WO2010092172A1 - Methods for configuring and operating radio nodes of a radio network - Google Patents

Abstract

The present invention relates to methods for configuring and operating radio nodes (5 to 10) of a radio network (1). The present invention further relates to a radio node, to a radio network, and to an automation network. According to the method for configuring radio nodes, a data frame corresponding to a radio standard is implemented (S1) in the radio nodes. The data frame is provided (S2) with a preamble that is parameterized (S3) by means of a radio-cell-specific value. According to the method for operating radio nodes, a preamble of data packets to be transmitted is adapted according to a preamble of the data frame implemented in the radio node (5 to 10) that is parameterized in a radio-cell-specific manner. A receiving radio node evaluates the validity of the data packets using at least one part of the radio-cell-specific value of the preamble in order to subsequently receive or block the data packets.

Description

description

Method for configuring and operating radio nodes of a radio network

The present invention relates to methods for configuring and operating radio nodes of a radio network. Furthermore, the present invention relates to a radio node, a radio network and an automation network.

Radio technologies have become increasingly important in recent years, especially in the industrial environment. This trend towards wireless technologies as a replacement for wired technologies will continue, especially for cost reasons. Because wireless networks can be installed at lower cost in almost any environment than wired networks. However, wireless networks can also be used to extend existing wired networks. A radio network is usually constructed by a wired infrastructure with radio network access points. For example, a wireless network access point is an access point, gateway, hot spot, coordinator, etc. The access points are interconnected via the wired infrastructure and each access point generates a corresponding radio cell, the radio cells forming the radio network.

Even in automation technology, it is no longer only wired bus systems that are used for data communication between devices. So are becoming increasingly common wireless

Networks constructed as part of an automation network, which are known in the art, for example, under the name "Wireless Sensor Actor Networks (WSAN)". Wireless terminals within the wireless network can exchange data with the wired infrastructure through appropriate access points. Under a wireless terminal, for example, a wireless field device to understand how eg a sensor or an actuator, which is part of the automation network.

Sensors and actuators are essential components of conventional automation solutions and are wirelessly coupled to distributed peripherals (e.g., gateway as a wireless network access point) which is wired to a fieldbus (e.g., Profinet / Profibus). Unlike wired sensors and actuators, radio cells (e.g., a WSAN) in which the wireless sensors and actuators reside must share existing frequencies. Potential conflicts in the use of the same frequencies are minimized by professional measurement of the environment and by consistent radio field planning and management of the radio frequencies. However, if interference still occurs in a communication between a wireless field device and a corresponding radio network access point, these are most often due to interference with one or more nearby wireless field devices operating in the same frequency range. Furthermore, it can happen when two radio cells that are far apart transmit on the same channel that packets from the respective other cell are monitored over and over again, which causes the listening radio cell to become out of tune. However, problems do not arise only when adjacent radio cells of the radio network operate on the same frequencies, but also when the respective frequencies are close to each other. For example, it may happen that a radio network access point of a first radio cell receives packets of a wireless field device as valid packets, which is actually assigned to a second radio cell, when the frequencies of the radio cells close to each other.

Common wireless field devices of an automation network, which act as radio transmitters when exchanging data with the wireline network, usually use the same frequency resources, such as the license-free ISM band between 2.400 GHz and 2.483 GHz. As a result, there is the danger, as described above, that interference with a data transmission can easily occur. comes. In practice, this can lead to a significant delay in the transmission time at high radio density, which in turn leads to a high latency. However, especially a wireless network in the industry compared to home and office applications meet much higher requirements, such as have particularly low latency.

The mutual interference of radio cells operating at the same frequency or adjacent frequencies, however, sometimes can not be solved even with accurate surveying and radio field planning, as radio waves propagate very differently and very dynamically. Hereinafter, known approaches will be described which deal with the problem of mutual interference of radio cells.

