Beam Reference Signal Multiplexing for Broadcast Decoding
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Solution Overview
Problem
In wireless communication systems operating in millimeter wave (mmW) spectrum, beamforming techniques can interfere with broadcast signals, preventing user equipment (UEs) not in the path of the beamformed signal from receiving system information necessary for system access, due to increased path loss and signal attenuation.
Innovation Solution
A method where a base station transmits subframes with physical broadcast channel (PBCH) signals interspersed within beam reference signals, using code division multiplexing of beam reference signals over multiple frequency tones, allowing UEs to generate channel estimates for PBCH signals, and employing orthogonal cover codes to facilitate decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If beamforming techniques are used to increase signal strength in mmW spectrum, then signal strength for targeted UEs is improved, but broadcast signal reception for UEs not in the beam path deteriorates
Solution Approach 1:
The broadcast signal transmission is segmented into multiple directional beams, each targeting a specific spatial sector. By dividing the coverage area into segments and transmitting dedicated broadcast signals in each segment, the system ensures that UEs in all directions can receive system information reliably, while still benefiting from beamformed signal strength enhancement in each specific direction.
Solution Approach 2:
The patent combines beamforming technology with broadcast signal transmission by integrating physical broadcast channels (PBCH) into beam reference signal structures. This merging allows the system to simultaneously achieve directional signal enhancement and omnidirectional broadcast coverage, resolving the contradiction between targeted signal strength improvement and general broadcast reliability.
2Loss of energy
If beamforming is applied to overcome path loss, then link budget is improved, but system information dissemination to all UEs deteriorates
Solution Approach 1:
The system employs periodic beam sweeping where beamformed broadcast signals are transmitted sequentially in different spatial directions across multiple time slots. This periodic action ensures that system information is disseminated to all UEs regardless of their location, while maintaining energy efficiency by concentrating transmission power directionally during each time slot rather than spreading it omnidirectionally.
Solution Approach 2:
Beam reference signals serve as intermediaries that carry system information while enabling channel estimation for PBCH decoding. These intermediary signals facilitate the transfer of broadcast information through beamformed paths, overcoming path loss effects while ensuring system information reaches all UEs through multiple directional transmissions.
3Device complexity
If PBCH signals are transmitted separately from beam reference signals, then signal structure simplicity is maintained, but decoding efficiency and channel characterization deteriorate
Solution Approach 1:
The patent merges PBCH signals with beam reference signals into a unified signal structure where beam reference signal resources carry both channel estimation functionality and broadcast system information. This integration eliminates the need for separate signal transmissions, maintaining structural efficiency while improving decoding performance through combined channel characterization and information delivery.
Solution Approach 2:
The beam reference signal structure is designed to serve multiple functions simultaneously: it provides channel estimation for demodulation, carries system information through PBCH, and enables synchronization. This multi-functionality reduces overall signal structure complexity while enhancing decoding efficiency, as the same signal resources fulfill multiple purposes rather than requiring separate dedicated signals for each function.
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AI summary
Methods, systems, and devices for wireless communication are described. A base station may transmit a subframe that includes physical broadcast channel (PBCH) signals interspersed within beam reference signals, where the subframe may be a synchronization subframe including one or more synchronization signals. In some cases, the beam reference signals from different antenna ports may be code division multiplexed or frequency division multiplexed over multiple frequency tones. A user equipment (UE) may use the beam reference signals to generate channel estimates for the PBCH signals. In some cases, orthogonal cover codes for code division multiplexed signals may be selected to facilitate generation of channel estimates for PBCH signals transmitted using nearby frequency tones.