U.S. patent application number 10/791221 was filed with the patent office on 2004-11-25 for high speed fixed wireless voice/data systems and methods.
This patent application is currently assigned to Kathrein-Werke KG. Invention is credited to Reudink, Douglas O., Reudink, Mark D..
Application Number | 20040235527 10/791221 |
Document ID | / |
Family ID | 33449608 |
Filed Date | 2004-11-25 |
United States Patent
Application |
20040235527 |
Kind Code |
A1 |
Reudink, Douglas O. ; et
al. |
November 25, 2004 |
High speed fixed wireless voice/data systems and methods
Abstract
Systems and methods adapted to optimize data throughput in
wireless communications network are shown and described. In the
preferred embodiment multiple antenna beam base stations are
utilized to provide reuse of communications channels. Reuse of the
communications channels by the base stations is preferably
optimized by considering mutually exclusive antenna beam pairs and
antenna beam pairs providing reduced signal quality. A preferred
embodiment control channel is taught which provides for the initial
and subsequent identification and use of a most preferred antenna
beam for establishing communications. Alternative embodiments of
the invention utilize multiple antenna beam remote stations.
Inventors: |
Reudink, Douglas O.; (Port
Townsend, WA) ; Reudink, Mark D.; (Seattle,
WA) |
Correspondence
Address: |
DALLAS OFFICE OF FULBRIGHT & JAWORSKI L.L.P.
2200 ROSS AVENUE
SUITE 2800
DALLAS
TX
75201-2784
US
|
Assignee: |
Kathrein-Werke KG
Rosenheim
DE
|
Family ID: |
33449608 |
Appl. No.: |
10/791221 |
Filed: |
March 1, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10791221 |
Mar 1, 2004 |
|
|
|
09422210 |
Oct 19, 1999 |
|
|
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Current U.S.
Class: |
455/561 ;
455/560 |
Current CPC
Class: |
H04W 16/24 20130101;
H04W 16/02 20130101; H04W 16/12 20130101; H04B 7/0491 20130101 |
Class at
Publication: |
455/561 ;
455/560 |
International
Class: |
H04M 001/00; H04B
001/38 |
Claims
What is claimed is:
1. A base station system adapted to provide simultaneous reuse of
channels at said base station, said system comprising: a multiple
narrow beam antenna system adapted to provide isolation of signals
radiated therein, wherein sectors of said base station are
associated with different ones of said antenna beams, wherein a
sector control channel is associated with each sector of said base
station; base station radio circuitry adapted for providing a
plurality of discrete simultaneous communications using a first
communication channel in different ones of said sectors; and
circuitry providing controllable coupling of said base station
radio circuitry to said multiple narrow beam antenna system.
2. The system of claim 1, wherein a different said sector control
channel as associated with each sector of said base station.
3. The system of claim 1, wherein said sector control channel is a
multiple beam antenna access channel adapted for use in identifying
a most preferred antenna beam of said multiple narrow beam antenna
system for use with each of a plurality of remote stations in
communication with said base station.
4. The system of claim 3, wherein said sector control channel
includes a forward link data packet comprising synch bits, overhead
information, RSSI information, number of antenna beams, current
antenna beam, and directed message.
5. The system of claim 3, wherein said sector control channel
includes a reverse link data packet comprising a leading and
trailing guard time, synch bits, RS identification information, and
report message.
6. A base station system adapted to provide simultaneous reuse of
channels at said base station, said system comprising: a multiple
narrow beam antenna system adapted to provide isolation of signals
radiated therein, wherein sectors of said base station are
associated with different ones of said antenna beams; base station
radio circuitry adapted for providing a plurality of discrete
simultaneous communications using a first communication channel in
different ones of said sectors; and circuitry providing
controllable coupling of said base station radio circuitry to said
multiple narrow beam antenna system, wherein said controllable
coupling circuitry is operable to redefine sectors of said base
station by associating different ones of said antenna beams
therewith.
7. The system of claim 6, wherein said controllable coupling
circuitry is adapted to provide independently controllable coupling
of each one of said plurality of discrete simultaneous
communications using said first communication channel to ones of
said antenna beams.
8. The system of claim 7, wherein said controllable coupling
circuitry is adapted to couple each one of said plurality of
discrete simultaneous communications using said first communication
channel to any one antenna beam of a sector associated with said
each one of said plurality of discrete simultaneous
communications.
9. The system of claim 6, wherein said first channel is a time
division duplex channel including a forward link portion and a
reverse link portion, wherein said forward link portion and said
reverse link portion are of different durations for a first remote
station in communication with said base station and a second remote
station in communication with said base station.
10. The system of claim 6, wherein said first channel is a
frequency division channel.
11. The system of claim 6, wherein said first channel is a time
division channel.
12. The system of claim 6, wherein said first channel is a code
division channel.
13. The system of claim 6, wherein said multiple narrow beam
antenna system is a fixed multiple beam antenna system.
14. The system of claim 6, wherein said multiple narrow beam
antenna system is an adaptive array antenna system.
15. The system of claim 6, wherein said multiple narrow beam
antenna system provides a plurality of substantially
non-overlapping antenna beams.
16. The system of claim 6, wherein said multiple narrow beam
antenna system provides a plurality of substantially overlapping
antenna beams.
17. A wireless communication system adapted to provide reuse of
channels at a base station, said system comprising: at least one
base station comprising: a multiple narrow beam antenna system
adapted to provide wireless communications to remote stations to
the exclusion of other remote stations, wherein multiple ones of
said antenna beams define sectors of said base station and said
provision of wireless communications to the exclusion of other
remote stations includes exclusion of other remote stations
disposed in a same sector; and base station radio circuitry adapted
for wireless communication with a number of remote stations
utilizing a first communication channel simultaneously in different
ones of said sectors; a plurality of remote stations, wherein said
plurality of remote stations include said number of remote
stations, ones of said plurality of remote stations comprising:
remote station radio circuitry adapted for wireless communication
utilizing said first communication channel; and circuitry providing
controllable coupling of said base station radio circuitry to said
multiple narrow beam antenna system, wherein said controllable
coupling circuitry is adapted to provide independently controllable
coupling of multiple discrete signals of said first channel to ones
of said antenna beams, wherein said controllable coupling circuitry
is adapted to couple ones of said antenna beams to different
portions of said base station radio circuitry to thereby provide
adjustable sector boundaries.
18. The system of claim 17, wherein said controllable coupling
circuitry is adapted to couple each one of said multiple discrete
signals of said first channel to any antenna beam of a sector
associated with said each one of said multiple discrete
signals.
19. The system of claim 17, wherein said controllable coupling
circuitry includes a switch matrix.
20. The system of claim 17, wherein said first channel is a time
division duplex channel including a forward link portion and a
reverse link portion.
21. The system of claim 17, wherein said forward link portion and
said reverse link portion are of different durations for a first
remote station of said number of remote stations and a second
remote station of said number of remote stations.
22. The system of claim 17, wherein said first channel is a
frequency division channel.
23. The system of claim 17, wherein said first channel is a time
division channel.
24. The system of claim 17, wherein said first channel is a code
division channel.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of co-pending and
commonly assigned U.S. patent application Ser. No. 09/422,210
entitled "High Speed Fixed Wireless Voice/Data Systems and
Methods," filed Oct. 19, 1999, the disclosure of which is
incorporated herein by reference.
TECHNICAL FIELD
[0002] The invention relates to wireless communication systems and
more particularly to systems and methods useful in establishing
wireless communication systems capable of providing high data
bandwidth channels at a plurality of base stations optimizing use
of radio frequency spectrum.
BACKGROUND OF THE INVENTION
[0003] It is often desirable to utilize wireless radio links to
provide information communication. The use of wireless links may be
advantageous where wired infrastructure (e.g., copper and/or fibre
communication network) is not in place to provide information
communication or where user demand, whether the number of users
and/or the capacity required by users, does not make it economical
to provide wired infrastructure. For example wireless local loop
(WLL) is often thought of to provide voice services in places where
wireline service is not available, such as in less developed
countries and remote areas within the United States.
[0004] In addition to providing voice services to remote sites not
otherwise provided wireline service, it may also be desired to use
radio to provide high rate data services to fixed users where
wireline service is inadequate or not available. However, a problem
with providing high rate data services, such as 1 MB/s, is that RF
spectrum is limited and expensive. For example, to attain high peak
rates often required or desired by data systems, spectrum bandwidth
on the order of 1 MHZ is typically required. Spectrum in the 1-3
GHz range may be utilized to attain high peak rates such as 1 MB/s.
Such frequencies may also be suitable for use in providing data
system communication as their frequency propagation conditions
typically allow partial line-of-sight or even non-line-of-sight
between a base station (BS) and a remote station (RS), thus
simplifying deployment of a network.
[0005] Although possibly providing suitable spectrum for data
system communications, spectrum in the 1-3 GHz range is becoming
widely used for a range of wireless communications. This results in
both the spectrum being expensive as well as potentially having a
high level of noise energy, caused by multiple uses of the
[0006] At millimeter wave (mm-wave) frequencies a great deal of
spectrum is available. However, such frequencies have disadvantages
associated with their use. For example, mm-wave propagation is
typically limited to line-of-sight between a BS and a RS.
Additionally, mm-wave radio propagation is severely limited by rain
and terrain, requiring complex control systems to deal with
temporary rain fades or increased transmit power to allow for a
worst case scenario. Such increase power, in addition to the
obvious expense in such a brute force solution, can limit reuse of
frequencies because of the overlapping radiation patterns
experienced when the conditions requiring the increased power are
not present or are not fully present in a particular antenna beam.
Nevertheless, multibeam antennas can provide benefit to this
frequency band.
