JP2793991B2 - Reservation cancellation method in wireless packet communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio packet communication system, and more particularly to a radio packet communication system employing a CDMA system as a multiple access system and a reservation access system as an access system from a mobile station to a base station. Regarding the release method.

[0002]

2. Description of the Related Art Conventionally, a random access method and a reservation access method have been known as access methods in wireless packet communication such as a wireless LAN and a mobile communication system. The random access method is a method in which each mobile station or each wireless terminal arbitrarily transmits a packet,
If the packets collide, they are transmitted again. On the other hand, the reservation access method is a method for reserving the transmission time of a packet by reserving it, and it is possible to prevent packet collision and improve transmission efficiency. As one of the reservation access methods, the R-ALOHA method is known (for example,
“Packet BroadcastNetworks-A Performance Analysi
s of the R-ALOHA Protocol ”IEEE TRANSACTIONS ON CO
MPUTERS, VOL.C-29, NO.7, JULY, 1980, p596-603)
Please refer to).

[0005] FIG. 5 is a time chart showing an example of packet transmission by the R-ALOHA system. In this figure, the uplink shows an example of packet transmission on the uplink from each wireless terminal (mobile station) to the base station, and the downlink shows a signal transmitted from the base station to the mobile station. As shown in the figure, in the R-ALOHA system, one frame is constituted by a plurality of time slots,
In the example shown in this figure, one frame is composed of four time slots of time slots 1 to 4. The status of reservation of each time slot is usually reported from the base station to each mobile station. In this example, as shown, the status of reservation of time slots is reported through the downlink. Has been made. Each mobile station makes a reservation by transmitting a packet (reservation packet) requesting a reservation to a time slot without a reservation according to the reservation situation broadcast in this way, secures the slot, and transmits it. Works like that. This reservation packet is transmitted by the random access method. In addition,
The reservation packet in the R-ALOHA system is similar to a normal data packet, and is not a special control packet.

In FIG. 5, a time slot 1 of frame 1 is reserved by a first mobile station MS1, and a time slot 4 is reserved by a sixth mobile station MS6. Packets from those mobile stations correspond to each other. To be sent to the slot. Time slots 2 and 3 of frame 1 are empty slots that are not reserved. As shown in the figure, a broadcast packet from the base station to the mobile station is transmitted in the latter half of each slot in the downlink, and the next slot 2 in the uplink is transmitted at a timing corresponding to slot 1 of frame 1 in the uplink. Information (I) indicating an empty slot and information (I) indicating that the next slot 3 is empty are transmitted at the timing corresponding to slot 2. Similarly, at the timing of slot 3, information (R) indicating that the next slot (slot 4) is a reserved slot, and in slot 4 indicating that the next slot 1 (frame 2) is a reserved slot. Information (R) is being transmitted. The broadcast packet from the base station to the mobile station also includes response information to a reservation request packet in the uplink of the slot.

In such a state, for example, when a packet to be transmitted occurs in the mobile station MS2,
Since the downlink broadcast information corresponding to slot 1 of frame 2 is (I), indicating that slot 2 of frame 2 is an empty slot, the mobile station MS 2
It is assumed that a reservation request packet has been transmitted to slot 2 of. At this time, if there is no other mobile station that has transmitted the reservation request packet to this slot, the reservation request packet is normally received as shown in the figure. In response, the base station transmits information notifying that the reservation by the mobile station MS2 has been acquired through the downlink. Thereafter, slot 2 is used for mobile station MS2.
, The broadcast information transmitted at the timing of slot 1 in downlink frame 3 is information (R) indicating that the slot is a reserved slot, as shown in the figure. Thus, the mobile station MS2 can continue to transmit packets using the time slot 2 exclusively.

[0006] When the transmission of a packet to be transmitted is completed in the mobile station that has reserved the reservation, the reservation of the slot is released, and the time slot is released. As the method of canceling the reservation, the following two methods are known. The first method is a method that does not use the “use end” flag, and the base station does not transmit a signal to the reserved slot of the frame next to the frame that transmitted the last packet, so that the base station can transmit. This is a method of determining that the reservation has been completed and canceling the reservation. Also, the second
Is a method that uses the “end of use” flag.
"End of use" in the last packet transmitted by the mobile station being reserved
This is a method in which a flag is inserted and the reservation is released by the base station detecting the "use end" flag.

