Source: https://patents.google.com/patent/JP4641877B2/en
Timestamp: 2020-01-26 06:57:39
Document Index: 298285145

Matched Legal Cases: ['art 115', 'art 214', 'arts 505', 'art 101', 'art 102', 'art)\n103', 'art)\n109']

JP4641877B2 - Transmission control method, terminal-side transmission method, interference power measurement method, control station apparatus, and terminal apparatus - Google Patents
Transmission control method, terminal-side transmission method, interference power measurement method, control station apparatus, and terminal apparatus Download PDF
JP2007013344A (en
JP2007013344A5 (en
2005-06-28 Priority to JP2005189029A priority Critical patent/JP4641877B2/en
2007-01-18 Publication of JP2007013344A publication Critical patent/JP2007013344A/en
2011-03-02 Publication of JP4641877B2 publication Critical patent/JP4641877B2/en
The present invention relates to a transmission control method, a terminal-side transmission method, an interference power measurement method, a control station apparatus, and a terminal apparatus that measure interference power in a system that performs wireless communication using a multicarrier transmission scheme.
1-cell repetitive OFDM / (TDMA, FDMA) (Orthogonal Frequency Division Multiplexing / Time Division Multiple Access, Frequency Division Multiple Access) uses OFDM as a modulation method, TDMA and FDMA as an access method, and uses the same frequency in all cells. This is a communication system. Thus, when the same frequency is used in all cells, high frequency utilization efficiency can be achieved. Hereinafter, OFDM / (TDMA, FDMA) will be briefly described.
FIG. 11 is a diagram illustrating an example of an OFDM / (TDMA, FDMA) two-dimensional frame configuration. FIG. 11 shows frequency on the vertical axis, time on the horizontal axis, the downlink frame on the upper level, and the uplink frame on the lower level. In FIG. 11, one of the squares constituting the frame is a slot. A slot is a minimum unit used for data transmission, and slots composed of a plurality of OFDM symbols are periodically arranged. A frame is formed by arranging slots according to this cycle.
FIG. 11 shows an example of the configuration for one frame. The slots are divided into control slots, random slots, and data slots. In FIG. 11, in the downlink frame, a control slot is arranged at the head and a data slot is arranged behind the control slot. In the uplink frame, a random slot is arranged at the head and a data slot is arranged behind the random slot. In FIG. 11, one control slot in the time axis direction, three random slots, and eight data slots are arranged in one frame, but this number varies depending on the system. In addition, twelve slots are arranged in the frequency axis direction, and this number also differs depending on the system. The control slot includes information indicating which data slot is allocated to which terminal device. The random slot is used when the terminal apparatus transmits data to the base station in a state where no data slot is allocated. A group of slots in the frequency axis direction at the same time is defined as a frequency channel, and a group of slots in the time axis direction at the same frequency is defined as a time channel.
When communicating from a base station to a terminal device, the base station indicates information indicating that a downlink slot has been allocated to a communication partner terminal device in a control slot, and information addressed to the corresponding terminal device in the allocated slot. Send. When communicating from a terminal device to a base station, the terminal device first makes a slot allocation request to the base station using a random slot. When the base station receives a slot allocation request using this random slot, the base station indicates information indicating that an uplink slot has been allocated to the terminal apparatus that has requested the slot allocation in the control slot. The terminal device confirms that uplink slot allocation has been performed for the control slot, and transmits using the data slot. As described above, the OFDM / (TDMA, FDMA) system is a system in which a plurality of terminal apparatuses perform data transmission / reception with a base station at different frequencies and times based on the above-described matters.
Next, a transmission circuit and a reception circuit used for OFDM / (TDMA, FDMA) will be described. FIG. 12 is a block diagram showing a schematic configuration of a transmission circuit used for OFDM / (TDMA, FDMA), and FIG. 13 is a block diagram showing a schematic configuration of the reception circuit. However, here, the case where the number of frequency channels is 12 and the number of subcarriers transmitted in one frequency channel is 64 is shown.
The transmission circuit shown in FIG. 12 includes a multiplex unit 1000, error correction code units 1001-a to 1001-l, serial / parallel conversion units (S / P conversion units) 1002-a to 1002-l, and a modulation scheme determination unit 1003. , Mapping section 1004, transmission power control section 1005, IFFT (Inverse Fast Fourier Transform) section 1006, parallel / serial conversion section (P / S conversion section) 1007, guard interval insertion section (GI insertion section) 1008 , A digital / analog conversion unit (D / A conversion unit) 1009, a wireless transmission unit 1010, and an antenna unit 1011. The error correction code units 1001-a to 1001-l and the serial / parallel conversion units (S / P conversion units) 1002-a to 1002-l are provided with the same number as the number of frequency channels (here, 12 indicated by a to l).
The multiplex unit 1000 separates the control data and information data into a sequence of the number of frequency channels (here, 12) in units of packets. That is, in the multiplex unit 1000, the OFDM / (TDMA, FDMA) slot designated by the control unit (not shown in FIG. 12) is physically designated. The data separated into the series corresponding to the number of frequency channels is error-correction-coded in the error-correcting code units 1001-a to 1001-l, and separated into 64 systems in the S / P conversion units 1002-a to 1002-l. Then, the mapping unit 1004 modulates each carrier. The mapping unit 1004 may perform modulation using a different modulation scheme for each frequency channel or subcarrier. The modulation scheme determination unit 1003 selects a modulation scheme to be used for each frequency channel or subcarrier.
Modulation scheme determining section 1003 selects a modulation scheme based on the reception status of each frequency channel or each subcarrier on the receiving side. For subcarriers with extremely poor reception conditions, a technique for preventing the occurrence of errors by making no transmission (carrier holes) may be used. The modulation scheme determining unit 1003 is not essential for the OFDM / (TDMA, FDMA) system, and is necessary when constructing a system that uses a different modulation scheme for each frequency channel or subcarrier. In addition, when using a different modulation scheme for each frequency channel or subcarrier, it is necessary to notify the receiving side of the modulation scheme information of each frequency channel or each subcarrier, and the modulation scheme before the data symbol in the data slot A symbol for information notification must be provided. For this reason, the modulation method determined by the modulation method determination unit 1003 is also input to the multiplex unit 1000 as modulation method information, and is transmitted along with the information data through the subsequent processing.
After modulation in the mapping unit 1004, the modulated data is converted into transmission power for each frequency channel specified by the control unit by the transmission power control unit 1005, and IFFT unit 1006 performs IFFT processing. Thereafter, a guard interval is inserted by the guard interval insertion unit 1008 via the P / S conversion unit 1007. Then, after being converted into an analog signal by the D / A conversion unit 1009 and converted to a frequency to be transmitted by the wireless transmission unit 1010, it is transmitted from the antenna unit 1011.
Next, the receiving circuit will be described. 13 includes an antenna unit 1100, a wireless reception unit 1101, an analog / digital conversion unit (A / D conversion unit) 1102, a synchronization unit 1103, a guard interval removal unit (GI removal unit) 1104, and a serial / parallel. Conversion unit (S / P conversion unit) 1105, FFT (Fast Fourier Transform) unit 1106, received power measurement unit 1107, transmission path estimation demapping unit 1108, parallel / serial conversion unit (P / S conversion unit) 1109-a to 1109-l, error correction decoding units 1110-a to 1110-l, and a demultiplexing unit 1111.
In the receiving circuit, first, a signal received by the antenna unit 1100 is frequency-converted to a frequency band where A / D conversion is possible by the wireless receiving unit 1101. The data converted into a digital signal by the A / D conversion unit 1102 is subjected to OFDM symbol synchronization by the synchronization unit 1103 and the guard interval is removed by the guard interval removal unit 1104. Thereafter, the S / P converter 1105 parallelizes the data to 1024. The FFT unit 1106 performs 1024-point FFT and converts the signal into signals for each subcarrier. Received power measuring section 1107 measures received signal power for each subcarrier. The received signal power information is fed back to the transmission side and used when the modulation scheme determining unit 1103 selects the modulation scheme for each frequency channel or each subcarrier. Further, the signal after FFT is sent to propagation path estimation demapping section 1108, where 768 subcarriers are demodulated. Usually, propagation path estimation is performed by using a known signal sent from a transmitter to a receiver. Demapping is performed based on modulation scheme information notified from the transmission side. Thereafter, every 12 systems of data is input to the P / S converters 1109-a to 1109-l. Then, error correction decoding processing is performed by the error correction decoding units 1110-a to 1110-1 and input to the demultiplexing unit 1111. In the demultiplex unit 1111, the control data and the information data are processed and output.
Since the OFDM / (TDMA, FDMA) system performs communication using the same frequency in all cells, high frequency utilization efficiency can be achieved, but reception characteristics deteriorate due to the influence of interference coming from adjacent cells. It is possible. Japanese Patent Laid-Open No. 2003-46437 (Patent Document 1) discloses an example of a technique for reducing the influence of inter-cell interference.
