Note: Descriptions are shown in the official language in which they were submitted.
PUSH-TO-TALK-OVER-CELLULAR (POC)
BACKGROUND
1. Field.
This disclosure relates in general to mobile phone networks, and more
specifically, to push-to-talk-over-cellular (PoC).
2. Description of Related Art.
Advanced voice services (AVS), also known as Advanced Group Services
(AGS), such as two-way half-duplex voice calls within a group, also known as
Push-to-
Talk-over- Cellular (PoC), Push-to-Talk (PTT), or Press-to-Talk (P2T), as well
as other
AVS functions, such as Push-to-Conference (P2C) or Instant Conferencing, Push-
to-
Message (P2M), etc., are described in co-pending and commonly-assigned patent
applications. These AVS functions have enormous revenue earnings potential for
wireless communications systems, such as cellular networks and personal
communications systems (PCS) networks.
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Currently, there are two major approaches employed in providing advanced
voice services in wireless communications systems. One approach is based on
circuit-
switched technology, wherein voice circuits are reserved during the entire
duration of
an AVS or PoC call. Circuit-switched PoC is deployed by many operators around
the
world with technologies such as NEXTEL's iDEN and Kodiak Network's RTX.
Another approach to PoC is based on packet or voice-over-IP (VoIP)
technologies. This approach capitalizes on the "bursty" nature of PoC
conversations
and makes network resources available only during talk bursts and hence is
highly
efficient from the point of view of network and spectral resources. This
approach
promises compliance with newer and emerging packet-based standards, such as
GPRS
(General Packet Radio Service), UMTS (Universal Mobile Telecommunications
System), 3G, 4G, LTE, etc.
Nonetheless, there is a need in the art for improvements to the methods and
systems for delivering the advanced voice services, such as PoC, that comply
with both
existing and emerging wireless packet-based standards and yet provide superior
user
experiences. Many existing implementations of PoC suffer from an inferior user
experience, such as slow call setup. The present disclosure satisfies the need
for a
superior user experience, and also defines procedures for practical
implementation of
PoC in commercial, standards-based, cellular networks, with a focus on
features, such
as provisioning, fault tolerance, roaming support, support for SIM swap and
dual SIM,
interaction of PoC with GSM cellular calls, etc.
3
SUMMARY
To address the limitations in the prior art described above, and to address
other
limitations that will become apparent upon reading and understanding the
present
specification, the present disclosure discloses a Push-to-Talk-over-Cellular
(PoC)
implementation for use in wireless communications networks, such as cellular
mobile
phone networks and wireless data networks, wherein one or more servers
interface to
the wireless communications network to perform PoC call sessions. Both the
servers
and the mobile units that use the PoC call sessions communicate with each
other using
SIP/IP (Session Initiation Protocol/Internet Protocol) control messages within
the
wireless communications network, and one or more of the servers switches
RTP/IP
(Realtime Transport Protocol/Internet Protocol) voice packets, RTCP/IP
(Realtime
Transport Control Protocol /Internet Protocol), or MBCP/IP (Media Burst
Control
Protocol /Internet Protocol) controlling/signaling packets for the PoC call
sessions
between the mobile units across the wireless communications network.
In one embodiment, there is provided a system for providing voice services in
a
communications network. The system includes one or more servers that interface
to
the communications network to perform voice services, the voice services
including an
instant two-way half-duplex voice call within a group of users of the
communications
network comprising a Push-to-Talk-over-Cellular (PoC) call session. The
servers
communicate with a handset that uses the voice services using control messages
within
the communications network, and at least one of the servers switches voice
packets for
the voice services between the handset across the communications network. A
media
server of the one or more servers receives a wakeup trigger from a PoC client
on the
handset. The wakeup trigger is transmitted, by the PoC client, in response to
an
indication of intent to initiate a PoC call. In response to the wakeup
trigger, the media
server transmits a wakeup message to an additional PoC client on an additional
handset
prior to the PoC client attempting to initiate the PoC call. The media server
selects the
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additional PoC client from a predictive wakeup list of the PoC client. The
predictive
wakeup list is created, by the media server, before receiving the wakeup
trigger from
the PoC client. The predictive wakeup list is created in accordance with
quantities of
times the PoC client previously called other PoC clients in the PoC call
session, when
the PoC client most recently called the other PoC clients in the PoC call
session, and
whether the PoC client recently received alerts from the other PoC clients in
the PoC
call session. Subscriber provisioning is initiated by the network's operator
such that an
XML Document Management (XDM) Server receives an activation request from the
PoC client on the handset, the XDM server storing user-specific service-
related
information, the activation request including a unique identifier generated by
the PoC
Client that is used for verifying the subscriber's identity. Subscriber
provisioning is
initiated by the network's operator such that the XDM Server receives a
password from
the PoC client via a Web Group Provisioning (WGP) Server, the password is used
with
the unique identifier generated by the PoC Client for verifying the
subscriber's identity,
the WGP server providing a web interface for an administrator to manage PoC
contacts
and groups, and the XDM Server sets up the subscriber's account by creating
default
documents including contacts for the subscriber. Subscriber provisioning is
initiated by
the network's operator such that the XDM Server updates a PoC Server and the
PoC
Server responds to the WGP Server with the subscriber's configuration, which
is stored
on the XDM Server, and the XDM Server returns the subscriber's configuration
to the
PoC Client in response to the activation request via the WGP Server.
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The subscriber's configuration may include a username to be used for
authentication, the username may be generated based on the subscriber's mobile
number.
The password may be transmitted separately from the activation request, and
the
XDM Server may store the password against the username and uses it for
authenticating the PoC Client.
The username and password may be used by the PoC Client for registration and
for authenticating the XDM Server's operations.
A duplicate activation by the PoC Client may result in the XDM Server
updating the activation request, overwriting a previous activation request,
and using a
last received activation request.
A request failure by the PoC Client may result in the PoC Client re-sending
the
activation request.
An activation failure may result in the PoC Client sending the activation
request
again.
The XDM Server may check the handset against a list of allowed devices and
grants or denies the activation based on the check.
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A PoC Client executed by the handset may initially store a first subscriber
identity read from a subscriber identity module (SIM) on the handset when the
handset
is first activated, and the PoC client detects when a user changes the SIM on
the
handset, and the PoC client re-activates in response to the user changing the
SIM.
A PoC Client executed by the handset may initially store a first subscriber
identity read from a subscriber identity module (SIM) on the handset when the
handset
is first activated, and the PoC client supports dual subscriber identity
modules (SIMs)
on the handset being used for PoC service.
One or more of the servers may support geographical redundancy, a PoC Client
executed by the handset maintains a first pre-established session with a first
one of the
one or more servers supporting geographic redundancy, a PoC Client executed by
the
handset maintains a second pre-established session with a second one of the
one or
more servers supporting geographic redundancy, and the first pre-established
session is
separate from and simultaneous with the second pre-established session.
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One or more of the servers may be a Web Group Provisioning (WGP) Server
that provides a Corporate Administration Tool (CAT) for providing subscriber
management, group management, contact management and associations between
corporations, and the CAT restricts availability of a subscriber by not
allowing the
subscriber to change a presence status of the subscriber.
A PoC Client executed by the handset may be configured to provide a specific
corporate user experience on the handset, and the PoC Client displays a Call
History
showing Instant Personal Alerts.
A PoC client executed by the handset may be registered with a PoC server, the
PoC Client reports any changes to a country or network identifier for the
wireless
communications network to the PoC Server, the PoC client re-registers with the
PoC
server based on the changes to the country or the network identifier for the
wireless
communications network, and the PoC Server determines whether the PoC Client
can
re-register based on the country or network identifier for the wireless
communications
network.
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A PoC Client executed by the handset may display an Answer or Ignore option
when a cellular service call overlaps with the PoC call session.
One or more of the servers may be a controlling server that manages the PoC
call session by acting as an arbitrator for the PoC call session, and the
controlling
server sends connect messages for the PoC call session to calling and called
parties,
and the controlling server uses acknowledgments for the connect messages to
determine whether the called parties have joined the PoC call session or not.
BRIEF DESCRIPTION OF THE DRAWINGS
Referring now to the drawings in which like reference numbers represent
corresponding parts throughout:
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FIG. 1 is a block diagram that illustrates an exemplary embodiment of a
wireless
communications network according to a preferred embodiment of the present
invention.
