(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2016/0192292 A1
`Höglund et al.
`(43) Pub. Date:
`Jun. 30, 2016
`
`US 2016O192292A1
`
`(54) NETWORK NODE AND MOBILE DEVICE
`FOR USE IN A COMMUNICATION
`NETWORK, METHODS OF OPERATING THE
`SAME AND COMPUTER PROGRAM
`PRODUCTS
`
`(71) Applicant: TELEFONAKTIEBOLAGET L M
`ERICSSON (PUBL), Stockholm (SE)
`(72) Inventors: Andreas Höglund, Solna (SE); Gunnar
`Mildh, Sollentuna (SE); Tuomas
`Tirronen, Helsinki (FI); Emre Yavuz,
`Stockholm (SE)
`14/909,778
`
`(21) Appl. No.:
`
`(22) PCT Filed:
`(86). PCT No.:
`S371 (c)(1),
`(2) Date:
`
`Jul. 4, 2014
`PCT/SE2014/050857
`
`Feb. 3, 2016
`
`Related U.S. Application Data
`(60) Provisional application No. 61/863.989, filed on Aug.
`9, 2013.
`
`Publication Classification
`
`(2006.01)
`(2006.01)
`(2006.01)
`
`(51) Int. Cl.
`H04752/02
`H04768/00
`H04W 76/04
`(52) U.S. Cl.
`CPC ........ H04W 52/0216 (2013.01); H04W 76/048
`(2013.01); H04 W 68/00 (2013.01)
`ABSTRACT
`(57)
`According to one aspect, there is provided a method of oper
`ating a network node in a communication network with the
`communication network comprising at least one mobile
`device that is operating in a discontinuous reception, DRX,
`mode with a DRX cycle length that is longer than a modifi
`cation period in the network. In the method, when an update
`to system information is to occur in an updated information
`modification period, the modification period immediately
`preceding the updated information modification period com
`prising a change notification modification period, a paging
`message is transmitted to the mobile device during a modifi
`cation period other than the change notification modification
`period and the updated information modification period, the
`paging message informing the mobile device that an update to
`system information is to occur in the updated information
`modification period.
`
`2
`
`
`
`8
`
`V
`V
`w
`W
`W
`
`W
`s
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`Figure 1
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`32
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`34
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`36
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`12Y
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`30ry
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`Memory module
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`- - - - - - - - - - - -
`
`User equipment
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`49
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`42
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`44
`
`- - - -
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`Memory as
`module
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`- - - -
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`10
`
`- - - -
`Core network
`Linterface
`48 ya eNodeB
`interface
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`40
`Figure 3
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`52
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`56
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`Processing
`module
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`information update
`required?
`
`
`
`103
`
`Transmit a paging message indicating the SI update to
`an extended DRX UE during a modification period that
`OCCurs before the change notification period
`Figure 7
`
`111. Configure UE to operate in an
`extended DRX mode
`
`113. Periodically activate a receiver in the UE to
`receive a paging message from an eNodeB
`
`115. Process received paging message message
`to determine if an update to system
`information is to OCCur
`
`
`
`
`
`e
`
`N.
`
`na
`
`N
`
`e
`
`3. 1 Update to N No
`a OCCur? - 1
`117
`asf Yes
`
`119
`\asy
`
`V
`Y.
`a ra
`- - - - - - - - - - - - -
`s No
`- 1
`Activate receiver during updated
`<pata to transm? >-'s -
`information modification period to
`a N
`1
`determine the updated system information
`""" 121-
`Yes
`
`123
`
`Activate receiver to determine
`the updated system information
`-----
`
`Apply updated SI
`125
`----- - and transmit data
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`150
`
`
`
`100
`
`5 O
`
`O
`
`50
`
`100 150 200 250 300 350 400
`DRX cycle length(s)
`
`Figure 9
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`NETWORKNODE AND MOBILE DEVICE
`FOR USE IN A COMMUNICATION
`NETWORK, METHODS OF OPERATING THE
`SAME AND COMPUTER PROGRAM
`PRODUCTS
`
`TECHNICAL FIELD
`0001. The technology described relates to communication
`networks, and in particular to the signalling of updates to
`system information for mobile devices operating with an
`extended discontinuous reception (DRX) period.
