Multiplex Communication having circuits or apparatus for combining or dividing signals for the purpose of transmitting the signals simultaneously or sequentially over the same transmission path, and monitoring arrangements therefor.

Class H04 Electric communication technique covers electrical communication systems with propagation paths employing beams of corpuscular radiation, acoustic waves or electromagnetic waves. Subclass H04J refers to multiplex communication in general. If the multiplex communication is specially adapted for particular applications classification is made in other subclasses of class H04.

Frequency Division Multiplexing, FDM, by multiplexing two or more data sources. Covers particularly hierarchical multiplexing electrical frequencies in stages of power of 2, e.g. 8kHz, 64Khz.

Systems for transposing frequency channels carrying information onto frequency carriers Covers also FDM multiplexers, demultiplexers

H04J 1/08 takes precedence

Frequency translators, FDM multiplexers, demultiplexers, operating with digital techniques

H04J 1/08 takes precedence

Frequency allocation, including by demand or to reduce intermodulation;

Hierarchical frame structures, the structure repeats continuously at a fixed rate. Typically these are standard TDM frame structures at 8kHz rate like PDH, SDH or OTN. Other fixed rates frames should also be classified here and related fields.

Synchronization of TDM Frames

Packet transmission is classified for some specific applications:

Transmission of synchronous services like voice via packets, e.g. VoIP, is classified in H04J 3/0632, when the source clock is recovered.

Alignment of packets using packet flags should be in H04J 3/0602 for fixed line systems and in H04L 7/04 in wireless, satellite or radio systems.

Ranging of packets in an uplink in systems with a TDM frame defined in the downlink, see H04J 3/0682.

Note 1: Ranging or time alignment of a radio/wireless channel preferably in H04W 56/00. For radio/wireless systems data transmitted via a fixed network, e.g. connections between Mobile Switching Centre (MSC) and Base Station (BS) or between several Access Points (AP), documents referring to specific data of the radio/wireless channel are in H04W 56/00, e.g. alignment for handover.

Allocation of packets within a TDM frame, e.g. Ethernet in OTN payload, see H04J 3/16 or lower.

Allocation of packets in an uplink of a systems with a TDM frame defined above in the downlink, H04J 3/1694.

Note 1 : This group refers to the allocation of the bandwidth.

Note 2 : Allocation in wireless systems, see H04W or H04B 7/00;

Note 3 : Allocation of timeslots in PON, H04Q 11/0001 takes precedence

Synchronization of TDMA or packets in the meaning of time alignment, the minimum entity of detection or correction is a bit. Smaller sub-bit values refer to bit synchronization of H04L 7/00

Details of multiplexing or demultiplexing of bits or bytes in arrangements specially adapted for time multiplexing.

Distributors with transistors or integrated circuits

Details of bit and byte multiplexers or demultiplexers per se, e.g. 2:1 pulse multiplexers and tree structures thereof, H03M 9/00 takes precedence.

Synchronization of TDM networks and some specific synchronization arrangements in TDMA or packet networks.

Synchronization of TDM networks covers:

Detection of FAW and alignment of frames, H04J 3/0602;

Absorbing of phase or frequency differences by buffers, H04J 3/062;

Distribution of synchronization information and organisation of the synchronization network, H04J 3/0635.

Specific synchronization arrangement of packet or TDMA networks are:

Distribution of synchronization information and organisation of the synchronization network, H04J 3/0635

Source clock recovery over packet or ATM networks, e.g. VoIP, H04J 3/0632.

Synchronization of wireless network when mobility of radio channel is relevant, H04W 56/00.

A FAW is used as synchronising information for a TDM frame.

Design rules of constructing FAW.

variable FAW, e.g. for low rate signalling, depending on the synchronization state.

FAW of standardized frames, e.g. T1, SONET, SDH or OTN are known per se are not classified here. Their detection is classified in H04J 3/0608.

Detection of FAW by correlators, state machines, forward or backward protection.

PN codes used for synchronisation, if the PN synchronisation signals is varying during transmission, e.g. by a feedback Shift-register. Fixed synchronisation signals, e.g. unique words or FAW signals, are not to be classified in this group. This also applies even if the synchronisation signal can be presented as a state of such a PN-code generator. Only if the generator shifts, then the document is classified here.

H04J 3/0608 takes precedence for detection

Rate differences are compensated in a lossless way, e.g. by an elastic buffer or FIFO

Compensation of fluctuating rates in SDH/SONET or OTN

Recovery of source clock of Continuous Bit Rate (CBO) service, e.g. VoIP. The invention is located at the edge of the packet network and the output is a stream of bits, e.g. control of playout rate.

