JPH04252526A - Base station control mini-slot reservation random access control system - Google Patents

Abstract

PURPOSE:To realize the random access control system with excellent frequency utilization efficiency and excellent throughput characteristic with respect to the random access control system for mobile communication. CONSTITUTION:The system is constituted such that a base station informs a signal designating whether a kind of a slot of an incoming control channel is a reservation slot or a message transfer slot to each mobile equipment via an outgoing control channel, informs a signal designating a mobile equipment for message transmission through the relevant when the kind of the relevant slot is the message transfer slot and the mobile equipment accesses the base station according to a signal for designating the kind of the slot from the base station and a signal for designating the mobile equipment.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a random access control system in mobile communications.

0002

[Prior Art] ICMA-DR (Idle-si
gnal casting multiple
access with data slot r
eservation) method is adopted. ICM
The A-DR method is an improved version of the conventional ICMA method. This ICMA method is a method of reporting the usage status of uplink control channels on downlink control channels in order to reduce signal extinction due to collisions between uplink control signals sent from mobile devices to base stations. This method broadcasts a line signal to permit access to each mobile station, and when it is in use, broadcasts a prohibition signal to prohibit other mobile stations from making calls. The ICMA-DR system incorporates reservation control into the above-mentioned ICMA system in order to further improve communication efficiency.

FIG. 5 is a diagram illustrating control channel signals in the above-mentioned ICMA-DR system. As shown in the figure, the random access signal from the mobile device to the base station consists of a short reservation signal 5-1 followed by a message signal 5-2.
The accessing mobile device first sends only a reservation signal to the base station. When the base station receives the reservation signal correctly, it transmits a reservation confirmation signal 5-3 to the mobile device and changes the idle line signal 5-4 to a prohibition signal 5-5. After receiving the reservation confirmation signal from the base station, the mobile device transmits a message signal via an uplink control channel.

On the other hand, the wireless transmission system for mobile communication is TDMA.
In this case, message signals are separated by short slots, so as a method for applying the conventional ICMA-DR method to TDMA communication, the literature [Umeda et al., "Intermittent slot idle line control method in mobile communication random access", 1990]
Spring IEICE University, B351. ] proposed an intermittent slot idle line control system.

FIG. 6 is a diagram illustrating control channel signals of the intermittent slot empty line control system in 3ch TDMA. As shown in the figure, the idle line/inhibition signals 6-1, 6-2, 6-3, and 6-4 broadcast by the base station are transmitted to each uplink control slot 6-5, 6-6, 6-7, and 6-8, and the mobile device transmits a reservation signal 6-5 to the base station in the slotted ALOHA mode when the idle signal 6-1 is present. In the base station, if the reservation signal is correctly received, the control signal for the following slot is changed to the prohibition signal 6-2, and the message signals 6-6, 6-7, and 6-8 of the mobile device are transmitted. Encourage sending. In this method, it is possible to obtain characteristics similar to those of the conventional ICMA-DR method only when message signals are transferred over a plurality of slots.

[0006] Furthermore, as a channel access method in conventional satellite communication, the document [L. G. Roberts,
“Dynamic allocation of
attellite capacity through
gh packet reservation”,
in Proc. AFIPS Nat. Compu
t. Conf. , June 1973, pp. 711
-716. There is a random reservation method proposed in ].

FIG. 7 is a diagram showing the concept of a random reservation system when a certain earth station transfers a message of 3 slots. As shown in the figure, the channel between the earth and the satellite station is divided into slots. Furthermore, a reservation slot 7-1 is provided for each M slot, in which one slot is divided into V mini-slots. The earth station that performs the message transfer randomly selects one of the V mini-slots in the reservation slot and selects the slotted ALOH
A reservation signal 7-2 is transmitted in A mode. (For example, let this transmission time be t=0)

[0008] The earth station that has accessed the earth station performs a sum check of its own reservation signal returned from the satellite station to determine a signal collision. As a result of this determination, for example, t=1
If it is confirmed that the signal has reached the satellite station without collision at time 0, the following processing is performed.

