JP2011071569A - Radio communication system - Google Patents

Abstract

A wireless communication system capable of suppressing deterioration of communication quality that requires real-time performance.
A wireless communication system 2 detects a use state of a frequency spectrum of the wireless communication systems 102-1 to 102-N and is not used by the wireless communication systems 102-1 to 102-N at a certain time and place. Communication is performed using the frequency spectrum. The usage spectrum determining unit 224 determines, as a usage spectrum, a frequency spectrum that is used by a primary usage system having a higher priority among primary usage systems whose spectrum availability indicates “vacant”. The frequency spectrum used by the primary usage system set to be low is determined as the reserve spectrum.
[Selection] Figure 1

Description

  The present invention relates to a wireless communication system.

For the purpose of effectively using a limited frequency band (resource), a so-called cognitive radio system type radio system has been studied. A cognitive radio system generally uses a primary usage system that primarily uses a frequency spectrum and a secondary usage of a frequency spectrum that is not used by the primary usage system in a temporary or limited area. It is comprised by the next use system. With such a configuration, the frequency spectrum that is not used by the primary usage system can be used by the secondary usage system, and effective use of frequency resources can be achieved.
As a technique related to such a cognitive radio system, for example, Patent Document 1 is a radio communication system in which a radio space configured by radio frequency channels having different bands is shared between a plurality of radio stations. The station searches for a radio frequency channel that can be used in a wide band, and then detects the channel status of the radio frequency channel by analyzing the received signal, and allocates transmission data to each radio frequency channel based on the channel status Means and a means for selecting a suitable transmission data rate variable modulation scheme that complements the difference in transmission quality and transmittable data rate between different radio frequency channels and modulating the transmission signal to an ultra-wideband load sharing type radio communication Disclose the system.

JP 2006-313993 A

However, in the above-described cognitive radio system, when frequency usage switching from the secondary usage system to the primary usage system is performed in a specific frequency spectrum, interference occurs between the two systems, and communication that requires real-time characteristics is required. However, there is a problem that communication quality deteriorates.
The present invention has been made to solve such a problem, and an object of the present invention is to provide a wireless communication system capable of suppressing deterioration in communication quality that requires real-time performance.

  The wireless communication system according to the present invention includes a detecting means for detecting whether or not a frequency band is used in one or more other types of wireless communication systems different from the wireless communication system, and the other wireless communication Frequency band determining means for determining, based on a priority set according to the type of information communicated in the system, that the wireless communication system uses a frequency band detected as not being used by the detecting means. And have.

  According to the wireless communication system according to the present invention, it is possible to suppress deterioration in communication quality that requires real-time performance.

It is a figure which shows the structure of a radio | wireless communication network and a radio | wireless communications system. It is a figure which shows the utilization spectrum management table produced by the utilization spectrum determination part. It is a figure which illustrates the utilization condition of the frequency spectrum by a primary usage system and a secondary usage system. It is a figure which illustrates the time transition of the utilization condition of the frequency spectrum by the primary usage system and secondary usage system which were illustrated in FIG. It is a figure which illustrates the time transition of the utilization condition of one frequency spectrum. It is a figure which shows the utilization spectrum management table produced by the utilization spectrum determination part of the radio | wireless communications system concerning 2nd Embodiment. It is a figure which illustrates the utilization condition of the frequency spectrum by the primary usage system and secondary usage system in 2nd Embodiment.

[First Embodiment]
First, the first embodiment will be described.
FIG. 1 is a diagram showing a configuration of a wireless communication network 1 and a wireless communication system 2.
As shown in FIG. 1A, a wireless communication network 1 includes a plurality of wireless communication systems 102-1 to 102-N (N is an integer equal to or greater than 1. However, N is not always the same number) A wireless communication system 2 is connected via a network 100.
The radio communication systems 102-1 to 102-N and the radio communication system 2 perform communication using the frequency spectrum assigned to each.
The wireless communication systems 102-1 to 102-N and the wireless communication system 2 can also communicate with each other via the network 100.
The radio communication systems 102-1 to 102-N and the radio communication system 2 are different types of radio communication systems. For example, the radio communication system 102-1 is a terrestrial digital broadcast radio system or the like. The communication system 2 is a mobile phone radio system or the like.

