CN109274414B

CN109274414B - Method for network coding and edge cache to cooperate in multi-direction wireless relay interaction channel

Info

Publication number: CN109274414B
Application number: CN201810833018.8A
Authority: CN
Inventors: 黄联芬; 何维晟; 陈琳然; 饶慧婷; 高志斌
Original assignee: Xiamen University
Current assignee: Xiamen University
Priority date: 2018-07-26
Filing date: 2018-07-26
Publication date: 2021-07-09
Anticipated expiration: 2038-07-26
Also published as: CN109274414A

Abstract

A method for cooperation of network coding and edge caching in a multi-way wireless relay interaction channel comprises the following steps: setting a relay base station comprising an MEC server; the method comprises the steps that an MEC server collects potential requirements of communication of peripheral users, machine learning is carried out by combining network real-time hot content and file sizes, potential file requirements suitable for the peripheral users are obtained, the file requirements are sent to a core network, and then MEC files needing to be used subsequently are obtained from the core network and cached to a relay base station; and when the peripheral users do not need to use the MEC file, the relay base station synchronously sends the user interactive data packet to each user. The invention can solve the problem of time slot resources between the MEC file transmission and the user interaction data packet in the multi-directional wireless relay interaction channel model, thereby improving the operation efficiency of the network.

Description

Method for network coding and edge cache to cooperate in multi-direction wireless relay interaction channel

Technical Field

The present invention relates to the field of wireless communication technologies, and in particular, to a method for cooperating network coding and edge caching in a multi-directional wireless relay interaction channel, and relates to a relay base station, a multi-directional wireless relay interaction channel, and a network coding technology, which are commonly used in a mobile cellular network, and an MEC (mobile edge caching, which may be referred to as an MEC or an edge caching hereinafter).

Background

The relay is a functional mode for carrying communication between two points, and can receive and amplify a signal from a previous communication point and then transfer the signal to a next communication point, and has respective applications in many different industry fields. In a cellular network, a "Relay" specifically refers to a wireless Relay Station (Relay Station), also called a repeater, and is a bidirectional radio frequency, common frequency, broadband linear amplification Relay device. It receives and transmits signals from macro Base Station and Mobile Station, and is used to assist the macro Base Station (Base Station) to solve the communication in shadow area, blind area, dead angle and tunnel caused by terrain or man-made obstacle in the communication network of cellular Mobile phone, and improve the communication quality of Mobile Station (Mobile Station).

The relay cellular network is a product of merging a relay technology, a multi-hop structure and a traditional cellular network. In a traditional cellular network architecture, a relay base station is introduced, and a multi-hop link is used, so that a mobile terminal can be connected with the base station through one or more relay stations, thereby enhancing cell coverage, improving throughput and resisting channel fading. Cellular network relays are widely used in today's cellular networks because they are functionally close to macro base stations, but are less expensive than macro base stations in cost, and are very flexible. The specific use meanings comprise: (1) the method is used for improving the communication performance of cell edge users, (2) increasing the system capacity, (3) expanding the cell coverage, (4) eliminating coverage blind spots in cells, (5) providing the communication coverage of buildings, tunnels and underground communication sites, and (6) providing temporary emergency communication.

The relay base station is a quite common base station in the cellular network of today, and due to the specific advantages of the relay base station, the relay base station can be flexibly combined with other network technologies in a cooperative mode, so that more efficient communication schemes can be achieved.

Referring to fig. 1, a multi-directional wireless relay interaction channel is a typical application model in wireless relay communication, where there are N users (denoted by S), and the users cannot communicate directly with each other, and information interaction must be performed by means of a relay R. The scene means that each user has a respective corresponding data file, the whole scene has N data packets, and information interaction is required by means of the relay R, so that each user can have the N data packets completely after a plurality of time slots. The essential model of multi-party conferencing in actual applications today is similar to this model.

Network coding is a research hotspot emerging in recent years. The conventional coding idea focuses on the source side, or the main work of coding is borne by the source. The core idea of network coding is to allow a network intermediate node to re-code different information streams into one information stream, which breaks the theoretical limitation that independent irrelevant bit information cannot be compressed any more, and it can be considered that network coding is a more generalized routing technology of traditional store-and-forward.

Network coding is the linear or non-linear processing of information received on various channels at various nodes in a network, and then forwarding to downstream nodes, with intermediate nodes playing the role of encoders or signal processors. The traditional mode of transmitting data by communication network nodes is store-and-forward, that is, nodes except a sending node and a receiving node of the data are only responsible for routing without any processing on data content, an intermediate node plays the role of a repeater, network coding changes the role of the traditional node, and data is coded and processed on the node, so that the method is an effective method for improving network throughput, robustness and safety, and is developed and combined in the fields of wireless networks, P2P systems, distributed file storage, network safety and the like at present.

