JP4340126B2 - Base station apparatus selection method and terminal apparatus using the same - Google Patents

Description

  The present invention relates to a base station apparatus selection technique, and more particularly to a base station apparatus selection method for selecting a base station apparatus for communication from a plurality of base station apparatuses and a terminal apparatus using the same.

  In recent years, a cdma2000 1x-EV DO (hereinafter referred to as “EV-DO”) system has been developed as a next-generation high-speed wireless communication system. The EV-DO system is a cdma2000 1x (hereinafter also referred to as “1x”) system that extends the cdmaOne system and is compatible with the third generation system, and is a system that further specializes in data communication and increases the transmission rate. is there. Here, “EV” means Evolution, and “DO” means Data Optimized.

  In the EV-DO system, the configuration of the uplink radio interface from the radio communication terminal to the base station is almost the same as that of the cdma2000 1x system. Regarding the downlink radio interface configuration from the base station to the radio communication terminal, the bandwidth defined in 1.23 MHz is the same as that of the cdma2000 1x scheme, but the modulation scheme, multiplexing method, etc. are greatly different from those of the cdma2000 1x scheme. . The modulation scheme is switched from QPSK, HPSK used in the cdma2000 1x scheme to QPSK, 8-PSK, 16QAM in the EV-DO scheme according to the downlink reception state in the radio communication terminal. As a result, when the reception state is good, a high transmission rate with low error resistance is used, and when the reception state is bad, a transmission rate with low error but high error resistance is used.

  In addition, a multiplexing method for simultaneously performing communication from one base station to a plurality of wireless communication terminals is not code division multiple access (CDMA) used in the cdmaOne method or the cdma2000 1x method. The time is divided in units of 1/600 seconds, and communication is performed with only one wireless communication terminal within that time. Further, the wireless communication terminals to be communicated are switched every unit time to communicate with a plurality of wireless communication terminals. Use time division multiple access (TDMA) to perform.

  The wireless communication terminal measures the carrier-to-interference wave ratio (hereinafter referred to as “CIR: Carrier to Interference power Ratio”) of the pilot signal as the reception state of the downlink from the base station to be communicated, The reception state at the reception timing is predicted, and the expected “maximum transmission rate that can be received at a predetermined error rate or less” is notified to the base station as a data rate control bit (hereinafter referred to as “DRC: Data Rate Control bit”). To do. Here, the predetermined error rate depends on the system design, but is usually about several percent. The base station receives DRCs from a plurality of radio communication terminals, and the scheduler function in the base station determines which radio communication terminal to communicate with in each time division unit. Therefore, the highest possible transmission rate is used based on the DRC from the wireless communication terminal.

The EV-DO system enables a maximum transmission rate of 2.4 Mbps (Mega-bit per second) per sector in the downlink with the above configuration. However, this transmission rate is the total amount of data communication with a plurality of wireless communication terminals to which one base station is connected in one frequency band and one of a plurality of sectors, which is usually a plurality of frequencies. If the band is used, the transmission rate also increases.
JP 2002-300634 A

  Generally, an EV-DO wireless communication terminal derives DRCs for a plurality of base stations, and selects a base station apparatus having the highest transmission rate corresponding to the DRC as a communication target. On the other hand, since a base station of the EV-DO system connects a plurality of wireless communication terminals by TDMA, even if the transmission speed corresponding to DRC is high, if the number of connected wireless terminal apparatuses is large, it is substantially The data transmission speed becomes low. That is, in order to increase the data transmission rate of the wireless terminal device, it is necessary to consider the number of wireless terminal devices connected to the base station device.

  The present inventor has recognized the above situation and made the present invention. The purpose of the present inventor is to provide a base station apparatus selection method considering the number of terminal apparatuses connected to the base station apparatus and a terminal apparatus using the same. It is to provide.

One embodiment of the present invention is a terminal device. The apparatus includes: a derivation unit that derives an expected transmission rate for each of a plurality of communicable base station apparatuses based on signals received from a plurality of communicable base station apparatuses; and a plurality of communicable base station apparatuses Based on each of the acquisition means for acquiring the number of terminal devices connected to a plurality of communicable base station devices, the estimated transmission rate for the derived base station device, and the number of acquired terminal devices. A new transmission rate for a plurality of communicable base station devices is calculated, and a base station device to be communicated is selected from the plurality of communicable base station devices based on the calculated new transmission rate. Selection means and communication means for communicating with the selected base station apparatus.
With the above apparatus, in order to use the expected transmission rate and the number of terminal devices for selection of the base station device to be communicated, a base station device in which the transmission rate with the base station device becomes substantially high You can choose.

