WO2016117985A1

WO2016117985A1 - Method for managing a radio resource management measurement at user equipment

Info

Publication number: WO2016117985A1
Application number: PCT/KR2016/000784
Authority: WO
Inventors: Mangesh Abhimanyu INGALE; Kyeongin Jeong; Sharma NEHA; Jaehyuk Jang; Soenghun Kim
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2015-01-23
Filing date: 2016-01-25
Publication date: 2016-07-28
Anticipated expiration: 2017-07-23

Abstract

Embodiments herein provide a method for managing a Radio Resource Management (RRM) measurement at a User Equipment (UE).The method includes receiving, at the UE, from a primary cell a signaling message indicating measurement configuration for at least one second frequency. Further, the method includes performing, at the UE, a power measurement on a first resource element of the second frequency and a power measurement on a second resource element of the second frequency. Further, the method includes determining, at the UE, at least one of a corrupted measurement and a clean measurement based on the power measurement on the first resource element and the power measurement on the second resource element. Furthermore, the method includes reporting, at the UE, one of a RRM measurement based on the clean measurement, and a ratio of subframes encountered with the corrupted measurement.

Description

METHOD FOR MANAGING A RADIO RESOURCE MANAGEMENT MEASUREMENT AT USER EQUIPMENT

The present invention relates to a broad area of Licensed Assisted Access (LAA) and more particularly to a Radio Resource Management (RRM) measurement for a component carrier configured for a User Equipment (UE) from an unlicensed band and enhancement of an uplink transmission such as random access procedure and uplink Hybrid automatic repeat request (HARQ) for a component carrier configured for the UE from an unlicensed band. The present application is based on, and claims priority from an Indian Application Number 364/CHE/2015 filed on 23rd January, 2015, the disclosure of which is hereby incorporated by reference herein.

Generally, a Licensed-Assisted Access (LAA) concept in a Long Term Evolution (LTE) system is based on a carrier aggregation (CA) operation where a secondary cell (SCell) for a UE is served on a carrier from an unlicensed band or a license exempt band or an Industrial Scientific Medical (ISM) band (for example, 5.0 GHz) while a primary cell (PCell) is served on a carrier from a licensed band. Due to unlicensed (license exempt) nature of a secondary carrier, the SCell is prone to interference from other LAA cells or wireless fidelity (Wi-Fi) Access Points (APs) which are interference sources leading to a degradation of the UE throughput performance on the desired LAA SCell.

The principal object of the embodiments herein is to provide a method for managing a Radio Resource Management (RRM) measurement at a User Equipment (UE).

Another object of the embodiments herein is to provide a method for receiving, at a UE, from a primary cell a signaling message indicating measurement configuration for a second frequency, where the second frequency is to be configured as a secondary cell for the UE while the primary cell is served on a first frequency.

Another object of the embodiments herein is to provide a method for performing, at a UE, a power measurement on a first resource element of a second frequency and a power measurement on a second resource element of a second frequency.

Another object of the embodiments herein is to provide a method for determining, at a UE, at least one of a corrupted measurement and a clean measurement based on a power measurement on a first resource element and a power measurement on a second resource element.

Another object of the embodiments herein is to provide a method for reporting, at a UE, one of a RRM measurement based on a clean measurement, and a ratio of subframes encountered with a corrupted measurement.

Another object of the embodiments herein is to provide a method for handing a Random Access Channel (RACH) procedure at a UE.

Another object of the embodiments herein is to provide a method for initiating, at a UE, a RACH procedure on a secondary cell served by a second frequency upon activation.

Another object of the embodiments herein is to provide a method for preparing, at a UE, a RACH preamble transmission to obtain uplink synchronization on a secondary cell.

Another object of the embodiments herein is to provide a method for detecting one of: an activated secondary cell served by a second frequency is unavailable based on channel sensing or transmission power is limited to perform parallel RACH on a primary cell and the secondary cell.

Another object of the embodiments herein is to provide a method for dropping, at a UE, a transmission of a RACH preamble.

Another object of the embodiments herein is to provide a method for indicating, at a UE, a power suspension for not incrementing a preamble transmission counter to avoid a transmission power ramping.

Another object of the embodiments herein is to provide a method for starting, at a UE, a timer for holding a RACH preamble.

Accordingly the embodiments herein provide a method for managing a Radio Resource Management (RRM) measurement at a User Equipment (UE). The method includes receiving, at the UE, from a primary cell a signaling message indicating measurement configuration for at least one second frequency. The second frequency is to be configured as a secondary cell for the UE while the primary cell is served on a first frequency. Further, the method includes performing, at the UE, a power measurement on a first resource element of the second frequency and a power measurement on a second resource element of the second frequency. Further, the method includes determining, at the UE, at least one of a corrupted measurement and a clean measurement based on the power measurement on the first resource element and the power measurement on the second resource element. Furthermore, the method includes reporting, at the UE, one of a RRM measurement based on the clean measurement and a ratio of subframes encountered with the corrupted measurement.

Accordingly the embodiments herein provide a method for handing Random Access Channel (RACH) procedure at a User Equipment (UE).The method includes initiating, at the UE, a Random Access Channel (RACH) procedure on a secondary cell served by the second frequency upon activation. The UE is configured with the secondary cell on the second frequency by the primary cell, when the ratio of subframes served on secondary cell encountered with the corrupted measurement is less than a threshold. Further, the method includes preparing, at the UE, a RACH preamble transmission to obtain uplink synchronization on a secondary cell. Further, the method includes detecting, at the UE, one of: the activated secondary cell served by the second frequency is unavailable based on channel sensing or transmission power is limited to perform parallel RACH on the primary cell and the secondary cell. Further, the method includes dropping, at the UE, the transmission of the RACH preamble, and indicating, at the UE, a power suspension for not incrementing a preamble transmission counter to avoid the transmission power ramping. Furthermore, the method includes starting, at the UE, a timer for holding the RACH preamble.

Accordingly the embodiments herein provide a User Equipment (UE) for managing a Radio Resource Management (RRM) measurement. The UE is configured to receive, from a primary cell, a signaling message indicating measurement configuration for at least one second frequency. The second frequency is to be configured as a secondary cell for the UE while the primary cell is served on a first frequency. The UE is further configured to perform a power measurement on a first resource element of the second frequency and a power measurement on a second resource element of the second frequency. The UE is further configured to determine at least one of a corrupted measurement and a clean measurement based on the power measurement on the first resource element and the power measurement on the second resource element. The UE is further configured to report one of a RRM measurement based on the clean measurement, and a ratio of subframes encountered with the corrupted measurement.

Accordingly the embodiments herein provide a User Equipment (UE) for handing Random Access Channel (RACH) procedure. The UE is configured to initiate the RACH procedure on a secondary cell served by a second frequency upon activation. The UE is configured with the secondary cell on the second frequency by the primary cell when the ratio of subframes served on secondary cell encountered with the corrupted measurement is less than a threshold. The UE is further configured to prepare a RACH preamble transmission to obtain uplink synchronization on the secondary cell. The UE further configured to detect one of: the activated secondary cell served by the second frequency is unavailable based on channel sensing or transmission power is limited to perform parallel RACH on the primary cell and the secondary cell. The UE is further configured to drop the transmission of the RACH preamble. The UE is further configured to indicate a power suspension for not incrementing a preamble transmission counter to avoid the transmission power ramping. The UE is further configured to start a timer for holding the RACH preamble.

Accordingly the embodiment herein discloses a computer program product including a computer executable program code recorded on a computer readable non-transitory storage medium. The computer executable program code when executed causing the actions includes receiving, at a User Equipment (UE), from a primary cell, a signaling message indicating measurement configuration for at least one second frequency. The computer executable program code when executed causing the actions includes performing, at the UE, a power measurement on a first resource element of the second frequency and a power measurement on a second resource element of the second frequency. The computer executable program code when executed causing the actions includes determining, at the UE, at least one of a corrupted measurement and a clean measurement based on the power measurement on the first resource element and the power measurement on the second resource element. The computer executable program code when executed causing the actions includes reporting, at the UE, one of a Radio Resource Management (RRM) measurement based on the clean measurement and a ratio of subframes encountered with the corrupted measurement.

Accordingly the embodiment herein discloses a computer program product including a computer executable program code recorded on a computer readable non-transitory storage medium. The computer executable program code when executed causing the actions includes initiating, at a User Equipment (UE), a Random Access Channel (RACH) procedure on a secondary cell served by the second frequency upon activation. The computer executable program code when executed causing the actions includes preparing, at the UE, a RACH preamble transmission to obtain uplink synchronization on the secondary cell. The computer executable program code when executed causing the actions includes detecting, at the UE, that one of: the activated secondary cell served by the second frequency is unavailable based on channel sensing or transmission power is limited to perform parallel RACH on the primary cell and the secondary cell. The computer executable program code when executed causing the actions includes dropping, at the UE, the transmission of the RACH preamble. The computer executable program code when executed causing the actions includes indicating, at the UE, a power suspension for not incrementing a preamble transmission counter to avoid the transmission power ramping. The computer executable program code when executed causing the actions includes starting, at the UE, a timer for holding the RACH preamble.

These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

Advantages, and salient features of the invention will become apparent

to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

Accordingly present invention, a radio resource management measurement at a user equipment can be managed efficiently.

This invention is illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:

FIG. 1 illustrates a Long Term Evolution (LTE) subframe depicting time-frequency resource elements;

FIG. 2 illustrates an energy or a power level measured on resource elements, according to embodiments as disclosed herein;

FIG. 3illustrates various units of a User Equipment (UE), according to embodiments as disclosed herein;

FIG. 4 is a flow diagram depicting a method for managing a Radio Resource Management (RRM) measurement at a UE, according to embodiments as disclosed herein;

FIG. 5 illustrates a sequence diagram for reporting to a primary cell (PCell) corrupted measurement on a licensed assisted access (LAA) secondary cell(SCell) when an interference level is high, according to embodiments as disclosed herein;

FIG. 6 is a flow diagram depicting a UE operation regarding a RRM measurement when a UE is configured with a LAA SCell on an unlicensed carrier, according to embodiments as disclosed herein;

FIG. 7 is a flow diagram depicting an eNodeB (eNB) operation when a UE is configured with a LAA operation with a SCell on an unlicensed carrier, according to embodiments as disclosed herein;

FIG. 8 depicts an averaged layer 1 measurement reporting to a layer 3 for a Radio Resource Control (RRC) filtering, according to embodiments as disclosed herein;

FIG. 9 shows measurements used for a RRM purpose at a layer 1 performed at resource elements carrying reference signals such as CRS and DRS, according to embodiments as disclosed herein;

FIG. 10 depicts a periodic transmission of discovery signals (DRS)with DRS occasions on LAA SCells and combining RRM measurements, according to embodiments as disclosed herein;

FIG. 11 illustrates a sequence diagram for reporting to a PCell about wireless local area network (WLAN)/Wi-Fi ON/OFF status when a network (NW) intends to configure a UE with a LAA operation by adding LAA SCell, according to embodiments as disclosed herein;

FIG. 12 illustrates a sequence diagram for reporting to a PCell about WLAN/Wi-Fi ON/OFF status when a UE is already operating in a LAA mode of operation, according to embodiments as disclosed herein;

FIGS. 13a to 13c are sequence diagrams illustrating possible ways for a UE to indicate a NW about the WLAN/Wi-Fi ON/OFF status through a RRC message, according to embodiments as disclosed herein;

FIG. 14a and FIG. 14b illustrate a sequence diagram for RRC signaling options to indicate a NW about a WLAN/Wi-Fi ON/OFF status through a RRC message, according to embodiments as disclosed herein;

FIG. 15 illustrates a sequence diagram of a UE behavior when the UE is not able to send a RACH preamble due to unavailability of a LAA channel, according to a prior art;

FIG. 16 is a flow diagram depicting a method for handing a Random Access Channel (RACH) procedure at a UE, according to embodiments as disclosed herein;

FIG. 17 illustrates a sequence diagram of a UE behavior when the UE is not able to send a RACH preamble due to unavailability of a LAA channel, according to embodiments as disclosed herein;

FIG. 18 depicts a UE operation when the UE is not able to send the RACH preamble due to unavailability of a LAA channel or power limited or some other scenario when preamble transmission is dropped by a Physical (PHY) layer, according to embodiments as disclosed herein;

FIG. 19a depicts a uplink (UL) HARQ operation for a LAA SCell, according to a prior art; and

FIG. 19b and FIG. 19c depict a UL HARQ operation for a LAA SCell, according to embodiments as disclosed herein.

The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. Also, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments. The term “or” as used herein, refers to a non-exclusive or, unless otherwise indicated. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein can be practiced and to further enable those skilled in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

The terms LAA SCell and LTE-Unlicensed (LTE-U) SCell are used interchangeably throughout the document. The terms physical layer, PHY layer and layer 1 are used interchangeably throughout the document. The terms MAC layer and layer 2 are used interchangeably throughout the document. The terms RRC layer and layer 3 are used interchangeably throughout the document. The terms carrier and frequency are used interchangeably throughout the document. The terms EUTRAN, network (NW) and eNode-B (eNB) are used interchangeably throughout the document.

The embodiments herein achieve a method for managing a Radio Resource Management (RRM) measurement at a User Equipment (UE). The method includes receiving, at the UE, from a primary cell (PCell) a signaling message indicating measurement configuration for at least one second frequency. The second frequency is to configure a secondary cell (SCell) for the UE while the primary cell is served on a first frequency. Further, the method includes performing, at the UE, a power measurement on a first resource element of the secondary cell and a power measurement on a second resource element of the secondary cell served by second frequency.

Further, the method includes estimating a difference between the power measurement on the first resource element and the power measurement on the second resource element. Further, the method includes comparing the difference with a configured threshold value. Further, the method includes determining at least one of the corrupted measurement when the difference is less than the threshold value and the clean measurement when the difference is greater than the threshold value.

Furthermore, the method includes reporting, at the UE, one of a RRM measurement based on the clean measurement, and a ratio of subframes encountered with the corrupted measurement.

In an embodiment, the configured threshold value is indicated to the UE in a Radio Resource Control (RRC) configuration message.

