U.S. patent application number 15/413080 was filed with the patent office on 2017-09-14 for wireless communications systems using multiple radios.
The applicant listed for this patent is HMicro, Inc.. Invention is credited to James C. Beck, Surendar Magar, Ali Niknejad, Venkateswara Rao Sattiraju, Louis C. Yun.
Application Number | 20170264338 15/413080 |
Document ID | / |
Family ID | 40952727 |
Filed Date | 2017-09-14 |
United States Patent
Application |
20170264338 |
Kind Code |
A1 |
Yun; Louis C. ; et
al. |
September 14, 2017 |
WIRELESS COMMUNICATIONS SYSTEMS USING MULTIPLE RADIOS
Abstract
The present invention relates to a communication system and
methods of use thereof. The system includes sets of complementary
radios for transmitting and receiving signals to achieve high
reliability and reduced costs. The sets of complementary radios are
in wireless communication with each other. A new connection is made
by selecting from amongst the complementary radios. Switching
between complementary radios during a connection is also permitted.
Optimized protocols and hardware for implementing the system are
disclosed.
Inventors: |
Yun; Louis C.; (Los Altos,
CA) ; Niknejad; Ali; (Berkeley, CA) ;
Sattiraju; Venkateswara Rao; (Union City, CA) ; Beck;
James C.; (Berkeley, CA) ; Magar; Surendar;
(Dublin, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HMicro, Inc. |
Fremont |
CA |
US |
|
|
Family ID: |
40952727 |
Appl. No.: |
15/413080 |
Filed: |
January 23, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15008286 |
Jan 27, 2016 |
9595996 |
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15413080 |
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14531977 |
Nov 3, 2014 |
9277534 |
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15008286 |
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12866189 |
Jan 21, 2011 |
8879983 |
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PCT/US2009/033490 |
Feb 6, 2009 |
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14531977 |
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61026710 |
Feb 6, 2008 |
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61114418 |
Nov 13, 2008 |
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61114427 |
Nov 13, 2008 |
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61114431 |
Nov 13, 2008 |
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61114449 |
Nov 13, 2008 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 72/02 20130101;
H04W 72/082 20130101; Y02D 70/166 20180101; Y02D 70/26 20180101;
Y02D 70/1222 20180101; H04L 25/02 20130101; H04W 28/04 20130101;
H04W 52/0238 20130101; H04W 84/045 20130101; H04W 88/06 20130101;
H04W 88/10 20130101; H04W 72/0453 20130101; Y02D 70/162 20180101;
H04B 1/712 20130101; H04W 72/085 20130101; Y02D 70/142 20180101;
H04W 72/06 20130101; Y02D 70/144 20180101; Y02D 30/70 20200801;
H04B 1/385 20130101; Y02D 70/21 20180101; H04W 88/085 20130101 |
International
Class: |
H04B 1/712 20110101
H04B001/712; H04B 1/3827 20150101 H04B001/3827; H04L 25/02 20060101
H04L025/02; H04W 28/04 20090101 H04W028/04; H04W 52/02 20090101
H04W052/02; H04W 72/02 20090101 H04W072/02; H04W 72/06 20090101
H04W072/06; H04W 72/08 20090101 H04W072/08 |
Claims
1.-31. (canceled)
32. A reconfigurable transceiver configured to operate in a first
mode and a second mode, comprising: an antenna; a reconfigurable
amplifier coupled to the antenna configured to operate in the first
mode and the second mode; a plurality of mixers coupled to the
reconfigurable amplifier; and an oscillator configured to drive the
plurality of mixers.
33. The reconfigurable transceiver of claim 32, wherein the
reconfigurable amplifier is configured to operate in the first mode
or the second mode according to a desired performance
objective.
34. The reconfigurable transceiver of claim 33, wherein the desired
performance objective comprises reduced power consumption, reduced
interference to other devices, increased channel capacity to
support many parallel connections, or increased reliability of new
connection
35. The reconfigurable transceiver of claim 32, wherein the
amplifier comprises an inductor configured to form a load of the
amplifier.
36. The reconfigurable transceiver of claim 35, wherein the
inductor comprises a plurality of connected layers stacked in
series.
37. The reconfigurable transceiver of claim 36, wherein each layer
of the plurality comprises spirals.
38. The reconfigurable transceiver of claim 36, wherein the
inductor comprises lower metal layers.
39. The reconfigurable transceiver of claim 38, wherein the lower
metal layers are thinner than other layers of the plurality of
connected layers.
40. The reconfigurable transceiver of claim 32, wherein the
amplifier comprises one or more transistors.
41. The reconfigurable transceiver of claim 40, wherein the one or
more transistors comprise a programmable current source.
42. The reconfigurable transceiver of claim 40, wherein the
amplifier comprises one or more alternating current capacitors
configured to couple alternating current signals from a first of
the one or more transistors to a second of the one or more
transistors.
43. The reconfigurable transceiver of claim 32, further comprising
a power source and a switch coupled to the power source.
44. The reconfigurable transceiver of claim 43, wherein the switch
is configured to provide a periodic signal to the antenna in the
first mode.
45. The reconfigurable transceiver of claim 43, wherein the switch
is configured to provide a single pulse to the antenna in the
second mode.
46. The reconfigurable transceiver of claim 32, wherein the first
mode is a wideband mode and the second mode is a narrowband
mode.
47. The reconfigurable transceiver of claim 32, wherein the
amplifier is a low-noise amplifier.
48. The reconfigurable transceiver of claim 32, wherein each of the
plurality of mixers is driven with different phases of the
oscillator.
49. The reconfigurable transceiver of claim 32, further comprising
an analog-to-digital converter configured to sample the output of
the plurality of mixers.
50. The reconfigurable transceiver of claim 32, further comprising
a plurality of analog-to-digital converters each coupled to the
plurality of mixers.
51. The reconfigurable transceiver of claim 32, wherein the
reconfigurable amplifier comprises a reconfigurable bandpass
filter.
Description
CROSS-REFERENCE
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/026,710, filed Feb. 6, 2008; U.S. Provisional
Application No. 61/114,449, filed Nov. 13, 2008; U.S. Provisional
Application No. 61/114,427, filed Nov. 13, 2008; U.S. Provisional
Application No. 61/114,431, filed Nov. 13, 2008; and U.S.
Provisional Application No. 61/114,418, filed Nov. 13, 2008, which
applications are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to wireless
communication systems and specifically to wireless communications
systems using multiple radios.
BACKGROUND OF THE INVENTION
[0003] Wireless communications are implemented by any of a variety
of radio technologies, depending on the type of application.
Cellular phones, for example, may use the Global System for Mobile
communications (GSM.TM.), the IS-54 Time Division Multiple Access
(TDMA) or the IS-95 Code Division Multiple Access (CDMA) radio
technologies, whereas a wireless local area network may use
Wi-Fi.TM., Bluetooth.TM. or ZigBee.RTM. radio technologies. In an
ad-hoc, or peer-to-peer, network, a wireless device communicates
directly with another wireless device. In an infrastructure
network, a wireless device communicates with another wireless
device through one or more intermediary gate devices, such as a
base station or an access point. Generally, a wireless device uses
a single radio technology to effect communication with its peer (in
the case of a peer-to-peer network) or with the access point (in
the case of an infrastructure network). In the prior art, dual
radios are used in a wireless device to support different air
interface standards, in order to provide compatibility with
different wireless service providers. For example, a dual-radio
device may support GSM, a cellular phone service, and Wi-Fi, a
wireless Local Area Network (LAN) service, and uses one of these
two radios for communication, depending on which service (GSM or
Wi-Fi) is available in a geographic area. Generally, such a
wireless device selects and uses a single radio for the duration of
the connection or service.
[0004] The present invention relates to an innovative wireless
communications system employing multiple radios. The communications
system selects amongst and switches between multiple
radios--possibly multiple times--while a connection or session is
in progress. This switching allows the communications system to
achieve one or more of the following performance objectives: [0005]
Maximize communications reliability and robustness against
interference and other impairments [0006] Minimize interference to
co-existing users [0007] Minimize power consumption [0008]
Accommodate any disparity between the uplink and downlink
bandwidths
[0009] Moreover, the multiple radio system can reduce the physical
footprint of the radio nodes and lead to improved data rates and
communication range.
[0010] When a single radio type is used, the degrees of freedom are
limited for desired optimization. A given radio can be optimized,
for example, by the following means: [0011] Switch transmission
channels within the given band to dynamically mitigate interference
(to improve reliability). [0012] Adjust transmitted power as needed
(to improve power dissipation or reliability).
[0013] There are few other meaningful operations that can be
performed to optimize single-radio systems. With a single type of
radio, it is particularly challenging to design a system that calls
for simultaneous optimization of multiple factors--for example,
optimization of all of these four factors: link range/reliability,
node power, node cost and low interference to other radios. If a
radio is optimized for one factor, it will typically negatively
impact other factors. For example, if power is reduced for a
low-power design, it would typically reduce the range/reliability.
If an ultra-wideband (UWB) radio is deployed to cause minimum
interference to other radios, it would result in short range, high
complexity and potentially high cost (the UWB receiver being
complex and high power).
[0014] Accordingly, a radio scheme is desired for a wireless
communication system that addresses the optimization of multiple
factors.
SUMMARY OF THE INVENTION
[0015] In one aspect, the present invention discloses a node
comprising a first radio constructed and arranged to function as at
least one of a transmitter and a receiver, and a second radio
constructed and arranged to function as at least one of a
transmitter and a receiver, wherein the first radio and second
radios are complementary. In some embodiments, the first radio is
constructed and arranged to transmit and to receive signals and the
second radio is also constructed and arranged to transmit and to
receive signals.
[0016] In another aspect, the present invention discloses a
communication system comprising a node as described above, the node
forming a first node and the first and second radios forming a
first set of complementary radio. The communication further
comprises a second node, the second node including a second set of
complementary radios for transmitting and receiving signals. The
first and second nodes are in wireless communication via the first
and second sets of complementary radios.
[0017] In another aspect, the present invention discloses a
communication system comprising a node as described above, the node
forming a first node and the first and second radios forming a
first set of complementary radios. The communication further
comprises a second node comprising a second set of complementary
radios for transmitting and receiving signals. The first and second
nodes are constructed and arranged to wirelessly communicate via
both the first and second sets of complementary radios.
