WO2001084783A1 - Transmission de donnees dans un reseau point a multipoint - Google Patents

Transmission de donnees dans un reseau point a multipoint Download PDF

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Publication number
WO2001084783A1
WO2001084783A1 PCT/EP2001/003982 EP0103982W WO0184783A1 WO 2001084783 A1 WO2001084783 A1 WO 2001084783A1 EP 0103982 W EP0103982 W EP 0103982W WO 0184783 A1 WO0184783 A1 WO 0184783A1
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WO
WIPO (PCT)
Prior art keywords
terminal
transmission
permit
data
central node
Prior art date
Application number
PCT/EP2001/003982
Other languages
English (en)
Inventor
Rolf Engstrand
Original Assignee
Telefonaktiebolaget L.M. Ericsson
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from EP00109345A external-priority patent/EP1152572A1/fr
Priority claimed from US09/563,952 external-priority patent/US6671260B1/en
Application filed by Telefonaktiebolaget L.M. Ericsson filed Critical Telefonaktiebolaget L.M. Ericsson
Priority to AU2001262181A priority Critical patent/AU2001262181A1/en
Publication of WO2001084783A1 publication Critical patent/WO2001084783A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/04—Selecting arrangements for multiplex systems for time-division multiplexing
    • H04Q11/0428—Integrated services digital network, i.e. systems for transmission of different types of digitised signals, e.g. speech, data, telecentral, television signals
    • H04Q11/0478—Provisions for broadband connections
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/50—Allocation or scheduling criteria for wireless resources
    • H04W72/56—Allocation or scheduling criteria for wireless resources based on priority criteria
    • H04W72/566—Allocation or scheduling criteria for wireless resources based on priority criteria of the information or information source or recipient
    • H04W72/569—Allocation or scheduling criteria for wireless resources based on priority criteria of the information or information source or recipient of the traffic information
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/54—Store-and-forward switching systems 
    • H04L12/56—Packet switching systems
    • H04L12/5601—Transfer mode dependent, e.g. ATM
    • H04L2012/5603—Access techniques
    • H04L2012/5604—Medium of transmission, e.g. fibre, cable, radio
    • H04L2012/5607—Radio
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/54—Store-and-forward switching systems 
    • H04L12/56—Packet switching systems
    • H04L12/5601—Transfer mode dependent, e.g. ATM
    • H04L2012/5603—Access techniques
    • H04L2012/5609—Topology
    • H04L2012/561—Star, e.g. cross-connect, concentrator, subscriber group equipment, remote electronics
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/54—Store-and-forward switching systems 
    • H04L12/56—Packet switching systems
    • H04L12/5601—Transfer mode dependent, e.g. ATM
    • H04L2012/5629—Admission control
    • H04L2012/5631—Resource management and allocation
    • H04L2012/5632—Bandwidth allocation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/54—Store-and-forward switching systems 
    • H04L12/56—Packet switching systems
    • H04L12/5601—Transfer mode dependent, e.g. ATM
    • H04L2012/5672—Multiplexing, e.g. coding, scrambling
    • H04L2012/5675—Timeslot assignment, e.g. TDMA

