WO2016151389A1

WO2016151389A1 - A wireless communication method for activating a secondary carrier

Info

Publication number: WO2016151389A1
Application number: PCT/IB2016/000340
Authority: WO
Inventors: Yan Meng; Feng Han; Jianguo Liu; Tao Tao; Zhuo WU
Original assignee: Alcatel Lucent
Priority date: 2015-03-26
Filing date: 2016-03-04
Publication date: 2016-09-29
Also published as: CN106162836A; TW201642692A; CN106162836B

Abstract

A method of activating a secondary cell in a base station of an LTE communication system, wherein the secondary cell is an unlicensed carrier, the method comprising: performing, by the base station, a clear channel assessment on the secondary cell to determine whether the secondary cell is idle; transmitting, by the base station, a preamble signal on the secondary cell when the secondary cell is idle, wherein the preamble signal includes information indicating that the base station activates the secondary cell.

Description

A WIRELESS COMMUNICATION METHOD FOR ACTIVATING A SECONDARY CARRIER

FIELD OF THE INVENTION

[0001] The present invention relates to the technical field of communication, and more specifically relates to the technical field of wireless communication.

BACKGROUND OF THE INVENTION

[0002] In the field of wireless communication, a conventional deployment approach is generally that a system operates on a licensed band, that is, the entire spectral resource is reserved for use by the system. Typically, an LTE communication system operates with the licensed band.

[0003] However, with further increase of wireless traffic, the demanding on the capacity and band of a wireless communication system also becomes higher. In this case, the licensed band resources of the LTE system appear relatively insufficient. Therefore, one of hot issues of research in the LTE field is how to utilize unlicensed band resources to shunt highly bursting data traffics. This solution is referred to as an LTE in Unlicensed spectrum (shortly referred to as LTE-U) system.

[0004] For example, in a typical scenario, the LTE system uses a band of a WiFi system, that is, a scenario where cells of the LTE system and cells of the WiFi systems are at least partially co-existent at a geographical location. In this scenario, if the LTE system may shunt traffic using the band of WiFi at some high-load times, it is apparent that system performance may be greatly enhanced, and thereby a high-load application scenario is effectively dealt with.

[0005] Apparently, in a scenario where the LTE is co-existent with the WiFi system, it is a most straightforward option that a licensed carrier of the LTE system is used to assist an unlicensed carrier of the WiFi system in access. Therefore, Licensed-Assisted Access (shortly referred to as LAA) has become one of hot issues in the field of mobile communication in recent years. [0006] With the LAA technology, an existing procedure of the LTE system can be inherited to the utmost extent so as to implement carrier aggregation (shortly referred to as CA) scheduling of the licensed carrier and unlicensed carrier. However, in order to be compatible with the system of the unlicensed carrier, some new mechanisms also need to be introduced, wherein one of the principal problems is how to implement Listen Before Talk (shortly referred to as LBT) for the unlicensed carrier in an LTE-LAA system.

[0007] For example, typically, a certain unlicensed carrier as a secondary cell (shortly referred to as Scell) of the LTE system is aggregated with a certain licensed carrier as a primary cell (shortly referred to as Pcell). Then, before the Pcell attempts to activate the Scell, the base station must determine that the Scell is not occupied by other systems. Therefore, the base station needs to perform clear channel assessment (shortly referred to as CCA) on the Scell to determine that the channel is clear, and then perform an operation of activating the Scell. However, when a load base equipment (shortly referred to as LBT) mode is employed, the Pcell only attempts to activate the Scell when there is a load that needs to be transmitted. In other words, it is uncertain when the base station performs CCA, while the base station cannot-determine in advance whether the Scell is clear at this time. In this case, it becomes a problem to be solved how the base station notifies its user equipment ("UE") that a certain Scell has been activated/ deactivated.

