KR20080083460A - Apparatus and method for dynamic channel allocation in multi-cell downlink system - Google Patents

Abstract

A method for dynamically allocating channels in a multi-cell downlink system is provided to increase performance about throughput per unit area as compared to other channel allocation techniques by allocating a channel in consideration of a mobile terminal's interference range dependent on the distance between a base station and the mobile terminal. A base station, if a channel allocation request is detected, checks whether unassigned channels exist(600,602). If unassigned channels exist, the base station selects one of the unassigned channels(604). On the assumption that the selected channel is allocated, the base station judges whether the selected channel has influence on mobile terminals which belong to neighbor base stations(606). In case it is judged that any of the mobile terminals which belong to neighbor base stations is not influenced by the selected channel, the base station allocates the selected channel(610). Then the base station transmits downlink channel allocation information to the neighbor base stations, including allocated channel information(612).

Description

Apparatus and method for dynamic channel allocation in multi-cell downlink system {APPARATUS AND METHOD FOR DYNAMIC CHANNEL ALLOCATION IN MULTI-CELL DOWNLINK SYSTEM}

1 is a diagram illustrating an interference region according to a distance between a base station and a terminal in an environment of a general multi-cell downlink system;

2 is a diagram illustrating a configuration of a base station apparatus in a multi-cell downlink system for allocating channels in consideration of an interference region according to an embodiment of the present invention;

 3 is a diagram illustrating a configuration of a scheduler in a base station apparatus of a multi-cell downlink system for allocating channels in consideration of an interference area according to an embodiment of the present invention;

4 is a diagram illustrating information transmitted by a base station and a terminal to a neighboring base station of a multi-cell downlink system according to an embodiment of the present invention;

5 illustrates a structure of a frame transmitted / received by a base station of a multi-cell downlink system according to an embodiment of the present invention;

6 is a flowchart illustrating a process of allocating a channel in consideration of interference effects in a base station of a multi-cell downlink system according to an embodiment of the present invention;

7 is a flowchart illustrating a process of allocating a channel in consideration of interference effects and channel conditions in a base station of a multi-cell downlink system according to an embodiment of the present invention;

8 illustrates a multi-cell downlink system including 37 cells having three sectors each;

9 is a graph illustrating performance of channel allocation in a multi-cell downlink system according to an embodiment of the present invention.

The present invention relates to an apparatus and method for allocating a dynamic channel in a multi-cell downlink system. In particular, the present invention relates to a method for allocating a channel in a base station of a multi-cell downlink system to measure an interference degree of a terminal belonging to a neighboring base station. An apparatus and method for allocating a channel so as not to interfere with a terminal.

One of the major issues considered in the next generation mobile communication system is the selection of multiplexing technology that can effectively distribute the limited frequency, time, and space among users. This is because the selection of the multiplexing technique is important for determining the quality of service (hereinafter referred to as 'QoS').

In recent years, Orthogonal Frequency Division Multiplex Access (hereinafter referred to as 'OFDMA') is a frequency division multiple access (hereinafter referred to as 'FDMA') scheme in which all users use high speed downlink. Fast Fourier Transform (FFT) The space is shared and subcarriers can be allocated according to the user's data rate.

The OFDMA has no user-interference in the same cell, but the user outside the cell has a high influence of the interference of the neighboring cell, and thus has a high probability of not satisfying the user QoS. In other words, the OFDMA technique has problems of complex resource allocation and low frequency usage efficiency due to an increase in the number of users, and therefore, a study for reducing neighbor cell interference is needed.

There are two conventional resource management techniques for channel allocation. The first is a technique for dealing with channel allocation in a single cell environment. The research of the initial OFDMA system corresponds to this, and there are studies for allocating power to several subchannels to obtain maximum throughput or allocating minimum power while satisfying a given rate condition. Second, there are studies to reduce intercell interference in a multicell environment. Here, too, there are two main directions: centralized and distributed. The centralized method is a method in which a controller grasps a resource allocation state of a network to determine an optimal allocation and then broadcasts the result. The centralized method includes a frequency reuse factor (FRF) technique for determining available channels for each cell. As a distributed method, many studies have been conducted to reduce interference by power control by collecting only minimum information of each cell.

Many technologies that deal with resource management in a single cell environment are not immediately applicable in a multicell environment. This is because there is insufficient consideration of interference from adjacent cells. Among the techniques for reducing the inter-cell interference in a multi-cell environment, the centralized method is a problem that it is not easy to apply in real time because the overhead of the state information exchanged between cells and the complexity of resource allocation calculation is complicated. In addition, as a problem applied to a distributed scheme, the actual OFDMA system does not perform power control in the downlink due to low performance improvement compared to the difficulty in implementation, but the conventional techniques try to reduce inter-cell interference through power control. On the other hand, the techniques for adjusting the FRF have a problem that is not adaptive to changes in the channel environment and the user.

