KR100747600B1 - Frequency Reuse Partitioning Based Dynamic Channel Allocation Method for OFDMA/FDD System and Frame Transmission Method - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to a dynamic resource allocation method based on a frequency reuse rate division scheme for an orthogonal frequency division multiple access system and a frame transmission method therefor.

2. The technical problem to be solved by the invention

The present invention selects a cell scheme that divides one cell into an inner cell and an outer cell based on frequency reuse partitioning for an OFDM / FDD system. Dynamic based on frequency reuse rate partitioning scheme to increase system capacity by dynamically allocating sub-channels to users in consideration of channel information fed back from each user and fairness of each user Its purpose is to provide a resource allocation method and a frame transmission method therefor.

3. Summary of Solution to Invention

According to the present invention, there is provided a dynamic resource allocation method based on a frequency reuse rate division method, comprising: a cell division step of dividing a cell based on a frequency reuse rate division method; A user selection step of selecting a channel assignment candidate user to which a channel is allocated by obtaining a ratio (S / R) of a transmission rate assigned by a user located in the divided cell to the present time and a transmission rate requested by the user; Obtaining user distance information for obtaining distance information on the selected channel assignment candidate user; And after checking whether the selected channel allocation candidate user is in an inner cell region or an outer cell region by using the acquired distance information, the frequency reuse rate (FRF) is lower than a threshold among the subgroups. And assigning subcarriers of the selected subgroup by selecting a subgroup to be allocated among subgroups having a frequency reuse rate (FRF) higher than the threshold to a user in an outer cell.

4. Important uses of the invention

The present invention is used in orthogonal frequency division multiple access system.

OFDMA, FDD, frequency reuse rate partitioning, dynamic resource allocation, frame composition, multi-user diversity

Description

Frequency resource allocation method based on frequency reuse rate division method for orthogonal frequency division multiple access system and frequency transmission method therefor {Frequency Reuse Partitioning Based Dynamic Channel Allocation Method for OFDMA / FDD System and Frame Transmission Method}

1 is a diagram illustrating an embodiment of a general frequency reuse rate division scheme;

2 is a diagram illustrating an embodiment of a cell partitioning method in a dynamic resource allocation method based on a frequency reuse rate partitioning scheme according to the present invention;

3 is a diagram illustrating an example of a structure of a radio resource that can be used in a cluster in a dynamic resource allocation method based on a frequency reuse rate division method according to the present invention;

4 is a diagram illustrating an embodiment of a channel allocation method in a dynamic resource allocation method based on a frequency reuse rate division scheme according to the present invention;

5 is a diagram illustrating another embodiment of a channel allocation method in a dynamic resource allocation method based on a frequency reuse rate division scheme according to the present invention;

6 is a flowchart illustrating a dynamic resource allocation method based on a frequency reuse rate division scheme according to the present invention;

7 is a diagram illustrating an embodiment of a downlink frame structure for an OFDMA / DCA platform according to the present invention;

8 is a diagram illustrating an embodiment of basic parameters of a target system in a dynamic resource allocation method based on a frequency reuse rate division method according to the present invention;

9 is a diagram illustrating an embodiment of a slot structure in uplink and downlink superframes according to the present invention;

10 is a diagram illustrating another embodiment of a slot structure in uplink and downlink superframes according to the present invention;

11A and 11B are exemplary diagrams illustrating the total amount of downlink and uplink overhead occurring when performing the dynamic resource allocation method according to the present invention;

12 is a diagram illustrating an embodiment of a slot structure in uplink and downlink frames according to the present invention;

13A and 13B are diagrams illustrating another exemplary embodiment of the overall amount of downlink and uplink overhead occurring when performing the dynamic resource allocation method according to the present invention.