[0007] There are some lower frequencies where spectrum is still
available. For example, there is unused personal communications
services (PCS) spectrum and under utilized ultra-high frequency
(UHF) television channel spectrum available in many geographic
regions of the United States. Additionally spectrum associated with
multichannel multipoint distribution service (MMDS), 200 MHZ
bandwidth at 2.5 GHz, remains available in many areas. These
portions of the spectrum often remain under/un-utilized because of
the inability of service providers to efficiently and economically
allocate the spectrum for use to multiple users.
[0008] In order to provide the desired data rate (data bandwidth)
in the available spectrum to multiple users in an efficient and
economical manner, it is advantageous to reuse frequencies. The
reuse of frequencies in wireless systems has been done in cellular
communication systems, where a plurality of BSs are allocated
particular frequencies or ranges of frequencies to provide
communications in an associated service area and where adjacent BSs
or portions thereof are restricted from use of same frequencies.
The use of narrow antenna beams in cellular systems can provide
capacity gains of 100% or more, compared to ordinary sectorized
cellular systems. However, the spectral reuse efficiency is still
less than 25%, i.e., at most 25% of the spectrum is available for
use at a single sight.
[0009] Code division multiple access (CDMA) cellular systems can
reuse the spectrum 3 times at a cell sight. However, CDMA
communications are quite inefficient in throughput. For example,
one CDMA sector typically provides only 100 kbs (15 walsh
codes.times.13 kbls) while using at least 1.5 MHZ bandwidth.
[0010] To make the best use of such frequencies, what is needed in
the art is a robust, spectrally efficient system and method to
provide voice and high rate data on demand to multiple
geographically dispersed users.
SUMMARY OF THE INVENTION
[0011] These and other objects, features and technical advantages
are achieved by a system and method which establishes a wireless
system capable of providing high bandwidth data channels, i.e.,
several megabit data channels, at every BS in a network while using
only a small amount of spectrum, i.e., a relative few radio
frequency (RF) channels. It shall be appreciated that as used
herein, channels may be comprised of frequency divisions, time
divisions, and/or code divisions.
[0012] The preferred embodiment of the present invention utilizes a
network of BSs deployed in a configuration to provide coverage to
the RSs for which it is desired to provide wireless data
communication services. For example, the network of BSs could
include a deployment of BSs dense enough to assure coverage to a
plurality of RSs throughout a particular geographic area, such as a
metropolitan area.
[0013] The deployment of BSs to provide wireless data communication
services in a defined geographic service area associated with each
particular BS shall be referred to herein as having "cells"
associated with each BS, wherein RSs disposed within the geographic
boundaries of a cell communicate principally with the BS thereof.
However, it should be appreciated that deployment of BSs of the
present invention is not limited to the regular spacing intervals
generally thought of when considering a typical cellular or PCS
mobile wireless communication system. For example, it is
anticipated that data communication will be provided to fixed point
RSs in a preferred embodiment of the present invention.
Accordingly, BSs may be deployed such that service areas sufficient
to encompass a predetermined number of fixed point RSs without
providing fully blanketed coverage throughout an area.
[0014] The BSs of the present invention preferably utilize multiple
narrow beam antennas, multiple beam antennas (MBA), capable of
directing energy into and out of any antenna beam on command. A
preferred embodiment of the BSs of the present invention utilize
multiple beam antennas providing 12 substantially non-overlapping
antenna beams to provide directional wireless signal coverage in an
area 360.degree. around an associated BS. Additionally or
alternatively, the multiple beam antennas of the BSs of the present
invention may provide antenna beams which substantially overlap,
such as to allow redundancy and/or to provide the ability for RSs
to change to different channels, such as based on interference
conditions.
[0015] The RSs of the present invention also preferably utilize
multiple narrow beam antennas. Specifically, a most preferred
embodiment of the RSs of the present invention utilize multiple
beam antennas providing 12 substantially non-overlapping antenna
beams to provide directional wireless signal coverage in an area
360.degree. around an associated RS. The use of such directive
antennas at the RSs of the preferred embodiment provides for a
reduction in signal scattering and, thus, a reduction of unwanted
energy in various antenna beams. However, the systems and methods
of the present invention will work with some or all of the RSs
having omnidirectional antennas. It should be appreciated that the
result will be higher system capacity if directive antennas,
whether multibeam or not, are used at the RSs.
[0016] Capacity is lowered in the network as radiation from a
network BS reaches RSs outside the BSs service area and/or
radiation from an RS reaches BSs outside the BS service area in
which the RS is operating. This limitation is partially due to the
limits on signal isolation of the BS and RS antenna patterns and
partially due to signal scattering and propagation conditions.
Accordingly, BSs of a preferred embodiment of the present invention
include resources, such as interference cancellers in the receive
links, to mitigate outside interference. Where BSs are provided
such resources and the RSs are not, capacity is generally a
downlink limitation.
[0017] Accordingly, a preferred embodiment of the present invention
includes resources, such as interference cancellers, at the RSs.
However, it should be appreciated that most data applications tend
to be non-symmetric, with most of the traffic flowing from the BSs
to the RSs, thus diminishing the effect of such downlink capacity
limitations. Accordingly, a most preferred embodiment of the
present invention forgoes the expense of inclusion of interference
cancellers at the network RSs.
[0018] The preferred embodiment of the present invention employs
systems and methods for determining which beams of a BS may be
utilized with a particular channel simultaneously to provide
increased data communication without intolerable co-channel
interference. Additionally or alternatively, the systems and
methods so employed provide determination of which network RSs
within a particular cell may be operated simultaneously with
tolerable co-channel interference. Accordingly, the present
invention operates to determine resource (antenna beam, RS,
communication channel, and the like) utilization sequences and
combinations (resource utilization solutions) adapted to provide
optimal capacity, desired quality/priority of service, and/or like
considerations.
[0019] In a preferred embodiment, determination of resource
utilization solutions in which particular resources may be utilized
includes the provision of a database or matrix of a particular
cell's resources for which simultaneous use is prohibited. In an
alternative embodiment, this database includes additional
information such as resource utilization solutions in which
particular resources which, although causing undesired results such
as co-channel interference, may be utilized at a diminished or
reduced capacity. The capacity of a particular cell is optimized
according to a preferred embodiment of the present invention by
considering signal quality measurements, such as signal to noise
ratio (SNR) and/or signal to interference ratio (SIR), as well a
capacity needs for each RS in the cell. Accordingly, various
resource utilization solutions may be analyzed with reference to
the preferred embodiment database in order to determine a resource
utilization solution which provides a desired level of service,
whether based on capacity (in either or both the forward and
reverse links), quality of service, and/or the like.
[0020] According to the present invention, given proper
interference conditions, simultaneous use of two or more antenna
beams with a same communication channel is possible. Moreover,
where good beam isolation is present, reuse factors of three and
four within a single cell are easily achievable according to the
present invention.
[0021] Additionally or alternatively, the systems and methods of
the present invention operate to determine inter-cell interference.
The preferred embodiment of the present invention employs systems
and methods for determining the amount of interference caused to
RSs outside of the area outside of a cell associated with a
particular BS. Preferably a database or matrix of mutually
exclusive beam pairs between a home BS and an adjacent BS, or the
BSs surrounding the home BS, is developed. In an alternative
embodiment, this database includes additional information such as
particular beam pairs which, although causing undesired results
such as co-channel interference, may be utilized at a diminished or
reduced capacity.
[0022] In order to allocate particular antenna beams of the above
mentioned inter-cell pairs of antenna beams among the BSs of a
network, a preferred embodiment of the present invention utilizes a
reference clock, such as that provided by the global positioning
system (GPS), available at interfering ones of the BSs.
Additionally or alternatively, embodiments of the present invention
may utilize inter-cell communications to coordinate use of
particular inter-cell interfering pairs of antenna beams. For
example, antenna beams of an inter-cell interfering pair of antenna
beams may be assigned for use at a first BS on a first come first
served basis, using inter-cell BS communications to notify another
BS of use of an antenna beam of the inter-cell interfering
pair.
[0023] Accordingly, the preferred embodiment of the present
invention examines various combinations of the cell and inter-cell
databases, and/or other available BS/RS/beam/channel information,
to determine a resource utilization solution which provides a
desired level of service, whether based on capacity (in either or
both the forward and reverse links), quality of service, and/or the
like. Preferably, all BS, beam, channel pairings are examined and
assignments with respect to simultaneous usage are made to those
pairs that provide a signal quality measurement, such as SIR, that
just exceeds a threshold determined to provide a desired quality of
service. Accordingly, the greatest number of uses/reuses of the
spectrum may be used to provide optimization.
[0024] Preferred embodiments of the present invention utilize time
division multiple access (TDMA) communication channels to allow
time sharing of RF channels among multiple users. Accordingly, the
present invention may use the preferred embodiment multi-beam
architecture (MBA) to switch or direct energy to the proper antenna
during the proper time slot to achieve system optimization as
discussed above. Moreover, where bandwidth is available, multiple
carriers may be simultaneously utilized in the multiple antenna
beams to provide additional capacity.
[0025] Additionally, or Alternatively, embodiments of the present
invention utilize CDMA communication channels to allow code sharing
of RF channels among multiple users. For CDMA systems, the greatest
efficiency occurs when transmission and reception between a BS and
RS occur only on a single beam. Accordingly, embodiments of the
present invention using CDMA, or other interference limited
channels, acquire and identify the strongest received signal beam
from an individual BS, such as by performing a correlation of the
target RS on all BS antenna beams. Thereafter, the present
invention may use the MBA to switch or direct energy to particular
antenna beams to achieve system optimization as discussed
above.
