Reference Signal Initialization for Enhanced Control Channels
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Solution Overview
Problem
Current techniques for assigning and applying reference signals in wireless communication networks, particularly in LTE systems, are inadequate for robust channel estimation in shared cell scenarios, common search spaces, initial access to carriers, and stand-alone carriers, and result in high signaling overhead.
Innovation Solution
The use of dynamic reference signal sequences for enhanced control channels, determined by factors such as search space type, transmission type, and initial access, allows for different sequences to be used for different types of enhanced control channels, even when transmitted simultaneously, optimizing antenna ports and time-frequency resources for improved channel estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single reference signal sequence is used for all enhanced control channels in a shared cell scenario, then device complexity is reduced, but channel estimation performance deteriorates due to interference between geographically distributed nodes
Solution Approach 1:
The patent segments the reference signal sequences into different types (first reference signal sequence and second reference signal sequence) based on the transmission type of enhanced control channels. This segmentation allows different sequences to be used for different purposes: one sequence type for localized transmission and another for distributed transmission, thereby avoiding interference in shared cell scenarios while maintaining manageable device complexity through structured sequence selection
Solution Approach 2:
The patent implements dynamic reference signal sequence selection where the UE determines which sequence to use based on the transmission type (localized or distributed) of the enhanced control channel. This dynamic adaptation allows the system to optimize channel estimation performance for each specific transmission scenario while maintaining a unified reference signal framework, resolving the contradiction between simplicity and performance
2Measurement precision
If UE-specific reference signals are used for enhanced control channels, then channel estimation precision is improved, but signaling overhead increases due to dynamic selection requirements
Solution Approach 1:
The patent changes the parameters of the reference signal sequences by defining two distinct sequence types with different initialization approaches. The first sequence uses initialization based on cell ID and resource block index, while the second uses initialization based on cell ID and subframe number. This parameter differentiation enables UE-specific channel estimation precision without requiring complex dynamic signaling, as the sequence type can be determined from existing system parameters
Solution Approach 2:
The patent enables UEs to self-determine which reference signal sequence to use based on the transmission type of the enhanced control channel, without requiring explicit dynamic signaling from the base station. The UE can autonomously select the appropriate sequence based on whether the transmission is localized or distributed, thereby achieving UE-specific channel estimation precision while minimizing signaling overhead through self-service sequence selection
3Reliability
If reference signals are optimized for specific transmission types, then channel estimation performance is improved, but device complexity increases due to multiple sequence management
Solution Approach 1:
The patent applies local quality by optimizing reference signal sequences for specific local conditions - localized transmission types use one sequence type optimized for that scenario, while distributed transmission types use another sequence type optimized for their conditions. This localized optimization improves channel estimation performance for each transmission type without requiring the device to manage all possible sequence variations, as only two sequence types need to be maintained
Solution Approach 2:
The patent implements a dynamic yet simplified sequence selection mechanism where the UE determines the appropriate reference signal sequence based on the transmission type. This dynamic selection is based on simple criteria (localized vs. distributed transmission) rather than complex multi-parameter decisions, thereby achieving optimized channel estimation performance while keeping device complexity manageable through rule-based sequence selection
Data Source
AI summary
A transmitting node uses different reference signal sequences for different types of enhanced control channels. An example method begins with generating (1410) a first reference signal sequence, from a first initialization value, and generating (1420) a second reference signal sequence, from a second initialization value. These reference signal sequences are associated with two corresponding enhanced control transmissions. A first enhanced control channel and reference symbols taken from the first reference signal sequence are transmitted (1430), using first time-frequency resources and a first set of transmission points or a first set of antenna ports or both, and a second enhanced control channel and reference symbols taken from the second reference signal sequence are also transmitted (1440), using a differing second set of transmission points and/or a differing second set of antenna ports and/or a differing second set of time-frequency resources, in the same subframe or group of subframes.