WO2005029882A1 - Audio configuration in mobile radio equipment - Google Patents

Audio configuration in mobile radio equipment

Info

Publication number
WO2005029882A1
WO2005029882A1 PCT/NZ2004/000233 NZ2004000233W WO2005029882A1 WO 2005029882 A1 WO2005029882 A1 WO 2005029882A1 NZ 2004000233 W NZ2004000233 W NZ 2004000233W WO 2005029882 A1 WO2005029882 A1 WO 2005029882A1
Authority
WO
Grant status
Application
Patent type
Prior art keywords
audio
path
ancillary
radio
system
Prior art date
Application number
PCT/NZ2004/000233
Other languages
French (fr)
Inventor
Lindsay Allan Lilburn
John Alexander Graham
Original Assignee
Tait Electronics Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date

Links

Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04MTELEPHONIC COMMUNICATION
    • H04M1/00Substation equipment, e.g. for use by subscribers; Analogous equipment at exchanges
    • H04M1/60Substation equipment, e.g. for use by subscribers; Analogous equipment at exchanges including speech amplifiers
    • H04M1/6025Substation equipment, e.g. for use by subscribers; Analogous equipment at exchanges including speech amplifiers implemented as integrated speech networks
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04MTELEPHONIC COMMUNICATION
    • H04M1/00Substation equipment, e.g. for use by subscribers; Analogous equipment at exchanges
    • H04M1/72Substation extension arrangements; Cordless telephones, i.e. devices for establishing wireless links to base stations without route selecting
    • H04M1/725Cordless telephones
    • H04M1/72519Portable communication terminals with improved user interface to control a main telephone operation mode or to indicate the communication status
    • H04M1/72522With means for supporting locally a plurality of applications to increase the functionality
    • H04M1/72527With means for supporting locally a plurality of applications to increase the functionality provided by interfacing with an external accessory

Abstract

A versatile audio processing system for mobile radio equipment. The system is implemented in software and has receive and transmit paths that may be configured for a range of different purposes. Internal or external ancillary devices may be connected to the system and the configuration may be modified during operation of the equipment. A software controller instructs a digital signal processor according to configuration data stored in a database. Ancillary devices are typically identified by their PTT signals.

Description

AUDIO CONFIGURATION IN MOBILE RADIO EQUIPMENT

FIELD OF THE INVENTION

This invention relates to audio systems in mobile radio equipment, and in particular to an audio system that is based in software and can be configured for interaction with a range of ancillary devices. The term "mobile radio equipment" is intended to cover a wide range of devices including both mobile and portable units, network infrastructure, and associated equipment such as line interfaces which may or may not have full radio functionality.

BACKGROUND TO THE INVENTION

Mobile radios are used in many countries for a range of applications and should be able to accommodate a variety of ancillary devices, either external or internal to the radio hardware. Many of these ancillary devices use an audio interface to the radio. The nature of the audio interface required varies widely, creating the need for a versatile audio system in the radio.

Ancillary devices include encryption devices, signalling encoders, modems or other radios for example. These devices usually have different audio interfacing requirements. To some extent the devices can be incorporated into the radio however in many cases this is not possible. Encryption devices, particularly high security types, often use undisclosed proprietary designs or there maybe legal restrictions on distribution for reasons of national security. Certain signalling encoders and modems use proprietary schemes that are only available as hardware modules and cannot be integrated with the radio as a software entity.

In a conventional mobile radio there is a receiver audio processing path and transmit audio processing path. In many prior art systems these chains have been implemented as a series of hardware processing blocks permanently connected together. Every access point within the path requires a separate input or output line. Due to hardware design constraints audio levels and coupling impedances are different for each point, complicating the interface.

Many prior art systems have used semi-discrete hardware or customised analog integrated circuits to provide the necessary audio inputs and outputs from the radio. Semi-discrete hardware based systems either require many 10 lines to enable ancillary access to the necessary points within the audio system or complex and costly analog multiplexing devices with limited flexibility to reduce the IO count. The printed circuit board space and number of components required is also relatively large. Customised analog integrated circuits can overcome many of the disadvantages of a semi-discrete solution but have high engineering costs and require high volume manufacture to be economic. Making a change to a customised analog integrated circuit can also be relatively slow and expensive.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a versatile audio system for at least some types of mobile radio equipment, or at least to provide a useful alternative to existing systems. In general terms, this can be achieved by implementing most of the audio configuration and processing in software with hardware processing limited to a few functions such as level control and buffering. A software controller connects ancillary devices into the audio system through predetermined input and output nodes as required.

