U.S. patent application number 16/839065 was filed with the patent office on 2020-07-23 for signaling methods for communication systems with widely spaced downlink and uplink frequency channels.
The applicant listed for this patent is Phazr, Inc.. Invention is credited to Shadi Abu-Surra, Robert Clark Daniels, Farooq Khan, Sudhir Ramakrishna, Rakesh Taori.
Application Number | 20200235721 16/839065 |
Document ID | / |
Family ID | 66096586 |
Filed Date | 2020-07-23 |
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United States Patent
Application |
20200235721 |
Kind Code |
A1 |
Taori; Rakesh ; et
al. |
July 23, 2020 |
Signaling Methods for Communication Systems with Widely Spaced
Downlink and Uplink Frequency Channels
Abstract
A method of wireless communication includes receiving a
plurality of parameter values at a user equipment (UE) using a
first local oscillator (LO) frequency value, where the plurality of
parameter values includes indications of a downlink frequency
channel and an uplink frequency channel. The method further
includes determining a second LO frequency value at the UE, where
the second LO frequency value is determined using the indications
of downlink and uplink frequency channels. The method further
includes receiving downlink signals from an associated base station
using the second LO frequency value.
Inventors: |
Taori; Rakesh; (McKinney,
TX) ; Khan; Farooq; (Allen, TX) ; Daniels;
Robert Clark; (Round Rock, TX) ; Abu-Surra;
Shadi; (Plano, TX) ; Ramakrishna; Sudhir;
(Plano, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Phazr, Inc. |
Allen |
TX |
US |
|
|
Family ID: |
66096586 |
Appl. No.: |
16/839065 |
Filed: |
April 2, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15898196 |
Feb 15, 2018 |
10637445 |
|
|
16839065 |
|
|
|
|
62574164 |
Oct 18, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 5/06 20130101; H04W
72/0453 20130101; H04W 16/10 20130101; H03J 7/065 20130101; H04W
16/14 20130101; H04L 5/003 20130101; H04B 1/0053 20130101 |
International
Class: |
H03J 7/06 20060101
H03J007/06; H04L 5/00 20060101 H04L005/00; H04W 16/10 20060101
H04W016/10; H04W 16/14 20060101 H04W016/14; H04L 5/06 20060101
H04L005/06; H04W 72/04 20060101 H04W072/04 |
Claims
1. A method of wireless communication, comprising: receiving a
plurality of parameter values at a user equipment (UE), wherein the
plurality of parameter values includes indications of an uplink
frequency channel and a local oscillator (LO) frequency value;
determining a downlink frequency channel at the UE, wherein the
downlink frequency channel is determined using the indications of
the uplink frequency channel and the LO frequency value; and
receiving downlink signals on the downlink frequency channel from
an associated base station.
2. The method of claim 1, wherein at least one of the uplink and
downlink frequency channels are unknown to the UE prior to
receiving the indications.
3. The method of claim 1, wherein the downlink frequency channel is
in a millimeter wave band.
4. The method of claim 1, wherein the uplink frequency channel is
in a sub-7GHz band.
5. A method of wireless communication, comprising: receiving a
plurality of parameter values at a base station, wherein the
plurality of parameter values includes channel properties and
indications of an uplink frequency channel; determining a downlink
frequency channel using a predetermined channel mapping and the
indications of an uplink frequency channel; and transmitting at
least the indication of the downlink frequency channel to an
associated user equipment (UE).
6. The method of claim 5, wherein the predetermined channel mapping
maps the uplink channel to the downlink channel to optimize
utilization of a spectrum.
7. The method of claim 5, wherein the predetermined channel mapping
maps the uplink frequency channel to the downlink frequency channel
to reduce interference.
8. The method of claim 5, wherein the channel properties include
channel properties of neighboring base stations.
9. The method of claim 5, wherein the downlink signal is in a
millimeter wave band.
10. The method of claim 5, wherein the uplink signal is in a
sub-7GHz band.
11. A method of wireless communication, comprising: receiving a
plurality of parameter values at a user equipment (UE), wherein the
plurality of parameter values includes indications of a downlink
frequency channel and a local oscillator (LO) frequency value;
determining an uplink frequency channel at the UE, wherein the
uplink frequency channel is determined using the indications of the
downlink frequency channel and the LO frequency value; receiving
downlinks signals on the indicated downlink frequency channel; and
transmitting uplink signals on the uplink frequency channel to an
associated base station.
