JP2014022994A - Radio communication device, transmission power controller and radio communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maximize the communication capacity of a non-priority system while suppressing interference on a priority system by inter-subcarrier interference caused by the non-priority system at or below a permitted level in the case where the priority system and the non-priority system, which are not synchronized with each other, share a frequency.SOLUTION: A radio communication device communicating by use of a plurality of frequency elements in a second communication system sharing a frequency with a first communication system includes: a transmission power control unit which determines transmission power of each of the frequency elements so that interference power on a second frequency element (s) will be less than a permitted interference power level using at least a leakage power ratio (R) between transmission power (P) of a first frequency element (x) in the second communication system and power (P) generated on the second frequency element (s) in the first communication system; and means for generating and transmitting a transmission signal by converting a signal of a frequency domain in which the transmission power is determined into a signal of a time domain.

Description

  The present invention relates to a wireless communication device, a transmission power control device, a wireless communication method, and the like.

  In recent years, a method in which a plurality of systems use the same frequency as a cognitive radio system has been studied (refer to Non-Patent Document 1, for example). Conventionally, a method of allowing individual radio frequency bands divided by the frequency division multiplexing (FDM) method to be allocated exclusively to a specific service or user (method not sharing the frequency) has been common. . On the other hand, when the frequency is shared, the non-priority system can use the frequency of the priority system under the restriction that no harmful interference is given to the priority system. In the present application, both “priority system” and “non-priority system” mean a communication system. In the “priority system”, communication can be executed without considering other systems. On the other hand, in the “non-priority system”, communication can be performed under the condition that the priority system does not cause interference more than an allowable level. Therefore, in order to avoid harmful interference to the priority system, the transmitter of the non-priority system grasps the surrounding situation by accessing the database or performing sensing, and determines whether transmission is possible. I do. Further, in the case of the method described in Non-Patent Document 2, in order to improve the frequency utilization efficiency of the entire system, the transmission station of the non-priority system is trying to appropriately control the transmission power.

For example, as shown in FIG. 1, frequency bands B _A , B _B , and B _C are respectively assigned to the transceiver pairs of the priority system communication devices TxA and RxA, TxB and RxB, TxC and RxC, and the non-priority system It is assumed that a part of the frequency band used by the pair of communication devices TxD and RxD affects the receiver of the adjacent priority system. However, it is not a special case where the priority system and the non-priority system use the same wireless interface and are completely synchronized. In the case of the illustrated example, a phenomenon occurs in which part of the signal power in the non-priority system leaks to the frequency band (B _{B in the} illustrated example) of the surrounding priority system due to inter-subcarrier interference. Inter-subcarrier interference is caused not only by interference between the same subcarriers but also by the influence of nonlinear elements such as transmission power amplifiers and mixers, and signal discontinuity between symbols, even between subcarriers with different frequency positions. Interference occurs, and the amount of interference changes due to a shift in the position of the carrier wave or carrier or subcarrier. Therefore, for example, when the non-priority system is a communication system using an orthogonal frequency division multiplexing (OFDM) system, it is not sufficient to suppress the power of subcarriers in the occupied band of the priority system among the subcarriers of the non-priority system. It is. This is because the non-priority system includes not only a frequency band used for OFDM communication but also power leaking to an adjacent band, and the leaked power causes harmful interference to the priority system.

  In the invention described in Non-Patent Document 2, only a general technique for controlling transmission power is shown, and a specific method for controlling transmission power is unknown. Furthermore, in Non-Patent Document 2, transmission power control can be realized by acquiring information on adjacent channel leakage power generated according to a pattern of a transmission signal to be used in advance. However, in this method, the control pattern is practically limited, and there is a problem that the frequency cannot be sufficiently effectively used in the non-priority system. Adjacent channel leakage power is the priority system communication method (single carrier method or multi-carrier method), priority system subcarrier position and non-priority system subcarrier position, non-priority system subcarrier usage status, non-priority system Depends on transmission power (in each subcarrier), propagation path conditions between the non-priority system transmitter and the priority system receiver, etc. For this reason, since there are a great many control patterns, it is not a realistic solution to hold adjacent channel leakage power information for all patterns in advance as in Non-Patent Document 2.

  In Patent Document 1, transmission power in a non-priority system is to be controlled based on information on a propagation path from a non-priority system transmitter to a priority system receiver. However, in the invention described in Patent Document 1, it is assumed that the priority system and the non-priority system are synchronized with each other, and only attempts to deal with non-linearities such as a transmission power amplifier. In the case of an asynchronous system, influences due to discontinuity between symbols considered to be dominant in adjacent channel leakage power, subcarrier position shift, and the like are not considered, and transmission power cannot be controlled appropriately. As a result, the non-priority system has not been able to maximize the communication capacity of the non-priority system while suppressing the interference on the priority system below an allowable level.

  The problem of the present invention is that when the first system (priority system) and the second system (non-priority system) that are not synchronized with each other share the frequency, the second system is subject to the first due to intersubcarrier interference. In other words, the communication capacity of the second communication system is maximized while the interference on the system is suppressed to an allowable level or less.

A wireless communication device according to an embodiment includes:
A wireless communication device that communicates using a plurality of frequency elements in a second communication system that shares a frequency with the first communication system,
A first signal generation unit that generates a frequency domain signal including information to be transmitted;
Transmission power (P _x ) of the first frequency element (x) included in the signal communicated in the second communication system, and the first frequency element (x) due to the first frequency element (x) Using at least the leakage power ratio (R _xs ) between the power (P _s ) generated in the second frequency element (s) in the communication system, a plurality of signals included in the signal communicated in the second communication system The interference power ranging from the entire frequency element (x∈X) to the second frequency element (s) is less than a predetermined allowable interference power level in the second frequency element (s). A transmission power control unit that determines transmission power of each frequency element included in the signal;
A second signal generation unit that generates a transmission signal by converting a signal in the frequency domain in which transmission power is determined, to a signal in the time domain;
And a wireless communication unit that transmits the transmission signal.

  According to the embodiment of the present invention, when the first system (priority system) and the second system (non-priority system) that are not synchronized with each other share the frequency, the second system performs inter-subcarrier interference. As a result, it is possible to maximize the communication capacity of the second communication system while suppressing the interference on the first system below an allowable level.

The figure which shows a mode that a priority system and a non-priority system coexist. The figure which shows the communication system containing the radio | wireless communication apparatus of a non-priority system and a priority system. FIG. 3 is a diagram showing a configuration when a transmission signal is generated by a single carrier method in the wireless communication apparatus shown in FIG. FIG. 3 is a diagram showing a configuration when a transmission signal is generated by a multicarrier method in the wireless communication apparatus shown in FIG. The flowchart which shows the transmission power control method. The figure which shows typically the relationship between the allowable interference power level and frequency in a priority system. The figure which shows the example by which the allowable interference electric power level is prescribed | regulated at three levels of high value PH, medium value PM, and low value PL in steps. The figure which shows the specific example of the allowable interference power level in a priority system, the signal shape of a priority system, and a critical point. The figure which shows a mode that the point where the distance between the intersection Q of the straight line (y 'axis) passing through the origin O and the line representing the allowable interference power level and the origin O is minimized is determined as a critical point in the xy plane. . The figure which shows a mode that interference arises in a priority system resulting from the interference between subcarriers. The figure which shows a mode that interference arises in a priority system resulting from the interference between subcarriers. The figure which shows a mode that the transmission power from subcarrier (xm) to Kth subcarrier (xm + K) is set to the maximum value (Pmax), and the transmission power of other subcarriers is set to zero. The figure for demonstrating the method to allocate transmission power to the subcarrier in a hall | hole. The figure for demonstrating the method to allocate transmission power to the subcarrier in a hall | hole. The figure for demonstrating the method to allocate transmission power to the subcarrier in a hall | hole. The figure which shows a spectrum waveform when the subcarrier space | interval in a priority and a non-priority system is equal. The figure which shows a spectrum waveform in case a subcarrier space | interval in a priority and a non-priority system differs.

  As a method of sharing the frequency between the priority and non-priority systems, it can be considered that the bandwidths of the priority and non-priority systems are the same and different. In the present invention described below, transmission power in the non-priority system (even if the system synchronization between the systems is not completely established, regardless of the difference in system bandwidth between the priority system and the non-priority system) Density) can be controlled appropriately.

