Patent Description:
Typical wireless communication systems (e.g., a user equipment device) may employ multi-radio access technologies to perform communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power). Examples of such multiple-access technologies include a code division multiple access (CDMA) technology, a time division multiple access (TDMA) technology, a frequency division multiple access (FDMA) technology, an orthogonal frequency division multiple access (OFDMA) technology, a single-carrier frequency division multiple access (SC-FDMA) technology, a time division synchronous code division multiple access (TD-SCDMA) technology, a global system for mobile communications (GSM) technology, and a long-term evolution (LTE) technology.

As the demand for emerging radio access technologies (e.g., a narrowband internet-of-things (NB-IoT) technology, an enhanced machine-type communication (eMTC) technology, a new radio (NR) technology, etc.) continues to increase, there exists a need for further improvements in terms of performing communication in a network including two or more above-mentioned radio access technologies. Existing wireless communication systems employing the multi-radio access technologies, however, cannot support communications in such a network. Thus, existing wireless communication systems employing the multi-radio access technologies are not entirely satisfactory.

<CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT> are some examples of background art related documents.

The exemplary embodiments disclosed herein are directed to solving the issues relating to one or more of the problems presented in the prior art, as well as providing additional features that will become readily apparent by reference to the following detailed description when taken in conjunction with the accompanying drawings. In accordance with various embodiments, exemplary systems, methods, devices and computer program products are disclosed herein. It is understood, however, that these embodiments are presented by way of example and not limitation, and it will be apparent to those of ordinary skill in the art who read the present disclosure that various modifications to the disclosed embodiments can be made while remaining within the scope of the invention.

In one embodiment, a method performed by a wireless communication node is provided by the independent claim <NUM>.

In a further embodiment, a method performed by a wireless communication device is provided by the independent claim <NUM>.

Various exemplary embodiments of the invention are described below with reference to the accompanying figures to enable a person of ordinary skill in the art to make and use the invention. As would be apparent to those of ordinary skill in the art, after reading the present disclosure, various changes or modifications to the examples described herein can be made without departing from the scope of the invention. Thus, the present invention is not limited to the exemplary embodiments and applications described and illustrated herein.

<FIG> illustrates an exemplary wireless communication network, or system, <NUM> in which techniques disclosed herein may be implemented, in accordance with the present disclosure. Such an exemplary network <NUM> includes a base station <NUM> (hereinafter "BS <NUM>") and a user equipment device <NUM> (hereinafter "UE <NUM>") that can communicate with each other via a communication link <NUM> (e.g., a wireless communication channel), and a cluster of notional cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> overlaying a geographical area <NUM>.

In <FIG>, the UE <NUM> is located within a respective geographic boundary of cell <NUM> that is defined by the BS <NUM> (typically referred to as BS <NUM>'s cell coverage range). Each of the other cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> that are typically referred to as the cell <NUM>'s neighboring cells may include at least one base station operating at its allocated bandwidth to provide adequate radio coverage to its intended users. For example, the neighboring cell <NUM> may include a BS <NUM> that defines a respective cell coverage range of the cell <NUM>. Although the respective cell coverage ranges of the cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> do not overlap with one another in the illustrated embodiment of <FIG>, it is noted that the respective cell coverage ranges of some of the cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> may overlap with one another while remaining within the scope of the present disclosure.

In some embodiments, the BS <NUM> may operate at an allocated channel transmission bandwidth to provide adequate coverage to the UE <NUM>. Such communication nodes may be capable of wireless and/or wired communications, in accordance with various embodiments of the invention.

<FIG> illustrates a block diagram of an exemplary wireless communication system <NUM> for transmitting and receiving wireless communication signals, e.g., OFDM/OFDMA signals, in accordance with the invention. The system <NUM> may include components and elements configured to support known or conventional operating features that need not be described in detail herein. In one exemplary embodiment, system <NUM> can be used to transmit and receive data symbols in a wireless communication environment such as the wireless communication environment <NUM> of <FIG>, as described above.

The BS <NUM> communicates with the UE <NUM> via a communication channel <NUM>, which can be any wireless channel or other medium known in the art suitable for transmission of data as described herein.

