U.S. patent application number 10/116186 was filed with the patent office on 2003-06-26 for wireless communications handset for facilitating licensed and unlicensed wireless communications, and method of operation.
Invention is credited to Mohammed, Jahangir.
Application Number | 20030119490 10/116186 |
Document ID | / |
Family ID | 27540550 |
Filed Date | 2003-06-26 |
United States Patent
Application |
20030119490 |
Kind Code |
A1 |
Mohammed, Jahangir |
June 26, 2003 |
Wireless communications handset for facilitating licensed and
unlicensed wireless communications, and method of operation
Abstract
A wireless communication handset includes licensed wireless
communication signal processing circuitry and unlicensed wireless
communication signal processing circuitry. A control circuit is
connected to the licensed wireless communication signal processing
circuitry and the unlicensed wireless communication signal
processing circuitry. The control circuit transitions a
communication session without interruption from the licensed
wireless communication signal processing circuitry to the
unlicensed wireless communication signal processing circuitry.
Inventors: |
Mohammed, Jahangir;
(Mountain View, CA) |
Correspondence
Address: |
COOLEY GODWARD, LLP
3000 EL CAMINO REAL
5 PALO ALTO SQUARE
PALO ALTO
CA
94306
US
|
Family ID: |
27540550 |
Appl. No.: |
10/116186 |
Filed: |
April 2, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10116186 |
Apr 2, 2002 |
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09912883 |
Jul 24, 2001 |
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60271766 |
Feb 26, 2001 |
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60271767 |
Feb 26, 2001 |
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60271768 |
Feb 26, 2001 |
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60271769 |
Feb 26, 2001 |
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Current U.S.
Class: |
455/414.1 ;
455/403 |
Current CPC
Class: |
H04W 36/0066 20130101;
H04W 4/16 20130101; H04W 36/14 20130101; H04L 63/083 20130101; H04W
74/00 20130101; H04W 12/35 20210101; H04W 12/06 20130101; H04W
36/18 20130101; H04W 12/08 20130101; H04W 16/16 20130101; H04M
3/42246 20130101; H04W 16/14 20130101; H04W 8/12 20130101; H04L
63/0869 20130101 |
Class at
Publication: |
455/414 ;
455/403 |
International
Class: |
H04M 001/68 |
Claims
1. A wireless communication handset, comprising: licensed wireless
communication signal processing circuitry; unlicensed wireless
communication signal processing circuitry; and a control circuit
connected to said licensed wireless communication signal processing
circuitry and said unlicensed wireless communication signal
processing circuitry, said control circuit transitioning a
communication session without interruption from said licensed
wireless communication signal processing circuitry to said
unlicensed wireless communication signal processing circuitry.
Description
[0001] This application claims priority to the following
provisional patent applications: Nos. 60/271,766; 60/271,767;
60/271,768; and 60/271,769, each of which was filed on Feb. 26,
2001.
BRIEF DESCRIPTION OF THE INVENTION
[0002] This invention relates generally to telecommunications. More
particularly, this invention relates to a technique for seamlessly
integrating voice and data telecommunication services across a
licensed wireless system and an unlicensed wireless system.
BACKGROUND OF THE INVENTION
[0003] Licensed wireless systems provide mobile wireless
communications to individuals using wireless transceivers. Licensed
wireless systems refer to public cellular telephone systems and/or
Personal Communication Services (PCS) telephone systems. Wireless
transceivers include cellular telephones, PCS telephones,
wireless-enabled personal digital assistants, wireless modems, and
the like.
[0004] Licensed wireless systems utilize wireless signal
frequencies that are licensed from governments. Large fees are paid
for access to these frequencies. Expensive base station equipment
is used to support communications on licensed frequencies. Base
stations are typically installed approximately a mile apart from
one another. As a result, the quality of service (voice quality and
speed of data transfer) in wireless systems is considerably
inferior to the quality of service afforded by landline (wired)
connections. Thus, the user of a licensed wireless system pays
relatively high fees for relatively low quality service.
[0005] Landline (wired) connections are extensively deployed and
generally perform at a lower cost with higher quality voice and
higher speed data services. The problem with landline connections
is that they constrain the mobility of a user. Traditionally, a
physical connection to the landline was required. Currently,
unlicensed wireless communication systems are deployed to increase
the mobility of an individual using a landline. The mobility range
associated with such systems is typically on the order of 100
meters. A common unlicensed wireless communication system includes
a base station with a physical connection to a landline. The base
station has a RF transceiver to facilitate communication with a
wireless handset that is operative within a modest distance of the
base station. Thus, this option provides higher quality services at
a lower cost, but the services only extend a modest distance from
the base station.
[0006] Thus, there are significant shortcomings associated with
current landline systems and licensed wireless systems. For this
reason, individuals commonly have one telephone number for landline
communications and one telephone number for licensed wireless
communications. This leads to additional expense and inconvenience
for an individual. It would be highly desirable if an individual
could utilize a single telephone number for both landline
communications and licensed wireless communications. Ideally, such
a system would allow an individual, through seamless handoffs
between the two systems, to exploit the benefits of each
system.
SUMMARY OF THE INVENTION
[0007] A wireless communication handset includes licensed wireless
communication signal processing circuitry and unlicensed wireless
communication signal processing circuitry. A control circuit is
connected to the licensed wireless communication signal processing
circuitry and the unlicensed wireless communication signal
processing circuitry. The control circuit transitions a
communication session without interruption from the licensed
wireless communication signal processing circuitry to the
unlicensed wireless communication signal processing circuitry.
[0008] Advantageously, services that would typically be provided
via a licensed wireless system can be delivered to the unlicensed
base station using inexpensive and high quality landline networks.
The unlicensed base station subsequently provides service to a
handset using unlicensed, free spectrum (e.g., spectrum around 2.4
GHz or 5 GHz). Thus, when a subscriber is within range of the
unlicensed base station, the subscriber enjoys low cost, high
speed, and high quality voice and data services. In addition, the
subscriber enjoys extended service range since the handset can
receive services deep within a building. This type of service range
is not reliably provided by a licensed wireless system.
[0009] The invention also allows the subscriber to roam outside the
range of the unlicensed base station without dropping
communications. Instead, roaming outside the range of the
unlicensed base station results in a seamless handoff (also
referred to as a hand over) wherein communication services are
automatically provided by the licensed wireless system.