`
`BACKGROUND
`0002. In a typical cellular radio system, radio or wireless
`terminals (also known as mobile stations and/or user equip
`ment units (UES)) communicate via a radio access network
`(RAN) to one or more core networks. The radio access net
`work (RAN) covers a geographical area which is divided into
`cell areas, with each cell area being served by a base station,
`e.g., a radio base station (RBS), which in some networks may
`also be called, for example, a "NodeB” (in a Universal Mobile
`Telecommunications System (UMTS) network) or “eNo
`deB” (in a Long Term Evolution (LTE) network). A cell is a
`geographical area where radio coverage is provided by the
`radio base station equipmentatabase station site. Each cell is
`identified by an identity within the local radio area, which is
`broadcast in the cell. The base stations communicate over the
`air interface operating on radio frequencies with the user
`equipment units (UES) within range of the base stations.
`0003. In some radio access networks, several base stations
`may be connected (e.g., by landlines or microwave) to a radio
`network controller (RNC) or a base station controller (BSC).
`The radio network controller supervises and coordinates vari
`ous activities of the plural base stations connected thereto.
`The radio network controllers are typically connected to one
`or more core networks.
`0004. The Universal Mobile Telecommunications System
`(UMTS) is a third generation mobile communication system,
`which evolved from the Global System for Mobile Commu
`nications (GSM). Universal Terrestrial Radio Access Net
`work (UTRAN) is essentially a radio access network using a
`wideband code division multiple access (WCDMA) air inter
`face between user equipment units (UES) and radio access
`network (RAN).
`0005. In a forum known as the Third Generation Partner
`ship Project (3GPP), telecommunications suppliers propose
`and agree upon standards for third generation networks and
`UTRAN specifically, and investigate enhanced data rate and
`radio capacity. The Third Generation Partnership Project
`(3GPP) has undertaken to evolve further the UTRAN and
`GSM based radio access network technologies. The first
`release for the Evolved Universal Terrestrial Radio Access
`Network (E-UTRAN) specification has issued, and as with
`most specifications, the standard is likely to evolve. The
`Evolved Universal Terrestrial Radio Access Network (E-UT
`RAN) comprises the Long Term Evolution (LTE) and System
`Architecture Evolution (SAE).
`0006 Long Term Evolution (LTE) is a variant of a 3GPP
`radio access technology where the radio base station nodes
`are connected to a core network (via Access Gateways
`(AGWs)) rather than to radio network controller (RNC)
`nodes. In general, in LTE the functions of a radio network
`controller (RNC) node are distributed between the radio base
`
`stations nodes (eNodeB's in LTE) and AGWs. As such, the
`radio access network (RAN) of an LTE system has what is
`sometimes termed a “flat architecture including radio base
`station nodes without reporting to radio network controller
`(RNC) nodes.
`0007. A currently popular vision of the future of cellular
`networks includes machines or other autonomous devices
`communicating between each other (or with an application
`server) without human interaction. A typical scenario is to
`have sensors sending measurements infrequently, where each
`of the transmissions would consist of only small amounts of
`data. This type of communication is called machine to
`machine (M2M) communication in the literature, or
`machine-type communication (MTC), in 3GPP
`0008 UEs in cellular systems (such as 3GPP WCDMA,
`LTE) are most commonly battery driven and the power con
`Sumption of these devices is therefore an important factor.
`0009. In the context of MTC, many of the devices are
`expected to be battery operated as well. Sensors and other
`devices may reside in remote locations and the number of
`deployed devices could be so large that it would be practically
`infeasible to replace or frequently recharge the batteries in
`these kinds of devices. Thus, it is an important goal to aim for
`reduction in the power consumption when considering
`improvements for current cellular systems.
`0010. An existing means to reduce the battery power con
`Sumption is to use discontinuous reception (DRX), a feature
`in which the UEs receiver is switched off except during
`configured periods at configured intervals.
`0011 Currently the longest specified DRX cycle lengths
`are 2.56 seconds and 5.12 seconds for EUTRA and UTRA,
`respectively. However, it would beneficial to extend the DRX
`cycle lengths beyond currently specified values to further
`reduce the battery power consumption, especially for the
`benefit of MTC devices where there is no possibility for
`interactive charging or changing of the battery on a regular
`basis. Although longer DRX cycle lengths naturally cause
`larger delays in the downlink, this is typically not a problem
`for delay insensitive traffic such as that generated by MTC
`devices. However, there are procedures such as those used by
`mobile devices to maintain up to date system information that
`may need to be aligned accordingly in case the DRX cycles
`are extended beyond the current limits.
