Note: Descriptions are shown in the official language in which they were submitted.
HARDENED VOICE OVER IF (VOIP) SYSTEM
FIELD OF THE INVENTION
[0001] The present invention relates generally to fault tolerant mobile
communication
systems, and specifically relates to hardened voice over IP (VoIP) systems
with push to
talk (PTT) functionality that integrate into existing land mobile radio (LMR)
systems.
BACKGROUND OF THE INVENTION
[0002] LMR systems are wireless communications systems generally intended for
use by
terrestrial users in vehicles or on foot. Such systems are often used by
emergency first
responder organizations such as police, fire and ambulance services, public
works
organizations, dispatched services such as taxis, and companies with large
vehicle fleets
or numerous field staff. LMR systems are often independent, but can be
connected to
other fixed systems such as the public switched telephone network (PSTN) or
cellular
networks.
[0003] Radio over Internet Protocol (RoIP) is similar to VoIP, but augments
two-way
radio communications rather than telephone calls. With RoIP, at least one node
of a
network is a radio (or a radio with an IP interface device) connected via IP
to other nodes
in the radio network. The other nodes can be two-way radios, but can also be
dispatch
consoles, either traditional (hardware) or modern (software on a PC), plain
old telephone
service (POTS) telephones, softphone applications running on a computer such a
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smartphone or some other communications device accessible over IP. RoIP has
been
deployed over private networks as well as the Internet. RoIP has shown to be
useful in
land mobile radio systems used by public safety depaitments and utility fleets
spread over
a broad geographic area. Like other centralized radio systems such as trunked
radio
systems, issues of delay or latency and reliance on centralized infrastructure
can be
impediments to adoption by public safety agencies.
[0004] Examples of previous attempts to integrate LMR with VoIP include U.S.
Patent
No. 8,145,262 issued to Martinez that claims to disclose a multimode LMR and a
method
of communicating LMR content using an LMR device. The Martinez LMR system
includes an LMR communication portion and a cellular data network
communication
portion.
[0005] U.S. Patent No. 8,169,983 issued to Janky claims to disclose a
transcoder
architecture and method for transcoding in LMR systems. The Janky LMR system
includes a first communication site configured to communicate using a first
LMR
communication protocol and a second communication site configured to
communicate
using a second LMR communication protocol. The Janky LMR system further
includes a
transcoder configured to receive LMR content from the first communication site
communicated using the first LMR communication protocol and digitally convert
the
LMR content to the second LMR communication protocol to be communicated to the
second communication site.
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[0006] U.S. Patent No. 8,634,799 issued to Economy claims to disclose an
incident
commander computing device that dynamically reconfigures subscriber unit usage
of
radio access networks by first identifying, based at least on a type of
incident occurring
within a particular geographic area, a first incident response group having a
first higher
priority for responding to the incident and a second incident response group
having a
second lower priority for responding to the incident, then identifying a first
higher
priority radio access network having a sufficient coverage level across the
particular
geographic area and a second lower priority radio access network having a
sufficient
coverage level across the particular geographic area, and finally assigning
the first
incident response group to the first higher priority radio access network and
assigning the
second incident response group to the second lower priority radio access
network.
[0007] U.S. Patent No. 8,676,243 issued to Blanco claims to disclose a
communication
system that provides dual-watch and multi-watch capability for group PTT
services
where incoming PTT calls are prioritized and played out in accordance with
prioritization
protocols. In the Blanco system a user of multiple communication devices can
hear
received audio traffic being played out in accordance with the priority
assigned to the
group call and the priority assigned to the communication device, and numerous
calls can
be simultaneously received and managed.
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SUMMARY OF THE INVENTION
[0008] A hardened VoIP system is presented that includes secure PTT voice
functionality. Through the addition of encryption, authentication, user
filtering, and
integration with new and existing LMR systems, a secure voice platform ensures
malicious software, unauthorized access and brute force security attacks will
not
compromise the voice communications of the system. The VoIP system is
engineered to
ensure graceful system degradation in the event of maintenance activities,
natural
disasters and failure modes. The hardened VoIP system offers the functions a
LMR
trun king system while utilizing broadband connections. Private calls, group
calls,
Emergency Alarms with covert monitoring capability, scanning and priority
scanning
may be incorporated into the system. The system includes a VoIP controller
that serves
as a trunking controller, manages available VoIP based conference bridges, and
assigns
them as needed to the parties involved in each voice call.