[0010] While the invention provides advantages to the subscriber,
the invention also provides advantages to the wireless system
service provider. First, the unlicensed base stations are
relatively low cost and therefore the wireless system service
provider is in a position to extend services without incurring
significant infrastructure expense. Further, the integration of the
landline and wireless systems allows a single communication service
provider to secure fee-paying accounts for both landline and
wireless services. Finally, since the invention relies upon
installed wireless system infrastructure for services such as
authentication, expensive system upgrades are not required.
BRIEF DESCRIPTION OF THE FIGURES
[0011] The invention is more fully appreciated in connection with
the following detailed description taken in conjunction with the
accompanying drawings, in which:
[0012] FIG. 1 illustrates an apparatus for integrating a licensed
wireless system and an unlicensed wireless system in accordance
with an embodiment of the invention.
[0013] FIG. 2 illustrates a subscriber device configured in
accordance with an embodiment of the invention.
[0014] FIG. 3 illustrates a base station configured in accordance
with an embodiment of the invention.
[0015] FIGS. 4A-4D illustrate various base station configurations
utilized in accordance with embodiments of the invention.
[0016] FIG. 5 illustrates a system server for integrating
unlicensed and licensed wireless communication systems in
accordance with an embodiment of the invention.
[0017] FIG. 6 illustrates a base station service region and
associated transition points between licensed and unlicensed
wireless communication services.
[0018] FIG. 7 illustrates a transition between an unlicensed
wireless service and a licensed wireless service in accordance with
an embodiment of the invention.
[0019] FIG. 8 illustrates transitions between unlicensed wireless
base stations in accordance with an embodiment of the
invention.
[0020] FIG. 9 illustrates the forwarding of a licensed wireless
call to a base station in accordance with an embodiment of the
invention.
[0021] FIG. 10 illustrates a prior art licensed wireless
authentication procedure.
[0022] FIG. 11 illustrates an unlicensed wireless authentication
procedure utilized in accordance with an embodiment of the
invention.
[0023] FIG. 12 illustrates system components utilized in a
provisioning operation associated with an embodiment of the
invention.
[0024] FIG. 13 illustrates provisioning operations performed in
accordance with an embodiment of the invention.
[0025] Like reference numerals refer to corresponding parts
throughout the several views of the drawings.
DETAILED DESCRIPTION OF THE INVENTION
[0026] FIG. 1 illustrates a system 10 that may be operated in
accordance with an embodiment of the present invention. The system
10 includes a subscriber device 12, which is a wireless
transceiver, such as a cellular telephone, a PCS telephone, a
wireless data modem, a wireless enabled Personal Digital Assistant,
a wireless enabled computer, and the like. This subscriber device
12 is in wireless electronic communication with a licensed wireless
communication service that provides voice and/or data services. By
way of example, the invention is disclosed in connection with a
licensed wireless communication service in the form of a cellular
network 14. When the subscriber device 12 is within an unlicensed
wireless service coverage area 16, the licensed wireless service is
substituted, without interruption, with an unlicensed wireless
service that is facilitated through a base station 18.
[0027] The base station 18 wirelessly transmits telephone signals
from a standard Public Switched Telephone Network (PSTN) 20 and, if
necessary, a standard Private Base eXchange (PBX) 22, to a
subscriber device 12. Specifically, when a device 12 is within an
unlicensed wireless service coverage area 16, the originating base
station 18 provides the device 12 with wireless telephone service
originating from a PSTN 20 rather than a cellular network 14. Since
the PSTN 20 is used, the subscriber device 12 receives high quality
voice or data services at a relatively low cost. If the user of the
subscriber device 12 roams outside of the unlicensed wireless
service coverage area 16, the same communication session can be
maintained without interruption by transitioning to the licensed
wireless service provided by the cellular network 14. Techniques
for implementing seamless transitions of this type are discussed in
detail below.
[0028] A system server 24 facilitates seamless transitions between
the licensed wireless service and the unlicensed wireless service.
The system server 24 is in electronic communication with the
standard cellular network 14. In one embodiment of the invention as
shown in FIG. 1, the system server 24 is also in electronic
communication with the base station 18 through a Local Area Network
(LAN) 28 and a larger network 30, such as the Internet. The system
server 24 and the base station 18 may be linked through any number
of communication services, including Digital Subscriber Line (DSL),
cable, satellite, and the like.
[0029] FIG. 1 illustrates that the cellular network 14 includes
standard components, such as a cellular core network 15, a Mobile
Switching Center (MSC) 26, Visitor Location Register (VLR) 32, a
Home Location Register (HLR) 34, an Authentication Center (AC) 38,
and a Base Station Controller (BSC) 38. As discussed below, these
standard components are utilized in a novel manner in order to
provide extended functionality for a subscriber device 12.
[0030] FIG. 2 illustrates a subscriber device 12. As previously
indicated, the subscriber device 12 may be a wireless telephone or
a wireless modem. In the case of a wireless telephone, the
subscriber device 12 includes a display 100, keypad 102, and a
control circuit 104. The display 100 may be used to provide a
visual indication to a user when the subscriber device 12 is within
the service range of the base station 18. The keypad 102 is used in
a conventional manner. The control circuit 104 may be in the form
of a processor, a hardwired circuit, a programmable logic device,
an application specific integrated circuit, and the like.
[0031] The control circuit 104 is also connected to a memory module
106 and, via audio switch 108, to an audio input/output circuit
110. Wireless signals in the unlicensed spectrum are received by an
antenna 110 and are filtered by a filter 112 to improve signal
clarity and/or strength. The wireless signals are then processed by
unlicensed wireless circuitry 114, which is also referred to as
unlicensed wireless communication signal processing circuitry. The
unlicensed wireless circuitry operates as a standard transceiver
for processing unlicensed wireless signals. The circuitry 114 may
support any number of unlicensed wireless standards. For example,
currently in the U.S., unlicensed wireless signals may be sent at
frequencies around 900 MHz, 2.4 GHz, or 5 GHz. Unlicensed wireless
communication may be implemented in accordance with the invention
utilizing any number of unlicensed spectrum communications
protocols, including Bluetooth, IEEE 802.11a, IEEE 802.11b, and
Hyper-LAN. Advantageously, many licensed wireless subscriber
devices are currently being configured to include unlicensed
wireless circuitry for such applications as remote microphones and
speakers. In accordance with the invention, this circuitry is used
for a new application, namely, communicating with a base station,
as discussed below.