In one aspect the invention may broadly be said to consist in an audio system for mobile radio equipment, comprising: a receive path including an RF receiver, digital receive processing stages, and a speaker; a transmit path including a microphone, digital transmit processing stages, and an RF transmitter; an ancillary input path including an input port and a receive path node; an ancillary output path including an output port and a transmit path node; and a path control system that operates the digital receive and transmit processing stages, determines requirements of a range of ancillary devices that may be connected to the input and output ports, and connects the receive and transmit path nodes of the ancillary input and output paths to the digital receive and transmit processing stages.

In another aspect the invention may be said to consist in a method of operating an audio system in mobile radio equipment, comprising: routing outgoing audio signals through digital processing stages of a transmit path, routing incoming audio signals through digital processing stages of a receive path, connecting one or more ancillary audio devices to nodes in the transmit and receive paths, and routing the outgoing and incoming signals through or to the ancillary devices. Preferably the requirements of one or more predetermined ancillary devices such as a fist microphone, encryption module or modem are stored in a database during customisation of the radio. If there is more than one device, then preferably the control system receives PTT signals from the devices and prioritises their access to the audio paths.

LIST OF FIGURES

Preferred embodiments of the invention will be described with respect to the accompanying drawings, of which: Figure 1 schematically shows the main components of a mobile radio unit, Figure 2 outlines the architecture of a software based audio system for the unit, Figure 3 outlines the main components of a microprocessor and signal processing kernel for the audio system, Figure 4 shows a range of nodes that may be used in the audio system, Figure 5 is an example of an internal ancillary device connected to the system, and Figure 6 is an example of an external ancillary device connected to the system.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings it will be appreciated that an audio system according to the invention may be implemented in a variety of ways in a range of different radio equipment. The overall structure and operation of such equipment will be known to a skilled reader and full details need not be given here.

Figure 1 schematically shows a two-way mobile radio including a microprocessor μP, digital signal processor DSP and memory M, all connected through a data bus. The radio provides a speaker 10, microphone 11, push-to-talk PTT control 12 and a keypad 13 for the user. The microphone and speaker are connected to an antenna 14 through respective transmit and receive paths formed by audio hardware 15, RF hardware 16 and codecs 17, in conjunction with the digital signal processor. The RF hardware typically includes an RF transmitter and receiver arrangement having a signal generator, modulator, power amplifier and demodulator, while the audio hardware typically includes audio amplifiers for each of the speaker and microphone, all under control of the microprocessor. An external audio interface 18 is also provided with input and output ports for a range of ancillary devices.

Figure 2 shows how the microprocessor μP and digital signal processor DSP may be implemented to provide a versatile system for audio processing in the radio of Figure 1. The microprocessor operates controller software 20 that interacts with a kernel 21 in the DSP. The controller receives internal and external control signals such as PTT activations and releases and mute/unmute requests. Software in the DSP enables a series of processing blocks in a receive path 22 including a level normaliser, low pass filter LPF, high pass filter HPF, de-emphasis filter, audible and subaudible signalling decoders, and other optional stages as required. Similarly the DSP software enables a series of processing blocks in a transmit path 23 including a level sealer, limiter and low pass filter LPF, pre- emphasis filter, high pass filter HPF, audible and subaudible signalling encoders, and other optional stages as required. Blocks in the receive path are connected by nodes R1-R7 while blocks in the transmit path are connected by nodes T1-T6. The node concept facilitates software controlled configuration of the audio processing with both internal and external access to points or "taps" within the audio system. Note that Figure 2 shows a time averaged perspective of the DSP audio processing system with all blocks represented as being active. In practice, the processing stages are sequential and only one block is active at any time. The nodes act as buffers where input and output data for their respective blocks is stored. The kernel 21 schedules the blocks and the configuration of the nodes. The kernel is effectively a primitive operating system in that it manages the movement of data within the DSP and sets the rules for taps and connections between nodes. These rules ensure that only compatible nodes are connected together, for example the sample rate for all data involved in a node connection must be identical. The kernel has the ability to connect any node to any other node or nodes provided the rules are not violated. The kernel 21 in Figure 2 is a slave to the control software 20 in the microprocessor. The control software instructs the kernel which audio configuration is required at a particular instant and the kernel in turn then executes the instructions and configures the blocks and nodes. The control software therefore indirectly defines the configuration of the audio system, in response to a range of control signals from inside and outside the radio. A database in the radio memory contains data for a range of predetermined and programmable configurations.

