GB2621413A - Mobile opportunistic network node congestion avoiding method and system - Google Patents
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L47/00—Traffic control in data switching networks
- H04L47/10—Flow control; Congestion control
- H04L47/12—Avoiding congestion; Recovering from congestion
- H04L47/127—Avoiding congestion; Recovering from congestion by using congestion prediction
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W28/00—Network traffic management; Network resource management
- H04W28/02—Traffic management, e.g. flow control or congestion control
- H04W28/0284—Traffic management, e.g. flow control or congestion control detecting congestion or overload during communication
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L47/00—Traffic control in data switching networks
- H04L47/10—Flow control; Congestion control
- H04L47/12—Avoiding congestion; Recovering from congestion
- H04L47/122—Avoiding congestion; Recovering from congestion by diverting traffic away from congested entities
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W28/00—Network traffic management; Network resource management
- H04W28/02—Traffic management, e.g. flow control or congestion control
- H04W28/0289—Congestion control
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Abstract
The present invention relates to the field of network node congestion detection and avoidance. Disclosed are a mobile opportunistic network node congestion avoiding method and system. The method comprises: predicting a cache increment of a target node in a current time slot according to the number of bytes of an inflowing message packet and the number of bytes of an outflowing message packet of the target node in a previous time slot, and a residual cache space of the target node when the current time slot starts, and detecting whether the target node is congested in the current time slot; if yes, firstly determining a managed node set; determining an unloading set of a congested node according to a forwarding probability of each message packet of the congested node; and then unloading message packets to be unloaded in the unloading set of the congested node to a managed node in the managed node set. According to the present invention, nodes having high congestion risks are detected by using a traffic sensing strategy, and the congestion risks of the nodes are reduced by using a message unloading strategy.
Description
METHOD AND SYSTEM FOR AVOIDING NODE CONGESTION IN MOBILE
OPPORTUNISTIC NETWORKS
TECHNICAL FIELD
[0001] The present disclosure relates to the field of detection and avoidance of network node congestion, and in particular, to a method and system for avoiding node congestion in mobile opportunistic networks (OppNets).
BACKGROUND ART
[0002] In recent years, with the development of a large number of low-cost, convenient smart devices with short-range wireless communication capabilities, mobile opportunistic networks (mobile OppNets), as a new type of mobile self-organizing network, have emerged. OppNets are typically characterized by unstable topology, mobile devices and intermittent connection. In most cases of lacking a complete end-to-end connectivity link, a "store-carry-forward" mechanism is adopted and messages are collaboratively transmitted through encounter opportunities offered by device movement. In the message transmission process, a multi-copy forwarding strategy is used to improve the success rate of message transmission, and messages need to be temporarily stored in relay nodes during distribution and delivery. However, the limited storage resources of mobile devices and the large number of redundant messages generated by the multi-copy mechanism are prone to cause congestion among some devices, resulting in cache overflow. Consequently, a large number of carried and forwarded messages are discarded, and the transmission performance of the network is reduced. Therefore, it is urgently desired to design an efficient mechanism for congestion detection and avoidance in the mobile OppNets to prevent devices from congestion and improve the reliability of network transmission.
[0003] Due to the intermittent connection and incomplete end-to-end links of the mobile OppNets, the congestion avoidance method for the conventional Internet cannot be applied to the mobile OppNets. Some related methods and strategies have been proposed to reduce the impact of node congestion on network performance in the existing mobile OppNets For example, in a congestion control method based on node status sensing, the network congestion condition is determined by predicting the numbers of saturated nodes and unsaturated nodes, the upper limit of the number of messages to be sent is determined based on the indirectly sensed congestion status, and the number of message copies in the network is balanced by using the diffusion rate of message. For another example, in a social congestion control algorithm, the node congestion level is determined based on the packet loss rate, and then the network congestion risk is determined based on the node congestion level and the historical encounter information among the nodes. For another example, in a congestion control strategy of limiting the number of message copies, the congestion level of the node is determined based on the packet loss rate. Then the number of new message copies to be generated by the node is determined, thus limiting the total number of messages in the network and reducing the redundant copies. The above existing methods mainly alleviate network congestion conditions through controlling network message packets and cache management, and network congestion is alleviated by controlling the number of message packets in the network and discarding the message packets with low transmission success rate. The disadvantages are as follows: Node congestion cannot be sensed in advance, and the alleviation processing can only be performed after node congestion occurs, greatly affecting the transmission performance of the network. In addition, the existing methods only alleviate the network congestion independently at each node without considering the storage resource sharing among the nodes in the network, which leads to low usage efficiency of storage resources at many nodes without congestion and also affects the transmission performance of the network.
