KR101167326B1 - Method for transmitting user data in a multi-carrier radio communication system, and corresponding receiver - Google Patents

Abstract

The present invention relates to a method of transmitting user data between a transmitter and a receiver in a multi-carrier wireless communication system having a plurality of orthogonal frequency subcarriers, wherein the user data is to be transmitted between the transmitter and the receiver. Selecting a set of subcarriers.

According to the invention, the method comprises the steps of: transmitting an indication relating to a threshold from the transmitter before the transmission of the user data; Determining a quality level for each subcarrier at the receiver; And selecting a subcarrier at the receiver to receive the user data as a function of the indication and the quality level related to a threshold.

Multi-carrier wireless communication system, feedback forward channel, subcarrier, quality level, user data

Description

METHOD FOR TRANSMITTING USER DATA IN A MULTI-CARRIER RADIO COMMUNICATION SYSTEM, AND CORRESPONDING RECEIVER}

1 illustrates a network that uses multi-carrier transmission on the downlink and transmits feed forward signaling indicative of subcarriers to be used in the downlink.

2 illustrates an implementation of a method for transmitting user data in a multi-carrier wireless communication system in accordance with the present invention.

3 shows an implementation of a transmitter according to the invention.

4 shows an implementation of a receiver according to the invention.

<Explanation of symbols for the main parts of the drawings>

11: mobile terminal

12: base station

13: subcarrier

The present invention claims EP application 05300634.2, which is incorporated herein by reference.

The present invention relates to a method for optimizing the use of a feedback forward channel in a multi-carrier system.

Such multi-carrier systems often implement Orthogonal Frequency Division Multiplexing (OFDM) as a multi-carrier transmission technique. OFDM is used, for example, in the HIPERLAN / 2 standard as well as an extension of the IEEE 802.11a standard for the 5 Ghz region. OFDM can provide a reasonable alternative for high speed mobile applications, thus presenting a key step for a next generation mobile radio system for a fourth generation air interface. Accordingly, third generation partnership project for standardization of high-speed broadband wireless mobile communication system ^{(3GPP; 3 rd Generation Partnership Project} ) , recently, high-speed data packet access between the Radio Access Network (RAN) and user equipment (UE) (HSDPA; High Speed Data Packet Access (IF) is considering the application of OFDM technology for air interface communication.

In a multi-carrier system such as an OFDM transmission system, the transmitted data is divided into multiple parallel data streams, each data stream being used to modulate individual subcarriers. In other words, a wideband wireless carrier is a plurality of narrowband subcarriers independently modulated using, for example, QPSK, 16 QAM, 64 QAM, or higher order modulation that allows higher data rates per subcarrier. Or subcarrier.

In such an OFDM system, subcarrier frequencies may be assigned to user carriers on a short term basis (e.g., 2ms total), and the modulation order per subcarrier that defines the transmission carrier for each user is It must be updated on a short-term basis.

A very important task of this multi-carrier system is to provide efficient subcarrier / modulation assignment to different users. This is necessary to optimize and expand the performance of the multi-carrier system.

The choice of the optimal subcarrier for each user should take into account that in a mobile environment with multipath wireless carriers, some subcarriers may be very strongly attenuated when viewed by a given user. This subcarrier may be allocated to this user useless due to fading. Conversely, such subcarriers may be received with good quality by other users.

The selection of subcarriers to be used between the base station and the UE should be coordinated between the transmitter and the receiver to avoid errors. In the prior art, a message indicating the subcarrier to be used is exchanged between the transmitter and the receiver on a feed-forward carrier, i. This kind of signaling information consumes insignificant bandwidth and time, thereby reducing the effective payload data rate.

The message containing the subcarrier to be used represents a considerable amount of signaling information (around 100 Kbits), especially in multi-carrier systems with up to 1000 subcarriers.

It is a particular object of the present invention to provide a method for more effectively transmitting information of a subcarrier to be used between a transmitter and a receiver, so that the amount of signaling information of a feed forward carrier is reduced, but this is not sufficient for efficient resource allocation in a multi-carrier system. It is to be enough.