In the embodiment described below, leakage power information (R _xs ) leaking from each of a plurality of signal elements included in a non-priority system signal to a signal element in the priority system is a wireless communication device ( Held by the transmitter). The signal element is typically a subcarrier in OFDM, but more generally indicates a frequency band to which data is mapped in the frequency domain. Based on this information, when all subcarriers (x∈X) used for communication are used, the interference from the non-priority system to the priority system is expressed for each subcarrier or for each subcarrier group (for each frequency division). Adjacent channel leakage power information is calculated. Based on this, transmission power control in the non-priority system is performed.

  Embodiments will be described from the following viewpoints with reference to the accompanying drawings. In the figures, similar elements are given the same reference numbers or reference signs.

1． Communications system
2． Transmission power control method
2.1 Band division
2.2 Estimation of interference power
2.3 Calculation of transmit power
2.4 Transmission power transmission
3． Modified example
3.1 Stepwise allowable interference power level
3.2 Power allocation to the hall
3.3 Subcarrier blocking
3.4 Subcarrier spacing The classification of these items is not essential to the present invention, and the items described in two or more items may be used in combination as necessary. May be applied to matters described in other items (unless they contradict).

<1. Communication system>
FIG. 2 shows a communication system including a non-priority system and a wireless communication device of the priority system. The wireless communication device is typically a base station or an access point, but the present invention is not limited to this form, and the wireless communication device may be a user device. Specific examples of the user device include a mobile phone, an information terminal, a high-performance mobile phone, a smartphone, a tablet computer, a personal digital assistant (PDA), a portable personal computer, a palmtop computer, a laptop computer, a desktop computer, and the like. However, it is not limited to these. Since the present invention focuses on transmission power control in the non-priority system, the radio communication device TxD on the transmission side in the non-priority system and the radio communication device RxB on the reception side in the priority system are illustrated. FIG. 2 shows various processing units or functional units included in the wireless communication apparatus that are particularly relevant to the present invention. The wireless communication apparatus may use either a single carrier system or a multicarrier system. The present invention is applicable to any system. The radio communication device TxD on the transmission side includes at least a first transmission signal generation unit 20, a transmission power control unit 21, a second transmission signal generation unit 22, an RF signal generation unit 23, and a common control unit 24.

  The first transmission signal generation unit 20 generates a frequency domain baseband signal including information to be transmitted. Information to be transmitted includes control information, user traffic data, and the like.

  The transmission power control unit 21 performs transmission power control on the output from the first transmission signal generation unit in accordance with an instruction from the common control unit 24. A specific transmission power control method will be described later.

  The second transmission signal generation unit 22 converts the frequency domain baseband signal, whose transmission power is controlled, into a time domain baseband signal.

  The RF signal generation unit 23 generates a transmission signal for wireless communication from a time-domain baseband signal.

  The sharing control unit 24 calculates a transmission power value set in the transmission power control unit 21 based on information from the priority system, and notifies the first transmission signal generation unit 20 and the transmission power control unit 21 of the transmission power value. More specific operations will be described later with reference to FIG. 3A and the like.

  On the other hand, the radio communication device on the receiving side of the priority system includes at least a baseband (BB) signal generation unit 25, an interference signal detection unit 26, a desired signal detection unit 27, an interference allowable condition determination unit 28, and a feedback unit 29.

  A baseband (BB) signal generation unit 25 generates a baseband signal from a signal received by an RF signal reception unit (not shown).

  The interference signal detection unit 26 detects an interference signal received from the radio communication device TxD on the transmission side of the non-priority system.

  The desired signal detection unit 27 extracts a desired signal from the received signals and determines the reception state of the desired signal. The reception state is expressed by, for example, received signal power, radio resources to be used (for example, using the entire band or using a part of the band), and the like.

  The interference allowable condition determining unit 28 determines the level of interference signal power that is allowable in the frequency band of the priority system (allowable interference signal power level).

  The feedback unit 29 feeds back information (information necessary for transmission power control) to the wireless transmission device on the transmission side in the non-priority system as necessary. For example, information such as interference power received from the non-priority system in the priority system may be fed back. Note that the transmitter of the non-priority system may collect information necessary for transmission power control by a method other than such direct feedback. For example, a server that previously collects information related to the priority system (for example, the position, reception performance, operating status, etc. of the receiver of the priority system) notifies the transmission side wireless transmission device of the non-priority system of necessary information. May be. In this case, the wireless communication device on the receiving side of the priority system may transmit information necessary for transmission power control to the server at an appropriate timing, and update the information necessary for transmission power control.

  By the way, the radio communication device TxD on the transmission side in the non-priority system of FIG. 2 may perform communication by a single carrier method or may perform communication by a multicarrier method. However, the configurations of the first and second transmission signal generation units 20 and 22 differ depending on which method is used.

<< In case of single carrier system >>
FIG. 3A shows a configuration when a transmission signal is generated by a single carrier method in the wireless communication apparatus shown in FIG. The first transmission signal generation unit 20 in this case includes a transmission symbol generation unit 201, a signal generation control unit 202, a control signal generation unit 203, a multiplexing unit 204, and an FFT unit 205.

  Transmission symbol generation section 201 receives user data transmitted from radio communication apparatus TxD as an input, and generates a transmission symbol string in accordance with an instruction from signal generation control section 202. The transmission symbol generation unit 201 generates a transmission symbol sequence by adding an error detection code, performing interleaving, performing error correction coding, and performing processing such as symbol mapping. The generated transmission symbol sequence is a time-domain baseband signal.

  The signal generation control unit 202 performs different operations depending on whether the wireless communication device TxD is a base station or a user device. When the radio communication apparatus TxD is a base station, the signal generation control unit 202 determines information necessary for generating a transmission symbol sequence based on the input information, and transmits a transmission symbol generation unit 201 and a control signal generation Notification to unit 203 and multiplexing unit 204. Specifically, the information input to the signal generation control unit 202 includes information fed back from user devices, information on traffic transmitted to each user device, information from the shared control unit 24 (when limiting transmission power) Transmission power value). Also, information necessary for generating a transmission symbol sequence is specifically a data modulation scheme, a channel coding scheme, radio resources for carrying each data, and the like. When the signal generation control unit 202 is a user apparatus, the signal generation control unit 202 specifies information necessary for generating a transmission symbol sequence according to information from the base station, and transmits the transmission symbol generation unit 201, the control signal Notify the generation unit 203 and the multiplexing unit 204.

  The control signal generation unit 203 generates a control signal to be transmitted in accordance with an instruction from the signal generation control unit 202.

  Multiplexer 204 multiplexes the transmission symbol sequence (data) from transmission symbol generator 201 and the control signal from control signal generator 203. The multiplexing method may be any appropriate method known in the art, but as an example, the multiplexing unit 204 may multiplex the transmission symbol sequence and the control signal by the time division multiplexing method.

  The FFT unit 205 performs fast Fourier transform (FFT) on the time-domain baseband signal multiplexed by the multiplexing unit 204 to generate a frequency-domain baseband signal, which is given to the transmission power control unit 21. Each output from the FFT unit 205 is a subcarrier component or signal element. The signal input to the FFT unit 205 may be a multisampled signal or a non-multisampled signal. Further, the FFT size may be set so that signals corresponding to a plurality of symbols can be collectively processed. Multisampling and FFT size are the total bandwidth and control granularity (bandwidth when performing control, i.e. bandwidth of signal elements) when controlling the frequency shape, so these values are subcarriers of the priority system. It is preferable that the position is appropriately determined in consideration of the position and width.

  The sharing control unit 24 receives the frequency sharing related information as input and determines the transmission power (signal amplitude) of each subcarrier. Specifically, frequency sharing related information includes the frequencies used in the priority system (center frequency and bandwidth), the interference power level allowed in the priority system (allowable interference power level), and between non-priority and priority systems. Propagation gain (propagation status, propagation loss or path loss), propagation loss in the non-priority system, information on the radio communication device on the receiving side of the priority system, time window information in IFFT, information on the RF signal generation unit 23, and the like. As shown in the figure, the shared control unit 24 includes a processing unit including a critical point specifying unit 241 and a transmission power determining unit 242. These functions will be described later.

