KR102402835B1 - Apparatus and method for retransmitting communication packet - Google Patents

Abstract

The present invention relates to an apparatus and method for performing communication packet retransmission. A communication device communicating with a carrier aggregation (CA) method using a plurality of component carriers (CCs) according to the present invention comprises: a determination unit for determining whether a retransmission event for a packet previously transmitted to a counterpart device occurs; a selection unit for selecting a CC for retransmission from among the plurality of CCs based on communication channel quality information for each CC received from the counterpart device when a retransmission event for a previously transmitted packet occurs as a result of the determination of the determination unit; and a packet transmission control unit for controlling the retransmission of the previously transmitted packet to the counterpart device using the retransmission CC selected by the selection unit.

Description

Apparatus and method for performing communication packet retransmission {APPARATUS AND METHOD FOR RETRANSMITTING COMMUNICATION PACKET}

The present invention relates to an apparatus and method for retransmitting a communication packet, and more particularly, to an apparatus and method for retransmitting a communication packet during communication using a carrier aggregation (CA) method.

Recently, various communication methods have been introduced for communication services for mobile communication terminals, and a representative one of them is CA (Carrier Aggregation).

The CA method is a method used in LTE-A (LTE-Advanced) for communication by using a plurality of frequency bands at the same time for communication service by creating a wide band for communication.

In the 3GPP (3rd Generation Partnership Project) standard specification, various maximum data rates are defined for each release depending on the bandwidth size, antenna configuration, and modulation method. It is defined and the antenna configuration is based on multiple-input multiple-output (MIMO) 2x2. In particular, in the LTE-A standard, the bandwidth is defined up to 100 MHz and the antenna configuration is defined to be possible up to 8x8.

There are two ways in which the LTE-A system operates with, for example, a 20 MHz bandwidth. That is, there are a method of using a bandwidth of 20 MHz (wideband) and a method of combining two 10 MHz bandwidths into one and using them simultaneously (carrier aggregation; CA), and the present invention corresponds to the case of using the CA method.

Since the frequency bands used by each operator vary, there may be several types of CA combinations. In LTE, a single carrier of 1.4, 3, 5, 10, 15, and 20 MHz is defined, and in LTE-A, a carrier defined in LTE is defined. is defined as a component carrier (CC), and CA technology that bundles CCs and uses them at the same time is defined. That is, when using the CA method, a frequency corresponding to each band can be referred to as a CC. In the CA method, a substantial bandwidth increase can be achieved by using a plurality of CCs bundled together, and thus more data can be transmitted. Communication service users can experience an increase in communication speed.

Meanwhile, during communication, a case may occur in which a packet transmitted from a base station or the like is not normally received by the communication terminal due to various unexpected reasons. In this case, the base station retransmits the communication packet that is not normally received to the communication terminal.

In the conventional CA method, such retransmission packets are processed in the same manner as new packets without taking a separate action.

For example, in the case of the CA method using three CCs, assuming that the three CCs are CC1, CC2, and CC3, respectively, the base station sequentially uses CC1, CC2, and CC3 without discriminating whether it is a new packet or a retransmission packet. control to be transmitted.

However, since the retransmission packet corresponds to a packet that has failed to be transmitted once, there is a need to increase the transmission success rate compared to a new packet.

Patent Publication No. 10-2012-0030919

SUMMARY OF THE INVENTION The present invention has been devised to solve the above-described problems in the prior art, and an object of the present invention is to provide a communication device for maximizing a transmission success rate for a retransmission packet and a method for controlling the same.

In order to achieve the above object, a communication device communicating in a CA (Carrier Aggregation) method using a plurality of CC (Component Carrier) according to the present invention determines whether a retransmission event for a packet previously transmitted to a counterpart device occurs wealth; a selection unit for selecting a CC for retransmission from among the plurality of CCs based on communication channel quality information for each CC received from the counterpart device when a retransmission event for a previously transmitted packet occurs as a result of the determination of the determination unit; and a packet transmission control unit that controls to retransmit a packet that has been previously transmitted to the counterpart device using the retransmission CC selected by the selection unit.

In addition, in order to achieve the above object, according to the present invention, a method for controlling a communication device communicating in a carrier aggregation (CA) method using a plurality of component carriers (CC) according to the present invention generates a retransmission event for a packet previously transmitted to a counterpart device. determining whether or not; selecting a CC for retransmission from among the plurality of CCs based on communication channel quality information for each CC received from the counterpart device when a retransmission event for a previously transmitted packet occurs as a result of the determination; and retransmitting the previously transmitted packet to the counterpart device 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.