[0026] Variable data rates are used in a preferred embodiment of
the present invention. Accordingly, higher data rates may be
provided between a BS and particular RSs, where conditions allow.
For example, in the above described CDMA embodiment higher
capacities may be achieved through increased reuse and/or coding
gain decrease. RSs disposed relatively close to a BS (RSs
experiencing low path loss between the BS and RS) do not require
highly spread codes to achieve low error rate data. Accordingly,
allowing higher bit energy to noise density (E.sub.b/N.sub.o) for
RSs which require little power can be traded for a slight rise in
E.sub.b/N.sub.o for other RSs. Having a higher E.sub.b/N.sub.o
allows changing spreading codes to get higher throughput according
to one embodiment of the present invention.
[0027] Similar concepts are applied in TDMA system of the present
invention. Specifically RSs which are disposed relatively close to
a BS, or otherwise receive a strong signal, can operate at a
reduced power level and/or establish a link with a higher data
rate. For example, quadrature amplitude modulation (QAM) is an
example of modulation where the same bandwidth, i.e., the same baud
rate, provides multiple levels of modulation. Various orders of QAM
are utilized according to one embodiment of the present invention
to obtain higher throughput.
[0028] As described above, in a preferred embodiment of the present
invention, restrictions exist on the simultaneous use of two or
more antenna beams in a cell using a same channel. Accordingly,
sectors may be established which define channel sets and/or antenna
beams which may be used simultaneously. The highest capacity is
likely to be achieved when each sector carries an equal share of
the data traffic. Accordingly, a preferred embodiment of the
present invention provides for variable sector boundaries to allow
dynamic adjustment of sectors depending on traffic conditions on an
entire cell.
[0029] As described above, the present invention provides a robust,
spectrally efficient system and method to provide voice and high
rate data on demand to multiple geographically dispersed users. A
technical advantage of the present invention is that efficient use
of available frequencies may be made in providing high data rate
communications. A further technical advantage is provided in
determining which antenna beams and which RSs can operate
simultaneously with tolerable co-channel interference in order that
optimal capacity may be achieved.
[0030] The foregoing has outlined rather broadly the features and
technical advantages of the present invention in order that the
detailed description of the invention that follows may be better
understood. Additional features and advantages of the invention
will be described hereinafter which form the subject of the claims
of the invention. It should be appreciated by those skilled in the
art that the conception and specific embodiment disclosed may be
readily utilized as a basis for modifying or designing other
structures for carrying out the same purposes of the present
invention. It should also be realized by those skilled in the art
that such equivalent constructions do not depart from the spirit
and scope of the invention as set forth in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] For a more complete understanding of the present invention,
and the advantages thereof, reference is now made to the following
descriptions taken in conjunction with the accompanying drawing, in
which:
[0032] FIG. 1 shows a preferred embodiment multiple beam cell
utilized according the present invention;
[0033] FIG. 2 shows alternative embodiments of base station
circuitry of the present invention;
[0034] FIG. 3 shows reuse of channels by the circuitry of FIG.
2;
[0035] FIG. 4 shows a network of cells according to the present
invention;
[0036] FIG. 5 shows flow diagrams of the identification of antenna
beams for communication at remote stations and at base
stations;
[0037] FIG. 6 shows the degradation of a signal with varying
amounts of interference;
[0038] FIG. 7A shows a cell adapted to provide reuse of channels
according to the present invention;
[0039] FIG. 7B shows preferred embodiment optimization circuitry
for the optimization of data packets for the channel reuse of FIG.
7A;
[0040] FIG. 8 shows a network of cells according to the present
invention;
[0041] FIGS. 9 and 10 show preferred embodiment circuitry for the
acquisition of most preferred antenna beams;
[0042] FIG. 11 shows a preferred embodiment data container for a
forward link access channel;
[0043] FIG. 12 shows progression of the forward link access channel
through a preferred embodiment multiple beam antenna;
[0044] FIG. 13 shows a preferred embodiment data container for a
reverse link access channel;
[0045] FIG. 14 shows a preferred embodiment data container for a
direction message;
[0046] FIG. 15 shows preferred embodiment TDD circuitry of the
present invention; and
[0047] FIG. 16 shows overlap experienced in reuse of TDD
channels.
DETAILED DESCRIPTION
[0048] The present invention is directed to a wireless system
capable of providing several megabit channels at a plurality of
base stations (BSs) in a communication network while using only a
few RF channels. According to the preferred embodiment of the
present invention, a relatively small amount of spectrum is
utilized by the present invention in providing high data rate
communications to a number of geographically dispersed remote
stations (RSs). In order to provide a desired high data rate (high
data bandwidth) in the available spectrum to multiple users in an
efficient and economical manner, reuse of frequencies and/or other
communication channels is preferably utilized. In the preferred
embodiment, multiple antenna beams are provided in order to
facilitate the reuse of communication channels at a cell and/or
within the communication network.
[0049] A preferred embodiment of the present invention uses TDMA to
time share a single resource (frequency, channel, etcetera) among
multiple users. In utilizing TDMA techniques with the MBA of the
preferred embodiment, a switch or other controllable circuitry is
used to direct energy to the proper antenna beam during the proper
time slot. Alternatively, an adaptive antenna may "point" an
antenna beam directly at each user and quickly re-point to another
user. This has more complex circuitry, but works the same for
systems where any one antenna beam needs only a fraction of the
system capacity, such solutions are very efficient. It should be
appreciated that in an adaptive array one such adaptive antenna
beam may be utilized to provide signals in various azimuthal angles
as well as a variety of radiation pattern shapes. Accordingly,
multiple beams and multiple beam antennas as used herein includes
an adaptive array providing a single antenna radiation pattern at
any one instant, as well as those providing multiple simultaneous
antenna beams.
[0050] Hybrid systems, wherein both adaptive arrays and fixed beam
arrays are used, may be utilized according to the present
invention. For example, a preferred embodiment of the present
invention utilizes an adaptive array (or feed network coupled to a
common antenna array) on the uplink and a fixed beam array (or feed
network coupled to the common antenna array) on the downlink.
Accordingly, selection of a downlink antenna beam to use may be
made from the uplink signals to provide a system which adapts on a
per user basis for the uplink and selects one of N fixed beams for
downlink transmission.
[0051] Growth scenarios with multibeam TDMA are simple. For
example, initial deployment may begin with one RF carrier per BS.
Thereafter as demand dictates, and where bandwidth is available,
another carrier may be delegated to the BS. Using linear power
amplifiers (LPAs), multiple carriers may be communicated through
the same antenna beam simultaneously. Alternatively, restricting
usage to different antenna beams for different carriers may avoid
the use of LPAs, although such a configuration reduces flexibility
and throughput. If neighboring BSs in a communication network have
different RF channels, then growth at each BS, as well as the
utilization of the RF channels, proceeds independently. However,
according to a preferred embodiment of the present invention, reuse
of channels, both within a cell and throughout neighboring cells,
is utilized according to resource utilization solutions which may
be optimized to achieve increased capacity and/or desired levels of
throughput, quality of service, etcetera.
[0052] A preferred embodiment of the present invention uses CDMA to
code share a single resource (frequency, channel, etcetera) among
multiple users. In utilizing CDMA techniques with the MBA of the
preferred embodiment, the greatest efficiency occurs when
transmission and reception between a BS and RS occur only on a
single beam of the BS. This is because CDMA techniques are
interference limited. Therefore, limiting the area in which a
particular code signal is radiated will reduce the energy level
experienced outside this area and, thus, allow additional capacity
in these areas. Accordingly, a preferred embodiment of the present
invention provides selective coupling of signals to particular
antenna beams of the MBA, such as through a switch matrix or other
controllable circuitry, or form multiple beams aimed at individual
RSs.
[0053] BS 101 adapted according to the present invention is shown
in FIG. 1 as having a set of, preferably 12, narrow antenna beams
(beams 111-122) providing wireless communication within cell 102.
BS 101 is preferably adapted to direct energy into and out of any
antenna beam on command. A preferred embodiment of circuitry of BS
101 adapted as described above is shown in FIG. 2.
[0054] It should be appreciated that the multiple narrow antenna
beams utilized according to the present invention may be provided
by a multiple beam antenna array, by individual antennas adapted to
provide narrow beams, or by any other means deemed desirable.
Additionally, it should be appreciated that the number of antenna
beams utilized according to the present invention is not limited to
the 12 antenna beams illustrated. The antenna beams utilized
according to the present invention may be formed from a fixed beam
array (such as a Butler matrix switched beam array) or from
adaptive array (such as an adaptive beam forming array using
adjustable phase progressions and weighting to form antenna beams
and nulls).
[0055] Moreover, embodiments of the present invention may include
multiple elevation angles per antenna beam or per antenna beam
azimuthal position. Accordingly, increased capacity may be achieved
by further isolating the communication of signals, such as by
dedicating more unique pointing slots in a signal. Communication
timing may cycle through X azimuth angles at 0* and then Y azimuth
angles for a next elevation angle, and so on.
[0056] As shown in FIG. 2A, BS 101 includes BS radio 201 coupled to
antennas 211-222 through switch matrix 202 to direct energy between
any of antennas 211-222 and BS radio 201 (into and out of beams
1-N) on command. Control of switch matrix 202 and/or radio 201 is
preferably provided by a processor based control system (BS
controller 203), preferably having a central processing unit,
memory, and a control algorithm operable therewith. It should be
appreciated that BS controller 203 may be adapted to provide
additional functionality such as digital signal processing (DSP),
interference canceling, signal quality analysis, and the like.
[0057] According to the preferred embodiment of the present
invention, simultaneous use of 2 or more antenna beams in a single
cell, such as cell 102, is possible. One overriding determinant of
such reuse is antenna beam isolation. Some antennas are better than
others at providing isolation, but cost and size is an issue.