12. A method of wireless communication, comprising: receiving a
plurality of parameter values at a user equipment (UE), wherein the
plurality of parameter values includes indications of a downlink
frequency channel and an uplink frequency channel; estimating a
carrier frequency offset at the UE; determining a sampling
frequency offset at the UE, wherein the sampling frequency offset
is determined using the estimated carrier frequency offset and the
indications of a downlink frequency channel; receiving downlink
signals on the indicated downlink frequency channel using the
carrier frequency offset and the sampling frequency offset; and
transmitting uplink signals on the indicated uplink frequency
channel.
13. The method of claim 12, wherein the carrier frequency offset is
estimated by self-correlation of digital sequences at the UE.
14. The method of claim 12, further comprising using the estimated
sampling frequency offset to reduce misalignment between a digital
to analog converter and an analog to digital converter at the
UE.
15. A method of wireless communication, comprising: receiving a
plurality of parameter values at a user equipment (UE), wherein the
plurality of parameter values includes indications of a frequency
channel and a relationship between a carrier frequency offset and a
sampling frequency offset; estimating the carrier frequency offset
at the UE; determining the sampling frequency offset at the UE,
wherein the sampling frequency offset is determined using the
estimated carrier frequency offset and the relationship between the
carrier frequency offset and the sampling frequency offset; and
receiving downlink signals on the indicated frequency channel using
the carrier frequency offset and the sampling frequency offset.
16. The method of claim 15, further comprising using the sampling
frequency offset to reduce misalignment between a digital to analog
converter and an analog to digital converter at the UE.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. application Ser.
No. 15/898,196 filed Feb. 15, 2018, which claims priority to U.S.
Provisional Application No. 62/574,164 filed Oct. 18, 2017, which
are hereby incorporated by reference in their entirety.
BACKGROUND
[0002] Aspects of the present disclosure relate generally to
wireless communication systems, and more particularly to methods of
signaling downlink and uplink frequency channels in a communication
system relying on widely-spaced downlink and uplink frequency
channels.
DESCRIPTION OF THE RELATED ART
[0003] Wireless communication networks are deployed to enable
voice, video, data, messaging, and various other form of
communication. The wireless networks support multiple users by
sharing available network resources. Examples of wireless networks
include Time Division Multiple Access (TDMA) networks, Frequency
Division Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA)
and Code Division Multiple Access (CDMA) networks.
[0004] A wireless communication network may include a number of
base stations or access points that facilitate communication for a
number of user equipments (UEs). A UE may communicate with a base
station via the downlink or uplink. The uplink refers to the
communication link from the UE to the base station, with signal
transmission from the UE and signal reception at the base station.
The downlink refers to the communication link from the base station
to the UE, with signal transmission from the base station and
signal reception at the UE.
[0005] Currently, wireless access is based on two popular
standards: a wide area network (WAN) standard referred to as The
Fourth Generation Long Term Evolution (4G LTE); and a local area
network (LAN) standard called Wi-Fi. Wi-Fi is generally used
indoors as a short-range wireless extension of wired broadband
systems. The 4G LTE systems on the other hand provide wide area
long-range connectivity both outdoors and indoors using dedicated
infrastructure such as cell towers and backhaul to connect to a
communication network such as the Internet.
[0006] As more people connect to the Internet, increasingly chat
with friends and family, watch videos, listen to streamed music,
and indulge in virtual or augmented reality, data traffic continues
to grow at unprecedented rates. In order to address the
continuously growing wireless capacity challenge, the next
generation LAN and WAN systems are expected to rely on higher
frequencies referred to as millimeter wave bands in addition to
currently used frequency bands below 7 GHz. Table 1 provides
examples of millimeter wave bands.
TABLE-US-00001 TABLE 1 Examples of millimeter wave bands Bands
[GHz] Frequency [GHz] Bandwidth [GHz] 24 GHz Bands 24.25-24.45
0.200 25.05-25.25 0.200 LMDS Band 27.5-28.35 0.850 29.1-29.25 0.150
31-31.3 0.300 39 GHz Band 38.6-40 1.400 37/42 GHz Bands 37.0-38.6
1.600 42.0-42.5 0.500 60 GHz 57-64 7.000 64-71 7.000 70/80 GHz
71-76 5.000 81-86 5.000 90 GHz 92-94 2.900 94.1-95.0 95 GHz 95-100
5.000 105 GHz 102-105 7.500 105-109.5 112 GHz 111.8-114.25 2.450
122 GHz 122.25-123 0.750 130 GHz 130-134 4.000 140 GHz 141-148.5
7.500 150/160 GHz 151.5-155.5 12.50 155.5-158.5 158.5-164
SUMMARY
[0007] Various aspects of the present disclosure are directed to
methods for communication systems utilizing widely-spaced downlink
and uplink frequency channels.
