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Claims  |
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We claim:
1. In a wireless broadband communication system, a method of delivering a
variety of broadband/narrowband services to an end user of the system;
comprising the steps of:
coupling end user equipment to the communication system by wireless
transmission media utilizing a combination of spread spectrum and time
division multiplex transmission to an access antenna;
at the end user premises re-transmitting a down link spread spectrum and
time division transmission from the access antenna and transmitting up
link spread spectrum and time division transmission to the access antenna;
partitioning available spectrum into specific channel/conduit components
aligned to specific services to the end user and allocating sub channels
and conduits to provide needed bandwidth for a particular application by
the steps of defining asymmetrical broadband channels and bidirectional
symmetrical narrowband channels by assigning channels into specific
service categories; and
subdividing the channels into conduits of specified bandwidth each of which
may be combined to be assigned to a specific service.
2. In a wireless broadband communication system, a method of delivering a
variety of broadband/narrowband services to an end user of the system, as
claimed in claim 1,
wherein the step of partitioning further includes the step of selecting
conduits within channels to match bandwidth requirements of services to be
provided.
3. In a wireless broadband communication system, a method of delivering a
variety of broadband/narrowband services to an end user of the system, as
claimed in claim 2,
wherein the step of partitioning further includes the step of mapping of a
single service onto several conduits selected to match bandwidth
requirements of that single service.
4. In a wireless broadband communication system, a method of delivering a
variety of broadband/narrowband services to an end user of the system, as
claimed in claim 3,
wherein conduits are assigned based on modulation requirements of a service
by selecting CDMA modulation for narrowband and TDM for broadband service.
5. In a wireless broadband communication system, a method of delivering a
variety of broadband/narrowband services to an end user of the system, as
claimed in claim 4,
wherein channels are assigned to service classes to match static and
variability in demand.
6. In a wireless broadband communication system, a method of delivering a
variety of broadband/narrowband services to an end user of the system, as
claimed in claim 5,
wherein a channel is encoded by a modulation schema by utilizing CDMA for
optimizing narrow band frequency reuse; and
optimizing broadband applications by means of compression and by using TDM
schema.
7. In a wireless broadband communication system, a method of delivering a
variety of broadband/narrowband services to an end user of the system, as
claimed in claim 6,
maximizing channel utilization while providing uniform service quality by
varying conduit bit rate to match program requirements while maintaining
an average bit rate for all conduits in a channel.
8. In a communication network for providing broadband and narrowband
services with a wireless connection between the network and end users; a
method of allocating frequency spectrum to satisfy service bandwidth
requirements of a plurality of services;
comprising the steps of:
periodically setting a re-allocation time;
static allocating of channels to meet service demand on a known
predetermined allocation basis supported by time and date records at a
periodic reallocation time to meet anticipated demand at that time and
date;
dynamic allocating of channels to meet service demand on immediate service
requests in real time by determining an idle capacity of channels,
measuring a number of channels assigned to incumbent service classes,
determining if a number of idle channels exceeds the channels assigned to
incumbent service classes by a block number, determining channels to be
assigned to a different service class; and
the dynamic allocating having precedence over the static allocating.
9. In a communication network for providing broadband and narrowband
services with a wireless connection between the network and end users, a
method of allocating frequency spectrum to satisfy service bandwidth
requirements of a plurality of services, as claimed in claim 8:
determining if there is blocking on channels to be assigned to a different
service class; and
reassigning unused channels to a different service class.
10. In a communication network for providing broadband and narrowband
services with a wireless connection between the network and end users, a
method of allocating frequency spectrum to satisfy service bandwidth
requirements of a plurality of services, as claimed in claim 9:
establishing a waiting period before a subsequent dynamic allocation.
11. In a communication network for providing broadband and narrowband
services with a wireless connection between the network and end users, a
method of allocating frequency spectrum to satisfy service bandwidth
requirements of a plurality of services, as claimed in claim 9:
reallocations of channels from one service class to another service class
are in incremental integer numbers of channels.
12. In a communication network for providing broadband and narrowband
services with a wireless connection between the network and end users; a
method of allocating frequency spectrum in both spread spectrum and TDM
transmissions to satisfy service bandwidth requirements in providing end
users with a plurality of services;
comprising the steps of:
periodically setting a re-allocation time;
statically allocating channels to meet service demand on a known
predetermined allocation basis supported by time and date records at the
reallocation time;
dynamically allocating channels to meet service demand on immediate service
requests in real time; statically and dynamically allocating channels by
partitioning of the available frequency spectrum, and
the dynamic allocating having precedence over the static allocating.