A first known solution is used, for example, in the IEEE 802.15.4 standard, which defines the low layers of network access (link layer, also known as MAC layer, and physical layer, also known as physical layer). For this purpose, the standard defines suitable security mechanisms to secure the communication between two radio nodes. The basic idea here is an access control list (ACL) which stores a key and the corresponding MAC address for each radio node (for example sensor, actor, access point, etc.) of a radio network. The checking of an incoming packet is realized by the hardware of the radio chip access point radio chip based on the ACL. The disadvantage of this solution, however, lies in the fact that the security function must be switched on for the communication. In cases where very low latencies are required, such as in the manufacturing industry, turning on the security function to secure communication results in high latency and is therefore unacceptable.

According to a second known solution, the problem of interferences is solved applicatively in the respective radio node, for example by means of a security application. However, this solution leads to long and thus unacceptable latencies for certain applications. Because according to this solution, false packets must first pass through the entire protocol stack in order to call the security application, which then detects the wrong packets not belonging to this radio cell.

A major disadvantage of the above solutions is performance. The time required to read a packet completely and apply the preconfigured security mechanisms can only be accepted in automation systems where the latency between the occurrence and processing of an alarm can be relatively long. However, for example, in the manufacturing industry, permissible latencies are very short (between 5 and 50 ms), which can not be met with the known safety mechanisms.

The invention is therefore based on the object to ensure a trouble-free operation of adjacent radio cells of a radio network, with very short latencies are met.

The present invention provides a method for configuring radio nodes of a radio network having at least one radio cell. In the radio nodes, a data frame is implemented according to a radio standard, which is provided with a preamble. According to the invention, this preamble is parameterized by means of a radio-cell-specific value.

A data frame, which can also be referred to as a data telegram or data frame, for example, has a specific structure depending on the radio standard used. Among other things, the radio standard used determines the communication process between radio nodes in a radio cell of the radio network. The data frame may include, for example, delimiters for marking the start and end of the frame, destination and source addresses, control information, payload data and checksums. Furthermore, the preamble is dependent on the radio Standard either part of or preceded by the data frame. Conventionally, the preamble must contain prescribed values depending on the standard used, so that data packets can be detected at a receiving radio node using the same radio standard as a transmitting radio node. As described above, it is therefore possible that a receiving radio node also listens to data packets that are not intended for him. However, these data packets are conventionally discarded only after a security mechanism has recognized, after a processing time that is too long for many applications, that received data packets are invalid.

In order to shorten the processing time and the associated latency significantly, it is proposed according to the invention to parameterize the preamble by means of a radio-cell-specific value. In this case, radio-cell-specific means that the value differs in the individual radio cells of a radio network. In other words, each radio node is assigned to a radio cell and the radio cell-specific value for radio nodes of a radio cell is identical. Thus, although the preamble parameterized according to the invention is not standard compliant, it prevents radio nodes from unintentionally listening to packets which are not intended for them.

According to a particularly preferred embodiment, if a radio network comprises a plurality of radio cells, the radio cells can be generated by cloning a single radio cell. For this purpose, only the preambles of data frames in radio nodes of the respective radio cells with a radio cell-specific value must be parameterized after cloning. That is, the radio cells are basically identical cells, which differ only in the preamble of the data frames implemented in the radio nodes. As a result, the radio nodes can unambiguously allocate data packets, even if the cloned radio cells operate on the same channel. By cloning a single radio cell can Setting up a wireless network is greatly simplified and accelerated.

Furthermore, the present invention provides a method for operating radio nodes of a radio network having at least one radio cell, wherein a data frame corresponding to a radio standard is implemented in the radio nodes. A preamble to be sent data packets is adjusted according to a preamble of the data frame, which is parameterized by means of a radio cell-specific value. The thus adapted data packets are sent from a transmitting radio node to a receiving radio node. Then, a validity of the data packets in the receiving radio node is evaluated based on at least a part of the radio cell specific value of the preamble, which is also included in the preamble of data packets sent due to the adaptation to the preamble of the data frame. As validated data packets are received in the receiving radio node, whereas the receiving radio node blocks as invalidated data packets.

