USOO8995357B2
`
`(12) United States Patent
`US 8,995,357 B2
`(10) Patent N0.:
`Dahlman et al.
`
`(45) Date of Patent: Mar. 31, 2015
`
`(54) TRANSMISSION OF SYSTEM INFORMATION
`ON A DOWNLINK SHARED CHANNEL
`
`(58) Field of Classification Search
`USPC ................ 370/311, 3287334, 468; 455/422.1
`See application file for complete search history.
`
`(75)
`
`Inventors: Erik Dahlman, Bromma (SE); Vera
`Vukajlovic, Stockholm (SE)
`
`(56)
`
`(73) Assignee: Telefonaktiebolaget LM Ericsson
`(publ), Stockholm (SE)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 337 days.
`
`(21) Appl. N0.:
`
`12/664,347
`
`(22) PCT Filed:
`
`Apr. 10,2008
`
`(86) PCT N0.:
`
`PCT/SE2008/050407
`
`§ 371 (0(1),
`(2), (4) Date:
`
`Dec. 11, 2009
`
`(87) PCT Pub. No.: W02008/156412
`
`PCT Pub. Date: Dec. 24, 2008
`
`(65)
`
`Prior Publication Data
`
`US 2010/0297991A1
`
`Nov. 25, 2010
`
`Related US. Application Data
`
`(60) Provisional application No. 60/944,628, filed on Jun.
`18, 2007.
`
`(51)
`
`(2009.01)
`(2006.01)
`(2006.01)
`
`Int. Cl.
`H04W4/00
`H04L 1/08
`H04L 1/00
`(52) us. Cl.
`CPC ........... H04L 1/08 (2013.01); H04L 2001/0093
`(2013.01)
`USPC ........... 370/329; 370/311; 370/330; 370/332;
`370/334; 370/469; 455/422.1
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`3/2010 Arundale et a1.
`7,675,852 B1 *
`3/2010 Cheng et a1.
`7,680,507 B2 *
`2004/0219917 A1* 11/2004 Love et a1.
`
`............. 370/229
`
`455/522
`.................... 455/436
`
`(Continued)
`
`FOREIGN PATENT DOCUMENTS
`
`EP
`WO
`
`1799003 A1
`2007/052917 A1
`
`6/2007
`5/2007
`
`OTHER PUBLICATIONS
`
`3rd Generation Partnership Project. “System Information Scheduling
`and Change Notification.” 3GPP TSG-RAN2 Meeting #58, Tdoc
`R2-071912, Kobe, Japan, May 7-11, 2007.
`(Continued)
`
`Primary Examiner 7 Un C Cho
`Assistant Examiner 7 Siming Liu
`(74) Attorney, Agent, or Firm 7 Coats and Bennett, PLLC
`
`(57)
`
`ABSTRACT
`
`In one embodiment, a method of transmitting system infor-
`mation on a down link shared channel structured as succes-
`sive subframes includes transmitting (400-416) system infor-
`mation in regularly occurring time windows, each time
`window spanning some number of successive subframes. The
`method further includes indicating (406/408) to receiving
`user equipment (120) which subframes within a given time
`window carry system information. The method and variations
`of it are applied, for example, to the transmission of dynamic
`system information on the down link shared channel or other
`down link channel in a 3GPP E-UTRA wireless communica-
`tion network (100).
`
`24 Claims, 6 Drawing Sheets
`
`SET SUBFRAME : FIRST SUEFRAME
`IN THE SYSTEM INFORMATION WINDOW
`
`500
`
`
`
`
`
`DEMODULATE AND DECODE
`THE L1/L2 CONTROL CHANNEL
`
`OF THE CURRENT SUBFRAME
`
`
`DEMODULATE AND DECODE CORRESPONDING
`DL-SCH TRANSPORT ELOCK
`
`CONTROL CHANNEL
`RNTI = SI-RNTI OR
`
`ESl-RNTI?
`
`
`
`
`CONTROL CHANNEL
`NEXT SUBFRAME
`RNTI = ESl-RNTI 0R
`
`IN THE WINDOW
`LAST SUEFRAME?
`
`
`
`
`
`1
`
`SAMSUNG 1001
`
`SAMSUNG 1001
`
`1
`
`