13. A communication network for providing broadband and narrowband services
with a wireless connection between the network and end users, comprising:
an asynchronous transport mode network and a synchronous transport mode
network;
a service node connected to the asynchronous transport mode network and the
synchronous transport mode network and an access node which is in turn
connected to a microport including an antenna for radiating radio signals
to a receiving antenna of an end user;
a channel allocation server, connected to the service node, for estimating
blocking probabilities across service chases and for identifying channels
to be moved from one service class to another to accommodate service
demands;
communication circuitry for communicating and for providing communication
network routing control;
wherein the communication network apportions communication channels and
conduits to specific communication services;
and wherein the service node measures channel occupancy of the channels
controlled by the communication system and assigns network trunks to
operate as access trunks;
the access node combining and splitting channels to conform with the
mapping of services onto channels;
the microport having radiant apparatus to transmit and receive signals over
air media and associating wired channels of the networks to a RF channel;
and
the access port connecting received wireless signals to wired and wireless
equipment of the end user and transmitting wireless signals from the end
user to the microport.
14. A communication network for providing broadband and narrowband services
with a wireless connection between the network and end users, as claimed
in claim 13, comprising:
a signaling server for providing signaling services to end user devices.
15. A communication network for providing broadband and narrowband services
with a wireless connection between the network and end users, as claimed
in claim 13, comprising:
a billing operations, administration, maintenance and provision server for
providing integrated billing across all broadband and narrowband services
to end users.
16. A communication network for providing broadband and narrowband services
with a wireless connection between the network and end users, as claimed
in claim 13, comprising:
a security server for providing security authentication and fraud
prevention services.
17. A communication network for providing broadband and narrowband services
with a wireless connection between the network and end users, as claimed
in claim 13, comprising:
a customer profile server for storing end user data including subscriber
preferences.
18. A communication network for providing broadband and narrowband services
with a wireless connection between the network and end users, as claimed
in claim 13, comprising:
a user registration server for maintaining real time data concerning a
users location and service area related data.
19. A communication network for providing broadband and narrowband services
with a wireless connection between the network and end users, as claimed
in claim 13, comprising:
a signaling server, an Interactive Video On Demand (IVOD) server, a
security server, a billing operations, administration, maintenance and
provision server server, a customer service profile server and a location
and user registration server, and a channel allocation server; all
integrated within the system to provide integrated service across
end-to-end of the network to end users across an entire portfolio of
services.
20. A communication network for providing broadband and narrowband services
with a wireless connection between the network and end users, as claimed
in claim 13, further comprising:
the access node dividing channels into a fixed plurality of conduits, the
plurality of conduits each being variable in bandwidth, with the plurality
of conduits having a fixed overall bandwidth and the average bandwidth of
the each conduit of the plurality of conduits remaining fixed.
21. A communication network for providing broadband and narrowband services
with a wireless connection between the network and end users, as claimed
in claim 13, further comprising:
a radiant apparatus comprises a sectored antenna with three sectors and
radiating three levels of channels for interactive broadcast video
services, interactive video on demand services and narrowband services;
and
the channel allocation server controlling transfers of channel assignments
from one level to another.
22. A communication network for providing broadband and narrowband services
with a wireless connection between the network and end users, as claimed
in claim 20 or 21, further comprising:
the access node being connected to the service node with a SONET ring.
23. A communication network for providing broadband and narrowband services
with a wireless connection between the network and end users, as claimed
in claim 22, further comprising:
antenna means for accepting satellite signals to support broadcast video,
multimedia, and information services.
24. A communication network for providing broadband and narrowband services
with a wireless connection between the network and end users as claimed in
claim 20 or 21, further comprising:
the access node being connected to the service node with a point-to-point
microwave connection.
25. A communication network for providing broadband and narrowband services
with a wireless connection between the network and end users, as claimed
in claim 20 or 21, further comprising:
the access node being connected to the service node with a point-to-point
infrared connection.
26. A communication network for providing broadband and narrowband services
with a wireless connection between the network and end users, as claimed
in claim 20 or 21, further comprising:
the access node being connected to the service node with a star connection.
27. A communication network for providing broadband and narrowband services
with a wireless connection between the network and end users as claimed in
claim 20 or 21, further comprising:
the access node extending available services by adding interactive services
by providing interactive uplink channels.
