KR100650116B1 - Method and frame structure for supporting dynamic channel allocation and dynamic power allocation in frequency reuse partitioning based ofdma system - Google Patents

Abstract

A dynamic channel allocation method and a dynamic power allocation method of an OFDMA system based on a frequency reuse partitioning scheme, and a frame structure for supporting the same are provided to enable a mobile terminal to receive a better channel by dynamically allocating a sub carrier of a channel group having a high SINR(Signal to Interference and Noise Ratio). A dynamic channel allocation method of an OFDMA system based on a frequency reuse partitioning scheme includes the steps of: selecting a mobile terminal having a minimum ratio that the sum of an allocated transmission ratio is divided by a transmission ratio, which the mobile terminal requests, as a prior channel allocation candidate(S410); and dynamically allocating a sub carrier of the sub channel group by selecting a predetermined sub channel group of sub channel groups having a first frequency reuse ratio by a mobile terminal in an inner cell, and a predetermined sub channel group of sub channel groups having a second frequency reuse ratio by a mobile terminal in an outer cell(S420).

Description

Dynamic Channel Allocation Method and Dynamic Power Allocation Method and Supported Frame Structure in ODFDMA System Based on Frequency Reuse Rate Partition System

1 is a schematic diagram illustrating a general frequency reuse rate division scheme.

2 is a basic cell structure diagram of a frequency reuse rate division scheme based OFDMA platform for implementing the present invention;

3 is a diagram illustrating a radio resource structure for applying a dynamic channel allocation scheme based on a frequency reuse rate division scheme according to the present invention.

4 is a flow diagram for a dynamic channel allocation algorithm in accordance with the present invention.

5A illustrates mobile terminal selection for allocating channels on a fairness basis to allocate radio resources to mobile terminals according to the dynamic channel allocation algorithm in accordance with the present invention.

FIG. 5B is a diagram illustrating allocating a best subcarrier to a mobile terminal within a subchannel group having a frequency reuse rate of 1 or 3 based on location information of the mobile terminal according to the dynamic channel allocation algorithm according to the present invention.

6 is a flow diagram for a dynamic power allocation algorithm in accordance with the present invention.

7 illustrates a proposed frame structure for applying a dynamic channel and power allocation scheme based on a frequency reuse rate division scheme according to the present invention.

8 illustrates basic parameters for applying a dynamic channel and power allocation scheme according to the present invention.

9 illustrates a first phase, downlink slot starting a super frame for a dynamic channel and power allocation scheme in accordance with the present invention.

FIG. 10 is a diagram illustrating a first phase and a downlink slot other than the first phase and downlink slot starting a super frame for a dynamic channel and power allocation scheme according to the present invention. FIG.

11 and 12 are diagrams illustrating the amount of downlink and uplink overhead generated when applying a dynamic channel and power allocation scheme according to the present invention.

13 is a diagram illustrating uplink and downlink slot structures for performing adaptive modulation only in units of slots according to the present invention.

14 and 15 are diagrams illustrating the amount of downlink and uplink overhead generated when adaptive modulation in units of slots and dynamic resource allocation in units of frames are applied to reduce overhead of the dynamic channel and power allocation scheme according to the present invention. .

<Explanation of symbols for main parts of the drawings>

201-207: cell 201a-207a: inner cell

201b-207b: foreign cell

The present invention relates to an orthogonal frequency division multiple access system, and more particularly, in an orthogonal frequency division multiple access (OFDMA) system, an adaptive transmission power allocation scheme considering a dynamic resource allocation scheme is proposed. The present invention relates to a dynamic channel allocation method and a dynamic power allocation method of a frequency reuse rate division based OFDMA system capable of improving performance, and a frame structure and a slot structure supporting the same.

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 (hereinafter, referred to as OFDM) is one of the most noticed technologies because of high transmission efficiency and simple channel equalization.

The operation of a transmitter (base station) and a receiver (mobile terminal) in a wireless communication system using the OFDM scheme will be briefly described as follows.

In an OFDM transmitter, input data is modulated into a sub-carrier through a scrambler, an encoder, and an interleaver. In this case, the transmitter may provide various variable data rates, and have different coding rates, interleaving sizes, and modulation schemes according to the data rates.

