GB2468500A - Protection switching for multimedia equipment - Google Patents

Abstract

A method and system for providing protection against equipment failure for multimedia (audio and/or video data) equipment to improve resiliency and availability. Protection switching is provided such that transmitting and receiving circuitry is duplicated in the system and the redundant circuitry is used when a failure is detected in the active circuitry. Duplicate redundant circuitry may be provided at the user device transmitters (such as video cameras, microphones, musical instruments etc) or may be provided at the user device receivers (such as headphones (IEM, in-ear monitoring), display screens/monitors, PA systems etc.) or at a central location such as at the base station or mixer console of a studio arrangement. In analogue systems the equipment may be monitored using in band tones. In digital systems the equipment may be monitored using CRC or parity checking. A mix of protected and unprotected devices may be used in the system. Replacement/redundant circuits may be switched to without any disruption to the system. Embodiments include TV studios, film studios, recording studios, concert venues, theatres, stadiums, clubs, conference centres, hotels, halls and the like. The protection is provided without any increase in wireless bandwidth used by the system.

Description

1. Technical Field

The present invention described herein relates to multi media systems that are used with microphones, musical instruments, video cameras and/or for transmitting signals to In Ear Monitoring (IEM) systems, fold back monitors, visual display screens and the like which improves resiliency and availability of such systems.

2.. Background Art

Professional multi media systems can be deployed in many environments such as TV studios, film studios, recording studios, concert venues, theatres, stadiums, clubs, conference centres, hotels, halls and the like.

Typically comprising of a transmitting and a receiving device, these systems are used during live performances, for recording music or for conference speakers etc and can receive audio signals transmitted from microphones, musical instruments, or visual/video signals from cameras and typically deploy wireless technology, although cables, infra-red and other such technologies can be used. Refer to Fig.1 (Typical Multimedia equipment setup.) The multimedia signals are transmitted to, and received from the various user devices and are typically connected to external equipments such as audio mixers, recording equipment, sound re-enforcement systems, video mixers, visual display equipment etc. These systems are also used for transmitting audio signals to In Ear Monitoring (IEM) systems, fold back monitors, and visual and video signals to visual display equipment and the like.

Many of these systems operate within the analogue domain and typically work with one device either receiving signals from it, or by transmitting signals to it either by wire or by use of a specific radio frequency. Examples of these include single channel wireless microphone or instrument systems and single channel IEM (In Ear Monitoring) systems manufactured by many suppliers.

More recently, digital techniques permit the transport of many different multi-media signals to multiple receivers via a packet based, or multiplex structured signal using a common carrier frequency. Each receiving device and each transmitting device is allocated a specific timeslot within this signal and the corresponding receiver decodes the appropriate signal from the multiplexed signal. Here, as signals are both transmitted and received from one unit, this is in effect a transceiver and it can be deployed with separate transmitting devices (e.g. radio microphones) and receiving devices (e.g. an In Ear Monitoring system).

There is also a move within the industry for digital microphones whereby analogue to digital conversion takes place within the microphone body itself and the analogue signal is sent in digital form (e.g. USB, USB 2 and the like over cable or digitally via a suitable radio technology) to a digital mixer, recording system or sound reinforcement system etc. However, all of the available systems can be described as follows. They deploy one transmitting unit and one receiving unit; or one transceiver with typically a combination of multiple single channel transmitters (e.g. wireless microphones) and multiple single channel receivers (e.g. wireless In Ear Monitoring systems) and hence suffer from single points of failure.

The present invention provides a novel approach to resoMng this issue for all of these various systems

3. Summary of the present invention

The present invention provides a method and system for protecting multimedia equipment by implementing the following unique and novel attributes. The unique approach described herein applies protection to all elements of the system without requiring any increase in wireless bandwidth.

Further details on each unique element of the present invention follow later in this paper.

The system comprises of receivers and transmitters connected to end user devices and a base station that can transmit to and receive the necessary multimedia signals from these devices.

In essence the present invention is described by adding protection to a typical system set up as shown in Fig.1 (Typical Multimedia equipment setup. The protected version is shown in Fig.2 (Typical scheme for a protected multimedia system). However, it would be possible to apply the invention to other similar multimedia system configurations, or to extend it to other areas such as personal communication systems, security systems and like products.

