CN106304368B

CN106304368B - Method and equipment for transmitting data in base station

Info

Publication number: CN106304368B
Application number: CN201510312123.3A
Authority: CN
Inventors: 孟艳; 刘建国; 韩锋; 陶涛; 武卓; 王钧; 谷俊嵘
Original assignee: Nokia Shanghai Bell Co Ltd
Current assignee: Nokia Shanghai Bell Co Ltd
Priority date: 2015-06-09
Filing date: 2015-06-09
Publication date: 2020-12-25
Anticipated expiration: 2035-06-09
Also published as: CN106304368A

Abstract

The invention aims to provide a method and equipment for realizing frequency reuse under an LBT mechanism based on LBE. A base station of an LTE-LAA system detects energy of a certain channel, and if the detected energy is lower than the first threshold value, the channel is determined to be idle; otherwise, judging whether the interference in the same operator exists or not; determining that the channel is idle if there is interference within the same operator. If the channel is idle, the base station transmits data on the channel and always transmits interference in the same operator during the period that the channel is occupied by the base station. By adopting the invention, different base stations under the jurisdiction of the same operator can simultaneously use the same channel, thereby improving the resource utilization rate and solving the problem that the LBT mechanism based on LBE in the prior art can not realize frequency reuse.

Description

Method and equipment for transmitting data in base station

Technical Field

The invention relates to the technical field of communication, in particular to a data transmission technology in LTE.

Background

Cellular technology and WiFi have now become the two most successful wireless technologies. For many years, they have been complementary in superiority and are now fused with each other. Conventional cellular technologies, such as LTE systems, operate on licensed spectrum (licensed spectrum), while WiFi operates on unlicensed spectrum (unlicensed spectrum).

With the rapid growth of wireless services, the capacity and spectrum requirements of wireless communication systems have increased. In this case, the licensed band resource of the LTE system is relatively insufficient. Therefore, 3GPP proposes an LTE-U (LTE in Unlicensed spectrum, abbreviated as LTE-U) technology framework, which extends an LTE system from a Licensed frequency band to an Unlicensed frequency band, and splits best-effort (best-effort) traffic through a Carrier Aggregation (CA) framework, so the LTE-U is also called Licensed Assisted Access (LAA). In the framework, the primary cell carries data with high service quality requirements such as key control signaling, mobility and user data in an authorized frequency band, and the secondary cell carries best effort service with low service quality requirements in an unauthorized frequency band.

One of the great challenges of the LTE-LAA technology is to solve the problem of harmonious coexistence of LTE and Wi-Fi in the unlicensed band. Wi-Fi uses a listen-before-talk (LBT) mechanism, i.e., any device wishing to use the frequency band must listen first to see if the frequency band is occupied. If the band is not busy, the device may occupy and begin transmitting. This band is maintained for only 10 ms at the maximum, and then released and LBT is repeated. This ensures fair access to the medium and is also a very efficient way of sharing unlicensed spectrum. The problem to be solved is how to use LBT in the unlicensed band and achieve the best implementation. The feasibility of LTE-LAA techniques may be limited if the LBT mechanism is not well implemented.

Currently, there are two main methods for implementing the LBT mechanism:

the first method comprises the following steps: method Based on FBE (frame Based Equipment)

As shown in fig. 1(a), in the FBE method, CCA (Clear Channel Assessment) is performed at every fixed time interval, which is called fixed frame period. The channel occupancy time (i.e., the maximum transmission duration) varies from 1 ms to 10 ms, and the idle time should be at least 5% of the channel occupancy time.

And the second method comprises the following steps: LBE (load Based Equipment) -Based method

As shown in fig. 1(b), in the LBE method, after a device detects that a channel is occupied while performing CCA, it may continue to perform extended CCA, that is, perform CCA again, until it is detected that the channel is idle, and after N consecutive CCAs detect that the channel is idle, data may be transmitted. The definition of N may be different for each device. In fig. 1(b), N is 5, that is, after 5 CCA detects that the channel is clear, data transmission is started.