The number of terminal devices acquired by the acquisition unit may be the number of terminal devices communicating with each of a plurality of communicable base station devices. The number of terminal devices connected to a plurality of communicable base station devices acquired by the acquisition means further includes the number of terminal devices waiting for each of the plurality of communicable base station devices It is good also as the number of .

The selection means may select a base station apparatus to be communicated from among a plurality of communicable base station apparatuses when the communication means transmits a signal. Derived acquired the expected transmission rate to the base station apparatus and the number of terminal devices further includes a storage means for storing each of the selection means, based on the respective numbers of stored in the storage unit expected transmission rate and the terminal device a plurality A new transmission rate for the communicable base station device is selected, and a base station device to be communicated is selected from a plurality of communicable base station devices based on the calculated new transmission rate. Also good.

One embodiment of the present invention is a base station apparatus selection method. This method obtains an expected transmission rate for each of a plurality of communicable base station devices derived from signals received from a plurality of communicable base station devices and one of the plurality of communicable base station devices. Based on the number of terminal devices already connected to each of the plurality of communicable base station devices, a new transmission rate for the plurality of communicable base station devices is calculated, and based on the calculated new transmission rate The base station device to be communicated is selected from a plurality of communicable base station devices.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the base station apparatus selection method in consideration of the number of terminal devices connected to the base station apparatus, and a terminal apparatus using the same can be provided.

  An embodiment of the present invention relates to a terminal device that is in an environment capable of communicating with a plurality of base station devices and selects a base station device to be communicated from among them. The terminal device is assumed to be compatible with the EV-DO system. The terminal apparatus according to the present embodiment receives pilot signals from a plurality of base station apparatuses and derives DRCs corresponding to the respective base station apparatuses. Also, the number of terminal devices with which the base station device is communicating is acquired from a plurality of base station devices. Further, the terminal device calculates an expected communication speed corresponding to a plurality of base station devices based on the DRC and the number of terminal devices, and determines a base station device having the maximum expected communication speed as a communication target.

FIG. 1 shows a configuration of a communication system 100 according to an embodiment of the present invention. The communication system 100 includes a first base station device 12a, a second base station device 12b, and a network 32, which are collectively referred to as a terminal device 10 and a base station device 12. The terminal device 10 includes a communication unit 14, a data processing unit 16, a derivation unit 18, an acquisition unit 20, a storage unit 22, a selection unit 24, a control unit 30, and a determination unit 34. The selection unit 24 includes a calculation unit 26. The comparison unit 28 is included.
The base station apparatus 12 can communicate with a plurality of terminal apparatuses 10 in accordance with the EV-DO system. Here, two base station apparatuses 12 are shown, but more base station apparatuses 12 may be connected to the network 32. The network 32 is connected to a communication device such as a server having a predetermined function such as a WWW server.

  The communication unit 14 is compatible with the EV-DO system and communicates with the base station apparatus 12. The communication unit 14 includes an RF circuit, a frequency conversion circuit, an amplification circuit, a modulation circuit, a demodulation circuit, and the like. Data transmitted or to be transmitted between the base station apparatus 12 and the communication unit 14 is processed by the data processing unit 16. That is, the data processing unit 16 receives a request from the user via a predetermined interface, and provides the user with predetermined information based on the received data.

  The determination unit 34 sets the active base station device 12 as “Active Set” while waiting, and sets “Neighbor Set” as the “Neighbor Set” of other surrounding base station devices 12 that have a somewhat strong pilot signal strength. It is determined whether to shift from “Neighbor Set” to “Active Set”, that is, “Idel Hand-off”. On the other hand, during communication, the base station apparatus 12 that is currently communicating and the base station apparatus 12 that has a pilot signal strength that is strong enough to enable hand-off is referred to as “Active Set”, and the base station apparatus that has a pilot signal strength weaker than those. 12 is set as “Neighbor Set”, and it is determined whether or not to move from “Neighbor Set” to “Active Set”.

  The acquisition unit 20 receives a signal including the number of terminal devices 10 with which the base station device 12 is communicating from the base station device 12, and from the received signals, the terminal device 10 with which the base station device 12 is communicating. Get the number of. It is assumed that a signal including the number of terminal devices 10 with which the base station device 12 is communicating is transmitted at a timing described later. Note that the number of terminal apparatuses 10 included in the signal transmitted from the base station apparatus 12 may further include the number of terminal apparatuses 10 that are on standby with respect to the base station apparatus 12. In addition, the acquisition part 20 shall each receive the said signal from the several base station apparatus 12 like illustration.

