KR20060014639A - Method for and apparatus transmission of packet data according to priority of data in enhanced uplink dedicated channel - Google Patents

Abstract

The present invention provides a method for transmitting packet data from a plurality of priority queues having different priorities by a plurality of retransmission processors in a mobile communication system supporting reverse packet service. If there is a retransmission processor available, and if there is no retransmission processor available, the priority of the retransmission PDUs processed by the plurality of retransmission processors to check the priority of the new PDU Determining whether a retransmission PDU exists, and if there is a retransmission PDU having a lower priority than the new PDU, stopping retransmission of the retransmission PDU, and transmitting the new PDU in the retransmission processor where the retransmission is stopped. Characterized by including The priority has the effect to stop the retransmission of data and lower priority ranking, by the appropriate limit the process of transferring high data, preventing the waste of transmission resources.

CDMA, Preemption, HARQ, TTI, EUDCH

Description

Method for and apparatus transmission of packet data according to priority in uplink packet data service according to priority of data In Enhanced uplink dedicated channel             

1 is a diagram illustrating the basic concept of general Node B scheduling.

2 is a diagram illustrating a process of transmitting packet data using a data rate for general EUDCH packet data transmission.

3 is a diagram illustrating a protocol structure of a mobile communication system supporting a general EUDCH.

4 is a view showing the operation of the MAC-e hierarchical structure and HARQ of the terminal according to the present invention.

5 is a diagram illustrating a flow of a control message for transmitting a preemption related parameter to a terminal according to the present invention.

6 illustrates a MAC-e hierarchical structure according to the present invention.

7 illustrates the operation of a MAC-e layer entity in accordance with the present invention.

The present invention relates to a mobile communication system for transmitting packet data over the uplink, and more particularly, to a method for a user terminal to stop retransmission of low priority data and to start transmission of new data.

Asynchronous wideband code division multiple access (WCDMA) communication system uses an enhanced uplink dedicated channel (hereinafter referred to as "EUDCH"). The EUDCH is a channel proposed to improve the performance of packet transmission in reverse communication in an asynchronous code division multiple access communication system.

The mobile communication system supporting the EUDCH maximizes the efficiency of uplink transmission by using a fast scheduling technique and a hybrid automatic retransmission request (HARQ) technique. The HARQ is By executing HARQ between the UE and the Node B, it is to increase the transmission success rate compared to the transmission output. That is, the data block reception success probability is increased by performing soft combining with the retransmitted data block without discarding the data block in which the error occurs through the HARQ technique.

In the fast scheduling scheme, the Node B reports the channel status and the buffer status of the UE, and controls backward transmission of the UEs based on the received information. That is, a large amount of data transmission is allowed to UEs in good channel conditions, and data transmission for UEs in poor channel conditions is minimized, thereby enabling efficient use of limited uplink transmission resources.

Uplink signals transmitted by a plurality of user terminals (hereinafter, referred to as "UE") do not maintain orthogonality with each other, and thus act as interference signals. Therefore, as the uplink signal received by the Node B increases, the amount of interference signal for the uplink signal transmitted by a specific UE also increases. Therefore, as the amount of the interference signal for the uplink signal transmitted by a specific UE increases, the reception performance of the Node B decreases. For this reason, the Node B has been proposed a method as shown in Equation 1 below to limit the amount of uplink signal that can be received, while ensuring the reception performance.

RoT = Io / No

Io is the total received broadband power spectral density of the Node B, and No represents the thermal noise power spectral density of the Node B. The ROT becomes a radio resource that the Node B can allocate for the EUDCH packet data service in the uplink.

Node B scheduling may be regarded as an operation of distributing the RoT to each UE based on channel conditions and buffer conditions of UEs performing EUDCH communication.

1 is a diagram illustrating the basic concept of Node B scheduling.

Referring to FIG. 1, Node B1 100 supports EUDCH, and UEs 110-116 transmit EUDCH. When the data rate of one UE increases, the reception power received by the Node B1 100 from the UE increases. Therefore, the ROT of the UE occupies a large part of the total ROT. On the other hand, when the data rate of another UE is lowered, the reception power received by the Node B1 100 from the UE becomes small. Therefore, the ROT of the other UE occupies a small portion of the total ROT. The Node B1 100 performs Node B scheduling on the EUDCH packet data in consideration of the relationship between the data rate and radio resources and the data rate requested by the UEs 110 to 116.