In an embodiment, the first frequency belongs to a licensed band and the second frequency belongs to an unlicensed band.

In an embodiment, the first resource element is a reference signal resource element and the second resource element is a non-reference signal resource element.

In an embodiment, the power measurement on the first resource element and the power measurement on the second resource element are performed during a subframe and averaged over a period indicated by number of subframes in the RRC signaling message from the primary cell.

In an embodiment, the power measurement on the first resource element of the subframes served by the second frequency includes at least one of a Reference Signal Received Power (RSRP) measurement and a Reference Signal Received Quality (RSRQ) measurement.

In an embodiment, the power measurement on the second resource element of the subframes served by the second frequency includes at least one of a received power from a desired transmission source and a contribution of received power due to transmissions from an interference sources such as Wi-Fi AP or other LAA secondary cell operating on the same second frequency.

In an embodiment, the method includes determining, at the UE, a number of subframes encountered with the corrupted measurement from a number of subframes indicated to the UE when the difference is less than the threshold value. Further, the method includes determining, at the UE, a number of subframes encountered with the clean measurement from a number of subframes indicated to the UE when the difference is greater than the threshold value. Further, the method includes calculating, at the UE, a ratio of subframes encountered with the corrupted measurements. Further, the method includes reporting, by the UE, one of the RRM measurement averaged over subframes encountered with the clean measurement, and the ratio of subframes encountered with the corrupted measurement to the primary cell.

In an embodiment, the UE is operating on a licensed carrier served by the PCell. Due to data demand for the UE, an Evolved Universal Terrestrial Access Network (EUTRAN) decides to configure the UE for a carrier aggregation (CA) mode based on LAA operation using a LTE-U SCell (i.e. unlicensed carrier served as SCell). Before sending the LTE-U SCell configuration, the EUTRAN configures the UE to provide the RRM measurements for the LTE-U SCell. On receiving the RRM measurements from the UE, EUTRAN may decide to configure the UE with one or more LTE-U SCell(s) if the ratio of subframes served on LTE-U SCell encountered with the corrupted measurement is less than a threshold. EUTRAN sends the RRC reconfiguration message with the SCell addition message to the UE on the PCell. The SCell addition message may include one or more SCell(s) associated with SCell index and physical cell identity (PCI) intended to be served by one or more carriers from the unlicensed band. Depending on the RRM measurements received from the UE for the configured LTE-U SCells and after performing channel sensing eNB may send the Media Access Control (MAC) Control Element (MAC CE) message or L1 indication message to activate one or more configured LTE-U SCell(s). On receiving the activation command, the UE is operating in the Licensed Assisted Access (LAA) mode of the CA operation i.e., the PCell on the licensed carrier and the SCell on the unlicensed carrier. The UE is uplink synchronized with the PCell of the licensed carrier. Assuming that the activated LTE-U SCell does not belong to a primary Timing Advance Group (pTAG) and belongs to a secondary TAG (i.e. sTAG) then there is need of the uplink synchronization between the UE and the SCell served by unlicensed carrier. The EUTRAN sends a Physical downlink Control Channel (PDCCH) order for the specific LTE-U SCell belonging to the sTAG. On receiving the PDCCH order, the UE initiates the Random Access procedure on the activated LTE-U SCell.

The embodiments herein achieve a method for handing Random Access Channel (RACH) procedure at the UE. The UE is configured with the secondary cell on the second frequency by the primary cell, when the ratio of subframes encountered with the corrupted measurement is less than a threshold. Further, the method includes preparing, at the UE, a RACH preamble transmission to obtain uplink synchronization on the secondary cell. Further, the method includes detecting, at the UE, one of: the activated secondary cell served by the second frequency is unavailable based on channel sensing or transmission power is limited to perform parallel RACH on the primary cell and the secondary cell. Further, the method includes dropping, at the UE, the transmission of the RACH preamble, and indicating, at the UE, a power suspension for not incrementing a preamble transmission counter to avoid the transmission power ramping. Furthermore, the method includes starting, at the UE, a timer for holding the RACH preamble.

In an embodiment, the method includes detecting, at the UE, status of the timer. Further, the method includes instructing, at the UE, to retransmit the RACH preamble when the timer is running and maximum preamble count is not reached. Further, the method includes incrementing, at the UE, the preamble transmission counter to facilitate the transmission power ramping, if the power suspension is not indicated.

In an embodiment, the method includes detecting, at the UE, status of the timer. Further, the method includes reporting, at the UE, a failure of the RACH procedure to the primary cell when the timer is expired or maximum preamble count is reached.

In an embodiment, the timer is configured by one of: the primary cell or the UE.

In an embodiment, the timer is stopped and reset when one: of a random access response message is received including an identifier of the RACH preamble transmitted by the UE or a grant is received for uplink transmission by the UE.

Unlike the conventional systems and methods, the proposed method can be used to perform the RRM measurements for the component carrier configured for the UE from an unlicensed band. The proposed method indicates a WLAN status at the UE to the network, so that it can decide to configure/release or activate/deactivate the UE with component carrier from the unlicensed band. The proposed method handles the random access procedure which will be initiated for the component carrier configured for the UE from the unlicensed band. Further, the proposed method handles the random access procedure during preamble dropping/power suspension at a physical layer. The proposed method activates and deactivates the component carrier configured from the unlicensed band through a physical layer (layer 1) command or indication. The proposed method performs an uplink HARQ retransmission for the UE on the component carrier configured from the unlicensed band. The proposed method handles the DRX re-transmission timer of the UE for the component carrier configured from the unlicensed band.

Referring now to the drawings, and more particularly to FIGS. 1 to 14, 16 to 18, 19b, and 19c and there are shown preferred embodiments.

FIG. 1 illustrates a Long Term Evolution (LTE) subframe 100 depicting time-frequency resource elements, according to embodiments as disclosed herein. In an embodiment, a secondary cell (SCell) served on a carrier from an unlicensed band operates using same physical layer numerology of a LTE specification (i.e., TS 36.211, TS 36.213) as shown in the FIG. 1 for a single subframe in a time-frequency grid. The LTE operation of the UE on the SCell configured from the unlicensed band is also termed as a LTE-U operation. The terms LAA operation and LTE-U operation are used interchangeably throughout the description. The LTE subframe 100 depicts the time-frequency resource elements including Reference Signal resource elements (RSREs), Non reference signal resource elements (Non-RSREs), and other Physical signals.

The LTE subframe 100 is 1 ms in duration comprising 14 Orthogonal Frequency Division Multiplexing (OFDM) symbols 102 with normal cyclic prefix in a time domain and several orthogonal sub-carriers 104 in a frequency domain depending on a channel bandwidth (i.e., 10MHz or 20 MHz). The granularity of the time-frequency grid in terms of one OFDM symbol and one sub-carrier is termed as

resource elements

101, 103. Reference signals (RS) are transmitted on some resource elements 103 to facilitate the UE operation for a channel estimation, a data de-modulation, a synchronization, a time-frequency tracking, channel state information (CSI) measurements, radio resource management (RRM) measurements, or the like. The reference signals can be, at least one of cell-specific reference signals (CRS), a CSI-RS, discovery signals (DRS), UE-specific reference signals, or the like. A Resource Element(s) (REs) carrying the reference signals 103 are known signals to the UE while the REs where the reference signals are not present (Non-RSRE )101 are used for a data transmission. Further, there are other LTE physical signals 105 transmitted on some REs like primary synchronization signals (PSS) and secondary synchronization signals (SSS). The REs103 carrying the reference signals are known to the UE by decoding the physical signals like (PSS/SSS) or can be determined based on the higher layer configuration provided by the PCell for the periodic DRS. Since, the reference signals (RS) are known signals to the UE, when the UE decodes the reference signals, energy level measured by the UE on the Non-RSREs 101 can correspond to as shown in the FIG. 2.

As shown in the FIG. 2, energy or power level measured on the REs including Non-RSREs 101 are illustrated. The energy or the power level measured on the RSRE 103 and difference in the power levels are illustrated when the interference is present. While decoding the reference signals, the maximum energy is captured for the LTE reference signal 203 since it is known signal whereas the energy measured on the Non-RSRE 101 captures energy from both LTE data signals as well as interference power from other sources transmitting in the concerned channel bandwidth. As shown in the FIG. 2, the notation “A” depicts the energy or power 201 measured on the Non-RSREs 101 assuming there is no contribution of the interference power from other sources apart from the LTE data signals. Normally, the received energy 203 captured in the RSRE 103 is high compared to the energy 201 captured in the non RSRE 101 in the absence of the interference from other sources as shown by the notation “B” of the FIG. 2. When there is the interference from other sources then the contribution of the interference power adds to the power of the LTE data signal in the non RSREs101 as shown by the notation “C” and “D” of the FIG. 2. Even in the presence of the interference from other sources, the UE is able to decode the RS since the RS is known signals and the measured power 203 on the RSRE 103 can still be higher than measured power 201on the non RSRE 101. Average interference power 205 measured on all resource elements (REs) is summation of average power 203 measured on RSREs 103 and average power 201 measured on the non RSREs 101. When the power difference 207 i.e. difference between average power 203 measured on the RSRE 103 and the average interference power 205 is still greater than or equal to some threshold value, the UE is still able to decode the LTE data signals like Physical Downlink Shared Channel (PDSCH) transmitted in the non RSREs 101 with low block error probability (BLER).

However, when the interference power from other sources becomes dominating then the power difference 207 i.e. difference between the average power 203 measured on the RSRE 103 and the average interference power 205 can become lower than a threshold value as shown by the notation “D” in the FIG. 2 in which case the BLER of the PDSCH increases beyond an acceptable limit. In such a scenario, the RRM measurements like Reference signal received power/Reference signal received quality (RSRP/RSRQ) 203 performed on the RSRE 103 are corrupted due to dominant interference and cannot be useful for the SCell management in the LAA operation. It would be desirable that the UE filters out these measurements and do not account in the layer 3 processing of the RRM measurements. These power measurements of the RSRE 103 (i.e. 203) and the non RSRE 101 (i.e., 201) are instantaneous measurements performed at the physical layer averaged over one subframe in time domain and may be across the channel bandwidth. Normally, at the physical layer, the UE averages these measurements over more than one subframe and reports these measurements to the layer 3 typically every 200 ms for the layer 3 filtering for the RRM purpose. The averaging period over which the

power measurements

201, 203, 205 are averaged is indicated by number of subframes in the signaling message from the primary cell. When the physical averaged difference 207 i.e. difference between the power 203 measured on RSREs 103 and the average interference power 205is higher than a threshold value then, the UE reports the RSRP/RSRQ measurements 203 performed on the RSRE 103 to the layer 3 (i.e. clean measurements are sent to the layer 3 filer) otherwise the corrupted measurements are not sent to the layer 3 filter. In an embodiment, when the average difference 207 is lower than the threshold then, the UE reports the average difference value to the PCell or the ratio of subframes where average difference 207 is lower than the threshold compared to the total number of subframes where measurements are performed i.e. the ratio of subframes encountered with corrupted measurements.

FIG. 3 illustrates various units of the UE 300, according to embodiments as disclosed herein. The UE 300 can be, for example but not limited to, a cellular phone, a personal digital assistant (PDA), a satellite radio, a tablet, a smart phone, a laptop, a global positioning system, a multimedia device, a video device, a game console, or the like. The UE 300 may also be referred to by those skilled in the art as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, or the like. The UE 300 is compliant with multiple, different communication protocols that can operate as a multi-mode device by communicating within a fourth generation (4G) network employing any common type of LTE or LTE-Advanced (LTE-A) radio access technology (RAT), as well as within a third generation (3G)or second generation2G network employing any common type of legacy RAT.

In an embodiment, the UE 300 includes a communication unit 302, a processor unit 304, a display unit 306, a storage unit 308, a control unit 310, an Arithmetic Logic Unit (ALU) 312, networking devices 314, Input/output (I/O) devices 316, and a memory 318. The communication unit 302 includes a cellular radio 302a, a controller 302b, and an industrial, scientific and medical (ISM) radio 302c. The cellular radio 302a is capable of operating in one or more frequency bands for the LTE operation which can be configured to communicate with the network and the ISM radio 302c is capable of operating in one or more unlicensed frequency bands for the Wi-Fi, and the Bluetooth operation. The cellular radio 302a and ISM radio 302c may be integrated in the same communication unit 302 such that activities of the cellular radio 302a and the ISM radio 302c are coordinated with the processor unit 304.The processor unit 304 is configured to perform one or more actions for achieving Radio Resource Management (RRM) measurements for the component carrier configured for the UE 300 from the unlicensed band. The storage unit 308 is provided with a memory 318. The memory 318 is configured to store a plurality of instructions to be executed by the processor unit 304.The display unit 306 includes a user interface that allows a user to interact with the UE 300.

In an embodiment, the storage unit 308 is configured to store information generated from a charging process, including an historical record of the battery pack temperature, and state of charge at different times. The storage unit 308 may include one or more computer-readable storage media. The storage unit 308 may include non-volatile storage elements. Examples of such non-volatile storage elements may include magnetic hard disc, optical discs, floppy discs, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable (EEPROM) memories. In addition, the storage unit 308 may, in some examples, be considered a non-transitory storage medium. The term “non-transitory” may indicate that the storage medium is not embodied in a carrier wave or a propagated signal. However, the term “non-transitory” should not be interpreted that the storage unit 308 is non-movable. In some examples, the storage unit 308 can be configured to store larger amounts of information than the memory unit. In certain examples, a non-transitory storage medium may store data that can, over time, change (e.g., in Random Access Memory (RAM) or cache). In an embodiment, the communication unit 308 is configured for communicating internally between internal units and with external devices via one or more networks.

Further, the processor unit 304 is equipped with the control unit 310, the ALU 312, the memory 318, the storage unit 308, a plurality of networking devices 314 and the plurality I/O devices 316. The processor unit 304 is responsible for processing the instructions of the technique. The processor unit 304 receives commands from the control unit 310 in order to perform its processing. Further, any logical and arithmetic operations involved in the execution of the instructions are computed with the help of the ALU 312.

