WO2013131267A1

WO2013131267A1 - Spectrum sensing and cross-carrier scheduling

Info

Publication number: WO2013131267A1
Application number: PCT/CN2012/072088
Authority: WO
Inventors: Haiming Wang; Xinying Gao; Chunyan Gao; Pengfei Sun
Original assignee: 5Renesas Mobile Corporation
Priority date: 2012-03-08
Filing date: 2012-03-08
Publication date: 2013-09-12

Abstract

When a location of a user equipment is detected where spectrum sensing to find out possible free resources for radio communication is defined, a sensing function is enabled for performing the spectrum sensing by using symbols of a control portion of a component carrier, which are free to be used due to a cross-carrier scheduling, and the cross-carrier scheduling is enabled. Alternatively, when receipt of a first network command to configure cross-carrier scheduling is detected, enabling the cross-carrier scheduling and the sensing function are enabled. A sensing configuration may be associated to a number of the symbols free to be used due to the cross-carrier scheduling.

Description

SPECTRUM SENSING AND CROSS-CARRIER SCHEDULING

BACKGROUND OF THE INVENTION

Field of the invention

The present invention relates to enabling spectrum sensing to find out possible free resources for radio communication, and cross-carrier scheduling.

Related background Art

The following meanings for the abbreviations used in this specification apply:

CA Carrier Aggregation

CC Component Carrier

D2D Device to Device

DFA Dynamic Frequency Access

DL Downlink

DwPTS Downlink Pilot Time Slot

eNB evolved Node B

FD Full Duplex

GP Guard Period

LTE Long-Term Evolution

OFDM Orthogonal Frequency Division Multiplex

OS OFDM Symbol

PDCCH Physical Downlink Control CHannel

Rx Receiver

Tx Transmitter

UE User Equipment

Unlicensed band utilization for an LTE system is becoming an important topic. It may offer the operator an opportunity to offload traffic from expensive licensed LTE bands to zero-cost unlicensed bands when necessary. By using unlicensed bands for the LTE system, some valuable benefits can be obtained, e.g. balancing traffic load when necessary, improving a peak data rate, and thus improving spectrum efficiency in general for the operator.

For efficient coexistence of different radio systems on unlicensed bands, spectrum sensing is important to get aware of spectrum usage in order to avoid inter-system interference. In a cognitive radio concept, measurement and sensing are a first step to find out possible free channels. Recently developed wireless standards have started to include some sort of spectrum sensing for dynamic frequency access (DFA) adaptation.

According to another situation, in local area simultaneous transmission and reception on the same carrier (full-duplex, FD) has been demonstrated to be feasible in recent research. Compared to non-FD transmission, FD operation is more susceptible to exterior interference due to simultaneous DL and UL. Hence, to achieve the expected increase in throughput through FD operation, performing sensing before FD enablement is also significant for obtaining knowledge of an interference level on FD resources in radio environment.

Spectrum sensing is performed in order to get aware of spectrum usage and existence of primary users in a geographical area. This awareness can be obtained by using geo-location and database, by using beacons, or by local spectrum sensing at cognitive radio bands. In LTE D2D scenario, possible resources for sensing are at GP in DwPTS, PDCCH symbols, etc. SUMMARY OF THE INVENTION

The present invention aims at enabling spectrum sensing to find out possible free resources for radio communication that can be implemented in an efficient way in a radio communications network system.

In addition, the invention aims at efficiently utilizing resources for the spectrum sensing. This is at least in part achieved by the methods and apparatuses as defined in the appended claims. The invention may also be implemented by a computer program product. According to an embodiment of the invention, a sensing function is coupled with cross-carrier scheduling.

According to another embodiment of the invention, a configuration of the sensing function is associated to a number of control symbols which are free due to the cross-carrier scheduling.

