KR20170043006A - Apparatus and method for retransmitting communication packet - Google Patents

Abstract

The present invention relates to an apparatus and a method for retransmitting a communication packet. According to the present invention, in a communication apparatus communicating in a carrier aggregation (CA) type in which a plurality of component carriers (CC) are used, the communication apparatus comprises: a determination unit determining whether or not to generate a retransmission event with respect to a pre-transmitted packet to a counter apparatus; a selection unit selecting a re-transmitting CC among the plurality of CCs on the basis of quality information for each CC received from the counter apparatus when the retransmission event is generated based on a determination result by the determination unit; and a packet transmission control unit controlling such that the pre-transmitted packet to the counter apparatus is retransmitted by using the retransmitting CC selected by the selection unit.

Description

[0001] APPARATUS AND METHOD FOR RETRANSMITTING COMMUNICATION PACKET [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an apparatus and method for performing retransmission of a communication packet, and more particularly, to an apparatus and method for retransmitting a communication packet during communication using a CA (Carrier Aggregation) method.

2. Description of the Related Art [0002] Recently, various communication methods have been introduced for communication service for a mobile communication terminal. CA (Carrier Aggregation) is a typical example of the communication method.

The CA method is a method used in LTE-A (LTE-Advanced) when LTE (Long Term Evolution) communication is taken as an example of communication by making a broadband using a plurality of frequency bands simultaneously for communication service.

In 3GPP (3rd Generation Partnership Project) standard, various maximum transmission rates are defined according to bandwidth, antenna configuration, and modulation method for each release. In LTE standard, the bandwidth is 1.4, 3, 5, 10, In the LTE-A standard, the bandwidth is defined up to 100MHz and the antenna configuration is defined to be up to 8x8.

There are two ways in which an LTE-A system may operate at a 20 MHz bandwidth, for example. That is, there is a method of using a bandwidth of 20 MHz (wide band) and a method of using two 10 MHz bandwidths together and using a carrier aggregation (CA). The present invention corresponds to a case of using the CA method.

In LTE, a single carrier is defined at 1.4, 3, 5, 10, 15, and 20 MHz. In LTE-A, carriers defined in LTE Is defined as a component carrier (CC) and the CC technologies are defined by concatenating the CCs. That is, the frequency corresponding to each band when using the CA scheme can be referred to as CC. In the CA scheme, a substantial increase in bandwidth can be achieved by using a plurality of CCs together, thereby enabling more data to be transmitted It becomes possible to experience an increase in the communication speed in the case of the communication service user.

Meanwhile, during communication, a packet transmitted from a base station or the like may not be normally received by the communication terminal due to various unexpected reasons. At this time, the base station retransmits a communication packet that is not normally received to the communication terminal.

In the conventional CA scheme, such a retransmission packet has been processed in the same manner as a new packet without taking any other action.

For example, assuming that three CCs are CC1, CC2, and CC3, respectively, in case of a CA scheme using three CCs, the base station sequentially uses CC1, CC2, and CC3 to distinguish packets Has been controlled to be transmitted.

However, since the retransmission packet corresponds to a packet that fails to be transmitted once, there is a need to increase the transmission success rate as compared with a new packet. However, a method or apparatus for achieving such an effect has not yet been proposed.

Published patent application No. 10-2012-0030919

SUMMARY OF THE INVENTION It is an object of the present invention to provide a communication apparatus and a control method thereof for maximizing a transmission success rate for a retransmission packet.

According to an aspect of the present invention, there is provided a communication apparatus for performing communication using a carrier aggregation (CA) scheme using a plurality of CCs, comprising: a determination unit configured to determine whether a retransmission event is generated for a packet Wealth; Selecting a CC for retransmission among the plurality of CCs based on the communication channel quality information for each CC received from the counterpart when a retransmission event for the transmitted packet occurs as a result of the determination by the determination unit; And a packet transmission control unit for controlling the transmission of the packet previously transmitted to the counterpart apparatus by using the retransmission CC selected by the selection unit.

