WCDMA NodeB Uplink Signaling Slot Formats
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Solution Overview
Problem
In closed-loop WCDMA systems, there is a trade-off between signaling overhead and UE performance due to the need for frequent updates of pre-coding weights for uplink beam forming and MIMO transmissions, which increases the complexity of channel management and resource allocation.
Innovation Solution
Implementing a dedicated downlink physical channel with multiple WCDMA slot formats to efficiently transmit Transmit Power Commands and other instructions, such as beam forming and MIMO stream settings, allowing adaptive allocation based on UE speed and resource availability, using the WCDMA F-DPCH channel structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large codebook with many code words is used to provide fine-grained pre-coding weight signaling, then UE performance is improved, but signaling overhead increases
Solution Approach 1:
The patent segments the downlink signaling into two separate WCDMA slot formats: one dedicated for TPC commands and another for other uplink transmission instructions including pre-coding weight selections. This segmentation allows efficient resource allocation where TPC commands can be signaled frequently with minimal overhead while pre-coding weights are updated at appropriate intervals, resolving the contradiction between fine-grained control and signaling overhead
Solution Approach 2:
The patent implements dynamic adaptation by allowing the NodeB to flexibly configure the ratio of slots dedicated to TPC versus other instructions based on UE speed and channel conditions. For fast-moving UEs, more slots are allocated to TPC, while for slow-moving UEs, more slots can carry pre-coding weight information, optimizing the balance between precision and overhead adaptively
2Reliability
If pre-coding weights are updated frequently to track fast channel variations, then UE performance is improved, but channel management complexity increases
Solution Approach 1:
The patent implements periodic updates of pre-coding weights through the second WCDMA slot format, which carries other uplink transmission instructions including pre-coding weight selections. This periodic signaling approach allows the system to track channel variations effectively while maintaining manageable complexity through structured, interval-based updates rather than continuous complex management
Solution Approach 2:
The system dynamically adapts the update frequency and slot allocation based on UE speed and channel conditions. For fast-fading channels, updates occur more frequently; for stable channels, updates are reduced. This dynamic behavior maintains high reliability while adapting complexity to actual channel conditions
3Productivity
If multiple instructions are transmitted to multiple UEs in the same WCDMA symbol, then resource efficiency is improved, but instruction allocation complexity increases
Solution Approach 1:
The patent segments instructions into two distinct types handled by two different slot formats: TPC commands in the first format and other uplink transmission instructions (including pre-coding weights, MIMO stream settings, beam forming parameters) in the second format. This segmentation simplifies the allocation complexity by providing clear, separate channels for different instruction types while maintaining high resource efficiency through the shared downlink physical channel structure
Solution Approach 2:
The downlink physical channel structure is designed to be universal and multi-functional, capable of carrying both TPC commands and other uplink transmission instructions to multiple UEs simultaneously. The same physical channel infrastructure supports both instruction types through different slot formats, improving resource efficiency while managing complexity through standardized multi-purpose channel design
Data Source
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AI summary
A NodeB (110) for a WCDMA system (100), arranged to transmit instructions to a UE (120) for the UE's uplink transmissions. The NodeB (110) is arranged to transmit the instructions on a dedicated downlink physical channel which the NodeB is arranged to use for transmissions to a plurality of UEs and which comprises a plurality of radio frames, where each radio frame comprises a number of slots and each slot comprises a number of WCDMA symbols. The instructions to the UE comprise Transmit Power Commands as well as other instructions to the UE (120) for the UE's uplink transmissions. The NodeB (110) is arranged to use a first WCDMA slot format for the TPC commands to the UE and a second WCDMA slot format for the other instructions to the UE.