JP2002159038A - Mobile communication system and channel switching method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that the communication load increases to cause lowering of communication rate when a large number of mobile terminals use an identical packet communicable channel and radio resources can not be utilized effectively because a portable telephone can do nothing under such a situation. SOLUTION: Mean traffic Mavg in communication area A2 calculated at a base station 4 and information of a packet communicable channel are delivered to a base station 3 through a packet processor 5. The base station 3 informs the mean traffic Mavg and the information of a packet communicable channel to portable telephones 1 and 2 using extra information of an idle unit. If the packet traffic under communication with a base station calculated by the portable telephone 2 is smaller than the mean traffic Msum of the base station 4 informed from the idle unit as a result of comparison, the portable telephone 2 performs switching to the channel of a packet communicable base station 4 informed from the idle unit principally through the portable telephone.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication system and a channel switching method, and more particularly to a mobile communication system for communicating between a portable telephone having a wireless packet communication function and a partner terminal, and a channel switching method for switching a used channel. .

[0002]

2. Description of the Related Art In a conventional mobile communication system, a plurality of base stations as relay stations each have a unique communication area, and a mobile terminal such as a portable telephone is located at a base located at the center of a communication area where the mobile terminal is located. Perform wireless communication with the station. Since the base station is connected to the public network etc. through the higher-level control station,
A call between a mobile terminal and a partner terminal of a public network can be made via a base station. A base station in this mobile communication system performs wireless communication using a time slot of a channel allocated to a mobile terminal.

Further, in order to improve the communication quality, the mobile terminal measures the electric field strength of radio waves transmitted from one or more base stations other than the base station which is not communicating with the mobile station, and determines the most intense of the measured electric field strengths. Switching a communication channel to a base station transmitting a radio wave with a strong electric field strength (so-called handover) has been conventionally known. Furthermore, in the conventional mobile communication system, the mobile terminal performing packet communication switches the communication channel even when the received electric field strength is deteriorated or the error rate of the received data becomes worse than a predetermined threshold. Do.

[0004]

However, in a conventional mobile communication system that communicates with a mobile terminal having a packet communication function, the deterioration criteria of the received electric field strength, the error rate of the received data, and the electric field strength of the peripheral channel are only used as criteria. Since the channel for packet communication is switched, the reception electric field strength of the channel currently performing packet communication is high,
Even if the error rate of the received data is good, if there are many mobile terminals using the same packet-communicable channel, the communication load increases and the communication speed decreases. .

[0005] Even in such a situation, the cellular phone cannot do anything, and must only continue packet communication at a reduced communication speed, and the communication load cannot be distributed, and radio resources can be used effectively. Absent. Conventionally, in order to secure the amount of information to be transmitted, it is not possible to notify a plurality of channels that can perform packet communication.

[0006] The present invention has been made in view of the above points,
It is an object of the present invention to provide a mobile communication system and a channel switching method capable of switching from a communicating mobile terminal to a communication channel with a low traffic.

It is another object of the present invention to provide a mobile communication system and a channel switching method capable of notifying a plurality of channels capable of performing packet communication.

It is a further object of the present invention to provide a mobile communication system and a channel switching method in which a mobile terminal itself can automatically select a channel with a light communication load.

[0009]

In order to achieve the above object, a mobile communication system according to the present invention comprises a plurality of base stations for transmitting radio packets to and from a mobile terminal located within its own communication area. In a mobile communication system in which communication is performed, a plurality of base stations calculate calculation means for calculating a first communication amount in their own communication area, and transmit information of the first communication amount and a channel capable of performing packet communication to neighboring base stations. A transmitting unit for periodically transmitting, and a notifying unit for notifying the mobile terminal located in the communication area of the own station of the information of the first communication amount and the channel capable of packet communication received from the other base station. The mobile terminal has a receiving unit that receives the first traffic transmitted from the base station performing the packet communication and the information of the channel capable of performing the packet communication, based on the information of the received channel,
An electric field strength measuring means for measuring a received electric field strength of a frequency used by a base station other than the base station performing packet communication specified by the information, and calculating a second communication amount of the base station performing packet communication. Communication amount calculating means, comparing means for comparing the measurement result of the received electric field strength with a predetermined threshold value, and comparing the second communication amount with the first communication amount received by the receiving means; By means, a comparison result is obtained that the measurement result of the received electric field strength is larger than a predetermined threshold value and that the second traffic is larger than the first traffic by a predetermined value or more. In such a case, a switching means for switching to a channel capable of packet communication received by the receiving means is provided.

According to the present invention, during the packet communication between the mobile terminal and the base station, the measurement result of the received electric field strength of the frequency used by another base station is larger than a predetermined threshold value, When a comparison result is obtained that the second traffic during the packet communication is larger than the first traffic of the other base station by a predetermined value or more, the received packet-communicable channel Since the channel is switched to another base station based on the information, packet communication can be performed with the base station having a smaller load.

[0011] Here, the notifying means notifies the mobile terminal during packet communication of the information of the first communication amount and the channel capable of packet communication using the idle unit, thereby reducing the load of packet communication. Desirable for

The calculating means of the base station calculates an integrated value of the number of communication slots used in one superframe in superframe units, and weights the previous integrated value and the current integrated value to calculate a moving average. The moving average is obtained as the latest integrated value and is obtained as the first communication amount.

