CN116668358A - Route searching method based on optimized ant algorithm and distributed conference system - Google Patents
Route searching method based on optimized ant algorithm and distributed conference system Download PDFInfo
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Abstract
The invention discloses a route searching method and a distributed conference system based on an optimized ant algorithm, wherein the method comprises the following steps: determining a start route and an end route in broadband communication; wherein the initial route and the final route and each route communicated between the initial route and the final route are used as nodes for optimizing ant algorithm; releasing ants from each node according to a preset period, searching each node by utilizing the ants, wherein the number of each ant searching node does not exceed a set threshold value; dividing a plurality of packets by using the routing paths obtained by each ant searching node, and calculating the communication time required by the routing paths corresponding to each packet; and determining the shortest route path between the initial route and the end route according to the communication time corresponding to each packet. The invention can shorten the search time and avoid algorithm stagnation, and can be widely applied to the field of Internet communication.
Description
Technical Field
The invention relates to the field of internet communication, in particular to a route searching method based on an optimized ant algorithm and a distributed conference system.
Background
The distributed interconnection system is used for constructing the interconnection and intercommunication relation of audio, video and control signals among the operation command center, the conference room, the sub-control points and the video monitoring system, realizing sufficient information sharing or distribution and avoiding the formation of information islands. In group collaborative computing tools that have become hot spots in the computer field, videoconferencing systems are an important component. Video conferencing systems in circuit switched networks have a more sophisticated model like the ITU h.320 standard, etc., but the use of packet switched networks, including Ethernet, internet, etc., is becoming increasingly popular, and new solutions have to take into account how to implement video systems with such networks. The ant algorithm in the existing distributed conference system can have long searching time when the iteration times, the ant number and the node number are relatively large. The algorithm may suffer from stagnation, i.e. the search proceeds to some extent with all individual found solutions being identical.
Therefore, the above-described problems are to be solved.
Disclosure of Invention
In view of the above, the embodiment of the invention provides a route searching method and a distributed conference system based on an ant optimization algorithm, which are used for solving the defects of the existing ant optimization algorithm.
An aspect of the present invention provides a route searching method based on an optimized ant algorithm, including:
determining a start route and an end route in broadband communication; wherein the starting route and the destination route and the respective routes communicated between the starting route and the destination route act as nodes for optimizing an ant algorithm;
releasing ants from each node according to a preset period, searching each node by utilizing the ants, wherein the number of the nodes searched by each ant does not exceed a set threshold value;
dividing a plurality of packets by using a routing path obtained by searching the nodes by each ant, and calculating the communication time required by the routing path corresponding to each packet;
and determining the shortest route path between the initial route and the end route according to the communication time corresponding to each packet.
Optionally, the routing table of each node stores information element strength;
the searching each of the nodes using the ants includes:
and selecting the node to be searched according to the pheromone intensity in the routing table of the node and the load state of the node.
Optionally, the method further comprises:
When the load state of each node changes, the corresponding routing table is updated according to the actual load state of each node.
Optionally, when the load state of each node changes, updating the corresponding routing table according to the actual load state of each node, including:
the destination node set and the adjacent node set of the original routing table of each node are the same;
when the target node of the ant is not in the routing table, storing the target node in the routing table, and updating the corresponding pheromone intensity;
when the target node is a neighboring node, if the link bandwidth to the neighboring node meets the requirement, the next node selects the neighboring node;
when the target node is not a temporary node, selecting the next node of the ant according to the total bandwidth of the link of the temporary node and the spare bandwidth of the link, and adding the node passed by the ant into the path memory of the ant; wherein, the nodes passed by the advancing ants do not modify the intensity of the pheromone;
and when the ants reach the destination node, generating backward ants, returning the backward ants according to the path original path in the path memory, and modifying the routing table passing through the node.
Optionally, in the process that the ant searches each node, the discovery process of each node includes:
the source node broadcasts a forward ant packet for searching the destination node;
the intermediate node receives the forward ant packet discard from the forward node; judging whether a loop appears according to a node list carried by the forward ant packet, and discarding the forward ant packet with the loop; for the forward ant packet without loop, determining whether to create record for the forward ant packet according to whether the destination node and the next hop node exist in the routing table of the intermediate node;
after the forward ant packet reaches the destination node, the destination node creates a backward ant packet according to the whole route discovery information contained in the received forward ant packet, sequentially extracts all nodes in the node list domain of the forward ant packet, obtains a path passed by the forward ant packet, and inserts the passed path into the node list domain of the backward ant packet after reverse sequence; the backward ant packet selects a next hop node to forward to the source node according to the node list domain and the source route mode, and the forward ant packet dies;
after receiving the backward ant packet from the backward node, the intermediate node refreshes the pheromone probability value of each table item in the routing table according to the pheromone probability value refreshing method; the intermediate node modifies the value of the hop number domain in the backward ant packet, and uses the value as a pointer to select a corresponding node in the node list domain of the backward ant packet as the next hop to forward the backward ant packet;
The source node establishes a path to the destination node according to the received first backward ant packet, and each node in the path selects a path hop by hop in a mode that a neighbor node corresponding to a table item with a maximum pheromone probability value to the destination node is selected as a next-hop node to reach the destination node in a routing table, so that the destination node is finally reached.
Optionally, the method further comprises:
and carrying out data packet transmission according to a path corresponding to the maximum pheromone probability value in the routing table of the source node, sequentially selecting a path hop by hop according to the corresponding maximum pheromone probability value by each intermediate node, and finally transmitting the data packet to the destination node.