The present invention relates to a dynamic resource allocation method based on a frequency reuse rate division scheme for an orthogonal frequency division multiple access system, and a frame transmission method therefor. More specifically, Orthogonal Frequency Division Multiple Access / Frequency Division Based on the Duplexing system, each base station receives the channel status from the mobile station (terminal) that provides its service and allocates good channels to each mobile station in consideration of fairness of each mobile station to multi-user diversity. The present invention relates to a dynamic resource allocation method for obtaining a multi-user diversity gain and a frame transmission method therefor, wherein the user of an outer cell region far from the base station is divided into an inner cell region and an outer cell region for one base station. To assign channels with high frequency reuse By applying cell reuse scheme of frequency reuse rate division scheme, it improves downlink throughput and outage probability, and proposes downlink and uplink frame structure necessary to operate the dynamic resource allocation method. As an alternative to quantitatively analyze the overhead occurring in the downlink and uplink to provide a more substantial downlink throughput improvement scheme and to reduce the overhead incurred in operating the dynamic resource allocation method. Adaptive modulation and coding (AMC) is applied as a unit, and frequency reuse rate division scheme for an orthogonal frequency division multiple access system, which uses a combination of dynamic channel allocation (DCA) and adaptive modulation and coding (AMC) on a frame basis. The present invention relates to a dynamic resource allocation method based on and a frame transmission method therefor.

Recently, as interest in 4G mobile communication has increased at home and abroad, studies on systems that satisfy the requirements of 4G mobile communication systems are being actively conducted. In particular, orthogonal frequency division multiplexing (hereinafter, referred to as " OFDM ") has attracted attention as one of the methods suitable for the 4G mobile communication system because of its high transmission efficiency and simple channel equalization.

Typical multiple access schemes based on the OFDM scheme include OFDM-FDMA (Frequency Division Multiple Access), OFDM-CDMA (Code Division Multiple Access), and OFDM-TDMA (Time Division Multiple Access). Since the method allocates different subchannels to each user, there is no Multiple Access Interference (MAI) in the intra cell, and the subchannels are allocated to each user according to the required transmission rate and channel status of each user. The number of channels and the modulation level can be effectively changed, which is advantageous for adaptive loading. In addition, the OFDM-FDMA scheme is suitable for the use of a large number of subcarriers, and is effectively applied to a wireless communication system having a large area cell with a large time delay spread. (High Vehicular) has the advantage of having the characteristics suitable for the system has attracted the most attention as a multiple access method of the fourth generation mobile communication system.

On the other hand, there are two types of duplexing methods: frequency division duplex (FDD) and time division duplex (TDD).

The FDD scheme uses different frequency bands for uplink and downlink, and the spacing of these frequency bands is large enough to ignore mutual interference. The FDD scheme is mainly used for macro-cells where time delay spread is relatively large and a high moving speed must be provided.

In the TDD scheme, the uplink and the downlink share the same frequency band, but are distinguished by different times. The TDD scheme can support services having an asymmetric data rate by adjusting the number of uplink and downlink slots constituting a frame, and uplink based on the characteristics of the channel's Reciprocity. ) And downlink channel estimation need not be performed separately. However, the TDD method requires a guard time due to round trip time, and is mainly used for cells such as a micro cell or a hot spot due to a power problem.

4G mobile communication systems are required to support high data rates and to guarantee various quality of service using limited radio resources. This requires the development of cell programming and resource allocation algorithms for increasing cell capacity and effectively allocating radio resources to users.

On the other hand, there is a need for a new service that guarantees mobility and enables high-speed transmission in a wireless environment, and according to such a need, mobile Internet service and mobile high-speed wireless packet data MBWA (Mobile Broadband Wireless Access) in the 2.3GHz band are being developed in Korea. Technology development and standardization work for the service is in progress.

As mentioned above, the OFDM scheme is one of the most attracting technologies because of its high transmission efficiency and simple channel equalization scheme.

Here, the most important characteristic for determining the performance of an OFDM multiple access based system in a cellular environment in which mobility is considered is frequency reuse efficiency. Here, the frequency reuse rate represents the number of frequency sets used per cluster of mobile phone cells. In the mobile phone business, it is important to accommodate the maximum number of subscribers with a limited assigned frequency, and the parameter that indicates indirectly is the frequency reuse index. In addition to improving the reuse rate as a characteristic of the wireless method itself, the service area may be subdivided into cells, micro cells, pico cells, etc., subdividing the antenna sector within the same cell, or using a technology such as a smart antenna. You can also increase the reuse rate.

If the frequency reuse rate is set to "1", since the base station can use all the radio resources, it is most ideal in terms of throughput of the base station. However, the inter-cell interference is set by selecting the frequency reuse rate as "1". Severe performance degradation occurs.

