JP3819356B2 - Wireless packet transmission system and method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is used in a wireless packet transmission system in which a plurality of frequency channels exist as lines from a mobile station to a center station, and the number of mobile stations is larger than the number of frequency channels that can be used as in satellite communication. In particular, the present invention relates to a technology for assigning frequency channels to mobile stations fairly and a technology for achieving high data throughput.
[0002]
[Prior art]
(ALOHA method)
The ALOHA method was established in 1970 by N. A wireless packet communication protocol published by Abramson, which was actually used on the University of Hawaii computer network as ALOHASYSTEM.
[0003]
When the ALOHA method is applied to an apparatus configuration that is the subject of the present invention composed of a plurality of mobile stations and one center station, as shown in FIG. A channel is randomly selected from the frequency channels 6 of the communication line in the direction, and packets can be transmitted at any time according to the request. The success of the transmission is recognized by receiving the confirmation signal 52 from the center station within a predetermined time. When a packet collision 53 occurs, packet retransmission 54 is performed, but the retransmission interval is randomly determined so that the retransmission packets between mobile stations are not synchronized.
[0004]
(ICMA method)
The ICMA (Idle-signal Casting Multiple Access) system is adopted in the digital car phone system. There are technologies aiming at further data throughput improvement based on the ICMA method (see, for example, Patent Documents 1, 2, and 3). FIG. 6 shows a channel assignment sequence when these techniques are applied to an apparatus configuration as the object of the present invention. The center station monitors the usage status of the uplink channel and broadcasts empty channel information 61 to each mobile station. The mobile station 62 accesses a free channel based on the free channel information 61 from the center station and makes a channel reservation.
[0005]
A specific channel reservation method is performed by the mobile station 62 transmitting a reservation packet 63 storing the time required for communication. The center station 2 that has received the reservation packet 63 without colliding returns a packet 64 that stores the channel number assigned to the mobile station 62. At the same time, the center station 2 has reserved the channel for the time required for communication. Broadcast channel information 61.
[0006]
Since there is a delay until the empty channel information 61 for which the channel has been reserved reaches the mobile station 62, another mobile station 65 can transmit the reservation packet 66 to the channel using the same channel as the mobile station 62. In this case, the center station 2 returns a packet 67 storing a channel number separately assigned to the mobile station 65.
[0007]
[Patent Document 1]
JP-A-10-209956
[Patent Document 2]
JP 2000-341292 A
[Patent Document 3]
JP 2000-324164 A
[0008]
[Problems to be solved by the invention]
In the wireless packet transmission system, since the number of channels of frequencies that can be used is limited, there is a possibility that a plurality of mobile stations transmit packets simultaneously on the same channel, and packet collision cannot be completely eliminated. Packet collision leads to packet loss in wireless space.
[0009]
In the conventional ALOHA system, each mobile station randomly selects a channel from among uplink channels and transmits a packet. Then, a successful transmission is recognized by receiving a confirmation signal from the center station within a certain period of time. When there is no confirmation signal from the center station, a packet collision is recognized. When a packet collision occurs, the packet is retransmitted, but the retransmission interval is randomly determined so that the retransmitted packets between the mobile stations are not synchronized.
[0010]
When the number of mobile stations is larger than the number of uplink channels, many packets are transmitted on the uplink, and packet collisions increase. When packet collisions increase, the number of retransmitted packets also increases, resulting in a vicious circle in which more packets are transmitted on the uplink. Since the packet causing the collision is lost in the wireless space, the data throughput is reduced.
[0011]
In the conventional ICMA system, a part of packet collision can be avoided by performing communication using a channel reserved in advance. A specific method of channel reservation is triggered by a communication start request generated inside the mobile station, and the mobile station transmits a reservation packet storing the time required for communication to the center station once using an unreserved channel. To do. The center station that has received the reservation packet returns a reservation confirmation packet to the mobile station. The mobile station that has received the confirmation packet thereafter performs packet communication using the reserved channel.
