U.S. patent application number 14/842659 was filed with the patent office on 2017-03-02 for time-controlled spatial interference rejection.
The applicant listed for this patent is QUALCOMM Incorporated. Invention is credited to Louay Jalloul.
Application Number | 20170063574 14/842659 |
Document ID | / |
Family ID | 56555736 |
Filed Date | 2017-03-02 |
United States Patent
Application |
20170063574 |
Kind Code |
A1 |
Jalloul; Louay |
March 2, 2017 |
TIME-CONTROLLED SPATIAL INTERFERENCE REJECTION
Abstract
A dual-modem device opportunistically switches between spatial
filtering techniques to enhance the received symbol estimates based
at least in part on identifying, at a first modem, an interfering
communication from a second modem. A WLAN modem can determine the
timing of a WWAN transmission from a coexisting WWAN modem that
interferes with a WLAN transmission and toggle between MRC and IRC
receive techniques based at least in part on the determined
timing.
Inventors: |
Jalloul; Louay; (San Jose,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
QUALCOMM Incorporated |
San Diego |
CA |
US |
|
|
Family ID: |
56555736 |
Appl. No.: |
14/842659 |
Filed: |
September 1, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 88/06 20130101;
H04W 84/12 20130101; H04J 11/0023 20130101; H04L 1/00 20130101;
H04W 72/1215 20130101; H04B 15/00 20130101; H04B 1/10 20130101;
H04W 24/08 20130101; H04L 25/021 20130101 |
International
Class: |
H04L 25/02 20060101
H04L025/02; H04B 1/10 20060101 H04B001/10; H04B 15/00 20060101
H04B015/00; H04W 24/08 20060101 H04W024/08 |
Claims
1. A method for wireless communication in a wireless device,
comprising: determining a timing of an interfering transmission by
a first modem of the wireless device according to a first radio
access technology (RAT); receiving a control message at a second
modem of the wireless device, the control message indicating the
determined timing of the interfering transmission; and toggling a
use of interference rejection combining (IRC) during receive
operations of the second modem of the wireless device according to
a second RAT, wherein the toggling is based at least in part on the
determined timing of the interfering transmission.
2. The method of claim 1, wherein toggling the use of IRC during
the receive operations at the second modem comprises: using IRC to
receive a signal at the second modem during the interfering
transmission by the first modem.
3. The method of claim 1, wherein toggling the use of IRC during
the receive operations at the second modem is further based at
least in part on a signal strength of the interfering
transmission.
4. The method of claim 3, wherein toggling the use of IRC during
the receive operations of the second modem comprises: using IRC to
receive a signal at the second modem when the signal strength of
the interfering transmission is above a threshold.
5. The method of claim 1, wherein toggling the use of IRC during
the receive operations of the second modem comprises: using maximal
ratio combining (MRC) to receive a signal at the second modem when
the first modem is not transmitting the interfering
transmission.
6. The method of claim 1, further comprising: determining a channel
estimate of a signal received by the second modem; estimating a
covariance of the interfering transmission using the determined
channel estimate; and determining a weight vector for the IRC using
the estimated covariance.
7. The method of claim 6, wherein the covariance of the interfering
transmission is estimated based at least in part on a training
field of a preamble associated with the signal received by the
second modem.
8. The method of claim 6, further comprising: dividing a bandwidth
of the signal received by the second modem into multiple subbands;
wherein estimating the covariance of the interfering signal is
performed by estimating the covariance over each of the multiple
subbands.
9. The method of claim 8, wherein determining the weight vector for
the IRC comprises: determining a respective weight vector for the
IRC for each of the multiple subbands using the estimated
covariance for the corresponding subband.
10. A communications device comprising: coexisting first and second
modems; a transmission timing identifier to determine a timing of
an interfering transmission by the first modem according to a first
radio access technology (RAT); a control line between the first
modem and the second modem to provide a control signal to the
second modem, the control signal indicating the determined timing
of the interfering transmission; and a filter selector to toggle a
use of interference rejection combining (IRC) during receive
operations of the second modem according to a second RAT, wherein
the toggling is based at least in part on the determined timing of
the interfering transmission.
11. The communication device of claim 10, wherein the filter
selector to toggle the use of IRC during the receive operations at
the second modem is further configured to: use IRC to receive a
signal at the second modem during the interfering transmission by
the first modem.
12. The communication device of claim 10, wherein toggling the use
of IRC during the receive operations at the second modem is further
based at least in part on a signal strength of the interfering
transmission.
13. The communication device of claim 12, wherein the filter
selector to toggle the use of IRC during the receive operations at
the second modem is further configured to: use IRC to receive a
signal at the second modem when the signal strength of the
interfering transmission is above a threshold.
14. The communication device of claim 10, wherein the filter
selector to toggle the use of IRC during the receive operations at
the second modem is further configured to: use maximal ratio
combining (MRC) to receive a signal at the second modem when the
first modem is not transmitting the interfering transmission.
15. The communication device of claim 10, further comprising: a
channel monitor to determine a channel estimate of a signal
received by the second modem; a weight generator to estimate a
covariance of the interfering transmission using the determined
channel estimate; and determine a weight vector for the IRC using
the estimated covariance.
16. The communication device of claim 15, wherein the covariance of
the interfering transmission is estimated based at least in part on
a training field of a preamble associated with the signal received
by the second modem.
17. The communication device of claim 15, further comprising: a
channel monitor to divide a bandwidth of the signal received by the
second modem into multiple subbands; wherein estimating the
covariance of the interfering signal is performed by estimating the
covariance over each of the multiple subbands.
18. The communication device of claim 17, wherein the weight
generator to determine the weight vector for the IRC is further
configured to: determine a respective weight vector for the IRC for
each of the multiple subbands using the estimated covariance for
the corresponding subband.
19-27. (canceled)
28. A non-transitory computer-readable medium storing
computer-executable code for wireless communication, the code
executable by a processor to: determine a timing of an interfering
transmission by a first modem of a wireless device according to a
first radio access technology (RAT); transmit a control signal to a
second modem of the wireless device, the control message indicating
the determined timing of the interfering transmission; and toggle a
use of interference rejection combining (IRC) during receive
operations of the second modem according to a second RAT, wherein
the toggling is based at least in part on the determined timing of
the interfering transmission.
29. The non-transitory computer-readable medium of claim 28,
wherein the code executable by the processor to toggle the use of
IRC during the receive operations at the second modem further
comprises code executable by the processor to: use IRC to receive a
signal at the second modem during the interfering transmission by
the first modem.
30. The non-transitory computer-readable medium of claim 28,
wherein the toggling is further based at least in part on a signal
strength of the interfering transmission.
Description
BACKGROUND
[0001] Field of the Disclosure
[0002] The following relates generally to wireless communication,
and more specifically to techniques for time-controlled spatial
interference rejection at a wireless local area network (WLAN)
receiver.
[0003] Description of Related Art
[0004] Wireless communications systems are widely deployed to
provide various types of communication content such as voice,
video, packet data, messaging, broadcast, and so on. These systems
are often multiple-access systems capable of supporting
communication with multiple users by sharing the available system
resources (e.g., time, frequency, and power). WLANs are an example
of such systems and are widely deployed and used. Other examples of
such multiple-access systems include code-division multiple access
(CDMA) systems, time-division multiple access (TDMA) systems,
frequency-division multiple access (FDMA) systems, and orthogonal
frequency-division multiple access (OFDMA) systems.