In order to solve the performance degradation problem caused by the inter-cell interference, and to realize the frequency reuse ratio "1", "Flarion" developed Flash-OFDM system, and Flash-OFDM. The system uses a frequency hopping method for changing the OFDM subcarriers into a constant pattern, and uses a Low Density Parity Check (LDPC) channel code to prevent performance degradation due to inter-cell interference. 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 the case of the system maintaining the frequency reuse rate of "1", as the traffic load increases, there is a problem in that performance deterioration occurs at the cell boundary with poor channel conditions due to inter-cell interference. Therefore, interest in frequency reuse partitioning (Frequency Reuse Partitioning) is increasing as a method for not only improving frequency efficiency but also ensuring the performance of users located in regions with poor channel conditions such as cell boundaries.

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

1 is a diagram illustrating an embodiment of a general frequency reuse rate division scheme.

The basic idea of the frequency reuse rate division scheme is that the inner cells 101 and the outer cells are based on the distance of each cell 111 to 117 from the base station to the user terminal or the strength of the pilot signal transmitted from the base station to the user terminal. The cell is divided into an outer cell 102, and different frequency reuse rates are applied to the inner cell 101 and the outer cell 102, respectively.

Referring to the case of FIG. 1, when the user terminal exists in the region of the outer cell 102 (111, 112, 113, 116), a subchannel having a frequency reuse rate of "7" is allocated, and the user terminal is the inner cell 101. In the region 114, 115, and 117, it can be seen that a subchannel having a frequency reuse rate of "1" is allocated.

As described above, the reason for assigning a channel having different frequency reuse rates to the inner cell 101 and the outer cell 102 is generally due to a path loss compared to a terminal far from the base station in case of a terminal close to the base station. Although the channel condition is relatively good because the power loss due to the path loss is small, the terminal near the cell boundary is severely affected by the power loss and the inter-cell interference due to the path loss, resulting in deterioration of performance and data transmission rate. This is because it is an important factor to limit the cell radius of the cellular system.

Therefore, when the frequency reuse rate division scheme is used, the user terminals 114, 115, and 117 in the inner cell 101 region generally have good channel conditions, and thus, low frequency reuse can be guaranteed to ensure an appropriate level of quality of service (QoS). Allocate a channel with a rate to increase the capacity of the cell, and the user terminals 111, 112, 113, and 116 in the outer cell region have a relatively poor channel situation, thereby increasing a cell radius by allocating a channel having a high frequency reuse rate. The user terminal of the boundary can also guarantee the same level of quality of service (QoS) and data rate as the terminal present in the inner cell.

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

If the channel is stationary and the channel response of the user is assumed to be known correctly at the transmitting end, a method combining water-filling and adaptive modulation is known to be optimal. However, water-filling schemes have been mainly studied only in single-user systems or multi-user systems that support fixed resource allocation. For example, time-division multiple access (TDMA) A system using frequency division multiple access (FDMA) allocates a fixed time slot or frequency channel for each user, and then applies an adaptive modulation scheme to each user's channel.

However, there is a problem in that the optimal resource allocation that can be provided by an actual system cannot be achieved by the multi-user OFDM scheme in which the adaptive modulation scheme is applied based on the fixed resource allocation as described above. The reason is that it is used 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 hard to allocate a lot of power. This is because there are many channels that do not exist.

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, each subchannel constituting OFDM becomes deep to all users. The probability of being a deep fading channel is less and less. In other words, as the number of users increases, the user experiences an independent channel, thereby obtaining a multi-user diversity gain.

Therefore, if we dynamically allocate a relatively good channel to each user based on the channel information of all users and apply adaptive modulation schemes using those channels, we will be closer to the optimal resource allocation that the system can provide. Because of this, research on this is necessary.

The present invention has been proposed to solve the above-mentioned problems, and includes an inner cell and an outer cell in which one cell is based on a frequency reuse partitioning scheme for an OFDM / FDD system. In order to increase the cell radius by selecting a cell scheme divided by, and to dynamically allocate a subchannel to a user in consideration of channel information fed back from each user and fairness of each user, An object of the present invention is to provide a dynamic resource allocation method based on the frequency reuse rate division method and a frame transmission method therefor.