[0012]
A reservation packet transmitted to an unreserved channel may collide with a reservation packet transmitted from another mobile station, but a communication packet transmitted after channel reservation does not collide. In general, the number of reserved packets is very small compared to the number of communication packets, so that the amount of packet collision can be greatly reduced compared to the ALOHA method.
[0013]
However, in the ICMA system, when the number of mobile stations is larger than the number of uplink channels, a situation occurs in which all channels are reserved. In this case, other mobile stations postpone the start of communication until the communication of the mobile station that has reserved the channel is completed. As a result, the mobile station that has postponed the start of communication has a longer time from the start to the end of the communication, resulting in a decrease in data throughput. In addition, while all channels are reserved, a specific mobile station occupies the channel, and channel assignment to all mobile stations cannot be performed fairly.
[0014]
For the above reasons, when the ALOHA method is applied to a system such as satellite communication in which the number of mobile stations is very large relative to the number of usable frequency channels, the number of packets on the uplink increases. The impact of collisions is increased, thus reducing the data throughput. Further, when the ICMA method is applied, since some mobile stations occupy channels, it is impossible to allocate channels fairly to all mobile stations, and the data throughput of mobile stations that cannot allocate channels. Will drop.
[0015]
In view of the above, an object of the present invention is to realize an access scheme in which channels can be allocated fairly to all mobile stations and high data throughput can be obtained for all mobile stations.
[0016]
[Means for Solving the Problems]
In order to solve the above problem, the present invention comprises a plurality of mobile stations and one center station, and performs communication between the mobile station and the center station, from the mobile station to the center station. In the wireless packet transmission system in which the uplink communication line is divided into radio frequencies and there are multiple frequency channels, the center station monitors the usage status of the uplink channel that changes every moment. Broadcast the idle channel information to the mobile station, and at the same time, monitor the data throughput that changes from moment to moment so that the data throughput between the center station and the mobile station is the highest. Determine the channel release time and broadcast the channel release time to the mobile station, the mobile station Information and a channel release time are received, a channel is selected based on the empty channel information at the start of communication, and communication is performed. At the same time, when the communication time after selecting the channel reaches the channel release time, the communication is temporarily stopped. Then, the communication is resumed based on the empty channel information and the channel release time, and the communication is resumed and temporarily suspended.
[0017]
As a result, it is possible to avoid that a specific mobile station occupies a channel and to assign a channel to each mobile station fairly. At this time, the mobile station does not forcibly release the channel after a lapse of a certain time, but in the present invention, the channel release time at which the data throughput is highest between the center station and the mobile station is determined. Since the mobile station releases the channel during this channel release time, it is necessary for the mobile station in communication to interrupt the communication, but as a result, communication with high data throughput can be realized.
[0018]
In other words, the first aspect of the present invention is composed of a plurality of mobile stations and one center station, performs communication between the mobile station and the center station, and the upstream direction from the mobile station to the center station The communication line is a wireless packet transmission system that divides a radio frequency and has channels of a plurality of frequencies.
[0019]
Here, a feature of the present invention is that the center station broadcasts empty channel information to the mobile station based on the usage status of an uplink channel, and the center station and the center station Channel release time transmission means for determining a channel release time between the center station and the mobile station based on a predicted value of the channel release time that maximizes the data throughput with the mobile station, and broadcasting to the mobile station The mobile station selects a channel prior to the start of communication based on the broadcast free channel information, and communicates when the channel release time is reached during communication based on the broadcast channel release time. And temporarily re-selecting the channel based on the empty channel information There is in the place with.
[0020]
The mobile station includes means for calculating data throughput between the mobile station and the center station and reporting the data throughput to the center station. The center station reports data throughput in each mobile station reported from the reporting means. The channel release time transmission means includes a data throughput between the center station and the mobile station based on the data throughput information stored in the storage means, and a channel release time. It is desirable to provide a means for executing a simulation for predicting the relationship between the mobile station and broadcasting the channel release time with the highest data throughput to the mobile station based on the simulation result.
