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`US008891676B2
`
`(12) United States Patent
`Ringstrom et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 8,891,676 B2
`Nov. 18, 2014
`
`(75)
`
`(54) ANTENNA DEVICE AND METHOD IN A
`MIMOSYSTEM
`Inventors: Markus Ringstriim, Stockholm (SE);
`Bo Giiransson, Sollentuna (SE);
`Fredrik Ovesjii, Alvsjii (SE); Henrik
`Asplund, Stockholm (SE)
`
`(73) Assignee: Optis Cellular Technology, LLC,
`Plano, TX (US)
`
`( *) Notice:
`
`Subject to any disclaimer, the term ofthis
`patent is extended or adjusted under 35
`U.S.C. 154(b) by O days.
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`2007/0223423 Al
`2009/0181708 Al
`2012/0140801 Al
`
`9/2007 Kim et al.
`7/2009 Kim et al.
`6/2012 Asplund et al.
`
`FOREIGN PATENT DOCUMENTS
`
`WO WO 2008/022243 A2
`WO WO 2011/019310 Al
`
`2/2008
`2/2011
`
`OTHER PUBLICATIONS
`
`(21) Appl. No.:
`(22) PCT Filed:
`
`13/824,746
`Sep.23,2010
`
`(86) PCT No.:
`
`PCT /SE2010/051024
`
`§ 371 (c)(l),
`(2), ( 4) Date: Mar. 18, 2013
`
`(87) PCT Pub. No.: WO2012/039659
`
`PCT Pub. Date: Mar. 29, 2012
`Prior Publication Data
`
`(65)
`
`(51)
`
`Jul. 18, 2013
`
`(2006.01)
`(2006.01)
`(2006.01)
`(2006.01)
`(2006.01)
`
`US 2013/0182794Al
`Int. Cl.
`H04K 1/02
`H04L25/03
`H04L25/49
`H04B 7104
`H04B 7106
`(52) U.S. Cl.
`CPC ............ H04B 710456 (2013.01); H04B 710469
`(2013.01); H04B 710434 (2013.01); H04B
`710617 (2013.01)
`USPC ............................ 375/297; 375/295; 375/296
`( 58) Field of Classification Search
`CPC ... H04B 7/0434; H04B 7/0617; H04B 7/0456
`USPC .......................................................... 375/297
`See application file for complete search history.
`
`International Search Report, Application No. PCT/SE2010/051024,
`May 20, 2011.
`
`(Continued)
`
`Primary Examiner - Erin File
`(74) Attorney, Agent, or Firm - Vincent J. Allen; James H.
`Ortega; Carstens & Cahoon, LLP
`
`ABSTRACT
`(57)
`The invention relates to the technical field of radio commu(cid:173)
`nications, and in particular to an antenna device for a radio
`base station, and a method of operating an antenna device in
`a Multiple-Input Multiple-Output system. Embodiments of
`the invention disclose a secondary precoder (24) in series
`with a Multiple-Input Multiple-Output precoder (22). The
`Multiple-Input Multiple-Output precoder (22) has a first plu(cid:173)
`rality of inputs (26, 28) for one or more Multiple-Input Mul(cid:173)
`tiple-Output data streams, and a first plurality of outputs (30,
`32) for the one or more Multiple-Input Multiple-Output data
`streams. The secondary precoder has a second plurality of
`inputs (34, 36) and a second plurality of outputs (38, 40). The
`first plurality of outputs (30, 32) are in communication with
`the second plurality of inputs (34, 36). The antenna device
`further comprises a controller device (64), and the antenna
`device is operable to control an output power value of the one
`or more data streams at the second plurality of outputs (38,
`40).
`
`19 Claims, 6 Drawing Sheets
`
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`Samsung Ex. 1008
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`

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`US 8,891,676 B2
`Page 2
`
`(56)
`
`References Cited
`
`OTHER PUBLICATIONS
`
`Written Opinion of the International Searching Authority, Applica(cid:173)
`tion No.PCT/SE2010/051024, May 20, 2011.
`Ericsson et al: "HSDPA MIMO codebook subset restriction", 3gpp
`Draft; Rl-094977 HSDPA MIMO Codebook Subset Restriction, 3rd
`Generation Partnership Project (3gpp ), Mobile Competence Centre ;
`
`650, Route Des Lucioles, F-06921 Sophia-Antipolis Cedex, France,
`No. Jeju; 20091109, Nov. 9, 2009, XP050389331.
