US 6,445,686 B1 · Method and apparatus for improving the quality of speech signals transmitted over wireless communication facilities

Abstract

It has been recognized that in a wireless communication system certain frames of encoded speech data transmitted between a base station and a mobile unit, or between a mobile unit and a base station, are more critical than others. A frame may be determined to be erased by the receiving base station or mobile unit due to noise or interference over the wireless transmission medium. If an erased frame cannot be recreated from one or more preceding frames, then it is more critical than a frame that can be recreated by an extrapolation of data from one or more preceding frames. Accordingly, on a frame-by-frame basis, each frame in a sequence of frames is identified as being critical or non-critical. Each frame that is identified as being critical is then transmitted in a manner that is more robust than the manner in which non-critical frames are transmitted to decrease the likelihood that a receiver will determine that the frame is erased. In a CDMA system, a current frame is identified as being critical by forming a weighted sum of the differences between corresponding frame parameters that represent the current frame and frame parameters that represent a previous frame. That weighted sum is compared with a threshold. If the weighted sum exceeds the threshold, then the current frame is classified as being a critical frame and is transmitted at a higher output level than non-critical frames are transmitted.

Claims32

Dependent claims

A method for transmitting a digital signal that is arranged in a sequence of frames to a receiver over a transmission medium, the method comprising the steps of:

on a frame-by-frame basis, determining before being transmitted whether a current frame as a whole in the sequence of frames is a critical frame or a non-critical frame by comparing the current frame with at least one previous frame in the sequence of frames;
if the current frame is determined to be a non-critical frame, transmitting the entire non-critical current frame as a whole in a first manner;
and
if the current frame is determined to be a critical frame, transmitting the entire critical current frame as a whole in a second manner that is more robust than the first manner, the second manner being such that there is less of a likelihood as compared to the first manner that the receiver will determine that the current frame is an erased frame.

1 more element

A method of transmitting a digital speech signal that is arranged in a sequence of frames over a wireless transmission medium to a receiver from a transmitter, the method comprising the steps of:

on a frame-by-frame basis, determining at the transmitter before being transmitted whether a current frame as a whole in the sequence of frames is a critical frame or a non-critical frame by comparing the current frame with at least one previous frame in the sequence of frames;
if the current frame is determined to be a non-critical frame, transmitting the entire non-critical frame as a whole over the wireless transmission medium in a first manner;
and
if the current frame is determined to be a critical frame, transmitting the entire critical current frame as a whole over the wireless transmission medium in a second manner that is more robust than the first manner, the second manner being such that there is less of a likelihood, as compared to the first manner, that the receiver will determine that the current frame is an erased frame.

1 more element

A transmitter for transmitting a digital speech signal that is arranged in a sequence of frames over a wireless transmission medium to a receiver comprising:

means for determining before it is transmitted whether a current frame as a whole in the sequence of frames is a critical frame or a non-critical frame on a frame-by-frame by comparing the current frame with at least one previous frame in the sequence of frames;
and
means for transmitting the entire current frame as a whole in a manner determined according to whether the current frame is-determined to be a critical or a non-critical frame, an entire non-critical frame being transmitted as a whole in a first manner and an entire critical frame being transmitted as a whole in a second manner that is more robust than the first manner, the second manner being such that there is less of a likelihood as compared to the first manner that the receiver will determine that the current frame is an erased frame.

Dependencies are inferred from the claim text.

Method and apparatus for improving the quality of speech signals transmitted over wireless communication facilities

Life of this patent

Method and apparatus for improving the quality of speech signals transmitted over wireless communication facilities

Life of this patent

Abstract

Claims32