[0005] A WLAN, such as a Wi-Fi (IEEE 802.11) network, includes one
or more access points (APs). The AP simultaneously supports
communications for multiple mobile devices or stations (STAs) over
a shared radio frequency spectrum. A WLAN can operate in the
presence of a wireless wide area network (WWAN) network, such as an
LTE/LTE-A network. The WWAN network includes one or more base
stations that support communication from multiple mobile devices or
UEs. WWAN communications occur over dedicated radio frequency
spectrum, shared radio frequency spectrum, or a combination of the
two. Some STAs are equipped with both a WLAN modem and a WWAN modem
to support both WLAN and WWAN communications. In some examples,
transmissions to/from one modem (e.g., the WWAN modem) interfere
with reception at the other modem (e.g., the WLAN modem).
[0006] STAs are equipped with interference mitigation techniques,
such as time-domain and frequency domain filtering (e.g., spatial
filtering). Certain spatial filtering techniques achieve enhanced
performance based at least in part on the type of interference seen
at a receiver.
SUMMARY
[0007] A multi-mode device opportunistically switches between
spatial filtering techniques to enhance the received symbol
estimates based at least in part on identifying, at a first modem,
timing information about an interfering communication from a second
modem. For example, a WLAN modem determines the timing of a WWAN
transmission from a coexisting WWAN modem that interferes with a
WLAN transmission. The WLAN modem toggles between maximal ratio
combining (MRC) and interference rejection cancellation (IRC)
receive techniques based at least in part on the determined timing.
Thus, the WLAN modem receives a signal from the WWAN modem
indicating the WWAN transmission timing. Accordingly, the WLAN
modem determines that an interfering transmission is occurring and
toggles the receiver mode to use IRC for subsequent reception. The
WLAN modem generates IRC weights based at least in part on a
computed interference covariance and a channel estimate that is
computed during a training symbol field of a received WLAN
frame.
[0008] A method of wireless communication is described. The method
includes coexisting first and second modes, a transmission timing
identifier to determine a timing of an interfering transmission by
the first modem according to a first radio access technology (RAT),
and a filter selector to toggle a use of interference rejection
combining (IRC) during receive operations of the second modem
according to a second RAT, wherein toggling is based at least in
part on the determined timing of the interfering transmission.
[0009] A communications device is described. The communications
device includes means for determining a timing of an interfering
transmission by the first modem according to a first radio access
technology (RAT), and means for toggling a use of interference
rejection combining (IRC) during receive operations of the second
modem according to a second RAT, wherein toggling is based at least
in part on the determined timing of the interfering
transmission.
[0010] Another communications device is described. The
communications device may include a processor, memory in electronic
communication with the processor, and instructions stored in the
memory and operable, when executed by the processor, to cause the
apparatus to determine a timing of an interfering transmission by
the first modem according to a first radio access technology (RAT),
and toggle a use of interference rejection combining (IRC) during
receive operations of the second modem according to a second RAT,
wherein toggling is based at least in part on the determined timing
of the interfering transmission.
[0011] A non-transitory computer-readable medium comprising
coexisting first and second modems and storing code for wireless
communication is described. The code may include instructions
executable to determine a timing of an interfering transmission by
the first modem according to a first radio access technology (RAT),
and toggle a use of interference rejection combining (IRC) during
receive operations of the second modem according to a second RAT,
wherein toggling is based at least in part on the determined timing
of the interfering transmission.
[0012] In some examples of the method, apparatuses, or
non-transitory computer-readable medium described herein, toggling
the use of IRC during the receive operations at the second modem
includes using IRC to receive a signal at the second modem during
the interfering transmission by the first modem. Additionally or
alternatively, in some examples toggling the use of IRC during the
receive operations at the second modem is further based at least in
part on a signal strength of the interfering transmission.
[0013] In some examples of the method, apparatuses, or
non-transitory computer-readable medium described herein, toggling
the use of IRC during the receive operations of the second modem
comprises using IRC to receive a signal at the second modem when
the signal strength of the interfering transmission is above a
predefined threshold. Additionally or alternatively, in some
examples toggling the use of IRC during the receive operations of
the second modem comprises using maximal ratio combining (MRC) to
receive a signal at the second modem when the first modem is not
transmitting the interfering transmission.
[0014] Some examples of the method, apparatuses, or non-transitory
computer-readable medium described herein may further include
processes, features, means, or instructions for determining a
channel estimate of a signal received by the second modem,
estimating a covariance of the interfering transmission using the
determined channel estimate, and determining a weight vector for
the IRC using the estimated covariance. Additionally or
alternatively, in some examples the covariance of the interfering
transmission is estimated based at least in part on a training
field of a preamble associated with the signal received by the
second modem.
[0015] Some examples of the method, apparatuses, or non-transitory
computer-readable medium described herein may further include
processes, features, means, or instructions for dividing a
bandwidth of the signal received by the second modem into multiple
subbands, and the estimating the covariance of the interfering
signal is performed by estimating the covariance over each of the
multiple subbands. Additionally or alternatively, in some examples
the determining the weight vector for the IRC comprises determining
a respective weight vector for the IRC for each of the multiple
subbands using the estimated covariance for the corresponding
subband.
[0016] Some examples of the methods, apparatuses, or non-transitory
computer-readable media described herein further include processes,
features, means, or instructions for time-controlled spatial
interference rejection. Further scope of the applicability of the
described systems, methods, apparatuses, or computer-readable media
will become apparent from the following detailed description,
claims, and drawings. The detailed description and specific
examples are given by way of illustration only, since various
changes and modifications within the scope of the description will
become apparent to those skilled in the art.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] A further understanding of the nature and advantages of the
present disclosure may be realized by reference to the following
drawings. In the appended figures, similar components or features
may have the same reference label. Further, various components of
the same type may be distinguished by following the reference label
by a dash and a second label that distinguishes among the similar
components. If just the first reference label is used in the
specification, the description is applicable to any one of the
similar components having the same first reference label
irrespective of the second reference label.
[0018] FIG. 1 illustrates an example of a wireless communications
system that supports time-controlled spatial interference rejection
in accordance with various aspects of the present disclosure;
[0019] FIG. 2 illustrates an example of a wireless communications
subsystem for time-controlled spatial interference rejection in
accordance with various aspects of the present disclosure;
[0020] FIGS. 3A to 3C illustrate examples of shared channels that
support time-controlled spatial interference rejection in
accordance with various aspects of the present disclosure;
[0021] FIG. 4 illustrates an example of a dual modem configuration
that supports time-controlled spatial interference rejection in
accordance with various aspects of the present disclosure;
[0022] FIG. 5 illustrates an example of a process flow for
time-controlled spatial interference rejection in accordance with
various aspects of the present disclosure;
[0023] FIG. 6A illustrates an example of a partitioned channel for
time-controlled spatial interference rejection in accordance with
various aspects of the present disclosure;
[0024] FIG. 6B illustrates an example of subband processing
component for time-controlled spatial interference rejection in
accordance with various aspects of the present disclosure;
[0025] FIGS. 7A and 7B show block diagrams of an example STA that
supports time-controlled spatial interference rejection in
accordance with various aspects of the present disclosure; and
[0026] FIG. 8 shows a flow chart that illustrates one example of a
method for wireless communication, in accordance with various
aspects of the present disclosure.