The example system proposed uses the unique properties of wireless transport in that all wireless transmissions are seen' -or received -by all receivers.

Where duplicated the wireless transmitters and receivers could share a common antenna but for clarity individual antenna are shown on the diagrams.

The system described in Fig.2 could comprise the following sub systems: User Devices: Transmitters (hereinafter referred to as U DI), User Devices: Receivers (hereinafter referred to as UDR) and the Basestation UDT. A device whose primary function is to transmit user data from a user device (e.g. radio microphone, musical instrument, video camera and the like) to the receiver section of the Basestation. (Other functions associated with this sub system are described in this paper) UDR. A device whose primary function is to receive user data from the transmitter section of the Basestation and is then connected to a user device (e.g IEM headphones, video screen/display unit and the like). (Other functions associated with this sub system are described in this paper) Basestation. Primary function is to transmit data to the UDR5 and receive data from the UDTs and to perform synchronisation, control and monitoring and to enable switching from a failed equipment to a redundant (standby) equipment thus maintaining signal integrity.

In general the description in this document is focused on analogue sources and output signals. In an alternative embodiment, digital multimedia input signals (e.g. from a digital audio mixing desk) could be employed on such a system whereby the monitoring would be achieved by use of a digital technique such as CRC, parity checking and the like, otherwise the system is as described for the analogue case.

3.1. User Devices: Transmitter (UDT) The UDT could convert the analogue audio signal supplied by the user (microphone/musical instrument etc) into a digital format by use of an ADC (Analogue to Digital Converter.) A header packet could be added to each digital stream in order that the signal can be identified for correct decoding and then wirelessly transmitted in a predeflned wireless timeslot to the Basestation.

Duplicated circuits ensure that in the event of a detected failure the standby circuit could take over the full functions of the failed path.

For reasons of costfbattery life and size (in the case of portable units) the device could be single ended' i.e. unprotected and the system can be deployed with a mix of both protected and un-protected devices.

A back channel from the Basestation deploying duplicated receiving and decoding circuits could provide a protected path for synchronisation, monitoring and switching configuration control for the UDT ref para 5.(Wireless Transmitter Synchronization) 3.2. User Devices: Receiver (UDR) The UDR could receive wireless signals from the Basestation for an end user (In Ear Monitoring, Display Units, PA systems etc). The signal could encompass multiple digitised audio or data sources. The signal could be broadcast providing each UDR with multiple signals for individual selection, or directed to a specific end user with suitable addressing schemes.

Duplicated circuits ensure that in the event of a detected failure the standby circuit could take over the full functions of the failed path.

For reasons of cost/battery life and size (in the case of portable units) the device could be single ended' i.e. unprotected and the system can be deployed with a mix of both protected and un-protected devices.

3.3. Basestation The Basestation is the hub of the system providing the link between the User Devices and the AudioNideo Mixer Console, or other external equipment.

The Basestation could be split into two duplicated halves. Each half could comprise a wireless receiver function to receive data from the UDT's, a wireless transmitting function for transmitting data to the UDR's and a central processor controlling and co-ordinating changeover, bandwidth management, configuration and monitoring.

Each half is configured as either a Main or a Standby unit. Failure of any of the monitored functions in the worker (normally the Main) path wit cause the controlling processor to transfer the failed path to the Standby unit and indicate failure of the Main unit to instigate repair and maintenance. Failure of common circuits, (for instance power supply), processor functions etc. will cause all circuits to be transferred to the redundant (normally the Standby) system.

As the Basestation offers a duplicated transmitter and receiver functions it is necessary to provide a splitter and combiner function for analogue signals. This is to enable each separate input to, and output from the Basestation to be connected to a single port on the external equipment (for example a video or audio mixing desk). This is shown in Fig.2 Typical scheme for a protected multimedia system' 4. Detailed description of the preferred embodiments 4.1. The UDT 1) Transmitter function (e.g. those used in radio microphones and instrument systems, video cameras and the like) is uniquely implemented by using a pair of transmitters which are both physically separate to enhance the redundancy and transmit their signal in a digital format. The two transmitters are designated main" and "standby with only the worker (normally the main) transmitting a wireless signal. The input analogue signal source to the transmitter function could be converted into a digital stream along with the in-band monitoring (see below). The signal could then be formatted, packetised together with the required device header/ID data and wirelessly transmitted. In the event of a fault being detected in the main' transmitter all functions automatically divert to the "standby 2) Receiver function. Even though the primary function of the User Device Transmitter is to send user data to the Basestation, it also incorporates a duplicated receiver function which could receive low rate back channel packets from the working transmitter within the Basestation. The back channel data could be monitored by digital means (i.e. CRC or panty scheme or similar) in order that a working path can be selected from either one of these duplicated receivers.