Typically, the coder uses code rates such as 1/2, 3/4, etc., and the size of the interleaver to prevent the aggregation error is determined according to the number of encoded bits per OFDM symbol. The modulation scheme uses QPSK (Quarature Phase Shift Keying), 8PSK (8ary PSK), 16ary Quarature Amplitude Modulation (16QAM), and 64QAM (64ary QAM) according to the required data rate.

The above described symbols are modulated into a predetermined number of subcarriers and pass through the IFFT block to form one OFDM signal. The OFDM signal is inserted through a symbol waveform generator after a guard time is inserted to remove intersymbol interference in a multipath channel environment and finally transmitted to a radio channel by a radio frequency unit.

Correspondingly, in the receiver, the reverse process of the transmitter occurs and a synchronization process is added. First, a process of estimating a frequency offset and a symbol offset using predetermined symbols should be preceded. After that, the data symbol having the guard interval inserted from the transmitter is passed through the FFT block and restored to a predetermined number of subcarriers including a predetermined number of pilots.

To overcome the path delay phenomenon, the equalizer estimates the channel state and removes the signal distortion caused by the channel from the received signal. The data whose channel response is compensated through the equalizer is converted into a bit string, passed through a deinterleaver, and then restored to final data through a decoder and a descrambler for error correction.

In such an OFDM scheme, instead of performing high-speed transmission of input data on a single carrier, low-speed transmission is performed in parallel on a plurality of carriers. That is, the OFDM scheme enables efficient digital implementation of the modulation / demodulation unit and has a small effect on frequency selective fading or narrowband interference.

Meanwhile, in a cellular environment in which mobility is considered, frequency reuse efficiency is the most important characteristic that determines system performance based on OFDM multiple access.

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 method that changes the OFDM subcarriers to a certain pattern. Low Density Parity Check) A method that prevents performance degradation due to inter-cell interference is maximized by using channel codes.

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

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

Therefore, interest in frequency reuse partitioning (Frequency Reuse Partitioning) is increasing as a method for ensuring the performance of a mobile station located in an area with poor channel conditions such as cell boundary as well as improving frequency efficiency.

Frequency reuse rate division is one of the effective ways to increase the frequency efficiency of cellular systems.

1 illustrates a concept of a general frequency reuse rate division scheme.

The basic idea of the frequency reuse rate division scheme is that the inner cell and the outer cell are based on the distance of the cell from the base station to the mobile station or the strength of the pilot signal transmitted from the base station to the mobile station. Separate by. In addition, different frequency reuse rates are applied to the inner and outer cells.

In the case of FIG. 1, a subchannel having a frequency reuse rate of 7 is allocated when the mobile terminal exists in the outer cell region, and a subchannel having a frequency reuse rate 1 is allocated when the mobile terminal is located in the inner cell region.

As described above, the reason for allocating channels having different frequency reuse rates to the inner cell and the outer cell is generally due to a path loss caused by a path loss compared to a mobile terminal far from the base station. Although the channel condition is relatively good because of the low power loss, the mobile terminal located near the cell boundary is severely affected by the power loss and inter-cell interference due to the path loss, thereby degrading performance and limiting the data rate. This is because it becomes an important factor for limiting the cell radius of the cellular system.

Therefore, when the frequency reuse rate division scheme is used, the mobile station in the internal cell region generally has a good channel condition. Therefore, a channel having a low frequency reuse rate is allocated to guarantee a proper level of quality of service (QoS). In addition, since the capacity of the mobile terminal in the outer cell region is relatively poor in channel conditions, the channel radius is increased by allocating a channel having a high frequency reuse rate, and the mobile terminal at the cell boundary has the same level as the mobile terminal in the inner cell. QoS and data rate can be guaranteed.

Recently, a radio resource allocation scheme for effectively using limited frequency resources while reducing inter-cell interference has been studied.

If the channel is stationary and the mobile terminal knows the channel response accurately, it is known that a method combining water-filling and adaptive modulation is 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, TDMA (Time Division) A system using multiple access (FDMA) or frequency division multiple access (FDMA) allocates a predetermined time slot or frequency channel for each mobile terminal and then applies an adaptive modulation scheme to the channel of each mobile terminal.

However, based on the fixed resource allocation as described above, the multiple mobile terminal OFDM scheme using the adaptive modulation scheme cannot perform the optimal resource allocation that can be provided by an actual system.

