GB2500210A - Providing identities of secondary cells to apparatus for discovery in a physical discovery channel - Google Patents

Abstract

A primary cell (PCell) configures 40 a physical discovery channel (PDCH) for a plurality of secondary cells (SCells). The configuring may include interference management among the SCells and coordinating transmission periodicity of the PDCH transmitted by the configured SCells. The primary cell (PCell) provides 42 individual identities of the secondary cells (SCells) to user equipment (UE) for discovery in the PDCH of at least one secondary cell (SCell) using at least one of the provided individual identities. The primary cell (PCell) may receive 44 from the user equipment (UE) a report of discovery of the at least one secondary cell (SCell). The primary cell (PCell) may configure 46 the at least one secondary cell (SCell) for transmitting additional data to the user equipment (UE) on a secondary carrier to provide carrier aggregation (CA) of the secondary carrier with a primary carrier of the primary cell (PCell).

Description

1

APPARATUS, METHODS AND COMPUTER PROGRAMS FOR SECONDARY CELL DISCOVERY FOR CARRIER AGGREGATION

Technical Field

5 The present invention relates to apparatus, methods and computer programs for secondary cell discovery for carrier aggregation. The exemplary and non-limiting embodiments of this invention relate generally to wireless communications and specific embodiments to configuring a PDCH for SCell identification on an additional carrier type for carrier aggregation, e.g. in LTE-A systems.

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Background

The following abbreviations which may be found in the specification and/or the drawing figures are defined as follows:

15

3 GPP

3rd Generation Partnership Project

ABS

almost blank subframes

ARQ

automatic repeat request

BCH

broadcast channel

CA

carrier aggregation

20

CC

component carrier

CoMP

coordinated multi-point

CQI

channel quality indicator

CRC

cyclic redundancy check

CRS

cell-specific reference signal

25

CSI

channel state information\

CSI-RS

channel state information reference signal

DCI

downlink control information

DL

downlink

DM RS

demodulation RS

30

eNB, eNodeB

evolved node B /base station in an E-UTRAN system

E-UTRAN

evolved UTRAN (LTE)

FFT

fast Fourier transform

2

FSVB

fast synchronization verification block

HARQ

hybrid automatic repeat request

HetNet heterogeneous network

ICIC

inter-cell interference coordination

5

ID

identification, identifier, identity

IE

information element

LI

layer 1 (physical layer)

LTE

Long Term Evolution

LTE-A

Long Term Evolution Advanced

10

MAC

medium access control

MCS

modulation and coding schemes

MIB

master information block

Pcc primary carrier component

PCell primary cell

15

PCFICH

physical control format indicator channel

PBCH

physical broadcast channel

PDCCH

physical downlink control channel

PDCH

physical discovery channel

PHICH

physical hybrid ARQ indicator channel

20

PMI

precoding matrix indicator

PRB

physical resource block

P-SCH

primary synchronization channel

PSS

primary synchronization signal

P/S-SCH

primary/secondary synchronization channel

25

PUSCH

physical uplink shared channel

RAN

radio access network

RS

reference signal

RRC

radio resource control

RRH

remote radio head

30

RRM

radio resource management

RSRP

reference signal received power

RSRQ

reference signal received quality

3

SCell secondary cell

SFN

subframe number

SIB

system information block

S-SCH

secondary synchronization channel sss secondary synchronization signal

TB

transport block

TD

time division

UE

user equipment

UL

uplink

UTRAN

Universal Terrestrial Radio Access Network

WI

work item

WID

work item description

X2

interface between eNBs

15 A new carrier type was proposed in the study item of LTE 3GGP Release-10

but postponed to LTE 3GGP Release-11. In RAN Meeting #51, a new 3GGP Release-11 CA enhancements WID was approved (RP-1104551, "LTE Carrier Aggregation Enhancements", 3GGP TSG RAN Meeting #51, Kansas City, USA, March 15-18, 2011). This includes study of additional carrier types including non-20 backwards compatible elements such as carrier extension (see also Rl-100809 "Carrier types offline discussion", Huawei, 3GPP RANI #59bis). An extension carrier must be a part of a component carrier set where at least one of the carriers in the set is a backwards compatible component carrier. It could be characterized by the following features: no PBCH/Release-8 SIB/Paging; no PSS/SSS; no 25 PDCCH/PHICH/PCFICH; no CRS; and 3GGP Release-10 mobility is based on measurements in backwards compatible CC(s).

Summary

According to a first aspect of the present invention, there is provided a method 30 comprising: configuring by a primary cell a physical discovery channel for a plurality of secondary cells; and providing by the primary cell individual identities of the plurality of secondary cells to at least one user equipment for discovery in the

4

physical discovery channel of at least one secondary cell comprised in the plurality of secondary cells using an identity of the at least one secondary cell, the identity being one of the provided individual identities.

