U.S. patent application number 11/332442 was filed with the patent office on 2006-06-01 for voice over ip portable transreceiver.
Invention is credited to Gerald Callow, Kent Wotherspoon.
Application Number | 20060114854 11/332442 |
Document ID | / |
Family ID | 32711011 |
Filed Date | 2006-06-01 |
United States Patent
Application |
20060114854 |
Kind Code |
A1 |
Wotherspoon; Kent ; et
al. |
June 1, 2006 |
Voice over IP portable transreceiver
Abstract
Described below is a system to provide voice communication over
a data network. The system is described as an access point
connected to the data network adapted to exchange network messages
over the data network and a wireless terminal including a
transmitter component and a software module, the transmitter
component adapted to exchange wireless messages with the access
point over a wireless network, and the software module configured
to provide a plurality of virtual channels. Each of the virtual
channels being carried over the wireless network and the data
network, the software module being configured to enable reception
of the voice communication and to enable transmission of the voice
communication over selected virtual channels.
Inventors: |
Wotherspoon; Kent;
(Winnipeg, CA) ; Callow; Gerald; (Winnipeg,
CA) |
Correspondence
Address: |
FAY KAPLUN & MARCIN, LLP
15O BROADWAY, SUITE 702
NEW YORK
NY
10038
US
|
Family ID: |
32711011 |
Appl. No.: |
11/332442 |
Filed: |
January 13, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10338938 |
Jan 8, 2003 |
7023821 |
|
|
11332442 |
Jan 13, 2006 |
|
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60372219 |
Apr 12, 2002 |
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Current U.S.
Class: |
370/329 ;
370/401 |
Current CPC
Class: |
H04W 80/00 20130101;
H04L 65/1069 20130101; H04M 1/2535 20130101; H04L 29/06027
20130101; H04W 4/10 20130101; H04W 84/12 20130101; H04W 76/45
20180201; H04M 1/57 20130101; H04L 29/06 20130101; H04M 1/72403
20210101; H04L 65/1096 20130101; H04L 69/14 20130101; H04L 65/1083
20130101 |
Class at
Publication: |
370/329 ;
370/401 |
International
Class: |
H04Q 7/00 20060101
H04Q007/00 |
Claims
1. A system to provide voice communication over a data network,
comprising: an access point connected to the data network adapted
to exchange network messages over the data network; and a wireless
terminal including a transmitter component and a software module,
the transmitter component adapted to exchange wireless messages
with the access point over a wireless network, the software module
configured to provide a plurality of virtual channels, each of the
virtual channels being carried over the wireless network and the
data network, the software module being configured to enable
reception of the voice communication and to enable transmission of
the voice communication over selected virtual channels.
2. The system according to claim 1, wherein the terminal are a
voice-enabled terminal.
3. The system according to claim 1, wherein the software module is
configured for at least one of (i) enabling half duplex
transmission and reception on the virtual channels, (ii) preventing
collision of transmissions on each of the virtual channels, (iii)
prioritizing simultaneous transmissions on each of the selected
channels, such that only one of the simultaneous transmissions is
enabled, (iv) initiating a peer to peer full-duplex call with a
further wireless terminal, (v) transmitting redundant data packets
representing the voice communication.
4. The system according to claim 1, wherein the terminal includes
at least one of a speaker and a PTT switch.
5. The system according to claim 3, wherein transmission on an
active channel is disabled when the active channel is in use.
6. The system according to claim 3, wherein a user notification is
generated when initiating transmission on one of the selected
channels if the selected channel is in use.
7. The system according to claim 1, further providing a priority
channel enabled to override transmission and reception on the
plurality of virtual channels.
8. The system according to claim 3, wherein the wireless terminal
receives a voice transmission from the further wireless terminal
over one of the plurality of virtual channels.
9. The system according to claim 3, wherein the peer to peer full
duplex call overrides reception and transmission of the voice
communication over the plurality of virtual channels.
10. The system according to claim 1, wherein the wireless terminal
includes a memory adapted to store and replay a portion of the
voice communication.
11. The system according to claim 1, further comprising a directory
service of the data network adapted to associate names with the
virtual channels.
12. The system according to claim 1, wherein the software module
compresses data packets representing the voice communication before
transmission.
