CN109417792B

CN109417792B - Method and apparatus for supporting access to unlicensed radio resources in a wireless communication system

Info

Publication number: CN109417792B
Application number: CN201780023834.6A
Authority: CN
Inventors: 柳光
Original assignee: JRD Communication Shenzhen Ltd
Current assignee: JRD Communication Shenzhen Ltd
Priority date: 2016-05-13
Filing date: 2017-05-03
Publication date: 2023-04-04
Anticipated expiration: 2037-05-03
Also published as: CN114095941A; GB201608407D0; WO2017193843A1; GB2550200B; GB2550200A; CN109417792A

Abstract

The embodiments of the present application disclose a method for supporting access to an unlicensed communication channel using a Listen Before Talk (LBT) procedure in an LTE system, comprising parameters in a downlink control information message sent from an eNB (101) to a user equipment (103 a) for assisting the user equipment to access the unlicensed channel more efficiently. One parameter relates to the remaining MCOT (maximum channel occupancy time). In one embodiment, the user equipment has the capability to determine whether a type 4 LBT procedure can be delayed from being performed when a previous LBT procedure fails.

Description

Method and apparatus for supporting access to unlicensed radio resources in a wireless communication system

Technical Field

Embodiments of the present invention relate to wireless communication systems, and more particularly, to an apparatus and method for supporting access to an unlicensed communication channel using a Listen Before Talk (LBT) procedure. The invention can be (but is not limited to) applied to an enhanced license Assisted Access (eLAA) technology in a Long Term Evolution (LTE) upgraded (LTE-Advanced) wireless communication system.

Background

Wireless communication systems, such as the third-generation (3G) mobile telephone standards and technologies, are well known. Such 3G standards and techniques were developed by the third generation partnership project (3 GPP). Third generation wireless communications have generally evolved to support macrocell mobile telephone communications. Such macro cells utilize high power base stations (i.e., nodebs) to communicate with wireless communication units over a relatively large geographic coverage area. Generally, a Radio communication apparatus (also referred to as a User Equipment (UE)) communicates with a Core Network (Core Network, CN) of a 3G Radio communication system via a Radio Network Subsystem (RNS). A wireless communication system typically includes multiple radio network subsystems, each including one or more cells to which a UE may attach and thereby connect to the network. Each macro cellular RNS further includes a Controller in the form of a Radio Network Controller (RNC) that is operatively coupled to one or more node bs. Communication systems and networks have evolved towards broadband mobile systems. The third generation partnership project has developed Long Term Evolution (LTE) and Long Term Evolution advanced (LTE advanced) solutions, namely Evolved Universal Mobile telecommunications System terrestrial Radio Access Network (E-UTRAN) for Mobile Access networks, and System Architecture Evolution (SAE) solutions, namely Evolved Packet Core (EPC) for Mobile Core networks. A macro cell in an LTE system is supported by a base station called eNodeB or eNB (evolved node B).

Current wireless communication networks operate using licensed wireless spectrum, where multiple access to the communication resources of the licensed wireless spectrum is tightly controlled. A variety of multiple access techniques (such as, but not limited to, frequency division multiplexing, time division multiplexing, code division multiplexing, space division multiplexing, or a combination of one or more of these techniques) may be used to provide "one-chip" of spectrum resources for each user in the network. Even with the combined use of these technologies, current and future network capacity is still quite limited due to the popularity of mobile telecommunications technology, particularly with licensed wireless spectrum.

The network operator may also use unlicensed radio spectrum in order to increase or supplement capacity. For example, networks based on the LTE/LET advanced standard have an enhanced downlink that may use Licensed-Assisted-Access (LAA) procedures to operate on unlicensed spectrum. All communication devices need to complete a Listen Before Talk (LBT) procedure before accessing an unlicensed channel.

Some LAA techniques use a Clear Channel Assessment (CCA) check on the unlicensed spectrum to determine if there are other signals that preferentially use the channel. A base station (eNB) may start downlink transmission on an idle carrier, while a user equipment or terminal needs to send a signal to monitor the downlink carrier indicated by the base station. In general, the UE may implement CAA checking using energy detection to determine whether other signals are present on a particular carrier, resource block, and/or channel to determine whether the carrier, resource block, and/or channel is in an idle state. The LBT procedure may be used for LAA carriers in unlicensed spectrum. Typically, carriers in the licensed spectrum are reserved exclusively for each UE, so there is no need to perform LBT procedures and/or CCA checks.

Currently, for LAA in LTE, downlink DL and uplink UL can be implemented in different ways, and a base station eNB can start DL transmission on any channel at any time, while a UE can only start UL transmission on a specific subframe or a specific channel allocated by the eNB using a UL grant message. Therefore, the UE has relatively few opportunities to access the unlicensed carrier, resulting in limited UL performance.

There is a need to provide a method that can improve the efficiency with which a UE can access an unlicensed wireless communication channel.

