Classifications

• • 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
  • H04L12/5602—Bandwidth control in ATM Networks, e.g. leaky bucket
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/14—Relay systems
  • H04B7/15—Active relay systems
  • H04B7/185—Space-based or airborne stations; Stations for satellite systems
  • H04B7/18578—Satellite systems for providing broadband data service to individual earth stations
  • H04B7/18584—Arrangements for data networking, i.e. for data packet routing, for congestion control
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/14—Relay systems
  • H04B7/15—Active relay systems
  • H04B7/204—Multiple access
  • H04B7/212—Time-division multiple access [TDMA]
  • H04B7/2121—Channels assignment to the different stations
  • H04B7/2123—Variable assignment, e.g. demand assignment
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J3/00—Time-division multiplex systems
  • H04J3/24—Time-division multiplex systems in which the allocation is indicated by an address the different channels being transmitted sequentially
  • H04J3/247—ATM or packet multiplexing
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J2203/00—Aspects of optical multiplex systems other than those covered by H04J14/05 and H04J14/07
  • H04J2203/0001—Provisions for broadband connections in integrated services digital network using frames of the Optical Transport Network [OTN] or using synchronous transfer mode [STM], e.g. SONET, SDH
  • H04J2203/0028—Local loop
  • H04J2203/003—Medium of transmission, e.g. fibre, cable, radio
  • H04J2203/0037—Satellite
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J2203/00—Aspects of optical multiplex systems other than those covered by H04J14/05 and H04J14/07
  • H04J2203/0001—Provisions for broadband connections in integrated services digital network using frames of the Optical Transport Network [OTN] or using synchronous transfer mode [STM], e.g. SONET, SDH
  • H04J2203/0064—Admission Control
  • H04J2203/0067—Resource management and allocation
  • H04J2203/0069—Channel 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
  • H04L2012/5603—Access techniques
  • H04L2012/5604—Medium of transmission, e.g. fibre, cable, radio
  • H04L2012/5608—Satellite
• • 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
  • H04L2012/5636—Monitoring or policing, e.g. compliance with allocated rate, corrective actions

Definitions

• the present invention relates generally to resource control for satellite telecommunications networks implementing the asynchronous time technique ATM (Asynchronous Transfer Mode).
• ISDN-LB integrated broadband digital networks
• an information transfer unit called a "cell”, or also a “packet”, which is the basic element processed by all the means making up the network: terminals, multiplexers and switches.
• a cell an information transfer unit, called a "cell”, or also a “packet”, which is the basic element processed by all the means making up the network: terminals, multiplexers and switches.
• an ATM cell comprises 53 bytes, 48 being allocated for the transmission of information and 5 for routing the cell in the network,
• the mode selected is the "virtual circuit" mode for the transmission of cells through the nodes of the network, of the type comparable to X.25 networks.
• circuit mode the main component of the digital network integrating "narrowband" services, solve all of their problems of controlling resources when calls are admitted into the network: once a call is established, a resource with a fixed rate is reserved for a user.
• circuit mode would not be suitable for the ISDN-LB network for obvious reasons of underuse of the transmission means due to the very sporadic nature of certain communications.
• the ATM technique relies on packet mode communications and therefore on queue operation.
• oversizing the network or monitoring traffic step by step between network nodes is inconceivable for a broadband network in which the rates can reach a hundred Mbit / s.
• the control mechanisms significantly penalize transmission times and prove to be ineffective.
• One solution is to turn the problem upside down: if network congestion cannot be controlled (deterioration of transmission times), it must be avoided by resource allocation mechanisms when requesting access to the network.
• this precondition requires the evaluation of the resource to be reserved as a function of the service: the easier it is to determine a resource to be reserved for a service request with constant or variable speed, the more difficult it is to define a resource to be reserved for high sporadicity services.
• the request When a source user issues a call set-up request, the request must contain the address destination but also the capacity required to carry traffic associated with the request. This request is routed within the network, from one node to another, along paths determined by a routing algorithm. The call is accepted if there is at least one path between the source user and the destination such that each internodal link of said path has sufficient capacity to satisfy the transmission capacity required by the user.
