U.S. patent application number 09/809218 was filed with the patent office on 2004-05-20 for adaptive personal repeater.
This patent application is currently assigned to SPOTWAVE WIRELESS, INC.. Invention is credited to Bongfeldt, David, Simpson, Paul, Young, Shane.
Application Number | 20040097189 09/809218 |
Document ID | / |
Family ID | 4167425 |
Filed Date | 2004-05-20 |
United States Patent
Application |
20040097189 |
Kind Code |
A1 |
Bongfeldt, David ; et
al. |
May 20, 2004 |
Adaptive personal repeater
Abstract
An adaptive personal repeater transparently mediates signaling
between a wireless communications device (WCD) and a wireless
communications network. The repeater includes a Directional Donor
Unit (DDU) and a Subscriber Coverage Unit (SCU). The DDU maintains
a network link with a transceiver (base station) of the wireless
communications network. The SCU maintains a local link with the WCD
within a personal wireless space of the repeater. The SCU generally
includes, means for detecting respective uplink and downlink
channel frequencies of the wireless communications device, and
control means for controlling at least the SCU to selectively
receive and transmit signals within the detected uplink and
downlink channel frequencies. Total system gain is divided between
the DDU and the SCU, so that a separate gain and system control
unit is not required. This division of system gain also enables
high-performance on-frequency repeater functionality to be obtained
without the use of high-cost components.
Inventors: |
Bongfeldt, David;
(Stittsville, CA) ; Simpson, Paul; (Lanark,
CA) ; Young, Shane; (Nepean, CA) |
Correspondence
Address: |
OGILVY RENAULT
1981 MCGILL COLLEGE AVENUE
SUITE 1600
MONTREAL
QC
H3A2Y3
CA
|
Assignee: |
SPOTWAVE WIRELESS, INC.
3701 CARLING AVENUE P.O. BOX 11490
STN H OTTAWA
ON
K2H 8S2
|
Family ID: |
4167425 |
Appl. No.: |
09/809218 |
Filed: |
March 16, 2001 |
Current U.S.
Class: |
455/7 |
Current CPC
Class: |
H04W 52/10 20130101;
H04B 7/15535 20130101; H04W 52/52 20130101; H04B 7/2606 20130101;
H04B 7/15578 20130101; H04W 16/26 20130101 |
Class at
Publication: |
455/007 |
International
Class: |
H04B 003/36; H04B
007/14 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 18, 2000 |
CA |
2,323,881 |
Claims
We claim:
1. A repeater adapted to transparently mediate signaling between a
wireless communications device and a wireless communications
network, the repeater comprising: a Directional Donor Unit (DDU)
adapted to maintain a network link with a transceiver of the
wireless communications network; a Subscriber Coverage Unit (SCU)
adapted to maintain a local link with the wireless communications
device within a personal wireless space of the repeater, the SCU
comprising: means for detecting respective uplink and downlink
channel frequencies of the wireless communications device; and
control means adapted to control at least the SCU to selectively
receive and transmit signals within the detected uplink and
downlink channel frequencies.
2. A repeater as claimed in claim 1, wherein the DDU comprises: a
directional donor antenna (DDA) adapted to receive downlink channel
signals from a base station of the wireless communications network,
and to transmit uplink channel signals within a comparatively
narrow beam to the base station; and a transceiver diplexer (TRD)
adapted to amplify received downlink channel signals and control a
transmit power level of the uplink signals.
3. A repeater as claimed in claim 2, wherein the DDA is vertically
polarized.
4. A repeater as claimed in claim 2, wherein the DDA and the TRD
are integrated into a single unit.
5. A repeater as claimed in claim 1, wherein the SCU comprises: a
subscriber coverage antenna (SCA) adapted to receive uplink RF
signals from the wireless communications device, and transmit
downlink RF signals as a comparatively wide beam; and a
dual-directional processor (DDP) adapted to control respective
power levels of the uplink and downlink RF signals.
6. A repeater as claimed in claim 5, wherein the SCA is
horizontally polarized.
7. A repeater as claimed in claim 5, wherein the SCA and the DDP
are integrated into a single unit.
8. A repeater as claimed in claim 5, wherein the DDP comprises
means for controlling a transmit power level of the uplink RF
signals based on a received power level of the downlink RF
signals.
9. A repeater as claimed in claim 1, wherein the DDU and the SCU
are integrated into a single unit.
10. A repeater as claimed in claim 1, wherein the DDU and the SCU
are provided as separate units coupled together by a transmission
path adapted to convey the uplink and downlink RF signals.
11. A repeater as claimed in claim 1, wherein the control means
comprises: means for detecting at least one of an uplink channel
and a downlink channel of the wireless communications device; and
means for tuning respective uplink and downlink paths to
selectively amplify RF signals within the detected uplink and
downlink channels.
12. An adaptive repeater as claimed in claim 11, wherein the means
for detecting at least one of an uplink channel and a downlink
channel comprises means for acquiring weak desired RF signals
embedded within respective broad-band channels.
13. An adaptive repeater as claimed in claim 12, wherein the means
for acquiring a weak desired signal comprises: a respective narrow
band path adapted to sample RF signals within each of the uplink
and a downlink paths; and a detector coupled to each narrow band
path and adapted to detect the weak RF signals within the sampled
RF signals.
14. An adaptive repeater as claimed in claim 11, wherein the means
for tuning respective uplink and downlink paths comprises:
respective uplink and downlink Intelligent Gain Controllers (IGCs)
adapted to control a power level of corresponding uplink and
downlink RF signals; and a digital controller adapted to control a
gain of each IGC based on detection at least one of an uplink
channel and a downlink channel.
15. A repeater as claimed in claim 1, wherein the control means
further comprises means for dynamically adjusting a coverage area
of the personal wireless space in accordance with a location of the
wireless communications device relative to the SCU.
16. A repeater as claimed in claim 15, wherein the means for
dynamically adjusting a coverage area of the personal wireless
space comprises means for controlling a transmit power level of
downlink RF signals transmitted by the SCA based on detected signal
power of uplink RF signals received by the SCA.
17. A repeater as claimed in claim 16, wherein the means for
controlling the transmit power level of downlink RF signals
comprises: a broadband path adapted to sample the uplink RF signal
received by the SCA; and a variable gain amplifier coupled to the
broadband path and adapted to adjust a power level of the downlink
RF signal based on the sampled uplink RF signal.
18. A method of providing wireless communications services of a
wireless communications network to a subscriber located in an area
that is poorly serviced by the wireless communications network, the
method comprising a step of providing the subscriber with a
personal repeater adapted to transparently mediate signaling
between at least one wireless communications device and a base
station of the wireless communications network.
19. A method of enabling a subscriber located in an area that is
poorly serviced by a wireless communications network to access
wireless communications services of the wireless communications
network, the method comprising a step of providing the subscriber
with a personal repeater adapted to transparently mediate signaling
between a wireless communications device and a base station of the
wireless communications network.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is the first application filed for the present
invention.
MICROFICHE APPENDIX
[0002] Not Applicable.
TECHNICAL FIELD
[0003] The present application relates to wireless access networks,
and in particular to an adaptive personal repeater for enabling a
wireless subscriber to improve wireless services within a personal
wireless space.
BACKGROUND OF THE INVENTION
[0004] In the modern communications space, wireless access networks
are increasingly popular, as they enable subscribers to access
communications services without being tied to a fixed, wireline
communications device. Conventional wireless access network
infrastructure (e.g., base stations) is typically "built out", by a
network services provider, using a network-centric approach. Thus
the build-out normally begins with major Metropolitan Service Areas
(MSAs) using base stations located at the center of overlapping
coverage areas or "cells". The build-out, and corresponding
wireless communications services, subsequently migrates outward
from the MSAs to areas of lower population/service densities (e.g.,
urban to suburban to rural, etc.). At some point, usually dictated
by economics, the build-out slows and/or becomes spotty leaving
many individual wireless subscribers with unreliable or
non-existent service.