The wireless communication system 2 detects the usage state of the frequency spectrum of the wireless communication systems 102-1 to 102-N, and uses the frequency spectrum that is not used by the wireless communication systems 102-1 to 102-N at a certain time and place. And can communicate.
However, when the radio communication systems 102-1 to 102-N use the frequency spectrum again, the radio communication system 2 stops using the frequency spectrum.
That is, in the wireless communication network 1 in the present embodiment, the frequency spectrum between the wireless communication systems 102-1 to 102-N and the wireless communication system 2 depends on the usage status of the wireless communication systems 102-1 to 102-N. Can be shared.

Hereinafter, in the case where any one of a plurality of components such as the wireless communication systems 102-1 to 102-N is indicated without being specified, the wireless communication system 102 may be simply abbreviated.
Hereinafter, the wireless communication system 102 may be referred to as a primary usage system, and the wireless communication system 2 may be referred to as a secondary usage system.
Further, hereinafter, the wireless communication systems 102-1 to 102-N are referred to as wireless communication systems # 1 to #N (or simply systems # 1 to #N), respectively, which are these identifiers, and the wireless communication system 2 is This identifier may be referred to as wireless communication system #X (or simply system #X).
In the following description, devices that can be the subject of information processing and communication in a wireless communication network, such as the wireless communication system 102, may be collectively referred to as nodes.
In the following drawings, substantially the same components are denoted by the same reference numerals.

As shown in FIG. 1B, the radio communication system 2 includes an antenna 200, a transmission / reception processing unit 210, an application unit 202, a radio resource control unit 22, a radio resource management database (DB) 204, and an adaptive transmission control unit 230. Composed.
Note that the wireless communication system 102 may have the same configuration as the wireless communication system 2.

The application unit 202 creates and stores information to be transmitted / received to / from other nodes (transmission information, reception information, or these are collectively referred to as transmission / reception information).
Further, the application unit 202 outputs the transmission request information type to the utilization spectrum determination unit 224.
Here, the transmission request information type is an identification code for identifying the type of information (for example, data, audio, video, etc.) transmitted via the frequency spectrum used by the secondary usage system.
The transmission / reception processing unit 210 transmits transmission information input from the application unit 202 to other nodes via an antenna based on utilization spectrum information from the radio resource control unit 22 to be described later. The reception information received from other nodes is output to the application unit 202.
Here, the transmission / reception information is, for example, data such as text data, digital audio information, digital video information, or analog audio.

The radio resource control unit 22 performs processing for determining radio resources to be used by the transmission / reception processing unit 210.
The radio resource control unit 22 includes a spectrum detection unit 222 and a use spectrum determination unit 224.

The spectrum detection unit 222 receives a control signal including the identifier of the wireless communication system 102 from the use spectrum determination unit 224 at a predetermined detection cycle.
Moreover, the spectrum detection part 222 receives a signal via the antenna 200 from the radio | wireless communications systems 102-1 to 102N (primary utilization system).
Further, the spectrum detection unit 222 detects the use state of the frequency spectrum in the wireless communication system 102 corresponding to the identifier included in the received control signal by performing energy detection or the like on the received signal.
Further, the spectrum detection unit 222 outputs a detection result indicating the use status (in use or stopped) of the detected frequency spectrum to the use spectrum determination unit 224.
Note that the spectrum detection unit 222 detects the usage state of the frequency spectrum in the primary usage system while the transmission / reception processing unit 210 is transmitting / receiving transmission / reception information.
However, during the transmission period of the secondary usage system, the spectrum usage status (resumption of use) of the primary usage system cannot be detected for the spectrum (frequency band) used for the transmission. Stop transmission of next-use system and perform spectrum detection.