The reason for this is that when the water-filling algorithm is applied because there are sub-channels that undergo deep fading due to the characteristics of frequency selective channels or sub-channels that are difficult to allocate a lot of power, This is because there are many unused channels.

However, a channel that appears to be deep fading to one mobile terminal may not be a deep fading channel to another mobile terminal. In general, as the number of mobile terminals increases, the probability that each subchannel constituting OFDM is a deep fading channel to all mobile terminals This is getting less and less.

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

Therefore, the system by dynamically allocating a relatively good channel to each mobile terminal based on the channel information of all mobile terminals, applying the adaptive modulation scheme using such channels, and then assigning dynamic power according to the state of the allocated channel. There are ways to get closer to this optimal resource allocation that can be provided.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and an object of the present invention is to combine a concept of a frequency reuse rate division scheme in an OFDMA system based on the channel situation of a mobile terminal, and thus has a high SINR (Signal to Interference and Noise Ratio). The present invention provides a dynamic channel allocation method of a frequency reuse rate division based OFDMA system in which a mobile station can be allocated a better channel by dynamically allocating a carrier.

Another object of the present invention is to dynamically allocate power according to a state of a channel allocated to each mobile station to obtain a multi-user diversity gain. To provide an allocation method.

Another object of the present invention is to apply only AMC (Adaptive Modulation and Coding) as a slot unit and support DAC (Dynamic Channel Allocation) as a frame unit to support dynamic resource allocation such as dynamic channel allocation and dynamic power allocation scheme for an OFDMA system. In the present invention, the present invention provides a frame structure and a slot structure for supporting dynamic channel and power allocation in an OFDMA system based on a frequency reuse rate division scheme using a dynamic power allocation (DPA) and an AMC.

In order to achieve the object of the present invention, a dynamic channel allocation method of a frequency reuse rate division based OFDMA system according to the present invention has a cell structure formed of cells each consisting of a plurality of sectors, and the cells are orthogonal to each other. In a channel allocation method of an OFDMA system that performs data communication with mobile terminals in a corresponding cell through at least one subchannel group having a terminal, the sum of transmission rates allocated so far by the mobile terminal is determined as the transmission rate requested by the mobile terminal. Selecting a mobile terminal having the smallest ratio as a preferred channel allocation candidate; And among the sub-channel groups in which the mobile terminal in the inner cell has a first frequency reuse rate using channel information and distance information of the mobile terminal selected as the preferred channel assignment candidate, the mobile terminal in the outer cell reuses the second frequency. And selecting a predetermined subchannel group from among the subchannel groups having a rate and dynamically allocating subcarriers of the corresponding subchannel group.

The first frequency reuse rate is a frequency reuse rate of 1, the second frequency reuse rate is a frequency reuse rate of 3, and the predetermined subchannel group is a subchannel group having a high Signal to Interference and Noise Ratio (SINR). It is done.

A dynamic power allocation method of the frequency reuse rate division scheme based OFDMA system of the present invention for achieving the above object has a cell structure formed of cells each consisting of a plurality of sectors, wherein the cells have at least one orthogonality In a power allocation method of an OFDMA system that performs data communication with mobile terminals in a corresponding cell through a sub-channel group, power of a reference MCS level is determined from power of a mobile terminal having a SINR of more than a predetermined modulation and coding scheme (MCS). Subtracting and storing; And performing dynamic power allocation for each subchannel of the mobile terminal by adding power required for the mobile terminal having a minimum SINR value for increasing one current MCS level among mobile terminals having a SINR below a predetermined MCS level. It is done.

Dynamic channel and power allocation method of the frequency reuse rate division scheme based OFDMA system of the present invention to achieve the above object, each cell is composed of a plurality of sectors, each cell is composed of an inner cell and an outer cell In a method of allocating resources of an OFDMA system in which a cell structure is formed and the cells perform data communication with mobile terminals in a corresponding cell through at least one subchannel group having mutual orthogonality, each base station is provided with its own service. Allocating sub-channel groups having a high SINR to each mobile terminal in consideration of fairness of each mobile terminal by receiving a feedback of the channel condition from the providing mobile terminal; And allocating power according to a state of a channel allocated to each mobile terminal to obtain multiple mobile terminal diversity gains.