[0005] On-frequency repeaters are known in the art for improving
wireless services within defined regions of a wireless network
(e.g. within a building or a built-up area). Such on-frequency
repeaters are typically provided by the wireless network provider
in order to improve signal quality in high noise or attenuation
environments, where signal levels would otherwise be too low for
satisfactory quality of service. In some cases, a wireless network
provider may install a repeater in order to improve service in an
area lying at an edge of the coverage area serviced by a base
station, thereby effectively extending the reach of the
base-station.
[0006] Prior art repeaters are part of a network-centric view of
the wireless network space, in that they are comparatively large
systems provided by the network provider in order to improve
wireless service to multiple subscribers within a defined area. As
such, they form part of the network "build-out plan" of the network
provider. These systems suffer the disadvantage in that an
individual subscriber cannot benefit from the improved services
afforded by the repeater unless they happen to be located within
the coverage area of the repeater. However, there are many
instances in which wireless subscribers may reside or work in areas
where the coverage area of the wireless network is unreliable.
Typical examples include mobile subscribers, and subscribers
located in suburban and rural areas. Also, in-building coverage can
be unreliable even within MSAs, depending on the size, location and
construction of buildings and/or other obstacles. In such cases, it
may be uneconomical for a network provider to build-out the network
to provide adequate coverage area, thereby leaving those
subscribers with inadequate wireless services.
[0007] Accordingly, a method and apparatus that enables an
individual subscriber to cost-effectively access high quality
wireless communications services, independently of the location of
the subscriber, remains highly desirable.
SUMMARY OF THE INVENTION
[0008] An object of the present invention is to provide an
apparatus that enables an individual subscriber to cost-effectively
access high quality wireless communications services, independently
of a location of the subscriber.
[0009] Accordingly, an aspect of the present invention provides a
repeater adapted to transparently mediate signaling between a
wireless communications device and a wireless communications
network. The repeater comprises a Directional Donor Unit (DDU) and
a Subscriber Coverage Unit (SCU). The DDU is adapted to maintain a
network link with a transceiver (base station) of the wireless
communications network. The SCU is adapted to maintain a local link
with the wireless communications device within a personal wireless
space of the repeater. The SCU generally includes, means for
detecting respective uplink and downlink channel frequencies of the
wireless communications device, and control means adapted to
control at least the SCU to selectively receive and transmit
signals within the detected uplink and downlink channel
frequencies.
[0010] The DDU and SCU are preferably provided as highly integrated
antenna/amplifier units coupled together by a bi-directional signal
path, such as a coaxial cable. In this arrangement, the total APR
gain can be divided between the DDU and the SCU, so that a separate
gain and system control unit is not required. Additionally,
division of system gain between the DDU and SCU also enables
high-performance on-frequency repeater functionality to be obtained
without the use of high-cost components, and at the same time
facilitates isolation between the system antennas.
[0011] Another aspect of the present invention provides a method by
which a network service provider can provide wireless
communications services to a subscriber or a collocated group of
subscribers located in an area that is poorly serviced by a
wireless communications network. Rather than build-out the network
with high-cost equipment, in accordance with the present invention,
the network service provider can provide the subscriber(s) with a
personal repeater adapted to transparently mediate signaling
between wireless communications devices of the subscriber(s) and a
base station of the wireless communications network. This provides
the network service provider with a cost-effective means of
addressing service quality issues on an individual subscriber
basis, in areas where network build-out is uneconomical.
[0012] Another aspect of the present invention provides a method by
which a third-party vendor can enable subscribers located in an
area that is poorly serviced by a wireless communications network
to access wireless communications services of the wireless
communications network. Thus the third-party vendor can provide the
subscriber(s) with a personal repeater adapted to transparently
mediate signaling between a wireless communications device of the
subscriber and a base station of the wireless communications
network. Because the personal repeater is transparent to both the
wireless communications network and the subscriber's wireless
communications device, the subscriber(s) can install and operate
the personal repeater independently of the network service
provider, without any adverse impact on operation of the base
station.
[0013] The APR of the present invention represents a
Subscriber-Centric Technology (SCT), in that it complements
existing wireless communications networks (such as cellular and PCS
networks) by providing a cost-effective product solution for the
individual subscriber who has inadequate or non-existent wireless
coverage. The Adaptive Personal Repeater (APR) of the present
invention allows the wireless subscriber or collocated group of
subscribers to access the wireless communications network by
reaching back from the outside of the reliable network without the
need for any further network-centric build out. Thus the APR
provides the subscriber with a means to address poor or
non-existent coverage when, and where, they need it, and thereby
empowers the individual subscriber to manage their own "personal
wireless space".
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Further features and advantages of the present invention
will become apparent from the following detailed description, taken
in combination with the appended drawings, in which:
[0015] FIG. 1 is a block diagram schematically illustrating an
Adaptive Personal Repeater in accordance with an embodiment of the
present invention;
[0016] FIG. 2 is a block diagram schematically illustrating
principle elements of the Adaptive Personal Repeater of FIG. 1;
[0017] FIG. 3 is a block diagram schematically illustrating
principle elements of an exemplary directional donor unit (DDU)
usable in the embodiment of FIG. 2;
[0018] FIG. 4 is a block diagram schematically illustrating
principle elements of an exemplary subscriber coverage unit (SCU)
usable in the embodiment of FIG. 2;
[0019] FIG. 5 is a block diagram schematically illustrating
principle elements of an exemplary downlink AGC usable in the SCU
of FIG. 4;
[0020] FIG. 6 is a block diagram schematically illustrating
principle elements of an exemplary uplink AGC usable in the SCU of
FIG. 4;
[0021] FIG. 7 is a state diagram illustrating exemplary states and
state transitions traversed during operation of the Adaptive
Personal Repeater of FIG. 1; and
[0022] FIG. 8 is a flow chart illustrating principle operations of
an exemplary adaptive control algorithm during initialization and
operation of the Adaptive Personal Repeater of FIG. 1.
[0023] It will be noted that throughout the appended drawings, like
features are identified by like reference numerals.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0024] The present invention provides an Adaptive Personal Repeater
(APR) 2, which enables cost-effective delivery of high quality
wireless communications services to subscriber(s) located outside a
reliable coverage area of an existing wireless communications
network 4. In general, the APR 2 operates to create a personal
wireless space 6 encompassing the subscriber's wireless
communications device(s), and "reaches back" into the reliable
coverage area of the wireless communications network 4 in order to
access wireless communications services. FIG. 1 is a block diagram
schematically illustrating operation of the APR 2 in accordance
with the present invention.
[0025] As shown in FIG. 1, a conventional wireless communications
network 4 comprises a plurality of base stations 8, each of which
provides wireless communications services within a respective
coverage area or cell 10. Mobile communications devices (not shown)
within a cell 10 access wireless communications services of the
network 4 by negotiating a wireless connection with the respective
base station 8 of the cell 10, in a manner known in the art. The
size and shape of each cell 10 may be irregular, and will depend on
many factors, including, for example, distance from the respective
base station 8, and the presence of obstacles (e.g. buildings and
geographical features such as hills, valleys etc.) which tend to
attenuate radio signals. Within a multi-cell network 4 such as
shown in FIG. 1, inter-cell boundaries 12 are determined as the
point at which a mobile communications device is switched or
"handed-off" from one base station 8 to a base station 8 of an
adjacent cell 10. Typically, this is determined on the basis of
signal power. At the edge of the wireless communications network 4,
the cell boundary corresponds with the network coverage area
boundary 14, which may nominally be determined as the point at
which the signal-to-noise (S/N) ratio becomes too low to permit
negotiation of a satisfactory connection between the nearest base
station 8 and a mobile communications device.