The receiver function also includes monitoring its own wireless transmission to determine if there has been a failure of the currently selected worker transmitter (see above and also para. 6 (Monitoring and protection switching) 3) In band monitoring could be a tone selected from either below or above the range of the analogue signal -typically for audio this could be 20Hz or 18kHz which is transported along with the required signal (in digital format) to the receiver section of the Basestation where it is converted back to analogue, filtered and monitored (further details in para. 6 (Monitoring and protection switching) 4) To cater for multiple UDT's, each said device could use different wireless channels or timeslots ref. para. 5 (Wireless Transmitter Synthronization).

5) Synchronisation. A synchronisation packet transmitted from the working transmitter within the Basestation over the back channel could align all the User Devices to a common point in time. See para. 5 (Wireless Transmitter Synchronization) 6) Bandwidth management. UDT's could be deployed with the system that require different data rates. These could be widely varied devices such as audio devices or video camera's requiring different wireless bandwidths. Bandwidth management could be deployed programming each User Device with its specific timeslot related to its bandwidth requirement. The bandwidth management could be configured via the back channel path and managed from the Basestation.

7) Provision for indicating the UDT status, subsystem failure and traffic changeover to facilitate maintenance and repair.

8) Dying gasp'. In the event of major disruption to common elements (power circuits, processors etc) the UDT could be programmed to transmit a short wireless alarm message to alert the Basestation control.

9) Single ended unprotected UDT. It is envisaged that unprotected UDT could be required. This may be for cost/power or space requirements but provision could be made for a channel locked' to the Main circuit only with no changeover facilities.

Pursuant to the above requirements the specific UDT could also be outside the synchronisation domain and transmit its data when an opportunity presents itself utilising the normal Receive Signal Strength Indicator (RSSI) facility provided on wireless modules.

42. The UDR 1) Receiver Function: A receiver function providing a service for In Ear Monitoring devices, Visual Display Units, PA systems etc is uniquely implemented by using a pair of receivers which are physically separate to enhance the redundancy. The receiver function could consist of a wireless receiver and digital header/to decoding along with suitable digital-analogue conversion and in band monitoring detectors.

2) Circuit protection: In the event of a detected failure indicated by the monitoring circuits, the worker path is re-directed to the standby with the main path effectively de-activated.

3) A means of indicating the UDR status, subsystem failure and traffic changeover to facilitate maintenance and repair.

4) Single ended' unprotected UDR. It is envisaged that unprotected UDR devices could be required. This may be for cost/power or space requirements but provision could be made for a channel locked' to the Main circuit only with no changeover facilities 4.3. Basestation 1) Transmit multimedia data function. An in-band monitor could be combined with each analogue input (e.g. from an audio mixer) to the Basestation transmitter and the complete stream converted into digital using an ADC. The stream could then be multiplexed, formatted and packetised together with the required device header/ID data and wirelessly transmitted for reception by the UDR's.

2) Receiving multimedia data function. Function could receive wireless data packets from the UDT's. The data could be re-formatted and converted to analogue using a DAC for monitoring and selection of the worker path.

3) All transceiver functions (transmitter and receiver) of the Basestation could be duplicated and designated the Main and Standby for maximum availability.

Transmitter: Only the worker (normally the Main) device transmits data packets. In the event of a detected failure all Transmitter functions would transfer to the Standby.

This would then become the worker'.

