WO2009068721A1

WO2009068721A1 - Method and system for transmitting data asynchronously in a data transmission network

Info

Publication number: WO2009068721A1
Application number: PCT/FI2007/000281
Authority: WO
Inventors: Tapio Marttinen
Original assignee: Wiseriver Oy Ltd
Priority date: 2007-11-28
Filing date: 2007-11-28
Publication date: 2009-06-04
Also published as: EP2220831A4; EP2220831A1

Abstract

The invention relates to a method and system (100) for transmitting data asynchronously in a data transmission network (102) with at least two nodes (the main node and connection node, 104, 108). The system also includes a loop (106a, 106b), in which data is transmitted in a primary carrier frame (400) via channels (3, 7, 11, 12, 13, 23, 25, 127). The main node (104, 108) administers the loop and generates to it also the data transmitting primary carrier frame (400). Devices connected to the connection node belong to an application, to which a channel is assigned in the loop, which means a data transmission resource separated from the carrier frame in a time-shared manner; a data field, in which the user's data unit is transmitted divided into as many parts of the length of the data field as are needed for transmitting the whole data unit. The slices are transmitted to the receiver transparently as a bit string independent of the data transmission protocol via the said channel in the data field of the carrier frame without touching the contents or structure of the data unity to be transmitted and without reading its possible address or length fields. A connection circuit (109a) in the data transmitting node is adapted to provide as output a first electric signal to be transmitted in the bit stream transmitted in the data transmission network, indicating the starting point for the data unit in the bit stream transmitted in the data transmission network. In this case the receiving node can form a timely electric signal indicating the beginning of the bits belonging to the data unit in the connection circuit of the node receiving the electric signal.

Description

Method and system for transmitting data asynchronously in a data transmission network

The invention relates to a method and system for asynchronous data transmission in a data transmission network. In particular, the invention relates to a system described in the preamble of claim 1 and to a method described in the preamble of claim 20 for transmitting data asynchronously in a data transmission network.

Different data transmission solutions are nowadays very common in different kinds of buildings, such as business premises and residential buildings. Buildings have own cablings for data transmission methods used by e.g. television, computers, telephones, house automation, sound reproduction systems and other state-of- the-art systems requiring data transmission. Thus, these systems often have different types of media according to the mechanical connection modes for equipment and systems or other requirements? In addition, several communication con- nections can still be left totally outside these systems.

Distinct problems are associated with the above mentioned issues. For example, installation of several different types of cables and systems, and also their service and alteration, is expensive and complex. These kinds of systems require even physically many kinds of plug sockets or connection points for connecting equip- ment and applications to a data transmission network supporting it. In the state of the art there are known some solutions and attempts to combine all data transmission solutions to one medium. Nevertheless, also these are very complicated and vulnerable systems, because they typically contain a lot of electronics for the correct reading, interpreting and transmitting of data elements according to various protocols. Further, the more different applications there are connected in the solution according to a known system, the more counting capacity and memory resources are required from the processor running the system. Thus, system overloads and the "jamming" of data communications are very often due to the complexity and operational principles of the known systems. The object of the invention is thus to achieve such a solution, with which above- mentioned drawbacks relating to the state of the art can be reduced. The object of the invention is to create a universal data transmission system, from which the transmission capacity needed by all kinds of data transmission applications can be separated for all of them. When applications using data transmission, such as lo- cal area networks, sound reproduction equipment, telephone systems and antenna networks are taken into use, they traditionally require the installation of a separate cabling for them. Thus, the object of the invention is, by programmatic measures, to separate an independent data transmission connection or a data transmission connection to be connected to en external network restricted to a certain area. In particular, it is an object of the invention to make possible the connecting of e.g. an antenna network, telephone network, LAN, and data transmission network of house automation and the connecting of equipment in the building especially inside the building so that data transmission is possible with one cable or fibre or a similar wireless arrangement, irrespective of the data transmission application.

The objects of the present invention will be achieved with the system and method described in the independent claims.

The system of the present invention is characterised in what is shown in the char- acterising part of the system claim 1.

The method of the present invention is characterised in what is shown in the characterising part of the method claim 20.

The system according to the invention relates to asynchronous data transmission in a data transmission network, in which the data transmission network comprises at least two nodes, namely at least one main node and at least one connection node. The data transmission network further comprises at least one loop administered by the main node so that the main node is adapted to generate to the loop a primary carrier frame (CF) transmitting data in the loop.

The loop has at least one connection node, to which at least one device, such as TV, stereos, loudspeaker, telephone or computer, is connected. The device is linked to an application, which provides the devices with a data transmission connection, through which the devices can communicate with each other or to an external network. According to an embodiment, connecting the device can act as a trigger for the generation of the application (plug & play). The invention is also characterised in that in the node data is only transmitted to one direction in the primary carrier frame via at least one channel. The channel is typically a data transmission resource which is separated from the transmission capacity of the data transmission network in a time shared manner and which is assigned to the application, the resource being assigned to the use of the embodiment most typically when arranging or forming an application.

In the system, a data unit to be transmitted between the transmitting and receiving node is divided into slices to be transmitted at equal intervals according to the size of the data field determined for the channel, the transmitted data unit relating to the application being data according to any data transmission protocol. After having been divided into slices (or in some cases, even during the division), each slice of the data nit divided into slices is transmitted transparently to the recipient as a bit string independent of the data transmission protocol through the channel in question in the data field of the primary carrier frame, without touching the contents or structure of the transmitted data entity and without reading its possible address or length fields.

In accordance with the invention, a connection circuit in the data transmitting node has been adapted to provide as output an electric signal to be transmitted in the bit string transmitted in the data transmission network, indicating the starting point of the data unit in the bit stream transmitted in the data transmission network. By means of the said signal, the receiving node is made to form a timely electric signal indicating the beginning of the bits in the data unit in the connection circuit of the receiving node so that the receiving node can pick the starting point of the data unit assigned to it in the bit stream transmitted in the data transmission network.

