MIMO Network Node Null Space Control Transmission
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Solution Overview
Problem
In Massive MIMO wireless networks, the transmission of control information without channel state information (CSI) leads to inefficient use of time-frequency resources, as beamforming cannot be used, resulting in wasted resources and reduced system capacity.
Innovation Solution
The method involves utilizing the unused degrees of freedom in the downlink channel to simultaneously beamform user data to terminals with CSI and broadcast control information using a diversity scheme in the null space of the channel, allowing for efficient use of resources and enhanced throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If space-time block coding is used to transmit control information without CSI, then control information can be transmitted to all user terminals, but time-frequency resources are wasted and system capacity is reduced
Solution Approach 1:
The patent segments the transmission resources by dividing the available degrees of freedom into two independent parts: one for beamformed user data transmission and another for diversity-scheme control information transmission. This is achieved through separate precoding matrices that operate in orthogonal subspaces, allowing simultaneous transmission without resource conflict.
Solution Approach 2:
The patent extends the transmission space by utilizing the null space of the channel matrix as an additional dimension. By projecting control information into this unused dimensional space through precoding, the system enables control information transmission without interfering with beamformed data transmission, effectively adding a new transmission dimension.
2Productivity
If beamforming is used to transmit user data, then throughput is improved, but control information cannot be transmitted without CSI
Solution Approach 1:
The patent makes the downlink transmission system multi-functional by enabling it to simultaneously perform two distinct functions: beamformed user data transmission and diversity-scheme control information transmission. The precoding structure allows the same physical resources to serve both purposes, with beamforming vectors for data and precoding matrices for control information operating independently in orthogonal subspaces.
Solution Approach 2:
The patent introduces precoding matrices as an intermediary mechanism that enables control information transmission in the null space of the channel. This intermediary structure allows control information to be transmitted without requiring CSI, while the beamforming vectors continue to provide directional gain for user data, with both operations coordinated through the precoding layer.
3Productivity
If the same communication resource is used for both user data and control information, then resource utilization is improved, but interference between transmissions may occur
Solution Approach 1:
The patent applies the counterweight principle by using the null space of the channel matrix as a counterbalancing dimension. The precoding matrix for control information is specifically designed to be orthogonal to the beamforming vectors, creating a counterweight that cancels out potential interference. This ensures that control information transmission does not degrade beamformed data transmission and vice versa.
Data Source
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AI summary
The disclosure relates to a method (30) performed in a network node (2) for transmitting data in a wireless network (1). The network node (2) is configurable for controlling a multiple input multiple output antenna system (5). The method (30) comprises beamforming (31) user specific data streams to one or more communication devices, UEI,..., UEK, wherein the beamforming (31) is based on respective channel information available for each of the one or more communication devices, UEI,..., UEK, precoding (32) control information streams using a transmit diversity scheme; and transmitting (33) the beamformed user specific data streams and the precoded control information streams in a same transmission resource. The disclosure relates to a network node, method in communication device, communication device and computer programs and computer program products.