JP2005244906A - Mobile communication system, mobile station device, sector device and communication control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce interference quantity in a sector device depending on the interference quantity in the sector device. <P>SOLUTION: A mobile communication system by a code division multiplex access system including a plurality of sector devices comprises an interference measurement unit 42 for measuring information indicating interference quantity at least in one sector device, and a handover management unit 40 for performing an instruction to allow at least one mobile station during communication at least with the one sector device to perform handover to anther sector device if the information indicating the interference quantity exceeds a predetermined threshold. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a mobile communication system, a mobile station apparatus, a sector apparatus, and a communication control method.

  For example, in a mobile communication system such as a cellular phone system, a mobile station apparatus receives a large number of receivable pilot signals transmitted from each sector apparatus of a base station apparatus. And it communicates with the sector apparatus with the best reception state of the pilot signal. In this way, communication can be performed in the most favorable state.

In Patent Document 1, in a wireless communication system including a plurality of wireless base stations and a plurality of wireless terminals, the roaming frequency of the wireless terminals is reduced, the communication load is distributed to the plurality of wireless base stations, and the wireless terminals As a final effect, an invention relating to obtaining an improvement in the throughput of a wireless communication system is disclosed by always connecting a wireless base station with a high reception strength and performing stable communication.
JP 2003-235069 A

  However, in the conventional method, when the mobile phone system uses a CDMA (Code Division Multiple Access) method, the amount of interference for each sector device may be biased. That is, there are cases where many of the mobile station devices communicate with one sector device even though they can communicate with other sector devices, such as when a large number of mobile station devices exist locally. In such a case, since the amount of interference in the sector device becomes large, it may be impossible to obtain an information code by demodulation and communication may not be possible.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a mobile communication system, a mobile station device, and a sector device that can reduce the amount of interference in the sector device according to the amount of interference in the sector device. And providing a communication control method.

  In order to solve the above problems, the present invention is a mobile communication system based on a code division multiple access system including a plurality of sector devices, measuring means for measuring information indicating the amount of interference in at least one sector device, Handover instruction means for instructing at least one mobile station apparatus communicating with the at least one sector apparatus to perform handover to another sector apparatus when the information indicating the amount of interference exceeds a predetermined threshold; It is characterized by including.

  In this way, when the interference amount in the sector device exceeds a predetermined threshold, the mobile station device communicating with the sector device can be handed over to another sector device that can communicate, and the interference amount is predetermined. The amount of interference in the sector device exceeding the threshold value can be reduced.

  In the communication system, a storage unit that stores one or a plurality of sector device identification information that respectively identifies one or a plurality of other sector devices with which the at least one mobile station device can communicate, and a storage unit that stores the information Among the one or more other sector devices identified by the one or more sector device identification information, the at least one mobile station device selects a sector device to be handed over in accordance with an instruction from the handover instruction means And a handover destination sector selecting means. In this way, the mobile station apparatus can continue communication after the handover.

  Further, in the communication system, the storage means associates the sector device identification information with the reception intensity of the radio waves from other sector devices identified by the sector device identification information in the at least one mobile station device. Further, the handover destination sector selection means is based on the reception strength from the one or more other sector devices identified by the one or more sector device identification information stored in the storage means. The sector device to be handed over by the at least one mobile station device may be selected. In this way, the mobile station apparatus can continue communication in a good communication state after the handover.

  Further, in the communication system, the handover destination sector selection unit includes the one or more other sector devices identified by the one or more sector device identification information stored in the storage unit. The sector device to be handed over by the at least one mobile station device may be selected based on information indicating the interference amount of one or a plurality of sector devices. In this way, the mobile station apparatus can continue communication with the sector apparatus with less interference after the handover.

  In addition, the mobile station apparatus according to the present invention includes handover means for handing over the mobile station apparatus to another sector apparatus capable of communication when the information indicating the amount of interference in the communicating sector apparatus exceeds a predetermined threshold. It is characterized by that. In this way, when the information indicating the amount of interference in the sector device exceeds a predetermined threshold, the mobile station device can autonomously perform handover and reduce the amount of interference in the sector device.