[0008] In one aspect of the disclosure, a method of wireless
communication includes receiving a plurality of parameter values at
a user equipment (UE) using a first local oscillator (LO) frequency
value, where the plurality of parameter values includes indications
of a downlink frequency channel and an uplink frequency channel.
The method further includes determining a second LO frequency value
at the UE, where the second LO frequency value is determined using
the indications of downlink and uplink frequency channels. The
method further includes receiving downlink signals from an
associated base station using the second LO frequency value.
[0009] In an additional aspect of the disclosure, a method of
wireless communication includes receiving a plurality of parameter
values at a user equipment (UE), where the plurality of parameter
values includes indications of an uplink frequency channel and a
local oscillator (LO) frequency value. The method further includes
determining a downlink frequency channel at the UE, where the
downlink frequency channel is determined using the indications of
the uplink frequency channel and the LO frequency value. The method
further includes receiving downlink signals on the downlink
frequency channel from an associated base station.
[0010] In an additional aspect of the disclosure, a method of
wireless communication includes receiving a plurality of parameter
values at a base station, where the plurality of parameter values
includes channel properties and indications of an uplink frequency
channel. The method further includes determining a downlink
frequency channel using a predetermined channel mapping and the
indications of an uplink frequency channel. The method further
includes transmitting at least the indication of the downlink
frequency channel to an associated user equipment (UE).
[0011] In an additional aspect of the disclosure, a non-transitory
computer-readable medium includes program code recorded for
wireless communications. The program code includes code to receive
a plurality of parameter values at a user equipment (UE) using a
first local oscillator (LO) frequency value, where the plurality of
parameter values includes indications of a downlink frequency
channel and an uplink frequency channel. The program code also
includes code to determine a second LO frequency value at the UE,
where the second LO frequency value is determined using the
indications of downlink and uplink frequency channels. The program
code also includes code to receive downlink signals from an
associated base station using the second LO frequency value.
[0012] In an additional aspect of the disclosure, a method of
wireless communication includes receiving a plurality of parameter
values at a user equipment (UE), where the plurality of parameter
values includes indications of a downlink frequency channel and an
uplink frequency channel. The method also includes estimating a
carrier frequency offset at the UE, and determining a sampling
frequency offset at the UE, where the sampling frequency offset is
determined using the estimated carrier frequency offset and the
indications of a downlink frequency channel. The method also
includes receiving downlink signals on the indicated downlink
frequency channel using the carrier frequency offset and the
sampling frequency offset. The method also includes transmitting
uplink signals on the indicated uplink frequency channel.
[0013] In an additional aspect of the disclosure, a method of
wireless communication includes receiving a plurality of parameter
values at a user equipment (UE), where the plurality of parameter
values includes indications of a frequency channel and a
relationship between a carrier frequency offset and a sampling
frequency offset. The method also includes estimating the carrier
frequency offset at the UE and determining the sampling frequency
offset at the UE, where the sampling frequency offset is determined
using the estimated carrier frequency offset and the relationship
between the carrier frequency offset and the sampling frequency
offset. The method also includes receiving downlink signals on the
indicated frequency channel using the carrier frequency offset and
the sampling frequency offset.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Reference is now made to the following descriptions taken in
conjunction with the accompanying drawings, in which:
[0015] FIG. 1 illustrates a wireless communication system in
accordance with disclosed embodiments;
[0016] FIG. 2 illustrates an exemplary channel numbering
scheme;
[0017] FIG. 3 shows wireless communication between an access point
and a user equipment;
[0018] FIGS. 4-5 illustrate exemplary mapping schemes;
[0019] FIGS. 6A-6C are block diagrams conceptually illustrating
exemplary frame structures in which resource blocks are partitioned
for transmission of parameter values;
[0020] FIG. 7 is a block diagram of an access point transmitter and
a user equipment receiver;
[0021] FIG. 8 illustrates wireless communication between an access
point and a user equipment
[0022] FIG. 9 is a block diagram of a receiver configured to
determine CFO and SFO; and
[0023] FIG. 10 is a flow diagram of a method according to disclosed
embodiments.