Additional beam isolation can be obtained by using cross
polarization transmission at adjacent beams. Cross polarization in
a same beam is technically possible, but such an embodiment tends
to cause the BS to be very expensive. Regardless of how isolation
is provided, an RF carrier is preferably dedicated to a particular
sector of the cell, defined as using K beams where K may be as
narrow as one antenna beam or may encompass a full 366.degree..
[0058] Accordingly, alternative embodiments of the circuitry of BS
101 are shown in FIGS. 2B through 2D. For example, FIG. 2B shows 2
BS radio units, BS radio 201b and BS radio 204b, coupled to
antennas 211-222. However in this embodiment BS radio 201b is
coupled to antennas 1 through k (here antennas 211-215 preferably
defining a first sector) through switch matrix 202b, while BS radio
204b is coupled to antennas k+1 through n (here antennas 216-222
preferably defining a second sector) through switch matrix 205b.
Control of switch matrixes 202b and 205b and/or radios 201b and
204b is preferably provided by BS controller 203b, preferably
configured substantially as BS controller 203 described above.
[0059] Each of BS radios 201b and 204b are preferably adapted to
provide communications on a same channel or channels as the other
one of BS radios 201b and 204b. Accordingly, as shown in FIG. 3A, a
same channel may be utilized within cell 102, such as at both beam
113 associated with BS radio 201b and beam 118 associated with BS
radio 204b, to provide increased communication capacity within the
cell as compared with the exclusive use of available channels
within that cell.
[0060] FIG. 2C shows 3 BS radio units, BS radio units 201c, BS
radio 204c, and BS radio 206c, coupled to antennas 211-222. However
in this embodiment BS radio 201c is coupled to antennas 1 through k
(here antennas 211-214 preferably defining a first sector) through
switch matrix 202c, while BS radio 204c is coupled to antennas k+1
through l (here antennas 215-218 preferably defining a second
sector) through switch matrix 205c, and while BS radio 206c is
coupled to antennas l+1 through n (here antennas 219-222 preferably
defining a third sector) through switch matrix 207c. Control of
switch matrixes 202c, 205c, and 207c and/or radios 201c, 204c, and
206c is preferably provided by BS controller 203c, preferably
configured substantially as BS controller 203 described above.
[0061] Each of BS radios 201c, 204c, and 206c are preferably
adapted to provide communications on a same channel or channels as
the other one of BS radios 201c, 204c, and 206c. Accordingly, as
shown in FIG. 3B, a same channel may be utilized within cell 102,
such as at each of beams 111 associated with BS radio 201c, 115
associated with BS radio 204c, and 119 associated with BS radio
206c to provide increased communication capacity within the cell as
compared with the exclusive use of available channels within that
cell.
[0062] FIG. 2D shows 4 BS radio units, BS radio units 201d, BS
radio 204d, BS radio 206d, and BS radio 208d coupled to antennas
211-222. However in this embodiment BS radio 201d is coupled to
antennas 1 through k (here antennas 211-213 preferably defining a
first sector) through switch matrix 202d, while BS radio 204d is
coupled to antennas l+1 through l (here antennas 214-216 preferably
defining a second sector) through switch matrix 205d, while BS
radio 206d is coupled to antennas l+1 through m (here antennas
217-219 preferably defining a third sector) through switch matrix
207d, and while BS radio 208d is coupled to antennas m+1 through n
(here antennas 220-222 preferably defining a fourth sector) through
switch matrix 209d. Control of switch matrixes 202d, 205d, 207d,
and 209d and/or radios 201d, 204d, 206d, and 208d is preferably
provided by BS controller 203d, preferably configured substantially
as BS controller 203 described above.
[0063] Each of BS radios 201d, 204d, 206d, and 208d are preferably
adapted to provide communications on a same channel or channels as
the other one of BS radios 201d, 204d, 206d, and 208d. Accordingly,
as shown in FIG. 3C, a same channel may be utilized within cell
102, such as at each of beams 113 associated with BS radio 201d,
116 associated with BS radio 204d, 119 associated with BS radio
206d, and 122 associated with BS radio 208d to provide increased
communication capacity within the cell as compared with the
exclusive use of available channels within that cell.
[0064] It should be appreciated that the use of separate radios
and/or separate switching circuits is not required according to the
present invention. For example, radio circuitry capable of
providing separate communications on a same channel to multiple RSs
may be utilized according to the present invention. In addition to
there being no limitation that separate switching circuitry or
radios be used, there is no limitation to the use of particular
antenna beams with particular radios and/or channels according to
the present invention. For example, multiple radios may be coupled
to a switching array allowing connection of any radio to any
antenna beam, alone or in combination, if desired. Additionally, it
should be appreciated that, as shown in the embodiment of FIGS. 2B
and 3A, there is no limitation to there being an equal number of
antenna beams associated with radios, channels, or other resources,
according to the present invention. Likewise, there is no
limitation to the antenna beams being the same size, or even of a
fixed size, according to the present invention.
[0065] The highest capacity will generally be achieved when each
sector of a BS carries a substantially same traffic load and/or
cells of the network carry a substantially same traffic load.
Accordingly, a preferred embodiment of the present invention
utilizes variable sector boundaries to allow loading to be balanced
between the sectors. For example, during particular parts of a day
or week particular RSs may require more data capacity than other
times of the day or week. If changes in required data capacity are
not substantially uniformly distributed amongst the sectors, a
switching matrix or other controlled coupling circuitry may be
utilized to adjust the coupling of antenna beams to communication
equipment, such as traffic channel radios, pilot radios, and the
like, to redefine sector boundaries, such as those described above
with respect to FIGS. 2B-2D. Systems and methods for providing
dynamic adjusting of sector sizes utilizing multiple antenna beams
are shown and described in U.S. Pat. No. 5,889,494, the disclosure
of which is incorporated herein by reference.
[0066] In addition to operational determinations made with respect
to traffic in various sectors of a BS as described herein, a
preferred embodiment of the present invention utilizes inner cell
communication/control to optimize operations. For example, the
above described load balancing may be accomplished at least in part
through handing communications off to an adjacent cell.
Additionally or alternatively, such inter-cell
communication/control may be utilized to provide network load
balancing. Systems and methods for providing such inter-cell
communication/control are shown in U.S. Pat. No. 5,884,147,
entitled "Method and Apparatus for Improved Control over Cellular
Systems," the disclosure of which is incorporated herein by
reference.
[0067] Experimentation has revealed that a BS which can select the
most preferred one of 12 narrow antenna beams which cover a service
area, as compared to an omnidirectional antenna covering the same
service area, has an 11 dB advantage in terms of interference
rejection and power transmitted. Even more benefits in terms of
reduced interference and radiated power occur when the RS is
capable of directing a narrow beam antenna toward the best
servicing BS. Accordingly, the greatest efficiency in the use of
available resources according to a preferred embodiment of the
present invention occurs when transmission and reception between a
BS and RS occur only on a single antenna beam of the BS. According
to a preferred embodiment, a most preferred antenna beam for
communications with each active RS is identified and subsequent
communication occurs using this most preferred antenna beam.
Preferably, the most preferred antenna beam for each RS is an
antenna beam having a "strongest" signal associated with that RS.
It should be appreciated that the antenna beam determined according
to the present invention to be the "strongest" may meet criteria
other than or in addition to the received signal strength of
greatest magnitude. For example, the determination of "strongest"
may be made for an antenna beam having the best signal quality,
i.e., highest SIR or SNR, the most direct path or shortest path, or
the like. Likewise, an adaptive beam former can create a
"strongest" beam to the RS using similar criteria.
[0068] A difficulty in using multiple beam antennas is in the
initial assignment and subsequent tracking of the best serving base
station and the most preferred antenna beam associated therewith.
The difficulty is exacerbated in TDMA system, where it becomes
important to know both when and where antenna beams are pointing
and the distance between the BS and RS. To some extent utilizing an
omnidirectional antenna beam can aid in acquisition, but the use of
an omnidirectional antenna beam in combination with the multiple
antenna beams adds to the complexity of both the BS and the RS and
typically would not provide information with regard to selection of
a most preferred antenna beam. Therefore, the preferred embodiment
of the present invention provides a technique to initialize and
track multibeam antennas at both a BS and RS without using
omnidirectional antennas.
[0069] Acquiring and identifying the most preferred antenna beam at
the BS is preferably performed by the BS correlating the target RS
on all antenna beams, or some subset thereof determined to be
candidates for establishing communications with the target RS.
Since "strongest" antenna beams rarely change in a fixed point
communication system, as opposed to mobile cellular systems where
the strongest antenna beam can potentially change several times per
second, determining the correct antenna beam for a fixed RS is not
generally a time critical issue. Shown in FIG. 9 is preferred
embodiment circuitry adapted to provide time shared acquisition of
most preferred antenna beams. Accordingly, correlation circuitry is
provided which is coupled to the multiple antenna beams through a
switch matrix, allowing antenna beams to be selectively provided to
the correlator for determination of a most preferred antenna
beam.
[0070] Where determination of a most preferred antenna beam is more
time critical, such as where ones of the RSs are likely to change
position and/or where propagation conditions are subject to
material change, the simultaneous acquisition circuitry of FIG. 10
may be more desired. In the embodiment of FIG. 10, each antenna
beam is provided with associated correlation circuitry in order to
allow simultaneous acquisition of a signal on all antenna
beams.
[0071] According to a preferred embodiment, where timing is divided
into bits, slots, frames, superframes, etcetera, with N.sub.1
bits/slot, N.sub.2 slots/frame, N.sub.3 frames/superframe,
etcetera, initialization occurs using a dedicated multiple beam
antenna access channel (MBAACH). A preferred embodiment MBAACH data
container is shown in FIG. 11 as packet 1100.
