ERICSSON MINI-LINK HC (01) PDF Document

Technical Features

• 155 Mbit/s traffic capacity, both electrical and optical interfaces

• Compact and integrated design

• The radio and antenna form an integrated outdoor part

• High system gain and spectrum utilization with an advanced modulation process and coding

• Standardized interfaces

• Low weight and power consumption

• Web based Local Craft Terminal (LCT)

• Facilitates remote management from generic element manager, equipped with SNMP interface

Reliability

• High Mean Time Between Failure (MTBF) value

• Progress with backward compatibility

• Part of the Ericsson system portfolio

• 30 years’ experience of microwave transmission

• World’s largest production of microwave transmission systems

• The equipment can cope with extreme environmental conditions

Services

• Ericsson turnkey capability

• Customer training programs worldwide

• Total field maintenance services

• Ericsson local presence in more than 140 countries

A terminal is one side of a microwave radio link hop and consists of an indoor part and an outdoor part.

• The indoor part comprises a Traffic Unit (TRU), Modem Unit (MMU), Access Module Magazine (AMM) and a fan unit.

• The outdoor part comprises a Radio Unit (RAU) with an antenna.

• A radio cable connects the RAU and the MMU.

Apart from the main units, the system offers a number of well-adapted auxiliary units and accessories, both hardware and software.

The indoor units of a terminal are briefly described below:

• Modem Unit (MMU): The MMU is the indoor interface with the radio unit and contains a modulator/demodulator. One MMU per radio unit is required.

• Traffic Unit (TRU): The TRU generates and terminates the STM-1/OC-3 traffic signal. It also contains a protection switching function used for protected terminal configurations. At least one TRU per terminal is required.

• Access Module Magazine (AMM): The AMM houses the MMU(s) and TRU(s) and provides electrical interconnection through its backplane. It fits in 19″ racks and cabinets, as well as in ETSI and BYB cabinets. One or two terminals can be integrated into one common AMM.

• Fan Unit: A fan unit is always fitted on top of the AMM to guarantee sufficient cooling. The cooling air enters at the front of the AMM, flows between the units and out through openings at the back of the magazine on both sides of the backplane.

• DC Distribution Unit (DDU) (optional): The optional DC Distribution Unit (DDU) can be used to distribute primary power to the MMU(s) and fan unit.

The outdoor units of a terminal are briefly described below:

• Radio Unit (RAU): The RAU generates and receives the RF signal and converts it to/from the signal format used in the radio cable.

• Antenna: The compact antenna combines high performance with minimum outdoor visibility. The antenna is normally installed integrated with the radio unit, but a separate installation is also possible.

• Radio Cable: The radio cable, which connects the RAU to the MMU, is a single coaxial cable carrying full duplex traffic, DC supply voltage and service traffic as well as operation and maintenance data.

• Power Splitter: The power splitter is used in 1+1 systems connecting two radio units to one antenna. The power splitter is available in a symmetrical and in an asymmetrical version. An integrated power splitter is also available.

An unprotected terminal 1+0 consists of:

• One RAU

• One antenna

• One AMM (AMM 1U-1 or AMM 2U-4)

• One MMU

• One TRU

• One radio cable for interconnection

Both the AMM 1U-1 and the AMM 2U-4 can be used. When the AMM 2U-4 is used, one or two 1+0 terminals can be installed. An AMM 2U-4 with two unprotected terminals, 2x(1+0), can be utilized when there is a need for doubling the traffic capacity in one direction, a common AMM for traffic in different directions or a repeater site.

A protected terminal 1+1 consists of:

• Two RAUs and one of the following:

– Two antennas

– One antenna with one power splitter and two waveguides

– One antenna with one integrated power splitter (RAU2 L)

– One antenna with one integrated power splitter and one waveguide (RAU1 L)

• One AMM 2U-4

• Two MMUs

• One TRU

• Two radio cables for interconnection

Protected configuration should be considered for traffic requiring high availability, but also in case of severe reflections or harsh atmospheric conditions. It is possible to remove and insert the non-active MMU or RAU without loss of traffic. A protected 1+1 terminal can be configured for hot standby or working standby.