In order to achieve the above object, a control method of a communication apparatus for performing communication using a Carrier Aggregation (CA) scheme using a plurality of Component Carriers (CCs) according to the present invention includes: generating a retransmission event Judging whether or not it is possible; Selecting a CC for retransmission of the plurality of CCs based on the communication channel quality information for each CC received from the counterpart when a retransmission event for the transmitted packet occurs as a result of the determination; And transmitting the packet previously transmitted to the counterpart apparatus using the selected CC for retransmission.

As described above, according to the present invention, it is possible to maximize the transmission success rate for the retransmission packet.

Particularly, a new packet is separated from a new packet and a retransmission packet is used. In selecting a CC, a conventional method such as a random method is used as it is. On the other hand, in case of a retransmission packet, By selecting the ARQ retransmission packet, the ARQ retransmission packet can be transmitted more successfully than the new RLC packet, thereby enabling high-speed data transmission under the CA environment.

That is, the bottleneck phenomenon due to the accumulation of the retransmission packets in the RLC is reduced, thereby enabling high-speed data transmission.

1 is a schematic configuration diagram of an entire communication system including a communication device according to an embodiment of the present invention,
Fig. 2 is a functional block diagram of the communication device of Fig. 1,
Figure 3 is an example of tables stored in the communication device of Figure 1,
4 is a diagram illustrating an example of a protocol layer included in the communication apparatus of FIG. 1,
5 is a control flowchart of a communication apparatus according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Hereinafter, embodiments of the present invention will be described in order to facilitate understanding of the present invention, and the present invention is not limited to these embodiments. In particular, the present invention can be configured by combining at least any one of individual components, individual functions, or individual steps included in each embodiment.

Hereinafter, each signal referred to in the embodiments of the present invention may refer to one signal transmitted by one connection or the like, but may also mean a series of signals transmitted for the purpose of performing a specific function . That is, in each embodiment, a plurality of signals transmitted after a predetermined time interval or after receiving a response signal from the counterpart device can be represented by a single signal name for convenience.

A schematic configuration of an entire communication system including the communication device 100 according to an embodiment of the present invention is as shown in FIG.

As shown in the figure, the entire communication system includes the base station 100 and the mobile communication terminal 200.

Here, the mobile communication terminal 200 may correspond to a mobile phone, a smart phone, a feature phone, a PDA (Personal Digital Assistants), or the like, which communicates with a counterpart by a user's operation.

The base station 100 communicates with a communication terminal through a radio section, and performs a relay function of a communication signal between a mobile communication network (for example, an LTE (Long Term Evolution) communication network) and a communication terminal.

Of course, if the base station 100 and the entire mobile communication network are referred to as EPS (Evolved Packet System), the mobile communication network corresponds to an EPC (Evolved Packet Core), and the base station 100 corresponds to an Evolved UTRAN (Evolved UTRAN )).

The communication apparatus 100 according to an embodiment of the present invention may be a base station or a mobile communication terminal in FIG.

1 will be referred to as "communication device 100" according to the present invention, and the mobile communication terminal 200 of FIG. Is referred to as "counterpart device 200"

The communication apparatus 100 communicates with the counterpart apparatus 200 through a CA (Carrier Aggregation) scheme using a plurality of CCs (Component Carriers). The CA scheme uses a plurality of frequency bands simultaneously for a communication service to create a wideband , And each carrier bound together at this time is referred to as a CC (component carrier).

Intra-band contiguous CA used when bundling CCs in the same band. Intra-band non-contiguous CA used when bundling CCs that are not contiguous in the same band. When bundling CCs in different bands There are inter-band CAs used. The definition of CC and CA and the technique of broadening the communication band by grouping a plurality of CCs correspond to the known technologies, and therefore, the detailed description is omitted.

The functional block of such a communication device 100 is as shown in Fig.

The communication apparatus 100 includes a determination unit 110, a selection unit 120, a packet transmission control unit 130, and a reception unit 140, as shown in the figure.