FIG. 14 is a diagram showing a cell configuration of the technique disclosed in Japanese Patent Laid-Open No. 2003-46437 (Patent Document 1). In FIG. 14, a hexagonal cell indicated by a solid line is defined as one cell region, and a hexagon indicated by a dotted line is indicated in each cell. The B0 cell will be described as an example. In the B0 cell, the area farthest from the base station is Ts1, the next area is Ts2, and the nearest area is Ts3. Ts1 to Ts3 represent a time (time zone) in which the base station performs communication, and one frame is configured with Ts1 to Ts3. In B0, communication is performed with the highest transmission power during Ts1, and communication is performed with power reduced to Ts2 and Ts3. Similarly, each cell performs communication by changing transmission power in accordance with each time.
In B0, when communication is performed with a high transmission power during Ts1, other adjacent cells are not set to perform communication with the highest transmission power, so B0 is an interference from other cells. It is possible to communicate with less state. Similarly, the cells B1 to B6 can be communicated in a state where the influence of inter-cell interference is reduced. Further, the invention disclosed in Japanese Patent Laid-Open No. 2003-46437 (Patent Document 1) is such that transmission power in a plurality of areas set in accordance with the distance from the base station is temporally changed in each cell. However, when this is applied to an OFDM / (TDMA, FDMA) system, it is also possible to change the transmission power in each area for each frequency channel instead of changing it in terms of time. .
On the other hand, since a time channel for performing communication with high (low) power in a certain area set according to the distance from the base station is predetermined for each cell, a new base station is It cannot respond adaptively when it is built in the vicinity. In this regard, it is possible to flexibly cope with changes in the surrounding environment by measuring the amount of interference arriving from adjacent cells constantly or periodically and changing the time channel assignment according to the amount of interference. When performing such adaptive control in downlink communication, it is necessary to measure the amount of interference coming from an adjacent cell on the terminal device side. This is because a slot to which a terminal device is not allocated in its own cell (empty slot). ) Can be realized by measuring the power. The measurement of the interference power can be performed by the reception power measurement unit 1107 shown in FIG. 13 as with the measurement of the desired signal power.
JP 2003-46437 A
However, in the above-described technique, traffic in a cell increases, terminal devices are allocated to almost all slots, and a situation occurs in which there are very few empty slots. Under such circumstances, the terminal device cannot measure interference power, and the base station cannot obtain effective interference power information for use in scheduling or the like. Therefore, there arises a problem that channels (slots) cannot be allocated flexibly corresponding to changes in the surrounding environment.
The present invention has been made in view of such circumstances, and a transmission control method, a terminal-side transmission method, and an interference that enable measurement of interference power even in a situation where multi-carrier transmission has very few empty slots. An object is to provide a power measurement method, a control station apparatus, and a terminal apparatus.
(1) A transmission control method according to the present invention is a transmission control method of a control station apparatus that performs radio transmission to a terminal apparatus to be controlled by a multicarrier transmission method, and is a subcarrier set in a carrier hole in a neighboring cell It is characterized in that subcarriers having different frequencies from those of the above are set as carrier holes and transmitted wirelessly.
As described above, since the carrier holes are arranged at different positions (frequencies) between adjacent cells, the positions (frequencies) at which the carrier holes are set do not overlap. As a result, the interference power from the adjacent cell can be accurately measured even in a situation where there are few slots available.
(2) Further, the transmission control method according to the present invention is a transmission control method of a control station apparatus that performs radio transmission to a terminal device to be controlled by a multicarrier transmission method, and is one or more determined by a certain length of time. Using a communication frame composed of a plurality of communication slots specified by one time channel and one or more frequency channels defined in a certain frequency band, setting a carrier hole for each communication slot, and transmitting wirelessly It is a feature.
In this way, by setting a carrier hole for each slot, interference power information can be acquired from the terminal device to which the slot is assigned. Even when the number of empty slots is very small, interference power can be measured in the carrier holes set in the slots. As a result, based on the measured interference power information, it is possible to assign slots that flexibly respond to changes in the surrounding environment.
(3) Further, in the transmission control method according to the present invention, for each communication slot, a subcarrier having a frequency different from a subcarrier set as a carrier hole in a neighboring cell is set as a carrier hole, and wireless transmission is performed. It is a feature.
In this way, since carrier holes are arranged at different positions (frequency) between adjacent cells, the positions (frequency) at which carrier holes are set do not overlap. The interference power from the cell can be accurately measured.
(4) Also, in the transmission control method according to the present invention, the carrier hole is set to a subcarrier that is determined to have a poor reception status when a signal transmitted from the control station apparatus is received by the terminal apparatus. It is characterized by.
In this way, by setting a subcarrier whose reception status is not preferable in a carrier hole and measuring the interference power, it is possible to improve the reception status by measuring the interference power without reducing the amount of data transmission. .
(5) In the transmission control method according to the present invention, information indicating the position of the carrier hole is transmitted to the terminal device.
In this way, by notifying the terminal device of information indicating the position of the carrier hole, the terminal device can grasp the position of the carrier hole. As a result, the received power of the carrier hole can be measured and notified to the control station apparatus as interference power information.
(6) In the transmission control method according to the present invention, the interference power information is received from a plurality of terminal apparatuses for each communication slot, and the average interference power is averaged by averaging the plurality of interference power information for each communication slot. It is characterized by calculating a value.
Thus, since interference power information measured by a terminal device is collected from a plurality of terminal devices for each slot and the plurality of interference power information is averaged, it is possible to acquire accurate interference power information, and accuracy Slot allocation can be performed based on a high reception situation.
(7) Moreover, the transmission control method according to the present invention weights the plurality of interference power information based on distance information of each of the plurality of terminal devices, and averages the plurality of weighted interference power information. It is characterized by.
In this way, since the interference power information is weighted using the distance information where the terminal device where the interference power is measured is placed, the interference power information reflecting the location where the terminal device is placed can be acquired. .
(8) Further, in the transmission control method according to the present invention, the distance information is a magnitude of transmission power to each of the plurality of terminal devices.
Thus, by making the distance information with the terminal device the magnitude of the transmission power, the level difference of the interference power information caused by the difference in the position of the terminal device can be corrected.
(9) Further, in the transmission control method according to the present invention, a predetermined number of pieces of interference power information are selected and averaged for each communication slot among the plurality of pieces of interference power information.
As described above, since a predetermined number of pieces of interference power information are selected and averaged from a plurality of pieces of interference power information, the measurement result of the terminal device that cannot accurately measure the interference power due to the influence of shadowing or distance is excluded. be able to.
(10) In the transmission control method according to the present invention, position information is received from each of the plurality of terminal apparatuses, and the average interference power calculation unit classifies the plurality of interference power information in association with the position information. The interference power value is calculated by averaging the classified interference power information.
In this way, a plurality of pieces of interference power information are classified in correspondence with the position information, and the interference power value is calculated by averaging the classified interference power information. Therefore, based on the positional relationship with the terminal device, from a specific direction The incoming interference power can be calculated for each slot.
(11) Moreover, in the transmission control method according to the present invention, the location information is identifiers of a plurality of control station devices received by the plurality of terminal devices during cell search, and among the plurality of terminal devices, It is characterized by averaging the interference power information measured by the terminal devices having the same identifier.
In this way, by using the identifier of the control station device of the adjacent cell, it becomes possible to classify the terminal devices that exist in the same direction, and the terminal device also uses the result of the cell search, Processing can be simplified.
(12) In addition, in the transmission control method according to the present invention, the control station apparatus uses a directional antenna, divides the cell into a plurality of sectors, performs wireless communication, and transmits from a terminal apparatus arranged in the same sector. The received interference power information is averaged for each communication slot.
As described above, when a directional antenna is used, a sector where a cell is divided can be used to grasp a direction in which a terminal device exists, and interference power arriving from a certain direction can be calculated for each slot.
(13) A terminal transmission method according to the present invention is a terminal-side transmission method of a terminal device that receives a signal transmitted from a control station device by a multicarrier transmission method, and specifies a carrier hole from the control station device. The received power in the carrier hole is measured, an average value of the measured received power is calculated, and the average value of the received power is transmitted as interference power information to the control station apparatus. .
Thus, since the information specifying the carrier hole is received from the control station apparatus, it is possible to specify the position (frequency) of the subcarrier set in the carrier hole and measure the interference power of the carrier hole. As a result, it is possible to measure the interference power even in a situation where there are few empty slots, and the control station apparatus can allocate slots flexibly corresponding to changes in the surrounding environment.
(14) In the terminal transmission method according to the present invention, the control station apparatus receives slot allocation information in which a communication slot is allocated to each of a plurality of terminal apparatuses, and to which terminal apparatus based on the slot allocation information In the communication slot that is not allocated, the received power of each of the plurality of subcarriers is measured, or the received power of the subcarrier set in the carrier hole in the communication slot allocated to any terminal device Is measured, an average value of the received power measured for each communication slot is calculated, and the average value of the received power is transmitted to the control station apparatus as interference power information.
