WO1996019069A1

WO1996019069A1 - Digital cellular telephone with voice feedback

Info

Publication number: WO1996019069A1
Application number: PCT/US1995/016003
Authority: WO
Inventors: Michael T. Coad; James A. Hutchison
Original assignee: Qualcomm Incorporated
Priority date: 1994-12-12
Filing date: 1995-12-11
Publication date: 1996-06-20
Also published as: AU4419796A

Abstract

A cellular radiotelephone (100) which uses voice feedback to announce which key of the keypad (155) has been depressed or to indicate the status of radiotelephone (100). The voice signals for the feedback are stored in memory (150) in a digitized and compressed format. The radiotelephone's speech CODEC (140) decompresses the appropriate digital signal. The CODEC (140) transforms the digital signal to an analog voice signal for use by the radiotelephone's audio output device.

Description

DIGITAL CELLULAR TELEPHONE WITH VOICE FEEDBACK

BACKGROUND OF THE INVENTION

I. FIELD OF THE INVENTION

The present invention relates to radiotelephone communications. More particularly, the present invention relates to voice feedback from a digital cellular telephone.

II. DESCRIPTION OF THE RELATED ART

There are presently multiple types of cellular radiotelephone systems operating. These systems include the advanced mobile phone system (AMPS) and the two digital cellular systems: time division multiple access (TDMA and GSM), and code division multiple access (CDMA). The digital cellular systems are being implemented to handle capacity problems that AMPS is experiencing.

All the cellular radiotelephone systems operate by having multiple antennas covering a geographic area. The antennas radiate into an area referred to in the art as a cell. The antenna coverage allows a mobile cellular telephone to communicate with landline telephones or other radiotelephones while traveling through the geographic area. Cellular radiotelephones typically have a keypad with ten numerical keys and one or more function keys. When making a cellular radiotelephone call, it is necessary to enter the desired telephone number or press a key sequence to recall the desired telephone number from the repertory directory, and press the send key. In order to confirm that the desired telephone number is correct, it is further necessary to review the desired telephone number in the handset display. The foregoing operation requires many actions by the user that are both time consuming and distracting from operation of the vehicle.

Cellular radiotelephones also typically provide status indications to the radiotelephone user. These indications include: roaming, digital or analog cellular service, battery condition, and signal strength. These indications keep the user informed of what the radiotelephone is doing. However, checking the radiotelephone's status requires the user to look at the display indicators. A few analog cellular radiotelephones on the market today provide various types of voice feedback. These types of radiotelephones require a speech generation circuit to generate the voice signal. The speech generator adds cost, weight, and complexity to the analog radiotelephone. There is a resulting need for a more economical way to provide voice feedback in a radiotelephone.

SUMMARY OF THE INVENTION

The present invention encompasses a radiotelephone, with compressed voice feedback, that has the capability of operating in a cellular system. The radiotelephone has a keypad for entering data. Memory stores digital data that is representative of at least one voice signal. A compression/decompression device transforms the digital data from memory into a digital form representative of an analog voice signal. A digital to analog converter transforms the digital voice signal into an analog voice signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of a radiotelephone incorporating the voice feedback of the present invention.

FIG. 2 shows a flowchart of the voice feedback process of the present invention.

DETAILED DESCRD7TTON OF THE PREFERRED EMBODIMENT

The voice feedback function of the present invention is accomplished by using the digital cellular radiotelephone's speech CODEC to decompress stored digital data. The digital data represents a voice signal announcing different functions, receipt of keypad input, or status indications of the radiotelephone. A digital to analog converter then converts the decompressed data into an analog voice signal to be radiated by an audio output device. Since the speech CODEC is already used by the radiotelephone for operation in a digital radiotelephone system, no extra components are required.

A block diagram of the voice feedback apparatus of the present invention, incorporated in a digital cellular radiotelephone (100), is illustrated in FIG. 1. In the preferred embodiment, this apparatus is incorporated in a CDMA type radiotelephone. Alternate embodiments use other types of radiotelephones, including the personal communication system (PCS).

Still another alternate embodiment uses a car kit adapter or desktop adapter to expand the functionality of the voice feedback apparatus. The car kit accessory or desktop adapter includes additional memory to store compressed voice feedback signals and also may provide a speaker phone for hands-free operation. This embodiment provides additional voice signals beyond those stored in the radiotelephone. Such an adapter includes a larger vocabulary than the radiotelephone by itself and may provide additional languages stored in the memory.

The CDMA cellular radiotelephone (100) is comprised of an antenna (105) that radiates and receives the radiotelephone signals. The antenna is connected to a duplexer (110) that couples the receive and transmit paths of the radiotelephone to the antenna. The transmit path modulates (125) and upconverts (115) the signal to be transmitted to the transmit frequency. The receive path downconverts (120) the received signals to baseband and demodulates the signal (130).

Radiotelephone (100) includes a user interface in the form of a display and keypad (155). As is well known in the art, the keypad portion of display and keypad (155) is comprised of a plurality of switches. The radiotelephone display and keypad (155) along with other radiotelephone hardware, including the memory (150), it> controlled by a processor (135). The processor's tasks also include controlling the data to the modulator (125) and from the demodulator (130). This data is in a compressed, digital form that must be converted to an analog voice signal. The digital to analog conversion is accomplished by a coder/decoder (CODEC) (145). The analog voice signal from the CODEC (145) is then broadcast by the radiotelephone audio output device. The CODEC (145) also digitizes an analog voice signal from the radiotelephone's microphone in order for the voice signal to be transmitted by the radiotelephone in a digital cellular system.

If the analog voice signal was just sampled and digitized, a high data rate would be required to transmit the information and large amounts of memory would be needed if the information is to be stored. As an example, using a data rate of 64 kilobits/second to transmit speech.