The basic idea of network coding is described below as a typical example of network coding. Referring to fig. 2, a single source two sink multicast network is shown. Suppose that two information streams u are transmitted from a₁,u₂To the sink end F and G, each point-to-point link is error-free and has a maximum capacity of '1'.

For multicast implementation, the conventional routing mechanism is shown in fig. 3, in which the dashed line indicates the information flow u₁The solid line represents the information flow u₂Is transmitted. It can be seen that the link from D to E is used twice, limited by the capacity of the link from D to E, i.e. the "network bottleneck".

If network coding is adopted, the routing strategy is redesigned. Referring to FIG. 4, node D merges u1 and u2 information streams

And sending out the fused information stream. The signal destination F receives

And u1 by calculation

To obtain u 2; similarly, the sink G can also obtain u 1. Therefore, the transmission of an information flow is reduced for the link from D to E, and the bottleneck of the link between D and E is well avoided.

As can be seen from this example, if network-coded routing is not performed at the D-node, and queuing for storage is necessary for conventional routing, the sink end can receive only 1.5 information streams per time slot on average. After network coding is carried out, the throughput of the whole network is also improved, and each sink terminal can receive 2 information streams simultaneously.

The above-mentioned scheme is the simplest and most efficient scheme in network coding, but the most basic idea of actual network coding is to perform coding operation of a linear equation on a galois field according to a certain mapping rule on a received data packet, and it is a coding result and a coding coefficient vector to forward an original data packet after coding. When the information sink node receives enough linear uncorrelated coding vectors, the inverse operation can be completed on the Galois field and the original data can be obtained through mapping return.

From the current research results, the advantages of network coding include: (1) the method comprises the steps of (1) improving network throughput, (2) balancing network load, (3) improving bandwidth utilization rate, and (4) improving network robustness.

Network coding can bring great promotion to the whole operating efficiency of network, because it can increase the work load of network to a certain extent, increase the complexity of operation and bring bigger expenses, so have not got very extensive application of falling to the ground in recent years yet, considerable scholars are still studying how to fall to the ground to realize network coding technique better, conveniently and efficiently.

The xor scheme of the network coding in the example is actually the simplest scheme of the linear equation coding, and although the xor scheme has application limitation in the overall huge network environment, the xor scheme has quite high convenience, high efficiency and feasibility in an independent partial model, and is therefore very suitable for being combined with other network technologies to generate a new and efficient communication scheme.

Applying network coding to the aforementioned multi-way wireless relay interaction channel has proved that one time slot can be saved compared to the general case. In general, the N user interaction models shown in fig. 1 need to consume 2N time slots (the relay works in a half-duplex mode, and the receiving and sending cannot be performed simultaneously but information can be broadcasted), that is, each user in the first N time slots sends information to the relay R, and the N +1 th to 2N th time slots are used for the relay to broadcast N data packets sequentially, so that all data packets of the N users complete interaction after the 2N time slots. If the scheme of network coding is adopted, one time slot can be omitted, namely from the 2N +1 time slot to the 2N-1 time slot, the relay R broadcasts the coding information to each S, the coding information of each time slot is obtained by selecting 2 data packets from the N data packets to carry out exclusive-or coding, and the coding information sent by each time slot is different. Finally, after N-1 time slots of broadcasting, N users can use the owned data packets to perform network coding decoding operation, so that the N users complete information interaction.

For a more intuitive explanation, the example is given here, assuming that there are 5 users interacting, each with a data packet: s1-a, S2-b, S3-c, S4-d, S5-e, the content transmitted from the 6 th time slot to the 9 th time slot after the network coding process is:

these 4 packets. At this time, the data packets owned by each user are: at least one of the S1-a,

S2-b，

S3-c，

S4-d，

S5-e，

obviously, each user can obtain 5 complete data packets of a, b, c, d and e through the operation of exclusive or, thereby completing the interaction.

Although the research result has certain innovation value and practical value, the current income effect is not obvious enough, and meanwhile, the corresponding application scene is temporarily lacked, so the research result is not actually used on the ground.

Mobile Edge Computing (MEC) is intended to cater for the 5G era to a new network communication scheme proposed by the european telecommunications standardization institute ETSI in 2014. The arrival of the 5G era can lead to the network communication to be reformed again, it must be a faster, more efficient, more humanized, more intelligent era, MEC is then proposed in order to solve the bandwidth that the high in the clouds service brought inadequately and high time delay scheduling problem, MEC server is through carrying out content perception and caching in advance to nearby user, can improve network performance, alleviate core network pressure, bring more efficient, more intelligent network service for the user simultaneously.