  When the single carrier method is used, the second transmission signal generation unit 22 includes an IFFT unit 221 and a GI addition unit 222.

  IFFT section 221 performs inverse fast Fourier transform (IFFT) on the symbol sequence mapped to each subcarrier after transmission power control is performed, and generates a symbol in the time domain. A guard interval (GI) or a cyclic prefix (CP) is added to the time domain symbol to generate a transmission symbol.

  The RF signal generation unit 23 generates a transmission signal (RF signal) for radio transmission from the input transmission symbol. Although not shown in detail for the sake of simplicity, the RF signal generator 23 actually removes an unnecessary signal component from an oscillator that generates a carrier frequency, a mixer that modulates a baseband signal at the carrier frequency, and the like. And includes elements such as a filter for shaping the frequency shape and an amplifier for amplifying the signal.

  When the single carrier method is used, the radio communication device on the reception side may receive a signal while executing a frequency equalization method as shown in Non-Patent Document 3, for example.

<< In case of multi-carrier system >>
FIG. 3B shows a configuration when the transmission signal is generated by the multicarrier scheme in the wireless communication apparatus shown in FIG. The first transmission signal generation unit 20 in this case includes a transmission symbol generation unit 201, a signal generation control unit 202, a control signal generation unit 203, and a subcarrier mapping unit 207. Elements already described in FIG. 3A have the same reference numerals.

  Subcarrier mapping section 207 maps the transmission symbol sequence from transmission symbol generation section 201 and the control signal from control signal generation section 203 to subcarriers in the format specified by signal generation control section 202. A signal in which information is mapped to each subcarrier is given to transmission power control section 21. The signal for which transmission power is set in transmission power control unit 21 is converted into a symbol in the time domain by IFFT unit 221. The GI addition and time window application unit 223 adds a guard interval (GI) to the time domain symbol to match the time window.

  As shown in FIGS. 3A and 3B, the present invention can be applied to both a single carrier system and a multicarrier system.

<2. Transmission power control method>
FIG. 4 shows a transmission power control method performed by the radio communication apparatus on the transmission side as shown in FIG. For simplicity of explanation, the transmission power control is described as being executed in the wireless communication device, but the present invention is not limited to that form. A device different from the wireless communication device (a part of 21 and 24 in FIGS. 2, 3A and 3B) calculates transmission power by the method shown in FIG. 4, and the calculation result is the wireless communication device. May be notified. The operation flow shown in FIG. 4 is divided into four steps: band division (2.1), interference power estimation (2.2), transmission power calculation (2.3), and transmission power transmission (2.4). Have Hereinafter, processes, procedures or operations relating to these steps will be described.

<< 2.1 Band division >>
In step 2.1 of FIG. 4, the wireless communication device on the transmission side in the non-priority system divides the frequency band of the non-priority system into one or more sections as a premise for executing the transmission power control method. The wireless communication device on the transmission side in the non-priority system acquires information such as the frequency of the priority system and the allowable interference power level as frequency sharing related information. The allowable interference power level is defined by the relationship between the frequency and the interference power level allowable at the frequency.

  FIG. 5 schematically shows the relationship between the allowable interference power level and the frequency in the priority system. In the illustrated example, the allowable interference power level is defined by a rectangular shape, but this is not essential to the present invention and may be defined by any suitable shape. In the case of defining with a rectangular shape, the allowable interference power level may be defined with two or more arbitrary levels in a staircase pattern. In the case of the illustrated example, the allowable interference power level is defined by two levels of a high value PH and a low value PL. The center frequency of the frequency range in which the allowable interference power level is the low value PL is designated or specified as the “hole center” frequency. Further, the center of the range surrounded by two “hole centers” adjacent on the frequency axis is designated or specified as the frequency of the “non-hole center”. The wireless transmission device of the non-priority system divides a range surrounded by a hole center frequency and an adjacent non-hole center frequency as one section. Note that, at the end of the system band of the non-priority system, a range surrounded by the frequency of the end and the frequency of the hall center or the non-hall center forms a division. In the case of the illustrated example, six sections 1-6 are formed in the system bandwidth of the non-priority system. Transmission power control, which will be described later, is performed for each of these sections. FIG. 5 also schematically shows the transmission power level determined by the transmission power control method according to the present invention.

  The critical point specifying unit 241 provided in the shared control unit 24 of the wireless communication device specifies, designates or determines a frequency that becomes a critical point from the allowable interference power level. The frequency that becomes the critical point is based on the assumption that the interference power density from each subcarrier monotonously decreases with respect to the separation frequency, and when the interference level at the critical point is less than the allowable interference power level, It refers to the point where the interference level is below the allowable power level. In the example shown in FIG. 5, there are six critical points C1-C6, and one critical point exists in one division.

  By the way, the allowable interference power level may be defined by a stepped rectangle having more than two levels. As an example, as shown in FIG. 6, it is assumed that the allowable interference power level is defined in a stepped manner at three levels of a high value PH, a medium value PM, and a low value PL. In this case, the critical point A exists at the boundary point of the frequency range where the allowable interference power level is a predetermined level PM lower than the maximum value PH. A critical point B also exists at a boundary point in the frequency range where the allowable interference power level is a predetermined level PL lower than the maximum value PH. FIG. 7 shows a specific example of the relationship between the allowable interference power level in the priority system, the signal shape of the priority system, and the critical point. FIGS. 5-7 are merely examples, and any suitable shape may be used.

  FIG. 8 shows an example in which, on the xy plane, a point at which the distance between the intersection Q between the straight line passing through the origin O (y ′ axis) and the line representing the allowable interference power level and the origin O is minimized is determined as the critical point. Indicates. Specifically, the point that becomes the minimum when the angle θ between the y-axis and the y′-axis is larger than 0 ° and smaller than 90 ° corresponds to the critical point.

  Next, based on the identified critical point, subcarriers (signal elements) belonging to one division of the frequency band are classified into the hole or the hole. If the allowable interference power shape between any two adjacent critical points or at the frequency band edge that is assumed to be an arbitrary critical point includes a part that protrudes upward in (i) section, this section is outside the hall (ii) If a section that does not protrude upward is included in the section, this section is defined as a hole.

  A subcarrier closer to the non-hole center than a critical point closest to the non-hole center in the classification is classified as a subcarrier outside the hole. Conversely, subcarriers far from the critical point from the non-hole center are classified as subcarriers in the hole. In the example shown in FIG. 6, a subcarrier closer to the non-hole center than the critical point A closest to the non-hole center is classified as a subcarrier outside the hole. Conversely, a subcarrier far from the critical point A from the non-hole center is classified as a subcarrier in the hole. Thus, the frequency band is divided into one or more sections, and the subcarriers within the sections are classified outside and inside the holes.

  Critical points have the following properties. When the wireless communication device of the non-priority system transmits data on the critical point frequency (subcarrier) with a certain transmission power, the signal received by the priority system is less than the allowable interference power level. . In this case, the signal received by the priority system is also less than the allowable interference power level for frequencies (subcarriers) other than the critical point. In other words, the suitability of individual transmission powers set for a large number of subcarriers included in a signal in a non-priority system can be determined by the suitability of the transmission power set for subcarriers at a critical point. The reason can be explained as follows. When transmission power set for a specific subcarrier in a non-priority system leaks into the priority system and becomes interference power, the interference power level tends to monotonously decrease as the distance from the subcarrier increases. Furthermore, the total interference power from all subcarriers having such a tendency also tends to decrease monotonously. The interference allowable power level changes greatly at frequencies before and after the critical point. Therefore, if the interference power that monotonously decreases is less than the allowable interference level at the critical point, it can be estimated that the other subcarriers are also less than the allowable interference power level.

In some cases, such an inference does not hold strictly. For example, even if the critical point is less than the allowable interference power level, the subcarrier other than the critical point may not be lower than the allowable interference power level. In order to cope with this problem, it is conceivable to use a stricter allowable interference power level instead of using the allowable interference power level as it is. In this case, the permissible value is set smaller than the permissible interference power level by a predetermined margin. Further, instead of or in addition to correcting the allowable interference power level, a leakage power ratio R _xs described later may be corrected. Specifically, it is not the value at the frequency (s) of the target priority system, but the leakage power ratios R _xs , R _{xs ± 1} , R _{xs ± 1} , ... Thus, the value that yields the largest interference power may be used. For example, the transmission power for subcarrier (x) in a non-priority system is P _x , the interference power received on subcarrier (s) in the priority system is P _s , and the interference power is P _x / R _xs / When expressed by L _x ′, the smallest value among the leakage power ratios R _xs , R _{xs ± 1} , R _{xs ± 1} ,... _May be used for subcarriers near subcarrier s.

