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Operating System for Telecommunications
Field of the Invention
The present invention relates generally to telecommunications, and more
specifically, to an operating system and apparatus for telecommunications
networks.
Background of the Invention
Telecommunications systems, such as those for telephony and the Internet,
are composed of terminal equipment such as telephones or personal computers;
an
access network such as a telephony local loop or a radia link, and switches or
routers; and a backbone network such as the public switched telephone network
(PSTN) or the intercity data networks. One design challenge is that the needs
of
users at the terminals are very varied, but the backbone networks must handle
highly
standardized loads in order to operate reliably and efficiently.
Telecommunications systems need to process the data flowing through them
in complex ways, often with processing occurring on computer systems separated
both geographically and administratively. Many communications paths are
simultaneously active, and the processing applied to the various flows of data
changes frequently and in a wide variety of ways. The software needed to
control
these computer systems is generally large, complex and difficult to change.
When the data flowing through the system represents voice, such as in a
modern digital telephone network, special processing must be applied to
implement
such features as three-way or mufti-way calling, voice-mail, voice recognition
and
authentication, call waiting, encryption; voice coding and dual-tone multi-
frequency
(DTMF) detection. For data applications in general, such as electronic mail,
remote
computing, file transfer between computers or Web (browsing, there are needs
for
security functions such as firewalls and encryption as well as datastream
functions
such as traffic shaping, error handling, prioritization, caching, format
translation and
multicast.
While telecom systems are already complex, there is a market for new
services such as video telephony, Internet games, video on demand, Internet
audio,
remote collaborative work and telemedicine. These services will need new
families of
features to be overlaid on the existing network, making the software
development
task even more complex.
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As well, even for a single application, different: users may have different
needs, for example, requiring different degrees or forms of encryption. This
makes
the development of communications applications slow due to the complexity of
handling many cases.
Figure 1 presents a typical implementation of a telephony system 90. This
telephony system 10 includes switches 12 controlled by large computer programs
in
switch controllers 14. Switches 12 are interconnected with one another by
trunks 16
which carry the actual communication signals and m<~y consist of a variety of
physical
media, such as optical fibre and coaxial cables. Switch controllers 14 are
also
9 0 interconnected, generally by means of signalling lines 18 rather than over
the
communication trunks 16.
These systems 10 also include computing means to implement such features
as conference calling 20, voice mail 22 and toll services 24. Telephony
features,
such as call forwarding, may be implemented by addling code to the programs
running the switches 12 or by adding specialized hardware to the telephony
network
10. The features available to particular users are defined in databases
accessed by
the switch 12 software, and adding a new type of feature may involve changing
these
databases together with all of the switch 12 software that uses them, and may
also
involve purchasing and installing new types of hardware in the network.
Specialized
software is also used to check the consistency of the features assigned to a
particular
user. For example, call-waiting and call-forward-on-k>usy features define
different
behaviours for the same event, a busy receiver; so both features may not be
assigned to a user simultaneously.
The access network for telephones 26 in a classical telephony system
consists of little more than the "focal loop" wiring 28 kaetween terminals
owned by
customers and the switching network operated by a telephone company. Advanced
functionality is all concentrated in the switches 12.
In general, signal processing for telephony i done in hardware specialized for
each type of task, for example, there is different hardlware for tone decoding
and
conferencing. This limits the speed with which new features can be introduced
since
new hardware has to be designed, tested, manufactured and deployed. The fixed
assignment of tasks also makes it impossible to share loads between different
types
of hardware, for example to use idle tone-decoding hardware to help with an
overload
of voice-conferencing.
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The switching software implements a feature such as conference calling by
arranging for telephone switches 12 to direct streams of data representing
user
voices to and from hardware or software 20 specialized to do the camputations
necessary to add these voice streams together in a way that emphasizes active
speakers and suppresses background noise. When a user expresses a wish to
enter
a conference call, either by making appropriate entries via the keypad of a
telephone
26 or by communicating with an operator, the operating system of the switch 12
searches for and then allocates an unused set of inputs and outputs on
conferencing
hardware 20. if the switch 12 succeeds, it then searches for and allocates
paths to
and from those inputs and outputs, respectively from and to the telephone sets
26 of
the participants in the call, an such channels as multiplexed buses and
synchronous
optical networks. The manner in which this software searches for and allocates
these resources is entirely under the control of software written by the
manufacturer
of the switch 12 and is controlled by the owner of the' switch 12, so that a
third party
cannot make improvements. These telephony features are in fact little used by
members of the public, because the user interface is. difficult to understand.
Changes to existing telecommunication networks 10 are therefore very
complicated to make. There is a rigid model and hardware structure is
difficult to
extend. Therefore, existing telcos can not offer new features such as high
quality
voice. As well, existing telco's take a long time to bring such features to
market.
The complexity of present telecommunications systems software, and the
extensive interactions between its software components, makes the development
of
new features very difficult. As well, telecomm services have traditionally
been
provided by large monopolies who employed proprietary equipment that only they
had access to. Another complexity is that new services had to be backward
compatible to handle their existing ciientel.
Software development is therefore limited to a "closed" group of trusted
developers, which reduces the talent pool available and shuts out developers
with
new ideas for niche markets.
Traditional telecomm does not consider diffeirentiation, but focuses on
provision of single services. Therefore, telecomm providers would not be
encouraged to offer varied services at a cost reduction to users, for example,
reduced quality of voice telephony on Christmas Dar, simply to provide
additional
connections or reduced cost. As well, small niche markets have gone unserved
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completely as the cost of developing and implementing the additional products
does
not net sufficient profits.
Users can exercise a small degree of control over their telecommunications
by use of software running on their personal computers (PCs). For example,
there is
currently a Telephony Applications Programming Interface (TAPI) that allows
software running on a general-purpose computer to control the switching
decisions of
a type of switch known as a private branch exchange: (PBX).
