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    • 专利摘要:
    The present invention relates to a method of allocating transmission slots in a wireless optical system. The allocation of resources is made taking into account the dissymmetry of the interference diagrams on the up and down channels and by adopting, for each channel, a reuse of the transmission slots in the areas where the interference is absent. In some embodiments, the allocation method provides relaying between access points across the network to take account of the fact that the access point offering the best uplink (or downlink) can be distinct from the point of access. associated access to the terminal
    公开号:FR3069401A1
    申请号:FR1756914
    申请日:2017-07-21
    公开日:2019-01-25
    发明作者:David MIRAS；Luc Maret；Mickael MAMAN
    申请人:Commissariat a lEnergie Atomique CEA；Commissariat a lEnergie Atomique et aux Energies Alternatives CEA；
    IPC主号:
    专利说明:

    SCHEDULING METHOD FOR UPLINK AND DOWNLINK OF AN OPTICAL TRANSMISSION SYSTEM
    DESCRIPTION
    TECHNICAL AREA
    The present invention relates generally to the field of wireless optical communications and more particularly that of Li-Fi (Light Fidelity) communication systems.
    PRIOR STATE OF THE ART
    Optical Wireless Communications (OWC) systems have recently been the subject of significant research because of their ability to solve the problem of spectral occupancy and to supplement or even replace Wi-Fi systems.
    Schematically, Li-Fi systems are analogous to Wi-Fi systems (obeying the IEEE 802.11 standard) but use the visible spectrum instead of the RF spectrum. The physical layer (PHY) and the MAC layer of Li-Fi systems have already been standardized in the IEEE 802.15.7 standard.
    Insofar as the optical signals do not pass through the opaque partitions, the interference between the cells separated by such partitions is nonexistent. However, when these Li-Fi cells are deployed in a free space, it is necessary to remove the interference between adjacent cells.
    A first technique for reducing intercellular interference in an optical telecommunications system consists in adopting a frequency reuse pattern. Thus, the article by C. Chen et al. entitled “Fractional frequency reuse in optical wireless cellular network” published in Proc, of the 2013 24th International Symposium on Personal, Indoor and Mobile Radio Communications, pp. 3594-3598, proposes to divide the cells into a central region, in which the entire band can be used, and a peripheral region, affected by intercellular interference, in which only sub-bands are used so that that two peripheral zones of two adjacent cells are covered by separate sub-bands.
    A second technique for managing interference in optical telecommunication systems consists in detecting the spatial position of the users under light sources and then in splitting the light flux between these users in the time domain. Thus, two spatially separate users are served by spatially adapted cells at separate times. This technique was described in the proposal by S. Rajagopal et al. titled “IEEE 802.15.7 VLC PHY / MAC proposalSamsung ETRI” IEEE Standard, October 31, 2009. However, it requires the deployment of a large number of optical sources.
    The aforementioned techniques do not take into account the asymmetry of the interferences which can take place between uplinks and downlinks.
    Figs. IA and IB schematically illustrate an example of an optical communication system exhibiting interference asymmetry between the uplink and the downlink.
    The optical telecommunications system comprises a plurality of light access points or APs, 110, connected to the main network, 100, for example by means of Ethernet links. Each access point is equipped with a modem coupled to an LED light source emitting in the visible range, the modem modulating the supply current of the source so as to modulate the intensity of the light emitted.
    The terminals, 120, are equipped with a "dongle" including an optical receiver. This optical receiver receives the light signal, converts it into an electrical signal, demodulates it and recovers the transmitted data. Conversely, the dongle or the terminal itself is also equipped with an infrared diode, the data to be transmitted on the uplink serving to modulate the infrared signal. The infrared signal is received by a photodiode mounted on the access point, then is demodulated to transmit the data via the main network.
    In the example shown, the luminous access points have been designated by ÎAP ^ IAP ^ .ÎAR and by D P D 2 the user terminals.
    Fig. IA illustrates the respective optical coverage areas of the access points IAP X , IAP 2 , IAP 3 . Note that the terminal D x is located in the coverage areas of LAP V and LAP 2 , and that the terminal D 2 is located in the only coverage area of LAP. Thus, if the terminal D x is associated with the access point LAP ^, the downlink between LAP X and D, is interfered with by the signal transmitted by LAP on the downlink.
    Fig. IB illustrates the corresponding interference situation on the uplink.
    Note that the LAP 2 access point receives the signals sent by the terminals Dj and D 2 on the uplink, while the signals received by LAP X and LAP. ,, respectively from D v and D 2 are not interfered with .
    In general, the spatial distributions of the coverage areas on the uplink and on the downlink are not symmetrical: the receiver can be offset from the transmitter, the radiation pattern of the transmitter and the reception diagram of the receiver are rarely equivalent (pointing angle, directivity). In addition, the use of refractive optical components such as lenses can increase the directivity of the radiation patterns, which further increases the asymmetry of the interference on the uplink and downlink.
