U.S. patent application number 15/413016 was filed with the patent office on 2017-05-11 for managing transmit power for better frequency re-use in tv white space.
The applicant listed for this patent is QUALCOMM Incorporated. Invention is credited to Santosh ABRAHAM, Hemanth Sampath, Stephen Shellhammer, Rahul Tandra, Sameer Vermani.
Application Number | 20170135050 15/413016 |
Document ID | / |
Family ID | 45768317 |
Filed Date | 2017-05-11 |
United States Patent
Application |
20170135050 |
Kind Code |
A1 |
ABRAHAM; Santosh ; et
al. |
May 11, 2017 |
Managing transmit power for better frequency re-use in TV white
space
Abstract
Certain aspects of the present disclosure provide techniques and
apparatus for managing transmit power in a television white space
(TVWS) network. One example method generally includes transmitting
a sequence of request-to-send (RTS) messages at different transmit
power levels to an apparatus and determining if a clear-to-send
(CTS) message was received in response to at least one of the RTS
messages corresponding to a particular one of the transmit power
levels. Another example method generally includes receiving, at a
first apparatus from a second apparatus, a packet that cannot be
decoded by the first apparatus; determining at least one of a time
or a duration corresponding to the packet; transmitting a query
with an indication of the at least one of the time or the duration;
and receiving a message from the second apparatus in response to
the query, the message identifying the second apparatus as a source
of the packet.
Inventors: |
ABRAHAM; Santosh; (San
Diego, CA) ; Vermani; Sameer; (San Diego, CA)
; Sampath; Hemanth; (San Diego, CA) ; Shellhammer;
Stephen; (Ramona, CA) ; Tandra; Rahul; (San
Diego, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
QUALCOMM Incorporated |
San Diego |
CA |
US |
|
|
Family ID: |
45768317 |
Appl. No.: |
15/413016 |
Filed: |
January 23, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13397450 |
Feb 15, 2012 |
|
|
|
15413016 |
|
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|
61443587 |
Feb 16, 2011 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 1/06 20130101; H04B
7/12 20130101; H04W 52/325 20130101; H04W 74/0816 20130101; H04W
52/04 20130101; H04L 1/0027 20130101; H04L 1/0002 20130101; H04W
16/14 20130101; H04L 1/0009 20130101; H04W 52/367 20130101 |
International
Class: |
H04W 52/32 20060101
H04W052/32; H04W 16/14 20060101 H04W016/14; H04W 74/08 20060101
H04W074/08 |
Claims
1-17. (canceled)
18. A first apparatus for wireless communications, comprising: a
receiver configured to receive from a second apparatus a packet
that cannot be decoded by the first apparatus; a processing system
configured to determine at least one of a time or a duration
corresponding to the packet; and a transmitter configured to
transmit a query with an indication of the at least one of the time
or the duration, wherein the receiver is configured to receive a
message from the second apparatus in response to the query, the
message identifying the second apparatus as a source of the
packet.
19. The first apparatus of claim 18, wherein the transmitter is
configured to transmit a sequence of request-to-send (RTS) messages
at different transmit power levels to the second apparatus and
wherein the processing system is configured to determine if a
clear-to-send (CTS) message was received in response to at least
one of the RTS messages corresponding to a particular one of the
transmit power levels.
20. The first apparatus of claim 19, wherein the transmit power
levels are increasing in the sequence of RTS messages.
21. The first apparatus of claim 19, wherein the particular one of
the transmit power levels comprises a minimum transmit power level
for transmitting one of the RTS messages to the second apparatus
and receiving the CTS message in response.
22. The first apparatus of claim 19, wherein the transmitter is
configured to transmit at least one of data, a subsequent RTS
message, or a subsequent CTS message to the second apparatus based
on the particular one of the transmit power levels.
23. The first apparatus of claim 18, wherein the transmitter is
configured to transmit the query via one or more channels in a
television white space (TVWS).
24. The first apparatus of claim 18, wherein the transmitter is
configured to transmit to the second apparatus a request and
wherein the receiver is configured to receive a response from the
second apparatus indicating a link margin based on the request.
25. The first apparatus of claim 24, wherein the transmitter is
configured to transmit data to the second apparatus based on the
link margin.
26. The first apparatus of claim 18, wherein the message indicates
a power used by the second apparatus to transmit the message.
27. A method for wireless communications, comprising: at a first
apparatus, receiving from a second apparatus a packet that cannot
be decoded by the first apparatus; determining at least one of a
time or a duration corresponding to the packet; transmitting a
query with an indication of the at least one of the time or the
duration; and receiving a message from the second apparatus in
response to the query, the message identifying the second apparatus
as a source of the packet.
28. The method of claim 27, further comprising determining if a
clear-to-send (CTS) message was received, wherein the transmitting
comprises transmitting a sequence of request-to-send (RTS) messages
at different transmit power levels to the second apparatus and
wherein determining if the CTS message was received comprises
determining if the CTS message was received in response to at least
one of the RTS messages corresponding to a particular one of the
transmit power levels.
29. The method of claim 28, wherein the transmit power levels are
increasing in the sequence of RTS messages.
30. The method of claim 28, wherein the particular one of the
transmit power levels comprises a minimum transmit power level for
transmitting one of the RTS messages to the second apparatus and
receiving the CTS message in response.
31. The method of claim 28, further comprising transmitting at
least one of data, a subsequent RTS message, or a subsequent CTS
message to the second apparatus based on the particular one of the
transmit power levels.
32. The method of claim 27, wherein transmitting the query
comprises transmitting the query via one or more channels in a
television white space (TVWS).
33. The method of claim 27, further comprising: transmitting to the
second apparatus a request; and receiving a response from the
second apparatus indicating a link margin based on the request.
34. The method of claim 33, further comprising transmitting data to
the second apparatus based on the link margin.
35. The method of claim 33, wherein the message indicates a power
used by the second apparatus to transmit the message.
36. A first apparatus for wireless communications, comprising:
means for receiving from a second apparatus a packet that cannot be
decoded by the first apparatus; means for determining at least one
of a time or a duration corresponding to the packet; and means for
transmitting a query with an indication of the at least one of the
time or the duration, wherein the means for receiving is configured
to receive a message from the second apparatus in response to the
query, the message identifying the second apparatus as a source of
the packet.
37. A computer-program product for wireless communications,
comprising a computer-readable medium comprising instructions
executable to: receive, at a first apparatus from a second
apparatus, a packet that cannot be decoded by the first apparatus;
determine at least one of a time or a duration corresponding to the
packet; transmit a query with an indication of the at least one of
the time or the duration; and receive a message from the second
apparatus in response to the query, the message identifying the
second apparatus as a source of the packet.
38. A wireless node, comprising: at least one antenna; a receiver
configured to receive, from an apparatus via the at least one
antenna, a packet that cannot be decoded by the wireless node; a
processing system configured to determine at least one of a time or
a duration corresponding to the packet; and a transmitter
configured to transmit, via the at least one antenna, a query with
an indication of the at least one of the time or the duration,
wherein the receiver is configured to receive a message from the
apparatus in response to the query, the message identifying the
apparatus as a source of the packet.
39. A first apparatus for wireless communications, comprising: a
transmitter configured to transmit a packet at a particular time
with a certain duration; a receiver configured to receive from a
second apparatus a query with an indication of at least one of a
query time or a query duration for the packet; and a processing
system configured to: store at least one of the particular time or
the certain duration for the packet; and determine that the at
least one of the query time or the query duration substantially
matches the at least one of the stored time or the stored duration,
wherein the transmitter is configured to transmit a message to the
second apparatus in response to the query, the message identifying
the first apparatus as a source of the packet.
40. The first apparatus of claim 39, wherein the receiver is
configured to receive a request-to-send (RTS) message from the
second apparatus and wherein the transmitter is configured to
transmit a clear-to-send (CTS) message in response to the RTS
message.
41. The first apparatus of claim 39, wherein the receiver is
configured to receive the query via one or more channels in a
television white space (TVWS).
42. The first apparatus of claim 39, wherein the receiver is
configured to receive from the second apparatus a request and
wherein the transmitter is configured to transmit a response to the
second apparatus indicating a link margin based on the request.
43. The first apparatus of claim 42, wherein the request comprises
a transmit power control (TPC) request and wherein the response
comprises a TPC response.
44. The first apparatus of claim 39, wherein the message indicates
a power used by the first apparatus to transmit the message.
45. A method for wireless communications, comprising: at a first
apparatus, transmitting a packet at a particular time with a
certain duration; storing at least one of the particular time or
the certain duration for the packet; receiving from a second
apparatus a query with an indication of at least one of a query
time or a query duration for the packet; determining that the at
least one of the query time or the query duration substantially
matches the at least one of the stored time or the stored duration;
and transmitting a message to the second apparatus in response to
the query, the message identifying the first apparatus as a source
of the packet.
46. The method of claim 45, further comprising: receiving a
request-to-send (RTS) message from the second apparatus; and
transmitting a clear-to-send (CTS) message in response to the RTS
message.
47. The method of claim 45, wherein receiving the query comprises
receiving the query via one or more channels in a television white
space (TVWS).
48. The method of claim 45, further comprising: receiving from the
second apparatus a request; and transmitting a response to the
second apparatus indicating a link margin based on the request.
49. The method of claim 48, wherein the request comprises a
transmit power control (TPC) request and wherein the response
comprises a TPC response.
50. The method of claim 45, wherein the message indicates a power
used by the first apparatus to transmit the message.
51. A first apparatus for wireless communications, comprising:
means for transmitting a packet at a particular time with a certain
duration; means for storing at least one of the particular time or
the certain duration for the packet; means for receiving from a
second apparatus a query with an indication of at least one of a
query time or a query duration for the packet; and means for
determining that the at least one of the query time or the query
duration substantially matches the at least one of the stored time
or the stored duration, wherein the means for transmitting is
configured to transmit a message to the second apparatus in
response to the query, the message identifying the first apparatus
as a source of the packet.
52. A computer-program product for wireless communications,
comprising a computer-readable medium comprising instructions
executable to: transmit from a first apparatus a packet at a
particular time with a certain duration; store at least one of the
particular time or the certain duration for the packet; receive
from a second apparatus a query with an indication of at least one
of a query time or a query duration for the packet; determine that
the at least one of the query time or the query duration
substantially matches the at least one of the stored time or the
stored duration; and transmit a message to the second apparatus in
response to the query, the message identifying the first apparatus
as a source of the packet.