In accordance with some embodiments, the UE transceiver <NUM> may be referred to herein as an "uplink" transceiver <NUM> that includes a RF transmitter and receiver circuitry that are each coupled to the antenna <NUM>. Similarly, in accordance with some embodiments, the BS transceiver <NUM> may be referred to herein as a "downlink" transceiver <NUM> that includes RF transmitter and receiver circuity that are each coupled to the antenna <NUM>. The operations of the two transceivers <NUM> and <NUM> are coordinated in time such that the uplink receiver is coupled to the uplink antenna <NUM> for reception of transmissions over the wireless transmission link <NUM> at the same time that the downlink transmitter is coupled to the downlink antenna <NUM>. Preferably there is close time synchronization with only a minimal guard time between changes in duplex direction.

In some exemplary embodiments, the UE transceiver <NUM> and the base station transceiver <NUM> are configured to support industry standards such as the Long Term Evolution (LTE) and emerging <NUM> standards, and the like. It is understood, however, that the invention is not necessarily limited in application to a particular standard and associated protocols.

The BS <NUM> may be an evolved node B (eNB), a serving eNB, a target eNB, a femto station, or a pico station, for example. The UE <NUM> may be embodied in various types of user devices such as a mobile phone, a smart phone, a personal digital assistant (PDA), tablet, laptop computer, wearable computing device, etc. The processor modules <NUM> and <NUM> may be implemented, or realized, with a general purpose processor, a content addressable memory, a digital signal processor, an application specific integrated circuit, a field programmable gate array, any suitable programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof, designed to perform the functions described herein.

A wireless communication system/network (e.g., system <NUM> of <FIG>) that employs a plurality of radio access technologies (RAT's) is provided. For example, the plurality of RAT's include a global system for mobile communications (GSM) technology, a narrowband Internet-of-Things (NB-IoT) technology, an enhanced machine-type communications (eMTC) technology, a long-term evolution (LTE) technology, a new radio (NR) technology, and any of a variety of developed or currently developing radio access technologies. In some embodiments, the BS(s) contained in each cell (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, etc.) of the system <NUM> uses at least one RAT. However, it is noted that one BS may support two or more RAT's and define two respective cells in which different RAT's are used. For example, the cells <NUM> and <NUM> may be both defined by a single BS (either BS <NUM> or BS <NUM>) but different RAT's are used therein. For purposes of clarity, in the following discussions, the BS(s) that define the respective cells using different RAT's are herein referred to as different BS's, for example, the BS <NUM> using a first RAT to define the cell <NUM> and the BS <NUM> using a second RAT, different from the first RAT, to define the cell <NUM>.

<FIG> illustrates an exemplary method <NUM> collectively performed by a first BS, a second BS, and a UE to perform communication in a multi-RAT network, in accordance with the present disclosure. In various embodiments, the operations of the method <NUM> are performed by the respective components illustrated in <FIG>. For purposes of discussion, the following embodiment of the method <NUM> will be described in conjunction with <FIG>. The illustrated embodiment of the method <NUM> is merely an example. Therefore, it should be understood that any of a variety of operations may be omitted, re-sequenced, and/or added while remaining within the scope of the present disclosure.

In some embodiments, the method <NUM> starts with operation <NUM> in which the first BS transmits a message to the UE. In some embodiments, a first cell (e.g., <NUM>) is defined by the first BS (e.g., <NUM>) using a first RAT to have a cell coverage range (e.g., the outline of the cell <NUM> as shown in <FIG>); and a second cell (e.g., <NUM>) is defined by the second BS (e.g., <NUM>) using a second RAT to have a cell coverage range (e.g., the outline of the cell <NUM> as shown in <FIG>). For example, the first RAT may be an NB-IoT technology, and the second RAT may be an LTE technology. In some embodiments, the first cell <NUM>, where the UE <NUM> currently stays, may be referred to as a "serving cell;" and the second cell <NUM> may be referred to as a "neighboring cell. " Further, in such embodiments, the UE <NUM> may be in a radio resource connection (RRC) idle mode, typically knows as an "RRC_IDLE mode.