[0021]
Further, the idle channel information transmitting means and the channel release time transmitting means comprise means for broadcasting at regular time intervals, or the idle channel information transmitting means immediately after the idle channel information in the center station changes. It is desirable to provide means for broadcasting.
[0022]
Alternatively, the means for broadcasting the channel release time calculates an average value of data throughput for the mobile station based on information accumulated in the means for accumulating at regular time intervals, and the average value falls below the previous average value. In this case, it is possible to provide means for executing the simulation and broadcasting a channel release time at which the data throughput is highest based on the simulation result to the mobile station.
[0023]
According to this, since the conditions for executing the simulation can be limited, it is possible to reduce the number of times the simulation is executed with a high processing load and effectively use the resources.
[0024]
A second aspect of the present invention is composed of a plurality of mobile stations and one center station, performs communication between the mobile station and the center station, and performs upstream communication from the mobile station to the center station. The line is a center station provided in a wireless packet transmission system that divides a radio frequency and has channels of a plurality of frequencies.
[0025]
Here, the feature of the present invention is that the idle channel information transmitting means for broadcasting idle channel information to the mobile station based on the usage status of the uplink channel, and between the mobile station and the own station. Channel release time transmission means for determining a channel release time between the center station and the mobile station based on a predicted value of the channel release time that maximizes data throughput and broadcasting to the mobile station. is there.
[0026]
Means for accumulating data throughput information in each mobile station reported from the mobile station, the channel release time transmitting means and the mobile station based on the data throughput information accumulated in the accumulating means It is desirable to provide means for executing a simulation for predicting the relationship between the data throughput with the station and the channel release time and broadcasting the channel release time at which the data throughput is highest based on the simulation result.
[0027]
Further, the idle channel information transmitting means and the channel release time transmitting means comprise means for broadcasting at regular time intervals, or the idle channel information transmitting means broadcasts immediately after the idle channel information in its own station changes. It is desirable to provide means for
[0028]
Alternatively, the means for broadcasting the channel release time calculates an average value of data throughput for the mobile station based on information accumulated in the means for accumulating at regular time intervals, and the average value falls below the previous average value. In this case, it is possible to provide means for executing the simulation and broadcasting a channel release time at which the data throughput is highest based on the simulation result to the mobile station.
[0029]
A third aspect of the present invention comprises a plurality of mobile stations and one center station, performs communication between the mobile station and the center station, and performs upstream communication from the mobile station to the center station. The channel divides the radio frequency, and there are channels of a plurality of frequencies. The center station broadcasts free channel information to the mobile station based on the usage status of the uplink channel, and the center station A radio packet transmission system that determines a channel release time between the center station and the mobile station based on a predicted value of a channel release time that maximizes data throughput with the mobile station, and broadcasts to the mobile station Is a mobile station.
[0030]
Here, the present invention is characterized in that means for selecting a channel prior to the start of communication based on the broadcast free channel information and the channel release time during communication based on the broadcasted channel release time. Means for temporarily suspending communication once again and reselecting the channel based on the empty channel information again.
[0031]
It is desirable to provide means for calculating the data throughput between the own station and the center station and reporting it to the center station.
[0032]
A fourth aspect of the present invention comprises a plurality of mobile stations and one center station, performs communication between the mobile station and the center station, and performs upstream communication from the mobile station to the center station. A line is a radio packet transmission method applied to a radio packet transmission system in which radio frequencies are divided and channels of a plurality of frequencies exist.
[0033]
Here, a feature of the present invention is that the center station monitors the usage status of the uplink channel that changes from moment to moment, and broadcasts free channel information to the mobile station. The data throughput that changes from moment to moment is monitored, the channel release time is determined so that the data throughput between the center station and the mobile station is the highest, and the channel release time is set to the mobile station. The mobile station receives the vacant channel information and the channel release time of the uplink to be broadcast, selects a channel based on the vacant channel information at the start of communication, performs communication, and simultaneously selects the channel. Communication time after reaching the channel release time, the communication is temporarily suspended, and then the free channel information is again The resume communication based on the channel release time, there is to be repeated interruption of the communication resumption and temporary.
