PHICH Group Energy Allocation for LTE Reliability
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Solution Overview
Problem
In LTE systems, the existing resource allocation methods for acknowledgement channels, such as PHICH, fail to ensure sufficient transmit energy for all mobile terminals, leading to varying error rates due to differing channel conditions, and require equal transmit energy per resource element across groups, which limits energy sharing and increases computational complexity.
Innovation Solution
A method where acknowledgement channels are assigned to channel groups based on predetermined criteria, with required transmit energy determined by channel conditions, and normalized if total energy exceeds available power, allowing energy sharing among groups to ensure reliable transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If equal transmit energy per resource element is allocated across all PHICH groups, then the assignment process is simplified, but mobile terminals with poor channel conditions do not receive sufficient energy for reliable acknowledgement detection
Solution Approach 1:
The patent applies local quality by allocating different transmit energy levels to different PHICH groups based on the channel conditions of mobile terminals assigned to each group. Specifically, PHICH groups serving terminals with poor downlink channel conditions receive higher transmit energy, while groups serving terminals with good channel conditions receive lower energy. This is implemented by calculating required energy per resource element (RE) for each PHICH group based on terminal channel quality metrics (e.g., path loss, SINR) and then allocating energy accordingly, rather than using uniform energy allocation across all groups.
2Reliability
If transmit energy is allocated based on individual mobile terminal channel conditions, then reliable acknowledgement detection is achieved, but the device complexity and computational overhead increase
Solution Approach 1:
The patent segments the PHICH resources into multiple PHICH groups, where each group serves a specific subset of mobile terminals with similar channel conditions. This segmentation allows the base station to manage energy allocation at the group level rather than individually for each terminal, reducing computational complexity. The base station calculates required energy for each PHICH group based on the worst-case or average channel conditions of terminals in that group, then allocates energy to the group, simplifying the overall allocation process while maintaining reliability for all terminals in the group.
Solution Approach 2:
The patent implements partial action by allocating transmit energy to PHICH groups selectively based on the channel conditions of terminals assigned to each group. Instead of uniformly allocating energy to all PHICH groups or calculating individual energy requirements for every terminal, the system calculates and allocates energy only for groups that require it, based on terminal channel quality metrics. This partial allocation approach reduces computational overhead while ensuring that terminals with poor channel conditions receive the necessary energy for reliable detection.
3Quantity of substance
If the number of PHICH groups is increased to serve more mobile terminals, then more terminals can be supported, but the available transmit power per group decreases
Solution Approach 1:
The patent applies dynamics by making the PHICH group configuration adaptive rather than fixed. The base station dynamically determines the number of PHICH groups and the allocation of terminals to groups based on current system conditions, including the number of active terminals, their channel conditions, and available transmit power. This dynamic configuration allows the system to optimize the trade-off between serving more terminals and maintaining sufficient power per group, as groups can be created, merged, or reconfigured based on real-time requirements.
Solution Approach 2:
The patent changes the parameter of transmit energy allocation from a fixed value to a variable that depends on terminal channel conditions and group composition. By adjusting the energy allocation parameter based on measured channel quality indicators (such as path loss, signal-to-interference ratio) and the specific terminals assigned to each PHICH group, the system can serve more terminals with varying power requirements while ensuring that each group receives appropriate energy levels for reliable acknowledgement detection.
4Productivity
If PHICH resources are shared among multiple mobile terminals in the same group, then resource utilization improves, but the transmit energy per terminal must be reduced
Solution Approach 1:
The patent resolves this contradiction by applying local quality at the PHICH group level, where each group is configured with transmit energy appropriate for the channel conditions of its assigned terminals. When multiple terminals share a PHICH group, the group's total transmit energy is allocated based on the channel conditions of the terminals in that group, not on a fixed per-terminal basis. This allows efficient resource sharing while maintaining appropriate energy levels for reliable detection, as the energy allocation is localized to each group's specific requirements rather than applying a uniform reduction across all shared terminals.
Data Source
AI summary
A method and apparatus is provided for assigning resources for an acknowledgement channel, such as the PHICH in LTE systems. Acknowledgement channels for the mobile terminals are assigned to channel groups based on a predetermined assignment criteria. All acknowledgment channels in the same channel group receive acknowledgements on the same downlink resources (e.g., resource elements in OFDM system). A required transmit energy for each channel is determined. If the total required transmit energy for all channels exceeds an available transmit power, the allocated transmit energy for each channel is either scaled down so that the total actual transmit power for all acknowledgment channels is equal to the available transmit power, or some acknowledgment channels are not transmitted.