Other objects and advantages of the present invention can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

According to an aspect of the present invention, there is provided a dynamic resource allocation method based on a frequency reuse rate division method, comprising: a cell division step of dividing a cell based on a frequency reuse rate division method; A user selection step of selecting a channel assignment candidate user to which a channel is allocated by obtaining a ratio (S / R) of a transmission rate assigned by a user located in the divided cell to the present time and a transmission rate requested by the user; Obtaining user distance information for obtaining distance information on the selected channel assignment candidate user; And after checking whether the selected channel allocation candidate user is in an inner cell region or an outer cell region by using the acquired distance information, the frequency reuse rate (FRF) is lower than a threshold among the subgroups. And a subcarrier allocation step of allocating subcarriers of the selected subgroup by selecting a subgroup to be allocated among subgroups having a frequency reuse rate (FRF) higher than the threshold to a user in an outer cell.

Meanwhile, another method of the present invention is a frame transmission method for a dynamic resource allocation method based on a frequency reuse rate division scheme for an orthogonal frequency division multiple access system, the structure of a frame to include a first predetermined number of slots And a structure of a super frame to include a second predetermined number of frames, wherein channel information necessary for operating a dynamic channel allocation (DCA) is determined according to the rate of change of the channel, Characterized in that the transmission from the base station to the mobile station or the reverse (the mobile station to the base station) in units of the super frame.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, whereby those skilled in the art may easily implement the technical idea of the present invention. There will be. In addition, in describing the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a diagram illustrating an embodiment of a cell partitioning method in a dynamic resource allocation method based on a frequency reuse rate partitioning scheme according to the present invention, and orthogonal frequency division multiple access / dynamic channel allocation (OFDMA / DCA) platform Represents basic cell planning for.

The cell partitioning method in the dynamic resource allocation method based on the frequency reuse rate division method according to the present invention considers a regular hexagonal cell structure 201, and each cell 201 is divided into three sectors (1, 2, 3). Is done. In addition, the concept of the frequency reuse rate division scheme is introduced into each sector so that each sector 1, 2, 3 is divided into an inner cell region 221 and an outer cell region 222. In addition, the entire network is divided into several clusters 202, each of which consists of three sectors belonging to three different cells and neighboring each other.

3 is a diagram illustrating an embodiment of a radio resource that can be used in a cluster in the dynamic resource allocation method based on the frequency reuse rate division method according to the present invention.

As shown in FIG. 3, in the frequency domain, the entire band is composed of 32 subchannel groups (subgroups) (301). It is assumed that each subchannel group is composed of 27 subcarriers. A defined set of subcarriers 303 is defined as bin 302.

One of the nine subcarriers 303 constituting the bin 302 is a pilot subcarrier that can be used for various purposes such as channel estimation and signal-to-interference plus noise ratio (SINR) measurement. In addition, it is assumed that each subcarrier transmission power is fixed. Different sub-channel groups 301 may use different frequency reuse rate values, and one of two values "1" and "3" may be used as the frequency reuse rate value. If the frequency reuse rate of a subchannel group 301 is "1", all three sectors of the cluster may use all subcarriers of this group. In the case of a subchannel group having a reuse rate of "3", only one of three bins 302 constituting one subchannel group is distributed to three sectors forming a cluster.

The user feeds back the average Signal-to-Interference plus Noise Ratio (SINR) value for all sub-channel 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 signal-to-interference plus noise ratio (SINR) value to the user based on the feedback information to obtain a multi-user diversity gain. do.

The basic method of the dynamic channel allocation method according to the present invention is as follows.

In order to assign a channel to a user, two things should be considered. The first is the ratio of the transmission rate that the user has been allocated so far and the transmission rate required by the user. In other words, the dynamic channel allocation method preferentially allocates the channel to the user having the smallest ratio of the sum of the allocated transmission rates divided by the transmission rate requested by the user.

The second consideration is whether the user is in the inner cell area or the outer cell area.

The basic method of the frequency reuse rate division method allocates a channel having a frequency reuse rate lower than a threshold (for example, 2) to a terminal near a base station, and assigns a channel having a frequency reuse rate higher than a threshold to a terminal far from the base station. Therefore, by applying the above method to the dynamic channel allocation method, the terminal close to the base station has a sub-channel whose frequency reuse rate is "3" among the sub-channel groups whose frequency reuse rate is "1". Among the groups, the subcarrier 303 of the good subchannel group 301 having a high signal-to-interference plus noise ratio (SINR) is dynamically allocated based on the channel condition of the user.