In order to achieve the above object, a frame structure supporting dynamic resource allocation in an OFDMA system based on a frequency reuse rate division scheme may be applied to a frame structure of an OFDMA system for supporting dynamic resource allocation based on a frequency reuse rate division scheme. In this case, one frame is composed of four slots, and one super frame is composed of five frames.

The slot structure for supporting dynamic resource allocation of the frequency reuse rate division scheme based OFDMA system of the present invention for achieving the above object is a slot structure of the OFDMA system for supporting dynamic resource allocation based on the frequency reuse rate division scheme. In the slot, the slot has a preamble for CINR measurement so that the mobile station measures the CINR values of all sub-channel groups, and in each super frame, to distinguish whether the mobile station is in the inner cell region or the outer cell region. The mobile terminal has an OFDM symbol for transmitting location information of the mobile terminal, and has a plurality of OFDM symbols for subcarrier reallocation and adaptive modulation using channel information of the mobile terminal.

The slot is a downlink slot, characterized in that the first downlink slot to start a super frame.

The slot structure for supporting dynamic resource allocation of the frequency reuse rate division scheme based OFDMA system of the present invention for achieving the above object is a slot structure of the OFDMA system for supporting dynamic resource allocation based on the frequency reuse rate division scheme. The slot includes a preamble for CINR measurement so that the mobile station measures CINR values of all subchannel groups in each slot, and has a plurality of OFDM symbols for subcarrier reallocation and adaptive modulation using channel information of the mobile station. It is characterized by.

The slot is a downlink slot, characterized in that the downlink slot other than the first downlink slot starting the super frame.

A slot structure for supporting dynamic resource allocation in an OFDMA system based on a frequency reuse rate division scheme according to the present invention for achieving the above object is a slot structure of an OFDMA system for supporting a dynamic resource allocation scheme based on a frequency reuse rate division scheme. In the group, the slot has a preamble for CINR measurement so that the mobile station measures the CINR value of all sub-channel groups in each slot for adaptive modulation in every slot, and for transmitting the location information of the mobile terminal every super frame It is characterized by having an OFDM symbol and a plurality of OFDM symbols for adaptive modulation.

A method for operating a dynamic resource allocation method of an OFDMA system based on a frequency reuse rate division scheme according to the present invention for achieving the above object is a method for operating a dynamic channel and power allocation scheme in an OFDMA system based on a frequency reuse rate division scheme. In the present invention, the overhead is reduced by performing Dynamic Channel Allocation (DCA) and Dynamic Power Allocation (DPA) every frame while performing Adaptive Modulation and Coding (AMC) in every slot.

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.

The present invention is based on a frequency reuse rate division based OFDMA / FDD (Frequency Division Duplexing) system. Like OFDM, the OFDMA transmits input data in parallel on a plurality of subcarriers through IFFT and FFT transformation. There is a difference in that a signal is transmitted by a multiple access scheme in which the plurality of subcarriers are allocated to a plurality of subscriber mobile terminals, and the present invention is based on a general frequency reuse rate division based OFDMA system. .

2 illustrates basic cell planning for a frequency reuse rate division scheme based OFDMA platform according to the present invention.

As shown, each cell 201-207 has a regular hexagonal structure, and each cell 201-207 is composed of three sectors 1, 2, and 3, respectively.

In addition, the concept of the frequency reuse ratio dividing scheme is introduced into each of the sectors 1, 2, 3 of each cell 201-207 so that each of the sectors 1, 2, 3 has an internal cell 201a-207a. And the foreign cells 201b-207b.

The entire network is divided into several clusters. As shown in FIG. 2, each cluster is composed of three sectors of the same cell. That is, in the present invention, one cell becomes one cluster.

3 illustrates a radio resource structure that can be used in one cluster of FIG. 2.

In the frequency domain, as shown in (301), the entire band is composed of 32 subchannel groups (only a part is shown in the drawing), and each subchannel group is assumed to be composed of 27 subcarriers. Define a set of bins as 302. One of the nine subcarriers constituting the bin 302 such as 303 is a pilot subcarrier that can be used for various purposes such as channel estimation and SINR measurement.

It is also assumed that each subcarrier initial transmit power is fixed. Different subchannel groups may use different frequency reuse rates, and may use one of two values, ie, frequency reuse rates 1 and 3, respectively.

