U.S. patent application number 16/428695 was filed with the patent office on 2020-08-20 for system and method for setting link parameters in a wifi link.
The applicant listed for this patent is Samsung Electronics Co., Ltd.. Invention is credited to Ruchen Duan, Wook Bong Lee, Moumita Ray.
Application Number | 20200266918 16/428695 |
Document ID | 20200266918 / US20200266918 |
Family ID | 1000004142921 |
Filed Date | 2020-08-20 |
Patent Application | download [pdf] |
United States Patent
Application |
20200266918 |
Kind Code |
A1 |
Lee; Wook Bong ; et
al. |
August 20, 2020 |
SYSTEM AND METHOD FOR SETTING LINK PARAMETERS IN A WIFI LINK
Abstract
A system and method for operating a link. In some embodiments,
the method includes transmitting a first quantity of data, using a
first number of spatial streams, and a first bandwidth, receiving
N1 acknowledgment signals, N1 being a nonnegative integer;
receiving N2 negative acknowledgment signals, N2 being a
nonnegative integer; adjusting an estimated signal to interference
and noise ratio for the first number of spatial streams and the
first bandwidth, based on N1 and N2; estimating a first throughput
for the first number of spatial streams and the first bandwidth;
estimating a second throughput for a second number of spatial
streams and a second bandwidth; determining whether the second
throughput exceeds the first throughput; and in response to
determining that the second throughput exceeds the first
throughput, transmitting a second quantity of data, using the
second number of spatial streams, and the second bandwidth.
Inventors: |
Lee; Wook Bong; (San Jose,
CA) ; Ray; Moumita; (San Jose, CA) ; Duan;
Ruchen; (Santa Clara, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Electronics Co., Ltd. |
Suwon-si |
|
KR |
|
|
Family ID: |
1000004142921 |
Appl. No.: |
16/428695 |
Filed: |
May 31, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62807544 |
Feb 19, 2019 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 5/0055 20130101;
H04B 17/336 20150115; H04L 5/0051 20130101; H04L 1/203 20130101;
H04L 1/0005 20130101 |
International
Class: |
H04L 1/00 20060101
H04L001/00; H04L 5/00 20060101 H04L005/00; H04L 1/20 20060101
H04L001/20; H04B 17/336 20060101 H04B017/336 |
Claims
1. A method for operating a link, the method comprising: adjusting
a respective estimated signal to interference and noise ratio for
each of a plurality of combinations of spatial stream numbers and
bandwidths; determining a modulation and coding scheme for each of
the plurality of combinations; estimating a plurality of
throughputs, each corresponding to a respective one of the
plurality of modulation and coding schemes; selecting a maximum
throughput from the plurality of throughputs; and transmitting data
according to the modulation and coding scheme, spatial stream
number, and bandwidth associated with the maximum throughput.
2. The method of claim 1, wherein the adjusting of the respective
estimated signal to interference and noise ratio for a first
combination of the plurality of combinations of spatial stream
numbers and bandwidths comprises: transmitting a first quantity of
data, using the first combination; receiving N1 acknowledgment
signals, N1 being a nonnegative integer; receiving N2 negative
acknowledgment signals, N2 being a nonnegative integer; and
adjusting an estimated signal to interference and noise ratio for
the first combination, based on N1 and N2.
3. The method of claim 2, wherein the adjusting of the estimated
signal to interference and noise ratio comprises: adding, to a
previously estimated signal to interference and noise ratio for the
first combination, an adjustment based on an estimated error rate,
the adjustment being: greater than zero when the estimated error
rate is zero, and less than zero when the estimated error rate is
one.
4. The method of claim 3, wherein: the number of spatial streams of
a second combination of the plurality of combinations of spatial
stream numbers and bandwidths, exceeds the number of spatial
streams of the first combination, or the bandwidth of the second
combination exceeds the bandwidth of the first combination, and the
estimating of the throughput corresponding to the modulation and
coding scheme of the second combination comprises adjusting an
estimated signal to interference and noise ratio for the second
combination, the adjusting of the estimated signal to interference
and noise ratio for the second combination comprises adding, to a
previously estimated signal to interference and noise ratio for the
second combination, the adjustment based on the estimated error
rate.
5. The method of claim 4, wherein: the previously estimated signal
to interference and noise ratio for the first combination is a sum
of: a first reference signal to interference and noise ratio, and
an offset; and the adding of the adjustment to the previously
estimated signal to interference and noise ratio for the first
combination comprises adding the adjustment to the offset.
6. The method of claim 5, further comprising calculating the first
reference signal to interference and noise ratio based on a signal
to interference and noise ratio measured during reception of a
beacon signal.
7. The method of claim 5, wherein the calculating of the adjustment
comprises: determining whether: the estimated error rate is less
than a target error rate, a current modulation coding scheme is
equal to a maximum modulation coding scheme, and the offset exceeds
a first threshold; and in response to determining that: the
estimated error rate is less than the target error rate, the
current modulation coding scheme is equal to the maximum modulation
coding scheme, and the offset exceeds the first threshold, setting
the adjustment to zero.