S U NI MARY
[0004] Based on this, embodiments of the present disclosure provide a method and system for avoiding node congestion in mobile OppNets, to detect nodes with high congestion risk by using a traffic sensing strategy and reduce congestion risk of the nodes by using a message offloading strategy, thereby improving the transmission performance of the network.
100051 To achieve the above objective, the present disclosure provides the following technical solutions.
[0006] A method for avoiding node congestion in mobile OppNets, including: [0007] predicting a cache increment of a target node in a current slot based on a number of bytes of inflow message packets flowing into the target node and a number of bytes of outflow message packets flowing out of the target node in a previous slot; [0008] determining whether the target node is congested in the current slot based on the cache increment of the target node in the current slot and remaining cache space of the target node at a beginning of the current slot; and [0009] determining the target node as a congested node when the target node is congested in the current slot, and performing a congestion avoidance operation, where 100101 the congestion avoidance operation may include: [0011] determining a hosting node set, where each hosting node in the hosting node set satisfies following hosting condition: the hosting condition is a one-hop neighbor node of the congested node and is not congested in the current slot, an encounter probability between the hosting node and the congested node is greater than a predetermined probability, and available cache space of the hosting node in the current slot is larger than storage space of to-be-offloaded message packets to be offloaded by the congested node; [0012] determining an offload set of the congested node based on forwarding probabilities of message packets of the congested node; and 100131 offloading the to-be-offloaded message packets in the offload set of the congested node to the hosting node in the hosting node set.
[0014] In some embodiments, the predicting a cache increment of a target node in a current slot based on a number of bytes of inflow message packets flowing into the target node and a number of bytes of outflow message packets flowing out of the target node in a previous slot may specifically include: [0015] obtaining the number of bytes of inflow message packets and the number of bytes of outflow message packets of the target node in the previous slot; and [0016] using a difference between the number of bytes of inflow message packets and the number of bytes of outflow message packets of the target node in the previous slot, as the cache increment of the target node in the current slot.
[0017] In some embodiments, the determining whether the target node is congested in the current slot based on the cache increment of the target node in the current slot and remaining cache space of the target node at a beginning of the current slot may specifically include: [0018] detecting the remaining cache space of the target node at the beginning of the current slot; and [0019] determining that the target node is congested, when the cache increment of the target node in the current slot is larger than the remaining cache space of the target node at the beginning of the current slot.
[0020] In some embodiments, the determining a hosting node set may specifically include: [0021] broadcasting, by the congested node, a message offload request packet to all neighbor nodes and receiving message offload response packets from candidate hosting nodes, where the candidate hosting nodes each are a node of the neighbor nodes that is not congested in the current slot, and the message offload response packets each include available cache space and an identity (ID) of a corresponding node; [0022] determining, as a final hosting node, a candidate hosting node whose encounter probability with the congested node is greater than the predetermined probability and whose available cache space is larger than the storage space of the message packets to be offloaded by the congested node; and [0023] constructing the hosting node set with the final hosting node.
[0024] In some embodiments, the determining an offload set of the congested node based on forwarding probabilities of message packets of the congested node may specifically include: [0025] calculating the forwarding probabilities of the message packets of the congested node, and ranking the forwarding probabilities in ascending order to obtain a probability sequence; [0026] determining message packets corresponding to first specified number of forwarding probabilities in the probability sequence as the to-be-offloaded message packets, where the storage space of the to-be-offloaded message packets is not smaller than a difference between the cache increment and the remaining cache space of the congested node; and [0027] constructing the offload set with the to-be-offloaded message packets.
[0028] In some embodiments, the offloading the to-be-offloaded message packets in the offload set of the congested node to the hosting node in the hosting node set may specifically include: [0029] selecting a hosting node from the hosting node set as a target hosting node and obtaining available cache space of the target hosting node; and [0030] selecting a to-be-offloaded message packet from the offload set as a target to-be-offloaded message packet, and offloading, by the congested node, the target to-be-offloaded message packet to the target hosting node when the storage space of all the to-be-offloaded message packets in the offload set is not larger than the available cache space of the target hosting node.
[0031] The present disclosure further provides a system for avoiding node congestion in mobile OppNets, including: [0032] a cache increment prediction module, configured to predict a cache increment of a target node in a current slot based on a number of bytes of inflow message packets flowing into the target node and a number of bytes of outflow message packets flowing out of the target node in a previous slot; [0033] a congestion detection module, configured to determine whether the target node is congested in the current slot based on the cache increment of the target node in the current slot and remaining cache space of the target node at a beginning of the current slot; and [0034] a congested node determining module, configured to determine the target node as a congested node when the target node is congested in the current slot, and execute a congestion avoidance module, where [0035] the congestion avoidance module may include: [0036] a hosting node set determining unit, configured to determine a hosting node set, where each hosting node in the hosting node set satisfies following hosting condition: the hosting node is a one-hop neighbor node of the congested node and is not congested in the current slot, an encounter probability between the hosting node and the congested node is greater than a predetermined probability, and available cache space of the hosting node in the current slot is larger than storage space of to-be-offloaded message packets to be offloaded by the congested node; [0037] an offload set determining unit, configured to determine an offload set of the congested node based on forwarding probabilities of message packets of the congested node; and 100381 an offload unit, configured to offload the to-be-offloaded message packets in the offload set of the congested node to the hosting node in the hosting node set.
