JP2004173099A - Radio packet transmission system and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To impartially assign a channel to all mobile stations and to allow all of the mobile stations to obtain high throughput. <P>SOLUTION: A center station monitors a use state of a channel of an uplink, broadcasts free channel information to the mobile stations, simultaneously monitors data throughput, determines a channel release time so as to make data throughput to be the highest between the center station and the mobile stations and broadcasts the channel release time to the mobile stations. The mobile stations receive the broadcasted free channel information and channel release time of the uplink, select a channel on the basis of the free channel information at a communication start to perform communication, simultaneously temporarily stops the communication when a communication time after selecting the channel reaches the channel release time, sequentially restarts the communication on the basis of the free channel information and the channel release time and repeats communication restart and temporary interruption. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
INDUSTRIAL APPLICABILITY The present invention is used for a wireless packet transmission system in which a plurality of frequency channels exist as a line from a mobile station to a center station and the number of mobile stations is larger than the number of usable frequency channels such as satellite communication. In particular, the present invention relates to a technique for fairly allocating a frequency channel to a mobile station and a technique for achieving high data throughput.
[0002]
[Prior art]
(ALOHA method)
The ALOHA method was introduced in 1970 by N.U. A wireless packet communication protocol announced by Abramson, and was actually used in the University of Hawaii computer network as ALOHASYSTEM.
[0003]
When the ALOHA method is applied to an apparatus configuration to which the present invention is applied, which includes a plurality of mobile stations and one center station, as shown in FIG. A channel can be selected at random from the frequency channel 6 of the communication line in the direction, and a packet can be transmitted at any time according to the request. Then, by receiving the confirmation signal 52 from the center station within a certain time, the success of the transmission is recognized. When the packet collision 53 occurs, the packet retransmission 54 is performed, but the retransmission interval is determined at random so that the retransmission packets between the mobile stations are not synchronized.
[0004]
(ICMA method)
The ICMA (Idle-signal Casting Multiple Access) system is adopted in a digital car telephone system. There is a technique for further improving data throughput based on the ICMA method (for example, see Patent Documents 1, 2, and 3). FIG. 6 shows a channel allocation sequence when these techniques are applied to an apparatus configuration to which the present invention is applied. The center station monitors the use status of the uplink channel, and broadcasts free 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 the packet 64 storing the channel number assigned to the mobile station 62, and at the same time, sets the channel as reserved for the time required for communication. Broadcast the channel information 61.
[0006]
Since there is a delay before the vacant channel information 61 for which the channel has been reserved reaches the mobile station 62, another mobile station 65 can transmit a 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 allocated to the mobile station 65.
[0007]
[Patent Document 1]
JP-A-10-20956
[Patent Document 2]
JP-A-2000-341292
[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 usable frequency channels is limited, there is a possibility that a plurality of mobile stations transmit packets simultaneously on the same channel, so that packet collision cannot be completely eliminated. Packet collisions lead to packet loss in wireless space.
[0009]
In the conventional ALOHA system, each mobile station randomly selects a channel from uplink channels and transmits a packet. Then, by receiving a confirmation signal from the center station within a certain period of time, it recognizes the success of the transmission. If there is no confirmation signal from the center station, it recognizes a packet collision. When a packet collision occurs, the packet is retransmitted, but the retransmission interval is randomly determined so that the retransmission packets between the mobile stations are not synchronized.
[0010]
When the number of mobile stations is larger than the number of channels of the uplink, more packets are transmitted on the uplink, so that packet collisions increase. When the number of packet collisions increases, the number of retransmitted packets also increases, resulting in a vicious cycle in which more packets are transmitted to the uplink. Since the packet that caused the collision is lost in the wireless space, the data throughput decreases.
[0011]
In the conventional ICMA method, a part of packet collision can be avoided by performing communication using a channel reserved in advance. As a specific method of channel reservation, a communication start request generated inside the mobile station is used as a trigger, and the mobile station sends a reservation packet containing the time required for communication to the center station once using an unreserved channel. I do. The center station receiving the reservation packet returns a reservation confirmation packet to the mobile station. After receiving the confirmation packet, the mobile station 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 as compared with the ALOHA system.
[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, until the communication of the mobile station making the channel reservation ends, the other mobile stations postpone the start of communication. As a result, a mobile station that has postponed the start of communication has a longer time from the start to the end of the communication, so that the data throughput decreases. While all channels are reserved, a specific mobile station occupies the channel, and it is not possible to allocate channels fairly to all mobile stations.