The invention contains only a few general definitions for the mode of transmitted data (Transmission Mode, TM). However, the facts mentioned above are common to all these transmission modes; for example, defining the starting point of the data unit. Nevertheless, the processing of the transmission modes in the buffers devi- ates somewhat from each other. The modes of the invention are the following:

- TM1 : Interconnected channel, packet end identification;

- TM2: Interconnected channel, no packet end identification

- TM3: Standard frame length, free repetition frequency, one transmitter;

- TM4: Free frame length, free repetition frequency, one transmitter, and - TM5: Point-to-Point P-P, free repetition frequency, free frame length, but however, in most applications standard repetition frequency and frame length, bidirectional connection between two points. There may also be other possible modes, but they will not be discussed in connection with this document.

The said transmission modes are based on the transmission of a free-length packet in a transparent manner. They are characterised in the use of a reservation bit (R-bit) in front of the channel. The first slice of the packet begins from the beginning of the data field used by the channel. The end again generally impinges on something in the middle of the data field. The end point is found in a manner discussed later in this document. The transmission modes TM2 - TM5 are special cases of TM1.

The most common use of the TM1 mode is the Ethernet application. In this transmission mode, the channel is in common use (Ethernet's original Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol is in use). The transmitting device of the user is connected to the connection node. When the device transmits the packet, the Ethernet transmitter/receiver circuit of the connec- tion node sets active the signal "Receive Data valid, RXDV". This signal is active to the end of the last bit in the packet. In this mode, there is a "reservation bit", R- bit, in front of the channel used by the application. The "Data valid" signal of the transmitter/receiver circuit sets active the R-bit (=1 ), if the channel is free. If, for example, 1 Mbit/s has been selected as transmission capacity for the application, the data field of the channel in the carrier frame (CF) is 16 data bits (because CF is repeated 64000 times a second).

The transmitting connection node fills the 16-bit "slices" in successive primary carrier frames in the channel reserved for it as long as there are bits in the packet. The last slice is usually not whole. The transmitter changes the R-bit to zero in the last slice belonging to the transmission. When the R-bit is zero for the first time after the reservation, the channel is not free, and no connection node attempts to reserve the channel then.

With the above method, timely data is conveyed to the receiving end to control the status of the signal "Transmit Enable, Txen" in the transmitter side of the Ethernet transmitter/receiver circuit located there. Also the connection from one loop to another in the main node needs exact information on the exact location of the data packet end.

The method is possible from a channel with the width of five bits (5x64=320kbit/s) onwards. With smaller widths, the channel field assigned by "significant bits" al- ways contains the number of the significant bits in the previous slice, and no sign is needed.

TM2 has a frame of standard measure, so the end of the packet in the last slice will be known from this. The R-bit is only intended for the reservation of the chan- nel. TM3 is similar to TM2, but only one transmitter is allowed. TM3 has a frame of standard measure, in practice often also standard repetition frequency. The R-bit is used, but only for finding the beginning of the frame. Typical applications are in sound reproduction (e.g. CD format and S/PDIF).

TM4 is the same as TM1 , but only one transmitter is allowed. A typical application is e.g. the transmission of TV channels. TM5 has the same principle as TM1 , but in this mode the transmission takes place between two points. The use of the R-bit is the same as in TM1 , but both points terminate the coming bit string and transmit, if there is something to transmit. The R-bit must not pass the connection node as such, even though there is nothing to transmit. The repetition frequency and frame length can be standard, but they may also vary just as well. Typical applications are e.g. intercommunication stations and videophones.

The following concepts, among others, are used in this patent application:

- "Channel" is a resource (Channel or Resource) assigned to an application in the primary carrier frame. The channel length can vary from zero to the size of the entire effective load. All capacity free at a specific time is in the channel #127. Typically, for example, one TV channel (with the capacity of 2-5 Mbit/s) takes up one channel according to the invention. Also the Ethernet application is one channel.

- "Device" is a device to be connected to the connection node, such as TV, loudspeaker, CD player, telephone or computer. The device is associated with an application, which will be defined later.

- "Transparency" refers in this invention to that the contents or structure of the transmitted data entity will not be touched and possible address or length fields will not be read.

- "Mode" is either a transmission mode (TM1 - TM7) or an internal mode SI or

AS (modes have been explained elsewhere in this document). - "Primary carrier frame" is the primary transmission unit the invention uses in a loop, carrier frame (CF), which is repeated 64000 or 8000 times a second.

- "Delimiter bit" (D) follows temporally the reservation bit (R) in the data stream. The delimiter bit is active only when the last bits of a sliced data unit are in the data field of the primary carrier frame of the channel.

- "Loop" is a typical topology for the data transmission solution used by the invention. For backup reasons, the lower level loop has been divided into four segments, which are also independent loops. In accordance with the invention, the loop is administered by at least one node in the loop, the main node. The system may have several loops, either of different or same level

(hierarchy). Typical total capacity for an upper level loop is at present 1 Gbit/s, but it is obvious that as technology evolves, this will increase. In addition it has to be taken into account that the loop can be duplicated so that the total capacity of the system is 2 Gbit/s on the upper level. One higher- level loop has typically 1024 channels and a lower-level loop has 128 channels, but it is also obvious that the numbers of channels presented here are only exemplary, and the invention is by no means restricted to the said number of channels.

- "Node" is either a connection node or main node in the loop. A device is con- nected to the loop via the connection node. The main node again administers the said loop.