5 According to a second aspect of the present invention, there is provided a method, comprising: receiving by a user equipment from a primary cell information which at least includes individual identities of a plurality of secondary cells comprising a neighbourhood list; and discovering by the user equipment in a physical discovery channel transmitted by the plurality of secondary cells at least one 10 secondary cell comprised in the plurality using an identity of the at least one secondary cell, the identity being one of the provided individual identities.

According to a third aspect of the present invention, there is provided apparatus comprising a processing system constructed and arranged to cause the 15 apparatus to: configure a physical discovery channel for a plurality of secondary cells; and provide individual identities of the plurality of secondary cells to at least one user equipment for discovery in the physical discovery channel of at least one secondary cell comprised in the plurality of secondary cells using an identity of the at least one secondary cell, the identity being one of the provided individual identities.

20

According to a fourth aspect of the present invention, there is provided apparatus comprising a processing system constructed and arranged to cause the apparatus to: upon receipt from a primary cell of information which at least includes individual identities of a plurality of secondary cells comprising a neighbourhood list, 25 discover in a physical discovery channel transmitted by the plurality of secondary cells at least one secondary cell comprised in the plurality using an identity of the at least one secondary cell, the identity being one of the provided individual identities.

The processing systems described above may comprise at least one processor 30 and a memory storing a set of computer instructions, in which the processor and the memory storing the computer instructions are configured to cause the apparatus to operate as described above.

5

According to a fifth aspect of the present invention, there is provided a computer program comprising instructions such that when the computer program is executed on a computing device, the computing device carries out a method 5 comprising: configuring by a primary cell a physical discovery channel for a plurality of secondary cells; and providing by the primary cell individual identities of the plurality of secondary cells to at least one user equipment for discovery in the physical discovery channel of at least one secondary cell comprised in the plurality of secondary cells using an identity of the at least one secondary cell, the identity being 10 one of the provided individual identities.

According to a sixth aspect of the present invention, there is provided a computer program comprising instructions such that when the computer program is executed on a computing device, the computing device carries out a method 15 comprising: receiving by a user equipment from a primary cell information which at least includes individual identities of a plurality of secondary cells comprising a neighbourhood list; and discovering by the user equipment in a physical discovery channel transmitted by the plurality of secondary cells at least one secondary cell comprised in the plurality using an identity of the at least one secondary cell, the 20 identity being one of the provided individual identities.

There may be provided a non-transitory computer readable memory encoded with a computer program comprising computer readable instructions recorded thereon for execution of a method as described above.

25

Further features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, given by way of example only, which is made with reference to the accompanying drawings.

30 Brief Description of the Drawings

Figures la and lb show schematic diagrams of HetNet scenarios for an additional carrier type;

6

Figure 2 shows a time diagram of an example of PDCH TD transmission patterns according to exemplary embodiments of the invention;

5 Figures 3 and 4 show flow charts demonstrating examples of implementations of exemplary embodiments of the invention; and

Figure 5 shows a block diagram of an example of wireless devices for practising exemplary embodiments of the invention.

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Detailed Description

A method, apparatus and software-related product (e.g. a computer program or a computer-readable memory) are presented for configuring a PDCH for SCell identification on an additional carrier type by UEs, thus accomplishing effective CA,

15 e.g. in LTE-A systems. The embodiments of the invention can provide fast SCell discovery of neighbouring SCells using PDCH which may be used for traffic load balancing and SCell activation/de-activation for inter-SCell interference management. Robust SCell discovery due to the coordination of the TD PDCH transmission across SCells (aggregated with the same PCell or different PCells) may be further provided.

20 Also minimum user data rate on the SCell may be guaranteed during other SCell muting period for a UE suffering from excessive inter-SCell interference using interference management.

By way of introduction, carrier extensions are considered for HetNet

25 deployment optimization in Rl-114071, "Issues Regarding Additional Carrier Type in Re 1-11 CA", DoCoMo, 3GGP TSG RAN Meeting #67, San Francisco, USA, November 14-18, 2011. Some inter-band scenario examples are illustrated in Figures la and lb as further explained below (also see 3GPP TS 36.300, V10.6.0 (2011-12).

30 Figure la demonstrates inter-band CA with PCell 2 on macro eNB backward-

compatible carrier and SCell 4 on pico eNB non-backward compatible carriers. PCell 2 and SCell 4 may be co-located with SCell 4 having smaller coverage area, so that

7

the SCell 4 may be used to improve throughput. PCell 2 and SCell 4 may have different bands, e.g. PCell 2 may have 800 MHz or 2 GHz, and SCell 4 may have 3.5 GHz, etc. It is expected that aggregation is possible between overlaid cells PCell 2 and SCell 4.

5

Figure lb demonstrates Inter-band CA with PCell 6 on micro or pico eNB backward-compatible carrier and SCell 8 on Remote Radio Head (RRH) non-backward compatible carriers. RRHs (SCell 8) may be used to improve throughput at hot spots. It is expected that RRHs cells (SCell 8) can be aggregated with the 10 underlying macro/pico cell (PCell 6).

