U.S. patent application number 12/479260 was filed with the patent office on 2009-10-01 for wireless communication method and apparatus for forming, steering and selectively receiving a sufficient number of usable beam paths in both azimuth and elevation.
This patent application is currently assigned to INTERDIGITAL TECHNOLOGY CORPORATION. Invention is credited to Steven Jeffrey Goldberg.
Application Number | 20090245411 12/479260 |
Document ID | / |
Family ID | 36261853 |
Filed Date | 2009-10-01 |
United States Patent
Application |
20090245411 |
Kind Code |
A1 |
Goldberg; Steven Jeffrey |
October 1, 2009 |
WIRELESS COMMUNICATION METHOD AND APPARATUS FOR FORMING, STEERING
AND SELECTIVELY RECEIVING A SUFFICIENT NUMBER OF USABLE BEAM PATHS
IN BOTH AZIMUTH AND ELEVATION
Abstract
A wireless communication method of exploiting the radio
frequency (RF) physical environment to establish a sufficient
number of usable multiple paths of RF propagation for facilitating
communications. The method is implemented in a wireless
communication system including at least one transmitter and at
least one receiver. The receiver's antenna is directed towards one
of a plurality of reception paths and receives a data stream from
the transmitter via the reception path that the receiver antenna is
directed towards. The receiver decodes the data stream,
reconstructs a modulation pattern of the decoded data stream, and
subtracts the reconstructed data stream from a sum of all of the
signals received by the receiver via the reception paths. The
receiver provides received signal direction information associated
with reception paths to the transmitter. The transmitter adjusts
and/or eliminates one or more of the reception paths that are
unusable based on the signal direction information.
Inventors: |
Goldberg; Steven Jeffrey;
(Downingtown, PA) |
Correspondence
Address: |
VOLPE AND KOENIG, P.C.;DEPT. ICC
UNITED PLAZA, SUITE 1600, 30 SOUTH 17TH STREET
PHILADELPHIA
PA
19103
US
|
Assignee: |
INTERDIGITAL TECHNOLOGY
CORPORATION
Wilmington
DE
|
Family ID: |
36261853 |
Appl. No.: |
12/479260 |
Filed: |
June 5, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11014290 |
Dec 16, 2004 |
7551680 |
|
|
12479260 |
|
|
|
|
60622899 |
Oct 28, 2004 |
|
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Current U.S.
Class: |
375/267 |
Current CPC
Class: |
H01Q 1/241 20130101;
H04B 7/0617 20130101; H04B 7/086 20130101; H04L 1/02 20130101 |
Class at
Publication: |
375/267 |
International
Class: |
H04L 1/02 20060101
H04L001/02 |
Claims
1. A wireless communication receiver configured to: receive, from a
sender, an omni-directional beam or a broad beam; determine the
direction from which it receives signals by noting significant
change information in the received signals; and return the
significant change information to the sender.
2. A wireless communication transmitter configured to send a
wireless communication to a receiver using an omni-directional beam
or a broad beam adjusted according to received feedback
information, from the receiver, that includes at least one
significant change information based on adjustments to the
omni-directional beam or the broad beam.
3. The transmitter of claim 2, further configured to change azimuth
or elevation of the beams to cause the beams to scatter in various
directions which changes a multipath.
4. The transmitter of claim 2, further configured to narrow its
beam transmission based upon the at least one received significant
change information.
5. A method for wireless communication comprising: receiving, by a
wireless receiver, an omni-directional beam or a broad beam from a
sender; the receiver determining the direction from which it
receives signals by noting significant change information in the
received signals; and the receiver returning the significant change
information to the sender.
6. A method for determining signal direction comprising: a
transmitter using an omni-directional beam or a broad beam adjusted
according to received feedback information that includes at least
one significant change information based on adjustments to the
omni-directional beam or the broad beam.
7. The method of claim 6, further comprising: the transmitter
changing azimuth or elevation of the beams causing the beams to
scatter in various directions which changes a multipath.
8. The method of claim 6, wherein the beam transmission is narrowed
based upon the at least one received significant change
information.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 11/014,290, filed Dec. 16, 2004, which claims
priority from U.S. Provisional Patent Application No. 60/622,899,
filed Oct. 28, 2004, which is incorporated by reference as if fully
set forth.