[0013] Further, in order to achieve the above object, the mobile communication system of the present invention is a mobile communication system in which a plurality of base stations perform packet communication by radio waves with mobile terminals located within their own communication area. In the system, the plurality of base stations are:
Calculating means for calculating the amount of packet communication in its own communication area; transmitting means for periodically transmitting information on the amount of packet communication and a channel capable of packet communication to peripheral base stations; and packets received from other base stations Notifying means for notifying the mobile terminal located in the communication area of the own station of the communication amount and the information of the channel capable of performing packet communication, respectively, and the mobile terminal is configured to receive the information from the base station performing the packet communication. Receiving means for receiving the information of the transmitted packet traffic and the channel capable of packet communication, and using the received channel information in a base station other than the base station in packet communication specified by the information; Electric field intensity measuring means for measuring a received electric field intensity of a frequency which is present, a first traffic volume of all packets of a current channel in packet communication, and a current traffic in packet communication. A traffic calculating means for calculating the channel of the second traffic packets addressed to the own station, respectively, first
Threshold value calculating means for calculating a value obtained by subtracting a value obtained by multiplying the second communication amount by a predetermined value from the communication amount as a threshold value, and comparing the measurement result of the received electric field strength with a predetermined judgment value, Comparing means for comparing the amount of packet communication received by the receiving means with the threshold value calculated by the threshold value calculating means; and a measuring result of the received electric field strength by the comparing means being larger than the judgment value, and When a comparison result indicating that the communication amount is smaller than the threshold value is obtained, there is provided a switching unit for switching to a packet-communicable channel received by the receiving unit.

According to the present invention, during the packet communication between the mobile terminal and the base station, the measurement result of the received electric field strength of the frequency used by the other base station is larger than a predetermined threshold value. In addition, the received value is smaller than a threshold obtained by subtracting a value obtained by multiplying a second communication amount of the packet addressed to the own station by a predetermined value from the first packet communication amount of the current channel during the packet communication. When the packet communication volume at the peripheral base station is smaller, based on the received packet communication-capable channel information, the channel is switched to the channel of the other base station. Packet communication can be performed between

Further, according to the present invention, the information of the channel capable of performing packet communication includes at least a channel switching designation group including a grouping number and a designation group, and a frequency code. Only when the remainder obtained by dividing the mobile station identifier having a unique number by the number of groupings in the received channel switching designated group matches the designated group in the received channel switching designated group, the comparing operation by the comparing means is performed. Is performed.

Further, in order to achieve the above object, the method of the present invention provides a method in which a mobile terminal located in a communication area of a base station establishes a channel for performing packet communication with the base station by radio waves. In a channel switching method of a mobile communication system to be switched, a base station calculates a first traffic in its own communication area, and periodically transmits the first traffic and information of a channel capable of packet communication to a neighboring base station. And transmits information of the first communication amount and the channel capable of packet communication from the peripheral base station to the mobile terminal that is performing packet communication, and the mobile terminal transmits the first communication amount to the mobile terminal that is performing packet communication. 2
A first step of calculating the communication amount of the packet, a second step of receiving the information of the first communication amount and the channel capable of performing the packet communication transmitted from the base station performing the packet communication, A third step of measuring a received electric field strength of a frequency used by a base station other than the base station performing packet communication specified by the information, based on the information, a measured result of the received electric field strength and a predetermined threshold value And a fourth step of comparing the second communication amount with the first communication amount received in the second step, wherein the measurement result of the received electric field strength is larger than a predetermined threshold value. And when a comparison result indicating that the second traffic is larger than the first traffic by a predetermined value or more is obtained, a fifth step of switching to a channel capable of receiving the received packet is performed. It is characterized by including.

According to the present invention, the channel is switched to the channel of another base station based on the received channel-communicable channel information, so that packet communication can be performed with the base station having the smaller load.

Further, in order to achieve the above object, the method of the present invention calculates the amount of packet communication in its own communication area, and calculates the amount of packet communication and information on the channel capable of packet communication in the vicinity. And periodically transmits information to the mobile terminal that is performing packet communication, and transmits information on the amount of packet communication from the neighboring base stations and information on the channels that can perform packet communication. A first communication amount of all packets of the channel of the first channel, a first step of calculating a second communication amount of the packet addressed to the own station of the current channel during the packet communication, and a first communication amount from the first communication amount. A second step of calculating, as a threshold value, a value obtained by subtracting a value obtained by multiplying the communication amount of (2) by a predetermined value, and a packet communication amount transmitted from the base station during packet communication and a packet communication available amount. A third step of receiving the information of the channel, and, based on the received information of the channel, measuring a received electric field strength of a frequency used by a base station other than the base station performing the packet communication specified by the information. A fourth step of comparing the measurement result of the received electric field strength with a predetermined determination value, and comparing the packet communication amount received in the third step with the threshold value calculated in the second step; In step 5, when the comparison result that the measurement result of the received electric field strength is larger than the determination value and the packet communication amount is smaller than the threshold value is obtained, the received packet communication Switching to a possible channel.