In some embodiments, the message may be broadcasted as a system information block (e.g., a system information block type <NUM>, a system information block type <NUM>, a yet defined system information block type, or the like) through a broadcast channel. In some embodiments, various information can be indicated by such a message, for example, information indicating whether to stay in either the first cell <NUM> or the second cell <NUM> based on a coverage mode of the UE <NUM> ; information indicating whether to stay in either the first cell <NUM> or the second cell <NUM> based on respective measured reference signal received power (RSRP) values in the first cell <NUM> (typically known as "Qmeas,s") and the second cell <NUM> (typically known as "Qmeas,n") and a predefined offset between the respective RSRP values (typically known as "Qoffsets,n"); information indicating whether to stay in either the first cell <NUM> or the second cell <NUM> based on a predefined cell selection priority value (typically known as "cellReselectionPriority" or "cellReslectionSubPriority"); information indicating whether the first and second cells <NUM> and <NUM> are associated with at least one equivalent public land mobile network (PLMN) identity (typically known as "equivalent PLMN"); respective PLMN identities associated with the first and second cells <NUM> and <NUM>; information indicating whether the first cell <NUM> or second cell <NUM> is access barred; and scheduling information of multimedia broadcast multicast service (MBMS) and/or single cell point to multipoint (SC-PTM) respectively provided by the first cell <NUM> and second cell <NUM> (e.g., respective starting times of the MBMS and/or SC-PTM, the respective RAT's that the MBMS and/or SC-PTM uses, the respective carriers (e.g., frequency locations) that the MBMS and/or SC-PTM uses, etc.).

Next, the method <NUM> continues to operation <NUM> in which the UE receives the message and uses the message to select either the first cell or the second cell to stay.

In the above example where the message includes the information for making selection based on the coverage mode of the UE <NUM>, when the UE <NUM> is in a normal coverage mode, as indicated by the information, the UE <NUM> may select the cell using the eMTC technology; and when the UE <NUM> is in an enhanced coverage mode, as indicated by the information, the UE <NUM> may select the cell using the NB-IoT technology.

In the above example where the message includes the information of equivalent PLMN, when the PLMN identities of the first and second cells <NUM> and <NUM> are equivalent, the UE <NUM> may select the second cell <NUM>. In the above example where the message includes the information of the first cell <NUM>'s and second cell <NUM>'s respectively associated PLMN identities, the UE <NUM> may make the selection between the first and second cells <NUM> and <NUM> based on whether the UE <NUM> are previously authorized to access the respective PLMN's as identified by the PLMN identities.

In the above example where the message includes information of Qmeas,s, Qmeas,n, and Qoffsets,n, the UE <NUM> may use a relationship between Qmeas,s, Qmeas,n, and Qoffsets,n (e.g., whether Qmeas,n minus Qoffsets,n is greater than Qmeas,s by a predefined constant, in which Qoffsets,n can be tunable by the BS <NUM>) to make the selection between the first and second cells <NUM> and <NUM>. For example, when Qmeas,n minus Qoffsets,n is greater than Qmeas,s by the predefined constant, the UE <NUM> may switch to the second cell <NUM> to stay.

In the above example where the message includes the information of whether the cell access is barred, when the loading of either the first cell <NUM> or second cell <NUM> is above a predefined threshold, the information indicates the cell as "access barred (AB)" or "extended access barred (EAB);" or the information indicates a percentage of each of the loadings of the first cell <NUM> and second cell <NUM>. As such, the UE <NUM> may select the cell not indicated as AB or EAB, with a loading percentage not greater than a predefined threshold that is broadcasted by the BS <NUM>, or with a relatively lighter loading.

In the above example where the message includes the scheduling information of MBMS and/or SC-PTM, the UE <NUM> may use at least one of the respective starting times of the MBMS and/or SC-PTM, the respective RAT's that the MBMS and/or SC-PTM uses, and the respective carriers (e.g., frequency locations) that the MBMS and/or SC-PTM uses to select whether to stay at the first cell <NUM> or the second cell <NUM>.