[0039] In some embodiments, the hosting node set determining unit may specifically include: [0040] a candidate node determining subunit, configured to broadcast, by the congested node, a message offload request packet to all neighbor nodes and receive message offload response packets from candidate hosting nodes, where the candidate hosting nodes each are a node of the neighbor nodes that is not congested in the current slot, and the message offload response packets each include available cache space and an identity (ID) of a corresponding node; [0041] a final node determining subunit, configured to determine, as a final hosting node, a candidate hosting node whose encounter probability with the congested node is greater than the predetermined probability and whose available cache space is larger than the storage space of the message packets to be offloaded by the congested node; and [0042] a hosting set construction subunit, configured to construct the hosting node set with the final hosting node.
[0043] In some embodiments, the offload set determining unit may specifically include: 100441 a forwarding probability calculation subunit, configured to calculate the forwarding probabilities of the message packets of the congested node, and rank the forwarding probabilities in ascending order to obtain a probability sequence; [0045] an offload message determining subunit, configured to determine message packets corresponding to first specified number of forwarding probabilities in the probability sequence as the to-be-offloaded message packets, where the storage space of the to-be-offloaded message packets is not smaller than a difference between the cache increment and the remaining cache space of the congested node; and [0046] an offload set construction subunit, configured to construct the offload set with the to-be-offloaded message packets.
100471 In some embodiments, the offload unit may specifically include: 100481 a target hosting node selection subunit, configured to select a hosting node from the hosting node set as a target hosting node and obtain available cache space of the target hosting node; and [0049] a target message packet offload subunit, configured to select a to-be-offloaded message packet from the offload set as a target to-be-offloaded message packet, and offload, by the congested node, the target to-be-offloaded message packet to the target hosting node when the storage space of all the to-be-offloaded message packets in the offload set is not larger than the available cache space of the target hosting node.
[0050] Compared with the prior art, the present disclosure achieves the following beneficial effects: [0051] The embodiments of the present disclosure propose a method and system for avoiding node congestion in mobile OppNets. A cache increment of a target node in a current slot is predicted based on a number of bytes of inflow message packets flowing into the target node and a number of bytes of outflow message packets flowing out of the target node in a previous slot, and whether the target node is congested in the current slot is detected based on the cache increment and remaining cache space of the target node at a beginning of the current slot, thereby detecting nodes with high congestion risk by using a traffic sensing strategy. When the target node is congested, a hosting node set is determined first, then an offload set of the congested node is determined based on forwarding probabilities of message packets of the congested node, and to-be-offloaded message packets in the offload set of the congested node are offloaded to a hosting node in the hosting node set, thereby reducing the node congestion risk by using a message offloading strategy. The embodiments can effectively predict whether congestion occurs at a node in a next cycle based on an analysis on the number of bytes of inflow message packet and the number of bytes of outflow message packet of the node, and avoid node congestion through message offloading and hosting. This fully utilizes the idle storage resources and encounter opportunities of other nodes in the network, to share idle storage resources among the nodes, thereby effectively improving the transmission performance of the network.
BRIEF DESCRIPTION OF THE DRAWINGS
[0052] To describe the embodiments of the present disclosure or the technical solutions in the related art more clearly, the accompanying drawings required in the embodiments are briefly introduced below. Apparently, the accompanying drawings described below are only some embodiments of the present disclosure. A person of ordinary skills in the art may further obtain other accompanying drawings based on these accompanying drawings without creative labor. [0053] FIG 1 shows a process of offloading and returning cached message packets according to an embodiment of the present disclosure, where figure (a) is a schematic diagram of a process of offloading the cached message packets and figure (b) is a schematic diagram of a process of returning messages by a hosting node; [0054] FIG. 2 is a flowchart of a method for avoiding node congestion in mobile OppNets according to an embodiment of the present disclosure; 100551 FIG. 3 is a schematic diagram of a process of dividing slots according to an embodiment of the present invention; [0056] FIG. 4 is a schematic diagram of a cache occupation status of a node nk according to an embodiment of the present disclosure; and 100571 FIG. 5 is a stmctural diagram of a system for avoiding node congestion in mobile OppNets according to an embodiment of the present disclosure.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0058] The technical solutions of the embodiments of the present disclosure are clearly and completely described below with reference to the accompanying drawings according to the embodiments of the present disclosure. Apparently, the described embodiments are merely a part rather than an of the embodiments of the present disclosure. All other embodiments obtained by those of ordinary skills in the art based on the embodiments of the present disclosure without creative efforts shall fall within the protection scope of the present disclosure.
