KR100726334B1 - Apparatus and method for maximize the transmitted efficiency of the bi-user sub-channel allocation of ofdma system - Google Patents

Abstract

The present invention provides an apparatus and method for allocating a subchannel in consideration of maximizing transmission efficiency between users of an OFDMA system. The subchannel allocation method of the present invention provides optimal data among subchannels of a specific user, which are allocated in order of fairness. Calculating a data rate at which a plurality of subchannels of a specific user, which is an order to be allocated, can be guaranteed to other users, when there are a plurality of subchannels guaranteeing a rate; A second step of determining a subchannel rank to be allocated to a user currently assigned in an order which does not guarantee sufficient data rate to other users by using the calculated result; And a third step of allocating a specific subchannel having the highest predetermined rank among a plurality of subchannels of a user currently allocated to the subchannel.

Consider OFDMA, subchannel allocation, data rate, channel situation between users

Description

Sub-channel allocation apparatus and method considering maximizing transmission efficiency between users of OPDMMA system {APPARATUS AND METHOD FOR MAXIMIZE THE TRANSMITTED EFFICIENCY OF THE BI-USER SUB-CHANNEL ALLOCATION OF OFDMA SYSTEM}

1 illustrates a BABS algorithm, which is a conventional subchannel allocation technique.

2 illustrates an ACG algorithm, which is a conventional subchannel allocation technique.

3 is a diagram illustrating a user-specific subchannel allocation result by a BABS + ACG algorithm, which is a conventional subchannel allocation technique.

4 illustrates an enhanced ACG algorithm, which is a conventional subchannel allocation technique.

FIG. 5 is a diagram illustrating a user-specific subchannel allocation result by BABS + an improved ACG algorithm, which is a conventional subchannel allocation technique. FIG.

6 illustrates an SSA algorithm that is a conventional subchannel allocation scheme.

FIG. 7 is a diagram illustrating a user-specific subchannel allocation result by the SSA algorithm, which is a conventional subchannel allocation technique. FIG.

8 is a schematic block diagram of an apparatus for allocating a subchannel in consideration of maximizing transmission efficiency between users in an OFDMA system for implementing the present invention.

9 illustrates a sector and a 2-tier cell structure which are basic units to which a subchannel allocation scheme according to the present invention is applied.

10 illustrates a radio resource structure for applying a subchannel allocation scheme according to the present invention.

11 illustrates basic parameters of a target system for applying a subchannel allocation scheme according to the present invention.

12 illustrates an ASA algorithm, which is a subchannel allocation scheme according to the present invention.

13 is an operational flowchart of the present invention.

14 is a diagram illustrating a user-specific subchannel allocation result by the ASA algorithm, which is a subchannel allocation scheme according to the present invention.

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

111: CRC inserter 113: encoder

115: symbol mapper 117: sub-channel allocator

119: serial / parallel converter 121: pilot symbol inserter

123: IFFT Converter 125: Parallel / Serial Converter

127: protection interval inserter 129: D / A converter

131: Radio Frequency Processor

The present invention relates to an Orthogonal Frequency Division Multiple Access (OFDMA) system. In particular, when a subchannel having the same SINR exists in one user, the user of the OFDMA system can identify the situation among all users and allocate an optimal subchannel. The present invention relates to an apparatus and method for allocating subchannels considering maximization of inter-transmission efficiency.

There is a need for a new service that guarantees mobility in a wireless environment and enables high-speed transmission. In accordance with this need, technology development and standardization for mobile Internet service in the 2.3 GHz band and mobile high-speed wireless packet data MBWA (Mobile Broadband Wireless Access) service is in progress.

Orthogonal Frequency Division Multiplexing (OFDM) is one of the most popular technologies because of its high transmission efficiency and simple channel equalization.

One of the important characteristics that determines the performance of an OFDM multiple access based system in a cellular environment where mobility is considered is frequency reuse factor.

If the frequency reuse rate is set to 1, the base station can use all the radio resources, which is the most ideal in terms of throughput of the base station.However, when the frequency reuse rate is set to 1, severe performance due to inter-cell interference is achieved. Deterioration occurs.

