USOO7664533B2
`
`(12)
`
`United States Patent
`Logothetis et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7.664,533 B2
`Feb. 16, 2010
`
`(54) METHOD AND APPARATUS FORA
`MULT-BEAMANTENNA SYSTEM
`
`(75) Inventors: Andrew Logothetis, Uppsala (SE):
`David Astely, Stockholm (SE)
`(73) Assignee: Telefonaktiebolaget LM Ericsson
`(publ), Stockholm (SE)
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 498 days.
`(21) Appl. No.: 10/704,158
`
`(*) Notice:
`
`(22) Filed:
`
`Nov. 10, 2003
`
`(65)
`
`Prior Publication Data
`US 2005/O1 O1352 A1
`May 12, 2005
`
`(51) Int. Cl.
`(2006.01)
`H04M I/00
`(52) U.S. Cl. ................... 455/562.1:455/276.1, 342/81
`342/368
`(58) Field of Classification Search ................. 455/561,
`455/562. 1, 101, 134, 135, 137,276.1, 226.3,
`455/63.1, 67.11, 25.63, 63.4, 67.16, 91; 375/144,
`375/147, 148; 342/372, 378, 81, 82,350,
`342/354,367, 368; 343/751, 757
`See application file for complete search history.
`References Cited
`U.S. PATENT DOCUMENTS
`6,218,987 B1
`4/2001 Derneryd et al.
`6,549,164 B2 * 4/2003 Paschen et al. .............. 342,371
`6.999,794 B1* 2/2006 Lindskog et al.
`... 455,562.1
`7,069,050 B2 * 6/2006 Yoshida ..........
`... 455,562.1
`7,155,231 B2 * 12/2006 Burke et al. ................ 455,450
`(Continued)
`
`(56)
`
`FOREIGN PATENT DOCUMENTS
`
`EP
`
`O 639 035
`
`2, 1995
`
`(Continued)
`OTHER PUBLICATIONS
`International Search Report and Written Opinion mailed Feb. 16.
`2005 in corresponding PCT Application PCT/SE2004/001551.
`(Continued)
`Primary Examiner Patrick N Edouard
`Assistant Examiner—Anthony S Addy
`(74) Attorney, Agent, or Firm Nixon & Vanderhye P.C.
`
`(57)
`
`ABSTRACT
`
`An antenna array in a radio node includes multiple antenna
`elements for transmitting a widerbeam covering a majority of
`a sector cell that includes a common signal and a narrower
`beam covering only a part of the sector cell that includes a
`mobile user-specific signal. Transmitting circuitry is coupled
`to the antenna array, and processing circuitry is coupled to the
`transmitting circuitry. The processing circuitry ensures the
`user-specific signal and the common signal in a mixed beam
`embodiment are in-phase and time-aligned at the antenna
`array. In a steered beam embodiment, the processing circuitry
`ensures the user-specific signal and the common signal are
`time-aligned and have a controlled phase difference when
`received at mobile stations in the sector cell. In both embodi
`ments, distortions in the common signal and the user-specific
`signal associated with their conversion from baseband fre
`quency to radio frequency are also compensated. And in the
`steered beam embodiment, beam forming weights are used
`not only to radiate a narrower beam to the desired mobile user
`but also to direct a wider common signal beam to reach all
`mobile users in the cell.
`
`58 Claims, 13 Drawing Sheets
`
`Beam Forming Network
`(BFN)
`
`Signal
`Processing
`
`
`
`(decoded
`mobile user
`signal)
`
`
`
`common signal)
`
`(user-specific signal)
`
`Ford Motor Co.
`Exhibit 1011
`Page 001
`
`