Disclosure of Invention

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter

According to an aspect of the present application, there is provided a network element for supporting a communication function in a wireless communication system, comprising: transmitter circuitry to transmit a message receivable by a wireless communication device in a wireless communication system, the message including information to assist the wireless communication device in accessing unlicensed wireless resources, wherein the network element is to configure a licensed spectrum assisted access (LAA) uplink channel including a plurality of subframes, each subframe having n Orthogonal Frequency Division Multiplexing (OFDM) symbols, where n is an integer and at least one symbol is blank to establish a gap within which the wireless communication device can perform a Listen Before Talk (LBT) procedure, and the network element is further to configure a Maximum Channel Occupancy Time (MCOT) within which a channel of unlicensed wireless resources can be occupied, and the message includes information regarding at least one of: the position of the gap; a remaining time available to the wireless communication device in the MCOT; a remaining time available to the wireless communication device in the MCOT; instructions for causing the wireless communication device to delay a class 4 LBT procedure after a previous LBT procedure fails.

The network element may be an eNB.

The message may be included in downlink control information.

In one embodiment, the network element and the wireless communication device are configured to support Listen Before Talk (LBT) procedures. In one embodiment, the wireless communication system is an LTE-advanced system that supports licensed spectrum assisted access (LAA) technology and uses LBT procedures. LBT procedures can be divided into four categories. Class 1 has no LBT; class 2 with LBT without random backoff; class 3 has LBT with random backoff and fixed size contention window; class 4 has LBT with random back-off and variable size contention window. In 3gpp Release 13, class 4 is specified as the only LBT available for downlink.

The instructions for switching the wireless communication device from the class 4 to the class 2 LBT procedure include one bit indicator per subframe.

The instructions for causing the wireless communication device to delay the class 4 LBT procedure after a previous LBT procedure fails are indicated by one bit per subframe.

In some embodiments, the message may include information regarding at least one of: an uplink subframe size and an uplink subframe position.

The message also includes information indicating in which subframe the blank gap reserved for LBT is located for a plurality of wireless communication devices multiplexing an LAA uplink channel.

According to another aspect of the present invention, there is provided a wireless communication device for performing a listen-before-talk procedure, having receiver circuitry for receiving a message from a network element supporting a communication function in a wireless communication system; wherein the message includes information to assist the wireless communication device in accessing unlicensed radio resources using a licensed Spectrum assisted Access (LAA) uplink channel comprising a plurality of subframes, each subframe having n Orthogonal Frequency Division Multiplexing (OFDM) symbols, where n is an integer, at least one symbol is blank to establish a gap within which the wireless communication device may perform a Listen Before Talk (LBT) procedure, and the message includes information relating to at least one of: (i) a position of the gap; (ii) A remaining time of a Maximum Channel Occupancy Time (MCOT) available to the wireless communication device; (ii) A remaining time of a Maximum Channel Occupancy Time (MCOT) available to the wireless communication device; (iv) Instructions for causing the wireless communication device to delay a class 4 LBT procedure after a previous LBT procedure failed.

The wireless communication device may be a user equipment or similar mobile communication device.

In one embodiment, the message further comprises information indicating in which subframe the blank gap reserved for LBT is located for a plurality of wireless communication devices multiplexing LAA uplink channels.

The wireless communication device may include a signal processor to determine whether a class 4 LBT procedure may be delayed upon receipt of a message from the network element, the message including a location related to the gap and a remaining time of the MCOT, failing a previous LBT procedure.

In one embodiment, the signal processor is configured to determine, on a subframe-by-subframe basis, whether class 4 LBT may be delayed.

In one embodiment, the signal processor is configured to defer the class 4 LBT procedure for a subframe if LBT in a previous subframe allocated to a single UE fails.

In another embodiment, the wireless communication device comprises a signal processor for determining whether the wireless communication device can switch from a class 4 LBT procedure to a class 2 LBT procedure based on information received from the network element relating to a remaining time of the MCOT (and, optionally, a location of the gap).

According to another aspect of the present application, there is provided a method for enabling a communication function for a wireless communication device in a wireless communication system, comprising: transmitting, at a network element of the wireless communication system, a message to the wireless communication device, the message including information for assisting the wireless communication device in accessing unlicensed wireless resources; configuring a licensed spectrum assisted access (LAA) uplink channel comprising a plurality of subframes, each subframe having n Orthogonal Frequency Division Multiplexing (OFDM) symbols, wherein n is an integer and at least one symbol is blank to establish a gap within which the wireless communication device may perform a Listen Before Talk (LBT) procedure; configuring a Maximum Channel Occupancy Time (MCOT) within which channels of unlicensed radio resources may be occupied; including in the message at least one of the following information: (i) a position of the gap; (ii) A remaining time available to the wireless communication device in the MCOT; (ii) Remaining time available to the wireless communication device in MCOT; (iv) Instructions for causing the wireless communication device to delay a class 4 LBT procedure after a previous LBT procedure failed.