The UE 300 can operate in a computing environment that can be composed of multiple homogeneous or heterogeneous cores, multiple CPUs of different kinds, special media and other accelerators. The processor unit 304 is responsible for processing the instructions of the technique. Further, the plurality of processor units 304 may be located on a single chip or over multiple chips.

The technique comprising of instructions and codes required for the implementation are stored in either the memory 318 or the storage unit 308 or both. At the time of execution, the instructions may be fetched from the corresponding memory 318 or the storage unit 308, and executed by the processor unit 304.

In case of any hardware implementations various networking devices 314 or external I/O devices may be connected to the computing environment to support the implementation through a networking unit and the I/O device 316.

Although the FIG. 3 shows a limited number of units of the UE 300 but, it is to be understood that other embodiments are not limited thereon. In other embodiments, the UE 300 may include less or more number of units. Further, the labels or names of the units are used only for illustrative purpose and does not limit the scope of the invention. One or more units can be combined together to perform same or substantially similar function to perform the RRM measurements.

FIG. 4 is a flow diagram depicting a method 400 for managing the RRM measurement at the UE 300, according to embodiments as disclosed herein. At step 402, the method 400 includes receiving, from the primary cell served by the first frequency in the licensed band, a signaling message indicating measurement configuration for the second frequency in the unlicensed band. The second frequency is to be configured the secondary cell for the UE 300 while the primary cell is served on the first frequency. In an embodiment, the method 400 allows the communication unit 302 to receive, from the primary cell served by the first frequency in the licensed band, the signaling message indicating measurement configuration for the second frequency in the unlicensed band.

At step 404, the method 400 includes performing the power measurement on the first resource element of the second frequency and the power measurement on the second resource element of the second frequency. In an embodiment, the first frequency belongs to the licensed band, and the second frequency belongs to the unlicensed band. In an embodiment, the first resource element is the RSRE 103 and the second resource element is the non-RSRE 101.

In an embodiment, the first resource element is also called as a first radio resource that corresponds to theRSRE103 where either cell-specific reference signals (CRS) or a channel state information Reference signals (CSI-RS) can be transmitted. Further, the second resource element is also called as a second radio resource that corresponds to resource elements where the signals other than the reference signal are transmitted.

In an embodiment, the method 400 allows the processor unit 304 to perform the power measurement on the first resource element of the second frequency and the power measurement on the second resource element of the second frequency.

At step 406, the method 400 includes determining at least one of a corrupted measurement and a clean measurement based on the power measurement on the first resource element and the power measurement on the second resource element. In an embodiment, the method 400 allows the processor unit 304 to determine at least one of the corrupted measurement and the clean measurement based on the power measurement on the first resource element and the power measurement on the second resource element.

At step 408, the method 400 includes reporting one of a RRM measurement based on the clean measurement and a ratio of subframes encountered with the corrupted measurement. In an embodiment, the method 400 allows the processor unit 304 to report one of the RRM measurement based on the clean measurement and the ratio of subframes encountered with the corrupted measurement.

The various actions, acts, blocks, steps, or the like in the method 400 may be performed in the order presented, in a different order or simultaneously. Further, in some embodiments, some of the actions, acts, blocks, steps, or the like may be omitted, added, modified, skipped, or the like without departing from the scope of the invention.

FIG. 5 illustrates a sequence diagram for reporting to, the PCell, the corrupted measurements on the LAA SCell, when the interference level is high, according to embodiments as disclosed herein. In an embodiment, the UE 300 is capable of carrier aggregation mode operation. It also supports the LAA operation in the unlicensed band (e.g. 5 GHz). The UE 300 establishes the RRC connection with the eNB 500a on the carrier served by the eNB 500a in the licensed band which the UE 300 supports. This becomes the PCell for the UE 300. The UE 300 indicates (502) its capability for support of the licensed band and the unlicensed band including the band combination supports for carrier aggregation to the eNB 500a on the PCell through the RRC message.

Based on the UE capability indicated in the step 502, the eNB 500a configures the UE 300 with one or more SCells intended to be served with carrier frequencies belonging to either licensed band or unlicensed band. When the SCell belongs to the licensed band, the carrier aggregation follows the legacy operation. However, when the SCell belongs to the unlicensed band then, the LAA operation is configured for the UE 300. This is achieved by sending the RRC message.

The reconfiguration message (504) is transmitted to the UE 300 on the PCell. The reconfiguration message 504 includes the SCell configuration and the measurement configuration. The SCell configuration may include one or more SCell(s) associated with SCell index and physical cell identity (PCI) intended to be served by one or more carriers from the unlicensed band. The measurement configuration includes a measurement object, measurement identities, reporting configuration and threshold to compare the difference of measurement on a first radio resource and a second radio resource.

In an embodiment, the first radio resource corresponds to theRSRE103 where either CRS or the CSI-RS can be transmitted. Further, the second radio resource corresponds to the REs where the signals other than the reference signal are transmitted. The energy or power measurements on the first radio resource correspond to either RSRP or the RSRQ measurement. The measurements on the second radio resource correspond to the LTE data signal power plus interference power from other sources. The measurements on the first radio resource are feasible if the reference signals can be detected by the UE 300. The reference signal cannot be detected by the UE 300, if there is another LAA SCell transmitting the reference signal with the same physical cell identity (PCI) which can occur due to lack of the PCI co-ordination. The UE 300 can report such problem to the PCell through a L1 signaling message, a Media Access Control (MAC) Control Element (MAC CE) message or the RRC message like the UEAssistanceInformation. On receiving the UE indication, the eNB 500a can change the SCell of the UE 300. When the UE 300 is able to detect the reference signals on the first radio resource then, the UE 300 performs difference of measurement on the first radio resource and the second radio resource to estimate the interference from nearby Wi-Fi AP or the LAA SCell which cannot be detected by the eNB 500a during the channel sensing. If the difference in measurement is lower than a threshold then, the UE 300 may report the average value of the difference or the ratio of subframes where the difference is lower than the threshold through either the UEAssistanceInformation or new RRC message. Instead of power difference on the first radio resource and second radio resource, the RSRQ may be used as metric to estimate the level of interference from the nearby Wi-Fi AP or the LAA SCell. When the difference in the measurement is higher than the threshold, the interference free measurements are passed to the layer 3 to be taken into account for the RRM purpose.

The eNB 500a decides (506) to activate one of the configured SCell for the UE 300 based on the channel sensing and determining the channel is free for the LTE transmission. The UE 300 is informed by the PCell through L1 signaling message such as downlink control information (DCI) format that the configured SCell for an associated SCell index is activated. The L1 indication includes at least one of the ON indication for the associated SCell index and the period for which that the concerned SCell is activated. The UE 300 can also be informed by the PCell through Activation/Deactivation MAC Control element (CE) so that the configured SCell for an associated SCell index is activated (508). On activating the SCell, the eNB 500a starts (510) transmitting the reference signals on the activated SCell indicated to the UE 300 through the L1 command message. The SCell transmits on the RS RE at least one of the reference signals such as CRS, DRS, CSI-RS or the like. The UE 300 assumes that the PCell and the activated SCell are time synchronized (i.e., the system frame number (SFN) of the PCell and the SCell are same) such that the subframe boundaries of the PCell and the SCell are time aligned. Since the PCI of the SCell is known to the UE 300 through the RRC signaling message and the SFN are time aligned, the UE 300 knows the RSRE103 of the SCell and starts decoding the reference signals transmitted on the unlicensed carrier. It may be possible that the eNB 500a during the channel sensing is not able to detect a transmission node such as the Wi-Fi AP or the LTE node of a different public land mobile network (PLMN) which may be in a vicinity of the UE 300 but far away from the eNB 500a occupying the same unlicensed channel which is activated as the SCell for the UE 300. The other transmission node transmitting on the unlicensed carrier activated as the SCell for the UE 300 becomes the source of interference for the LTE data transmission on the SCell towards the UE 300. It may also be possible that if the interference source is the LTE node of different PLMN than the PLMN of the UE 300, and the concerned LAA SCell also has the same PCI as the PCI of the SCell then the UE 300 may not be able to decode (512) the reference signals transmitted by the SCell.

If the UE 300 unable to detect the reference signals transmitted on the RSREs 103 of the SCell then, the UE 300 indicates (514) the non-detected reference signal status to the PCell in the eNB 500a through the L1 signaling message, the MAC CE message, the RRC message like UEAssistanceInformation, or the like. If the UE 300 is able to detect the reference signals on the SCell then the UE 300 starts (516) performing the power/energy measurements on the first resource element (i.e. power measurements on the RSREs 103) of the second frequency and the power measurement on the second resource element (i.e. power measurements on the non-RSREs 101) of the second frequency. The UE 300 expects (518) PDSCH transmissions on the non-RSREs 101 scheduled by the SCell. The power measurements on the RSREs 103 of the SCell performed by the UE 300 include at least one of the RSRP and RSRQ measurements. The power measurements performed by the UE 300 on the non-RSREs 101 of the SCell includes the received power from the PDSCH transmission scheduled by the SCell and contribution of the power due to transmissions from other interference sources such as Wi-Fi AP or other LAA SCell operating on the same unlicensed carrier. Based on the L1 command received, the UE 300 is aware of the period for which it can expect the reference signal reception on the SCell. The UE 300 performs the difference of the power measurements on the RSREs 103 and non-RSREs 101 during the subframes indicated by the period in the L1 command message. The UE 300 determines (520) that the difference between the power measurements on the RSREs 103 and the non-RSREs 101 is less than or greater than the -threshold received by the UE 300 in the measurement configuration. This comparison of the power measurements can be associated with an existing or new measurement event configured for the UE 300 in the measurement configuration. If the difference between the power measurements on the RSREs 103 and the non-RSREs 101 is less than threshold then, the UE 300 may report (522), on the PCell of the eNB 500a, the average value of the difference or the ratio of subframes with corrupted measurement where the difference is lower than the threshold through either UEAssistanceInformation or new RRC message. When such situation occurs then the instantaneous measurements at the physical layer for those subframes are assumed to be corrupted by interference and need to be filtered out by not sending those corrupted measurements to the layer 3 of the UE 300 to be taken into account for the L3 filtering for the RRM purpose. Only those measurements for which the difference between the power measurements on the RSREs 103 and the non-RSREs 101 is greater than the threshold that is assumed (524) to be clean measurements which are passed to the layer 3 filtering at the clean measurement process to be accounted towards the RRM. In another embodiment, the physical layer sends both the corrupted measurements and clean measurements to the layer 3 and the

steps

520, 522 and 524 are executed at the layer 3 of the UE 300.

FIG. 6 is a flow diagram depicting the UE 300 operation regarding the RRM measurement when the UE 300 is configured with the LAA SCell on the unlicensed carrier, according to embodiments as disclosed herein. At step 602, after establishing the RRC connection with the eNB 500a on the PCell licensed carrier, the UE 300 indicates through the RRC message its capability for support of the licensed band and the unlicensed band including the band combination it supports for the carrier aggregation. At step 604, the UE 300 receives the RRC reconfiguration message on the PCell which includes the SCell configuration for at least one second frequency along with measurement configuration and threshold. The SCell configuration may include one or more SCell(s) associated with SCell index and PCI intended to be served by one or more carriers from the unlicensed band.

In an embodiment, the measurement configuration includes the measurement object, the measurement identities, reporting configuration and threshold to compare the difference of measurement on the first radio resource (i.e. power measurements on the RSRE 103) and the second radio resource (i.e. power measurements on non-RSREs 101). At step 606, the UE 300 receives L1 command or activation/deactivation MAC control element on the PCell indicating one of the configured SCell is activated. The L1 indication in the form of the DCI format includes at least one ON indication for the associated SCell index and the period for which that the concerned SCell is activated. At step 608, the UE 300 attempts to detect the reference signals transmitted by the activated SCell. If the UE 300 is not able to detect the reference signals transmitted on the RSREs 103 of the activated SCell then, at step 610, the UE 300 indicates the non-detection information to the PCell in the eNB 500a through one of L1 signaling, the MAC CE message, the RRC message like UEAssistanceInformation, or the like. After reporting the problem to the eNB 500a, the UE 300 goes back to the step 606 where it may expect de-activation command from the eNB 500a for the concerned SCell and activation of some other configured SCell. If the UE 300 is able to detect the reference signals transmitted on the RSREs 103 of the activated SCell then at step 612, the UE 300 starts receiving the PDSCH transmission scheduled either through a Physical downlink Control Channel (PDCCH) or the ePDCCH on the activated SCell. At step 614, the UE 300 performs the power measurements on the first resource element of the second frequency and the power measurement on the second resource element of the second frequency during the subframes indicated by the period in the L1 command. The first resource element refers to the RSREs 103 and the second resource element refers to the non-RSREs 101.At step 616, if it is determined that the difference between the power measurements on the RSREs 103 and the non-RSREs 101 is less than the threshold received by the UE 300 in the measurement configuration then, at step 618, the average value of the difference or the ratio of subframes with corrupted measurement where the difference is lower than the threshold is reported to the eNB 500a through either UEAssistanceInformation message or new RRC message. At step 620, the UE 300 considers these measurements as clean measurements and used for RRM purpose where the difference between the power measurements on the RSREs 103 and the non-RSREs 101 is greater than the threshold. In an embodiment, the

steps

616, 618, and 620 are performed either at the layer 3 (i.e. RRC layer) or optionally at the physical layer of the UE 300. At step 622, the operations 614 to 620 are repeated for the period where the SCell remains activated. When the SCell is de-activated, the UE 300 operation reverts back to the step 606.

The various actions, acts, blocks, steps, or the like in the method 600 may be performed in the order presented, in a different order or simultaneously. Further, in some embodiments, some of the actions, acts, blocks, steps, or the like may be omitted, added, modified, skipped, or the like without departing from the scope of the invention.