SUMMARY OF THE INVENTION An object of the present invention is to provide a dynamic channel allocation apparatus and method for a multi-cell downlink system.

Another object of the present invention is to provide an apparatus and method for allocating a dynamic channel considering an interference region in a multi-cell downlink system.

Another object of the present invention is to provide an apparatus and method for allocating a channel in consideration of an interference area of a terminal belonging to a neighboring base station when allocating a channel in a base station of a multi-cell downlink system.

According to a first aspect of the present invention for achieving the above objects, a multi-cell downlink system for dynamically allocating a channel includes a terminal for transmitting an uplink frame in which information about the allocated channel is inserted, and a channel assignment. When requested, the terminal receives downlink channel allocation information received from neighboring base stations and an uplink signal transmitted by a terminal located at an adjacent cell boundary, and the data is transmitted by using the downlink channel allocation information and the uplink signal of the terminal. It is characterized by allocating channel by reducing interference effect between terminals.

According to a second aspect of the present invention for achieving the above objects, a base station of a multi-cell downlink system for dynamically allocating channels selects a channel to be allocated from among channels that are requested to allocate a channel and not allocated. And a channel interference measuring unit for measuring whether the channel selected by the channel selecting unit affects a neighboring terminal, which is a terminal included in a neighboring base station, and the channel interference measuring unit, as a result of the measurement. And a channel allocator for allocating the selected channel.

According to a third aspect of the present invention for achieving the above objects, a dynamic channel allocation method of a base station in a multi-cell downlink system, if a channel allocation request is made, a process of checking whether there is an unallocated channel, Selecting a channel to be allocated when an unallocated channel exists; measuring interference of the selected channel on terminals included in neighboring base stations before allocating the selected channel; and determining a measurement result to allocate a channel It characterized in that it further comprises a process.

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

The present invention relates to a dynamic channel allocation apparatus and method for reducing interference to terminals belonging to a neighboring base station by measuring an interference area of a terminal belonging to a neighboring base station when allocating a channel in a base station of a multi-cell downlink system.

Prior to the detailed description of the present invention will be described with reference to Figure 1 below for the interference region of the terminal that varies depending on the distance between the base station and the terminal in a multi-cell downlink system. 1 is a diagram illustrating an interference region according to a distance between a base station and a terminal in an environment of a general multi-cell downlink system.

Referring to FIG. 1, an example of the multi-cell downlink system environment includes base stations 110 to 170 divided by identifiers of BS1 to BS7, and the base station 110 includes two terminals separated by identifiers of MT1 to MT2. (111, 112).

In this case, an interference range, which is an area where each of the terminals 111 and 112 may be interfered with by a neighboring base station, is affected by the distance between the terminal and the base station. The size of the area has a small area and conversely, the longer the distance between the terminal and the base station, the larger the size of the interference area. The circle indicated by the dotted line in FIG. 1 indicates the interference area of the terminal 111 close to the base station 110, and the circle indicated by the dashed line indicates the terminal that is relatively far from the base station 110. An interference region of 112 is shown.

That is, in the case of the terminal 111, since the interference region indicated by the dotted line belongs completely to the base station 110 receiving the service, even if the neighboring base station allocates the same channel, the terminal 111 is not affected. However, in the case of the terminal 112 located in the neighboring cell, interference occurs when the same channel is allocated by the neighboring base stations 120 to 170 of the interference region indicated by the dashed-dotted line. When allocating channels within cells using the same frequency, collisions may occur when the same channel is allocated between adjacent cells by randomly assigning among a plurality of channels. In the case of OFDMA communication, it is inefficient to allocate the same channel in the same cell. However, in the case of different cells, it is possible to allocate the same channel when allocating channels to minimize interference.

Then, referring to the measuring method of the interference region, the interference region may be measured by Equation 1 below.

Where R _I is the radius of the interference region, R is the distance between the base station and the terminal, SINR _th is the limit value of the Signal to Interference plus Noise Ratio (SINR), and α is the path loss index. .

2 is a diagram illustrating a configuration of a base station apparatus in a multi-cell downlink system for allocating channels in consideration of an interference region according to an exemplary embodiment of the present invention. Referring to FIG. 2, the base station apparatus of the present invention includes a scheduler 210, a modulator 220, a digital-to-analog converter 230, and an RF processor 240.