According to the method for operating radio nodes, the implemented data frame ensures that data packets to be sent have a preamble with a radio cell-specific value, which is given to them by the transmitting, preconfigured radio node. As a result, the receiving radio node can already carry out the evaluation on a leading part of the data packet since, in principle, it first receives the preamble. In other words, a comparison between a preamble of the data frame implemented in the receiving radio node and a preamble of the received data packet is performed. A data packet is therefore evaluated as valid if it is received by a radio node which belongs to the same radio cell as the transmitting radio node. Because in this case, the radio cell-specific values of the respective preambles match. In the context of the present invention, blocking of data packets means that reception of a data packet is stopped immediately as soon as the receiving radio node has recognized from the radio cell-specific preamble of the data packet that the data packet is not intended for it. This means that the receipt of a data packet can already be aborted before the entire data packet is received at all, since the preamble already indicates whether it is a valid or invalid data packet. Thus, further contents of a data packet do not have to be considered at all, so that the effort and the time for an evaluation of the validity are significantly reduced. Preferably, all information received (usually only a few bits or bytes) until it detects an invalidity of a data packet is discarded immediately.

The present invention thus ensures that invalid data packets are detected in the fastest possible way at the receiving radio node, whereby a latency compared to conventional solutions is significantly reduced or minimized. As a result, the solution according to the invention is also suitable for fields of application in which particularly short latencies are prescribed (for example between 5 and 50 ms). Furthermore, a trouble-free operation of adjacent radio cells is ensured, which on the same or adjacent

Frequencies are sparking. In particular, a monitoring of data packets described at the beginning which is not intended for the receiving radio node is prevented. As a result, both adjacent and remote radio cells are destroyed, which spark on the same frequency and between which, for example, another radio cell can be provided which radiates on a different frequency.

According to one embodiment of the present invention, the data frame has a frame structure in which protocol and data information is mapped. In this frame structure, the preamble is then the first data field which has a radio cell deviating from the radio standard used. has specific value. However, the preamble of the data frame continues to consist of a 1-0 bit combination, which among other things serves to enable the receiver to synchronize to the transmitter. Furthermore, it can be ensured by means of the frame structure that the data frames are constructed identically in all radio nodes of a radio network. This is important because instances on the sender and receiver side must operate according to established rules. The definition of such rules is usually described in the protocol information mapped in the frame structure.

According to another embodiment of the present invention, the data frame is a data frame of a physical layer when describing tasks of communication in a layer model. Thus, the data of the physical layer, which is also known to the person skilled in the art as a physical layer, is provided with the radio-cell-specific preamble. The layer model forms a functional subdivision of the communication tasks. One layer's job is to provide services for the next higher layer, using the services of the underlying layer. In general, for a layered model, a layer N on a device A, for example a first radio node, only communicates with the corresponding layer N on a device B, for example a second radio node. It sets the rules for communication in the protocols for each layer, with the protocols including additional structural and procedural information. In a preferred embodiment, the layer model corresponds to the OSI reference model of the ISO, which is known to the person skilled in the art and will therefore not be described further here.

According to yet another embodiment of the present invention, the data frame is implemented in a radio chip of the radio node. For this purpose, the radio chip must have a certain flexibility, so that the preamble of the data frame can be manipulated accordingly. That is, the radio chip must allow access to the corresponding register in order to replace a preamble that complies with the respective standard with a radio-cell-specific preamble or to adapt a value of the standard-compliant preamble to a radio-cell-specific value. Thus, according to the present invention, only one radio chip can be used in the radio node, which allows to violate the respective standard. An example of a radio chip that possesses such flexibility is the ChipCon chip CC2420 with which the solution according to the invention has already been verified.

According to a further aspect, the present invention relates to a radio node which is set up for communication with at least one further radio node. The radio node comprises a radio chip in which a data frame is implemented in accordance with a radio standard which comprises a preamble which is parameterized by means of a radio-cell-specific value. In other words, such a radio node corresponds to a radio node as described in relation to the methods according to the invention. For example, the radio node may be a radio network access point or a wireless field device of a radio network and part of an automation network.

According to a further aspect, the present invention relates to a radio network, comprising at least one radio cell with at least two of the radio nodes described above. In this case, the at least two radio nodes of a radio cell are set up for communication with one another.

In yet another aspect, the present invention relates to an automation network comprising at least one wireless network as described above.

Hereinafter, preferred embodiments of the invention will be explained in more detail with reference to the drawings. FIG. 1 shows a radio network with three radio cells and a plurality of radio nodes.