An application programming interface (API) converts a series of comparatively
simple and high level functions into the lower level instructions necessary to
execute
those functions, simplifying use of an operating syst~:m. Using Windows APIs,
for
example, a program can open windows, files, and message boxes, as well as
perform more complicated tasks, by executing single instructions. Windows has
several classes of APIs that deal with telephony, me;>saging, and other
communication issues.
These APIs can be implemented in Java, which is a popular computer
language enhanced by features that facilitate loadincl programs across the
Internet
and which can enforce strict rules that ensure that such programs do not
contain
software viruses that could interfere with the operation of the system to
which they
are downloaded. Java is also widely used for programming advanced graphical
user
interfaces (GUIs) such as those used on some Web pages, so that one skilled in
the
art can readily write a GUI that controls a telephony switch. A system known
as
JTAPI is an example of a Java Telephony API.
The TAPi consists of a large collection of specialized subroutine calls that
allow a user to set up and tear down circuits connecting particular physical
devices,
including telephone sets and servers for functions such as voice-mail. It also
allows
the user to define how the system should respond to events such as hangups.
A system known as Parlay implements a telephony API that can be used to
control the central office telephone switches owned by large telephone
companies.
This is similar in concept to the use of a telephony AIPI to control a PBX,
but security
concerns are of prime concern because of the number of telephone users who
would
be inconvenienced by a failure.
Parlay, TAPI, J-TAPI and similar systems permit third parties a degree of
control over how telephone switches interconnect end users and specialized
equipment such as voice-conferencing servers, but do not allow third parties
to add
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new features such as encryption or voice coding. They are also unable to
describe
the handling of Internet traffic, and so it is necessary for a distinct system
to be used
to handle such functions as routing Internet browsing data through computers
acting
as security firewalls.
In a cellular telephone system or personal communications system (PCS), the
mobile telephones contain embedded computers that process the radio and voice
signals and that implement control protocols to camtnunicate with
basestations. The
basestations also contain embedded computers for these purposes, so that the
collection of mobile telephones and base stations forms a network that allows
the
mobile telephones access to the public switched telephone network (PSTN) or
other
access networks.
This access network for cellular telephony is much more sophisticated than
that for classical telephony, in that it performs advanced signal processing
functions
such as data compression for voice and advanced call processing functions such
as
support for handoff of telephone conversations from one base station to
another
during a call. A key difficulty is that the functions that the embedded
computers in the
mobile telephone can perform are fixed in advance; programmed into them with
read-only memories and limited by the capabilities of the standard protocol
used to
communicate with the basestations. The voice compression algorithms used to
reduce data traffic, for example, are fixed in advance; and cannot be easily
changed
when a new algorithm is developed.
Networks for telephony and data transmission have developed separately, but
the economic rationale for having distinct physical networks is very weak and
therefore the technologies are converging. They appear to be converging on a
model
closer to that for data than that for telephony, partly 'because of its
greater generality.
The dominant data network is currently the Internet.
>'igure 2 presents a layout of an exemplary Internet communications system
30. The Internet 32 itself is represented by a number of routers 34
interconnected by
an intemet backbone 3fi network designed for high-:speed transport of large
amounts
of data. Users computers 38 may access the Internet in a number of manners
including modulating and demodulating data over a l:elephone line using audio
frequencies which requires a modem 40 and connection to the Public Switched
Telephone Network 42, which in turn connects to the: Internet 32 via a point
of
presence 44 and access controller 46. Another mariner of connection is the use
of
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set top boxes 50 which modulate and demodulate data onto high frequencies
which
pass over existing telephone or television cable networks 52 and are connected
directly to the Internet via controNer 54. Generally, these high frequency
signals are
transmitted outside the frequencies of existing servicEa passing over these
telephone
or television cable networks 52.
Part of the access network in these systems is usually a set of computer
systems 38 at the edge of the backbone network 36 vvhich perform functions
such as
authentication of users and control of the toad that they place on the
backbone
network 36. Communications between users' computers 36 and the rest of the
network 3fi are standardized by means of defined cornmunications protocols.
Communications over the Internet can take the form of various protocols, over
a variety of physical transfer media. A protocol is a set of conventions or
rules that
govern transfer of data between hardware devices. The simplest protocols
define
only a hardware configuration while more complex protocols define timing, data
1"5 formats, error detection and correction techniques and software
structures.
The Internet is a connectionless network service, in that a single
communication may be broken up into a multitude of data packets that follow
different
paths in flowing between the same source and destination. Traditional
telephony in
contrast, establishes a single path that all of the data in the communication
follow.
2D Socket mechanisms are widely used to describe connections between
applications programs running on operating systems ouch as UNIX and Windows.
They can be used to set up connections between applications programs running
on
different computers, such that packets of data are passed between them across
such
networks as an Ethernet or the Internet. In Java, for example, the expression
'new
25 Socket("www.wireless-sys.com", 8888)' returns an object that represents a
connection to "port 8888" on a computer on the Internet whose name is
"www.wireless-sys.com". This object can be used with other Java methods to
send
data to, and receive data from, this computer. The "port number" is used by
convention to define the type of data expected.
30 When using a socket to communicate with a process on another computer,
the programmer defines one side of a communication but must rely on the
administrators of the other computer to have set up the other side. The port
number
is used by convention to describe the functionality of i:he program expected.
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Sockets typically use the Internet Protocol (IP) and can further be set up to
use either the Unreliable Datagram Protocol (UDP) which sends packets without
checking to see if they have been received, or the Transport Control vrotocoi
(TCP)
which will retry until it receives a confirmation of receipt. Telephony
applications
typically use UDP, because data that does not arrives on time is of no value,
while fife
transfer programs typically use TCP so that accurate delivery is assured. The
user is
generally required to choose between these two mechanisms to specify handling
of
error conditions in packet delivery or to write a new rnechanism ab initio.