8. The method of claim 5, wherein the calculating of the adjustment
comprises: determining whether: the estimated error rate is greater
than a target error rate, a current modulation coding scheme is
equal to a minimum modulation coding scheme, and the offset is less
than a second threshold; and in response to determining that: the
estimated error rate is greater than the target error rate, the
current modulation coding scheme is equal to the minimum modulation
coding scheme, and the offset is less than the second threshold,
setting the adjustment to zero.
9. The method of claim 3, wherein the adjustment is calculated
according to (1-PER)*snrStep/(1/targetPer-1)+PER*(-snrStep),
wherein: PER is the estimated error rate, targetPer is a target
error rate, and snrStep is an adjustment rate parameter.
10. The method of claim 9, wherein the estimated error rate is
calculated as N2/(N1+N2).
11. The method of claim 9, wherein the target error rate is
calculated based on a number of consecutive errors.
12. A system comprising a WiFi transmitter comprising a processing
circuit, the processing circuit being configured to: adjust a
respective estimated signal to interference and noise ratio for
each of a plurality of combinations of spatial stream numbers and
bandwidths; determine a modulation and coding scheme for each of
the plurality of combinations; estimate a plurality of throughputs,
each corresponding to a respective one of the plurality of
modulation and coding schemes; select a maximum throughput from the
plurality of throughputs; and transmit data according to the
modulation and coding scheme, spatial stream number, and bandwidth
associated with the maximum throughput.
13. The system of claim 12 wherein the adjusting of the respective
estimated signal to interference and noise ratio for a first
combination of the plurality of combinations of spatial stream
numbers and bandwidths comprises: transmitting a first quantity of
data, using the first combination; receiving N1 acknowledgment
signals, N1 being a nonnegative integer; receiving N2 negative
acknowledgment signals, N2 being a nonnegative integer; and
adjusting an estimated signal to interference and noise ratio for
the first combination, based on N1 and N2.
14. The system of claim 13, wherein the adjusting of the estimated
signal to interference and noise ratio comprises: adding to a
previously estimated signal to interference and noise ratio an
adjustment based on an estimated error rate, the adjustment being:
greater than zero when the estimated error rate is zero, and less
than zero when the estimated error rate is one.
15. The system of claim 14, wherein: the number of spatial streams
of a second combination of the plurality of combinations of spatial
stream numbers and bandwidths, exceeds the number of spatial
streams of the first combination, or the bandwidth of the second
combination exceeds the bandwidth of the first combination, and the
estimating of the throughput corresponding to the modulation and
coding scheme of the second combination comprises adjusting an
estimated signal to interference and noise ratio for the second
combination, the adjusting of the estimated signal to interference
and noise ratio for the second combination comprises adding, to a
previously estimated signal to interference and noise ratio for the
second combination, the adjustment based on the estimated error
rate.
16. The system of claim 15, wherein: the previously estimated
signal to interference and noise ratio for the first combination is
a sum of: a first reference signal to interference and noise ratio,
and an offset; and the adding of the adjustment to the previously
estimated signal to interference and noise ratio for the first
combination comprises adding the adjustment to the offset.
17. The system of claim 16, wherein the processing circuit is
further configured to calculate the first reference signal to
interference and noise ratio based on a signal to interference and
noise ratio measured during reception of a beacon signal.
18. The system of claim 16, wherein the calculating of the
adjustment comprises: determining whether: the estimated error rate
is less than a target error rate, a current modulation coding
scheme is equal to a maximum modulation coding scheme, and the
offset exceeds a first threshold; and in response to determining
that: the estimated error rate is less than the target error rate,
the current modulation coding scheme is equal to the maximum
modulation coding scheme, and the offset exceeds the first
threshold, setting the adjustment to zero.
19. The system of claim 16, wherein the calculating of the
adjustment comprises: determining whether: the estimated error rate
is greater than a target error rate, a current modulation coding
scheme is equal to a minimum modulation coding scheme, and the
offset is less than a second threshold; and in response to
determining that: the estimated error rate is greater than the
target error rate, the current modulation coding scheme is equal to
the minimum modulation coding scheme, and the offset is less than
the second threshold, setting the adjustment to zero.
20. A system comprising a WiFi transmitter comprising means for
processing, the means for processing being configured to: transmit
a first quantity of data, using a first number of spatial streams,
and a first bandwidth; receive N1 acknowledgment signals, N1 being
a nonnegative integer; receive N2 negative acknowledgment signals,
N2 being a nonnegative integer; adjust an estimated signal to
interference and noise ratio for the first number of spatial
streams and the first bandwidth, based on N1 and N2; estimate a
first throughput for the first number of spatial streams and the
first bandwidth; estimate a second throughput for a second number
of spatial streams and a second bandwidth; determine whether the
second throughput exceeds the first throughput; and in response to
determining that the second throughput exceeds the first
throughput, transmit a second quantity of data, using the second
number of spatial streams, and the second bandwidth.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] The present application claims priority to and the benefit
of U.S. Provisional Application No. 62/807,544, filed Feb. 19,
2019, entitled "SYSTEM AND METHOD FOR ENHANCED OPEN LOOP LINK
ADAPTATION", the entire content of which is incorporated herein by
reference.
