WO2015005835A1

WO2015005835A1 - Interface arrangement between network node and radio access unit

Info

Publication number: WO2015005835A1
Application number: PCT/SE2013/050890
Authority: WO
Inventors: Elmar Trojer; Miguel Berg; Karl-Axel LIND; Robert Lindgren
Original assignee: Telefonaktiebolaget L M Ericsson (Publ)
Priority date: 2013-07-10
Filing date: 2013-07-10
Publication date: 2015-01-15

Abstract

The present invention relates to an interface arrangement configured to convert signals transported on a coaxial cable between a network node and a radio access unit. The interface arrangement comprises overvoltage protection arranged to interface with the coaxial cable. Further, the interface arrangement comprises an Ethernet-over-coax adapter arranged to convert between Ethernet signals of a first format transported on the coaxial cable connected to the network node via a first interface and Ethernet signals of a second format transported over a second interface connected to the radio access unit. Moreover, the interface arrangement comprises powering means arranged to provide DC voltage to the radio access unit via the second interface.

Description

INTERFACE ARRANGEMENT BETWEEN NETWORK NODE AND RADIO

ACCESS UNIT

TECHNICAL FIELD

The invention relates to an interface arrangement. BACKGROUND

In prior art microwave link installations as shown in Figure l, radio signals as well as DC power is transported between an outdoor radio access unit (RAU) 10 and indoor unit n by a coaxial cable 12. In such a split-architecture, the indoor unit network node 11 performs microwave baseband signal processing whereas the RAU 10 performs RF functions such as frequency up- and down-

10 conversion, power amplification, low-noise amplification, and further

comprises an antenna interface. Analog radio signals for transmission and reception are transported at distinct intermediate frequencies (IF) via frequency division duplexing (FDD) on the coaxial cable 12. The RAU 10 is powered remotely via the coaxial cable 12 from a power supply unit

collocated with the indoor unit 11. As the coaxial cable 12 is partly outdoors, overvoltage protection (OVP) circuitry 13a, 13b are placed in the signal path close to or within the RAU 10 as well as indoor unit 11 to protect the

equipment from lightning strikes.

Recent technology evolvements have enabled integration of all radio

0 functions, including baseband processing, into the outdoor unit 10. Thus,

new generations of microwave- and other mobile radio equipment are

Ethernet-based. With reference to Figure 2, the cabling requirements have changed; as the outdoor unit 10 contains both baseband processing and RF functions, a regular Ethernet interface comprising a small-formfactor

5 pluggable (SFP) is provided at the outdoor unit 10.

In order to backhaul packet traffic to the indoor unit network node 11, a new hybrid cable 14 has to be installed. The hybrid cable 14 contains two fibers for the Ethernet link as well as copper cables for direct current (DC) powering. Such a hybrid cable is more expensive than a coaxial cable as shown in Figure l, but this is usually not a problem for green-field deployments since the labor cost for cable deployment is much higher than the actual cable cost.

However, when migrating from legacy split-architecture systems as shown in Figure ι to the new Ethernet-based microwave systems, substantial savings in time and money would be possible if the existing coaxial cable could be reused for Ethernet transport.

SUMMARY

An object of the present invention is to solve, or at least mitigate this problem in the art. This object is attained in a first aspect of the present invention by an interface arrangement configured to convert signals transported on a coaxial cable between a network node and a radio access unit. The interface arrangement comprises overvoltage protection arranged to interface with the coaxial cable. Further, the interface arrangement comprises an Ethernet-over-coax adapter arranged to convert between Ethernet signals of a first format transported on the coaxial cable connected to the network node via a first interface and Ethernet signals of a second format transported over a second interface connected to the radio access unit. Moreover, the interface arrangement comprises powering means arranged to provide DC voltage to the radio access unit via the second interface.

Thus, the interface arrangement of the first aspect of the invention is configured to be positioned at a radio access unit-side of the coaxial cable typically located outdoors.

