GB2330493A - Digital receiver in which user is audibly informed on drop in signal quality - Google Patents

Abstract

In analog receivers hissing accompanies poor reception. In digital receivers no such forewarning of signal loss occurs and so some indication may be artificially provided. This application describes the use of audible tones whose number indicates the signal quality. The tones may be delivered at a convenient position in the speech signal.

Description

A Radio Receiver Field Of Invention This invention relates to a radio receiver particularly, but not exclusively, for use in a digital portable radio.

Background Of The Invention Users of portable analogue radio transmitting and receiving apparatus will be familiar with the loss in signal quality that accompanies use close to the limits of reception. As the signal gets weaker because of the increase in range or by approach to a poor reception area the quality of the received signal is readily apparent to the user. The user is thus aware that the limits of the coverage are being approached and can walk around the poor reception area or otherwise prepare for a break in contact.

With digital radio communication there is little or no warning of the range of coverage being reached for quality is maintained to the point when the transmitted signal is lost. This can be very frustrating to a user of the radio for the user does not have the opportunity to "walkaround" the poor reception area or else to prepare for the break in contact.

One known attempt to alleviate this problem has been to introduce so called "comfort noise" at a received audio level which varies in an inverse manner to the received signal strength. This artificially recreates the gradual degradation present in analogue systems. Thus, while an indication is given to the user that the limits of coverage are being reached the audio signal is also be degraded in quality.

It is an object of the invention to provide an indication of the approach of a limit of coverage is being approached which does not result in significant degradation of the audio signal.

Summarv Of The Invention According to the invention there is provided a radio receiver comprising: an audio output section, a receiver section for detecting a signal to be received by the receiver, a received signal quality determinater for providing an output according to a received signal quality, an auditory generator, responsive to an output of the received signal quality determinater, for generating at least one audible output by the audio output section indicative of the signal quality in addition to an auditory output derived from the received signal.

By providing an auditory output indicative of the signal quality in addition to rather than in combination with the approach of a poor reception area can be indicated without the desired auditory output being masked or otherwise corrupted. Thus, the clarity of the communication remains to the extremes of reception but an indication of the possibility of communication breakdown is also given.

There are a number of ways in which the signal quality may be determined. For example, the strength of the received signal may be used as the quality indication utilising a received signal strength indicator. That is to say, the stronger the signal is the higher the quality is considered to be.

The bit error rate may also be used to provide an indication of the signal quality. The higher the bit error rate that is detected, the lower is the quality of the signal.

A combination of the ways is also possible, for example, a combination of both received signal strength and bit error rate may also be used to generate a quality indication.

The auditory output indicative of the quality may be output at the start of a message, the end of the message or periods of the message that would otherwise be silent or any combination of these. Where the output is provided at the end of the message it will usefully serve as an indication that the message has finished.

Brief Description Of The Drawings A specific embodiment of the invention will now be described by way of example only with reference to the drawings in which: Figure 1 is a receiver in accordance with a preferred embodiment of the invention; Figure 2 is a set of explanatory drawings showing speech output together with pulses which indicate the received signal strength.

Detailed Description Of A Specific Embodiment With reference to Fig 1 a portable radio transceiver 1 includes a microprocessor 2 linked to memory 3. The microprocessor 2 is also linked to a receiver section 4, a transmitter section 5, an antenna switch 6 , a received signal quality determinater in the form of a received strength signal indicator 7, an audio amplifier 8 and an input amplifier 9.

The antenna switch 6 selectively couples the receiver and transmitter sections to an antenna 10 under the control of the microprocessor in a well known manner.

The amplifier 8 drives a speaker 11 whilst the input amplifier is connected to a microphone 12. An analogue to digital converter 13 is provided between the input amplifier 9 and the microprocessor 2. A digital to analogue converter 14 is connected between the audio amplifier 8 and the microprocessor 2.