`

`US 8,995,357 B2
`Page 2
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`2/2006 Nguyen ........................ 370/345
`2006/0034245 A1 *
`9/2007 Kashima et a1.
`. 370/330
`2007/0217362 A1*
`
`.............. 370/310
`9/2008 Marinier et a1.
`2008/0225765 A1*
`9/2008 Tenny ........................... 370/345
`2008/0225823 A1*
`
`5/2009 Dimou ........
`. 455/436
`2009/0131057 A1*
`................. 370/329
`2009/0303939 A1* 12/2009 Umesh et a1.
`
`OTHER PUBLICATIONS
`
`3rd Generation Partnership Project. “Draft Text Proposal Capturing
`Agreements on System Information.” 3GPP TSG-RAN2 Meeting
`#58, Tdoc R2-072205, Kobe, Japan, May 7-11, 2007.
`
`3rd Generation Partnership Project. “Transmission of Dynamic Sys-
`tem Information.” 3GPP TSG-RAN2 Meeting #58bis, R2-072543,
`Orlando, FL, US, Jun. 25-29, 2007.
`3rd Generation Partnership Project. “Transmission of Dynamic Sys-
`tem Information.” 3GPP TSG-RAN2 Ad-hoc Meeting, Tdoc
`R2-075559, Vienna, Austria, Dec. 13-14, 2007.
`3rd Generation Partnership Project. 3GPP TS 36.300 V8.0.0 (Mar.
`2007). 3rd Generation Partnership Project; Technical Specification
`Group Radio Access Network; Evolved Universal Terrestrial Radio
`Access (E-Utra) and Evolved Universal Terrestrial Radio Access
`network (E-UTAN); Overall description; Stage 2 (Release 8).
`
`* cited by examiner
`
`2
`
`

`

`U.S. Patent
`
`Ddar.31,2015
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`US. Patent
`
`Mar. 31, 2015
`
`Sheet 3 of6
`
`US 8,995,357 B2
`
`400
`
`SET SUBFRAME : FIRST SUBFRAME
`IN THE SYSTEM INFORMATION WINDOW
`
` TRANSMIT SYSTEM
`INFORMATION IN THE
`SUBFRAME?
`
`402
`
`
`LAST SUBFRAME
`
`SET CONTROL
`
`IN THE WINDOW?
`CHANNEL
`
`
`RNTI = ESI-RNTI
`
`
`
`SET CONTROL CHANNEL
`
`RNTI = SI’RNTI
`
`
`
`
`TRANSMIT SYSTEM INFORMATION
`ON THE DL-SCH WITHIN THE SUBFRAME
`
`
`
`
`
`
`NEXT SUBFRAME
`
`IN THE WINDOW
`
`
`LAST SUBFRAME
`IN THE WINDOW?
`
`412
`
`
`
`416
`
`FIG. 4
`
`5
`
`

`

`US. Patent
`
`Mar. 31, 2015
`
`Sheet 4 of6
`
`US 8,995,357 B2
`
`500
`
`SET SUBFRAME = FIRST SUBFRAME
`IN THE SYSTEM INFORMATION WINDOW
`
`
`
`
`DEMODULATE AND DECODE
`THE L1/L2 CONTROL CHANNEL
`OF THE CURRENT SUBFRAME
`
`
`
`
`
`CONTROL CHANNEL
`RNTI : SI-RNTI OR
`ESI-RNTI?
`
`YES
`
`DEMODULATE AND DECODE CORRESPONDING
`DL-SCH TRANSPORT BLOCK
`
`
`
`IN THE WINDOW
`
`
`510
`
`
`CONTROL CHANNEL
`
`RNTI = ESI-RNTI OR
`
`LAST SUBFRAME?
`
`
`
`NEXT SUBFRAME
`
`512
`
`FIG. 5
`
`6
`
`