DETAILED DESCRIPTION
[0027] According to the present disclosure, a multi-mode device
opportunistically switches between spatial filtering techniques to
enhance the received symbol estimates based at least in part on
identifying, at a first modem, an interfering communication from a
second modem. Aspects of the disclosure are described in the
context of a wireless communication system. For example, a STA that
supports WLAN and WWAN communications can communicate with both an
AP and a base station. The STA toggles an IRC receive chain "on"
for a WLAN transmission, while the STA concurrently transmits a
WWAN communication. The WWAN modem enables the IRC receive chain
based at least in part on determining the transmission timing for
the WWAN communication. The WWAN modem determines a channel
estimate and interference covariance measurement based at least in
part on the location of the WWAN communication in relation to the
received WLAN communication.
[0028] In one example, a STA has a dual-modem configuration that
includes an LTE modem and a Wi-Fi modem. The Wi-Fi modem determines
an transmission timing for communication from/to the LTE modem.
When the LTE modem begins transmitting, the Wi-Fi modem
concurrently employs an IRC receiver. The Wi-Fi modem also
identifies whether the LTE transmission overlaps with the LTF field
of the Wi-Fi transmission that is used for channel estimation. The
Wi-Fi modem uses the LTF field of the Wi-Fi transmission to
determine a channel estimate with or without including the
interference from the LTE transmission. The Wi-Fi modem then
generates the interference covariance associated with the LTE
transmission based at least in part on determining whether the
interference overlaps with the LTF field. The channel estimate and
interference covariance are used to determine IRC weights for
processing the Wi-Fi transmission and decoding the Wi-Fi data.
[0029] When the LTE modem ceases transmissions, the Wi-Fi modem
toggles the IRC receiver off and uses an MRC receiver. The MRC
receiver determines MRC weights and applies processes Wi-Fi
transmission while there is not interference from the LTE modem.
These and other aspects of the disclosure are further illustrated
by and described with reference to apparatus diagrams, system
diagrams, and flowcharts.
[0030] FIG. 1 illustrates an example of a wireless communications
system 100 that supports time-controlled spatial interference
rejection in accordance with various aspects of the present
disclosure. The WLAN 100 includes an access point (AP) 105 and STAs
110 labeled as STA 1 through STA 7. The STAs 110 can be mobile
handsets, tablet computers, personal digital assistants (PDAs),
other handheld devices, netbooks, notebook computers, tablet
computers, laptops, desktop computers, display devices (e.g., TVs,
computer monitors, etc.), printers, etc. While only one AP 105 is
illustrated, the WLAN 100 can have multiple APs 105. STAs 110, can
also be referred to as a mobile stations (MS), mobile devices,
access terminals (ATs), user equipment (UEs), subscriber stations
(SSs), or subscriber units. The STAs 110 associate and communicate
with the AP 105 via a communication link 115. Each AP 105 has a
coverage area 125 such that STAs 110 within that area are within
range of the AP 105. The STAs 110 are dispersed throughout the
coverage area 125. Each STA 110 is stationary, mobile, or a
combination thereof Some STAs 110, such as STA 110-a, also
communicate with a base station 150 over a wireless wide area
network (WWAN). A WWAN may utilize shared spectrum, dedicated
spectrum, or a combination of the two for communications to/from a
STA.
[0031] Although not shown in FIG. 1, a STA 110 can be covered by
more than one AP 105 and can therefore associate with multiple APs
105 at different times. A single AP 105 and an associated set of
STAs 110 is referred to as a basic service set (BSS). An extended
service set (ESS) is a set of connected BSSs. A distribution system
(DS) (not shown) is used to connect APs 105 in an extended service
set. A coverage area 125 for an AP 105 can be divided into sectors
making up only a portion of the coverage area (not shown). The WLAN
100 includes APs 105 of different types (e.g., metropolitan area,
home network, etc.), with varying sizes of coverage areas and
overlapping coverage areas for different technologies. Although not
shown, other devices can communicate with the AP 105.
[0032] While the STAs 110 are capable of communicating with each
other through the AP 105 using communication links 115, STAs 110
can also communicate directly with each other via direct wireless
communication links 120. Direct wireless communication links can
occur between STAs 110 regardless of whether any of the STAs is
connected to an AP 105. Examples of direct wireless communication
links 120 include Wi-Fi Direct connections, connections established
by using a Wi-Fi Tunneled Direct Link Setup (TDLS) link, and other
peer-to-peer (P2P) group connections.
[0033] The STAs 110 and APs 105 shown in FIG. 1 communicate
according to the WLAN radio and baseband protocol including
physical (PHY) and medium access control (MAC) layers from IEEE
802.11, and its various versions including, but not limited to,
802.11b, 802.11g, 802.11a, 802.11n, 802.11ac, 802.11ad, 802.11ah,
802.11z, etc. Some STAs 110 are capable of operating over both a
WWAN and WLAN network. For instance, STA 110-a communicates with
base station 150 via communication link 115. The WWAN network
utilizes one or both of shared and dedicated spectrum for
communications between base station 150 and STA 110-a. WWAN
communications are often scheduled by a central node, such as a
base station 150. WWAN communications over shared spectrum can also
be scheduled by a base station 150. For instance, the base station
150 schedules downlink and uplink subframes for transmissions
between base station 150 and STA 110-a. Additionally or
alternatively, STA 110-a can transmit a scheduling request to base
station 150 without scheduling from base station 150.
[0034] STAs 110 communicating over shared spectrum, such as a WLAN
network, use contention-based procedures prior to transmitting to
prevent collisions between transmissions from multiple STAs 110.
Request to Send (RTS)/Clear to Send (CTS) is one example of a
contention based procedure during which a STA 110 sends an RTS
frame to an AP 105. Once the recipient device receives the RTS
frame, the recipient device can confirm the communication link by
sending a CTS frame. After the CTS frame is received by the STA,
the STA begins transmitting data to the recipient device. In this
way, RTS/CTS messaging reduces frame collisions by enabling
devices, such as a STA 110 or AP 105, to in essence clear the
communication path before transmitting data. Enhanced Distributed
Channel Access (EDCA) is another contention-based procedure used to
transmit over shared spectrum. EDCA utilizes interframe spacing,
contention windows, and energy detection to prevent collisions
without pre-coordination.
[0035] Accordingly, WWAN communications also use contention-based
protocols to communicate over shared spectrum. In order to access
and transmit over a carrier that uses shared spectrum, STA 110-a
and base station 150 perform clear channel assessments (CCAs) prior
to transmitting. A CCA is conducted according to listen before talk
(LBT) parameters (e.g., contention window size, deferral period,
CCA threshold, etc.), and is associated with a duration during
which a WWAN device monitors the shared channel for transmission
activity. In one example, a base station 150 uses energy detection
techniques to determine if the channel is occupied, and after
determining the channel is clear, transmits downlink data over the
shared spectrum (e.g., 2.5 GHz and/or 5 GHz bands). The downlink
data includes both scheduling information for subsequent uplink
transmissions (e.g., designated uplink subframes) and data for the
STA 110-a. STA 110-a similarly performs CCA procedures prior to
transmitting uplink data during the scheduled uplink transmissions
periods. In cases where the base station 150 does not identify the
channel is clear, the base station 150 refrains from transmitting
until a successful CCA is performed. Despite using these contention
based techniques, WWAN communications over the shared spectrum
still interfere with WLAN communications over the shared spectrum.