28. A communication network for providing broadband and narrowband services
with a wireless connection between the network and end users, as claimed
in claim 20 or 21, further comprising:
the access node adding new services by utilizing compression techniques to
pack existing services into a subset of channels to free channels for new
services. |
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Claims |
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Description |
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FIELD OF THE INVENTION
This invention relates to communication system architectures and to a
particular network architecture for providing narrowband/broadband two-way
point-to-multipoint services to fixed and portable terminals in high
teledensity areas. It is specifically concerned with a communication
system that utilizes wireless transmission and dynamically allocates
channels/bandwidth for specific present applications.
BACKGROUND OF THE INVENTION
Telecommunication systems provide numerous services requiting both
broadband and narrowband capabilities to the corporate and individual
subscriber. These services normally require that each customer be provided
with wide bandwidth communications transmission media (e.g., cable or
fiber) for broadband services and with narrowband transmission media
(e.g., twisted pair) for narrowband services if all needed services are to
be accommodated. This hard-wired physical media-based capability is
expensive to install and maintain and the associated capital may be
unrecoverable if the end user decides to change the service provider after
installation. These same costs may also limit system deployment if these
costs become prohibitive and fail to yield profitable life cycle
economics.
However, wireless systems have inherent flexibility because of their
untethered nature. If the end user changes carriers, no capital is
stranded, since the wireless termination device can be recovered and
redeployed.
SUMMARY OF THE INVENTION
A wireless broadband communication system architecture is structured to
provide an array of narrowband and broadband services on demand to an end
user. The system embodied by this invention maximizes frequency reuse by a
judicious combination of spread spectrum techniques and time division
multiplexing, and matching service requirements with appropriate sectoring
of radiant signaling energy. The bandwidth of delivery is dynamically
adjusted to satisfy service requirements by providing the appropriate
bandwidth needed. Bandwidth-on-demand is provided in accord with the
invention by rearranging (i.e. remapping) spectrum allocation to
simultaneously achieve two objectives: (1) assign users channels matched
to their requirements, and (2) rearrange channel assignments to maximize
spectrum utilization. The communications system is designed to utilize
wireless communication for end point delivery to fixed site customer areas
and portable customer terminals. The system supplies basic telephone
service, wireless ISDN service, wireless data service, wireless multimedia
service, and various other wireless broadband services including
interactive video and broadcast video. Furthermore, the system provides
signaling capability in support of all the services.
Efficient use of spectrum is achieved at various levels of the system. At
one level, channel assignment is performed in response to varying demand
for different classes of service. In another aspect, conduits (which are
subdivisions of channels) are varied in bit rate to accommodate service
bandwidth requirements as long as the channels' conduits conform to an
average throughput. In yet another aspect, service bandwidth requirements
are matched to channels that are divided into high, medium and low
bandwidth in order to achieve spectral efficiency.
In a particular scenario making use of the invention, the communication
system provides bandwidth on demand by utilizing a combination of spread
spectrum technique (CDMA) and time division multiplexing (TDM) operating
over a broadband spectrum that is allocated to specific channels on
demand. The CDMA/TDM signal is transmitted between the system network and
to a customer premise dynamic access director station. The use of CDMA/TDM
along with signal compression techniques allows the use of spectrum that
up until now has only supplied a few channels for a small subset of
services.
Spectral efficiency is enhanced by allocating/sharing the same
bandwidth/channels to differing services based on a demand schedule
matched to demand patterns. In another scenario using the interface,
channels are allocated to services on a demand-driven basis.
In addition the network architecture provides for a set of network servers,
and signaling/control means between the servers and end user devices for
providing integrated services on an end-to-end network basis.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a pictorial schematic of a broadband wireless network topology
embodying the principles of the invention;
FIG. 2 is a functional schematic of a broadband wireless network
architecture embodying the principles of the invention;
FIG. 3 is a graph of illustrative spectrum allocation in accord with the
invention;
FIG. 4 is a flowchart illustrating a method of static channel assignment to
meet predictable service demand variations;
FIG. 5 is a flowchart illustrating a method of dynamic channel assignment
to meet service demands;
FIG. 6 is a graphical depiction of the distribution of procedures to
implement static and dynamic channel assignments;
FIG. 7 is a graph of an incremental channel reassignment process across
service classes;
FIG. 8 shows how the spectrum is partitioned into channels and conduits;
and
FIG. 9 illustrates a subchannel assignment scheme for servicing broadband
(i.e., video) services.