DETAILED DESCRIPTION
[0024] The detailed description set forth below, in connection with
the appended drawings, is not intended to represent only
configurations in which the concepts described herein may be
practiced. The detailed description includes specific details for
the purpose of providing a thorough understanding of the various
concepts. However, it will be apparent to those skilled in the art
that these concepts may be practiced without these specific
details.
[0025] FIG. 1 shows a wireless communication system 100 in
accordance with disclosed embodiments. System 100 includes a number
of nodes 104, 108 and 112 and other network entities. Each node
includes a plurality of base stations or access points. As shown in
FIG. 1, node 104 includes access points A0-A15, node 108 includes
access points B1-B4, and node 112 includes access points C1-C4.
Each access point may communicate with a plurality of user
equipments (UEs), e.g., smartphones, tablets, laptop computers,
desktop computers, and phablets within a coverage area. By way of
example, the access points of node 104 communicate with UEs D1, D2,
M1 and S1, and the access points of node 112 communicate with UEs
D3 and S2.
[0026] According to disclosed embodiments, downlink (DL) and uplink
(UL) transmissions are performed on widely-spaced frequency bands.
While the exemplary embodiments herein utilize a sub-7 GHz band for
UL and a millimeter wave band (e.g., 28 GHz) for DL, it will be
apparent to those skilled in the art that the embodiments disclosed
herein are applicable to other widely separated DL and UL frequency
bands.
[0027] One example of a sub-7GHz (e.g., 5 GHz) wireless
communications transceiver is a commercially-available IEEE
802.11ac standard-compliant Wi-Fi system on a chip (SoC), where
transmit and receive ports service 5 GHz unlicensed band. Another
example of a sub-7 GHz wireless communications transceiver is a
commercially-available IEEE 802.11ac standard-compliant Wi-Fi
baseband combined with 5 GHz radio frequency (RF) integrated
circuits, where transmit and receive ports service the sub-7 GHz
unlicensed band.
[0028] Referring to the lower half of FIG. 2, the channel numbering
used for 20 and 80 MHz channels in accordance with the IEEE 802.11
standard is shown. The 20 MHz channel located between 5170 MHz and
5190 MHz, centered at 5180 MHz, is numbered as Channel #36.
Similarly, the 80 MHz channel located between 5170 MHz and 5250
MHz, centered at 5210 MHz, is numbered Channel #42.
[0029] Referring now to the upper half of FIG. 2, an exemplary
channel numbering scheme for the 28 GHz band is illustrated in
accordance with disclosed embodiments. The 28 GHz band shown in
FIG. 2 begins at 27.5 GHz and is 850 MHz wide. Channel numbering
for the 28 GHz band starts at Channel #1 for a 20 MHz channel
located between 27500 MHz and 27520 MHz, centered at 27510 MHz. A
grid of 5 MHz is used. Thus, the next channel located between 27520
and 27540, centered at 27530 is numbered Channel #5. The numbering
may start at some other number instead of 1, and a spacing other
than 5 MHz may be chosen.
[0030] FIG. 3 shows wireless communication between an access point
304 and a UE 308 relying on a millimeter wave band (e.g., 28 GHz)
band for downlink (DL) transmission and a sub-7 GHz band for uplink
(UL) transmission in accordance with disclosed embodiments. In the
access point 304, a mixer 328 upconverts a 5 GHz signal to 28 GHz
by taking the analog product of a local oscillator (LO) frequency,
generated through a phase-locked loop (PLL) 332 and 5 the GHz
signal. The 28 GHz signal is then transmitted over the air as a DL
transmission. The UE 308 receives the 28 GHz DL signal and
down-converts to a 5 GHz signal using a mixer 344 with the same
local oscillator frequency (LO) frequency generated using a PLL
348.
[0031] An exemplary mapping is illustrated in FIG. 4, where a 20
MHz channel in the 5 GHz band, channel #36 maps to channel #1 in
the 28 GHz band. Thus, if AP 304 receives UL transmission on
channel #36 in the 5 GHz band, AP 304 selects channel #1 in the 28
GHz band for DL transmission. Similarly, channel #52 in the 5 GHz
band maps to channel #17 in the 28 GHz band, and channel #100 in
the 5 GHz band maps to channel #65 in the 28 GHz band. In another
exemplary mapping illustrated in the same FIG. 4, an 80 MHz channel
in the 5 GHz band, channel #42 maps to channel #7 in the 28 GHz
band.
