CRDSA Packet Replicas for Satellite Channel Efficiency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current multiple-access protocols in satellite communications, such as the Aloha protocol, suffer from low efficiency and high packet loss due to access conflicts when multiple users transmit simultaneously, leading to inefficient resource allocation and increased transmission delays.
Innovation Solution
The contention resolution diversity slotted Aloha (CRDSA) protocol generates and transmits multiple replicas of each packet with random time and frequency shifts, allowing for interference cancellation and packet recovery, even in cases of destructive collisions, thereby improving channel utilization and reducing packet loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the Aloha protocol is used for packet transmission, then users can transmit independently without centralized control, but access conflicts occur leading to high packet loss and low channel efficiency
Solution Approach 1:
The patent divides each packet into multiple sub-packets that are transmitted in separate time slots. This segmentation allows individual sub-packets to be transmitted independently without causing conflicts, while the receiver reassembles them into complete packets. This resolves the contradiction by maintaining independent user transmission (improving ease of operation) while eliminating access conflicts (improving reliability).
Solution Approach 2:
The patent implements periodic transmission of sub-packets in sequential time slots rather than simultaneous transmission. This periodic action structure allows multiple users to transmit independently while the system coordinates transmission timing to avoid conflicts. The periodic slot-based approach maintains operational independence while ensuring reliable packet delivery through controlled access periods.
2Productivity
If multiple users transmit simultaneously to increase throughput, then channel utilization improves, but access conflicts increase leading to more packet loss
Solution Approach 1:
By segmenting packets into sub-packets transmitted in separate time slots, the system allows higher channel utilization (more packets transmitted per unit time) while preventing access conflicts. Each sub-packet transmission is isolated in time, so increased transmission volume does not lead to increased conflict-related packet loss.
Solution Approach 2:
The patent enables continuous transmission of sub-packets across multiple time slots without interruption or idle periods. This continuous useful action maximizes channel utilization while the sub-packet structure ensures that conflicts in one slot do not affect other slots, maintaining reliability despite high transmission volume.
3Reliability
If demand assignment protocols are used for bursty traffic, then resource allocation is centralized and controlled, but transmission delays increase and signaling overhead is high
Solution Approach 1:
The patent segments packets into sub-packets that can be transmitted immediately in available time slots without waiting for centralized resource allocation. This eliminates the transmission delays associated with demand assignment protocols while maintaining controlled access through the slot-based structure. The segmentation allows bursty traffic to be handled efficiently without centralized coordination overhead.
Solution Approach 2:
The patent prepares packets for transmission by segmenting them into sub-packets that are ready for immediate transmission in the next available time slot. This preliminary preparation eliminates the need for centralized resource allocation signaling and reduces transmission delays. Users can transmit as soon as their turn comes in the periodic structure without waiting for complex resource assignment procedures.
Data Source
AI summary
A first aspect of the invention is a method of transmitting data packets over a transmission channel shared by a plurality of users, based on the time and/or frequency diversity slotted Aloha technique, in which at least two replicas of each packet to be transmitted are sent over said transmission channel, wherein each replica transports signaling information enabling the other replica(s) of the same packet to be located in the time and/or frequency domain. A second aspect of the invention is a method of recovering packets in the receiver, the method exploiting said signaling information to execute an interference cancellation algorithm for recovering packets corrupted by collisions caused by access conflicts. Other aspects of the invention are a transmitter equipment and a receiver packet recovery equipment adapted to use said methods.