Furthermore, it was proposed for additional carrier types in Rl-114071 quoted above so that (i) physical signal structure (reference signals or synchronization signals) can be redesigned for energy savings and low mobility; (ii) configurable 15 blank sub frames can be supported without CRS for resource efficiency and ICIC; (iii) a new physical channel referred to as the physical discovery channel (PDCH) be provided that can be optimized to SCell discovery in the additional carrier. There are some issues associated with the PDCH that will need solutions, as disclosed further herein.

20

The proposed PDCH has long periodicity (i.e. a few seconds assuming relaxed measurement requirements for energy saving and low mobility) and sufficient time/frequency radio resource density for one-shot PDCH reception by the UE for efficient UE battery consumption (e.g. full use of a few subframes). This would be 25 reasonable for accurate SCell discovery on additional carrier type, but not sufficient for accurate time synchronization (due to narrow bandwidth assuming PDCH in mid-6 PRBs in the configured system bandwidth) and frequency synchronization tracking (i.e. due to low time density) and frequency synchronization of the UE assuming inter-band CA. Further, using the PDCH instead of P/S-SCH may not have 30 significant advantage compared to using the P/S-SCH.

8

Moreover, complexity will be high as a number of ADD-COMP operations in the PDCH correlator increases with the size of the PDCH (about 4 times longer than of the P-SCH).

5 Still further, the P-SCH allows to detect one in 3 cell identity groups, N(2)id parameter, in each cell-identity group. The S-SCH allows detecting one in 168 cell-identity groups, N( l 'id. This allows 504 cell identities Ncc11id = 3N(1)id + N(2)id • This 3GGP Release-8 specification allows to break down the complexity of synchronization (in time/frequency) and cell ID determination (needed to know the 10 cell specific RS sequence used). The post-FFT S-SCH detector requires the pre-FFT P-SCH detector stage that provides initial time/frequency synchronization (i.e. with a few sample accuracy, and with a sub-carrier accuracy). This also allows greatly simplified processing by the S-SCH detector because it can estimate the S-SCH signal at near optimum time (i.e. only a few correlator window shifts are needed). Then 15 using a new PDCH for detection of one in 504 possible sequences used for the SCell determination could be very complex and prone to detection error.

Furthermore, CRS or CSI-RS may be used in various ways on the additional carrier types by the UE for synchronization, channel estimation, automatic frequency 20 control (AFC), channel state information (CSI) such as channel quality indicator (CQI) and precoding matrix indicator (PMI), reference signal received power (RSRP) and reference signal received quality (RSRQ) for RRM measurements, and so on.

Thus the embodiments of the invention propose a new physical layer design 25 using the PDCH for fast SCell discovery on the additional carrier type assuming that (i) the P/S-SCH is transmitted; (ii) CRS or CSI-RS may be transmitted.

Moreover, a fast synchronization verification block (FSVB) was proposed in PCT application no. PCT/CN2011/081833 "Synchronization Mechanism on Un-30 licensed Band" filed on November 4, 2011, to help UE synchronized on SCell mapped to a carrier in un-licensed band. The FSVB is characterized by the following features: (i) FSVB includes an LI/MAC control element to verify / activate / de

9

activate the SCell; (ii) FSVB is mapped to the physical broadcast channel (PBCH); (iii) FSVB and MIB are attached to separate BCH TB before mapping to separate physical resources on PBCH (i.e. no multiplexing of the FSVB and MIB on BCH TB). Further, it was proposed that the FSVB is transmitted with periodicity matching 5 that of the P/S-SCH. The focus in PCT application no. PCT/CN2011/081833 was WiFi interference with LTE system transmitting on SCell according to ON-OFF patterns based on SFN as configured via a higher layer. No special consideration was given to traditional interference from cellular systems on the SCell, which is the focus of the exemplary embodiments described herein.

10

According to an embodiment of the present invention, RRC configuration parameters and procedure for a PDCH are configured to optimize the SCell identification on an additional carrier type in the LTE system, for example using HetNet scenarios shown in Figures la and lb. The PDCH may share characteristics 15 of the FSVB outlined above as further described herein.

A PDCH detection procedure for the SCell discovery by the UE may have (but is not limited to) the following features. The periodicity of the PDCH is configurable via a higher layer on the PCell. The PDCH payload can include a new RRC 20 information element, PDCH-identity, which contains the identities of the SCells in the UE neighbourhood that the UE should try to discover. The indicated SCell IDs form the SCell neighbourhood list, which corresponds to a subset of prioritized candidate SCells, Scandidates, in the set of pre-configured SCells, S. This allows the UE to fetch the relevant SCell RRC configuration as indicated by the PCell to prioritize the PDCH 25 detection for the SCell discovery in a most efficient way. The UE may update its priority list each time it detects successfully a SCell. For example, the PDCH may include a CRC scrambled with the SCell ID to allow CRC checking, i.e. using CRC and SCell ID to check if the PDCH detection is not erroneous.

30 According to another embodiment, a PDCH configuration may be used for managing inter-SCell interference co-ordination. For example, PDCH TD transmission patterns may be pre-configured on the PCell for SCell muting to allow

10

UEs that cannot access the SCell or suffer significant interference on the SCell to make measurements and/or get minimum data coverage on other SCells or on the PCell. This removes the potential problem of black holes for these UEs.