Just as for
telephony, it is difficult to add encryption or signal pnacessing features to
the handling
of an IP stream.
The key advantages of a protocol like 1P are 'that it allows a large network
to
function efficiently and that it offers a standardized means by which
applications
software can use that network. Disadvantages are that it does not allow
specification
of processing to be performed on data streams and that it does not accurately
specify
requirements on quality of service.
The resource reservation protocol (RSVP} is an extension to IP that permits
specification of quality of service at a technical level, in terms of
parameters such as
data rates and latencies. It has had limited acceptance due to the complexity
it adds
to backbone networks and the need for their switching hardware to be updated,
and it
fails to include mechanisms to specify the costs associated with the QoS
demands
that it makes.
Asynchronous Transfer Mode (ATM) network, use standard protocols for
addressing packets of data (as does IP), setting up connections (as does TCP),
and
specifying QoS {as does RSVP}. ATM networks have typically been deployed in
the
core of backbone networks because of the high speeds at which ATM equipment
operates, but their capabilities have not been directly visible to end users
(because of
the dominance of IP as an applications standard and the high costs of ATM
equipment). Because ATM routers are not directly accessible and because of the
complexity of their mechanisms for describing QoS, these mechanisms have not
been used by applications software. Also, these QoS mechanisms, like RSVP, do
not include methods by which to describe the costs associated with a QoS
demand.
Besides the 1P and ATM networks mentioned above, there are other networks
such as Frame Relay and Ethernet. As well, the PS'TN may also be used to carry
data, for example using trellis coding, which maps digital data onto an
analogue
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signal. Variants are also evolving of each major type of network, and
engineering
differences between implementations of these networks result in different
performance. The complexity induced by this variety makes it difficult for
users and
application software to exploit all the networks available, and to exploit any
to its
fullest.
The access networks known in the art have severe limitations that come from
their having been designed for overly narrowly defined telecommunications
applications, such as telephony or fife transfer. Therefore, an invention
which allows
an access network to have the sophisticated functionality necessary for a
mixture of
telecommunications services is required.
There is therefore a need for a method and system of providing
telecommunication services that are flexible and efficient, and improve upon
the
problems described above. This design must be provided with consideration for
ease
of implementation and recognize the pervasiveness of existing infrastructure.
Summary of the Invention
It is therefore an object of the invention to provide an operating system and
apparatus for telecommunications networks which improves upon the problems
outlined above.
(3ne aspect of the invention is broadly defined as a method of implementing a
communication over a telecommunications network comprising the steps of:
defining
the communication as a stream of data; and transposing the stream of data over
the
telecommunications network by identifying and executing operating system
software
functions in real-time, where the operating system software functions are
distributed
over the telecommunications network.
Another aspect of the invention is defined as a telecommunications system
comprising: a calling party; a called party; a mixed-protocol
telecommunications
network interconnecting the calling party and the called party; the calling
party being
operable to: define the communication as a stream of data; and the
telecommunications network being operable to: transport the stream of data to
the
called party by identifying and executing operating system software functions
in real-
time, where the operating system software functions are distributed over the
telecommunications network.
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Another aspect of the invention includes a computer readable memory
medium, storing computer software code executable> to perform the steps of:
defining
the.communication as a stream of data; and transporting the stream of data
over the
telecommunications network by identifying and executing operating system
software
functions in real-time, where the operating system software functions are
distributed
over the telecommunications network.
Another aspect of the invention includes a computer data signal embodied in
a carrier wave, the computer data signal comprising a set of machine
executable
code being executable by a computer to perform the steps of: defining the
communication as a stream of data; and transporting the stream of data over
the
telecommunications network by identifying and executing operating system
software
functions in real-time, where the operating system software functions are
distributed
over the telecommunications network.
A further aspect of the invention include a cellular telephone comprising:
central processar means; wireless communication input and output means
connected
to the central processor means; memory storage means connected to the central
processor for storing software code downloaded via the wireless communication
input and output means, the software code being executable on the central
processor; real-time distributed operating system kernel software code
executable on
the central processor; and user interface means interconnected with the
central
processor.
The invention provides for a distributed oper~~ting system with real-time
characteristics and advanced security and accounting and management features
to
be provided with an API suitable for development of a wide variety of
services. It
provides for this software to run on hardware specialized for connection to
such
devices as telephones and personal computers, which may be found in homes and
offices, and also on hardware suitable for connection to backbone networks. It
also
provides for physical means of communications betvveen these types of
hardware,
and therefore constitutes an access network.
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Brief Description of the Drawings
These and other features of the invention will become more apparent from the
following description in which reference is made to the appended drawings in
which:
Figure 1 presents a physical layout of an exemplary telephony network known in
the
art;
Figure 2 presents a physical layout of an exemplary Internet network known in
the
art;
Figure 3 presents a flow chart of a method for implementing a communications
system in a broad manner of the invention;
Figure 4 presents a physical schematic of a communications system in a broad
manner of the invention;
Figures 5A and 5B present a flow chart of a method for implementing a
communications system in a preferred embodiment of the invention;
Figure 6 presents a physical schematic of a communications system in a prefer-
ed
embodiment of the invention; and
Figure 7 presents an electrical block diagram of a cellular telephone in a
manner of
the invention.