The UEs 110 to 116 transmit the packet data at different transmit powers of reverse channels according to the distance from the Node B1 100. The UE 110 farthest from the Node B1 100 transmits packet data at the transmit power 120 of the highest reverse channel, and the UE 114 closest from the Node B1 100 is the closest. The packet data is transmitted at a transmit power 124 of a low reverse channel. That is, the Node B1 100 may schedule the data to be inversely proportional to the strength of the transmit power of the reverse channel by adjusting the ICI for other cells while maintaining a constant total ROT. As a result, a small data rate is allocated to the UE 110 having the highest transmit power of the reverse channel, and a high data rate is allocated to the UE 114 having the lowest transmit power of the reverse channel.

2 is a diagram illustrating a process of transmitting packet data using a data rate for EUDCH packet data transmission. Here, the UE 202 is allocated a data rate for EUDCH packet data transmission from the Node B1 200, and the UE 202 transmits the packet data using the allocated data rate.

Referring to FIG. 2, in step 210, EUDCH is set between the Node B 300 and the UE 302. The EUDCH establishment process includes a process of transmitting and receiving messages through a dedicated transport channel. In step 212, the UE 202 transmits information on a data rate required for the Node B 200 and information for identifying an uplink channel condition. The uplink channel state information includes uplink transmission power transmitted by the UE 202 and a transmission power margin of the UE 203.

In step 213, the Node B1 200 estimates a forward channel condition by comparing the transmit power and the receive power of the uplink channel. Specifically, the Node B1 200 determines that the reverse channel situation is good when the difference between the uplink transmit power and the uplink receive power is small, and that the reverse channel situation is poor when the difference between the transmit power and the receive power is large. . When the UE 202 transmits a transmission power margin, the Node B1 200 may estimate the uplink transmission power by subtracting the transmission power margin from the maximum possible transmission power of the UE 202. . The Node B1 200 uses the estimated channel status of the UE and information about the data rate required by the UE 202 to determine the maximum possible data rate for the uplink packet channel of the UE 202. Decide

In step 214, the Node B1 200 notifies the UE 202 of the determined maximum possible data rate. The UE 202 determines the data rate of the packet data to be transmitted within the range of the maximum possible data rate received and transmits the packet data to the Node B 200 at the determined data rate in step 216.

3 is a diagram illustrating a protocol structure of a mobile communication system supporting EUDCH.

Referring to FIG. 3, the UE 305 is provided with a physical layer 325, a MAC-e layer 320, a MAC-d layer 315, and other upper layers 310.

The upper layer 310 includes an application in which actual user data is generated, and a radio link control (RLC) layer for reconfiguring user data to a size suitable for wireless channel transmission. The MAC-d 315 layer inserts multiplexed information into data received from the upper layer 310 to form a MAC-d protocol data unit (hereinafter referred to as a 'MAC-d PDU'). Do it.

The medium access control for EUDCH (MAC-e) layer 320 receives a MAC-d PDU received from the MAC-dedicated transport channel (MAC-d) layer 315 according to a priority buffer (Priority Queue, Hereinafter referred to as 'PQ'. In addition, the MAC-e layer 320 transmits a buffer status report considering the states of the PQs and a channel quality report on uplink transmission power to the Node B 330. Thereafter, scheduling allocation information is received from the Node B 330, and data stored in the PQ is transferred to the lower layer 325 according to the scheduling allocation information. In this case, the MAC-e layer 320 receives a response signal (a recognition signal ACK) and a negative recognition signal (NACK signal) received from the Node B 330 with respect to the uplink data transmitted to the lower layer 425. ), And performs the HARQ operation.

The physical layer 325 processes the data transmitted by the MAC-e layer 320 and transmits the data to the Node B 330 through a wireless channel.

The Node B 330 includes a MAC-e layer 335 and a physical layer 340, and is provided with an L1 / L2 layer 445 for transmitting packet data to the RNC 350. The physical layer 340 processes the signal transmitted through the physical layer 325 of the UE 305 and delivers the signal to the MAC-e layer 335.

The MAC-e layer 335 delivers the data transmitted by the physical layer 340 to the L2 / L1 layer 345 and reports the buffer status report and the channel quality transmitted by the UE 305. Based on the scheduling for a plurality of UEs. Thereafter, the determined scheduling information is transmitted to the corresponding UE, and the HARQ operation is performed.