FIG. 7 is a flow diagram depicting the operation of eNB 500a when the UE 300 is configured with the LAA operation with the SCell on the unlicensed carrier, according to embodiments as disclosed herein. At step 702, the eNB 500a receives indicating its capability for support of the licensed band and the unlicensed band including the band combination it supports for carrier aggregation, through the RRC message on the first frequency served by PCell from the UE 300. At step 704, the eNB 500a sends the RRC reconfiguration message on the PCell which includes the SCell configuration on the second frequency and the measurement configuration. The SCell configuration may include one or more SCell(s) associated with the SCell index and the PCI intended to be served by one or more carriers from the unlicensed band. The measurement configuration includes the measurement object, the measurement identities, reporting configuration and threshold to compare the difference of measurement on the first radio resource (i.e. power measurements on the RSREs 103) and the second radio resource (i.e. power measurements on the non-RSREs 101). At step 706, the eNB 500a performs the channel sensing on configured second frequency to determine if any of the carriers from the unlicensed band configured for the UE 300 are free i.e. the eNB 500a performs energy detection on those carriers from the unlicensed band and if it finds the energy detected on one of the carrier is less than the certain threshold then the channel is assumed to be free. For the channel determined to be free and belonging to the SCell configuration of the UE 300, at step 708, the eNB 500a sends the L1 command to the UE 300. The L1 command is in the form of the DCI format or the like and includes at least one ON indication for the free channel associated with the SCell index in the SCell configuration and the period for which that the concerned SCell is activated. The eNB 500a also starts transmitting the reference signals on the activated SCell and starts scheduling the PDSCH transmission if there is data in its buffer for the concerned UE 300. At step 710, if the eNB 500a receives the indication from the UE 300 that it is not able to detect the reference signals then, at step 714, the eNB 500a explicitly sends OFF command through the L1 indication on the PCell to the UE 300 so that the eNB500a can de-activate the concerned SCell. If no indication is received from the UE 300then, at step 710, the eNB 500a continues the transmitting reference signals on the activated SCell and schedules the PDSCH transmission to the concerned UE 300 if the data available for that UE 300 or for other UEs served by concerned activated SCell at step 712. If the eNB 500a receives the report on the PCell , at the step 716,from the UE 300 through either UEAssistanceInformation message or new RRC message indicating that the average value of the clean measurement performed by the UE 300 or the ratio of subframes with the corrupted measurement where the difference is lower than the threshold configured by the eNB 500a then, the eNB 500a goes to the step 714where the eNB 500a may send OFF command to the UE 300 to de-activate the SCell or the eNB 500a may also consider to remove the concerned SCell from the SCell configuration of the UE 300. If no such report is received from the UE 300 then, the eNB 500a operation reverts back to the step 706 after the ON period where the eNB 500a again starts performing channel sensing to check if any carriers configured for the UE 300 are free.

The various actions, acts, blocks, steps, or the like in the method 700 may be performed in the order presented, in a different order or simultaneously. Further, in some embodiments, some of the actions, acts, blocks, steps, or the like may be omitted, added, modified, skipped, or the like without departing from the scope of the invention.

FIG. 8 depicts an average layer 1 measurement reporting to the layer 3 for the RRC filtering, according to embodiments as disclosed herein. According to the 3GPP specification TS 36.133, the UE 300 performs measurements on the reference signals such as CRS at the physical layer i.e. Layer 1 and reports the averaged measurements to the layer 3 as input to the RRC filter with a reporting periodicity typically of 200 ms. During the 200 ms measurement window, it is left to the UE 300 implementation which subframes are used for measurements. Typically, the UE 300 performs measurements on the subframes corresponding to the on duration timer of the configured DRX cycle. However, the averaged measurements reported to the layer 3 shall meet the accuracy performance requirements specified in the TS 36.133. Since the input to the RRC filter is 200 ms, the RRC filtered output measurements are also available every 200 ms for the RRM purpose like mobility handover decisions or SCell management decision when the UE 300 is configured for the carrier aggregation. The RRC filtering is standardized and the configuration of the RRC filter is provided to the UE 300 by the RRC signaling message.

FIG. 9 shows the measurements used for the RRM purpose at the layer 1 performed at the resource elements carrying the reference signals such as CRS and DRS, according to embodiments as disclosed herein. The measurements used for the RRM purpose are the RSRP measurements or the RSRQ measurements. At layer 1, these measurements are performed on the REs carrying the reference signals such as CRS or CSI-RS as shown in the notation "A" of the FIG. 9.

The SCell(s) configured for the UE 300 served by the unlicensed carrier frequency (e.g. from 5.0 GHz band) are not expected to have continuous transmission since the unlicensed carrier is subject to co-existence with other radio access technologies like Wi-Fi. Therefore, the LAA SCell is subject to the cell ON/OFF mechanism for fair co-existence. With cell ON/OFF, the UE 300 expects the transmission of the reference signals on the LAA SCell only during the ON period i.e., when the unlicensed carrier is occupied by the eNB 500a for the LTE transmission. The UE 300 does not expect the transmission of the reference signals on the LAA SCell during the OFF period. For fair co-existence with the Wi-Fi, from system perspective reference signals are not transmitted when the LTE eNB assesses the unlicensed carrier is occupied by the Wi-Fi or other RAT. In Release-12 specification, the cell ON/OFF mechanism introduced discovery signals (DRS) transmissions as shown in the notation "B" of the FIG.9, where the UE 300 may be configured to measure the DRS for the RRM purpose. The UE 300 configured with the DRS based measurements may discover the LAA SCell based on the discovery signals. The discovery signals measurement timing configuration (DMTC) is provided to the UE 300 through the RRC signaling message and has a periodicity of 40ms or 80ms or 160 ms. The DMTC duration is 6ms while the duration of DRS occasion is configurable depending on the configured cell is Time-division duplexing (TDD) or Frequency-division duplexing (FDD) as shown in the notation "B" of the FIG.9. The 1st subframe of the DRS occasion consists of primary synchronization signal (PSS) and secondary synchronization signal (SSS) as depicted in notation "B" of the FIG.9. The subframes in the DRS occasion consist of the cell-specific reference signals (CRS) and additionally the CSI-RS can be configured optionally. Since the LAA SCell would also employ the cell ON/OFF mechanism, the UE 300 configured with such LAA SCell may also be configured with the DMTC. Even though the DRS occasion is periodic, if the carrier is not available for the LTE operation when the DRS occasion occurs then the DRS is not transmitted. This means whenever the LAA SCell is ON and the DRS occasion coincides with the ON period of the LAA SCell then the DRS is transmitted on the LAA SCell otherwise it is not transmitted. Since the DRS configuration is provided to the UE 300 through the RRC signaling message and the physical layer (layer 1) commands on the PCell indicate to the UE 300 whether the configured LAA SCell is activated (ON) or de-activated (OFF), the UE 300 can assume transmission of the DRS during the DRS occasion based on the layer 1 command received on the PCell. The ON period of the LAA SCell depends on the channel occupancy time based on regulation set by different geographical regions of the world. For e.g. Japanese regulations allow channel occupancy time of less than 4 ms when transmissions are done on the carrier frequency belonging to 5.0 GHz band. In an example, the European regulations allow the channel occupancy time of 10 ms when transmissions are done on carrier frequency belonging to 5.0 GHz band. The channel occupancy time also depends on whether co-existence mechanism is provided based on frame based equipment (FBE) or a load based equipment (LBE). However, the DRS occasion may either overlap the channel occupancy time i.e. ON period of LAA SCell i.e., 4 ms or may coincide with a portion of channel occupancy time of LAA SCell when ON period is 10 ms.

FIG. 10 depicts a periodic transmission of the DRS with the DRS occasions on the LTE-U SCells and combining the RRM measurements, according to embodiments as disclosed herein. The FIG. 10 depicts the periodic transmission of the DRS with the DRS occasions marked with shaded circle, where the UE 300 assumes transmission of the DRS on the LAA SCell for the RRM measurement purpose or the cell discovery purpose. These DRS occasions coincide with the ON period of the LAA SCell i.e., unlicensed carrier is available for the LTE operation. The DRS occasions marked with cross where the UE 300 assumes the DRS is not transmitted on the LAA SCell where these DRS occasions coincide with the OFF period of the LAA SCell i.e., the unlicensed carrier is not available for the LTE operation. If the channel occupancy time of the LAA SCell is more than the configured duration of the DRS occasion then, the UE 300 can assume transmission of the reference signals such as CRS in the subframes apart from the subframes where the DRS is transmitted. As shown in the FIG. 10, during the ON period of LAA SCell coinciding with the DRS occasion, the UE 300 performs the layer 1measurement on the reference signals transmitted in the DRS occasion and the layer 1 measurement on reference signals transmitted outside the DRS occasion during the ON period. If the reference signal is of the same type e.g. CRS then the UE 300 shall combine the layer 1 measurement on the reference signals transmitted in the DRS occasion and the layer 1 measurement on the reference signals transmitted outside the DRS occasion during the ON period. The measurement instances marked as the solid circle where the DRS occasion does not coincide with the ON period of the LAA SCell. The UE 300 performs the layer 1 measurement on the reference signals transmitted in the subframes corresponding to the channel occupancy time. As shown in the FIG. 8 and FIG. 10, the UE 300 performs the layer 1 measurements over the measurement window of 200 ms and reports the averaged measurement to the layer 3 for the RRC filtering. During this 200 ms measurement window, the UE 300 combines the measurements performed on the reference signals occurring during the DRS occasion and reference signals occurring in the subframes outside the DRS occasion during the ON period of the LAA SCell. The measurements on the reference signals can be combined when the reference signals are of the same type such as CRS as shown by the notation “A” and by the notation “B” in the FIG. 9. The transmission of the reference signals during the ON period may be like legacy CRS transmission as shown by the notation “A” in the FIG. 9 where the reference signals are transmitted in every subframe of the ON period of the LAA SCell. It may be possible that the transmission of the reference signals is sparse i.e., the reference signals occur only on few subframes of the ON period of the LAA SCell. Regardless of whether the reference signals transmitted on the LAA SCell are legacy CRS or sparse CRS transmission, the UE 300 combines the measurements on these reference signals and measurements on the reference signals occurring in the DRS occasion for the RRM purpose. In an example, the CSI-RS measurements from the DRS occasion can be combined with the CSI-RS measurements on the reference signals during ON period of the LAA SCell outside the DRS occasion.

If the reference signals transmitted during the DRS occasion and those transmitted during ON period outside the DRS occasion are not of the same type then the UE 300 does not combine measurements and report the independent measurements to the layer 3. It may be possible that during the 200 ms measurement window, the layer 1 averaged measurement (RSRP or RSRQ) may not meet the accuracy performance requirements similar to the measurements when continuous transmission of reference signals is assumed. In such scenario, the number of measurement samples for the LAA SCell may be limited due to availability of the reference signals during the 200 ms measurement window, then relaxed accuracy requirements need to be specified in the 3GPP TS 36.133 for these measurements.

In an embodiment, the configured LAA SCell may be configured with relaxed performance requirement indicator (i.e., reduced measurement flag in the measurement object) indicating the UE 300 that discovery of cells on the configured unlicensed carrier is subject to relaxed cell detection time requirement and also the measurements (RSRP/RSRQ) on the concerned unlicensed carrier have relaxed accuracy requirement compared to normal carriers not marked with reduced measurement flag.

In an embodiment, the PCell is on the licensed carrier while the LAA SCell belongs to the unlicensed band, so that the RRM measurements on the PCell are performed assuming continuous transmission of the reference signals whereas the RRM measurements on the LAA SCell are performed assuming discrete transmission of the reference signals. If the accuracy requirements for the PCell RRM measurements are different from the accuracy requirement for the LAA SCell (i.e. relaxed performance and accuracy requirement) then the measurement window for the PCell measurements is different than the measurement window for the LAA SCell measurements. In such scenario, the UE 300 needs to implement a separate layer 3 filter (i.e., RRC filter) for the PCell and the LAA SCell RRM measurements.

In an embodiment, the RRM measurements on the licensed carrier (i.e., PCell) and the RRM measurements on the unlicensed carrier (i.e. LAA SCell) are filtered using separate RRC filters such that configuration parameters for the independent RRC filters are different according to performance requirements.

In an embodiment, an Evolved Universal Mobile Telecommunications System Terrestrial Radio Access Network (EUTRAN) may indicate the UE300 configured with the LTE-U SCells. The LTE-U SCell measurements are compared for intra-frequency and inter-frequency measurements for which indication is received in concerned measurement object that the measurements for this frequency is compared with other frequencies configured from the unlicensed band.

In an embodiment, when the UE 300 receives restricted measurement indication in a measurement object for the concerned frequency then the UE 300 compares the intra-frequency measurements and the inter-frequency measurements for the cells on the concerned frequency with other frequencies configured from the unlicensed band.

FIG. 11 illustrates a sequence diagram for reporting to the PCell about the WLAN)/Wi-Fi ON/OFF status when the NW intends to configure the UE 300 with the LAA operation by adding LTE-U SCell, according to embodiments as disclosed herein. From an interference point of view (i.e. severe in-device interference), it does not seem reasonable that the LTE-U operation and the WLAN/Wi-Fi operation to be active at the same time (i.e. concurrently) within the UE 300. This can lead to severe interference issues which cannot be resolved and hence impact the user data on both LTE-U and Wi-Fi interfaces. Since both the LTE-U and the WLAN will use unlicensed spectrum (e.g. 5.0 GHz band) so ideally it would make sense if they would share the spectrum on timely basis which will be further controlled by the NW. In case where the UE 300 is configured to access the Wi-Fi and the LTE-U radio access concurrently (i.e. at the same time), it can lead to severe in-device co-existence interference problem leading to an erroneous scenario, hence loss of data on both the radio access. Currently there is no mechanism provisioned in the specification through which the NW is aware about the WLAN status in the UE 300 whether it is active or disabled, so that the NW can enable and disable the LTE-U configuration of the UE 300.This WLAN status in the UE 300 can also be used by NW to enable and disable the WLAN configuration of the UE 300 during the LTE-WLAN aggregation. The UE 300 may be supporting the Wi-Fi in the 5.0 GHz band and the user can switch on the same to access data through the Wi-Fi, so in that case there is need to inform the NW about the Wi-Fi activity status in the UE 300 for below mentioned cases.

Case 1: LTE-U SCell is not configured:

In this case, the NW can take decision whether to configure the UE 300 with the LTE-U SCells or not based on the WLAN status indication. The various steps involved in the FIG. 11 are described below.