[0059] To make the above-mentioned objective, features, and advantages of the present disclosure clearer and more comprehensible, the present disclosure will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.
[0060] The embodiments can avoid node congestion in mobile OppNets based on traffic sensing. Through analyzing the essential causes of node congestion in the mobile OppNets, a congestion sensing strategy based on a detection of remaining cache and an analysis of content inflow and outflow is proposed, in which the node can senses congestion by monitoring remaining cache space and the ratio of inflow messages to outflow messages in each slot. Further, a congestion avoidance method based on message offloading is proposed, in which the node, when sensing high congestion risk, offloads some cached messages to a neighbor non-congested node for hosting, thereby reducing the node congestion risk.
[0061] By analyzing the causes of congestion, it is found that the message inflow rate of some active nodes in the network is much faster than the message outflow rate of the active nodes in the period, and the messages increment exceeds the remaining cache capacity, resulting in cache overflow. To this end, the embodiments propose a congestion detection and avoidance strategy based on traffic sensing, the basic idea of which is to discover nodes with high congestion risk by using a traffic sensing strategy and reduce the congestion risk of the nodes by using a message offloading strategy. In the method, each node senses whether there is a high congestion risk by monitoring the remaining cache space and the numbers of inflow message and outflow message. If a node senses a high congestion risk, it offloads some cached messages to a one-hop neighbor node, thus freeing up enough storage resources to prevent congestion.
[0062] As shown in FIG. 1, figure (a) shows a process of offloading cached message packets. In a slot t1, a node no is a high congestion risk node with the cache space being fully occupied, and the node no offloads some messages to one-hop neighbor nodes ni and ns. In the case, the cache status of no is changed to the normal cache status as indicated by the rectangular dashed box, effectively reducing the congestion risk of the node no. Figure (b) shows a process of returning messages by a hosting node. In a slot t2, the node ni encounters the node no, and if the node no is currently a normal node, the node ni returns the hosted messages to the node no * [0063] The method for avoiding node congestion in mobile OppNets according to the embodiments is described in detail below.
[0064] Referring to FIG. 2, the method according to the embodiments includes following steps S101 to 5103.
[0065] In step 5101, a cache increment of a target node in a current slot is predicted based on a number of bytes of inflow message packets flowing into the target node in a previous slot and a number of bytes of outflow message packets flowing out of the target node in the previous slot. [0066] This step may specifically include: obtaining the number of bytes of inflow message packets and the number of bytes of outflow message packets of the target node in the previous slot; and determining a difference between the number of bytes of inflow message packets and the number of bytes of outflow message packets of the target node in the previous slot as the cache increment of the target node in the current slot.
[0067] In step S102, it is determined whether the target node is congested in the current slot based on the cache increment of the target node in the current slot and remaining cache space of the target node at the beginning of the current slot.
[0068] This step may specifically include: detecting the remaining cache space of the target node at the beginning of the current slot; and determining that the target node is congested when the cache increment of the target node in the current slot is larger than the remaining cache space of the target node at the beginning of the current slot.
[0069] In step S103, the target node is determined as a congested node when the target node is congested in the current slot, and a congestion avoidance operation is performed.
[0070] The congestion avoidance operation may include following steps 5301 to S303.
[0071] In step S301, a hosting node set is determined, where each hosting node in the hosting node set satisfies the following hosting condition: the hosting node is a one-hop neighbor node of the congested node and is not congested in the current slot; an encounter probability between the hosting node and the congested node is greater than a predetermined probability; and available cache space of the hosting node in the current slot is larger than storage space of to-be-offloaded message packets to be offloaded by the congested node. This step may specifically include: [0072] broadcasting, by the congested node, a message offload request packet to all neighbor nodes and receiving message offload response packets from candidate hosting nodes, where the candidate hosting nodes each are a node of the neighbor nodes that is not congested in the current slot, and the message offload response packets each include available cache space and an ID of a corresponding node; [0073] determining, as a final hosting node, a candidate hosting node whose encounter probability with the congested node is greater than the predetermined probability and whose available cache space is larger than the storage space of the message packets to be offloaded by the congested node; and [0074] constructing the hosting node set with the final hosting node.