5 Moreover, the pre-configured PDCH TD transmission patterns may be indicated via a bitmap index implicitly linked to the cell ID of the PCell used for the SCell pre-configuration to facilitate such inter-eNB TD co-ordination. This allows the network to coordinate the PDCH TD transmission patterns between the SCells aggregated with different PCells automatically as further described below.

10

In one embodiment, initial time/frequency synchronization on the SCell can be made based on the detection of P/S-SCH signals transmitted on the SCell. The PDCH CRC checking can be used instead of MIB CRC checking to confirm that P/S-SCH detection on SCell is not erroneous. The longer periodicity of the PDCH may not be 15 an issue for the SCell synchronization since low mobility is assumed.

The PDCH can be characterized by the following features: (i) the PDCH includes an Ll/MAC control element to verify/activate/de-activate the SCell; (ii) the PDCH is mapped to the PBCH; (iii) the PDCH and MIB are attached to separate BCH 20 TB before mapping to separate physical resources on the PBCH (i.e. no multiplexing of the PDCH and MIB on the BCH TB).

Moreover, RRC IE such as PDCH-identity, can provide knowledge of the identities of the SCells on which the UE should try to detect the PDCH. The SCell 25 IDs may be used as configuration parameters for the SCell detector in the UE. Before verification, there is detection on the SCell. The UE needs to switch to SCell carrier and detect the PDCH in the configured bandwidth. These SCell RRC parameters are pre-configured in the UE for potentially many SCells. However, in practice, only a subset of SCells needs to be detected, e.g. from a neighbourhood list with SCell IDs 30 provided by the PCell to the UE. The CRC scrambled with the Sell ID in the detected PDCH subframe can be used to verify the SCell discovery, as further described herein.

11

In a practical PDCH detector, initially the SCell discovery by the UE may be done blindly for the SCell candidates in the set of pre-configured SCells, S, as indicated by the PCell. A simple PDCH detector procedure may be used as follows.

5 A rough energy detection of a signal power level for the combined signals (i.e. PDCH, PSS/SSS, RS, signalling and data) can be performed on each SCell candidate in the set S. Then first evaluate by the running PDCH detector on an SCell candidate with the highest signal power level detected. If the PDCH CRC is valid for this candidate (i.e. the ID recovered from the CRC matches the ID of one of the SCells in

10 the neighbourhood list provided to the UE by the PCell), then set this SCell as the serving SCell. If the PDCH CRC is not valid, evaluate another SCell with a next highest signal power level detected by the running PDCH detector again; and so on. When the UE correctly detects PDCH (as determined by the PDCH CRC checking) and obtains the SCell ID of the serving SCell, it may report it to the PCell.

15

In another embodiment, measurements methods after detection of the SCell are further addressed. In 3GGP Release 10, the measurement period with deactivated SCell is based on the RCC parameter measCycleSCell included in the MeasObjectEUTRA information element configured for the SCell (e.g. see 3GPP TS

20 36.331, "Radio Resource Control", vlO.4.0, 2011-12). There may be a MeasObjectEUTRA information element configured for each pre-configured SCell in the set S. The SCell neighbourhood list allows the UE to select the SCells in the set S that are needed to be detected, with measurement parameters indicated in the MeasObjectEUTRA information elements configured for these SCells.

25

When the UE correctly detects one SCell, referred to as the serving SCell, it checks the MAC IE and obtains the SCell IDs of the neighbouring SCells, referred to as target SCells, and it may further do the following.

30 If a closed-loop SCell measurement method is used, the UE reports the serving

SCell ID to the eNB (e.g. via Pcc UL), so that the eNB can configure some reference

12

signal pattern and measurement object regarding the newly found serving SCell and the target SCells.

If an open-loop SCell measurement method is used, the UE just does some 5 measurements on the serving SCell and target SCells based on a predefined or pre-configured reference signal pattern. Then the UE can report cell IDs (for the serving SCell and target SCells) and measurement results to the eNB (PCell) via Pcc UL.

Also, the UE may update its priority list each time it detects successfully a 10 SCell. Further, the UE may report the priority list in a new field neighborhoodListSCell in the MeasResults IE within the MeasurementReport message for the measID for which the measurement procedure was triggered.

Additional examples of PDCH measurement reports sent by the UE to the 15 eNB (PCell) for the closed-loop measurement method could contain serving SCell ID and target SCells IDs if available.

Additional examples of PDCH measurement reports sent by the UE to the eNB (PCell) for the open-loop measurement method could contain serving SCell ID 20 {RSRP, RSRQ} and/or a list of targets ID {RSRP, RSRQ} if available.

Additional examples of eNB measurement report objects in the case of a closed-loop measurement report method may contain: a reference signal pattern for serving SCell and/or target SCells and/or event trigger configured for serving SCell 25 and/or target SCells.

