POWERLINE COMMUNICATION SYSTEM

The invention relates to a powerline communication system and more particularly to a method of surveillance of a network of modems on a powerline carrier .

The powerline communication technology, called PLC (powerline communication) , which consists in superposing a high-frequency signal, for example 1- 30 MHz, on a low-frequency voltage (50 or 60 Hz) , makes it possible to use the conventional electrical power wiring instead of another network, for example an Ethernet network, to transport digital data.

Initially restricted to commanding or controlling domestic equipment, this technology has been opened up to the transport of Internet data in buildings, such as for example homes, hotels, schools, without making use of additional cabling. Recent changes in this technology are making it possible today to envisage the distribution within buildings of several SD (standard definition) and HD (high definition) videos on various power outlets. This technology is also perfect for applications of Internet connectivity distribution over the electricity mains of a campus or a village.

However, the transport of high-frequency signals more particularly of video signals requires, in addition to a sufficient bandwidth (several tens of Mb/s in the case cited above) , the guarantee of a quality of service over the network in question. However, several interfering elements, due for example to devices connected to the power outlets, will unfortunately be able to compromise the quality of this network.

The quality of the signal, as described in US patent 2003/0122552, is determined with the aid of a particular quality measurement modem comprising its own

measurement device, that can be connected to the network to be tested and that comprises a built-in signal quality indicator. This modem can be connected to one of the power outlets of the network. The quality measurement is based on one-way metric measurements, that do not make it possible to deduce information on the origin of the interference.

In addition, the network can be tested only with the addition of this additional measurement modem.

The invention aims to remedy these disadvantages and proposes a test method that can be adapted to any type of modem connected to the network and is based on bidirectional metric measurements, irrespective of the PLC technology used on this network.

The invention is a method of network surveillance for a powerline carrier communication system applicable on any one of the network modems. It comprises the steps: of identifying the modems present in the network via a scanning procedure; of measuring the bidirectional quality parameters between the identified modems; - of deducing a quality index with reference to the applications envisaged on the network; and of transmitting an information message depending on this quality index.

The invention has the advantage of testing the quality of service necessary for the desired applications without adding an additional test modem, the software implementing the steps described above running on one of the items of equipment connected to the PLC modems.

Preferably, the quality parameter measurements correspond to the bidirectional measurements of available bit rates.

According to one variant of the invention, the surveillance method comprises the step, following the identification of an inadequate quality index, of locating an interfering element by detecting an asymmetry of the bidirectional measurements between two modems .

According to another variant of the invention, following the identification of an inadequate quality index, the surveillance method comprises the step of identifying an interfering element by comparing the effective degradation of the bit rates with a database stored in a terminal.

Preferably, the steps are reiterated regularly during the transmission process in order to detect a degradation of transmission quality and help the user to remedy this degradation.

The invention simplifies troubleshooting because, in most cases, it allows the problem to be solved by the user, which avoids the use of the troubleshooting service (hotline) or the unnecessary return of products catalogued as defective. It is therefore a precious aid for establishing a diagnosis.

The features and advantages of the invention mentioned above and others will appear more clearly on reading the following description, made in relation to the appended drawings, in which:

Figure 1 represents the diagram of a network installation serving as a support to the method according to the invention for a powerline communication system. - Figure 2 represents an example of a flow chart used by a method produced according to the invention.

Figure 1 represents an example of a domestic network using powerline communication technology. It is connected to the mains 1 via an electric meter 3.

This electric network comprises various branches A, B, C and D, connected to different power outlets 11 to i4 which can be plugged modems 12 connected to terminals 13 such as for example digital decoders, computers, laptops (PC) or IP (for Internet protocol) telephones. Most of the terminals comprise screens or are connected to screens.

In certain applications, the modem 12 is built into the terminal 13.

The method according to the invention can be executed by one of the terminals 13 connected to a modem.