FIELD OF THE INVENTION
[0002] The present invention relates to a wireless communication
system including a transmitter and a receiver. More particularly,
the present invention relates to forming, steering and selectively
receiving usable beam paths.
BACKGROUND
[0003] A multipath in radio frequency (RF) communications refers to
the existence of multiple paths of RF propagation between a
transmitter and a receiver. In situations when the paths contain
the same data, but are spaced apart in time, the resultant
reception can be destructive. There are however circumstances when
it is actually desirable to have multiple paths. In these cases
each path can carry a different data stream. This technique is
referred to as a layered space approach, or under the broader
category of multiple input and multiple output (MIMO) communication
systems. If the transmitter and receiver are capable of utilizing
each path, the effective data bandwidth of the link between the two
can be increased by the number of unique usable paths.
[0004] One problem is that not enough natural paths, or existing
paths with discernable characteristics, may be exploitable for the
capabilities of the transmitters and receivers to be fully
utilized. The prior art exploits the elevation variable
characteristics of a transmitter. This path may not always be
available due to the lack of intervening physical obstacles to
scatter the signals. Even when this option is available, it may not
provide sufficient paths to fully utilize the ability of the
transmitter and receiver.
[0005] FIG. 3 illustrates a prior art wireless communication system
300 which includes a transmitter 305 and a receiver 310. The
transmitter 305 forms a multipath (i.e., a first path 315 and an
additional path 320) via an elevation antenna pattern. However, the
additional path 320 formed by the transmitter 305 is formed by
directing a beam towards the ground 325.
[0006] Conventional wireless communication systems use beam forming
for non-MIMO purpose. Therefore, a method and apparatus is desired
for exploiting the RF physical environment by combining beam
forming with MIMO to provide a sufficient number of paths.
SUMMARY
[0007] The present invention is related to a wireless communication
method of exploiting the RF physical environment to establish a
sufficient number of usable multiple paths of RF propagation for
facilitating communications. The method is implemented in a
wireless communication system including at least one transmitter
and at least one receiver. The receiver's antenna is directed
towards one of a plurality of reception paths and receives a data
stream from the transmitter via the reception path that the
receiver antenna is directed towards. The receiver decodes the data
stream, reconstructs a modulation pattern of the decoded data
stream, and subtracts the reconstructed data stream from a sum of
all of the signals received by the receiver via the reception
paths. The receiver provides received signal direction information
associated with reception paths to the transmitter (i.e., the
receiver is configured to determine the direction the incident
signals are coming from). The transmitter adjusts and/or eliminates
one or more of the reception paths that are unusable based on the
received signal direction information (i.e., the transmitter is
configured to direct beam nulls toward the signals to be
attenuated).
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] A more detailed understanding of the invention may be had
from the following description, given by way of example and to be
understood in conjunction with the accompanying drawings
wherein:
[0009] FIG. 1 illustrates a conventional coordinate system which
depicts a nominal orientation;
[0010] FIG. 2 facilitates the visualization and interpretation of
the three dimensional situations shown in FIGS. 3, 4 and 9-14;
[0011] FIG. 3 illustrates multipath creation via elevation as
implemented by conventional wireless communication systems;
[0012] FIG. 4 illustrates multipath creation via azimuth in
accordance with the present invention;
[0013] FIG. 5 illustrates an antenna (or an antenna array) on a
finite groundplane with an RF choke inserted on the edge of the
groundplane in accordance with one embodiment of the present
invention;
[0014] FIG. 6 illustrates a beam formed by the antenna of FIG. 6
before and after inserting the RF choke on the edge of the
groundplane;
[0015] FIG. 7 shows an antenna system including a Shelton-Butler
matrix feeding a circular array, thus forming a 4-port
Shelton-Butler matrix fed circular array in accordance with one
embodiment of the present invention;
[0016] FIG. 8 shows an antenna system including a 2-tier stacked
Shelton-Butler matrix feeding a stacked circular array in
accordance with another embodiment of the present invention;
[0017] FIG. 9 illustrates line of sight and azimuth paths in
accordance with the present invention;
[0018] FIG. 10 illustrates azimuth and elevation usage in
accordance with the present invention;
[0019] FIG. 11 illustrates line of sight, azimuth and elevation
paths in accordance with the present invention;
[0020] FIG. 12 illustrates line of sight, azimuth and elevation
with only boresights in accordance with the present invention;
[0021] FIG. 13 illustrates azimuth opportunities in accordance with
the present invention;
[0022] FIG. 14 illustrates general elevation opportunities in
accordance with the present invention; and
[0023] FIG. 15 is a block diagram of an exemplary receiver
configured according to a preferred embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0024] The preferred embodiments will be described with reference
to the drawing figures where like numerals represent like elements
throughout.