`

`US. Patent
`
`Mar. 31, 2015
`
`Sheet 5 of6
`
`US 8,995,357 B2
`
`/
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`
`ONEFRAME
`
`FIG.6H\
`
`
`
`
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`SYSTEMINFORMATIONWINDOWS
`
`7
`
`

`

`U.S. Patent
`
`2
`
`US 8,995,357 B2
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`

`US 8,995,357 B2
`
`1
`TRANSMISSION OF SYSTEM INFORMATION
`ON A DOWNLINK SHARED CHANNEL
`
`BACKGROUND
`
`1. Technical Field
`
`The present invention generally relates to wireless commu-
`nication networks, and particularly relates to the transmission
`of system information to user equipment (UE) operating in
`such networks, such as the transmission of system informa-
`tion by radio base stations in a wireless communication net-
`work configured according to 3GPP E-UTRA (evolved Uni-
`versal Terrestrial Radio Access) standards, also referred to as
`3GPP LTE (Long Term Evolution).
`2. Background
`In the 3GPP LTE, downlink user-data transmission is car-
`ried out on the Downlink Shared Channel (DL-SCH) trans-
`port channel. In LTE, the time dimension is divided into radio
`frames of length 10 ms, where each radio frame consists of 10
`subframes, each of length 1 ms corresponding to 14 OFDM
`(orthogonal frequency-division multiplexing) symbols. Each
`subframe consists oftwo slots, each of length 0.5 ms or seven
`OFDM symbols. Note that, in case of Time Division Duplex
`(TDD), only a subset of the subframes of one frame is avail-
`able for downlink transmission. On the other hand, in case of
`Frequency Division Duplex (FDD), all subframes on a down-
`link carrier are available for downlink transmission.
`
`time/frequency-domain physical
`the overall
`In LTE,
`resource is divided into resource blocks, where each resource
`block consists of twelve OFDM subcarriers during one slot.
`DL-SCH transmission to a UE is carried out using a set of
`such resource blocks during one subframe. Layer 1/Layer 2
`(L1/L2) control signaling, also known as the Physical Down-
`link Control Channel (PDCCH), is transmitted at the begin-
`ning of each subframe. The L1/L2 control channel is typically
`used to inform a UE about various items. For example, the
`L1/L2 control channel may identify whether the DL-SCH
`carries data to the UE in the given subframe. More specifi-
`cally, the L1/L2 control channel then includes the RNTI (Ra-
`dio Network Temporary Identifier) associated with the UE for
`which the DL-SCH carries data in the given subframe. The
`L1/L2 control channel
`then also identifies the physical
`resource, more specifically the specific set of resource blocks
`that is used for the DL-SCH transmission to the specific UE in
`the given subframe. Moreover, the L1/L2 control channel
`then identifies the transport format (e.g.
`the modulation
`scheme and coding rate) used for DL-SCH transmission to
`the specific UE in the given subframe. Separate DL-SCH
`transmissions, using different physical resources (different
`resource blocks), can be carried out to different UEs during
`the same subframe. In this case there are multiple L1/L2
`control channels, one for each UE that is to receive DL-SCH
`transmission in the given subframe.
`In addition to user data, system information is also trans-
`mitted on the downlink within each cell. The system infor-
`mation may, e.g.,
`include: public Land Mobile Network
`(PLMN) identity/identities,
`identifying the operator(s) to
`which the cell “belongs”; Neighbor-cell list, i.e. a list of the
`cells that are neighbors to the current cell; and different
`parameters used by the user terminal when accessing the
`system, e.g.
`random-access parameters and cell-access
`restrictions. The system information can be divided into two
`parts, one part being fixed and the other part being dynamic.
`The fixed part of the system information is transmitted on a
