KR20000038096A - Method for allocating channel in satellite network for transmitting data - Google Patents

Abstract

PURPOSE: A method for allocating channel in satellite network for transmitting data is provided to offer an improved service in a subscriber terminal station and increase the accessibility by converting a time slot with limited numbers into a fixing allocation mode, a competition mode and a reserved allocation mode according to a kind of a request of a subscriber and a service. CONSTITUTION: General subscriber terminal stations hold a time slot of a competition mode in common(S41). A reserved request message is transmitted to a central station when a length of a transmission queue is greater than a reserved request threshold length(S42,43). The terminal, which transmits the reserved request message, judges a message received from the central station(S46). The terminal judges as to whether the length of the transmission queue is less than a reserved release limit length when a reserved rejection message is received(S44). The terminal transmits data in a reserved allocation mode when a reserved approval message is received(S47). The terminal judges whether the length of the transmission queue is less than the reserved release limit length(S48). The terminal transmits a reserved release request message to the central station when the length of the transmission queue is less than the reserved release limit length(S50).

Description

Channel allocation method in data communication satellite network

The present invention relates to a channel allocation method for processing a variety of services in a molded satellite network consisting of one central station and n terminal stations, and in particular, when n terminal stations sharing one frequency transmit data to the central station. The present invention relates to a channel allocation method in a satellite network for data transmission in which time slots are allocated in different ways according to the service type of the network.

The molded satellite communication network composed of one central station and n terminal stations has two types of data transmission methods, an outbound transmission for transmitting data from the central station to the terminal station, and data from the terminal station to the central station. There is an inbound transmission that transmits. At this time, a time division multiplexing method is used for outbound transmission, and a time division multiple access method is used for inbound transmission.

In general, a slotted-ALOHA method is used as a satellite channel access method shared by a plurality of terminal stations. The slotted-ALOHA method significantly improves network productivity, that is, utilization, as compared to the conventional PURE ALOHA method.

Therefore, there is a need to apply such a satellite channel access method to a molded satellite network in which a plurality of terminal stations communicate through one central station.

Accordingly, the present invention has been made to meet the above necessity, and when a plurality of terminal stations want to transmit data to one central station using one satellite channel, a method of obtaining a timeslot of a shared channel is provided. The purpose is to provide.

In addition, the channel allocation method in the satellite network for data transmission can be used to efficiently accommodate a limited time slot and to accommodate the maximum number of subscribers requesting various data communication services by varying the time slot allocation method according to the service level of the terminal station. The purpose is to provide.

1 is a diagram illustrating a timeslot allocation state of a superframe according to an embodiment of the present invention;

2 is a diagram illustrating a state in which a mode is switched from a contention mode to a reservation allocation mode or a mode from the reservation allocation mode to the contention mode according to an embodiment of the present invention;

3 is a diagram illustrating a state in which a contention mode is switched from a contention mode to a reservation allocation mode or a contention mode from the reservation allocation mode according to another embodiment of the present invention;

4 is a flowchart illustrating a channel allocation method in a satellite network for data transmission at a terminal station side according to an embodiment of the present invention;

5 is a flowchart illustrating a channel allocation method in a satellite network for data transmission at a central station according to an embodiment of the present invention.

In order to achieve the above object, the present invention provides a channel to each terminal station when a plurality of terminal stations sharing one superframe transmit data to the central station in a satellite network for data transmission composed of one central station and a plurality of terminal stations. In the method for assigning,

Assign a time slot in fixed allocation mode to a particular high subscriber station, making it permanently exclusive,

Assigns a time slot in a competitive mode to a general subscriber station to share and use;

Provided is a channel allocation method in a satellite network for data transmission, which allocates a time slot of a reservation allocation mode to a general subscriber station that satisfies a specific condition so that it is temporarily used exclusively.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

The molded satellite network according to the present invention is composed of one central station, a plurality of terminal stations sharing one satellite frequency, and a communication satellite for data transmission using a communication satellite.