The RNC 350 includes an upper layer 370, a MAC-d layer 365, and a MAC-e layer 360, and an L1 / L2 layer for receiving data transmitted by the Node B 330 ( 455 is provided.

In the MAC-e layer 360 provided in the RNC 350, additional functions that are difficult to implement in the MAC-e layer 335 of the Node B 330 are additionally implemented. For example, it may be a function of classifying packet data transmitted by a plurality of UEs including the UE 305 by PQ, and rearranging the order within the PQ.

As described above, the UE 305 has PQs and stores data to be transmitted on the EUDCH according to priority. In this case, the PQs are configured in the MAC-e layer 320 of the UE 305 when the EUDCH is configured, and the number of PQs is determined according to the number of applications to be serviced through the EUDCH. Accordingly, the UE 305 notifies the Node B 330 of the amount of data stored for each PQ, and accordingly, the Node B 330 determines the channel status of the UEs and the data stored in the PQ. The scheduling is performed in consideration of the priority and the like.

In the prior art EUDCH operating as described above, data were processed according to priority. However, when the priority of data retransmitted by the HARQ function is lower than the priority of data awaiting transmission in the PQ, there is a problem that high priority data is blocked by low priority data and thus cannot be transmitted.

Accordingly, an object of the present invention, which was devised to solve the problems of the prior art operating as described above, excludes a case where high priority data is not transmitted due to retransmission of low priority data in a reverse packet data service. In other words, it provides a method for smoothly transmitting high-priority data.

 Another object of the present invention is to provide a method of stopping retransmission of low priority data when necessary and transmitting high priority data using an available HARQ processor.                         

A method according to an embodiment of the present invention, which is designed to achieve the above object, includes a plurality of retransmissions of packet data from a plurality of priority queues having different priorities in a mobile communication system supporting a reverse packet service. A method for transmitting by processors,

When a new protocol data unit (PDU) occurs, checking whether there is an available retransmission processor,

If there is no retransmission processor available, determining the retransmission PDU having a lower priority than the new PDU by checking the priority of the retransmission PDUs processed by the plurality of retransmission processors;

If there is a retransmission PDU having a lower priority than the new PDU, characterized in that it comprises a step of stopping the retransmission of the retransmission PDU, and transmitting the new PDU in the retransmission processor where the retransmission is stopped.

According to an embodiment of the present invention, an apparatus for transmitting packet data having different priorities in a mobile communication system supporting reverse packet service,

A plurality of queues storing packet data by priority;

A plurality of retransmission processors for transmitting the packet data;

A new protocol data unit (PDU) is constructed by reading the packet data stored in the plurality of queues, and checking whether there is an available retransmission processor, and if there is no available retransmission processor, the plurality of retransmission processors are processed. The priority of retransmission PDUs is checked to determine whether there is a retransmission PDU having a lower priority than the new PDU, and if there is a retransmission PDU having a lower priority than the new PDU, the retransmission of one of the retransmission PDUs is stopped. And a retransmission control unit for determining whether to transmit the new PDU.

Hereinafter, with reference to the accompanying drawings will be described in detail the operating principle of the preferred embodiment of the present invention. Like reference numerals are used to designate like elements even though they are shown in different drawings, and detailed descriptions of related well-known functions or configurations are not required to describe the present invention. If it is determined that it can be blurred, the detailed description thereof will be omitted. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

4 is a diagram illustrating the operation of the MAC-e layer structure and HARQ of the terminal according to the present invention.

Referring to FIG. 4, the MAC-e layer 460 of the terminal is provided with priority queues 405 and an HARQ entity 410. The Priority Queues 405 store data received from higher layers according to priorities. One terminal may be provided with a plurality of PQs, and one PQ stores data for at least one service having the same priority. Priorities are typically assigned per logical channel. The logical channel is a channel configured between the RLC layer and the MAC layer, and any user application is often mapped to one logical channel. Therefore, one PQ may be connected with one logical channel or with multiple logical channels having the same priority.

The HARQ entity 410 is an entity that controls the operation of HARQ processors. That is, it is in charge of initial transmission / retransmission determination through interpretation of the ACK / NACK signal, and controls transmission / reception of each of the HARQ processes 415 to 435.

