Performance Analysis of Large Intelligent Surfaces (LISs): Asymptotic Data Rate and Channel Hardening Effects (1810.05667v4)

Abstract: The concept of a large intelligent surface (LIS) has recently emerged as a promising wireless communication paradigm that can exploit the entire surface of man-made structures for transmitting and receiving information. An LIS is expected to go beyond massive multiple-input multiple-output (MIMO) system, insofar as the desired channel can be modeled as a perfect line-of-sight. To understand the fundamental performance benefits, it is imperative to analyze its achievable data rate, under practical LIS environments and limitations. In this paper, an asymptotic analysis of the uplink data rate in an LIS-based large antenna-array system is presented. In particular, the asymptotic LIS rate is derived in a practical wireless environment where the estimated channel on LIS is subject to estimation errors and interference channels are spatially correlated Rician fading channels. Moreover, the occurrence of the channel hardening effect is analyzed and the performance bound is asymptotically derived for the considered LIS system. The analytical asymptotic results are then shown to be in close agreement with the exact mutual information as the numbers of antennas and devices increases without bounds. Moreover, the derived ergodic rates show that noise and interference from estimation errors and the non-line-of-sight path become negligible as the number of antennas increases. Simulation results show that an LIS can achieve a performance that is comparable to conventional massive MIMO with improved reliability and a significantly reduced area for antenna deployment.

• The paper derives asymptotic uplink data rate expressions under realistic conditions, including channel estimation errors and hardware impairments.
• The study rigorously evaluates the channel hardening effect, showing that the variance of channel capacity diminishes with an increasing number of antennas.
• Comparative simulations reveal that Large Intelligent Surfaces can match or surpass massive MIMO performance while mitigating interference challenges.

Performance Analysis of Large Intelligent Surfaces: Asymptotic Data Rate and Channel Hardening Effects

The paper "Performance Analysis of Large Intelligent Surfaces (LISs): Asymptotic Data Rate and Channel Hardening Effects" explores the emerging paradigm of large intelligent surfaces in wireless communications, positioning them as a potential advancement over traditional massive MIMO systems. The paper focuses on analyzing the achievable uplink data rate and channel hardening effects under realistic conditions such as channel estimation errors, hardware impairments, and interference modeling.

Key Contributions

1. Asymptotic Data Rate Derivation: The paper presents a comprehensive asymptotic analysis of the uplink data rate. It evaluates the performance of an LIS-based large antenna-array system in environments that include channel estimation errors, spatially correlated Rician fading interference channels, and the presence of hardware impairments. The authors derive expressions for the mean and variance of the uplink rate, offering insights into system reliability and ergodic capacity.
2. Channel Hardening Effect: The occurrence of the channel hardening effect is rigorously analyzed. This effect, crucial for large-scale antenna systems, ensures that the variance of the channel capacity diminishes as the number of antennas increases, leading to more predictable and reliable communication channels.
3. Comparative Analysis with Massive MIMO: Through simulations, the results are compared against conventional massive MIMO systems. The LIS paradigm is shown to potentially achieve comparable performance with fewer spatial requirements and improved reliability. The paper suggests that interference, noise, and channel estimation errors become negligible with increasing antennas, which contrasts with massive MIMO where interference can still play a significant role.
4. Hardware Impairments and Practical Considerations: The paper takes into account real-world limitations such as hardware impairments which typically degrade the performance of antenna systems. The analytical results remain consistent with mutual information outcomes as the number of antennas and devices increases, underscoring the robustness of the LIS framework in practical applications.

Implications and Future Directions

The practical implications of adopting LISs include enhanced reliability due to reduced variance in data rates and the ability to achieve high data rates without extensive spatial resources. This would ensure higher spectral efficiency in dense IoT environments, potentially surpassing traditional massive MIMO systems in applications with severe space constraints.

From a theoretical perspective, this work lays the groundwork for further exploration of LISs in various wireless conditions, including diverse propagation environments and in combination with advanced signal processing techniques. Future research could delve into optimizing LIS deployment patterns, examining specific interference mitigation strategies, and real-world prototyping and testing to validate theoretical findings.

Conclusion

The analysis conducted in the paper offers a detailed insight into LIS systems' potential, particularly in terms of asymptotic performance advantages and inherent channel hardening effects. By addressing physical impairments and inaccuracies in channel estimation, the paper provides a realistic assessment of LIS capabilities, advocating their suitability for next-generation wireless networks. As the field progresses, further refinement and practical validation of LIS technology could solidify its role in future wireless communication systems.