That is, the access signal status of other earth stations is monitored in advance, and at the time when there is a reserved mini-slot, that is, at the time of reservation (t=5), a slot reserved by another earth station is selected. For example, if the number is 13, transmission is possible after 13 slots from t = 6, so the number of slots t that can be transmitted by the own station is
=21, 22, 24 are determined by calculation, and messages are transmitted 7-3, 7-4, 7-5 at t=16, 17, 19, taking propagation delay into account.

[0010] Furthermore, if the number of slots reserved by other earth stations is exhausted, all slots are reserved. In this method, each earth station attempting to transfer a message monitors in advance the status of each earth station's reservation signal returning from the satellite station and understands which earth station has reserved which slot. , we need to determine the number of slots currently reserved.

[0011]

In a TDMA mobile communication system where the transmission speed is high, the real time length of a signal is short, so control signals such as call origination can often be sufficiently transmitted in one slot. In this case, if the conventional intermittent slot idle line control method is used, the ratio of the reserved signal length to the total signal length a (=reserved signal length/total signal length) is a parameter that determines the performance of the idle line control of this system. becomes large to 0.5,
It is not possible to set a such that the control is effective, and no improvement in throughput can be expected.

In FIG. 4, the curve 4-1 for m=1 is the throughput characteristic (simulation value) in the intermittent slot empty line control method when the number of data slots is 1 in FIG. 6 uses only one slot of the message signal without using the reservation signal.
This figure shows the throughput characteristics (theoretical value) when transmitting using Lotted ALOHA. This figure shows the traffic and throughput of only data slots, excluding the reservation signal in the intermittent slot idle line control method, in order to make the comparison in accordance with an actual system. It can be seen from this that the characteristics are worse when the intermittent slot empty line control is performed than when the slotted ALOHA is used.

[0013] Furthermore, when using the random reservation method proposed for satellite communications, the base station needs to broadcast the received reservation signal and message signal from each mobile device to each mobile device in the same way as the satellite station. At the same time, before each mobile device accesses the base station, it monitors the reservation signal and message signal broadcast from the base station for a long time, understands the number of slots currently reserved, and then transmits the reservation signal. This creates problems such as frequency usage efficiency, increased power consumption due to monitoring of slot reservation status of mobile devices, and connection delay time.

[0014]

[Means for Solving the Problems] In order to solve the above problems, the present invention provides an uplink control channel from the mobile device to the base station and a downlink control channel from the base station to the mobile device between the base station and the mobile device. A mobile communication system having a channel, in which an uplink control channel is divided into slots with a predetermined time width, and the slots further include reservation slots in which the inside of the slot is divided into mini-slots with a small time width;
It consists of two types of slots: an undivided message transfer slot, and a signal used when a mobile device accesses a base station is divided into a reservation signal and a message signal. Randomly select one mini-slot from multiple mini-slots,
By transmitting the reservation signal in a random access manner, a reservation is made to use the message transfer slot, and the mobile device further transmits a message signal to the base station via the message transfer slot reserved by the reservation signal. In the random reservation type access method for transmission, the base station informs each mobile device, via the downlink control channel, whether the type of the slot on the uplink control channel is a reservation slot or a message transfer slot. If the type of the slot is a message transfer slot, a signal designating a mobile device to which the message should be transmitted is broadcast, and the mobile device receives the message from the base station in the slot. The feature is that the access operation to the base station is performed according to the type designation signal and the mobile device designation signal.