`pre-determined physical resource, i.e. a specific set of OFDM
`subcarriers during a specific time interval, using a pre-deter-
`mined transport format. There is thus no flexibility in the
`
`2
`
`amount of information in the fixed part of the system infor-
`mation. There is also no flexibility in the transmission struc-
`ture (the physical resource and the transport format) used for
`the fixed part ofthe system information. In LTE, the fixed part
`of the system information is transmitted using the BCH
`(broadcast control channel) transport channel. Furthermore,
`for LTE it is currently assumed that the BCH is transmitted in
`the six centre resource blocks in subframe #0 of each frame.
`The dynamic part of the system information is assumed to
`be transmitted using the DL-SCH, or at least a DL-SCH-like
`transport channel, similar to normal data transmission as
`described above. New UEs continuously “enter” the cell,
`either entering from a neighbor cell, due to power-on, or upon
`return from out-out-service, and the UEs must quickly
`acquire the system information. Thus the system information
`(both the fixed part on the BCH and the dynamic part on the
`DL-SCH or a DL-SCH-like channel) should be repeated
`regularly.
`As an example, in LTE the fixed part of the system infor-
`mation (transmittedusing the BCH) is assumed to be repeated
`every 40 ms. Also the dynamic part ofthe system information
`should be repeated more or less regularly. However, different
`portions of the dynamic part of the system information are
`more or less time critical, in the sense of how quickly the UE
`must acquire it, and thus need to be repeated more or less
`often. This can be described so that the dynamic part of the
`system information is divided into different so-called sched-
`uling units, also referred to as System Information Messages.
`In general,
`information corresponding to scheduling unit
`number 11 should be repeated more often than information
`corresponding to scheduling unit number n+1. As an
`example, scheduling unit #1 (SU-l) may be repeated (ap-
`proximately) once every 80 ms, scheduling unit #2 (SU-2)
`may be repeated (approximately) once every 160 ms, sched-
`uling unit #3 (SU-3) may be repeated (approximately) once
`every 320 ms, etc.
`
`SUMMARY
`
`The invention described below allows for transmission of
`
`the dynamic part of the system information fulfilling these
`requirements and desirable properties while, at the same time,
`allowing for low UE complexity. One aspect of the teachings
`presented herein is to transmit system information in regu-
`larly occurring (system information) windows, with specific
`RNTIs indicating the presence of system information in a
`subframe, and with another specific RNTI indicating the end
`of system information transmission. This enables UEs to stop
`receiving, demodulating and decoding subframes when no
`more system information is expected during the current win-
`dow.
`
`In one embodiment, a method oftransmitting system infor-
`mation on a downlink shared channel structured as successive
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`subframes includes transmitting system information in regu-
`larly occurring time windows, each time window spanning
`some number of successive subframes. The method further
`
`55
`
`includes indicating to receiving user equipment which sub-
`frames within a given time window carry system information.
`Of course, the present invention is not limited to the above
`features and advantages. Indeed, those skilled in the art will
`recognize additional features and advantages upon reading
`the following detailed description, and upon viewing the
`accompanying drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`60
`
`65
`
`FIG. 1 is a block diagram of an embodiment of a wireless
`network that overlays or otherwise defines a recurring
`
`9
`
`