4 is a diagram illustrating an embodiment of a channel allocation method in a dynamic resource allocation method based on a frequency reuse rate division scheme according to the present invention.

In FIG. 4, the user "1" 410 having the smallest S / R ratio obtained by dividing the sum of the transmission rates allocated so far by the user requested rate for each user 410, 420, 430, and 440 is channeled. It can be seen that it is selected as an allocation candidate.

5 is a diagram illustrating another embodiment of a channel allocation method in a dynamic resource allocation method based on a frequency reuse rate division scheme according to the present invention.

In FIG. 5, among the sub-channel groups having the frequency reuse rate (FRF) "1" for the user in the inner cell using the channel information and the distance information of the user "1" 510, the frequency reuse rate for the user in the outer cell ( FRF) A subchannel group having the best characteristics is selected among the subchannel groups "3" and the subcarriers of the subchannel group are allocated.

That is, the channel is allocated to each user by repeating the process of using the ratio (S / R) obtained by dividing the sum of transmission rates allocated to the transmission rate requested by the user and the distance information of the user.

6 is a flowchart illustrating an embodiment of a dynamic resource allocation method based on a frequency reuse rate division scheme according to the present invention.

First, a cell is divided based on a frequency reuse rate dividing scheme (601), and a ratio (S / R) of a transmission rate requested by a user to a current rate allocated by a user located in the divided cell to the present time is calculated. In operation 602, a channel allocation candidate user to be allocated is selected.

Subsequently, after obtaining the distance information on the selected channel allocation candidate user (603), it is determined whether the channel allocation candidate user to be allocated the current channel is in the inner cell region or the outer cell region, and then the frequency in the inner cell Among the subchannel groups having a reuse rate (FRF) of "1", the user in the outer cell selects a subchannel group having the best characteristics among the subchannel groups having a frequency reuse rate (FRF) of "3" (604). The subcarriers of the subchannel group are allocated (605).

7 is a diagram illustrating an embodiment of a downlink frame structure for an OFDMA / DCA platform according to the present invention.

The super frame 701 may be composed of five frames 702, and one frame 702 may be configured as four slots 703 of 5 ms units. That is, a frame structure is formed to include four slots, and a super frame structure is formed to include five frames.

The channel information required to operate the dynamic channel allocation (DCA) is based on the rate of change of the channel, and is transmitted from the base station to the mobile station or vice versa in each slot 703, frame 702, or super frame 701 unit. The base station).

In order to calculate the overhead required to perform dynamic resource allocation, the target system must be specified.

8 is a diagram illustrating an embodiment of basic parameters of a target system in a dynamic resource allocation method based on a frequency reuse rate division method according to the present invention.

As shown in FIG. 8, the basic parameters of the target system considered in the present invention include the number of subcarriers 801, the number of effective subcarriers 802, the number of pilot subcarriers 803, and the sampling frequency 804. , Number of subgroups 805, number of subcarriers per subgroup 806, number of subgroups with frequency reuse rate "1" 807, and number of subgroups with frequency reuse rate "3" 808 Basic parameters of the target system.

Since the dynamic resource allocation is performed every slot in order to calculate the amount of overhead according to the dynamic resource allocation, the mobile station feeds back channel information for all groups to the base station on a slot basis, and the base station provides a channel to the mobile station on a slot basis. The newly allocated subcarrier location is transmitted according to the information. In addition, the position information of the mobile station is transmitted once in a super frame unit. Then, overhead to be transmitted by the base station in order to perform dynamic resource allocation can be classified into the following three types.

The first is orthogonal frequency division multiplexing provided by the base station to allow the mobile station to measure the carrier-to-interference-and-noise-rate (CINR) of all subchannel groups. (OFDM) Preamble (in units of slots), and the third is allocation information (in units of slots) of subcarriers allocated by the base station to the mobile station.

FIG. 9 is an exemplary diagram illustrating slot structures in uplink and downlink superframes according to the present invention, and illustrates a first uplink and downlink slot structure starting a superframe.