[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 with respect to the number of usable frequency channels, the number of packets on the uplink increases, The impact of this collision is greater, thus reducing data throughput. Further, when the ICMA method is applied, some mobile stations occupy the channel, so that the channels cannot be allocated fairly to all the mobile stations, and the data throughput of the mobile station that cannot allocate the channel. Will decrease.
[0015]
Therefore, an object of the present invention is to realize an access scheme that can allocate channels fairly to all mobile stations and that can obtain high data throughput for all mobile stations.
[0016]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, in the present invention, a plurality of mobile stations and one center station are configured to perform communication between the mobile station and the center station. In a wireless packet transmission system in which an uplink communication line divides a radio frequency and a plurality of frequency channels are present, the center station monitors the usage status of the uplink channel, which is constantly changing. Broadcasting the idle channel information to the mobile station, and at the same time, monitoring the data throughput that changes every moment, so that the data throughput between the center station and the mobile station is the highest. Determining the channel release time and broadcasting the channel release time to the mobile station, wherein the mobile station transmits Information and a channel release time, and at the start of communication, select a channel based on the free channel information and perform communication.At the same time, when the communication time after selecting the channel reaches the channel release time, the communication is temporarily stopped. The communication is resumed based on the idle channel information and the channel release time, and the restart and the suspension of the communication are repeated.
[0017]
As a result, it is possible to prevent a specific mobile station from occupying a channel, and to allocate a channel fairly to each mobile station. In this case, the mobile station does not simply forcibly release the channel after a lapse of a predetermined time.In the present invention, the channel release time at which the data throughput becomes 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 communicating mobile station to interrupt the communication halfway, but as a result, communication with high data throughput can be realized.
[0018]
That is, a first 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 an uplink from the mobile station to the center station. Is a wireless packet transmission system that divides a radio frequency and has a plurality of frequency channels.
[0019]
Here, a feature of the present invention is that the center station broadcasts free channel information to the mobile station based on the use state of the uplink channel, and the free channel information transmitting means; Channel release time transmitting means 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 data throughput with the mobile station is maximized and broadcasting to the mobile station Means for selecting a channel prior to the start of communication based on the broadcasted free channel information, and communication when the channel release time is reached during communication based on the broadcasted channel release time. Means for temporarily suspending and reselecting a channel based on the free channel information again; There is in the place with.
[0020]
The mobile station includes means for calculating a data throughput between the mobile station and the center station and reporting the calculated data throughput to the center station. The center station calculates a data throughput in each mobile station reported from the reporting means. Means for accumulating the information of, the channel release time transmission means, the data throughput and the channel release time between the center station and the mobile station based on the information of the data throughput stored in the storage means, It is preferable to include a means for executing a simulation for estimating the relationship and broadcasting the channel release time at which the data throughput becomes the highest to the mobile station based on the simulation result.
[0021]
Further, the free channel information transmitting means and the channel release time transmitting means may include means for broadcasting at a fixed time interval, or the free channel information transmitting means may be configured to perform the process immediately after the free channel information in the center station changes. It is desirable to have means for broadcasting.
[0022]
Alternatively, the means for broadcasting the channel release time calculates an average value of the data throughput for the mobile station based on the information accumulated in the accumulation means at regular time intervals, and the average value is lower than the previous average value. If so, means for executing the simulation and broadcasting the channel release time at which the data throughput becomes the highest based on the simulation result to the mobile station may be provided.
[0023]
According to this, since the conditions for executing the simulation can be limited, the number of times of executing the simulation with a high processing load can be reduced, and the resources can be used effectively.
[0024]
A second aspect of the present invention is configured by a plurality of mobile stations and one center station, performs communication between the mobile station and the center station, and performs uplink 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 a plurality of frequency channels.
[0025]
Here, the feature of the present invention is that an empty channel information transmitting unit that broadcasts empty channel information to the mobile station based on the use state of the channel of the uplink, between the own station and the mobile station. Channel release time transmitting means 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 data throughput is maximized and broadcasting to the mobile station. is there.
[0026]
Means for storing information on data throughput in each mobile station reported from the mobile station, wherein the channel release time transmitting means communicates with the own station based on the information on data throughput stored in the storing means. It is desirable to have means for executing a simulation for estimating 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 becomes highest based on the simulation result.
