JP5455566B2 - Wireless communication system and radio wave radiation control method for reducing power consumption of entire base station - Google Patents

Description

The present invention relates to a radio communication system and a radio wave radiation control method for reducing power consumption of an entire base station.

  Reduction of power consumption in communication devices has become necessary not only for reducing energy costs but also for environmental considerations such as reducing carbon dioxide emissions. In particular, the amount of power consumed by mobile phone communication base stations may occupy approximately 60% of the amount of power consumed by mobile phone operators (see Non-Patent Document 1, for example). Therefore, in recent years, a wireless communication system with low power consumption, that is, an environmentally friendly wireless communication system has been researched and developed.

  FIG. 1 is a system configuration diagram showing radio wave radiation of a base station.

  According to FIG. 1, all the base stations A to G are starting up and radiate radio waves in all directions. Further, the cover areas of the base stations B to G exist around the cover area of the base station A. The wireless terminals a to d communicate with the base station. The radio terminal a exists in the cover area of the base station A, the radio terminal b exists in the cover area of the base station B, and the radio terminals c and d exist in the cover area of the base station C.

  FIG. 2 is a system configuration diagram showing radio wave radiation of a base station in a time zone with a small amount of communication traffic.

  The time zone with a small amount of communication traffic is, for example, the night in the city center. According to FIG. 2, power consumption in the entire system is reduced by stopping some base stations (stopping the power amplifier or turning off the power supply) in a time zone with a small amount of communication traffic. On the other hand, the active base station can cover the area of the inactive base station by increasing the transmission power of radio wave radiation. (For example, refer nonpatent literature 2).

  According to FIG. 2, among the seven base stations, only the central base station A is activated, and the other base stations B to G are suspended. As a result, the coverage areas of the base stations B to G are simply out of the communication range. Therefore, the central base station A covers the areas of the base stations B to G by increasing the transmission power of radio wave radiation.

  The coverage area of the base station A shown in FIG. 2 is 1.8 times the radius of the coverage area of the base station A shown in FIG. At this time, the electric field strength is generally inversely proportional to the square of the distance in free space, and inversely proportional to the third to the fourth power of the distance in an urban area or the like. Therefore, the transmission power of the base station A in FIG. 2 is 3.2 to 10.5 times that of the transmission power of the base station A in FIG. Nevertheless, the base station A in FIG. 2 cannot cover the entire area of the system in FIG.

JP 2004-253832 A

Vodafone UK publishes CorporateResponsibility Report-CR Review 2007/08 M. A. Marsan, et al., “Optimal Energy Savingsin Cellular Access Networks”, GreenComm'09, Jun. 2009 Haruki Izumikawa, Dirk Kutscher, Yoji Kishi, "DelayTolerance for Energy-Efficient Mobile Communications", IEICE Society Conference, September 2009, [online], [October 26, 2009 search], Internet <URL: http://secure1.gakkai-web.net/gakkai/ieice/program2/html/index/au_alpha_main.html> P. Vishwanath, D. Tse, R. Laroia, "Opportunistic Communication: A New System Design", IT 2002, [online], [October 26, 2009 search], Internet <www.stanford.edu/class/ee360 /lecture8_wonchae.ppt> Ryosuke Amano, Toshiyuki Maeyama, Takashi Inoue, Yoshio Takeuchi, “Study of Simple Beam Control Antenna in Packet Cellular System”, KDDI Research Institute, IEICE Mobile Communication Workshop, March 2005, [online], [Heisei 21 Search on October 26, 2010], Internet <URL: http://ci.nii.ac.jp/naid/110003204616/> Takashi Hirose, Masato Tsuru, Yuji Oie, “Effectiveness of Scheduling Considering Time / Frequency Domain in Next Generation Mobile Communication”, Kyushu Institute of Technology, Technical Report on Network System Study Group, IEICE, March 2007 , [Online], [October 26, 2009 search], Internet <URL: http://ci.nii.ac.jp/naid/110006249091> CHIANTI project, “Challenged Internet Access Network Technology Infrastructure”, [online], [searched on November 2, 2009], Internet <URL: http://www.chianti-ict.org/home/>

  However, according to the technique described in Non-Patent Document 2 (see FIG. 2), since the antenna power is determined by a law such as the Radio Law, the transmission power of the activated base station is increased without limit. I can't. In addition, since the active base station includes the coverage area of the inactive base station as a service area, it is necessary to optimize various parameters as the base station. On the other hand, even if various parameters are optimized, at least the location of the active base station is not designed to include the coverage area of the inactive base station in the service area. By increasing the user convenience, the user convenience also decreases.

