CN101197653A - Wireless communication device and wireless communication method - Google Patents

Abstract

The present invention provides a radio communication device and a radio communication method capable of providing a communication channel with little inter-cell interference and suppressing fluctuations in inter-cell interference. A base station disposed in a wireless communication system that implements frequency division multiple access using a frequency division multiplexing method as a modulation method, divides a cell into an inner area and an outer area, and has an allocation control unit ( 30) The control unit is configured to perform sub-channelization through a completely orthogonal channel in an outer area of the cell, and perform sub-channelization through a quasi-orthogonal channel in an inner area of the cell.

Description

Wireless communication device and wireless communication method

technical field

The present invention relates to a wireless communication device and a wireless communication method.

Background technique

Conventionally, wireless communication systems using a frequency division multiple access method such as FDMA (Frequency Division Multiple Access) are known. In particular, wireless communication systems using orthogonal frequency division multiple access methods such as OFDMA (Orthogonal Frequency Division Multiple Access) have attracted attention in recent years.

In a radio communication system using such an OFDMA scheme, when there are three adjacent cells, for example, a configuration is known in which the same frequency band (fMHz) is used in each of the cells 1 to 3 (see FIG. 18 ) and a structure in which a certain frequency band (fMHz) is logically divided into three segments and each divided frequency band (f/3MHz) is allocated to cells 1 to 3 (see FIG. 19 ).

In the former structure (refer to FIG. 18 ), there is a problem that since a plurality of cells 1 to 3 use a certain frequency band as a whole, high throughput can be achieved when interference from other cells is small, but since neighboring cells also use In the same frequency band, inter-cell interference increases, and sufficient communication quality (transmission rate, call loss rate, etc.) cannot be provided for mobile terminals (users) located at the end of the cell.

On the other hand, in the latter configuration (see FIG. 19 ), there is a problem that since different frequency bands are used between adjacent cells, it is easy to suppress inter-cell interference, but since a certain frequency band is divided into three segments, Therefore, the upper limit of the achievable peak throughput is 1/3 of that when using the entire frequency band, and radio resources cannot be fully utilized when the traffic between cells is uneven.

Therefore, a configuration has been proposed (see Patent Document 1) in which each cell is divided into an outer area and an inner area as shown in FIG. , the frequency bands F1 to F3 respectively used in each cell are allocated to the outside area where interference from other cells is large.

[Patent Document 1] JP-A-2005-80286

Contents of the invention

In the prior art described above, since voice communication is targeted, the inter-cell interference has a relatively gentle temporal variation.

However, there is a characteristic in data communication that, in terms of the nature of communication traffic, short packets are intermittently transmitted on a one-to-one link in particular, and thus the amount of fluctuation in interference to the surroundings becomes large.

On the other hand, there is a problem that although data communication has the feature of being able to perform retransmission processing, since the transmission power or MCS (Modulation coding sets) is determined according to the interference amount before the data transmission time, the fluctuation amount of the interference amount The big picture isn't ideal.

Furthermore, assuming that the OFDMA method is used, both "perfectly orthogonal channels (described below)" and "quasi-orthogonal channels (described below)" that cannot be realized in the FDMA method can be realized in the same frequency band of the same wireless communication system.

Therefore, the present invention was made in view of the above problems, and an object of the present invention is to provide a wireless communication device and a wireless communication method capable of providing communication with little inter-cell interference and suppressing inter-cell interference. amount of change.

A first feature of the present invention is a wireless communication device that is arranged in a wireless communication system that implements a frequency division multiple access method using a frequency division multiplexing method as a modulation method and divides a cell into inner an area and an outer area, wherein an allocation control unit is provided, and the allocation control section allocates a completely orthogonal channel as a sub-channel usable in the outer area, and allocates a quasi-orthogonal channel as a sub-channel usable in the inner area. All the subcarriers included in the completely orthogonal channel allocated as subchannels usable in the outer area of the adjacent cell are orthogonal to each other, and are allocated as subchannels usable in the inner area of the adjacent cell Among the subcarriers included in the quasi-orthogonal channel, some of them are repeated and some of them are orthogonal.

In the first aspect of the present invention, the allocation control unit allocates a subchannel usable in the outer area to a mobile terminal whose desired wave reception power is lower than a preset predetermined threshold value, and the desired wave reception power is lower than the predetermined threshold. Subchannels usable in the inner area are assigned to mobile terminals with a higher threshold.

In the first aspect of the present invention, the inner area is divided into a plurality of areas, and the allocation control unit allocates quasi-orthogonal channels with different usage rates as usable channels in the divided inner areas. sub-channel.

In the first aspect of the present invention, the allocation control unit uses a burst allocation pattern specified by a combination of at least one completely orthogonal channel and at least one symbol in the data frame structure for mobile terminals located in the outer area of each cell. , allocate radio resources, and the burst allocation mode is the same among all the cells.

In the first aspect of the present invention, the allocation control unit allocates the switching call to the subchannel available in the outer area.

In the first aspect of the present invention, the inner area is divided into a plurality of areas, and the assignment control unit assigns the switching call to a subchannel usable in one of the divided inner areas. .

In the first aspect of the present invention, the allocation control unit allocates the handover call to an area close to an area to which the preamble is allocated in the data frame structure.

In the first aspect of the present invention, the assignment control unit assigns the mobile terminal in either the inner area or the outer area based on the downlink communication quality notified by the mobile terminal. The subchannel to use.

In the first aspect of the present invention, the allocation control unit uses a burst allocation pattern specified by a combination of at least one completely orthogonal channel and at least one symbol in the data frame structure for mobile terminals located in the outer area of each cell, Allocating wireless resources; the allocation control unit changes the burst allocation mode according to radio wave conditions.

In the first aspect of the present invention, the allocation control unit allocates at least one notification signal to a subchannel usable in the outer area.

In the first aspect of the present invention, the allocation control unit exclusively allocates a part of the sub-channels usable in the outer area for notification signal transmission.

