WO2018108427A1

WO2018108427A1 - Method for transmitting data in a multihop network

Info

Publication number: WO2018108427A1
Application number: PCT/EP2017/079384
Authority: WO
Inventors: Jens Braband
Original assignee: Siemens Aktiengesellschaft
Priority date: 2016-12-15
Filing date: 2017-11-16
Publication date: 2018-06-21
Also published as: DE102016225164A1

Abstract

According to the invention, a method for transmitting data packets in a wireless multi-hop network having a plurality of nodes (N) is proposed that restricts the range of the transmission of a data packet. To this end, each node (N) of its type is assigned a weight (w). Further, a limit value (G₁) for limiting the range of the data packet is stipulated. Further, a counter (S) at each node (N) is incremented by the weight (w_ij) associated with the node (N), and the data packet is not forwarded if the counter (S) exceeds the limit value (G).

Description

description

The invention relates to a method for data transmission in a multihop network, in particular an ad hoc network, and to a multihop network for data transmission.

A network based on the invention consists of a number of mesh-linked nodes that can communicate with each other. In a so-called meshed or meshed network, not every node of the network is connected to all other nodes of the network, but each node of the network is connected to at least one other node of the network. In such a network will be

Transfer messages from an initial node to an end or destination node. The destination node is not within range of the initial node, intermediate nodes are used to Wei ^¬ terleitung the message. By way of example, an initial node sends a message z. B. to a first intermediate node, this sends the message to a second intermediate node and this in turn can forward the message to the destination node. The network thus serves to transmit messages in multiple steps or "hops" between two nodes along a transmission path Therefore, such a network is also called "multi-hop network" and the form of data transmission is referred to as multi-hopping. In this case, the number of steps that a packet has to cover on its way from the starting node to the destination node can be counted as a so-called "hop count." The data load can be distributed more advantageously in a meshed network, since data is passed on from node to node until they reach their recipient without the need for a one-stop-shop.

The spread of wireless communication networks continues to increase against ^¬ wärtig. Wireless networks after the WLAN Standard (WLAN = Wireless Local Area Network) IEEE 802.11, z. B. IEEE 802.11-p, are now among the most frequently ^¬ th used technologies in wireless data transmission. More and more objects of everyday daily life such as mobile radios, PDAs, etc. in this case have the possibility of Emp ^¬ fanges and sending messages. The objects can be permanently installed, resting or moving. In many situations, such as As in road or rail transport, a coordination of such items (such as, for example, vehicles, trains, etc.) makes sense to z. B. to support the security or management of the data. So it can be used in rail transport applications z. B. be useful to enable a signal preview over a be ^¬ voted number of signals along the route of a train. Here can z. B. the train itself but also a railroad crossing with a network technology to node a multihop network be formed.

Increasingly important are ad-hoc wireless networks, which connect two or more objects as nodes to a meshed mobile network and set up and configure independently.

An ad-hoc network constantly adapts when nodes move, add or fail.

However, with meshed networks, the limitation of forwarding messages (hopping) is an important one

Measure, as otherwise network overload may occur. As a rule, in the prior art, data packets or messages are discarded statically or time-dependently, in particular in the case of ad hoc networks, in which the subscribers do not know each other and the network is constantly changing.

The task is to size the range of messages in multihop networks. According to the invention, a method is proposed for transmitting data packets in a multi-hop wireless network having a plurality of nodes, which determines the range of the Transmission of a data packet is limited depending on its type or its meaning.

For this purpose, each node is assigned a node type. Furthermore, a limit is set for limiting the range of the data packet. There are assigned weights wi _j to each node in depen ^¬ dependence of a type "i" of the respective node, and the type "j" of the transmitted data packet. The data packet is transmitted from an initial node over several nodes, with a counter being incremented by the weight assigned to the node. A forwarding of the data packet is omitted if the counter exceeds the limit.

In the following, the term message can also be used interchangeably for a data packet.

Preferably, the counter is initially set to zero.

The advantage of the invention consists in an application-oriented, dynamic forwarding of messages in

Multihop networks, such as B. in ad hoc meshed networks, such as z. B. in automotive or railway applications can be realized. The application can dimension or limit the range of the data packet or the message. According to the invention a distinction is made according to the type of bone and ^¬ least the message and the transmission is defined in terms of weights and thresholds.

In other words, at each node received, the current counter S in the course of each transmission between two nodes, that is, every so-called jump, becomes a weight w ± _j , which depends on the type of the receiving node i and the type of the data packet j , increased, ie

Snew ⁼ S _a i + Wi

After the increment, it is checked at the node concerned whether the current counter value is greater than the first limit value Gi: Snew> Eq

Thus, data packets can be prioritized and given a higher weight than other data packets.