• the problem is posed: what flow capacity must be required to carry very sporadic traffic?
• the temporal distribution of a satellite channel between several stations was mainly considered using two techniques:
• a frame format using the TDMA principle and used in the TDMA-Reservation protocol is shown in Fig. 2.
• a frame T r is divided into a data sub-frame STD r and a signaling sub-frame STS r .
• the sub-frames STD r and STS r are respectively allocated to the transmission of the data and to the transmission of allocation request / resource allocation response messages.
• the STS r sub-frame has a variable length as a function of the line bit rate.
• the TDMA-Reservation protocol consists of the transmission of a reservation message in an assigned ITS i interval of an STS signaling sub-frame r after complete reception of d '' a burst of cells generated by a sporadic service from a user station.
• a central station SC receiving all the reservation messages originating from earth stations, allocates the required capacity to the earth station ST i when sufficient transmission capacity is available.
• This TDMA-Reservation protocol advantageously informs the central station SC by means of the signaling sub-frame STS r on a precise allocation request since the earth station only issues its request after complete reception of the burst, and therefore taken taking into account its length.
• this "store and forward" management which consists in storing the entire burst of cells before processing an allocation request, is not satisfactory for services introducing very long bursts since such management induces delays in transmission unacceptable for certain services (interrogation of image banks).
• the present invention aims to remedy the aforementioned drawbacks and more particularly to provide a method for reducing the time required for resource allocation, by transmitting a resource allocation request in the signaling subframe for a burst of a sporadic connection well before this burst is completely received by the earth station. For each burst of the connection, a resource allocation request is then transmitted by an earth station to the central station before complete reception in the earth station of said burst. Since no information on the lengths of the bursts of the connection can then be transmitted respectively in the allocation requests, the invention provides an algorithm allowing to selectively accept or refuse the establishment of a connection. After acceptance of the connection, the resource allocation requests relating to the bursts of this connection are then satisfied successively, whatever the traffic.
• a method of allocating resources to earth stations by a central station in an asynchronous time telecommunications network by satellite the earth stations receiving bursts of data cells transmitted by user stations during connections. respective sporadic, said bursts being transmitted in a data subframe of a time-division multiple access periodic frame, a sporadic connection being defined by an average length of the bursts to be transmitted during said connection, sporadicity and a maximum rate, an earth station having received a complete burst transmitting an end message which includes the length of the burst, in a signaling subframe of the periodic frame to the central station in order to release a resource allocated to the burst in the data subframe when the entire burst is transmitted by the earth station,
• the decision to accept or refuse a sporadic connection given to establish following a request of sporadic connection in the signaling subframe by an earth station, said decision being determined according to an algorithm in which the average lengths of the bursts and sporadicities are considered as predetermined constants and which depends on maximum bit rates and bit rates average bit rates of the connections in progress and of said given connection, the maximum bit rate and said average bit rate relating to said given sporadic connection being included in said connection request,
• the algorithm consists, for said sporadic connection request, in calculating an equivalent charge ratio for the sporadic connections in progress as well as for said given connection as a function in particular of said constants and of the maximum bit rates of the sporadic connections, calculating the sum of the average bit rates of sporadic connections, calculating the product of said sum by said equivalent charge ratio, and accepting the connection request when said product is less than a total capacity available for sporadic connections.
• the invention also provides for constant speed connections to be established between user stations in the network.
• the algorithm for a speed connection constant then consists in subtracting the constant speed from the total capacity available to establish a second capacity available for sporadic connections, calculating said product for sporadic connections in progress, and accepting the request for connection at constant speed when said product is lower at the second available capacity.
• Figs.1A and 1B respectively show a broadband satellite network and a temporal representation of sporadic communication in this network
• - Fig.2 shows a frame format used in the TDMA-Reservation protocol according to the prior art and implementing the TDMA (time division multiple access) mode;
• - Fig.3 is a state diagram according to the TDMA-Reservation protocol
• Fig.4 is a state diagram of the resource allocation method according to the invention.
