WO2012053240A1

WO2012053240A1 - Wireless communication system, low-power base station, and communication control method

Info

Publication number: WO2012053240A1
Application number: PCT/JP2011/059021
Authority: WO
Inventors: 敦久稲越
Original assignee: 京セラ株式会社
Priority date: 2010-10-18
Filing date: 2011-04-11
Publication date: 2012-04-26

Abstract

A PeNB (300) acquires a macro-UE number or a macro-connection UE ratio which are information relating to the number of macro-UE, and a pico-UE number or a pico-connection UE ratio which are information relating to the number of pico-UE. Further the PeNB (300) controls a bias value in accordance with the increase/decrease of the acquired macro-UE number or the macro-connection UE ratio, and the pico-UE number or the pico-connection UE ratio.

Description

Wireless communication system, low power base station, and communication control method

The present invention relates to a radio communication system including a high power base station and a low power base station having a transmission output smaller than that of the high power base station, the low power base station in the radio communication system, and the low power base. The present invention relates to a communication control method in a station.

As a next-generation wireless communication system that realizes high-speed and large-capacity communication, there is LTE standardized by 3GPP, which is a standardization organization for wireless communication systems. The technical specification of LTE is determined as 3GPP Release 定 8. Currently, LTE Advanced, which is an advanced LTE, is being studied.

In 3GPP, a low power base is a small base station that has a small transmission output and forms a cell (small cell) that is a communication area with a radius of about [m] to about a dozen [m]. Standardization is in progress for detailed functions and requirements of stations (PeNB). The low-power base station has a larger transmission output than the low-power base station, and distributes the traffic of the high-power base station (MeNB) that forms a cell (large cell) that is a communication area with a radius of about several hundred meters. Installed as a purpose. Such a configuration of the wireless communication system is referred to as a heterogeneous network.

In 3GPP, in a heterogeneous network, a technique for preventing traffic from being concentrated on a high power base station or a low power base station is being studied. This is because when the traffic concentrates on one base station, the downlink throughput of the entire cell deteriorates, and as a result, the communication quality deteriorates.

Therefore, an object of the present invention is to provide a radio communication system, a low power base station, and a communication control method that effectively distribute traffic in a heterogeneous network.

In order to solve the above-described problems, the present invention has the following features. A feature of the present invention is a wireless communication system (wireless communication system 1) configured by a high power base station (MeNB 100) and a low power base station (PeNB 300) having a transmission output smaller than that of the high power base station. The low-power base station controls a bias value that is a value that is used to extend the cell range of the low-power base station and that is a value that is used in the process of determining the connection destination of the wireless terminal (UE 400). A control unit (control unit 320) that controls the bias value based on information from the high power base station, and the information from the high power base station The gist of the present invention is information on the number of wireless terminals connected to.

In such a wireless communication system, the low power base station appropriately distributes traffic by controlling the bias value, and performs wireless communication between the high power base station and the wireless terminals under the high power base station. The applied interference can be appropriately reduced.

A feature of the present invention is a low-power base station having a transmission power smaller than that of a high-power base station, a value used for extending the cell range of the low-power base station, and a connection destination of a wireless terminal A control unit that controls a bias value that is a value used in the determining process and transmission power of the low-power base station, the control unit based on information from the high-power base station The transmission power is controlled, and the information from the high power base station is information on the number of wireless terminals connected to the high power base station.

A feature of the present invention is that when the control unit recognizes that the number of wireless terminals connected to the high power base station has increased, the increase in the bias value and the transmission power of the low power base station The main point is to reduce the

A feature of the present invention is that when the control unit recognizes that the number of wireless terminals connected to the high power base station has decreased, the bias value decreases and the transmission power of the low power base station increases. The main point is to increase.

A feature of the present invention is that the control unit obtains information on the number of wireless terminals connected to the low power base station, and based on the information on the number of wireless terminals connected to the low power base station. The gist is to control the bias value and the transmission power of the low power base station.

A feature of the present invention is that when the control unit recognizes that the number of wireless terminals connected to the low power base station has increased, the bias value decreases and the transmission power of the low power base station The main point is to increase.

A feature of the present invention is that, when the control unit recognizes that the number of wireless terminals connected to the low power base station has decreased, the increase of the bias value and the transmission power of the low power base station The main point is to reduce the

A feature of the present invention is a communication control method in a low power base station having a transmission output smaller than that of a high power base station, which is a value used for extending a cell range of the low power base station, and a radio terminal Including a step of controlling a bias value, which is a value used in a process of determining a connection destination of the low-power base station, and a transmission power of the low-power base station. In the controlling step, based on information from the high-power base station The bias value and the transmission power are controlled, and the information from the high power base station is information on the number of wireless terminals connected to the high power base station.

According to the characteristics of the present invention, traffic can be effectively distributed in a heterogeneous network.

1 is an overall schematic configuration diagram of a wireless communication system according to an embodiment of the present invention. It is a block diagram which shows the structure of the low electric power base station which concerns on embodiment of this invention. It is a flowchart which shows the 1st operation | movement of the low electric power base station which concerns on embodiment of this invention. It is a flowchart which shows the 2nd operation | movement of the low electric power base station which concerns on embodiment of this invention. It is a flowchart which shows the 3rd operation | movement of the low electric power base station which concerns on embodiment of this invention. It is a flowchart which shows operation | movement of the low electric power base station control 1 which concerns on embodiment of this invention. It is a flowchart which shows operation | movement of the low electric power base station control 2 which concerns on embodiment of this invention. It is a flowchart which shows operation | movement of the low electric power base station control 3 which concerns on embodiment of this invention. It is a flowchart which shows operation | movement of the low electric power base station control 4 which concerns on embodiment of this invention. It is a flowchart which shows the 4th operation | movement of the low electric power base station which concerns on embodiment of this invention.