53. A wireless node, comprising: at least one antenna; a
transmitter configured to transmit, via the at least one antenna, a
packet at a particular time with a certain duration; a receiver
configured to receive, from an apparatus via the at least one
antenna, a query with an indication of at least one of a query time
or a query duration for the packet; and a processing system
configured to: store at least one of the particular time or the
certain duration for the packet; and determine that the at least
one of the query time or the query duration substantially matches
the at least one of the stored time or the stored duration, wherein
the transmitter is configured to transmit a message to the
apparatus in response to the query, the message identifying the
wireless node as a source of the packet.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 13/397,450 (Atty. Dkt. No. 111024U1), filed Feb. 15, 2012,
which claims benefit of U.S. Provisional Patent Application Ser.
No. 61/443,587 (Atty. Dkt. No. 111024P1), filed Feb. 16, 2011,
which is herein incorporated by reference.
BACKGROUND
[0002] Field of the Invention
[0003] Certain aspects of the present disclosure generally relate
to wireless communications and, more particularly, to managing
transmit power in a television white space (TVWS) network.
[0004] Relevant Background
[0005] Wireless communication networks are widely deployed to
provide various communication services such as voice, video, packet
data, messaging, broadcast, etc. These wireless networks may be
multiple-access networks capable of supporting multiple users by
sharing the available network resources. Examples of such
multiple-access networks include Code Division Multiple Access
(CDMA) networks, Time Division Multiple Access (TDMA) networks,
Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA
(OFDMA) networks, and Single-Carrier FDMA (SC-FDMA) networks.
[0006] In order to address the issue of increasing bandwidth
requirements demanded for wireless communications systems,
different schemes are being developed. One scheme known as
"white-fi" entails expanding Wi-Fi technology with the unused
frequency spectrum in the television (TV) band (i.e., the TV white
space). An Institute of Electrical and Electronics Engineers (IEEE)
802.11af task group has been created to define an amendment to the
IEEE 802.11 standard for using the TV white space (TVWS). The IEEE
802.11 denotes a set of Wireless Local Area Network (WLAN) air
interface standards developed by the IEEE 802.11 committee for
short-range communications (e.g., tens of meters to a few hundred
meters). However, by using the TVWS with frequencies below 1 GHz,
IEEE 802.11af may offer greater propagation distances to be
achieved, in addition to the increased bandwidth offered by the
unused frequencies in the TV spectrum.
SUMMARY
[0007] Certain aspects of the present disclosure generally relate
to managing transmit power in a television white space (TVWS)
network. By managing transmit power as described herein, medium
re-use may be improved in such a network, and unfair usage problems
may be alleviated.
[0008] Certain aspects of the present disclosure provide a first
apparatus for wireless communications. The first apparatus
generally includes a transmitter configured to transmit a sequence
of request-to-send (RTS) messages at different transmit power
levels to a second apparatus and a processing system configured to
determine if a clear-to-send (CTS) message was received in response
to at least one of the RTS messages corresponding to a particular
one of the transmit power levels.
[0009] Certain aspects of the present disclosure provide a method
for wireless communications. The method generally includes
transmitting a sequence of RTS messages at different transmit power
levels to an apparatus and determining if a CTS message was
received in response to at least one of the RTS messages
corresponding to a particular one of the transmit power levels.
[0010] Certain aspects of the present disclosure provide a first
apparatus for wireless communications. The first apparatus
generally includes means for transmitting a sequence of RTS
messages at different transmit power levels to a second apparatus
and means for determining if a CTS message was received in response
to at least one of the RTS messages corresponding to a particular
one of the transmit power levels.
[0011] Certain aspects of the present disclosure provide a
computer-program product for wireless communications. The
computer-program product generally includes a computer-readable
medium having instructions executable to transmit a sequence of RTS
messages at different transmit power levels to an apparatus and to
determine if a CTS message was received in response to at least one
of the RTS messages corresponding to a particular one of the
transmit power levels.
[0012] Certain aspects of the present disclosure provide a wireless
node. The wireless node generally includes at least one antenna; a
transmitter configured to transmit, via the at least one antenna, a
sequence of RTS messages at different transmit power levels to an
apparatus; and a processing system configured to determine if a CTS
message was received in response to at least one of the RTS
messages corresponding to a particular one of the transmit power
levels.
[0013] Certain aspects of the present disclosure provide a first
apparatus for wireless communications. The first apparatus
generally includes a receiver configured to receive from a second
apparatus a packet that cannot be decoded by the first apparatus; a
processing system configured to determine at least one of a time or
a duration corresponding to the packet; and a transmitter
configured to transmit a query with an indication of the at least
one of the time or the duration, wherein the receiver is configured
to receive a message from the second apparatus in response to the
query, the message identifying the second apparatus as a source of
the packet.
[0014] Certain aspects of the present disclosure provide a method
for wireless communications. The method generally includes
receiving, at a first apparatus from a second apparatus, a packet
that cannot be decoded by the first apparatus; determining at least
one of a time or a duration corresponding to the packet;
transmitting a query with an indication of the at least one of the
time or the duration; and receiving a message from the second
apparatus in response to the query, the message identifying the
second apparatus as a source of the packet.
[0015] Certain aspects of the present disclosure provide a first
apparatus for wireless communications. The first apparatus
generally includes means for receiving from a second apparatus a
packet that cannot be decoded by the first apparatus; means for
determining at least one of a time or a duration corresponding to
the packet; and means for transmitting a query with an indication
of the at least one of the time or the duration, wherein the means
for receiving is configured to receive a message from the second
apparatus in response to the query, the message identifying the
second apparatus as a source of the packet.
[0016] Certain aspects of the present disclosure provide a
computer-program product for wireless communications. The
computer-program product generally includes a computer-readable
medium having instructions executable to receive, at a first
apparatus from a second apparatus, a packet that cannot be decoded
by the first apparatus; to determine at least one of a time or a
duration corresponding to the packet; to transmit a query with an
indication of the at least one of the time or the duration; and to
receive a message from the second apparatus in response to the
query, the message identifying the second apparatus as a source of
the packet.
[0017] Certain aspects of the present disclosure provide a wireless
node. The wireless node generally includes at least one antenna; a
receiver configured to receive, from an apparatus via the at least
one antenna, a packet that cannot be decoded by the wireless node;
a processing system configured to determine at least one of a time
or a duration corresponding to the packet; and a transmitter
configured to transmit, via the at least one antenna, a query with
an indication of the at least one of the time or the duration,
wherein the receiver is configured to receive a message from the
apparatus in response to the query, the message identifying the
apparatus as a source of the packet.
[0018] Certain aspects of the present disclosure provide a first
apparatus for wireless communications. The first apparatus
generally includes a transmitter configured to transmit a packet at
a particular time with a certain duration, a receiver configured to
receive from a second apparatus a query with an indication of at
least one of a query time or a query duration for the packet, and a
processing system. The processing system is typically configured to
store at least one of the particular time or the certain duration
for the packet and to determine that the at least one of the query
time or the query duration substantially matches the at least one
of the stored time or the stored duration, wherein the transmitter
is configured to transmit a message to the second apparatus in
response to the query, the message identifying the first apparatus
as a source of the packet.
[0019] Certain aspects of the present disclosure provide a method
for wireless communications. The method generally includes
transmitting, at a first apparatus, a packet at a particular time
with a certain duration; storing at least one of the particular
time or the certain duration for the packet; receiving from a
second apparatus a query with an indication of at least one of a
query time or a query duration for the packet; determining that the
at least one of the query time or the query duration substantially
matches the at least one of the stored time or the stored duration;
and transmitting a message to the second apparatus in response to
the query, the message identifying the first apparatus as a source
of the packet.
[0020] Certain aspects of the present disclosure provide a first
apparatus for wireless communications. The first apparatus
generally includes means for transmitting a packet at a particular
time with a certain duration; means for storing at least one of the
particular time or the certain duration for the packet; means for
receiving from a second apparatus a query with an indication of at
least one of a query time or a query duration for the packet; and
means for determining that the at least one of the query time or
the query duration substantially matches the at least one of the
stored time or the stored duration, wherein the means for
transmitting is configured to transmit a message to the second
apparatus in response to the query, the message identifying the
first apparatus as a source of the packet.
[0021] Certain aspects of the present disclosure provide a
computer-program product for wireless communications. The
computer-program product generally includes a computer-readable
medium having instructions executable to transmit from a first
apparatus a packet at a particular time with a certain duration; to
store at least one of the particular time or the certain duration
for the packet; to receive from a second apparatus a query with an
indication of at least one of a query time or a query duration for
the packet; to determine that the at least one of the query time or
the query duration substantially matches the at least one of the
stored time or the stored duration; and to transmit a message to
the second apparatus in response to the query, the message
identifying the first apparatus as a source of the packet.
[0022] Certain aspects of the present disclosure provide a wireless
node. The wireless node generally includes at least one antenna; a
transmitter configured to transmit, via the at least one antenna, a
packet at a particular time with a certain duration; a receiver
configured to receive, from an apparatus via the at least one
antenna, a query with an indication of at least one of a query time
or a query duration for the packet; and a processing system. The
processing system is typically configured to store at least one of
the particular time or the certain duration for the packet and to
determine that the at least one of the query time or the query
duration substantially matches the at least one of the stored time
or the stored duration, wherein the transmitter is configured to
transmit a message to the apparatus in response to the query, the
message identifying the wireless node as a source of the
packet.
[0023] Certain aspects of the present disclosure provide an
apparatus for wireless communications. The apparatus generally
includes a processing system configured to determine a highest
transmit power for transmitting data frames from the apparatus and
a transmitter configured to transmit a message with an indication
of the highest transmit power.
[0024] Certain aspects of the present disclosure provide a method
for wireless communications. The method generally includes
determining a highest transmit power for transmitting data frames
and transmitting a message with an indication of the highest
transmit power.
[0025] Certain aspects of the present disclosure provide an
apparatus for wireless communications. The apparatus generally
includes means for determining a highest transmit power for
transmitting data frames from the apparatus and means for
transmitting a message with an indication of the highest transmit
power.
[0026] Certain aspects of the present disclosure provide a
computer-program product for wireless communications. The
computer-program product generally includes a computer-readable
medium having instructions executable to determine a highest
transmit power for transmitting data frames from an apparatus and
to transmit a message from the apparatus with an indication of the
highest transmit power.
[0027] Certain aspects of the present disclosure provide an access
point (AP). The AP generally includes at least one antenna, a
processing system configured to determine a highest transmit power
for transmitting data frames from the access point, and a
transmitter configured to transmit, via the at least one antenna, a
message with an indication of the highest transmit power.
[0028] Certain aspects of the present disclosure provide a first
apparatus for wireless communications. The first apparatus
generally includes a receiver configured to receive, from a second
apparatus, a message with an indication of a highest transmit power
used by the second apparatus for transmitting data frames; and a
processing system configured to determine that the second apparatus
is a dominant interferer based, at least in part, on the highest
transmit power.
[0029] Certain aspects of the present disclosure provide a method
for wireless communications. The method generally includes
receiving, from an apparatus, a message with an indication of a
highest transmit power used by the apparatus for transmitting data
frames; and determining that the apparatus is a dominant interferer
based, at least in part, on the highest transmit power.