In some embodiments, the method <NUM> continues to optional operation <NUM> in which the UE monitors the second BS. In some embodiments, the UE <NUM> may perform such a monitoring in response to the UE <NUM> selecting to stay at the second cell <NUM> defined by the second BS <NUM>. For example, the UE <NUM> may monitor the cell 140through camping on the cell <NUM>, receiving one or more SIB's broadcasted by the BS <NUM> within the cell <NUM>, performing RSRP/RSRQ (reference signal received power/reference signal received quality) measurement based on the SIB's broadcasted by the BS <NUM>.

In some embodiments, the method <NUM> starts with operation <NUM> in which the first BS transmits a message to the UE. In some embodiments, a first cell (e.g., <NUM>) is defined by the first BS (e.g., <NUM>) using a first RAT to have a cell coverage range (e.g., the outline of the cell <NUM> as shown in <FIG>); and a second cell (e.g., <NUM>) is defined by the second BS (e.g., <NUM>) using a second RAT to have a cell coverage range (e.g., the outline of the cell <NUM> as shown in <FIG>). For example, the first RAT may be an NB-IoT technology, and the second RAT may be an LTE technology. In some embodiments, the first cell <NUM>, where the UE <NUM> currently stays, may be referred to as a "serving cell;" and the second cell <NUM> may be referred to as a "neighboring cell. " Further, in such embodiments, the UE <NUM> may be in a radio resource connection (RRC) connected mode, typically known as an "RRC_CONNECTED mode.

In some embodiments, the message may be broadcasted as a system information block (e.g., a system information block type <NUM>, a system information block type <NUM>, a yet defined system information block type, or the like) through a broadcast channel. In some embodiments, various information can be indicated by such a message, for example, respective cell coverage ranges of the first and second cells <NUM> and <NUM>; information indicating a correspondence between a first service that the UE <NUM> is configured to receive (or trigger) and the first RAT (e.g., a correspondence between a data rate of the first service and the first RAT, a correspondence between the first service and the first RAT, etc.); information indicating a correspondence between a second service that the UE <NUM> is configured to receive (or trigger) and the second RAT (e.g., a correspondence between a data rate of the second service and the second RAT, a correspondence between the second service and the second RAT, etc.); information indicating a correspondence between a first moving speed of the UE <NUM> and the first RAT; information indicating a correspondence between a second moving speed of the UE <NUM> and the second RAT; information indicating whether the first and second cells <NUM> and <NUM> are associated with at least one equivalent public land mobile network (PLMN) identity (typically known as "equivalent PLMN"); information indicating whether the first cell <NUM> or second cell <NUM> is access barred; respective timing synchronization information of the first and second cells <NUM> and <NUM>; a portion of at least one system information block associated with the first cell <NUM>; and a portion of at least one system information block associated with the second cell <NUM>.

In the above example where the message includes the information of respective cell coverage ranges of the first and second cells <NUM> and <NUM>, if the cell coverage ranges of the first and second cells <NUM> and <NUM> are substantially similar or the cell coverage range of the second cell <NUM> includes the cell coverage range of the first cell <NUM>, the UE <NUM> may select the second cell <NUM> to stay; and if the cell coverage ranges of the first and second cells <NUM> and <NUM> are substantially different or the cell coverage range of the second cell <NUM> does not include the cell coverage range of the first cell <NUM>, the UE <NUM> may remain at the first cell <NUM> or selects another cell using the same RAT as the second cell <NUM> to stay.

In the above example where the message includes the information of whether the cell access is barred, when the loading of either the first cell <NUM> or second cell <NUM> is above a predefined threshold, the information indicates the cell as "access barred (AB)" or "extended access barred (EAB);" or the information indicates a percentage of each of the loadings of the first cell <NUM> and second cell <NUM>. As such, the UE <NUM> may select the cell not indicated as AB or EAB, or with a loading percentage not greater than a predefined threshold.