The use spectrum determination unit 224 determines that the frequency spectrum indicated as being stopped (vacant) in the detection result from the spectrum detection unit 222 can be used in the wireless communication system 2 (secondary use system).
Further, the use spectrum determining unit 224 is used for transmission in the wireless communication system 2 (secondary use system) from one or more frequency spectra determined to be usable based on the transmission request information type from the application unit 202. The frequency spectrum (utilization spectrum) to be determined is determined.
Further, the use spectrum determination unit 224 determines whether or not the frequency spectrum (channel) determined to be usable can be used based on the transmission request information type from the application unit 202.
For example, when the transmission request information type indicates “video”, it is determined that the audio channel cannot be used even if the audio channel is empty.

Here, when the radio communication system 2 (secondary usage system) uses the frequency spectrum, the quality of the frequency spectrum may be degraded, or the radio communication system 102 (primary system that has been stopped) may have stopped. In some cases, the wireless communication system 2 (secondary usage system) needs to yield (that is, stop using) this frequency spectrum.
Therefore, the use spectrum determining unit 224 also determines a spare frequency spectrum (a spare spectrum) in preparation for such a case.
Furthermore, the utilization spectrum determination unit 224 outputs utilization spectrum information, which is information relating to the utilization spectrum and the reserve spectrum, to the transmission / reception processing unit 210.
Here, the usage spectrum information includes a carrier frequency, a transmission bandwidth, and a transmission information type (data, audio, video, etc.) for each of the usage spectrum and the backup spectrum.

The transmission / reception processing unit 210 includes a modulation / demodulation processing unit and a broadband wireless transmission / reception circuit (not shown) corresponding to each frequency band.
The modulation / demodulation processing unit performs modulation / demodulation processing by switching the specifications of the modulation / demodulation processing based on the transmission bandwidth and the transmission information type included in the usage spectrum information from the usage spectrum determining unit 224.
The broadband wireless transmission / reception circuit switches the transmission / reception circuit to be used based on the carrier frequency and the transmission bandwidth included in the usage spectrum information from the usage spectrum determination unit 224. The transmission / reception processing unit 210 can transmit / receive a plurality of transmission / reception information simultaneously using a plurality of frequency spectra.
The adaptive transmission control unit 230 performs transmission control such as adaptive modulation. Specifically, the adaptive transmission control unit 230 controls the transmission / reception processing unit 210 by creating transmission control information and outputting it to the transmission / reception processing unit 210.

The radio resource management DB 204 stores and manages information for the use spectrum determining unit 224 to create a use spectrum management table, which will be described later with reference to FIG.
The wireless communication system 102 (primary usage system) accesses this wireless resource management DB 204 and updates the stored information at predetermined intervals.
The utilization spectrum determination unit 224 creates and stores the utilization spectrum management table shown in FIG. 2 based on the information from the radio resource management DB 204 and the detection result from the spectrum detection unit.

FIG. 2 is a diagram illustrating a utilization spectrum management table created by the utilization spectrum determination unit 224.
The “wireless communication system identifier” indicates an identifier of the wireless communication system 102 (primary usage system).
“Carrier frequency” indicates a carrier frequency used in each wireless communication system 102 (primary usage system). For example, system # 1 uses X1 Hz as the carrier frequency.
“Transmission bandwidth” indicates a transmission bandwidth used in each wireless communication system 102 (primary usage system). For example, system # 1 uses Y1 Hz as the transmission bandwidth.
“Transmission information type” indicates the type of information transmitted in each wireless communication system 102 (primary usage system). For example, system # 1 transmits data.

These “wireless communication system identifier”, “carrier frequency”, “transmission bandwidth”, and “transmission information type” are created based on information stored in the radio resource management DB 204.
That is, the above information is acquired by the wireless communication system 2 (secondary usage system) before detection by the spectrum detection unit 222.

“Spectrum availability” indicates whether or not the wireless communication system 102 (primary usage system) is using a frequency spectrum. For example, system # 1 is in use and system # 2 is stopped (that is, corresponding) The frequency spectrum to be used is empty.
This “spectrum availability” is created based on the detection result from the spectrum detector 222.
In addition, the “spectrum availability” is updated in synchronization with a predetermined detection cycle of the spectrum detection unit 222, and further, in synchronization with this update, the use spectrum determination unit 224 determines the use spectrum and controls the transmission / reception processing unit 210. To do.
The “secondary usage status” indicates the usage spectrum and the backup spectrum determined by the usage spectrum determination unit 224. In the example of FIG. 2, the frequency spectrum used by the system # 5 is assigned as the usage spectrum, and the system # 2 indicates that the frequency spectrum used by 2 is allocated as a spare spectrum.