[0072] The preferred embodiment MBAACH data container of FIG. 11
includes synch bits, overhead information, RSSI information, number
of antenna beams, current antenna beam, and directed message. The
synch bits of the preferred embodiment set the beginning of the
MBAACH message. The overhead information includes information such
as system identification, number of carriers, BS identity, timing
information, etcetera. The RSSI information is information designed
to allow the quick determination of received signal strength. The
number of antenna beams information provides information regarding
the number of antenna beams associated with this carrier and,
preferably, the pointing angles of these antenna beams. The current
antenna beam information provides the current antenna beam number
and pointing angle. The directed message provides instructions to
individual RSs.
[0073] Preferably, the MBAACH is provided in a slot of a traffic
channel. Accordingly, one slot of the traffic channel is dedicated
to beam acquisition, paging, and slot assignment. The frequency of
occurrence of a MBAACH slot depends on the number of users and the
desired set-up time.
[0074] In operation according to a preferred embodiment, a BS is
aligned with antenna beam 1 facing north, antenna beam 2 facing
north easterly, etcetera as illustrated in FIG. 1. Preferably, for
the MBAACH, slot 1 corresponds to the MBA pointed in direction 1,
in the next repetition of the MBAACH slot, the MBA would point in
direction 2, etcetera. The progression of the MBAACH slots
according to this embodiment of the present invention is shown in
FIG. 12.
[0075] According to the preferred embodiment, the RS listens for
the synch burst and attempts to measure the signal strength. Most
of the time the RS will measure low values for the signal strength.
As the MBA points toward the RS, the signal strength will increase.
If the RS also has a MBA, then after every K frames, corresponding
to the BS having stepped through every pointing angle or every
pointing angle associated with a particular carrier, the RS will
preferably increment its MBA by one antenna beam and repeat the
search. Preferably, after exhausting all angels, the RS increments
to the next RF carrier. The RS preferably logs the carrier numbers
and the beam numbers that produce a strongest receive signal
strength, for example a first and second most preferred carrier and
beam combination may be determined. Thereafter the RS preferably
adjusts its antenna beam angle to the strongest BS and transmits in
the time slot reverse link dedicated to MBA access channel (reverse
MBAACH) information regarding the most preferred carrier and beam
combination. For example, the RS locks onto the best carrier,
antenna beam, receive signal strength combination and transmits the
reverse MBAACH to the appropriate BS.
[0076] A preferred embodiment reverse MBAACH data container is
shown in FIG. 13. The preferred embodiment reverse MBAACH data
container of FIG. 13 includes a leading and trailing guard time,
synch bits, RS identification information, and report message. The
guard times are adapted to prevent the RS from accidentally
transmitting and overlapping its transmission with other RSs, i.e.,
the guard band insures that messages from distant RSs arrive within
the time window of a time slot and do not overlap with other RSs on
adjacent slots. The synch bits of the preferred embodiment set the
beginning of the reverse MBAACH message. The RS identification
information identifies the RS sending the reverse MBAACH message.
The report message provides information such as carriers detected,
angles and beam numbers above threshold, etcetera.
[0077] After having provided the appropriate information in the
reverse MBAACH, the RS listens on a direction MBAACH portion of the
channel, corresponding to the beam number used, for a unique
message. The received direction message of a preferred embodiment
may instruct the RS that the identified best carrier, angle and
beam is acceptable for communication or, if unavailable, perhaps to
look for another BS or RF carrier.
[0078] A preferred embodiment of the direction message from the BS
is shown in FIG. 14. The preferred embodiment direction message
includes synch bits, RS identification information, BS
identification information, carrier number, antenna beam number,
timing advance information, and end bits. The synch bits of the
preferred embodiment set the beginning of the direction message.
The RS identification information identifies the RS to which the
direction message is directed. The BS identification information
identifies the BS from which the direction message was sent. The
carrier number identifies the carrier to which the direction
message relates. The beam number identifies the beam to which the
direction message relates. The timing advance information provides
timing information related to the RSs relative position to the BS
in order to allow reduced reliance on guard times in communication
of data packets. The end bits set the end of the direction
message.
[0079] In the preferred embodiment, operation of the present
invention in initializing antenna beams, carriers, and the like as
described above, includes protocols for handling messages which are
corrupted or collide. For example, each RS may be assigned a
particular reverse MBAACH time slot in order to avoid collisions in
providing the reverse MBAACH message. Additionally or
alternatively, the RS may wait for a particular predetermined time
for a direction message from the BS and if not received therein,
retransmit the reverse MBAACH message due to its having collided
with another message or otherwise having been corrupted as received
at the BS.
[0080] It should be appreciated that the above described
initialization technique allows MBA antennas at both the BS and the
RS to align themselves. Moreover, such alignment may be
accomplished prior to, and independent of, any other
application.
[0081] For forward links it is often customary to use a pilot
signal, different at each BS, so that a RS can identify the BS with
the best or most preferred signal path. In a preferred embodiment,
the forward and reverse path antenna beams are selected to be the
same, since it is likely the forward and reverse links will
experience the same or similar propagation conditions. Accordingly,
in the preferred embodiment either the BS or RS may be equipped to
determine the most preferred antenna beam for each.
[0082] For a single cell, such as that shown in FIG. 1,
beam-to-beam isolation is an important factor in determining the
cell capacity, as the ability to reuse a communication channel of
BS radio 201 simultaneously in any of beams 1-N depends on the
ability of the antenna beams to isolate the signal from other ones
of beams 1-N. Isolation in free space can be increased through the
use of improved antenna designs, such as designs which provide
lower sidelobes, reduced back scatter, and the like. However, in
practice scattering around the BS and RSs causes unwanted energy to
appear in beams other than that intended. Scattering near the BS
can be reduced by raising the BS above local obstacles, however
this is not always practical due to zoning and other restrictions.
Scattering around the RS can be reduced by using directive antennas
pointing toward the BS. The present invention will operate with
some or all of the RSs having omnidirectional or broad beam
antennas. However, in order to provide higher system capacity, the
preferred embodiment of the present invention uses directive
antennas at some or all RSs. Accordingly, a preferred embodiment RS
according to the present invention utilizes a multibeam antenna
substantially as shown in FIG. 1.
[0083] In order to provide communication services to a number of
RSs disposed throughout a geographic area, the preferred embodiment
of the present invention utilizes a plurality of BSs such as BS 101
of FIG. 1 to establish a cellular communication network. The system
preferably determines a BS which a RS should be served by through
reference to existing and learned network conditions. For example,
reference may be made to traffic patterns, interference conditions,
loading, and the like. Additionally or alternatively, signal
strength maybe utilized in determining a BS to serve a particular
RS.
[0084] A simple multibeam BS network is illustrated in FIG. 4. It
should be appreciated from the network of FIG. 4 that the antenna
beams utilized according to the present invention are not limited
to a particular number or even a particular size. As shown in FIG.
4, various size antenna beams may be utilized, such as where RSs
within a cell are not evenly distributed and thus loading on the
various antenna beams may be balanced.
[0085] BSs 401 and 403 of FIG. 4, preferably each configured
substantially as illustrated in FIG. 2, are deployed to provide
communication services within cells 402 and 404 respectively.
Disposed at various positions throughout cells 402 and 404 are RSs
451-455 (cell 402) and 461-464 (cell 404) being provided
communication services by BSs 401 and 403. The communication
services provided to these RSs include high rate data services,
such as 1 MB/s data communications. However, as the RF spectrum is
limited and expensive, operation of the present invention
efficiently utilizes the available spectrum to provide each of the
RSs the desired communication services.
[0086] As the designs of most practical antennas trade physical
size and other practical considerations against beam-to-beam
isolation, it is assumed that adjacent antenna beams of an antenna
system utilized according to the present invention will couple too
much energy to carry separate independent signals of a same
communication channel. Therefore, according to a preferred
embodiment of the present invention, adjacent beams are not allowed
to transmit a same communication channel simultaneously. Although
this restriction may be avoided by cross-polarization or other
isolation techniques, but such an embodiment may require RSs to
have dual polarity antennas which would tend to increase their
cost. For example, referring to FIG. 4, at BS 401 RSs 451, 453, and
455 or 452, 454, and 455 may be served with the same channel
simultaneously. However, RSs 452 and 453 would not be served with
the same channel simultaneously because it is expected that the
antennas utilized at BS 401 cannot provide sufficient signal
isolation.
[0087] It should be readily appreciated from the illustration in
FIG. 4, that the problems of co-channel interference are not
limited to communications associated with BS 401. For example, RS
453 of BS 401 and RS 462 of BS 403, if simultaneously operating on
a same communication channel may experience co-channel
interference. However, depending on the relative power levels at
RSs 453 and 462, and the discrimination of the RS antennas,
co-channel interference at RSs 453 and 462 may be limited or
avoided. Accordingly, a preferred embodiment of the present
invention utilizes directional antennas at some or all of the RSs.
Such directional antennas may, for example, be a single narrow beam
focused on a particular BS or may be a multiple beam array such as
illustrated in FIG. 1 suitable for establishing communication with
multiple network BSs.