[0034]
The mobile station calculates data throughput between the mobile station and the center station and reports the data throughput to the center station. The center station reports data throughput information of each mobile station reported from the reporting means. Based on the accumulated data throughput information, a simulation is performed to predict the relationship between the data throughput for the mobile station and the channel release time. Based on the simulation result, the channel release time at which the data throughput is highest is obtained. It is desirable to determine and broadcast to the mobile station.
[0035]
The idle channel information and the channel release time may be broadcast at regular time intervals, or the idle channel information may be broadcast immediately after the idle channel information in the center station changes.
[0036]
Alternatively, when the average value of the data throughput for the mobile station is calculated at regular time intervals and the average value is lower than the previous average value, the simulation is executed and the data throughput is highest based on the simulation result. The channel release time can be broadcast to the mobile station.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
A configuration of a wireless packet transmission system according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an overall configuration diagram of a wireless packet transmission system according to the present embodiment. FIG. 2 is a block diagram of the mobile station of this embodiment. FIG. 3 is a block diagram of the center station of this embodiment.
[0038]
This embodiment is composed of a plurality of mobile stations 1 and one center station 2, and performs communication between the mobile station 1 and the center station 2, and the upstream communication line from the mobile station 1 to the center station 2 is A radio packet transmission system in which radio frequencies are divided and channels of a plurality of frequencies exist.
[0039]
Here, the feature of the present embodiment is that the center station 2 has a free channel information transmitting unit 39 that broadcasts free channel information to the mobile station 1 based on the use status of the uplink channel, and the center station 2. Channel release time for determining the channel release time between the center station 2 and the mobile station 1 based on the predicted value of the channel release time that maximizes the data throughput between the mobile station 1 and the mobile station 1 and broadcasting to the mobile station 1 The mobile station 1 includes a reservation packet generator 29 that selects a channel prior to the start of communication based on the broadcast free channel information, and the mobile station 1 during communication based on the broadcast channel release time. When the channel release time is reached, communication is temporarily suspended and the channel is selected again based on the free channel information. It is in place and a timer section 26 and release the packet generating unit 27 and the reservation packet generator 29 that.
[0040]
The mobile station 1 includes an information packet generator 225 that calculates data throughput between the mobile station 1 and the center station 2 and reports the data throughput to the center station 2. The center station 2 is reported from the information packet generator 225. A throughput storage unit 38 for storing data throughput information in each mobile station 1 is provided, and a channel release time transmission unit 331 is based on the data throughput information stored in the throughput storage unit 38, the center station 2, the mobile station 1, A simulation for predicting the relationship between the data throughput and the channel release time is executed, and the channel release time with the highest data throughput is broadcast based on the simulation result.
[0041]
Also, the empty channel information transmission unit 39 and the channel release time transmission unit 331 broadcast at regular time intervals, or the empty channel information transmission unit 39 broadcasts immediately after the empty channel information in the center station 2 changes. .
[0042]
Alternatively, the channel release time transmission unit 331 calculates the average value of the data throughput for the mobile station 1 based on the information accumulated in the throughput storage unit 38 at regular time intervals, and the average value is lower than the previous average value. In this case, the simulation is executed, and the channel release time that provides the highest data throughput is broadcast to the mobile station 1 based on the simulation result.
[0043]
Embodiments of the present invention will be described below. The wireless packet transmission system of the present embodiment is composed of a plurality of mobile stations 1, one center station 2, and a satellite 3, and the center station 2 is connected to the Internet 5 via a GW (gateway) 4. The uplink from the mobile station 1 to the center station 2 uses FDMA (frequency division multiple access), and the downlink from the center station 2 to the mobile station 1 uses TDM (time division multiplexing).
