Universal Device Driver Reference Manual

1.647 Symmetric-Site-Switch

The Symmetric-Site-Switch logical device controls the equipment of one transmit chain for a site diversity application between two uplink ground stations. As the driver name implies, the device works completely symmetrically, there is no preference for a primary or a backup site.

As shown in the figure above, the Symmetric-Site-Switch logical device is operated at one of the two sites. There it controls the local RX device and the TX redundancy control device if there is any configured.

The devices of the second (remote) site are mapped as Proxy devices, providing control for these devices at the other site.

Site switch procedure

Switching the uplink from the one site to site to the other is a simple sequence of actions and checks. The procedure is exactly the same for switching from one site to the other and back. In the description below the site which transmits before the switchover is called 'source', the site which wil be transmitting after tge switchover is called 'destination'

Check if the destination TX equipment states a fault. Abort the the switchover in this case.
Switch off the protection for the TX equipment at the source site. Every type of protection (1:1, N:1, N:M) uses its own method to sitch off protection.
Check if the protection is actually off at the source site. Abort with an error if this fails
Switch off the carrier at the source site. For this first evaluate which is the tx equipment actually used for the carrier.
After a configurable wait time check if the carrier at the source site has been switched off. Repeatedly check this up to 10 seconds if the carrier does not respond. After this abort with an error.
Switch on the carrier at the destination site. For this first evaluate which is the tx equipment actually used for the carrier. protection switch if a N-TO-1 protection is configured
After a configurable wait time check if the carrier at the destination site has been switched on. Repeatedly check this up to 10 seconds if the carrier does not respond. After this abort with an error.
Restore the destination site protection on/off setting from the value which has beed saved just before the carrier had been switched away from this site the last time.
Check if the protection is actually set to the commanded state at the destination site. Abort with an error if this fails
Successfully switched to the destination site.

Switching back to the original site works the same way the other way round.

Redundancy configuration

The Symmetric-Site-Switch supports four different modes of redundancy for the transmit devices. These modes are configured individually for both sites, this means you can have two 1:1 redundant HPAs at the one site and at the other site HPAs which are part of a N:1 redundancy. The redundancy modes are:

NONE: There is no redundancy at all for this site. The device only controls the primary TX device at this site and skips all steps regarding the redundancy.
1-TO-1: The TX devices at this site are in a symmetric 1:1 redundancy. The site switch device always controls both TX devices at the same time, their carriers are simultaneously switched on/off, the carrier is assumed to be off if both devices report RF OFF.
N-TO-1: The TX devices at this site are in a N:1 redundancy. The site switch device uses the redundant device if the protection controller has switched this in place of the configured primary device.
POOL: The TX devices are controlled in a N:M redundancy by individual Modem-Protection-Controller devices and a Protection-Switch-N-To-M. This works the same way for configurations which get the spare device from a pool of spares and configurations which use a 1:1 reservation of a spare device.

The protection controller mode for a site also has some impact how the Symmetric-Site-Switch expects some of its configuration parameters:

NONE: txDeviceA/B contains the name of the TX device, txRedDeviceA/B and protectDeviceA/B are empty.
1-TO-1: txDeviceA/B contains the name of one of the TX devices, txRedDeviceA/B the name of the other device in the 1:1 redundancy. protectDeviceA/B has to be set to the name of the 1:1 protection controller.
N-TO-1: txDeviceA/B contains the name of the primary TX device, txRedDeviceA/B the name of the spare device in the N:1 redundancy. protectDeviceA/B has to set to the name of the N:1 protection controller and chainNoA/B must be set to the chain number of the primary TY device in the redundancy configuration.
POOL: With the POOL based N:M redundancy, txDeviceA/B does not contain the name of a TX device but the name of the Modem-Protection-Controller managing the TX device. protectDeviceA/B has to be set to the name of the N:M protection controller, txRedDeviceA/B and chainNoA/B may be left empty.

Device window pages

The following table shows which device window pages are available with this individual device type. Tool-bar functions not mentioned here are described at the general description of device windows .

--- Shows / commands actual uplink location.
--- The device info page.
--- The maintenance page. The configuration parameters from this page are described below.

Configuration parameters

At the maintenance page of the device window there are a couple of configuration parameter which must be set to interconnect the device with the devices that will perform the carrier on/off settings.

parameter	description
abortOn	The Symmetric-Site-Switch aborts a switchover procedure if one of the transmit devices reports a fault. This setting selects if this shall happen in case of a FAULT or also if the device reports a WARNING.
protectModeA/B	Selects the type of protection switch used with the TX equipment at the particular site. May be one of NONE, 1-TO-1, N-TO-1 or POOL. Should be set to the value describing the protection mode of the TX equipment.
protectDeviceA/B	The name of the protection controller device used at the particular site. Must be set if the protectMode is set to another value than NONE
txDeviceA/B	The device name of the transmit device (typically an HPA) which produces the carrier at the particular site. With protectMode POOL this is the Modem-Protection-Controller device managing the the redundancy to this carrier
txRedDeviceA/B	The name of the backup TX device at this particular site. For a symmetrical 1:1 redundancy this is the name of the second HPA (see redundancy configuration above). Not requires if protectMode is NONE or POOL
chainNoA/B	Must be set with N:1 redundancy configuration to the chain number of the txDevice in the protection device (1..12). Not used with the other protection mode options.
nameA/B	A short (one word) name for the this site.
descriptionA/B	A descriptive name for the site. This appears in event log entries and in status messages of the device, hence it should not be to long (max 15 characters are recommended)
txChgReadDelayA/B	This parameter sets the delay between an RF ON/OFF command sent to the TX device and the first read back which is done to check if the carrier is really at the commanded state. Some devices echo the RF ON/OFF state without switching the carrier and report the true state two seconds later because the command could not be executed as expected. Increasing the delay can help to suppress the consequences of this effect.
comment	The text is presented in the device's GUI as a description of the carrier which is switched between the sites.

Variables defined by this device driver

name	type	flags	range
info.driver	TEXT	R/O	StringRange R/O
info.type	TEXT	R/O	StringRange R/O
info.frame	TEXT	R/O	StringRange R/O
info.protectModeA	TEXT	R/O	StringRange R/O
info.protectModeB	TEXT	R/O	StringRange R/O
info.hasBeamOnA	TEXT	R/O	StringRange R/O
info.hasBeamOnB	TEXT	R/O	StringRange R/O
config.abortOn	CHOICE	SAVE SETUP	EnumRange (WARNING FAULT)
config.protectModeA	CHOICE	SAVE SETUP	EnumRange (NONE 1-TO-1 N-TO-1 POOL)
config.protectModeB	CHOICE	SAVE SETUP	EnumRange (NONE 1-TO-1 N-TO-1 POOL)
config.protectDeviceA	TEXT	SAVE SETUP	StringRange
config.protectDeviceB	TEXT	SAVE SETUP	StringRange
config.txDeviceA	TEXT	SAVE SETUP	StringRange
config.txDeviceB	TEXT	SAVE SETUP	StringRange
config.txRedDeviceA	TEXT	SAVE SETUP	StringRange
config.txRedDeviceB	TEXT	SAVE SETUP	StringRange
config.txChainNoA	INTEGER	SAVE SETUP	IntegerRange (0 .. 0)
config.txChainNoB	INTEGER	SAVE SETUP	IntegerRange (0 .. 0)
config.nameA	TEXT	SAVE SETUP	StringRange
config.nameB	TEXT	SAVE SETUP	StringRange
config.descriptionA	TEXT	SAVE SETUP	StringRange
config.descriptionB	TEXT	SAVE SETUP	StringRange
config.comment	TEXT	SAVE SETUP	StringRange
gotoA	TEXT		StringRange
gotoB	TEXT		StringRange
reset	TEXT		StringRange
progressReport	TEXT	R/O	StringRange R/O
progressIcon	TEXT	R/O	StringRange R/O
location	TEXT	R/O	StringRange R/O
savedState	INTEGER	SAVE	IntegerRange (0 .. 0)
savedProtectionA	TEXT	SAVE	StringRange
savedProtectionB	TEXT	SAVE	StringRange