First, the receiving unit 140 performs a function of receiving communication data or control data from the counterpart device 200. [ Here, the communication data refers to data transmitted by the counterpart device 200 in order to communicate with another terminal (not shown), and the control data is data for controlling various functions of the communication device 100, The control unit 200 can transmit the communication channel quality information for each CC to the communication device 100. At this time, the communication channel quality information for each CC transmitted by the counterpart device 200 also corresponds to the control data.

The determination unit 110 determines whether a retransmission event for a packet transmitted to the counterpart device 200 is generated.

For example, when the determination unit 110 receives a negative acknowledgment (NACK) signal from the counterpart apparatus 200 after receiving a packet to the counterpart apparatus 200 or does not receive an acknowledgment (ACK) signal within a predetermined period of time It can be determined that a retransmission event for the packet has occurred.

Here, the NACK is a signal for notifying that the partner device 200 fails to receive a predetermined packet from the communication device 100 within a predetermined time, and the ACK is a signal for the partner device 200 to communicate with the communication device 100 When a predetermined packet is received from the base station.

That is, the determination unit 110 may not receive an ACK signal indicating that the packet has been normally received from the correspondent device 200 after the predetermined packet is transmitted to the correspondent device 200, It is possible to determine that a retransmission event has occurred when a NACK signal indicating that the packet has not been normally received is received.

When the determination unit 110 determines that a retransmission event has occurred for the transmitted packet, the selection unit 120 selects a CC for a plurality of CCs based on the communication channel quality information for each CC received from the counterpart device 200 As shown in FIG.

That is, the selection unit 120 selects at least one of the plurality of CCs used for the CA scheme as the retransmission CC. For example, in the case where the communication device 100 and the counterpart device 200 according to the present invention communicate with each other via the CA method in which the three CCs (CC1, CC2, and CC3 respectively) are bundled, One CC (for example, CC1) can be selected as the CC for retransmission.

At this time, in selecting the CC for retransmission, the selection unit 120 may use the communication channel quality information for each CC received from the counterpart device 200. Here, the communication channel quality information for each CC is, for example, And may correspond to a CQI (Channel Quality Indicator).

In this case, the selection unit 120 selects a CQI for each CC received from the counterpart device 200, an initial value of an MCS (Modulation and Coding Scheme) matched to the CQI, a Hybrid Automatic Retransmission request (HARQ) And the number of HARQ NACKs during the CQI period, and the CC corresponding to the last MCS having the highest value among the calculated plurality of final MCS values can be selected as the CC for retransmission have.

For example, the counterpart apparatus 200 can transmit a CQI defined in the LTE standard as shown in FIG. 3A. When the CQI is received by the receiver 140, The MCS initial value matching the CQI of each CC can be extracted using the prepared CQI-MCS initial value mapping table.

Meanwhile, the CQI may be received from the counterpart device 200 at predetermined time intervals. The selector 120 determines the number of received HARQ ACKs during a time interval (i.e., a CQI period) during which the CQI is received, The number of HARQ NACKs is considered together to calculate the final MCS.

In this case, the HARQ is retransmitted when an abnormal transmission of a packet or the like is detected in a MAC (Medium Access Control) layer matched for each CC. The HARQ transmission and the HARQ ACK or HARQ NACK thus received are transmitted to a known technique So that detailed description will be omitted.

Specifically, the selection unit 120 can select the final MCS using the following equation (1).

---식(1)

--- Equation (1)

here,

The packet transmission control unit 130 performs control to transmit a packet previously transmitted to the counterpart apparatus 200 by using the retransmission CC selected by the selection unit 120. [

For example, when the CC1 selected by the selecting unit 120 is selected as the CC for retransmission, the packet transmission controller 130 controls the CC1 to transmit using the CC1 when retransmitting the previously transmitted packet, Is selected as the CC for retransmission, the packet transmission control unit 130 controls to transmit using the CC2 when retransmitting the previously transmitted packet.

4, the communication apparatus 100 includes a Radio Link Control (RLC) layer, a Medium Access Control (MAC) layer, a PHY (Physical) layer.