• - Figs.5A, 5B, and 5C are time diagrams of signal exchange for purposes of performance comparison between the TDMA-Reservation protocol and the method according to the invention
• - Fig.6 is a diagram of traffic distribution in a digital broadband network
• FIG.7, 8 and 9 are diagrams for developing an algorithm for accepting / refusing a connection for implementing the method according to the invention.
• Figs.10 and 11 are diagrams for explaining equivalences of parameters according to the method according to the invention.
• Fig. 12 shows the acceptance / refusal algorithm for connection according to the invention.
• - Fig.13 is a schematic block diagram of a connection refusal / acceptance automaton for an implementation of the algorithm according to the invention.
• a presentation of the advantage of the method according to the invention is introduced compared to the known TDMA-Reservation protocol concerning the transmission by each earth station of a transmission of a request for resource allocation for each burst received. This comparison could be extended to any type of known protocol using an unexpected resource reservation mode.
• a second part of the description relates to an algorithm according to the invention, installed in a central station and making it possible to determine whether a connection request should or should not be accepted.
• the resource allocation requests for the bursts transmitted during a connection are independent of the characteristics of said bursts and all must therefore be satisfied.
• Fig.1A schematically shows a dual-beam broadband digital network architecture.
• the network establishes communications between a group of first user stations SU 1 , ... SU i , ... SU I of a first beam A, and a group of second user stations of a second beam B (not shown) via a satellite, for example in the context of intercontinental communications.
• the term "user station” arbitrarily designates a user station or terminal, or else a local area network to which a plurality of user stations is attached.
• the user stations SU i i being an integer varying between 1 and I, are attached to respective earth stations ST i , through user interfaces IU i .
• the earth stations also provide modulation and coding functions for the information transmitted by the different user stations for retransmission to the SA satellite.
• a central management station SC provides instantaneous management of the common resource: at least one carrier frequency satellite channel, supervision and control of the various earth stations ST 1 to ST I , and the establishment and release of connections as it will be seen later.
• a control station performs a so-called "echo"function; this "echo" function essentially consists in retransmitting to the opposite beam, here beam A, the signaling sub-frame received from this opposite beam in frames in TDMA format.
• this "echo" function contributes to the retransmission of connection request and resource allocation request messages, transmitted by the earth stations in the signaling subframe, to the central station SC, which guarantees acceptance decisions. connections.
• the digital broadband technique prohibits control of flows between links by conventional methods. Resource allocation mechanisms must be implemented precisely before access to resources. It is the role of the central station SC to manage all of the connection requests that the earth stations ST i require to satisfy the resource allocation mechanism according to the invention.
• connection bursts are transmitted between the earth station ST i and any other station in beam B via the satellite
• the different sporadic services integrated in the different user stations of the digital "broadband" network generate, during respective connections, messages of variable lengths T (line a), the lengths being expressed in number of bits.
• the messages pass through the network in the form of ATM cells (line b) already defined above.
• These various digital services constitute sporadic traffic sources which are characterized by relatively long time intervals IT between successive messages whose bits are generated at a maximum bit rate D max .
• D max maximum bit rate
• the various messages generated by a digital service are transmitted in the digital network in the form of ATM cells according to the established standard.
• the word "burst" used below designates a set of cells in ATM format originating from the segmentation of a service message of sporadic nature into cells transmitted at the bit rate of the network DR greater than D max .
• connections established between the earth stations of the two beams are of two types depending on the nature of the services:
• sporadic connections defined by trains of cells spaced apart by relatively long time intervals.
• a state diagram E1 to E5 for an earth station ST i establishing connections via the SA satellite through the central station SC relates to the TDMA-Reservation protocol, resource allocation protocol burst by burst.
• This known protocol is used for dynamic allocation of resources by the central station SC to the various earth stations in order to establish communications via the SA satellite.
• the central station SC also manages the resource allocations allocated to the various earth stations ST i for connections to be established via the satellite SA.