In the above example where the message includes the information of the respective correspondence between the first service and the first RAT and correspondence between the second service and the second RAT, the UE <NUM> may rely on such correspondences to make the selection between the first and second cells <NUM> and <NUM>. In an example, when the data rate of a current service that the UE <NUM> is configured to receive (or trigger) is less than <NUM> kbps (kilobits per second) and the size of data that the UE <NUM> is configured to send is less than <NUM> kbyte (kilobyte), per indicated by the correspondences, the UE <NUM> may select the cell using the NB-IoT technology; when the data rate of the current service that the UE <NUM> is configured to receive (or trigger) is equal to or greater than <NUM> kbps and the size of data that the UE <NUM> is configured to send is equal to or greater than <NUM> kbyte, per indicated by the correspondences, the UE <NUM> may select the cell using the LTE or eMTC technology. In another example, when the UE <NUM> is to trigger a voice service, since the NB-IoT technology does not support the voice service as indicated by the correspondences, the UE <NUM> may select the cell using a RAT that supports the voice service, e.g., the LTE or eMTC technology.

In the above example where the message includes the information of correspondences between different moving speeds of the UE <NUM> and RAT's, the UE <NUM> may rely on such correspondences to make the selection between the first and second cells <NUM> and <NUM>. For example, when the moving speed of UE <NUM> is lower than a predefined threshold, the UE <NUM> may select the cell using the NB-IoT technology; and when the moving speed of UE <NUM> is equal to or higher than the predefined threshold, the UE <NUM> may select the cell using the LTE or eMTC technology.

In some embodiments, subsequently to operation <NUM>, the UE <NUM> may perform an optional operation in which the UE <NUM> is indicated to select the cell that uses a RAT different from the first RAT, e.g., the second cell <NUM>. In such an embodiment, the message, sent at operation <NUM>, may be indicative of prioritizing the different RAT over the first RAT, or exclude the first RAT from selection (e.g., directly indicating the second RAT used by the second cell <NUM>). Next, the method <NUM> continues to operation <NUM> in which the UE initiates a random access procedure in the selected cell. For example, when, at operation <NUM>, the UE <NUM> selects the second cell <NUM> based on the message, received at operation <NUM>, the UE <NUM> may send a preamble to the BS <NUM> to initiate a random access procedure, which is illustrated as dotted line <NUM>-<NUM> of <FIG>. On the other hand, when, at operation <NUM>, the UE <NUM> selects the first cell <NUM> based on the message, received at operation <NUM>, the UE <NUM> may send the preamble to the BS <NUM> to initiate the random access procedure, which is illustrated as dotted line <NUM>-<NUM> of <FIG>.

It is noted that in the embodiments where the message includes the information of the respective timing synchronization information of the first and second cells <NUM> and <NUM>, as discussed above, when the UE <NUM> selects the second cell <NUM> and initiates the random access procedure in the second cell <NUM>, the UE <NUM> may not need to perform a synchronization procedure in the second cell <NUM>. Similarly, in the embodiments where the message includes the portion of at least one system information block associated with the first cell <NUM> and the portion of at least one system information block associated with the second cell <NUM>, as discussed above, when the UE <NUM> selects the second cell <NUM> and initiates the random access procedure in the second cell <NUM>, the UE <NUM> may not need to decode any system information blocks broadcasted in the second cell <NUM>.

In some embodiments, the method <NUM> starts with operation <NUM> in which the UE sends a random access preamble (hereinafter "preamble") to the first BS. In some embodiments, a first cell (e.g., <NUM>) is defined by the first BS (e.g., <NUM>) using a first RAT to have a cell coverage range (e.g., the outline of the cell <NUM> as shown in <FIG>); and a second cell (e.g., <NUM>) is defined by the second BS (e.g., <NUM>) using a second RAT to have a cell coverage range (e.g., the outline of the cell <NUM> as shown in <FIG>). For example, the first RAT may be an NB-IoT technology, and the second RAT may be an LTE technology. In some embodiments, the first cell <NUM>, where the UE <NUM> currently stays, may be referred to as a "serving cell;" and the second cell <NUM> may be referred to as a "neighboring cell. " Further, in such embodiments, the UE <NUM> may be in a radio resource connection (RRC) connected mode, typically known as an "RRC_CONNECTED mode," and configured to initiate a random access procedure in the first (serving) cell <NUM>.

