CN101399645A - ACK/NACK scheduling method and scheduling device for LTE-TDD system - Google Patents

Abstract

The invention discloses an LTE-TDD system ACK/NACK scheduling method, comprising: the network side counts the distribution of downlink service data of each user equipment UE, and monitors whether the downlink service data is scheduled for each UE; determines that the downlink service data of a certain UE is scheduled After scheduling, a message is sent to the UE to inform the channel for feeding back ACK/NACK; the UE feeds back ACK/NACK on the corresponding channel according to the received message. The present invention proposes an ACK/NACK feedback scheme aiming at the LTE-TDD system, and ensures effective transmission of the ACK/NACK under the condition that the downlink subframes are more than the uplink subframes. Corresponding to the above method, the present invention also provides an LTE-TDD system ACK/NACK scheduler.

Description

LTE-TDD system ACK/NACK scheduling method and scheduler

This application claims the priority of the Chinese patent application with the application number 200710164202 and the X invention title "LTE-TDD System ACK/NACK Scheduling Method and Scheduler" submitted to the China Patent Office on September 30, 2007, the entire content of which is passed References are incorporated in this application.

technical field

The present invention relates to the technical field of LTE (Long Time Evolution, long-term evolution) of mobile communication, relate in particular to a kind of LTE-TDD (Time Division Duplex, time division duplex) system uplink ACK (ACKnowledge, confirmation information)/NACK (Non-ACKnowledge, Unconfirmed information) scheduling method and scheduler.

Background technique

The LTE system supports two frame structures. The first type of frame structure is suitable for TDD and FDD (Frequency Division Duplex, frequency division duplex) systems. This type of frame structure is shown in Figure 1. The frame length of this type of wireless frame is 10ms and consists of 20 time slots. The length of each time slot is 0.5ms, and the time slots are marked 0 to 19 as shown in the figure. Two consecutive time slots are defined as a subframe, and subframe i is composed of time slots 2i and (2i+1), where i=0, 1...9. For the FDD system, since the uplink and downlink are separated in the frequency domain every 10 ms, there are 10 subframes available for uplink and downlink. For the TDD system, a total of 10 subframes are available for uplink and downlink every 10 ms, and except subframe 0 and subframe 5 are always allocated for downlink transmission, the remaining subframes are either allocated for uplink or downlink. The second type of frame structure is only applicable to the TDD system. Refer to Figure 2 for this type of frame structure. The frame length of this type of wireless frame is also 10ms. Each frame is split into two half frames of 5ms. Each half frame consists of 7 business hours. slots (marked 0 to 6) and 3 special time slots (downlink pilot, guard interval and uplink pilot). Each subframe is defined as a business slot. Wherein, subframe 0 and downlink pilot time slot are always used for downlink transmission, while uplink pilot and subframe 1 are always used for uplink transmission.

In order to perform fast feedback and retransmission of erroneous data blocks, and make full use of the information carried by erroneous data blocks by merging data blocks, the LTE system adopts HARQ (Hybrid Automatic Repeat Request, Hybrid Automatic Repeat Request) technology. Uplink ACK/NACK signaling is a part of uplink control signaling. There are two transmission methods. One is that when UE (User Equipment, user equipment) has uplink service data transmission, ACK/NACK signaling and service data are multiplexed. Transmission; the other is that when the UE has no uplink service data, ACK/NACK signaling is transmitted in the frequency bands reserved on both sides of the working bandwidth, and frequency hopping is used to improve transmission performance. This article discusses the second case. For the second ACK/NACK transmission mode, the scheme determined by the LTE system is: 1-bit ACK/NACK (corresponding to a single code character) is mapped to BPSK (Binary Phase Shift Keying, bi-phase shift keying) symbols, 2 Bit ACK/NACK (corresponding to 2 codewords) is mapped to QPSK (Quadrature Phase Shift Keying, Quadrature Phase Shift Keying) symbols, and each modulation symbol is spread as CAZAC (Constant Envelope Zero Autocorrelation Sequence), using coherent Modulated method of transmission. For the first type of frame structure shown in Figure 1, each PRB (Physical Resource Block, physical resource block) can support up to 18UE multiplexing; for the second type of frame structure shown in Figure 2, a frequency hopping structure is also used per PRB Support up to 12UE multiplexing. Since ACK/NACK signaling is generally only 1 bit or 2 bits, adding additional UE identification information will greatly increase information redundancy and reduce transmission efficiency. Therefore, in the LTE-FDD system, it has been determined to adopt the implicit indication method A mapping relationship between the ACK/NACK signaling and the sequence number of the control channel occupied by the corresponding downlink scheduling control signaling is established, so that the eNB (evolved base station) can determine the UE and the data block corresponding to the ACK. Referring to Fig. 3, it is a schematic diagram of the method for indicating the ACK channel based on the implicit mode in the existing LTE-FDD system, wherein, by establishing the mapping relationship between the ACK/NACK signaling channel and the corresponding downlink scheduling control signaling channel in advance, the eNB can determine UE and data block corresponding to ACK signaling.