First, there is a first downlink slot structure 910 that starts a super frame.

The first downlink slot structure 910 that starts a super frame includes a downlink data traffic fields 911 and 914, a reference frequency reuse field (912) and a distance information broadcast. A (Distance Metric Broadcasting) field 913 and a Subcarrier Allocation Broadcasting field 915.

In each slot, one preamble for carrier-to-interference-and-noise-ratio (CINR) measurement is used by the mobile station to measure carrier-to-interference-and-noise-ratio (CINR) values of all subgroups. Included in the allocation broadcast field 915, one OFDM symbol is used in the distance information broadcast field 913 to transmit the position information of the mobile station in each sector every super frame.

Whether the mobile station is in the inner cell region or the outer cell region is included in the reference frequency reuse rate broadcast field 912, and the mobile station may perform dynamic resource allocation in the subgroup having frequency reuse rate (FRF) "1". Or whether to perform dynamic resource allocation in a subgroup of frequency reuse rate (FRF) "3".

If the mobile station 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, separate coding is performed for transmitting the same location information of the mobile station to subcarriers assigned to the respective mobile stations. It is possible to transmit their position information to each mobile station as one OFDM symbol without. In the latter part of the slot, a subcarrier allocation broadcast field 915 is provided so that four OFDM symbols are transmitted for subcarrier reallocation and adaptive modulation using channel information of the mobile station.

On the other hand, the reason why the four sub-carrier allocation broadcast field 915 is used as described above is as follows.

In order to calculate the amount of subcarrier allocation information allocated by the base station to the mobile station based on the channel information transmitted by the mobile station to the base station, it is assumed that the maximum number of users that can be supported in one sector is "64", and the mobile station has low mobility ( It demands low mobility and high data rate, and when the base station distributes the subcarriers of the base station to the mobile station based on the channel information of each mobile station, 9 consecutive subcarriers at a time Suppose you assign them. Then, for a sector with 16 groups of frequency reuse (FRF) "1" and 16 groups of frequency reuse (FRF) "3", 64 (16) units of 9 consecutive subcarriers X 3 + 16 = 64). Each sector thus allocates a set of 64 nine consecutive subcarriers to the mobile station. Therefore, 6 bits are required to distinguish 64 people, and 64 bits are required, so "6 x 64 = 384" bits are required. Also, considering "1/2 Turbo + 4 Repetition" as the channel coding, a total of "384 x 2 x 4 = 3072 bits" is required. Also, considering quadrature phase shift keying (QPSK) as modulation, the overhead of downlink required for subcarrier allocation information transmission for dynamic channel allocation (DCA) is " 3072 / (768 × 2) = 2 OFDM Symbols ". to be.

Therefore, the downlink overhead required for dynamic channel allocation (DCA) per slot corresponds to one OFDM preamble and subcarrier allocation information used for carrier-to-interference-and-noise-ratio (CINR) measurement. The sum of two OFDM symbols is a total of 3 OFDM symbols.

Assuming a user with low mobility, not only dynamic channel allocation (DCA) but also adaptive modulation and coding (AMC) can be used together. If it has 9 selectable adaptive modulation and coding (AMC) modes and it is assumed that adaptive modulation and coding (AMC) is possible in units of bins composed of 9 adjacent subcarriers, each slot unit If we assume that adaptive modulation and coding (AMC) is applied, it takes 4 bits to distinguish nine adaptive modulation and coding (AMC) modes, and it is " 1/2 Turbo + " as channel coding and modulation (AMC). Considering 4 Repetition and Quadrature Phase Shift Keying (QPSK), the additional required data amount is "(4 x 64 x 2 x 4) / (768 x 2) <2 OFDM symbols". Accordingly, the amount of data information required for subcarrier reallocation and adaptive modulation by channel information of the mobile station is 4 OFDM symbols.

Next, the first uplink slot structure 920 starting the super frame will be described.

The first uplink slot structure 920 that initiates the super frame is uplink data traffic fields 921 and 923, and CSI feedback for frequency reuse rates 1 or 3 (CSI Feedback for FRF 1 or 3). Field 922).

The amount of overhead required for dynamic channel allocation is as follows.