According to the invention, and as shown by the flow chart of Figure 2, during the installation of the PLC network, or during the addition of a new modem, the method begins with a step 101 of scanning the various modems 12 connected to terminals 13. The invention is therefore a method whose first step consists in scanning and registering the various modems 12 via a particular protocol, for example the ICMP (for Internet Control Message Protocol) protocol, at the initiative of one of the terminals 13.

During the second step 102 of the method, a bidirectional measurement of the bit rate is carried out between all the modems registered during the first step. It involves measuring the bit rate also called the useful bit rate, for example, a UDP (for User Datagram Protocol) or TCP (Transport Control Protocol) bit rate. This measurement can be carried out for example by sending a file from one terminal 13 to another and measuring the speed of transfer of the data

of this file. This step will then be repeated for the various registered modems.

Following a comparison between these measured bit rate values and preregistered values corresponding to certain envisaged applications for example, it is possible to evaluate the bit rate margin available relative to the bit rate used on all the links established between the various modems . A check is made to ascertain that the measured bit rates make it possible to run the envisaged applications on this network with a certain margin compatible with the desired quality of service and, during the next step 103, a quality index is deduced relative to the desired quality of this service. The user is then informed of the network quality according to the value of this index. Preferably, a bargraph is used to indicate the network quality level to the user on a screen connected to the terminal 13.

If, after the third step, the network quality is deemed adequate 104, the network may operate. Regular surveillance based on this bit rate measurement principle will then be initiated during the next step 105. It involves regularly sending, without interfering with the payload data stream, a test data stream making it possible to evaluate the available bit rate margin relative to the bit rate used on all the links established between the various modems.

On the other hand, if, after the third step, the network quality is deemed inadequate, the information on the bidirectional bit rates measured will make it possible to determine the type of interfering element and locate it.

The type of interfering element will be determined during a step 107 for comparing the information obtained via the bit rate measurements and information

relating to the interfering elements registered in a memory. Specifically, a list of the different interfering elements associated with different values of bit rate loss is stored in a memory and forms a reference database 106 which will make it possible to identify this interfering element. It may, for example, be a bad device connection to the network or be the use of a multiple-outlet unit or the proximity of a mobile telephone charger. The list of interfering elements is derived from site tests and is not finite. It may be supplemented gradually as interference is encountered.

Each registered interfering element is therefore associated with an average data bit rate loss value or minimum and maximum bit rate loss values. Other information available inside the modems may also be used either in isolation or in combination with these bit rate measurements to form this database 106 and subsequently establish the diagnosis of the PLC network. This information may for example be a frequency response or a signal-to-noise ratio or a transmission power or an error check or any other parameter sensitive to local interference.

The interfering element is located during a step 108 by comparing the asymmetry of the data bit rates between the modems connected to the network. For example, on a network that comprises only the terminals A and B, if the method according to the invention is executed by the terminal A and the bidirectional bit rate between the terminals A and B is measured, an asymmetry of the measurements of the incoming and outgoing bit rates of A will make it possible to indicate whether the interfering element is situated closer to A or to B. If the bit rate from A to B is degraded relative to the bit rate from B to A, it is possible to conclude therefrom that the modem B has, in receive mode, a bad quality signal-to-noise level and that the interfering element is therefore close to the modem B.

It is therefore thanks to the asymmetry of these bit rates that it is then possible to indicate to the user during the step 109 the probable position of the interfering element.

The invention has not only a detection role but will also have an important role of providing information and helping to isolate the interfering element or the faulty element. This may be, for example, the use of a filter isolating the interfering element from the rest of the PLC network. It is not limited to the example previously described but relates to maintenance on the PLC network or a bidirectional parameter measurement makes it possible to determine and locate an interfering element.

As indicated above, regular surveillance is carried out based on the principle of bit rate measurement. If, during this surveillance, the network quality is deemed inadequate, the procedures described above for determining the type of interfering element and its location are then applied. The user alarm information is transmitted, for example, to a "pop-up" window appearing on the screen, for example, of the device selected for the installation procedure.