[0025] FIG. 1 illustrates the coordinate system utilized in a
nominal orientation. The present invention will operate with
adjustments being made for deviations from the orientations that
are described using the coordinate system of FIG. 1. For example,
obstacles (e.g., buildings) may not always present a displacement
only in the Z direction. Slanted, curved, or irregular structures
exist, somewhat randomizes their orientation with respect to the
present invention's components, resulting in a spread of
reflections and refractions. The general direction of signals
however is preserved sufficiently to affect the needs of the
present invention.
[0026] It can be somewhat difficult to visualize the three
dimensional situations to be depicted. To facilitate this need, two
views of each situation as illustrated in FIGS. 3-10 are presented,
as depicted in FIG. 2. The Elevation view represents a view from
the surface of the earth looking at the antennas. The Azimuth view
will represent a view from above the antennas looking down towards
the Earth. As shown in FIG. 2, one dimension will therefore always
be "compressed into the page." Additionally, the pattern outlines
of the beams are approximations to the actual outline of the beams,
and represent power levels relative to the peak at the boresight.
Lower degree lobes are not shown for clarity. Likewise, during
reflections, refractions, and propagations through some obstacles,
the patterns may become very irregular and numerous.
[0027] In conventional wireless communication systems, the
transmission and receive antenna patterns are at most set up to
provide maximum power transmission and reception between the
transmitter and receiver. In its simplest form, the present
invention uses multiple antenna beam forming elements at the
transmitter and receiver. Reflectors may be placed behind the
elements to direct the overall antenna pattern in a general
direction. The antennas used by the present invention have the
ability to beam form either or both the transmitter and receiver
arrays. The present invention exploits the availability of beam
steering in both the azimuth and elevation aspects. It further
exploits the availability of beam forming at both the transmitter
and receiver when available.
[0028] FIG. 4 illustrates a wireless communication system 400 which
includes a transmitter 405 and a receiver 410. The transmitter 405
forms a multipath via an azimuth antenna pattern which reflects off
an obstruction 415 to the intended receiver 410 in accordance with
one embodiment of the present invention. The transmitter 405 forms
the additional path by directing the beam towards an elevation
obstruction.
[0029] For example, beams in one plane may be deflected, while
antenna elements are used to create various beam patterns in an
orthogonal plane. Scattering of the groundplane is controlled or
eliminated, and beam tilt and depression is made variable. Thus, in
accordance with the present invention, a beam formed by transmitter
405 may be pointed in any desired elevation angle, while the
conventional transmitter provides only fixed, substantially horizon
beams.
[0030] As disclosed by co-pending U.S. Provisional Patent
Application No. 60/619,763, filed on Oct. 18, 2004, an antenna or a
MIMO array, situated over a finite groundplane is shown in FIG. 5,
along with an enlarged cut away view of the groundplane. A
continuous radio frequency (RF) choke 505 is placed on the edge
(i.e., rim) of the groundplane. The RF choke 505 is a parallel
plate waveguide, which can be a printed circuit board with two
conducting surfaces. The RF choke 505 may include a plurality of
chokes connected in series to increase the choking effect. The RF
choke 505 may be formed from any other type of transmission line or
lumped element equivalent that fits the geometry of the groundplane
edge. The shunt 510 shown in FIG. 5 can be formed from conducting
rivets, or the equivalent. The distance between the shunt 510 and
the opening 515 determines the impedance at the waveguide opening.
For an infinite impedance at the opening 515, the distance between
the shunt 510 and the opening 515 should be a quarter-wavelength in
the propagating medium.