13. A portable terminal comprising: a memory storing software
instructions; a transmitter section adapted for exchanging data
with an access point via a wireless network, the access point being
connected to a data network; and a processor adapted to execute the
software instructions, the software instructions comprising:
instructions to provide a plurality of virtual channels carried
over the wireless network and the data network; instructions to
generate data packets representing an outbound voice communication,
and transmit the data packets over selected ones of the virtual
channels; and instructions to receive data packets over the
selected ones of the virtual channels and regenerate an inbound
voice communication from the data packets.
14. The terminal according to claim 13, wherein the processor
further comprises instructions for at least one of (i) establishing
semi duplex communications over selected ones of the virtual
channels, (ii) establishing a full duplex communication with a
selected addressee, (iii) disabling transmission of the data
packets over a virtual channel that is in use, (iv) transmitting
the data packets redundantly and (v) monitoring selected ones of
the virtual channels for the data packets.
15. The terminal according to claim 13, further comprising a
digital signal processor adapted for compressing the data
packets.
16. The terminal according to claim 13, further comprising a push
to talk button.
17. The terminal according to claim 13, further comprising a memory
module adapted for storing the inbound voice communication.
18. The terminal according to claim 13, further comprising a
display adapted to show a user interface of the software
instructions.
19. The terminal according to claim 18, wherein the display shows
an origin identification of the inbound voice transmission.
20. The system according to claim 13, Wherein the terminal is a
voice-enabled terminal.
21. A method for conducting voice communications over a data
network, comprising: providing a plurality of virtual channels
carried over a wireless network and the data network; transmitting
data packets representing an outbound voice communication over a
selected one of the virtual channels by a first wireless terminal;
receiving the data packets over the selected one of the virtual
channels by a second wireless terminal; and regenerating an inbound
voice communication from the data packets by the second wireless
terminal.
22. The method according to claim 20, further comprising:
establishing one of full duplex and semi duplex communications over
the selected one of the virtual channels
23. The method according to claim 20, further comprising: disabling
transmission of the data packets over a virtual channel that is in
use.
24. The method according to claim 20, further comprising:
transmitting the data packets redundantly.
25. An arrangement for conducting wireless communications,
comprising: a storage means for storing software instructions; a
communication means for exchanging data with an access point via a
wireless network, the access point being connected to a data
network; and a processing means adapted to execute the software
instructions, the software instructions comprising: instructions to
provide a plurality of virtual channels carried over the wireless
network and the data network; instructions to generate data packets
representing an outbound voice communication, and transmit the data
packets over selected ones of the virtual channels; and
instructions to receive data packets over the selected ones of the
virtual channels and regenerate an inbound voice communication from
the data packets.
Description
PRIORITY CLAIM
[0001] The present application is a continuation application of
U.S. patent application Ser. No. 10/338,938 filed Jan. 8, 2003
"Voice Over IP Portable Transreceiver", the entire disclosure of
which is expressly incorporated herein by reference.
DESCRIPTION OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to methods and systems that
provide voice communications over a data network.
[0004] 2. Background of the Invention
[0005] In recent times there has been an increase in the use of
portable two way radios, commonly referred to as walkie-talkies, in
a variety of settings. Walkie-talkies have been long used in
work-related activities, for example to let employees remain in
contact with one another and with a central office. Typical uses
include warehouse and retail settings, where workers are requested
to move goods, and where specific employees can be summoned.
Portable transreceivers are routinely used as an alternative to
telephone communications in any setting where the communicating
users are relatively close to one another. The security and public
safety fields have been early users of walkie-talkies and related
two way radio equipment, to help agents stay in contact and receive
instructions.
[0006] More recently, as two way radio devices have become less
expensive, recreational and family uses have become increasingly
common for these devices. Family members use simple walkie-talkies
to stay in touch and find each other, for example when hiking,
skiing etc. Two way radios of various levels of sophistication have
found a place in all types of sport and recreational events, to
enhance safety and to increase the information level of the
participants. Walkie-talkies have become almost a fashion accessory
in certain cases, and have become available in various shapes and
colors, ranging from inexpensive low power units to sophisticated
units capable of encrypting their transmissions.
[0007] Typical walkie-talkies and other types of two way radios,
however, suffer from various drawbacks that limit their usefulness
in many situations. Perhaps the most serious limitation is the
range of these devices, which often is very limited. Since the
voice transmissions are carried from one station to another by
radio waves, any physical obstacles to the propagation of those
waves affects the range and quality of the received transmission.