[0008] In the existing discussions, there are two proposals about this problem. One proposal is to cause the UE to blind-decode PDCHH or a cell reference signal (shortly referred to as CRS) on the Scell. If the PDCCH or CRS can be successfully decoded, it is indicated that the base station has activated the Scell. Although this method does not have to introduce a new signaling, it requires the UE to constantly perform an extra blind decoding operation on the Scell, which means an extremely large power consumption. Considering that use of the unlicensed carrier is very sparse, such power consumption causes a considerable waste of the UE's standby time. The other method is to explicitly indicate activation of the Scell by transmitting an indication signaling on the licensed carrier (i.e., Pcell). An advantage of doing so is that power may be saved. However, it requires an introduction of new signaling interaction. More importantly, because the UE does not know when the base station will transmit the indication signaling, the UE has to cache data of each subframe on the Scell, so as to correctly process data transmission on the Scell after receiving the indication signaling from the Pcell. Apparently, such caching of UE likewise causes a considerable waste, which cannot be used as an ideal solution.

[0009] Therefore, an objective of the present invention is to seek for a novel method of activating an Scell. This method needs to be capable of causing a base station to effectively notify a UE that a certain Scell has been activated in the case of LAA, while trying best to avoid a waste of UE power and cache.

SUMMARY OF THE INVENTION

[0010] In order to solve the above problem in the prior art, the present invention provides a novel method of activating an Scell. By causing a base station to add information indicating activation when transmitting a preamble signal of the Scell, it is ensured that the UE may accurately know in time that the Scell has been activated.

[0011] Specifically, according to a first aspect of the present invention, there is provided a method of activating a secondary cell in a base station of an LTE communication system, wherein the secondary cell is an unlicensed carrier, the method comprising: performing, by the base station, a clear channel assessment on the secondary cell, to determine whether the secondary cell is idle; transmitting, by the base station, a preamble signal on the secondary cell when the secondary cell is idle, wherein the preamble signal includes information indicating that the base station activates the secondary cell.

[0012] Preferably, herein, there further comprises after the second step: transmitting, by the base station, a first message on a primary cell, wherein the first message is used for notifying a first number of UEs that the base station will communicate with the first number of UEs on the secondary cell, wherein the first number of UEs are UEs scheduled by the base station to communicate on the secondary cell.

[0013] More preferably, there further comprises after the above step: transmitting, by the base station, a second message on the primary cell, wherein the second message is used for notifying the first number of UEs that the base station will no longer communicate with the first number of UEs on the secondary cell.

[0014] Preferably, herein, the information indicating that the base station activates the secondary cell includes an orthogonal sequence associated with a cell identity of the base station.

[0015] More preferably, herein, the orthogonal sequence associated with the cell identity of the base station includes a primary synchronization signal sequence and/or a secondary synchronization signal sequence of the base station.

[0016] According to a second aspect of the present invention, there is provided a method of activating a secondary cell in a UE of an LTE communication system, wherein the secondary cell is an unlicensed carrier, the method comprising: receiving, by the UE, a preamble signal transmitted by a base station on the secondary cell, wherein the preamble signal includes information indicating that the base station activates the secondary cell. [0017] Preferably, there further comprises after the above step: receiving, by the UE, a first message transmitted by the base station on a primary cell, wherein the first message is used for notifying the UE that the base station will communicate with the UE on the secondary cell.

[0018] More preferably, there further comprises after the above step: receiving, by the UE, a second message transmitted by the base station on the primary cell, wherein the second message is used for notifying the UE that the base station will no longer communicate with the UE on the secondary cell.

[0019] According to a third aspect of the present invention, there is provided an apparatus for activating a secondary cell in a base station of an LTE communication system, wherein the secondary cell is an unlicensed carrier, the apparatus comprising: an assessment module for performing, by the base station, a clear channel assessment on the secondary cell, to determine whether the secondary cell is idle; a preamble transmitting module for transmitting, by the base station, a preamble signal on the secondary cell when the secondary cell is idle, wherein the preamble signal includes information indicating that the base station activates the secondary cell.

[0020] Preferably, there further comprises a first transmitting module for transmitting, by the base station, a first message on a primary cell, wherein the first message is used for notifying a first number of UEs that the base station will communicate with the first number of UEs on the secondary cell, wherein the first number of UEs are UEs scheduled by the base station to communicate on the secondary cell.

[0021] More preferably, there further comprises a second transmitting module for transmitting, by the base station, a second message on the primary cell, wherein the second message is used for notifying the first number of UEs that the base station will no longer communicate with the first number of UEs on the secondary cell.