[0032] According to some disclosed embodiments, a UL channel in the
sub-7 GHz band can be mapped to an arbitrary DL channel in the 28
GHz band (more generally the millimeter wave bands), and vice
versa, by using an appropriate LO frequency, in accordance with the
relationship:
f.sub.DL.sup.c=f.sub.UL.sup.c+f.sub.LO
[0033] In the foregoing example of FIG. 4, channel #36 (a 20 MHz
channel) in the 5 GHz band, with a center frequency
f.sub.UL.sup.c=5.18 GHz is mapped using an LO frequency
f.sub.LO=22.33 GHz, to channel #1 (a 20 MHz channel) in the 28 GHz
band with center frequency f.sub.DL.sup.c=27.510 GHz.
[0034] Referring now to FIG. 5, by using another LO frequency
f.sub.LO=22.01 GHz, channel #100 in the 5 GHz band can be mapped to
Channel #1 in the 28 GHz band. Such flexible mappings from a
channel in the sub-7 GHz to channels in the millimeter wave bands
using different LO frequencies allow optimal use of the spectrum
and allow the needed flexibility to avoid, or minimize
interference. For example, all operators may not have the license
to use the entire 850 MHz in the 28 GHz bands. Alternatively, it is
possible that certain channels in the unlicensed 5 GHz band are
disallowed for use in certain regions based on the presence of
other primary users.
[0035] Thus, a UE with its LO tuned to 22.01 GHz, will down convert
a 28 GHz transmitted in Channel #1 down to Channel #100 in the 5
GHz band, while another UE with its LO tuned to 22.33 GHz will down
convert the same signals from Channel #1 down to channel #36 in the
5 GHz band. While the DL signal may still be received, the UL
signals from the UEs will not reach the AP correctly as the AP
cannot be listening on two different channels in the 5 GHz band at
the same time. For a system to interoperate correctly, it is
necessary that the receiver of a UE listens to the same millimeter
wave frequency channel that the transmitter of an AP is
transmitting over, and at the same time the transmitter of the UE
selects the same 5 GHz channel for transmission that the receiver
of the access point is listening on.
[0036] According to disclosed embodiments, a BS or AP periodically
transmits indication of the DL center frequency and the UL center
frequency used on the wireless link in a signaling message. The UE
receives the signaling packet over the air on the millimeter wave
frequency band and down converts the received packet to sub-7 GHz
band and passes the signal for baseband processing where the
message is decoded. The LO frequency is computed from the DL center
frequency and the UL center frequency with the relationship
described hereinafter:
f.sub.LO=f.sub.DL.sup.c-f.sub.UL.sup.c
[0037] In another embodiment, the AP may transmit DL and UL channel
numbers that correspond to a pre-specified channel center frequency
instead of the DL and UL channel center frequencies. The UE may
convert the DL and UL channel numbers to channel center frequencies
f.sub.DL.sup.c and f.sub.UL.sup.c respectively, in accordance with
a specified fixed mapping for the respective DL and UL frequency
spectrum bands. After converting the channel numbers to the center
frequencies, the LO frequency f.sub.LO may be computed using the
relationship described before.
[0038] In yet another embodiment, the AP may transmit a channel
number (corresponding to a center frequency of the UL channel) and
channel frequency information (corresponding to the center
frequency of the DL channel). The channel number is converted to
the corresponding channel center frequency and the relation
described before can be used for computing the LO frequency
f.sub.LO.
[0039] According to disclosed embodiments, uplink and downlink
frequencies are unknown to the UE prior to receiving the
indications of the uplink and downlink frequencies from the base
station or access point. After receiving the indications of uplink
and downlink frequencies, the UE determines the appropriate LO
frequency. The UE receives downlink signals using the appropriate
LO frequency.
[0040] According to some disclosed embodiments, wherein the AP and
the client devices communicate using the IEEE 802.11 protocol,
beacon messages are transmitted periodically by the AP. The beacon
messages transmitted by the AP include the sub-7 GHz channel number
and DL channel information. The DL channel information, which may
include DL channel center frequency or DL channel number, is
transmitted using an information element (IE) as a part of the
beacon message to explicitly indicate the DL channel information
corresponding to the millimeter wave band channel used for
communication.