In hot standby mode, one transmitter is working while the other one is on standby, that is, not transmitting but ready to transmit if the active transmitter malfunctions. Both RAUs are receiving signals. The TRU selects the best received signal according to alarm priority lists.

In hot standby mode, the terminal can be configured for space diversity, placing the receiving antennas at a mutual distance where the impact of fading is reduced.

Receiver switching due to fading in space diversity configurations is hitless.

In working standby mode, both radio paths are active in parallel. The same signal is transmitted at two different frequencies under the assumption that multipath fading (flat or selective) phenomena that affect one frequency will not affect the other one. The TRU selects the best received signal according to the alarm priority lists.

In working standby mode, the terminal is configured for frequency diversity with space diversity as an option.

The Equipment and Line Protection (ELP) functionality is able to simultaneously protect the STM-1/OC-3 line interface and the radio equipment against any single point of failure (e.g. the single TRU). On the radio side, it uses a single frequency (hot standby configuration).

In this mode the radio section performs protection switching on the transmitter side. Receiver switching in the TRU is disabled. The ADMs at both ends carry out the receiver protection switching.

The system is able to transmit and receive data at 155 Mbit/s. The following channels are physically connected at the TRU front for further transportation over the hop:

• Main Traffic (155 Mbit/s): SDH STM-1 electrical and optical standards or SONET OC-3 standard. Implemented in the payload of the SDH/SONET frame and handled by the TRU.

• Wayside Traffic (1.5/2 Mbit/s): Implemented in RFCOH and handled by the MMU.

• Service Channel V.11 (64 kbit/s): Implemented in RSOH in the SDH/SONET frame and handled by the TRU.

• Service Channel G.703 (64 kbit/s): Implemented in RSOH in the SDH/SONET frame and handled by the TRU.

The following bytes in the RSOH (Regenerator Section Overhead) in the SDH/SONET frame are used for service channels and internal communication channels:

* The RSOH bytes for the service channels are software selectable.

The radio output power can be controlled in fixed or adaptive mode.

Fixed Mode

In fixed mode the output power Pout ranges from a minimum level Pfix min to a maximum level Pmax. A value Pset is manually set, in 1 dB increments, locally or remotely from the management system.

Adaptive Mode

In adaptive mode the Automatic Transmit Power Control (ATPC) function is used to automatically control the output power Pout. The output power is continuously adjusted in order to maintain a minimum input level (set from the LCT) at the far-end terminal. The ATPC function varies the output power, between a selected maximum level Pset and a minimum level Padapt min.

The receiver input level at the far-end and the maximum transmitter power level Pset are set, locally and remotely from the management system. Under normal path conditions the ATPC maintains the output power at a reduced level resulting in a lower interference level in the radio network.

The MINI-LINK HC terminal is a flexible system where both hardware and software can be upgraded and reconfigured. Below follow some examples:

• An unprotected terminal can be converted to a protected or dual terminal with addition of required hardware.

• Exchanging an MMU 155/16 for an MMU 155/128 results in reduced air interface bandwidth.

• When a site configuration requires an optical traffic interface it is possible to exchange a TRU EL. for a TRU OPT./EL..

• When the system is to be upgraded with a new software revision, a download is performed to the non-volatile memory in the TRU. The change to the new revision is then handled from the LCT.

All connections to and from the RAU are made at the rear.

Radio Cable

1. Radio cable connection to the MMU, 50 Ω N-type connector. The connector is equipped with gas discharge tubes for lightning protection.

Grounding

2. Protective ground point to connect to mast ground.

ALIGNMENT

3. Test port for antenna alignment.

LED Indicators

4. Two LED Indicators:

• Red light: Unit alarm

• Green light: Power on

Waveguide Interface

The vertical frame has a waveguide interface for connection to the antenna (placed on the front side).

The channel frequency of a terminal is determined entirely by the RAU, which are available for different frequency channels and sub-bands. The two RAUs needed for a hop are matched in pairs. Each of the radio units covers a sub-band of the frequency band and has a fixed duplex distance, the difference between the transmitted and the received frequency.