`

`US 8,995,357 B2
`
`3
`sequence of time windows for the transmission of dynamic
`system information using subframes falling within the
`defined time windows.
`
`FIG. 2 is a diagram of an embodiment of different system-
`information time windows having different repetition peri-
`ods.
`
`5
`
`FIG. 3 is a diagram of an embodiment of overlaying or
`otherwise defining a recurring sequence of time windows for
`the transmission of dynamic system information using sub-
`frames falling within the defined time windows.
`FIG. 4 is a flow diagram of an embodiment of program
`logic for overlaying or otherwise defining a recurring
`sequence of time windows for the transmission of dynamic
`system information using subframes falling within the
`defined time windows.
`
`FIG. 5 is a flow diagram of an embodiment of program
`logic for processing recurring system-information time win-
`dows containing dynamic system information included in
`subframes falling within the defined time windows.
`FIG. 6 is a diagram of an embodiment of variably sized
`recurring system-information time windows for the transmis-
`sion of system information.
`FIG. 7 is a diagram of an embodiment of different system-
`information time windows.
`
`10
`
`15
`
`20
`
`25
`
`DETAILED DESCRIPTION
`
`FIG. 1 illustrates an embodiment of a wireless network 100
`
`including one or more network transmitters 110 such as a
`radio base station which services one or more UEs 120. The
`
`30
`
`network transmitter 110 includes a baseband processor 130
`for generating one or more scheduling units 132 (also referred
`to as System Information Messages) including dynamic parts
`ofthe system information. The network transmitter 11 0 sends
`the scheduling units 132 to the UE 120 using different sys-
`tem-information windows. In one embodiment, the system-
`information windows occur with a period corresponding to
`the repetition period of the most frequently occurring sched-
`uling unit 132 as shown in FIG. 2 where “SU-n” refers to the
`nth scheduling unit 132. System information corresponding
`to the mo st frequently occurring scheduling unit 132 is trans-
`mitted within each system-information window while less
`frequently-occurring scheduling units 132 are transmitted
`only within a sub-set of the system-information windows,
`where system information is shown as a shaded area in FIG.
`2. For illustrative purposes only, system information corre-
`sponding to a second one ofthe scheduling units 132 could be
`transmitted within every second window, system information
`corresponding to a third one ofthe scheduling units 132 could
`be transmitted within every fourth window, and so on.
`In one embodiment, the transmission timing correspond-
`ing to each scheduling unit 132 can be pre-specified when a
`limited amount of transmission periods are employed by the
`network 100. In another embodiment, the window transmis-
`sion timing can be signaled to the UE 120, e.g. when more
`specific values for transmitted scheduling units 132 are speci-
`fied. Either way, a variable window size can be used if the
`amount of system information is not the same in each win-
`dow. In one embodiment, the window size is increased when
`system information from additional scheduling units 132 is
`transmitted.
`
`FIG. 3 illustrates one embodiment of transmitting the
`dynamic (possibly changing) system information within
`regularly occurring windows with well-defined starting
`points (specific subframes) and of a certain size in number of
`(consecutive) subframes. In the illustration, the system-infor-
`mation windows, more generally regarded as recurring time
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`10
`
`4
`
`windows defined for the transmission of system information,
`start at subframe #5 of the frame with frame number 8*k and