For instance, out-of-band emissions associated with data
transmissions to/from base station 150 to STA 110-a interfere with
concurrent data reception at STA 110-a from AP 105.
[0036] A received signal y(f) is mathematically modeled as shown
below:
y(f)=h.sub.1(f)x.sub.1(f)+z(f)+n(f), (1)
where y(f) is the received N.sub.r.times.1 signal vector (e.g., a
WLAN signal); x.sub.1(f) is the modulation symbol during the data
region of the frame or a known pilot tone in the case of the
preamble region of the frame; h.sub.1(f) is the received
N.sub.r.times.1 channel (e.g., a shared channel) associated with
the desired signal; z(f) is the received N.sub.r.times.1
interfering signal (e.g., an WWAN transmission); and n(f) is the
received N.sub.r.times.1 thermal noise. The thermal noise
covariance R.sub.nn is shown below:
R.sub.nn=E.sub.f[n(f)n*(f)]=.sigma..sup.2I.sub.N.sub.r, (2)
where E.sub.f [.cndot.] is the expectation operation (or averaging)
over frequency tones and the interfering signal covariance R.sub.zz
is computed as:
R.sub.zz=E.sub.f[z(f)z*(f)]. (3)
The system model can be re-written as:
y(f)=h.sub.1(f)x.sub.1(f)+u(f), (4)
u(f)=z(f)+n(f), (5)
where u(f) is the combined noise and interference.
[0037] A STA 110 uses a myriad of techniques to mitigate
interference, such as z(f), at a receiver, one of which is
time-domain filtering. Another technique, for STAs 110 with
multiple antennas, is spatial filtering, which exploits the signals
received at each of N.sub.r antennas. Each received signal
experiences different channel conditions during the transmissions
process and can be combined at a STA 110 to create a refined
signal. Linear minimum mean-squared error (LMMSE), interference
rejection combining (IRC), and maximal-ratio combining (MRC) are
examples of interference mitigation techniques used by a STA 110.
MRC reconstructs a received signal based at least in part on the
corresponding channel conditions, while IRC reconstructs a received
signal based at least in part on the corresponding channel
conditions and interference over the channel. Both MRC and IRC
generate weight vectors that are applied to a received signal to
reconstruct the transmitted signal. The MRC receiver weights are
computed to be:
w.sub.MRC(f)=h.sub.1(f), (6)
and the soft symbol output (i.e., original symbol estimate) after
MRC is computed to be:
{circumflex over (x)}.sub.1,MRC(f)=w*.sub.MRC(f)y(f), (7)
It is assumed in (6) and (7) that the noise variance across the
receiver chains are identical. On the other hand the IRC receiver
weights are computed to be:
w.sub.MRC(f)=R.sub.uu.sup.-1h.sub.1(f), (8)
where the combined interference covariance R.sub.uu is given
as:
R.sub.uu-R.sub.zz+.sigma..sup.2I.sub.N.sub.r, (9)
and the soft symbol output for IRC is computed to be:
{circumflex over (x)}.sub.1,IRC(f)=w*.sub.IRC(f)y(f). (10)
[0038] In certain scenarios, MRC techniques provide enhanced symbol
estimates over IRC techniques and vice versa. For instance, MRC
techniques provide improved symbol estimates over IRC techniques
when interference is not present on a shared channel, while IRC
provides improved symbol estimates over MRC when interference, such
as a WWAN transmission, is present. In one example, a STA 110, such
as STA 110-a, opportunistically switches between spatial filtering
techniques to enhance the transmitted symbol estimate based at
least in part on identifying interference on the shared channel. In
one example, the WLAN modem determines the timing of a WWAN
transmission from the WWAN modem that is interfering or will
interfere with a WLAN transmission and toggles between MRC and IRC
techniques based at least in part on the determined timing. For
instance, the WWAN modem at STA 110-a sends a signal to the WLAN
modem at STA 110-a to indicate that the WWAN modem is transmitting.
Accordingly, the WLAN modem determines that an interfering
transmission is occurring and toggles the receiver mode to use IRC
for subsequent reception. The WLAN modem generates IRC weights
based at least in part on a computed interference covariance and a
channel estimate that is computed during a training symbol field of
a received WLAN frame.
[0039] FIG. 2 illustrates an example of a wireless communications
subsystem 200 for time-controlled spatial interference rejection in
accordance with various aspects of the present disclosure. Wireless
communications subsystem 200 includes STA 110-b, AP 105-a, and base
station 150-a which are examples of a STA 110, an AP 105, or a base
station 150 described above with reference to FIG. 1. In one
example STA 110-b is an example of STA 110-a, as described in FIG.
1, and toggles between spatial filtering techniques for data
reception. In this example, STA 110-b includes both a Wi-Fi modem
and an LTE modem and is capable of communicating using a Wi-Fi
network and a LTE network. Base station 150-a is an LTE device and
AP 105- is a Wi-Fi device. STA 110-b communicates with base station
150-a via communication link 205 and with AP 105-a via
communication link 215.
[0040] In a first example, STA 110-b transmits data to base station
150-a and the LTE modem transmits a control signal to the Wi-Fi
modem indicating that an LTE transmission is occurring.
Accordingly, the Wi-Fi modem toggles the spatial filtering
technique used at the Wi-Fi receiver to IRC. Subsequently, STA
110-b begins receiving a Wi-Fi transmission from AP 105-a. The
Wi-Fi transmission includes preamble fields, such as short training
fields (STFs), long training fields (LTFs), and signal fields
(SIGs). The symbols transmitted during an LTF are known to STA
110-b and are used to develop channel estimates. In this example,
the LTE transmissions continue throughout the Wi-Fi transmission,
and the Wi-Fi preamble includes an LTF that the Wi-Fi modem uses to
determine an estimate for the shared channel h.sub.1 (f). After
determining the shared channel estimate, the Wi-Fi modem also
determines a combined interference estimate
u(f)=y(f)-h.sub.1(f)x.sub.1(f), f.epsilon.F based at least in part
on the received signal y(f), the shared channel estimate
h.sub.1(f), and the known LTF signal/symbol x.sub.1. Wi-Fi modem
then determines the combined interference covariance
R uu = 1 F f .di-elect cons. F u ^ ( f ) u ^ * ( f ) .
##EQU00001##
Alternately, the interference covariance is computed by
R.sub.uu=R.sub.uu-R.sub.hh, where R.sub.hh is the estimated channel
correlation matrix. The IRC weights w.sub.IRC(f)=R.sub.uu.sup.-1
h.sub.1(f) are generated and applied to subsequently received data.
In this example, at the expiration of the preamble, the Wi-Fi modem
begins receiving Wi-Fi data. The IRC weights are applied to the
subsequently received data signals and a soft symbol outputs
{circumflex over (x)}.sub.1,IRC is be generated as {circumflex over
(x)}.sub.1,IRC(f)=w*.sub.IRC(f)y(f).