The systems shown in Figures 1 and 2 are highly schematic and may be manufactured and configured in a variety of different ways. The control software and signal processing software may reside on common or separate processor chips for example. Then memory also may be provided on a common chip with the control software. In some mobile radio equipment, only part of the overall system may be provided, such as in a line interface device for example, which simply connects other radio devices together and does not necessarily have speaker, microphone, keypad or an external PTT switch for example. Other devices may provide only one or other of the transmit and receive paths. Further, as the core audio system is highly generic there are a large number of possible configurations and in a practice rationalisation is required. Rationalisation is provided by the control software and/or an external programming application resident on a personal computer, for example, that restricts user access or configuration of the audio system to desired levels.

External access to the audio system in Figure 2 is provided through auxiliary input and output ports 24 which are part of the radio hardware. These ports allow an ancillary device 25 to interact with the DSP and tap into or out of the receive and transmit paths 22 and 23. The device is identified by its push-to-talk PTT control signal through a dedicated input port. The auxiliary audio input typically includes DC removal, anti-alias filtering and analog-to-digital conversion ADC, provided as hardware components. The bandwidth and dynamic range of the analog-to-digital converter are chosen to exceed that required by the radio and have minimal effect on signal characteristics. The input is then typically sample rate modified and level scaled within the DSP as required. At this point the data signal is connected to node Al allowing versatile access into the audio system. The auxiliary audio output begins at node AO within the audio system. The sample rate of the data signal at this node is changed to match that of the digital-to-analog converter DAC. The signal is then level scaled and fed to the digital-to-analog converter. Anti-alias filtering is applied to the resulting analog signal and buffered before being fed to the external interface 24. An interface of this kind may also be provided within the radio for internal devices.

Figure 3 shows a range of possible node types in the digital signal processor. Node function can be represented in terms of equivalent hardware elements such as switches. There are typically up to two inputs and outputs on a node. The "Standard" node type simply connects two audio processing blocks together. A node not used as a tap can have this form. The "Bypass-in" node disconnects the audio path and allows injection of an ancillary signal. This is useful for signalling encoders and modem connection. The "Combine" node sums two input signals together into one output. This is useful for the injection of sidetones. The "Bypass-out" node diverts audio out to an ancillary device and disconnects it from the audio chain. This is useful for data modem connection. The "Split" node taps off audio samples to the ancillary device but does not disconnect the signal from the audio chain. This is useful for signalling decoders such as selcall. The "Splice" node combines the Bypass-in and Bypass-out type nodes. This allows the insertion of an ancillary audio processing block in series with the audio chain and is useful for connection of encryption modules. Other node types may also be designed.

Figure 4 shows the control software 20 and kernel software 21 of Figure 2 in more detail. The control software 20 monitors all internally or externally generated events that may influence the configuration or state of the audio tap inputs and outputs. PTT management block 40 monitors and prioritises PTT transitions in the form of assertions or releases, including primary PTT, secondary PTT and ancillary PTT signals. TX and RX management blocks 41 and 42 monitor internal events that request a change in the mute state of the audio taps including mute/unmute requests generated by internal transmit and receive subsystems. Audio source and destination management block 43 receives input from management blocks 40, 41, 42 and also receives external mute/unmute requests from user programmed inputs. Management block 43 arbitrates these internal and external inputs using information from database 44 and generates control signals for the kernel 21. Information from the database includes tap points, types and mute conditions and is updated with changes made to the transmit and receive paths by the kernel.

The kernel 21 in figure 4 receives instructions from the controller 20 and is responsible for operation of the transmit and receive software audio paths through the radio and for creating new taps when required. The kernel maintains a database 45 of node data for the audio paths including audio levels and sample rates. Node search block 46 receives requests from management block 43 and locates the nodes at which to connect the input and output points Al and AO for the ancillary device 25. The search block instructs multiplexer 47 to connect Al and AO to the nearest nodes appropriate for the particular ancillary device. The search block also instructs sealer and rate block to 48 to determine the appropriate interpolation/decimation filtering for the audio tap input or output to which Al and AO are connected, using information from the database 45. The audio sample rates and signal levels at AO or Al are then set before the ancillary device is connected into the audio paths.

The configuration of processing blocks and nodes is usually different for different ancillary devices. For example, the transmit mode audio configuration might be different depending on which device initiated a transmission. Transmission might be initiated by a user pressing the external PTT control on a fist microphone attached to the radio, by an ancillary device or by a standard device internal to the radio. The control software detects which device initiated the transmission from the PTT signal and configures the audio path accordingly. Different devices are prioritised through their PTT signals.

Figure 4 also indicates how the kernel may enable one or more audio probes RN and TN to be attached to any active processing node within an audio path. These taps can be selected from the node types indicated in Figure 3. There are three fundamental forms of audio tap available: Audio Tap Input - the data formed at this processing node is routed to node AO, where it is subsequently filtered as appropriate, and converted to analog form; Audio Tap Output - the data received from node Al is appropriately filtered, digitized, and blended into the real-time audio path; Soft Tap Input - a tone generator capability allows a software generated tone to be introduced into the audio path.