`

`US 7,664,533 B2
`Page 2
`
`U.S. PATENT DOCUMENTS
`7.221,699 B1* 5/2007 Lindskog .................... 375,147
`7.263,082 B1* 8/2007 Lindskog .................... 370,335
`2002fO150065 A1 * 10, 2002 Ponnekamti ...
`370,334
`2003/01982O1 A1* 10, 2003 Yitalo et al. ............... 370,329
`2004/00 14433 A1
`1/2004 Hamada et al. ............. 45.5/101
`2005/00 14474 A1
`1/2005 Jitsukawa et al. ........... 45.5/10
`
`
`
`FOREIGN PATENT DOCUMENTS
`
`EP
`EP
`
`1175O22
`1229669
`
`1, 2002
`8, 2002
`
`WO
`
`O169814
`9, 2001
`OTHER PUBLICATIONS
`Adaptive Antennas for GSM and TDMA Systems, IEEE Personal
`Communications, Jun. 1999, Anderson et al., pp. 74-86.
`Adaptive Antennas in WCDMA Systems-Link Level Simulation
`Results Based on Typical User Scenarios, Bo Goransson et al., pp.
`157-164.
`Nortel Networks CDMA Advantages of AABA Smart Antenna Tech
`nology, The CDG Technology Forum, Oct. 1, 2002, Martinez-Munoz
`et al.
`Translation of Chinese official action, Mar. 6, 2009, in corresponding
`Chinese Application No. 200480032946.0.
`* cited by examiner
`
`Ford Motor Co.
`Exhibit 1011
`Page 002
`
`

`

`U.S. Patent
`
`Feb. 16, 2010
`
`Sheet 1 of 13
`
`US 7.664,533 B2
`
`Adaptive Array
`Antenna
`
`Interferer
`
`Fig. 1
`
`Interferer
`
`
`
`RNC / BSC
`
`Ford Motor Co.
`Exhibit 1011
`Page 003
`
`

`

`U.S. Patent
`
`Feb. 16, 2010
`
`Sheet 2 of 13
`
`US 7.664,533 B2
`
`
`
`
`
`||30 JO400S
`
`Ford Motor Co.
`Exhibit 1011
`Page 004
`
`

`

`U.S. Patent
`
`Feb. 16, 2010
`
`Sheet 3 of 13
`
`US 7.664,533 B2
`
`14
`
`14
`
`14
`
`V. V V 2
`A1
`A2
`A3
`
`10
`
`Beam Forming Network
`(BFN)
`B2
`
`B
`1
`
`B3
`
`16
`
`20
`
`18
`
`
`
`22
`
`Rx
`
`24
`
`26
`
`Signal
`
`32
`
`GE
`
`GE
`
`CE
`
`18
`
`UL
`
`Processing 1S
`
`W
`
`W2
`
`(decoded
`mobile user
`Sional
`gnal)
`
`28
`sy
`33 (-w?
`f5.
`301.f4
`30
`30
`
`DL
`(user-specific signal)
`
`W.
`3
`
`29
`
`DL
`(Common signal)
`
`Fig. 4
`
`Ford Motor Co.
`Exhibit 1011
`Page 005
`
`

`

`U.S. Patent
`
`Feb. 16, 2010
`
`Sheet 4 of 13
`
`US 7.664,533 B2
`
`Sector Covering Method Using Random Beam Weights
`
`
`
`-60
`
`40
`
`-20
`
`40
`
`60
`
`20
`O
`angle of arrival (deg)
`Fig. 5A
`
`O
`
`-60
`
`-40
`
`-20
`
`40
`
`60
`
`20
`O
`angle of arrival (deg)
`Fig. 5B
`
`Ford Motor Co.
`Exhibit 1011
`Page 006
`
`

`

`U.S. Patent
`
`Feb. 16, 2010
`
`Sheet 5 of 13
`
`US 7.664,533 B2
`
`Sector Covering Method Using Optimized Beam Weights
`
`
`
`an
`9.
`S
`92
`Cl
`s
`C
`92
`C
`s
`
`-15
`-60
`
`.
`
`-40
`
`-20
`
`40
`
`60
`
`20
`O
`angle of arrival (deg)
`Fig. 5C
`
`150
`O
`100
`9.
`is 50
`3 0
`Vs
`5-50
`9-100
`-150
`
`-60
`
`-40
`
`-20
`
`20
`O
`angle of arrival (deg)
`Fig. 5D
`
`40
`
`60
`
`Ford Motor Co.
`Exhibit 1011
`Page 007
`
`