In this way, the received power of each of the plurality of subcarriers is measured in a communication slot that is not allocated to any terminal device, or the carrier hole is measured in the communication slot that is allocated to any terminal device. When there is an empty slot, the received power is measured in the empty slot. On the other hand, if there are few or no empty slots, it is already set in one of the terminal devices. It is possible to measure received power in a carrier hole that is forcibly set in an assigned communication slot. As a result, even when there are few empty slots, more accurate interference power information can be collected in the control station apparatus, and the reception situation can be improved.
(15) In the terminal transmission method according to the present invention, position information indicating a position within a control range of the control station apparatus is transmitted to the control station apparatus.
Thus, the terminal device can notify the control station device of the location information of the terminal device by notifying the control station device of the location information, and the control station device can notify the location information of the terminal device. Since the interference power information can be used, the reception situation can be improved.
(16) In the terminal transmission method according to the present invention, the location information is an identifier of at least one control station apparatus received at the time of cell search.
Thus, since the terminal device uses the result of the cell search, the processing can be simplified. Moreover, the control station apparatus can classify terminal apparatuses existing in the same direction by using the identifiers of the control station apparatuses of adjacent cells, and can improve the reception status more flexibly.
(17) An interference power method according to the present invention is an interference power measurement method in the case where radio communication is performed between a control station apparatus and a terminal apparatus to be controlled by a multicarrier transmission method, and the control The station apparatus is characterized in that at least one subcarrier to which data can be allocated is set in a carrier hole, and information specifying the set carrier hole is transmitted to the terminal apparatus.
In this way, at least one of the subcarriers that can be used for data transmission is forced to be a carrier hole, so even if the number of empty slots is very small, the interference power is measured in the carrier hole. Can do. As a result, based on the measured interference power information, it is possible to assign slots that flexibly respond to changes in the surrounding environment.
(18) An interference power method according to the present invention is an interference power measurement method in the case where wireless communication is performed between a control station apparatus and a terminal apparatus to be controlled by the multicarrier transmission method, and the terminal In the apparatus, information identifying a carrier hole set in at least one subcarrier to which data can be allocated is received from the control station apparatus, the received power in the carrier hole is measured, and an average value of the measured received power is obtained. The average value of the received power is calculated and transmitted to the control station apparatus as interference power information.
(19) Moreover, the control station apparatus according to the present invention includes a plurality of communication slots specified by one or more time channels defined by a certain time length and one or more frequency channels defined by a certain frequency band. A control station device that wirelessly transmits a configured communication frame to a terminal device to be controlled by a multi-carrier transmission method, comprising a carrier pattern setting unit that sets a carrier hole for each communication slot .
(20) A terminal apparatus according to the present invention is a terminal apparatus that receives a signal transmitted from a control station apparatus by a multicarrier transmission method, and that receives information identifying a carrier hole from the control station apparatus. A reception power measurement unit that measures reception power in the carrier hole, calculates an average value of the measured reception power as interference power information, and a transmission unit that transmits the interference power information to the control station device. It is characterized by providing.
According to the present invention, it is possible to measure interference power even in a situation where multicarrier transmission has very few empty slots.
Next, embodiments of the present invention will be described with reference to the drawings. In addition, embodiment described below is only an example of this invention and is not limited to these.
In the present invention, the control station apparatus sets at least one subcarrier to which data can be allocated to the carrier hole, notifies the terminal apparatus of information identifying the carrier hole, and the terminal apparatus measures the received power in the carrier hole. To do. Then, the control station device receives the interference power information from the terminal device. Alternatively, the control station apparatus receives, from the terminal apparatus, interference power information indicating interference power from an adjacent cell measured in a frequency band of a subcarrier that is determined not to allocate data in advance among a plurality of subcarriers. To do. As a result, the interference power can be measured even in a situation where there is little slot space.
The control station apparatus controls a terminal apparatus that performs wireless communication. The control station apparatus includes a wireless communication base station and a wireless LAN (Local Area Network) access point.
The terminal device performs wireless communication under the control of the control station device. The terminal device includes a mobile station in a cellular system and a station in a wireless LAN system regardless of whether the terminal device is a fixed terminal device or a mobile terminal device.
Multi-carrier transmission uses a carrier composed of a plurality of subcarriers to which data is allocated, and a carrier (frequency band composed of a plurality of subcarriers that enables encoding / transmission power change for each subcarrier. ) To transmit data.
A carrier hole is a subcarrier to which no data is allocated. The communication slot is a minimum unit used for data transmission, and is specified by one or more time channels defined by a certain time length and one or more frequency channels defined by a certain frequency band. The communication slot is also referred to as a slot. The communication frame is composed of a plurality of communication slots. The communication frame is also referred to as a frame.
In the following embodiments, the present invention is applied to wireless communication in a one-cell repetitive OFDM / (TDMA, FDMA) system, and a base station as a control station device and a terminal device (mobile station) perform wireless communication. A case will be described as an example. However, the present invention is not limited to the application of these wireless communications, and when an access point as a control station device controls a station as a terminal device to perform wireless communication, for example, in a wireless LAN or the like. Can be applied.
The first embodiment describes a case where the interference power received by each terminal apparatus is measured in the slot to which each terminal apparatus is allocated even in a situation where traffic in the cell increases and there are very few empty slots.
FIG. 1 is a diagram illustrating an example of a symbol configuration in which a base station according to an embodiment of the present invention sets a carrier hole. The lower part of FIG. 1 shows two frames of downlink communication that constitute an OFDM symbol. Further, the upper part of FIG. 1 shows subcarrier arrangements for the first data slot of the frame and the first symbol of the second data slot for each of the two frames. It is assumed that other symbols and other data slots have similar subcarrier arrangements.
In the symbol configuration shown in FIG. 1, in downlink communication from a base station to a terminal device, 8 subcarriers (subcarrier positions indicated by arrows in FIG. 1) per carrier frequency channel (64 subcarriers) are carrier holes. Is set. Each slot in a frame has a carrier hole set in the same pattern, and each frame uses a pattern in which a carrier hole is set at a subcarrier position different from that of the previous frame. Is arranged. In FIG. 1, the base station sets the subcarrier position specified by n satisfying (Equation 1) as a carrier hole.
(N + x + b) mod 8 = 0 (Formula 1)
Here, n is the number of a subcarrier constituting one frequency channel, and identifies any of the 64 subcarriers. As shown in FIG. 1, each subcarrier in each frequency channel is assumed to be assigned an integer from 0 to 63 in advance. x is a frame number indicating the number of frames to be transmitted, and is an integer of x ≧ 1. Assume that the value of x is reset to 1 again after a certain period of time (a certain number of frames are transmitted), and a common value is used in all base stations. b is a number assigned to each base station in advance, and a different number is always less than 8 in adjacent base stations (since one carrier hole is set for every 8 subcarriers in FIG. 1). It shall be.
Thus, by making the value of b different at adjacent base stations, the carrier holes set at each base station can also be at different subcarrier positions. Therefore, by setting the position of the subcarrier where n satisfying (Equation 1) is assigned as the subcarrier number as the carrier hole, one carrier hole per 8 subcarriers is shifted for each frame and each adjacent base station. Can be placed in position. Note that (Equation 1) shows an example in which a carrier hole is set for every 8 subcarriers, but the present invention is not limited to this.
In the terminal device that has received the signal in which the carrier hole is set, the reception power at the subcarrier position that is the carrier hole is measured for the signal in the frequency domain obtained after the FFT. Then, the received power in eight carrier holes arranged per frequency channel is averaged, and this average value is used as interference power information between cells. By notifying the interference power information measured in this way from the terminal device to the base station, the amount of interference received by the terminal device assigned to the slot can be grasped at the base station.
As described above, in the first embodiment, subcarriers in a symbol in downlink transmission are set / transmitted in a carrier hole based on a predetermined pattern expressed by (Equation 1), and are set in the carrier hole. This is a technique for estimating the amount of interference coming from an adjacent cell by measuring the power at the subcarrier position at the terminal device. The measurement of interference power using such a carrier hole does not include the signal of the own cell because the subcarrier set in the carrier hole is not transmitted, and only the interference component is present at the position of the corresponding subcarrier (carrier hole). This is possible because of the observation.
Next, the configurations of the base station and the terminal device in the first embodiment will be described. FIG. 2 is a block diagram illustrating an example of a schematic configuration of the base station according to the first embodiment. FIG. 3 is a block diagram illustrating an example of a schematic configuration of the terminal device according to the first embodiment.