`0012. In particular, it is important for a mobile device
`operating with DRX to maintain up-to-date system informa
`tion because otherwise it cannot interact with the network in
`an interoperable manner. In particular, if the mobile device
`does not have recent system information, it must acquire the
`latest version of the system information prior to access, which
`means that it cannot access the system (e.g. transmit random
`access requests, etc.) before it has obtained the latest version
`of the system information. On the other hand, frequent acqui
`sition of system information has an adverse impact on the
`battery life time. In E-UTRA networks, the information
`required to enable reliable communications with the network
`is referred to as System Information (SI) and is transmitted to
`the UE in a number of different System Information Blocks
`(SIBs) and a Master Information Block (MIB). One such
`element of System Information in E-UTRAN is the System
`Frame Number (SFN), which the UE uses to keep synchro
`nisation with the network and which acts as a timing refer
`CCC.
`0013 The SFN is defined in a Master Information Block
`(MIB) in a “systemFrameNumber” field which defines the 8
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`most significant bits of the system frame number (SFN).
`3GPP TS 36.211 “E-UTRA; Physical Channels and Modu
`lation v11.1.0 (2012-12) section 21, 6.6.1 indicates that the
`2 least significant bits of the SFN are acquired implicitly in
`the physical broadcast channel (P-BCH) decoding, i.e. timing
`of 40 ms P-BCH transmission time interval (TTI) indicates
`the 2 least significant bits (within 40 ms P-BCHTTI, the first
`radio frame: 00, the second radio frame: 01, the third radio
`frame: 10, the last radio frame: 11). One value applies for all
`serving cells (the associated functionality is common i.e. not
`performed independently for each cell).
`0014 Procedures exist for notifying mobile devices oper
`ating with DRX that system information (SI) has changed. In
`particular, in E-UTRAN, when System Information is
`updated in a cell, the UEs in the cell are informed about this
`by a flag (called the system InfoModification-flag) being set in
`the paging message sent to each UE. If the flag is set, the UES
`then activate the receivers to receive and read the relevant
`broadcast (e.g. SIB1) accordingly. This paging is sent out to
`UEs during a SI modification period, which is equal to the
`SFN period (i.e. the period required for the SFN to cycle
`through the full range of SFN values) or a fraction of it, thus
`ensuring that all UEs have been notified of the SI change.
`During the following modification period, UEs read the rel
`evant SIB and apply the new SI. According to the 3GPP
`Technical Specification 36.331 v1.1.3.0 (section 5.2.1.3), the
`boundaries of the modification period are defined as the SFN
`for which SFN mod m=0, where m is the length of the modi
`fication period in number of radio frames. Therefore, modi
`fication periods longer than the maximal SFN of 1024 are not
`possible.
`
`SUMMARY
`0015 Using current SI update procedures, for UEs with
`DRX cycles longer than the SFN period/SI modification
`period (which are referred to below as extended DRXUEs),
`it cannot be assured that these UEs can be made aware of an
`SI change. That is, it is possible for an extended DRX UE to
`be in sleep mode with its receiver turned off during an entire
`modification period, which means that it is unable to receive
`paging information about changed SI and to adjust its opera
`tion inaccordance with the change system information before
`the UE's next active period (e.g. data transmission and/or
`reception).
`0016 One unsatisfactory solution to this problem is to
`force extended-DRX UEs to read the current system infor
`mation (for example one or more SIBs, e.g. SIB1) prior to
`data transmission. However, since changes to SI are relatively
`rare, this will in general result in the UE reading the SIB when
`no update has occurred, and this causes an increase in power
`consumption from unnecessarily reading SI, which may
`negate the gains in battery life provided by using extended
`DRX cycles (i.e. DRX cycles beyond the currently specified
`limits).
`0017 Thus, in some embodiments, mobile devices oper
`ating in an extended DRX cycle (i.e. with a DRX cycle longer
`that the SFN period or SI modification period) can be
`informed about the change to the system information prior to
`the normal modification period (i.e. the modification period
`in which UEs operating in non-DRX modes or conventional
`DRX modes are informed of the change). This early notifi
`cation of the system information change for extended DRX
`UEs allows DRX cycles to be used that are longer than the
`modification period.
`
`0018. In particular embodiments, the extended DRX UEs
`are informed about the change to the system information prior
`to the normal modification period through an additional or
`dedicated paging message (i.e. dedicated to extended DRX
`UEs) that includes a flag for indicating whether system infor
`mation is about to change. This flag can be labelled system
`InfoModification-flag as in the conventional paging mes
`Sages.