`

`U.S. Patent
`
`Feb. 16, 2010
`
`Sheet 6 of 13
`
`US 7.664,533 B2
`
`Mean and Standard Deviation of Phase Offset Between
`the Dedicated and Common Pilot Channels. AS = 5.0 deg.
`
`
`
`AOA (degrees)
`
`Fig. 6A
`
`Ford Motor Co.
`Exhibit 1011
`Page 008
`
`

`

`U.S. Patent
`
`Feb. 16, 2010
`
`Sheet 7 of 13
`
`US 7.664,533 B2
`
`Mean and Standard Deviation of Phase Offset Between
`the Dedicated and Common Pilot Channels. AS = 10.0 deg.
`
`
`
`-60
`
`-40
`
`-20
`
`40
`
`60
`
`O
`20
`AOA (degrees)
`
`Fig. 6B
`
`Ford Motor Co.
`Exhibit 1011
`Page 009
`
`

`

`U.S. Patent
`
`Feb. 16, 2010
`
`Sheet 8 of 13
`
`US 7.664,533 B2
`
`
`
`UL
`d
`
`Signal
`
`<>
`
`W.1 W2. W3.
`
`2
`(decoded
`mobile user
`Signal)
`
`V V2 V3
`
`*
`
`29
`area
`
`7
`$g V3
`54 1 A N 54
`54
`
`28
`
`/ ly
`Ox)
`i R w?
`30 VLAN 30
`30
`
`DL
`(common signal)
`
`DL
`(user-specific signal)
`
`Fig. 7
`
`Ford Motor Co.
`Exhibit 1011
`Page 010
`
`

`

`U.S. Patent
`
`Feb. 16, 2010
`
`Sheet 9 of 13
`
`US 7.664,533 B2
`
`A1
`
`
`
`A2
`
`A3
`
`(decoded
`mobile user
`Signal)
`
`30
`
`30
`
`DL
`(common signal)
`
`DL
`(user-specific signal)
`
`Fig. 8
`
`Ford Motor Co.
`Exhibit 1011
`Page 011
`
`

`

`U.S. Patent
`
`Feb. 16, 2010
`
`Sheet 10 of 13
`
`US 7,664,533 B2
`
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`
`Ford Motor Co.
`Exhibit 1011
`Page 012
`
`(gp) ules Aeuy euuajuy
`
`Ford Motor Co.
`Exhibit 1011
`Page 012
`
`

`

`U.S. Patent
`
`Feb. 16, 2010
`
`Sheet 11 of 13
`
`US 7.664,533 B2
`
`
`
`G6 (61-)
`
`Ford Motor Co.
`Exhibit 1011
`Page 013
`
`

`

`U.S. Patent
`
`Feb. 16, 2010
`
`Sheet 12 of 13
`
`US 7.664,533 B2
`
`14 14 14
`
`V. V. V/
`
`
`
`14 14 14
`
`V. V V
`
`36
`
`Common
`Signal
`Distribution
`
`DL
`
`RxDB1
`
`User-specific
`Signal
`Distribution
`
`37
`
`DL
`
`RXDB2
`
`UL d
`
`Signal
`
`32
`
`W. W.2 w8
`
`Fig. 10
`
`Ford Motor Co.
`Exhibit 1011
`Page 014
`
`

`

`U.S. Patent
`
`Feb. 16, 2010
`
`Sheet 13 of 13
`
`US 7.664,533 B2
`
`
`
`TxDB1
`
`TxDB2
`
`Common
`Signal
`Distribution
`
`User-specific
`Signal
`Distribution
`
`UL
`d
`
`Signal
`Igna
`
`V
`V
`2
`V3
`
`w W2 W
`Fig. 11
`
`Ford Motor Co.
`Exhibit 1011
`Page 015
`
`