[0041] In a second example, STA 110-b receives a Wi-Fi transmission
prior to the LTE transmission, and the LTE transmission is
initiated prior to the LTF of the Wi-Fi preamble used for channel
estimation. As above, the Wi-Fi modem determines the LTE
transmission timing and enables IRC for receiving the Wi-Fi
transmission. Also as above, the Wi-Fi modem uses the LTF received
during the Wi-Fi preamble to determine the combined interference
covariance for generating IRC weights and the soft symbol outputs
for the received Wi-Fi data.
[0042] In a third example, STA 110-b receives a Wi-Fi transmission
prior to the LTE transmission, and the LTE transmission is
initiated after the LTF of the Wi-Fi preamble used for channel
estimation is transmitted. In this example, the LTE transmission is
further initiated during the second half of the Wi-Fi
transmission's data region. Accordingly, STA 110-b uses the
combined interference covariance computed from a previous LTF
(e.g., the latest computed combined interference signal
covariance), in addition to a channel estimate from the current LTF
to determine the IRC weights. Additionally or alternatively, STA
110-b directs the LTE modem to transmit a low power signal during
the LTF preamble to determine a combined interference covariance
estimate. Each of the above examples may be further understood with
respect to at least the following figures: FIGS. 3A to 3C.
[0043] FIGS. 3A to 3C illustrate examples of shared channels 300
that support time-controlled spatial interference rejection in
accordance with various aspects of the present disclosure. A shared
channel 300 illustrates aspects of a transmission between a STA
110, an AP 105, and a base station 150, as described above with
reference to FIGS. 1-2. A shared channel 300 includes Wi-Fi
transmissions 305 and LTE transmissions 310. A Wi-Fi transmission
305, based at least in part on IEEE 802.11ac, includes a legacy
preamble 320, a very high throughput (VHT) preamble 325, and a
payload 365, which includes data for a receiving STA 110. The
legacy preamble 320 includes as short training field (STF) 330,
long training field (LTF) 335, and a signaling (SIG) 340, and the
VHT preamble 325 includes a first SIG field, SIG-A 345, a second
SIG field, SIG-B 360, a VHT-STF 350, and a VHT-LTF 355.
[0044] FIG. 3A illustrates a first example, where a Wi-Fi
transmission 305 and an interfering LTE transmission 310-a occur
over shared channel 300-a. In this example, a STA 110 transmits LTE
transmission 310-a over shared channel 300-a prior to a STA 110
receiving a Wi-Fi transmission 305. The Wi-Fi modem determines the
transmission timing for LTE transmission 310-a. In one example, the
Wi-Fi modem determines the transmission timing based at least in
part on a control signal sent by the LTE modem to the Wi-Fi modem
concurrently with the start of LTE transmission 310-a. In another
example, the Wi-Fi modem determines the transmission timing based
at least in part on scheduling information provided by the LTE
modem, such as start time, end time, periodicity, etc. In either
case, the control signal indicates that LTE transmission 310-a is
in progress, and after receiving the indicator, the Wi-Fi modem
enables IRC spatial filtering at the Wi-Fi receiver for the
duration of LTE transmission 310-a. During VHT-LTF 355, the Wi-Fi
modem determines a channel estimate for the received signal. This
channel estimate is used to determine the combined interference
estimate u(f) and the combined interference covariance R.sub.uu. As
above, R.sub.uu and the channel estimate h.sub.1(f) are used to
determine the IRC weights.
[0045] LTE transmission 310-a continues throughout payload 365 and
the determined IRC weights are applied to the data received during
payload 365 to produce the soft symbol outputs {circumflex over
(x)}.sub.1,IRC. In some examples, LTE transmission 310-a terminates
prior to the end of payload 365. In one example, the LTE modem
signals to the Wi-Fi modem that the LTE transmission 310-a has
completed and the Wi-Fi modem toggles from the receiver from using
IRC to a different spatial filtering technique (e.g., MRC). In
other example, the Wi-Fi modem determines the transmission is
complete based at least in part on received scheduling
information.
[0046] FIG. 3B illustrates a second example, where a Wi-Fi
transmission 305 and an interfering LTE transmission 310-b occur
over shared channel 300-b. In this example, a STA 110 transmits LTE
transmission 310-b while the STA 110 is receiving Wi-Fi
transmission 305. The Wi-Fi modem determines the transmission
timing for LTE transmission 310-b as based at least in part on a
control signal received from the LTE modem. The Wi-Fi modem enables
IRC spatial filtering at the Wi-Fi receiver for the duration of LTE
transmission 310-b based at least in part on the determined
transmission timing. Since LTE transmission 310-b occurs prior to
VHT-LTF 355, the Wi-Fi modem uses VHT-LTF 355 to determine a
channel estimate and the combined interference covariance estimate
for the received signal as described above.
[0047] FIG. 3C illustrates a third example, where a Wi-Fi
transmission 305 and an interfering LTE transmission 310-c occur
over shared channel 300-c. In this example, a STA 110 transmits LTE
transmission 310-b while the STA 110 is receiving the payload 365
of Wi-Fi transmission 305. The Wi-Fi modem determines the
transmission timing for LTE transmission 310-b as based at least in
part on a control signal from the LTE modem. Since LTE transmission
310-c occurs in the subsequent to the beginning of payload 365, the
Wi-Fi modem uses a first spatial filtering technique (e.g., MRC)
during time period 370 and uses a IRC during the time period 375
when LTE transmission 310-c is in progress. In this example, LTE
transmission 310-c does not overlap with VHT-LTF 355, and therefore
the Wi-Fi modem uses a prior combined interference covariance
estimate in addition to the current channel estimate obtained from
VHT-LTF 355 to determine the IRC weights. In this example, the
Wi-Fi modem uses the most recent combined interference covariance
to determine the IRC weights and the soft outputs for the data
transmitted during time period 375. In other examples, the Wi-Fi
modem averages a number of prior combined interference covariance
measurements. Additionally or alternatively, the LTE modem
transmits a low power signal during VHT-LTF 355 to enable a
combined interference covariance estimate to be generated. In some
cases, VHT preamble 325 is implemented as HE (high efficiency)
preamble, based at least in part on IEEE 802.11ax. An HE preamble
has a similar structure as a VHT preamble and includes a first
signal field, SIG-A, a second signal field, SIG-B, an HE-STF, and
an HE-LTF. The HE preamble can be included in a Wi-Fi transmission,
such as Wi-Fi transmission 305, which also includes a legacy
preamble and a payload.
[0048] FIG. 4 illustrates an example of a dual modem configuration
400 that supports time-controlled spatial interference rejection in
accordance with various aspects of the present disclosure. The dual
modem configuration 400 illustrates aspects of a transmission
between a STA 110, an AP 105, and a base station 150, as described
above with reference to FIGS. 1-3. Dual modem configuration 400
includes WLAN modem 409 and WWAN modem 439. In one example, the
dual modem configuration 400 is included in the STA 110-b as
described in FIG. 2, where the WWAN modem 439 is an LTE modem and
the WLAN modem 409 is a Wi-Fi modem. WLAN modem 409 includes a
transmitter a modulator 412, decoder 415, spatial filter(s) 418,
transmitter 424, receiver 421, transmitter DAC 427, and receiver
ADC 430. The WLAN modem 409 is coupled to the RF front end, WLAN RF
436 via analog traces 433 and the WLAN MAC 403. WLAN analog traces
433 include a trace for transmitting data and two traces for
receiving data over the main antenna 475-a and the diversity
antenna 475-b. WLAN RF 436 also includes an analog component 466,
such as a power amplifier for transmitting or a bandpass filter for
receiving.