When the scheduler 210 receives a channel allocation request, the scheduler 210 receives downlink channel allocation information received at a predetermined interval from neighboring base stations and an uplink signal transmitted by a terminal located in an adjacent cell (hereinafter, referred to as a "neighbor terminal"). For example, by using the downlink channel allocation information such as a pilot signal transmitted from a terminal and an uplink reception signal of the neighboring terminal, a channel having no interference effect is selected and allocated to the neighboring terminal and transmitted to the allocated channel. Data is allocated and output to the modulator 220. In this case, the uplink signal of the neighboring terminal received by the base station is an uplink signal of the neighboring terminal that can be received by the base station, and is not an uplink of all terminals included in the neighboring base station. For example, a transmission signal of a neighboring terminal that can be received by a neighboring base station may use an existing pilot signal without transmitting an additional signal. Each base station does not receive pilot signals transmitted from terminals belonging to other base stations other than neighboring terminals. Alternatively, the neighboring terminal selects not only the base station in service by measuring the strength of the downlink signal, that is, the SINR, etc. of the neighboring base station, but also several base stations with a high SINR value, and allocates a separate channel to transmit the measured SINR value to the selected base station. There is also a method of transmission. The scheduler 210 selects and allocates a channel having no interference effect to the neighboring terminal by using the downlink channel allocation information and the uplink of the neighboring terminal. Through the configuration will be described later.

The modulator 220 receives data allocated to each channel from the scheduler 210 and modulates the modulator 220 according to a predetermined modulation scheme. Here, the modulation scheme may be Quadrature Phase Shift Keying (QPSK), 16 Quadrature Amplitude Modulation (16QAM), 64QAM, or the like.

The digital-to-analog converter 230 converts the output from the modulator 220 into an analog baseband signal and outputs it to the RF processor 240. The RF processor 240 converts the baseband signal provided from the digital-to-analog converter 230 into an RF signal by transmitting the frequency upward and transmits the RF signal through an antenna.

3 is a diagram illustrating a configuration of a scheduler in a base station apparatus of a multi-cell downlink system for allocating a channel in consideration of an interference region according to an exemplary embodiment of the present invention.

Referring to FIG. 3, the scheduler 210 of the present invention includes a channel selector 312, a channel interference measurement unit 314, and a channel allocator 316.

When the channel selector 312 receives a request for channel allocation, the channel selector 312 selects one of the unassigned channels and provides the channel interference measurer 314. In this case, when selecting one of channels not allocated by the channel selector 312, a channel having a good channel state may be selected. Here, a good channel is a channel whose signal-to-interference plus noise ratio (SINR) value of the channel is higher than the reference SINR value preset by the experiment to distinguish the channel state.

The channel interference measurement unit 314 is a channel provided from the channel selection unit 312 by using downlink channel allocation information received from neighboring base stations at predetermined intervals and a receivable uplink signal transmitted from the neighboring terminal. Check whether the peripheral terminal is affected by interference, and if it is confirmed that the peripheral terminal is interfered with, the channel selector 312 is requested to select another channel, and if it is determined that the peripheral terminal is not interfered with, the channel is allocated. The selected channel is provided to the unit 316. The configuration of the uplink transmitted by the neighboring terminal will be described below with reference to FIG. 5.

In the channel interference measuring unit 314, the method of measuring interference using downlink channel allocation information of the neighbor base station and the uplink of the neighboring terminal is allocated when the channel interference measuring unit 314 randomly selects a channel. The SINR value of the neighboring terminal using the same channel changed by the channel is measured, and the SINR value of the neighboring terminal is compared with the measured interference reference SINR value, which is a reference for determining whether the interference is measured. If the SINR is greater than the interference reference SINR value, the neighboring terminal is determined not to be interfered with by the selected channel. If the SINR value of the peripheral terminal is less than or equal to the interference reference SINR value, the neighboring terminal is determined to be interfered by the selected channel. do. The predetermined SINR value is a variable value of the system, and a value acting as a variable may be determined in consideration of a data type (data, voice), a variable value for each time zone in which a service is used.

Then, a method of determining whether the channel interference measuring unit 314 belongs to the interference region of the neighboring terminal, which is a terminal included in the neighboring base station, will be described below using Equation 3 through Equation 2.

Considering a case where base station i has a transmission on channel c, and base station j attempts to allocate channel c, when base station j allocates channel c, the SINR of the neighboring terminal included in base station i is expressed by Equation 2 below. same.

Here, SIRN _i is the SINR value of the terminal to which the channel to be allocated included in the neighboring base station i, P ₀ is the strength of the data signal transmitted to the terminal included in the neighboring base station i, g _{ii and} the neighboring base station i G _ij is the channel gain of the base station j to which the channel is to be allocated and the terminal to which the channel to be assigned to the neighboring base station i is assigned, and I _i is the neighbor base station i N _i is the interference already received by the terminal to which the channel to be allocated is included, and N _i is the Gaussian noise of the terminal to which the channel to be allocated included in the neighboring base station i is allocated.