  In addition, power allocation or transmission power control in each segment should take into account interference from adjacent segments and add a specified margin to the allowable interference power level (stricter than the original allowable interference power level). Thus, transmission power determination procedures for a plurality of sections may be processed in parallel. Alternatively, power allocation of a plurality of sections may be performed sequentially for each section. In this case, when calculating the power of the category to be controlled, the allowable interference power level at the critical point of the category is changed from “original allowable interference power level” to “from one or more categories for which transmission power control has already been performed. By subtracting the “interference power”, the transmission power in that section may be determined.

<< 2.2 Estimation of interference power >>
In step 2.2 in FIG. 4, the wireless communication device (transmitter) on the transmission side in the non-priority system estimates the interference power exerted on the priority system by the non-priority system.

The non-priority system transmitter uses the transmit power (P _x ), leakage power ratio (R _xs ), and propagation gain (L _x ') in subcarrier (x) to be included in the non-priority system signal. The interference power reaching a certain subcarrier (s) of the priority system is estimated from all of the plurality of frequency elements (x∈X). Leakage power ratio (R _xs ) is the transmission power (P _x ) in one (x) of multiple subcarriers included in the signal transmitted and received in the non-priority system, and the subcarrier (x) Is a ratio with the leakage power (P _s ) generated by leakage of a signal component to a certain subcarrier (s) in the priority system. The transmission power of the subcarrier (x) included in the signal of the non-priority system is determined so that the interference power due to this leakage power is less than the predetermined allowable interference power level in that subcarrier (s). The

<<< Propagation gain >>>
The propagation gain (L _x ′) represents a propagation gain from a certain subcarrier (x) of the non-priority system to a certain subcarrier (s) of the priority system. The propagation gain may be referred to as a propagation state, a propagation loss, a path loss, or the like. The value of the propagation gain measured or estimated in advance may be used continuously as a static value, or a dynamic measurement value may be used. Incidentally, L _x ′ is a propagation gain between systems, but Lx described later is a propagation gain in a non-priority system.

  When static measurements of propagation gain are used, for example, the receiving wireless communication device in the priority system is fixedly installed (not moved) in a specific location, and is pre- The measured propagation gain is notified directly to the wireless communication device of the non-priority system or indirectly through the server. In the latter case, the propagation gain measured for each area is registered in, for example, a server or a database center. Based on the location information of the wireless communication device on the transmission side of the non-priority system and the location information of the wireless communication device on the reception side of the priority system, the database server responds to the inquiry from the wireless communication device of the non-priority system, Propagation gain required for transmission power control in a wireless communication device of a non-priority system is provided. However, when static measurements of propagation gain are used, appropriate transmission power control is performed based on the propagation gain of each subcarrier in a communication situation where temporal fluctuations are affected by high-speed fading. It becomes difficult. Therefore, when using a static measurement value of the propagation gain, it is preferable to perform transmission power control based on the average propagation gain of the entire frequency band when it is affected by high-speed fading. .

  When a dynamic measurement of propagation gain is used, for example, the propagation gain measured by some wireless communication device in the communication area at regular or irregular timing is directly transmitted to the wireless communication device of the non-priority system. Or indirectly via a server. In the latter case, the propagation gain measured for each area is registered in, for example, a server or a database center. Based on the location information of the wireless communication device on the transmission side of the non-priority system and the location information of the wireless communication device on the reception side of the priority system, the database server responds to the inquiry from the wireless communication device of the non-priority system, Propagation gain required for transmission power control in a wireless communication device of a non-priority system is provided. Specifically, for example, it is conceivable that the wireless communication device on the transmission side of the non-priority system senses (monitors, monitors or detects) the signal of the priority system. For example, the wireless communication device on the transmission side of the non-priority system may receive a known signal transmitted from the priority system and measure the propagation gain based on the transmission power and reception power of the known signal. Or conversely, the priority system measures the signal from the non-priority system and feeds back the measurement result from the priority system to the non-priority system, so that the wireless communication device of the non-priority system obtains the measured value of the propagation gain. May be.

<<< Leakage power ratio >>>
In general, when both non-priority and priority systems sharing a frequency communicate using a plurality of signal elements (subcarriers), usually, between different subcarriers between systems, part of the signal power in the non-priority system is: Inter-subcarrier interference leaks into the frequency band of the surrounding priority system. However, in a special situation where both systems use the same wireless interface and are completely synchronized, it is not necessary to consider interference from different subcarriers, so it can be suppressed relatively easily. Such a situation is not common. As described above, the leakage power ratio (R _xs ) is one (x) of a plurality of subcarriers included in a signal transmitted / received in a non-priority system, as shown in FIG. This is the ratio between the transmission power (P _x ) and the leakage power (P _s ) generated when the transmission power of the subcarrier (x) leaks to a certain subcarrier (s) in the priority system.

FIG. 10 shows subcarriers (upper diagram) included in a non-priority system signal and received spectrum waveforms (lower diagram) when these signals are received by the priority system. The upper diagram highlights the subcarriers of the non-priority system subcarrier (frequency element or signal element) f _n . In practice also other subcarrier components as shown in dashed lines exist, for simplicity of explanation, consider a signal component in one sub-carrier f _n. The lower diagram shows the FFT output signal (received spectrum waveform) after the signal of the subcarrier f _n of the non-priority system is received by the priority system and subjected to fast Fourier transform (FFT). By obtaining such an FFT output signal (received spectrum waveform) for each subcarrier in the non-priority system, one of the subcarriers in the non-priority system can determine what interference power is applied to each subcarrier in the priority system. Or it can be known whether it causes leakage power. The ratio between the transmission power at frequency f _n and the reception power (leakage power or interference power) at frequency f _m is the leakage power ratio (R _nm ). Therefore, in principle, there are as many leakage power ratios as the number of combinations of one of the plurality of subcarriers in the non-priority system and one of the subcarriers in the priority system.

  The leakage power ratio is obtained by, for example, transmitting a known signal from a non-priority system, receiving and measuring the known signal by the wireless communication device of the priority system, and feeding back the measurement result from the priority system to the non-priority system. May be. The known signal is a signal that is known in advance by the transmitter and the receiver before the start of communication, and may be referred to as a pilot signal, a reference signal, a sounding reference signal, a training signal, a reference signal, or the like.

  Alternatively, the leakage power ratio may be estimated based on the information obtained by the wireless communication device of the non-priority system acquiring information necessary for estimating the leakage power ratio from the priority system. The necessary information includes, for example, information on the communication method and reception filter of the priority system, and information on the signal format of the non-priority system. The information on the communication method of the priority system includes, for example, information indicating that the single carrier method is used (including information on the system bandwidth in that case) and information indicating that the multicarrier method is used (that information) (Including subcarrier bandwidth in some cases). The reception filter information indicates the type and performance of the reception filter used in the wireless communication apparatus of the priority system. In general, a receiver uses a band-pass filter in order to avoid an out-of-band signal from degrading the quality of the in-band signal. Therefore, it is possible to estimate how much interference occurs in the receiver depending on what band pass filter is used in the receiver. Non-priority system signal format information includes system bandwidth information, single-carrier transmission filter shape information, multi-carrier transmission subcarrier count, guard interval length (GI length), and time window. Contains information.

<<< Interference estimation >>>
Next, in order to perform transmission power control of the non-priority system, it is necessary to estimate interference power generated in the priority system due to the non-priority system. For simplicity of explanation, it is assumed that the non-priority and priority systems both use the multi-carrier scheme based on OFDM, but this is not essential, and the present invention is applied to the case of the single-carrier scheme. Is also applicable. This is because the transmission power control method in the case of the single carrier method is the same as the case where the number of subcarriers is one in the transmission power control for the multicarrier method.