According to the present invention, the threshold value calculated from the total packet communication amount of the current channel calculated by the mobile terminal itself and the packet communication amount addressed to its own station, the received packet of the channel at the peripheral base station, By comparing the traffic with the base station and selecting whether or not to perform channel switching based on the comparison result, packet communication can always be performed with the base station having the smaller load.

[0020]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a system configuration diagram of an embodiment of a mobile communication system according to the present invention. In the figure, mobile phones (MS) 1 and 2 having a wireless packet communication function as an example of a mobile terminal are located in a communication area A1 of a base station (BS) 3. Also,
The mobile phone 2 is also located in the communication area A2 of the base station (BS) 4. Therefore, the mobile phone 1 can perform packet communication only with the base station 3, and the mobile phone 2 is at a position where packet communication can be performed with any of the base stations 3 and 4. Here, it is assumed that the mobile phones 1 and 2 are performing wireless packet communication with the base station 3.

The packet processing device 5 converts the packet data from the mobile phones 1 and 2 received from the base stations 3 and 4 into
It repairs duplication and omission of signals generated when the mobile phones 1 and 2 switch channels, and sends the repaired packet data to the gateway device 6. Gateway device 6
Performs protocol conversion, address conversion, and the like on the input packet data, and then sends the packet data to the Internet 7.

On the other hand, when there is a data transmission request from the Internet 7 to the mobile phone, the gateway device 6
The relevant mobile phone searches for a communicable packet processing device, and performs protocol conversion processing as packet data.
The packet is transmitted to the searched packet processing device (5 in FIG. 1). Also, the information of the corresponding mobile phone is transmitted.

The packet processing device 5 searches for a base station in which the mobile phone transmitted from the gateway device 6 is located, and transmits the packet data to the relevant base station. The base station transmits packet data to the corresponding mobile phone using wireless communication. In addition, the base station 3 and 4 have a function of mutually notifying the information of the channel capable of performing packet communication and the amount of communication of the channel capable of performing packet communication.

Next, the operation of this embodiment will be described with reference to FIG.
This will be described with reference to FIGS. In the present embodiment, time division multiple access (TDMA: Time Division Multiplex Acce
The operation in the packet communication system using the digital mobile phone of the ss) system will be described. Now, it is assumed that the mobile phones 1 and 2 located in the communication area A1 of the base station 3 are in a packet communication state with the base station 3. However, the mobile phone 2 is also located within the communication area A2 of the base station 4, and is in a position where packet communication with the base station 4 is possible.

The base station 3 communicates with the mobile phones 1 and 2
TDM signals at the timing shown in FIG. 2 using radio waves
A transmission is performed using the A method. That is, in FIG. 2, the transmission unit of the wireless communication has a minimum unit of 6.67 mse.
One subframe (20 msec) with three slots of c
, And one superframe (720 msec) is composed of 36 subframes.

The base station 3 transmits the packet data to be transmitted to the portable telephones 1 and 2 at the same slot number timing. In FIG. 2, the base station 3
Divides packet data to be transmitted to the mobile phone 1 (MS1) into six slot units, and generates slot numbers #
It is transmitted using 0. In addition, the mobile phone 2 (MS
There are two packet data to be transmitted for 2), one is divided into four slot units and the other is divided into two slot units, and both are transmitted using slot number # 2. Is done.

When there is no packet data to be transmitted to the portable telephones 1 and 2, the base station 3 transmits “IDL” in FIG.
The base station information (mainly layer 1 level wireless communication parameters) called an idle unit indicated by “E” is transmitted to the mobile phones 1 and 2.

Further, the base station 3 notifies the portable telephones 1 and 2 how many data slots are to be transmitted using the first 8 bits of each slot. This 8-bit information is called a W information bit. A method of using the W information bit will be described with reference to FIG. The W information bit is
As shown in FIG. 3A, the first bit is called F1 and the next one bit is called F2. F1 indicates whether the corresponding slot is the first unit. When the value is “0”, it is a non-first unit, and when the value is “1”, it is a first unit. F2 indicates whether the slot is the last unit. When the value is “0”, it indicates a non-final unit, and when the value is “1”, it indicates a last unit.

The remaining 6 bits of the W information bit are called W0, and indicate the number of valid bytes when F2 indicates the last unit, and indicate the number of remaining units when F2 indicates that the unit is not the last unit (F2). Wr). As shown in FIG. 2, Wr is used after being counted down from the head. When Wr is "0", that is, the slot in which all the W information bits are "0" is an idle unit.

To summarize the above, when F1 = 1 and F2 = 0, the head unit shown in FIG. 3B is obtained, and F1 = F2
When = 0, as shown in FIG. 3C, the continuation unit is neither the first unit nor the last unit, and F1 = 0,
When F2 = 1, the final unit shown in FIG.
Wr indicates the number of valid bytes L, and F1 = F2 = Wr
When = 0, the idle unit shown in FIG.

In the present embodiment, information of another channel capable of packet communication is set in an unused portion of the idle unit. This idle unit will be described in more detail with reference to FIG.