Therefore, when an LTE system works on unlicensed bands or performs FD transmission at least one of the following benefits can be achieved with the present invention :

- a terminal can couple data and sensing function with backward compatibility,

- there is no need to blank one sensing function totally,

- idle OFDM symbols can be fully used, and

- good co-existence with other radio systems or non-FD UEs can be achieved. In the following the invention will be described by way of exemplary

embodiments thereof with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a diagram illustrating free time slots (symbols) of component carriers used for cross-carrier scheduling.

Fig. 2 shows a flowchart illustrating a process of enabling a sensing function according to an exemplary embodiment of the invention.

Fig. 3 shows a flowchart illustrating a process of enabling a sensing function according to an exemplary embodiment of the invention.

Fig. 4 shows a flowchart illustrating a process of enabling a sensing function according to an exemplary embodiment of the invention. Fig. 5 shows a diagram illustrating an implementation example of coupling a sensing function with cross-carrier scheduling according to an embodiment of the invention.

Fig. 6 shows time charts illustrating examples of a sensing configuration of the sensing function according to an embodiment of the invention.

Fig. 7 shows a simplified block diagram of various electronic devices that are suitable for use in practicing the exemplary embodiments of the present invention.

DESCRIPTION OF THE EMBODIMENTS Considering an LTE system as an example of a communications network system, operation on an unlicensed band or efficient FD transmission requires a sensing function of a UE, and a time gap is needed for performing the sensing function. In addition, a design with backward compatibility is preferred, i.e. network modification should not be required when the sensing function is enabled.

For an inter-band CA case, each band has one Tx/Rx chain. If it is not used for data transmission or reception, potentially it can be used for other purposes.

When cross-carrier scheduling is enabled, a control portion on a concerned CC is free to be used, as shown in Fig. 1. Fig. 1 shows component carriers CC1 and CC2 which are used in the cross-carrier scheduling. The control portion of the CC2 contains free OFDM symbols which may be used to perform the sensing function. The sensing function may be designed to be implemented by each UE since an eNB may want to know whether an unlicensed band is suitable for a certain UE.

In order to support efficient LTE utilization on unlicensed bands or full-duplex (FD) operation, it is proposed to configure a sensing pattern of a sensing function by high-layer signaling and enable it by a cross-carrier scheduling command implicitly and automatically. According a first alternative, when the sensing function has been enabled by a UE in a location where sensing is defined, cross-carrier scheduling is enabled automatically. According to a second alternative, the sensing function, e.g. whether to perform sensing in free OFDM symbols, is enabled or disabled by a cross-carrier scheduling command implicitly. In other words, if cross-carrier scheduling is configured for a UE, the sensing function of the UE is enabled, and when cross- carrier scheduling is de-configured for the UE, the sensing function of the UE is disabled.

It is to be noted that in the location where sensing is not defined, the UE may follow a network command, e.g. a command from a base station of the

communications network system, on whether cross-carrier scheduling is to be used.

The base station, e.g. an eNB, may configure the sensing function. According to an automatic connection between OS number and sensing pattern, a different number of free control OFDM symbols may enable different sensing patterns automatically.

Therefore, a sensing function can be linked to cross-carrier scheduling efficiently, e.g. one function will enable or disable the other function automatically.

Alternatively or in addition, a sensing configuration can be linked to the number of free control OFDM symbols automatically.

Fig. 2 shows a flowchart illustrating a process of enabling a sensing function according to an exemplary embodiment of the invention. The process may be executed by a user equipment.

In step S31, it is checked whether or not a location of the user equipment (UE) is detected where spectrum sensing to find out possible free resources for radio communication is defined. In case the location is detected (YES in S31), a sensing function is enabled for performing the spectrum sensing by using symbols (e.g. control OFDM symbols) of a control portion of a component carrier, which are free to be used due to a cross-carrier scheduling, and the cross-carrier scheduling is enabled in step S32.

In case the location is not detected (NO in S31), the cross-carrier scheduling may be enabled or disabled upon receipt of a corresponding network command in step S36.