`0019. In accordance with an aspect, there is provided a
`method of operating a network node in a communication
`network, the communication network comprising at least one
`mobile device that is operating in a discontinuous reception,
`DRX, mode with a DRX cycle length that is longer than a
`modification period in the network. When an update to system
`information is to occur in an updated information modifica
`tion period, the modification period immediately preceding
`the updated information modification period comprising a
`change notification modification period, the method com
`prises transmitting a paging message to the mobile device
`during a modification period other than the change notifica
`tion modification period and the updated information modi
`fication period, the paging message informing the mobile
`device that an update to system information is to occur in the
`updated information modification period.
`0020. In some embodiments, the method described above
`comprises transmitting the paging message informing the
`mobile device about the update to system information to the
`mobile device during a modification period that occurs before
`the change notification modification period.
`0021. In other embodiments, for example where a mobile
`device does not need to apply the updated system information
`in order to continue to receive paging messages, the method
`described above comprises transmitting the paging message
`informing the mobile device about the update to system infor
`mation to the mobile device during a modification period that
`occurs after the updated information modification period.
`0022. In accordance with another aspect, there is provided
`a network node for use in a communication network, the
`communication network comprising at least one mobile
`device that is operating in a discontinuous reception, DRX,
`mode with a DRX cycle length that is longer than a modifi
`cation period in the network. The network node comprises a
`transceiver module and a processing module configured to
`control the transceiver module to transmit paging messages to
`the mobile device, and the processing module is configured
`Such that, when an update to system information is to occur in
`an updated information modification period, the modification
`period immediately preceding the updated information modi
`fication period comprising a change notification modification
`period, the processing module controls the transceiver mod
`ule to transmit a paging message during a modification period
`other than the change notification modification period and the
`updated information modification period, the paging message
`informing the mobile device that an update to system infor
`mation is to occur in the updated information modification
`period.
`0023. According to another aspect there is provided a net
`work node for use in a communication network that com
`prises at least one mobile device that is operating in a discon
`tinuous reception, DRX, mode with a DRX cycle length that
`is longer than a modification period in the network. The
`network node is adapted to transmit a paging message to the
`mobile device during a modification period other than a
`change notification modification period and an updated infor
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`mation modification period when an update to system infor
`mation is to occur in the updated information modification
`period, the change notification modification period being the
`modification period immediately preceding the updated
`information modification period, the paging message inform
`ing the mobile device that an update to system information is
`to occur in the updated information modification period.
`0024. According to another aspect there is provided a net
`work node for use in a communication network that com
`prises at least one mobile device that is operating in a discon
`tinuous reception, DRX, mode with a DRX cycle length that
`is longer than a modification period in the network. The
`network node comprises a processor and a memory, the
`memory containing instructions executable by said processor
`whereby the network node is operative to transmit a paging
`message to the mobile device during a modification period
`other than a change notification modification period and an
`updated information modification period when an update to
`system information is to occur in the updated information
`modification period, the change notification modification
`period being the modification period immediately preceding
`the updated information modification period, the paging mes
`sage informing the mobile device that an update to system
`information is to occur in the updated information modifica
`tion period.
`0025. According to another aspect, there is provided a
`method of operating a mobile device in a communication
`network, the communication network comprising a network
`node. The method comprises operating the mobile device in a
`discontinuous reception, DRX, mode with a DRX cycle
`length that is longer than a modification period in the net
`work; periodically activating a receiver in the mobile device
`to receive a paging message from the network node; process
`ing a received paging message to determine if an update to
`system information is to occur in an updated information
`modification period, the updated information modification
`period being preceded by a change notification modification
`period, wherein a paging message indicating an update to
`system information is to occur is received during a modifica
`tion period other than the change notification modification
`period and the updated information modification period.
`0026. In some embodiments, the paging message indicat
`ing an update to system information is received during a
`modification period that occurs before the change notification
`modification period.
`0027. In other embodiments, for example where a mobile
`device does not need to apply the updated system information
`in order to continue to receive paging messages, the paging
`message indicating an update to system information is
`received during a modification period that occurs after the
`updated information modification period.
`0028. In some embodiments, the method of operating a
`mobile device further comprises activating the receiver in the
`mobile device during the updated information modification
`period to determine the updated system information if an
`update to system information is to occur.
