JP2014014117A - Communication control method, communication device, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an effective framework for avoiding collision of signals and suppressing interference when a frequency band is secondarily utilized.SOLUTION: A method for controlling communication of a second communication service secondarily utilizing a frequency band allocated to a first communication service, includes the following steps of: receiving a wireless signal transmitted for the first communication service within a first section on a temporal axis by using a communication device; deciding a parameter value used for controlling the communication of the second communication service, on the basis of the wireless signal received within the first section; observing a wireless signal transmitted for the second communication service within a second section following the first section; and transmitting a beacon for the second communication service on the basis of the parameter value within a third section following the second section in the case that no wireless signal for the second communication service is detected within the second section.

Description

  The present invention relates to a communication control method, a communication device, and a program.

  In recent years, discussions have been underway to make it possible to use a frequency band for a secondary communication service in accordance with the usage status of a frequency band (spectrum) used primarily. For example, a standard for opening unused channels (TV white space) included in the frequency band of digital TV broadcasting in the United States to wireless communication is being studied by the IEEE 802.22 working group (see Non-Patent Document 1 below). ).

  Also, according to a recommendation from the FCC (Federal Communications Commission) in November 2008, secondary use of the TV white space is permitted using a communication device that satisfies certain conditions and is permitted. . This FCC recommendation allowed the IEEE 802.22 standard, which was a pioneer in standardizing secondary use of TV white space, and also covered the movement of the IEEE New Study Group. As a technical content, for example, signal detection at a level of −114 [dBm] (for example, assuming that NF (Noise Figure) = 11 [dB] is about SNR = −19 [dB]) using existing technology is performed. Therefore, it is expected that an auxiliary function such as geo-location database access (Geo-location Database Access) is required (see Non-Patent Document 2 below). In addition, the FCC is seeking to open a part of the 250 GHz band of the 5 GHz band as a channel for new secondary use.

  Also, in the EU, there is a movement to assign a dedicated control channel called CPC (Cognitive Pilot Channel) for realizing DSA (Dynamic Spectrum Access) in common throughout the world under a long-term strategy. The CPC allocation is incorporated in the 2011 ITU (International Telecommunication Union) -WP11 agenda. Furthermore, technical studies for the secondary usage system that performs DSA are also being carried out in IEEE Standards Coordinating Committee (SCC) 41.

  Against this background, in recent years, some research reports have been made on secondary usage of frequency bands when a broadcasting system, satellite communication system, or mobile communication system is assumed to be a primary system. ing. For example, the following Non-Patent Document 3 proposes a system architecture for operating a wireless system using the IEEE 802.11a standard on a UHF (Ultra High Frequency) TV white space. Non-Patent Document 4 below also proposes a form in which the position information of the service area of the primary system is used as external information, similarly targeting TV white space.

  During secondary use of a frequency band, the secondary use system (secondary system) is usually required to operate so as not to degrade the communication quality of the primary system. Therefore, when transmitting a radio signal in the secondary system, it is desirable to control the transmission power to avoid interference with the node of the primary system.

  With regard to such transmission power control, in the case of secondary use of TV white space as in Non-Patent Document 3 or 4 below, it is possible to confirm in advance that the secondary used channel is not completely used. It can often be determined that the maximum level of transmit power may be used. On the other hand, Non-Patent Document 5 below proposes to adaptively control transmission power in a system with low priority to protect nodes in the system with high priority.

  Further, Non-Patent Document 6 below describes communication before and after secondary use in a primary system when a system such as a mobile communication system in which the reception environment of a terminal changes due to the influence of fading or the like depending on the location is used as the primary system. The ratio of capacity (communication capacity retention rate) is adopted as a protection standard, and a technique of transmission power control for satisfying the communication capacity retention ratio is proposed.

“IEEE802.22 WG on WRANs”, [online], [searched January 5, 2009], Internet <URL: http://www.ieee802.org/22/> “SECOND REPORT AND ORDER AND MEMORANDUM OPINION AND ORDER”, [online], [searched July 10, 2009], Internet <URL: http://hraunfoss.fcc.gov/edocs_public/attachmatch/FCC-08-260A1. pdf> Alan Bok et al., “Cognitive Radio System using IEEE802.11a over UHF TVWS”, Motorola, Oct 2008 D. Gueny et al., “Geo-location database techniques for incumbent protection in the TV White space”, DySPAN, Oct 2008 Fujii, Yoshino “Transmission power control type frequency sharing method for non-priority systems”, IEICE technical report. SR, Software Radio, Nov 2007, pp.15-20 Inage et al., “Examination of cognitive radio frequency sharing based on primary communication capacity retention ratio”, IEICE Technical Report SR2009, May 2009

  Here, in order to use the limited frequency band sufficiently effectively, the above-described white space, that is, a frequency band in a region where a communication service related to primary use (hereinafter referred to as a first communication service) is not provided. It is not enough to realize secondary use of. One reason for this is that secondary use of white space seeks to make use of frequency bands that are clearly vacant in the medium to long term in a specific area. This is because the communication service is limited to an area where there are few users. In addition, for example, regarding secondary use of TV white space in the United States, it is predicted that a part of the frequency band will be auctioned and the band left for secondary use will be small.

  Thus, for example, it is conceivable that the frequency band is secondarily used within the service area of the first communication service with the permission of the coordinator (eg, base station) of the first communication service. In addition, for example, in the area inside or around the service area of the first communication service, the first communication is performed in an area where the signal reception status is relatively poor due to the influence of shadowing (fading) or fading. It is also conceivable to use secondary frequency bands that cannot be used for services. In such a secondary usage case, it is assumed that the primary system node (hereinafter referred to as the primary usage node) and the secondary system node (hereinafter referred to as the secondary usage node) are closer to each other. . In this case, the radio signal (secondary signal) of the second communication service transmitted from the secondary usage node is received by the primary usage node (primary signal). The possibility of collision with the primary signal or interference with the primary signal. Therefore, it is beneficial to provide a secondary use framework of the frequency band for avoiding signal collision and suppressing interference in the secondary use of the frequency band according to surrounding communication conditions.

  For example, in the method described in Non-Patent Document 6, the overall communication capacity of the primary system in one cell is reduced at a certain rate, and the reduced amount is allocated to the secondary system. There remains a risk that reception of the primary signal at the node is locally difficult due to interference from the surrounding secondary usage nodes.

  Therefore, the present invention provides a novel and improved communication control method and communication apparatus capable of providing an effective framework for avoiding signal collision and suppressing interference during secondary use of a frequency band. And to provide a program.

  According to an embodiment of the present invention, there is provided a method for controlling communication of a second communication service that secondarily uses a frequency band assigned to a first communication service, the communication device using the communication device, Receiving a radio signal transmitted for the first communication service within a first interval on a time axis, and based on the radio signal received within the first interval, the second Determining a parameter value used for communication control of the communication service, and observing a radio signal transmitted for the second communication service in a second interval following the first interval And when the radio signal for the second communication service is not detected in the second interval, the second interval is determined based on the parameter value in the third interval following the second interval. For 2 communication services Method comprising the steps of: transmitting a configuration, is provided.

  The communication apparatus can correspond to, for example, an SSC (Secondary Spectrum Coordinator) described later. According to such a configuration, for example, the SSC receives a primary signal transmitted for the first communication service in the first interval when the frequency band is secondarily used. Next, the SSC determines a parameter value used for controlling communication of the second communication service based on the primary signal received within the primary signal observation period. The parameter value determined here may be, for example, transmission power, frequency, or modulation order used for transmission of the secondary signal. Next, the SSC senses (observes) the secondary signal within the second interval. Then, the SSC transmits a beacon for the second communication service based on the parameter value described above in the third section when the secondary signal is not detected in the second section.

  The step of determining the parameter value may include determining transmission power of the beacon transmitted in the third section based on the radio signal received in the first section. .

  The method may further include a step of receiving a connection request to the second communication service from a secondary usage node that has received the beacon within a fourth period following the third period.

  Further, the transmission power of the connection request transmitted from the secondary usage node in the fourth section is determined based on data included in the beacon transmitted from the communication apparatus in the third section. May be.

  In addition, for each secondary usage node that is the source of the connection request received in the fourth interval, the slot included in the fifth interval following the fourth interval is set as data by the secondary usage node. Allocating for transmission may further be included.

  The beacon includes data indicating a beacon period, and the first section, the second section, the third section, the fourth section, and the fifth section correspond to the beacon period. It may be repeated with a period.

  The method may further include a step of changing the beacon period when a data rate required for the second communication service changes.

  Further, a guard interval may be further provided after the fifth section.

  In addition, when a collision between the beacon transmitted in the third section and another radio signal is detected by a secondary usage node, a beacon collision occurs in the fourth section. The method may further include receiving a notification to be shown from the secondary usage node.

  In addition, the method may further include a step of receiving, from the secondary usage node, data relating to the communication status of the first communication service or the second communication service observed at the secondary usage node within the fourth section. Good.

  Further, the method may further include receiving a reference signal for synchronizing the sections among the plurality of communication apparatuses from a node outside the communication apparatus within the first section.

  According to another embodiment of the present invention, a communication unit capable of transmitting and receiving a radio signal for a second communication service that secondarily uses a frequency band assigned to the first communication service, and the communication unit A control unit that controls communication according to the above, wherein the control unit causes the communication unit to receive a radio signal transmitted for the first communication service within a first interval on a time axis, and Based on the radio signal received in the first section, a parameter value to be used for controlling the communication of the second communication service is determined, and in the second section following the first section. When a radio signal transmitted for the second communication service is observed through the communication unit and a radio signal for the second communication service is not detected in the second section, Within the third section following the second section, the parameters Based on the data value to transmit a beacon for the second communication service to the communication unit, a communication device, it is provided.

  According to another embodiment of the present invention, a communication apparatus comprising: a communication unit capable of transmitting and receiving a radio signal for a second communication service that secondarily uses a frequency band assigned to the first communication service. A control unit for controlling communication by the communication unit, wherein the communication unit receives a radio signal transmitted for the first communication service within a first interval on a time axis. And determining a parameter value to be used for controlling the communication of the second communication service based on the radio signal received in the first interval, and a second value following the first interval. A radio signal transmitted for the second communication service in the section was observed through the communication unit, and a radio signal for the second communication service was not detected in the second section. If followed by the second interval above Within third section based on the parameter value to transmit a beacon for the second communication service to the communication unit, a control unit, a program to function as is provided.

  As described above, according to the communication control method, the communication apparatus, and the program according to the present invention, an effective framework for avoiding signal collision and suppressing interference in the secondary use of the frequency band. Can be provided.

It is a schematic diagram which shows the 1st example in which a primary utilization node receives interference by the secondary utilization of a frequency band. It is a schematic diagram which shows the 2nd example in which a primary utilization node receives interference by secondary utilization of a frequency band. It is a 1st schematic diagram for demonstrating the influence of the interference according to a communication system and a channel direction. It is a 2nd schematic diagram for demonstrating the influence of the interference according to a communication system and a channel direction. It is a 3rd schematic diagram for demonstrating the influence of the interference according to a communication system and a channel direction. It is a 4th schematic diagram for demonstrating the influence of the interference according to a communication system and a channel direction. It is a 1st schematic diagram for demonstrating the interference between 2nd communication services. It is a 2nd schematic diagram for demonstrating the interference between 2nd communication services. It is explanatory drawing for demonstrating the framework for the secondary utilization of a frequency band. It is explanatory drawing which shows a mode that the beacon period for the secondary utilization of a frequency band is changed. It is a schematic diagram which shows the positional relationship of the secondary usage node in the 1st scenario regarding the collision of secondary signals. It is a sequence diagram which shows the 1st scenario regarding the collision of secondary signals. It is a schematic diagram which shows the positional relationship of the secondary usage node in the 2nd scenario regarding the collision of secondary signals. It is a sequence diagram which shows the 2nd scenario regarding the collision of secondary signals. It is explanatory drawing for demonstrating the outline | summary of the communication system which concerns on 1st Embodiment. It is a block diagram which shows an example of the logical structure of the management node which concerns on 1st Embodiment. It is a flowchart which shows an example of the flow of the transmission power determination process which concerns on 1st Embodiment. It is a flowchart which shows an example of the flow of the transmission power distribution process which concerns on 1st Embodiment. It is a block diagram which shows an example of a logical structure of the secondary usage node (SSC) which concerns on 1st Embodiment. It is a flowchart which shows an example of the flow of the secondary usage start process of the secondary usage node (SSC) which concerns on 1st Embodiment. It is explanatory drawing for demonstrating the outline | summary of the transmission power control based on the position of a secondary utilization node (SUE). It is explanatory drawing for demonstrating the classification | category of the position of a secondary usage node (SUE). It is a block diagram which shows an example of a logical structure of the secondary usage node (SUE) which concerns on 1st Embodiment. It is a flowchart which shows an example of the flow of the transmission power control process by the secondary usage node (SUE) which concerns on 1st Embodiment. It is explanatory drawing for demonstrating the outline | summary of the communication system which concerns on 2nd Embodiment. It is a block diagram which shows an example of the logical structure of the management node which concerns on 2nd Embodiment. It is a block diagram which shows an example of a logical structure of the secondary usage node (SSC) which concerns on 2nd Embodiment. It is a flowchart which shows an example of the flow of the secondary usage start process of the secondary usage node (SSC) which concerns on 2nd Embodiment. It is explanatory drawing for demonstrating the application to TV band.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

