JP2527660B2 - Communication method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication method and apparatus in which a plurality of mobile stations randomly transmits to a central station.

[0002]

BACKGROUND OF THE INVENTION In many multiple access systems, multiple mobile stations are capable of communicating with a central station using split channels. These systems are called random multiple access. One of these systems is
Messages are sent randomly from multiple mobile stations to the central station without full coordination between the mobile stations.

For example, in cellular radio, each cell is controlled by a base station that is in communication with many mobile stations. Each cell uses a set of radio frequency channels. At least one channel is used to set up a radiotelephone call in each cell. This setup channel is allocated for all mobile stations to communicate with the base station. This set channel is a full-duplex channel having different frequencies in the forward direction (direction from the base station to the mobile station) and the reverse direction (direction from the mobile station to the base station). The forward setup channel is used by the base station to send messages to all mobile stations. This channel allows all mobile stations to receive all messages sent from the base station,
It is a broadcast channel. The reverse channel is a random contention multiple access channel so that the mobile station can send messages to the base station with almost no coordination. Access is based on contention. Access is random in that mobile stations are not assigned a fixed transmission schedule. A mobile station with a message to send tries to seize the channel. if,
If multiple mobile stations start transmitting at the same time, the messages will collide and destroy each other. If one message has much higher received power than the other message, then the higher received message may be received correctly at the base station. In any case, when the message transmitted from the mobile station is not properly received by the base station, it needs to be transmitted again after a while.

[0004]

A conventional multiple access protocol of this type is ALOHA, CSMA, C.
There are SMA-CD and the like. Due to the nature of random transmission and unavoidable collisions, random access protocols
A throughput efficiency of 00% cannot be achieved. The random delay after collision causes an additional message delay between the mobile station and the central station. In the North American analog cellular system, base stations and mobile stations transmit on different frequencies that make up a full-duplex channel. The base station broadcasts on a multiple access setup channel so that all mobile stations can periodically communicate with the base station. The busy / empty bit inserted for every 11 bits of the transmission signal from the base station to the mobile station indicates that the multiple access channel from the mobile station to the base station is busy or "empty" in the last cycle. Indicates. In this way, by periodically feeding back the status of the mobile station and transmitting from the base station, the mobile station can confirm that the channel is "empty" before retransmitting. The mobile station continues to monitor the busy / empty bit during transmission. If the busy / empty bit does not change from "empty" to busy during the first short time of message transmission, the transmitting mobile station is presumed to have a collision and the transmission is immediately disconnected. . However, the problem with this approach is that it cannot distinguish whether the busy / empty bit indicates a collision condition or an empty condition. Without such information, the mobile station cannot more efficiently determine when to start or stop transmission.

Many multiple access protocols have varying slot sizes. In the slot protocol, each slot is long enough to contain a fixed size message. The slot ALOHA called reserved ALOHA transmits by changing the message length of multiple slots (words) so as not to interrupt the complete transmission of the first message word.
In reserved ALOHA, if a mobile station correctly transmits a predetermined time slot, all subsequent slots are fully reserved for that mobile station until the mobile station stops transmitting. It The problem with this scheme is that one empty slot is used to indicate abandonment of the channel. The use of such channel resources is inefficient. Therefore, a new multiple access protocol is needed which improves access efficiency while reducing access delay.

An object of the present invention is to provide a new access protocol that improves transmission efficiency while reducing access delay. Another object of the invention is to use a short data area for sending feedback information from the central station to the mobile station indicating the status of the access channel. Yet another object of the present invention is the new data area used to indicate the abandonment of multiple access channels in bursts from each base station to the mobile station and to eliminate the required empty slots between messages. To provide various access protocols.

[0007]

According to the present invention, in a mobile communication method for transmitting information indicating a state of a transmission / reception channel between a plurality of mobile stations and a central station, each mobile station transmits transmission channel information from its own station to a central station. The central station transmits the last received transmission channel information of the mobile station and the information code indicating the status of the last mobile station transmitted from the mobile station to the central station.

[0008]

In the present invention, each mobile station transmits the transmission channel information from itself to the central station, and the central station transmits the transmission channel information of the last received mobile station and the mobile station to the central station. By transmitting the information code indicating the state of the last mobile station, the access delay at the time of contention when each mobile station transmits at random is reduced, and the transmission efficiency can be improved.