FIG. 5 shows an example of packet transmission when the first method is adopted. In FIG. 5, assuming that the transmission of the first mobile station MS1 ends in slot 1 of frame 1, slot 1 of frame 2 in the figure is a reserved slot of the mobile station MS1,
Nothing is sent. At this time, the base station detects this state, that is, a state in which a valid packet is not detected even though it is a reserved slot, and releases the reservation of this slot. Accordingly, broadcast information (broadcast information indicating the reservation status of slot 1 of frame 3) transmitted from the base station at the timing of slot 4 of frame 2 is:
This is information (I) indicating an empty slot.

In the second method using the "end of use" flag, the mobile station transmits a last transmission packet with a flag ("use end flag") indicating the end of use of the slot, and transmits the packet to the base station. This is a method in which the station detects the use end flag and releases the reservation of the slot. For example, the mobile station MS1 attaches a use end flag to a packet transmitted in slot 1 of frame 1 and transmits the packet. Thereby, the base station detects that the use end flag is attached to the packet, and releases the reservation of the slot 1. Therefore, in this case, when the signal of the slot 1 of the frame 1 is received, it is determined that the reservation may be released, and the downlink broadcast information corresponding to the slot 4 of the frame 1 is empty. (I) indicating the following.

In the case of the first system which does not use the use end flag, an empty slot for indicating the end of transmission is required when releasing a reservation, and a time slot is wasted. Further, according to the second method using the “use end” flag, it is possible to prevent the empty slot from being wasted as in the first method, but the base station always monitors the “use end” flag. Must be performed, complicated control is required as compared with the case of the first method, and mounting is difficult.

[0010]

SUMMARY OF THE INVENTION As a multiple access system, C
When the aforementioned R-ALOHA system is applied to a wireless packet communication system employing the DMA system, CDMA
Due to the nature of the method, the following problems occur. That is, since the same frequency band is used in the CDMA system, there is a property that when a predetermined amount or more of interference occurs, all signals in a time zone in which the interference exists cannot be received. As described above, R-AL
Since reserved packets in the OHA method are transmitted by the random access method, if reserved packets are concentrated in empty slots, packets in reserved slots of other code channels in the same time slot as the empty slots are not received. I will. Therefore, when the above-described first reservation release method is employed, the base station does not receive a valid packet, and thus releases the reservation of all slots in the time slot including the reserved slot. It will be. In addition, even when the second reservation canceling method is adopted, a problem that the state in which the reservation is not canceled continues as described later occurs.

These problems will be described in detail with reference to FIG. This figure is a time chart showing an example of packet transmission when the CDMA system is adopted as the multiple access system and the above-mentioned R-ALOHA system is adopted as the access system from the mobile station to the base station. In this figure,
(A) shows the case where the above-described first method which does not use the “use end” flag as the reservation release method is adopted, and (b) shows “
The figure shows a case where the second method using the "use end" flag is adopted. Also, as shown in the figure, it is assumed that three code channels of code channels 1 to 3 are multiplexed in one time slot. I do.

First, the case of the first system shown in FIG. 6A will be described. In this figure, (1) a diagonal hatching is made around the slot, and the slot in which the name of the mobile station MSn that transmitted the slot is written is a reserved slot, and the mobile station MSn transmits a normal packet. (2) Slots with diagonal hatching around the periphery and blank in the center are reserved slots but no packets transmitted,
(3) The slot in which the name of the mobile station that transmitted the slot MSn is written at the center is an empty slot, and the mobile station MSn
(4) Blank slots are empty slots, no reserved packets have been transmitted from any mobile station, and (5) Horizontal lines are hatched in a plurality of slots. The reservation packet transmitted from the mobile station of No. 3 collides and becomes unreceivable, and (6) the oblique hatching around the periphery and the slot marked with “x” above the number of the mobile station are reserved. This indicates a state in which the mobile station has transmitted a packet in the slot but has become unreceivable due to interference or the like.

In FIG. 6A, the mobile station MS1 is
Code channel 1 in slot 1 is reserved, and packets from the mobile station MS1 are transmitted in frames 1 and 2. When the frame 3 is reached, the mobile station MS1
Is not transmitted, and the base station releases the reservation of the code channel 1 of the slot 1 as described above. In frame 4, only the mobile station MS2 transmits a reservation packet to an empty slot where the reservation has been released. Also, code channels 2 and 3 in slot 1 are also reserved slots, which span frames 1-4.
Each packet transmitted from the mobile station is transmitted.

All of the code channels 1 to 3 in slot 2 are empty slots in frame 1. In frame 2, reservation packets from a plurality of mobile stations concentrate on code channel 1 in slot 2, and none of the mobile stations can acquire a reservation. In the frame 3, the mobile station that transmitted the reservation packet to the code channel 1 of the slot 2 is only the mobile station MS3. The mobile station MS3 acquires the reservation of this slot, and in the frame 4, this slot becomes the reserved slot of the mobile station MS3. Has become. In addition,
Code channels 2 and 3 in slot 2 remain empty slots.

Code channel 1 in slot 3 is frame 1
Is a reserved slot of the mobile station MS4, and a packet from the mobile station MS4 is being transmitted. Since the transmission of the mobile station MS4 ends in this frame 1 and the mobile station MS4 does not transmit a packet in the code channel 1 of the slot 3 of the frame 2, the code channel 1 of the slot 3 of the frame 2 is a reserved slot. A packet is not transmitted, and the reservation of this slot is released. Only the mobile station MS5 that has prepared the packet to be transmitted transmits a reservation packet to the code channel 1 of this time slot of the frame 3, and the code channel 1 of this time slot 3 becomes the reserved slot of this mobile station MS5. It has become. The code channel 2 in slot 3 is a reserved channel, and a packet from the mobile station is being transmitted. Further, in the code channel 3 of the slot 3, a reservation packet is transmitted in the frame 1, and after the frame 2, the reservation packet of the mobile station is used. The above operation is the same as that of R described with reference to FIG.
-The operation is the same as in the case of the ALOHA system packet transmission example, and no particular problem occurs particularly when the CDMA system is adopted.

[0016] Code channel 1 in slot 4 is a reserved slot for mobile station MS6 in frame 1, and a packet from mobile station MS6 is being transmitted. It is also assumed that the code channel 2 in slot 4 is also a reserved slot for another mobile station, and that a packet from the mobile station is being received. Further, it is assumed that the code channel 3 in slot 4 is a reserved slot and the mobile station does not transmit a packet. At this time, since the reservation of the code channel 3 is released and becomes an empty channel, a plurality of mobile stations having no reservation in the code channel 3 of the slot 4 of the frame 2 transmit a reservation packet, and a collision occurs. . At this time, if there are many mobile stations transmitting the reservation packet, the number of multiplexes satisfying the required quality in CDMA will be exceeded, and the packet transmitted to that slot will be lost in all code channels.

As described above, since the CDMA system is employed, interference from other mobile stations due to multiple access increases, and when a signal received by the base station falls below a required quality, the base station performs The packet cannot be received correctly, and the slot is determined as an empty slot. Therefore, in slot 4 of frame 2, signals cannot be normally received not only in code channel 3 but also in code channels 1 and 2. At this time, since the base station did not receive the packet in the code channels 1 to 3 of the time slot 4 of the frame 2, all the reservations of the code channels 1 to 3 of the time slot are released. That is, although the mobile station having the reservation holds the packet to be transmitted in the subsequent frame, the reservation is canceled and a new reservation must be requested.

In this case, the mobile station must make a new reservation request. Even when a new reservation request is made, as shown in code channel 1 of slot 4 in frame 3, the mobile station may again make a reservation packet collision. In some cases, reservations cannot be obtained. That is, the reservation packet from the mobile station that has released the reservation despite having the reservation and the mobile station that has transmitted the reservation packet to the code channel 3 of the slot 4 of the frame 2 is the code of the time slot 4 of the frame 3. If it concentrates on channel 1, as shown in the figure, it will be in an unreceivable state. As a result, the code channel 1 of the time slot 4 is determined to be an empty slot again, and a similar state occurs in the code channel 1 of the slot 4 of the frame 4 and the reception disabled state continues. In some cases.

As described above, in the CDMA system, the problem that the reservation is canceled due to the interference of the reservation packet from another mobile station, and the concentration of the reservation packet continues to reduce the transmission efficiency. There is a problem that it may occur.

Next, a case where the second reservation canceling method is adopted will be described with reference to FIG. In this case, the first data packet is provided with a "use" flag (U), and the last data packet is provided with a "use end" flag (E). It is different from the case of the method. In this figure, the state of each slot is the same as that in the case of FIG. 6 (a).
Since the end-of-use flag (E) is added, empty slots can be eliminated as described above. That is, in FIG. Although the code channel 1 of slot 3 in 2 is an empty slot, in the case of the second system, it is not an empty channel and the transmission efficiency is improved.