[0030] Certain aspects of the present disclosure provide a first
apparatus for wireless communications. The first apparatus
generally includes means for receiving, from a second apparatus, a
message with an indication of a highest transmit power used by the
second apparatus for transmitting data frames; and means for
determining that the second apparatus is a dominant interferer
based, at least in part, on the highest transmit power.
[0031] Certain aspects of the present disclosure provide a
computer-program product for wireless communications. The
computer-program product generally includes a computer-readable
medium having instructions executable to receive, from an
apparatus, a message with an indication of a highest transmit power
used by the apparatus for transmitting data frames; and to
determine that the apparatus is a dominant interferer based, at
least in part, on the highest transmit power.
[0032] Certain aspects of the present disclosure provide a wireless
node. The wireless node generally includes at least one antenna; a
receiver configured to receive, from an apparatus via the at least
one antenna, a message with an indication of a highest transmit
power used by the apparatus for transmitting data frames; and a
processing system configured to determine that the apparatus is a
dominant interferer based, at least in part, on the highest
transmit power.
[0033] Certain aspects of the present disclosure provide an
apparatus for wireless communications. The apparatus generally
includes a processing system configured to determine a first
transmit power for transmitting data frames from the apparatus and
a transmitter configured to transmit a control or management
message at a second transmit power, wherein the control or
management message comprises a first indication of the first
transmit power and a second indication of the second transmit
power.
[0034] Certain aspects of the present disclosure provide a method
for wireless communications. The method generally includes
determining a first transmit power for transmitting data frames and
transmitting a control or management message at a second transmit
power, wherein the control or management message comprises a first
indication of the first transmit power and a second indication of
the second transmit power.
[0035] Certain aspects of the present disclosure provide an
apparatus for wireless communications. The apparatus generally
includes means for determining a first transmit power for
transmitting data frames from the apparatus and means for
transmitting a control or management message at a second transmit
power, wherein the control or management message comprises a first
indication of the first transmit power and a second indication of
the second transmit power.
[0036] Certain aspects of the present disclosure provide a
computer-program product for wireless communications. The
computer-program product generally includes a computer-readable
medium having instructions executable to determine a first transmit
power for transmitting data frames from an apparatus and to
transmit a control or management message at a second transmit
power, wherein the control or management message comprises a first
indication of the first transmit power and a second indication of
the second transmit power.
[0037] Certain aspects of the present disclosure provide a wireless
node. The wireless node generally includes at least one antenna; a
processing system configured to determine a first transmit power
for transmitting data frames from the wireless node; and a
transmitter configured to transmit, via the at least one antenna, a
control or management message at a second transmit power, wherein
the control or management message comprises a first indication of
the first transmit power and a second indication of the second
transmit power.
[0038] Certain aspects of the present disclosure provide a first
apparatus for wireless communications. The first apparatus
generally includes a receiver configured to receive, from a second
apparatus, a control or management message with a first indication
of a first transmit power used by the second apparatus for
transmitting data frames; and a processing system configured to
determine that the second apparatus is a dominant interferer based,
at least in part, on the first transmit power.
[0039] Certain aspects of the present disclosure provide a method
for wireless communications. The method generally includes
receiving, from an apparatus, a control or management message with
a first indication of a first transmit power used by the apparatus
for transmitting data frames and determining that the apparatus is
a dominant interferer based, at least in part, on the first
transmit power.
[0040] Certain aspects of the present disclosure provide a first
apparatus for wireless communications. The first apparatus
generally includes means for receiving, from a second apparatus, a
control or management message with a first indication of a first
transmit power used by the second apparatus for transmitting data
frames; and means for determining that the second apparatus is a
dominant interferer based, at least in part, on the first transmit
power.
[0041] Certain aspects of the present disclosure provide a
computer-program product for wireless communications. The
computer-program product generally includes a computer-readable
medium having instructions executable to receive, from an
apparatus, a control or management message with a first indication
of a first transmit power used by the apparatus for transmitting
data frames; and to determine that the apparatus is a dominant
interferer based, at least in part, on the first transmit
power.
[0042] Certain aspects of the present disclosure provide a wireless
node. The wireless node generally includes at least one antenna; a
receiver configured to receive, from an apparatus via the at least
one antenna, a control or management message with a first
indication of a first transmit power used by the apparatus for
transmitting data frames; and a processing system configured to
determine that the apparatus is a dominant interferer based, at
least in part, on the first transmit power.
[0043] Certain aspects of the present disclosure provide an
apparatus for wireless communications. The apparatus generally
includes a processing system configured to determine a modulation
and coding scheme (MCS) for transmitting data frames from the
apparatus and a transmitter configured to transmit a request
message comprising an indication of the MCS.
[0044] Certain aspects of the present disclosure provide a method
for wireless communications. The method generally includes
determining a modulation and coding scheme (MCS) for transmitting
data frames and transmitting a request message comprising an
indication of the MCS.
[0045] Certain aspects of the present disclosure provide an
apparatus for wireless communications. The apparatus generally
includes means for determining a modulation and coding scheme (MCS)
for transmitting data frames from the apparatus and means for
transmitting a request message comprising an indication of the
MCS.
[0046] Certain aspects of the present disclosure provide a
computer-program product for wireless communications. The
computer-program product generally includes a computer-readable
medium having instructions executable to determine a modulation and
coding scheme (MCS) for transmitting data frames from an apparatus;
and to transmit a request message comprising an indication of the
MCS.
[0047] Certain aspects of the present disclosure provide a wireless
node. The wireless node generally includes at least one antenna; a
processing system configured to determine a modulation and coding
scheme (MCS) for transmitting data frames from the wireless node;
and a transmitter configured to transmit, via the at least one
antenna, a request message comprising an indication of the MCS.
[0048] Certain aspects of the present disclosure provide an
apparatus for wireless communications. The apparatus generally
includes a receiver configured to receive a request message
comprising an indication of a modulation and coding scheme (MCS)
for transmitting data frames to be received; a processing system
configured to determine a link margin based on the MCS; and a
transmitter configured to transmit a response message with an
indication of the link margin.
[0049] Certain aspects of the present disclosure provide a method
for wireless communications. The method generally includes
receiving a request message comprising an indication of a
modulation and coding scheme (MCS) for transmitting data frames to
be received; determining a link margin based on the MCS; and
transmitting a response message with an indication of the link
margin.
[0050] Certain aspects of the present disclosure provide an
apparatus for wireless communications. The apparatus generally
includes means for receiving a request message comprising an
indication of a modulation and coding scheme (MCS) for transmitting
data frames to be received; means for determining a link margin
based on the MCS; and means for transmitting a response message
with an indication of the link margin.
[0051] Certain aspects of the present disclosure provide a
computer-program product for wireless communications. The
computer-program product generally includes a computer-readable
medium having instructions executable to receive a request message
comprising an indication of a modulation and coding scheme (MCS)
for transmitting data frames to be received, to determine a link
margin based on the MCS, and to transmit a response message with an
indication of the link margin.
[0052] Certain aspects of the present disclosure provide a wireless
node. The wireless node generally includes at least one antenna; a
receiver configured to receive, via the at least one antenna, a
request message comprising an indication of a modulation and coding
scheme (MCS) for transmitting data frames to be received; a
processing system configured to determine a link margin based on
the MCS; and a transmitter configured to transmit, via the at least
one antenna, a response message with an indication of the link
margin.
BRIEF DESCRIPTION OF THE DRAWINGS
[0053] So that the manner in which the above-recited features of
the present disclosure can be understood in detail, a more
particular description, briefly summarized above, may be had by
reference to aspects, some of which are illustrated in the appended
drawings. It is to be noted, however, that the appended drawings
illustrate only certain typical aspects of this disclosure and are
therefore not to be considered limiting of its scope, for the
description may admit to other equally effective aspects.
[0054] FIG. 1 illustrates a diagram of a wireless communications
network in accordance with certain aspects of the present
disclosure.
[0055] FIG. 2 illustrates a block diagram of an example access
point and user terminals in accordance with certain aspects of the
present disclosure.
[0056] FIG. 3 illustrates a block diagram of an example wireless
device in accordance with certain aspects of the present
disclosure.
[0057] FIG. 4 illustrates a table of device modes for television
white space (TVWS) as defined by the Federal Communications
Commission (FCC), in accordance with certain aspects of the present
disclosure.
[0058] FIG. 5 illustrates different ranges at which a fixed device
may be detected and may detect portable devices, in accordance with
certain aspects of the present disclosure.
[0059] FIG. 6 illustrates a transmit power control (TPC) report
element in accordance with certain aspects of the present
disclosure.
[0060] FIG. 7 illustrates example operations to determine, from the
perspective of a portable device, interfering fixed devices using a
sequence of messages sent at different transmit power levels, in
accordance with certain aspects of the present disclosure.
[0061] FIG. 7A illustrates example components for performing the
operations shown in FIG. 7.
[0062] FIG. 8 illustrates an example hidden node problem in
accordance with certain aspects of the present disclosure.
[0063] FIG. 9 illustrates an example exposed node problem in
accordance with certain aspects of the present disclosure.
[0064] FIG. 10 illustrates a node causing interference and deferral
to a neighboring node in accordance with certain aspects of the
present disclosure.
[0065] FIG. 11 illustrates using a start time of a packet to force
identification of an unknown node, in accordance with certain
aspects of the present disclosure.
[0066] FIG. 12 illustrates example operations to learn, from the
perspective of a wireless node, the transmit power used by an
unknown neighboring node, in accordance with certain aspects of the
present disclosure.
[0067] FIG. 12A illustrates example components for performing the
operations shown in FIG. 12.
[0068] FIG. 13 illustrates example operations to provide, from the
perspective of a wireless node unknown to a neighboring node, the
transmit power used by the wireless node, in accordance with
certain aspects of the present disclosure.
[0069] FIG. 13A illustrates example components for performing the
operations shown in FIG. 13.
[0070] FIG. 14A illustrates a TPC request element and a TPC report
element, in accordance with certain aspects of the present
disclosure.
[0071] FIG. 14B illustrates a TPC request element with a modulation
and coding scheme (MCS) field and a TPC report element, in
accordance with certain aspects of the present disclosure.
[0072] FIG. 15 illustrates example operations to utilize, from the
perspective of a transmitter, a TPC request message with a desired
MCS, in accordance with certain aspects of the present
disclosure.
[0073] FIG. 15A illustrates example components for performing the
operations shown in FIG. 15.
[0074] FIG. 16 illustrates example operations to utilize, from the
perspective of a receiver, a TPC request message with a desired
MCS, in accordance with certain aspects of the present
disclosure.
[0075] FIG. 16A illustrates example components for performing the
operations shown in FIG. 16.