The base station shown in FIG. 2 includes a multiplex unit 100, error correction code units 101-a to 101-l, serial / parallel conversion units (S / P conversion units) 102-a to 102-l, and a modulation scheme determination unit 103. , Mapping section 104, transmission power control section 105, IFFT section 106, parallel / serial conversion section (P / S conversion section) 107, guard interval insertion section (GI insertion section) 108, digital / analog conversion section (D / A conversion) Unit) 109, a radio transmission unit (transmission unit) 110, an antenna unit 111, a radio reception unit (reception unit) 112, an uplink receiver 113, a carrier hole setting unit 114, and a slot allocation unit 115. The error correction code units 101-a to 101-l and the S / P conversion units 102-a to 102-l have the same number as the frequency channels (here, 12 shown by a to l).
The multiplex unit 100 separates the control data and information data into packets for the number of frequency channels (here, 12) in units of packets, and the error correction code units 101-a to 101-l The S / P converters 102-a to 102-l separate the error-corrected encoded data into 64 systems.
The modulation scheme determining unit 103 creates modulation scheme information using the terminal apparatus side received power information and the carrier hole pattern. In the first embodiment, the modulation scheme determination unit 103 selects a modulation scheme for subcarriers to which data is allocated using received power information on the terminal device side, and uses subcarriers to be carrier holes using a carrier hole pattern. Modulation method information for setting the carrier hole is created.
The mapping unit 104 performs modulation for each subcarrier based on the modulation scheme information.
The transmission power control unit 105 converts the modulated subcarriers into predetermined transmission power based on the transmission power control information. The transmission power control information is created in advance by a control unit (not shown in FIG. 2). The control unit is a module that is executed under the control of a CPU (Central Processing Unit). The IFFT unit 106 performs IFFT processing on the converted data, the P / S conversion unit 107 serially converts the data, the GI insertion unit 108 inserts a guard interval, and the D / A conversion unit 109 converts the data. Convert to analog signal.
The wireless transmission unit 110 transmits a signal (control signal, data) via the antenna unit 111.
The wireless reception unit 112 receives signals (control signals and data) transmitted from each terminal device via the antenna unit 111.
The uplink receiver 113 performs conversion processing (demodulation, decoding, etc.) on the signal received by the radio reception unit 112, and extracts information data, interference power information for each terminal device, and reception power information on the terminal device side.
The carrier hole setting unit 114 sets at least one subcarrier to which data can be assigned as a carrier hole. That is, the carrier hole setting unit 114 sets the position of the subcarrier to be a carrier hole and creates a carrier hole pattern that identifies the subcarrier set to the carrier hole. In this embodiment, the carrier hole setting unit 114 sets a carrier hole using (Equation 1). The carrier hole setting unit 114 forcibly sets “at least one subcarrier to which data can be allocated”, that is, at least one of subcarriers used for data transmission, as a carrier hole. Thereby, a carrier hole is forcibly set to a subcarrier to which data can be allocated.
In the first embodiment, the carrier hole setting unit 114 uses (Equation 1) to set a subcarrier having a frequency different from the subcarrier set as the carrier hole in the adjacent cell as the carrier hole, A carrier hole pattern that identifies a subcarrier set as a carrier hole among a plurality of subcarriers to which data can be assigned is created. The created carrier hole pattern is output to modulation scheme setting section 103 and incorporated into modulation scheme information.
The slot allocation unit 115 allocates the slot used by each terminal device based on the received power information on the terminal device side input from the uplink receiver 113, the allocation status to other terminals, and the amount of information data to be transmitted. Determine and create slot allocation information.
Next, the terminal device will be described. 3 includes an antenna unit 200, a radio reception unit (terminal device side reception unit) 201, an analog / digital conversion unit (A / D conversion unit) 202, a synchronization unit 203, a guard interval removal unit (GI removal unit). ) 204, serial / parallel converter (S / P converter) 205, FFT unit 206, received power measuring unit 207, transmission path estimation demapping unit 208, parallel / serial converter (P / S converter) 209- a-209-l, error correction decoding units 210-a-210-l, a demultiplexing unit 211, an uplink transmitter 212, a wireless transmission unit (terminal device side transmission unit) 213, and a control unit 214. The P / S conversion units 209-a to 209-l and the error correction decoding units 210-a to 210-l are provided with the same number as the number of frequency channels (here, 12 shown by a to l).
The radio reception unit (terminal device side reception unit) 201 receives a signal (control signal, data) transmitted from the base station via the antenna unit 200.
The A / D conversion unit 202 converts the signal into a digital signal, the synchronization unit 203 performs OFDM symbol synchronization, the GI removal unit 204 removes the guard interval, and the S / P conversion unit 205 Parallelize to data. The FFT unit 206 performs 1024-point FFT and converts it to a signal for each subcarrier.
Received power measuring section 207 measures the received power of the subcarriers set in the carrier hole based on the carrier hole pattern, and calculates the average value of the measured received power as interference power information. In the base station of the connection destination, since the transmission power is set to zero for the subcarriers set in the carrier hole, the reception power of the carrier hole becomes interference power from the adjacent cell.
The propagation path estimation demapping unit 208 demodulates the 768-wave subcarriers subjected to the FFT processing. The P / S conversion units 209-a to 209-l convert every 12 systems of data, and the error correction decoding units 210-a to 210-l perform error correction decoding processing.
The demultiplexing unit 211 outputs the carrier hole pattern (which may be included in the modulation scheme information) to the reception power measurement unit 207 in addition to processing the error-corrected data into control data and information data. .
Uplink transmitter 212 converts information to be transmitted from the terminal device into a signal for transmission (encoding, modulation, etc.), and outputs the converted signal to radio transmission section 213.
The wireless transmission unit 213 transmits a signal (control signal, data) to the base station via the antenna.
The control unit 214 receives the control data and detects information on the slot to which the terminal device is assigned based on the slot assignment information included in the control data. The detected information is output to the received power measuring unit 207.
Next, the interference power measurement operation of the first embodiment will be described. FIG. 4 is a flowchart illustrating an example of the operation of measuring interference power in the first embodiment. In the flowchart, the base station side processing is shown on the left side, the terminal device side processing is shown on the right side, and the arrows show how information is transmitted and received between the base station and the terminal device (the flowcharts in other drawings are the same). Take the form).
First, the base station transmits a control signal to the terminal device (step S100). The control signal is a signal modulated by a modulation scheme common to all subcarriers determined in advance so as to be received by all terminal apparatuses in the cell. Next, the base station determines a subcarrier number to be set in the carrier hole (step S101). Specifically, the carrier hole setting unit 114 obtains n satisfying (Equation 1), creates a carrier hole pattern, and delivers the created carrier hole pattern to the modulation scheme determination unit 103. Next, modulation scheme determining section 103 sets a subcarrier assigned a subcarrier number corresponding to n as a carrier hole based on the carrier hole pattern, and further determines a modulation scheme for subcarriers other than the carrier hole. Then, modulation scheme information is created (step S102). The modulation scheme information created in this way includes carrier hole information indicating the position of the carrier hole and the modulation scheme. For the modulation scheme information, a carrier hole is identified in the modulation scheme information by a method determined in advance with the terminal device, such as attaching a specific symbol (mark) to the subcarrier set in the carrier hole. Next, each subcarrier is modulated based on the modulation scheme information (step S103), modulation scheme information necessary for notifying the reception side of the modulation scheme of each subcarrier is added to the data, and the data is transmitted to the wireless transmission unit. 110 is transmitted to the terminal device (step S104).
The terminal device first receives the transmitted control signal and acquires slot allocation information (step S110). Further, the terminal device receives data to be transmitted thereafter (step S111). The data is demodulated based on the added modulation method information (step S112). Next, the received power measurement section 207 of the terminal device identifies the position of the subcarrier set in the carrier hole from the carrier hole information included in the modulation scheme information, and receives the subcarrier set in the carrier hole. Measure power (interference power). Received power measuring section 207 measures received power and calculates received power information for subcarriers to which data is assigned (subcarriers not set in carrier holes) (step S113).
Next, the received power measurement unit 207 calculates an average value by averaging the received power in eight carrier holes provided per frequency channel, and the calculated average value is calculated by the terminal device assigned to the corresponding slot. Interference power information between cells in the corresponding slot is received (step S114). The uplink transmitter 212 converts the received power information and the interference power information into a signal for transmission, and transmits the signal to the base station from the radio transmission unit 213 (step S115).
The radio reception unit 112 of the base station receives the converted signal, and the uplink receiver 113 performs conversion processing on the received signal and acquires reception power information and interference power information (step S105).
In this way, the base station can acquire the interference power information from the terminal device to which the slot is assigned for each of the plurality of slots included in one frame. The interference power information acquired by the base station is used as follows. The slot allocation unit 115 performs slot scheduling and the like in consideration of the influence of adjacent cells using the acquired plurality of interference power information. Moreover, the slot allocation part 115 acquires the received power information of each subcarrier with interference power information about the allocated slot from each of a plurality of terminal devices. The acquired received power information of each subcarrier is used for determining the modulation scheme of each subcarrier when transmitting the next frame. With the above procedure, a plurality of subcarriers can be set as a carrier hole, and the power of interference coming from an adjacent cell can be measured through the set carrier hole.