`
`have a size of l 3 subframes. The network transmitter 110 only
`transmits the dynamic part of the system information within
`these windows. Moreover, the window occurs (is repeated)
`often enough to fulfill the repetition rate of the most often
`repeated system information (in LTE terminology, system
`information corresponding to the first scheduling unit 132, as
`described above).
`In one or more embodiments, within each recurring time
`window, the transmission of system information is carried out
`similar to the transmission ofuser data on DL-SCH (dynamic
`resource and transport format with signaling on Ll/L2 con-
`trol channel), with some exceptions. Instead ofusing an RNTI
`of a specific UE 120, a specific System-Information RNTI
`(SI-RNTI), indicating that system information to be read by
`all UEs 120 is being transmitted, is included in the corre-
`sponding Ll/L2 control signaling. Also, for the last piece of
`system information to be transmitted within the window, the
`SI-RNTI is replaced with an End-of—System-Information
`RNTI (ESI-RNTI). The reception of an ESI-RNTI informs
`the UE 120 that no more system information is transmitted
`within the window. The UE 120 can stop demodulating and
`decoding the Ll/L2 control channel when there is no more
`system information to be transmitted in the window, thus
`improving UE power-saving performance.
`Moreover, the system information does not have to be
`transmitted in consecutive subframes. This way, the network
`transmitter 110 can dynamically avoid transmitting system
`information in certain subframes when a more pressing need
`for subframes arises, e.g., when a subframe is needed for high
`priority downlink data transmission or for uplink transmis-
`sion in case ofTDD. In addition, the set of subframes in which
`system information is actually transmitted does not have to be
`the same between consecutive windows. Furthermore, the
`network transmitter 110 can dynamically vary the number of
`subframes used to carry system information without prior
`knowledge ofthe UE 120 (i.e., prior to the UE 120 reading the
`Ll/L2 control channel).
`As non-limiting examples, the teachings presented herein
`for transmitting system information yields several desirable
`properties. For example, there are several requirements and
`desired properties for the transmission of the dynamic part of
`the system information. From a UE power-consumption point
`of-view, it is desirable to transmit the different parts of the
`system information as close in time as possible to each other,
`in the ideal case in a set of consecutive subframes. This
`
`enables the UE 120 to receive the maximum amount of sys-
`tem information during a minimum reception time, reducing
`UE reception time and UE power consumption.
`The teachings herein also allow system information to be
`transmitted in recurring time windows, where the particular
`subframes within each window used for carrying system
`information are selectable. If current conditions, e.g., com-
`peting transmission priorities permit, the system information
`can be transmitted in a contiguous set of subframes within the
`time window.
`
`It is also desirable to have flexibility in terms of exactly
`where the system information is transmitted,
`i.e., exactly
`which set of subframes within a given time window carries
`the system information. Some subframes, depending on the
`situation, may not be available for transmitting system infor-
`mation. For example, some TDD subframes may not be avail-
`able for downlink transmission. In another example, for
`latency reasons there may, in some situations, be a benefit to
`not having too many consecutive subframes used for trans-
`mission of system information, thus making them unavailable
`
`10
`
`