- "Application" is always a data transmission application. The application includes devices, for example, loudspeakers in a sound reproduction system and their sound source, which is e.g. provided with a digital S/PDIF connec- tion; or e.g. PC and its connection equipment connected to a local network

(LAN) and a connection to an external network are applications. An application is typically created automatically (plug-and-play) on the user side by connecting a first device that belongs to the application to a connection node. Arranging transmission resources needed by external service provid- ers requires measures by a person authorised for (distant) administration of the system. The applications are fully independent, and they can be defined to comprise desired areas in any parts of a building (or block, different houses in housing corporations). In a big building there can be thousands of separate applications. Space can be made for a new application any time without disturbing the other applications. One application generally needs one channel.

- "Data field" is a field reserved for a channel in the primary carrier frame.

- "Data unit" (packet or frame) is a user's data unit, which is transmitted be- tween at least two devices belonging to an application.

- "Reservation bit" (R) is located temporally first in the data flow, indicating whether the said shared channel is currently reserved or free. The reservation bit is associated with the alternative method for finding the end of the packet. - "Slice" is a part of data divided from the data unity to be transmitted and intended to be transmitted in accordance with the invention. The thickness of the slice depends in each case on the transmission speed needed. In accordance with the invention, the data unit is sliced into pieces or slices of 1/64000 or 1/8000 seconds.

According to an embodiment of the invention, the connection circuit of a data transmitting node is adapted to provide as output a second electric signal to be transmitted in a bit stream transmitted in the data transmission network. The signal indicating the length of the data unit is delivered in the data transmission network through the nodes in the data transmission network to at least one data receiving node, in which the signal controls the receiving node to read the length of the transmitted data unit.

According to another embodiment of the invention the connection circuit of the data transmitting node is adapted to provide as output a third electric signal to be transmitted in the bit stream transmitted in the data transmission network, indicating the end point for the data unit in the bit stream transmitted in the data transmission network. By means of the said signal, the receiving node is made to form a timely electric signal indicating the end of the bits belonging to the data unit in the connection circuit of the receiving node so that the receiving node can pick the end point of the data unit assigned to it in the bit stream transmitted in the data transmission network.

Alternatively it is also possible that the connection circuit of the data transmitting node provides as output one signal, which, in addition to the starting point, also indicates the end point for the data unit. Such a signal can be, for exam- pie, an RxDV signal (receive data valid), which typically is active during the transmission of the whole data unit, i.e. the transmission of all slices. In isochronous transmission (e.g. pulse-code modulated transmission (PCM) of a telephone, a framing signal is used, which indicates only the beginning, but the length of data is constant). By means of the said signal, the receiving node is made to form a timely electric signal indicating the beginning of the bits in the data unit and, in addition, a timely electric signal indicating the end of the bits in the data unit in the connection circuit of the receiving node so that the receiving node can pick the starting and end points for the data unit assigned to it in the bit stream transmitted in the data transmission network.

According to an embodiment of the invention, the channel is in shared use by at least two devices so that the first bit preceding the data field temporally is a reservation bit (R) indicating, whether the said shared channel is currently reserved or free. According to another embodiment of the invention, the reservation bit (R) is temporally followed by a delimiter bit (D), which is active only when the last bits of the sliced data unit are present in the data field of the primary carrier frame in the channel.

In addition, according to an embodiment of the invention, following temporally the delimiter bit (D) there is a fixed number of bits (so many bits that by means of them it is possible to indicate the length of the data field = significant bits) indicating the number of significant bits in the last slice associated with the sliced data unit to be transmitted in the data field reserved for the channel assigned for the application.

Further, according to an embodiment of the invention, the reservation bit (R) is set to be inactive only in the next data field of the primary carrier frame after the transmission of the last bits associated with the sliced data unit.

According to an embodiment of the invention, the setting of the reservation bit (R) to be inactive is adapted to cause the respective control signal to become inactive in the receiving node, such as e.g. to deliver the "transmit enable" signal to the Ethernet transmitter/receiver.

According to an embodiment of the invention, the delimiter bit (D) is set to be active only in connection with the next data field of the primary carrier frame, if the last bits of the sliced data unit cannot fit to the data field of the primary car- rier frame of the channel, when the data indicating the number of last bits in the sliced data unit has been temporally added in front of the said last bits in the sliced data unit (i.e. the data field), in which case the number of bits is indicated with a minus sign indicating that the data representing the number of bits con- cerns temporally the previous received slice.

According to an embodiment of the invention, the reservation bit (R) is arranged to indicate the beginning of the data field in the sliced data unit to be transmitted especially when the transmitted data unit is a frame with constant length. In addition, according to an embodiment of the invention, the main node is adapted to time the transmission of the primary carrier frame and to fill its necessary fields with data supplied by different data transmitting nodes and to copy the required fields from the basic carrier frame arriving from the loop to be transmitted again to the loop. The main node can also be adapted to connect and administer several loops, to which the main node is adapted to generate the basic carrier frame (CF) transmitting data in the loops. Further, according to an embodiment of the invention, the main node is adapted to combine several loops administered by it to at least one higher-level loop as a bigger system, the higher-level loop being administered by at least one main node relating to a higher-level loop. According to an embodiment of the invention, the main node administering at least one higher-level loop can also connect the said loops and the related main nodes to at least one external data network.

According to the invention, it is further possible to alter the transmission speed (Variable Bit Rate support, VBR), for example, in Video streaming use, when the amount of data transmitted as constant stream changes. For example, a packed transmission of a TV channel contains very little information when the picture does not change or when it is, for example, mainly monochromatic, in which case it is possible to use the alteration of the transmission speed (VBR) downwards. Respectively, if the picture changes or if the amount of information otherwise increases, the transmission speed can be increased. In practice,

VBR will only be used in a higher-level loop (HLR), but it is generally determin- able. In the invention, the VBR additional attribute can be set to any transmission mode so that the application mainly negotiates the minimum and maximum length for the channel (the number of bits in the channel) with the main node. The duration of a multi frame (MF) is 512 primary carrier frames (CF). Of this, the first quarter (also called as sub-multi frame, SMF) contains the initial addresses for all the 128 possible channels in CF, as has been explained earlier. In the second (or third) SMF, the transmitting node of the application using VBR can write the capacity it needs next at a place determined by the number of its own channel. After the next successful transmission of MF (everyone has reported to have received it without errors), the new bandwidth will be taken into use for the channel.