A second feature of the present invention is a wireless communication method used in a wireless communication system that implements a frequency division multiple access method using a frequency division multiplexing method as a modulation method and divides a cell into inner an area and an outer area, wherein the wireless communication device allocates a completely orthogonal channel as a sub-channel usable in the outer area, and allocates a quasi-orthogonal channel as a sub-channel usable in the inner area, The subcarriers included in the completely orthogonal channels allocated as subchannels usable in the outer area of the adjacent cell are all orthogonal to each other, and all the subcarriers included in the channel allocated as the subchannel usable in the inner area of the adjacent cell are orthogonal to each other. Among the sub-carriers included in the quasi-orthogonal channel, some of them overlap and some of them are orthogonal.

Description of drawings

FIG. 1 is a functional block diagram of a base station according to the first to ninth embodiments.

FIG. 2 is an explanatory diagram illustrating the concepts of subcarriers and subchannels used in the wireless communication systems of the first to ninth embodiments.

FIG. 3 is an explanatory diagram illustrating the concepts of orthogonal channels and quasi-orthogonal channels used in the wireless communication systems of the first to ninth embodiments.

FIG. 4 is an explanatory diagram of an example of a data frame structure used in the wireless communication system according to the first embodiment.

FIG. 5 is an explanatory diagram of a subchannel allocation method in the radio communication system according to the second embodiment.

6 is an explanatory diagram of an example of a data frame structure used in the wireless communication system according to the third embodiment.

FIG. 7 is a diagram showing an example of a cell configuration in a radio communication system according to a third embodiment.

FIG. 8 is a diagram (Part 1) showing an example of a burst allocation pattern used in the radio communication system according to the third embodiment.

FIG. 9 is a diagram (part 2 ) showing an example of a burst allocation pattern used in the wireless communication system according to the third embodiment.

10 is an explanatory diagram of the operation of the mobile terminal during handover in the radio communication system according to the fourth embodiment.

Fig. 11 is a diagram (part 1) showing an example of a burst allocation pattern used in the radio communication system according to the fifth embodiment.

Fig. 12 is a diagram (Part 2) showing an example of a burst allocation pattern used in the wireless communication system according to the fifth embodiment.

Fig. 13 is a diagram (Part 3) showing an example of a burst allocation pattern used in the wireless communication system according to the fifth embodiment.

FIG. 14 is an overall configuration diagram of wireless communication systems according to seventh and eighth embodiments.

FIG. 15 is an explanatory diagram of an example of a data frame structure used in the wireless communication system of the seventh embodiment.

FIG. 16 is an explanatory diagram of an example of a data frame structure used in the wireless communication system according to the eighth embodiment.

FIG. 17 is an explanatory diagram of an example of a data frame structure used in the radio communication system according to the ninth embodiment.

FIG. 18 is an explanatory diagram (Part 1) of a conventional bandwidth allocation method.

FIG. 19 is an explanatory diagram (Part 2) of a conventional bandwidth allocation method.

FIG. 20 is an explanatory diagram (Part 3) of a conventional bandwidth allocation method. Symbol Description

11: Symbol mapping section; 12: Distribution section; 13: IFFT; 14: Parallel/serial conversion section; 15: Protection interval insertion section; 16: DAC/RF circuit; 17: Antenna; 21: Antenna; 22: ADC/RF circuit; 23: guard interval removal unit; 24: parallel/serial conversion unit; 25: FFT; 26: signal extraction unit; 27: symbol demapping unit; 30: distribution control unit.

Detailed ways

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings below, the same or similar symbols are attached to the same or similar parts. However, it should be noted that the drawings are schematic diagrams.

(The wireless communication system according to the first embodiment of the present invention)

The wireless communication system according to the first embodiment of the present invention is a multi-user communication system using an orthogonal frequency division multiplexing (OFDM) method as a modulation method.

In the radio communication system according to this embodiment, an Orthogonal Frequency Division Multiple Access (OFDMA) scheme is implemented by allocating a part of a plurality of subcarriers included in one communication path to one mobile station (user).

In addition, in the wireless communication system according to this embodiment, as shown in FIG. 20 , one cell is divided into an inner area and an outer area.

Here, in the inner area, use the same frequency band (F4 in the example of FIG. In the example of FIG. 20 , F1 is used in the outer area of cell 1, F2 is used in the outer area of cell 2, and F3 is used in the outer area of cell 3).

Also, in the radio communication system according to this embodiment, a base station (radio communication device) allocates subchannels usable in the outer area or inner area of a cell under the base station to a plurality of mobile terminals.

In this embodiment, in order to make it easier to understand, an example in which the subchannels are orthogonal in the frequency direction is described, but the present invention is not limited to this example, and can also be applied to when the subchannels are orthogonal in the time direction or when the subchannels are orthogonal to each other. An example when it is orthogonal on a combination of the time direction and the frequency direction.

As shown in FIG. 1 , the base station in the wireless communication system according to this embodiment includes: a symbol mapping unit (symbol mapping) 11, an allocation unit 12, an IFFT 13, a parallel/serial conversion unit 14, a guard (guard) interval insertion unit 15, and a DAC. /RF circuit 16, antennas 17, 21, ADC/RF circuit 22, guard interval removal unit 23, parallel/serial conversion unit 24, FFT 25, signal extraction unit 26, symbol demapping unit (symboldemapping) 27 and allocation control unit 30.

The symbol mapping unit 11 maps the input transmission signal sequence (bit sequence) to symbols according to the applied modulation scheme, and outputs the symbols.

The allocating unit 12 allocates the transmission signal sequence mapped to the symbol input from the symbol mapping unit 11 to the (in the frequency axis Arranged above) subcarriers, and then output.

The IFFT 13 outputs time signals (digital signals) obtained by inverse Fourier transforming the plurality of subcarriers input from the allocating unit 12 as described above.

The parallel/serial conversion unit 14 performs parallel/serial conversion on the inverse Fourier transformed time signal (digital signal).

The guard interval insertion unit 15 inserts a guard interval into the time signal (digital signal) input from the parallel/serial conversion unit 14 .

The ADC/RF circuit 16 converts the guard interval-inserted time signal (digital signal) into an analog signal, and then transmits the OFDM signal (analog signal) obtained by performing necessary analog processing such as amplification and frequency conversion through the antenna 17 .

On the other hand, when the antenna 21 receives an OFDM signal (analog signal), the ADC/RF circuit 22 converts the received OFDM signal (analog signal) into a digital signal after performing necessary analog processing such as amplification and frequency conversion.