[0009]

DETAILED DESCRIPTION In cellular radio, each cell is served by a base station which communicates with a number of mobile stations. The channel is
It is set in the forward direction (from the base station to the mobile station) and in the reverse direction (from the mobile station to the base station) by the full-duplex method using different frequencies. This forward channel is used by the base station to send messages to mobile stations. This channel is a broadcast channel so that all mobile stations can receive all messages transmitted from the base station. The reverse channel is a random contention multiple access channel that allows mobile stations to send messages to the base station with almost no coordination.

FIG. 1 shows that the channel from the central office is transmitted by the forward channel 10 and the channel from the mobile station is transmitted by the reverse channel 11. In the preferred embodiment of the present invention, a new multiple access protocol is used in the channel. In the figure, the forward channel 10
And the reverse channel 11 are both divided into time slots. This forward channel 10 and reverse channel 1
The time slot of 1 is that the mobile station transmits the burst 12 on the reverse channel 11, then the confirmation burst 13 is transmitted from the base station, and the mobile station transmits the confirmation burst 13 before the mobile station transmits the burst 14. It is configured to receive. This timeslot does not have to completely occupy the channel. The periods not used in the forward or reverse direction are allocated to form other services or other pairs of time division multiple access channels.

For each transmission burst in both directions, two fields are used to operate the multiple access protocol. In the forward direction, the forward access / confirmation field (FAA) 15 and the forward direction more field (F
M) 16. In the reverse direction, reverse access /
There is a confirmation field (RAA) 17 and a backward direction more field (RM) 18. In the reverse channel 11,
RAA field is the abbreviated identifier (ID) of the mobile station
Will be sent. This ID does not need to identify the mobile station as long as the probability of error confirmation is much smaller than the probability of normal confirmation. If the ID in the RAA field does not identify the transmitting mobile station, the rest of the message must contain enough identifier to identify the mobile station. The message in either direction may include one or more bursts (words). The RM is a binary field and if the current message does not follow the next burst this RM is set to "empty", otherwise this RM is set to "reserved".

In the forward direction, the FAA field is used to return the access result in the last received slot in the reverse channel. If the last received slot in the reverse channel contains a correctly transmitted burst, the FAA provides a confirmation code that is the same as the RAA field content of the last slot received at the base station. If the last received reverse channel slot is "empty", the FAA contains another empty code that is different from all the abbreviated IDs available to the mobile station. If the mobile stations transmitted in the last reverse channel slot collide with each other and the message is destroyed, another collision code different from all the abbreviated IDs available to the mobile station is transmitted.

The FM field is represented by binary data indicating either "empty" or "reserved" status. "Sky"
A value or state that indicates that the next reverse channel slot is used for contention access. The reserved value is the next reverse channel slot reserved for the mobile station
Are transmitted in the FAA field of the current forward burst. The base station sets the FAA and FM fields as follows according to the result of the last reverse slot. Final reverse access RM FM FAA Channel slot status Empty n / a Empty code 1 successful transmission Empty empty omitted ID reserved reservation omitted ID Successful once with multiple transmissions Empty empty omitted ID reserved reservation omitted ID Multiple successful transmissions no x Empty collision code Radio channel error x Transmission by empty collision code n / a: Indicates not applicable x: Ignore

The mobile station having the message to be transmitted to the base station uses the following algorithm determined at the time of transmission. (1) Wait until the FM field indicates that the next slot is "empty" due to contention. (2) Send the first word of the message in the next reverse slot, with the RAA set to the mobile station's abbreviated ID. (3) Check if the FAA field is equal to the mobile station's abbreviated ID in the next forward burst. (A) If equal, continue to send the current message in consecutive backward slots. (B) If they are not equal, stop sending the remaining messages and wait a random period according to the sending algorithm.
Go to step 1 and execute step 1 again.

