WO2019028719A1

WO2019028719A1 - Methods and devices for transmission of synchronization signals and system information

Info

Publication number: WO2019028719A1
Application number: PCT/CN2017/096744
Authority: WO
Inventors: Haijing LIU; Yu Chen; He Wang; Li Yang; Srinivasan Selvaganapathy; Rapeepat Ratasuk; Muneender Chiranji; Nitin MANGALVEDHE
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Technologies Oy
Priority date: 2017-08-10
Filing date: 2017-08-10
Publication date: 2019-02-14
Also published as: CN111165038B; CN111165038A

Abstract

Embodiments of the present disclosure relate to methods, a network device and a terminal device for transmission of narrowband synchronization signals and narrowband system information transmission. In example embodiments, a method implemented at a network device in a wireless communication system is provided. According to the method, narrowband synchronization signals are transmitted, to a terminal device, on a first anchor carrier. It is determined whether a NB-MIB in narrowband system information is to be transmitted on the first anchor carrier or a second anchor carrier. The second anchor carrier has a first frequency offset from the first anchor carrier. The NB-MIB is transmitted to the terminal device based on the determination.

Description

METHODS AND DEVICES FOR TRANSMISSION OF SYNCHRONIZATION SIGNALS AND SYSTEM INFORMATION

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to the field of telecommunication， and in particular， to methods， a network device and a terminal device for transmission of narrowband synchronization signals and narrowband system information.

BACKGROUND

Internet of Things (IoT) technology is being introduced into Public Land Mobile Network (PLMN) networks. For example， Narrowband IoT (NB-IoT) is being introduced into Long Term Evolution (LTE) . Currently， NB-IoT only supports half-duplex Frequency Division Duplex (FDD) . However， Time Division Duplex (TDD) spectrum exists globally， including regulatory environments and operator markets where there is strong un-met demand for NB-IoT. Therefore， there is a new work item (WI) on NB-IoT Enhancements， aiming at introducing TDD mode support into NB-IoT.

SUMMARY

In general， example embodiments of the present disclosure provide methods， a network device and a terminal device for transmission of narrowband synchronization signals and narrowband system information.

In a first aspect， there is provided a method implemented by a network device in a wireless communication system. The method comprises transmitting， to a terminal device， narrowband synchronization signals on a first anchor carrier. The method also comprises determining whether a Narrowband Master Information Block (NB-MIB) in narrowband system information is to be transmitted on the first anchor carrier or a second anchor carrier. The second anchor carrier has a first frequency offset from the first anchor carrier. The method further comprises transmitting， based on the determination， the NB-MIB to the terminal device.

In some embodiments， the method further comprises determining a pattern of the narrowband synchronization signals based on the determination.

In some embodiments， determining the pattern of the narrowband synchronization signals comprises determining a pattern of a Narrowband Primary Synchronization Signal (NPSS) .

In some embodiments， transmitting the narrowband synchronization signals comprises： transmitting a Narrowband Primary Synchronization Signal (NPSS) in a first subframe on the first anchor carrier； and transmitting a Narrowband Secondary Synchronization Signal (NSSS) in a second subframe on the first anchor carrier， a subframe offset between the first subframe and the second subframe being determined based on the determination.

In some embodiments， the method further comprises in response to determining that the NB-MIB is to be transmitted on the first anchor carrier， determining whether a first Narrowband System Information Block (NB-SIB) in narrowband system information is to be transmitted on the first anchor carrier or the second anchor carrier， the first NB-SIB including information that enables the terminal device to camp in a cell that is provided by the network device， and transmitting the first NB-SIB based on determining whether the first NB-SIB is to be transmitted on the first anchor carrier or the second anchor carrier. In some embodiments， the method further comprises in response to determining that the NB-MIB is to be transmitted on the second anchor carrier， transmitting the first NB-SIB on the second anchor carrier.

In some embodiments， the NB-MIB includes at least one of： an indication of a subframe in which the first NB-SIB is transmitted， and an indication of one of the first and second anchor carriers on which the first NB-SIB is transmitted.

In some embodiments， the method further comprises transmitting a second NB-SIB in the narrowband system information on at least one of the first anchor carrier， the second anchor carrier and a third anchor carrier， the second NB-SIB being different from the first NB-SIB， the third anchor carrier having a second frequency offset from the first anchor carrier.

In some embodiments， the first NB-SIB includes information concerning at least one of： a subframe in which the second NB-SIB is transmitted， and the at least one of the first anchor carrier， the second anchor carrier and the third anchor carrier on which the second NB-SIB is transmitted.

In some embodiments， transmitting the NSSS comprises transmitting the NSSS including an identifier of a cell that is provided by the network device.

In some embodiments， a frequency of the second anchor carrier is associated with the identifier of the cell.

In a second aspect， there is provided a method implemented at a terminal device in a wireless communication system. The method comprises receiving， from a network device， narrowband synchronization signals on a first anchor carrier. The method also comprises determining whether a Narrowband Master Information Block (NB-MIB) in narrowband system information is to be received on the first anchor carrier or a second anchor carrier， the second anchor carrier having a first frequency offset from the first anchor carrier. The method also comprises receiving， based on the determination， the NB-MIB from the network device.

In some embodiments， the determining comprises determining based on a pattern of the received narrowband synchronization signals.

In some embodiments， receiving the narrowband synchronization signals comprises receiving a Narrowband Primary Synchronization Signal (NPSS) ； and the determining comprises determining based on a pattern of the received NPSS.

In some embodiments， receiving the narrowband synchronization signals comprises： receiving a Narrowband Primary Synchronization Signal (NPSS) in a first subframe on the first anchor carrier； and receiving a Narrowband Secondary Synchronization Signal (NSSS) in a second subframe on the first anchor carrier， the second subframe having a determined subframe offset from the first subframe.

In some embodiments， the determining comprises determining based on the subframe offset.

In some embodiments， the method further comprises in response to determining that the NB-MIB is to be received on the first anchor carrier， determining whether a first Narrowband System Information Block (NB-SIB) in narrowband system information is to be received on the first anchor carrier or the second anchor carrier， the first NB-SIB including information that enables the terminal device to camp in a cell that is provided by the network device， and receiving the first NB-SIB based on determining whether the first NB-SIB is to be received on the first anchor carrier or the second anchor carrier； and in response to determining that the NB-MIB is to be received on the second anchor carrier， receiving the first NB-SIB on the second anchor carrier.