Next, an embodiment of the present invention will be described with reference to the drawings. Specifically, (1) the configuration of the wireless communication system, (2) the operation of the low-power base station, (3) the operation and effect, and (4) other embodiments will be described. In the description of the drawings in the following embodiments, the same or similar parts are denoted by the same or similar reference numerals.

(1) Configuration of Radio Communication System (1.1) Overall Schematic Configuration of Radio Communication System FIG. 1 is an overall schematic configuration diagram of a radio communication system 1 according to an embodiment of the present invention. The wireless communication system 1 has, for example, a configuration based on LTE Release 9 which is a 3.9th generation (3.9G) mobile phone system and LTE-Advanced which is positioned as a 4th generation (4G) mobile phone system.

As shown in FIG. 1, a radio communication system 1 includes a high power base station (high output power base station, high output base station) (for example, a macro cell base station) that forms a large cell (eg, macro cell) MC1 that is a coverage area. : MeNB) 100 and a low power base station (low output power base station, small output base station) having a transmission output (transmission power) smaller than that of the MeNB 100 and forming a small cell (eg, pico cell) PC2 that is a coverage area (E.g., picocell base station: PeNB) 300. The radius of the large cell MC1 is, for example, about several hundreds [m], and the radius of the small cell PC2 is, for example, about several [m] to several tens [m].

Under the control of the MeNB 100, in other words, the radio terminal (UE) 200 exists in an area within the large cell MC1 and not within the small cell PC2. MeNB100 and UE200 can perform radio | wireless communication. Also. Under the control of the PeNB 300, in other words, a radio terminal (UE) 400 exists in the small cell PC2. PeNB300 and UE400 can perform radio | wireless communication. Hereinafter, UE 200 is referred to as macro UE 200, and UE 400 is referred to as pico UE 400 from the viewpoint of improving frequency utilization efficiency. The same frequency band is shared by the communication between the MeNB 100 and the macro UE 200 and the communication between the PeNB 300 and the pico UE 400.

The MeNB 100 is installed at a location based on a station placement design that considers inter-cell interference. On the other hand, PeNB300 is installed in arbitrary places. The PeNB 300 is installed in the large cell MC1 for the purpose of distributing traffic of the MeNB 100 and the like. By the MeNB 100 and the PeNB 300, the wireless communication system 1 has a heterogeneous network configuration. MeNB100 and PeNB300 can mutually communicate via the X2 interface 500 which is a logical communication path set to the backhaul.

When the MeNB 100 and the macro UE 200 are connected to perform radio communication, the frequency band of the downlink (link from the MeNB 100 to the macro UE 200, hereinafter referred to as “macro downlink”) used for the radio communication. When the PeNB 300 and the pico UE 400 are connected to perform radio communication, the downlink used for the radio communication (the link from the PeNB 300 to the pico UE 400, hereinafter referred to as “pico downlink”). When the frequency band overlaps, the macro UE 200 that is performing radio communication with the MeNB 100 receives interference due to a radio signal transmitted from the PeNB 300 to the pico UE 400 using the pico downlink.

When the MeNB 100 and the macro UE 200 are connected to perform radio communication, the frequency band of the uplink used for the radio communication (link directed from the macro UE 200 to the MeNB 100, hereinafter referred to as “macro uplink”) When the PeNB 300 and the pico UE 400 are connected to perform radio communication, the uplink used for the radio communication (the link from the pico UE 400 to the PeNB 300, hereinafter referred to as “pico uplink”). When the frequency band overlaps, the MeNB 100 that is performing radio communication with the macro UE 200 receives interference due to a radio signal transmitted from the pico UE 400 to the PeNB 300 using the pico uplink.

In this embodiment, the PeNB 300 reduces the interference received by the MeNB 100 and the macro UE 200, in other words, the interference received by the radio communication between the PeNB 300 and the pico UE 400 by the radio communication between the MeNB 100 and the macro UE 200. Further, the PeNB 300 increases the bias value in CRE (Cell Range Range Expansion), thereby connecting more UEs and distributing traffic, specifically, preventing the UEs connected to the MeNB 100 from becoming excessive. Plan. Here, the bias value is a value used for extending the cell range (communication possible range) of PeNB 300, and is a value used in a process of determining a UE connection destination. Also, CRE refers to the PeNB 300 when the UE determines the connection destination to one of the MeNB 100 and the PeNB 300 based on the received power of the signal from the MeNB 100 and the received power of the signal from the PeNB 300 in celery selection. By adding a bias value to the received power of the signal from, it means that the cell range of PeNB 300 is expanded and the possibility that the UE connects to PeNB 300 is increased. The CRE is measurement that is information including information indicating the received power of the signal from the PeNB 300 and information indicating the received power of the signal from the MeNB 100 in a state where the UE is connected to the PeNB 300 in the handover. When the report is notified to the PeNB 300, when the PeNB 300 determines the UE connection destination based on the measurement report, the cell range of the PeNB 300 is expanded by adding a bias value to the value of the received power from the PeNB 300, This means that the possibility that the UE will continue to be connected to the PeNB 300 is increased.

(1.2) Configuration of Low Power Base Station FIG. 2 is a block diagram showing the configuration of PeNB 300. As illustrated in FIG. 2, the PeNB 300 includes an antenna unit 301, a wireless communication unit 310, a control unit 320, a storage unit 330, and an I / F unit 340.

The radio communication unit 310 is configured using, for example, a radio frequency (RF) circuit, a baseband (BB) circuit, and the like, and transmits and receives radio signals to and from the pico UE 400 via the antenna unit 301. In addition, the wireless communication unit 310 performs encoding and modulation of the transmission signal and demodulation and decoding of the reception signal.