[0026] Within each cell 10, the quality of wireless service access
may vary widely. For example, within a built-up area, multiple
reflections from the surfaces of buildings can create a high-noise
or attenuation environment which degrades reliability of access to
the wireless communications network. Within buildings, both signal
scattering and attenuation can prevent reliable access to the
wireless communications network.
[0027] The Adaptive Personal Repeater (APR) 2 of the present
invention operates to define a personal wireless space 6 for the
subscriber(s), and reaches back to a base station 8a to enable the
subscriber(s) to reliably access the wireless communications
services of the network 4. The personal wireless space 6 may be
defined within a poorly served area of the wireless network 4 (e.g.
within a building or other high noise/attenuation area) or, as
shown in FIG. 1, in an area beyond the network coverage area
boundary 14. In either case, the APR 2 is functionally positioned
between the base station 8a and the subscriber's Wireless
Communications Device(s) (WCD) 16. The subscriber's WCD(s) 16 may
take the form of any conventional wireless communications device,
such as, for example, Personal Digital Assistants (PDA's), wireless
telephone handsets, pagers, and one and two-way messaging
devices.
[0028] Between the APR 2 and the base station 8a, a network link is
established, in which respective uplink and downlink channel power
levels are detected and adjusted in order to optimize performance
of the link. Similarly, between the APR 2 and the subscriber's
mobile communications device 16, a local wireless link 20 is
established, in which respective uplink and downlink channel power
levels are detected and adjusted as will be described in greater
detail below. However, the APR 2 does not terminate any connections
intermediate the base station 8a and the subscriber's mobile
communications device 16, and does not perform any signal format or
communications protocol conversions. Accordingly, the APR 2 is
functionally transparent to both the network and conventional
mobile communications devices, and thereby enables protocol- and
signal format-independent interaction between the base station 8a
and the subscriber's mobile communications device 16. Once the
respective links 18, 20 between the APR 2 and the base station 8a,
and between the APR 2 and the WCD 16 have been set up, and
respective up-link and down-link channel powers negotiated, the APR
2 operates to transparently facilitate signaling between the WCD 16
and the base station 8a. Thus the WCD 16 interacts with the base
station 8a to negotiate communications links (e.g. protocols,
signal formats, time slots etc.) in a conventional manner, so that
wireless communications services of the network 4 can be seamlessly
accessed by the subscriber using the WCD 16. However, as described
in greater detail below, the transmit and receive performance of
the APR 2 exceeds that of a conventional mobile communications
device, thereby enabling a connection between the WCD 16 and the
base station 8a to be established over a greater distance and/or in
a higher noise/attenuation environment than would be possible if
the WCD 16 were communicating with the base station 8a directly.
Moreover, the APR adaptively maintains a reliable link between the
WCD and the base station.
[0029] The APR 2 of the present invention is an "on-frequency"
repeater, in that uplink and downlink RF signals are conveyed
through the APR 2 without altering the respective channel
frequencies. In operation, transmissions from the subscriber's
WCD(s) 16 are detected by the APR 2, which then adapts to the RF
characteristics of the subscriber's WCD(s) 16 by acquiring
appropriate uplink and downlink channel frequencies. Thereafter,
the APR 2 operates to selectively receive, amplify, and retransmit
RF signals within these uplink and downlink channel
frequencies.
[0030] FIGS. 2-6 schematically illustrate principal elements of an
APR 2 in accordance with an embodiment of the present invention. As
shown in FIG. 2, the APR 2 generally comprises a Directional Donor
Unit (DDU) 22 and a Subscriber Coverage Unit (SCU) 24. The DDU 22
and SCU 24 may be integrated into a single device, or may be
provided as separate components suitably coupled to each other
(e.g. via a coaxial cable or the like). For ease of description,
each of the DDU 22 and SCU 24 are described below as separate
devices coupled together by a suitable connection path 26 (e.g. a
coaxial cable connection).
[0031] In the illustrated embodiment, each of the DDU 22 and SCU 24
are provided as highly integrated units, which co-operate to
implement the entire functionality of the APR 2. As described
below, this arrangement improves performance, lowers cost and
eliminates the need for an electronic unit separate from the
antennas to house the repeater's functional building blocks.
[0032] Conventional On-Frequency Repeaters (OFRs) generally
comprise one or more power amplification and control units
connected to two passive antennas via respective lengths of coaxial
cable. These electronic units are usually located at some distance
from the passive antennas, requiring the need for expensive coaxial
cable to minimize losses and maintain isolation between each unit
and the antennas. Also, because even expensive coaxial cables have
some amount of loss, expensive high performance building blocks,
such as highly linear power amplifiers are required to overcome the
loss and meet the system performance specifications. High
performance functional blocks and high grade cables are necessary
to meet not only the transmit power requirements, but to preserve
the receive signal quality as well. Since OFRs are non-frequency
translating and the system gain within the unit can approach 100
dB, the possibility of internal system instabilities are high.
Thus, it is frequently necessary to implement separate shielding
for all internal building blocks, typically by using expensive
multiple aluminum enclosures within each electronic unit.
[0033] In the illustrated embodiment, the functionality of the APR
2 is provided by two highly integrated units, each of which
provides a portion of the system gain necessary to meet the
repeater's overall performance requirements. As will be described
in further detail below, this division of system gain substantially
reduces the need for high performance (and thus expensive)
components and high shielding requirements within each unit.
[0034] In accordance with the present invention, the DDU 22 and SCU
24 implement a technique of Adaptive Interference Mitigation, in
which RF interference in the subscriber's personal wireless space 6
is mitigated by a combination of one or more of: physical antenna
separation; cross polarization; RF power management; and the use of
a narrow beam network link 18 between the APR 2 and the base
station 8a. Interference has become a problem in most wireless
service networks. The type and degree of interference varies from
one network to the other. So-called "Smart" antenna technology has
been used in a wide variety of applications to combat interference
in these networks. This smart antenna technology can be effectively
applied at a base station to reduce the interference problem for
both the downlink (interference to the handset from other base
stations) and the uplink (interference to the base station from
other handsets) communication paths. However, smart antenna
technology has not been used to mitigate interference occurring at
the handset end of the link. This is largely due to the size and
power constraints of the handset, and the requirement that the
handset antenna must be omni-directional to successfully connect
to, and communicate with the base station in a wide area
network.
[0035] The APR 2 of the present invention provides a means to
mitigate interference at the handset end of the network for both
the downlink and the uplink propagation paths. The APR 2 operates
to transform the handset's omni-directional antenna pattern of the
WCD 16(for the local wireless link 20, which is confined to a small
area of reliable coverage) into a directional antenna pattern (of
the network link 18) by masking over the weak handset signal with a
strong conditioned signal in a specific direction. Additionally,
the APR 2 adaptively provides continuous interference mitigation
within the subscriber's personal wireless space 6, and minimizes
any possible interference that may be generated, by confining the
size of the personal wireless space 6 to only the subscriber's
position.
[0036] Directional antennas radiate RF energy in one direction more
than in other directions. The APR 2 uses an external directional
antenna to reach back into the network and radiate RF power to the
base station 8a from the subscriber's personal wireless space 6. By
virtue of the directionality of the antenna, the subscriber's
personal wireless space 6 not only can discriminate against
interference coming from outside the antenna's beam-width, but also
can prevent generating possible interference to other base stations
8 in other directions. This in itself passively mitigates the
interference in both the downlink and uplink paths. The antenna's
discrimination provides the means to spatially separate the desired
signal from possible sources of interference from other base
stations. With this discrimination in hand, the APR 2 then
amplifies and conditions the desired signal and adaptively
transmits it to ensure that at the WCD 16, the desired signal
remains relatively constant in level regardless of the subscriber's
position or movement within the personal wireless space 6. Unlike
conventional mitigation schemes, where the interference is reduced
relative to the desired signal or itself, the APR 2 operates to
increase the desired signal level relative to the interference
within the subscriber's personal wireless space 6.