FIELD
[0002] One or more aspects of embodiments according to the present
disclosure relate to wireless communications, and more particularly
to a system and method for setting link parameters in a WiFi
link.
BACKGROUND
[0003] In a WiFi system, various parameters may be adjusted when
data are transmitted. These parameters include the modulation
coding scheme, the number of spatial streams and the bandwidth. The
throughput of a WiFi link may depend on the channel and on the
parameters chosen, and, as such, it may be advantageous to use link
adaptation, e.g., to adapt the parameters to the operating
conditions of the link.
[0004] Thus, there is a need for a system and method for setting
link parameters in a WiFi link.
SUMMARY
[0005] According to some embodiments of the present disclosure,
there is provided a method for operating a link, the method
including: adjusting a respective estimated signal to interference
and noise ratio for each of a plurality of combinations of spatial
stream numbers and bandwidths; determining a modulation and coding
scheme for each of the plurality of combinations; estimating a
plurality of throughputs, each corresponding to a respective one of
the plurality of modulation and coding schemes; selecting a maximum
throughput from the plurality of throughputs; and transmitting data
according to the modulation and coding scheme, spatial stream
number, and bandwidth associated with the maximum throughput.
[0006] In some embodiments, the adjusting of the respective
estimated signal to interference and noise ratio for a first
combination of the plurality of combinations of spatial stream
numbers and bandwidths includes: transmitting a first quantity of
data, using the first combination; receiving N1 acknowledgment
signals, N1 being a nonnegative integer; receiving N2 negative
acknowledgment signals, N2 being a nonnegative integer; and
adjusting an estimated signal to interference and noise ratio for
the first combination, based on N1 and N2.
[0007] In some embodiments, the adjusting of the estimated signal
to interference and noise ratio includes: adding, to a previously
estimated signal to interference and noise ratio for the first
combination, an adjustment based on an estimated error rate, the
adjustment being: greater than zero when the estimated error rate
is zero, and less than zero when the estimated error rate is
one.
[0008] In some embodiments: the number of spatial streams of a
second combination of the plurality of combinations of spatial
stream numbers and bandwidths, exceeds the number of spatial
streams of the first combination, or the bandwidth of the second
combination exceeds the bandwidth of the first combination, and the
estimating of the throughput corresponding to the modulation and
coding scheme of the second combination includes adjusting an
estimated signal to interference and noise ratio for the second
combination, the adjusting of the estimated signal to interference
and noise ratio for the second combination includes adding, to a
previously estimated signal to interference and noise ratio for the
second combination, the adjustment based on the estimated error
rate.
[0009] In some embodiments: the previously estimated signal to
interference and noise ratio for the first combination is a sum of:
a first reference signal to interference and noise ratio, and an
offset; and the adding of the adjustment to the previously
estimated signal to interference and noise ratio for the first
combination includes adding the adjustment to the offset.
[0010] In some embodiments, the method further includes calculating
the first reference signal to interference and noise ratio based on
a signal to interference and noise ratio measured during reception
of a beacon signal.
[0011] In some embodiments, the calculating of the adjustment
includes: determining whether: the estimated error rate is less
than a target error rate, a current modulation coding scheme is
equal to a maximum modulation coding scheme, and the offset exceeds
a first threshold; and in response to determining that: the
estimated error rate is less than the target error rate, the
current modulation coding scheme is equal to the maximum modulation
coding scheme, and the offset exceeds the first threshold, setting
the adjustment to zero.
[0012] In some embodiments, the calculating of the adjustment
includes: determining whether: the estimated error rate is greater
than a target error rate, a current modulation coding scheme is
equal to a minimum modulation coding scheme, and the offset is less
than a second threshold; and in response to determining that: the
estimated error rate is greater than the target error rate, the
current modulation coding scheme is equal to the minimum modulation
coding scheme, and the offset is less than the second threshold,
setting the adjustment to zero.
[0013] In some embodiments, the adjustment is calculated according
to (1-PER)*snrStep/(1/targetPer-1)+PER*(-snrStep), wherein: PER is
the estimated error rate, targetPer is a target error rate, and
snrStep is an adjustment rate parameter.
[0014] In some embodiments, the estimated error rate is calculated
as N2/(N1+N2).
[0015] In some embodiments, the target error rate is calculated
based on a number of consecutive errors.
[0016] According to some embodiments of the present disclosure,
there is provided a system including a WiFi transmitter including a
processing circuit, the processing circuit being configured to:
adjust a respective estimated signal to interference and noise
ratio for each of a plurality of combinations of spatial stream
numbers and bandwidths; determine a modulation and coding scheme
for each of the plurality of combinations; estimate a plurality of
throughputs, each corresponding to a respective one of the
plurality of modulation and coding schemes; select a maximum
throughput from the plurality of throughputs; and transmit data
according to the modulation and coding scheme, spatial stream
number, and bandwidth associated with the maximum throughput.