It can be seen that the FBE-based LBT mechanism is simple to implement, but the resource utilization of the LBE-based LBT mechanism is higher. Devices implementing LBE can know and occupy the channel as soon as it becomes clear, while devices implementing FBE need to wait for the next CCA time, possibly missing a channel occupancy opportunity.

Frequency reuse is an important feature of LTE, that is, different cells of the same operator can use a certain channel at the same time, aiming to improve the utilization rate of frequency. Naturally, LTE-LAA also wants to maintain this feature. Frequency multiplexing is also feasible in LTE-LAA, provided that certain conditions are met. It is generally known that frequency reuse can only be achieved when the CCA times of different cells are synchronized, i.e. the base stations of different cells perform CCA at almost the same time, detect a clear channel almost simultaneously, and subsequent transmissions are also intentionally "colliding".

It is clear that the FBE based LBT mechanism easily achieves frequency reuse because different cells of the same operator have the same CCA time and transmission time. However, for LBE-based LBT, since different cells have different interference environments, different CCA times, and different extended CCA observation periods, it is difficult to implement simultaneous transmission for different cells of the same operator, and thus it is difficult to implement frequency reuse.

Therefore, the present invention provides a method for implementing frequency reuse under an LBE-based LBT mechanism, so that different cells of the same operator can implement simultaneous transmission on the same channel.

Disclosure of Invention

The invention aims to provide a method and equipment for realizing frequency reuse under an LBT mechanism based on LBE.

According to a first aspect of the present invention, there is provided a method for transmitting data in a base station of an LTE-LAA system, the method comprising the steps of: a. detecting energy of a certain channel, and judging whether the detected energy is lower than a first threshold value; b. determining that the channel is idle if the detected energy is below the first threshold; c. otherwise, judging whether the interference in the same operator exists or not; d. determining that the channel is idle if there is interference within the same operator.

Preferably, the step d further comprises: d1. determining that the channel is busy if the interference within the same operator is greater than a second threshold; d2. otherwise, subtracting the interference in the same operator from the detected energy to obtain the residual energy; d3. determining that the channel is busy if the remaining energy includes interference from other operators or interference of other RATs and the interference is greater than a third threshold; d4. otherwise, determining that the channel is idle.

Preferably, the method further comprises: if the channel is idle, transmitting data on the channel and transmitting interference in the same operator all the time during the period that the channel is occupied by the base station.

Preferably, the interference in the same operator is a pilot signal of the same operator, and the pilot signal is an orthogonal sequence bound with an operator identity.

Preferably, the step c further comprises: and judging whether interference exists in the same operator according to a predefined pilot signal of the operator and the transmission mode of the pilot signal.

Preferably, the transmission of the pilot signal is restricted to a specific subcarrier of each OFDM symbol of one LTE subframe.

Preferably, the transmission of the pilot signals is restricted to certain OFDM symbols of one LTE sub-frame.

According to a second aspect of the present invention, there is provided an apparatus for transmitting data in a base station of an LTE-LAA system, the apparatus comprising: the first judgment device is used for detecting the energy of a certain channel and judging whether the detected energy is lower than a first threshold value; first determining means for determining that the channel is idle when the detected energy is below the first threshold; second judging means for judging whether or not there is interference within the same operator when the detected energy is not lower than the first threshold; second determining means for determining that the channel is idle when there is interference within the same operator.

Preferably, the second determining means is further configured to: determining that the channel is busy if the interference within the same operator is greater than a second threshold; otherwise, subtracting the interference in the same operator from the detected energy to obtain the residual energy; determining that the channel is busy if the remaining energy includes interference from other operators or interference of other RATs and the interference is greater than a third threshold; otherwise, determining that the channel is idle.

Preferably, the apparatus further comprises: transmitting means for transmitting data on the channel when the channel is idle and for always transmitting interference within the same operator during the period when the channel is occupied by the base station.

Preferably, the second determination device is further configured to: and judging whether interference exists in the same operator according to a predefined pilot signal of the operator and the transmission mode of the pilot signal.

