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11. Protected Terminals

Monitored Hot Stand By (MHSB)

This section describes configuring the protected terminal in MHSB mode.

A protected terminal in MHSB mode comprises two radios interconnected using a MHSB switch. This MHSB switch comprises one RF switch and up to four tributary switches depending on the number of tributaries requiring switching:

The MHSB switch protect terminals against any single failure in one radio. It also monitors the alarm output of each radio and switches between radios if major radio link alarms occur. The MHSB switch will not allow a switch to a faulty radio.

The MHSB switch uses a CPU to monitor the alarm status received from both the connected radios' alarm ports. When a relevant major radio link alarm is detected on the active radio (that is, transmitter, receiver, power supply or modem), the CPU switches a bank of relays that switches all the interfaces and the transmit port from the main radio to a functioning stand-by radio. The stand-by radio now becomes the active radio.

The MHSB switch has a hysteresis of 30 seconds to prevent switching on short alarm transients.

The tributary switch and the RF switch are both a 19-inch rack-mount 1U high chassis. The MHSB switch option is available for all Aprisa XE frequency bands.

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Tributary Switch Front Panel

No.	Description	Explanation
1	Power supply input	Input for DC power or AC power
2	Protective earth	M5 terminal intended for connection to an external protective
		conductor for protection against electric shock in case of a fault
3	Interface ports	Port for connecting to customer interface equipment
4	Radio A interfaces	These connect to the interface ports on radio A
5	Radio B interfaces	These connect to the interface ports on radio B
6	Console	For factory use only
7	Ethernet	Port for connecting to customer Ethernet network. This port is
		also used to set up and manage the radios remotely over an IP
		network
8	Radio A Ethernet	Connects to an Ethernet port on radio A
9	Radio B Ethernet	Connects to an Ethernet port on radio B
10	Alarms	Alarm input/output connections for customer equipment
11	Radio A alarms	Connects to the alarm port on radio A
12	Radio B alarms	Connects to the alarm port on radio B
13	RF SW	Provides power and signalling to the RF switch
14	Mode switch	Three-position locking toggle switch to set the MHSB switch into
		automatic mode or radio A / radio B test mode
15	LEDs	Mode and status LEDs

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Tributary Protection Switch LEDs
	LED	Colour	Appearance	Explanation
	A	Green	Solid	The radio is active and is OK
		Green	Flashing	The radio is in standby mode and is OK
		Red	Solid	The radio is active and there is a fault
		No colour (off)	-	The tributary switch is in 'slave' mode and the
				switching is controlled by the master tributary
				switch
		Red	Flashing	The radio is in standby mode, and there is a fault
	B	Green	Solid	The radio is active and is OK
		Green	Flashing	The radio is in standby mode and is OK
		Red	Solid	The radio is active and there is a fault
		No colour (off)	-	The tributary switch is in 'slave' mode and the
				switching is controlled by the master tributary
				switch
		Red	Flashing	The radio is in standby mode, and there is a fault
	~	Green	Solid	The tributary protection switch is in 'auto' mode
		Green	Flashing	The tributary protection switch is in 'slave' mode
		Red	Solid	The tributary protection switch is in 'manual'
				mode (A or B)
	On	Blue	Solid	Indicates that there is power to the tributary
				protection switch

RF Switch Front Panel

No.	Description	Explanation
1	Radio QMA	QMA connectors for connecting the protected radios
2	Protective earth	M5 terminal intended for connection to an external protective
		conductor for protection against electric shock in case of a fault
3	Antenna port	N-type female connector for connection to the antenna feeder
		cable. This view shows an internally mounted duplexer. If an
		external duplexer is fitted, the antenna port will be on the
		external duplexer
4	Slave tributary	Connects to secondary tributary switch for control of additional
	switch outputs	interfaces
5	Tributary switch	Connects the RF switch to the tributary switch (the master if
		more than one tributary switch is required)
6	LEDs	Status LEDs

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RF Protection Switch LEDs

LED	Colour	Appearance	Explanation
Tx A	Green	Solid	RF is being received from radio A
Tx B	Green	Solid	RF is being received from radio B
On	Blue	Solid	Indicates that there is power to the RF protection switch

Slave Tributary Switches

Each tributary switch protects up to eight ports. Up to three slave tributary switches may be added to a MHSB terminal to protect up to 32 ports. Each slave tributary switch is interconnected by means of the slave tributary switch ports on the RF switch, as shown below.

