U.S. patent application number 09/195315 was filed with the patent office on 2001-11-22 for apparatus and methods for assigning spectral and non-spectral resource charges in wireless communications systems.
Invention is credited to IRVIN, DAVID R., KHAYRALLAH, ALI S..
Application Number | 20010044294 09/195315 |
Document ID | / |
Family ID | 22720936 |
Filed Date | 2001-11-22 |
United States Patent
Application |
20010044294 |
Kind Code |
A1 |
KHAYRALLAH, ALI S. ; et
al. |
November 22, 2001 |
APPARATUS AND METHODS FOR ASSIGNING SPECTRAL AND NON-SPECTRAL
RESOURCE CHARGES IN WIRELESS COMMUNICATIONS SYSTEMS
Abstract
Charge for communication of a message in a wireless
communications system is assigned commensurate with the spectral
and non-spectral resource demand associated with the service used
to communicate the message. A service may be identified from a
plurality of services in response to a user request to communicate
a message, for example, and charge for the communication of the
message assigned to the user based on the service identified.
According to another aspect, the system may first determine whether
sufficient system resources are available to communicate the
message using the selected service. According to another aspect,
the system may first determine whether the user is authorized to
communicate the message using the selected service.
Inventors: |
KHAYRALLAH, ALI S.; (APEX,
NC) ; IRVIN, DAVID R.; (RALEIGH, NC) |
Correspondence
Address: |
MYERS BIGEL SIBLEY & SAJOVEC
PO BOX 37428
RALEIGH
NC
27627
US
|
Family ID: |
22720936 |
Appl. No.: |
09/195315 |
Filed: |
November 18, 1998 |
Current U.S.
Class: |
455/406 |
Current CPC
Class: |
H04M 15/745 20130101;
H04M 15/8044 20130101; H04M 15/8033 20130101; H04M 15/8016
20130101; H04M 15/49 20130101; H04M 2215/0168 20130101; H04W 4/24
20130101; H04M 2215/0108 20130101; H04M 2215/46 20130101; H04M
2215/7414 20130101; H04M 2215/745 20130101; H04M 2215/32 20130101;
H04W 12/08 20130101; H04M 2215/42 20130101; H04M 15/00 20130101;
H04M 2215/7435 20130101 |
Class at
Publication: |
455/406 |
International
Class: |
H04M 011/00 |
Claims
That which is claimed is:
1. In a wireless communications system, a method of operating
comprising the steps of: identifying a service of a plurality of
services offered by the wireless communications system, a
respective one of the plurality of services having a respective
spectral demand and a respective non-spectral demand associated
therewith; communicating a message according to the identified
service; and assigning a charge for communication of the message
according to the identified service commensurate with at least one
of the spectral demand and the non-spectral demand associated
therewith.
2. A method according to claim 1, wherein said step of
communicating is preceded by the step of determining if system
resources sufficient to meet the spectral demand and the
non-spectral demand associated with the identified service are
present, and wherein said step of communicating comprises the step
of communicating a message according to the identified service if
sufficient system resources are present.
3. A method according to claim 1, wherein said step of identifying
comprises the step of identifying a service in response to a user
request to communicate a message.
4. A method according to claim 3, wherein said step of identifying
comprises the step of identifying a predetermined service
associated with an intended recipient of the message.
5. A method according to claim 1, wherein said step of identifying
comprises the step of identifying a service in response to a user
request for the identified service.
6. A method according to claim 5, wherein said step of
communicating comprises the step of communicating a message
according to the identified service if use of the identified
service is authorized.
7. A method according to claim 1, wherein the plurality of services
comprises a first service having a first spectral demand associated
therewith and a second service having a second spectral demand
associated therewith, wherein the second spectral demand is greater
than the first spectral demand.
8. A method according to claim 1, wherein the plurality of services
comprises a first service having a first non-spectral demand
associated therewith and a second service having a second
non-spectral demand associated therewith, wherein the second
non-spectral demand is greater than the first non-spectral
demand.
9. A method according to claim 8, wherein the first service
provides a first redundancy level and wherein the second service
provides a second redundancy level greater than the first
redundancy level.
10. A method according to claim 8, wherein the first service has
first transmit power level associated therewith and wherein the
second service has a second transmit power level associated
therewith, the second transmit power level greater than the first
transmit power level.
11. A method according to claim 1, wherein said step of assigning a
charge is preceded by the step of identifying a tariff associated
with the identified service, and wherein said step of assigning a
charge comprises the step of assigning a charge for communication
of the message according to the identified tariff.
12. A method according to claim 1, wherein said step of assigning a
charge comprises the step of assigning a charge to one of a source
of the communicated message and a recipient of the communicated
message.
13. In a wireless communications system, a method of operating
comprising the steps of: identifying a service of a plurality of
services offered by the wireless communications system, a
respective one of the plurality of services providing a respective
redundancy level; communicating a message according to the
identified service; and assigning a charge for communication of the
message according to the identified service commensurate with the
redundancy level provided thereby.
14. A method according to claim 13, wherein said step of
communicating is preceded by the step of determining if system
resources sufficient to meet a system resource demand associated
with the identified service are present, and wherein said step of
communicating comprises the step of communicating a message
according to the identified service if sufficient system resources
are present.
15. A method according to claim 13, wherein said step of assigning
a charge is preceded by the step of identifying a tariff associated
with the identified service, and wherein said step of assigning a
charge comprises the step of assigning a charge for communication
of the message according to the identified tariff.
16. In a wireless communications system, an apparatus comprising:
means for identifying a service of a plurality of services offered
by the wireless communications system, a respective one of the
plurality of services having a respective spectral demand and a
respective non-spectral demand associated therewith; means,
responsive to said means for identifying, for communicating a
message according to the identified service; and means, responsive
to said means for communicating, for assigning a charge for
communication of the message according to the identified service
commensurate with at least one of the spectral demand and the
non-spectral demand associated therewith.
17. An apparatus according to claim 16, further comprising means
for determining if system resources sufficient to meet the spectral
demand and the non-spectral demand associated with the identified
service are present, and wherein said means for communicating
comprises means for communicating a message according to the
identified service if sufficient system resources are present.
18. An apparatus according to claim 16, wherein said means for
identifying comprises means for identifying a service in response
to a user request to communicate a message.
19. An apparatus according to claim 18, wherein said means for
identifying comprises means for identifying a predetermined service
associated with an intended recipient of the message.