Distribution of synchronisation information among nodes, e.g. master/slave signalling or SSM.

TOD synchronization.

Signalling to prevent or recover from a failure in the synchronization network.

Adding or modification of delay information, e.g. residence time in PTP

Exchange of synchronization information, e.g. buffer fill.Coupling clocks, e.g. by adding weighted signals of clock or phase errors.

Determination or initialisation of clock distribution path among more than two levels of nodes according to parameters, e.g. priority, path length, number of hops, clock quality, statistics.Avoidance of clock loops or timing islands.

RTD measurement in TDM or TDMA networks for the purpose of timing adjustment, clock correction or time alignment.

Variable length stuffing; self marking stuff indications

This subgroup does not refer to stuffing of packet flags as line coding to interrupt a long sequence of identical bit values.

Stuffing in OTN

ADM Add Drop Multiplexers

Protection in TDM ring networks

Bit stealing for signalling, e.g. winking in PDH T1.

Protection Switching; Testing of TDM systems.

Covering variable time slot allocation.

H04J 3/1605 fixed standard frame structures.

H04J 3/1611 SDH

H04J 3/1623 PDH

H04J 3/1652 OTN;

H04J 3/1682 statistical multiplexers, allocation changes per frame cycle

H04J 3/1694 distributed multiplexers, e.g. access multiplexer

For specific applications, e.g. video H04N 7/00; or physical medium, e.g. radio H04B 7/00, see more specialized classes

Refers to systems according to ITU recommendations G.707 - G.709 in the versions of 1990 (SDH/SONET)

Radio, satellite and microwave transmission according to the standards mentioned above.

Covers switches, nodes and Cross-connects and respective internal or proprietary formats

SPE carries ATM cells or payload data packets

H04J 2203/0082 Services, Interaction of SDH with non-ATM protocols

H04J 2203/0083 Support of the IP protocol

H04J 2203/0085 Support of Ethernet

Covers switches, nodes and Cross-connects and respective internal or proprietary formats.

Also covers transport of packets via a plesiochronous network, e.g. "ATM over E1".

Time slot allocation according to rules, e.g. to evenly distributed slots to various users while minimizing the distance to ideal evenly distributed slot allocation for a single user.

Format conversion of PDH frames of different standards, e.g. ETSI and ANSI

DS0, DS1, DS3 or European PDH, PCM30/32, E1 to E4 according to ITU recommendation G.703. Covers the hardware structure of programmable TDM multiplexer, e.g. internal construction by bus, as described in ITU recommendation G.797.

Variable allocation of elementary units like time slots, subslots or fragments. The allocation can be modified by splitting elementary units or by combining elementary units to units of larger bandwidth. The overall frame length remains constant.

Refers to systems according to ITU recommendation G.707 - G.709 in the versions of 2000.

Covers radio and microwave transmission according to the standards mentioned above.

Covers switches, nodes and Cross-connects and respective internal or proprietary formats.

H04J 3/1664 takes precedence for payloads with different packet types

H04J 3/1664 takes precedence

Allocation of bandwidth changes instantaneously, e.g. on demand or according to buffer fill.

Different symbol rates in the slots of the TDM frame.

Different or variable user rates or source rates are classified under H04J 3/1605 or sub-groups.

CDMA and Spread-spectrum communication, H04J 13/00 takes precedence.

Generic packet or ATM multiplexing

Time frequency encoded transmission. The combination of time and frequency is determined by the receiver address and the transmitted information.

Transmission of address by Pulse Position Modulation (PPM).

Random sampling of analog sources

Translation of TDM into FDM and vice versa.

Simultaneous transmission of analog and digital, e.g. by overmodulation

Orthogonal multiplex systems at the physical layer, techniques relating to problems arising from the multiplexing of users / base stations. Aspects that are covered include

cell search, i.e. how a mobile phone finds the identity of base stations;

interference handling and cancellation, at the transmitter, the receiver or both, especially

subtractive interference cancellation

intercell interference cancellation at the physical layer.

Examples of orthogonal multiplexing techniques are OFDMA [Orthogonal Frequency Division Multiple Access ], SC-FDMA [ Single Carrier Frequency Division Multiple Access ].

Examples of systems using orthogonal multiplexing are LTE [ Long Term Evolution ], LTE-advanced.

Code multiplexing techniques, orthogonal or not, are classified in H04J 13/00 if the focus is on the code multiplexing aspects and in H04B 1/69 if the focus is on the implementation of the spread-spectrum technique (e.g. details of how the signals are physically transmitted, received and processed).

Additional information is classified with the corresponding CPC codes. Classification of additional information is compulsory.

Code division multiplexing techniques which are related to the division of the communication medium according to codes.

Aspects that are covered include types of codes, generation of codes and allocation of codes to channels.

With regard to spread-spectrum techniques, the borderline between H04J 13/00 and H04B 1/69 should be determined based on whether the features relevant for classification are focused on the code multiplexing aspects or the implementation of the spread-spectrum technique (e.g. details of how the signals are physically transmitted, received and processed).

Documents classified in H04J 13/00 containing aspects of spectral spreading of interest for search, may also be classified in group H04B 1/69.

With regard to systems that use frequency hopping as a means to divide the communication medium, it has been agreed that that frequency hopping is excluded from H04J 13/00 even if it is used within the context of multiple access. Because the concepts dealt with in H04J 13/00 do not have relevance for FH-CDMA even though frequency hopping can be used for CDMA (i.e. FH-CDMA), this subject-matter is exclusively classified in H04B 1/713.

Additional information is classified with the corresponding CPC codes. Classification of additional information is compulsory.

When classifying in this group, any aspect of spread spectrum techniques not specific to frequency hopping, and which is considered to represent information of interest for search, may also be classified in group H04B 1/69.

Coherence Multiplex for data transmission

Optical code division multiplexing systems

Orthogonal optical code division multiplexing systems

Wavelength division multiplex systems, in general, as well as WDM equipment terminal, e.g. WDM sources and WDM receivers.

Optical add and drop multiplexing systems for WDM systems

Internal arrangements details of OADM for WDM systems

OADM arrangements that first broadcast the input signals, typically implemented with an optical splitter at the input of the OADM, and then select among the signals before they are output.

OADM arrangements that first selects among the input signals at the input of the OADM and then combines the signals before they are output, typically implemented with an optical combiner at the output of the OADM

OADM arrangements that allow express channels to be directly brought from the input of the OADM to the input of the OADM, typically for minimising the insertion losses incurred by those channels.

OADM arrangements that include multiplexing and/or demultiplexing using interleavers, e.g. processing the odd and even WDM channels separately.

OADM arrangements where multiplexing and/or demultiplexing are implemented by a cascading of multiple stages.

Reconfigurable or tuneable OADM arrangements where the optical channels that are actually added or dropped can be changed during the operation of the OADM.

OADM arrangements where the reconfiguration is accomplish by using optical switches or wavelength selective switches.

Colourless and/or directionless and/or contentionless reconfigurable ADM arrangements where there is no dependency to wavelength and/or for any added and dropped channels, any direction can be selected and/or for any added and dropped channels the same wavelength can be selected.

Reconfigurable ADM arrangements where channels are multicast/broadcast to a plurality of directions, e.g. multicast OADM (MC-OADM).

OADM arrangements where the groups of channel or wave bands are processed together.

Architectures aspects of OADM in WDM systems in terms of how they relate to the WDM networks where they are in.

OADM architectures that are prepared to be used in bidirectional networks, meaning that the ports of the OADM are input and output ports at the same time and consequently the fibres connected at those ports transmit optical WDM signals in both directions.

OADM architectures that have more than one input and/or more than one output (the degree of a node in a network is defined as the number of input plus output ports of such node).

OADM architectures constituted by modules that are repeated to increase the capabilities of the node, typically to upgrade the number of channels that can be added or dropped.

OADM architectures that are used for interconnecting different WDM networks, e.g. interconnected rings.

Power control in a WDM system. Subject covers equalizing power of the different wavelengths, e.g. to keep the total optical power constant or to control the optical power per channel in a WDM system so as to maintain constant a particular performance related characteristic. Also covers control of power transients due to add and drop wavelengths, wavelength switching, e.g. caused by protection switching, or wavelength re-allocation.

Arrangements for controlling/equalizing the optical power per channel or for groups of channels in a WDM system by adding a signal not carrying data, e.g. dummy wavelength(s), noise or pilot signal.

Arrangements for controlling/equalizing the optical power per channel or for groups of channels in a WDM system by adding/dropping/reallocating data channels, e.g. by adding/dropping/shuffling channel(s).

Arrangements for controlling/equalizing the optical power per channel or for groups of channels in a WDM system by controlling attenuation/gain of the data channel(s).

Controlling/equalizing the optical power per channel or for group of channels in a WDM system where management of power control is central, e.g. configured by the Network Management System (NMS).

Controlling/equalizing the optical power per channel or for group of channels in a WDM system where each node of the system acts independently to control/equalize power.

Conversion from WDM signals into OTDM or vice versa to facilitate the multiplexing or demultiplexing of optical channels.

WDM irregular allocation plans, typically to overcome non-linear effects or to accommodate optical channels of different bit rate. This group covers also regular schemes in which carriers remain unused, e.g. to avoid interference.

Fixed carrier allocation according to service or for a particular use, e.g. dummy channels to keep the power constant.

Wavelength allocation and assignment for WDM and the application of management to WDM networks. It covers routing, e.g. use of tables for wavelength routing, and wavelength allocation algorithms, dynamic allocation of wavelengths and use of a dedicated wavelength for OAM, e.g. optical service channel, and pilot tones for OAM. It also covers optical channel and optical multiplex identification and labelling, optical signalling in WDM networks and WDM networks restoration (in network restoration, as opposed to network protection, all available resources in the network are considered when looking for a new path to be established).

Spectrum allocation/assignment/optimisation for WDM systems, e.g. allocating flex-grid slots for channels, assigning super-channels or optimising spectral resources via de-fragmentation.

WDM arrangements for medium access of radio-frequencies networks; wavelength allocation rules for such arrangement, e.g. any haul transport network for LTE/5G networks, for example via PON.

WDM optical networks defined by the type of interconnection between WDM nodes

WDM systems using a point to point network connection between two WDM nodes.

Multiple WDM nodes connected to two adjacent WDM nodes, except for the two nodes constituting the bus head-end, and using a common optical fibre supporting a WDM signal.

A common WDM node is connected via multiple fibres to a multiplicity of other WDM nodes. It also covers the case of star networks, where multiple WDM nodes are interconnected to other WDM nodes using multiple optical fibres each supporting a WDM signal, typically using a star coupler.

WDM architecture where all WDM nodes are connected to two adjacent nodes using a common optical fibre supporting a WDM signal.

WDM architecture where each WDM node is typically connected to every other node using multiple optical fibres, each supporting a WDM signal.

WDM networks where different layers of interconnection between the different WDM nodes. Each layer can be of the same type of network architecture or of different types.

WDM architecture of Data Centre Networks (DCN).

Protection aspects in WDM systems, typically switching from a protected resource to a protection resource when a failure occurs. As opposed to network restoration, network protection considers only resources that have a priori been labelled as protection resources.

Protection is carried out at the level of the whole WDM multiplex.

A WDM multiplex is duplicated and transmitted simultaneously using two WDM multiplex signals. The selection of which WDM signal to receive is done at the WDM level and at the receiver end, typically without considering any specific signalling from the transmitter end.

A WDM multiplex is transmitted using working resources and in case that a failure occurs, then the WDM multiplex is switched to the protection resource, typically shared by different nodes. At the receiver end the WDM signal coming via the protection resource is selected, typically this mechanism involves switching or bridging at both transmitter and receiver ends at the WDM multiplex level any requires some signalling between transmitter and receiver ends. The protection WDM multiplex can be used by low priority traffic until protection takes place.

A WDM channel is duplicated and transmitted simultaneously using two WDM channels. The selection of which WDM channel to receive is done at the channel level and at the receiver end, typically without considering any specific messaging from the transmitter end.

WDM channels are transmitted using working resources and in case that a failure occurs, then the WDM channel is switched to the protection resource, typically shared by different WDM channels. At the receiver end the WDM signal coming via the protection resource is selected, typically this mechanism involves switching or bridging at both transmitter and receiver ends at the channel level any requires some signalling between transmitter and receiver ends. The protection channels can be used by low priority traffic until protection takes place.

WDM is duplicated to protect the equipment against internal faults.

Sub-carrier multiplexing system, e.g. for CATV.

WDM arrangements, e.g. equipment, included in terminals or line to enable WDM transmission.

WDM arrangements, e.g. equipment for end terminals, e.g. WDM transmitters/receivers or wavelength converters.

Multiplexers or demultiplexers, e.g. odd/even multiplexing or multistage.

Systems where the different modes of transmission in the optical fibres are used to multiplex different channels of information.

Systems where either optical wireless (i.e. free space), multiplexing (e.g. MIMO) or space division multiplexing (e.g. multicore) is used for multiplexing different channels of information.

Systems where the different cores of a multicore fibre are used to multiplex different channels of information.

System where the different states of polarisation of the light are used to multiplex different channels of information.

Systems where different orbital angular momenta of the light phase are used to multiplex different channels of information.

Systems using optical time division multiplexing (OTDM). Time multiplexing of optical pulses.

Optical add and drop multiplexing systems for OTDM systems.

Medium access in OTDM systems.