Most publicly available non-licensed 2 way radios are limited to a
small power output (5 watts or less), which further limits their
range. Interference from other radios or various sources of
electromagnetic noise also affects reception quality. In addition,
there is no mechanism in conventional radios to prevent two
transmissions on the same frequency (or channel) from interfering
with each other, without the source or the recipient of either
transmission being aware of the interference. In many cases users
have to carry various electronic tools such as portable computers
or scanners, and having to carry an additional transreceiver device
can be very cumbersome.
SUMMARY OF THE INVENTION
[0008] In one aspect, embodiments of the present invention include
a system to provide voice communication over a data network which
has wireless voice enabled terminals, access points connected to
the data network adapted to exchange network messages over the data
network, and a transmitter component of each of the terminals
adapted to exchange data with the access points over a wireless
network. The system also includes a software module executing on
each of the terminals configured to provide a plurality of virtual
channels, each of the virtual channels being carried over the
wireless network. The software module is configured to enable
reception of the voice communication from the terminals over a
selected virtual channel, and to enable transmission of the voice
communication to the terminals over the selected virtual
channel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 shows wireless voice enabled terminals connected to a
data network according to an exemplary embodiment of the present
invention;
[0010] FIG. 2 shows a diagram representing a software architecture
of a voice enabled terminal according to an embodiment of the
present invention;
[0011] FIG. 3 shows an exemplary voice enabled terminal according
to an embodiment of the present invention; and
[0012] FIG. 4 shows an exemplary screen shot of the controls for
the voice enabled terminal according to one embodiment of the
invention.
DETAILED DESCRIPTION
[0013] The present invention may be further understood with
reference to the following description and the appended drawings,
wherein like elements are referred to with the same reference
numerals. Conventional portable transreceiver radios, such as the
Walkie Talkie.TM. manufactured by Motorola.RTM., are used in a
multitude of situations, both for pleasure and in work related
settings. However, the performance of radio frequency (RF) based
portable transreceivers is severely limited by inherent
shortcomings of that technology. For example, the range of those
radios is limited by the power of the transmitter, and the terrain
separating transmitter and receiver. Only receivers within the
transmitter's range can be contacted. RF based portable
transreceivers generally can transmit on many channels, with each
channel being assigned a discrete frequency so that only radios
tuned to the same channel can receive the transmission. However,
multiple radios may be transmitting on the same channel, so that a
transmission from one radio may be "stepped over" by another
radio's transmission, and neither radio transmission can be
heard.
[0014] The present invention uses a different technology to provide
Walkie Talkie.TM.-like functionality to a voice enabled terminal.
In addition, several features that are not available with RF based
portable transreceivers may be implemented within the system
according to the present invention. As will be described more fully
below, communications between the voice enabled terminals travel
over a data network, and thus are not subject to the same range
limitations affecting RF based devices. There may be portions of
the network that are based on radio communications, for example the
sections connecting the wireless voice enabled terminal to a
network access point. However, these are generally used over short
distances, and do not affect the communications range between the
various voice enabled units. According to embodiments of the
invention, the voice enabled terminals have the "feel" and general
usage characteristics of conventional RF portable transreceivers,
so that their usage is intuitive to anyone familiar with the
conventional RF units.
[0015] FIG. 1 shows one exemplary embodiment of a voice over IP
(VOIP) portable transreceiver system, which mimics the
functionality of RF based systems while incorporating additional
features. In this embodiment, a plurality of voice enabled
terminals 10 are interconnected and can provide voice
communications amongst each other. Typically, each terminal 10 is
given to an user or group of users. Since terminals 10 are
portable, they are capable of connecting to a wireless network, and
are sufficiently small to be easily carried. For example, terminals
10 may be specifically designed to be used as portable
transreceivers, or may be hand held devices with different
purposes, to which the portable transreceiver functionality has
been added. In one embodiment, the terminal is based on a personal
digital assistant (PDA) such as those using the Windows.RTM. CE
operating system, or similar. The PDA may be a multi purpose PDA
executing a software module which provides the portable
transreceiver functionality, or may be a more specialized unit such
as a PDA-scanner combination, which is also usable to read bar
codes. As will be apparent to those skilled in the art, different
types of voice enabled terminals may be used to communicate over
the same data network, as long as they operate under compatible
protocols.