In FIG. 4, up to 11 octets of the idle unit is the same as in the conventional case, and 12 octets are newly set in this embodiment. In the following, each added octet will be described. In the octet of the twelfth octet, a “channel switching designation group” is set. This channel switching designation group is used to control not to switch to the channel to which all the mobile phones receiving the idle unit are notified at the same time. Using the upper 4 bits of the channel switching designation group, the number of groups into which the mobile phone is to be divided is designated, and the group divided by the remaining lower 4 bits is designated.

A total of 16 bits at the 13th octet and the 14th octet are used to notify the frequency code of another packet-communicable channel. The upper 4 bits of the 13th octet are used to report a frequency band identifier, and the lower 4 bits of the 13th octet and a total of 12 bits of the 14th octet are used to report a frequency code. The fifteenth octet is used for notifying the color code capable of packet communication, and the sixteenth octet is used for notifying the scramble code of the channel capable of packet communication. The last 17th octet is a communication amount notification, which is used to notify the current communication state (packet communication amount) of another channel capable of packet communication.

Next, an embodiment of an algorithm for calculating a communication amount indicating a communication state according to the present invention will be described with reference to FIG.
This will be described with reference to a flowchart of Although this algorithm is used on the base station side, it is used as it is for some mobile phones. First, the traffic average value Mavg and the variable Init
Are initialized to 0 (step 101), and then 1
The communication frame integrated value Msum and the slot count number n in the super frame are each initialized to 0 (step 1).
02).

Subsequently, when a slot interrupt is detected (step 103), the slot count n becomes "10".
7 ”(step 10).
4) If it is less than "107", it is a slot within one superframe, so it is checked whether all W information bits are "0" (step 105).

If any of the W information bits is "0", it is determined that the unit is a unit other than an idle unit, and the communication amount integrated value Msum is incremented by "1" (step 106). To "1"
Is incremented by one (step 107). If all the W information bits are "0", it is determined that the unit is an idle unit, and the communication count integrated value Msum is not incremented, and only the slot count n is incremented by "1" (step 107). After the process of step 107, the process returns to step 103 again to detect a slot interrupt.

On the other hand, when it is determined in step 104 that the slot count number n is larger than "107", that is, n = 108, it is determined that the accumulation of the communication amount for one superframe slot has been completed, and the variable Init is determined. Is "0" (step 108). Since the variable Init is initially initialized to "0" in step 101, Init is "0" at the time of the first one superframe, and at this time, the traffic volume average value Mavg is integrated with the traffic volume in one superframe. The value Msum is substituted as it is, and the variable Init is set to "1" (step 10).
9). Thus, in the second and subsequent superframes, the value of Init is “1”.

On the other hand, when it is determined in step 108 that the variable Init is “1”, that is, when it is determined that the superframe is the second or subsequent super frame, Mav
An average communication amount Mavg is calculated by an arithmetic expression g = (Mavg + Msum × 2) / 3 (step 11).
0). This arithmetic expression is obtained by adding the previous traffic average value Mavg and the present traffic superimposed value Msum in one superframe to two.
The multiplied value is added, and the value obtained by averaging the added value to 1/3 is defined as the current communication traffic average value Mavg.

When the processing in step 109 or 110 is completed, the flow returns to step 102 again, and the communication amount integrated value Msum
And the slot count n is initialized to “0”, and the average traffic value Mavg of the next one superframe is calculated again in the same manner as above. That is, for the second and subsequent superframes, a moving average is calculated by weighting the previous traffic average value Mavg and the current traffic integrated value Msum in one superframe in superframe units and calculating the moving average. Average value Mavg (step 10
3-108, 110).

Each of the base stations 3 and 4 in FIG. 1 independently operates in accordance with the above-described algorithm to calculate the average traffic amount Mavg of its own station.
And the calculated average value of the traffic amount Mavg and the information of the channel capable of packet communication are stored in the neighboring base stations (the base station 4 in the case of the base station 3 and the base station 3 in the case of the base station 4).
The base station 3 (4) transmits the above average traffic value Mavg received from the other base station 4 (3) and the information of the channel capable of packet communication to the base station 3 (4). Using the additional information of the idle unit shown in FIG. 4, the notification is made to the mobile phone located in the communication area of the own station. The mobile phone uses the above average communication amount Ma
Upon receiving information on a channel capable of performing packet communication with vg, channel switching is performed as necessary.

Next, the above-described channel switching operation of the portable telephone will be described with reference to the flowchart of FIG. First, the mobile phone monitors whether it has received an idle unit during packet communication (step 20).
1) When an idle unit is received, its own group is calculated by using the received group number of the “channel switching designation group” of the 12th octet of the idle unit. The specific calculation method is the mobile phone 1 written in the mobile phone.
The mobile station identifier, which is a number unique to each mobile station, is divided by the number of groups in the received idle unit to obtain a remainder.
It is checked whether the obtained remainder matches the specified group of the “channel switching specified group” (step 202). This is to prevent the mobile phone from switching channels simultaneously to a channel with a light communication load.

If they match, the received electric field strength of the channel of the peripheral base station of the frequency code specified by the idle unit is measured by the same method as in the past (step 20).
3). Subsequently, the mobile phone compares the measured received electric field strength with the RSSI determination value of the FEC control determination parameter notified in the idle unit that has received the received signal (step 2).
04). The RSSI determination value of the FEC control determination parameter indicates a threshold value of the received electric field strength at which packet communication can be performed without any problem without performing an error correction function in performing wireless packet communication.