[0076] FIG. 17 illustrates an example station (STA) surrounded by
interfering STAs, in accordance with certain aspects of the present
disclosure.
[0077] FIG. 18 illustrates an example beacon information element
(IE) for indicating the transmit power of data frames transmitted
from an access point (AP), in accordance with certain aspects of
the present disclosure.
[0078] FIG. 19 illustrates example operations to transmit, from the
perspective of an AP, a broadcast message with an indication of the
highest transmit power for transmitting data frames, in accordance
with certain aspects of the present disclosure.
[0079] FIG. 19A illustrates example components for performing the
operations shown in FIG. 19.
[0080] FIG. 20 illustrates example operations to determine, from
the perspective of a STA, dominant interferers based on a received
broadcast message with an indication of a highest transmit power
for transmitting data frames, in accordance with certain aspects of
the present disclosure.
[0081] FIG. 20A illustrates example components for performing the
operations shown in FIG. 20.
[0082] FIG. 21 illustrates an example control or management frame
format with an IE for indicating the transmit power of data frames
transmitted from a STA and another IE for indicating the transmit
power used for transmitting the control or management frame, in
accordance with certain aspects of the present disclosure.
[0083] FIG. 22 illustrates example operations to transmit, from the
perspective of a STA, a control or management message with an
indication of a transmit power for transmitting data frames and
another indication of a transmit power used when transmitting the
control or management message, in accordance with certain aspects
of the present disclosure.
[0084] FIG. 22A illustrates example components for performing the
operations shown in FIG. 22.
[0085] FIG. 23 illustrates example operations to determine, from
the perspective of a STA, dominant interferers based on a received
control or management message with an indication of a transmit
power for transmitting data frames and another indication of a
transmit power used when transmitting the control or management
message, in accordance with certain aspects of the present
disclosure.
[0086] FIG. 23A illustrates example components for performing the
operations shown in FIG. 23.
DETAILED DESCRIPTION
[0087] Various aspects of the disclosure are described more fully
hereinafter with reference to the accompanying drawings. This
disclosure may, however, be embodied in many different forms and
should not be construed as limited to any specific structure or
function presented throughout this disclosure. Rather, these
aspects are provided so that this disclosure will be thorough and
complete, and will fully convey the scope of the disclosure to
those skilled in the art. Based on the teachings herein one skilled
in the art should appreciate that the scope of the disclosure is
intended to cover any aspect of the disclosure disclosed herein,
whether implemented independently of or combined with any other
aspect of the disclosure. For example, an apparatus may be
implemented or a method may be practiced using any number of the
aspects set forth herein. In addition, the scope of the disclosure
is intended to cover such an apparatus or method which is practiced
using other structure, functionality, or structure and
functionality in addition to or other than the various aspects of
the disclosure set forth herein. It should be understood that any
aspect of the disclosure disclosed herein may be embodied by one or
more elements of a claim.
[0088] The word "exemplary" is used herein to mean "serving as an
example, instance, or illustration." Any aspect described herein as
"exemplary" is not necessarily to be construed as preferred or
advantageous over other aspects.
[0089] Although particular aspects are described herein, many
variations and permutations of these aspects fall within the scope
of the disclosure. Although some benefits and advantages of the
preferred aspects are mentioned, the scope of the disclosure is not
intended to be limited to particular benefits, uses, or objectives.
Rather, aspects of the disclosure are intended to be broadly
applicable to different wireless technologies, system
configurations, networks, and transmission protocols, some of which
are illustrated by way of example in the figures and in the
following description of the preferred aspects. The detailed
description and drawings are merely illustrative of the disclosure
rather than limiting, the scope of the disclosure being defined by
the appended claims and equivalents thereof.
An Example Wireless Communication System
[0090] The techniques described herein may be used for various
broadband wireless communication systems, including communication
systems that are based on an orthogonal multiplexing scheme.
Examples of such communication systems include Spatial Division
Multiple Access (SDMA), Time Division Multiple Access (TDMA),
Orthogonal Frequency Division Multiple Access (OFDMA) systems,
Single-Carrier Frequency Division Multiple Access (SC-FDMA)
systems, and so forth. An SDMA system may utilize sufficiently
different directions to simultaneously transmit data belonging to
multiple user terminals. A TDMA system may allow multiple user
terminals to share the same frequency channel by dividing the
transmission signal into different time slots, each time slot being
assigned to a different user terminal. An OFDMA system utilizes
orthogonal frequency division multiplexing (OFDM), which is a
modulation technique that partitions the overall system bandwidth
into multiple orthogonal sub-carriers. These sub-carriers may also
be called tones, bins, etc. With OFDM, each sub-carrier may be
independently modulated with data. An SC-FDMA system may utilize
interleaved FDMA (IFDMA) to transmit on sub-carriers that are
distributed across the system bandwidth, localized FDMA (LFDMA) to
transmit on a block of adjacent sub-carriers, or enhanced FDMA
(EFDMA) to transmit on multiple blocks of adjacent sub-carriers. In
general, modulation symbols are sent in the frequency domain with
OFDM and in the time domain with SC-FDMA.
[0091] The teachings herein may be incorporated into (e.g.,
implemented within or performed by) a variety of wired or wireless
apparatuses (e.g., nodes). In some aspects, a wireless node
implemented in accordance with the teachings herein may comprise an
access point or an access terminal.
[0092] An access point ("AP") may comprise, be implemented as, or
known as a Node B, Radio Network Controller ("RNC"), evolved Node B
(eNB), Base Station Controller ("BSC"), Base Transceiver Station
("BTS"), Base Station ("BS"), Transceiver Function ("TF"), Radio
Router, Radio Transceiver, Basic Service Set ("BSS"), Extended
Service Set ("ESS"), Radio Base Station ("RBS"), or some other
terminology.
[0093] An access terminal ("AT") may comprise, be implemented as,
or known as a subscriber station, a subscriber unit, a mobile
station ("MS"), a remote station, a remote terminal, a user
terminal ("UT"), a user agent, a user device, user equipment
("UE"), a user station, or some other terminology. In some
implementations, an access terminal may comprise a cellular
telephone, a cordless telephone, a Session Initiation Protocol
("SIP") phone, a wireless local loop ("WLL") station, a personal
digital assistant ("PDA"), a handheld device having wireless
connection capability, a Station ("STA"), or some other suitable
processing device connected to a wireless modem. Accordingly, one
or more aspects taught herein may be incorporated into a phone
(e.g., a cellular phone or smart phone), a computer (e.g., a
laptop), a tablet, a portable communication device, a portable
computing device (e.g., a personal data assistant), an
entertainment device (e.g., a music or video device, or a satellite
radio), a global positioning system (GPS) device, or any other
suitable device that is configured to communicate via a wireless or
wired medium. In some aspects, the node is a wireless node. Such
wireless node may provide, for example, connectivity for or to a
network (e.g., a wide area network such as the Internet or a
cellular network) via a wired or wireless communication link.
[0094] FIG. 1 illustrates a multiple-access multiple-input
multiple-output (MIMO) system 100 with access points and user
terminals. For simplicity, only one access point 110 is shown in
FIG. 1. An access point is generally a fixed station that
communicates with the user terminals and may also be referred to as
a base station or some other terminology. A user terminal may be
fixed or mobile and may also be referred to as a mobile station, a
wireless device, or some other terminology. Access point 110 may
communicate with one or more user terminals 120 at any given moment
on the downlink and uplink. The downlink (i.e., forward link) is
the communication link from the access point to the user terminals,
and the uplink (i.e., reverse link) is the communication link from
the user terminals to the access point. A user terminal may also
communicate peer-to-peer with another user terminal. A system
controller 130 couples to and provides coordination and control for
the access points.
[0095] While portions of the following disclosure will describe
user terminals 120 capable of communicating via Spatial Division
Multiple Access (SDMA), for certain aspects, the user terminals 120
may also include some user terminals that do not support SDMA.
Thus, for such aspects, an AP 110 may be configured to communicate
with both SDMA and non-SDMA user terminals. This approach may
conveniently allow older versions of user terminals ("legacy"
stations) to remain deployed in an enterprise, extending their
useful lifetime, while allowing newer SDMA user terminals to be
introduced as deemed appropriate.
[0096] The system 100 employs multiple transmit and multiple
receive antennas for data transmission on the downlink and uplink.
The access point 110 is equipped with N.sub.ap antennas and
represents the multiple-input (MI) for downlink transmissions and
the multiple-output (MO) for uplink transmissions. A set of K
selected user terminals 120 collectively represents the
multiple-output for downlink transmissions and the multiple-input
for uplink transmissions. For pure SDMA, it is desired to have
N.sub.ap.gtoreq.K.gtoreq.1 if the data symbol streams for the K
user terminals are not multiplexed in code, frequency or time by
some means. K may be greater than N.sub.ap if the data symbol
streams can be multiplexed using TDMA technique, different code
channels with CDMA, disjoint sets of subbands with OFDM, and so on.
Each selected user terminal transmits user-specific data to and/or
receives user-specific data from the access point. In general, each
selected user terminal may be equipped with one or multiple
antennas (i.e., N.sub.ut.gtoreq.1). The K selected user terminals
can have the same or different number of antennas.
[0097] The MIMO system 100 may be a time division duplex (TDD)
system or a frequency division duplex (FDD) system. For a TDD
system, the downlink and uplink share the same frequency band. For
an FDD system, the downlink and uplink use different frequency
bands. MIMO system 100 may also utilize a single carrier or
multiple carriers for transmission. Each user terminal may be
equipped with a single antenna (e.g., in order to keep costs down)
or multiple antennas (e.g., where the additional cost can be
supported). The system 100 may also be a TDMA system if the user
terminals 120 share the same frequency channel by dividing
transmission/reception into different time slots, each time slot
being assigned to different user terminal 120.
[0098] FIG. 2 illustrates a block diagram of access point 110 and
two user terminals 120m and 120x in MIMO system 100. The access
point 110 is equipped with N.sub.t antennas 224a through 224t. User
terminal 120m is equipped with N.sub.ut,m antennas 252ma through
252mu, and user terminal 120x is equipped with N.sub.ut,x antennas
252xa through 252xu. The access point 110 is a transmitting entity
for the downlink and a receiving entity for the uplink. Each user
terminal 120 is a transmitting entity for the uplink and a
receiving entity for the downlink. As used herein, a "transmitting
entity" is an independently operated apparatus or device capable of
transmitting data via a wireless channel, and a "receiving entity"
is an independently operated apparatus or device capable of
receiving data via a wireless channel. In the following
description, the subscript "dn" denotes the downlink, the subscript
"up" denotes the uplink, N.sub.up user terminals are selected for
simultaneous transmission on the uplink, N.sub.dn user terminals
are selected for simultaneous transmission on the downlink,
N.sub.up may or may not be equal to N.sub.dn, and N.sub.up and
N.sub.dn may be static values or can change for each scheduling
interval. The beam-steering or some other spatial processing
technique may be used at the access point and user terminal.