When a plurality of terminal stations transmit data to the central station, synchronization is performed between the central station and the terminal station in units of super frames. This superframe consists of a number of timeslots whose size is equal to the length of the data packet being transmitted. The timeslot constituting the superframe is allocated to the terminal station by three modes of access methods as shown in FIG. There are three modes: fixed assignment mode, reserved assignment mode and competition mode.

The time slot in fixed allocation mode is a time slot that is fixedly allocated to high subscribers. The time slot in reservation allocation mode is a time slot in the central station when the length of the transmission queue of the general subscriber exceeds the threshold (TH). When the request message is sent and a response is received, the timeslot in the reservation assignment mode is assigned to the terminal station. The terminal station assigned the time slot in the reserved assignment mode transmits data using the time slot in the reserved assignment mode until the length of the transmission queue becomes lower than the threshold length. A terminal station that has not been allocated a time slot in the reservation allocation mode uses the time slot in the contention mode. The number of timeslots in the reserved allocation mode is as follows.

'0 ≤ number of timeslots in the reserved allocation mode ≤ number of maximum reserved timeslots.

here,

The maximum number of reserved timeslots = the total number of timeslots in the superframe-(the number of fixed allocation mode timeslots + the number of minimum contention timeslots).

Finally, the number of timeslots in the competitive mode is given by

The number of minimum contention timeslots <number of time slots in contention mode <number of maximum contention timeslots.

here,

Maximum number of contention timeslots = total number of timeslots in superframe-number of timeslots in fixed assignment mode,

The minimum number of contention timeslots is a fixed value determined during network operation.

As described above, the number of timeslots belonging to other modes in addition to the number of timeslots belonging to the fixed allocation mode is changed according to the network situation. The central station manages all of the time slot assignment information of these superframes.

Next, a procedure of allocating timeslots to each terminal station will be described. First, a signaling procedure will be described, and a channel allocation method performed in the central station and each terminal station according to the received signal will be described.

A subscriber station using a time slot in fixed assignment mode receives a fixed time slot from the network manager when it joins the network and uses the time slot exclusively. Therefore, no collision occurs during data transmission. Also, no mode switching procedure or the like occurs. In the present invention, description of the fixed allocation mode is omitted.

The general subscriber station stations share and use the time slots of the contention mode (step S41), and when the length of the transmission queue becomes larger than the reservation request threshold length (TH1) (step S42), the time slot request message, that is, the reservation request message is used as the central station. Transmit (step S43). When the reservation request message is received from the terminal station (step S61), the central station calculates a time slot that can be reserved (step S62) and determines whether there is a time slot that can be reserved (step S63).

If there is a reserved time slot, the process proceeds to step S64, and if there is no reserved time slot, the process proceeds to step S68. In step S64, a reservation acknowledgment message is sent to all terminal stations, and in step S65, the reservation period timer is operated. This reservation acknowledgment message includes information on the timeslot of the reservation assignment mode to be allocated. In step S68, the reservation rejection message is transmitted to the terminal station that has transmitted the reservation request message.

The terminal station which has sent the reservation request message to the central station determines the message received from the central station (step S46). When the reservation rejection message is received from the central station, the process proceeds to step S45. When the reservation approval message is received from the central station, the process proceeds to step S47. After receiving the reservation rejection message in step S45, the terminal station waits for a predetermined time and then determines in step S44 whether the length of the transmission queue is smaller than the reservation release limit length TH2. If the length of the transmission queue is smaller than the reservation release limit length, the flow proceeds to step S41 to transmit data in a competitive mode. If the transmission queue length is larger than the reservation release limit length, the flow advances to step S43 to send a reservation request message to the central station.

Upon receiving the reservation approval message in step S47, the terminal station transmits data in the reservation allocation mode.

The reservation acknowledgment message transmitted from the central station is received by all the terminal stations. The terminal station which has sent the reservation request message transmits data using the assigned time slot, and the other terminal stations do not use the time slot of the corresponding reserved allocation mode. Do not. Therefore, the terminal station using the time slot in the reserved assignment mode can exclusively use the reserved time slot and thus can transmit data in a short time without collision of packets like the fixed assignment mode temporarily.