• a first state El the earth station STÎ is waiting for a burst. As already indicated, this means that the station ST i is awaiting reception of a message burst produced by one of the sporadic connections established by this station ST i (FIG. 1A). As soon as the start of the burst is detected, the earth station ST i is in a second state E2 to store the burst. This memorization is carried out according to the "store and forward" mechanism, meaning that no action is taken by the earth station ST i before a complete memorization of the burst.
• the earth station ST i After detecting the end of the burst, the earth station ST i calculates the length of the burst LR expressed in number of cells received (state E3), the cells having a constant length expressed in a number of bits. After the calculation of the length of the burst, corresponding to a given resource necessary for the earth station ST i to transmit the burst via the satellite SA, the station ST i is waiting for a time interval of signaling ITS i which is assigned to it in the TDMA format frame shown in Fig. 2 (state E4).
• the earth station ST i transmits a resource reservation request accompanied by information concerning the length of the burst LR to be transmitted.
• a resource allocation device in the central station SC receives the reservation message MR i by echo retransmission of a terminal of the beam B. This allocation device manages different reservation requests transmitted by means of respective reservation messages MR l , ... MR I by the different earth stations ST l , ... ST I in order to allocate resources.
• the allocation device of the central station SC allocates resources to the earth station ST i at the end of a time waiting Your traffic function in the network. This allocation of resources results in an allocation of a time interval IT i in a data sub-frame STD i to the earth station ST i by the central station SC.
• the length of the time interval IT i assigned to the earth station ST i is directly proportional to the length of the burst transmitted in the reservation message MR i .
• a resource (state E5) is allocated to the earth station ST i so that the latter transmits the entire burst received, in the form of ATM cells.
• the station ST i At the end of the transmission of the burst by the earth station ST i corresponding to a release of resources or of time interval IT i by the central station SC, the station ST i returns to the first state E1 waiting for a next burst.
• reaction times must be very short in order to provide users with good quality service in fields as varied as image, real-time querying of databases, etc.
• the asynchronous temporal technique is above all a packet-based technique based on queue management.
• a request for allocation of resources to the central station SC by an earth station ST i by means of a reservation message MRi is made only after complete memorization of the burst, for transmission of this burst to the destination earth station.
• the reservation message is then stored in a FIFO queue of the allocation device of the central station SC to be processed after a waiting time Ta.
• the transmission time "round trip" 2T t and the waiting time Ta are difficult to modify since they depend on intrinsic characteristics of the network according to the chosen embodiment (capacity, lines, location).
• the duration of the burst TR induces critical delays when the burst or the message from which it comes has a long duration (image services).
• the method according to the invention aims mainly at reducing the time for allocating resources, as indicated in the state diagram ET1, ET2-ET2 ', ET3'-ET3 and ET4 shown in Fig.4.
• ET1, ET2-ET2 ', ET3'-ET3 and ET4 shown in Fig.4.
• the earth station ST i goes to a second state ET2 for start memorizing the burst.
• the earth station ST i is waiting for its own signaling time interval ITS i in the signaling sub-frames STS r .
• the earth station ST i transmits in the latter an allocation request message MD i to the central station SC (state ET2 ').
• This allocation request message MD i received by the central station SC is stored in a memory FIFO of the resource allocation device.
• All messages MD l to MD I originating from earth stations ST l to ST I and relating to resource allocation requests are thus processed according to their order of arrival by the allocation device; this device processes the various resource allocation requests stored in the queue in turn and allocates resources, materialized by periodic time intervals IT i , to the various corresponding remote earth stations as a function of the available resource capacity.
• the method according to the invention provides for the transmission of a message request for allocation MD i by the earth station ST i to the central station SC as soon as a burst begins.