Definitions

  • the inyention relates to the exchange of data between communication devices in a point-to-multipoint configuration. It has particular relevance to packet- switched communication systems.
  • MAC media access control
  • the central node In point-to-multipoint communication systems wherein a central node transmits and receives data to and from multiple terminals, the central node must utilise a mechanism to determine which of the terminals is allowed access to the transmission medium at any one time. This mechanism is commonly termed the media access control (MAC) protocol.
  • MAC media access control
  • the MAC In packet or cell switched networks, such as ATM networks, the MAC typically divides the transmission bandwidth into time slots. These slots are then allocated to terminals for transmitting data. Since the central node controls access to the transmission medium, it sends information or transmission permits to the terminals specifying in which future time slot data may be sent. Permits may be sent as part of payload data sent to the terminals from the node. Alternatively, the central node may send one or more permits separately, for example at scheduled times.
  • MAC media access control
  • transmission permits are allocated only to those terminals that have traffic awaiting transmission.
  • Information about the amount of data requiring transmission is sent to the central node. This information may be tagged onto payload data transmitted to the central node in response to a permit allocating a time slot. Alternatively, the information may be sent as a part of a separate packet in response to a polling request from the central node.
  • the central node transmits frames of data downstream to said terminals in timeslots and said terminals transmit data packets upstream in timeslots allocated by transmission permits contained in the downstream data.
  • the central node reserves a time period in the future downstream data stream during which data destined for that terminal will be blocked from transmission.
  • the reserved time period commences at a time location in the future data stream and has a duration, such that data transmitted in a timeslot immediately following the reserved time period will arrive at the terminal after the same has terminated transmission of data in response to the permit.
  • the time period corresponds at least equal to the time required by the terminal for_ transmitting a data packet.
  • the processing delay is the time required for a terminal to commence outputting a data packet after receipt of a permit. If the time required to terminate transmission of the data in the downstream frame containing the permit is greater than the processing delay, the remaining data must either be always destined for another terminal, or alternatively, a priority must be established between the data packet in the frame and the permit. When the permit, or rather or return data packed from the terminal, has a higher priority, the permit will be transmitted and the data packet will be delayed.
  • the central node When permits are issued on a regular or scheduled basis, such that their transmission timeslot or the interval between transmission timeslots is known in advance, the central node preferably also blocks a further time period immediately before the timeslot containing a scheduled permit. In this way it can be ensured that a scheduled permit will always arrive at the destination terminal after this terminal has finished transmitting data in response to an earlier permit.
  • the duration of this second time period preferably corresponds to the terminal processing time and the time required for transmitting a data packet. In other words, transmission to the terminal is blocked for a period which covers the time required by a terminal to receive, process and respond in full to a permit from the central node.
  • the invention further resides in an arrangement in the central node that includes means for selecting transmission permits and data packets for transmission in each timeslot to said terminals.
  • Means are further provided for storing a schedule of the downstream transmission timeslots, wherein for each terminal, the schedule is blocked for a time period after transmission of a permit to said terminal. The time period terminates at an interval after transmission of the permit that corresponding to the delay required in the terminal for receiving the permit and outputting a data packet in response to the permit.
  • the selecting means are adapted to consult the storage means and select transmission permits and data packets for terminals that are not blocked for a current time slot.
  • Fig. 1 schematically depicts a point-to-multipoint radio link in an ATM network
  • Fig. 2 schematically depicts the handling of transmission requests between the central node and terminals
  • Fig. 3 schematically illustrates the framer for selecting data packets for transmission from the central node to the terminals;
  • Fig. 4 schematically illustrates the transmission timing between the central node and a terminal;
  • Figs. 5 to 18 schematically illustrate the procedure for reserving time slots to prevent simultaneous reception and transmission at the terminals.
  • the ATM radio network depicted in Fig. 1 includes a central node 10 and multiple remote terminals 20.
  • the ATM network transports ATM cells across the transmission medium between the central node 10 and the terminals 20, which are situated at different distances from the central node.
  • the central node includes a network control unit (NCU) 110, which controls the formatting of data and also access to the transmission medium.
  • the NCU includes a framer block 111 for handling the queuing of ATM cells and the formatting of these cells into the proprietary radio frame format used in the downstream transmission direction, and a deframer block 112 decoding the frames transmitted from the terminals into ATM cells.
  • a device processor (DP) 113 is also contained in the NCU 110 for handling the signing-on of terminals 20, fault management, performance monitoring and communication with other processors in the network.