[0099] On the uplink, at each user terminal 120 selected for uplink
transmission, a TX data processor 288 receives traffic data from a
data source 286 and control data from a controller 280. TX data
processor 288 processes (e.g., encodes, interleaves, and modulates)
the traffic data for the user terminal based on the coding and
modulation schemes associated with the rate selected for the user
terminal and provides a data symbol stream. A TX spatial processor
290 performs spatial processing on the data symbol stream and
provides N.sub.ut,m transmit symbol streams for the N.sub.ut,m
antennas. Each transmitter unit (TMTR) 254 receives and processes
(e.g., converts to analog, amplifies, filters, and frequency
upconverts) a respective transmit symbol stream to generate an
uplink signal. N.sub.ut,m transmitter units 254 provide N.sub.ut,m
uplink signals for transmission from N.sub.ut,m antennas 252 to the
access point.
[0100] N.sub.up user terminals may be scheduled for simultaneous
transmission on the uplink. Each of these user terminals performs
spatial processing on its data symbol stream and transmits its set
of transmit symbol streams on the uplink to the access point.
[0101] At access point 110, N.sub.ap antennas 224a through 224ap
receive the uplink signals from all N.sub.up user terminals
transmitting on the uplink. Each antenna 224 provides a received
signal to a respective receiver unit (RCVR) 222. Each receiver unit
222 performs processing complementary to that performed by
transmitter unit 254 and provides a received symbol stream. An RX
spatial processor 240 performs receiver spatial processing on the
N.sub.ap received symbol streams from N.sub.ap receiver units 222
and provides N.sub.up recovered uplink data symbol streams. The
receiver spatial processing is performed in accordance with the
channel correlation matrix inversion (CCMI), minimum mean square
error (MMSE), soft interference cancellation (SIC), or some other
technique. Each recovered uplink data symbol stream is an estimate
of a data symbol stream transmitted by a respective user terminal.
An RX data processor 242 processes (e.g., demodulates,
deinterleaves, and decodes) each recovered uplink data symbol
stream in accordance with the rate used for that stream to obtain
decoded data. The decoded data for each user terminal may be
provided to a data sink 244 for storage and/or a controller 230 for
further processing.
[0102] On the downlink, at access point 110, a TX data processor
210 receives traffic data from a data source 208 for N.sub.dn user
terminals scheduled for downlink transmission, control data from a
controller 230, and possibly other data from a scheduler 234. The
various types of data may be sent on different transport channels.
TX data processor 210 processes (e.g., encodes, interleaves, and
modulates) the traffic data for each user terminal based on the
rate selected for that user terminal. TX data processor 210
provides N.sub.dn downlink data symbol streams for the N.sub.dn
user terminals. A TX spatial processor 220 performs spatial
processing (such as a precoding or beamforming, as described in the
present disclosure) on the N.sub.dn downlink data symbol streams,
and provides N.sub.ap transmit symbol streams for the N.sub.ap
antennas. Each transmitter unit 222 receives and processes a
respective transmit symbol stream to generate a downlink signal.
N.sub.ap transmitter units 222 providing N.sub.ap downlink signals
for transmission from N.sub.ap antennas 224 to the user
terminals.
[0103] At each user terminal 120, N.sub.ut,m antennas 252 receive
the N.sub.ap downlink signals from access point 110. Each receiver
unit 254 processes a received signal from an associated antenna 252
and provides a received symbol stream. An RX spatial processor 260
performs receiver spatial processing on N.sub.ut,m received symbol
streams from N.sub.ut,m receiver units 254 and provides a recovered
downlink data symbol stream for the user terminal. The receiver
spatial processing is performed in accordance with the CCMI, MMSE
or some other technique. An RX data processor 270 processes (e.g.,
demodulates, deinterleaves and decodes) the recovered downlink data
symbol stream to obtain decoded data for the user terminal.
[0104] At each user terminal 120, a channel estimator 278 estimates
the downlink channel response and provides downlink channel
estimates, which may include channel gain estimates, SNR estimates,
noise variance and so on. Similarly, a channel estimator 228
estimates the uplink channel response and provides uplink channel
estimates. Controller 280 for each user terminal typically derives
the spatial filter matrix for the user terminal based on the
downlink channel response matrix H.sub.dn,m for that user terminal.
Controller 230 derives the spatial filter matrix for the access
point based on the effective uplink channel response matrix
H.sub.up,eff. Controller 280 for each user terminal may send
feedback information (e.g., the downlink and/or uplink
eigenvectors, eigenvalues, SNR estimates, and so on) to the access
point. Controllers 230 and 280 also control the operation of
various processing units at access point 110 and user terminal 120,
respectively.
[0105] FIG. 3 illustrates various components that may be utilized
in a wireless device 302 that may be employed within the MIMO
system 100. The wireless device 302 is an example of a device that
may be configured to implement the various methods described
herein. The wireless device 302 may be an access point 110 or a
user terminal 120.
[0106] The wireless device 302 may include a processor 304 which
controls operation of the wireless device 302. The processor 304
may also be referred to as a central processing unit (CPU). Memory
306, which may include both read-only memory (ROM) and random
access memory (RAM), provides instructions and data to the
processor 304. A portion of the memory 306 may also include
non-volatile random access memory (NVRAM). The processor 304
typically performs logical and arithmetic operations based on
program instructions stored within the memory 306. The instructions
in the memory 306 may be executable to implement the methods
described herein.
[0107] The wireless device 302 may also include a housing 308 that
may include a transmitter 310 and a receiver 312 to allow
transmission and reception of data between the wireless device 302
and a remote location. The transmitter 310 and receiver 312 may be
combined into a transceiver 314. A single or a plurality of
transmit antennas 316 may be attached to the housing 308 and
electrically coupled to the transceiver 314. The wireless device
302 may also include (not shown) multiple transmitters, multiple
receivers, and multiple transceivers.
[0108] The wireless device 302 may also include a signal detector
318 that may be used in an effort to detect and quantify the level
of signals received by the transceiver 314. The signal detector 318
may detect such signals as total energy, energy per subcarrier per
symbol, power spectral density and other signals. The wireless
device 302 may also include a digital signal processor (DSP) 320
for use in processing signals.
[0109] The various components of the wireless device 302 may be
coupled together by a bus system 322, which may include a power
bus, a control signal bus, and a status signal bus in addition to a
data bus.
CSMA Operation in TVWS
[0110] As described above, IEEE 802.11af is an extension of the
IEEE 802.11 standard into the TV white space. As used herein, the
term "white space" generally refers to unused frequencies in the
electromagnetic spectrum, and the term "TV white space" generally
refers to the unused frequency spectrum in the TV band (e.g., the
radio frequencies historically allocated for analog television, but
now available due to the conversion to digital television). No
physical (PHY)/MAC (media access control) layer changes are being
considered in this extension. Several frame formats are added for
the enablement procedure.
[0111] FIG. 4 illustrates a table 400 of device modes for
television white space (TVWS) as defined by the Federal
Communications Commission (FCC). TVWS devices include fixed
devices, which may most likely be installed by a professional and
have the locations of the individual devices entered into a
database. The maximum transmit power for fixed devices is 36 dBm.
Mobile/portable TVWS devices include Mode 1 and Mode 2 devices,
whose locations are not registered. The maximum transmit power for
portable devices is 20 dBm. Fixed and Mode 2 devices are termed
enabling stations (STAs), while a device in a Mode 1 operational
state is termed a dependent STA. Although transmit power control is
not required in the IEEE 802.11 standard, the FCC recommends (or
may even mandate) using transmit power control in the TVWS.
[0112] Once devices are enabled, the devices are expected to use
Carrier Sense Multiple Access (CSMA) MAC for communication.
However, a number of problems are expected when using CSMA in the
TVWS. For example, larger propagation range available with TVWS
increases the likelihood of hidden nodes and increases the number
of contending nodes. CSMA performance is sensitive to the presence
of hidden nodes and the number of contending nodes. Another problem
is diversity in transmit powers due to fixed and portable devices
using different transmit powers and to the utilization of transmit
power control. Such diversity causes asymmetry in the coverage
areas of different transmitters, leading not only to the increased
possibility of hidden or exposed nodes, but also to increased
collisions and unfair access.
[0113] Accordingly, what is needed are techniques and apparatus for
improved CSMA operation between fixed and portable devices in an
effort to at least alleviate, if not completely solve, these
problems.
Transmit Power Management in TVWS
[0114] The difference in transmit power between fixed and portable
devices is substantial. The range of fixed devices is larger than
that of portable devices. For example, there is a 10 dBm link
budget difference between the range at which a portable device
hears a fixed device and the range at which a fixed device hears a
portable device.
[0115] FIG. 5 illustrates a fixed TVWS device 500, such as an
access point (AP) 110. The inner circle 502 represents a range at
which the fixed device 500 can detect portable devices, whereas the
outer circle 504 represents the range at which the fixed device 500
can be detected. The radius of the inner circle 502 is
approximately half the radius of the outer circle 504. The area
between the inner circle 502 and the outer circle 504 represents a
region 506 where the fixed device 500 does not defer to portable
devices.
[0116] To allow for co-existence of fixed and portable devices,
portable devices may most likely use a channel that has a
neighboring fixed device only if the fixed device is sufficiently
close to hear the portable device. To determine interfering fixed
devices, a report element the same as, or at least similar to, a
transmit power control (TPC) report element in IEEE 802.11 may be
used.
[0117] FIG. 6 illustrates a TPC report element 600, in accordance
with certain aspects of the present disclosure. The TPC report
element 600 may comprise an element identification (ID) field 602,
a length field 604, a transmit power field 606, and a link margin
field 608. Each of these fields 602-608 may have a length of one
octet (8 bits).
[0118] For certain aspects, portable devices may implement a
two-step procedure to determine interfering fixed devices. First, a
portable device may identify high transmit power fixed devices by
monitoring the TPC element in the beacons received. Next, the
portable device may send a probe request with a wild card service
set identifier (SSID) and a TPC request. This request may be sent
at the lowest PHY rate. Response TPC elements from fixed devices
may most likely contain the link margin based on the TPC request.
As used herein, the "link margin" generally refers to the
difference between a wireless receiver's sensitivity and the actual
received power, typically measured in decibels (dB). The portable
device may use the link margin to determine transmit power to
ensure that transmissions from the portable devices are "heard" at
fixed devices. If several fixed devices do not respond to the TPC
request, the portable device may assume that the portable device
itself is "hidden" from such fixed devices and may move to another
channel. This two-step procedure may entail a standards change to
ensure that a TPC response to TPC requests with a wild card SSID is
mandatory.