• the earth station ST i After detection of a time interval IT i in the data sub-frame assigned to the earth station ST i by the central station SC, following the processing of the allocation request message MD-j_, the earth station ST i begins the transmission of the burst in the interval IT i . After complete storage of a burst, the earth station ST i performs in state ET3 a calculation of the length LR or duration TR of the stored burst. Information concerning the length of the burst is then transmitted by the earth station ST i to the central station SC in an end message MF i after detection of a signaling time interval ITS i , as indicated in state ET4 of the Fig. 4. The end message MF i notably makes it possible to inform the central station SC about the length of the burst in order to release the assigned interval IT i when the entire burst is transmitted by the earth station via the satellite.
• FIGS. 5A, 5B and 5C schematically illustrates the exchange of signals during a communication or connection established between an earth station ST i and the central station SC and consisting of a transmission of a burst.
• Fig.5A shows lengths LR of bursts transmitted as a function of time t.
• Figs.5B and 5C schematically show phases of transmission of a burst between the earth station ST i and the central station SC respectively according to the aforementioned protocol and according to the method according to the invention.
• the earth station ST i transmits a reservation message MR i only after complete storage of the burst according to the "store and forward" mechanism.
• This reservation message MR i received by the central station SC after a transmission delay 2T t is only processed by the latter after a waiting time Ta corresponding to a processing time for the reservation message MR i stored in a queue of the resource allocation device of the central station SC.
• the allocation of resources by the central station SC results in that of a time interval IT i in the data sub-frame STD i to the earth station ST i according to a burst length information included in the message reservation MR i and precedes the transmission of the burst by the earth station for a time (t " f - t i ").
• an allocation request message MD i is transmitted by the earth station ST i to the central station SC following a start of burst detection after detection of an interval ITS signaling time j .
• a flow rate D i max is then assigned to the earth station ST i by the central station SC, also after a waiting time Ta.
• the message MD i being transmitted on reception of a first cell of the burst by the earth station ST i , the gains in transmission time, in particular for bursts of long duration, are substantial.
• part of the total capacity C t of the satellite channel is allocated to the STS signaling subframe, while two other parts are allocated respectively to the continuous connections and to the sporadic connections established between earth stations of the beams A and B and are included in the data sub-frame STD.
• the useful part assigned to sporadic connections is very variable, while the part allocated to continuous connections, that is to say having constant flow rates, varies more slowly. Indeed, the time interval IT i allocated to a continuous connection following a single connection-allocation request has a constant length and is periodic.
• I earth stations ST l to ST I of the beam have each established a connection COM l to COMj, although in practice an earth station establishes several connections respectively for several terminals of a user station attached to it.
• the network configuration is entirely defined by I groups of three parameters relating respectively to the I COM l to COM I connections established between the beams A and B and by a global network parameter which is the total available capacity allocated to the sporadic connections C S.
• the three respective parameters relating to each COMi of the established connections are:
• the STS signaling sub-frame represents at least 5% of the total frame of duration 30 ms and that the ground-satellite-ground transmission delay is 300 ms.
• the performance of the resource network using the resource allocation mode characterizing the invention and presented in the first part of the description is measured in terms of delay (in seconds) between the start of reception of a burst by a station given earth and the retransmission of the received burst to any station in beam B.
• the three parameters defined above characterizing connections established respectively between the different earth stations ST i in beam A and stations in beam B are assumed to be identical ; it is a homogeneous configuration of connections.
• the "simulated" connections between the various stations are characterized by average lengths of burst Lm, sporadicities SP and charge ratios RA respectively identical. The action of each of the parameters on the performance of the network in terms of delay is thus studied.
• Fig. 7 is shown the influence of the average burst length Lm, assumed to be identical for each of the connections established between earth stations ST i of beam A and stations of beam B via the central station SC, on the delay of transmission R 99 , expressed in seconds.
• This delay in transmission R 99 must be perceived as an average statistical data and more precisely must be analyzed as a 99% probability of obtaining a real delay less than R 99 .
• the load ratio C S / D max is assumed to be equal to 4, and different curves are represented for sporadicities respectively equal to 23, 45 and 90.
• l the increase in the average length Lm of the bursts results in a decrease in the transmission delay R 99 .