[0032] Selected signals, such as location update data or signal
strength data, are sent to the control circuit 104. Audio data is
converted to an audio signal by audio circuitry 116 and is sent to
an audio switch 108 for broadcast by an audio input/output circuit
109. Audio signals transmitted to the audio input/output circuit
109 are transmitted by audio switch 108 to the control circuit 104,
which is capable of sending audio and other data to unlicensed
wireless circuitry 114. Unlicensed spectrum signals are then sent
through the filter 112 and on to the antenna 110, where they are
broadcast to the base station 18.
[0033] In similar manner, wireless signals from a licensed cellular
network 14 are transmitted to the antenna 111, filtered by the
filter 113, and are then processed by the licensed wireless
circuitry 118, also referred to as licensed wireless communication
signal processing circuitry. These signals are subsequently
converted to an audio signal by audio circuitry 120 or are
processed by control circuit 104. As above, signals originating
from the device 12 can also be sent out, but here the destination
is a licensed wireless communication network (e.g., cellular
network 14) rather than a base station 18. In the event of a data
modem, the audio input/output circuit 109 is omitted and a data
source is applied directly to the control circuit 104. Audio
signals transmitted from the audio input 109 are transmitted by
audio switch 108 to the control circuit 104, which is capable of
sending audio and other data to licensed wireless circuitry 118.
Wireless signals are then sent through the filter 113 to the
antenna 111, where they are broadcast to the licensed wireless
network 14.
[0034] The individual subscriber device components discussed up to
this point are standard. The combination of these devices is
believed to be novel, as is the operation of these devices in
accordance with a set of executable programs stored in memory 106.
The executable programs within memory 106 are shown by way of
example. The same functionality may be realized through hardwired
circuits, application specific integrated circuits, programmable
logic devices, and the like. Indeed, the various components of the
subscriber device 12 may be combined or integrated in any number of
ways. The embodiment of FIG. 2 is for the purpose of
illustration.
[0035] The executable programs 106 reside on top of standard
licensed wireless system call processing software. In addition, the
programs 106 reside on top of standard unlicensed wireless link
protocol software (e.g., standard Bluetooth or 802.11b software).
The programs 106 bridge these systems by exchanging messages
between the separate software stacks. Advantageously, this approach
allows a large portion of the existing software protocols in the
subscriber device 12 to be reused without any changes.
[0036] The memory module 106 contains a location tracking module
122 that records the current location of the device 12 (i.e.,
whether the device is within an unlicensed coverage area 16). In
addition, the module 106 contains an authentication and
authorization module 124 to coordinate an authentication procedure
for validating that the device 12 is licensed for use within the
unlicensed coverage area 16. As discussed below, the invention
utilizes the authentication infrastructure associated with the
licensed wireless system to authenticate and authorize a subscriber
device for unlicensed wireless system services. The memory 106 also
includes a handoff module 126 to coordinate seamless service
exchanges between a base station 18 supporting unlicensed wireless
communications and a licensed wireless communications network, such
as a cellular network 14. The operations associated with each of
the modules stored in memory 106 are discussed in further detail
below.
[0037] FIG. 3 illustrates an embodiment of a base station 18 in
accordance with an embodiment of the present invention. When the
subscriber device 12 is within the coverage area 16 of the base
station 18, the base station 18 can be used to provide the
subscriber device 12 with landline quality data and voice service
via an unlicensed wireless communication link. In particular, the
base station 18 interconnects to the existing telephone network to
provide a final link to a subscriber device 12 through a
short-range two-way radio link.
[0038] In one embodiment of the invention, the base station 18 is
controlled by a control circuit 200, which is in communication with
the LAN 28 and therefore the system server 24 via router jack 202
and/or Ethernet jack 204. The control circuit 200 may be a
processor, a hardwired circuit, a programmable logic device, an
application specific integrated circuit and the like. Signals from
the system server 24 travel through one of these jacks into network
interface circuitry 206 and on to the control circuit 200. This
allows the base station 18 to communicate with the system server
24. As discussed below, the server 24 determines whether and when
to route phone service over the unlicensed wireless system (e.g.,
via the PSTN 20 and base station 18) or the licensed wireless
system (e.g., via cellular network 14).
[0039] The control circuit 200 is also in communication with a
landline (PSTN 20 and, in the typical business context, PBX 22) via
a phone line jack 208 and/or phone extension jack 210. These jacks
transmit information between the PSTN 20 and control circuit 200
through Plain Old Telephone Service (POTS) interface circuitry 212.
Audio data is translated by audio circuitry 214, while other data
can be directly exchanged with the control circuit 200.
[0040] The base station 18 communicates wirelessly with devices 12
using a radio frequency circuit 216. This circuit 216 includes
standard circuitry to receive and transmit electronic voice and/or
data in an unlicensed wireless signal format. For example,
currently in the U.S., unlicensed wireless signals may be sent in
the frequency range between 2.4 GHz and 5 GHz. Unlicensed wireless
communication may be implemented in accordance with the invention
utilizing any number of unlicensed spectrum communications
protocols, including Bluetooth, IEEE 802.11a, IEEE 802.11b, and
Hyper-LAN.
[0041] A typical circuit 216 consists of transmission circuitry 218
for transmitting signals to a device 12, receiving circuitry 220
for receiving signals from the device 12, and base band circuitry
222. The baseband circuitry 222 contains standard circuitry for
down converting unlicensed wireless signals to base band signals,
which allows for the extraction of relevant information by the
control circuit 200. The base band circuitry 222 also contains
standard circuitry for up converting base band data from the
control circuit 200 to unlicensed wireless signals for broadcast by
transmission circuitry 218.
[0042] The control circuit 200 is also connected to a memory module
224. The memory module 224 contains a provisioning module 226 that
is used to facilitate the initial configuration and servicing of
the base station 18 and subscriber device 12. The module 224 also
includes a subscriber interface module 228. The subscriber
interface module 228 instructs the control circuit 200 to
periodically broadcast a signal (e.g., an unlicensed wireless
communication base station identification signal). If a subscriber
device 12 responds to the signal, then the-base station 18 knows
that the subscriber device 12 is within the unlicensed coverage
area 16. The module 224 also contains an authentication module 230
to coordinate the authentication of a subscriber device 12 that has
entered the unlicensed coverage area 16. In one embodiment of the
invention, the memory 224 includes an enhanced service module 232.