It is particularly advantageous to transmit the limit value G and the counter S together with the data packet to be transmitted itself. As a result, the data packet only has to be expanded by a small amount of information and no or hardly any additional time is spent for transmission in the network.

In a preferred embodiment, it is further checked whether the age of the message T has exceeded a predetermined second time limit value G2. For this, the time of generation of the data packet or a synonym of the date of commencement de transmission of the data packet übertra ^¬ gen, preferably as part of the data packet. Is the second

Limit G2 exceeded, so there is no forwarding of the data packet.

Thus, the age of the message also has an influence on the forwarding of the data packet. Alternatively, the age of the message may also be included in the weight w at each node (wi, _j , _t ), where t is a time index.

In an advantageous embodiment, a first type of node is a node that is application-relevant for the type of data packet, and a second type of node is only for

Transmission of the data packet of relevant nodes. The node of the first type is assigned a higher weight than nodes of the second type. Thus, it is possible to distinguish between subscribers that are application-relevant with regard to the transmitted data packets and those which are only relevant for transmission technology. Node of the second type the possibility to obtain, for example, a Ge ^¬ weight of zero. Advantageously, thus intermediate stations, which are only important for the transmission, not the counter S. By setting the first limit value Gi can then be determined exactly how many application-relevant nodes to reach the data packet.

Each node may be assigned a weight greater than zero in one embodiment. Then all nodes contribute to the counter increment according to the respective weight.

The first limit may be determined depending on the density or frequency of nodes in the network that are relevant to an application of the type of data packet. This ensures that at least one application-relevant node is always reached.

The data packet may include data of a railway application and the mobile network may be configured to transmit data from railway applications.

In addition, a controller of a node of a wireless multihop network is proposed, which is adapted to receive a first limit value for limiting the range of forwarding of a received data packet, ei ^¬ nen counter to an increment the weight attributed to the node, and a Forwarding a received data packet when the counter exceeds the first limit, to refrain.

Furthermore, a wireless multihop network is proposed, which is designed to carry out a method according to one of the preceding claims.

The above-described characteristics, features and advantages of this invention, as well as the manner in which they are achieved, become clearer and more clearly understandable in the context of the invention. In conjunction with the following description of the embodiments, which are explained in more detail in conjunction with the drawings. FIG. 1 shows a multihop network according to the invention.

In the following a solution of the mentioned problem will be presented, which makes the hopping more flexible depending on the application. For this purpose, each node N is assigned a weight w ± _{j as} a function of its type i and also of the type of the data packet j. Each data packet D, which is sent, is thus accumulates preferably two additional information is ^¬, namely a first limit value Gi for the dynamic weight of the data packet and the counter S itself. Before the start of transmission of meter preferably receives a start value S = 0. If a node N D, a data packet with the parameters gi and S, so it determines its assigned weight wi _j, wel ^¬ ches depending on the data packet type and the type j was ^¬ nes node type is i. The respective weight may be stored in the node or it may be calculated by the node according to an algorithm.

Preferably, at each node, the counter is then incremented by the respective weight at node w ± _j . If, in a preferred embodiment, the counter is S> Gi, the node N consumes the data packet D, ie it still evaluates it but does not forward it any further. This achieves a dynamic range depending on the type of nodes involved and the importance of the message.

FIG. 1 shows a multihop network according to the invention. By way of example and not limitation, a web ^¬ application is illustrated. By way of example and not ^limitation, all devices along one route are equipped with WLAN-p components. The example application is intended to enable a signal preview over a certain number of signals. The transmission is directed along the route in both directions, but it is not always direct between adjacent signals possible. Intermediate stations can z. B. also railroad crossings or trains or stations, etc. It shows a route, a train and two signals No and N ₄ . In the example, the train with its nodes i and ₂ and a railroad crossing N ₃ serve as intermediate nodes for the transmission of a data packet between two route signals o and N ₄ along the route of the train. The Da ^¬ tenpaket case contains data of the signal o. In a first jump, the data packet is transmitted by the signal No to a node i of a first end of a train. In a second

Jump will transmit the data packet to a node N ₂ on the second, ge ^¬ genüberliegenden end of the train. From this second end of the train, the data packet is transmitted to a level crossing N ₃ . From the level crossing N ₃ , the data packet is transmitted to a second signal N ₄ .