Another object of the present invention is to provide a receiver corresponding to the method.

This object, and other objects which will be revealed below, are achieved by a method for transmitting user data in a multi-carrier wireless communication system according to claim 1 and a receiver according to claim 6.

The method according to the invention provides the advantage of being able to transmit useful data at higher throughput on the feed forward carrier while reducing the signaling load on the feed forward channel.

Another advantage of the invention is defined in the dependent claims.

Other features and advantages of the present invention will become apparent from the following description of the preferred embodiments provided as a non-limiting example, the accompanying drawings.

1 shows a diagram of a network using multi-carrier transmission in the downlink. The mobile terminal 11 receives the multi-carrier frequency signal from the base station 12 via the plurality of subcarriers 13 in the downlink. The base station 12 also transmits to the mobile terminal 11 an indication of the subcarrier to be used for transmission before transmission of the user data.

The multi-carrier network can include up to 1000 subcarriers that can be assigned to the mobile terminal 11. Preferably, in order to meet the high throughput received from the base station 12 on the downlink, a number of subcarriers 13 are assigned to each mobile terminal 11. The frequency division between subcarriers is chosen such that the subcarriers are orthogonal to each other (ie, data transmitted on one subcarrier does not collide with data transmitted on another subcarrier).

According to the invention, an indication relating to the subcarrier to be used for transmission by the base station 12 to the different mobile terminals 11 is transmitted on at least one subcarrier of the feed forward carrier. This subcarrier is known at the mobile terminal 11.

Optionally, the plurality of subcarriers may comprise an indication relating to a threshold, which is combined with a specific identifier of the mobile terminal. The mobile terminal then listens to the subcarrier and, upon detecting the specific mobile terminal identifier of that subcarrier, reads the corresponding indication related to the threshold. Other methods of sending an indication related to the threshold to the mobile terminal may also be considered without departing from the scope of the present invention.

In contrast to the prior art solutions, the extensive references of the subcarrier to be used are not transmitted on the feed forward carrier. Only an indication related to the threshold is sent to the feed forward carrier. Due to the additional concordant information present in the transmitter 12 and the receiver 11, the receiver 11 infers a set of subcarriers in the transmission performed by the base station 12 from an indication relating to a threshold. can do.

According to the invention, the additional match information present in the receiving base station 12 as well as the receiving mobile terminal 11 is the quality level for the different subcarriers of the system. Preferably this information is the SIR for the different subcarriers measured at the mobile terminal 11 and transmitted to the base station 12 as a feedback carrier.

Preferably, this quality level is transmitted according to the method of parallel European patent application No. 05 290 0177, filed by the applicant and incorporated herein by reference.

Preferably, the quality level is determined for a group of subcarriers. Subcarriers are grouped in the following way: A predetermined number of N consecutive subcarriers form one group and the next N consecutive subcarriers form the next group. This grouping is preferably defined at system initialization.

The quality level of the subcarrier group may be an average value of carrier quality values measured in the subcarriers 13 belonging to the subcarrier group.

Optionally, a quality level can be determined for each single subcarrier. However, this will require additional signaling.

The feed forward carrier may be advantageously implemented in accordance with the HSDPA details, in which the information for selecting subcarriers in accordance with the present invention is a High Speed Shared Control Channel (HSSCCH; High Speed) with a capacity of about 60 Kbit / s. Is transmitted from the base station 12 to the mobile terminal 11 through the shared control channel.

2 illustrates an implementation of a method for transmitting user data in a multi-carrier wireless communication system. According to the invention, the method comprises the following steps:

Step 21 consists of sending an indication relating to a threshold from base station 12 to mobile terminal 11 before transmission of user data. This indication is preferably sent to a predetermined subcarrier of the multi-carrier system and received at the mobile terminal 11. Optionally, the plurality of subcarriers may comprise an indication relating to a threshold, which is combined with a mobile terminal specific identifier. The mobile terminal then knows the subcarrier and, upon detecting the specific mobile terminal identifier of that subcarrier, reads the corresponding indication related to the threshold.