Therefore, in order to solve the performance degradation problem caused by the inter-cell interference and implement the frequency reuse rate 1, the Flash-OFDM system developed by Flarion uses a frequency hopping scheme that changes the subcarrier of the OFDM to a certain pattern. (Low Density Parity Check) This method uses the channel code to prevent the performance degradation caused by the inter-cell interference as much as possible.

In addition, in order to reduce frequency collision between adjacent cells and subcarriers in order to implement frequency reuse rate 1, a method of randomly puncturing subcarriers has been studied.

However, in a system that maintains a frequency reuse rate of 1, as the traffic load increases, performance degradation at the cell boundary with poor channel conditions is expected due to intercell interference.

Therefore, there is a growing interest in radio resource allocation to effectively use limited frequency resources as a way to reduce inter-cell interference and improve frequency efficiency, as well as to ensure the performance of users located in regions with poor channel conditions such as cell boundaries. It is actively being studied.

If it is assumed that the channel is stationary and the user's channel response is accurately known at the transmitter, a method combining water-filling and adaptive modulation is known to be optimal.

However, the water-filling method has been mainly studied only in a single user system or a multi-user system that supports fixed resource allocation. For example, a system using TDMA or FDMA uses each user. After allocating a certain time slot or frequency channel, an adaptive modulation scheme is applied to each user's channel.

However, the multi-user OFDM scheme using the adaptive resource allocation based on the above fixed resource allocation cannot provide the optimal resource allocation that the real system can provide. The reason is that due to the nature of the frequency selective channel (Frequency Selective Channel), there are subchannels that undergo deep fading or subchannels that are difficult to allocate a lot of power. Because it exists.

However, a channel that appears to be deep fading to one user may not be a deep fading channel to another user, and in general, as the number of users increases, it is increasingly likely that each subchannel constituting OFDM is a deep fading channel to all users. Will be reduced.

In other words, as the number of users increases, the user experiences an independent channel, thereby obtaining a multi-user diversity gain.

Accordingly, methods for increasing the transmission efficiency of the system have been sought by selectively allocating relatively good channels to each user based on channel information of all users, and applying an adaptive modulation scheme using such channels. The subchannel allocation schemes of hereinafter will be described.

1 is a bandwidth allocation based on SNR (BABS) algorithm (Kivanc D. Guoqing Li, and Hui Liu, "Computationally Efficient Bandwidth Allocation and Power Control for OFDMA", IEEE, Transaction, vol. , pp. 1150-1158, Nov. 2003.).

The BABS algorithm first determines the data rate R _k required by the k th user. After that, the average SINR value of all subchannels fed back from each user is used to obtain the data rate R _max that one subchannel can provide in the current channel situation, and to satisfy the data rate required by each user. _{Find the} number m _k (= R _k / R _max ).

At this time, if the total number of subchannels m _k (k: 1 ~ K) allocated to each user exceeds the total number of subchannels, the total number of subchannels of the users who are assigned the smallest subchannels is the total number of m _k . Cancel one by one until the number of channels is not exceeded.

In addition, if the sum of the number of subchannels m _k (k: 1 to K) allocated to each user is less than the total number of subchannels, the user who can allocate one more subchannel with the addition of the least power G _k . Further allocation is performed until the sum of m _k is equal to the total _number of subchannels. Through this series of BABS algorithms, the number of subchannels to be allocated to each user is obtained.

FIG. 2 shows an Amplitude Craving Greedy (ACG) algorithm (Kivanc D. Guoqing Li, and Hui Liu, "Computationally Efficient Bandwidth Allocation and Power Control for OFDMA," IEEE, Transaction, vol. , pp.1150-1158, Nov. 2003.), the base station first assigns the first subchannel to a user who can guarantee the highest data rate in the first subchannel.

Thereafter, the second subchannel is allocated to the user k ^* , which is guaranteed the highest data rate, and sequentially assigned to the last subchannel.

If the j-th user satisfies the number of subchannels m _j to be allocated to the j-th user through the BABS algorithm during the allocation process, the remaining j-th user of the j-th user is no longer allocated to the j-th user. Initialize the guaranteeable data rate of the sub channel to "0". Finally, the user who does not meet the data rate required by the user becomes outage.

The ACG algorithm has the advantage that the complexity of the system is small because it is sequentially assigned to the user from the first subchannel to the last subchannel, but has a disadvantage of low throughput of the overall system.

