JP5103139B2 - Interference amount measuring method and communication apparatus - Google Patents

Description

  The present invention relates to an interference amount measuring method and a communication device in a wireless network system that performs wireless communication between communication devices such as wireless base stations of a mobile communication system.

  In recent years, in mobile communication systems, it has been studied that radio base stations (hereinafter simply referred to as base stations) form a radio network and perform communication between base stations via the radio network. For example, it is considered to configure a wireless network between base stations of a wireless access method called “Mobile WiMAX” compliant with the IEEE (Institute of Electrical and Electronic Engineers) standard “IEEE802.16e”.

  In “IEEE802.16e”, wireless communication between a base station and a mobile station is performed using a wireless frame in the format shown in FIG. FIG. 8A shows a downlink (downlink: DL) frame format in a direction from the base station to the mobile station. FIG. 8B shows an uplink (uplink: UL) frame format in a direction from the mobile station to the base station. As shown in FIG. 8A, the base station transmits a DL frame having a synchronization pattern at the head. The mobile station detects a synchronization pattern in the DL frame and receives data of subsequent slots in the DL frame. Further, as shown in FIG. 9, the mobile station transmits a UL frame following the DL frame.

Conventionally, in an inter-base station wireless network system, a maintenance person manually measures the amount of interference between base stations using a measuring instrument such as a spectrum analyzer or a power meter. The measurement result of the interference amount is used for examining the connection form (network topology) between base stations.
IEEE Std 802.16e-2005, “IEEE Standard for Local and metropolitan area networks Part 16: Air Interface for Fixed and Mobile Broadband Wireless Access Systems Amendment 2: Physical and Medium Access Control Layers for Combined Fixed and Mobile Operation in Licensed Bands and Corrigendum 1 ”, §8.3.5 Frame structure

  However, the interference amount measuring method using the conventional measuring device described above has a problem that the measurement takes time and labor, and the measurement cost is high. Also, because it takes time to measure, if the measurement time and the actual network topology change time are significantly different, the measured interference amount will differ from the interference amount at the time of network topology change, and the desired The wireless communication quality may not be obtained. For this reason, there is a desire to be able to automatically measure the amount of interference at each base station in the radio network system between base stations. However, in order to automatically measure the amount of interference at each base station, it is necessary for each base station to start the interference amount measurement operation at the same time and to simultaneously switch between the transmitting station and the receiving station. It is.

  The present invention has been made in view of such circumstances, and its purpose is to enable each base station to simultaneously start an interference amount measurement operation and simultaneously perform switching between a transmitting station and a receiving station. An object of the present invention is to provide an interference amount measuring method and a communication apparatus capable of automatically measuring the amount of interference in each base station.

  In order to solve the above problems, a communication device according to the present invention includes a time synchronization unit that synchronizes time between communication devices and synchronization between communication devices in a wireless network system in which a plurality of communication devices are wirelessly connected. The downlink frame transmitting means for transmitting the downlink frame at a predetermined transmission timing based on the determined time, the downlink frame receiving means for receiving the downlink frame, and the interference between the communication devices based on the received signal of the downlink frame The measurement means for measuring the amount of interference, and the interference amount measurement operation is started at a designated time synchronized between the communication devices, and the downlink according to the measurement schedule in which the order and the transmission timing of the communication devices transmitting the downlink frame are defined Measurement control means for switching between transmitting a frame and receiving a downlink frame. And wherein the Rukoto.

  In the communication apparatus according to the present invention, a measurement management unit that collects interference amount measurement data is provided, and the communication apparatus includes an uplink frame transmission unit that transmits an uplink frame based on a reception timing of the downlink frame. An uplink frame receiving means for receiving an uplink frame based on the downlink frame transmission timing, wherein the measurement control means defines the order and transmission timing of the communication devices that transmit the uplink frame. Controlling whether to transmit an uplink frame or receiving an uplink frame according to a measurement data transmission schedule, and transmitting the interference amount measurement data of each communication device to the measurement management means using the uplink frame It is characterized by.

  The communication apparatus according to the present invention is characterized by comprising measurement management means for transmitting the measurement schedule to the communication apparatus.

  An interference amount measuring method according to the present invention is an interference amount measuring method in a wireless communication system including a plurality of communication devices. One communication device is a main communication device and another communication device is a slave communication device. The measuring step in which the slave communication device measures the intensity of a predetermined signal to be transmitted is repeated a predetermined number of times while changing the main communication device in the plurality of communication devices.

  According to the present invention, the base stations can simultaneously start the interference amount measurement operation and simultaneously switch between the transmitting station and the receiving station. This makes it possible to automatically measure the amount of interference at each base station.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. This embodiment is based on “IEEE802.16e”.

  FIG. 1 is a block diagram showing a configuration of a radio network system between base stations according to an embodiment of the present invention. In FIG. 1, the inter-base station wireless network system includes a plurality of base stations 1 to 5 (5 in the example of FIG. 1). Each base station 1-5 is arrange | positioned in the place where the radio area of all the base stations 1-5 has overlapped. Therefore, each base station 1-5 can receive the radio wave transmitted from all the other base stations 1-5. Note that the base stations 1 to 5 perform radio communication between base stations using the same frequency band.

  Of the base stations 1 to 5, the base station 1 is a base station corresponding to the root of a communication path in the wireless network. From the base station 1, a communication path related to the base station 2 and the base station 4 and a communication path related to the base station 3 and the base station 5 extend. Adjacent base stations communicate directly. Non-adjacent base stations communicate via adjacent base stations. Although the base station 2 communicates directly with the base station 1, the base station 4 communicates with the base station 1 via the base station 2. Similarly, base station 3 communicates directly with base station 1, but base station 5 communicates with base station 1 via base station 3.

  The base station 1 is connected to a network management device (Network Management Center: NMC) 6. The NMC 6 is a device for operating and maintaining the inter-base station wireless network system. The NMC 6 collects and records interference amount measurement data.

  FIG. 2 is a diagram showing a functional structure of base stations 1 to 5 in the inter-base station wireless network system shown in FIG. In FIG. 2, each of the base stations 1 to 5 includes a BS unit having a base station (BS) function and an MSS unit having a mobile subscriber station (MSS) function. The BS unit performs wireless communication with the MSS unit of another station. Wireless communication using the downlink is performed from the BS unit to the MSS unit of the other station. Wireless communication using the uplink is performed from the MSS unit to the BS unit of the other station.

  In the present embodiment, in the downlink, a downlink (DL) frame having a format shown in FIG. The downlink frame includes a synchronization pattern, a signaling slot, and a user data slot for a partner station. The indication of the measurement schedule and the measurement start time and the collection of measurement data are controlled using a signaling slot. In the uplink, an uplink (UL) frame having the format shown in FIG. 8B is used. And it is a time division duplex (TDD) system as FIG. 9 shows, and the same frequency is utilized in an uplink and a downlink.

  FIG. 3 is a block diagram showing a hardware configuration of base stations 1 to 5 in the inter-base station wireless network system shown in FIG. In FIG. 3, base stations 1 to 5 include an antenna 11, a radio module 12, a communication module 13, a GPS (Global Positioning System) device 14, a CPU (Central Processing Unit) 15, a memory 16, an operation unit 17, and a display unit 18. With. In addition, the said base stations 1-5 respond | correspond to the communication apparatus which concerns on this invention.

  The wireless module 12 transmits and receives wireless signals via the antenna 11. A wirelessly transmitted signal is input from the CPU 15 to the wireless module 12. The wirelessly received signal is output from the wireless module 12 to the CPU 15. The wireless module 12 measures a received signal strength indicator (RSSI) of a wirelessly received signal. In the RSSI measurement, a known synchronization pattern included in the DL frame is used.

The communication module 13 has a wired communication function for connecting and communicating with the core network. The base station 1 performs communication with the NMC 6 through the communication module 13.
The GPS device 14 detects a radio wave transmitted from an artificial satellite and acquires time based on time information in the received signal. The acquired time is output from the GPS device 14 to the CPU 15.

  The CPU 15 implements various information processing functions (device control function, BS function, MSS function, measurement control function, etc.) by executing programs stored in the memory 16. The memory 16 stores a program executed by the CPU 15 and various data. The CPU 15 can access the memory 16 and read / write data.

  The operation unit 17 includes input devices such as a keyboard, a numeric keypad, and a mouse, and performs data input according to the operation of the base station operator. The input data is output from the operation unit 17 to the CPU 15. The display unit 18 includes a display device such as a liquid crystal display device and displays data. The displayed data is input from the CPU 15 to the display unit 18.

  FIG. 4 is a functional block diagram according to the base stations 1 to 5 for realizing the interference amount measurement system in the radio network system between base stations according to the present embodiment. However, FIG. 4 shows portions related to the BS function, the MSS function, and the measurement control function in the block configuration in which the function realized by the CPU 15 shown in FIG. 3 executing the program stored in the memory 16 is expanded. .

In FIG. 4, base stations 1 to 5 include a BS unit 30, an MSS unit 40, a measurement control unit 51, and an interference amount calculation unit 52.
The BS unit 30 includes a time synchronization unit 31, a DL frame transmission unit 32, and a UL frame reception unit 33.

The time synchronizer 31 synchronizes the time of its own base station with the time received from the GPS device 14. Thereby, the time synchronization between base stations is taken.
The DL frame transmission unit 32 transmits the DL frame having the format shown in FIG. The transmission timing for wirelessly transmitting the DL frame is a predetermined timing based on the time at which the time synchronization unit 31 has achieved synchronization between base stations. Conditions for defining the DL frame transmission timing are set in common to all the base stations 1 to 5. Thereby, all the base stations 1-5 share the transmission timing of DL frame.

  The UL frame receiving unit 33 receives the UL frame having the format shown in FIG. As shown in FIG. 9, the time position of the UL frame is defined by a relative positional relationship following the DL frame.

The MSS unit 40 includes a DL frame reception unit 41 and a UL frame transmission unit 42.
The DL frame receiving unit 41 detects a synchronization pattern from the signal received by the wireless module 12 and receives a DL frame.
The UL frame transmission unit 42 transmits the UL frame by the wireless module 12 at the transmission timing determined from the reception timing of the DL frame. As shown in FIG. 9, the transmission timing of the UL frame is defined by a relative positional relationship following the DL frame.

The measurement control unit 51 controls the measurement of the amount of interference between base stations according to the measurement schedule. The measurement control unit 51 performs control using the signaling slot for the measurement schedule and the measurement start time instruction and the collection of the measurement data.
The interference amount calculation unit 52 calculates the interference amount based on the RSSI value measured by the wireless module 12.

  Next, the interference amount measuring operation according to the present embodiment will be described.

  First, as a preparation stage for measuring the amount of interference, the base stations 1 to 5 hold a common measurement schedule. As a method of inputting the measurement schedule to each of the base stations 1 to 5, an operator may perform an input operation, or the NMC 6 may transmit the measurement schedule to the base stations 1 to 5. In FIG. 1, the measurement schedule transmitted from the NMC 6 to the base stations 1 to 5 is first transmitted to the base station 1, and then transmitted from the base station 1 to the base stations 2 and 4 and the base stations 3 and 5. Each base station 1 to 5 holds the received measurement schedule in the memory 16.

  FIG. 5 shows an example of a measurement schedule. As shown in FIG. 5, the measurement schedule defines the order of base stations that transmit DL frames and the transmission timing. In the example of FIG. 5, it is defined that DL frames are transmitted in the order of base stations 1, 2, 3, 4, and 5. Also, the transmission timing of the DL frame is defined.

  Next, in the measurement stage, each base station 1 to 5 starts an interference amount measurement operation at a designated time for starting measurement. The start of the interference amount measurement operation is synchronized with each of the base stations 1 to 5 at the time when the synchronization between the base stations is established. The method of setting the designated measurement start time to each of the base stations 1 to 5 may be input by the operator as in the measurement schedule, or the NMC 6 may designate the measurement start time for the base stations 1 to 5. May be sent. Hereinafter, the interference amount measurement operation in the measurement stage will be described in detail.

In each base station 1-5, when the measurement start designated time comes, the measurement control unit 51 starts the interference amount measurement operation, and whether the own station transmits the DL frame or receives the DL frame according to the measurement schedule. Switch.
In the measurement schedule, the measurement control unit 51 instructs the DL frame transmission unit 32 to transmit a DL frame at the DL frame transmission timing of the local station. In response to this instruction, the DL frame transmission unit 32 transmits a DL frame. Thereby, the radio module 12 transmits radio waves from the own station at the DL frame transmission timing of the own station. Further, the measurement control unit 51 instructs the DL frame transmission unit 32 to stop transmitting the DL frame during a period that is not the DL frame transmission timing of the own station in the measurement schedule. As a result, radio waves are not transmitted from the own station during a period that is not the DL frame transmission timing of the own station. In the measurement schedule of FIG. 5, for example, the base station 2 transmits radio waves in the period (3), and does not transmit radio waves in the other periods (1), (2), and (4) to (14).