[0088] In addition to the above described co-channel interference
associated with RSs which, although being disposed in different
cells, are located in relative close proximity, more distant RSs
may too experience co-channel interference. For example, RS 461 may
"see" BS 401, i.e., receive a signal from BS 401 with sufficient
amplitude to cause undesired results at RS 461, when BS 401
transmits to RS 453. However, if the signal from BS 403 to RS 461
is sufficiently strong, then both RS 453 and RS 461 can operate
simultaneously on a same communication channel according to the
present invention. It should be appreciated that various network
parameters may be adjusted to allow the signal between BS 403 and
RS 461 to be sufficiently strong to allow the simultaneous
operation of RSs 453 and 461. For example, the power level of a
signal transmitted from BS 401 to RS 453 may be reduced to a level
sufficiently low for simultaneous operation of RS 461, while
sufficiently high to provide a desired quality of service at RS
453. Additionally or alternatively, the power level of a signal
transmitted from BS 402 to RS 461 may be increased to a level
sufficiently high for simultaneous operation of RSs 461 and 453,
while sufficiently low to avoid causing undesired results in other
communication links of the network.
[0089] A preferred embodiment of the present invention operates to
determine which network resources, i.e., which antenna beams and
RSs, may be operated on a same channel simultaneously with
tolerable co-channel interference so that optimal capacity can be
achieved in the network. Preferably, such determinations are made
on various system levels, such as determinations with respect to
each BS considered alone (intra-cell interference) and
determinations with respect to RSs outside the coverage area of
each BS (inter-cell interference).
[0090] The discussion below with respect to the determining of
acceptable simultaneous use of network resources assumes previously
measured and/or well modeled radiation paths, e.g., empirically
measured communication attributes (whether during live
communications or during a test period) and/or computer modeling of
interference conditions based upon know propagation
characteristics. It should be appreciated that such measurements
may be incorporated as an integral part of the communication
network and would require only a small fraction of the network
capacity to keep current. For example, BS 101 as illustrated in
FIG. 2 may include a signal quality, or other attribute,
measurement apparatus, such as a receive signal strength indicator
(RSSI), SNR, and/or SIR measurement device, disposed in the signal
path between BS radio 201 and switch matrix 202 to measure the
signals coupled thereto. Additionally or alternatively, each of the
antenna beams 1-N may be switchably coupled to such a measurement
apparatus, such as through a port on switch matrix 202 or through
inclusion of a second switch matrix, to allow selection of antenna
beams for signal quality measurement independent of the operation
of radio 201. Similarly, each or ones of the RSs may include signal
quality measurement apparatus. Several techniques allow individual
RSs a way to report their measurements. For example, in TDMA
systems polling, slotting, time assigned and/or random reporting,
with repeats if collisions occur, are all techniques which may
allow an RS a clear time slot to report.
[0091] The signal attribute information may be communicated to a
centralized processor operable to control or otherwise process
information for all or several of the BSs. Additionally or
alternatively, this information may be utilized at each of the BSs,
such as by the above described BS controller, to control operation
of the BS.
[0092] In a preferred embodiment of intra-cell interference
determinations it is assumed that each RS is aimed at the BS that
provides the greatest strength signal, such as using the steps
described above. Accordingly, a communication path may be set up so
that from time to time each RS logs onto the network and identifies
what BS and what beam provides the strongest signal thereto. Of
course, it should be appreciated that the use of multiple antenna
beams at the RSs is within the scope of the present invention and,
thus, an antenna beam aimed at the BS may be but one of a plurality
of RS antenna beams (others of which may be aimed at other BSs).
Similarly, omni directional antenna beams at the RS are within the
scope of the present invention and, thus, aiming of such a beam may
correspond to deployment such that communications are possible.
[0093] Directing attention to FIG. 5A, an algorithm operable to
cause RSs to periodically identify and provide BS antenna beam
selection information to the network is shown. This algorithm is
preferably operable on a processor based system of the RS and
provides control of the RS to identify the desired antenna beam
information and provide this information to a corresponding network
system, such as the aforementioned BS or network controller.
Specifically, at step 501 a determination is made as to whether an
antenna beam determination event has occurred. This event may be a
predetermined time period, a threshold amount of data communication
having been accomplished, a threshold data error rate (such as a
bit error rate (BER)), a predetermined signal quality level not
having been maintained, or the like. If the triggering event has
not transpired, then processing loops back to step 501 to forego
further antenna beam determination processing until the event has
transpired.
[0094] If the triggering event has transpired, processing continues
to step 502 where the BS antenna beam providing the a most desired
signal attribute, such as a strongest signal, is identified. A
preferred embodiment technique providing identification of a BS
antenna beam and/or RS antenna beam according to the present
invention is described in detail above with respect to the
MBAACH.
[0095] It should be appreciated that identification of a BS antenna
beam at step 502 is not limited to a best or most desired antenna
beam. Accordingly, a determination may be made as to whether the RS
receives energy above an interference threshold on BS antenna beams
other than the strongest BS antenna beam. For example, a first and
second best antenna beam may be identified in order to readily
identify an alternative communication link in case of communication
anomaly or in order to select optimized resource utilization
solutions. Likewise, identification of a BS antenna beam at step
502 may encompass a determination of various ones of multiple RS
antenna beams the signal of a particular BS antenna beams is/are
best or otherwise desirable.
[0096] After a BS antenna beam has been identified at step 502,
processing continues to step 503. At step 503 information regarding
the BS antenna beam is provided to the network. As discussed above,
this information may be provided to the "home" BS for that
particular RS, it may be provided to a centralized controller, or
the like. Irrespective of the particular network element to which
the information is provided, after submitting the information to
the proper network element processing loops back to step 501 to
await the next occurrence of a determination triggering event.
[0097] According to the preferred embodiment, each BS logs the
signal strength or other signal attribute from the RSs operable
therewith (preferably the RSs located in a cell associated
therewith, and alternatively including the RSs disposed in a
position suitable for establishing communications of a desired
signal quality therewith) on various antenna beams of that BS.
Preferably logging of RS signal attributes are for each antenna at
the BS so as to determine the interference levels likely to be
experienced with simultaneous communication with another RS in any
area of the cell.
[0098] Directing attention to FIG. 5B, an algorithm operable to
cause BSs to periodically measure signal attributes associated with
RSs in communication therewith (or for which communication
therewith is possible) is shown. This algorithm is preferably
operable on a processor based system of the BS, such as the above
described BS controller. The information measured may be retained
by the BS and/or provided to other network systems if desired.
[0099] At step 510 a determination is made as to whether a
triggering event has transpired for the determining of RS beam
information. This event may be a predetermined time period, a
threshold amount of data communication having been accomplished, a
threshold data error rate (such as a BER), a predetermined signal
quality level not having been maintained, or the like. If the
triggering event has not transpired, then processing loops back to
step 510 to forego further antenna beam determination processing
until the event has transpired.
[0100] If the triggering event has transpired, processing continues
to step 511 where an RS is selected for signal measurements. As
previously mentioned, the RS may be selected from those RSs
disposed within the cell associated with the BS or RSs capable of
communications with the BS (i.e., RSs disposed within or relatively
near the BS). Additionally or alternatively, RSs may be selected
from a subset of those RSs meeting a particular criteria, such as
those experiencing a particular error rate, signal quality, data
throughput, or the like.
[0101] After selection of the RS for measurement a first antenna
beam of the multiple BS antenna beams is selected for measurement
with respect to the selected RS (step 512). Of course, it should be
appreciated that there is no limitation to the particular order of
selection of the RS and antenna beams according to the present
invention. Accordingly, the present invention is not limited to the
order of steps illustrated in the preferred embodiment.
[0102] At step 512 the antenna beam is preferably selected from all
the BS antenna beams so as to provide for measurement of signal
attributes associated with the selected RS on each BS antenna beam.
In alternative embodiments selection of the antenna beams may be
from a subset of available antenna beams, such as only those likely
to receive a signal of consequence from the selected RS based on
modeling predictions.
[0103] After selection of the BS antenna beam for measurement has
been made, processing proceeds to step 513 where desired signal
attributes of the selected beam with respect to the selected RS are
measured. As discussed above, the measured signal attributes may
include RSSI, SNR, SIR, BER, and/or the like.
[0104] Thereafter, a determination is made as to whether there are
additional BS antenna beams for which measurements with respect to
the currently selected RS are desired (step 514). If there are
additional BS antenna beams for which measurements are desired,
such as if all BS antenna beams or the BS antenna beams of a
preselected subset have not been measured for the selected RS,
processing proceeds to step 515.
[0105] At step 515 a next BS antenna beam of the antenna beams for
which measurements are to be made is selected. Thereafter
processing proceeds again to step 513 for measurement of the signal
attributes.
[0106] If at step 514 a determination is made that no additional BS
antenna beams are to be measured with respect to the currently
selected RS, processing continues to step 516. At step 516 a
determination is made as to whether there are additional RSs for
which measurements are desired. If there are additional RSs for
which measurements are desired, such as if all RSs within the cell
or in communication with the BS have not been measured, processing
proceeds to step 517.
[0107] At step 517 a next RS of the RSs for which measurements are
to be made is selected. Thereafter processing proceeds again to
step 512 for selection of a first BS antenna beam for
measurement.
[0108] If at step 516 a determination is made that no additional
RSs are to be measured, processing returns again to step 510 to
await a measurement triggering event.
[0109] After inter-cell interference data is determined, preferably
using the algorithms discussed above, the preferred embodiment of
the present invention operates to create a forbidden beam matrix.
Such a matrix is preferably created for each BS individually, such
as one for BS 301 of FIG. 4 and another for BS 403 of FIG. 4. An
example of a portion of a forbidden beam matrix is illustrated in
the table below.
1 Beam 1 Beam 2 Beam 3 Beam 4 Beam 5 Beam 6 Beam 7 . . . Beam 1 --
X R Beam 2 X -- X R Beam 3 R X -- X R Beam 4 R X -- X X R Beam 5 R
X -- X Beam 6 X X -- X . . .