[0075] In step S302, an offload set of the congested node is determined based on forwarding probabilities of message packets of the congested node. This step may specifically include: [0076] calculating the forwarding probabilities of the message packets of the congested node, and ranking the forwarding probabilities in ascending order to obtain a probability sequence; [0077] determining message packets corresponding to first specified number of forwarding probabilities in the probability sequence as the to-be-offloaded message packets, where the storage space of the to-be-offloaded message packets is not smaller than a difference between the cache increment and the remaining cache space of the congested node; and [0078] constructing the offload set with the to-be-offloaded message packets.
[0079] In step 5303, the to-be-offloaded message packets in the offload set of the congested node are offloaded to the hosting node in the hosting node set. This step may specifically include: [0080] selecting a hosting node from the hosting node set as a target hosting node and obtaining available cache space of the target hosting node; and [0081] selecting a to-be-offloaded message packet from the offload set as a target to-be-offloaded message packet, and offloading, by the congested node, the target to-be-offloaded message packet to the target hosting node when the storage space of all the to-be-offloaded message packets in the offload set is not larger than the available cache space of the target hosting node.
[0082] Steps 101 and 102 are processes of node congestion detection in the mobile OppNets, and step 103 is a process of node congestion avoidance in the mobile OppNets.
[0083] In practical applications, the specific implementation process of the method for avoiding node congestion in the mobile OppNets is as follows.
[0084] (1) Node congestion detection process based on traffic sensing in the mobile OppNets [0085] Congestion sensing is the prerequisite for resolving the congestion problem in the mobile OppNets. The node with high congestion risk has characteristics of a small remaining cache space and a higher message inflow rate with respect to the message outflow rate. Based on the characteristics, the embodiments design a node congestion detection method based on cache detection and traffic analysis of inflow and outflow messages, which senses the node congestion risk by detecting the remaining cache space and the ratio of inflow messages to outflow messages of each node.
[0086] First, the system time is divided into multiple slots of equal length, as shown in FIG. 3. The node statistics the total number of bytes of inflow message packets and the total number of bytes of outflow message packets in each slot. /(,,k,ti) and 0(,k,,i) denote a number of bytes of inflow message packets and a number of bytes of outflow message packets of a node nk in a slot ti, respectively. At the end of each slot, each node can calculate /oik,to -0("k,to to sense the trend of cache increase or decrease in this slot. The cache increment Ab(cik,t1+,) of the node nk in the next slot ti+, is predicted, that is, ,6,b(Inksi_Fi) Totkiti) - [0087] The node detects remaining cache space at the beginning of each slot. As shown in FIG. 4, bf,"ksi and knksi respectively denote the remaining cache space and the occupied cache space of the node nk at the beginning of the slot t. bf,"kiti = Bnk -b 0 tnkiti, where Bnk is the size of the cache of the node nk.
[0088] It can be concluded that if a predicted cache increment of a node in a slot is larger than the remaining cache space, the node is congested in the slot. To this end, the embodiments define the following criteria for determining whether a node is congested in a slot.
[0089] Congestion determining criterion: If Abn'k,ti > bititmti, the node nk will experience congestion in the slot ti; otherwise, the node nk will not experience congestion in the slot ti. [0090] Obviously, at the beginning of each slot, the node uses this criterion to sense its congestion status in this slot, and the congestion status of the node nk in the slot ti is denoted as Crik,ti, where = ( 1, if ALIT,' k,ti > brinkiti (7) nk't i o, else 100911 Cnksi= 1 indicates that the node nk has a high congestion risk in this slot, and = 0 indicates that the node has no congestion risk.
[0092] (2) Method for selecting a hosting node [0093] In order to successfully offload the contents and avoid more node congestion, a suitable hosting node should be selected to store the offloaded contents. The hosting node should satisfy the following conditions: 0 the selected hosting node is a one-hop neighbor node of the congested node; CZ the selected hosting node should have the congestion status Crti = 0 and will not be congested in this slot after storing the offloaded contents; and OD the selected hosting node has a high encounter probability with the congested node, and the hosted messages are returned if the congestion status of the congested node is Ctt = 0.
100941 If the node nk senses that the congestion status in the slot t is Cnksi = 1, the following steps Si to 54 are performed to offload the contents.
[0095] In step Si, the node nk broadcasts a message offload request packet to all neighbor nodes.
[0096] In step 52, when a neighbor node nj receives a message offload request packet from the node nk, if its congestion status is Citfiti = 0, the neighbor node nj returns a message offload response packet to the node nk. For selecting a suitable hosting node, the content of the response packet is the available cache space ba,n1s1 of the node nj in the slot ti, denoted as = br,"pti - (8).