DETAILED DESCRIPTION
System Network Topology For Wireless Network With Spectrum Allocation
FIG. 1 illustrates one version of a network topology of a broadband
wireless network embodying the principles of the invention. An ATM
(asynchronous transfer mode) network 101 and a STM (synchronous transfer
mode) network 102 are shown connected to a service node 103 coupled in
turn to a fiber based SONET/SDH access ring 104. The use of a fiber based
SONET/SDH ring for access and link purposes is for illustrative purposes
and is not essential for the disclosed Illustrative network. A star
network using non-fiber transmission, including point-to-point microwave
and/or infrared communication could just as easily be used. Access nodes
105-1 to 105-4 couple the SONET/SDH access ring 104 to a plurality of
access antennas or intelligent microports (IMP) 106-1 to 106-4. The
intelligent microport 106-2 is shown connected by wireless to an access
director or wireless repeater 107 at a residential customer premise. This
access director/wireless repeater contains a plurality of equipment
functionality [including a telephone, ISDN terminals data communication
devices (e.g., PC), signaling devices/adjuncts, television/set-top boxes,
multimedia worksataions, etc] supplying a broad array of
narrowband/broadband services, each of which requires differing bandwidth
capability. The microport 106-2 is also shown as directly serving a
wireless handset 108 external to the customer premise. A microport 106-4
is shown coupling service to an industrial/office site in a manner similar
to that of the residence premises. A satellite ground station 109 is shown
connecting the SONET/SDH access ring 104 to a satellite 110 via access
node 105-4. Communication between the SONET/SDH access ring 104 and the
end user recipients is by wireless, permitting the spectrum to be
partitioned into multiple channels of sufficient bandwidth as required by
a particular service or application.
Functional Partitioning of the Network to Achieve Optimal Spectral
Implementation
An architecture suitable for the broadband wireless network is shown in the
FIG. 2 in terms of the communication of the network to a particular end
user. A channel allocation server 222 is provided to identify and store
information regarding uses of different services over time to control
static and dynamic reallocations of spectrum to individual services.
A signaling server 213 provides signaling services to end user devices:
Acting as a gateway between end user devices and the network's internal
signaling system; distributing control data to other servers, such as
billing/OAM&P (operations, administration, maintenance, and provisioning)
data to billing/OAM&P server; etc. IVOD server 214 supports IVOD services,
enhancements to normal video; (e.g., pause, rewind etc. interactivity),
menu driven user interface, etc. Billing/OAM&P server 215 provides for
integrated billing/OAM&P to end users across all services taking into
account any special service options and plans (e.g., 60 minutes of any
program per month for a fixed fee). Security server 218 provides for
security authentication and fraud prevention services to service providers
and to end users. Customer service profile server 216 stores end user data
including subscriber server preferences, etc. Location and user
registration server 217, contains real time data on a user's current
location and service area related data.
Signaling server 213, IVOD server 214, security server 218, billing/OAM&P
server 215, customer service profile server 216, location and user
registration server 217 and the channel allocation server 222 are coupled
to the ATM network 101, STM network 102, and/or the service node 103. The
ATM network 101 and STM network 102 are connected to a service node 103
which is in turn connected to an access node 105-N. A national headend 201
is connected to the local headend 211 via a satellite 110 and satellite
ground station 109. The local headend 211 is also connected to an access
node 105-N. An intelligent microport (access antenna) 106-N provides the
air interface to the access director 107, which is in turn connected to
the premise equipment or neighborhood wireless terminal 108 by either
internal wiring or by a short air interface.
The service node 103 performs traffic grooming (e.g. aligning radio
frequency/access lines to land line trunks and to channels in low, medium
and high arrays to sub-channels with low, medium and high bit rate
services) and further performs circuit/synchronous transfer mode (STM) and
cell/asynchronous transfer mode (ATM) switching. It is also a control for
feature invocation and execution. The national headend 201 originates
video/multimedia broadcast information for national distribution. A local
headend 211 or the access director 107 receives the video/multimedia
information for local distribution. The access node 105-N adds and drops
trunks to the ring/access links and provides multiplexing and
demultiplexing capability. The intelligent microport 106-N implements both
narrowband and broadband services by supporting a variety of multiple air
interfaces. It provides both static and dynamic channel allocation to meet
changing service demands by providing bandwidth on demand. The access
director 107 is a gateway/repeater providing a link between the microport
and customer premises equipment (both wireless 108 and wired). The
neighborhood wireless terminal 108, supports a broad array of services
including wireless multimedia services.