The guard interval removal unit 23 removes a guard interval from the digital signal input from the ADC/RF circuit 22 .

The parallel/serial conversion unit 24 performs parallel/serial conversion on the digital signal from which the guard interval has been removed.

The FFT 25 performs Fourier transform on the digital signal input from the parallel/serial conversion unit 24 to extract each subcarrier.

The signal extraction unit 26 extracts a symbol from each subcarrier input from the FFT 25 in accordance with an instruction from the allocation control unit 30 .

The symbol demapping unit 27 demaps the symbols extracted by the signal extracting unit 26 to obtain a received signal sequence.

The allocation control unit 30 allocates "completely orthogonal channels" as subchannels usable in the outer area of the cell, and assigns "quasi-orthogonal channels" as subchannels usable in the inner area of the cell.

That is, the allocation control unit 30 controls the sub-channelization method depending on whether the mobile terminal serving as a communication target is located in the outer area or the inner area of the cell.

Specifically, the allocation control unit 30 performs sub-channelization using a complete orthogonal channel in the outer area of the cell, and performs sub-channelization based on a quasi-orthogonal channel in the inner area of the cell.

Here, the subcarriers included in the "perfectly orthogonal channel" allocated as subchannels usable in the outer area of the adjacent cell are all orthogonal to each other.

In addition, some of the subcarriers included in the "quasi-orthogonal channel" allocated as subchannels usable in the inner area of the adjacent cell overlap and some of them are orthogonal to each other.

Hereinafter, "perfectly orthogonal channels" and "quasi-orthogonal channels" will be described with specific examples. In this embodiment, a wireless communication system based on IEEE802.16 will be described as an example of a wireless communication system using the OFDMA method. However, the present invention is not limited to this wireless communication system, but can also be applied to a general system using OFDMA.

Generally, in a wireless communication system employing the OFDMA method, since one frequency band consists of a very large number of subcarriers (frequencies), controlling "which mobile station (user) to use (assign)" for each subcarrier is considered in terms of control. The simplicity and efficiency of controlling semaphores are not high.

Therefore, in this radio communication system, a plurality of subcarriers (frequencies) are combined into groups, and radio resources (subcarriers) to mobile terminals (users) are assigned in units of the groups.

As shown in FIG. 2 , in IEEE802.16, a group obtained by combining a plurality of subcarriers (frequencies) as described above is called a "subchannel".

And, the combination mode of the sub-channel is determined by a parameter called "IDcell".

In the example in Figure 2, when "IDcell=1", subchannel 1 is composed of subcarriers 1, 2, and 3, subchannel 2 is composed of subcarriers 4, 5, and 6, and subchannel 3 is composed of subcarriers 7, 8, and 9. .

Also, when "IDcell=2", subchannel 1 is composed of subcarriers 1, 4, and 7, subchannel 2 is composed of subcarriers 2, 5, and 8, and subchannel 3 is composed of subcarriers 3, 6, and 9.

Here, when the "IDcell" in the adjacent cells A and B is the same, when the same subchannel is allocated to both the mobile terminal A under the cell A and the mobile terminal B under the cell B, the mobile terminal All subcarriers (frequencies) assigned to A and mobile terminal B are the same.

On the other hand, when the "IDcells" in adjacent cells A and B are the same, when different subchannels are assigned to both mobile terminal A under cell A and mobile terminal B under cell B, the mobile All subcarriers (frequencies) allocated to terminal A and mobile terminal B are different.

For example, as shown in FIG. 3(a), when the “IDcells” in adjacent cells A and B are the same, since all the subcarriers (frequencies) constituting the subchannel sc1 assigned to mobile terminal A under cell A are identical to All the subcarriers (frequencies) constituting the subchannel sc2 assigned to the mobile terminal B under the cell B are completely orthogonal, so both the cells A and B appear to perform subchannelization through a "completely orthogonal channel" .

That is, in this case, the subcarriers included in the complete orthogonal channels sc1 and sc2 allocated as subchannels usable in the outer regions of the adjacent cells A and B are all orthogonal to each other. Furthermore, the subchannel sc1 and the subchannel sc2 have different subchannel numbers (ie, SC1, SC2). In the above case, it appears that the sub-channel SC1 is orthogonal to the sub-channel SC2.

On the other hand, as shown in FIG. 3(b), when the “IDcells” of adjacent cells A and B are different, even the subchannel sc1 assigned to mobile terminal A under cell A and the mobile terminal under cell B When the subchannel sc2 allocated to the terminal B is different, part of the subcarriers allocated to the mobile terminal A and the mobile terminal B overlap.

For example, when the "IDcells" of adjacent cells A and B are different, the subcarriers (frequency) included in subchannel sc1 used in cell A and the subcarriers (frequency) included in subchannel sc2 used in cell B Among them, some orthogonal relations are established, while some repetitive relations are established, so the two are called "quasi-orthogonal".

That is, some of the subcarriers included in the quasi-orthogonal channels sc1 and sc2 allocated as subchannels usable in the inner regions of the adjacent cells A and B overlap and some of them are orthogonal. In the case of the above, it appears that the sub-channel sc1 is quasi-orthogonal to the sub-channel sc2

In addition, as shown in FIG. 4 , the allocation control unit 30 allocates each sub-channel (perfect orthogonal channel) usable in the outer area of the cell as a dedicated channel in each cell.

As shown in FIG. 4 , for example, the allocation control unit 30 can construct a data frame structure in such a manner that the information of the mobile terminals located in the area outside the cell is stored in the area to which the preamble is allocated, and the information of the mobile terminals located in the area inside the cell is stored in the next area. Information about mobile terminals.

In addition, the allocation control unit 30 can allocate a subchannel corresponding to an "IDcell" different from that of the adjacent cell as a subchannel usable in the inner area of the cell, and can allocate a subchannel corresponding to the same "IDcell" as the adjacent cell. Among the subchannels, the subchannel allocated to the own cell is a subchannel usable in the outer area of the cell.

