Wireless Content Distribution Using Selective Block Retransmission
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Solution Overview
Problem
In multi-hop networks, using erasure correction codes for content distribution leads to inefficiencies due to increased packet collisions, power consumption, and retransmissions when reception stations cannot directly communicate with the transmission station, necessitating data transfer among stations, which exacerbates communication issues.
Innovation Solution
A content distribution system that employs erasure correction coding with a transmission unit transmitting selected encoded and redundant blocks based on reception responses, reducing unnecessary retransmissions by selecting blocks that have not been successfully received, thereby optimizing communication efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If erasure correction coding is used for content distribution in multi-hop networks, then data reliability is improved, but communication efficiency deteriorates due to increased packet collisions and power consumption
Solution Approach 1:
The content data is divided into multiple encoded blocks, and the system selectively transmits only the necessary number of blocks based on reception responses. This segmentation allows the system to maintain reliability through erasure correction while improving communication efficiency by avoiding unnecessary transmissions of all blocks to all reception stations.
Solution Approach 2:
The system transmits a partial set of encoded blocks (K2 pieces selected from K1 encoded blocks and M redundant data blocks) rather than all possible blocks. By transmitting only the necessary subset based on actual reception needs indicated in reception responses, the system achieves sufficient reliability without the excessive action of transmitting all blocks to all stations, thereby reducing packet collisions and power consumption.
2Reliability
If all reception stations transfer received data in multi-hop networks, then data delivery is ensured, but packet collisions and power consumption increase
Solution Approach 1:
The system enables reception stations to selectively transfer data based on local conditions and needs. Instead of all stations uniformly transferring all received data, each station determines whether to forward specific blocks based on reception responses and local decoding status, reducing unnecessary transmissions and power consumption while ensuring data delivery where needed.
Solution Approach 2:
Reception stations perform partial data transfer by forwarding only the specific encoded blocks that are needed and have been successfully received, rather than transferring all received data. This selective partial action reduces the overall number of packets in the network, decreasing packet collisions and power consumption while maintaining data delivery reliability.
3Reliability
If retransmission is performed for all reception stations when decode failure occurs, then data reliability is maintained, but communication efficiency declines as the number of reception stations increases
Solution Approach 1:
The system implements a feedback mechanism where reception stations send reception responses indicating which blocks were successfully received and which need retransmission. Based on this feedback, the transmission station selectively retransmits only the necessary blocks to the specific reception stations that need them, rather than performing blanket retransmissions to all stations. This maintains data reliability while improving communication efficiency by reducing unnecessary retransmission traffic.
Data Source
AI summary
A subject distribution apparatus, which is a content distribution apparatus, includes a transmission unit (121). The transmission unit (121) transmits K2 pieces of blocks selected from among K1 pieces of encoded blocks (132) and M pieces of redundant data blocks (133) based on erasure correction coding, together with a transmission source identifier, as wireless signals. Further, when a destination identifier indicated in a reception response received from each content distribution apparatus is consistent with an apparatus identifier of the subject distribution apparatus, the transmission unit (121) transmits K2-Rmin pieces of blocks selected from among blocks that have not been transmitted among the K1 pieces of encoded blocks (132) and the M pieces of redundant data blocks (133), as wireless signals, where the relatively small number of blocks among the number of blocks that have succeeded to be received as indicated in each received reception response is denoted as Rmin.