Step 22 consists of determining, at the mobile terminal, a quality level for a subcarrier of the multi-carrier system. Preferably, the quality level consists of SIR measurements at the mobile terminal. This measurement should preferably be made at regular time intervals to track channel changes as quickly as possible and to avoid conflicting with the channel quality available at base station 12 and mobile terminal 11.

Step 23 consists of determining at the mobile terminal the subcarrier to be listened to and receiving user data intended for the mobile terminal as a function of an indication relating to the quality level and threshold of the subcarrier.

Preferably, the function performed in step 23 arranges the subcarriers in descending order of the quality level, starting at the subcarrier with the highest quality level, and decreasing in succession until an indication relating to the threshold is reached. And selecting a subcarrier with.

The indication related to the threshold may be the number of subcarriers to be selected. If this indication is N, then the receiver must select the N subcarriers with the highest quality level.

Optionally, the indication related to the threshold may be a quality threshold. And if the quality threshold is indicated as Qthr, then the receiver should select a subcarrier with a quality level higher than Qthr.

It will be apparent to those skilled in the art that indications relating to other types of thresholds may be considered without departing from the scope of the present invention.

It will also be apparent to those skilled in the art that other types of functions may be considered without departing from the scope of the present invention.

Embodiments of the present invention will be described below.

Four quality levels (QLs) are defined in the system, which are assigned to each group SCG of N subcarriers, and N is set to eight.

The result of the quality level report in mobile terminal A may be as follows:

QL = 4 at SCG 1, 2, 6, 8; QL = 2 on SCG 3, QL = 1 on SCG 4, 5, 7

The result of the quality level report in mobile terminal B may be as follows:

QL = 4 in SCG 4; QL = 3 in SCG 7, QL = 1 in SCG 1, 2, 3, 5, 6, 8

In a first embodiment, the indication related to the threshold is a quality level threshold:

The mobile terminal A receives an indication when the quality level threshold is considered QL = 4.

The mobile terminal B receives an indication when the quality level threshold is considered QL = 3.

According to the invention, the following description is carried out in a mobile terminal:

The mobile terminal A may be scheduled to all subcarriers SC belonging to SCGs having a QL of 4 or more, that is, SCGs 1, 2, 6, and 8, that is, 32 SCs belonging to SCGs 1, 2, 6, and 8. will be.

The mobile terminal B will be scheduled with 16 SCs belonging to SCGs having a QL of 3 or more, that is, SCGs 4 and 7.

In a second embodiment, the indication related to the threshold is the number of SCGs:

Mobile terminal A receives an indication that the number of SCGs is four.

Mobile terminal B receives an indication that the number of SCGs is two.

According to the invention, the following description is carried out in a mobile terminal:

The mobile terminal A is divided into four SCGs having the highest QL, that is, all subcarriers (SCs) belonging to SCGs 1, 2, 6, and 8, that is, 32 SCs belonging to SCGs 1, 2, 6, and 8. Will be scheduled.

Mobile terminal B will be scheduled with two SCGs with the highest QL, that is, 16 SCs belonging to SCGs 4 and 7.

In general, when a quality level is defined in such a way as to indicate in advance a threshold for using a given modulation scheme (e.g., QL = 1 for BPSK, QL = 2 for QPSK, 16 for QAM). QL = 3, QL = 4 for 64QAM), the UE can identify in advance the modulation scheme to be used in the different SC. For example, the result is:

Mobile terminal A will receive 64 QAM modulated signals from 32 SCs belonging to SCG 1, 2, 6, 8.

The mobile terminal B will receive 16 QAM modulated signals from 8 SCs belonging to SCG 7 and 64 QAM modulated signals from 8 SCs belonging to SCG 4.

3 shows an implementation of a transmitter according to the invention. The transmitter comprises means 31 for selecting a set of subcarriers of user data to be transmitted to the receiver and means 32 for transmitting an indication relating to a threshold in the feed forward channel prior to transmission of the user data. It allows the receiver to infer a set of subcarriers to be used for transmission from matching information available at the transmitter as well as the receiver.

The match information is preferably quality information in the form of signal-to-noise ratio (SIR) for different subcarriers, preferably measured at the receiver and sent back to the transmitter in a feedback channel, which information is available on both sides of the radio link, Matches.