Therefore, the RS of the FEC control determination parameter is
If the measured electric field strength is higher than the SI determination value, it is determined that the packet communication can be continued without any problem even after the channel switching, and the mobile phone itself has calculated by the same algorithm as in FIG. The average traffic value Mavg of the neighboring base stations notified by the traffic notification in the idle unit from the base station performing packet communication by the predetermined value α is larger than the packet traffic of the channel of the base station currently performing packet communication.
Are compared to see if the value obtained by adding is smaller (step 205). The above-mentioned predetermined value α is an adjustment amount for preventing the load of the base station of the channel switching destination from becoming larger than the load of the base station of the channel switching source due to the channel switching described later.

When the portable telephone obtains a comparison result that the value obtained by adding the predetermined value α to the average traffic value Mavg of the peripheral base station is smaller than the packet communication traffic of the portable telephone, the portable telephone operates as follows. A channel switching operation is performed to a channel of a peripheral base station capable of packet communication notified by the idle unit (step 206). Although the channel switching operation itself is conventionally known and will not be described in detail, when a channel switching request is notified to a base station that is communicating on a control channel, a channel with a switching destination base station is transmitted via a packet processing device. Switching is performed.

In step 202, the mobile station identifier is
If a comparison result indicating that the remainder obtained by dividing by the number of groupings in the received idle unit does not match the designated group of “channel switching designated group” is obtained, or step 20
In step 4, the measured electric field strength is the RSS of the FEC control determination parameter.
If it is determined that the value is equal to or less than the I determination value, or if it is determined in step 205 that the packet communication amount of the mobile phone is equal to or smaller than the average communication amount Mavg of the peripheral base station,
The above channel switching procedure is not executed, and the process returns to step 201 to monitor the reception of the idle unit.

As described above, according to the present embodiment, for example, while the portable telephones 1 and 2 in FIG. 1 are performing packet communication with the base station 3, their own communication area A calculated by the base station 4 is calculated.
2, the information of the communication traffic average Mavg and information of the channel capable of performing packet communication are periodically transmitted to the base station 3 through the packet processing device 5, and the base station 3 receives the above communication received from the base station 4. Using the additional information of the idle unit shown in FIG. 4, the mobile phone 1 and the mobile phones 1 and 2 located in the communication area A1 of their own station are notified of the information on the channel that can perform packet communication with the amount average value Mavg.

Here, the mobile phone 2 calculates the packet communication amount currently being communicated with the base station 3 calculated by itself,
Base station 4 notified by communication amount notification in idle unit
When the comparison result that the communication traffic average value Msum is smaller than that of the base station 4 obtained by the idle unit, the channel switching operation is performed by the mobile phone initiative to the channel of the base station 4 capable of packet communication (however, as described above). In this way, the remainder obtained by dividing the mobile station identifier by the number of groupings in the received idle unit matches the specified group of “channel switching specified group”, and the measured electric field strength is the RSSI of the FEC control determination parameter. It shall be larger than the judgment value.)

Thus, after channel switching, the base station 3
It is possible to communicate at a higher speed than the communication with. Also, since a plurality of channels capable of packet communication can be broadcast using the idle unit, the load of packet communication on the base station can be further reduced.

Next, another embodiment of the present invention will be described. In the above embodiment, the communication amount indicating the communication state is described to be calculated by the base station according to the algorithm of the flowchart of FIG. 5, but in this embodiment, the mobile telephone is calculated according to the algorithm of the flowchart of FIG. It is characterized in that the side calculates the communication amount addressed to itself (addressed to the own station).

A description will be given of the traffic calculation algorithm by the mobile telephone with reference to the flowchart of FIG. 7. First, the traffic average OMavg and the variable Init addressed to the own station will be described.
Are initialized to 0 (step 301), and then the integrated traffic value OMsum and the slot count n in one superframe (720 msec) addressed to the own station are set to 0, respectively.
(Step 302).

Subsequently, when a slot interrupt is detected (step 303), the slot count n becomes "10".
7 ”(step 30).
4) If it is less than "107", it is a slot within one superframe, so it is checked whether all W information bits are "0" (step 305).

If any of the W information bits is "0", it is determined that the unit is a unit other than the idle unit, and it is determined whether or not the unit has data addressed to its own station (step 306). If the slot count n is incremented by "1" (step 307), the slot count n is incremented by "1".
Is incremented by one (step 308).

If the W information bits are all "0", it is determined that the unit is an idle unit, and the own station-directed communication amount integrated value OMsum is not incremented, and only the slot count n is incremented by "1". (Steps 305, 308). Similarly, even in a unit other than the idle unit, when there is no data addressed to the own station in the unit, similarly, the increment of the communication amount integrated value OMsum addressed to the own station is not performed, and only the slot count n is set to “1”. (Steps 306 and 30)
8). After the process of step 308, the process returns to step 303 again to detect a slot interrupt.

On the other hand, when it is determined in step 304 that the slot count number n is larger than "107", that is, n = 108, it is determined that the accumulation of the communication amount for one superframe slot has been completed, and the variable Init is determined. Is determined to be "0" (step 309). Since the variable Init is initially initialized to "0" in step 301, Init is "0" at the time of the first one superframe, and at this time, the local station average communication amount OMavg is set at one superframe. The communication amount integrated value OMsum to the own station is substituted as it is, and the variable Init is set to “1” (step 310). Thus, in the second and subsequent superframes, the value of Init is “1”.