[0037] The DDU 22 operates to establish and maintain the network
link 18 between the APR 2 and the base station 8a of the wireless
communications network 4. As is known in the art, signal
attenuation within such a wireless link 18 is generally a function
of distance between the base station 8a and the DDU 22.
Accordingly, the DDU 22 preferably enables the APR 2 to maintain a
connection with the base station 8a over a wide range of receive
and transmit power levels. The DDU 22 may, for example, be
advantageously designed to receive downlink signal power levels to
as low as -120 dBm. Additionally, the DDU 22 may be designed to
transmit uplink signals to the base station to as high as +37 dBm,
which will typically be on the order of 10 dB greater than that of
conventional cellular handsets. This transmit and receive
performance of the DDU 22 enables maintenance of the network link
18 with the base station 8a, even when the DDU 22 is located well
beyond the conventional cell (and network coverage area) boundary
14.
[0038] In the embodiment illustrated in FIG. 2, the Directional
Donor Unit (DDU) 22 is provided as a single port active antenna
comprising a Directional Donor Antenna (DDA) 28 integrated with a
Transceiver Diplexer (TRD) 30. A bi-directional port 32 couples the
DDU 22 to the SCU 24 through the coaxial cable connection 26.
[0039] In the illustrated embodiment, the DDA 28 is provided as a
high performance, vertically polarized, directional antenna. The
DDU 22 is positionable (i.e. rotatable in a horizontal plane) to
allow for alignment of the DDA 28 to the base station 8a during
installation. Directionality of the DDA 28 helps to fine tune
positioning. Vertical polarization maximizes coupling to the
typically vertical electromagnetic (EM) field of the (conventional)
base station 8a.
[0040] The DDU 22 can beneficially be designed for outdoor use. In
such cases, fewer components with better temperature ratings can be
used in this unit to implement the functional performance
requirements of the DDU 22 while keeping costs down. The DDU 22
components may, for example, represent less than 20% of the APR's
total component count, all of which are designed to operate in an
outdoor environment. The DDU 22 may also include a low-cost plastic
enclosure that protects the functional components from the outdoor
elements. This enclosure houses an integrated high gain antenna and
Transceiver Diplexer (TRD) on a common Printed Wiring Board (PWB).
As part of the TRD, a low noise amplifier is used to preserve the
downlink receive signal quality, while a power amplifier delivers
the necessary power in the uplink path. Since both devices are
connected directly to the integrated antenna via a diplexer, the
system performance is maximized while keeping component costs
comparatively low. This means that the low noise amplifier and
power amplifier requirements can be relaxed by 3 to 5 dB in
comparison to conventional OFRs so that costs are significantly
lower. Performance is enhanced by virtue of little or no loss
between the antenna and the diplexer. Also, the system reliability
can be improved by using lower power devices. The DDU gain for both
the uplink and the downlink paths can be less than 40 dB, keeping
isolation requirements within the unit moderately low.
Consequently, individual components or building blocks do not
require separate aluminum enclosures for shielding, but rather the
uplink and downlink paths can be separated and the building blocks
shielded together as functional sections, using simple board-level
shields to increase isolation and prevent circuit coupling of
unwanted high-level signals. Since the DDU 22 sets the system Noise
Figure (NF) of the APR 2 in the downlink path, and provides the
necessary gain for a given input to produce a +37 dBm EIRP output
in the uplink path, the loss of the coaxial cable 26 can be
relatively high, without adversely affecting the system
performance. For this reason, in comparison with conventional OFR
systems, a much lower grade cable (e.g. RG58 verses 1/2 inch
heliax) can be used, hence the cost of the cable can be very low by
comparison (e.g. by a factor of 10 or more for a given length).
Lower cost cable usually means a much smaller cable diameter, which
greatly improves ease of installation by allowing for a tighter
bend radius. Also, because the isolation requirements are lower,
the shielding of the cable is not as critical.
[0041] In operation, the DDA 28 simultaneously transmits uplink RF
signals and receives downlink RF signals through the network link
18. For example, the DDA 28 may be designed to transmit uplink RF
signals within a frequency band from 824 to 849 MHz and receive
downlink RF signals within a frequency band from 869 to 894 MHz. A
12 dBi antenna gain is required to transmit a maximum EIRP of +37
dBm in the uplink path for a +25 dBm TRD output.
[0042] The bi-directional port 32 simultaneously receives and
transmits both uplink and downlink frequency bands through the
coaxial connection 26. For example, the port 32 may be designed to
receive uplink RF signals from the SCU 24 within the uplink
frequency band of 824 to 849 MHz and transmit downlink RF signals
to the SCU 24 within the downlink frequency band of 869 to 894
MHz.
[0043] As shown in FIG. 3, the TRD 30 comprises respective uplink
and downlink signal paths 34, 36 connected between a DDA diplexer
38 coupled to the DDA 28, and a TRD port diplexer 40 coupled to the
port 32. The DDA diplexer 38 operates to separate the signal paths
34, 36 at the DDA 28. Similarly, the TRD port diplexer 40 operates
to separate the signal paths at the port 32. The respective TRD
port and DDA diplexers 38, 40 also operate to define and limit the
frequency band(s) over which the system must maintain
stability.
[0044] In the illustrated embodiment, the uplink path 34 comprises:
a two-stage driver 42 including a pair of series connected driver
amplifiers 44a and 44a; and a power amplifier (PA) 46 connected in
series with the two-stage driver 42. This arrangement of cascaded
driver and power amplifier circuits connected directly to the DDA
via the DDA diplexer 38 reduces output power requirements of the PA
46. For example, the output power of the PA 46 at the DDA 28, which
may be automatically controlled (i.e. enabled or disabled) by a
simple detection circuit 48, can be approximately 3 dB lower than
the equivalent output power of a conventional cellular handset.
This arrangement minimizes losses between the PA 46 and the DDA 28;
improves performance, power consumption and reliability; while at
the same time lowering cost.
[0045] The two-stage driver 42 and the power amplifier 46 within
the uplink path 34 facilitate automatic RF power management, and so
allows the DDU 22 to reliably maintain the network link 18 with the
base station 8a. This operation is simplified by the fact that the
propagation environment of the network link 18 is comparatively
static due to the fixed locations of the base station 8a and the
DDU 22. Reliable maintenance of the network link 18 can thus be
achieved by measuring the power of downlink RF signals received
from the base station 8a, and using the measured power to control
the signal power of uplink RF signals transmitted to the base
station 8a. For example, if the measured power of the received
downlink RF signals is greater than a predetermined minimum
threshold, then the uplink RF signal transmit power can be reduced
to improve spectrum efficiency, conserve energy, increase
reliability and reduce system gain. Conversely, if the measured
power of the received downlink RF signals drops below the
predetermined minimum threshold, then the uplink RF signal transmit
power can be increased to improve the signal-to-noise ratio. In the
illustrated embodiment, control of the uplink RF signal transmit
power in this manner is accomplished within the SCU 24, as will be
described in greater detail below. It will be appreciated, however,
that uplink RF signal transmit power control may be effected within
the TRD 30 using a suitable cross-over circuit (not shown) in
which, for example, the PA 46 is provided as a variable gain
amplifier controlled by a controller unit coupled to the downlink
path 36 to detect the received downlink RF signal power.
[0046] To further improve the reliability of the PA 46, an isolator
50 may be placed in series between the PA 46 and the DDA diplexer
38 to prevent reflected power from appearing at the output of the
PA 46 (due, for example, to any mismatch between the DDA 28 and the
DDA diplexer 38). Additionally, the isolator 50 can provide
constant impedance matching for the DDA diplexer 38 when the PA 46
is enabled and disabled. As may be appreciated, frequency crossover
noise may contaminate the uplink RF signal in the uplink path 34.