Compared with the prior art, the invention provides a data transmission technology capable of realizing frequency reuse under an LBT mechanism based on LBE. The technology of the invention can enable different base stations under the jurisdiction of the same operator to use the same channel at the same time, improve the resource utilization rate and solve the problem that the LBT mechanism based on LBE in the prior art can not realize frequency reuse.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments made with reference to the following drawings:

fig. 1(a) shows a data transmission diagram of an FBE-based LBT mechanism;

fig. 1(b) shows a data transmission diagram of an LBE-based LBT mechanism;

fig. 2 shows a flow chart of a method for transmitting data in a base station of an LTE-LAA system according to an embodiment of the invention;

FIG. 3(a) is a diagram of time and frequency for transmitting pilot signals according to one embodiment of the present invention;

FIG. 3(b) is a diagram of time and frequency for transmitting pilot signals according to another embodiment of the present invention;

fig. 4 shows a schematic diagram of data transmission in a base station according to an embodiment of the invention;

fig. 5 shows a schematic diagram of an apparatus for transmitting data in a base station according to an embodiment of the present invention.

The same or similar reference numbers in the drawings identify the same or similar elements.

Detailed Description

In order to realize frequency reuse under an LBT mechanism based on LBE, when a cell detects that a channel is busy during CCA, whether the channel is occupied by other cells under the same operator is continuously judged, if the channel is occupied by other cells under the same operator, the channel is considered to be available, and the channel is started to be used, so that a plurality of cells under the same operator can use the channel at the same time.

According to an application scenario of the present invention, in an LTE-LAA system, there is at least one base station, which includes base station eNB1 and base station eNB 2. Base station eNB1 and base station eNB2 both employ an LBE-based LBT mechanism and are both affiliated with operator OP 1.

The present invention is described in further detail below with reference to the attached drawing figures.

Fig. 2 illustrates a method for transmitting data in a base station eNB1 of an LTE-LAA system according to one embodiment of the present invention. The method begins at step S21.

In step S21, the bs performs energy detection on a channel CH1, and determines whether the detected energy E1 is lower than a first threshold T1.

Then, in step S22, if the detected energy E1 is lower than the first threshold T1, it is determined that the channel CH1 is idle.

If the detected energy E1 is not lower than the first threshold T1, then, in step S23, it is determined whether there is interference within the same operator in the energy E1.

Then, in step S24, if there is intra-operator interference in the energy E1, the base station eNB1 may determine that the channel CH1 is being occupied by other cells under the same operator OP1, and then determine that the channel CH1 is idle.

In one embodiment, the step S24 further includes: step S241 (not shown in the figure), step S242 (not shown in the figure), step S24 (not shown in the figure) 3, and step S244 (not shown in the figure).

In step S241, it is determined that the channel CH1 is busy if the intra-operator interference is greater than a second threshold T2. If the interference in the same operator is too large, it indicates that the two cells are too close, in which case the TDM transmission mode has higher efficiency.

In step S242, if the intra-operator interference is not greater than the second threshold T2, the remaining energy is subtracted from the detected energy E1.

Then, in step S243, if the remaining energy includes interference from other operators or interference of other RATs and the interference is greater than a third threshold T3, it is determined that the channel CH1 is busy.

In step S244, if the remaining energy does not include interference from other operators or interference of other RATs, it is determined that the channel CH1 is idle.

In yet another embodiment, the method further comprises step S25 (not shown in the figure).

In step S25, if channel CH1 is idle, then base station eNB1 starts transmitting data on channel CH1 and transmits the above-mentioned intra-operator interference all the time while channel CH1 is occupied by base station eNB 1. This ensures that other cells under the same operator OP1 detect interference within the same operator when doing CCA, thereby enabling the cell to determine that the channel is being occupied by a cell under the same operator OP 1.

In yet another embodiment, the interference within the same operator is a pilot signal of the same operator, the pilot signal being an orthogonal sequence bound to an operator identity. Different operators have different pilot signals. The cells under the same operator are pre-configured with the pilot signal of the operator and the transmission mode of the pilot signal.