  In addition, the sector device according to the present invention includes a measuring unit that measures information indicating an interference amount in the own sector device, and at least one during communication with the own sector device when the information indicating the interference amount exceeds a predetermined threshold. And handover instruction means for instructing one mobile station apparatus to perform handover to another sector apparatus.

  The communication control method according to the present invention includes a step of measuring information indicating an amount of interference in at least one sector device, and the information indicating the amount of interference exceeds the predetermined threshold when the information indicating the amount of interference exceeds a predetermined threshold. Instructing at least one mobile station apparatus in communication to perform handover to another sector apparatus.

  Embodiments of the present invention will be described with reference to the drawings. A mobile communication system 4 according to the present embodiment includes a plurality of mobile station apparatuses 1, a plurality of base station apparatuses 2, and a communication network 3, as shown in FIG. The base station device 2 normally communicates with a plurality of mobile station devices 1.

  As the mobile telephone system 4 using the CDMA (Code Division Multiple Access) system, there are CDMA2000 and W-CDMA. In these systems, a signal (information code) including certain information is first-ordered into a signal such as ASK (amplitude shift keying), FSK (frequency conversion modulation), or PSK (phase shift keying) on the transmission side. Modulated. Next, the first-order modulated primary modulated wave is a waveform called a PN (Pseudorandom Noise) sequence, for example, a waveform in which +1 or −1 appear in a random order, and is multiplied by a function having extremely high autocorrelation. By doing so, it is converted into a secondary modulated wave. Then, the secondary modulated wave is transmitted to the radio section through processing such as superposition on a carrier wave. Here, obtaining the secondary modulation wave from the primary modulation wave is called diffusion. On the demodulation side, the original primary modulated wave can be obtained by multiplying the received secondary modulated wave by the same PN sequence. Here, obtaining the primary modulation wave from the secondary modulation wave is called despreading. By doing so, even when an interference wave enters during transmission / reception, the interference wave cannot be despread even if multiplied by the PN sequence, and is further diffused. For this reason, even when there is interference, there is an effect that the possibility of demodulation is high.

  In the above scheme, by making the PN sequence different for each mobile station device, signals to be transmitted / received to / from each mobile station device are identified. For this reason, for example, when there are a large number of mobile station apparatuses and each transmits a signal by the above method, each signal becomes an interference wave with respect to another signal. When there are many interference waves, the influence of the interference waves cannot be ignored when despreading. When the interference waves exceed a certain amount, a primary modulated wave cannot be obtained by despreading. That is, new calls and new information codes are not accepted by the base station. The amount of the interference wave is generally called an interference amount, and is usually represented by a signal-to-noise ratio (S / N ratio) or a carrier power-to-noise power ratio (C / N ratio). The amount of interference can be calculated for each mobile station device 1, and the amount of interference for the sector device as a whole can be the statistical amount. Specifically, it may be the total amount of interference for each mobile station apparatus 1 or an average value.

  In the present embodiment, the amount of interference in the sector device can be reduced according to the amount of interference in the sector device. The process will be described in detail below.

  As shown in FIG. 3, the mobile station device 1 used in the present embodiment includes a control unit 11, a communication unit 12, a storage unit 13, an operation unit 14, and a display unit 15. Yes. The control unit 11 controls each unit of the mobile station device 1 and executes processing related to a call and data communication. Moreover, the control part 11 is also performing the process for determining the transmission rate, when transmitting the packet for communication used in data communication via the communication part 12. FIG. The communication unit 12 includes an aerial line, and in accordance with an instruction input from the control unit 11, modulates a voice signal, a communication packet, and the like and outputs the modulated signal or the voice signal arriving at the aerial line. It receives and demodulates and outputs it to the control unit 11.

  The storage unit 13 operates as a work memory for the control unit 11. The storage unit 13 holds programs and parameters related to various processes performed by the control unit 11. The operation unit 14 is, for example, a numeric keypad, and receives a telephone number or a character string from a user and outputs it to the control unit 11. The display unit 15 is configured to include, for example, a liquid crystal display device, and displays and outputs information according to a signal input from the control unit 11.