FIGS. 2-9 illustrate call flows for various scenarios according to the
preferred
embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
In the following description of the preferred embodiment, reference is made to
the
accompanying drawings which form a part hereof, and in which is shown by way
of
illustration the specific embodiment in which the invention may be practiced.
It is to be
understood that other embodiments may be utilized as structural changes may be
made
without departing from the scope of the present invention.
1 Overview
The present invention discloses a system for implementing Push-to-Talk-over-
Cellular (PoC) that provides a feature-rich server architecture with a
flexible client strategy.
This system is an Open Mobile Alliance (OMA) standards-compliant solution that
can be
easily deployed, thereby enabling carriers to increase their profits, improve
customer
retention and attract new customers without costly upgrades to their network
infrastructure.
This system is built on a proven, reliable all-IP (Internet Protocol)
platform. The highly
scalable platform is designed to allow simple network planning and growth.
Multiple servers
can be distributed across operator networks for broad geographic coverage and
scalability to
serve a large and expanding subscriber base.
1.1 Definitions
The following table defines various acronyms, including industry-standard
acronyms,
that are used in this specification.
Acronym Description
ATCA Advanced Telecommunications Computing Architecture
DnD Do not Disturb
DNS Domain Name Server
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Acronym Description
GPRS General Packet Radio Service
GSM Global System for Mobile communications
HTTP Hypertext Transport Protocol
HTTPS Secure Hypertext Transport Protocol
IMSI International Mobile Subscriber Identity
IP Internet Protocol
IPA Instant Personal Alert
InstaPoC "Instant" PoC, namely predictive wakeup for PoC calls
MBCP Media Burst Control Protocol
MCC Mobile Country Code
MDN Mobile Directory Number
MNC Mobile Network Code
MS-ISDN Mobile Station International Subscriber Directory Number
OMA Open Mobile Alliance
PoC Push-to-talk-over-Cellular
PTT Push-To-Talk
PW Predictive Wakeup ¨ synonymous with InstaPoC
RTCP Realtime Transport Control Protocol
RTP Realtime Transport Protocol
SDP Session Description Protocol
SIM Subscriber Identity Module
SIP Session Initiation Protocol
SMMP Short message peer-to-peer protocol
SMS Small message service
URI Uniform Resource Identified
XCAP XML Configuration Access Protocol
XDM XML Document Management
XML Extensible Mark-up Language
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The following table defines various terms, including industry-standard terms,
that are
used in this specification.
Term Description
1-1 PoC Session A feature enabling a PoC User to establish a PoC Session
with another
PoC User.
1+1 Redundancy A configuration where the each primary server has a
dedicated
secondary server configured in the same chassis. The primary server is
configured as active and the secondary server is configured as standby.
Ad Hoc PoC Group A PoC Group Session established by a PoC User to PoC Users
listed
Session on the invitation. The list includes PoC Users or PoC Groups
or both.
Answer Mode A PoC Client mode of operation for the terminating PoC
Session
invitation handling.
Controlling PoC A function implemented in a PoC Server, providing
centralized PoC
Function Session handling, which includes media distribution, Talk
Burst
Control, Media Burst Control, policy enforcement for participation in
the PoC Group Sessions, and participant information.
Corporate These subscribers will only receive contacts and groups from
a
corporate administrator. That means they cannot create their own
contacts and groups from handset.
Corporate Public These subscribers receive contacts and groups from a
corporate
administrator in addition to user-created contacts and groups.
Corporate A user who manages corporate subscribers, their contacts and
groups.
Administrator
Geo Redundancy A configuration where each serving server has a
geographically
separated standby server. This standby server takes over the active role
only when the serving server fails.
Home PoC Server The PoC Server of the PoC Service Provider that provides
PoC service
to the PoC User.
In-Chassis A redundancy scheme where secondary servers are configured
on the
Redundancy same chassis as primary servers. In-chassis redundancy can
be 1+1,
n+k, or load shared modes.
Instant Personal Alert A feature in which a PoC User sends a SIP based instant
message to a
PoC User requesting a 1-1 PoC Session.
Law Enforcement An organization authorized by a lawful authorization based
on a
Agency national law to request interception measures and to receive
the results
of telecommunications interceptions.
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Term Description
Lawful Interception The legal authorization, process, and associated
technical capabilities
and activities of Law Enforcement Agencies related to the timely
interception of signalling and content of wire, oral, or electronic
communications.
Load Shared A redundancy scheme in which all the servers are in an
active mode at
the same time and traffic is distributed across all these servers.
N+K Redundancy A configuration where "n" primary servers (1 or more) have a
group of
"k" secondary servers (1 or more) configured in the same chassis.
Typically, "k" is less than "n".
Notification A message sent from the Presence Service to a subscribed
watcher
when there is a change in the Presence Information of some presentity
of interest, as recorded in one or more Subscriptions.
Participating PoC A function implemented in a PoC Server, which provides
PoC Session
Function handling, which includes policy enforcement for incoming PoC
Sessions and relays Talk Burst Control and Media Burst Control
messages between the PoC Client and the PoC Server performing the
Controlling PoC Function. The Participating PoC Function may also
relay RTP Media between the PoC Client and the PoC Server
performing the Controlling PoC Function.
PoC Client A functional entity that resides on the User Equipment that
supports
the PoC service.
Pre-Arranged PoC A SIP URI identifying a Pre-Arranged PoC Group. A Pre-
Arranged
Group Identity PoC Group Identity is used by the PoC Client, e.g., to
establish PoC
Group Sessions to the Pre-Arranged PoC Groups.
Pre-Arranged PoC A persistent PoC Group. The establishment of a PoC Session
to a Pre-
Group Arranged PoC Group results in the members being invited.
Pre-Established The Pre-Established Session is a SIP Session established
between the
Session PoC Client and its Home PoC Server. The PoC Client
establishes the
Pre-Established Session prior to making requests for PoC Sessions to
other PoC Users. To establish a PoC Session based on a SIP request
from the PoC User, the PoC Server conferences other PoC Servers or
users to the Pre-Established Session so as to create an end-to-end
connection.
Presence Server A logical entity that receives Presence Information from a
multitude of
Presence Sources pertaining to the Presentities it serves and makes this
information available to Watchers according to the rules associated
with those Presentities.
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Term Description
Presentity A logical entity that has Presence Information
associated with it. This
Presence Information may be composed from a multitude of Presence
Sources. A Presentity is most commonly a reference for a person,
although it may represent a role such as "help desk" or a resource such
as "conference room #27". The Presentity is identified by a SIP URI,
and may additionally be identified by a tel URI or a pres URI.
Public These subscribers create and manage their contacts and
groups.
Serving Server A set of primary and secondary servers.
Subscription The information kept by the Presence Service about a
subscribed
watcher's request to be notified of changes in the Presence Information
of one or more Presentities.
Watcher Any uniquely identifiable entity that requests Presence
Information
about a Presentity from the Presence Service.
2 System Architecture
FIG. 1 illustrates the system architecture used in the present invention. This
architecture conforms to the Advanced Telecommunications Computing
Architecture
(ATCA) standard to support the PoC solution of the present invention. ATCA is
an open
standards-based, high-availability telecommunications platform architecture.
Preferably, the system 100 includes one or more PoC Service Layers 102 and one
or
more Management Layers 104, each of which is comprised of one or more servers
interconnected by one or more IP networks 106. Specifically, the PoC Service
Layer 102
includes one or more XML Document Management (XDM) Servers 108, Presence
Servers
110, PoC Servers 112, and Media Servers 114, while the Management 1,ayer 104
includes
one or more Element Management System (EMS) Servers 116, Lawful Intercept (LI)
Servers
118, Web Customer Service Representative (WCSR) Servers 120, and Web Group
Provisioning (WGP) Servers 122. These various servers are described in more
detail below.
The PoC Service Layer 102 and Management Layer 104 are connected to one or
more
wireless communications networks, such as cellular phone networks 124 and
wireless data
networks 126, as well as one or more IP networks 106. Note that the cellular
phone networks
124 and wireless data networks 126 may be implemented in a single network or
as separate
networks. The cellular phone network 124 includes one or more Short Message
Service
Centers (SMSCs) 128, Mobile Switching Centers (MSCs) 130, and Base Station
Components
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(BSCs) 132, wherein the BSCs 132 include controllers and transceivers that
communicate
with one or more customer handsets 134 (also referred to as a mobile unit,
mobile station,
mobile phone, cellular phone, etc.) executing a PoC Client 136. The wireless
data network
126 includes one or more Gateway GPRS Support Nodes (GGSNs) 136 and Serving
GPRS
Support Nodes (SGSNs) 138, which also communicate with customer handsets 134
via BSCs
132.