  • the central node 10 further includes a radio unit (RAU) 120, which handles the transmission, reception and control of the radio link.
  • RAU radio unit
  • Each ATM cell or data packet includes a header containing a destination address.
  • all transmission is from the central node 10.
  • All terminals 20 decode the transmission and determine from the addresses in the cell headers whether a user connected to the terminal 20 is the intended recipient of the cell.
  • the terminals 20 transmit data to the central node 10. Upstream transmission is timed such that the node 10 receives signals from only one terminal at a time. This is achieved by dividing the upstream transmission path into time slots for the transmission of a single ATM cell. Only one terminal is permitted to transmit in any single time slot.
  • the MAC function 114 in the central node 10 issues permits indicating which terminal may transmit in a future time slot.
  • the transmission medium bandwidth is allocated according to need.
  • the terminals 20 send requests to the central node 10 indicating the traffic awaiting transmission. These requests are also issued in response to a permit or polling by the central node.
  • polling is performed regularly, preferably according to a defined schedule.
  • a request from a terminal 20 occupies 1/8 of an ATM cell time slot. The request from one terminal is thus sent in a mini-slot, with eight mini-slots making up a single time slot. If more than 8 terminals are signed on to the central node 10, these are grouped into groups of eight terminals. Each poll permit then addressed one group of eight terminals.
  • Fig. 2 illustrates schematically how requests are handled in the network of Fig. 1.
  • the central node 10 holds an occupancy table 100 in its NCU 110 which is accessed by the MAC block 114 .
  • Each terminal 20 contains queue buffers 21.
  • the queue buffers 21 for three terminals numbered 0, 1 and 2 are shown in Fig. 2.
  • two types of data are transmitted over the link. These include constant bit rate (CBR) services and unspecified bit rate (UBR) services.
  • CBR constant bit rate
  • UBR unspecified bit rate
  • the queue buffers 21 in the terminals 20 include two separate buffers for cells of each type of service.
  • the occupancy table 100 in the central node 10 indicates the number of cells of each service type awaiting transmission for each terminal 20.
  • each terminal 20 in the addressed group of eight terminals sends in turn information concerning the status of the queue buffers.
  • the first mini-slot is used by terminal 0, which sends the information 1, 27 indicating that a single CBR cell and 27 UBR cells are awaiting transmission.
  • terminal 1 sends the status of its queue buffers, 1, 0. The following six terminals then follow suit until the full time slot is used.
  • Time slots in both the upstream and downstream directions are designated for different functions.
  • some slots are used for polling, i.e. for sending requests of the queue status of the terminals, some for transmitting permits and some for transmission of ATM cells.
  • some time slots are used for the transmission of requests and some for the transmission of ATM cells.
  • Some timeslots may also carry dummy data, when no data is awaiting transmission.
  • the designation of each timeslot may be defined by a cyclical plan or schedule, designed to make optimal use of the bandwidth for the number of terminals 20 signed on.
  • the central node 10 uses the occupancy table to determine which terminals should be permitted to transmit, and also what type of data this terminal may transmit. Different permits are used for CBR and UBR cells. As long as the occupancy table 100 indicates that CBR service requests are unserviced, these will be handled first. Only when no CBR service requests are indicated in the occupancy table 100 will permits be sent in response to UBR service requests. If more than one terminal has unserviced requests of the same priority, that is for either CBR or
  • UBR services one request for each terminal will be handled in a round robin fashion, in numerical order.
  • a CBR permit will be sent first to terminal 0, then to terminal 1.
  • a UBR permit will be sent to terminal 0 and then to terminal 2.
  • the central node will then send a further UBR permit to terminals 0 and 2 in that order until either no further requests are recorded, or other requests arrive.
  • a downstream frame composed in the central node includes a transmission permit and a data packet.
  • the NCU 110 must also determine which terminal is to receive the data packet. This is determined in a similar fashion to the permits. This is illustrated in Fig. 3.
  • the framer 111 holds a queue buffer 211 for the various types of data that may be assembled into a downstream frame. As for upstream data, this will include CBR and UBR service data for each terminal, TO, Tl, etc. This service data is received as traffic by the node and is stored in an intermediate buffer before being sorted into the different types. Control information, for example defining the bit rates for any particular service will also be received by the framer 111. Although not shown in Fig.
  • control information that is not received as traffic, but originates from other elements within the central node may also be assembled into a downstream frame.
  • a priority multiplexer 212 selects the various data according to priority and sends this to a framer 213 for the final assembly.
  • the priority multiplexer 212 is further controlled by the MAC function 114 to select data packets as a function of the terminals to which they are destined as will be described below. As for the permits, data relating to a CBR service will have priority over data for a UBR service. Also control data will generally have the highest transmission priority.
  • Permits issued for polling for control information from the terminals that are signed on are scheduled and queued with the highest priority.