Further, the “DETAILED DESCRIPTION OF THE INVENTION” will be described in the following order.
1. 1. Interference control model according to one embodiment 1-1. Example of interference due to secondary use of frequency band 1-2. Explanation of interference control model 1-3. Comparison of channels for secondary use 1-4. Examination of interference between second communication services 1-5. Distribution of transmission power between second communication services 1-6. Framework for secondary use 1-7. Collision detection and avoidance method 1-8. Scope of the term secondary use First embodiment 2-1. Overview of communication system 2-2. Configuration example of management node 2-3. Configuration example of secondary usage node (SSC) 2-4. Configuration example of secondary usage node (SUE) 2-5. Summary of first embodiment Second embodiment 3-1. Overview of communication system 3-2. Configuration example of management node 3-3. Configuration example of secondary usage node (SSC) 3-4. Summary of Second Embodiment 4. Application to TV band

<1. Interference Control Model According to One Embodiment>
[1-1. Example of interference due to secondary use of frequency band]
First, with reference to FIG. 1A and FIG. 1B, a simplified example in which a primary usage node receives interference due to secondary usage of a frequency band will be described. FIG. 1A and FIG. 1B are schematic diagrams illustrating an example in which any primary usage node included in the primary system receives interference due to secondary usage of a frequency band.

Referring to FIG. 1A, primary usage nodes Pn ₁ and Pn ₂ are located inside the cell 10 of the first communication service. Among these, the primary usage node Pn ₁ is a base station (PBS: Primary Base Station) that provides a first communication service to terminal devices (also referred to as user equipment (UE)) located inside the cell 10. is there. The first communication service may be any communication service including, for example, a digital TV broadcast service, a satellite communication service, or a mobile communication service. On the other hand, the primary usage node Pn ₂ is a terminal device (PUE: Primary User Equipment) that receives provision of the first communication service. The primary usage node Pn ₁ and the primary usage node Pn ₂ and the other primary usage nodes in the figure form a primary system by transmitting and receiving radio signals using the frequency band allocated to the first communication service. .

FIG. 1A also shows a plurality of secondary usage nodes Sn ₁ , Sn ₂ , Sn ₃ and Sn ₄ located inside the cell 10. These secondary usage nodes use part or all of the frequency band allocated to the first communication service in accordance with a predetermined spectrum policy (frequency usage rule) (that is, secondary use of the frequency band). ) Operate the second communication service to form a secondary system. The second communication service may be a wireless communication service implemented according to any wireless communication protocol such as, for example, IEEE 802.11a / b / g / n / s, Zigbee, or WiMedia. A plurality of secondary systems may be formed in one cell. In the example of FIG. 1A, different secondary systems are formed in the regions 12a, 12b, and 12c inside the cell 10, respectively. Although the primary usage node and the secondary usage node are described separately from the viewpoint of clarity of explanation here, a part of the primary usage node may operate as the secondary usage node.

As shown in FIG. 1A, when the second communication service is operated inside the cell 10 of the first communication service, the radio signal transmitted for the second communication service is the first communication service. There is a risk of interference. The example of FIG. 1A shows the possibility that radio signals transmitted from the secondary usage nodes Sn ₁ , Sn ₂ and Sn ₃ may interfere with uplink signals transmitted from the primary usage node Pn ₂ to the primary usage node Pn ₁ . ing. In this case, the primary usage node Pn ₁ may not normally receive the uplink signal or may not obtain the desired service quality even if it can be received.

Similar to FIG. 1A, also in FIG. 1B, the primary usage nodes Pn ₁ and Pn ₂ are located inside the cell 10 of the first communication service, and the primary usage node Pn ₁ as a base station is the primary usage node Pn _1. first communication service is provided to the usage node Pn _2. Further, secondary usage nodes Sn ₁ , Sn ₂ , Sn ₃ and Sn ₄ are shown inside the cell 10 of the first communication service. In the example of FIG. 1B, the radio signals transmitted from the secondary usage nodes Sn ₁ , Sn ₂ , Sn ₃ and Sn ₄ can interfere with the downlink signal transmitted from the primary usage node Pn ₁ to the primary usage node Pn ₂ . Showing sex. In this case, the primary usage node Pn ₂ may not normally receive the downlink signal or may not obtain the desired quality of service even if it can be received.

  One solution to prevent such interference due to secondary use of the frequency band and not to adversely affect the first communication service, such as degradation of communication quality, is used for transmission of radio signals from the secondary use node. Is to reduce the transmission power to be transmitted. On the other hand, if the transmission power is low, the communication capacity of the second communication service decreases and the communication quality also deteriorates. Therefore, it is beneficial to increase the transmission power for the second communication service as much as possible without causing interference to the first communication service. Then, next, the relationship between the interference to the 1st communication service by the secondary usage of a frequency band and the transmission power used in a secondary usage node is demonstrated.

[1-2. Explanation of interference control model]
When attention is paid to a one-to-one relationship between a secondary usage node that gives interference by secondary usage and a primary usage node that receives interference (hereinafter referred to as an interfered node), the interference is the affected node. In order to be permitted, the following relational expression (1) needs to be satisfied. The interfered node may correspond to, for example, the primary usage node Pn _{1 in} FIG. 1A or the primary usage node Pn ₂ in FIG. 1B.

Here, SINR _required represents the minimum SINR (Signal to Interference and Noise Ratio) _required in the interfered node. SINR _required may be, for example, the minimum reception sensitivity of the interfered node or the minimum SINR given according to QoS (Quality of Service). P _{rx_primary and primary} represent the reception level of the radio signal required in the first communication service, and P _{rx_primary and secondary} represent the reception level of the radio signal transmitted from the secondary usage node at the interfered node. N _primary represents interference or noise level (including one or both of interference level and noise level) that can be applied to the interfered node.

  Further, the reception level of the radio signal is represented by the transmission power and path loss of the radio signal, as shown in the following formulas (2) and (3).

Here, P _{tx_secondary} represents the transmission power of the radio signal in the secondary usage node, and L _{path_tx_secondary} represents the path loss on the communication path from the secondary usage node to the interfered node. P _{tx_primary} represents the transmission power of the radio signal in the first communication service, and L _{path_tx_primary} represents the path loss on the communication path of the radio signal in the first communication service. Therefore, the relational expression (1) is transformed as the following expression.

The interference or noise level N _primary included in the equations (1) and (4) is, for example, the Boltzmann constant k = 1.38 × 10 ⁻²³ [J / K], the absolute temperature T [K], noise Using the exponent (noise figure) NF and the band BW [Hz], it can be calculated as:

Here, I _primary is interference between adjacent cells in the first communication service, and interference in a cell in a heterogeneous environment in which a femto cell, a small cell or a relay node is overlaid on a macro cell, or out-of-band radiation. Interference may be included. Further, the path loss on the communication path of the radio signal usually depends on the distance d between the two nodes, and can be calculated as the following equation as an example.

Here, d ₀ is the reference distance, λ is the wavelength of the carrier frequency, and n is the propagation coefficient.

  Next, the relational expression (4) is further transformed as the following expression.

  If the transmission power of the secondary usage node is controlled so that this relational expression (7) is satisfied, at least in the local one-to-one relationship between the secondary usage node and the interfered node, the interference is It can be tolerated at the interfered node. Furthermore, when there are a plurality of secondary usage nodes, it is required to satisfy the following relational expression, where n is the total number of secondary usage nodes that are interference sources.

Therefore, assuming that the largest possible communication capacity or high communication quality is ensured even in the second communication service, the interference power level I _{acceptable that} is generally allowed for the second communication service is given by the following equation. Given.

Here, since the parameter on the right side and the value of the path loss L _{path_tx_secondary, i on} the left side in Expression (9) are known, only the transmission power P _{tx_secondary, i} corresponding to the interference power level I _acceptable is a parameter to be determined. . Equation (9) may be understood as an evaluation equation for evaluating the total amount of interference power allowed to be given to the primary system by the secondary system.

  That is, the secondary usage node that secondary uses the frequency band allocated to the first communication service transmits the transmission power within a range that satisfies the formula (9) as a whole when focusing on each interfered node. It is desirable to control power.

[1-3. Comparison of channels for secondary use]
FIG. 2A to FIG. 2D are schematic diagrams for explaining the influence of interference at the time of secondary use according to the communication method used for the first communication service and the channel direction.

Each figure shows a primary usage node Pn ₁ as a base station and three primary usage nodes Pn ₂ , Pn ₃ and Pn _{4 as} PUEs. These primary usage nodes Pn ₁ , Pn ₂ , Pn ₃ and Pn ₄ form a primary system using an OFDMA (Orthogonal Frequency Division Multiple Access) scheme in the example of FIGS. 2A and 2B. . The primary system in that case may be, for example, a WiMAX (registered trademark) system, an LTE (Long Term Evolution) system, or an LTE-A (LTE-Advanced) system. In addition, the primary usage nodes Pn ₁ , Pn ₂ , Pn _3, and Pn ₄ form a primary system using a CDMA (Code Division Multiple Access) method in the examples of FIGS. 2C and 2D. The primary system in that case may be, for example, UMTS (Universal Mobile Telecommunications System) or W-CDMA (Wideband-CDMA).

Each figure also shows the secondary usage node Sn ₁ . The secondary usage node Sn ₁ transmits / receives a radio signal (secondary signal) for the second communication service to / from another secondary usage node located in the region 12d, and thereby the primary usage node Pn ₁ , Pn ₂ , Pn ₃ and Pn ₄ may occur. The influence range of the interference depends on the communication method and channel direction of the first communication service that is the target of secondary use, as will be described below.

First, referring to FIG. 2A, when an OFDMA based uplink channel is secondarily used, interference may only occur for uplink signals from any one PUE of the primary system to the base station. In the example of FIG. 2A, the secondary signal from the secondary usage node Sn ₁ interferes with the uplink signal from the primary usage node Pn ₂ to the primary usage node (base station) Pn ₁ . In this case, uplink signals from other PUEs are pre-assigned to different resource blocks (or different frequency slots or time slots) and thus are not affected by the secondary signal.

Next, with reference to FIG. 2B, if the OFDMA based downlink channel is secondarily utilized, interference may occur for the downlink signal from the base station of the primary system to each PUE. In the example of FIG. 2B, the secondary signal from the secondary usage node Sn ₁ interferes with the downlink signal from the primary usage node (base station) Pn ₁ to the primary usage nodes Pn ₂ , Pn ₃ and Pn ₄ . . This is because a downlink signal (for example, a control channel signal) can be transmitted using a common resource block or the like for a plurality of PUEs.

Next, with reference to FIG. 2C, if a CDMA based uplink channel is secondary utilized, interference may occur for the uplink signal from each PUE of the primary system to the base station. In the example of FIG. 2C, the secondary signal from the secondary usage node Sn ₁ interferes with the uplink signal from the primary usage nodes Pn ₂ , Pn ₃ and Pn ₄ to the primary usage node (base station) Pn ₁ . . In general, in the CDMA system, since the primary signal is spread over the entire band using a spreading code assigned to each PUE and transmitted simultaneously, the secondary signal interferes with the primary signals from a plurality of PUEs in this way. obtain.

Next, with reference to FIG. 2D, if a CDMA downlink channel is secondarily utilized, interference may occur for the downlink signal from the primary system base station to each PUE. In the example of FIG. 2D, the secondary signal from the secondary usage node Sn ₁ interferes with the downlink signal from the primary usage node (base station) Pn ₁ to the primary usage nodes Pn ₂ , Pn ₃ and Pn ₄ . . This is because downlink signals (for example, control channel signals) can be commonly received by a plurality of PUEs, and primary signals are spread over the entire band and transmitted at the same time as CDMA uplink channels. Is the cause.

  Table 1 summarizes the range of influence of interference and technical requirements when the four types of channels described above are used for secondary use.