Figure 2 shows an example of PDCH TD transmission patterns, according to exemplary embodiments of the invention. The PDCH transmission is shown to occur within one subframe 10 in the example. In practice, the PDCH could be a multiple of 30 subframes depending on the synchronization requirements and presence/absence of the P/S-SCH on the SCell.

13

Almost Blank Subframes (ABS) 12 on the SCells on the additional carrier are coordinated by the eNB on the PCell and across eNBs on the PCells. A bitmap may use a value "0" to indicate ABS and "1" for PDCH transmission. Note that in 3GGP Release 10, the TD ICIC patterns are used to schedule UEs during ABS subframes.

5 In the examples of embodiments of invention described herein, the PDCH TD patterns are used to schedule the PDCH transmission subframes 10 of a given SCell free of interference from (neighbouring) SCell transmission and may also be used to scheduled UEs on spare PRBs not used by the PDCH transmission. This may help to secure fast and reliable PDCH detection. For example, as shown in Figure 2, during 10 the first subframe, only the top transmission pattern (SCell #i) has PDCH, but the synchronized first subframes for the rest of the transmission patterns (SCells # j, #m and #n) have ABS subframes, thus minimizing interference for the first subframe of the SCell #i.

15 In case the PDCH signal does not occupy the full system bandwidth, but only occupies a fixed subset of PRBs denoted by S, the TD PDCH coordination only needs to be done over the PRBs in the subset S. On the other PRBs not included in the subset S, the UEs may be scheduled freely (in current 3GPP Release-10 specification, TD ICIC mechanisms are only applied to PCells). This may reduce impact on the 20 system efficiency.

Note that in the GPP Release-10 TD ICIC, muting patterns in macro and pico scenarios are assumed to be configured dynamically, i.e. by new X2 signalling introduced in the 3GPP Release-10. In the case of 3GGP Release-10, CA scenario #2 25 in 3GPP TS 36.330, V10.6.0, 2011-12 Annex J (PCell on macro and SCell on pico eNBs), X2 signalling between macro eNBs could be considered for the muting patterns in the PDCH TD transmission on SCells aggregated to different PCells on neighbouring macro eNBs. In the case of 3GGP Release-10, CA scenario #4 in 3GPP TS 36.330, V10.6.0, 2011-12 Annex J (PCell on pico/micro eNBs and SCell on 30 RRHs), X2 signalling could be considered for the muting patterns in the PDCH TD transmissions of RRHs on Scells aggregated to different Pcells on neighbouring pico

14

eNBs. For SCells aggregated to the same PCell, no X2 signalling is required for the muting patterns.

Figure 3 shows an exemplary flow chart demonstrating an example of an 5 implementation of embodiments of the invention by the PCell (e.g. on macro or pico eNB). It is noted that the order of steps shown in Figure 3 is not absolutely required, so in principle, the various steps may be performed out of the illustrated order. Also certain steps may be skipped, different steps may be added or substituted, or selected steps or groups of steps may be performed in a separate application or operation.

10

In a method according to this exemplary embodiment, as shown in Figure 3, in a first step 40, a PCell configures a PDCH for a plurality of SCells, including interference management among the plurality of SCells and coordinating transmission periodicity of the PDCH transmitted by the configured Scells, as described herein. In 15 a next step 42, the PCell provides individual identities (IDs) of the plurality of SCells to at least one UE for discovery in the PDCH of at least one SCell comprised in the plurality of SCells using an ID of the at least one SCell.

In a next step 44, the PCell receives from the at least one UE a report of 20 discovery of the at least one SCell. In a next step 46, the PCell configures the at least one SCell for transmitting additional data to the at least one UE on a secondary carrier to provide carrier aggregation of the secondary carrier with a primary carrier of the PCell.

25 Figure 4 shows an exemplary flow chart demonstrating an example of an implementation of embodiments of the invention by the UE. It is noted that the order of steps shown in Figure 4 is not absolutely required, so in principle, the various steps may be performed out of the illustrated order. Also certain steps may be skipped, different steps may be added or substituted, or selected steps or groups of steps may 30 be performed in a separate application or operation.

15

In a method according to this exemplary embodiment, as shown in Figure 4, in a first step 60, a UE receives from a PCell information (for discovery SCells using PDCH) which at least includes: individual IDs of a plurality of secondary cells comprising a neighbourhood list, and a bitmap of ABS and PDCH subframes in SCell 5 transmission patterns.

In a next step 62, the UE detects a combined signal comprising the PDCH being transmitted by at least one SCell and having a highest detected power among combined signals transmitted by the plurality of SCells.

10

In a next step 64, it is determined whether the detected combined signal is erroneous. If that is the case, the process goes back to step 62 to detect a further combined signal from another SCell with the next highest power. If, however, it is determined in step 64 that the detected combined signal is not erroneous, in a next

15 step 66, the UE reports the identity of the discovered at least one SCell to the PCell, (possibly including a closed loop or an open loop measurement report of the discovered at least one SCell and other SCells of the plurality of SCells in the neighbourhood list). In a next step 68, the UE updates priority in the neighbourhood list based on the discovered at least one SCell.