The base station j to allocate the channel needs to know the channel gains g _ii and g _ij in order to determine whether the base station j has interference with the neighboring terminals. At this time, N _i can be assumed to be negligibly small compared to interference, and I _i can be assumed to have a small value if the proposed channel allocation reduces the amount of interference sufficiently, so that it does not have a large effect. .

Therefore, Equation 2 may be changed to Equation 3 below.

Here, SIRN _i is the SINR value of the terminal to which the channel to be allocated included in the neighboring base station i, P ₀ is the strength of the data signal transmitted to the terminal included in the neighboring base station i, g _{ii and} the neighboring base station i G _ij is the channel gain of the base station j to which the channel is to be allocated and the terminal to which the channel to be allocated to the neighboring base station i is allocated, P _M is the neighbor base station i The strength of the pilot signal inserted into the preset position of the uplink by the terminal to which the channel to be allocated is included in the uplink, q _j is the terminal allocated to the channel to be allocated to the neighboring base station i to the preset position of the uplink Signal strength when the inserted pilot signal is received by the base station j.

Q _j in Equation 3 may be measured by Equation 4 below in the system.

Here, q _j is the signal strength when the base station j receives a pilot signal inserted in the uplink preset position by the terminal that is allocated the channel to be included in the neighboring base station, P _M is the allocation included in the neighboring base station The strength of the pilot signal inserted by the terminal assigned to the channel to the predetermined position of the uplink, g _lj is the channel gain of the terminal assigned to the channel to be assigned to the base station j and the neighboring base station l to allocate the channel, S Is a set of neighboring base stations.

When q _j is measured using Equation 4 and substituting this into Equation 3 to determine whether the selected channel is interference, the base station j to which the channel is to be allocated is interference area of each terminal belonging to S. Although not belonging to the above equation, the result of Equation 3 may appear as an interference larger than a predetermined interference reference SINR value. This is because the channel usage of the base station j is a modest interference but interferes with many peripheral terminals belonging to the S. Therefore, in this case, the channel is not used according to the determination using Equation 3.

값이 기설정된 간섭기준 SINR값보다 클 경우에 주변 단말기에 간섭영향을 끼치지 않음으로 판단한다.In other words, in Equation 2, Equation 4 is used, the channel interference measurement unit 314 is configured to determine neighboring terminals by the selected channel.

If the value is larger than the predetermined interference reference SINR value, it is determined that the interference does not affect the neighboring terminals.

The channel allocator 316 allocates a channel provided from the channel interference measurer 314 and generates downlink channel allocation information, which is information on channel allocation, and transmits the downlink channel allocation information to the neighbor base stations.

Next, the downlink channel allocation information of the neighbor base station and the uplink transmission transmitted by the neighbor terminal will be described below with reference to FIG. 4. 4 is a diagram illustrating information transmitted from a base station and a terminal to an adjacent neighbor base station of a multi-cell downlink system according to an exemplary embodiment of the present invention.

4 is a diagram illustrating an example of a signal transmitted from a base station and a terminal to a neighbor base station when the present invention is applied in the multi-cell downlink system environment of FIG. 1. Referring to FIG. 4, the base station 110 The downlink channel allocation information 400 is transmitted to the neighboring base stations 120 to 140 at predetermined time intervals, and the terminals 111 to 113 included in the base station 110 transmit uplink signals. For example, when the uplink signal 402 of the terminal 111 is viewed, a pilot signal is inserted into a preset position (contrast '2') and transmitted.

Then, when the base station 120 allocates a channel having a channel identifier of '2' through the downlink channel assignment information 400 and the uplink signal 402 that can be received, the base station 120 interferes with the terminal 111. It can be determined whether or not to give, and if no interference can be assigned to channel '2'.

The method selects and assigns a channel to be allocated in consideration of the downlink channel allocation information received from the neighboring base station and the uplink reception signal of the terminal measured by the base station. Channel assignment scheduling can be enabled. That is, each base station transmits a value obtained by measuring downlink channel allocation information and uplink reception signal of a neighboring terminal, and transmits channel information assignable by the base station control station to the base station with the corresponding value.

5 is a diagram illustrating a structure of a frame transmitted / received by a base station of a multi-cell downlink system according to an exemplary embodiment of the present invention. Referring to FIG. 5, the frame structure of the present invention includes a downlink frame 510 and an uplink frame 520.

The downlink frame 510 basically includes a downlink (DL) MAP 511, an uplink (UL) MAP 512, and downlink data bursts of various channels 513 to 516. The uplink frame 520 includes a downlink channel allocation map (DCA-MAP) 521, a ranging region 522, and an uplink data burst region defined in accordance with the present invention. It is composed.

The DL MAP 511 of the downlink frame 510 includes information indicating an area of downlink data bursts, and the UL MAP 512 includes information indicating a structure of an uplink frame.