  Referring to Table 1, as described above, the influence range of interference is the smallest in the uplink channel of the OFDMA scheme. That is, when the OFDMA uplink channel is secondarily used, interference may only occur in the link from one UE (“a UE”) to the base station, while the other channel is used as the secondary channel. When utilized, interference may occur on links associated with multiple UEs. From the viewpoint of functional requirements, in the CDMA system, it is necessary to detect a spreading code for sensing the primary signal, whereas in the OFDMA system, only UL (Uplink) or DL (Downlink) synchronization is required. Is easier to implement. Furthermore, the minimum receiving sensitivity is, for example, -120 dBm (in the case of UMTS) in the CDMA system, and -90 dBm (in the case of WiMAX) in the OFDMA system, and it can be said that the OFDMA system is less susceptible to interference. Therefore, it can be said that, in the secondary use of the frequency band, it is desirable to secondary use the frequency band of the uplink channel among the frequency bands of the first communication service using the OFDMA scheme. Therefore, in an embodiment described later in this specification, description will be made on the premise that secondary use of an OFDMA-type uplink channel is performed. However, the present invention is also applicable to an OFDMA downlink channel or a channel using a communication method other than the OFDMA method.

[1-4. Examination of interference between second communication services]
So far, the interference that the secondary use of the frequency band gives to the first communication service has been described. Next, interference between the second communication services when there are a plurality of second communication services that secondarily use the frequency band assigned to the first communication service will be described.

  3A and 3B are schematic diagrams for explaining interference between second communication services. Among these, FIG. 3A shows an example in which the second communication service is operated in each of the adjacent different cells. On the other hand, FIG. 3B shows an example in which two second communication services are operated in the same cell.

Referring to FIG. 3A, a primary usage node Pn _1d that is a base station located inside the cell 10d and a primary usage node Pn _1e that is a base station located inside the cell 10e are shown. The cell 10d includes secondary usage nodes Sn _1d and Sn _2d and a secondary usage node Sn _2e . The cell 10e includes secondary usage nodes Sn _1e and Sn _2e and a secondary usage node Sn _2d . Among these, the secondary usage nodes Sn _1d and Sn _2d operate the second communication service within the area 12d. Further, the secondary usage nodes Sn _1e and Sn _2e operate the second communication service in the area 12e.

Here, when the first communication service uses, for example, the OFDMA scheme, typically, different frequencies are assigned to channel frequencies used between adjacent cells by an interference avoidance algorithm between adjacent cells. In the example of FIG. 3A, the uplink channel frequency of the cell 10d is F1, and the uplink channel frequency of the cell 10e is F2. Therefore, when the OFDMA uplink channel is a secondary usage target, the frequency used for communication between the secondary usage nodes Sn _1d and Sn _2d is F1, and the secondary usage nodes Sn _1e and Sn _2e are The frequency used for communication between is F2. As a result, although the area 12d and the area 12e overlap each other in the example of FIG. 3A, the secondary signals transmitted and received by the secondary usage node Sn _2d and the secondary usage node Sn _2e located at the overlapping locations are as follows: They do not interfere (or collide) with each other.

On the other hand, referring to FIG. 3B, a primary usage node Pn _1d, which is a base station located inside the cell 10d, is shown. The cell 10d includes secondary usage nodes Sn _1d and Sn _2d and secondary usage nodes Sn _1f and Sn _2f . Among these, the secondary usage nodes Sn _1d and Sn _2d operate the second communication service within the area 12d. Also, the secondary usage nodes Sn _1f and Sn _2f operate the second communication service within the area 12f. In this case, the frequency used for the communication between the secondary usage nodes Sn _1d and Sn _2d and the frequency used for the communication between the secondary usage nodes Sn _1f and Sn _2f are both F1. As a result, in the secondary usage node Sn _2d and the secondary usage node Sn _2f that are located where the region 12d and the region 12f overlap, there is a possibility that secondary signals transmitted and received by both will interfere (or collide). is there.

  Therefore, when the second communication service is operated by secondary use of, for example, an OFDMA uplink channel among the frequency bands allocated to the first communication service, at least another second communication in the same cell. It is understood that it is desirable to consider the existence of services.

[1-5. Distribution of transmission power between second communication services]
When the allowable interference power of the second communication service is determined according to the above-described interference control model, if two or more second communication services exist in the same cell, the allowable communication power is determined between the second communication services. It is necessary to further distribute the transmission power according to the interference power. For example, when a plurality of secondary usage nodes start secondary usage of a frequency band as a coordinator, the transmission power of each beacon is such that the transmission power of the beacon transmitted by each coordinator satisfies the allowable interference power as a whole. Should be controlled. It is also conceivable that transmission power is further distributed between secondary usage nodes that subscribe to the second communication service. Three standards of equality, non-uniformity, and interference margin reduction are proposed as such transmission power distribution criteria.

(Equal type)
The equal type is a distribution criterion that equally assigns transmission power according to the allowable interference power determined according to the above-described interference control model to two or more second communication services. In the uniform distribution standard, the transmission power value P _{tx_secondary, i} allocated to the i-th (i = 1,..., N) second communication service among the n second communication services is expressed by the following equation. Led.

The right side of Expression (10) is obtained by dividing the right side of Expression (9) by a coefficient K based on path loss L _{path_tx_secondary, i} . According to such a transmission power distribution standard, communication opportunities can be equally provided to the coordinators of the individual second communication services, so that the service is fair and clear from the user's point of view. However, the individual interference levels that the secondary usage node gives to the primary usage node are non-uniform. When the transmission power is distributed among the secondary usage nodes that subscribe to the second communication service, the value of n in the determination of the coefficient K is the second value instead of the total number of the second communication services. It may be the total number of secondary usage nodes that subscribe to the communication service.

(Non-uniform type)
The non-equal type is a distribution criterion that non-uniformly allocates transmission power according to the allowable interference power determined according to the above-described interference control model to two or more second communication services. In the non-uniform distribution criterion, the transmission power value P _{tx_secondary, i} depends on the distance between the secondary usage node and the interfered node, and is derived according to the following equation.

  In the right side of equation (11), the value obtained by dividing the right side of equation (9) by the total number n of the second communication services is further weighted by the ratio of the path loss for each secondary usage node to the total path loss. Is. According to such a transmission power distribution standard, a secondary usage node having a longer distance to the interfered node can obtain more communication opportunities or communication distances. Thereby, the communication range as a whole can also be maximized.

(Interference margin reduction type)
The interference margin reduction type further reduces the risk of causing interference to the primary usage node by estimating the number of secondary usage nodes serving as interference sources to include the surplus number (that is, providing an “interference margin”). ) Distribution standard. In the distribution criterion of the interference margin reduction type, the transmission power value P _{tx_secondary, i} is derived according to the following equation.

N _{estimation in} Expression (12) represents a value obtained by estimating the total number of secondary usage nodes serving as interference sources so as to include the surplus number. For example, the value of N _estimation is such that if the total number of secondary usage nodes as interference sources is 10, the transmission power is reduced by 10 [dB], and if it is 100, the transmission power is reduced by 20 [dB]. Can be set.

  The characteristics of these three transmission power distribution standards are summarized in Table 2.

  Note that the node that distributes the transmission power may distribute the transmission power according to one criterion selected in advance among the three transmission power distribution criteria described above. Instead, the nodes that distribute the transmission power are evaluated values such as the total communication capacity given to all secondary usage nodes (or secondary usage nodes with high priority), or the total number of secondary links established. The transmission power may be distributed by adaptively selecting the criterion that results in the maximum.

[1-6. Framework for secondary use]
In the determination process of the allowable transmission power and the transmission power distribution process according to the interference control model described above, the position data of the interfered node (for example, a base station) of the primary system, the position data of the secondary usage node, and the path Data including loss etc. is used. Therefore, in the secondary usage of the frequency band, the second communication is centrically performed using a special (typically one) secondary usage node that can access the location data of the interfered node of the primary system. The service is preferably controlled. In the present specification, such a secondary usage node that is the center of control of the second communication service is referred to as SSC (Secondary Spectrum Coordinator).

  FIG. 4 is an explanatory diagram for explaining a framework for secondary use on the assumption that the SSC centrically controls the second communication service.

Referring to FIG. 4, the frame structure repeated with a period corresponding to the beacon period T _b is shown along the time axis. One repetition period includes six sections from the first section (# 1) to the sixth section (# 6). Among these, the second section (# 2) to the sixth section (# 6) constitute a superframe for the second communication service.

  The first section (# 1) is a primary signal observation section (Primary Sensing Period). In the first section, sensing (observation) of the primary signal is performed by the SSC. For example, the SSC identifies the control channel of the first communication service in the first interval and acquires uplink channel synchronization. In addition, for example, in the first section, the SSC performs the location data of the interfered node (for example, the base station of the primary system) transmitted on the control channel, the value of allowable transmission power, the spectrum mask, or the secondary usage Receive the modulation method etc. to be used for. In response, the SSC can determine a parameter value, such as transmission power, frequency, or modulation order used to control communication of the second communication service.

  In the first section (# 1), a reference signal for synchronizing the timing of the superframe illustrated in FIG. 4 among a plurality of SSCs may be supplied on the control channel. The reference signal may be, for example, a signal that notifies the start timing of the first section (# 1) and the beacon period Tb. Further, the reference signal may include a clock signal, for example. The reference signal can be supplied to a plurality of SSCs from, for example, a management node that commonly manages secondary usage of a frequency band. In this case, communication opportunities after the second section (# 2), which will be described later, are given evenly (or fairly) using the random backoff procedure, or non-equally according to the priority of each SSC. Can be given.

  The SSC detects another channel to be used for secondary use when it is determined that sufficient transmission power cannot be used for the operation of the second communication service as a result of sensing the primary signal. In order to do so, further sensing may be attempted within the first interval. In addition, when it is possible to sense a plurality of channels at a time, the SSC senses the plurality of channels and determines parameter values for controlling communication of the second communication service. May be. In that case, the SSC can present, using a beacon, two or more channel options that can be used by the SUE for secondary use within a third or fourth interval described later. At this time, by setting two or more channels presented as options as close as possible to each other, the load on the device that subscribes to the second communication service can be reduced. The plurality of channels to be sensed are, for example, channels that are primarily used in two or more adjacent cells, or are used in combination in one cell by spectrum aggregation adopted in LTE-A. There may be two or more channels. Individual channels can typically be distinguished as a single band with respect to a certain center frequency (for example, in the case of LTE, the operating modes for each bandwidth of 5 MHz, 10 MHz, 15 MHz, and 20 MHz are available). Exist). Instead, for example, a minimum unit of resource scheduling (for example, in the case of LTE, a resource block including 12 subcarriers of OFDM becomes a minimum unit of resource scheduling) may be treated as an individual channel.

  Next, the second section (# 2) is a secondary signal observation section (Secondary Sensing Period). In the second interval, the secondary signal is sensed by the SSC. The sensing here is mainly performed for the purpose of avoiding collision of secondary signals between adjacent subcells. That is, the SSC observes the presence or absence of a secondary signal transmitted from another communication apparatus within the second interval. And SSC transmits the beacon mentioned later in the 3rd section following the 2nd section, when the secondary signal transmitted from other communication devices is not detected. On the other hand, when a secondary signal is detected in the second interval, the SSC tries to transmit a beacon again after a predetermined time has elapsed. In this regard, the SSC preferably includes, for example, information on the time until the superframe ends or the end time of the superframe in the beacon (and other secondary signals) transmitted by the SSC. As a result, the other SSCs that have detected the secondary signal in the second section decode the secondary signal and acquire the information, thereby waiting for the beacon to be transmitted (the predetermined time). Time).

  Next, the third section (# 3) is a control frame transmission period. For example, the SSC transmits a beacon for the second communication service in the third interval when a secondary signal transmitted from another communication device is not detected in the second interval. At this time, for example, the value of the transmission power of the beacon is set to a value determined based on the radio signal received in the first section. In addition, the beacon includes, for example, an identifier (such as a subcell ID) for individually identifying the second communication service, and data such as a transmission power value indicating the transmission power of the beacon. Such a beacon is received by a secondary user node (SUE) located around the SSC. Then, the SUE that desires data communication by the second communication service transmits a connection request to the second communication service to the SSC within the fourth period following the third period.

  In addition, when there are two or more channels that can be used for secondary usage, the SSC may transmit beacons in parallel on each channel within the third interval. In that case, each beacon may include the parameter values determined for the channel corresponding to the beacon.

  Next, the fourth period (# 4) is a connection and scheduling period (Connection and Scheduling Period). In the fourth period, the SSC receives a connection request for the second communication service from the SUE. Then, after performing association and authentication for the received connection request, the SSC performs scheduling for the SUE that permits the connection. More specifically, the SSC, for example, allocates each SUE that permits connection to any one of slots 1 to n included in a fifth section to be described later (may be a criterion for first-come-first-served basis). Then, the SSC broadcasts SUE allocation information (scheduling information) for each slot. Thereby, each SUE can recognize the slot allocated to itself, and can perform data communication by the second communication service in the allocated slot.