The enhanced service module may be used to provide improved
services to a subscriber device. For example, if the user of a
subscriber device is playing a low latency on-line game, different
screen displays can be cached in the base station 18 and then be
quickly downloaded to the subscriber device 12. Each of the modules
stored in memory 224 can also be implemented as hardwired circuits,
application specific integrated circuits, programmable logic
devices, and the like.
[0043] The enhanced service module 232 may also be used to
implement other advanced features. For example, the enhanced
service module 232 can be configured to append a set of prefix
digits before dialed digits to instruct the server 24 to route long
distance calls on a specific service provider network.
[0044] The enhanced service module 232 can also be used to
simultaneously support multiple subscribers. For example, the base
station 18 may support multiple subscriber devices through a single
or multiple landline connections.
[0045] Preferably, the subscriber interface module 228 of the base
station 18 is configured to advise a subscriber device when the
landline associated with the base station 18 is occupied. In such a
case, the handoff module 126 of the subscriber device will no
longer attempt to make contact with the base station 18, but will
continue to utilize the licensed wireless system for call
servicing.
[0046] In order to provide landline-quality service to subscriber
devices 12, a base station 18 is installed directly in the path of
a typical phone system. FIG. 4A illustrates a typical office or
workplace, where a telephone 300 is connected to a PBX 22. The PBX
22 is installed between the telephone 300 and PSTN 20 to provide a
private telephone network in which a number of telephones 300 share
a certain number of outside lines from the PSTN 20. FIG. 4A
illustrates that a Personal Computer (PC) 302 can be connected to
the LAN 28 for communication with the Internet 30.
[0047] FIG. 4B illustrates the workplace environment of FIG. 4A
modified to incorporate the base station 18 of the invention. The
base station 18 is placed in electronic communication with both the
telephone 300 (e.g., via phone line jack 208) and the LAN 28 (e.g.,
via Ethernet jack 204). This configuration allows base station 18
to receive landline voice and data from a PSTN 20 and broadcast it
to subscriber devices 12 when they are within the coverage area 16.
The base station 18 is also connected to a LAN 28, which allows it
to communicate with the system server 24 in order to coordinate
handoffs between the licensed wireless and unlicensed wireless
systems. Advantageously, the base station 18 operates transparently
with respect to the PBX 22, the LAN 28, the telephone 300, and the
PC 302. In the event that the PBX 22 is Internet Protocol based,
the base station 18 can be connected solely to the LAN 28.
[0048] FIG. 4C illustrates a typical home setting, which is usually
similar to the workplace setting of FIG. 4A minus the LAN 28 and
PBX 22. The telephone 300 is ordinarily connected directly with
Plain Old Telephone Service (POTS) 304, which is simply another
term for PSTN 20. Connection to the Internet 30 is provided by a
modem 306 in communication with a PC 302. FIG. 4D illustrates the
placement of base station 18 within this typical home setting.
Here, the base station 18 is placed in electronic communication
with both a telephone 300 and modem 306, allowing it to communicate
directly with the POTS 304/PSTN 20 and, through modem 306, with the
Internet 30 and system server 24. Once again, the base station 18
operates transparently with respect to the modem 306, the POTS 304,
the telephone 300, and the PC 302.
[0049] In both the workplace and home settings, the base station 18
can be in simultaneous communication with both a telephone landline
and a system server 24. When a subscriber device 12 roams inside
the coverage area 16, the base station 18 can thus provide
landline-quality service to device 12. The invention should thus be
construed to include an apparatus and method for the seamless
switching of telephone service between a cellular network 14 and a
landline-based base station 18 that can be used in either a
residential or commercial setting.
[0050] As mentioned above, for purposes of this invention a
landline can be interchangeably referred to as a POTS 304 or PSTN
20. However, the invention should not be construed as limited to
simply the POTS or PSTN context. Rather, the invention discloses a
base station 18 that can provide landline-quality service to a
subscriber device 12 by communicating with any landline network.
Examples of such networks include, but are not limited to, DSL,
cable or cable modem networks.
[0051] FIG. 5 illustrates a system server 24, which manages the
mobility of subscriber devices 12 between a landline-based
unlicensed wireless service from a base station 18 and a licensed
wireless service, such as from a cellular network 14. A typical
system server 24 is controlled by a central processing unit (CPU)
400, which is connected to a bus 401. Network interface cards 402
(e.g., Ethernet cards) for communicating with the Internet 30 are
also connected to the bus 401. Licensed network interface cards 404
(e.g., SS7 cards) for communicating with cellular networks 14 are
also connected to the bus 401. This allows the system server 24 to
use Internet Protocol (IP) and/or SS7 protocol and/or MAP &
IS-41 protocols to connect to the Internet and cellular core
networks.
[0052] The system server 24 also contains a memory module 406 that
stores a number of programs, databases and other assorted modules.
More specifically, the module 406 contains signaling control
programs 408. The signaling control programs 408 are standard
programs for establishing communications with the licensed wireless
network. Therefore, for example, the signaling control programs 408
may include a Transaction Capability Application Part (TCAP)
module, a Message Transfer Part (MTP) module, and an Interim
Standard (IS41) module to support Time Division Multiple Access
(TDMA) and Code Division Multiple Access (CDMA). Memory 46 may also
store datapath control programs 410. By way of example, the
datapath control programs may include standard programs to
facilitate computer network data transfers. By way of example, the
datapath control programs may include an Internet Protocol (IP)
module and a Gateway Tunnel Protocol (GTP) module.
[0053] The memory 406 also stores various system server application
programs 412. These application programs include system bridge
programs 414 for handling transitions in service from licensed to
unlicensed wireless services and vice versa. The memory 406 also
stores a location database 416 for storing the current location of
devices 12 and indicating whether they are within the coverage area
16. Also included is a billing module 418 for recording usage
statistics for billing purposes. The billing module 418
distinguishes between charges for licensed wireless services and
unlicensed wireless services. A provisioning module 420 is included
to facilitate the installation of new base stations. An
authentication module 422 is used to facilitate the authentication
of a subscriber device within an unlicensed wireless service area.
As discussed below, the authentication module 422 includes data and
executable instructions to emulate certain components of a licensed
wireless network. For example, the authentication module emulates a
mobile switching center during the authentication process.
[0054] The major components of the invention--the subscriber device
12, the base station 18, and the system server 24--have now been
described. The operations of these devices are more fully
appreciated with the following discussion.