[0017] In some embodiments, the adjusting of the respective
estimated signal to interference and noise ratio for a first
combination of the plurality of combinations of spatial stream
numbers and bandwidths includes: transmitting a first quantity of
data, using the first combination; receiving N1 acknowledgment
signals, N1 being a nonnegative integer; receiving N2 negative
acknowledgment signals, N2 being a nonnegative integer; and
adjusting an estimated signal to interference and noise ratio for
the first combination, based on N1 and N2.
[0018] In some embodiments, the adjusting of the estimated signal
to interference and noise ratio includes: adding to a previously
estimated signal to interference and noise ratio an adjustment
based on an estimated error rate, the adjustment being: greater
than zero when the estimated error rate is zero, and less than zero
when the estimated error rate is one.
[0019] In some embodiments: the number of spatial streams of a
second combination of the plurality of combinations of spatial
stream numbers and bandwidths, exceeds the number of spatial
streams of the first combination, or the bandwidth of the second
combination exceeds the bandwidth of the first combination, and the
estimating of the throughput corresponding to the modulation and
coding scheme of the second combination includes adjusting an
estimated signal to interference and noise ratio for the second
combination, the adjusting of the estimated signal to interference
and noise ratio for the second combination includes adding, to a
previously estimated signal to interference and noise ratio for the
second combination, the adjustment based on the estimated error
rate.
[0020] In some embodiments: the previously estimated signal to
interference and noise ratio for the first combination is a sum of:
a first reference signal to interference and noise ratio, and an
offset; and the adding of the adjustment to the previously
estimated signal to interference and noise ratio for the first
combination includes adding the adjustment to the offset.
[0021] In some embodiments, the processing circuit is further
configured to calculate the first reference signal to interference
and noise ratio based on a signal to interference and noise ratio
measured during reception of a beacon signal.
[0022] In some embodiments, the calculating of the adjustment
includes: determining whether: the estimated error rate is less
than a target error rate, a current modulation coding scheme is
equal to a maximum modulation coding scheme, and the offset exceeds
a first threshold; and in response to determining that: the
estimated error rate is less than the target error rate, the
current modulation coding scheme is equal to the maximum modulation
coding scheme, and the offset exceeds the first threshold, setting
the adjustment to zero.
[0023] In some embodiments, the calculating of the adjustment
includes: determining whether: the estimated error rate is greater
than a target error rate, a current modulation coding scheme is
equal to a minimum modulation coding scheme, and the offset is less
than a second threshold; and in response to determining that: the
estimated error rate is greater than the target error rate, the
current modulation coding scheme is equal to the minimum modulation
coding scheme, and the offset is less than the second threshold,
setting the adjustment to zero.
[0024] According to some embodiments of the present disclosure,
there is provided a system including a WiFi transmitter including
means for processing, the means for processing being configured to:
transmit a first quantity of data, using a first number of spatial
streams, and a first bandwidth; receive N1 acknowledgment signals,
N1 being a nonnegative integer; receive N2 negative acknowledgment
signals, N2 being a nonnegative integer; adjust an estimated signal
to interference and noise ratio for the first number of spatial
streams and the first bandwidth, based on N1 and N2; estimate a
first throughput for the first number of spatial streams and the
first bandwidth; estimate a second throughput for a second number
of spatial streams and a second bandwidth; determine whether the
second throughput exceeds the first throughput; and in response to
determining that the second throughput exceeds the first
throughput, transmit a second quantity of data, using the second
number of spatial streams, and the second bandwidth.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] These and other features and advantages of the present
disclosure will be appreciated and understood with reference to the
specification, claims, and appended drawings wherein:
[0026] FIG. 1 is a flowchart for a portion of a method for setting
link parameters in a WiFi link, according to an embodiment of the
present disclosure;
[0027] FIG. 2 is a flowchart for a portion of a method for setting
link parameters in a WiFi link, according to an embodiment of the
present disclosure;
[0028] FIG. 3 is a flowchart for a portion of a method for setting
link parameters in a WiFi link, according to an embodiment of the
present disclosure;
[0029] FIG. 4 is a table of signal to interference and noise ratio
(in dB) required for various modes of operation, for a 1458 byte
packet size, according to an embodiment of the present
disclosure;
[0030] FIG. 5 is a table of transmit power level for different
modes of operation, according to an embodiment of the present
disclosure; and
[0031] FIG. 6 is a table of signal to interference and noise ratio
(in dB) required for various modes of operation, taking into
account transmit power differences, according to an embodiment of
the present disclosure.
DETAILED DESCRIPTION
[0032] The detailed description set forth below in connection with
the appended drawings is intended as a description of exemplary
embodiments of a system and method for setting link parameters in a
WiFi link provided in accordance with the present disclosure and is
not intended to represent the only forms in which the present
disclosure may be constructed or utilized. The description sets
forth the features of the present disclosure in connection with the
illustrated embodiments. It is to be understood, however, that the
same or equivalent functions and structures may be accomplished by
different embodiments that are also intended to be encompassed
within the scope of the disclosure. As denoted elsewhere herein,
like element numbers are intended to indicate like elements or
features.