[0015]

[Operation] According to the present invention, by the control configured as described above, even in high-speed TDMA mobile communication where the number of data slots of message signals is small, frequency utilization efficiency, power consumption of mobile equipment, connection delay time, etc. are sacrificed. It is possible to obtain throughput characteristics equivalent to random access in conventional mobile communications without having to do so. Furthermore, when the number of data slots of a message signal is large, throughput characteristics better than that of the conventional method can be obtained.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram illustrating an embodiment of the present invention, and shows an example of the configuration of a control channel when a base station controlled minislot reservation random access control method is applied to 4ch TDMA-TDD. . Here, one slot out of four slots in one frame is used as a control channel (CCH), and the other slots are used as communication channels (TCH).
), and the uplink period from the mobile device to the base station and the downlink period from the base station to the mobile device are alternately assigned to each frame.

There are two types of uplink control channels, 1-1 for reservation and 1-2 for message transfer. In the case of slots for reservation, there are a plurality of (5 in FIG. 1) mini-slots 1-2 in the slot. It is divided into 3 parts. Here, reservation signals 1-4 are transmitted from the mobile device in the reservation mini-slot.
Therefore, it is preferable to make the signal length as short as possible in order to increase the number of mini-slots, and to use the same reservation signal pattern in each mobile station to facilitate collision determination at the base station.

Further, the message signal may include, for example, location registration, call, dial information, etc. For the downlink control channel, there is an R (Reset) that specifies whether the control channel of the frame in the next uplink period is for reservation or for message transfer.
rvation)/M (Message) signals 1-5 and, if the message is for message transfer, a reservation acceptance number 1-6 for specifying a reserved mobile station. Other signals 1-7 include, for example, incoming call information and communication channel designation information.

The designation of the mobile device for the reservation acceptance numbers 1-6 is not by the ID of the mobile device but by the number of the mini-slot for which the reservation was accepted in the immediately preceding reservation frame. That is, when a reservation is accepted, the mobile device stores the minislot number used for the reservation, and the base station designates the minislot using that number. This is because the mobile device ID has a large number of digits and transmission efficiency is not good.

In FIG. 1, reservation signals are accepted in mini-slots 1 and 5, so the reservation reception number for the downlink control channel in this case is 1 or 5. When multiple reservations are accepted, the base station continuously uses the uplink control channel for message transfer and broadcasts the reservation acceptance number in sequence, thereby transmitting message signals for all reservations accepted in the reservation slot. accept. Conversely, if the reservation is not accepted, the uplink control channel is continuously used for reservation until the reservation is accepted.

FIG. 2 is a flowchart showing the operation algorithm of the base station in the base station controlled minislot reservation random access control system. Broadcast the R signal on the downlink control channel (the control signal at this time is
-1), if there is no reservation signal from the mobile device in the next reservation slot, the base station continues to broadcast the R signal, and if there is a reservation signal, the base station performs error detection on the reservation signal of each mini-slot, Performs signal collision determination. If the error is less than the set value, it is assumed that there is no collision with a reservation signal from another mobile device, the reservation is accepted, and the M signal and the number n of the mini-slot that received the reservation signal are transmitted on the next downlink control channel. Downlink control signal (reservation reception number)
The control signal at this time is indicated by 2-2).

[0022] After receiving the message signal from the mobile device corresponding to the reservation reception number specified on the next uplink control channel (for message transfer), if multiple reservation signals are received in the reservation slot described above, The next reservation acceptance number and M signal are broadcast, and the process is repeated until all the mobile devices reserved in the aforementioned reservation slot complete transmission. When all reserved mobile station transmissions are completed, the R signal is broadcast again and a reservation signal from the mobile station is awaited.

FIG. 3 is a flowchart showing the operation algorithm of the mobile device in this system. A mobile device that attempts to access a base station for calls, location registration, etc. first monitors the R/M signal of the downlink control channel (CCH) and determines whether the next uplink control channel is for reservation or message transfer. to judge whether When the M signal is used for message transfer, the downlink control channel is continuously monitored, and when the R signal is reached, a reservation signal is transmitted at the timing of a randomly selected minislot on the next uplink control channel.