[0119] For certain aspects, an alternate procedure may be used to
determine interfering fixed devices, which need not entail a
standards change. In this alternate procedure, a sequence of
request-to-send (RTS) messages may be sent at increasing powers to
each of the identified high transmit power fixed devices, and the
minimum power level involved for a clear-to-send (CTS) response may
be determined. If several fixed devices do not respond to the RTS
messages, even at the highest power, the portable device may most
likely assume that the device itself is "hidden" from such fixed
devices and move to another channel.
[0120] Because fixed devices may typically be designed to register
their location and utilized channel, a database may aid in the
discovery of fixed devices. Portable devices may most likely be
capable of querying for the fixed devices in the vicinity of the
portable devices. For example, a portable device may be able to
obtain a list of fixed devices in a 200 m radius from the portable
device's location. A response from the database may include the
locations, operating channels, and transmit power levels of the
fixed devices.
[0121] FIG. 7 illustrates example operations 700 to determine, from
the perspective of a portable device, for example, interfering
fixed devices using a sequence of messages sent at different
transmit power levels, in accordance with certain aspects of the
present disclosure. The operations may begin, at 702, with the
portable device transmitting a sequence of request-to-send (RTS)
messages at different power levels to an apparatus, such as a fixed
TVWS device. For certain aspects, the sequence of RTS messages may
comprise RTS messages transmitted with increasing power. The
portable device may transmit the sequence of RTS messages via one
or more channels in the TVWS.
[0122] At 704, the portable device may determine if a clear-to-send
(CTS) message was received in response to at least one of the RTS
messages corresponding to a particular one of the transmit power
levels. For certain aspects, the portable device may transmit at
least one of data, a subsequent RTS message, or a subsequent CTS
message at 706 to the apparatus, based on the particular one of the
transmit power levels. For certain aspects, the particular one of
the transmit power levels is a minimum transmit power level for
transmitting one of the RTS messages to the apparatus and for
receiving the CTS message in response.
[0123] According to certain aspects, the portable device may
identify the apparatus. The apparatus may identify the apparatus by
sending a query about any fixed apparatuses nearby (i.e., in a
vicinity of the portable device) and receiving a response to the
query. The response may include at least one of a location of the
fixed apparatus, an operating channel for the fixed apparatus, or a
transmit power level of the fixed apparatus.
[0124] For certain aspects, the portable device may transmit the
sequence of RTS messages using a first channel. If the CTS message
is not received, the portable device may transmit the sequence of
RTS messages using a second channel, different than the first
channel.
[0125] When transmit devices use transmit power control, larger
medium re-use and decreased contention may result if the range of
individual transmit devices is small. However, diversity in
transmit powers may cause hidden node problems with higher
collision probability and/or unfair medium access for devices that
use lower power when neighboring devices use higher power.
Therefore, the transmit power used may most likely be high enough
to ensure the highest possible modulation and coding scheme (MCS)
is received. This may lead to carrier sense at potentially
interfering neighbors.
[0126] FIG. 8 illustrates an example hidden node problem in
accordance with certain aspects of the present disclosure. In FIG.
8, node A transmits at a lower power than node C. Node C does not
defer to transmissions of node A, thereby causing collisions at
node B. In order to solve this problem, packet-drop-based rate
adaptation may involve a transmit power increase at the transmitter
side. The transmit power may be increased to a level to force
deferral at node C. If RTS/CTS is used, node B may adjust the power
of the CTS to ensure that node B's interfering neighbors are quiet
as another solution to this problem at the receiver side. These
solutions may also be combined. Methods for identifying interfering
neighbors are described below.
[0127] FIG. 9 illustrates an example exposed node problem with
transmit power control in accordance with certain aspects of the
present disclosure. If node A has a lower transmit power than node
C such that node A defers to node C, but node C does not defer to
node A, then medium access at node A would be lower than that at
node C. If transmissions of node A are received at node B, then
there are no collisions to trigger a power increase at node A. To
ensure fair access, node A may most likely be able to determine if
node A's lower access is due to a few nodes that do not defer to
node A or due to a network with many nodes. This may entail a
method to identify neighbors that cause deferral at node A,
although decoding of the transmissions to determine MAC addresses
may not be feasible. If the neighbors can be identified, then node
A may ramp up node A's transmit power to force deferral at node A's
neighbors.
[0128] FIG. 10 illustrates a node causing interference and deferral
to a neighboring node in accordance with certain aspects of the
present disclosure. In FIG. 10 transmissions from node B cause
deferral at node A. In order to discover neighbors that cause
interference and deferral, two different cases may be considered.
In the first case, node A is able to decode packets from node B.
Therefore, node A may send a TPC request to node B to determine the
transmit power of node B. Node A may then use sufficient power to
ensure deferral at node B.
[0129] In the second case, node A cannot decode packets from node B
(e.g., due to the MCS used). Accordingly, what is needed is a
method for node A to be able to determine its potential neighbors
and then transmit at a suitable power level.
[0130] FIG. 11 illustrates using a start time of a packet 1100
having a preamble 1102 and a payload 1104 to force identification
of an unknown node, in accordance with certain aspects of the
present disclosure. In this manner, neighbor discovery may be
accomplished based on the packet start time. When node A defers to
a transmission from an unknown node, node A decodes the preamble
1102 and records the exact time at which the node received the
preamble. Node A then sends a query with a broadcast receive
address and the time stamp (relative to the transmit time of the
packet that caused deferral). For certain aspects, time stamps for
several packets in the past may be included in an effort to
discover multiple neighbors.
[0131] STAs (such as node B) may receive the query check if the
STAs had transmitted a packet at the time provided in the query
message. If the time stamp in the query matches the transmit time
at one of the STAs, this STA sends a response message to node A.
The response message may include a TPC element providing link
margin information to node A. Based on the link margin, node A may
then determine a suitable power level to ensure deferral at node B
and that a CTS sent by node A is received at node B. Suitable
transmit power may also computed by sending a sequence of RTSs and
increasing power levels until a CTS is received from a STA, such as
node B, as described above.
[0132] FIG. 12 illustrates example operations 1200 to learn, from
the perspective of a wireless node, for example, the transmit power
used by an unknown neighboring node, in accordance with certain
aspects of the present disclosure. The operations 1200 may begin,
at 1202, by receiving, at a first apparatus from a second
apparatus, a packet that cannot be decoded by the first apparatus.
At 1204, the first apparatus may determine at least one of a time
or a duration corresponding to the packet. The first apparatus may
transmit a query with an indication of the at least one of the time
or the duration at 1206. For certain aspects, the query may be
transmitted via one or more channels in the TVWS. At 1208, the
first apparatus may receive a message from the second apparatus in
response to the query, the message identifying the second apparatus
as a source of the packet. For certain aspects, the message
indicates a power used by the second apparatus to transmit the
message.
[0133] According to certain aspects, the first apparatus may
transmit a sequence of request-to-send (RTS) messages at different
transmit power levels to the second apparatus. The first apparatus
may determine if a clear-to-send (CTS) message was received in
response to at least one of the RTS messages corresponding to a
particular one of the transmit power levels. For certain aspects,
the transmit power levels may be increasing in the sequence of RTS
messages. The particular one of the transmit power levels may
comprise a minimum transmit power level for transmitting one of the
RTS messages to the second apparatus and for receiving the CTS
message in response. The first apparatus may transmit at least one
of data, a subsequent RTS message, or a subsequent CTS message to
the second apparatus based on the particular one of the transmit
power levels.
[0134] For certain aspects, the first apparatus may transmit a
request to the second apparatus and may receive a response from the
second apparatus indicating a link margin based on the request. The
first apparatus may transmit data to the second apparatus based on
the link margin.
[0135] FIG. 13 illustrates example operations 1300 to provide, from
the perspective of a wireless node unknown to a neighboring node,
for example, the transmit power used by the wireless node, in
accordance with certain aspects of the present disclosure. The
operations 1300 may begin, at 1302, with the first apparatus
transmitting a packet at a particular time with a certain duration.
At 1304, the first apparatus may store at least one of the time or
the duration for the packet. The first apparatus may receive from a
second apparatus a (broadcast) query with an indication of at least
one of a query time or a query duration for the packet at 1306. For
certain aspects, the first apparatus may receive the query via one
or more channels in the TVWS. At 1308, the first apparatus may
determine that the at least one of the query time or the query
duration substantially matches the at least one of the stored time
or the stored duration. At 1310, the first apparatus may transmit a
message to the second apparatus in response to the query, the
message identifying the first apparatus as a source of the packet.
For certain aspects, the message may indicate a power used by the
first apparatus to transmit the message.
[0136] According to certain aspects, the first apparatus may
receive a request-to-send (RTS) message from the second apparatus.
The first apparatus may transmit a clear-to-send (CTS) message in
response to the RTS message.
[0137] For certain aspects, the first apparatus may receive a
request from the second apparatus. The first apparatus transmit a
response to the second apparatus indicating a link margin based on
the request. The request may comprise a transmit power control
(TPC) request, and the response may comprise a TPC response.
[0138] As described above, using a high transmit power causes CSMA
deferral over a larger area due to the lower path loss in the TVWS
band. Deferral over large areas limits spatial re-use. Therefore,
one object of aspects of the present disclosure is to increase
spatial re-use of TVWS channels. This may be accomplished by an
intelligent reduction of transmit power of RTS, CTS, and data.
Naive reduction of transmit power is not sufficient because if the
transmit power is too low, the receiving STA may likely see
interference from a large number of "hidden nodes," thus preventing
reception. However, high transmit powers may be "overkill" in many
scenarios, leading to wasted battery power, for example.
[0139] Accordingly, what is needed are techniques and apparatus to
adjust data transmit power to ensure reception at the intended PHY
rate at the receiver and to adjust CTS power to cause deferral only
at selected interferers. Ideally, implementations would involve
only minimal changes to the IEEE 802.11 standard.
[0140] Transmit power adaptation may be accomplished for the RTS,
the CTS, and/or data. Transmit power determination for the RTS/data
may involve a method for a receiver-side (Rx-side) device to
determine and convey a transmitter-side (Tx-side) transmit power.
This transmit power determination may use request response messages
similar to current TPC messages, described below. Transmit power
determination for CTS may entail a method to calculate the CTS
transmit power sufficient to block out dominant interferers.
Beacons and RTSs may be augmented with data transmit power
information as described below. Transmit power determination for
CTS may involve a method for a STA to identify interferers to quiet
with the CTS and send CTS with sufficient transmit power to reach
those interferers.
[0141] A TPC request/response mechanism has been defined in IEEE
802.11. This mechanism allows transmitter/receiver pairs to
determine a suitable transmit power.
[0142] FIG. 14A illustrates a TPC request element 1400 and a TPC
report element 600, in accordance with certain aspects of the
present disclosure. The TPC request element 1400 may comprise an
element ID field 1402 and a length field 1404. Each of these fields
1402, 1404 may have a length of one octet (eight bits).