Here, the allocation control unit 30 changes the subchannels allocated as subchannels usable in the outer area or inner area of the cell. For example, the outer channel may be allocated to a mobile terminal whose desired wave reception power is lower than a predetermined threshold value set in advance. Subchannels usable in the area are assigned subchannels usable in the inner area to mobile terminals whose desired wave reception power is higher than the predetermined threshold.

According to the base station of the first embodiment, the sub-channelization is performed by the complete orthogonal channel in the outer area of the cell, and the sub-channelization by the quasi-orthogonal channel is performed in the inner area of the cell.

In this way, by making each cell a dual structure, it is possible to provide communication with less inter-cell interference in the outer area of the cell, and it is possible to form a situation in which the MCS is appropriately selected in the inner area of the cell.

In the outer area of the cell, communication with less inter-cell interference can be provided because completely orthogonal channels are used and appropriate reuse distances are set for these sub-channels.

On the other hand, in the inner area of the cell, the reason why it is possible to form a situation in which an MSC is suitable for selection is as follows.

Conventionally, the base station determines the transmission power or the MCS based on the interference amount before the transmission time. Therefore, it is not preferable that the interference amount fluctuates greatly.

When allocating a completely orthogonal channel to a mobile terminal located in the inner area of a cell, it is expected that the mobile terminal will use the same sub-channel according to whether the same sub-channel is used in the adjacent cell, and further according to the position (especially uplink) of the sub-channel used. The amount of interference varies greatly.

On the other hand, when a quasi-orthogonal channel is assigned to a mobile terminal located in the inner area of a cell, the subchannels used in the adjacent cell receive less interference each time, so the amount of interference in the mobile terminal as a whole fluctuates. The amount becomes small, enabling the MCS to operate efficiently.

Furthermore, when the subchannels used by adjacent cells are not orthogonal to each other, the amount of interference in each mobile terminal becomes larger than when the subchannels used by adjacent cells are orthogonal.

Therefore, according to the base station of this embodiment, by making the subchannels used at the boundary between adjacent cells orthogonal to each other (allocating completely orthogonal channels as subchannels usable at the boundary between adjacent cells), it is possible to ensure A subchannel with a very small amount of interference can provide good communication even for a mobile terminal at a long distance from a base station or a mobile terminal with low reception power such as indoors.

In addition, according to the base station of this embodiment, subchannels that can be used in the outer area of the cell are assigned to mobile terminals whose desired wave received power is lower than a preset predetermined threshold, and mobile terminals whose desired wave received power is higher than the predetermined threshold Subchannels usable in the inner area of the cell are allocated.

By assigning such subchannels, the following effects can be obtained.

In the entire area of the entire cell, the start or end of the use of a specific subchannel in an adjacent cell affects the amount of inter-cell interference received by a mobile terminal located in the inner area of the cell compared to the case of using a completely orthogonal channel for communication. Since the influence of the fluctuation is not large, the fluctuation amount of the disturbance amount can be easily predicted.

In data communication, since the control of transmission power or the selection of MCS is performed based on the estimated amount of inter-cell interference, it is possible to estimate the amount of inter-cell interference more accurately, and it is conceivable that these controls work more efficiently and can be obtained more efficiently. High system throughput.

On the other hand, in the entire area of the entire cell, compared with the case of using quasi-orthogonal channels for communication, in the case of using a completely orthogonal channel in the outer area of the cell, it is possible to provide communication with little inter-cell interference, and especially reduce The outage rate for mobile terminals located at the end of the cell.

In addition, according to the base station of this embodiment, instead of simply using the perfect orthogonal channel and the quasi-orthogonal channel together, the number of sub-channels available in the cell is shortened based on these concepts called "reuse partitioning". Substantial reuse distance of the channel, thereby enabling higher system throughput.

(second embodiment)

Hereinafter, the wireless communication system according to this embodiment will be described focusing on differences from the wireless communication system according to the first embodiment described above.

In the second embodiment of the present invention, as shown in FIG. 5 , the inner area of the cell is divided into a plurality of areas, and the allocation control unit 30 allocates quasi-orthogonal channels with different usage rates as the channels available in the divided inner areas. The subchannel to use.

At this time, the allocation control unit 30 sets the area using the quasi-orthogonal channel with a high usage rate inside the area using the quasi-orthogonal channel with a low usage rate.

In the example of FIG. 5 , the allocation control unit 30 allocates a quasi-orthogonal channel with a usage rate of 60% as a sub-channel available in the inner area B, and allocates a quasi-orthogonal channel with a usage rate of 90% as a sub-channel available in the inner area A. The subchannel to use.

For example, the assignment control unit 30 may assign quasi-orthogonal channels with high usage rates to mobile terminals with higher received power.

With such a configuration, high system throughput can be achieved by efficiently using quasi-orthogonal channels with high usage rates in each cell.

In addition, the assignment control unit 30 can adaptively change the usage rate of quasi-orthogonal channels available in each area.

For example, the utilization rate of the quasi-orthogonal channels available in each area by the allocation control unit 30 may be determined based on the blocking (blocking) rate of surrounding cells using the same frequency band, or may be determined based on the setting values of the surrounding cells and the measured Observation information is used to make decisions to maximize area throughput.

In addition, the assignment control unit 30 may set a plurality of completely orthogonal channels with different reuse distances.

(third embodiment)

Hereinafter, the radio communication system of this embodiment will be described mainly in terms of differences from the radio communication systems of the above-mentioned first and second embodiments.

As described above, in the first and second embodiments, the allocation control unit 30 fixedly allocates subchannels usable in the outer area of each cell.

In this case, it can be used through simple control, but in the case of low traffic in a certain cell and many unused sub-channels, and in the case of high traffic in adjacent cells and insufficient sub-channels, even by making other Cells can use these unused sub-channels to achieve higher system throughput, but by limiting radio resources to more than necessary, there may be many mobile terminals that cannot achieve sufficient transmission speed in cells with high traffic.

On the other hand, when these subchannels are allowed to be used in other cells, when a mobile terminal located at the end of the cell attempts to communicate, the subchannels may not be able to be used due to interference from other cells.

Therefore, it is preferable to share quasi-dedicated channels among a plurality of cells within a range that does not affect the outage rate of mobile terminals located at cell ends.