  Next, as shown in FIG. 2, the base station apparatus 2 includes three sector apparatuses 101d, 102d, and 103d. The number of sector devices is not limited to three, and is usually configured by one to six. Each of the sector devices 101d, 102d, and 103d includes a sector control unit 21, a network interface unit 22, a wireless communication unit 23, and a storage unit 24. The sector control unit 21 controls each unit of the sector device, and executes processing related to telephone calls and data communication. The network interface unit 22 is connected to the communication network 3 and receives an audio signal, a communication packet, and the like from the communication network 3 and outputs them to the sector control unit 21, or according to an instruction from the sector control unit 21 A communication packet or the like is transmitted to the communication network 3. The wireless communication unit 23 includes an antenna, receives and demodulates a voice signal, a communication packet, and the like from at least one mobile station apparatus 1 and outputs the received signal to the sector control unit 21 or input from the sector control unit 21. In accordance with the instruction, the voice signal or communication packet input from the sector control unit 21 is modulated and output via the antenna. The storage unit 24 operates as a work memory for the sector control unit 21. Further, the storage unit 24 holds programs and parameters related to various processes performed by the sector control unit 11.

  As shown in FIG. 8, each sector device included in the base station device 2 forms a wireless communication area, that is, a first sector 101a, a second sector 102a, and a third sector 103a in each direction around the base station device 2. To do. Each sector sometimes overlaps with other sectors. Then, the sector device 101d communicates with a plurality of normal mobile station devices 1 located in the corresponding first sector 101a. The sector device 102d communicates with a plurality of normal mobile station devices 1 located in the corresponding second sector 102a. Further, the sector device 103d communicates with a plurality of normal mobile station devices 1 located in the corresponding third sector 103a. In the figure, since the mobile station apparatus 1 is in both the first sector 101a and the third sector 103a of the base station apparatus 2, the first sector apparatus 101d and the third sector apparatus 103d of the base station apparatus 2 are used. It is possible to communicate with any of these. In such a case, in the prior art, the mobile station apparatus 1 performs communication by selecting a sector apparatus with a better pilot signal reception state. In the figure, a single base station apparatus 2 is shown. However, when there is another base station apparatus 2 and communication with the sector apparatus of the other base station apparatus 2 is possible, the sector A pilot signal from the apparatus is also received, and a sector apparatus having the best pilot signal reception state is selected to perform communication.

  Furthermore, the base station apparatus 2 includes a base station apparatus control unit 25 and a storage unit 26 that are common to the sector apparatuses. The base station device control unit 25 controls the sector control unit 21 of each sector device. The storage unit 26 operates as a work memory for the base station apparatus control unit 25. Further, the storage unit 26 holds programs and parameters related to various processes performed by the base station apparatus control unit 25.

  When each sector device of the base station device 2 communicates with the mobile station device 1 using the wireless communication unit 23, a traffic channel and a control channel can be used as logical channels. Traffic channels include uplink and downlink communication channels and power control channels. Voice signals and communication packets are transmitted and received on the upstream and downstream communication channels. Uplink means communication from the mobile station apparatus 1 to each sector apparatus of the base station apparatus 2, and downlink means communication from each sector apparatus of the base station apparatus 2 to the mobile station apparatus 1. The power control channel is a channel for each sector device of the base station device 2 to control the antenna power of the mobile station device 1. The control channel includes an uplink access channel, a downlink pilot channel, a synchronization channel, and a paging channel. The access channel is a channel for transmitting a signal from the mobile station device 1 to each sector device of the base station device 2, and includes an uplink dedicated control channel. The pilot channel and the synchronization channel are channels for synchronizing each sector device of the base station device 2 and the mobile station device 1. The paging channel is a channel for each sector device of the base station device 2 to transmit control information of the mobile station device 1 to the mobile station device 1, and is transmitted to all mobile station devices 1 that can communicate at the same time. Common downlink control channels and downlink individual control channels for communicating with individual mobile station apparatuses 1 are included. In the common control channel, specifically, information indicating the amount of interference and information such as transmission restrictions are broadcast to all mobile station apparatuses that can communicate. In the dedicated control channel, various signals used in the communication sequence for controlling each mobile station apparatus are transmitted and received.