• This phenomenon is in accordance with the principle of resource allocation according to the invention. Indeed, for short bursts transmitted by the various earth stations S Ti during respective connections, the transmission delays of the end of storage messages MF i transmitted to the central station SC and containing information relating to the allocation duration of resources for the resource allocation device in the central station SC, are all the more significant as the bursts are short.
• a part of the resources of the satellite channel is then allocated to an earth station for a relatively long time compared to an effective transmission of bursts. Aside from this phenomenon, for bursts greater than 50 cells, an increase in the average length of the bursts leads to an increase in the transmission delay R 99 .
• Fig. 8 illustrates the effect of the sporadicity of the connections established between the various earth stations of the first beam A and stations of the beam B via the central station SC on the transmission delay R 99 .
• the curve shown in Fig. 8 was also obtained by simulating a homogeneous configuration in which the three parameters defining each connection are identical. It should be noted that an increase in the sporadicity of the connections leads to an increase in the delay R 99 .
• Fig. 9 shows the effect of increasing the C S / D max load ratio on the transmission delay R99.
• the performance of the method according to the invention is improved when the available capacity C S for the sporadic connections C S increases with respect to the maximum bit rate D i max of the sporadic connections.
• the study of the performances of a "homogeneous" configuration as described with reference to Figs. 7, 8 and 9 is too far from the actual operating conditions to design the final implementation of the method according to the invention in the context of a digital network integrating broadband services in which many characterized digital services coexist by connections that do not have identical parameter values (Sporadicity, Average length of gusts, Allocation report).
• a more general study is required to deduce an implementation of the process for developing a refusal or acceptance of a connection.
• connections are studied within the framework of heterogeneous connections coexisting in the network and characterized by parameters which can take different values.
• the study of this heterogeneous configuration should not relate simultaneously to the three parameters characterizing the various connections established between earth stations of beam A and stations of beam B. It is necessary to study each of the parameters separately to deduce the effect of l heterogeneity on each of them.
• Figs. 10 and 11 contribute to studying respectively the effect of heterogeneity on two parameters, mean length of bursts Lm i and sporadicity SP i , the other two respective parameters RA and SP, or Lm and RA, being assumed to be homogeneous.
• Fig. 10 relates to a simulation of k connections established respectively by earth stations via the central station SC, k being for example equal to 50.
• k being for example equal to 50.
• the "simulated" connections are only differentiated by different values, two in number, from their respective average burst length Lm i .
• the two possible values of the lengths of bursts are equal to 50 and 200 cells for purposes of simplification of simulation.
• the abscissa axis in Fig. 10 relates to the arithmetic mean of the burst lengths of the
• a first curve in solid line shows the delay R 99 of communication transmission as a function of the arithmetic mean ⁇ Lm i > of the lengths of the respective bursts of the k connections.
• the k connections are thus simulated with burst lengths equal to 50, and 200 cells, which corresponds to an arithmetic average varying between a minimum average for which all the connections consist of bursts equal to 50 cells, and a maximum average for which all connections are characterized by burst lengths equal to 200 cells.
• a dashed line curve is obtained by a simulation of k connections for which the average lengths of the respective bursts Lm i are identical and equal to the average of the average lengths ⁇ Lm i > of the bursts for the k connections in the heterogeneous model.
• Fig. 11 relates to a simulation of k connections established respectively by k earth stations ST i via the central station SC.
• sporadicity values vary from one established connection to another. For simplification purposes, the number of possible sporadicity values is limited to two: 100 and 1000.
• the abscissa axis in Fig. 11 is relative to the arithmetic mean of the sporadicity values ⁇ SP i > of the k connections, and the ordinate axis is relative to the transmission delay R 99 in seconds.
• a first curve in solid line shows the delay R 99 of transmission of the connections as a function of the arithmetic mean ⁇ SP i > of the sporadicity values of the k connections, which varies between a minimum arithmetic mean for which all the connections have sporadicity values equal to 100, and a maximum arithmetic mean for which the sporadicity values of the k connections are equal to 1000.