[0027]
Also, the free channel information transmitting means and the channel release time transmitting means may include means for broadcasting at a fixed time interval, or the free channel information transmitting means may broadcast immediately after the free channel information in its own station changes. It is desirable to provide a means for performing this.
[0028]
Alternatively, the means for broadcasting the channel release time calculates an average value of the data throughput for the mobile station based on the information accumulated in the accumulation means at regular time intervals, and the average value is lower than the previous average value. If so, means for executing the simulation and broadcasting the channel release time at which the data throughput becomes the highest based on the simulation result to the mobile station may be provided.
[0029]
A third aspect of the present invention is a communication system comprising a plurality of mobile stations and one center station, performing communication between the mobile station and the center station, and performing uplink communication from the mobile station to the center station. The line divides the radio frequency, and there are channels of a plurality of frequencies, and the center station broadcasts free channel information to the mobile station based on the use state of the channel of the uplink, and communicates with the center station. 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 data throughput with the mobile station is maximized, and broadcasting to the mobile station. The mobile station provided in.
[0030]
Here, the feature of the present invention is that a means for selecting a channel prior to the start of communication based on the broadcast free channel information, and that the channel release time during communication based on the broadcast channel release time Means for temporarily suspending communication upon reaching and reselecting a channel again based on the free channel information.
[0031]
It is desirable to have means for calculating the data throughput between the own station and the center station and reporting the data throughput to the center station.
[0032]
A fourth aspect of the present invention is a communication system comprising a plurality of mobile stations and one center station, performing communication between the mobile station and the center station, and performing uplink 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 a radio frequency is divided and a plurality of frequency channels exist.
[0033]
Here, the feature of the present invention is that the center station monitors the usage status of the uplink channel that changes every moment, and broadcasts free channel information to the mobile station. Monitoring the data throughput that changes from moment to moment, determines the channel release time so that the data throughput between the center station and the mobile station is the highest, and determines the channel release time for the mobile station. The mobile station receives the free channel information and channel release time of the uplink to be broadcasted, selects a channel based on the free channel information at the time of starting communication, performs communication, and at the same time selects a channel. When the communication time after the communication reaches the channel release time, the communication is temporarily suspended, and then the free channel information is returned 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 a data throughput between the mobile station and the center station and reports the calculated data throughput to the center station. The center station transmits data throughput information on each mobile station reported from the reporting means. Accumulating, and executing a simulation for estimating the relationship between the data throughput and the channel release time for the mobile station based on the accumulated information on the data throughput, and setting the channel release time at which the data throughput becomes highest based on the simulation result. Preferably, it is determined and broadcast to the mobile station.
[0035]
It is preferable that the empty channel information and the channel release time are broadcast at regular time intervals, or that the empty channel information is broadcast immediately after the empty channel information in the center station changes.
[0036]
Alternatively, at regular time intervals, the average value of the data throughput for the mobile station is calculated, and when the average value is lower than the previous average value, the simulation is executed and the data throughput is the highest based on the simulation result. A different channel release time may be broadcast to the mobile station.
[0037]
BEST MODE FOR CARRYING OUT 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 the wireless packet transmission system of 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 the present 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. An uplink communication line from the mobile station 1 to the center station 2 is provided. This is a wireless packet transmission system that divides a radio frequency and has a plurality of frequency channels.
[0039]
Here, a feature of the present embodiment is that the center station 2 includes an empty channel information transmitting unit 39 that broadcasts empty channel information to the mobile station 1 based on the use state of the uplink channel, 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 at which the data throughput between the mobile station 1 and the mobile station 1 is maximized and broadcasting to the mobile station 1 The mobile station 1 includes a transmission unit 331, wherein the mobile station 1 selects a channel prior to the start of communication based on the broadcasted free channel information, and a reservation packet generation unit 29, which performs the communication based on the broadcasted channel release time. When the channel release time is reached, the communication is suspended and the channel is reselected based on the available channel information again. 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 the 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 receives the information from the information packet generator 225. The mobile station 1 includes a throughput storage unit 38 for storing information on data throughput. The channel release time transmitting unit 331 communicates with the center station 2 and the mobile station 1 based on the data throughput information stored in the throughput storage unit 38. , A simulation for estimating the relationship between the data throughput and the channel release time is executed, and the channel release time at which the data throughput becomes the highest is broadcast based on the simulation result.