  • a further type of permit is issued by the central node for timeslots in the upstream direction.
  • this terminal will need to use some upstream timeslots for sending a predetermined pattern to enable the central node 10 to perform measurements for synchronisation and attenuation.
  • a timeslot carrying this kind of information is called a ranging slot.
  • the central node 10 should ideally allow continual use of all timeslots both downstream and upstream. Transmission and reception of data at the central node 10 occurs simultaneously. This is possible by using different carrier frequencies for data in the two directions.
  • the radio unit RAU 120 of the central node 10 contains radio transmission and reception circuitry and a filter arrangement to prevent interference between the receiver and transmitter.
  • the central node 10 In order that the upstream data received from different terminals 20 fits into a continual sequence of time slots, the central node 10 must know the round trip delay between transmission of a permit and reception of a data packet in response to the permit for each terminal. In the present system, a maximum delay is selected for all terminals. This maximum delay corresponds to a specified distance from the central node 10.
  • a terminal 20 If a terminal 20 is located at a distance from the central node which is nearer than this specified distance, it will be instructed by the central node to add a delay to its processing, such that the round trip delay of each terminal 20 is the same.
  • the central node 10 When the central node 10 is advised of a new terminal connected to the network it measures the initial transmission delay by issuing a ranging permit and determining when the response In is received. If the response arrives too soon to fit into the correct time slot in the upstream data stream, the central node 10 sends a further message instructing the terminal 20 to add a specified delay before responding to permits. In order to prevent collisions, dummy data is transmitted before and after a ranging permit, since the central node 10 cannot know when it will receive a response.
  • Each terminal 20 also contains transmission and reception circuitry.
  • the terminals do not contain a filter arrangement for preventing interference between these elements. Since such a filter arrangement conventionally represents a major proportion of the total cost of such terminals, the cost of installing a new terminal is substantially reduced. There is however, still a danger that the reception circuitry may interfere with transmission when both circuits are active simultaneously.
  • this is prevented by controlling the timing of data reception and transmission of any one terminal such that the two never occur simultaneously. Since transmission by any terminal occurs only when permitted by the central node 10, this node times the issue of permits such that transmission and reception by any terminal cannot overlap.
  • the NCU 110 in the central node 10 generates a record of when any one terminal is likely to be either receiving or transmitting data.
  • the central node 10 can avoid transmitting data that will arrive at the terminal when this is already transmitting data and likewise, the central node can avoid transmitting a permit that will provoke a transmission response from the terminal when other data with higher priority is scheduled to arrive at the terminal.
  • Fig. 4 shows the timing between the central node 10 and a terminal 20.
  • Figs. 5 to 18 show a table 115 stored in the central node 10 for controlling permit issues to each terminal connected to the network.
  • a permit is sent from the central node 10 to the terminal 20. This is received at time 2.
  • the terminal 20 requires a finite amount of time to process the permit before starting to issue a data packet in response.
  • the real processing time for each terminal will be the same and known to the central node 10.
  • the terminals 20 will impose possibly different, additional delays depending on their relative distances from the central node 10. If the central node is not informed in advance about the real processing delay within a terminal 20 this may be communicated to the node 10 in the ranging message sent in reply to the ranging permit described above.
  • the processing delay indicated between times 2 and 3 is the total delay for processing a permit before commencing transmission of a data packet.
  • the terminal 20 commences transmission of a data packet in the allocated time slot. Transmission is terminated at time 4.
  • a corresponding shaded time period A is marked as blocked in the downstream data schedule. This blocked time period A is thus delayed with respect to the time the permit was transmitted by a time corresponding to the terminal processing delay. It also has a duration equal to the transmission time for the data packet. The next permit destined for this terminal must therefore arrive either before time 3 or after time 4. This naturally assumes that two permits will never be transmitted so close in time to one another that the permitted data packets overlap. This mechanism is intended to prevent simultaneous transmission and reception at the terminal. It is assumed as given that the system will be arranged to prevent separate items of data being either received or transmitted at the same time.
  • a permit will arrive at the terminal 20 after time 4. Taking account of the transmission delay between the central node 10 and the terminal, the next permit will thus be sent after time 5.
  • polling permits for obtaining transmission requests from the terminals are issued by the central node 10 at regular or scheduled intervals. These permits have the highest priority. It will be understood that other permit types may also be issued on a scheduled basis, and not on the basis of queue status information. Such permits may be used for enabling transmission of delay-critical services, such as emulated circuit-switched traffic services.
