KR20100019860A - Method of transmitting data - Google Patents

Abstract

PURPOSE: A method of transmitting data is provided to reduce signaling overhead and to improve system performance by assign radio resource based on the advantage of the collision-based transmission mode and scheduling-bases transmission mode. CONSTITUTION: A multiple access pointer is received from a base station. The multiple access pointer indicates scheduling or collision based mode for transmitting the uplink data. In case of the scheduling base mode, the uplink data is transmitted through a scheduling based block transmitting data according to the scheduling base mode among wireless resource frames. In case of the collision based mode, the uplink data is transmitted through a collision based block transmitting data according to the collision based mode.

Description

Method of Transmitting Data

The present invention relates to wireless communication, and more particularly, to a radio resource allocation method according to a multiple access method in a wireless communication system.

Wireless communication systems are widely used to provide various kinds of communication. For example, voice and / or data are provided by a wireless communication system. Typical wireless communication systems provide multiple users with one or more shared resources. For example, a wireless communication system may use various multiple access schemes such as code division multiple access (CDMA), time division multiple access (TDMA), and frequency division multiple access (FDMA).

Orthogonal Frequency Division Multiplexing (OFDM) uses multiple orthogonal subcarriers. OFDM uses an orthogonal characteristic between an inverse fast Fourier Transform (IFFT) and a Fast Fourier Transform (FFT). At the transmitter, data is sent by performing an IFFT. The receiver performs FFT on the received signal to recover the original data. The transmitter uses an IFFT to combine multiple subcarriers, and the receiver uses a corresponding FFT to separate multiple subcarriers.

According to OFDM, the complexity of the receiver can be reduced in a frequency selective fading environment of a wideband channel, and the spectral efficiency can be increased through selective scheduling in a frequency block by using different channel characteristics between subcarriers. . Orthogonal Frequency Division Multiple Access (OFDMA) is a multiple access scheme based on OFDM. According to OFDMA, the efficiency of radio resources can be improved by assigning different subcarriers to multiple users.

The wireless communication system employs one or more base stations that provide a coverage area. A typical base station can transmit multiple data streams for broadcast, multicast and / or unicast services. The data stream is a stream of data that the terminal can independently receive. In addition, the terminal may transmit a data stream to the base station or another terminal.

Hereinafter, downlink means communication from the base station to the terminal, and uplink means communication from the terminal to the base station.

In general, the base station schedules radio resources. Radio resources become uplink resources in uplink and downlink resources in downlink. In downlink, a base station informs a user equipment of a downlink resource allocated to a data stream, and the terminal receives the data stream through the downlink resource. In uplink, a base station informs a user equipment of an allocated uplink resource, and the terminal transmits a data stream through the uplink resource.

The size of the allocated radio resource may vary according to the amount of data stream to be transmitted, the channel state, or the quality of service (QoS). If the amount of data stream is large, many radio resources must be allocated. However, since the size of radio resources is finite, radio resources should be allocated efficiently.

In the case of allocating resources according to the scheduling-based scheme, there is no risk of collision, but the number of users that can be accommodated is limited because there should be no interference between users. In addition, there is a problem that is not suitable for services that require the transmission of low-speed data in real time.

However, in case of allocating resources according to the collision-based scheme, high spectral efficiency cannot be obtained because the scheduling protocol is not used and channel conditions are not considered. Accordingly, the present invention is to provide a radio resource allocation method that can provide a high spectrum efficiency to more users.

According to an aspect of the present invention, there is provided a data transmission method comprising: receiving, from a base station, a multiple access indicator indicating whether to transmit uplink data according to a scheduling based method or a collision based method; And when the multiple access indicator indicates transmission of the scheduling based scheme, the uplink data is transmitted through a scheduling based block in which data is transmitted according to a scheduling based scheme among radio resource frames, and the multiple access indicator is based on the collision. And transmitting the uplink data through a collision based block in which data is transmitted according to the collision based scheme among the radio resource frames when instructing transmission of the scheme.