The method may further comprise: determining, at the wireless communication device, whether a class 4 LBT procedure may be delayed after a previous LBT procedure fails.

According to another aspect of the invention, there is provided a non-transitory computer readable medium having computer readable instructions stored thereon for performing the foregoing method by a processor.

The non-transitory computer-readable medium may include at least one of a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a read-only memory, a programmable read-only memory, an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory, and a flash memory.

Drawings

Further details, aspects and embodiments of the invention will be described below, by way of example only, with reference to the accompanying drawings. For simplicity and clarity of illustration, elements in the figures have not necessarily been drawn to scale. To facilitate understanding, like reference numerals have been used throughout the various figures.

Fig. 1 is a simplified block diagram of a portion of a cellular communication system and operation of an embodiment of the present application.

Fig. 2 is a first timing diagram illustrating a licensed spectrum assisted access method using a listen-before-talk procedure.

Fig. 3 and 4 illustrate second and third timing diagrams of a licensed spectrum assisted access method for a plurality of UEs.

The table in fig. 5 shows the relevant parameters for a UE when accessing unlicensed spectrum.

Detailed Description

Those skilled in the art will recognize and appreciate that the specifics of the described examples are merely illustrative of some embodiments and that the teachings herein are applicable to a variety of alternatives.

Referring to fig. 1, fig. 1 illustrates a portion of an LTE cellular communication system, indicated generally at 100, operating in accordance with an embodiment of the present application and including an evolved node B (eNB) 101 supporting an LTE cell 102. In other embodiments, the eNB 101 may support multiple cells. The evolved node B101 comprises a part of a radio access network, which in this example may be an E-UTRAN. The

user equipments

103a, 103b and 103c are all located within the coverage area of the cell 102. Although only three user equipments are shown in fig. 1, in an actual situation, at any point in time, more or fewer user equipments may be located in the cell 102 and in connected mode. An Evolved Packet Core (EPC) in the wireless communication system of fig. 1 may include a packet gateway P-GW 104 and a serving General Packet Radio Service (GPRS) support node (SGSN) 105.P-GW 104 may be used to connect a wireless access network and a packet data network (e.g., packet switched data network PSDN, internet). SGSN 105 performs routing and tuning functions for traffic to and from cell 102, while P-GW 104 is connected to an external packet network. The EPC also includes a Mobility Management Entity (MME) 106. The eNB 101 is connected to the SGSN 105 via the mobility management entity 106.eNB 101 is also connected to P-GW 104 via the mobility management entity 106 and serving gateway S-GW 107. MME 106 may handle signaling control and mobility while S-GW 107 is a local anchor for user data. The eNB 101 is provided with receiver circuitry (Rx) 108 and transmitter circuitry (Tx) 109 for transmitting messages to one or

more user equipments

103a, 103b, 103 c. The transmitted message includes certain information (described in detail later) for assisting the user equipment in accessing the unlicensed radio resources, which is information provided by the eNB other than the licensed carrier. In Carrier Aggregation (Carrier Aggregation) technology, unlicensed carriers may work together with licensed carriers. These messages may be included in Downlink Control Information (DCI). Each

user equipment

103a, 103b, and 103c may comprise a receiver 110 for receiving messages from the eNB 101 and a signal processor 111 for determining certain factors from information contained in the received messages, as will be described in detail below.

As previously mentioned, the LBT procedures for the downlink and uplink may be implemented in various forms. 3GPP TS 36.213 describes one way of downlink LBT and defines four levels of priority. A contention window is defined for each priority level and a random value is selected and used to determine the number of CCAs that need to be performed in one LBT procedure. By selecting a random value, the chance of collision when different enbs attempt to access the same unlicensed channel may be minimized. The size of the contention window may be determined according to the load of the channel, and although a small contention window may help the eNB quickly occupy the channel, it may limit the time available for the eNB to transmit data to a relatively short period of time. According to the currently proposed downlink LBT procedure, the eNB 101 listens to the unlicensed channel to determine whether the channel has been used by other devices. Once the channel is detected as idle, the eNB 101 may begin a delay period before the CCA countdown. If a signal is detected during the countdown period, the eNB will pause the countdown until the signal disappears, and then the countdown procedure can resume after the end of another delay period. When the countdown value equals zero, the eNB may start transmitting, but the transmission time cannot exceed the time allowed by the current priority (e.g., several milliseconds). Downlink LBT belongs to class 4.