[0041]
The free channel information transmitting unit 39 and the channel release time transmitting unit 331 broadcast at a fixed time interval, or the free channel information transmitting unit 39 broadcasts immediately after the free 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 stored 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 at which the data throughput becomes highest is broadcast to the mobile station 1 based on the simulation result.
[0043]
Hereinafter, embodiments of the present invention will be described. The wireless packet transmission system according to the present embodiment includes 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 according to the present embodiment. Uplink frequency 6 is set from channel # 1 to channel #N, and free channel information 41 and channel release time 42, which are information on channel usage, are broadcast from the center station to all mobile stations. Every mobile station overwrites and saves in its own memory each 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 request to start communication is generated within the mobile station 1, the mobile station 1 selects a channel based on the available channel information 41, and determines the mobile station number allocated 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 has been successful. Since there is a delay before the vacant 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, the center station 2 returns the packet 4 storing the channel number individually assigned to the mobile station 45.
[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 the mobile station. 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]
Then, after a time interval, the communication is restarted again based on the idle channel information and the channel release time, and the restart and the relay are repeated until the communication ends. When the communication is completed, an information packet 401 storing the mobile station number and the value of the data throughput is transmitted.
[0049]
Next, FIG. 2 shows a detailed configuration of the mobile station. The mobile station temporarily buffers packets generated in the mobile station in the order of buffer A21 and buffer B22, and then inputs the packets to the modulator 23. The modulator 23 modulates the packet into a radio signal and transmits the radio signal from the small antenna 25 using the channel stored in the channel storage 24.
[0050]
In the timer section 26, the timer value is increased every moment. When the timer value reaches the channel release time, the release packet is transmitted through the release packet generation unit 27, the timer value and the channel of the channel storage unit 24 are cleared, and the packet output from the buffer A21 is stopped. Thereafter, the timer value is restarted, and after reaching the retransmission time, the timer value is cleared and the packet output from the buffer A21 is restarted.
[0051]
If no channel is stored in the channel storage unit 24, the packet output from the buffer B22 is stopped, and at the same time, a 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 demodulation unit 221 demodulates the signal received from the small antenna 25, and the packet contents are released by the packet classification unit 222. When the content is the assigned channel number, free channel information, or channel release time, they are stored in the channel storage unit 24, the free 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 the communication end time from the packet input / output unit 224 and the amount of data transmitted, generates an information packet at the end of the communication, and transmits the information packet through the modulator 23. .
[0054]
Next, a detailed configuration of the center station 2 is shown in FIG. The signal received by the large antenna 31 is input to the demodulation group unit 32, and the demodulation unit # K33 (where K is a channel number and an arbitrary number between 1 and N) corresponding to the channel used for transmission from the mobile station. The packet demodulated by (natural number) 33 is demodulated through a packet classification unit 34 according to the content thereof as follows.
[0055]
If the demodulated packet is a communication packet, it is extracted from the center station 2 to the outside through the packet input / output unit 35.
[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 reservation 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, the mobile station number is stored. If another mobile station is already stored, the mobile station number 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 transmitting unit 37 is stored in the packet to Send to the station.
[0058]
In the case of an information packet, the combination of the mobile station number and the value of the data throughput is stored in the throughput storage unit 38.
[0059]
Further, the vacant channel information transmitting unit 39 retrieves an unreserved channel from the channel storage unit, creates vacant channel information, and broadcasts it to all mobile stations at certain time intervals.
[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 between the channel release time 71 and the average value 72 of the data throughput with the channel release time (sec) taken on the horizontal axis and the data throughput (kbps) taken on the vertical axis. The 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 at which the data throughput has a 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 increases, causing a decrease in data throughput.On the other hand, if the channel release time is too short, the mobile station acquires and releases the channel. The number of times of repetition increases, the overhead takes time, and the data throughput is reduced. The data throughput is maximized for the channel release time at which these two effects are minimized.
[0062]
FIG. 8 shows the number of mobile stations on the horizontal axis and the data throughput (kbps) on the vertical axis, and shows a comparison between the ALOHA system, the ICMA system, and the data throughput of the present invention. As described above, by setting the channel release time so that the data throughput becomes the maximum value, the present invention always realizes a high data throughput with respect to the number of all mobile stations. Although not shown in the graph, the present invention provides a channel release time, whereby each mobile station temporarily suspends communication. What can be shared can easily be inferred.