Note: A tributary switch that is operating as a slave (rather than a master) has a RJ-45 V.24 loopback connector plugged into the console port. If the connector is missing, contact Customer Support. Alternatively, you can make this connector. Follow the standard pinouts for a V.24 RJ-45 connection (see ‘QV24 Interface connections’ on page 273).

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MHSB Cabling

The two radios are interconnected as follows:

CAUTION: Do not connect Transmit to Receive or Receive to Transmit as this may damage the radio or the MHSB switch.

Cables supplied with MHSB

The following cables are supplied with a MHSB terminal:

Ethernet interface: RJ-45 ports standard TIA-568A patch cables .

Alarm interface: RJ-45 ports standard TIA-568A patch cables.

RF ports: two QMA male patch cables are supplied.

MHSB Power Supply

See ‘DC Power Supply’ on page 37 and ‘AC Power Supply’ on page 40.

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Configuring the Radios for Protected Mode

The MHSB switch does not require any special software. However, the radios connected to the MHSB switch must be configured to work with the MHSB switch. This sets the alarm outputs and inputs to function in MHSB mode.

You must configure the interfaces of both radios connected to the MHSB switch identically. To perform this, you can either connect directly to the radio or use the test mode of the MHSB switch.

MHSB Terminal IP Addresses

Before configuring the link, you must ensure that the two independent links have correctly configured IP address details.

All four radios in the protected link must be on the same subnet.

Example of MHSB IP addressing

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Mounting the MHSB Radios and Switches

Once the IP addresses are correctly configured, it is important to connect the A and B radios' Ethernet and Alarm ports correctly. In general, mount radio A above the MHSB switch and radio B below the MHSB switch:

There is an Ethernet connection between any of the four Ethernet ports on each radio and the Ethernet port on the Tributary switch. There is also a connection between radio A and radio B, which ensures Ethernet traffic is maintained if a radio loses power.

The Ethernet port on the protection switch can be connected to an Ethernet hub or switch to allow multiple connections.

Important: The management Ethernet capacity on each of the four radios in the protected terminal must be identical for remote communications to work and there should only be one IP connection to the management network (via the tributary switch Ethernet port).

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Configuring the Terminals for MHSB

It is recommended that you configure the local and remote A side first, then the local and remote B side. Both the local A and B radios must be configured identically, and both the remote A and B radios must be configured identically.

Tip: As illustrated below, you may find it helpful to have two browser sessions running simultaneously. You can then easily see both the A and B sides of the protected link.

To configure MHSB operation:

1. Select Link > Maintenance > MHSB.

2.Enable MHSB mode.

3.Select whether the radio is A or B.

Ensure that the radio connected to the A side of the protection switch (normally above the MHSB switch) is set to Radio A and the radio connected to the B side of the protection switch (normally below the MHSB switch) is set to Radio B.

In the event of a power outage, the radios will switch over to the A side of the protection switch when the power is restored. The A side is also the default active side.

4.When you have made your changes, click Apply to apply changes or Reset to restore the previous configuration.

5.Repeat steps 2 to 4 for the other side of the protected link.

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Clearing MHSB Alarms

If a switchover event occurs, the OK LED on the front panel and on the Terminal status and menu bar in SuperVisor changes to amber.

1. Select Clear Switched Alarm from the MHSB Command drop-down list.

2. Click Apply to apply changes or Reset to reset the page.

Note: When MHSB mode is enabled, external alarm input 2 is used by the protection system to carry alarms from the protection switch to the radio. In MHSB mode, therefore, only external alarm input 1 is available for user alarms.

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Hitless Space Diversity (HSD)

HSD provides hitless RF receive path protection and hot standby transmitter redundancy. It is typically deployed for paths where high path availability is required.

An Aprisa XE hitless space diversity terminal comprises two radio terminals, radio A and radio B.

Radio A is the primary radio which is fitted with the interface cards and connects to antenna A.

Antenna A always carries the transmitted signal and the received signal for Radio A.

Radio B is the secondary radio the receiver of which connects to antenna B. The transmitter in this radio is the standby transmitter.

In the event of a radio A active transmitter failure, radio B transmitter becomes active.

Antenna B only carries the received signal for Radio B. This antenna is physically separated on the tower by a pre-determined distance from Antenna A.

As both radios have a receive path, traffic from the path with the best received bit error rate is routed to the customer interfaces in radio A.

In an HSD terminal, a HSD Protection Switch Card (PSC) is always fitted in slot H in Radio A and a HSD Protection Interface Card (PIC) is always fitted in slot H in Radio B. The PSC card has a card front switch which controls the hardware setting of the HSD system Active Radio (Auto Select, Radio A or Radio B).