`

`US 8,995,357 B2
`
`5
`for downlink user data transmission. As such, it is also desir-
`able to dynamically (with low delay) decide in exactly what
`subframes the system information is to be transmitted.
`Further, it is desirable to have flexibility in the rate by
`which different parts ofthe system information is repeated. In
`this way, a higher repetition rate (shorter repetition period)
`can be used, e.g. in the case of wider overall transmission
`bandwidth, when the overhead of the system-information
`transmission is less of a concern. It is desirable to have flex-
`
`ibility in the number of subframes used to transmit the system
`information. As an example, in case of smaller overall band-
`width or larger cells, more subframes may be needed to trans-
`mit a given set of system information. Moreover, the amount
`of system information, e.g. neighbor lists and PLMN lists
`may be of different sizes for different cells.
`The teachings presented herein provide for methods and
`apparatuses where system information is transmitted within
`recurring time windows, but with flexible selection of which
`subframes within those windows are used to carry system
`information. FIG. 4 illustrates one embodiment of program
`logic for transmitting system information from the network
`transmitter 1 1 0 to the UE 120. According to this embodiment,
`the baseband processor 13 0 included in the network transmit-
`ter 110 initializes the first subframe in the system-information
`window (Step 400). The baseband processor 130 then deter-
`mines whether the current subframe is to be used for trans-
`
`mission of system information (Step 402). If so, the baseband
`processor 130 determines whether the current subframe is the
`last subframe in the window (Step 404). If the current sub-
`frame is the last subframe, the RNTI of the Ll/L2 control
`channel is set to ESI-RNTI for indicating to the UE 120 that
`the subframe is the last subframe in the window containing
`system information. (Step 406). Otherwise, the control chan-
`nel RNTI is set to SI-RNTI for indicating to the UE 120 that
`the subframe contains system information, but is not the last
`subframe. (Step 408). The corresponding system information
`is transmitted on the DL-SCH within the current subframe
`
`(Step 410). The baseband processor 130 determines whether
`the last window subframe has been transmitted (Step 412). If
`not, Steps 402-412 are repeated for the next subframe within
`the window. The system information transmission process
`ends when the last subframe is transmitted (Step 416).
`FIG. 5 illustrates one embodiment ofprogram logic carried
`out by the UE 120 for processing the system information
`transmitted by the network transmitter 110. According to this
`embodiment, the UE 120 includes a baseband processor 140
`for demodulating and decoding received subframes. A win-
`dow detection and evaluation unit 150 included in or associ-
`
`ated with the baseband processor 140 begins the window
`reception process by initializing the first subframe received
`within the window (Step 500). The baseband processor 150
`then demodulates and decodes the Ll/L2 control channel of
`
`the current subframe (Step 502). The window detection and
`evaluation unit 150 determines whether either SI-RNTI or
`
`ESI-RNTI is detected for the current subframe (Step 504). If
`so, the baseband processor 140 demodulates and decodes the
`corresponding DL-SCH transport block to retrieve the system
`information provided therewith (Step 506). The window
`detection and evaluation unit 150 then determines whether
`the current subframe is the last subframe in the window or the
`
`last subframe containing system information, e.g., whether
`the RNTI of the control channel is ESI-RNTI (Step 508). If
`neither condition exists, Steps 502-508 are repeated for the
`next subframe within the window (Step 510). The baseband
`processor 140 stops demodulating and decoding DL-SCH
`transport blocks when either the last subframe or ESI -RNTI is
`detected, indicating no more system information is forthcom-
`
`6
`ing (Step 512). Thus, the UE 120 demodulates and decodes
`the control channel starting with the first subframe in the
`system information window and checks for specific system
`information RNTIs until either the ESI-RNTI is detected or
`the last window subframe is received.
`
`As discussed above, some parts of the system information
`(corresponding to the scheduling units 132) may not need to
`be repeated as often as some other parts of the system infor-
`mation, implying that certain windows will include more data
`(more scheduling units 132) than other windows. Thus, the
`window size may be of varying length, with a longer window
`at the time instances where more system information (more
`scheduling units 132) is to be transmitted. FIG. 6 provides an
`illustration of a variable-length window embodiment.
`Note that the window size can be specified in either the
`radio-access specification or be configurable. In case of a
`configurable window size, the UE 120 can use a default
`(large) window size before it is informed (via the system
`information) about the actual window size. Moreover, the
`RNTI may indicate more thanjust system information such as
`more details about the system information. In one embodi-
`ment, several different SI-RNTIs could be used, e.g., SI-
`RNTI1. SI-RNTIZ, SI-RNTI3, .
`.
`. ,with corresponding mul-
`tiple ESI-RNTIs, e.g., ESI-RNTIl, ESI-RNTIZ, ESI-RNTI3,
`etc.
`
`In one embodiment, the scheduling units 132 transmitted at
`the same time use the same system-information window as
`shown in the upper part of FIG. 7. Alternatively, the schedul-
`ing units 132 are transmitted using different system-informa-
`tion windows as shown in the lower part of FIG. 7. In either
`embodiment, system information is transmitted in regularly
`occurring system-information windows, with specific RNTIs
`indicating the presence of system information in a subframe,
`and with another specific RNTI indicating the end of system
`information transmission.
`
`Of course, other variations are contemplated. Thus, the
`foregoing description and the accompanying drawings repre-