The mobile edge computing MEC may download part of the hot content and intelligent computing functions of the network to the edge near the end user. Therefore, the efficiency of accessing network contents by a terminal user is improved, the burden of the traditional communication network is reduced, more efficient and humanized services are brought, and the following three advantages can be summarized:

● low latency, high bandwidth; because the cached content is close to the user at the edge, the frequent occupation of network resources is reduced, the response delay is reduced to a certain extent, and the real-time response capability of the network is improved, which is the most prominent characteristic of the MEC.

● network information context intelligent perception; the past communication links are often referred to as "dummy pipes" and the communication links supported by the MEC can then obtain a lot of user information, such as location information, while also obtaining communication parameters on the part of the operator, which provides the basis for subsequent big data applications.

● network information calculation management; the MEC server is arranged in a corresponding mobile base station, can analyze and calculate the acquired user information, intelligently manages network contents, and opens an interface to a third party to apply, so that more humanized and intelligent services become possible.

The MEC is an emerging technology which is proposed only in recent years, but the practicality is strong, so that the MEC is very suitable for the upcoming 5G network communication, and therefore, a great number of students and internet companies are dedicated to developing the MEC server and striving for the implementation of the MEC technology in the early days. At present, a part of large internet manufacturers have already completed the development of the MEC server to some extent, and the popularization of the MEC server is expected to be seen in the near future.

A part of core functions of the MEC edge cache are to sense potential needs of edge users to perform cache in advance, which brings new overhead burden to existing network communication to a certain extent, and even occupies resources of normal network communication with a certain probability, so that how to coordinate normal communication content and time slot resources of cache in advance is a problem to be solved urgently.

Disclosure of Invention

The invention provides a method for cooperation of network coding and edge caching in a multidirectional wireless relay interaction channel, which combines a wireless relay with network coding and combines an MEC server with a relay base station (RS); in a multidirectional wireless relay interaction channel model, the time slot contradiction problem caused by using MEC to cache in advance can be solved by using network coding, so that the operation efficiency of a network is improved, and the reliability of information transmission is improved.

The invention adopts the following technical scheme:

a method for cooperation of network coding and edge caching in a multi-way wireless relay interaction channel comprises the following steps: setting a relay base station comprising an MEC server, wherein the relay base station works in a half-duplex mode and can wirelessly communicate with a core network and N peripheral users; the MEC server collects the potential requirements of communication of peripheral users, performs machine learning by combining network real-time hot content and file size to obtain the potential file requirements suitable for the peripheral users, sends the file requirements to a core network, and then obtains an MEC file X which needs to be used subsequently from the core network and caches the MEC file X to a relay base station; and when the peripheral users do not need to use the MEC file X, the relay base station synchronously sends the MEC file X and the user interactive data packets to each user.

Preferably, when a peripheral user needs to use the MEC file X, the relay base station synchronously sends the MEC file X and the user-interactive data packet to each user in a network coding manner, which specifically includes:

each user in the first N time slots sequentially sends respective data packets s1, s2, s3, a.

The relay base station in the N +1 to 2N time slots uses network coding to encode N +1 data packets s1, s2, s3, … …, sn and X into N data packets which are broadcast to N users in sequence;

after 2N slots, N users decode to obtain N +1 packets.

Preferably, the N +1 to 2N timeslots of the relay base station use network coding to encode N +1 data packets s1, s2, s3, … …, sn, and X into N data packets, which are sequentially broadcast to N users, and specifically include:

the relay base station in the N +1 to 2N time slots uses network coding to encode N +1 data packets s1, s2, s3, … …, sn and X into N data packets which are broadcast to N users in sequence.

Preferably, the step of synchronously sending the data packets interacted with the user to each user by the relay base station when the peripheral user does not need to use the MEC file X specifically includes:

each user in the first N time slots sequentially sends respective data packets s1, s2, s3, … … and sn to the relay base station;

the relay base station broadcasts N data packets s1, s2, s3, … … and sn to N users in sequence in N +1 to 2N time slots;

after 2N time slots, N user data packet interactions of one cycle are completed.

Preferably, when the relay base station performs data interaction with the peripheral users, the MEC server synchronously collects the potential requirements of communication of the peripheral users, performs machine learning by combining network real-time hot content and file sizes to obtain potential file requirements suitable for the peripheral users, sends the file requirements to a core network, and then obtains MEC files X required to be used subsequently from the core network and caches the MEC files X to a storage module of the relay base station.