2.1 Cellular Phone Network
The PoC Service Layer 102 interacts with the SMSC 128 on the cellular phone
network 124 to handle Short Message Service (SMS) operations, such as routing,
forwarding
and storing incoming text messages on their way to desired endpoints.
2.2 Wireless Data Network
The PoC Service Layer 102 also interacts with the following entities on the
wireless
data network 126:
= The GGSN 136 transfers IP packets between the PoC Client 136 and the
various servers:
= SIP/IP signaling messages between the PoC Server 112 and PoC
Client 136 for control traffic exchange (i.e., control packets) for PoC
call sessions.
= RTP/IP, RTCP/IP and MBCP/IP packets between the Media Server
114 and PoC Client 136 for bearer traffic exchange (i.e., voice
packets) for PoC call sessions.
= SIP/IP signaling messages between the Presence Server 110 and PoC
Client 136 for presence information.
= XCAP/HTTP/IP and SIP/IP signaling between the XDM Server 108
and PoC Client 136 for document management.
= The SMSC 128 handles authentication:
= The XDM Server 108 communicates with the SMSC 128 via SMPP/IP
for receiving the authentication code required for PoC Client 136
activation from the handset 134.
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2.3 PoC Service Layer Elements
As noted above, the PoC Service Layer 102 is comprised of the following
elements:
= PoC Server 112,
= Media Server 114,
= Presence Server 110, and
= XDM Server 108.
'these elements are described in more detail below.
2.3.1 PoC Server
The PoC Server 112 handles the PoC call session management and is the core for
managing the PoC services for the PoC Clients 136 using SIP protocol. The PoC
Server
112 implements a Control Plane portion of Controlling and Participating PoC
Functions.
A Controlling PoC Function acts as an arbitrator for a PoC Session and
controls the
sending of control and bearer traffic by the PoC Clients 136. A Participating
PoC Function
relays control and bearer traffic between the PoC Client 136 and the PoC
Server 112
performing the Controlling PoC Function.
The PoC Server 112, along with the Media Server 114, also implements InstaPoC
technology for faster PoC call session setup. One version of the InstaPoC
technology,
known as Predictive Wakeup, is described in co-pending and commonly-assigned
U.S.
Utility Application Serial Number 13/093,542, filed April 25, 2011, by
Brahmananda R.
Vempati, Krishnakant M. Patel, Pratap Chandana, Anand Narayanan, Ravi
Ayyasamy,
Bruce D. Lawler, Basem A. Ardah, Ramu Kandula, Gorachand Kundu, Ravi Shankar
Kumar, and Bibhudatta Biswal, and entitled "PREDICTIVE WAKEUP FOR PUSH-TO-
TALK-OVER CELLULAR (PoC) CALL SETUP OPTIMIZATIONS,", now U.S. patent
no. 8,478,261 . The functions of the InstaPoC technology implemented by the
PoC Server
112 are described in more detail below.
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2.3.2 Media Server
The Media Server 114 implements a User Plane portion of the Controlling and
Participating PoC Functions. The Media Server 114 supports the Controlling PoC
Function by duplicating voice packets received from an originator PoC Client
136 to all
recipients of the PoC Session. The Media Server 114 also supports the
Participating PoC
Function by relaying the voice packets between PoC Clients 136 and the Media
Server
114 supporting the Controlling PoC Function. The Media Server 114 also handles
packets
sent to and received from the PoC Clients 136 for floor control during PoC
call sessions.
2.3.3 Presence Server
The Presence Server 110 implements a presence enabler for the PoC Service. The
Presence Server 110 accepts, stores and distributes Presence Information for
Presentities,
such as PoC Clients 136.
The Presence Server 110 also implements a Resource List Server (RLS), which
accepts and manages subscriptions to Presence Lists. Presence Lists enable a
"watcher"
application to subscribe to the Presence Information of multiple Presentities
using a single
subscription transaction.
The Presence Server 110 uses certain XDM functions to provide these functions,
which are provided by XDM Server 108.
2.3.4 XDM Server
The XDM Server 108 implements an XDM enabler for the PoC Service. The XDM
enabler defines a common mechanism that makes user-specific service-related
information
accessible to the functions that need them. Such information is stored in the
XDM Server
108 where it can be located, accessed and manipulated (e.g., created, changed,
deleted,
etc.). The XDM Server 108 uses well-structured XML documents and HTTP protocol
for
access and manipulation of such XML documents. The XDM Server 108 also
connects to
the
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operator SMSC 128 for the purposes of PoC Client 136 activation using SMS. In
addition,
the XDM Server 108 maintains the configuration information for all PoC
subscribers.
2.4 Management Layer Elements
As noted above, the Management Layer 104 is comprised of the following
elements:
= Element Management System (EMS) Server 116,
= Lawful Intercept (LI) Server 118,
= Web Group Provisioning (WGP) Server 122, and
= Web Customer Service Representative (WCSR) Server 120.
These elements are described in more detail below.
2.4.1 EMS Server
The EMS Server 116 is an operations, administration, and maintenance platform
for
the system 100. The EMS Server 116 enables system administrators to perform
system-
related configuration, network monitoring and network performance data
collection
functions. All functions of the EMS Server 116 are accessible through a web-
based
interface.
2.4.2 LI Server
The LI Server 118 is used for tracking services required by various Lawful
Enforcement Agents (LEAs). The LI Server 118 generates and pushes an IRI
(Intercept
Related Information) Report for all PoC Services used by a target. The target
can be added
or deleted in to the PoC Server 112 via the LI Server 118 using a Command Line
Interface
(CLI).
2.4.3 WGP Server
The WGP Server 122 provides a web interface for corporate administrators to
manage
PoC contacts and groups. The web interface includes contact and group
management
operations, such as create, delete and update contacts and groups.
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2.4.4 WCSR Server
The WCSR Server 120 provides access to customer service representatives (CSRs)
for managing end user provisioning and account maintenance.
Typically, it supports the following operations:
= Create Subscriber account.
= Update Subscriber account,
= Delete Subscriber account,
= Mobile number change command,
= View Subscriber details (MDN, Group, Group members),
= Manage Corporate Accounts,
= Add CSR account,
= Delete CSR account.
3 System Functions
The following sections describe various functions performed by each of the
components of the system architecture.
3.1 PoC Service Layer
3.1.1 PoC Server
The PoC Server 112 controls PoC call sessions, including 1-1, Ad Hoc and Pre-
Arranged PoC call sessions. The PoC Server 112 also controls Instant Personal
Alerts.
The PoC Server 112 expects the PoC Clients 136 to setup "pre-established
sessions"
at the time of start up and use these sessions to make outgoing PoC calls. The
PoC Server
112 also uses pre-established sessions to terminate incoming PoC calls to the
PoC Clients
136. The PoC Clients 136 are setup in auto-answer mode by default. The use of
pre-
established sessions and auto-answer mode together allow for faster call setup
for PoC call
sessions.
The PoC Server 112 allocates and manages the media ports of the Media Services
114
associated with each SIP INVITE dialog for pre-established sessions and
controls the Media
Servers 114 to dynamically associate these ports at run time for sending RTP
packets during
PoC call sessions. Media ports are assigned and tracked by the PoC Server 112
at the time of
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setting up pre-established sessions. The PoC Server 112 instructs the Media
Server 114 to
associate the media ports of various subscribers dynamically into a session
when a PoC call
is originated and this session is maintained for the duration of the call. The
PoC Server 112
also controls the floor states of the various participants in a PoC call
session by receiving
indications from the Media Servers 114 and sending appropriate requests back
to the Media
Servers 114 to send MBCP messages to the participants in the PoC call. The
Media Server
114 uses the media ports association and current talker information to send
the RTP packets
from the talker's media port onto the listeners' media ports.
In addition, the PoC Server 112 handles the incoming and outgoing Instant
Personal
Alerts (IPAs) by routing SIP MESSAGE requests to the PoC Clients 136 and
remote PoC
Servers 112 for final delivery as applicable.
The PoC Server 112 also receives InstaPoC triggers from the PoC Clients 136
and
sends wakeup messages to the PoC Clients 136 of the subscribers likely to be
called. The
PoC Server 112 sends and receives these messages and triggers through the
Media Server
114, as these messages are sent to and received from PoC Clients 136. The
lists of potential
called parties to be woken up for each caller are created and maintained by
the PoC Server
112 as described in more detail below.
