[Paper Review] Full-Duplex Massive MIMO Relaying Systems with Low-Resolution ADCs

Chuili Kong, Caijun Zhong+4 more|arXiv (Cornell University)|May 14, 2017

Full-Duplex Wireless Communications35 references3 citations

TL;DR

This paper proposes a full-duplex massive MIMO relaying system with low-resolution ADCs at both the relay and destinations, using pilot training and maximum-ratio combining/transmission to mitigate interference. It derives exact and approximated sum rate expressions, showing that massive relay antennas can compensate for low-resolution ADCs at the relay but not at the destination, and establishes a power scaling law where source transmit power scales as $1/M$ to maintain constant rate.

ABSTRACT

This paper considers a multipair amplify-and-forward massive MIMO relaying system with low-resolution ADCs at both the relay and destinations. The channel state information (CSI) at the relay is obtained via pilot training, which is then utilized to perform simple maximum-ratio combining/maximum-ratio transmission processing by the relay. Also, it is assumed that the destinations use statistical CSI to decode the transmitted signals. Exact and approximated closed-form expressions for the achievable sum rate are presented, which enable the efficient evaluation of the impact of key system parameters on the system performance. In addition, optimal relay power allocation scheme is studied, and power scaling law is characterized. It is found that, with only low-resolution ADCs at the relay, increasing the number of relay antennas is an effective method to compensate for the rate loss caused by coarse quantization. However, it becomes ineffective to handle the detrimental effect of low-resolution ADCs at the destination. Moreover, it is shown that deploying massive relay antenna arrays can still bring significant power savings, i.e., the transmit power of each source can be cut down proportional to $1/M$ to maintain a constant rate, where $M$ is the number of relay antennas.

Motivation & Objective

• To analyze the performance of a multipair full-duplex massive MIMO relaying system with low-resolution ADCs at both relay and destinations.
• To investigate the impact of coarse quantization on system spectral efficiency and identify key performance-limiting factors.
• To derive exact and approximated closed-form expressions for the achievable sum rate to enable efficient system evaluation.
• To design an optimal relay power allocation scheme and characterize the power scaling law for constant-rate operation.
• To evaluate the effectiveness of massive antenna arrays in compensating for performance loss due to low-resolution ADCs.

Proposed method

• Employs pilot training at the relay to estimate channel state information (CSI), which is then used for maximum-ratio combining and transmission.
• Uses statistical CSI at the destinations for signal decoding, reducing feedback overhead.
• Derives exact and approximated closed-form expressions for the achievable sum rate using stochastic geometry and random matrix theory.
• Analyzes the impact of key parameters such as ADC resolution, number of relay antennas, and power allocation via expectation-based signal-to-interference-plus-noise ratio (SINR) analysis.
• Introduces a power scaling law where source transmit power scales inversely with the number of relay antennas $M$ to maintain constant rate.
• Models loop interference and quantization noise explicitly in the system model, accounting for both relay and destination ADC resolution.

Experimental results

Research questions

• RQ1 How does low-resolution ADC quantization at the relay affect the achievable sum rate in a full-duplex massive MIMO relaying system?
• RQ2 Can massive MIMO arrays at the relay effectively compensate for the rate degradation caused by coarse ADCs?
• RQ3 What is the optimal power allocation strategy at the relay to maximize sum rate under low-resolution ADC constraints?
• RQ4 How does the performance of the system degrade when low-resolution ADCs are deployed at the destinations instead of the relay?
• RQ5 What is the power scaling law for maintaining a constant sum rate as the number of relay antennas increases?

Key findings

• Increasing the number of relay antennas effectively compensates for the rate loss caused by low-resolution ADCs at the relay, enabling high spectral efficiency despite coarse quantization.
• The performance gain from massive relay arrays does not extend to low-resolution ADCs at the destinations, where the rate loss remains significant.
• The system achieves a power scaling law where source transmit power scales as $1/M$ to maintain a constant sum rate, enabling substantial energy savings.
• With only 4–5 bits of ADC resolution at the relay, the system maintains high spectral efficiency due to array gain, confirming robustness against coarse quantization.
• The optimal training pilot length is significantly longer than in unquantized systems, highlighting the need for advanced channel estimation techniques.
• The derived sum rate expressions are accurate and enable efficient evaluation of system performance under various configurations.