Speech Packet Compression for Bandwidth-Limited Retransmission
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Solution Overview
Problem
In CDMA vocoder systems, excessive packet loss due to low transmission power results in unacceptable voice quality, and retransmitting full-rate packets in limited bandwidth channels is challenging while maintaining adequate voice quality.
Innovation Solution
A method for vocoder systems that involves receiving negative acknowledgments for corrupted speech packets, compressing and combining current and replacement packets to form a combined packet, allowing for efficient retransmission in limited bandwidth channels by encoding current speech segments at a lower rate and generating replacement speech parameters from preceding packets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If transmission power is decreased to minimize power consumption, then power efficiency is improved, but packet loss increases resulting in unacceptable voice quality
Solution Approach 1:
The system performs preliminary compression of the speech packet before retransmission. By compressing the packet in advance and combining it with the current packet, the system prepares a reduced-size retransmission that can fit within the limited bandwidth channel, thereby enabling retransmission without requiring excessive power or sacrificing voice quality.
Solution Approach 2:
The invention changes the data rate parameter of the retransmitted packet by compressing it to a lower rate (e.g., half rate or eighth rate instead of full rate). This parameter change allows the retransmitted packet to occupy less bandwidth, enabling the system to maintain acceptable voice quality while operating at lower transmission power levels.
2Reliability
If retransmission is implemented to maintain voice quality, then voice quality is improved, but available bandwidth for retransmission is reduced
Solution Approach 1:
The system changes the data rate parameter of the retransmitted packet by compressing it to a lower rate. This reduces the bandwidth requirement for the retransmission, allowing the limited available bandwidth to accommodate both the current packet and the retransmitted packet without requiring excessive channel capacity.
Solution Approach 2:
The invention merges the current packet and the compressed retransmitted packet into a single combined packet structure. By combining these packets and transmitting them together, the system efficiently utilizes the available bandwidth, ensuring that both the current speech data and the retransmitted data can be conveyed within the limited channel capacity.
3Reliability
If full-rate packets are retransmitted to maintain voice quality, then voice quality is improved, but transmission power requirements increase
Solution Approach 1:
The system changes the data rate parameter of the retransmitted packet by compressing it to a lower rate (half rate or eighth rate). This parameter change reduces the amount of data that needs to be transmitted, thereby lowering the transmission power requirements while still maintaining adequate voice quality through the combination of compressed and current packets.
Data Source
AI summary
The invention provides a method of retransmitting a speech packet. In one embodiment, the method includes receiving (S702) at a transmitting device (140) a first negative acknowledgement (NACK) from a receiving device (120). The NAK indicates a corrupted first speech packet transmission. The transmitting device then retrieves (S706) a first speech packet associated with the first NACK and compresses (S714-S720) the speech packet to form a replacement speech packet. Next, a current segment of speech is encoded (S808) to form a current speech packet and current speech packet is combined with the replacements speech packet. The combined speech packet is then transmitted (S814) to the receiving device.