[0110] In operation there may be several RSs per beam. It should be
appreciated that not all RSs in a particular beam will cause the
same inter-beam interference. Therefore, in the preferred
embodiment forbidden beam matrix is statistically determined based
on the probability of interference considering each RS disposed in
the particular antenna beams. However, in an alternative
embodiment, forbidden beam matrixes may be developed with respect
to individual ones of the RSs, if desired.
[0111] It should be appreciated that in a preferred embodiment TDMA
system, only one RS is served per BS antenna beam channel at any
one time slot. Interference may occur on the downlink when a RS
disposed relatively far from the BS in the primary beam requires
extra power. This extra energy may cause energy to "spill over"
into adjacent BS antenna beams. If the energy is simply in the beam
side lobes, it can be easily determined mathematically whether
simultaneous usage of the same channel a beam or so away from this
primary beam is feasible. However, when the energy from the primary
beam is scattered to adjacent beams, such as due to terrain
conditions, this situation is preferably measured using a reporting
system. For example, the measurement algorithms above may make
measurements based on various signal transmission levels to emulate
or model disposition of RSs far and/or near. Additionally, or
alternatively, measurements may be made during actual communication
operations to thereby measure actual use conditions, including the
power levels at which particular communications links are
operated.
[0112] It can readily be appreciated from the table above that,
with respect to one particular BS of the exemplary communication
network, antenna beams 1, 2, and 3 exclude their nearest neighbors
while antenna beam 4 excludes simultaneous use of antenna beams 3,
5, and 6. In this example, resources (i.e., channels and/or antenna
beams) would preferably be allocated to avoid simultaneous use of
the indicated antenna beams with respect to a same channel so that
intolerable co-channel interference does not occur.
[0113] It should be appreciated that information in addition to the
above shown forbidden simultaneous antenna beam information may be
utilized according to the present invention. For example,
information may be associated with each antenna beam, either within
the above shown forbidden antenna beam table or external thereto,
which provides network communication information of interest.
Specifically, information regarding particular RSs disposed within
particular antenna beams, information regarding position and/or
distance of the RSs, information regarding the quality of service
and/or capacity needs for the RSs, and the like may be stored
and/or utilized according to the present invention. This
information may be provided by an operator or other source, such as
upon initial deployment or thereafter, determined through system
operation, and/or be compiled as historical information.
[0114] A preferred embodiment of the present invention provides for
the use of a plurality of channels by ones of the RSs. Accordingly,
although the use of a particular channel in a particular antenna
beam may be prohibited or restricted as discussed above, an RS may
change to another channel for communications, if desired. Using
information, such as that shown above, for each such channel in
each beam communications may be optimized. It should be appreciated
that, as sources of interference may be from uncontrollable sources
outside the communication system of the present invention, the
ability for RSs to change communications channels may provide
advantages in quality of communications beyond optimizing
communications.
[0115] In a preferred embodiment of the present invention
allocation of resources is based on per beam traffic needs, such as
may be determined through historical information or initial network
configuration parameters. Alternatively, allocation of resources is
based on first come (first requiring/requesting communication
services) first served, causing later to come (later to
require/request communication services) to be blocked on particular
antenna beams with respect to simultaneous use of a particular
channel.
[0116] As described above, that simultaneous use of a channel
potentially creates co-channel interference. Depending on factors
such as the antenna design and the position of the RS in the
antenna beam, the SIR or other signal quality measurement affected
by co-channel interference, can vary greatly. In a system using MBA
such as in the preferred embodiment of the present invention,
beam-to-beam isolation, i.e., the ability of the antenna beams to
isolate the signal from other ones of the antenna beams, affects
capacity which may be achieved in a cell through the simultaneous
use of channels. The graph of FIG. 6 illustrates the degradation of
a simple binary signal with varying SIR, as might be experienced in
various antenna beams due to simultaneous use of a particular
channel at other ones of the antenna beams. The results of such
interference are much more amplified for high order modulation,
such as high level QAM constellations.
[0117] Coding, such as that of spread spectrum CDMA, allows error
free transmission at much lower SIR. The penalty in providing such
error free transmissions in the presence of higher levels of
interference is reduced throughput. However, the use of various
rate codes may be utilized to maximize throughput for the
particular communication attributes experienced in the link.
[0118] Solutions of resource allocation according to the present
invention allow simultaneous use of 2 antenna beams, but at a
reduced throughput. For example, in a CDMA system RSs disposed
relatively close to the BS, i.e., low path loss between BS and RS,
do not require highly spread codes to achieve low error rate data.
In cellular IS-95 systems, E.sub.b/N.sub.o is essentially constant
for every user. However, according to a preferred embodiment of the
present invention allowing higher E.sub.b/N.sub.o for RSs requiring
little power can be traded for a slight rise in E.sub.b/N.sub.o for
other users. Having a higher E.sub.b/N.sub.o allows changing
spreading codes to achieve higher throughput.
[0119] As indicated in the table above, antenna beams 1 and 3 are
not fully mutually exclusive antenna beams, i.e., although
co-channel interference is present in sufficient magnitude to cause
signal qualities to be less than a desired threshold, simultaneous
communications may still be established. The use of a reduced rate
code provides communications which are more immune to interference
than the higher throughput communications possible with the network
equipment. For example, simultaneous rate 2/3 convolution codes
could be utilized with each of antenna beams 1 and 3, such as may
be determined to be acceptable through reference to the above
described information, to provide reduced rate simultaneous
communications therewith. Such a use of 22/3 rate communication
channels provides more capacity than the single full rate code
which might otherwise be used with antenna beam 1 to the exclusion
of antenna beams 2 and 3.
[0120] A similar concept may be applied in TDMA systems. RSs which
are disposed relatively close to a BS, or otherwise receive a
strong signal, may be operated at a reduced power level and/or
operated at a higher data rate. As discussed in more detail below,
QAM is an example of modulation where in the same bandwidth, i.e.,
using a same baud rate, higher levels of modulation may be used to
obtain higher data rates.
[0121] In the preferred embodiment of the present invention the
system operates to automatically optimize simultaneous use of a
channel by the affected antenna beams. For example, a database
inquiry is performed according to one embodiment of the invention
to determine receive energy levels on the primary and interfering
antenna beams for both RSs for which simultaneous use of a channel
is considered. Thereafter, a determination is made as to whether
simultaneous use is desirable, such as through the use of SIR
calculations for the user pairs. Such determinations may be carried
out for any number of simultaneous uses, such as to three or more
RSs simultaneously using a channel by calculating the SIR on each
link associated with these RSs.
[0122] According to a preferred embodiment of the present
invention, the capacity of a cell is optimized by considering the
SNR and SIR as well as capacity needs for each RS in the cell. For
example, depending upon the SNR available at the RS, the capacity,
e.g., the number of bits which may be transmitted to the RS during
a defined time slot, may vary greatly. As shown in the table below,
an 8 fold capacity increase is obtainable when an extremely high
SNR is achievable.
2 Capacity Increase QAM Constellation E.sub.b/N.sub.o @ 10.sup.-6
SNR 1 4 10.5 13.5 2 16 15 21.5 4 64 18.5 27 8 256 24 33
[0123] Where a very high SNR or SIR is achievable, a high order
modulation technique, such as high order modulation available in
QAM, phase shift keying (PSK), or quadrature phase shift keying
(QPSK), may be used to provide increased capacity. For example,
where 33 dB SNR is achievable, an 8 fold capacity increase may be
realized using 256 QAM to transmit 8 bits per symbol. Where lower
SNR is achievable, such as 20 dB, lower order modulation, such as 4
QAM or even possibly 16 QAM, may be utilized. However, it should be
appreciated that such lower order modulation techniques may provide
no or little capacity increase.
[0124] From the above, it should be appreciated that for any given
channel condition, there may be determined an optimum bit density,
i.e., modulation/coding combination, that maximizes throughput at a
particular acceptable communication quality threshold. For example,
a particular preselected BER may be maintained during simultaneous
use of a communication channel in various antenna beams through
altering modulation or coding techniques to adjust throughput.
According to the preferred embodiment of the present invention,
determinations of the particular antenna beams at a cell
simultaneously utilizing a particular channel are made with respect
to optimizing throughput achievable with particular antenna beam
combinations, particular available bit densities, and/or quality of
service considerations with respect to the RSs.
[0125] When simultaneous usage of a resource is prohibited, i.e., a
particular channel is already utilized in a particular antenna beam
thus blocking the use of this channel in that or another antenna
beam, a preferred embodiment of the present invention operates to
delay communication, such as where data users are present using
packet data. For example, the data packet of a particular user
desiring use of a resource for which simultaneous usage is
prohibited may be delayed one or more time slots for subsequent
rechecking of the particular resource. If the resource becomes
available, such as may be determined by checking SIR information or
the like, the delayed data packet may be communicated using the
previously prohibited resource. In a preferred embodiment, class of
service, such as data versus voice communication, is used to
determine the particular data packet or packets which get delayed
or which experience the most delay etcetera.
[0126] In addition to determining allowable simultaneous use of
channels within antenna beams of a single cell, a preferred
embodiment of the present invention makes determinations regarding
inter-cell interference, i.e., interference caused to
communications associated with RSs outside the coverage area of a
particular cell. Preferably, such determinations are based on a
number of modeling and/or empirical measurements, such as described
above with respect to intra-cell interference. Based upon this
modeling and/or measurements, mutually exclusive antenna beam pairs
between the "home" BS and the BSs surrounding the home BS are
identified. The table below shows an example of mutually exclusive
antenna beam pairs as determined for the exemplary communication
network of FIG. 8.