FIG. 2 shows a physical layer and a security layer according to the IEEE 802.15.4 standard.

FIG. 3 shows a method according to an exemplary embodiment of the present invention.

1 shows a radio network 1 with three radio cells 2, 3, 4 and a plurality of radio nodes 5, 6, 7, 8, 9, 10. According to the embodiment described here, the radio network 1 of FIG. 1 is based on the IEEE 802.15.4 standard , This standard describes a Wireless Sensor and Actor Networks (WSAN) transmission protocol, which defines the physical layer (PHY layer) and the link layer (MAC layer) of the ISO / OSI reference model. For radio transmission, the ISM bands 868/915 MHz and 2.45 GHz are available, whereby mainly the 2.45 GHz band is used.

In the radio network 1 of Figure 1, the plurality of radio nodes 5-10 form a radio network. Three of the illustrated radio nodes are radio network access points 8, 9, 10 and the other radio nodes are wireless field devices 5, 6, 7

In the exemplary embodiment, the radio network access point 8 and the wireless field devices 5 are assigned to the first radio cell 2, the radio network access point 9 to the second radio cell 3 and the wireless network access point 10 and the wireless field devices 7 to the third radio cell 4. The wireless field devices of a radio cell communicate with the corresponding radio network access point and vice versa. The radio network of Figure 1 is part of a wired automation network (not shown), and the radio network access points are as a distributed peripheral to a

Fieldbus (not shown) coupled. Thus, the radio network access points provide interfaces between the wired and wireless networks. As part of the automation network, the radio network access points 8, 9, 10 are wireless gateways, for example, PNIO (Profinet Input Output) gateways according to the IEEE 802.15.4 standard. The wireless field devices 5, 6, 7 are sensors or actuators, for example PNIO sensors / actuators according to the IEEE 802.15.4 standard. In general, the IEEE 802.15.4 standard for radio nodes provides two levels of complexity, FFD (Füll Function Device) and RFD (Reduced Function Device). An FFD offers special functions so that a device can act as a coordinator, for example. Furthermore, different FFDs can communicate directly with each other. For this reason, the radio network access points 8, 9, 10 of Figure 1 should be considered FFDs if they are PNIO gateways according to the IEEE 802.15.4 standard. An RFD, on the other hand, can only communicate directly with a FFD because it has limited functionalities. For this reason, the wireless field devices 5, 6, 7 of FIG. 1 are to be regarded as RFDs if they are PNIO sensors / actuators according to the IEEE 802.15.4 standard.

Usually, the radio cells of a radio network partially overlap, so that in principle there is a risk that a radio network access point of a radio cell listens to data packets that are not intended for him. Thus, it may happen in the case illustrated in FIG. 1 that the radio network access point 8 of the first radio cell 2 hears data packets from a wireless field device 7 that are actually intended for the radio network access point 10 of the third radio cell 4. This danger exists especially if in the first and the third

Radio cell 2, 4 is sparked with the same frequency. Furthermore, there is the risk that the radio network access point 8 of the first radio cell 2 listens to data packets provided for the radio network access point 9 of the second radio cell 3, even if in the first and the second radio cell 2, 3 with different but consecutive frequencies (adjacent channels ) is sparked. Likewise, in the case illustrated in FIG. 1, there is a risk that the radio network Access point 9 of the second radio cell 3 monitors data packets that are intended for the radio network access point 8 of the first radio cell 2, since a wireless field device 5 of the first radio cell 2 is arranged at a cell edge of the second radio cell 3.

FIG. 2 shows a physical layer (PHY layer) and a data link layer (MAC layer) according to the IEEE 802.15.4 standard. As described above, in known solutions, a check of the validity of data packets is performed at the earliest in the MAC level. The present invention proposes to perform this check already in the PHY plane of a radio node, for example to solve the problems described with reference to FIG. For this purpose, the preamble in the PHY level is parameterized with a radio-cell-specific value. As shown in Figure 2, the preamble of the PHY level in accordance with the IEEE 802.15.4 standard contains 4 bytes with the value 0. According to the invention, these 4 bytes are given the value 0 per radio cell with a different value. In order to manipulate the preamble of the PHY level, a register interface accesses a preamble holding register of a radio chip of the radio node in which the data frame shown in FIG. 2 is implemented and writes the corresponding radio cell-specific value into the register. Through this manipulation of the preamble of the physical layer a performance gain is achieved, which is explained mainly by the hardware support in the PHY plane.