Cross-carrier scheduling is configured by high-layer signaling, and it does not take effect immediately when the UE receives this configuration signaling. Hence, the sensing function should not take effect as well to avoid collision when receiving cross-carrier scheduling signaling. For example, as illustrated in Fig. 5, only when the UE can receive control signaling from another CC after cross- carrier scheduling configuration (e.g. valid timing points of cross-carrier scheduling), it may enable its sensing function. Fig. 5 shows that control OFDM symbols of CC2 are used for the sensing function.

Referring again to Fig . 2, in step S33 it may be checked whether or not the control signaling is received from the component carrier of the cross-carrier scheduling, and sensing according to the sensing function may be enabled after receipt of such control signaling (step S34).

In step S35 a sensing configuration, e.g. as configured by the network, may be associated to a number of the symbols free to be used due to the cross-carrier scheduling. Step S35 is shown as process which may be implemented in addition or alternatively to steps S31-S34 and S36.

According to the process of S35, the sensing configuration may be associated to the number of the symbols such that a smaller number of the symbols results in enabling sensing according to the sensing function more often in time domain.

In other words, basically the sensing pattern to utilize control domain is configurable and implicitly linked to the number of available control symbols. As illustrated in Fig. 6, less number of free OFDM symbols will enable more density of configuration in time domain. For example, in a first row in Fig. 6, there is one control OS available, so the sensing is enabled every radio subframe (i.e. every 1ms). In a second row in Fig. 6, there are two control OSs available, so the sensing is enabled every other radio subframe (i.e. every 2ms). In a third row in Fig. 6, there are three control OSs available, so the sensing is enabled every fourth radio subframe (every 4ms). Of course, as illustrated in rows 4 and 5, a more detailed sensing sequence in time domain can be designed as well.

Fig. 3 shows a flowchart illustrating a process of enabling a sensing function according to an alternative exemplary embodiment of the invention. The process may be executed by a user equipment.

In step S41 it is checked whether a first network command to configure cross- carrier scheduling or a second network command to de-configure cross-carrier scheduling is received. When the first network command is received in S41, the cross-carrier scheduling is enabled and a sensing function is enabled in step S42 for performing spectrum sensing to find out possible free resources for radio communication by using symbols (e.g. control OFDM symbols) of a control portion of a component carrier, which are free to be used due to the cross-carrier scheduling.

In case the second network command is received in S41, the cross-carrier scheduling is de-configured and the sensing function is disabled in step S46. The processes of steps S43 and S44 are similar to those of steps S33 and S34 and, thus, it is referred to the description of steps S33 and S34 and repetition of their description is omitted here.

Fig. 4 shows a flowchart illustrating a process of enabling a sensing function according to an exemplary embodiment of the invention. The process may be executed by a network apparatus, e.g. a base station such as an eNB,

In step S51, signaling of a sensing configuration is caused, for a sensing function to be performed by a user equipment for performing spectrum sensing to find out possible free resources for radio communication by using symbols (e.g. control OFDM symbols) of a control portion of a component carrier, which are free to be used due to a cross-carrier scheduling.

In step S52, transmittal of a first network command is caused to configure the cross-carrier scheduling in order to enable the sensing function. Moreover, in step S52 transmittal of a second network command may be caused to de- configure the cross-carrier scheduling in order to disable the sensing function.

Now reference is made to Fig. 7 for illustrating a simplified block diagram of various electronic devices that are suitable for use in practicing the exemplary embodiments of this invention.

A user equipment 10 includes processing resources 11, memory resources 12 and interfaces 13, which are connected through a link 14. The memory resources 12 may store one or more programs, and the interfaces 13 may include a suitable radio frequency (RF) transceiver coupled to one or more antennas (not shown) for bidirectional wireless communications over one or more wireless links 30 with a network apparatus 20 e.g. a base station such as an eNB. The user equipment 10 may execute the processes of enabling the sensing function illustrated in Figs. 2 and 3 and, alternatively, the process of steps S35, S45 alone, by using its processing resources 11, memory resources 12 and interfaces 13. The network apparatus 20 includes processing resources 21, memory resources 22 and interfaces 23, which are connected through a link 24. The memory resources 22 may store one or more programs, and the interfaces 23 may include a suitable radio frequency (RF) transceiver coupled to one or more antennas (not shown) for bidirectional wireless communications over one or more wireless links 30 with the user equipment 10.