[0018] In another aspect, the present invention discloses a
communication system comprising a base node for transmitting and
receiving signals, the base node comprising a first plurality of
resources; and at least one peripheral node for transmitting and
receiving signals, the at least one peripheral node comprising a
second plurality of resources. The base node and the at least one
peripheral node are in wireless communication and the first
plurality of resources is greater than the second plurality of
resources.
[0019] In another aspect, the present invention discloses a
communication system comprising a base node comprising a first set
complementary radios for transmitting and receiving signals, and at
least one peripheral node comprising a second set of complementary
radios for transmitting and receiving signals. The base node and
the at least one peripheral node are constructed and arranged to
wirelessly communicate via both the first and second sets of
complementary radios. In some embodiments, the base node consumes
more power than each individual peripheral node.
[0020] In another aspect, the present invention discloses a
communication system comprising a base node comprising a first set
of complementary means for transmitting and receiving signals, and
at least one peripheral node comprising a second set of
complementary means for transmitting and receiving signals. The
base node and the at least one peripheral node comprise a means for
wirelessly communicating via both the first and second sets of
complementary means for transmitting and receiving signals. In some
embodiments, the base node consumes more power than each individual
peripheral node.
[0021] In another aspect, the present invention discloses a method
for using two or more complementary radios in a communication
system comprising either or both of the following steps: 1)
selecting one or more of the complementary radios to form a
connection; and 2) switching between one or more of the
complementary radios to maintain a connection.
[0022] In another aspect, the present invention discloses a method
for using two or more complementary radios in a communication
system comprising either or both of the following steps: 1)
activating at least one complementary radio to form a connection;
and 2) activating one or more inactive complementary radios to
maintain a connection.
[0023] In another aspect, the present invention discloses a method
for using two or more complementary radios in a communication
system comprising either or both of the following steps: 1)
selecting one complementary radio from the at least two
complementary radios to form a new connection; and 2) switching
between a first complementary radio and a second complementary
radio during a connection.
[0024] In some embodiments of the above methods, only one of the
complementary radios is selected or activated to form a connection
and only one of the complementary radios is switched to or
activated to maintain a connection. In other embodiments of the
above methods, the communication system selects which of the
complementary radios is active. In other embodiments of the above
methods, the communication system selects which of the
complementary radios is used to form or maintain a connection in
order to meet a performance objective. In other embodiments of the
above methods, the transmitter associated with each of the
complementary radios transmits substantially simultaneously and the
receiver associated with each of the complementary radios combines
signals from the complementary radios.
[0025] In another aspect, the present invention discloses a device
for implementing a complementary radio system comprising two or
more complementary radios, means for selecting one or more of the
complementary radios to form a connection, and means for switching
between one or more of the complementary radios during the
connection.
[0026] In another aspect, the present invention discloses a device
for implementing a complementary radio system comprising two or
more complementary radios, means for activating one or more of the
complementary radios simultaneously, means for transmitting a
signal from each of the complementary radios substantially
simultaneously, and means for combining signals from the
complementary radios.
[0027] In another aspect, the present invention discloses a method
for switching radio connections in a complementary radio
communication system, comprising establishing a forward radio
connection and a reverse radio connection between a first node and
a second node, each node comprising two or more complementary
radios, wherein the forward radio connection transmits data from
the first node to the second node, and the reverse radio connection
transmits data from the second node to the first node. The method
further comprises monitoring the communication quality of the
forward radio connection on the second node until the communication
quality of the forward radio connection falls below a performance
criteria, then transmitting a control message from the second node
to the first node using the reverse radio connection established
above. The control message comprises a message to switch to an
alternate radio connection selected by the second node. The
connection is then reestablished using the alternate radio
connection. In some embodiments of the method, transmission of the
control message is repeated until the first node transmits data to
the second node on the alternate radio connection within a
predetermined time interval. In some embodiments, the second node
continues to listen on the forward radio connection in the initial
step until the first node transmits data to the second node on the
alternate radio connection within the predetermined time interval.
In some embodiments, the data transmitted from the first node to
the second node comprises an acknowledgement in response to the
control message. In some embodiments, the second node consumes more
resources than the first node.
[0028] In another aspect, the present invention discloses a
receiver comprising a means for amplification, a configurable means
for filtering comprising a means for communication with the
amplification means, and at least one configurable device
comprising means for communication with the configurable filter.
The receiver also comprises at least one means for analog to
digital conversion further comprising means for communication with
the at least one configurable device. The configurable means for
filtering is constructed and arranged to function as a bandpass
filter when the receiver is used as a narrowband receiver and to
function as a low pass filter when the receiver is used as an
ultra-wideband receiver.
[0029] In another aspect, the present invention discloses a
receiver comprising a means for amplification, a configurable means
for filtering in electronic communication with the means for
amplification, and at least one configurable device electrically
communicable with the configurable means for filtering. The
receiver also comprises at least one means for analog to digital
conversion in electrical communication with the at least one
configurable device. The configurable means for filtering is
constructed and arranged to function as a bandpass filter when the
receiver is used as a narrowband receiver and to function as a low
pass filter when the receiver is used as an ultra-wideband
receiver.
[0030] In another aspect, the present invention discloses a
receiver comprising an amplifier, a configurable filter comprising
means for communication with the amplifier, at least one
configurable device comprising means for communication with the
configurable filter, and at least one analog to digital converter
comprising means for communication with the at least one
configurable device. The wherein the configurable filter is
constructed and arranged to function as a bandpass filter when the
receiver is used as a narrowband receiver and to function as a low
pass filter when the receiver is used as an ultra-wideband
receiver.
[0031] In another aspect, the present invention discloses a
receiver comprising an amplifier, a configurable filter in
electronic communication with the amplifier, at least one
configurable device in electrical communication with the
configurable filter, and at least one analog to digital converter
in electrical communication with the at least one configurable
device. The configurable filter is constructed and arranged to
function as a bandpass filter when the receiver is used as a
narrowband receiver and to function as a low pass filter when the
receiver is used as an ultra-wideband receiver.
[0032] In another aspect, the present invention discloses a
receiver comprising an amplifier, a configurable filter coupled to
the amplifier, a bank of configurable devices coupled to the
configurable filter, and a plurality of analog to digital
converters coupled to the bank of configurable devices. The
configurable filter is configured into a bandpass filter when the
receiver is utilized as a narrowband receiver and is configured
into a low pass filter when the receiver is utilized as an
ultra-wideband receiver.
[0033] In some embodiments of the receivers of the invention, the
configurable device is configured as a means for mixing when the
receiver is used as a narrowband receiver and is configured as a
means for switching when the receiver is an ultra-wideband
receiver.
[0034] In other aspects, the present invention discloses a kit
comprising one or more nodes as described above. In still other
aspects, the present invention discloses a kit comprising a
communication system as described above. In other aspects, the
present invention discloses a kit comprising one or more receivers
as described above.
INCORPORATION BY REFERENCE
[0035] All publications, patents, and patent applications mentioned
in this specification are herein incorporated by reference to the
same extent as if each individual publication, patent, or patent
application was specifically and individually indicated to be
incorporated by reference.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] The novel features of the invention are set forth with
particularity in the appended claims. A better understanding of the
features and advantages of the present invention will be obtained
by reference to the following detailed description that sets forth
illustrative embodiments, in which the principles of the invention
are utilized, and the accompanying drawings of which:
[0037] FIG. 1 illustrates a wireless communications system
deploying a single radio type;
[0038] FIG. 2 illustrates a conventional asymmetric wireless
communication system deploying a single radio type;
[0039] FIG. 3 illustrates a system for deploying multiple radios in
accordance with the present invention;
[0040] FIG. 4 illustrates the different elements of a digital
radio;
[0041] FIG. 5 illustrates one embodiment of the multi-radio scheme
containing one narrow band (NB) radio and one ultra-wideband (UWB)
radio;
[0042] FIG. 6 illustrates the range of the UWB/NB radio system in
accordance with an embodiment;
[0043] FIG. 7 illustrates a multi-radio system in accordance with
an embodiment. Multiple antennas can be used for the Wi-Fi radio of
the A-Node to increase robustness;
[0044] FIG. 8 illustrates a flow chart for addressing the
constrained optimization approach;
[0045] FIG. 9 illustrates an approach for reliably switching radio
connections on a base node;
[0046] FIG. 10 illustrates an approach for reliably switching radio
connections on a peripheral node in communication with the base
node of FIG. 9;
[0047] FIG. 11 illustrates a modification to FIG. 9 for reliably
switching radio connections on a base node;
[0048] FIG. 12 illustrates an alternate approach for reliably
switching radio connections on a base node;
[0049] FIG. 13 illustrates an approach for reliably switching radio
connections on a peripheral node in communication with the base
node of FIG. 12;
[0050] FIG. 14 illustrates a modification to FIG. 12 for reliably
switching radio connections on a base node;
[0051] FIG. 15 illustrates a generic narrowband receiver;
[0052] FIG. 16 illustrates the receiver configured into an
ultra-wide band (UWB) receiver;
[0053] FIG. 17 illustrates a generic transmitter configured as a
narrowband transmitter in accordance with the present
invention;
[0054] FIG. 18 shows that, when the transmitter is in UWB mode, a
single pulse to a switch is provided such that a single transmitter
can be easily reconfigured into either a narrowband or a UWB
mode;
[0055] FIG. 19 illustrates an embodiment of a circuit which can
provide either narrowband or UWB mode dependent upon the input
signal to the transistor;
[0056] FIG. 20 illustrates the reconfigurable receiver implemented
in CMOS technology;
[0057] FIG. 21 shows the layout of the inductors in the present
invention; and
[0058] FIGS. 22A and 22B show the operation of the reconfigurable
transmitter in more detail.
DETAILED DESCRIPTION OF THE INVENTION
[0059] A wireless communications system 10 comprises at least two
nodes 12 and 14 communicating with each other as shown in FIG. 1.
The two nodes 12 and 14 communicate through a radio system, 16a and
16b, respectively, via antennas 20a and 20b. The radios on both
sides (16a and 16b) are of the same type, called Radio X. As shown,
the data can be optionally preprocessed by processor 18a, making it
suitable for radio transmission, before it is fed to radio system
16. On the receiving end, the data can be post processed by the
processor 18b to recover the originally sent data. Based on the
requirements of a given system, the radio system 16 can be
optimized in certain ways. Following are some examples of the
factors that can be optimized: [0060] Low power dissipation of
nodes; [0061] Low cost of nodes; [0062] High link reliability
(immunity to fading, interference and noise); [0063] Small physical
foot print of the nodes; [0064] High data rates; [0065] Large
communication range; or [0066] Cause minimum interference to other
radio systems (e.g., quiet radio).