    In such a situation of asymmetry, the same strategy for allocating transmission resources on the uplink and downlink is suboptimal.
    The object of the present invention is therefore to propose a method of reducing interference in an optical wireless telecommunications system which is simple and effective while taking into account the asymmetry of the interference on the uplink and downlink.
    STATEMENT OF THE INVENTION
    The present invention is defined, according to a first embodiment, by a method of allocating transmission intervals in a wireless optical system comprising a plurality of access points connected to a wired network and controlled by a network controller , and a plurality of terminals, in which:
    - Each terminal is associated with an access point among said plurality of access points, such that the average of the qualities of the uplink and downlink between this access point and said terminal is maximum;
    each terminal associated with an access point determines coverage information containing the identifiers of the access points received by the terminal;
    - when the terminal coverage information is reduced to the identifier of the access point associated with the terminal, the access point allocates to the downlink a transmission interval within an available time range managed by the data controller. network (CFP ^ 7 (AP));
    - when the terminal coverage information includes a plurality of access point identifiers, the network controller allocates the downlink a transmission interval in an available time range (CFP ^ n (AP n )) and correspondingly amputates the available time ranges of the access points belonging to the coverage information of the transmission interval thus allocated.
    Advantageously:
    each access point determines reception information containing the identifiers of the terminals received by the access point;
    - when the identifier of a terminal only appears in the reception information of the access point associated with it, the latter allocates to the uplink a transmission interval in an available time range managed by the data controller. network (CFP- e (AP));
    - when the terminal identifier appears in a plurality of reception information, the network controller allocates to the uplink a transmission interval in an available time range (CFP “ r p ee (AP n )) and correlatively cuts the available time slots of the transmission interval thus allocated for all the access points containing the terminal identifier in their reception information.
    According to a second embodiment, the invention is defined by a method of allocating transmission intervals in a wireless optical system, comprising a plurality of access points connected to a wired network and controlled by a network controller , and a plurality of terminals, in which:
    - Each terminal is associated with an access point among said plurality of access points, such that the quality of the uplink of said terminal and this access point is maximum;
    each terminal associated with an access point determines coverage information containing the identifiers of the access points received by the terminal as well as indicators of the quality of the downlink with these access points, said coverage information being transmitted to the network controller via access points;
    - when the terminal coverage information is reduced to the identifier of the access point associated with the terminal, the access point allocates to the downlink a transmission interval within an available time range managed by the data controller. network (CFP ^ 7 (AP));
    - when the coverage information comprises a plurality of access point identifiers, the network controller determines among said plurality an auxiliary access point such as the quality of the downlink between the auxiliary access point and the terminal is maximum, the downlink between the associated access point and the terminal comprising a first link through the wired network between the associated access point and the auxiliary access point and a second downlink between the access point auxiliary access and terminal;
    - the network controller allocates to the second downlink a transmission interval within an available time range (CFP'Jfi (AP n )) and correlatively cuts the available time ranges of the access points belonging to the coverage information of the 'transmission interval thus allocated.
    According to a third embodiment, the invention is defined by a method of allocating transmission intervals in a wireless optical system, comprising a plurality of access points connected to a wired network and controlled by a network controller , and a plurality of terminals, in which:
    - Each terminal is associated with an access point among said plurality of access points, such that the quality of the downlink between this access point and said terminal is maximum;
    each access point determines reception information containing the identifiers of the terminals received by the access point as well as uplink quality indicators with these terminals, said reception information being transmitted to the network controller;
    - when the identifier of a terminal only appears in the reception information of the access point associated with it, the latter allocates to the uplink a transmission interval in an available time range managed by the data controller. network (CFP- e (AP));
    when the identifier of a terminal appears in a plurality of information of reception of access points, the network controller determines among said plurality an auxiliary access point such as the quality of the uplink between the terminal and this auxiliary access point is maximum, the uplink between the terminal the associated access point comprising a first uplink between the terminal and the auxiliary access point and a second link in the wired network between the access point auxiliary and the associated access point.
    Whatever the embodiment, the optical system preferably conforms to the IEEE 802.15.7 standard.