[0033] FIG. 1 is a flowchart for a portion of a method for setting
link parameters in a WiFi link, according to an embodiment of the
present disclosure. Referring to FIG. 1, in some embodiments, a
method for setting link parameters in a WiFi link begins with
setting, for each combination of (i) the number of spatial streams
to be transmitted, and (ii) the transmission bandwidth, a reference
signal to interference and noise ratio, as discussed in further
detail below, forming a table, for example. For example, a beacon
signal may be received (at 105), and a reference signal to
interference and noise ratio may be calculated (at 110) based on
the signal to interference and noise ratio measured for the beacon.
As used herein, "signal to interference and noise ratio" may be
abbreviated to "SINR", "SNR", "snr", or "Snr". The calculating of
the reference signal to interference and noise ratio may include
adjusting the signal to interference and noise ratio value to 20
MHz for adaptive bandwidth allocation and for adaptive number of
spatial streams, as follows:
refSnrLinear(Nss,BW)=(snr of Beacon*.sup.2.sup.BW-1)*(Maximum
Nss)/Nss
saving refSnr(Nss,BW)=10*log 10(refSnrLinear(Nss,BW)).
[0034] Where Maximum Nss is maximum number of supported spatial
streams at the device, Nss is number of spatial stream, and BW
represents bandwidth index.
[0035] FIG. 2 is a flowchart for a portion of a method for setting
link parameters in a WiFi link, according to an embodiment of the
present disclosure. Referring to FIG. 2, an adjustment may be
formed, based on acknowledgment signals and negative acknowledgment
signals received (as part of a block acknowledgement (BA), at 205),
in response to transmitted signals, with the estimated signal to
interference and noise ratio, for the current combination of the
number of spatial streams and the transmission bandwidth, generally
being adjusted upwards when the acknowledgment signals and negative
acknowledgment signals indicate a low packet error rate, and
generally being adjusted downwards when the acknowledgment signals
and negative acknowledgment signals indicate a high packet error
rate. The method may then add an adjustment (at 210) to some (or
all) of the reference signal to interference and noise ratios, to
form a table of estimated signal to interference and noise ratios,
as discussed in further detail below. In some cases, exceptions to
the above-described adjustment process are made, as discussed in
further detail below, to avoid the method becoming "stuck" at one
combination of the number of spatial streams and the transmission
bandwidth in certain circumstances.
[0036] FIG. 3 is a flowchart for a portion of a method for setting
link parameters in a WiFi link, according to an embodiment of the
present disclosure. Once a table of estimated signal to
interference and noise ratios is available (having been generated
using the methods of FIGS. 1 and 2), the method may proceed as
illustrated in FIG. 3, to identify the number of spatial streams,
bandwidth, and modulation coding scheme to be used for a
transmission. Before the transmission starts, the throughput is
calculated for each combination of the number of spatial streams
and the transmission bandwidth. This calculation is performed
within two nested loops, including an outer loop (at 315 through
335) that iterates over all values of the number of spatial
streams, and an inner loop (at 315 through 330) that iterates over
all values of the bandwidth. A subsequent bandwidth and a
subsequent Nss are selected (at 330 and 335, respectively) at each
iteration of the inner and outer loops, respectively. The
throughput is calculated, at 315, for each combination of the
number of spatial streams and the transmission bandwidth, and
compared to a greatest value found so far.
SINReff(Nss,BW)=refSnr(Nss,BW)+deltaSnr(Nss,BW)
[0037] and maximum MCS may then be obtained based on SINReff.
[0038] If the current value exceeds, at 320, the previously found
maximum throughput, then the current, newly found, maximum value of
the throughput is saved, at 325, along with the corresponding
values of the number of spatial streams and the bandwidth.
[0039] The calculating of the throughput, for each iteration of the
inner loop, may be performed as follows. For a combination of the
number of spatial streams and the transmission bandwidth, the
estimated signal to interference and noise ratio may be obtained
from the table of estimated signal to interference and noise ratios
generated according to the method of FIG. 2. FIG. 4 is a table of
signal to interference and noise ratio (in dB) required for various
modes of operation, for a 1458 byte packet size, according to an
embodiment of the present disclosure. The estimated signal to
interference and noise ratio may be used to identify the maximum
modulation coding scheme that may be used, using the table of FIG.
4; once the modulation coding scheme has been selected, the
throughput may be calculated, based on the modulation coding
scheme, the number of spatial streams, the transmission bandwidth.
In the table of FIG. 4, the first (left-most) column contains the
index of modulation coding scheme; the third, fifth, and seventh
columns contain the signal to interference and noise ratio (in dB)
required for the modulation coding scheme shown in the first column
if convolutional code (CC) is used, and the modulation coding
schemes shown in the second, fourth, and sixth columns,
respectively. The eighth column shows the signal to interference
and noise ratio (in dB) required for the modulation and coding
scheme shown in the first column if low-density parity-check (LDPC)
code is used.
[0040] Some embodiments of the present disclosure try to maintain a
target packet error rate (PER) by estimating an effective signal to
interference and noise ratio (SINReff) (which may be referred to
herein as an "estimated signal to interference and noise ratio").