Optionally, the determining whether to create a record for the forward ant packet according to whether there is a destination node and an entry of a next hop node in the routing table of the intermediate node for the forward ant packet without the loop includes:
if the routing table of the intermediate node has no information element table item of the destination node and the next hop node, adding an information element table item in the routing table of the intermediate node, wherein the information element table item comprises: the identification of the destination node, the identification of the next hop node and the pheromone probability value from the node to the source node through the forward node; refreshing the pheromone probability values of all routing table items of the neighbor nodes of the destination node and the next hop node;
If the destination node and the next hop node information element list items exist in the routing list of the intermediate node, the information element probability values of all the destination node and the next hop node information element list items in the routing list are directly refreshed.
Another aspect of the embodiment of the present invention further provides a route searching device based on an optimized ant algorithm, including:
a node determining unit for determining a start route and an end route in broadband communication; wherein the starting route and the destination route and the respective routes communicated between the starting route and the destination route act as nodes for optimizing an ant algorithm;
a node search unit configured to release ants from each of the nodes according to a preset period, and search each of the nodes by using the ants, the number of the nodes searched by each of the ants not exceeding a set threshold;
a time calculation unit, configured to divide a plurality of packets by using a routing path obtained by searching the nodes by each ant, and calculate a communication time required by a routing path corresponding to each packet;
and the path determining unit is used for determining the shortest route path between the initial route and the end route according to the communication time corresponding to each packet.
Another aspect of the embodiments of the present invention further provides a distributed conference system based on an optimized ant algorithm, including: the system comprises an acquisition layer, a transmission layer and a presentation layer; the route searching method based on the optimized ant algorithm is applied to the transmission layer;
the acquisition layer comprises a plurality of audio and video acquisition terminals;
the transmission layer comprises a networked audio and video server;
the presentation layer comprises a plurality of audio and video output terminals.
Optionally, the transport protocol of the transport layer adopts a centralized management model of h.323;
the transport layer is configured to implement at least one of multicast, composition of compressed data streams, privacy of sessions, clock synchronization, audio video synchronization, or directory service functions of the network.
Optionally, the system adopts a JPEG2000 audio/video signal processing scheme architecture applied to a networked distributed system.
Another aspect of the embodiment of the invention also provides an electronic device, which includes a processor and a memory;
the memory is used for storing programs;
the processor executes the program to realize the route searching method based on the optimized ant algorithm.
Another aspect of the embodiments of the present invention also provides a computer-readable storage medium storing a program executed by a processor to implement the route searching method based on the optimized ant algorithm.
Embodiments of the present invention also disclose a computer program product or computer program comprising computer instructions stored in a computer readable storage medium. The computer instructions may be read from a computer-readable storage medium by a processor of a computer device, and executed by the processor, to cause the computer device to perform the foregoing method.
After each node of broadband communication is determined, ants are generated according to the ant algorithm, and when each node is searched by utilizing the ants, the number of each ant searching node is set to be not more than a set threshold, namely, the executing node of each ant algorithm is controlled within a set range, so that a plurality of groups can be divided by the route paths obtained by each ant searching node, then each group of results can be added to obtain a total communication time, and finally, all the results are compared to obtain the fastest path, thereby solving the problem that the existing ant optimization algorithm is not fast in convergence and is often stagnant.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is an exemplary block diagram of a distributed conference system based on an optimized ant algorithm according to an embodiment of the present invention;
fig. 2 is an exemplary architecture diagram of a JPEG2000 audio/video signal processing scheme architecture applied to a networked distributed system according to an embodiment of the present invention;
fig. 3 is a flow chart of a route searching method based on an optimized ant algorithm according to an embodiment of the present invention;
fig. 4 is an explanatory diagram of element items corresponding to each destination node and adjacent nodes in a routing table according to an embodiment of the present invention;
FIG. 5 is an exemplary code diagram for calculating a shortest time provided by an embodiment of the present invention;
fig. 6 is a schematic diagram of an ARPA network according to an embodiment of the present invention;
fig. 7 is a block diagram of a route searching device based on an optimized ant algorithm according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The proposal of the invention is not aimed at a specific network, but is designed according to the requirement of a multipoint video conference system on the Internet. The invention fully utilizes the multicast function and high bandwidth characteristics of the packet switched network, is a distributed multipoint conference system based on RTP protocol, and the end host is a solaris2.X system supporting IP multicast, and has the following characteristics: the data of each node reaches other nodes through multicast; the synthesis of the audio and the video is completed by an end host; good synchronization of the transmitting/receiving codec is achieved without using a reference clock, and packet jitter and loss are well controlled; the dynamic flow control mechanism allows the video compressor to adjust the transmission rate according to the network state; a directory service system which is suitable for an IP network and can pass through a firewall is adopted; key technology of the distributed video conference system; control and data transfer of conference systems.
This is the main function of the MCU in a centralized approach, which may be implemented by the network and/or end nodes in a distributed system. In the embodiment of the invention, the data transmission mainly utilizes the multicast function of the distributed network, and a plurality of control functions are realized by the end host and the network together.
The effective use of bandwidth and quality of service guarantees that the multiplexing mechanism of the packet switched network can make effective use of bandwidth, but can also lead to message jitter and even loss. The Internet has largely not yet achieved quality of service (OoS), and conventional applications are typically guaranteed reliable transmissions by higher layer TCP/IP protocols. The TCP realizes reliable transmission by using a retransmission mechanism, and an internal flow control mechanism thereof dynamically adjusts the sending rate according to the acknowledgement packet. For real-time conferences, the retransmission-induced delay is intolerable, so the transport layer protocol uses UDP without reliable transport and internal flow control, while the tasks of end-to-end synchronization and flow control are passed on to the videoconferencing system.