In some embodiments， the NB-MIB includes at least one of： an indication of a subframe in which the first NB-SIB is to received， and an indication of one of the first and second anchor carriers on which the first NB-SIB is to be received.

In some embodiments， the method further comprises receiving a second NB-SIB in the narrowband system information on at least one of the first anchor carrier， the second anchor carrier and a third anchor carrier， the second NB-SIB being different from the first NB-SIB， the third anchor carrier having a second frequency offset from the first anchor carrier.

In some embodiments， wherein the first NB-SIB includes information concerning at least one of： a subframe in which the second NB-SIB is to be received， and the at least one of the first anchor carrier， the second anchor carrier and the third anchor carrier on which the second NB-SIB is to be received.

In some embodiments， receiving the NSSS comprises receiving the NSSS including an identifier of a cell that is provided by the network device.

In some embodiments， the method further comprises determining a frequency of the second anchor carrier based on the identifier of the cell.

In a third aspect， there is provided a network device in a wireless communication system. The network device includes a processor； and a memory coupled to the processing unit and storing instructions thereon， the instructions， when executed by the processing unit， causing the network device to perform the method according to the first aspect.

In a fourth aspect， there is provided a terminal device in a wireless communication system. The terminal device includes a processor； and a memory coupled to the processing unit and storing instructions thereon， the instructions， when executed by the processing unit， causing the terminal device to perform the method according to the second aspect.

In a fifth aspect， there is provided a computer program product that is tangibly stored on a computer readable storage medium. The computer program product includes instructions which， when executed on at least one processor， cause the at least one processor to carry out the method according to the first aspect or the second aspect.

In a sixth aspect， there is provided a computer readable storage medium having instructions stored thereon. The instructions， when executed on at least one processor， cause the at least one processor to carry out the method according to the first aspect or the second aspect.

Other features of the present disclosure will become easily comprehensible through the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Through the more detailed description of some embodiments of the present disclosure in the accompanying drawings， the above and other objects， features and advantages of the present disclosure will become more apparent， wherein：

Fig. 1 is a block diagram of a communication environment in which embodiments of the present disclosure can be implemented；

Fig. 2 is a flowchart illustrating a process for transmission of NB synchronization signals and NB system information according to some embodiments of the present disclosure；

Fig. 3 is a diagram illustrating an anchor carrier configuration for NPSS， NSSS and NB-MIB according to one embodiment of the present disclosure；

Fig. 4 is a diagram illustrating an anchor carrier configuration for NPSS， NSSS and NB-MIB according to another embodiment of the present disclosure；

Fig. 5 is a diagram illustrating an anchor carrier configuration for NPSS， NSSS and NB-MIB according to yet another embodiment of the present disclosure；

Fig. 6 is a diagram illustrating an anchor carrier configuration for NPSS， NSSS and NB-MIB according to still another embodiment of the present disclosure；

Fig. 7 is a diagram illustrating an anchor carrier configuration for NPSS， NSSS， NB-MIB and NB-SIB 1 according to one embodiment of the present disclosure；

Fig. 8 is a diagram illustrating an anchor carrier configuration for NPSS， NSSS， NB-MIB and NB-SIB 1 according to another embodiment of the present disclosure；

Fig. 9 is a diagram illustrating an anchor carrier configuration for NPSS， NSSS， NB-MIB and NB-SIB 1 according to yet another embodiment of the present disclosure；

Fig. 10 is a diagram illustrating an anchor carrier configuration for other SIBs according to an embodiment of the present disclosure；

Fig. 11 illustrates a flowchart of an example method according to some embodiments of the present disclosure；

Fig. 12 illustrates a flowchart of an example method according to some other embodiments of the present disclosure； and

Fig. 13 is a simplified block diagram of a device that is suitable for implementing embodiments of the present disclosure.

Throughout the drawings， the same or similar reference numerals represent the same or similar element.

DETAILED DESCRIPTION

Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure， without suggesting any limitations as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones described below.

In the following description and claims， unless defined otherwise， all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

As used herein， the term “network device” or “base station” (BS) refers to a device which is capable of providing or hosting a cell or coverage where terminal devices can communicate. Examples of a network device include， but not limited to， a Node B (NodeB or NB) ， an Evolved NodeB (eNodeB or eNB) ， a Remote Radio Unit (RRU) ， a radio head (RH) ， a remote radio head (RRH) ， a low power node such as a femto node， a pico node， and the like. For the purpose of discussion， in the following， some embodiments will be described with reference to eNB as examples of the network device.

As used herein， the term “terminal device” refers to any device having wireless or wired communication capabilities. Examples of the terminal device include， but not limited to， user equipment (UE) ， personal computers， desktops， mobile phones， cellular phones， smart phones， personal digital assistants (PDAs) ， portable computers， image capture devices such as digital cameras， gaming devices， music storage and playback appliances， or Internet appliances enabling wireless or wired Internet access and browsing and the like. In some examples， the terminal device includes an Internet of Things (IoT) device which is the network of physical objects or “things” embedded with electronics， software， sensors， and connectivity to enable objects to exchange data with the manufacturer， operator and/or other connected devices. For the purpose of discussion， in the following， some embodiments will be described with reference to UEs as examples of terminal devices and the terms “terminal device” and “user equipment” (UE) may be used interchangeably in the context of the present disclosure.

As used herein， the singular forms “a” ， “an” and “the” are intended to include the plural forms as well， unless the context clearly indicates otherwise. The term “includes” and its variants are to be read as open terms that mean “includes， but is not limited to. ” The term “based on” is to be read as “based at least in part on. ” The term “one embodiment” and “an embodiment” are to be read as “at least one embodiment. ” The term “another embodiment” is to be read as “at least one other embodiment. ” The terms “first， second， ” and the like may refer to different or same objects. Other definitions， explicit and implicit， may be included below.

In some examples， values， procedures， or apparatus are referred to as “best， ” “lowest， ” “highest， ” “minimum， ” “maximum， ” or the like. It will be appreciated that such descriptions are intended to indicate that a selection among many used functional alternatives can be made， and such selections need not be better， smaller， higher， or otherwise preferable to other selections.