Thus, by forcibly setting a carrier hole to a subcarrier to which the base station can allocate data, it is possible to measure interference power information in the carrier hole. Accordingly, the base station can acquire the interference power information even when the number of empty slots is very small, and can allocate slots flexibly corresponding to changes in the surrounding environment.
When carrier holes are set according to a predetermined pattern, the same interference power can be measured even if a carrier hole is set using another pattern instead of the carrier hole setting pattern shown in FIG. It is. In this case, as shown in FIG. 1, more accurate interference power can be measured by setting carrier holes with a predetermined interval. This is because the reception power of adjacent subcarriers has a high correlation, so when carrier holes are provided together, interference power is measured very high due to fading, or conversely very low. This is because the influence of interference that the corresponding slot receives on average may not be correctly evaluated. On the other hand, as shown in FIG. 1, even when carrier holes are set at certain intervals, there are carrier holes that are measured with high interference power and carrier holes that are measured with low interference due to fading. By averaging, the interference power received by the measurement terminal apparatus in the corresponding slot can be obtained more accurately.
Further, when diversity reception using a plurality of antennas is performed in the terminal device, the received power that is different for each antenna is averaged and then reported to the base station. In addition to this, a configuration may be adopted in which the largest value among the interference powers observed for each carrier hole in each antenna is selected for each carrier hole, averaged, and then reported to the base station. By adopting such a configuration, it is possible to avoid that the interference power is estimated to be low due to the influence of fading.
The carrier hole setting unit 114 uses (Equation 1) to create the same carrier hole pattern for each slot in one frame, but may create a different carrier hole pattern for each slot. The carrier hole setting unit 114 can set carrier holes to subcarriers having different relative positions in each frequency channel, or set carrier holes to subcarriers having different relative positions in each time channel. You can also
Furthermore, in the above description, the base station has been described as the transmitting side and the terminal device as the receiving side, but the present invention is not limited to this. For example, a configuration is adopted in which a reception power measurement unit is provided in the base station and a carrier hole setting unit is provided in the terminal device. Then, the base station transmits request information indicating which subcarrier should be a carrier hole to the terminal device, sets the carrier hole in the terminal device, performs uplink communication, and the base station measures the interference power in the carrier hole. It is also possible to take the form.
Moreover, when applying 1st Embodiment to the communication which uses wireless LAN, it is not necessary to consider the carrier hole pattern of an adjacent cell. Since the control station apparatus includes a carrier hole setting unit that forcibly sets data to subcarriers to which data can be allocated, the present invention can be applied.
In the second embodiment, a case will be described in which a plurality of terminal devices measure interference power in one slot and the interference power information measured in each terminal device is notified to the base station.
FIG. 5 is a block diagram illustrating an example of a schematic configuration of the base station according to the first embodiment. The base station has a configuration in which a changeover switch 316, a weighting unit 317, and an interference power calculation unit 318 are added to the configuration shown in FIG. In addition, a function is added to the carrier hole setting unit 314.
The carrier hole setting unit 314 outputs the created carrier hole pattern to the changeover switch 316 in addition to the functions described in FIG. Also, it is assumed that the carrier hole setting unit 314 creates a carrier hole pattern using (Equation 1), as in the first embodiment.
The changeover switch 316 selects either the modulation scheme information created by the modulation scheme decision unit 103 or the carrier hole pattern created by the carrier hole setting unit 314 and passes it to the multiplex unit 100. The changeover switch 316 selects the carrier hole pattern when the control data is input as the data input to the multiplex unit 100, and selects the modulation scheme information when the information data is input. That is, the changeover switch 316 selects a carrier hole pattern when transmitting control data, and selects modulation scheme information of each subcarrier when transmitting control data, according to data transmitted from the base station to the terminal device. Hand over to.
The weighting unit 317 weights interference power information transmitted from a plurality of terminal devices using predetermined information regarding the terminal devices. The predetermined information includes distance information between each terminal device and the base station, position information of each terminal device, and the like. In the second embodiment, a case where the weighting unit 317 performs weighting according to distance information will be described. Specifically, the weighting unit 317 includes a maximum transmission power Pmax that can be transmitted by the base station per frequency channel and a transmission power Pi (i is a terminal) required for downlink transmission per frequency channel to each terminal device. The ratio (Pmax / Pi) of device numbers: i = 1, 2,..., The number of terminal devices) is multiplied by the measured interference power information. However, in downlink transmission from the base station to each terminal device, transmission power control is performed so that the received power at the terminal is constant.
When the transmission power control is correctly performed in the downlink transmission to each terminal device in the cell, the weighting is reported by the terminal device located near the cell edge (the transmission power required for the downlink transmission is close to the maximum transmission power). The received interference power information is multiplied by a weight having a value close to 1 (substantially no weight), and conversely, is located near the base station (the transmission power required for downlink transmission is much lower than the maximum transmission power). Will be multiplied by a very large weight. Interference due to downlink transmission of adjacent cells is usually observed largely in terminal devices located near the cell edge, but in the vicinity of the base station of the own cell that is far from the interference source (base station of the adjacent cell). Not as large as near the cell edge. However, just because no interference is observed (or very weak) in the terminal devices located around the base station of the own cell, the interference power coming from the neighboring cell is not always weak, and it is far away from the interference source. In a terminal device located in the vicinity of a base station, a slot in which even slight interference is observed can be considered to be a slot in which a signal with a large power is transmitted from a base station in an adjacent cell. The weighting corrects the level difference of the measurement interference power caused by the difference in the position of the measurement terminal device according to the distance between the base station and the terminal device.
The average interference power calculation unit 318 averages a plurality of pieces of interference power information measured by each terminal device to calculate an average interference power value, and uses the calculated average interference power value as interference power information of each slot. Output to. Also, the average interference power calculation unit 318 performs the following processing because the interference power information of each slot notified from each terminal device has a large number of samples. The average interference power calculation unit 318 extracts the interference power information of each slot input from the weighting unit 317 for each slot by a predetermined number of samples in the order of interference power information having a larger numerical value. Next, the interference power information of each slot is calculated by averaging the extracted interference power information for each slot.
In this way, by extracting only the one having a large numerical value from the interference power information of each slot input to the average interference power calculation unit 318, the base station of the adjacent cell transmits a signal (interference). Nevertheless, it is possible to exclude the measurement result by the terminal device that cannot observe the interference at all due to the influence of shadowing or distance, and to avoid the interference power being estimated lower than the actual.
In FIG. 5, components having the same reference numerals as those in FIG. 2 have the same names and similar functions, and thus description thereof is omitted. Further, the terminal device can be realized with the same configuration as the terminal device shown in FIG.
In the second embodiment, since each terminal apparatus measures interference using a carrier hole even in a slot to which another terminal apparatus is allocated, the setting status of carrier holes in all slots to which the terminal apparatus is allocated Need to be understood by all terminal devices. If there is an empty slot (a slot to which no terminal device is assigned), measure the interference power for all subcarriers in the empty slot (measurement of interference power in the empty slot is the same as the conventional method). And For this reason, the terminal device also grasps all the allocation situations other than its own allocation slot. Here, also in the second embodiment, as in the first embodiment, assuming that each slot in a frame sets a carrier hole in the same pattern, each slot in the first control slot of each frame is set. By including information indicating the carrier hole pattern together with the allocation information, the carrier hole pattern of all slots can be easily grasped in all terminal apparatuses. Also, when different carrier hole patterns are set in each slot in the frame, although the amount of information indicating the carrier hole pattern increases, all the terminal devices can be obtained by putting such information in the control slot. It is possible to grasp the positions of the carrier holes in all slots. With such a configuration, it is possible to transmit control data including allocation information of all slots in a frame and a carrier hole pattern toward all terminal apparatuses.
Also, it is assumed that each terminal apparatus measures interference power in as many slots as possible within a range not exceeding the number of frequency channels that can be received, and reports all the measurement results to the base station.
FIG. 6 is a diagram illustrating an example of a configuration of a reception power measurement unit of the terminal device according to the second embodiment. FIG. 6 is a diagram illustrating an example of a configuration of the reception power measurement unit 207 that realizes the function of measuring interference power according to the second embodiment. The reception power measurement unit 207, the uplink transmitter 212, and the control The relationship with the part 214 is shown. The received power measurement unit 207 includes a measurement unit 501, a selection unit 502, a local slot processing unit 503, an empty slot processing unit 504, and another slot processing unit 505.
The uplink transmitter 212 has the same function as in FIG. The control unit 214 determines the slot type based on the slot allocation information included in the control data, and outputs the slot type to the selection unit 502 of the received power measurement unit 207. The slot type designates one of a self slot to which the terminal device is assigned, another slot to which another terminal device is assigned, and an empty slot to which no terminal device is assigned. Measurement unit 501 measures the received power of the signal input from FFT unit 206. In the example illustrated in FIG. 6, the measurement unit 501 measures the reception power of each subcarrier, and the measured reception power is transmitted to the own slot processing unit 503, the empty slot processing unit 504, and other slots via the selection unit 502. The example of a structure delivered to either of the process parts 505 is shown.
