KR101012372B1 - Method of transmitting and deciding ACK/NACK in mobile packet communication system - Google Patents

Abstract

The present invention relates to an ACK / NACK transmission method and an ACK / NACK determination method in a wireless packet communication system. The ACK / NACK transmission method according to the present invention, in a wireless packet communication system for determining whether there is an error in a packet transmitted from a terminal and transmits an acknowledgment signal (ACK) or a retransmission request signal (NACK) to the terminal, Measuring a path loss value of a downlink connected to the terminal; Selecting a transmission method of the ACK or the NACK according to the measured path loss value; And transmitting the ACK or NACK according to the selected transmission method.

HARQ, ACK / NACK, Path Loss, E-DCH

Description

Method of transmitting and deciding ACK / NACK in mobile packet communication system

Figure 1a is a configuration diagram of the connection between the base station and the terminal in the soft handover state.

Figure 1b is a configuration diagram of the connection between the base station and the terminal in the soft handover state.

2 is a flowchart illustrating an outline of a method of transmitting ACK / NACK according to the present invention.

3 is a process flowchart showing an example of a method for measuring a path loss value.

4 is a view for explaining an embodiment of an ACK / NACK transmission method according to the present invention.

5 is a view for explaining another embodiment of the ACK / NACK transmission method according to the present invention.

6 is a procedure flow diagram of an embodiment of an ACK / NACK determination method according to the present invention.

FIG. 7 is a diagram illustrating a result of simulating overall ACK / NACK signaling performance according to performance of each link when ACK / NACK transmission time interval (TTI) length of 2 ms is applied.                 

8A and 8B are graphs showing the relationship between the various thresholds, the difference in path loss values per link, and the average transmit power (Tx Ec / Ior) of ACK / NACK by simulation.

The present invention relates to an ACK / NACK transmission method and an ACK / NACK determination method in a wireless packet communication system. More specifically, in a wireless packet communication system including a wireless mobile communication system, a soft hand method and a soft hand can more efficiently transmit an acknowledgment signal (ACK) or a retransmission request signal (NACK) to a terminal according to a path loss value. The present invention relates to a method for efficiently determining an ACK / NACK transmitted from a base station according to a path loss value in a terminal in an over region.

Recently, in the wireless mobile communication system, there is an active discussion on a high-speed packet communication scheme in uplink that transmits data from a terminal to a base station in response to a demand for uplink speed and capacity increase. A representative example is the Enhanced Uplink Dedicated CHannel (E-DCH) technology, which is being discussed in the 3GPP WCDMA wireless mobile communication system. In the E-DCH technology, uplink packet scheduling by a base station (Node B) and HARQ (Hybrid ARQ) in the physical layer are introduced into an existing 3GPP WCDMA uplink dedicated channel (DCH) to improve efficiency of uplink. I'm trying.

In the mobile communication system adopting the HARQ scheme among the various technologies discussed, the base stations receiving the uplink data in order to indicate the successful reception in the uplink data transmission through the HARQ from the terminal to the base station, the ACK signal means a successful reception In case of failure, NACK is transmitted in downlink. In the present invention, a method for transmitting an ACK / NACK signal more efficiently according to a downlink state from a base station to a terminal and a method for receiving an ACK / NACK signal more efficiently by a terminal in a soft handover state are newly developed. Suggest.

In the following description, generally, the UE receives the ACK and the NACK by dividing the UE into the soft handover state and the soft handover state.

First, as shown in FIG. 1A, a case where the terminal is not in a soft handover state will be described. In this case, since only the performance of a single link influences reception of ACK and NACK, the base station needs to transmit an ACK / NACK signal at a transmission power that satisfies a BER (Bit Error Rate) request corresponding to each reception. First, an example of a system request for a probability that a reception error occurs in the case of transmitting ACK and NACK may be set as follows.

Pr {NACK ｜ ACK} <10 ⁻² , Pr {ACK ｜ NACK} <10 ⁻³ (where Pr {NACK ｜ ACK} is the probability that the base station transmits an ACK, but is incorrectly received by the terminal as a NACK, and Pr {ACK | NACK} means that the base station transmits a NACK, but is incorrectly received by the terminal as an ACK.)

The reason why the error rate is defined as above is that the wrong reception of NACK as ACK has a greater effect on the performance of the system. Specifically, if the base station transmits an ACK but the terminal incorrectly recognizes this as a NACK, the terminal wastes channel resources because the terminal retransmits the previous transport packet, but the base station already ignores the retransmitted packet because the base station has already received the previous packet. This is not a big problem for the whole network. On the other hand, when the base station transmits a NACK and the terminal incorrectly recognizes it as an ACK, the terminal deletes a previously transmitted packet from a buffer and transmits a new packet, thereby causing packet loss, which is only recoverable in a higher network. May cause fatal packet transmission and reception delays.

