Wireless Control Channel False Alarm Reduction
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Solution Overview
Problem
In wireless communication systems, particularly in LTE and LTE-A, the probability of false alarms occurs when terminals incorrectly detect control channel messages, leading to erroneous uplink transmissions and interference, especially with a large number of configured carriers, as the existing systems lack effective mechanisms to mitigate false alarm probabilities without increasing the size of DCI messages.
Innovation Solution
A terminal is configured to transmit a response only if it receives correctly decoded codewords on both a control channel and another channel, applying additional conditions such as grouping cells or messages to ensure valid receptions, thereby reducing the likelihood of false alarms by requiring simultaneous or specific message characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the terminal monitors multiple control channel candidates across multiple carriers, then the coverage and reliability of control channel reception is improved, but the probability of false alarms increases
Solution Approach 1:
The patent applies feedback by having the terminal send an uplink transmission only when it receives a downlink control channel message, creating a response loop. The base station monitors these uplink transmissions and can provide feedback through acknowledgments or by adjusting subsequent control channel transmissions, thereby reducing false alarms while maintaining reliable communication.
Solution Approach 2:
The patent changes the parameter of response transmission by making it conditional rather than automatic. The terminal evaluates multiple parameters including the presence of valid control channel messages, uplink resource availability, and transmission conditions before deciding whether to transmit, thereby reducing false alarms while maintaining system reliability.
2Speed
If the terminal transmits response to every detected control channel message, then the system responsiveness is improved, but the interference from erroneous transmissions increases
Solution Approach 1:
The patent uses feedback mechanisms where the base station monitors uplink transmissions from terminals and can provide feedback through acknowledgments, power control commands, or scheduling adjustments. This feedback loop allows the system to maintain high responsiveness while reducing interference from erroneous transmissions by correcting terminal behavior based on base station observations.
Solution Approach 2:
The patent changes the transmission parameter from always transmitting to conditionally transmitting based on multiple factors including valid control channel detection, uplink resource allocation, and transmission conditions. This parameter change maintains system responsiveness by transmitting when appropriate while reducing interference by suppressing transmissions when conditions indicate potential errors.
3Reliability
If additional validation conditions are applied to response transmission, then the false alarm probability is reduced, but the device complexity increases
Solution Approach 1:
The patent segments the validation process into distinct conditional checks: control channel message validity, uplink resource availability, and transmission condition evaluation. Each segment handles a specific aspect of the validation, making the overall complex process more manageable and implementable while maintaining high false alarm reduction effectiveness.
Solution Approach 2:
The patent applies preliminary action by having the terminal pre-configure validation rules and thresholds before actual transmission occurs. The terminal prepares by monitoring control channels, evaluating conditions, and deciding whether to transmit in advance, which reduces false alarms while keeping the actual transmission logic relatively simple and manageable.
Data Source
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AI summary
A technique for reducing the probability of false alarms leading to responses of terminals (1) to control channel messages in a wireless communication system, false alarms being when a terminal detects and responds to a control channel message when no such message was sent. This is a particular problem in carrier aggregation in LTE when large numbers of carriers may be configured for a terminal. The terminal is expected to blindly search for a number of possible control channel messages from the base station (21, 22, ... 2n) for each carrier, and determine whether such a message has been correctly received by means of a Cyclic Redundancy Check. With a large number of candidates the probability of falsely detecting a message and responding (e.g. with an erroneous uplink transmission causing interference) can be significant. It is assumed that when there is active data transmission, more than one message (or data packet) is likely to be sent to the terminal (1) at any given moment. Thus by making the validity of a control channel message depend on additional conditions being satisfied, the probability of false alarm can be greatly reduced, without otherwise impacting system operation, for example if the terminal (1) only responds if two (or more) messages with particular characteristics are received in the same subframe.