The selection unit 502 inputs the slot type from the control unit 214, selects one of the processing functions of the own slot processing unit 503, the empty slot processing unit 504, and the other slot processing unit 505 based on the input slot type, The received power measured by the measurement unit 501 is transferred to the selected processing function. The selection unit 502 serves as a switch for selecting a processing function.
The own slot processing unit 503 calculates received power information and interference power information using the received power and modulation scheme information obtained by measuring the signal of the own slot, and outputs the calculated information to the uplink transmitter 212.
The vacant slot processing unit 504 calculates received power information by averaging the received power of each subcarrier constituting the vacant slot.
The other slot processing unit 505 calculates interference power information using the received power and the carrier hole pattern obtained by measuring the signals of the other slots. The carrier hole pattern is acquired from the control data transmitted to the terminal device and input to the other slot processing unit 505.
By adopting such a configuration, even when interference power information of each slot is reported from a plurality of terminal devices, the level difference of the measurement result due to the difference in the position of the measurement terminal device is corrected and used for scheduling, etc. It is possible to calculate effective interference power information.
Next, the operation of measuring interference power according to the second embodiment will be described. FIG. 7 is a flowchart showing an example of operation of interference power measurement in the second embodiment. In the base station, the carrier hole setting unit 314 calculates a subcarrier number to be set for the carrier hole, and creates a carrier hole pattern (step S200). Here, (Formula 1) is used as in the first embodiment. Next, the changeover switch 316 inputs the created carrier hole pattern to the multiplex unit 100 at the timing when the control data is transmitted. The carrier hole pattern is converted into a control signal together with the control data and the slot assignment information, and transmitted from the base station to the terminal device (step S201). The transmitted control signal is received by a plurality of terminal devices existing in the cell, and the carrier hole pattern and slot allocation information in the transmitted frame are notified.
Each terminal apparatus acquires a carrier hole pattern and slot allocation information from the received control signal (step S210). From the slot allocation information, a slot and an empty slot for demodulating the information signal are recognized. In the terminal device, the slot allocation information is output to the control unit 214, and the carrier hole pattern is output to the received power measurement unit 207. The control unit 214 inputs slot allocation information and determines the slot type.
On the other hand, in the base station, following the transmission of the control signal, the modulation scheme determination unit 103 determines the modulation scheme of each subcarrier, sets a carrier hole based on the carrier hole pattern, and creates modulation scheme information (step) S202). The changeover switch 316 inputs the created modulation scheme information to the multiplex unit 100 at the timing when the information data is transmitted. The modulation scheme information of each subcarrier is added to the information data, and the information data to which the modulation scheme information is added is modulated based on the modulation scheme information and converted into an information signal (step S203). Information signals are sequentially transmitted from the base station to the terminal device for each time channel (step S204).
Information signals transmitted from the base station are sequentially received by the terminal device. The selection unit 502 inputs the slot type from the control unit 214, and determines whether or not the slot of the transmitted information signal is a slot allocated to the terminal device of itself based on the slot allocation information (Step S502). S211). If it is determined that the slot is not assigned to its own terminal device (NO in step S211), it is determined whether the slot is an empty slot (step S212). When the slot is an empty slot (NO in step S212), measurement section 501 measures the received power (interference power) of all the subcarriers in the empty slot, and empty slot processing section 504 measures the measured interference power of each subcarrier. Are averaged to calculate interference power information of empty slots (S213). On the other hand, when another terminal device is assigned (not an empty slot) (YES in step S212), other slot processing unit 505 detects a subcarrier set in the carrier hole using the carrier hole pattern. The reception power (interference power) of the carrier hole is acquired from the reception power measured by the measurement unit 501 (step S214). Next, the other slot processing unit 505 calculates the interference power information in the corresponding slot by averaging the measured interference powers of the plurality of carrier holes (step S215). The calculated interference power information is output to the uplink transmitter 212 and notified from each terminal device to the base station (step S216).
If the selection unit 502 determines that the slot is assigned to the terminal device of itself based on the slot type (Yes in step S211), the terminal device demodulates the received information signal (step S218). . The own slot processing unit 503 acquires the received power (interference power) in the carrier hole and the received power of each subcarrier from the received power of the slot measured by the measuring unit 501 (S219). Next, the own slot processing unit 503 calculates the interference power in the corresponding slot by averaging the measured interference power (step S220). The calculated interference power information for each slot and the received signal power of each subcarrier are output to the uplink transmitter 212 and notified from each terminal device to the base station (step S221). In addition, the process shown to step S211-step S221 is repeatedly performed in each slot of each frequency channel in a terminal device.
The base station acquires interference power information (and received signal power of each subcarrier) in each slot from each terminal device (step S205). The weighting unit 317 weights the acquired plurality of pieces of interference power information according to the distance between the base station and the measurement terminal device (step S206). The average interference power calculation unit 318 extracts N samples (N is an integer greater than or equal to 1 in advance) from the largest numerical value for each slot for the plurality of weighted interference power information (step S207). An average of the extracted samples is calculated for each slot and used as interference power information of the corresponding slot (step S208). The calculated interference power information of each slot is output to the slot allocation unit 115 and used for scheduling or the like considering the influence of neighboring cells.
As described above, in the second embodiment, a plurality of terminal devices located at different locations measure the interference power in each slot and notify the measured interference power information to the base station. That is, each terminal device measures interference power even for a slot to which its own terminal device is not assigned. As a result, the interference power in each slot can be measured more accurately. In the first embodiment, since the terminal device assigned to the slot measures the interference power in the assigned slot, one terminal device measures the interference power for one slot. However, since the interference power largely depends on the position of the terminal device that performs the measurement (distance from the interference source) and the like, the interference power received by the corresponding slot is not always correctly represented. Such a problem can be solved.
The weighting method described in this embodiment is an example, and various other weighting methods can be considered. It is also possible to calculate an average value of interference power information without weighting.
In addition, the configuration of the reception power measurement unit 207 illustrated in FIG. 6 is an example, and is not limited thereto. FIG. 6 illustrates an example in which the selection unit 502 distributes the received power measured by the measurement unit 501 to each processing unit (any of the own slot processing unit 503, the empty slot processing unit 504, and the other slot processing unit 505). The measurement unit 501 may output the measurement result to each processing unit. In addition, each processing unit may be provided with the function of the measurement unit 501 and may have other configurations.
In the third embodiment, a case will be described in which interference power is measured in consideration of the positional relationship between a base station and a terminal device.
FIG. 8 is a block diagram illustrating an example of a schematic configuration of a base station according to the third embodiment. In the base station, the weighting unit 317 is removed from the configuration of the base station shown in FIG. 5, and the base station ID (base station identifier) received at the time of cell search by each terminal device is connected to the connected base station by uplink communication. A function of receiving base station ID information.
The uplink 413 performs conversion processing (demodulation, decoding, etc.) on the signal received by the radio reception unit 112, and receives information data, interference power information for each terminal device, received power information on the terminal device side, and a receiving base station of each terminal device Take out the ID information.
The average interference power calculation unit 418 inputs a plurality of interference power information measured by each terminal device and a base station ID (position information) reported from each terminal device, and uses the plurality of interference power information as a base station ID. Classification is performed in association with each other, and the interference power value is calculated by averaging the classified interference power information. That is, average interference power calculation section 418 treats terminal devices having the same base station ID as a terminal device group, and averages the interference power information reported from terminal devices belonging to the same terminal device group for each slot. Thereby, the interference power coming from a certain direction can be calculated for each slot.
In FIG. 8, components having the same reference numerals as those in FIG. 2 or FIG. 5 have the same names and similar functions, and thus description thereof is omitted.
Also, the terminal device in the third embodiment can be realized by substantially the same configuration as the terminal device in the first embodiment shown in FIG. However, in the third embodiment, each terminal device notifies the base station ID included in the control signal received at the time of cell search to the connected base station, so that the demodulated base station ID is updated as shown in FIG. A configuration is required that can input to the link transmitter 212 and notify the base station ID information to the base station through uplink communication.
In the third embodiment, a base station ID included in a control signal received when a terminal device performs a cell search is used as means for classifying a plurality of terminal devices distributed in a cell according to directions with respect to the base station. Shall. Specifically, among the terminal devices in the cell, the terminal devices having the same base station ID included in the control signal received during the cell search are set as the terminal devices located in the same direction, and are located in the same direction. The result of averaging the interference powers reported from the terminal devices is taken as interference power arriving in the direction in which those terminal devices are located. This is because terminal devices located in the same direction as viewed from the base station often receive control signals from the same adjacent base station during cell search, and the terminal devices having the same received base station ID are the same. This is because it can be determined that the terminal device is located in the direction. Also in this embodiment, similarly to the above-described embodiment, a carrier hole with a known pattern is set in a slot to which a terminal device is assigned, and interference power is measured in the set carrier hole.
