By means of the routing tables thus configured, unicast communications can be made by any pair of node devices in the mesh communication network 120. Intermediate node devices therefore serve as relays when the node devices in said pair are not in the network neighbourhood of each other, and the communications thus take place gradually, each node device relying on one of its own neighbours to convey messages to their respective destinations.

To communicate between neighbouring node devices (i.e. node devices that are in the network neighbourhood of each other), the messages are transmitted in the form of modulated frames. When a modulated frame is specifically addressed to a neighbouring node device and is correctly demodulated by it, said neighbouring device retransmits an acknowledgement ACK to the node device that sent it said modulated frame on the frequency band or the RF channel on which the modulated frame was sent. A plurality of frequency bands and at least one RF channel are defined for supporting the transmission of these modulated frames, an adapted modulation scheme being associated with each of these frequency bands and with the RF channel. Each frame transmitted in the form of modulated signals begins with a preamble predefined according to the modulation scheme according to which said signals were modulated. The preamble is adapted for making it possible to synchronise in reception on said frame, i.e. to be able to determine an actual instant of start of frame. To do this, the preamble typically comprises a plurality of successive copies of one and the same symbol. The actual content and the duration of the preamble are thus predefined and depend on the modulation scheme used. The preambles of several frames are identical when the same modulation scheme is applied, and different otherwise. In the remainder of the document, to alleviate the text, the term “frequency band” is used indifferently to designate a PLC frequency band or an RF channel.

The modulation schemes (and corresponding demodulation schemes) applicable are preferentially multicarrier modulation schemes (or respectively demodulation schemes) of the OFDM type (Orthogonal Frequency Division Multiplex) in PLC or SUN-FSK (the English acronym for “Smart Utility Network—Frequency Shift Keying”) in RF.

In terms of frequency bands that can be used in the context of the implementation of the mesh communication network 120, mention can be made of: the CENELEC A frequency band, which ranges approximately from 35 kHz to 91 kHz; the FCC frequency band, which ranges approximately from 150 kHz to 480 kHz; the ARIB frequency band, which ranges approximately from 150 kHz to 400 kHz; the CENELEC B frequency band, which ranges approximately from 98 kHz to 122 kHz and the RF radio channel, which ranges approximately from 863 MHz to 870 MHz. It is then possible to use: a first thirty-six carrier modulation scheme in the CENELEC A frequency band; a second seventy-two carrier modulation scheme in the FCC frequency band; a third fifty-four carrier modulation scheme in the ARIB frequency band; a fourth sixteen carrier modulation scheme in the CENELEC B frequency band and a fifth modulation scheme of the SUN-FSK type for the RF radio channel of G3-PLC Hybrid PLC & RF. The SUN-FSK modulation is defined in section 20 of the document IEEE 802.15.4:2015.

FIG. 2 illustrates schematically the various layers of an OSI model in the particular case of the G3-PLC Hybrid PLC & RF standard as defined in Annex H of the ITU-T recommendation G.9903 (2017) Amendment 1 (May 2021).

A message to be transmitted coming from an application layer 200 is transmitted to a transport layer 201. The transport layer 201 contains all the protocols responsible for managing errors and controlling the network flows. The two main protocols used are the TCP and UDP protocols. The transport layer 201 creates packets by adding headers to the data coming from the application layer 200. The packets are next transmitted to an IP layer 202, e.g. IPv6. The IP layer 202 encapsulates the packets coming from the transport layer 201 by adding in particular an IP header, e.g. IPv6. An IPv6 packet can do up to 1400 bytes. In the case where the packet has a size above a threshold value, this packet is fragmented into at least two fragments in order to adapt it to the constraints of a MAC sublayer 204a or 204b, in particular to the size of the MAC frames.

For this purpose, the G3-PLC Hybrid PLC & RF standard incorporates the 6LoWPAN protocol, which makes it possible to adapt IPv6 data packets to the constraints of the MAC sublayers 204a or 204b, in particular by fragmenting them. This is because the MAC frames used are of much smaller sizes (400 bytes maximum available per packet for the IP part) than the IPv6 packets of 1400 bytes.

An adaptation sublayer 203a incorporating the 6LoWPAN protocol and located between the IP network layer 202 and the MAC sublayer 204a or 204b of the OSI model receives, from the IP network layer 202, IPv6 packets of 1280 bytes and where applicable fragments them. Naturally, in the case of an IP packet that is sufficiently small to be contained in a single MAC G3-PLC or MAC RF frame, no fragmentation is performed.

A hybrid abstraction layer 203b next transfers the fragment, or the IP packet in the case of absence of fragmentation, to the appropriate MAC sublayer 204a or 204b according to the medium selected for transmission thereof. Hereinafter the term fragment is used for designating both a fragment obtained from a fragmented IP packet or the IP packet itself in the case of absence of fragmentation.