As a method for transmitting an ACK and a NACK by the base station, a method of borrowing part of an existing downlink data transmission channel and a method of newly assigning and using a specific OVSF code channel may be considered. In this case, the former is a method of puncturing a part of a data transmission channel and inserting a desired amount of ACK / NACK symbol, and in the latter case, the terminal is considered by considering the independent ACK / NACK transmission channel. It is used exclusively or shared. In terms of downlink OVSF code saving, a method using part of an existing channel can be an efficient method if only the above BER condition is satisfied. However, if the channel is not in good condition, this method requires much more power allocation than that of a dedicated allocation channel, which may cause problems in all cases.

Secondly, as shown in FIG. 1B, the case where the terminal is in the soft handover state will be described. In this case, the terminal determines the ACK and NACK with a signal transmitted from at least two base stations. Since the reception result of the packet transmitted from the terminal in each base station is independent of each other, the ACK or NACKs received by the terminal in feedback thereto may not match each other. In addition, the state of the downlink receiving the ACK / NACK signal from each base station may be different. The following algorithm may be applied to a method in which the terminal finally determines ACK or NACK when the terminal is in soft handover state with two or more base stations.

1) When any one of several base stations transmits an ACK: In this case, it may be considered that an ACK reception error has occurred in the UE in the following cases. (ACK to NACK error)

Case 1. {All base stations send ACK} → {Terminal receives NACK from all base stations}

Case 2. {Some base stations send ACK and remaining base stations send NACK} → {The terminal receives NACK from all base stations}

2) All base stations transmit NACK: In this case, the UE may consider that an error has occurred in NACK reception in the following cases.

Case 1. {All base stations send NACK} → {terminal receives at least one ACK}

In the prior art, since ACK and NACK must be transmitted in consideration of a large path loss, a large amount of power or code resources are allocated regardless of the path state, thereby reducing downlink data rate and increasing interference between links. Let's go. In addition, when the allocated resources for transmitting the ACK / NACK signal in the downlink does not sufficiently compensate the path loss amount of the downlink, there is a problem that a significant performance degradation occurs when receiving the ACK / NACK signal at the terminal.

The present invention has been made to solve the problems of the prior art as described above, and an object of the present invention is a reception acknowledgment signal (ACK) or a retransmission request signal (NACK) according to a path loss value in a base station in a wireless packet communication system. The present invention provides a method for more efficiently transmitting a to a terminal and a method for efficiently determining an ACK / NACK transmitted from a base station according to a path loss value in a terminal in a soft handover region.

Summary of the Invention

In one aspect of the present invention, the ACK / NACK transmission method according to the present invention, by determining the presence of an error in the packet transmitted from the terminal to transmit an acknowledgment signal (ACK) or retransmission request signal (NACK) to the terminal A wireless packet communication system, comprising: measuring a path loss value of a downlink connected to the terminal; Selecting a transmission method of the ACK or the NACK according to the measured path loss value; And transmitting the ACK or NACK according to the selected transmission method.

In another aspect of the present invention, an ACK / NACK determination method according to the present invention is a method for determining an ACK / NACK in a terminal in which a link is connected to a plurality of base stations and is in a soft handover area in a mobile communication system. Measuring a path loss value for each star; Measuring a difference in path loss between links; Determining a threshold for ACK / NACK determination of each link according to the difference in path loss values between the links; And determining the ACK / NACK for each link according to the threshold value.

Example

Hereinafter, exemplary embodiments of an ACK / NACK transmission method and an ACK / NACK determination method in a wireless packet communication system according to the present invention will be described with reference to the accompanying drawings. The following embodiments are described with reference to Enhanced Uplink Dedicated CHannel (E-DCH), which is discussed in Third Generation Partnership Project (3GPP) WCDMA systems, but the present invention is directed to any wireless packet communication system using HARQ scheme. It may also be applicable.

2 is a schematic flowchart illustrating a method of transmitting ACK / NACK in a wireless packet communication system according to the present invention. As described above, in the mobile communication system employing the HARQ scheme, the base stations that receive the uplink data in order to indicate the successful reception in the uplink data transmission through the HARQ from the terminal to the base station receive an ACK signal in the sense of successful reception. In case of failure, the NACK is transmitted in downlink. The present invention proposes a method for efficiently transmitting the ACK or NACK according to a downlink state from a base station to a terminal and an effective ACK / NACK reception method for a terminal in a soft handover region.                     

Embodiment of ACK / NACK Transmission Method in Base Station

In FIG. 2, the base station measures a path loss value of downlink [S11]. The path loss value refers to a value lost by noise or fading while a signal transmitted from a base station is transmitted through a wireless channel.