Referring to fig. 1, the overall structure of a distributed conference system based on an optimized ant algorithm according to an embodiment of the present invention may be a three-layer structure, and is divided into an acquisition layer, a transmission layer, and a presentation layer, where a route searching method based on an optimized ant algorithm according to an embodiment of the present invention is applied to the transmission layer, and the method according to an embodiment of the present invention is described below.
Specifically, the acquisition layer comprises a plurality of audio and video acquisition terminals; the transmission layer comprises a networked audio and video server; the presentation layer comprises a plurality of audio and video output terminals.
The main hardware of the distributed conference system of the embodiment of the invention can include:
audio/video capture/talk back card. The sound, image and data are transmitted as different streams and the recipient can choose to receive only sound from a certain source, which is particularly useful for end nodes without image processing functions, to use silence detection to avoid sending audio streams when not speaking.
Codec and DSP, i.e., digital signal processor cards. The DSP synthesizes video and audio sources according to the selection of the end user, and also has the functions of shielding clock asynchronism, sound/image asynchronism, packet loss and the like. The card is also provided with an Ethernet card, and the conference system can be directly connected to the LAN without the participation of a CPU. A direct interface is arranged between the audio/video capturing/playback card and the Codec/DSP card, so that the system total route can be bypassed, and the CPU time is saved.
Next, a transport layer of the distributed conference system according to the embodiment of the present invention is described, where a transport protocol of the transport layer adopts a centralized management model of h.323; the transport layer is configured to implement at least one of multicast, composition of compressed data streams, privacy of sessions, clock synchronization, audio video synchronization, or directory service functions of the network.
Specifically, it may include;
(1) Selection of a transport layer protocol.
Since UDP does not provide end-to-end reliable transport, RTP protocols based on UDP, which provide transport layer services exclusively for real-time communications, emerge. Although RTP itself does not realize the quality of service guarantee, the multiplexing, sequence number, time scale, monitoring and flexible interface to IP multicast provided by RTP are very important to the methods of multicasting, synchronizing, encrypting session data, dynamic flow control, directory service, security traversing firewall, etc. designed by the embodiments of the present invention. RTP is an open protocol that provides adequate flexibility for upper layer applications. However, the loose management and monitoring functions provided by RTCP (real-time transport control protocol), which is one of the components of RTP, cannot meet the control and management functions (such as dynamically acquiring and distributing multicast addresses, distributing session keys, etc.) required in the embodiments of the present invention, so the embodiments of the present invention use the centralized management model of h.323.
(2) Multicasting of the network.
Multicast is not implemented in existing networks, in which case embodiments of the present invention consider the way multicast is implemented to be several:
a multicast network is constructed over the Internet by Tunnel functions between hubs using a switched ethernet Hub implementing DVMRP.
Replication and forwarding of packets is done in a conventional manner over the Internet, and the end system emulates multicasting by replicating and forwarding packets for each destination node.
When data is sent from a local area network implementing multicasting to an unrealized local area network, a Translator using RTP emulates the multicasting function. The third embodiment of the invention can be used, and in order to realize more convenient address allocation and security and confidentiality functions, the directory service with dynamic, distributed and security characteristics is also required to be matched.
(3) And synthesizing the compressed data stream.
In a distributed system, the multicast function of the network allows each end node to receive images and sound from multiple sources simultaneously, while the composition is implemented by the end system. In order to reduce overhead, the composition of the embodiments of the present invention is performed on a compressed video stream. The synthesis algorithm of the compressed video stream is also a current research hotspot, and the algorithm of the embodiment of the invention utilizes the following facts; almost all standard video compression data contains a series of independent code groups separated by predefined separators, and the compressed data stream can be divided into pixel areas by examining the separation. After each segment of compressed data is associated with a pixel region, the data can be reassembled according to user settings.
(4) The confidentiality of the session.
The multicast initiated by the receiver makes the sender uncontrollable to the user receiving the data, and the broadcasting nature of the local area network makes it possible for any host on the local area network to listen to the session, so that it is necessary to encrypt the session data. The session key may be distributed using the session initiation protocol, or may be saved using the RTP session profile (this approach is less secure). To prevent known plaintext attacks, one-time and unpredictable information should be added to each message. The timestamp field of the RTP header provides this mechanism for embodiments of the present invention, and a random number should be added before encrypting the RTCP message before encrypting the message to be encrypted.
(5) Clock synchronization and sound/video synchronization.
In the point-to-point connection, the receiver realizes synchronization with the server according to the data arrival rate.
There are multiple transmit/receive pairs to synchronize in a distributed multipoint conference, which is not suitable. The embodiment of the invention designs a simple and effective method for solving the problems of clock asynchronism and sound/image asynchronism of the same source. The method uses the time stamp provided by RTP, and can be briefly summarized as: silence suppresses the transmission of audio packets. The sound is played back at the receiving end with the receiving audio clock, the asynchronization of the audio clock being counteracted during silence. Synchronization of audio/video is achieved by dropping some delayed video frames or reusing some video frames at the beginning of each audio burst. This mechanism does not require synchronization of the playback clock with the capture clock, and it can achieve the desired performance is based on the fact that: the burst average duration is relatively short compared to the silence duration.