[0097] In step 53, the node nk receives response packets from multiple neighbor nodes and extracts available cache space b","1,t1 and an ID of the neighbor node nj from each response packet to obtain a set of candidate hosting nodes in the slot ti, denoted as Mne ksi = {n1, n2, n3, * * * , nj}.
[0098] In step S4, the node nk calculates an encounter probability with each node in the set Ain(' ksi in the future period and selects a node with a high encounter probability and larger available cache space bayipti as the hosting node. The node nk finally obtains a hosting node set in the slot ti, denoted as Mnksi = {n3, *** , nj} c /14j,ck,ji.
[0099] (3) Method for congestion avoidance based on message offloading [0100] At the beginning of each slot ti, if the node nk has a high congestion risk and Mnksi 0, the node offloads the messages in the following steps SI to 54.
[0101] In step Si, the node nk determines a total number of bytes of messages to be offloaded in the slot ti. The total number of bytes of messages to be offloaded in the slot ti is denoted as bm,,,k,ti, satisfying: Abnr k*ti (9).
[0102] In step S2, the node nk calculates the forwarding efficiency of each message in the cache. mnck,ji = fmi, m2, *-* , mit} denotes a set of messages in the cache of the node nk.
101031 In step 53, the node nk selects messages to be offloaded. it,, selects the message mi with lower forwarding efficiency in the cache space and add the message mi to an offload set rtin'ksi. Then, the node nk repeats step S3 until Inthiksi I. Finally, the node nk obtains the offload set mn°,i in the slot ti, where ingk,ji = [m3, * * * , c mnck,ji.
[0104] In step S4, the node nk offloads the messages to the hosting node. The node nk selects a hosting node nj from the set Mrik,ti, obtains available cache space ban1t1 of the hosting node ni, and then extracts a message mi from the set mt. If ElIntI ba,npti, the node nk offloads the message mi to the hosting node ill. The node nk repeats step S4 until the set mn'icsi or the set Mnic,ti is empty, and the offloading ends.
[0105] The messages in the cache of the node with high congestion risk can be offloaded to the hosting node by using the above four steps, and thus the node congestion can be avoided.
[0106] The method for avoiding node congestion in the mobile OppNets according to the foregoing embodiments can effectively predict whether congestion occurs at a node in a next cycle based on analysis on the number of bytes of inflow message packet and the number of bytes of outflow message packet of the node, and avoid node congestion through message offloading and hosting. This fully utilizes the idle storage resources and encounter opportunities of other nodes in the network, to share idle storage resources among the nodes, thereby effectively improving the transmission performance of the network.
[0107] The present disclosure further provides a system for avoiding node congestion in mobile OppNets. Referring to FIG. 5, the system includes a cache increment prediction module 501, a congestion detection module 502, a congested node determining module 503, and a congestion avoidance module 504.
[0108] The cache increment prediction module 501 is configured to predict a cache increment of a target node in a current slot based on a number of bytes of inflow message packets and a number of bytes of outflow message packets of the target node in a previous slot.
101091 The congestion detection module 502 is configured to determine whether the target node is congested in the current slot based on the cache increment of the target node in the current slot and remaining cache space of the target node at a beginning of the current slot.
[0110] The congested node determining module 503 is configured to determine the target node as a congested node when the target node is congested in the current slot, and execute a congestion avoidance module 504.
[0111] The congestion avoidance module 504 may include a hosting node set determining unit, an offload set determining unit, and an offload unit.
[0112] The hosting node set determining unit is configured to determine a hosting node set, where each hosting node in the hosting node set satisfies the following hosting condition: the hosting node is a one-hop neighbor node of the congested node, and is not congested in the current slot; an encounter probability between the hosting node and the congested node is greater than a predetermined probability; and available cache space of the hosting node in the current slot is larger than storage space of message packets to be offloaded by the congested node.
[0113] The offload set determining unit is configured to determine an offload set of the congested node based on forwarding probabilities of message packets of the congested node 101141 The offload unit is configured to offload the to-be-offloaded message packets in the offload set of the congested node to the hosting node in the hosting node set.
[0115] In an example, the hosting node set determining unit may specifically include a candidate node determining subunit, a final node determining subunit and a hosting set construction subunit.
[0116] The candidate node determining subunit is configured to broadcast, by the congested node, a message offload request packet to all neighbor nodes and receive, by the congested node, message offload response packets from candidate hosting nodes, where the candidate hosting nodes each are a node of the neighbor nodes that is not congested in the current slot, and the message offload response packets each include available cache space and an ID of the corresponding node.
101171 The final node determining subunit is configured to determine, as a final hosting node, a candidate hosting node whose encounter probability with the congested node is greater than the predetermined probability and whose available cache space is larger than the storage space of the message packets to be offloaded by the congested node.