Such frequency cross-over noise is attenuated by the DDA and port
diplexers 36, 38. Further attenuation of frequency crossover noise
within the uplink path 34 may be accomplished using an uplink Band
Pass Filter (BPF) 52, connected in series between the two driver
stages 44a and 44a. Isolation of the DDA diplexer 38 prevents the
PA 46 from saturating the downlink path amplifiers (described
below). This isolation is critical because the transmit power from
the PA 46 into the DDA diplexer 38 can be as high as +28 dBm.
[0047] The downlink path 36 generally comprises a Low Noise
Amplifier (LNA) 54, a downlink band pass filter (BPF) 56, and a
downlink signal driver 58 connected in series between the DDA
diplexer 38 and port diplexer 40. The LNA 54 is preferably a high
performance amplifier providing, for example, 15 dB of gain with a
noise figure of about 1.5 dB. The LNA gain and noise figure, in
combination with the DDA 28 gain and losses in the DDA diplexer 38,
determine the minimum signal strength and quality (i.e.
signal-to-noise [S/N] ratio) of received downlink RF signals. For
example, in the illustrated embodiment, a received downlink RF
signal of -120 dBm in a 25 kHz noise bandwidth yields a S/N ratio
of +17 dB at the output of the bi-directional port 32, excluding
any environmental noise.
[0048] The downlink BPF 56 (which may, for example, be a SAW BPF)
operates to reject both image and frequency crossover noise, and
further attenuates any uplink RF signal in the downlink path 36.
The downlink signal driver 58 is conveniently provided as an
amplifier which operates as a buffer and gain stage to compensate
for losses in the (coaxial cable) connection 26 between the DDU 22
and SCU 24. Because cable losses in low-cost coaxial cable tend to
be relatively high, it is preferable to amplify the received
downlink RF signal upstream of the connection 26, and thus before
the loss is incurred, to preserve the S/N ratio established by the
DDA 28, LNA 54, and DDA diplexer 38.
[0049] Total APR gain is the summation of both the DDU 22 and SCU
24 gains minus the losses in the coaxial cable connection 26, and
may be limited by the isolation between the units achieved during
installation. The DDA 28 preferably has a front to back ratio of
greater than 25 dB to help maximize the isolation between the two
units, and therefore achieve sufficient APR gain to maintain a
reliable network link 18.
[0050] Referring back to FIG. 2, the Subscriber Coverage Unit (SCU)
24 operates to create the subscriber's personal wireless space 6 by
maintaining the local wireless link 20 between the APR 2 and the
subscriber's WCD(s) 16. As with a conventional cell 10 of the
wireless communications network 4, the subscriber's personal
wireless space 6 may be irregular in shape. However, the coverage
area will not only be determined as a function of RF signal power
and/or signal-to-noise ratio of uplink RF signals received by the
SCU 24, but also as a function of the position of the subscriber's
WCD 16 relative to the SCU 24. In all cases, it is anticipated that
the coverage area of the subscriber's personal wireless space 6
will be very much smaller than a conventional cell 10 of the
wireless communications network 4. For example, in some
embodiments, it is expected that the subscriber's personal wireless
space 6 will extend 25 m (or less) from the SCU 24. Such
embodiments are particularly suited for enabling the subscriber to
access wireless communications services of the network 4 from, for
example, any location in and about their residence or place of
business. Other embodiments may provide a larger or smaller
personal wireless space 6, if desired.
[0051] In any event, it is preferable for the subscriber's WCD 16
to operate at a minimum signal transmission power. Thus the SCU 24
implements a technique of Adaptive Coverage Breathing (ACB), such
that the coverage area of the subscriber's personal wireless space
6 is automatically adjusted in order to ensure acceptable
signal-to-noise ratio in both the uplink and downlink paths of the
local link 20, while at the same time minimizing transmission (i.e.
uplink RF signal) power in the WCD 16.
[0052] In general, Adaptive Coverage Breathing (ACB) comprises a
technique of RF power management that allows the coverage area of
the subscriber's personal wireless space 6 to "breathe" by
adaptively expanding and contracting to the position of the
subscriber's WCD 16 relative to the SCU 24. This allows both the
subscriber's WCD 16 and the SCU 24 to radiate only the necessary
powers needed to maintain reliable signaling over the local link
20. As the subscriber's WCD 16 moves relative to the SCU 24, the
coverage area of the personal wireless space 6 changes continuously
to adapt to the movement. As the WCD 16 moves towards the APR 2,
the coverage area automatically contracts, so that the personal
wireless space 6 is limited to just encompass the WCD 16. This can
be accomplished by measuring the signal power of uplink RF signals
received from the WCD 16, and then adjusting the transmission power
of downlink RF signals accordingly. If two or more wireless
communications devices 16 are being used simultaneously, then the
SCU 24 can operate to expand the coverage area to accommodate the
WCD 16 located furthest from the SCU 24 (or transmitting the
weakest uplink RF signals). This is achieved by measuring the power
of uplink RF signals received from each of the wireless
communications devices 16, and adjusting the downlink transmit
power to account for the difference between the measured signal
power levels.
[0053] Two major benefits for the subscriber resulting from the ACB
concept include reduced RF radiation, and increased battery life
within the subscriber's WCD 16. Reduced RF radiation for the
subscriber is a major benefit, particularly in view of growing
concerns that high level RF radiation in close proximity to the
subscriber's body (typically the head) may be hazardous to human
health. The ACB concept implemented by the present invention
permits the RF power radiation of the subscriber's WCD 16 to be
significantly reduced (in comparison to that required for
communications within the conventional wireless communication
network 4), by maintaining reliable balanced power levels in the
uplink and downlink paths. Typically, the single most
power-consuming section in a wireless communications device is the
uplink channel RF amplifier. This amplifier is normally a class AB
or C amplifier, which consumes battery power proportional to the RF
input signal level. That is, a large RF input signal will cause the
uplink channel RF amplifier to consume a large amount of battery
power to produce the necessary uplink RF signal power through the
antenna. Lowering the uplink RF signal power requirement of the WCD
16, as enabled by the present invention, significantly extends the
battery life, and thus the "talk time" of the WCD 16.
[0054] In the illustrated embodiment, a minimum acceptable uplink
channel RF signal power of the WCD 16 is negotiated at a start of a
communications session. This uplink channel RF signal power is then
maintained constant (during the communications session), and the
SCU 24 adapts to changes in the position of the WCD 16 by accepting
widely varying uplink channel RF signal powers from the WCD 16.
With this arrangement, the variation in received uplink channel RF
signal power may be as high as 50 to 60 dB, depending largely on
the proximity of the WCD 16 to the SCU 24. Accordingly, the SCU 24
is preferably designed to receive uplink channel RF signal power
levels varying between, for example, 0 dBm to -60 dBm.
[0055] The received uplink channel RF signal power level can be
measured by the SCU 24, and used to control the downlink channel RF
signal power. For example, if the received power of the uplink RF
signals is greater than a predetermined minimum threshold, then the
downlink RF signal transmit power can be reduced (i.e. the coverage
area of the subscriber's personal wireless space 6 reduced) to
improve spectrum efficiency, conserve energy, increase reliability
and reduce system gain. Conversely, if the measured power of the
received uplink RF signals drops below the predetermined minimum
threshold, then the downlink RF signal transmit power can be
increased (i.e. the coverage area of the subscriber's personal
wireless space 6 expanded)to improve the signal-to-noise ratio.