The LBT procedure specified by 3GPP may define a Maximum Channel Occupied Time (MCOT) that determines the Maximum length of downlink bursts that an eNB may transmit on an unlicensed Channel. However, in practical cases the eNB 101 may not use the entire MCOT time, and therefore, the remaining part may also be shared by one or more of the

UEs

103a, 103b, 103c according to the unicast mode or the second type LBT procedure. Unlike the downlink, the uplink needs to multiplex multiple UEs, so the eNB 101 needs to coordinate the access of these devices to the same channel at the same time. To support multi-UE multiplexing, all UEs must start transmitting at exactly the same time, otherwise the signal from the UE that starts transmitting the earliest will make the LBT procedure of other UEs unable to pass. In this example, the licensed spectrum assisted access uplink transmission may be in a subframe. Each subframe has n OFDM symbols and at least one symbol is blank to establish a gap. In these gaps, the UE may perform LBT procedures and begin transmitting immediately after the gap. In one embodiment, each subframe is 1ms long and has 14 symbols, where the first and/or second symbol is blank. According to an embodiment of the application, the eNB may indicate the location of these gaps to the

UEs

103a, 103b and 103 c. In these gaps, the UE may perform a type 2 LBT when its subsequent transmission burst is within the existing MCOT; the UE may perform class 4 LBT when a subsequent transmission burst of the UE cannot be completed within the existing MCOT. If class 4 LBT cannot be completed in one slot, the LBT procedure must be continued in the next slot, which is at least 1ms later.

In order for the UE to be able to select a more appropriate LBT procedure (e.g., class two or class 4), the UE is preferably able to know how much of the MCOT remains. For example, the UE will know how long it takes to transmit data, so if the UE can know the length of the remaining MCOT, it will be able to deduce whether the transmission can be completed in the remaining MCOT window. For example, if the UE concludes that the transmission does not fall outside the MCOT window, it may perform a type 2 LBT procedure. On the other hand, if the UE concludes that the transmission will fall outside the MCOT window, it may choose to perform a type 4 LBT procedure. In some cases, the class 4 LBT may be performed late after the second type LBT fails, as will be described in detail later.

In an embodiment, the remaining MCOTs may be signaled to the UE by the eNB 101. This information may comprise, for example, 3 bits and is contained within a message sent by the eNB in the downlink control information. Alternatively, the remaining MCOT may be derived by the signal processor 111 in the UE by inverting the subframe from the predefined MCOT value when the UE detects a downlink transmission, but this alternative has the disadvantage if the downlink transmission is not detected correctly. In this case, the remaining MCOT time is not correctly calculated. This may result in the UE occupying unlicensed channel time if LBT is performed incorrectly.

For the LAA uplink, the class 2 LBT procedure is more preferred because it can help the UE to acquire the unlicensed channel with a higher probability than other classes of procedures. In an embodiment of the present application, the eNB 101 may send an instruction to the UE instructing the UE to switch from a class 4 to a class 2 LBT procedure in some cases. This instruction may be contained within a message sent by the eNB in the downlink control information. A single bit of indication information may be used within each subframe. If this bit information is not sent, the UE continues to use type 4 LBT. Alternatively, the UE may infer whether to switch from a type 4 to a type 2 LBT procedure from other signal fields.

Please refer to the timing diagram of fig. 2. It will be appreciated that gaps between transmissions within the same MCOT period of greater than 25 milliseconds need not be included in the total transmission duration. Therefore, it can be said that the subframe for the UE to perform LBT but not pass does not belong to a part of the MCOT.

In the example of fig. 2, a frame 201 corresponding to a total length of 10ms contains four downlink subframes (0 to 3) and six uplink subframes (4 to 9), which are allocated to one UE, while the downlink LBT creates one MCOT of 8 ms. Before starting uplink transmission, a single UE needs to complete 25 μ s LBT (i.e. unicast mode/class 2 LBT), and if the 25 μ s LBT fails, the UE needs to wait for the start of the next subframe before performing another LBT procedure.

Two examples are shown in figure 2. The 1 st example shows how the class 4 LBT is delayed from executing when the LBT procedure fails. In example 1, the UE (e.g., 103a in fig. 1) does not pass its first LBT at the beginning of subframe 4, but successfully passes a second LBT after one subframe. Thus, the UE starts uplink transmission from subframe 5 and does not stop transmission until the beginning of subframe 9, after which the eNB-initiated MCOT ends. In example 2, the UE passes the first LBT, so uplink transmission starts at subframe 4 and stops until the beginning of subframe 8, after which the eNB-initiated MCOT ends. In both example 1 and example 2, the total transmission time is not longer than the eNB-initiated MCOT time window. Thus, the UE can continue with another transmission after a successful class 4 LBT procedure (at the beginning of subframe 9 in the 1 st example or at the beginning of subframe 8 in the 2 nd example). In order to comply with the standard, a type 4 LBT procedure must be executed. Therefore, in the case shown in example 1, the class 4 LBT procedure may be delayed.

The eNB may include a signal indicator in a message sent to the UE to indicate, for each uplink subframe, whether performing class 4 LBT can be postponed for a subsequent subframe when the LBT procedure fails within the subframe. Alternatively, by receiving a message indicating the remaining MCOT duration and acquiring the number and positions of already allocated subframes, the signal processing capability of the UE may determine how many subframes may be delayed by class 4 LBT after LBT fails.