Next, the method <NUM> continues to operation <NUM> in which the first BS transmits a message to the UE. In some embodiments, the message may be transmitted, by the first BS <NUM>, as a random access response (RAR) message. In some embodiments, various information can be indicated by such a message, for example, respective frequencies of carriers used by the second RAT that the second cell <NUM> uses; a cell identity of the second cell <NUM>; and information of the second RAT (e.g., a type of the second RAT). The method <NUM> then proceeds to operation <NUM> in which the UE receives the message and uses the message to select either the first cell or the second cell to stay. For example, the UE <NUM> may select the second cell <NUM> according to the various information about the second RAT indicated by the RAR message (operation <NUM>); and on the other hand, when no information about the second RAT is indicated by the RAR message, the UE <NUM> may remain at the first cell <NUM> to continue the random access procedure, as discussed below.

In some embodiments, the method <NUM> continues to operation <NUM> in which the UE continues the random access procedure or initiates another random access procedure in the selected cell. For example, when, at operation <NUM>, the UE <NUM> selects the second cell <NUM> based on the message, received at operation <NUM>, the UE <NUM> may send another preamble to the BS <NUM> to initiate another random access procedure in the second cell <NUM> (e.g., sending a preamble to the BS <NUM>), which is illustrated as dotted line <NUM>-<NUM> of <FIG>. On the other hand, when, at operation <NUM>, the UE <NUM> remains at the first cell <NUM> based on the message, received at operation <NUM>, the UE <NUM> may send subsequent RRC messages (e.g., Msg <NUM>, typically known as a connection request message) to the BS <NUM> to continue the random access procedure in the first cell <NUM>, which is illustrated as dotted line <NUM>-<NUM> of <FIG>.

In some embodiments, the method <NUM> starts with operation <NUM> in which the UE sends a random access preamble (hereinafter "preamble") to the first BS. In some embodiments, a first cell (e.g., <NUM>) is defined by the first BS (e.g., <NUM>) using a first RAT to have a cell coverage range (e.g., the outline of the cell <NUM> as shown in <FIG>); and a second cell (e.g., <NUM>) is defined by the second BS (e.g., <NUM>) using a second RAT to have a cell coverage range (e.g., the outline of the cell <NUM> as shown in <FIG>). For example, the first RAT may be an NB-IoT technology, and the second RAT may be an LTE technology. In some embodiments, the first cell <NUM>, where the UE <NUM> currently stays, may be referred to as a "serving cell;" and the second cell <NUM> may be referred to as a "neighboring cell. " Further, in such embodiments, the UE <NUM> may be in a radio resource connection (RRC) connected mode, typically knows as an "RRC_CONNECTED mode," and configured to initiate a random access procedure in the first (serving) cell <NUM>.

In response to receiving the preamble, the method <NUM> continues to operation <NUM> in which the first BS sends a random access response (RAR) message to the UE. In response to receiving the RAR message, the method <NUM> continues to operation <NUM> in which the UE sends a connection request message to the first BS.

Next, in some embodiments, the method <NUM> continues to operation <NUM> in which the first BS transmits a message to the UE. In some embodiments, the message may be transmitted, by the first BS <NUM>, as one of the following RRC messages: an RRCConnectionResume message, an RRCConnectionSetup message, an RRCEarlyDataComplete message, an RRCConnectionReject message, an RRCConnectionReconfiguration message, an RRCConnectionReestablishment message, and an RRCConnectionRelease message. In some embodiments, various information can be indicated by such a message, for example, scheduling grant information of the second cell <NUM>; respective frequencies of carriers used by the second RAT; a cell identity of the second cell <NUM>; information of the second RAT (e.g., a type of the second RAT); respective timing synchronization information of the first and second cells <NUM> and <NUM>; a portion of at least one system information block associated with the first cell <NUM>; and a portion of at least one system information block associated with the second cell <NUM>.