The UE 300 is operating on the licensed carrier served by the PCell. Due to data demand for the UE 300, the EUTRAN decides to configure the UE 300 for the CA operation using the LTE-U SCell. Before sending the LTE-U SCell configuration, the EUTRAN configures (1102) the UE 300 to provide the WLAN status indication.

The UE 300 is provided with timers for the Wi-Fi trigger status and the Wi-Fi indication. The Wi-Fi trigger status timers have two timers namely, T_WifiTrigger_ON and T_WifiTrigger_OFF which are started when the user turns ON and OFF Wi-Fi respectively. When the user receives the configuration to provide the Wi-Fi status indication it checks whether the Wi-Fi radio (e.g. operating on 5.0 GHz) within the UE 300 is turned ON or OFF. If the WLAN/Wi-Fi radio is turned OFF, the UE 300 starts (1104) the T_WifiTrigger_OFF timer.

On expiry of the T_WifiTrigger_OFF, the UE 300 sends (1106) the indication to the NW about the WLAN status as OFF through the RRC message, the MAC CE, the L1 indication message or the like.

On receiving the Wi-Fi OFF indication from the UE 300, the eNB 500a may take decision to add the LTE-U SCells on the second frequency for configuring the UE 300 with the LAA mode of operation.

The eNB 500s sends (1108) the RRC reconfiguration message with the LTE-U SCell addition to the UE 300 on the PCell. The SCell addition may include one or more SCell(s) associated with SCell index and PCI intended to be served by one or more carriers from the unlicensed band.

Depending on the RRM measurements received for the configured LTE-U SCells and after performing channel sensing eNB 500a may send (1110) the MAC CE message or L1 indication message to activate one or more configured LTE-U SCell(s). Channel sensing at the eNB 500a ensures the fair co-existence of the LTE access and nearby operation of the Wi-Fi APs.

On receiving the activation command, the UE 300 is operating (1112) in the LAA mode of the CA operation and if during the data session through the LTE-U SCell when the user turns ON WLAN/Wi-Fi then, the UE 300 starts (1114) T_WifiTrigger_ON timer.

On expiry of T_WifiTrigger_ON, the UE 300 sends (1116) the indication to the NW on the PCell about the WLAN status as ON through the RRC message, the MAC CE message, the L1 indication message or the like.

On receiving the Wi-Fi ON indication from the UE 300, the eNB 500a may take (1118) decision to deactivate the LTE-U SCell served by the second frequency as one option and wait for further Wi-Fi OFF indication from the UE 300. The eNB 500a may send the MAC CE message or the L1 indication message to deactivate one or more configured LTE-U SCell(s). The eNB 500a may also decide to release the LTE-U SCell configuration for the UE 500a based on the Wi-Fi ON indication.

The eNB 500a may send the RRC reconfiguration message with the LTE-U SCell release as another option. The SCell release may include one or more SCell(s) associated with SCell index intended to release one or more carriers from the unlicensed band.

FIG. 12 illustrates reporting to the PCell about WLAN/Wi-Fi ON/OFF status when the UE 300 is already operating in the LAA mode of operation, according to embodiments as disclosed herein.

Case 2: LTE-U SCell is configured and activated:

In this case, the NW can decide whether to disable (de-activate) the configured LTE-U SCells or release the LTE-U SCell configuration since the user want to access data through the Wi-Fi radio access.

Case 3: LTE-U SCell is configured and deactivated:

In this case, the NW can hold its decision to activate the LTE-U SCell and can wait till the UE 300 indicates the WLAN off status or release the LTE-U SCell configuration.

In any of above cases, the UE 300 needs to inform the NW about Wi-Fi ON/OFF status. The various steps involved in the FIG. 12 are described below.

The UE 300 is operating (1202) in the LAA i.e. PCell on Licensed carrier and SCell on the Unlicensed carrier and WLAN/Wi-Fi is OFF. It is assumed that the EUTRAN has configured the UE 300 to provide WLAN status indication before configuring the UE 300 for the LAA operation through the LTE-U SCell configuration.

It is assumed that the UE 300 is configured (1204) with timers for the Wi-Fi trigger status and the Wi-Fi indication. The Wi-Fi trigger status timers have two timers namely, T_WifiTrigger_ON and T_WifiTrigger_OFF which are started when the user turns ON and OFF the Wi-Fi respectively. When the user turned ON WLAN/Wi-Fi, the T_WifiTrigger_ON is started.

On expiry of T_WifiTrigger_ON, the UE 300 sends (1206) the indication to the NW about the WLAN status as ON through the RRC message, the MAC CE message, the L1 indication message or the like. After receiving the Wi-Fi ON indication from the UE 300, the eNB 500a may take (1208) the decision to deactivate or release the LTE-U SCell and wait for further Wi-Fi OFF indication from the UE300. The eNB 500a may also decide to release the LTE-U SCell configuration for the UE 300 based on the Wi-Fi ON indication.

The eNB 500a may send the RRC reconfiguration message with the LTE-U SCell release as one option or MAC CE message or L1 indication message to deactivate the LTE-U SCell as another option. After completing the data session through the Wi-Fi radio access, when the user turns OFF WLAN/Wi-Fi, the T_WifiTrigger_OFF is started (1210).On expiry of the T_WifiTrigger_OFF, the UE 300 sends (1212) the indication to the NW about the WLAN status as OFF through the RRC message, the MAC CE message, the L1 indication message, or the like.

On receiving the Wi-Fi OFF indication from the UE 300,the eNB 500a takes(1214) the decision to activate the LTE-U SCell if the LTE-U SCell is not released previously and there is still high data demand from the UE 300 on the LTE interface. If the NW has previously released the LTE-U SCell configuration then the eNB 500a may decide to add the LTE-U SCell configuration for the UE 300 based on the Wi-Fi OFF indication. The eNB 500amay send the RRC reconfiguration message with the LTE-U SCell add as one option or MAC CE message or L1 indication message to activate the LTE-U SCell as another option.

The UE 300 may also supports the Wi-Fi operation in both 5 GHz unlicensed band and 2.4 GHz unlicensed band. The above mentioned method or procedure in the FIG.11 and FIG.12 will be applicable for both 5 GHz unlicensed band and 2.4 GHz unlicensed band. So while sending the WLAN status indication, the UE 300may optionally include below mentioned information:

a. Operating Band: It shall indicate the WLAN operating band/frequency i.e. 5 GHz or 2.4 GHz along with ON/OFF indication.

b. WLAN channel number: It shall indicate the WLAN channel number when the status indication is ON so that the NW can take appropriate decision if it receives the channel number or operating frequency.

c. Operation Mode: It shall indicate the type of version/modes of the WLANi.e.it may also indicate the different version of Wi-Fi/WLAN/WiMAX i.e. 802.11b, 802.11g, 802.11a, 802.11n, 802.11ac, 802.16m,802.16a etc.

The above optional fields may not be sent to the NW and only the WLAN status indication is sent when the UE 300 is only operating in 5.0 GHz band. The UE 300 may indicate OFF status if it is active in 2.4 GHz while it is inactive in 5.0 GHz. In the above mentioned signaling option where only the WLAN indication is sent, it is also possible that there may not be any interference issue due to the UE 300 operation in 2.4 GHz unlicensed band, so in that case the UE 300 can do as below:

If (WLAN is operating in 5.0 GHz unlicensed band and is turned ON/OFF)

-Send the WLAN status to the Network

Else if (WLAN is operating in 2.4 GHz unlicensed band and is turned ON/OFF)

-Do not send the WLAN status to the Network or send OFF status

In an embodiment, the UE 300 may not send any WLAN status to the NW when it is operating in 2.4 GHz unlicensed band.

In an embodiment, the Wi-Fi/WLAN indication as mentioned above can be done through the RRC message, the MAC CE message or the like through the Layer 1. The contents of the indication comprise the ON/OFF status and at least one of: the operating band, the WLAN channel number, and the operation mode.

FIGS. 13a to 13c are sequence diagrams illustrating possible ways for the UE 300 to indicate the NW about the WLAN/Wi-Fi ON/OFF status through the RRC message, according to embodiments as disclosed herein. As shown in the FIG. 13a, the RRC connection reconfiguration message is exchanged (1302a) between the UE 300 and the EUTRAN 500b. The NW may configure the UE 300 to provide the WLAN indication through the RRC reconfiguration message. Based on the RRC connection reconfiguration message, the UE sends (1304a) the UEAssistanceInformation to the EUTRAN 500b.

As shown in the FIG. 13b, the RRC connection reconfiguration message is exchanged (1302b) between the UE 100 and the EUTRAN 500b.The NW may configure the UE 300 to provide the WLAN indication through the RRC reconfiguration message. Based on the RRC connection reconfiguration message, the UE 300 sends (1304b) the WLAN indication information to the EUTRAN 500b.

As shown in the FIG. 13c, the RRC connection reconfiguration message is exchanged (1302c) between the UE 100 and the EUTRAN 500b.The NW may configure the UE 300 to provide the WLAN indication through the RRC reconfiguration message. Based on the RRC connection reconfiguration message, the UE 300 sends (1304c) the InDeviceCoexIndiaction information to the EUTRAN 500b.

Indication to the NW through the RRC message:

The UE 300 can indicate the NW about the WLAN/Wi-Fi status through the RRC message. The various possible options are shown in the FIGS. 13a to 13c. The EUTRAN 500b may configure the UE 300 to provide the WLAN indication through the RRC reconfiguration message through new IE say “WLAN indication or WLAN status config”. This configuration is provided to the UE 300 and, the NW comes to know UE 300 is capable of LAA mode of operation. The LAA capable UE 300 may provide WLAN/Wi-Fi status indications in the RRC_CONNECTED in several cases including upon being configured to provide WLAN/Wi-Fi indications by the EUTRAN 500b and upon change of the WLAN/Wi-Fi status operation at the UE 300. The UE 300 can initiate this procedure in below two cases:

a.If configured to provide the WLAN/Wi-Fi indications by the EUTRAN 500b

b.During WLAN/Wi-Fi status from ON/OFF to OFF/ON

Optionally these WLAN/Wi-Fi indications through the RRC message can be further controlled by timer T_WifiIndication, else the UE 300 may end up in sending frequent indication for this WLAN indication. If the current WLAN/Wi-Fi status is different from the one indicated in the last indication through the RRC message and timer T_WifiIndication is not running then initiate transmission of the RRC message through various options as shown in the FIG. 13a to 13c. This timer T_ WifiIndication works as below.

This timer can only be started when transmitting WLAN/Wi-Fi indication as “ON” or “OFF” only. This timer can be configured by the NW through common or dedicated RRC message or can be specific to vendor implementation.

The timers T_WifiTrigger_ON and T_WifiTrigger_OFF can be configured by the NW through dedicated or broadcast messages like SIB or can be specific to vendor implementation. Usually T_WifiTrigger_ON should be of smaller duration as compared to T_WifiTrigger_OFF as once WLAN is ON and the UE 300 is already operating in the LAA mode, then it can cause severe interference so fast network action is required. The T_WifiTrigger_OFF may have larger value than T_WifiTrigger_ON so to provide some time margin if the user turns on the WLAN ON within a very short time, and the T_WifiTrigger_ON and T_WifiTrigger_OFF can work as below.

The NW may configure the UE 300 with either the T_WifiIndication timer or T_WifiTigger_ON and T_WifiTigger_OFF timers. It would be preferable to configure the UE 300 with T_WifiTigger_ON and T_WifiTigger_OFFtimers. The various possible RRC messages through which this indication can be send are listed below.

Option A: UE Assistance Information:

The purpose of this procedure is to inform the E-UTRAN 500b of the UE’s WLAN/Wi-Fi status. The EUTRAN 500b may optionally configure the UE 300 to provide the WLAN indication or status through the RRC reconfiguration message through new IE say “WLAN indication or WLAN status config“. The UE 300 shall send the WLAN status or indication in UEAssistanceInformation message as ON/OFF and other optional fields as mentioned above based on whether WLAN/Wi-Fi is active or not. The UE 300 optionally may start/restart timer when it sends the status. The UE 300 shall only indicate the WLAN status in the UEAssistanceInformationmessage if other already existing fields like powerPrefIndication is not applicable or condition is not triggered to set the powerPrefIndication field or NW has not configured the UE 300 to send the powerPrefIndication field.

Option B: WLAN/Wi-Fi Indication:

The purpose of this procedure is to inform the E-UTRAN 500b of the UE’s WLAN/Wi-Fi status. The EUTRAN 500b may optionally configure the UE 300 to provide the WLAN indication or status through the RRC reconfiguration message through new IE say “WLAN indication or WLAN status config“. The UE 300 sends the WLAN status or indication in the WLAN/Wi-Fi Indication message as ON/OFF and other optional fields as mentioned above based on whether WLAN/Wi-Fi is active or not. The UE 300 optionally may start/restart timer when it send the status.

Option C: InDeviceCoexIndication:

The purpose of this procedure is to inform the E-UTRAN 500b of the UE’s WLAN/Wi-Fi status. The EUTRAN 500b may optionally configure the UE 300 to provide the WLAN indication or status through the RRC reconfiguration message through new IE say “WLAN indication or WLAN status config“. The UE 300 shall send the WLAN status or indication in the InDeviceCoexIndication message as ON/OFF and other optional fields as mentioned above based on whether the WLAN/Wi-Fi is active or not. The UE 300 optionally may start/restart timer when it send the status. The UE 300 shall only indicate the WLAN status in the InDeviceCoexIndication message if other already existing fields like affected Carrier is not applicable or condition is not triggered to set this field or the NW has not configured the UE 300 to send this field.

Indication to the NW through MAC Control element (CE):

New MAC CE needs to be defined to indicate the NW whether WLAN is ON/OFF. A Logical Channel identification (LCID) can be defined from the current reserved values (01011-11000). The WLAN ON/OFF MAC control element is identified by a MAC PDU subheader with the LCID. Different LCID can represent as WLAN ON/OFF. The status information can be signaled through 1 bit, where value of bit 0 refers to the WLAN ON and bit 1 refers to the WLAN as OFF. The operating band information can be signaled through 1 bit, where value of bit 0 refers to 2.4 GHz operation and value of bit 1 refers to 5.0 GHz operation. The WLAN channel number may be 3 bits or 4 bits while the operation mode may be 3 bits or 2 bits. The MAC CE therefore is 8 bits and octet aligned.