3 is a process flow diagram illustrating a process of measuring a path loss value. When the base station transmits the pilot signal to the terminal at a predetermined transmission power [S21], the terminal receives the pilot signal and measures the reception power of the received pilot signal [S22]. The terminal transmits the measured reception power to the base station [S23], and the base station measures a path loss value by the difference between the transmission power and the reception power [S24].

When the path loss value is measured by the above process [S11], the base station selects a variable ACK / NACK transmission method according to the measured path loss value [S12]. As a variable ACK / NACK transmission method determined according to a path loss value, the following methods are proposed.

The first is a method of varying the type of channel through which ACK / NACK is transmitted according to the path loss value. Specifically, the threshold PR _th1 for the path loss value is set in advance, and when the measured path loss value is smaller than the PR _th1 , the ACK / NACK is punctured in the downlink data transmission channel. Is inserted and transmitted, and if the measured path loss is greater than or equal to PR _{th1, an} independent code channel is allocated to transmit ACK / NACK. In case of a UE in soft handover state, the ACK / NACK transmission method may be different for each base station where a link is formed. An ACK / NACK is transmitted by puncturing a part, and a link having a large path loss can be transmitted through an independent code channel.

The second method is to vary the number of symbols for ACK / NACK transmission according to the path loss value. In other words, the larger the path loss value is, the more symbols are used for ACK / NACK transmission, thereby improving the reception performance in the terminal receiving the ACK / NACK. 4 is a view for explaining an example of a method of changing the number of symbols for ACK / NACK transmission according to the path loss value. In FIG. 4, since the path loss value of the link (b) is larger than that of the link, the number of symbols during the symbol period is increased. In the case of the UE in the soft handover state, ACK / NACK configured with different symbol numbers may be received according to the path loss value of each link.

Third, as shown in FIG. 5, the larger the path loss value according to the path loss value, the more ACK / NACK is repeatedly transmitted during the TTI (Time Transmit Interval). In FIG. 5, ACK / NACK is transmitted only once for one TTI for a link having a small path loss value, but ACK / NACK is repeatedly transmitted twice for one TTI for a link having a large path loss value. It shows what you did.

Fourthly, different transmission power amounts are allocated and transmitted according to the required performances of the ACK and the NACK. That is, a case in which a NACK is incorrectly received as an ACK has a greater effect on the performance of the system than the other case, and thus a larger transmission strategy amount is allocated to the NACK than the ACK. This method is generally applicable regardless of the path loss value.

Fifthly, the above four methods are appropriately mixed and used. For example, an independent code channel for ACK / NACK transmission may be allocated according to a path loss value, and the number of ACK / NACK repetitive transmissions may be adjusted during a transmission time interval. Even when transmitting, the number of puncturing during the symbol period may be adjusted. In addition, various combinations will be possible.

In the above methods for selecting an ACK / NACK transmission method according to a path loss value, the ACK / NACK is based on a running average of path loss values that are measured instantaneously and obtained for a predetermined period, rather than a path loss value having a large amount of change. It is desirable to select a transmission method.

ACK / NACK Determination Method in UE in Soft Handover State

6 is a flowchart illustrating an embodiment of an ACK / NACK determination method according to a difference in path loss values between links in a terminal in a soft handover state. As shown in Fig. 1B, the terminal in the soft handover state has a link established with two or more base stations. The terminal measures a path loss value for each link [S71]. When a base station having a link with a terminal transmits a pilot signal to the terminal at a predetermined transmission power, the terminal knows the transmission power in advance, and thus receives the pilot signal and measures the reception power to determine the transmission power and the reception power. The path loss value for each link can be obtained by the difference. In this case, it is desirable to obtain and use a running average of path loss values measured over a period of time rather than path loss values that are measured instantaneously.

The difference between the path loss values between each link is measured based on the measured path loss values for each link [S72]. The difference in path loss between each measured link is compared with a preset reference value [S73]. If the difference in path loss is greater than or equal to the reference value, the ACK / NACK of the link having the large path loss is excluded from the final ACK / NACK decision. [S75]. If the difference between the path loss values between the links is greater than or equal to the reference value, it means that an ACK / NACK transmitted on a link having a large path loss value is unreliable.

FIG. 7 illustrates a simulation result of overall ACK / NACK signaling according to the performance of each link when an ACK / NACK transmission time interval (TTI) length of 2 ms is applied. In case of 6dB, the base station transmits an ACK, but the terminal determines the NACK (AtN: ACK to NACK) and the base station transmits a NACK, the terminal determines the ACK (NtA: NACK to ACK) and the performance between each link Shows the performance analysis when the symbol is repeated 60 times and the symbol is repeated 3 times. In Fig. 7, it can be seen that the curve performance of the link with 6dB performance degradation has a great influence on the performance of NtA (NACK to ACK) in particular. Therefore, it can be seen that in the case of such a performance degradation, it is preferable to exclude ACK / NACK signals transmitted on a link having a large path loss value when determining ACK / NACK.