The method <NUM> then proceeds to operation <NUM> in which the UE receives the message and uses the message to select either the first cell or the second cell to stay. For example, the UE <NUM> may select the second cell <NUM> according to the various information about the second RAT indicated by the RRC message (operation <NUM>); and on the other hand, when no information about the second RAT is indicated by the RRC message, the UE <NUM> may remain at the first cell <NUM> to continue the random access procedure, as discussed below. In some embodiments, the method <NUM> continues to operation <NUM> in which the UE continues the random access procedure or initiates another random access procedure in the selected cell. For example, when, at operation <NUM>, the UE <NUM> selects the second cell <NUM> based on the message, received at operation <NUM>, the UE <NUM> may send another preamble to the BS <NUM> to initiate another random access procedure in the second cell <NUM> (e.g., sending a preamble to the BS <NUM>), which is illustrated as dotted line <NUM>-<NUM> of <FIG>. On the other hand, when, at operation <NUM>, the UE <NUM> remains at the first cell <NUM> based on the message, received at operation <NUM>, the UE <NUM> may send subsequent RRC messages (e.g., Msg <NUM>, typically known as an RRCConnectionSetupComplete message) to the BS <NUM> to continue the random access procedure in the first cell <NUM>, which is illustrated as dotted line <NUM>-<NUM> of <FIG>.

In some embodiments, the method <NUM> starts with operation <NUM> in which the first BS sends a paging message to the UE. In some embodiments, a first cell (e.g., <NUM>) is defined by the first BS (e.g., <NUM>) using a first RAT to have a cell coverage range (e.g., the outline of the cell <NUM> as shown in <FIG>); and a second cell (e.g., <NUM>) is defined by the second BS (e.g., <NUM>) using a second RAT to have a cell coverage range (e.g., the outline of the cell <NUM> as shown in <FIG>). For example, the first RAT may be an NB-IoT technology, and the second RAT may be an LTE technology. In some embodiments, the first cell <NUM>, where the UE <NUM> currently stays, may be referred to as a "serving cell;" and the second cell <NUM> may be referred to as a "neighboring cell. " Further, in such embodiments, the UE <NUM> may be in a radio resource connection (RRC) idle mode, typically knows as an "RRC_IDLE mode.

In some embodiments, various information can be indicated by such a paging message, for example, respective frequencies of carriers used by the second RAT that the second cell <NUM> uses; a cell identity of the second cell <NUM>; and information of the second RAT (e.g., a type of the second RAT).

The method <NUM> then proceeds to operation <NUM> in which the UE receives the paging message and uses the paging message to select either the first cell or the second cell to stay. For example, the UE <NUM> may select the second cell <NUM> according to the various information about the second RAT indicated by the paging message (operation <NUM>); and on the other hand, when no information about the second RAT is indicated by the paging message, the UE <NUM> may remain at the first cell <NUM> to initiate a random access procedure, as discussed below. In some embodiments, the method <NUM> continues to operation <NUM> in which the UE initiates a random access procedure in the selected cell. For example, when, at operation <NUM>, the UE <NUM> selects the second cell <NUM> based on the paging message, received at operation <NUM>, the UE <NUM> may send a preamble to the BS <NUM> to initiate a random access procedure in the second cell <NUM> (e.g., sending a preamble to the BS <NUM>), which is illustrated as dotted line <NUM>-<NUM> of <FIG>. On the other hand, when, at operation <NUM>, the UE <NUM> selects the first cell <NUM> based on the paging message, received at operation <NUM>, the UE <NUM> may send a preamble to the BS <NUM> to initiate a random access procedure in the first cell <NUM> (e.g., sending a preamble to the BS <NUM>), which is illustrated as dotted line <NUM>-<NUM> of <FIG>.

Next, in some embodiments, the method <NUM> continues to operation <NUM> in which the first BS transmits a message to the UE to indicate the UE to switch to the second cell to stay. In some embodiments, the message may be transmitted, by the first BS <NUM>, as one of the following RRC messages: an RRCConnectionResume message, an RRCConnectionSetup message, an RRCEarlyDataComplete message, an RRCConnectionReject message, an RRCConnectionReconfiguration message, an RRCConnectionReestablishment message, and an RRCConnectionRelease message. In some embodiments, various information can be indicated by such a message, for example, scheduling grant information of the second cell <NUM>; respective frequencies of carriers used by the second RAT; a cell identity of the second cell <NUM>; information of the second RAT (e.g., a type of the second RAT); respective timing synchronization information of the first and second cells <NUM> and <NUM>; a portion of at least one system information block associated with the first cell <NUM>; and a portion of at least one system information block associated with the second cell <NUM>.