[0143] For RTS or data transmit power determination, the Tx-side
device may send a TPC request message to the Rx-side device. The
Rx-side device may respond with a TPC report message that contains
a link margin field 608. The link margin may be measured during the
reception of the corresponding TPC request. The transmit power
field 606 may indicate a transmit power of the TPC report message.
The Tx-side device may determine the indicated transmit power from
the link margin indicated in the TPC report message.
[0144] FIG. 14B illustrates a TPC request element 1450 with a
modulation and coding scheme (MCS) field 1452 and a TPC report
element 600, in accordance with certain aspects of the present
disclosure. In order to enable the Tx-side device to request the
power level desired for reception at a given MCS from an Rx-side
device, the Rx-side device should be able to provide a transmit
power that is based on the path loss to the Tx-side device and
potential interference at the Rx-side device. To accomplish this,
the Tx-side device may send a request message with the desired
transmit MCS. The Rx-side device may compute a power margin M.sub.1
that may most likely be applied to the transmit power of the
request message to support the requested MCS based on the received
power (e.g., the RSSI, or received signal strength indicator) of
the request message. The Rx-side device may adjust (e.g., reduce)
the computed power margin M.sub.1 in the above step by a further
factor (e.g., a factor of tolerable interference) to obtain the
feedback link margin M.sub.2. Any suitable method of determining
the tolerable interference factor may be employed. The Rx-side
device may then send a message with the margin M.sub.2 to the
Tx-side device. The Tx-side device may apply the fed-back margin
M.sub.2 to the transmit power used for the request message to
determine the power to be used for data transmissions at the
requested MCS.
[0145] For certain aspects, the Tx-side device may send a TPC
request element 1450 with the MCS field 1452. The Rx-side device
may respond with a TPC report element 600 with the link margin
field 608 set according to the MCS, a path loss between the Rx-side
device and the Tx-side device, and a desired
signal-to-interference-plus-noise ratio (SINR) at the Rx side.
Then, the Tx-side device may use the minimum transmit power
indicated for the requested MCS based on the link margin
returned.
[0146] FIG. 15 illustrates example operations 1500 to utilize, from
the perspective of a Tx-side device, for example, a TPC request
message with a desired MCS, in accordance with certain aspects of
the present disclosure. The operations 1500 may begin, at 1502,
with the Tx-side device determining a MCS for transmitting data
frames. At 1504, the Tx-side device may transmit a TPC request
message comprising an indication of the MCS. The Tx-side device may
transmit the TPC request message via one or more channels in a
TVWS. For certain aspects, the indication of the MCS may comprise
an IE in the request message. The Tx-side device may receive a TPC
response message comprising an indication of a link margin, wherein
the link margin is based on the MCS at 1506. At 1508, the Tx-side
device may transmit data using the MCS and a transmit power based
on the link margin.
[0147] FIG. 16 illustrates example operations 1600 to utilize, from
the perspective of a Rx-side device, for example, a TPC request
message with a desired MCS, in accordance with certain aspects of
the present disclosure. The operations 1600 may begin, at 1602,
with the Rx-side device receiving a TPC request message comprising
an indication of a MCS for transmitting data frames to be received.
For certain aspects, the indication of the MCS may comprise an IE
in the request message. At 1604, the Rx-side device may determine a
link margin based on the MCS. The Rx-side device may transmit a TPC
response message with an indication of the link margin at 1606. The
Rx-side device may transmit the TPC response message via one or
more channels in a TVWS.
[0148] According to certain aspects, the Rx-side device may
determine a signal-to-interference-plus-noise ratio (SINR) and a
path loss, wherein the link margin is based on the MCS, the SINR,
and the path loss. The Rx-side device may determine a received
power associated with the request message, determine a power margin
based on the received power associated with the request message,
and adjust the power margin by a factor to obtain the link margin.
For certain aspects, the factor may be a tolerable interference
factor.
[0149] FIG. 17 illustrates an example station (STA) 1700 surrounded
by interfering STAs 1710, in accordance with certain aspects of the
present disclosure. The CTS range 1702 of the STA 1700 is chosen
according to AP transmit power and desired interference level.
[0150] In determining a transmit power for CTS messages, the
Rx-side device (e.g., the STA 1700) may observe RTSs and beacons
from neighboring interferers (e.g., interfering STAs 1710). Beacons
of neighboring APs contain the maximum transmit power used by the
AP to transmit data. For certain aspects, the beacons may contain
the transmit power of the beacon, as well. Details for the beacon
frame format are described below with respect to FIG. 18. Some RTSs
transmitted from a STA are augmented with power used for the
following data and the power used for transmitting the RTS. Details
on augmented RTS frame format are provided below with respect to
FIG. 21.
[0151] The Rx-side device may use data transmit power information
along with path loss (determined from RSSI of the Beacon/RTS) to
determine dominant interferers. The Rx-side device may send a CTS
message at a power level sufficient to reach all the device's
dominant interferers determined based on the data transmit power.
Transmit power used for the beacon or augmented RTS may be larger
in order to ensure decode at a longer range. Using the beacon
transmit power may lead to an unnecessarily large range for the
CTS.
[0152] FIG. 18 illustrates an example beacon information element
(IE) 1800 for indicating the transmit power of data frames
transmitted from an access point (AP), in accordance with certain
aspects of the present disclosure. An AP may transmit beacons with
the beacon IE 1800. The beacon IE 1800 may comprise an element ID
field 1802, a length field 1804, and a data transmit power field
1806. The data transmit power field 1806 may contain the highest
transmit power used by the AP to send data frames. Each of the
fields 1802, 1804, 1806 may have a length of one octet (8
bits).
[0153] FIG. 19 illustrates example operations 1900 to transmit,
from the perspective of an AP, for example, a broadcast message
with an indication of the highest transmit power for transmitting
data frames, in accordance with certain aspects of the present
disclosure. The operations 1900 may begin, at 1902, with the AP
determining a highest transmit power for transmitting data frames.
At 1904, the AP may transmit a (broadcast) message with an
indication of the highest transmit power. The AP may transmit the
message via one or more channels in a TVWS.
[0154] According to certain aspects, the message may comprise a
beacon. The indication may comprise an IE in the beacon. For other
aspects, the message may comprise another indication of a second
transmit power for transmitting the message. The AP may transmit
the message using the second transmit power.
[0155] FIG. 20 illustrates example operations 2000 to determine,
from the perspective of a STA, for example, dominant interferers
based on a received broadcast message with an indication of a
highest transmit power for transmitting data frames, in accordance
with certain aspects of the present disclosure. The operations 2000
may begin, at 2002, with the STA receiving, from an apparatus
(e.g., an AP), a (broadcast) message with an indication of a
highest transmit power used by the apparatus for transmitting data
frames. For certain aspects, the message comprises a beacon, and
the indication comprises an IE in the beacon. At 2004, the STA may
determine that the apparatus is a dominant interferer based, at
least in part, on the highest transmit power. For certain aspects,
this determination may also be based on the path loss. At 2006, the
STA may determine a received power of the message. The STA may
determine a path loss based on the received power at 2008. At 2010,
the STA may transmit a CTS message at a transmit power level
sufficient to reach the dominant interferer.
[0156] According to certain aspects, the message may comprise
another indication of a second transmit power for transmitting the
message. The STA may determine a received power of the message and
a path loss based on the received power and the second transmit
power. The STA may determine that the dominant is a dominant
interferer is also based on the path loss.
[0157] For certain aspects, the STA may receive from multiple
apparatuses (e.g., a second or a third apparatus), messages with
indications of the highest transmit power used by each of the
apparatuses for transmitting data frames. For example, the STA may
receive from a second apparatus another message with another
indication of a highest transmit power used by the second apparatus
for transmitting data frames. The STA may determine that any one or
more of these apparatuses are dominant interferers based, at least
in part, on the highest transmit power used by each of the
apparatuses. The STA may then transmit a CTS message at the highest
transmit power level sufficient to reach all of the dominant
interferers (i.e., at the higher of a first transmit power level
sufficient to reach the apparatus and a second transmit power level
sufficient to reach the second apparatus).
[0158] FIG. 21 illustrates an example control or management frame
format 2100 with an IE for indicating the transmit power of data
frames transmitted from a STA and another IE for indicating the
transmit power used for transmitting the control or management
frame, in accordance with certain aspects of the present
disclosure. The frame format 2100 may comprise a frame control (FC)
field 2102, a duration field 2104, a receiver address (RA) field
2106, a transmitter address (TA) field 2108, a frame transmit power
field 2110, a data transmit power field 2112, and a frame check
sequence (FCS) field 2114. The data transmit power field 2112 may
indicate the transmit power for transmitting data frames, while the
frame transmit power field 2110 may indicate the power used for
transmitting the control or management frame containing the frame
transmit power field 2110.
[0159] For certain aspects, the control or management frame may be
a power calibration frame, which may be a type of management frame.
For other aspects, the control or management frame format 2100 may
be an RTS frame format augmented with the frame and data transmit
power fields 2110, 2112.
[0160] FIG. 22 illustrates example operations 2200 to transmit,
from the perspective of a STA, for example, a control or management
message with an indication of a transmit power for transmitting
data frames and another indication of a transmit power used when
transmitting the control or management message, in accordance with
certain aspects of the present disclosure. The operations 2200 may
begin, at 2202, with the STA determining a first transmit power for
transmitting data frames. At 2204, the STA may transmit a control
or management message at a second transmit power. The control or
management message may comprise a first indication of the first
transmit power and a second indication of the second transmit
power. The STA may transmit the control or management message via
one or more channels in a TVWS.
[0161] For certain aspects, the control or management message may
comprise a RTS message or a power calibration frame. According to
certain aspects, the first and second indications may comprise an
IE in the control or management message.
[0162] FIG. 23 illustrates example operations 2300 to determine,
from the perspective of a STA, for example, dominant interferers
based on a received control or management message with an
indication of a transmit power for transmitting data frames and
another indication of a transmit power used when transmitting the
control or management message, in accordance with certain aspects
of the present disclosure. The operations 2300 may begin, at 2302,
with the STA receiving from an apparatus (e.g., another STA), a
control or management message with a first indication of a first
transmit power used by the apparatus for transmitting data frames.
The STA may receive the control or management message via one or
more channels in a TVWS. For certain aspects, the control or
management message may also comprise a second indication of a
second transmit power used by the apparatus for transmitting the
control or management message. At 2304, the STA may determine that
the apparatus is a dominant interferer based, at least in part, on
the first transmit power.
[0163] At 2306, the STA may determine a received power of the
control or management message. The STA may determine a path loss
based on the received power and the second transmit power at 2308.