20. An apparatus according to claim 16, wherein said means for
identifying comprises means for identifying a service in response
to a user request for the identified service.
21. An apparatus according to claim 20, wherein said means for
communicating comprises means for communicating a message according
to the identified service if use of the identified service is
authorized.
22. An apparatus according to claim 16, wherein the plurality of
services comprises a first service having a first spectral demand
associated therewith and a second service having a second spectral
demand associated therewith, wherein the second spectral demand is
greater than the first spectral demand.
23. An apparatus according to claim 16, wherein the plurality of
services comprises a first service having a first non-spectral
demand associated therewith and a second service having a second
non-spectral demand associated therewith, wherein the second
non-spectral demand is greater than the first non-spectral
demand.
24. An apparatus according to claim 23, wherein the first service
provides a first redundancy level and wherein the second service
provides a second redundancy level greater than the first
redundancy level.
25. An apparatus according to claim 23, wherein the first service
has first transmit power level associated therewith and wherein the
second service has a second transmit power level associated
therewith, the second transmit power level greater than the first
transmit power level.
26. An apparatus according to claim 16, further comprising means
for identifying a tariff associated with the identified service,
and wherein said means for assigning a charge comprises means for
assigning a charge for communication of the message according to
the identified tariff.
27. An apparatus according to claim 16, wherein said means for
assigning a charge comprises means for assigning a charge to one of
a source of the communicated message and a recipient of the
communicated message.
28. In a wireless communications system, an apparatus comprising:
means for identifying a service of the plurality of services
offered by the wireless communications system, a respective one of
the plurality of services providing a respective redundancy level;
means, responsive to said means for identifying, for communicating
a message according to the identified service; and means,
responsive to said means for communicating, for assigning a charge
for communication of the message according to the identified
service commensurate with the redundancy level provided
thereby.
29. An apparatus according to claim 28, further comprising means
for determining if system resources sufficient to meet a system
resource demand associated with the identified service are present,
and wherein said means for communicating comprises means for
communicating a message according to the identified service if
sufficient system resources are present.
30. An apparatus according to claim 28, further comprising means
for identifying a tariff associated with the identified service,
and wherein said means for assigning a charge comprises means for
assigning a charge for communication of the message according to
the identified tariff.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to communications systems and
methods, and more particularly, to wireless communications systems
and methods.
BACKGROUND OF THE INVENTION
[0002] Wireless communications systems are commonly employed to
provide voice and data communications to subscribers. For example,
analog cellular radiotelephone systems, such as those designated
AMPS, ETACS, NMT-450, and NMT-900, have been long been deployed
successfully throughout the world. Digital cellular radiotelephone
systems such as those conforming to the North American standard
IS-54 and the European standard GSM have been in service since the
early 1990's. More recently, a wide variety of wireless digital
services broadly labeled as PCS (Personal Communications Services)
have been introduced, including advanced digital cellular systems
conforming to standards such as IS-136 and IS-95, lower-power
systems such as DECT (Digital Enhanced Cordless Telephone) and data
communications services such as CDPD (Cellular Digital Packet
Data). These and other systems are described in The Mobile
Communications Handbook, edited by Gibson and published by CRC
Press (1996).
[0003] FIG. 1 illustrates a typical terrestrial cellular
radiotelephone communication system 20. The cellular radiotelephone
system 20 may include one or more radiotelephones (terminals) 22,
communicating with a plurality of cells 24 served by base stations
26 and a mobile telephone switching office (MTSO) 28. Although only
three cells 24 are shown in FIG. 1, a typical cellular network may
include hundreds of cells, may include more than one MTSO, and may
serve thousands of radiotelephones.
[0004] The cells 24 generally serve as nodes in the communication
system 20, from which links are established between radiotelephones
22 and the MTSO 28, by way of the base stations 26 serving the
cells 24. Each cell 24 will have allocated to it one or more
dedicated control channels and one or more traffic channels. A
control channel is a dedicated channel used for transmitting cell
identification and paging information. The traffic channels carry
the voice and data information. Through the cellular network 20, a
duplex radio communication link may be effected between two mobile
terminals 22 or between a mobile terminal 22 and a landline
telephone user 32 through a public switched telephone network
(PSTN) 34. The function of a base station 26 is to handle radio
communication between a cell 24 and mobile terminals 22. In this
capacity, a base station 26 functions as a relay station for data
and voice signals.
[0005] As illustrated in FIG. 2, a satellite 42 may be employed to
perform similar functions to those performed by a conventional
terrestrial base station, for example, to serve areas in which
population is sparsely distributed or which have rugged topography
that tends to make conventional landline telephone or terrestrial
cellular telephone infrastructure technically or economically
impractical. A satellite radiotelephone system 40 typically
includes one or more satellites 42 that serve as relays or
transponders between one or more earth stations 44 and terminals
23. The satellite conveys radiotelephone communications over duplex
links 46 to terminals 23 and an earth station 44. The earth station
44 may in turn be connected to a public switched telephone network
34, allowing communications between satellite radiotelephones, and
communications between satellite radio telephones and conventional
terrestrial cellular radiotelephones or landline telephones. The
satellite radiotelephone system 40 may utilize a single antenna
beam covering the entire area served by the system, or, as shown,
the satellite may be designed such that it produces multiple
minimally-overlapping beams 48, each serving distinct geographical
coverage areas 50 in the system's service region. The coverage
areas 50 serve a similar function to the cells 24 of the
terrestrial cellular system 20 of FIG. 1.
[0006] Traditional analog cellular systems generally employ a
system referred to as frequency division multiple access (FDMA) to
create communications channels. As a practical matter well known to
those skilled in the art, radiotelephone communications signals,
being modulated waveforms, typically are communicated over
predetermined frequency bands in a spectrum of carrier frequencies.
In a typical FDMA system, each of these discrete frequency bands
serves as a channel over which cellular radiotelephones communicate
with a cell, through the base station or satellite serving the
cell.
[0007] The limitations on the available frequency spectrum presents
several challenges as the number of subscribers increases.
Increasing the number of subscribers in a cellular radiotelephone
system requires more efficient utilization of the limited available
frequency spectrum in order to provide more total channels while
maintaining communications quality. This challenge is heightened
because subscribers may not be uniformly distributed among cells in
the system. More channels may be needed for particular cells to
handle potentially higher local subscriber densities at any given
time. For example, a cell in an urban area might conceivably
contain hundreds or thousands of subscribers at any one time,
easily exhausting the number of channels available in the cell.