  Therefore, the present invention reduces the power consumption of the entire base station in the radio communication system, maintains a configuration of base station-to-multiple terminals, and can obtain a communication opportunity even if the terminal does not move. It is another object of the present invention to provide a radio wave radiation control method.

According to the present invention, in a radio communication system having a plurality of base stations that radiate radio waves, a radio terminal that communicates with the base stations, and a control device that controls radio emission of the base stations,
The wireless terminal has a link disconnection resistance protocol that hides the communication disconnection from the application on the transport layer,
The control device stops some of the base stations in the plurality of base stations during a time period when the communication traffic is reduced to a predetermined amount or less for the entire system or for each predetermined area composed of a plurality of base stations. ,
The starting base station emits radio waves so as to intermittently give communication opportunities to wireless terminals while changing the radiation direction and / or angle farther than the normal radio wave radiation range,
If the radio terminal cannot receive radio waves radiated from the base station according to the link disconnection tolerance protocol, the wireless terminal temporarily holds the generated data, and then receives the radio waves radiated from the base station. Transmitting to the base station spontaneously without any operation .

According to another embodiment of the wireless communication system of the present invention,
The active base station has an array antenna,
The active base station controls the array antenna transmit array weight vector to radiate a directional radio wave at a predetermined angular velocity at random or at a constant angular velocity to the surrounding azimuth. It is also preferable to do.

According to another embodiment of the wireless communication system of the present invention,
The active base station preferably radiates radio waves having different flight distances by controlling the beam tilt angle of the array antenna.

According to another embodiment of the wireless communication system of the present invention,
The active base station has a sector antenna,
It is also preferable that the active base station radiates radio waves having directivity by controlling the start / stop for each sector of the sector antenna.

According to another embodiment of the wireless communication system of the present invention,
The sector antenna is composed of an array antenna for each sector.
The active base station controls the array antenna's transmit array weight vector in the active sector to rotate the directional radio waves randomly to a different direction every predetermined time or to the surrounding direction at a constant angular velocity. It is also preferable to radiate.

According to another embodiment of the wireless communication system of the present invention,
The active base station emits directional radio waves while changing the horizontal direction by controlling the reflectors in the active sector and changing the vertical direction (radiation distance) by controlling the beam tilt angle. It is also preferable to do.

According to another embodiment of the wireless communication system of the present invention,
The base station is a base station for mobile phone communication, a small base station for femtocells, and / or an access point for a wide area / narrow area radio access network,
It is also preferable that base stations, small base stations, and access points are mixedly arranged.

According to the present invention, in a radio wave radiation control method in a radio communication system having a plurality of base stations that radiate radio waves, a radio terminal that communicates with the base station, and a control device that controls radio wave radiation of the base station,
The wireless terminal has a link disconnection resistance protocol that hides the communication disconnection from the application on the transport layer,
The control device stops some of the base stations in the plurality of base stations during a time period in which the communication traffic is reduced to a predetermined amount or less for the entire system or for each predetermined area constituted by a plurality of base stations. A first step;
A second step in which the active base station emits radio waves so as to intermittently give a communication opportunity to the wireless terminal while changing the radiation direction and / or angle farther than the normal radio wave radiation range;
If the radio terminal cannot receive radio waves radiated from the base station according to the link disconnection tolerance protocol , the wireless terminal temporarily holds the generated data, and then receives the radio waves radiated from the base station. And a third step of spontaneously transmitting to the base station without any operation .