  A signal on each logical channel, which is directed from the base station device 2 to the mobile station device 1, is included in a physical downlink channel composed of CDMA radio carriers, and is transmitted from the mobile station device 1 to the base station. A signal directed to the station apparatus 2 is included in a physical uplink channel (hereinafter referred to as an “uplink channel”) composed of CDMA radio carriers.

  FIG. 4 is a functional block diagram of mobile station apparatus 1 and base station apparatus 2 used in the present embodiment. The mobile station device 1 is functionally configured to include a handover control unit 43, a reception intensity measurement unit 45, and a data transmission unit 47. On the other hand, the base station apparatus 2 includes each sector device including a handover management unit 40, an interference measurement unit 42, a pilot signal transmission unit 44, and a data reception unit 46. Furthermore, the base station apparatus 2 includes an interference state management unit 48 that is common to the sector apparatuses. The interference state management unit 48 can also be provided in an exchange or SCP (Service Control Point) installed on the communication network 3 in addition to the base station apparatus 2. In this way, handover by the process shown in the present embodiment can be performed not only between sector devices of the same base station device, but also between sector devices straddling different base stations and exchanges. For simplicity in the present embodiment, the interference state management unit 48 will be described as being provided in the base station apparatus 2. That is, when the mobile station apparatus 1 exists in a portion where areas overlap each other in each sector apparatus in the same base station apparatus 2, the processing according to the present embodiment is performed. In the initial state of the present embodiment, it is assumed that mobile station apparatus 1 is communicating with first sector apparatus 101d of base station apparatus 2.

  Hereinafter, a specific example of processing performed in this embodiment will be described in detail with reference to FIGS. 4 to 7. FIG. 5 is a sequence diagram of processing according to the present embodiment.

  The pilot signal transmission unit 44 of each sector device transmits a pilot signal to all mobile station devices 1 that can communicate using the pilot channel (S102, S103, S104). Then, the reception intensity measuring unit 45 of the mobile station apparatus 1 that has received the pilot signal from each sector apparatus of each base station apparatus 2 associates the reception intensity of the pilot signal with the sector apparatus identification information in FIG. This is stored in the illustrated table (handover destination candidate sector list). The sector device identification information is usually a sector number uniquely determined in the communication network 3 for each sector. However, it is a sector device that spans different base stations or exchanges within its own base station device, and can be handed over to a sector device that uses a different frequency band, in which case, in order to identify the sector device, In addition to the sector number, information indicating a frequency band is preferably added to the list in the sector device identification information.

  The reception strength measurement unit 45 further determines the transmission rate and antenna power when the data transmission unit 47 transmits the information code using the uplink communication channel based on the reception strength of the pilot signal from the communicating sector device. Decide and notify the data transmitter 47.

  The data transmission unit 47 transmits the information code of the transmission rate to the first sector device 101d as a modulated wave obtained by modulating / spreading. Then, the data receiving unit 46 of the first sector device 101d receives the transmitted modulated wave and performs despreading / decoding, etc., thereby obtaining an information code, transmitting the information code to the communication network 3, etc. Data processing is performed.

  The transmission / reception of the information code and the transmission / reception of the pilot signal and the update of the handover destination candidate sector list (S105) from the mobile station apparatus 1 to the first sector apparatus 101d are continuously performed during the processing according to the present embodiment. Implemented (S101, S102, S103, S104).

  Next, the interference measurement unit 42 of the first sector device 101d measures the uplink channel interference amount. Specifically, the amount of interference may be measured from the ratio of the signal received in the uplink channel and noise, or the amount of interference may be measured from the ratio of carrier power and noise power in the uplink channel. When the measured amount of interference exceeds a predetermined threshold, it is detected that the amount of interference is large (S106), and it is determined that there is excessive interference and all mobile station apparatuses 1 in communication are in communication. In contrast, the common control channel is used to notify that there is excessive interference (S108). At the same time, the handover management unit 40 is also notified.