[0067] There can be many more optimization factors. As shown in
FIG. 1, conventional communication systems employ a single radio
type X that can be designed to achieve certain level of
optimization. Some examples of Radio X are Wi-Fi, Bluetooth.TM. and
Zigbee.RTM..
I. Asymmetric Wireless Systems
[0068] In many applications there exists an asymmetry between two
nodes wirelessly communicating with each other, as shown in FIG. 2.
In these systems, there is an anchor node (A-Node) 102 which
collects data from one or more nodes called peripheral nodes
(P-Node or P-Nodes) 104a-104n. The P-Nodes 104a-104n typically
operate using a small power source (e.g., a small battery or an
energy harvesting device). The A-Node 102 typically has access to a
higher capacity power source (larger battery or a power supply).
Furthermore, in such systems, P-Nodes 104a-104n primarily transmit
the data to A-Node 102. The data flow from A-Node 102 to P-Nodes
104a-104n is usually minimal, comprising mostly signals to control
the P-Nodes 104a-104n. In summary, there can be an asymmetry in
terms of data flow and power sources in the system of FIG. 2. The
following are some examples of this type of asymmetric systems.
[0069] Wireless Healthcare Systems:
[0070] In wireless health monitoring systems, P-Nodes 104a-104n can
reside on wireless patches attached to a person's body or they can
reside on wireless devices implanted within a person's body. These
wireless patches/devices collect physiological data from various
body sensors attached to P-Nodes 104a-104n and wirelessly transmit
data to the A-Node 102 within the range of P-Nodes 104a-104n. The
P-Nodes 104a-104n can send the data to the A-Node 102 using various
schemes, e.g., continuously, periodically or episodically. Some
examples of physiological data sent by P-Nodes 104a-104n are
electrocardiogram (ECG), electroencephelogram (EEG), electromyogram
(EMG), heart rate, temperature, saturation of peripheral oxygen
(SpO2), respiration, blood pressure, blood glucose and patient's
physical activity (movement). The A-Node 102 receiving data from
P-Nodes 104a-104n, will normally reside in some type of patient
monitoring device that collects, analyzes and manages the
physiological data. Some examples of patient monitors are bed-side
patient monitors in hospitals, Holter monitors (ambulatory
electrocardiography device) for ambulatory ECG, blood glucose
monitors, wearable physiological parameter monitors for athletes,
safety monitoring units for industrial workers and SmartPhones
supporting patient monitoring.
[0071] Wireless Industrial Sensors:
[0072] In such systems, P-Nodes 104a-104n can reside on various
industrial or home devices such as furnaces, smoke detectors,
movement detectors, electrical/gas/water usage meters, etc. The
P-Nodes 104a-104n can transmit various types of sensor data (e.g.
temperature, mechanical stress, chemicals, and meter readings) or
some other type of information. The A-Nodes 102 can reside on
portable readers, data gathering computers, wireless access points,
etc.; these devices wirelessly receive data from the devices
connected to P-Nodes 104a-104n.
[0073] Active Radio-Frequency Identification (RFID):
[0074] In such applications, P-Nodes 104a-104n can reside on
various assets that need to be tracked or inventoried, such as
capital equipment in hospitals, factories, offices, etc. The
A-Nodes 102 can reside on devices such as portable readers,
wireless access points and computers. These devices will wirelessly
receive data from the devices having P-Nodes 104a-104n.
Furthermore, locations of asset items can be tracked by using an
array of wireless access points and certain location tracking
algorithms. The location of patients can also be tracked using the
same scheme.
[0075] Wireless Audio Systems:
[0076] In such systems, P-Nodes 104a-104n can reside on devices
such as wireless microphones and wireless musical instruments,
e.g., electric guitar, and wirelessly transmit audio or voice
signals. The A-Node 102 can reside on devices such as wireless
speakers, amplifiers, cellular phones or access points enabling
subsequent data transmission. The devices having A-Node 102 will
wirelessly receive data from the devices having P-Nodes
104a-104n.
[0077] Wireless Video Systems:
[0078] In such systems, P-Nodes 104a-104n can reside on devices
such as wireless cameras (or any device containing a camera such as
a laptop, cell phone, etc), digital video disk (DVD) players,
television tuners and television set top boxes. Such devices can
transmit video signals. The A-Node 102 can reside on devices such
as wireless displays, access points, or access points enabling
subsequent transmission. The devices having A-Node 102 will
wirelessly receive data from the devices having P-Nodes
104a-104n.
[0079] The above systems typically communicate wirelessly within a
range of about 25-50 meters in an indoor or outdoor environment,
the range of a typical wireless local area network (WLAN). Some
applications can dictate a larger range.
II. Optimized Asymmetric Wireless System
[0080] The commercial viability of asymmetric wireless systems
discussed above (shown in FIG. 2) imposes special design
constraints. These systems need to continuously transmit sensitive
data in real time within a defined range, typically 25 to 50
meters. Within this range, wireless communication should be highly
reliable without any data loss. Many radios are severely hampered
by interference and multi-path fading. The present invention
discloses schemes devised to overcome such issues. In addition, it
can be desirable for P-Nodes 104a-104n to use low power as they may
have to operate from small power sources for many days.
Furthermore, in many of the applications discussed above, P-Nodes
104a-104n can be cost sensitive. For example, P-Nodes 104a-104n can
be part of disposable wireless patches in the case of healthcare
applications. Also, it can be desirable for P-Nodes 104a-104n to be
physically small, typically realized in one, or a few,
semiconductor chips so as to have a small footprint. The present
invention discloses a radio scheme suitable for such semiconductor
chip integration.
[0081] In summary, these asymmetric wireless systems can be
optimized to achieve at least the following factors: [0082] High
reliability--Highly robust wireless links within its range, with a
very high degree of mitigation capability against the effects of
multipath fading, noise and interference; [0083] Low power--Low
power dissipation by the P-Nodes 104a-n in order to work for
several days in continuous transmission mode from a small power
source; [0084] Low cost--Low cost P-Nodes 104a-104n for commercial
viability; and [0085] Small physical size--Suitable radio
functionality for implementation as low cost semiconductor devices
(small silicon area).
[0086] The P-Nodes can be constrained low power, low cost, and
small. On the other hand, the A-Nodes can sometimes afford to be
higher power, higher cost and larger due to the asymmetrical nature
of various applications.
[0087] An asymmetric wireless system that is optimized to achieve
the above mentioned factors is referred to as optimized asymmetric
wireless (OAW) system. The realization of OAW system requires a
highly optimized radio scheme as a foundational technology. This
radio can be combined with other functions and technologies to
realize an integrated chip(s) based solution to implement the
P-Nodes and A-Nodes.
[0088] Traditionally, as shown in FIG. 2, wireless systems are
built using one basic type of radio (shown as Radio 16a, 16b) that
establishes a wireless link between the two given nodes. This radio
typically operates within certain defined bandwidth and the overall
design is typically optimized for a class of applications. Below
are some examples of the radios that have been previously used for
local area type of networks.
[0089] Wi-Fi:
[0090] This radio type, which operates in the 2.4 GHz unlicensed
Industrial, Scientific and Medical (ISM) band, has been optimized
for wirelessly networking computers and computer related devices
within a range up to about 50 meters. The power dissipation and
reliability is modest. The modest reliability can be tolerated by
the target applications.
[0091] Bluetooth:
[0092] This radio type, which also operates in 2.4 GHz unlicensed
ISM band, has been optimized to wirelessly cable various peripheral
devices to cellular phones and laptop computers. It is somewhat
lower data rate, lower power and lower cost than Wi-Fi radios but
is shorter range (about 10 meters) and lacks extensive networking
capability. Its reliability is modest per target applications.
[0093] ZigBee:
[0094] ZigBee is the name of a specification for a suite of high
level communication protocols using small, low-power digital radios
based on the IEEE 802.15.4-2006 standard for wireless personal area
networks (WPANs). ZigBee is targeted at radio-frequency (RF)
applications that require a low data rate, long battery life, and
secure networking. This radio type operates in the 2.4 GHz, 915 MHz
and 868 MHz unlicensed ISM bands. It was defined to wirelessly
network various low data rate sensors with data collection devices.
It was intended to be lower power than Wi-Fi style radios but is
little different in practice.
[0095] 900 MHz Industrial, Scientific and Medical (ISM) Band
Radios:
[0096] Radios have been realized in this unlicensed band for
various consumer and other applications, e.g., cordless phones,
remote control toys. The general characteristics of such radios
(power, reliability, cost, etc.) are similar to Wi-Fi radios.
[0097] Medical Implantable Communications System (MICS):
[0098] These radios operate in unlicensed 400 MHz band that has
been designated for wireless implanted medical devices. It operates
in extremely small bandwidth, typically having a short range of
about 5 meters and very low data rates associated with implanted
medical devices.
[0099] Wireless Medical Telemetry Service (WMTS):
[0100] The WMTS radios operate in the 600 MHz and 1400 MHz. These
radios are designed for use in hospital environments. Again,
general characteristics of these radios are similar to Wi-Fi
radios.
[0101] The radios discussed above fall generally in a class defined
as Narrowband (NB) radios. There is another class of radios called
ultra-wideband (UWB) radios. UWB radios transmit over a much larger
bandwidth than NB radios but UWB transmitted power density is far
lower than the NB radios. For example, the Federal Communications
Commission (FCC) defines UWB as fractional bandwidth measured at
-10 decibel (dB) points where (f_high-f_low)/f_center>20% or
total bandwidth>500 MHz. NB radio, as used herein, is any radio
that is not ultra-wideband (UWB) radio. Alternatively, a NB radio
may be characterized in terms of the UWB radio, the NB radio having
a channel bandwidth that is smaller than the UWB radio channel
bandwidth by an order of magnitude or more. The UWB and NB radios
have complementary properties as discuss later.