  Note that the SUE in which data to be communicated by the second communication service is not generated in the superframe at that time continues to sense the primary signal or the secondary signal until the third interval, In the section, the sensing result may be reported to the SSC. Instead, the SUE may report the sensing result to the SSC within the fifth interval in which the slot was acquired at the next connection opportunity. The sensing result reported here may include, for example, data related to the communication status indicating the reception level of the primary signal or the secondary signal, or the presence of a nearby primary usage node or secondary usage node. Thereby, SSC can grasp | ascertain the surrounding communication condition more correctly, and can improve the precision of interference control.

  In addition, when beacons are transmitted in parallel on two or more channels that can be used for secondary usage, the SUE receives the two or more beacons and receives the channel with the best reception conditions (for example, The channel having the highest beacon reception level may be selected. In that case, the SUE may send a connection request as a response to the beacon to the SUE on the selected channel.

  Next, the fifth section (# 5) is a data communication period. As shown in FIG. 4, the fifth section typically includes a plurality of slots 1 to n (which can be distinguished from each other by time, frequency or code, or a combination thereof). Each SUE performs data communication by the second communication service in any of the plurality of slots 1 to n according to the scheduling information provided from the SSC within the fourth period.

Next, the sixth section (# 6) is a guard time period. The sixth section can also be referred to by the term guard interval. By providing the sixth section, it is possible to avoid deterioration in communication quality due to interference between a radio signal delayed on the communication path and a radio signal transmitted in the next cycle. The length of the sixth section, for example, set a predetermined time alpha was as such time T _{d +} alpha to addition to the time T _d to packet transmitted reaches the SSC in the last slot of the fifth segment obtain.

As described above, the second to sixth intervals shown in FIG. 4 constitute one superframe for the second communication service. Moreover, each of these sections are repeated with a period corresponding to the beacon period T _b. However, when it is determined from the result of sensing the primary signal in the first section that, for example, sufficient transmission power cannot be used for the operation of the second communication service, the SSC performs sensing of the primary signal. Continue. In other words, in this case, the primary signal is further sensed by the SSC (and / or SUE) instead of the superframe including the second period to the sixth period periodically appearing.

Further, the beacon period T _b of FIG. 4 is not necessarily a constant period. In other words, beacon period T _b, for example, if the requested data rate for the application to be implemented on the second communication service is high, increase the proportion of data communications section occupied in the superframe (a fifth section) Therefore, it may be dynamically changed to a longer period. For example, in the example of FIG. 5, the beacon period T _b1 (see 5a) having the same length as the beacon period T _b shown in FIG. 4 is changed to the beacon period T _b2 (see 5b), The proportion of data communication sections in the superframe is increased. In this case, the SSC preferably inserts the value of the next beacon period into the beacon transmitted in the third interval. Thereby, SUE (or other SSC located in the surroundings) which received the beacon can synchronize the operation | movement of an own apparatus autonomously to a new beacon period. Furthermore, the SUE that has received a beacon and has detected a change in the beacon period may insert the value of the new beacon period into a frame transmitted by itself within the same superframe. Thereby, the SUE (or other SSC) in a position where the beacon from the SSC cannot be directly received can also know the change of the beacon period.

  In the above, the SSC can sense a plurality of channels at a time in the first section, but the configuration of the receiver for sensing a plurality of channels at a time is as follows. Can be considered. That is, for example, the SSC simultaneously receives radio signals over a plurality of channels using a wideband filter or a filter bank, and the signal level of the received signal (which may be either an analog domain or digital domain such as RSSI) is equal to or greater than a predetermined threshold The subsequent demodulation processing is performed according to the channel. Thereby, the SSC can sense a plurality of channels at a time. For example, in 40M mode of IEEE802.11n, assuming the coexistence with legacy terminals, power is measured for the FFT processing result of the baseband signal after A / D conversion, and the lower 20 MHz of 40M full channel or 40 MHz It can be determined which of the top 20 MHz is being used. The subsequent digital demodulation operation is dynamically changed according to the determination result. Such a receiver configuration can be applied to sensing of a plurality of channels by SSC.

[1-7. Collision detection and avoidance method]
According to the framework described with reference to FIGS. 4 and 5, the second communication service is centric controlled by the SSC having the role as a coordinator. In this case, the beacon transmission power is determined by the SSC according to the above-described interference control model. Also, the transmission power to be used by the SUE for connection request transmission or data communication can be determined by the SUE based on a beacon transmitted from the SSC (this will be further described later). As a result, it is prevented that substantial interference occurs in the primary system due to secondary use of the frequency band. However, in this framework, since the communication procedure in the CSMA (Carrier Sense Multiple Access) method is employed particularly in the second and third sections, there is a possibility that collision between secondary signals may occur. . Therefore, a method for detecting a collision between secondary signals and avoiding the collision will be described with reference to FIGS. 6 and 7.

(First scenario)
6A and 6B are explanatory diagrams for describing a first scenario in which a secondary signal collision occurs in the framework described with reference to FIG. Among these, FIG. 6A shows the positional relationship of the secondary usage nodes in the first scenario. On the other hand, FIG. 6B is a sequence diagram illustrating an example of a communication flow according to the first scenario.

Referring to FIG. 6A, the base station Pn _1d that provides the first communication service inside the cell 10d, and the secondary usage nodes Sn _1g and Sn _2g that secondary use the frequency band allocated to the first communication service. , Sn _1h and Sn _2h are shown. Among these, the secondary usage node Sn _1g has a role of a coordinator of the second communication service, and transmits a beacon for the second communication service to the secondary usage node located inside the area 12g. On the other hand, the secondary usage node Sn _1h also serves as a coordinator for the second communication service, and transmits a beacon for the second communication service to the secondary usage node located inside the area 12h. However, in FIG. 6A, the secondary usage node Sn _1g exists in the area 12h. Further, a secondary usage node Sn _1h exists inside the region 12g. Therefore, if the secondary usage node Sn _1g and the secondary usage node Sn _1h transmit beacons at the same time, the beacons may collide.

In such a positional relationship, in the sequence diagram of FIG. 6B, it is assumed that the secondary usage node Sn _1g starts secondary usage before the secondary usage node Sn _1h . Referring to FIG. 6B, first, the secondary usage node Sn _1g senses (observes) the primary signal within the first interval when starting the second communication service (step S10). Then, the secondary usage node Sn _1g acquires synchronization by sensing and determines the transmission power of the beacon.

Next, the secondary usage node Sn _1g senses (observes) the secondary signal within the second interval (step S12). Then, when the secondary usage node Sn _1g confirms that the secondary signal is not transmitted from the other secondary usage nodes, the transmission power determined in step S10 is used in the third interval to generate the region 12g. A beacon for the second communication service is transmitted inside (Step S14).

On the other hand, when the beacon is transmitted from the secondary usage node Sn _1g , the secondary usage node Sn _1h is also about to start secondary usage. In that case, the secondary usage node Sn _1h senses the primary signal within the first interval (step S16), and then senses the secondary signal within the second interval (step S18). At this time, when the secondary usage node Sn _1h detects the beacon transmitted from the secondary usage node Sn _1g , the secondary usage node Sn _1h stops transmission of its own beacon in the subsequent third interval and waits for a predetermined time. (Step S28). Here, as described above, the predetermined time may be, for example, a time determined from the end time of the superframe acquired by decoding the beacon transmitted from the secondary usage node Sn _1g .

Although not shown, the secondary usage node Sn _1h waits for a predetermined time in step S28, and if there are other channel candidates that can be used secondary, You may try to form a superframe.

Meanwhile, while the secondary usage node Sn _1h is waiting, the secondary usage node Sn _{2 g} of a beacon has been received from the secondary usage node Sn _{1 g,} the connection request in the fourth section to the secondary usage node Sn _{1 g} Is transmitted (step S20). Then, authentication and scheduling are performed by the secondary usage node Sn _1g , and connection permission (including scheduling information) is transmitted from the secondary usage node Sn _1g to the secondary usage node Sn _2g (step S22). Thereafter, the secondary usage node Sn _2g performs data communication using the assigned slot in the fifth section (step S24).

When the predetermined time elapses, the secondary usage node Sn _1h senses the primary signal again in the first interval (step S30), and then senses the secondary signal in the second interval (step S30). S32). Then, when the secondary usage node Sn _1h confirms that the secondary signal is not transmitted from the other secondary usage nodes, the secondary usage node Sn _1h is set in the area 12h for the second communication service within the third interval. A beacon is transmitted (step S34). Then, secondary usage node _Sn secondary usage node _{Sn 2h} that received the beacon from _1h transmits a connection request to the secondary usage node _{Sn 1h} in the fourth section (step S36). Since the subsequent communication flow is the same as that in steps S20 to S24, description thereof is omitted.

(Second scenario)
7A and 7B are explanatory diagrams for describing a second scenario in which a secondary signal collision occurs in the framework described with reference to FIG. Among these, FIG. 7A shows the positional relationship of the secondary usage nodes in the second scenario. On the other hand, FIG. 7B is a sequence diagram illustrating an example of a communication flow according to the second scenario.

Referring to FIG. 7A, the base station Pn _1d that provides the first communication service within the cell 10d, and the secondary usage nodes Sn _1i and Sn _2i that secondary use the frequency band allocated to the first communication service. , Sn _1j and Sn _2j are shown. Among these, the secondary usage node Sn _1i has a role of a coordinator of the second communication service, and transmits a beacon for the second communication service to the secondary usage node located inside the area 12i. On the other hand, the secondary usage node Sn _1j also serves as a coordinator of the second communication service and transmits a beacon for the second communication service to the secondary usage node located inside the area 12j. Here, in FIG. 7A, the secondary usage node Sn _2i and the secondary usage node Sn _2j are located close to each other. Therefore, when the secondary usage node Sn _2i transmits a secondary signal, the secondary signal collides with another radio signal to be received at the secondary usage node Sn _2j (for example, a beacon from the secondary usage node Sn _1j ). there's a possibility that.

In such a positional relationship, in the sequence diagram of FIG. 7B, it is assumed that the secondary usage node Sn _1i starts secondary usage before the secondary usage node Sn _1j . Referring to FIG. 7B, first, the secondary usage node Sn _1i senses (observes) the primary signal within the first interval when starting the second communication service (step S60). Then, the secondary usage node Sn _1i acquires synchronization by sensing and determines the transmission power of the beacon.

Next, the secondary usage node Sn _1i senses (observes) the secondary signal within the second interval (step S62). Then, when the secondary usage node Sn _1i confirms that the secondary signal is not transmitted from the other secondary usage nodes, the transmission power determined in step S60 is used in the third interval to generate the region 12i. A beacon for the second communication service is transmitted inside (step S64). Next, the secondary usage node _{Sn 2i} which has received a beacon from the secondary usage node _{Sn 1i} transmits a connection request to the secondary usage node _{Sn 1i} in the fourth section (step S66). Then, authentication and scheduling are performed by the secondary usage node Sn _1i , and connection permission (including scheduling information) is transmitted from the secondary usage node Sn _1i to the secondary usage node Sn _2i (step S68). Thereafter, the secondary usage node Sn _2i performs data communication using the allocated slot in the fifth section (step S70).

On the other hand, when data communication is performed by the secondary usage node Sn _2i , the secondary usage nodes Sn _1j and Sn _2j are also about to start secondary usage. In that case, the secondary usage node Sn _1j senses the primary signal in the first section (step S80) and then senses the secondary signal in the second section (step S82). Then, when the secondary usage node Sn _1j confirms that the secondary signal is not transmitted from the other secondary usage node, the secondary usage node Sn _1j is set in the area 12j for the second communication service within the third interval. A beacon is transmitted (step S84). At this time, when the data signal transmitted from the secondary usage node Sn _2i and the beacon transmitted from the secondary usage node Sn _1j arrive at the same timing to the secondary usage node Sn _2j , the two secondary signals are transmitted. A collision occurs. Then, the secondary usage node Sn _2j cannot normally receive the beacon transmitted from the secondary usage node Sn _1j . For example, the secondary usage node Sn _2j senses the SINR level in advance by sensing itself and cannot receive a beacon (or other secondary signal) even though the SINR is at a sufficient level. It can be determined that a secondary signal collision has occurred.

In this case, the secondary usage node Sn _2j notifies the secondary usage node Sn _1j that a secondary signal collision has occurred within the fourth interval (step S86). Then, the secondary usage node Sn _1j performs an operation for avoiding the collision, for example, by excluding the secondary usage node Sn _2j from the scheduling target or switching the channel to another secondary usage channel candidate. .