The transmission mode of the pilot signal, i.e. the time-frequency resource for transmitting the pilot signal, is configurable.

In one embodiment, the transmission of pilot signals may be restricted to certain subcarriers of each OFDM symbol of the LTE subframe. As shown in fig. 3(a), subcarriers #2, #5, #8, #11 are used to transmit pilot signals. According to this transmission scheme, if the base station eNB1 occupies a certain channel, it will transmit pilot signals on these subcarriers to facilitate frequency reuse of other cells of the same operator OP 1. Data may be transmitted on other subcarriers.

In yet another embodiment, to reduce the complexity and overhead of detection, the transmission of pilot signals may be limited to some OFDM symbols of one LTE subframe rather than all OFDM symbols. As shown in fig. 3(b), OFDM symbols #1, #5, #8, #12 are used for transmitting pilot signals, and the other OFDM symbols are used for transmitting data.

Accordingly, the base station eNB1 may perform step S23 according to the pre-configured pilot signal of the operator OP1 and the transmission manner of the pilot signal, i.e., determine whether the pilot signal of the operator OP1 exists in the detected energy E1. Specifically, if the pilot signal of the operator OP1 is transmitted on the subcarriers #2, #5, #8, #11, the base station eNB1 checks the detected subcarriers of the energy E1 to detect whether the pilot signal of the operator OP1 is included therein.

Accordingly, in step S25, during the period that the channel CH1 is occupied by the base station eNB1, the base station eNB1 may always transmit the pilot signal according to the pilot signal of the operator OP1 configured in advance and the transmission manner of the pilot signal. Specifically, if the pilot signal of operator OP1 is transmitted on OFDM symbols #1, #5, #8, #12, then the eNB1 would transmit the pilot signal of operator OP1 on these particular OFDM symbols.

FIG. 4 shows a diagram of data transmission in base station eNB1 and base station eNB2, according to one embodiment of the present invention.

In this embodiment, the base station eNB1 and the base station eNB2 both use the LBT mechanism based on LBE and are both pre-configured with the pilot signal of the operator OP1 and the transmission mode of the pilot signal.

In the downlink direction, when base station eNB1 and base station eNB2 are doing extended CCA, base station eNB1 first detects that channel CH1 is clear and thus occupies the channel. The base station eNB1 transmits the pilot signal on the channel CH1 in accordance with the pilot signal of the operator OP1 and the transmission method of the pilot signal configured in advance while transmitting data on the channel CH 1.

When the base station eNB2 performs the extended CCA, the base station eNB2 determines that the channel CH1 is not idle according to the detected energy, and then continuously detects whether the channel CH contains the interference in the same operator, namely the pilot signal of the operator OP 1. Specifically, the base station eNB2 determines whether the pilot signal of the operator OP1 is included in the pilot signal of the operator OP1 according to the pre-configured pilot signal and the transmission method of the pilot signal.

In this embodiment, the base station eNB2 determines that the detected energy includes a pilot signal of the operator OP1, so the base station eNB2 can determine that the channel CH1 is being occupied by other cells of the operator OP 1.

The base station eNB2 then subtracts the detected interference within the same operator, i.e. the pilot signal of operator OP1, from the detected energy to get the remaining energy.

Next, the base station eNB2 determines whether the remaining energy contains interference from other operators or other RATs, and detects that the remaining energy does not contain interference from other operators or other RATs, so that the base station eNB2 determines that the channel CH1 is idle.

Next, the base station eNB2 transmits data on the channel CH1, so that different cells of the same operator transmit data on the same channel at the same time, thereby achieving the purpose of frequency reuse. While the base station eNB2 is transmitting data on channel CH1, the base station eNB2 is always transmitting the pilot signal on channel CH1 in accordance with the pilot signal of operator OP1 and the transmission method of the pilot signal, which are configured in advance. In this way, when the other cell of the operator OP1 does CCA, it can identify the pilot signal, and know that the channel CH1 is occupied by the other cell of the operator OP1, thereby determining that the channel is available and implementing frequency reuse.