Transmitting a fragment on the PLC medium, i.e. on the powerline, conventionally comprises various steps, in particular a segmentation of the fragments in order to adapt them to a G3-PLC PHY physical layer 205a and an OFDM modulation of the signal. The segmentation consists in partitioning a MAC frame into PSDUs (the English acronym for “PHY Service Data Unit”). All the PSDUs coming from one and the same fragment are modulated using the same modulation scheme.

Transmitting a fragment by radio frequency over the RF channel comprises various steps, in particular a segmentation of the fragments in order to adapt them to an RF PHY physical layer 205b and a SUN-FSK modulation of the signal. As in the PLC case, the segmentation consists in partitioning a MAC frame into PSDUs (the English acronym for “PHY Service Data Unit”). All the PSDUs coming from one and the same fragment are modulated using the same modulation scheme. The specification of the RF PHY physical layer is given in sections 10, 11 and 20 of IEEE 802.15.4-2015 as amended by IEEE 802.15.4v:2017 and supplemented by Table H-5-1 of the ITU-T recommendation G.9903 (2017) Amendment 1 (May 2021).

In order to use all the flexibility offered by PLC/RF hybridisation, the communication methods described with reference to FIGS. 3 to 11 are implemented for distributing the data supplied by the adaptation sublayer 203a between the two RF MAC and PLC MAC layers optimally in order in particular to endure greater robustness to errors. More precisely, the methods described are implemented at the hybrid abstraction layer 203b.

FIG. 3 illustrates schematically a method for transmitting data according to a particular embodiment. The data come for example from the IP layer.

In an optional step S10, the data coming from the IP layer possibly fragmented in accordance with the 6LoWPAN protocol are encoded, e.g. by a convolutional encoder such as an encoder of the Reed-Solomon type. In a particular embodiment, the Reed-Solomon encoder is parameterised as follows: N=255, K=247 and T=4, where N is a number of symbols transmitted, K is a number of information signals, referred to as payload, and T is a number of correctable erroneous symbols. Reed-Solomon codes are block codes. This is because they take as an input a block of data of fixed size K, each data item being a symbol of m bits. For example, m=1, 2, 3, 4, 8 or 16. 2T check symbols are added to this block, thus forming an output block of fixed size equal to N.

In a step S12, the N encoded data are distributed into two groups G_RFand G_PLCby an interlacing operation, each group being associated with a particular communication medium from powerline and radio frequency.

In a step S14, each encoded data item is transmitted to the MAC layer of the communication medium associated with the group to which it belongs. In other words, the encoded data that belong to the group G_RFare transmitted to the RF MAC layer and the encoded data that belong to the other group are transmitted to the PLC MAC layer.

The node device receiving the data transmitted by PLC and RF operates in a reverse fashion. In other words, the receiving node device deinterlaces the data in a reverse manner to what is performed by the sending node device in the step S12. The data thus deinterlaced are next decoded using the decoder performing the operation that is the reverse of the one performed at the step S10. In a particular embodiment, a Reed-Solomon decoder is used.

FIG. 4 illustrates schematically a method for transmitting data according to a particular embodiment. This method comprises the step S10, identical to that of the method described with reference to FIG. 3.

In a step S120, a first bit stream is generated that comprises N bits b_kwith k∈[0; N−1], i.e. as many bits as there are symbols S_kcontained in an output block of the encoding step S10.

In a step S122, the bits of the first bit stream are permuted, for example using a bit-reversal permutation method. Such a permutation method makes it possible to keep the same number of zeros and ones as in the first bit stream and is reversible. The bit stream after permutation is called the second bit stream.

In an example embodiment, for N=255, the following F function is used:

F=[0, 128, 64, 192, 32, 160, 96, 224, 16, 144, 80, 208, 48, 176, 112, 240, 8, 136, 72, 200, 40, 168, 104, 232, 24, 152, 88, 216, 56, 184, 120, 248, 4, 132, 68, 196, 36, 164, 100, 228, 20, 148, 84, 212, 52, 180, 116, 244, 12, 140, 76, 204, 44, 172, 108, 236, 28, 156, 92, 220, 60, 188, 124, 252, 2, 130, 66, 194, 34, 162, 98, 226, 18, 146, 82, 210, 50, 178, 114, 242, 10, 138, 74, 202, 42, 170, 106, 234, 26, 154, 90, 218, 58, 186, 122, 250, 6, 134, 70, 198, 38, 166, 102, 230, 22, 150, 86, 214, 54, 182, 118, 246, 14, 142, 78, 206, 46, 174, 110, 238, 30, 158, 94, 222, 62, 190, 126, 254, 1, 129, 65, 193, 33, 161, 97, 225, 17, 145, 81, 209, 49, 177, 113,241, 9, 137, 73, 201, 41, 169, 105, 233, 25, 153, 89, 217, 57, 185, 121, 249, 5, 133, 69, 197, 37, 165, 101, 229, 21, 149, 85, 213, 53, 181, 117, 245, 13, 141, 77, 205, 45, 173, 109, 237, 29, 157, 93, 221, 61, 189, 125, 253, 3, 131, 67, 195, 35, 163, 99, 227, 19, 147, 83,211, 51, 179, 115,243, 11, 139, 75, 203, 43, 171, 107, 235, 27, 155, 91, 219, 59, 187, 123, 251, 7, 135, 71, 199, 39, 167, 103, 231, 23, 151, 87, 215, 55, 183, 119, 247, 15, 143, 79, 207, 47, 175, 111, 239, 31, 159, 95, 223, 63, 191, 127, 255]

For any k∈[0; N−1], B_k=b_F(k)where B_kis a bit of the second bit stream. For example, the value of the bit B₅is equal to the value of the bit b₁₆₀. If the F function is applied twice in a row, the starting bit stream is found again.

Thus the second bit stream defines two groups of data G_RFand G_PLC. The group G_RFcomprises for example all the data corresponding to a bit at 1 in the second bit stream and the group G_PLCcomprises all the data corresponding to a bit at 0 in the second bit stream, or vice-versa.

In the step S14, the encoded data that belong to the group G_RFare transmitted to the RF MAC layer and the encoded data that belong to the group G_PLCare transmitted to the PLC MAC layer. In other words, each encoded data item is transmitted to the communication medium associated with the value of the bit corresponding to said encoded data item in the second bit stream.

Thus, for any k∈[0; N−1], if B_kis equal to 0, then the symbol S_koutput at the encoding step is transmitted to the G3-PLC MAC layer, and if B_kis equal to 1, then the symbol S_koutput at the encoding step is transmitted to the RF MAC layer.

The transmission method described therefore makes it possible to distribute the data between the two communication media, and this reversibly. In the embodiment described above, the bit at 1 is associated with the RF communication medium and the bit at 0 is associated with the PLC communication medium. Naturally, this is a starting convention and a different choice may be made, i.e. associating a bit at 0 with the RF communication medium and associating a bit at 1 with the PLC communication medium.

FIG. 5 illustrates in detail the step S120 of the data transmission method of FIG. 4 according to a particular embodiment.

Parameters k, N_PLCand N_RFare initialised to 0. k is an index that identifies a bit b_kin the first bit stream. N_PLC(or respectively N_RF) represents the number of bits transmitted on the PLC (or respectively RF) medium.

In a step S120-1, a rate D_PLCis compared with a rate D_RF. D_PLCis a rate of data available for the powerline communication medium and D_RFis a rate of data available for the radio-frequency communication medium. Each available data rate D_PLCand D_RFis known.

For powerline, D_PLCis defined in the ITU-T document G.9903 (2017) Amendment 1 (May 2021), and more precisely in section 7.3.1, and depends on the frequency band, on the number of carriers and on the encoding that are currently selected.

For the radio frequency, D_RFis defined in the specifications IEEE 802.15-4 and IEEE 802.15-4v_2017, and more precisely in section 20.3, and depends on the operating mode currently configured. The operating mode 1 or 2 of SUN FSK translates frequency separations that are different between the channels.

If D_PLC<D_RF, then the bit b_kis set to 1 (S120-2) and N_PLCis incremented by 1 (S120-3). If D_PLC≥D_RF, then the bit b_kis set to 0 (S120-4) and N_RFis incremented by 1 (S120-5).

In a step S120-6, N_PLC/(N_PLC+N_RF) is compared with D_PLC/(D_PLC+D_RF). If N_PLC(N_PLC+N_RF)≤D_PLC(D_PLC+D_RF), the following bit b_k+1is set to 0 (S120-7) and N_PCLis incremented by 1 (S120-8).

If N_PLC/(N_PLC+N_RF)>D_PLC/(D_PLC+D_RF), the following bit b_k+1is set to 1 (S120-9) and N_RFis incremented by 1 (S120-10).

In a step S120-11, (k+1) is compared with (N−1). If (k+1)<(N−1), then k is incremented by 1 and the method resumes at the step S120-6, otherwise the step S120 ends since all the bits b_kwith k∈[0; N−1] of the first bit stream are determined and therefore the first bit stream is generated. In the embodiment described above, the bit at 1 is associated with the RF communication medium and the bit at 0 is associated with the PLC communication medium. Naturally this is a starting convention and a difference choice can be made, i.e. associating a bit at 0 with the communication medium RF and associating a bit at 1 with the PLC communication medium. Thus, in the example in FIG. 5, the zeros can be replaced by ones and the ones by zeros.