In particular, the new packet and the retransmission packet are distinguished, and the existing algorithm such as a random method is used as it is in selecting a CC for the new packet. On the other hand, in the case of a retransmission packet, the most appropriate CC is selected based on the CQI information received from the counterpart device. By selecting the ARQ retransmission packet, the transmission success rate can be higher than that of the new RLC packet, so that high-speed data transmission can be made possible in the CA environment.

That is, by reducing the bottleneck caused by the cumulative storage of retransmission packets in the RLC, high-speed data transmission becomes possible.

1 is a schematic configuration diagram of an entire communication system including a communication device according to an embodiment of the present invention;
Figure 2 is a functional block diagram of the communication device of Figure 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 device of FIG. 1;
5 is a control flowchart of a communication device according to an embodiment of the present invention.

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

Hereinafter, each embodiment according to the present invention is merely an example for helping the understanding of the present invention, and the present invention is not limited to these embodiments. In particular, the present invention may be composed of a combination of at least any one of individual components, individual functions, or individual steps included in each embodiment.

In addition, each signal referred to in each embodiment according to the present invention below may mean one signal transmitted by one connection, etc., but may also mean a series of signal groups transmitted for the purpose of performing a specific function to be described later. . That is, in each embodiment, a plurality of signals transmitted at a predetermined time interval or after receiving a response signal from a counterpart device may be expressed as one 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 shown in FIG. 1 .

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

Here, the mobile communication terminal 200 is a terminal that a user manipulates and communicates with a counterpart, and may correspond to, for example, a mobile phone, a smart phone, a feature phone, and personal digital assistants (PDA).

The base station 100 communicates with a communication terminal through a wireless section, and performs a communication signal relay function between a mobile communication network (eg, a Long Term Evolution (LTE) communication network) and the communication terminal.

Of course, if the base station 100 and the entire mobile communication network are referred to as an Evolved Packet System (EPS), the mobile communication network corresponds to an Evolved Packet Core (EPC), and the base station 100 is an Evolved Universal Terrestrial Radio Access Network (E-UTRAN). )) can be matched.

The communication device 100 according to an embodiment of the present invention may be a base station in FIG. 1 or a mobile communication terminal.

Hereinafter, in describing the present embodiment, the base station 100 of FIG. 1 is referred to as a "communication device 100" according to the present invention, and the mobile communication terminal 200 of FIG. It is referred to as "the counterpart device 200" that communicates.

The communication device 100 communicates with the counterpart device 200 in a CA (Carrier Aggregation) method using a plurality of CCs (Component Carriers), where the CA method uses a plurality of frequency bands simultaneously for a communication service to create a broadband It means to communicate, and at this time, each carrier bundled together is called a CC (component carrier).

In the CA method, Intra-band contiguous CA used to bundle CCs contiguous in the same band, Intra-band non-contiguous CA used to bundle CCs that are not consecutive in the same band, and CCs in different bands are bundled together. There is an Inter-band CA to be used, and the definition of these CCs and CAs and the technology itself for broadening the communication band by tying a plurality of CCs corresponds to a known technology, so a more detailed description will be omitted.

The functional blocks of the communication device 100 are as shown in FIG. 2 .

As shown in the drawing, the communication device 100 includes a determination unit 110 , a selection unit 120 , a packet transmission control unit 130 , and a reception unit 140 .

First, the receiver 140 performs a function of receiving communication data or control data from the counterpart device 200 . Here, the communication data means data transmitted by the counterpart device 200 to communicate with another terminal (not shown), and the control data is data for controlling various functions of the communication device 100 , for example, the counterpart device. 200 may transmit communication channel quality information for each CC to the communication device 100. In this case, communication channel quality information for each CC transmitted by the counterpart device 200 also corresponds to control data.

The determination unit 110 performs a function of determining whether a retransmission event has occurred for a packet previously transmitted to the counterpart device 200 .

For example, after the determination unit 110 transmits a packet to the counterpart device 200 , it receives a negative acknowledgment (NACK) signal from the counterpart device 200 or fails to receive an acknowledgment (ACK) signal within a preset time. In this case, it may be determined that a retransmission event for the corresponding packet has occurred.