[0044]
Next, FIG. 4 shows a sequence of the channel assignment method of this embodiment. Uplink frequency 6 is set from channel # 1 to channel #N, and vacant channel information 41 and channel release time 42, which are information related to channel usage, are broadcast from the center station to all mobile stations. Every mobile station overwrites and saves in its own memory every time the free channel information 41 and the channel release time 42 are broadcast, and always has the latest free channel information and channel release time.
[0045]
When a communication start request is generated within the mobile station 1, the mobile station 1 selects a channel based on the empty channel information 41, and sets the mobile station number assigned to the mobile station toward the selected channel and the selected channel number. The stored reservation packet 43 is transmitted.
[0046]
On the other hand, the center station 2 returns the assigned channel number 44 to indicate that the channel reservation is successful. Since there is a delay before the free channel information 41 for which the channel has been reserved reaches the mobile station 1, another mobile station 45 can transmit the reservation packet 49 to the channel using the same channel as the mobile station 1. In this case, however, the center station 2 returns a packet 4 in which the channel number individually assigned to the mobile station 45 is stored.
[0047]
Thereafter, the mobile station 1 transmits the subsequent packet 47 using the channel of the returned channel number 44. At the same time, the mobile station 1 starts a timer within itself. Thereafter, when the timer reaches the channel release time, the release packet 48 storing the mobile station number and the channel number to be released is transmitted, and then the communication is interrupted.
[0048]
Thereafter, after a time interval, the communication is resumed again based on the empty channel information and the channel release time, and the resumption of communication and the relay are repeated until the communication is completed. At the end of communication, an information packet 401 storing the mobile station number and the data throughput value is transmitted.
[0049]
Next, the detailed configuration of the mobile station is shown in FIG. The mobile station once buffers the packet generated in its own station in the order of the buffer A 21 and the buffer B 22, and then inputs the packet to the modulation unit 23. The modulation unit 23 modulates the packet into a radio signal and transmits the packet from the small antenna 25 using the channel stored in the channel storage unit 24.
[0050]
In the timer unit 26, the timer value is increased every moment. When the timer value reaches the channel release time, a release packet is transmitted through the release packet generation unit 27, the channel of the timer value and the channel storage unit 24 is cleared, and the packet output from the buffer A21 is stopped. Thereafter, the timer value is started again, and after reaching the retransmission time, the timer value is cleared and the packet output from the buffer A21 is restarted.
[0051]
When the channel is not stored in the channel storage unit 24, the packet output from the buffer B22 is stopped. At the same time, the channel is selected from the free channel information stored in the free channel information storage unit 28, and the selected channel is selected. The reservation packet is transmitted from the modulation unit 23 through the reservation packet generation unit 29. Thereafter, the channel number which is a channel assignment signal from the center station 2 is received, the channel is stored in the channel storage unit 24, and the packet output from the buffer B22 is started.
[0052]
The demodulator 221 demodulates the signal received from the small antenna 25, and the packet contents are released by the packet sorting unit 222. In the case of the assigned channel number, empty channel information, or channel release time, the contents are stored in the channel storage unit 24, the empty channel information storage unit 28, and the channel release time storage unit 223, respectively.
[0053]
The information packet generation unit 225 calculates the data throughput from the communication start time and communication end time from the packet input / output unit 224 and the amount of transmitted data, generates an information packet at the end of communication, and transmits it through the modulator 23. .
[0054]
Next, a detailed configuration of the center station 2 is shown in FIG. A signal received by the large antenna 31 is input to the demodulation group unit 32, and a demodulation unit # K33 (K is a channel number) corresponding to the channel used for transmission from the mobile station. The packet demodulated by the (natural number) 33 is demodulated through the packet sorting unit 34 according to the contents as follows.
[0055]
When the demodulated packet is a communication packet, the packet input / output unit 35 extracts the packet from the center station 2 to the outside.