[0009] The system allows for standard LMR functionality and the ability for
supervisor
tablets and smartphones to participate in and monitor VoIP calls between the
dispatch
center, mobile workforce and revenue vehicles. The system also provides
supervisor
tablets and smart phones the capability to scan talk groups in active calls,
setup calls to
other users, including closed microphone users, without dispatch or other
third party
intervention using the private call feature.
[0010] The hardened VoIP system provides an integrated mobile product that
allows the
system to gracefully fallback to the LMR infrastructure in the event of a
broadband
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network outage. The integration of hardened VoIP and LMR allows new or
existing
LMR capital resources to be used to bridge various radio technologies and
further allows
switching algorithms to seamlessly and gracefully degrade from hardened VoIP
to LMR
without user intervention in the event of a broadband outage.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Preferred embodiments are described with reference to the following
drawings,
wherein:
[0012] Figure 1 illustrates an exemplary embodiment of a hardened VoIP system.
[0013] Figure 2 illustrates an example of a VoIP solution for mobile devices.
[0014] Figure 3 illustrates an improved VoIP solution for mobile devices.
[0015] Figure 4 illustrates a method of a VoIP controller registering client
devices and
updating talk group databases.
[0016] Figure 5 illustrates an example of data that may be found in a talk
group database.
[0017] Figure 6 is a flow diagram of a client device transitioning between
numerous
communication methods and systems.
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DETAILED DESCRIPTION
[0018] The present invention may be used with any type of hardened
communication
system and is particularly suited for police, fire, and transit systems.
However, for
descriptive purposes, the present invention will be described in use with a
municipal bus
system.
[0019] Figure 1 shows a schematic of a hardened VoIP communication system 10
that
includes a server 105 connected to a switch 110 that relays data to a data
communication
controller 115. Users may configure and/or monitor the system through the use
of client
devices 120 with access the switch 110. The server 105 also communicates with
the VoIP
channel controller 125 that receives and stores data from a VoIP database 130.
The
channel controller 125 is configurable to transmit data to both a local VoIP
switch 135, a
hosted VoIP Switch 140, and a hosted conference bridge 145. The local VoIP
switch 135,
the hosted VoIP switch 140, and the hosted conference bridge 145 are all
session devices
137 that create SIP RTP sessions with mobile devices. A terminal 150 may be
used to
access and/or configure the VoIP Channel controller 125.
[0020] The VoIP switches (135, 140) are configured to communicate with
commercial
cellular towers 155 to transmit communications in an LTE, WiMax, EvD0 UMTS,
HSPA or similar format to distant communication devices.
[0021] In addition to communicating with the cellular towers 155 via the VoIP
cannel
controller 125, the server 105 is configured to also be able to communicate
with the
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cellular towers 155 via the switch 110 through a firewall 160. In one example
of the
system, the switch 110 transmits data to the cellular towers 155 via an access
point name
gateway while in alternative embodiments an independent internet service
provider is
utilized to transmit data to the cellular towers.
[0022] In addition to communicating through cellular data formats, the switch
110 may
transmit communications data through a firewall 165 to a server 170, such as a
Zetron
ACOM EVO server, that relays the communication to a dispatch switch 175 and a
router
panel 180 such as the Telex IP-224 Dual IP Remote Adapter Panel. The router
panel 180
is connected by 4 wire audio to an RoIP rack 185 with Ethernet or cellular
data
connectivity and also via 4 wire audio to auxiliary LMR radios 190.
Dispatchers may
access the system through a console client 195 such as a Zetron ACOM EVO
Client that
communicates with the dispatch switch 175 via a dispatcher server 200.