[0056] In the illustrated embodiment, the Subscriber Coverage Unit
(SCU) 24 is provided as a single port active antenna comprising a
Subscriber Coverage Antenna (SCA) 60 integrated with a
dual-directional processor (DDP) 62. A single bi-directional port
64 couples the DDP 62 to the TRD 30 via the coaxial cable 26. As
shown in FIG. 4, the DDP 62 comprises respective uplink and
downlink signal paths 66 and 68 connected between an SCA diplexer
70 coupled to the SCA 60, and a port diplexer 72 coupled to the
bi-directional port 64. The SCA diplexer 70 operates to separate
the signal paths 66, 68 at the SCA 60. Similarly, the port diplexer
72 operates to separate the signal paths 66 and 68 at the
bi-directional port, P2 64. The respective SCA and port diplexers
70 and 72 also operate to define and limit the frequency band(s)
over which the system must maintain stability.
[0057] In the illustrated embodiment, the SCA 60 is provided as a
wide beam-width, horizontally polarized, directional antenna.
Vertical positioning of the SCU 24 (and thus the SCA 60) provides a
mechanism to improve isolation between the DDA 28 and SCA 60, as
well as to optimize total APR gain. A wide beam-width of the SCA 60
ensures adequate forward coverage to create a "bubble-effect" for
the personal wireless space 6. Horizontal polarization creates an
orthogonal relationship to the polarization of the DDA 28, further
improving isolation between the SCA 60 and the DDA 28, while
increasing the field coupling between the SCA 60 and the WCD 16.
System isolation is further improved by the front to back ratio of
the SCA 60, which may, for example, be >10 dB.
[0058] The SCU 24 can beneficially be designed as an indoor unit
that incorporates the SCA 60 integrated with the dual directional
processor (DDP) 62. In some embodiments, the radiating element of
the antenna can be physically attached to the printed wiring board
(PWB) shields, which can then serve as the reflector portion of the
antenna. The DDP 62 includes two intelligent gain controllers
(IGCs) 92 and 94, each sharing a common IF down-converter and
narrowband detector, and being controlled by a single digital
controller in accordance with an adaptive control algorithm. The
number of components in the SCU 24 may, in some embodiments,
account for over 80% of the APR's total component count, all of
which can be low power devices with a commercial temperature rating
to satisfy the indoor environment, which in turn helps to keep
costs down.
[0059] The gain in the SCU 24 can be less than 60 dB for both the
uplink and downlink paths. This gain is manageable in a single PWB,
without the need to separately enclose the individual building
blocks. As with the DDU 22, the uplink and downlink paths are
separated, and the building blocks can be shielded together as
functional sections using simple, conventional, board-level shields
to increase isolation and prevent circuit coupling of unwanted
high-level signals. The digital controller can be shielded from the
RF and analog sections (also be means on conventional board-level
shields), to prevent digital noise from radiating to the RF and
analog sections. This simple shielding requirement helps to lower
the product cost while improving the reliability by maintaining
unit stability.
[0060] The SCA 60 operates to transmit downlink RF signals to the
subscriber's WCD 16, and receives uplink RF signals from the
subscriber's WCD 16. An antenna gain of 6 dBi is required, but not
limited to radiate a maximum -20 dBm EIRP in the downlink channel.
Maximum EIRP, minus the antenna gain, determines the output of the
DDP 62, which may, for example, be about -26 dBm.
[0061] The bi-directional port 64 simultaneously receives and
transmits both uplink and downlink frequency bands. For example,
the bi-directional port 64 may accept downlink RF signals from the
DDU 22 within a frequency band from 869 to 894 MHz, and transmit
uplink RF signals to the DDU 22 within a frequency band from 824 to
869 MHz.
[0062] In the illustrated embodiment, the dual-directional
processor (DDP) 62 is provided as a combined RF and digital
processing module. RF signals within the uplink and downlink paths
66 and 68 are separately amplified, conditioned and processed (over
their entire 25 MHz bands). This processing scheme improves
performance while reducing complexity, thus lowering product cost.
The DDP 62 comprises: the uplink path 66 including a wideband
uplink Automatic Gain Controller (AGC) 74 series connected with a
slaved variable gain amplifier (VGA) 76 and an output amplifier 78;
the downlink path 68 including a preamplifier 80, wideband downlink
automatic gain controller (AGC) 82, a slaved variable gain
amplifier (VGA) 84, and an output amplifier 86; a switched common
down-converter 88; and a digital controller 90 operating under
software control.
[0063] The uplink path 66 interfaces with the down-converter 88 and
digital controller 90 to define an uplink intelligent gain control
(IGC) 92. Similarly, the downlink path 68 interfaces with the
down-converter 88 and digital controller 90 to define a downlink
IGC 94.
[0064] As is known in the art, on-frequency repeaters can oscillate
if the system gain exceeds the antenna isolation. For this reason,
and depending on the required link performance, installation of
on-frequency repeaters can be very difficult. In accordance with
the present invention, the IGCs incorporate the concepts of
Adaptive Coverage Breathing (ACB) and Coverage Area Signature (CAS)
to prevent and eliminate the possibility of oscillations occurring
due to system instability during installation and subsequent
operation of the APR 2. The ACB concept ensures only the necessary
power is transmitted in both the uplink and downlink paths to
maintain a reliable local link 20, hence the system gain is only as
high as it needs to be in both paths, which ultimately increases
system stability. The CAS concept provides a means to de-correlate
the leakage signals that appear at the APR inputs (DDA 28 and SCA
60) from the incoming received signals. This de-correlation allows
the APR 2 to separate the leakage signal from the incoming signals
in order to adaptively adjust the APR gain to maintain a defined
level of stability.
[0065] An unconditionally stable system requires that total system
isolation (comprising the front to back ratios of the DDA 28 and
SCA 60; polarization loss; propagation path loss; and cable losses)
must be greater than the maximum combined gain of the DDP 62 and
the TRD 30. System stability within a defined band can be
maintained by operation of the uplink and downlink IGCs 92 and 94
which adaptively adjust the hardware gain in the uplink and
downlink paths 66 and 68 independently, so as to minimize the
transmit power in both directions, via a hardware and software
control algorithm. Gain reduction as a result of insufficient
isolation only reduces the coverage area of the personal wireless
space 6. It does not limit the ability of the APR 2 to maintain
reliable links 18, 20 in both directions for the reduced coverage
area of the personal wireless space 6.
[0066] As part of the IGC, the down-converter 88 and digital
controller 90 operate to implement a digital offset correction
method which enables the output of a wideband AGC to be set for RF
signals that have not captured the AGCs 74 and 82. As in known in
the art, a wideband AGC will level to the highest signal that
captures the AGC within a defined bandwidth. If no signals are
present, the AGC may level to the thermal and system noise of a
given bandwidth. If weak desired (i.e. uplink or downlink RF)
signals are present, and the AGC bandwidth is much larger than the
signal bandwidth (such that noise masks the weak signals) the AGC
will be captured by the noise rather than the weak desired signal.
In the present invention, narrowband detection is used as a means
to detect the (weak) desired signals embedded in the noise.
Detection of the desired uplink and downlink signals is then used
by the digital controller 90 to offset the output to which the
appropriate AGCs 74 and 82 level. This same technique can also be
used to detect weak desired signals in the presence of high-level
unwanted signals that would otherwise capture an AGC and limit the
system gain for the desired signals.
[0067] As shown in FIG. 4, the down-converter 88 comprises a
switching input 96, an active mixer 98, a Xtal band pass filter
100, a log amp detector 102, and a tunable synthesizer 104, which
is tuned by the digital controller 90 to 45 MHz above the uplink
channel frequency and 45 MHz below the downlink channel frequency.