`0029. In alternative embodiments, the method of operat
`ing a mobile device further comprises following receipt of a
`paging message indicating that an update to system informa
`tion is to occur, activating the receiver in the mobile device to
`determine the updated system information when the mobile
`device is to transmit data to the network node.
`0030. According to yet another aspect, there is provided a
`mobile device for use in a communication network, the com
`
`munication network comprising a network node, the mobile
`device comprising a receiver or transceiver module; and a
`processing module configured to control the receiver or trans
`ceiver module to operate in a discontinuous reception, DRX,
`mode with a DRX cycle length that is longer than a modifi
`cation period in the network. The processing module is fur
`ther configured to periodically activate the receiver or trans
`ceiver module to receive a paging message from the network
`node and to process a received paging message to determine
`if an update to system information is to occur in an updated
`information modification period, the updated information
`modification period being preceded by a change notification
`modification period, wherein a paging message indicating an
`update to system information is to occur is received during a
`modification period other than the change notification modi
`fication period and the updated information modification
`period.
`0031. According to another aspect, there is provided a
`mobile device for use in a communication network that com
`prises a network node, the mobile device comprising a
`receiver, and the mobile device being adapted to operate in a
`discontinuous reception, DRX, mode with a DRX cycle
`length that is longer than a modification period in the net
`work; periodically activate the receiver to receive a paging
`message from the network node; and process a received pag
`ing message to determine if an update to system information
`is to occur in an updated information modification period.
`The updated information modification period is preceded by
`a change notification modification period, and a paging mes
`sage indicating an update to system information is to occur is
`received during a modification period other than the change
`notification modification period and the updated information
`modification period.
`0032. According to another aspect there is provided a
`mobile device for use in a communication network that com
`prises a network node, the mobile device comprising a
`receiver, a processor and a memory, the memory containing
`instructions executable by the processor whereby said mobile
`device is operative to operate in a discontinuous reception,
`DRX, mode with a DRX cycle length that is longer than a
`modification period in the network; periodically activate the
`receiver to receive a paging message from the network node:
`and process a received paging message to determine if an
`update to system information is to occur in an updated infor
`mation modification period. The updated information modi
`fication period is preceded by a change notification modifi
`cation period, wherein a paging message indicating an update
`to system information is to occur is received during a modi
`fication period other than the change notification modifica
`tion period and the updated information modification period.
`0033 According to another aspect, there is provided a
`computer program product having computer readable code
`embodied therein, the computer readable code being config
`ured such that, on execution by a Suitable computer or pro
`cessor, the computer or processor is caused to performany of
`the method embodiments described above.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`0034 FIG. 1 is a non-limiting example block diagram of
`an LTE cellular communications network;
`0035 FIG. 2 is a block diagram of a mobile device accord
`ing to an embodiment;
`0036 FIG.3 is a block diagram of a base station according
`to an embodiment;
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`0037 FIG. 4 is a block diagram of a core network node
`according to an embodiment;
`0038 FIG. 5 illustrates a conventional procedure for sig
`nalling a change of system information;
`0039 FIG. 6 illustrates the signalling of a change of sys
`tem information for a mobile device operating with an
`extended DRX cycle;
`0040 FIG. 7 is a flow chart illustrating a method of oper
`ating a network node according to an embodiment;
`0041
`FIG. 8 is a flow chart illustrating a method of oper
`ating a mobile device according to an embodiment; and
`0042 FIG. 9 is a graph illustrating the potential improve
`ments in battery life provided by the embodiments described
`herein.
`
`DETAILED DESCRIPTION
`0043. The following sets forth specific details, such as
`particular embodiments for purposes of explanation and not
`limitation. But it will be appreciated by one skilled in the art
`that other embodiments may be employed apart from these
`specific details. In some instances, detailed descriptions of
`well known methods, nodes, interfaces, circuits, and devices
`are omitted so as not obscure the description with unneces
`sary detail. Those skilled in the art will appreciate that the
`functions described may be implemented in one or more
`nodes using hardware circuitry (e.g., analog and/or discrete
`logic gates interconnected to perform a specialized function,
`ASICs, PLAS, etc.) and/or using software programs and data
`in conjunction with one or more digital microprocessors or
`general purpose computers. Nodes that communicate using
`the air interface also have Suitable radio communications
`circuitry. Moreover, the technology can additionally be con
`sidered to be embodied entirely within any form of computer
`readable memory. Such as Solid-state memory, magnetic disk,
`or optical disk containing an appropriate set of computer
`instructions that would cause a processor to carry out the
`techniques described herein.
