Millimeter Wave Synchronization Signal Transceiving Scheme
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Solution Overview
Problem
The initial access procedures in millimeter wave (mmWave) cellular systems are inefficient due to sequential beam scanning, which increases overhead and reduces bandwidth, making it difficult to determine channel direction information accurately.
Innovation Solution
A synchronization signal transceiving scheme that generates multiple orthogonal synchronization signals, each specific to a direction of departure (DoD), transmitted over the same time-frequency resource, allowing for simultaneous transmission and feedback-based selection of the most preferable beam direction for improved beam forming and multiplexing gains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sequential beam scanning is used to scan the whole DoD/DoA angular spaces, then channel direction information can be obtained by comparing received power levels, but the overhead increases significantly and the initial access procedure slows down
Solution Approach 1:
The patent employs periodic synchronization signal transmissions with different beam patterns across multiple occasions. Instead of sequentially scanning all beams once, the system periodically transmits synchronization signals using different beam patterns, allowing the UE to detect and report the best beam direction earlier in the periodic cycle, thereby reducing the effective access time while maintaining measurement accuracy through multiple periodic opportunities.
Solution Approach 2:
The patent segments the beam scanning process by having the UE report only the best beam direction index among multiple transmitted synchronization signals, rather than requiring the network to sequentially test all beams. This segmentation allows parallel transmission of multiple beam patterns and selective reporting, reducing the time loss associated with sequential scanning while preserving the ability to accurately determine channel direction information.
2Adaptability or versatility
If multiple directional beam patterns are transmitted over distinct frequency sub-bands, then channel DoD information can be determined by detecting the sub-band with highest signal power, but the bandwidth for each directional synchronization signal is reduced leading to low timing accuracy
Solution Approach 1:
The patent resolves the bandwidth-timing accuracy tradeoff by introducing a new dimension for beam differentiation. Instead of relying solely on frequency sub-bands, the system uses different time occasions or periodic transmissions with distinct beam patterns. This dimensional shift allows multiple directional beams to be transmitted without fragmenting the bandwidth, thereby maintaining sufficient bandwidth for each synchronization signal to achieve accurate timing synchronization while still providing comprehensive directional coverage.
3Adaptability or versatility
If a wide bandwidth is used to contain a large number of sub-bands for transmitting many directional beams, then more directional synchronization signals can be transmitted, but the overhead increases
Solution Approach 1:
The patent makes the synchronization signal resource universal by allowing the same time-frequency resource to carry multiple directional beam information across different periodic transmissions. Instead of allocating dedicated wide bandwidth for each directional beam, the system uses a single synchronization signal resource that is repeatedly transmitted with different beam patterns, enabling multiple directional beams to be supported without proportionally increasing the bandwidth or overhead.
Solution Approach 2:
The system uses periodic synchronization signal transmissions to support multiple directional beams without requiring wide bandwidth. By transmitting synchronization signals periodically with different beam patterns in different periods, the system achieves versatile directional coverage while keeping the bandwidth and overhead per transmission low, as the same resource is reused across multiple periods rather than allocating separate wide bandwidth for each direction.
4Area of stationary object
If only a few sub-carriers are assigned to each sub-band, then bandwidth requirements are reduced, but the dimension of synchronization signals is reduced and waveform design becomes complicated
Solution Approach 1:
The patent compensates for the reduced signal dimension due to fewer sub-carriers per sub-band by utilizing the time dimension. Instead of relying on frequency diversity within a single sub-band, the system employs multiple periodic transmissions with different beam patterns, effectively moving the differentiation to the time domain. This approach maintains simpler waveform design with fewer sub-carriers while achieving comprehensive directional coverage through temporal diversity.
Data Source
AI summary
A network node for a wireless communication system includes a processor and a transceiver, the processor being configured to generate a set of at least two synchronization signal sequences; construct a synchronization signal for each synchronization signal sequence to create a set of synchronization signals, such that each of the synchronization signals in the set of synchronization signals has an auto correlation and cross correlation below a threshold value with any other synchronization signal in the set of synchronization signals; generate a set of directional beam patterns, wherein each beam pattern in the set of directional beam patterns corresponds to one of the synchronization signals in the set of synchronization signals; and wherein the transceiver is configured to transmit the synchronization signals in the set of synchronization signals using the beam pattern for each synchronization signal over a same time frequency resource.