HARQ processors 1 to n (415, 425, 430, 435) have a soft buffer and are responsible for HARQ operation on a wireless channel. Here, the HARQ operation is a technique of maximizing the retransmission gain by performing retransmission and soft combining on the data processed in the physical layer.

HARQ processors 1 to n (415, 425, 430, 435) on the transmitting side transmit data to HARQ processors 1 to n (440, 445, 450, 455) on the receiving side, and store the transmitted data in a soft buffer. Put it.

The receiving HARQ processors 1 to n (440, 445, 450, and 455) determine whether an error occurs in the received data, and if an error does not occur, transmits an ACK, and the transmitting side HARQ processors 1 to n (415, 425). , 430 and 435 discard the error-free data stored in the soft buffer when the ACK is received. If an error occurs as a result of the determination, receiving HARQ processors 1 to n (440, 445, 450, 455) transmit NACK, and transmitting HARQ processors 1 to n (415, 425, 430, 435), The data stored in the soft buffer is retransmitted in response to the NACK. In addition, the receiving HARQ processors 1 to n (440, 445, 450, and 455) soft combine the retransmitted data with the transmitted data stored in the soft buffer, thereby maximizing the retransmission gain.

Hereinafter, operation of the transmitting / receiving side of HARQ will be described.

When the HARQ processor receives the ACK after transmitting the data, it flushes the soft buffer to transmit new data, or stores it in the soft buffer when the NACK is received. Resend the current data.

After receiving the data, the HARQ processor transmits an ACK if an error has not occurred, flushes the soft buffer of the processor, or transmits a NACK if an error occurs, and stores the data in the soft buffer. . If the data is retransmitted later, after soft combining with the data stored in the soft buffer, an error is confirmed.

The HARQ transmission / reception side operations are performed for each HARQ processor.

The terminal may be equipped with a plurality of HARQ processors, and each HARQ processor is assigned an identifier. Node B is provided with the same number of HARQ processors corresponding to the HARQ processors of the terminal, a pair of HARQ processors corresponding to each other has the same identifier. The HARQ operations proceed between HARQ processors having the same identifier.                     

Only one HARQ processor transmits data during any transmission time interval (TTI). The TTI may vary from call to call at a transmission interval defined by UTRAN. For example, a TTI of about 10 to 80 msec may be defined in a call through a dedicated channel, and a TTI of 2 msec or 10 msec is expected to be used in an EDCH. do.

If all HARQ processors are performing a retransmission operation at a specific time point, data stored in the PQs cannot be transmitted, and must wait until one of the HARQ processors successfully transmits and the corresponding soft buffer is flushed. In EUDCH, it is expected to require two retransmissions on average until the transmission is successful. In this case, it is highly likely that all HARQ processors are used.

In a preferred embodiment of the present invention, a new parameter related to preemption to retransmission is defined, and the parameter is set for each PQ or logical channel. For convenience of explanation, hereinafter, a current retransmission is stopped to transmit data of a specific PQ, and transmission of data of the PQ is called preemption.

As parameters related to the preemption, for example, a parameter indicating whether or not data of a specific PQ can generate a preemption (hereinafter referred to as 'P-capability'), and the data of a specific PQ is a preemption. A parameter indicating whether or not to be a target (Pre-emption Vulnerability: hereinafter referred to as 'P-Vlulnerability').

The 'P-capability' indicates whether a preemption can occur (trigger preemption) or not trigger preemtion (not trigger preemtion), and the 'P-Vulnerability' can be preemptable. Or not preemtable.

If the P-Capability of any PQ is set to 'trigger preemption' and the P-Vulnerability is set to 'not preemptable', the HARQ processor in which the P-Vulnerability is set to 'preemptable' is being retransmitted. The retransmission may be stopped and a new transmission may be performed on the data of the PQ. However, since P-Vulnerability of the PQ is not preemptable, retransmission is not stopped by data of another PQ.

Preemption related parameters of the PQ are determined by which logical channel the PQ is connected to. For example, if a logical channel with a very high priority and no delay is connected to any PQ, the P-capability of the PQ is set to 'trigger preemption' and the preemption vulnerability is set to 'not preemptable'. As another example, if a low priority priority logical channel is connected to any PQ, the P-capability of the PQ is set to 'not trigger preemption' and the P-vulnerability is set to 'preemptable'.