[0102] Typically only one radio is used for a given communication
link. This could be a single radio type from the above mentioned
types or some other custom design. A system and method in
accordance with the present invention relates to combining multiple
radio types with complementary characteristics to enable and
maintain communication link between two nodes. The complementary
radios are switched in and out, as needed, to dynamically manage
the link characteristics to achieve the desired optimization.
[0103] When multiple radios have been integrated on a single chip,
the purpose has been primarily the optimization of the cost and
physical footprint and only one radio is used for a given
communication link. One example is integration of a wireless
protocol utilizing short-range communications technology
facilitating data transmission over short distances from fixed and
mobile devices, creating wireless personal area networks (PANs)
such as Bluetooth.TM., and a wireless technology used in networks,
mobile phones, and other electronic devices that require some form
of wireless networking capability, such as Wi-Fi, which typically
covers the various IEEE 802.11 technologies including 802.11a,
802.11b, 802.11g, and 802.11n. This integration of multiple radios,
e.g., Bluetooth and Wi-Fi, can be achieved in a single chip or a
single module. If such module is deployed, for example, in a laptop
computer, the Wi-Fi radio is used to wirelessly network with other
computers, whereas the Bluetooth radio is used to connect
wirelessly with peripherals such as keyboard and mouse. Another
example consists of dual radios used in a mobile phone to support
different air interface standards, in order to provide
compatibility with different wireless service providers. For
example, a dual-radio phone may support cellular service such as a
global system for mobile communications (GSM) and a wireless LAN
service such as IEEE 802.11b, and switch between the two radios
depending on which service is available in a geographic area.
[0104] In these examples, the communication device selects and uses
a single radio for the duration of the connection or service. These
systems contain no concept of combining multiple radios with
complementary properties to establish and maintain a single
communication link between two or more points. In contrast, the
present invention provides a system involving multiple radios with
complementary characteristics for selecting amongst and choosing
between those multiple radios in order to achieve, for example, one
or more of the following performance objectives: [0105] Maximize
communications reliability and robustness against interference and
other impairments; [0106] Minimize interference to co-existing
users; [0107] Minimize power consumption; and [0108] Accommodate
disparity between the uplink and downlink bandwidths.
[0109] Moreover, switching from one radio to another can
occur--possibly multiple times--while a connection or session is in
progress. This radio switching differs from typical channel
assignment. Channel assignment is the process of selecting one out
of multiple channels for communication, where the channels share a
common structure. For example, in frequency division multiple
access, all channels are frequency bands; and in time division
multiple access, channels consist of timeslots. By contrast, in the
present invention, radio switching needs to take into account the
structures of the radios, which are considerably more complex than
the structure of a radio channel. Moreover, the structure of one
radio may have little in common with the structure of another. For
example, the receiver sensitivity, spectrum usage, permissible
radiated power and inherent interference mitigation generally
differ between the radios. The differences in radio structures,
together with the set of performance objectives and the radio
propagation environment, can be used to determine the initial radio
selection and subsequent radio switching.
III. Complementary Multi-Radios
[0110] In one embodiment, a system 200 in accordance with the
present invention deploys multiple radios to realize an optimized
asymmetric wireless (OAW) system, as shown in FIG. 3. As shown, the
P-Nodes 204a-204n comprise multiple radios 216a1-216an. There are
corresponding multiple radios 216b1-216bn on the A-Node 202 to
facilitate wireless communication between the P-Nodes and the
A-Node. Each of these radios 216a1-216an (and corresponding radios
216b1-216bn) can be optimized for different factors, thereby
complementing each other. At any given time, one or more of these
radios 216a1-216an (and corresponding radios 216b1-216bn) can be
activated for communication depending on the optimization required
and real-time dynamics of the wireless link/channel.
[0111] In some embodiments, one of the radios, for example radio
216a.sub.1 and 216b.sub.1, can be the dominant radio that is used
most commonly. This radio pair 216a.sub.1/216b.sub.1 can be
designed to achieve the optimization most critical for the given
application. In an OAW system, one can, e.g., achieve low power
with high reliability within a given range, for example, 25 meters.
In one example, the P-Nodes 204a-204n remain within 10 meters of
the A-Node 202 most of the time, e.g., more than 50% of the time,
more than 60% of the time, more than 70% of the time, more than 80%
of the time, or more than 90% of the time. For this application,
the dominant radio (radio 216a.sub.1) can be a radio that operates
at ultra low power within 10 meters of the range. Furthermore, this
radio 21614/216b.sub.1 can be designed to be highly reliable within
this range causing minimum outages in the target operating
environment. In this application, another radio, for example the
radio pair 216a.sub.2/216b.sub.2, can be employed with a range up
to 25 meters but dissipating more power than radio 216a1/216b1. In
some embodiments, the outage characteristics of radio
216a.sub.2/216b.sub.2 can be complementary to radio
216a.sub.1/216b.sub.1 so that radio 216a.sub.2/216b.sub.2 will most
likely work if there is an outage of radio 216a.sub.1/216b.sub.1
due to interference, multi-path fading or any other reason. Radio
216a.sub.2/216b.sub.2 can also takeover when P-Node 204a-204n moves
beyond the range served by radio 216a.sub.1/216b.sub.1. Also, radio
216a.sub.2/216b.sub.2 can takeover if there is an outage of radio
216a.sub.1/216b.sub.1 (provided radio 216a.sub.2/216b.sub.2 is not
impacted by the circumstances that caused outage on radio
216a.sub.1/216b.sub.1). In some embodiments, a third or more radios
216a.sub.1-216a.sub.n can be used to cover different operating
conditions if necessary. In other embodiments, two radios serve the
targeted applications. In these embodiments, low power can be
achieved where low power radio 216a.sub.1/216b.sub.1 is
predominantly in use. Other radios can be used only as needed and
for short durations when possible. In aggregate, these embodiments
can achieve low power for the P-Nodes, high reliability with
minimal outages, and work within a given range of 25 meters.
[0112] The above embodiments illustrate the complementary radios
216a.sub.1-216a.sub.n (and corresponding set 216b.sub.1-216b.sub.n)
and combinations thereof to serve a given requirement. The radios
216a.sub.1-216a.sub.n can be complementary in other ways. Some
example complementary properties follow.
[0113] Bandwidth:
[0114] One radio can use a wide bandwidth signal but a narrow time
signal. The other radio can use a narrow bandwidth having a wide
time signal (many cycles of a carrier) and occupy a narrow range of
frequencies. Both radios will have different resulting
characteristics.
[0115] Power Levels:
[0116] One radio may transmit more power in one band to attain
larger range but the implementation of a transmitter in this band
may be less power efficient. The other radio can work in a
different band where transmission is more power efficient.
[0117] Receiver Sensitivity (Range/Reliability):
[0118] One radio may be more sensitive in one band but may not be
power efficient. The other radio in a different band may be power
efficient but less sensitive.
[0119] Interference to Other Radios ("Quietness"):
[0120] One radio can act as an interferer to other radios in a
given radio environment whereas the other radio can be quiet.
[0121] Fading Characteristics:
[0122] Fading of the transmitted signal can result from multi path
effects resulting in signal loss or total outage at the receiver.
Different frequencies suffer different fading. Two radios can be
designed to have somewhat complementary fading characteristics to
reduce the probability of both having severe fading under the same
conditions.
[0123] The complementary radios can be all narrowband (NB) radios
with different optimizations or they all can be Ultra-wide band
(UWB) radios with different optimizations, or they can be a mixture
of NB and UWB radios. The UWB and NB radios are highly
complementary in many ways as discussed below: [0124] UWB radios
typically have a short range in an indoor environment (up to about
10 meters). On the other hand, NB radios can provide larger range
by transmitting higher power as allowed by FCC in the operating
band. [0125] UWB transmitters are typically simple to implement,
resulting in small silicon area and low power dissipation. NB radio
transmitters take up larger silicon area and result in higher power
dissipation than UWB transmitters. [0126] UWB receivers are complex
and dissipate high power. NB radio receivers have modest complexity
and dissipate modest power. [0127] UWB radios cause minimum
interference to other radios because they operate close to the
noise floor of other radios. NB radios cause interference to other
radios when operating in unlicensed bands. [0128] UWB can handle
some narrowband interference via its de-spreading (narrowband
interference) capability at the receiver. However, a strong
narrowband interferer could degrade its signal quality. A NB radio
can switch to a different channel within its band of operation when
another strong NB interferer appears in the current channel. It can
survive low broadband interference, but it cannot mitigate strong
broadband interference as all NB channels degrade equally.
[0129] Within a given system, the designs with optimum
complementary properties can be used to realize the radios
216a.sub.1-216a.sub.n/216b.sub.1-216b.sub.n shown in FIG. 3.
IV. Cost and Physical Size
[0130] Embodiments of the present invention disclosed above
illustrate how low power and high reliability can be achieved for a
given range in a multi-radio optimized asymmetric wireless (OAW)
system. As stated before, OAW systems also need to optimize the
cost and physical footprint, particularly for the P-Nodes 204a-n.
This can be achieved using various concepts as discussed below.
[0131] Firstly, complementary multiple radio schemes can be chosen
in such a way that semiconductor implementation complexity of the
P-Nodes 204a-n remains much lower than the complexity of A-Node
202. As discussed previously, in a typical OAW system, the data
mostly flows from the P-Nodes 204a-n to A-Node 202. Radios for the
P-Nodes 204a-n predominantly need a reliable transmitter for
continuous transmission and a receiver only for less frequent
reception. Radios for the P-Nodes 204a-n can be chosen that are
optimized to achieve these two functions at a low complexity.
[0132] As shown in FIG. 3, the multi-radio system also includes a
controller 240 to coordinate the selection and functionality all
the radios. The controller 240 continuously assesses the
communication link quality and runs algorithms to determine which
radio to use at a given time. It also sends commands to radios of
the A-Node 202 and P-Nodes 204a-n to activate/deactivate the radios
in real time. Such switching constantly may maintain the
communication link without any data loss. As shown in FIG. 3, the
controller 240 can reside in A-Node 202 to keep the complexity of
P-Nodes 204a-n low.
[0133] Furthermore, in some embodiments, one or more radios out of
216b.sub.1-216b.sub.n on the A-Nodes 202 can use multiple smart
antenna schemes to increase the link reliability and range. This
involves replicating one or more antennas 220b.sub.1-220b.sub.n for
the radio or radios chosen for the multiple-antenna scheme.