If the difference between the path loss values between the links is smaller than the reference value, a threshold for each link for ACK / NACK determination is determined [S74]. The threshold for ACK / NACK determination is variably determined based on the difference in the path loss value for each link based on the link with the small path loss value. The link having a large path loss value is considered to have a lower reliability of the received ACK / NACK than a link having a small path loss value. In addition, as described above, the fact that the NACK is incorrectly received as an ACK has a greater effect on the performance of the system, which should be considered when determining the threshold value for each link according to the difference in the path loss value.

8A and 8B are graphs showing the relationship between the difference between the various threshold values and the path loss values per link and the average transmit power (Tx Ec / Ior) of ACK / NACK by simulation. FIG. 8A is a transmission power of an ACK required to satisfy Pr {NACK | ACK} <10 ^-2 , and FIG. 8B is a transmission power of a NACK required to satisfy Pr {ACK | NACK} <10 ^-3 . In FIG. 8A and FIG. 8B, the difference in the horizontal path loss value is 0 dB for the link having the smallest path loss value. When the ACK / NACK transmission power (Tx Ec / Ior) is known at the base station, A threshold for determining an ACK / NACK can be obtained. At this time, as described above, it is preferable to refer to FIG. 8B in consideration of the fact that the case where the NACK is incorrectly received as the ACK has a greater effect on the performance of the system.

If the threshold for determining the ACK / NACK for the link having the smallest path loss value is determined, the threshold for determining the ACK / NACK is determined for the other link by the difference of the path loss value with the reference link. Can be.

In actual implementation of the threshold determination method as described above, the difference between the various threshold values as shown in FIGS. 8A and 8B, the path loss value per link, and the average transmit power of the ACK / NACK (Tx Ec / Ior) It may be desirable to store the relationship in a table and then obtain a threshold based on the table. In addition, the terminal may determine the threshold for determining the ACK / NACK in the same manner as described above, but if the base station determines the threshold value and informs the terminal in the same manner, the terminal determines the ACK / NACK using it How to do this may also be considered.

If a threshold for determining ACK / NACK is determined, ACK / NACK is determined based on the threshold [S76]. The ACK / NACK determination method may be determined by various methods known in the art.

Various embodiments of the ACK / NACK transmission method in the base station and the ACK / NACK determination method in the terminal described above may be implemented in various combinations according to the system situation to improve the ACK / NACK reception performance of the terminal. .

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the above detailed description should not be construed as limiting in all aspects and should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention.

According to the ACK / NACK transmission method and the ACK / NACK determination method in the wireless packet communication system according to the present invention, there is an effect that can improve the ACK / NACK reception performance in the terminal.

Claims (10)

In the ACK / NACK transmission method of the wireless packet communication system for determining whether there is an error in the packet transmitted from the terminal and transmits an acknowledgment signal (ACK) or retransmission request signal (NACK) to the terminal, Measuring a path loss value of a downlink connected to the terminal, The path loss value measuring step comprising: transmitting a pilot signal at a predetermined transmission power, receiving a reception power from a terminal receiving the pilot signal, and calculating a difference between the transmission power and the reception power; Selecting a transmission method of the ACK or the NACK according to the measured path loss value; And And transmitting the ACK or NACK according to the selected transmission method. delete The method of claim 1, If the path loss value is less than a preset threshold, puncturing a portion of a downlink data transmission channel to transmit the ACK or NACK, and if the path loss value is greater than or equal to the threshold value, an independent code channel is used. ACK / NACK transmission method characterized in that for transmitting the ACK or NACK. The method according to any one of claims 1 to 3, The greater the path loss value, the greater the number of symbols for the ACK or NACK transmission to transmit the ACK / NACK transmission method. The method according to any one of claims 1 to 3, The greater the path loss value, the greater the number of repetitions of the ACK or NACK in the transmission interval is transmitted ACK / NACK transmission method characterized in that. The method of claim 4, wherein The greater the path loss value, the greater the number of repetitions of the ACK or NACK in the transmission interval is transmitted ACK / NACK transmission method characterized in that. The method of claim 1, And transmitting different amounts of transmission power according to the required performance of the ACK and the NACK. A method for determining ACK / NACK in a terminal connected to a plurality of base stations and in a soft handover area in a mobile communication system, Measuring a path loss value for each link; Measuring a difference in path loss between links; Determining a threshold for ACK / NACK determination of each link according to a difference in path loss values between the respective links; Determining a threshold value based on the threshold value matching the difference between the path loss values between the links; And And determining an ACK / NACK for each link according to the threshold. delete The method of claim 8, And the ACK / NACK received signal from the link having the large path loss value is not used for the final ACK / NACK determination when the difference between the path loss values between the respective links is greater than or equal to a preset reference value.

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