FIG. 3 is a diagram illustrating the usage state of the frequency spectrum by the primary usage system and the secondary usage system, where the horizontal axis represents frequency and the vertical axis represents power.
As illustrated in FIG. 3A, the primary usage system uses the frequency spectrum over the entire frequency band.
After that, as illustrated in FIG. 3B, the systems # 2 and # 5 stop using the corresponding frequency spectrum, and the corresponding frequency spectrum becomes empty.
At this time, the secondary usage system (system #X) corresponds to the system # 5 as illustrated in FIG. 3C by the processing of the radio resource control unit 22 of the radio communication system 2 (secondary usage system). The frequency spectrum to be used is used.

FIG. 4 is a diagram illustrating the temporal transition of the usage state of the frequency spectrum by the primary usage system and the secondary usage system illustrated in FIG. 3, where the horizontal axis indicates time and the vertical axis indicates frequency.
As illustrated in FIG. 4, the system # 5 stops using the frequency spectrum at time A and restarts using the frequency spectrum at time B.
Therefore, the secondary usage system (system #X) uses the frequency spectrum corresponding to the system # 5 in the period between the time A and the time B.

FIG. 5 is a diagram illustrating the temporal transition of the usage status of one frequency spectrum (for example, the frequency spectrum corresponding to the system # 5), and the time transitions from left to right.
As illustrated in FIG. 5A, the system # 5 stops using the frequency spectrum at time A and resumes using the frequency spectrum at time B.
On the other hand, as illustrated in FIG. 5B, the spectrum detection unit 222 of the system #X detects that the frequency spectrum corresponding to the system # 5 is in an empty state at the time C delayed from the time A. .
Furthermore, the spectrum detector 222 of the system #X detects that the system # 5 has resumed using the frequency spectrum at the time D delayed from the time B.
In this way, the detection result is delayed because in the spectrum detection process, the detection result for each short section (for example, 100 ms) is accumulated for a longer time (for example, several seconds) in order to improve the detection accuracy. This is because a final decision will be made later.
Therefore, as the accumulation time becomes longer, a delay occurs in the detection of the change point of the use situation.
In the above description, it is assumed that the time B in FIG. 5 and the start point of the spectrum detection period substantially coincide with each other, but actually, as described above, the spectrum use period in the secondary use system. Since the spectrum detection in the middle is performed by stopping the transmission of the secondary usage system at a predetermined cycle, the delay shown in FIG. 5B is further increased in consideration of the time until the detection is started.

Because of the detection result as shown in FIG. 5B, as shown in FIG. 5C, the system #X has a frequency spectrum corresponding to the system # 5 in the period between the time C and the time D. I will use it.
For this reason, as shown in FIG. 5D, since both the system #X and the system # 5 use the same frequency spectrum in the period between the time B and the time D, the system #X ( Interference from system (secondary usage system) to system # 5 (primary usage system) occurs.
Due to the occurrence of this interference, the system # 5 (primary usage system) becomes unable to communicate during the period between time B and time D, and transmission information may be lost.

Here, when the system # 5 (primary use system) is used for a data communication channel such as e-mail transmission / reception or file transfer, the missing transmission information can be retransmitted by an automatic reproduction request or the like.
On the other hand, when the system # 5 (primary use system) is used for real-time communication such as voice communication and video communication, the head of the talk is cut (and voice is not transmitted) and the image quality is deteriorated.
In particular, in the case of voice communication, when the period between time B and time D is several tens of ms or more, degradation of intelligibility due to speech breaks and deterioration of subjective quality become problems.
The wireless communication system according to the second embodiment described below is configured to solve the above-described problems.