`Qualcomm Europe, MIMO Codebook restrictions for single stream
`transmissions, 3GPP Draft; Rl-0958068 MIMO Codebook Restric(cid:173)
`tions, 3rd Generation Partnership Project (3GPP), Mobile Compe(cid:173)
`tence Centre; 650, Rout Des Lucioles; F-06921 Sophia-Antipolis
`Cedex; France Nov. 9, 2009.
`Supplementary European Search Report, Application No.
`EP10857591.l dated Feb. 27, 2014.
`
`Samsung Ex. 1008
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`

`

`U.S. Patent
`
`Nov. 18, 2014
`
`Sheet 1 of 6
`
`US 8,891,676 B2
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`Samsung Ex. 1008
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`8
`6
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`------1 UE Capability Info
`(MIMO Support etc)
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`Cell Capability Info ~ 7 0
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`
`/76
`
`User Data Info
`
`~!:~ 11--1 _ _ _ _ _ :1
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`+
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`Scheduler
`
`•
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`
`~64
`
`Fig 3
`
`66
`
`Available power
`7 2~ (per PA or Total Power)
`
`Number of available
`HS-POSCH codes
`
`------74
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`Samsung Ex. 1008
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`/78
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`
`Transport Block Number of HS-
`Size
`PDSCH codes
`
`Precoder weight
`
`Modulation
`
`Power
`
`User 1
`MIMO Stream 1
`MIMO Stream 2
`User 2
`MIMO Stream 1
`MIMO Stream 2
`-
`-
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`
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`MIMO Stream 2
`
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`Samsung Ex. 1008
`
`

`

`80~
`
`Operating the
`antenna device
`usmga
`controller device
`to control an
`output power
`value of data
`streams at the
`second plurality
`of outputs.
`
`Controlling
`an input
`power value
`to control
`the output
`power
`value.
`
`84
`
`82
`
`Operating
`the controller
`device so
`that the
`output power
`value of one
`stream is less
`than or equal
`to Ptot/2.
`
`I
`86
`
`Fig 5a
`
`Operating
`theMIMO
`precoder
`with a set of
`weights.
`
`Excluding
`selected
`weights to
`control the
`output power
`value.
`
`1---+
`
`88
`
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`
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`
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`Samsung Ex. 1008
`
`

`

`Determining
`if the output
`power values
`of the data
`streams are
`different.
`
`Determining if
`more than one
`user device is
`scheduled in a
`transmission
`time interval of
`the antenna
`device.
`
`Operating the
`controller
`device to allow
`the output
`power value to
`exceed Ptot/2
`when selected
`weight are used.
`
`Operating the
`controller
`device to allow
`the output
`power value to
`exceed Ptot/2 up
`to a predefined
`threshold value.
`
`Using a preferred
`weight if the output
`power value of one
`of the data streams
`at the second
`plurality of outputs
`is within a
`predefined
`threshold value.
`
`92
`
`94
`
`98
`
`100
`
`Fig 5b
`
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`
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`Samsung Ex. 1008
`
`

`

`US 8,891,676 B2
`
`1
`ANTENNA DEVICE AND METHOD IN A
`MIMOSYSTEM
`
`CROSS REFERENCE TO RELATED
`APPLICATION
`
`5
`
`This application is a 35 U.S.C. §371 national stage appli(cid:173)
`cation of PCT International Application No. PCT/SE2010/
`051024, filed on 23 Sep. 2010, the disclosure and content of
`which is incorporated by reference herein in its entirety. The 10
`above-referenced PCT International Application was pub(cid:173)
`lished in the English language as International Publication
`No. WO 2012/039659 Al on 29 Mar. 2012.
`
`TECHNICAL FIELD
`
`The invention relates to the technical field of radio com(cid:173)
`munications, and in particular to an antenna device for a radio
`base station, and a method of operating an antenna device in
`a Multiple-Input Multiple-Output (MIMO) system.
`
`BACKGROUND
`
`2
`transmitted from each MIMO antenna have the same power,
`particularly in the case of Channel Quality Indicator (CQI)
`reporting when each UE calculates the quality of each data
`stream. In practice this may not always happen due to restric-
`tions at a scheduler device within the BTS which is a control-
`!er device that allocates radio resources and when data for a
`plurality of UEs is to be transmitted. In general, to support
`both MIMO enabled and non-MIMO enabled UEs a MIMO
`precoder may be used in series with a secondary precoder,
`with each precoder imparting respective matrices on the data
`stream. At a data stream level the power allocation input to the
`MIMO precoder may be uneven, and the two precoders then
`distribute this power over the two PAs. In some instances a
`15 power imbalance may then be seen between the PAs, which is
`undesirable because it is a suboptimal use ofresources.
`, is the total power available at two
`In another scenario, if P,0
`PAs, and P,o/2 is allocated to one data stream at one PA, and
`if a second data stream is formed by the scheduler device
`20 when a transmit buffer of the BTS only contains a small
`amount of data, the transmit power of the second data stream
`at the second PA may be less than P,o/2. Such a scenario also
`provides an imbalance of power between the data streams
`from the PAs which is undesirable.
`Other situations may also lead to the PAs allocating differ-
`ent power to the two data streams for dual stream MIMO
`operation. In one scenario this may be caused by power cal(cid:173)
`culation rounding errors when calculating the number of bits
`for an available transport format. In another scenario this may
`30 be caused when one of the MIMO data streams is required to
`be retransmitted if Hybrid Automatic Repeat Request
`(HARQ) is used. When using HARQ, if a radio charmel has
`deteriorated since an original transmission, one data stream
`may need to be transmitted using more power than used for
`the initial transmission. If P,0 /2 was used for the initial trans(cid:173)
`mission of one data stream this will mean that the retransmit-
`ted stream will have a power of more than P ,o/2, and the other
`stream will be transmitted with less than P,o/2, which is
`undesirable for the above reasons.
`
`The evolution of radio interface standards has been
`strongly focused on increased data rates, and in the Third 25
`Generation Partnership Project (3GPP) Release 7 a technol(cid:173)
`ogy known as Multiple Input Multiple Output (MIMO) was
`introduced. Such technology uses multiple antennas at both
`the transmitter and receiver to theoretically double the down(cid:173)
`link data rate using multiple data stream transmission.
`Certain User Equipment (UE) categories are able to use
`MIMO technology, but other legacy UE categories are not be
`able to use MIMO technology. A network must be able to
`support both MIMO enabled and non-MIMO enabled UEs.
`Support for legacy UEs may be provided by transmitting all 35
`system vital information and traffic charmels on a single
`antenna. However, if there are separate Power Amplifiers
`(PA) for the multiple antennas, which is typically the case, the
`utilization of the PAs is suboptimal. This is because one
`antenna may be transmitting and receiving much more data 40
`than another antenna which represents an under utilisation of
`resources. In effect there is no power sharing between the
`PAs.
`The problem of uneven power sharing may be alleviated by
`using Butler matrices at a Base Transceiver Station (BTS),
`also known as the NodeB. Such Butler matrices distribute the
`load equally over the PAs, but have the drawback of requiring
`more hardware and introducing a power loss. Furthermore,
`Butler matrices are not always useable for power balancing if
`the data streams from the transmit antennas are correlated,
`which is the case for example with single stream MIMO.
`Another solution is to transmit all channels not using
`MIMO from the antennas through the use of Space-Time
`Transmit Diversity (STTD) encoding, which is an open loop
`transmit diversity scheme standardized in 3GPP Release 99.
`Such STTD encoding is supported by most UEs on the mar(cid:173)
`ket. However, even though STTD transmission alleviates the
`PA power balancing problem and may be beneficial for com(cid:173)
`mon charmels, there is less benefit for dedicated charmels and
`in particular the High-Speed Downlink Shared Channel (HS(cid:173)
`DSCH). The use of STTD encoding may actually harm the
`performance in certain cases, especially on the HS-DSCH
`which is a shared charmel and a scheduled resource.
`Further problems are also encountered with dual-stream
`MIMO transmission when providing mobile communication
`systems that support both MIMO enabled and non-MIMO
`enabled UEs. Typically it is assumed that the two data streams
`
`SUMMARY
`
`It is desirable to provide a way of operating radio commu(cid:173)
`nications hardware more efficiently, and to reduce at least
`45 some of the above-mentioned power balancing problems.
`According to a first aspect of the invention, there is pro(cid:173)
`vided an antenna device for a radio base station. The device
`comprising a Multiple-Input Multiple-Output precoder and a
`secondary precoder arranged in series therewith. The mul-
`50 ti pie-input multiple-output precoder having a first plurality of
`inputs for one or more Multiple-Input Multiple-Output data
`streams, and a first plurality of outputs for the one or more
`Multiple-Input Multiple-Output data streams. The secondary
`precoder having a second plurality of inputs and a second
`55 plurality of outputs. The first plurality of outputs being in
`communication with the second plurality of inputs. Wherein
`the antenna device further comprises a controller device and
`the antenna device is operable to control an output power
`value of the one or more data streams at the second plurality
`60 of outputs.
`Such an antenna device provides the advantage of being
`able to control the power between Power Amplifiers (PAs)
`associated with a respective antenna when it is appropriate.
`Such power control is achieved by the use of the controller
`65 device in combination with the Multiple-Input Multiple-Out(cid:173)
`put precoder and the secondary precoder which operates to
`control the signal power at the second plurality of outputs.
`
`Samsung Ex. 1008
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`

`

`US 8,891,676 B2
`
`10
`
`,
`
`3
`The power control is achieved without the power loss asso(cid:173)
`ciated with Butler matrices of the prior art.
`In one embodiment the controller device is operable to
`control an input power value of the one or more data streams
`input to the one or more of the first plurality of inputs to
`control the output power value of the one or more data streams
`at the second plurality of outputs. Such an arrangement is a
`convenient way to control the power at the second plurality of
`outputs when dual stream MIMO signals are being transmit(cid:173)
`ted.
`In another embodiment the antenna device includes a
`respective amplifier device in communication with each sec(cid:173)
`ond plurality of outputs, the controller device being operable
`so that the output power value of one of the data streams from
`the amplifier devices is less than or equal to P,0 /2, where P,0
`is the total available output power of the amplifier devices.
`Such an arrangement permits the controller device to be
`involved with controlling the power of the one or more data
`streams output from the antenna device.
`Preferably the Multiple-Input Multiple-Output precoder is
`operable with a set of weights w 1 , w 2 , w 3 , w 4 according to the
`Third Generation Partnership Project Technical Standard
`25.214. In one embodiment the antenna device is operable to
`exclude selected weights of the set of weights to control at
`least one output power value of the one or more data streams
`at the second plurality of outputs. Excluding said weights is a
`convenient way to control the power at the second plurality of
`outputs.
`The Multiple-Input Multiple-Output precoder may be
`operable such that if the output power value of one data
`stream is different to the output power value of another data
`stream at the second plurality of outputs the w2 weights
`(l-j)/2 and (-l+j)/2 are excluded.
`In one embodiment the antenna device includes a respec(cid:173)
`tive amplifier device in communication with each second
`plurality of outputs, the controller device being operable such
`that if the output power value of one of the data streams from
`the amplifier devices exceeds P,0 /2 said w2 weights (l-j)/2
`, is the total available
`and (-l+j)/2 are excluded, where P,0
`output power of the amplifier devices. Such an arrangement
`may allow a combination of the controller device and the
`Multiple-Input Multiple-Output precoder to control the
`power at the second plurality of outputs.
`In another embodiment the Multiple-Input Multiple-Out(cid:173)
`put precoder is operable to exclude thew 2 weights (l-j)/2 and 45
`(-1 +j)/2 if more than one user device is scheduled in a trans(cid:173)
`mission time interval of the antenna device. Such an arrange(cid:173)
`ment may further reduce an imbalance of power at the second
`plurality of outputs.
`In one embodiment the antenna device includes a respec(cid:173)
`tive amplifier device in communication with each second
`plurality of outputs, the controller device being operable to
`permit the output power value of one of the data streams from
`the amplifier device to exceed P ,0 /2 when the Multiple-Input
`Multiple-Output precoder is operated with the w2 weights
`(l+j)/2 and (-1-j)/2, where P,0
`, is the total available output
`power of the amplifier devices. The controller device may be
`operable to permit the output power value of one of the data
`streams from the amplifier devices to exceed P,0 /2 up to a
`predefined threshold value. Preferably the predefined thresh(cid:173)
`old value is given by (P,o/2)k, where k is 1 <ksl.2. Such an
`arrangement may help to avoid further problems with power
`imbalance, for example, when HARQ is used.