Next, the interference power measurement operation of the third embodiment will be described. FIG. 9 is a flowchart illustrating an example of the operation of measuring interference power in the second embodiment. The terminal device performs a cell search when starting communication (step S310). In general, the cell search is a process of receiving a control signal transmitted from a plurality of base stations and searching for a base station to be connected, that is, a base station that has transmitted a signal with the highest received power. After the cell search, the terminal apparatus notifies the base station to be connected of the transmission source base station ID included in all control signals received during the cell search together with the connection request (step S311).
The base station receives the connection request and the base station ID from the terminal device (step S300). In the base station, the slot allocation unit 115 allocates slots to the terminal apparatus that has notified the connection request (step S301). Any method may be used for slot allocation. After determining the allocation slot, the carrier hole setting unit 314 creates a carrier hole pattern (step S302). Here, as in the first embodiment, it is assumed that carrier holes are set using (Equation 1). Next, the slot allocation information is transmitted as a control signal together with the carrier hole pattern to all terminal apparatuses in the cell (step S303). Next, a carrier hole is set, and a data signal subjected to adaptive modulation is transmitted (steps S304 to S306). The steps S303 to S306 perform the same operations as the steps S201 to S204 in FIG.
The terminal device receives the control signal transmitted in step S303, and acquires the carrier hole pattern and slot allocation information (step S312). The step S312 performs the same process as the step S210 of FIG. Further, the terminal device performs each of steps S211 to S221 in FIG. 7 on the data signal transmitted in step S306 (step S313). Through these steps, the terminal apparatus notifies the base station of interference power information measured in a carrier hole or an empty slot.
The base station receives the measurement results of the interference power information and the reception power information in each terminal apparatus, selects a terminal apparatus with the previously notified base station ID and reports the interference power reported from those terminal apparatuses. An average value is calculated (step S308). By performing such processing, the interference power reported from the terminal device having the same transmission source base station ID of the signal received during the cell search, that is, the terminal device located in the same direction as viewed from the base station. Can be calculated for each slot, and the interference power coming from adjacent cells can be determined for each direction. The control flow shown in FIG. 9 shows control in the first frame after connection for a terminal device that newly requests a connection and a base station corresponding to the terminal device. Steps S308 and S312 to S313 are repeated for each frame.
As described above, in the third embodiment, the interference power information reported from the terminal devices located in the same direction as viewed from the connected base station is collected, and the power of inter-cell interference coming from each direction is calculated. be able to. Thus, in order to perform scheduling and the like in consideration of the arrival direction of interference coming from the adjacent cell, it is possible to grasp how much interference comes from which direction. Therefore, it is possible to measure the interference power considering not only the distance between the base station and the terminal device but also the direction in which the measurement terminal device is located.
In addition, when a sector antenna having directivity is used in the base station and the inside of the cell is sectorized, a plurality of terminal devices accommodated in the same sector are located in the same direction as viewed from the base station. It is considered a thing. Therefore, the average interference power calculation unit 418 averages the interference power information received from the terminal devices arranged in the same sector for each slot. In this way, by averaging the interference power information reported from the terminal apparatus accommodated in each sector for each sector and for each slot, it is possible to calculate interference power coming from a certain direction.
Further, by adding the weighting unit 317 shown in FIG. 5 to the schematic configuration of the base station shown in FIG. 8 and performing weighting as shown in the second embodiment, the interference power can be obtained more accurately. Is possible.
In the fourth embodiment, instead of setting a carrier hole according to a predetermined pattern, a subcarrier that is judged to have a low reception power and a bad reception status is set as a carrier hole at the base station. The interference power in the carrier hole is measured by the terminal device.
The base station can use the configuration shown in FIG. 2, and the terminal device can use the configuration shown in FIG. 3, but the following points are different. The base station does not use the function of the carrier hole setting unit 114. Also, modulation scheme determining section 103 uses received power information to determine a subcarrier to be set in the carrier hole, and inserts a symbol or the like that can identify the subcarrier set in the carrier hole into the modulation scheme information. Symbols and the like that have been agreed with the terminal device in advance may be used as long as the carrier hole can be specified. Further, the modulation scheme determining unit 103 does not need to input a carrier hole pattern. The received power measuring section 207 of the terminal device specifies the position of the subcarrier set in the carrier hole by using a symbol inserted in the modulation scheme information.
Next, the interference power measurement operation of the fourth embodiment will be described. FIG. 10 is a flowchart illustrating an example of the operation of measuring interference power in the first embodiment. The base station transmits a control signal (step S400). The control signal is a signal modulated by a modulation scheme common to all subcarriers. The modulation scheme determining unit 103 of the base station determines the modulation scheme of each subcarrier based on the reception status of each subcarrier notified from the terminal device. At this time, the modulation scheme determination unit 103 sets a subcarrier whose reception status in the terminal device is extremely bad (reception power is extremely low) as a carrier hole (step S401).
In this way, modulation scheme determining section 103 creates modulation scheme information including carrier hole information that identifies a carrier hole by a symbol or the like. Next, each subcarrier is modulated by the determined modulation scheme (step S402), and data to which modulation information necessary for notifying the receiving side of the modulation scheme of each subcarrier is transmitted (step S402). Step S403). Steps S404 and S411 to S415 are the same as steps S105 and S111 to S115 in FIG. The terminal device measures the interference power using the carrier hole and the received power of each subcarrier, and notifies the base station of the result.
As described above, the difference between the fourth embodiment and the first embodiment is that, in the first embodiment, the carrier hole setting unit 114 is obtained by (Equation 1) as shown in Step S100 of FIG. In contrast to creating a carrier hole pattern determined for each frame, in the fourth embodiment, a subcarrier having a significantly poor propagation path condition is used as a carrier hole for measuring interference power. Is adaptively changing.
As described above, in the fourth embodiment, a subcarrier that is determined to have a significantly poor reception condition is set as a carrier hole. However, a subcarrier whose reception condition is remarkably deteriorated in one frequency channel under a frequency selective fading environment. The number is not so large, and since it is distributed to some extent, it is considered that even if the interference power in the set carrier hole is measured, the influence of interference that the corresponding slot receives on average cannot be evaluated correctly. . However, as in the second embodiment, the interference power received by the corresponding slot from the adjacent cell can be calculated more accurately by evaluating together the measurement results from a plurality of terminal devices located at different points in the cell. Is possible.
In the first embodiment described above, since carrier holes are set according to a predetermined pattern, subcarriers with good reception conditions are often set as carrier holes. In this case, transmission is performed with one symbol. However, in the second embodiment, subcarriers with extremely poor reception conditions, that is, subcarriers with a high possibility of causing errors are used as carrier holes, and data on subcarriers with good reception conditions is data. Since it is used for transmission, the amount of data that can be transmitted with one symbol can be maintained while reducing errors.
In the fifth embodiment, a technique for measuring interference power without setting a carrier hole will be described. In general, an FFT output signal when synchronization is established with respect to an incoming signal appears at each subcarrier position to which the signal is assigned during transmission, but an FFT output signal when synchronization is not established is received. It spreads over the entire band (all FFT points) that the machine can observe. That is, when the desired signal arriving from the connected base station and the interference signal arriving from the adjacent cell base station are not synchronized, the receiver performs the receiving operation in synchronization with the desired signal. Will be observed over the entire band that the receiver can observe. Based on such properties, in the fifth embodiment, subcarrier positions (frequency region sample points) that are not used for transmission of information signals within the band when the reception timing of the desired signal and the interference signal are shifted. Assume that the interference power is measured.
In the fifth embodiment, the base station can use the configuration shown in FIG. 2, and the terminal device can use the configuration shown in FIG. 3, but the following points are different. The function of the carrier hole setting unit 114 is not used. Further, the modulation scheme determining unit 103 does not need to input a carrier hole pattern, and does not need to notify the terminal side of information indicating the carrier hole. Therefore, in the base station, at least radio transmission section 110 transmits data to the terminal apparatus using a plurality of subcarriers to which data can be allocated, and radio reception section 112 has sample points in all bands that the terminal apparatus can observe. It is only necessary to have a function of receiving, from a terminal device, interference power information indicating interference power from an adjacent cell measured at a sample point that is determined not to be assigned data in advance.
In addition, the reception power measurement unit 207 of the terminal apparatus measures power at subcarrier positions (sample points) that are not used for predetermined transmission. That is, the received power measurement unit 207 measures the received power from the adjacent cell at the sample points where it is determined in advance that no data is allocated among the sample points in all observable bands, and the average value of the measured received power Ask for. Radio transmission section 213 transmits the average value of received power to the base station as interference power information. For example, in FIG. 3, while the number of FFT points is 1024, the number of subcarriers used for information transmission is 768 (64 × 12), and there are only 1024-768 = 256 samples that are not used for transmission. In this embodiment, the interference power is measured at these 256 sample points.