Customer interfaces are provided on radio A only in interface slots A to G. Interface connections to Ethernet and the external alarm inputs and outputs are also provided on radio A only.

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HSD Terminal Cabling

The two HSD radios are interconnected as follows:

Cables Supplied with HSD Terminal

The following cables are supplied with a HSD terminal:

RF cable

A 110 mm QMA female to QMA female low loss RF cable is required to interconnect between the TX ports of both radio A and radio B. This cable carries the radio B transmitter output to the radio A transmitter switch.

Ethernet Cable

A 200 mm RJ45 to RJ45 Ethernet cable between the Ethernet ports of radio A and radio B. This cable carries management IP traffic between radio A and radio B.

Traffic Cable

A 200 mm RJ45 to RJ45 Ethernet cable between the PSC and PIC. This cable carries all user traffic between Radio A and Radio B.

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HSD Terminal IP Addresses

Each radio in the HSD link is assigned a unique IP address. All four radios in the HSD link must be on the same subnet.

The IP address of the four terminals can only be changed by logging into the relevant radio A or radio B.

When the IP addresses have been setup, an ethernet connection to any of the four radios can access all four radios in the HSD link. The usual ethernet connection is to the near end Radio A (see ‘IP Addressing of Terminals’ on page 53).

Example of IP addressing

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Configuring HSD Terminals

To simplify the management and configuration of the HSD terminals, SuperVisor provides four windows which display the parameters for all four radios, the local and remote, radios A and B. The HSD System menu item displays the four windows.

When a parameter is changed in the four window mode, the relevant parameter is automatically changed to the same setting on the corresponding radio e.g. if a radio A modulation type is changed, the radio B modulation type is also changed to the same setting.

The Local and Remote menus continue to display the parameters for the local and remote radios for the near end terminal logged into.

The majority of SuperVisor HSD System pages contain the same parameters and controls as the standard 1+0 XE terminal. The main exceptions are the HSD Control page and the HSD Performance Summary page.

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HSD Active Radio Control

The HSD system ‘Active Radio’ control determines if the selection of Radio A or Radio B is automatic or manual. This controls both the radio transmitters and receivers.

The Active Radio can be set with the hardware switch on the PSC card front or with the SuperVisor software control. The last change of hardware / software control determines the state of the HSD system.

The SuperVisor software control will always reflect the state of the HSD system.

After terminal startup or reboot, the state of the PSC mode switch determines the setting used by the system and the SuperVisor software control is set to reflect the state of the HSD system.

The PSC card has two card front LEDs which indicate the status of the HSD system:

PSC Mode		Hardware Control Change						Software Control Change
Switch
		LED A			LED B			LED A		LED B
Radio A		Solid Amber			Off			Flashing Amber		Off
Auto Select		Solid Green			Solid Green			Flashing Amber		Flashing Amber
Radio B		Off			Solid Amber			Off		Flashing Amber

To set the HSD controls:

1. Select HSD System > Maintenance > Control.

2. Set the Active Radio parameter.

Active Radio	Mode of Operation
Auto Select	Automatic mode:
(default)	The hitless receive will select traffic from the receive path of best
	performance
	The HSD system will switch to the standby transmitter if the active
	transmitter fails (TX failure alarm)
Radio A Only	Manual selection of radio path A only for both the transmitter and
	receiver i.e. no automatic switching
Radio B Only	Manual selection of radio path B only for both the transmitter and
	receiver i.e. no automatic switching

Note: There is no timeout for a manual selection of the Active Radio setting (Radio A only or Radio B only) but a ‘Mode Switch Software Override’ alarm will warn if the software has overwritten the PSC Mode Switch.

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3. Set the Parameter Compare Checking.
	Parameter Compare Checking	Option
	On	Any mismatch in parameters shown in Terminal Settings
	(default)	between Radio A and Radio B will generate a Parameter
		Mismatch alarm.
	Off	No Parameter Mismatch alarm will be generated.

To view the HSD System Performance Summary:

1. Select HSD System > Performance > Summary.

Field	Explanation
Terminal UCEs	The total number of HSD terminal uncorrectable blocks since the last
	reset
Terminal Errored	The total number of HSD terminal operational seconds with errored
seconds	traffic since the last reset
Terminal Error free	The total number of HSD terminal error free operational seconds since
seconds	the last reset
Terminal BER	The system will report an estimated HSD terminal Bit Error Rate up to a
	maximum of 1 in 1021
Active Transmitter	Dislays the current active transmitter (TxA or TxB)

Click Reset Counters to reset the error counters to zero.