The switching input 96 is controlled by the digital controller 90
to supply an RF signal from a selected one of the uplink and
downlink AGCs 74 and 82 to the active mixer 98. Similarly, the
synthesizer 104 is controlled by the digital controller 90 to
supply an RF synthesized signal to the mixer 98. The output of the
mixer 98 is channeled by the Xtal BPF 100 and supplied to the
detection log amplifier 102, which operates to detect the uplink
and downlink signals within their respective channels. The output
of the detection log amplifier 102 is supplied to the digital
controller 90, and is used for decision making in accordance with
the adaptive control algorithm. Thus when the switching input 96
supplies an RF signal from the uplink path 66 to the mixer 98, the
Xtal BPF 100 and detection log amplifier 102 operate to detect the
level and number of desired signals within the uplink channel, and
this information can be used by the digital controller 90 to set
the appropriate power in the uplink path 66 and to tune the
synthesizer 104 to the corresponding downlink channel frequency.
Conversely, when the switching input 96 supplies an RF signal from
the downlink path 68 to the mixer 98, the Xtal BPF 100 and
detection log amplifier 102 operate to detect weak desired signals
within the downlink channel, and this information can be used by
the digital controller 90 to set the appropriate power in the
downlink path 94. This arrangement enables the digital controller
90 to detect any number of weak desired uplink and downlink signals
that are below either high-level wanted signals and/or adjacent
carrier signals, or the -95 dBm system noise floor within a
respective 25 MHz bandwidth. The digital controller 90 provides a
digital correction to each of the AGCs 74 and 82, thereby
offsetting the respective leveled outputs to the weak desired
signals.
[0068] The digital controller 90 comprises a micro-processor 106
operating under software control, a configuration switch 108
enabling a user to control an operating configuration of the
micro-processor 106, and one or more Digital-to-Analog converters
(DACs) 110 and Analog-to-Digital Converters (ADCs) 112 for enabling
interaction between the micro-processor 106 and other elements of
the DDP 62. The digital controller 90 operates in accordance with
an adaptive control algorithm (described in greater detail below),
which provides the necessary processing control for APR operation
as a stand-alone unit without intervention after the installation.
It may also control APR operations during system set-up, in order
to simplify installation of the APR 2.
[0069] The DACs 110 accept respective digital output signals
generated by the micro-processor 106, and convert these digital
output signals into analog control signals which are used, for
example, for setting AGC gain in both the uplink and downlink paths
66 and 68. The ADCs 112 convert analog RF signals into digital
input signals, which are supplied to the micro-processor 106.
During operation, the micro-processor 106 processes these input
signals, under software control, to determine system parameter
levels (e.g. AGC gain levels) and generate appropriate digital
output signals. This processing may include comparing digital input
signals to one or more predetermined threshold values, and
determining the system parameter levels in accordance with the
comparison result.
[0070] The configuration switch 108, which may be provided as a
conventional DIP switch having one or more settings, allows the
subscriber to select an operating configuration of the
micro-processor 106. Exemplary settings of the configuration switch
includes: a "set-up" setting which may be used during installation
of the APR 2; a "run" setting which may be used during normal
operation of the APR 2; a carrier A/B band select setting which may
be used by the subscriber to select the desired carrier. Carrier
A/B bands may be selected together or individually. For example,
when the configuration switch 108 is placed in the "set-up"
setting, the micro-processor 106 may operate under software control
to reduce AGC gain and transmission power levels to enable the
subscriber to adjust the placement and positioning of the DDU 22
and SCU 24. Additionally, the configuration switch 108 may have one
or more settings by which the subscriber can choose to limit the
coverage area of the subscriber's personal wireless space 6, e.g.
by causing the micro-processor 106 to limit gain within the
downlink path 68.
[0071] The DDP downlink path 68 is preferably designed to receive,
process and transmit the entire 869 to 894 MHz cellular frequency
band. As mentioned above and shown in FIG. 4, the DDP downlink path
68 comprises a preamplifier 80, AGC 82, slaved VGA 84 and an output
amplifier stage 86. These elements can be cascaded with a band-pass
filter (BPF) 114 and inter-stage filters 116a, 116b.
[0072] The preamplifier 80 operates to preserve the S/N ratio
established by the TRD LNA 54, and buffers the port diplexer 72
from the first BPF 114 in the downlink path 68. This BPF 114,
together with the port diplexer 72 limits the downlink bandwidth to
25 MHz, rejecting both image and frequency crossover noise and any
out-of-band signals, including RF signals in the uplink path
66.
[0073] The downlink AGC 82 is designed to provide substantially
constant output leveling over a wide input range. As shown in FIG.
5, the downlink AGC 82 is preferably provided as an extremely fast,
wide dynamic range, highly linear block comprising a single VGA
stage 118, a fixed-gain amplifier 120 cascaded with a pair of
band-pass filters 122a and 122b, and a directional coupler 124.
Inter-stage filters 126a-126c may also be included to reduce
cascaded noise.
[0074] The downlink AGC VGA 118 preferably has approximately 60 dB
of gain variation, and is cascaded with the fixed gain amplifier
120 to enhance system linearity while minimizing the cascaded noise
figure. The BPFs 122a-122b operate to limit VGA noise to the 25 MHz
downlink bandwidth, thereby preventing out-of-band signals from
capturing the downlink AGC 82 and saturating the downlink path 68
output amplifier 86.
[0075] The directional coupler 124, which may be a 17 dB
directional coupler, samples the downlink RF signal downstream of
the VGA 118. The sample signal is supplied to a feedback path 127
which includes a cascaded RF amplifier 128 and log amplifier 130,
and a feedback directional coupler 132 which samples the RF signal
within the feedback path 127 and supplies the sample signal to the
switching input 96 of the downconverter 88. The RF log amplifier
130 is preferably a variable detection log amplifier controlled by
the digital controller 90. The RF log amplifier 130 output supplies
a gain control signal to the downlink AGC VGA 118 and the uplink
path VGA 76, and may also be supplied to the digital controller 90
to facilitate monitoring and decision functions of the adaptive
control algorithm. The feedback path 127 preferably provides a 25
MHz bandwidth path which operates to ensure system stability by
providing substantially instantaneous RF AGC feedback. The feedback
path 127 closes the AGC loop, which in turn limits system
oscillation by automatically adjusting gain of the VGA 118 in the
event of inadequate isolation between the antennas 28 and 60. The
feedback path 127 also provides a means by which the gain of the
downlink AGC 82 can be forced to a low level by the digital
controller 90 to maintain stability during system setup, thereby
ensuring the detection of weak desired signals without the need for
initial system isolation maximization.
[0076] The downlink slaved VGA 84 accepts a gain control input from
the uplink path AGC 74 to provide a hardware means to adaptively
minimize the downlink output power, and thereby implement, in part,
the ACB and CAS concepts. The output amplifier 86 increases the
downlink RF signal power at the output of the slaved VGA 84 to -26
dBm at the output of the DCA diplexer 70, when the received uplink
RF signal power is at a minimum.
[0077] Referring now to FIG. 4, the DDP uplink path 66 is designed
to receive, process and transmit the entire 824 to 849 MHz uplink
channel frequency band. This path 66 comprises the uplink AGC 74,
slaved VGA 76 and an output amplifier stage 78, each of which may
be cascaded with inter-stage filters 132a, 132b. The uplink AGC 74
functions similarly to the downlink AGC 82. Referring to FIG. 6,
the uplink AGC 74 is preferably provided as an extremely fast, wide
dynamic range, highly linear block including a single VGA stage
134, fixed-gain amplifiers 136a and 136b cascaded with band-pass
filters 138, and a directional coupler 140. Inter-stage filters 142
may also be included to reduce cascaded noise.
[0078] The uplink AGC VGA 134 preferably has approximately 60 dB of
gain variation, and is cascaded with the fixed gain amplifiers 136
to enhance system linearity. This is important, because the
received uplink RF signals are much stronger than received downlink
signals. The BPFs 138 following the VGA 134 limit the VGA noise to
the uplink band, thereby preventing out-of-band signals from
capturing the uplink AGC 74 and saturating the uplink output
amplifier 78.