In addition, when the secondary usage node Sn _2j cannot normally receive the beacon from either the secondary usage node Sn _{1j or} another coordinator, the secondary usage node Sn _2j observes the interference signal, so that the interference signal becomes a secondary It may be determined that the signal is from the usage node Sn _2i . If it is determined that the secondary usage node Sn _2j has received an interference signal from the neighboring secondary usage node Sn _2i , the secondary usage node Sn _2j is subscribed to another second communication service when the next connection opportunity is obtained. The presence of the neighboring SUE can be notified to the secondary usage node Sn _1j . Even in that case, the secondary usage node Sn _1j is for avoiding the collision, for example, by excluding the secondary usage node Sn _2j from the scheduling target or switching the channel to another secondary usage channel candidate. Perform the action. Further, the secondary usage node Sn _1j may monitor the number of retransmissions of the secondary signal and may determine that a collision of the secondary signals has occurred when the number of retransmissions increases.

  As described above, in the secondary usage of the frequency band, the secondary usage node having the role of coordinator controls the second communication service in a centric manner according to the framework shown in FIG. Thus, signal collision can be detected or avoided, and interference can be suppressed.

[1-8. Scope of the term secondary use]
Here, in the present specification, the term “secondary use” is typically used additionally or partially using all or part of the frequency band allocated to the first communication service, as described above. The use of an alternative communication service (second communication service). In the meaning of the term “secondary use”, the first communication service and the second communication service may be different types of communication services, or may be the same type of communication services. . The different types of communication services are, for example, two or more that can be selected from any communication service such as a digital TV broadcast service, a satellite communication service, a mobile communication service, a wireless LAN access service, or a P2P (Peer To Peer) connection service. Refers to different types of communication services. On the other hand, the same type of communication service is, for example, a service by a macro cell provided by a communication carrier in a mobile communication service and a service by a femto cell operated by a user or a mobile virtual network operator (MVNO). The relationship between can be included. The same type of communication service covers a spectrum hall and a service provided by a base station in a communication service compliant with WiMAX, LTE (Long Term Evolution), LTE-A (LTE-Advanced), or the like. Therefore, the relationship between services provided by a relay station (relay node) may also be included. Furthermore, the second communication service may use a plurality of fragmented frequency bands aggregated using a spectrum aggregation technique. Further, the second communication service is provided by the femtocell group, the relay station group, and the small / medium base station group that provides a smaller service area than the base station, which exist in the service area provided by the base station. It may be a simple communication service. The gist of each embodiment of the present invention described in the present specification is widely applicable to all kinds of secondary usage forms.

  Up to this point, the proposed interference control model and secondary usage framework have been described, and the relevant technical considerations have been described in order. Next, based on these, two embodiments of a communication control method for avoiding signal collision and suppressing interference during secondary use of a frequency band will be described.

<2. First Embodiment>
[2-1. Overview of communication system]
FIG. 8 is an explanatory diagram for explaining an overview of the communication system according to the first embodiment of the present invention.

  Referring to FIG. 8, a primary system 102 in which the first communication service is operated and secondary systems 202a and 202b in which the second communication service is operated are shown. Among these, the primary system 102 includes a management node 100 and a plurality of primary usage nodes 104.

  The management node 100 is a primary usage node having a role of managing secondary usage of the frequency band assigned to the first communication service. In the example of FIG. 8, a base station is shown as the management node 100, but the management node 100 is not limited to this example. That is, the management node 100 may be a primary usage node other than a base station, or may be another node (for example, a data server) connected to the base station by wire or wireless. In the present embodiment, the management node 100 can access the database 106 that holds position data representing the position of the primary usage node included in the primary system 102.

  The primary usage node 104 is a node that transmits and receives a radio signal for the first communication service in the primary system 102. When the primary usage node 104 joins the primary system 102, location data representing the location is registered in the database 106.

  Database 106 is typically implemented as a geolocation database. In the present embodiment, the database 106 outputs location data for each primary usage node to the management node 100 in response to a request from the management node 100. The database 106 may be configured integrally with the management node 100, or may be configured as a separate device from the management node 100.

  On the other hand, the secondary system 202a includes an SSC 200a and a plurality of SUEs 204a. Similarly, the secondary system 202b includes an SSC 200b and a plurality of SUEs 204b.

  The SSCs 200a and 200b are secondary usage nodes having the above-described coordinator role for controlling the second communication service. That is, each of the SSCs 200a and 200b determines whether secondary usage is possible according to a predetermined spectrum policy, receives transmission power allocation from the management node 100, and starts the second communication service together with the SUE 204a or 204b. The SSCs 200a and 200b may operate as an engine for cognitive radio (CE), for example.

  The SUEs 204a and 204b are secondary usage nodes (or terminal devices or UEs) that transmit and receive radio signals for the second communication service in the secondary systems 202a and 202b, respectively.

  In the following description of the present specification, when it is not necessary to distinguish the SSCs 200a and 200b from each other, the alphabet at the end of the code is omitted and the SSC 200 is generically named. The same applies to secondary systems 202a and 202b (secondary system 202) and SUEs 204a and 204b (SUE 204).

[2-2. Example of management node configuration]
(Description of each functional block)
FIG. 9 is a block diagram illustrating an example of a logical configuration of the management node 100 illustrated in FIG. Referring to FIG. 9, the management node 100 includes a communication unit 110, a database input / output unit 120, a storage unit 130, and a control unit 140.

  The communication unit 110 transmits and receives radio signals to and from the primary usage node 104 using a communication interface that may include an antenna, an RF circuit, a baseband circuit, and the like, according to a predetermined communication method of the first communication service. Communication unit 110 receives position data of SSC 200 from SSC 200 and outputs the received position data to control unit 140, as will be further described later.

  The database input / output unit 120 mediates access to the database 106 by the control unit 140. That is, the database input / output unit 120 acquires position data representing the position of the primary usage node 104 from the database 106 in response to a request from the control unit 140, and outputs the acquired position data to the control unit 140. Further, when the location data is received from the primary usage node 104 newly joined to the primary system 102 via the communication unit 110, the database input / output unit 120 registers the location data in the database 106. Further, the database input / output unit 120 may acquire and output position data stored in the database 106 in response to an inquiry from an external device.

  The storage unit 130 stores programs and data used for the operation of each unit of the management node 100 using a recording medium such as a hard disk or a semiconductor memory. Furthermore, in the present embodiment, the storage unit 130 stores various parameters required for transmission power calculation according to the above-described interference control model. The parameters stored in the storage unit 130 include, for example, parameters related to the quality of radio signals required in the first communication service (for example, required radio signal reception level, signal-to-interference and noise ratio), and Parameters regarding interference or noise level in the first communication service may be included. Note that the values of these parameters may be updated dynamically. For example, the required radio signal quality value may be dynamically updated according to the type of application to be provided to the primary usage node. Further, for example, the value of the interference or noise level can be dynamically updated by sensing via the communication unit 110.

  The control unit 140 controls the overall functions of the management node 100 using a control device such as a CPU (Central Processing Unit). In the present embodiment, the control unit 140 determines the transmission power allowed for the second communication service according to the above-described interference control model when the SSC 200 secondarily uses the frequency band assigned to the first communication service. decide. The transmission power determination process performed by the control unit 140 will be described in detail later. Furthermore, when there are two or more second communication services, the control unit 140 distributes the determined transmission power to the two or more second communication services. The transmission power distribution process performed by the control unit 140 will be described in detail later. Then, the control unit 140 notifies each SSC 200 of the determined or distributed transmission power value via the communication unit 110.

(Transmission power decision process flow)
FIG. 10 is a flowchart illustrating an example of a flow of transmission power determination processing for determining transmission power allowed for the second communication service by the control unit 140 of the management node 100.

  Referring to FIG. 10, first, the control unit 140 receives the position data of the SSC 200 from the SSC 200 via the communication unit 110 (step S102). In this specification, the position data refers to, for example, latitude and longitude values measured using the GPS function, or coordinate values based on a predetermined reference point measured by applying an arrival direction estimation algorithm, etc. May be included. Further, the control unit 140 may receive not only the position data of the SSC 200 but also the position data of each SUE 204 from the SSC 200.

  Next, the control unit 140 acquires the location data of the primary usage node from the database 106 via the database input / output unit 120. The control unit 140 acquires necessary parameters from the storage unit 130 (step S104). Note that, as in the example illustrated in FIG. 2A, when the OFDMA uplink channel is secondarily used, the interfered node is only the base station. Therefore, in such a case, in step S104, the control unit 140 may acquire only the position data of the management node 100 that is the base station as the position data of the primary usage node. The necessary parameters in step S104 are, for example, the quality of the radio signal required in the first communication service described above, and the interference or noise level in the first communication service (or parameters for calculating these levels). ) Etc.

Next, the control unit 140 determines the interference power allowed for the second communication service based on the position data and parameters received in step S102 and acquired in step S104 (step S106). More specifically, the control unit 140 can determine the interference power allowed for the second communication service, for example, according to the equation (9) in the above-described interference control model. At that time, for example, the quality of the radio signal required in the first communication service corresponds to the term P _{rx_primary, primary} / SINR _required in Equation (9). The interference or noise level corresponds to the N _Primary term in equation (9). Furthermore, the value of the path loss L _{path_tx_secondary, i} in Expression (9) can be calculated according to Expression (6) using the distance d derived from the position data of the primary usage node and the position data of each SSC 200. For example, instead of calculating the value of each path loss L _{path_tx_secondary, i} from the position data, the control unit 140 may receive the value of each path loss L _{path_tx_secondary, i} from each SSC 200 in step S102. . The value of the path loss L _{path_tx_secondary, i} can be calculated, for example, as the difference between the transmission power value of the downlink signal from the base station and the reception level of the downlink signal in each SSC 200.

  Next, the control unit 140 determines whether or not it is necessary to distribute the transmission power value (step S108). For example, as illustrated in FIG. 8, when secondary use is performed by two or more SSCs 200, the control unit 140 determines that the transmission power value needs to be distributed among the two or more SSCs 200. Is done. In that case, the process moves to step S110, and the transmission power distribution process is performed by the control unit 140 (step S110). On the other hand, for example, when there is only one SSC 200 that performs secondary usage and there is no need to distribute the value of transmission power, step S110 may be skipped.

  Then, the control unit 140 notifies the determined or distributed transmission power value to each SSC 200 via the communication unit 110 (step 112). At this time, the control unit 140 sends additional information such as a policy (for example, a transmission spectrum mask, a modulation method, etc.) to be observed by the secondary usage node in the secondary usage of the frequency band to each SSC 200 together with the value of the transmission power. You may be notified. Thereafter, a second communication service may be initiated between the SSC 200 and each SUE 204.

(Transmission power distribution process flow)
FIG. 11 shows a flow of transmission power distribution processing by the control unit 140 of the management node 100 when two or more SSCs 200 exist, that is, when two or more second communication services are operated in the same cell. It is a flowchart which shows an example.

  Referring to FIG. 11, first, control unit 140 distributes transmission power (allowable transmission power) according to the allowable interference power determined in step S106 of FIG. 10 according to the first criterion (step S202). . Next, the control unit 140 distributes the transmission power corresponding to the same interference power as in step S202 according to the second criterion (step S204). Here, the first reference and the second reference may be, for example, the above-described equal transmission power distribution standard and non-uniform transmission power distribution standard, respectively.

  Next, the control unit 140 evaluates the transmission power distributed according to the first criterion and the transmission power distributed according to the second criterion based on a predetermined evaluation condition (step S206). The predetermined evaluation condition may be, for example, a total communication capacity that is eventually given to all the SSCs 200. In that case, the total communication capacity C can be evaluated according to the following equation.

_Here, P tx_secondary, _i is the i-th transmission power distributed to the SSC200, _{N i} denotes the noise level of the i th SSC200.

  Moreover, the control part 140 is good also considering only SSC200 with a high priority among n SSC200 in Formula (13) as an object of totalization of communication capacity. Here, the priority may be given, for example, according to the type or content of the second communication service. For example, a high priority may be defined for a service that requires low delay, such as video distribution or a communication game. Further, a high priority may be defined for a service for which a high service charge is set so as to guarantee a certain service quality. Then, for example, the priority can be received together with the position data of the SSC 200 in step S102 of FIG.

  Further, in step S206, the control unit 140 evaluates the total number of links of the second communication service that can be established using the distributed transmission power instead of the communication capacity as in Expression (13). May be. In that case, it is first determined whether or not each pair of secondary usage nodes that desires communication can establish communication according to the transmission power distributed to each SSC 200. Then, the number of links determined to be able to establish communication can be aggregated as the total number of links of the second communication service.