`In one embodiment the antenna device includes a respec(cid:173)
`tive amplifier device in communication with each second
`plurality of outputs, and a user device in communication with
`the antenna device which is configured to report a preferred
`
`4
`weight to the antenna device, wherein if the difference in
`output power value of the data streams from the amplifier
`devices is within a predefined threshold value the preferred
`weight is used to operate the Multiple-Input Multiple-Output
`precoder. Such an arrangement may have the advantage of
`improving a Block Error Rate (BLER) for receipt ofuser data
`by the user device.
`In one embodiment the Multiple-Input Multiple-Output
`precoder is operable with the w2 weights (l-j)/2 and (-1 +j)/2,
`and the antenna device is operable such that IPl -P2 1/(Pl +
`P2 )<x, where xis a predefined threshold value, and where Pl
`and P2 are the input power values of the input data streams.
`According to a second aspect of the invention there is
`15 provided a transmitter including an antenna device according
`to the first aspect of the invention.
`According to a third aspect of the invention there is pro(cid:173)
`vided a method of operating an antenna device in a Multiple(cid:173)
`Input Multiple-Output system. The Multiple-Input Multiple-
`20 Output system having a Multiple-Input Multiple-Output
`precoder and a secondary precoder arranged in series there(cid:173)
`with. The Multiple-Input Multiple-Output precoder having a
`first plurality of inputs for one or more Multiple-Input Mul(cid:173)
`tiple-Output data streams. The Multiple-Input Multiple-Out-
`25 put precoder having a first plurality of outputs for the one or
`more Multiple-Input Multiple-Output data streams. The sec(cid:173)
`ondary precoder having a second plurality of inputs and a
`second plurality of outputs. The first plurality of outputs
`being in communication with the second plurality of inputs.
`30 The second plurality of outputs being in communication with
`respective antennas. The method including operating the
`antenna device using a controller device to control an output
`power value of the one or more data streams at the second
`35 plurality of outputs.
`Such a method provides the advantage of being able to
`control the power between PAs associated with a respective
`antenna when it is appropriate. Such power control is
`achieved by using the controller device in combination with
`40 the Multiple-Input Multiple-Output precoder and the second(cid:173)
`ary precoder which is operable to control the signal power at
`the second plurality of outputs. The power control is achieved
`without the power loss associated with Butler matrices of the
`prior art.
`In one embodiment the method further includes controlling
`an input power value of the one or more data streams input to
`the one or more first plurality of inputs to control the output
`power value of the one or more data streams at the second
`plurality of outputs. Such an arrangement is a convenient way
`50 to control the power at the second plurality of outputs when
`dual stream MIMO signals are being transmitted.
`In another embodiment each second plurality of outputs is
`in communication with a respective amplifier device, the
`method including operating the controller device so that the
`55 output power value of one of the data streams from the ampli(cid:173)
`fier devices is less than or equal to P,0 /2, where the total
`available output power of the amplifier devices is given by
`,. Such an arrangement permits the controller device to be
`P,0
`involved with controlling the power of the one or more data
`60 streams output from the antenna device.
`Preferably the method further includes operating the Mul(cid:173)
`tiple-Input Multiple-Output precoder with a set of weights
`w 1 , w 2 , w 3 , w 4 according to the Third Generation Partnership
`Project Technical Standard 25.214. In one embodiment the
`65 method further includes operating the antenna device to
`exclude selected weights of the set of weights to control at
`least one output power value of the one or more data streams
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`5
`at the second plurality of outputs. Excluding said weights is a
`convenient way to control the power at the second plurality of
`outputs.
`The method may include determining whether the output
`power values of the data streams at the second plurality of
`outputs are different and operating the Multiple-Input Mul(cid:173)
`tiple-Output precoder to exclude the w2 weights (l-j)/2 and
`(-l+j)/2.