In addition, according to the invention, the correctness of the initial addresses for the channels can always be checked. The alternatives are the adding of a parity bit (CRC, Cyclic Redundance Check) or an error-correcting code. All the alternatives need a certain number of additional bits. Each node checks the correctness of the reception of the initial addresses for the channels used by it (i.e. once in an MF) (in a connection node, there are e.g. 6 gates, each with its own channel). If the node detects a bit error, it reports this in the parameter field of the third SMF channel, number 127 (the last channel, because its parameter field will not be needed for another purpose), the first SMF containing the initial addresses for all 128 channels, by changing all bits in it to ones. The main node still repeats this by changing these bits to ones also in the fourth SMF, because in this way also the connection nodes located before the node detecting the error are notified of it. All the connection nodes will then "know" that the new recently divided channel configuration will not be taken in to use, but a new round will be waited for.

In the invention, capacity is thus divided for the applications in a time-shared manner. In addition, data transmission is transparent in the present invention.

For example, the length field or address field of the user's data unit will not be read, but data travels to the area that has been determined for it as if the area had its own data transmission line. The arrangement according to the present invention should thus be understood logically as a line infrastructure, of which e.g. data transmission lines will be taken into use for (one) LAN (or LAN segment) of a certain enterprise, the lines travelling in the enterprise's premises (in any selected rooms even in a big building). In the solution of the invention, only devices connected to the system read addresses travelling in the "lines", i.e. no other components of the invention (with the exception of a higher-level main node, which sees to traffic out from the system of the invention i.e. to an external data network) read addresses or length field data. The basic idea of the invention can thus be expanded into a larger system so that the invention can comprise e.g. two levels of hierarchies, a lower (Lower Level Ring (LLR)) and higher (Higher Level Ring, HLR) level. The higher level can be used, for example, for connecting the applications in an apartment or office to extend to an external network and to each other. The lower level can be used for connecting e.g. the devices in an office to each other (e.g. 128 applications / apartment). The lower level typically consists of four loops, which are called segments, and between which a connection will occur according to applications via the main node in the loop. A certain kind of hierarchy is thus essential in the invention so that it is possible to form several independent, locally restricted or unrestricted data transmission applications, in which data transmission is transparent, guaranteeing that any data can be transmitted, even such data, which has not even been developed yet. The invention thus determines for the transmission a limited number of universally valid transmission modes (explained in more detail below in the description of the invention), by means of which any transmission protocol can be transmitted in the system between desired nodes (2 or several) and returned to the receiver in the mode in which it was at the input point.

It has to be noted that only some applications in use "come out" from apart- ments. For example, an application connecting loudspeakers and a CD player etc. is at least in a normal case restricted either to a room or at least an apartment. An office can instead be located in several floors. In addition, some floors may contain other offices. LANs of an office are typically used in the area of all premises used by the office.

The present invention thus includes undisputed advantages in relation to solutions known from the state of the art. With the system of the invention it is possible to achieve excellent security. In the nodes, electronics process the data stream on an electric logic level (or programmatically), when no operational malfunction of a microprocessor, congestion or error can affect the progress of data. In addition, because the invention processes all data in the same way as

"slices", without caring from their interpretation or transmission mode, the different data transmission modes of the applications are really "transparent" in accordance with the inventive idea, which ensures that data transmission is undelayed and that the system does not suffocate to the unloading, conversion and packing of user's data. In addition, the invention offers e.g. the following advantages: the amount of electronics needed in the connection nodes is minimal; no processing of the microprocessor is needed for data transmission, in which case data transmission cannot be jammed to a program error; the system according to the inven- tion can have an innumerable number of different applications; and the lack of performance of the microprocessor will not rise to be a hindrance; no new cables need to be installed after the implementation of the system of the invention, even though new equipment or data transmission applications were to be added to the data transmission system of the invention; and the devices can be connected to the system e.g. by USB, Ethernet (10/100Base-T) or Bluetooth connections by using e.g. UpnP (Universal Plug and Play) (a protocol, which negotiates the transmission resources and finds associated devices and can connect them to the correct network).

Some advantageous embodiments of the invention are shown in the depend- ent patent claims.

Advantageous embodiments of the invention will next be explained in more detail, referring to the enclosed drawings, in which:

Figure 1 illustrates a first exemplary system for transferring data asynchro- nously in a data transmission network according to an embodiment of the pre- sent invention;

Figures 2A-C illustrate a second exemplary system for transferring data asyn- chronously in a data transmission network according to an embodiment of the present invention;

Figure 3 illustrates a third exemplary system for transferring data asynchro- nously in a data transmission network according to an embodiment of the present invention;

Figure 4 illustrates an exemplary structure for a data transmission system for transferring data asynchronously in a data transmission network according to an embodiment of the present invention; Figures 5A-E illustrate an exemplary buffer system for transferring data asynchronously in a data transmission network according to an embodiment of the invention; Figure 6 illustrates an exemplary arrangement of data buses used between buffers according to an embodiment of the present invention;

Figures 7A-B illustrate an exemplary method for processing data contained in slices in a node according to an embodiment of the present invention; and

Figures 8A-B illustrate some exemplary methods for transferring data between buffers and for processing data in a node according to an embodiment of the present invention.

