Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
  • H04L12/40—Bus networks
  • H04L12/40052—High-speed IEEE 1394 serial bus
  • H04L12/40065—Bandwidth and channel allocation
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
  • H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
  • H04B7/2643—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile using time-division multiple access [TDMA]
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
  • H04L12/2803—Home automation networks
  • H04L12/2838—Distribution of signals within a home automation network, e.g. involving splitting/multiplexing signals to/from different paths
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
  • H04L12/40—Bus networks
  • H04L12/403—Bus networks with centralised control, e.g. polling
  • H04L12/4035—Bus networks with centralised control, e.g. polling in which slots of a TDMA packet structure are assigned based on a contention resolution carried out at a master unit
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W72/00—Local resource management
  • H04W72/20—Control channels or signalling for resource management
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
  • H04L12/2803—Home automation networks
  • H04L2012/284—Home automation networks characterised by the type of medium used
  • H04L2012/2841—Wireless
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W28/00—Network traffic management; Network resource management
  • H04W28/16—Central resource management; Negotiation of resources or communication parameters, e.g. negotiating bandwidth or QoS [Quality of Service]
  • H04W28/26—Resource reservation
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W72/00—Local resource management
  • H04W72/12—Wireless traffic scheduling

Definitions

• the invention relates to a method of transmission in a communication network in which at least certain connections are of the “wireless” type.
• the invention applies in particular in the field of home communication networks.
• a home communication network In a home communication network, several types of multimedia equipment can coexist. Some of this equipment can be connected to each other via cables. They then form a cable group.
• a home communications network can have multiple wired groups.
• a home communication network comprising several wired groups can also include wireless links. These wireless links are intended to connect the wired groups to each other. The number of wireless links must be sufficient for each wired group to be connected to at least one other wired group.
• Communication by wireless link can be constituted simply by a link between two devices in so-called 'point-to-point' mode. More generally, however, there may be several simultaneous point-to-point links in the same home network. More generally still, these wireless links can together constitute what is called a bridge in network terminology, that is to say a set of “multipoint-multipoint” links allowing the interconnection of cabled buses of the type IEEE1394-1995.
• the set of wireless links constitutes the domestic wireless communication network.
• the wired groups of the home communication network constitute the elements of the home wireless communication network.
• the available bandwidth is a limited resource and must be used as efficiently as possible.
• the efficient use of frequency is understood to mean any frequency allocation scheme which in particular minimizes the transmission of service data, such as for example data used for the coordination of network members (devices).
• the object of the invention is to propose an efficient method of accessing the wireless channel.
• the subject of the invention is a method of transmission in a transmission network comprising devices connected to the network, at least certain devices being connected by at least one wireless link, characterized in that:
• the wireless communications are carried out according to an isochronous TDMA type protocol, in which a frame is divided into time windows allocated on reservation to devices, - the allocation of a window of a frame to a device being such that it can be deduced by any device from the number of windows reserved per frame by each device and from at least one other parameter which identifies the device which made the request.
• an isochronous TDMA type protocol in which a frame is divided into time windows allocated on reservation to devices, - the allocation of a window of a frame to a device being such that it can be deduced by any device from the number of windows reserved per frame by each device and from at least one other parameter which identifies the device which made the request.
• the allocation of the windows of a frame is carried out according to an unequivocal method known to each device of the network, which can thus know this allocation using a minimum of parameters.
• each frame comprises a control window per device connected to the wireless part of the network, the position and order of the control windows in each frame being known by all the devices of this wireless part of the network.
• control windows are distributed in the frame and the positions of these windows are identical to each frame.
• position of the control windows in a frame is determined following a reset of the network, for example following the connection or disconnection of a device from the network.
• a change in topology induces a modification of the allocation of windows in a frame. This information should therefore also be disseminated.
• a serial number is assigned to it, the order of the control windows being deduced from the order of the numbers assigned to the devices of the network.
• this number is the "physical address" of a device.
• control window of an appliance optionally includes a window reservation data packet.
• a device receiving a data packet relating to a reservation includes it in its next control window.
• the reservation information is thus propagated step by step to all the devices on the network.
• each device transmits an echo-type signaling in its control window, said signaling being intended to be broadcast in the network and to be returned by each of the other devices, l 'device having sent the signaling determining from the signaling references by the other devices the duration of broadcasting of its reservation request in the network.
• a device By changing the network topology, we mean connecting or disconnecting a device connected to the wireless part of the network.
• a device learns using the above method the time it takes for one of its frames to reach all the devices on the network.
• a device having issued a window reservation request does not implement this reservation until after a duration corresponding to the duration of dissemination of its control data in the network.
• a frame further comprises a time interval whose use is governed by a contentious process and reserved for an asynchronous transmission.