[0049] WWAN modem 439 includes a modulator 442, a decoder 445, a
transmitter 448, a receiver 451, a transmitter DAC 454, and a
receiver ADC 457. WWAN modem 439 is coupled to the WWAN MAC 406 and
to the RF front end, WWAN RF 463, via WWAN analog traces 460. WWAN
analog traces 460 include a trace for transmitting data and two
traces for receiving data over the main antenna 475-c and the
diversity antenna 475-d. WWAN RF 463 also include an analog
component for receiving and transmitting signals. The WLAN modem
409 and the WWAN modem 439 share a common clock 478 and WWAN modem
439 provides control signals via control line 481 to the WLAN modem
409. A timing signal from crystal oscillator 472 is provided to
analog component 466 and analog component 469.
[0050] In one example, WWAN modem 439 provides a control signal via
control line 481 to WLAN modem 409 that indicates to the WLAN modem
409 a transmission timing for a WWAN communication (e.g.,
transmission or reception). The WWAN modem 439 toggles between a
first spatial filter 418-a in the receive chain (e.g., MRC) and a
second spatial filter 418-b in the receive chain (e.g., IRC) based
at least in part on the received control signal. For instance, WLAN
modem 409 determines that an interfering WWAN transmission is in
progress and activates spatial filter 418-b. If the WLAN modem 409
is receiving a WLAN signal at the time the control signal is
received, the WLAN modem determines a channel estimate and a
combined interference covariance. In this example, the channel
estimate and interference covariance are generated as described
with respect to FIGS. 3A to 3C. The WLAN modem 409 uses the channel
estimate and combined interference covariance to generate IRC
weights for spatial filter 418-b. The IRC weights are applied to
the received WLAN signal via spatial filter 418-b and the WLAN
signal is deinterleaved, decoded, and or appended with a cyclic
redundancy check (CRC) at decoder 415.
[0051] FIG. 5 illustrates an example of a process flow 500 for
time-controlled spatial interference rejection in accordance with
various aspects of the present disclosure. Process flow 500 is be
performed by WWAN modem 439-a and WLAN modem 409-a, which are
examples of a WWAN modem 439 and a WLAN modem 409 and are utilized
for transmissions between a STA 110 and a base station 150
described above with reference to FIGS. 1-4. In some examples, the
WWAN modem 439-a indicates to the WLAN modem 409-a, a transmission
timing during which a WLAN modem 409-a toggles between filtering
techniques (e.g., IRC and MRC).
[0052] At 505, WWAN modem 439-a determines the transmission timing
for subsequent WWAN transmissions. WWAN modem 439-a determines the
transmission timing based at least in part on identifying the
beginning of a WWAN communication, identifying the end of the WWAN
communication, identifying a WWAN communication is ongoing,
identifying that a WWAN communication is scheduled, etc.
[0053] At 510, WWAN modem 439-a transmits a control message to WLAN
modem 409-a that indicates the determined transmission timing. In
this example, the control message is transmitted via a control line
between WWAN modem 439-a and WLAN modem 409-a, such as control line
481 described in FIG. 4. The timing between WWAN modem 439-a and
WLAN modem 409-a is also synchronized based at least in part on a
common clock.
[0054] At 515, WLAN modem 409-a determines the WWAN transmission
520 timing based at least in part on the received control message.
As mentioned above, the transmission timing can alert WLAN modem
409-a to the start and/or end times of a transmission, an ongoing
transmission, and/or a communication schedule. Based at least in
part on the received control message, WLAN modem 409-a can
determine the transmission timing subsequent to, concurrently with,
or prior to WWAN transmission 520. In this example, WLAN modem
409-a determines the transmission timing prior to WWAN transmission
520. WWAN transmission 520 is transmitted from WWAN modem 439-a to
base station 150-b over a band that interferes with (e.g., is
nearby or overlaps with a the band) the band used by WLAN modem
409-a and AP 105-b. WWAN transmission 520 can start prior to WLAN
modem 409-a receiving a WLAN transmission, such as WLAN
transmission 530, during the preamble of WLAN transmission 530,
subsequent to the preamble of the WLAN transmission 530, etc., as
shown with respect to FIGS. 3A to 3C. In this example, the WWAN
transmission occurs prior to a received WLAN signal.
[0055] At 525, WLAN modem 409-a selects a filtering technique 525
based at least in part on the determined transmission timing. For
control messages that alert WLAN modem 409-a that a transmission is
currently in progress, the WLAN modem 409-a immediately enables IRC
filtering at the receiver. For control messages that alert WLAN
modem of a communication schedule or a start time, WLAN modem 409-a
enables IRC filtering at the receiver according to the scheduled
time.
[0056] At 530, WLAN modem 409-a receives a WLAN transmission using
IRC filtering techniques based at least in part on the determined
transmission timing and based at least in part on identifying that
there is an ongoing WWAN transmission.
[0057] At 535, WLAN modem 409-a determines an interference
covariance for the IRC filter based at least in part on the
received WLAN transmission. WLAN modem 409-a uses an LTF within a
WLAN preamble associated with received WLAN transmission 530 to
determine a channel estimate. The channel estimate, the received
signal, and the known signal included in the LTF are used to
determine the interference covariance and to determine the IRC
receiver weights. The IRC receiver weights are applied to the
received WLAN transmission.
[0058] At 540, WLAN modem 409-a decodes the WLAN transmission based
at least in part on the received signal and the applied IRC
receiver weights. WLAN modem 409-a applies the receiver weights
through the data region of the WLAN transmission to enhance the
estimate of the received data symbols. In this example, the WWAN
transmission extends through the WLAN transmission and WLAN modem
409-a applies the IRC weights throughout the WLAN data region.
[0059] At 545 and at 550, the WWAN transmission and the WLAN
transmission end. The WWAN transmission can end prior to,
subsequent to, or simultaneously with the WLAN transmission. For
the case where the WWAN transmission terminates prior to the WLAN
transmission, WLAN modem 409-a can toggle the spatial filtering
techniques used to decode the WLAN transmission (e.g. toggle to use
MRC filtering). In some examples, WLAN modem 409-a identifies the
end of the WWAN transmission through a second control message
indicating the end of the WWAN transmission or based at least in
part on the end time or scheduling information provided in the
first control message.
[0060] FIG. 6A illustrates an example of a partitioned channel
600-a for time-controlled spatial interference rejection in
accordance with various aspects of the present disclosure.