Further, the radio communication unit 310 receives a radio signal from the MeNB 100 when the MeNB 100 and the macro UE 200 are connected to perform radio communication using the macro downlink.

The control unit 320 is configured using, for example, a CPU (Central Processing Unit), a DSP (Digital Signal Processor), and the like, and controls various functions provided in the PeNB 300.

The storage unit 330 is configured using, for example, a memory, and stores various types of information used for controlling the PeNB 300 and the like. The I / F unit 340 performs communication with the outside via a wired communication network (not shown). The I / F unit 340 is connected to the X2 interface 500.

The control unit 320 includes an information acquisition unit 321, a CRE bias control unit 322, and a pico transmission power control unit 323.

MeNB100 measures the throughput (communication speed) in the radio | wireless communication between the said MeNB100 and UE200 periodically. MeNB100 calculates the average value of the throughput measured within the predetermined period. The MeNB 100 transmits information on the average value of the throughput to the PeNB 300 via the X2 interface 500.

The PeNB (other PeNB) other than the PeNB 300 that exists in the large cell MC1 periodically measures the throughput in radio communication between the other PeNB and the UE. The other PeNB calculates the average value of the throughput measured within a predetermined period. The other PeNB transmits information on the average value of the throughput to the PeNB 300 via the X2 interface 500.

The MeNB 100 and other PeNBs may transmit the average throughput information to the PeNB 300 via the X2 interface 500 in a predetermined cycle (for example, 20 ms cycle). In addition, when the information acquisition unit 321 transmits a message requesting information on the average value of the throughput from the I / F unit 340 to the MeNB 100 and other PeNBs via the X2 interface 500, the MeNB 100 and other PeNBs The throughput average value information may be transmitted to the PeNB 300 via the X2 interface 500 in response to a message requesting the throughput average value information.

The information acquisition unit 321 in the control unit 320 of the PeNB 300 receives the average throughput information from the MeNB 100 and the average throughput information from other PeNBs from the I / F unit 340. The information acquisition unit 321 multiplies the average value of the throughput from the MeNB 100 by a time corresponding to a predetermined period. The information acquisition unit 321 multiplies an average value of throughput from other PeNBs by a time corresponding to a predetermined period. The information acquisition unit 321 adds each multiplication value. The added value is a traffic amount within a predetermined period corresponding to the large cell MC1. The amount of traffic within a predetermined period corresponding to the large cell MC1 means that the UE within the large cell MC1 other than the UE 400 connected to the PeNB 300 and the wireless communication between the MeNB 100 and another PeNB within the predetermined period. Means traffic volume. Each time the information acquisition unit 321 calculates the traffic amount within a predetermined period corresponding to the large cell MC1, the information acquisition unit 321 stores the traffic amount within the predetermined period corresponding to the large cell MC1 in the storage unit 330.

Also, the MeNB 100 transmits information on the number of UEs (macro UEs) 200 (macro UEs) connected to the MeNB 100 to the PeNB 300 via the X2 interface 500. Here, the information on the number of macro UEs is the information on the number of macro UEs themselves, the ratio of the number of UEs currently connected to the MeNB 100 to the maximum number of UEs that can be connected to the MeNB 100 (number of allowed connections) (the macro connection UE ratio). ).

MeNB100 may transmit the information regarding the number of macro UEs at that time to PeNB300 via X2 interface 500 with a predetermined cycle (for example, 20ms cycle). Further, when the information acquisition unit 321 transmits a message requesting information on the number of macro UEs from the I / F unit 340 to the MeNB 100 via the X2 interface 500, the MeNB 100 requests information on the number of macro UEs. In response to the message to be transmitted, information regarding the number of macro UEs may be transmitted to the PeNB 300 via the X2 interface 500.

The information acquisition unit 321 in the control unit 320 of the PeNB 300 receives information on the number of macro UEs from the MeNB 100 from the I / F unit 340. Each time the information acquisition unit 321 receives information on the number of macro UEs, the information acquisition unit 321 stores information on the number of macro UEs in the storage unit 330.

Also, the information acquisition unit 321 acquires information related to the number of UEs connected to the PeNB 300 (number of pico UEs). Here, the information on the number of pico UEs is information on the number of pico UEs themselves, a ratio of the number of pico UEs currently connected to the PeNB 300 to the maximum number of UEs to which the PeNB 300 can be connected (connection allowable number) (pico connected UEs). Ratio). Each time the information acquisition unit 321 acquires information about the number of pico UEs, the information acquisition unit 321 stores information on the number of pico UEs in the storage unit 330.

The CRE bias control unit 322 controls the bias value in the CRE. Furthermore, the CRE bias control unit 322 transmits a message including the controlled bias value via the wireless communication unit 310 and the antenna unit 301 in celery selection.

When the UE receives a message including a bias value, the UE adds the bias value to the value of received power of a signal (for example, a reference signal) from the PeNB 300. The UE compares the value of the received power of the signal from the MeNB 100 with the value obtained by adding the bias value to the received power value of the signal from the PeNB 300 (for example, a reference signal). Further, when the received power value of the signal from the MeNB 100 is larger, the UE selects a cell corresponding to the MeNB 100, and the value obtained by adding the bias value to the received power value of the signal from the PeNB 300 is larger. In the case, a cell corresponding to PeNB 300 is selected. When the UE performs such processing, the larger the bias value, the greater the possibility that the UE selects a cell corresponding to the PeNB 300.