`0044 Hardware implementation may include or encom
`pass, without limitation, digital signal processor (DSP) hard
`ware, a reduced instruction set processor, hardware (e.g.,
`digital or analog) circuitry including but not limited to appli
`cation specific integrated circuit(s) (ASIC) and/or field pro
`grammable gate array(s) (FPGA(s)), and (where appropriate)
`state machines capable of performing Such functions.
`0045 Interms of computer implementation, a computer is
`generally understood to comprise one or more processors,
`one or more processing modules or one or more controllers,
`and the terms computer, processor, processing module and
`controller may be employed interchangeably. When provided
`by a computer, processor, or controller, the functions may be
`provided by a single dedicated computer or processor or
`controller, by a single shared computer or processor or con
`troller, or by a plurality of individual computers or processors
`or controllers, some of which may be shared or distributed.
`Moreover, the term “processor or “controller also refers to
`other hardware capable of performing such functions and/or
`executing software, Such as the example hardware recited
`above.
`0046 Although the description is given for user equip
`ment (UE), it should be understood by the skilled in the art
`that “UE' is a non-limiting term comprising any mobile or
`wireless device or node equipped with a radio interface allow
`ing for at least one of transmitting signals in uplink (UL) and
`receiving and/or measuring signals in downlink (DL). A UE
`
`herein may comprise a UE (in its general sense) capable of
`operating or at least performing measurements in one or more
`frequencies, carrier frequencies, component carriers or fre
`quency bands. It may be a “UE operating in single- or
`multi-radio access technology (RAT) or multi-standard
`mode. As well as “UE, the term “mobile device' is used
`interchangeably in the following description, and it will be
`appreciated that such a device, particularly a MTC device,
`does not necessarily have to be mobile in the sense that it is
`carried by a user. Instead, the term “mobile device' encom
`passes any device that is capable of communicating with
`communication networks that operate according to one or
`more mobile communication standards, such as GSM,
`UMTS, LTE, etc.
`0047. A cell is associated with a base station, where a base
`station comprises in a general sense any node transmitting
`radio signals in the downlink (DL) and/or receiving radio
`signals in the uplink (UL). Some example base stations, or
`terms used for describing base stations, are eNodeB, eNB,
`NodeB, macro/micro/pico/femto radio base station, home
`eNodeB (also known as femto base station), relay, repeater,
`sensor, transmitting-only radio nodes or receiving-only radio
`nodes. A base station may operate or at least perform mea
`Surements in one or more frequencies, carrier frequencies or
`frequency bands and may be capable of carrier aggregation. It
`may also be a single-radio access technology (RAT), multi
`RAT, or multi-standard node, e.g., using the same or different
`base band modules for different RATs.
`0048. It should be noted that use of the term “network
`node' as used herein can refer to a base station, such as an
`eNodeB, a network node in the RAN responsible for resource
`management, such as a radio network controller (RNC), or a
`core network node. Such as a mobility management entity
`(MME).
`0049. The signalling described is either via direct links or
`logical links (e.g. via higher layer protocols and/or via one or
`more network nodes). For example, signalling from a coor
`dinating node may pass another network node, e.g., a radio
`node.
`0050 FIG. 1 shows an example diagram of an E-UTRAN
`architecture as part of an LTE-based communications system
`2. Nodes in the core network 4 include one or more Mobility
`Management Entities (MMEs) 6, a key control node for the
`LTE access network, and one or more Serving Gateways
`(SGWs) 8 which route and forward user data packets while
`acting as a mobility anchor. They communicate with base
`stations 10 referred to in LTE as eNBs, over an interface, for
`example an S1 interface. The eNBs 10 can include the same or
`different categories of eNBs, e.g. macro eNBs, and/or micro/
`pico/femto eNBs. The eNBs 10 communicate with each other
`over an interface, for example an X2 interface. The S1 inter
`face and X2 interface are defined in the LTE standard. A UE
`12 can receive downlink data from and send uplink data to one
`of the base stations 10 with that base station 10 being referred
`to as the serving base station of the UE 12.
`0051
`FIG. 2 shows a user equipment (UE) 12 that can be
`used in one or more of the non-limiting example embodi
`ments described. The UE 12 may in some embodiments be a
`mobile device that is configured for machine-to-