`

`US 7,664,533 B2
`
`1.
`METHOD AND APPARATUS FOR A
`MULT-BEAMANTENNA SYSTEM
`
`BACKGROUND
`
`2
`In adaptive antenna systems, user-specific data signals are
`transmitted using narrower beams (whether fixed or steer
`able). But system-specific or common signals are generally
`transmitted via another antenna that has a wider covering
`beam, e.g., a sector antenna. A typical common signal is the
`base station (primary) pilot signal. The pilot signal includes a
`known data sequence which every mobile radio uses to esti
`mate the radio propagation channel. As the mobile moves, the
`radio propagation channel also changes. Because a good
`channel estimate is essential in order to detect the user-spe
`cific data, the pilot signal is used as a “phase reference. A
`beam-specific secondary pilot signal may be present on each
`beam and may also be used as a phase reference. Mobile users
`whose signals are transmitted with the same beam then use
`the same secondary pilot signal. Alternatively, mobile-dedi
`cated pilot signals may be transmitted with the same beam as
`the user-specific signal and be used as a phase reference. The
`mobile user is instructed by the network which phase refer
`ence should be used.
`There are several drawbacks of current multi-beam archi
`tectures. A first drawback is cost. A fixed-beam antenna array
`that forms the narrow beams at radio frequency may require
`an additional sector covering antenna to be implemented. The
`hardware complexity and cost are related to the: number of
`feeder cables equal to the number of beams+1 (for the sector
`covering antenna), physical weight determined by the size of
`the antennas, and the height and size of the antenna mast.
`Different sector and narrow beam antennas add significantly
`to the cost of the base station.
`A second drawback relates to phase reference mismatch
`and Quality of Service (QoS) degradation. The radio channel
`of the primary pilot signal transmitted by the sector covering
`antenna and the radio channel of the user-specific data trans
`mitted through a narrow beam are not necessarily the same. If
`the mobile is instructed to use the primary pilot signal as a
`phase reference, then the mobile will expect that the user
`specific data to be subject to the same radio channel as the
`primary pilot signal. But those channels are different. As a
`result, the phase reference is wrong, detection and decoding
`errors increase, and the Quality of Service (QoS) is degraded.
`A third drawback is poor resource utilization. To compen
`sate for the phase reference mismatch, the mobile can be
`instructed to use a beam-specific secondary pilot signal or a
`user-specific dedicated pilot signal as a phase reference. In
`the former case, all users within the same beam use the same
`pilot signal, whereas in the latter case, each user utilizes a
`unique pilot signal. The QoS is improved but at the expense of
`additional allocated resources, (e.g., power, codes, etc). Con
`sequently, less power is available to other mobile users,
`adversely impacting system capacity and data throughput.
`A further drawback concerns inflexibility and signaling
`delays. Suppose a mobile could receive a better signal from an
`alternative, secondary pilot per beam. The network must
`therefore periodically investigate which secondary pilot is
`most appropriate, i.e., received at maximum power. The
`antenna system and the mobile radio must be signaled by the
`network to report back several measurement reports. If the
`network determines that a new beam should be used to trans
`mit the user-specific data, then the antenna system is
`instructed to change beams, and the mobile radio is signaled
`to start using the alternative secondary pilot channel as a
`phase reference. Such procedures cause delays and require
`significant signaling overhead.
`Receiver diversity is widely used in today's wireless infra