[0016] Voice enabled terminals 10 include a transmitter section
including an antenna 12, which enables them to communicate without
being connected to wires. For example, a wireless local area
network (WLAN) 14 may be used to connect each of the terminals 10
to access points 20. As long as the terminal 10 is within radio
transmission range of at least one access point 20, the device can
be used to communicate with any other terminals 10. A multi purpose
WLAN 14 can be used, or the WLAN 14 may be a dedicated network used
only for voice communications. Access points 20 form the connection
between WLAN 14 and the data network 16 to which all terminals 10
are ultimately connected. Access points 20 act as a two way
conduit, which receives radio transmissions from the transmitter
section of terminals 10, and forwards the transmissions to the data
network 16 using the appropriate protocols. For example, an
internet protocol such as TCP/IP may be used to direct the
transmission to its intended recipients on data network 16. Various
levels of data processing may be carried out by access points 20,
for example for error correction or encryption purposes.
[0017] Data network 16 is the principal means by which voice
messages are carried between terminals 10. This network can be any
network useable to transmit data, such as between microprocessors,
and may be a local area network (LAN), a wide area network (WAN) or
the Internet. Using a data network to carry the voice
communications gives a distinct advantage to the system according
to the invention. The range of the portable transreceiver-like
terminals 10 is restricted only by the extent of data network 16.
When the Internet is used for this purpose, the range of terminals
10 can be essentially unlimited, as long as an access point 20
connected to network 16 is within range of each of the users. The
structure of data networks 16, such as the Internet, provides a
certain amount of redundancy since in case of failure of certain
segments of the network other segments can be used to carry the
data. In addition, as will be described in greater detail below,
the network protocol according to the present invention provides
additional redundancy to minimize loss of data. The VoIP system of
the invention thus is more robust than conventional RF based
portable transreceivers, which are subject to disruptions and
interference. The system according to the invention may also
provide security benefits compared to RF based devices. Since the
transmissions travel over the airwaves only for short distances at
low power, it is more difficult to intercept them. Also, since the
signals are already in a form that can be used by a microprocessor,
encryption operations are easier to carry out, for example using
the Kerberos or Wired systems.
[0018] In one exemplary embodiment according to the present
invention, the VoIP portable transreceiver (WT) system provides
packet-based voice communication between users of wireless voice
enabled terminals, such as those based on PDA devices manufactured
by Symbol Technologies. The exemplary wireless terminals operate
under the 802.11b standard for wireless LAN's, thus providing
interoperability between products of different manufacturers. The
exemplary embodiment uses direct sequence radio frequency
transmissions. However, frequency hopping spread spectrum RF modes
and other non RF modes, such as infrared transmissions, may also be
employed within WLAN 14. One benefit of using the 802.11b standard
is that existing infrastructures using that standard may be adapted
to support the VoIP WT system with minimal modifications. Most
voice enabled terminal devices supporting that standard may be used
as the portable transreceiver handset, often requiring simply a
software upgrade to operate according to the invention.
[0019] One of the most basic capabilities of the VoIP WT system
according to embodiments of the present invention is that it
provides the user with an interface consistent with conventional RF
based systems. The operation of the VoIP WT system should appear
familiar to users accustomed to conventional RF devices. In one
exemplary embodiment, terminals 10 execute software modules that
provide multiple "virtual" communications channels, which appear to
the user as analogous to the different frequency channels found on
RF units. Each VoIP WT unit may be configured to have a primary
channel that is used as the default channel for transmitting and
for receiving, but the user can set the terminal to transmit and
receive on any other desired channel, and to monitor some or all
the available virtual channels. In the exemplary embodiment, the
VoIP WT is capable of receiving and transmitting over at least 256
discrete channels. Although the exemplary unit is capable of
receiving any or all of those 256 channels, those of skill in the
art will understand that all the channels must still travel over a
common WLAN, since there is no separate network for each channel.
Accordingly, irrespective of the number of channels supported by
the VoIP WT, the system can deliver simultaneously only as many
messages as can be supported by data networks 14 and 16. The number
of simultaneous messages that can be processed depends on the
802.11b network architecture and on the specific site
implementation.