The DCA-MAP 521 of the uplink frame 520 includes a pilot signal inserted into a predetermined region corresponding to the allocated channel by each terminal to which the channel is allocated. The DCA-MAP 521 is used as information for determining whether or not interference in neighboring base stations. The ranging region 522 of the uplink frame 520 is a region in which a terminal can raise a code without allocation of a base station. The ranging region 522 may be configured to perform an initial network access, request a handoff, or request resource allocation. Used as

The configuration of the frame is determined by the base station, and the terminal can know the frame structure and allocation information by receiving the DL MAP 511 and the UL MAP 512 of each downlink frame transmitted by the base station every frame. Referring to the downlink frame 510 and the uplink frame 520 of FIG. 5, it can be seen that the base station transmitting and receiving the frame has allocated channels '1', '2', and '3'.

Hereinafter, a dynamic channel allocation method considering an interference region in a multi-cell downlink system constructed as described above will be described with reference to the accompanying drawings. 6 is a flowchart illustrating a process of allocating a channel in consideration of interference effects in a base station of a multi-cell downlink system according to an exemplary embodiment of the present invention.

Referring to FIG. 6, when the base station of the present invention detects a channel allocation request in step 600, it proceeds to step 602 to check whether there is a channel that is not allocated by the base station. If there is no channel assigned as a result of the check in step 602, the base station proceeds to step 614 to notify the channel allocation failure and ends.

If there is an unassigned channel as a result of the check in step 602, the base station selects one channel to be allocated among the unassigned channels in step 604, and in step 506, the selected channel when allocating the selected channel. It is determined whether there is a neighboring terminal belonging to the neighboring base station interfered with.

The method of checking whether the interference is performed in step 606 uses the downlink channel allocation information received at predetermined intervals from the neighbor base stations and the uplink transmitted from the uplink transmitted from the neighbor terminal included in the neighbor base station. The SINR value of the neighboring terminal is measured through Equation 3, and the SINR value of the neighboring terminal is determined by comparing the measured SINR value of the neighboring terminal with a preset interference reference SINR value, which is a criterion for determining whether the interference is detected. If the SINR value is greater than the neighboring terminal is determined not to be interfered by the selected channel, and if the SINR value of the peripheral terminal is less than or equal to the interference reference SINR value, the neighboring terminal is determined to be interfered by the selected channel.

As a result of checking in step 606, if there is a neighboring terminal interfered by the selected channel, the base station returns to step 602. If there is no neighboring terminal interfered by the selected channel as a result of step 606, the base station allocates the selected channel to step 610, and proceeds to step 612, and the downlink channel includes the allocated channel information. The allocation information is transmitted to the neighbor base stations.

7 is a flowchart illustrating a process of allocating a channel in consideration of interference effects and channel conditions in a base station of a multi-cell downlink system according to an exemplary embodiment of the present invention.

Referring to FIG. 7, when the base station of the present invention detects a channel allocation request in step 700, the base station determines whether a channel that is not allocated by the base station exists in step 702. If there is no channel assigned as a result of the check in step 702, the base station proceeds to step 714 to inform the channel allocation failure and ends.

If there is an unassigned channel as a result of the check in step 702, the base station selects one channel to be allocated among the unassigned channels in step 704, and in step 506, the selected channel when allocating the selected channel. It is determined whether there is a neighboring terminal belonging to the neighboring base station interfered with.

The method of checking whether the interference is performed in step 706 is performed using downlink channel allocation information received at predetermined intervals from neighboring base stations and uplink available from uplink transmitted from a neighboring terminal included in the neighboring base station. The SINR value of the neighboring terminal is measured through Equation 3, and the SINR value of the neighboring terminal is determined by comparing the measured SINR value of the neighboring terminal with a preset interference reference SINR value, which is a criterion for determining whether the interference is detected. If the SINR value is greater than the neighboring terminal is determined not to be interfered by the selected channel, and if the SINR value of the peripheral terminal is less than or equal to the interference reference SINR value, the neighboring terminal is determined to be interfered by the selected channel.

As a result of the checking in step 706, if there is a neighboring terminal interfered by the selected channel, the base station returns to step 702. If there is no neighbor terminal interfered by the selected channel as a result of the check in step 706, the process proceeds to step 708 to determine whether the channel state of the selected channel is good.

In the method of determining whether the channel state of the selected channel is good in step 708, the SINR value of the selected channel is compared with a reference SINR value preset by experiment to distinguish the channel state. If it is equal to or equal to one, it is determined to be a bad channel.

If the channel state of the selected channel is poor as a result of checking in step 708, the base station returns to step 702. However, if it is determined in step 708 that the channel state of the selected channel is good, the base station allocates the selected channel to step 710 and proceeds to step 712 to allocate the downlink channel including the channel information allocated. Send information to neighboring base stations.

