KR20070063113A - Apparatus and method for space division multiple access communication - Google Patents

Abstract

An SDMA(Space Division Multiple Access) communication apparatus and a method thereof are provided to efficiently allocate radio space resources by selecting user equipments in consideration of channel quality, inter-user interference, and BS Tx power in transmitting data to a plurality of user equipments through a multicast channel in an SDMA communication system. An OFDM(Orthogonal Frequency Division Multiplexing) communication system for implementing an SDMA scheme comprises a data scheduler(610), an encoder(630), a constellation mapper(640), a subchannel mapper(650), and an OFDM modulator(670). The data scheduler receives priority information for users, who will transmit data, and data to be transmitted, from a scheduler and executes data scheduling. The encoder encodes the scheduled data. The constellation mapper performs constellation mapping for the encoded data. The subchannel mapper carries out subchannel mapping for the data according to the resource allocation information of a resource allocator. The OFDM modulator executes OFDM modulation for the subchannel mapped data and transmits the modulated data to user equipments.

Description

Space division multiple access communication apparatus and method {APPARATUS AND METHOD FOR SPACE DIVISION MULTIPLE ACCESS COMMUNICATION}

1 is a diagram illustrating a base station for each functional module of an SDMA communication system according to the present invention;

2 is a diagram illustrating a data transmission process when supporting multiple transport channels in an SDMA communication system according to the present invention;

3 is a view conceptually illustrating a radio resource request-acceptance allocation process in an SDMA communication system according to the present invention;

4 is a flowchart illustrating a process in which a user selects a radio resource allocator in a radio resource request step in an SDMA communication system according to the present invention;

5 is a flowchart illustrating a process of a resource allocator selecting a user in a radio resource acceptance step in the SDMA communication system according to the present invention;

6 is a configuration diagram of an OFDM communication system implementing the SDMA scheme applying the radio resource allocation request-acceptance process according to the present invention.

The present invention provides an apparatus and method for efficiently allocating radio resources when transmitting data to a plurality of user terminals through multiple transport channels in a space division multiple access (SDMA) communication system.

 SDMA system uses an adaptive antenna that can transmit a beam in a specific direction, a wireless communication technology that dramatically increases system capacity by allocating radio resources to multiple terminals at the same time at the same frequency to be.

In a user terminal that is allocated radio resources at the same time from a base station of an SDMA system at the same time, a factor that is influenced by signal reception from a base station is interference between another terminal and a required power amount requested by the terminal according to channel conditions.

Herein, a radio resource means a radio space resource, a transmission power, or the like.

The transmit power that a base station can use for a particular data transmission can be determined within the system-wide power limits. Therefore, the system efficiency can be increased by effectively allocating limited transmission power resources according to channel conditions of terminals allocated to radio resources at the same time at the same frequency. However, even when receiving data from the same antenna of the base station, since the channel quality of each terminal is different from each other, the amount of power required to transmit a certain amount of data varies depending on the user terminal. In other words, a terminal with a good channel state can receive data with less transmit power, whereas a terminal with a poor channel state requires more transmit power to transmit the same amount of data.

Meanwhile, in order to be allocated radio space resources at the same time at the same frequency, mutual interference between terminals must also be small. That is, in order to successfully receive data for all the terminals allocated the radio space resources at the same time in the same frequency in the SDMA system, the mutual spatial interference between the terminals must be small. Otherwise, if the radio space resources are allocated at the same time to the terminals with large interferences at the same frequency, the radio signal is allocated due to the reduction of the Carrier to Interference and Noise Ratio (CINR) due to mutual interference. The received terminals do not correctly detect the received signal and thus receive no data.

Accordingly, there is a need for an apparatus and method for efficiently allocating radio resources when transmitting data to a plurality of user terminals in a space division multiple access (SDMA) communication system.