[0022] According to a fourth aspect of the present invention, there is provided an apparatus for activating a secondary cell in a UE of an LTE communication system, wherein the secondary cell is an unlicensed carrier, the apparatus comprising: a preamble receiving module for receiving, by the UE, a preamble signal transmitted by a base station on the secondary cell, wherein the preamble signal includes information indicating that the base station activates the secondary cell. [0023] Preferably, there further comprises: a first receiving module for receiving, by the UE, a first message transmitted by the base station on a primary cell, wherein the first message is used for notifying the UE that the base station will communicate with the UE on the secondary cell. [0024] More preferably, there further comprises: a second receiving module for receiving, by the UE, a second message transmitted by the base station on the primary cell, wherein the second message is used for notifying the UE that the base station will no longer communicate with the UE on the secondary cell.

[0025] In the present invention, by indicating the information of activation using an existing preamble signal, it is ensured that the UE does not have to perform an extra blind-decoding operation, which thereby saves power; by transmitting a preamble signal before transmitting data, it is ensured that the UE only starts caching the subframes on the Scell after determining that the Scell has been activated, which thereby saves the cache space; moreover, in a preferred solution, a part of UEs scheduled may only be notified, which thereby reduces a waste of the overall performance of the system and achieves the objective of the present invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0026] Other features, objectives and advantages of the present invention will become more apparent through reading the following detailed description of the non-limiting embodiments with reference to the accompanying drawings.

[0027] Fig. 1 shows a flow diagram of a method for activating an Scell in a base station of an LTE communication system according to the present invention;

[0028] Fig. 2 shows a flow diagram of a method for activating an Scell in a UE of an LTE communication system according to the present invention;

[0029] Fig. 3 shows a block diagram of an apparatus for activating an Scell in a base station of an LTE communication system according to the present invention; [0030] Fig. 4 shows a block diagram of an apparatus for activating an Scell in a UE of an LTE communication system according to the present invention;

[0031] wherein, same or like reference numerals represent the same or corresponding step features or means/modules.

DETAILED DESCRIPTION

[0032] In detailed description of the following preferred embodiments, accompanying drawings constituting a part of the present invention will be referenced. By way of example, the accompanying drawings show specific embodiments that can implement the present invention. The exemplary embodiments are not intended to exhaust all embodiments of the present invention. It may be understood that without departing from the scope of the present invention, other embodiments may be employed, or structural or logical modifications may be made. Therefore, the following detailed description is not limitative, and the scope of the present invention is limited by the appended claims.

[0033] First, according to an application scenario of the present invention, there is an area covered by an LTE communication system and including at least one base station and UE and a licensed carrier linking them, i.e., a Pcell. Furthermore, there are also other unlicensed carriers in the area, wherein the unlicensed carrier may also be used by other LTE or WiFi communication systems.

[0034] Because the base station operates in an LBE mode, only when the base station believes it necessary to use the unlicensed carrier as the Scell for transmission, will the base station perform CCA or ECCA (Extended CCA) operation on the unlicensed carrier, so as to conform whether the unlicensed carrier is idle and available at this time. However, consider that the CCA/ECCA operation occupies an extremely short time (the shortest time is about 20 microseconds), which is far shorter than the time of an LTE subframe. Therefore, the base station's CCA/ECCA operation may occur within one subframe of the Scell. This means that even the base station determines that the Scell is idle at the current subframe, a complete data transmission can only be done in a next subframe. However, because the current subframe does not end yet, the base station has to occupy a remaining portion of the current subframe in a certain manner; otherwise, in a remaining time of the current subframe, if other system also performs the CCA/ECCA operation, it will also be determined that the Scell is idle and available, which inevitably causes conflict in the next subframe. In order to solve the problem that the current subframe occupies an unlicensed carrier, a solution has already been proposed in the industry: after confirming that the Scell is available, the base station transmits a preamble signal within the remaining time of the current subframe, such that other devices, when performing CCA/ECCA operation subsequently, can sense that the carrier has been occupied by a certain system. Moreover, it is further proposed that the preamble signal may also be used for a receiving end to adjust an automatic gain control (AGC). For this purpose, the UE may blind-decode the preamble signal on the Scell. [0035] Based on the above solution, the present invention further proposes that information indicating that the base station has activated the Scell may be added in the preamble signal; in this way, when the UE blind-decodes the preamble signal, the UE may know simultaneously that the base station will start data transmission on the Scell from the next subframe. Thereby, the UE is able to accurately know when to start caching the data on the Scell, without a need of caching the data of each subframe on the Scell. Meanwhile, the blind-decoding operation is originally to be performed by the UE; therefore, no new operation causing power consumption is introduced. Thereby, the objective of the present invention is achieved.