[0020] In one embodiment, a channel may be dedicated as a priority
channel, for example to be used for high priority security
messages. All the units connected to the data network, such as
terminals 10 on network 16, will receive the priority channel, and
the messages received on the priority channel will override any
other messages transmitted on different channels. When a message on
the priority channel is received, all the units that are
transmitting a message will abort the transmission, and notify the
user that the transmission was discontinued. For example, an
audible alert may be provided to the user for that purpose. Units
that are in the receive mode will be prevented from starting a
transmission while a priority message is being broadcast. All the
units may have the ability to broadcast on the priority channel, or
that feature may only be reserved for selected units.
[0021] When the portable transreceiver according to the present
invention is not active on the default channel or on the priority
channel, it is capable of monitoring any of an assigned group of
channels for incoming transmissions. However, before the unit is
able to transmit on one of the monitored channels, a specific
channel must be selected by the user. In another embodiment, units
may be given the ability to transmit on multiple channels.
Selecting a channel for transmission does not affect the channel
that has been defined as the default channel for transmission and
reception in a unit, which is also referred to as the designated
primary channel of the unit. If a unit receives more than one
message on different channels, which message is actually processed
by the unit depends on a specific priority scheme. Priority or
security broadcasts are handled first, so they are always played to
the user. Priority messages are followed by messages broadcast on
the unit's designated primary channel, and finally by broadcasts on
any other of the monitored channels. Messages that are received on
the monitored channels are not interrupted by another, later
message with the same priority level. Within messages of the same
priority, the earlier received message is played.
[0022] Conventional RF based portable transreceiver units do not
have any mechanism to prevent more than one unit from
simultaneously broadcasting on the same channel when the users
press the PTT switch. The VoIP WT system according to the invention
provides a mechanism to prevent this collision of transmissions.
Before a transmission is permitted by one of the units, software in
the unit is configured to verify that the channel selected is not
already in use. If the selected channel is not in use, the
transmission is broadcast normally. If, when the user presses the
PTT switch a message is already being received on that channel, the
transmit mode of the unit is disabled and a notification is issued
to the user to indicate that the selected channel is busy.
[0023] Despite these precautions, a race condition can take place
when two or more units have their PTT switches pressed
simultaneously, while using the same channel. In that case,
multiple portable transreceiver units may be allowed to begin their
transmission streams. The race can be resolved by configuring each
voice enabled terminal unit in the system so that no more than one
message is heard by all the units on the channel, to prevent any
two listeners from hearing different messages after the collision
has been detected. Once a VoIP WT unit that is transmitting detects
another transmission on the same channel, one of several acceptable
actions may be taken. For example, all the units may stop
transmitting, and may provide to the relevant users a notification
of the race condition. Alternatively, a priority mechanism may be
specified, to allow only one of the transmissions to continue,
while suppressing all other interfering transmissions. As will be
apparent to those skilled in the art, different priority schemes
may be envisioned to prevent a broadcast collision from occurring.
The principal requirements for this are that only one transmission
per channel at a time be received by the users, and that the
relevant users be notified when their transmission is
suppressed.
[0024] As shown in FIG. 1, a directory server 22 may be connected
to the data network 16 to provide a naming service for the system.
A "group", in the context of the present invention, is a named list
of users that subscribe to a particular channel. The VoIP WT system
supports a common directory based on server 22 which allows the
management of user groups. The implementation of this functionality
requires the presence of a centralized server 22, and will thus be
optional. The directory service is used to correlate a group name
to a channel number, so that users don't have to remember which
channel numbers correspond to which set of users. For example, a
user may request that the VoIP WT unit monitor the "Purchasing" or
the "Loading Bay 1" groups, without having to remember which
channel numbers are associated with those groups. Changes to
channel membership are centralized under this system, which
simplifies maintenance of the groups information. In one example, a
public API may be used to provide an application directory access
to a centralized directory hosted on a server using the lightweight
directory access protocol (LDAP). Alternatively, the application
directory may access a local directory implemented in a static text
file. One suitable LDAP directory server may be a server running
Windows 2000.RTM., particularly using Active Directory.RTM.
software.
[0025] The system according to embodiments of the present invention
can also provide a telephone-like caller ID on each terminal, which
indicates to each user an identification of who originated a
transmission. This feature of the terminals is not dependent on the
directory service described above, although in some cases the
directory service may be tied to the identification function. To
provide the caller ID feature, a name that identifies either the
unit or the person using the unit is sent in the transmission,
together with the data packets describing the voice communication
and any other pertinent data. Each receiving unit can then display
the name of the sender or the originating terminal, as
applicable.