In FIG. 9, the leakage power ratio from the subcarrier x of the non-priority system to the subcarrier (s) of the priority system is R _xs . Furthermore, it is assumed that the transmission power in the subcarrier (x) of the non-priority system is (P _x ) and the propagation gain from the subcarrier (x) of the non-priority system to the priority system is L _x ′. In this case, the leakage power or interference power (P _s ) received by the wireless communication device of the priority system in the subcarrier ( _s ) is
P _s = P _x × R _xs / L _x '
It becomes. This is leakage power from one subcarrier (x) of the non-priority system to one subcarrier (s) of the priority system. Therefore, the interference power received from the non-priority system in the subcarrier (s) of the priority system is the sum of the interference powers from the individual subcarriers of the non-priority system. If the set of all subcarriers of the non-priority system is X, the interference power or leakage power generated from all subcarriers of the non-priority system to the subcarrier (s) of the priority system is
Σ _(x∈X) [P _x × R _xs / L _x '] (1)
Can be calculated as

If the system bandwidths of the priority system and the non-priority system are the same, assuming that synchronization is established, the leakage power leaking out of the band is very small. Therefore, the leakage power ratio may be calculated after establishing synchronization. In addition, when the subcarrier position and the subcarrier interval in the priority and non-priority systems are the same, the leakage power ratio R _xs from the subcarrier (x) to the subcarrier (s) is calculated from the subcarrier (x + k). It becomes equal to the leakage power ratio R _{x + ks + k} to the subcarrier (s + k). Therefore, in this case, if the influence of the reception filter is not considered, if the leakage power ratio from one subcarrier (x) of the non-priority system to one subcarrier (s) of the priority system is known, The leakage power ratio between subcarriers is also known. This situation corresponds to a situation where the priority and non-priority systems use the same wireless interface, and in a one-to-many system, the receivers of the adjacent priority system use only a specific part of the band. To do.

  When calculating the above equation (1), if the transmission power of each subcarrier of the non-priority system is different, the interference power can be calculated in consideration of the weighting according to the transmission power. Also, when there is a fluctuation in leakage power or interference power from each subcarrier of the non-priority system to the priority system due to fading of the propagation path, weighting according to the fluctuation of the propagation path is performed in the same manner as above. Thus, an appropriate interference power can be calculated.

<< 2.3 Calculation of transmission power >>
In Step 2.3 of FIG. 4, the transmitting side wireless communication device (transmitter) in the non-priority system sets the transmission power (more precisely, the maximum value of the transmission power) for each of the plurality of subcarriers included in the signal to be transmitted. decide.

<<< Calculation of transmission power (1) >>>
Non-priority so that the interference power for the subcarrier (s) calculated from the leakage power ratio (R _xs ) and propagation gain (L _x ′) is less than the predetermined allowable interference power level in the subcarrier (s). The transmission power (P _x ) of the subcarrier (x) included in the system signal is determined. One method for determining such transmission power is to simply determine the transmission power by limiting the possible value of the transmission power (P _x ) to zero or the maximum value (Pmax). For example, in one of the sections determined in step (2.1) shown in FIG. 4, the subcarrier (xm) farthest from the frequency band of the priority system is specified, and the transmission power of this subcarrier (xm) is The maximum value (Pmax) is set. Next, when the transmission power of subcarrier (xm + 1) adjacent to subcarrier (xm) is set to the maximum value (Pmax), whether or not the interference power generated in the priority system is less than the allowable interference power level Determine. When the interference power generated in the priority system is less than the allowable interference power level, priority is given when the transmission power of the subcarrier (xm + 2) adjacent to the subcarrier (xm + 1) is set to the maximum value (Pmax). It is determined whether or not the interference power generated in the system is less than the allowable interference power level. Thereafter, the same processing is performed, and when the transmission power of the subcarrier (xm + K) is set to the maximum value (Pmax), the interference power is less than the allowable interference power level, but the subcarrier (xm + K + 1) It is assumed that the interference power is not less than the allowable interference power level when the transmission power is set to the maximum value (Pmax). In this case, as shown in FIG. 11, the transmission power from the subcarrier (xm) to the Kth subcarrier (xm + K) is set to the maximum value (Pmax), and transmission of other subcarriers is performed. The power is set to zero. Note that the maximum value (Pmax) of transmission power is set to a value (allowable interference power level −α) that is smaller than the allowable interference power level by a specified margin. For example, α is a predetermined fixed value (positive decibel value), and it is preferable to set α = 3 dB or more as an example. When the system parameters of the priority system and the non-priority system are known in advance, the value of α can be optimized in advance.

<<< Calculation of transmission power (2) >>>
Another way to determine the transmit power is to use the x sub-bands of the non-priority system signal under the constraint that the interference power level generated on the N _s sub-carriers belonging to the priority system band is below the threshold Ths. It is to maximize the communication capacity of the entire carrier.

  For example, the amount of signal that can be transmitted in the unit frequency unit transmission period of a non-priority system such as TTI (Transmission Time Interval), that is, the communication capacity CAPACITY can be written as follows.

CAPACITY = log (1 + S ₁ / N) + log (1 + S ₂ / N) + ・ ・ ・ + log (1 + S _x / N)
Therefore, it is necessary to determine the transmission power that maximizes the communication capacity CAPACITY.

max (CAPACITY) = max [log (1 + S ₁ / N) + log (1 + S ₂ /N)+...+log(1+S _x /N)]...(2)
here,
S _i = P _i / L _i (i = 1, ..., x) (3)
And S _i represents the received power of the signal received by the receiver in the non-priority system from the transmitter in the non-priority system (reception power in the i-th subcarrier). Note that S _i is not interference power because S _i is a signal transmitted and received in the non-priority system. L _i represents the propagation gain between the transmitter and the receiver in the non-priority system. N represents the noise power at the receiver of the non-priority system.

  When maximizing the above-described communication capacity CAPACITY, the interference power from the non-priority system to the priority system needs to be less than the allowable interference power level. As described above, the interference signal observed in the subcarrier (s) of the priority system is obtained by summing the contributions from each of the plurality of subcarriers of the non-priority system. The total value needs to be less than the threshold Ths.

S ₁ '× R _1s + S ₂ ' × R _2s + ・ ・ ・ + S _x '× R _xs ≦ Ths (4)
here,
S _i '= P _i / L _i '; (i = 1, ..., x) ... (5)
And S _i ′ represents received power when the receiver of the priority system receives the signal component of the subcarrier (i) of the non-priority system. P _i represents the transmission power for subcarrier (i). L _i ′ represents the propagation gain from the non-priority system to the priority system for subcarrier (i). _Ris represents leakage power or interference power at which the signal component of the subcarrier (i) of the non-priority system leaks to the subcarrier (s) of the priority system. Ths represents the allowable interference power level in the subcarrier (s) of the priority system. That is, it is necessary to maximize the communication capacity expressed by Equation (2) under the constraint condition expressed by Equation (4). This problem can be solved, for example, by Lagrange's undetermined coefficient method. For example, the Lagrangian equation F can be written as

F = {log (1 + S ₁ / N) + log (1 + S ₂ /N)+...+log(1+S _x / N)}-λ {S ₁ '× R _1s + S ₂ ' × R _2s + ・ ・ ・ + S _x '× R _xs -Ths} ・ ・ ・ (6)
Here, λ represents Lagrange's undetermined coefficient. Using Equations (3) and (5) above, Equation (6) can be written as:

F = {log (1 + P ₁ / L ₁ / N) + log (1 + P ₂ / L ₂ / N) + ・ ・ ・ + log (1 + P _x / L _x / N)}-λ {P ₁ × R _1s / L ₁ '+ P ₂ × R _2s / L ₂ ' + ・ ・ ・ + P _x × R _xs / L _x '-Th _s } ・ ・ ・ (7)
The solution to this problem is obtained under the condition that the partial derivative or partial differential coefficient of Equation (7) with respect to the transmission power P _i is zero.

δF / δP _i = (1 + P _i / L _i / N) ^-1 × (1 / L _i / N) -λ / L _i '/ R _is ; (i = 1, ..., x)・ (8)
If ΔF / ΔP _i = 0, the transmission power Pi can be expressed as follows.

P _i = L _i ′ / R _is / λ−L _i N; (i = 1,..., X) (9)
The undetermined constant λ is determined by substituting Equation (9) into Equation (4).