Figure 1 illustrates a first exemplary system 100 for transmitting data asyn- chronously in a data transmission network 102 according to an embodiment of the present invention. The data transmission network in Figure 1 comprises e.g. an upper-level main node 104, and further at least one loop 106a administered by the main node, to which loop the main node is adapted to generate a primary carrier frame (CF, Figure 4) transmitting data in the loop. The data transmission network also comprises several lower-level (LLR) main nodes 108 associated with the loop generated by the main node. The nodes 108 comprise at least one loop 106b, which they administer themselves, and in which case the said nodes 108 are main nodes of the said look 106b, i.e. lower-level main nodes 108 in the system 100. In addition, the loop 106b can have several connection nodes 1099 for connecting devices 110 to the data transmission sys- tern. The devices 110 are linked to an application, in which data transmitted by the devices or coming from an external network is transmitted via the data transmission system of the invention between devices belonging to the same application.

It has to be noted that the main node can also be adapted to connect and ad- minister several loops. Further, the main node, especially an upper-level main node, can, when needed, connect the loops administered by it and the lower- level main nodes and the lower-level loops administered by them to at least one external data network 112.

The system of the invention can be expanded almost endlessly. The loop struc- ture can be duplicated to two loops transmitting data to opposite directions, in which case the advantage is achieved that the system will tolerate one complete cable break without disturbing the operation.

Figures 2A-C illustrate a typical loop 106b administered by the lower-level main node 108. Typically four loops administered by the said main loop 108 can be connected to the lower-level main node 108, which loops can comprise a certain number of connection nodes 109. The loops 106b administered by the lower level can be chains among themselves, in which data is transmitted uni- directionally to the last node and then turns back, or they can be duplicated loops. At this moment it is typical for the invention that each loop can transmit data with the speed of 95 Mbit/s, i.e. by means of four loops it is possible to transmit 380 M/bit/s per apartment.

Figure 2A illustrates two chained loops 201 , 202. In Figure 2B there is a secured loop 203, which can tolerate one complete cable break. Figure 2C again illustrates a connection node 108, which has two gates under a lid, to which temperature, twilight, anti-theft and other sensors and actuators 204 required by the house automation can be connected, such as relays and digital-to- analogue converters. These can be connected to an automation system separate for each apartment or to a system common to the whole house. According to an embodiment the connection can be converted programmatically for several standardised connections.

Figure 3 illustrates a system 300 administered by one lower-level main node 108, which has three different loops 301 , 302, 303, of which the loops 301 and 303 are chained, and the loop 302 is a secured loop. The loops have connec- tion nodes 109, to which different devices 110, such as e.g. PC, TV and telephone, can be connected. It also has to be noted that also some elements essential for house automation, such as temperature sensors 204 are connected to the connection nodes.

The connection node 109 is characterised by a connection circuit 109a, which according to an embodiment of the invention provides different signals (described elsewhere in this document) for indicating e.g. the starting and/or end points and length information on the data.

Figure 4 illustrates an exemplary structure for a data transmission system 400 for transmitting data asynchronously in a data transmission network according to an embodiment of the invention, in which the structure is a primary carrier frame 400 transmitting data and generated by the main node administering the loop. According to the invention, the primary carrier frame is divided into channels, for example 128 channels. It is characteristic of the invention that in the loop data is transmitted to one direction only in the primary carrier frame 400 via at least one channel 3, 7, 11 , 12, 13, 23, 25, 127. "One direction" has to be understood so that the primary carrier frame "travels" e.g. clockwise so that data is available at the points A, B, C in an order according to their mutual sequence. However, it has to be noted that (when the situation so allows) data can be delivered between the points A, B and C arbitrarily, i.e. A can deliver data, for example, to the point C, and data can be delivered from the point C back to the point A, i.e. in this sense data can be transmitted between two points "bidirectionally". A channel is typically a data transmission resource assigned to an application and separated from the transmission capacity of the data transmission network in a time-shared manner, the resource being assigned to the use of the application upon establishment, most typically when connecting the first device associated with the application to a connection node of the loop. According to an embodiment of the invention, the length of each channel can vary between 0 -

1441 units so that the transmission capacity of one unit is 64 kbit/s, and the primary carrier frame rotating the loop 64,000 times in a second. The channel lengths can be varied any time without disturbing other traffic. The primary carrier frame typically fills the loop entirely. In the example in Figure 4, part of the channels 0-25 is in use and the rest are unused so that their length is zero. The channel 127 has the whole capacity remaining unused by the other channels. When connecting a new device to the connection node, it will automatically switch to the channel 127, after which, for example, the main node assigns a suitable channel for the application in ques- tion on the basis of messages transmitted by the new device. For example, when the application is TV (the device has to have an Ethernet connection, or a digital box with such a connection has to be used), it will upon connection connect to a connection node in a channel used at first by PCs.

The main node routes the traffic transmitted by the TV to the upper-level main node, which identifies the desired service provider (if there is one). After this, the lower-level main node arranges an own channel (from the resource loop) for the TV (2-5 Mbit/s). The capacity will be reduced from the PC resource. The lower-level main node connects the channel (resource) of the channel reserved for this TV to the channel (resource) of the upper-level loop, to which the up- per-level loop feeds the data of the desired TV channel. The upper-level main node arranges a new channel (from the resource loop) to the upper-level loop, if the TV channel in question is not currently watched in the apartment. Each TV turned on in the apartment will get an own channel (resource) from the loop. According to an embodiment, if a certain TV channel (e.g. TV1 ) is already being watched in the apartment (or in some TV connected to the connection node of the loop) and a second TV is connected to the loop, with which one wants to watch the same TV channel (here TV1 ), the main node can give the said TVs the same channel (resource) from the loop for saving transmission capacity.