According to an embodiment of the present invention, radio resources are allocated by combining the advantages of the scheduling-based transmission method and the collision-based transmission method. As a result, the performance of the system can be improved while reducing the signaling overhead in data transmission.

1 is a block diagram illustrating a wireless communication system. Wireless communication systems are widely deployed to provide various communication services such as voice and packet data.

Referring to FIG. 1, a wireless communication system includes a user equipment (UE) 10 and a base station 20 (BS). The terminal 10 may be fixed or mobile and may be called by other terms such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), and a wireless device. The base station 20 generally refers to a fixed station that communicates with the terminal 10, and in other terms, such as a Node-B, a Base Transceiver System, or an Access Point. Can be called. One or more cells may exist in one base station 20.

There is no limitation on the multiple access scheme applied to the wireless communication system. Various multiple access techniques such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), and Orthogonal Frequency Division Multiple Access (OFDMA) can be used. For clarity, the following description will be made of an OFDMA-based wireless communication system.

The present invention can be applied to uplink transmission or downlink transmission. Hereinafter, a frame becomes an uplink frame in uplink transmission and becomes a downlink frame in downlink transmission. The frame may include an uplink frame and a downlink frame. The uplink transmission and the downlink transmission may use a time division duplex (TDD) scheme that is transmitted using different times, or may use a frequency division duplex (FDD) scheme that is transmitted using different frequencies.

2 shows an example of a frame.

2, one axis of the frame represents an OFDMA symbol index in the time domain and the other axis represents a subchannel index in the frequency domain. The subchannel includes a plurality of subcarriers. The frame includes a plurality of OFDMA symbols in the time domain and a plurality of subchannels in the frequency domain. Transmission Time Interval (TTI) refers to the time required to transmit one frame.

Here, one frame includes N + 1 OFDMA symbols and K + 1 subchannels (N and K are arbitrary natural numbers), but the number of OFDMA symbols and the number of subchannels are not limited. The OFDMA index and the subchannel index may also be variously changed.

That is, when radio resources are allocated on the frame shown in FIG. 2, the radio resource allocation information includes the number and offset of unit radio resources constituting the frame, and through the radio resource allocation information, the terminal identifies the radio resource allocated to itself. Able to know. The offset is a value indicating the position of a radio resource allocated to the terminal.

 Radio resource allocation information for allocating radio resources to the terminal may be defined as shown in Table 1 below.

Name Number of bits Description OFDMA symbol offset 8 Offset from start symbol of frame Subchannel offset 7 Offser from start subchannel of frame Number of OFDMA symbols 7 - Number of subchannels 7 - Reserved 3 -

OFDMA symbol offset indicates the OFDMA symbol index from which allocation is started, subchannel offset indicates the subchannel index from which allocation is started, the number of OFDMA symbols indicates the number of allocated OFDMA symbols, and the number of subchannels is assigned Indicates the number of channels. The names and number of bits shown in Table 1 are merely examples, and are not intended to limit the scope of the present invention. The name and number of bits can vary from system to system.

Unit radio resources having a predetermined size are defined in advance, and the number and offset of unit radio resources are generated as radio resource allocation information and transmitted to the terminal. The radio resource may be allocated to the terminal at an arbitrary position and any size within one frame through the number and offset of the unit radio resources. This can be said that the degree of freedom of radio resource allocation. Radio resources can be flexibly allocated according to the size of radio resources required by the terminal. However, this method increases the size of radio resource allocation information. In the example of Table 1, at least 32 bits of radio resource allocation information are needed to indicate one allocated radio resource.

Hereinafter, an area allocated to the terminal in the frame is called an allocation area A1, and the allocation area A1 refers to a radio resource allocated to the terminal. The size or position of the allocation area A1 is merely an example. The allocation area A1 is a set of resource elements including at least one resource element and may be represented by the number and offset of the resource elements. The allocation area A1 according to an example includes 24 resource elements, and using the expression of Table 1, "OFDMA symbol offset = 2, Subchannel offset = 3, Number of OFDMA symbols = 4, Number of subchannels = 6". Can be represented.