In addition, when a multi-transmission channel such as an orthogonal frequency division multiplexing (OFDM) scheme is used in an SDMA communication system, the user terminal may have different reception sensitivity depending on the transmission channel. This is because the quality of the channel varies according to the location and time of the terminal for each frequency band. Therefore, system performance varies greatly depending on which user terminal is assigned to which transport channel. Accordingly, there is a need for an apparatus and a method capable of efficiently allocating radio resources in consideration of the selective reception characteristic of each terminal due to the selective frequency characteristics generated when using multiple transmission channels.

In other words, there is a need for an apparatus and method for efficiently allocating radio resources when transmitting data to a plurality of user terminals through a multiple transmission channel in a space division multiple access (SDMA) communication system.

SUMMARY OF THE INVENTION In order to solve the above problems, an object of the present invention is to provide a method and apparatus for allocating a radio space resource that can improve system performance when transmitting data at the same time to multiple user terminals in an SDMA system.

Another object of the present invention is to provide a method and apparatus for allocating a radio space resource that can improve system performance when a multi-transmission channel such as an orthogonal frequency division multiplexing (OFDM) scheme is used in an SDMA system.

In order to solve the above-described object, the present invention is a spatial interference with the user terminal of the user terminal that has not been allocated a transmission power value (P _i ) and radio space resources for the user terminal is constant Provided is a space division multiple access communication system including a resource allocator for allocating radio resources to a corresponding user terminal using C _{i /} P _i , which is a ratio of the number of users C _i equal to or less than a value.

The present invention also provides an encoder for encoding input data, a resource allocator for transmitting radio resource allocation information to a subchannel mapper, and encoded data encoded by the encoder according to the radio resource allocation information received from the resource allocator. The present invention provides an OFDM communication system using a wireless division multiple access scheme in which the subchannel mapper mapped to the subchannels and the subchannel mapped data are received from the subchannel mapper and OFDM modulated to be transmitted through an antenna.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the case where it is determined that the gist of the present invention may be unnecessarily obscured, the detailed description thereof will be omitted.

1 is a diagram illustrating a base station of each function module of a space division multiple access (SDMA) communication system according to the present invention. When the base station 100 receives downlink data to be transmitted from the upper layer to the terminal, the queue management module 110 stores the received data. The queue management module 110 transmits the stored data to the scheduler module 120. The scheduler module 120 determines the amount of data to be allocated in this frame and the priority of the user to be allocated according to the service allocation information for the user. The scheduler module 120 performs a radio resource allocation function for efficiently selecting a user receiving a service in a corresponding frame in a space division multiple access communication system. The scheduler module 120 may include a type of service that a user wants to receive, for example, an unsolicited guaranteed service (UGS), a real time-variable rate service (RT-VR), and an NRT (NRT). Users are selected for service according to Non Real Time, Best effort, etc., and different resource allocation policies are determined according to the type of service. The scheduler module 120 transmits the determined data and the priority of the user to the resource management module 130. The resource management module 130 allocates user and data information to physical radio space resources according to priorities. That is, a radio resource allocation process for allocating a radio space resource to a user who has determined a radio space resource according to the determined resource allocation target user and the amount of data transmission to the user is performed. The transmission module 140 loads data in a corresponding frame using the allocated information and transmits the data to the corresponding user terminal.

2 is a diagram illustrating a data transmission process when supporting multiple transport channels in an SDMA communication system according to the present invention. When the scheduler module determines the resource allocation target user and the amount of data to be transmitted (210), the resource management module allocates (220) radio space resources to the user according to the determination and transmits them via the antenna (230).

In a system supporting multiple transport channels, channel quality of a user terminal is different for each channel. Therefore, assigning a channel having good quality to the user terminal can maximize the system performance.

3 is a diagram conceptually illustrating a radio resource request-acceptance allocation process in an SDMA communication system according to the present invention. In the SDMA communication system, since space resources and transmit powers, which are radio resources, are restricted by the system, it is necessary to allocate space resources and transmit powers according to the amount of data required by the terminal user 310. To meet these conditions, the following request-accepted multi-radio resource allocation method is used.