Brief Description of the Broad invention
A method of implementing a communication over a telecommunications
network which addresses the objects outlined above, is presented as a flow
chart in
Figure 3. Using this method the communication is df:fined in terms of a stream
of
data at step 56, which could be delivered as a series of packets in the manner
of
TCPIIP. This data stream is they transported over the telecommunications
network
by identifying and executing operating system software functions in real-time
at step
58, where the operating system software functions are distributed aver the
telecommunications network:
A physical representation of this system is presented in Figure 4. This figure
presents a telecommunications system 60 which allows a calling party 62 to
communicate with a called party 64 over a mixed-protocol telecommunications
network 66 which physically interconnects the two parties. As an example, the
calling
party 62 is shown to include a general purpose computer 68 with an audio
interface,
which may be a standard telephone 70, which the computer 68 is connected to
via a
telephony card. The signal processing functions necessary for telephony are
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implemented with a specialized computer on the telephony card, while the
control
functions are implemented on the computer 68 itself. This allows for
sophisticated
access control, since the computer 68 can be seen as part of the access
network.
In this figure, the called party 64 is shown to I~e a telephone, but of course
it
could be any telephony device such as a fax machine or modem. Other suitable
devices and arrangements would be clear to one skilled in the art.
The invention is realized by the calling party tit having the functionality to
define a communication as a stream of data or data packets, and the
telecommunications network 66 being operable to transport the stream of data
over
70 the network 66 by identifying and executing operating system software
functions in
real-time, where the operating system software functions are distributed over
the
telecommunications network 66.
An operating system is generally a set of software that interfaces the
hardware with the user or application programs, schedules tasks, allocates
storage
and interfaces control of the hardware. The facilities an operating system
provides
and its general design philosophy exert an extremely strong influence on
programming style and on the technical cultures that grow up around its host
machines.
Real-time operating systems are operating systems where certain functions
are required to be executed within certain time limits, giving the user the
perception of
continuous operation. In voice communication for example, users will not
generally
acceptable total unidirectional time delays, referred to as latencies, of
greater than
200 milliseconds. Therefore, total execution time of all functions that affect
the voice
signal will have to be executed in less than 200 milliseconds.
Real-time operating systems generally break software code up into multiple
executable units called threads, which are scheduled for execution within
their
corresponding time limits. Execution of threads is done by priority, for
example, a
thread handling a live voice transmission will generally have higher priority
than a
data transmission.
Such techniques are known in the art of computer software and in embedded
systems in particular, but have not been applied to telephony networks for
several
reasons.
Firstly, the dominant telecomm providers have been slow to stray from their
vast PSTN infrastructures which were not thought suitable for open systems.
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Because outside users are not able to access and modify the PSTN, they are
limited
to the functionality that the PSTN system provides. (However, as the existing
PSTN is
in fact a real-time system, the invention does not aite;r the PSTN itself, but
sends if a
stream of data encapsulated as PSTN packets which can traverse the PSTN
network. Access to the PSTN is controlled by means of proxies, and enabling by
use
of gateways.
Existing telecomm providers seek to continue use of their intelligent network
(IN) and advanced intelligent network (AIN) services because of their enormous
investments in the hardware and software to provide these services. The
invention
does not have to address integration with these systems because it is far
easier to
simply create new software to provide the same services. However, it is
preferred
that the operating system of the invention include S~~7 stacks that allow user
processes to control it and interact with it.
Secondly, it is difficult to implement real-time systems over mixed protocol
networks without incurring quality problems. This was thought to be a
hindrance to
the integration of PSTN and data networks. Those quality problems and their
solutions will be described in greater detail with respect to the preferred
embodiment.
Distributed operating systems are computer programs that coordinate the
operation of a collection of computers so that tasks rnay be run
interchangeably on
any of them, giving the whole collection of computers the appearance of a
single
unified system to applications programs and to end users. They allow end users
at
terminal equipment or who are directly using the computers running the
distributed
operating system, access to all of the resources of the system.
Implementing a distributed operating system over a variety of networks with
different protocols requires gateways to interface the various networks. These
gateways must recognize and compensate for need s of related networks.
In the invention, the network is both real-time and distributed. Therefore,
time
limits must be included in the executable threads when they are distributed.
The application of a real-time distributed operating system to a mixed-
protocol
telecommunication network in a manner of the invention offers a number of
advantages over the prior art.
The real-time functionality allows the use of audio, video and voice signals
to
be transported with sufficient speed to be comfortable to users. Many existing
telecommunications systems, particularly those employing the Internet as a
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communications medium, suffer from serious quality problems including chatter
and
lost packets. The invention provides a means for maintaining quality of
service in
transmission over such networks. This will be described in greater detail
hereinafter.
The distributed nature of the invention offers a number of operational
advantages including:
1. Greater reliability as faults are more likely to occur at distributed
functions
rather than at the kernel. This way, the kernell does not fail if there is a
software problem and the system may continiue to operate.
2. Flexibility in that devices may be upgraded functionality, or new features
accessed without having to reboot.
3. Redundancy is provided at the software levels rather than the hardware
level
as the PSTN had used in the past. This reduction in hardware by a matter of
50% reduces capital, operating and maintenance costs, building services and
support staff, all without comprising efficiency and reliability. In fact,
reliability
can easily be increased by orders of magnitude be adding an additional layer
of software redundancy.
4. The scalability of this system also allows for an incremental
implementation,
adding new gateways as new networks are added. As new networks evolve
which replace the existing PSTN, Internet, AT'M and similar networks, new
gateways can be added to leverage off the existing infrastructure.
5. This system does not have a single point of failure, as communications can
be
re-routed in the event of a node or line failing.
As well, the system of the invention offers a simplified physical installation
as
only a single physical network is required to transport multiple services such
as a
combination of voice telephone via PSTN or PBX, or data, via Internet; local
area
network (LAN) or other network. This results in a reduction of installation
materials
and labour, and reduction in maintenance of the neccasary wiring and routing
hardware. For example, a typical business office may have had separate PBX and
LAN networks in the past, but the invention provides both services over a
single
physical network.
It is preferred that this system be "active" in the sense of allowing signal
processing functions such as voice conferencing or IP filtering to be
inserted. It
should use general-purpose hardware to the greatest extent possible to gain
the
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economies of scope that come when a single piece of hardware can serve many
purposes.