For certain aspects, the STA may determine that the apparatus is a
dominant interferer at 2304 based on the path loss, as well as the
first transmit power. At 2310, the STA may transmit a CTS message
at a transmit power level sufficient to reach the dominant
interferer.
[0164] For certain aspects, the control or management message may
comprise a RTS message or a power calibration frame. According to
certain aspects, one of the first and second indications may
comprise an IE in the control or management message.
[0165] For certain aspects, the STA may receive, from a second
apparatus, another control or management message with a third
indication of a third transmit power used by the second apparatus
for transmitting data frames. The STA may determine that the second
apparatus is another dominant interferer based, at least in part,
on the third transmit power. The STA may also transmit a CTS
message at the higher of a first transmit power level sufficient to
reach the apparatus and a second transmit power level sufficient to
reach the second apparatus.
[0166] The various operations of methods described above may be
performed by any suitable means capable of performing the
corresponding functions. The means may include various hardware
and/or software component(s) and/or module(s), including, but not
limited to a circuit, an application specific integrated circuit
(ASIC), or processor. Generally, where there are operations
illustrated in figures, those operations may have corresponding
counterpart means-plus-function components with similar numbering.
For example, operations 700 illustrated in FIG. 7 correspond to
components 700A illustrated in FIG. 7A.
[0167] For example, means for transmitting may comprise a
transmitter, such as the transmitter unit 222 of the access point
110 illustrated in FIG. 2, the transmitter unit 254 of the user
terminal 120 depicted in FIG. 2, or the transmitter 310 of the
wireless device 302 shown in FIG. 3. Means for receiving may
comprise a receiver, such as the receiver unit 222 of the access
point 110 illustrated in FIG. 2, the receiver unit 254 of the user
terminal 120 depicted in FIG. 2, or the receiver 312 of the
wireless device 302 shown in FIG. 3. Means for processing, means
for determining, means for identifying, or means for adjusting may
comprise a processing system, which may include one or more
processors, such as the RX data processor 270, the TX data
processor 288, and/or the controller 280 of the user terminal 120
or the RX data processor 242, the TX data processor 210, and/or the
controller 230 of the access point 110 illustrated in FIG. 2. Means
for storing may comprise memory or other storage media, such as the
memory 306 of the wireless device 302 shown in FIG. 3.
[0168] As used herein, the term "determining" encompasses a wide
variety of actions. For example, "determining" may include
calculating, computing, processing, deriving, investigating,
looking up (e.g., looking up in a table, a database or another data
structure), ascertaining and the like. Also, "determining" may
include receiving (e.g., receiving information), accessing (e.g.,
accessing data in a memory) and the like. Also, "determining" may
include resolving, selecting, choosing, establishing and the
like.
[0169] As used herein, a phrase referring to "at least one of" a
list of items refers to any combination of those items, including
single members. As an example, "at least one of: a, b, or c" is
intended to cover: a, b, c, a-b, a-c, b-c, and a-b-c.
[0170] The various illustrative logical blocks, modules and
circuits described in connection with the present disclosure may be
implemented or performed with a general purpose processor, a
digital signal processor (DSP), an application specific integrated
circuit (ASIC), a field programmable gate array (FPGA) or other
programmable logic device (PLD), discrete gate or transistor logic,
discrete hardware components, or any combination thereof designed
to perform the functions described herein. A general-purpose
processor may be a microprocessor, but in the alternative, the
processor may be any commercially available processor, controller,
microcontroller, or state machine. A processor may also be
implemented as a combination of computing devices, e.g., a
combination of a DSP and a microprocessor, a plurality of
microprocessors, one or more microprocessors in conjunction with a
DSP core, or any other such configuration.
[0171] The steps of a method or algorithm described in connection
with the present disclosure may be embodied directly in hardware,
in a software module executed by a processor, or in a combination
of the two. A software module may reside in any form of storage
medium that is known in the art. Some examples of storage media
that may be used include random access memory (RAM), read only
memory (ROM), flash memory, EPROM memory, EEPROM memory, registers,
a hard disk, a removable disk, a CD-ROM and so forth. A software
module may comprise a single instruction, or many instructions, and
may be distributed over several different code segments, among
different programs, and across multiple storage media. A storage
medium may be coupled to a processor such that the processor can
read information from, and write information to, the storage
medium. In the alternative, the storage medium may be integral to
the processor.
[0172] The methods disclosed herein comprise one or more steps or
actions for achieving the described method. The method steps and/or
actions may be interchanged with one another without departing from
the scope of the claims. In other words, unless a specific order of
steps or actions is specified, the order and/or use of specific
steps and/or actions may be modified without departing from the
scope of the claims.
[0173] The functions described may be implemented in hardware,
software, firmware, or any combination thereof. If implemented in
hardware, an example hardware configuration may comprise a
processing system in a wireless node. The processing system may be
implemented with a bus architecture. The bus may include any number
of interconnecting buses and bridges depending on the specific
application of the processing system and the overall design
constraints. The bus may link together various circuits including a
processor, machine-readable media, and a bus interface. The bus
interface may be used to connect a network adapter, among other
things, to the processing system via the bus. The network adapter
may be used to implement the signal processing functions of the PHY
layer. In the case of a user terminal 120 (see FIG. 1), a user
interface (e.g., keypad, display, mouse, joystick, etc.) may also
be connected to the bus. The bus may also link various other
circuits such as timing sources, peripherals, voltage regulators,
power management circuits, and the like, which are well known in
the art, and therefore, will not be described any further.
[0174] The processor may be responsible for managing the bus and
general processing, including the execution of software stored on
the machine-readable media. The processor may be implemented with
one or more general-purpose and/or special-purpose processors.
Examples include microprocessors, microcontrollers, DSP processors,
and other circuitry that can execute software. Software shall be
construed broadly to mean instructions, data, or any combination
thereof, whether referred to as software, firmware, middleware,
microcode, hardware description language, or otherwise.
Machine-readable media may include, by way of example, RAM (Random
Access Memory), flash memory, ROM (Read Only Memory), PROM
(Programmable Read-Only Memory), EPROM (Erasable Programmable
Read-Only Memory), EEPROM (Electrically Erasable Programmable
Read-Only Memory), registers, magnetic disks, optical disks, hard
drives, or any other suitable storage medium, or any combination
thereof. The machine-readable media may be embodied in a
computer-program product. The computer-program product may comprise
packaging materials.
[0175] In a hardware implementation, the machine-readable media may
be part of the processing system separate from the processor.
However, as those skilled in the art will readily appreciate, the
machine-readable media, or any portion thereof, may be external to
the processing system. By way of example, the machine-readable
media may include a transmission line, a carrier wave modulated by
data, and/or a computer product separate from the wireless node,
all which may be accessed by the processor through the bus
interface. Alternatively, or in addition, the machine-readable
media, or any portion thereof, may be integrated into the
processor, such as the case may be with cache and/or general
register files.
[0176] The processing system may be configured as a general-purpose
processing system with one or more microprocessors providing the
processor functionality and external memory providing at least a
portion of the machine-readable media, all linked together with
other supporting circuitry through an external bus architecture.
Alternatively, the processing system may be implemented with an
ASIC (Application Specific Integrated Circuit) with the processor,
the bus interface, the user interface in the case of an access
terminal), supporting circuitry, and at least a portion of the
machine-readable media integrated into a single chip, or with one
or more FPGAs (Field Programmable Gate Arrays), PLDs (Programmable
Logic Devices), controllers, state machines, gated logic, discrete
hardware components, or any other suitable circuitry, or any
combination of circuits that can perform the various functionality
described throughout this disclosure. Those skilled in the art will
recognize how best to implement the described functionality for the
processing system depending on the particular application and the
overall design constraints imposed on the overall system.
[0177] The machine-readable media may comprise a number of software
modules. The software modules include instructions that, when
executed by the processor, cause the processing system to perform
various functions. The software modules may include a transmission
module and a receiving module. Each software module may reside in a
single storage device or be distributed across multiple storage
devices. By way of example, a software module may be loaded into
RAM from a hard drive when a triggering event occurs. During
execution of the software module, the processor may load some of
the instructions into cache to increase access speed. One or more
cache lines may then be loaded into a general register file for
execution by the processor. When referring to the functionality of
a software module below, it will be understood that such
functionality is implemented by the processor when executing
instructions from that software module.
[0178] If implemented in software, the functions may be stored on
or transmitted over as one or more instructions or code on a
computer-readable medium. Computer-readable media include both
computer storage media and communication media including any medium
that facilitates transfer of a computer program from one place to
another. A storage medium may be any available medium that can be
accessed by a computer. By way of example, and not limitation, such
computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or
other optical disk storage, magnetic disk storage or other magnetic
storage devices, or any other medium that can be used to carry or
store desired program code in the form of instructions or data
structures and that can be accessed by a computer. Also, any
connection is properly termed a computer-readable medium. For
example, if the software is transmitted from a website, server, or
other remote source using a coaxial cable, fiber optic cable,
twisted pair, digital subscriber line (DSL), or wireless
technologies such as infrared (IR), radio, and microwave, then the
coaxial cable, fiber optic cable, twisted pair, DSL, or wireless
technologies such as infrared, radio, and microwave are included in
the definition of medium. Disk and disc, as used herein, include
compact disc (CD), laser disc, optical disc, digital versatile disc
(DVD), floppy disk, and Blu-ray.RTM. disc where disks usually
reproduce data magnetically, while discs reproduce data optically
with lasers. Thus, in some aspects computer-readable media may
comprise non-transitory computer-readable media (e.g., tangible
media). In addition, for other aspects computer-readable media may
comprise transitory computer-readable media (e.g., a signal).
Combinations of the above should also be included within the scope
of computer-readable media.
[0179] Thus, certain aspects may comprise a computer program
product for performing the operations presented herein. For
example, such a computer program product may comprise a
computer-readable medium having instructions stored (and/or
encoded) thereon, the instructions being executable by one or more
processors to perform the operations described herein. For certain
aspects, the computer program product may include packaging
material.
[0180] Further, it should be appreciated that modules and/or other
appropriate means for performing the methods and techniques
described herein can be downloaded and/or otherwise obtained by a
user terminal and/or base station as applicable. For example, such
a device can be coupled to a server to facilitate the transfer of
means for performing the methods described herein. Alternatively,
various methods described herein can be provided via storage means
(e.g., RAM, ROM, a physical storage medium such as a compact disc
(CD) or floppy disk, etc.), such that a user terminal and/or base
station can obtain the various methods upon coupling or providing
the storage means to the device. Moreover, any other suitable
technique for providing the methods and techniques described herein
to a device can be utilized.
[0181] It is to be understood that the claims are not limited to
the precise configuration and components illustrated above. Various
modifications, changes and variations may be made in the
arrangement, operation and details of the methods and apparatus
described above without departing from the scope of the claims.
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