[0063]
The channel release time transmission unit 331 calculates an average value of the data throughput for all the mobile stations 1 from the throughput storage unit 38 at regular time intervals, and when the average value is lower than the previous average value, the throughput storage unit 38. A simulation is performed based on the information of the data throughput stored in the memory, and the relationship between the data throughput and the channel release time shown in FIG. 7 is recognized. Broadcast transmission to all the mobile stations 1. By dynamically setting the channel release time in this way, the data throughput of the entire mobile station 1 is automatically set so as to be the maximum value. The broadcast of the channel release time may be performed at fixed time intervals, or may be performed immediately after newly executing the simulation.
[0064]
The packet input from the packet input / output unit 35 is controlled by the packet transmission control unit 332 so as not to collide with the packets from the channel information transmitting unit 37, the empty channel information transmitting unit 39, and the channel release time transmitting unit 331. After being modulated by the modulator 333, the signal is transmitted from the large antenna 31.
[0065]
【The invention's effect】
As described above, according to the present invention, channels can be fairly allocated 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 according to an embodiment of the present invention.
FIG. 2 is a diagram showing a configuration of a mobile station of the wireless packet transmission system according to 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 diagram showing timings of channel reservation and channel release in the embodiment of the present invention.
FIG. 5 is a diagram showing the timing of ALOHA-based channel reservation and channel release.
FIG. 6 is a diagram showing timings of channel reservation and channel release in the ICMA system.
FIG. 7 is a diagram showing a relationship between a channel release time and a 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 channels
21 Buffer A
22 Buffer B
23 Modulation section of mobile station
24 Channel storage unit of mobile station
25 Small antenna
26 Timer section
27 Release packet generator
28 Free channel information storage
29 Reserved packet generator
221 Demodulation unit of mobile station
222 Packet classification unit 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 Demodulation unit #K
34 Packet Classification Unit
35 Packet input / output unit
36 channel storage unit
37 Channel information transmitter
38 Throughput storage unit
39 Free channel information transmission unit
331 Channel release time transmission unit
332 packet transmission control unit
333 Modulation part of center station
41 Free channel information of this system to be broadcast
42 Broadcast channel release time
43 Reserved packet of this method
44 Confirmation signal of this method
46 Confirmation signal transmitted to mobile station 45 of this system
47 communication packets
48 Release packets of this method
49 Reserved packet transmitted to mobile station 45 of this system
401 Information packet of this method
52 ALOHA system confirmation signal
53 ALOHA packet collision
54 packet retransmission
61 ICMA free channel information
63 Reserved packet transmitted from ICMA mobile station
64 A confirmation signal transmitted to the ICMA mobile station 62
66 Reserved packet transmitted from ICMA mobile station 65
67 Confirmation signal transmitted to ICMA mobile station 65
71 Channel release time
72 Average data throughput of all mobile stations
73 Ratio of mobile station to uplink channel number

Claims (17)

Composed of a plurality of mobile stations and one center station, performs communication between the mobile station and the center station, an uplink communication line from the mobile station to the center station, divides the radio frequency, In a wireless packet transmission system having a plurality of frequency channels,
The center station,
Free channel information transmitting means for broadcasting free channel information to the mobile station based on the use status of the uplink channel,
A channel release time between the center station and the mobile station is determined based on a predicted value of a channel release time at which the data throughput between the center station and the mobile station is maximized, and broadcast to the mobile station. Channel release time transmission means,
The mobile station comprises:
Means for selecting a channel prior to the start of communication based on the broadcast free channel information,
Means for temporarily suspending communication when reaching the channel release time during communication based on the broadcasted channel release time and reselecting a channel again based on the free channel information. system. 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 includes means for accumulating information on data throughput in each mobile station reported from the reporting means,
The channel release time transmitting means,
A simulation is performed to predict the relationship between the data throughput between the center station and the mobile station and the channel release time based on the information on the data throughput stored in the storage means, and the most data is obtained based on the simulation result. 2. The wireless packet transmission system according to claim 1, further comprising: means for broadcasting a channel release time at which a throughput increases to the mobile station. 2. The wireless packet transmission system according to claim 1, wherein said free channel information transmitting means and said channel release time transmitting means include means for broadcasting at a fixed time interval. 2. The wireless packet transmission system according to claim 1, wherein said free channel information transmitting means includes means for broadcasting immediately after the free channel information in said center station changes. The means for broadcasting the channel release time calculates an average value of the data throughput for the mobile station based on the information accumulated in the accumulation means 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 becomes highest based on the simulation result to the mobile station. Composed of a plurality of mobile stations and one center station, performs communication between the mobile station and the center station, an uplink communication line from the mobile station to the center station, divides the radio frequency, In a center station provided in a wireless packet transmission system having a plurality of frequency channels,