The deriving unit 18 measures the CIR from the received pilot signal, and derives the DRC corresponding to the CIR of the measurement result. Note that the deriving unit 18 receives pilot signals from the plurality of base station apparatuses 12 as illustrated and derives DRCs corresponding thereto.
The storage unit 22 stores the number of terminal devices 10 acquired by the acquisition unit 20 and the DRC value derived by the deriving unit 18.

The calculation unit 26 calculates an expected communication speed from the maximum transmission rate with the base station apparatus 12 corresponding to the DRC value, the maximum DRC value, the DRC value derived by the deriving unit 18, and the number of terminal devices 10. Calculate as follows.
(Equation 1)
Expected communication speed = (maximum transmission speed with base station apparatus 12 corresponding to DRC value) / (number of terminal apparatuses 10 × (maximum DRC value / DRC value derived by deriving unit 18))

  Here, the correspondence between the DRC used in the derivation unit 18 and the transmission rate is shown in FIG. As shown in the figure, the DRC value is associated with a predetermined transmission rate, and both have a relationship that the transmission rate increases as the DRC value increases. An example of calculation of an expected communication speed is shown. Here, the maximum value of DRC is “12” as shown in FIG. The number of terminal devices 10 acquired by the acquiring unit 20 is “3”, the DRC derived by the deriving unit 18 is “6”, that is, the maximum transmission rate with the base station device 12 corresponding to DRC is “614. In the case of “4 (kbps)”, the expected communication speed is “102.4 (kbps)”. When the DRC derived by the deriving unit 18 is “9”, that is, when the maximum transmission rate with the base station apparatus 12 corresponding to the DRC is “1228.8 (kbps)”, the expected communication rate is “807”. .2 (kbps) ". When the DRC derived by the deriving unit 18 is “12”, that is, the maximum transmission speed with the base station apparatus 12 corresponding to the DRC is “2457.6 (kbps)”, the expected communication speed is “819.2”. (Kbps) ". The influence of other terminal devices 10 (not shown) connected to the base station device 12 can be taken into account by such an expected communication speed.

Another calculation example of the expected communication speed is shown. When the number “8” of the terminal devices 10 is received from the first base station device 12a and the DRC of the first base station device 12a derived by the deriving unit 18 is “12”, the expected communication speed is “307.2 ( kbps) ". On the other hand, when the number “3” of the terminal devices 10 is received from the second base station device 12b and the DRC of the second base station device 12b derived by the deriving unit 18 is “10”, the expected communication speed is “341. 3 (kbps) ". Thus, the base station apparatus 12 with a small DRC may be selected.
The comparison unit 28 selects the base station apparatus 12 having a high expected communication speed as a communication target. The control unit 30 controls the timing of the terminal device 10 and the like.

  This configuration can be realized in terms of hardware by a CPU, memory, or other LSI of an arbitrary computer, and in terms of software, it is realized by a program having a reservation management function loaded in memory. The functional block realized by those cooperation is drawn. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  FIG. 3 is a sequence diagram illustrating the handoff process. The sequence diagram is an EV-DO system handoff process including the present embodiment, and is used to indicate a signal including the number of terminal devices 10 communicating with the base station device 12 described above. The terminal device 10 measures the strength of the pilot signal from the first base station device 12a (S10). Further, the strength of the pilot signal from the second base station apparatus 12b is also measured (S12). The terminal device 10 selects the first base station device 12a as a communication target, and transmits a “Connection Request Message” to the first base station device 12a (S14). The first base station apparatus 12a transmits “Traffic Channel Assignment Message” to the terminal apparatus 10 (S16), and the terminal apparatus 10 transmits “Traffic Channel Complete Message” to the first base station apparatus 12a (S18). A communication line between one base station apparatus 12a is set. Here, the first base station apparatus 12 a includes “the number of terminal apparatuses 10 in communication” in the “Traffic Channel Assignment Message”.

  Thereafter, the terminal apparatus 10 measures the strength of the pilot signal from the first base station apparatus 12a (S20). Also, the strength of the pilot signal from the second base station apparatus 12b is measured (S22). When the determination unit 34 determines that the second base station device 12b can also communicate, the terminal device 10 transmits “Route Update Message” to notify the first base station device 12a (S24). The first base station apparatus 12a transmits a “TrafficChannelAssignmentMessage” indicating that the second base station apparatus 12b can also be used to the terminal apparatus 10 (S26), and the terminal apparatus 10 transmits “TrafficChannelComplete Message” to the first base station apparatus 12a. ”(S28), the terminal device 10 and the second base station device 12b can also communicate with each other. Here, “TrafficChannelAssignmentMessage” in step 26 can include “the number of terminal devices 10 in communication” of the first base station device 12a and “the number of terminal devices 10 in communication” of the second base station device 12b. .