The PoC Server 112 uses static and dynamic data related to each subscriber to
perform these functions. Static data include subscriber profile, contacts and
groups.
Dynamic data include the subscriber's registration state, PoC settings and SIP
dialog states
are maintained only on the PoC Server 112.
3.1.2 Media Server
The Media Server 114 handles the flow of data to and from the PoC Clients 136
as
instructed by the PoC Server 112. Each Media Server 114 is controlled by a
single PoC
Server 112, although multiple Media Servers 114 may be controlled by a PoC
Server 112
simultaneously.
The Media Server 114 is completely controlled by the PoC Server 112. As noted
above, even the media ports of the Media Server 114 are allocated by the PoC
Server 112 and
then communicated to the Media Server 114. Likewise, floor control requests
received by
the Media Server 114 from PoC Clients 136 are sent to the PoC Server 112, and
the PoC
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Server 112 instructs the Media Server 114 appropriately. Based on these
instructions, the
Media Server 114 sends floor control messages to the PoC Clients 136 and sends
the RTP
packets received from the talker to all the listeners.
3.1.3 InstaPoC
The system 100 also includes a mechanism known as lnstaPoC or predictive
wakeup
for forcing the radio access network to setup a channel for the PoC Clients
136 of a list of
subscribers who are most likely to be called by a user. This mechanism,
together with PoC
pre-established sessions and default auto-answer mode of PoC Clients 136,
allows much
shorter call setup times than what is normally expected for Push-to-Talk.
In InstaPoC, a wakeup trigger is received by the Media Server 114 from the
caller's
PoC Client 136, and then forwarded to the PoC Server 112, which instructs the
Media Server
114 to send wakeup messages to the PoC Clients 136 of potential called parties
in response to
the wakeup trigger, before the actual PoC call is attempted by the caller.
InstaPoC may be
triggered in any number of different ways, such as when a user selects a
contact on the
handset 134, or selects a group on the handset 134, or selects an entry in the
call history on
the handset 134, or presses a button on the handset 134, or in any other way
that indicates an
intent to initiate a PoC call.
In one embodiment, the PoC Server 112 receives the wakeup trigger from the
Media
Server 114 and retrieves or generates one or more predictive wakeup (PW) lists
corresponding to the subscriber whose PoC Client 136 sent the trigger. The PoC
Server 112
separates the list into sub-lists of subscribers who are served by different
PoC Servers 112
including this PoC Server 112 (i.e., itself). Finally, the PoC Server 112
refines the local sub-
list further by removing all offline subscribers as well as those who have
enabled DnD (Do
not Disturb). The PoC Server 112 then sends a PW list message to each of the
remote PoC
Servers 112 containing the corresponding sub-list, and each of the PoC Servers
112 instructs
its local Media Servers 114 to send wakeup packets to each PoC Client 136
served by this
PoC Server 112 (i.e., itself).
The PoC Server 112 creates and maintains the PW lists for each subscriber
based on
various types of information. The PoC Server 112 may use various data for the
PW lists,
such as the number of times a subscriber calls a contact, when was the last
call made,
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CA 02798720 2012-12-12
whether an Instant Personal Alert was received recently from a contact, etc.
Moreover, the
size of the PW lists is configurable.
3.1.4 Presence Server
The Presence Server 110 accepts presence information published by PoC Clients
136,
as well as availability information received from other entities. The Presence
Server 110
keeps track of these presence states and sends notifications to various
"watcher" applications
whenever a presence state changes. The Presence Server 110 maintains a
separate
subscription for each watcher and dynamically applies the presence
authorization rules for
each watcher independently.
The Presence Server 110 also accepts resource list subscriptions from the
watchers,
which identify one or more entities ("Presentities") whose presence should be
monitored.
The Presence Server 110 then aggregates all the presence information into one
or more
presence notifications transmitted to each watcher. This allows watchers to
subscribe to
large number of Presentities without putting strain on the network as well as
client and server
resources.
3.1.5 XDM Server
The XDM Server 108 performs client authentication and subscription functions.
The
XDM Server 108 also stores subscriber and group information data. The XDM
Server 108
also interacts with the SMSC 128 to receive PoC Client 136 activation
commands.
All subscriber provisioning and CSR operations in the XDM Server 108 are
performed through the WCSR Server 120, while corporate administrative
operations, as well
as contacts and group management, are handled through the WGP Server 122.
The XDM Server 108 includes a Subscriber Profile Manager module that provides
subscriber management functionality, such as creation, deletion and
modification of
subscriber profiles. The subscriber profile includes data such as the MDN,
subscriber name,
subscriber type, etc. This also determines other system-wide configurations
applicable for
the subscriber including the maximum number of contacts and groups per
subscriber and the
maximum number of members per group.
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The XDM Server 108 includes a Subscriber Data Manager module that manages the
subscriber document operations, such as contact and group management
operations, initiated
by the PoC Clients 136 or the WGP Server 122.
3.2 Management Layer
3.2.1 EMS Server
The EMS Server 116 is the central management entity in the system and includes
the
following modules:
= A central application where all management business logic resides.
= A web server for serving the network operator's internal users. A
corresponding client provides a user interface for viewing fault,
configuration,
performance and security information.
= A subsystem is provided for health monitoring of network elements
deployed
in the system and also to issue any maintenance commands as applicable.
3.2.2 WCSR Server
The WCSR Server 120 provides a web user interface for customer service
representatives (CSRs) to carry out various operations. The web user interface
provides
access to CSRs for managing subscriber provisioning and account maintenance.
Typically, it
supports the following operations.
= Create Subscriber account,
= Update Subscriber account,
= Delete Subscriber account,
= Mobile number change command,
= Forced synchronization of a Subscriber,
= Deactivate a Subscriber account,
= Reactivate a Subscriber account,
= View Subscriber details, such as MDN, Group, Group members.
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3.2.3 WGP Server
The WGP Server 122 allows provides for central management of all corporate
subscribers and associated contacts and groups within a corporation. The WGP
Server 122
allows corporate administrators to manage contacts and groups for corporate
subscribers.
The WGP Server 122 includes a Corporate Administration Tool (CAT) that is used
by corporate administrators to manage contacts and groups of corporate
subscribers. The
CAT has a Web User Interface for corporate administrators that supports the
following
operations:
= group management,
= contact management, and
= associations between corporations.
With regard to group management, the CAT of the WGP Server 122 includes the
following operations:
= Create, Update, Delete and View Corporate Groups,
= Add, Update, Delete and View Members of a Corporate Group,
= Manage Subscribers,
= Activate and Deactivate a Corporate Subscriber,
= Change a Subscriber type from "Corporate" to "Corporate And Public", and
vice versa,
= Restrict Availability, i.e., do not allow subscriber to change their
presence
status, and
= Manage number porting or name change via phone assignment.
With regard to contact management, the CAT of the WGP Server 122 includes the
following operations:
= Phone list management,
= NxN Contact Add (e.g., N contacts may be members of N groups),
= Add, Update, Delete and View Contacts for a specific subscriber, and
= Export and Import contacts at both the subscriber and corporate level.
With regard to associations between corporations, the CAT of the WGP Server
122
includes the following operations:
= Corporate Associations Attributes,
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= Association Name,
= Association ID,
= Association Mode (e.g., One-way, Two-way), and
= Restricted List.
Once the association is created and accepted, corporate administrators can
create
contacts and groups using the association policies. Administrators from other
corporations
can view the contacts, and may or may not have the capability to add, update
or delete the
contacts.
= Corporate ID associated per corporate subscriber,
= Central management of corporate subscribers, groups, and contacts,
= Intercorporate associations, including contacts and white lists,
= Phone list management (e.g., NxN contact add),
= Restrict Availability, and
= Import and Export contacts at both the subscriber and corporate level.
Note that, if the association is deleted, then usually all intercorporate
contacts and
group members will be deleted.
3.3 PoC Client
The PoC Client 136 is an OMA-compatible client application executed on a
handset
134. The following features are supported by the PoC Client 136:
= PoC Calls and Instant Personal Alert,
= Presence,
= Contact and Group Management.
The PoC Client 136 includes a database module, a presence module, an XDMC
module and a client module.
The database module stores configuration information, presence information,
contact
and group information, user settings, and other information in an optimized
and persistent
way. Information is preserved when the user unregisters with the PoC Server
112 or power
cycles the device. The database module also has a mechanism to reset the data
and
synchronize from the XDM Server 108 when the data in the database module is
corrupt or
unreadable.