Free channel information transmitting means for broadcasting free channel information to the mobile station based on the use status of the uplink channel,
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 at which the data throughput between the own station and the mobile station is maximized and broadcasting to the mobile station A center station comprising release time transmitting means. Means for accumulating information of data throughput in each mobile station reported from the mobile station,
The channel release time transmitting means,
A simulation is performed to predict the relationship between the data throughput between the own station and the mobile station and the channel release time based on the information on the data throughput stored in the storage means, and the data throughput is determined based on the simulation result. 7. The center station according to claim 6, further comprising: means for broadcasting a channel release time at which the mobile station time becomes higher to the mobile station. 7. The center station according to claim 6, wherein said vacant channel information transmitting means and said channel release time transmitting means include means for broadcasting at predetermined time intervals. 7. The center station according to claim 6, wherein said vacant channel information transmitting means comprises means for broadcasting immediately after the vacant channel information in the station changes. The means for broadcasting the channel release time calculates an average value of the data throughput for the mobile station based on the information accumulated in the accumulation means at regular time intervals, and the average value is lower than the previous average value. 8. The center station according to claim 7, further comprising: means for executing the simulation and broadcasting a channel release time at which the data throughput becomes highest based on the simulation result to the mobile station. Composed of a plurality of mobile stations and one center station, performs communication between the mobile station and the center station, an uplink communication line from the mobile station to the center station, divides the radio frequency, There are channels of a plurality of frequencies, the center station broadcasts free channel information to the mobile station based on the use status of the channel of the uplink, and the data throughput between the center station and the mobile station. In the mobile station provided in the wireless packet transmission system to determine the channel release time between the center station and the mobile station based on the predicted value of the maximum channel release time, and broadcast to the mobile station,
Means for selecting a channel prior to the start of communication based on the broadcast free channel information,
Means for temporarily suspending communication when reaching the channel release time during communication based on the broadcasted channel release time and reselecting a channel again based on the free channel information. The mobile station according to claim 11, further comprising means for calculating a data throughput between the own station and the center station and reporting the data throughput to the center station. Composed of a plurality of mobile stations and one center station, performs communication between the mobile station and the center station, an uplink communication line from the mobile station to the center station, divides the radio frequency, In a wireless packet transmission method applied to a wireless packet transmission system having a plurality of frequency channels,
The center station monitors the usage status of the ever-changing uplink channel, broadcasts free channel information to the mobile station, and simultaneously monitors the ever-changing data throughput. Determining a channel release time so that the data throughput between the center station and the mobile station is the highest, broadcasting the channel release time to the mobile station, and the mobile station is broadcasted Receives uplink free channel information and channel release time, selects a channel based on the free channel information at the start of communication, performs communication, and at the same time, the communication time after selecting a channel reaches the channel release time. Then, the communication is temporarily suspended, and then the communication is restarted again based on the idle channel information and the channel release time. Wireless packet transmission method characterized by, and repeated interruption of communication resumption and temporary. The mobile station calculates a data throughput between the mobile station and the center station and reports the calculated data throughput to the center station.The center station accumulates information on the data throughput of each of the reported mobile stations. A simulation is performed to predict the relationship between the data throughput and the channel release time for the mobile station based on the accumulated information of the data throughput, and the channel release time at which the data throughput becomes highest is determined based on the simulation result. 14. The wireless packet transmission method according to claim 13, wherein the broadcast is broadcast to a mobile station. 14. The wireless packet transmission method according to claim 13, wherein the empty channel information and the channel release time are broadcast at regular time intervals. 14. The wireless packet transmission method according to claim 13, wherein the free channel information is broadcast immediately after the free channel information in the center station changes. For each fixed time interval, calculate the average value of the data throughput for the mobile station and, if the average value is lower than the previous average value, execute the simulation and execute the simulation to determine the channel having the highest data throughput based on the simulation result. The wireless packet transmission method according to claim 14, wherein a release time is broadcast to the mobile station.

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