Multiple antennas add complexity to the chosen radio or radios
since multiple radio frequency (RF) transceivers must be built for
the multiple antennas and a signal processor is needed for antenna
combining algorithms. The corresponding radios of P-Nodes 204a-n
can still have single antenna schemes 216a.sub.1-216a.sub.n. This
embodiment provides the advantages of multiple antennas to increase
the range and reliability of the wireless link, but only adds the
circuit and processing complexity to the A-Node 202 to reduce the
complexity and cost of the P-Nodes 204a-n.
[0134] The above mentioned embodiments help to keep the P-Nodes
204a-n relatively simple and low cost by pushing the complexity to
the A-Nodes 202.
[0135] The deployment of multiple radios, in general, can escalate
the cost if precautions are not taken. To minimize costs, the
multiple radios can be implemented effectively by sharing resources
between them when possible. The different elements of a typical
radio, shown as 216 in FIG. 4, can be described as below.
[0136] MAC (Media Access Control) 306:
[0137] The MAC section implements a protocol that allows data to
flow through the radio to and from multiple sources.
[0138] Baseband Processor 304:
[0139] The baseband section modulates or demodulates the data and
performs other signal processing functions for the radio to
function and contains digital/analog and analog/digital converters
to interface to the radio frequency (RF) transceiver.
[0140] Radio Frequency (RF) Transceiver 302:
[0141] The RF section converts the baseband analog signal to radio
frequency that is fed to antenna 220 for transmission. Signal
received from antenna 220 can be converted back to the baseband
signal.
[0142] Antenna 220.
[0143] To reduce costs, it is desirable to use complementary radios
where resources of the above mentioned sections are shared or
configured to realize multiple radios, thereby reducing overall
semiconductor implementation costs. For example: [0144] RF: The RF
transceiver 302 can be reconfigurable to realize different types of
radios by varying carrier frequencies, bandwidth, transmitted
power, etc. [0145] Baseband: The baseband processor 304 can use a
programmable processor to implement certain functions for different
radios. Certain sections of the baseband can be hardwired for
different radios. Other sections of the baseband can be shared and
reused for different radios. Such mixed programmable/custom
architecture typically results in a low cost implementation. [0146]
MAC: A single MAC 306 protocol can be designed to serve multiple
chosen radios. Furthermore, the main core of the protocol can be
implemented using a programmable processor that provides some
customization for different radios. [0147] Antenna: Antenna 220
architectures can be defined to work at wide ranging carrier
frequencies and bandwidths to support multiple radios.
[0148] The combination of various concepts discussed in this
section can result in cost effective and physically small chipsets
for the P-Nodes 204a-n and A-Node 202. Certain specific embodiments
of these concepts are discussed below.
V. Complementary NB/UWB System
[0149] As disclosed herein, multiple complementary radios in an OAW
system can comprise: [0150] All NB radios with different desired
characteristics; [0151] All UWB radios with different desired
characteristics; or [0152] A mix of NB and UWB radios.
[0153] One embodiment of a multi-radio scheme contains one NB radio
452 and one UWB 450 radio, as shown in FIG. 5. This NB/UWB scheme
can be useful for a variety of OAW systems. As discussed before,
the NB 452 and UWB 450 radios have complementary characteristics,
making them suitable for an OAW system. The complementary UWB/NB
radio system can operate as shown in FIG. 6. The ranges of the UWB
and NB radios are respectively X and X+Y, where the UWB range is
usually smaller than the NB radios. In many embodiments, the
P-Nodes remain primarily within distance X of the A-Node, in range
of the UWB radio. If P-Nodes move beyond distance X from the
A-Node, but remain within the X+Y range, the NB radio can take
over. Also, if the UWB radio suffers an outage for any reason, the
NB radio can be used for communication. Dominant use of the UWB
radio results in overall lower power dissipation and causes minimal
interference to other radios. On the other hand, the NB radio,
which primarily backs up the UWB radio, guarantees a larger system
range up to X+Y. The availability of both UWB and NB radios can
greatly increase the system reliability due to radio diversity. The
UWB and NB radios normally suffer outages due to different types of
circumstances (different interferences, different multi-patch
fading effects, different wall penetration properties, etc.).
Therefore, this embodiment increases the probability that one of
the radios is available for communication.
[0154] As mentioned previously, there are many types of standards
based radios that can be deployed as NB radios, including Wi-Fi,
Bluetooth, ZigBee, WMTS, MICS, 900 MHz ISM band radios, 2.4 GHz ISM
band radios, 5 GHz ISM band radios, 60 GHz ISM band radios, etc. In
some embodiments, custom NB radios can be deployed as dictated by
the system requirements.
[0155] The multi-radio system embodied in FIG. 7 exemplifies
another optimized solution for many current and emerging
applications. As shown, the system employs a UWB transmitter 550a
on the P-Nodes 504a-n and corresponding UWB receiver 550b on the
A-Node 502. The UWB transmitter 550a and receiver 550b can be
asymmetrical. Typically, the UWB transmitter 550a section can be
built in a small silicon area and dissipates low power. The UWB
receiver 550b has a more complex silicon implementation and
dissipates higher power than the corresponding transmitter 550a. In
target applications, P-Nodes 504a-n mostly transmit the data to
A-Nodes 502, and therefore mostly use this link. P-Nodes 504a-n
also implement a Wi-Fi compatible radio 560 which is a NB radio.
There is corresponding Wi-Fi radio 562 on A-Node 502 for
communication with P-Nodes 504a-n. The Wi-Fi radios 560 and 562 can
use one or more modes of the Wi-Fi standard--802.11, 802.11b,
802.11g, 802.11a, etc. The Wi-Fi radios 560 and 562 can be used for
communication in at least the following circumstances: [0156] When
P-Nodes 504a-n move out of the range covered by UWB radio
550a/550b. [0157] If UWB radio 550a/550b suffers an outage due to
some other reason. [0158] When A-Node 502 transmits data to P-Nodes
504a-n (assumed to be infrequent for target applications). [0159]
On demand wherein an application can force the use of Wi-Fi radio
560/562.
[0160] Unlike the UWB transmitter 550a and UWB receiver 550b, the
NB transmitter 560 and receiver 562 can be symmetrical. Their
silicon area and power dissipation are comparable for both transmit
and receive functions, and both transmit and receive functions take
modest amount of silicon area and dissipate modest power. The use
of Wi-Fi radio 560 and 562 as a NB radio results in an additional
advantage: by making the system compatible with Wi-Fi standard
based devices, the P-Nodes 504a-n and A-Nodes 502 can communicate
with other Wi-Fi enabled devices.
[0161] The Wi-Fi radio can be further enhanced, if needed, by using
multiple antennas 570a-n on the Wi-Fi radio of the A-Node 502. The
corresponding Wi-Fi radio of the P-Node 504a-n can use a single
antenna to reduce complexity. Through multiple antennas processing
gain, the Wi-Fi link is more robust with a larger range. The
multiple antenna configuration can thereby increase the system
reliability and robustness at no additional complexity to the
P-Nodes 504a-n. Although the complexity, cost and power of the
A-Nodes 502 increase when using multiple antenna processing, in
many embodiments, this is not a sensitive issue in the targeted OAW
systems.
[0162] In embodiments using complementary radios in a communication
system, two methodologies are employed: where only one radio is
active at a time, which will be referred to hereinafter as the
"Unicast" methodology; and where two or more complementary radios
are active at the same time, referred to hereinafter as the
"Simulcast" methodology. The following describes the feature of
these methodologies in more detail.
[0163] (a) Unicast Methodology
[0164] The unicast methodology includes initial radio selection,
whereby a radio is chosen from multiple radios to initiate a new
connection between two devices, and radio switching, whereby one
radio is switched to another during the course of a connection. It
is also feasible for the unicast methodology to consist solely of
initial radio selection or solely of radio switching. When the
unicast methodology consists solely of radio switching, the initial
radio to be used for a new connection can be chosen by any of a
number of means, e.g., random selection, user or factory
configuration, or in accordance with a default setting, or others.
The following sections describe initial radio selection and radio
switching in more detail.
[0165] Initial Radio Selection
[0166] The method for initially selecting a radio for a new
connection depends on the performance objective. The performance
objective may be hardwired or user-programmable. Example
performance objectives are described in the following sections.
[0167] (1) Minimal Power Consumption
[0168] In one embodiment, the objective is to minimize power
consumption, and the initial choice of radio depends on the
different radio structures. For example, a multi-radio device may
include a narrowband (NB) radio and an ultra-wideband (UWB) radio
as described herein. The RF and baseband circuitry implementing the
UWB radio may operate with lower transmission power than the
narrowband radio. Accordingly, one would choose UWB, the radio with
lower transmit power, for initiating the connection.
[0169] (2) Minimal Interference to Other Devices
[0170] In another embodiment, the objective may be to minimize the
interference caused by the new connection to other devices sharing
the radio spectrum. In one embodiment, the initial choice of radio
is based on the differences in radio structures. Consider a
multi-radio device comprising a NB radio and a UWB radio. If NB
radio devices sharing a common air interface standard are the sole
users of the radio spectrum (as a result of government regulation,
for example), and the air interface provides for cooperative
channel partitioning, then the NB radio is preferred for initiating
a new connection.
[0171] In some embodiments, however, the devices sharing the radio
spectrum may not be cooperative or even known a priori. In this
situation, a UWB radio offers the advantage of having a very low
radiated power spectral density--potentially below the thermal
noise floor--and hence would be the preferred initial radio.
[0172] In an alternate embodiment, measurements of the radio
environment experienced by each radio can be used to predict the
amount of interference introduced. Consider a system consisting of
a mobile device and a base station, wherein the base station to
mobile connection comprises the downlink connection and the mobile
to base station connection comprises the uplink connection. At the
base station, one measures the power spectral density (PSD) over
the spectrum range corresponding to each radio. The received power
for a radio then serves as a predictor of the interference from the
new downlink connection on existing users for that radio. The lower
the received power for a radio, the less interference the
corresponding downlink is likely to produce.
[0173] Similarly, at the mobile device, the power spectral density
is measured over the spectrum range corresponding to each radio.
The received power for each radio at the mobile device is a
predictor of the interference from the new uplink connection on
existing users for that radio.