Figure 3 shows the result of assigning the number of sub-channels for each user through the BABS algorithm, and then assigning sub-channels to each user through the ACG algorithm.

Each subchannel value of each user illustrated in FIG. 3 represents a data rate calculated through the SINR value of the subchannel allocated to the user. The order of assignment is as follows.

First, the first subchannel is allocated to a second user who can obtain the highest data rate in the first subchannel.

The second subchannel is allocated to the fourth user who can obtain the highest data rate in the next second subchannel. As mentioned above, up to the eighth sub-channel is allocated to the user. In FIG. 3, Acquired Datarate is the total data rate in terms of the overall system.

4 is an improved Improved Amplitude Craving Greedy (ACG) Algorithm (Li Zhen, Zhu G. Wang W. Song Junde, "Improved Algorithm of Multiuser Dynamic Subcarrier Allocation in OFDMA System", Proceedings of ICCT) , 2003.).

First, the base station finds the user k ^* and the subchannel n ^* that can guarantee the highest data rate among all the subchannels of all users.

If the i th subchannel of the k th user guarantees the highest data rate in the whole, assign the i th sub channel to the k th user and set the guaranteeable data rate of the i th sub channel of the other user to "-1". By initializing, the i-th subchannel is no longer assigned to other users.

After that, if the k-th user satisfies the number of subchannels m _k to be allocated to the k-th user through the BABS algorithm, the subchannel is no longer assigned to the kth user. Initialize the guaranteeable data rate of all remaining subchannels of the k-th user to "-1" so as not to allocate. Finally, the user who does not meet the data rate required by the user becomes outage.

The improved ACG algorithm has a disadvantage in that the complexity of the system is higher than that of the ACG algorithm, which is sequentially assigned to the user from the first subchannel to the last subchannel. However, the throughput of the overall system is higher than that of the ACG algorithm.

5 shows the result of assigning subchannels to each user through an improved ACG algorithm after determining the number of allocated subchannels for each user through the BABS algorithm.

In FIG. 5, each subchannel value of each user represents a data rate calculated through the SINR value of the subchannel allocated to the user. The order of assignment is as follows.

The first user who can obtain the highest data rate among the total subchannels, and the first user of the fourth user, the number of the fourth subchannel of the first user is faster than the number of the eighth subchannel of the fourth user. After allocating the fourth subchannel, the data rate of the fourth subchannel of the entire user is set to "-1" so that no other user is allocated the fourth subchannel.

Since the eighth subchannel of the next fourth user guarantees the highest data rate among the total subchannels of all users, after assigning the eighth subchannel to the fourth user, as in the previous case, Set the data rate to "-1".

In the middle of allocating the subchannels to the user, the user who is allocated the predetermined number through the BABS algorithm is no longer allocated the subchannels. In FIG. 5, Acquired Datarate is a total data rate in terms of the entire system.

6 illustrates a specific subcarrier allocation (SSA) algorithm, which is one of conventional subchannel allocation techniques. The SSA algorithm differs from the above-mentioned ACG and enhanced ACG algorithms in that there is no process for determining the number of subchannel allocations per user through the BABS algorithm. In other words, the SSA algorithm provides fairness by allocating sub-channels first to users assigned the lowest data rates.

First, the base station finds the user k ^* assigned the lowest data rate. After that allows assignment of k ^* that will yield the highest data rate among the users of the sub-channel sub-channel n ^*.

If, k ^* user was assigned to the lowest data rate, if the n ^* subchannel in the k ^* user sub-channels ensures the highest data rate, k ^* haejugo assigning a second user n ^* th subchannel, k ^* The n ^* th subchannels are no longer allocated to other users by inserting n ^* into the assigned subchannel set A _{k *} of the first user and excluding the subchannel n ^* from A, the set of assignable subchannels. Subsequently, subchannels are allocated to the users through the same process, and the user who does not meet the required data rate is outtage.

Although the SSA algorithm does not have a BABS algorithm process, the system complexity is less than that of the aforementioned ACG and improved ACG algorithms because the fairness of the user must be considered in the assignment process. The throughput of the overall system is similar to the ACG algorithm and lower than the improved ACG algorithm.

7 shows a result of allocating a subchannel to each user through the SSA algorithm. In FIG. 7, a value for each subchannel of each user represents a data rate calculated through a signal to interference and noise ratio (SINR) value of a subchannel allocated to a user.

