Wireless Access Sub-Channel Selection for Collision Avoidance
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Solution Overview
Problem
In radio communication systems, concurrent access request signals from multiple communication terminals often result in collisions, leading to increased time required to initiate communication and reduced throughput due to the need for retransmissions and random back-off times.
Innovation Solution
A communication terminal apparatus that selects a different sub-channel for retransmitting access request signals based on the reception quality of pilot signals, reducing the probability of collisions and eliminating the need for random back-off times by dynamically changing the sub-channel selection scheme.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If multiple communication terminals transmit access request signals concurrently on the same RACH resource, then the access request can be sent quickly, but collision occurs and the base station cannot receive the signals
Solution Approach 1:
The RACH resource is segmented into multiple sub-channels in the frequency domain. Terminals select different sub-channels for transmission, dividing the collision-prone single resource into multiple independent transmission paths, thereby reducing collision probability while maintaining fast access.
Solution Approach 2:
The patent introduces frequency domain diversity by allocating multiple sub-channels, transforming the single-dimensional time-based access into a multi-dimensional resource allocation scheme that includes frequency resources, thus providing alternative paths for signal transmission.
2Reliability
If random back-off time is used for retransmission, then collision probability is reduced, but the time required to start communication becomes long
Solution Approach 1:
The sub-channel selection is dynamically adjusted based on transmission history. The terminal selects a different sub-channel for each retransmission attempt, creating a dynamic resource allocation strategy that systematically explores available resources rather than using static random back-off timing.
Solution Approach 2:
The terminal preliminarily determines the sub-channel selection sequence before actual transmission. By pre-planning which sub-channel to use for each retransmission attempt, the system avoids the need for random waiting periods and can immediately retry on a different frequency resource.
3Device complexity
If the same sub-channel is used for retransmission, then the transmission process is simple, but collision probability remains high
Solution Approach 1:
The frequency resource is segmented into multiple sub-channels, providing diverse transmission paths. This segmentation maintains simplicity in the transmission process while significantly improving reliability by offering alternative frequency resources when collisions occur.
Data Source
AI summary
A communication terminal apparatus that exhibits a shorter time period required until a start of communication and causes the throughput in the wireless communication system to be less reduced. In this apparatus, when the number, N, of retransmissions notified by a response determining part (107) is zero, a subchannel-to-be-used selecting part (108) selects a subchannel, among others, which exhibits the highest order one of the reception qualities of the subchannels notified by a reception quality determining part (106), and then notifies the selected subchannel to a subchannel allocating part (113). When the notified number, N, of retransmissions is one or more, the response determining part (107) selects a subchannel which exhibits the N-th lower order reception quality than the highest order reception quality, based on the reception qualities of the subchannels notified by the reception quality determining part (106) for a pilot signal received after a transmission of the latest access request signal, and then notifies the selected subchannel to the subchannel allocating part (113).