Preferably, the relay base station transceiving may not be performed simultaneously, and there is only one available channel with each user.

As can be seen from the above description of the present invention, compared with the prior art, the present invention has the following advantages:

(1) the invention realizes the technical fusion of the MEC and the network coding technology under the scene of a multidirectional interaction channel model through the relay base station, so that the intelligence and the convenience of the MEC are realized under the scene through the high efficiency of the network coding by virtue of the flexibility of the relay base station, and the invention is a technical scheme with innovativeness, practicability and feasibility;

(2) the invention solves the problem of time slot of the MEC cache in advance to a certain extent; if the traditional scheme is adopted, although the intermediate novel relay RS caches the files which are possibly needed by N users in the future in advance, if the files are dispatched to each user who is interacting information under the scene during calling, a large number of time slots are occupied, so that the information interaction efficiency of each user is influenced, the contradiction is smoothly solved by applying network coding, so that each user can complete the reception of the MEC file while the information interaction is carried out, and the operation efficiency of the whole network is improved;

(3) the invention improves the robustness of network coding to a certain extent (in recent years, a plurality of researches show that a plurality of effective information can be decoded by intercepting different data packets of the same file or having a certain probability, the content of coding in the invention comprises the data packet of normal transmission and the data packet of future file X, and the two data packets have no correlation under general conditions), and simultaneously improves the stability of the whole network operation of the scene.

The present invention is described in further detail with reference to the drawings and the embodiments, but the method for cooperation of network coding and edge buffering in the interaction channel of the multi-directional wireless relay is not limited to the embodiments.

Drawings

FIG. 1 is a schematic diagram of a multidirectional wireless relay interaction channel model;

FIG. 2 is a schematic diagram of a single source, two sink multicast network;

FIG. 3 is a diagram of a conventional routing mechanism for solving the problem of single-source two-sink multicasting;

FIG. 4 is a schematic diagram of a single-source two-sink multicast routing strategy using network coding;

FIG. 5 is a schematic diagram of a multidirectional wireless relay interaction channel model of the present invention;

FIG. 6 is a flow chart of the method of the present invention.

Detailed Description

The invention is further described below by means of specific embodiments.

The invention discloses a method for cooperation of network coding and edge caching in a multidirectional wireless relay interaction channel. The relay base station RS with the MEC server not only has communication and wireless transmission capabilities of the base station, but also has the capability of intelligently sensing and storing data by the MEC content. The method comprises the steps of collecting potential requirements of communication of peripheral users, outputting a plurality of potential requirement files which are most suitable for the peripheral users in a machine learning mode by combining hot content in a network and file formats, sizes and other conditions of related content, feeding the requirement files back to a core network, obtaining files which are possibly used in the future from the core network, caching the files into a storage module of a relay base station, and sending the files to the users synchronously with normally interactive data packets in a network coding mode when the users who interact with the peripheral users do need the files.

Referring to fig. 5, a model diagram of a multidirectional wireless relay interaction channel of the present invention is shown, in which RS represents a relay base station, MEC represents an MEC server, and X represents a file that is cached by MEC in advance and needs to be used in the future. The model not only has the function of base station information transmission, but also has the functions of intelligent analysis, advanced caching and the like of MEC, specifically works in a half-duplex mode, can not simultaneously receive and transmit, only has one available channel (assuming that the channel is not interfered) with each user, has the functions of broadcasting and storing, and can be accessed to a core network for communication.

The following description is made with respect to fig. 5. In the figure, S1 and S2 … … Sn represent N users in the multi-directional wireless relay interaction channel scenario, and the device in the center of the figure is a relay base station RS with an MEC server function, where a black circle X represents a file that is cached in advance by the device through MEC technology analysis and may need to be used in the future, and is cached in a storage module of the relay base station. The two-way arrows represent uplink and downlink. S1, s2 and s3 … … sn are used to represent the data packets of each user, and x represents the data packets that need to be transmitted to each user when the MEC cache file is called.