`sent non-limiting examples of the methods and apparatus
`taught herein for the transmission of system information. As
`such, the present invention is not limited by the foregoing
`description and accompanying drawings. Instead, the present
`invention is limited only by the following claims and their
`legal equivalents.
`
`What is claimed is:
`
`1 . A method oftransmitting system information on a down-
`link shared channel of a wireless communication network,
`comprising:
`transmitting system information on the downlink shared
`channel in recurring time windows, each time window
`spanning a plurality of subframes;
`dynamically selecting which subframes within a given
`time window are to be used for carrying the system
`information; and
`including an indicator in each of the selected subframes to
`indicate to receiving user equipment that the subframe
`carries system information,
`wherein the wireless communication network is config-
`ured for operation in accordance with 3GPP E-UTRA
`standards and wherein the indicator is a System infor-
`mation Radio Network Temporary Identifier (SI-RNTI).
`2. The method of claim 1, wherein dynamically selecting
`which subframes within a given time window are to be used
`for carrying system information comprises selecting a con-
`tiguous set of subframes within the given time window.
`3. The method of claim 1, wherein dynamically selecting
`which subframes within a given time window are to be used
`
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`US 8,995,357 B2
`
`7
`for carrying system information comprises selecting a non-
`contiguous set of subframes within the given time window.
`4. The method of claim 1, wherein dynamically selecting
`which subframes within a given time window are to be used
`for carrying system information comprises selecting which
`subframes to use for transmitting system information in view
`of competing transmission priorities associated with other
`control or data signaling.
`5. The method of claim 1, wherein including an indicator in
`each of the selected subframes to indicate to receiving user
`equipment that the subframe carries system information
`includes using an end-of-system-information indicator in a
`last subframe of the given time window that carries system
`information.
`
`6. The method of claim 1, further comprising varying win-
`dow sizes of the recurring time windows.
`7. The method of claim 1, further comprising dynamically
`configuring a window size for the recurring time windows.
`8. The method of claim 1, wherein including an indicator in
`each of the selected subframes to indicate to receiving user
`equipment that the subframe carries system information
`includes using different indicators corresponding to different
`types of system information, such that the indicator used for
`a particular subframe indicates the type of system informa-
`tion carried in that subframe.
`
`9. A network transmitter for transmitting system informa-
`tion on a downlink shared channel in a wireless communica-
`
`tions network, the network transmitter configured to transmit
`system information in recurring time windows, each time
`window spanning a plurality of subframes; the network trans-
`mitter comprising a baseband processor configured to:
`dynamically select which subframes on the downlink
`shared channel within a given time window are to be
`used for carrying system information; and
`include an indicator in each of the selected subframes to
`
`indicate to receiving user equipment that the subframe
`carries system information,
`wherein the wireless communication network is config-
`ured for operation in accordance with 3GPP E-UTRA
`standards and wherein the indicator is a System infor-
`mation Radio Network Temporary Identifier (SI-RNTI).
`10. A method of transmitting system information on a
`downlink shared channel structured as successive subframes,
`the method comprising:
`transmitting system information on the downlink shared
`channel in regularly occurring time windows, each time
`window spanning a plurality of successive subframes;
`dynamically selecting which subframes within the time
`windows are to be used for carrying system information;
`indicating to receiving user equipment which subframes
`within the time windows carry system information, by
`including an indicator in each subframe within the time
`windows that carries system information,
`wherein the wireless communication network is config-
`ured for operation in accordance with 3GPP E-UTRA
`standards and wherein the indicator is a System infor-
`mation Radio Network Temporary Identifier (SI-RNTI).
`11. The method of claim 10, wherein indicating to receiv-
`ing user equipment which subframes within the time win-
`dows carry system information includes indicating the last
`subframe within each time window that carries system infor-
`mation, thereby allowing the receiving user equipment to
`cease monitoring for system information within each time
`window.
`
`8
`12. A method, in a mobile station, for receiving system
`information on a downlink shared channel from a network
`
`transmitter in a wireless communication network, the method
`comprising:
`monitoring for the receipt of system information on the
`downlink shared channel in recurring time windows
`used for transmission of system information, each time
`window spanning a plurality of subframes, by monitor-
`ing, within each time window, each subframe for an
`indication indicating presence of system information in
`the subframe and reading system information from the
`subframe if such information is present; and
`terminating monitoring at or before the end of the time
`window,
`wherein the wireless communication network is config-
`ured for operation in accordance with 3GPP E-UTRA
`standards and wherein the indicator is a System infor-
`mation Radio Network Temporary Identifier (SI-RNTI).
`13. The method of claim 12, further comprising recogniz-
`ing an end-of—system-information indicator in a subframe
`received within the time window and terminating monitoring
`for receipt of system information within the time window in
`response.
`14. T