  According to the wireless communication system and the radio wave emission control method of the present invention, the power consumption of the entire base station in the wireless communication system is reduced, and the communication is performed even when the terminal does not move while maintaining the configuration of the base station versus the plurality of terminals. You can get an opportunity.

It is a system block diagram showing the radio wave radiation of a base station. It is a system configuration | structure figure showing the radio wave radiation of the base station in the time slot | zone with little communication traffic volume. It is explanatory drawing in the protocol for link cutting | disconnection tolerance networks. It is explanatory drawing showing control of the radio wave radiation of the base station in this invention. It is a system block diagram showing the radio wave radiation of the starting base station which has an array antenna. FIG. 6 is a system configuration diagram showing radio wave radiation of the active base station following FIG. 5. It is a system configuration | structure figure showing the radio wave radiation of the starting base station which has a sector antenna. It is a system configuration figure showing beam control in a sector. It is explanatory drawing showing the beam tilting in a sector. It is a functional block diagram of the base station in this invention. It is a system configuration diagram in which a small base station or an access point is arranged around a base station. It is explanatory drawing showing the radio wave radiation of a small base station or an access point.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 3 is an explanatory diagram of the link disconnection resistant network protocol.

  The wireless terminal in the system that is the subject of the present invention executes a protocol for link disconnection resistance technology (see, for example, Non-Patent Document 7). This assumes that the communication link is not always available (often broken) and is unreliable. Here, the wireless terminal does not always exist within the radio wave emission range of the base station.

  When the communication link is not always available and the reliability is low, when the wireless terminal requests data communication, the communication link is not always established with the base station. Normally, in such a case, a communication error is returned to the data origin such as an application. However, by using the link disconnection resistance technology, when the wireless terminal cannot receive the radio wave radiated from the base station, the generated data is temporarily held. Thereafter, when the radio terminal can receive radio waves radiated from the base station due to movement of the radio terminal or the like, the generated data is transmitted to the base station without any user operation.

  According to FIG. 3 (a), when the wireless terminal b is located within the radio wave emission range of the base station B, that is, when it can receive the radio wave radiated from the base station B, data is transmitted according to the user's operation. Send.

  On the other hand, according to FIG. 3B, the base station B is stopped, and the wireless terminal b cannot receive the radio wave radiated from the base station B. Therefore, the wireless terminal b cannot immediately transmit the data generated according to the user operation to the base station B.

  At this time, since the wireless terminal b is executing the link disconnection resistance technique, the generated data is temporarily held. Thereafter, when the wireless terminal b possessed by the user moves and is located within the radio wave emission range of the base station A, that is, when the radio wave radiated from another base station A can be received, it is retained. The transmitted data is transmitted to the base station A. In this case, unless the wireless terminal b moves, radio waves radiated from other base stations cannot be received, and the wireless terminal cannot obtain a communication opportunity (see, for example, Non-Patent Document 3).

  FIG. 4 is an explanatory diagram showing control of radio wave radiation of the base station in the present invention.

  The base station in the present invention radiates radio waves having directivity farther than the omnidirectional radio wave radiation range. The base station has an array antenna and controls a transmission array weight vector of the array antenna. Directional radio waves are radiated randomly in different directions at predetermined time intervals. Further, the radio wave having directivity may be radiated by rotating to a surrounding direction at a constant angular velocity.

  According to FIG. 4A, the base station B is stopped, and the wireless terminal b cannot receive the radio wave radiated from the base station A. Therefore, the wireless terminal b cannot immediately transmit the data generated according to the user operation to the base station B. At this time, since the wireless terminal b is executing the link disconnection resistance technique, the generated data is temporarily held.

  According to FIG. 4B, it is assumed that the radio wave radiated from the base station A then temporarily reaches the wireless terminal b. At this time, the wireless terminal b can transmit the generated data to the base station A. According to the present invention, the wireless terminal b can receive radio waves radiated from other base stations without moving and can obtain a communication opportunity.

  FIG. 5 is a system configuration diagram showing radio wave radiation of an active base station having an array antenna.