Hereinafter, a procedure of transmitting a preemption related parameter to a terminal according to the present invention will be described in detail with reference to FIG. 5.

5 is a diagram illustrating a flow of a control message for transmitting a preemption related parameter to a terminal according to the present invention.                     

Referring to FIG. 5, the RNC 510 transmits a control message 515 for setting an EUDCH to an arbitrary terminal 505 to the terminal. The control message 515 includes HARQ related information, physical channel related information, and PQ related information. The HARQ-related information is the number of HARQ processors and the size of the soft buffer, and the physical channel-related information is code information of a physical channel to receive ACK / NACK. The PQ-related information is the P-capability and P-vulnerability which are PQ identifiers, PQ priorities, and preemption related parameters for each PQ. When the terminal 505 receives the control message 515, the terminal 505 sets a MAC-e entity and a physical layer entity according to the configuration information.

Hereinafter, the MAC-e hierarchical structure set by the terminal 505 that receives the control message 515 will be described with reference to FIG. 6.

6 illustrates a MAC-e hierarchical structure according to the present invention.

Referring to FIG. 6, the MAC-e layer entity may be a priority / scheduling handling block (hereinafter, referred to as 'PSH') 620, a PQ distribution 615, and PQ1 to 4 s. 625, and HARQ entity 630.

The PSH 620 performs an operation of scheduling data stored in each PQs. That is, it determines which PQ to which data to transmit to the next TTI, and controls the PQ.

The PQ distributor 615 distributes the data 605 delivered in the upper layer to the appropriate PQ. That is, the MAC-e layer entity receives data from a plurality of logical channels, and the PQ distributor 615 delivers the data to the appropriate PQ depending on which logical channel the data is delivered from.

The PQ1 ˜ 625 stores data for each priority, and the HARQ entity 630 controls HARQ processors (not shown).

Upon receiving the control message 515 of FIG. 5, the UE configures the MAC-e layer entities and the PQ1-4 625, and then transfers P-Capability and P-Vulnerability information to each of the PQ1-4 625. The MAC-e layer entity determines data to be transmitted to the next TTI in the future by referring to the P-Capability and the P-Vulnerability information of the respective priority queues.

7 is a diagram illustrating operation of a MAC-e layer entity according to the present invention.

Referring to FIG. 7, in step 705, the MAC-e layer determines what data is to be transmitted in one TTI before one TTI starts.

In step 710, the MAC-e layer determines how much data is transmitted from which PQ according to the data rate allowed for the one TTI, and configures a new MAC-e PDU to be transmitted to the new TTI.

In step 715, the MAC-e layer checks whether there is an available HARQ processor in the TTI. If there is an available HARQ processor, the MAC-e layer proceeds to step 725. In step 725, the MAC-e layer transmits the new MAC-e PDU in the TTI through the available HARQ processor.

If there is no HARQ processor available as a result of the check, the process proceeds to step 717 to determine whether the preemption.

In step 717, the MAC-e layer determines the priority of the retransmission MAC-e PDUs stored in the soft buffer of the HARQ processors to determine whether the priority of the new MAC-e PDU is higher than the priority of the retransmission MAC-e PDU. . In this case, when data read from two or more PQs are stored in the MAC-e PDUs, the priority of the PQ having a high priority may be regarded as the priority of the MAC-e PDU.

If the priority of the new MAC-e PDU is higher than the priority of the retransmitted MAC-e PDU, the process proceeds to step 720; otherwise, in step 730, the MAC-e layer proceeds to retransmission without performing preemption.

In step 720, the MAC-e layer checks whether P-capability of the new MAC-e PDU is 'trigger preemption' and P-vulnerability of the retransmitted MAC-e PDU is 'preemptable'. Here, when data of two or more PQs are stored in the MAC-e PDU, P-capability and P-vulnerability of the MAC-e PDU are determined as follows.

First, when the P-capability of at least one PQ in which data included in the MAC-e PDU is stored is 'trigger preemption', the P-capability of the MAC-e PDU is determined as 'trigger preemption'. In addition, when the P-capability of all PQs is 'not trigger preemption', the P-capability of the MAC-e PDU is determined as 'not trigger preemption'.

Next, when the P-vulnerability of at least one PQ in which data included in the MAC-e PDU is stored is 'not preemptable', the P-vulnerability of the MAC-e PDU is determined as 'not preemptable'. In addition, if the P-vulnerability of all PQ is preemptable, the P-vulnerability of the corresponding MAC-e PDU is determined as 'preemptable'.