In one example, the eNB sends one or more parameters to the UE in a broadcast manner to indicate how many uplink subframes have been allocated and where. Such an indicator may be referred to as a "size of subframe" and may include 3 to 4 bits. The subframes allocated to a particular UE may be discontinuous. The UE must know the size of the subframe or else the uplink channel cannot be configured correctly. For multiple UEs, an information field called "multi-UE bitmap (one bit per planned uplink subframe)" may be used to indicate to the UEs in which subframes blank gaps need to be set for LBT procedures.

In another example, the eNB sends one or more parameters to the UE in a unicast format to indicate how many uplink subframes have been allocated and where. The subframes allocated to a particular UE may be discontinuous. For multiple UEs, an information field called "multi-UE bitmap (one bit for each planned uplink subframe)" may be used to indicate to the UE in which subframes blank gaps need to be set for LBT procedures.

Another information field, referred to as "MCOT remaining time", may be used to send information related to the remaining MCOT duration, which may include 3 bits, which the UE may use after the eNB completes the downlink transmission. In one example, this remaining duration is in subframes and indicates the remaining duration of the eNB-initiated MCOT. If the uplink transmission can be completed within this remaining period, then a type 2 LBT needs to be performed. Otherwise, class 4 LBT needs to be performed. This information field may be sent in a broadcast form or a unicast form, and if it is sent in a unicast form to the UE, the eNB may adjust its value according to the subframe intended for this particular UE.

Please refer to the timing diagrams in fig. 3 and 4, wherein an example of multiple UEs is considered. In fig. 3 and 4, a frame 301 with a total length of 10ms, which contains four downlink subframes (0 to 3) and six uplink subframes (4 to 9), is allocated to two UEs, UE1 and UE2 (e.g., 103a and 103b in fig. 1), while a downlink LBT creates an MCOT of 8 ms. Before starting uplink transmission, each UE needs to complete 25 μ s LBT (i.e. unicast mode/class 2 LBT), and if the 25 μ s LBT fails, the UE needs to wait for the start of the next subframe before performing another LBT procedure. If a subframe is not used by any UE, it does not need to be considered when calculating the remaining MCOT duration. If a subframe is used by any UE, it needs to be included in the remaining MCOT duration. In fig. 3, subframes 4 to 9 are allocated for UE1 use, while subframes 6 to 8 are allocated for UE2 use. In fig. 4, subframes 4 to 9 are allocated for UE1 use, while subframes 4 to 6 are allocated for UE2 use. Two UEs may use the same subframe but must be allocated different resource blocks. In example 1 shown in fig. 3, after type 2 LBT by UE1 at subframe 4 fails, type 4 LBT by subframe may be delayed because subframe 4 is not used by any UE and is therefore not included in the MCOT. On the other hand, in example 1 shown in fig. 4, type 4 LBT of UE1 cannot be delayed because subframe 4 is allocated to UE2 and therefore is assumed to be used by UE2 and must be included in the MCOT.

The information fields of fig. 3 and 4 may be as follows. The first information field is "uplink subframe size", and, in these examples of fig. 3 and 4, this field value is 6, that is, 6 subframes are allocated in total. The second information field is a "multi-UE bitmap" for indicating the location of subframes used by one or more UEs. In the example of fig. 3, the field has a value of 001110, meaning that the third, fourth, and fifth subframes are allocated to a plurality of UEs, while the first, second, and sixth subframes are allocated to only one UE. In the example of fig. 4, the value of this field is 111000, meaning that the first, second, and third subframes are allocated to a plurality of UEs, and the fourth, fifth, and sixth subframes are allocated to only one UE. The third information field is "MCOT remaining time" and has a value of 4, that is, the remaining MCOT duration (after completion of downlink transmission) includes four subframes. These information fields may be transmitted from the eNB to the UE through an uplink grant message, or may be broadcast at the same time as the uplink grant transmission.

Referring again to fig. 3, since the first two subframes are only allocated (or scheduled) to UE1, the signal processing function of UE1 may conclude that LBT class 4 may be delayed for at least two consecutive subframes if the LBT procedure fails. Referring again to fig. 4, since the first subframe is planned for multiple UEs, the signal processing functions of UE1 and UE2 may conclude that class 4 LBT may not be deferred after LBT fails.