[0026] Another feature that can be provided in a VoIP WT unit is
the integration of a peer-to-peer private mode with the traditional
portable transreceiver mode of operation. Traditional RF based WT
units can only provide a one-to-many broadcast mode, where the
transmission is half duplex, meaning that only one user at a time
may speak. This is replicated in the WT mode of operation of the
VoIP WT system. The private mode permits one-to-one calling between
two users, with full duplex transmissions in which both addressees
may speak simultaneously. This mode provides the same functionality
as a telephone call between the two users. In one exemplary
embodiment, a user at a receiving unit will be able to initiate a
private callback to the initiator of the last, or most recently
active WT mode message. In addition to the increased privacy
aspects of using the private mode, additional benefits include
reduced broadcast traffic, minimized distractions to other users
not party to the peer-to-peer communication, and extended operating
life of the non-participating units due to lower battery usage.
This is possible since only two units participate in a private mode
communication. Instead of tying up every terminal unit tuned to a
specific virtual channel in the WT mode, users can select the
private mode to limit communications to the two participating
units.
[0027] Specialized message traffic rules may be used to prioritize
the reception of peer-to-peer mode messages and of the normal WT
mode messages. For example, if a WT mode message is received while
the unit is participating in a peer-to-peer call, the peer-to-peer
call is given higher priority. The user may be given a notification
that a message is being received under the WT mode, and may be
given the option of switching back to the WT mode of operation. In
general, when a WT mode message has been received by a unit, the
user can be given the option of responding to the message by using
the normal broadcasting WT mode, or by using the private
peer-to-peer mode. Selection of the WT mode may be made by simply
pressing the PTT button of the unit. Peer-to-peer mode may be
initiated by a separate soft or hard key, since it is not the
default mode of operation of the VoIP WT device.
[0028] Another feature that is unique to the VoIP WT system
according to embodiments of the present invention is the ability to
store messages for future replay. In one embodiment, each portable
transreceiver unit includes a memory that can buffer the most
recent incoming voice message to provide a replay capability. In
one embodiment, if the message is longer than the configured buffer
size, only the last portion of the message will be saved. The user
will then be able to replay the buffered message. In the case that
a message is received while an earlier message is being played
back, playback of the buffer may be interrupted to permit reception
of the new message, particularly if the new message is received on
the priority channel. An audio alert may be used to further notify
the user that buffer playback has been suspended to receive a
real-time message. In one exemplary embodiment, the buffer may be
sufficient to store about 60 seconds of message.
[0029] According to embodiments of the invention, the VoIP WT
system is designed to minimize network loading as much as
practical, since it must operate in a network that is used also by
other types of network traffic. Latency of the WT system is reduced
as much as possible, but to a certain extent is dependent on the
actual network architecture. Latency of the half-duplex WT mode is
not as critical as latency of the full-duplex private mode, since
in WT mode multiple participants cannot speak simultaneously but
instead have to take turns speaking. The network protocol chosen
for the invention takes advantage of this lessened requirement of
the WT mode to include redundant transmission of the voice data.
This adds some latency to the message, but greatly improves the
quality of the message. The redundant transmission allows the
receiver to reconstruct missing voice data due to network
interference or errors.
[0030] In one embodiment, the latency in the WT mode from the
microphone of the transmitting unit to the speaker of the receiving
unit averages less than 500 milliseconds, excluding network delays.
In the peer-to-peer or private mode, the latency from the
transmitter's microphone to the receiver's speaker is less than 300
milliseconds, also excluding network delays. Various signal
compression methods may be used to reduce the amount of bandwidth
used by the VoIP WT application. For example, a G.729A codec is
provided for voice compression, however other more effective
methods may also be incorporated.
[0031] FIG. 2 is a diagram showing an exemplary embodiment of the
software architecture and hardware interface used to control a VoIP
WT unit such as the voice enabled terminal 10. FIG. 2 shows the
software as applied to a PDT8100X3 platform, manufactured by Symbol
Technologies.RTM., using the 802.11b protocol. The exemplary
platform is a hand help PDA that also includes a bar code scanner
in addition to the portable transreceiver features, and is
particularly useful where users need to communicate with one
another and to identify merchandise, such as in a warehouse. It
will be apparent to those of skill in the art that a similar
software architecture can be used in different voice enabled
devices, without affecting the functionality of the device. In the
example, an hardware interface 50 includes the PDT8100X3 unit 52
and a Spectrum 24 adapter 54 having a radio network card with a
transmitter/receiver used to connect terminal 10 to the access
points 20 via WLAN 14. The hardware component also includes a
digital signal processor (DSP) 56, used to process the voice
communications, such as to perform signal compression tasks.