3 shows an example of data transmission through a scheduling based scheme.

Referring to FIG. 3, the terminal transmits an access preamble to the base station (S310). Then, the base station allocates a resource for a scheduling request (SR) to the terminal (S320). The terminal transmits the scheduling request to the base station by using the radio resource allocated for the scheduling request (S330). The base station allocates radio resources for transmission of uplink data according to the scheduling request of the terminal (S340), and the terminal transmits uplink data to the base station (S350).

It also receives information about the resources and channel status of the terminal. The base station schedules and allocates radio resources to the terminal in response to the request of the terminal. That is, the base station allocates radio resources to the terminal by a scheduling method.

As described above, in the scheduling-based radio resource allocation method, the terminal transmits a radio resource allocation request to the base station, and the base station correspondingly allocates radio resources to the terminal according to the scheduling of the base station. For example, according to the scheduling-based scheme, the base station allocates an advantageous radio resource to each user terminal at every frame transmission.

4 shows an example of data transmission through a collision based method.

According to the collision-based method, a radio resource is allocated between a base station and a terminal without scheduling and data is transmitted immediately. Therefore, referring to FIG. 4, which shows an embodiment of transmitting data based on a collision-based scheme, the terminal immediately transmits data without having to allocate radio resources for a separate scheduling request to the base station (S410). In this case, according to an example, data may be transmitted through a random access channel. Compared to the data transmission based on the scheduling based scheme illustrated in FIG. 3, the data transmission based on the collision based scheme illustrated in FIG. 4 may be simplified.

Hereinafter, a radio resource allocation method and a data transmission method according to an embodiment of the present invention will be described. The present invention relates to a hybrid multiple access scheme, which means a rule for a plurality of users to cooperatively use a given band. The entire communication channel can be divided into subchannels, which are assigned to the terminals of the respective users. Usually the number of users is greater than the number of subchannels allowed, and only some of those users have data to send in a particular time frame. Therefore, users who have data to transmit should be able to utilize radio resources efficiently.

However, due to the characteristics of wireless communication, in order for a user's terminal to successfully transmit data or a signal, it is necessary to consider data transmission of another user terminal. That is, data transmission can be successful only when interference with another user's terminal can be controlled or avoided. Multiple simultaneous wireless transmissions can cause collisions or distort signals. Therefore, the multi-access protocol discusses the resource allocation scheme.

In the hybrid multiple access, the scheduling based scheme described with reference to FIG. 3, the collision based scheme and the leap based scheme described with reference to FIG. 4 are used. In the present invention, a hybrid radio resource allocation or data transmission method is a combination of a scheduling-based radio resource allocation method and a collision-based method.

As described above, the scheduling-based scheme allocates an advantageous radio resource to each user terminal at every data transmission, whereas the collision-based scheme does not undergo scheduling in using radio resources and transmits and receives data before or after data transmission regardless of the state of the terminal. It is a resource allocation method that can greatly reduce signaling overhead by using a leap pattern known in advance.

In addition, the scheduling-based scheme is complicated because resource allocation advantageous to each user must be efficiently allocated without interfering with each other. On the other hand, since the collision-based method allocates resources regardless of channel information, high spectral efficiency cannot be obtained in a frequency selective fading environment.

The collision based method is a method in which a connection is made without scheduling in using radio resources on a frequency band and a time base. The collision-based approach shortens the time to access the network when the traffic load is low. However, the collision-based method is used when there are a large number of users or a large variation in the number of users, or when low / medium-speed data user terminals have periodic or aperiodic traffic.

5 is a diagram illustrating a frame of radio resources configured according to an embodiment of the present invention. Referring to FIG. 5, a frame is divided into a plurality of resource blocks 501, 502, 503, and 504. Each unit block is allocated to the terminal in a different manner.