[0041] FIG. 6A is a block diagram conceptually illustrating an
exemplary frame structure 600 for an information element which may
be contained in, for example, a beacon message of systems
communicating using IEEE 802.11 protocol. In the exemplary frame
structure 600, the available resource blocks are partitioned into
sections for transmissions of Element ID, Length, Organization
Identifier and vendor specific content. The sections may have
configurable size. A vendor specific information element (IE) is
depicted and an example of an IEEE-assigned OUI (Organizationally
unique identifier) is shown to indicate the vendor's ID. The IE
carries a 8-bit signaling field indicated as "Sig Field", followed
by a body. The body of the IE carries various information based on
a bit map carried in the Sig Field. Each bit in the bitmap flags
the presence of a certain parameter value. Thus, for instance, if
the UL Frequency Flag is set to 1, the body will contain a 16 bit
value indicating the UL frequency in MHz. If the UL Frequency Flag
is set to 0, then in this example only the DL channel center
frequency is present. In some embodiments, the Sig Field may be
more than 8 bits or less than 8 bits, and the UL channel center
frequency can be more than 16 bits or less than 16 bits. In some
embodiments, instead of the UL channel center frequency, a channel
number corresponding to a unique channel center frequency can be
carried in the body. Also, in some embodiments, the information may
not necessarily be a vendor specific IE but may be a standard IE
according to a protocol or any other standard.
[0042] In another embodiment, regardless of the explicit presence
of the DL and UL channel information, the UE derives the local
oscillator (LO) frequency by noting whether the UL channel number
in the signaling message is the same as the channel number
corresponding to the UL frequency that the UE is using. If the
channel number in the signaling message is the same as the channel
number being used by the UE then the LO frequency chosen by the UE
matches that used by the transmitting device, in this case the AP.
When the channel information indicated in the signaling message is
not the same as the channel number being used by the UE, the UE
derives the LO frequency that the AP is using by computing the
difference between the DL channel center frequency that the UE is
using, and the sub-7 GHz channel center frequency corresponding to
the channel number indicated in the signaling message.
[0043] In another embodiment, the AP may transmit the LO frequency
value in addition to the destination DL and/or UL channel
information. As a result, switching time is reduced if the AP
decides to change the channel or the AP is caused to change the
channel based on instructions from a radio resource management
entity. Explicit transmission of LO information also reduces the
switching time when scanning neighboring APs.
[0044] FIG. 6B is a block diagram conceptually illustrating an
exemplary frame structure 610 according to disclosed embodiments.
In the exemplary frame structure 610, the available resource blocks
are partitioned into sections for transmissions of UL channel
center frequency and the LO frequency. As discussed before, the sig
field carries a bit map of which each bit flags presence of certain
parameters. In the exemplary frame structure of FIG. 6B, UL
frequency Flag and the LO Frequency Flag are both set to 1, and
therefore both the UL center frequency and the LO frequency values
(16 bits each) are present. According to some embodiments, the
order of flags in the bitmap is pre-specified. In this example, the
first flag (1 bit) flags the presence/absence of the UL frequency,
while the second bit flags the presence/absence of the LO
frequency.
[0045] According to some disclosed embodiments, an AP may transmit
the channel information regarding the channels used by the
neighboring APs on the same node. For example, referring to FIG. 1,
A0 on node 104 may transmit information about A1 or A2 on the same
node 104. In other embodiments, A0 may transmit channel information
regarding the channels used by neighboring APs on neighboring
nodes. For example, A0 on node 104 may transmit information about
B1 on node 108 or C1 on node 112. The UE can utilize this
information to scan the channels and gauge the channel conditions,
traffic load etc. on the neighboring APs. If more favorable
conditions exist at the neighboring APs, the UE may initiate a
handover a handover to another AP resulting in an optimal use of
the spectrum band.
[0046] FIG. 6C is a block diagram conceptually illustrating an
exemplary frame structure 620 in which the available resource
blocks are partitioned for transmission of channel information
about neighboring APs of the transmitting AP. The Sig field carries
a bit map of which each bit flags presence of certain parameters.
In this illustration, the 3.sup.rd bit in the Sig field flags the
presence/absence of neighbor information. If this flag is set to 1,
a specific sequence of field is added to the IE body. The first
such field is the "number of neighbors" whose information is
carried in the IE body. Then for each neighbor, the AP/BS ID, the
DL channel center frequency, the UL channel center frequency and
the LO frequency is carried. For each neighbor, other information
(not shown in FIG. 6C), such as whether or not the AP is on the
same Sector of the Base Station or not, whether it is co-located on
the same physical site or not, may also be carried.