On the other hand, when it is determined in step 309 that the variable Init is “1”, that is, when it is determined that the superframe is the second or subsequent superframe, OMa
An average communication amount OMavg to the own station is calculated by an arithmetic expression of vg = (OMavg + OMsum × 2) / 3 (step 311). This equation is obtained by adding the previous average value OMavg of the communication amount addressed to the own station to a value obtained by doubling the integrated value OMsum of the communication amount addressed to the own station in one superframe this time, and reducing the added value to 1/3. The averaged value is the current average communication amount to the own station OMavg.

When the processing in step 310 or 311 is completed, the flow returns to step 302 again, and the communication amount O
The Msum and the slot count number n are initialized to “0”, and the communication amount average value OMavg to the own station of the next one superframe is calculated again in the same manner as described above. That is, 2
For the subsequent superframes, the previous traffic average value OMavg addressed to the own station and the integrated traffic value OMs for one superframe addressed to the current self station in superframe units.
The weighted um is weighted to calculate a moving average, and the moving average is calculated as the latest communication traffic average OMavg addressed to the own station (steps 303 to 3).
09, 311).

Next, another embodiment of the channel switching operation of the portable telephone will be described with reference to the flowchart of FIG. First, it is monitored whether or not the mobile phone has received an idle unit during packet communication (step 401). When the idle unit is received, a grouping of the "channel switching designation group" of the received octet of the twelfth octet is performed. Calculate your group using numbers. The specific calculation method is the same as the method described in step 202 of FIG. 6, and the mobile station identifier written to the mobile phone, which is a unique number for each mobile phone, is stored in the received idle unit. Divide by the number of groupings to find the remainder. It is checked whether the obtained remainder matches the designated group of the “channel switching designated group” (step 402).

If they match, the received electric field strength of the channel of the peripheral base station of the frequency code specified by the idle unit is measured by the same method as the conventional one (step 40).
3). Subsequently, the mobile phone compares the measured received electric field strength with the RSSI determination value of the FEC control determination parameter notified in the idle unit that has received the signal (step 4).
04). If the measured electric field strength is higher than the RSSI determination value of the FEC control determination parameter, it is determined that packet communication can be continued without any problem even after channel switching, and whether the mobile phone satisfies the following equation. A determination is made (step 405).

Communication notification <Mavg−OMavg × 2 Here, in the above equation, Mavg is obtained by calculating the same algorithm as in FIG. 5 inside the mobile phone in the channel where the mobile phone is currently performing packet communication. This is the packet communication amount (average value), and is the total packet communication amount in the channel on which the own station is currently performing packet communication, including not only packets addressed to the own station but also packets addressed to other stations. Also, OM
avg is the average value of the communication traffic of the packet addressed to the own station calculated by the algorithm described with reference to FIG. 7 in the channel that is currently performing the packet communication.

The "communication amount notification" in the above equation is calculated by the base station in the vicinity of the base station with which communication is currently being performed according to the flowchart of FIG. This is the packet communication volume (corresponding to Mavg in FIGS. 5 and 6) transmitted and received by the mobile phone through the currently communicating base station and indicated by the "communication volume notification" of the 17th octet of the idle unit.

Accordingly, the above equation is defined as a threshold value obtained by subtracting a value obtained by doubling the average value OMavg of the communication traffic addressed to the own station from the packet communication traffic Mavg calculated inside the mobile phone. An inequality indicating whether or not it is larger than a communication amount notification (packet communication amount) of the idle unit received from the base station is shown. If this inequality is satisfied, packet communication of the channel of the peripheral base station notified by the idle unit is shown. Since the amount is smaller, a channel switching procedure for switching from the channel currently performing packet communication to the channel of the peripheral base station notified by the communication amount notification in the idle unit is executed (step 406).

In the above formula, the reason why the value obtained by doubling the average value of the communication amount OMavg addressed to the own station is subtracted is that the channel switching by the above-mentioned channel causes the communication amount of the channel on which the portable telephone has been performing packet communication up to now to be smaller. This is to prevent the number of channels from decreasing and repeating the above-described channel switching.

The above-described channel switching operation itself is conventionally known and will not be described in detail. However, when a channel switching request is notified to a base station that is communicating on a control channel, the switching destination base station is transmitted via a packet processing device. Channel switching with the station is performed.

In step 402, the mobile station identifier is
If the result of comparison that the remainder obtained by dividing by the number of groupings in the received idle unit does not match the designated group of the “channel switching designated group” does not match, the result does not match the designated group. If it is determined that the measured electric field strength is equal to or less than the RSSI determination value of the FEC control determination parameter in step 405, it is not guaranteed that packet communication after channel switching can be continued, and the inequality described above is not satisfied in step 405. Is determined, the packet traffic on the channel after the channel switching cannot be said to be surely smaller than the packet traffic addressed to the own station on the channel before the channel switching. Instead, the process returns to step 401 to monitor the reception of the idle unit.