Each resource allocator 320 has a resource allocator 320 for each channel in a multi-radio space resource request-accept allocation process. Referring to FIG. 3, the radio space resource allocation process is divided into a radio space resource request step (User) and a radio space resource allocator (Grant). Radio space resource allocation is repeated until this procedure no longer allocates radio space resources to new users.

4 is a flowchart illustrating a process in which a user selects a resource allocator in a radio resource request step in the SDMA communication system according to the present invention. This process is to arrange in order the user's considerations in the radio space resource request phase. First, the channel quality between the user and the resource allocator is determined to select the best resource allocator (410). Next, the terminal user determines whether there is a space resource that can be allocated (420). If there is no spatial resource, the resource allocator is excluded (450). If there is a space resource, when the radio space resource is allocated to the next step, it is determined whether the transmission power is greater than or equal to a predetermined value so that the user can transmit all desired data to the base station (430). If the transmit power is less than a predetermined value, the resource allocator is excluded (450). If the transmission power is greater than or equal to a predetermined value, it is determined whether the radio space interference with the terminal already allocated to the corresponding radio space resource is small enough to withstand the predetermined value or less (440). If the radio spatial interference is greater than a predetermined value, the resource allocator is excluded (450). If the radio space interference is less than or equal to a predetermined value, the resource allocator requests the radio space resource allocation (460). In this case, the order of steps 410 to 440 may be changed.

That is, n users have enough radio space resources to be allocated among the m resource allocators in parallel, and have enough interference to transmit all the data required by the users with little interference with the already allocated users. Among the radio resource allocators with sufficient transmission power, the resource allocator having the best channel condition is selected to request radio resource allocation.

5 is a flowchart illustrating a process in which a resource allocator selects a user in an accepting step in an SDMA communication system according to the present invention. Since the user's resource allocator selection is performed in parallel, the resource allocator may be required to allocate resources from several user terminals at the same time. Therefore, in the acceptance phase, the resource allocator first selects a user who can use the wireless resources most efficiently based on various conditions and accepts the resource allocation. Referring to FIG 5, first, it calculates the transmission power value for the user (P _i) (510). Next, the number C _i of user terminals whose spatial interference with the corresponding user terminal is equal to or less than a predetermined value among the user terminals not allocated the radio space resources is calculated (520). That is, since the spatial interference with the user terminal is less than a predetermined value, the number of users who can make a resource request to the corresponding radio allocator at the next resource request step is calculated. In the next step, the user terminal having the maximum value of C _i / P _i , which is (transmission power value) / (number of users of the next radio resource request), is selected (530). Thereafter, the mobile terminal accepts the radio space resource request (540).

The order of steps 510 and 520 may be reversed.

As described above, the resource allocator selects a user with a small transmission power required to transmit data. In addition, among the users who can be allocated to the corresponding radio resource but have not yet been assigned any radio resource, the users who have spatial interference with the user below a certain value are searched for, and the number of the users is large. Select a user who can guide the radio allocator to make a resource request.

 After the request-acceptance stage for the radio resources, the resource allocator calculates and updates the remaining space resources and the remaining transmission power. A resource allocator with no remaining space resources or no remaining transmit power is excluded from the list of resource allocator targets for the next round. In the same way, the user who has already been allocated a radio resource is deleted from the next round of resource request user target lists. This process is repeated until no more radio space resources can be allocated to new users.

6 is a block diagram of an orthogonal frequency division multiplexinng (OFDM) communication system implementing an SDMA scheme applying a radio resource allocation request-acceptance process according to the present invention. The data scheduler 610 receives data from a scheduler 620 and priority information of data to be transmitted and performs data scheduling. An encoder 630 encodes the scheduled data. The constellation mapper 640 maps the encoded data to constellations. Next, the subchannel mapper 650 subchannels the data according to the resource allocation information of the resource allocator 660. An orthogonal frequency division multiplexing (OFDM) modulator (OFDM) modulates the subchannel-mapped data and transmits the modulated data to the user terminal through the antenna 680.

There are many ways in which the present invention may be modified from the above-described embodiments while remaining within the scope of the claims set out in the claims. In other words, there may be many other ways in which the invention may be practiced without departing from the scope of the following claims.