[Second Embodiment]
Next, a second embodiment will be described.
The wireless communication system 2 according to the second embodiment has the same configuration as that of FIG. 1A, but the processing of the used spectrum determining unit 224 and the used spectrum management table are the same as those of the first embodiment. It is different from the case of.

FIG. 6 is a diagram illustrating a utilization spectrum management table created by the utilization spectrum determination unit 224 of the wireless communication system 2 according to the second embodiment.
The utilization spectrum management table shown in FIG. 6 is obtained by adding priorities to the utilization spectrum management table shown in FIG.
The priority is set based on the transmission information type, and when the transmission information type indicates information (for example, audio or video) that requires real-time property, the priority of the frequency spectrum used by the primary usage system Is set low.
On the other hand, when the transmission information type indicates information that does not require real-time characteristics relatively (for example, data communication that can be retransmitted), the priority of the frequency spectrum used by the primary usage system is set high.

The usage spectrum determining unit 224 determines, as a usage spectrum, a frequency spectrum that is used by a primary usage system having a higher priority among primary usage systems whose spectrum availability indicates “vacant”. The frequency spectrum used by the primary usage system set to be low is determined as the reserve spectrum.
Note that the priority can be set in a stepwise manner in accordance with the required degree of real-time transmission information type.
For example, the priority corresponding to data communication may be set to “high”, the priority corresponding to video communication may be set to “medium”, and the priority corresponding to audio communication may be set to “low”. Then, a use spectrum may be assigned.

FIG. 7 is a diagram illustrating the usage state of the frequency spectrum by the primary usage system and the secondary usage system in the second embodiment, where the horizontal axis indicates frequency and the vertical axis indicates power.
As illustrated in FIG. 7A, the primary usage system uses the frequency spectrum over the entire frequency band.
Thereafter, as illustrated in FIG. 7B, the systems # 2 and # 5 stop using the corresponding frequency spectrum, and thus the corresponding frequency spectrum becomes empty.
At this time, the secondary usage system (system #X) has higher priority as illustrated in FIG. 7C by the processing of the radio resource control unit 22 of the radio communication system 2 (secondary usage system). The frequency spectrum corresponding to system # 2 is used.

In this way, by providing priority to the usage spectrum of the secondary usage system according to the type of transmission information in the primary usage system, it is possible to suppress deterioration in communication quality for highly real-time communications in the primary usage system.
More specifically, the timing of the change in the spectrum detection result in the secondary usage system is delayed with respect to the timing of the change in the actual usage state of the frequency spectrum in the primary usage system. Even if there is inter-interference and transmission information is lost in communication in the primary usage system, the secondary usage system preferentially uses a channel of transmission information type (for example, data communication) with low real-time characteristics. By controlling in this way, the frequency of transmission information type (for example, voice and video communication) having a high real-time property is less frequently used by the secondary usage system, and information head breaks, deterioration, and the like can be reduced.

In this embodiment, the priority is set to the corresponding frequency spectrum according to the degree of real-time property of the information transmitted by the primary usage system. However, for transmission of information that requires real-time property. Use of the allocated frequency spectrum may be prohibited.
That is, regarding the frequency spectrum allocated for transmission of information (for example, audio and video) that requires real-time characteristics, the secondary usage system should use the frequency spectrum even if the frequency spectrum is empty. May be configured to be prohibited.

  The present invention is applicable to a wireless communication system.

DESCRIPTION OF SYMBOLS 1 ... Wireless communication network, 100 ... Network, 102-1 to 102-N ... Wireless communication system, 2 ... Wireless communication system, 200 ... Antenna, 210 ... Transmission / reception processing part, 202 ... Application unit, 22 ... Radio resource control unit, 222 ... Spectrum detection unit, 224 ... Used spectrum determination unit, 204 ... Radio resource management DB, 230 ... Adaptive transmission control Part

Claims (1)

A wireless communication system,
Detecting means for detecting whether or not a frequency band is used in one or more other types of wireless communication systems different from the wireless communication system;
Based on the priority set according to the type of information communicated in the other radio communication system, the radio communication system determines to use the frequency band detected as not being used by the detection means. A wireless communication system comprising:

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