Assume that all users require the same data rate. Up to now, since no user is assigned, subchannels are allocated in order from the first user.

First, because the fourth subchannel of the first user's subchannels guarantees the highest data rate, the fourth subchannel is allocated to the first user, and then the fourth subchannel of the subchannel candidates that other users can be allocated. Exclude the channel.

In Fig. 7, the data rate is changed to " 0 " to indicate that the candidate is excluded from the candidate. After assigning a third subchannel that can guarantee the highest data rate among the second user's subchannels to the second user, the third subchannel is excluded from the candidate.

The second subchannel capable of guaranteeing the highest data rate among the next third user's subchannels is allocated to the third user, and then the second subchannel is excluded from the candidate. After assigning the eighth sub-channel capable of guaranteeing the highest data rate among the fourth user's sub-channels to the fourth user, the eighth sub-channel is excluded from the candidate.

Since the guaranteed data rate for each user is different from now on, the third user with the lowest data rate starts the allocation and proceeds until all subchannels are allocated. Acquired Datarate is the total data rate in terms of the overall system.

As such, the conventional subchannel allocation schemes do not consider which subchannel should be allocated when there are subchannels capable of guaranteeing the same data rate in the user. The impact is not considered.

The present invention has been made in view of the above, and an object of the present invention is to provide throughput and outlink of downlink by allocating subchannels in consideration of the effect on other users when there are subchannels capable of guaranteeing the same data rate within a specific user. The present invention provides an apparatus and method for allocating subchannels in consideration of maximizing transmission efficiency between users of an OFDMA system to improve outage probability.

In order to achieve the object of the present invention, an apparatus for allocating a subchannel in consideration of maximizing transmission efficiency between users of an OFDMA system according to the present invention is an apparatus for allocating subchannels in an OFDMA system. Sub-channel allocating means for allocating sub-channels so that other users can be allocated a lot of sub-channels that are advantageous to the user when there are a plurality of sub-channels guaranteeing the same data rate among the sub-channels of the user; And transmission means for transmitting data through the assigned subchannels when data to be transmitted is generated.

The sub-channel allocating means calculates a data rate that a plurality of sub-channels of a specific user in the order of allocation can guarantee each other user, and does not guarantee a sufficient data rate to other users by using the calculated result. It is preferable to determine the subchannel rank to be allocated to the users in the current allocation order in an unsuccessful order, so that the specific subchannel having the highest ranking is assigned to the specific users in the order to be allocated.

In order to achieve the object of the present invention, a subchannel allocation method in consideration of maximizing transmission efficiency between users of an OFDMA system according to the present invention, an optimal data rate among subchannels of a specific user ordered by fairness in an OFDMA system A method for allocating subchannels when there are a plurality of subchannels for guaranteeing the data, the method comprising: a first step of calculating a data rate at which a plurality of subchannels of a specific user, which is an order to be allocated, can guarantee to each other user; A second step of determining a subchannel rank to be allocated to a user currently assigned in an order which does not guarantee sufficient data rate to other users by using the calculated result; And a third step of allocating a specific subchannel having the highest predetermined rank among a plurality of subchannels of a user currently allocated to the subchannel.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the following examples are merely to illustrate the invention is not limited to the contents of the present invention.

8 schematically illustrates a structure of a transmitter of an OFDMA mobile communication system for implementing the present invention.

As shown, a Cyclick Redundancy Check (CRC) inserter (111), an encoder (113), a symbol mapper (115), a sub-channel allocator 117, a serial to parallel converter 119, a pilot symbol inserter 121, an Inverse Fast Fourier Transform (IFFT), hereinafter referred to as "IFFT" 123, parallel to serial converter 125, guard interval inserter 127, digital to analog converter 129, radio frequency (RF) Radio frequency, hereinafter referred to as " RF ".

When user data bits and control data bits to be transmitted in this configuration are generated, the user data bits and the control data bits are input to the CRC inserter 111. Here, the user data bits and the control data bits will be referred to as "information data bits".

When the information data bit is input, the CRC inserter 111 inserts the CRC bit therein and outputs the CRC bit to the encoder 113. The encoder 113 codes the signal output from the CRC inserter 111 by using a preset coding scheme, and then outputs the signal to the symbol mapper 115.