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12. In-Service Commissioning

Before You Start

When you have finished installing the hardware, RF and the traffic interface cabling, the system is ready to be commissioned. Commissioning the terminal is a simple process and consists of:

1.Powering up the terminals

2.Configuring both the local and remote terminals using SuperVisor

3.Aligning the antennas

4.Synchronizing the terminals

5.Testing the link is operating correctly. As a minimum, conduct the suggested tests to ensure correct operation. More extensive testing may be required to satisfy the end client or regulatory body requirements.

6.Connecting up the client or user interfaces

What You Will Need

Appropriately qualified commissioning staff at both ends of the link.

Safety equipment appropriate for the antenna location at both ends of the link. Communication equipment, that is, mobile phones or two-way radios.

SuperVisor software running on an appropriate laptop, computer, or workstation at one end of the link.

Tools to facilitate loosening and re-tightening the antenna pan and tilt adjusters.

Predicted receiver input levels and fade margin figures from the radio link budget (You can use Surveyor (see ‘Path planning’ on page 23) to calculate the RSSI, fade margin, and availability).

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Applying Power to the Terminals

WARNING:

Before applying power to a terminal, ensure you have connected the safety earth and antenna cable.

Apply power to the terminals at each end of the link.

When power is first applied, all the front panel LEDs will illuminate red for several seconds as the system initializes.

After the system is initialized, the OK LED on the front panel should illuminate green and if the terminals are correctly configured, the TX and RX LED should also be illuminated green.

If the RX LED is:
Red	the antennas are may be significantly mis-aligned with no signal being
	received
Amber	the antennas may be roughly aligned with some signal being received
Green	the antennas are well-aligned and adequate signal is being received to create
	a reliable path
If the TX LED is:
Red	the transmitter is faulty
Amber	there is a fault in the antenna connection or feeder cable
Green	the transmitter is working normally

Review the Link Configurations Using SuperVisor

1.Connect a PC, with SuperVisor installed, to both terminals in the link.

2.Log into the link.

3.Select Link > Summary and confirm the following basic information:

Terminal IP address(es)

Terminal TX and RX frequencies

RSSI (dBm)

TX power (dBm)

SNR (dBm)

Note: If the terminals have not already been configured, refer to ‘Configuring the terminal’ on page 69, ‘Configuring the traffic interfaces’ on page 91, and ‘Configuring the traffic cross connections’ on page 145.

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Antenna Alignment

For any point-to-point link, it is important to correctly align the antennas to maximize the signal strength at both ends of the link. Each antenna must be pointing directly at the corresponding antenna at the remote site, and they must both be on the same polarization. The antennas are aligned visually, and then small adjustments are made while the link is operating to maximize the received signal.

Directional antennas have a radiation pattern that is most sensitive in front of the antenna, in line with the main lobe of the radiation pattern. There are several other lobes (side lobes) that are not as sensitive as the main lobe in front of the antenna.

For the link to operate reliably, it is important that the main lobes of both antennas are aligned. If any of the side lobes are aligned to the opposite antenna, the received signal strength of both terminals will be lower, which could result in fading. If in doubt, check the radiation patterns of the antennas you are using.

Checking the Antenna Polarization

Check that the polarization of the antennas at each end of the link is the same.

Antenna polarization of grid antennas are normally indicated by an arrow or with ‘H’ and ‘V’ markers (indicating horizontal and vertical).

On Yagi antennas, ensure the orientation of the elements are the same at each end of the link.

Transmit frequency and power, and antenna polarization would normally be defined by a regulatory body, and typically licensed to a particular user. Refer to your license details when setting the antenna polarization.

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Visually Aligning Antennas

1.Stand behind the antenna, and move it from side to side until it is pointing directly at the antenna at the remote site. The remote antenna may be made more visible by using a mirror, strobe light, or flag.

If the remote end of the link is not visible (due to smoke, haze, or local clutter, etc), align the antenna by using a magnetic compass. Calculate the bearing using a scale map of the link path.

When setting the antenna on the desired bearing ensure that you use the appropriate true-north to magnetic-north offset. Also ensure that the compass reading is not affected by standing too close to metallic objects.

2.Once the antenna is pointing at the remote antenna, tighten the nuts on the U-bolt or antenna clamp just enough to hold it in position. Leave the nuts loose enough so that small adjustments can still be made. Check that the antenna is still pointing in the correct direction.

3.Move the antenna up or down until it is pointing directly at the remote site.

4.Tighten the elevation and azimuth adjustment clamps.

5.Mark the position of the antenna clamps so that the antenna can be returned to this rough aim point easily when accurately aligning the antennas.

6.Repeat steps 1-5 at the opposite site.

Note: Low gain antennas need less adjustment in elevation as they are simply aimed at the horizon. They should always be panned horizontally to find the peak signal.

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Accurately Aligning the Antennas

Once the antennas are visually aligned, accurately align both antennas by carefully making small adjustments while monitoring the RSSI. This will give the best possible link performance.

Note: Remember that it is important to align the main radiation lobes of the two antennas to each other, not any side lobes. It may be easier to perform this procedure if you can communicate with someone at the remote site by telephone, mobile, or two-way radio.

1.Connect a laptop PC running SuperVisor software and power up the terminals at both ends of the link. Select Link > Performance > Summary so that you can see the RSSI indication for the local terminal. Alternatively, use the RSSI test point on the front panel together with a multimeter (see ‘Measuring the RSSI’ on page 202).

2.Move the antenna through a complete sweep horizontally (known as a 'pan') either side of the point established in the visual alignment process above. Note down the RSSI reading for all the peaks in RSSI that you discover in the pan.

3.Move the antenna to the position corresponding to the maximum RSSI value obtained during the pan. Move the antenna horizontally slightly to each side of this maximum to find the two points where the RSSI drops slightly.

4.Move the antenna halfway between these two points and tighten the clamp.

5.If the antenna has an elevation adjustment, move the antenna through a complete sweep (known as a 'tilt') vertically either side of the point established in the visual alignment process above. Note down the RSSI reading for all the peaks in RSSI that you discover in the tilt.

6.Move the antenna to the position corresponding to the maximum RSSI value obtained during the tilt. Move the antenna slightly up and then down from the maximum to find the two points where the RSSI drops slightly.

7.Move the antenna halfway between these two points and tighten the clamp.

8.Recheck the pan (steps 2-4) and tighten all the clamps firmly.

9. Perform steps 1-8 at the remote site.

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Measuring the RSSI

Measure the RSSI value with a multimeter connected to the RSSI test port on the front of the terminal (see ‘Front panel connections and indicators’ on page 31).

1.Insert the positive probe of the multimeter into the RSSI test port, and clip the negative probe to the chassis of the terminal (earth).

2.Pan and tilt the antenna until you get the highest VDC reading. The values shown in the table below relate the measured VDC to the actual received signal level in dBm regardless of bandwidth and frequency.

RSSI test	RSSI		RSSI test	RSSI		RSSI test	RSSI
port value	reading		port value	reading		port value	reading
(VDC)	(dBm)		(VDC)	(dBm)		(VDC)	(dBm)
0.000	- 100		0.675	- 73		1.350	- 46
0.025	- 99		0.700	- 72		1.375	- 45
0.050	- 98		0.725	- 71		1.400	- 44
0.075	- 97		0.750	- 70		1.425	- 43
0.100	- 96		0.775	- 69		1.450	- 42
0.125	- 95		0.800	- 68		1.475	- 41
0.150	- 94		0.825	- 67		1.500	- 40
0.175	- 93		0.850	- 66		1.525	- 39
0.200	- 92		0.875	- 65		1.550	- 38
0.225	- 91		0.900	- 64		1.575	- 37
0.250	- 90		0.925	- 63		1.600	- 36
0.275	- 89		0.950	- 62		1.625	- 35
0.300	- 88		0.975	- 61		1.650	- 34
0.325	- 87		1.000	- 60		1.675	- 33
0.350	- 86		1.025	- 59		1.700	- 32
0.375	- 85		1.050	- 58		1.725	- 31
0.400	- 84		1.075	- 57		1.750	- 30
0.425	- 83		1.100	- 56		1.775	- 29
0.450	- 82		1.125	- 55		1.800	- 28
0.475	- 81		1.150	- 54		1.825	- 27
0.500	- 80		1.175	- 53		1.850	- 26
0.525	- 79		1.200	- 52		1.875	- 25
0.550	- 78		1.225	- 51		1.900	- 24
0.575	- 77		1.250	- 50		1.925	- 23
0.600	- 76		1.275	- 49		1.950	- 22
0.625	- 75		1.300	- 48		1.975	- 21
0.650	- 74		1.325	- 47		2.000	- 20

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Checking Performance

The amount of testing performed on the completed installation will depend on circumstances. Some customers may need to prove to a local licensing regulatory body that the link complies with the license provisions. This may require special telecommunications test equipment to complete these tests. Most customers simply want to confirm that their data traffic is successfully passing over the link, or that the customer interfaces comply with known quality standard.

However, the most important performance verification checks are:

Receive input level

Fade margin

Long-term BER

Checking the Receive Input Level

The received signal strength at the local terminal is affected by many components in the system and has a direct relationship with the resulting performance of the link. A link operating with a lower than expected signal strength is more likely to suffer from degraded performance during fading conditions. The receive input level of a link is normally symmetrical (that is, similar at both ends).

1.Compare the final RSSI figure obtained after antenna alignment with that calculated for the link.

2.If the RSSI figure is in excess of 3 dB down on the predicted level, recheck and correct problems using the table below and then recheck the RSSI. Alternatively, recheck the link budget calculations.

Possible cause	Terminal(s)
Is the terminal operating on the correct frequency?	Local & remote
Is the remote terminal transmit power correct?	Remote
Are all the coaxial connectors tight?	Local & remote
Is the antenna the correct type, that is, gain and frequency of operation?	Local & remote
Is the antenna polarized?	Local & remote
Is the antenna aligned?	Local & remote
Is the path between the terminals obstructed?

Note: If following the above steps does not resolve the situation, contact Customer Support for assistance.

3.Record the RSSI figure on the commissioning form.

4.Repeat steps 1 to 2 for the other end of the link.

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Checking the Fade Margin

The fade margin is affected by many components in the system and is closely related to the received signal strength. A link operating with a lower than expected fade margin is more likely to suffer from degraded performance during fading conditions. A reduced fade margin can be due to operating the link too close to the noise floor, or the presence of external interference. The fade margin of a link can be asymmetrical (that is, different at each end).

Possible causes of low fade margin are as follows:

Problem	Terminal
Low receive signal strength (see above table)	Local and Remote
Interfering signals on the same, or very close to, the frequency of the	Local
local terminal receiver.
Intermodulation products that land on the same or very close to the	Local or Remote
frequency of the local terminal receiver.
Operating near the local receiver noise floor	Local

To check the fade margin:

1.Confirm (and correct if necessary) the receive input level (see the previous test).

Note: If the receive input level is lower than expected, the fade margin may also be low.

2.Select Link > Performance > Summary and check the current BER of the link in its normal condition is better than 10-6 (If necessary, clear out any extraneous errors by clicking Reset Counters).

3.Check the signal to noise (S/N) indication on the Link > Performance > Summary page. This shows the quality of the signal as it is being processed in the modem. It should typically be better than 30 dB. If it is less than 25 dB, it means that either the RSSI is very low or in-band interference is degrading the S/N performance.

4.Temporarily reduce the remote site's transmit power using either an external attenuator or SuperVisor (Remote > Terminal > Basic).

Note: Ideally, the transmit power of the remote site should be reduced by up to 20 dB, which will require the use of an external 50 ohm coaxial attenuator capable of handling the transmit power involved. In the absence of an attenuator, reduce the transmit power using SuperVisor.

5.Check and note the current BER of the link in its now faded condition (Again, if necessary, clear out any extraneous errors (introduced by the power reduction step above) by clicking Reset Counters).

6.Compare the unfaded and faded BER performance of the link (steps 2 and 4). Continue to reduce the remote transmit power until either the BER drops to 10-6 or the remote transmitter power has been reduced by 20 dB.

Note: The fade margin of the link is expressed as a number (of dB) that the link can be faded (transmitter power reduced) without reducing the BER below operating specifications (1 * 10-6 BER). A 20 dB fade margin is adequate for most links.

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7.Record the fade margin and SNR results on the commissioning form.

Note: If the transmit power is reduced using SuperVisor rather than an external attenuator, the fade margin should be recorded as ‘Greater than x dB’ (where x = the power reduction).

8.Restore the remote terminal transmit power to normal.

9.Repeat steps 1 to 7 for the other end of the link.

Note: If following all the guidelines above does not resolve the situation, contact Customer Support for assistance.

Checking the Long-Term BER

The BER test is a measure of the stability of the complete link. The BER results of a link can be asymmetrical (that is, different at each end).

1.Select Link > Performance > Summary and check the current BER and error counters of the link. If necessary, clear out any extraneous errors by selecting Reset Counters.

2.Wait 15 minutes, and check the BER display and error counters again. If there are a small number of errors and the BER is still better than 1 x 10-9, continue the test for 24 hours. If there are a significant number of errors, rectify the cause before completing the 24 hour test.

Note: It is normal to conduct the BER test in both directions at the same time, and it is important that no further work be carried out on the equipment (including the antenna) during this period.

3.The BER after the 24 hour test should typically be better than 1 x 10-8.