[0174] As an alternative to measuring the power spectral density
over the spectrum range, the received background noise and
interference power level can be measured individually on each
channel of the radio spectrum. This can be done at either of the
two communicating devices. To perform the tests on the different
radios and different radio channels, quiet periods or quiet
intervals--intervals during which all the devices do not
transmit--can be used. For example, such quiet periods are
described as part of the 802.11 protocol specification.
[0175] In some embodiments, the initial radio is selected to
minimize downlink interference or uplink interference. In other
embodiments, the radio is selected to minimize an aggregate of both
uplink and downlink interferences. For this approach, the power
received on the uplink and downlink for each radio are aggregated,
and the radio with the lowest aggregate received power is selected.
For example, the mobile device may communicate the downlink
interference estimates to the base station over a control channel;
the base station can aggregate the uplink and downlink interference
for each radio and select an appropriate radio.
[0176] In another embodiment, the communications system is capable
of using one radio for the downlink communication and optionally a
different radio for the uplink communication. In this system, the
system need not aggregate the uplink and downlink interference
estimates to perform radio selection. Instead, the downlink radio
can be chosen to minimize the downlink interference, and the uplink
radio can be chosen to minimize the uplink interference.
[0177] (3) Maximal Reliability of New Connection
[0178] In some embodiments, the most important objective is not to
minimize interference to other devices, but rather to maximize the
reliability of the new connection. To accomplish this, the signal
quality of the communications for each candidate radio can be
estimated or predicted. In one embodiment, the communications
protocol allows for each radio to transmit a pilot signal on the
downlink, the uplink, or optionally both links. The pilot signal
may include, e.g., a sequence of symbols or data bits.
Alternatively, the signal quality can be measured directly from the
symbols or data bits of the control signals or data signals that
are ordinarily transmitted during the course of communication. This
latter approach has the advantages of not using the additional
radio bandwidth required by the pilot signal approach for signal
quality estimation, and is more amenable to backward compatibility
with existing radio standards. On the uplink, the base station
receiver measures the signal quality for each radio using a signal
quality estimator, which will be described shortly. Likewise, the
mobile receiver measures the signal quality of each radio on the
downlink. The radio is chosen with the best uplink signal quality
or the best downlink signal quality.
[0179] In some embodiments, the radio may be chosen based on both
uplink and downlink signal quality predictors. The appropriate
radio can be chosen by aggregating the signal quality statistics
together at the communications device that performs the radio
selection. There are several ways of accomplishing this aggregation
of signal quality characteristics. For example, the mobile device
can communicate the downlink signal quality estimates to the base
station over a control channel. The base station can then compute a
score for each radio as the lesser of its uplink quality and its
downlink quality, and can select the radio with the highest score.
Alternatively, the base station may narrow the field to only those
radios whose uplink and downlink signal quality exceed a minimum
threshold. From this group, the base station then selects the radio
that maximizes downlink signal quality or uplink quality.
In a further embodiment, the communications system uses one radio
for the downlink communication and optionally a different radio for
the uplink communication. In this system, there is no need to
aggregate the uplink and downlink signal quality predictors to
perform radio selection. Instead, the system can choose the
downlink radio with the maximum downlink signal quality predictor,
and chooses the uplink radio with the maximum uplink signal quality
predictor.
[0180] (4) Support Uplink and Downlink Bandwidth Disparities
In some embodiments, there may be a large disparity in the downlink
and uplink data rates. For example, in a mobile Web access
application, the mobile device spends a large fraction of time
downloading Web content after clicking on http hyperlinks. Such
usage patterns results in large amounts of data being sent on the
downlink but little data transmitted on the uplink. We accommodate
this disparity in uplink and downlink bandwidths with a
communications system capable of using one radio for the downlink
communication and optionally a different radio for the uplink
communication; for example, selecting the UWB radio for the
downlink and the NB radio for the uplink.
[0181] (ii) Signal Quality Estimation
[0182] As described above, several of the methods require an
estimate of the signal quality. There are many possible methods of
estimating signal quality. In one embodiment, the signal quality
can be estimated as the received signal strength indicator (RSSI).
In another embodiment, the signal quality can be estimated as the
packet error rate or bit error rate. In another embodiment, the
signal quality can be estimated by monitoring the background noise
and interference level of the link; the higher the background noise
and interference level, the lower the quality of the link. Another
embodiment for estimating the signal quality is:
Estimated signal
quality=.parallel.s.parallel..sup.2/.parallel.s-.parallel.s.parallel..sup-
.2/.parallel.d.parallel..sup.2*d.parallel..sup.2,
where s is the received signal vector immediately prior to decision
slicing, d is a known pilot vector of symbols, and
.parallel..parallel. denotes the norm of a vector. The received
signal vector and the pilot vector have the same prescribed number
of symbols. Typically, 20 or more symbols are sufficient, and more
symbol generate a more accurate signal quality estimate.
Alternatively, in the absence of known pilot symbols, as would be
the case if signal quality estimation is performed directly on the
data or control signal, a decision-directed approach can be used to
derive d. In this case, d is the vector of detected symbols after
decision slicing.
[0183] (iii) Multiple Performance Objectives
[0184] The preceding embodiments described procedures that allow a
multi-radio communications system to meet individual performance
objectives. In other embodiments, a multi-radio communications
system can allow for simultaneously achieving multiple performance
objectives using a constrained optimization approach.
[0185] It may not be possible to select a radio that is optimal for
every objective. For example, a radio that is optimal for
communications reliability may have suboptimal power consumption.
In some embodiments, such a system considers one objective from
various objectives to have the greatest importance; hereinafter
referred to as the primary objective. For each of the remaining
objectives, a threshold of acceptable performance is set;
hereinafter referred to as the performance constraint. The
constrained optimization approach can be described by the
following: find the radio that optimizes the primary objective,
subject to the performance constraint being met for the other
objectives.
[0186] FIG. 8 shows a flow chart for addressing the constrained
optimization approach. Referring to the FIG. 8, for each
non-primary objective, determine the subset of radios satisfying
the performance constraint, via step 802. Depending on the
non-primary objective, methods for executing step 802 are described
above for the Unicast Method to minimize power consumption,
minimize interference to other devices, maximize reliability of new
connection, or support uplink and downlink bandwidth
disparities.
[0187] Next, take the intersection of all subsets derived from the
previous step to determine the candidate set of radios, via step
804. Finally, from the candidate set of radios, choose the radio
that optimizes the primary objective, via step 806. Methods for
executing step 806 given the primary objecting are also described
herein.
[0188] In an example embodiment, suppose the primary objective is
to minimize interference, subject to achieving a minimum signal
quality, in a dual-radio system comprising a narrowband (NB) radio
and an ultra-wideband (UWB) radio. First, procedures described
herein can be applied to estimate the signal quality for both the
narrowband and UWB radios, and determine a candidate set of radios
with acceptable signal quality. If both radios meet the performance
constraint, then a procedure can be used to pick the radio that
minimizes interference. If only one radio meets the performance
constraint, that radio can be chosen. If neither radio meets the
constraints, the constraints can be relaxed to find a feasible
solution.
[0189] (b) Simulcast Method
[0190] In the simulcast method, both radios are active at the same
time. Both radios simultaneously transmit, and the receiver
combines the signals from both radios. Several uses are envisioned
for this method. For example, when switching from one radio to
another, the simulcast method can help ensure that the connection
remains throughout the switch so that there is no outage; i.e., it
provides soft handoff or make-before-break switching between the
two complementary radios. Alternately, when reliable communications
are of paramount importance, both radios can transmit
simultaneously all the time. The simulcast method is effectively an
advanced form of radio diversity, which can be exploited by the
receiver.
[0191] In one embodiment, two complementary radios use the same
symbol constellation alphabet for encoding data, e.g., Binary
Phase-Shift Keying (BPSK), and the signals from the two radios can
be combined in baseband. There are many ways to perform the
combining. In one embodiment, the signal from each radio undergoes
its normal receive processing (down conversion from RF to baseband,
amplification, sampling and equalization/matched filtering), except
that in the final stage before slicing, the baseband signal of each
radio path immediately prior to slicing are summed together, and
the combined signal goes to a single slicer. In an alternate
embodiment, an enhanced form of RAKE reception is used:
Input to slicer=c1,1*x1[1]+ . . . +c1,n*x1[n]+c2,1*x2[1]+ . . .
+c2,m*x2[m]
ci,j=the j-th tap, or coefficient, of the RAKE filter for radio
i
xi[j]=the j-th time sample of baseband signal of radio i
[0192] A RAKE receiver is a radio receiver designed to counter the
effects of multipath fading by using several sub-receivers called
fingers, wherein each finger independently decodes a single
multipath component that are later combined in order to make the
most use of the different transmission characteristics of each
transmission path. The taps of the RAKE filter can be derived for
each of the complementary radios using any of a number of methods
known in the art; for example, maximum ratio combining (MRC) or
optimizing for minimum mean square error (MMSE). The time between
successive taps and between successive baseband signal samples may
be the symbol period, or it may be a fraction of the symbol period,
in the case of Nyquist sampling or over-sampling.
[0193] Combining of the signals from the two radios before slicing
can improve the reliability of the communications, providing
robustness against channel impairments in one or both of the radio
paths.
VI. Robust Radio Switching Protocols
[0194] Radio switching is the process of changing from one radio to
another after a connection is established in order to improve on
one or more performance objectives for the connection.
[0195] (a) Radio Switching
[0196] In one embodiment, the steps for radio switching comprise
the following:
[0197] Step 1: For each performance objective of interest, set a
threshold of acceptable performance objectives and monitor each
performance objective for the current radio using methods as
described herein. For example, if the performance objective is
minimizing interference, monitoring of interference can be
performed. If reliability is the performance objective, the signal
quality can be estimated for the current radio. If both reliability
and interference objectives are of interest, monitor the predictors
for both objectives for the current radio;
[0198] Step 2: If there is only one performance objective and its
measured performance metric falls below the acceptable threshold,
switch to an alternate radio. If there are multiple performance
objectives, switch to an alternate radio based on one of the
following criteria: (i) if any one performance objective is not
met; (ii) if all performance objectives are not met; or (iii) if
the primary performance objective is not met. If there are more
than one alternate radios to choose from, then the optimal radio
can be selected using any one of the methods outlined herein;
and
[0199] Step 3: After switching, optionally return to Step 1.