CA 02798720 2012-12-12
The presence module creates and maintains the presence information for the
subscriber. Typically, the presence information supports Available,
Unavailable and Do-not-
Disturb (DnD) states. The presence module also subscribes to the Presence
Server 110 as a
"watcher" of all contacts in the handset 134 and updates the user interface of
the handset 134
whenever it receives a notification with such presence information.
The XDMC module communicates with the XDM Server 108 for management of
contacts and groups. The XDMC module may subscribe with the XDM Server 108 to
send
and receive any changes to the contacts or group list, and updates the user
interface of the
handset 134 based on the notifications it receives from the XDM Server 108.
The client module provides the most important function of making and receiving
PoC
calls. To support PoC calls, the client module creates and maintains pre-
established sessions
with the PoC Server 112. The client module supports 1-1, Ad Hoc and Pre-
Arranged PoC
calls. The client module also supports sending and receiving Instant Personal
Alerts (IPA).
To support faster call setup, the client module implements InstaPoC.
3.3.1 SIM Swap / Dual SIM
The PoC Client 136 has built-in logic to detect if the user changes a SIM on
the
handset 134 being used for PoC service. The PoC Client 136 also supports dual
SIMs on the
handset 134 being used for PoC service.
With regard to SIM swap, the PoC Client 136 initially stores the IMSI of the
SIM
when the handset 134 is first successfully activated with the PoC Server 112.
Thereafter,
when the user changes the SIM of the handset 134 and power-cycles the handset
134, the
Poe Client 136 reads the new 1M SI from the SIM at power-on, and finds that
the activated
IMSI is different than the !MS! that was initially stored. As a result, the
PoC Client 136
sends a new activation request to the PoC Server 136, and cleans up its
internal data
(configuration, contacts, groups, etc.). When the activation is completed, the
PoC Client 136
fetches all the configuration, contacts and groups for that new IMSI.
With regard to Dual SIM, which means a dual IMSI scenario, when the handset
134
registers with a second network, the existing data connection is disconnected
from a first
network and established with a second network. This triggers the PoC Client
136 to fetch the
current IMSI from the SIM, and to compare the current IMSI against the
initially stored
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IMSI. If the PoC Client 136 finds that the current IMSI is different than the
initially stored
IMSI, the PoC Client 136 sends a new activation request to the PoC Server 136,
cleans up its
internal data (configuration, contacts, groups, etc.), and when the activation
is completed, the
PoC Client 136 fetches all the configuration, contacts and groups for that new
IMSI.
If the SIM was changed, but the IMSI did not change, then the PoC Client 136
would
retrieves its previous configuration, contacts and groups. In addition, if the
new IMSI is not
a valid PoC subscriber, then activation would fail and an error is reported to
the user.
3.3.2 Corporate Subscriber Support
The PoC Client 136 may be configured to provide a specific "corporate user
experience" displayed on the handset 134.
For example, the PoC Client 136 may display a Status Bar showing the
subscriber's
Personal Availability Status (i.e., Available or Busy/Do Not Disturb). The PoC
Client 136
may display a Main Navigation Bar including a Home page, Contacts,
Conversations, and
Favorite (e.g. Groups). The PoC Client 136 may display a Call History showing
Instant
Personal Alerts and recent PoC call sessions. The PoC Client 136 may display
an Action Bar,
which can be used to launch a Private PoC Call, a Group PoC Call, Send Instant
Personal
Alert or a Direct Dial Call.
During a PoC call session, the PoC Client 136 will show the Call Status,
including
Group Name, Call Start Time and Call Timer, as well as a Call Participant
List, including
Member Name, Member Presence, Member Number and Who's Talking.
Also, a certain amount of customization for the PoC Client 136 is available
for
corporate subscribers, such as Branding, including a Header bar that may
display a corporate
logo for the subscriber's company, a Selected Filter Color and an Application
launch icon on
a device application list. User customization can include Group Colors and
Show/Hide
Contact Avatars.
3.3.3 Roaming Detection and Support
The PoC Client 136 reports any changes to the MCC or MNC to the PoC Server
112.
When the PoC Client 136 is registered with the PoC Server 112 and the user
moves from one
location to another that triggers a change in either the MCC or MNC, it re-
registers with the
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CA 02798720 2012-12-12
PoC Server 112 (via a SIP REGISTER method) and sends the current MCC or MNC to
the
PoC Server 112.
The PoC Client 136 may implement a throttling mechanism using a de-bounce
timer
to ensure that, under bouncy network conditions, it does not flood the network
with too many
requests. Once the timer expires and the location has stabilized, the PoC
Client 136 sends the
request to the PoC Server 112.
In response, the PoC Server 112 checks the location information sent by the
PoC
Client 136 against a set of "allowed" networks to determine if the PoC Client
136 can
successfully register. If the subscriber is not allowed to roam, then a "BAD
LOCATION"
error is sent as a response for any SIP REGISTER message.
A subscriber is said to be roaming nationally, when they move out of their
home
carrier network, but remain in the home country (i.e., the reported MCC is in
the home
network list and the MNC is out of the MNC list). A subscriber is said be
roaming
internationally, when they move out of their home country (i.e., the reported
MCC is out of
the MCC list).
With regard to server-based roaming detection, the PoC Server 112 detects
roaming
by the PoC Client 136 based on location information (MCC/MNC) sent by the PoC
Client
136. Registration events are reported to the PoC Server 112 by the PoC Client
136 when:
= the MCC or MNC changes,
= a data session is re-established,
= there is tiered billing for PoC,
= the PoC Client 136 is in its Home network,
= the PoC Client 136 is roaming nationally,
= the PoC Client 136 is roaming internationally in a preferred country
(e.g.
North America), or
= the PoC Client 136 is attempting to roam internationally in a blacklisted
country.
Each of these events can be enabled or disabled on a per-subscriber basis.
The roaming information (MCC and MNC) is added to the call detail records
(CDRs)
during the following events:
= when the user makes or receives a call,
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CA 02798720 2012-12-12
= when the PoC Client 136 is roaming into a different country:
= either at power-on or when traversing through a border area,
= when a data session is established or re-established,
= when the PoC Client 136 obtains the current MCC/MNC location information
and sends a SIP REGISTER message, or
= when the PoC Server 112 checks if the international roaming feature is
enabled for the PoC Client 136.
3.4 Call Flow Diagrams
FIGS. 2-9 are call flow diagrams illustrating the messaging sequences for
initiating 1-
1, Ad Hoc and Pre-Arranged PoC call sessions, as well as floor control,
Instant Personal
Alerts, InstaPoC and Provisioning.
3.4.1 1-1 PoC Calls
FIG. 2 shows the message flow for a 1-1 PoC call when the caller and called
party are
"homed" on different PoC Servers 112. Since the PoC Clients 136 use pre-
established
sessions for making and receiving PoC calls, the caller sends a SIP REFER
request with the
called party's URI. The caller's PoC Server 112 determines that the called
party is homed on
a different PoC Server 112 and initiates a SIP INVITE dialog to the other PoC
Server 112.
The PoC Servers 112 allocate separate media ports for the inter-PoC Server 112
call leg. The
originating/controlling PoC Server 112 sends MBCP Connect messages to both
calling and
called parties. This is also valid on the called party's side since all PoC
Clients 136 are set up
in auto-answer mode. Then, the caller's PoC Server 112 (which assumes the role
of the
Controlling PoC Function), instructs its Media Server 114 to send appropriate
floor control
messages to the two parties.
The messages are described below:
1. The caller's PoC Client 136 initiates a 1-1 PoC call on the pre-established
session
dialog by sending a SIP REFER request to its PoC Server 112. Since the call is
initiated on
an existing SIP dialog, the PoC Client 136 specifies the called party's URI in
the SIP Refer-
To header. The PoC Server 112 checks whether the call origination is
authorized and accepts
the request.
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2. The PoC Server 112 finds that the called party is homed on a different PoC
Server
112 and initiates a SIP INVITE dialog with the remote PoC Server 112. The
caller's home
PoC Server 112 allocates a new set of media ports for this purpose and informs
the Media
Server 114 of the same. The remote PoC Server 112 acknowledges the request to
stop SIP
retransmissions.