If a subchannel group has a reuse rate of 1, all three sectors of the cluster may use all subcarriers of the subchannel group. In the case of a subchannel group having a reuse rate of 3, only one of three bins constituting one subchannel group is distributed to three sectors constituting the cluster.

The mobile station feeds back an average SINR value for all subchannel groups to a sector to which it belongs during one super frame. Each sector allocates a channel of a sub-channel group having a good SINR value to the mobile terminal based on feedback information, and then allocates power based on the received SINR of the allocated channel to multi-user diversity gain (Multi-user Diversity). Gain).

The channel allocation algorithm proposed by the present invention will be described with reference to FIG. 4.

In order to allocate a channel to a mobile terminal, first, a ratio of a sum of transmission rates allocated to the mobile terminal and a transmission rate requested by the mobile terminal is considered. That is, the channel is preferentially allocated to the mobile terminal having the smallest ratio of the sum of the allocated transmission rates divided by the transmission rate requested by the mobile terminal (S410).

Next, the channel is allocated in consideration of whether the mobile terminal is in the inner cell area or the outer cell area (S420).

Since the basic concept of the frequency reuse rate division scheme is to assign a channel with a low frequency reuse rate to a mobile terminal near a base station, and to assign a channel with a high frequency reuse rate to a mobile terminal in a distant place, this concept is referred to as a channel allocation algorithm. In conjunction with, the mobile terminal in close proximity to the base station has a SINR based on the channel state of the mobile terminal in sub-channel groups having a frequency reuse rate of 1, and the mobile terminal far from the base station has a frequency reuse rate in a sub channel group having a frequency reuse rate of 3. The subcarriers of this high good subchannel group are dynamically allocated.

FIG. 5A illustrates a first portion of a channel allocation algorithm according to the present invention, in which a mobile station 1 having the smallest ratio of the sum of the transmission rates allocated to each mobile terminal divided by the transmission rate requested by the mobile terminal is selected as the channel allocation candidate. Is showing.

FIG. 5B is a view illustrating the best use of a subchannel group having a frequency reuse rate of 1 in a mobile terminal in an inner cell using a channel information and distance information of a mobile terminal 1, and a subchannel group having a frequency reuse rate 3 in a mobile terminal in an outer cell. A process of selecting a subchannel group with characteristics and assigning subcarriers of the subchannel group. This process is repeated to allocate a channel to each mobile terminal.

Next, a dynamic power allocation algorithm according to the present invention will be described with a flowchart of FIG. 6A.

In order to allocate power to a mobile terminal, power is allocated to all mobile terminals in the following two steps based on channel conditions.

First, the power of the mobile station having a SINR of a specific Modulation and Coding Scheme (MCS) level or higher is subtracted from the power of the reference MCS level and then stored (S610).

Here, a brief description of the reference MCS level, the system generally describes a number of available MCS levels for AMC. For example, in the case of a WiBro system, nine MCS levels are set. The lowest MCS level corresponds to 1/12 Turbo Coding & QPSK for WiBro and the highest MCS level corresponds to 5/6 Turbo Coding & 64QAM. The reference MCS level corresponds to any one of nine MCS levels, for example the sixth MCS level.

As described above, the step S610 of recovering power from a user having a channel higher than a reference MCS level stores the reduced power of all mobile terminals having an SINR higher than a specific MCS level.

Thereafter, a step of distributing power (S620) is performed based on the power recovered in the step S610. In step S620, the mobile station having a SINR below a specific MCS level adds power to a mobile station having a minimum SINR value required to increase one current MCS level and performs dynamic power allocation for each subchannel of the mobile station. .

In this case, the steps S610 and S620 are operated independently for the inner cell and the outer cell, and the sum of the powers increased to the MSs having a low SINR is the sum of the powers obtained from the MSs having a high SINR. Can't go over

Rather than allocating the same power to all mobile terminals, multi-mobile terminal diversity can be obtained by allocating power for each subchannel based on channel conditions.

7 shows a downlink frame structure for an OFDMA platform based on a frequency reuse rate division scheme according to the present invention.

One super frame 701 is composed of five frames 702, and the frame is composed of four slots 703 in units of 5 ms.

The channel information necessary for operating the DCA and the DPA may be transmitted from the mobile terminal to the base station in units of slots 703, frames 702, or super frames 701 according to the rate of change of the channel.

8 shows parameters for the implementation of the present invention.