[0031] The result of using the RF choke 505 is depicted in FIG. 6,
where a beam 605 is formed with a tilt using a regular groundplane,
and a beam 610 formed using a groundplane with the RF choke 505 in
accordance with the present invention redirects the beam toward the
horizon.
[0032] In another example, a more sophisticated means to direct
multiple beams with equal resolution in three dimensions may be
used in accordance with the present invention. As disclosed by
co-pending U.S. Provisional Patent Application No. 60/619,223,
filed on Oct. 15, 2004, using a Shelton-Butler matrix feeding a
circular array creates isolated omni-directional pancake beams that
are isolated from each other. The phase of each mode is
characteristic of the signal's direction of arrival. By comparing
the phases of two modes, information of the direction of arrival
can be derived. Some mode pair selections allow unambiguous linear
relationship between the phase and the angle of arrival. That
greatly simplifies subsequent processing.
[0033] In elevation, amplitude comparison can be used. A complete
elevation and azimuth direction finding system can thus be
implemented by sharing the received single "bit" of incoming wave.
A bit or pulse which contains both amplitude and phase information
is shared in a manner where the amplitude information is used by
elevation determination, and phase information is used for azimuth
determination.
[0034] The same antenna system can electronically and automatically
form a beam in the direction of the targeted incoming signal
without resorting to a separate system. This system can provide
enough gain for wireless applications. For a system that requires
higher gain, lenses, reflectors, and electronic controlled
parasitic antennas can be used to further increase directivity to
meet the need of such applications.
[0035] A single array system can be used to perform direction
finding and automatic beam forming in the desired direction. This
system provides 360 degree instantaneous azimuth coverage, where
conventional systems cannot.
[0036] FIG. 7 shows an antenna system 700 including a
Shelton-Butler matrix 705 feeding a circular array 710, thus
forming a 4-port Shelton-Butler matrix fed circular array. The
ports 715 shown on top connect to the antennas of the circular
array 710. The ports 720 on the bottom are mode ports. The
Shelton-Butler matrix 705 includes a plurality of hybrids and fixed
phase shifters which can be line-lengths. The antenna system 700
forms multiple but isolated orthogonal omni-directional pancake
shaped radiation patterns. The antenna system 700 forms a plurality
of available orthogonal omni-directional modes. The orthogonality
preserves the full strength of each mode, which is in contrast to
conventional mode formation using a power-divider, where the power
is all used up in forming one mode. The phase of the antenna system
700 is linear to the angle of arrival. Linear simplicity and high
precision are the products of the antenna system 700, whereby angle
of arrival information is provided for both azimuth and
elevation,
[0037] Elevation angle detection requires two Shelton-Butler
matrices 705 which form two new modes, a sum-mode and a
difference-mode. The ratio of the sum-mode over the difference-mode
indicates the angle away from boresight.
[0038] In order to form a beam in the direction of the arriving
signal, a phase shift is inserted in the sum-and-difference matrix
to steer the sum-mode beam to the elevation boresight. This
sum-mode can be used as the beam for communication. However, the
beam shape in azimuth is still omni-directional. To form a
directive beam in azimuth, all the modes in azimuth have to be
aligned. This requires a power divider at the output, and phase
shifters in the divided branches. The azimuth beam can be
synthesized using a fast Fourier transform. The phase shifters will
drive the beam to the required direction.
[0039] FIG. 8 shows an antenna system 800 including a 2-tier
stacked Shelton-Butler matrix 805 feeding a stacked circular array
810. The Shelton-Butler matrix 805 includes two azimuth boards 815
feeding eight antennas of the array 810. The azimuth boards 815 are
fed by a row of elevation matrices 820 that separate the family of
azimuth beams into two families with different elevation angles. In
this case, each elevation matrix 820 is a 2-port hybrid with proper
phase delays.
[0040] In FIG. 9, a line of sight path and an elevation path are
shown. From the elevation view both paths are parallel, while in
the azimuth they are shown to be distinct.
[0041] Both elevation and azimuth usage can be exploited, as
illustrated in FIG. 10. The thin pattern is reflected in elevation,
and the thick one in azimuth.
[0042] In FIG. 11, a line of sight path, an azimuth path and an
elevation path are shown, with the dotted line representing the
line of sight between the antennas. The simple pattern
approximations become rapidly difficult to visualize.