Referring to the table in fig. 5, a method of how the UE deduces whether the type 4 LBT procedure can be delayed according to the indicator from the eNB is described in the example of fig. 5. In the example of fig. 5, the remaining MCOT time (after the eNB completes the downlink transmission) is equal to 3 (3 ms or 3 subframes) and this value is sent by the eNB to the UE in an uplink grant message. The uplink subframe is configured by the eNB and is represented by numbers 4 to 9 in row 501 in fig. 5. The multi-UE bit map in row 502 with a value of 010000 indicates that only the subframe number 5 is used by multiple UEs, while the other subframes are used by only a single UE (but not meant to be used by the same UE at a time). In row 503,

shaded subframes

4, 5, 7, 8, and 9 are allocated to UE1. Line 504 shows the results of the LBT procedure, where "x" indicates that type 2 LBT failed and "V" indicates a pass. Line 505 shows whether a particular subframe is marked as a transmission, depending on whether the remaining MCOT is involved. Line 506 is the remaining MCOT time inferred by UE1 after each subframe. Row 507 shows the categories of LBT procedures performed at a particular subframe.

At subframe 4, UE1 performs a class 2 (25 msec) LBT. This LBT failed. However, subframe 4 is only planned for a single UE (bitmap value 0), and UE1 knows that it is the only UE that is planned to use this subframe. When the LBT fails, UE1 knows that the subframe is not used by any other UE and therefore can be excluded from the remaining MCOT time. Thus, at the end of subframe 4, the remaining MCOT time remains at a value of 3.

Subframe 5 is planned for a number of UEs (bitmap value 1) and UE1 knows that it is only one of the UEs that plan to use this subframe. When this LBT fails, UE1 cannot know whether the UE is used by other UEs. Therefore, this subframe must be calculated within the transmission time. Thus, after subframe 5, the remaining MCOT time is decreased by 1, which is equal to 2.

Subframe 6 is intended for a single UE and UE1 is not intended to use this subframe (i.e., the subframe is blank). UE1 cannot know whether the UE is used by other UEs. This subframe must be calculated within the transmission time. Thus, after subframe 6, the MCOT remaining time is reduced by 1, which is equal to 1.

Subframe 7, like subframe 4, is also only scheduled for use by UE1, and in this example the LBT performed by UE1 on subframe 7 does not pass, and therefore this subframe is not accounted for in transmission time. As such, after subframe 7, the remaining MCOT time is not reduced, and remains equal to 1.

Subframe 8 is only scheduled for UE1 and UE1 passes the LBT procedure (denoted by the letter V in the table) and occupies the subframe. After subframe 8, the remaining MCOT time is decreased by 1, and its value is decreased to 0, which means that class 4 LBT needs to be performed from subframe 9.

As can be seen from the above, the UE can determine when to perform a class 4 LBT procedure. This determination process may be performed by a single processor in the UE.

In another embodiment, the UE is not configured to derive the remaining MCOT time on a subframe-by-subframe basis as shown in fig. 5, but rather is determined from the eNB's signal. For example, the "remaining MCOT time parameter" may be included in a Downlink Control Information (DCI) message that is common to a plurality of UEs. In this embodiment, the UE may monitor for downlink signal transmissions. If no downlink signaling is received, the UE may default to the class 4 LBT procedure. If a downlink signal transmission is received and the "remaining MCOT time parameter" indicates that the remaining time is 0, the UE must perform class 4 LBT. If a downlink signal transmission is received and the "remaining MCOT time parameter" indicates that the remaining time is 1, the UE performs type 2 LBT in the first subframe and type 4 LBT in the next subframe. If a downlink signal transmission is received and the "remaining MCOT time parameter" is 2 or more, type 2 LBT may be performed in the first two and/or the next subframes.

In another embodiment, the UE is not configured to determine whether the class 4 LBT may be delayed, but is determined according to the signal of the eNB. Another field may be used that takes the

value

0 or 1, where a value of 0 indicates that deferral is allowed to proceed when LBT in this subframe fails, and a value of 1 indicates that deferral is not allowed to proceed. Taking the example of fig. 5, the following table shows the corresponding case.

Subframes planned for a UE	4	5	6	7	8	9
							Whether or not to allow delay	0	1	1	0	0	0

Subframe 5 is not allowed because another UE is multiplexed and can use this subframe. Subframe 6 is also not allowed because this subframe is scheduled for another UE. All other subframes are allowed, then the class 4 LBT procedure may be delayed as soon as the 25 μ s LBT fails. The number of subframes that can be delayed is the same as the number of subframes that do not pass LBT and have "0" (i.e., delay allowed). Alternatively, subframe 6 may be removed from the signal described above, since it is not allocated to UE1 and UE1 knows this as well. This option uses more downlink signals and uses the eNB to control all the above operations.

The signal processing functions of the embodiments of the present application may be implemented using computing systems or architectures known to those skilled in the art. Computing systems, such as desktop, laptop or notebook computers, handheld computing devices (PDAs, cell phones, palmtops, etc.), mainframes, servers, clients, or any other type of special or general purpose computing device may be used as may be suitable or appropriate for a particular application or environment. The computing system may include one or more processors, which may be implemented using a general or special purpose processing engine such as, for example, a microprocessor, microcontroller or other control processing module.