`In one embodiment each second plurality of outputs is in
`communication with a respective amplifier device, the
`method including determining if the output power value of
`one of the data streams at the amplifier devices exceeds P tol2,
`where P tot is the total available output power of the amplifier
`devices, and operating the controller device to exclude said
`w2 weights (l-j)/2 and (-l+j)/2. Such an arrangement may
`allow a combination of the controller device and the Multiple(cid:173)
`Input Multiple-Output precoder to control the power at the
`second plurality of outputs.
`In another embodiment the method includes determining if
`more than one user device is scheduled in a transmission time
`interval of the antenna device, and operating the Multiple(cid:173)
`Input Multiple-Output precoder to exclude the w 2 weights
`(l-j)/2 and (-l+j)/2. Such an arrangement may further
`reduce an imbalance of power at the second plurality of
`outputs.
`In one embodiment each second plurality of outputs is in
`communication with a respective amplifier device, the
`method including operating the Multiple-Input Multiple(cid:173)
`Output precoder using thew 2 weights (1 +j)/2 and (-1-j)/2, 30
`and operating the controller device to permit the output power
`value of one of the data streams from the amplifier devices to
`exceed Pto/2, where P tot is the total available output power of
`the amplifier devices. The method may further include oper(cid:173)
`ating the controller device to permit the output power value of 35
`one of the data streams from the amplifier devices to exceed
`Pto/2 up to a predefined threshold value. Preferably the
`method includes using the predefined threshold value given
`by (Ptol2)k, where k is 1 <ksl .2. Such an arrangement may
`help to avoid further problems with power imbalance, for 40
`example, when HARQ is used.
`In one embodiment each second plurality of outputs is in
`communication with a respective amplifier device, and a user
`device is provided in communication with the antenna device
`to report a preferred weight to the antenna device, the method 45
`including operating the Multiple-Input Multiple-Output pre(cid:173)
`coder using the preferred weight if the difference in output
`power values of the data streams from the amplifier devices is
`within the predefined threshold value. Such an arrangement
`may have the advantage of improving a Block Error Rate 50
`(BLER) for receipt of user data by the user device.
`In one embodiment the method further includes operating
`the Multiple-Input Multiple-Output precoder using the w2
`weights (l-j)/2 and (-1 +j)/2, and operating the antenna
`device such that IPl -P2 1/(Pl +P2 )<x, where x is a pre- 55
`defined threshold value, and where Pl and P2 are the input
`power values of the input data streams.
`According to a fourth aspect of the invention there is pro(cid:173)
`vided a communications network including an antenna
`device according to the first aspect of the invention, or includ- 60
`ing a transmitter according to the second aspect of the inven(cid:173)
`tion, or using a method according to the third aspect of the
`invention.
`According to a fifth aspect of the invention there is pro(cid:173)
`vided a radio base station including an antenna device accord- 65
`ing to the first aspect of the invention, or using a method
`according to the third aspect of the invention.
`
`6
`According to a sixth aspect of the invention there is pro(cid:173)
`vided a computer program product operable to control the
`antenna device according to the first aspect of the invention,
`or the transmitter of the second aspect of the invention, or the
`radio base station according to the fifth aspect of the inven(cid:173)
`tion, or to perform a method according to the third aspect of
`the invention.
`According to an alternative characterisation of the inven(cid:173)
`tion there is provided an antenna device for a radio base
`10 station. The device comprising a common precoder having a
`first plurality ofinputs and a first plurality ofoutputs. The first
`plurality of inputs for receiving a respective data stream. Each
`first plurality of inputs being in communication with each first
`plurality of outputs. The antenna device further comprises a
`15 controller device. The antenna device being operable to con(cid:173)
`trol an output power value of the one or more data streams at
`the first plurality of outputs.
`Preferably the common precoder is arranged in series with
`a Multiple-Input Multiple-Output precoder which has a sec-
`20 ond plurality of inputs for one or more Multiple-Input Mul(cid:173)
`tiple-Output data streams, and a second plurality of outputs
`for one or more data streams, the second plurality of outputs
`in communication with the first plurality of inputs.