The transmitting frequency is set on site using the LCT. Increments of 0.25 MHz within a sub-band are possible.

The microwave sub-unit houses the Slave Processor (SP) for control and supervision of the RAU with main functions as described below.

Alarm Collection

Collected alarms and status signals from the RAU are sent to the indoor MMU processor. Summary status signals are visualized by LEDs on the RAU.

Command Handling

Commands from the indoor units are executed. These commands include transmitter activation/deactivation, channel frequency settings, output power settings and RF loop activation/deactivation.

RAU Control and Message Handling

In addition to the above, the processor controls the unit’s internal processes and loops.

Mounting kits are available for the 0.2 m, 0.3 m, and 0.6 m antennas.

• 0.2 m compact antenna mounting kit: Can be adjusted by ±13° in elevation and by ±90° in azimuth.

• Mounting kit for 0.3 m and 0.6 m compact antennas: Can be adjusted by ±15° in elevation and ±40° in azimuth. Both elevation and azimuth have a mechanism for fine adjustment.

The support can be clamped to poles with a diameter of 50 – 120 mm or on L-profiles 40x40x5 – 80x80x8 mm with two anodized aluminum clamps. All screws and nuts for connection and adjustment are in stainless steel. NORD-LOCK washers are used to secure the screws.

The main function of the MMU is to modulate the STM-1/OC-3 digital data to an analogue signal suitable for microwave transmission and demodulate the received signal from the RAU. Two MMU versions are available:

• MMU 155/16 with 50/55/56/80 MHz of bandwidth (using 16 QAM)

• MMU 155/128 with 27.5/28/40/50 MHz of bandwidth (using 128 QAM)

The MMU front panel has the following interfaces:

1. Input Power: The primary power supply (DC) is connected at the MMU front.

2. Radio Cable: The radio cable to the RAU is connected at the MMU front.

3. LED Indicators: Two LED indicators:

• Green light: Power on

• Red light: Unit alarm

The modulator includes the functions below:

• Scrambler: Randomizes the digital data stream to break up any repetitive bit patterns before the modulation process.

• Forward Error Correction Encoder (FEC): Inserts FEC bits according to a Reed-Solomon encoder. The frame format is formed by 255 bytes.

• Interleaver: Spreads the data to be transmitted in the time domain, in order to reduce the effect of burst errors.

• QAM Mapper: Converts the baseband stream into two parallel binary bitstreams. The mapper generates the symbols for the in-phase and quadrature channels.

• Digital Filtering: Implements the pulse shaping according to a square root raised cosine filter.

• IF Modulator: Consists of an oscillator operating at 350 MHz. For test purposes an IF loop signal of 140 MHz is also generated. This is accomplished by mixing the 350 MHz signal with a 490 MHz signal.

The demodulator shifts the 140 MHz signal to the baseband and includes the functional blocks described below:

• Clock Synchronization: The data synchronisation is recovered from the incoming traffic signal.

• Digital Filtering: Completes the shaping of the signal at the receiving side according to a Nyquist filter.

• Adaptive Equalization: A linear synchronous digital equalizer counteracts the effect caused by selective fading.

• Carrier Frequency Error Compensation: Compensates for errors in carrier frequency, in order to have a coherent modulation.

• QAM Demapper: Conversion of the QAM symbol to corresponding bits.

• FEC Decoding: Performs the frame alignment and the error correction by means of the Reed-Solomon decoder.

• De-interleaver: Reassembles the received data in the proper temporal order.

• Descrambler: Transforms the signal to its original state enabling the demultiplexer to distribute the received information to its destinations.

Main Traffic

1. STM-1 (155 Mbit/s) Electrical Interface

2. STM-1/OC-3 (155 Mbit/s) Optical Interface (only TRU OPT./EL.)

Auxiliary Channels

3. G.703 Service Channel (64 kbit/s)

4. V.11 Service Channel (64 kbit/s)

5. Wayside Traffic (1.5/2 Mbit/s)

Operation and Maintenance Interfaces

6. RS 232 for connection of the LCT

7. Ethernet 10/100BaseT for supervision through a Data Communication Network (DCN) or connection of the LCT

8. User I/O ports: 12 selectable input/output ports for connection of external user alarms or control of external equipment.

