Integrated sensing and communication (ISAC) is a key enabling technology for sixth-generation (6G) mobile communication systems, achieving seamless integration of communication and sensing functions. Cooperative sensing, where the transmitter and receiver are not co-located, serves as a key enabler for ISAC, significantly enhancing the sensing performance while reducing the implementation complexity of the receiver. However, practical deployments of cooperative sensing still face numerous challenges, such as synchronization and interference. This paper presents a set of advanced beam management methods specifically designed for the cooperative sensing system, offering a comprehensive framework to address these challenges. Specifically, we first analyze the strong/weak path effect (SWPE), a critical phenomenon caused by diverse target reflectivities and propagation paths, which severely degrades both synchronization accuracy and target detection. To counteract this, we propose an adaptive path power allocation method compatible with both all-digital and hybrid beamforming architectures. This method intelligently allocates power across different paths to mitigate the SWPE, thereby ensuring reliable synchronization via the direct path while enhancing the detectability of weak targets. As a result, the proposed method improves the target detection probability by over 30%. Furthermore, an adaptive interference suppression method is designed to reduce interference while maintaining sensing/communication quality, which obtains the SINR gain of around 5 dB, compared to the traditional full nulling method. Experimental results validate the effectiveness of robust synchronization and our proposed power allocation. This study lays a solid foundation for beamforming optimization in cooperative sensing systems, facilitating high-accuracy sensing and communication in complex environments.

Over the past two decades, advances in materials science and electronics have greatly supported the progress of the communication industry, and the emergence of new materials has made it possible to design higher performance communication modules. As a potential key technology for future 6G networks, the standardisation and industrialisation of visible light communication (VLC) cannot be separated from the improvement of the communication devices. In this paper, we first analyse and summarise the performance enhancement of new materials and designs of VLC devices. Then the support of improved capabilities of novel VLC devices for 6G new services is prospected. As device performance improves, VLC is expected to support more scenarios in 6G.

Visible light communications (VLC) is considered a potential key technology for 6G. However, the performance of transceiver devices of VLC determines the upper limit of system. InGaN/GaN based light-emitting diodes (LEDs) have widely been used as the transmitter. In this paper, a VLC transceiver system is designed on the basis of InGaN/GaN blue light laser diode (LD). The transmitted signals are designed based on the 5G new radio (NR) physical layer protocol. The experiment verifies the feasibility of 256 quadrature amplitude modulation (QAM) and the blue LD-based VLC system can achieve up to 14Gbit/s system sum rate when adopting 5G NR protocol, which contributes to the application of VLC in 6G systems.

As a visible light communications (VLC) modulation method, the layered asymmetrically clipped optical orthogonal frequency division multiplexing (LACO-OFDM) is promising. The layers in LACO-OFDM provide a high flexibility for power allocation and modulation selection. In this paper, we analyze the impacts of LACO-OFDM layer selection, layer power allocation and modulation selection. Firstly, we compare the BER performance of different power allocation methods and investigate the impact of layers on BER and optical power. On this basis, we propose a joint layer selection and power allocation algorithm. Simulation results show that the proposed power allocation scheme has a better bit error ratio (BER) performance than the common schemes. Finally, we verify the layer modulation selection and propose a search method with low time complexity.

As the transmitter in visible light communications (VLC) system, when the electrical current signal exceeds the input range of light emitting diode (LED), it will cause a nonlinear distortion. Since the electrical current is proportional to the optical power, the nonlinear distortion of electrical current signal is equivalent to the nonlinear distortion of optical power signal. This paper studies the impacts of optical power signal nonlinear distortion on signal distribution and capacity. Firstly, we derive the maximum entropy distribution of the optical power signal and obtain the corresponding capacity lower bound using the entropy power inequality (EPI). Then the nonlinear distortion is modelled as the signal clipping noise, and we analyze the impacts of upper-clipping and lower-clipping on system performance. Numerical results show that a certain degree of signal clipping is acceptable at low optical signal-to-noise ratio (OSNR). However, the clipping should be minimum at high OSNR.

In visible light communications, adding direct current (DC) bias is the most common solution to the bipolar problem of signal, so that the precoding and optical orthogonal frequency division multiplexing (O-OFDM) can be performed. Moreover, it will be easier to achieve dimming control. In this paper, we analyze the impact of DC bias on optical power signal in the view of distribution, capacity and nonlinear distortion. Firstly, we classify the impacts of DC bias into two types depends on the total power, and derive their maximum entropy distributions. Then we investigate the capacity of two different channels with DC bias. Finally, we study the nonlinear distortion of power signal. Derivation and simulation results show that the capacity would decrease as the DC bias increases in most cases. The conclusions will help the consideration of DC bias in future system design.

As one of the potential candidate technologies for sixth generation (6G), visible light communication (VLC) can provide indoor communication services with high data rate when combined with multiple-input multiple-output (MIMO). In this paper, we first study the impact of precoding on zonotopes model of channel and then derive the capacity of VLC-MIMO with precoding when the number of transmitters is greater than receivers. Based on the zonotopes graph, two design principles for VLC-MIMO optimal precoding are obtained. Simulation results show that the commonly used radio frequency (RF)-MIMO precodings can hardly catch the capacity lower bound. The optimal precoding in RF may not be optimal in VLC.

Visible light communication (VLC), as an auxiliary method of radio-frequency (RF) communication, can solve the problem of spectrum shortage in 6G. Due to the channel correlation caused by the layout of light-emitting diodes (LEDs) and photo detectors (PDs) in indoor scenario, the performance of VLC MIMO systems may get a significant degradation. This paper proposes a lamp selection scheme to select the optimal lamp subset to maximize the energy efficiency (EE) while meeting the illumination requirement. Simulation results verify that the performance of the proposed lamp selection scheme is close to that of the optimal scheme while reducing the complexity significantly.

Visible light communication (VLC) multiple-input multiple-output (MIMO) technology is a promising technology in 6G. However, the existing capacity formulae for radio frequency (RF) cannot be directly used for VLC due to the constraints of transmitted signals and unique channel characteristics. In this paper, we make a comparison of different signal distribution. Firstly, we analyze the relationship between transmitted and received signals based on zonotopes model. Then the capacity gap between the truncated Gaussian distribution and uniform distribution is analyzed. Simulations show that the uniform distribution has a better performance than truncated Gaussian, which may promote new signal design for VLC.