  Then, the handover management unit 40 makes a peripheral sector state inquiry to the interference state management unit 48 (S107). The interference state management unit 48 creates a new peripheral sector interference amount list by performing an interference state inquiry (S115) to each sector device (S116), and notifies the handover management unit 40 (S109). The peripheral sector interference amount list is a table that stores the sector device identification information and the interference amount of each sector device in association with each other as illustrated in FIG. The total S / N ratio for each mobile station apparatus in the table indicates the amount of interference, and the larger the value, the smaller the amount of interference. In addition to the total S / N ratio, for example, a C / N ratio may be used. That is, any value indicating the influence of radio waves emitted from one mobile station apparatus on decoding of signals from other mobile station apparatuses in CDMA may be used.

  On the other hand, when notified from the interference measurement unit 42 of the first sector device 101d that there is excessive interference, the handover control unit 43 reads the handover destination candidate sector list stored in the reception intensity measurement unit 45, and It transmits to the handover management part 40 of the 1st sector apparatus 101d using a control channel (S110). Here, only the sector device identification information included in the list may be transmitted. Then, the handover management unit 40 extracts only the sector devices existing in the handover destination candidate sector list received from the handover control unit 43 from the peripheral sector interference amount list received from the interference state management unit 48 and extracts the peripheral sector interference amount list. The same sector interference amount list is created (S111) and notified to the handover control unit 43 (S112). Then, the handover control unit 43 selects the most suitable sector device (sector device with good pilot signal reception state and low interference) based on the information on the interference amount of each sector device included in the sector interference amount list. select. For example, “a sector device having a pilot signal reception strength of 10 dB or more and an interference amount of 0 dB or more” or “a sector device having the highest pilot signal reception strength within −5 dB and the most interference among the sector devices. It is also possible to impose a specific selection condition such as “a sector apparatus having a small amount” and select a sector apparatus satisfying the selection condition. Then, the data transmission unit 47 of the mobile station apparatus 1 transmits a handover request to the selected sector apparatus (S113). When there is a handover request response from the sector device that transmitted the handover request (S114), a handover process is performed with the sector device.

  In addition, when notifying the over-interference state to the mobile station apparatus 1 in S108, the over-interference state may be notified only to a specific mobile station apparatus. Specifically, for example, it may be notified only to the mobile station apparatus 1 in which the received power in the first sector apparatus 101d exceeds a predetermined value. Moreover, it is good also as notifying only the mobile station apparatus 1 with the largest transmission waiting data amount of a downlink communication channel among the mobile station apparatuses 1 in communication. In these cases, the over-interference state notification in S108 may be performed through the dedicated control channel. As a result, the first sector device 101d can perform handover by designating a specific mobile station device 1.

  According to the present embodiment, when a large number of mobile station devices exist locally, a part of the mobile station devices can be handed over to another sector device, thereby reducing the bias of the interference amount for each sector device. Can do. In addition, the mobile station device 1 can continue communication after the handover. In handover, a sector device having the best condition can be selected from communicable sector devices. Furthermore, when the amount of interference in the sector device is large, the sector device does not become a handover destination, so that the mobile station device 1 performs handover to the handover destination sector device, which adversely affects the communication of other mobile station devices 1. There is less fear.

  The present invention is not limited to the above embodiment.

  For example, in the processing in S111 and S112 of FIG. It is also possible to select a candidate sector device to be notified and notify the handover control unit 43 of it. That is, in the first sector device 101d, the most suitable sector device (the reception state of the pilot signal is good) based on information on the sector device with which the mobile station device 1 can communicate and information on the interference amount of each sector device. , A sector apparatus having a small amount of interference) is selected and notified to the handover control unit 43. When the handover control unit 43 does not notify the first sector device 101d of the handover destination candidate sector list, the first sector device 101d may transmit the peripheral sector interference amount list to the handover control unit 43. It should be noted that the criteria for a suitable sector device are based on station data in order to determine an appropriate range according to the circumstances of each base station device, such as the installation location of the sector device, the influence of fading, and the time zone. It is good also as setting.