Here, the coding scheme may be a turbo coding scheme or a convolutional coding scheme having a predetermined coding rate.

The symbol mapper 115 modulates the coded bits output from the encoder 113 by using a preset modulation scheme to generate a modulated symbol, and then outputs the modulated symbols to the sub-channel allocator 117. . Here, the modulation scheme may be a Quadrature Phase Shift Keying (QPSK) scheme, a Quadrature Amplitude Modulation (QAM) scheme, a 16QAM scheme, or the like.

The subchannel allocator 117 allocates a subchannel to the modulation symbols input from the symbol mapper 115 and outputs the subchannel to the serial / parallel converter 119. Here, the subchannel allocation operation of the subchannel allocator 117 is performed according to the subchannel allocation method proposed by the present invention, and the subchannel allocation method proposed by the present invention will be described below. Will be omitted.

The serial / parallel converter 119 converts the serial modulation symbols allocated to the subchannels output from the subchannel allocator 117 in parallel and then outputs them to the pilot symbol inserter 121.

The pilot symbol inserter 121 inserts pilot symbols into the parallel-converted modulated symbols output from the serial / parallel converter 119 and outputs the pilot symbols to the IFFT unit 123.

The IFFT unit 123 performs IFFT on the signal input from the pilot symbol inserter 121 and then outputs the parallel / serial converter 125. The parallel / serial converter 125 converts the signal output from the IFFT device 123 in series and then outputs the signal to the guard interval inserter 127.

The guard interval inserter 127 receives the signal output from the parallel / serial converter 125, inserts a guard interval signal, and outputs the signal to the D / A converter 129. Here, the guard interval is inserted to remove interference between the OFDM symbol transmitted at the previous OFDM symbol time and the current OFDM symbol transmitted at the current OFDM symbol time when the OFDM symbol is transmitted in the OFDMA communication system.

In addition, the guard interval is a "Cyclic Prefix" scheme of copying the last constant samples of the OFDM symbols in the time domain and inserting them into a valid OFDM symbol or the first constant samples of the OFDM symbols in the time domain. It can be used in a "Cyclic Postfix" manner of copying and inserting into a valid OFDM symbol.

The D / A converter 129 converts the signal output from the guard interval inserter 127 into an analog signal and outputs the analog signal to the RF processor 131.

The RF processor 131 may include components such as a filter and a front end unit, and may transmit a signal output from the D / A converter 129 on actual air. After the RF process, the transmission is performed on air through a Tx antenna.

Hereinafter, the subchannel allocation method proposed by the present invention will be described.

First, FIG. 9 illustrates basic cell planning for an OFDMA platform for the present invention.

As shown, each cell is composed of three sectors, and is composed of 57 sectors in total, and there is a base station for each sector. Target cells (Sector 0, 1, 2) existing in the middle are affected by interference from 54 neighboring sectors, respectively.

FIG. 10 shows a structure of a radio resource that can be used in one sector. In the frequency domain, the entire band consists of 32 subchannels, and each subchannel consists of three bins. Each bin consists of nine consecutive subcarriers, one of which is used as a pilot subcarrier for various purposes such as channel estimation and SINR measurement. In addition, it is assumed that the subcarrier initial transmission power is fixed constantly.

The user feeds back the average SINR value for all subchannels to the base station to which it belongs. Each sector base station can obtain a multi-user diversity gain by assigning a sub channel having a good SINR value to a user based on feedback information.

11 is a table showing the basic system parameters of the target system for applying the sub-channel allocation method of the present invention.

The total band consists of a total of 1024 subcarriers, of which 864 subcarriers are used, and 768 subcarriers except 96 pilot subcarriers are effective subcarriers. Each subchannel consists of 27 contiguous subcarriers, three of which are pilot subcarriers.

12 illustrates an Aggressive Subchannel Allocation (ASA) algorithm, which is a subchannel allocation scheme according to the present invention, and FIG. 13 illustrates a flowchart thereof.

The ASA algorithm does not have a process of determining the number of subchannel allocations per user through the BABS algorithm like the conventional SSA algorithm.

That is, the ASA algorithm provides fairness by allocating subchannels to the k ^* users who are assigned the lowest data rate like the SSA algorithm.