The frame includes a resource block 501 for transmitting an access preamble, a resource block 502 for transmitting a scheduling request, a scheduling base block 503 that is a resource block allocated to a terminal according to a scheduling of a base station, and data is transmitted. Conflict-based block 504, which is a resource block without data transmission, is included. Depending on the system, some types of resource blocks may be absent. Resource blocks of the same type do not necessarily have to be contiguous and may be scattered.

The length of data transmitted or received by each terminal may be different, and the amount of traffic of an uplink channel or a downlink channel corresponding to each terminal may also be different. Therefore, resource blocks are allocated in consideration of each state of the terminal. For example, if the length of data to be transmitted between a specific terminal and the base station is short, the terminal is assigned a collision based block 504. In the opposite case, the unit block of the scheduling base block 503 is allocated.

In determining what kind of resource block is to be allocated, the number of terminals in a cell may be considered in addition to the length of data. That is, when the number of terminals in the cell is small or below a certain level, collision-based blocks may be allocated, and in contrast, scheduling-based blocks may be allocated.

In addition, traffic volume or channel conditions may be considered. That is, a resource block having a small amount of traffic or a radio resource capable of increasing a channel gain may be preferentially allocated to a terminal having data to be transmitted. Accordingly, the radio resource allocation method according to an embodiment of the present invention is a mixture of a scheduling-based radio resource allocation method and a collision-based radio resource allocation method. In order to determine which unit block to allocate to the terminal, the base station may receive information on channel conditions such as channel quality indication (CQI) from the terminal.

In addition, according to the channel state of each resource block, the relative ratio between the scheduling base block 503 and the collision-based block 504 may be predetermined. That is, in the embodiment of the present invention, the size, the ratio, and the position in the frame of the scheduling based block 503 and the collision based block 504 are fixed. However, the area occupied by the scheduling-based block and the area occupied by the collision-based block in the radio resource frame may be fixed in various methods and forms according to the channel condition, the state of the terminal, and the amount of data.

The ratio of scheduling-based blocks in a radio resource frame may vary depending on whether the number of highly active terminals among the terminals is large. That is, as the number of terminals having high activity in a cell increases, the ratio of scheduling-based blocks increases. In this case, these terminals may mainly require a high speed data service. On the other hand, the ratio of collision-based blocks increases as the number of terminals with low activity increases. In this case, the terminals may request a relatively low / medium speed data service.

6 is a flowchart illustrating a process of transmitting data through an allocated radio resource according to an embodiment of the present invention.

The terminal receives a multiple access indicator from the base station (S610). In the embodiment of the present invention, in addition to the general content regarding resource allocation, the multi-access indicator may transmit uplink data according to a scheduling scheme or uplink data without scheduling according to a collision-based scheme when a terminal in a cell transmits uplink data. Contains information indicating whether to send.

A terminal attempting multiple access receives the multiple access indicator and loads uplink data to be transmitted to a resource block corresponding to the multiple access indicator. The multiple access indicator may be transmitted to a specific terminal through a dedicated channel or to all terminals in a group through a shared channel.

That is, the multi-access indicator includes resource allocation information indicating which resource block the UE transmits uplink data from among the collision-based block and the scheduling-based block included in the radio resource frame.

The terminal transmits uplink data through a scheduling based block or a collision based block according to the contents of the multiple access indicator (S620).

When the base station generates a multi-access indicator corresponding to each terminal and transmits it to each corresponding terminal, the number of terminals in the cell, length of uplink data, channel state, etc. may be taken into consideration. For example, when there are a large number of terminals in a cell, a multi-access indicator instructing the UEs to transmit uplink data in a scheduling-based manner is transmitted, and vice versa, a multi-access indicator instructs the transmission of uplink data in a collision-based manner. do. Many and few of the terminals in the cell can be determined by the base station using a preset reference value. As such, a large number or a small number of terminals or an increase or a decrease in the number of terminals may be considered in which manner of data transmission is indicated by the multiple access indicator.