  According to FIG. 5, the radio communication system has a plurality of base stations 1 that radiate radio waves, a radio terminal 2 that communicates with the base stations, and a control device 3 that controls radio wave emissions of the base stations.

  The control device 3 stops some base stations among the plurality of base stations in a time zone in which the communication traffic decreases to a predetermined amount or less for the entire system or for each predetermined area constituted by a plurality of base stations. To do. According to FIG. 5, base stations B to G are stopped and only base station A is activated.

  Next, the active base station A radiates radio waves while changing the radiation direction, which is far from the normal radio wave radiation range. If the maximum reachable distance of radio waves to be radiated is the same, radiating radio waves having directivity can reduce power consumption compared to radiating radio waves in all directions. In addition, if the power consumption is the same, it is possible to radiate a radio wave having directivity far away than to radiate in all directions.

  Then, the wireless terminal 2 that has received the directional radio wave transmits the generated data packet to the base station 1 without any user operation.

  According to FIG. 5, the wireless terminal b is located within the coverage area of the base station B, but the base station B is stopped. At this time, the wireless terminal b cannot receive the radio wave radiated from the base station A.

  FIG. 6 is a system configuration diagram showing radio wave radiation of the active base station following FIG.

  At this time, the wireless terminal b can receive the radio wave radiated from the base station A. At this time, the wireless terminal b can obtain a communication opportunity even when the base station B is stopped. Further, the wireless terminal c is located within the coverage area of the base stations B and C, but the base stations B and C are stopped. At this time, the wireless terminal c cannot receive the radio wave radiated from the base station A.

  FIG. 7 is a system configuration diagram showing radio wave radiation of an active base station having a sector antenna.

  The start / stop of the power control unit (or power supply) of the base station can be controlled in units of sectors of the base station. Therefore, by intermittently radiating radio waves in units of a plurality of base stations, a communication opportunity can be given to a wireless terminal located within the coverage area of the base station being stopped.

  According to FIG. 7, the base station is divided into, for example, three sectors, and by sequentially starting / stopping each sector, the power consumption is reduced and a communication opportunity is given to the wireless terminal. Here, one sector in each of the base stations A, C and E is activated. Thereafter, by switching activation / deactivation of the base station and the sector, a communication opportunity is given to another wireless terminal.

  FIG. 8 is an explanatory diagram showing beam control in a sector.

  According to FIG. 8, the active base station radiates radio waves having directivity while changing the horizontal direction by controlling the reflector in the active sector. When an array antenna is used in units of sectors, a directional radio wave is radiated while changing the radiation direction for each sector by controlling the transmission array weight vector of the array antenna.

  FIG. 9 is an explanatory diagram showing beam tilting in the sector.

  According to FIG. 9, the vertical direction (radiation distance) can be changed by controlling the beam tilting angle in units of sectors. Increasing the tilt angle θ with respect to the horizontal direction of the antenna shortens the radiation distance, and decreasing the tilt angle θ increases the radiation distance.

  FIG. 10 is a functional configuration diagram of the base station in the present invention.

  According to FIG. 10, the base station 1 includes an array antenna (or sector antenna) 10, a phase level adjustment unit 11 for each antenna, a distributor 12, an encoding / decoding unit 13, and a communication carrier network interface unit. 14, a control unit 15, a power supply unit 16, and a management message receiving unit 17.

  The array antenna 10 radiates directional radio waves and has two or more antenna elements in order to change the radiation direction. The phase level adjustment unit 11 adjusts the amplitude and phase of a signal to be transmitted and received for each antenna element. The distributor 12 distributes the transmission signal between the encoding / decoding unit 13 and the plurality of antenna elements. The encoding / decoding unit 13 performs encoding or decoding processing on a signal to be transmitted / received. The telecommunications carrier network interface unit 14 is connected to the telecommunications carrier network.