In this case, the determination unit 110 and the determination unit 120 may be included in the RLC layer, and the packet transmission control unit 130 may be included in the MAC layer.

In this embodiment, an ARQ (Automatic Retransmission ReQuest) operation can be performed in the RLC layer. When ARQ retransmission occurs in a packet transmitted in the RLC AM (acknowledged mode), retransmission of the lost packet is handled will be.

In contrast, the HARQ is performed in the MAC layer, not in the RLC layer, and attempts to correct the received data and determine whether to retransmit the data using a simple error detection code such as a CRC (Cyclic Redundancy Check).

The HARQ scheme includes a Type-I HARQ Scheme, a Type-I HARQ Scheme with Chase Combining, and a Type-II HARQ Scheme (Incremental Redundancy Scheme). Since the HARQ scheme in the MAC layer corresponds to a known technique, .

As described above, in the case where a retransmission event occurs, that is, when it is determined that retransmission of a predetermined packet is necessary, the communication apparatus 100 according to the present invention determines, based on the communication channel quality information for each CC received from the counterpart device 200 Selects a CC for retransmission among the plurality of CCs, and performs packet retransmission using the selected CC for retransmission.

In the conventional communication apparatus 100, a first algorithm for communicating in the CA mode may be stored. In addition to the first algorithm, the communication apparatus 100 according to the present invention may further include the above-described algorithm for the retransmission packet, A second algorithm may be included.

Herein, the process of selecting the CC for retransmission according to the second algorithm is as described above, and the process of selecting the CC according to the first algorithm may include known methods such as sequentially selecting a plurality of CCs .

Therefore, the communication apparatus 100 according to the present invention can select and transmit a CC according to a first algorithm for a new packet, and select and transmit a CC for a retransmission packet according to the second algorithm described above, It is possible to increase the transmission success rate of the retransmission packet by judging based on the communication channel quality information for each CC received from the counterpart device 200. [

For example, in the case of using the CA communication method, the primary communication cell may be referred to as a primary cell and the secondary communication cell may be referred to as a secondary cell (SCell). The communication device 100 transmits a retransmission packet to a predetermined CC If the SCell radio environment is good but the PC environment is bad, the transmission efficiency of the retransmission packet is degraded. However, according to the present invention, Thereby solving the problems related to the transmission efficiency.

In particular, whether the retransmission packet is transmitted or not can be determined in the RLC layer as described above. If the transmission efficiency of the retransmission packet becomes poor, high-speed data transmission is obstructed by flow control in the RLC layer.

Here, the flow control is described. In the RLC transmission buffer, the packet is stored until an ACK is received for the transmitted packets. If the lost packet is not recovered due to a normal retransmission, packets are accumulated in the RLC buffer it means.

Therefore, if packets are excessively accumulated in the RLC buffer due to the flow control, the packets that can be transmitted to the MAC layer are reduced and the data transmission speed is slowed down.

Accordingly, increasing the transmission success rate of the retransmission packet by the communication apparatus 100 according to the present invention solves such conventional problems.

Hereinafter, a control process of the communication apparatus 100 according to an embodiment of the present invention will be described with reference to FIG.

First, the communication device 100 determines the type of packet to be transmitted (step S1).

If it is determined that the transmission packet to be transmitted is a new packet other than the retransmission packet (step S3), the communication apparatus 100 selects a specific CC according to the previously registered first algorithm, and transmits a new packet using the selected CC (Step S5).

Here, the process of selecting a specific CC according to the first algorithm corresponds to a known technique, and thus a detailed description thereof will be omitted.

If the packet to be transmitted is a retransmission packet (step S3), the communication apparatus 100 determines a CQI for each CC received from the counterpart device 200 (step S7), and based on the determined CQI, (Step S9).

An example of a formula for calculating the MCS is shown in equation (1) above.

Subsequently, the communication apparatus 100 selects a CC corresponding to the highest MCS as a result of MCS calculation as a CC for retransmission (step S11), and transmits a retransmission packet using the CC for retransmission (step S13).

