Joint Time-Frequency Division Multiplexing for Massive MIMO Pilot Capacity
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Solution Overview
Problem
Current wireless communication systems face challenges in achieving high data rates due to the limited number of pilots that can be multiplexed without causing interference, which restricts the capacity of high-order or massive MIMO systems, especially in channels with long delay spreads.
Innovation Solution
The implementation of joint time-frequency division multiplexing (JTFDM) allows for the efficient multiplexing and de-multiplexing of pilot sequences that are localized in the joint time-frequency plane, using sequences like Zadoff-Chu and generalized chirp-like sequences, which are spread in both time and frequency, enabling the transmission of a maximum number of pilots without performance degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of transmit antennas is increased to achieve higher wireless capacity, then the wireless capacity is improved, but the number of pilot signals required increases, which occupies more transmit resources and limits the transmit data rate
Solution Approach 1:
The patent combines time-division multiplexing and frequency-division multiplexing into a unified joint time-frequency division multiplexing framework. This merging allows pilot signals to be multiplexed in both time and frequency dimensions simultaneously, achieving denser packing of pilots without interference, thereby supporting more transmit antennas while maintaining data rate efficiency
Solution Approach 2:
The patent transitions from traditional single-dimensional (time or frequency) pilot multiplexing to two-dimensional joint time-frequency multiplexing. By utilizing both time and frequency dimensions for pilot arrangement, the system achieves exponential increase in the number of multiplexed pilots, enabling support for massive MIMO systems with many transmit antennas
2Productivity
If more pilot signals are multiplexed into fewer transmit resources, then the transmit data rate is improved, but interference between received pilot sequences may occur, degrading channel estimation accuracy
Solution Approach 1:
The patent applies local quality by designing pilot sequences with specific properties localized in the joint time-frequency plane. Each pilot sequence is assigned a unique time-frequency location with controlled auto-correlation and cross-correlation properties, ensuring that pilots can be densely multiplexed while maintaining orthogonality and preventing interference, thus preserving channel estimation accuracy
Solution Approach 2:
The patent changes the parameters of pilot sequences by using generalized chirp-like sequences with adjustable time-frequency localization characteristics. By optimizing sequence parameters such as chirp rate and time-frequency support, the system achieves maximum pilot multiplexing capacity while maintaining low cross-correlation and high channel estimation accuracy
3Adaptability or versatility
If pilots are spread both in time and frequency without localization, then the frequency selectivity is improved, but the maximum number of pilots per symbol is limited due to long channel delay spreads
Solution Approach 1:
The patent segments the time-frequency plane into distinct regions for different pilot sequences. Each pilot is assigned a localized time-frequency support region, allowing multiple pilots to coexist without overlapping in the joint time-frequency domain. This segmentation enables the system to handle frequency selectivity while maximizing the number of multiplexed pilots per symbol
Solution Approach 2:
The patent introduces joint time-frequency division multiplexing as an intermediary framework that bridges the gap between frequency-selective channel requirements and high pilot multiplexing needs. This intermediary structure organizes pilots in a two-dimensional time-frequency grid with controlled spacing and localization, enabling both frequency selectivity handling and high pilot capacity
Data Source
AI summary
In some embodiments, a signal transmitter includes a processor that converts information to be emitted into a plurality of signals, each signal having an emitting waveform, wherein at least two of the time-frequency distributions of emitting signal waveforms are separated from one another in the joint time-frequency plane by a parallelogram shaped regions. In some embodiments, a signal receiver includes a processor that separates received time-frequency spread waveforms from one another, the time-frequency spread waveforms are parallelogram-shaped in the joint time-frequency plane.