In handover, the control unit 320 adds the controlled bias value to the received power value corresponding to the information indicating the received power of the signal from the PeNB 300 included in the measurement report. Further, the control unit 320 compares the value obtained by the addition with the value of the received power corresponding to the information indicating the received power of the signal from the MeNB 100 included in the measurement report, and corresponds to the larger value. MeNB100 or PeNB300 is determined as a connection destination of UE.

The pico transmission power control unit 323 controls the transmission power of the PeNB 300.

Hereinafter, specific processing (first processing to third processing) of bias value control and transmission power control of PeNB 300 will be described.

(First process)
The CRE bias control unit 322 sets the bias value to 0 in the initial state. Moreover, the pico transmission power control part 323 sets the transmission power of PeNB300 to the minimum value in an initial state.

Thereafter, the CRE bias control unit 322 increases the bias value. As the bias value increases, the coverage area PC2 of the PeNB 300 expands. As the coverage area PC2 of the PeNB 300 expands, the connection destination of some UEs connected to the MeNB 100 is switched to the PeNB 300. For this reason, the traffic corresponding to the large cell MC1 is distributed.

Next, the CRE bias control unit 322 determines whether or not the number of macro UEs or the macro connection UE ratio that is information on the number of macro UEs has decreased. Specifically, the CRE bias control unit 322 reads the latest macro UE number or macro connection UE ratio information and the previous macro UE number or macro connection UE ratio information from the storage unit 330. Further, the CRE bias controller 322 increases the number of macro UEs or the ratio of macro connected UEs when the latest number of macro UEs or the ratio of macro connected UEs is larger than the number of previous macro UEs or the ratio of macro connected UEs. Judge. On the other hand, the CRE bias control unit 322 determines that the number of macro UEs has decreased when the latest number of macro UEs or macro connection UE ratio is smaller than the previous number of macro UEs or macro connection UE ratio.

Generally, when the bias value increases, the possibility that the UE will connect to the PeNB 300 increases, and the number of macro UEs or the macro connected UE ratio decreases. However, when the UE is located remotely from the PeNB 300, even if the bias value increases, the UE may not connect to the PeNB 300, and the number of macro UEs or the macro connected UE ratio may not decrease.

When the number of macro UEs or the macro connection UE ratio decreases as a result of increasing the bias value, the CRE bias control unit 322 further increases the bias value. Thereby, the coverage area PC2 of the PeNB 300 is further expanded, and traffic is distributed. Even when the bias value is increased, the CRE bias control unit 322 continues to increase the bias value until the number of macro UEs or the macro connected UE ratio does not decrease.

On the other hand, if the number of macro UEs or the ratio of macro connected UEs is not increased even though the bias value has increased, it means that the increase in the bias value cannot be expected to distribute traffic. In this case, when the transmission power of the PeNB 300 is not the maximum value, the pico transmission power control unit 323 performs control to increase the transmission power of the PeNB 300. Further, the CRE bias control unit 322 decreases the bias value. An increase in the transmission power of the PeNB 300 prompts an increase in the coverage area PC2 of the PeNB 300, and a decrease in the bias value prompts a decrease in the coverage area PC2 of the PeNB 300. Therefore, by increasing the transmission power of the PeNB 300 and decreasing the bias value at the same time, it is possible to reduce the variation in the coverage area PC2 of the PeNB 300.

In addition, in the case where the number of macro UEs or the macro connection UE ratio is not decreased and the transmission power of the PeNB 300 is the maximum value despite the increase in the bias value, the CRE bias control unit 322 Decrease the value.

Thereafter, the CRE bias control unit 322 determines whether the number of macro UEs or the macro connected UE ratio has increased. When the bias value decreases, the UE is less likely to connect to the PeNB 300, and the number of macro UEs or the macro connection UE ratio increases. However, when the UE is located remotely from the MeNB 100, even if the bias value decreases, the UE may not connect to the MeNB 100, and the number of macro UEs or the macro connected UE ratio may not increase.

If the number of macro UEs or the macro connection UE ratio does not increase even if the bias value decreases, it is considered that the degree of decrease in the bias value is small. In this case, the CRE bias control unit 322 further decreases the bias value.

On the other hand, when the number of macro UEs or the macro connected UE ratio increases as a result of the decrease in the bias value, it is estimated that the number of macro UEs or the macro connected UE ratio decreases as the bias value increases. In this case, the CRE bias control unit 322 increases the bias value. Thereby, the coverage area PC2 of PeNB300 expands and traffic distribution is achieved.

Thereafter, when the transmission power of the PeNB 300 is not the minimum value, the pico transmission power control unit 323 performs control to decrease the transmission power of the PeNB 300. Further, the CRE bias controller 322 increases the bias value. The decrease in the transmission power of the PeNB 300 promotes the reduction of the coverage area PC2 of the PeNB 300, and the increase of the bias value promotes the expansion of the coverage area PC2 of the PeNB 300. Therefore, by reducing the transmission power of the PeNB 300 and increasing the bias value at the same time, it is possible to reduce fluctuations in the coverage area PC2 of the PeNB 300 that can distribute traffic.

(Second process)
The CRE bias control unit 322 sets the bias value to 0 in the initial state. Also, the pico transmission power control unit 323 sets the pico transmission power value to the minimum value in the initial state.

Thereafter, the CRE bias control unit 322 increases the bias value. By increasing the bias value, the coverage area PC2 of the PeNB 300 is expanded and traffic is distributed.