[0008] For these reasons, conventional cellular systems employ
frequency reuse to increase potential channel capacity in each cell
and increase spectral efficiency. Frequency reuse involves
allocating frequency bands to each cell, with cells employing the
same frequencies geographically separated to allow radiotelephones
in different cells to simultaneously use the same frequency without
interfering with each other. By so doing, many thousands of
subscribers may be served by a system of only several hundred
frequency bands.
[0009] Another technique which can further increase channel
capacity and spectral efficiency is the use of time division
multiple access (TDMA). A TDMA system may be implemented by
subdividing the frequency bands employed in conventional FDMA
systems into sequential time slots. Communication over a frequency
band typically occur on a repetitive TDMA frame structure that
includes a plurality of time slots. Examples of systems employing
TDMA are those conforming to the dual analog/digital IS-54B
standard employed in the United States, in which each of the
frequency bands of the traditional analog cellular spectrum are
subdivided into 3 time slots, and systems conforming to the GSM
standard, which divides each of a plurality of frequency bands into
8 time slots. In these TDMA systems, each user communicates with
the base station using bursts of digital data transmitted during
the user's assigned time slots.
[0010] A channel in a TDMA system typically includes at least one
time slot on at least one frequency band. As discussed above,
channels are used to communicate voice, data or other information
between users, for example, between a radiotelephone and a landline
telephone. Channels may be assigned to predetermined slots of
predetermined frequency bands, as in the case of dedicated control
channels. Included in the typical set of dedicated control channels
transmitted in a cell are forward control channels which are used
to broadcast control information in a cell of the radiotelephone
system to radiotelephones which may seek to access the system. The
control information broadcast on a forward control channel may
include such things as the cell's identification, an associated
network identification, system timing information and other
information needed to access the radiotelephone system from a
radiotelephone.
[0011] Channels in a TDMA system may also be dynamically assigned
by the system when and where needed. In addition, some systems,
such as those conforming to the GSM standard, "frequency hop"
traffic channels, i.e., change the frequency band on which a
particular traffic channel is transmitted on a frame-by-frame
basis. Frequency hopping can reduce the probability of interference
events between channels, by reducing the likelihood that the same
two stations will use the same frequency at the same time. This can
help provide for communications quality related to average instead
of worst case interference.
[0012] Instead of or in addition to FDMA and TDMA techniques,
wireless communications systems may employ Code Division Multiple
Access (CDMA) or "spread spectrum" techniques. In a CDMA system, a
channel is defined by modulating a data-modulated carrier signal by
a unique spreading code, i.e., a code that spreads an original
data-modulated carrier over a wide portion of the frequency
spectrum in which the communications system operates. The
transmitted signal is demodulated by a receiver unit using the same
spreading code using signal correlation techniques. Because the
transmitted signal is spread across a wide bandwidth, CDMA
communications can be less vulnerable to coherent noise sources
which might "jam" other communications signals. The use of the
unique spreading code allows several channels to effectively share
the same bandwidth.
[0013] The quality of service provided by a wireless communications
systems such as cellular systems is subject to environmental
effects. For example, a cellular radiotelephone call placed under
system operating parameters designed to produce an acceptable level
of communications quality under a set of nominal environmental
conditions can be disrupted by fading, shadowing by intervening
objects such as hills, and attenuation by distance and by
structures such as buildings. Such environmental factors can result
in service outages.
[0014] An example of such a service disruption occurs when a mobile
radiotelephone enters an outage region of a cellular radiotelephone
system. Such a region might include a hole in cellular coverage
between cells, or an area of degraded reception or transmission
within a cell, such as the interior of a building or a tunnel. When
the mobile radiotelephone enters such a disadvantaged location, it
may be unable to continue a call in progress, to receive
notification of an incoming call, or to place an outgoing call.
[0015] A wireless communications system can be designed to reduce
service disruptions in many ways. Improved service to subscriber
units in disadvantaged locations can be achieved by providing a
selective high-power paging system that can contact such units of
an incoming call. In such a system, a base station sends a paging
message to a disadvantaged unit over a specially-designated high
power channel. The paged unit can then moved to a less
disadvantaged location in order to answer the page.
[0016] Conventional system operating techniques may fail to
accurately apportion costs associated with particular services.
Each user is typically billed according to minutes of use, which
can result in a cross subsidy flowing to users of specialized
service that may require increase bandwidth, transmit power, or
system infrastructure.
SUMMARY OF THE INVENTION
[0017] In light of the foregoing, it is an object of the present
invention to provide wireless communications systems and methods
that more accurately apportion system usage costs across a
subscriber base.
[0018] This and other objects, features and advantages are provided
according to the present invention by wireless communications
apparatus and methods in which charge for the communication of a
message in a wireless communications system is assigned
commensurate with the spectral and non-spectral resource demand
associated with the service used to communicate the message. A
service may be identified from a plurality of services in response
to a user request to communicate a message, for example, and charge
for the communication of the message assigned to the user based on
the service identified. According to another aspect of the present
invention, the system may first determine whether sufficient system
resources are available to communicate the message using the
selected service. According to another aspect of the present
invention, the system may first determine whether the user is
authorized to communicate the message using the selected
service.
[0019] Apparatus and methods according to the present invention can
provide a more accurate and equitable apportionment of operating
costs. By tying tariffs to the type of service used to communicate
a message, both directly measurable cost indices such as power
usage and bandwidth usage can be commensurately billed, as well as
indirect costs attributable to the more complex and expensive
equipment need to provide certain types of premium or robust
services.
[0020] In particular, according to the present invention, a service
of a plurality of services offered by a wireless communications
system is identified, for example, in response to a user request. A
respective one of the plurality of services has a respective
spectral demand and a respective non-spectral demand associated
therewith, for example, "normal" services, "robust" services which
provide increased redundancy at the same level of spectral resource
use as the "normal" services but with increased non-spectral
resource demand, and "premium" services which provide increased
power or bandwidth with commensurate increased spectral demand. A
message is communicated according to the identified service. A
charge for communication of the message is assigned according to
the identified service commensurate with at least one of the
spectral demand and the non-spectral demand associated
therewith.
