Synchronization Signal Transmission in High-Frequency Wireless Networks
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Solution Overview
Problem
Existing methods for transmitting synchronization signals in wireless communications networks are ineffective at high frequency carriers, leading to synchronization failures due to increased path loss and the need for narrow beamforming, which complicates cell detection and system information acquisition for wireless devices.
Innovation Solution
A method where a network node repeatedly transmits a first synchronization signal in N OFDM symbols within a subframe, with an associated information message sent at a pre-defined time and frequency position, allowing wireless devices to detect synchronization signals more reliably and synchronize with the network node, even when the precise beam is unknown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If narrow beamforming is used to compensate for high path loss at high frequency carriers, then signal transmission reliability is improved, but synchronization signal detection becomes more difficult and cell detection complexity increases
Solution Approach 1:
The synchronization signal transmission is segmented across multiple OFDM symbols within a subframe. The network node transmits the first synchronization signal in N OFDM symbols, where N≥1, allowing the wireless device to detect synchronization signals through multiple opportunities rather than relying on a single narrow beam transmission.
Solution Approach 2:
The synchronization signal is transmitted periodically across multiple OFDM symbols with a predetermined pattern. The wireless device can detect the synchronization signal at any of these periodic occurrences, making the detection process more robust against beam misalignment while maintaining the benefits of narrow beamforming for path loss compensation.
2Area of stationary object
If narrow beamforming is used at high frequency carriers, then coverage is improved through beamforming gain, but the number of beams required to cover a sector increases
Solution Approach 1:
The transmission opportunity is segmented into multiple OFDM symbols, allowing the network to use fewer narrow beams over time rather than requiring all possible narrow beams to be transmitted simultaneously. The wireless device can detect synchronization from any symbol where its serving beam is active.
Solution Approach 2:
The network node transmits synchronization signals in advance across multiple OFDM symbols with known positioning information. This preliminary transmission allows wireless devices to acquire synchronization and system information before actual data transmission begins, reducing the need for extensive beam sweeping.
3Loss of time
If synchronization signals are transmitted in a single OFDM symbol, then transmission time is reduced, but detection reliability fails in high frequency environments with high path loss
Solution Approach 1:
Instead of a single transmission, the synchronization signal is transmitted periodically across multiple OFDM symbols. This periodic transmission maintains relatively short total transmission time while significantly improving detection reliability through multiple detection opportunities, especially important in high frequency environments with high path loss.
Solution Approach 2:
The synchronization signal transmission continues across multiple OFDM symbols rather than being confined to a single symbol. This continuous transmission ensures that wireless devices can detect the signal reliably even when some symbols are received with lower quality due to channel conditions or beam misalignment.
Data Source
AI summary
Embodiments herein relate to methods and apparatuses. A method performed by a network node (210) for sending to a wireless device (250) a first synchronization signal and an associated information message, for synchronization of the wireless device (250) with the network node (210) is provided. The network node (210) sends the first synchronization signal in OFDM symbols within a subframe, at least once in a time and frequency position in every one of the N OFDM symbols. For each sending of the first synchronization signal, the network node (210) sends an associated information message at a pre-defined time and frequency position in an OFDM symbol. The pre-defined time and frequency position is relative to the time and frequency position of the first synchronization signal. Embodiments herein also relate to a wireless device and method therein.