It can also be seen from FIG. 2 that a synchronization header in the PHY plane, in addition to the preamble, also includes a start of frame delimiter, which, however, can not be manipulated. Otherwise there would be a risk that the radio chip is no longer working properly. The Start of Frame Delimiter signals the beginning of a frame to a receiver. According to the IEEE 802.15.4 standard, the Start of Frame Delimiter has the value 0xa7. However, the start of frame delimiter and the others, in Figure 2 displayed data fields of the PHY level and the MAC level has no effect on the present invention. Since those skilled in the art also their functions are known, they will not be further described here.

FIG. 3 shows a method according to an exemplary embodiment of the present invention. According to this method, radio nodes of a radio network are configured with at least one radio cell. For example, the radio nodes shown in FIG. 1, which are designed as radio network access points and wireless field devices and are arranged in different radio cells, can be configured in this way. This can influence a later communication of these radio nodes. In the configuration, a data frame according to a radio standard is implemented in the radio nodes S1, for example the data frame of FIG. 2 according to the IEEE 802.15.4 standard. This data frame is provided with a preamble S2, which is parameterized by means of a radio-cell-specific value S3. By way of example, referring to FIG. 1, this means that the same data frame is implemented in all radio nodes 5, 6, 7, 8, 9, 10 of the radio network 1. However, the preamble of the data frames of the radio nodes in the respective radio cells 2, 3, 4 is parameterized differently. That is, the preambles of the radio nodes 5, 8 of the radio cell 2, the radio node 6, 9 of the radio cell 3 and the radio nodes 7, 10 of the radio cell 4 are each assigned a specific value. As a result, in the radio cells 2, 3, 4 of FIG. 1, the same frequency can be transmitted, even if the radio cells partially overlap, without them interfering with each other in the communication.

Claims

claims Method for configuring radio nodes (5 to 10) of a radio network (1) with at least one radio cell (2, 3, 4), comprising the steps: Implementing (Sl) a data frame according to a radio standard in the radio nodes (5 to 10), Providing (S2) the data frame with a preamble, and parameterizing (S3) the preamble by means of a radio-cell-specific value. 2. Method for operating radio nodes (5 to 10) of a radio network (1) with at least one radio cell (2, 3, 4), wherein in the radio nodes (5 to 10) a data frame is implemented according to a radio standard, comprising the steps: Adapting a preamble to data packets to be sent according to a preamble of the data frame which is parameterized by means of a radio-cell-specific value, Sending the data packets from a transmitting radio node to a receiving radio node, Evaluating a validity of the data packets in the receiving radio node based on at least a portion of the radio cell specific value of the preamble, Receiving those data packets in the receiving radio node which are evaluated as valid, and Blocking those data packets at the receiving radio node that are considered invalid. 3. The method according to any one of the preceding claims, wherein the data frame has a frame structure in which protocol and data information is mapped. The method of any one of the preceding claims, wherein the data frame is a physical layer data frame when describing tasks of communication in a layer model. 5. The method according to any one of the preceding claims, wherein the data frame is implemented in a radio chip of the radio node (5 to 10). 6. radio node (5 to 10), which is set up for communication with at least one further radio node, comprising a radio chip, in which a data frame is implemented according to a radio standard, which comprises a preamble, which is parameterized by means of a radio cell-specific value , 7. radio node (5 to 10) according to claim 6, which a radio network access point (8, 9, 10) or a wireless field device (5, 6, 7) of a radio network. 8. radio node (5 to 10) according to claim 7, which is part of an automation network. 9. A radio network, comprising at least one radio cell (2, 3, 4) with at least two radio nodes (5 to 10) according to any one of claims 6 to 8, wherein the at least two radio nodes of a radio cell are arranged for communication with each other. 10. An automation network, comprising at least one radio network according to claim 9.