CN109039934B - Space DTN network congestion control method and system - Google Patents

Abstract

The invention discloses a space DTN network congestion control method and a space DTN network congestion control system, and belongs to the technical field of satellite communication. The method comprises the following steps: in a spatial DTN network, if node v_jAnd node v_iMeet and the message will be from node v_jTransmission to node v_iThen according to node v_iNode v for estimating cache occupation state and number of neighbor nodes_iA congestion probability after receiving the message; node v_iRefusing to receive the message by the congestion probability if the node v_iRefuse to receive the message, node v_iRejection of message input, node v_jContinuing to store the message, and waiting for the next encounter to try to transmit the message; else node v_iAccepting message input. The invention also realizes a space DTN network congestion control system; the technical scheme of the invention is used for the spatial DTN, can effectively reduce the occurrence of node congestion, reduces the discarding probability of the whole network message and improves the network performance.

Description

Space DTN network congestion control method and system

Technical Field

The invention belongs to the technical field of satellite communication, and particularly relates to a method and a system for controlling space DTN network congestion.

Background

In a space DTN (Delay Tolerant network) network, space-level chips are often used for spacecraft nodes in a space environment, and the storage resource of each node is limited, so that some nodes in the network may take on more information transfer tasks than other nodes in a period of time, which may cause cache (Buffer) resources of message competition nodes. Especially in deep space communication, the end-to-end delay is larger, and a message may need to be stored for a long time before being forwarded to a next hop, so that cache management (including cache allocation, cache management policy and the like) of a node is very important;

in addition, in the DTN protocol system, a "store-carry-forward" strategy is adopted for message transmission, and when a proper relay node is not encountered and a received message cannot be sent in time, the node can only buffer the message. However, since the storage resources of nodes in a spatial DTN network are limited, congestion occurs when a received message exceeds the buffer capacity. The message discarding strategy adopted by the traditional congestion control method is not suitable for the spatial DTN network, because the message retransmission cost is too high in the spatial DTN network with very large time delay. Therefore, the congestion control method of the spatial DTN network must look at reducing the drop rate of messages when congestion occurs. Since there are limited opportunities for contact between spatial nodes, it may be difficult to alleviate congestion with limited opportunities for contact between nodes after congestion occurs, and therefore congestion control strategies are preferably performed before congestion occurs to try to prevent node cache exhaustion from having to drop messages.

Disclosure of Invention

In view of the above defects or improvement requirements of the prior art, the present invention provides a method and a system for controlling spatial DTN network congestion, which aim to estimate the probability of node congestion according to the local available cache of a spatial node and the number of its neighbor nodes when a new message arrives, and then reject the arriving message with the probability, thereby solving the technical problem of congestion control of the existing spatial DTN network.

In order to achieve the above object, the present invention provides a method for controlling spatial DTN network congestion, which comprises the following steps:

(1) in a spatial DTN network, if node v_jAnd node v_iMeet and the message will be from node v_jTransmission to node v_iThen according to node v_iNode v for estimating cache occupation state and number of neighbor nodes_iA congestion probability after receiving the message;

(2) for node v_iRefusing to receive the message by the congestion probability if the node v_iIf the message is refused to be received, the step (3) is entered, otherwise, the step (4) is entered;

(3) node v_iRejection of message input, node v_jContinuing to store the message, and waiting for the next encounter to try to transmit the message;

(4) node v_iAccepting message input.

Further, the node v is a function of_iNode v for estimating cache occupation state and number of neighbor nodes_iThe congestion probability after receiving the message is specifically:

wherein, P_r ⁱIs a node v_iReceivingCongestion probability after the message; node v_iTotal amount of cache is K_iThe buffer margin is k_i(ii) a Node v_iHaving m_iEach adjacent node carries no less than k messages_i(ii) a The capacity of a single buffer unit is set to be equal to the size of a single message.

According to another aspect of the present invention, the present invention provides a spatial DTN network congestion control system, where the system specifically includes:

a congestion probability estimation module used for if the node v in the spatial DTN network_jAnd node v_iMeet and the message will be from node v_jTransmission to node v_iThen according to node v_iNode v for estimating cache occupation state and number of neighbor nodes_iA congestion probability after receiving the message;

probability selection module for node v_iRefusing to receive the message by the congestion probability if the node v_iIf the receiving of the message is refused, executing a refusing message input module, otherwise executing an accepting message input module;

rejection message input module for node v_iRejection of message input, node v_jContinuing to store the message, and waiting for the next encounter to try to transmit the message;

accept message input module for node v_iAccepting message input.

Further, the node v is a function of_iNode v for estimating cache occupation state and number of neighbor nodes_iThe congestion probability after receiving the message is specifically:

wherein, P_r ⁱIs a node v_iA congestion probability after receiving the message; node v_iTotal amount of cache is K_iThe buffer margin is k_i(ii) a Node v_iHaving m_iEach adjacent node carries no less than k messages_i(ii) a Setting the capacity of a single buffer unit and a single messageAre equal in size.