Fig. 5 shows a schematic diagram of an apparatus for transmitting data in a base station eNB1 of an LTE-LAA system according to an embodiment of the present invention. The apparatus 500 comprises first determining means 501, first determining means 502, second determining means 503 and second determining means 504.

The operation of the apparatus 500 is described in detail below with reference to fig. 2 and 3.

First, the first determination device 501 performs energy detection on a certain channel CH1, and determines whether the detected energy E1 is lower than a first threshold T1.

Then, if the detected energy E1 is below the first threshold T1, the first determining means 502 determines that the channel CH1 is idle.

If the detected energy E1 is not lower than the first threshold T1, then the second determining means 503 determines whether there is interference within the same operator in the energy E1.

Then, if there is intra-operator interference in the energy E1, the second determining means 504 determines that the channel CH1 is being occupied by other cells under the same operator OP1, and determines that the channel CH1 is idle.

In one embodiment, the second determining means 504 is further configured to:

-determine that channel CH1 is busy if the interference within the same operator is greater than a second threshold T2. If the interference in the same operator is too large, it indicates that the two cells are too close, in which case the TDM transmission mode has higher efficiency.

-if the intra-operator interference is not greater than a second threshold T2, subtracting the intra-operator interference from the detected energy E1 resulting in a remaining energy.

-determine that channel CH1 is busy if the remaining energy contains interference from other operators or other RATs and the interference is greater than a third threshold T3.

-determine that channel CH1 is idle if the remaining energy does not contain interference from other operators or other RATs.

In yet another embodiment, the apparatus 500 further comprises a sending means 505 (not shown in the figure).

If the channel CH1 is idle, then the transmitting device 505 starts transmitting data on channel CH1 and the transmitting device 505 is transmitting the same intra-operator interference described above for the duration that channel CH1 is occupied by the base station eNB 1. This ensures that other cells under the same operator OP1 detect interference within the same operator when doing CCA, thereby enabling the cell to determine that the channel is being occupied by a cell under the same operator OP 1.

In one embodiment, the transmission of pilot signals may be restricted to certain subcarriers of each OFDM symbol of the LTE subframe. As shown in fig. 3(a), subcarriers #2, #5, #8, #11 are used to transmit pilot signals. According to this transmission method, if the base station eNB1 occupies a certain channel, the transmitter 505 transmits pilot signals on these subcarriers to facilitate frequency reuse of other cells of the same operator OP 1. Data may be transmitted on other subcarriers.

Accordingly, the second determining device 503 may determine whether the pilot signal of the operator OP1 exists in the detected energy E1 according to the pre-configured pilot signal of the operator OP1 and the transmission manner of the pilot signal. Specifically, if the pilot signal of the operator OP1 is transmitted on the sub-carriers #2, #5, #8, #11, the second determining means 503 checks the detected sub-carriers of the energy E1 to detect whether the pilot signal of the operator OP1 is contained therein.

Accordingly, the transmitting device 505 may always transmit the pilot signal according to the pilot signal of the operator OP1 configured in advance and the transmission method of the pilot signal during the period that the channel CH1 is occupied by the base station eNB 1. Specifically, if the pilot signal of the operator OP1 is transmitted on OFDM symbols #1, #5, #8, #12, the transmitting apparatus 505 transmits the pilot signal of the operator OP1 on these specific OFDM symbols.

It should be noted that the present invention may be implemented in software and/or in a combination of software and hardware, for example, as an Application Specific Integrated Circuit (ASIC), a general purpose computer or any other similar hardware device. In one embodiment, the software program of the present invention may be executed by a processor to implement the steps or functions described above. Also, the software programs (including associated data structures) of the present invention can be stored in a computer readable recording medium, such as RAM memory, magnetic or optical drive or diskette and the like. Further, some of the steps or functions of the present invention may be implemented in hardware, for example, as circuitry that cooperates with the processor to perform various steps or functions.