  On the other hand, the measurement control unit 51 instructs the DL frame reception unit 41 to receive a DL frame at the DL frame transmission timing of another station in the measurement schedule. In response to this instruction, the DL frame receiving unit 41 receives a DL frame. Further, the RSSI value at the time of DL frame reception is measured by the wireless module 12. In the measurement schedule of FIG. 5, for example, the base station 2 receives the radio wave from the base station 1 in the period (1), receives the radio wave from the base station 3 in the period (5), and the base station in the period (7). 4 is received and the radio wave from the base station 5 is received in the period (9).

  The interference amount calculation unit 52 calculates the interference amount based on the RSSI value measured by the wireless module 12. The interference amount calculation unit 52 receives the RSSI value from the wireless module 12 for each DL frame transmission timing of the other station in the measurement schedule. For example, the base station 2 receives the RSSI value of the radio wave from the base station 1 in the period (1), receives the RSSI value of the radio wave from the base station 3 in the period (5), and receives the RSSI value from the base station 4 in the period (7). The RSSI value of the radio wave is received, and the RSSI value of the radio wave from the base station 5 is received in the period (9). The interference amount calculation unit 52 calculates the interference amount using the RSSI value of the radio wave (desired wave) from the desired station and the RSSI value of the radio wave (interference wave) from the undesired station. As the amount of interference, for example, a carrier to interference and noise power ratio (CNIR), a carrier power to interference power ratio (CIR), or the like can be used.

  According to the above-described embodiment, each of the base stations 1 to 5 starts the interference amount measurement operation at a designated time at which the synchronization between the base stations is achieved, and simultaneously switches the transmission station and the reception station according to the measurement schedule. It can be carried out. Thereby, in the radio network system between base stations, it becomes possible to automatically measure the interference amount in each of the base stations 1 to 5.

  In the present embodiment, the TDD scheme is used, and the same frequency is used for the uplink and the downlink, so that the amount of interference between the downlink and the uplink can be regarded as the same.

Next, an operation for transmitting the interference amount measurement data of each of the base stations 1 to 5 to the NMC 6 will be described.
FIG. 6 is an example of a transmission schedule of interference amount measurement data. As shown in FIG. 6, in the measurement data transmission schedule, the order of base stations that transmit UL frames and the transmission timing are defined. In the example of FIG. 6, it is defined that UL frames are transmitted in the order of base stations 5, 4, 3, and 2. In addition, the transmission timing of the UL frame is defined. Each base station 1-5 stores interference amount measurement data in a UL frame and transmits it according to a measurement data transmission schedule.

  In the example of FIG. 6, first, the base station 5 sends its own interference amount measurement data to the base station 3 using a UL frame in the period (8). Next, in the period (10), the base station 4 sends the interference amount measurement data of the own station to the base station 2 using a UL frame. Next, in the period (12), the base station 3 transmits the interference amount measurement data of the own station and the interference amount measurement data received from the base station 5 to the base station 1 by the UL frame. Next, in the period (14), the base station 2 transmits the interference amount measurement data of the own station and the interference amount measurement data received from the base station 4 to the base station 1 by the UL frame. Thereby, the base station 1 receives the interference amount measurement data of the base stations 2 to 5. The base station 1 sends the interference amount measurement data of its own station and the interference amount measurement data of the base stations 2 to 5 to the NMC 6. Thereby, the NMC 6 receives and records the interference amount measurement data of the base stations 1 to 5.

FIG. 7 is a flowchart showing a procedure of an interference amount measuring method according to an embodiment of the present invention.
In FIG. 7, in step S <b> 1, one communication device is set as a main communication device and another communication device is set as a slave communication device among communication devices constituting the wireless communication system. In the example of FIG. 1, base stations 1 to 5 are communication devices that constitute a wireless communication system. In step S2, the slave communication device measures the intensity of a predetermined signal transmitted by the master communication device. In step S3, it is determined whether all the communication devices to be measured have become main communication devices. As a result, if there remains a measurement target communication device that is not yet the main communication device, the process returns to step S1 to change the main communication device to perform measurement. On the other hand, if all the communication devices to be measured become main communication devices, the process is terminated.