Since DCA and DPA are performed in every slot 703 to calculate the amount of overhead according to DCA and DPA, the mobile station feeds back channel information for all groups to the base station on a slot 703 basis. It is assumed that the slot 703 transmits a newly allocated subcarrier position by channel information to the mobile terminal.

In addition, it is assumed that the location information of the mobile terminal is transmitted once in the unit of the super frame 701. Then, overhead to be transmitted by a base station in order to perform DCA and DPA can be classified into three types as follows.

＊ location information of mobile terminal (in super frame)

OFDM preamble provided by the base station so that the mobile station can measure the carrier to interference and noise ratio (CINR) of all sub-channel groups (in units of slots)

＊ subcarrier allocation information assigned by the base station to the mobile terminal (in every slot)

9 shows a first, uplink, and downlink slot for starting a super frame for the dynamic resource allocation algorithm according to the present invention, and 901 is a first downlink slot structure for starting a super frame.

In each slot, there is one preamble for CINR measurement so that the mobile station measures CINR values of all sub-channel groups, and one OFDM symbol is used to transmit the position information of the mobile station in each sector every superframe. .

Whether the mobile station is in the inner cell region or the outer cell region determines whether the mobile station performs DCA and DPA in a subchannel group with frequency reuse rate 1 or DCA and DPA in a subchannel group with frequency reuse rate 3 It is an important factor in deciding whether to perform.

If the mobile terminal is marked with 0 if it is in the inner cell area, and if it is marked with 1 if it is in the outer cell area, if the location information of the mobile terminal is transmitted to the subcarriers assigned to each mobile terminal in the same manner, no coding is required. It is possible to transmit their location information to each mobile terminal as one OFDM symbol.

In addition, four OFDM symbols are transmitted to the rear part of the slot for subcarrier reallocation and adaptive modulation using channel information of the mobile terminal. Here, the reason why four OFDM symbols are used is as follows.

In order to calculate the amount of subcarrier allocation information allocated by the base station to the mobile terminal based on the channel information transmitted by the mobile station to the base station, it is assumed that the maximum number of mobile terminals that can be supported in one sector is 64. It requires low mobility and high data rate, and when the base station distributes the subcarriers owned by the base station to the mobile terminal based on the channel information of each mobile terminal, nine contiguous at a time Assume that subcarriers are allocated.

Then, for a sector having a channel group having 16 frequency reuse rates 1 and a channel group having 16 frequency reuse rates 3, there are (16 * 3 + 16) = 64 units of 9 consecutive subcarriers.

Thus, each sector allocates a set of nine consecutive subcarriers, 64 each to a mobile terminal. Therefore, 6 bits are required to distinguish 64 people, and since 64 must be there, 6 * 64 = 384 bits.

Also, considering 1/2 Turbo + 4 Repetition as the channel coding, it takes a total of 384 * 2 * 4 = 3072 bits. In addition, considering QPSK as modulation, the overhead of the downlink required for transmitting subcarrier allocation information for DCA is 3072 / (768 * 2) = 2 OFDM symbols.

Therefore, the downlink overhead required for DCA and DPA per slot is a total of 3 OFDM symbols, which is the sum of one OFDM preamble used for CINR measurement and two OFDM symbols corresponding to subcarrier allocation information.

Assuming a mobile terminal with low mobility, it is possible to use AMC as well as DCA and DPA. If it has 9 selectable AMC modes and assumes that AMC is possible in units of bins composed of 9 adjacent subcarriers, and assuming that AMC is applied in every slot unit, it is possible to distinguish 9 AMC modes. Taking 4 bits and taking into account 1/2 Turbo + 4 Repetition and QPSK as channel coding and modulation, the additional data required is (4 * 64 * 2 * 4) / (768 * 2) <2 OFDM symbols.

Therefore, the amount of data information required for subcarrier reallocation and adaptive modulation by channel information of the mobile terminal is 4 OFDM symbols.

9, 902 is a first uplink slot structure starting a super frame. The amount of overhead overhead required for DCA and DPA is as follows.

Each mobile station transmits the CINR measurement value for the subchannel group determined by the frequency reuse rate if the mobile station is in the inner cell region for the entire subchannel group through the downlink downlink OFDM preamble for CINR measurement. If it is in the outer cell region, it transmits the CINR measurement for the sub-channel group determined by the frequency reuse rate 3.