In the case of the second system, when all the code channels are in the reception disabled state in the slot 4 of the frame 2 as in the case of FIG.
Since the base station has not detected the "use end" flag, it does not release the reservation. Therefore, the mobile station MS6 or the like that has reserved the reservation transmits the packet to the same code channel 1 and 2 in the slot 4. Also, a plurality of mobile stations that have transmitted the reservation packet to code channel 3 in slot 4 of frame 2
When the reserved packet is transmitted to the receiver, interference exceeding the allowable amount occurs again, and a reception impossible state occurs as shown in the figure. In addition, the same state also occurs in frame 4.
May continue. As described above, once reservations are concentrated and interference exceeding an allowable amount occurs, a reception impossible state may continue and transmission efficiency may be reduced.

The present invention has been made in order to solve such a problem, and eliminates the problem of losing a reservation due to interference caused by a signal from another mobile station. The aim is to provide a scheme.

[0023]

In order to achieve the above object, a first reservation cancellation method according to the present invention comprises a base station and a plurality of mobile stations. Movement where a signal to be transmitted occurred in uplink packet transmission
Stations randomly access packets toward empty slots
Transmission, and if the transmission succeeds, the time slot
The mobile station that has obtained the reservation occupies the reservation grant slot.
A reservation release method in a wireless packet communication system employing an R-ALOHA method capable of transmitting a signal and employing a CDMA method as a multiple access method, wherein the base station includes a valid packet from a received signal. And a reservation control unit for controlling reservation of each code channel and monitoring a reservation grant slot, wherein the valid signal detection means does not detect a valid packet in the reservation grant slot. In addition, the reservation control unit refers to the signal detection status of the other reservation grant slots at the time, and when the number of reservation grant slots for which no valid packet is detected is equal to or greater than a preset threshold, all reservation grants are performed. The slot reservation is not released.

[0024] In the above-mentioned reservation canceling method, the reservation control unit cancels the reservation of the slot when the valid packet is not detected continuously for a predetermined number of times or more from the same reservation grant slot. It was made.

Further, the second reservation release method in the wireless packet communication system of the present invention comprises a base station and a plurality of mobile stations, and should transmit the uplink packet transmission from the mobile station to the base station. The mobile station that generated the signal
Random access method for packets toward empty slots
And send it successfully and make a reservation for that time slot.
The acquired mobile station occupies the reserved slot and signals
R-ALOHA method that can transmit
And a reservation release method in a wireless packet communication system adopting a CDMA method as a multiple access method, wherein the base station comprises: a valid signal detecting means for detecting a valid packet from a received signal; A reservation control unit for performing control and monitoring of a reservation grant slot, wherein when the valid signal detection means does not continuously detect a valid packet from the same reservation grant slot for a preset number of times or more, the reservation is performed. The control unit releases the reservation of the slot.

[0026]

FIG. 1 is a block diagram showing a configuration example of a mobile station and a base station in a wireless packet communication system to which a reservation release system of the present invention is applied. In this figure, reference numeral 10 denotes a mobile station. The mobile station 10 converts a packet information into a radio signal and transmits / receives the radio signal, assembles a packet, inserts an error correction code, and transmits a control signal from a base station. , A transmission buffer 13 for storing packet information to be transmitted, a packet generation source 14 for generating packet information to be transmitted, and a transmission control unit for controlling packet transmission according to the control signal from the base station described above. 15 is comprised.

Reference numeral 20 denotes a base station.
Is a radio unit 21 for converting received radio signals into packet information or transmitting packet information to radio signals, and a control unit for disassembling or correcting received packets or assembling transmission control information to be transmitted into packets. 22,
Receive buffer 2 for temporarily storing received packet information
3. It comprises a signal detection unit 24 for detecting a valid packet from the signals received by the control unit 22, and a reservation control unit 25 for controlling slot reservation and monitoring a reservation grant slot. The reservation control unit 25 includes a reservation status data storage unit for storing the reservation status of each slot,
A reception status data storage unit for storing a reception status of data in a past frame of each slot.

The operation of the wireless packet communication system thus configured will be described with reference to the time chart of FIG. 2 and the flowchart of the reservation release processing shown in FIG.