However, in the case of the improved ACG algorithm and the SSA algorithm, a plurality of subchannels of the k ^* th user's subchannels can be guaranteed if the order of k ^* th users is assigned a subchannel due to fairness. If there are subchannels, they are allocated in subchannel number order without considering which subchannel should be allocated to the k ^* th user.

On the other hand, since one subchannel is not allocated to a plurality of users to exclude intra-cell interference, if the i-th subchannel is allocated to the k-th user, all other users are i-th. Even if the subchannel guarantees itself a high data rate, the i-th subchannel cannot be allocated.

The following situation is assumed.

     1. Assume that the k-th user can be allocated one of the i-th and h-th subchannels that can guarantee the same data rate.

2. It is assumed that other users can be assured of a higher data rate than other subchannels in the i-th subchannel.

3. It is assumed that other users are guaranteed very low data rates on the h subchannel.

4. Assume that the number of the i-th subchannel is earlier than the number of the h-th subchannel.

5. Since the subchannel numbers are assigned in order, the k-th user is allocated the i-th subchannel among the two i-h-th subchannels guaranteeing the same data rate.

6. Other users can no longer be assigned the i th subchannel because the k th user has been assigned the i th subchannel.

7. From the position of the k-th user, even though the h-th subchannel is allocated, the final throughput does not change as compared with the case of the i-th subchannel.

8. From a system-wide perspective, the k-th user is assigned the i-th subchannel, resulting in lower overall system throughput.

In other words, the existing subchannel allocation scheme lowers the data rate of other users by allocating subchannels that can guarantee the same data rate to the specific users, which are ordered by fairness, in numerical order. Lower the throughput of the system.

However, the subchannel allocation scheme of the present invention assumes that there are a plurality of subchannels that guarantee an optimal data rate among subchannels of a specific user ordered to be allocated by fairness.

At this time, the sub-channel allocator 117 of the base station calculates a data rate that can be guaranteed to each of the plurality of sub-channels of a specific user in the order of allocation (S110).

The sub-channels to be allocated to specific users are determined in order of not guaranteeing sufficient data rates to other users (S120).

Thereafter, among the plurality of subchannels of the user in which the subchannels are to be allocated, the specific subchannel having the highest ranking is allocated (S130).

That is, by allocating a subchannel guaranteeing the smallest data rate to another user among the plurality of subchannels guaranteeing the same optimal data rate of the user in the order to be allocated, the assigned user can obtain the user. It ensures the opportunity to get better subchannels from other users while preserving the data rate.

For example, if the n *, m *, and h * subchannels among the subchannels of user k ^* , which are currently allocated, can guarantee the highest data rate to the user k *, then other users will receive the n * subchannels. The sum of the data rates obtained from the n * subchannels by comparing the sum of the data rates obtained from the channels with the sum of the data rates obtained from the m * subchannels and the sum of the data rates obtained from the h * subchannels. If this is smaller than m * and h *, n * subchannels are best assigned to the user who is assigned to the user in order to be allocated.

The n ^* th subchannel is no longer assigned to another user by inserting n ^* into the assigned subchannel set A _{k *} of the k ^* th user and excluding the sub channel n ^* from A, the set of assignable subchannels. Do not

This gives other users the opportunity to assign n * subchannels that have guaranteed low data rates to k * users and to ensure that they have the opportunity to be assigned to their favorite m * and h * subchannels. You can increase the throughput, which in turn increases the throughput of the entire system.

14 shows a result of assigning a subchannel to each user through the ASA algorithm.

In FIG. 14, a value for each subchannel of each user represents a data rate calculated through the SINR value of the subchannel allocated to the user. Assume that all users require the same data rate.

Until now, since no user is assigned, subchannels are allocated in order from the first user.

First, because the fourth subchannel of the first user's subchannels guarantees the highest data rate, the fourth subchannel is allocated to the first user, and then the fourth subchannel of the subchannel candidates that other users can be allocated. Exclude the channel. In Fig. 13, the data rate is changed to "0" to express that the candidate is excluded.

Next, after assigning a third subchannel capable of guaranteeing the highest data rate among the subchannels of the second user to the second user, the third subchannel is excluded from the candidate.

Next, after assigning a second subchannel capable of guaranteeing the highest data rate among the third user's subchannels to the third user, the second subchannel is excluded from the candidate.