Indication to the NW through Layer 1:

The UE300 can alternatively choose to inform the NW through a Physical Uplink Control Channel (PUCCH) or a Physical Uplink Shared Channel (PUSCH) channel, where through 1-bit it can identify whether the WLAN is ON/OFF. In case of Layer 1 on the PUCCH of the PCell, only 1-bit ON/OFF indication seems sufficient. In case of the PUSCH indication on the PCell in addition to 1-bit ON/OFF indication other optional fields as mentioned above may also be included.

In all the above three indications, the NW can take a decision to perform one of configuration, release, activate or deactivation of the LTE-U SCells.

Indication of supporting WLAN indication through UE-EUTRA-Capability:

The UE 300 can inform the NW through UE-EUTRA capability message whether it supports the WLAN indications or not in addition to the LAA support indication. A new IE say “wlanInd” can be added in the capability message. The NW on receiving this capability indication can either configure the UE 300 to provide the WLAN indication through the RRC reconfiguration message or the UEInformationRequest message. The UE 300 may indicate to the NW as mentioned above through the RRC message or through the MAC CE message or the layer 1 indication on the PCell. The NW on receiving the same will take care of indications, the UE 300 while configuring LTE-U SCells. The WLAN indication capability can also be indicated through the FGI bits.

In an embodiment, whenever the user turns ON the WLAN and the UEs 300 are operating in the LAA, then the UE 300 can deactivate the LTE-U cell and inform the NW through the MAC CE message or it should stop reporting Channel Quality Indication (CQI)/report the CQI with low value so that the NW deactivate the LTE-U SCell.

FIG. 14a and 14b illustrates a sequence diagram for RRC signaling options to indicate the NW about the WLAN/Wi-Fi ON/OFF status through the RRC message, according to embodiments as disclosed herein. In this signaling option, the UE 300 receives (1402a and 1402b) the RRC reconfiguration message with the LTE-U SCell configuration. The SCell addition may include one or more SCell(s) associated with SCell index and PCI intended to be served by one or more carriers from the unlicensed band. On receiving the SCell addition configuration, the UE 300 checks the Wi-Fi/WLAN status through the controller 302b coordinating the cellular radio 302a and ISM radio 302c and send (1404a and 1404b) the RRC connection reconfiguration complete message with a new IE WLAN status which comprises ON/OFF status bit and may consist of optional fields. On receiving the RRC connection reconfiguration complete message, the EUTRAN 500b may optionally configure (1406a and 1406b) the UE 300 to provide further WLAN indication status through the RRC reconfiguration message. Based on the status in the RRC connection reconfiguration complete message, the EUTRAN 500b may activate or keep de-activated the added LTE-U SCells. On receiving the configuration for providing further Wi-Fi/WLAN status indications, the UE 300 can provide (1408a) the WLAN indication if the new indication is different from the one provided in the RRC connection reconfiguration complete message.

In an embodiment, after receiving RRC reconfiguration complete with the WLAN status, the NW may send the RRC message to the UE 300, where the RRC message includes the UE 300 information request as shown in the FIG. 14b asking for the WLAN status. The UE 300 will respond (1408b) about the WLAN status through the UE300 information response if the new indication is different from the one provided in the RRC connection reconfiguration complete message.

In an embodiment, the UE is operating on a licensed carrier served by the PCell. Due to data demand for the UE, an Evolved Universal Terrestrial Access Network (EUTRAN) decides to configure the UE for a carrier aggregation (CA) mode based on LAA operation using a LTE-U SCell (i.e. unlicensed carrier served as SCell). Before sending the LTE-U SCell configuration, the EUTRAN configures the UE to provide the RRM measurements for the LTE-U SCell. On receiving the RRM measurements from the UE, EUTRAN may decide to configure the UE with one or more LTE-U SCell(s) if the ratio of subframes served on LTE-U SCell encountered with the corrupted measurement is less than a threshold. EUTRAN sends the RRC reconfiguration message with the SCell addition message to the UE on the PCell. The SCell addition message may include one or more SCell(s) associated with SCell index and physical cell identity (PCI) intended to be served by one or more carriers from the unlicensed band. Depending on the RRM measurements received from the UE for the configured LTE-U SCells and after performing channel sensing eNB may send the Media Access Control (MAC) Control Element (MAC CE) message or L1 indication message to activate one or more configured LTE-U SCell(s). On receiving the activation command, the UE is operating in the Licensed Assisted Access (LAA) mode of the CA operation i.e., the PCell on the licensed carrier and the SCell on the unlicensed carrier. The UE is uplink synchronized with the PCell of the licensed carrier. Assuming that the activated LTE-U SCell does not belong to a primary Timing Advance Group (pTAG) and belongs to a secondary TAG (i.e. sTAG) then there is need of the uplink synchronization between the UE and the SCell served by unlicensed carrier. EUTRAN sends a Physical downlink Control Channel (PDCCH) order for the specific LTE-U SCell belonging to the sTAG. On receiving the PDCCH order, the UE initiates the Random Access procedure on the activated LTE-U SCell.

FIG. 15 illustrates a sequence diagram of the UE behavior when the UE 300 is not able to send the RACH preamble due to unavailability of the LTE-U channel, according to a prior art. The LTE-U channel may not be available always for scheduling the UE 300 as it is using unlicensed spectrum which is being shared from the system perspective along with the WLAN/Wi-Fi APs in the neighborhood of the LTE-U cell. With LTE-U SCell operation, it is possible that the UE 300 may not able to access the LTE-U channel for the uplink transmission as a result it will not be able to transmit any data or RACH preamble to the network.

The UE 300 is operating in the LAA mode of the CA operation i.e., the PCell on Licensed carrier and SCell on Unlicensed carrier. The UE 300 is uplink synchronized (1502) with the PCell of licensed carrier. Assuming that the configured LTE-U SCell does not belong to a pTAG and belongs to a sTAG then there is need of the uplink synchronization between the UE 300 and the SCell served by unlicensed carrier then, the NW sends (1504) the PDCCH order for the specific LTE-U SCell belonging to the sTAG. On receiving the PDCCH order from the serving cell, the UE 300 initiates a Random Access procedure on this configured SCell. The Physical layer (PHY) or layer 1 of the UE 300 sends (1506) the indication to the MAC layer so that it can initiate (1508) the Random access procedure on the LTE-U SCell. The MAC on receiving the same shall do the following.

Set the PREAMBLE_TRANSMISSION_COUNTER to 1

Proceed to the selection of the Random Access Resource and to transmit the Random Access Preamble set PREAMBLE_RECEIVED_TARGET_POWER to preambleInitialReceivedTargetPower + DELTA_PREAMBLE + (PREAMBLE_TRANSMISSION_COUNTER - 1) * powerRampingStep; Instruct the physical layer to transmit a preamble using the selected PRACH, corresponding RA-RNTI, a preamble index and a PREAMBLE_RECEIVED_TARGET_POWER.

The UE 300 determines (1510) the LTE-U channel accesses on the SCell based on the channel sensing. Once the physical layer receives instruction from the MAC layer for the preamble transmission then upon performing channel sensing the UE 300 may or may not have access to that particular LTE-U channel since the LTE-U channel is subject to fair co-existence with the Wi-Fi. If access to the channel is available then the PHY layer sends (1512) the preamble on the LTE-U SCell using the dedicated preamble provided by the network. If the channel is not free, then the PHY layer shall not be able to perform (1514) the RACH on the LTE-U SCell and drop the RACH preamble at the layer 1.

This dropping of preamble transmission happen due to the non-availability of the LTE-U access channel, so there is need to define new procedure which will take care of such scenario and ensure that the UE 300 shall not increase the preamble transmission power in the next retransmission to avoid any interference issues or power consumption issues. Therefore, a new trigger needs to be introduced for the preamble dropping at the layer1 due to unable to access the LTE-U channel.

FIG. 16 is a flow diagram illustrating a method 1600 for handing the RACH procedure at the UE 300, according to an embodiment as disclosed herein. At step 1602, the method 1600 includes initiating the RACH procedure on the secondary cell served by the second frequency from the unlicensed band upon activation. In an embodiment, the UE 300 is configured with the secondary cell on the second frequency by the primary cell, when the ratio of subframes encountered with the corrupted measurement is less than the threshold. In an embodiment, the method 1600 allows the processor unit 304 to initiate the RACH procedure on the secondary cell served by the second frequency from the unlicensed band upon activation.

At step 1604, the method 1600 includes preparing the RACH preamble transmission to obtain uplink synchronization on the secondary cell. In an embodiment, the method 1600 allows the processor unit 304 to prepare the RACH preamble transmission to obtain the uplink synchronization on the secondary cell. At step 1606, the method 1600 includes detecting that one of the activated secondary cell served by the second frequency is unavailable based on the channel sensing and the transmission power is limited to perform parallel RACH on the primary cell and the secondary cell. In an embodiment, the method 1600 allows the processor unit 304 to detect one of the activated secondary cell served by the second frequency is unavailable based on the channel sensing and the transmission power is limited to perform parallel RACH on the primary cell and the secondary cell.

At step 1608, the method 1600 includes dropping the transmission of the RACH preamble. In an embodiment, the method 1600 allows the processor unit 304 to drop the transmission of the RACH preamble. At step 1610, the method 1600 includes indicating the power suspension for not incrementing the preamble transmission counter to avoid the transmission power ramping. In an embodiment, the method 1600 allows the processor unit 304 to indicate the power suspension for not incrementing the preamble transmission counter to avoid the transmission power ramping. At step 1612, the method 1600 includes starting the timer for holding the RACH preamble. In an embodiment, the method 1600 allows the processor unit 304 to start the timer for holding the RACH preamble.

The various actions, acts, blocks, steps, or the like in the method 1600 may be performed in the order presented, in a different order or simultaneously. Further, in some embodiments, some of the actions, acts, blocks, steps, or the like may be omitted, added, modified, skipped, or the like without departing from the scope of the invention.

FIG. 17 illustrates a sequence diagram of the UE behavior when the UE 300 is not able to send the RACH preamble due to unavailability of the LTE-U channel, according to embodiments as disclosed herein. The UE 300 is uplink synchronized (1702) with the PCell of the licensed carrier. Assuming that the configured LTE-U SCell does not belong to the pTAG and belongs to the sTAG then there is need of the uplink synchronization between the UE 300 and the SCell served by the unlicensed carrier then, the eNB 500a sends (1704) the PDCCH order for the specific LTE-U SCell belonging to the sTAG. On receiving the PDCCH order from the serving cell, the UE 300 initiates the Random Access procedure on the configured SCell. The PHY layer or layer 1 of the UE 300 sends (1706) the indication to the MAC layer so that it can initiate (1708) the Random access procedure on the LTE-U SCell. The UE 300 determines (1710) the LTE-U channel accesses on the SCell based on the channel sensing.

Once the physical layer receives instruction from the MAC layer for the preamble transmission then upon performing channel sensing the UE 300 may or may not have access to that particular LTE-U SCell channel since the LTE-U channel is subject to fair co-existence with the Wi-Fi. If access to the channel is available then the PHY layer sends (1712) the preamble on the LTE-U SCell using the dedicated preamble provided by the network. If the channel is not free, then the PHY layer shall not be able to perform (1714) the RACH on the LTE-U SCell and drop the RACH preamble at the layer 1. The PHY layer sends (1716) indicates the preamble dropping or power suspension to the MAC layer.

In an embodiment, once the physical layer drops the preamble transmission for the LTE-U SCell at the physical layer, it should indicate the preamble transmission drop to the MAC layer for preamble dropping or power suspension due to unavailability of the LTE-U access channel. On receiving the preamble transmission drop, the MAC layer shall not increment the PREAMBLE_TRANSMISSION_COUNTER and should try for the RACH again at the next PRACH opportunity without increasing the preamble power.

New trigger for preamble dropping or power suspension need to define in case UE 300 is performing the RACH procedure on the LTE-U channel and it is unable to perform the RACH due to the non-availability of the LTE-U channel, so that the MAC layer can take appropriate action.

RACH handling during preamble dropping /power suspension at the layer 1:

In 3GPP Release 12 it has agreed that the preamble may be dropped in power limited scenarios and in this case the UE 300 shall not increase the preamble transmission power.

Once preamble dropping happens at the layer 1, there is no need for power ramping for the next retransmission and as per Release-12 MAC specification PREAMBLE_TRANSMISSION_COUNTER is not incremented based on the power suspension indication sent (1706) by the PHY layer to the MAC layer.

In an embodiment, when the PHY layer decides to drop preamble transmission due to unavailability of the LTE-U channel (SCell) access for the preamble transmission during the RACH procedure then the PHY layer sends the power suspension indication to the MAC layer.

The maximum retries for the preamble transmission is controlled by the NW configured parameter preambleTransMax such that the variable PREAMBLE_TRANSMISSION_COUNTER is incremented by one whenever the UE 300 does not receive the Random Access Response (RAR) or Contention Resolution is considered not successful.

This variable is also used to calculate the RACH preamble transmission power as shown below.

PREAMBLE_RECEIVED_TARGET_POWER = preambleInitialReceivedTargetPower + DELTA_PREAMBLE + (PREAMBLE_TRANSMISSION_COUNTER - 1) * powerRampingStep;

Since the UE 300 does not increment thePREAMBLE_TRANSMISSION_COUNTER” when the power suspension indication is received at the MAC layer, the UE 300 holds the dedicated RACH resources (preamble provided through the PDCCH) for long duration, which is not good from the system point of view.

There is a need to introduce a new UE behavior which will take care of the UE 300 not holding the dedicated preamble for long duration when preamble dropping happens at the layer1 in above mentioned LTE-U scenario or some other scenario like power limitation.

FIG. 18depicts the operation 1800 of the UE 300 when the UE 300 is not able to send the RACH preamble due to the unavailability of the LTE-U channel or the power limited or some other scenario when preamble transmission is dropped by the PHY layer, according to embodiments as disclosed herein. At step, 1802, the UE receives the PDCCH order to perform the RACH on the SCell and the UE 300 initiates the Random access procedure on the configured SCell. In an embodiment, the UE 300 may initiate the parallel RACH procedure based on various RACH triggers like synchronization, UL/DL data, or the like.