As described above, normally, in the R-ALOHA protocol, the mobile station 10 requests the base station 20 to make a reservation and sequentially transmits the packet data stored in the transmission buffer 13 to the slot in which the reservation has been obtained. ing. That is, the mobile station 10, at the timing of slot own station has acquired the reservation, it is determined that the controller 12 own reservation acquisition slot in packetizes the packet data in the transmission buffer 13 in the controller 12 , Radio section
11 to the base station 20. On the other hand, the base station 20
Receives a received signal from the mobile station 10 at the control unit 22 through the radio unit 21, the control unit 22 performs packet disassembly, error correction, and the like, stores the received packet information in the reception buffer 23, and outputs it to the subsequent stage.

In the base station 20, a reservation granting process and a reservation canceling process are executed. The reservation granting process is the same as the above-described conventional technology. When the signal detection unit 24 detects a reservation packet transmitted to an empty slot, the signal is transmitted to the mobile station that transmitted the reservation packet. This is a process of giving a reservation to the mobile station and notifying the mobile station of control information as described above.

FIG. 3 shows a flowchart of the reservation release processing. When this process is started, first, the signal detection unit 2
4 stores the data output from the control unit 22 in the reservation control unit 25
It is determined whether or not the data is valid data for all the code channels while referring to the reservation status data held in step S41 (step S41). The result of this determination is notified to the reservation control unit 25, and if there is a slot for which no valid data is detected even though the slot is a reservation grant slot, the reservation control unit 25 transmits a reservation grant for another code channel at the same time. With reference to the reception status of valid data in the slot, it is determined whether or not the number of slots that are reserved slots and for which no valid data is detected is equal to or greater than a preset threshold (step S42). . If the result of this determination is not less than the threshold, the process returns to step S41 without releasing all reservations for the slot concerned, and the same processing is executed for the next slot. On the other hand, if it is less than the threshold, the reservation of the slot is canceled (step S43).

As described above, when the CDMA system is employed, the reason why a valid packet is not detected despite the fact that the slot is a reservation grant slot is as follows. And
(B) There are two cases: a case where a signal cannot be received due to interference from another station even though the mobile station that has acquired the reservation is transmitting a packet. This (b)
In the same time slot, signals cannot be received in the same time slot due to the interference.
By the judgment of 42, the case (a) and the case (b) can be distinguished. Therefore, when the result of the determination in step S42 is YES, it is determined that interference is caused by (b), and the reservation is not released. When the result of the determination in step S42 is NO, it is determined that the mobile station has not transmitted the packet, and the reservation is released as in the case of the related art.

FIG. 2 is a diagram showing an example of packet transmission according to the present invention, and shows a state similar to that of FIG. 6 described above. FIG. 2A is a timing chart when the “use end” flag is not used, and FIG. 2B is a timing chart when the “use end” flag is used. When the interference from another mobile station becomes large and the signal of this slot is not received, as in slot 4 of frame 2 in FIG. 2A, the above-described first reservation release method of the present invention is used. For example, since the reservation of the mobile station that has acquired the reservation is not released, as shown in code channels 1 and 2 in slot 4 of frame 3 in FIG. It is possible to transmit packets continuously.

The threshold value is usually the number of slots to which a reservation has been given (the number of code channels to which a reservation has been given in the slot). For example, a smaller number can be set as the threshold value.

When such a reservation release method is employed, interference may occur in a subsequent frame and a state in which a valid packet is not received may continue. This also occurs, for example, in a cellular system or the like, when the amount of interference due to a signal from another mobile station increases due to the influence of movement of the mobile station. With reference to the flowchart shown in FIG. 4, a description will be given of a second reservation cancellation method according to the present invention, which solves such a disadvantage.

In this case, first, the signal detection unit 24
It is determined whether valid data has been received for all code channels of the time slot with reference to the reservation status data held by the reservation control unit 25 (step S5).
1) Notify the reservation control unit 25 of the result. The reservation control unit 25 sequentially stores the monitoring results of valid data in the reservation grant slot for each frame notified from the signal detection unit 24 (step S52). And the reservation control unit 2
5, when the signal detection unit 24 notifies that the valid data in the reserved slot has not been detected, the signal detection unit 24 checks the past valid data detection status in the slot (step S54), and performs the check. If the result is that the valid data has not been detected continuously for a predetermined number of times or more, the reservation of the slot is canceled (step S55). In other cases, the reservation of the slot is held and the reception of a packet in the next frame is waited.

According to the second reservation release method, when the first reservation release method is adopted, when it becomes difficult to receive packets continuously, all reservations in the slot are temporarily stopped. By canceling, it is possible to prevent continuation of meaningless packet transmission.

