ACK/NACK Channel Segmentation in OFDMA Systems
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Solution Overview
Problem
The existing methods for signaling ACK/NACK messages in OFDMA communication systems lead to varying control channel sizes, causing inefficiencies and requiring additional signaling or complex recovery mechanisms.
Innovation Solution
The method involves separating the ACK/NACK messages from the control channel and transmitting them on a dedicated ACK/NACK channel using a different subset of sub-carriers, with the sub-carriers determined by a direct mapping function based on the uplink data sub-carriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If ACK/NACK messages are sent in the downlink control channel, then the control channel can carry both control data and acknowledgment information, but the size of the control channel will vary depending on the situation of the user device
Solution Approach 1:
The patent segments the downlink resources into two separate channels: a control channel for control data and a dedicated ACK/NACK channel for acknowledgment messages. This segmentation resolves the contradiction by fixing the control channel size while providing a separate variable-sized ACK/NACK channel, thus maintaining adaptability without control channel size variation.
Solution Approach 2:
The patent extracts the ACK/NACK messaging function from the control channel and places it in a separate dedicated channel. This extraction resolves the contradiction by removing the source of size variation from the control channel while preserving the adaptability of the overall system through the dedicated ACK/NACK channel.
2Adaptability or versatility
If control channel size varies depending on user device situation, then the channel can adapt to different needs, but additional signaling or complex recovery mechanisms are required
Solution Approach 1:
By segmenting control data and ACK/NACK messages into separate channels, the patent eliminates the need for additional signaling to indicate ACK/NACK resource allocation. The control channel maintains a fixed size while the dedicated ACK/NACK channel handles variable acknowledgment needs, reducing signaling overhead.
3Productivity
If ACK/NACK messages are transmitted on the same channel as control data, then resource utilization is maximized, but resource allocation becomes complex and less uniform
Solution Approach 1:
The patent segments resources into dedicated control channel resources and dedicated ACK/NACK channel resources. This segmentation simplifies resource allocation by providing clear, separate resource pools for different functions, reducing allocation complexity while maintaining high overall resource utilization through the dedicated ACK/NACK channel.
Data Source
AI summary
A communications system is described in which user devices are allocated sub-carriers on which to transmit uplink data to a base station. ACK/NACK messages for the data transmitted on the uplink are then transmitted by the base station on sub-carriers that depend on the sub-carriers used to carry the uplink data. A direct mapping function is preferably used to determine the sub-carriers to be used for the ACK/NACK messages from the uplink sub-carriers. In another embodiment, the ACK/NACK messages are transmitted to the user devices on sub-carriers that are previously identified to the user devices, preferably by transmitting one or more index values to the user device in a control channel thereof.