  FIG. 4 is a sequence diagram showing TDMA processing. The sequence diagram is a TDMA process in the EV-DO system including the present embodiment, and is used to explain data transmission when a plurality of terminal apparatuses 10 are connected to one base station apparatus 12. Note that the terminal device 10 includes a first terminal device 10a and a second terminal device 10b. The first terminal device 10a outputs a data request A to the network server (S50). The second terminal device 10b outputs a data request B to the network server (S52). The network server performs data transfer A and B in response to these requests (S54). The base station apparatus 12 writes data A and B in the buffer (S56). The first terminal apparatus 10a transmits DRC to the base station apparatus 12 (S58), and the second terminal apparatus 10b also transmits DRC to the base station apparatus 12 (S60).

As a result, the base station apparatus 12 performs scheduling (S62) and determines the terminal apparatus 10 that performs data transfer. Here, the scheduling performed by the base station apparatus 12 is to determine the terminal apparatus 10 to which data should be transferred from two points of the DRC of the terminal apparatus 10 and the average transmission rate transmitted in the past for a certain period every 1.66 milliseconds. The terminal device 10 that performs data transfer at a short interval is switched. The base station apparatus 12 reads data B from the buffer (S64), and performs data transfer B to the second terminal apparatus 10b (S66). The first terminal apparatus 10a transmits DRC to the base station apparatus 12 (S68), and the second terminal apparatus 10b also transmits DRC to the base station apparatus 12 (S70). The base station apparatus 12 performs scheduling (S72), the base station apparatus 12 reads data A from the buffer (S74), and performs data transfer A to the first terminal apparatus 10a (S76).
The first terminal apparatus 10a transmits DRC to the base station apparatus 12 (S80), and the second terminal apparatus 10b also transmits DRC to the base station apparatus 12 (S82). The base station apparatus 12 performs scheduling (S84), the base station apparatus 12 reads data B from the buffer (S86), and performs data transfer B to the second terminal apparatus 10b (S88). The first terminal apparatus 10a transmits DRC to the base station apparatus 12 (S90), and the second terminal apparatus 10b also transmits DRC to the base station apparatus 12 (S92). The base station apparatus 12 performs scheduling (S94), the base station apparatus 12 reads data A from the buffer (S96), and performs data transfer A to the first terminal apparatus 10a (S98). As described above, when a plurality of terminal devices 10 are connected to the base station device 12, the transmission speed is influenced by other terminal devices 10 in addition to the radio propagation environment between the terminal device 10 and the base station device 12. Receive.

  FIG. 5 is a flowchart showing the selection process of the base station apparatus 12. The acquisition unit 20 acquires the number of terminal devices 10 connected by each base station device 12 (S100). The deriving unit 18 derives a DRC for each base station apparatus 12 (S102). The calculation unit 26 calculates the expected communication speed (S104). The comparison unit 28 selects the base station device 12 with the highest expected communication speed, and the communication unit 14 starts data communication with the base station device 12 (S106).

  FIG. 6 is a flowchart showing the handoff process. The communication unit 14 is in data communication with a predetermined base station apparatus 12 (S120). The acquisition unit 20 acquires the number of terminal devices 10 in the connected base station device 12 and the number of terminal devices 10 in other base station devices 12 (S122). The deriving unit 18 derives the DRC in the connected base station apparatus 12 and the DRC in the other base station apparatus 12 (S124). The calculation unit 26 calculates the expected communication speed (S126). If the expected communication speed at the other base station apparatus 12 is higher than the expected communication speed of the connected base station apparatus 12 (Y in S128), the comparison unit 28 determines handoff (S130). On the other hand, if the expected communication speed in the other base station apparatus 12 is not higher than the expected communication speed of the connected base station apparatus 12 (N in S128), the data communication is continued.

  According to the present embodiment, in order to select the base station apparatus to be communicated in consideration of the number of terminal apparatuses in addition to the radio propagation environment, it is possible to select a base station apparatus that has a substantial communication speed.

  Next, an embodiment will be described in which the base station apparatus 12 is selected when the terminal apparatus 10 is on standby or when a communication channel is set. In order for the terminal device 10 to acquire the number of terminal devices 10 connected to the base station device 12, the base station device 12 is in the broadcast information transmitted from the base station device 12 to the terminal device 10 during standby. Notification is made including the number of terminal devices 10 connected to the station device 12.