FIG. 6 illustrates schematically a data transmission method according to a particular embodiment. This method comprises the step S10 identical to that of the method described with reference to FIG. 3.

In the step S12, two interlacing tables are obtained, one table being associated with the PLC communication medium and the other table being associated with the RF communication medium.

In the step S14, the encoded data are transmitted to the RF MAC layer and to the PLC MAC layer according to the interlacing tables obtained. More precisely, each encoded data item is transmitted to the MAC layer of the communication medium associated with the interlacing table in which said data item is located.

The transmission method described therefore makes it possible to distribute the data between the two communication media, and this reversibly.

FIGS. 7 to 11 illustrate a method for obtaining the interlacing tables used at the step S14.

FIG. 7 illustrates a first interlacing table T, obtained from the concatenation of second interlacing tables T1 and T2. The interlacing tables T1 and T2 have respective dimensions (number of rows m_iand of columns n_i) defined from the type of communication medium used. According to a particular embodiment, a first medium uses powerline and a second medium uses radio frequency. Thus the interlacing table T1 is associated with the RF communication medium. In the example of FIG. 7, its dimensions are defined by 2 rows and 3 columns. The number of columns corresponds to the number of channels and the number of rows corresponds to a number of bits to be interlaced. The number of channels is for example defined in IEEE 802.15.4v_2017 according to the operating mode, e.g. in operating mode 1 there are 69 channels and 35 channels in operating mode 2. So as to simplify the description, 3 channels are considered on FIG. 7 and therefore 3 columns for the interlacing table T1. In a similar manner, the interlacing table T2 is associated with the PLC communication medium. In the example of FIG. 7, its dimensions are defined by 4 rows and 5 columns. The interlacing table T2 is defined in the same manner as the interlacing table used at the PHY layer in sections 7.10.1 and 7.10.2 of the G3-PLC standard. Thus the dimensions of the interlacing table T2 are defined so that the number of columns is equal to the number of subcarriers used in the frequency band used for transmitting data and the number of rows depends on the number of bits to be interlaced. The interlacing table T2 of FIG. 7 corresponds to the PLC medium configured in frequency band FCC with 5 subcarriers and a QPSK modulation.

The first interlacing table T is obtained by a concatenation of second interlacing tables T1 and T2. Indices T1-11 to T1-13 symbolise the various positions of the first row of the interlacing table T1, and indices T1-21 to T1-23 symbolise the various positions of the second row of the interlacing table T1. In the same way, indices T2-11 to T2-15 symbolise the various positions of the first row of the interlacing table T2, indices T2-21 to T2-25 symbolise the various positions of the second row of the interlacing table T2, indices T2-31 to T2-35 symbolise the various positions of the third row of the interlacing table T2 and indices T2-41 to T2-45 symbolise the various positions of the fourth row of the second interlacing table T2. Thus, more generally, an index Ti [m_i,n_i] symbolises in the present description a position at the m^throw and at the n^thcolumn of a table Ti. The indices previously mentioned are affixed in the various positions of the interlacing table T obtained by concatenating the interlacing tables T1 and T2, on FIG. 7 to best illustrate the concatenation mode used. According to one embodiment, the interlacing tables T1 and T2 are concatenated to define the first table T by making the first row of the interlacing table T1 agree with the first row of the interlacing table T2, then the second row of the interlacing table T1 with the second row of the interlacing table T2. Thus the definition of the first interlacing table T corresponds to the addition of the interlacing table T1 and of the interlacing table T2, to which an interlacing table T′ (shown in grey tint on FIG. 7) is added so that the first interlacing table T has the same number of positions in each of its columns and in each of its rows. In order to simplify the interlacing operations according to the embodiment described, the positions included in the interlacing table T′, i.e. included in the first interlacing table T but not included in at least one of the interlacing tables T1 and T2, are said to be “invalid”. This is because, after an interlacing implemented in the first interlacing table T, data could be moved in one of these positions.

An interlacing operation in an interlacing table usually consists in shifting the content of each of the rows and columns a certain number of times by circular permutations of the bits contained in the positions in the table.

FIG. 8 illustrates the correspondence of the tables particular to an identification of the positions in the first interlacing table T with the indices particular to an identification of the positions in each of the interlacing tables T1 and T2, or invalid positions of the interlacing table T′. Thus, for example, the position T1-11 of the interlacing table T1 corresponds to the position T-11 of the first interlacing table T, and the position T2-32