101181 The hosting set construction subunit is configured to construct the hosting node set with the final hosting node.
101191 In an example, the offload set determining unit may specifically include a forwarding probability calculation subunit, an offload message determining subunit, and an offload set construction subunit.
[0120] The forwarding probability calculation subunit is configured to calculate the forwarding probabilities of the message packets of the congested node, and rank the forwarding probabilities in ascending order to obtain a probability sequence 101211 The offload message determining subunit is configured to determine message packets corresponding to first specified number of forwarding probabilities in the probability sequence as the to-be-offloaded message packets, where the storage space of the to-be-offloaded message packets is not smaller than a difference between the cache increment and the remaining cache space of the congested node.
[0122] The offload set construction subunit is configured to construct the offload set with the to-be-offloaded message packets 101231 In an example, the offload unit may specifically include a target hosting node selection subunit and a target message packet offload subunit.
[0124] The target hosting node selection subunit is configured to select a hosting node from the hosting node set as a target hosting node and obtain available cache space of the target hosting node.
101251 The target message packet offload subunit is configured to select a to-be-offloaded message packet from the offload set as a target to-be-offloaded message packet, and offload, by the congested node, the target to-be-offloaded message packet to the target hosting node when the storage space of all the to-be-offloaded message packets in the offload set is not larger than the available cache space of the target hosting node.
[0126] Each embodiment of the present specification is described in a progressive manner, each embodiment focuses on the difference from other embodiments, and the same and similar parts between the embodiments may refer to each other. Since the system disclosed in an embodiment corresponds to the method disclosed in another embodiment, the description is relatively simple, and reference can be made to the method description.
[0127] Specific examples are used herein to explain the principles and embodiments of the present disclosure. The foregoing description of the embodiments is merely intended to help understand the method of the present disclosure and its core ideas; besides, various modifications may be made by a person of ordinary skills in the art to specific embodiments and the scope of application in accordance with the ideas of the present disclosure. In conclusion, the content of the present specification shall not be construed as limitations to the present disclosure.
Claims (10)
- WHAT IS CLAIMED IS: I. A method for avoiding node congestion in mobile opportunistic networks (OppNets), comprising: predicting a cache increment of a target node in a current slot based on a number of bytes of inflow message packets flowing into the target node and a number of bytes of outflow message packets flowing out of the target node in a previous slot; determining whether the target node is congested in the current slot based on the cache increment of the target node in the current slot and remaining cache space of the target node at a beginning of the current slot; and determining the target node as a congested node when the target node is congested in the current slot, and performing a congestion avoidance operation, wherein the congestion avoidance operation comprises: determining a hosting node set, wherein each hosting node in the hosting node set satisfies following hosting condition: the hosting node is a one-hop neighbor node of the congested node and is not congested in the current slot, an encounter probability between the hosting node and the congested node is greater than a predetermined probability, and available cache space of the hosting node in the current slot is larger than storage space of to-be-offloaded message packets to be offloaded by the congested node; determining an offload set of the congested node based on forwarding probabilities of message packets of the congested node; and offloading the to-be-offloaded message packets in the offload set of the congested node to the hosting node in the hosting node set.
- 2. The method for avoiding node congestion in mobile OppNets according to claim 1, wherein the predicting a cache increment of a target node in a current slot based on a number of bytes of inflow message packets flowing into the target node and a number of bytes of outflow message packets flowing out of the target node in a previous slot comprises: obtaining the number of bytes of inflow message packets and the number of bytes of outflow message packets of the target node in the previous slot; and determining a difference between the number of bytes of inflow message packets and the number of bytes of outflow message packets of the target node in the previous slot, as the cache increment of the target node in the current slot.
- 3 The method for avoiding node congestion in mobile OppNets according to claim 1, wherein the determining whether the target node is congested in the current slot based on the cache increment of the target node in the current slot and remaining cache space of the target node at a beginning of the current slot comprises: detecting the remaining cache space of the target node at the beginning of the current slot; and determining that the target node is congested, when the cache increment of the target node in the current slot is larger than the remaining cache space of the target node at the beginning of the current slot.
- 4. The method for avoiding node congestion in mobile OppNets according to claim 1, wherein the determining a hosting node set comprises: broadcasting, by the congested node, a message offload request packet to all neighbor nodes and receiving message offload response packets from candidate hosting nodes, wherein the candidate hosting nodes each are a node of the neighbor nodes that is not congested in the current slot, and the message offload response packets each comprise available cache space and an identity (ID) of a corresponding node; determining, as a final hosting node, a candidate hosting node whose encounter probability with the congested node is greater than the predetermined probability and whose available cache space is larger than the storage space of the message packets to be offloaded by the congested node; and constructing the hosting node set with the final hosting node.