The method <NUM> then proceeds to operation <NUM> in which the UE receives the message and then switches to the second cell to stay. For example, the UE <NUM> may directly switch to stay at the second cell <NUM> when the RRC message, transmitted at operation <NUM>, contains the above-described information about the second cell <NUM>. In some embodiments, the UE <NUM> continues the random access procedure to send subsequent RRC messages (e.g., Msg <NUM>, typically known as an RRCConnectionSetupComplete message) to the BS <NUM> in the second cell <NUM>, which is illustrated as operation <NUM> in <FIG>. For example, when the RRC message transmitted at operation <NUM> includes the scheduling grant information and the timing synchronization information of the second cell <NUM>, at operation <NUM>, the UE <NUM> may send Msg <NUM> using resources indicated by the scheduling grant information.

It is noted that in the embodiments where the message includes the information of the respective timing synchronization information of the first and second cells <NUM> and <NUM>, as discussed above, when the UE <NUM> selects the second cell <NUM> and initiates the random access procedure in the second cell <NUM>, the UE <NUM> may not need to perform a synchronization procedure in the second cell <NUM>. Similarly, in the embodiments where the message includes the portion of at least one system information block associated with the first cell <NUM> and the portion of at least one system information block associated with the second cell <NUM>, as discussed above, when the UE <NUM> selects the second cell <NUM> and initiates the random access procedure in the second cell <NUM>, the UE <NUM> may not need to decode any system information blocks broadcasted in the second cell <NUM>. If the message includes the information of the respective timing synchronization information of the first and second cells <NUM> and <NUM>, and scheduling grant information of the second cell <NUM>, as discussed above, when the UE <NUM> selects the second cell <NUM>, the UE <NUM> may not need to perform a random access procedure in the second cell <NUM> before sending Msg5 in the second cell <NUM>.

<FIG> illustrates an exemplary method <NUM> collectively performed by a UE, a BS, and a network entity of a core network (e.g., a mobility management entity (MME)) to perform communication in a multi-RAT network, in accordance with the present disclosure. In various embodiments, the operations of the method <NUM> are performed by the respective components illustrated in <FIG>. For purposes of discussion, the following embodiment of the method <NUM> will be described in conjunction with <FIG>. The illustrated embodiment of the method <NUM> is merely an example. Therefore, it should be understood that any of a variety of operations may be omitted, re-sequenced, and/or added while remaining within the scope of the present disclosure.

In some embodiments, the method <NUM> starts with operation <NUM> in which the BS sends a first message to the MME. In some embodiments, the BS (e.g., <NUM>) may send the first message , which includes a PLMN identity associated with the cell <NUM> defined by the BS <NUM>, a tracking area code (TAC) associated with the cell <NUM>, a first RAT that the cell <NUM> uses, etc., to the MME when the BS <NUM> establishes or updates a connection between the BS <NUM> and the MME. The method <NUM> continues to operation <NUM> in which the UE sends a second message to the MME. In some embodiments, the UE (e.g., <NUM>) may send the second message, which includes a PLMN identity associated with the cell where the UE <NUM> is currently located, a tracking area code (TAC) associated with the cell, a second RAT that the cell uses, etc., to the MME when the UE <NUM> perform an attach procedure or a tracking area update procedure. The method <NUM> proceeds to operation <NUM> in which the MME determines a paging range based on the first and second messages. In some embodiments, the first and second RAT's can be different from each other. Although operation <NUM> is performed subsequently to operation <NUM> and operation <NUM> is performed subsequently to operation <NUM> in the illustrated embodiment of <FIG>, it is noted that operation <NUM> does not necessarily occur after operations <NUM> or <NUM>, and operation <NUM> does not necessarily occur after operation <NUM>.

Claim 1:
A method performed by a wireless communication node, comprising:
receiving a random access preamble from a wireless communication device which currently camps in a first cell in which a first radio access technology, RAT, is used,
transmitting a message as a random access response, RAR, to the wireless communication device for the wireless communication device to select a second cell to stay,
wherein the message indicates information about the second cell in which a second RAT, different from the first RAT, is used, wherein the information indicates whether to switch to the second cell based on a coverage mode of the wireless communication device.