For the FDD system, the uplink and downlink are separated in frequency, and the uplink and downlink subframes can easily establish a one-to-one correspondence. That is to say, the ACK/NACK signaling of an uplink subframe only corresponds to a unique downlink subframe, and the corresponding relationship is relatively simple and fixed. , therefore, in the LTE system standard meeting, for the discontinuous scheduling service, the implicit indication method introduced above is used to determine the ACK feedback scheme. However, for the TDD system, the uplink and downlink adopt a proportionally variable asymmetric structure to support asymmetric services. This asymmetric structure makes it impossible to establish a simple one-to-one correspondence between the uplink and downlink. Therefore, the ACK feedback method of the TDD system needs to be redesigned.

Contents of the invention

In view of this, the present invention provides an ACK/NACK scheduling method and a scheduler in an LTE-TDD system to adapt to the asymmetry of uplink and downlink services in a time division duplex system.

For this reason, the embodiment of the present invention adopts following technical scheme:

An LTE-TDD system ACK/NACK scheduling method, comprising: the network side counts the distribution of downlink service data of each user equipment UE, and monitors whether the downlink service data is scheduled for each UE; after determining that the downlink service data of a certain UE is scheduled, send The UE sends a message to inform the physical resource for feeding back the ACK/NACK; the UE feeds back the ACK/NACK on the corresponding physical resource according to the received message.

The network side notifies the UE of the physical resource for feeding back ACK/NACK by adding an additional message in the downlink control signaling.

The network side notifies the UE of the physical resources for feeding back ACK/NACK through the BCH broadcast message.

The method is aimed at the situation that the number of uplink subframes is smaller than the number of downlink subframes.

When the number of uplink subframes is greater than or equal to the number of downlink subframes: before sending downlink service data, pre-set the mapping relationship between the channel occupied by the downlink control signaling and the feedback ACK/NACK channel; the network side sends the downlink control through the mapping relationship Signaling, the UE side feeds back ACK/NACK through the mapping relationship.

An LTE-TDD system ACK/NACK scheduling method, comprising: the network side puts the service data to be scheduled of each UE into a buffer; during the period when a certain UE service data in the buffer is scheduled, the UE downlink service data distribution in the buffer is used , sending a message to the UE to inform the physical resource for feeding back the ACK/NACK; the UE feeds back the ACK/NACK on the corresponding physical resource according to the received message.

The network side notifies the UE of the physical resource for feeding back ACK/NACK by adding an additional message in the downlink control signaling.

The network side notifies the UE of the physical resources for feeding back ACK/NACK through a BCH broadcast message.

The method is aimed at the situation that the number of uplink subframes is smaller than the number of downlink subframes.

When the number of uplink subframes is greater than or equal to the number of downlink subframes: before sending downlink service data, pre-set the mapping relationship between the channel occupied by the downlink control signaling and the feedback ACK/NACK channel; the network side sends the downlink control through the mapping relationship Signaling, the UE side feeds back ACK/NACK through the mapping relationship.