1 is a configuration diagram of a mobile communication system according to an embodiment of the present invention. It is a block diagram of the configuration of a base station apparatus according to an embodiment of the present invention. FIG. 2 is a configuration block diagram of a mobile station apparatus according to an embodiment of the present invention. 1 is a functional block diagram of a mobile communication system according to an embodiment of the present invention. It is a sequence diagram of processing according to an embodiment of the present invention. It is a figure which shows the handover destination candidate sector list which concerns on embodiment of this invention. It is a figure which shows the surrounding sector interference amount list | wrist which concerns on embodiment of this invention. It is a block diagram of the sector apparatus which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mobile station apparatus, 2 Base station apparatus, 3 Communication network, 4 Mobile communication system, 11 Control part, 12 Communication part, 13 Storage part, 14 Operation part, 15 Display part, 21 Sector control part, 22 Network interface part, 23 wireless communication unit, 24 storage unit, 25 base station apparatus control unit, 26 storage unit, 40 handover management unit, 42 interference measurement unit, 43 handover control unit, 44 pilot signal transmission unit, 45 reception strength measurement unit, 46 data reception Unit, 47 data transmission unit, 48 interference state management unit, 101a, 102a, 103a sector, 101d, 102d, 103d sector device.

Claims (7)

A mobile communication system using a code division multiple access system including a plurality of sector devices,
Measuring means for measuring information indicating the amount of interference in at least one sector device;
Handover information means for instructing at least one mobile station apparatus communicating with the at least one sector apparatus to perform handover to another sector apparatus when the information indicating the interference amount exceeds a predetermined threshold;
A mobile communication system comprising: The mobile communication system according to claim 1, wherein
Storage means for storing one or a plurality of sector device identification information for respectively identifying one or a plurality of other sector devices with which the at least one mobile station device can communicate;
Among the one or more other sector devices identified by the one or more sector device identification information stored in the storage means, the at least one mobile station device performs handover according to an instruction from the handover instruction means. A handover destination sector selection means for selecting a sector device;
A mobile communication system, further comprising: The mobile communication system according to claim 2, wherein
The storage means further stores, in association with the sector device identification information, a reception intensity at the at least one mobile station device of a radio wave from another sector device identified by the sector device identification information,
The handover destination sector selection unit is configured to select the at least one of the one or more other sector devices identified by the one or more sector device identification information stored in the storage unit based on the reception strength. One mobile station device selects a sector device to be handed over,
A mobile communication system. The mobile communication system according to any one of claims 2 to 3,
The handover destination sector selecting means includes the one or more sector devices identified from the one or more other sector devices identified by the one or more sector device identification information stored in the storage means. Based on the information indicating the amount of interference, the sector device to be handed over by the at least one mobile station device is selected.
A mobile communication system. A mobile station apparatus used in a mobile communication system using a code division multiple access system including a plurality of sector apparatuses,
Handover means for handing over the mobile station apparatus to another sector apparatus capable of communication when information indicating the amount of interference in the communicating sector apparatus exceeds a predetermined threshold;
A mobile station apparatus comprising: A sector device used in a mobile communication system using a code division multiple access system including a plurality of sector devices,
Measuring means for measuring information indicating the amount of interference in the own sector device;
Handover information means for instructing at least one mobile station apparatus in communication with its own sector apparatus to perform handover to another sector apparatus when the information indicating the amount of interference exceeds a predetermined threshold;
A sector apparatus comprising: A communication control method used in a mobile communication system using a code division multiple access system including a plurality of sector devices,
Measuring information indicating an amount of interference in at least one sector device;
Instructing at least one mobile station apparatus communicating with the at least one sector apparatus to perform handover to another sector apparatus when the information indicating the interference amount exceeds a predetermined threshold;
The communication control method characterized by including.

Images