In some embodiments the method begins from a reference SINR, and
adjusts an estimated signal to interference and noise ratio (SINR)
based on a delta signal-to-noise ratio (delta SNR), which may in
turn be based on acknowledgement (ACK) and negative acknowledgement
(NACK) signals of a transmitted packet.
[0041] In some embodiments, different numbers of spatial streams
(Nss, e.g., different ranks) and different bandwidths (BW, e.g., 20
MHz, 40 MHz, 60 MHz, and 80 MHz bandwidths) may have different
SINReff that can be estimated separately.
[0042] In operation, the system may calculate an estimated signal
to interference and noise ratio for each possible combination of
(i) the number of spatial streams and (ii) the bandwidth, as
follows:
SINReff(Nss,BW)=refSnr(Nss,BW)+deltaSnr(Nss,BW)
[0043] where refSnr(Nss,BW) is a reference signal to interference
and noise ratio (discussed in further detail below), and
deltaSnr(Nss,BW) is an offset that is periodically updated.
[0044] When acknowledgment signals and negative acknowledgment
signals are received, the system may adjust the estimated signal to
interference and noise ratio, for the number of spatial streams and
the bandwidth currently being used, based on the number of
acknowledgment signals and on the number of negative acknowledgment
signals received. For example, the AMPDU (Aggregated MAC Protocol
Data Unit) Tx Status may be evaluated to calculate a current PER
(packet error rate) based on a number of successful MPDUs (MAC
Protocol Data Units) and a number of failed MPDUs. For example, the
system may adjust the offset according to the equation:
deltaSnr(Nss,BW)+=(1-PER)*snrStep/(1/targetPer-1)+PER*(-snrStep),
[0045] (i.e., an adjustment equal to
(1-PER)*snrStep/(1/targetPer-1)+PER*(-snrStep) may be added to the
offset), where Nss is an index for the transmitted number of
streams, BW is an index for the transmitted bandwidth, snrStep is
an SNR step size (which acts as an adjustment rate parameter)
(which may be set to 2 dB), targetPer is a target packet error rate
(or "target error rate") (e.g. 10%), and PER is an error rate (or
an "estimated error rate") (e.g., a packet error rate) which may be
based on the current packet from BA. If the current packet includes
only one media access control (MAC) protocol data unit (MPDU), then
the packet error rate may be 1 or 0. In some embodiments, use of
the above equation may result in frequent changes of modulation
coding scheme. This effect may be reduced by using, instead of a
constant targetPer, the following:
targetPer(X)=(8-X)/(56+X),
[0046] where X is a number of consecutive errors.
[0047] In some embodiments, the offset may be adjusted only for the
number of spatial streams and the bandwidth currently being used,
and for certain other combinations of the number of spatial streams
and the bandwidth, (e.g., for (Nss+1,BW) and for (Nss,BW+1), as
discussed in further detail below). For other combinations of the
number of spatial streams and the bandwidth, the offset may remain
the same, or no adjustment may be added to the offset.
[0048] In some embodiments, it may be desirable to limit the
maximum and minimum values deltaSnr may take. In some embodiments,
the method implements a restriction not to increase deltaSnr when
(i) the packet error rate is less than the target error rate (ii),
the current modulation coding scheme (MCS) is equal to the maximum
modulation coding scheme, and (iii) the offset (deltaSnr) exceeds a
first threshold; the adjustment may be set to zero in this
circumstance.
[0049] Similarly, the method may implement a restriction not to
decrease deltaSnr when (i) the packet error rate is greater than
the target error rate, (ii) the current modulation coding scheme
(MCS) is equal to the minimum modulation coding scheme, and (iii)
the offset (deltaSnr) is less than a second threshold (less than
the first threshold, e.g., less than zero); the adjustment may also
be set to zero in this circumstance.
[0050] When the reference signal to interference and noise ratio is
underestimated, it may be possible for the number of spatial
streams to become "stuck", i.e., for the number of spatial streams
used to remain unchanged even though a larger number of spatial
streams may provide better performance. In some embodiments, to
avoid this behavior, the offset for the next higher number of
spatial streams (deltaSnr(Nss+1,BW)) may be increased when (i) the
packet error rate is less than the target error rate and (ii) the
current modulation coding scheme exceeds a certain MCS (e.g., MCS
7).
[0051] When the reference signal to interference and noise ratio
for a certain bandwidth is not correctly estimated, then, in some
embodiments, it may be adjusted. In order to change from an
incorrect bandwidth, when the bandwidth is less than the bandwidth
of the basic service set (BSS), the present system may increase the
offset for the next higher bandwidth (deltaSnr(Nss,BW+1)) when (i)
the packet error rate is less than the target error rate and (ii)
the current MCS is greater than a certain MCS (e.g. MCS 7). The
bandwidth of the BSS may be the maximum bandwidth that can be used
with the AP. The AP may set its maximum bandwidth to be used for
operation. It may change the BSS bandwidth by updating it and
informing it through the beacon.