Fig. 1 shows an example communication network 100 in which embodiments of the present disclosure can be implemented. The network 100 includes a network device 110 and a terminal device 120 served by the network device 110. The serving area of the network device 110 is called as a cell 102. It is to be understood that the number of network devices and terminal devices is only for the purpose of illustration without suggesting any limitations. The network 100 may include any suitable number of network devices and terminal devices adapted for implementing embodiments of the present disclosure. Although not shown， it would be appreciated that one or more terminal devices may be located in the cell 102 and served by the network device 110.

The communications in the network 100 may conform to any suitable standards including， but not limited to， Global System for Mobile Communications (GSM) ， Extended Coverage Global System for Mobile Intemet of Things (EC-GSM-IoT) ， Long Term Evolution (LTE) ， LTE-Evolution， LTE-Advanced (LTE-A) ， Wideband Code Division Multiple Access (WCDMA) ， Code Division Multiple Access (CDMA) ， GSM EDGE Radio Access Network (GERAN) ， and the like. Furthermore， the communications may be performed according to any generation communication protocols either currently known or to be developed in the future. Examples of the communication protocols include， but not limited to， the first generation (1G) ， the second generation (2G) ， 2.5G， 2.75G， the third generation (3G) ， the fourth generation (4G) ， 4.5G， the fifth generation (5G) communication protocols.

In the communication network 100， the network device 110 can communicate data and control information to the terminal device 120 and the terminal device 120 can also communication data and control information to the network device 110. A link from the network device 110 to the terminal device 120 is referred to as a downlink， while a link from the terminal device 120 to the network device 110 is referred to as an uplink.

Generally， two different duplex modes may be employed for transmissions between the terminal device 120 and the network device 110： Frequency Division Duplex (FDD) and Time Division Duplex (TDD) . In the TDD mode， a single bandwidth is shared between UL and DL， with the sharing being performed by allocating different periods of time to UL and DL.

In the TDD mode， there are seven different patterns of UL-DL switching， termed UL-DL configurations #0 through #6， which are schematically illustrated in Table 1.

Table 1： UL-DL configurations

As can be seen from Table 1， compared with the FDD mode， DL time resources become fewer in the TDD mode because of Time Division Multiplexing (TDM) of UL and DL on a single anchor carrier. For example， in UL-DL configuration #0， only about 35％time resources are available for DL transmissions. Thus， with introduction of the TDD mode support into NB-IoT， there are some challenges in ensuing DL transmissions with the fewer DL time resources in the TDD mode.

As known， before the terminal device 120 can communicate with the network device 110， the terminal device 120 has to perform a cell search to find a cell that is provided by the network device 110 and to acquire synchronization to the cell. In order to assist the cell search by the terminal device 120， the network device 110 transmits narrowband synchronization signals to the terminal device 120 on an anchor carrier.

By means of the cell search， the terminal device 120 may achieve synchronization to the cell. In order to access the cell， the terminal device 120 needs to obtain narrowband system information for the cell. Examples of the narrowband system information may include， but not limited to， Narrowband Master Information Block (NB-MIB) and Narrowband Systemlnformation Blocks (NB-SIBs) .

For LTE in the TDD mode， synchronization signals and system information can only be transmitted on a single anchor carrier. The transmission of the synchronization signals and MIB on the anchor carrier will occupy (1+1/2+1) /10＝25％DL time resources and the transmission of the SIB on the anchor carrier will occupy about 25％DL time resource. For NB-loT in the TDD mode， for the purpose of providing extended coverage， a larger amount of narrowband synchronization signals and narrowband system information need to be transmitted. This overhead might exceed a load capacity of the single anchor carrier in some UL-DL configurations having less DL time resources.

In order to address at least some of the above problems and other potential problems， according to embodiments of the present disclosure， there is proposed a solution for transmissions of narrowband synchronization signals and narrowband system information. In this solution， multiple anchor carriers can be used by a network device for transmissions of narrowband synchronization signals and narrowband system information. Therefore， the transmissions can be ensured with sufficient DL time resources on multiple carriers.

Principle and implementations of the present disclosure will be described in detail below with reference to Fig. 2， which shows a process 200 for transmissions of narrowband synchronization signals and narrowband system information according to an embodiment of the present disclosure. For the purpose of discussion， the process 200 will be described with reference to Fig. 1. The process 200 may involve the network device 110 and the terminal device 120 in Fig. 1.

The network device 110 transmits (210) ， to the terminal device 120， narrowband synchronization signals on a first anchor carrier. Examples of the narrowband synchronization signals may include， but not limited to， Narrowband Primary Synchronization Signal (NPSS) and Narrowband Secondary Synchronization Signal (NSSS) . Correspondingly， the terminal device 120 receives， from the network device 110， the narrowband synchronization signals on the first anchor carrier.

The network device 110 determines (220) whether a NB-MIB in narrowband system information is to be transmitted on the first anchor carrier or a second anchor carrier. The second anchor carrier has a first frequency offset from the first anchor carrier. A frequency of the first anchor carrier may be determined based on radio access technology employed in the network 100. For example， for NB-IoT， the frequency of the first anchor carrier may be 180kHz. Of course， any appropriate frequency of the first anchor carrier may be employed. The scope of the present disclosure is not limited in this regard.

In some embodiments， the network device 110 may determine whether the NB-MIB is to be transmitted on the first anchor carrier or the second anchor carrier based on available DL time resources.

In example embodiments， the network device 110 may determine the available DL time resources according to an UL-DL configuration to be used. As can be seen from Table 1， some UL-DL configurations， such as UL-DL configurations #2， #3， #4 and #5， have more DL time resources (i.e.， more than six DL subframes) in one frame while other UL-DL configurations， such as UL-DL configuration #0 and UL-DL configuration#6， have less DL time resources (i.e.， two or three DL subframs) in one frame.

In this regard， for the UL-DL configurations having more DL time resources， the network device 110 may determine that the NB-MIB is to be transmitted on the first anchor carrier. That is， both the narrowband synchronization signals and the NB-MIB are transmitted on the first anchor carrier. For the UL-DL configurations having less DL time resources， the network device 110 may determine that the NB-MIB is to be transmitted on the second anchor carrier. In this manner， DL time resources on both the first anchor carrier and the second anchor carrier can be used for transmissions of the narrowband synchronization signals and the narrowband system information.