  The management message receiving unit 17 receives a management message from the control device 3. The contents of the management message are (1) power supply control “starting” and “stopping” of the base station, and (2) “directional radiation” and “normal radiation” when it is active. The management message receiving unit 17 instructs the power supply unit 16 to “starting” and “stopping”, and also instructs the control unit 15 to perform “directional radiation” and “omnidirectional radiation”. When the base station 1 is configured in sectors (for example, 3 sectors), the control device 3 may determine the processes (1) and (2) for each sector. In this case, the management message received by the management message receiving unit 17 also includes information indicating the management content for each sector.

  When “directional radiation” is instructed, the control unit 15 controls the transmit array weight vector of the array antenna. At this time, control is performed so that radio waves having directivity are radiated randomly in different directions at predetermined time intervals. In addition, the radio wave having directivity is controlled so as to be radiated by rotating to a surrounding direction at a constant angular velocity. When changing the vertical direction, the tilt angle is changed. Further, the sector antenna base station is instructed to start / stop for each sector. In addition, when the beam is further changed in the horizontal direction within the sector, the position of the reflector is also controlled.

  When “stopping” is instructed, the power supply unit 16 turns off the power supply or power amplifier of the base station. According to this embodiment, in the case of the base station 1 having the sector antenna, it is also preferable to turn off the power amplifier of the target sector.

  Also, according to FIG. 10, the wireless terminal 2 has a DTN protocol processing unit. The DTN protocol processing unit in this embodiment is located on the transport layer and hides the communication disconnection from the application.

  Furthermore, according to FIG. The control device 3 stops some base stations among the plurality of base stations in a time zone in which the communication traffic decreases to a predetermined amount or less for the entire system or for each predetermined area constituted by a plurality of base stations. To do. Here, the control device 3 may actually measure the amount of communication traffic for each predetermined area configured by the entire system or a plurality of base stations, and determine whether to stop some of the base stations. However, some base stations may be stopped only during a predetermined time zone at night. The control device 3 sends to each base station 1 a management message of (1) power source control “starting” and “stopping” of the base station, and (2) “directional radiation” and “omnidirectional radiation” when starting. Send.

  FIG. 11 is a system configuration diagram in which small base stations or access points are arranged around the base station. For example, a small base station for femtocell and / or an access point for wide area / narrow area wireless access network may be mixed and arranged around a base station for mobile phone communication.

  FIG. 12 is an explanatory diagram showing radio wave radiation of a small base station or access point. The activated small base station or access point may emit a radio wave having directivity far away from the radio wave radiation range in all directions. By stopping a base station with high power consumption and starting a small base station or access point with low power consumption, the power consumption of the entire system can be reduced.

  Finally, the effect based on changing the radiation direction of radio waves having directivity at random or at a constant angular velocity will be described.

  Conventionally, there is a MaxCIR or Proportional Fair technique as a typical time division scheduling method in a base station of a wireless communication system (see Non-Patent Document 6, for example). According to the MaxCIR technology, a communication opportunity is assigned to a wireless terminal having the best reception state at each time point. According to the technology of Proportional Fair, a communication opportunity is preferentially given to a wireless terminal that could not communicate in the past, but a communication opportunity is assigned when the reception state is good. For this reason, when a wireless terminal in a poor reception state due to interference between cells of a plurality of base stations is in a stationary state, the reception state hardly fluctuates (the reception state does not improve). Eventually, the radio terminal also decreases the frequency of obtaining communication opportunities and the throughput.

  On the other hand, there is a technique called “Opportunistic Beamforming” (see, for example, Non-Patent Documents 4 and 5). In this technique, a transmit array weight vector is randomly controlled using an array antenna including a two-element array antenna for diversity that is generally used as a base station antenna. As a result, pseudo fading fluctuations are generated, thereby changing the reception state of the wireless terminal in a stationary environment and improving low throughput. This is to reduce the influence of interference waves on an area where the reception environment is steadily bad due to interference between cells.

  On the other hand, the present invention stops some base stations to reduce power consumption in the entire base station, and exists in the coverage area of the stopped base stations and is in a stationary state. A communication opportunity is given to the terminal. Therefore, an effect completely different from the technique of “Opportunistic Beamforming” can be obtained.