If the P-capability of the new MAC-e PDU is 'trigger preemption' and the P-vulnerability of the MAC-e PDU to be retransmitted is 'preemptable', the operation proceeds to step 725. Proceed. In step 725, the MAC-e layer transmits the new MAC-e PDU through the HARQ processor that processed the retransmission MAC-e PDU by executing preemulation.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

In the present invention operating as described in detail above, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

According to the present invention, in the uplink packet data service supporting HARQ, by stopping the retransmission of the low priority data and appropriately limiting the process of transmitting the high priority data, it is possible to prevent unnecessary waste of transmission resources. There is.

Claims (12)

A method for transmitting packet data from a plurality of priority queues having different priorities by a plurality of retransmission processors in a mobile communication system supporting a reverse packet service, the method comprising: When a new protocol data unit (PDU) occurs, checking whether there is an available retransmission processor, If there is no retransmission processor available, determining the retransmission PDU having a lower priority than the new PDU by checking the priority of the retransmission PDUs processed by the plurality of retransmission processors; If there is a retransmission PDU having a lower priority than the new PDU, stopping the retransmission of the retransmission PDU, and transmitting the new PDU in the retransmission processor where the retransmission is stopped. The method of claim 1, And if there is no retransmission PDU having a lower priority than the new PDU, continuing to retransmit the retransmission PDUs. The method of claim 1, wherein the transmitting step comprises: Whether 'the priority for retransmission can be generated' of the new PDU is set to 'Yes', and whether the priority of the retransmission of the 'retransmission PDU' having a lower priority than the new PDU can be the target. If 'Yes' is set, stopping the retransmission of the retransmission PDU. The method of claim 3, wherein If the first parameter indicating whether the priority of retransmission can be generated for at least one packet data among the packet data included in the new PDU is set to YES, the new PDU is destined for retransmission. Determining that the priority can be generated. The method of claim 3, wherein If the second parameter indicating whether the priority of the retransmission of all the packet data included in the retransmission PDU can be the object of priority for retransmission is set to YES, the retransmission PDU is the object of priority for retransmission. Determining that it can be. The method of claim 3, wherein Whether the priority of retransmission of the new PDU can be set to no, or the priority of retransmission of the retransmission PDU of the retransmission PDU is no. If set to, characterized in that for performing the retransmission of the retransmission PDUs. An apparatus for transmitting packet data having different priorities in a mobile communication system supporting a reverse packet service, A plurality of queues storing packet data by priority; A plurality of retransmission processors for transmitting the packet data; A new protocol data unit (PDU) is constructed by reading the packet data stored in the plurality of queues, and checking whether there is an available retransmission processor, and if there is no available retransmission processor, the plurality of retransmission processors are processed. The priority of retransmission PDUs is checked to determine whether there is a retransmission PDU having a lower priority than the new PDU, and if there is a retransmission PDU having a lower priority than the new PDU, the retransmission of one of the retransmission PDUs is stopped. And a retransmission control unit for determining whether to transmit the new PDU. The method of claim 7, wherein the retransmission control unit, And if there is no retransmission PDU having a lower priority than the new PDU, continuing to retransmit the retransmission PDUs. The method of claim 7, wherein the retransmission control unit, 'Whether the priority for retransmission can be generated' of the new PDU is set to 'Yes', and whether the priority of the retransmission of the retransmission PDU having a lower priority than the new PDU can be the target of the retransmission. Is set to yes, the retransmission of the retransmission PDU is stopped. The method of claim 9, wherein the retransmission control unit, If the first parameter indicating whether the priority of retransmission can be generated for at least one packet data among the packet data included in the new PDU is set to YES, the new PDU is destined for retransmission. And determine that the priority can be generated. The method of claim 9, wherein the retransmission control unit, If the second parameter indicating whether or not the priority of retransmission of all packet data included in the retransmission PDU is set to 'yes', the retransmission PDU is to be subjected to priority of retransmission. And determine that it can. The method of claim 7, wherein the retransmission control unit, If whether or not the priority for retransmission of the new PDU can be set to 'No', or whether or not to be the priority of the retransmission of the retransmission PDU is set to 'No', And determine to continue performing retransmission of retransmission PDUs.

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