• FIG. 1 schematically represents an example of a communication network in which the method according to this example is implemented
• FIG. 2a is a diagram illustrating an example of window distribution in a TDMA frame
• FIG. 2b is a diagram representing the power level received by a first device of FIG. 1 for each window of the frame of FIG. 2a,
• FIG. 2c is a diagram representing the power level received by a second device of Figure 1 for each window of the frame of Figure 2a
• FIG. 3 shows schematically the distribution of windows with service data and windows containing useful data in a frame
• FIG. 4 schematically represents several successive frames illustrating the propagation of an update of the allocation of the windows in the network of FIG. 1.
• the bit rate to be transmitted is dimensioned by the DV format (IEC 1083) up to 40 Mbit / s.
• a master element is an element which has decision-making power which it can apply to all the other elements of the network.
• the envisaged domestic wireless communication network is therefore a network constructed according to a distributed type architecture, that is to say without a master element.
• a first mechanism known per se which one could think of for managing the access of a device to the channel is the so-called 'FDMA' mechanism for 'Frequency Division Multiplex Access' in English.
• This mechanism amounts to separating the band into as many sub-bands as there are possible links.
• the power received by a device on the network varies according to the transmitting device, since the location of the devices is of a random nature in the rooms of the house. The distances between devices are therefore variable, as is the signal attenuation introduced by obstacles such as walls or furniture.
• each sub-band could be received by the same device with levels so disparate that the extraction by filtering of a sub-band becomes impossible, unless the spacing between sub-band and decrease the overall bandwidth.
• a second mechanism consists in sharing the channel by using an orthogonal spreading code - the so-called 'CDMA' mechanism for
• the mechanism implemented by the invention is the time sharing mechanism - or 'TDMA' for Time Division Multiplex Access in English - where each device takes possession of the total bandwidth during a time interval called 'window'. Speech, that is to say access to the channel, is then determined by a frame on which all the members of the network are synchronized.
• This TDMA mechanism is flexible in that the throughput of each link is determined by the proportion of windows allocated to it. The greater the number of windows per frame, the higher the speed of each link can be defined in detail.
• the TDMA frame is divided into useful and control data windows for each device on the network.
• the control windows convey, among other things, the information necessary to determine the allocation of the windows to each device of the wireless network, that is to say the identity of the emission sources for each window.
• the speed assigned to each link can be variable: one link between a VCR and a monitor can occupy 8 Mbit / s and another between the digital decoder and a personal computer can only occupy 1 Mbit / s.
• the configuration of the connections can change according to the establishments and interruptions. Some links have a constant maximum rate known in advance (especially when they carry an audio video stream), others are at variable and unpredictable rate (for example in the case of file transfer). It follows that the window allocation scheme is likely to change for each frame.
• the quality of the radio link between any two devices on the network can be very variable. This quality may be such that a given connection may have to be considered as non-existent.
• the link of any device on the network with any other device on this network is not necessarily justified. Connecting two monitors may, in a given context, not be of interest justifying the creation of a link. Given the potential existence of faulty links between at least some devices, even devices that cannot communicate must coordinate to access the wireless channel, i.e. they must be synchronized on the same frame TDMA. We are therefore faced with the problem of broadcasting the same TDMA frame - that is to say its structure and position - over a network with incomplete connectivity.
• FIG. 1 illustrates a network according to the present exemplary embodiment in which these problems may exist: Five devices, numbered from 1 to 5, are connected by wireless transmission in the following manner (Table 1): Wireless Link Device
• FIG. 2a illustrates a distribution of the windows of a frame (which includes nine windows) in the case of the network of FIG. 1.
• FIG. 2b illustrates the power received in each window, seen from the device 2.
• the power received of device 5 (dotted line) is too weak for the signal to be processed.
• FIG. 2c illustrates the power received by the device 5: the latter can only receive the emissions from the device 4.
• each device of the network uses the same radio frequency band. Due to the nature of these links, each device is sometimes a transmitter and sometimes a receiver (so-called 'half-duplex' operation in English). When it is not transmitting, a device must successively listen to different other parties. For this, it cannot implement conventional synchronization techniques on a continuous signal over time using servo-control, but must synchronize quickly on the fly with any packet received at the start of each window.
• This packet synchronization is all the more difficult as on the one hand the bandwidth of the received signal is large, which does not leave room for sophisticated synchronization implementations, and on the other hand that the source of transmission of the packet may change with each window.
• This almost instantaneous synchronization must adapt each time to different power levels, carrier frequency deviations and temporal positioning deviations.
• a wireless network interconnecting wired networks of the IEEE1394 type that is to say an IEEE1394 wireless bridge must transmit from a device in connection with the IEEE1394 node called "net cycle master" a clock 8 KHz.
• the specifics of the transmission of this clock in the context of cable networks interconnected by wireless links are the subject of a French patent application filed in the name of the Applicant on the same day as the present application and bearing the number 98 04982 .
• Each device on the network must warn any other device of its intention to use bandwidth, that is to say of the number of windows per frame that it wishes to use in the future. Only devices communicating directly with the device sending this information are notified directly. In order for this information to be known to all, it is, according to the present exemplary embodiment, repeated in the control windows transmitted by these devices directly reached, and it thus passes step by step to all the devices in the network.