- 5. The method for avoiding node congestion in mobile OppNets according to claim 1, wherein the determining an offload set of the congested node based on forwarding probabilities of message packets of the congested node comprises: calculating the forwarding probabilities of the message packets of the congested node, and ranking the forwarding probabilities in ascending order to obtain a probability sequence; determining message packets corresponding to first specified number of forwarding probabilities in the probability sequence as the to-be-offloaded message packets, wherein the storage space of the to-be-offloaded message packets is not smaller than a difference between the cache increment and the remaining cache space of the congested node; and constructing the offload set with the to-be-offloaded message packets.
- 6 The method for avoiding node congestion in mobile OppNets according to claim 1, wherein the offloading to-be-offloaded message packets in the offload set of the congested node to the hosting node in the hosting node set comprises: selecting a hosting node from the hosting node set as a target hosting node and obtaining available cache space of the target hosting node; and selecting a to-be-offloaded message packet from the offload set as a target to-be-offloaded message packet, and offloading, by the congested node, the target to-be-offloaded message packet to the target hosting node when the storage space of all the to-be-offloaded message packets in the offload set is not larger than the available cache space of the target hosting node.
- 7. A system for avoiding node congestion in mobile opportunistic networks (OppNets), comprising: a cache increment prediction module, configured to predict a cache increment of a target node in a current slot based on a number of bytes of inflow message packets flowing into the target node and a number of bytes of outflow message packets flowing out of the target node in a previous slot; a congestion detection module, configured to determine whether the target node is congested in the current slot based on the cache increment of the target node in the current slot and remaining cache space of the target node at a beginning of the current slot; and a congested node determining module, configured to determine the target node as a congested node when the target node is congested in the current slot, and execute a congestion avoidance module, wherein the congestion avoidance module comprises: a hosting node set determining unit, configured to determine a hosting node set, wherein each hosting node in the hosting node set satisfies following hosting condition: the hosting node is a one-hop neighbor node of the congested node and is not congested in the current slot; an encounter probability between the hosting node and the congested node is greater than a predetermined probability, and available cache space of the hosting node in the current slot is larger than storage space of to-be-offloaded message packets to be offloaded by the congested node; an offload set determining unit, configured to determine an offload set of the congested node based on forwarding probabilities of message packets of the congested node; and an offload unit, configured to offload the to-be-offloaded message packets in the offload set of the congested node to the hosting node in the hosting node set.
- 8. The system for avoiding node congestion in mobile OppNets according to claim 7, wherein the hosting node set determining unit comprises: a candidate node determining subunit, configured to broadcast, by the congested node, a message offload request packet to all neighbor nodes and receive message offload response packets from candidate hosting nodes, wherein the candidate hosting nodes each are a node of the neighbor nodes that is not congested in the current slot, and the message offload response packets each comprise available cache space and an identity (ID) of a corresponding node; a final node determining subunit, configured to determine, as a final hosting node, a candidate hosting node whose encounter probability with the congested node is greater than the predetermined probability and whose available cache space is larger than the storage space of the message packets to be offloaded by the congested node, and a hosting set construction subunit, configured to construct the hosting node set with the final hosting node.
- 9. The system for avoiding node congestion in mobile OppNets according to claim 7, wherein the offload set determining unit comprises: a forwarding probability calculation subunit, configured to calculate the forwarding probabilities of the message packets of the congested node, and rank the forwarding probabilities in ascending order to obtain a probability sequence; an offload message determining subunit, configured to determine message packets corresponding to first specified number of forwarding probabilities in the probability sequence as the to-be-offloaded message packets, wherein the storage space of the to-be-offloaded message packets is not smaller than a difference between the cache increment and the remaining cache space of the congested node; and an offload set construction subunit, configured to construct the offload set with the to-be-offloaded message packets.
- 10. The system for avoiding node congestion in mobile OppNets according to claim 7, wherein the offload unit comprises: a target hosting node selection subunit, configured to select a hosting node from the hosting node set as a target hosting node and obtain available cache space of the target hosting node; and a target message packet offload subunit, configured to select a to-be-offloaded message packet from the offload set as a target to-be-offloaded message packet, and offload, by the congested node, the target to-be-offloaded message packet to the target hosting node when the storage space of all the to-be-offloaded message packets in the offload set is not larger than the available cache space of the target hosting node. Is
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| CN202210351008.7A CN114567908A (en) | 2022-04-02 | 2022-04-02 | Method and system for avoiding congestion of mobile opportunity network node |
| PCT/CN2022/093202 WO2023184669A1 (en) | 2022-04-02 | 2022-05-17 | Mobile opportunistic network node congestion avoiding method and system |
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