[0036] On this basis, according to one embodiment of the present invention, there is provided a method for activating an Scell in a base station of an LTE communication system. Specifically:

[0037] First, the base station performs an CCA/ECCA operation on the Scell to determine whether the Scell is idle. [0038] In a second step, if a result is that the Scell is idle, the base station transmits a preamble signal via the Scell, the preamble signal including information indicating activation of the Scell.

[0039] Preferably, an orthogonal sequence associated with a cell identity (Cell ID) of the base station may be used for indication. Typically, a primary synchronization signal (shortly referred to as PSS) sequence and/or a secondary synchronization signal (shortly referred to as SSS) sequence of the base station may be used for indication.

[0040] In addition, after the second step, the base station may also transmit a first message on the Pcell for notifying those UEs scheduled onto the Scell that the base station will communicate with them on the Scell. An advantage of doing so is that considering only a part of UEs will be scheduled onto the Scell, it is not needed to make all UEs to cache data on the Scell, and it may be directly specified through signaling on the Pcell which UEs need to cache data of Scell, and thereby cache spaces of other UEs are saved. [0041] Further, when the base station is to deactivate the Scell, the base station may also transmit a second message on the Pcell to notify these UEs scheduled on the Scell that the base station will no longer communicate with them on the Scell. In this way, those UEs will know that the data on the Scell will not be needed to cache any more from the next subframe, thereby releasing the cache space. [0042] Fig. 1 shows a flow diagram of activating an Scell according to the above embodiments, comprising:

[0043] SI 1. performing, by the base station, a clear channel assessment on the secondary cell, to determine whether the secondary cell is idle;

[0044] S12. transmitting, by the base station, a preamble signal on the secondary cell when the secondary cell is idle, wherein the preamble signal includes information indicating that the base station activates the secondary cell. [0045] Accordingly, according to another embodiment of the present invention, there is provided a method of activating an Scell in a UE of an LTE communication system. Specifically:

[0046] The UE receives a preamble signal transmitted by the base station on the Scell, the preamble signal including information indicating the base station activates the Scell.

[0047] Further, the UE receives the first message transmitted by the base station on the Pcell, and the first message is used for notifying the UE that the base station will communicate with the UE at the Scell. [0048] Preferably, next, the UE may receive a second message transmitted by the base station on the Pcell, and the second message is used for notifying the UE that the base station will no longer communicate with the UE on the Scell.

[0049] Fig. 2 shows a flow diagram of activating the Scell according to the above embodiments, comprising: [0050] S21. receiving, by the UE, a preamble signal transmitted by a base station on the secondary cell, wherein the preamble signal includes information indicating that the base station activates the secondary cell.

[0051] Hereinafter, the apparatuses corresponding to the methods provided by the present invention will be introduced with reference to the accompanying drawings. In view that the unit/means features therein have a correspondence relationship with the step features in the method, the apparatuses will be described in brief.

[0052] Fig. 3 shows a block diagram of an apparatus 30 for activating an Scell in a base station of an LTE communication system according to the present invention, the apparatus comprising: [0053] an assessment module 3001 for performing, by the base station, a clear channel assessment on the secondary cell, to determine whether the secondary cell is idle;

[0054] a preamble transmitting module 3002 for transmitting, by the base station, a preamble signal on the secondary cell when the secondary cell is idle, wherein the preamble signal includes information indicating that the base station activates the secondary cell.

[0055] Fig. 4 shows a block diagram of an apparatus 40 for activating an Scell in a UE of an LTE communication system according to the present invention, the apparatus comprising:

[0056] a preamble receiving module 4001 for receiving, by the UE, a preamble signal transmitted by a base station on the secondary cell, wherein the preamble signal includes information indicating that the base station activates the secondary cell.

[0057] The embodiments of the present invention have been described above. However, the present invention is not limited to a specific system, device, or protocol. Those skilled in the art may make various variations or modifications within the scope of the appended claims.