An LTE-TDD system ACK/NACK scheduler, comprising: a statistical unit for counting the distribution of downlink service data to be scheduled by each UE; a monitoring unit for monitoring whether each UE has downlink service data to be scheduled, and if so, sending A certain UE is instructed to be scheduled; the ACK/NACK channel determination unit determines the physical resources for the UE to feed back ACK/NACK according to the statistical results of the statistical unit; the message unit sends an ACK message to the UE after the monitoring unit sends an instruction. /NACK the message of the physical resource determined by the channel determination unit.

The message is an additional message in the downlink control signaling, or is a BCH broadcast message.

An LTE-TDD system ACK/NACK scheduler, including: a buffer module, including a plurality of buffers, and each buffer is used to buffer each UE to be scheduled service data; a buffer statistics module, used to count the buffers, to know each UE downlink service data distribution; monitoring module, used to monitor whether each UE has downlink service data to be scheduled, if so, send a certain UE to be scheduled; ACK/NACK channel determination module, according to the statistical results of the buffer statistics module, determining the physical resource for the UE to feed back ACK/NACK; the message module, after the monitoring module sends an instruction, sends a message including the physical resource determined by the ACK/NACK channel determining module to the UE.

The message is an additional message in the downlink control signaling, or is a BCH broadcast message.

The technical effect analysis for the above-mentioned technical scheme is as follows:

Starting from the asymmetric characteristics of time division duplex uplink and downlink services, the present invention provides an ACK/NACK feedback method based on a scheduling mechanism: for the case where the uplink subframe is more than or equal to the downlink subframe, that is, the case of single ACK/NACK, for the uplink When the subframe is smaller than the downlink subframe, the direct indication method is adopted, which specifically includes the buffer direct indication method and the immediate direct indication method. It can be flexibly selected according to system requirements.

Description of drawings

FIG. 1 is a schematic diagram of a frame structure of the first type in the prior art;

FIG. 2 is a schematic diagram of a frame structure of the second type in the prior art;

FIG. 3 is a schematic diagram of an LTE-FDD system feedback ACK scheme in the prior art;

FIG. 4 is one of schematic diagrams of ACK/NACK and service subframe mapping;

FIG. 5 is the second schematic diagram of ACK/NACK and service subframe mapping;

Figure 6 is the third schematic diagram of ACK/NACK and service subframe mapping;

Fig. 7 is a flow chart of buffer direct indication method;

Figure 8 is a schematic diagram of an example of the buffer direct indication method;

Fig. 9 is a flowchart of instant direct instruction method;

Figure 10 is a schematic diagram of an example of the instant direct instruction method;

Fig. 11 is a schematic diagram of the first scheduler;

Fig. 12 is a schematic diagram of the second scheduler.

Detailed ways

The present invention proposes an ACK/NACK feedback scheme aiming at the characteristics of the TDD system, especially when there are more downlink subframes than uplink subframes, to ensure effective transmission of ACK/NACK signaling and uplink single-carrier characteristics. The so-called single-carrier characteristic here can be understood as: the channel for transmitting ACK/NACK is continuous in the frequency domain, and uses the same ZC (Zadoff-Chu) sequence.

As introduced above, for the TDD system, due to the asymmetric characteristics of the uplink and downlink, it cannot always establish a one-to-one correspondence like the FDD system. Referring to FIG. 4 , when the downlink subframe is less than or equal to the uplink subframe, the mapping relationship between the transmission ACK/NACK and the service subframe can be determined by agreement. Referring to Figure 5, when there are more downlink subframes than uplink subframes, it means that one uplink time slot needs to send ACK/NACK signaling corresponding to multiple downlink time slot data blocks. In the most extreme case, the first type of frame structure The row ratio is 1/9, and the uplink and downlink ratio of the second type of frame structure is 1/6, which means that each uplink subframe needs to transmit ACK/NACK signaling corresponding to 9 or 6 downlink subframe data blocks. In order to guarantee the single-carrier characteristic of uplink transmission, multiple ACK/NACK signaling must be arranged uniformly. In fact, those skilled in the art may think of adopting the following solution: set multiple ACK/NACK regions in the UL subframe, each region corresponds to a downlink subframe, and then use the method of the FDD system. However, since the maximum The number of UEs is used for resource allocation, which occupies more resources. However, in practical applications, it is rare for multiple UEs to send ACK/NACK at the same time. Therefore, a large waste of resources is caused; When a data block is transmitted, multiple ACK/NACKs are mapped to multiple areas, which will destroy the uplink single-carrier characteristic.