This system should include very general mechanisms for the specification of
QoS parameters such as bandwidth and latency, and a means of negotiating for
them.
Because an access network generally connects two domains administered by
different parties (such as an end user and a service provider), it should
include
trustworthy mechanisms for both to operate it; this might include such things
as
software proxies responding to the needs and interests of the different
parties and
Libraries of filters with known characteristics.
This network should also ideally allow new parties to contribute to its
functionality, such as by administering technically difficult systems in the
interests and
at the behest of end users.
Description of the Preferred Embodiments of the Invention
The real-time distributed operating system of the invention preferably has a
number of other major features including data packet synchronization, load
management and fault resistance. These features will now be described by means
of
reference to the preferred embodiment.
Figures 5A and 5B present a flow chart of the preferred method of
communication over a telecommunications system in a manner of the invention.
The method begins at step 72 of Figure 5A by defining a communication as a
series of Internet Protocol data packets each of which includes a time stamp
for
synchronization purposes. As will be described in greater detail hereinafter,
the
2a Internet Protocol data packets will be encapsulated into other protocols
necessary to
carry them over networks with other protocols. In fact, almost any protocol
which
carries data could be chosen as the basic protocol.
A time stamp is prepared and included with each data packet and will be used
to synchronize the timing of the data packets as they arrive at the
destination.
Synchronisation is important, particularly in the use of connectionless
protocols such
as the IP. As each packet travels independently, they may not arrive at their
destination in the same order, and almost certainly not with the same
intervals as
they originated. The called party therefore uses the time stamps to ensure
proper
order of the data packets and their spacings.
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The time stamping may be done in a number of manners which may be
grouped generally into local or system clocking. Loc;af clocking would
include, for
example, making reference to global positioning system (GPS} data, national
clock
broadcast, onto Internet clocking services which are generaEly available
worldwide.
System clocks would include those used for :synchronization of ATM and T1
services. i=or example, ATM networks are generally provided with a 8 kHz sync
broadcast capability which is universally accessible and was originally
provided for
ATM to synchronize constant bit rate transmissions (CBR). ATM clocks running
at
192 kHz are also available on some networks.
If the input data is audio, video or voice, this data may be digitized and
streamed as known in the art to create data packets continuously from the
incoming
signal.
Alternatively, the sequence number of arriving packets may be used to sort
their order rather than time stamps. However, this results in poorer
performance as it
does not account for timing differences themselves.
At step 74, the Internet Protocol (IP) data packets are then encapsulated into
the protocol compatible with the next telecommunications network in the
system,
preferably by means of a gateway. In networking, a gateway is combination of
hardware and software that links two different types of networks, acting as an
entrance from one network into another. Gateways between e-mail systems, for
example, allow users on different e-mail systems to exchange messages.
In the preferred embodiment of the invention, all communications will be in
IP,
encapsulated as necessary to traverse networks having other protocols.
Gateways
between different networks will therefore strip the encapsulation for the
packet
arriving and replace it with the encapsulation necessary to traverse the next
network.
At step 76, the encapsulated data packets are then transported over the real-
time, fault tolerant, distributed telecommunications network by identifying
and
executing operating system software functions in real-time.
Implementation of a real-time and distributed operating system has been
generally described above. However, it is also desirable that the operating
system
and resulting network also function with much greater reliability than many
networks,
and in particular, the Internet, has in the past. The public has high
expectations for
reliability in a telecommunications system, but an Internet system contains a
large
number of components prone to failure. The system should therefore be fault
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tolerant, in the sense that failure of individual nodes ar links within it
does not cause
failure of the entire system.
It is desirable that connections, whether for telephony, data, or new
applications, survive the failure of the individual computers and links that
implement
them. This can be implemented automatically by having the system reroute links
on
failure, as is done now for telephony and Internet connections, or by having
the
various proxies that originally built the connection rebuild it on failure. If
the nodes on
which the proxies themselves are running fail, they should be reinstantiated
on
functioning nodes. Techniques known in the art of database technology can be
used
to ensure that the proxies are able to recover enough of their state to be
able to
continue, for example, by storing program state on redundant nodes at
programmer-defined checkpoints.
At step 78, the data packet is then received at its destination and is
decoded.
This step will include, of course, removing extraneous headers or
encapsulation
protocol data, to obtain the signal data from the packet. This data must then
be
synchronized and coordinated with other received data packets in accordance
with
the time stamp. As described above, the time stamp and synchronization may be
performed in a number of manners.
At step 80, the determination is made as to vvhether the data packet has
arrived at its destination. If not, control returns to repeat steps 76 and 78
until the
network or networks have been traversed by the dai:a packet.
At step 82, the components in the network then update, in real-time, their
respective tables of Load schedules for nodes and paths in the network. This
is done
so that each component has the necessary data to manage the system load
balancing and fault tolerance, which are described hereinafter with respect to
steps
84 through 98 of Figure 3B. This updating is showrnas a finite step in a
sequence,
but is expected that it will be updated periodically, or even in real-time.
A valuable function of distributed operating systems is load balancing: the
system assigns new tasks to lightly loaded processors and moves tasks around
(dynamic load balancing) as loads change with time. fn general-purpose
computing
the physical location of files is also considered when balancing computing
loads so
that network traffic does not become a bottleneck. f=or a telecom system these
optimizations are also desirable, and it is preferred that the optimizations
be extended
to balance use of critical data transmission links. In a telecom access
network that
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uses radio links and that permits double or multiple illumination of customer
premises
equipment, the choice of which of the two or several radio links to prefer
should also
be optimized as part of load balancing. Load balanciing can be implemented by
optimization methods known in the field of operations research.
