Analog radio system with acoustic transmission properties
AssigneeTelecommunications Research Laboratories
InventorGrant McGibney
Life of this patent
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Abstract
This invention modulates voice signals so that the radio waves behave the same in the radio medium as sound waves would in the acoustic medium. This is accomplished by segmenting the voice signal and compressing the segments in time before transmitting them through the radio channel. If the compression factor is correct, the distortion sounds natural to the ear because the characteristics of the radio channel match those normally encountered in the acoustic channel. The radio signal will then inherit many of the good properties of acoustic voice signals including resistance to flat fading and tolerance of frequency selective fading.
Claims29
A method of radio communication, the method comprising the steps of:
- time compressing a speech signal to form a time compressed speech signal;
- time multiplexing the time compressed speech signal with digital control signals to generate a TCM signal, the speech signal being compressed sufficiently to avoid flat fading without producing noticeable multipath echoes in a speech signal recovered from the TCM signal;
- and
- transmitting the TCM signal to a receiver.
Apparatus for radio communication, the apparatus comprising:
- a time compression circuit connected to receive a speech signal and having as output a time compressed speech signal, the time compression circuit having a compression factor that maps radio channel delay spread to acoustic delay spread;
- a multiplexer connected to receive the time compressed speech signal and a digital control signal and having as output a TCM signal;
- and
- a transmitter connected to receive and broadcast the TCM signal.
Apparatus for radio communication, the apparatus comprising:
- a receiver connected to receive a TCM signal including a time compressed signal and a control signal;
- a controller connected to receive the control signal;
- and
- a time decompression circuit connected to receive the time compressed signal and having as output a time expanded speech signal, in which the time expanded speech signal is expanded from a compression factor selected to map radio channel delay spread.
A method of radio communication, the method comprising the steps of:
- time compressing a speech signal to form a time compressed speech signal by forming the speech signal into voice segments and time compressing the voice segments to form time compressed voice segments;
- adding a precursor to each time compressed voice segment before transmitting the time compressed voice segment;
- time multiplexing the time compressed speech signal with digital control signals to generate a TCM signal;
- and
- transmitting the TCM signal to a receiver using a linear modulator.
Dependencies are inferred from the claim text.