In order to reduce the data transmission rate and memory required to store speech quality data, a speech CODEC (140) compresses the digitized voice signal from the CODEC (145) and decompresses the digitized voice signal from the processor (135). To accomplish this, the speech CODEC (140) analyzes an analog voice signal to extract the relevant parameters that are then transmitted over the channel and the speech CODEC resynthesizes a received digital voice signal by using the parameters received over the channel. In the preferred embodiment, the speech CODEC (140) uses a code excited linear predictive coding (CELP) scheme. An example of this speech coding process is illustrated in A 4.8 kbps Code Excited Linear Predictive Coder, Thomas E. Tremain et al., Proceedings of the Mobile Satellite Conference (1988).

The function of the speech CODEC (140) is to compress the digitized speech signal into a low bit rate signal by removing all of the natural redundancies due primarily to the filtering operation of the human vocal tract and long term redundancies due to the excitation of the vocal tract by the vocal cords. The preferred embodiment's CELP coder models these operations by two filters: a short term formant filter and a long term pitch filter.

Once the redundancies are removed, the resulting residual signal can be modeled as white gaussian noise that is also encoded. This technique computes the parameters of a filter, referred to in the art as an linear predictive coder (LPC) filter, that performs short-term prediction of the speech wave form using a model of the human vocal tract.

Additionally, long-term effects related to the pitch of the speech are modeled by computing the parameters of a pilch filter that models the human vocal cords.

Finally, these filters must be excited. This is accomplished by determining which one of a number of random excitation waveforms in a code book results in the closest approximation to the original speech when the waveform excites the LPC and pitch filters.

By performing this process, the speech CODEC (140) can significantly reduce the amount of data required to represent speech. This enables the memory (150) to store a greater number of digitized voice signals for the voice feedback function of the present invention.

The memory (150) of the present invention, in the preferred embodiment, is electrically erasable programmable read only memory (EEPROM) or some other type of non-volatile storage. The EEPROM is accessed by the processor (135) to store and retrieve data. Alternate embodiments use other types of memory such as read only memory, electrically programmable read only memory, flash programmable read only memory, battery backed random access memory, or nonvolatile random access memory. In the preferred embodiment, the digitized and compressed voice signals stored in EEPROM are stored at the time of manufacture. Alternate embodiments allow the radiotelephone user to store their own voice enunciators. Other embodiments store the voice signals subsequent to manufacture at a carrier's service center or the store where the phone is purchased. In this way, foreign languages can be used for the voice feedback.

In the preferred embodiment, the memory (150) contains digitized and compressed representations of analog voice signals for annunciating each of the radiotelephone's keys. The memory additionally contains the digitized and compressed voice for the radiotelephone's status indications that include whether the radiotelephone is roaming, incoming call alert, low battery indication, and the type of cellular system (digital or analog) in which the radiotelephone is operating. The voice feedback process of the present invention is illustrated in

FIG. 2. The voice feedback function of the present invention operates by some activity initiating the function such as a key depression or some status indication being required (205). The processor senses these activities and accesses memory for the appropriate digitized and compressed response for that specific activity (210).

The digitized and compressed data is then decompressed by the speech CODEC (215) using the stored speech parameters that were accessed along with the voice data. The speech CODEC then outputs the decompressed digital signal to the CODEC. The CODEC converts the signal from a digital signal to an analog voice signal (220) that is transmitted by the radiotelephone audio output device.

The apparatus and process of the present invention enable a radiotelephone to provide voice feedback without the expense, weight, and extra power requirements of additional speech integrated circuits. By utilizing the speech CODEC already present in a digital cellular radiotelephone, the apparatus of the present invention can store more digitized voice data while providing more accurate voice renditions of the voice feedback.

We claim:

Claims

1. A cellular radiotelephone having voice feedback, the radiotelephone having the capability of operating in a digital cellular mode, the radiotelephone comprising: a plurality of switches for entering data; a first converter for transforming a first analog voice signal into a first digital signal; memory for storing digital data representative of at least one voice signal; an encoder/decoder for transforming the first digital signal into a digital form representative of the first analog voice signal and the encoder/ decoder transforming the digital data, in response to activation of a first switch of the plurality of switches, into a digital voice signal; and a second converter for transforming the digital voice signal into a second analog voice signal.

2. A cellular radiotelephone having voice feedback, the radiotelephone having a plurality of status indications and the capability of operating in a digital cellular mode, the radiotelephone comprising: a plurality of switches for entering data; a first converter for transforming a first analog voice signal into a first digital signal; memory for storing digital data representative of at least one voice signal; an encoder/decoder for transforming the first digital signal into a digital form representative of the first analog voice signal and the encoder/decoder transforming the digital data, in response to a first status of the plurality of status indications, into a digital voice signal; and a second converter for transforming the digital voice signal into a second analog voice signal.

3. A cellular radiotelephone having voice feedback, the radiotelephone having a plurality of status indications and the capability of operating in a digital cellular mode, the radiotelephone comprising: a plurality of switches for entering data; memory for storing digital data representative of at least one voice signal; a speech CODEC for transforming the digital data, in response to either a first status of the plurality of status indications or a depression of a first switch of the plurality of switches, into a digital voice signal; and a CODEC for transforming the digital voice signal into an analog voice signal.

4. The cellular radiotelephone of claim 3 and further including an adapter coupled to the cellular radiotelephone, the adapter comprising a second memory for storing additional digital data.

5. The cellular radiotelephone of claim 3 and further including an adapter coupled to the cellular radiotelephone, the adapter comprising: a second memory for storing additional digital data; and a speaker for transmitting the analog voice signal.