[0047] According to some disclosed embodiments, the access point
(AP) may communicate a UL transmission center frequency as well as
UL transmission channel numbers. The UE may use the DL channel
information signaled by the AP to remove mismatches between the
digital-to-analog converter (DAC) sampling frequency in the AP
transmitter and the analog-to-digital converter (ADC) sampling
frequency in the UE receiver. FIG. 7 is a block diagram of an AP
transmitter 704 and a UE receiver 708. At the transmitter, the
digital to analog converter (DAC) and the upconverters are based on
the same clock reference processed through a phase locked loop
(PLL) to generate local oscillator (LO) and sampling clock
frequencies. Similarly, at the receiver, the analog to digital
converter (ADC) and the downconverters are based on the same clock
reference.
[0048] FIG. 8 illustrates a system 800 which relies on 28 GHz band
for DL transmission and on 3.5 GHz for UL transmission in
accordance with disclosed embodiments. System 800 includes AP 801
and UE 816 that communicate wirelessly. As shown in FIG. 8, DL
transmission 805 from AP 801 to UE 816 is conducted over the 28 GHz
band, while UL transmission 812 from client device 816 to AP 801 is
conducted over the 3.5 GHz band. In System 800, a mixer 804 is used
to upconvert the 5 GHz signal 802 to 28 GHz by taking the analog
product of the Local Oscillator (LO) frequency, generated through a
phase-locked loop (PLL) 803, and the 5 GHz band signal. The 28 GHz
signal is then transmitted over the air as a DL transmission. The
UE 816 receives the 28 GHz signal and down-converts to a 5 GHz band
signal using a mixer 806 with the same local oscillator frequency
(LO) frequency generated using a PLL 807.
[0049] For the transmit path, a mixer 811 is used to down-convert a
5 GHz signal 809 to the 3.5 GHz band by taking the analog product
of the Local Oscillator (LO) frequency, generated through a
phase-locked loop (PLL) 810, and the 5 GHz band signal. The 3.5 GHz
band signal is then transmitted over the air as a UL transmission
812. The AP 801 receives the 3.5 GHz band signal and up-converts to
a 5 GHz band signal using a mixer 813 with the same local
oscillator frequency (LO) frequency generated using a PLL 814. In
other embodiments, the UL transmission frequency band may lie above
the 5 GHz band.
[0050] According to disclosed embodiments, a base station or access
point transmitter, in addition to transmitting the DL and UL center
frequencies, also transmits the UL transmission center frequency,
denoted as f.sub.UL,TX.sup.c, which is obtained by the UE on
decoding the DL packet. The UL center frequency (e.g., 5 GHz) is
the center of the channel used in, for example, a modem or SoC,
while UL transmission center frequency (e.g., 3.5 GHz) is the
center frequency of the channel actually used for transmission. In
some embodiments, wherein the UL transmission center frequency
f.sub.UL,TX .sup.c is larger than the UL center frequency
f.sub.UL.sup.c, the UE calculates the LO frequency required for UL
transmissions, denoted as f.sub.LO.sup.UL, as
f.sub.LO.sup.UL=f.sub.UL,TX.sup.c-f.sub.UL.sup.c. Referring to FIG.
8, the mixer 811 and the PLL 810 are configured to output a sum of
the 5 GHz frequency 809 and the UL LO frequency, whereas the mixer
813 and the PLL 814 are configured to output a difference of the UL
transmission frequency and the UL LO frequency.
[0051] In other embodiments, wherein the UL transmission center
frequency f.sub.UL,TX.sup.c is smaller than the UL center frequency
f.sub.UL.sup.c, the UE calculates the LO frequency as
f.sub.LO.sup.UL=f.sub.UL.sup.c-f.sub.UL,TX.sup.c. In such
embodiments, referring to FIG. 8, the mixer 811 and PLL 810 are
configured to output a difference of the 5 GHz frequency 809 and
the UL LO frequency, whereas the mixer 813 and PLL 814 are
configured to output a sum of the UL transmission frequency and the
UL LO frequency.
[0052] According to some disclosed embodiments, in addition to the
DL and UL channel numbers, the AP may transmit a UL transmission
channel number. The UE converts the UL transmission channel number
to a UL transmission channel center frequency f.sub.UL,TX.sup.c in
accordance with a specified fixed mapping for the frequency
spectrum band for UL transmission, which may be used to derive the
UL LO frequency f.sub.LO.sup.UL.
[0053] In wireless communication systems, there is often a mismatch
between transmitter and receiver clock references. This impacts the
link in two ways: [0054] a. It creates misalignment between the
upconverters and the downconverters, also known as channel
frequency offset (CFO); [0055] b. It creates misalignment between
the DAC and ADC, also known as sampling frequency offset (SFO).