`structure and it offers substantial benefits in terms of uplink
`coverage and capacity. Further, transmit diversity can be use
`to improve the downlink performance and it may become a
`
`The invention relates generally to wireless communication
`nodes, and more particularly, to wireless communications
`nodes that utilize a multi-beam antenna system.
`Adaptive antenna arrays have been used successfully in
`various cellular communications systems, e.g., the GSM sys
`tem. An adaptive antenna array replaces a conventional sector
`antenna by two or more closely-spaced antenna elements.
`The antenna array directs a narrow-beam of radiated energy
`to a specific mobile user to minimize the interference to other
`users. Adaptive antenna arrays have been shown in GSM and
`TDMA systems to substantially improve performance, mea
`Sured in increased system capacity and/or increased range,
`compared to an ordinary sector covering antenna.
`Adaptive antenna Systems may be grouped into two cat
`egories: fixed-beam systems, where radiated energies are
`directed to a number of fixed directions, and steered-beam
`systems, where the radiated energy is directed towards any
`desired location. Both types of narrow beam systems are
`generally illustrated in FIG. 2, which also shows a sector
`beam that covers the sector cell. The benefits of adaptive
`antenna systems include: efficient-utilization of spectral
`resources by exploiting the spatial (angular) separation of
`users, cost efficiency, increased range or capacity, and easy
`integration, i.e., no mobile terminal changes are required as
`would be in other schemes such as Multiple Input Multiple
`Output (MIMO) schemes which employ multiple antennas at
`both the terminal and the base stations.
`Fixed beams can be generated in baseband frequency or in
`Radio Frequency (RF). Baseband generation requires a cali
`bration unit that estimates and compensates for any signal
`distortion present in the signal path from baseband via the
`Intermediate Frequencies (IF) and the RF up to each antenna
`element in the array. The RF method generates the fixed
`beams using, for example, a Butler matrix at radio frequency.
`Under Some assumptions, for example a uniform linear
`array where the antenna elements are separated by a half
`wavelength, there is a one-to-one correspondence between a
`certain direction-of-arrival (DOA) of an incoming wavefront
`and the phase shift of the signals at the output of the antenna
`elements. By appropriately phase shifting the signals prior to
`transmission (or reception), an adaptive antenna system can
`steer the radiated energy towards (or from) the desired mobile
`user, while at the same time, minimize the interference to
`other mobile users. Steered-beams require calibration to esti
`mate and compensate for any signal distortion present in the
`signal path from baseband to the antenna elements and Vice
`WSa.
`Time-varying, multipath fading seriously degrades the
`quality of the received signals in many wireless communica
`tion environments. One way to mitigate deep fade effects and
`provide reliable communications is to introduce redundancy
`(diversity) in the transmitted signals. The added redundancy
`may be in the temporal or the spatial domain. Temporal (time)
`diversity is implemented using channel coding and interleav
`ing. Spatial (space) diversity is achieved by transmitting the
`signals on spatially-separated antennas or using differently
`polarized antennas. Such strategies ensure independent fad
`ing on each antenna. Spatial transmit diversity can be Sub
`divided into closed-loop or open-loop transmit diversity
`modes, depending on whether feedback information is trans
`mitted from the receiver back to the transmitter.
`
`10
`
`15
`
`25
`
`30
`
`35
`
`40
`
`45
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`50
`
`55
`
`60
`
`65
`
`Ford Motor Co.
`Exhibit 1011
`Page 016
`
`