The network apparatus 20 may execute the processes of enabling the sensing function illustrated in Fig. 4, by using its processing resources 21, memory resources 22 and interfaces 23. The terms "connected," "coupled," or any variant thereof, mean any connection or coupling, either direct or indirect, between two or more elements, and may encompass the presence of one or more intermediate elements between two elements that are "connected" or "coupled" together. The coupling or connection between the elements can be physical, logicai, or a combination thereof. As employed herein two elements may be considered to be "connected" or "coupled" together by the use of one or more wires, cables and printed electrical

connections, as well as by the use of electromagnetic energy, such as

electromagnetic energy having wavelengths in the radio frequency region, the microwave region and the optical (both visible and invisible) region, as non- limiting examples.

At least one of the programs stored in the memory resources 12, 22 is assumed to include program instructions that, when executed by the associated

processing resources 11, 21, enable the electronic device to operate in

accordance with the exemplary embodiments of this invention, as detailed above. Inherent in the processing resources 11, 21 is a clock to enable synchronism among the various apparatus for transmissions and receptions within the appropriate time intervals and slots required, as the scheduling grants and the granted resources/sub-frames are time dependent. The transceivers included in the interfaces 13, 23 include both transmitter and receiver, and inherent in each is a modulator/demodulator commonly known as a modem. The processing resources 21 also are assumed to include a modem to facilitate communication over one ore more hardwire links within the network.

In general, the exemplary embodiments of this invention may be implemented by computer software stored in the memory resources 12, 22 and executable by the processing resources 11, 21, respectively, or by hardware, or by a

combination of software and/or firmware and hardware in any or all of the devices shown. Further in this regard it should be noted that the various process step descriptions above may represent interconnected circuitries.

As used in this application, the term 'circuitry' refers to all of the following :

(a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and (b) to combinations of circuits and software (and/or firmware), such as (as applicable): (i) to a combination of processor(s) or (ii) to portions of

processor(s)/software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and

(c) to circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present. This definition of 'circuitry' applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term 'circuitry' would also cover an implementation of merely a processor (or multiple processors) or portion of a processor and its (or their) accompanying software and/or firmware. The term 'circuitry' would also cover, for example and if applicable to the particular claim element, a baseband integrated circuit or applications processor integrated circuit for a mobile phone or a similar integrated circuit in server, a cellular network device, or other network device.

In general, the various embodiments of the user equipment 10 can include, but are not limited to, mobile stations, cellular telephones, personal digital assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback appliances having wireless communication capabilities, Internet appliances permitting wireless Internet access and browsing, as well as portable units or terminals that incorporate combinations of such functions.

The memory resources 12, 22 may be of any type suitable to the local technical environment and may be implemented using any suitable data storage

technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The processing resources 11, 21 may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multi-core processor architecture, as non-limiting examples.

According to an aspect of the invention, an apparatus, e.g. the user equipment shown in Fig. 7, comprises detecting means for detecting a location of the user equipment where spectrum sensing to find out possible free resources for radio communication is defined, and enabling/disabling means for, upon detecting the location, enabling a sensing function for performing the spectrum sensing by using symbols of a control portion of a component carrier, which are free to be used due to a cross-carrier scheduling and enabling the cross-carrier scheduling.

In a location where the spectrum sensing is not defined, the enabling/disabling means may enable/disable the cross-carrier scheduling upon receipt of a corresponding network command.

The apparatus may comprise associating means for associating a sensing configuration to a number of the symbols free to be used due to the cross-carrier scheduling. The associating means may associate the sensing configuration to the number of the symbols such that a smaller number of the symbols results in enabling sensing according to the sensing function more often in time domain .

