SU-MIMO Reference Signal Allocation via Cyclic Shifts
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Solution Overview
Problem
In LTE wireless networks, SU-MIMO transmission faces challenges due to stale channel estimates and interference, particularly at high UE speeds, which affect the reliability and efficiency of MIMO operations.
Innovation Solution
The implementation of an open-loop spatial multiplexing scheme with fixed precoding matrices, avoiding adaptive precoding and using cyclic shifts for DMRS resources, allows for efficient SU-MIMO transmission without introducing new signaling schemes, reusing existing spatial multiplexing and adaptive precoding methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If adaptive precoding is used to improve MIMO transmission efficiency, then system capacity increases, but channel estimation accuracy deteriorates at high UE speeds due to stale channel estimates
Solution Approach 1:
The patent changes the precoding parameter from adaptive to fixed, where the precoding matrix is determined based on the reference signal resource allocation rather than adapting to changing channel conditions. This resolves the contradiction by eliminating the need for accurate real-time channel estimation while maintaining MIMO transmission efficiency through predetermined precoding matrices.
Solution Approach 2:
The precoding matrix is predetermined and allocated in advance based on reference signal resources, rather than adapting dynamically to channel conditions. This preliminary determination of precoding parameters eliminates the dependency on real-time channel estimation accuracy, allowing MIMO transmission to proceed efficiently even when channel estimates become stale at high UE speeds.
2Adaptability or versatility
If multiple DMRS resources are allocated for SU-MIMO to support multiple layers, then spatial multiplexing capability improves, but signaling complexity increases
Solution Approach 1:
The patent makes the reference signal resource allocation serve multiple functions: it simultaneously determines the precoding matrix and identifies the DMRS resources for multiple layers. This multi-functionality eliminates the need for separate signaling for precoding indication, reducing signaling complexity while maintaining full spatial multiplexing capability through the universal reference signal resource allocation mechanism.
3Device complexity
If fixed precoding matrices are used to simplify signaling, then signaling complexity reduces, but transmission adaptability to channel conditions decreases
Solution Approach 1:
The system uses the existing reference signal resource allocation structure to self-determine the precoding matrix without requiring additional adaptive signaling. The fixed precoding matrices are selected based on the allocated reference signal resources, allowing the system to maintain transmission adaptability through the resource allocation pattern itself rather than through explicit adaptive precoding signals.
Data Source
AI summary
Transmission with multiple antennas in a wireless network is performed by transmitting a plurality of reference sequences (RS) from a UE. A first RS s1[k] is produced using a first cyclic shift and a base sequence s0[k], wherein k={1, 2 . . . K} is an element index. A second RS s2[k] is produced using a second cyclic shift and s0[k]. A first symbol sequence x1[k] is produced using at least s1[k] and s2[k], for at least one k. A second symbol sequence x2[k] is produced using at least s1[k] and s2[k], for at least one k. x1[k] is transmitted using a first transmit antenna and x2[k] is transmitted using a second transmit antenna.