Balancing loads in computing and telecommunications systems requires
estimates of the toads of particular applications. In a~ general computing
environment
these faads are usually estimated statisticafiy from recent behaviour of the
application, but in a telecommunications environment it is often possible to
estimate
the computing and data transmission loads a priori: un telephony, for example,
the
signal processing operations in voice coding and the resulting data rates are
precisely known. It is desirable to use this information where available so as
to
improve the quality of load balancing and to be able 'to guarantee that
overloads will
not occur. For this reason it is desirable when using a distributed operating
system to
operate an access network that the individual filters be characterized as to
their
computing Toad and data bandwidth requirements.
in the preferred embodiment of the invention, it is intended that access to
resources of the network be negotiated in the manner described in the co-
pending
patent application under the Patent Cooperation Tresaty, Serial No. , titled
"Method and System for Negotiating Telecommunication Resources".
Therefore, at step 84 of Figure 5B, the system determines whether excessive
loading has caused data quality to fall to an unacceptable level. It is
preferred that
this analysis be made at the device closest to the receiving party that has
the
capability of making that determination. If for example, the receiving device
is a
personal computer with a telephony card, it may make this determination.
However, if
the receiving device is a simple telephone, it may not.
If it is determined that the quality is unacceptable, the system will make
reference to the resource loading database at step 86,.so that hand-offs may
be
proposed and confirmed at step 88. This shedding of Loads may then be effected
at
step 90, re-routing the communications that aPe bogc,~ing down the network:
In the preferred embodiment, the shedding of loads is managed by
implementing a leaky bucket load shaping model. LE:aky buckets are used both
in
ATM and RSVP to specify average bandwidth. Traffic is modelled in terms of the
average output rate and the size of the input buffer needed to smooth bursts
out to
that rate. A long burst will overflow the bucket, and packets that overflow
the bucket
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are typically marked as candidates for deletion if the network overloads. For
a radio
link one might interpret these parameters literally, allocating enough radio
slotslchannels to handle the rate, and putting a buffE:r at the sending side.
For an
optical link it may be interpreted only as a specification that defines which
packets
may be marked for sacrifice.
A variant mechanism is a "token bucket" that: allows bursts at full speed
until
the flow has used up a bucket full of tokens, then restricts flow rate to the
required
average as tokens dribble in. These mechanisms diirectly express queueing
behaviour, which is fundamental to networking and rnay be advantageously
applied
in implementing the invention.
The choice of what to do with overflow packets is typically fixed in present
systems, with packets marked as candidates for deletion, but the system of the
invention is flexible enough to allow a wide variety of policies, such as
backpressure
mechanisms, to be defined.
For coded voice, the average data rate is about 50% of the peak (this is also
called the voice activity factor), but users would want to allocate enough
bandwidth
for the peak so that monologues don't get delayed in a buffer. The radio
system still
benefits from low voice activity, though, because interference is reduced. A
model for
8kbls coded voice might be a token bucket (don't delay data) with an input
rate of
8kb/s, refilled with tokens at 5kbls (a little margin over 50% utilization)
and tens of
seconds deep (so that it doesn't empty for 99% of speech bursts). The decision
of
how to handle data overruns depends on to desired voice quality and whether
there
is competing traffic, for example the price could go up, a lower-rate coder
could be
substituted, or a greater FER accepted.
The leaky bucket model doesn't provide all the information that needs to be
known in setting up a path: in a packet-switching system there are generally
internal
queues whose length is a function of aggregate traffic, and the interaction of
the
sources is significant. One may need to develop a rnore informative model, but
it will
have to degenerate easily to the leaky bucket, because that is what both ATM
and
RSVP use. One example would be to use a collection of buckets to describe
average
rates when measured at a variety of queue sizes; a generalization would be
some
mathematical function describing the relation between queue length and
expected
rate; and yet more general would be a set of functions relating queue length
to a
collection of rate statistics (mean and variance, or a collection of
percentiies)~. One
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should not expect typical developers to be able to figure these things out,
but a skilled
technician in the art could develop and provide the necessary profiling tools
to apply
them.
A system and method for negotiating systems resources is described in the
co-pending patent application under tEle Patent Cooperation Treaty, Serial No.
titled "Method and System for Negotiating Telecommunication
Resou rtes".
Returning now to Figure 5B, the routine for fault detection is presented by
means of steps 92 through 98. This routine begins at step 92 with the
detection of a
fault.
When a fault is detected, reference is made to the resource loading database
at step 94, so that hand-offs may be proposed and confirmed at step 96. As
noted
above, the resource loading database is updated in real-time with the
negotiation of
new communications, and completion of others. In the preferred embodiment,
confirmation will be made with resource managers, .agents who administer the
loading of the network. These hand-offs may then be effected at step 98, re-
routing
the effected communications through acceptable nodes and links.
As in the case of step 84, fault detection 92 rnay be performed in a periodic
manner, or continuously in real-time. It is preferred that continuous
monitoring be
provided by periodic transfers through the network.
Other features of the preferred embodiment will now be described with
respect to the physical schematic presented in Figure 6. In this embodiment of
the
invention, there are two types of subsystems connected by a wireless data link
100,
which preferably uses third generation ("3G") CDMPv technology as described by
one
of the radio transmission technologies proposed to the International
Telecommunications Union {ITU). One of these types of subsystems is on the
premises of an end user, hereafter called NetPorts X102, the other type,
hereafter
referred to as NPMs (for NetPort Managers) 104 is mounted on telephone poles
or
on buildings and is owned by a network service provider such as a telephone
company. A single distributed operating system, known as NetOS, runs across
this
collection of equipment as described below.
In the preferred embodiment of the invention, a NetPort 102 contains a simple
computer 106 including one or more central processing unit or units and
memory, a
modem 718, radio circuitry and antenna 120 necessary to implement the 3G link,
and
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other components such as a power supply and user interface. The NetPort 102
will
also contain the circuitry necessary to connect the computer 106 to a
conventional
telephone 100 through an RJ-11 connector and circuitry necessary to connect
the
computer 106 to an Ethernet local area network (LA!N) 114 through an RJ-45
connector.