[0032] The software components include software elements 60 that
are part of the Windows CE.RTM. operating system, and software
elements 70 that are specific to the portable transreceiver
application, both of which are executed on a processor of the voice
enabled device. It will be apparent that other operating systems
adapted to run on portable devices may be used, such as Palm.RTM.
operating systems, etc. Windows CE.RTM. operating system components
60 are well known in the art, and include Wave in and out modules
62 to process sounds, Winsock module 64 to manage network sockets,
and various drivers 66 for the display screen, etc. Additional
software modules may be included with software elements 70, which
are developed specifically to manage operation of the VoIP WT
functionality. The WT application module 72 is the primary
application that enables terminal 10 to be used as a portable
transreceiver. WT application module 72 is designed to minimize
interference with other applications that may be executed
simultaneously on the unit, in particular other applications that
use the notification driver 86 to provide audio cues.
[0033] Generally, the WT application module 72 operates in the
background on the device, so that the full screen of the device
(i.e. terminal 10) may be used for other applications. The
application interface may be displayed automatically when needed,
such as when an incoming message is detected. If the user needs to
see the VoIP WT application interface, for example to see the
caller ID function, a "display pop" key may be provided to toggle
the WT application interface from the background to the foreground,
and vice versa, each time it is pressed. This toggle key may be a
physical button or a touch screen region of the device. To maximize
battery life, the user has the option of operating in a low power
mode, which may be entered by using a key. This mode blanks the
screen and may perform other functions to reduce power consumption.
In power save mode the unit is fully functional and can send or
receive voice messages. If the user wants to see the screen, a key
may be pressed to resume normal operations. If an event occurs
which requires the user to see the screen, normal mode may be
resumed automatically.
[0034] Private call transport module 74 enables the terminal 10 to
be used in private mode communications, as described above. This
mode uses, for example, the H.323 session protocol for
telephone-like full duplex performance. Private call transport
module 74 typically does not provide session control, since that is
handled by the H.323 protocol. In one embodiment, the application
accesses H.232 for session control through the Microsoft Telephony
API (TAPI). The Telephony service provider (TSP) manages call
setup, call tear down and call control via the H.323 stack, and
negotiates a common compression codec with the destination unit. To
prolonge battery life, module 74 may also include power management
functions, such as switching the unit between the power save mode
(PSP) and the full power mode (CAM) as necessary.
[0035] To maximize battery life the unit normally operates in the
lowest power mode. When a transmission is made, the unit is
switched to full-power mode. When the unit is in standby mode, for
example when waiting for an incoming message, the unit watches for
a wake-up message, which is sent prior to a transmission as part of
the protocol. If a wake-up message is received, the unit switches
to full power mode. Since it is possible for a wake-up message to
be lost, the radio also watches for regular voice packets.
Therefore, if one of the regular voice packets is detected, the
unit is also turned on to full power mode. After the last packet in
a transmission is received, the unit waits a short time interval to
see if additional packets will be received. If there are no
additional data packets within a specified timeout period, the unit
switches back into the low-power mode.
[0036] The normal portable transreceiver mode of operation for
terminal 10 is implemented through WT call transport module 76.
Module 76 provides one-to-many half duplex communications that
replicate the functioning of a RF portable transreceiver. In the
exemplary embodiment the voice signals are sent using a multicast
realtime transport protocol (RTP) standard for streaming, using a
packet switched network. WT call transport module 76 also provides
a method to increase the audio quality of the transmission over an
unreliable network. Since transmission over a data network can be
unreliable and subject to various data errors, some form of error
correction mechanism is required. The transmission of voice data
must occur in real time, thus re-broadcasting the data packets
representing the voice communication is not feasible. According to
embodiments of the invention, a simple redundancy scheme is used,
in which each voice data packet is transmitted multiple times, and
is reassembled at the receiver. Any missing information from any of
the transmissions is likely to be present in the redundant
transmission. In one exemplary embodiment, two redundant packets
are used, resulting in each voice sample being sent three
times.
