DPCCH2 Power Control for Weak Uplink Links
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Solution Overview
Problem
In wireless communication networks, especially in heterogeneous environments, weak uplink control channels can lead to unreliable reception of important control information due to link quality imbalances between radio access nodes, particularly during soft handover scenarios, where the best uplink cell is a non-serving cell.
Innovation Solution
The introduction of a dedicated physical control channel2 (DPCCH2) with a separate fractional dedicated physical channel for transmit power control, allowing power control solely by the serving cell, and using a different slot format to ensure reliable communication of transmit power control commands, thereby addressing the issue of weak links and link imbalances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If DPCCH is power controlled by all cells in active set including non-serving cell, then power control is distributed across multiple nodes, but reliable reception of control information at serving cell cannot be guaranteed
Solution Approach 1:
The patent segments the power control function by introducing a separate DPCCH2 channel that is exclusively power-controlled by the serving cell, distinct from the original DPCCH channel. This segmentation allows the serving cell to independently control the power of control information channels without being constrained by the distributed power control of the non-serving cell, thereby ensuring reliable reception at the serving cell while maintaining the benefits of multi-node power control for other channels.
Solution Approach 2:
The DPCCH2 channel acts as an intermediary mechanism that bridges the gap between distributed power control requirements and serving cell reception reliability. By introducing this intermediate channel with dedicated serving cell power control, the system can maintain distributed power control for data channels while ensuring that control information channels are reliably received by the serving cell.
2Device complexity
If legacy DPCCH is used as reference channel for HS-DPCCH and E-DPCCH, then channel structure is maintained, but difficult to ensure reliable reception at serving cell when best UL is non-serving cell
Solution Approach 1:
The patent segments the reference channel function by introducing DPCCH2 as a dedicated reference channel for control information channels. This allows HS-DPCCH and E-DPCCH to have separate reference channels optimized for serving cell reception, rather than relying on the legacy DPCCH that is power-controlled by all cells including non-serving cells.
Solution Approach 2:
The patent applies local quality by making DPCCH2 specifically optimized for serving cell power control and reference functionality. Instead of using a universal DPCCH channel that serves multiple purposes and is controlled by multiple nodes, the DPCCH2 channel has localized quality characteristics tailored for ensuring reliable reception at the serving cell.
3Reliability
If separate DPCCH2 channel is introduced with serving cell-only power control, then reliable control information reception is ensured, but device and network complexity increases
Solution Approach 1:
The DPCCH2 channel is designed with multi-functionality to reduce overall system complexity. It serves as both a reference channel for power control and a reference for demodulation of control information channels, combining multiple functions into a single channel structure. This universal approach reduces the need for additional separate channels while maintaining reliability.
Data Source
AI summary
A method in a network node (115A-C, 120, 130) comprises providing (704) to a user equipment (UE) (110A-C) a dedicated physical control channel (DPCCH), the DPCCH having an associated first fractional dedicated physical channel (F-DPCH) for conveying transmit power control (TPC) commands to the UE for power controlling the DPCCH, the first F-DPCH having a first allocated slot format; providing (708) to the UE a dedicated physical control channel2 (DPCCH2) (502), the DPCCH2 comprising an uplink control channel power controlled by the network node for communicating TPC commands to the network node, the DPCCH2 having an associated second F-DPCH for conveying transmit power control commands to the UE for power controlling the DPCCH2, the second F-DPCH having a second allocated slot format different from the first allocated slot format; and communicating (712) to the UE an uplink TPC command on the second F-DPCH having the second allocated slot format.