Reduced Transmission Time Interval for Radio Access Network Latency
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Solution Overview
Problem
Current LTE networks face significant latency issues, which hinder the implementation of ultra-low latency services requiring one-way air interface latency of 1 millisecond or less, especially in emerging applications like vehicular networks.
Innovation Solution
The implementation of a reduced transmission time interval (rTTI) in radio access networks, allowing for rTTI block-wise operations to reduce overhead and enable multiplexing of data and reference signals within an OFDM symbol, along with novel techniques for code block segmentation, uplink resource element mapping, and hybrid automatic repeat request (HARQ) cycle timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a reduced transmission time interval (rTTI) is implemented, then air interface latency is reduced, but system complexity increases due to rTTI block-wise operations and overhead management
Solution Approach 1:
The patent segments the transmission time interval into reduced TTI (rTTI) blocks, where operations are performed in rTTI block-wise fashion. This segmentation enables latency reduction by processing smaller time units while managing complexity through structured block operations and overhead reduction techniques.
Solution Approach 2:
The patent introduces dynamic rTTI configurations that can be adapted to different service requirements. The system dynamically adjusts rTTI parameters including block size, multiplexing patterns, and HARQ timing to optimize latency performance while managing system complexity through flexible, condition-based operation modes.
2Loss of substance
If data and reference signals are multiplexed within an OFDM symbol, then overhead is reduced, but signal detection difficulty increases
Solution Approach 1:
The patent merges data and reference signals within the same OFDM symbol through frequency-domain multiplexing. This combining reduces overhead by eliminating separate reference signal symbols while maintaining signal integrity through carefully designed multiplexing patterns that preserve detectability.
Solution Approach 2:
The patent moves reference signal placement from the time dimension (separate symbols) to the frequency dimension (subcarrier multiplexing within the same symbol). This dimensional transition reduces time-domain overhead while managing detection complexity through frequency-domain separation and orthogonality principles.
3Loss of time
If novel techniques for code block segmentation and HARQ cycle timing are implemented, then latency is reduced, but implementation complexity increases
Solution Approach 1:
The patent changes key parameters including code block segmentation sizes, HARQ cycle timing intervals, and rTTI block configurations to optimize latency. These parameter adjustments reduce latency by aligning processing intervals with ultra-low latency requirements while managing implementation complexity through standardized parameter sets and configuration procedures.
Data Source
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AI summary
Latency reduction techniques for radio access networks are described. In various embodiments, a reduced transmission time interval (rTTI) may be implemented in order to reduce air interface latency in a radio access network. In some embodiments, an rTTI block may be defined, and some operations may be performed in rTTI block-wise fashion in order to reduce the marginal overhead associated with implementation of the rTTI. In various embodiments in which an rTTI is implemented, DM-RS granularity may be improved by use of techniques that enable data and reference signals to be multiplexed within a same OFDM symbol. In some embodiments, a current transmission time interval (TTI) may be maintained, and latency reduction may be achieved via the use of novel techniques for one or more of code block (CB) segmentation, uplink (UL) resource element (RE) mapping, and HARQ cycle timing. Other embodiments are described and claimed.