Receiver: Both receivers (Main and Standby) could receive and monitor data packets however only one path (normally the Main) is selected as the worker. If a failure is detected in the Main path the circuit is reconfigured and user data taken from the Standby. This would then become the worker' 4) Transmitter monitoring: All data packets wirelessly transmitted from the transmit multimedia data function are received for monitoring purposes by both the Main and Standby Basestation receiver's. (i.e. the Basestation is monitoring its own transmissions). A detected failure at both the receiver's in-band monitors could instigate changeover of the Transmitter Function to the Standby. Also see para. 6 (Monitoring and protection switching).

5) Transmitting back channel function. A wireless back channel' enabling a data path from the Basestation to the UDTs (see 4.1, para 2). Data packets could be sent from the working Basestation transmitter function to the various UDT receivers for synchronisation and configuration. Ref: para. 5. (Wireless Transmitter Synchronization) 6) Bandwidth management. The synchronisation and timeslot management of the UDT's could be calculated/organised by the Basestation and transmitted via, the Transmitting Back Channel function.

7) Switchover control interface. An interface that permits connection of two Basestation halves (Main and Standby) such that the units can indicate the status of the received test tone. See para.6 (Monitoring and protection switching) and also to control the switch over from the designated main unit to the standby unit following the detection of a failure. This interface is also used to force switch over from designated main to standby by manual (user) control.

8) Control and management function. This function could interface with for example a PC or workstation to permit configuration of the Basestation's, providing the control, management, bandwidth management, configuration, alarm and diagnostic interface.

9) Failure of common elements. Upon the failure of common circuit elements (power supply, processor etc) all the functions on the failed system will be transferred to the Standby system.

10) It is envisaged that some UDTs or UDR5 may not require protection and these will be locked to the worker Basestation 11) Alarm and diagnostics function. This function could provide the required display and electronic interface facilitating service and maintenance and can display alarms and equipment status via visual and/or audible means integrated into the Basestation (in addition to the ability to read alarms via the Control and Management function interface described above.

5. Wireless Transmitter Synchronization The wireless transmission could be synchronized across all transmitters in the system to ensure that only one transmitter is enabled at any time to maximise bandwidth, minimise latency and avoid wireless phasing and interference effects. The active wireless transmitters on the system could include both the Basestation worker wireless transmitter and all worker UDTs.

A low rate synchronization packet could be broadcast from the Basestation to all UDT's over the back-channel (see Error! Reference source not found. para 5) The synchronisation packet contains the timeslot allocation for each transmitter based on its required bandwidth.

The Basestation transmitters are locally synchronised as the Basestation itself controls the synchronisation function Refer to Fig.3 Timing Diagram showing the relationship between the Synchronisation signal sent from the Basestation to each UDT and the data from the "n" UDT) and Fig.4 (Broadcast synchronization packet topology) 6. Monitoring and protection switching Several monitoring and protection embodiments are possible and a suitable scheme is detailed below. However other embodiments can be envisaged and the novelty and uniqueness of the patent shall stand if other schemes are deployed.

6.1. In band Test Tone monitoring A high frequency (above the required analogue band) or low frequency (below the required analogue band) in band monitoring tone could be deployed as a test tone. Each path could carry an in band test tone injected as close a possible at the analogue input and monitored as close as practical to the analogue output. The test tone could be carried along with the user data across the complete path. The test tone would be filtered out of the received analogue path and monitored. Depending on the status of the received test tone, a decision is taken to switch either the transmit or receiver end of the path as descnbed below. (If the test tone monitoring indicates the path is working normally, then no action is taken) Note that this test tone is sent from all transmitters whether deployed in the base station or the U Dl's. The ability to detect and monitor the test tone is incorporated in all receiver pairs -namely the Basestation, UDT's and UDR's. It is this ability that enables end switching to occur on detection of a fault at any of the elements deployed in this system.

6.2. Receive end switching At the receiving end the working path could be selected from either the main or standby depending on the state of the Test Tone monitor see Fig.5 (Protection switching and monitoring at the receiving end).

6.3. Transmit end switching As previously explained, each transmitting function (Basestation or UDT) also contains a pair of receivers that are local (typically in the same package/enclosure) to the transmitter.

These receivers could be configured to receive the packets from its own local transmitter on both Main and Standby receivers. Thus a decision can be made as to whether the worker transmitter (normally the Main) has failed and if necessary reconfigure all the transmit functions to the standby. See Fig.6 (Protection switching and monitoring at the transmit end)