`

`3
`key feature in the 3" generation wireless systems. But trans
`mit diversity signals are transmitted throughout the cell caus
`ing increased interference to other users, even though the
`intended mobile user is located in a certain direction. None
`theless, combining transmit diversity with narrower, directed
`beams can offer significant benefits.
`The above-identified drawbacks of current multi-beam
`architectures are overcome with an antenna system that
`includes an antenna array fortransmitting a common signal in
`a wider beam covering a a sector cell and a mobile-user
`specific signal in a narrower beam covering only part of the
`sector cell. Transmitting circuitry is coupled to the antenna
`array and to filtering circuitry. In a first, “mixed beam”
`embodiment, the filtering circuitry filters the user-specific
`and common signals to compensate for distortions associated
`with their conversion from baseband frequency to radio fre
`quency. The filtering circuitry and beam weighting circuitry
`ensure that the user-specific and common signals are Substan
`tially time-aligned and in-phase at the antenna array (prefer
`ably at a center antenna element). User-specific signal
`weights are designed to radiate a narrowerbeam (compared to
`the wide, sector-covering beam) in the direction of the mobile
`station Such that each mobile can use the same common signal
`as a phase reference for channel estimation and demodula
`tion.
`In a second, “steered beam’ embodiment, the filtering cir
`cuitry filters the user-specific and common signals to com
`pensate for distortions associated with their conversion from
`baseband frequency to radio frequency. The filtering circuitry
`and beam weighting circuitry ensure that the user-specific
`and common signals are time-aligned and have a controlled
`phase difference when received at each mobile user in the
`cell. Each mobile user can use the common signal as a phase
`reference for channel estimation and demodulation. That
`phase difference is preferably controlled to obtain a good
`tradeoff between required transmit power, radiated interfer
`ence, and quality of service to the users. Beam forming
`weights are used not only to radiate a narrower beam to the
`desired mobile user (as in the mixed beam embodiment) but
`also to direct wider common signal beam to reach all mobile
`users in the cell.
`In an example, Steered-beam implementation, the wide
`beam carrying the common signal is transmitted only from a
`centerantenna element in the antenna array. Using the center
`antenna element to generate the wide common beam permits
`a correlation of the controlled phase difference between the
`common and user-specific signals received by the mobile user
`to be less than or equal to a target value that ensures a desired
`quality of service. Alternatively, the wide beam carrying the
`common signal may be generated using multiple antenna
`elements in the antenna array. Since the antenna elements are
`generally fixed in a predetermined “look direction” during the
`antenna array installation, all antenna elements can be uti
`lized in conjunction with baseband signal processing to form
`a wide beam with desired characteristics, which could change
`with time depending on the cell planning. Beam forming
`weights applied to user-specific signal results in steering a
`narrower beam towards the mobile user from the antenna
`array. Providing such beam steering for both the user-specific
`signal beam and the common signal beam permits more intel
`ligent aiming of both signal types in the cell.
`In a more detailed, non-limiting example of the mixed
`beam embodiment, the antenna array includes Nantenna
`elements, where N is an odd positive integer greater than one.
`A beam forming network is coupled between the antenna
`array and the transmitting circuitry. The beam forming net
`work receives in each beam the user-specific and common
`
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`US 7,664,533 B2
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`4
`signals and generates N signals which are provided to the
`antenna array. Before the beam forming network receives the
`N signals, each signal passes through beam-specific transmit
`filtering circuitry. The beam transmit filters cancel the com
`mon signal in all outputs of the beam forming network except
`at a centerantenna element output. But the common signal is
`transmitted simultaneously on the N beams with equal or
`approximately equal power and phase.
`Beam-weighting circuitry weights the user-specific signal
`with a beam weight corresponding to each beam and provides
`weighted, user-specific signals to the corresponding beam
`transmit filters. Each user-specific beam weight may be a
`function of the uplink average power received in the corre
`sponding beam. An example function is the square root. The
`user-specific beam weights are selected to direct radiated
`energy in a relatively narrow beam from the antenna array to
`a desired mobile user.
`Receiving circuitry is coupled to the beam forming net
`work and to a signal processor. The signal processor com
`bines signals received on the N beams to estimate a received
`signal and determines an average uplink power for each
`beam. Those average uplink powers are used to determine the
`user-specific beam weights. The mixed beam embodiment
`may be implemented in transmit diversity branches and/or in
`receive diversity branches.
`In a more detailed example of the steered beam embodi
`ment, the antenna array includes Nantenna elements, where
`N is a positive integer even or odd. The filtering circuitry
`includes Nantenna transmit filters, and each antenna transmit
`filter is associated with a corresponding antenna element. The
`common signal and the user-specific signal may be transmit
`ted simultaneously from all Nantenna elements. The user
`specific signal is transmitted with N user-specific beam
`weights, each user-specific beam weight corresponding to
`one of the Nantenna elements. The beam weights are com
`plex numbers used to phase-rotate and amplify the user-spe
`cific signal. The common signal is transmitted with N com
`mon signal beam weights, each common signal beam weight
`corresponding to one of the Nantenna elements. These beam
`weights may also be complex numbers used to phase-rotate
`and amplify the common signal. Alternatively, the common
`signal may be transmitted from only one antenna Such as the
`central antenna element. In this case, the beam weights for the
`other antenna elements may be set to Zero.
`In the steered beam embodiment, the user-specific and
`common signal beam forming weights are determined (1) to
`yield high antenna gain so that the generated interference is
`reduced and (2) to keep the phase difference between the
`user-specific signal and the common signal at an acceptable
`level. The common signal is the phase reference signal for all
`mobiles in the cell, and the controlled phase difference
`between the common and user-specific signals can be viewed
`as random with its distribution being affected by statistics of
`the channel as well as the transmitter weights used.
`In the receive side of the antenna system in the steered
`beam embodiment, a beam forming network, (which is not
`required in the steered beam embodiment on the transmit
`side), may be coupled to the Nantenna elements for generat
`ing N received beams. Receiving circuitry is coupled to the
`beam forming network and to a signal processor. The signal
`processor processes signals received on the N received beams
`to estimate a received signal. The signal processor determines
`uplink channel statistics per user and predicts the correspond
`ing downlink channel statistics. The steered beam embodi
`ment may also be used in transmit and/or receive diversity
`branches.
`
`Ford Motor Co.
`Exhibit 1011
`Page 017
`
`