[0023] A DMZ switch 205 is connected to the dispatch switch 175 and acts as a
demilitarized zone, or perimeter network, that contains and exposes the
system's
external-facing services to a larger untrusted network. In addition to the DMZ
switch
205, the radio dispatch functionality is also protected by another firewall
210.
[0024] The land mobile radio equipment includes LMR towers 215 that
communicate
with first and second routers (220, 225) via a backhaul switch 230. The first
router 220
communicates with a LAN switch 235 and receives communications from VMS
servers
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(240, 245). The second router 225 communicates with the DMZ switch 205, a
gateway
GPRS Support Node 250 and a PDG 255 via a second LAN switch 260.
[0025] By transmitting via both the cellular towers 155 and the LMR towers
215, the
system is able to communicate with a variety of devices including LMR based
devices
265 such as the Motorola APX6500. The system is able to communicate with bi-
functional devices 270 such as the Motorola LEX L10 that has LTE connectivity
as well
as LMR connectivity. Additionally, the bi-functional devices 270 may be used
to extend
connectivity to Wi-Fl devices 275 that are closely located with the bi-
functional devices
270. The system may also communicate with cellular exclusive devices 280 such
as the
Digi Router WR44, a commercial grade cellular to Wi-Fi converter. Through a
Universal
Radio Logic Controller 285 and proprietary onboard hardware 290, the cellular
exclusive
device 280 provides data to a vehicle logic unit 295 that delivers processing
power and
communication with other on-board technologies and may provide real-time
access to
schedule, route and traffic information, on-time performance data, and
messages to and
from dispatch. The Universal Radio Logic Controller 285 and the vehicle logic
unit 295
are also be connected to an LMR Radio 300 that provides redundancy in the
event off a
malfunction in the cellular towers 155 or the cellular exclusive device 280.
[0026] The VoIP channel controller 125 of the illustrated system is a hardened
VoIP
controller and is configured to provide VoIP encryption, authentication,
authorization,
and accounting in a bandwidth efficient manner for the system. The VoIP
channel
controller 125 is shown as a single device in figure I, however it should be
appreciated
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that multiple geographically redundant VoIP channel controllers may be
utilized in
exemplary embodiments of the system such that an occurrence (fire, flood,
power outage,
etc.) at a single location would not disrupt communications in the overall
system.
[0027] The RoIP rack 185 performs 4 wire LMR to VoIP conversions and has
Ethernet
or cellular connectivity. While there is a single RoIP rack 185 shown in
Figure I, in an
exemplary embodiment there is one module per talk group such that multiple
RoIP racks
may be utilized by the system. In the event of an RoIP rack failure, the multi-
rack system
is configured to automatically shift talk groups over to any available module
on the other
RoIP racks to ensure seamless degradation of the system upon a component
failure.
[0028] The console client 195 is interfaced with the RoIP rack 185 and allows
dispatchers to access specific talk groups, and or reconfigure specific talk
groups as
needed. CSSI, DFSI, and AFSI links may also be used to interface to LMR radio
infrastructure.
[0029] Figure 2 illustrates an example of a call setup from a client device
120 to a vehicle
with a vehicle logic unit 295. The client 120 sends a setup message 305 to the
server 105
that responds with a call progress message 310 that includes conference and
channel
numbers. Using the received information, the client device 120 establishes a
conference
bridge 315 to the session device 137 and transmits a call status confirmation
320 to the
server 105 that relays a control message 325 to the vehicle logic unit 295
that in turn
establishes a conference 330 with the preselected session device 137 while
transmitting a
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confirmation 335 to the server 105. The server 105 then provides a progress
message 340
to the client device 120.
[0030] While the system of Figure 2 provides mobile VoIP capabilities there
are a few
issues with the system. In particular, the system requires a large amount of
system
bandwidth (e.g., 12 Mbps for a 350 vehicle call) due to iLBC vocoder
requirements.
Additionally, the system loses operability if the server 105 is taken offline
or if the
system is placed in to administrative fall back.
