Method and Network Devices for Splitting of a Data Stream Technical Field

Embodiments of the present invention relate generally to wireless communications and more particularly to network devices and methods in wireless communication networks. The invention relates to a method for splitting of a data stream. Moreover, the invention relates to network devices, to a communication system, to a computer program product and to a computer-readable medium. Background

In communication systems microwaves may be utilized for transmission of data. Microwaves are electromagnetic waves in the frequency range of about 1 GHz to about 30 GHz

corresponding to wavelengths between about 30 cm and about 1 cm. Microwaves may be used for transmitting digital signals as well as analog signals between a plurality of locations, for example two locations. The connections may be built up in a line-of-sight connection or nearly-line-of-sight

connection. Depending on the weather conditions, especially on humidity and rain, the attenuation conditions along the propagation path may vary.

A communication system may comprise several radio channels which use different frequencies and/or polarizations. A plurality of radio channels may be combined into a radio link. One aspect to use several radio channels in parallel may be to add additional link capacity. However, when scaling up the system for providing a plurality of radio channels, there may be an opportunity to make the system more reliable by introducing additional redundancy.

In order to protect a radio link against a degradation or a failure of a single radio channel there may be different solutions .

EP 1 411 745 Bl "Packet switching for packet data

transmission systems in a multi channel radio arrangement" describes a system with channel protection. A channel protection may be provided by transmitting the same

information over two radio channels. Extra bandwidth may be made available in a co-channel system, i.e. by using the cross polarized channel.

As far as Ethernet packet networks are concerned, the usage of multiple links in parallel to increase the speed beyond the limit of the single link may be commonly based upon the LACP (Link Aggregation Control Protocol) , defined in IEEE 802.1AX-2008 (previously clause 43 of IEEE 802.3-2005

Ethernet Standard) . In this standard the Ethernet packets may be assigned to a physical link belonging to the link

aggregation group according to some specific values in the packet header, e.g. the source or destination MAC addresses or the Ethernet type field. A common approach may be to apply a hash function to the selected information to generate the link number over which the packet may be transmitted. The hash function approach may work well when the links have a constant capacity. This may be not the case with a microwave radio link operating with adaptive modulation and coding. The hash function approach may also work well when the data packets belong to a big number of conversations. In such a case the hash function may balance the load among the links. Utilizing a hash function in relation to microwave links may cause problems. This may reduce the usage of individual microwave channels.

There may be a need to provide a more efficient usage of microwave channels.

Summary of the Invention According to an aspect of the invention there may be provided a method for splitting of a data stream. The method may comprise splitting a data stream into a first partial stream and a second partial data stream, transmitting or sending the first data stream over a first path comprising a first channel and transmitting or sending the second data stream over a second path comprising a second channel. Moreover, the method may comprise receiving the first data stream and the second data stream and merging the first data stream and the second data stream into an output data stream, wherein the splitting may be performed according to a capacity of the first channel and to a capacity of the second channel. The operation of merging may depend on the previous splitting of the data stream. The method may provide a usage of the entire or almost entire capacity available over all radio channels. Moreover, there may be provided a protection of the overall radio link against phenomena affecting individual radio channels. According to an exemplary embodiment of the present invention the data may be split into blocks of one or more bytes.

This may be performed independently of a potential packet framing of the data to be split. The transmission of the individual bytes of a packet frame in parallel over more one channel may have the implication that the frame will be transmitted in a shorter time, i.e. with a greater

transmission speed, as if it were sent over only one channel. Transmitting the individual bytes in parallel over more than one channel may reduce the latency, which is of special importance for services sensitive to delay, like IEEE 1588 Timing over Packet, or Circuit Emulation Services-over-Packet (CESoP) . In addition no storage of entire packet frames may be required, and no necessity for re-ordering the packet frames may arise, as it might happen when sending entire frames over the individual partner channels, e.g. when using a packet based strategy for splitting the data traffic.

According to an exemplary embodiment of the present invention the split data may be embedded in frames of a duration which is the same for the first channel and the second channel independent of the actual channel capacity of the first channel and the second channel. According to an exemplary embodiment of the present invention the data may be split according to predefined profiles.

According to an exemplary embodiment of the present invention the predefined profiles may be stored in pre-calculated parameter arrays.

According to an exemplary embodiment of the present invention the capacity of each channel may be matched to the actual transmission conditions by Adaptive Coding and Modulation.

The capacity of one channel may change independently from that of the other channel, e.g. according to the Adaptive Coding and Modulation (ACM) scheme chosen due to the

transmission conditions on the channel. This transition may be hitless by changing the ACM scheme at the beginning of a new radio frame.

According to an exemplary embodiment of the present invention the channel capacity of a channel may be set to zero, if at least one quality parameter of the channel falls below a predefined threshold, e.g. due to a low signal-to-noise ratio . In this case the channel may be configured to a "No Data Mode", and no payload, but only padding data should be transmitted over this channel. Otherwise the defective data of this channel would corrupt the payload of all channels: The defective data of this channel would be combined with the data of the other channels to a corrupted data stream. With the "No Data Mode" the payload is transmitted only over functional channels, and even the total failure of an

individual channel may be compensated. According to an exemplary embodiment of the present invention a network device for splitting of a data stream comprising a bandwidth controller and a splitter may be provided.

The bandwidth controller may be adapted to control the splitter. The splitter may be adapted to split the data stream into a first partial data stream and a second partial data stream, to transmit the first partial data stream over a first path comprising a first channel and to transmit the second partial data stream over a second path comprising a second channel. The bandwidth controller may be adapted to control a splitting, wherein the splitting is performed according to a first capacity of the first channel and to a second capacity of the second channel. According to an exemplary embodiment of the present invention a network device for merging a first partial data stream and a second partial data stream may be provided The network device may comprise a bandwidth controller and a merger. The bandwidth controller may be adapted to control the merger. The merger may be adapted to receive the first partial data stream, to receive the second partial data stream and to merge the first partial data stream and the second partial data stream into an output data stream. The bandwidth controller may be adapted to control a merging, wherein the merging may be performed according to a first capacity of the first channel and to a second capacity of the second channel.

According to an exemplary embodiment of the present invention a system comprising

a first network device and a second network device may be provided .

The first network device may be connected with the second network device over a first path and over a second path.

According to an exemplary embodiment of the present invention a system may be provided, wherein the first path and the second path may be operated in parallel.

Parallel may be understood in the sense of the parallelity of electrical lines, but also in the sense of the synchronous operation of electrical devices.

According to an exemplary embodiment of the present invention a system may be provided, wherein the bandwidth controller receives information on the capacity of the first channel from a first Adaptive Coding and Modulation engine and information on the capacity of the second channel from a second Adaptive Coding and Modulation engine.

An Adaptive Coding and Modulation engine may be a device which may, depending on the quality of a channel, decide on a coding and modulation scheme for this channel and this way define the capacity of this channel.

According to an exemplary embodiment of the present invention a computer program product may be provided comprising code portions for causing a network device on which the computer program may be executed to carry out the data splitting or the data merging. According to an exemplary embodiment of the present invention a computer-readable medium may be provided embodying the computer program product.

Brief Description of the Drawings

Embodiments of the present invention are described below with reference to the accompanying drawings, wherein: Fig. 1 illustrates an exemplary embodiment of a transmission section of a system,

Fig. 2 illustrates an exemplary embodiment of a receiving section of a system,

Fig. 3 illustrates a method according to an exemplary

embodiment of the present invention,

Fig. 4 illustrates an exemplary embodiment of a data

splitting section of a system,

Fig. 5 illustrates an exemplary embodiment of a data merging section of a system, Fig. 6 illustrates an exemplary embodiment of a suitable structure for storing the pre-calculated data of a system, and

Fig. 7 illustrates an exemplary embodiment of a method according to an aspect of the present invention.

Detailed Description The illustration of the drawings is schematic. In different drawings, similar or identical elements are provided with the same reference numerals.

The exemplary embodiments in Fig. 1 to Fig. 7 show a system comprising two radio channels. The system may be a frequency diversity system with two channels on different frequencies or a co-channel system with two orthogonally polarized channels including Cross Polar Interference Cancellers

("XPICs") . The system may be generalized to a system with more radio channels using different frequencies and one or two polarizations. Adaptive Coding and Modulation (ACM) may be included in the embodiment as well.

In the exemplary embodiment with two radio channels the system may comprise on each side of the radio link one In

Door Unit (IDU) 100 and two Out Door Units (ODUs) 200, 300.

Each Out Door Unit has three interfaces: An interface with the In Door Unit (IDU) 100, a radio interface 101 or 102, which may be proprietary, for exchanging data with the remote partner of the radio link, and an interface to the co-located

Out Door Unit, which may be proprietary, for performing the functionalities described in the following.

The two ODUs 200, 300 at the same side of the radio link may be designated as "master" and "slave". The master ODU 200 is the one linked to the IDU 100. Besides its radio interface functionality it manages the centralized functions, such as Layer 2 and/or Layer 3 functionalities, e.g. Ethernet

switching, as well as the bandwidth sharing and bandwidth merging algorithms, which are the very object of the

invention. The slave ODU 300 receives the data payload to be transmitted as well as the management and control data from the master ODU 200 and is used mainly as an additional radio interface increasing the radio link capacity. It should be mentioned that from an IDU perspective the overall capacity is seen as a single bundle, i.e. the IDU perceives the two radio channels as a single radio link with double capacity.

Dashed lines and dashed blocks in Fig. 1 and Fig. 2 may not participate in the bandwidth sharing and merging described in the following; they may be unused parts of the slave ODU 300 which may be used for protection switching in the case of a partial failure of the master ODU 200. For a protection switching functionality the IDU 100 may be connected with both the master ODU 200 and the slave ODU 300 at the Cable Interfaces 201 and 301. In case of a failure of e.g. the components 201, 203, 204, 205 or 212 the Protection Switch 207 of the master ODU 200 and the Protection Switch 307 of the slave ODU 300 may be switched and the Cable Interface 301 may be activated. The former master ODU 200 may then work as slave ODU and the former slave ODU 300 may then work as master ODU.

Fig. 1 illustrates an exemplary embodiment of a transmission section of a system. An In Door Unit 100 may be connected to a master ODU 200. Over a Cable Interface 201, an Ethernet Switch 203, controlled by a microcontroller 202, and an HDLC Framer 204 data may be conveyed to a Bandwidth Sharing Unit 205. A Bandwidth Sharing Unit 205 may get a PHY profile from an ACM Engine 206 over a link 511 and a PHY profile from an ACM Engine 306 of a co-located ODU over a link 510; PHY is a common abbreviation for the physical layer of the Open

Systems Interconnection (OSI) model. The Adaptive Coding and Modulation engines 206 and 306 may decide, depending on the quality of radio channels 101 and 102, on the coding and modulation scheme of the radio channels and this way define the bandwidth of the respective radio links. This bandwidth information may govern the splitting operation of a Bandwidth Sharing Unit 205 which may allocate the data to the radio channels 101 and 102. The data may be routed over Protection Switches 207 and 307 and Coding, Modulation and Radio

Frequency Interfaces 208 and 308 to the radio channels 101 and 102.

Fig. 2 illustrates an exemplary embodiment of a receiving section of a system. Signals from radio channels 101 and 102 may be received in Radio Frequency Interfaces 210 and 310 and may be conditioned, demodulated and decoded in Cross Polar

Interference Cancelling, Demodulation and Decoding Units 211 and 311. Over a Cross Channel for a Cross Polar Interference Canceller 522 information necessary for cancelling the cross talk between the both polarization modes may be exchanged.

Two data streams decoded by units 211 and 311 may be merged in a Bandwidth Merger 212. The combined data stream may be conveyed over an HDLC Framer 204, an Ethernet Switch 203, controlled by a microcontroller 202, and a Cable Interface 201 to an In Door Unit 100.

Fig. 3 illustrates a communication system 500 using a method according to an exemplary embodiment of the present

invention. An incoming data stream 530 may comprise a plurality of data packets 550, 551, 552, 553. The data stream 530 may arrive via an incoming data link 529 at a first unit 205, which may split the incoming data stream 530 into two partial data streams 531, 532. The first partial data stream

531 may comprise packets 560, 561, 562, 563 and may be conveyed over a transmission path 111 comprising a

transmission unit 208, a radio channel 101 and receiving devices 210 and 211. The second partial data stream 532 may comprise packets 570, 571, 572, 573 and may be conveyed over a transmission path 112 comprising a transmission unit 308, a radio channel 102 and receiving devices 310 and 311. The two radio channels 101, 102 may be e.g. the two polarizations in a co-channel case, or two frequencies in a frequency

diversity case. Both data streams may be merged in a further device 212 and sent to a outgoing data link 534. The output of 212 may be a merged outcoming data stream 533. The data stream 533 may comprise data packets 580, 581, 582, 583.

The data structure in the partial data streams 531, 532 may be characterized by synchronous frames on both transmission paths 111 and 112, named "radio frames" in the following. The Bandwidth Sharing Unit 205 may generate these radio frames, one for the master ODU 200 and one for the slave ODU 300. These frames may move synchronously over the

transmission paths 111 and 112 and may be terminated

synchronously at a merging device 212. A delay compensation may be foreseen in the device 212 for the frame time re ^¬ alignment. The radio frames may be of fixed time duration and may contain a pre-determined number of bytes according to the actual channel capacity of either transmission path 111 and 112. They may ignore a potential framing of the incoming data stream 530, e.g. an Ethernet framing, regarding the incoming data stream 530 just as a rough flow of data bytes to be split to either transmission path 111 and 112. Fig. 4 illustrates an exemplary embodiment of a data

splitting section of a system. Over an Ethernet Switch 203, which may be controlled by a microcontroller 202, and over an HDLC Framer 204 an incoming data stream 530 may be conveyed to a Bandwidth Sharing Unit 205 comprising a Splitter 411, a Bandwidth Controller 410 with a memory 512 and Radio Framers 412 and 413. The Bandwidth Sharing Unit 205 may get a PHY profile from an ACM Engine 206 over a link 511 and a PHY profile from an ACM Engine 306 of a co-located ODU over a link 510. On the basis of these data and supported by a pre- calculated data table stored in a memory 512 a Bandwidth Controller 410 may generate a Switch Control Signal 513, which may govern the switching operation of a Splitter 411. The two data streams generated by the Splitter 411 may be routed to the Radio Framers 412 and 413. In the Radio Framers 412 and 413 the frame format may be changed: The incoming data stream 530 at the interface between the HDLC Framer 204 and the Splitter 411 may have the classical Ethernet format with an Ethernet header 600 and an Ethernet payload 601, whereas in the partial data stream 531 at the link from the Radio Framer 412 to a Radio Interface 208 and in the partial data stream 532 at the data link 520 to the co-located ODU the Ethernet data are encapsulated forming radio frames with a radio frame header 602 and a payload 603.

The partial data stream 531 may be routed over the Radio Interface 208 to the radio channel 101, another partial data stream 532 may be routed over an interface link 520 to a co- located ODU. An additional interface link 514 may carry a transmission frame synchronization signal to the co-located ODU.

Fig. 5 illustrates an exemplary embodiment of a data merging section of a system. A signal from a radio channel 101 may be received in a Radio Frequency Interface 210 and may be conditioned, demodulated and decoded in an XPIC, Demodulation and Decoding Unit 211. The data decoded by the unit 211 and the data delivered by a co-located ODU via a link 521 may be merged in a Bandwidth Merger 212 comprising a Merger 418, a Bandwidth Controller 410 with a memory 512, Radio De-framers 416 and 417 and Payload Buffers 414 and 415. The Radio De- framers may eliminate the radio frames and may reconstruct the former partial data streams from the radio frame

payloads. The Unit 211 may provide a PHY profile of the radio channel 101; together with a PHY profile of a radio channel 102 delivered by a co-located ODU over a link 510 and

supported by a pre-calculated data table stored in a memory 512 a Bandwidth Controller 410 may generate a Switch Control Signal 513, which may govern the operation of a Merger 418. The data stream merged in the Bandwidth Merger 212 may be conveyed over a HDLC Framer 204 to an Ethernet Switch 203, which may be controlled by a microcontroller 202. Fig. 6 illustrates an exemplary embodiment of a suitable structure for storing the pre-calculated data of a system. This example refers to the possible ACM states 32QAM, 16QAM, and "No Data Mode" in the two radio channels each having a radio frequency bandwidth of 28 MHz. A Quadrature Amplitude Modulation (QAM) may be understood as a modulation scheme conveying two digital bit streams by modulating the

amplitudes of two carrier waves. These two waves, usually sinusoids, are out of phase with each other by 90° and are thus called quadrature carriers or quadrature components. With 32QAM modulation 13129 Bytes may be carried per radio frame and with 16QAM modulation 10500 Bytes may be carried per radio frame.

The "Multiplier", see fourth column in Fig. 6, indicates how many times the switches in the Splitter and in the Merger may perform a switching action for sending and receiving "Sizel" and "Size2" bytes on channel 1 and channel 2. Two other counters "Remainderl" and "Remainder2" may be utilized to manage the remainder bytes which complete the radio frame.

As an example the profile combination "M+6" may be considered representing 32QAM on channel 1 and 16QAM on channel 2. Here groups of 5 and 4 bytes are sent alternatively over channel 1 and channel 2 for 2625 times. After that 4 more bytes are sent over channel 1. This gives together 2625 x 5 + 4 Bytes = 13129 Bytes for channel 1, i.e. the link capacity for 32QAM, and 2625 x 4 Bytes = 10500 Bytes for channel 2, i.e. the channel capacity for 16QAM. So following this splitting instruction both channel are entirely used according to their actual channel capacity.

At the next frame a different combination, i.e. row in Fig. 6 can be selected, according to the radio propagation

conditions .

Fig. 7 illustrates an exemplary embodiment of a method 700 according to an aspect of the present invention.

The method may comprise splitting of a data stream into a first partial data stream and a second partial data stream according to a capacity of a first channel and a capacity of a second channel, see box 701, transmitting the first partial data stream over a first path comprising the first channel, see box 702, and transmitting the second partial data stream over a second path comprising the second channel, see box 703.

The method may further comprise receiving the first partial data stream and the second data partial stream, see box 704, and merging the first partial data stream and the second partial data stream into an output data stream according to the capacity of the first channel and the capacity of the second channel, see box 705. It may be understood, that further boxes or operations may be added .

In general it is to be noted that respective functional elements according to above-described aspects can be

implemented by any known means, either in hardware and/or software, respectively, if it is only adapted to perform the described functions of the respective parts. The mentioned method steps can be realized in individual functional blocks or by individual devices, or one or more of the method steps can be realized in a single functional block or by a single device .

Furthermore, method steps and functions likely to be

implemented as software code portions and being run using a processor at one of the entities are software code

independent and can be specified using any known or future developed programming language such as e.g. Java, C++, C, and Assembler. Method steps and/or devices or means likely to be implemented as hardware components at one of the entities are hardware independent and can be implemented using any known or future developed hardware technology or any hybrid of these, such as MOS, CMOS, BiCMOS, ECL, TTL, etc, using for example ASIC components or DSP components, as an example. Generally, any method step is suitable to be implemented as software or by hardware without changing the idea of the present invention. Devices and means can be implemented as individual devices, but this does not exclude that they are implemented in a distributed fashion throughout the system, as long as the functionality of the device is preserved. Such and similar principles are to be considered as known to those skilled in the art.

The network devices or network elements and their functions described therein may be implemented by software, e.g. by a computer program product for a computer, or by hardware. In any case, for executing their respective functions,

correspondingly used devices comprise several means and components which are required for control, processing and communication/signaling functionality. Such means may

comprise, for example, a processor unit for executing

instructions, programs and for processing data, memory means for storing instructions, programs and data, for serving as a work area of the processor and the like (e.g. ROM, RAM, EEPROM, and the like) , input means for inputting data and instructions by software (e.g. floppy diskette, CD-ROM, EEPOM, and the like) , user interface means for providing monitor and manipulation possibilities to a user (e.g. a screen, a keyboard and the like) , interface means for

establishing links and/or connections under the control of the processor unit (e.g. wires and wireless interface means, an antenna, etc.) and the like.

Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific

embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although the foregoing

descriptions and the associated drawings describe example embodiments in the context of certain example combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and/or functions other than those explicitly described above are also

contemplated as may be set forth in some of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

It should be noted, that reference signs in the claims shall not be construed as limiting the scope of the claims.

List of Abbreviations

ACM Adaptive Coding and Modulation

CESoP Circuit Emulation Services-over-Packet IDU In Door Unit

LACP Link Aggregation Control Protocol

ODU Out Door Unit

PHY PHYsical layer

QAM Quadrature amplitude modulation

XPIC Cross Polar Interference Canceller

List of References

100 In Door Unit (IDU)

101, 102 Radio Channels

111, 112 Transmission Paths

200 Master OutDoor Unit (ODU)

201 Cable Interface

202 Microcontroller

203 Ethernet Switch

204 HDLC Framer

205 Bandwidth Sharing Unit

206 Adaptive Coding and Modulation (ACM) engine

207 Protection Switch

208 Coding, Modulation, Radio Frequency Interface

210 Radio Frequency Interface

211 Cross Polar Interference Cancelling, Demodulation,

Decoding Unit

212 Bandwidth Merger

300 Slave OutDoor Unit (ODU)

301 Cable Interface

302 Microcontroller

303 Ethernet Switch

304 HDLC Framer

305 Bandwidth Sharing Unit

306 Adaptive Coding and Modulation (ACM) engine

307 Protection Switch

308 Coding, Modulation, Radio Frequency Interface

310 Radio Frequency Interface

311 Cross Polar Interference Cancelling, Demodulation,

Decoding Unit

312 Bandwidth Merger 410 Bandwidth Controller 411 Splitter

412 Radio Framer for Master ODU

413 Radio Framer for Slave ODU

414 Payload Buffer for Master ODU

415 Payload Buffer for Slave ODU

416 Radio De-framer for Master ODU

417 Radio De-framer for Slave ODU

418 Merger 500 Splitting Strategy

510 PHY Profile from Co-located Slave ODU

511 PHY Profile from own ACM Engine

512 Pre-calculated Data for Generation of Switch Control Signal

513 Switch Control Signal

514 Transmission Frame Synchronization Signal to Co-located Slave ODU

520 Data to Co-located ODU Modulator

521 Data from Co-located ODU Demodulator

522 Cross Channel for Cross Polar Interference Canceller

529 Incoming Data Link

530 Incoming Data Stream

531 Data Stream appointed to Transmission Path 111

532 Data Stream appointed to Transmission Path 112

533 Outgoing Data Stream

534 Outgoing Data Link

550, 551, 552, 553 Incoming Data Blocks

560, 561, 562, 563 Data Blocks appointed to Transmission

Path 111

570, 571, 572, 573 Data Blocks appointed to Transmission

Path 112

580, 581, 582, 583 Re-combined Data Blocks

600 Ethernet Header

601 Ethernet Payload Radio Frame Header

Radio Frame Payload

Box comprising an operation of a method