In example embodiments， the network device 110 may determine the available DL time resources according to a traffic model employed by the network device 110. For example， the network device 110 may provide the terminal device 120 with Multimedia Broadcast/Multicast Services (MBMS) . To this end， the network device 110 will transmit to the terminal device 120 MBMS messages occupying a large number of DL time resources. Although such UL-DL configurations as UL-DL configurations #2， #3， #4 and #5 have more DL time resources in one frame， the DL time resources might not be enough for transmission of the narrowband synchronization signals and the narrowband system information. In this situation， the network device 110 may determine that the NB-MIB is to be transmitted on the second anchor carrier.

In other embodiments， the network device 110 may determine， based on a pre-configuration， whether the NB-MIB is to be transmitted on the first anchor carrier or the second anchor carrier. For example， the second anchor carrier may be pre-configured at both sides of the network device 110 and the terminal device 120 for transmission of the NB-MIB. Due to the pre-configuration， the terminal device 120 does not need to identify the anchor carrier on which the NB-MIB is transmitted. Thus， no decoding complexity increase will be caused at the terminal device 120. This is very important for low-cost terminal devices.

Still referring to Fig. 2， corresponding to the determination (220) at the network device 110， the terminal device 120 determines (230) whether the NB-MIB is to be received on the first anchor carrier or the second anchor carrier.

The network device 110 transmits (240) ， based on the determination (220) ， the NB-MIB to the terminal device 120. Accordingly， the terminal device 120 receives， based on the determination (230) ， the NB-MIB from the network device 110. In turn， the terminal device 120 may initiate access to a cell that is provided by the network device 110 by using the received narrowband synchronization signals and narrowband system information.

It should be appreciated that while actions as shown in Fig. 2 are depicted in a particular order， this should not be understood as requiring that such actions be performed in the particular order shown or in sequential order to achieve desirable results. In certain circumstances， the actions may be performed in a different order from the order as shown in Fig. 2. For example， the action 220 may be performed prior to the action 210. In addition， parallel performance of more actions may be advantageous. For example，

actions

210 and 240 may be performed in parallel.

To help understand the solution proposed in the present disclosure， details of embodiments of the present disclosure will be described hereinafter with reference to Figs. 3 to 9. In Figs. 3 to 9， frames are numbered 0， 1， ...， N (where N is a natural number) ， and each of the frames includes ten subframes that are numbered 0 to 9. The frames that are numbered 0， 1， ...， N are also referred to as frame#0， frame#l， ...， frame#N. The subframes that are numbered 0 to 9 are also referred to as subframe#0， subframe#1， ...， subframe#9.

Fig. 3 is a diagram illustrating an anchor carrier configuration for NPSS， NSSS and NB-MIB according to one embodiment of the present disclosure. As shown， NPSS 301， NSSS 302 and NB-MIB 303 are all transmitted on the first anchor carrier. NPSS 301 is transmitted in the subframe#0 of each frame， NSSS 302 is transmitted in the subframe#5 of each even numbered frame (for example， frame#0， frame#2... ) ， and NB-MIB is transmitted in the subframe#9 of each frame.

Fig. 4 is a diagram illustrating an anchor carrier configuration for NPSS， NSSS and NB-MIB according to another embodiment of the present disclosure. As shown， NPSS 301 is transmitted in the subframe#0 of each frame on the first anchor carrier， NSSS 302 is transmitted in the subframe#5 of each even numbered frame on the first anchor carrier， and NB-MIB 303 is transmitted in the subframe#0 of each frame on the second anchor carrier.

In embodiments where the second anchor carrier is not pre-configured at both sides of the network device 110 and the terminal device 120 for transmission of the NB-MIB 303， the terminal device 120 should be able to identify the anchor carrier on which the NB-MIB 303 is transmitted so as to correctly receive the NB-MIB 303 from the network device 110. For this purpose， in some embodiments， the network device 110 may determine a pattern of the narrowband synchronization signals based on the determination (220) . In this way， the terminal device 120 may identify， based on the pattern， the anchor carrier on which the NB-MIB 303 is transmitted.

In embodiments where the NPSS 301 is to be transmitted， the network device 110 may indicate， by using a pattern of the NPSS 301， the anchor carrier on which the NB-MIB 303 is transmitted.

For example， the NPSS 301 may be given by the following equation：

where d_l (n) denotes the NPSS 301， u denotes a ZC root sequence index and S (l) denotes a predetermined sequence.

In order to indicate the anchor carrier on which the NB-MIB 303 is transmitted， the network device 110 may employ different ZC root sequence indices or different predetermined sequences S (l) so as to determine different patterns of NPSSs. For example， the network device 110 may employ a ZC root sequence index of 5 or S (l) ＝ [1， 1， 1， 1， -1， -1， 1， 1， 1， -1， 1] to determine a first pattern of the NPSS 301， indicating that the NB-MIB 303 is transmitted on the first anchor carrier. The network device 110 may also employ a ZC root sequence index of 6 or S (l) ＝ [1， 1， 1， -1， -1， -1， 1， -1， -1， 1， -1] to determine a second pattern of the NPSS 301， indicating that the NB-MIB 303 is transmitted on the second anchor carrier. Upon receiving the NPSS 301 having the first pattern， the terminal device 120 may determine that the NB-MIB 303 is transmitted on the first anchor carrier. Upon receiving the NPSS 301 having the second pattern， the terminal device 120 may determine that the NB-MIB 303 is transmitted on the second anchor carrier.

In embodiments where the NPSS 301 and NSSS 302 are to be transmitted， the network device 110 may indicate， by using relative subframe positions of NPSS 301 and NSSS 302， the anchor carrier on which the NB-MIB 303 is transmitted.

Specifically， the NPSS 301 is to be transmitted in a first subframe on the first anchor carrier， and the NSSS 302 is to be transmitted in a second subframe on the first anchor carrier. The network device 110 may determine a subframe offset between the first subframe and the second subframe based on the determination (220) .

For example， based on determining that the NB-MIB 303 is to be transmitted on the first anchor carrier， the network device 110 may determine the subframe offset to be one. Then， the network device 110 may transmit the NPSS 301 in the first subframe and transmit the NSSS 302 in the second subframe having the subframe offset of one from the first subframe， as shown in Fig. 5.