  • a permit is scheduled at time 6. In order that this scheduled permit does not encounter interference at the terminal, it must be ensured that all transmission in response to an earlier permit has terminated. However, if a permit were sent at time 5 as indicated with a dashed line, the transmission of a data packet would overlap with the arrival of the scheduled permit. In order to ensure no overlap, a time interval corresponding to the transmission time of a data packet must be held free before transmission of the scheduled permit. This time interval is positioned in advance of the scheduled terminal.
  • the start of the blocked time is defined by the following expression: scheduled time of permit - terminal processing delay - length of permitted data packet.
  • the end of the blocked time period is defined by the expression: scheduled time of permit - terminal processing delay + length of the scheduled permit.
  • This second blocked time period is indicated by the shaded area B in the figure.
  • a permit for another terminal is selected for transmission in this time slot.
  • the scheduled permit also gives rise to a blocked time period later in the downstream data stream. This time period corresponds to the time when the terminal is transmitting the data packet in response.
  • the associated blocked time periods must be reserved in advance. This reservation must occur when the central node is deciding on the transmission of a permit and the due time of a scheduled permit is less than the processing delay in the terminal + maximum length of the permitted packet after the transmission time of the permit being considered.
  • a downstream frame consists of one data packet preceded by one permit. If the timing arrangement illustrated in Fig. 4 is to achieve the separation in time of transmission and reception at a terminal, data packets must also respect the blocking imposed at the central node 10. If the time between sending a permit, for example at 1 and the start of the blocked time period A, in other words the processing delay in the terminal, is shorter than the time required to transmit all the data packet with the permit, then the data packet cannot be sent to the same node as the permit, as this would otherwise overlap the blocked period A. In this case, a frame must always be organised such that the permits and payload data are not destined for the same terminal.
  • a priority algorithm may be employed, whereby either a permit or a data packet would be sent with priority, such that the other permit or data packet would be delayed by at least one time slot.
  • the MAC 114 would decide on the priority and control the selection from the occupancy table 100 and the queue buffers 211 by the priority multiplexer 212 accordingly.
  • the blocking period A is delayed relative to the transmission time of the permit by a time equivalent to the processing delay in the terminal. Thus there will always be time for the data packet to be transmitted before the terminal 20 commences transmission in response to the permit.
  • a table 115 for controlling the issuing of permits to the terminals is illustrated. Only four terminals are connected to the central node 10, these are labelled terminals 1, 2, 3 and 4. In practice many more terminals might communicate with a single central node.
  • the NCU 110 of the central node 10 will then include timeslot entries for all signed-on terminals.
  • each terminal 20 It is assumed that the sign-on procedure for each terminal 20 is completed and that the central node 10 has knowledge of the processing delay for each terminal 20.
  • the terminals are listed in the first column of the table 115.
  • the processing delays of the terminal 20 are listed. These delays correspond to the time period between start of reception of a permit from the central node to start of transmission of a data packet in response to this permit.
  • the backlog is given in the third column.
  • the requests received for each terminal are given in the fourth column.
  • a downstream frame consists of one data packet preceded by one permit.
  • the downstream frame is thus 10 time units long.
  • a timeslot is the period of time required for the transmission of a full frame. One timeslot is thus equal to 10 time units.
  • Fig. 5 indicates the reservation for timeslots 1 to 6 (time unit 0 to 59).
  • Terminal 1 is to receive scheduled permits with 40 time unit intervals, starting in slot 1 (time 0). These permits will thus be sent in slots 1, 5, 9, 13 and so on.
  • timeslots preceding the scheduled permit must be blocked for permits to the same terminal, as these will provoke a transmission response that may occur simultaneously with the arrival of the scheduled permit. Since the table is concerned only with time starting from time unit , there is no need to reserve time before the first scheduled permit. However, the second scheduled permit sent in timeslot 5 will generate blocked time. Since the scheduled time for transmitting the scheduled permit is 40 time units, the processing delay for
  • This range lies in timeslot 3. This period is thus marked with 's' to indicate that permits to Terminal 1 are blocked by a future scheduled permit.
  • Requested permits are distributed in a round-robin fashion in ascending order of the terminal numbers.
  • the terminal which is next in turn for a requested permit is marked with the character '@'.
  • Terminal 1 is the next terminal to receive a requested ATM permit.
  • the first column thus contains @ in the row corresponding to Terminal 1.
  • a scheduled permit for terminal 1 is then issued at time 0 as dictated by the schedule. This causes permit blocking in the range 17 to 26, i.e. between the time when Terminal 1 starts transmitting the data packet in response to the scheduled permit and the time when transmission of the data packet, which is 9 time units in length, is terminated. This time period corresponds to the permit timeslot 3. This is then blocked by insertion of 'i' to indicate blocking by an issued permit.
  • the table is then completed by recording the scheduled permits issued to Terminal 1 in the final row, by indicating the terminal number followed by '(s)' for a scheduled permit.