`

`5
`The technology described in this application provides
`numerous advantages. First, common and user-specific sig
`nals can be transmitted without requiring a separate sector
`antenna. Second, neither secondary nor dedicated pilot sig
`nals are required as a phase reference. Third, the common and
`user-specific signals are transmitted without being distorted
`as a result of travel/processing from baseband outputs to the
`antenna elements. Fourth, the common and user-specific sig
`nals are received at the mobile terminals approximately in
`phase (in the mixed beam case) or subject to Some controlled
`random variations (in the steered beam case) and time
`aligned, i.e., Subject to approximately the same channel delay
`profile. Fifth, because the antenna array radiates the user
`specific channels in a narrower beam directed to the desired
`mobile user, interference is Suppressed to spatially-separated
`mobile users. Sixth, combining beam forming and transmit
`diversity or transmit/receive diversity offers significant ben
`efits. A seventh advantage is transparency. Mobile users need
`not be aware of the architecture or the implementation of the
`antenna array. Eighth, backward compatibility permits ready
`system integration. No change to radio network controllers in
`the radio network is required. Ultimately, the invention may
`be used in any wireless system that can exploit downlink
`beam forming.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 illustrates an adaptive antenna system transmitting
`in a sector cell;
`FIG. 2 illustrates a cellular network with a base station
`transmitting a sector beam, a base station transmitting a
`multi-beam, and a base station transmitting a steerable beam;
`FIG. 3 illustrates a cellular communication system;
`FIG. 4 illustrates an antenna system in accordance with a
`mixed beam example embodiment;
`FIGS. 5A-5D illustrate beam patterns for the synthesized
`sector covering beam and the narrow beams as well as the
`relative phase offset between the synthesized sector beam and
`a narrow beam as a function of direction of arrival;
`FIGS. 6A-6B illustrate relative phase offset between the
`received common signal and a received user-specific signal as
`a function of mobile direction;
`FIG. 7 illustrates an antenna system in accordance with a
`steered beam example embodiment;
`FIG. 8 illustrates an antenna system in accordance with a
`special case of the steered beam example embodiment;
`FIGS. 9A-9B illustrate performance of the mixed and
`steered beam example embodiments;
`FIG. 10 illustrates an example, mixed-beam, diversity
`embodiment; and
`FIG. 11 illustrates an example, steered-beam, diversity
`embodiment.
`
`DETAILED DESCRIPTION
`
`The following description, for purposes of explanation and
`not limitation, sets forth specific details to provide an under
`standing of the present invention. But it will be apparent to
`one skilled in the art that the present invention may be prac
`ticed in other embodiments that depart from these specific
`details. In other instances, detailed descriptions of well
`known methods, devices, and techniques, etc., are omitted so
`as not to obscure the description with unnecessary detail.
`Individual function blocks are shown in one or more figures.
`Those skilled in the art will appreciate that functions may be
`implemented using discrete components or multi-function
`hardware. Processing functions may be implemented using a
`
`US 7,664,533 B2
`
`6
`programmed microprocessor or general-purpose computer,
`using one or more application specific integrated circuits
`(ASICs), and/or using one or more digital signal processors
`(DSPs).
`The invention relates to a multi-beam antenna system. A
`non-limiting example of a multi-beam antenna system is an
`adaptive array antenna, Such as that shown in FIG. 1, which
`illustrates an example narrow antenna beam transmitted from
`the adaptive antenna encompassing a relatively narrow area in
`the sector cell where a desired mobile station is located.
`Because the side lobes are relatively low, there is less inter
`ference caused by the narrow beam to other mobiles and
`adjacent cells. Moreover, the intended mobile radio is more
`likely to receive the desired transmission at a higher signal
`to-noise ratio using the directed narrow beam shown in FIG.
`1.
`FIG. 2 illustrates a cellular network with a base station
`transmitting a sector beam in one sector cell, a base station
`transmitting a fixed multi-beam antenna pattern in another
`sector cell, and a base station transmitting a steerable beam in
`a third sector cell. Both FIGS. 1 and 2 illustrate how adaptive
`antennas spread less interference in the downlink direction
`and Suppress spatial interference in the uplink direction. This
`increases the signal-to-interference in both uplink and down
`link directions, and therefore, increases overall system per
`formance.
`An example cellular system 1 is shown in FIG. 3 in which
`the present invention may be employed. A radio network
`controller (RNC) base station controller (BSC) 4 is coupled to
`multi base stations 8 and to other networks represented by a
`cloud 2. Each illustrated base station BS1 and BS2 services
`multiple sector cells. Base station BS1 services sector cells
`S1, S2, and S3, and base station BS2 services sector cells S4,
`S5, and S6.
`An antenna System in accordance with a mixed beam,
`non-limiting, example embodiment is now described in con
`junction with FIG. 4. The antenna system 10 includes an
`antenna array 12 with multiple antenna elements 14. The
`antenna array 12 includes an odd integer number Nofantenna
`elements designated A. A. . . . . A. In the example of FIG.
`4, N=3. A single beam forming network (BFN) 16 generates
`N narrow beams. The same beams are used for both uplink
`and downlink. A beam forming network is a multiple input,
`multiple output port device. Each beam forming network port
`corresponds to one of the narrow beams of the multi-beam
`antenna system. A beam forming network may include active
`or passive components. With passive components, the beams
`are designed during the manufacturing process and remain
`fixed. For active components, the beams may be steered adap
`tively. A well-known, Suitable, passive beam forming net
`work operating in the radio frequency (RF) range that pro
`duces multiple narrow beams from an array of uniformly
`spaced antenna elements is a Butler matrix.
`The beam forming network 16 in FIG. 4 operates in both
`transmission and reception directions. A signal to be trans
`mitted is connected to one of the input ports of the beam
`forming network 16 which then directs the signal and trans
`mits it on all antenna elements. Depending upon the input port
`chosen, each signal designated to a particular antenna ele
`ment is subject to a particular phase rotation. The overall
`result is that the main lobe or beam is generated at a certain
`direction. When an alternative beam port is used, the beam
`appears in another direction. In short, the output of the
`antenna elements is a formed beam.
`Each beam input to the beam forming network is coupled to
`a corresponding duplex filter (DX) 18. Duplex filters 18 pro
`vide a high degree of isolation between the transmitter and the
`
`10
`
`15
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`Ford Motor Co.
`Exhibit 1011
`Page 018
`
`