Fig. 5 is a diagram illustrating an anchor carrier configuration for NPSS， NSSS and NB-MIB according to yet another embodiment of the present disclosure. As shown， NPSS 301， NSSS 302 and NB-MIB 303 are all transmitted on the first anchor carrier. NPSS 301 is transmitted in the subframe#0 of each frame， NSSS 302 is transmitted in the subframe#9 of each evennumbered frame (for example， frame#l， frame#3... ) ， and NB-MIB 303 is transmitted in the subframe#5 of each frame. It can be seen from Fig. 5 that there is a subframe offset of one between the subframe#0 for transmission of the NPSS 301 and the subframe#9 for transmission of the NSSS 302. Upon receiving the NPSS 301 and NSSS 302， the terminal device 120 may determine， based on the subframe offset of one， the NB-MIB 303 is transmitted on the first anchor carrier.

For another example， based on determining that the NB-MIB 303 is to be transmitted on the second anchor carrier， the network device 110 may determine the subframe offset to be five. Then， the network device 110 may transmit the NPSS 301 in the first subframe and transmit the NSSS 302 in the second subframe having the subframe offset of five from the first subframe， as shown in Fig. 6.

Fig. 6 is a diagram illustrating an anchor carrier configuration for NPSS， NSSS and NB-MIB according to still another embodiment of the present disclosure. As shown， NPSS 301 is transmitted in the subframe#0 of each frame on the first anchor carrier， NSSS 302 is transmitted in the subframe#5 of each even numbered frame on the first anchor carrier， and NB-MIB 303 is transmitted in the subframe#0 of each frame on the second anchor carrier. It can be seen from Fig. 6 that there is a subframe offset of five between the subframe#0 for transmission of the NPSS 301 and the subframe#5 for transmission of the NSSS 302. Upon receiving the NPSS 301 and NSSS 302， the terminal device 120 may determine， based on the subframe offset of five， the NB-MIB 303 is transmitted on the second anchor carrier.

Upon determining that the NB-MIB 303 is to be received on the second anchor carrier， the terminal device 120 needs to determine a frequency of the second anchor carrier.

In some embodiments， the frequency of the second anchor carrier may be pre-configured at both sides of the network device 110 and the terminal device 120.

In other embodiments， the frequency of the second anchor carrier may be associated with an identifier of a cell that is provided by the network device 110. The network device 110 may transmit the NSSS including the identifier of the cell. Upon receiving the NSSS， the terminal device 120 may obtain the identifier of the cell from the NSSS. In turn， the terminal device 120 may determine the frequency of the second anchor carrier based on the identifier of the cell.

As described above， examples of the narrowband system information may include NB-MIB and NB-SIBs. Typically， NB-MIB includes a limited amount of the narrowband system information and NB-SIBs include the main part of the narrowband system information.

Specifically， the NB-SIBs are characterized by the type of information that is included within them. Specifically， the NB-SIBs may include a first NB-SIB， which is also referred to as NB-SIB1. The first NB-SIB or NB-SIB1 includes information that enables the terminal device 120 to camp in a cell that is provided by the network device 110. In addition to the NB-SIB1， the NB-SIBs may also include one or more other NB-SIBs， such as NB-SIB2， NB-SIB3， NB-SIB4， NB-SIB5， NB-SIB14， NB-SIB15， NB-SIB16， NB-SIB20， NB-SIB22. For example， NB-SIB2 includes information that the terminal device 120 needs in order to be able to access the cell.

The transmissions of the NPSS， NSSS and MIB are described above with reference to Figs. 3 to 6. Hereinafter， the transmissions of the NB-SIBs will be described with reference to Figs. 7 to 10.

In some embodiments， it may be pre-configured that the NB-SIB1 and the NB-MIB are transmitted on the same anchor carrier， for example， the first anchor carrier or the second anchor carrier. In such embodiments， the NB-MIB may include an indication of a subframe in which the NB-SIB 1 is transmitted. For example， the indication of the subframe may occupy three bits in the NB-MIB.

Fig. 7 is a diagram illustrating an anchor carrier configuration for NPSS， NSSS， NB-MIB and NB-SIB1 according to one embodiment of the present disclosure. As shown in Fig. 7， NPSS 301， NSSS 302， NB-MIB 303 and NB-SIB1 304 are all transmitted on the first anchor carrier. Upon receiving the NPSS 301 and NSSS 302， the terminal device 120 may determine that the NB-MIB 303 is also transmitted on the first anchor carrier. Then， according to the pre-configuration， the terminal device 120 may determine that the NB-SIB 1 304 is transmitted on the same anchor carrier as that of the NB-MIB 303. Upon reading the NB-MIB 303， the terminal device 120 may determine the subframe in which the NB-SIB1 304 is transmitted， e.g.， subframe#6 in Fig. 7.

Fig. 8 is a diagram illustrating an anchor carrier configuration for NPSS， NSSS， NB-MIB and NB-SIB1 according to another embodiment of the present disclosure. As shown in Fig. 8， NPSS 301 and NSSS 302 are transmitted on the first anchor carrier， and NB-MIB 303 and NB-SIB1 304 are transmitted on the second anchor carrier. Upon receiving the NPSS 301 and NSSS 302， the terminal device 120 may determine that the NB-MIB 303 is transmitted on the second anchor carrier. Then， according to the pre-configuration， the terminal device 120 may determine that the NB-SIB1 304 is transmitted on the same anchor carrier as that of the NB-MIB 303. Upon reading the NB-MIB 303， the terminal device 120 may determine the subframe in which the NB-SIB1 304 is transmitted， e.g.， subframe#5 in Fig. 8.

In other embodiments， the NB-MIB and the NB-SIB1 may be transmitted on different anchor carriers. For example， the NB-MIB may be transmitted on the first anchor carrier and the NB-SIB1 may be transmitted on the second anchor carrier. Information concerning the second anchor carrier to be used for transmission of the NB-SIB 1 may be given either explicitly or implicitly by the NB-MIB.

In one example， the information concerning the second anchor carrier frequency location may be associated with the identifier of the cell of the network 100. Thus， the terminal device 120 may determine the information concerning the second anchor carrier frequency location based on the identifier of the cell of the network 100.