Next, the R/M signal of the downlink control channel is monitored again, and if it is not an M signal, it is assumed that the transmission of the reservation signal has failed and a retransmission schedule is entered. If it is an M signal, the reservation reception number is then decoded, and if it matches the minislot number selected by the local station at the time of transmission, the message signal is transmitted on the subsequent uplink control channel. If the reservation acceptance number does not match the minislot number selected by the own station, R/M of the downlink control channel continues.
The signal and the reservation reception number are monitored, and if the reservation reception numbers do not match and the signal becomes R, it is assumed that the transmission of the reservation signal has failed, and a retransmission schedule is started.

[0025]

Effects of the Invention: By using the base station controlled mini-slot reservation random access control system of the present invention, a high-speed TDM system in which a message signal can be sufficiently transmitted in one slot can be achieved.
In the A mobile communication system as well, it is possible to improve throughput characteristics to the same level or better than the conventional idle line control method without sacrificing frequency utilization efficiency, power consumption of mobile devices, and connection delay time. In FIG. 4, the throughput characteristics (theoretical values) of slotted ALOHA are compared with the throughput characteristics (simulated values) when the number m of mini-slots is varied from 1 to 5 using the present invention, and the effects of the present invention are shown. Ta. Here, the number of message signal slots is 1. The horizontal axis in the figure represents message signal traffic, and the vertical axis represents message signal throughput. Here, as described above, the reservation signal is assumed to have no information content, and the reservation signal is subtracted from the total traffic and throughput to be displayed. From this figure, when m = 1, that is, in the case of intermittent slot empty line control method, the throughput is sl
Although it deteriorates compared to slotted ALOHA, it can be seen that when m is 3 or more, the characteristics are greatly improved compared to slotted ALOHA.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating an embodiment of the present invention.

FIG. 2 is a flowchart illustrating an example of the operation of a base station.

FIG. 3 is a flowchart showing an example of the operation of a mobile device.

FIG. 4 is a diagram illustrating the effect of improving throughput characteristics of the present invention.

FIG. 5 is a diagram illustrating a control channel signal of the ICMA-DR system.

FIG. 6 is a diagram illustrating signals of a control channel of a 3ch TDMA system.

FIG. 7 is a diagram showing the concept of a random reservation system.

[Explanation of symbols]

1-1 Reservation uplink control channel 1-2
Uplink control channel for message transfer 1-3 Mini slot 1-4 Reservation signal 1-5 R/M signal 1-6 Reservation acceptance signal 1-7 Other downlink control signals 2-1, 2-2 Control signal 4-1 Mini Throughput characteristics when the number of mini slots is 1 4-2 Throughput characteristics when the number of mini slots is 2 4-3 Throughput characteristics when the number of mini slots is 3 4-4 Throughput characteristics when the number of mini slots is 4 4-5 When the number of mini slots is 4 Throughput characteristics in case of 5 4-6 slotted
Throughput characteristics for ALOHA

Claims (1)

[Claims] Claim 1: A mobile communication system having, between a base station and a mobile device, an uplink control channel from the mobile device to the base station and a downlink control channel from the base station to the mobile device, wherein the uplink control channel is predetermined. The slots are divided into slots each having a time width, and each of the slots further includes a reservation slot whose interior is divided into mini-slots each having a small time width;
It consists of two types of slots: an undivided message transfer slot, and a signal used when a mobile device accesses a base station is divided into a reservation signal and a message signal. By randomly selecting one minislot from a plurality of minislots and transmitting the reservation signal in a random access manner, a reservation is made to use the message transfer slot, and the mobile terminal also makes a reservation for using the message transfer slot. In a random reservation type access method in which a message signal is transmitted to a base station via a message transfer slot reserved by a signal, the base station transmits the slot type of the uplink control channel to each mobile device via the downlink control channel. broadcast a signal specifying whether the slot is a reservation slot or a message transfer slot, and if the type of the slot is a message transfer slot, the slot further specifies the mobile device to which the message should be transmitted. base station-controlled mini-slot reservation random access, wherein the mobile device performs an access operation to the base station according to a signal for specifying the slot type and a signal for specifying the mobile device from the base station. control method.