  Next, the control unit 140 determines which of the first standard and the second standard is appropriate by comparing the communication capacity or the total number of links evaluated in step S206 (step S208). For example, if the transmission power distributed according to the first standard can achieve a larger communication capacity than the transmission power distributed according to the second standard, it is determined that the first standard is more suitable. obtain. If the transmission power distributed according to the second standard can achieve a larger communication capacity than the transmission power distributed according to the first standard, it is determined that the second standard is more suitable. obtain. If it is determined that the first reference is more suitable, the process proceeds to step S210. On the other hand, if it is determined that the second reference is more suitable, the process proceeds to step S212.

  In step S210, the transmission power distributed according to the first criterion determined to be more suitable is allocated to each SSC 200 (step S210). On the other hand, in step S212, the transmission power distributed according to the second criterion determined to be more suitable is allocated to each SSC 200 (step S212). Then, the transmission power distribution process shown in FIG. 11 ends.

  Note that, here, an example has been described in which the first standard and the second standard that can correspond to the uniform type and the non-uniform type are evaluated in terms of communication capacity or the number of links that can be established. However, the present invention is not limited to this example. For example, transmission power distribution standards other than the uniform type and the non-uniform type may be adopted. Also, evaluations may be made for three or more transmission power distribution criteria.

[2-3. Configuration example of secondary usage node (SSC)]
(Description of each functional block)
FIG. 12 is a block diagram illustrating an example of a logical configuration of the SSC 200 illustrated in FIG. Referring to FIG. 12, the SSC 200 includes a first communication unit 210, a second communication unit 220, a storage unit 230, and a control unit 240. In the present embodiment, the SSC 200 can communicate with the management node 100 via the first communication unit 210, and can transmit and receive a radio signal for the second communication service via the second communication unit 220. it can.

  The first communication unit 210 communicates with the management node 100 according to a predetermined communication method. The channel used for communication between the first communication unit 210 and the management node 100 may be, for example, a cognitive pilot channel (CPC) that is a control channel. The CPC may include, for example, an in-band CPC in which CPC information is extrapolated in an existing communication system (eg, the primary system 102) or an out-band CPC that is a dedicated channel in which CPC information is interpolated.

  For example, the first communication unit 210 sends position data representing the position of its own device to the management node 100 in response to an instruction to start secondary use of the frequency band (an instruction operation by a user or a request from another node). Send. The position data representing the position of the device itself may be data measured using a GPS (Global Positioning System) function, for example. Thereafter, the first communication unit 210 receives the value of the allowable transmission power determined according to the above-described method from the management node 100, and outputs the value to the control unit 240. In addition, the first communication unit 210 receives the location data of the interfered node that receives interference from the management node 100 when the secondary use is started, and outputs the received location data to the control unit 240. In the present embodiment, the interfered node that receives interference when secondary use is started corresponds to the management node 100 that is a base station of the primary system 102.

  The second communication unit 220 transmits and receives radio signals to and from the SUE 204 according to a predetermined communication method. For example, the second communication unit 220 first senses a radio signal of the first communication service and acquires uplink channel synchronization. And the 2nd communication part 220 transmits a beacon regularly to the surrounding SUE204 using the said uplink channel which acquired the synchronization. At this time, the transmission power used by the second communication unit 220 is limited to a range in which no substantial interference is given to the primary usage node under the control of the control unit 240. In addition, the beacon transmitted to the surrounding SUE 204 includes the value of the allowable interference power received by the first communication unit 210 and the location data of the interfered node and the SSC 200. These allowable interference power values and position data are used for transmission power control processing by the SUE 204, as will be further described later.

  When the communication link between the first communication unit 210 and the management node 100 is a wireless link, the first communication unit 210 and the second communication unit 220 include an antenna, an RF circuit, a baseband circuit, and the like. The same physical communication interface that may be included may be shared. A communication link between the first communication unit 210 and the management node 100 may be referred to as a backhaul link.

  The storage unit 230 stores programs and data used for the operation of each unit of the SSC 200 using a recording medium such as a hard disk or a semiconductor memory. Further, in the present embodiment, the storage unit 230 stores various parameters for operation of the second communication service and transmission power control. The parameters stored in the storage unit 230 include, for example, the location data of the own device (and other secondary usage nodes that subscribe to the second communication service as necessary), and the permission notified from the management node 100. Transmission power, spectrum mask, modulation method, and the like may be included.

  The control unit 240 controls the overall functions of the SSC 200 using a control device such as a CPU, for example. For example, in the present embodiment, the control unit 240 sets the value of the transmission power used for transmitting the radio signal by the second communication unit 220 to a value within the allowable transmission power range notified from the management node 100. . Then, the control unit 240 causes the second communication unit 220 to transmit a beacon including the above-described allowable interference power value and each position data. Further, when receiving a connection request for the second communication service from the SUE 204 that has received the beacon, the control unit 240 performs authentication of the connection request, scheduling of the SUE 204 (slot allocation), and the like.

(Secondary usage start processing flow)
FIG. 13 is a flowchart illustrating an example of the flow of secondary usage start processing by the SSC 200.

  In FIG. 13, for example, when an instruction to start secondary usage is detected, the first communication unit 210 transmits the position data of the SSC 200 to the management node 100 (step S302). At this time, not only the position data of the SSC 200 but also the position data of another SUE 204 may be transmitted to the management node 100.

  Next, the first communication unit 210 receives the value of the allowable transmission power determined according to the above-described interference control model and the position data of the management node 100 that is an assumed interfered node from the management node 100. (S304). For example, in addition to the allowable transmission power, additional information such as a transmission spectrum mask and a modulation method may be received.

  Next, the control unit 240 senses the primary signal within the primary signal observation period, and acquires synchronization of the uplink channel of the first communication service (step S306). In addition, the control unit 240 senses the secondary signal within the secondary signal observation section, and confirms that the secondary signal is not transmitted from the surrounding communication device (step S308). Here, if a secondary signal from a surrounding communication device is detected, the process proceeds to step S316. On the other hand, if a secondary signal from a surrounding communication device is not detected, the process proceeds to step S312.

  In step S312, the control unit 240 uses the transmission power within the range of the allowable transmission power received in step S304, and the beacon for the second communication service from the second communication unit 220 within the control frame transmission period. Is transmitted (step S312). The beacon includes the value of the allowable transmission power allocated to the second communication service, and the location data of the interfered node and the SSC 200.

  Next, when receiving a connection request from the SUE 204 to the second communication service via the second communication unit 220 within the connection and scheduling interval, the control unit 240 authenticates the connection request and schedules the SUE 204 ( Step S314). As a result, the SUE 204 can perform data communication using the second communication service within the data communication period. At this time, the SUE 204 controls the transmission power used for transmission of the radio signal for the second communication service based on the value of the allowable transmission power and each position data included in the beacon transmitted from the SSC 200 in step S312. To do. Note that the transmission power control processing by the SUE 204 here will be further described later.

  On the other hand, in step S316, the control unit 240 waits for a predetermined time in order to avoid a collision between the secondary signal transmitted from another communication device and the beacon transmitted by itself (step S316). Thereafter, the process returns to step S306.

  By such secondary use start processing, the SSC 200 suppresses the transmission power of the beacon transmitted by itself and the secondary signal transmitted from the SUE to a range that does not substantially interfere with the primary system, and between the secondary signals. Collisions can be avoided.

[2-4. Configuration example of secondary usage node (SUE)]
As described above, in the present embodiment, the SUE 204 receives a beacon for the second communication service from the SSC 200. Then, the SUE 204 controls the connection power to be transmitted within the connection and scheduling interval, and the transmission power of the data signal to be transmitted within the data communication interval, based on the SSC 200 and the location data of the interfered node included in the received beacon. . Therefore, in this section, first, an overview of transmission power control based on the position data by the SUE 204 will be described using FIG. 14A.

  FIG. 14A is an explanatory diagram for describing an overview of transmission power control based on a position by a secondary usage node (SUE). FIG. 14B is an explanatory diagram for describing the classification of the position of the secondary usage node (SUE).

  In the upper left of FIG. 14A is shown a management node 100 that is interfered by the second communication service in this embodiment (mainly referred to as the base station 100 when focusing on the side that is the interfered node). ing. The base station 100 provides a first communication service in a cell surrounded by the boundary 101 partially shown. FIG. 14A also shows an SSC 200 that is a coordinator of the second communication service. The SSC 200 has a distance D <b> 1 with the base station 100. Then, the SSC 200 transmits a beacon for the second communication service that can be received within the range surrounded by the boundary 201 using the transmission power that does not exceed the allowable transmission power determined according to the above-described interference control model.

  Furthermore, FIG. 14A shows a plurality of SUEs 204 (204-1 to 204-4). The SUE 204 is classified into four types (types 1 to 4) according to the positional relationship between the base station 100 and the SSC 200.

(Type 1)
The type 1 is classified as the distance from the interfered node (that is, the base station 100) to the own device is longer than the distance from the interfered node to the beacon transmission source node (that is, the SSC 200) and receives the beacon SUE located in a possible area. For example, in FIG. 14A, the distance between the base station 100 and the SSC 200 is D1. Further, the position where the beacon transmitted from the SSC 200 can be received is a position inside the boundary 201. Therefore, the SUE 204 located in the region R1 shaded with diagonal lines in FIG. 14B is classified as type 1.

  More specifically, SUEs 204-1a and 204-1b (collectively referred to as SUE 204-1) shown in FIG. 14A are classified as type 1. Since the SUE 204-1 is located farther from the base station 100 than the SSC 200, the SUE 204-1 uses the transmission power equivalent to the transmission power of the beacon received from the SSC 200, and does not interfere with the base station 100. A signal can be transmitted. Further, the SUE 204-1 may operate as a gateway that relays (relays) a secondary signal by ad hoc communication, for example, to a UE that cannot receive a beacon from the SSC 200.

(Type 2)
Next, type 2 and type 3 are also SUEs located in an area where the beacon can be received. Of these, the type 2 classification is that the distance from the interfered node to the own device is closer than the distance from the interfered node to the beacon transmission source node, and the distance from the interfered node to the own device is The SUE is located in a region farther than the distance from the own device to the beacon transmission source node. For example, in FIG. 14A, as described above, the distance between the base station 100 and the SSC 200 is D1. A dotted line D2 is a straight line that follows a position where the distance to the base station 100 and the distance to the SSC 200 are equal. Accordingly, the SUE 204 located in the region R2 shaded with dots in FIG. 14B is classified as type 2.

  More specifically, the SUE 204-2 shown in FIG. 14A is classified as type 2. When the SUE 204-2 uses a transmission power equivalent to the transmission power of the beacon received from the SSC 200, there is a risk of giving an unacceptable level of interference to the base station 100. However, the SUE 204-2 can transmit the secondary signal without causing interference to the base station 100 by using an appropriate transmission power smaller than the transmission power of the beacon. Further, the SUE 204-2 may operate as a gateway that relays a secondary signal by ad hoc communication to a UE that is located closer to the base station 100, for example.

(Type 3)
Also, the type 3 is classified as follows: the distance from the interfered node to the own device is closer than the distance from the interfered node to the transmission source node of the beacon, and the distance from the interfered node to the own device is The SUE is located in a region closer to the distance from the own device to the beacon transmission source node. That is, the SUE 204 located in the region R3 shaded with a horizontal line in FIG. 14B is classified as type 3.

  More specifically, the SUE 204-3 shown in FIG. 14A is classified as type 3. If the SUE 204-3 directly transmits the secondary signal to the SSC 200, the SUE 204-3 may cause unacceptable interference to the base station 100. Therefore, even if the SUE 204-3 can receive a beacon from the SSC 200, it is desirable that the SUE 204-3 does not directly respond to the beacon. Therefore, the SUE 204-3 waits for transmission of a response to the beacon until another node (for example, the SUE 204-2 in FIG. 14A) located between the SSC 200 and the own device is detected. For example, when the SUE 204-3 receives a relay beacon transmitted from the SUE 204-2, the SUE 204-3 transmits a response to the relay beacon using low transmission power that can be received only by the SUE 204-2. . In this case, the SUE 204-2 relays the response from the SUE 204-3 to the SSC 200, so that the SUE 204-3 can also subscribe to the second communication service. Note that the relay beacon from the SUE 204-2 can be transmitted using low-level transmission power that does not interfere with the interfered node, for example, by ad hoc communication for relaying the secondary signal.