3. The remote PoC Server 112 (i.e., the called party's home PoC Server 112)
checks
whether the called party is authorized to receive the call, finds that the PoC
Client 136 is in
auto-answer mode and accepts the call. It allocates a new set of media ports
for this INVITE
dialog and informs its Media Server 114 of the same. The caller's home PoC
Server 112
receives the SIP "200 Ok" response and sends a SIP ACK request to complete the
transaction.
4. Upon successful SIP dialog setup, the originating/controlling PoC Server
112 sends
MBCP Connect messages to both calling and called parties, and to connect the
media ports
related to the pre-established session dialog to that of the inter-server SIP
INVITE dialog.
5. The calling party's Media Server 114 sends a MBCP Connect message to the
calling party's PoC Client 136. This indicates to the calling party that the
called party has
accepted the call. Similarly, the called party's Media Server 114 sends a MBCP
Connect
message to the called party. This message is the first indication to the
called party regarding
the incoming call and includes both caller and PoC session information. Since
the PoC
Client 136 of the called party is setup in auto-answer mode, the call is
already accepted.
6. For 1-1 PoC calls, the calling party's home PoC Server 112 assumes the
Controlling PoC Function. After sending the MBCP Connect message to the
calling party,
the PoC Server 112 instructs the Media Server 114 to send appropriate floor
control requests
to the calling and called parties.
7. The Media Server 114 directly sends a MBCP Floor Granted message to the
calling
party, since the Media Server 114 is associated with the home PoC Server 112
of the caller,
and this is where the media ports for the pre-established session dialog were
set up. Note that
this MBCP message may not be sent in the case where the caller had requested
an implicit
floor grant at the time of setting up the pre-established session.
8. The Media Server 114 sends a MBCP Floor Taken message to the called party
through the called party's home Media Server 114. The MBCP messages between
the two
CA 02798720 2012-12-12
Media Servers 114 use the media ports allocated for the inter-server SIP
INVITE dialog,
while the MBCP messages are sent to the called party's PoC Client 136 using
the media ports
allocated for the pre-established session.
3.4.2 Ad Hoc PoC Calls
FIG. 3 shows the message flow for an Ad Hoc PoC call where all the
participants are
homed on the same PoC Server 112. Similar to the 1-1 PoC call described above,
the PoC
Client 136 uses the pre-established session dialog to initiate the call by
sending a SIP REFER
request, wherein the called parties are listed in the message body. The PoC
Server 112
authorizes the call attempt (both originating and terminating parties) and
sends a MBCP
Connect message to each participant to join them in the call. The PoC Server
112 then sends
appropriate floor control messages to the participants to initially grant the
floor to the caller
and subsequently to manage the floor as required.
The messages are described below:
1. The PoC Client 136 initiates an Ad Hoc PoC call using the pre-established
session
by sending a SIP REFER request. The list of called parties is included in the
message body
of the SIP REFER request.
2. Since the calling and called parties are homed on the same PoC Server 112
and all
of them use pre-established sessions in auto-answer mode, the PoC Server 112
authorizes the
call origination and termination attempts and instructs the Media Server 114
to send MBCP
Connect messages to the PoC Clients 136. It also specifies which party should
be connected
in which mode, e.g., whether as talker (calling party) or listener (called
parties).
3. The Media Server 114 sends a MBCP Connect message to the calling party,
followed by a MBCP Floor Granted message. The MBCP Floor Granted message is
optional
depending on whether the calling party had requested for implicit floor grant
at the time of
setting up the pre-established session.
4. The Media Server 114 then sends MBCP Connect and MBCP Floor Taken
messages to the called parties. The first indication of an incoming call for
the called parties
is when they receive the MBCP Connect message with both caller and PoC session
details.
Since the PoC Clients 136 are set up in auto-answer mode, the calls are
already accepted, and
the PoC Clients 136 start receiving voice RTP packets when the caller starts
speaking (RTP
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packets not shown in the message flow).
3.4.3 Pre-Arran2ed PoC Calls
FIG. 4 shows the message flow for a Pre-Arranged PoC call where the caller is
homed on a different PoC Server 112 than the other members of the group. Since
the group
is owned by another member of the group, the group itself is also homed on a
different PoC
Server 112 than the caller, e.g., the Pre-Arranged PoC groups may always be
homed on the
same PoC Server 112 as the owner of the group. The PoC Client 136 uses the pre-
established session dialog to initiate the call by sending a SIP REFER
request. Since this is a
Pre-Arranged PoC call, the caller specifies the group URI in the SIP REFER
request instead
of the individual members. The caller's PoC Server 112 authorizes the
originating call
attempt and finds that the group is homed on a different PoC Server 112. It
initiates a SIP
INVITE dialog with the group home PoC Server 112 after allocating the media
ports for this
leg. In this case, the caller's PoC Server 112 sends a MBCP Connect message to
the caller
after the SIP INVITE transaction is completed. The group home PoC Server 112
sends
MBCP Connect messages to the other participants since they are homed on this
PoC Server
112. The group home PoC Server 112 assumes the role of the Controlling PoC
Function and
sends appropriate floor control messages to the participants to initially
grant the floor to the
caller and subsequently to manage the floor as required.
The messages are described below:
1. The PoC Client 136 initiates a Pre-Arranged PoC call using the pre-
established
session by sending a SIP REFER request that specifies the PoC group URI in the
SIP Refer-
To header. The SIP REFER request is sent to the caller's home PoC Server 112,
and the PoC
Server 112 checks whether the caller is authorized to make this PoC call and
then accepts the
request.
2. The PoC Server 112 finds that the PoC group is homed on a different PoC
Server
112 (the group owner's home PoC Server 112). It then allocates a new set of
media ports
and creates and sends a SIP INVITE request to the remote PoC Server 112 with
the request
URI set to the PoC group URI. The PoC Server 112 then informs the Media Server
114 of
these media ports. The remote PoC Server 112 acknowledges the SIP INVITE
request to
stop retransmissions.
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3. The remote PoC Server 112 (group home PoC Server 112) checks the validity
of
the group URI and checks whether the caller is allowed to initiate the call,
as well as whether
at least one member is able to receive the call. Men, it allocates a new set
of media ports for
the inter-server SIP INVITE dialog and sends a SIP "200 Ok" response to the
caller's home
PoC Server 112. The caller's home PoC Server 112 sends a SIP ACK request to
complete
the SIP transaction.
4. When the inter-server SIP INVITE dialog is successfully set up, the
caller's home
PoC Server 112 connects the caller-side inter-server media ports to the
caller's pre-
established session media ports.
5. At the same time, the group home PoC Server 112 instructs the Media Server
114
to connect the calling party and each of the called parties and join them into
the conference,
along with the group-home-side inter-server media ports. The Media Server 114
sends
MBCP Connect messages to the calling party and each of the called parties and
includes both
caller and PoC session details. This message also includes the PoC group 11R1
to provide
additional context for the call. Since the PoC Clients 136 are set up in auto-
answer mode, the
MBCP Connect message will be the first indication of the incoming call for
called parties.
The call itself is already accepted and the PoC Client 136 will start
receiving the voice RTP
packets when the caller starts speaking.
6. The group home PoC Server 112 assumes the role of Controlling PoC Function
as
described above and controls the floor by sending a MBCP Floor Granted message
to the
caller and MBCP Taken messages to each of the called parties.
3.4.4 Floor Control
MBCP messages are used by the PoC Client 136 and PoC Server 112 to exchange
floor control messages within a PoC session. A MBCP Connect message is used
for
terminating an incoming PoC session to an invited party when the invited party
has auto-
answer enabled. This is also used for connecting the calling party to the call
when at least
one of the called parties accepts or auto-answers the call. Similarly, a MBCP
Disconnect
message is used for disconnecting the calling and called parties.
FIG. 5 shows floor exchange scenario for a 1-1 PoC call where both the
participants
are homed on the same PoC Server 112. This message flow can be easily applied
for other
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types of PoC calls including those scenarios that involve multiple PoC Servers
112, with
appropriate modifications similar to that shown in the PoC call message flows
described in
the previous sections.
In this message flow, the first few messages show the MBCP Connect and
associated
intra-servcr messages that are used for joining the participants in the call,
as well as the initial
floor assignment. The direction of the RTP packets show whose voice packets
get replicated
to the other participants. The rest of the message flow show a floor release
request from the
current talker, a floor idle indication to all the participants, and
subsequent floor request and
grant for another participant in the call.
The messages are described below:
1. This set of messages is for a 1-1 PoC call to between subscribers A and B
using a
pre-established session (SIP signaling messages are not shown in the figure).