At step 1804, the MAC layer initiates the RACH procedure by incrementing the preamble counter, calculating the preamble transmission power, and instructing the physical layer to transmit the RACH preamble. At step 1806, based on the channel sensing mechanism, the physical layer checks whether the LTE-U channel is available on the SCell to send the RACH preamble message or the UL power is not limited to perform the parallel RACH procedure on the primary cell and the secondary cell.

In case, the UE 300 is not able to meet the criteria as mentioned above i.e., if the LTE-U channel is not available or there is issue due to power then, at step 1808, the physical layer indicates the preamble dropping or power suspension to the MAC layer. At step 1812, the UE 300 determines whether the T_Holdpreamble timer is expired.

At step 1814, based on received power suspension indication, the MAC layer starts the timer T_HoldPreamble if the timer T_HoldPreamble is not running. This timer can be either configured by the NW or can be calculated by the UE 300. In case the timer T_HoldPreamble is already expired then, at step 1824, the UE 300 considers that the RACH procedure is not successful and the UE 300 may inform to the PCell that the timer has expired so that the dedicated preamble can be allocated to some other UE. The UE 300 may inform the NW about the expiry of timer T_HoldPreamble through the RRC message, the MAC CE message, the L1 indication message or the like.

At step 1816, based on the received power suspension indication, if the timer is not expired then, the UE 300 starts the timer T_HoldPreamble if not running, and the UE 300 does not increment the PREAMBLE_TRANSMISSION_COUNTER. This process will ensure that UE 300 did not increment the preamble transmission power and it will reuse the value which was used for preamble transmission in a previous trail (i.e. when preamble was dropped by the layer 1). The UE 300 attempts re-transmission of preamble in the next PRACH opportunity and accesses the availability of the LTE-U channel or check if it is not power limited.

At step 1810, if the channel is available or there is no issue due to power then the physical layer transmits the preamble using the selected PRACH resource and it follows the RACH procedure as defined in the Rel-12 3GPP TS 36.321. At step 1818, the UE 300 determines whether the Random access response or the PDCCH with grants are received. If the UE 300 receives the Random access response or the PDCCH with grants then, at step 1820, the RACH procedure is successful. In that case the UE 300 stops the timer T_HoldPreamble or T_HoldCounter (if running) and reset the timer value.

If the UE 300 did not receive the Random access response during Contention free Random Access procedure and timer T_HoldPreamble is running then, at step 1822, the UE 300 should not stop or reset the T_HoldPreambletimer and go to increment the PREAMBLE_TRANSMISSION_COUNTER.

If the UE 300 does not receives the Random access response or the PDCCH with grants or the contention resolution message (i.e. MSG 4 during Contention based Random Access procedure and timer T_HoldPreamble is running), then the UE 300 should not stop or reset T_HoldPreambletimer and go to the increment the counter to increment the PREAMBLE_TRANSMISSION_COUNTER.

If the T_HoldPreamble timer has expired then, at step 1824, the UE 300 considers that the RACH procedure is not successful and it may informs to the PCell that the timer has expired.

T_HoldPreamble Timer or T_holdCounter timer or Txxx:

This timer which is controlling the RACH procedure during the power suspension or the preamble dropping at the layer 1. The timer mentions the maximum duration of the UE 300, such that the UE 300 can hold the dedicated preamble resources or maximum time UE 300 can retry for the RACH procedure once preamble dropping happen at the layer 1 due to non-availability of the LTE-U channel or the power limitation while performing the RACH. The timer can be either configured by the NW or can be calculated by the UE 300.

Option A: UE calculate the timer value:

The timer can be calculated internally by the UE 300 as below

T_HoldPreamble = (preambleTransMax - PREAMBLE_TRANSMISSION_COUNTER) * Ra-ResponseWindowSize + Scaling Factor

Where preambleTransMax and Ra-ResponseWindowSize is provided in SIB2.

PREAMBLE_TRANSMISSION_COUNTER: Counter UE maintain for RACH procedure.

Scaling Factor: This value can be provided by the NW in the broadcast manner or the dedicated RRC message or through the MAC CE message or calculated by UE 300 internally on basis of multiple RACH opportunity in different sub frames/frames. The scaling factor ensures that the T_HoldPreamble timer did not get expired before making more than one attempts of RACH as configured by the NW.

If this timer expires, then the UE 300 may inform to the PCell that the timer has expired so that the dedicated preamble can be allocated to some other UE. The indication to the NW can be done through new/existing RRC message or MAC CE message which will indicate this timer has expired and go on the PCell or the SCell. The indication can also be sent through the layer 1.

Option B: NW provides the scaling factor but UE 300 calculates the timer value:

The NW may choose to provide the scaling factor which is used to calculate the timer value. If this timer expires then, the UE 300 may inform to the PCell that the timer has expired so that the dedicated preamble can be allocated to some other UE.

Option C: NW provides the timer value:

Alternatively, the timer T_HoldPreamble can be configured by the NW and can be started as soon as the MAC layer obtains the preamble dropping indication from the layer 1 while the timer is not running. In this case, the UE 300 can reuse the timer value as provided by the NW. This timer can be configured by the NW through the broadcast message or the dedicated RRC message. In this case, it may not be needed to inform the NW at the expiry of the timer because the NW would have an idea about the expected expiry of timer with reference to the time when the PDCCH order is provided to the UE 300.

Option D: PDCCH order indicate T_HoldPreamble timer value:

Once the NW provided the PDCCH order for the RACH it can also share the validity of these resources. This information can come in any of DCI where new field say validity can be mentioned. Alternatively it can also come in the MAC control element.

T _HoldPreamble Timer or T_HoldCounter timer or Txxx works in below way:

Section 5.1.4 in Rel-12 TS 36.321 specification gets affected as follows with the introduction of T_HoldPreamble.

Section 5.1.5 in Rel-12 TS 36.321 specification gets affected as follows with the introduction ofT_HoldPreamble.

Adding new parameter in preamble power calculation:

A new parameter say Delta or Factor can be introduced in existing preamble power calculation as shown below. Once the physical layer indicates the power ramping suspension indication/preamble dropping to upper layers, set Delta = 1, else set it as zero.

The random-access procedure shall be performed as follows:

-set PREAMBLE_RECEIVED_TARGET_POWER to preambleInitialReceivedTargetPower + DELTA_PREAMBLE + (PREAMBLE_TRANSMISSION_COUNTER - 1 - Delta) * powerRampingStep; Reset this variable Delta or factor in next RACH trail.

Activation and Deactivation of the LTE-U SCells through layer 1 command:

The LTE channel may not be available always for scheduling to the UE 300 as it is using the unlicensed spectrum which is being shared from the system perspective along with the WLAN/Wi-Fi APs in the neighborhood of the LTE-U cell. The UE 300 may not be aware about the channel (resource) sharing or allocation between the LTE-U and the WLAN, so it may keep monitoring the PDCCH of the configured LTE-U SCell continuously. This continuous monitoring/decoding on the LTE-U SCell may cause increase in the UE 300 power consumption and may also cause interference for the ongoing WLAN/Wi-Fi activities (if active). Moreover, the HARQ retransmission issues may occur at the time when the UE 300 is expecting retransmission it may not get that the LTE-U channel as that subframe/slot/frame may be accessed by the WLAN.

There is need to define the behavior where the UE 300 should be aware that when the LTE-U SCell can carry the data or it is required to monitor the PDCCH. To do the same there is a need to do fast activation/deactivation of the SCells which can reduce the delay for data resumption and also take care of some of above mentioned problems. Currently the network activates and deactivates the SCell(s) through the MAC control element. Activation/Deactivation through the MAC CE requires the MAC PDU and further decoding of the PDSCH which causes delay i.e., typically it takes 64ms to activate or de-activate the SCell through the MAC CE message.

To avoid the delay in data resumption on the LTE-U SCells, there is a need to activate or deactivate the LTE-U SCells through the Physical layer signaling itself. The physical layer signaling will be more suitable for the fast ON/OFF of the LTE-U SCells through the PDCCH by introducing new DCI formats or extending existing DCI formats. The multiple options to indicate activation/On and Deactivation/OFF of the LTE-U cells are mentioned below.

Option 1: Defining new DCI format e.g.5A/1E/2E/3B/4A/5

There is need to define new DCI format which is used for indicate On/Off for the LTE-U SCells. The various fields present in this DCI format are as below. This new format can be defined in multiple way as mentioned below

Option 1a: On period/timer(3-bit) and activation/deactivation of multiple SCells (7-bit)

SCellIndex is signaled through the RRC message when the SCell addition is performed.

Each bit position of the SCell Indicator indicates whether the one or more added SCell indicated by the SCellIndex through the RRC message is activated or de-activated. Bit value 0 indicates the de-activation/OFF and Bit value 1 indicates the activation/ON.

Option 1b: On period/timer(3-bit) and activation of single SCell(3bit)

SCell Index field indicates which added SCell indicated by the SCellIndex through the RRC message is activated.

Option 1c: On period/timer(3-bit) and activation/deactivation of single SCell(3bit) and Flag(1-bit)

SCellIndex is signaled through the RRC message when SCell addition is performed.

SCell Index field indicates which added SCell indicated by the SCellIndex through RRC is activated or de-activated using the Flag_Type bit.

Option 1d: Activation/decativation of mutiple SCells (7-bit)

Each bit position of the SCell Indicator indicates whether the one or more added SCell indicated by the SCellIndex through the RRC message is activated or de-activated. Bit value 0 indicates the de-activation/OFF and the Bit value 1 indicates activation/ON.

Option 1e: Activation/deactivation of the single SCell(3bit) and Flag(1-bit)

SCell Index field indicates which added the SCell indicated by the SCellIndex through the RRC message is activated or de-activated using the Flag_Type bit.

Option 2: Adding new fields in existing DCI format like 1A/2A/3A etc.

New field can be added in existing DCI format which can be used in multiple ways. The example is taken with one particular DCI format but it can be applicable in all the existing formats.

In an example, the DCI format 2A new field Flag indicator and SCell index can be added in the 3GPP TS 36.212 section 5.3.3.1.5A which can be impacted as below.

The same is valid for other DCI formats mentioned in different section of specification. Moreover the different options as mentioned in Option 1 (1a ~ 1e) is valid here also.

Option 3: Reuse the existing DCI formats by extending their functionality

In this case, new condition can be added in the DCI format like below. The example is taken with one particular DCI format but it can be applicable in all the existing formats. In 3GPP TS 36.212 section 5.3.3.1.5A can be impacted as below:

Option 4: Reusing the carrier indicator field in DCI format with addition of new fields:

In all DCI formats, the carrier indicator field is present which is 3bits and is only used when a Component Carrier Selection (CCS) is configured. If the CCS is not configured then the proposed technique can reuse the carrier indicator field as below by adding new parameters in the DCI format. The example is taken with one particular DCI format but it can be applicable in all the existing formats. In 3GPP TS 36.212 section 5.3.3.1.5A can be impacted as below:

Option 5: Adding the timer which will activate/deactivate the SCell to deactivate/activate state

There are mutiple ways through which this timer can be used

1.In this case, the activation/decativation will hold true until the timer expires as provided in the DCI.

2.This timer can be applicable to all configured SCells or specific SCell provided by the NW. As soon as the UE 300 obtains this value it should start the timer and then change the original status i.e., should be change from On/Off to Off/On.

3.Once the UE 300 obtains the DCI it should immediately change the status of the SCell status On/Off to Off/On and start the timer. Once this timer is expired, the SCell will again change fromOn/Off to Off/On

New field can be added in the existing DCI format which can be be used in mutiple ways. The example is taken with one particluar DCI fomat but it can be applicable in all the existing formats. In 3GPP TS 36.212 section 5.3.3.1.5A can be impacted as below:

Same is applicable for other DCI format.

The all above mentioned options may be used to extend any one of the DCI formats whose payload is less and after extending the payload becomes equal to the maximum payload of Rel-12 DCI format.

UL HARQ and Retransmission procedure:

FIG. 19a depicts the UL HARQ operation for the LTE-U SCell, according to a prior art. The UL HARQ operation for the FDD carrier is synchronous in nature which means if the initial transmission on the PUSCH of the UL carrier is performed on the subframe n, then the ACK/NACK for the concerned transmission is sent on the DL carrier at subframe“n+4” by a Physical channel HybridARQ Indicator Channel (PHICH) channel. If the HARQ feedback through the PHICH is a ‘NACK’ then the retransmission for the corresponding initial transmission occurs on the subframe‘n+4’ with reference to the reception of the PHICH. This means for an initial transmission on subframe‘n’ the 1st retransmission happens on subframe ‘n+8’ if the HARQ feedback is a ‘NACK’.

Assuming the UL transmission occurs on the UL LTE-U SCell carrier on the subframe ‘n’, then the corresponding ACK/NACK shall be sent on the DL LTE-U SCell at subframe ‘n+4’ which may not be possible because the DL subframe ‘n+4’ is unavailable for the LTE access since the DL carrier is from the unlicensed band and subject to fair co-existence with the Wi-Fi or the like. Even if HARQ feedback is possible on the PHICH on the DL subframe ‘n+4’ the 1st re-transmission on the UL LTE-U SCellcarrier‘n+4’ subframe thereafter may not be possible. There is a need to address the HARQ feedback and re-transmission issue for the UL transmission on the LTE-U SCell.

The simplest solution to address the UL HARQ operation on the LTE-U SCell is to support fixed number of the re-transmissions without the HARQ feedback on the PHICH. The UE 300 shall transmit the fixed number of re-transmissions regardless of the PHICH. This could be realized with two options as shown in the FIG 19b and the FIG 19c respectively.