    BRIEF DESCRIPTION OF THE DRAWINGS
    Other characteristics and advantages of the invention will appear on reading a preferred embodiment of the invention, made with reference to the attached figures among which:
    Figs. IA and IB schematically represent an example of an optical telecommunication system exhibiting interference asymmetry on the uplink and the downlink;
    Fig. 2 schematically represents an optical telecommunication system having a coordinated topology;
    Fig. 3 schematically represents the structure of a superframe used in an optical telecommunication system;
    Fig. 4A schematically represents an interference diagram between access points of an optical wireless telecommunication system;
    Fig. 4B shows an interference point graph for the access points for the optical wireless telecommunications system of FIG. 4A;
    Fig. 4C shows an example of allocation of transmission intervals for the optical wireless telecommunications system of FIG. 4A;
    Fig. 5 shows the flow diagram of an allocation of control signal transmission intervals in an optical wireless telecommunication system, which can be implemented in any one of the embodiments of the invention;
    Fig. 6A represents the flowchart of a method for allocating transmission intervals for the downlinks of an optical wireless telecommunication system, according to a first embodiment of the invention;
    Fig. 6B represents the flowchart of a method for allocating transmission intervals for the uplinks of an optical wireless telecommunication system, according to a first embodiment of the invention;
    Fig. 7 shows the application of the transmission interval method, according to the first embodiment of the invention, to the optical wireless telecommunication system of FIGS. IA and IB;
    Fig. 8 represents the application of a method for allocating transmission intervals, according to a second embodiment of the invention, to the optical wireless telecommunication system of FIGS. IA and IB;
    Fig. 9 represents the application of a method for allocating transmission intervals, according to a third embodiment of the invention, to the optical wireless telecommunication system of FIGS. IA and IB.
    DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS
    We will consider in the following a wireless optical communication network (Li-Fi), as described for example in the IEEE 802.15.7rl standard. This network includes a plurality of access points connected to a backhaul network.
    It is assumed that this network has a centralized interference management mechanism. As illustrated in Fig. 2, the network access points (also called coordinators), 210, are connected to a network controller (global controller), 250, by means of the backhaul network, according to a coordinated topology, within the meaning of the aforementioned standard. More specifically, each terminal 230 is capable of detecting an interference between signals received from two access points and of reporting an interference report (a metric) to the network controller, 250, via said access point. Similarly, each access point 210 is capable of analyzing the level of interference between signals transmitted by two terminals and of transmitting an interference report to the network controller 250. Based on the interference reports on the downlink and uplink, the network controller transmits to the access points, via the backhaul network, a time allocation of control signal transmission intervals, as described in detail below.
    The function of the network controller is in particular to synchronize the transmission of superframes by the access points and to allocate them access to the medium according to a time distribution mechanism (TDMA).
    More specifically, the transmission on the downlink / uplink uses a superframe structure as shown in FIG. 3.
    A superframe is delimited by successive beacons emitted by each access point (also called coordinators) synchronously. It is divided into three successive parts: a first part, called the control period or BP (Beacon Period), dedicated to the transmission of control messages (on the downlink and on the uplink), a second part or CAP (Contention Access Period) in which the terminals can transmit randomly and a third party or CFP (Contention-Free Period), itself divided into guaranteed transmission intervals or GTSs (Garanteed Time Slots) in which the terminals (resp. Points can transmit without risk of access conflict on the uplink (resp. on the downlink).
    The interference management is carried out by the network controller which in a first step determines an interference table (or interference matrix) between access points. This interference matrix can be determined beforehand from a survey of the coverage areas during the deployment of the various access points or else constructed progressively using the interference reports reported by the terminals. to the network controller, via the access points.
    The interference matrix is binary and symmetrical. It indicates for each pair of access points controlled by the network controller if there is an intersection of the coverage areas of these two access points (whether on the uplink or downlink). The absence or existence of such an intersection is represented by a binary value.
    Interference can be detected on the downlink or on the uplink. On the downlink, interference between access points is detected from terminal interference reports, which are reported to the network controller via these access points. On the uplink, interference is detected as soon as an access point receives a signal which is not intended for it from a terminal. The interference report is then transmitted by the access point in question to the network controller. When interference between access points is detected, whether on the uplink or downlink, this interference is taken for granted even if it is no longer observed later. Indeed, it is understood that this interference will only be detected as long as a terminal is in the intersection of the coverage areas of the access points. The interference matrix thus keeps track of the interference detected between the access points over time.
    By way of example, if we consider the interference diagram between the access points AP l , ..., AP è of FIG. 4A, the interference table will be given by:
    ΑΡ γ ap 2 ap 3 ap 4 ap 5 ^ 6X 1 0 1 1 01 X 1 1 1 1 ap 3 0 1 X 0 1 1 ap 4 1 1 0 X 1 0 ap 5 1 1 1 1 X 10 1 1 0 1 X
    The interference table (or matrix) can be considered as an adjacency matrix of a graph, called incompatibility graph, whose vertices are the access points of the network. According to this representation, two interfering access points on the downlink are represented by adjacent vertices in the incompatibility graph.
    Fig. 4B represents the graph of the incompatibilities corresponding to the interference diagram of FIG. 4A.