Connecting an analogue phone to the connection node typically requires an adapter. When the adapter is connected to a connection node, it will first be connected to the channel used by PCs. The lower-level main node identifies the call signal sent by the adapter and arranges an own channel (resource) typically of e.g. 64 kbit/s for the connection. The lower-level main node connects the apartment level channel to the channel reserved for telephone com- munications in the upper-level loop. This is a so-called group channel or resource, which thus is one channel, but containing an own internal resource for each phone in the house. The gateway in the upper-level main node converts the telephone conversation into an IP conversation (VoIP) in a general network. Figures 5A-E illustrate an exemplary buffer system 500 for transmitting data asynchronously in a data transmission network according to an embodiment of the invention. In Figure 5A there is an example of a buffer structure 500 used in a lower-level main node, the structure typically having eight internal buffers 502, 504 (one for each loop in an arrangement with four loops) and three ex- ternal buffers 506, 508, 510. Of the external buffers, the buffers Biext and Bo- ext 506, 508 operate as buffers between the main node and the upper-level loop, of which the buffer Biext 506 receives data from the upper-level loop, and from the buffer Boext 508 data is delivered to the upper-level loop. The buffer eB operates as a buffer between several loops administered by the lower-level main node. Of the internal buffers, four are input buffers (Bin (n=0, 1 , 2, 3) and four are output buffers (Bon, (n=0, 1 , 2, 3). For the sake of clarity, only two internal buffers are shown in Figure 5A.

Figure 5B(1 ) illustrates an example of the first input buffer 502 BiO, to which the data contained in the primary carrier frame and circulated in the lower-level loop is read. Depending on the case, data is read possibly for each loop to its own buffer BiO, BM , Bi2, Bi3 that, however, are identical with each other. Figure 5B(2) illustrates a principal view of the operation of the input buffer 502. It can be imagined that the buffer 502 has two replaceable halves 502a, 502b (swapi , swap2) so that data can be received to the one and the other can already be fully received. It is possible to write successively to the input buffer, but its halves 502a, 502b can be read in free order. On the read side, there are typically 64 pointers. This restricts the number of active channels to 64 in the loop, but it has to be noted that this can be changed in accordance with buffer principle known from the state of the art.

Figure 5C illustrates an example of the first output buffer 504 BoO, in which data is transmitted to the primary carrier frame circulating in the lower-level loop. The output buffer can be written in free order and it is read in channel order, but e.g. the whole data structure of isochronous channels has to be stored to the output buffer. That is why each channel, which is active in the loop, has its own pointer. The output buffer in the example has 64 read and write point- ers, that is the maximum of 64 channels or channel groups (successive, identical channels are treated as one channel) can be active in the loop.

Figure 5D illustrates an example of the external buffer eB 510 (External Buffer) intended for data transmission between loops. The data bus of the buffer in the example is 8-bit so it can serve all four lower-level loops in a time multiplexed manner (data transmission between internal buffers is 1-bit). All shared transmission modes use the external buffer, because the channel can be reserved in the next loop. While waiting for release, several packets may end up in a queue. That is why there are 8 layers (LayerO - Layer7) in each channel buffer (CB), each of which can accommodate one packet.

Figure 5E illustrates an example of the input and output buffers 506, 508

(Buffer for External Traffic, Biext, Boext), which are organised otherwise in the same manner as eB, but they have only one channel buffer (CB) for one active channel (four in eB, because there are four loops).

It has to be noted that the invention uses two internal modes, which define whether the data is restricted to one loop (Segment Internal, Sl) or to all four

(All Segments, AS). The reason for their implementation is that a fully free connection inside the main node is not possible. It would lead to such a complex connection that the circuit would either be impossible or at least very difficult to realise. Nevertheless, the channel number thus always concerns all four loops. The channel in the SI mode reserves the number also in the loops, in which it is not active (and does not reserve capacity). The channel in the SI mode can read directly from the upper-level loop or an external network. This possibility exists e.g. because of TV applications.

Figure 6 illustrates an exemplary arrangement 600 of data buses used be- tween buffers according to an embodiment of the invention. The thicker arrows

602 illustrate only the routes possible in the SI mode. Vertical transmissions between internal buffers are on a 1-bit, the other ones on an 8-bit data bus.

Figure 7A illustrates an exemplary method 700 for processing data processed by slices in a node according to an embodiment of the invention, especially in TM1 mode. In the figure, the slice 4 of the packet to be transmitted (Slice #4) is arriving at the main node. It will be loaded to a layer to be filled in eB, which layer accommodates the whole packet.

In this example, the sequence started from the point when the R bit of the channel in question was active for the first time (R=1 ). From then on, the arriv- ing slices are loaded to the free layer in turn. No internal buffers have been drawn to the figure, through which the bits are transmitted between the lower- level loop and eB. The figure shows the channel in question, which has become free at the same time in the following segment, and the slice 0 is being transmitted from the layer 0 to the loop 2. Thus, one had to wait for the release for four Ethernet packets. The layer will most advantageously be reserved so big that it will accommodate the biggest data unit that comes to question, which in case of Ethernet is 1560 bytes.

Figure 7B illustrates an exemplary case 702 for processing data processed by slices in a node according to an embodiment of the invention, especially in TM1 mode. The packet of the example contains 151 bytes, which is 1208 bits.

The slice in the Figure is 15 bits so 80 slices are 1200 bits and, consequentially, of the 1208 bits of the whole packet 8 remain in the last slice. In the last slice belonging to the packet, the R bit is thus 0 for the first time, and at the beginning of it there is a number which indicates the number of faultless bits, i.e. the number of bits belonging to the packet after the number, if the number is positive. If the number is negative, the last bits belonging to the packet were already in the previous slice. The number is recorded to the register "Valid Bits Count", and "Bit Counter" stays to indicate the first free place in the buffer. The number field in the last slice has to be so long that it accommodates the maximum length for the slice.