Spectrum Allocation and Partitioning
Allocation or partitioning of available spectrum in accord with the
principles of the invention is shown in the FIG. 3. A service channel map
shows how various channels may be apportioned to various illustrative
service classes. Blocks of channels each enabling a 6 or 10 MHz bandwidth
are shown arranged linearly. Two channels 301 are shown distinct and
isolated from the main array. These channels are dedicated to signaling
for set up of connections and control of interactive commands. They also
convey data useful in provisioning, billing/OAM&P, and maintaining
services to end users on an end-to-end basis across all services in an
integrated manner. This data communicated between the end user terminals
and the network servers (213 through 222 in FIG. 2) include user identity,
destination address, authentication service request codes, billing
options, OAM&P messages, security/encryption code, service priority,
location, grades of service requested, etc. This data is used by the
network servers to provide services to end users in accordance with
service requests. Channels 301 are wireless packet signaling channels in
this embodiment and are comprised of two 6 MHz channels. In addition to
utilizing channel 301, channel 308 (auxiliary packet response channel)
could be used for this signaling and control messages, based on the amount
that such messages need to be supported. Finally in addition to the
dedicated channels (301, 308) these messages could also be exchanged via
the same channels (303-307) use for the bearer services.
The total array of bearer channels covers a span of 198 MHz in this
illustrative array. Channels 303 are narrowband service class access
downlink channels. Channels 304 are downlink broadcast video service
channels. Channels 305 are downlink interactive video on demand channels.
The channels designated 306 provide guard spectrum for duplex
filters/attenuation rolloff used in the network. Channels 307 are uplink
narrowband service class access channels. Channel 308 is an auxiliary
packet response channel. In the illustrative embodiment, channels
designated 301 are bounded between 2150 MHz and 2162 MHz, and channels
designated 303 through 308 are bounded between 2500 MHz and 2690 MHz. In
this embodiment, both the frequencies and the bandwidth of the channels
can be adapted to meet different requirements.
Static Channel Assignment Process
FIG. 4 flowcharts a process of static channel assignment. This process is
repeated periodically to conform to the channel reassignments to known
customer demands at specified intervals. The process assigns channels and
bandwidth on the basis of established traffic patterns on specific days
and at specific times of day. The instructions of the first process block
401 monitor the time of day and the day of the week and identify the
occurrences of special days that are relevant to traffic demands. The
traffic demands are categorized as to specific services and are evaluated
with an allocation algorithm to specify channel transfers at time T.sub.k
according to: C.sub.sisj from service class si to service class sj. A
subsequent decision block 403 evaluates the data of block 401 to determine
if static channel allocation is necessary. If it is not the flow proceeds,
via terminal 409, to a dynamic allocation flow process shown in the FIG.
5. If a static allocation is needed the flow proceeds to instruction block
405 which specifies the reallocation of channels to meet the expected
traffic demands. In the process the channel C.sub.sisj is transferred from
service class si to service class sj for all i and j where j=1 to N and i
does not equal j and C.sub.sisj =-C.sub.sjsi. The flow then proceeds to
the process of FIG. 5, via terminal 411.
Dynamic Channel Allocation Process
The process of dynamic assignments is described in the flowchart shown in
FIG. 5. It begins in terminal 500 which proceeds from the process shown in
FIG. 4. The initial instruction block 501 defines an existing allocation
of channels and bandwidth to services. The flow process begins in response
to a handoff from the static process of FIG. 4, via terminal 502, at the
entry to decision block 503. The instruction for block 503 determines idle
channel capacity and compares the number of idle channels assigned to an
incumbent service class (i.e. existing service assignments) over a
specified time interval with a threshold of a minimum number of channel
blocks .DELTA. C that may within the the system be assigned to a different
candidate service S.sub.j. This minimum number corresponds to the transfer
increment .DELTA. C discussed herein below with reference to FIG. 7. If
the available idle capacity does not exceed this threshold, the process
recycles to reevaluate the number of idle channels available for such
purposes.
If it is determined that a sufficient number of channels exist to satisfy
the threshold requirement, the subsequent decision block 505 determines if
there is blocking on channels assigned to the candidate services over the
same period investigated in the evaluation of the block 503. If no such
blocking exists the flow returns to the input in block 503.