Here, NACK is a signal indicating the fact that the counterpart device 200 does not receive a predetermined packet from the communication device 100 within a preset time, and ACK is a signal that the counterpart device 200 sends the communication device 100 within a preset time. ), it is a signal notifying the fact that a predetermined packet has been received.

That is, after the predetermined packet is transmitted to the counterpart device 200 , the determination unit 110 fails to receive an ACK signal indicating that the packet has been normally received from the counterpart device 200 , or the counterpart device 200 . When a NACK signal indicating that the packet has not been normally received is received from the , it can be determined that a retransmission event has occurred.

When a retransmission event for a previously transmitted packet occurs as a result of the determination of the determination unit 110, the selection unit 120 determines CC for retransmission among a plurality of CCs based on the communication channel quality information for each CC received from the counterpart device 200. performs the function of selecting

That is, the selector 120 selects at least one of a plurality of CCs used for the CA method as a retransmission CC. For example, when the communication device 100 and the counterpart device 200 according to the present invention communicate in a CA method in which three CCs (referred to as CC1, CC2, and CC3, respectively) are bundled, the selection unit 120 selects any one of them. One (eg, CC1) may be selected as a CC for retransmission.

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

In this case, the selector 120 determines the CQI for each CC received from the counterpart device 200, the initial value of the Modulation and Coding Scheme (MCS) matched to the CQI, and the number of Hybrid Automatic Retransmit reQuest (HARQ) ACKs during the CQI period. And, the final MCS value for each CC is calculated using the number of HARQ NACKs during the CQI period, and the CC corresponding to the final MCS having the highest value among the calculated plurality of final MCS values can be selected as a CC for retransmission. have.

For example, the counterpart device 200 may transmit a CQI defined in the LTE standard as shown in FIG. 3( a ). When this CQI is received by the receiver 140 , the selector 120 may transmit the CQI as shown in FIG. 3( b ). An MCS initial value matching the CQI for each CC may be extracted using a previously provided CQI-MCS initial value mapping table.

On the other hand, such CQIs may be received at predetermined time intervals from the counterpart device 200, and the selector 120 determines the number of received HARQ ACKs during the time interval (ie, CQI period) during which these CQIs are received, and The final MCS is calculated by considering the number of HARQ NACKs together.

Here, HARQ is to retransmit when a transmission error such as a packet is detected in the MAC (Medium Access Control) layer matched for each CC. The transmission of this HARQ and the HARQ ACK or HARQ NACK received accordingly are based on a known technology. Therefore, a more detailed description will be omitted.

Specifically, the selection unit 120 may select the final MCS using Equation (1) below.

---식(1)

---Equation (1)

here,

The packet transmission control unit 130 performs a function of controlling to retransmit the previously transmitted packet to the counterpart device 200 using the retransmission CC selected by the selection unit 120 .

For example, when the selection unit 120 selects CC1 for retransmission as the CC for retransmission, the packet transmission control unit 130 controls the transmission using CC1 when retransmitting a previously transmitted packet, and the selection unit 120 uses CC2 In the case of selecting as CC for retransmission, the packet transmission control unit 130 controls transmission using CC2 when retransmitting a previously transmitted packet.

On the other hand, if a function performed in the communication device 100 is described based on a layer according to a communication standard, the communication device 100 is a Radio Link Control (RLC) layer, a Medium Access Control (MAC) layer, and a PHY as shown in FIG. 4 . (Physical) layer may be included.

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

In this embodiment, an automatic retransmit reQuest (ARQ) operation may be performed in the RLC layer. ARQ retransmission is when a loss occurs for a packet transmitted in RLC AM (Acknowledged Mode). Retransmission of the lost packet is processed. will be.

In contrast, the above-described HARQ is performed in the MAC layer, not the RLC layer. Error correction is attempted on the received data, and a simple error detection code such as a CRC (Cyclic Redundancy Check) is used to determine whether to retransmit.

Such HARQ includes Type-I HARQ Scheme, Type-I HARQ Scheme with Chase Combining, Type-II HARQ Scheme (Incremental redundancy Scheme), and the like. Since the HARQ technique performed in the MAC layer corresponds to a known technology, a more detailed description omit

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

The conventional communication device 100 may store a first algorithm for communicating in the CA method. In the communication device 100 according to the present invention, in addition to the first algorithm, the above-described algorithm for retransmission packets, that is, A second algorithm may be included.