In another example， one or more fixed frequency offsets between the first anchor carrier and the second anchor carrier may be pre-configured. Each of the fixed frequency offsets may be associated with an indication or an index. In addition， the NB-MIB may include an index of one of the fixed frequency offsets.

Fig. 9 is a diagram illustrating an anchor carrier configuration for NPSS， NSSS， NB-MIB and NB-SIB1 according to yet another embodiment of the present disclosure. As shown in Fig. 9， NPSS 301， NSSS 302 and NB-MIB 303 are transmitted on the first anchor carrier， and NB-SIB1 304 is transmitted on the second anchor carrier. NSSS 302 is transmitted in subframe#9 of each even numbered frame. NB-MIB 303 is transmitted on subframe#5 of each frame. The NB-MIB 303 may include an index of one of the fixed frequency offsets and an indication of a subframe in which the NB-SIB 1 304 is transmitted.

Upon receiving NPSS 301 and NSSS 302， the terminal device 120 may determine that NB-MIB 303 is transmitted on the same carrier as NPSS 301 and NSSS 302， i.e.， the NB-MIB 303 is also transmitted on the first anchor carrier. By reading the NB-MIB 303， the terminal device 120 obtains the frequency information of the anchor carrier on which NB-SIB1 304 is transmitted. Moreover， the terminal device 120 may obtain information concerning the subframe (e.g.， subframe#0 in Fig. 9) in which the NB-SIB1 304 is transmitted.

Fig. 10 is a diagram illustrating an anchor carrier configuration for other SIBs according to an embodiment of the present disclosure. As shown in Fig. 10， NPSS 301 is transmitted in subframe#0 on the first anchor carrier， NSSS 302 is transmitted in subframe#5 of every even numbered frame on the first anchor carrier. NB-MIB 303 is transmitted in the subframe#0 on the second anchor carrier. Other SIBs 305 are transmitted on at least one of the first anchor carrier， the second anchor carrier and a third anchor carrier. The third anchor carrier has a second frequency offset from the first anchor carrier. Moreover， it may be pre-configured that the NB-SIB1 304 is transmitted on the same carrier as that of NB-MIB 303.

Upon receiving the NPSS 301 and NSSS 302， the terminal device 120 may determine that the NB-MIB 303 is transmitted on the second anchor carrier. After reading NB-MIB 303 in the subframe#0 on the second anchor carrier， the terminal device 120 may determine that subframe#5 on second anchor is used for transmission of the NB-SIB1 304. Then， the terminal device 120 receives the NB-SIB1 304 in subframe#5 on the second anchor carrier. The NB-SIB1 304 may include information concerning at least one of： subframes in which other SIBs are transmitted， and the at least one of the first anchor carrier， the second anchor carrier and the third anchor carrier on which other SIBs are transmitted. Thereby， the terminal device 120 can do reception of other SIBs in the indicated subframes on the corresponding anchor carriers.

An example of the part of NB-SIB1 is given as below：

In this example， the umber (i.e.， -55... 54) is used to show the PRB index offset to the first anchor carrier.

Fig. 11 shows a flowchart of an example method 1100 implemented at a network device in a wireless communication system in accordance with some embodiments of the present disclosure. The method 1100 can be implemented at the network device 110 as shown in Fig. 1. For the purpose of discussion， the method 1100 will be described from the perspective of the network device 110 with reference to Fig. 1.

At block 1110， the network device 110 transmits， to the terminal device 120， narrowband synchronization signals on a first anchor carrier.

At block 1120， the network device 110 determines whether a Narrowband Master Information Block (NB-MIB) in narrowband system information is to be transmitted on the first anchor carrier or a second anchor carrier， the second anchor carrier having a first fiequency offset from the first anchor carrier.

At block 1130， the network device 110 transmits， based on the determination， the NB-MIB to the terminal device 120.

In some embodiments， the method 1100 further comprises determining a pattern of the narrowband synchronization signals based on the determination.

In some embodiments， determining the pattern of the narrowband synchronization signals comprises determining a pattern of a NPSS.

In some embodiments， transmitting the narrowband synchronization signals comprises： transmitting a NPSS in a first subframe on the first anchor carrier； and transmitting a NSSS in a second subframe on the first anchor carrier. A subframe offset between the first subframe and the second subframe is determined based on the determination.

In some embodiments， the method 1100 further comprises in response to determining that the NB-MIB is to be transmitted on the first anchor carrier， determining whether a first Narrowband System Information Block (NB-SIB) in narrowband system information is to be transmitted on the first anchor carrier or the second anchor carrier， the first NB-SIB including information that enables the terminal device to camp in a cell that is provided by the network device， and transmitting the first NB-SIB based on determining whether the first NB-SIB is to be transmitted on the first anchor carrier or the second anchor carrier. The method 1100 further comprises in response to determining that the NB-MIB is to be transmitted on the second anchor carrier， transmitting the first NB-SIB on the second anchor carrier.

In some embodiments， the method 1100 further comprises transmitting a second NB-SIB in the narrowband system information on at least one of the first anchor carrier， the second anchor carrier and a third anchor carrier， the second NB-SIB being different from the first NB-SIB， the third anchor carrier having a second frequency offset from the first anchor carrier.

It is to be understood that all operations and features related to the network device 110 described above with reference to Figs. 2 to 10 are likewise applicable to the method 1100 and have similar effects. For the purpose of simplification， the details will be omitted.

Fig. 12 shows a flowchart of an example method 1200 implemented at a terminal device in a wireless communication system in accordance with some embodiments of the present disclosure. The method 1200 can be implemented at the terminal device 120 as shown in Fig. 1. For the purpose of discussion， the method 1200 will be described from the perspective of the terminal device 120 with reference to Fig. 1.

At block 1210， the terminal device 120 receives， from the network device 110， narrowband synchronization signals on a first anchor carrier.

At block 1220， the terminal device 120 determines whether a NB-MIB in narrowband system information is to be received on the first anchor carrier or a second anchor carrier， the second anchor carrier having a first frequency offset from the first anchor carrier.

At block 1230， the terminal device 120 receives， based on the determination， the NB-MIB from the network device 110.

In some embodiments， receiving the narrowband synchronization signals comprises receiving a NPSS； and the determining comprises determining based on a pattern of the received NPSS.