[0056]
In the case of a release packet, the mobile station number assigned to the channel is deleted from the channel storage unit 36.
[0057]
In the case of a reserved packet, the channel storage unit 36 determines whether or not the mobile station number is stored in the channel. If the mobile station number is not stored, it is stored. If another mobile station is already stored, it is stored. After selecting a channel from the unreserved channels, the combination of the selected channel and the mobile station number is stored, and at the same time, the channel number finally selected from the channel information transmission unit 37 is stored in the packet and the mobile Send to the station.
[0058]
In the case of an information packet, the throughput storage unit 38 stores the combination of the mobile station number and the data throughput value.
[0059]
Also, the empty channel information transmission unit 39 searches for an unreserved channel from the channel storage unit, creates empty channel information, and broadcasts it to all mobile stations at a certain time interval.
[0060]
Here, before describing the role of the channel release time transmission unit 331, the effect of the channel release time on the present invention will be described. FIG. 7 shows a simulation result showing the relationship of the average value 72 of the data throughput with respect to the channel release time 71, with the channel release time (sec) on the horizontal axis and the data throughput (kbps) on the vertical axis. A ratio 73 of the number of mobile stations to the number of uplink channels is used as a parameter. From the figure, it can be seen that there is a channel release time such that the data throughput becomes the maximum value.
[0061]
If the channel release time is too long, the number of mobile stations that cannot acquire a channel within a certain period of time will increase, leading to a decrease in data throughput. The number of repetitions increases, overhead time is required, and data throughput is reduced. Data throughput is maximized relative to channel release time where these two effects are minimized.
[0062]
In FIG. 8, the horizontal axis represents the number of mobile stations, the vertical axis represents the data throughput (kbps), and the ALOHA method, the ICMA method, and the data throughput of the present invention are compared. In this way, by setting the channel release time so that the data throughput becomes the maximum value, a high data throughput is always realized when the present invention is used for the number of all mobile stations. Although not shown in the graph, according to the present invention, since each mobile station temporarily suspends communication by providing a channel release time, more mobile stations can use the uplink channel within a certain time. It can be easily inferred that it can be shared.
[0063]
The channel release time transmission unit 331 calculates the average value of the data throughput for all the mobile stations 1 from the throughput storage unit 38 at regular time intervals. If the average value is lower than the previous average value, the throughput storage unit 38 The simulation is executed based on the data throughput information stored in the data, and the relationship between the data throughput and the channel release time shown in FIG. 7 is recognized. The channel release time is broadcast to all mobile stations 1. As described above, by dynamically setting the channel release time, the data throughput of the entire mobile station 1 is automatically set to the maximum value. Note that the channel release time may be broadcast at regular time intervals or immediately after the simulation is newly executed.
[0064]
The packet input control unit 332 controls the packet input from the packet input / output unit 35 so that it does not collide with the packets from the channel information transmission unit 37, the empty channel information transmission unit 39, and the channel release time transmission unit 331. After being modulated by the modulation unit 333, it is transmitted from the large antenna 31.
[0065]
【The invention's effect】
As described above, according to the present invention, channels can be allocated fairly to all mobile stations, and high data throughput can be achieved.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a wireless packet transmission system in an embodiment of the present invention.
FIG. 2 is a diagram showing a configuration of a mobile station of the wireless packet transmission system in the embodiment of the present invention.
FIG. 3 is a diagram showing a configuration of a center station of the wireless packet transmission system according to the embodiment of the present invention.
FIG. 4 is a view showing channel reservation timing and channel release timing in the embodiment of the present invention.
FIG. 5 is a diagram illustrating the timing of ALOHA channel reservation and channel release.
FIG. 6 is a diagram showing the timing of ICMA channel reservation and channel release.
FIG. 7 is a diagram showing a relationship between channel release time and data throughput in the embodiment of the present invention.
FIG. 8 is a diagram showing a comparison of data throughput between the present invention and the prior art.