If such blocking is found to exist the process flow proceeds to instruction
block 507 which controls the assignment of channels to transfer channels
from service class si to service class sj. At the time of transfer it is
determined if all service classes si to sj have been checked and
evaluated. If it has the flow proceeds to instruction block 509 which
halts the flow for a specified time interval. Instruction block 509 then
returns the process to the input of block 503 where the dynamic assignment
process resumes.
If all such service classes have not been evaluated, the flow proceeds to
instruction block 511 which increments i or j and the flow returns to the
input of block 503 where the dynamic assignment process resumes.
Network Distribution of Spectrum Allocation Functions
The procedures of channel assignment are distributed within the network
system, as shown in FIG. 6, with instruction block 601 being performed in
the service node to measure channel occupancy data. The flow proceeds to
decision block 605 in the channel allocation server which in process block
603 estimates the blocking probabilities in each service classes. The flow
proceeds within the channel allocation server to decision block 605, which
determines if it is necessary to reallocate channel assignments due to
changes in static or dynamic conditions. The process continuously recycles
in this block if there is no need to reallocate spectrum. If there is a
need to reallocate spectrum, the flow proceeds to instruction block 607
which identifies the channels C.sub.sisj that are to be moved from si to
sj service classes according to the defined static and dynamic assignment
processes as described in the flow charts of FIGS. 4 and 5.
The flow proceeds to instruction blocks 609, 611, 613 and 615 located in
the service node, the access node, the intelligent microport and the
access director, respectively. Instructions of block 609 assign network
trunks to the access trunks. The instructions of block 611
demultiplex/multiples channels or combine/split channels to align mapping
of blocks of channels. Instructions of block 613 associate wired channels
with RF channels and instructions of block 615 assign channels to conform
with assignments in the intelligent microport.
Spectrum Transfer Increments Illustrated
A graphical depiction of incremental channel reassignment in the system
across service classes is illustrated in the FIG. 7 in which three
circular charts 701, 702 and 703 each define a different category of
service classes. Each channel in the illustrative embodiment has a
plurality of conduits of different bandwidth, with the conduits in each
channel totaling 6 or 10 MHz. These conduits may be joined or separated
and varied in bandwidth to form channels for specific service
requirements. Each conduit or group of conduits is associated with
supporting a specific service. These conduits are time slots in some
applications (TDM) and are part of the shared spectrum band in other
applications (CDMA).
The initial disk representation of disk 701, in the illustrative
embodiment, represents nine channels normally assigned to interactive
broadcast video services. Disk 701 is sectorized into three 120 degree
sectors each of which uses the same nine channels (i.e., a sectorized omni
approach). A sectorized approach is used in place of omni radio signal
radiation in order to use a single antenna for all services, to minimize
power requirements, and minimize heat loads on the intelligent microport.
Channels that are so sectorized are in effect omnidirectional, so that
channel sectorization is designed to improve signal reception quality and
limit geographical area covered to the requesting subscriber. The chosen
sectorization scheme represents a single sectorized antenna that will
support all the service classes depicted by the three representational
graphical discs 701, 702 and 703.
The channels depicted on disk 702 are normally dedicated to interactive
video services and include three sectors each of which includes three
channels. It is apparent that the minimum increment of channels that can
be transferred between the interactive broadcast video disc 701 and the
interactive video-on-demand disc 702 is three channels total. The first
and second discs 701 and 702 are one way broadcast only signals from the
intelligent micro port to the access antenna of the end user.
The third disk 703 depicts the collection of ISDN, voice and data services
with four channels, paired to support duplex operations (e.g. two pairs
related to each of the three sectors). The transfer increment between disk
702 and 703 is two channels per sector. All the channels on the discs 702
and 703 in the original set up are different in frequency from one
another. The transfer increment between the first disk 701 and the third
disc 703 is six channels total.
Intelligence for executing this transfer of channels preferably (though not
necessarily) appears at the intelligent microport at the network access
point. For example, a change of application of channels from disk 701 to
disk 703 would require a minimum of six channels total to be transferred
from disk 701 to the application defined by disk 703. These channels would
be filled to accommodate the new application, conduit by conduit, until
the recipient channels were filled. Then additional channels (if
available) would be transferred to the service requiring additional
capacity.