20

Figure 5 shows an example of a block diagram demonstrating examples of LTE devices including PCell eNB 80 (which could be for example a macro or pico eNB) comprised in a network 20, SCell network element 82 (which could be for example a pico eNB or RRH) and UE 84, according to embodiments of the invention.

25 Figure 5 shows simplified block diagrams of various electronic devices that are suitable for practising the exemplary embodiments of this invention, e.g. with reference to Figures 1 to 4, and a specific manner in which components of an electronic device are configured to cause that electronic device to operate. The UE 84 may be implemented as a mobile phone, a wireless communication device, a camera

30 phone, a portable wireless device and the like.

16

The eNB 80 may comprise e.g. at least one transmitter 80a, at least one receiver 80b, at least one processor 80c, at least one memory 80d and a CA and PDCH application module 80e. The transmitter 80a and the receiver 80b and corresponding antennas (not shown in Figure 5) may be configured to provide 5 wireless communications with the device 84 (and others not shown in Figure 5). The eNB 80 may communicate through an X2 interface with the network element 82 using a corresponding link 81 and with the UE 84 using a link 83, according to the embodiments of the invention. The transmitter 80a and the receiver 80b may be generally means for transmitting/receiving and may be implemented as a transceiver, 10 or a structural equivalent thereof. It is further noted that the same requirements and considerations are applied to transmitters and receivers of the devices 82 and 84.

Various embodiments of the at least one memory 80d (e.g. computer readable memory) may include any data storage technology type that is suitable to the local 15 technical environment, including but not limited to semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, removable memory, disc memory, flash memory, DRAM, SRAM, EEPROM and the like. Various embodiments of the processor 80c include but are not limited to general purpose computers, special purpose computers, microprocessors, 20 digital signal processors (DSPs) and multi-core processors. Similar embodiments are applicable to memories and processors in other devices 82 and 84 shown in Figure 5.

The CA and PDCH application module 80e may provide various instructions for performing steps 40 to 46 shown in Figure 3. The module 80e may be 25 implemented as an application computer program stored in the memory 80d, but in general it may be implemented as software, firmware and/or hardware module or a combination thereof. In particular, in the case of software or firmware, one embodiment may be implemented using a software related product such as a computer readable memory (e.g. non-transitory computer readable memory), computer 30 readable medium or a computer readable storage structure comprising computer readable instructions (e.g. program instructions) using a computer program code (i.e. the software or firmware) thereon to be executed by a computer processor.

17

Furthermore, the module 80e may be implemented as a separate block or may be combined with any other module/block of the device 80, or it may be split into several blocks according to their functionality.

5

The devices 82 and 84 may have similar components as the network element 80, as shown in Figure 5, so that the above discussion about components of the eNB 80 is fully applicable to the components of the devices 82 and 84.

10 The SCell discovery application module 87 in the UE 84 may provide various instructions for performing steps 60 to 68 shown in Figure 5. The module 87 may be implemented as an application computer program stored in the memory of the device 84, but in general it may be implemented as software, firmware and/or hardware module or a combination thereof. In particular, in the case of software or firmware,

15 one embodiment may be implemented using a software related product such as a computer readable memory (e.g. non-transitory computer readable memory), computer readable medium or a computer readable storage structure comprising computer readable instructions (e.g. program instructions) using a computer program code (i.e. the software or firmware) thereon to be executed by a computer processor.

20

It is noted that various non-limiting embodiments described herein may be used separately, combined or selectively combined for specific applications.

Further, some of the various features of the above non-limiting embodiments

25 may be used to advantage without the corresponding use of other described features. The foregoing description should therefore be considered as merely illustrative of the principles, teachings and exemplary embodiments of this invention, and not in limitation thereof.

30 The above embodiments are to be understood as illustrative examples of the invention. Further embodiments of the invention are envisaged. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in

18

combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, 5 which is defined in the accompanying claims.

19

Claims (1)

1. A method, comprising:

configuring by a primary cell a physical discovery channel for a plurality of 5 secondary cells; and providing by the primary cell individual identities of the plurality of secondary cells to at least one user equipment for discovery in the physical discovery channel of at least one secondary cell comprised in the plurality of secondary cells using an identity of the at least one secondary cell, the identity being one of the provided 10 individual identities.

2. A method according to claim 1, wherein the configuring of the physical discovery channel for the plurality of secondary cells by the primary cell comprises coordinating a transmission periodicity of the physical discovery channel transmitted

15 by the configured secondary cells.

3. A method according to claim 1 or claim 2, wherein the primary cell is a macro eNB and the secondary cells are pico eNBs.

20 4. A method according to claim 1 or claim 2, wherein the primary cell is a pico or macro eNB and the secondary cells are on remote radio heads.

5. A method according to any of claims 1 to 4, wherein carriers of the plurality of secondary cells are different from a primary carrier of the primary cell.