    The network controller allocates transmission intervals (transmission intervals of control signals in the BP part, guaranteed transmission intervals GTS in the CFP part) to the different access points, so that interfering access points are allocated disjoint transmission intervals. When an access point does not interfere with any of its neighbors, it can allocate a transmission interval independently.
    The allocation of transmission intervals by the network controller can be carried out by means of an algorithm for coloring the graph of the incompatibilities. By graph coloring, we mean that we assign a color to each vertex of the graph while ensuring that two adjacent vertices cannot be the same color. This can be done using a fair coloring algorithm known from the state of the art, for example the Welsh and Powell algorithm. Such an algorithm in fact ensures that two adjacent vertices of the graph are colored with different colors as illustrated in FIG. 4B. Advantageously, the number of different colors of the graph will be minimized.
    There is shown in FIG. 4C an example of allocation of transmission intervals, in accordance with the graph of incompatibilities in FIG. 4B. Each line corresponds to an access point and represents a superframe transmitted on the downlink, comprising the BP, CAP and CFP parts. We note for example that the lines corresponding to the AP l and AP 3 access points are the same color: a transmission of control signals can occur simultaneously on the downlink without risk of interference. On the other hand, the line corresponding to the AP 2 access point has a distinct color from that of the AP t and AP 3 access points. Thus, AP 2 cannot transmit at the same time as AP 3 and AP 3 without risking causing interference for the terminals located in the coverage area.
    Transmission intervals for control signals are thus allocated to the various access points within the superframe. Thus, for example, the access points AP 3 and AP 3 can send their control messages in the first interval BP t from BP, the access point AP 2 can send in the second interval BP 2 from BP, the points AP 4 and AP 6 can transmit in the BP 3 BP interval, and finally the AP 5 access point can transmit in the BP 4 interval.
    Fig. 5 shows the flow diagram of an allocation of transmission intervals in a wireless electronic telecommunications system, which can be implemented in any one of the embodiments of the invention.
    This first phase concerns the allocation of transmission intervals during the control part (BP) of the superframe.
    In step 510, the interference between access points on the downlink is detected. This interference detection is performed by the network controller from the interference reports (on the downlink) sent by the terminals to the controller via the access points. Interference between access points on the uplink is also detected. This interference detection is carried out by the network controller from the interference reports (on the uplink) returned by these access points.
    This step may have been carried out during the deployment of the network for example.
    In step 520, the network controller determines an interference matrix between access points from the interference previously detected. Detection of interference between access points, on the uplink or downlink, corresponds to a first binary value in the matrix and an absence of interference to an inverse binary value.
    In step 530, the network controller constructs a graph of the incompatibilities whose vertices are the access points and whose adjacency matrix is given by the interference matrix.
    In step 540, the network controller allocates transmission intervals on the downlink to the access points of non-zero degree of the graph. This allocation is achieved by coloring the incompatibility graph obtained in the previous step: two access points of distinct colors are allocated disjoint transmission intervals within the control part. Thus, two access points with overlapping coverage areas are necessarily allocated separate transmission intervals and two access points with overlapping coverage areas can be allocated identical transmission intervals. Minimizing the number of colors in the graph results in minimizing the number of distinct transmission intervals.
    When an access point corresponds to a node of zero degree of the incompatibility graph, this allocates in 550 transmission intervals on the downlink, independently of the other access points.
    A terminal wishing to connect to the network selects the access point for which the quality of the downlink and that of the uplink is highest. The quality of a link can for example be estimated by means of a signal-to-noise ratio metric. It then transmits to the selected access point an association request in the reception interval reserved for this access point in the superframe control part.
    The network controller can allocate guaranteed transmission intervals (GTS) to the access points in the CFP (Contention-Free Period) part of the superframe, on the downlink. Similarly, the network controller can allocate to the terminals guaranteed transmission intervals in the CFP part of the superframe, on the uplink.
    In this regard, it should be noted that the same guaranteed transmission interval can be allocated to the downlink and to the uplink of an access point, the separation of the uplink and downlink being ensured by the use of disjoint spectral ranges (for example visible on the downlink and infrared on the uplink).
    First, the interference on the downlink is detected. More precisely, each terminal determines in which coverage area it is located. This information (for example the list of identifiers of the detected access points), called terminal coverage information, is transmitted on the uplink and supplied to the network controller.
    If the terminal coverage information includes only one access point identifier, we conclude that there is no interference on the downlink. The last access point can then allocate independently to the terminal (that is to say without referring to the network controller) a guaranteed transmission interval on the downlink. In other words, the access point can autonomously manage the allocation of the GTS transmission intervals on the downlink in its own coverage area, that is to say not shared with the coverage area d 'a nearby access point. However, this autonomous allocation can only be made within the area of the CFP part not already allocated by the network controller, called CFP'Jff (AP n ), defined below. Of course, within this same area, the transmission interval must not have been allocated by the access point to another downlink.