3 Home BS0 BS1 BS2 BS3 BS4 BS5 BS6 Cell 800 Cell 801 Cell 802 Cell
803 Cell 804 Cell 805 Cell 806 800-1 801-1 801-5 801-6 800-2 801-6
802-2 802-3 802-9 802-10 800-3 802-8 800-4 803-3 803-4 803-5 803-11
. . .
[0127] Shown in FIG. 8 is a communication network including 7
cells, cell 800 surrounded by cells 801-806. Each cell utilizes
multiple antenna beams of the preferred embodiment discussed above.
For the example described with respect to the table above, cell 800
will be considered as the "home" cell for inter-cell interference
determinations. However, it should be appreciated that any cell of
the network may be considered as a "home" cell for this purpose. In
fact, a preferred embodiment of the present invention makes
determinations of mutually exclusive antenna beam pairs for each
cell, thereby identifying each cell a "home" cell with respect to
its associated inter-cell interference determinations.
[0128] As shown in the table above, there are particular
combinations of antenna beams that, when one antenna beam of the
combination is in use other ones of the combination will experience
interference. For example, if antenna beam 800-1 of cell 800 is
transmitting, RSs operating in antenna beams 801-1, 801-5 and 801-6
of cell 801 may receive interference too strong to decode their
intended transmissions. Accordingly, it may be desired to avoid
simultaneous use of such antenna beams, such as with respect to a
same channel, to avoid communication errors.
[0129] With no communication among BSs of the network, a solution
would be to apportion the available resources, i.e., time slots or
frequencies, among the cell beam pairs according to their traffic
needs. For such time slot operations, the stations would preferably
utilize a reference clock such as GPS to ensure synchronization
among the BSs of the network. For example, in a single channel
system, beam 800-1 of cell 800 may share 1/2 of its time slots with
neighboring antenna beams. With centralized timing, the use of beam
800-1 could easily be prevented or avoided when beams which would
cause unacceptable interference, such as antenna beams 801-1,
801-5, and/or 801-6, are in use. Without such a clock, frequency
division becomes a preferred alternative.
[0130] It should be appreciated that time offsets due to differing
propagation paths may affect more than a single coincident time
slot at a neighboring BS. Accordingly, a preferred embodiment of
the present invention may operate to prohibit the use of multiple
time slots at ones of the antenna beams and/or make determinations
as to distance etcetera in order to determine particular time slots
to identify as prohibited with respect to simultaneous use of
antenna beams.
[0131] Optimization with communication among BSs is conceptually
simpler than that described above. For example, if the BS
associated with cell 800 knows or can determine what slots are
available with respect to particular antenna beams due to internal
and external usage, a next slot assignment may be made on a first
come first served basis, sharing the available resources between
the cells. In providing a fully optimized solution, a preferred
embodiment of the present invention allows buffering of several
time slots and optimizing time slot assignments over several slots.
Accordingly, the system examines all BS/antenna beam/channel pairs
and assigns simultaneous usage to those pairs that just exceed a
predetermined threshold, such as a SIR threshold, thereby packing
the greatest number of uses of the spectrum into the system
operation. It should be appreciated that the use of pairs that just
exceed the established threshold is preferred as assigning the
least interfering pairs to simultaneous usage may result in low
interference, but at a cost in capacity.
[0132] In a preferred embodiment employing packet data, a packet
optimizer is utilized, such as may be embodied in the circuitry
and/or programming of the above described BS controller. The packet
optimizer of the most preferred embodiment operates to achieve
maximum throughput as is possible subject to communication
constraints. Specifically, a preferred embodiment of the present
invention optimizes throughput of packets based on considerations
regarding allowable delay (such as may be packet or service
dependent), allowable SIR (i.e., a low available SIR requires
reduced data rate), transmit power level (typically related to the
distance from the BS to RS, and ideally known for each packet based
on the RS it is associated with, subject to noise and
interference), forbidden simultaneous beams (reference to
information as described above as to antenna beams which may not be
transmitted simultaneously or only at a reduced transmission rate),
outside interference levels per antenna beam, the number of
transmitters available, and/or the like.
[0133] Directing attention to FIG. 7A, BS 101 deployed in cell 102
is shown adapted to provide communication of packet types A and B,
such as may be associated with a first radio A and a second radio B
(intra-cell reuse N=1/2). It should be appreciated that the
configuration of FIG. 7A provides for communication of packet type
A throughout antenna beams 111-110 and 121 and 122 and of packet
type B throughout antenna beams 111, 112, and 115-122. Accordingly,
both packet types A and B may be communicated throughout antenna
beams 111, 112, 115-110, 121, and 122. Accordingly, there are three
classes of transmission: A and B simultaneously, A and B
simultaneously at a reduced throughput, and only A or B. With
random arrivals in all beams, there would frequently be a need to
transmit 2 packets simultaneously in a same antenna beam or a pair
of adjacent antenna beams.
[0134] Having the ability to delay packet transmissions according
to the preferred embodiment, the system is adapted to pair
simultaneous packets better than their random arrivals to improve
or optimize throughput. For example, if packets arrive with equal
probability for any of the antenna beams, then there is a 50%
probability of blockage, i.e., if a same packet type arrives in a
same, or possibly nearby, antenna beam blockage results.
Specifically, the case of simultaneous arrival of a pair of A
packets (AA) or a pair of B packets (BB) represent blockage,
whereas the simultaneous arrival of one each of an A packet and a B
packet (AB or BA) is acceptable for communications. However, if
delays are utilized in the simultaneous arrival of a pair (either
AA or BB), 2 acceptable pairings may be made (i.e., 2 AB pairs).
For example, if a BB packet paring is delayed until an AA packet
paring arrives, one of the B packets may be delayed 3 slots and the
other 4 slots, along with one of the A packets being delayed 1 slot
to form an AB and BA set of packet parings. With equal probability
of arrival for both A and B packets and with infinite time delay,
all packets may be communicated with optimum efficiency. However,
applying constraints, such as an 8 packet allowable delay,
optimization may be reduced and/or communication quality may
degrade, i.e., an approximately 1% packet drop may be experienced
in packet optimization utilizing the above described
assumptions.
[0135] Directing attention to FIG. 7B, a block diagram of the
operation of a preferred embodiment packet optimizer is shown.
Packet optimizer 700, such as may be deployed in the BS controller
and/or disposed in the signal path between the BS radios and the BS
antennas, is shown. Preferably, packet optimizer 700 includes
packet sorter 701 into operational categories, i.e., packets of
type A only, packets of type B only, and packets which may be
utilized as A or B type. Thereafter, packet optimization module 702
provides sequencing of the packets, preferably utilizing the
considerations discussed above, to achieve optimization. The
optimized pairings and/or sequences of packets are output from
packet optimizer 700 for use by other BS equipment, such as may be
provided to air interface converters for ultimate provision to BS
radios.
[0136] In a preferred embodiment, time division duplexing (TDD) is
used with frequency reuse to provide increased communication
capacity in the cell. One advantage of TDD systems is that a single
switch matrix may be readily utilized in coupling the radios and
MBA. Directing attention to FIG. 15, a preferred embodiment of the
circuitry of a TDD system providing for multichannel multibeam
wireless communications is shown. Specifically multiple (K) BS
radios, radios 1501-1502, are selectively coupled to the antenna
beams of a multiple beam antenna. Accordingly in the preferred
embodiment of FIG. 15 switch 1503 is disposed in the signal paths
between radios 1501-1502 and antennas 211-222 and provides
selectable communication between any combination thereof.
[0137] It should be appreciated that, for TDD systems having
frequency reuse within a cell, a difficulty occurs when the packet
sizes of forward and reverse links are not the same for each
antenna beam, i.e., reuse of the channel. This difficulty is caused
because the forward link of one channel may overlap with the
reverse link of a reuse of that channel. This situation is
illustrated in FIG. 16. Shown in FIG. 16 are 2 RF channels A and B
(A and B are assumed to be at the same frequency) serving different
angular areas (sectors) of a cell. The B channel in this situation
is overpowered by leakage from the A channel antenna in the overlap
region.
[0138] Accordingly, a preferred embodiment of the present
invention, wherein TDD is employed, operates to balance the traffic
among the antenna beams. For example, where an adjustment of a
forward or reverse link frame for one channel is also made for
other channels where overlap would be a problem. Such balancing may
utilize the above mentioned variable sector boundaries in order to
balance the traffic on the channels in order to make it possible to
provide the desired communications with the adjusted TDD frames.
Additionally or alternatively, the present invention may operate to
delay temporarily traffic to eliminate the overlap. Also
additionally or alternatively the present invention may employ
interference cancellers during he overlap time period to minimize
the impact of the overlap.
[0139] It should be appreciated that the systems of the present
invention may utilize diversity reception and/or transmission at
either or both of the BSs and RSs. Such diversity may be provided
due to an independent signal path associated with polarization
diversity, space diversity, angle diversity, or any combination
thereof. The use of such diversity may be relied upon to provide
higher signal qualities and, thus, more capacity and/or higher
throughput.
[0140] Although the present invention and its advantages have been
described in detail, it should be understood that various changes,
substitutions and alterations can be made herein without departing
from the spirit and scope of the invention as defined by the
appended claims. Moreover, the scope of the present application is
not intended to be limited to the particular embodiments of the
process, machine, manufacture, composition of matter, means,
methods and steps described in the specification. As one of
ordinary skill in the art will readily appreciate from the
disclosure of the present invention, processes, machines,
manufacture, compositions of matter, means, methods, or steps,
presently existing or later to be developed that perform
substantially the same function or achieve substantially the same
result as the corresponding embodiments described herein may be
utilized according to the present invention. Accordingly, the
appended claims are intended to include within their scope such
processes, machines, manufacture, compositions of matter, means,
methods, or steps.
* * * * *