The difference between FIG. 6 and FIG. 7 is the same as that of FIGS. 6 and 7 except that the channel state is further considered in step 708 of FIG. 7. After the process of determining whether or not interference is in progress, the order may be changed.

Then, the present invention as described above will be described below by comparing the performance with other channel allocation methods through practical examples with reference to FIGS. 8 and 9. The environment of the multi-cell downlink system experimented first is as shown in Figure 8 below.

8 illustrates a multi-cell downlink system including 37 cells having 3 sectors each. Referring to FIG. 8, in the experimental environment, channel allocation is performed in 37 cells divided into three sectors, and the performance measurement is performed in seven cells inside the sound range. The reason for the performance measurement was only in the inner seven cells because there is less interference toward the outer cells, resulting in errors in the measurement. The channel model uses path loss with a path loss exponent of -4 and ignores Gaussian noise. In addition, the SINR _th required for the measurement of the interference domain and the interference reference SINR value for determining whether the interference was 5 dB were used. There are 21 channels, and data rate is obtained from SINR using MCS level of WiBro system of Table 1 below.

Level Modulation Coding rate Required SIR Data rate (kbps) One QPSK 1/12 -1.8 9.78 2 QPSK 1/6 -0.3 19.55 3 QPSK 1/3 2.6 39.11 4 QPSK 2/5 4.2 46.93 5 16QAM 1/4 5.2 58.67 6 16QAM 1/3 6.8 78.21 7 16QAM 2/5 8.3 93.87 8 16QAM 1/2 11.3 117.33

Then, the performance of the present invention and other existing channel assignment techniques in the experimental environment as described above will be compared through FIG. 9 below. 9 is a graph illustrating performance of channel allocation in a multi-cell downlink system according to an embodiment of the present invention.

Referring to FIG. 9, the present invention of FIG. 6 (hereinafter referred to as 'basic') considering interference and the present invention of FIG. 7 (hereinafter referred to as 'comb') considering both interference and a channel state are known. Compared to other channel allocation techniques of FRF1, FRF3 and conv, the performance is evaluated.

Here, FRF1 is a technique for channel allocation by selecting a channel that is not allocated by one base station without considering channel assignment of a neighboring base station. FRF3, like FRF1, does not consider channel allocation of a neighbor base station at one base station. Select and assign a channel that has not been assigned. However, FRF3 classifies allocable channels into three groups before allocating channels, and sets a channel group that can be used for each base station, and allocates them using only channels included in the preset group.

Detailed descriptions of the FRF1 and the FRF3 can be found in the following papers (S. Yoon, Y. Cho, C.-B. Chae, and H. Lee, “System level performance of OFDMA forward link with proportional fair scheduling,” in Proc. PIMRC 2004, Barcelona, Spain, Sep. 2004.).

The conv is a technique of selecting a channel having the best channel state among channels not allocated by one base station without considering channel assignment of a neighboring base station. For a detailed description of the conv, reference may be made to the European next generation mobile communication standard document "IST-2003-507581 WINNER D2.10, Final report on identified key radio interface technologies, system concepts and their assessment, Dec. 2005."

Referring to FIG. 9, a unit amount obtained by a terminal according to distance from a base station in a sector is represented. This result was used to determine the fairness of the throughput according to the position of the cell in the terminal. FRF 1 performs best at the center of the cell, but drops sharply towards the edges. That is, it has very low fairness. FRF 3 shows almost constant performance regardless of location. Conv has better fairness than FRF 1, but it can be seen that the cell edge terminal still suffers much interference. The present inventions proposed in this article further improve fairness and provide cell edge terminals with throughput similar to FRF 3.

Apparently, there are many ways to modify these embodiments while remaining within the scope of the claims. In other words, there may be many other ways in which the invention may be practiced without departing from the scope of the following claims.

As described above, the present invention provides a terminal for transmitting an uplink frame into which information about an allocated channel is inserted, and a downlink channel allocation information received from neighboring base stations when a channel allocation request is received, and a neighboring terminal included in the neighboring base station. The present invention relates to a multi-cell downlink system including a base station for receiving a transmitting uplink and selecting and allocating a channel having no interference effect to the neighboring terminal by using the downlink channel allocation information and the uplink of the neighboring terminal. In addition, since the channel is allocated in consideration of the interference area of the terminal according to the distance between the base station and the terminal, the performance per unit area according to the distance between the base station and the terminal has an excellent effect compared to other channel allocation techniques.

