Uplink Control Channel Multiplexing for LTE-A Overhead Reduction
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Solution Overview
Problem
The existing LTE-A system faces challenges in optimizing uplink control channel transmission to maintain backward compatibility with LTE Rel. 8 terminals, particularly in Local Area (LA) environments, where the increased bandwidth and different assumptions lead to inefficiencies in control signaling, power consumption, and channel estimation errors.
Innovation Solution
The solution involves applying time division multiplexing and frequency division multiplexing between a sounding reference signal, a control channel, and a data channel, with clustered sub-carrier mapping, allowing the sounding reference signal to function as a demodulation reference signal for the control channel, and transmitting these during the same sub-frame, thereby optimizing frequency diversity and reducing overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate resources are allocated for control signaling and data transmission in LTE-A, then backward compatibility with LTE Rel. 8 is maintained, but uplink control overhead increases and frequency diversity is reduced
Solution Approach 1:
The patent merges control channel transmission with data channel transmission by allowing control signaling to be multiplexed on the same physical uplink shared channel (PUSCH) resources as data transmission. This combining approach eliminates the need for separate dedicated control resources, thereby reducing overall uplink control overhead while maintaining backward compatibility through proper resource allocation schemes.
Solution Approach 2:
The patent makes uplink resources universal by enabling the same physical uplink shared channel resources to serve dual purposes: both data transmission and control signaling. This multi-functionality allows control information to be carried alongside data on shared resources, improving resource utilization efficiency and reducing dedicated control overhead.
2Reliability
If dedicated control resources are allocated in LTE-A, then control signaling reliability is improved, but power consumption increases due to continuous transmission
Solution Approach 1:
The patent implements discontinuous transmission (DTX) for control signaling by allowing control information to be transmitted periodically only when uplink data is present. This periodic action on shared resources eliminates continuous dedicated control transmission, significantly reducing user equipment power consumption while maintaining control signaling reliability through HARQ mechanisms and proper timing alignment.
3Measurement precision
If sounding reference signal and control channel use different resources, then channel estimation accuracy is improved, but resource allocation complexity increases
Solution Approach 1:
The patent applies preliminary action by performing channel estimation using sounding reference signals (SRS) before control channel demodulation. The SRS are transmitted in advance to provide channel state information, which is then used to pre-compute channel estimates that facilitate accurate control channel demodulation without requiring separate dedicated reference signals, thereby simplifying resource allocation.
Solution Approach 2:
The patent makes the sounding reference signal universal by enabling it to serve dual functions: both uplink channel sounding for channel quality indicator (CQI) reporting and demodulation reference signal for control channel demodulation. This multi-functionality eliminates the need for separate control-demodulation reference signals, reducing resource allocation complexity while maintaining channel estimation accuracy.
Data Source
AI summary
A method for performing uplink signaling and data transmission between a terminal device and a network element is described. The method includes applying, during a transmission, at least one of TDM and FDM between a SRS, a control channel, a DRS and a data channel. Clustered sub carrier mapping is applied for the SRS and the control channel. The SRS is transmitted so as to function as a DRS for the control channel. The control channel and the data channel are transmitted during a same sub-frame. The method also includes receiving the SRS and receiving the control channel and the data channel during a same sub-frame. Control information and data are extracted from the control channel and the data channel. The SRS is used as a DRS for the control channel is included in the method. Apparatus and computer readable media are also described.