An NPM 104 in the preferred embodiment contains: a high performance
computer system including one or more several cenitral processing units 116
and
memory 117, a modem 118 and radio circuitry and antennas 120 necessary to
implement the 3G link and other components such as a power supply, user
interface,
and nonvolatile storage such as disk drives. An NPM 104 will also have
circuitry
necessary to connect the computer system to a backbone network or networks
such
as the Internet 124 or the public switched telephone network (PSTN) 126.
Both in the NetPorts 102 and the NPMs 104, the memories preferably include
both dynamic memory (DRAM) arid persistent storac,~e such as ROM, EEPROM or
flash memory. The persistent memory is used to "boot" the computers, providing
an
initial simple program permitting them to load the rernaining software from
disk
storage or over their links to other computers.
After booting, both NetPorts 102 and NPMs 1104 run an operating system
kernel such as real-time Linux or VxWorks, which starts and stops system and
application processes and controls their access to such resources as computer
memory and the interfaces to inputloutput devices. Certain of the system
processes
are given special privileges, such that their requests for resources will be
respected,
while others are not. System processes may be described as daemons, filter
runtime
environments (FREs), Java Virtual Machines (JVMs;d, or servers as described
below.
Applications processes may be described as filters or agents as described
below
One desirable type of daemon is an "authentication daemon", which other
programs use to verify that information purporting to come from another
NetPort 102
or NPM 104 in the system does in fact come from there, or that another NetPort
102
or NPM X04 is in fact running the software that it ought to.
A second desirable type of daemon is a "remoteExec" daemon which can be
used by one NPM 104 or NetPort 102 to cause another NPM 104 or NetPort 102 to
start a process on another. !t does this, after verifying with the
authentication daemon
that such a request is legitimate and after checking with a database that the
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requesting process has the appropriate privileges, by using the kernel to
cause a new
process to begin execution with access to the remotely requested resources.
Most modern operating systems, such as Unix, contain a number of features
useful in controlling a distributed operating system, such as commands to
"kill" a
process, to perform housekeeping tasks at stated times, to list processes
currently
running, and to list and search disk files. All of these: can be remotely
invoked, and
so can be used by any processor to control another.
Protection mechanisms, which ensure that the control commands described
above are not misused, intentionally or otherwise, are required for any robust
distributed system and are of importance for the application of distributed
computing
to a telecommunications access network for two reasons: the communications
links
and even component computers of the distributed system are inherently exposed
to
malicious users; and a large system with high user expectations for
reliability must be
designed to be robust. In the preferred embodiment cryptographic protocols and
signatures are used for all operating system control messages over exposed
links,
and extensive checking is done of the legitimacy of a request.
A standardized protocol for communication among the processors, such as an
IP stack running over Ethernet or ATM, permits softvvare to be written in a
consistent
manner. Similarly, a consistent standard for reporting performance or failure,
such as
Simple Network Management Protocol (SNMP) simplifies the software required for
system maintenance. SNMP is the most widely-used network management protocol
on TCPIIP-based networks.
The value of the system is considerably increased if the streams of data
representing particular connections, for example the data streams that encode
voice,
can be passed through "fiiters". For telephony, filter, may be defined, inter
alia, to:
compress the stream so as to reduce required bandwidth;
Il. encrypt the voice signal, so that interception its made difficult;
lil. store the signal on disk, or convert it to an e-mai6 attachment, far
voice mail;
IV. apply tone controls, such as bass boost, to the signal to improve the
subjective quality of the call;
V. combine multiple streams into one, for voice conferencing;
Vl. combine multiple streams for rate matching in a CDMA communications
system;
VII. monitor a stream for TouchTone dialing;
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VI II. monitor a stream for voice commands;
IX. authenticate a person's identity by comparing his voice pattern to a
stored
template; or
X. acquire the voice stream from, or play it to, the physical coders and
decoders
connected to a telephone.
A particular type of process which may be started on a NetPort 102 or NPM
104 is known as a Filter Runtime Environment {FRE). This is a process which
can be
used to run a collection of filters, which are described above. In one
embodiment the
filters are implemented as subroutines that are interconnected dynamically to
allow
an FRE to have a behaviour defined flexibly by the particular interconnection
of filters
that compose it: for example to apply tone controls, compress voice, then
encrypt it
far transmission and store a copy of the encrypted voice on voice-mail, and to
cryptographicaliy sign the resulting voice-mail as having originated from the
claimed
caller.
A collection of proxies and protocols as described below is used to implement
a "call processing" or "connection management" layer of software. This
software is
responsible for negotiating and defining the collections of filters that will
implement
the actual telephone calls, data connections, or other telecommunications
services.
Proxy or "agent" software represents the requirements of individual users and
of terminals (such as telephones); a proxy for an end-user might constrain the
time of
day at which calls will be accepted, while a proxy for a telephone in a public
area
might not permit long-distance calls to be placed. Similarly, for an IP data
stream a
proxy for a computer in a school might filter out pornographic content.
Since it is desirable that a large number of developers should be able to
write
these proxies, it is also desirable that the security of the overall system
cannot be
compromised by them. This can be arranged by requiring that proxies run in a
secure "sandbox" such as provided by Java. The "sandbox" approach to security
is
one in which an applet is only allowed to operate within certain bounds (the
sandbox).
This constrained runtime environment prevents applets from accessing and
altering
unauthorized areas, or performing otherwise harmful operations, such as
reading or
writing files to the Client's hard disk or establishing network connections
except to the
server that the applet came from.