Referring to FIG. 6 , it is a schematic diagram of the mapping relationship between ACK/NACK and service subframes when there are more downlink subframes than uplink subframes. Among them, for the UL ACK/NACK signaling that only maps one DL time slot, it is obvious that the LTE FDD method can be directly used to establish a corresponding relationship with the control channel number. When the uplink subframe is smaller than the downlink subframe, only one uplink subframe can be arranged to transmit multiple ACK signaling. The frame needs to send ACK/NACK signaling corresponding to 2, 4, and 6 downlink time slot data blocks. These three cases are collectively referred to as "multiple ACK/NACK cases". The following focuses on giving a specific solution to the multi-ACK situation.

For multiple ACK/NACK situations, the present invention uses a direct indication method to schedule ACK/NACK. For example, in the DL scheduling signaling of the eNB, a specific bit is added to indicate its ACK feedback channel. This includes two specific implementation methods, which will be introduced separately below.

The first is the buffered direct indication method:

Referring to Fig. 7, it is a flow chart of buffer direct indication method, including:

Step 701: For each UE, determine whether there is downlink data transmission, if yes, execute step 702, otherwise, continue to wait;

Step 702: put the downlink data of each UE into the buffer;

Step 703: Is the downlink data put into the buffer scheduled? If so, execute step 704, otherwise, wait;

Step 704: according to the number of downlink data blocks of the UE in the buffer, add specific information to the downlink scheduling signaling to indicate the UE uplink ACK/NACK physical resources (channels);

Step 705: The UE feeds back ACK/NACK on the corresponding channel according to the instruction in the specific information.

In step 704, in addition to adding characteristic information to the downlink scheduling signaling to inform the UE of the channel for feeding back the ACK/NACK, it may also be notified by way of BCH broadcast.

Now a specific example is used to describe this buffer direct instruction method.

Referring to FIG. 8 , taking the second type of frame with a ratio of uplink and downlink time slots of 1:6 as an example, the uplink ACK/NACK corresponding to the downlink time slot marked down2 in the figure is sent in the uplink time slot marked up2, and the rest are similar. The six downlink time slot transmission requests are all waiting in the buffer zone before being scheduled (at time t1). During the time period from t1 to t2, the ACK feedback information of the six downlink time slot services is uniformly arranged and scheduled to ensure that the Multiple ACKs of the same UE are arranged on the same physical resource, so as to satisfy the single carrier characteristic. The specific operation is to add the corresponding ACK/NACK information to the DL scheduling control signaling according to the downlink service situation of the UE in the buffer. According to the received ACK/NACK indication information at time t3, multiple ACK/NACK signaling generated by each UE according to its CRC (Cyclic Redundancy Check) check result are transmitted in the up2 time slot.

This processing method is simple and easy, and the processing of eNB and UE is very simple. On the eNB side, it only needs to put the downlink data into the buffer, and add a specific bit in the DL scheduling control information to inform the ACK/NACK transmission channel. On the UE side, no additional judgment is required, and only ACK/NACK needs to be fed back on corresponding physical resources according to the instructions of the eNB.

The second is the immediate direct instruction method:

In the above first method, it is easy to realize the downlink data of a certain UE in a time slot through the buffer zone, but it will relatively increase the delay. In this method, the eNB counts the downlink service data sent to each UE in advance, so that when the last time slot service data is sent to a certain UE, it adds specific information to the downlink scheduling signaling to inform the UE to feed back ACK/NACK physical resources.