In order to calculate the overhead value of the uplink, it is assumed that the mobile station is allocated 24 valid subcarriers for the uplink.

Assuming the mobile terminal is in an inner cell, the mobile station should send a CINR value to the base station for the 16 subchannel groups assigned with frequency reuse rate 1.

The CINR value is divided into 32, and thus, represented by 5 bits, the amount of information to be transmitted to the base station by the mobile station is 16 * 5 = 80 bits.

In addition, considering channel coding and QPSK modulation of 1/2 Turbo + 2 Repetition, the actual number of required OFDM symbols is (80 * 2 * 2) / (24 * 2) <7 OFDM symbols.

10 illustrates a first phase starting a super frame for the dynamic resource allocation scheme and a remaining downlink slot except for a downlink slot, wherein 1001 and 1002 are slots starting a super frame. The structure of uplink and downlink slots for all other cases.

The uplink slot structure 1001 has the same structure as the first uplink slot structure 902 which starts the super frame, and the downlink slot structure 1002 has the same structure as the first downlink slot structure that starts the super frame ( Unlike 901, there is no OFDM symbol indicating the location information of the mobile terminal.

11 and 12 correspond to the total amount of downlink and uplink overhead generated when performing DCA and DPA. It can be seen that the overhead required to be provided by the mobile station and the base station in order to perform DCA and DPA in each slot is considerable.

Therefore, as an alternative to reduce the overhead caused by DCA and DPA, consider performing DCA and DPA once every frame while adaptively modulating every slot, instead of performing adaptive modulation with DCA and DPA every time.

In this case, the downlink and uplink slot structures for performing only adaptive modulation are the same as in (1301) and (1302) of FIG. 13, and the first slot starting every frame simultaneously performs adaptive modulation and DCA and DPA. 10 has a slot structure such as 1001 and 1002, and a slot starting every super frame performs adaptive modulation and DCA and DPA, and transmits the location information of each mobile terminal to the slot of FIG. 901 and 902, respectively.

Therefore, the overall downlink overhead is reduced as shown in FIG. Considering that the overhead of only adaptive modulation in each slot is 3/42 * 100 = 7.1%, the DCA and DPA schemes are added, and an additional overhead of about 1.35% is generated.

In addition, since the uplink overhead needs to transmit only the CINR for the subchannel allocated to each slot, only one OFDM symbol is required. The CINR value for the entire subchannel group is transmitted once per frame for dynamic resource allocation. do.

15 corresponds to overhead of the uplink. Rather than performing dynamic resource allocation and adaptive modulation in every slot unit, a significant amount of uplink overhead can be reduced by simply performing adaptive modulation in every slot unit and dynamically allocating resources in every frame unit.

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, each base station receives the channel status from the mobile terminal providing its service and allocates good channels to each mobile terminal in consideration of the fairness of each mobile terminal, and then powers them according to the status of the allocated channel for each mobile terminal. The dynamic resource allocation algorithm divides one base station into an inner cell region and an outer cell region and allocates a channel having a high frequency reuse rate to a mobile terminal in an outer cell region far from the base station. The throughput and outage probability of the downlink can be improved by applying to the cell planning method of the frequency reuse partitioning scheme to be allocated.

Second, it reduces overhead by applying only AMC as a slot unit and using DAC, DPA and AMC as a unit of slot, and improves downlink throughput by quantitatively analyzing overhead occurring in downlink and uplink. You can do it.

Claims (13)