In some embodiments， receiving the narrowband synchronization signals comprises： receiving a NPSS in a first subframe on the first anchor carrier； and receiving a NSSS in a second subframe on the first anchor carrier， the second subframe having a determined subframe offset from the first subframe.

In some embodiments， the method 1200 further comprises in response to determining that the NB-MIB is to be received on the first anchor carrier， determining whether a first NB-SIB in narrowband system information is to be received on the first anchor carrier or the second anchor carrier， the first NB-SIB including information that enables the terminal device to camp in a cell that is provided by the network device， and receiving the first NB-SIB based on determining whether the first NB-SIB is to be received on the first anchor carrier or the second anchor carrier； and in response to determining that the NB-MIB is to be received on the second anchor carrier， receiving the first NB-SIB on the second anchor carrier.

In some embodiments， the method 1200 further comprises receiving a second NB-SIB in the narrowband system information on at least one of the first anchor carrier， the second anchor carrier and a third anchor carrier. The second NB-SIB is different from the first NB-SIB， and the third anchor carrier has a second frequency offset from the first anchor carrier.

In some embodiments， the first NB-SIB includes information concerning at least one off a subframe in which the second NB-SIB is to be received， and the at least one of the first anchor carrier， the second anchor carrier and the third anchor carrier on which the second NB-SIB is to be received.

In some embodiments， the method 1200 further comprises determining a frequency of the second anchor carrier based on the identifier of the cell.

It is to be understood that all operations and features related to the terminal device 120 described above with reference to Figs. 2 to 10 are likewise applicable to the method 1200 and have similar effects. For the purpose of simplification， the details will be omitted.

Fig. 13 is a simplified block diagram of a device 1300 that is suitable for implementing embodiments of the present disclosure. The device 1300 can be considered as a further example implementation of the terminal device 120 or the network device 110 as shown in Figs. 1 and 2. Accordingly， the device 1300 can be implemented at or as at least a part of the terminal device 120 or the network device 110.

As shown， the device 1300 includes a processor 1310， a memory 1320 coupled to the processor 1310， a suitable transmitter (TX) and receiver (RX) 1340 coupled to the processor 1310， and a communication interface coupled to the TX/RX 1340. The memory 1320 stores at least a part of a program 1330. The TX/RX 1340 is for bidirectional communications. The TX/RX 1340 has at least one antenna to facilitate communication， though in practice an Access Node mentioned in this application may have several ones. The communication interface may represent any interface that is necessary for communication with other network elements， such as X2 interface for bidirectional communications between eNBs， S1 interface for communication between a Mobility Management Entity (MME) /Serving Gateway (S-GW) and the eNB， Un interface for communication between the eNB and a relay node (RN) ， or Uu interface for communication between the eNB and a terminal device.

The program 1330 is assumed to include program instructions that， when executed by the associated processor 1310， enable the device 1300 to operate in accordance with the embodiments of the present disclosure， as discussed herein with reference to Figs. 2 to 12. The embodiments herein may be implemented by computer software executable by the processor 1310 of the device 1300， or by hardware， or by a combination of software and hardware. The processor 1310 may be configured to implement various embodiments of the present disclosure. Furthermore， a combination of the processor 1310 and memory 1320 may form processing means 1350 adapted to implement various embodiments of the present disclosure.

The memory 1320 may be of any type suitable to the local technical network and may be implemented using any suitable data storage technology， such as a non-transitory computer readable storage medium， semiconductor based memory devices， magnetic memory devices and systems， optical memory devices and systems， fixed memory and removable memory， as non-limiting examples. While only one memory 1320 is shown in the device 1300， there may be several physically distinct memory modules in the device 1300. The processor 1310 may be of any type suitable to the local technical network， and may include one or more of general purpose computers， special purpose computers， microprocessors， digital signal processors (DSPs) and processors based on multicore processor architecture， as non-limiting examples. The device 1300 may have multiple processors， such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

Generally， various embodiments of the present disclosure may be implemented in hardware or special purpose circuits， software， logic or any combination thereof. Some aspects may be implemented in hardware， while other aspects may be implemented in firmware or software which may be executed by a controller， microprocessor or other computing device. While various aspects of embodiments of the present disclosure are illustrated and described as block diagrams， flowcharts， or using some other pictorial representation， it will be appreciated that the blocks， apparatus， systems， techniques or methods described herein may be implemented in， as non-limiting examples， hardware， software， firmware， special purpose circuits or logic， general purpose hardware or controller or other computing devices， or some combination thereof.

The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computer-executable instructions， such as those included in program modules， being executed in a device on a target real or virtual processor， to carry out the process or method as described above with reference to any of Figs. 2， 6， and 7. Generally， program modules include routines， programs， libraries， objects， classes， components， data structures， or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device， program modules may be located in both local and remote storage media.

Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer， special purpose computer， or other programmable data processing apparatus， such that the program codes， when executed by the processor or controller， cause the functions/operations specified in the flowcharts and/or block diagrams to be implemented. The program code may execute entirely on a machine， partly on the machine， as a stand-alone software package， partly on the machine and partly on a remote machine or entirely on the remote machine or server.

The above program code may be embodied on a machine readable medium， which may be any tangible medium that may contain， or store a program for use by or in connection with an instruction execution system， apparatus， or device. The machine readable medium may be a machine readable signal medium or a machine readable storage medium. A machine readable medium may include but not limited to an electronic， magnetic， optical， electromagnetic， infrared， or semiconductor system， apparatus， or device， or any suitable combination of the foregoing. More specific examples of the machine readable storage medium would include an electrical connection having one or more wires， a portable computer diskette， a hard disk， a random access memory (RAM) ， a read-only memory (ROM) ， an erasable programmable read-only memory (EPROM or Flash memory) ， an optical fiber， a portable compact disc read-only memory (CD-ROM) ， an optical storage device， a magnetic storage device， or any suitable combination of the foregoing.