As described above, according to the present embodiment, the mobile communication device calculates the packet communication amount of the currently communicating channel and the average value of the packet communication amount addressed to the own station, and calculates the calculated result and the idle unit. Since it is determined whether or not to execute the channel switching procedure based on the packet communication amount (communication amount notification) of the peripheral base station notified in the above, after performing the channel switching, the communication with the base station with a light communication load is performed. Thus, packet communication can be reliably continued without lowering the communication speed.

The present invention is not limited to the above embodiment. For example, the barometer indicating the traffic shown in FIG. 5 may be changed to the number of idle units. Step 1 in
Weighting other than the arithmetic expressions 10, 311 is also possible.

Further, in the above embodiment, information exchange of traffic between base stations has been described. However, since a single base station can operate a plurality of packet communicable channels even within a single base station, one base station can be used. The same method can be applied to the case where a plurality of packet communication channels are used in one base station. Also, the order of steps 204 and 205 and the order of steps 404 and 405 may be reversed. Furthermore, the present invention can be applied to other mobile terminals such as a portable information terminal having a bucket communication function other than the mobile phone.

[0068]

As described above, according to the present invention,
Based on the received packet communication channel information,
By switching to the channel of another base station with a lighter communication load under the initiative of the mobile terminal, packet communication can be performed with the base station with the lighter load. In addition to data quality, switching to a base station with a light communication load according to the current communication state enables packet communication to be continued without a reduction in communication speed led by mobile terminals, enabling wireless communication. Resources can be used effectively.

Further, according to the present invention, since a plurality of channels capable of packet communication are notified to the mobile terminal using the unused portion of the idle unit, the number of channels for packet communication is transmitted. The amount of information can be reduced more than before, and the load of packet communication can be further reduced.

Further, according to the present invention, a threshold value calculated from the total packet traffic of the current channel calculated by the mobile terminal itself and the packet traffic addressed to the own station is provided;
By comparing the received packet traffic of the neighboring base station with the packet traffic of the channel and selecting whether or not to perform the channel switching based on the comparison result, the packet communication with the base station with the smaller load is always performed. In addition, by setting the above-described threshold value, it is possible to perform control so that the mobile terminal does not switch channels simultaneously to channels with a light communication load. In addition, since the above-described threshold for channel switching is calculated in consideration of the amount of packet communication addressed to the mobile terminal of the mobile terminal, the channel is switched to a channel with a lighter communication load after the channel switching than before the channel switching. Can be switched.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram according to an embodiment of the present invention.

FIG. 2 is a diagram showing a signal transmission timing from the base station to the mobile phone in FIG. 1;

FIG. 3 is an explanatory diagram of how to use W information bits.

FIG. 4 is an explanatory diagram of an example of an idle unit used in the present invention.

FIG. 5 is a flowchart showing an embodiment of a traffic calculation algorithm according to the present invention.

FIG. 6 is a flowchart for explaining the operation of the embodiment of the mobile phone according to the present invention.

FIG. 7 is a flowchart showing another embodiment of the traffic calculation algorithm according to the present invention.

FIG. 8 is a flowchart for explaining the operation of another embodiment of the mobile phone according to the present invention.

[Explanation of symbols]

 1, 2 mobile phone (MS) 3, 4 base station (BS) 5 packet processing device 6 gateway device 7 Internet A1, A2 communication area

Claims (11)