Next, the CRE bias control unit 322 determines whether the number of pico UEs or the pico connected UE ratio, which is information on the number of pico UEs, has increased. Specifically, the CRE bias control unit 322 reads the latest pico UE number or pico connection UE ratio information and the previous pico UE number or pico connection UE ratio information from the storage unit 330. Further, the CRE bias controller 322 increases the number of pico UEs or the pico connection UE ratio when the latest number of pico UEs or the pico connection UE ratio is larger than the previous number of pico UEs or the pico connection UE ratio. Judge. On the other hand, when the latest number of pico UEs or pico connection UE ratio is smaller than the previous number of pico UEs or pico connection UE ratios, the CRE bias control unit 322 reduces the number of pico UEs or pico connection UE ratios. Judge.

Generally, when the bias value increases, the UE is more likely to connect to the PeNB 300, and the number of pico UEs or the pico connected UE ratio increases. However, when the UE is remotely located from the PeNB 300, even if the bias value increases, the UE does not connect to the PeNB 300, and the number of pico UEs or the pico connected UE ratio may not increase.

As a result of increasing the bias value, when the number of pico UEs or the pico connection UE ratio increases, the CRE bias control unit 322 further increases the bias value. Thereby, the coverage area PC2 of the PeNB 300 is further expanded, and traffic is distributed.

On the other hand, if the number of pico UEs or the pico connected UE ratio does not increase even though the bias value has increased, this means that the increase in the bias value cannot be expected to distribute traffic. In this case, when the transmission power of the PeNB 300 is not the maximum value, the pico transmission power control unit 323 performs control to increase the transmission power of the PeNB 300. Further, the CRE bias control unit 322 decreases the bias value. By increasing the transmission power of the PeNB 300 and decreasing the bias value at the same time, the variation of the coverage area PC2 of the PeNB 300 can be reduced.

In addition, when the bias value increases, the number of pico UEs or the pico connection UE ratio does not increase and the transmission power of the PeNB 300 is the maximum value, the CRE bias control unit 322 Decrease the value.

Thereafter, the CRE bias control unit 322 determines whether or not the number of pico UEs or the pico connection UE ratio has decreased. When the bias value decreases, the UE is less likely to connect to the PeNB 300, and the number of pico UEs or the pico connection UE ratio decreases. However, when the UE is located remotely from the MeNB 100, even if the bias value decreases, the UE does not connect to the MeNB 100, and the number of pico UEs or the pico connected UE ratio may not decrease.

If the number of pico UEs or the pico connection UE ratio does not increase even if the bias value decreases, the CRE bias control unit 322 further decreases the bias value.

On the other hand, if the number of pico UEs or the pico connection UE ratio decreases as a result of the decrease in the bias value, it is estimated that if the bias value increases, the number of pico UEs or the pico connection UE ratio increases. In this case, the CRE bias control unit 322 increases the bias value. Thereby, the coverage area PC2 of PeNB300 expands and traffic distribution is achieved.

Thereafter, when the transmission power of the PeNB 300 is not the minimum value, the pico transmission power control unit 323 performs control to decrease the transmission power of the PeNB 300. Further, the CRE bias controller 322 increases the bias value. By reducing the transmission power of the PeNB 300 and increasing the bias value at the same time, it is possible to reduce the variation in the coverage area PC2 of the PeNB 300 in which traffic can be distributed.

(Third process)
The pico transmission power control unit 323 determines whether the number of macro UEs or the macro connection UE ratio that is information on the number of macro UEs has increased. Specifically, the pico transmission power control unit 323 reads the latest macro UE number or macro connection UE ratio information and the previous macro UE number or macro connection UE ratio information from the storage unit 330. Further, the pico transmission power control unit 323 increases the number of macro UEs or the ratio of macro connected UEs when the latest number of macro UEs or the ratio of macro connected UEs is larger than the previous number of macro UEs or the ratio of macro connected UEs. Judge that On the other hand, the pico transmission power control unit 323 reduces the number of macro UEs or the ratio of macro connected UEs when the latest number of macro UEs or the ratio of macro connected UEs is less than the number of macro UEs or macro connected UEs one before. Judge that

Also, the pico transmission power control unit 323 determines whether or not the traffic amount corresponding to the large cell MC1 has decreased. Specifically, the pico transmission power control unit 323 reads the traffic amount information corresponding to the latest large cell MC1 and the traffic amount information corresponding to the previous large cell MC1 from the storage unit 330. Further, the pico transmission power control unit 323 increases the traffic volume corresponding to the large cell MC1 when the traffic volume corresponding to the latest large cell MC1 is larger than the traffic volume corresponding to the previous large cell MC1. Judge that On the other hand, the pico transmission power control unit 323 reduces the traffic volume corresponding to the large cell MC1 when the traffic volume corresponding to the latest large cell MC1 is smaller than the traffic volume corresponding to the previous large cell MC1. Judge that

When the number of macro UEs or the macro connection UE ratio is increased and the traffic volume corresponding to the large cell MC1 is increasing, the control unit 320 performs the following low power base station control 1 processing.

In the process of the low power base station control 1, the pico transmission power control unit 323 determines whether or not the transmission power of the PeNB 300 is the minimum value. When the transmission power of the PeNB 300 is the minimum value, the CRE bias control unit 322 increases the bias value. As the bias value increases, the coverage area PC2 of the PeNB 300 expands. As the coverage area PC2 of the PeNB 300 expands, the connection destination of some UEs connected to the MeNB 100 is switched to the PeNB 300. For this reason, the traffic corresponding to the large cell MC1 is distributed.

On the other hand, when the transmission power of the PeNB 300 is not the minimum value, the pico transmission power control unit 323 performs control to reduce the transmission power of the PeNB 300. Further, the CRE bias controller 322 increases the bias value. By reducing the transmission power of the PeNB 300, it is possible to prevent interference from occurring in wireless communication between the MeNB 100 and the UE 200. Further, the coverage area PC2 of the PeNB 300 is expanded due to the increase of the bias value, and the connection destination of some UEs connected to the MeNB 100 is switched to the PeNB 300. For this reason, the traffic corresponding to the large cell MC1 is distributed.