The non-synchronization of the clocks at the capturing end and the playback end is small. These two points make synchronization of audio/video unlikely to drift much during the shorter burst duration. The embodiment of the invention does not take any control on the sequence relation between different source data streams. With the use of protocols such as RMP (reliable multicast protocol) in group communications, embodiments of the present invention will control this order.
(6) Directory service function.
Unlike circuit-switched networks, the Internet has no unified addressing mechanism, and in addition, has the problem that firewalls and addresses are not disclosed, so directory services are important problems to be solved in distributed conference systems.
IP directory services are important in both centralized and distributed conferences. Nodes in the circuit switched network are identified by fixed numbers and nodes in the packet switched network are identified by IP addresses. In heterogeneous networks, ATM nodes are identified by e.164, POTS and ISDN nodes are identified by telephone numbers, and Internet nodes are identified by IP addresses, which would be very convenient if directory services were able to convert the names of conference participants to physical addresses. In mobile communications, conference participants may access the Internet from different locations, using dynamic addresses, directory services may be more necessary. The functionality of the directory service would be more complex if the user within the firewall does not want to expose his own IP address.
The Internet domain name service system (DNS) is a distributed directory service solution, but the conventional DNS system does not support dynamically assigned IP addresses. The dynamic IP address query scheme requires a real-time registration mechanism to obtain the IP address dynamically allocated when the user logs in. The existing real-time registration protocols include SDP, LDAP, and DNS with safe dynamic update (distributed). Internet database providers also offer proprietary real-time registration protocols (centralized) for a variety of applications. The centralized approach is easy to implement, but has poor scalability and requires that all conference members register with the same service provider. The distribution mode is based on a DNS system, and practice proves that the system is stable in operation and good in expansion performance. A dynamically updated DNS that is secure is an ideal choice.
None of the directory services proposed at present take the firewall traversal problem into account. The most common method of traversing firewalls is to use proxy servers. The general proxy server can also perform IP address translation and has a whole set of powerful security functions, but their versatility also brings the following problems: meanwhile, a plurality of applications can cause delay in use, and real-time performance cannot be ensured; providing a breachable vulnerability for hackers; the domain name query service among different subnets cannot be provided; in the case of IP address translation concatenation, unexpected situations can occur. The special agent used in the embodiment of the invention can overcome the defects and can be realized on a Mixer or a Translator of RTP.
Assuming that a and B are located within two different firewalls, respectively, embodiments of the present invention may have a proxy PA and PB on each firewall of the subnetwork where a and B are located, and a public directory service provider on the Internet to which they are commonly connected. Let a be the caller and B be the reported caller. The following is the process of communication across a firewall:
user a registers with the PA when logging onto the network. The PA establishes an internal record for a registering the IP address and E-mail address of a. The PA then registers the user name of a (E-mail address) and its own IP address with the external directory service provider. When the user B logs in, B and PB perform the same operation.
When A wants to communicate with B, A sends a call request to PA to give the E-mail address of the call destination B.
PA issues a request to the external directory service provider to resolve name B. The external directory service will return the address registered for B in step 1 (i.e. IP of PB). Based on some special information provided by B's domain name or directory service, PA can know B's certain firewall.
The PA issues a connection request to the PB giving the names a and B of the calling and called parties. Therefore, the PA and PB can establish a virtual connection for the A and the B, and an optimal scheme is provided for solving the PA-PB connection by an optimized ant algorithm based on a grouping algorithm. The latter communication may be via the a-PA-PB-B link.
In order to ensure signal quality, the distributed conference system of the embodiment of the present invention may employ a JPEG2000 audio/video signal processing scheme architecture applied to a networked distributed system, as shown in fig. 2.
And a professional audio and video signal processing scheme and an autonomous research and development algorithm are given, the system delay can reach below 40ms when processing 4K, and the resolution below 4K can further shorten the delay. The method solves the problem that the application of the distributed system is the most core and the most critical, and is the most basic guarantee of efficient signal scheduling and professional effective command.
The system backbone link is formed by the deployment of 150 m (maximum) twisted pair and/or 80KM (maximum) optical fiber signals, and the system is standardized to facilitate rapid deployment; digitization, the image is well analyzed, and the interference of the environment to the signal is avoided; IP, can conveniently erect a very large scale system.
In broadband communication networks, routing is always an important problem, and distributed routing transmits routing information between network nodes, so that the routing method has high reliability and is widely applied to the Internet. The Ant Colony (ACS) algorithm is a novel heuristic optimization algorithm with self-organization capability, which is obtained according to the phenomenon that ants in nature always find the shortest distance between food sources of ant pockets. There are many studies on it such as TSP problems, traffic scheduling.
The embodiment of the invention provides a method for updating a routing table by using an ACS algorithm, which is different from the existing routing table in that the strength of pheromones is stored in the routing table. The ACS algorithm is a combinatorial optimization algorithm that uses the strength of the pheromone in the routing table and the current link load conditions as criteria when routing and updating.
First, an ant optimization algorithm will be described.
Specifically, a main starting point of the ant optimization algorithm is to use a pheromone trace applied by ants to make time indirect communication and interaction between ants so as to realize positive feedback effect of overall optimization of an acceleration system, and the basic principle and specific implementation process of the ant optimization algorithm can include: assuming two paths ADB and ACD from a to B, two ants 1, 2 and 3, 4 advance toward each other at node a and node B, respectively. Initially, since no clues are available for reference, the ant will choose a path with the same probability, with the result that 1, 3 choose ACB,2, 4 choose ADB, and release pheromone along the path. Since the ADB path is short, when 2, 4 ants reach the destination, 1, 3 ants are on the way, so the pheromone concentration of the ADB path is greater than ACB. Therefore, when the subsequent ants of the A, B node select routes, the probability of selecting the ADB path is larger than that of the ACB path, the number of ants selecting the ADB path is also larger than that of the ACB path, and the pheromone concentration of the ADB path is higher, so that positive feedback is formed. The end result is that all ants have selected the shortest path ADB.