[0021] According to an aspect of the present invention, prior to
communication of the message, a determination is made if system
resources sufficient to meet the spectral demand and the
non-spectral demand associated with the identified service are
present. The message is communicated according to the identified
service if sufficient system resources are present. According to
another aspect, the message is communicated according to the
identified service based on a prior determination if use of the
service is authorized. According to yet another aspect, assignment
of a charge is preceded by the step of identifying a tariff
associated with the identified service. A charge for the
communication is then assigned according to the identified
tariff.
[0022] In an embodiment of the present invention, an apparatus is
provided in a wireless communications system, the apparatus
including means for identifying a service of a plurality of
services offered by the wireless communications system, a
respective one of the plurality of services having a respective
spectral demand and a respective non-spectral demand associated
therewith. Means are provided, responsive to said means for
identifying, communicate a message according to the identified
service. Means are also provided, responsive to said means for
communicating, for assigning a charge for communication of the
message according to the identified service commensurate with at
least one of the spectral demand and the non-spectral demand
associated therewith. Improved apportionment of communications
charges may thereby be provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 illustrates a conventional terrestrial cellular
radiotelephone communications system.
[0024] FIG. 2 illustrates a conventional satellite-based cellular
radiotelephone communications system.
[0025] FIG. 3 illustrates a structure for an IS-136 Digital Control
Channel (DCCH).
[0026] FIG. 4 illustrates a protocol stack for generating an IS-136
DCCH.
[0027] FIGS. 5A-B illustrate respective transmitter and receiver
structures for an IS-136 system.
[0028] FIGS. 6A-B illustrate exemplary transmitting unit and
receiving unit structures for a multi-service wireless
communications system.
[0029] FIG. 7 illustrates an exemplary protocol stack for
generating high penetration messages.
[0030] FIG. 8 illustrates an exemplary frame structure for a high
penetration messaging channel.
[0031] FIGS. 9A-B illustrate exemplary transmitting unit and
receiving unit structures for a multi-service wireless
communications system
[0032] FIG. 10 illustrates exemplary operations for communicating
messages over one of a normal communications channel and a
high-penetration communications channel.
[0033] FIG. 11 illustrates exemplary operations for assigning
communications charges according to aspects of the present
invention.
DETAILED DESCRIPTION OF EMBODIMENTS
[0034] The present invention now will be described more fully
hereinafter with reference to the accompanying drawings, in which
embodiments of the invention are shown. This invention may,
however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein; rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
invention to those skilled in the art. Like numbers refer to like
elements throughout.
[0035] The present invention relates to communication over channels
in wireless communications systems such as cellular radiotelephone
systems. As those skilled in the art will appreciate, terms such as
"channel" are not always consistently used in the literature; for
example, the IEEE Standard Dictionary of Electrical Terms defines a
"channel" as both a communications path and a band of frequencies.
In a conventional FDMA system, for example, a "channel" may refer
or corresponds to a "physical" channel comprising a band of
frequencies occupied by a modulated carrier. In a TDMA system such
as GSM, a physical channel may comprise a group of time slots on
one or more frequency bands, for example, the periodic time slots
on particular frequency bands that are allocated to the so-called
"common channels." In some contexts, a channel may be a "logical
channel" defined by an addressing or field assignment scheme that
may have no particular correlation to the frequency or time of
transmission. For purposes of the present application, "channel"
refers to a communications path defined in a communications
interface such as the air interface of a wireless communications
system, whether it be an actual physical channel comprising a
frequency band, a time slice thereof, or the like, or a logical
channel carried by such a physical channel.
[0036] "Frequency band" as used herein refers to a frequency range
over which a communications signal, e.g., a modulated carrier
signal, is distributed. This band may be, but need not necessarily
be, centered about a central carrier frequency. Those skilled in
the art will appreciate that the carrier frequency bands described
herein need not be non-overlapping or contiguous; for example,
modulated carriers typically may overlap in their spectral
distributions without producing unacceptable levels of
interference. In fact, in some systems the overlap may be
sizable.
[0037] The embodiments discussed herein relate to a wireless
communications system in which "short messages," e.g., alphanumeric
messages such as those conforming to standards such a GSM or
IS-136, are transmitted on at least one of a "normal"
communications channel having a first channel coding that produces
a first redundancy level or a "high penetration" communications
channel having a second channel coding that produces a second
redundancy level that is greater than the first redundancy level.
In this manner, a system with "regular" and "robust" service
capabilities can be implemented.
[0038] Those skilled in the art will appreciate, however, that the
apparatus and methods of the present invention are also applicable
to wireless communications systems that provide other types of
"premium" services, such as services using high-power and/or
high-bandwidth channels for increase fidelity and/or reliability.
In general, these robust and premium services can be used for the
communication of short messages, control messages, voice and/or
data.
[0039] An Exemplary Wireless Communications System with a Robust
High-Penetration Messaging Capability
[0040] The following discussion describes exemplary wireless
communications systems with both "standard," "robust," and
"premium" service capabilities. Examples of such systems include
wireless communication systems that provide for robust service
using higher-redundancy alternative channels as described, for
example, in related U.S. patent applications entitled "Wireless
Communications Systems with Standard and Robust Services and
Methods of Operation Therefor," and "Apparatus and Methods for
Providing High-Penetration Messaging in Wireless Communications
Systems," both of which are assigned to the assignee of the present
invention, filed concurrently herewith and incorporated by
reference herein as if the text is physically present. Exemplary
wireless communication systems that provide both standard services
and high-power premium services are described in a U.S. patent
application Ser. No. 08/719,282, filed Sep. 24, 1996, assigned to
the assignee of the present invention, and incorporated herein by
reference in its entirety as if the text is physically present.
[0041] The embodiments described hereafter relate to wireless
communications systems in which messages may be communicated over a
standard messaging channel, e.g., the standard short message
service provided via the Digital Control Channel (DCCH) specified
in the IS-136 standard, or over a high-penetration messaging
channel that uses substantially the same bandwidth but provides
higher redundancy through increased block coding. These embodiments
are described illustrate an exemplary environment in which the
apparatus and methods of the present invention may be practiced.
Those skilled in the art will appreciate that other types of
multi-service capable wireless communications systems may also be
used with the present invention, such as systems offering either
standard and "premium" services as described above, or systems
offering a combination of standard, robust and premium
services.