[0056] Modern wireless communications receivers, including those
that implement the IEEE 802.11ac standard, must remove CFO and SFO
to optimize performance. For example, both CFO and SFO can be
removed digitally through numerically controlled oscillators (NCOs)
and phase slope adjustments, respectively. To remove CFO and SFO,
numerical estimates of both quantities must be available to the
receiver. CFO is often measured through self-correlation of
periodic digital sequences at the receiver. SFO may be mapped from
CFO if the DL center frequency is known. For example, let f.sub.tx
be the frequency of the clock reference at the transmitter. The DAC
sampling clock has frequency f.sub.dac and is derived by applying a
conversion factor K through the PLL such that f.sub.dac=K*f.sub.tx.
The 5 GHz upconversion LO has frequency f.sub.uc,5 and is derived
by applying a conversion factor L such that f.sub.uc,5=L*f.sub.tx.
The 28 GHz upconversion LO has frequency f.sub.uc,28 and is derived
by applying a conversion factor M such that f.sub.uc,28=M*f.sub.tx.
At the receiver, the same conversion factors apply such that
f.sub.adc=K*f.sub.rx, f.sub.dc,5=L*f.sub.rx, and
f.sub.dc,28=M*f.sub.rx are ADC sampling clock frequency, the 5 GHz
downconversion LO frequency, and the 28 GHz down-conversion LO
frequency, respectively. Together, this means that the CFO of the
link equals (L+M)*(f.sub.rx-f.sub.tx) and the SFO of the link
equals K*(f.sub.rx-f.sub.tx). Consequently, we can relate CFO to
SFO through the relationship SFO=K*CFO/(L+M). After we measure the
CFO it is possible to calculate SFO, assuming we know the 28 GHz
conversion factor, which is implicit in the 28 GHz downlink center
frequency.
[0057] According to some disclosed embodiments, the signaling of
the DL center frequency is used to inform the CFO to SFO mapping as
shown in FIG. 9. A receiver 904 processes the message through the
medium access control and physical layer (MAC+PHY) and extracts the
downlink center frequency. The receiver 904 also estimates the CFO.
Both the CFO and the downlink center frequency are used to generate
and estimate of SFO, which is also provided to the PHY for future
processed messages to cancel SFO degradations.
[0058] FIG. 10 is a flow diagram illustrating example blocks
executed to implement one aspect of the present disclosure. In
block 1004, a plurality of parameter values is received at a user
equipment (UE) using a first local oscillator (LO) value, where the
plurality of parameter values includes indications of downlink
frequency channel and uplink frequency channel. (e.g., channel
number or frequency in MHz). In block 1008, a second LO frequency
value is determined at the UE, where the second LO frequency value
is determined using the indications of downlink and uplink
frequency channels. In block 1012, downlink signals are received
from an associated base station using the second LO frequency
value.
[0059] Those skilled in the art will recognize that, for simplicity
and clarity, the full structure and operation of all systems
suitable for use with the present disclosure is not being depicted
or described herein. Instead, only so much of a system as is unique
to the present disclosure or necessary for an understanding of the
present disclosure is depicted and described. The remainder of the
construction and operation of the disclosed systems may conform to
any of the various current implementations and practices known in
the art.
[0060] Of course, those of skill in the art will recognize that,
unless specifically indicated or required by the sequence of
operations, certain steps in the processes described above may be
omitted, performed concurrently or sequentially, or performed in a
different order. Further, no component, element, or process should
be considered essential to any specific claimed embodiment, and
each of the components, elements, or processes can be combined in
still other embodiments.
[0061] It is important to note that while the disclosure includes a
description in the context of a fully functional system, those
skilled in the art will appreciate that at least portions of the
mechanism of the present disclosure are capable of being
distributed in the form of instructions contained within a
machine-usable, computer-usable, or computer-readable medium in any
of a variety of forms, and that the present disclosure applies
equally regardless of the particular type of instruction or signal
bearing medium or storage medium utilized to actually carry out the
distribution. Examples of machine usable/readable or computer
usable/readable mediums include: nonvolatile, hard-coded type
mediums such as read only memories (ROMs) or erasable, electrically
programmable read only memories (EEPROMs), and user-recordable type
mediums such as floppy disks, hard disk drives and compact disk
read only memories (CD-ROMs) or digital versatile disks (DVDs).
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