The computing system may also include a main memory, such as a Random Access Memory (RAM) or other dynamic memory, for storing information and instructions to be executed by the processor. Such main memory may also be used for storing temporary variables or other intermediate information during execution of instructions to be executed by the processor. The computing system may also include a Read Only Memory (ROM) or other static storage device for the processor that stores static information and instructions.

The computing system may also include an information storage system, which may include, for example, a media drive and a removable storage interface. The media drive may include a drive or other mechanism to support fixed or removable storage media, such as a hard disk drive, a floppy disk drive, a magnetic tape drive, an optical disk drive, a Compact Disc (CD), a Digital Video Drive (DVD), a read or write drive (R or RW), or other removable or fixed media drive. For example, the storage media may include, for example, a hard disk, floppy disk, magnetic tape, optical disk, CD or DVD, or other fixed or removable medium that is read by and written to by the media drive. The storage media may include a computer-readable storage medium having stored therein particular computer software or data.

In alternative embodiments, the information storage system may include other similar components for allowing computer programs or other instructions or data to be loaded into the computing system. For example, these components may include removable storage units and interfaces, such as program cartridges and cartridge interfaces, removable memory (e.g., flash memory or other removable memory modules) and memory slots, and other removable storage units and interfaces that allow software and data to be transferred from the removable storage unit to the computing system.

The computing system may also include a communications interface. Such computing systems may be used to allow software and data to be transferred between the computing system and external devices. In this embodiment, the communication interface may include a modem, a network interface (e.g., an Ethernet or NIC card), a communication port (e.g., a Universal Serial Bus (USB) port), a PCMCIA slot and card, etc. Software and data transferred via the communications interface are in the form of signals which may be electronic, electromagnetic, optical or other signals capable of being received by the communications interface medium.

In this document, the terms "computer program product," "computer-readable medium" and the like may be used generally to refer to tangible media, such as memory, storage devices, or storage units. These and other forms of computer-readable media may store one or more instructions for use by a processor, including a computer system, to cause the processor to perform specified operations. These instructions, generally referred to as 'computer program code' (which may be grouped in the form of computer programs or other groupings), when executed, enable the computing system to perform functions of embodiments of the present invention. Notably, the code can directly cause the processor to perform specified operations, be compiled to do so, and/or be combined with other software, hardware, and/or firmware elements (e.g., libraries for performing standard functions) to do so.

In embodiments where the elements are implemented using software, the software may be stored in a computer-readable medium and loaded into the computing system using, for example, a removable storage drive. When executed by a processor in a computer system, the control module (in this example, software instructions or executable computer program code) causes the processor to perform the functions of the invention as described herein.

Furthermore, the inventive concept may be applied to any circuit for performing a signal processing function within a network element. It is further contemplated that, for example, a semiconductor manufacturer may use the concepts of the present invention in the design of a stand-alone device, such as a microcontroller and/or any other subsystem components of a Digital Signal Processor (DSP) or application-specific integrated circuit (ASIC).

It will be appreciated that for purposes of clarity, embodiments of the invention have been described above with reference to a single processing logic. However, the inventive concept may equally be implemented by means of a plurality of different functional units and processors to provide the signal processing functions. Hence, references to specific functional units are only to be seen as references to suitable means for providing the described functionality rather than indicative of a strict logical or physical structure or organization.

Aspects of the invention may be implemented in any suitable form including hardware, software, firmware or any combination of these. Alternatively, the invention may be implemented at least partly as computer software running on one or more data processors and/or digital signal processors or configurable modular components (e.g. FPGA devices). Thus, the elements and components of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way. Indeed the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units.

Although the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the invention is limited only by the accompanying claims. In addition, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognize that various features of the described embodiments may be combined. In the claims, the term "comprising" does not exclude the presence of other elements or steps.

Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented by e.g. a single unit or processor. Furthermore, although individual features may be included in different claims, these may possibly advantageously be combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous.

Furthermore, the inclusion of a feature in one category of claims does not imply a limitation to this category but rather indicates that the feature is equally applicable to other claim categories.

Furthermore, the order of features in the claims does not imply any specific order in which the features must be performed and in particular the order of individual steps in a method claim does not imply that the steps must be performed in this order. Rather, the steps may be performed in any suitable order. Further, singular references of an element do not exclude a plurality of such elements. Thus, references to "a", "an", "first", "second", etc., do not preclude a plurality.

Although the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein.

Rather, the scope of the invention is limited only by the accompanying claims. In addition, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognize that various features of the described embodiments may be combined. In the claims, the term "comprising" does not exclude the presence of other elements or steps.