9. Fan Alarm for connection of an alarm cable from the fan unit

LED Indicators

10. Three LED indicators:

• Green light: Power On

• Yellow light: Test Mode

• Red light: Unit Alarm

LCT Reset

11. Pressing the button initiates a warm reboot of the unit. This operation does not disturb traffic.

Transmitter switching only applies to hot standby systems. Two modes of operation are available.

Manual Mode

Transmitter selection is controlled locally from the LCT or remotely from an element manager.

Automatic Mode

Transmitter selection is based on alarm information from the radio section physical interface. Alarm information from the transmitting side is collected in the control and supervision processor in each MMU and the switch logic controls the transmitter on/off function in the corresponding RAU.

Receiver selection applies to both hot standby and working standby systems. Two modes of operation are available.

Manual Mode

It is possible to make the receiver switch to one side locally from the LCT or remotely from an element manager. Manual switching to one side is not guaranteed to be hitless.

Automatic Mode

Receiver selection is based on alarm information from the receiver section of the RAU or the MMU. Alarm information is collected in the control and supervision processor in each MMU and sent to the switch logic unit in the TRU. An alarm with higher priority overrides an alarm with lower priority. In the event of a failure, the receiver with the lowest alarm priority is selected. Receiver changeover due to HW failure is not guaranteed to be hitless.

In the ELP configuration, the switching criteria are based on transmission alarms, which cause the switching from the transmitting terminal to the other terminal of the same site. When one of these alarms is detected, the transmitting terminal turns its own radio off and orders the other MMU to turn its own radio on. The switching criteria added in ELP configuration to those existing in hot standby are:

• Loss of Signal (LOS) Line to Radio at the TRU traffic interface

• Loss of Frame (LOF) Line to Radio at the TRU traffic interface

• TX CLOCK Line to Radio failure on the TRU board

This block implements the following functions available at the user I/O interface:

• Twelve ports selectable as input or output from the LCT

• Alarms conditions and severity are selectable from the LCT

• The input ports are selectable as active high or active low

• The output ports are selectable as “normally open” or “normally closed” in power off state, if not configured as Severity alarms. In the latter case the outputs are “normally closed” in power off state.

The user I/O interface can be configured to collect alarms for fire, power supply failure, intrusion or a summary alarm from different sources. Furthermore, it can also be used for remote control of external equipment like turning on a mast light.

The AMM provides mechanical housing and backplane connection for the MMU and TRU. Two AMMs for different applications are available:

• AMM 1U-1: for a single unprotected terminal configuration, housing one MMU and one TRU.

• AMM 2U-4: for protected or unprotected terminal configurations, housing up to two MMUs and two TRUs.

The DDU is used to distribute power supply to up to five MMUs or fan units. Each output is protected by an automatic type fuse (6 A) combined with an ON/OFF switch. The DDU is available in two versions:

• Negative ground, for +24 V: The positive pole is connected to the DDU and the negative pole is connected to ground.

• Positive ground, for -48 V: The negative pole is connected to the DDU and the positive pole is connected to ground.

The terminal can be managed from any of the following types of management system:

• Local Craft Terminal (LCT): Has a web based user interface and accesses the terminal using HTTP. Local management at site is performed from the LCT, which allows access to all operation and maintenance facilities on the terminal, by communication with a web server in the terminal.

• MINI-LINK Manager: Presents the terminal in the network list. A web based user interface, similar to the one in the LCT, can also be opened for alarm monitoring and further configuration facilities. Can be connected to the terminal using SNMPv3 (or SNMPv1) protocol.

• Other NMS: The terminal can be supervised remotely from any Network Management System (NMS) when connected to a TCP/IP based Data Communication Network (DCN). Can be connected using SNMPv3 (or SNMPv1) protocol.

The channels are used for internal and external communication, that is for communication between units in the terminal, over the hop and to peripheral systems. The following channels are used:

• Data Communication Channel (DCC)

• Embedded Operation and Maintenance Channel (EOC)

• Internal Communication Channel (ICC)

• Radio Communication Channel (RCC)

External Communication

RSOH bytes are reserved for embedded communication channels, DCC and EOC, for transmission of control and supervision data. Each channel has a capacity of 192 kbit/s. The DCC channel is the standard DCN channel in SDH systems. The EOC channel is implemented in bytes reserved for media dependent use. The user can either choose the DCC channel or, when it is not available, the EOC channel.

Internal Communication

The CP (Central Processor) communicates with Slave Processors (SP) in the MMU(s) and RAU(s) through internal channels, ICC and RCC. The ICC has a transfer rate of 128 kbit/s and connects the CP and the SP on the MMU through the backplane. The RCC is used for communication between the MMU and RAU and has a transfer rate of 31.5 kbit/s.

The LCT user interface has following main menus:

• Setup: During Setup the initial settings for the AMM, protection mode, DCN connection, transmitting frequency and output power are made.

• Configuration: From the Configuration menu the settings for operation of the terminal and traffic are made.

• View: From the View menu the user can view and monitor alarms and performance measurements. The use of filters allows the operator to remove unwanted information, thus being able to focus on relevant data.

• SW Download: Software can be downloaded by means of the SW Download facility. The upgrading of the program revision in the terminal is performed as a background process and does not lead to any traffic disturbance.

The terminal software can be upgraded remotely from an element manager as well as locally from the LCT. The traffic is not affected during this procedure.

A software package, including all images of the units, is downloaded into the terminal from the LCT. The package is compressed to reduce its size. It is then activated either at the end of a successful download or at a later time. When the new software version is downloaded the old version is stored in a memory area, which enables the user to switch back to the old revision if the update fails.

Alarms are divided into different severity levels depending on how they affect the traffic.

• Minor alarms are related to malfunctions that do not affect the traffic.

• Major alarms are generated when a function is unable to perform a required action. This may cause a disturbance in the traffic.

• Critical alarms affect the traffic and should be attended to immediately.

Near-end test loops are used to find out if any of the units in the near-end terminal is faulty (TRU, MMU or RAU). The following near-end test loops are available:

• TRU Tx Loop (N1): the received traffic signal is looped back, at the SPI block, to the output of the TRU.

• TRU Tx Loop (N2): the transmitted traffic signal is looped back, at the RPS block, to the receiving side.

• MMU IF Loop (N3): the signal to be transmitted is, after being modulated, mixed with the frequency of a local oscillator and looped back for demodulation (on the receiving side).

• RAU RF loop (N4): a fraction of the RF signal transmitted is shifted in frequency and looped back to the receiving side.

The Alarm Indication Signal (AIS) is used to indicate faults or states, for example that a loop test is set. AIS is inserted in the radio signal when:

• LOS is detected at the traffic input port or inside the equipment

• LOF is detected at the receiver or inside the equipment

• BER is exceeding a user-defined threshold (this insertion can be enabled by the user)

• The J0 byte, extracted from the received SDH stream, differs from the data written in J0 register (this function is enabled from the LCT)

• Near-end N1 loop and far-end F1 loop

The Central Processor (CP) computes the following values using B1 BIP-8 parity:

• Errored Seconds (ES)

• Severely Errored Seconds (SES)

• Unavailable Seconds (UAS)

• Background Block Errors (BBE)

The RAU computes the following values:

• Received Level Tide Mark (RLTM)

• Transmitted Level Tide Mark (TLTM)

• Received Level Threshold Seconds (RLTS1 and RLTS2)

• Transmitted Level Threshold Seconds (TLTS)

For protected terminals, the Protection Switch Actual Count (PSAC) is also counted.

The user has to log on to the management system by using a user name and a password. The following modes are available:

• Local Control

• Local View

• Remote Control

• Remote View

The local modes are performed from the LCT and the remote modes refer to the user interface started from MINI-LINK Manager. The remote user can do fewer settings than a local user. Depending on the selected mode the user will be able to get read only access or read/write access to the system.

• Control: view settings, make and save changes

• View: view settings only. Not allowed to make changes