[0200] In an alternate embodiment, the performance objective is
continuously or periodically monitored for some or all of the
radios, e.g., monitoring for the best signal quality, the lowest
interference or a combination of performance objectives. If the
current radio is not the optimal radio, then switch to the optimal
radio. If there is only one performance objective and if the
performance metric of at least one alternate radio exceeds that of
the present radio by some prescribed amount, then switch to the
best alternate radio. If there are multiple performance objectives,
switch to an alternate radio if (i) a majority or all of the
performance metrics of at least one alternate radio exceed those of
the present radio by some prescribed amount; or (ii) the primary
performance metric of at least one alternate radio exceeds that of
the present radio by some prescribed amount.
[0201] (b) Handshaking Protocols
[0202] As stated earlier, a performance objective of the
communications system can be increased reliability. Hence, when
communication using one radio experiences poor quality, excessive
radio interference or other impairments, it can be desirable to
switch to an alternate radio. However, the control signal messages
that direct the overall communications may be transmitted on the
same poor quality communications channel as the data. A problem is
how to signal the radio switching reliably, since the radio
switching is needed precisely when the communications channel is
experiencing poor quality. If the control signaling is not done
correctly, the transmitter and the receiver may end up in a state
where they are not in agreement as to which radio to use, resulting
in a broken communications link. The present invention discloses a
communications protocol method which can ensure highly reliable
switching from one radio to another, even if the communications
channel over which the control messages are transmitted is
unreliable.
[0203] In many practical systems, the two wireless devices
communicating with each other differ in the amount of power
available to them. For example, in a cellular telephony
application, a cellular phone generally communicates with a base
station. The base station is fixed in location and connected to the
power grid, so it does not have the power limitations imposed upon
a battery-powered cellular phone. This difference in the amount of
available power is not limited to whether the device is portable or
stationary.
[0204] The cellular phone may comprise a SmartPhone. Although there
is no standard definition of a SmartPhone, such a device is
generally a cellular phone offering advanced capabilities,
including but not limited to Electronic Mail (E-mail) and Internet
capabilities. A SmartPhone can be thought of as a mini-computer
offering cellular phone services. SmartPhones commonly use
operating systems (OS) including the iPhone OS from Apple, Inc.,
the RIM Blackberry OS, the Palm OS from PalmSource, and the Windows
Mobile OS from Microsoft, Inc. Other operating systems can be
used.
[0205] For example, in a medical sensor network, a sensor device
may be placed on the body to collect physiological data, and then
wirelessly communicate the data to a SmartPhone. Both devices are
portable and require self-contained power sources, but the sensor
device may have a smaller form factor and be constrained to run on
a smaller battery than the SmartPhone. The sensor device may be
designed to be disposable and supplied with a cheap, low capacity
battery, whereas the SmartPhone is a reusable device designed with
a more expensive, higher capacity battery. In summary, there may be
a disparity in the energy capacities of two devices communicating
over a wireless link because of differences in their mobility
(stationary versus portable), physical size and cost.
[0206] Because processing power is proportional to energy usage, it
can be desirable to design the communications protocol for radio
switching to have low compute processing requirements. However, if
the switching protocol is asymmetric, and designed to support
different amounts of compute processing at different radio nodes,
then radios with lower power capacity can conserve energy by doing
less processing, while higher power capacity radios will do more
processing.
[0207] The communications protocol method of the present invention
is applicable to point-to-point as well as multiple access systems.
As described herein, the dynamic radio switching can be integrated
together with the selection of which radio channel to use. The
partitioning of radio spectrum into channels can be accomplished by
frequency band partitioning, by time slot partitioning, by the use
of frequency hopping sequences, direct sequence spreading codes,
pulse position offsets, pulse position hopping, or by other
means.
[0208] The following embodiments exemplify approaches to switching
between a base node device and a peripheral node. In some
embodiments, the base node consumes more resources than the
peripheral node or nodes. For example, as illustrated in the
following embodiments, the base node can comprise a high-powered
device (HPD) and the peripheral node or nodes can comprise low
powered devices (LPD). A specific embodiment comprises the cell
phone and cell tower arrangement as described above. Those of
ordinary skill in the art will appreciate that the following
protocols readily generalize to alternate embodiments, e.g., where
the two devices in communication are of similar power capacity.
[0209] FIGS. 9 and 10 depict one embodiment of the communication
protocol method for a HPD and a LPD, respectively. The forward link
is the communication link from the LPD to HPD, and the reverse link
is the communications link from the HPD to the LPD. The HPD
monitors the communications quality of the forward link on the
Current Channel of the Current Radio (step 602), as described
above. The HPD determines whether the communication quality is
acceptable (step 604). If the communication quality becomes
unacceptable, it then selects a best Alternate Channel and a best
Alternate Radio (step 606). The HPD then transmits a control
message on the reverse link to the LPD, indicating the Alternate
Channel and the Alternate Radio to switch to (step 608). The HPD
then switches to the Alternate Channel and Alternate Radio (step
610). It listens on this new channel and radio for an
acknowledgement message from the LPD indicating that it had
received the message to switch to the Alternate Radio and Alternate
Channel, as well as for any data communication from the LPD (step
610). Verification that the message is a valid acknowledgement or a
valid data packet can be accomplished using by a number of ways;
for example, by use of a cyclic redundancy check or a checksum. By
listening for the acknowledgement on the new Alternate Channel of
the Alternate Radio (step 612), the communications of the
acknowledgement avoids using the already impaired Current Channel
of the Current Radio. If the HPD does not receive an
acknowledgement within a prescribed time interval, it will
retransmit the control message to switch to the Alternate Radio and
Alternate Channel (step 614). Optionally (not shown in FIG. 9), the
HPD may re-evaluate the candidate channels of the candidate radios
to select a new best Alternate Radio and Alternate Channel. The HPD
will then periodically retransmit the control message to switch to
the Alternate Radio and Alternate Channel until it receives an
acknowledgement from the LPD. Once the acknowledgement is received,
the switch to the new Alternate Channel of the Alternate Radio by
the HPD and LPD is complete and the HPD returns to monitoring the
forward link (step 602).
[0210] In contrast with the operation of the HPD, the steps in the
communications protocol taken by the LPD (shown in FIG. 10) are
computationally relatively simple. If the LPD receives a control
signal message on the Current Channel of the Current Radio from the
HPD indicating that that it should switch (step 702), the LPD will
switch to the specified Alternate Channel of the Alternate Radio
(step 704). It then sends an acknowledgement to the HPD on the
Alternate Channel of the Alternate Radio, indicating that it
received the message to switch (step 706). It then uses the
Alternate Channel of the Alternate Radio for subsequent data
transmission on the forward link.
[0211] In a related embodiment, the operation of the communication
protocol is depicted in FIG. 11 for the HPD. The HPD monitors the
communications quality of the forward link on the Current Channel
of the Current Radio (step 602). The HPD determines whether the
communication quality is acceptable (step 604). If the
communication quality becomes unacceptable, the HPD selects a best
Alternate Channel and best Alternate Radio (step 606), and then
transmits the control message "Switch to the Alternate Channel and
Alternate Radio on the forward link" to the LPD (step 608). As
before, it then listens on the Alternate Channel of the Alternate
Radio for an acknowledgement from the LPD (step 610a); however, the
HPD will concurrently continue to receive data from the LPD on the
Current Channel of the Current Radio until it receives an
acknowledgement from the LPD on the Alternate Channel of the
Alternate Radio (step 610a). This method introduces additional
complexity to the HPD, but has the advantage of minimizing
potential lapse or dead time in data communications during the
radio switch.
[0212] In another embodiment, FIGS. 12 and 13 depict the operation
of the communication protocol method for the HPD and the LPD,
respectively. As before, the HPD monitors the communications
quality of the forward link on the Current Channel of the Current
Radio (step 602). The HPD determines whether the communication
quality is acceptable (step 604). If the communication quality
becomes unacceptable, the HPD selects a best Alternate Channel and
best Alternate Radio (step 606), and then transmits the control
message "Switch to the Alternate Channel and Alternate Radio" to
the LPD (step 608). It then switches to the Alternate Channel,
Alternate Radio (step 610b) for the forward link. It listens on
this new channel and radio for data communication from the LPD, but
does not wait for an acknowledgement from the LPD (step 610b).
Instead, the HPD will periodically retransmit the message "Switch
to Alternate Radio, Alternate Channel on forward link" to the LPD
until it receives data on the new channel and radio. The switch to
the new Alternate Channel of the Alternate Radio by the HPD is
complete once the HPD begins receiving data on the new channel and
radio (step 612a). As shown in FIG. 13, the corresponding operation
required by the LPD is very simple: when it receives a control
message instructing it to switch (step 702), the LPD will switch to
the specified Alternate Radio, Alternate Channel on the forward
link, and perform subsequent data transmission on the new channel
and radio (step 704). This embodiment has the advantage of a
simplified communication protocol for both the HPD and the LPD, and
is particularly suitable in applications where data is sent either
continuously or at frequent, regular intervals on the forward
link.
[0213] FIG. 14 depicts the operation of the HPD in a variation of
the aforementioned method. As before, the HPD monitors the
communications quality of the forward link on the Current Channel
of the Current Radio (step 602). The HPD determines whether the
communication quality is acceptable (step 604). If the
communication quality becomes unacceptable, the HPD selects a best
Alternate Channel and best Alternate Radio (step 606), and then
transmits the control message "Switch to the Alternate Channel and
Alternate Radio" to the LPD (step 608). The difference is that the
HPD continues to listen on the Current Radio, Current Channel for
data from LPD on the forward link (step 610c). As long as it
continues to receive data on the current radio and channel (step
612a), the HPD will periodically retransmit the message "Switch to
Alternate Radio, Alternate Channel on forward link" to the LPD
(step 614). Once the HPD stops receiving data for a prescribed time
interval on the current radio and channel, it then switches to the
Alternate Radio and Alternate Channel for subsequent reception of
data from the LPD (step 616). This method of operation is most
suitable for applications where data is sent either continuously or
at frequent, regular intervals on the forward link.