  • Timeslot 2 As shown in Fig. 6.
  • This table now includes timeslot 7. No scheduled permits are to be issued in timeslot 7, so this timeslot remains unreserved for the present.
  • timeslot 2 no permit is scheduled. This means that a permit request may be serviced.
  • Terminal 1 is the next terminal marked to receive a requested permit, so a permit is issued to this terminal.
  • a ' 1' is entered in the final row of the table 115 corresponding to timeslot 2 indicating that a permit has been issued to
  • Fig. 7 shows the status for the next timeslot, 3. No scheduled permits are indicated in timeslot 3. Terminal 2 is next in line for a requested permit. This timeslot is not blocked for terminal 2, so a permit is issued and entered in the final row under timeslot 3. This permit generates blocking over the range 26 to
  • Terminal 3 is next in line for a requested permit. This generates blocking in timeslot 7.
  • the request value for Terminal 3 is decremented to 2.
  • Terminal 4 is next line for a requested permit.
  • a permit is scheduled for terminal 1. This is issued and generates blocking in timeslot 7.
  • timeslot 6 shown in Fig. 10 no scheduled permits are indicated.
  • Terminal 4 is next in line for a requested permit.
  • a permit is issued and generates blocking in slot 11.
  • Terminal 1 is next in line for a requested permit.
  • timeslot 7 is blocked for permits for Terminal 1 both by an issued permit (i) and by a future scheduled permit (s).
  • the permit thus goes to the next terminal in ascending order, which is Terminal 2.
  • This generates blocking in timeslot 8.
  • Terminal 2 requests are decremented. Because Terminal 1 was missed in the normal round-robin order, it receives a backlog notation in column 3.
  • a backlog notation is services with a higher priority than the normal request permit order.
  • a permit is scheduled in timeslot 13. This is entered in the last row of the table 115. This future scheduled permit also generates a block in timeslot 11. For the current timeslot 8, Terminal 3 is marked for the next requested permit. However, Terminal 1 has a backlog notation and so must be serviced first. Terminal 1 thus receives a permit in timeslot 8 and generates a block in timeslot 10. The backlog and request count for terminal 1 are both decremented.
  • Terminal 1 is to receive a scheduled permit This is issued which generates blocking in timeslot 11.
  • Terminal 3 receives a request permit in timeslot 10 shown in Fig. 14. A block is entered for this terminal in timeslot 13. The requests for terminal 3 are decremented. Terminal 3 now has no outstanding requests.
  • Terminal 4 is marked for a request permit. However Terminal 4 is blocked in this timeslot. Terminal 1 is next in turn, however Terminal 1 is also blocked for timeslot 11. The permit thus goes to Terminal 2. A block is entered in timeslot 12 for terminal 3. The requests for Terminal 2 are reduced to 0. Terminals 4 and 1 both receive a backlog notation. Terminal 3 is marked as the next terminal for a request permit.
  • Fig. 16 timeslot 17 is shown.
  • a scheduled permit for Terminal 1 is marked in this timeslot.
  • a corresponding block is entered for Terminal 1 in timeslot 15.
  • the backlog notation of Terminal 4 means that this terminal receives a requested permit in timeslot 17.
  • a block is entered in slot 17. Both the backlog notation and request count for Terminal 4 is decremented. Terminal 4 now also has no outstanding requests for service.
  • a scheduled permit is issued to Terminal 1. This generates a block in timeslot 15.
  • the backlog request for Terminal 1 is services by issuing a requested permit. A corresponding block is entered in timeslot 16. From this point onwards dummy permits will be issued until another permit is scheduled, or the requests are incremented following a poll permit from the central node 10.
  • the table 115 illustrated in Figs. 5 to 18 has included only data for issuing permits. It will be understood that all other data sent to the terminals must be controlled in the same fashion. In the illustrated tables only the timeslots corresponding to blocked permits are noted for ease of understanding. However, for those cases when the actual blocked time periods overlap two timeslots, data packets addressed to the terminal in question may be blocked for both time slots. For Terminal 2, a further constraint exists. The processing delay of Terminal 2 is 6 time units. However, the time required to transmit or receive a data packet is 9 time units. Thus a permit sent in one timeslot to Terminal 2 will effectively block data packets to the same terminal for that time slot and also the following time slot.
  • a data packet for Terminal 2 can never be transmitted in the same time slot as a permit for Terminal 2.
  • time slots in the downstream data path may also be applied to other frame structures. Depending on the structure, more than one timeslot may be blocked by any single earlier permit or scheduled permit.
  • the terminals may accordingly turn off their receivers while transmitting data in order to prevent the risk of interference.
  • the central node 10 will ensure that no data is addressed to a terminal while this terminal is transmitting data. This effectively results in half duplex transmission at each of the terminals registered in the table. Costly filter circuitry for preventing interference between emitter and transmitter circuits within the same terminal is thus no longer required.
  • the table 115 may be used to block full duplex transmission to only some terminals in the network, in particular when traffic constraints at some nodes require full duplex transmission at least part of the time.
  • the possibility of half duplex transmission as described above may then be used at those nodes carrying lower traffic densities, or only for new terminals as a lower cost manner or extending the network.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Data Exchanges In Wide-Area Networks (AREA)