Therefore, in the third embodiment, when allocating perfect orthogonal channels as subchannels usable in each cell, the allocation control unit 30 classifies them into dedicated channels and quasi-dedicated channels as shown in FIG. 6 and allocates them.

Here, a dedicated channel is a subchannel specially assigned to each cell, and a quasi-dedicated channel is a subchannel shared by multiple cells under certain conditions.

Specifically, in principle, the allocation control unit 30 in each cell follows "a quasi-dedicated channel allocated as a subchannel (completely orthogonal channel) usable in other cells" and "a subchannel (completely orthogonal channel) allocated as a Sub-channels are allocated to mobile terminals in order of priority of "quasi-dedicated channels allocated as sub-channels (perfectly-orthogonal channels) available in the own cell" and "dedicated channels allocated as sub-channels (completely-orthogonal channels) available in the own cell".

Then, when all the "dedicated channels allocated as subchannels (completely orthogonal channels) usable in the own cell" are allocated to the mobile terminal, the allocation control unit 30 prohibits other cells from using the quasi-dedicated channels allocated for the sub-channels used (completely orthogonal channels).

As a result, a decrease in the blocking rate in each cell is caused.

FIG. 7 shows an example in which "dedicated channels" and "quasi-dedicated channels" are allocated by the cell allocation control unit 30. In FIG. In the example of FIG. 7 , the allocation control unit 30 allocates different "dedicated channels" and "quasi-dedicated channels" as subchannels (perfectly orthogonal channels) usable in adjacent cells.

In addition, the allocation control unit 30 can perform the permission and prohibition of the use of the quasi-dedicated channel through the wired network.

Furthermore, the allocation control unit 30 may allocate in order from quasi-dedicated channels allocated as sub-channels that can be used in cells with a low traffic load of the perfect orthogonal channel.

Here, the allocation control unit 30 may grasp the traffic load through a wired network.

Furthermore, the allocation control unit 30 may increase the allocation threshold value of the "quasi-dedicated channel" in another cell as the operation method of the "quasi-dedicated channel" and the "dedicated channel".

Here, the allocation control unit 30 may use the ratio of received power to the interference level of the entire quasi-dedicated channel as a reference for allocating the "quasi-dedicated channel".

Alternatively, the allocation control unit 30 may determine the allocation threshold of the quasi-dedicated channel in the cell 1 based on the interference level in the dedicated channel in the cell 1 .

Moreover, the allocation control unit 30 may monitor the situation for each data frame, and when a situation exceeding the allocation threshold occurs, the "quasi-dedicated channel" is not allocated (the "quasi-dedicated channel" does not continue to be used once allocated).

As a result, in the own cell, when the traffic load is low, the allocation control unit 30 allocates a "quasi-dedicated channel" as a sub-channel usable in a cell with a high traffic load, and the traffic load in each cell When it increases, the inter-cell interference level increases, making it difficult for each cell to use a "quasi-dedicated channel" allocated as a sub-channel usable by other cells.

Also, in the downlink specified in IEEE802.16, as shown in FIG. 8 , the allocation control unit 30 allocates radio resources in a burst allocation pattern to mobile terminals located in each cell. The allocation pattern is defined by a combination of at least one subchannel (subchannel number) and at least one symbol (OFDM symbol number, corresponding to the allocation time of the subchannel) in the data frame structure.

Such a unit of allocation of radio resources to mobile terminals is called a "burst". When a "quasi-dedicated channel" is allocated as a subchannel usable in each cell, this burst allocation pattern is the same among all cells.

This is because, as shown in Figure 9(a), when the burst allocation mode is not unified among all cells, orthogonalization is realized in units of sub-channels, and the sub-channels usable in adjacent cells cannot be guaranteed in terms of burst units Orthogonality can be achieved between them.

On the other hand, as shown in FIG. 9( b ), when the burst allocation pattern is unified among all cells, the subchannels usable by adjacent cells are orthogonal to each other in burst units.

(fourth embodiment)

Hereinafter, the wireless communication system of this embodiment will be described mainly in terms of differences from the wireless communication systems of the first to third embodiments described above.

In the first to third embodiments described above, the allocation control unit 30 allocates subchannels that can be used in either the inner area or the outer area of the cell according to the received power in the mobile terminal or the like.

Conceptually, this means that the allocation control unit 30 determines the subchannels to be allocated according to the position of the mobile terminal in the cell.

However, the position of a mobile terminal (a mobile terminal moving at high speed) that is transmitting and receiving a handover call changes momentarily.

Therefore, it is expected that the amount of interference received by the mobile terminal moving at high speed and the amount of interference generated around it due to the movement of the mobile terminal moving at high speed will greatly affect the system throughput.

Therefore, in the present embodiment, the assignment control unit 30 uses not only the received power of the mobile terminal but also information about the moving speed of the mobile terminal to allocate subchannels usable in either the inner area or the outer area of the cell.

Next, a subchannel allocation method for a handover call is shown. Here, the handover call includes not only a call sent and received by a mobile terminal handed over from outside the cell, but also a call sent and received by a mobile terminal moving at high speed.

In addition, the allocation control unit 30 allocates the handover call to a subchannel usable in the outer area of the cell.

As shown in Figure 10, regarding the subchannels available in the inner area of the cell, the statistical results show that the interference power from the cell end is relatively large, so if the mobile terminal moves to the cell end, it is easy to switch, and the possibility of subchannel switching more sexual.

In addition, subchannel switching requires subchannel search and exchange of control signals.

Furthermore, if the frequency of subchannel switching is high, inter-cell interference fluctuates rapidly, making it difficult to predict the amount of interference.

In addition, particularly in the uplink, there is a problem in that the amount of interference to mobile terminals in the vicinity of adjacent cells increases, which greatly affects the decrease in throughput.

Therefore, when no subchannel dedicated to the handover call is provided, it is preferable that the allocation control unit 30 allocates the handover call to a subchannel usable in the outer area of the cell.

Alternatively, the inner area of the cell may be divided into a plurality of areas, and the allocation control unit 30 may allocate a handover call to a subchannel usable in one of the divided inner areas.

In this case, the allocation control unit 30 preferably uses an allocation control unit 30 that does not depend on the usage status of subchannels in adjacent cells when the amount of interference in the mobile terminal or the amount of interference from the mobile terminal to other cells exceeds a predetermined threshold. Orthogonal channels.