[0042] In a wireless communications system conforming to the IS-136
standard, short messages are communicated over a Digital Control
Channel (DCCH). FIG. 3 illustrates an IS-136 Digital Control
Channel DCCH configuration. The Digital Control Channel DCCH is a
"physical channel," that is, an actual portion of a signal
propagation resource defined in terms of frequency and time
divisions. Several "logical" channels are mapped onto the Digital
Control Channel DCCH. These logical channels include a multiplexed
Broadcast Channel BCCH designed to convey information about system
configuration and system access rules, and a multiplexed
point-to-point short message service (SMS), paging and access
response channel SPACH.
[0043] The Broadcast Channel BCCH is further divided into logical
channels. These logical channels include a Fast Broadcast Channel
(F-BCCH) F for conveying time-critical information such as system
identification (ID) and registration information, an Extended
Broadcast Channel (E-BCCH) E for conveying less time critical
information such as neighboring cell lists, and an SMS Broadcast
Channel (SMS-BCCH) S. The combined SMS, paging and access response
channel SPACH comprises a short message service channel (SMSCH) for
carrying messages, a paging channel (PCH) for conveying system
pages, and an access response channel (ARCH) for providing system
response to queries from subscriber units and other administration
information.
[0044] The slots of each Digital Control Channel DCCH frame start
with F-BCCH slots F, followed by E-BCCH slots E, S-BCCH slots S and
then the SMS, paging and access slots SPACH. The number of each
type of slot in each frame is determined by system setup. As
illustrated, each slot 310 of the Digital Control Channel DCCH
includes 28 synchronization bits SYNC, 12 Shared Channel Feedback
bits SCF bits for supporting a Random Access Channel (RACH), 260
data bits Data, 12 Coded Super Frame Phase bits CSFP for detecting
the phase of the Super Frame, and 2 reserved bits RSVD.
[0045] A DCCH Super Frame (SF) includes 32 Digital Control Channel
DCCH frames. When a subscriber unit such as a mobile radiotelephone
first is turned on, the unit's receiver electronics search for a
DCCH by reading the CSFP; if the CFSP is changing, the mobile unit
has acquired the DCCH. From the CSFP the mobile unit can determine
which slot is the first slot in the Super Frame, which allows the
unit to then read the F-BCCH. The F-BCCH conveys information
regarding the number of F-BCCH, E-BCCH and S-BCCH slots are present
in the Super Frame. The mobile unit receives paging group
information on the E-BCCH. Once this information is received, the
mobile can determine which SPACH slot carries paging and SMS
information directed to it. The mobile unit then reads the
identified slot once per Super Frame to monitor for the presence of
an incoming page or a short message. This periodic reading allows
for the creation of a sleep mode cycle, i.e., the mobile can
conserve power during times when it is not required to be actively
monitoring for the arrival of a page or short message during its
assigned slot.
[0046] A Hyper Frame includes two Super Frames, with the second
Super Frame of a Hyper Frame being a repeat of the first Super
Frame. If a subscriber unit is unable to read its slot in the SPACH
in the first Super Frame of a Hyper Frame, it can attempt to read
it again during the second Super Frame. If the subscriber unit is
able to read its assigned SPACH slot in the first Super Frame,
however, it can skip reading the second Super Frame.
[0047] FIG. 4 illustrates a protocol stack 400 for generating a
DCCH. A Data Link Layer (Layer 2) frame 410 includes a 7-bit
header, 102 message bits, a 16-bit cyclic redundancy check (CRC)
value, and 5 tail bits that are used for convolutional coding. The
130 bits of a Data Link Layer frame 410 are encoded according to a
rate 1/2 convolutional code and then interleaved to produce 260
bits, which are then formatted and supplement to form a Physical
Layer (Layer 1) slot 310. The Data Link Layer frame 410 is
generated from a Message Layer (Layer 3) message 420 that includes
a 2-bit protocol discriminator (PD) field and a 6-bit message type
(MT) field.
[0048] The information in the Message Layer message 420 can be of
variable length, depending on the particular message being sent. If
the information in a given Message Layer message extends beyond 102
bits, multiple Data Link Layer frames 410 are used to transmit the
Message Layer message 420. Accordingly, information in a Message
Layer message 420 may be transmitted using a number of Physical
Layer slots 310. When information in a Message Layer message
extends beyond 102 bits, the message is typically transmitted using
every other SPACH slot, with a bit in the header of each Data Link
Layer frame 410 being set to a predetermined value to tell units in
the particular paging group to look at every other SPACH slot for
paging or SMS messages. In this manner, messages can be efficiently
transmitted while reducing paging delays to units in other paging
groups.
[0049] FIGS. 5A and 5B illustrate an exemplary transmitter
structure 510 and an exemplary receiver structure 550,
respectively, for communicating messages under a conventional
standard such as IS-136. Referring to FIG. 5A, a Data Link Layer
frame 410 is convolutionally encoded by convolutional coding means
511, with the convolutionally encoded bit stream then being
interleaved by interleaving means 512. The encoded and interleaved
bits are then modulated by modulating means 513, e.g, a
.pi./4-DQPSK modulator. The output of the modulator 513 is then
passed on to transmitting means 514 which transmits a corresponding
radio communications signal 515.
[0050] Referring to FIG. 5B, the radio communications signal 515 is
then received and coherently demodulated by coherent demodulating
means 551 to produce a demodulated signal. The demodulated signal
is then de-interleaved by de-interleaving means 552 and decoded by
Viterbi decoding means 553 to produce a Data Link Layer frame 410'
that represents an estimate of the originally transmitted Data Link
Layer frame 410.
[0051] As illustrated by FIGS. 6A-10, a "high-penetration"
messaging service is provided in addition to a conventional
messaging service such as that described above to allow
communication with a subscriber unit when it is in a disadvantaged
location, such as location falling between normal cell coverage
regions or a location inside a building or other structure. The
high penetration messaging service is provided by using a separate
high-penetration channel that utilizes substantially the same
transmission rate and power, and thus the substantially the same
amount of spectral resource, as the normal messaging channel. The
high-penetration channel, however, uses additional coding to
provide higher redundancy and which allows the use of non-coherent
detection techniques. The additional coding also preferably allows
the use of common transmitter elements and receiver elements for
both the normal messaging channel and the high-penetration
channel.