The information related to the threshold may be a quality threshold indicating that the subcarrier used is a subcarrier with an SIR greater than the threshold. Optionally, the information related to the threshold may be a natural number representing the number of subcarriers to be used, starting from the subcarrier with the highest SIR and then descending SIR in descending order until reaching the natural number. Subcarrier.

In a preferred embodiment of the invention, the transmitter is, for example, a base station in an OFDMA system, but is not limited to HSDPA and WIMAX.

4 shows an implementation of a receiver according to the invention.

The receiver comprises means 41 for selecting a set of subcarriers for receiving user data from the transmitter, means for receiving and storing thresholds 42, and a quality level for each subcarrier or group of subcarriers. Determining means 43. The means 41 for selecting a set of subcarriers is connected to means 42 for storing the threshold and means 43 for determining the quality level.

The means 41 for selecting one set of subcarriers selects the subcarrier referred to by the means 43, which has a quality level higher than the threshold stored by the means 42.

Optionally, the means 41 starts with a subcarrier with the highest quality level referred to by the means 42, and then until the threshold stored in means 42 reaches the number of subcarriers indicated. Select subcarriers with decreasing quality levels.

In a preferred embodiment of the invention, the receiver is, for example, one terminal of an OFDMA system, but is not limited to HSDPA and WIMAX.

The present invention provides a method for more effectively transmitting information of a subcarrier to be used between a transmitter and a receiver, thereby enabling efficient resource allocation in a multi-carrier system while reducing the amount of signaling information of a feed forward carrier. .

Claims (7)

In a multi-carrier wireless communication system having a plurality of orthogonal frequency subcarriers, the method of transmitting user data between a transmitter and a receiver, the method comprising: At the receiver, determining quality levels for the subcarriers; Transmitting the quality levels from the receiver to the transmitter; Based on the quality levels, selecting a set of subcarriers to which the user data is to be transmitted between the transmitter and the receiver; Transmitting an indication related to a threshold from the transmitter, prior to the transmission of the user data, wherein the indication and the quality levels may cause the receiver to induce a set of the subcarriers to which the user data is to be sent. To ensure that-; And At the receiver, selecting one set of the subcarriers to which the user data is to be transmitted as a function of the indication and the quality levels &Lt; / RTI &gt; The method of claim 1, wherein the function is further configured to receive the user data, starting with a subcarrier with the highest quality level and subsequently selecting a subcarrier with a decreasing quality level until reaching the threshold. Selecting the subcarrier. The method of claim 1, wherein the threshold is related to a quality level threshold. The method of claim 1, wherein the threshold is related to the maximum number of subcarriers to be used. The method of claim 1, wherein the quality level is calculated at the receiver for a group of subcarriers. In a multi-carrier wireless communication system having a plurality of orthogonal frequency subcarriers, an apparatus that enables communication of user data, the apparatus comprising: Means for selecting from the plurality of subcarriers a set of subcarriers to communicate user data from a transmitter to a receiver, the selection being based at least in part on at least one of a threshold indication and subcarrier quality levels associated with the subcarriers And the quality levels are sent from the receiver to the transmitter, the threshold indication is sent from the transmitter to the receiver, and the threshold indication and the quality levels are one of the subcarriers to which the receiver will communicate the user data. Allows to infer a set-; And A wireless link for communicating user data over the set of selected subcarriers, The receiver is configured to receive user data from the transmitter via the wireless link, The receiver includes: Means for selecting a set of the subcarriers to receive the user data from the transmitter; Means for determining quality levels of the subcarriers; Means for transmitting the quality levels to the transmitter; And Means for receiving and storing the threshold indication from the transmitter, wherein the threshold indication and the quality levels allow the receiver to infer a set of the subcarriers to receive the user data; And the set of subcarriers to receive the user data is inferred as a function of the threshold indication and the quality levels. 7. The apparatus of claim 6, wherein the threshold indication is one of a maximum number of subcarriers within a set of subcarriers and a minimum subcarrier quality level for one set of subcarriers.

Images