This object is attained in a second aspect of the present invention by an interface arrangement configured to convert signals transported on a coaxial cable between a network node and a radio access unit. The interface arrangement comprises overvoltage protection arranged to interface with the coaxial cable, and an Ethernet-over-coax adapter arranged to convert between Ethernet signals of a first format transported on the coaxial cable connected to the radio access unit via a first interface and Ethernet signals of a second format. Further, the interface arrangement comprises an Ethernet media converter arranged to convert between the Ethernet signals of the second format and Ethernet signals of a third format transported over a second interface connected to the network node. Moreover, the interface arrangement comprises powering means arranged to provide DC voltage to the radio access unit over the first interface via said overvoltage protection, said DC voltage being extracted from the signals transported over the second interface from the network node.

Thus, the interface arrangement of the second aspect of the invention is configured to be positioned at a network node-side of the coaxial cable typically located indoors.

Advantageously, by providing the interface arrangement according to embodiments of the present invention, either at the outdoor radio access unit or at the indoor network node, existing coaxial cable can be reused when migrating from the previously discussed split-architecture systems to new Ethernet-based systems.

Given the existence of coaxial cable with high channel capacity, low capital expenditures (CAPEX) can be achieved during the migration by allowing operators to re-use the existing coaxial cabling by using the interface arrangement of the present invention, thereby limiting system upgrades to active endpoints, i.e. either at the outdoor radio access unit or at the indoor network node, without having to modify the cable installation.

A further disadvantage with existing products is that they are unsuitable for outdoor telecom applications with regards to issues like weather protection, overvoltage protection, ease-of installation etc.

Various embodiments of the present invention will be discussed in the following

It is noted that the invention relates to all possible combinations of features recited in the claims. Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. Those skilled in the art realize that different features of the present invention can be combined to create embodiments other than those described in the following. BRIEF DESCRIPTION OF THE DRAWINGS

The invention is now described, by way of example, with reference to the accompanying drawings, in which:

Figure l shows a prior art microwave link installation connecting an outdoor radio access unit to an indoor network node with a coaxial cable; Figure 2 shows a prior art Ethernet-based microwave link installation connecting an outdoor radio access unit to an indoor network node with a hybrid cable;

Figure 3 shows an embodiment of an interface arrangement configured to convert signals transported on a coaxial cable between a network node and a radio access unit;

Figure 4 illustrates a further embodiment of an interface arrangement according to the present invention;

Figure 5 illustrates yet a further embodiment of an interface arrangement according to the present invention; and Figure 6 illustrates an embodiment of an interface arrangement of a second aspect of the present invention, where the interface arrangement is configured to be positioned at a network node-side of the coaxial cable.

DETAILED DESCRIPTION

The invention will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout the description.

Figure l shows a prior art microwave link installation connecting an outdoor RAU io to an indoor network node n with a coaxial cable 12 as previously has been discussed.

Figure 2 shows a prior art Ethernet-based microwave link installation connecting an outdoor RAU 10 to an indoor network node 11 with a hybrid cable 14 containing two fibers for the Ethernet link as well as copper cables for DC powering as previously has been discussed.

Figure 3 shows an embodiment of an interface arrangement 20 configured to convert signals transported on a coaxial cable 12 between a network node 11 and a radio access unit 10. The interface arrangement comprises overvoltage protection 21 arranged to interface with the coaxial cable 12. The overvoltage protection (OVP) 21 advantageously protects the interface arrangement from overcurrents/-voltages caused e.g. by lighting and should in certain applications be able to withstand 4 kA, 10/350 pulse. The overprotection maybe embodied in the form of a fuse or a switch.

The interface arrangement 20 further comprises an Ethernet-over-coax (EoC) adapter 22 arranged to convert between Ethernet signals of a first format transported on the coaxial cable 12 connected to the network node 11 via a first interface 23 and Ethernet signals of a second format. The first interface 23 maybe embodied in the form of e.g. an N-type, a Threaded Neill- Concelman (TNC) or a SubMiniature version A (SMA) connector, or similar. In this particular exemplifying embodiment, the Ethernet signals on the coaxial cable 12 are converted to 1000BASE-X, i.e. the physical layer standard for gigabit Ethernet using optical fiber. Further, the interface arrangement 20 of the present invention comprises powering means 25 arranged to provide DC voltage to the radio access unit 10 via a second interface 24. This is generally referred to as a Powered Device (PD), being a controller for supporting multiple power levels of Power over Ethernet.

