Dynamic Uplink Reference Signal Sequence Group Allocation
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Solution Overview
Problem
In 3GPP LTE communications systems, the use of fixed cell identification based sequence groups for uplink reference signals (UL RS) leads to interference between UEs operating in close proximity, as they often cannot share the same sequence group, resulting in suboptimal demodulation performance due to non-orthogonal signals.
Innovation Solution
A dynamic sequence group allocation technique is implemented, allowing UEs to switch between sequence groups and use different cyclic shifts or Walsh codes to achieve orthogonality, even if they belong to different cells, thereby reducing interference and improving spatial multiplexing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed cell identification based sequence groups are used for uplink reference signals, then each cell can independently identify and manage its reference signals, but interference occurs between UEs operating in close proximity that cannot share the same sequence group
Solution Approach 1:
The patent implements dynamic sequence group allocation where the network can assign different sequence groups to UEs based on current channel conditions and interference patterns. This allows the system to adaptively change sequence group assignments rather than being fixed to cell identification, enabling UEs in close proximity to share sequence groups when orthogonal transmission is achieved through dynamic control parameters.
Solution Approach 2:
The patent changes the basis for sequence group selection from static cell identification to dynamic network-controlled parameters. By introducing new parameters such as sequence group indices that can be independently assigned and modified by the network, the system enables flexible sequence group sharing while maintaining orthogonality through controlled parameter variations in cyclic shifts and Walsh codes.
2Reliability
If UEs use different sequence groups to avoid interference, then orthogonality is maintained, but resource allocation efficiency decreases due to inability to share resources
Solution Approach 1:
The patent makes sequence groups universally assignable across different cells and UEs rather than being cell-specific. The same sequence group can be assigned to multiple UEs in different cells or the same cell, enabling resource sharing while maintaining orthogonality through network-controlled differentiation via cyclic shifts and Walsh codes. This multi-functional approach allows sequence groups to serve multiple UEs simultaneously.
Solution Approach 2:
The patent segments the orthogonality control into multiple independent parameters: sequence group selection, cyclic shift values, and Walsh code assignments. This segmentation allows the sequence group to be shared while other parameters provide the necessary differentiation for orthogonal transmission, enabling both resource sharing and interference avoidance.
3Productivity
If dynamic sequence group allocation is implemented, then UE interference is reduced and spatial multiplexing improves, but signaling overhead and system complexity increase
Solution Approach 1:
The patent introduces the network as an intermediary that centrally manages sequence group allocations. Rather than UEs independently determining sequence groups based on cell ID, the network acts as a mediator that assigns sequence groups and coordinates allocations across multiple UEs and cells. This centralized mediation simplifies the overall system by providing a single point of control for managing the complexity of dynamic sequence group allocation.
4Adaptability or versatility
If UEs in different cells use cell-specific sequence groups, then each cell maintains independent control, but UEs operating in close proximity experience interference
Solution Approach 1:
The patent transforms the static cell-specific sequence group assignment into a dynamic network-controlled mechanism. The network can override cell-specific assignments and allocate sequence groups dynamically based on actual interference conditions, allowing UEs from different cells to share sequence groups when beneficial while maintaining the ability to provide cell-specific control when needed.
Data Source
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AI summary
A system and method for signaling and transmitting uplink reference signals are provided. A method for communications controller operations includes signaling information about a set of sequence groups to a first communications device (block 605), where the first communications device uses a sequence in the set of sequence groups to modulate a reference signal. The method also includes selecting a sequence group from the set of sequence groups (block 615) and signaling information about the selected sequence group to the first communications device (block 620).