Referring to fig. 6, a detailed workflow is shown, which is divided into a general case and two cases when an X file is called and accessed:

(1) in the general case:

the general situation is wholly described as that N users carry out information interaction through a relay base station RS, and an MEC server of the relay base station constantly carries out context-aware analysis on the interactive content to find out the potential file need, acquires a corresponding file from a core network and stores the file into a storage module, and the file is marked as X, and the method specifically comprises the following steps:

in general, the network coding scheme is not enabled in this scenario (considering that the use of network coding increases overhead but brings less significant benefits), and 2N time slots are required for N users to complete one information interaction. Each user in the first N time slots sequentially sends respective data packets to the RS, the data packets of each user are sequentially broadcast by the RS in the (N + 1) th to the (2N) th time slots, and one interaction is completed after the 2N time slots;

all information interaction passes through the relay base station RS, so that when multi-party interaction is analyzed by utilizing the context sensing function of the MEC server, N users can possibly use which files in the future, and meanwhile, machine learning comprehensive analysis is carried out by combining multi-party factors such as file hotspots, file sizes, file types and the like of a core network at the moment, files suitable for caching of the peripheral users in advance are analyzed in advance, accessed and obtained from the core network, stored in a storage module of the RS and marked as a file X;

since the interaction channel between N users does not conflict with the MEC file cache-ahead channel at this time, it is generally synchronized.

(2) When the X file is called to be accessed:

when the X file is called to access (specifically meaning that N users of the scene all need to use the file X), what is different from the general case is that the X file also needs to be broken into a plurality of data packets X of corresponding sizes and sequentially distributed to each user using data channels of N user interactions. Because the channel used by the MEC file X is a channel for user information interaction, if a conventional communication mode is adopted, normal interactive communication is necessarily affected, and the time slot cost is increased, so that a network coding technology needs to be introduced, and N +1 data packets are still sent to each user by using 2N time slots and the same channel capacity, specifically as follows:

in this case, network coding is enabled, and the specific coding scheme can refer to the case of the background section above. From the time slot, each user in the first N time slots sends respective data packets s1, s2, s3, … … and sn to the relay base station RS in sequence as before, and a network coding scheme is used from the N +1 time slot, at this time, N +1 data packets including s1, s2, s3, … …, sn and x need to be broadcast to each user by the relay base station RS, and the network coding scheme is adopted, so that the data packet interaction of the N users can be completed after 2N time slots, and the x data packets are also sent to each user;

the MEC intelligent analysis module of the novel RS can still be used as it is because the MEC intelligent analysis module does not have resource use conflict with the file distribution work.

According to the scheme, the problem of the MEC file transmission time slot of the multi-direction wireless relay interaction channel model can be smoothly solved. Generally, transmission is performed according to a traditional scheme, and an X file needs to be called and reused for network coding, so that the cost of one-time interactive time slot of the whole scene is always kept as 2N time slot, the cost of channel capacity is not increased, and the time slot problem of MEC file transmission is solved at the cost of high cost performance.

The technology of network coding has been developed relatively maturely in recent years, so the temporary lack of landing application is because the complete network coding work is a quite huge operation engineering system and needs to be supported from equipment in a large scale, and the network coding used by the invention is the most basic exclusive-or coding mode, so that the relative cost is small, the effect is obvious, and the implementation feasibility is strong.

After the hardware supporting equipment (the relay base station provided with the MEC server) provided by the invention is realized, the invention scene in life is only required to be arranged and replaced, and meanwhile, the scheme of the invention can be realized by properly adjusting the working mode of part of the structure of the network according to the scheme of the invention, so that the problem of time slot resources between the MEC file transmission and the normal user interactive communication content in a multi-way wireless relay interactive channel model is solved, and the operation efficiency of the network is improved.

The above description is only an embodiment of the present invention, but the design concept of the present invention is not limited thereto, and any insubstantial modifications made by using the design concept should fall within the scope of infringing the present invention.

Claims

1. A method for cooperation of network coding and edge caching in a multi-way wireless relay interaction channel is characterized by comprising the following steps: setting a relay base station comprising an MEC server, wherein the relay base station works in a half-duplex mode and can wirelessly communicate with a core network and N peripheral users; the relay base station can not transmit and receive simultaneously, and only one available channel exists between the relay base station and each user; the MEC server collects the potential requirements of communication of peripheral users, performs machine learning by combining network real-time hot content and file size to obtain the potential file requirements suitable for the peripheral users, sends the file requirements to a core network, and then obtains an MEC file X which needs to be used subsequently from the core network and caches the MEC file X to a relay base station; when peripheral users need to use the MEC file X, the relay base station synchronously sends the MEC file X and the user interactive data packet to each user in a network coding mode without additionally increasing time slot resource overhead;

the method for synchronously sending the MEC file X and the user interactive data packet to each user by the relay base station in a network coding mode when the peripheral user needs to use the MEC file X specifically comprises the following steps:

after 2N time slots, N users decode to obtain N +1 data packets;

the N +1 to 2N timeslots, using network coding, of the relay base station encode N +1 data packets s1, s2, s3, … …, sn, and X into N data packets, which are sequentially broadcast to N users, specifically including: