Method of communicating data in communication systems

DESCRIPTION

METHOD FOR REPORTING DATA IN COMMUNICATION SYSTEMS

The present invention relates to a method for data communication in communication systems, in particular, but not exclusively, in optical communication systems. The invention also relates to a communications system operating according to the method.

In conventional optical communication systems including interconnected node networks, information is routed from a first node to a second node by modulating optical radiation generated at the first node and guiding radiation, for example along fiber optic waveguides, to the second node where radiation is detected and demodulated to provide the information contained therein. Modulation can be either digital or analog.

When digital modulation is employed, it is conventional practice to modulate a radiation source, such as a laser, between two states corresponding to two mutually different levels of laser radiation output. In contrast, when analog modulation is employed, for example to route time division multiplexed analog voice information, the laser is modulated to

102109239 a continuous form over a range of optical radiation intensities.

When assessing the quality of optical communication in conventional systems employing analog modulation, it is relatively easy to measure the performance of the signal-to-noise ratio at the second node. However, if the analog modulator signal is modulated with digital data, it is extremely difficult to determine a corresponding error bitrate performance on the second node; error bitrate is not simply correlated with signal-to-noise ratio performance. Furthermore, it is also problematic to include control information in the digital complementary information when analog modulation is employed .

In conventional communication systems employing digital modulation, additional digital information may be added to customer payload data to be sent for error bit rate determination and control purposes. Such conventional systems are operable to receive customer payload data to be sent at the first node and arrange them into fixed length data blocks to which the control override data is added to provide an aggregate of data for transmission. Examples of such conventional systems will now be described with reference to published patent applications and granted patents.

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In a European Patent Application Published No.² EP 0 663 776, a method of communicating block encoded digital data with associated synchronization and control data is disclosed. In the method, block encoded digital data is communicated with associated complementary data data in a data bit stream having a sequence of coded blocks. Each block contains N symbols where M of the symbols include information to be transmitted and the remaining NM of the symbols include error correction data. The M / N ratio includes a first information rate. The coded blocks in the data bit stream are divided into a succession of frames including each frame F of the coded blocks. A frame complementary information symbol is added by each frame to provide the data required for a receive function such as synchronization. Addition of the frame complementary information symbols effectively lowers the first information rate to a second information rate Μ '/ Ν' as provided by Equation 1 (Eq. 1):

M _ (M '+ b) ~ N ~ (N' + b]

Where b = an integer chosen to provide the second information rate with a desired value.

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N is less than 2^no+ l, where n is the number of bits in each of the symbols. The number of coded blocks F in each frame is determined from Equation 2 (Eq. 2):

M'P (NM) b

Eq. 2 where

P = an integer with the smallest value that makes F an integer, where P is the number of additional information symbols added per frame.

A plurality of Xs of frames are formed into a multi-frame containing FX coded blocks and PX frame complementary information symbols. X is chosen to provide sufficient n-bit frame complementary information symbols to implement the desired receive function.

In another European Patent Application Published No.² EP 0 540 007, a method and apparatus for transmitting a signal containing information by:

(a) generating a plurality of block signals based on the signal containing the information;

(b) generating a plurality of parity block signals based on the plurality of data block signals;

(C) generating a frame signal containing the plurality of data block signals and the parity block signals;

and (d) sending the frame signal.

In the method, each data block signal includes a first sync signal block indicating the start of the data block signal, a data signal containing the information signal, and a first parity signal derived by encoding the signal. Dice. Each of the parity block signals includes a second block synchronization signal indicating the start of the parity block signal, a second parity signal, and a third parity signal. Bit signals located at the same bit positions at the respective second parity signals are derived by encoding bit signals located at the same positions at the respective data signals. Bit signals located at the same positions in the respective third parity signals are derived by encoding the bit signals located in the same bit positions in the respective first parity signals; alternatively, the third parity signal in each parity block signal is derived by encoding the second parity signal in each parity block signal.

In an International Application No.² PCT / FI99 / 00477, methods of data transmission on a system are described.

Telecommunications ΡΕ2109239. The methods are related to the use of payload numbering instead of or in addition to conventional frame numbering. The data in the system is divided into fixed length data blocks or payload units. The size of a block is preferably equal to or smaller than the smallest frame information field of the protocols used. Each protocol frame contains one or more payload units. Optimally, the length of the information field in a protocol frame is equal to n times the length of the payload unit where n is an integer. Alternatively or additionally, the protocol frame carries payload numbers both to indicate the payload units carried on the protocol frame and to acknowledge receipt of received blocks.

In a United States Patent granted

N.² No. 5,490,142, a VT group optical extension interface and a VT group optical extension format method are described. In the method, a VT group extension format defines a transport frame for the transfer of 135 bytes, each byte including 8 bits, the format providing a line rate of 8 640 Mbit / s. Each frame includes a complementary transport information portion and a payload portion. The transport portion includes 27 bytes and defines various operations, administration and maintenance functions. In addition, the payload portion includes 108 bytes that correspond directly to a VT group of an STS-N frame. The fee of

ΡΕ2109239 VT group optical extension format line is determined as a multiple integer m of an STS-N network element clock where m6seNelemél8 seNé 3. An optical extension interface is provided between a VT bus and an optical extension, the interface responding to providing a multiplexed VT group payload on the VTG bus to provide a corresponding VT group optical extension transport frame at the optical extension, the interface further responding to the provision of a VT group optical extension transport frame on the optical extension to provide a multiplexed VT group payload and associated complementary path information for the VTG bus.

It is conventional practice in contemporary optical communication systems where customer data to be transmitted is not precisely split into blocks, partially filling the blocks with customer data for transmission, and then adding alignment code after customer data for transmission to ensure that blocks are completely filled. This practice is known as alignment and assists in ensuring, for example, satisfactory radiation spectra in conventional systems.

The amount of alignment employed is a function of payload data that may vary from customer to customer. When aggregate data is received on the second

In the node, the information in the supplementary information is isolated and interpreted, and then the data blocks are processed to remove alignment to provide the payload data. Thus, it is not possible to measure the bit error rate for aggregate data on the second node without completely decoding the aggregate data to isolate the data from the payload; Such complete decoding is a complex process.

In large and complex communication systems including many thousands of nodes and employing the aforementioned digital modulation, it is often desirable to be able to monitor the modulated aggregate data on optical radiation at intermediate sub-nodes between the first and second nodes in order to determine therein. occurrence of errors. Such monitoring is especially useful when the first and second nodes are spatially separated by several hundred kilometers and optical radiation is carried between them across a number of fibers and associated optical repeaters and regenerators. Determining the error rate at the sub nodes allows the performance of specific parts of the system to be measured, for example the quality of the repeaters therein or the transmission medium employed. Such measurement allows repeaters and defective fibers to be insulated and, if necessary, bypassed or replaced. Systems experience a problem that the error rate at subnodes cannot be easily determined without completely decoding aggregate data to determine the

102109239 error bits; This problem arises because of the alignment that is employed.

United States Patent US 5787074 describes a system for monitoring performance on a SONET telecommunications network in which monitoring point failure can be detected.

It is conventional practice for communications system operators to rent communications channels to customers on a contractual basis that the error bit rate does not exceed a contract-specified limit. In the case of communication systems employing analog modulation, the assurance of error bit rate performance is difficult to determine based on measurement of the signal to noise ratio. Similarly, in the case of communications systems employing digitally aligned modulation, the error bitrate can be measured but requires complete demodulation of the aggregate data to determine the error bitrate.

The inventors have understood that it is possible to employ an alternative method of encoding data in a communications system that addresses the above problems.

According to a first aspect of the present invention, there is provided an optical transmitter according to Claim 1.

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Such an optical communication system provides at least one of the advantages that:

(a) the amount of time fluctuation in aggregate data propagating through the system is capable of being reduced, thereby reducing the occurrence of system errors; and (b) system error checking performance is capable of being improved, for example the error bitrate is more readily determinable from the aggregate data taking into account the fixed ratio.

Advantageously, depending on the system application, the fixed ratio of payload bits to supplementary information bits is in a range from 2: 1 to 100: 1. A ratio greater than 100: 1 may result in synchronization problems in the receiving means, so the above range is a practical compromise. Preferably, the fixed ratio of payload bits to supplementary information bits is 31: 1.

Alignment of payload data within aggregate data may result in the need for complex methods to decode aggregate data. The inventors have understood in the method of the invention that it is advantageous not to apply additional alignment to the payload data received when generating the aggregate data.

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Conveniently, the system includes a plurality of channels, each channel being capable of adapting to a data rate of its associated payload data, the channels being therefore capable of operating asynchronously. Such asynchronous operation is important to circumvent a need to perform system alignment, thus providing the benefits of simplified aggregate data decoding on the receiving means. In order to achieve such asynchronous operation in practice, it is desirable for each channel to include the means of a phase lock ring to synchronize the channel with its associated payload data.

In order to make the supplementary information data included in the aggregate data less vulnerable to burst interference, the supplementary information data and payload data are preferably interlaced with the aggregate data.

Advantageously, the aggregate data includes a plurality of frames arranged in multi-frames, the frames and multi-frames being identifiable in the receiving means by interpreting the positions of complementary information data within the aggregate data. The background information thus provides the benefit function of synchronizing the background information in the receiving means. However, the data block structure present in the payload data can be asynchronous to frames and multi-frames as

This is a consequence, although this does not affect system operation.

The inventors have found in practice that each multi-frame conveniently includes a range of 2 to 100 frames. This range is chosen as a compromise between being able to include a number of specialized functions in the complementary information data but not having many frames in each multi-frame so that multi-frame synchronization in the receiving means becomes problematic. In practice, it is preferable for each multi-frame to include eight frames.

The specialized functions mentioned above

<td>incorporate</td><td>advantageously</td><td>an</td><td colspan="2">Sync function.</td>

<td>So it is</td><td>convenient</td><td>what</td><td>the data of</td><td>information</td>

<td colspan="2">complementary members</td><td colspan="2">every single plot</td><td>include a</td>

<td>code of</td><td>synchronization</td><td>(FAW)</td><td>to help</td><td>the means of</td>

reception to synchronize with the multi-frames. For example, the synchronization code may include four synchronization bytes, FAW1 through FAW4, in the supplementary information data. In addition, the four synchronization bytes FAW1 through FAW4 can have, for example, binary values ​​from 1111 0110._B, 111 0110_B, 0010 1000_B and 0010 1000_B assigned to them respectively.

When ensuring that multi-frames are not lost on aggregate data when communicated via the means of transport, it is desirable that

Further information associated with each frame includes an identity code (MIC) for use in identifying the frame. Lost multi-frames are preferably identified on the receiving means.

<td>determining</td><td>whether or not the identity code is</td>

<td>incremented</td><td>in a consistent manner for successive</td>

<td>multi-weft,</td><td>. Inconsistent increment is indicative</td>

missing multi-frames on reception by the receiving means. Conveniently, the identity code is incremented in module mode, for example in module 255; This allows a single byte to be used in the supplementary information data to represent the code.

<td>In practice,</td><td>found to be particularly beneficial</td>

<td>increment</td><td>the identity code in steps of a</td>

<td>plurality</td><td>of counts for example in steps of 3</td>

counts, for successive multi-plots. In practice, it has been found that the inclusion of the MIC code also assists in synchronizing the receiving means with the aggregated data.

Ensuring proper dc level stability from photodetectors used to detect aggregated data can be problematic where ac coupling is employed to remove dc shifts from such photodetectors. In order to address this problem, the complementary information data associated with each

<td>multi-plot</td><td>advantageously include balancing code</td>

<td>(BAL) to</td><td>ensure that the bytes of the information</td>

<td>complementary</td><td>associated with the multi-frame include</td>

<td>0's and 1's</td><td>substantially equal.</td>

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In addition, to ensure that channel connections are performed correctly in the system, it is desirable for the supplementary information data to include identity information regarding at least one of the transmission means and the receiving means. Thus, conveniently, the complementary information data associated with each multi-frame includes path identification code (TTI) for use by the receiving means to confirm whether or not it is connected to its correct corresponding transmission means.

In communications systems including a plurality of channels, failure of one or more of the channels may occasionally occur in practice. It is therefore desirable that the supplementary information data may be able to invoke a channel substitution in the event of the channel failure. Thus, preferably, the complementary information data associated with each frame includes automatic protection switching code (APS) to instruct the system to use alternative channels to route payload data in the event of a channel failure in the system.

When interference occurs in the routing media, damage to aggregate data will often be limited to individual frames. It is therefore preferable that the complementary information data associated with each multi-frame include an interleaved bit parity (BIP) code for each multi-frame frame,

102109239 being the interleaving parity code usable by the receiving means to detect corruption of the payload data associated with the frame. As a consequence of the number of bits of supplementary information being in a fixed ratio to the number of payload bits, the BIP code provides a direct indication of the bitrate of error in the aggregated data; Such a direct indication enables relatively simple monitors to be used to measure the bitrate of error along the routing means, for example for fault detection purposes. Thus, unlike prior art systems, the method of the invention provides a code indicative of a fixed error rate density relative to the customer payload data regardless of the customer payload data rate.

In order to assist the receiving means to synchronize correctly with the aggregate data and to apply appropriate processing, for example regeneration, it is desirable that the supplementary information data include an indication of the aggregate data rate at which the channel is expected to operate. Thus, advantageously, the complementary information data associated with each multi-frame includes a payload type indicator (PTI) code indicative of the payload data rate provided to the transmission means.

The invention is applicable to communications systems.

102109239 operating at serial bit rates approaching the highest 10 Gbits / s. It is presently relatively difficult and expensive to provide logical switching devices capable of operating at such high bit rates. Therefore, it is highly desirable to convert high bit rate serial data into parallel data to facilitate processing tasks performed on the transmission means as well as the receiving means. Thus, advantageously, the transmission means is operable to receive the payload data as serial data and to convert it to parallel data to combine it with the complementary information data to generate the aggregated data as serial data for transmission via of the means of referral.

In practical communication systems, it is preferred that the routing means include one or more fiber optic waveguides for routing the aggregate data, the aggregate data being modulated into optical radiation, for example radiation generated by a distributed feedback laser source. (DFB), which is guided from the transmission means to the receiving means along one or more fiber waveguides. In order to make full use of the fiber bandwidth, it is desirable for a multitude of system channels to be optically multiplexed along a single fiber optic waveguide of the routing means.

Alternatively, for example when system portability is an important consideration, the routing means advantageously includes a

ΡΕ2109239 radio connection or electric coaxial cable to route aggregate data.

When implementing the system in practice, it has been found to be advantageous for transmission means incorporating an adapter unit for combining payload data with complementary information data to generate aggregate data, and for receiving means incorporating a corresponding adapter unit to separate payload data from supplementary information data. Each adapter unit beneficially includes

<td>one or more circuits</td><td colspan="2">clock</td><td>of ring</td><td>blocking</td><td>in</td>

<td>phase to sync</td><td>at</td><td colspan="2">units to</td><td>data that in them</td><td>give</td>

<td>input.</td><td></td><td></td><td></td><td></td><td></td>

<td>The systems</td><td>in</td><td colspan="2">communications</td><td>usually have</td><td>what</td>

<td colspan="2">serve the requirements</td><td>in</td><td>several</td><td colspan="2">customers. Like this,</td>

<td>conveniently, the</td><td colspan="2">system</td><td>includes</td><td>a plurality</td><td>in</td>

channels operable to adapt to the rate at which they receive payload data, and thus the channels are capable of operating asynchronously. Such asynchronous operation allows the system to accommodate payload data that is provided from different clients at mutually different payload bit rates without the need to employ aggregate data alignment.

In a second aspect of the present invention, there is provided a method for data transmission according to Claim 4.

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In a third aspect of the present invention there is provided an optical receiver according to Claim 7.

In a fourth aspect of the present invention, there is provided a method for receiving data according to Claim 10.

Embodiments of the invention will now be described, by way of example only, with reference to the following diagrams in which:

Figure 1 is a schematic illustration of a communication channel of a communication system according to the invention;

Figure 2 is a schematic illustration of a communication system according to the invention incorporating a plurality of communication channels as shown in Figure 1;

Figure 3 is a diagram of an adapter unit included in the communication channel illustrated in Figure 1;

Figure 4 is a diagram of an alternative adapter unit included in the communication channel illustrated in Figure 1;

Figure 5 is a representation of a structure of

102109239 data frame used in the channel and system illustrated in

Figures 1 and 2 respectively, including the frame structure of client payload data interlaced with complementary information data in a fixed ratio of 31: 1; and

Figure 6 is a byte representation of complementary information of a multi-frame structure used in the channel and system illustrated in Figures 1 and 2 respectively, including the eight frame multi-frame structure of a type shown in Figure 5.

Referring to Figure 1, a communication channel of a communication system according to the invention is shown; channel 10 is generally indicated by 10. Channel 10 includes a transmission unit 20, a fiber optic connection 30 and a receiving unit 40 shown as contained within the interrupted lines 25, 35, 45 respectively.

In a larger view, channel 10 operates by the transmission unit 20 receiving incoming payload data from a sending client (not shown). The transmission unit 20 proceeds to encode the payload data by organizing them into frames and multi-frames to which additional information data is added to provide the corresponding aggregate data. The aggregated data is routed as modulated optical radiation from the transmission unit 20 via the fiber link.

102109239 for the receiving unit 40. The receiving unit 40 receives the modulated radiation and derives the aggregate data from it. In addition, the receiving unit 40 decodes the aggregate data to separate the supplementary information data from the payload data, and then outputs the payload data to the receiving client (not shown). In addition, the supplementary information data present in the aggregate data is interpreted by the receiving unit 40 allowing it to apply management and control functions. These functions will be described in more detail later and include path identification, automatic protection switching (APS), interleaved bit parity (BIP), forward and reverse quality indication (FQI and BQI), forward fault indication. and inverse (FDI and BDI).

The component parts of channel 10 will now be described in more detail.

Transmission unit 20 includes a first optical to electrical converter 100, a complementary information generating unit 105, an adapter unit 110 and a second electrical to optical converter 120. The first converter 100 is connected at its optical input to the sending client. through an optical fiber 130. An electrical output from converter 100 is connected to a first electrical input of adapter 110. In addition the information data

102109239 generated in complementary information unit 105 are routed via an electrical connection by connecting complementary information unit 105 to a second electrical input of adapter unit 110. An electrical outlet from adapter unit 110 is connected to an electrical input of second converter 120. In addition, the fiber bond 30 is connected at its first end to an optical outlet of the second converter 120. The complementary information generating unit 105 is also linked to complementary information generating units from other channels, as well as to local and regional management systems (not shown in Figure 1).

The receiving unit 40 includes a third optical to electric converter 200, an adapter unit 210, a fourth electric to optical converter 215 and a complementary information generating unit 220. The third converter 200 is connected at its optical input to a second fiber connection end 30. An electrical output of converter 200 is connected to an electrical input of adapter 210. Adapter 210 includes a first and second electrical outlet; the first output is connected to an electrical input of the fourth converter 215 and the second output is connected to an input of the complementary information generating unit 220. The interpretation unit 220 is also connected to other channel interpretation units, to a local management and also to the regional management system mentioned

102109239 above (not shown in Figure 1). An optical output from the conversion unit 215 is connected via an optical fiber to the receiving client (not shown).

In operation, the first converter 100 receives payload data from the sending client over fiber 130. Transmission unit 20 is designed to accommodate payload data from the sending client at data bit rates of up to 10 Gbits / second. and larger. The converter 100 converts the payload data into a corresponding electrical signal that propagates from the electrical freckle of the converter 100 to the first electrical input of the adapter unit 110. The complementary information unit 105 receives management instructions from local and regional management systems and generates the corresponding supplementary information data that propagates to the second electrical input of the adaptation unit 110. The adaptation unit 110 then interleaves the complementary information with the payload data so that 31 bits of payload data are accompanied by 1 bit of supplementary information data in a fixed ratio of 31: 1. Adapter unit 110 joins interleaved data into frames, each frame including 2048 bits of which 1984 bits and 64 bits correspond to payload data and supplementary information data respectively. In addition, the adapter unit 110 additionally joins frames into groups of eight frames, thereby generating corresponding multi-frames. The structures of the frames and

102109239 multi-frames will be described in more detail later.

The multi-frames exit through the electrical output of the adapter unit 110 in the form of aggregated data that propagates to the electrical input of the second converter 120. 0 converter 120 converts the aggregated data into the corresponding digitally modulated optical radiation that is output by the optical output to the fiber link 30 along which the radiation propagates to the receiving unit 40; converter 40 includes a modulated infrared laser operable to emit radiation at a wavelength in the order of 1550 nm.

The third converter 200 receives the modulated radiation and converts it to a corresponding electrical signal that the adapter unit 210 receives at its electrical input; This conversion is performed by associated optical amplifiers, regenerators and photodetectors within the converter 200. The adapter unit 210 processes the electrical signal corresponding to the aggregated data by removing the complementary information data and passing it to the interpretation unit 220. The adapter unit 210 further decodes the frames and multi-frames to extract the payload data that is sent from the adapter unit 210 to the electrical input of the fourth converter 215. Converter 215 converts the payload data and modulates it in optical radiation that is sent by the optical output of converter 215 and propagates to the receiving client.

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The shape of the aggregate data in channel 10 differs from that of conventional communication systems in that the number of the complementary information data bits and the payload data in the aggregate data is always at a fixed ratio. In addition, alignment is not employed with a consequence that the data blocks provided by the sending client are asynchronous to channel 10 frames and multi-frames. As a consequence of the adapter unit 210 removing the complementary information data and decoding the frames and multi-frames, the transmission from the sending client to the receiving client is transparent in the sense that the receiving client will be unaware that frames and multi-frames are used. frames for forwarding the payload data through channel 10.

Because channel 10 alignment is not used and the payload data bit number for supplementary information data is in a fixed ratio, it is much easier to determine the error bit rate on the channel not just on the receiving unit. 40 but also in sub nodes (not shown) along the fiber bond 30. Such ease in determining the bitrate of error allows, in a communication system incorporating a plurality of channels similar to channel 10, faulty channels to be more easily identified and, if necessary, corresponding protection channels to be selected instead.

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A communication system may be constructed according to the invention which includes a plurality of channels similar to channel 10 where modulated optical radiation is optically multiplexed over a single fiber optic link. Such a system is illustrated in Figure 2 and generally indicated by 300.

System 300 includes N transmission units, for example transmission units 20a, 20b corresponding to channels 1 and 2 respectively. Each transmission unit 20 is connected at its optical input to a corresponding sending client, for example channels 1 and 2 are connected to sending clients 1 and 2 respectively. The transmission units 20 are interconnected in their associated complementary information generating units 105 such that, for example, the payload data of the sending client 1 may be routed through channel N in the event that channel 1 becomes defective as in switching. of protection. The optical outputs of the transmission units 20 are connected to an optical multiplexer 310 that combines the outputs to provide a composite optical output. The composite output is connected to the first end of fiber 150 of fiber link 30. Second converters 120 of transmission units 20 in system 300 are configured to send their optical radiation at mutually different wavelengths. For example, channel 1, 2 and N converters 120 can be configured to emit optical radiation at nominal wavelengths of 1550,

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1560 and 1600 nm respectively, although other wavelengths may alternatively be used if necessary.

The fiber 150 is connected at its second end to an optical demultiplexer 320 including a plurality of Bragg network optical filters, for example a filter 330, for isolating radiation components from the multiplexer 310 corresponding to each transmission unit 20. The demultiplexer 320 is connected at its optical outputs to associated receiving units 40 which are in turn connected to associated receiving clients. The receiving units 40 are interconnected in their respective interpretation units 220 so that functions such as switching to a protection channel, for example channel N, may be implemented in the event that another channel develops a fault.

<td></td><td>In</td><td>operation, the data</td><td>in</td><td>charge</td><td colspan="2">received at</td>

<td>leave</td><td>From</td><td colspan="2">dispatching customers</td><td>are</td><td>coded</td><td>in the</td>

<td>units</td><td>in</td><td>transmission 20</td><td colspan="3">to generate the</td><td>their</td>

<td colspan="3">corresponding aggregate data.</td><td>The</td><td>Dice</td><td>aggregates of</td><td>each</td>

<td>unity</td><td>in</td><td>transmission 20 are</td><td colspan="4">modulated in a radiation</td>

optical carrier whose nominal wavelength is specific to each transmission unit 20. Output optical radiation from transmission units 20 is optically combined in multiplexer 310 to generate the composite radiation propagating via

102109239 fiber 30.

Demultiplexer 320 receives composite radiation at its optical input and filters the aggregate radiation corresponding to each transmission unit 20. The aggregate radiation propagates to its respective receiving unit 40 which then decodes the aggregate data to provide the load data. useful to your associated receiving customer.

When a large number of channels are required, for example several hundred channels, system 300 may be duplicated to provide an extended system comprising multiple multiplexers, demultiplexers and fiber optic links. Each transmission unit and receiving unit in such an extended system may be connected to other transmission units and receiving units respectively to provide functions such as protection switching in the event of a fiber link, demultiplexer or multiplexer becoming defective. .

Each channel in system 300 adapts to a rate at which payload data is provided from its respective shipping client. Thus, channels in system 300 are capable of operating asynchronously. Such channel adaptation to the rates at which payload data is provided by the sending customers is performed by the adapter units 110, 210 of each

102109239 channel.

Although system 300 shown in Figure 2 is operable to provide communications links from the sending clients to the receiving client, it will be understood that two-way communication between sending clients and receiving clients is provided by the inclusion of corresponding inversely directed channels (not presented) from receiving clients to sending clients, the inversely directed channels being of similar design to the channels illustrated in Figures 1 and 2.

In order to further describe asynchronous channel operation, the adapter unit 110 will be described in more detail with reference to Figure 3. The ability of system 300 channels to function mutually asynchronously circumvents the need for alignment in the aggregate data, thereby allowing a fixed ratio of payload bits to supplemental information bits to be achieved which greatly simplifies such complementary information functions. such as error bit rate (BER) determination, and also reduces phase instability in the aggregate data propagating on channel 10 and system 300.

The adapter unit 110, shown enclosed within an interrupted line 490, includes a 1 to 31,500 demultiplexer, a 32 to 1,510 multiplexer, a first phase lock ring (PLL1)

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520, a second phase lock ring (PLL2) 530 and a data encoder 540. Encoder 540 is implemented as a field programmable logic device (FPDL), for example as manufactured by Xilinx Inc.

The electrical output of the first converter 100 is connected to a demultiplexer 500 serial data input and a PLL1 520 reference input. A first output of the PLL1 520 is connected to a demultiplexer 500 CLK clock input. PLL1 520's second output is connected to a PLL2 530 reference input. The demultiplexer 500 includes parallel D outputs._O to D₃₀which are connected to corresponding data inputs of data encoder 540. The complementary information unit 105 includes a supplementary information data output connected to a complementary information data input K_O 540. The 540 also includes parallel data outputs E_O to E₃₁ connected to corresponding parallel inputs of multiplexer 510. An output of PLL2 530 is connected to a CLK clock input of multiplexer 510. Multiplexer 510 includes a multiplexed output connected to the electrical input of second converter 120.

In a larger view, the adapter unit 110 operates by receiving serial payload data from the first converter 100 at a rate of up to 10 Gbits / s or more. The PLL1 520 synchronizes itself with the payload data and generates a corresponding output signal.

102109239 Synchronized clock continuously generating clock pulses even when payload data remains in a particular logical state for several clock cycles. PLL1 520 generates clock pulses for both demultiplexer 500 and PLL2 530. Payload data is converted from a serial bit stream to 31 bit wide parallel words in the demultiplexer 500. Payload data is transferred in 31-bit words from demultiplexer 500 to encoder 540. Encoder 540 adds one bit of supplementary information data received from the complementary information generating unit 105 to each 31 bits of payload data at a ratio. fixed to provide output words in outputs E_O a Ε₃χ. The output words are passed to the multiplexer 510 which converts the output words to a corresponding serial bit stream, namely the aggregate data, which is passed to the second converter 120 where they are modulated into optical radiation for transmission over fiber 150. . The inclusion of demultiplexer 500 provides the benefit of encoder 540 receiving data in the form of words and does not need to be able to generate clock pulses at the rate of about 10 Gbits / s; Encoder 540 generates clock pulses at rates in the order of 300 MHz when the payload data bit rate approaches 10 Gbits / s. However, the demultiplexer 500 is designed to be capable of handling up to 10 Gbits / s or higher serial data bitrates.

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The inclusion of supplementary data in the aggregate data means that the data bitrate in the aggregate data is 32/31 times higher than the payload traffic presented by the sending client to adapter unit 110. This is the purpose of PLL2 530. provide a clock signal at a rate of F₂ which is the frequency fixed to the clock signal at a rate F₂from the PLL1 520. The clock signal from the PLL2 530 sends clock pulses to the multiplexer 510 at a rate 32/31 times higher than the demultiplexer 500 is controlled by the PLL1 520. Such a transformation of the Bit rate prevents a payload data accumulation on adapter unit 540 that would occur if demultiplexer 500 and multiplexer 510 were controlled at identical rates.

In adapter unit 210, an inverse operation is performed than in adapter unit 110. In reverse operation, aggregate data is first loaded into a 1 to 32 demultiplexer operable to convert serial data to data in 32-bit words, so the supplemental information bit is extracted from the 32-bit word to provide a 31-bit word. which is passed to a 31 to 1 bit multiplexer to convert the 31 bit word to the corresponding serial payload data. Adapter unit 210 also incorporates two PLLs as shown in Figure 3 except that the second PLL connected to the multiplexer is operable to provide a 31/32 times frequency conversion.

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In addition, data encoder 540 included in adapter unit 110 is replaced with a decoder in adapter unit 210 which is operable to output supplementary information data to its associated interpretation unit 220.

In practice, obtaining 1 to 31 demultiplexers and 32 to 1 multiplexers for transmission units 20a, 20b, and likewise 1 to 32 demultiplexers and 31 to 1 multiplexers for receiving units 40a, 40b is not easy when 10Gbit / s serial data bitrate performance is required. Own standard multiplexers and demultiplexers capable of operating at this bit rate are often 16 to 1 and 1 to 16 devices. When such proprietary portions are employed in adapter unit 110, unit 110 is deployable as illustrated in Figure 4.

In Figure 4, a 1 to 1640 demultiplexer is used instead of the 500 demultiplexer in Figure 3. In addition, a 16 to 1 550 multiplier is used instead of the 510 multiplier in Figure 3. In addition, An FPLD 560 data encoder including a buffer 570 is used instead of the 540 encoder in Figure 3.

In operation, payload data in the form of a serial bit stream passes from converter 100 to demultiplexer 540 which converts the bit stream into

ΡΕ2109239 series in corresponding 16-bit parallel words. Words are loaded by encoder 560 in its buffer 570 to provide it with payload data. Encoder 560 then adds an appropriate complementary information bit to each current group of 31-bit payload data in memory 570 to generate aggregate data thereon, and then proceeds to output the 16-bit word aggregate data to multiplexer 550 . The multiplexer 550 converts the 16-bit words into a serial bit stream of the aggregated data which is then output from coding unit 110 to

<td>second</td><td>converter 120</td><td>to the</td><td>your</td><td>modulation</td><td>in radiation</td>

<td>optics</td><td>for transmission</td><td>over</td><td>gives</td><td>fiber 150.</td><td></td>

<td></td><td>The conversion</td><td>of the rate</td><td>in</td><td>bits that</td><td>occurs in</td>

adapter units 110, 120 circumvent the need for alignment of the aggregate data, thereby simplifying the aggregate data and allowing sub-nodes to determine the error bit rate to be performed.

Aggregate data, as briefly described above, is serial data and plotted and multi-plotted by virtue of the bit values ​​of the supplementary information data added in a fixed ratio to the payload data on the adapter unit 110. Eight words in sequence in the aggregate data form a multi-frame. The structure of a plot is illustrated in

Figure 5 and indicated by 600. Each frame 600 starts with a complementary information bit A1 which is followed by 31 bits.

102109239 of the sending client payload data (31 bits P / L) which, in turn, are followed by a complementary information bit A2 and so on. For example, a complementary information bit A8 in the aggregate data is followed by 31 aggregate data bits which in turn are followed by a complementary information bit B1 and so on. Frame 600 terminates with a complementary information bit H8 followed by 31 payload data bits. As illustrated in Figure 5, each complementary information data bit in frame 600 is accompanied by 31 payload data bits in a fixed ratio of 1:31.

Aggregate data corresponding to frame 600 can be conceptually viewed as frame 600 being read row by row as represented by an arrow 610 indicating the direction of the row and an arrow 620 indicating the direction of the column. The frame 600 is thus read from its upper left top (START) to its lower right end (END) row by row to provide the aggregate data.

In frame 600, the complementary information bits A1 to A8 form a byte A, the complementary information bits BI to B8 form a byte B, and so on. Therefore, the complementary information bits for each frame can be represented as shown in Table 1 as eight bits; Payload data from the sending customer is not shown in the table.

102109239

Table 1

Supplementary Information Byte A

Supplementary Information Byte B

Supplementary Information Byte C

Supplementary Information Byte D

Supplementary Information Byte E

Supplementary Information Byte F

Supplementary Information Byte G

Supplementary Information Byte H

Eight frames similar to frame 600 are sequentially output to the aggregate data to form a multi-frame. The complementary information bytes of the eight frames constituting the multi-frame may be represented by symbols where byte A_x corresponds to the complementary information byte A of frame x where an index x is in the range of 1 to 8. Thus, a byte Αχ corresponds to a complementary information byte A of the first frame in the multi-frame and one byte H₈ corresponds to one byte of complementary information H of the eighth frame in the multi-frame.

For convenience, the bytes of complementary information of the frame may be arranged in table form as in Table 2.

102109239

Table 2

Plot 1 Plot 2 Plot 3 Plot 4 Plot 5 Plot 6 Plot 7 Plot 8

<td>Teχ byte</td><td>Byte A₂</td><td>Byte A₃</td><td>Byte A₄</td><td>Byte A5</td><td>Byte A₆</td><td>Byte A₇</td><td>Byte Ag</td>

<td>Byte Bi</td><td>Byte B₂</td><td>Byte B₃</td><td>Byte B₄</td><td>Byte B₅</td><td>Byte B₆</td><td>Byte B₇</td><td>Byte Bg</td>

<td>Byte Ci</td><td>Byte C₂</td><td>Byte C₃</td><td>Byte C₄</td><td>Byte C5</td><td>Byte Cê</td><td>Byte C₇</td><td>Byte Cg</td>

<td>Byte Di</td><td>Byte D₂</td><td>Byte D₃</td><td>Byte D₄</td><td>Byte D₅</td><td>Byte D₆</td><td>Byte D₇</td><td>Byte Dg</td>

<td>Byte Hey</td><td>Byte E₂</td><td>Byte E₃</td><td>Byte E₄</td><td>Byte E₅</td><td>Byte E₆</td><td>Byte E₇</td><td>Byte Eg</td>

<td>Byte Fi</td><td>Byte F₂</td><td>Byte F₃</td><td>Byte F₄</td><td>Byte F₅</td><td>Byte F₆</td><td>Byte F₇</td><td>Byte Fg</td>

<td>Byte Gi</td><td>Byte G₂</td><td>Byte G₃</td><td>Byte G₄</td><td>Byte G5</td><td>Byte Gê</td><td>Byte G₇</td><td>Byte Gg</td>

<td>Hi Byte</td><td>Byte H₂</td><td>Byte H₃</td><td>Byte H₄</td><td>Byte H₅</td><td>Byte H₆</td><td>Byte H₇</td><td>Byte Hg</td>

In aggregate data, bytes of supplementary information appear in a sequence, although punctuated by payload data, so that Byte Αχ is followed by byte Βχ and so on to byte Ηχ followed by byte A₂ and so on up to byte H₈ at the end of the multi-plot.

Units 105, 220 use the complementary information bytes to perform a number of complementary information functions which will now be described with reference to Figure 6; This diagram shows a byte representation of complementary information of a multi-frame structure used on channel 10 and the system.

300 The complementary information bytes perform different functions, for example as indicated by abbreviations in the diagram, namely:

102109239 frame alignment word;

multi-frame identity code;

balance byte;

free byte;

route identifier;

automatic protection channel;

FAW

MIC

BAL

SPA

TTI

PHC

IDF

BDI

FQI

BQI

PTI

BEEP

<td>recommendation</td><td>in</td><td>defect for</td><td>forward;</td>

<td>recommendation</td><td>in</td><td>defect for</td><td>back;</td>

<td>indicator</td><td>in</td><td>quality in</td><td>front;</td>

<td>indicator</td><td>in</td><td colspan="2">backwardness;</td>

<td>indicator</td><td>in</td><td>load type</td><td>useful; and</td>

bit parity interlaced.

In system 10, the complementary information generating unit 105 generates the complementary information bytes shown in Figure 6. The values ​​of some of the complementary information bytes are determined locally in the complementary information unit 105 while others are generated in response to received commands. from the above mentioned local and regional management systems, eg TTI values. In other words, the complementary information bytes are generated based on information provided internally in the transmission unit 2020 from the aforementioned management systems. These bytes are communicated in the aggregated data to the adapter unit 210 which isolates the complementary information bytes and passes them to the interpretation unit 220 for interpretation.

102109239

Interpretation 220 uses the complementary information bytes FAW1, FAW2, FAW3, FAW4 to identify where multi-frames start in aggregate data, particularly for multi-frame synchronization. On channel 10 and system 300, these bytes FAW1, FAW2, FAW3, FAW4 have fixed values ​​of 1111 0110b, 1111 0110_B, 0010 1000_B, 0010 1000_B respectively where an index b indicates a binary number. Alternative values ​​for these FAW1 through FAW4 bytes may be used as long as these values ​​provide channel 10 and system 300 with multi-frame synchronization capability.

The MIC Multi-Frame Identification Code is a byte value that is incremented by the complementary information generating unit 105 for each subsequent multi-frame. For example, a first multi-frame has a value of MIC 0000 0001_B, a second multi-frame following the first multi-frame has a value of MIC 0000 0010_B and so on; when the identity code reaches a value 1111 1111b to 255^The the MIC resets to a value of 0000 0000b for

256^The multi-frame and so on in a form of module 255. Incrementation in other modules, for example in module 8, is also possible for MIC code instead of using module 255.

Interpretation unit 220 is operable to monitor the identity code and ensure that the correct increment occurs; any errors in incrementing the

102109239

MICs are identified by interpretation unit 220 as indicative of missing multi-frames. Furthermore, the inclusion of the MIC code in the aggregate data helps the receiving unit 40 to synchronize with the aggregated data, namely frame alignment is thus improved in the receiving unit 40.

As an option, the MIC value may be incremented by more than 1 count for each subsequent multi-frame, for example the increment may be in three count steps so that a typical MIC count sequence may be 1111 1110_B (decimal 254) for a first multi-frame, 0000 0001b (decimal 1) for a second multi-frame, 0000 0100_B (decimal 4) for a third multi-frame and so on.

Interpretation unit 220 uses the BAL equilibrium complementary information bytes for dc restoration purposes. The value of the equilibrium bytes is defined by the complementary information generating unit 105 so that for each of frames 2 to 8 of the multi-frame As shown in Figure 6, the number of 0's and 1's in their associated complementary information bytes are equal. This balance is advantageous when channel 10 and 300 photodetectors are employed having their electrical outputs at and

coupled to remove dc offset to convert modulated radiation with aggregated data into electrical signals for adapter unit 210 and its units

Interpretation 2109239 220 associated.

The multi-frame in Figure 6 also includes SPA free bytes that are not initially assigned but can be assigned by system users to perform additional functions after system commissioning 300 if such functions prove necessary to assist system operation. The generator and interpretation units 105, 220 are software controlled and are therefore likely to have their performance updated by software modification.

The TTI path identifier supplemental bytes include a 16-byte string that is included from the supplementary information byte B₂ from frame 2 to supplementary information byte D₅ of bytes 5 as shown in Figure 6. Bytes 2 through 16 of the string are user-definable ASCII characters and byte 1 of the string includes a CRC-7 checksum value generated by the complementary information unit 105 in accordance with a specification. Communication ITU G. 707 Annex Β. The string is used by the system 300 to ensure that a receiving client is connected to its correct corresponding sending client.

The APS1 to APS4 automatic protection channel supplemental information bytes, namely the supplementary information bytes A₆ to D₆ of frame 6 are used by system 300 when a channel

It has to be bypassed and another system channel 300 assigned instead to route its payload data. Interpretation unit 220 interprets these bytes of complementary information to determine whether or not its associated channel is to be bypassed and the identity of an alternate system channel 300 to be assigned instead. The complementary information and interpretation units 105, 220 are operable in combination with the aforementioned local and regional management systems to determine interconnections within system 300 when overrides occur to route payload data from an affected shipped customer to its customer. associated receiver.

The forward FDI indication byte FDI, namely the supplementary information byte A₇ of frame 7 is used in channel 10 and system 300 to indicate downstream, namely at the fiber link end 30 of the receiving client, that an upstream deficiency condition has been detected, namely towards the corresponding sending client. Similarly, the backward fault indication byte BDI is used, namely byte B₇complementary information of the frame 7 when a receive path defect is detected, namely at the fiber link end 30 of the receiving client. The bytes of supplementary information FDI and BDI thus allow

Thus, the location of a defect in system 300 is easily and quickly identified.

forward quality indication complementary information byte FQI, namely frame 7 complementary information byte C7, is used to forward an error bit count of a preceding multi-frame. Thus, the FQI is used to indicate downstream an upstream error. Similarly, the backward quality indication byte BQI is used, namely the supplementary information byte D₇ of frame 7 to forward an error bit count of the preceding multi-frame payload data.

The complementary information byte indicating the payload type PTI, namely the information byte

<td>complementary</td><td>THE₈</td><td>weft,</td><td>Is it used</td><td>for</td><td>indicate the</td>

<td colspan="2">composition of</td><td>data from</td><td colspan="2">payload or 0</td><td>state of</td>

<td>maintenance of</td><td>one</td><td colspan="2">communication path</td><td>what</td><td>forwards</td>

<td>multi-plot and</td><td>the</td><td>your data</td><td>payload</td><td colspan="2">associated. Per</td>

<td>example,</td><td colspan="2">interpretations</td><td>to 0 byte</td><td>in</td><td>information</td>

ITP complies with Table 3.

102109239

Table 3

<td>Binary value</td><td>Interpretation applied by the interpretation unit</td>

<td>byte PTI</td><td> 220</td>

<td> 0000</td><td>Not equipped, in particular there is a complete communication from the sending client to the receiving client but the client did not turn on your equipment to the route.</td>

<td> 0001</td><td>Indicates a linear transponder mode, namely that a signal is being routed that does not require digital regeneration and so any regenerators along the way should be turned off.</td>

<td> 0010</td><td>Indicates payload data rate is 155.52 Mbits / s (STM-1 mode) and requires retrofitting / regeneration of the adapter unit to this rate.</td>

<td> 0011</td><td>Indicates that the payload data rate is 622, 08 Mbits / s (STM-4 mode) and requires the retrofitting / regeneration of the adapter unit to this rate.</td>

<td> 0100</td><td>Indicates payload data rate is 1.0625 Gbits / s (fiber channel) and requires the retrofitting / regeneration of the adapter unit to this rate.</td>

<td> 0101</td><td>Indicates payload data rate is 1.25 Gbits / s (as with Gigabit Ethernet) and requires the retrofitting / regeneration of the adapter unit to this rate.</td>

<td> 0110</td><td>Indicates that the payload data rate is 2.48832 Gbits / s (STM-16) and requires re-timing / regeneration of the adapter unit at this rate.</td>

<td> 0111</td><td>Indicates that the payload data rate is 9, 95328 Gbits / s (STM-64) and requires retiming / regeneraç will of the adapter unit at this rate.</td>

<td>1000 to 1110</td><td>Not used</td>

<td> 1111</td><td>Indicates failure of the sending client signal (for example signal interruption)</td>

102109239

Finally, the BIP interleaved bit parity complementary information bytes, namely the complementary information bytes Εχ to E₈, include a BIP-8 parity check value; A detailed definition is provided in ITU G.707 standard. Each frame has its associated BIP parity value which provides a parity check for the frame payload data. In the presented multi-frame illustrated in Figure 6, the inventors have understood that it is preferable to have one BIP byte associated with each frame rather than to agglomerate the BIP bytes, for example at the end of the multi-frame. Such assignment of the BIP byte to each frame reduces the need for high-speed memory on channel 10 receiving unit 40. Thus, the distribution of BIP byte bytes by frames is preferable to concatenating the BIP bytes together in the multi-frame. The BIP code provides a direct indication of the bit error rate in the payload data because the ratio between the number of payload bits and the number of supplementary information bits is maintained in system 300 at a fixed rate.

It will be appreciated that modifications may be made to channel 10 and system 300 and their method of operation without departing from the scope of the invention.

For example, although supplementary information data and payload data are interlaced on adapter unit 110 at a fixed ratio of 1:31 bits, other ratios are possible. The adapter units 110, 210

102109239 can be modified such that the ratio is in the range of 1: 2 bits to 1: 100 bits depending on the degree of complementary information control required. An important point is that the ratio should be fixed and not dynamically variable as in the prior art communication systems where alignment is employed.

Further, in channel 10 and system 300, the number of frames constituting a multi-frame may be changed from eight frames constituting the multi-frame as mentioned above. For example, the number of frames forming a multi-frame may be varied over a range of 2 to 100, although including more than 50 frames in a multi-frame makes synchronization more difficult in the receiving unit.

Additionally, in Figure 6, the positions of the complementary information bytes performing specific functions may be modified as long as they continue to perform their associated functions, for example, the positions of the MIC to PTI complementary information bytes may be exchanged in a modified version. of the multi-plot. Additionally, the BIP complementary information bytes of each frame may be arranged to be included in the last complementary information byte of each frame, for example in the complementary information byte H₄ for plot 1.

As mentioned earlier the binding by

The fiber 30 may include one or more optical fibers. In alternative versions of channel 10 and system 300, the fiber link 30 may be replaced by a radio link, for example a satellite microwave link. Where lower data rate operation is employed, fiber link 30 may be replaced by one or more coaxial cable wire links; Such coaxial cable connections generally have a lower data transport capacity compared to fiber optic connections.

Also provided is a method of data communication in communication systems (300), each system including at least one channel (10) including transmission means (20), receiving means (40) and data routing means (30). for routing data from the transmission means (20) to the receiving means (40), the method comprising the steps of:

(a) combining payload and supplementary information data in the transmission means (20) to form aggregate data (600) thereof for transmission to the receiving means (40), the aggregate data (600) being divided into structures of the type frame in which the number of bits of supplementary information is in a fixed ratio to the number of payload bits;

(b) transmitting aggregated data (600) from the transmission means (20) to the receiving means (40) via the

21109239 routing means (30);

(c) receiving the aggregate data (600) on the receiving means (40), decoding the aggregate data to isolate the supplementary information data from the payload data, and interpreting the supplementary information data to control and manage the data from payload in the system (300), characterized in that the transmission means (20) are operable to generate the aggregate data (600) at a rate that is greater than the rate of reception of the payload data in a fraction substantially (R_P + R_O) / (R_P) where R_P is

<td>the fee of</td><td>reception of</td><td>Dice</td><td>payload on media</td><td>in</td>

<td>streaming</td><td>(20) and Ro</td><td>and the</td><td>rate at which data</td><td>in</td>

<td>information</td><td>complementary</td><td>are</td><td>added in the media</td><td>in</td>

<td>streaming</td><td colspan="2">(20) to generate the</td><td>aggregated data (600).</td><td></td>

<td>THE</td><td>fixed ratio</td><td colspan="2">from payload bits to bits</td><td>in</td>

<td>information</td><td>complementary</td><td>can</td><td>be in a range of 2: 1</td><td>The</td>

100: 1, and preferably 31: 1.

The system may be operable not to apply additional alignment to payload data when generating aggregate data (600).

The number of bytes of supplementary information indicative of error rate occurrence in the aggregated data for the number of payload bytes may be in a fixed ratio, thus providing a density

ΡΕ2109239 Fixed error reason bytes for payload bytes.

The number of bytes of supplementary information indicative of the occurrence of the error ratio to the number of corresponding payload bytes may be in a fixed ratio of 1: 248.

System (300) may include a plurality of channels (20a, 20b, 40a, 40b), each channel (20a, 20b,

40a, 40b) are capable of adapting to the data rate of their associated payload data, so channels 20a, 20b, 40a, 40b are capable of operating asynchronously.

The complementary information data and the payload data may be interlaced in the aggregate data (600).

Frame-like structures may include a plurality of frames (600) arranged in multi-frames (Figure 5), the frames and multi-frames being identifiable in the receiving means (40) by interpreting the position of the complementary information data within the data. aggregates.

Each multi-frame may include a range of 2 to 100 frames, and preferably 8 frames.

The supplementary information data associated with

102109239 each multi-frame may include a synchronization code (FAW) to assist the receiving means to synchronize with the multi-frames.

Synchronization code may include four synchronization bytes (FAW1 to 4) in the supplementary information data.

The four synchronization bytes (FAW1 to 4) can have binary values ​​of 1111 0110b, 1111 0110b, 0010 1000b θ 0010 1000b assigned to them respectively.

The complementary information data associated with each multi-frame may include an identity code (MIC) for use in multi-frame identification.

The identity code (MIC) may be incremented for successive multi-frames, preferably the identity code (MIC) is incremented in a module form, or alternatively the identity code (MIC) is incremented in steps of a plurality of counts to. successive multi-plots.

The receiving means may be operable to determine whether or not multi-frames are missing by checking whether the identity code (MIC) is consistently incremented from multi-frame to multi-frame.

102109239

The complementary information data associated with each multi-frame may include balancing code (BAL) to ensure that the complementary information bytes associated with the multi-frame include substantially equal numbers of 0'a and 1's.

The complementary information data associated with each multi-frame may include path identification code (TTI) for use by the receiving means to confirm whether or not it is connected to its corresponding correct transmission means (20).

The complementary information data associated with each multi-frame may include automatic protection switching code (APS) to instruct the system (300) to use alternate channels to route the payload data in the event of system channel failure (300). ).

The complementary information data associated with each multi-frame may include interleaved bit parity code (BIP) for each multi-frame frame, the interleaved bit parity code usable by the receiving means 40 to detect the occurrence. corruption of the payload data associated with the frame.

The complementary information data associated with each frame may include a payload type indicator (PTI) code indicative of the input payload data rate for the transmission means (20).

102109239

The transmission means (20) may be operable to receive the payload data as serial data and to convert it to parallel data (D_O to D₃₀) to match them with the supplementary information data (K_O) to generate the aggregate data (600) as serial data for transmission through the routing means (30).

Also provided is a communications system (300) operable according to the methods described above.

Transmission means (20) may incorporate an adapter unit (110) for combining payload data with supplementary information data to generate aggregate data (600), and receiving means (40) incorporate a corresponding adapter unit (210) to decode aggregate data to separate payload data from supplementary information data.

The system may include a plurality of channels (20a, 20b, 40a, 40b) operable to adapt to the rate at which they receive payload data, the channels (20a, 20b, 40a, 40b) being able to operate mutually. asynchronously.

Each adapter unit (110, 210) may incorporate an electrical multiplexer (510) and an electrical demultiplexer (500) for converting data serially thereon to parallel data (D_O to D₃₀) for processing on the adapter unit (110, 210) and back

102109239 in serial data again after processing performed on the adapter unit (110, 210).

be