Meanwhile, it goes without saying that the process of performing each of the above-described embodiments can be performed by a program or an application stored in a predetermined recording medium (for example, a computer-readable). Here, the recording medium includes an electronic recording medium such as a RAM (Random Access Memory), a magnetic recording medium such as a hard disk, and an optical recording medium such as a CD (Compact Disk).

At this time, the program stored in the recording medium may be executed on hardware such as a computer or a smart phone to perform each of the above embodiments. In particular, at least one of the functional blocks of the communication device according to the present invention described above can be implemented by such a program or an application.

The present invention is not limited to the above-described specific embodiments, and various modifications and changes may be made without departing from the gist of the present invention. It is to be understood that such variations and modifications are intended to be included in the scope of the appended claims.

100: communication device 200:
110: Judgment section 120:
130: Packet transmission control unit 140:

Claims (11)

1. A communication apparatus for communicating by a CA (Carrier Aggregation) scheme using a plurality of CCs (Component Carriers)
A determination unit for determining whether a retransmission event is generated for a packet transmitted to the counterpart apparatus;
Selecting a CC for retransmission among the plurality of CCs based on the communication channel quality information for each CC received from the counterpart when a retransmission event for the transmitted packet occurs as a result of the determination by the determination unit;
And a packet transmission control unit for controlling to retransmit the packet previously transmitted to the counterpart apparatus by using the retransmission CC selected by the selection unit. The method according to claim 1,
Wherein the communication channel quality information is a CQI (Channel Quality Indicator)
The selecting unit may calculate a CQI for each CQI received from the counterpart, a MQ (Modulation and Coding Scheme) initial value matched to the CQI, a number of HARQ ACKs for a CQI period, and a number of HARQ NACKs for a CQI period, Calculates a final MCS value for each CC, and selects a CC corresponding to the last MCS having the highest value among the plurality of calculated final MCS values as the CC for retransmission. 3. The method of claim 2,
And the selection unit calculates the final MCS by the following equation.

here,

The method according to claim 1,
In the step (a), if the NACK signal is received from the counterpart device after the packet is transmitted to the counterpart device, or if the ACK signal is not received within a predetermined time, it is determined that a retransmission event for the packet has occurred Lt; / RTI > The method according to claim 1,
Wherein the determination unit and the selection unit are included in an RLC (Radio Link Control) layer,
Wherein the packet transmission control unit is included in a Medium Access Control (MAC) layer. A control method of a communication apparatus communicating by a CA (Carrier Aggregation) scheme using a plurality of CCs (Component Carriers)
(a) determining whether or not a retransmission event is generated for a packet transmitted to the counterpart device;
(b) selecting a CC for retransmission among the plurality of CCs based on the communication channel quality information for each CC received from the counterpart when a retransmission event for a previously transmitted packet occurs as a result of the determination in step (a) Wow;
(c) transmitting the packet previously transmitted to the counterpart apparatus using the CC for retransmission selected in the step (b). The method according to claim 6,
The communication channel quality information in step (b) is a CQI (Channel Quality Indicator)
In step (b), a CQI for each CC received from the counterpart, an initial value of a Modulation and Coding Scheme matched to the CQI, a number of HARQ ACKs for a CQI period, and a number of HARQ NACKs for a CQI period Calculates a final MCS value for each CC, and selects a CC corresponding to the last MCS having the highest value among the plurality of calculated final MCS values as the CC for retransmission. 8. The method of claim 7,
Wherein the final MCS is calculated by the following equation.

here,

The method according to claim 6,
In the step (a), if the NACK signal is received from the counterpart device after the packet is transmitted to the counterpart device, or if the ACK signal is not received within a predetermined time, it is determined that a retransmission event for the packet has occurred The control method comprising: A computer-readable recording medium storing a program for executing the method according to any one of claims 6 to 9. 10. An application stored on a medium for executing the method of any one of claims 6 to 9 in combination with hardware.

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