Further， while operations are depicted in a particular order， this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order， or that all illustrated operations be performed， to achieve desirable results. In certain circumstances， multitasking and parallel processing may be advantageous. Likewise， while several specific implementation details are contained in the above discussions， these should not be construed as limitations on the scope of the present disclosure， but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely， various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

Although the present disclosure has been described in language specific to structural features and/or methodological acts， it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather， the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

A method implemented at a network device in a wireless communication system， comprising：

transmitting， to a terminal device， narrowband synchronization signals on a first anchor carrier；

determining whether a Narrowband Master Information Block (NB-MIB) in narrowband system information is to be transmitted on the first anchor carrier or a second anchor carrier， the second anchor carrier having a first frequency offset from the first anchor carrier； and

transmitting， based on the determination， the NB-MIB to the terminal device.
The method of claim 1， further comprising：

determining a pattern of the narrowband synchronization signals based on the determination.
The method of claim 2， wherein determining the pattern of the narrowband synchronization signals comprises：

determining a pattern of a Narrowband Primary Synchronization Signal (NPSS) .
The method of claim 1， wherein transmitting the narrowband synchronization signals comprises：

transmitting a Narrowband Primary Synchronization Signal (NPSS) in a first subframe on the first anchor carrier； and

transmitting a Narrowband Secondary Synchronization Signal (NSSS) in a second subframe on the first anchor carrier， a subframe offset between the first subframe and the second subframe being determined based on the determination.
The method of any of claims 1 to 4， further comprising：

in response to determining that the NB-MIB is to be transmitted on the first anchor carrier，

determining whether a first Narrowband System Information Block (NB-SIB) in narrowband system information is to be transmitted on the first anchor carrier or the second anchor carrier， the first NB-SIB including information that enables the terminal device to camp in a cell that is provided by the network device， and

transmitting the first NB-SIB based on determining whether the first NB-SIB is to be transmitted on the first anchor carrier or the second anchor carrier； and

in response to determining that the NB-MIB is to be transmitted on the second anchor carrier， transmitting the first NB-SIB on the second anchor carrier.
The method of claim 5， wherein the NB-MIB includes at least one of：

an indication of a subframe in which the first NB-SIB is transmitted， and

an indication of one of the first and second anchor carriers on which the first NB-SIB is transmitted.
The method of claim 6， further comprising：

transmitting a second NB-SIB in the narrowband system information on at least one of the first anchor carrier， the second anchor carrier and a third anchor carrier， the second NB-SIB being different from the first NB-SIB， the third anchor carrier having a second frequency offset from the first anchor carrier.
The method of claim 7， wherein the first NB-SIB includes information concerning at least one of：

a subframe in which the second NB-SIB is transmitted， and

the at least one of the first anchor carrier， the second anchor carrier and the third anchor carrier on which the second NB-SIB is transmitted.
The method of claim 1， wherein transmitting the narrowband synchronization signals comprises：

transmitting a Narrowband Secondary Synchronization Signal (NSSS) ， the NSSS including an identifier of a cell that is provided by the network device.
The method of claim 9， wherein a frequency of the second anchor carrier is associated with the identifier of the cell.
A method implemented at a terminal device in a wireless communication system， comprising：

receiving， from a network device， narrowband synchronization signals on a first anchor carrier；

determining whether a Narrowband Master Information Block (NB-MIB) in narrowband system information is to be received on the first anchor carrier or a second anchor carrier， the second anchor carrier having a first frequency offset from the first anchor carrier； and

receiving， based on the determination， the NB-MIB from the network device.
The method of claim 11， wherein the determining comprises：

determining based on a pattern of the received narrowband synchronization signals.
The method of claim 12， wherein：

receiving the narrowband synchronization signals comprises：

receiving a Narrowband Primary Synchronization Signal (NPSS) ； and

the determining comprises：

determining based on a pattern of the received NPSS.
The method of claim 11， wherein receiving the narrowband synchronization signals comprises：

receiving a Narrowband Primary Synchronization Signal (NPSS) in a first subframe on the first anchor carrier； and

receiving a Narrowband Secondary Synchronization Signal (NSSS) in a second subframe on the first anchor carrier， the second subframe having a pretermined subframe offset from the first subframe.
The method of claim 14， wherein the determining comprises：

determining based on the subframe offset.
The method of any of claims 11 to 15， further comprising：

in response to determining that the NB-MIB is to be received on the first anchor carrier，

determining whether a first Narrowband System Information Block (NB-SIB) in narrowband system information is to be received on the first anchor carrier or the second anchor carrier， the first NB-SIB including information that enables the terminal device to camp in a cell that is provided by the network device， and

receiving the first NB-SIB based on determining whether the first NB-SIB is to be received on the first anchor carrier or the second anchor carrier； and

in response to determining that the NB-MIB is to be received on the second anchor carrier， receiving the first NB-SIB on the second anchor carrier.
The method of claim 16， wherein the NB-MIB includes at least one of：

an indication of a subframe in which the first NB-SIB is to received， and

an indication of one of the first and second anchor carriers on which the first NB-SIB is to be received.
The method of claim 17， further comprising：

receiving a second NB-SIB in the narrowband system information on at least one of the first anchor carrier， the second anchor carrier and a third anchor carrier， the second NB-SIB being different from the first NB-SIB， the third anchor carrier having a second frequency offset from the first anchor carrier.
The method of claim 18， wherein the first NB-SIB includes information concerning at least one of：

a subframe in which the second NB-SIB is to be received， and

the at least one of the first anchor carrier， the second anchor carrier and the third anchor carrier on which the second NB-SIB is to be received.
The method of claim 11， wherein receiving the narrowband synchronization signals comprises：

receiving a Narrowband Secondary Synchronization Signal (NSSS) ， the NSSS including an identifier of a cell that is provided by the network device.
The method of claim 20， further comprising：

determining a frequency of the second anchor carrier based on the identifier of the cell.
A network device， comprising：

a processor； and

a memory coupled to the processor and storing instructions thereon， the instructions， when executed by the processor， causing the network device to perform the method according to any of claims 1 to 10.
A terminal device， comprising：

a processor； and

a memory coupled to the processor and storing instructions thereon， the instructions， when executed by the processor， causing the terminal device to perform the method according to any of claims 11 to 21.
A computer readable medium storing instructions thereon， the instructions， when executed by at least one processing unit of a machine， causing the machine to perform the method according to any of claims 1 to 10.
A computer readable medium storing instructions thereon， the instructions， when executed by at least one processing unit of a machine， causing the machine to perform the method according to any of claims 11 to 21.