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

Therefore, the communication device 100 according to the present invention can select and transmit a CC for a new packet according to the first algorithm, and for a retransmission packet, select a CC for retransmission according to the above-described second algorithm and transmit, in particular, the retransmission. In selecting a CC for use, it is possible to increase the transmission success rate of the retransmission packet by determining based on the communication channel quality information for each CC received from the counterpart device 200 .

For example, in case of using the CA communication method, the main communication cell may be referred to as a PCell (Primary Cell) and the secondary communication cell may be referred to as a SCell (Secondary Cell). For example, if it is set to transmit using the CC corresponding to the PCell (Primary Cell), when the wireless environment of the SCell is good but the wireless environment of the PCell is bad, the transmission efficiency of the retransmission packet deteriorates. This will solve the problem related to the transmission efficiency.

In particular, whether or not to transmit the retransmission packet can be determined in the RLC layer as described above. If the transmission efficiency of the retransmission packet deteriorates, high-speed data transmission is hindered by flow control in the RLC layer.

To explain flow control, the RLC transmission buffer stores the transmitted packets until an ACK is received. it means.

Therefore, when packets are excessively piled up in the RLC buffer by such flow control, the number of packets that can be transmitted to the MAC layer is inevitably reduced, which in turn slows down the data transmission speed.

Therefore, increasing the transmission success rate of the retransmission packet by the communication device 100 according to the present invention solves these conventional problems.

Hereinafter, a control process of the communication device 100 according to an embodiment of the present invention will be described with reference to FIG. 5 .

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

As a result of the determination, if the transmission packet to be transmitted is a new packet rather than a retransmission packet (step S3), the communication device 100 selects a specific CC according to the first registered algorithm and then transmits a new packet using the selected CC. (Step S5).

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

As a result of the determination, if the packet to be transmitted is a retransmission packet (step S3), the communication device 100 determines the CQI for each CC received from the counterpart device 200 (step S7), and selects the MCS based on the determined CQI is calculated (step S9).

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

Subsequently, the communication device 100 selects a CC corresponding to the highest MCS as a result of the 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 may be performed by a program or application stored in a predetermined recording medium (eg, computer-readable). Here, the recording medium includes an electronic recording medium such as a random access memory (RAM), a magnetic recording medium such as a hard disk, and an optical recording medium such as a compact disk (CD).

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

In addition, the present invention is not limited to the specific embodiments described above, but can be practiced with various modifications and modifications within the scope without departing from the gist of the present invention. It will be apparent that such modifications and variations are included in the present invention provided they fall within the scope of the appended claims.

100: communication device 200: counterpart device
110: judgment unit 120: selection unit
130: packet transmission control unit 140: receiving unit

Claims (11)

In a communication device communicating in a CA (Carrier Aggregation) method using a plurality of CC (Component Carrier),
a determination unit for determining whether a retransmission event has occurred for a packet previously transmitted to a counterpart device;
a selection unit for selecting a CC for retransmission from among the plurality of CCs based on communication channel quality information for each CC received from the counterpart device when a retransmission event for a previously transmitted packet occurs as a result of the determination of the determination unit;
and a packet transmission control unit for controlling to retransmit a packet previously transmitted to the counterpart device using the retransmission CC selected by the selection unit;
The communication channel quality information is a CQI (Channel Quality Indicator),
The selector uses the CQI for each CC received from the counterpart device, the MCS (Modulation and Coding Scheme) initial value previously matched to the CQI, the number of HARQ ACKs during the CQI period, and the number of HARQ NACKs during the CQI period. A communication device comprising calculating a final MCS value for each CC, and selecting a CC corresponding to a final MCS having the highest value among a plurality of calculated final MCS values as a CC for retransmission. delete According to claim 1,
The selection unit is a communication device, characterized in that the final MCS is calculated by the following equation.

here,

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

here,

7. The method of claim 6,
In step (a), after transmitting a packet to the counterpart device, when a NACK signal is received from the counterpart device or an ACK signal is not received within a preset time, it is determined that a retransmission event for the corresponding packet has occurred. A method of controlling a communication device. 10. A computer-readable recording medium recording a program for executing the method of any one of claims 6, 8 to 9. 10. An application stored on a medium in combination with hardware to execute the method of any one of claims 6, 8 to 9.

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