25

6. A method according to any of claims 1 to 5, comprising:

receiving by the primary cell from the at least one user equipment a report of discovery of the at least one secondary cell; and configuring by the primary cell the at least one secondary cell for transmitting 30 additional data to the at least one user equipment on a secondary carrier to provide carrier aggregation of the secondary carrier with a primary carrier of the primary cell.

20

7. A method according to any of claims 1 to 6, wherein the configuring of the physical discovery channel for the plurality of secondary cells by the primary cell comprises interference management among the plurality of secondary cells.

5 8. A method according to claim 7, wherein the interference management comprises scheduling of transmission patterns of the physical discovery channel for each of the plurality of secondary cells by muting others of the plurality of secondary cells during physical discovery channel transmission of the each of the plurality of secondary cells.

10

9. A method according to any of claims 1 to 8, wherein the physical discovery channel is mapped to a physical broadcast channel.

10. A metho d, comprising:

15 receiving by a user equipment from a primary cell information which at least includes individual identities of a plurality of secondary cells comprising a neighbourhood list; and discovering by the user equipment in a physical discovery channel transmitted by the plurality of secondary cells at least one secondary cell comprised in the

20 plurality using an identity of the at least one secondary cell, the identity being one of the provided individual identities.

11. A method according to claim 10, wherein the discovering comprises:

detecting by the user equipment a combined signal comprising the physical

25 discovery channel and transmitted by the at least one secondary cell and having a highest power among combined signals transmitted by the plurality of secondary cells; and verifying that the detection is not erroneous using a cyclic redundancy check scrambled with the identity of the at least one secondary cell in the physical discovery

30 channel of the detected combined signal and the individual identities of the plurality of secondary cells comprised in the neighbourhood list.

21

12. A method according to claim 11, wherein initial time-frequency synchronization by the user equipment before the detecting is performed using detecting primary and secondary synchronization channels.

5 13. A method according to any of claims 10 to 12, comprising:

reporting the identity of the discovered at least one secondary cell to the primary cell; and updating priority in the neighbourhood list based on the discovered at least one secondary cell.

10

14. A method according to any of claims 10 to 13, comprising:

providing by the user equipment to the primary cell a closed loop or an open loop measurement report of the discovered at least one secondary cell and others of the plurality of secondary cells in the neighbourhood list.

15

15. A method according to any of claims 10 to 14, wherein the information comprises a bitmap of almost blank subframes and physical discovery channel subframes in secondary cell transmission patterns.

20 16. Apparatus comprising:

a processing system constructed and arranged to cause the apparatus to: configure a physical discovery channel for a plurality of secondary cells; and provide individual identities of the plurality of secondary cells to at least one user equipment for discovery in the physical discovery channel of at least one 25 secondary cell comprised in the plurality of secondary cells using an identity of the at least one secondary cell, the identity being one of the provided individual identities.

17. Apparatus according to claim 16, wherein the processing system is arranged such that the configuring of the physical discovery channel for the plurality of 30 secondary cells by the apparatus comprises coordinating a transmission periodicity of the physical discovery channel transmitted by the configured secondary cells.

22

18. Apparatus according to claim 16 or claim 17, wherein the primary cell is a macro eNB, and the secondary cells are pico eNBs.

19. Apparatus according to claim 16 or claim 17, wherein the primary cell is a 5 pico or macro eNB and the secondary cells are on remote radio heads.

20. Apparatus according to any of claims 16 to 19, wherein carriers of the plurality of secondary cells are different from a primary carrier of the primary cell.

10 21. Apparatus according to any of claims 16 to 20, wherein the processing system is arranged to cause the apparatus to:

upon receipt from the at least one user equipment of a report of discovery of the at least one secondary cell, configure the at least one secondary cell for transmitting additional data to the at least one user equipment on a secondary carrier 15 to provide carrier aggregation of the secondary carrier with a primary carrier of the primary cell.

22. Apparatus according to any of claims 16 to 21, wherein the configuring of the physical discovery channel for the plurality of secondary cells by the apparatus

20 comprises interference management among the plurality of secondary cells.

23. Apparatus according to claim 22, wherein the interference management comprises scheduling of transmission patterns of the physical discovery channel for each of the plurality of secondary cells by muting others of the plurality of secondary

25 cells during physical discovery channel transmission of the each of the plurality of secondary cells.

24. Apparatus according to any of claims 16 to 23, wherein the physical discovery channel is mapped to a physical broadcast channel.

30

25. Apparatus comprising:

a processing system constructed and arranged to cause the apparatus to:

23

upon receipt from a primary cell of information which at least includes individual identities of a plurality of secondary cells comprising a neighbourhood list, discover in a physical discovery channel transmitted by the plurality of secondary cells at least one secondary cell comprised in the plurality using an identity of the at 5 least one secondary cell, the identity being one of the provided individual identities.

26. A method according to claim 25, wherein the processing system is arranged to cause the apparatus to:

detect a combined signal comprising the physical discovery channel and 10 transmitted by the at least one secondary cell and having a highest power among combined signals transmitted by the plurality of secondary cells; and verify that the detection is not erroneous using a cyclic redundancy check scrambled with the identity of the at least one secondary cell in the physical discovery channel of the detected combined signal and the individual identities of the plurality 15 of secondary cells comprised in the neighbourhood list.