Claims (29)

A system for allocating a channel to a channel request of a terminal in a multi-cell downlink system for allocating a channel, A channel measuring unit configured to receive an uplink signal transmitted by a terminal located at a boundary of an adjacent cell; A channel allocator for selecting a channel having no interference effect to the terminal requesting the channel allocation by using downlink channel allocation information received from adjacent neighbor base stations and the uplink signal of the terminal; The multi-cell downlink system, characterized in that for transmitting to the allocated channel through the channel allocator. The method of claim 1, The multi-cell downlink system of selecting a channel assignable by the channel allocator, selects a channel not used by the neighboring base station from the downlink channel allocation information value received from the neighboring base station. The method of claim 1, The multi-cell downlink system of selecting a channel assignable by the channel allocator, the strength of the uplink signal received from the terminal located in the adjacent cell. The method of claim 3, wherein The base station measures a signal to noise ratio (SINR) or a bit error rate (BER), etc. from the uplink signal received from the terminal. The method of claim 1, In selecting an allocable channel in the channel allocator, the terminal located in the neighbor cell is identified from the downlink channel allocation information value received from the neighbor base station, and the uplink received signal received from the corresponding terminal is determined. And a process of comparing the strength with a preset signal strength value. The method of claim 1, The uplink signal transmitted from the terminal is a multi-cell downlink system, characterized in that the pilot signal. The method of claim 6, And transmitting information by inserting information about a channel when the terminal transmits an uplink signal. The method of claim 1, The channel allocator receives a downlink channel allocation information transmitted from the neighboring base station and an uplink received signal strength value of a terminal located in an adjacent cell measured by each base station, and selects an assignable channel in the base station control station. A multi-cell downlink system characterized by transmitting to a base station to which the terminal requesting allocation belongs. The method of claim 1, The system characterized in that the uplink received signal of the terminal includes a signal strength value, the terminal measures the signal of the downlink signal of the neighboring base station to measure the strength of the signal and transmit it selectively or to all base stations Multi-cell downlink system characterized by. A system for allocating a channel to a channel request of a terminal in a multi-cell downlink system for allocating a channel, A terminal for inserting and transmitting information about a channel allocated when transmitting an uplink signal; A channel allocator configured to select downlink channel allocation information received from neighboring neighbor base stations and uplink signals received from the terminal to select a channel having no interference effect on the terminal requesting channel allocation; The multi-cell downlink system, characterized in that for transmitting to the allocated channel through the channel allocator. A base station of a multi-cell downlink system for dynamically allocating a channel, A channel selector which selects a channel to be allocated among the channels that are requested to allocate the channel and are not allocated; A channel interference measuring unit for measuring whether the channel selected by the channel selecting unit affects the neighboring terminal which is the terminal included in the neighboring base station; And a channel allocator for allocating the selected channel if the channel interference measurement unit does not affect the neighboring terminal as a result of the measurement of the channel interference measurement unit. The method of claim 11, The channel selector, A base station of a multi-cell downlink system, characterized in that for selecting the channel to be allocated among the unallocated channels, a channel having a good channel state is selected. The method of claim 12, The channel in good channel condition is, A base station of a multi-cell downlink system, wherein a signal to interference plus noise ratio (SINR) value of a channel is higher than a reference SINR value preset by an experiment to distinguish a channel state. The method of claim 11, The channel interference measuring unit, Multi-cell downlink measuring downlink channel allocation information received from the neighboring base stations at intervals and the uplink transmitted from the neighboring terminal affects the neighboring terminal using interference Base station of a link system. The method of claim 14, The peripheral terminal, And transmitting pilot information at a predetermined position corresponding to the allocated channel in DCA-MAP (Downlink Channel Allocation MAP) included in the uplink when transmitting uplink frame information. Base station of a multi-cell downlink system. The method of claim 14, The channel interference measuring unit, Signal to Interference plus Noise Ratio (SINR) of the neighboring terminal to determine whether the selected channel is interference using the downlink channel allocation information of the neighboring base station and the uplink of the neighboring terminal. If the SINR value of the peripheral terminal is greater than the interference reference SINR value compared to the preset interference reference SINR value that is a reference for determining whether the measured SINR value of the peripheral terminal is interference, the peripheral terminal Determining that the interference is not interfered by the selected channel, and if the SINR value of the neighboring terminal is less than or equal to the interference reference SINR value, the neighboring terminal is determined to be interfered by the selected channel of the multi-cell downlink system Base station. The method of claim 16, The channel interference measuring unit, The base station of the multi-cell downlink system, characterized in that for measuring the SINR value of the peripheral terminal using Equation 5 below.