[0031] Figure 3 illustrates an improved example of a VoIP call setup from a
client device
120 client to a vehicle with a vehicle logic unit 295. In the illustrated
example, the client
device 120 sends a setup message 345 to the server 105 which relays the setup
request
350 to the data communications controller 115. The data communications
controller 115
transmits a setup signal 355 to the cellular exclusive devices 280 such as the
Digi Router
WR44 on board a vehicle. The cellular exclusive device 280 relays the setup
request 360
to the vehicle logic unit 295 via the universal radio logic controller 285. In
response to
the setup request, the vehicle logic unit 295 sends a configuration
communication 365 to
the universal radio logic controller 285 to unmute audio and enable push-to-
talk
communication. The vehicle logic unit 295 sends an acknowledgment 370 to the
data
communications controller 115 wherein the voice call setup is relayed 375 to
the client
device 120 via the server 105. The client device 120 selects 380 the voice
resource for the
console client 195. The server 120 relays (385, 390, and 395) a VoIP call
setup request to
the Universal Radio Logic Controller 285 and a VoIP module 286 with Universal
Radio
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Logic Controller 285. The VoIP module 286 establishes at 400 a session
initiation
protocol (SIP) real-time protocol (RTP) session with one of the session
devices 137 (local
VoIP switch 135, the hosted VoIP switch 140, or the hosted conference bridge
145).
Upon the completion 405 of the session (either intentionally or
unintentionally) the
Universal Radio Logic Controller 285 signals 410 the vehicle logic unit 295
which relays
(415, 420) the termination of the session to the client device 120 via the
data
communication controller 115.
[0032] Figure 3 illustrates an example of a registration method and graceful
fallback in
the event of a system deterioration. In step 425, the VoIP controller receives
an initiation
communication from a user client device and assigns the device to a talk group
(fire talk
group, transit talk group, police talk group, etc.). At regular intervals, at
step 430, the
VoIP controller transmits control signals to the client devices. The regular
flow of
transmissions from the VoIP controller to the client devices allows the
Universal Mobile
Access Radio Link Control (URLC) devices on the client devices to quickly
determine if
there has been a deterioration in the cellular based communication. In
addition to
regularly transmitting control signals in step 430, the VoIP controller is
configured to
regularly receive status updates from client devices at step 435. Similar to
the control
signal from the VoIP controller allowing the client devices to determine if
there has been
a breakdown in VoIP communications, the status signals from the client devices
allow the
VoIP controller to determine which devices are active. In an exemplary
embodiment of
the invention, the control signals and status signals are both of small file
size such that
the cellular data usage is minimized while the system is in standby mode.
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[0033] At step 440, the VoIP controller updates the database associated with
active client
database. Shown in Figure 5 are examples of some of the information that may
be
associated with the various clients in the active client database. In step
445, the VoIP
controller receives an intentional shutdown signal from a first client device,
and in step
450 the VoIP controller removes the first client device from the active client
database.
[0034] In step 455, the VoIP controller fails to receive a regular status
signal from a
second client device. Reasons for possible loss in signal include the second
client device
moving outside of a zone having cellular data coverage, a problem with a
cellular tower,
or a malfunction with the cellular data transmitter associated with the second
client
device. Before the cellular data communication failure, LMR communication
frequencies
were associated with the second client device and stored by both the second
client device
and the VoIP controller. With the cellular breakdown, the predetermined LMR
frequencies are assigned to the second client device, and at step 460 the talk
groups
unassociated with the second client device are reassigned LMR communication
frequencies. At step 465, in response to a push-to-talk signal, the VoIP
controller
facilitates a voice communication to the client devices in the first talk
group. While the
second client device receives communications via LMR, the other devices in the
talk
group may receive the communication via cellular data, or even local Wi-Fi. In
an
exemplary embodiment of the invention, the transition from cellular LTE to LMR
communications occurs seamlessly and without any manual configuration by the
users of
the client devices. In one embodiment of the invention, the system initiates
the transition
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from LTE to LMR communications upon a detection that the LTE signal strength
has
fallen below a non-zero predetermined threshold.