[0052] For example, as illustrated in FIGS. 6A and 6B, the
additional coding may comprise an additional Walsh-Hadamard or
other orthogonal or quasi-orthogonal code that introduces
additional redundancy. An exemplary transmitting unit 610 includes
convolutional coding means 511 and interleaving means 512. In a
normal messaging channel 520, the interleaved and convolutionally
encoded signal produced by the interleaving means 512 is supplied
directly to a modulating means 513, e.g., a .pi./4-DQPSK modulator,
for transmission by transmitting means 514. In a high-penetration
channel 620, the interleaved and convolutionally encoded signal is
additionally encoded by additional coding means 611, e.g., an
encoder implementing a Walsh-Hadamard or other orthogonal or
quasi-orthogonal code. The additionally encoded signal is mapped by
mapping means 612 to produce a sequence that constrains the signal
mapping of the modulating means 513 into a signal subset that
produces a radio communications signal 515 that is amenable to
non-coherent demodulation. An example of such a mapping is a bit
repetition mapping that maps 4-level .pi./4-DQPSK modulation into a
binary .pi./4-DBPSK modulation scheme, as described in a U.S.
patent application entitled "High-Performance Half-Rate Coding
Apparatus and Method for a TDM System," assigned to the assignee of
the present application, filed Oct. 16, 1998, and incorporated by
reference herein in its entirety as if the text is physically
present.
[0053] As illustrated in FIG. 6B, a receiving unit 650 for
receiving both normal and high penetration messages includes a
coherent receiving branch 560 including means 551 for coherently
demodulating a received radio communications signal 515, as well as
a non-coherent receiving branch 660 including a de-rotating means
651 and a non-coherent demodulating means 652, e.g., a detector
that implements a Walsh Hadamard transform. The output of the
either the coherent receiving branch 560 or the non-coherent
receiving branch 660 are then passed on to de-interleaving means
552 for de-interleaving and then to Viterbi decoding means 553 to
recover a Data Link Layer frame 410' that represents an estimate of
the originally transmitted Data Link Layer frame 410.
[0054] The additional coding preferably is an orthogonal or
quasi-orthogonal code such as a Walsh-Hadamard or
Nordstrom-Robinson code. The additional coding helps to raise the
signal to noise ratio when communicating with a unit that is
located in a disadvantaged location. The use of such a code with a
mapping that maps the normal M-ary modulation into a binary
modulation scheme that can be demodulated at the receiving terminal
using non-coherent detection techniques. Coherent and non-coherent
modulation techniques are well known to those skilled in the art.
Several examples of these modulation techniques, as well as a
discussion of Walsh-Hadamard and other codes may be found in
Digital Communications, by Proakis, published by McGraw-Hill
(3.sup.rd ed., 1995).
[0055] The use of noncoherent demodulation can avoid the need to
perform channel estimation and tracking operations associated with
coherent demodulation. Noncoherent demodulation is applied to an
appropriately modulated signal, e.g., a differentially modulated,
orthogonally modulated, quasi-orthogonally modulated, or similar
signal. In a channel with significant delay spread, an appropriate
demodulator is a so-called RAKE receiver, in which a received
signal is correlated with each of the modulating sequences (e.g.,
the orthogonal, quasi-orthogonal, or other sequences used to
produce the modulated signal), with different delays that model the
delay spread of the channel. This and other demodulation techniques
are described in the aforementioned text Digital Communications, by
Proakis.
[0056] Those skilled in the art will appreciate that the components
of the illustrated exemplary transmitting unit 610, i.e., the
convolutional coding means 511, interleaving means 512, modulating
means 513, and transmitting means 514, may comprise conventional
transmission components typically found in base stations, mobile
terminals or other similar communications apparatus. These
components may include, for example, conventional transmitter
circuits, antennas, processing circuits implemented in special
purpose hardware such as an application-specific integrated circuit
(ASIC) or in more general purpose hardware such as a digital signal
processor (DSP), and the like. Similarly, elements of the receiving
unit 650, i.e., the coherent demodulating means 551, de-rotating
means 651, non-coherent demodulating means 652, de-interleaving
means 552, and Viterbi decoding means 553, may comprise
conventional receiving components commonly used in base stations,
mobile terminals and the like. These components may include, for
example, conventional antennas, mixers, signal and other processing
circuits implemented in special purpose hardware such as an
application-specific integrated circuit (ASIC) or in more general
purpose hardware such as a digital signal processor (DSP) or
microprocessor, and the like. Those skilled in the art will
appreciate that, in general, the transmitting unit 610 and the
receiving unit 650 may be implemented using special purpose analog
or digital hardware, software running on general-purpose hardware,
or combinations thereof.
[0057] Those skilled in the art will also appreciate that the
structures of FIGS. 6A and 6B may be implemented in either base
stations or subscriber terminals of a wireless communications
system. For example, the normal and high-penetration messaging
channels may be configured to communicate short messages from a
base station to a subscriber unit, or to convey short message
acknowledgements from a subscriber unit to a base station. More
generally, the normal and high-penetration messaging channels may
be used to provide voice and data messaging in either
direction.
[0058] A protocol stack for implementing a high-penetration channel
in an IS-136 compatible system is illustrated in FIG. 7. A Message
Layer message 420 is formatted into a Data Link Layer frame 410 as
described in reference to FIG. 5. In forming a modified
high-penetration Physical Layer slot 720, however, an additional
coding operation 710, here a (32,5) Walsh-Hadamard coding, is
applied to increase redundancy in transmitting the information in
the Message Layer message 420. The modified Physical Layer slot
310' includes a CDL field and a constant CSFP so that other units
do not mistake the high-penetration slot 310' for a normal DCCH
slot.
[0059] A different Super Frame structure may be used for the
high-penetration messaging channel to enable the receiving unit to
gain synchronization with the transmitting station. Accordingly, as
illustrated in FIG. 8, 4 slots 810 are used for synchronization
bursts in each Super Frame SF. The synchronization slots 810 can be
used for both channel acquisition and fine synchronization. The
synchronization slots 810 may be irregularly spaced throughout the
Super Frame SF so that the receiving unit can identify the first
slot in the Super Frame SF.
[0060] As a result of the increased coding, the information of a
Message Layer message transmitted using a high-penetration channel
is spread out over a larger number of Physical Layer slots than in
a conventional messaging channel. For example, in the modified
IS-136 structure illustrated in FIGS. 7 and 8, a Data Link Layer
frame is requires 13 Physical Layer slots, i.e., a Hyper Frame HF
includes 13 Super Frames SF. This can introduce a delay in
recovering the message in relation to a message transmitted on a
conventional messaging channel, but does not require changing the
sleep mode cycle of the receiving unit, as the unit still can be
constrained to be active for one slot in each Super Frame SF.