Partitioned channel 600-a extends across channel bandwidth 605,
which includes guard tones 610 and used tones 615. Used tones 615
are partitioned into K subbands 620-a to 620-k and include unused
DC tones 625. Signals transmitted via used tones 615 extend over a
duration of time 635. The channel estimate 630 is oftentimes based
at least in part on the duration of time 635. For instance, some
channels have characteristics that vary significantly over short
durations of time while other channel experience stable
characteristics for longer durations of time. In one example,
partitioning the used tones 615 into K subbands is based at least
in part on a channel estimate. For instance, channel estimate 630,
which can be computed from an LTF, provides gain characteristics
across the channel bandwidth 605, which a device then uses to
determine the subband 620 bandwidths. The subband 620 bandwidths
oftentimes will partition the channel bandwidth 605 into different
sized subbands 620 in size based at least in part on the channel
estimate (e.g., the frequency selectivity or the channel delay
spread associated with a subband). In some examples, the subbands
are evenly partitioned across the channel bandwidth 605.
[0061] FIG. 6B illustrates an example of subband processing
component 650 for time-controlled spatial interference rejection in
accordance with various aspects of the present disclosure. Subband
processing component 650 may receive a signal over a channel
bandwidth that is partitioned into multiple subbands, as described
above with respect to FIG. 6A. Subband processing component 650
also includes subband processor 655, which includes a filter 660,
channel estimators 665-a to 665-k, covariance estimators 670-a to
670-k, weight generators 675-a to 675-k, and processor 680, and is
coupled to antennas 690 via analog front end 685.
[0062] In one example, a signal is received at antennas 690 and
processed by the analog front end 685. The analog front end 685
passes the processed signal to filter 660, where the signal is
separated into multiple signals associated with the different
subbands. The separated signals are passed to channel estimators
665 and channel estimates, h.sub.k(f) for each subband, k, is
determined, by using the received signals, y.sub.k(f), that are
associated with each subband and the known signal transmitted in an
LTF, where the LTF is included in the received signals. Using the
channel estimate, the received signal, and the known LTF symbol,
covariance estimators 670 determine covariance estimates,
R.sub.uu.sub._.sub.k. The weight generators 675 then determine
weights, w.sub.IRC.sub._.sub.k(f), for each subband, and use the
weights to generate soft symbol outputs. The soft symbol outputs
are combined at processor 680 where the soft symbol outputs can be
averaged, added, or otherwise processed. In one example, soft
symbol outputs associated with certain frequency subbands are given
more weight in relation to other frequency subbands. For instance,
a device can provide more weight to soft symbol outputs from a
subband that is determined to have enhanced channel characteristics
than to a subband that has degraded channel characteristics. In one
example, a device determines a subband has enhanced channel
characteristics based on the derived channel estimates.
[0063] FIG. 7A shows a block diagram 700-a of an example STA 110-c
that supports time-controlled spatial interference rejection in
accordance with various aspects of the present disclosure and with
respect to FIGS. 1-6. The STA 110-c includes a processor 705, a
memory 710, one or more transceivers 720, one or more antennas 725,
a transmission timing identifier 730, a filter selector 735,
spatial filter(s) 740, a channel monitor 745, and an weight
generator 750. The processor 705, memory 710, transceiver(s) 720,
transmission timing identifier 730, filter selector 735, spatial
filter(s) 740, channel monitor 745, and weight generator 750 are
communicatively coupled with a bus 755, which enables communication
between these components. The antenna(s) 725 are communicatively
coupled with the transceiver(s) 720. Aspects of the dual modem
configuration 400, as described with respect to FIG. 4, are also be
implemented in STA 110-c.
[0064] The processor 705 is an intelligent hardware device, such as
a central processing unit (CPU), a microcontroller, an
application-specific integrated circuit (ASIC), etc. The processor
705 processes information received through the transceiver(s) 720
and information to be sent to the transceiver(s) 720 for
transmission through the antenna(s) 725.
[0065] The memory 710 stores computer-readable, computer-executable
software (SW) code 715 containing instructions that, when executed,
cause the processor 705 or another one of the components of the STA
110-c to perform various functions described herein, for example,
triggering a roaming scan and determining whether to roam to a
different channel.
[0066] The transceiver(s) 720 communicate bi-directionally with
other wireless devices, such as APs 105, base station 150, STAs
110, or other devices. The transceiver(s) 720 include modem, such
as WWAN modem 439 and WLAN modem 409 as described in FIG. 4, to
modulate packets and frames and provide the modulated packets to
the antenna(s) 725 for transmission. The modems are additionally
used to demodulate packets received from the antenna(s) 725.
[0067] The transmission timing identifier 730, filter selector 735,
spatial filter(s) 740, channel monitor 745, and weight generator
750 implement the features described with reference to FIGS. 1-6,
as further explained below.
[0068] Again, FIG. 7A shows only one possible implementation of a
device executing the features of FIGS. 1-6 While the components of
FIG. 7A are shown as discrete hardware blocks (e.g., ASICs, field
programmable gate arrays (FPGAs), semi-custom integrated circuits,
etc.) for purposes of clarity, it will be understood that each of
the components may also be implemented by multiple hardware blocks
adapted to execute some or all of the applicable features in
hardware. Alternatively, features of two or more of the components
of FIG. 7A may be implemented by a single, consolidated hardware
block. For example, a single transceiver 720 chip may implement the
processor 705, memory 710, transmission timing identifier 730,
filter selector 735, spatial filter(s) 740, channel monitor 745,
and weight generator 750.
[0069] In still other examples, the features of each component may
also be implemented, in whole or in part, with instructions
embodied in a memory, formatted to be executed by one or more
general or application-specific processors. For example, FIG. 7B
shows a block diagram 700-b of another example of a STA 110-d in
which the features of the transmission timing identifier 730-a,
filter selector 735-a, spatial filter(s) 740-a, channel monitor
745-a, and weight generator 750-a are implemented as
computer-readable code stored on memory 710-a and executed by one
or more processors 705-a. Other combinations of hardware/software
may be used to perform the features of one or more of the
components of FIGS. 7A and 7B.
[0070] FIG. 8 shows a flow chart that illustrates one example of a
method 800 for wireless communication, in accordance with various
aspects of the present disclosure. The method 800 can be performed
by any of the STAs 110 discussed in the present disclosure, but for
clarity the method 800 will be described from the perspective of
STA 110-c and STA 110-d, of FIGS. 7A and 7B. Aspects of the
transmission timing identifier 730, filter selector 735, spatial
filter(s) 740, channel monitor 745, and weight generator 750
described in FIGS. 7A and 7B may be incorporated into one or both
of a WWAN modem and a WLAN modem.
[0071] Broadly speaking, the method 800 illustrates a procedure by
which a WLAN modem at either STA 110-d or STA 110-k, determines a
timing of an interfering transmission (e.g., a WWAN transmission)
by a first modem (e.g., a WWAN modem) that operates according to a
first RAT (e.g., LTE), and toggles a use of IRC during receive
operation of a second modem (e.g., WLAN) that operates according to
a second RAT (e.g., Wi-Fi) wherein the toggling is based at least
in part on the determine timing of the interfering transmission.
The procedure may be broadly applied to other scenarios where the
modems are associated with other RATs (e.g., LTE, WLAN, Bluetooth
(BT), global positioning system (GPS), etc.).