  The terminal device 10 selects and switches the base station device 12 that waits based on the number of the terminal devices 10 included in the broadcast information (Idle Hand-off). Alternatively, the base station apparatus 12 is selected based on the number of terminal apparatuses 10 when performing negotiation to set a communication channel (Traffic Channel) (Access Hand-off). That is, during standby, a handoff is always performed to the base station apparatus 12 with a small number of terminal apparatuses 10, or the base station apparatus 12 with a small number of terminal apparatuses 10 is selected when setting a communication channel.

  Further, in order to improve accuracy, in addition to the terminal device 10, the selection of the base station device 12 is determined by using the strength of the pilot signal measured every time broadcast information is received or the DRC derived based on the strength of the pilot signal. Is more preferable. With such a system configuration, the base station device 12 is selected in consideration of the number of terminal devices 10 connected to the base station device 12 during standby or when setting a communication channel. Can be determined as a communication target.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. is there.

  In the present embodiment, “the number of terminal devices 10 in communication” is included in the “Traffic Channel Assignment Message”. However, the present invention is not limited to this. For example, a new signal may be defined to transmit “the number of terminal apparatuses 10 in communication”. Alternatively, “Traffic Channel Assignment Message” from the communicating base station device 12 transmits “the number of communicating terminal devices 10” in other base station devices 12 installed around the communicating base station device 12. May be. Also according to this modification, it is possible to notify the terminal device 10 of “the number of terminal devices 10 in communication”. Alternatively, a dedicated new channel may be provided. Also according to this modification, it is possible to notify the terminal device 10 of “the number of terminal devices 10 in communication”.

It is a figure which shows the structure of the communication system which concerns on the Example of this invention. It is a figure which shows a response | compatibility with DRC used by the derivation part of FIG. 1, and a transmission rate. It is a sequence diagram which shows the handoff process of FIG. It is a sequence diagram which shows the TDMA process of FIG. It is a flowchart which shows the selection process of the base station apparatus of FIG. It is a flowchart which shows the handoff process of FIG.

Explanation of symbols

  10 terminal devices, 12 base station devices, 14 communication units, 16 data processing units, 18 derivation units, 20 acquisition units, 22 storage units, 24 selection units, 26 calculation units, 28 comparison units, 30 control units, 32 networks, 100 Communications system.

Claims (6)

Deriving means for deriving an expected transmission rate for each of the plurality of communicable base station devices based on signals received from the plurality of communicable base station devices;
Obtaining means for obtaining the number of terminal devices connected to the plurality of communicable base station devices from any of the plurality of communicable base station devices;
A new transmission rate for the plurality of communicable base station devices is calculated based on each of the derived estimated transmission rate for the base station device and the obtained number of terminal devices, and based on the calculated new transmission rate. Te, selection means for selecting a base station apparatus to be a communication target from among the plurality of communication base station capable device,
Communication means for communicating with the selected base station apparatus;
The terminal device characterized by including.   The terminal device according to claim 1, wherein the number of terminal devices acquired by the acquiring unit is the number of terminal devices communicating with each of the plurality of communicable base station devices.   The number of terminal devices connected to the plurality of communicable base station devices acquired by the acquiring unit further includes the number of terminal devices waiting for each of the plurality of communicable base station devices. The terminal device according to claim 2, wherein the number is a number of terminal devices. Said selecting means, when transmitting a signal in the communication means, of claims 1 to 3, characterized in that selects a base station apparatus to be a communication target from among the plurality of communication base station capable device The terminal device in any one. Storage means for storing the expected transmission rate for the derived base station device and the number of the obtained terminal devices, respectively.
The selection unit calculates a new transmission rate for the plurality of communicable base station devices based on the expected transmission rate and the number of terminal devices stored in the storage unit , and the calculated new transmission rate based on, the terminal apparatus according to any one of 4 claims 1, characterized in that selects a base station apparatus to be a communication target from among the plurality of communication base station capable device. The expected transmission rate for each of the plurality of communicable base station devices derived based on signals received from a plurality of communicable base station devices, and the one obtained from any of the plurality of communicable base station devices A new transmission rate for the plurality of communicable base station devices is calculated based on the number of terminal devices already connected to each of the plurality of communicable base station devices, and based on the calculated new transmission rate A base station apparatus selection method comprising: selecting a base station apparatus to be a communication target from the plurality of communicable base station apparatuses.

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