[0061] FIGS. 9A and 9B illustrate a general example of a
communications system 900 having normal and high-penetration
messaging capabilities. Referring to FIG. 9A, a transmitting unit
910 includes first and second channel coders 920a, 920b which
receive a message 410 and encode it according to respective first
and second codes having respective first and second coding rates
R1, R2. As illustrated, the second coding rate R2 is less than the
first coding rate R1, e.g., R2=1/4 and R1=1/2, and thus the second
channel coder 920b introduces less redundancy than the first
channel coder 920a. A selected one of the first and second channel
coders 920a, 920b is coupled to a modulator 940, perhaps after
interleaving in an interleaver 930, producing a modulated signal.
The modulated signal is transmitted as a radio communications
signal 515 in a radio communications medium by a transmitter
950.
[0062] Referring to FIG. 9B, in a receiving unit 960, a demodulator
970 demodulates the transmitted signal, producing a demodulated
signal. The demodulated signal is then deinterleaved in a
deinterleaver 980, and passed on to an appropriate one of a first
channel decoder 990a or a second channel decoder 990b, which decode
the deinterleaved signal according to the respective first and
second codes, producing an estimate 410' of the original message
410.
[0063] FIG. 10 illustrates exemplary operations 1000 for
communicating messages using one of a normal messaging channel and
a high-penetration messaging channel. A message is transmitted on
one of normal communications channel or a high-penetration
communications channel (Block 1010). A radio communications signal
is received on one of the normal communications channel or the
high-penetration communications channel (Block 1020). The received
radio communications signal is demodulated using a demodulation
scheme that is selected based on whether the radio communications
signal is received on the normal communications channel or the
high-penetration communications channel (Block 1030).
[0064] Those skilled in the art will appreciate that the operations
of FIG. 10 can be implemented in a number of different ways, and
that specific steps for performing these operations may depend on
the type of message being communicated. For example, broadcast
control messages, e.g., messages containing system identification
and synchronization information, may be concurrently transmitted by
a base station on both a normal communications channel and a
high-penetration communications channel so that subscriber units
can acquire the system using one of the channels. A subscriber unit
attempting to acquire the system might first tune to the normal
channel and, failing to successfully receive the transmitted
control information on that channel, retune to the high-penetration
channel to gain access. Alternatively, in a point-to-point
messaging context, a base station might transmit a message first on
a normal communications channel in an attempt to reach a particular
subscriber unit, and then transmit the message on the
high-penetration communications channel in the event that an
acknowledgement of the message transmitted on the normal channel is
not received within a predetermined time.
[0065] Other variations of the embodiments of FIGS. 6A-10 are
possible. For example, the actual data, e.g., the actual "bits"
sent over the alternative normal and high-penetration channels need
not be identical. As used herein, "message" refers to a quantum of
information content. This content may be represented in a number of
different ways, depending on the channel being used; for instance,
information content contained in a Message Layer message
transmitted over a normal channel may be represented in a
streamlined or compact format on a high-penetration channel to
reduce the negative effects of message delay over the
high-penetration channel. An example of such a technique could
involve sending a set of control information via a logical channel
defined in a normal channel such as an IS-136 DCCH under normal
conditions and, for purposes of simply maintaining contact with a
unit in a disadvantaged location, a smaller subset of the set of
control channel information may be transmitted on a
high-penetration channel.
[0066] Service-Based Charge Assignment
[0067] In broad terms, a wireless communications system such as the
system described above offers a plurality of services, including
"regular" services such as regular DAMPS messaging and "robust"
higher-reliability services such as the high-penetration messaging
described above. Such services may also be combined with other
types of services, such as services that use increased bandwidth
and/or transmit power to improve fidelity and/or other performance
characteristics.
[0068] For purposes of the following discussion, three types of
services are defined. "Standard" or "regular" services include
services normally provided in wireless systems, e.g., standard
voice, data or control channels. "Premium" services include
services that use significantly increased bandwidth and/or transmit
power, such as high-power short messaging systems along the line of
the system described in the aforementioned U.S. patent application
Ser. No. 08/719,282. "Robust" services include services that
utilize substantially the same bandwidth and transmit power as
standard services, but which provide increase reliability through
such mechanisms as the increased coding used in the
high-penetration messaging described above.
[0069] These types of services can be categorized according to both
the spectral demand and non-spectral demand that they place on the
wireless communications system. Spectral demand may include such
things as bandwidth required to operate the service, both in terms
of the frequency band occupied by the signals used to communicate
according to the service and in terms of the bandwidth consumed by
reduced frequency reuse and additional interference associated with
increased transmit power. Non-spectral demand may include
additional hardware, software and operational complexity introduced
by the service that can lead to increased capital equipment and
operational costs, such as the additional encoding and message
delay associated with a robust service such as the high-penetration
messaging service described above.
[0070] Generally speaking, "premium" services such as those
described above tend to have higher associated spectral demand in
comparison to corresponding standard services, while "robust"
services typically have high associated non-spectral demand in
comparison to corresponding standard services. For example, a
high-bandwidth high fidelity voice service generally requires
additional bandwidth that could otherwise could be used for other
channels. A high-power messaging service may have higher associated
spectral demand arising from increased interference caused by
higher transmission power levels. As mentioned above, a high
redundancy service such as the high-penetration messaging service
described above generally requires additional system complexity.
However, those skilled in the art will appreciate that "premium"
services may also have additional associated non-spectral demand in
comparison to corresponding standard services, and "robust"
services may also have additional associated spectral demand in
comparison to corresponding standard services.
[0071] The present invention arises from the realization that both
spectral and non-spectral demand should be accounted for when
apportioning costs to users of a wireless communications system. A
more accurate and equitable apportionment of costs can be achieved
within the context of the operation of the system by associating
different tariffs or price schedules with different services in a
manner such that a charge is assigned to user in a manner that is
commensurate with the actual system resources used.
[0072] As described herein, charges are assigned to a user based on
operational costs associated with the services utilized by the
user. Those skilled in the art will appreciate that as used herein,
"assigning a charge" in a communications system generally
encompasses associating potential revenue of the communications
system with a particular user. Accordingly, "assigning a charge"
may encompass, for example, simply maintaining records, e.g., call
records, that associate a particular user with a portion of the
potential revenue stream of the system. Assigning a charge need not
necessarily encompass the actual "billing" of the user. Those
skilled in the art will also appreciate that charges associated
with use may be expressed in monetary units or in non-monetary
units.