According to the present invention, when transmitting data to a plurality of user terminals through a multiple transmission channel in a space division multiple access (SDMA) communication system, the user terminal is considered in consideration of channel quality, interference between users, and base station transmission power. Selecting can efficiently allocate radio space resources, improving system performance.

Claims (13)

The transmission power value for the user terminal (P _i) and in that the user terminal being assigned to the wireless space resource, said number of the less spatial interference is a constant value of a user terminal user non-(ratio) of (C _i) C and a resource allocator for allocating radio resources to the corresponding user terminal using _{i /} P _i . The method of claim 1, The spatial division multiple access communication system further comprises a scheduler for determining a data transmission amount and a user priority. The method of claim 1, The resource allocator allocates a radio resource to a user whose C _{i /} P _i value is maximum. The method of claim 1 The radio resource is a spatial division multiple access system, characterized in that the transmission power and radio space resources. An encoder for encoding input data; A resource allocator for transmitting radio resource allocation information to the subchannel mapper; The subchannel mapper for mapping encoded data encoded by the encoder to subchannels according to the radio resource allocation information received from the resource allocator; And Orthogonal Frequency Division Multiplexinng (OFDM) communication system using a wireless division multiple access scheme for receiving the sub-channel mapped data from the sub-channel mapper, OFDM modulation to transmit through the antenna. The method of claim 5, The communication system further comprises a scheduler for transmitting to the encoder by scheduling according to the priority information of the user to be transmitted and the data to be transmitted to the encoder. The method of claim 5, The number of characters the resource allocation the transmission power value for the radio resource allocation information to the corresponding user terminal (P _i) and in that the user terminal being assigned to the wireless space resource, wherein the less spatial interference is a constant value of a user terminal user ( C _i) the ratio (ratio) of C _{i /} P _i OFDM communication system using space division multiple access, characterized in that determined by using the. The method of claim 7, wherein And the radio resource allocation information of the resource allocator allocates a radio resource to a user whose C _{i /} P _i value is maximum. An encoding step of encoding the input data to output encoded data; Transmitting radio resource allocation information to the subchannel mapper; Mapping the encoded data to subchannels according to the radio resource allocation information; And And a step of OFDM modulating the subchannel-mapped data and transmitting the OFDM-modulated data through an antenna. The method of claim 9, Among transmission power values (P _i) and the user terminal did not receive allocation of a wireless space resources for the wireless resource allocation information on the user terminal, the corresponding number of less space interference is a constant value of a user terminal user (C _i) An OFDM communication system data transmission method using a space division multiple access scheme, wherein the radio resources are allocated to a user whose ratio C _{i /} P _i is maximum. Selecting a resource allocator with the best channel quality; Is there a space resource that can be allocated, the transmission power is above a certain value enough to transmit all the desired data, and the extent to which the radio space interference with a terminal already allocated to the corresponding radio space resource is below a certain value. Determining whether small; And If there is a space resource that can be allocated, the transmit power is greater than or equal to a predetermined value to transmit all desired data, and the radio space interference with a terminal that is already allocated to the radio space resource is less than or equal to the predetermined value. A method for selecting a radio resource allocator by a user terminal in a space division multiple access communication system comprising requesting a radio space resource allocation. C _i / P _i value, which is the ratio of the number of user terminals (C _i ) whose spatial interference with the user terminal is equal to or less than a predetermined value among the users who have not been allocated the radio power resources (P _i ) and the radio space resources for the user terminal Selecting a user terminal which is the maximum value; And And a radio resource allocator selecting a user terminal in a space division multiple access communication system comprising accepting a request for a radio space resource from the corresponding user terminal. The method of claim 11, Before the user terminal selection step, the number of user terminals whose spatial interference with the user terminal is less than or equal to a predetermined value among users who have calculated a transmission power value Pi for the user terminal and have not been allocated radio space resources (C _i ). _{and i} ) calculating the user equipment by the radio resource allocator in the spatial division multiple access communication system.

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