[Explanation of symbols]
1, 45, 51, 62, 65 Mobile station
2 Center station
3 satellites
4 GW (gateway)
5 Internet
6 Frequency channel
21 Buffer A
22 Buffer B
23 Modulator of mobile station
24 Mobile station channel storage
25 Small antenna
26 Timer section
27 Release packet generator
28 Free channel information storage unit
29 Reserved packet generator
221 Demodulator of mobile station
222 Packet sorting part of mobile station
223 channel release time storage unit
224 packet input / output unit
225 Information packet generator
31 Large antenna
32 Demodulation group
33 Demodulator #K
34 Packet sorting part
35 Packet input / output section
36 channel storage
37 Channel information transmitter
38 Throughput storage
39 Free channel information transmitter
331 Channel release time transmitter
332 Packet transmission control unit
333 Modulator of center station
41 Free channel information of this system to be broadcast
42 Channel release time for this method to be broadcast
43 Reservation packet of this method
44 Confirmation signal of this system
46 Confirmation signal transmitted to mobile station 45 of this system
47 Communication packet of this method
48 Release packet of this system
49 Reserved packet transmitted to mobile station 45 of this system
401 Information packet of this method
52 ALOHA confirmation signal
53 ALOHA packet collision
54 packet retransmission
61 ICMA free channel information
63 Reserved packet transmitted from ICMA mobile station
64 Confirmation signal transmitted to ICMA type mobile station 62
66 Reserved packet transmitted from ICMA mobile station 65
67 Confirmation signal transmitted to mobile station 65 of ICMA system
71 channel release time
72 Average data throughput of the entire mobile station
73 Ratio of channel number between mobile station and uplink

Claims (17)

It is composed of a plurality of mobile stations and one center station, and performs communication between the mobile station and the center station, and an uplink communication line from the mobile station to the center station divides a radio frequency, In a wireless packet transmission system having multiple frequency channels,
The center station
Free channel information transmitting means for broadcasting free channel information to the mobile station based on the usage status of uplink channels;
A channel release time between the center station and the mobile station is determined based on a predicted value of the channel release time that maximizes the data throughput between the center station and the mobile station, and is broadcast to the mobile station. A channel release time transmission means,
The mobile station
Means for selecting a channel prior to the start of communication based on the broadcast free channel information;
Radio packet transmission comprising: means for temporarily suspending communication when the channel release time is reached during communication based on the broadcasted channel release time and reselecting a channel again based on the free channel information system. The mobile station comprises means for calculating data throughput between the mobile station and the center station and reporting to the center station,
The center station includes means for storing data throughput information in each mobile station reported from the means for reporting,
The channel release time transmitting means includes
Based on the data throughput information stored in the storage means, a simulation is performed to predict the relationship between the data throughput and the channel release time between the center station and the mobile station, and the most data based on the simulation result. 2. The radio packet transmission system according to claim 1, further comprising means for broadcasting a channel release time for increasing the throughput to the mobile station. 2. The wireless packet transmission system according to claim 1, wherein said idle channel information transmission means and said channel release time transmission means comprise means for broadcasting at regular time intervals. 2. The wireless packet transmission system according to claim 1, wherein said vacant channel information transmitting means comprises means for broadcasting immediately after vacant channel information in said center station changes. The means for broadcasting the channel release time calculates an average value of data throughput for the mobile station based on information accumulated in the means for accumulating at regular time intervals, and the average value is lower than the previous average value. 3. The wireless packet transmission system according to claim 2, further comprising means for executing the simulation and broadcasting a channel release time at which the data throughput is highest based on the simulation result to the mobile station. It is composed of a plurality of mobile stations and one center station, and performs communication between the mobile station and the center station, and an uplink communication line from the mobile station to the center station divides a radio frequency, In a center station provided in a wireless packet transmission system in which channels of a plurality of frequencies exist,
Free channel information transmitting means for broadcasting free channel information to the mobile station based on the usage status of uplink channels;
A channel for determining the channel release time between the center station and the mobile station based on the predicted value of the channel release time that maximizes the data throughput between the mobile station and the mobile station, and broadcasting to the mobile station A center station comprising release time transmission means. Means for storing data throughput information in each mobile station reported from the mobile station;