[0052] The reference signal to interference and noise ratio
(refSnr(Nss,BW)) may be a stored signal to interference and noise
ratio that may be updated by feedback or measured during previous
data reception. For example, acknowledgement signals (ACK), request
to send (RTS) signals, clear to send (CTS) signals, or a beacon
signal may be used to determine the reference signal to
interference and noise ratio. For example, a beacon signal may be
employed by a non-access point station (non-AP STA). The uplink
SINR may be the relevant information, but it may be information
that the non-AP STA does not have direct access to. Accordingly,
the uplink SINR may be estimated based on the reference SNR and the
delta SNR. As such, the reference SNR may be a starting point and
the delta SNR an adjustment to it.
[0053] If all interference levels are similar for the operating
bandwidth or if a non-AP STA does not have the capability to
measure the signal to interference and noise ratio per 20 MHz
bandwidth, then refSnr(Nss,1) may be derived from 20 MHz reference
signal to interference and noise ratio (if this is measured from
the beacon), and the reference signal to interference and noise
ratio may be reduced by 3 dB or 6 dB each, as the bandwidth is
increased to 40 MHz or 80 MHz, respectively. If the non-AP STA is
capable of measuring the signal to interference and noise ratio per
20 MHz bandwidth, and if narrow band interference from overlapping
basic service sets (OBSS) may be present, the reference signal to
interference and noise ratio may be measured and stored for
different bandwidths. This may be accomplished by measuring the
beacon signal to interference and noise ratio, using it as the
primary 20 MHz signal to interference and noise ratio, and
averaging the detected received signal strength indicator (RSSI)
level per 20 MHz bandwidth. This may be accomplished during a per
20 MHz clear channel assessment energy detected (CCA-ED)
measurement, when the primary 20 MHz is idle. Letting RSSI1 (NI1)
be the RSSI measured for the primary 20 MHz when it is idle,
letting refSnr(Nss,1) be the signal to interference and noise ratio
for the beacon, and letting RSSIi(NIi) be the RSSI measured for the
i-th 20 MHz band, the following may be derived:
refSnr(Nss,1)=Ptx(dBm)+PL(dBm)-NI1
Ptx(dBm)+PL(dBm)=refSnr(Nss,1)+NI1
Sinr_i=refSnr(Nss,1)+NI1-NIi
[0054] Then, the primary 20 MHz/40 MHz/80 MHz refSnr may be
obtained using the following.
[0055] For 20 MHz:
refSnr(Nss,1)=refSnr_Beacon,
[0056] for 40 MHz:
refSnr(Nss,2)=pow2db((db2pow(refSnr(Nss,1))+db2pow(Sinr_2))/4),
and
[0057] for 80 MHz:
pow2db((db2pow(refSnr(Nss,1))+db2pow(Sinr_2)+db2pow(Sinr_3)+db2pow(Sinr_-
4)))/16),
respectively.
[0058] In some embodiments, NIi may be measured using a moving
average so that it can capture current load information.
[0059] In some embodiments, downlink and uplink performance may
differ from each other. Also, different ranks (i.e., different
numbers of spatial streams) may have different values for the
reference signal to interference and noise ratio. Even though a
method according to some embodiments may converge without
adjustment (except when conditions are at an extreme of good or bad
conditions), some embodiments may estimate a closer value based on
available information such as a number of antennas and a transmit
power level. In one embodiment, the present system and method
includes adjusting a refSnr for different numbers of spatial
streams when a reference signal to interference and noise ratio is
available or estimated. A geometry signal to interference and noise
ratio may be obtained from received signal strength, using, for
example, the following relations:
refSnr(1)=geoSnr, then
refSnr(Nss)=refSnr(1)+pow2db(max((Nrx-Nss+1)/Nss,1)).
[0060] After determining an effective signal to interference and
noise ratio, some embodiments may estimate the packet error rate
for each MCS (e.g., using PHY abstraction), and thus the expected
throughput accordingly. Then, a transmitter may select the BW, MCS
and Nss that is expected to result in the greatest throughput.
[0061] FIG. 5 is a table of transmit power level for different
modes of operation, according to an embodiment of the present
disclosure. According to one embodiment, the present system may
transmit different power levels to meet an error vector magnitude
(EVM) requirement, as transmit power for different bandwidths,
different modulation levels, and different PHY modes may be
different, as shown in FIG. 5. FIG. 6 is a table of signal to
interference and noise ratio (in dB) required for various modes of
operation, taking into account such transmit power differences,
according to an embodiment of the present disclosure. For example,
in some embodiments, the present system may handle different
transmit power levels by adjusting the reference signal to
interference and noise ratio by -1 dB for a bandwidth of 40 MHz,
adjusting the reference signal to interference and noise ratio by
-2 dB for a bandwidth of 80 MHz, and adding -1 dB for reference
curves above 64QAM modulation level, for example to compensate for
the difference between MCS5 and MCS9.