When the number of macro UEs or the macro connection UE ratio increases and the traffic volume corresponding to the large cell MC1 does not increase, the control unit 320 performs the following low power base station control 2 processing.

In the process of the low power base station control 2, the pico transmission power control unit 323 determines whether or not the transmission power of the PeNB 300 is the maximum value. When the transmission power of the PeNB 300 is the maximum value, the CRE bias control unit 322 increases the bias value. As the bias value increases, the coverage area PC2 of the PeNB 300 expands. As the coverage area PC2 of the PeNB 300 expands, the connection destination of some UEs connected to the MeNB 100 is switched to the PeNB 300. For this reason, the traffic corresponding to the large cell MC1 is distributed.

On the other hand, when the transmission power of the PeNB 300 is not the maximum value, the pico transmission power control unit 323 performs control to increase the transmission power of the PeNB 300. Further, the CRE bias controller 322 increases the bias value. The coverage area PC2 of the PeNB 300 expands due to an increase in the transmission power of the PeNB 300 and an increase in the bias value, and the connection destination of some UEs connected to the MeNB 100 is switched to the PeNB 300. For this reason, the traffic corresponding to the large cell MC1 is distributed.

When the number of macro UEs or the ratio of macro connected UEs has not increased and the traffic volume corresponding to the large cell MC1 has increased, the control unit 320 performs the following low power base station control 3 processing: Do.

In the process of the low power base station control 3, the pico transmission power control unit 323 determines whether or not the transmission power of the PeNB 300 is the minimum value. When the transmission power of the PeNB 300 is the minimum value, the CRE bias control unit 322 decreases the bias value.

On the other hand, when the transmission power of the PeNB 300 is not the minimum value, the pico transmission power control unit 323 performs control to reduce the transmission power of the PeNB 300. Further, the CRE bias control unit 322 maintains the bias value. By reducing the transmission power of the PeNB 300, it is possible to prevent interference from occurring in wireless communication between the MeNB 100 and the UE 200.

When the number of macro UEs or the ratio of macro connected UEs does not increase and the traffic volume corresponding to the large cell MC1 does not increase, the control unit 320 performs the following low power base station control 4 processing: Do.

In the process of the low power base station control 4, the pico transmission power control unit 323 determines whether or not the transmission power of the PeNB 300 is the maximum value. When the transmission power of the PeNB 300 is the minimum value, the CRE bias control unit 322 decreases the bias value.

On the other hand, when the transmission power of the PeNB 300 is not the maximum value, the pico transmission power control unit 323 performs control to increase the transmission power of the PeNB 300. Further, the CRE bias control unit 322 maintains the bias value. As the transmission power of the PeNB 300 increases, the coverage area PC2 of the PeNB 300 expands, and the connection destination of some UEs connected to the MeNB 100 is switched to the PeNB 300. For this reason, the traffic corresponding to the large cell MC1 is distributed.

(2) Operation of Low Power Base Station Next, the operation of PeNB 300 will be described. FIG. 3 is a flowchart showing a first operation of PeNB 300 according to the embodiment of the present invention. The operation shown in FIG. 3 corresponds to the first process described above. In the following, information on the number of macro UEs is assumed to be the number of macro UEs.

In step S101, the control unit 320 sets the bias value to 0 and sets the transmission power (pico transmission power) of the PeNB 300 to the minimum value.

In step S102, the control unit 320 increases the bias value. In step S103, the control unit 320 determines whether or not the number of macro UEs has decreased. When the number of macro UEs decreases, the operation after the increase of the bias value in step S102 is repeated.

On the other hand, when the number of macro UEs has not decreased, in step S104, the control unit 320 determines whether or not the pico transmission power is the maximum value. When the pico transmission power is not the maximum value, in step S105, the control unit 320 increases the pico transmission power. Further, in step S106, the control unit 320 decreases the bias value. Thereafter, the operation after the increase of the bias value in step S102 is repeated.

When it is determined in step S104 that the pico transmission power is not the maximum value, the control unit 320 decreases the bias value in step S107. In step S108, the control unit 320 determines whether or not the number of macro UEs has increased. If the number of macro UEs has not increased, the operation after the decrease of the bias value in step S107 is repeated.

On the other hand, when the number of macro UEs increases, in step S109, the control unit 320 increases the bias value. Further, in step S110, control unit 320 determines whether or not the pico transmission power is the minimum value. When the pico transmission power is the minimum value, the operation after the increase of the bias value in step S102 is repeated.

If the pico transmission power is not the minimum value, the control unit 320 decreases the pico transmission power in step S111. Further, in step S112, the control unit 320 increases the bias value. Thereafter, the operation after the decrease of the bias value in step S107 is repeated.

FIG. 4 is a flowchart showing a second operation of PeNB 300 according to the embodiment of the present invention. The operation shown in FIG. 4 corresponds to the second process described above. In the following, information on the number of pico UEs is assumed to be the number of pico UEs.

In step S201, the control unit 320 sets the bias value to 0 and sets the transmission power (pico transmission power) of the PeNB 300 to the minimum value.

In step S202, the control unit 320 increases the bias value. In step S203, the control unit 320 determines whether or not the number of pico UEs has increased. When the number of pico UEs increases, the operation after the increase of the bias value in step S102 is repeated.

On the other hand, when the number of pico UEs has not increased, in step S204, the control unit 320 determines whether or not the pico transmission power is the maximum value. If the pico transmission power is not the maximum value, in step S205, the control unit 320 increases the pico transmission power. Further, in step S206, the control unit 320 decreases the bias value. Thereafter, the operation after the increase of the bias value in step S202 is repeated.