Referring to Figure 9, it is a flowchart of the instant direct instruction method, including:

Step 901: Before sending downlink service data to each UE, the eNB collects statistics on the distribution of downlink service data of each UE;

Step 902: Is there any UE downlink service data? If so, execute step 903, otherwise, wait;

Step 903: Is the downlink service data of the UE scheduled? If so, execute step 904, otherwise, wait;

Step 904: Before the UE feeds back the ACK/NACK, send downlink scheduling signaling including specific information indicating the ACK/NACK channel;

Step 905: the UE feeds back ACK/NACK signaling on the channel indicated by the specific information.

In step 904, in addition to adding characteristic information in the downlink scheduling signaling to inform the UE of the ACK/NACK feedback channel, it can also be notified by BCH (Broadcast Channel) broadcast.

The method is still described with a specific example.

Referring to FIG. 10 , for the second type of frame, if the uplink-downlink ratio is 1:6, the uplink ACK/NACK corresponding to the downlink time slot marked down2 in the figure is sent in the uplink time slot marked up2. At the moment of the last down2 subframe, the eNB has learned the service scheduling situation of each UE in the relevant period (all subframes marked as down2), then the eNB can arrange ACK/NACK feedback for all data packets of all UEs Physical resources can ensure the effective utilization of resources and single-carrier characteristics. It is sufficient to notify the UE of the ACK channel before the ACK/NACK feedback, and it is shown in the figure that the UE is notified by way of downlink control signaling at the moment of the last subframe of down2.

The two direct indication methods described above are described by taking the second type of frame as an example, and they are also applicable to the first type of frame.

In summary, the present invention introduces the ACK/NACK feedback method based on the scheduling mechanism in the LTE-TDD system: for the case where the uplink subframe is more than or equal to the downlink subframe, that is, the case of single ACK/NACK, the same method as LTE-FDD A similar method based on the implicit mapping of DL scheduling control channel numbers, that is, before sending downlink service data, the mapping relationship between the downlink control signaling channel and the feedback ACK/NACK channel is preset; the network side sends the downlink control channel through the mapping relationship. For signaling, the UE side feeds back ACK/NACK through the mapping relationship; for the case where the uplink subframe is smaller than the downlink subframe, the direct indication method is adopted, specifically including the buffer direct indication method and the immediate direct indication method introduced above.

Corresponding to the above method, the present invention also provides a scheduler, which exists in a network side device, for example, in an eNB.

Referring to FIG. 11 , it is a schematic structural diagram of the first scheduler, which corresponds to the immediate direct instruction method. It includes a statistical unit 1101, a monitoring unit 1102, an ACK/NACK channel determination unit 1103 and a message unit 1104, and the functions of each unit are introduced below:

The statistical unit 1101 is mainly used to count the distribution of downlink service data to be scheduled by each UE;

The monitoring unit 1102 is mainly used to monitor whether each UE has downlink service data to be scheduled, and if so, send an indication that a certain UE is scheduled;

The ACK/NACK channel determination unit 1103, according to the statistical results of the statistical unit 1101, determines the physical resource for the UE to feed back ACK/NACK;

The message unit 1104 sends a message including the physical resource determined by the ACK/NACK channel determination unit 1103 to the UE after the monitoring unit 1102 sends an instruction.

Referring to FIG. 12 , it is a schematic structural diagram of the second scheduler, corresponding to the buffer direct indication method. It includes a buffer module 1201, a buffer statistics module 1202, a monitoring module 1203, an ACK/NACK channel determination module 1204 and a message module 1205, and the functions of each module are introduced below:

The buffer module 1201 includes a plurality of buffers, and each buffer is used to buffer service data to be scheduled of each UE;

The buffer statistics module 1202 is used for statistical buffers, so as to obtain the distribution of downlink service data of each UE;

The monitoring module 1203 is used to monitor whether each UE has downlink service data to be scheduled, and if so, send a certain UE to be scheduled;

ACK/NACK channel determination module 1204, according to the statistical results of the buffer statistics module 1202, determine the UE feedback ACK/NACK channel;

The message module 1205 sends a message including the channel determined by the ACK/NACK channel determination module 1204 to the UE after the monitoring module 1203 sends an instruction.