• the method according to the invention therefore comprises the step of propagation step by step of the sharing information of the transmission channel among the various devices which constitute it.
• the speed of propagation of this information depends on the relative position of the control windows between them. If these are for example arranged in the frame according to the order of the numbers of the devices (see fig. 3 described below), the information coming from device 1 will be instantly transmitted to the devices reachable by wireless connection. who can repeat it during their control window during the same frame.
• Figure 3 is an example of the allocation of the windows of a frame to the five devices of Figure 1 where the control windows are distributed in the frame in the order of their numbering. The other windows of the segment reserved for useful data are distributed in the remaining space.
• information from a control window of the last device transmitting during the frame can only be transmitted to the other devices at the earliest during the next frame. This is for example the case of the device 5 in the case of the frame of FIG. 3.
• the depth of a device is defined as the number of frames necessary for information from this device to be broadcast throughout the network.
• the transmitter number 5 wants to announce its intention to modify the number of occupied windows, it will have to wait 2 frames after the current frame before being sure that all the members of the network will be notified. It is therefore only from the third frame following the current frame that it can effectively implement the new allocation. It will therefore be necessary to recalculate the depth of all members of the network each time a device is connected to the network or disconnected from the network.
• the format of this information must be concise: it is not possible to distribute the list of devices successively occupying each window in the frame for each of the windows.
• the number of windows occupied by each device is transmitted, coded according to a convention common to the devices and a parameter which characterizes the device which made the request.
• the coding convention in this list then allows each device to determine the frame configuration unambiguously.
• the frame contains 100 data windows and that the devices 1, 2, 3, 4, 5 occupy 10, 50, 10, respectively
• each device of the wireless network having a specific number is in this case the 10 windows of the member 1, then the 50 of 2, then the 10 of 3, then the 2 of 4 and finally the 5 of 5.
• the repetition of information in each control window only concerns a field of 5 times 7 bits, each group of 7 bits giving the number of windows relating to a given device. This convention is given as an example only, other conventions can also be used.
• FIG. 4 illustrates an example of the propagation according to the invention of the information relating to the allocation of windows to each device in the network of FIG. 1, a frame being structured as illustrated in FIG. 3.
• the device 4 determines a new allocation of windows. This new allocation is broadcast in the control window allocated to the device 4 in frame i, which is the first frame in FIG. 4. Since this control window is transmitted to the device 5, it is the first device which will be able to broadcast the updated allocation information, and this during frame i, to one or more devices with which it is in connection.
• the control window of the device 4 during the frame i is also received by the devices 1 and 2, but these can only propagate it during the frame i + 1.
• the device 4 determines a new allocation of windows. This new allocation is broadcast in the control window allocated to the device 4 in frame i, which is the first frame in FIG. 4. Since this control window is transmitted to the device 5, it is the first device which will be able to broadcast the updated allocation information, and this during frame i, to one or more devices with which
• Asynchronous and isochronous data can be transmitted in reservation mode as described above. There is a difference between the reservation for the transmission of isochronous and asynchronous data: in the case of asynchronous data, the reservation is renegotiated with each frame, while in the case of isochronous data, the reservation can only be negotiated when an isochronous connection is opened. In the case of asynchronous data, when transferring large volumes of data, it is preferable to use a reservation mode. On the other hand, in the case of small volumes of data, it may be advantageous to use a contention mode.
• the frame can be shared in an area reserved on the one hand for isochronous links (and asynchronous with reservation), and on the other hand in an area available for asynchronous links in contention mode.
• an asynchronous device does not have to wait for the broadcast of the number of packets that it intends to transmit shortly, but that it attempts transmission as soon as possible in the part of the frame reserved for the asynchronous transfer in compression mode. The receiving device is necessarily immediately informed since it is in direct radio contact with the sending device.
• Collision cases are managed by collision detection by the receiving device in the form of acknowledgment of receipt or non-reception and possible repetition after a random number of frames, a conventional process known as "Aloha".
• Aloha a conventional process known as "Aloha”.
• the reception function of the network devices know how to estimate the quality of a received packet, a probable assumption as soon as an error decoding by block is implemented.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Multimedia (AREA)
• Automation & Control Theory (AREA)
• Mobile Radio Communication Systems (AREA)
• Small-Scale Networks (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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Cited By (1)

Families Citing this family (32)

Citations (1)

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• 1999
  • 1999-04-21 JP JP2000545265A patent/JP4420561B2/ja not_active Expired - Fee Related
  • 1999-04-21 EP EP99914636A patent/EP1074099B1/fr not_active Expired - Lifetime
  • 1999-04-21 US US09/673,701 patent/US6816477B1/en not_active Expired - Lifetime
  • 1999-04-21 CN CN99805238.8A patent/CN1193517C/zh not_active Expired - Lifetime
  • 1999-04-21 DE DE69905242T patent/DE69905242T2/de not_active Expired - Lifetime
  • 1999-04-21 WO PCT/FR1999/000945 patent/WO1999055021A1/fr not_active Ceased
  • 1999-04-21 ES ES99914636T patent/ES2191425T3/es not_active Expired - Lifetime
  • 1999-04-21 AU AU33374/99A patent/AU3337499A/en not_active Abandoned

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