As a practical example, FAA is assigned a 7-bit field and can accommodate any value from 0 to 127 (decimal). As the short ID, the last two digits of the mobile station telephone number are used. Therefore, a valid short ID
Is in the range from 00 (decimal number) to 99 (decimal number). The empty code and collision code for the FAA field must be set to a number greater than 99.
This is because 00 to 99 are reserved for the short ID. In this embodiment, the empty code field is 120 (10
127 (decimal) is used for the collision code field. It is well known to a person skilled in the art that the above-mentioned empty code and collision code are arbitrarily assigned different numbers. The RAA field can be the same length as the FAA and the valid short ID range is 0-99 (decimal). Both RM and FM are assigned a 1-bit field, and "empty" is displayed as 0 and "reserved" is displayed as 1.

FIG. 2a shows the case where the transmission is successful without collision. In forward channel 10, bursts 21, 2
2 is transmitted and received by mobile stations A, B and C.
Mobile station A transmits burst 23 to the base station. This burst 23 contains a short ID, for example RAA = 72. The numeral 72 indicates the last two digits of the mobile station's telephone number and the reverse field RM = 0 indicates that only one burst has been transmitted. In the confirmation burst 24 transmitted by the base station on the forward channel 10, the FAA
The field indicates that the short ID transmitted from mobile station A has been received by the base station. The FM field is set to 0. This indicates that mobile station A transmitted only one burst, so that in the next reverse channel slot, all mobile stations have competitive access.

Upon receiving burst 24 from forward channel 10, mobile station B can use reverse channel 11,
A burst 25 having an ID of RAA = 37 and RM = 1 can be sent. The field with RM = 1 indicates that at least one other burst will be transmitted subsequently. The next burst 26 sent by the base station on the forward channel 10 contains a confirmation field of FAA = 37. The reserved field FM = 1 indicates that all mobile stations are reserved for the next burst with the mobile station having ID 37. Upon receiving the burst 26, the mobile station B confirms that the immediately previous burst reception by the base station has succeeded, and transmits the burst 27 including the ID of RAA = 37 and the reserved field RM = 1. Base station has similar burst 2
Transmit the forward channel with 8. Mobile station B sends a final burst 29 for the message. This burst 29 has the same ID field number (RAA = 3
7) is included, but the field RM = 0. This indicates that the next reverse channel slot can be used in contention. The base station transmits burst 30, indicating that all mobile stations have competitive access in the next reverse channel slot. If no mobile station sends a burst, the next two bursts 3 sent by the base station
0 and 31 indicate that the channel is "empty".

FIG. 2b shows the procedure for burst transmission when the messages from mobile stations B, C are destroyed by collision. In addition, the procedure for successful transmission by the subsequent retransmission of the message is also shown. Upon receiving burst 40 from the base station, the channel is "empty" (F
Since M = 0), mobile station B transmits burst 41 and mobile station C transmits burst 42. Burst 41, 42
Are transmitted simultaneously, resulting in collisions and burst bursts. The base station transmits the burst 43. This burst 43 indicates that a collision has occurred. After a randomly chosen delay, both mobile stations then retransmit the burst. In the example of Fig. 2b, mobile station C retransmits the burst after confirming that the channel is "empty". In this example, a one word message (eg, burst 46) is transmitted by mobile station C. After a random delay, mobile station B sends a two word message (eg bursts 44, 45).

FIG. 2c shows that both messages are simultaneously transmitted from mobile stations A and B, that is, when both messages collide with each other, mobile station A's transmission succeeds and mobile station B's transmission fails. Shows the burst transmission of. In this case, the FAA code in the burst transmitted by the base station is set to the abbreviated ID when the transmission of the mobile station is successful. In the case of this example, since the transmission of the mobile station A has succeeded, F
AA = 72. This occurs when the burst output of one mobile station is much higher than the output of another mobile station. Bursts from low power mobile stations are discarded as noise at the base station. In FIG. 2c, mobile station A
Transmits burst 50 and mobile station B transmits burst 51. The base station confirms the burst including the ID 72, and mobile station A is determined to have succeeded in the transmission. However,
The mobile station B determines that the transmission has failed, and transmits the second burst. After a random delay, mobile station B retransmits the message (eg burst 52, 53).