Wherein, the message that the above two schedulers send to the UE to inform the ACK/NACK channel may be an additional message in the downlink control signaling, or a BCH broadcast message.

The specific implementation details of the scheduler are similar to those in the method embodiments, and will not be repeated here.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (14)

1. A LTE-TDD system ACK/NACK scheduling method, characterized in that, comprising: The network side counts the distribution of downlink service data of each user equipment UE, and monitors whether the downlink service data is scheduled for each UE; after determining that the downlink service data of a certain UE is scheduled, sends a message to the UE to inform the physical resource of feedback ACK/NACK; According to the received message, the UE feeds back ACK/NACK on the corresponding physical resource. 2. The method according to claim 1, wherein the network side notifies the UE of the physical resource for feeding back ACK/NACK by adding an additional message in the downlink control signaling. 3. The method according to claim 1, wherein the network side notifies the UE of the physical resources for feeding back ACK/NACK through a BCH broadcast message. 4. The method according to claim 1, 2 or 3, characterized in that the method is aimed at the case that the number of uplink subframes is smaller than the number of downlink subframes. 5. The method according to claim 4, wherein when the number of uplink subframes is greater than or equal to the number of downlink subframes: Before sending downlink service data, pre-set the mapping relationship between the channel occupied by the downlink control signaling and the feedback ACK/NACK channel; The network side sends downlink control signaling through the mapping relationship, and the UE side feeds back ACK/NACK through the mapping relationship. 6. An LTE-TDD system ACK/NACK scheduling method, characterized in that, comprising: The network side puts the service data to be scheduled of each UE into the buffer; during the period when the service data of a certain UE in the buffer is scheduled, through the distribution of the downlink service data of the UE in the buffer, send a message to the UE to inform the physical resource of feedback ACK/NACK ; According to the received message, the UE feeds back ACK/NACK on the corresponding physical resource. 7. The method according to claim 6, wherein the network side notifies the UE of the physical resource for feeding back ACK/NACK by adding an additional message in the downlink control signaling. 8. The method according to claim 6, wherein the network side notifies the UE of the physical resource for feeding back ACK/NACK through a BCH broadcast message. 9. The method according to claim 6, 7 or 8, characterized in that the method is aimed at the case that the number of uplink subframes is smaller than the number of downlink subframes. 10. The method according to claim 9, wherein when the number of uplink subframes is greater than or equal to the number of downlink subframes: Before sending downlink service data, pre-set the mapping relationship between the channel occupied by the downlink control signaling and the feedback ACK/NACK channel; The network side sends downlink control signaling through the mapping relationship, and the UE side feeds back ACK/NACK through the mapping relationship. 11. An LTE-TDD system ACK/NACK scheduler, characterized in that it comprises: A statistical unit, configured to count the distribution of downlink service data to be scheduled by each UE; The monitoring unit is used to monitor whether each UE has downlink service data to be scheduled, and if so, send an indication that a certain UE is scheduled; The ACK/NACK channel determination unit determines the physical resource for the UE to feed back ACK/NACK according to the statistical results of the statistical unit; The message unit sends a message including the physical resource determined by the ACK/NACK channel determination unit to the UE after the monitoring unit sends an instruction. 12. The scheduler according to claim 11, wherein the message is an additional message added in the downlink control signaling, or is a BCH broadcast message. 13. An LTE-TDD system ACK/NACK scheduler, characterized in that it comprises: The buffer module includes a plurality of buffers, and each buffer is used to buffer the service data to be scheduled of each UE; The buffer statistics module is used for statistical buffers, and obtains the distribution of downlink service data of each UE; The monitoring module is used to monitor whether each UE has downlink service data to be scheduled, and if so, send an indication that a certain UE is scheduled; The ACK/NACK channel determination module determines the physical resources for the UE to feed back ACK/NACK according to the statistical results of the buffer statistics module; The message module sends a message including the physical resource determined by the ACK/NACK channel determination module to the UE after the monitoring module sends an instruction. 14. The scheduler according to claim 13, wherein the message is an additional message in downlink control signaling, or is a BCH broadcast message.

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