In the above-mentioned example, the mode in which the allocation control unit 30 does not provide a sub-channel dedicated to handover calls has been described. Control can be easily performed in this manner.

On the other hand, in the above example, since the allocation control unit 30 allocates subchannels available in the outer area of the cell to the handover call, for example, in the case of many handover calls, the subchannels that can be provided to the end of the cell may be significantly limited. communication quality of the mobile terminal.

Therefore, a method is considered in which the inner area of a cell is divided into a plurality of areas, and subchannels available in some of the divided inner areas are used as subchannels dedicated to handover calls.

However, if a specific sub-channel is used as a sub-channel dedicated to a handover call, since the sub-channel (radio resource) cannot be effectively used when there is no handover call, the specific sub-channel is usually used as a channel with a low usage rate. shared channel.

In addition, the allocation control unit 30 may adaptively change the rate at which the subchannel is allocated to the handover call in accordance with the state of handover calls in the own cell and neighboring cells.

Specifically, the allocation control unit 30 controls so that when there are many switching calls, the ratio of allocating the subchannel to other than switching calls is reduced, and when there are few switching calls, the ratio of allocating the subchannel to other than switching calls is increased. subchannel ratio.

In addition, the allocation control unit 30 may determine the rate at which the sub-channel is allocated in consideration of the traffic in each cell.

In addition, the allocation control unit 30 also allocates sub-channels other than the sub-channels dedicated to the switching call to the switching call even when the sub-channel dedicated to the switching call is provided.

In this case, the allocation control unit 30 may determine which subchannel to use for the handover call (the subchannel dedicated to the handover call or switch sub-channels other than call-only sub-channels).

In addition, in the above-mentioned embodiment, regarding the position within the data frame structure of the subchannel allocated to the handover call, in principle, it does not matter which position is allocated to which operation is critical.

In WiMAX, known signals are scattered and arranged in an area allocated to a preamble at the top of a data frame structure and an area allocated to data.

Then, use these known signals to perform time synchronization or frequency synchronization acquisition, or channel estimation.

Since the channel of a mobile terminal moving at high speed fluctuates quickly with time, it is considered that the radio resources (radio resources (sub-channels and OFDM symbols) for handover call transmission and reception) used in the mobile terminal are allocated to a time-dependent channel. If the area of the preamble is a distant area, the preamble cannot be effectively used, and the reception quality is liable to deteriorate.

Therefore, in the present embodiment, the allocation control unit 30 determines an area in which a switching call is allocated in the data frame structure as follows.

For example, as shown in FIG. 4 , the allocation control unit 30 constructs a data frame structure in such a manner that information on mobile terminals located near cell boundaries and mobile terminals in handover is stored in an area continuous with the area to which the preamble is allocated, Information on mobile terminals located near the cell is stored in the next continuous area.

In this way, in the data frame structure, it is preferable to allocate the handover call to an area close to the area to which the preamble is allocated.

Since the channel of a mobile terminal moving at high speed fluctuates greatly over time, when the radio resource (radio resource for handover call transmission and reception) usable by the mobile terminal is allocated to the latter part of the data frame structure, the sub-band estimated from the preamble The amount of variation between the channel and the subchannel in the area to which the handover call is allocated is large, and it is difficult to effectively use the channel estimation value using the preamble.

On the other hand, a static mobile terminal has little channel variation over time, and the preamble can be effectively used even when the radio resource usable by the mobile terminal is allocated to the latter area in the data frame structure, and it can be obtained that channel estimate.

Therefore, by placing handoff calls in an area close to the area to which the preamble is assigned, and placing radio resources usable by stationary mobile terminals (fixed terminals) behind it, all mobile terminals can obtain high-precision channel estimation. channel estimate.

(fifth embodiment)

Hereinafter, the wireless communication system of this embodiment will be described mainly in terms of differences from the wireless communication systems of the above-mentioned first to fourth embodiments.

In the first to fourth embodiments described above, the method of using subchannels in each cell has been described. In each cell, communications transmitted and received by a plurality of mobile terminals are generally multiplexed.

In the fifth embodiment of the present invention, a method of multiplexing communications transmitted and received by a plurality of mobile terminals will be described using the basic example shown in FIG. 11 .

As a first method, as shown in FIG. 11 , the allocation control unit 30 may also construct the following data frame structure: the size is fixed in advance, and the area A for allocating radio resources usable in the outer area of the cell is set; Data of area B of radio resources available in the inner area and sub-area C (area of radio resources that cannot be used in this cell in order to reduce interference with other cells and reduce the usage rate of sub-channels in the own cell) frame structure.

In this case, as shown in FIG. 12 , the allocation control unit 30 checks in order whether radio resources (subchannels and OFDM symbols) can be allocated in burst allocation modes 1 to 4 for mobile terminals located in each cell, and Radio resources are allocated in accordance with the initially allocatable burst allocation pattern.

Here, the assignment control unit 30 judges whether radio resources can be assigned based on the use status, received power, SINR, etc. of other mobile terminals in each cell.

In addition, when the amount of traffic in each cell is small, and the mobile terminal to which radio resources are allocated requires a very high transmission speed, the allocation control unit 30 may allocate radio resources in a plurality of burst allocation modes (corresponding to multiple bursty wireless resources).

In this case, the allocation control unit 30 preferably allocates radio resources corresponding to continuous areas (bursts) within the data frame structure.

As a second method, as shown in FIG. 13 , the allocation control unit 30 may construct a data frame structure for use by dividing the above-mentioned area (burst) as the number of mobile terminals located in each cell increases.

In this case, the allocation control unit 30 determines an area (burst) to be allocated to a specific mobile terminal.

Then, the allocation control unit 30 divides the area (burst) equally according to the number of mobile terminals to which radio resources corresponding to each area are allocated, or according to the transmission rate requested by each mobile terminal, etc. The wireless resource corresponding to the area divided by the terminal.

In this allocation method, especially when there are multiple areas to which radio resources usable in the inner area of the cell are allocated, the allocation control unit 30 needs to consider Status of mobile terminals in other cells.