Abstract

La présente invention concerne un réseau point à multipoint comprenant un noeud central et une pluralité de terminaux reliés au noeud central par un support de transmission. Le noeud central transmet des trames de données en aval vers les terminaux précités dans des tranches de temps et les terminaux précités transmettent les paquets de données en amont dans des tranches de temps attribuées par des permis de transmission contenus dans les données aval. Lors de la transmission d'un permis de transmission à un terminal, le noeud central réserve dans le flux futur de données aval une période de temps au cours de laquelle la transmission des données destinées au terminal sera bloquée. La période de temps réservée commence à un emplacement temporel dans le flux futur de données et possède une durée telle que les données transmises vers le terminal dans la tranche de temps qui suit immédiatement la période de temps réservée arrivent au terminal après que ce dernier a terminé la transmission des données en réponse au permis. L'invention permet de la sorte d'empêcher de manière fiable qu'un terminal ne transmette et reçoive des données simultanément et, par conséquent, d'éviter les interférences entre l'émetteur et le récepteur d'un terminal sans avoir recours à des circuits de filtrage dispendieux.
PCT/EP2001/003982 2000-05-02 2001-04-06 Transmission de donnees dans un reseau point a multipoint WO2001084783A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2001262181A AU2001262181A1 (en) 2000-05-02 2001-04-06 Data transmission in a point-to-multipoint network

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
EP00109345A EP1152572A1 (fr) 2000-05-02 2000-05-02 Transmission de données dans un réseau point à multipoint
EP00109345.9 2000-05-02
US09/563,952 2000-05-02
US09/563,952 US6671260B1 (en) 2000-05-02 2000-05-02 Data transmission in a point-to-multipoint network

Publications (1)

Publication Number Publication Date
WO2001084783A1 true WO2001084783A1 (fr) 2001-11-08

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2001/003982 WO2001084783A1 (fr) 2000-05-02 2001-04-06 Transmission de donnees dans un reseau point a multipoint

Country Status (2)

Country Link
AU (1) AU2001262181A1 (fr)
WO (1) WO2001084783A1 (fr)

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
YAMAMOTO M ET AL: "ACCESS CONTROL SCHEME FOR MULTIMEDIA ATM WIRELESS LOCAL AREA NETWORKS", IEICE TRANSACTIONS ON COMMUNICATIONS,JP,INSTITUTE OF ELECTRONICS INFORMATION AND COMM. ENG. TOKYO, vol. E81-B, no. 11, 1 November 1998 (1998-11-01), pages 2048 - 2055, XP000790232, ISSN: 0916-8516 *

Also Published As

Publication number Publication date
AU2001262181A1 (en) 2001-11-12

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