Each user has an OFDM preamble for carrier-to-interference-and-noise-ratio (CINR) downlink from the downlink, and if the mobile station is in the inner cell region for the entire subgroup, frequency reuse ratio (FRF) " Carrier-to-Interference-and-Noise-Ratio (CINR) measurements for subgroups defined as 1 " are transferred via the CSI Feedback for FRF 1 or 3 field 922 for frequency reuse 1 or 3. CSI feedback for frequency reuse rate 1 or 3, with carrier-to-interference-and-noise-ratio (CINR) measurements for subgroups defined as frequency reuse rate (FRF) "3," if in the outer cell region. It transmits through the (CSI Feedback for FRF 1 or 3) field 922.

Assume that the mobile station has been allocated 24 valid subcarriers for the uplink to calculate the overhead value of the uplink.

Assuming the mobile station is in an inner cell, the mobile station should send a carrier-to-interference-and-noise-ratio (CINR) value to the base station for the 16 subgroups assigned frequency reuse factor (FRF) " 1 ". do. The Carrier-to-Interference-and-Noise-Ratio (CINR) value is divided into 32, and thus, represented by 5 bits, the amount of information that the mobile station should transmit to the base station is "16 x 5 = 80" bits. Also, considering channel coding of 1/2 Turbo + 2 Repetition and Quadrature Shift Keying (QPSK), the actual number of OFDM symbols required is " (80 × 2 × 2) / (24 × 2) <7 OFDM Symbols ".

FIG. 10 is a diagram illustrating another embodiment of a slot structure in uplink and downlink superframes according to the present invention, and shows uplink and downlink slot structures in all cases other than the slot in which the superframe starts.

In the case of an uplink slot, the slot structure 920 for starting a super frame and the slot structure 1020 for a slot other than the slot for starting a super frame match, and in the case of a downlink slot, the slot structure 910 for starting a super frame is identical. Otherwise, the slot structure 1010 except for the slot starting the super frame has no OFDM symbol for the distance information broadcast field 913 indicating the position information of the mobile station.

11A and 11B are exemplary diagrams illustrating the total amount of downlink and uplink overhead generated when performing the dynamic resource allocation method according to the present invention.

It can be seen that there is a significant amount of overhead that must be provided by the mobile station and the base station to perform dynamic resource allocation in every slot. Therefore, as an alternative to reduce the overhead caused by dynamic resource allocation, dynamic resource allocation is performed once every frame while adaptive modulation is performed every slot, rather than dynamic resource allocation and adaptive modulation each time.

12 is a diagram illustrating an embodiment of a slot structure in uplink and downlink frames according to the present invention.

To reduce the overhead of dynamic resource allocation, instead of combining dynamic resource allocation and adaptive modulation every time, downlink slots that only perform adaptive modulation in case of dynamic resource allocation once per frame while adaptively modulating every slot ( 1201) and the uplink slot 1202, and the first slot starting every frame performs adaptive modulation and dynamic resource allocation at the same time, so that the slot other than the slot starting the super frame in the downlink of FIG. Slot structure 1010 and the slot structure is the same as the slot structure 1020 in the case of starting the super frame in the uplink, the slot starting every super frame performs the adaptive modulation and dynamic resource allocation, Since the location information of each user is transmitted here, start the super frame in the downlink and uplink Has a slot structure such as a slot structure (910, 920).

13A and 13B are diagrams illustrating another exemplary embodiment of the overall amount of downlink and uplink overhead occurring when performing the dynamic resource allocation method according to the present invention.

The overall downlink overhead is reduced as in FIG. 13A below. Here, considering that the overhead of only adaptive modulation in each slot is "3/42 * 100 = 7.1%", it can be seen that an additional overhead of about 1.35% is generated to add a dynamic resource allocation scheme. .

In addition, the overhead of the uplink is 1 OFDM symbol because only the carrier-to-interference-and-noise-rate (CINR) for the subchannel allocated to each slot is transmitted. Carrier-to-Interference-and-Noise-Ratio (CINR) values for all subgroups are transmitted for allocation.

FIG. 13B corresponds to overhead of an uplink and is not a method of dynamically allocating and adaptively modulating every slot, but merely by performing adaptive modulation every slot and dynamically allocating resources every frame. Significantly uplink overhead can be reduced.