The enabling/disabling means may enable sensing according to the sensing function after receipt of control signaling from the component carrier.

The detecting means, enabling/disabling means and associating means may be implemented by the processing resources 11, memory resources 12 and interfaces 13 shown in Fig. 7.

According to another aspect of the invention, an apparatus, e.g. the user equipment 10 shown in Fig. 7, comprises detecting means for detecting receipt of a first network command to configure cross-carrier scheduling, and

enabling/disabling means for, upon receipt of the first network command, enabling the cross-carrier scheduling and enabling a sensing function for performing spectrum sensing to find out possible free resources for radio communication by using symbols of a control portion of a component carrier, which are free to be used due to the cross-carrier scheduling. The detecting means may detect receipt of a second network command to de- configure the cross-carrier scheduling, and upon receipt of the second network command, the enabling/disabling means may disable the cross-carrier scheduling and disable the sensing function. The apparatus may comprise associating means for associating a sensing configuration to a number of the symbols free to be used due to the cross-carrier scheduling.

The associating means may associate the sensing configuration to the number of the symbols such that a smaller number of the symbols results in enabling sensing according to the sensing function more often in time domain.

The detecting means, enabling/disabling means and associating means may be implemented by the processing resources 11, memory resources 12 and interfaces 13 shown in Fig. 7. According to another aspect of the invention, an apparatus, e.g. the user equipment 10 shown in Fig. 7, comprises enabling/disabling means for enabling a sensing function for performing spectrum sensing to find out possible free resources for radio communication by using symbols of a control portion of a component carrier, which are free to be used due to cross-carrier scheduling, and associating means for associating a sensing configuration to a number of the symbols free to be used due to the cross-carrier scheduling.

The associating means may associate the sensing configuration to the number of the symbols such that a smaller number of the symbols results in enabling sensing according to the sensing function more often in time domain. The enabling/disabling means may enable sensing according to the sensing function after receipt of control signaling from the component carrier. The enabling/disabling means and associating means may be implemented by the processing resources 11, memory resources 12 and interfaces 13 shown in Fig. 7.

According to another aspect of the invention, an apparatus, e.g. the network apparatus 20 in Fig. 7, comprises means for causing signaling of a sensing configuration for a sensing function to be performed by a user equipment for performing spectrum sensing to find out possible free resources for radio communication by using symbols of a control portion of a component carrier, which are free to be used due to a cross-carrier scheduling, and means for causing transmittal of a first network command to configure the cross-carrier scheduling in order to enable the sensing function.

The apparatus may comprise means for causing transmittal of a second network command to de-configure the cross-carrier scheduling in order to disable the sensing function.

The above means for causing may be implemented by the processing resources 21, memory resources 22 and interfaces 23 shown in Fig. 7. According to an aspect of the invention, when a location of a user equipment is detected where spectrum sensing to find out possible free resources for radio communication is defined, a sensing function is enabled for performing the spectrum sensing by using symbols of a control portion of a component carrier, which are free to be used due to a cross-carrier scheduling, and the cross-carrier scheduling is enabled. Alternatively, when receipt of a first network command to configure cross-carrier scheduling is detected, enabling the cross-carrier scheduling and the sensing function are enabled. A sensing configuration may be associated to a number of the symbols free to be used due to the cross-carrier scheduling. It is to be understood that the above description is illustrative of the invention and is not to be construed as limiting the invention. Various modifications and applications may occur to those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims.

Claims

What is Claimed is:

1. A method for use by a user equipment, the method comprising :

detecting a location of the user equipment where spectrum sensing to find out possible free resources for radio communication is defined; and upon detecting the location, enabling a sensing function for performing the spectrum sensing by using symbols of a control portion of a component carrier, which are free to be used due to a cross-carrier scheduling and enabling the cross-carrier scheduling.