• a dashed line curve is obtained by simulating k homogeneous connections between earth stations ST i of beam A and stations of the beam B via the central station SC for which the respective sporadicity values are identical and equal to:
• a variable called “total minimum required capacity" CMR TOT is defined which makes it possible to assess whether said DC- [connection request must be accepted or refused by the central station SC.
• a value of the CMR TOT variable for the ki®me connection depends on the 3 respective parameters of the (k-1) connections already established as well as on the three parameters of the ki®me connection. This results in the equation:
• CMR TOT f (Lm l , ... Lm k ; ..., SP l , ... SP k ; C S / D i max , ... C S / D k max )
• the parameters in brackets designate the three parameters for the k connections established or to be established by arbitrarily chosen earth stations.
• a connection acceptance / refusal preparation automaton in the central station SC recognizes a connection request DC k for a given k th connection of sporadic nature being established. This automaton then uses the maximum speed D k max transmitted in the connection request DC k and the maximum speeds of the connections in progress previously memorized to deduce an equivalent charge ratio RA eq relative to all the connections, in accordance with equation (eq .3).
• the controller then calculates the sum of the average rate D k moy transmitted in the connection request DC k and average bit rates of previously stored (k-1) current connections for SOM.
• the sum obtained SOM is multiplied by the equivalent charge ratio RA eq .
• the result of the CMR TOT multiplication is compared with the total capacity available for sporadic connections C S. The connection is accepted if and only if this capacity C S is greater than the total minimum required capacity CMR TOT .
• a new available capacity relating to the sporadic connections C ′ S is deducted by subtraction of the bit rate D from the available capacity C S preceding the request for the new given connection.
• the total minimum required capacity CMR TOT, for established sporadic communications is calculated as above and compared with the new available capacity C ' S. If this new capacity C ′ S is greater than the capacity CMR TOT , the connection is accepted, otherwise it is refused.
• the connection is accepted if the latter does not affect the total capacity required for the sporadic connections in progress, so that these are interrupted.
• FIG. 13 A diagram of the automatic device for developing a refusal / acceptance of a connection in the central station for an implementation of the aforementioned algorithm is shown in Fig. 13.
• the circuit comprises a microprocessor 130, a program ROM memory 131, a memory of the maximum bit rates D i max of the connections in progress 132, a memory of the average bit rates D i avg of the connections in progress 133, a FIFO file 134, a circuit of reception 135 and a transmission circuit 136.
• the program memory 131 stores a program in low level language corresponding to the algorithm shown in Fig.12.
• the memories 131, 132, 133 and 134, and the microprocessor 130 are connected by means of an address bus BA and a data bus BD.
• the signaling sub-frame STS r conveying the connection request messages DC i retransmitted in an echo channel to the beam A is received and decoded by the reception circuit 135 to be applied to the microprocessor 130.
• the reception circuit 135 provides in particular demodulation, decoding and synchronization functions.
• a connection is accepted, following a calculation carried out by the microprocessor according to the algorithm presented in FIG. 12 in particular by reading the maximum bit rates in memory 132 to deduce an equivalent charge ratio RA eq , and by reading the average bit rates in memory 133 to calculate the total minimum required capacity CMR TOT from RA eq , the resource allocation device as presented in the first part of the description is used for each burst of this connection, without being affected by the other current connection requests.

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• 1991
  • 1991-10-04 FR FR9112257A patent/FR2682243A1/fr active Granted
• 1992
  • 1992-10-02 US US08/066,110 patent/US5363374A/en not_active Expired - Lifetime
  • 1992-10-02 JP JP5506617A patent/JP3008496B2/ja not_active Expired - Lifetime
  • 1992-10-02 EP EP92203053A patent/EP0535762B1/fr not_active Expired - Lifetime
  • 1992-10-02 DE DE69219266T patent/DE69219266T2/de not_active Expired - Lifetime
  • 1992-10-02 WO PCT/EP1992/002292 patent/WO1993007694A1/fr not_active Ceased

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