  When the transmission power calculated by Equation (9) exceeds the maximum transmission power applicable in the non-priority system, the transmission power for the subcarrier may be set to the maximum transmission power applicable. Furthermore, the allowable interference power level is updated to the value obtained by subtracting the “interference power from the subcarrier whose transmission power has already been determined” from the “original allowable interference power level”, and the transmission power is calculated again using the above method. You may try again. By repeating this process, more appropriate transmission power can be obtained. The number of iterations may be performed until a predetermined condition is satisfied. The predetermined condition may be, for example, that subcarriers to which power exceeding the maximum transmission power applicable in the non-priority system is assigned do not occur. Alternatively, the predetermined condition may be that power exceeding the maximum transmission power applicable in the non-priority system is allocated and the number of subcarriers limited to the maximum transmission power applicable is equal to or less than a predetermined number.

In the above method, the channel gain for each subcarrier is taken into consideration so that the influence of fast fading can be dealt with. In this case, the necessary information is not only the average power of the entire band, but also information on individual subcarriers, and the necessary information amount is multiplied by the number of subcarriers. Furthermore, since it is necessary to deal with temporal fluctuations, the transmitter of the non-priority system needs to acquire information at a high frequency. As a result, there is a possibility that the amount of information of propagation gain between the transmitter of the non-priority system and the receiver of the priority system will be very large. One way to deal with such a problem is to control the transmission power of the non-priority system by considering only the average gain of the entire band without considering fast fading. In this case, the processing can be simplified by setting the above-described propagation gain L _x to L = ΣL _x / N _s c and L _x ′ = ΣL _x ′ / N _s c.

In the receiver of the priority system, the interference power is sufficiently small at a certain time, but the interference power may exceed the allowable interference power level at another time. In such a case, it is conceivable that the allowable interference power level is set lower than the allowable interference power level by a predetermined margin. Further, when the transmission power is determined in consideration of the influence of the reception filter in the receiver of the priority system, the above propagation gain L _x ′ can be calculated by replacing it with L _x ′ × F _x . Here, F _x represents the filter gain of the reception filter in the frequency band near the subcarrier _x .

<< 2.4 Transmission of transmission power >>
In step 2.4 of FIG. 4, the transmitting-side radio communication device (transmitter) in the non-priority system transmits a signal with the transmission power determined for each subcarrier in step 2.3.

<3. Modification>
<< 3.1 Stepwise allowable interference power level >>
Consider the case where there are two or more critical points in one section as shown in FIGS. 6, 7 (b), (c) and FIG. 8. When there is one critical point in the section, in principle, the transmission power of individual subcarriers outside the hole is determined so that the interference power generated at the critical point is less than the allowable interference power level. However, when there are two or more critical points in a section, it is necessary to determine how to set the transmission power of subcarriers outside the hall. For example, assume that there are two critical points A and B as shown in FIG. First, the transmission power of the subcarrier outside the hole is obtained by the method in Step 2.3 of FIG. 4 so that the interference power generated at the critical point A is less than the allowable interference power level. Next, the transmission power of the subcarrier outside the hole is also obtained by the method in Step 2.3 of FIG. 4 so that the interference power generated at the critical point B is less than the allowable interference power level. Of the obtained transmission powers, the smaller one is determined as the transmission power for the subcarriers outside the hall. Furthermore, if the allowable interference power level is defined in N steps with more than 2, the interference power at the critical point is less than the allowable interference power level for each of the N critical points as described above. Then, the transmission power Pn of the subcarrier outside the hall is obtained (n = 1,..., N), and the minimum value (min (Pn)) of them may be determined as the transmission power of the subcarrier outside the hall. .

<< 3.2 Electricity allocation to the hall >>
When transmission power is determined for subcarriers outside the hole, generally, the interference power generated in the hole is significantly lower than the allowable interference power level as shown in FIG. 12A. This is because the signals of the individual subcarriers are monotonously decreasing in the frequency domain, and the overall interference power obtained by adding them is monotonously decreasing. This situation is not a problem for the priority system, since the interference is never small for the priority system. However, if the transmission power is set too small, the communication capacity in the non-priority system will be reduced accordingly. From such a viewpoint, this modification sets optimal transmission power for the subcarriers in the hole.

  First, the residual interference allowance Re is obtained for each subcarrier in the hole of the non-priority system.

(Residual interference tolerance Re) = (Allowable interference power level)-(Interference power from subcarriers for which transmission power has already been set)
Next, for each subcarrier in the hall of the non-priority system, power corresponding to the residual interference tolerance (Re) is provisionally allocated. It should be noted that the residual interference allowance (Re) in the hole is a value at the subcarrier position of the priority system and not at the subcarrier position of the non-priority system. Therefore, based on the (residual interference tolerance Re) at the subcarrier position of the priority system, interpolation (for example, nth order polynomial interpolation) is performed to estimate the (residual interference tolerance) at the subcarrier position of the non-priority system. can do. In this case, the transmission power may be set to zero for subcarriers for which the allocated power amount is less than the predetermined transmission power.

  For the power provisionally allocated by the above method, the (remaining interference allowable amount Re) at the subcarrier position of each non-prioritized system may not necessarily be an appropriate value. This is because the signal component of a specific subcarrier leaks to other subcarriers due to intersubcarrier interference as described above. That is, as a result of tentatively allocating power to a specific subcarrier as described above, interference power leaks to other subcarriers, interference power in other subcarriers increases, and allowable interference in other subcarriers. The power level may be exceeded.

Therefore, it is conceivable that the interference power is estimated using the above formula (1) for all the priority system subcarrier positions inside and outside the hall, and this interference power is maximized within the allowable range. For example, the estimated value of this interference power is I _s (I _s = Σ _(x∈X) [P _x / (R _xs × L _x ')]), and the residual interference tolerance in subcarrier (s) is Iaa _s To do. Then, a correction coefficient for transmission power that maximizes I _s / Iaa _s is obtained for all subcarriers of the priority system in the hall.

C = max (I _s / Iaa _s ) ... (10)
The optimum transmission power can be obtained by multiplying the transmission power of each subcarrier provisionally assigned by the correction coefficient C- ¹ . FIG. 12B shows a state in which transmission power is set in this way for subcarriers in a hole in a non-priority system. FIG. 12C shows the interference power occurring in the hall of the priority system. Furthermore, this correction may result in subcarriers where the allocated power does not meet the predetermined transmission power in some one or more subcarriers. In this case, it is conceivable to set the transmission power of those subcarriers to zero. Furthermore, when determining the transmission power for the subcarriers outside the hole, the allowable interference power level at the critical point is set to a specified margin so that the interference power caused by the transmission power allocated to the subcarriers inside the hole can be tolerated. It may be lowered by that amount.

<< 3.3 Subcarrier blocking >>
In the above example, the transmission power (more precisely, the maximum value of the transmission power) is determined for each subcarrier. Depending on the radio communication system, when a symbol is detected from a received signal, a channel estimation value is calculated based on the power (amplitude) and phase of pilot symbols sparsely distributed or arranged in both the time axis and the frequency axis . Therefore, if transmission power control is performed for each subcarrier, an appropriate channel estimation value may not be obtained. Alternatively, pilot symbols may be inserted into all subcarriers, but in this case, radio resources that can be used for user communication are reduced.

  Therefore, this modification addresses the above problem by controlling the transmission power in units of subcarrier blocks obtained by grouping a plurality of subcarriers. The subcarrier block may have any suitable size. For example, the subcarrier block may be a resource allocation unit in a point-to-multipoint communication system which is a form of a wireless communication system. Specific examples of such resource allocation units include resource blocks in 3GPP, subchannels in IEEE 802.16, and the like. The out-of-band radiation characteristics for each subcarrier block may be input in advance to the common control unit (24 in FIGS. 2, 3A, and 3B) as information in units of blocks. Alternatively, out-of-band radiation characteristics information for each subcarrier may be input to the shared control unit (24 in FIGS. 2, 3A, and 3B), and the out-of-band radiation characteristics in units of blocks may be calculated by combining them. .

