LTE Uplink Control Channel Resource Allocation
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Solution Overview
Problem
In LTE systems, the efficient transmission of channel quality indicators (CQI) and acknowledgement information (ACK/NACK) over the physical uplink control channel (PUCCH) is hindered by limited radio resources, necessitating methods to multiplex multiple users effectively.
Innovation Solution
A user device transmits uplink control channels using a single carrier scheme, employing channel quality indicator generating and transmitting units that utilize orthogonal sequences and block spreading code sequences to efficiently convey CQI and ACK/NACK, even when no radio resources are allocated for data channels, by structuring slots with reference symbols and specific symbol elements representing channel quality indicators and acknowledgement information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the proportion of the frequency band occupied by the PUCCH to the system frequency band is increased to enable more users to transmit control information, then the number of users who can smoothly report CQIs and ACK/NACK is improved, but the amount of resources for transmitting the physical uplink shared channel (PUSCH) is reduced
Solution Approach 1:
The PUCCH resource allocation is segmented by slot within each subframe. The invention assigns different CQI reporting opportunities to different slots (even and odd slots), allowing multiple users to report control information at different time instances. This temporal segmentation enables more users to access the PUCCH without requiring simultaneous frequency resources, thereby resolving the contradiction between supporting more users and preserving PUSCH resources.
2Productivity
If the proportion of the frequency band occupied by the PUCCH to the system frequency band is decreased to improve PUSCH throughput, then the throughput is improved, but users not transmitting PUSCH cannot smoothly report CQIs and ACK/NACK
Solution Approach 1:
The invention implements periodic CQI reporting where users report channel quality information at regular intervals (e.g., every other slot or subframe) rather than continuously. This periodic action reduces the instantaneous resource requirements for PUCCH, allowing more frequency resources to be allocated to PUSCH for improved throughput, while still ensuring reliable control information reporting at appropriate intervals for scheduling and link adaptation.
3Productivity
If multiple users are multiplexed in the PUCCH to efficiently use radio resources, then the efficiency of radio resource usage is improved, but methods for mapping CQIs and ACK/NACK and for multiplexing multiple users have not been fully discussed
Solution Approach 1:
The invention segments the multiplexing approach by separating CQI and ACK/NACK transmissions into different time slots and using different reference signal cyclic shifts for different user groups. This segmentation simplifies the multiplexing process compared to attempting to multiplex all control information types simultaneously, reducing implementation complexity while maintaining efficient resource usage through structured user separation.
Solution Approach 2:
The invention introduces the time dimension (slot structure within subframe) as an additional degree of freedom for user multiplexing. By allocating different users to different slots and using reference signal cyclic shifts, the system transforms a one-dimensional frequency-division multiplexing problem into a multi-dimensional resource allocation problem, enabling efficient multiplexing of multiple users without excessive complexity.
Data Source
AI summary
A user device transmitting at least an uplink control channel using a single carrier scheme includes a channel quality indicator generating unit configured to generate a channel quality indicator indicating a downlink radio propagation condition; and a transmitting unit configured to transmit the uplink control channel including the channel quality indicator using a dedicated frequency band when no radio resource is allocated for transmission of an uplink data channel. The transmitting unit is configured to transmit a predetermined number of unit blocks in each slot period. If a system bandwidth is greater than a predetermined value, a set of factors used to multiply some of the unit blocks belonging to the same slot and containing the same information represents an orthogonal sequence; and a predetermined number of symbol elements constituting each of the some of the unit blocks represent at least a part of the channel quality indicator.