In this particular embodiment, the powering means 25 is arranged to extract the DC voltage to be provided to the radio access unit 10 from the signals transported over the coaxial cable 12 from the network node 11 or a collocated power supply unit (not shown). However other alternatives are possible, as will be shown subsequently. The powering means 25 should in certain applications be able to deliver -48 V, 1 A to the radio access unit 10.

Moreover, depending on the particular format of the Ethernet signalling to be performed via the second interface 24, it may be necessary to include in the interface arrangement 20 an Ethernet media converter (PHY) 26 arranged to convert between the Ethernet signals of the second format, i.e. 1000BASE-X, and Ethernet signals of a third format transported over the second interface 24, in this particular example being the physical layer standard for twisted pair cable: 1000BASE-T. However, a number of alternatives is possible, such as e.g. 1000BASE-SX (multi-mode fibre), 1000BASE-LX (single-mode fibre), lOOoBASE-BX (single-mode/single fibre). The Ethernet media converter (PHY) 26 is an Ethernet physical transceiver sometimes referred to as a PHYceiver operating at a physical layer. Full duplex Gigabit Ethernet over coaxial cable can be achieved with such a transceiver, which takes nonreturn-to-zero (NRZ) encoded serial data and transmits the data over a coaxial cable using an analog hybrid circuit to separate transmission and reception, achieving full duplex.

The interface arrangement 20 maybe connected to the radio access unit 10 via an RJ45 connector and first cabling 27 in the form of e.g . a CAT5/5e/ 6/7 twisted pair cable or similar to an SFP connector (denoted S throughout the drawings) at the radio access unit 10. The -48V DC voltage is typically supplied to the radio access unit 10 via second cabling 28 in the form of e.g. a copper cable. Thus, the Ethernet signals and the DC voltage are in this particular embodiment transported separate from each other via the first and second cablings 27, 28. In an embodiment, the interface arrangement 20 comprises a management data input/output bus, a Media Independent Interface (Mil) serial bus defined for the Ethernet family of IEEE 802.3 standards, arranged to be coupled to the Ethernet media controller 26 and routed to the second interface 24. In order to control the Ethernet media controller 26, the Mil signals are routed over the second interface 24 to a control processor of the radio access unit 10.

With reference to Figure 3, the components of the interface arrangement 20, i.e. the overvoltage protection 21, the Ethernet-over-coax adapter 22, the powering means 25 and the Ethernet media converter 26, are advantageously integrated within the same device under the same housing, thus providing a "black-box"-like device which easily and straightforwardly can be connected to the network node 11 and the radio access unit 10 via a respective first and second interface 23, 24. In a further embodiment of the interface arrangement of the present invention, the interface arrangement 20 is provided as a dongle-like device which can be plugged into the radio interface unit 10 via the second interface 24 embodied in the form of a compound connector providing both the Ethernet signals and the DC voltage signals (and possibly management or control signals). The compound connector is arranged to receive a mating connector of the radio access unit 10 and the interface arrangement 20 can thus advantageously be plugged directly into the radio access unit 10.

Figure 4 illustrates a further embodiment of the present invention, where the interface arrangement 20 is embodied in the form of a so called coaxial SFP module. Use of a regular SFP module is unsuitable in many applications; for instance (a) no higher-power interface is available in the SFP, which means that the SFP module would need both a coax and a power connector, (b) SFPs are usually small, which means that it would be difficult to fit two connectors unless a small coaxial cable is used, e.g. SMA, (c) with internal lightning protection in the SFP module, an SMA would be too small to handle the current in case of a lightning strike (inner conductor would be vaporized); at least a TNC or N-type connector would be needed for proper function, and (d) the mechanical properties of a regular SFP module would not allow direct connection of a thick and stiff coaxial cable but rather require a short and thin coaxial cable with connectors to the existing thicker coaxial cable. Thus, an interface arrangement 20 configured to convert signals transported on a coaxial cable 12 between a network node 11 and a radio access unit 10 is provided. The interface arrangement comprises overvoltage protection 21 arranged to interface with the coaxial cable 12. The overvoltage protection 21 advantageously protects the interface arrangement from overcurrents/- voltages caused e.g. by lighting.

The interface arrangement 20 further comprises an Ethernet-over-coax adapter 22 arranged to convert between Ethernet signals of a first format transported on the coaxial cable 12 connected to the network node 11 via a first interface 23 and Ethernet signals of a second format transported over a second interface 24 connected to the radio access unit 10. The first interface 23 may be embodied in the form of e.g. an N-type, a TNC or an SMA connector.

In this particular exemplifying embodiment, the Ethernet signals on the coaxial cable 12 are converted to 1000BASE-X, i.e. the physical layer standard for gigabit Ethernet using optical fiber. Further, the interface arrangement 20 of the present invention comprises powering means 25 arranged to provide DC voltage to the radio access unit 10 via the second interface 24. This is generally referred to as a Powered Device (PD), being a controller for supporting multiple power levels of Power over Ethernet. In this particular embodiment, the powering means 25 is embodied in the form of a power source locally arranged at the interface arrangement 20. The second interface 24 comprises an SFP connector over which the 1000BASE-X type Ethernet signals can be transported to the radio access unit 10 via a suitable first cabling 27 and an SFP connector at the radio access unit 10. The 48V DC voltage is typically supplied to the radio access unit 10 via a second cabling 28 in the form of e.g. a copper cable. The components of the interface arrangement 20, i.e. the overvoltage protection 21, the Ethernet-over-coax adapter 22 and the powering means 25 are advantageously integrated within a coaxial SFP module which easily and straightforwardly can be connected to the network node 11 and the radio access unit 10 via a respective first and second interface 23, 24.

Figure 5 illustrates a further embodiment of the present invention where the Ethernet-over-coax adapter 22 is positioned at the SFP connector of the radio interface unit 10. In this embodiment, the first cabling 27 connected to the second interface 24 is a coaxial cable to be coupled to the SFP connector of the radio interface unit 10 housing the Ethernet-over-coax adapter 22.

Figure 6 illustrates an embodiment of an interface arrangement 30 of a second aspect of the present invention, where the interface arrangement 30 is configured to be positioned at a network node-side of the coaxial cable, which network node 11 typically is located indoors. The interface arrangement 30 comprises overvoltage protection 31 arranged to interface with the coaxial cable 12. The overvoltage protection 31 advantageously protects the interface arrangement from overcurrents/- voltages caused e.g. by lighting and should in certain applications be able to withstand 4 kA, 10/350 pulse. The overprotection maybe embodied in the form of a fuse or a switch.

The interface arrangement 30 further comprises an Ethernet-over-coax (EoC) adapter 32 arranged to convert between Ethernet signals of a first format transported on the coaxial cable 12 connected to the radio access unit 10 via a first interface 33 and Ethernet signals of a second format. The first interface 33 may be embodied in the form of e.g. an N-type, a TNC or an SMA connector.

In this particular exemplifying embodiment, the Ethernet signals on the coaxial cable 12 are converted to 1000BASE-X, i.e. the physical layer standard for gigabit Ethernet using optical fiber. Further, the interface arrangement 30 of the second aspect of the present invention comprises powering means 35 arranged to provide DC voltage to the radio access unit 10 via the first interface 33. This is generally referred to as a Power Sourcing Equipment (PSE), being a controller for supporting multiple power levels of Power over Ethernet. In this particular embodiment, the powering means 35 is arranged to extract the DC voltage to be provided to the radio access unit 10 from the signals transported over a second interface 34 from the network node 11. The powering means 35 should in certain applications be able to deliver -48 V, 1 A to the radio access unit 10. On the network node-side, the power maybe supplied by a power supply unit 13 (PSU) collocated with the network node 11.

Moreover, depending on the particular format of the Ethernet signalling to be performed via the second interface 34, it may be necessary to include in the interface arrangement 30 an Ethernet media converter (PHY) 36 arranged to convert between the Ethernet signals of the second format, i.e. loooBASE-X, and Ethernet signals of a third format transported over the second interface 34, in this particular example being the physical layer standard for twisted pair cable: loooBASE-T. However, a number of alternatives are possible, such as e.g. 1000BASE-SX (multi-mode fibre), loooBASE-LX (single-mode fibre), loooBASE-BX (single-mode/single fibre). The Ethernet media converter (PHY) 36 is an Ethernet physical transceiver sometimes referred to as a PHYceiver operating at a physical layer. Full duplex Gigabit Ethernet over coaxial cable can be achieved with such a transceiver, which takes NRZ encoded serial data and transmits the data over a coaxial cable using an analog hybrid circuit to separate transmission and reception, achieving full duplex. The Ethernet media controller can optionally also be controlled by an Mil bus routed over the second interface 34 to the networking unit 11.

The interface arrangement 30 may be connected to the network node 11 via an RJ45 connector and first cabling 37 in the form of e.g . a CAT5/5e/ 6/7 twisted pair cable or similar to an SFP connector at the network node 11. The -48V DC voltage is typically supplied to the radio access unit 10 via second cabling 38 in the form of e.g. a copper cable. Thus, the Ethernet signals and the DC voltage are in this particular embodiment transported separate from each other via the first and second cablings 37, 38.

This particular embodiment is advantageous e.g. since the interface arrangement 30 maybe located indoors in vicinity to the network node 11 which lowers requirements pertaining to for instance the ability to withstand moist and humidity.

The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.

Claims

1. Interface arrangement (20) configured to convert signals transported on a coaxial cable (12) between a network node (11) and a radio access unit (10), the interface arrangement (20) comprising:

overvoltage protection (21) arranged to interface with the coaxial cable

(12);

Ethernet-over-coax adapter (22) arranged to convert between Ethernet signals of a first format transported on the coaxial cable (12) connected to the network node (11) via a first interface (23) and Ethernet signals of a second format transported over a second interface (24) connected to the radio access unit (10); and

powering means (25) arranged to provide DC voltage to the radio access unit (10) via the second interface (24).

2. The interface arrangement (20) of claim 1, further comprising:

an Ethernet media converter (26) arranged to convert between the

Ethernet signals of the second format and Ethernet signals of a third format transported over the second interface (24).

3. The interface arrangement (20) of claim 2, further comprising:

a management data input/output, MDIO, bus arranged to be coupled to the Ethernet media controller (26) and routed to the second interface (24).

4. The interface arrangement (20) of any one of claims 1 or 2, the overvoltage protection (21), powering means (25), Ethernet-over-coax adapter (22) and Ethernet media converter being arranged in the same physical device.

5. The interface arrangement (20) of any one of claims 1-4, further comprising:

first cabling (27) arranged to be connected from the second interface (24) to the radio access unit (10).

6. The interface arrangement (20) of any one of claims 1-5, wherein the second interface (24) comprises a connector arranged to receive a mating connector of the radio access unit (10).

7. The interface arrangement (20) of claim 5, wherein the second interface (24) to the radio access unit (10) is arranged such that the Ethernet signals are transported on the first cabling (27) and the provided DC voltage is transported on a second cabling (28) separate from the first cabling.

8. The interface arrangement (20) of any one of the preceding claims, further being provided as a coaxial small -formfactor pluggable, SFP, module where the second interface (24) is connected to the radio access unit (10) via an SFP connector.

9. The interface arrangement (20) of any one of the preceding claims, wherein the powering means (25) is arranged to extract the DC voltage to be provided to the radio access unit (10) from the signals transported over the coaxial cable (12) from the network node (11).

10. The interface arrangement (20) of any one of claims 1-9, wherein the powering means (25) comprises a power source arranged to provide the DC voltage to the radio access unit (10).

11. The interface arrangement (20) of claim 6, wherein the second interface (24) comprises a compound connector carrying the Ethernet signals and the

DC voltage.

12. Interface arrangement (30) configured to convert signals transported on a coaxial cable (12) between a network node (11) and a radio access unit (10), the interface arrangement (30) comprising:

overvoltage protection (31) arranged to interface with the coaxial cable

(12);

Ethernet-over-coax adapter (32) arranged to convert between Ethernet signals of a first format transported on the coaxial cable connected to the radio access unit (10) via a first interface (33) and Ethernet signals of a second format;

an Ethernet media converter (36) arranged to convert between the Ethernet signals of the second format and Ethernet signals of a third format transported over a second interface (34) connected to the network node (11); and

powering means (35) arranged to provide DC voltage to the radio access unit (10) over the first interface (33) via said overvoltage protection, said DC voltage being extracted from the signals transported over the second interface (34) from the network node (11).