The channel release time transmitting means includes
Based on the data throughput information stored in the storage means, a simulation for predicting the relationship between the data throughput between the mobile station and the mobile station and the channel release time is performed, and the data throughput is determined based on the simulation result. 7. The center station according to claim 6, further comprising means for broadcasting to the mobile station a channel release time at which the time becomes higher. 7. The center station according to claim 6, wherein said vacant channel information transmission means and said channel release time transmission means comprise means for broadcasting at regular time intervals. 7. The center station according to claim 6, wherein said vacant channel information transmitting means comprises means for broadcasting immediately after vacant channel information in the own station changes. The means for broadcasting the channel release time calculates an average value of data throughput for the mobile station based on information accumulated in the means for accumulating at regular time intervals, and the average value is lower than the previous average value. The center station according to claim 7, further comprising means for executing the simulation and broadcasting to the mobile station a channel release time at which the data throughput is highest based on the simulation result. It is composed of a plurality of mobile stations and one center station, and performs communication between the mobile station and the center station, and an uplink communication line from the mobile station to the center station divides a radio frequency, There are multiple frequency channels, and the center station broadcasts free channel information to the mobile station based on the usage status of uplink channels, and the data throughput between the center station and the mobile station In a mobile station provided in a wireless packet transmission system for determining a channel release time between the center station and the mobile station based on a predicted value of a channel release time at which the maximum is released and broadcasting to the mobile station,
Means for selecting a channel prior to the start of communication based on the broadcast free channel information;
A mobile station, comprising: means for temporarily suspending communication when the channel release time is reached during communication based on the broadcasted channel release time, and reselecting a channel again based on the free channel information. 12. The mobile station according to claim 11, further comprising means for calculating data throughput between the own station and the center station and reporting the data throughput to the center station. It is composed of a plurality of mobile stations and one center station, and performs communication between the mobile station and the center station, and an uplink communication line from the mobile station to the center station divides a radio frequency, In a wireless packet transmission method applied to a wireless packet transmission system in which channels of a plurality of frequencies exist,
The center station monitors the usage status of the uplink channel that changes from moment to moment, broadcasts free channel information to the mobile station, and simultaneously monitors the data throughput that changes from moment to moment. The channel release time is determined so that the data throughput between the center station and the mobile station is maximized, and the channel release time is broadcast to the mobile station, and the mobile station is broadcast. Receives uplink idle channel information and channel release time, selects a channel based on the idle channel information at the start of communication, and performs communication. At the same time, the communication time after selecting the channel reaches the channel release time. Then, the communication is temporarily interrupted, and then the communication is resumed based on the empty channel information and the channel release time again. Wireless packet transmission method characterized by, and repeated interruption of communication resumption and temporary. The mobile station calculates data throughput between the mobile station and the center station, and reports the data throughput to the center station. The center station accumulates data throughput information for each of the reported mobile stations. Based on the accumulated data throughput information, a simulation for predicting the relationship between the data throughput and the channel release time for the mobile station is performed, and the channel release time with the highest data throughput is determined based on the simulation result, The radio packet transmission method according to claim 13, which broadcasts to a mobile station. The radio packet transmission method according to claim 13, wherein the idle channel information and the channel release time are broadcast at regular time intervals. The wireless packet transmission method according to claim 13, wherein the idle channel information is broadcast immediately after the idle channel information in the center station changes. When the average value of the data throughput for the mobile station is calculated at regular time intervals and the average value is lower than the previous average value, the simulation is executed and the channel with the highest data throughput based on the simulation result The radio packet transmission method according to claim 14, wherein a release time is broadcast to the mobile station.

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