`

`7
`receiver and permit one antenna to be used for both uplink
`reception and downlink transmission. Each beam also has a
`corresponding transmitter (TX)20 coupled to a corresponding
`duplex filter 18. The transmitter 20 typically includes power
`amplifiers, frequency up-converters, and other well-known
`elements. Each duplex filter 18 also is coupled to a corre
`sponding receiver (RX) 22. Each receiver 22 typically
`includes low noise amplifiers, intermediate frequency down
`converters, baseband down-converters, analog-to-digital
`converters, and other well-known elements. The outputs from
`the receivers 22 are provided to a signal processor 32 which
`decodes the received signal from a mobile user and generates
`an output shown as d". The signal processor 32 also gener
`ates N beam weights (w) to be applied to user-specific sig
`nals as shown in the weighting block 28.
`The user-specific signal, shown as d', is input to the
`weighting block 28 which includes N multipliers 30 for mul
`tiplying the user-specific signal with a corresponding beam
`weightw. The common signal c' is split into Ncopies of the
`common signal by a signal splitter 29 but is not weighted in
`this example. Each weighted, user-specific signal and the
`common signal are Summed at a corresponding Summer 26,
`where each summer 26 is associated with one of the beams.
`The output of each summer 26 is forwarded to a beam filter
`(F) 24, each beam having its own beam filter 24. The output
`of each beam filter 24 is then provided to its corresponding
`transmitter 20.
`The beam generated from one antenna element, the center
`element A in this example embodiment, will be wide. When
`two or more antenna elements are used in the antenna array,
`30
`the generated beam can be narrower. In contrast with conven
`tional, fixed-beam systems where the single uplink beam with
`the strongest average received power is used to transmit user
`specific signals in the downlink, the user-specific signals are
`transmitted in the downlink on all beam