(Type 4)
Next, SUEs that are classified in type 4 are located in an area where the beacon cannot be received. More specifically, the SUE 204-4 shown in FIG. 14A is classified as type 4. Since the SUE 204-4 cannot receive a beacon from the SSC 200, it cannot directly subscribe to the second communication service. Therefore, the SUE 204-4 waits until another node that relays the secondary signal (for example, the SUE 204-1b in FIG. 14A) is detected. And SUE204-4 will transmit the response to the beacon for relay concerned, for example, if the beacon for relay transmitted from SUE204-1b is received. In this case, the SUE 204-1b relays the response from the SUE 204-4 to the SSC 200, so that the SUE 204-4 can also subscribe to the second communication service. Note that the beacon for relay from the SUE 204-1b can also be transmitted using low transmission power that does not interfere with the interfered node, for example, by ad hoc communication for relaying the secondary signal.

  As described above, the SUE 204 controls the transmission power according to the positional relationship between the base station 100 and the SSC 200 that are typically classified into four types without causing interference to the base station 100. A connection request or data signal for the second communication service can be transmitted securely.

(Description of each functional block)
FIG. 15 is a block diagram illustrating an example of a logical configuration of the SUE 204 configured according to the above-described concept. Referring to FIG. 15, the SUE 204 includes a communication unit 205, a storage unit 206, and a control unit 207.

  The communication unit 205 can receive a beacon for the second communication service from the SSC 200 according to a predetermined communication method. In addition, the communication unit 205 receives a control from the control unit 207 and transmits a connection request or a data signal using transmission power in a range that does not substantially interfere with the primary usage node.

  The storage unit 206 stores programs and data used for the operation of each unit of the SUE 204 using a recording medium such as a hard disk or a semiconductor memory. Further, in the present embodiment, the storage unit 206 stores, for example, a value of transmission power included in a beacon received by the communication unit 205, position data, and the like.

  The control unit 207 controls the overall functions of the SUE 204 using a control device such as a CPU, for example. For example, in this embodiment, the control unit 207 determines the value of the transmission power used for transmission of the secondary signal by the communication unit 205 according to the positional relationship between the base station 100 and the SSC 200 as described above. Control. A specific flow of transmission power control processing by the control unit 207 will be described with reference to FIG.

(Transmission power control process flow)
FIG. 16 is a flowchart illustrating an example of the flow of transmission power control processing by the SUE 204.

  In FIG. 16, for example, when an instruction to start secondary usage is detected, the control unit 207 of the SUE 204 waits for reception of a beacon of the second communication service in the communication unit 205 (step S352). During this time, the control unit 207 may sense the secondary signal via the communication unit 205 and acquire data (eg, SINR) regarding the communication status of the second communication service. If the beacon of the second communication service is not received for a predetermined period, the process proceeds to step S356. On the other hand, for example, when a beacon transmitted from the SSC 200 is received by the communication unit 205, the process proceeds to step S358 (step S354).

  In step S356, since the beacon of the second communication service has not been received, the control unit 207 receives the relay beacon without transmitting the secondary signal as the process according to type 4 described above. Wait (step S356). Although not shown in FIG. 16, when the control unit 207 determines that the cause of the beacon not being received is a secondary signal collision, instead of waiting for the reception of the relay beacon, The SSC 200 may be notified that a next signal collision has occurred.

  On the other hand, in step S358, the control unit 207 acquires position data indicating the positions of the SSC 200 and the base station 100 included in the beacon received by the communication unit 205 (step S358).

  Next, the control unit 207 uses the acquired position data and its own position data to determine whether the distance from the base station 100 that is the interfered node to the own apparatus is longer than the distance from the base station 100 to the SSC 200. It is determined whether or not (step S360). If the distance from the base station 100 to the own apparatus is far, the process proceeds to step S364. On the other hand, if the distance from the base station 100 to the own apparatus is shorter, the process proceeds to step S362.

  In step S362, the control unit 207 determines whether or not substantial interference is caused to the base station 100 when the secondary signal as a response to the beacon is directly transmitted from the communication unit 205 to the SSC 200 (step S362). S362). For example, when the distance from the base station 100 to the own apparatus is shorter than the distance from the own apparatus to the SSC 200, it can be determined that if the secondary signal is directly transmitted to the SSC 200, the base station 100 is substantially interfered. . In that case, the process proceeds to step S374. on the other hand. If it is determined that the secondary signal can be directly transmitted to the SSC 200 without causing substantial interference to the base station 100 using a transmission power smaller than the transmission power of the beacon, the process proceeds to step S366.

  In step S364, since the distance from the base station 100 to the own apparatus is longer than the distance from the base station 100 to the SSC 200, the control unit 207 recognizes that the own apparatus is classified into the type 1 described above. In this case, the control unit 207 sets transmission power equivalent to the beacon received from the SSC 200 in the communication unit 205 (step S364).

  In step 366, although the distance from the base station 100 to the own apparatus is closer than the distance from the base station 100 to the SSC 200, the secondary signal can be directly transmitted to the SSC 200. Recognize that it is classified as type 2. In this case, the control unit 207 sets transmission power smaller than the beacon received from the SSC 200 in the communication unit 205 (step S364). The value of the transmission power set here is a value at which the secondary signal can be received by the SSC 200 while not giving substantial interference to the base station 100.

  Next, using the transmission power set in step S364 or step 366, control unit 207 transmits a connection request for the second communication service to SSC 200 as a response to the beacon. Then, after authentication and scheduling by the SSC 200, the control unit 207 receives scheduling information transmitted from the SSC 200. Thereafter, the SUE 204 can perform data communication using the second communication service in the allocated slot in the data communication period (step 368).

  Further, the control unit 207 may transmit a relay beacon to the surroundings in order to operate as an ad hoc gateway for other SUEs 204 (for example, the SUE 204-3 or the SUE 204-4) located around the own device, for example. (Step S370).

  On the other hand, in step S374, the control unit 207 recognizes that the own apparatus is classified into the above-described type 3 because the secondary signal is directly transmitted to the SSC 200, which causes substantial interference to the base station 100. To do. In this case, the control unit 207 waits for reception of a relay beacon without transmitting a secondary signal (step S374).

  Next, when the communication unit 205 receives a relay beacon in a situation where the control unit 207 is waiting for reception of a relay beacon (that is, in the case of type 3 or type 4), the control unit 207 As a response, a connection request to the second communication service is transmitted. Here, the transmission power used for transmission of the connection request is set to a value that does not give substantial interference to the base station 100. Then, the connection request is relayed to the SSC 200 by another SUE 204 operating as an ad hoc gateway. Then, after authentication and scheduling by the SSC 200, the control unit 207 receives scheduling information transmitted from the SSC 200 and relayed by another SUE 204. Thereafter, the SUE 204 can perform data communication using the second communication service in the assigned slot in the data communication interval (step 378).

[2-5. Summary of First Embodiment]
Up to this point, the first embodiment of the present invention has been described with reference to FIGS. According to the present embodiment, the SSC 200 controls the second communication service in accordance with the framework for secondary use described with reference to FIGS. 4 to 7B. More specifically, the SSC 200 receives the primary signal within the primary signal observation section (first section), for example, in the secondary usage of the frequency band, and based on the received primary signal, A parameter value such as transmission power, frequency, or modulation order used for transmission is determined. When the secondary signal is not detected in the secondary signal observation section (second section), the SSC 200, based on the parameter value described above, in the control frame transmission section (third section), A beacon for the second communication service is transmitted. Thereby, in the secondary use of a frequency band, while avoiding the collision of a primary signal and a secondary signal, or the signal of secondary signals, interference can be suppressed effectively.

  Further, according to the above-described interference control model, the transmission power of the beacon transmitted from the SSC 200 is the radio signal quality required in the first communication service, the interference or noise level in the first communication service, and one or more. Based on the path loss on the communication path for the secondary usage node, the interference at the interfered node is determined to be within an allowable range. Thereby, it is possible to eliminate (or at least mitigate) the risk of difficulty in receiving the primary signal locally at some primary usage nodes.

  Moreover, according to this embodiment, SUE204 receives the beacon transmitted within the control frame transmission area (3rd area). Then, the SUE 204 transmits a connection request or a data communication section (fifth) in the connection and scheduling section (fourth section) according to the positional relationship recognized based on the position data included in the received beacon. The transmission power of the data signal transmitted within (section) is controlled. Thereby, SUE204 can suppress the interference given to a primary system by a simple mechanism, without using a beam forming technique etc.

  In the present embodiment, an example of communication control at the start of the second communication service has been mainly described. However, the framework for secondary use and the transmission power control method described above can be applied at any time after the start of the second communication service.

  Further, in the present embodiment, an example has been described in which the uplink channel of the first communication service is secondarily used, that is, only the base station of the first communication service may be considered as an interfered node. However, it goes without saying that the present invention is also applicable when there are a plurality of interfered nodes.

<3. Second Embodiment>
In the first embodiment of the present invention, the allowable transmission power allocated to the second communication service is determined by the primary usage node (management node) that can access the database holding the location data of the primary usage node. This is a passive technique from the viewpoint of SSC. On the other hand, the SSC can acquire necessary parameters and actively determine the transmission power allowed for the second communication service. Therefore, in this section, an example in which a terminal device that performs secondary usage determines actively allowable transmission power will be described as a second embodiment of the present invention.

[3-1. Overview of communication system]
FIG. 17 is an explanatory diagram for explaining an overview of a communication system according to the second embodiment of the present invention.

  Referring to FIG. 17, a primary system 302 in which a first communication service is operated, and secondary systems 402a and 402b in which a second communication service is operated are shown. Among these, the primary system 302 includes a management node 300 and a plurality of primary usage nodes 104.

  The management node 300 is a primary usage node having a role of managing secondary usage of the frequency band assigned to the first communication service. In the example of FIG. 17, a base station is shown as the management node 300, but the management node 300 is not limited to such an example. In the present embodiment, the management node 300 can access the database 106 that holds location data representing the location of the primary usage node included in the primary system 302.

  On the other hand, the secondary system 402a includes an SSC 400a and a plurality of SUEs 204a. Similarly, the secondary system 402b includes an SSC 400b and a plurality of SUEs 204b.

  The SSC 400 (400a and 400b) is a secondary usage node having the above-described coordinator role that controls the second communication service. That is, the SSC 400 determines whether or not secondary usage is possible according to a predetermined spectrum policy, obtains necessary parameters from the management node 100, determines allowable transmission power, and then performs the second communication service. A beacon is transmitted to surrounding SUEs 204. For example, the SSC 400 may operate as an engine (CE) for cognitive radio.

[3-2. Example of management node configuration]
FIG. 18 is a block diagram illustrating an example of a logical configuration of the management node 300 illustrated in FIG. Referring to FIG. 18, the management node 300 includes a communication unit 310, a database input / output unit 120, a storage unit 130, and a control unit 340.

  The communication unit 310 transmits and receives radio signals to and from the primary usage node 104 using a communication interface that may include an antenna, an RF circuit, a baseband circuit, and the like, according to a predetermined communication method of the first communication service. Further, as will be further described later, the communication unit 310 uses the parameters used for determining the position data of the primary usage node 104 stored in the database 106 and the transmission power stored in the database 106 or the storage unit 130. Is transmitted to the SSC 400.

  The control unit 340 controls the overall functions of the management node 300 using a control device such as a CPU, for example. In this embodiment, the control unit 340 transmits the position data and parameters used when the SSC 400 determines the allowable transmission power according to the interference control model described above via the communication unit 310 (or other backhaul link). To transmit to the SSC 400. The transmission of the position data and parameters may be performed periodically using a predetermined channel such as CPC, for example. Instead, transmission of position data and parameters may be performed as a response to a transmission request from the SSC 400, for example.

[3-3. Configuration example of secondary usage node (SSC)]
(Description of each functional block)
FIG. 19 is a block diagram illustrating an example of a logical configuration of the SSC 400 illustrated in FIG. Referring to FIG. 19, the SSC 400 includes a first communication unit 410, a second communication unit 220, a storage unit 430, and a control unit 440.

  The first communication unit 410 receives a radio signal including the data and parameters transmitted from the management node 300 according to a predetermined communication method. The channel used for communication between the first communication unit 410 and the management node 300 may be the above-described CPC, which is a control channel.

  More specifically, the first communication unit 410 attempts to receive data and parameters used for determining transmission power from the management node 300 in response to an instruction such as start of secondary usage of a frequency band, for example. The data and parameters used to determine the transmission power include, for example, location data of the interfered node, radio signal quality required in the first communication service, and interference or noise level in the first communication service. Can be included. Further, the data used for determining the transmission power may include position data indicating the position of another secondary usage node. When the first communication unit 410 receives these data and parameters from the management node 300, the first communication unit 410 outputs the received data and parameters to the control unit 440. In addition, when the first communication unit 410 cannot receive necessary data and parameters for reasons such as poor signal reception environment, the first communication unit 410 notifies the control unit 440 to that effect.

