Unified Communications SRND Based on Cisco Unified Communications Manager
6.x - Emergency Services [Cisco Unified Communications Manager Version 6.1],” Cisco.
[Online].
Available:
http://cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/srnd/6x/uc6_1/e9-1-1.html.
[8] RedSky Technologies, Inc., “E9-1-1 Solutions for Branch Offices: Providing E9-1-1
protection to branch offices while gaining the benefits of IP Telephony.” RedSky
Technologies, Inc.
[9] G. Pattabiraman, “High Precision Urban and Indoor Positioning Services,” 14-Nov-2013.
[10] “Indoor Test Report to CSRIC III-WG3 Bay Area Stage-1 Test Bed,” Jan. 2013.
[11] “Accurate
indoor
location
enterprise
solutions.”
[Online].
Available:
http://www.iposi.com/advantages-solutions/indoor-location-accuracy. [Accessed: 17-Apr2014].
[12] “Technology | NextNav.” [Online]. Available: http://www.nextnav.com/technology#hva.
[Accessed: 10-Apr-2014].
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[13] B. Rosen and J. Polk, “Location Conveyance for the Session Initiation Protocol.”
[Online]. Available: http://tools.ietf.org/html/draft-ietf-sip-location-conveyance-13#section5.1. [Accessed: 16-Apr-2014].
[14] NENA: The 9-1-1 Association, “Understanding NENA’s i3 Architectural Standard for
NG9-1-1.”
[Online].
Available:
http://c.ymcdn.com/sites/www.nena.org/resource/collection/2851C951-69FF-40F0-A6B836A714CB085D/08003_Detailed_Functional_and_Interface_Specification_for_the_NENA_i3_Solution.pdf.
[Accessed: 20-Mar-2014].
List of Interviewees:
v D Terry Hall
Chief of Emergency Communications
Immediate Past President APCO International
York-Poquoson-Williamsburg Regional 9-1-1 Center
v Daryl Branson, MPA, ENP
Executive Director
Colorado 9-1-1 Resource Center
v Mark J. Fletcher, ENP
Chief Architect, Worldwide Public Safety Solutions
Avaya
v Roger Hixson, ENP
Technical Issues Director
NENA, The 9-1-1 Association
v Stephen Meer
President and Co-Founder
Packet Brothers Inc.
List of Interviewees from iPosi Management:
v Christopher Kurby
Senior Vice President of Engineering
iPosi Inc.
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v Eric Derbez
Senior GNSS & Software Architect
iPosi Inc.
v Richard Lee
Chief Executive Officer
iPosi Inc.
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