The audio configuration of the radio in Figure 2 may be predetermined for a particular ancillary device, or may be configured during normal operation. The ancillary access points Al and AO may be changed for example, depending on whether the radio is in receive or transmit mode. Encryption modules typically require an audio processing block to be inserted into the receive path in receive mode and the transmit path in transmit mode, for example. In this case splice type nodes are used and the ancillary access point would typically be node R5 in receive mode and node T3 in transmit mode. An ability to reconfigure during operation may also be useful within a single audio path. When a self- learning modem is operated through the radio for example, the paths may be optimised differently for voice or data signals. A low transmission rate might initially be required, and once the channel is found to be clear, the rate can be increased. A reduction in rate might be required if the channel subsequently becomes noisy. Specific functions such as pre or de emphasis may be added or removed from a path.

The digital signal processor used for audio processing is also used for encoding industry standard signalling schemes such as Selective Calling (SELCALL), Continuous Tone Controlled Squelch System (CTCSS) and/or Digital Controlled Squelch (DCS).

Figure 5 shows how an ancillary device may be connected internally to the audio system, specifically an encryption module 50 in this example. The radio is half duplex, and during transmission the encryption module is connected in the transmit path through a splice node at point T4, and during reception, is connected in the receive path through another splice node at point R7.

Figure 6 shows how an ancillary device may be connected externally to the audio system, specifically a high speed modem 60 in this example. The radio is connected to a computer DTE through the modem. A split node at point R2 transfers an incoming signal from the receive path of the radio to a decoder in the modem. A bypass-in node inserts data from the modem into the transmit path at point T12.

Claims

CLAIMS:
1. A control system for a software audio path in mobile radio equipment, including: a software controller that receives control signals from sources internal and external to the equipment including ancillary devices, a signal processor that operates the audio path and provides connection points into the audio path for the ancillary devices in response to the control signals from the software controller.
2. A system according to claim 1 wherein the audio path is either a transmit or receive path between RF hardware and audio hardware in the equipment.
3. A system according to claim 1 wherein the control signals received by the controller include PTT requests and mute/unmute requests.
4. A system according to claim 1 further including a database of information relating to connection of ancillary devices in the audio path.
5. An audio system for mobile radio equipment, including: a receive path including an RF receiver, digital receive processing stages, and a speaker; a transmit path including a microphone, digital transmit processing stages, and an RF transmitter; an ancillary input path including an input port and a receive path node; an ancillary output path including an output port and a transmit path node; and a path control system that: operates the digital receive and transmit processing stages, determines requirements of a range of ancillary devices that may be connected to the input and output ports, and connects the receive and transmit path nodes of the ancillary input and output paths to the digital receive and transmit processing stages.
6. A method of operating an audio system in mobile radio equipment, including: routing outgoing audio signals through digital processing stages of a transmit path, routing incoming audio signals through digital processing stages of a receive path, connecting one or more ancillary audio devices to nodes in the transmit and receive paths, and routing the outgoing and incoming signals through or to the ancillary devices.
PCT/NZ2004/000233 2003-09-25 2004-09-27 Audio configuration in mobile radio equipment WO2005029882A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
NZ528461 2003-09-25
NZ52846103 2003-09-25

Publications (1)

Publication Number Publication Date
WO2005029882A1 true true WO2005029882A1 (en) 2005-03-31

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Country Status (1)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2485270A (en) * 2010-11-04 2012-05-09 Epcos Ag Microphone arrangement

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1997041701A1 (en) * 1996-04-26 1997-11-06 Paradyne Corporation Cellular phone interface for a simultaneous voice/data modem
US6081724A (en) * 1996-01-31 2000-06-27 Qualcomm Incorporated Portable communication device and accessory system
US6128509A (en) * 1997-11-07 2000-10-03 Nokia Mobile Phone Limited Intelligent service interface and messaging protocol for coupling a mobile station to peripheral devices

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6081724A (en) * 1996-01-31 2000-06-27 Qualcomm Incorporated Portable communication device and accessory system
WO1997041701A1 (en) * 1996-04-26 1997-11-06 Paradyne Corporation Cellular phone interface for a simultaneous voice/data modem
US6128509A (en) * 1997-11-07 2000-10-03 Nokia Mobile Phone Limited Intelligent service interface and messaging protocol for coupling a mobile station to peripheral devices

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2485270A (en) * 2010-11-04 2012-05-09 Epcos Ag Microphone arrangement
GB2485270B (en) * 2010-11-04 2017-04-19 Epcos Ag Microphone arrangement

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