  The storage unit 430 stores programs and data used for the operation of each unit of the SSC 400 using a recording medium such as a hard disk or a semiconductor memory. Further, in the present embodiment, the storage unit 430 stores various parameters for determining the allowable transmission power for the second communication service and controlling the transmission power. The parameters stored in the storage unit 430 include, for example, the location data of the own device (and other secondary usage nodes that subscribe to the second communication service as necessary), and the management node 300 to the first communication unit. Such parameters received via 410 may be included.

  The control unit 440 controls the overall functions of the SSC 400 using a control device such as a CPU. For example, in the present embodiment, the control unit 440 determines the allowable transmission power for the second communication service according to the above-described interference control model when the frequency band assigned to the first communication service is secondarily used. To do. At this time, if the control unit 440 cannot receive the radio signal from the management node 300 and cannot acquire the latest location data and necessary parameters of the primary usage node, the control unit 440 reduces the possibility of causing interference to the primary usage node. The allowable transmission power is determined by including the margin for Then, the control unit 440 sets the value of the transmission power used for transmitting the beacon for the second communication service and other secondary signals by the second communication unit 220 within the determined allowable transmission power range. Control.

(Secondary usage start processing flow)
FIG. 20 is a flowchart illustrating an example of the flow of secondary usage start processing by the SSC 400.

  Referring to FIG. 20, first, the control unit 440 determines whether it is possible to receive a radio signal (primary signal) from the management node 300 via the communication unit 410 (step S502). Here, when the radio signal from the management node 300 can be received, the process proceeds to step S504. On the other hand, if the wireless signal from the management node 300 cannot be received, the process proceeds to step S508.

  In step S504, the control unit 440 acquires the location data of the primary usage node that is the interfered node received from the management node 300 via the communication unit 410. Similarly, the control unit 440 acquires parameters received from the management node 300 (step S504). Note that, as in the example illustrated in FIG. 2A, when the OFDMA uplink channel is secondarily used, the interfered node is only the base station. Therefore, in such a case, the control unit 440 may acquire only the position data of the management node 300 that is the base station as the position data of the primary usage node. The necessary parameters in step S504 are, for example, the quality of the radio signal required in the first communication service and the interference or noise level in the first communication service (or parameters for calculating these levels). ) Etc.

Next, the control unit 440 determines transmission power according to the interference power allowed for the second communication service based on the position data and parameters received in step S504 (step S506). More specifically, the control unit 440 can determine the transmission power according to the interference power allowed for the second communication service, for example, according to the equation (9) in the above-described interference control model. At that time, for example, the quality of the radio signal required in the first communication service corresponds to the term P _{rx_primary, primary} / SINR _required in Equation (9). The interference or noise level corresponds to the N _Primary term in equation (9). Furthermore, the value of the path loss L _{path_tx_secondary, i} in Equation (9) can be calculated according to Equation (6) using the distance d derived from the position data of the primary usage node and the position data of the SSC 400. For example, instead of calculating the value of the path loss L _{path_tx_secondary, i} from the position data, the control unit 440 determines the value of the path loss L _{path_tx_secondary, i} from the transmission power value of the downlink signal from the base station and the downlink. You may calculate as a difference with the reception level of a signal. Furthermore, when there is another second communication service, the control unit 440 may distribute the transmission power according to the equal expression (10) or the non-equal expression (11). .

  On the other hand, when the radio signal from the management node 300 cannot be received, in step S508, the control unit 440 acquires position data and parameters for determining transmission power from the storage unit 430 (step S508). For example, the control unit 440 receives the location data of the interfered node and necessary parameters via the first communication unit when communication with the management node 300 becomes possible, and uses them for later use. It can be stored in the storage unit 430. Also, for example, when the type of the first communication service that is the target of secondary use is limited to some candidates in advance, it represents the quality of the radio signal required in the first communication service. The parameter may be stored in the storage unit 430 as a default value.

Next, the control unit 440 determines transmission power according to interference power allowed for the second communication service based on the position data and parameters acquired in step S508 (step S510). However, in this case, the parameters that can be used for determining the transmission power may not be the latest. Therefore, the control unit 440 adds a predetermined margin to the value of the transmission power in order to reduce the possibility of causing interference to the primary usage node. More specifically, the control unit 440 can determine the transmission power according to the above-described interference margin reduction type equation (12), for example. The value of N _estimaion in Expression (12) is determined so as to include a surplus number, for example, according to the number of SUEs 204 that are expected to subscribe to the second communication service.

  Next, when the primary signal can be received from the management node 300, the control unit 440 senses the primary signal and acquires the synchronization of the uplink channel of the first communication service (step S516). If the primary signal from the management node 300 cannot be received, step S516 can be skipped. Next, the control unit 440 senses the secondary signal within the secondary signal observation section, and confirms that the secondary signal is not transmitted from the surrounding communication device (step S518). Here, if a secondary signal from a surrounding communication device is detected, the process proceeds to step S526. On the other hand, if the secondary signal from the surrounding communication device is not detected, the process proceeds to step S522 (step 520).

  In Step S522, the control unit 440 causes the second communication unit 220 to transmit a beacon for the second communication service within the control frame transmission period using the transmission power determined in Step S506 or Step S510 (Step S522). S522). The beacon includes the value of the allowable transmission power allocated to the second communication service, and the location data of the interfered node and the SSC 400.

  Next, when receiving a connection request from the SUE 204 to the second communication service via the second communication unit 220 within the connection and scheduling interval, the control unit 440 authenticates the connection request and schedules the SUE 204 ( Step S524). As a result, the SUE 204 can perform data communication using the second communication service within the data communication period. At this time, the SUE 204 determines the connection request and the transmission power of the data signal based on the allowable transmission power value and each position data included in the beacon transmitted from the SSC 400 in step S522.

  On the other hand, in step S526, control unit 440 waits for a predetermined time in order to avoid a collision between a secondary signal transmitted from another communication device and a beacon transmitted by itself (step S526). Thereafter, the process returns to step S516 (step S518 when the primary signal from the management node 300 cannot be received).

  By such secondary use start processing, the SSC 400 suppresses the transmission power of the beacon transmitted by itself and the secondary signal transmitted from the SUE to a range that does not substantially interfere with the primary system, and between the secondary signals. Collisions can be avoided.

[3-4. Summary of Second Embodiment]
Up to this point, the second embodiment of the present invention has been described with reference to FIGS. According to the present embodiment, the transmission power allowed in the second communication service that secondarily uses the frequency band allocated to the first communication service is in accordance with the above-described interference control model, and the coordinator of the second communication service. Is determined by the SSC 400 having the role of As a result, the SSC 400 actively determines the transmission power used for the second communication service, avoids collision between the primary signal and the secondary signal, or signals between the secondary signals, and effectively prevents interference. Can be suppressed.

  In addition, when the SSC 400 cannot receive the radio signal from the management node 300 and cannot acquire the latest location data of the primary usage node, the allowable transmission power reduces the possibility of causing interference to the primary usage node. It is determined by including the margin. As a result, even when the SSC 400 is located in a region where the signal reception status is relatively poor due to the influence of shadowing (fading) or fading, the SSC 400 autonomously and safely uses the secondary frequency band. You can start using it.

[4. Application to TV band]
FIG. 21 is an explanatory diagram for explaining application of the first or second embodiment described above to a TV band. In the example of FIG. 21, the primary usage node 900 is a television broadcasting station. The primary usage nodes 910a to 910c are television broadcast receiving stations. The primary usage node 900 provides a digital TV broadcast service on the frequency band F1 to the primary usage nodes 910a to 910c located inside the boundary 902 or 904. Inside the boundary 902 is a service area of a digital TV broadcast service. A region between the boundary 902 and the boundary 904 indicated by diagonal lines is a guard area where secondary use of the frequency band is restricted. On the other hand, the area between the boundary 904 and the boundary 906 is a TV white space. The secondary usage nodes 920a to 920c are located in the TV white space, and operate the second communication service on a frequency band F3 different from the frequency band F1, for example. However, even if a guard band is provided between the frequency band F1 of the first communication service and the frequency band F3 of the second communication service, for example, not only the secondary system but also the primary system is fatal at the position P0. There is a risk of unwanted interference. Such a risk is reduced, for example, by expanding the width of the guard area. However, expanding the width of the guard area means reducing the secondary usage opportunity of the frequency band. In contrast, by controlling the transmission power used for the second communication service according to the first or second embodiment described above, it is possible to allow interference given to the primary system without excessively expanding the width of the guard area Can be suppressed within the range.

  Note that it does not matter whether a series of processing according to the first and second embodiments described in this specification is realized by hardware or software. When a series of processes or a part thereof is executed by software, a program constituting the software is stored in advance in a recording medium such as a ROM (Read Only Memory) and read into a RAM (Random Access Memory). , Executed using a CPU.

  The gist of each embodiment described in the present specification can be widely applied to various secondary usage modes as described above. For example, as described above, the operation of the relay node or the femtocell for covering the spectrum hole of the first communication service can be said to be a form of secondary use of the frequency band. In addition, the mutual relationship between a macro cell, a RRH (Remote Radio Head), a Hotzone, a relay node, or a femto cell using a common frequency band is also a form of secondary use of the frequency band (for example, heterogeneous network). Can be formed.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. These are naturally understood to belong to the technical scope of the present invention.

100,300 Management node 102,302 Primary system 104 Primary usage node 106 Database 200,400 Secondary usage node (SSC)
210, 220, 410 First / second communication unit (SSC)
230,430 storage unit (SSC)
240,440 control unit (SSC)
202, 402 Secondary system 204 Secondary usage node (SUE)

Claims (13)

A method for controlling communication of a second communication service that secondary uses a frequency band assigned to a first communication service, using a communication device:
Receiving a radio signal transmitted for the first communication service within a first interval on a time axis;
Determining a parameter value used for controlling communication of the second communication service based on the radio signal received in the first interval;
Observing a radio signal transmitted for the second communication service in a second interval following the first interval;
When the radio signal for the second communication service is not detected in the second section, the second communication is performed based on the parameter value in the third section following the second section. Sending a beacon for the service;
Including methods.   The step of determining the parameter value includes determining a transmission power of the beacon transmitted in the third interval based on the radio signal received in the first interval. The method described in 1.   The method further comprises a step of receiving a connection request to the second communication service within a fourth period following the third period from the secondary usage node that has received the beacon. The method described in 1.   The transmission power of the connection request transmitted from the secondary usage node within the fourth interval is determined based on data included in the beacon transmitted from the communication device within the third interval. The method according to claim 3.   For each secondary usage node that is the transmission source of the connection request received in the fourth interval, the slot included in the fifth interval following the fourth interval is used for data transmission by the secondary usage node. 4. The method of claim 3, further comprising assigning for. The beacon includes data indicating a beacon period;
The method according to claim 5, wherein the first interval, the second interval, the third interval, the fourth interval, and the fifth interval are repeated with a period corresponding to the beacon period.   The method of claim 6, further comprising changing the beacon period when a required data rate for the second communication service changes.   The method according to claim 6, wherein a guard interval is further provided after the fifth interval.   Notification indicating that a beacon collision has occurred in the fourth section when a collision between the beacon transmitted in the third section and another radio signal is detected by a secondary usage node The method of claim 3, further comprising: receiving from the secondary usage node.   The method further comprises: receiving data on the communication status of the first communication service or the second communication service observed at the secondary usage node from the secondary usage node within the fourth interval. 3. The method according to 3.   The method according to claim 1, further comprising: receiving a reference signal for synchronizing intervals between a plurality of communication devices from a node outside the communication device within the first interval. A communication unit capable of transmitting and receiving a radio signal for the second communication service that secondarily uses the frequency band allocated to the first communication service;
A control unit for controlling communication by the communication unit;
With
The controller is
Causing the communication unit to receive a radio signal transmitted for the first communication service within a first section on a time axis;
Determining a parameter value to be used for controlling communication of the second communication service based on the radio signal received in the first interval;
Observing, via the communication unit, a radio signal transmitted for the second communication service in a second section following the first section;
When the radio signal for the second communication service is not detected in the second section, the second communication is performed based on the parameter value in the third section following the second section. Causing the communication unit to transmit a beacon for service;
Communication device. A computer that controls a communication device comprising a communication unit capable of transmitting and receiving a radio signal for a second communication service that secondary uses a frequency band assigned to the first communication service:
A control unit for controlling communication by the communication unit,
Causing the communication unit to receive a radio signal transmitted for the first communication service within a first section on a time axis;
Determining a parameter value to be used for controlling communication of the second communication service based on the radio signal received in the first interval;
Observing, via the communication unit, a radio signal transmitted for the second communication service in a second section following the first section;
When the radio signal for the second communication service is not detected in the second section, the second communication is performed based on the parameter value in the third section following the second section. Causing the communication unit to transmit a beacon for service;
A program for functioning as a control unit.

Images