[0072] The method 800 begins with a WLAN modem at a STA receiving a
control signal form a WWAN modem that indicates a WWAN transmission
timing. At block 805, the transmission timing identifier 730
determines a timing of an interfering transmission by the WWAN
modem. In one example, the WLAN modem receives a control signal
from the WWAN modem that indicates the WWAN modem is currently
transmitting, and the transmission timing identifier 730 determines
that a WWAN transmission is active. In another example, the WWAN
modem sends a control signal that includes a start and end time for
an upcoming transmission/reception, and the transmission timing
identifier 730 determines when a WWAN communication begins and
ends. In another example, the WWAN modem sends a control signal
that includes scheduling information such as communication
periodicity and the transmission timing identifier 730 identifies
when a WWAN communication will occur. The scheduling information
relates to either uplink or downlink transmissions between the WWAN
modem and a base station. In yet another example, the WWAN modem is
allocated, by the WWAN network, an interval during for uplink WWAN
transmission. The WLAN modem preemptively determines that a WWAN
transmission is in progress, however in some examples, the WWAN
modem fails to perform a successful CCA. Therefore, the WWAN modem
transmits a control signal to the WLAN modem indicating that the
CCA has failed and that an WWAN transmission is not active.
[0073] At block 810, the channel monitor 745 determines whether an
WWAN communication is or is expected to be active. If a WWAN
communication is active the filter selector 735 enables IRC
filtering, but if the WWAN communication is not the filter selector
735 enables MRC filtering.
[0074] At block 815, the filter selector 735 enables a spatial
filter 740, such as an IRC filter, based at least in part on
determining that an interfering WWAN communication is active at the
WWAN modem. At block 820, the channel monitor 745 determines
whether a WLAN transmission is currently being received. If no
signal is being received the channel monitor 745 continues to
monitor the shared channel for a WLAN transmissions. Additionally
or alternatively, the filter selector 735 selects a spatial filter
740 based at least in part on determining whether the signal
strength of the interference caused by the WWAN communication is
greater than a pre-determined threshold.
[0075] At block 825, the channel monitor 745 determines whether the
overlap between the received WLAN transmission and the WWAN
transmission includes an LTF field for channel estimation. If the
LTF field is present the channel monitor 745 uses the LTF to
determine a channel estimate with the interference present,
otherwise the channel monitor 745 determines the channel estimate
without interference.
[0076] At blocks 830 and 830-a, the channel monitor 745 estimates
the channel based at least in part on the received LTF. At block
835, the weight generator 750 estimates the interference covariance
based at least in part on the determined channel estimate, a
received signal, and a known signal transmitted during the LTF. At
block 835-a, the weight generator 750 estimates the interference
covariance based at least in part on prior interference covariance
estimates. In some examples, the weight generator 750 uses an
averaged interference covariance from multiple previous
interference covariance measurements.
[0077] At block 840, the weight generator 750 determines filter
weights for the IRC receiver based at least in part on the channel
estimate and the interference covariance estimated in either block
835 or 835-a. In one example, the channel monitor 745 divides the
WLAN transmission into subbands and the weight generator 750
estimates the interference covariance over each of the subbands.
The weight generator 750 then determines a respective weight vector
for each of the subbands using the interference covariance
associated with the corresponding subband.
[0078] At block 845, spatial filter 740, such as the IRC filter,
applies the filter weights to the received WLAN transmission. For
the data portion of the WLAN transmission the filter weights are
used to generate soft output estimates of the received symbols. At
block 850, the WLAN modem de-interleaves, decodes, and applies a
cyclic redundancy check to the soft output estimates to determine
the transmitted information.
[0079] At block 855, filter selector 735 enables a spatial filter
740, such as MRC filter, based at least in part on determining that
an interfering WWAN transmission is not active. At block 860, the
channel monitor 745 monitors the channel for a WLAN transmission.
At block 865, the channel monitor 745 determines a channel estimate
based at least in part on receiving a WLAN transmission. At block
870, a weight generator 750 determines filter weights for the
received signal based at least in part on the channel estimate. At
block 875, spatial filter 740, such as MRC filter, applies the
filter weights to the received signal, and at block 880 WLAN modem
decodes the received WLAN transmission.
[0080] The detailed description set forth above in connection with
the appended drawings describes examples and does not represent the
only examples that may be implemented or that are within the scope
of the claims. The terms "example" and "exemplary," when used in
this description, mean "serving as an example, instance, or
illustration," and not "preferred" or "advantageous over other
examples." The detailed description includes specific details for
the purpose of providing an understanding of the described
techniques. These techniques, however, may be practiced without
these specific details. In some instances, well-known structures
and apparatuses are shown in block diagram form in order to avoid
obscuring the concepts of the described examples.
[0081] Information and signals may be represented using any of a
variety of different technologies and techniques. For example,
data, instructions, commands, information, signals, bits, symbols,
and chips that may be referenced throughout the above description
may be represented by voltages, currents, electromagnetic waves,
magnetic fields or particles, optical fields or particles, or any
combination thereof
[0082] The various illustrative blocks and components described in
connection with the disclosure herein may be implemented or
performed with a general-purpose processor, a digital signal
processor (DSP), an ASIC, an FPGA or other programmable logic
device, 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
conventional 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, multiple microprocessors, one or more
microprocessors in conjunction with a DSP core, or any other such
configuration.
[0083] The functions described herein may be implemented in
hardware, software executed by a processor, firmware, or any
combination thereof. If implemented in software executed by a
processor, the functions may be stored on or transmitted over as
one or more instructions or code on a computer-readable medium.
Other examples and implementations are within the scope and spirit
of the disclosure and appended claims. For example, due to the
nature of software, functions described above can be implemented
using software executed by a processor, hardware, firmware,
hardwiring, or combinations of any of these. Features implementing
functions may also be physically located at various positions,
including being distributed such that portions of functions are
implemented at different physical locations. As used herein,
including in the claims, the term "and/or," when used in a list of
two or more items, means that any one of the listed items can be
employed by itself, or any combination of two or more of the listed
items can be employed. For example, if a composition is described
as containing components A, B, and/or C, the composition can
contain A alone; B alone; C alone; A and B in combination; A and C
in combination; B and C in combination; or A, B, and C in
combination. Also, as used herein, including in the claims, "or" as
used in a list of items (for example, a list of items prefaced by a
phrase such as "at least one of" or "one or more of") indicates a
disjunctive list such that, for example, a list of "at least one of
A, B, or C" means A or B or C or AB or AC or BC or ABC (i.e., A and
B and C).
[0084] Computer-readable media includes 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
general purpose or special purpose computer. By way of example, and
not limitation, computer-readable media can comprise RAM, ROM,
EEPROM, flash memory, 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 means in the form of instructions or data structures and that
can be accessed by a general-purpose or special-purpose computer,
or a general-purpose or special-purpose processor. 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, 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 disc where disks usually reproduce
data magnetically, while discs reproduce data optically with
lasers. Combinations of the above are also included within the
scope of computer-readable media.
[0085] The previous description of the disclosure is provided to
enable a person skilled in the art to make or use the disclosure.
Various modifications to the disclosure will be readily apparent to
those skilled in the art, and the generic principles defined herein
may be applied to other variations without departing from the scope
of the disclosure. Thus, the disclosure is not to be limited to the
examples and designs described herein but is to be accorded the
broadest scope consistent with the principles and novel features
disclosed herein.
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