[0062] In some embodiments, a processing circuit may perform the
methods of some embodiments, or portions of such methods. The term
"processing circuit" is used herein to mean any combination of
hardware, firmware, and software, employed to process data or
digital signals. Processing circuit hardware may include, for
example, application specific integrated circuits (ASICs), general
purpose or special purpose central processing units (CPUs), digital
signal processors (DSPs), graphics processing units (GPUs), and
programmable logic devices such as field programmable gate arrays
(FPGAs). In a processing circuit, as used herein, each function is
performed either by hardware configured, i.e., hard-wired, to
perform that function, or by more general purpose hardware, such as
a CPU, configured to execute instructions stored in a
non-transitory storage medium. A processing circuit may be
fabricated on a single printed circuit board (PCB) or distributed
over several interconnected PCBs. A processing circuit may contain
other processing circuits; for example a processing circuit may
include two processing circuits, an FPGA and a CPU, interconnected
on a PCB.
[0063] It will be understood that, although the terms "first",
"second", "third", etc., may be used herein to describe various
elements, components, regions, layers and/or sections, these
elements, components, regions, layers and/or sections should not be
limited by these terms. These terms are only used to distinguish
one element, component, region, layer or section from another
element, component, region, layer or section. Thus, a first
element, component, region, layer or section discussed herein could
be termed a second element, component, region, layer or section,
without departing from the spirit and scope of some
embodiments.
[0064] Spatially relative terms, such as "beneath", "below",
"lower", "under", "above", "upper" and the like, may be used herein
for ease of description to describe one element or feature's
relationship to another element(s) or feature(s) as illustrated in
the figures. It will be understood that such spatially relative
terms are intended to encompass different orientations of the
device in use or in operation, in addition to the orientation
depicted in the figures. For example, if the device in the figures
is turned over, elements described as "below" or "beneath" or
"under" other elements or features would then be oriented "above"
the other elements or features. Thus, the example terms "below" and
"under" can encompass both an orientation of above and below. The
device may be otherwise oriented (e.g., rotated 90 degrees or at
other orientations) and the spatially relative descriptors used
herein should be interpreted accordingly. In addition, it will also
be understood that when a layer is referred to as being "between"
two layers, it can be the only layer between the two layers, or one
or more intervening layers may also be present.
[0065] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
some embodiments. As used herein, the terms "substantially,"
"about," and similar terms are used as terms of approximation and
not as terms of degree, and are intended to account for the
inherent deviations in measured or calculated values that would be
recognized by those of ordinary skill in the art. As used herein,
the term "major component" refers to a component that is present in
a composition, polymer, or product in an amount greater than an
amount of any other single component in the composition or product.
In contrast, the term "primary component" refers to a component
that makes up at least 50% by weight or more of the composition,
polymer, or product. As used herein, the term "major portion", when
applied to a plurality of items, means at least half of the
items.
[0066] As used herein, the singular forms "a" and "an" are intended
to include the plural forms as well, unless the context clearly
indicates otherwise. It will be further understood that the terms
"comprises" and/or "comprising", when used in this specification,
specify the presence of stated features, integers, steps,
operations, elements, and/or components, but do not preclude the
presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof. As
used herein, the term "and/or" includes any and all combinations of
one or more of the associated listed items. Expressions such as "at
least one of," when preceding a list of elements, modify the entire
list of elements and do not modify the individual elements of the
list. Further, the use of "may" when describing some embodiments
refers to "one or more embodiments of the present disclosure".
Also, the term "exemplary" is intended to refer to an example or
illustration. As used herein, the terms "use," "using," and "used"
may be considered synonymous with the terms "utilize," "utilizing,"
and "utilized," respectively.
[0067] It will be understood that when an element or layer is
referred to as being "on", "connected to", "coupled to", or
"adjacent to" another element or layer, it may be directly on,
connected to, coupled to, or adjacent to the other element or
layer, or one or more intervening elements or layers may be
present. In contrast, when an element or layer is referred to as
being "directly on", "directly connected to", "directly coupled
to", or "immediately adjacent to" another element or layer, there
are no intervening elements or layers present.
[0068] Any numerical range recited herein is intended to include
all sub-ranges of the same numerical precision subsumed within the
recited range. For example, a range of "1.0 to 10.0" is intended to
include all subranges between (and including) the recited minimum
value of 1.0 and the recited maximum value of 10.0, that is, having
a minimum value equal to or greater than 1.0 and a maximum value
equal to or less than 10.0, such as, for example, 2.4 to 7.6. Any
maximum numerical limitation recited herein is intended to include
all lower numerical limitations subsumed therein and any minimum
numerical limitation recited in this specification is intended to
include all higher numerical limitations subsumed therein.
[0069] As used herein, the term "or" should be interpreted as
"and/or", such that, for example, "A or B" means any one of "A" or
"B" or "A and B"
[0070] Although exemplary embodiments of a system and method for
setting link parameters in a WiFi link have been specifically
described and illustrated herein, many modifications and variations
will be apparent to those skilled in the art. Accordingly, it is to
be understood that a system and method for setting link parameters
in a WiFi link constructed according to principles of this
disclosure may be embodied other than as specifically described
herein. Some embodiments are also defined in the following claims,
and equivalents thereof.
* * * * *