Processing in TM2 mode is otherwise similar to the one in Figures 7A and B, but "Valid Bit Count" is not in use and "Bit Counter" is constant (set upon implementation of the application). In TM3 (one transmitter) there will be no need for an external buffer, and space equivalent to one slice will be reserved to the internal buffer (Bo). The packet sets immediately off to the net loop (standard delay as consequence), "Bit Counter" is constant and "Valid Bit Count" is not in use in TM 3.

TM4 is a special case of TM1 (one transmitter). Data processing is similar to that in TM1 , but no external buffer is needed. Space for two slices can be reserved to the internal buffer (Bo), because the second last slice can be transmitted only after it becomes apparent from the last slice, whether the last or second last slice is incomplete. In TM4 the delay is constant, but one basic se- quene (1/64000 seconds) bigger in TM3. In TM4, "Bit Count" and "Valid Bit Count" are in use.

TM5 is associated with a bidirectional connection between two points, in which the processing in the main node is similar to that in TM4. Figure 8A illustrates an exemplary method 800 for transmitting data between buffers and for processing data in a node according to an embodiment of the invention, especially in TM1 transmission mode and AS mode, i.e. mode, in which data is transmitted between all loops.

In the example, the transmitting application (Source AN) is in the loop 1. The slice is immediately transmitted back to the own loop so that also possible devices connected to the connection nodes before the transmitter can read it. In addition, the slice is copied to the next loop via eB. However, in this mode, the data stream is terminated 802 before its return to the loop 1. SI mode differs from the one illustrated in Figure 8A in that in SI mode data is not copied to the next loop.

Figure 8B illustrates a second exemplary method 804 for transmitting data between buffers and for processing data in a node according to an embodiment of the invention, especially in TM5 transmission mode and AS mode, i.e. mode in which data is transmitted between all loops. In this example (differing from the previous one), the data stream circulates all loops and meets on the way the other party of the connection, which terminates 806 it (writes on it, if it has something to transmit). The differences can be seen in the figure at the tick (806) and in that there are two transmitters (Source AN1 , Source AN2), which naturally also are receivers. In the SI mode there is no difference compared with the example in Figure 8A (TM1 ) mode (mere arrow 808, i.e. data does not come out of the loop).

A so-called multi frame is known from several data communications protocols (PDH, Plesiochronous Digital Hierarchy (standard ITU-T G.703, G.704), and SDH, Synchronous Digital Hierarchy (G.707-709), with which slowly changing data is transmitted at certain intervals so that the multi frame consists of a multiply (e.g. 32) of an actual frame (repeated 8000 times a second). A field of the multi frame is concatenated as a frame. Likewise in the present invention, the initial addresses of the fields in each 128 channels are transmitted during 512 frames in 128 successive primary carrier frames (CF), which is typically repeated 64000 times a second. It has to be noted that the multi frame (MF) may typically also include other parameters.

PDH and SDH mentioned above are isochronous protocols, and they transmit a standard-length frame at standard intervals (8000 times a second).

Above, there have been shown only some embodiments according to the present invention. The principle of the invention can naturally be varied within the scope of protection defined by the patent claims, for example, concerning details of the implementation and ranges of use. Especially it has to be noted that the present invention is based on the electronic components, transmitter- receivers, connectors, cables and light fibres according to the Ethernet standard, and signal levels, forms and frequencies are in accordance with the Ethernet standard, in which the physical layer in the OSI model is Ethernet's, but the link layer is the invention's own. However, the invention can be varied in accordance with requirements of other possible data transmission systems and/or standards. Also the Ethernet connection has been shown as an example of the user's device connection. The connection can also be, for example, USB. The connection can, for example, be replaced by a wireless Bluetooth link.

Because transmission through the nodes of the invention is transparent and delays are of standard length, it is thus not possible to carry out a retransmis- sion in case of errors. However, the user's data can go through very many nodes and bit errors may occur. That is why an error correction code can be added to all transmission modes. Correction will be made on the slice level. This will increase the need for capacity by a few bits. The correction will be taken into use when needed. Audio or video applications do not suffer from rarely occurring mistakes.

Claims

1. System (100) for transmitting data asynchronously in a data transmission network (102), the data transmission network comprising at least two nodes (104, 108) namely at least one main node (104, 108) and at least one connection node (108, 109), the data transmission network comprising also at least one loop (106a, 106b) administered by the main node, to which loop the main node is adapted to generate a primary carrier frame (400) transmitting data in the loop, the loop comprising at least one connection node (109), to which at least one de- vice (110) is connected, the device being associated with an application, to which a channel has been assigned from the loop, and in which loop data is transmitted to one direction in the carrier frame via at least one channel (3, 7, 11 , 12, 13, 23, 25, 127), in which the channel is a data transmission resource assigned to the application and separated from the transmission capacity of the data transmission network in a time-shared manner, and in which system the transmitted data unit is divided into slices the size of the data field defined for the channel and transmitted in equal time periods , characterised in that when transferring data according to any data transmission protocol relating to the said application between at least two nodes (104, 108, 109), each slice of the data unit divided into slices is transmitted to the receiver transparently as a bit string independent of the data transmission protocol in the data field of the carrier frame without touching the contents or structure of the data unity to be transmitted and without reading its possible address and length fields, and the connection circuit (109a) in the data-transmitting node is adapted to provide as output a first electric signal to be transmitted in the bit stream transmitted in the data transmission network, the signal indicating the starting point for the data unit in the bit stream transmitted in the data transmission network, the said first electric signal being adapted to control the receiving node to form a timely electric signal indicating the beginning of the bits belonging to the data unit in the connection circuit (109a) of the receiving node.