The operation of the transceiver will be for the most part familiar to the man skilled in the art of radio transceivers. The transceiver 1 is a digital radio transceiver and it is controlled by the microprocessor 2 in accordance with a software program held in the memory 3.

Signals received by the antenna 10 are passed to the receiver section 4 where they are detected and amplified. The amplified detected signal are then passed to the microprocessor 2 where they are processed. The processed signals are then converted to analogue form by the digital to analogue converter 14 before being output by the speaker 11. This forms an audio output section, Speech is transmitted in the following way. A user of the transceiver speaks into the microphone 2 and the resultant electrical signal amplified by the input amplifier 9. The amplified signal is then converted by the analogue to digital converter 13 to digital form. The digital signal is processed by the microprocessor 2 and the processed signal passed to the transmitter section 5. here the signal is applied to a power amplifier and the amplified signals passed to the antenna 10 from whence they are transmitted.

The received signal strength indicator 7 is of conventional form and it provides a signal to the microprocessor 2 indicative of the received signal strength.

As well as the earlier referred to software program, the memory 3 also holds in digital form a strength indicator tone. This tone when passed by the microprocessor 2 via the digital to analogue converter 14 and the amplifier 8 to the speaker 11 will produce an audible tone to indicate to the user the strength of the received signal. Thus these components comprise an auditory generator. The manner in which this is achieved will now be described.

A transmission is received and the received signal strength measured by the received signal strength indicator 7. That value is compared with a set of threshold values by the microprocessor 2 (the threshold values being held in memory 2). This results in a quantification of the strength into six bands from the weakest signal to the strongest signal.

The tone is output before and after the received speech is passed from the microprocessor 2 to the audio amplifier 8 and speaker 11. The number of tones indicates the strength form the strongest signal indicated by five tones to the weakest signal indicated by the absence of a tone.

Figs 2a shows the output from the speaker 11 when the signal is at its strongest. It will be seen that there are five tones tl to t5 before and after the received speech.

As the signal weakens the number of tones output will fall. Fig 2b, 2c and 2d show the situation when four, three and one tones are output.

Fig. 2e shows the situation where the signal is at its weakest and no tones are output with the speech.

In this particular embodiment the variation of signal strength is indicated by the number of identical tones present. In alternative embodiments the auditory significance of the tones may be varied by varying the pitch, frequency or volume to indicate the variation in signal strength. The invention is also applicable to receivers.

In some embodiments it may be desirable to enable a user to configure set the levels to which the tones correspond. Also to avoid annoyance to the user it may be desirable for the tones or other auditory indicators to be output at certain signal levels only. For example, the tones might start to be output only as the received signal strength approaches critical levels. Thus, in normal operation the tones would not be present until the edge of coverage was approached. This might alleviate irritation that a user might otherwise experience.

Claims (8)

1. Claims Claim 1. A radio receiver comprising: an audio output section; a receiver section for detecting a signal to be received by the receiver; a received signal quality determinater for providing an output according to a received signal quality; an auditory generator, responsive to an output of the received signal quality determinater, for generating at least one audible output by the audio output section indicative of the signal quality in addition to an auditory output derived from the received signal.
2. Claim 2. A receiver as claimed in claim 1 wherein the auditory generator generates a tone or tones.
3. Claim 3. A receiver as claimed in claim 2 wherein the auditory generator varies the auditory significance of the tone or tones to indicate the signal quality.
4. Claim 4. A receiver as claimed in claim 3 wherein the auditory significance is varied by varying the number of tones.
5. Claim 5. A receiver as claimed in claim 4 wherein the number of tones varies such that the poorest quality signal has fewer tones than greater quality signals.
6. Claim 6. A receiver as claimed in claim 5 wherein the poorest quality signal results in no tones being output. Claim
7. 7. A receiver as claimed in any preceding claim wherein a tone is output before and after an auditory output derived from the received signal.
8. Claim 8. A receiver as hereinbefore described with reference to and as illustrated by the drawings.