If it is determined in step S204 that the pico transmission power is not the maximum value, the control unit 320 decreases the bias value in step S207. In step S208, control unit 320 determines whether or not the number of pico UEs has decreased. If the number of pico UEs has not decreased, the operation after the decrease of the bias value in step S207 is repeated.

On the other hand, when the number of pico UEs decreases, in step S209, the control unit 320 increases the bias value. Further, in step S210, control unit 320 determines whether or not the pico transmission power is the minimum value. When the pico transmission power is the minimum value, the operation after the increase of the bias value in step S202 is repeated.

If the pico transmission power is not the minimum value, in step S211, the control unit 320 decreases the pico transmission power. Further, in step S212, the control unit 320 increases the bias value. Thereafter, the operation after the decrease of the bias value in step S207 is repeated.

FIG. 5 is a flowchart showing a second operation of PeNB 300 according to the embodiment of the present invention. The operation shown in FIG. 5 corresponds to the third process described above. In the following, information on the number of macro UEs is assumed to be the number of macro UEs.

In step S301, the control unit 320 determines whether or not the number of macro UEs has increased. When it is determined in step S302 that the number of macro UEs has increased, in step S302, the control unit 320 determines whether or not the traffic amount corresponding to the large cell MC1 has increased. If it is determined in step S302 that the amount of traffic corresponding to the large cell MC1 has increased, the control unit 320 performs low power base station control 1 processing in step S303. After the process of the low power base station control 1, the operations after step S301 are repeated.

FIG. 6 is a flowchart showing the operation of the low power base station control 1. In step S401, the control unit 320 determines whether or not the pico transmission power is the minimum value. When the pico transmission power is the minimum value, in step S402, the control unit 320 increases the bias value. On the other hand, when the pico transmission power is not the minimum value, in step S403, the control unit 320 performs control to reduce the pico transmission power. In step S404, the control unit 320 increases the bias value.

Again, referring back to FIG. If it is determined in step S302 that the traffic volume corresponding to the large cell MC1 has not increased, the control unit 320 performs low power base station control 2 processing in step S304. After the process of the low power base station control 2, the operations after step S301 are repeated.

FIG. 7 is a flowchart showing the operation of the low power base station control 2. In step S501, control unit 320 determines whether or not the pico transmission power is the maximum value. When the pico transmission power is the maximum value, in step S502, the control unit 320 increases the bias value. On the other hand, when the pico transmission power is not the maximum value, in step S503, the control unit 320 performs control to increase the pico transmission power. In step S504, the control unit 320 increases the bias value.

Again, referring back to FIG. When it is determined in step S301 that the number of macro UEs has not increased, in step S305, the control unit 320 determines whether or not the traffic amount corresponding to the large cell MC1 has increased. When it is determined in step S305 that the traffic volume corresponding to the large cell MC1 has increased, the control unit 320 performs the low power base station control 3 process in step S306. After the process of the low power base station control 3, the operations after step S301 are repeated.

FIG. 8 is a flowchart showing the operation of the low power base station control 3. In step S601, control unit 320 determines whether or not the pico transmission power is a minimum value. When the pico transmission power is the minimum value, in step S602, the control unit 320 decreases the bias value. On the other hand, when the pico transmission power is not the minimum value, in step S603, the control unit 320 performs control to reduce the pico transmission power. In step S604, the control unit 320 maintains the bias value.

Again, referring back to FIG. In step S305, when it is determined in step S302 that the traffic volume corresponding to the large cell MC1 has not increased, the control unit 320 performs the low power base station control 4 process in step S307. After the process of the low power base station control 1, the operations after step S301 are repeated. After the process of the low power base station control 4, the operations after step S301 are repeated.

FIG. 9 is a flowchart showing the operation of the low power base station control 4. In step S701, control unit 320 determines whether or not the pico transmission power is the maximum value. When the pico transmission power is the maximum value, in step S702, the control unit 320 decreases the bias value. On the other hand, when the pico transmission power is not the maximum value, in step S703, the control unit 320 performs control to increase the pico transmission power. In step S704, the control unit 320 maintains the bias value.

FIG. 10 is a flowchart showing a third operation of the PeNB 300 according to the embodiment of the present invention. The operation shown in FIG. 10 corresponds to the third process described above. In the following, information on the number of macro UEs is assumed to be the number of macro UEs.

In step S801, the control unit 320 determines whether the traffic volume corresponding to the large cell MC1 has increased. When it is determined in step S801 that the traffic volume corresponding to the large cell MC1 has increased, in step S802, the control unit 320 determines whether or not the number of macro UEs has increased. If it is determined in step S802 that the number of macro UEs has increased, in step S803, the control unit 320 performs low power base station control 1 processing. The specific operation of the low power base station control 1 is shown in FIG. Therefore, the description is omitted.

When it is determined in step S802 that the number of macro UEs has not increased, in step S804, the control unit 320 performs the low power base station control 2 process. The specific operation of the low power base station control 2 is as shown in FIG. Therefore, the description is omitted.

When it is determined in step S801 that the traffic volume corresponding to the large cell MC1 has not increased, in step S805, the control unit 320 determines whether or not the number of macro UEs has increased. When it is determined in step S805 that the number of macro UEs has increased, in step S806, the control unit 320 performs low power base station control 3 processing. The specific operation of the low power base station control 3 is as shown in FIG. Therefore, the description is omitted.

When it is determined in step S805 that the number of macro UEs has not increased, the control unit 320 performs low power base station control 4 in step S807. The specific operation of the low power base station control 4 is shown in FIG. Therefore, the description is omitted.