[0214] The previously described protocols can also be applied in
the case where the roles of the HPD and the LPD are reversed; that
is, the forward link is the communication link from the HPD to LPD,
and the reverse link is the communications link from the LPD to the
HPD. The LPD then monitors the communications quality of the
forward link and initiates the radio switching. While this method
of operation can be suboptimal in terms of matching the low
processing complexity portion of the protocol with the LPD, it can
still help ensure reliable radio switching if the quality of the
communication link from the HPD to the LPD becomes poor. In an
alternate embodiment, the LPD may make a request to the HPD to
perform the monitoring and initiate the switching on the behalf of
the LPD. This approach can be used when the LPD does not have
sufficient computational and/or energy resources to perform the
monitoring and radio switching.
[0215] Those of ordinary skill in the art will appreciate that the
previously described protocols readily generalize to the case where
the two devices communicating are of similar power capacity.
VII. Dual Mode Ultra-Wideband/Narrowband Reconfigurable
Transceiver
[0216] A dual mode reconfigurable radio architecture can operate as
a narrowband transceiver and is reconfigurable to operate as a
broadband low power ultra-wideband transceiver.
[0217] (a) Generic Dual Mode Reconfigurable Receiver
[0218] FIG. 15 illustrates a generic narrowband receiver 900
comprising a low-noise amplifier (LNA) 902, a reconfigurable
bandpass filter 904 (which is often realized as part of the LNA
output tank), and a bank 906 of devices. In this embodiment, the
bank of devices includes a plurality of mixers 911a-911n. Each of
the mixers 911a-911n are driven with different phases 913a-913n of
the Local Oscillator (LO) signal 910. The most common approach is
to use two quadrature phases of the LO, or four differential
quadrature phases. The output of these mixers is in turn filtered
and sampled by analog-to-digital converter (ADC) 908a-908n (filter
not shown).
[0219] FIG. 16 illustrates the receiver configured into a wideband
receiver by bypassing or reconfiguring the filter 904 to be a low
pass filter (one technique to convert the RLC load into a
shunt-peaked load is described later) and converting the mixers 906
into sampling switches 906. In Complementary Metal-Oxide
Semiconductor (transistor type) (CMOS) technology this is easily
done by re-using the existing devices 911a-911n (in for example, a
Gilbert cell) as switches. The switches 911a-911n are now driven
with a periodic square waveform delayed by time delays 1011a-1011n
fractions of the period Ti-Tn in order to capture different
instants of the waveform. The ADCs 908 are clocked at a slower
rate, but in parallel ADCs 908 capture a wider bandwidth (bandwidth
extension is equal to the number of stages in parallel). While
signal-ended switches are shown, one of ordinary skill in the art
readily recognizes that this feature extends to differential
switches and to double-balanced switching architectures.
[0220] (b) Generic Dual Mode Reconfigurable Transmitter
[0221] FIG. 17 illustrates a generic transmitter 1100 configured as
a narrowband transmitter in accordance with the present invention.
The transmitter 1100 includes a power source 1102 coupled to a
switch 1104. The switch 1104 is coupled to an inductor-capacitor
(L-C) circuit 1106 and to an antenna 1108. The L/C circuit 1106 and
the power source 1102 are coupled to the ground. When in the
narrowband mode, the switch 1104 provides a periodic signal to the
antenna. Phase or frequency modulation can be applied to the switch
while the output power is controlled by the amplitude of the direct
current (DC) power source. As seen in FIG. 18, when the transmitter
is in UWB mode a single pulse to switch 1104 is provided. In so
doing, it is seen that a single transmitter can be readily
reconfigured into either a narrowband mode or a UWB mode. FIG. 19
illustrates an embodiment of a circuit 1250 which can provide
either mode dependent upon the input signal to the transistor
1252.
[0222] (c) Dual Mode Reconfigurable Transceiver
[0223] A particular embodiment of dual mode reconfigurable
transceiver is described in detail below. FIG. 20 illustrates the
reconfigurable receiver 1300 implemented in CMOS technology.
Transistors 1302/1304 comprise a complementary input stage low
noise amplifier (LNA) 1306 with low impedance to match to the
antenna. Transistor 1310 is a programmable current source which can
alter the input match and LNA gain 1306 to adapt to varying
conditions. Capacitor 1312 and capacitor 1314 are AC coupling
capacitors, and capacitor 1314 couples the alternating current (AC)
signal from transistor 1304 to transistor 1302, forming a current
summation at the drain of transistor 1302. The load of the LNA 1306
is formed by a large low Q inductor, inductor 1301 and inductor
1303, which forms a peaking load.
[0224] The layout of these inductors 1301 and 1303 is particularly
important as shown in FIG. 21. This inductors are a stacked series
connected structure, with spirals on each layer connected in series
with lower metal layers with the correct orientation to increase
the magnetic flux and hence to realize a large inductor. Referring
back to FIG. 20, transistor 1316 is connected as a switch between
the second layer and supply. A control signal on the gate of
transistor 1316 can short out the bottom layer turns of the
inductor. In this way, if transistor 1316 is off, then the load is
large peaking load. The resistance of the load is made up of the
bottom metal layers, which are typically thinner in an IC process.
When transistor 1316 is turned on, the AC signal is bypassed to
supply through transistor 1316 and the load is a small higher Q
inductor, which resonates with the load of the LNA 1306. In this
way, the LNA 1306 can be reconfigured from a broadband LNA for UWB
to a narrowband LNA.
[0225] Referring back to FIG. 20, transistors 1318, 1320, 1322 and
1324 comprise the core of the mixer/sampler stage. Each transistor
1318-1324 is biased to operate with zero DC current as a passive
switching mixer. In narrowband mode 1302, these transistors are
driven with a local oscillator (LO) 1304 which drives the top pair
of transistors 1318-1320 with an in-phase (I) 1308a differential
signal, and the bottom pair of transistors 1322-1324 with a
quadrature phase differential signal (Q) 1308. The outputs V.sub.o1
1326-V.sub.o2 1328 are a differential IF output signal for the I
1308a channel and the outputs V.sub.o3 1330-V.sub.o4 1332 are a
differential IF signal for the Q 1308 channel. Since the IF load is
capacitive and low pass, the effective load of the mixer seen by
the LNA 1316 is time-varying and can be shown to effectively form a
resonant tank which provides additional rejection of out of band
interference.
[0226] In ultra-wideband mode, each transistor/capacitor
combination (transistor 1318 and capacitor 1334, transistor 1320
and capacitor 1336, transistor 1322 and capacitor 1338, and
transistor 1324 and capacitor 1340) forms a sample-and-hold circuit
(for example, transistor 1318 and capacitor 1334) which samples the
RF signal directly on the capacitor (capacitors 1334-1340). Each
capacitor (capacitors 1334-1340) is sized large enough so that the
sampled kT/C noise meets the system specifications. The transistor
1318 is thus biased large enough to provide the bandwidth
requirements of the system. The gate of transistor 1318 is driven
with a clock signal at sampling instant T1 while the clock of
transistor 1320, transistor 1322 and transistor 1324 are sampled at
instants T1+.DELTA.d, T1+2.DELTA.d, T1+3.DELTA.d. In this way the
bandwidth requirement of each sampler is reduced by one quarter and
four parallel streams of data are used to capture the signal. The
output of each sampler is amplified by a switched capacitor circuit
and then digitized by the ADC. Alternatively, this sampler can form
the core of a Delta-Sigma to capture the signal in the digital
domain.
[0227] The operation of the circuit can be enhanced by placing a
VGA in the receiver path. The VGA forms the second stage of
amplification following the LNA. To accommodate both narrowband and
broadband modes, the VGA can operate up to the highest RF frequency
in the UWB mode. To save power in narrowband mode, however, the VGA
can be re-wired and connected after the mixers where the highest
frequency of operation is set by the IF and not the RF signal. The
current of the VGA stage is lowered to lower the bandwidth of the
mixer.
[0228] The most commonly used UWB transmitter circuit includes a
H-bridge structure where the gate of the transistors are driven
with the correct signals as to produce a sharp pulse across the
load of either positive or negative polarity. FIGS. 22A and 22B
show the operation of the reconfigurable transmitter 1500 in more
detail. Referring to FIG. 22A, in the first of a bit `0` period,
transistors 1502 and 1504 are turned on and transistors 1506 and
1508 are turned off to drive a current through the antenna load.
Referring to FIG. 22B, in the second half of the period, the
antenna is short circuited to ground via transistors 1506 and 1504.
This simple H-bridge circuit is compatible with low cost
technologies such as CMOS and the control signals for circuit are
easily generated with digital logic.
[0229] This H-bridge can be reconfigured as a narrowband
transmitter by driving the structure with the period LO signal
which can be frequency modulated in high efficiency mode or even
driven as a linear differential amplifier for standards that
require power amplifier (PA) linearity. Each switching transistor
can be biased in class A, A/B, C, D, or E, E/F modes of operation
to achieve the required linearity/efficiency trade-off. In class D
mode, for instance, the load is alternated in polarity between the
supply and ground, which results in maximum radiated power given by
the power supply and the antenna impedance. Power control can be
introduced by regulating the supply of the circuit or by employing
impedance matching.
VIII. Kits
[0230] Further provided herein are kits comprising devices of the
present invention. In one embodiment, an asymmetric wireless system
as described herein can be sold to end users in the form of a kit.
The kits can comprise multiple items, including but not limited to
integrated devices comprising one or more anchor, or base, node
devices and one or more peripheral node devices. The devices can
implement multiple radio communications. In some embodiments, a
peripheral node device is in the form of a patch. In some
embodiments, a kit can provide a system comprising multiple
peripheral node devices and one or more anchor node devices. In
some embodiments, the nodular devices use integrated
Application-specific integrated circuit (ASIC) implementations for
robust and cost effective communications. The devices can further
comprise dual mode reconfigurable transceivers as described herein.
In some embodiments, the kit can include a host device with an
integrated wireless base. In another embodiment, the kit provides
one or more peripheral node patch devices. These devices may be
disposable. Such a kit can be useful when the end user, e.g., a
hospital, has already purchased a kit comprising an anchor node and
needs to replenish the supply of disposable patch devices that
communicate with the anchor.
[0231] While preferred embodiments of the present invention have
been shown and described herein, it will be obvious to those
skilled in the art that such embodiments are provided by way of
example only. Numerous variations, changes, and substitutions will
now occur to those skilled in the art without departing from the
invention. It should be understood that various alternatives to the
embodiments of the invention described herein may be employed in
practicing the invention. It is intended that the following claims
define the scope of the invention and that methods and structures
within the scope of these claims and their equivalents be covered
thereby.
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