27. Apparatus according to claim 26, wherein initial time-frequency synchronization by the apparatus before the detecting is performed using detecting primary and secondary synchronization channels.

20

28. Apparatus according to any of claims 25 to 27, wherein the processing system is arranged to cause the apparatus to:

report the identity of the discovered at least one secondary cell to the primary cell; and

25 update priority in the neighbourhood list based on the discovered at least one secondary cell.

29. Apparatus according to any of claims 25 to 28, wherein the processing system is arranged to cause the apparatus to:

30 provide to the primary cell a closed loop or an open loop measurement report of the discovered at least one secondary cell and others of the plurality of secondary cells in the neighbourhood list.

24

30. Apparatus according to any of claims 25 to 29, wherein the information comprises a bitmap of almost blank subframes and physical discovery channel subframes in secondary cell transmission patterns.

5

31. A computer program comprising instructions such that when the computer program is executed on a computing device, the computing device carries out a method comprising:

configuring by a primary cell a physical discovery channel for a plurality of 10 secondary cells; and providing by the primary cell individual identities of the plurality of secondary cells to at least one user equipment for discovery in the physical discovery channel of at least one secondary cell comprised in the plurality of secondary cells using an identity of the at least one secondary cell, the identity being one of the provided 15 individual identities.

32. A computer program according to claim 31, wherein the configuring of the physical discovery channel for the plurality of secondary cells by the primary cell comprises coordinating a transmission periodicity of the physical discovery channel

20 transmitted by the configured secondary cells.

33. A computer program according to claim 31 or claim 32, wherein the primary cell is a macro eNB and the secondary cells are pico eNBs.

25 34. A computer program according to claim 31 or claim 32, wherein the primary cell is a pico or macro eNB and the secondary cells are on remote radio heads.

35. A computer program according to any of claims 31 to 34, wherein carriers of the plurality of secondary cells are different from a primary carrier of the primary cell.

30

36. A computer program according to any of claims 31 to 35, wherein the method comprises:

25

receiving by the primary cell from the at least one user equipment a report of discovery of the at least one secondary cell; and configuring by the primary cell the at least one secondary cell for transmitting additional data to the at least one user equipment on a secondary carrier to provide 5 carrier aggregation of the secondary carrier with a primary carrier of the primary cell.

37. A computer program according to any of claims 31 to 36, wherein the configuring of the physical discovery channel for the plurality of secondary cells by the primary cell comprises interference management among the plurality of secondary

10 cells.

38. A computer program according to claim 37, wherein the interference management comprises scheduling of transmission patterns of the physical discovery channel for each of the plurality of secondary cells by muting others of the plurality of

15 secondary cells during physical discovery channel transmission of the each of the plurality of secondary cells.

39. A computer program according to any of claims 31 to 38, wherein the physical discovery channel is mapped to a physical broadcast channel.

20

40. A computer program comprising instructions such that when the computer program is executed on a computing device, the computing device carries out a method comprising:

receiving by a user equipment from a primary cell information which at least 25 includes individual identities of a plurality of secondary cells comprising a neighbourhood list; and discovering by the user equipment in a physical discovery channel transmitted by the plurality of secondary cells at least one secondary cell comprised in the plurality using an identity of the at least one secondary cell, the identity being one of 30 the provided individual identities.

26

41. A computer program according to claim 40, wherein the discovering comprises:

detecting by the user equipment a combined signal comprising the physical discovery channel and transmitted by the at least one secondary cell and having a 5 highest power among combined signals transmitted by the plurality of secondary cells; and verifying that the detection is not erroneous using a cyclic redundancy check scrambled with the identity of the at least one secondary cell in the physical discovery channel of the detected combined signal and the individual identities of the plurality 10 of secondary cells comprised in the neighbourhood list.

42. A computer program according to claim 41, wherein initial time-frequency synchronization by the user equipment before the detecting is performed using detecting primary and secondary synchronization channels.

15

43. A computer program according to any of claims 40 to 42, wherein the method comprises:

reporting the identity of the discovered at least one secondary cell to the primary cell; and

20 updating priority in the neighbourhood list based on the discovered at least one secondary cell.

44. A computer program according to any of claims 40 to 43, wherein the method comprises:

25 providing by the user equipment to the primary cell a closed loop or an open loop measurement report of the discovered at least one secondary cell and others of the plurality of secondary cells in the neighbourhood list.

45. A computer program according to any of claims 40 to 44, wherein the 30 information comprises a bitmap of almost blank subframes and physical discovery channel subframes in secondary cell transmission patterns.

27

46. A method of secondary cell discovery for carrier aggregation, substantially in accordance with any of the examples as described herein with reference to and illustrated by the accompanying drawings.

5 47. Apparatus for secondary cell discovery for carrier aggregation, substantially in accordance with any of the examples as described herein with reference to and illustrated by the accompanying drawings.