Claims

1. A network element for supporting communication functions in a wireless communication system, characterized by:

comprising transmitter circuitry to transmit a message receivable by a wireless communication device in a wireless communication system, the message comprising information to assist the wireless communication device in accessing an unlicensed radio resource;

the network element is to configure a licensed spectrum assisted access (LAA) uplink channel comprising a plurality of subframes, each subframe having n Orthogonal Frequency Division Multiplexing (OFDM) symbols, where n is an integer and at least one symbol is blank to establish a gap within which the wireless communication device may perform a Listen Before Talk (LBT) procedure; and is provided with

The network element may be further operable to configure a Maximum Channel Occupancy Time (MCOT) within which a channel of an unlicensed radio resource may be occupied, and the message includes information regarding at least one of:

(i) The position of the gap;

(ii) A remaining time available to the wireless communication device in the MCOT;

(iii) Instructions for handing off the wireless communication device from a type 4 to a type 2 LBT procedure;

(iv) Instructions for causing the wireless communication device to delay a class 4 LBT procedure after a previous LBT procedure failed.

2. The network element of claim 1, wherein the message is included in Downlink Control Information (DCI).

3. The network element of claim 1 or 2, wherein the instruction to switch the wireless communication device from a type 4 to a type 2 LBT procedure comprises an indicator of one bit per subframe.

4. The network element of claim 1, wherein the instructions for the wireless communication device to delay a type 4 LBT procedure after a previous LBT procedure fails are indicated by one bit per subframe.

5. The network element of claim 1, wherein the message further comprises information regarding at least one of: an uplink subframe size and an uplink subframe position.

6. The network element of claim 1, wherein the message further comprises information for a plurality of wireless communication devices multiplexing an LAA uplink channel indicating in which subframe the gap reserved for LBT is located.

7. A wireless communication device for performing a listen before talk procedure, characterized by:

having receiver circuitry for receiving messages from network elements supporting communication functions in a wireless communication system;

the message includes information for assisting the wireless communication device in accessing unlicensed radio resources using a licensed spectrum assisted access (LAA) uplink channel comprising a plurality of subframes, each subframe having n Orthogonal Frequency Division Multiplexing (OFDM) symbols, where n is an integer and at least one symbol is blank to establish a gap within which the wireless communication device may perform a Listen Before Talk (LBT) procedure;

the message comprises information relating to at least one of:

(i) The position of the gap;

(ii) A remaining time of a Maximum Channel Occupancy Time (MCOT) available to the wireless communication device;

(iv) Instructions for causing the wireless communication device to delay a class 4 LBT procedure after a previous LBT procedure fails.

8. The wireless communication device of claim 7, wherein the message further comprises information for a plurality of wireless communication devices multiplexing an LAA uplink channel, the information indicating in which subframe the gap reserved for LBT is located.

9. The wireless communication device of claim 7 or 8, comprising a signal processor to determine whether a class 4 LBT procedure can be delayed after receiving a message from the network element and a previous LBT procedure failed, wherein the message comprises a location related to the gap and a remaining time of the MCOT.

10. The wireless communication device of claim 9, wherein the signal processor is configured to determine, on a subframe-by-subframe basis, whether a class 4 LBT procedure can be delayed after a previous LBT procedure fails.

11. The wireless communications apparatus of claim 10, wherein the signal processor is configured to defer the class 4 LBT procedure for a subframe if LBT in a previous subframe assigned to a single UE fails.

12. The wireless communication device of claim 7, comprising a signal processor to determine whether the wireless communication device is switchable from a type 4 LBT procedure to a type 2 LBT procedure based on information received from the network element relating to a time remaining for MCOT.

13. The wireless communication device of claim 12, wherein the signal processor determines whether the wireless communication device can switch from a type 4 LBT procedure to a type 2 LBT procedure based on information received from the network element relating to the location of the gap.

14. A method for enabling communication functionality for a wireless communication device in a wireless communication system, comprising:

transmitting, at a network element of the wireless communication system, a message to the wireless communication device, the message comprising information for assisting the wireless communication device in accessing an unlicensed radio resource;

configuring a licensed spectrum assisted access (LAA) uplink channel comprising a plurality of subframes, each subframe having n Orthogonal Frequency Division Multiplexing (OFDM) symbols, wherein n is an integer and at least one symbol is blank to establish a gap within which the wireless communication device may perform a Listen Before Talk (LBT) procedure;

configuring a Maximum Channel Occupancy Time (MCOT) within which channels of unlicensed radio resources may be occupied;

including in the message at least one of the following information:

(i) The position of the gap;

(iii) Instructions for handing off the wireless communication device from a class 4 to a class 2 LBT procedure;

15. The method of claim 14, further comprising: the message is included in Downlink Control Information (DCI).

16. The method of claim 14 or 15, further comprising: determining, at the wireless communication device, whether a class 4 LBT procedure may be delayed after a previous LBT procedure fails.

17. A non-transitory computer readable medium having stored thereon a plurality of computer readable instructions for execution by a processor to perform the method of claim 14.

18. The non-transitory computer-readable medium of claim 17, wherein the non-transitory computer-readable medium is at least one of a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a read-only memory, a programmable read-only memory, an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory, and a flash memory.