Specifically, the allocation control unit 30 may allocate equal (or predetermined ratio) radio resources used by mobile terminals to each area, and assign a mobile terminal with higher received power or a higher (CINR-required quality) The radio resources used in mobile terminals are allocated to areas with high usage rates.

At this time, the allocation control unit 30 may determine in advance the maximum number of multiplexed mobile terminals that can be allocated at one time in each area (burst).

(sixth embodiment)

Hereinafter, the wireless communication system of this embodiment will be described mainly in terms of differences from the wireless communication systems of the above-mentioned first to fifth embodiments.

In the above-mentioned first to fifth embodiments, in the downlink, since the receiving end is a mobile terminal, the base station cannot directly observe the SINR (especially the amount of interference).

Therefore, the base station needs to obtain or estimate the amount of interference in the mobile terminal.

Specifically, the allocation control unit 30 may allocate radio resources (subchannels and OFDM symbols) usable in the inner area of the cell or the outer area of the cell as Available radio resources (subchannels and OFDM symbols).

On the other hand, the allocation control unit 30 may cause the mobile terminal to report the communication quality in the downlink in a specific format.

In addition, the allocation control unit 30 may limit the candidates for subchannels allocated to the mobile terminal based on the received power in the uplink, and request the mobile terminal to measure and notify communication quality such as CQI (Channel Quality Indicator) information of these candidates. , allocate subchannels according to the reported CQI information.

In this case, since the communication quality of radio resources available in the inner area of the cell is considered constant in the inner area, it is not necessary to measure the communication quality (channel state) of each subchannel available in the inner area.

In addition, in the above example, a method of estimating the above-mentioned communication quality by the base station or a method of obtaining the communication quality using a dedicated control signal has been described.

In IEEE802.16, a mobile terminal transmits a CDMA code when making an initial frequency band utilization request. Here, the CDMA codes to be transmitted are randomly selected from a plurality of codes prepared in advance.

Moreover, the mobile terminal also periodically sends the CDMA code when not sending data, and adjusts the sending timing, sending power or frequency offset.

At this time, the CDMA codes to be transmitted are randomly selected from a plurality of codes prepared in advance (different from the codes used when making the initial bandwidth use request described above).

In addition, the assignment control unit 30 further divides the pre-prepared CDMA codes into a plurality of groups, and associates them with desired subchannels or types of subchannels (perfect orthogonal channels or quasi-orthogonal channels).

Then, the allocation control unit 30 selects a desired subchannel according to the received power and the state of interference on the mobile terminal side, and transmits a code corresponding to the subchannel.

In this way, by using a ranging code (ranging code), it is possible to transmit CQI information without separately preparing a control channel for transmitting CQI information.

(seventh embodiment)

Hereinafter, the wireless communication system of this embodiment will be described mainly in terms of differences from the wireless communication systems of the first to sixth embodiments described above.

In the above-mentioned first to sixth embodiments, an example in which a plurality of base stations in the same wireless communication system communicate using sub-channels (frequencies) within a specific frequency band has been described. However, in the seventh embodiment of the present invention, as shown in FIG. As shown in 14, base stations A and B of different wireless communication systems A and B perform communication using subcarriers (frequency) within the same frequency band.

Here, when a plurality of base stations in the same wireless communication system communicate using subcarriers (frequencies) within a specific frequency band, between the data frame structures used by both, centralized control in the wireless communication system can easily The area allocated to the fully orthogonal channel and the area allocated to the quasi-orthogonal channel are made to have the same configuration.

On the other hand, as in this embodiment, when base stations A and B of different wireless communication systems A and B communicate using subcarriers (frequency) in the same frequency band, as shown in FIG. Between the data frame structure of the wireless communication system B and the data frame structure used in the wireless communication system B, since the operators of the two wireless communication systems are different, it is difficult to separate the areas allocated with completely orthogonal channels and the areas allocated with quasi-orthogonal channels Make the same configuration. Therefore, the effect of the present invention may be reduced.

In order to solve the above-mentioned problems, in the present embodiment, the allocation control unit 30 determines the arrangement of areas to which complete orthogonal channels are allocated and areas to which quasi-orthogonal channels are allocated by the following method.

As a first method, the allocation control unit 30 may determine the allocation (burst allocation pattern) according to the number of wireless communication systems coexisting in each area.

Specifically, the allocation control unit 30 may determine in advance the correspondence relationship between the number of wireless communication systems coexisting in each area and the above configuration (the ratio of the area allocated with a complete orthogonal channel and the area allocated with a quasi-orthogonal channel), and use This correspondence determines the above configuration.

Here, the allocation control unit 30 may determine the number of wireless communication systems coexisting in each area according to the surrounding radio wave conditions, or may determine the number of wireless communication systems coexisting in each area by using a common control channel to communicate with base stations of other wireless communication systems. number of communication systems.

As a second method, the allocation control unit 30 matches the configuration of a wireless communication system with a smaller proportion of areas allocated with completely orthogonal channels to the configuration of a wireless communication system with a greater proportion of areas allocated with completely orthogonal channels.

(eighth embodiment)

Hereinafter, the wireless communication system according to this embodiment will be described mainly in terms of differences from the first to seventh embodiments described above.

In a wireless communication system that performs area development, the reach distance of a notification signal may be reported as one of the factors that limit the coverage of a cell.

Therefore, generally, in a wireless communication system that performs surface development, taking into account interference between base stations A and B of different wireless communication systems A and B, broadcast signals can be received at all positions in the virtual coverage area. To determine the configuration of the base station, the allocation of sub-channels and the transmission parameters of the notification signal.

Therefore, these broadcast signals are preferably transmitted using completely orthogonal subchannels that can easily secure subchannels with low interference levels.

Moreover, when base stations of different wireless communication systems communicate using subcarriers (frequencies) within a specific frequency band, unlike the case where base stations of the same wireless communication system communicate using subcarriers (frequency) within a specific frequency band, Estimating the amount of interference from other base stations makes it difficult to determine the arrangement of base stations, allocation of subchannels, and transmission modes of broadcast signals.

Therefore, the allocation control unit 30 allocates subchannels to broadcast signals in the following manner.

As a first method, the allocation control unit 30 may allocate at least one broadcast signal to a subchannel usable in the outer area of each cell.