Here, SIRN _i is the SINR value of the terminal to which the channel to be allocated included in the neighboring base station i, P ₀ is the strength of the data signal transmitted to the terminal included in the neighboring base station i, g _{ii and} the neighboring base station i G _ij is the channel gain of the base station j to which the channel is to be allocated and the terminal to which the channel to be allocated to the neighboring base station i is allocated, P _M is the neighbor base station i The strength of the pilot signal inserted into the preset position of the uplink by the terminal to which the channel to be allocated is included in the uplink, q _j is the terminal allocated to the channel to be allocated to the neighboring base station i to the preset position of the uplink Signal strength when the inserted pilot signal is received by the base station j. In a multi-cell downlink system for dynamically allocating channels, A terminal for transmitting an uplink frame into which information about an allocated channel is inserted; When a channel allocation request is received, downlink channel allocation information received from neighboring base stations and uplink transmitted by a neighboring terminal included in the neighboring base station are received, and the downlink channel allocation information is received using the uplink of the neighboring terminal. A multi-cell downlink system comprising a base station for selecting and allocating a channel having no interference effect to neighboring terminals. The method of claim 18, The terminal, When the information on the allocated channel is transmitted by transmitting a pilot signal at a predetermined position corresponding to the allocated channel in the downlink channel allocation map (DCA-MAP) included in the uplink when transmitting the uplink frame Multi-cell downlink system. The method of claim 18, The base station, And assigning a channel and transmitting downlink channel allocation information including the allocated channel information to the neighboring base stations at predetermined time intervals. A method for allocating a dynamic channel of a base station in a multi-cell downlink system, When requested to assign a channel, the process of checking whether there is an unallocated channel, If there is an unallocated channel, the process of selecting a channel to assign, When the selected channel is allocated, measuring whether the selected channel interferes with a neighboring terminal, which is a terminal included in a neighboring base station; If the measurement result does not affect the neighboring terminal, the method of dynamic channel allocation of the base station further comprising the step of assigning the selected channel. The method of claim 21, The base station, characterized in that the base station further comprises the step of re-selecting the channel to be allocated to return to the process of selecting the channel to be reassigned if the interference effect on the neighboring terminal as a result of the measurement of the process of measuring the interference effect on the peripheral terminal Dynamic channel allocation method. The method of claim 21, Before assigning the selected channel, The method may further include checking a channel state of the selected channel. The process of assigning the selected channel, And if the selected channel does not interfere with the neighboring terminals as a result of the measurement, and if the channel state is good as a result of the check, the selected channel is allocated. The method of claim 23, And if the channel state of the selected channel is poor, as a result of checking the channel state of the selected channel, returning to selecting a channel to be reassigned, and receiving a reselection of a channel to be allocated. Dynamic channel allocation method of the base station. The method of claim 23, wherein The channel in good channel condition is, A signal to interference plus noise ratio (SINR) value of a channel is a dynamic channel allocation method of a base station, characterized in that the channel is higher than the reference SINR value preset by the experiment to distinguish the channel state. The method of claim 21, The process of measuring whether the interference affects the surrounding terminals, Dynamic base station of the base station characterized by measuring the interference effect on the neighboring terminal using the downlink channel allocation information received from the neighboring base stations at regular intervals and the uplink that can be received from the uplink transmitted by the neighboring terminal Channel assignment method. The method of claim 26, The peripheral terminal, And transmitting pilot information at a predetermined position corresponding to the allocated channel in DCA-MAP (Downlink Channel Allocation MAP) included in the uplink when transmitting uplink frame information. Dynamic channel allocation method of base station. The method of claim 26, The process of measuring whether the interference affects the surrounding terminals, Signal to Interference plus Noise Ratio (SINR) of the neighboring terminal to determine whether the selected channel is interference using the downlink channel allocation information of the neighboring base station and the uplink of the neighboring terminal. If the SINR value of the peripheral terminal is greater than the interference reference SINR value compared to a preset interference reference SINR value that is a reference for determining whether the measured SINR value of the peripheral terminal is interference, the peripheral terminal And determining that the terminal is not interfered by the selected channel, and if the SINR value of the neighboring terminal is less than or equal to the interference reference SINR, the neighboring terminal is determined to be interfered by the selected channel. The method of claim 28, The process of measuring whether the interference affects the surrounding terminals, Dynamic channel allocation method of a base station characterized by measuring the SINR value of the peripheral terminal using Equation 6 below.

Here, SIRN _i is the SINR value of the terminal to which the channel to be allocated included in the neighboring base station i, P ₀ is the strength of the data signal transmitted to the terminal included in the neighboring base station i, g _{ii and} the neighboring base station i G _ij is the channel gain of the base station j to which the channel is to be allocated and the terminal to which the channel to be allocated to the neighboring base station i is allocated, P _M is the neighbor base station i The strength of the pilot signal inserted into the preset position of the uplink by the terminal to which the channel to be allocated is included in the uplink, q _j is the terminal allocated to the channel to be allocated to the neighboring base station i to the preset position of the uplink Signal strength when the inserted pilot signal is received by the base station j.

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