4.Record the BER results on the commissioning form.

Bit Error Rate Tests

A Bit Error Rate (BER) test can be conducted on the bench, (see ‘Bench Setup’ on page 43).

Attach the BER tester to the interface port(s) of one terminal, and either another BER tester or a loopback plug to the corresponding interface port of the other terminal.

This BER test can be carried out over the Ethernet, E1 / T1, V.24 or HSS interfaces. It will test the link quality with regard to user payload data.

CAUTION: Do not apply signals greater than -20 dBm to the antenna as they can damage the receiver. In a bench setup, there must be 60 - 80 dB at up to 2 GHz of 50 ohm coaxial attenuation (capable of handling the transmit power) between the terminals’ antenna connectors.

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Additional Tests

Depending on license requirements or your particular needs, you may need to carry out additional tests, such as those listed below.

Refer to the relevant test equipment manuals for test details.

Test	Test equipment required
TX power output measurements (at TX and	Power meter
duplexer outputs)
TX spectrum bandwidth	Spectrum analyzer
TX spectral purity or harmonic outputs	Spectrum analyzer
TX center frequency	Frequency counter or spectrum analyzer
Bulk capacity BER test	BER tester
LAN throughput or errors	LAN tester
G.703 / HDB3 waveforms	Digital oscilloscope
Serial interface BER	BER tester
Audio quality	PCM4 or SINAD test set

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Checking the Link Performance

For a graphical indication of the link performance, you can use the constellation analyzer.

The 'dots' are a graphical indication of the quality of the demodulated signal. Small dots that are close together indicate a good signal. If the dots become spaced further apart, this indicates that the signal quality is degrading. This signal quality degradation can be caused by low Rx signal level due to, for example:

external interference

failure of any of the following: modem, receiver, far end transmitter, an antenna (either end), a feeder or connector (for example, due to water damage)

path issues such as multipath fading or obstructions

To check the performance of the link using the constellation analyzer:

1. Select Link or Local or Remote > Performance > Constellation.

2.Click Start to start the constellation analyzer.

While the constellation analyzer is running, the terminal will temporarily stop collecting error performance statistics. If you want to run the constellation analyzer anyway, click OK when you see this warning message:

3.Click Stop to stop the constellation analyzer.

The terminal automatically resumes collecting error performance statistics.

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Viewing a Summary of the Link Performance

To view the performance summary for a terminal:

Select Link or Local or Remote > Performance > Summary.

Field	Explanation
Link Performance
Correctable errors	The total number of correctable blocks since the last reset
Uncorrectable errors	The total number of uncorrectable blocks since the last reset
SNR (dB)	The Signal to Noise Ratio of the link in dB
RSSI (dBm)	The Received Signal Strength Indication at the Rx input in dBm
Errored seconds	The total number of operational seconds with errored traffic since the
	last reset
Error free seconds	The total number of error free operational seconds since the last reset
BER	The system will report an estimated Bit Error Rate up to a maximum of
	1 in 1021
TX temperature	The measured temperature in the transmitter module in °C
RX temperature	The measured temperature in the receiver module in °C
Ethernet performance
Transmitted packets	The total number of transmitted Ethernet packets
Received packets	The total number of received Ethernet packets
Received packet errors	The total number of packets received with errors

Click Reset Counters to reset the error counters to zero.

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Saving the History of the Link Performance

Link performance history data is stored in a rolling buffer which can be saved as a *.cvs file (default filename is savedPerformanceHistory.csv). The maximum history data buffer is 1 week of 1 hour records and the last hour is displayed in minute records.

The parameters saved are:

Date / Time

SNR (minimum over period)

SNR (average over period)

SNR (maximum over period)

RSSI (minimum over period)

RSSI (average over period)

RSSI (maximum over period)

BER (value at end of period)

UCEs count (value at end of period)

Transmitter temperature (value at end of period)

To save the history of the link performance for a terminal:

Select Local > Performance > Save History.

