Transmitter Power Control for Non-Orthogonal Multiplexing
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Solution Overview
Problem
In contention-based wireless communication technologies, when the number of terminal apparatuses exceeds the number of receive antennas or spreading factor, inter-user interference occurs, and the base station faces significant challenges in detecting non-orthogonally multiplexed data signals due to increased computational complexity as the number of terminal apparatuses increases.
Innovation Solution
A transmitter that transmits data signals without receiving a UL grant, employing a spreading unit and transmit power control unit to manage transmit power based on the spreading factor or sequence of spreading codes, allowing for flexible power control and sequence switching, and generating control signals to request reconfiguration of transmit power parameters when maximum power is exceeded.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of terminal apparatuses exceeds the number of receive antennas or spreading factor, then more terminal apparatuses can be accommodated, but inter-user interference occurs and detection becomes difficult
Solution Approach 1:
The patent changes the parameter of transmit power by introducing a power offset specific to each spreading code. When multiple terminal apparatuses use the same spreading code, their transmit powers are differentiated through these offsets, enabling the base station to separate and detect their signals even when the number of terminals exceeds the number of receive antennas or spreading factor.
2Quantity of substance
If the number of terminal apparatuses increases, then more devices can communicate, but the amount of reception processing calculation becomes extremely large
Solution Approach 1:
The patent introduces transmit power offset as an additional parameter that creates a new dimension for signal differentiation. Instead of relying solely on spreading codes and receive antennas, the system now uses power level variations to distinguish between terminal apparatuses, thereby reducing the computational complexity of reception processing while accommodating more terminals.
3Reliability
If transmit power is increased to improve signal detection, then detection reliability improves, but interference to other signals increases
Solution Approach 1:
The patent applies different transmit power offsets locally to each spreading code or terminal apparatus. This allows each terminal to transmit at an optimized power level tailored to its specific conditions, improving its own signal detection reliability while minimizing interference to other signals. The base station can then differentiate between terminals based on these localized power variations.
Data Source
AI summary
In a case that a large number of terminal apparatuses that are accommodated by contention-based radio communication technologies share a frequency resource, the number of data signals of the terminal apparatus that are non-orthogonally multiplexed in the spatial domain increases. If terminal apparatuses, of which the number exceeds the number of receive antennas or the spreading factor transmit uplink data at the same time, it is tantamount to a presence of terminal apparatuses using the same spreading code, and inter-user interference becomes a problem. A transmitter for transmitting a data signal to a receiver, includes a transmission processing unit configured to transmit the data signal without receiving control information to permit transmission (UL grant) transmitted by the receiver; a spreading unit configured to spread the data signal; and a transmit power control unit capable of switching a plurality of methods of controlling transmit power of the data signal, wherein the methods of controlling transmit power are switched in accordance with at least one of a spreading factor or a sequence of spreading codes used by the spreading unit for spreading the data signal.