As described above, the method of the present invention may be implemented as a program and stored in a recording medium (CD-ROM, RAM, ROM, floppy disk, hard disk, magneto-optical disk, etc.) in a computer-readable form. Since this process can be easily implemented by those skilled in the art will not be described in more detail.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings.

As described above, the present invention selects a cell scheme that divides one cell into an inner cell and an outer cell based on a frequency reuse partitioning scheme for an OFDM / FDD system. Therefore, the cell radius is increased, and the capacity of the system can be increased by dynamically allocating sub-channels to users in consideration of channel information fed back from each user and fairness of each user.

In other words, when applied to an OFDMA / FDD system and the like, the multi-user diversity gain obtained from dynamic resource allocation may increase the downlink sector throughput while increasing the downlink sector throughput even if additional overhead is considered. Outage Probability can be reduced.

Claims (8)

In the dynamic resource allocation method based on the frequency reuse rate division method, Dividing the cell based on the frequency reuse rate dividing scheme; A user selection step of selecting a channel assignment candidate user to which a channel is allocated by obtaining a ratio (S / R) of a transmission rate assigned by a user located in the divided cell to the present time and a transmission rate requested by the user; Obtaining user distance information for obtaining distance information on the selected channel assignment candidate user; And After confirming whether the selected channel allocation candidate user is in an inner cell region or an outer cell region by using the acquired distance information, among the subgroups having a frequency reuse rate (FRF) lower than a threshold for the user in the inner cell, A subcarrier allocation step of allocating subcarriers of the selected subgroup by selecting a subgroup to be allocated among subgroups having a frequency reuse ratio (FRF) higher than the threshold to a user in an outer cell; Dynamic resource allocation method comprising a. The method of claim 1, The cell division step, Each cell is divided into three sectors, and the concept of frequency reuse ratio division is introduced into each sector, and each sector is divided into an inner cell region or an outer cell region, and the entire network is divided into a predetermined number of clusters. , Wherein each cluster is composed of three sectors belonging to three different cells and neighboring each other. The method of claim 1, The subgroup, In the frequency domain, the entire band is divided into a predetermined number of subgroups, each subgroup consisting of a set of bins which are a set of a plurality of consecutive subcarriers, wherein each bin is a channel estimation, A dynamic resource allocation method comprising a pilot subcarrier that can be used for the purpose of including signal-to-interference plus noise ratio (SINR) measurement. The method according to any one of claims 1 to 3, The user selection step, And assigning a channel to a user having the smallest ratio of the transmission rate (S / R) requested by the user to the present from the current position to the present. A frame transmission method for a dynamic resource allocation method based on a frequency reuse rate division scheme for an orthogonal frequency division multiple access system, The structure of the frame is formed to include the first predetermined number of slots, and the structure of the super frame is formed to include the second predetermined number of the frames, and the channel information necessary for operating the dynamic channel allocation (DCA) is obtained. And transmitting from the base station to the mobile station or the reverse direction (the mobile station to the base station) in units of the slots, the frames, or the super frames according to the change rate. The method of claim 5, The super frame, In the case of the first downlink slot that starts the super frame, one carrier-to-carrier for each mobile station to measure carrier-to-interference-and-noise-ratio (CINR) values of all subgroups in each slot. Interference-and-Noise-Ratio measurement preamble, one OFDM symbol for transmitting the position information of the mobile station in each sector every super frame, whether the mobile station is in the inner cell region or the outer cell region And a symbol for subcarrier reallocation and adaptive modulation using channel information of the mobile station. The method of claim 6, The super frame, In the case of downlink slots other than the first downlink slot starting the super frame, there is no one OFDM symbol for transmitting the position information of the mobile station in each sector, and the first uplink slot starting the super frame does not exist. And a symbol for transmitting a carrier-to-interference-and-noise-ratio (CINR) measurement value for the subgroup at a preset frequency reuse rate (FRF) value. The method according to any one of claims 5 to 7, The slot is, To reduce the overhead of performing dynamic resource allocation and adaptive modulation per slot, instead of combining dynamic resource allocation and adaptive modulation every time, dynamic resource allocation is performed once per frame, with each channel being adaptively modulated. The slot initiating a frame performs adaptive modulation and dynamic resource allocation and transmits location information of each user.

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