WO2012126512A1

WO2012126512A1 - Method and network devices for efficiently and reliably transferring data streams

Info

Publication number: WO2012126512A1
Application number: PCT/EP2011/054253
Authority: WO
Inventors: Alessandro Nevola; Luigi Sampietro; Gaudenzio FILIBERTI
Original assignee: Nokia Siemens Networks Oy
Priority date: 2011-03-21
Filing date: 2011-03-21
Publication date: 2012-09-27
Also published as: EP2689542A1

Abstract

The invention relates to a method for efficiently and reliably transferring data streams in wireless communication systems. Two different system modes may be foreseen: A High Throughput Mode maximizing the link capacity for highest throughput by Adaptive Coding and Modulation and a High System Gain Mode maximizing the link availability for maximum system gain by sending the same data over a plurality of radio channels and by consolidating the data streams received over the plurality of links.

Description

Method and Network Devices for Efficiently and Reliably

Transferring Data Streams

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 efficiently and reliably transferring data streams. 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 80 GHz

corresponding to wavelengths between about 30 cm and very much less than 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. Such a communication system may be used for a mix of legacy TDM traffic and packet traffic and for full packet data traffic.

Two important figures of merit of such a communication system are the system gain and the data throughput. The system gain is the ratio (or difference in dB) between the radio

frequency output power of a transmitter and the radio

frequency input power at the input of a receiver. For a fixed system configuration with given transmission power and with given receiver sensitivity a certain system gain may be required in order to provide a required minimum Quality of Service (QoS) , e.g. a bit error rate of 10^~6. If the

attenuation of the signal on the link, i.e. the system gain of the configuration is lower, there is excess system gain that may determine the capability of the system to counteract the varying attenuation conditions along the propagation path and is therefore related to the availability of the link under adverse weather conditions. The data throughput, in other words the link capacity, is the amount of data that may be transported over the radio link per time unit, e.g. per second, and is related to the efficiency of the link.

There is a trade-off between the system gain and the

throughput of the system: Less efficient modulation types, i.e. modulation types with a lower throughput, are in general more robust, i.e. they have a higher system gain and perform well even under more adverse weather conditions in the propagation path. The coding and modulation type may be adapted depending on the system gain met on the propagation path (Adaptive Coding and Modulation ACM) thus always

ensuring the highest throughput which is possible under the given conditions. So an increase of the available system gain may be obtained at the expense of a reduced throughput and vice versa.

Under extreme attenuation conditions, e.g. with heavy rain for frequencies greater than 10GHz, the system may come to the minimum throughput modulation type, the one with the greatest robustness. At this point no further step down to a more robust modulation type is possible, and with further degrading of the propagation conditions the link might be lost . So there may be a need to further improve the available system gain beyond the point which may be obtained by

switching to the most robust modulation type.

Summary of the Invention

Subject of the present invention is optimizing the operation of commonly used radio link hardware configurations. The aim is to achieve the best possible performance in terms of capacity and system gain by adaptively modifying the

operation of the system according to the actual radio channel condition. This may be done in conjunction with Adaptive Coding and Modulation, but there may be also other steps to further exploit the link adaptivity.

In order to come to a maximum of adaptivity two different system modes (PHY modes) may be foreseen. These two modes may be under normal propagation conditions: Maximizing the link capacity for highest throughput with lower system gain by Adaptive Coding and Modulation (High Throughput Mode) . under harsh propagation conditions: Maximizing the link availability for maximum system gain with lower

throughput by sending the same data over the plurality of radio channels and by consolidating the data streams received over the plurality of links (High System Gain Mode) .

The received data streams may be consolidated e.g. by hitless selection combining or by in-phase combining or equivalent. With two radio channels a 3dB improvement may be expected by in-phase combining. This may be compared with the almost 9dB that can be achieved with a MIMO system in MIMO (2x2) diversity mode, but with a much more complex system.

These two system modes may be obtained by reconfiguring the existing link hardware into one of the two system modes according to a suitable measure of the received signal quality, e.g. the Signal to Mean Squared Error ratio. The switching between the system modes should be implemented in a hitless way like the Adaptive Coding and Modulation

switching . In practice a third system mode exists, the protection mode against equipment failure. This is a usual and standard or quasi standard feature of the link hardware. Switching to the protection mode obviously does not need to be hitless. Two transmission schemes usually form the basis for

embodiments of the principles given above:

- Frequency Diversity transmission (FD) and

- Co-Channel transmission (CC) on orthogonal polarizations. When implementing the invention the hardware may usually be used as it is or with only marginal changes. In the following the basic embodiments are shown. The invention describes a method for transferring a first data stream (A) and a second data stream (B) over a first channel (50) and a second channel (51) . When the quality of at least one channel is above a predefined threshold,

- the first data stream (A) is transmitted over and received from the first channel (50) and

- the second data stream (B) is transmitted over and

received from the second channel (51),

otherwise

- the second data stream (B) is discarded and the first data stream (A) is duplicated into a first instance and a second instance (it is understood that the roles of data stream (A) and data stream (B) may be exchanged, i.e. data stream (A) could be discarded and data stream (B) could be duplicated) ,

- the first instance of the data stream is transmitted over and received from the first channel (50) and

- the second instance of the data stream is transmitted over and received from the second channel (51),

- and the first instance of the data stream and the second instance of the data stream are consolidated into an output data stream.

An exemplary embodiment of the method may comprise matching the capacity of each channel to the actual transmission conditions by Adaptive Coding and Modulation.

Other exemplary embodiments of the method may further comprise consolidating by hitless selection combining or by in-phase combining. The invention also describes a first network device for transmitting a first data stream (A) or a first data stream (A) and a second data stream (B) over a first channel (50) and a second channel (51) comprising a switch logic (105) and two data switches (104, 204),

- wherein the switch logic (105) is adapted to control the first data switch (104) and the second data switch (204),

- wherein the first data switch (104) is adapted to switch the first data stream (A) to the first channel (50),

- wherein the second data switch (204) is adapted to switch the first data stream (A) or the second data stream (B) to the second channel (51),

- wherein the switch logic (105) is adapted to control a

switching,

- wherein the switching is performed according to the

quality of the first channel (50) and according to the quality of the second channel (51) . The invention also describes a second network device for receiving a first data stream from a first channel (50) and a second data stream from a second channel (50) comprising a switch logic (407) and

two combiners (403, 503) ,

- wherein the switch logic (105) is adapted to control the first combiner (403) and the second combiner (503) ,

- wherein the first combiner (403) is adapted to receive a first data stream from the first channel (50),

- wherein the first combiner (403) is adapted to receive a second data stream from the second channel (51),

- wherein the first combiner (403) is adapted to consolidate the first data stream from the first channel (50) and the second data stream from the second channel (51) into an output data stream (A) , - wherein the first combiner (403) is adapted to route the first data stream from the first channel (50) into an output data stream (A) ,

- wherein the second combiner (503) is adapted to receive a second data stream from the second channel (51), wherein the second combiner (503) is adapted to route the second data stream from the second channel (51) into a second output data stream (B) ,

- wherein the switch logic (407) is adapted to control a

consolidating and a routing,

- wherein the consolidating and the routing is performed

according to the quality of the first channel (50) and according to the quality of the second channel (51) . The invention also describes a system comprising the first network device and the second network device wherein the first network device is connected with the second network device over a first channel (50) and over a second channel (51) wherein the first channel (50) and the second channel (51) may be operated in parallel.

In an exemplary embodiment of the invention a switch logic (105) in the first network device may receive information on the quality of the first channel (50) from a first

transmitter modem and radio frequency interface (106) and may receive information on the quality of the second channel (51) from a second transmitter modem and radio frequency interface (206) . In another exemplary embodiment of the invention a switch logic (407) in the second network device may receive

information on the quality of the first channel (50) from a first radio frequency interface and receiver modem (401) and may receive information on the quality of the second channel (51) from a second radio frequency interface and receiver modem (501) .

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 frequency diversity transmission system in the High Throughput Mode,

Fig. 2 illustrates an exemplary embodiment of a frequency diversity transmission system in the High System Gain Mode,

Fig. 3 illustrates an exemplary embodiment of a co-channel transmission system in the High Throughput Mode,

Fig. 4 illustrates an exemplary embodiment of a co-channel transmission system in the High System Gain Mode,

Fig. 5 illustrates an exemplary embodiment of a transmission section of a frequency diversity transmission system 100, 200 as shown in the Figures 1 to 4,

Fig. 6 illustrates an exemplary embodiment of a receiving section of a frequency diversity transmission system 400, 500 as shown in the Figures 1 to 4,

Fig. 7 illustrates an exemplary embodiment of a method

according to an aspect of the present invention, and

Fig. 8 illustrates an exemplary embodiment of possible

operational states of a radio link comprising two radio channels under different operating conditions of the two radio channels. 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. 4 show a system comprising two radio channels. In the exemplary embodiment with two radio channels the system may comprise on each side of the radio link two Out Door Units (ODUs) . The two at the same side of the radio link may be designated as "master" and "slave". The master ODU may manage the centralized functions, such as Layer 2 and/or Layer 3 functionalities, e.g. Ethernet switching, as well as the bandwidth handling algorithms. The slave ODU may receive the data payload to be transmitted as well as the management and control data from the master ODU and may be used mainly as an additional radio interface increasing the radio link capacity. It should be mentioned that from the perspective of the system the overall capacity is seen as a single bundle, i.e. the system perceives the two radio channels as a single radio link with double capacity.

The system may be for example a frequency diversity

transmission system with two channels on different

frequencies as shown in Figures 1 and 2 or a co-channel transmission system with two orthogonally polarized channels as shown in Figures 3 and 4. 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.

Fig. 1 illustrates an exemplary embodiment of a frequency diversity transmission system in the High Throughput Mode. Two data streams A and B may be routed into the transmission sections of two Out Door Units 100, 200, from which they may be sent over two radio channels 50, 51 to the receiving sections of the partner Out Door Units 400, 500. The radio channels may have the bandwidth of the Channel Spacing CS and may use the frequencies fl and f2 and the polarization H or V or a combination of the twos, e.g. H @ fl and V @ f2. The receiving sections of the partner Out Door Units may receive and decode the data streams and may output them as two outgoing data streams A and B.

Fig. 2 illustrates an exemplary embodiment of a frequency diversity transmission system in the High System Gain Mode. A data stream A may be routed into the transmission section of an Out Door Unit 100. There the data stream may be

duplicated, the copy data may be sent to a second Out Door

Unit 200. Both Out Door Units 100, 200 may send the same data stream A over the radio links 50, 51 to their partner Out Door units 400, 500. The radio channels may have the

bandwidth of the Channel Spacing CS and may use the

frequencies fl and f2 and the polarization H. The receiving sections of the partner Out Door Units may receive the data streams. Out Door Unit 500 may send its data to the master Out Door Unit 400, where the data streams received from the radio links 50, 51 may be consolidated into one outgoing data stream A.

Fig. 3 illustrates an exemplary embodiment of a co-channel transmission system in the High Throughput Mode. Two data streams A and B may be routed into the transmission sections of two Out Door Units 100, 200, from which they may be sent over two radio channels 50, 51 to the receiving sections of the partner Out Door Units 400, 500. The radio channels may have the bandwidth of the Channel Spacing CS and may use the frequency fl and the polarizations H and V. The receiving sections of the partner Out Door Units may receive and decode the data streams and may output them as two outgoing data streams A and B. Fig. 4 illustrates an exemplary embodiment of a co-channel transmission system in the High System Gain Mode. A data stream A may be routed into the transmission section of an Out Door Unit 100. There the data stream may be duplicated, the copy data may be sent to a second Out Door Unit 200. Both Out Door Units 100, 200 may send the same data stream A over the radio links 50, 51 to their partner Out Door units 400, 500. The radio channels may have the bandwidth of the Channel Spacing CS and may use the frequency fl and the polarizations H and V. The receiving sections of the partner Out Door Units may receive the data streams. Out Door Unit 500 may send its data to the master Out Door Unit 400, where the data streams received from the radio links 50, 51 may be consolidated into one outgoing data stream A. Fig. 5 illustrates an exemplary embodiment of a transmission section of a system as described in the Figures 1 to 4.

Each of the transmission sections of the Out Door Units 100, 200 may comprise a layer-2-switch 101, 201, a framer 102, 202, a control switch 103, 203, a data switch 104, 204, a switch logic 105, 205 and a transmitter modem and radio frequency interface 106, 206.

Dependent from the channel information given by the

transmitter modem and radio frequency interface 106 the switch logic 105 may decide on the system mode and may operate the data switches 104, 204 via the master/slave control switches 103, 203. Between the ODUs 100, 200 the master/slave control signals 304, 305, the system mode control signals 303, the switch control signals 301 and the data 302 may be exchanged. Fig. 6 illustrates an exemplary embodiment of a receiving section of a system as described in the Figures 1 to 4.

Each of the receiving sections of the Out Door Units 400, 500 may comprise a radio frequency interface and receiver modem 401, 501, a bit aligner 402, 502, an in-phase combiner 403, 503, a deframer 404, 504, a layer-2-switch 405, 505, a control switch 406, 506 and a switch logic 407, 507.

Dependent from the channel information given by the radio frequency interface and receiver modem 401 the switch logic 405 may decide on the system mode and may operate the

combiners 403, 503 via the master/slave control switches 406, 506. The combiners 403, 503 may consolidate the received data either by hitless selection combining or by in-phase

combining .

Between the ODUs 400, 500 the master/slave control signals 611, 621, the system mode control signals 603, the switch control signals 602 and the data 601 may be exchanged.

Dashed lines in Fig. 5 and Fig. 6 may be unused connections which may be used for protection switching in the case of a partial failure of the master ODUs 100, 400.

Fig. 7 illustrates an exemplary embodiment of a method 700 according to an aspect of the present invention. The method may comprise inquiring if the throughput (the capacity, which in turn is related to the channel quality) of at least one channel is above the minimum throughput of an Adaptive Coding and Modulation scheme, see rhomb 701.

If the inquiring results in "yes", the method may further comprise transmitting a first data stream A over a first channel 50, see box 710, transmitting a second data stream B over a second channel 51, see box 711, receiving the first data stream A from the first channel 50, see box 712, and receiving the second data stream B from the second channel 51, see box 713.

If the inquiring results in "no", the method may further comprise duplicating the first data stream A into a first instance of the data stream and a second instance of the data stream, see box 720, transmitting the first instance of the data stream over the first channel 50, see box 721,

transmitting the second instance of the data stream over the second channel 51, see box 722, receiving the first instance of the data stream from the first channel 50, see box 723, receiving the second instance of the data stream from the second channel 51, see box 724, and consolidating the first instance of the data stream and the second instance of the data stream into an output data stream, see box 725.

It may be understood, that further boxes or operations may be added . Fig. 8 illustrates an exemplary embodiment of possible operational states of a radio link comprising two radio channels under different operating conditions of the two radio channels 50, 51. In this example the data stream A may be considered to comprise a partial data stream P which shall be protected under adverse propagation conditions by transmitting it redundantly over both radio channels, and an unprotected partial data stream UP1 which may be discarded if the data rate of P + UP1 is greater than the actual capacity of the radio channel 50. The data stream B may comprise unprotected data UP2 only; it may be discarded in the case of bad

propagation conditions.

The classification of the transmission data into protected data P and unprotected data UP1 or UP2 may be made by another unit which may be located prior to the Out Door Unit. This other unit may also assign the transmission data to the protected data stream A or to the unprotected data stream B.

Fig. 8 shows, that in the High Throughput Mode all data up to the combined capacity of both channels may be transmitted. In the High System Gain Mode the capacity of the link may be limited to the minimum throughput for one channel of the adaptive coding and modulation scheme. If the data rate of the protected data stream P is not greater than the minimum throughput for one channel, the entire data stream P may be transmitted redundantly over both channels, so that it may profit from the enhanced reliability given by the High System Gain Mode.

In general it may 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

CS Channel Spacing

ODU Out Door unit

QoS Quality of Service

List of References

50, 51 Radio Channel

100, 200 Transmission section of Out Door Unit (ODU)

101, 201 Layer-2-Switch

102, 202 Framer

103, 203 Control Switch

104, 204 Data Switch

105, 205 Switch Logic

106, 206 Transmitter Modem + Radio Frequency Interface

301 Switch Control

302 Data Exchange

303 System Mode Control from Partner

304, 305 Master/Slave Control

400, 500 Receiving section of Out Door Unit (ODU)

401, 501 Radio Frequency Interface + Receiver Modem

402, 502 Bit Alignment

403, 503 Combiner

404, 504 Deframer

405, 505 Layer-2-Switch

406, 506 Control Switch

407, 507 Switch Logic 601 Data Exchange

602 Data Switch Control

603 System Mode Control from Partner ODU

610, 620 System Mode Control from own Modem (614, 624)

611, 621 Master/Slave Control

612, 622 Switch Control

613, 623 Data from own Modem

614, 624 System Mode Control to own Switch Logic (610, 620) 700 Box comprising an operation of a method

Claims

Claims l.A method for transferring a first data stream (A) and a second data stream (B) over a first channel (50) and a second channel (51), the method comprising

when the quality of at least one channel is above a

predefined threshold:

transmitting the first data stream (A) over the first channel (50) ;

transmitting the second data stream (B) over the

second channel (51);

receiving the first data stream (A) from the first channel (50) ;

receiving the second data stream (B) from the second channel (51) .

otherwise :

duplicating the data stream (A) into a first instance of the data stream and a second instance of the data stream;

transmitting the first instance of the data stream

over the first channel (50);

transmitting the second instance of the data stream over the second channel (51);

receiving the first instance of the data stream from the first channel (50);

receiving the second instance of the data stream from the second channel (51);

consolidating the first instance of the data stream and the second instance of the data stream into an output data stream. The method according to claim 1 the method further

comprising matching the capacity of each channel to the actual transmission conditions by Adaptive Coding and Modulation.

The method according to claims 1 or 2 further comprising consolidating by hitless selection combining.

The method according to claims 1 or 2 further comprising consolidating by in-phase combining.

A network device for transmitting a first data stream (A) or a first data stream (A) and a second data stream (B) over a first channel (50) and a second channel (51) comprising

a switch logic (105); and

two data switches (104, 204);

wherein the switch logic (105) is adapted to control the first data switch (104) and the second data switch (204) ;

wherein the first data switch (104) is adapted to switch the first data stream (A) to the first channel (50) ;

wherein the second data switch (204) is adapted to switch the first data stream (A) or the second data stream (B) to the second channel (51);

wherein the switch logic (105) is adapted to control a switching, wherein the switching is performed according to the quality of the first channel (50) and according to the quality of the second channel (51) .

6. A network device for receiving a first data stream from a first channel (50) and a second data stream from a second channel (50) comprising a switch logic (407); and

two combiners (403, 503) ;

wherein the switch logic (105) is adapted to control the first combiner (403) and the second combiner (503) ; wherein the first combiner (403) is adapted to receive a first data stream from the first channel (50);

wherein the first combiner (403) is adapted to receive a second data stream from the second channel (51);

wherein the first combiner (403) is adapted to

consolidate the first data stream from the first channel

(50) and the second data stream from the second channel

(51) into an output data stream (A);

wherein the first combiner (403) is adapted to route the first data stream from the first channel (50) into an output data stream (A) ;

wherein the second combiner (503) is adapted to receive a second data stream from the second channel (51); wherein the second combiner (503) is adapted to route the second data stream from the second channel (51) into a second output data stream (B) ;

wherein the switch logic (407) is adapted to control a consolidating and a routing, wherein the consolidating and the routing is performed according to the quality of the first channel (50) and according to the quality of the second channel (51) . A system comprising

a first network device according to claim 5 and a second network device according to claim 6,

wherein the first network device is connected with the second network device over a first channel (50) and over second channel (51) .

8. The system according to claim 7,

wherein the first channel (50) and the second channel (51) are operated in parallel.

9. The network device according to claim 5,

wherein the switch logic (105) receives information on the quality of the first channel (50) from a first

transmitter modem and radio frequency interface (106); and wherein the switch logic (105) receives information on the quality of the second channel (51) from a second transmitter modem and radio frequency interface (206) .

10. The network device according to claim 6,

wherein the switch logic (407) receives information on the quality of the first channel (50) from a first radio frequency interface and receiver modem (401) ; and

wherein the switch logic (407) receives information on the quality of the second channel (51) from a second radio frequency interface and receiver modem (501).

11. A computer program product comprising code portions for causing a network device, on which the computer program is executed, to carry out the method according to any of the claims 1 to .

12. A computer-readable medium embodying the computer program product according to claim 11.