[0055] The invention's facilitation of seamless transitions between
licensed and unlicensed wireless services is more fully appreciated
in connection with FIG. 6. Base station 18 broadcasts within a set
of boundaries B1, B2, B3 and B4. A subscriber device 12 located
outside these boundaries is serviced by a licensed wireless system,
such as a standard cellular network 14. However, once the device 12
crosses boundary B3, the handoff from the licensed wireless service
to the unlicensed wireless service begins. That is, at the B3
boundary the base station 18 is able to recognize the presence of
the subscriber device 12. As previously indicated, the base station
18 includes a subscriber interface module 228 that coordinates the
transmission of a service range signal that is identified by a
subscriber device 12. That is, the location tracking module 122 of
the subscriber device 12 is used to coordinate the identification
of a base station signal. In the presence of such a signal, the
location tracking module 122 coordinates the transmittal of an
acknowledgment signal to the base station 18.
[0056] Preferably, the subscriber interface module 228 of the base
station 18 identifies the boundary points of the service area 16 by
using the received signal strength and the transmit-power level
setting from the subscriber device 12. In particular, an automated
process is preferably used to learn the boundary distances through
heuristically measuring the success rate and adjusting the boundary
distance for optimal handoff success rates.
[0057] In one embodiment, the location tracking module 122 of the
subscriber device 12 is implemented to periodically wake the
unlicensed wireless circuitry 114 to sniff and thereby determine
whether it is within the range of a base station. If so, the
subscriber device registers with the base station 18, if not, the
unlicensed wireless circuitry 114 is activated at a later time.
[0058] Under the control of the subscriber interface module 228,
the base station 18 identifies the acknowledgement signal and
transmits a subscriber device present signal to the router jack
202, the Ethernet jack 204, the phone line jack 208, or the phone
extension jack 210. The subscriber device present signal is
subsequently directed through a network (e.g., the LAN 28 and
Internet 30) to the system server 24, which notes that the
subscriber device 12 is now within the service area of the base
station 18. In particular, the system server 24 logs this
information in the location database 416.
[0059] Once the system server 24 logs the fact that the subscriber
device 12 is within the service range of the base station 18, it
contacts the cellular network 14 to initiate a call to the landline
associated with the base station 18. It is known in the art to
utilize a cellular network 14 to establish a call to a landline
number. For example, FIG. 1 illustrates a link between the Mobile
Switch Center (MSC) 26 and the PSTN 22. In the prior art, this
feature is used to direct a call intended for a mobile device to a
landline telephone when the user of the mobile device has advised
the cellular system that the landline telephone can be used to
receive calls. Observe in this situation that the transition from
the cellular network to the landline telephone is established prior
to the call being placed. This prior art scenario stands in sharp
contrast to the present invention where during the course of an
already established communication session control is transferred
from a licensed wireless service to an unlicensed wireless service
or vice versa. This aspect of the invention is more fully
appreciated in connection with the following discussion.
[0060] As previously indicated, when the subscriber device 12
crosses the boundary B3, a landline call to or from the base
station 18 is initiated. Once the landline call is received at the
base station 18, the base station 18 begins transmitting to the
subscriber device 12 using the unlicensed wireless spectrum. These
transmissions are processed by the unlicensed wireless circuitry
114 of the subscriber device 12 (See FIG. 2). At this point, the
licensed wireless circuitry 118 is also active and the audio switch
108 is responsive to the licensed wireless circuitry 118. Thus, the
subscriber device 12 is processing both licensed wireless signals
and unlicensed wireless signals at this point. The handoff module
126 can coordinate this operation.
[0061] The subscriber interface module 228 of the base station 18
continues to monitor the signal strength from the subscriber device
12. When the signal strength reaches a threshold corresponding to
the crossing of boundary B4, the subscriber interface module 228
initiates a handoff command, which is applied to the RF circuit
216. The handoff command is received at the subscriber device 12
and is processed by the handoff module 126, which generates a
handoff signal that is applied to the audio switch 108. The handoff
signal causes the audio switch 108 to process information from the
audio circuitry 116 associated with the unlicensed wireless
circuitry 114.
[0062] At this point, the licensed wireless circuitry 118 can be
turned off. The ability to turn this circuitry off is a significant
advantage because it preserves battery life. Typically, the
licensed wireless circuitry remains active in order to provide
location information to the licensed wireless system
infrastructure. However, as discussed below, this location
information is available in accordance with the invention.
Therefore, the licensed wireless circuitry can be shut down to
obtain a significant extension in battery life. Alternately, the
licensed wireless circuitry 118 can remain in a low power state to
receive signaling or messages from the licensed wireless system,
while voice is carried over the unlicensed system.
[0063] The spacing between boundaries B3 and B4 allows time for the
establishment of simultaneous connections between the subscriber
device 12 and both the licensed network and unlicensed network.
This allows for the immediate switching of service to the
unlicensed network once the subscriber device 12 crosses boundary
B4, thus creating a seamless transition to base station service
that is transparent to the user.
[0064] Once the device 12 is within boundary B4, service is
originated within the PSTN 20 and broadcast wirelessly to the
device 12 by the base station 18. If the device 12 travels away
from this base station 18, service is handed off from the base
station 18 to a licensed wireless network 14 in a manner similar to
the process described above. Specifically, once the device 12
crosses boundary B2, a simultaneous link is established with a
licensed wireless network (e.g., cellular network 14). When the
device 12 further crosses boundary B1, a seamless handoff is made
from the unlicensed wireless service originating over the PSTN 20
to the licensed wireless network (e.g., cellular network 14). At
this point, the subscriber device 12 receives wireless services
from the cellular network 14 in a standard manner.
[0065] FIG. 7 provides a more detailed characterization of this
handoff process from an unlicensed wireless service to a licensed
wireless service. When the subscriber device 12 is within the
service area 16 of the base station 18, the subscriber device 12
transmits to the base station 18 information on the signal
strengths of the frequencies of the nearby licensed wireless base
stations. The base station 18 forwards this information to the
system server 24, which in turn sends the information to the
Visitor Location Register (VLR) 32. This operation is shown with
arrow 450 in FIG. 7.