[0037] The directory service described above is implemented through
the directory services module 78 of software elements 70. Directory
services module 70 manages the interaction with server 22, which
provides naming services for groups of users. Additional modules
that are part of the software elements 70 include the firmware and
the drivers 84 that manage the operation of the spectrum 24
adapter, to enable the radio communications to access WLAN 14. Also
included is a voice compression services module 80, which carries
out voice compression operations to reduce the amount of network
traffic required to transmit the voice data. In the exemplary
embodiment, module 80 interacts with the firmware and driver 82
providing G.729A codecs for compression, which is carried out by
the digital signal processor 56. It will be apparent to those
skilled in the art that the software architecture describe herein
is exemplary only, and that the same functionality may be obtained
using different operating systems and software configurations.
[0038] FIG. 3 shows a perspective view of an exemplary voice
enabled terminal 100 according to the invention. Terminal 100 is
based on Symbol Technologies' PDT8100X3 portable data terminal, and
includes a transmitter/receiver component 102 used to connect with
WLAN 14. For example, transmitter/receiver component 102 may be a
Spectrum 24 wireless network radio card used to transmit outbound
voice communications and receive inbound voice communications. The
primary components of terminal 100 are a microphone 104 and a
speaker 106 which are adapted to reproduce the frequency range of
human voice. Remote speakers and microphones may also be provided,
connectable to terminal 100 with jacks. A push to talk (PTT) button
108 is included to initiate a transmission, as is done in RF
portable transreceivers and CB radios. Although this function could
be carried out with a soft key or a screen command, a physical PTT
button is more natural and easy to use. In cases where the unit is
usable for multiple purposes, PTT switch 108 may also perform
different functions, depending on which application is being
executed by terminal 100. A display 110 may also be included to
present to the user a graphical interface to access the VoIP WT
system and other applications. A keyboard 112 may be provided, to
enter commands and to select options within the WT application, and
for other applications that are executable by terminal 100.
[0039] An exemplary screen shot of display 110 is shown in FIG. 4.
In this example, the WT application runs under the Microsoft
Windows CE operating system, or the Microsoft Pocket PC 2002
operating system. As indicated above, the PTT switch is preferably
a physical switch, but other functions of the WT application may be
selected using soft keys and/or the touchscreen 110 of the device.
Normally the WT application executes as a background process, and
only shows as a small icon on the PDA's display. When a
transmission is received, the WT application is activated, and a
display such as display 120 is shown. Display 120 is preferably
designed to follow the operating system's convention, such as
having a top bar 122 with the name of the application and a button
to minimize the window. A status area 124 may be provided to
indicate whether the portable transreceiver system is idle,
operating in the WT mode, or in the peer-to-peer mode. Additional
status messages may be displayed as necessary. A pair of touch
sensitive keys 126 can be used to select the channel to be
monitored and the channel to be used for transmitting. The channel
number is displayed in field 130, and the channel name in field
128. If required, submenus may be provided to select multiple
channels or groups to be monitored. A directory key 132 is used to
bring up additional screens that allow the user to access the
naming service of server 22.
[0040] Several other functions of the WT application may be
selected either with physical buttons or touch sensitive areas of
the display. For example, a volume bar 134 and muting button 136
may replace or supplement physical volume controls of terminal 100.
A replay button or touch sensitive area 138 can be used to play
back a portion of the latest received voice message, and an
additional screen may be invoked to let the user set recording and
playback parameters. A callback area 140 is provided to let the
user initiate a peer-to-peer communication with another user. In a
simple form, when key 140 is pressed, the user that originated the
last communication received would be called back. In more
sophisticated applications, a different screen may be provided
which lets the user select whom to contact in the peer-to-peer
mode. Additional screens may be provided as needed, to let the user
select options and set parameters for the various functions of the
WT application. A "tools" key 142 may be provided to access
functions not shown on primary screen 120. It will be apparent that
the specific screen configuration and layout of the physical
controls and touch screen areas can vary depending on the design of
the unit and the operating system being used.
[0041] The present invention has been described with reference to
specific embodiments associated with a multi purpose PDA running
the Windows CE operating system. However, other embodiments may be
devised that use different platforms and software without departing
from the scope of the invention. Accordingly, various modifications
and changes may be made to the embodiments without departing from
the broadest spirit and scope of the present invention as set forth
in the claims that follow. The specification and drawings are
accordingly to be regarded in an illustrative rather than
restrictive sense.
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