Unlicensed Spectrum Discovery Signal Transmission Density
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Solution Overview
Problem
In wireless communication systems, the uncertainty of channel availability in unlicensed radio frequency spectrum bands and the presence of radio frames with no data to transmit reduce the frequency of discovery signal transmission, making it difficult for user equipment (UE) to discover and synchronize with base stations effectively.
Innovation Solution
The method involves transmitting a higher density of reference signals in specific portions of OFDM symbols over unlicensed radio frequency spectrum bands, along with synchronization signals, to ensure more regular and robust transmission of discovery signals, allowing UEs to perform narrow band measurements and synchronize with base stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the base station performs clear channel assessment (CCA) before transmitting over unlicensed radio frequency spectrum band, then channel access conflict is avoided, but transmission frequency of discovery signals is reduced due to uncertainty of channel availability
Solution Approach 1:
The base station performs clear channel assessment (CCA) in advance before transmitting discovery signals over the unlicensed spectrum. This preliminary action ensures that the base station only transmits when the channel is confirmed to be available, avoiding conflicts with other devices while maintaining reliable channel access.
Solution Approach 2:
The base station transmits discovery signals periodically in available subframes of the unlicensed spectrum band. By utilizing the periodic nature of discovery signal transmission and selecting specific available subframes based on CCA results, the system maintains regular transmission patterns while adapting to channel availability, thus balancing reliability with transmission frequency.
2Reliability
If the base station transmits discovery signals frequently, then UE discovery and synchronization capability is improved, but channel access conflict in unlicensed spectrum increases
Solution Approach 1:
The base station performs clear channel assessment (CCA) before transmitting discovery signals to ensure the channel is free from other devices. This preliminary check prevents channel access conflicts while maintaining the ability to transmit discovery signals frequently when the channel is available, thus protecting UEs from interference during discovery and synchronization.
Solution Approach 2:
The base station uses CCA results as feedback to determine whether to transmit discovery signals in each subframe. This feedback mechanism allows the system to dynamically adjust transmission decisions based on real-time channel conditions, ensuring frequent transmission when possible while avoiding conflicts when the channel is occupied.
3Stability of the object's composition
If the base station transmits discovery signals in all subframes, then transmission regularity is improved, but energy consumption increases due to unnecessary transmissions in subframes with no data
Solution Approach 1:
Instead of transmitting discovery signals in all subframes, the base station selectively transmits only in available subframes where data transmission is scheduled. This partial action approach maintains sufficient transmission regularity for UE discovery and synchronization while avoiding unnecessary energy consumption in subframes where no data needs to be transmitted.
Solution Approach 2:
The base station dynamically adjusts discovery signal transmission based on actual data transmission requirements and channel availability. By making transmission decisions adaptive to real-time conditions rather than following a fixed schedule, the system maintains operational stability while optimizing energy consumption.
Data Source
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AI summary
Techniques are described for wireless communication. A first method includes receiving a first orthogonal frequency division multiplexing (OFDM) symbol including a plurality of reference signals (RSs) over a radio frequency spectrum band. The first method may also include receiving a second OFDM symbol including a first synchronization signal over the radio frequency spectrum band. A second method includes transmitting a first OFDM symbol including a plurality of RSs over an radio frequency spectrum band. The second method may also include transmitting a second OFDM symbol including a first synchronization signal over the radio frequency spectrum band. In each method, a first portion of the first OFDM symbol includes a higher density of the RSs than a remaining portion of the first OFDM symbol, and when included, the second OFDM symbol may be adjacent in time to the first OFDM symbol.