    On the other hand, if the coverage information includes several access point identifiers, in other words if the terminal is in an interference zone between downlinks, the guaranteed transmission interval allocation is carried out by the data controller. network.
    This manages for each access point AP n the CFP ^ e n (AP n ~) area of the CFP part.
    Before any allocation, in other words before establishing a downlink, each access point has an available time range equal to the entire CFP part of the superframe, CFP ^ fi 1 (AP n ) = CFP.
    When the network controller allocates to the terminal a guaranteed transmission interval (GTS) on the downlink, it can only do so by reducing the available time range CFP £ fi e n (AP n ) relative to the access point. When this allocation is made, the network controller deletes the transmission interval thus allocated from the available time slots (downlink) CFP ^ (AP m ) of the AP m access points appearing in the terminal coverage information.
    In practice, the network controller has a first memory area representing the available time range (downlink) for each access point. This memory area is divided into as many sections as transmission intervals in the CFP area. When a transmission interval is allocated to an access point for a downlink to a terminal, the access point identifier is stored in the corresponding sections of the first memory areas of the access points appearing in the information. terminal coverage. Conversely, when the downlink between the access point and the terminal is broken, the identifier of the access point is erased from the corresponding sections in question and the time slots are increased by the transmission interval previously allocated. Thus, when a section of the first memory area of an access point AP n contains no access point identifier, it can be concluded that it is part of the available time range CFP ^ fiJAPfi.
    Similarly, interference on the uplink is detected. More precisely, each access point determines a list of identifiers of the terminals that it receives on the uplink, hereinafter referred to as reception information.
    When the identifier of the terminal D only appears in the reception information of the access point associated with it, the allocation of the guaranteed transmission interval can be carried out autonomously by the latter.
    Otherwise, the uplink is interfered and the network controller is responsible for allocation. When the network controller allocates a guaranteed transmission interval (GTS) to the uplink between a terminal D and the access point AP n with which it is associated, it can only do so within the available time range (uplink) , CFP ^ / APJ, relating to the AP n access point in question. When this allocation is made, the network controller deletes the transmission interval thus allocated from the available time slots (uplink), CFP ^ ee (AP m ), relating to the AP m access points including the association information. includes the terminal identifier D.
    In practice, as for the downlink, the network controller has a second memory area representing the available time range (uplink) for each access point. This memory area is divided into as many sections as transmission intervals in the CFP area, each section containing the identifier of the terminal to which the corresponding transmission interval is allocated.
    When a transmission interval is allocated to an uplink, the terminal identifier is stored in the corresponding sections of the second memory areas of the access points whose reception information contains the terminal identifier. Conversely, when the uplink between the terminal and the access point is broken, the terminal identifier is deleted from the corresponding sections in question. Thus, when a section of the second memory area of an access point AP n does not contain any terminal identifier, it can be concluded that it is part of the available time range (uplink), CFP ^ AAPJ de this last.
    Fig. 6A represents the flowchart of a method for allocating transmission intervals for downlinks in a wireless electronic telecommunications system, according to the first embodiment of the invention.
    We consider a downlink between an access point AP n and a terminal D.
    In step 610, the terminal D determines its coverage information (list of identifiers of the access points detected) and transmits it to the network controller.
    In step 620, it is determined whether the coverage information is reduced to the access point AP n which is associated with it.
    If so, in 625, the access point AP n allocates to the downlink a transmission interval in the time range CFP ^ (AP n ).
    If not, the allocation is made by the network controller. In step 630, the network controller allocates a transmission interval to the downlink in the time range CFP ^ n (APJ.
    In step 640, the network controller cuts off the transmission interval allocated the time ranges CFP £ ™ (AP m ) relating to the access nodes AP m present in the terminal coverage information and therefore in particular the time range CFP ^ n (AP n ) relative to the associated access point.
    Fig. 6B represents the flowchart of a method for allocating transmission intervals for uplinks in a wireless electronic telecommunications system, according to the first embodiment of the invention.
    We consider an uplink between a terminal D and an access point AP n .
    In step 650, each access point determines its reception information (list of identifiers of the terminals detected) and transmits it to the network controller.
    In step 660, it is determined whether the identifier of the terminal D only appears in the reception information of the access point associated with it, AP n .
    If so, in 665, the access point AP n allocates to the uplink a transmission interval in the time range CFP '£' ee (AP n ).
    If not, the allocation is made by the network controller. In step 670, the network controller allocates a transmission interval to the uplink in the time range CFP ^ APJ.