In the exemplary embodiment the signals No and N ₄ are for the on ^¬ application of the signal data relevant to the application nodes. The data packet to be transmitted contains signal data. Simplified, the weight W dependent on the data packet and the node type has a value of W = 1 at the nodes No and N ₄ . Only nodes which are relevant for the transmission represent the intermediate nodes N ₁ -N _3. They are assigned a weight of W = 0. Routing data packets after a certain number of

No jumps or hops, so no range can be guaranteed. Nor can not be guaranteed a range or the reaching of an adjacent signal in pure zeitli ^¬ cher limitation. But sets a limit Gi fixed, in the embodiment of Figure 1 z. B. Gi = l and only signals a positive weight, z. 1, it is possible to control that a message reaches the next signal and then is consumed. 0 staging stations will not increase the counter, which is a type of dynamic weight. Accordingly, the following picture is produced at each of the nodes involved in the transmission:

Table 1: Parameters of the transmission at each node N

At node N ₄ , the counter S _{new is} equal to the first limit Gi. The node N ₄ , the second route signal, then evaluates the data packet, but no longer sends it. If, in another example, Gi = 4 is selected, then in this case the data packet would reach a fourth signal. Since the node _N4 then still _new S <Gi applies the data packet would thus be forwarded to the node N ₄ now. Of course, the weights can also be distributed differently. For example, each node can be assigned a small minimum weight. Also, the weight can be chosen depending on the type of message. Short-range Nachrich ^¬ th will receive a higher weight and thus be consumed faster.

The weight wi _j can be the sum of a weight q ± for the type of node and g _j for the type of data packet, so w ± _j = g ± + g.

It may also be useful to additionally include other criteria to z. For example, to prevent a data packet from being routed endlessly between other nodes. In addition, an age of the data packet can additionally be limited as the second limit value G ₂ . So z. B. G ₂ = 1 min fixed ^¬ laid. Then, at a node at which the age of the data packet is now 1.2 minutes, the forwarding of the data packet would be stopped because of aging. So z. B. a signal preview only makes sense if it is not too old. For this purpose, for example, the time of generation or the time of the first forwarding is transmitted together with the data packet.

Accordingly, the advantage of the invention is an application-oriented, dynamic forwarding of messages in ad hoc meshed networks. The application can size the range of the data packets in certain Ma ^¬ SEN. It can be advantageously distinguished between participants that are application-relevant and those that are technically relevant only transmission ^¬ .

Although the invention has been further illustrated and described in detail by way of preferred embodiments, the invention is not limited to the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

Claims

claims

A method of transmitting data packets in a multihop wireless network having a plurality of nodes (N), comprising the steps of:

Assigning weights (wi _j ) to each node (N) as a function of a type (i) of the respective node (N) and the type of data packet (j) to be transmitted,

Establishing a first limit (Gi) for limiting the range of forwarding of a data packet,

Transmission of a data packet from an initial node (NO) over several nodes (N),

Incrementing a counter (S) at each receiving node (N) by the weight (wi _j ) associated with the node (N), and

Refraining from forwarding the data packet if the counter (S) exceeds the first limit (Gi).

2. The method of claim 1, wherein the first limit value (Gi) and the counter (S) are transmitted together with the data packet to be transmitted.

3. The method according to claim 1 or 2, wherein

a first type of node is an application-relevant node for the type of data packet, and

a second type of node (N) is a node (N) relevant only to the transmission of the data packet, and

Node (N) of the first type is assigned a higher weight than node (N) of the second type.

The method of claim 3, wherein nodes (N) of the second type receive a weight of zero.

A method according to claim 3 or 4, wherein nodes (N) of the first type receive a weight of one.

6. The method according to any one of claims 1 to 3, wherein each node (N) is assigned a weight greater than zero.

7. The method according to any one of the preceding claims, wherein the limit value (Gi) depending on the density or frequency of ^¬ relevant for an application of the type of data packet node (N) in the network is set.

8. The method according to any one of the preceding claims, wherein the data packet contains data of a railway application and the mo ^¬ bile network is designed for the transmission of data from rail applications.

9. The method according to any one of the preceding claims, wherein in addition the time of generation (T) of the data packet is transmitted and when a second, time limit value (G ₂ ) of since the time (T) elapsed past the forwarding of the data packet is omitted.

10. The method of claim 9, wherein at each node (N), the exceeding of the second limit value (G ₂ ) is checked.

11. Control unit of a node of a wireless multihop network, which is designed to:

to receive a first limit value (Gi) for limiting the Reichwei ^¬ te of forwarding a received data packet at the node,

a counter (S) to increment a weight (wi _j ) associated with the node (N), and

forwarding the received data packet if the counter (S) exceeds the first limit value (Gi).

12. A wireless multihop network, which is designed to carry out a method according to any one of the preceding claims.