Next, referring to fig. 3, an embodiment of the present invention provides a route searching method based on an optimized ant algorithm, which specifically includes the following steps:
s100: determining a start route and an end route in broadband communication; wherein the start route and the end route and the respective routes communicating between the start route and the end route act as nodes for optimizing the ant algorithm.
S110: releasing ants from each node according to a preset period, searching each node by using the ants, wherein the number of the nodes searched by each ant does not exceed a set threshold value.
Specifically, since the routing table of each node stores the intensity of pheromone; therefore, the node to be searched can be selected according to the intensity of pheromone in the routing table of the node and the load state of the node.
Further, the embodiment of the invention can further comprise updating the corresponding routing table according to the actual load state of each node when the load state of each node is changed.
Thus, the routing table can be updated using the ant optimization algorithm.
From the above description of the ant optimization algorithm, the foraging process of ants is very similar to the routing in the communication network, and some research on the application of ACS algorithm in the communication network is available. In the routing method for dynamically updating by using ACS, the distributed dynamic routing algorithm and the dynamic updating of the routing table by using ACS are 2 parallel parts and run simultaneously. For each call, the routing table is consulted to determine the selected path, the access of the call causes a change in the network load condition, and the ACS algorithm uses this information to dynamically adjust the routing table. In the ACS algorithm, in the routing table of each node, a node (PNN) connected to the node is listed for each destination node, and when a packet arrives, the node to be arrived next can be known by querying the routing table. The element entries corresponding to each destination node and the adjacent node in the routing table may refer to fig. 4, which is specifically described as follows:
When the number of ants can be recorded as m and m is too large, the change of pheromones on the searched path tends to be average, and a target path is difficult to find; when m is too small, the unsearched path pheromone is easily reduced to 0, so that premature situations can occur, and the globally optimal solution cannot be found. The number of ants is set to 1.5 times of the number of cities.
Pheromone importance factor alpha: the pheromone factor alpha reflects the relative importance degree of the information quantity accumulated by ants in the moving process in guiding ant colony search, the alpha value is overlarge, the probability of the path which the ants pass before selecting is large, and the search randomness is weakened; if the value is too small, the search and the trapping are locally optimized similar to a greedy algorithm. The pheromone factor is approximately selected in the [1,4] interval.
Inspiring a function importance factor beta; the heuristic function factor beta reflects the relative importance degree of heuristic information in the process of guiding ant colony search, and the size reflects the prior property and the action strength of deterministic factors in the process of ant colony optimization. When beta is too large, the convergence speed is increased, but the local optimum is easily trapped; when the solution is too small, random search is easy to be trapped, and the optimal solution cannot be found. The heuristic factor is chosen to be in the interval 3, 5.
Pheromone volatilization factor rho: the pheromone volatilization factor represents the vanishing level of the pheromone, and the day and the small of the pheromone volatilization factor directly relate to the global searching capability and convergence speed of the ant colony algorithm. The pheromone volatilization factor selects the interval of [0.2,0.5 ].
The improved thought of the conventional ant optimization algorithm according to the embodiment of the invention can comprise:
by means of an extra means, edges most likely to be optimal paths are enhanced, so that the ant search range is converged more quickly and accurately.
Giving additional enhancements to all found best paths immediately after the algorithm starts, and noting the journey corresponding thereto later as Tb (globally optimal journey); when a pheromone update is performed, these trips are weighted, while ants passing through these trips are noted as "elites", thereby increasing the chance of selecting a better trip.
The pheromone update formula is as follows:
the multiple nodes are divided into groups, and although multiple grouping algorithms are added, each group of ant algorithm has fewer nodes, the convergence speed of the algorithm is high, the congestion problem is totally solved, the convergence is not fast, and the phenomenon of stagnation often occurs. The method has the advantages of higher communication capability, low implementation difficulty of the network algorithm, higher practical value and the like.
Next, a process of updating the routing table using the ant algorithm is specifically described.
Firstly, initializing the intensity of a node pheromone in a network, wherein the rule is as follows: the set of destination nodes of the original routing table of each node is the same as the set of adjacent nodes; when the destination node and the adjacent node are not the same node in initialization, the pheromone is 0, the transition probability is 0, otherwise, the pheromone is 1, and the transition probability is 1.
The more data a node carries, the more ants are sent to that node, the more ants are periodically released from each node, . The following rules should be followed when updating the routing table:
(1) When the destination node of ant is not in the routing table, filling the destination node into the routing table, initializing the pheromone of the line to 1/(N) x -1),N x The number of the adjacent nodes is x.
(2) When the destination node is a temporary node, if the link bandwidth to the temporary node meets the requirement, the next node unconditionally selects the temporary node.
(3) When the destination node is not the temporary node, the temporary node with N (x) as x has a bandwidth meeting the requirement of the ant cardamon and is not the last node set through which the ant passes,selecting the intensity of pheromone at point j and eta when ants with the destination node of i pass through point x xj The square of the free bandwidth rate for linking points x and j is defined as: η (eta)
C xj For the total bandwidth of the link linking points x and j,for the free bandwidth of the link, ants select the next node with the following probability:
nodes traversed by the advancing ants do not modify the pheromone intensity. The ant is sent to the next node j, and the node is added to the path memory of the ant.
(4) When the ant reaches the destination node, the line ant is generated, the backward line ant returns according to the path original path in the path memory, and the routing table passing through the node is modified in the following mode:
l is the hop count to the destination node, and L is the maximum value max When L>L max When the ant cannot reach the node, the ant dies. A. B is a constant for adjusting eta xj And L pair ofIn the embodiment of the present invention, A is 0.0001 and B is 0.0005, thus selectingThe link length and link load information of the seek are included. The smaller the number of nodes L passed from the source node to the destination node,the larger this is to encourage ants to choose a less loaded link to reach network balance.
Next, the process of ant invention routing, i.e., the discovery process of each node, in the process of ant optimization algorithm will be described.
Specifically, the method comprises the following steps:
Step 1, a source node s broadcasts a forward ant packet for searching a destination node d, a type field ant.type=forward ant, a hop count field ant.hop=0, a node set field ant.node= { s }, and a destination node identification field ant.destination=d.
Step 2, the intermediate node i discards the received forward ant packet from the node i-1 under the congestion condition, judges whether a loop appears according to a node list ant.node carried by the forward ant packet under the condition that a new route can be accepted, discards the ant packet with the loop, and decides whether to create a record for the forward ant packet according to whether a destination node is s and a table item of which the next hop node is i-1 in a pheromone table of the intermediate node for the forward ant packet without the loop: if the pheromone table of the intermediate node has no pheromone table item with the destination node being s and the next hop node being i-1, adding an pheromone table item in the pheromone table of the intermediate node, wherein the table item comprises: the identification of the destination node s, the identification of the next hop node i-1, and the pheromone probability value of the node i from the node i-1 to the source node s. Refreshing the pheromone probability values of all the pheromone table items of the neighbor nodes with the destination node s and the next hop node i; if the destination node is s and the next hop node is i-1 in the pheromone table of the intermediate node, directly refreshing the pheromone probability values of all the pheromone table items of which the destination node is s and the next hop node is the neighbor node of the node i in the pheromone table; after that, the node updates the hop count field ant.hop+1 and node list field ant.node ζ of the forward ant packet, and then forwards the forward ant packet. The intermediate node i performs a pheromone probability value of each entry in the pheromone table according to the pheromone probability value refreshing method (in this case, the destination node d is s here).
Step 3, after the forward ant packet reaches the destination node, the destination node creates a backward ant packet according to the whole route discovery information contained in the received forward ant packet: type field ant=backward ant, hop number field ant.hop=0, all nodes in the node list field ant.node of the forward ant packet are sequentially extracted, and the path s→ … …, →d traversed by the forward ant packet is obtained and inserted into the node list field ant.node of the backward ant packet after reverse order. And the backward ant packet selects a next-hop node to forward to the source node according to the node list domain in a source routing mode, and the forward ant packet dies.
And 4, after receiving the backward ant packet from the node i+1, the intermediate node i refreshes the pheromone probability values of all the entries in the pheromone table according to the pheromone probability value refreshing method, then the intermediate node i modifies the value of the hop number domain in the backward ant packet by an ant.hop +.ant.hop+1, and uses the modified value as a pointer to select a corresponding node in the node list domain ant.node of the backward ant packet as the next hop to forward the backward ant packet.
And 5, after the source node receives the first backward ant packet, establishing a path to the destination node, wherein each node in the path gradually selects a path by taking a neighbor node corresponding to a table item with the maximum pheromone probability value to the destination node in the pheromone table as a next-hop node (randomly selected if a plurality of maximum concentrations exist) reaching the destination node, and finally reaching the destination node, thereby completing the route discovery work.
And 6, the source node transmits the data packet according to the path corresponding to the maximum pheromone probability value in the node pheromone table, each intermediate node sequentially performs hop-by-hop route selection according to the maximum pheromone probability value, and finally, the data packet is transmitted to the destination node.
S120: dividing a plurality of packets by using the routing paths obtained by searching the nodes by each ant, and calculating the communication time required by the routing paths corresponding to each packet.
Referring to FIG. 5, an exemplary code diagram for calculating a shortest time is provided by an embodiment of the present invention.
Wherein the sums t1, t2, … … tn, each do not exceed S nodes. TTn is the total PA-PB time. T (T) M Is the minimum time of the PA-PB segment ant algorithm.
S130: and determining the shortest route path between the initial route and the end route according to the communication time corresponding to each packet.
Specifically, innovations of route discovery in the embodiment of the present invention may include: when the iteration times, the ant numbers and the node numbers of the conventional ant optimization algorithm are relatively large, the search time of the algorithm can become very long. The algorithm may suffer from stagnation, i.e. the search proceeds to some extent with all individual found solutions being identical. Therefore, the embodiment of the invention carries out route division, each ant algorithm does not exceed S nodes, wherein S is not easy to be set too large, and each group of results are added to obtain total time. And finally comparing all the results to obtain the fastest path. Therefore, the phenomenon that the convergence is not fast and stagnation occurs frequently in the prior art is solved.
The optimal grouping is obtained through comparison, and the optimal path is obtained through an ant algorithm, so that the method is also an optimal scheme for PA-PB connection in a distributed conference system.
The application of the present invention will be described in the following with specific examples.
The existing dynamic distributed routing algorithms commonly used at present are as follows: shortest path method (SPF) and least load method (LLR). The shortest path method takes the route with the lightest load as the final selection result.
Specifically, referring to fig. 6, an embodiment of the present invention provides an ARPA network schematic diagram.
Wherein, ARPA network, 21 nodes and 26 connections are selected in the simulation, which can be used for measuring the performance of the wide area network.
Specifically, the bandwidth of each edge of the ARPA network can be set to be 200 units, and each call is requestedThe bandwidth is found to be 1 unit, and the bandwidth required by ants in routing is also 1 unit. To examine the effect of the ACS algorithm of the present embodiment, it was compared with the shortest path method and the least loaded method. The test index is CBR (call rejection rate) and average path length (ARD) the call rejection rate is defined asThe average path length is defined as +.>K is the total number of calls. When the ith call is admitted, r i =1; otherwise r i ＝0.r i When=1, d i The number of nodes passed by the call; otherwise d i Requests for calls in experiments have 2 distributions: (1) uniformly distributing, namely randomly selecting source and destination node pairs; (2) the centralized distribution is that the requests of a specific node pair occupy p%, and the rest call requests are distributed uniformly. Because the calls are uniformly distributed, the load of the network is almost uniformly distributed, the minimum load method does not play a role, the CBR and ARD obtained by using the shortest path method algorithm are minimum, the result of the ACS algorithm is similar to that of the shortest path method algorithm, but the ARL is slightly larger. Routes obtained by the shortest path method are concentrated on a few edges, so that their bandwidths are used up quickly, which results in CBR higher than that obtained by the minimum load method when P% is larger, and ACS algorithm results are better than those obtained by the minimum load method.
Whether the calls are uniformly distributed or intensively distributed, the call rejection rate and the average path length obtained by using an ACS algorithm are smaller than the minimum load method result; when the calls conform to the centralized distribution, the rejection rate of the calls obtained by the ACS algorithm is lower than that of the shortest path method. In addition, the traditional routing algorithm broadcasts routing table information, when more network nodes exist, the routing table also becomes larger correspondingly, the broadcast routing information occupies a large network bandwidth, and the phenomenon cannot occur because the ants in the ant algorithm carry little information and are not broadcast data. And is more beneficial to data transmission.
Referring to fig. 7, an embodiment of the present invention provides a route searching apparatus based on an optimized ant algorithm, including:
a node determining unit for determining a start route and an end route in broadband communication; wherein the starting route and the destination route and the respective routes communicated between the starting route and the destination route act as nodes for optimizing an ant algorithm;
a node search unit configured to release ants from each of the nodes according to a preset period, and search each of the nodes by using the ants, the number of the nodes searched by each of the ants not exceeding a set threshold;
a time calculation unit, configured to divide a plurality of packets by using a routing path obtained by searching the nodes by each ant, and calculate a communication time required by a routing path corresponding to each packet;
and the path determining unit is used for determining the shortest route path between the initial route and the end route according to the communication time corresponding to each packet.
Embodiments of the present invention also disclose a computer program product or computer program comprising computer instructions stored in a computer readable storage medium. The computer instructions may be read from a computer-readable storage medium by a processor of a computer device, and executed by the processor, to cause the computer device to perform the method shown in fig. 3.
In some alternative embodiments, the functions/acts noted in the block diagrams may occur out of the order noted in the operational illustrations. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality/acts involved. Furthermore, the embodiments presented and described in the flowcharts of the present invention are provided by way of example in order to provide a more thorough understanding of the technology. The disclosed methods are not limited to the operations and logic flows presented by embodiments of the invention. Alternative embodiments are contemplated in which the order of various operations is changed, and in which sub-operations described as part of a larger operation are performed independently.
Furthermore, while the invention is described in the context of functional modules, it should be appreciated that, unless otherwise indicated, one or more of the described functions and/or features may be integrated in a single physical device and/or software module or one or more functions and/or features may be implemented in separate physical devices or software modules. It will also be appreciated that a detailed discussion of the actual implementation of each module is not necessary to an understanding of the present invention. Rather, the actual implementation of the various functional modules in the apparatus disclosed in the embodiments of the present invention will be understood within the ordinary skill of the engineer in view of their attributes, functions and internal relationships. Accordingly, one of ordinary skill in the art can implement the invention as set forth in the claims without undue experimentation. It is also to be understood that the specific concepts disclosed are merely illustrative and are not intended to be limiting upon the scope of the invention, which is to be defined in the appended claims and their full scope of equivalents.
The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention may be embodied essentially or in a part contributing to the prior art or in a part of the technical solution, in the form of a software product stored in a storage medium, comprising several instructions for causing a computer device (which may be a personal computer, a server, a network device, etc.) to perform all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a usb disk, a removable hard disk, a Read-only memory (ROM), a random access memory (RAM, randomAccessMemory), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
Logic and/or steps represented in the flowcharts or otherwise described herein, e.g., a ordered listing of executable instructions for implementing logical functions, can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. For the purposes of this description, a "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device.
More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic device) having one or more wires, a portable computer diskette (magnetic device), a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). In addition, the computer readable medium may even be paper or other suitable medium on which the program is printed, as the program may be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner, if necessary, and then stored in a computer memory.
It is to be understood that portions of the present invention may be implemented in hardware, software, firmware, or a combination thereof. In the above-described embodiments, the various steps or methods may be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, may be implemented using any one or combination of the following techniques, as is well known in the art: discrete logic circuits having logic gates for implementing logic functions on data signals, application specific integrated circuits having suitable combinational logic gates, programmable Gate Arrays (PGAs), field Programmable Gate Arrays (FPGAs), and the like.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
While embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that: many changes, modifications, substitutions and variations may be made to the embodiments without departing from the spirit and principles of the invention, the scope of which is defined by the claims and their equivalents.