[0043] As shown in FIGS. 12-14, the simple pattern approximations
are replaced by arrows showing just the boresight of the beams.
[0044] FIG. 12 illustrates line of sight, azimuth, and elevation
with only boresights. In actual deployments, there may be
obstructions to both sides of the line of sight, and irregularities
in their placement and form that allow for many more beams, as
shown in FIG. 13.
[0045] As shown in FIG. 14, deployments inside of buildings also
provide for more opportunities, as the ceilings or objects fastened
thereto become another obstacle.
[0046] While FIGS. 1-14 have been illustrated from the
transmitter's viewpoint of creating multipaths, consideration also
needs to be given to the receiver's operation. One means to
differentiate the received paths is by multi-user detection (MUD)
methods. The basic concept is that if a data stream can be properly
decoded, its modulation pattern can be reconstructed, and
subtracted from the summed reception of all the signals. This
process is repeated until all possible individual data streams are
decoded. Alternatively, receiver beams may be pointed at a
plurality of individual reception paths, whereby the receiver
decodes each path individually.
[0047] A very robust methodology is to combine both the MUD and
receiver beamforming methods. The beamforming basically reduces the
number of paths being seen by the decoder at any one time, and the
MUD separates any multiple path receptions that still exist. There
are also opportunities for a MUD and/or beam operational instance
to accurately decode one or more paths, and for the resultant
information to be utilized by the MUD in another beam instance to
enhance its operation.
[0048] FIG. 15 is a block diagram of an exemplary receiver 1500
configured according to a preferred embodiment of the present
invention. The receiver 1500 includes a multi-user detector 1505, a
beam selector 1510, a baseband decoder 1515 and an antenna 1520. A
group of signals A, B and C received by the antenna 1520 are
forwarded to the beam selector 1510 which separates the signal C
from the group of signals A, B and C. The signal C is sent from the
beam selector 1510 directly to the baseband decoder 1515. The
signals A and B are sent from the beam selector 1510 to the
multi-user detector 1505.
[0049] One of ordinary skill in the art would realize that any
actual utilization of the present invention is subject to real
world constraints. For example, irregularities in obstacles, the
movement of the obstacles themselves (e.g., cars, window, people),
weather condition changes, or the like, may change the multipath
environment.
[0050] The initial determination of the usable beam patterns may be
partially or in whole derived using the different embodiments
described below.
[0051] In one embodiment, a user of communication services observes
existing opportunities for paths from both the receiver and
transmitter perspectives is used to derive settings, which are then
entered (e.g., stored in a memory) using either the manual
directional controls of hardware equipment (e.g., a keyboard) or by
some sighting methodology (e.g., adjusting a signal to create a
path and pressing a button to lock in the coordinates when it is
adequately detected). For example, the observations could be that
there are buildings to the left of the main communication
direction, but an open area to the right. The present invention
would interpret this as meaning that reflection paths are possible
to the left, while it would be a waste of resources (e.g., beam
power) to direct any beams to the right.
[0052] In another embodiment, an omni-directional or broad beam is
sent in the general direction of the receiver. The receiver has the
capability to discern the direction from which it receives adequate
signals. This information is returned to the transmitter, which
narrows its beam transmission in a particular sequence to eliminate
some multipaths. The receiver notes the significant changes in the
received signals, and returns the information to the sender. This
ongoing interactive process determines the general characteristics
of the multipaths available.
[0053] In yet another embodiment, the transmitter scans narrow
beams (i.e., azimuth, elevation, or both) and receives indications
from the receiver as to the reception it detects at various times
in the scan. The scanning process reveals to the sender and
receiver which paths are useable.
[0054] Since paths may come and go, ongoing communication is best
served by coding redundancy and path redundancy. The degree to
which these overhead burdens degrade the effective data rate will
be very situational dependant. The potential gain obtainable by the
present invention, however, will in most cases greatly overshadow
the lost from the ideal knowledge of the paths situation.
[0055] While the present invention has been described in terms of
the preferred embodiment, other variations which are within the
scope of the invention as outlined in the claims below will be
apparent to those skilled in the art.
* * * * *