The two parties
are connected into the PoC session using MBCP Connect messages and an initial
set of floor
control messages are sent to the PoC Clients 136 as described in the 1-1 PoC
session
initiation scenario described above.
2. Since the floor is initially granted to the calling party, the voice RTP
packets from
subscriber A are sent to subscriber B by the Media Server 114. Although the
individual call
legs are established in full-duplex mode, the voice RTP packets originating
from the listeners
are dropped by the Media Server 114 to emulate half-duplex mode.
3. Subscriber A releases the floor after some time. The PoC Client 136 sends a
MBCP Release message to the Media Server 114, which sends the indication to
the PoC
Server 112.
4. The PoC Server 112 instructs the Media Server 114 to set the floor as idle
and
notify all parties in the call by sending a MBCP Idle message to the PoC
Clients 136.
5. Subscriber B requests for floor by sending a MBCP Request message to the
Media
Server 114. The Media Server 114 forwards the request to the PoC Server 112.
6. The PoC Server 112 grants the floor to subscriber 13 and instructs the
Media Server
114 to send appropriate MBCP messages to all parties in the call. The Media
Server 114
sends a MBCP Granted message to subscriber B's PoC Client 136 and a MBCP Taken
message to subscriber A's PoC Client 136.
7. Based on the current floor owner, the Media Server 114 starts forwarding
voice
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RTP packets from subscriber 13 to subscriber A, while dropping all RTP packets
from
subscriber A.
3.4.5 Instant Personal Alert
FIG. 6 shows the message flow for Instant Personal Alert. The messages are
delivered hop-by-hop with the PoC Server 112 immediately sending a SIP 200 Ok
response
before forwarding the SIP MESSAGE request. If the recipient PoC subscriber is
offline, the
IPA request is silently dropped without letting the originator know of the
failure.
3.4.6 InstaPoC
In InstaPoC, an RTCP App packet is transmitted from the PoC Client 136 to
trigger
the predictive wakeup algorithm in the PoC Server 112. A similar message is
used between
two PoC Servers 112 to notify the predictive wakeup list of potential invited
parties horned
on a different PoC Server 112 than the originator's home PoC Server 112. The
actual
wakeup of the potential invited parties as determined by the predictive wakeup
list is
performed by sending a dummy RTP packet of suitable size that forces the
access network to
allocate a DCH (Dedicated Transport Channel).
FIG. 7 shows the message flow for predictive wakeup. In this message flow, the
terms "InstaPoC Server" and "Geo InstaPoC Server" are used terms to represent
PoC Servers
112 that perform the InstaPoC functionality and the geographically redundant
InstaPoC
functionality (which is described in more detail below), respectively. FIG. 8
shows the
details of the message flow for the InstaPoC functionality including the
messages between
the Media Server 114 and the PoC Server 112.
The PoC Client 136 continues to send the predictive wakeup trigger packets
periodically as long as the user is actively browsing through the contacts or
groups. The
number of RTCP packets sent for each trigger as well as the frequency of
sending these
triggers is configured on the PoC Client 136.
As noted above, the InstaPoC functionality is implemented by the Media Server
114
and PoC Server 112 working together. For brevity, this message flow shows only
one trigger
going from the originating PoC Client 136. Every trigger will result in the
same set of
actions by the Media Servers 114 and PoC Servers 112 to determine the final
list of
CA 02798720 2012-12-12
terminating PoC Clients 136 and sending the wakeup packet to them.
The messages for FIG. 7 are described below:
1. Subscriber A launches the PoC Client 136 on the handset 134 and actively
browses
through the contacts, groups or call history in preparation to make a call.
This causes the
PoC Client 136 to send multiple "predictive wakeup" notification (PW Notify)
packets to the
PoC Server 112 via the Media Server 114 using the RTCP port allocated for the
pre-
established session. One or more bursts may be sent, wherein multiple packets
may be sent
in each burst for improved reliability.
2. The PoC Server 112 generates, retrieves or updates one or more predictive
wakeup
lists (PW list) corresponding to Subscriber A. The PW list may be generated,
retrieved or
updated for each subscriber in the background based on various events
involving each
subscriber and is available in a readily usable form. In addition, the PW list
may be
duplicated on the Geo PoC Server 112 through database replication.
3a. The POC Server 112 generates a final list of PoC Clients 136 to be woken
up by
removing all unreachable users (e.g., DnD, offline, suspended, etc.). The PoC
Server 112
sends wakeup packets to this final list of terminating PoC Clients 136.
3b. The Geo PoC Server 112 may also send the wakeup packets to the final list
of
terminating PoC Clients 136.
4. If Subscriber A continues to actively browse through their contacts, groups
or call
history, their PoC Client 136 sends additional PW Notify messages to the PoC
Server 112
periodically, as per a configured timer value or other mechanism.
5. In the duration between two successive PW Notify triggers, Subscriber B has
set
DnD or has gone offline. As a result, the final list of PoC Clients 136 to be
woken up will not
contain Subscriber B.
The messages for FIG. 8 are described below:
1. Subscriber A starts the PoC Client 136 on the handset 134 and browses
through the
contacts, groups or call history in preparation to make a call. This causes
the PoC Client 136
to send "predictive wakeup" notification (PW Notify) packets to the Media
Server 114 using
the RTCP port allocated for the pre-established session. The size and number
of predictive
wakeup notification packets are configured on the PoC Client 136 to ensure
allocation of
dedicated channel to the handset 134 by the radio access network. The Media
Server 114
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forwards a predictive wakeup notification indication to the PoC Server 112 and
specifies the
identity of the subscriber based on the port on which the RTCP packet was
received.
2. The PoC Server 112 retrieves one or more predictive wakeup lists (PW list)
corresponding to subscriber A. The PoC Server 112 then removes from this list
all the
potential called parties who are unavailable for an incoming call (such as
offline users or
those who have set DnD). The PoC Server 112 creates the final list of
subscribers to be
"woken up," which in this example consists of subscribers B, C and D.
3. Subscribers B and C are homed on the same PoC Server 112 as subscriber A.
The
PoC Server 112 instructs the Media Server 114 to send Wakeup RTCP packets to
the two
subscribers. The number and size of packets are configured on the Media Server
114 to
ensure dedicated channel allocation to the handsets 134 by the radio access
network. These
packets are again sent using the RTCP ports allocated for the respective pre-
established
sessions.
However, Subscriber A's home PoC Server 112 finds that subscriber D is homed
on a
different PoC Server 112 and sends a message to the remote PoC Server 112.
This message
can carry a list of subscribers homed on the receiving PoC Server 112, which
in this case is
only subscriber D. The remote PoC Server 112 then instructs its Media Server
114 to send
Wakeup RTCP packets to subscriber D's handset using the RTCP port allocated
for the pre-
established session.
3.4.7 Provisioning
FIG. 9 shows the message flow for subscriber provisioning and activation flow.
1. The Operations Support System (OSS) for the network's operator performs a
subscriber provisioning command, such as "Create Subscriber", and sends a
message to the
WCSR Server 120.
2. The subscriber is provisioned and is in "Provisioned" state. The subscriber
data is
added to the PoC Server 112.
3. The WCSR Server 120 sends a status message back to the OSS.
4. The PoC Client 136 is activated the first time it is launched for execution
on the
handset 134. The PoC Client 136 sends an activation request through SMS to the
XDM
Server 108. The activation request includes a unique activation identifier
generated by the
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PoC Client 136. The activation request including the unique identifier is used
for verifying
the identity of the subscriber whose PoC Client 136 is being activated. The
activation request
is followed by an HTTP request to the XDM Server 108 via the WGP Server 122
that also
includes the same unique identifier, so as to map the HT] P request to the
corresponding
SMS activation request. The HTTP request also includes the password generated
by the PoC
Client 136 that will be used for authenticating the PoC Client 136 when
performing further
operations. The XDM Server 108 sets up the subscriber's account by creating
the default
XDM documents (such as the contacts list, RLS list and the directory
document).
5. After authentication, the XDM Server 108, via the WGP Server 122, updates
the
PoC Server 112.
6. The PoC Server 112 responds to the WGP Server 122 with the subscriber's
configuration, which is stored on the XDM Server 108.