In addition, some of the present invention can be applied as a computer program product, such as computer program instructions, which when executed by a computer, can invoke or provide the method and/or technical solution according to the present invention through the operation of the computer. Program instructions which invoke the methods of the present invention may be stored on a fixed or removable recording medium and/or transmitted via a data stream on a broadcast or other signal-bearing medium and/or stored within a working memory of a computer device operating in accordance with the program instructions. An embodiment according to the invention herein comprises an apparatus comprising a memory for storing computer program instructions and a processor for executing the program instructions, wherein the computer program instructions, when executed by the processor, trigger the apparatus to perform a method and/or solution according to embodiments of the invention as described above.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned. Furthermore, it is obvious that the word "comprising" does not exclude other elements or steps, and the singular does not exclude the plural. A plurality of units or means recited in the apparatus claims may also be implemented by one unit or means in software or hardware. The terms first, second, etc. are used to denote names, but not any particular order.

Claims

1. A method for transmitting data in a base station of an LTE-LAA system, the method comprising the steps of:

a. detecting energy of a certain channel, and judging whether the detected energy is lower than a first threshold value;

b. determining that the channel is idle if the detected energy is below the first threshold;

c. otherwise, determining whether there is intra-operator interference therein, wherein the intra-operator interference is a pilot signal of the same operator, and the determining comprises: judging whether interference exists in the same operator according to a predefined pilot signal of the operator and a transmission mode of the pilot signal; and

d. determining that the channel is idle if there is interference within the same operator,

wherein the step d further comprises:

d1. determining that the channel is busy if the interference within the same operator is greater than a second threshold;

d2. otherwise, subtracting the interference in the same operator from the detected energy to obtain the residual energy;

d3. determining that the channel is busy if the remaining energy includes interference from other operators or interference of other RATs and the interference is greater than a third threshold;

d4. otherwise, determining that the channel is idle.

2. The method of claim 1, further comprising:

if the channel is idle, transmitting data on the channel and transmitting interference in the same operator all the time during the period that the channel is occupied by the base station.

3. The method of claim 1, wherein the pilot signal is an orthogonal sequence bound to an operator identity.

4. The method of claim 3, wherein the transmission of the pilot signals is restricted to specific subcarriers of each OFDM symbol of one LTE subframe.

5. The method of claim 3, wherein the transmission of the pilot signals is restricted to certain OFDM symbols of one LTE sub-frame.

6. An apparatus for transmitting data in a base station of an LTE-LAA system, the apparatus comprising:

the first judgment device is used for detecting the energy of a certain channel and judging whether the detected energy is lower than a first threshold value; first determining means for determining that the channel is idle when the detected energy is below the first threshold;

second judging means for judging whether or not there is interference within the same operator when the detected energy is not lower than the first threshold, wherein the interference within the same operator is a pilot signal of the same operator, and the second judging means is configured to judge whether or not there is interference within the same operator according to a predefined transmission pattern of the pilot signal of the operator and the pilot signal;

second determining means for determining that the channel is idle when there is interference within the same operator,

wherein the second determining means is further for:

-determining that the channel is busy if the interference within the same operator is greater than a second threshold;

-otherwise, subtracting the interference within the same operator from the detected energy resulting in a remaining energy;

-determining that the channel is busy if the remaining energy comprises interference from other operators or other RATs and the interference is greater than a third threshold;

-otherwise, determining that the channel is idle.

7. The apparatus of claim 6, the apparatus further comprising:

transmitting means for transmitting data on the channel when the channel is idle and for always transmitting interference within the same operator during the period when the channel is occupied by the base station.

8. The apparatus of claim 6, wherein the pilot signal is an orthogonal sequence bound to an operator identity.

9. The apparatus of claim 8, wherein transmission of the pilot signals is restricted to specific subcarriers of each OFDM symbol of one LTE subframe.

10. The apparatus of claim 8, wherein transmission of the pilot signals is limited to certain OFDM symbols of one LTE subframe.