A channel allocation method of an OFDMA system in which each cell has a cell structure formed of cells consisting of a plurality of sectors, and the cells perform data communication with mobile terminals in a corresponding cell through at least one subchannel group having mutual orthogonality. To Selecting a mobile terminal having the smallest ratio of the sum of the transmission rates allocated so far by the transmission rate requested by the mobile terminal as the preferred channel assignment candidate; And Based on the channel information and distance information of the mobile terminal selected as the preferred channel assignment candidate, the mobile terminal in the inner cell has a first frequency reuse rate, and the mobile terminal in the outer cell has a second frequency reuse rate. Dynamically allocating subcarriers of a corresponding subchannel group by selecting a predetermined subchannel group from among subchannel groups having a predetermined value; Dynamic channel allocation method of a frequency reuse rate division based OFDMA system, characterized in that consisting of. 2. The method of claim 1, wherein the first frequency reuse rate is 1 and the second frequency reuse rate is 3. A power allocation method of an OFDMA system in which each cell has a cell structure formed of cells consisting of a plurality of sectors, and the cells perform data communication with mobile terminals in a corresponding cell through at least one subchannel group having mutual orthogonality. To Subtracting and storing power of a predetermined reference MCS level from power of a mobile terminal having a Signal to Interference and Noise Ratio (SINR) of a predetermined Modulation and Coding Scheme (MCS) level or higher; And Performing dynamic power allocation for each subchannel of the mobile terminal by adding power required for the mobile terminal having the minimum SINR value required to increase the current MCS level among mobile terminals having a SINR below a predetermined MCS level by a minimum; Dynamic power allocation method of the frequency reuse rate division based OFDMA system, characterized in that consisting of. Each cell consists of an inner cell and an outer cell, and each cell has a cell structure formed of cells consisting of a plurality of sectors, and the cells are mobile terminals in the cell through at least one subchannel group having mutual orthogonality. In a dynamic channel and power allocation method of a frequency reuse rate division based OFDMA system for performing data communication with each other, Each base station receives the channel status from the mobile terminal providing its service and takes into account the fairness of each mobile terminal and distance information of the mobile terminal, and has a high SINR (Signal to Interference and Noise Ratio) for each mobile terminal. Assigning subchannel groups; And Allocating power according to a state of a channel allocated to each mobile terminal; A dynamic channel and power allocation method of a frequency reuse rate division scheme based OFDMA system, characterized in that to obtain multiple mobile terminal diversity gain. In a frame structure of an OFDMA system for supporting dynamic resource allocation based on a frequency reuse rate division scheme, A frame structure for supporting dynamic resource allocation in a frequency reuse rate division based OFDMA system, characterized in that one frame consists of four slots and one super frame consists of five frames. The frame structure of claim 5, wherein the slot is configured in 5 ms units. 6. A slot structure of an OFDMA system for supporting dynamic resource allocation based on a frequency reuse rate division scheme, The slot has a preamble for CINR measurement so that the mobile station measures the CINR values of all subchannel groups in every slot, and has an OFDM symbol for transmitting the location information of the mobile station every super frame, and the mobile station has an internal cell region. In order to distinguish whether a mobile station is located in a mobile station or an external cell region, the mobile station has an OFDM symbol for transmitting location information of the mobile station, and a plurality of OFDM symbols for subcarrier reallocation and adaptive modulation using channel information of the mobile station And a slot structure for supporting dynamic resource allocation in an OFDMA system. 8. The slot structure of claim 7, wherein the slot is a first downlink slot starting a super frame. 10. The method of claim 7, wherein the OFDM symbols for subcarrier reallocation and adaptive modulation using the channel information of the mobile terminal are four OFDM symbols. Slot structure. A slot structure of an OFDMA system for supporting dynamic resource allocation based on a frequency reuse rate division scheme, The slot has a preamble for CINR measurement so that the mobile station measures CINR values of all subchannel groups in every slot, has an OFDM symbol for transmitting location information of the mobile station every superframe, and uses channel information of the mobile station. A slot structure for supporting dynamic resource allocation in an OFDMA system, characterized by having a plurality of OFDM symbols for subcarrier reallocation and adaptive modulation. 12. The slot structure of claim 10, wherein the slot is a downlink slot and is a downlink slot other than the first downlink slot starting a super frame. . A slot structure of an OFDMA system for supporting dynamic resource allocation based on a frequency reuse rate division scheme, The slot has a preamble for CINR measurement so that the mobile station measures the CINR values of all subchannel groups in every slot for adaptive modulation in every slot, and provides an OFDM symbol for transmitting location information of the mobile station every superframe. And a slot structure for supporting dynamic resource allocation in an OFDMA system, characterized by having a plurality of OFDM symbols for adaptive modulation. A method for operating a dynamic resource allocation scheme in an OFDMA system based on a frequency reuse rate division scheme, Dynamic resources of the frequency reuse rate division based OFDMA system, which reduces overhead by performing Dynamic Channel Allocation (DCA) and Dynamic Power Allocation (DPA) every frame while performing Adaptive Modulation and Coding (AMC) in every slot. How assignment works.

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