  As described above in detail, according to the radio communication system and the radio wave emission control method of the present invention, the terminal moves while reducing the power consumption of the entire base station and maintaining the configuration of the base station vs. multiple terminals. Without having to do so, you can get communication opportunities. For example, by stopping some base stations in a time zone with little communication traffic such as at night, the power consumption of the entire base station can be reduced, and an environment-friendly wireless communication system can be provided.

  Various changes, modifications, and omissions of the above-described various embodiments of the present invention can be easily made by those skilled in the art. The above description is merely an example, and is not intended to be restrictive. The invention is limited only as defined in the following claims and the equivalents thereto.

DESCRIPTION OF SYMBOLS 1 Base station 10 Array antenna 11 Phase level adjustment part 12 Divider 13 Encoding / decoding part 14 Communication carrier network interface part 15 Control part 16 Power supply part 17 Management message receiving part 2 Wireless terminal 3 Control apparatus

Claims (8)

In a radio communication system having a plurality of base stations that radiate radio waves, a radio terminal that communicates with the base stations, and a control device that controls radio wave radiation of the base stations,
The wireless terminal has a link disconnection resistance protocol that hides communication disconnection from an application on the transport layer,
The control device is configured such that a part of the plurality of base stations is in a time zone in which communication traffic decreases to a predetermined amount or less for the entire system or for each predetermined area configured by a plurality of base stations. Stop
The starting base station emits radio waves so as to intermittently give the wireless terminal a communication opportunity while changing the radiation direction and / or angle farther than the normal radio wave radiation range,
When the radio terminal is unable to receive radio waves radiated from the base station according to the link disconnection tolerance protocol, temporarily holds the generated data, and then receives radio waves radiated from the base station, The wireless communication system , wherein the data is spontaneously transmitted to the base station without any user operation . The active base station has an array antenna,
The active base station, by controlling the transmit array weight vector of the array antenna, rotates a radio wave having directivity to a different azimuth randomly every predetermined time or to a surrounding azimuth at a constant angular velocity, The radio communication system according to claim 1, wherein the radio communication system radiates.   The wireless communication system according to claim 2, wherein the active base station radiates radio waves having different flight distances by controlling a beam tilt angle of the array antenna. The active base station has a sector antenna,
2. The wireless communication system according to claim 1, wherein the active base station radiates a radio wave having directivity by controlling start / stop for each sector of the sector antenna. The sector antenna is constituted by an array antenna for each sector,
The active base station controls the array antenna's transmit array weight vector in the active sector to rotate the directional radio waves randomly to a different direction every predetermined time or to the surrounding direction at a constant angular velocity. The radio communication system according to claim 4, wherein the radio communication system radiates.   The active base station emits directional radio waves while changing the horizontal direction by controlling the reflectors in the active sector and changing the vertical direction (radiation distance) by controlling the beam tilt angle. The wireless communication system according to claim 5, wherein: The base station is a base station for mobile phone communication, a small base station for femtocells, and / or an access point for a wide area / narrow area radio access network,
The radio communication system according to any one of claims 1 to 6 , wherein the base station, the small base station, and the access point are arranged in a mixed manner. In a radio wave radiation control method in a radio communication system having a plurality of base stations that radiate radio waves, a radio terminal that communicates with the base station, and a control device that controls radio wave radiation of the base station,
The wireless terminal has a link disconnection resistance protocol that hides communication disconnection from an application on the transport layer,
The base station of the plurality of base stations in a time zone in which the communication traffic is reduced to a predetermined amount or less for each predetermined area configured by the control system as a whole or a plurality of base stations. A first step of stopping
A second step in which the active base station emits radio waves so as to intermittently give a communication opportunity to the wireless terminal while changing the radiation direction and / or angle farther than the normal radio wave radiation range;
When the radio terminal is unable to receive radio waves radiated from the base station according to the link disconnection tolerance protocol, temporarily holds the generated data, and then receives radio waves radiated from the base station, And a third step of spontaneously transmitting the data to the base station without any user operation .

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