[0079] The directional coupler 140, which may be a 17 dB
directional coupler, samples the uplink RF signal downstream of the
VGA 134. The sample signal is supplied to a feedback path 144
comprising an RF log amplifier 146 and a feedback directional
coupler 148 which samples the RF signal within the feedback path
144 and supplies the sample signal to the switching input 96 of the
downconvertor 88. The RF log amplifier 146 is a variable detection
amplifier controlled by the digital controller 90. The RF log
amplifier 146 output supplies a gain control signal to the uplink
AGC VGA 134 and the downlink slaved VGA 84, and may also be
supplied to the digital controller 90 to facilitate monitoring and
decision function of the adaptive control algorithm. The feedback
path 144 provides a 25 MHz bandwidth path which operates to ensure
system stability by providing substantially instantaneous RF AGC
feedback. The feedback path 144 closes the uplink AGC loop, which
in turn limits system oscillation by automatically adjusting gain
of the VGA 134 in the event of inadequate isolation between the
antennas 28 and 60. The feedback path 144 also provides a means by
which the gain of the uplink AGC 74 and the downlink slaved VGA 84
can be forced to a low level by the digital controller 90 to
maintain stability during system setup, thereby ensuring the
detection of weak desired signals in the downlink path 68 without
the need for initial system isolation maximization.
[0080] The uplink slaved VGA 76 accepts a gain control input from
the downlink AGC 82 to provide the hardware means to adaptively
minimize the uplink channel output power, and thereby implements,
in part, the ACB and CAS concepts. The uplink output amplifier 78
increases the uplink RF signal power to +2 dBm at the port diplexer
72 output. This output power level is necessary to overcome losses
associated with the coaxial cable 26.
[0081] FIG. 7 is a state diagram illustrating exemplary states and
state transitions traversed during operation of the APR 2. Upon
application of power to the APR 2, the unit enters an
Initialization state 150. In the initialization state 150, the
digital controller 90 initializes the hardware (e.g. uplink and
downlink IGCs, 92 and 94) and performs a Power-up Built-In Test
(PBIT). The results of the PBIT test may be stored in a memory (not
shown). Upon successful completion of the PBIT, the APR 2
transitions to the Operational State 152. If the PBIT fails, the
APR 2 remains in the Initialize state 150, and in a Standby mode.
In addition, a fault message may be generated, for example for
display on a suitable display device (not shown).
[0082] Upon entering the Operational state 152, an Active mode is
selected as an initial default. In the Active mode, the digital
controller 90 operates under control of the Adaptive Control
Algorithm (ACA) to dynamically adjust the network wireless link 18
for optimum performance. The link status can be displayed on a
suitable display (not shown). While in the Operational state 152,
the digital controller 90 periodically performs a Continuous
Built-In Test (CBIT), the results of which may be stored in memory.
Upon detecting a CBIT failure 154, the APR 2 enters the Standby
mode of the Operational state 152. A fault message may also be
generated, for example for display to the Subscriber. A successful
completion of the CBIT 156 maintains the APR 2 in (or returns the
APR 2 to)the Active mode. Upon a reset event 158 (e.g. a watchdog
reset or a power interruption) the Operational state 152 is exited
and the Initialize state 150 is entered to reset (i.e. re-boot) the
APR 2. At any time, status request messages may be received by the
APR 2, for example, from an external maintenance system (not
shown). Such status requests received while the APR 2 is in the
Initialize state 150 may cause the APR 2 to enter the Test state
160. While in the Test state 160, the maintenance system may
initiate a download (e.g. of updated software) to the APR 2. The
Test state 160 is exited upon a Quit request, for example, from the
maintenance system. Status requests from the maintenance system
while the APR 2 is in the Operational state 152 allows the
maintenance system to extract status information from the APR
2.
[0083] As described above, the Adaptive Control Algorithm (ACA)
enables the APR 2 to control the subscriber's personal wireless
space 6 and the network wireless link 18. Both the subscriber's
personal wireless space 6 and the network wireless link 18 are
adjusted dynamically based on various parameters obtained through
non-intrusive measurements of the wireless signals within the
uplink and downlink paths. FIG. 8 is a flow chart illustrating
principle operations of an exemplary adaptive control algorithm
during initialization and operation of the APR 2.
[0084] As shown in FIG. 8, upon start-up, the adaptive control
algorithm places the APR 2 into the initialize state 150; sets the
signal power levels in the network and local wireless links 18 and
20 to their default values (at step S2); and performs the power-up
built-in test PBIT (at step S4). If the PBIT is completed
successfully, the adaptive control algorithm transitions the APR 2
to its operational state 152, and attempts to detect the presence
of a base station 8a (at step S6). If a base station is not
detected, the adaptive control algorithm sets default values of the
signal power levels in the network and local wireless links 18 and
20 (at step S8), and then measures signal and noise levels in each
of the uplink and downlink paths to test the quality of each of the
network wireless link 18 and local link 20 (at step S10). These
test results can be displayed on a suitable display device and may,
for example, be used during installation of the APR 2 (e.g. to
assist in obtaining proper positioning and alignment of the DDU
22).
[0085] If the base station is detected (at step S6), the adaptive
control algorithm attempts to detect a base station control channel
within the network wireless link 18 (at step S12). If the base
station control channel is detected at step S12, the adaptive
control algorithm attempts to detect a subscriber control channel
in the local wireless link 20 (at step S14). If the subscriber
control channel is detected at step S14, the adaptive control
algorithm uses measured signal power levels in the uplink and
downlink paths to adjust transmit power levels in each of the
network wireless link 18 and the local wireless link 20, in order
to optimize performance (at steps S16 and S18).
[0086] If control channels are not detected in either of the
network wireless link 18 or the local wireless link 20 (at Steps
S12 and S14), the adaptive control algorithm attempts to detect a
voice channel in the local wireless link 20 (at step S20). If a
subscriber voice channel is detected at step S20, the adaptive
control algorithm then attempts to detect a voice channel in the
network wireless link 18 (at step S22). If a base station voice
channel is detected at step S22, the adaptive control algorithm
returns to steps S16 and S18 to optimize the performance of the
uplink and downlink paths. Otherwise, if voice channels are not
detected in either the network wireless link 18 or the local
wireless link 20 (at steps S20 and S22), then the adaptive control
algorithm returns to steps S8 and S10 to set the default power
levels in the uplink and downlink paths, and measure signal and
noise levels to test the quality of each of the network and local
wireless links 18 and 20.
[0087] As described above, transmit signal power in the network
wireless link 18 is adjusted (at step S16 of FIG. 8) based on the
received signal power of downlink RF signals within either the base
station control channel and/or voice channel. Similarly, the
subscriber's personal wireless space 6 is adjusted by adjusting the
transmit power of downlink RF signals within either the control
channel and/or the voice channel, based on the received signal
power of uplink RF signals transmitted by the subscriber's wireless
communications device 16. This process of continuous adjustment of
the network and local wireless links 18 and 20 enables continuous
optimization of the performance of each of these links, and, within
the subscriber's personal wireless space 6, implements the adaptive
coverage breathing and coverage area signature functionality of the
present invention. Periodic detection of base station and
subscriber control and voice channels (at steps S12, S14, S20 and
S22 of FIG. 8) enables the APR 2 to adaptively accommodate multiple
subscriber wireless communications devices 16 within the
subscriber's personal wireless space 6.
[0088] Thus it will be seen that the present invention provides an
apparatus that enables an individual subscriber to cost-effectively
access and provide high quality wireless communications services,
independently of a location of the subscriber.
[0089] The embodiment(s) of the invention described above is(are)
intended to be exemplary only. The scope of the invention is
therefore intended to be limited solely by the scope of the
appended claims.
* * * * *