Example of file (simulated fade data):

PREVIOUS WEEK

TIME		SNR min	SNR avg	SNR max	RSSI min	RSSI avg	RSSI max	BER	UCEs	Tx Temp
		(dB)	(dB)	(dB)	(dBm)	(dBm)	(dBm)			(deg C)
Mon Apr	6 09:44:50 2009	35.14	35.26	35.39	-54.00	-54.00	-54.00	3.40E-12	144	50
Mon Apr	6 10:44:50 2009	35.14	35.26	35.40	-54.00	-53.90	-53.90	3.39E-12	144	50
Mon Apr	6 11:44:50 2009	35.14	35.26	35.40	-54.00	-53.90	-53.90	3.38E-12	144	50
Mon Apr	6 12:44:51 2009	15.31	25.77	58.54	-114.00	-77.00	-54.00	1.58E-05	1045	50
Mon Apr	6 13:44:51 2009	22.52	22.75	22.89	-84.10	-83.70	-83.60	6.92E-06	9912	51
Mon Apr	6 14:44:51 2009	16.20	26.05	54.61	-87.10	-77.40	-60.20	9.67E-05	72125	52
…
PREVIOUS HOUR
TIME		SNR min	SNR avg	SNR max	RSSI min	RSSI avg	RSSI max	BER	UCEs	Tx Temp
		(dB)	(dB)	(dB)	(dBm)	(dBm)	(dBm)			(deg C)
Mon Apr	6 14:11:51 2009	22.52	28.38	22.75	-84.10	-78.19	-83.80	5.89E-06	22821	52
Mon Apr	6 14:12:51 2009	22.55	25.67	22.75	-84.10	-80.89	-83.80	5.86E-06	23369	52
Mon Apr	6 14:13:51 2009	22.50	23.52	22.75	-84.10	-83.07	-83.70	5.84E-06	23847	52
Mon Apr	6 14:14:51 2009	22.50	24.35	22.78	-84.10	-82.23	-83.70	5.81E-06	24338	52
Mon Apr	6 14:15:51 2009	22.54	22.73	22.77	-84.10	-83.86	-83.80	5.78E-06	24855	52
Mon Apr	6 14:16:51 2009	22.52	26.67	22.75	-84.10	-79.90	-83.80	5.75E-06	25374	52
Mon Apr	6 14:17:51 2009	22.48	30.19	22.79	-84.10	-76.38	-83.70	5.73E-06	25918	52
Mon Apr	6 14:18:51 2009	22.49	28.87	22.74	-84.10	-77.68	-83.80	5.71E-06	26473	52
Mon Apr	6 14:19:51 2009	22.48	30.65	22.74	-84.10	-75.94	-83.80	5.68E-06	27007	52
Mon Apr	6 14:20:51 2009	22.50	29.99	22.75	-84.00	-76.59	-83.80	5.66E-06	27561	52
Mon Apr	6 14:21:51 2009	22.61	29.78	22.76	-84.00	-76.82	-83.80	5.64E-06	28167	52
Mon Apr	6 14:22:51 2009	22.46	25.70	22.74	-84.10	-80.86	-83.90	5.62E-06	28717	52
Mon Apr	6 14:23:51 2009	22.46	26.96	22.75	-84.10	-79.61	-83.80	5.59E-06	29237	52
Mon Apr	6 14:24:51 2009	22.47	24.71	22.75	-84.10	-81.86	-83.80	5.57E-06	29776	52
Mon Apr	6 14:25:51 2009	22.48	30.19	22.73	-84.10	-76.36	-83.80	5.55E-06	30368	52
Mon Apr	6 14:26:51 2009	22.49	25.97	22.75	-84.20	-80.61	-83.80	5.53E-06	30942	52
Mon Apr	6 14:27:51 2009	16.20	22.94	54.61	-87.10	-83.76	-83.90	7.30E-06	71751	52
Mon Apr	6 14:28:51 2009	16.23	26.84	49.90	-87.00	-73.31	-60.30	6.67E-03	72125	52
Mon Apr	6 14:29:51 2009	35.10	40.60	35.24	-60.50	-54.96	-60.30	1.70E-03	72125	52
Mon Apr	6 14:30:51 2009	35.08	39.17	35.28	-60.50	-56.40	-60.30	9.13E-04	72125	52
Mon Apr	6 14:31:51 2009	35.07	36.63	35.26	-60.50	-58.95	-60.20	6.11E-04	72125	52
Mon Apr	6 14:32:51 2009	35.06	36.68	35.24	-60.60	-58.90	-60.30	4.52E-04	72125	52
Mon Apr	6 14:33:51 2009	35.06	35.34	35.25	-60.60	-60.24	-60.30	3.56E-04	72125	52
Mon Apr	6 14:34:51 2009	35.09	36.28	35.24	-60.50	-59.28	-60.30	2.92E-04	72125	52
Mon Apr	6 14:35:51 2009	35.07	42.56	35.28	-60.60	-53.03	-60.30	2.46E-04	72125	52
…

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To save the alarm history from the Remote terminal, login to the Remote terminal and Select Local > Alarms > Save History.

Aprisa XE User Manual