[0035] Figure 5 illustrates some of the information that is stored by the VoIP
controller
in the active client database. With each client device there may be stored a
unique device
identifier 470 along with a MAC address 475 associated with Wi-Fi
communications and
an IMEI 480 associated with cellular communications. The talk group 485
associated
with each group is stored in the active client database along with the
currently utilized
communication form 490 and the talk 495 and receive 500 frequencies for backup
LMR
communications. Client devices 501-505 are listed as being in the first talk
group while
client devices 506-509 are in the second talk group. Most of the client
devices (501, 502,
505, 506, 508, and 509) are utilizing cellular communications protocols while
two
devices (503, 504) are communicating via LMR and one device 507 is
communicating
via a Wi-Fi link. The forms of communication in the database are not static
and are
expected to change. As an example, a client device 507 may be associated with
a fire
truck parked at a firehouse that communicates with the VoIP controller via the
firehouse
Wi-Fi. When the firetruck leaves the firehouse, the client device 507
automatically
switches over to a cellular communication protocol once the firehouse's Wi-Fi
access
point is out of range. Should cellular and Wi-Fi communications be
unavailable, the
client device 507 on the firetruck would automatically begin to communicate
using the
predetermined land mobile radio frequencies (857.3375 and 860.3375 MHz). In an
exemplary embodiment of the invention, the transition from Wi-Fi to cellular
data to
LMR and back is done automatically without any client user interaction and
provides
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seamless fallback functionality such that a user may communicate using
numerous
different methods (Wi-Fi, LMR, satellite, etc.) without the user being aware
that a change
has occurred.
[0036] Figure 6 illustrates an example of a client device gracefully
transitioning between
multiple communication methods. At step 510, the client device regularly
receives a
control signal from a VoIP controller via Wi-Fi while the client device is in
standby
mode. A SIP/RTP bridge could be established by the VoIP controller upon a
request to
talk by a user. At step 515, the URLC aboard the client device detects that
the control
signal has not been received and transitions the client device to cellular
communications.
At step 520, the client device is once again in standby mode and at step 525 a
SIP/RTP
bridge is created between the client device and the VoIP controller in
response to a voice
communication. At step 530, the SIP/RTP bridge is terminated, and at step 535
the client
device fails to receive the control signal via cellular or Wi-Fi
communications so the
client device transitions to land mobile radio communications. At step 540,
the VoIP
controller receives a LMR communication from the client device, and via
cellular
communications, establishes a SIP/RTP bridge with the other members of the
client
device's talk group. At step 545, the client device receives the control
signal via Wi-Fi,
and the LMR transmitter on the client device is deactivated.
[0037] In addition to the features previously discussed, numerous other
features may be
incorporated into the hardened VoIP system. For example, an authentication
subsystem
may be used to validate that a device is allowed to access the hardened VoIP
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infrastructure, and an authorization subsystem may be used to ensure that a
user and a
user's password for the system are valid. Numerous accounting/billing schemes
may be
utilized by a variety of agencies or groups. For example, a taxi dispatch
system may
purchase a hardened VoIP system while offsetting a portion of the cost by
selling talk
group functionality to other organizations or even individuals.
[0038] Numerous agencies (fire, police, EMT, etc.) of a municipality may be
supported
by a single system, and the talk group trunking functionality may be utilized
to allow the
various agencies to share communications lines without interfering with each
other. The
system may include encryption functionality that provides various levels of
encryption to
ensure user compliance with privacy, local, state and federal regulations. A
Network
Management Subsystem client may also be used that allows for the addition,
deletion,
and editing of system parameters such as system IDs, talk groups, agencies,
usemames,
device IDs and passwords. The system may be configured to allow two users to
converse
or text without the rest of the user group hearing the conversation, a private
call feature
may be implemented to allow communications between two users rather than being
broadcast to the active registered talk group users.
[0039] The inventors contemplate several alterations and improvements to the
disclosed
invention. Other alterations, variations, and combinations are possible that
fall within the
scope of the present invention. Although various embodiments of the present
invention
have been described, those skilled in the art will recognize more
modifications that may
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be made that would nonetheless fall within the scope of the present invention.
Therefore,
the present invention should not be limited to the specific examples
described.
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