<< 3.4 Subcarrier spacing >>
Since the non-priority system and the priority system are usually asynchronous in symbol timing, when the transmission signal of the non-priority system is received by the priority system, as shown in the lower side of FIG. 10, only the transmission frequency f _n In addition, inter-subcarrier interference also occurs in subcarriers in the surrounding frequencies. In general, the subcarrier intervals in the priority system and the non-priority system are different. The value of the interference power from the non-priority system that appears in each subcarrier of the priority system differs depending on the transmission subcarrier frequency of the non-priority system, and is determined by the relative relationship between the non-priority and subcarrier frequencies used in the priority system. From the system parameters of the non-priority system and the priority system, a spectrum waveform received by the priority system can be calculated in advance for each subcarrier frequency of the non-priority system.

Let N _c be the number of subcarriers in the non-priority system that contributes to the interference power in certain subcarriers in the priority system. The non-priority system holds the N _c reception spectrum waveforms obtained in advance for these N _c subcarriers, whereby the interference component generated in any subcarrier f _m of the priority system can be obtained.

  The reception spectrum waveform calculated in advance varies depending on the reception timing of the priority system with respect to the transmission timing of the non-priority system, the data modulation method used in the subcarrier of the target non-priority system, and the like. Therefore, the average of the interference power from the non-priority system is obtained by calculating the reception spectrum waveform in advance by varying the transmission timing difference between the priority system and the non-priority system and averaging these reception spectrum waveforms. Electric power can be obtained. The interference power caused by each transmission subcarrier of the non-priority system is obtained, for example, by computer simulation in which FFT is performed by changing the difference in transmission timing between systems in various ways. In addition, when it is necessary to calculate the peak interference power instead of the average interference power, the peak power can be used instead of the average power when determining the reception spectrum waveform for each subcarrier of the non-priority system.

FIG. 13 shows a received spectrum waveform observed in the priority system when the subcarrier intervals of the non-priority system and the priority system are equal. When the subcarrier spacing between the non-priority system and the priority system is equal, the relative relationship between the subcarrier frequencies of the non-priority system and the priority system is the same at any frequency of the non-priority system. Therefore, as shown in FIG. 7, even if the transmission frequency of the non-priority system changes as f _n , f _{n + 1} , f _{n + 2} , the FFT output signal waveform of the priority system is the same. For this reason, when the subcarrier intervals of the non-priority and priority systems are equal, only one type of received spectrum waveform is obtained and held in advance.

FIG. 14 shows a received spectrum waveform observed in the priority system when the subcarrier interval of the priority system is an integral multiple of the subcarrier interval of the non-priority system. In the illustrated example, the subcarrier interval of the priority system is twice that of the non-priority system. In this case, as shown in FIG. 14, in a case where the transmission frequency of the non-priority system in the case and f _{n + 1} of the f _n have different reception spectrum waveform. However, the received spectrum waveform is the same when the transmission frequency of the non-priority system is f _n and when it is f _{n + 2} . More generally, when the subcarrier spacing of the priority system is M _c times that of the non-priority system, the received spectrum waveform is the same when the transmission frequency of the non-priority system is f _n and f _{n + Mc.} . By utilizing this property, it is not necessary to hold the N _c type of the received spectrum waveform is the total number of sub-carrier of the non-priority system, only M _c type of the received spectrum waveform is held at the wireless communication device of the non-priority system Then, transmission power control can be performed. When estimating the interference power, the interference power can be calculated using the same received spectrum waveform at every frequency interval of M _c times the subcarrier interval among the subcarriers of the non-priority system.

  Specific examples of the disclosed invention are listed below.

[Section 1]
In an environment where the priority system and non-priority system share frequencies,
The radio signal transmission device of the non-priority system is
Leakage power ratio information in the priority system for each non-priority signal element,
Propagation path information between the non-priority system transmitting station and the priority system receiving station;
A non-priority system radio transmission apparatus that performs shared control for limiting transmission power to prevent the non-priority system from causing harmful interference to the priority system using the allowable interference power information.

[Section 2]
Non-priority systems are systems that use a communication scheme based on single signal elements,
The transmission power control unit is composed of IFFT, split band signal transmission power control unit and FFT unit,
2. The non-priority system radio transmission apparatus according to claim 1, wherein the IFFT output is a non-priority signal element.

[Section 3]
Non-priority systems are systems that use communication methods based on multi-signal elements,
2. The non-priority system radio transmission apparatus according to item 1, wherein the signal element is a non-priority signal element.

[Section 4]
Non-priority systems are systems that use communication methods based on multi-signal elements,
2. The non-priority system radio transmission apparatus according to item 1, wherein a signal element group corresponding to a resource allocation unit is set as a non-priority signal element.

[Section D1]
The leakage power ratio information in the priority system for each non-priority signal element is as follows:
Non-priority according to paragraph 1-4, characterized by the system bandwidth of the priority system (when the priority system is a single signal element) or the signal element bandwidth (when the priority system is a multi-signal element) System wireless transmitter.

[Section D2]
The leakage power ratio information in the priority system for each non-priority signal element is as follows:
The non-priority system radio transmission apparatus according to Item D1, which is determined using information related to a reception filter in addition to the above information.

[Section D3]
The leakage power ratio information in the priority system for each non-priority signal element is as follows:
The non-priority system radio transmission apparatus according to Item D1 or D2, wherein the non-priority system radio transmission apparatus according to Item D1 or D2 is determined using information related to a synchronization state in addition to the above information.

[Section D4]
The non-priority system radio transmission apparatus according to Item 1-4, wherein the leakage power ratio information in the priority system for each non-priority signal element is obtained from a transmission / reception result of a sounding signal.

[Section E1]
The non-prioritized system transmission device according to any one of the above, wherein the transmission power control means includes a critical point specifying unit and an out-hole transmission power control unit.

[Section E2]
The critical point specifying unit determines a condition that becomes a minimum point in the lower right or lower left direction from the interference tolerance condition group for the frequency as a critical point, and based on the critical point specified above, the system band center part Any of the above, wherein a signal element whose system band is closer to the center than the critical point closest to the center is an out-of-hall signal element, and conversely, a signal element farther from the system band center than the critical point is an in-hall signal element. The non-priority system transmission device according to item 1.

[Section E3]
The outside hall transmission power control unit
In each segment, when transmitting from the signal element component farthest from the priority system band to the _Xth signal element component with the maximum transmission power, the transmission power of the signal element satisfying the interference tolerance is set as the maximum transmission power, and the others The non-priority system transmission device according to any one of the above, wherein the transmission power of the signal element is 0 and these signal elements are not used.

[Section E4]
The outside hall transmission power control unit
2. The non-prioritized system transmission device according to any one of the above, wherein the transmission power of the calculation target signal element to be controlled is controlled based on the extreme value of the mathematical formula (7).

[Section E5]
The out-of-hall transmission power control unit includes a control target signal element (group) determination unit,
In each division, when transmitting from the signal element component farthest from the priority system band to the _Xth signal element component with the maximum transmission power, the signal element that satisfies the condition that the predetermined value is subtracted from the allowable interference power is excluded. The signal element group is the control target, and the interference tolerance condition is
(Allowable interference power)-(Amount of interference from uncontrolled signal elements)
The non-priority system transmission apparatus according to any one of the above, wherein only the control target signal element determines transmission power by the method described in the section E4.

[Section E6]
The out-of-hall transmission power control unit includes a control target signal element (group) determination unit,
The transmission power is calculated for all signal elements in each category using the method described in Section E4. The transmission power of the signal element whose calculation result exceeds the predetermined maximum transmission power is set as the maximum transmission power, and other signals. The transmission power is calculated again by the method shown in claim E4 with only the elements as control measures, and the interference tolerance condition in this case is set.
(Allowable interference power)-(Amount of interference from uncontrolled signal elements)
The non-prioritized system transmission device according to any one of the above, characterized in that:

[Section X1]
The transmission power control means further includes an in-hole transmission power control unit,
In the control target signal element determination unit, for the signal element in the hall,
Any one of the above features, wherein the transmission power limit value of the signal element in each hole is assigned based on the result of the power assignment of the signal element outside the hall assigned by the transmission power method. Non-priority system transmitter.

[Section X2]
The in-hall signal element power allocation unit is
The non-priority system transmission device according to any one of the above, wherein power is allocated with a certain margin expected from the estimated remaining allowable interference power.