[0066] In response to this message, the licensed wireless system
provides the parameters that are needed when the subscriber device
12 needs a handoff from the unlicensed wireless system to the
licensed wireless system. This information includes the identity of
the base station to which the handoff should be made. By way of
example, in a GSM cellular system, these parameters are CI (Cell
Identity) and LAC (Location Area Code). This handoff information
may be obtained and stored in the base station 18 before a call is
made or when a call is made. In any event, the handoff information
can be secured well before the subscriber device 12 roams outside
the coverage area of the base station 18. The availability of this
information allows the subscriber device 12 to quickly transition
to the licensed wireless system. In addition, this information
allows the licensed wireless circuitry 118 to be shut down for the
purpose of extending battery life.
[0067] The licensed wireless system connection information may be
delivered to the base station 18 via a landline connection as shown
with line 452. Alternately, the information may be delivered
through a communication session between the system server 24 and
the mobile switch center 26 and then the system server 24 and the
base station 18, as shown with arrows 454 and 456.
[0068] As shown with arrow 458 in FIG. 7, the base station 18
continuously makes power measurements of signals that are received
from the subscriber device 12. When the power measurements begin to
grow weak, the base station may notify the system server 24 to
initiate a handoff to the licensed wireless system. In turn, the
system server 24 may advise the Mobile Switch Center (MSC) 26 of
the hand over candidate, as shown with arrows 460 and 462.
[0069] When the power measurements at the base station 18 become
sufficiently weak, indicating that the subscriber device 12 is
moving away from the base station 18 (e.g., crossing boundary B2) a
formal hand over request is initiated. In particular, the base
station 18 transmits to the system server 24 the base station
identity (e.g., CI, LAC, etc.) to which the handoff should be
transferred, as shown with arrow 458. The system server 24 contacts
the MSC 26 to initiate a handoff, as shown with arrow 460. The MSC
26 contacts the Base Station Controller (BSC) 38, as shown with
arrow 462. In response, the BSC 38 generates a channel number, a
slot number and a handoff reference. As shown with arrow 464, this
information is passed to the Base Station Transceiver System (BTS)
500. The information is also passed back to the subscriber device
12 through the MSC 26, the system server 24, and the base station
18, as shown with arrows 466, 468, 470, and 472.
[0070] In response to this information, the BTS 500 turns on a
transmitter and receiver at the specified channel number and slot
number. Similarly, the subscriber device 12 turns on its
transceiver circuitry 118. The BTS 500 seeks a response from the
subscriber device with a matching reference number, as shown with
arrow 474. Once the subscriber device 12 receives the BTS
transmission, it sends a message to the BTS with the handoff
reference, as shown with arrow 476. At this point, a new licensed
wireless link is established on the given channel and slot number,
as shown with arrow 478. Once the licensed wireless link is
established, the unlicensed wireless link is turned off, as shown
with line 480 in FIG. 7. Thereafter, the BTS 500, the BSC 38, and
the MSC 26 operate in a standard manner to supply licensed wireless
services to the subscriber device 12. The foregoing operations may
be implemented using the handoff module 126 of the subscriber
device 12, the subscriber interface module 228 of the base station
18, and the system bridge programs 414 of the system server 24.
[0071] As previously indicated, a handoff from a licensed wireless
service to an unlicensed wireless service occurs in a similar but
reverse fashion. When the subscriber devices 12 cross boundary B3
from a remote location the base station 18 initiates a handoff
operation by sending a request to the system server 24, which
conveys the request to the MSC 26. The MSC 26 then hands off the
call to the landline number assigned to the base station 18.
[0072] Between boundaries B3 and B4, both the licensed wireless
(e.g., cellular) link and unlicensed wireless (e.g., landline
originated) link are simultaneously active. After a period in which
both links are simultaneously active, control of the communication
session is switched from the licensed wireless circuitry 118 to the
unlicensed wireless circuitry 114. The handoff module 126 may
coordinate this handoff in response to a handoff command initiated
at the subscriber interface module 228 of the base station 18. As
above, the maintenance of simultaneous licensed and unlicensed
wireless links for a period of time ensures a successful seamless
handoff. This reduces the number of dropped calls, and allows for
successful handoffs even when the signaling messages among
different elements of the cellular and landline-based systems
experience delays or latency.
[0073] The foregoing discussion was directed toward handoffs
between licensed wireless services and unlicensed wireless
services. The invention also includes a technique for seamless
handoffs between unlicensed wireless service base stations. Such a
technique would be valuable, for example, in the case where an
office building has a large number of base stations 18 to supply
unlicensed wireless services to a user that would otherwise receive
poor quality licensed wireless service within the office
building.
[0074] Thus, the invention includes a system wherein a plurality of
base stations 18 exist with overlapping coverage areas 16. This
allows a subscriber device 12 to roam freely among the coverage
areas 16.
[0075] FIG. 8 illustrates such a system. The subscriber device 12
is registered with base stations 600 and 602. Base stations 600 and
602 communicate with each other using LAN 28. The base stations 600
and 602 are shown installed in a typical workplace setting, with
telephones 300 and PCs 302 connected to a LAN 28 and PBX 22 in a
standard fashion. Note that the coverage areas 604 and 606 of the
base stations 600 and 602 overlap. As a device 12 moves from one
area 604 to another area 606, voice and data signals from the first
base station 600 are seamlessly handed off to the second base
station 602.
[0076] Periodically, the base stations 600 and 602 broadcast a
message over the LAN 28 to all other base stations connected to the
LAN 28. This message includes a time stamp, a signal indicating the
particular base station, the subscriber number, and a range number
indicating the distance between that base station and the device
12. A separate message is broadcast for each base station on the
LAN 28. A range number can be calculated by relying upon the
ability of the base station 18 to measure the signal strengths
emitted from the subscriber device or vice versa.
[0077] In accordance with this feature of the invention, there is
no centralized control mechanism for handling handoffs. Instead,
the subscriber interface module 228 of each base station 18 is used
to coordinate handoffs between base stations based upon signal
strengths and/or range numbers. For example, in FIG. 8, at position
T1 the base station 600 would transmit a time stamp, a base station
number, a subscriber number, and a range number indicating that the
subscriber device 12 is relatively close to the base station 600.
At T2 the base station 600 would transmit the same information
except a different range number indicating that the signal between
the base station 18 and the subscriber device 12 is weaker. By
position T3, the base station 602 would send a signal on the LAN 28
indicating that it has a range number indicating that the
subscriber device 12 is now closer to it than to base station 600.
Accordingly, both base stations would recognize that a transition
from base station 600 to base station 602 should transpire. Under
these circumstances, the second base station 602 transmits a signal
over LAN 28 to the first base station 600 requesting a transition.