For example, the multiple access indicator may require a fast data service and may instruct a terminal having high activity to transmit the uplink data according to a scheduling based scheme. In addition, a terminal having a relatively low activity may be instructed to transmit the uplink data according to the collision based scheme. In this case, a terminal having low activity may require a relatively medium / low speed data service.

In addition, when considering the length of data to be transmitted when generating the multi-access indicator, the base station compares the length of data to be transmitted by the terminal with a preset reference value, and as a result the length of the data is long, the scheduling based block according to the scheduling based method The multi-access indicator to the data to be transmitted through the transmission to the terminal.

Herein, the length of data may refer to the amount of data waiting to be transmitted to a transmission queue for each terminal or a transport block size. Information about the length of data is transmitted in advance by the terminal to the base station before transmitting the data substantially. In this case, the terminal may transmit the access preamble to the base station in advance.

When the terminal transmits uplink data through the scheduling base block, the terminal sends a scheduling request to the base station. In addition, a resource block (see 502 of FIG. 5) for scheduling request may be allocated from the base station for the scheduling request. According to the scheduling of the base station, the terminal receives a scheduling based block and transmits data through the scheduling based block.

As a result of comparing the length of uplink data to be transmitted by the terminal with a reference value, if the length of data is short, the terminal transmits uplink data without scheduling. The length of the data is as described above. In this case, the terminal leaps radio resources in the frame and transmits uplink data through the collision based block. Here, the terminal may be allocated a collision-based block without traffic among several collision-based blocks in the frame.

The invention can be implemented in hardware, software or a combination thereof. In hardware implementation, an application specific integrated circuit (ASIC), a digital signal processing (DSP), a programmable logic device (PLD), a field programmable gate array (FPGA), a processor, a controller, and a microprocessor are designed to perform the above functions. , Other electronic units, or a combination thereof. In the software implementation, the module may be implemented as a module that performs the above-described function. The software may be stored in a memory unit and executed by a processor. The memory unit or processor may employ various means well known to those skilled in the art.

Although the present invention has been described above with reference to the embodiments, it will be apparent to those skilled in the art that the present invention may be modified and changed in various ways without departing from the spirit and scope of the present invention. I can understand. Therefore, the present invention is not limited to the above-described embodiment, and the present invention will include all embodiments within the scope of the following claims.

1 is a block diagram illustrating a wireless communication system.

2 is a diagram illustrating an example of a frame.

3 is a diagram illustrating an example of data transmission through a scheduling based scheme.

4 is a diagram illustrating an example of data transmission through a collision based scheme.

5 is a diagram illustrating a frame of radio resources configured according to an embodiment of the present invention.

6 is a flowchart illustrating a process of transmitting data through an allocated radio resource according to an embodiment of the present invention.

Claims (5)

In the method for transmitting data in a wireless communication system, Receiving a multiple access indicator from a base station indicating whether to transmit uplink data according to a scheduling based method or a collision based method; And When the multiple access indicator indicates transmission of the scheduling based scheme, the uplink data is transmitted through a scheduling based block in which data is transmitted according to a scheduling based scheme among radio resource frames, and the multiple access indicator transmits the uplink data. And transmitting the uplink data through a collision-based block in which data is transmitted according to the collision-based scheme among the radio resource frames when instructing transmission of the data. The method of claim 1, And a position and a size of an area occupied by the scheduling based block and an area occupied by the collision based block in the radio resource frame are predetermined. The method of claim 1, If the number of terminals in a cell is larger than a reference value, the multi-access indicator instructs to transmit the uplink data according to the scheduling based scheme, and if the number of terminals is smaller than the reference value, the multi-access indicator indicates the collision with the uplink data. And transmitting data according to the base scheme. The method of claim 1, The ratio of the scheduling-based block in the radio resource frame increases as the number of terminals in a cell increases, the ratio of the collision-based block increases as the number of terminals decreases. The method of claim 1, Orthogonal resources orthogonal resources are allocated to each terminal in the scheduling based block or the collision based block.

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