[Section X3]
The in-hall signal element power allocation unit is
Assign the estimated residual allowable interference power, calculate the interference power received at all priority signal element positions in the hall,
The non-priority system transmission device according to any one of the above, wherein power multiplied by a correction coefficient is allocated so that these values satisfy an allowable amount.

[Section L1]
The above propagation path information is
2. The non-priority system transmission device according to any one of the above, wherein the non-priority system transmission device is information calculated based on an average received power in the entire band measured in a priority system band overlapping with the non-priority system.

[Section L2]
The above propagation path information is
2. The non-priority system transmission device according to any one of the above, wherein the non-priority system transmission device is information calculated based on an average received power in the entire band measured in the non-priority system band.

[Section L3]
The above propagation path information is
The non-priority according to any one of the above, wherein the non-priority is information calculated based on an average received power in a signal element (group) that is a control unit measured within a priority system band to be controlled System transmitter (sets a large allowable transmission power level for signal elements that reduce the received power at the priority system receiver).

  As mentioned above, although embodiment which performs transmission power control in consideration of leakage power for each subcarrier has been described, the present invention is not limited to such embodiment, and those skilled in the art will be able to make various modifications, modifications, and alternatives. You will understand substitution examples and the like. For example, the present invention may be applied to any appropriate mobile communication system that performs transmission power control in an area where a system sharing a frequency coexists. Although specific numerical examples have been described in order to facilitate understanding of the invention, these numerical values are merely examples and any appropriate values may be used unless otherwise specified. In addition, although specific mathematical formulas have been used to facilitate understanding of the invention, these mathematical formulas are merely examples unless otherwise specified, and other mathematical formulas that yield similar results may be used. Good. The classification of items in the above description is not essential to the present invention, and the items described in two or more items may be used in combination as necessary, or the items described in one item may be used in different items. It may apply to the matters described in (as long as there is no conflict). The boundaries between functional units or processing units in the functional block diagram do not necessarily correspond to physical component boundaries. The operations of a plurality of functional units may be physically performed by one component, or the operations of one functional unit may be physically performed by a plurality of components. For convenience of explanation, the communication terminal and the information processing apparatus have been described using functional block diagrams. However, such an apparatus may be realized by hardware, software, or a combination thereof. Software operating in accordance with the present invention includes random access memory (RAM), flash memory, read only memory (ROM), EPROM, EEPROM, registers, hard disk (HDD), removable disk, CD-ROM, database, server and other suitable It may be stored in any storage medium. The present invention is not limited to the above embodiments, and various modifications, modifications, alternatives, substitutions, and the like are included in the present invention without departing from the spirit of the present invention.

20 First transmission signal generator
21 Transmit power controller
22 Second transmission signal generator
23 RF signal generator
24 Shared control section
25 Baseband (BB) signal generator
26 Interference signal detector
27 Desired signal detector
28 Interference tolerance condition determination unit
29 Feedback section
201 Transmission symbol generator
202 Signal generation controller
203 Control signal generator
204 Multiplexer
205 FFT section
221 IFFT Department
222 GI addition part
223 GI addition and time window application section
241 Critical Point Identification Department
242 Transmit power decision unit

JP 2009-100452

FCC, "second momorandom opinion and order" ET Docket No. 04-186, ET Docket No.02-380 "", September, 2009 H. Fujii et al., "Spectrum sharing by Adaptive Transmit Power Control for Low Poriority systems and Achievable Capacity" IEICE Trans. Comun. Vol. E92.B, no 8, pp2568-2576, 2009 F. Adachi et al., "Frequency domain equalization for braodband single-carrier multiple access" IEICE Trans. Commun., Vol. E92-B, no. 5 May 2009

Claims (6)

A wireless communication device that communicates using a plurality of frequency elements in a second communication system that shares a frequency with the first communication system,
A first signal generation unit that generates a frequency domain signal including information to be transmitted;
Transmission power (P _x ) of the first frequency element (x) included in the signal communicated in the second communication system, and the first frequency element (x) due to the first frequency element (x) Using at least the leakage power ratio (R _xs ) between the power (P _s ) generated in the second frequency element (s) in the communication system, a plurality of signals included in the signal communicated in the second communication system The interference power ranging from the entire frequency element (x∈X) to the second frequency element (s) is less than a predetermined allowable interference power level in the second frequency element (s). A transmission power control unit that determines transmission power of each frequency element included in the signal;
A second signal generation unit that generates a transmission signal by converting a signal in the frequency domain in which transmission power is determined, to a signal in the time domain;
A wireless communication apparatus comprising: a wireless communication unit that transmits the transmission signal. Under the constraint that the interference power level generated in the N _s signal elements belonging to the band of the first communication system is less than or equal to a threshold value, N _x signals included in the signal of the second communication system 2. The wireless communication apparatus according to claim 1, wherein transmission power of each frequency element included in the signal in the frequency domain is determined so that a communication capacity of the entire signal element is maximized. A range including a frequency range in which the allowable interference power level is the lowest level is identified as a hole,
The transmission power control unit
Of the frequencies usable in the second communication system, when the maximum transmission power is permitted to the signal elements from the terminal element farthest from the hall to the Yth signal element, the Yth signal from the terminal signal element The interference power ranging from the entire signal element to the second frequency element (s) is less than a predetermined allowable interference power level in the second frequency element (s), while Y + from the terminal signal element The interference power ranging from the entire first signal element to the second frequency element (s) determines Y that is not less than a predetermined allowable interference power level in the second frequency element (s);
2. The radio transmission apparatus according to claim 1, wherein the transmission power of the signal elements from the terminal signal element to the Yth signal element is set to the maximum value, and the transmission powers of the other signal elements are set to zero. A wireless communication method performed by a wireless communication device that communicates using a plurality of frequency elements in a second communication system that shares a frequency with the first communication system,
Generating a frequency domain signal including information to be transmitted;
Transmission power (P _x ) of the first frequency element (x) included in the signal communicated in the second communication system, and the first frequency element (x) due to the first frequency element (x) Using at least the leakage power ratio (R _xs ) between the power (P _s ) generated in the second frequency element (s) in the communication system, a plurality of signals included in the signal communicated in the second communication system The interference power ranging from the entire frequency element (x∈X) to the second frequency element (s) is less than a predetermined allowable interference power level in the second frequency element (s). Determining the transmit power of each frequency element included in the signal;
A radio communication method comprising: generating a transmission signal by converting the frequency domain signal for which transmission power has been determined into a time domain signal, and transmitting the transmission signal. A system including a first communication system and a second communication system sharing a frequency with the first communication system,
A wireless communication device that communicates using a plurality of frequency elements in the second communication system,
A first signal generation unit that generates a frequency domain signal including information to be transmitted;
Transmission power (P _x ) of the first frequency element (x) included in the signal communicated in the second communication system, and the first frequency element (x) due to the first frequency element (x) Using at least the leakage power ratio (R _xs ) between the power (P _s ) generated in the second frequency element (s) in the communication system, a plurality of signals included in the signal communicated in the second communication system The interference power ranging from the entire frequency element (x∈X) to the second frequency element (s) is less than a predetermined allowable interference power level in the second frequency element (s). A transmission power control unit that determines transmission power of each frequency element included in the signal;
A second signal generation unit that generates a transmission signal by converting a signal in the frequency domain in which transmission power is determined, to a signal in the time domain;
A wireless communication unit that transmits the transmission signal. A first signal generation unit that generates a frequency domain signal including information to be transmitted, and a second signal that generates a transmission signal by converting the frequency domain signal for which transmission power is determined into a time domain signal A wireless transmission device having a signal generation unit and a wireless communication unit that transmits the transmission signal can perform communication using a plurality of frequency elements in a second communication system that shares a frequency with the first communication system. A transmission power control apparatus for determining the transmission power,
Transmission power (P _x ) of the first frequency element (x) included in the signal communicated in the second communication system, and the first frequency element (x) due to the first frequency element (x) Using at least the leakage power ratio (R _xs ) between the power (P _s ) generated in the second frequency element (s) in the communication system, a plurality of signals included in the signal communicated in the second communication system The interference power ranging from the entire frequency element (x∈X) to the second frequency element (s) is less than a predetermined allowable interference power level in the second frequency element (s). A transmission power control apparatus comprising: means for determining transmission power of each frequency element included in the signal.

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