    At step 680, the network controller cuts off the transmission interval allocated the time ranges CFP ^ e (AP m ) relating to the access nodes AP m whose reception information contains the identifier of the terminal D, therefore in particular the time range CFPff ee (AP n ) relative to the access point AP n which is associated with it.
    Fig. 7 shows an application of the method of allocating transmission intervals, according to the first embodiment of the invention, to the optical wireless telecommunication system of FIGS. IA and IB.
    The allocation of the transmission intervals in a superframe is shown here, indicating the BP, CAP and CFP parts of the latter.
    We have also distinguished in the upper part of the figure the allocation of transmission intervals on the downlink (DL) and in the lower part the allocation of transmission intervals on the uplink (UL).
    Regarding the control part (BP) of the superframe, we note that each access point has a transmission interval for control signals (B P B 2 , B 3 ) on the downlink which is consistent with the interference diagram of Fig. IA, each coverage area intersecting the other two. Similarly, on the uplink, a transmission interval of control signals is allocated to each terminal (D p D 2 ). Note that no control signal transmission interval is allocated in relation to the LAP 2 access point insofar as no uplink is established with the latter.
    With regard to the CFP part of the superframe, it is noted that for the downlink, the access point LAf enjoys all of its available time range apart from the data transmission interval (downlink), Tf L , allocated to it by the network controller to communicate with D 1 . In other words, said, CFP'f '; n (LA P) = CFP Tf L.
    This transmission interval has been correspondingly deleted from the available time slots (downlink) relating to the access points appearing in the coverage information of the terminal D lt, namely {L4 / d, LAR}. The LAP 2 access point enjoys all of its available time range insofar as it appears neither in the coverage information of the terminal D l nor in that of the terminal D 2 , that is to say CFP ^ fi (LAP 2 ~) = CFP. The available time range of the LAP access point is reduced by Tfi 'as indicated previously, in other words CFPfifi (LAP.,) = CFP Tfi. The allocation of the transmission interval Tff is carried out by LA R. within the available time range CF P 2 fi (LAP,) to communicate with D 2 . As the coverage information of the terminal D 2 is limited to {LAP 3 }, there is no need to delete this transmission interval from the available time ranges of LAP t and LAP 2 .
    On the uplink, the network controller allocates the data transmission interval Tfi 'to terminal D, to communicate with £ Aff. Since the reception information of LAP 2 , namely {D p D 2 }, includes the identifier of the terminal D lt this transmission interval is deleted from the available time range (uplink) of LAP 2 , in other words CFPfifiLAPfi = CFP Tfi. On the other hand, the reception information of LAP, namely {O 2 } not including the identifier of the terminal Lfi, the transmission interval Tfi 'is not deleted from the available time range (uplink) of LAP 3 .
    Likewise, the network controller allocates the transmission interval Tfi 'to the terminal D 2 for the uplink with LAP. Since the reception information of LAP 2 , namely {D P D 2 } includes the identifier of the terminal D 2 , this transmission interval must be correlatively deleted from the available time range (uplink) of LAP 2 , CFPffiLAPfi = CFP Tfi. Note that the section corresponding to Tfi 'of the second memory area of the LAP 2 access point contains the identifiers of D v D 2 . The rupture of one of the uplinks D ^ -lAP ^, D 2 -LAP, does not however release the transmission interval Tfi 'insofar as the identifier of the terminal whose link is not broken remains stored in the section in question.
    In a second embodiment, it is assumed that the association of an access point to the terminal is carried out only on the quality of the uplink.
    In this case, the reception information includes, in addition to the identifiers of the terminals, link quality indicators as measured by the access point. The access point offering the best uplink quality is chosen to be associated with the terminal.
    In step 610, the terminal not only detects the identifiers of the access points but also measures the quality of the signals received (signal / noise ratios) from these access points. In other words, the coverage information transmitted by a terminal to the network controller contains not only the list of visibility access points of the terminal but also indicators of the quality of the downlinks which could be established with these points. access.
    One then determines, among the access points appearing in the coverage information, the one presenting the best downlink quality indicator. In the case where the access point selected for the establishment of the downlink is identical to that selected for the establishment of the uplink, the situation described in relation to FIG. 6A. On the other hand, when the latter is different, the downlink is established by means of a first link, via the Ethernet network, between the associated access point and the access point having the best downlink quality indicator. , called auxiliary access point, and a second link, between this auxiliary access point and the terminal. In this case, there is both an optimal link quality both on the uplink and on the downlink. It is thus understood that there is dissociation between the access point associated with the terminal (and communicating with it during the BP control period) and the access point of the downlink, to which the transmission interval is allocated. .
    There is shown in FIG. 8 an application of the method of allocating transmission intervals, according to this second embodiment, to the optical wireless telecommunication system of FIGS. IA and IB.