While the preferred embodiment of the present invention has been described in detail, the present invention is not limited to the embodiments described above, and those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications or substitutions are included in the scope of the present invention as defined in the appended claims.
Claims (10)
1. A route searching method based on an optimized ant algorithm, comprising:
determining a start route and an end route in broadband communication; wherein the starting route and the destination route and the respective routes communicated between the starting route and the destination route act as nodes for optimizing an ant algorithm;
releasing ants from each node according to a preset period, searching each node by utilizing the ants, wherein the number of the nodes searched by each ant does not exceed a set threshold value;
dividing a plurality of packets by using a routing path obtained by searching the nodes by each ant, and calculating the communication time required by the routing path corresponding to each packet;
and determining the shortest route path between the initial route and the end route according to the communication time corresponding to each packet.
2. The route searching method based on the optimized ant algorithm according to claim 1, wherein the routing table of each of the nodes stores a pheromone intensity;
the searching each of the nodes using the ants includes:
and selecting the node to be searched according to the pheromone intensity in the routing table of the node and the load state of the node.
3. The route finding method based on the optimized ant algorithm according to claim 2, further comprising:
when the load state of each node changes, the corresponding routing table is updated according to the actual load state of each node.
4. The route searching method according to claim 3, wherein updating the corresponding routing table according to the actual load status of each node when the load status of each node is changed, comprises:
the destination node set and the adjacent node set of the original routing table of each node are the same;
when the target node of the ant is not in the routing table, storing the target node in the routing table, and updating the corresponding pheromone intensity;
when the target node is a neighboring node, if the link bandwidth to the neighboring node meets the requirement, the next node selects the neighboring node;
when the target node is not a temporary node, selecting the next node of the ant according to the total bandwidth of the link of the temporary node and the spare bandwidth of the link, and adding the node passed by the ant into the path memory of the ant; wherein, the nodes passed by the advancing ants do not modify the intensity of the pheromone;
And when the ants reach the destination node, generating backward ants, returning the backward ants according to the path original path in the path memory, and modifying the routing table passing through the node.
5. The route searching method according to claim 1, wherein the ant searches for each node, and the discovery process of each node comprises:
the source node broadcasts a forward ant packet for searching the destination node;
the intermediate node receives the forward ant packet discard from the forward node; judging whether a loop appears according to a node list carried by the forward ant packet, and discarding the forward ant packet with the loop; for the forward ant packet without loop, determining whether to create record for the forward ant packet according to whether the destination node and the next hop node exist in the routing table of the intermediate node;
after the forward ant packet reaches the destination node, the destination node creates a backward ant packet according to the whole route discovery information contained in the received forward ant packet, sequentially extracts all nodes in the node list domain of the forward ant packet, obtains a path passed by the forward ant packet, and inserts the passed path into the node list domain of the backward ant packet after reverse sequence; the backward ant packet selects a next hop node to forward to the source node according to the node list domain and the source route mode, and the forward ant packet dies;
After receiving the backward ant packet from the backward node, the intermediate node refreshes the pheromone probability value of each table item in the routing table according to the pheromone probability value refreshing method; the intermediate node modifies the value of the hop number domain in the backward ant packet, and uses the value as a pointer to select a corresponding node in the node list domain of the backward ant packet as the next hop to forward the backward ant packet;
the source node establishes a path to the destination node according to the received first backward ant packet, and each node in the path selects a path hop by hop in a mode that a neighbor node corresponding to a table item with a maximum pheromone probability value to the destination node is selected as a next-hop node to reach the destination node in a routing table, so that the destination node is finally reached.
6. The route finding method based on the optimized ant algorithm according to claim 5, further comprising:
and carrying out data packet transmission according to a path corresponding to the maximum pheromone probability value in the routing table of the source node, sequentially selecting a path hop by hop according to the corresponding maximum pheromone probability value by each intermediate node, and finally transmitting the data packet to the destination node.
7. The route searching method according to claim 5, wherein the determining whether to create a record for the forward ant packet according to whether there is a destination node or a next hop node in the routing table of the intermediate node is performed for the forward ant packet without the loop, comprising:
If the routing table of the intermediate node has no information element table item of the destination node and the next hop node, adding an information element table item in the routing table of the intermediate node, wherein the information element table item comprises: the identification of the destination node, the identification of the next hop node and the pheromone probability value from the node to the source node through the forward node; refreshing the pheromone probability values of all routing table items of the neighbor nodes of the destination node and the next hop node;
if the destination node and the next hop node information element list items exist in the routing list of the intermediate node, the information element probability values of all the destination node and the next hop node information element list items in the routing list are directly refreshed.
8. A distributed conference system based on an optimized ant algorithm, comprising: the system comprises an acquisition layer, a transmission layer and a presentation layer; wherein a route finding method based on an optimized ant algorithm as claimed in any one of claims 1 to 7 is applied to the transport layer;
the acquisition layer comprises a plurality of audio and video acquisition terminals;
the transmission layer comprises a networked audio and video server;
the presentation layer comprises a plurality of audio and video output terminals.
9. The distributed conference system based on the optimized ant algorithm according to claim 8, wherein the transport protocol of the transport layer adopts a centralized management model of h.323;
The transport layer is configured to implement at least one of multicast, composition of compressed data streams, privacy of sessions, clock synchronization, audio video synchronization, or directory service functions of the network.
10. The distributed conference system based on the optimized ant algorithm according to claim 8, wherein the system adopts a JPEG2000 audio video signal processing scheme architecture applied to a networked distributed system.
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