Generally, compared with the prior art, the technical scheme of the invention has the following technical characteristics and beneficial effects:

because the spatial DTN network node is difficult to acquire the state information of the whole network, the congestion control mechanism is based on the local information of the spatial node and is preferably independent of a routing protocol so as to be capable of conveniently realizing fusion with the routing protocol, the technical scheme of the invention provides a congestion control algorithm based on the node cache state and the number of neighbor nodes in the spatial DTN network from the buffer management perspective in the communication scene of the spatial DTN network, and simulation shows that the congestion control method can effectively reduce the occurrence of node congestion, reduce the discarding probability of the whole network message and improve the network performance.

Drawings

FIG. 1 is a schematic flow diagram of the process of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

As shown in fig. 1, the method of the present invention specifically comprises:

let node v_iHaving m_iA neighbor node with a total cache amount of K_iThe capacity of a single buffer unit is equal to the size of a single message. At time t, if node v_iHas a buffer margin of k_iAnd the number of messages carried by each neighbor node is not less than k_iThen, starting from t, node v_iIs provided with

Is likely to receive k_iA message, and node v_iIt is possible to receive 0 to k_iA message, so that the total possible number of received messages is

When node v_iReceives k_iA message, node v_iIs exhausted, congestion occurs, and thus node v_iThe probability of congestion occurring is:

if m_i1, i.e. node v_iWith only one neighbor node, node v_iAll messages received are from this neighbor, in which case node v_iThe probability of congestion occurring is:

taking the two situations into consideration, node v_iThe probability of congestion occurring can be expressed as:

since the spatial DTN network has limited communication opportunities, there may not be available communication opportunities to alleviate congestion after it occurs, and therefore congestion control is preferably performed before congestion occurs. In the invention, by establishing an early congestion detection mechanism, when other nodes send messages, the node v_iEstimating the probability of congestion, and refusing to receive the new message based on the congestion probability, namely if the estimated probability of node congestion is 0.8, then the refused probability of the new message is 0.8, so as to manage the node buffer memory, and avoid the node congestion as much as possible. Probability of congestion

And a cache margin k_iIn a relation ofDerived from equation (4):

from (5), P_r ⁱAnd k is_iIs in negative correlation, k_iThe larger the node v is, the larger the node v is_iThe smaller the probability of congestion occurring, the greater the probability of a new arrival message being received.

The specific flow of the method is shown as the following steps:

it will be appreciated by those skilled in the art that the foregoing is only a preferred embodiment of the invention, and is not intended to limit the invention, such that various modifications, equivalents and improvements may be made without departing from the spirit and scope of the invention.

Claims (2)

1. A method for controlling congestion of a spatial DTN network is characterized by comprising the following steps:

(1) in a spatial DTN network, if node v_jAnd node v_iMeet and the message will be from node v_jTransmission to node v_iThen according to node v_iNode v for estimating cache occupation state and number of neighbor nodes_iA congestion probability after receiving the message; the congestion probability is specifically:

wherein the content of the first and second substances,

is a node v_iA congestion probability after receiving the message; node v_iTotal amount of cache is K_iThe buffer margin is k_i(ii) a Node v_iHaving m_iA neighboring node, andthe number of messages carried by each adjacent node is not less than k_i(ii) a Setting the capacity of a single cache unit equal to the size of a single message;

(2) node v_iRefusing to receive the message by the congestion probability if the node v_iIf the message is refused to be received, the step (3) is entered, otherwise, the step (4) is entered;

(3) node v_iRejection of message input, node v_jContinuing to store the message, and waiting for the next encounter to try to transmit the message;

(4) node v_iAccepting message input.

2. A spatial DTN network congestion control system, the system comprising:

a congestion probability estimation module used for if the node v in the spatial DTN network_jAnd node v_iMeet and the message will be from node v_jTransmission to node v_iThen according to node v_iNode v for estimating cache occupation state and number of neighbor nodes_iA congestion probability after receiving the message; the congestion probability is specifically:

wherein the content of the first and second substances,

is a node v_iA congestion probability after receiving the message; node v_iTotal amount of cache is K_iThe buffer margin is k_i(ii) a Node v_iHaving m_iEach adjacent node carries no less than k messages_i(ii) a Setting the capacity of a single cache unit equal to the size of a single message;

probability selection module for node v_iRefusing to receive the message by the congestion probability if the node v_iIf the receiving of the message is refused, executing a refusing message input module, otherwise executing an accepting message input module;

the rejection message input module is configured to reject the message,for node v_iRejection of message input, node v_jContinuing to store the message, and waiting for the next encounter to try to transmit the message;

accept message input module for node v_iAccepting message input.

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