Such a method can be used in all terminal apparatuses in a system in which base stations of each cell are asynchronous, but cannot be used in all terminal apparatuses in a system synchronized with an adjacent cell. In a system that is synchronized with an adjacent cell, interference power can be measured only in a terminal device in which the reception timing of the desired signal and the interference signal varies even though the base stations are synchronized, Here, a condition of the terminal device that enables measurement of such interference power will be briefly described.
In general, when the base stations of all cells are completely synchronized, the desired signal and the interference signal are almost simultaneously transmitted to the terminal device located near the intermediate point between the connected base station and the adjacent base station serving as an interference source. Will arrive. However, when the terminal device is located around the base station to which it is connected and is far away from the interference source, the desired signal and the interference signal arrive with a time lag, so that demodulation (FFT) is performed synchronously. I can't. Therefore, the interference power can be accurately measured by using the interference power measurement method according to the present embodiment in a terminal device located in the vicinity of the connected base station.
One of the criteria for determining the distance between such a base station and a terminal device is a transmission power value when performing transmission power control. For example, the transmission power required for uplink communication is compared with a predetermined threshold, and if it is determined that the required transmission power is smaller than the predetermined threshold, the corresponding terminal device is far from the base station. Since it is considered that it is located at a point that does not exist, the interference power is measured and the result is reported to the base station. Conversely, if it is determined that the transmission power is greater than the threshold value, the corresponding terminal device is considered to be located at a point away from the base station (near the cell edge), and therefore interference power is not measured. .
Another criterion is whether or not the propagation path of interference signals coming from other cells can be observed. This is because when the propagation path fluctuation of a signal arriving from another cell can be observed, it is considered that the reception timing in the terminal device coincides with the timing at which the interference signal arrives. Is controlled not to measure the interference signal.
In a terminal device that satisfies such conditions, it is possible to measure the power of an interference signal arriving from an adjacent cell by measuring the received power at a subcarrier position (sample point) that is not always used for information transmission. . Then, the interference power reported from those terminal devices is averaged in the base station according to the procedure shown in the second embodiment or the third embodiment, thereby calculating the effective interference power when performing scheduling. Can do.
It is a figure which shows an example of the symbol structure which the base station which concerns on embodiment of this invention set the carrier hole. It is a block diagram which shows an example of schematic structure of the base station which concerns on 1st Embodiment. It is a block diagram which shows an example of schematic structure of the terminal device which concerns on 1st Embodiment. It is a flowchart which shows an example of the operation | movement of interference power measurement in 1st Embodiment. It is a block diagram which shows an example of schematic structure of the base station which concerns on 2nd Embodiment. It is a block diagram which shows an example of a structure of the received power measuring part of the terminal device which concerns on 2nd Embodiment. It is a flowchart which shows an example of the operation | movement of interference power measurement in 2nd Embodiment. It is a block diagram which shows an example of schematic structure of the base station which concerns on 3rd Embodiment. It is a flowchart which shows an example of the operation | movement of interference power measurement in 3rd Embodiment. It is a flowchart which shows an example of the operation | movement of interference power measurement in 4th Embodiment. It is a figure which shows an example of a frame structure of OFDM / (TDMA, FDMA) two-dimensional. It is a block diagram which shows schematic structure of the transmission circuit used for OFDM / (TDMA, FDMA). It is a block diagram which shows schematic structure of the receiving circuit used for OFDM / (TDMA, FDMA). It is a figure which shows the cell structure currently disclosed by patent document 1. FIG.
100 Multiplex part 101-a to 101-l Error correction code part 102-a to 102-l Serial / parallel conversion part (S / P conversion part)
103 Modulation method determination unit 104 Mapping unit 105 Transmission power control unit 106 IFFT unit 107 Parallel / serial conversion unit (P / S conversion unit)
108 Guard interval insertion part (GI insertion part)
109 Digital / analog converter (D / A converter)
110 Wireless transmitter (transmitter)
111 Antenna unit 112 Wireless receiving unit (receiving unit)
113, 413 Uplink receivers 114, 314 Carrier hole setting unit 115 Slot allocation unit 200 Antenna unit 201 Radio reception unit (terminal device side reception unit)
202 Analog / digital converter (A / D converter)
203 Synchronizing unit 204 Guard interval removing unit (GI removing unit)
205 Serial / parallel converter (S / P converter)
206 FFT unit 207 Received power measurement unit 208 Transmission path estimation demapping unit 209-a to 209-l Parallel / serial conversion unit (P / S conversion unit)
210-a to 210-l Error correction decoding unit 211 Demultiplexing unit 212 Uplink transmitter 213 Radio transmission unit (terminal device side transmission unit)
214 Control unit 316 Changeover switch 317 Weighting unit 318, 418 Average interference power calculation unit 501 Measurement unit 502 Selection unit 503 Own slot processing unit 504 Free slot processing unit 505 Other slot processing unit
A cellular system configured by a plurality of cells, in which a control station apparatus arranged in each cell performs radio transmission to a plurality of terminal apparatuses using a communication frame including a plurality of OFDM symbols,
The control station apparatus sets one or more resource units as resource units to which signals are not allocated among resource units called subcarriers that constitute the OFDM symbol and can allocate signals, and does not allocate signals Transmitting a transmission signal including a resource unit toward the plurality of terminal devices, receiving reception quality information transmitted from the plurality of terminal devices, obtaining terminal position information regarding the position of each of the plurality of terminal devices; Using the terminal location information, by averaging the reception quality information transmitted from the plurality of terminal devices, to generate information on interference coming from adjacent cells,
The plurality of terminal devices measure reception quality in resource units to which the signal is not assigned , generate reception quality information indicating a measurement result of the reception quality, and transmit the reception quality information to the control station device A cellular system characterized by that.
The terminal location information is information representing the distance between the control station device and each of the plurality of terminal devices, and the control station device weights the reception quality information based on the information representing the distance, and the weighting The cellular system according to claim 1, wherein the received reception quality information is averaged to generate information related to interference coming from adjacent cells.
3. The cellular system according to claim 2, wherein the information representing the distance is based on the magnitude of transmission power.
The control station device classifies the reception quality information notified from the plurality of terminal devices into a plurality of groups based on the terminal location information, averages the reception quality information for each of the classified groups, 2. The cellular system according to claim 1, wherein the information on interference arriving from an adjacent cell is generated.
The cellular system according to claim 4, wherein the plurality of terminal devices transmit their terminal location information to the control station device.
The terminal location information is an identifier of a control station apparatus received by each of the plurality of terminals at the time of cell search, and is an identifier different from an identifier of a control station apparatus currently performing radio transmission to itself. 6. A cellular system according to claim 5, wherein:
When the control station apparatus uses a directional antenna and divides the cell into a plurality of sectors, the terminal location information is information indicating a sector in which each of the plurality of terminal apparatuses is accommodated, and the control station The apparatus according to claim 1, wherein the apparatus averages the reception quality information notified from the plurality of terminal apparatuses accommodated in the same sector, and generates information on interference arriving from an adjacent cell for each sector. The cellular system described.
The plurality of terminal devices may receive the measurement result of the reception quality in a resource unit to which the signal is not assigned and the measurement result of the reception quality in a resource unit different from the resource unit to which the signal is not assigned. The cellular system according to any one of claims 1 to 7, wherein reception quality information to be notified to an apparatus is generated.
A control station apparatus configured in a plurality of cells and arranged in each cell is a control station apparatus in a cellular system that performs radio transmission to a plurality of terminal apparatuses using a communication frame including a plurality of OFDM symbols,
Among the resource units called subcarriers that constitute the OFDM symbol and can be assigned a signal, one or more resource units are resource units that are not assigned signals, and a transmission signal that includes resource units that are not assigned signals To the plurality of terminal devices, receive reception quality information transmitted from the plurality of terminal devices, obtain terminal location information regarding the location of each of the plurality of terminal devices, and use the terminal location information Then, the control station apparatus generates information on interference coming from an adjacent cell by averaging reception quality information transmitted from the plurality of terminal apparatuses.
JP2005189029A 2005-06-28 2005-06-28 Transmission control method, terminal-side transmission method, interference power measurement method, control station apparatus, and terminal apparatus Active JP4641877B2 (en)
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EP1865679B1 (en) * 2006-06-07 2009-09-30 Mitsubishi Electric R&D Centre Europe B.V. Multicarrier system with multiple null subcarriers in transmitted signal due to variable receive bandwidths and the resulting multiple potential dc subcarriers
JP2012124860A (en) * 2010-12-10 2012-06-28 Sharp Corp Communication system and communication method
JP2000138629A (en) * 1998-10-30 2000-05-16 Kokusai Electric Co Ltd Interfering quantity measuring method of unnecessary wave and radio communication system
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