Proxy software is also desirable to represent the interests of the network
operator, who must ration such resources as licensed spectrum and backhaul
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capacity, and perhaps the constraints imposed by the operator's service level
agreements with backbone operators. This software could be implemented in
Java,
but. could also be implemented as a distributed database application in C++
which is
preferred because these proxies may be required to operate at high speeds
while
managing large networks with complex constraints.
Standard protocols far negotiation among the various proxies permit
interoperability. In a simple embodiment, it is taken as a starting point that
all parties
to a negotiation agree on a given minimum or standard type of connection (such
as a
caller-paid connection to a message or terminal of the called party's
choosing, using
PCM voice coding}; the various parties are then permitted to exchange offers
far
connections that they consider more desirable in the hope of finding one that
is more
desirable to ail parties.
Accounting mechanisms are desirable for large systems, although they are
sometimes dispensed with in smaller networks serving a single organization.
They
can be implemented by having the network proxy maintain records of telephone
and
data traffic for later billing or by including payment negotiation in the act
of setting up
a connection.
Applications programming interfaces (APIs), implemented as libraries of Java
or C++ methods, can be used to describe desired connectivity: for example with
methods that request connection to a particular telephone number or IP
address, or
that give a website address {URL) or yams of a company or service. They can
also
describe desired quality of connection: for example un terms of desired
subjective
quality {Mean Opinion Scare) or bandwidth, failure rate and latency. Part of
the API
for describing connections can include a mechanism for responding to failures,
such
as a set of exceptions.
The power of the invention is also clear from its application to a cellular
telephone. Figure 7 presents a electrical block diagram of a cellular
telephone 128 in
a manner of the invention. Rather than a device with a predetermined and fixed
function, this cellular telephone 128 has far greater capability and
flexibility than
existing devices, and may be updated as necessary or even continuously.
This cellular telephone 128 consists of standard components such as the
audio input and output 130, which would include analogue to digital and
digital to
analogue converters to pass voice signals to and from the central controller
132.
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This central controller 132 may, for example, be a digital signal processor,
microprocessor or microcontroller.
Current microprocessors with MMXT"" technadogy could be modified for the
purposes of the invention. MMXTM is a PentiumrM microprocessor from Inteh""
that is
designed to run faster when playing multimedia applications. According to
InteIT"", a
PC with an MMXT"~ microprocessor runs a multimedia application up to 60%
taster
than one with a microprocessor having the same clock speed but without MMXTM.
In
addition, an MMXTM microprocessor runs other applications about 10% faster.
The MMXT"" technology consists of three improvements over the non-MMXTM
PentiumTM microprocessor:
57 new microprocessor instructions have been added that are designed to
handle video, audio, and graphical data more efficiently;
2. a new process, Single Instruction Multiple Data (SIMD), makes it possible
for
one instruction to perform the same operation on multiple data items; and
3. the memory cache on the microprocessor which has increased to 32
thousand bytes, meaning fewer accesses to memory that is off the
microprocessor.
Such microprocessors are a common commercial component and have
correspondingly low prices and broadly available applications software.
The microprocessor preferably stores the operating system kernel in an
internal memory cache, though this memory 134 ms~y be off-processor as shown
in
Figure 7. This off-processor memory 134 is preferably a non-volatile memory
such
as an electrically erasable programmable read only memory (EEPROM) or
FlashROM, but may also be a volatile memory such as a random access memory
(RAM). This memory 134 may be used to store the desired digitization,
encryption
and protocol algorithms, which are downloaded via the wireless inputloutput.
Because the operating system is distributed, it is noinecessary to store much
functionality in the cellular telephone 128, but is preferable to store
functions common
required because of the resulting increases in processing speed.
This cellular telephone 128 also includes a standard telephone keypad 138
and display 140, however, more advanced components could also be used. For
example, rather than a liquid crystal display (LCD) Hrith a single line of
alpha numeric
characters, the display 140 could comprise an LCD pixel matrix which could
display
graphics as well as alphanumerics. Rather than a traditional telephone keypad
138,
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the keypad 138 could comprise a mouse and pushbutton which drives a cursor on
the display 140 and selects icons in a graphic user interface (GUI) to execute
desired
functions.
Other arrangements would also be clear to one skilled in the art from the
teachings herein. The invention allows the cellular telephony or similar
telephony
device to be upgraded by downloading the latest software or new software
functions
that are desired. Existing cellular telephones have fiixed functionality and
become
obsolete when the networks are upgraded.
Similarly, a modem connected to a personal computer could be
programmable in the same manner. Of course, a comparable arrangement could be
made to any telephony device, be it a personal digiit<al assistant, fax
machine, pager,
point of sale computer, local area networks or private branch exchanges. While
particular embodiments of the present invention have been shown and described,
it is
clear that changes and modifications may be made i:o such embodiments without
departing from the true scope and spirif of the invention.
The method steps of the invention may be embodied in sets of executable
machine code stored in a variety of formats such as object code or source
code.
Such code is described generically herein as programming code, or a computer
program for simplification. Clearly, the executable machine code may be
integrated
with the code of other programs, implemented as subroutines, by external
program
calls or by other techniques as known in the art.
The embodiments of the invention may be e~;ecuted by a computer processor
or similar device programmed in the manner of method steps, or may be executed
by
an electronic system which is provided with means for executing these steps.
Similarly, an electronic memory means such compui;er diskettes, CD-Rams,
Random
Access Memory {RAM), Read Only Memory {ROM) or similar computer software
storage media known in the art, may be programmed to execute such method
steps.
As well, electronic signals representing these method steps may also be
transmitted
via a communication network.
It would also be clear to one skilled in the art that this invention need not
be
limited to the described scope of computers and computer systems. Credit,
debit,
bank and smart cards could be encoded to apply the invention to their
respective
applications. Again, such implementations would be clear to one skilled in the
art,
and do not take away from the invention.