7. If the subscriber is provisioned, the XDM Server 108 then returns all the
configuration parameters specific for the subscriber to the PoC Client 136 in
a response to
the HTTP response via the WGP Server 122. The configuration parameters also
include a
username to be used for authentication, wherein the username is generated
based on the
subscriber's MDN. The XDM Server 108 stores a password received in the
activation request
against the username and uses it for authenticating the PoC Client 136. These
username and
password are then used by the PoC Client 136 for SIP registration and for
authenticating the
XDM Server 108 operations. The subscriber is now in "activated" state and the
PoC Client
136 is ready for use.
A list of provisioning commands supported by the system 100 includes, but is
not
limited to, the following:
= Create Subscriber,
= Update Subscriber,
= Delete Subscriber,
= Deactivate Subscriber,
= Reactivate Subscriber,
= View Subscriber Details using MDN, and
= View Subscriber's contacts and groups.
Various scenarios may arise during provisioning, including duplicate
activation
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requests, request failure, activation failure, and unsupported handset 134
devices. The steps
involved in these scenarios are described in more detail below.
With regard to duplicate activation requests, this scenario occurs when the
XDM
Server 108 receives a duplicate SMS activation request over SMPP, followed by
a single
HTTP request. When the XDM Server 108 receives an activation request for a
user when an
earlier activation request is still pending, the XDM Server 108 checks and
updates a key for
the activation request, overwriting any previous key. When the HTTP request is
received, it
will check for the currently stored key (i.e., the last received).
With regard to request failure, this scenario occurs when the HTTP request
fails due
to any reason such as a timeout (no response from the XDM Server 108). When
the HTTP
request fails. the PoC Client 136 will re-send the SMS activation request
followed by another
HTTP request, reusing the key for the activation request. This process may be
repeated for
some set number of iterations, after which the PoC Client 136 will generate a
new key if
activation is re-attempted.
With regard to activation failure, this scenario occurs when the SMS
activation
request is lost due to transient error, although an acknowledgement was
returned for the SMS
message. The PoC Client 136 sends an HTTP request, but since the XDM Server
108 has
not received the SMS activation request, the HTTP request times out. The PoC
Client 136
re-attempts activation by sending the SMS activation request again with the
same key,
followed by the HTTP request. This process is repeated for some set number of
iterations,
after which the PoC Client 136 will generate a new key if activation is re-
attempted.
With regard to handling unsupported handsets 134, there could be situations
where a
network's operator wants to control PoC access to certain handsets or devices.
The operator
can identify a list of allowed devices. During activation, the XDM Server 108
checks the
device type of the handset 134 against this list and grants or denies the
activation request. In
addition, the XDM Server 108 may check for client type and platform (OS), and
accept the
activation request only if the device, client type and platform are supported.
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3.4.8 PoC Call Interaction with GSM Calls
In a GSM network 124, the following PoC call interaction occurs with incoming
cellular service calls. In one embodiment, the device is configured with an
Answer/Ignore
option for use when the cellular service calls overlap with PoC call sessions.
One embodiment concerns an incoming cellular service call when a PoC call
session
is active. If the Answer option is set, then the PoC Client 136 will
disconnect from the PoC
call session; otherwise, if the Ignore option is set, then the PoC Client 136
will continue with
the PoC call session.
Another embodiment concerns an incoming PoC call when a cellular service call
is
active. The PoC Client 136 will automatically send a disconnect response to
the incoming
PoC call with the reason set as "busy". The PoC Client 136 will show a "missed
call"
notification to the user after the cellular service call ends.
Yet another embodiment concerns an incoming PoC call when another PoC call
session is active. The PoC Server 112 will automatically reject the incoming
PoC call with
the reason set as "busy".
3.4.9 Improvements to the PoC Call Connect Procedure
As noted above in Section 3.4.1, the controlling PoC Server 112 sends MBCP
Connect messages to the calling and called parties, instead of their
respective home PoC
Servers 112, as set forth by the OMA standard. In this invention, the
controlling PoC Server
112 uses the acknowledgments for MBCP Connect messages to determine whether
the called
parties have joined the call or not.
For example, if the called party is busy in a regular cellular (GSM) call, the
PoC
Client 136 will reject an incoming PoC call even though auto-answer mode is
enabled. If the
home PoC Server 112 sends a MBCP Connect message, then, in inter-PoC Server
112 call
scenarios, the controlling PoC Server 112 would assume that the called party
has joined the
call based on successful establishment of the call leg between the two PoC
Servers 112.
Since the controlling PoC Server 112 uses this information to start playing
out buffered voice
packets, it may lead to a loss of voice packets, even for the first called
party who actually
joins the call later.
This invention has the following two advantages:
CA 02798720 2012-12-12
1. The OMA standard for PoC does not define a mechanism for the controlling
PoC
Server 112 to determine when or if the called parties have accepted and joined
the call,
specifically, in the scenario where pre-established sessions and auto-answer
mode are used
for PoC Clients 136 and inter-PoC Server 112 calls are involved. This
invention defines such
a mechanism.
2. This invention avoids defining the signaling messages between PoC Servers
112
and any associated complexities in state machines that would be required if
the home PoC
Servers 112 continue to send MBCP Connect messages to their respective
subscribers.
3.5 Fault Tolerance
3.5.1 In-Chassis Redundancy
The present invention supports in-chassis redundancy in 1+1 mode, i.e., a
dedicated
standby server blade is configured for each active instance of a Server. These
Servers are
referred to as "Primary" and "Secondary" Servers. The Primary and Secondary
Servers are
typically configured on the same chassis. A pair of Primary and Secondary
Servers together
is referred as "Serving Servers."
The Primary and Secondary Servers maintain a heartbeat mechanism to detect
failures and automatically switchover when failures occur.
The Primary and Secondary Servers also synchronize all relevant data through a
replication mechanism. This includes dialog information for the pre-
established sessions
created by the clients along with corresponding media port details and the
predictive wakcup
lists for each subscriber, used for InstaPoC feature.
The Primary and Secondary Servers share the same virtual IP address. This
virtual IP
address is normally assigned to the Primary Server. At the time of failover,
this virtual IP
address gets re-assigned to the Secondary Server, which then takes over as the
active Server.
This ensures seamless communication from the client point of view ¨ it always
uses the
virtual IP address to reach the Server for signaling. When the Primary server
failover occurs,
the newly active Secondary server takes over and start handling the PoC
sessions. The
clients continue to use the pre-established session with Serving Server to
make and receive
new PoC calls. Currently, active PoC call sessions are terminated as the data
sync does not
include information related to active sessions.
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3.5.2 Geographical Redundancy
The Servers also support geographical redundancy in addition to the in-chassis
redundancy. For each Serving Server (Primary/Secondary Servers), one
standalone Geo
Server is configured in standby mode. The Geo Server is configured on a
separate chassis in
a different location than the Serving Server chassis so as to provide
geographical redundancy.
The Serving Server and Geo Servers maintain a heartbeat mechanism to detect
failure
scenarios and automatically failover to the Geo Server when the both Primary
and Secondary
Servers fail.
The Serving Server and Geo Server replicate important stored data.
The PoC Client 136 maintains separate pre-established sessions with the
Serving
Server and Geo Server. This avoids any delay in setting up pre-established
sessions while
PoC Clients 136 falling back to Geo Servers.
As described in the in-chassis redundancy section above, the PoC Client 136
communicates with the Serving Server using a Virtual IP address of the Serving
Server. The
PoC Client 136 communicates with the Geo Server using an actual IP address
(i.e., a Physical
IP address) of the Geo Server. The Virtual IP address support is not required
as Geo Servers
are configured in standalone mode. The PoC Client 136 always attempts to set
up a session
with the Serving Server and, if that attempt fails, the PoC Client 136 falls
back to the Geo
Server for signaling.
The failover to the Geo Server may occur due following reasons:
= The heartbeat between the Serving Server and Geo Server fails (i.e., both
the
Primary and Secondary Servers fail). In this case, the Geo Server
automatically takes over the active role and starts serving the subscribers.
= Repeated failure of the critical processes within predefined window in
the
Serving Server.
= All Servers in the serving chassis have failed. In this case, the Serving
Server
triggers a failover since all Servers have failed.
When a failover occurs, all new PoC Sessions are handled by Geo Servers. The
PoC
Client 136 start using the Geo Server for new PoC Session initiations. The
existing PoC calls
are not preserved.
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Conclusion
The foregoing description of the preferred embodiment of the invention has
been
presented for the purposes of illustration and description. It is not intended
to be exhaustive
or to limit the invention to the precise form disclosed. Many modifications
and variations are
possible in light of the above teaching. It is intended that the scope of the
invention be
limited not with this detailed description, but rather by the claims appended
hereto.
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