    In the upper part of the figure, the uplink and downlink between the terminal D l and the access point LAP t have been indicated diagrammatically. The uplink between D l and LAP t is the one with the best link quality. On the other hand, on the downlink, the link between LAP 3 and D, is here of better quality than that between IAP X and D ,. Thus the downlink selected is made up of a first link via the wired network (Ethernet) between ΙΑΡ γ and LAP. and a second link (optical wireless) between LAP., and D ,.
    The allocation of the transmission intervals is shown in the lower part of the figure. It is noted that this allocation is unchanged on the uplink compared to that of FIG. 7. On the other hand, on the downlink, a data transmission interval is allocated to the link between LAP. and D, instead of being allocated to a link between ΙΑΡ γ and D v . The data flow is always transmitted by ΙΑΡ γ but relayed to LAP. via the network which transmits it to D ,.
    In a third embodiment, it is assumed that the association of an access point to the terminal is carried out only on the quality of the downlink. In this case, the coverage information includes, in addition to the identifiers of the access points, link quality indicators as measured by the terminal. The access point offering the best quality of downlink is chosen to be associated with the terminal.
    In this case, in step 650, the access points not only detect the identifiers of the terminals but also measure the quality of the signals received (signal / noise ratios) from these terminals. In other words, the reception information transmitted by an access point to the network controller contains not only the list of terminals visible from the access point but also indicators of the quality of the uplinks which could be established. with these access points.
    It is then determined, among the access points comprising the identifier of the terminal in their reception information, that presenting the best uplink quality indicator. In the case where the access point selected for the establishment of the uplink is identical to that selected for the establishment of the downlink, the situation described in relation to FIG. 7. On the other hand, when the latter is different, the uplink is established by means of a first link between the terminal and the access point having the best uplink quality indicator, called the auxiliary access point, and a second link, via the Ethernet network, between this auxiliary access point and the associated access point. In this case, there is both an optimal link quality both on the downlink and on the uplink. It is thus understood that there is dissociation between the access point associated with the terminal (and communicating with it during the BP control period) and the uplink access point, that is to say which is allocated the transmission interval and through which the data pass.
    There is shown in FIG. 9 an application of the method of allocating transmission intervals, according to the second embodiment, to the optical wireless telecommunication system of FIGS. IA and IB.
    In the upper part of the figure, the uplink and downlink between the terminal D 2 and the access point LAP 3 are indicated diagrammatically. The downlink between LAP 3 and D 2 is the one with the best link quality. On the other hand, on the uplink, the link between D 2 and LAP 2 is of better quality here than that between D 2 and LAP 3 . Thus, the uplink retained is composed of a first link (optical wireless) between D 2 and LAP 2 and a second link via the wired network (Ethernet) between LAP 2 and LAP 3 .
    The allocation of the transmission intervals is shown in the lower part of the figure. Note that this allocation is unchanged on the downlink compared to that of FIG. 7. On the other hand, on the uplink, a data transmission interval is allocated to the link between D 2 and LAP 2 instead of being allocated to a link between D 2 and LAP 3 . The data stream transmitted to LAP 2 is then relayed by the latter to LAP 3 via the Ethernet network.
    According to a fourth embodiment, the access point associated with the terminal is chosen on the basis of an average of the quality of the uplink and the quality of the downlink, the quality of a link being estimated for example based on a signal-to-noise ratio or error rate metric. In this case, the access point corresponding to the best quality of downlink and the access point corresponding to the best quality of uplink may both differ from the access point associated with the terminal. The allocation of a transmission interval is then carried out for a first auxiliary access point on the downlink, in accordance with the second embodiment, and for a second auxiliary access point on the uplink, in accordance with the third mode. of achievement. Ultimately, the associated access point 5 is then used only for signals and control messages.
    权利要求:
    Claims (5)
    [1" id="c-fr-0001]
    1. Method for allocating transmission intervals in a wireless optical system comprising a plurality of access points connected to a wired network and controlled by a network controller, and a plurality of terminals, characterized in that:
    - Each terminal is associated with an access point among said plurality of access points, such that the average of the qualities of the uplink and downlink between this access point and said terminal is maximum;
    each terminal associated with an access point determines (610) coverage information containing the identifiers of the access points received by the terminal;
    - when the terminal coverage information is reduced to the identifier of the access point associated with the terminal, the access point allocates (625) to the downlink, a transmission interval in a managed available time range by the network controller (CFP / AAAPJ);
    - when the terminal coverage information comprises a plurality of access point identifiers, the network controller allocates (630) to the downlink a transmission interval in an available time range (CFP ^ e n ( AP n )) and ampute (640) correlatively the available time ranges of the access points belonging to the coverage information of the transmission interval thus allocated.
    [2" id="c-fr-0002]
    2. Method for allocating transmission intervals according to claim 1, characterized in that:
    each access point determines (650) reception information containing the identifiers of the terminals received by the access point;
    - when the identifier of a terminal only appears in the reception information of the access point associated with it, the latter allocates (660) to the uplink a transmission interval in an available time range managed by the network controller (CFP ^ (AP „));
    - when the terminal identifier appears in a plurality of reception information, the network controller allocates (670) to the uplink a transmission interval in an available time range (CFPf ee (AP n )) and ampute (680 ) correlatively, the available time slots of the transmission interval thus allocated for all the access points containing the terminal identifier in their reception information.
    [3" id="c-fr-0003]
    3. Method for allocating transmission intervals in a wireless optical system, comprising a plurality of access points connected to a wired network and controlled by a network controller, and a plurality of terminals, characterized in that:
    - Each terminal is associated with an access point among said plurality of access points, such that the quality of the uplink of said terminal and this access point is maximum;
    each terminal associated with an access point determines (610) coverage information containing the identifiers of the access points received by the terminal as well as indicators of the quality of the downlink with these access points, said coverage information being escalated to the network controller via the access points;
    - when the terminal coverage information is reduced to the identifier of the access point associated with the terminal, the access point allocates (625) to the downlink a transmission interval in an available time range managed by the network controller (CFP ^ 7 (AP));
    - when the coverage information comprises a plurality of access point identifiers, the network controller determines among said plurality an auxiliary access point such as the quality of the downlink between the auxiliary access point and the terminal is maximum, the downlink between the associated access point and the terminal comprising a first link through the wired network between the associated access point and the auxiliary access point and a second downlink between the access point auxiliary access and terminal;
    - the network controller allocates to the second downlink a transmission interval in an available time range (CFP ^ n (AP n )) and correlatively cuts the available time ranges of the access points belonging to the coverage information of the 'transmission interval thus allocated.
    [4" id="c-fr-0004]
    4. Method for allocating transmission intervals in a wireless optical system comprising a plurality of access points connected to a wired network and controlled by a network controller, and a plurality of terminals, characterized in that:
    - Each terminal is associated with an access point among said plurality of access points, such that the quality of the downlink between this access point and said terminal is maximum;
    each access point determines (650) reception information containing the identifiers of the terminals received by the access point as well as indicators of uplink quality with these terminals, said reception information being transmitted to the network controller;
    - when the identifier of a terminal only appears in the reception information of the access point associated with it, the latter allocates (665) to the uplink a transmission interval in an available time range managed by the network controller (CFP “^ (AP n ));
    when the identifier of a terminal appears in a plurality of information of reception of access points, the network controller determines among said plurality an auxiliary access point such as the quality of the uplink between the terminal and this auxiliary access point is maximum, the uplink between the terminal the associated access point comprising a first uplink between the terminal and the auxiliary access point and a second link in the wired network between the access point auxiliary and the associated access point.
    [5" id="c-fr-0005]
    5. Method for allocating transmission intervals in a wireless optical system according to one of the preceding claims, characterized in that said optical system conforms to the IEEE 802.15.7 standard.
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    同族专利:
    公开号 | 公开日
    US10461860B2|2019-10-29|
    FR3069401B1|2019-08-30|
    US20190028193A1|2019-01-24|
    JP2019054508A|2019-04-04|
    KR20190010488A|2019-01-30|
    EP3432487A1|2019-01-23|
    EP3432487B1|2019-10-23|
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    法律状态:
    2019-01-25| PLSC| Search report ready|Effective date: 20190125 |
    2019-07-31| PLFP| Fee payment|Year of fee payment: 3 |
    2020-07-31| PLFP| Fee payment|Year of fee payment: 4 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1756914|2017-07-21|
    FR1756914A|FR3069401B1|2017-07-21|2017-07-21|METHOD OF SCHEDULING FOR UPLINAL AND DOWNWARDS OF AN OPTICAL TRANSMISSION SYSTEM|FR1756914A| FR3069401B1|2017-07-21|2017-07-21|METHOD OF SCHEDULING FOR UPLINAL AND DOWNWARDS OF AN OPTICAL TRANSMISSION SYSTEM|
    US16/038,701| US10461860B2|2017-07-21|2018-07-18|Scheduling method for uplink and downlink of an optical transmission system|
    JP2018135608A| JP2019054508A|2017-07-21|2018-07-19|Scheduling method for uplink and downlink of optical transmission system|
    KR1020180084774A| KR20190010488A|2017-07-21|2018-07-20|Scheduling method for uplink and downlink of an optical transmission system|
    EP18184784.9A| EP3432487B1|2017-07-21|2018-07-20|Scheduling method for uplink and downlink channels of an optical transmission system|
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