FIG. 3 illustrates a number of systems that can use the protocol described above. For example, the protocol of the present invention is used in the base station 60 and the mobile station 6
It can be used in the setting channel between 1 and 2. Similarly, this protocol can be used in the communication access channel of the trunk line 62 between the base station 60 and the MTX switch 63. Furthermore, the MTX switch 63 and the central office (CO) 6
4 or between the central station 64 and the satellite earth station 65. In a cellular communication system, this protocol can also be used in the wireless communication access channel between satellite earth station 65 and satellite 66. In addition,
The present invention can be used regardless of radio channel, cellular radio channel, satellite radio channel, packet radio channel, or wired channel.

[0021]

As described above, according to the present invention,
Since the information indicating the status of the access channel is transmitted from the mobile station to the central station and from the central station to the mobile station, the used data area can be shortened and the channel resources can be used efficiently. . Further, the access delay at the time of contention can be reduced and the transmission efficiency can be improved.

[Brief description of drawings]

FIG. 1 shows how a channel from a central station is transmitted by a forward channel and a channel from a mobile station is transmitted by a reverse channel.

FIG. 2a shows the procedure when multiple transmissions from the mobile station succeed without collision.

FIG. 2b shows a procedure for burst transmission when messages from mobile stations B, C are destroyed by collision.

FIG. 2c shows the case where both messages are simultaneously transmitted from mobile stations A and B, that is, when both messages collide.
The transmission of mobile station A is successful, and the transmission of mobile station B is a burst transmission in case of failure.

FIG. 3 illustrates a number of systems in which the protocol of the present invention can be used.

[Explanation of symbols]

 10 Forward Channel 11 Reverse Channel 12-14 Burst 15 Forward Access / Confirmation Field (FAA) 16 Forward More Field (FM) 17 Reverse Access / Confirmation Field (RAA) 18 Reverse More Field (RM) 21- 32 burst 40-46 burst 50-53 burst 60 base station 61 mobile station 62 trunk line 63 MTX switch 64 central station (CO) 65 satellite earth station 66 satellite

Continuation of front page (56) Reference JP-A-60-152144 (JP, A) JP-A-60-248039 (JP, A) JP-A-3-102925 (JP, A) JP-A-63-9322 (JP , A)

Claims (5)

(57) [Claims] 1. Controlling the use of opposite channels having multiple consecutive time slots by multiple terminals,
In a method of transmitting a message to a central office: a forward channel for transmitting a message from a central office to multiple terminals is provided, the forward channel having a plurality of consecutive time slots, each of the forward channels being The timeslot is between consecutive timeslots of two reverse channels and transmits a burst during each timeslot of the forward channel, which burst is used by the particular terminal for the next reverse channels timeslot. Are sent to the central office, each of which sends a burst during the time slot of the reverse channel, with a code indicating whether it is reserved for communication or is free due to contention of all terminals. Does the sending terminal request at least one more reverse channel time slot when it finishes sending? Communication method characterized in that it comprises a code indicating. 2. The method of claim 1, wherein for each burst transmitted during a forward channel time slot, the central station successfully receives a burst during a reverse channel last time slot. A communication method characterized by including a code indicating whether or not. 3. The communication method according to claim 2, wherein the code indicating whether the central station has successfully received the burst, the central station successfully transmitted the burst during the last time slot of the reverse channel. A communication method, characterized in that the communication method includes a terminal identifier transmitted when received. 4. The communication method according to claim 2, wherein the code indicating whether the central station has successfully received the burst has the burst successfully received by the central station during the last time slot of the reverse channel. Has a first code transmitted when not received by the central station and has a second code transmitted when the central station receives at least two bursts during the last timeslot of the reverse channel. , The at least two bursts are collisions without any of the bursts being successfully received by the central station. 5. The communication method according to claim 1, wherein when the terminal receives a code requesting at least one further reverse channel time slot when terminating the transmission of the message to the central station, The central station responds by sending a code indicating that the next time slot of the reverse channel has been reserved by the terminal, and when the terminal has finished sending the message to the central station, the terminal has at least one further backward direction. When the central station receives a code that does not require a time slot for the channel, the central station responds by sending a code indicating that the next time slot on the reverse channel is idle to all terminals, and the central station responds. If no burst is received, the central station is idle because the next time slot on the reverse channel is contending with all terminals. A communication method characterized by responding by indicating that