[Claims] 1. A mobile communication system in which a plurality of base stations perform packet communication by radio waves with mobile terminals located in their own communication area, wherein the plurality of base stations are located within a communication area of their own. Calculating means for calculating the first communication amount; transmitting means for periodically transmitting information on the first communication amount and the channel capable of performing packet communication to a peripheral base station; and the first unit receiving information from another base station. And a notifying unit for notifying the mobile terminal located in the communication area of the own station of the communication amount of the mobile station and information of a channel capable of performing packet communication. Receiving means for receiving the information on the first communication amount and the channel capable of packet communication transmitted from the base station, based on the received information on the channel, and Electric field intensity measuring means for measuring a received electric field intensity of a frequency used in a base station; communication amount calculating means for calculating a second communication amount of the base station during packet communication; and a measurement result of the received electric field intensity And a predetermined threshold value, and comparing the second communication amount with the first communication amount received by the receiving unit; and measuring the received electric field strength by the comparing unit. When a comparison result that the result is larger than a predetermined threshold value and the second traffic is larger than the first traffic by a predetermined value or more is obtained, Switching means for switching to the channel capable of packet communication received by the means. 2. The mobile communication terminal according to claim 1, wherein said notifying unit notifies said mobile terminal during packet communication of said first communication amount and information of a channel capable of packet communication using an idle unit. A mobile communication system according to claim 1. 3. The calculating means of the base station calculates an integrated value of the number of communication slots used in one superframe in superframe units, weights the previous integrated value and the current integrated value, and calculates a moving average. 2. The mobile communication system according to claim 1, wherein the mobile communication system calculates the moving average, obtains the moving average as the latest integrated value, and obtains the moving average as the first communication amount. 4. A mobile communication system in which a plurality of base stations perform packet communication by radio waves with a mobile terminal located in a communication area of the base station, wherein the plurality of base stations include a packet in the communication area of the base station. Calculating means for calculating the communication traffic; transmitting means for periodically transmitting information on the packet traffic and the channel capable of packet communication to peripheral base stations; and the packet traffic and packet communication received from other base stations Notification means for notifying the mobile terminal located in the communication area of the own station of information on a possible channel, wherein the mobile terminal transmits the packet transmitted from the base station during packet communication. Receiving means for receiving information on a communication amount and a channel capable of performing packet communication, based on the received information on the channel, the base station performing the packet communication specified by the information; Strength measuring means for measuring the received field strength of the frequency used by the base station other than the base station; the first traffic volume of all the packets of the current channel during the packet communication; and the current channel during the packet communication. Communication amount calculation means for calculating a second communication amount of a packet addressed to the own station; and a threshold value obtained by subtracting a value obtained by multiplying the second communication amount by a predetermined value from the first communication amount. Threshold calculation means, which is calculated as follows: The measurement result of the received electric field strength is compared with a predetermined determination value, and the packet communication amount received by the reception means is calculated by the threshold calculation means. A comparison unit that compares the threshold value, and the measurement result of the reception electric field strength is larger than the determination value by the comparison unit, and the packet communication amount is smaller than the threshold value. Comparison result with When obtained, the mobile communication system; and a switching means for switching said packet communication available channels received by the receiving means. 5. The mobile terminal according to claim 4, wherein the notification unit notifies the mobile terminal during packet communication of the packet communication amount and information of a channel capable of packet communication using an idle unit. Mobile communication system. 6. The communication amount calculation means of the base station calculates an integrated value of the number of slots used for communication in one superframe in superframe units, and weights the previous integrated value and the current integrated value to move. An average is calculated, the moving average is obtained as the first communication amount, and the integrated value of the number of communication use slots addressed to the own station in one superframe is calculated for each superframe. 5. A moving average is calculated by weighting the integrated value in the frame and the integrated value in one superframe addressed to the current station, and the moving average is obtained as the second communication amount. A mobile communication system according to claim 1. 7. The information of the channel capable of packet communication includes at least a channel switching designation group including a grouping number and a designation group, and a frequency code, and the mobile terminals are each one of the mobile terminals. Only when the remainder obtained by dividing the mobile station identifier having a unique number by the grouping number in the received channel switching designated group matches the designated group in the received channel switching designated group, the comparing means 5. The mobile communication system according to claim 1, wherein a comparison operation is performed. 8. A channel switching method for a mobile communication system in which a mobile terminal located within a communication area of a base station switches a channel for performing packet communication with the base station by radio waves, Calculates a first traffic in its own communication area, periodically sends the first traffic and information of a channel capable of packet communication to a neighboring base station, and Transmitting the information of the first communication amount and the channel capable of performing packet communication to the mobile terminal performing packet communication, and the mobile terminal calculates a second communication amount of the base station performing packet communication A first step, a second step of receiving information on the first communication amount and a channel capable of packet communication transmitted from the base station during packet communication, and a step of receiving the information on the received channel. A third step of measuring a reception field strength of a frequency used by a base station other than the base station performing packet communication specified by the information; and a measurement result of the reception field strength and a predetermined threshold value. Are compared, and
A fourth step of comparing the second communication amount with the first communication amount received in the second step, and the measurement result of the received electric field strength is larger than a predetermined threshold value; and When a comparison result that the second traffic is larger than the first traffic by a predetermined value or more is obtained, a fifth channel for switching to the received packet-communicable channel is used.
And a step of switching channels. 9. The base station notifies the mobile terminal during packet communication of the first communication amount from the peripheral base station and information of a channel capable of performing packet communication, using an idle unit. 9. The channel switching method according to claim 8, wherein: 10. A channel switching method of a mobile communication system in which a mobile terminal located within a communication area of a base station switches a channel for performing packet communication with the base station by radio waves, Calculates the amount of packet traffic in its own communication area, and periodically sends the information on the amount of packet traffic and the channel capable of performing packet communication to neighboring base stations,
The packet communication amount from the peripheral base station and information on a channel that can perform packet communication are transmitted to the mobile terminal that is performing packet communication, and the mobile terminal transmits all packets of the current channel that is performing packet communication. A first communication amount, a first step of calculating a second communication amount of a packet addressed to the own station of the current channel during the packet communication, and a second communication amount based on the first communication amount. A second step of calculating, as a threshold, a value obtained by subtracting a value obtained by multiplying a predetermined value by a predetermined value, and receiving information on the amount of packet communication and a channel capable of packet communication transmitted from the base station during packet communication. A third step;
A fourth step of measuring, based on the received information on the channel, a received electric field strength of a frequency used by a base station other than the base station performing the packet communication specified by the information; A fifth step of comparing the measurement result with a predetermined determination value, and comparing the packet traffic received in the third step with a threshold value calculated in the second step; When the measurement result of the electric field strength is larger than the determination value, and the comparison result that the packet traffic is smaller than the threshold value is obtained, the received packet communication is possible. And a sixth step of switching to a channel. 11. The method according to claim 11, wherein the base station broadcasts information on the amount of packet communication from the peripheral base station and information on a channel capable of performing packet communication to the mobile terminal performing packet communication using an idle unit. The channel switching method according to claim 10, wherein