Next, after assigning the eighth sub-channel capable of guaranteeing the highest data rate among the fourth user's sub-channels to the fourth user, the eighth sub-channel is excluded from the candidate.

Since the guaranteed data rate for each user is different, the allocation starts from the third user who received the least data rate.

Since the fifth and seventh subchannels of the third user's subchannels guarantee the same highest data rate, consider which of the two subchannels to allocate to the third user.

In the case of other users, since the fifth subchannel has a higher data rate than the seventh subchannel, the seventh subchannel is allocated to the third user, thereby guaranteeing the opportunity to be allocated to the fifth subchannel to the other users.

That is, the third user is assigned the seventh sub-channel so that the first user can be assigned the fifth sub-channel. As a result, the fourth user is also assigned the sixth sub-channel in the last allocation order.

This increases the throughput of the entire system. In FIG. 14, Acquired Datarate is a total data rate in terms of the entire system.

As described above, although described with reference to a preferred embodiment of the present invention, those skilled in the art various modifications of the present invention without departing from the spirit and scope of the invention described in the claims below Or it may be modified.

As described above, the present invention obtains the following effects.

First, in the present invention, each base station receives feedback of the channel status from the user providing the service and considers the fairness of each mobile station, and excludes one sub-channel to exclude interference in the same cell when allocating good channels to each user. By not assigning a channel to multiple users, multi-user diversity gain is achieved. By considering the sub-channel situation between users, all users can be allocated as many sub-channels as they are advantageous to the existing sub-channel allocation schemes. This can increase the total throughput of the OFDMA system downlink.

Second, by allocating an optimal subchannel to all users on the system, it is possible to reduce the total outage probability of the system by ensuring the quality of service (QoS) of the users.

Third, by being applied to the next generation wireless communication, it is possible to provide high quality service and easy cell planning by increasing the transmission efficiency of the whole system.

Claims (5)

An apparatus for allocating subchannels in an OFDMA system, If there are a plurality of sub-channels that guarantees the same data rate among the sub-channels of a specific user ordered to be allocated by fairness, the sub-channels are allocated so that all users can be allocated a lot of sub-channels that are advantageous to them. Channel allocation means; Transmitting means for transmitting data through the assigned subchannels when data to be transmitted is generated; Sub-channel allocation apparatus in consideration of maximizing the transmission efficiency between users of the OFDMA system comprising a. The method of claim 1, wherein the sub-channel allocation means If there are a plurality of sub-channels that guarantees the same data rate among the sub-channels of the specific user in the order to be allocated to the users in the order to be allocated, the data rate that each sub-channel guarantees to other users is determined. Sub-channel allocation apparatus in consideration of maximizing the transmission efficiency between users of the OFDMA system, characterized in that the calculation. The method of claim 2, wherein the sub-channel allocation means Based on the result of the calculation among the plurality of sub-channels guaranteeing the optimal same data rate among the sub-channels of a specific user in the order to be allocated to the user, the sufficient data rate cannot be guaranteed to each other user. Sub-channel allocation apparatus in consideration of maximizing the transmission efficiency between users of the OFDMA system, characterized in that for determining the sub-channel rank to be assigned to the user of the current order to be allocated. 4. The method of claim 3, wherein the order to be allocated to the specific user in the order of allocation is determined among the plurality of sub-channels which guarantees the user the optimal same data rate among the sub-channels of the specific user in the order of allocation. An apparatus for allocating a subchannel in consideration of maximizing transmission efficiency between users of an OFDMA system, wherein the subchannel having the highest rank among the subchannels is allocated. In the sub-channel allocation method when there are a plurality of sub-channels that guarantees the optimal same data rate among the sub-channels of a specific user ordered by fairness in the OFDMA system, Calculating a data rate at which a plurality of subchannels of a specific user, which is an order to be allocated, can guarantee to other users, respectively; A second step of determining a subchannel rank to be allocated to a user currently assigned in an order which does not guarantee sufficient data rate to other users by using the calculated result; And A third step of allocating a specific subchannel having the highest rank of the subchannel to be allocated to the users in the current allocation order determined in the second step among a plurality of subchannels of the users in the current subchannel allocation order; Sub-channel allocation method in consideration of maximizing the transmission efficiency between users of the OFDMA system comprising a.

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