Once the first base station 600 acknowledges this request, it
forwards the call to the second base station 602 and service is
continued without disruption. For example, the call may be
forwarded over LAN 28 using Voice Over Internet Protocol (VOIP)
techniques.
[0078] The discussion up to this point has been directed toward
seamless transitions between licensed and unlicensed wireless
services. Attention now turns to other aspects of the invention.
Another aspect of the invention is a technique for assigning a base
station to a landline telephone number. Another aspect of the
invention is a technique for authenticating a user for unlicensed
wireless services. Advantageously, authentication is implemented
through reliance upon existing authentication infrastructure
associated with the licensed wireless network. Thus, a separate
authentication scheme need not be implemented. Another aspect of
the invention that is discussed below is the provisioning of a base
station into the overall licensed wireless network. As discussed
below, the provisioning operation is automatically performed and
therefore does not require technical sophistication or expertise on
behalf of the user.
[0079] FIG. 9 illustrates a technique for assigning a landline
number to a base station 18. Upon installation and power-up, the
base station 18 queries the subscriber device 12 for the local
landline phone number to which the base station is connected. In
some embodiments, the base station 12 will also solicit the
Internet Protocol (IP) address for the system server 24. After the
user enters the phone number and/or IP address into the subscriber
device 12, the information is transmitted to the base station 18,
as shown with arrow 610 of FIG. 9. The base station 18 forwards the
same information to the system server 24, as shown with arrow 612.
The system server 24 then transmits this information for storage in
the HLR 34, as shown with arrow 614. Once stored in the HLR 34, the
MSC 26 can access the number as a mobile system roaming number
(MSRN), as shown with arrows 616 and 618. Thereafter, the mobile
system roaming number can be used in a conventional manner to route
a call to the base station 18. Alternately, the MSRN may be a
number corresponding to a number associated with the system server
24. In which case, the system server 24 sends the call to the base
station 18.
[0080] Another aspect of the invention is authentication. As
previously indicated, the invention utilizes the authentication
infrastructure associated with the licensed wireless network to
authenticate users for the unlicensed wireless network.
[0081] FIG. 10 illustrates a licensed wireless system
authentication process utilized in accordance with the prior art.
In this example, the subscriber device 12 moves from the coverage
area served by its home MSC (referred to as MSC-A) to the coverage
area served by MSC-B. As soon as the subscriber device 12 enters a
cell that is served by MSC-B, it registered with the system by
sending an authentication request and a location update to BSS 600,
as shown with arrow 650. The location update request includes an
international mobile subscriber identity (IMSI).
[0082] BSS 600 forwards this information to the VLR 32 associated
with MSC-B, as shown with arrow 652. The VLR of MSC-B in turn sends
a message to the VLR and HLR of the SMC-A, as shown with arrows 654
and 656. This information serves as a request for authentication of
the subscriber device 12 as well as to inform the HLR 34 of the
current location of the subscriber device 12 as served by the
MSC-B. The authentication is performed as follows.
[0083] The authentication center (AuC) 36 generates a parameter
called SRES (signed response). In order to generate the SRES, it
uses an authentication algorithm A3, such as a public key/private
key algorithm. The algorithm A3 processes a secret key Ki, a random
number RAND, and the IMSI to produce the SRES. The IMSI, RAND, and
SRES are passed to the MSC-A (arrow 658) and MSC-B (arrow 660). The
SRES is temporarily stored at the MSC-B until the authentication
operation is completed. The MSC-B passes the IMSI and the RAND to
the BSS, which passes the information to the subscriber device 12.
Based upon the IMSI and the RAND that it receives (referred to
herein as licensed wireless communication system security
information), along with the secret key Ki that it stores, the
subscriber device 12 executes the same authentication algorithm A3.
This results in the subscriber device 12 producing a SRES, which is
referred to as an authentication result. If the subscriber device
is legitimate, it has the same secret key Ki encoded in it as the
one in the HLR. The service provider encodes this key at the time
of activating the subscriber. This key is known only to the
subscriber device and to the HLR.
[0084] The SRES, or authentication result, generated by the
subscriber device 12 is passed with the IMSI to the BSS-B (arrow
666), which passes it to the MSC-B (arrow 668). The MSC-B compares
the SRES generated by the subscriber device 12 to the SRES
generated by the HLR. Authentication is only successful if the two
numbers match. The SRES generated by the HLR can be referred to as
an authentication value. If the authentication value from the HLR
matches the authentication result from the subscriber device 12,
then an authentication command is generated.
[0085] The above process assists in understanding the
authentication process included in the present invention, as the
new method is designed to utilize the existing authentication
process already existent in the licensed wireless system. FIG. 11
illustrates an authentication process in accordance with the
present invention. In accordance with the invention, the base
station 18 is designed to emulate a BSS 600, and the system server
24 is designed to emulate an MSC 26.
[0086] When the subscriber device 12 enters the service area of the
base station 18, it registers with the base station. The
authentication module 124 of the subscriber device 12 subsequently
intercepts the registration message that is typically sent to the
licensed wireless base station (e.g., BSS 600). This information,
referred to as a licensed wireless authentication request, is sent
to the base station 18, as shown with arrow 680. The base station
18, at the direction of the authentication module 230, routes the
information to the system server 24. In particular, the
authentication module 230 of the base station 18 forms an Internet
Protocol (IP) packet containing the information and routes it to
the system server 24. As shown with arrow 684, the system server 24
forwards the information to the MSC-A. The authentication module
422 of the system server 24 may be used for this purpose. In this
capacity, the authentication module 44 assists the system server 24
in its operation of emulating a VLR. The operations at arrows 656,
658, and 660 are identical to the operations performed in the prior
art system of FIG. 10.
[0087] At this point, the system server 24 stores the SRES, instead
of an MSC. The system server 24 forwards the IMSI and RAND
information to the base station 18, as shown with arrow 686. The
base station 18, emulating a BSS, passes this information to the
subscriber device 12. The authentication operation performed at the
subscriber device is conventional, with the subscriber device
returning an authentication result (e.g., an IMSI and a. SRES) to
the base station 18, as shown with arrow 690. The base station 18
passes this information to the system server 24, as shown with
arrow 692. The system server 24 then checks for an SRES match. That
is, the system server compares the authentication result produced
by the subscriber device 12 to the authentication value (e.g.,
SRES) received from the MSC-A. Recall that this operation was
performed by the MSC 26 in the prior art system of FIG. 10. In the
event of a match between the computed SRES values, an
authentication command is produced and unlicensed wireless services
may be delivered to the subscriber device 12 through the base
station 18.