2. System according to claim 1 , in which the connection circuit (109a) of the data-transmitting node is adapted to provide as output a second electric signal to be transmitted in the bit stream transmitted in the data transmission network, the signal indicating the length of the data unit, and in which case the system is adapted to transmit the said second electric signal in the bit stream transmitted in the said data transmission network through the nodes in the data transmission network to at least one data receiving node, the said second electric signal being adapted to control the receiving node to read the length of the said transmitted data unit.

3. System according to claim 1 , in which the connection circuit (109a) of the data-transmitting node is adapted to provide as output a third electric signal to be transmitted in the bit stream transmitted in the data transmission network, the signal indicating the end point of the data unit in the bit stream transmitted in the data transmission network, the said third signal being adapted to control the receiving node to form a timely electric signal indicating the end of the bits belonging to the data unit in the connection circuit of the receiving node.

4. System according to claim 1 , in which the said first electric signal is adapted to indicate, in addition to the starting point of the data unit, also the end position of the data unit in the bit stream transmitted in the data transmission network, the said first electric signal being then adapted to control the receiving node to form a timely electric signal indicating the beginning of the bits belonging to the data unit and also a timely electric signal indicating the end of the bits belonging to the data unit in the connection circuit of the receiving node.

5. System according to claim 1 , in which the said channel is commonly used by at least two devices (110) so that the first bit that precedes temporally the data field is a reservation bit (R) indicating whether the said shared channel is currently reserved or free.

6. System according to claim 5, in which the reservation bit (R) is temporally followed by a delimiter bit (D), which is active only when the data field of the primary carrier frame of the channel contains the last bits of the sliced data unit.

7. System according to claim 6, in which the delimiter bit (D) is temporally followed by a fixed number of bits indicating the number of significant bits in the last slice relating to the sliced data unit to be transmitted in the data field of the primary carrier frame reserved for the channel assigned to the application.

8. System according to claim 6, in which the reservation bit (R) is set inactive only in the next data field of the primary carrier frame after the transmission of the last bits relating to the sliced data unit.

9. System according to claim 8, in which setting the reservation bit (R) inactive has been adapted to cause that the respective control signal will become inactive in the receiver node.

10. System according to claim 7, in which the delimiter bit (D) is set active only in connection with the data field of the next primary carrier frame, if the bits of the latest sliced data unit cannot fit to the data field of the channel's primary carrier frame, when the data indicating the number of last bits in the sliced data unit is added in a time-shared manner in front of the said last bits of the last sliced data unit, in which case the number of bits is indicated with a minus sign indicating that the data representing the number of bits concerns temporally the preceding slice received.

11. System according to claim 5, in which the reservation bit (R) is arranged to indicate the beginning of the data field in the transmitted sliced data unit especially when the transmitted data unit is a frame with standard length.

12. System according to any of the preceding claims, in which the main node is adapted to time the transmission of the primary carrier frame and to fill its neces- sary fields with data delivered by different data transmitting nodes and to copy the necessary fields from the carrier frame arriving from the loop to be transmitted again to the loop.

13. System according to any of the preceding claims, in which the main node is adapted to connect and administer several loops, to which the main node is adapted to generate a primary carrier frame (CF) transmitting data in the loops.

14. System according to any of the preceding claims, in which the main node is adapted to connect several loops administered by it to at least one higher-level loop as a bigger system, the higher-level loop being administered by at least one main node associated with the higher loop.

15. System according to claim 14, in which the main node administering at least one higher-level loop connects the said loops and the associated main nodes to at least one external data network.

16. System according to claim 1 , in which the application is one of the following: TV, sound reproduction system, image reproduction system, system consisting of at least one computer and/or peripheral device associated with the computer, and telephone system.

17. System according to claim 1 , in which the data transmission speed is altered (Variable Bit Rate) as the amount of transmitted data changes as a function of time.

18. System according to claim 1 , in which the node consists at least two buffers (502, 504) per at least one lower-level loop administered by the said loop, the one being an input buffer (502) and the other being an output buffer (504), and further at least three separate buffers (506, 508, 510), of which at least two (506, 508) are between the said node and the upper-level loop, with which the said node is associated, receiving data from the said upper-level loop and delivering data to the said upper-level loop, and of which external buffers at least one (510) is arranged as a buffer between at least two loops administered by the said node.

19. System according to claim 18, in which the buffer has an own pointer for each channel.

20. Method for transmitting data asynchronously in a data transmission network (102), the data transmission network comprising at least two nodes (104, 108), namely at least one main node (104, 108) and at least one connection node (108, 109), the data transmission network comprising also at least one loop (106a, 106b) administered by the main node, to which loop the main node generates a carrier frame (400) transmitting data in the loop,

the loop comprising at least one connection node (109), to which node at least one device (110) is connected, the device being associated with an application, to which a channel is assigned in the loop, and in which loop data is transmitted to one direction in the primary carrier frame via at least one channel (3, 7, 11 , 12, 13, 23, 25, 127),

in which the channel is in a data transmission resource assigned to an application and separated from the transmission capacity of the data transmission network in a time-shared manner, and in which method the data unit to be transmitted is divided into slices of the size of the size of the data field defined for the channel and to be transmitted in equal time intervals,

characterised in that when transferring data according to any data transmission protocol relating to the said application between at least two nodes (104, 108, 109), each slice of the data unit divided into slices is transmitted transparently to the receiver as a bit string independent of the data transmission protocol in the data field of the primary carrier frame without touching the contents or structure of the data unity to be transmitted and without reading its possible address and length fields, and the connection circuit (109a) in the data-transmitting node is adapted to provide as output a first electric signal to be transmitted in the bit stream transmitted in the data transmission network, the signal indicating the starting point for the data unit in the bit stream transmitted in the data transmission network, the said first electric signal being adapted to control the receiving node to form a timely electric signal indicating the beginning of the bits belonging to the data unit in the connection circuit (109a) of the receiving node.