For example, as shown in FIG. 16, the assignment control unit 30 of the base station A assigns the radio resource corresponding to the area in which the complete orthogonal channel is assigned in the data frame structure as the radio resource for transmitting the notification signal in the radio communication system A. To perform allocation, the allocation control unit 30 of the base station B allocates radio resources corresponding to areas in which complete orthogonal channels are allocated in the data frame structure as radio resources for transmitting broadcast signals in the radio communication system B.

As a second method, the allocation control unit 30 may exclusively allocate a part of the subchannels usable in the outer area of each cell to broadcast signal transmission.

Specifically, the allocation control unit 30 of each radio communication system recognizes the perfect orthogonal channel used as the control channel, and does not use the perfect orthogonal channel for data transmission.

In addition, the allocation control unit 30 of each wireless communication system may identify the complete orthogonal channel using surrounding base stations in the same wireless communication system.

(ninth embodiment)

Hereinafter, the wireless communication system of this embodiment will be described mainly in terms of differences from the wireless communication systems of the first to eighth embodiments described above.

In the above-mentioned first to eighth embodiments, the allocation control unit 30 separates the area to which the complete orthogonal channel is allocated and the area to which the quasi-orthogonal channel is allocated in the time axis direction (OFDM symbol direction) in the data frame structure (see Figure 4, Figure 16, etc.).

On the other hand, in the wireless communication system according to this embodiment, as shown in FIG. 17 , the allocation control unit 30 separates, in the frequency axis direction (sub-channel direction), the area to which the completely orthogonal channel is allocated and the area to which the channel is allocated, in the data frame structure. The region of quasi-orthogonal channels.

It can be applied regardless of whether base stations of different wireless communication systems use subcarriers (frequency) in a specific frequency band to communicate, or base stations of the same wireless communication system use subcarriers (frequency) in a specific frequency band to communicate. This embodiment.

(Other implementations)

Although this invention was described by the above-mentioned embodiment, it should not be understood that this invention is limited by the statement and drawing which make a part of this indication. From this disclosure, various alternative embodiments, examples, and operating techniques should be apparent to those skilled in the art.

For example, in this embodiment, a base station has been described as an example of a wireless communication device having the allocation control unit 30, but the wireless communication device having the allocation control unit 30 may also be a wireless control device that controls a base station or a high-level device such as a switching center. .

As mentioned above, although this invention was demonstrated in detail using the said embodiment, it is obvious to those skilled in the art that this invention is not limited to embodiment demonstrated in this specification. The present invention can be modified and the embodiments can be changed without departing from the spirit and scope of the present invention defined by the claims. Therefore, the description of the present invention is only for the purpose of illustration and description, and does not limit the present invention in any way.

Claims (12)

1. A wireless communication device configured in a wireless communication system that implements a frequency division multiple access method using a frequency division multiplexing method as a modulation method, and divides a cell into an inner area and an outer area, its characterized in that, having an allocation control unit that allocates a complete orthogonal channel as a subchannel usable in the outer area, and allocates a quasi-orthogonal channel as a subchannel usable in the inner area, all the subcarriers included in the completely orthogonal channel allocated as subchannels usable in the outer area of the adjacent cell are orthogonal to each other, Some of the subcarriers included in the quasi-orthogonal channel allocated as subchannels usable in the inner area of the adjacent cell overlap and some of them are orthogonal. 2. The wireless communication device according to claim 1, wherein: The allocation control unit allocates a subchannel usable in the outer area to a mobile terminal whose desired wave reception power is lower than a predetermined threshold, and assigns a subchannel in the outer area to a mobile terminal whose desired wave reception power is higher than the predetermined threshold. Subchannels available in the inner zone. 3. The wireless communication device according to claim 1 or 2, wherein: The inner region is divided into a plurality of regions, The allocation control unit allocates quasi-orthogonal channels with different usage rates as sub-channels usable in the plurality of divided inner areas. 4. The wireless communication device according to any one of claims 1 to 3, characterized in that, The allocation control unit allocates radio resources to mobile terminals located in the outer area of each cell in a burst allocation pattern defined by a combination of at least one completely orthogonal channel and at least one symbol in the data frame structure, The burst allocation pattern is the same among all cells. 5. The wireless communication device according to any one of claims 1 to 4, characterized in that, The allocation control unit allocates the switching call to the subchannel available in the outer area. 6. The wireless communication device according to any one of claims 1 to 4, characterized in that, The inner region is divided into a plurality of regions, The allocation control unit allocates the handover call to a subchannel usable in one of the plurality of divided inner areas. 7. The wireless communication device according to claim 5 or 6, wherein: The allocation control unit allocates the handover call to an area close to an area to which the preamble is allocated in the data frame structure. 8. The wireless communication device according to any one of claims 1 to 7, characterized in that, The allocation control unit allocates subchannels usable in either the inner area or the outer area to the mobile terminal based on downlink communication quality notified by the mobile terminal. 9. The wireless communication device according to any one of claims 1 to 3, wherein: The allocation control unit allocates wireless resources to mobile terminals located in the outer area of each cell in a burst allocation mode specified by a combination of at least one completely orthogonal channel and at least one symbol in the data frame structure; The allocation control unit changes the burst allocation pattern according to radio wave conditions. 10. The wireless communication device according to any one of claims 1 to 9, wherein: The allocation control unit allocates at least one notification signal to a subchannel usable in the outer area. 11. The wireless communication device according to any one of claims 1 to 9, characterized in that, The allocation control unit exclusively allocates a part of the sub-channels usable in the outer area for notification signal transmission. 12. A kind of wireless communication method, this method is used in wireless communication system, this wireless communication system uses frequency division multiplexing method as modulation method to realize frequency division multiple access method, and subdistrict is divided into inner region and outer region, its characterized in that, having the following steps: the wireless communication device allocates a complete orthogonal channel as a subchannel usable in the outer area, allocates a quasi-orthogonal channel as a subchannel usable in the inner area, all the subcarriers included in the completely orthogonal channel allocated as subchannels usable in the outer area of the adjacent cell are orthogonal to each other, Some of the subcarriers included in the quasi-orthogonal channel allocated as subchannels usable in the inner area of the adjacent cell overlap and some of them are orthogonal.

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