(3) Action / Effect In the wireless communication system 1 according to the present embodiment, the PeNB 300 controls the bias value based on the increase or decrease in the number of macro UEs or the macro connection UE ratio. Specifically, the PeNB 300 increases the bias value when the number of macro UEs or the macro connection UE ratio increases, and maintains or decreases the bias value when the number of macro UEs or the macro connection UE ratio decreases. Let The number of macro UEs or the macro connected UE ratio is an index indicating the degree of traffic distribution. The PeNB 300 appropriately distributes traffic to the MeNB 100 and the PeNB 300 by controlling the bias value according to the increase / decrease of the number of macro UEs or the macro connection UE ratio. Moreover, since the transmission power of PeNB300 is maintained, the interference given to the radio | wireless communication between MeNB100 and macro UE200 under the said MeNB100 does not increase.

Moreover, PeNB300 performs transmission power control based on increase / decrease of the traffic volume corresponding to large cell MC1 with control of the bias value based on the number of macro UEs or a macro connection UE ratio. Specifically, PeNB300 reduces transmission power, when the traffic amount corresponding to large cell MC1 increases. When the traffic volume corresponding to the large cell MC1 is increasing, the number of radio communications that may cause interference due to radio communication between the PeNB 300 and the UE 400 among radio communications between the MeNB 100 and the UE 200 increases. Can be considered. For this reason, it can prevent that interference arises in the radio | wireless communication between MeNB100 and UE200 by the transmission power of PeNB300 reducing.

Moreover, PeNB300 increases transmission power, when the traffic amount corresponding to large cell MC1 reduces. When the transmission power of the PeNB 300 increases, there is a high possibility that interference occurs in radio communication between the MeNB 100 and the UE 200. However, when the traffic volume corresponding to the large cell MC1 is decreasing, even if the transmission power of the PeNB 300 is increased, it can be considered that the number of radio communications that may cause interference is decreasing. For this reason, PeNB300 increases transmission power. Thereby, traffic is appropriately distributed to MeNB100 and PeNB300.

(4) Other Embodiments As described above, the present invention has been described according to the embodiment. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

In the above-described embodiment, the PeNB 300 controls the bias value and the transmission power of the PeNB 300 in accordance with the increase or decrease in the number of macro UEs or the macro connection UE ratio, or the number of pico UEs or the pico connection UE ratio. However, the PeNB 300 may control the bias value and the transmission power in order to distribute traffic when the number of macro UEs 200 is equal to or greater than a predetermined value. In addition, when the ratio of the number of macro UEs 200 to the value obtained by adding the number of macro UEs 200 and the number of pico UEs 400 (the number of all UEs) is equal to or greater than a predetermined value, PeNB 300 Alternatively, the transmission power of PeNB 300 may be controlled.

In the above-described embodiment, the wireless communication system 1 is configured based on LTE Release 9 or LTE-Advanced, but may be configured based on other communication standards.

Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters in the scope of claims reasonable from this disclosure.

Note that the entire content of Japanese Patent Application No. 2010-233805 (filed on October 18, 2010) is incorporated herein by reference.

As described above, according to the wireless communication system, the low power base station, and the communication control method according to the present invention, traffic can be effectively distributed in the heterogeneous network, so that wireless communication such as mobile communication is possible. Useful in.

Claims

A wireless communication system including a high power base station and a low power base station having a transmission output smaller than that of the high power base station,
The low power base station includes a control unit that controls a bias value that is a value that is used to expand a cell range of the low power base station and that is a value that is used in a process of determining a connection destination of a wireless terminal. Prepared,
The controller is
Controlling the bias value based on information from the high power base station;
The wireless communication system, wherein the information from the high power base station is information related to the number of wireless terminals connected to the high power base station.
A low-power base station with lower transmission power than a high-power base station,
A control unit for controlling a bias value, which is a value used for extending a cell range of the low power base station, and a value used in a process of determining a connection destination of a wireless terminal;
The controller is
Controlling the bias value based on information from the high power base station;
The information from the high power base station is a low power base station that is information related to the number of wireless terminals connected to the high power base station.
The low power base station according to claim 2, wherein the control unit increases the bias value when recognizing that the number of wireless terminals connected to the high power base station has increased.
The low power base station according to claim 2, wherein the control unit maintains or decreases the bias value when recognizing that the number of wireless terminals connected to the high power base station has decreased.
The control unit acquires information on the number of wireless terminals connected to the low power base station, and controls the bias value based on the information on the number of wireless terminals connected to the low power base station. The low power base station according to claim 2.
The low power base station according to claim 5, wherein the control unit maintains or decreases the bias value when recognizing that the number of wireless terminals connected to the low power base station has increased.
The low power base station according to claim 2, wherein the control unit increases the bias value when recognizing that the number of wireless terminals connected to the low power base station has decreased.
The control unit controls transmission power of the low power base station based on information from the high power base station,
The low-power base station according to claim 2, wherein the information from the high-power base station is information related to a communication amount corresponding to a cell formed by the high-power base station.
The low power base station according to claim 2, wherein the control unit reduces the transmission power of the low power base station when a communication amount corresponding to a cell formed by the high power base station increases.
The low power base station according to claim 2, wherein the control unit increases the transmission power of the low power base station when a communication amount corresponding to a cell formed by the high power base station decreases.
A communication control method in a low power base station having a transmission output smaller than that of a high power base station,
Including a step of controlling a bias value which is a value used for extending a cell range of the low power base station and used in a process of determining a connection destination of a wireless terminal,
In the controlling step,
Controlling the bias value based on information from the high power base station;
The communication control method, wherein the information from the high power base station is information relating to the number of wireless terminals connected to the high power base station.