2. The method of claim 1, comprising :

in a location where the spectrum sensing is not defined,

enabling/disabling the cross-carrier scheduling upon receipt of a

corresponding network command.

3. A method for use by a user equipment, comprising :

detecting receipt of a first network command to configure cross- carrier scheduling; and

upon receipt of the first network command, enabling the cross-carrier scheduling and enabling a sensing function for performing spectrum sensing to find out possible free resources for radio communication by using symbols of a control portion of a component carrier, which are free to be used due to the cross-carrier scheduling.

4. The method of claim 3, comprising :

detecting receipt of a second network command to de-configure the cross-carrier scheduling; and

upon receipt of the second network command, disabling the cross-carrier scheduling and disabling the sensing function.

5. The method of any one of claims 1 to 4, comprising:

associating a sensing configuration to a number of the symbols free to be used due to the cross-carrier scheduling.

6. A method for use by a user equipment, the method comprising :

enabling a sensing function for performing spectrum sensing to find out possible free resources for radio communication by using symbols of a control portion of a component carrier, which are free to be used due to cross-carrier scheduling; and

7. The method of claim 5 or 6, comprising:

associating the sensing configuration to the number of the symbols such that a smaller number of the symbols results in enabling sensing according to the sensing function more often in time domain.

8. The method of any one of claims 1 to 7, comprising:

enabling sensing according to the sensing function after receipt of control signaling from the component carrier.

9. A method for use by a network apparatus of a communications network system, the method comprising :

causing signaling of a sensing configuration for a sensing function to be performed by a user equipment for performing spectrum sensing to find out possible free resources for radio communication by using symbols of a control portion of a component carrier, which are free to be used due to a cross-carrier scheduling; and

causing transmittal of a first network command to configure the cross- carrier scheduling in order to enable the sensing function.

10. The method of claim 9, comprising :

causing transmittal of a second network command to de-configure the cross-carrier scheduling in order to disable the sensing function.

11. A computer program product including a program for a processing device, comprising software code portions for performing the steps of any one of claims 1 to 10 when the program is run on the processing device.

12. The computer program product according to claim 11, wherein the computer program product comprises a computer-readable medium on which the software code portions are stored.

13. The computer program product according to claim 11, wherein the program is directly loadable into an internal memory of the processing device.

14. An apparatus comprising :

at least one processor; and

at least one memory including computer program code,

the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform : detecting a location of the apparatus where spectrum sensing to find out possible free resources for radio communication is defined; and

upon detecting the location, enabling a sensing function for

performing the spectrum sensing by using symbols of a control portion of a component carrier, which are free to be used due to a cross-carrier scheduling and enabling the cross-carrier scheduling.

15. The apparatus of claim 14, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform:

in a location where the spectrum sensing is not defined,

enabling/disabling the cross-carrier scheduling upon receipt of a

corresponding network command.

16. An apparatus comprising :

at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform : detecting receipt of a first network command to configure cross- carrier scheduling; and

17. The apparatus of claim 16, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform :

upon receipt of the second network command, disabling the cross- carrier scheduling and disabling the sensing function.

18. The apparatus of any one of claims 14 to 17, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform:

19. An apparatus comprising :

at least one processor; and

at least one memory including computer program code,

the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform : enabling a sensing function for performing spectrum sensing to find out possible free resources for radio communication by using symbols of a control portion of a component carrier, which are free to be used due to cross-carrier scheduling; and

20. The apparatus of claim 18 or 19, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform:

21. The apparatus of any one of claims 14 to 20, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform:

22. An apparatus comprising :

at least one processor; and

at least one memory including computer program code,

the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform: causing signaling of a sensing configuration for a sensing function to be performed by a user equipment for performing spectrum sensing to find out possible free resources for radio communication by using symbols of a control portion of a component carrier, which are free to be used due to a cross-carrier scheduling; and

causing transmittal of a first network command to configure the cross-carrier scheduling in order to enable the sensing function.

23. The apparatus of claim 22, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform: