Hybrid NOMA / TDMA communications method for clustered ad hoc networks

Abstract

The invention relates to a method for determining a multiple access and scheduling mode for communication links in an ad hoc network comprising a plurality of nodes grouped in one or more clusters. It comprises a step of transmitting to a decision-making node, information relating to a quality of the communication links, a step of partitioning the communication links between those using a NOMA type multiple access and those using a TDMA type multiple access, on a flow criterion, a third step of determining a temporal scheduling of the communication links, respecting the calculated multiple access types, a fourth step of transmitting the partitioning information and the temporal scheduling information to the nodes involved in the communication links. The invention also relates to a decision-making node implementing the method. Figure for the abstract: Fig. 2

Description

Title of the invention: NOMA / TDMA hybrid communications method for clustered ad hoc networks Technical field

[0001] The invention lies in the field of radio communications carried out in so-called clustered ad-hoc networks. It relates more particularly to a method for selecting a type of multiple access for the communication links so as to increase the network throughput in different situations compared to a conventional TDMA type function (English acronym for Time Division Multiple Access). Prior art

[0002] Ad hoc networks, or MANETs (English acronym for Mobile Ad hoc Network), are wireless networks that do not rely on an infrastructure with fixed access points, unlike cellular networks. Each node in the network participates in the routing of data, by retransmitting it to other nodes. The choice of nodes involved in a transmission is made dynamically, based on the connectivity of the network. Ad hoc networks are therefore self-configuring and dynamic networks, in which nodes are free to move. They are used when it is necessary to quickly deploy a radio communications network in an area where the infrastructure of cellular networks is insufficient or inaccessible. This may be the case, for example, for civil security forces (firefighters, police, ambulances, etc.)) during sporting events or shows, special events or disasters, for airports, or for military personnel on the ground.

[0003] Ad hoc networks are expected to be deployed en masse in future telecommunications networks, in order to create high-connectivity sub-bubbles to link connected objects. This is already the case with fifth-generation radio communications (5G), where the concept of Flying Ad hoc networks (FANET) has been introduced for drone control. VANETs (Vehicular Ad hoc Networks) are used to model road traffic management systems and information sharing between vehicles to improve road safety. SPANs (Smart Phone Ad hoc Networks) are ad hoc networks based mainly on Wi-Fi and Bluetooth technologies.

[0004] Within ad hoc networks, clusters are formed, which correspond to groupings of nodes, often based on proximity criteria. The allocations of Clusters can be created by configuration (to create operational groups) or dynamically based on the proximity of nodes, their capabilities, and their needs. Frequency resources (logical communication channels) are assigned to each cluster to minimize interference between clusters. Within a cluster, an elected node acts as a coordinator. This node is responsible for managing the cluster: adding or removing nodes, and allocating resources. Gateways can be created between different clusters to ensure node connectivity across the entire network.

[0005] Within a cluster, resource allocations are generally carried out according to a TDMA-type multiple access scheme, where a frame, representing the instants of transmission of the nodes in time, is divided into intervals called slots each allocated exclusively to a particular communication link. TDMA accesses make it possible to guarantee that the links communicate orthogonally without creating interference. The counterpart is that the performances obtained in terms of flow rates are suboptimal since they do not take into account the capacity of several users to transmit simultaneously.

[0006] There are other access control techniques that can also be applied to ad hoc networks, in particular the so-called NOMA (Non Orthogonal Multiple Access) multiple access techniques. These techniques consist of combining power management at the transmission and successive interference cancellation (SIC) at the reception. They are used for example in LTE Advanced (Long Term Evolution - Advanced, a cellular network standard), or in the ATSC 3.0 standard (Advanced Television Systems Committee, a digital television standard). NOMA-type multiple access has also been considered as relevant candidates for 5G applications.

[0007] NOMA-type multiple access techniques do not guarantee the absence of interference between the communication links, but process the signals in such a way that the sources can be dissociated by the receiver. NOMA techniques allow several links to be activated simultaneously, and are associated with precoding / decoding operations to eliminate interference at reception. If the length of the precoder (in terms of number of TDMA slots) is less than the number of slots required to communicate the same number of links in TDMA, then the overall throughput is increased. However, depending on the configuration of the links in the cluster, the NOMA solution may be less good than the TDMA solution (in terms of SNR, the English acronym for Signal to Noise Ratio). In addition, it does not guarantee a minimum throughput. It is therefore not It is possible to implement a communications method based solely on multiple accesses of the NOMA type without resorting to transmission power management processes for each node of the cluster, which are possible in the case of a cellular network but complex to implement within ad hoc networks.

[0008] An object of the invention is therefore to define a method for improving the overall throughput of an ad hoc network compared to a solution using TDMA type network access, while guaranteeing a minimum throughput per link. To this end, the method which is the subject of the present invention proposes to combine the NOMA and TDMA access techniques so as to take advantage of the best of both in any situation.

[0009] The paper RV Bhat, M. Motani and TJ Lim, "Hybrid NOMA for an Energy Harvesting MAC With Non-ldeal Batteries and Circuit Power," in IEEE Transactions on Wireless Communications, vol. 18, no. 8, pp. 3961-3973, Aug. 2019, doi: 10.1109 / TWC.2019.2919827, describes a hybrid NOMA / TDMA communications system for a non-ad hoc communications system. In this paper, the allocations of logical channels to TDMA or NOMA communications are made in such a way as to maximize the total throughput with a power and battery consumption constraint. However, the calculations require knowledge of the instantaneous channel of all radio links, which is not necessarily possible for ad hoc networks due to possible rapid channel fluctuations, transmission latencies in ad hoc networks and limited signaling exchange capabilities.Furthermore, the resolution is done by a computationally complex and suboptimal method (considering only a local optimum).

[0010] Another object of the invention is therefore to propose a method for making decisions regarding the access system to be used and the scheduling of TDMA and NOMA accesses which is simple to implement, and requires only few exchanges within the network, in particular by not relying on knowledge of the instantaneous propagation channel of the radio links. Summary of the invention

[0011] To this end, the present invention describes a method for determining a multiple access and scheduling mode for a plurality of communication links in an ad hoc network comprising a plurality of nodes grouped in one or more clusters, the communication links being operated on at least one logical channel. The method according to the invention comprises: • a first step, implemented by the nodes, of transmission to a node designated as a decision-making node, of information relating to the quality of the communication links, • a second step, implemented by the decision-making node, of partitioning the communication links between communication links using NOMA-type multiple access and communication links using TDMA-type multiple access, on a flow criterion calculated from the information relating to the quality of the communication links transmitted in the first step, • a third step, implemented by the decision-making node, of determining a temporal ordering of the communication links on the common logical channel(s), respecting the types of multiple access calculated during the second step, • a fourth step, implemented by the decision-making node, of transmitting the partitioning information calculated in the second step and the temporal scheduling information calculated in the fourth step to the nodes involved in the communication links.

[0012] According to different embodiments, the information relating to a quality of the communication links is, for each communication link: • statistical information on a propagation channel of the communication link, • statistical information on interfering propagation channels, and • a noise power level perceived by the destination node of the communication link.

[0013] Advantageously, the second step of partitioning the communication links comprises the implementation of an iterative algorithm comprising, for each communication link, the calculation of a user throughput using a TDMA type multiple access mode, the calculation of a user throughput using a NOMA type multiple access mode taking into account the multiple access modes used by the other communication links, and the choice of the access mode maximizing the user throughput of the communication link.

[0014] According to one embodiment of the method, the second step of partitioning the communication links comprises: • a step of calculating a user rate for each communication link when all the communication links are associated with TDMA type multiple access, • a step of calculating a user throughput for each communication link when all the communication links are associated with multiple access of the NOMA type, • a step of determining a set TN of communication links associated with a NOMA type multiple access and a set T of communication links associated with a TDMA type multiple access by comparing the respective user rates for each communication link, iteratively, until convergence: • a step of calculating a user throughput for each communication link of the TN set when only the communication links of said T set use multiple access of the NOMA type, • a step of searching for communication links belonging to the set T for which the user rate for TDMA type multiple access is greater than or equal to the user rate for NOMA type multiple access, and of transferring these communication links to the set T of communication links using TDMA type multiple access.

[0015] According to a particular embodiment, the NOMA type multiple access technique is based on the use of linear coders / decoders, and the second step of partitioning the communication links between communication links using NOMA type multiple access and communication links using TDMA type multiple access on a throughput criterion comprises the calculation of a linear coder / decoder size r and the calculation of coding / decoding matrices U and V adapted to the number of communication links using NOMA type multiple access.

[0016] According to one embodiment, the third step of partitioning the communication links comprises the definition of a long time interval, or frame, divided into a plurality L of short time intervals, or slots, and of distributing the L slots between the communication links in order to maximize the average overall throughput of the ad hoc communication network while guaranteeing a minimum throughput for each communication link.

[0017] According to a particular embodiment, IJC slots are allocated exclusively to each communication link using TDMA type multiple access, with p^ a minimum throughput constraint per link and p^ a physical throughput associated with the communication link, [ LR^ 1 slots are allocated to the communication links | ^NOMAjnin | using NOMA-type multiple access, with the residual slots being distributed between the communications links using NOMA type multiple access and the communications link using TDMA type multiple access with the highest physical throughput p^.

[0018] Advantageously, the third step of partitioning the communication links further comprises the calculation of an optimal frame length £* taking into account the results of the second step of partitioning the communication links.

[0019] According to one embodiment, the method for determining a multiple access and scheduling mode according to the invention is implemented jointly on a plurality of clusters, by grouping their logical channels.

[0020] The invention also relates to a decision-making node in an ad hoc network comprising a plurality of nodes grouped in one or more clusters and implementing a plurality of communication links on at least one logical channel. The decision-making node comprises calculation means configured to implement: • a first step of receiving information relating to a quality of the communication links, • a second step of partitioning the communication links between communication links using NOMA type multiple access and communication links using TDMA type multiple access, on a flow criterion calculated from the information relating to the quality of the communication links received in the first step, • a third step of determining a temporal ordering of said communication links on the logical channel(s), respecting the types of multiple access calculated during the second step, • a fourth step of transmitting the partitioning information calculated in the second step and the time scheduling information calculated in the fourth step to the nodes involved in said communication links. Brief description of the drawings

[0021] The invention will be better understood and other characteristics, details and advantages will appear more clearly on reading the following description, given without limitation, and thanks to the appended figures, given by way of example.

[0022] [Fig-1] [Fig. 1] represents an ad hoc network in which a method for determining a network access and scheduling mode according to the invention can be implemented.

[0023] [Fig.2] [Fig.2] is a block diagram of a method of determining of a multiple access and scheduling mode according to an embodiment of the invention.

[0024] [Fig.3] [Fig.3] a block diagram describing a possible implementation of a partitioning between multiple access of type TDMA and multiple access of NOMA type in a method for determining a multiple access and scheduling mode according to an embodiment of the invention.

[0025] [Fig.4] [Fig.4] represents an example of partitioning between communication links using TDMA type multiple access and communication links using NOMA type multiple access at the end of the second step of a method for determining a multiple access and scheduling mode according to an embodiment of the invention.

[0026] [Fig.5] [Fig.5] schematically represents the problem of optimizing the scheduling of communication links in a given application case for illustration purposes.

[0027] [Fig.6a] [Fig.6a] is an illustration of the partitioning of communication links carried out by the method according to the invention in the case of two clusters each having its own logical channel considered separately.

[0028] [Fig.6b] [Fig.6b] is an illustration of the partitioning of communication links carried out by the method according to the invention in the case of two clusters each having its own logical channel considered jointly.

[0029] [Fig.7a] [Fig.7a] gives theoretical average throughputs obtained as a function of the number of communication links in a given application case by way of illustration so as to observe the contribution of the method for determining a multiple access and scheduling mode according to the invention.

[0030] [Fig.7b] [Fig.7b] gives theoretical minimum throughputs per link obtained as a function of the number of communication links in a given application case by way of illustration so as to observe the contribution of the method for determining a multiple access and scheduling mode according to the invention.

[0031] [Fig.8] [Fig.8] is an illustration of the partitioning of communication links carried out by the method according to the invention in the case of two clusters jointly having a single logical channel.

[0032] [Fig.9a] [Fig.9a] gives theoretical average throughputs obtained as a function of the number of communication links in a given application case by way of illustration so as to observe the contribution of the method for determining a multiple access and scheduling mode according to the invention.

[0033] [Fig.9b] [Fig.9b] gives theoretical minimum throughputs per link obtained as a function of the number of communication links in a given application case by way of illustration so as to observe the contribution of the method for determining a multiple access and scheduling mode according to the invention.

[0034] [Fig. 10] [Fig. 10] is a block diagram of the steps of a method for determining a multiple access and scheduling mode according to the invention implemented by a decision-making node.

[0035] Identical references may be used in different figures when they designate identical or comparable elements. Description of the embodiments

[0036] [Fig. 1] represents an ad hoc network in which a method for determining a network access and scheduling mode according to the invention can be implemented.

[0037] It comprises a plurality of nodes 101, 102, 103, 104, etc. These nodes are part of the same subgroup of nodes, or cluster 110. The ad hoc network may comprise one or more clusters. Some nodes belonging to the same cluster implement communication links represented in Figure 1 in solid lines, such as for example the communication link 121 between the node 101 and the node 102. In the example of Figure 1, W = 5 communication links are established between ten nodes of the cluster 110. A link 1 is defined as being associated with a transmitter-receiver pair Tx7 - Rx7. We call Sj the symbol that the transmitter Tx7 wishes to transmit to the receiver Rx7. The links communicate on the same logical channel, which can create interference at reception when they transmit simultaneously, as in the case of multiple access of type NOM A. The interfering signals for the receivers are shown in dotted lines in [Fig.l].For example, signal 122 represents interference generated at receiver 102 by emissions from transmitter 104.

[0038] The method according to the invention applies in a context where the nodes of the network can communicate using a multiple access mode of the TDMA type or of the NOMA type. The method can be implemented regardless of the communications standard used to implement the TDMA or NOMA transmission. Indeed, the operating point, in terms of throughput, is likely to vary depending on the communications standard used, but this does not impact the general operation of the method for determining a multiple access and scheduling mode according to the invention.

[0039] For illustration purposes only, the description is subsequently based on a very simple NOMA multiple access technique, which can be implemented at low cost and without increasing complexity in most existing radio sets. This NOMA technique is based on the use of linear codes, and consists of: - on transmission: to multiply the symbol to be transmitted by precoding coefficients, - at reception: to multiply the precoded symbols received by decoding coefficients, before demodulating them by a conventional demodulator.

[0040] The description considers SISO transmissions (Single Input Single Output), where the transmitting and receiving nodes each have only one antenna, but the invention works also when the transmitter and / or receiver have multiple antennas and implement antenna processing techniques.

[0041] By applying the NOMA multiple access technique described above in SISO to all the links in the network, and by setting vj G p^2' as the linear precoder of the transmitter Tx7 and r € N* as the length of the coders, the signal sent by each transmitter TxJ is vJSÿ and the signal received at Rx2 can be written as: y,=vT Pi hnsi+husi+“ï where P is the transmitted power at Tx2, hjj is a realization of the complex random fading propagation channel, which corresponds to both large-scale fading and small-scale fading of the TxJ to Rx2 link, and where g Xrx^ represents the power noise vector Pn.

[0042] After applying the linear decoder of the receiver Rx2, denoted u. g pi*2', the symbol estimated in Rx2 can be written as being: = which can be reformulated as: = u.vf ^p] hnSi+^îUyvJ hijSj+u^. pi The emitted Pi powers are specific to the devices used as nodes in the network, and are known.

[0043] [Fig.2] is a block diagram of a method for determining a multiple access and scheduling mode according to an embodiment of the invention.

[0044] It applies to the case of communication links established between nodes of one or more clusters belonging to an ad hoc network. In the examples presented below, the communication links are operated between nodes belonging to the same cluster (intra-cluster communications), but the method applies in an identical manner to communications carried out between nodes belonging to distinct clusters (inter-cluster communications), provided that the nodes are configured to communicate on one or more common transmission channels, or logical channels.

[0045] The method for determining a multiple access and scheduling mode according to the invention comprises a first step 201 of transmitting, to a node designated as a decision-making node for the cluster or for a plurality of clusters, information relating to the quality of the communication links. This step is implemented implemented by receiving nodes of the communication links, and can be carried out continuously, or at each iteration of the process.

[0046] This step involves identifying a node as a decision-making node. For example, when the method is applied to a single cluster, as in [Fig.l], the decision-making node may be the cluster head node, determined in a usual manner in ad hoc communications networks to distribute resources between the nodes of a cluster. It may also be one of the nodes involved in the communication links, or another node belonging to the cluster, such as node 105.

[0047] When the method is applied to a plurality of clusters, the decision node may be a separate node for each cluster when the method is implemented separately on the different clusters, or be a common decision node for the plurality of clusters when they are considered jointly.

[0048] The decision node may be chosen based on performance considerations or geometric considerations, and / or be elected by the nodes of the cluster. The node designated as the decision node may be required to evolve dynamically over time.

[0049] According to one embodiment of the invention, the information relating to the quality of the communication links are power levels received by the reception nodes RxJ of the communication links, including the power level of the associated transmission node Tx1, but also the power levels of the signals received from the other transmitters on the interfering links and the noise power level perceived at the reception nodes Rx7.

[0050] Advantageously, in order to reduce the amount of signaling information transmitted in the cluster, the transmitted power levels can be averaged and transmitted periodically or upon request from the decision-making node.

[0051] According to another embodiment of the invention, the information relating to the quality of the communication links are instantaneous estimates, made by the RxJ nodes receiving the communication links, of the instantaneous propagation channel on the communication link which concerns them, but also of the instantaneous propagation channel on the interfering links hij such as the interfering link 122 for the node 102, and of the noise power level at the RxJ receiving nodes. These estimates can for example be made from known sequences present in the physical layer for the purposes of estimating the propagation channel.

[0052] According to a preferred embodiment of the invention, the information relating to the quality of the communication links is, for each communication link, statistics associated with the propagation channel of interest h^, and with the channels of interfering propagation hÿ, and the perceived noise power level at the receiving node Rx1.

[0053] Such statistical estimates of the propagation channel are known to those skilled in the art. For example, in the case of a flat Rayleigh channel, it is possible to estimate the statistical parameters of the channel by taking the empirical variance of the samples of estimates of hjj and removing the variance of the noise. For the Rice channel, a method for estimating the statistical parameters: - from noisy samples of the propagation channel is proposed in the article by X. Leturc, P. Ciblât and CJ Le Martret, "Estimation of the Ricean K-factor from noisy complex charnel coefficients" 2016 50th Asilomar Conference on Signais, Systems and Computers, 2016, pp. 1092-1096, - from noisy samples and under Nakagami-m masking phenomenon is proposed in X. Leturc et al., "Estimation of the Ricean K Eactor in the Presence of Shadowing" in IEEE Communications Letters, vol. 24, no. 1, pp. 108-112, Jan. 2020.

[0054] In the case where the estimation is done from SINR samples (Signal over Interference plus Noise Ratio), a method for estimating channel statistics in a flat Rayleigh channel with an interfering signal is proposed in the article by D. Jia, X. Leturc, M. Assaad and CL Martret, "Rayleigh Channel Statistics Estimation Using SINR Samples Under Single Interference" 2022 IEEE 95th Vehicular Technology Conference: (VTC2022-Spring), 2022, pp. 1-5.

[0055] Compared to other embodiments, the transmission of information relating to the quality of the communication links in the form of statistics associated with the propagation channels has the advantage of limiting the signaling transmitted on the network, and of not being impacted by one-off phenomena. Furthermore, the use of the instantaneous channel can be inefficient when the transmission of information is too slow compared to the temporal fluctuation of the propagation channel: the information received by the decision-making node is then no longer representative of the current propagation channel, and therefore does not allow appropriate decisions to be made.

[0056] The method for determining a multiple access and scheduling mode according to the invention comprises a second step 202, implemented by the decision-making node, of partitioning the communication links between communication links using NOMA type multiple access and communication links using TDMA type multiple access. This partitioning is done on a flow rate criterion, the flow rates being calculated from the information relating to the quality of the communication links transmitted to the decision-making node during the first stage.

[0057] This second step requires the calculation of the accessible user rates based on the multiple access chosen and the interference.

[0058] The physical throughput associated with an Rxf receiver using a TDMA-type multiple access mode is linked to the definition of the physical layer. One way to calculate this throughput at the receiver is to consider the Shannon capacity: pT := HAjjlog ( 1 + SNR ) °where Wb is the signal bandwidth and the SNR in RxJ is expressed as: SNR, — 1 rn

[0059] The “ operator is used to define a mathematical variable, unlike the — operator which is obtained after a mathematical deduction.

[0060] The average physical flow rate at the receiver RxJ is defined as follows: R? :~ E [ R^ ] with El the mathematical expectation.

[0061] The average physical throughput R^ in TDMA for the communications link 1 can therefore be calculated from the SNR. The SNR can be calculated for each communications link from the power levels (signal power and noise power for each communications link) of the values ​​of the direct propagation channels or the estimates of the statistics of the direct propagation channels transmitted by the nodes during step 201.

[0062] Other methods are possible for calculating this average physical rate R^ in TDMA, such as for example using formulas specific to the waveform considered, or by linking the SNR to a theoretical or measured bit or packet error rate.

[0063] When the multiple access mode is of the NOMA type, the transmitters communicate simultaneously, which induces interference. The physical throughput at the receiver RxJ can then be written as: Knoma / U, V) = Wilog^ l+SINRjtU, V) ) where the SINR at the receiving node RxJ depends on the NOMA method used, and : V:= \A / V1 are respectively the matrices containing the set decoders and precoders obtained by considering that all network links use a NOMA access technique.

[0064] In the case given here for illustration, with SISO nodes using a NOMA-type multiple access technique with linear precoders Vj g plxr of size r < N for the transmitter Tx and linear decoders y . ç p-^7 for the Rx7 receiver. The SINR in Rx7 is expressed as follows: SINRXUV)

[0065] This SINR can be calculated from the instantaneous estimates or statistical models of the direct and interfering propagation channels transmitted by the nodes during step 201. It can also be calculated using the power levels transmitted by the transmitter of interest and the interfering transmitters during step 201, considering that the power received for a link (direct or interfering) is equal to p. | fa.. |2 or 2. The definition of the SINR is specific to the NOMA scheme considered. For example, For example, in the case of a power NOMA where interference is processed by a SIC algorithm, the SNR formula does not include the vectors u and v.

[0066] The average physical flow rate at the receiver Rx7 is defined as follows: “Soma / U, V) = E[^0MA;(U, V) ]

[0067] The physical throughput for a communication link using a NOMA type access mode can therefore be calculated from the information received during step 201.

[0068] The user throughput is the throughput related to the protocol layer, and is equal to the physical throughput multiplied by the proportion of time allocated to the corresponding link during a transmission. To define it, we consider a frame containing L slots which we will call in the following “frame of length L”. The term “slot” is defined as being a sub-interval of time of the frame of length L, and constitutes the smallest unit of time that it is possible to allocate for communications on a given link. Each frame comprises L slots.

[0069] In the case of a TDMA type multiple access mode, we then define as the number of transmissions for each link ig -[1, A / } of the network, where the duration The elementary rate of a transmission is one slot. We assume that L > N so that each link can be allocated at least one transmission. In TDMA, the user rate at receiver Rx7 on a frame of length L can therefore be written as follows: RtDMA4 L •

[0070] Furthermore, we consider, in the context of a TDMA access mode, a scheme using a “round-robin” algorithm, the objective of which is to allocate the same number of slots to each link. To do this, the transmitters communicate at each slot one after the other, i.e. Tx1, then Tx^, In the following, we call this method "round-robin TDMA". Other methods could be considered in a similar way.

[0071] When applying the TDMA round-robin on a long frame, i.e. when L is large compared to N, we can make the approximation that the number of slots allocated is the same for each link, which is written as: «1 =.....=nN = ^.

[0072] Therefore, the average user throughput at the RxJ receiver when doing TDMA round-robin can be written as: f>u __ ^RRTDMM N •

[0073] In the case of a NOMA type multiple access, ^NOMA is defined as being equal to the number of times that a NOMA type multiple access is applied to a frame of length L. In NOMA, the user rate at the receiver RxJ on a frame of length L can therefore be written as follows: ■RnOMa / U, V) = ^«NOMA^U, V).

[0074] As with the TDMA type multiple access mode, the use of a NOMA type multiple access for the N communication links can use the following approximation for long frames, i.e. L large compared to r, r being the length of the linear coders of the NOMA when the NOMA access mode uses linear codes: ~ T nNOMA ~ T >

[0075] Which leads to the expression of the user rate in Rx1 as follows: ou (TT VI ^NOMA,AVJ ~ r

[0076] This formula is related to the NOMA scheme considered. For example, a NOMA scheme in power domain corresponds to r = 1.

[0077] The partitioning of the links into two groups of links, those using NOMA type multiple access and those using TDMA type multiple access, is then done iteratively on a throughput criterion, so as to favor the solution making it possible to obtain the highest throughputs for each communication link. To do this, we define Tjy as the set of links having a higher throughput when using NOMA type multiple access than when using TDMA type multiple access. Then, we define Td as the set of links having a higher throughput when using TDMA type multiple access than when using NOMA type multiple access. The sets TN and T are calculated from

[0078]

[0079] so that they form a partition of the set of all links {1, jy}, i.e. Tn U Td = {1, Td = 0. Figure 3 is a block diagram describing a possible implementation of this step 202 of partitioning the communications links into the TN and T d sets. It comprises three steps: - a first step 301 of calculating the user rates obtained by applying a “round-robin” criterion for TDMA access to all the communication links, by calculating the rates ,A . for all the communication links i; - a second step 302 of calculating the user rates obtained by applying a NOMA type multiple access to all the communication links over an elementary duration for a NOMA transmission, corresponding to r slots. These rates depend on the NOMA access technique used and the number of links transmitting simultaneously. In the case given for illustration purposes, they are obtained by also considering the matrices U(r)7V(r) and the length r, by calculating the rates -^NOMAï(U(r), V(r) ) For all the communication links 1; - a third step 303 of determining the sets of links and Td defined as being the sets of nodes assigned respectively to a multiple access of NOMA type and of TDMA type, on a flow criterion, with: Tn { if € { 1, ..., N} | -RnOMAj > -^RRTDMAj} T d ~ { 2 € { 1' • • • ' N} I ^NOMA^ — -RrRTDMA^} WHERE ^NOMAd is a simplification of the notation ^OMAj(U(r)z V(r)); - a fourth step 304 of calculating the user rates obtained by applying NOMA access to the communication links of the set T, i.e. by recalculating .Rnoma^UM' V(r) ) For all the ie TN . The rate obtained is then noted t^Tn; ■^NOMA,! - a fifth step 305 of determining the communication links belonging to the set TM for which ô11, and v ^NOMAJ — ^RRTDMAd transfer of said communication links from the TN set to the Td- set The fourth step 304 and the fifth step 305 of the method are iterated until the sets and T d converge. It can be shown that this algorithm converges since the limiting case comes down to the case where the set has only one link, and the set Ten has N -1. This situation amounts to using TDMA type multiple access on all the links in the network.

[0080] The implementation presented in [Fig.3] has the advantage that the flow rates used to determine the distribution of multiple accesses of the communication links are adjusted as closely as possible in relation to the flow rate accessible in NOMA.

[0081] Advantageously, in the case where the NOMA scheme considered is a scheme using linear precoders / decoders, the vectors and sizes of these linear precoders / decoders can be optimized with respect to the number N of communication links and the user rates during the second step 302 and the fourth step 304 of the method. In this case, at each of these steps, the length r of the linear precoders / decoders and the vectors U( T ) and V( L ) can be recalculated, to obtain the optimal values ​​r*, U* and V* before calculating the NOMA rates ^NOMa / U * ( r * ), V* (r* ) ) used during the third step 303 and the fifth step 305.

[0082] Indeed, in the case of multiple accesses of the NOMA type where the non-orthogonal access technique is based on the use of linear coders, the size r of the coders is between 2 and N -1 slots, (the case r = N amounts to doing TDMA).

[0083] The problem of joint optimization of linear encoders and their size can be written using the approximation of ^^0MA4(U, V) ' described above, as follows: U*V,r*= argmax S^Soma^U, V), U,VëPVx?^. JV-1} where the argmax() function gives the index of the maximum.

[0084] A possible method to solve this problem is to treat it sequentially for a fixed value 1, by solving for any value r = 2, N -1 the following problem: U*(r), = argmax^^SoMA^CU V) U / V€pJvxr where U*(r)V(r) are the optimal linear encoders among the linear encoders of size r.

[0085] We then calculate the total average user throughput of the network with the optimal coders U* and V* for this given value 1, which is expressed as:

[0086] Finally, we choose the value r* which maximizes the total flow rate, in other words: r* = argmax / îN0MA(r) n=2r.„Nl

[0087] The linear encoders used are those having been calculated for r = r*, i.e. U*(r*),V*(r*)-

[0088] Note that to solve the problem of calculating u* ( r ), V* ( r ) for an r

[0089] given, it is also possible to use non-convex optimization techniques such as alternating optimization, geometric programming or Riemannian optimization. The term does not depend on the instantaneous channel and can be ■^NOMAd calculated for example analytically. One possible method, considering a Rayleigh channel, is to use the following approximation: «NOMAj = log2( 1+ SINR?'1"') where SINR^ «1 approximation of the SINRj expressing itself as: qtntr hard _ )

[0090] The resolution can be done by combining an alternating optimization and gradient descent method for a given encoder length r, such that: U* (r), V* (r) = argmax^ log (1 + SINRf ardU (r), V (r)). UV€P'^r 1 1

[0091] Figure 4 represents an example of partitioning between communication links using TDMA type multiple access and communication links using NOMA type multiple access at the end of the second step (202) of a method for determining a multiple access and scheduling mode according to an embodiment of the invention. It can be seen that certain communication links, belonging to the set T, are associated with the TDMA multiple access mode 402, while the other communication links, belonging to the set TN, are associated with the NOMA multiple access mode 401.

[0092] The method according to the invention comprises a third step 203 of determining a time scheduling of the communication links, respecting the types of multiple access calculated during the second step 202. This step is implemented by the decision-making node. It consists of finding the best time slots to allocate to the communication links on the logical channels assigned to them.

[0093] Still considering a frame of length C, the objective is to optimize the number of slots allocated to each link taking into account the length of the frame L, in order to maximize the overall average network throughput while guaranteeing a minimum throughput for each network link. This task can be implemented in two ways: - considering that the frame has a given and fixed length L; - by jointly optimizing the length L of the frame and the overall flow rate network means.

[0094] Figure 5 schematically represents the optimization problem of the scheduling of communication links in the case of a 501 frame 5 gl. The problem is to best assign Tn = {L 2, 3}^Td of length L = 10 slots, with N = 6 communication links. Communication links 1, 2 and 3 (502) use a NOMA type multiple access mode, a NOMA implementation here having a duration of r = 2 slots. One or more pairs of slots must then be reserved in the frame for the simultaneous transmissions made by these three communication nodes. Communication links 4 (503), 5 (504) and 6 (505) use a TDMA type multiple access mode. At least one slot must be reserved in the frame for each of these communication links. We therefore have = {4 slots based on a minimum throughput per link, in order to optimize the overall network throughput. Frame definitions are valid until a new iteration of the process modifies the slot allocations.

[0095] In the case of a frame of fixed length L, the parameters nk for k GT d and ^NOMA must be optimized, nk corresponding to the number of transmissions for the communication link kET^ in the frame, and ^NOMA corresponding to the number of times a NOMA access is reserved in the frame. Since L corresponds to the total number of slots to be allocated, the parameters nk and ^NOMA are constrained by the following equality: X 111 + or = L where r is the duration of a NOMA realization. In addition, the ^i€Td NOMAX 1 ' overall average flow rate p^y of the network obtained following the second stage 202 of implementation ■fVsuin implementation of the method according to the invention can be written as follows: ^sum Z -^NOMAj + 2jk&T, TDMAJf ■ / .ad

[0096] Since the technical solution aims to maximize the overall network throughput by ensuring a minimum throughput per link, the scheduling optimization problem (PI) can be formulated as: ( ) kETd' ^noma — argmax -Rsum under constraints that: ' ^ idma k ^0 kÇ. Td °ù Rq is the minimum flow constraint by nU'i\ _ nu ^NOMAjnin — K0 ^k&Tdnk+ nNOMAr = k, link, configurable according to user needs and the feasibility of the problem, __£noma and .__minR^ ^NOMAjnin L ^NOMAjnin ^NOMAjnin ' ^^^NOMAJ

[0097] This problem can for example be solved using an analytical approach which allow : - to test feasibility analytically, i.e. without using any iterative procedure, - to find the optimal solution of (PI) analytically, i.e. without using any iterative procedure, which is significantly less complex than the heuristics proposed in the state of the art.

[0098] To test the feasibility of the optimization problem, we can demonstrate that (PI) is feasible if and only if we have the following condition: nmin a. nmin rc î where ■ T LRl tkeT ,k + nNOMAr — nmm dr <P pf ,\fkeTd min — [ 1 are respectively the minimum number of transmissions nN0MA | nNüMA,min I of the link k and the links in T such that (PI) is feasible, the operator designating the upper whole part.

[0099] This result is demonstrated by showing that the minimum number of transmissions of each communication link (21™in and H^Sma^ necessary to respect the flow constraint must not exceed the total number of slots L. Furthermore, it is

[0100] Interestingly, the feasibility of (PI) can be verified only through the condition described above, rather than through an iterative procedure. To express the optimal solution of (PI), we define the following variables: __V which corresponds to the total physical flow rate of the links 7vsum,TY — ZjeT' -^NOMAj FFJ of the TN set, which corresponds to the link with the most k&Td k physical high speed in Td, nkmæ the number of slots associated with the link km^ and Your X nniin - nPWl < a F which corresponds to the number of slots remaining after ^k^T, k "NOMA1 1 1 having allocated slots to the communication links to guarantee the feasibility of (PI), that is to say to respect the constraints of (PI).

[0101] The optimal solution of (PI), which is free from the TDMA round-robin rules, can be expressed as follows: if ô'P < p, the optimal solution of (PI) is: SU1H,7'^ — l^max ' n* _ nmm V c T \ JL 1 if r -, the optimal solution of nk~ nk • * K t 1 d \ \Kinaxj rCSum,T v > ^-k^ j nNOMA = 11NOMA InJ = n^+LreS ' Aniax Kmax (PI) is: 'ni = n^, VkeTd\ {k^} Td\{ÀmaI}designating the private set Td n* — nniin _i_ II 1 Ï2NOMA—nNOMA^ L r J , nk = nkin + Lres~ [ ] T *max Kmax 1 "■ of kinax, and the operator j denoting the lower integer part.

[0102] This result is demonstrated by noting that the optimal allocation of transmissions ( -¾) ct ^NOMA is carried out in a first step by allocating the slots necessary to guarantee the feasibility of (PI), that is to say by allocating n™in slots to the communication links k GT and ^nSma-^ s^ots to the ^ens communication of the set TIn a second step, the remaining Lres slots are either allocated to the links of the set T or to the links of the set TN, depending on the condition < rR^ ' indicates the link group (TN or T^) giving the highest throughput on 1 slots. If pR^ , T's links provide higher throughput SUm,Tv ^max that those of TN and the remaining Lres slots are allocated to kmax. If > pR^ , suni,T\ Lmax the links of T provide a higher throughput than those of T and the remaining Lre$ slots are allocated for NOMA-type multiple access, then if there are slots remaining (this number is necessarily less than r), they are allocated to the kmax link.

[0103] Another solution to this problem, compatible with the round-robin algorithm, consists of: - determine the maximum value of n^11 among the nodes of the set of nodes belonging to the set T ^(k& Tsoit := then kGTd successively allocate n1^1 slots to each link of the set T & - check the feasibility of the solution, i.e. check that there are enough slots to allocate in round-robin while ensuring a minimum throughput, i.e. the following condition: Mn^ + L, where M is the number of links in the set T d, if feasibility is assured, allocate the remaining slots to NOMA links, i.e. n* — nrnin I £22 | with Lres — L- Mnÿti1 - 1®^' otherwise, nNOMA-nNOMA+RR NOMA relax the constraints, or deviate slightly from the round-robin principle by allocating a different number of slots, less than or equal to, to certain links in the set T d.

[0104] Another solution is to simultaneously optimize the scheduling of the nodes and the length L of the frame. Indeed, since the frame length L has an influence on the overall average throughput of the network, this parameter can be optimized to improve the overall throughput. In addition, minimizing the frame length L makes it possible to reduce the latency in the network.

[0105] As before, an analytical approach can be used to determine a feasibility condition for the problem and the optimal solution. The corresponding optimization problem (P2) can be formulated as follows: = argmax under the constraints that: ^TDMAJr - V k ET d । Pu'Tn > t?u ^NOMAjnin —-^0 ( + ^NOMA-^ — L'

[0106] To test the feasibility of (P2), it is possible to demonstrate that (P2) is feasible if and only if one of the following conditions is verified: \ d 'U ^NOMA.miii / - 1 -L r \ = 1 and ( are 1 I 1 V ; -^NOMAjnin \ “UAjt ANON1A min / rational numbers.

[0107] The rationality of average flow rates is most of the time respected since we are considering digital communications.

[0108] To express the optimal solution of (P2), we define the following operators: the GCD (greatest common divisor) and the LCM (least common multiple). These two operators can be calculated with the Euclid algorithm. Moreover, in the following, the operation ppQjÿjf ( a ) corresponds to the LCM of all the terms of an, ne M and de b.

[0109] The optimal solution of (P2) can be obtained with the following procedure: - test the feasibility of (P2) using the feasibility condition defined above. This step consists of analyzing whether the conditions set are feasible or not to guarantee a minimum throughput per link, i.e. whether the number of slots to be allocated in the frame of length L is sufficient for each link to have a user throughput greater than the minimum user throughput imposed. U If this is not the case, the minimum flow constraint must be reduced, or the transmission power of the devices increased; calculate Rnomaj and k^ — argmaxÈ^'puls kerd compare ô and T,tj P Rsum,TN if T <rô^ , ■^sum,TjV — 1 • calculate the values ​​-, „ \ ( KT* \ 2 and (P^ € J (p ,q ) g 2 such that: k^NOMA 4NOMA? v 7 _ ^PNOMA_ WHERE = Xk\R^=R^ 1' Td \Kmax, ^QMAjmn max { I k kniJ GCD(pN0MA' ^noma) — let Y k € Tj \ Kmax, PGCD ( p^, = 1 • calculate L* = LCM|(g ) V k) keTd\Kinæ noma / calculate the values (¾ € (N')2and (Per ^o)€ (n*)2 such as: VkeT d> r\L~^kGTdRl where PGCD(pQ / qQ) = let VkeTd, PGCDfp^qr^l. - calculate * / L = LCM(^f)

[0110] [YES]

[0112]

[0113] - calculate the parameters (} and n^OMA by solving the problem (PI) on a frame length £*. Finally, the method for determining a multiple access and scheduling mode according to the invention comprises a fourth step (204), carried out by the decision-making node, of transmitting information concerning the multiple access modes to be used for the communication links and their temporal scheduling, at least to the nodes involved in the communication links. The method for determining a multiple access and scheduling mode according to the invention is divided into two main phases which are based on a flow criterion: - the partitioning of the communication links between links using a TDMA type multiple access mode and links using a NOMA type multiple access mode, carried out during the second step 202 using an iterative algorithm, and - the optimization of the scheduling of the communication links, carried out during the third step 203, which can be resolved in an optimal and very low-complexity manner. The method according to the invention can be implemented within a cluster in an ad hoc network. All nodes communicate on the same logical channel, and the second, third and fourth steps of the method according to the invention are implemented by a dynamically elected decision-making node. Implementing the method within the cluster makes it possible to improve the overall average throughput within the cluster, while guaranteeing a minimum throughput per communication link. Within an ad hoc network of K clusters, each cluster being named and containing nCk links, the method can be implemented on a grouping of P clusters, with 2< p< K.

[0114] Several application cases are possible. Firstly, we consider that the spectral resource is sufficient, that is to say that the grouping of clusters has access to P distinct logical channels. In this case, it is possible to allocate a logical channel to each cluster, and to apply the method for determining a multiple access and scheduling mode according to the invention to each of the clusters independently. For example, for p = 2 clusters named Cy and the links of Ci are assigned the logical channel f 1 and the decision node of Cj applies the method according to the invention. Similarly, the links of C2 communicate on the second logical channel f2. The decision node of C2 applies the method according to the invention independently of Cp.

[0115] Figure 6a is an illustration of the partitioning of the communication links carried out by the method according to the invention in this first case of application on p = 2 clusters, cluster 601 and cluster C2 602. Each cluster comprises six nodes and three communication links. Following the implementation of the method, the nodes of the cluster included in the zone 611 use a multiple access mode of the NOMA type and those of the zone 612 use a multiple access mode of the TDMA type on the logical channel fp. Similarly, the nodes of the cluster C2 included in the zone 613 use a multiple access mode of the NOMA type and those of the zone 614 use a multiple access mode of the TDMA type on the logical channel f2.

[0116] According to another embodiment, the problem is analyzed globally for the grouping of the P clusters. As an example, we consider an application case with p = 2 clusters associated respectively with a logical channel f^ and f2. In this case, the resources can be grouped between the two clusters, the logical channel f1 being able to be allocated to certain links of the P clusters of the grouping, and the second logical channel f2 being able to be allocated to the other links. It is therefore a question of jointly optimizing the NOMA / TDMA access mode, the allocation of the logical channels and the scheduling of the links.

[0117] For this, the method according to the invention can be implemented in the following manner: - a decision-making node common to the P grouped clusters is elected, - information on the quality of direct and interfering communication links, for example statistics related to propagation channels, is sent to the decision-making node by the cluster nodes, either directly or via intermediate nodes. Interfering links include links between nodes of distinct clusters, - based on this information, the decision-making node implements the method for determining a multiple access and scheduling mode according to the invention extended to the joint management of all the logical channels and accesses, namely in particular: • the implementation of the second step 202 of the method on the links of the two clusters jointly, in order to partition them between a set T of links operated with a TDMA type multiple access mode and a set TN of links operated with an access mode multiple NOMA type. This step is carried out on the assumption that all links communicate on the same logical channel. The calculation of the flow rates can be done indifferently by considering the band of a logical channel or the band of all the logical channels, • the allocation of part of the logical channels (for example the channel f J to the links of T using multiple access of the NOMA type, • the allocation of the other part of the logical channels (for example the channel to the links of T using a TDM access A. - the decision node sends the calculated parameters to the corresponding nodes in the network.

[0118] Equivalently, each cluster can elect a decision node for the cluster, and then the decision nodes elect a common decision node for the cluster grouping. The nodes transmit information about the quality of the communication links to the decision node of their cluster, which returns it to the common decision node. This solution makes it possible to limit intercluster transmissions.

[0119] Figure 6b is an illustration of this second case of application of the method on a grouping of p = 2 clusters, cluster 601 and cluster C2 602, respectively associated with a logical channel f 1 and f2- Each cluster comprises six nodes and three communication links. Following the implementation of the method, which here considers the interference linked to the emissions of nodes belonging to different clusters, the nodes included in the area 621 use a NOMA type multiple access mode on the logical channel f 15 and those in the area 622 use a TDMA type multiple access mode on the logical channel f2-

[0120] Compared to the previous embodiment, the solution for joint management of NOMA / TDMA accesses and logical channels has a better overall throughput than the solution where the method is applied to each cluster independently.

[0121] Figure 7a gives the average theoretical throughput obtained in the network as a function of the number of communication links, in order to quantify the contribution of the method according to the invention in an application case where the network comprises p= 2 clusters and two logical channels f 1 and f2. This is an overall theoretical throughput (sum of the throughputs of all the links) obtained by considering a logical channel with a bandwidth equal to 1 MHz. Curve 701 represents the performances obtained by implementing a TDMA type multiple access technique independently on all the communication links of each cluster, using a logical channel specific to the cluster. Curve 702 represents the same application case using a technique multiple access of the NOMA type. It is observed that the use of NOMA makes it possible to obtain better average throughputs than TDM A when the number of communication links increases. Curve 703 represents the performances obtained by implementing the method according to the invention independently on each of the clusters. It is observed that the implementation of the method according to the invention considerably improves the throughputs compared to the solutions based on the use of TDMA or NOMA. Finally, curve 704 represents the performances obtained by implementing the method according to the invention on the grouping of the P clusters. It is observed that the average throughput is even better, in particular when the number of communication links increases.

[0122] [Fig.7b] illustrates the theoretical minimum flow rate available per link, in the same application case than [Fig.7a]. Curve 711 corresponds to the application case of curve 701, and respectively for curves (712, 702), (713, 703) and (714, 704). It can be observed that the minimum available throughput in the case of a NOMA multiple access mode collapses when the number of available links increases, and that this minimum throughput is very good when the multiple access mode is TDMA. The proposed solution is less good than TDMA in terms of minimum throughput, but makes it possible to guarantee a minimum throughput, unlike the NOMA solution. The performances obtained by implementing the method according to the invention are comparable depending on whether the clusters are grouped or not.

[0123] Another application case is where the spatial reuse of the logical channels is not sufficient to guarantee orthogonality between the communication links of different clusters, i.e. the number of logical channels is less than the number of clusters. This may be the case, for example, in the case of spatial reuse of the transmission channels, which makes it possible to operate the network with fewer logical channels than clusters provided that the network topology allows the same channels to be reused in sufficiently distant clusters. Spatial reuse may not be sufficient when the clusters are too close to each other. In this case, a possible solution is to implement TDMA multiplexing between the clusters. However, this solution has the drawback of dividing the average throughput by P.

[0124] Another solution is to implement the method for determining a multiple access and scheduling mode according to the invention on a grouping of clusters and logical channels, as illustrated previously, even when the number of logical channels is less than the number of clusters.

[0125] Figure 8 is an illustration of this case of application of the method on a grouping of p = 2 clusters, cluster 801 and cluster C2 802, associated both on the same logical channel fh Each cluster comprises six nodes and three communication links. Following the implementation of the method, which here considers the interference linked to the emissions of nodes belonging to different clusters, the nodes included in the 811 zone use a NOMA type multiple access mode and those in the 812 zone use a TDMA type multiple access mode, scheduled on the logical channel fp

[0126] The advantages of this embodiment are that it makes it possible to obtain a much better overall theoretical throughput than a solution based on a TDMA type access mode between the nodes of the different clusters, and that it guarantees a minimum throughput, unlike a solution based on a NOMA type access mode where the minimum throughput tends towards zero when the number of communication links increases.

[0127] Figure 9a gives the theoretical average throughputs obtained in order to quantify the contribution of the method according to the invention in an application case where the network comprises p — 2 clusters and a single logical channel f The graph gives the average theoretical throughput obtained in the network as a function of the number of communication links. Curve 901 represents the performances obtained by implementing a TDMA type multiple access technique on all the communication links of the clusters, by distributing the use of the logical channel equally between the two clusters (round-robin). Curve 902 represents the same application case by optimizing the scheduling of the resources of the two clusters on the logical channel so as to maximize the overall throughput. Curve 903 represents the same application case using a NOMA type multiple access technique.It is observed that the use of NOMA makes it possible to obtain better average throughputs than TDMA, even optimized, in particular when the number of communication links increases. Curve 904 represents the performances obtained by implementing the method according to the invention on the grouping of the two clusters. It is observed that the implementation of the method according to the invention considerably improves the throughputs compared to the solutions based on the use of TDMA, optimized or not. The performances obtained are comparable to those obtained when the communication links all use multiple access of the NOMA type.

[0128] [Fig.9b] illustrates the theoretical minimum throughput available per link, in the same application case as [Fig.9a]. Curve 911 corresponds to the application case of curve 901, and respectively for curves (912,902), (913, 903) and (914, 904). It can be observed that the minimum throughput available in the case of a NOMA multiple access mode collapses when the number of available links increases, whereas it is very good when the multiple access mode is of the TDMA type. The proposed solution is slightly less good than that based on non-optimized TDMA, but it guarantees a minimum throughput, unlike the solution based on NOMA.

[0129] The performances presented in figures 7a, 7b, 9a and 9b are given by way of illustration for particular application cases where the number P of clusters is equal to two. However, the invention applies in a comparable manner for the grouping of a number of clusters greater than two.

[0130] The invention therefore relates to a method for determining a multiple access and scheduling mode for a plurality of communication links in an ad hoc network, but also to a node in an ad hoc network, comprising calculation means such as for example a microprocessor, a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), an ASIC (Application-Specific Integrated Circuit), any combination of these means, or any hardware component enabling it to implement the steps of the invention enabling it to play the role of decision-making node responsible for determining the access mode between a NOMA access mode and a TDMA access mode for each of the communication links, and for scheduling these communication links.

[0131] [Fig. 10] is a block diagram of the steps of a method for determining a multiple access and scheduling mode according to the invention implemented by a decision-making node. These steps comprise a first step (1001) of receiving, from nodes involved in the communication links, information relating to the quality of communication links operated between nodes of the ad hoc network, each communication link being implemented between nodes belonging to the same cluster, and successive steps 1002, 1003 and 1003 corresponding to the second (202), third (203) and fourth (204) steps of the method according to the invention described in [Fig. 2].

Claims

Claims

1. Method for determining a multiple access and scheduling mode for a plurality of communication links in an ad hoc network comprising a plurality of nodes grouped in one or more clusters, the communication links being operated on at least one logical channel, the method being characterized in that it comprises: - a first step (201), implemented by said nodes, of transmitting to a node designated as a decision-making node, information relating to a quality of said communication links, - a second step (202), implemented by said decision-making node, of partitioning said communication links between communication links using NOMA type multiple access and communication links using TDMA type multiple access, on a throughput criterion calculated from the information relating to the quality of said communication links transmitted in the first step (201),- a third step (203), implemented by said decision-making node, of determining a temporal scheduling of said communication links on said at least one logical channel, respecting the types of multiple access calculated during the second step, - a fourth step (204), implemented by said decision-making node, of transmitting the partitioning information calculated in the second step and the temporal scheduling information calculated in the third step to the nodes involved in said communication links.,

2. Method for determining a multiple access and scheduling mode according to claim 1, in which the information relating to a quality of the communication links is, for each communication link:

3.

4. - statistical information on a propagation channel of said communications link, - statistical information on interfering propagation channels, and - a noise power level perceived by the destination node of the communication link. Method for determining a multiple access and scheduling mode according to one of the preceding claims, in which the second step (202) of partitioning said communication links comprises the implementation of an iterative algorithm comprising, for each communication link, the calculation of a user throughput using a TDMA type multiple access mode, the calculation of a user throughput using a NOMA type multiple access mode taking into account the multiple access modes used by the other communication links, and the choice of the access mode maximizing the user throughput of the communication link. Method for determining a multiple access and scheduling mode according to one of the preceding claims, in which the second step (202) of partitioning said communication links comprises: - a step (301) of calculating a user throughput for each communication link when all the communication links are associated with a TDMA type multiple access, - a step (302) of calculating a user throughput for each communication link when all the communication links are associated with a NOMA type multiple access, - a step (303) of determining a set T of communication links associated with a NOMA type multiple access and a set T of communication links associated with a TDMA type multiple access by comparing the respective user throughputs for each communication link, - iteratively, until convergence: • a step (304) of calculating a user throughput for each communication link of the set Tjy when only the communication links of said set T use a NOMA type multiple access,• a step (305) of searching for communication links belonging to the set TN for which the user rate for TDMA type multiple access is greater than or equal to the user rate for NOMA type multiple access, and of transferring said communication links to the set T of communication links using TDMA type multiple access.,

5. Method for determining a multiple access and scheduling mode according to one of the preceding claims, in which the NOMA type multiple access technique is based on the use of linear coders / decoders, and where the second step (202) of partitioning said communication links between communication links using NOMA type multiple access and communication links using TDMA type multiple access on a throughput criterion comprises the calculation of a size r of linear encoder / decoder and the calculation of U and V coding / decoding matrices adapted to the number of communication links using NOMA type multiple access.

6. Method for determining a multiple access and scheduling mode according to one of the preceding claims, in which the third step (203) of partitioning said communication links comprises defining a long time interval, or frame, divided into a plurality L of short time intervals, or slots, and distributing said L slots between the communication links in order to maximize the average overall throughput of the ad hoc communication network while guaranteeing a minimum throughput for each communication link.

7. Method for determining a multiple access and scheduling mode according to the preceding claim, in which r LRq slots are allocated exclusively to each communication link using TDMA type multiple access, with a minimum throughput constraint per link and p^ a physical throughput associated with the communication link, F LR^ j slots are allocated 1 ^NOMAjniii | to the communication links using NOMA type multiple access, and where the residual slots are distributed between the communication links using NOMA type multiple access and the communication link using TDMA type multiple access having the highest physical throughput pf.

8. Method for determining a multiple access and scheduling mode according to one of claims 6 and 7, in which the third step (203) of partitioning said communication links further comprises the calculation of an optimal frame length p* taking into account the results of the second step (202) of partitioning the communication links.

9. Method for determining a multiple access and scheduling mode according to one of the preceding claims, implemented jointly on a plurality of clusters.

10. Decision node in an ad hoc network comprising a plurality of nodes grouped in one or more clusters and implementing a plurality of communication links on at least one logical channel, said decision node being characterized in that it comprises calculation means configured to implement: - a first step (1001) of receiving information relating to the quality of said communication links, - a second step (1002) of partitioning said communication links between communication links using NOMA type multiple access and communication links using TDMA type multiple access, on a flow criterion calculated from the information relating to the quality of said communication links received in the first step (201), - a third step (1003) of determining a temporal ordering of said communication links on the common logical channel(s), respecting the types of multiple access calculated during the second step, - a fourth step (1004) of transmitting the partitioning information calculated in the second step and the time scheduling information calculated in the third step to the nodes involved in said communication links.

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