[0088] Preferably, authentication is not performed every time the
subscriber device registers with the base station 18. Instead, the
authentication module 230 of the base station 18 preferably stores
previous authentication information and locally re-authenticates
without accessing the system server 24. This implementation is
faster and otherwise reduces network traffic.
[0089] Yet another aspect of the invention involves provisioning of
a base station in order to facilitate the licensed-to-unlicensed
wireless communications achieved in accordance with the invention.
By way of overview, the provisioning operation of the invention
entails the base station 18 automatically configuring itself. In
one embodiment, provisioning is accomplished by initially accessing
a provisioning server. Subsequently, the base station registers
with the system server. In the event that Internet access is
available to the base station, the base station uses the Internet
to access the provisioning server and the system server. If
Internet access is not available, a Short Message Service Center
may be used during the provisioning operation.
[0090] FIG. 12 illustrates equipment utilized during the
provisioning operation. In particular, the figure illustrates a
subscriber device 12 and a base station 18. In one embodiment, the
base station 18 uses the Internet 30 to access a provisioning
server 700. For example, the base station 18 may access the
Internet through a broadband modem, such as DSL. The provisioning
server 700 supplies a service profile to the system server 24, as
discussed more fully below. In another embodiment of the invention,
the base station 18 is provisioned through a wireless connection.
In particular, a wireless link is established using a Short
Messaging Service or packet data services supported by the cellular
system. For example, a short messaging service message can be sent
from the base station 18 to the subscriber device 12, which then
delivers the message to the BSS 600. The BSS 600 delivers the
message to the cellular network 14, which delivers the message to
the MSC 26. The MSC 26 routes the message to the Short Message
Service Center (SMSC) 702, which routes the message over the
Internet 30 to the provisioning server 700. Information from the
provisioning server 700 is delivered to the system server 24 and
the base station 18 through a reverse path.
[0091] FIG. 13 illustrates the process steps involved when the
system of FIG. 12 carries out the provisioning process. The process
is typically initiated upon installation and activation of a new
base station 18, and will be discussed in that context, but those
of skill in the art will see that it can be performed any time that
provisioning information must be updated.
[0092] When a base station 18 is initially powered up it contacts
the provisioning server 700 (step 800). The provisioning module 226
of the base station 18 coordinates this operation. In one
embodiment, contact is made through the Internet 30 using one or
more preprogrammed IP addresses for the provisioning server.
Alternately, the provisioning server may be accessed through the
SMSC, as discussed above. The base station 18 then identifies
itself to the provisioning server 700, for example, using a code
preprogrammed at the time of manufacture. If the provisioning
server 700 does not recognize the base station, the base station
preferably provides an error indication. If the provisioning server
700 recognizes the base station, that processing proceeds to block
806.
[0093] At this point, the base station broadcasts a signal to the
subscriber device 12 instructing it to define itself (block 806).
For example, the subscriber device 12 may define itself by sending
to the base station 18 an electronic serial number or a portion of
an electronic serial number. This defining information is used to
establish an association between the base station 18 and the
subscribe device 12. This local association is mapped with a local
authentication procedure. Thereafter, whenever the subscriber
device and the base station come into contact, they identify each
other by passing the local authentication procedure. The two
devices can only communicate if the local authentication procedure
is successful.
[0094] The provisioning module 127 of the subscriber device 12
prompts the user to enter the landline telephone number associated
with the base station 18 (block 808). This information is then
passed to the base station 18. The base station then delivers
information to the provisioning server (block 810). For example,
the base station will typically deliver the landline telephone
number and a base station identification number to the provisioning
server. The provisioning server then downloads a service profile to
the base station and the system server (block 812). The service
profile can include the landline telephone number and caller
services, such as call waiting, caller identification, and the
like. The service profile may also include an IP address for the
base station. The IP address allows packet data to be delivered to
the base station. The service profile also includes the IP address
of a system server 24 assigned to the base station 18. Typically,
the system server 24 is selected based upon proximity to the base
station, as derived from the area code associated with the landline
telephone number.
[0095] Observe that the provisioning server operates as a central
registration point for all devices within the system. This central
point makes it easier to modify system wide services. In addition,
the provisioning server provides the benefit that a single address
is programmed into each base station.
[0096] The base station takes the IP address of the system server
from the service profile and contacts the system server (block
814). If the service profiles match, an association is established
between the system server, the base station, and the subscriber
device. The system server subsequently updates the HLR of the
subscriber device with contents of the service profile (block 816).
At this point, the authentication process of FIG. 11 would
typically be performed. This provisioning process can be repeated
whenever a new device 12 or base station 18 is introduced into the
system.
[0097] Another aspect of the invention allows licensed wireless
service users to seamlessly change between a desktop phone and a
subscriber device 12 during a call, thus allowing them to use the
most comfortable device at a given time. Thus, when a subscriber
device 12 is located within a coverage area 16, a user can simply
pick up the desktop phone and continue their conversation. The
subscriber device 12 can then be disconnected without any
interruption in service. In this embodiment, the desktop phone and
the base station are connected to the same landline, thereby
providing this interchangeability. Likewise, when a caller is using
a desktop phone within an area 16, he or she can activate a
subscriber device 12 and continue a call from there. In this
instance, a button on the subscriber device is used to initiate
communication with the base station that is connected to same
landline. Subsequently hanging up the desktop phone will not
interrupt service. Observe in this context that when the subscriber
device is within the coverage area 16 of the base station 18, both
the subscriber device 12 and a desktop telephone may simultaneously
ring in response to a call. The user can then pick up either
device.
[0098] The foregoing description, for purposes of explanation, used
specific nomenclature to provide a through understanding of the
invention. However, it will be apparent to one skilled in the art
that specific details are not required in order to practice the
invention. Thus, the foregoing descriptions of specific embodiments
of the invention are presented for purposes of illustration and
description. They are not intended to be exhaustive or to limit the
invention to the precise forms disclosed; obviously, many
modifications and variations are possible in view of the above
teachings. The embodiments were chosen and described in order to
best explain the principles of the invention and its practical
applications, the thereby enable other skilled in the art to best
utilize the invention and various embodiments with various
modifications as are suited to the particular use contemplated. It
is intended that the following claims and their equivalents define
the scope of the invention.
* * * * *