According to the present embodiment, the following effects can be obtained.
(1) When constructing a wireless network system between base stations, the base stations constituting the network can automatically measure the interference amount in cooperation with each other.
(2) At the time of network start-up, the amount of interference in the actual operation state at each base station can be measured, and it is possible to perform radio channel setting in consideration of the amount of interference in the actual operation state.
(3) Since measurement is possible even after the operation of the wireless network system between base stations is started, it is possible to reset the wireless line setting according to the state of the interference amount in the actual operation state after the operation is started. Become. For example, in FIG. 1, when the amount of interference that adversely affects wireless communication between the base stations 3 and 5 increases, for example, a wireless link between the base stations 2 and 5 is newly provided to avoid interference. It becomes possible. Further, it is possible to monitor the interference in a plurality of frequency slots and to avoid the interference by changing the frequency according to the change in the amount of interference.

  As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the specific structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.

It is a block diagram which shows the structure of the radio network system between base stations which concerns on one Embodiment of this invention. It is a figure which shows the functional structure of the base stations 1-5 in the radio network system between base stations shown in FIG. It is a block diagram which shows the hardware constitutions of the base stations 1-5 in the radio network system between base stations shown in FIG. FIG. 6 is a functional block diagram according to base stations 1 to 5 for realizing an interference amount measurement system in the inter-base station wireless network system shown in FIG. 1. It is an example of the measurement schedule which concerns on one Embodiment of this invention. It is an example of the measurement data transmission schedule which concerns on one Embodiment of this invention. It is a flowchart which shows the procedure of the interference measuring method which concerns on one Embodiment of this invention. It is a figure which shows the radio | wireless frame format which concerns on IEEE802.16e. It is a figure which shows the transmission order of the radio | wireless frame which concerns on IEEE802.16e.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1-5 ... Base station (communication apparatus), 6 ... Network management apparatus (NMC), 11 ... Antenna, 12 ... Wireless module, 14 ... GPS apparatus, 15 ... CPU, 16 ... Memory, 30 ... BS part, 31 ... Time Synchronization unit, 32 ... DL frame transmission unit, 33 ... UL frame reception unit, 40 ... MSS unit, 41 ... DL frame reception unit, 42 ... UL frame transmission unit, 51 ... measurement control unit, 52 ... interference amount calculation unit

Claims (4)

In a wireless network system in which a plurality of communication devices are wirelessly connected,
The communication device
Time synchronization means for synchronizing time between communication devices;
A downlink frame transmission means for transmitting a downlink frame at a predetermined transmission timing based on a time at which synchronization between communication devices is achieved;
Downlink frame receiving means for receiving a downlink frame;
Measurement means for measuring the amount of interference between communication devices based on the received signal of the downlink frame;
Holding means for holding a measurement schedule in which the order and transmission timing of communication devices that transmit downlink frames are defined in common to the plurality of communication devices;
A measurement control unit that starts an interference amount measurement operation at a specified time when synchronization between communication devices is established, and switches between transmitting a downlink frame or receiving a downlink frame according to a measurement schedule held by the holding unit; ,
A communication apparatus comprising: Provide measurement management means to collect interference measurement data,
The communication device
An uplink frame transmission means for transmitting an uplink frame based on the reception timing of the downlink frame;
An uplink frame receiving means for receiving an uplink frame based on the downlink frame transmission timing;
The measurement control means controls whether to transmit an uplink frame or receive an uplink frame according to a measurement data transmission schedule in which the order and transmission timing of communication devices that transmit uplink frames are defined,
The communication apparatus according to claim 1, wherein interference amount measurement data of each communication apparatus is transmitted to the measurement management unit using an uplink frame.   The communication apparatus according to claim 1, further comprising a measurement management unit that transmits the measurement schedule to the communication apparatus. An interference amount measurement method in a wireless communication system including a plurality of communication devices,
In common to the plurality of communication devices, each communication device holds a measurement schedule in which the order and transmission timing of communication devices that transmit predetermined signals are defined, and according to the measurement schedule,
The main communication device 1 of the communication device, as a slave communication apparatus other communication devices, measurement step of the predetermined signal intensity the sub communication device measures each of the main communication device transmits, within said plurality of communication devices An interference amount measuring method characterized by repeating a predetermined number of times while changing a main communication device.

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