Efficient Packing of Spectrum Into Slots For Selective Assignment
The graph in FIG. 8 depicts a frequency spectrum divided into channels and
conduits. A band of frequency which in this particular example is chosen
to be 198 MHz and is shown divided into a number of contiguous frequency
channels 801-1 to 801-N. One of the channels 801-X is shown in an exploded
view to comprise several conduits 802-1 to 802-M which are smaller
frequency bands dividing a channel. The frequency band of each channel 801
in the illustrative embodiment is either six or ten MHz. Since the
bandwidth demands of different services vary, conduits may be dynamically
altered in size (i.e., bandwidth) to match the requirements of the various
services they support. In some instances a single conduit will suffice
whereas in others several conduits may be assigned to a service. The
optimum number of conduits assigned to a service is determined by the
demand for that service.
Each channel is assigned to a specific service class at any given time.
Services within a service class can share access to the channels assigned
to that service class (i.e., use any of the conduits of that channel) on
an unprovisioned (i.e., not preallocated) dynamic basis. In the allocation
scheme a channel is comprised of several conduits and a conduit is the
physical or logical partitioning of a channel. A conduit is the basic unit
to provide service to any service class. In the IVOD and IBV service
classes, the wireless modulation schema is TDM time slots corresponding to
a physical partitioning of spectrum. For narrowband service classes, CDMA
is the wireless modulation schema in which individual conduits are in
effect logical parts of the overall channel. In each instance, a service
assignment is handled by conduits wherein each conduit is assigned to
serving a user of a program.
Optimizing Assignment Based on Program Content Requirements
A division of spectrum of channels into high (921-1, 921-2, 92 1-H), medium
(911-1, 911-2, 911-M) and low (901-1, 901-2, 901-L) bit rate applications
for video services is illustrated in the FIG. 9. The video content is
encoded using the emerging MPEG (motion picture expert group) II standard,
that operates over a broad range of encoding rates (aproximately 1.544-9
Mbps). Different program content is encoded optimally at different rates
(e.g., movies at lower rates, sports at higher rates). Decoding MPEG II
sources at variables rates is automatically handled in the MPEG II
standard. Some channels are allocated for lower rate encoding, some for
medium rate encoding and some for higher rate encoding. The number of
channels assigned to each of these program types is based on the program
mix required at that time. Such allocations can be preset for static
allocation based on time of day and day of week or for dynamic allocation
on a real time basis as program content changes are required without prior
arrangement. Video programs may be groomed (i.e., channeled) to
appropriate channels based on bandwidth requirements. As video programs
are reassigned to different channels and conduits (i.e. channel x and
conduit y) that information is conveyed to the access director by the IMP.
In one illustrative embodiment it is conveyed as a mapping table.
Within a bit rate video service type, programs are encoded at variable
rates (within a narrow range around the base average rate specified for
the channel based on the program content requirements (e.g., based on the
amount of motion in the video picture) in a manner that balances bit rate
assignments across all the programs within that channel (e.g., in the 3
Mbps video channel type, one program may be given 2.7 Mbps and another one
3.3 Mbps at one time, and perhaps reversed later, keeping the average
across programs to 3 Mbps at all times). To facilitate such an approach, a
packetized scheme (i.e., ATM or another packet arrangement) is used
because of its inherent bandwidth on demand capability.
The benefit of assigning programs in this manner i.e., higher rates for
some programs and simultaneously lower rates for others by both techniques
described here, viz; by grooming techniques according to encoding rate
requirements and variable rate coding within the same encoding rate
levels, is that this ensures a uniform and a more manageable program
quality across the channels while simultaneously maximizing utilization of
spectrum across the channels.
Definitions of Terms
The following definitions define terms used in the above specification:
Channel: A block of continuous spectrum assigned to a particular class of
service. A channel is comprised of a plurality of conduits.
Conduit: Subportion of a channel assigned to a single user or program, for
one direction of a duplex communication. More than one conduit may be
combined to provide a wider band unidirectional transmission.
Sub-Channel A set of channels assigned to video services belonging to a
particular rate of encoding (i.e., low, medium and high).
Interactive Broadcast Video (IBV) (TDM): This service is comprised of two
parts: 1. Scheduled video content provided on a broadband (i.e., 1.5 Mbps
to 6 Mbps) broadcast downlink basis potentially to all users 2. A
narrowband uplink signal (<2.4 Kbps, via wireless data signaling or ISDN D
channel) for service re | | |