Looking at the method of switching from the reservation allocation mode to the competition mode, the terminal station transmitting data in the reservation allocation mode determines whether the length of the transmission queue is smaller than the reservation release limit length TH2 (step S48). If the length of the transmission queue is smaller than the reservation release limit length, the flow proceeds to step S50. If the length of the transmission queue is larger than the reservation release limit length, the flow proceeds to step 49.

In step S50, the terminal station transmits a reservation release request message to the central station.

On the other hand, the central station that has sent the reservation approval message to the terminal station detects whether the reservation period timer expires, and after a predetermined time elapsed by the reservation period timer, proceeds to step S67 and transmits the reservation cancellation message to all terminal stations. do.

In this way, when the terminal station receives the cancel message from the central station (step S49), the terminal station proceeds to step S41 to transmit data in the competitive mode. On the other hand, if the length of the transmission queue is smaller than the threshold length TH2, the terminal station transmits a reservation release request message to the central station in step S50. When the central station receives the reservation release request message from the terminal station, the central station transmits a reservation release approval message to all terminal stations in step S70, and returns to step S61.

In this way, when the terminal station receives the reservation cancel approval message from the central station (step S51), the terminal station proceeds to step S41 to transmit data in a competitive mode.

The de-reservation message or the de-reservation acknowledgment message sent from the central station includes information on the timeslot, and other terminal stations which receive these messages can use the timeslot.

Fig. 2 shows that when the length of the transmission queue of the terminal station that transmits data in the reservation allocation mode becomes smaller than the reservation release limit length TH2, it switches from the reservation allocation mode to the competition mode.

3 is to transmit a cancellation message from the central station to the terminal station when the reservation period is completed regardless of the length of the transmission queue of the terminal station. According to this method, it is possible to prevent the specific timeslot from operating in the reservation allocation mode permanently due to an error of the specific reservation terminal station.

As described above, according to the present invention, a limited number of timeslots are switched to the fixed allocation mode, the competition mode, and the reservation allocation mode according to the subscriber's request and the type of service, thereby providing more enhanced service to the subscriber station and There is an effect that can increase the utilization of the channel.

Claims (7)

In a method for allocating a channel to each terminal station when a plurality of terminal stations sharing one superframe transmit data to the central station in a satellite network for data transmission composed of one central station and a plurality of terminal stations, Assign a time slot in fixed allocation mode to a particular high subscriber station, making it permanently exclusive, Assigns a time slot in a competitive mode to a general subscriber station to share and use; A method of allocating a channel in a satellite network for data transmission, comprising allocating a time slot of a reservation allocation mode to a general subscriber station that satisfies a specific condition so as to be used exclusively temporarily. 2. The method of claim 1, wherein the time slot in the reserved allocation mode is allocated when the length of the transmission queue of the general subscriber station is greater than the reservation request threshold length (TH1). The terminal station of claim 1 or 2, wherein if the terminal station assigned the time slot of the reservation allocation mode satisfies the reservation release condition, the terminal station switches from the reservation allocation mode to the competition mode, and the time of the reservation allocation mode. The slot is a channel allocation method in a satellite network for data transmission, characterized in that the time slot of the contention mode is switched. The method of claim 3, wherein the cancellation conditions, And a length of a transmission queue of the terminal station is smaller than a reservation release threshold length. The method of claim 3, wherein the cancellation conditions, The channel assignment method in the satellite network for data transmission, characterized in that the duration of the reservation allocation mode duration of the terminal station exceeds a predetermined time. The method of claim 1, wherein the number of timeslots in the reservation allocation mode is a value between '0' and 'number of maximum reserved timeslots', and the number of maximum reserved timeslots is' the total number of timeslots in a superframe. -(Number of fixed allocation mode timeslots + number of minimum contention mode timeslots) ', and the number of minimum contention mode timeslots is a constant value determined during network operation. Way. The method of claim 1, wherein the number of contention mode timeslots is a value between 'number of minimum contention mode timeslots' and 'number of maximum contention time slots', and the number of maximum contention mode timeslots is determined by the number of superframes. The total number of timeslots minus the number of fixed allocation mode timeslots, and the minimum number of contention mode timeslots is a constant value determined during network operation.