[0073] FIG. 11 is a flowchart illustration of operations 1100 for
communicating and assigning charges in a wireless communications
system according to aspects of the present invention. It will be
understood that blocks of the flowchart illustration, and
combinations of blocks in the flowchart illustration, can be
implemented by computer program instructions which may be loaded
onto a computer or other programmable data processing apparatus to
produce a machine such that the instructions which execute on the
computer or other programmable data processing apparatus create
means for implementing the functions specified in the flowchart
block or blocks. For example, blocks of the flowchart illustration
may be implemented as computer instructions that are loaded and
executed at base stations, MTSO and/or mobile terminals of
radiotelephone systems such as those illustrated in FIGS. 1 and 2.
The computer program instructions may also be loaded onto a
computer or other programmable data processing apparatus to cause a
series of operational steps to be performed on the computer or
other programmable apparatus to produce a computer implemented
process such that the instructions which execute on the computer or
other programmable apparatus provide steps for implementing the
functions specified in the flowchart block or blocks.
[0074] Accordingly, blocks of the flowchart illustration support
combinations of means for performing the specified functions and
combinations of steps for performing the specified functions. It
will also be understood that each block of the flowchart
illustration, and combinations of blocks in the flowchart
illustration, can be implemented by special purpose hardware-based
computer systems which perform the specified functions or steps, or
combinations of special purpose hardware and computer
instructions.
[0075] It will also be understood that the blocks of the flowchart
illustration may implemented using the messaging apparatus and
methods illustrated in FIGS. 3-9. For example, functions
illustrated by the blocks of the flowchart illustration that relate
to communicating over robust, high-penetration messaging channels
may be performed using the apparatus and methods of FIGS.
6A-10.
[0076] Referring to FIG. 11, a user, e.g., a user at a mobile
terminal, selects a desired service, e.g., "regular" service, a
"robust" service or a "premium" service (Block 1105). Selection may
occur, for example, by selecting from a menu displayed at the
user's terminal. The user then enters a destination address, e.g.,
the telephone number or electronic mail address of a second user at
another mobile terminal, wireline telephone, or the like (Block
1110). The service request and destination address are conveyed to
the system, for example, via messages transmitted to a base station
via a radio communications signal or by wireline messages
transmitted to a MTSO via the PSTN (Block 1115). The system then
verifies that the selected service is supported and that the
sending and/or receiving unit is authorized to use the selected
service (Block 1120). For example, the system may check to see if
the sending or receiving unit is currently camped on a base station
that supports the selected service. If the service is not supported
or authorized, the system may terminate the communication (Block
1150).
[0077] If the service is supported and authorized, the system next
checks to see if adequate spectral and non-spectral resources are
available to establish communication between the sending unit and
the receiving unit according to the selected service (Blocks 1125,
1130). For example, the system may check to determine if adequate
channel capacity is available to serve a higher-bandwidth service,
or if the destination unit is currently camped onto a base station
that is capable of supporting a robust service such as the
high-penetration messaging service described above. If adequate
resources are not present, the communication is terminated (Block
1150).
[0078] If adequate resources are present, the system identifies an
appropriate tariff, e.g., a per minute or per message rate, fixed
surcharge or the like, associated with the selected service (Block
1135). The system then establishes communications between the first
and second users according to the selected service (Block 1135) and
assigns a charge to one of the users according to the identified
tariff (Block 1145).
[0079] The prices of a respective tariff associated with a
respective service are preferably proportional to the amount of
spectral and non-spectral demand associated with the service. For
example, a prices associated with a higher-spectral demand service
such as a high-power service preferably are greater than the prices
associated with a corresponding lower spectral demand standard
service that uses substantially the same amount of non-spectral
resources as the high-power service. Similarly, a tariff associated
with a robust service such as a high-redundancy messaging service
specifies higher prices than the tariff associated with a lower
non-spectral demand standard service that uses substantially the
same spectral resources as the robust service.
[0080] Several variations to the exemplary operations of FIG. 11
may be performed within the scope of the present invention.
Selection of a service may be implemented in several other ways
than by user selection. For example, the receiving user may
establish a "default" service that is to be utilized in response to
a request to contact the receiving user. Alternatively, the system
may query the sending or receiving unit to determine the type of
service desired.
[0081] Instead of terminating communication when a service is not
supported or authorized, the system may revert to another default
standard, robust or premium service for that is supported and
authorized. Similarly, when the spectral or non-spectral resources
needed to communicate a selected service are unavailable, the
system may revert to a default system for which adequate resources
are available.
[0082] Charge assignment according to the present invention can be
combined with more conventional cost-assignment metrics, such as
message duration, message size, time of day and the like. For
example, a charge may be determined by scaling message duration by
a multiplier that is selected according to the type of service
used. Service-based charge assignment according to the present
invention may also be implemented, for example, in the form of
surcharges that are assigned based on the service used to provide
communications.
[0083] The order of the exemplary operations described above may
also be varied. For example, the system may first determine if the
needed spectral resources are available before checking for support
or user authorization. The order of such steps may be determined,
for example, by the particular architecture of the wireless
communications system. For example, the system may be able to
verify system resource availability upon receiving a request to
communicate from a sending unit, but may be unable to determine
whether a particular service is supported or authorized for a
particular receiving unit until the receiving unit is actually
contacted.
[0084] Those skilled in the art will appreciate that although the
present invention is illustrated in the context of a
high-penetration messaging system such as illustrated in FIGS.
6A-10, the present invention is not limited to use with the
illustrated embodiments of FIGS. 6A-10. The methods and apparatus
of the present invention are also applicable to the communication
of other content than short messages; for example, similar
techniques could be used to communicate short message
acknowledgement, voice and data. The present invention is also
applicable to systems providing "premium" messaging services, such
as high-power short message services. In addition, the present
invention is also applicable to systems providing services that
represent a hybrid combination of the "robust" and "premium"
characteristics described above, for example, systems that offer
services with both increased power and redundancy that utilize both
increase spectral and non-spectral resources.
[0085] In the drawings and specification, there have been disclosed
typical preferred embodiments of the invention and, although
specific terms are employed, they are used in a generic and
descriptive sense only and not for purposes of limitation, the
scope of the invention being set forth in the following claims.
* * * * *