The second reservation release method is also effective in the case of the reservation release method using the "use end" flag described with reference to FIG. If the amount of interference increases due to changes or the effect of the movement of the mobile station, and it becomes difficult to receive packets in a certain slot, meaningless packets will not be received even though the base station cannot receive packets. It is possible to avoid that the transmission is continued. That is, FIG.
In (b), as shown in the slot 4 of the frame 4, it is possible to prevent the reservation of all the channels from being released once and the reservation state from continuing unreasonably.

In the above description, the reservations of all the channels are temporarily released. However, the present invention is not limited to this. Some mobile stations among the mobile stations that have obtained the reservations, For example, the reservation for 1/2 mobile station may be released.

[0040]

As described above, when the R-ALOHA system is used together with the CDMA system, according to the first reservation release system of the present invention having the above configuration, the reservation grant slots of a plurality of code channels can be used simultaneously. Even when the mobile station transmits a packet but cannot receive the packet due to interference or the like, the reservation of the reservation grant slot is not released. Since the reservation acquisition operation can be avoided, there is an effect that the wireless channel can be used effectively.

Further, according to the second reservation release method of the present invention, during the operation of the first reservation release method, the amount of interference due to signals from other cells or other mobile stations in the own cell is reduced by the mobile station. When the packet reception increases in the slot due to the influence of the movement of the packet and the reception of the packet in the slot becomes difficult continuously, the reservation is released to avoid the continuation of the meaningless packet transmission and the reservation is given again. This has the effect that the wireless channel can be used effectively.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a wireless packet communication system according to the present invention.

FIG. 2 is a diagram illustrating an example of packet transmission in a wireless packet communication system according to the present invention.

FIG. 3 is a flowchart for explaining the operation of the first reservation release method of the present invention.

FIG. 4 is a flowchart for explaining the operation of the second reservation release method of the present invention.

FIG. 5 is a diagram illustrating an example of packet transmission by the R-ALOHA method.

FIG. 6 is a diagram illustrating an example of packet transmission when the R-ALOHA method is applied to a CDMA method.

[Explanation of symbols]

 Reference Signs List 10 mobile station 11 radio section 12 control section 13 transmission buffer 14 packet generation source 15 transmission control section 20 base station 21 radio section 22 control section 23 reception buffer 24 signal detection section 25 reservation control section

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-172335 (JP, A) JP-A-8-154097 (JP, A) JP-A-8-167885 (JP, A) JP-A-9-1997 55693 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04J 13/00 H04B 7/26 H04L 12/56

Claims (3)

(57) [Claims] 1. A mobile station comprising: a base station and a plurality of mobile stations;
The uplink packet transmission to the base station from the mobile station, transmission
The mobile station where the signal to be transmitted is generated
Transmits the packet by random access method and succeeds
The mobile station that has obtained the reservation for that time slot
Signal can be transmitted by occupying the reservation grant slot
The R-ALOHA scheme is adopted that, and C in the multiple access scheme
What is claimed is: 1. A reservation release method in a wireless packet communication system adopting a DMA method, said base station comprising: a valid signal detecting means for detecting a valid packet from a received signal; And a reservation control unit that monitors the reservation. If the valid signal detection unit does not detect a valid packet in the reservation grant slot, the reservation control unit checks the signal detection status of another reservation grant slot at the time. See, when the number of reserved slots for which no valid packet has been detected is equal to or greater than a preset threshold, control is performed so as not to release reservations of all reserved slots. Reservation release method. 2. The method according to claim 2, wherein the reservation control unit cancels the reservation of the slot when the valid packet is not detected continuously for a predetermined number of times or more from the same reservation grant slot. A reservation cancellation method in the wireless packet communication system according to claim 1. 3. A mobile station comprising: a base station and a plurality of mobile stations;
The uplink packet transmission to the base station from the mobile station, transmission
The mobile station where the signal to be transmitted is generated
Transmits the packet by random access method and succeeds
The mobile station that has obtained the reservation for that time slot
Signal can be transmitted by occupying the reservation grant slot
The R-ALOHA scheme is adopted that, and C in the multiple access scheme
What is claimed is: 1. A reservation release method in a wireless packet communication system adopting a DMA method, said base station comprising: a valid signal detecting means for detecting a valid packet from a received signal; A reservation control unit for monitoring the validity signal, when the valid signal detection means does not detect a valid packet continuously more than a preset number of times from the same reservation grant slot, the reservation control unit A reservation cancellation method in a wireless packet communication system, wherein the reservation is canceled.