FIG. 19b and 19c depict the UL HARQ operation for the LTE-U SCell, according to embodiments as disclosed herein. As depicted in FIG 19b, the UE 300 is configured with the periodic transmission opportunity every Kth subframe with reference to the initial transmission. The number of periodic opportunity ‘R’ is also configurable such that if the initial transmission occurs on subframe ‘n’ then the transmission opportunity occurs periodically at subframe number ‘n+K’, ‘n+2K’….’n+RK’. The UE 300 is also configured with the fixed number of retransmission count ‘N’ such that N < R. It is possible that the UE 300 may not able to perform retransmission at the rKth periodic opportunity due to the unavailability of the LTE-U channel. However, by configuring R>N, the probability UE 300 has more than one retransmission opportunity is increased as shown in the FIG.19b. The UL HARQ parameters like periodic transmission opportunity period K, number of periodic opportunities R and number of retransmission count N are configured to the UE 300 through RRC signaling message from the PCell.

When the UE 300 receives the grant for the initial transmission and the periodic transmission opportunities get activated for the UE 300 because the relation between the grant on the PDCCH and UL transmission on the PUSCH is also ‘n+4’. The parameter R may also include the initial transmission opportunity. After performing fixed number of retransmissions, the eNB 500a may dynamically allocate the transmission opportunities to some other UEs. The time-frequency resources used for the initial transmission remains same for the rKth transmission opportunity so that there is no need to send grant to the UE 300 for each Kth transmission opportunity to indicate the time-frequency resources.

The FIG. 19cis an alternate realization to support fixed number of re-transmissions without HARQ feedback on PHICH. The transmission opportunities for the UL initial transmission and fixed number of re-transmissions are configured continuous. The time-frequency resources used for the initial transmission remains same for Nth retransmission. When the UE 300 receives the grant for the initial transmission, the continuous transmission opportunities for retransmission get activated for the UE 300. The number of retransmission count N is configured to the UE 300 through the RRC signaling message from the PCell. However, the retransmission count can be dynamically overridden with the PDCCH signaling message while providing the initial grant. A one bit or two bit field can be used in the DCI format providing the initial grant on the PDCCH order to override the retransmission count N signaled through the RRC message.

DRX re-transmission Timer:

The UE 300 is configured for the DRX cycle in a connected mode for providing power saving opportunity. When the UE 300 is configured for the carrier aggregation mode operation, the configured DRX cycle is per UE meaning that common across all the activated serving cells of the UE 300. The DRX configuration comprises the parameters like DRX cycle, DRX offset, on duration timer, inactivity timer, re-transmission timer or the like. If the DRX is not configured then after the initial transmission on the DL PDSCH, the UE 300 is allowed to sleep for the HARQ RTT period of 8 ms for the concerned HARQ process and then wake-up to receive the re-transmission if the feedback for the initial PDSCH transmission was the NACK. The UE 300 keeps monitoring the PDCCH for re-transmission until the re-transmission is scheduled after the HARQ RTT period of that HARQ process. To provide opportunity for power saving when the DRX is configured the UE 300 wakes after the HARQ RTT and monitors the PDCCH for a time window according to the configured re-transmission timer. After the expiry of the timer the UE 300 can go to sleep. In the context of the LAA operation, the DRX operation of the UE 300 needs some enhancement to address the management of timers for the DRX taking into account the fact that the LTE-U SCell subframes are divided for the LTE and the WLAN. Currently, the DRX is applicable for all activated component carriers according to the carrier aggregation configuration. Since the PCell is licensed and transmissions are continuous, it is safe to assume for the DRX UE follows the PCell for the on Duration timer and Inactivity timer. However, it is possible that while the drx-Retransmission Timer is running, the LTE-U SCell access is not provided. When the access is provided, if the timer expires then re-transmission is not possible on the LTE-U SCell for the PDSCH. A simple approach is configuring a high value for the re-transmission timer such as psf16 or psf24 i.e. (16 or 24 subframes) which would increase the power consumption of the UE 300. Another alternative is configuring small value for the re-transmission timer but the timer is started per activated serving cell and applicable per component carrier. This would ensure when the LTE-U SCell channel is available (i.e. activated) then only the timer starts running ensuring the re-transmission of the PDSCH within the re-transmission timer window.

Although exemplary embodiments of the present invention have been described in detail hereinabove, it should be understood that many variations and modifications of the basic inventive concept herein described, which may be apparent to those skilled in the art, will still fall within the spirit and scope of the exemplary embodiments of the present invention.

The embodiments disclosed herein can be implemented through at least one software program running on at least one hardware device and performing network management functions to control the elements. The elements shown in the FIGS. 1 to 14, 16 to 18, 19b, and 19c include blocks, elements, actions, acts, steps, or the like which can be at least one of a hardware device, or a combination of hardware device and software module.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

Claims

A method for managing a Radio Resource Management (RRM) measurement at a User Equipment (UE), the method comprising:

receiving, at the UE, from a primary cell a signaling message indicating measurement configuration for at least one second frequency, wherein the second frequency is to be configured as a secondary cell for the UE while the primary cell is served on a first frequency;

performing, at the UE, a power measurement on a first resource element of the second frequency and a power measurement on a second resource element of the second frequency;

determining, at the UE, at least one of a corrupted measurement and a clean measurement based on the power measurement on the first resource element and the power measurement on the second resource element; and

reporting, at the UE, one of a RRM measurement based on the clean measurement and a ratio of subframes encountered with the corrupted measurement.
The method of claim 1, wherein determining, at the UE, at least one of the corrupted measurement and the clean measurement based on the power measurement on the first resource element and the power measurement on the second resource element comprises:

estimating a difference between the power measurement on the first resource element and the power measurement on the second resource element;

comparing the difference with a configured threshold value; and

determining at least one of the corrupted measurement when the difference is less than the threshold value; and the clean measurement when the difference is greater than the threshold value.
The method of claim 2, wherein the configured threshold value is indicated to the UE in a Radio Resource Control (RRC) configuration message.
The method of claim 1, wherein the first frequency belongs to a licensed band, and the second frequency belongs to an unlicensed band, wherein the first resource element is a reference signal resource element and the second resource element is a non-reference signal resource element.
The method of claim 1, wherein the power measurement on the first resource element and the power measurement on the second resource element are performed during a subframe and averaged over a period indicated by number of subframes in the signaling message from the primary cell.
The method of claim 1, wherein the power measurement on the first resource element of the subframes served by the second frequency comprises at least one of a Reference Signal Received Power (RSRP) measurement and a Reference Signal Received Quality (RSRQ) measurement.
The method of claim 1, wherein the power measurement on the second resource element of the subframes served by the second frequency comprises at least one of a received power from a desired transmission source and a contribution of received power due to transmissions from one or more interference sources operating on the second frequency.
The method of claim 1, wherein the method further comprises:

determining, at the UE, a number of subframes encountered with the corrupted measurement from a number of subframes indicated to the UE based on the difference is less than the threshold value;

determining, at the UE, a number of subframes encountered with the clean measurement from a number of subframes indicated to the UE based on the difference is greater than the threshold value;

calculating, at the UE, a ratio of subframes encountered with the corrupted measurements; and

reporting, by the UE, one of the RRM measurement averaged over subframes encountered with the clean measurement, and the ratio of subframes encountered with the corrupted measurement to the primary cell.
A method for handing Random Access Channel (RACH) procedure at a User Equipment (UE), the method comprising:

initiating, at the UE, a Random Access Channel (RACH) procedure on a secondary cell served by a second frequency upon activation, wherein the UE is configured with the secondary cell on the second frequency by a primary cell served on a first frequency when a ratio of subframes served by the secondary cell encountered with a corrupted measurement is less than a threshold;

preparing, at the UE, a RACH preamble transmission to obtain an uplink synchronization on the secondary cell;

detecting, at the UE, that one of the activated secondary cell served by the second frequency is unavailable based on channel sensing and transmission power is limited to perform parallel RACH on the primary cell and the secondary cell;

dropping, at the UE, the transmission of the RACH preamble;

indicating, at the UE, a power suspension for not incrementing a preamble transmission counter to avoid the transmission power ramping; and

starting, at the UE, a timer for holding the RACH preamble.
The method of claim 9, the method further comprising:

detecting, at the UE, status of the timer;

instructing, at the UE, to retransmit the RACH preamble when the timer is running and maximum preamble count is not reached; and

incrementing, at the UE, the preamble transmission counter to facilitate the transmission power ramping.
The method of claim 9, the method further comprising:

detecting, at the UE, status of the timer;

reporting, at the UE, a failure of the RACH procedure to the primary cell when the timer is expired or maximum preamble count is reached.
The method of claim 9, wherein the timer is configured by one of the primary cell and the UE.
The method of claim 9, wherein the first frequency belongs to a licensed band and the second frequency belongs to an unlicensed band.
The method of claim 9, wherein the timer is stopped and reset when one of a random access response message is received comprising an identifier of the RACH preamble transmitted by the UE and a grant is received for an uplink transmission by the UE.
A User Equipment (UE) for managing a Radio Resource Management (RRM) measurement, wherein the UE is configured to:

receive, from a primary cell, a signaling message indicating measurement configuration for at least one second frequency, wherein the second frequency is to be configured as a secondary cell for the UE while the primary cell is served on a first frequency;

perform a power measurement on a first resource element of the second frequency and a power measurement on a second resource element of the second frequency;

determine at least one of a corrupted measurement and a clean measurement based on the power measurement on the first resource element and the power measurement on the second resource element; and

report one of a RRM measurement based on the clean measurement, and a ratio of subframes encountered with the corrupted measurement.
The UE of claim 15, wherein the UE is configured to determine at least one of the corrupted measurement and the clean measurement based on the power measurement on the first resource element and the power measurements on the second resource element by:

estimating a difference between the power measurement on the first resource element and the power measurement on the second resource element;

comparing the difference with a configured threshold value; and

determining at least one of the corrupted measurement when the difference is less than the threshold value; and the clean measurement when the difference is greater than the threshold value.
The UE of claim 16, wherein the configured threshold value is indicated to the UE in a Radio Resource Control (RRC) configuration message.
The UE of claim 15, wherein the first frequency belongs to a licensed band, the second frequency belongs to an unlicensed band; and wherein the first resource element is a reference signal resource element and the second resource element is a non-reference signal resource element.
The UE of claim 15, wherein the power measurement on the first resource element and the power measurement on the second resource element are performed during a subframe and averaged over a period indicated by number of subframes in the signaling message from the primary cell.
The UE of claim 15, wherein the power measurement on the first resource element of the subframes served by the second frequency comprises at least one of a Reference Signal Received Power(RSRP) measurement and a Reference Signal Received Quality (RSRQ) measurement.
The UE of claim 15, wherein the power measurement on the second resource element of the subframes served by the second frequency comprises at least one of a received power from a desired transmission source and a contribution of received power due to transmissions from one or more interference sources operating on the second frequency.
The UE of claim 15, wherein the UE is further configured to:

determine a number of subframes encountered with the corrupted measurement from a number of subframes indicated to the UE based on the difference is less than the threshold value;

determine a number of subframes encountered with the clean measurement from a number of subframes indicated to the UE based on the difference is greater than the threshold value

calculate a ratio of subframes encountered with the corrupted measurements; and

report one of the RRM measurement averaged over subframes encountered with the clean measurement, and the ratio of subframes encountered with the corrupted measurement to the primary cell.
A User Equipment (UE)for handing Random Access Channel (RACH) procedure, wherein the UE is configured to:

initiate a Random Access Channel (RACH) procedure on a secondary cell served by a second frequency upon activation, wherein the UE is configured with the secondary cell on the second frequency by a primary cell served on a first frequency when a ratio of subframes served by the secondary cell encountered with a corrupted measurement is less than a threshold;

prepare a RACH preamble transmission to obtain uplink synchronization on the secondary cell;

detect one of the activated secondary cell served by the second frequency is unavailable based on channel sensing and transmission power is limited to perform parallel RACH on the primary cell and the secondary cell;

drop the transmission of the RACH preamble;

indicate a power suspension for not incrementing a preamble transmission counter to avoid the transmission power ramping; and

start a timer for holding the RACH preamble.
The UE of claim 23, wherein the UE is further configured to:

detect status of the timer;

instruct to retransmit the RACH preamble when the timer is running and maximum preamble count is not reached; and

increment the preamble transmission counter to facilitate the transmission power ramping.
The UE of claim 23, wherein the UE is further configured to:

detect status of the timer;

report a failure of the RACH procedure to the primary cell when the timer is expired or maximum preamble count is reached.
The UE of claim 23, wherein the timer is configured by one of the primary cell and the UE.
The UE of claim 23, wherein the first frequency belongs to a licensed band and the second frequency belongs to a unlicensed band.
The UE of claim 23, wherein the timer is stopped and reset when one of a random access response message is received comprising an identifier of the RACH preamble transmitted by the UE and a grant is received for uplink transmission by the UE.
A computer program product comprising a computer executable program code recorded on a computer readable non-transitory storage medium, wherein the computer executable program code when executed causing the actions including:

receiving, at a User Equipment (UE), from a primary cell a signaling message indicating measurement configuration for at least one second frequency, wherein the second frequency is to be configured as a secondary cell for the UE while the primary cell is served on a first frequency;

performing, at the UE, a power measurement on a first resource element of the second frequency and a power measurement on a second resource element of the second frequency;

determining, at the UE, at least one of a corrupted measurement and a clean measurement based on the power measurement on the first resource element and the power measurement on the second resource element; and

reporting, at the UE, one of a Radio Resource Management (RRM) based on the clean measurement, and a ratio of subframes encountered with the corrupted measurement.
A computer program product comprising a computer executable program code recorded on a computer readable non-transitory storage medium, wherein the computer executable program code when executed causing the actions including:

initiating, at a User Equipment (UE), a Random Access Channel (RACH) procedure on a secondary cell served by a second frequency based on activation, wherein the UE is configured with the secondary cell on the second frequency by a primary cell served on a first frequency when the ratio of subframes served by the secondary cell encountered with a corrupted measurement is less than a threshold;

preparing, at the UE, a RACH preamble transmission to obtain uplink synchronization on the secondary cell;

detecting, at the UE, one of the activated secondary cell served by the second frequency is unavailable based on channel sensing and transmission power is limited to perform parallel RACH on the primary cell and the secondary cell;

dropping, at the UE, the transmission of the RACH preamble;

indicating, at the UE, a power suspension for not incrementing a preamble transmission counter to avoid the transmission power ramping; and

starting, at the UE, a timer for holding the RACH preamble.