`Optional features of the first and third characterisations of
`25 the invention may be used with the alternative characterisa(cid:173)
`tions of the invention respectively.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`Other features of the invention will be apparent from the
`following description of preferred embodiments shown by
`way of example only with reference to the accompanying
`drawings, in which;
`FIG. 1 shows a diagram of a mobile communications net(cid:173)
`work for describing embodiments of the invention;
`FIG. 2 is a schematic diagram of an antenna device accord(cid:173)
`ing to an embodiment of the invention;
`FIG. 3 shows a schematic diagram of a scheduler device
`shown in FIG. 2;
`FIG. 4 shows a table of a list of scheduled users; and
`FIG. 5 shows a flow diagram illustrating a method accord(cid:173)
`ing to an embodiment of the invention.
`
`DETAILED DESCRIPTION
`
`FIG. 1 shows a diagram of a mobile communications net(cid:173)
`work for describing embodiments of the invention, generally
`designated 10. The mo bile communications network 10 com(cid:173)
`prises a core network 12 in communication with a Radio
`Network Controller 13 (RNC). The RNC 13 is in communi(cid:173)
`cation with a Base Transceiver Station (BTS) 14, alternatively
`known as a NodeB, or a radio base station. The BTS 14 has an
`antenna arrangement 16 for communication with one or more
`user devices 18. Together the BTS 14, the antenna arrange(cid:173)
`ment 16, and the one or more user devices 18 form a Multiple(cid:173)
`Input Multiple-Output (MIMO) system 19.
`FIG. 2 is a schematic diagram of an antenna device accord(cid:173)
`ing to an embodiment of the invention, generally designated
`20. Like features to the arrangements of FIG. 1 are shown
`with like reference numerals. In FIG. 2 the antenna device 20
`is a device located inside the BTS 14 of FIG. 1. FIG. 2 shows
`the antenna device 20 to comprise a MIMO precoder 22 in
`communication with a secondary precoder 24, also known as
`a common precoder. The MIMO precoder 22 has a first input
`26 and a second input 28 for receiving MIMO data streams 1
`and 2 respectively. The inputs 26, 28 are in communication
`with a first output 30 and a second output 32 of the MIMO
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`US 8,891,676 B2
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`7
`precoder 22. The MIMO precoder 22 is a known item accord(cid:173)
`ing to the Third Generation Partnership Project Technical
`Standard 25.214 and will not be described further other than
`to mention that it is operable with a known set of precoding
`weights w 1 , w2 , w3 , w4 . Theprecodingweights w 1 and w3 are 5
`constant real valued scalars, and the precoding weights w2
`and w 4 are variable complex valued scalars. The weights w 1 ,
`w2 , w3 , w4 are given by:
`
`8
`The precoder matrix P imparts an orthogonal polarization
`and a phase shift between the signals output from the antenna
`arrangement 16. Since the power of data signals input to the
`multipliers 46, 48 and the multipliers 50, 52 is the same, the
`signals output from the outputs 38, 40 of the secondary pre(cid:173)
`coder 24 have an equal power in certain situations as men-
`tioned below for single stream transmission. This means that
`full power balancing can be achieved for the PAs 42, 44 for
`these situations. Whereas the precoder matrix is defined by P,
`10 it will be appreciated that other precoder matrices may be
`used to provide signals at the antenna arrangement 16 that are
`not orthogonal, but that are substantially orthogonal, or
`slightly away from orthogonal. The matrix P is just one
`example of a matrix providing orthogonal signals, and other
`15 matrices may also result in orthogonal signals.
`In the embodiment shown the secondary precoder 24 is
`implemented at baseband, which is prior to up-conversion of
`the data signals to Radio Frequency. Implementing the sec(cid:173)
`ondary precoder 24 at baseband is a convenient way for
`20 performing the transformation, but it will be appreciated that
`the precoder 24 could alternatively be implemented at differ(cid:173)
`ent parts of the network 10, or the BTS 14, such as in the
`digital parts of the BTS 14 or in the analogue parts of the BTS
`14.
`Also shown in FIG. 2 are first and second data stream
`combiners 58, 60 which are arranged in series between the
`first output port 30 of the MIMO precoder 22 and the first
`input port 34 of the secondary precoder 24. A third data
`stream combiner 62 is also shown between the second output
`port 32 of the MIMO precoder22 and the second input port 36
`of the secondary precoder 24. The first data stream combiner
`58 is shown to be able to receive data sent over a non-MIMO
`High-