[0058] A person skilled in the art may understand and implement other alterations to the disclosed embodiments by studying the specification, disclosure, drawings, and the appended claims. In the claims, the terminology "comprise" does not exclude other elements and steps, and the terminology "a" does not exclude plurality. In the present invention, "first" and "second" only indicate names, without representing a sequential relationship. In actual applications of the present invention, one component may execute functions of a plurality of technical features cited in the claims. No reference numerals in the claims shall be understood as limitation to the scope.

Claims

I/We Claim:

1. A method of activating a secondary cell in a base station of an LTE communication system, wherein the secondary cell is an unlicensed carrier, the method comprising:

a. performing, by the base station, a clear channel assessment on the secondary cell to determine whether the secondary cell is idle;

b. transmitting, by the base station, a preamble signal on the secondary cell when the secondary cell is idle, wherein the preamble signal includes information indicating that the base station activates the secondary cell.

2. The method according to claim 1, further comprising: after step b, c. transmitting, by the base station, a first message on a primary cell, wherein the first message is used for notifying a first number of user equipment (UEs) that the base station will communicate with the first number of UEs on the secondary cell, wherein the first number of UEs are UEs scheduled by the base station to communicate on the secondary cell.

3. The method according to claim 2, further comprising: after step c, d. transmitting, by the base station, a second message on the primary cell, wherein the second message is used for notifying the first number of UEs that the base station will no longer communicate with the first number of UEs on the secondary cell.

4. The method according to claim 1, wherein the information indicating that the base station activates the secondary cell includes an orthogonal sequence associated with a cell identity of the base station.

5. The method according to claim 4, wherein the orthogonal sequence associated with the cell identity of the base station includes a primary synchronization signal sequence and/or a secondary synchronization signal sequence of the base station.

6. A method of activating a secondary cell in user equipment (UE) of an LTE communication system, wherein the secondary cell is an unlicensed carrier, the method comprising:

A. receiving, by the UE, a preamble signal transmitted by a base station on the secondary cell, wherein the preamble signal includes information indicating that the base station activates the secondary cell.

7. The method according to claim 6, further comprising: after step A,

B. receiving, by the UE, a first message transmitted by the base station on a primary cell, wherein the first message is used for notifying the UE that the base station will communicate with the UE on the secondary cell.

8. The method according to claim 7, further comprising: after step B,

C. receiving, by the UE, a second message transmitted by the base station on the primary cell, wherein the second message is used for notifying the UE that the base station will no longer communicate with the UE on the secondary cell.

9. An apparatus for activating a secondary cell in a base station of an LTE communication system, wherein the secondary cell is an unlicensed carrier, the apparatus comprising:

an assessment module for performing, by the base station, a clear channel assessment on the secondary cell to determine whether the secondary cell is idle; a preamble transmitting module for transmitting, by the base station, a preamble signal on the secondary cell when the secondary cell is idle, wherein the preamble signal includes information indicating that the base station activates the secondary cell.

10. The apparatus according to claim 9, further comprising:

a first transmitting module for transmitting, by the base station, a first message on a primary cell, wherein the first message is used for notifying a first number of user equipment (UEs) that the base station will communicate with the first number of UEs on the secondary cell, wherein the first number of UEs are UEs scheduled by the base station to communicate on the secondary cell.

11. The apparatus according to claim 10, further comprising:

a second transmitting module for transmitting, by the base station, a second message on the primary cell, wherein the second message is used for notifying the first number of UEs that the base station will no longer communicate with the first number of UEs on the secondary cell.

12. An apparatus for activating a secondary cell in user equipment (UE) of an LTE communication system, wherein the secondary cell is an unlicensed carrier, the apparatus comprising:

a preamble receiving module for receiving, by the UE, a preamble signal transmitted by a base station on the secondary cell, wherein the preamble signal includes information indicating that the base station activates the secondary cell.

13. The apparatus according to claim 12, further comprising:

a first receiving module for receiving, by the UE, a first message transmitted by the base station on a primary cell, wherein the first message is used for notifying the UE that the base station will communicate with the UE on the secondary cell.

14. The apparatus according to claim 13, further comprising:

a second receiving module for receiving, by the UE, a second message transmitted by the base station on the primary cell, wherein the second message is used for notifying the UE that the base station will no longer communicate with the UE on the secondary cell.