Shuyi Shen

Sub-Band Pre-Distortion for PAPR Reduction in Spectral Efficient 5G Mobile Fronthaul

We propose a pre-distortion scheme in transmitter DSP to reduce the peak-to-average power ratio (PAPR) in multi-intermediate-frequency (IF)-over-fiber mobile fronthaul (MFH). In optical spectral efficient MFH, multiple modulated sub-bands are transmitted with different IFs serving multi-in multi-out and carrier aggregation in 5G. By applying phase pre-distortion on sub-bands in the transmitter DSP, we reduce the PAPR by more than 2.2 dB with 1% complementary cumulative distribution function value in MFH for 5G mobile networks and significantly increase the transmitted signal power and quality without modifying the system linearity and resolution. The proposed scheme generates small latency. It is DSP efficient and compatible with current mobile devices, without additional noise. With 32 sub-bands served, we demonstrated a 2-dB sensitivity improvement experimentally by applying the proposed scheme.

Enabling technologies for millimeter-wave radio-over-fiber systems in next generation heterogeneous mobile access networks

Fifth-generation (5G) wireless access network promises to support higher access data rate with more than 1,000 times capacity with respect to current long-term evolution (LTE) systems. New radio-access-technologies (RATs) based on higher carrier frequencies to millimeter-wave (MMW) radio-over-fiber, and carrier-aggregation (CA) using multi-band resources are intensively studied to support the high data rate access and effectively use of frequency resources in heterogeneous mobile network (Het-Net). In this paper, we investigate several enabling technologies for MMW RoF systems in 5G Het-Net. Efficient mobile fronthaul (MFH) solutions for 5G centralized radio access network (C-RAN) and beyond are proposed, analyzed and experimentally demonstrated based on the analog scheme. Digital predistortion based on memory polynomial for analog MFH linearization are presented with improved EVM performances and receiver sensitivity. We also propose and experimentally demonstrate a novel inter-/intra- RAT CA scheme for 5G Het- Net. The real-time standard 4G-LTE signal is carrier-aggregated with three broadband 60GHz MMW signals based on proposed optical-domain band-mapping method. RATs based on new waveforms have also been studied here to achieve higher spectral-efficiency (SE) in asynchronous environments. Full-duplex asynchronous quasi-gapless carrier aggregation scheme for MMW ROF inter-/intra-RAT based on the FBMC is also presented with 4G-LTE signals. Compared with OFDM-based signals with large guard-bands, FBMC achieves higher spectral-efficiency with better EVM performance at less received power and smaller guard-bands.

Efficient Mobile Fronthaul Incorporating VLC Links for Coordinated Densified Cells

We propose a hybrid optical spectral efficient mobile fronthaul (MFH) incorporating low-cost light-emitting diode-based visible light communication (VLC) links in the spatial densified network to enable multi-tier cell coordination. With proposed VLC links between multi-tier master remote radio heads (RRHs) and slave RRHs, fiber connection is not necessary for all RRHs, which simplifies the network structure, and reduces the deployment and operation cost. The proposed architecture can increase the flexibility and capability for network extension significantly by adding new RRHs without fiber deployment. Centralized and distributed pre-equalization are proposed and compared with the letter theoretically and experimentally. In the experiment, we demonstrated a MFH network serving one master RRH and six slave RRHs with only single fiber connection, delivering eight independent long term evolution (LTE) streams with multi-tier cell coordination. Experimental results verify the feasibility of the proposed scheme with high performances suitable for LTE and 64-quadratic-amplitude modulation (64-QAM).

Orthogonal and Sparse Chirp Division Multiplexing for MMW Fiber-Wireless Integrated Systems

Millimeter wave (MMW) bands provide enormous potential in accommodating the explosive mobile data traffic with an increased bandwidth. And fiber-wireless integration is feasible with reduced remote radio head complexity and improved performance by inter-cell coordination. Targeting on improving the wireless transmission reliability in ultra-reliable low-latency communication (URLLC) while maintaining high spectral efficiency in enhanced mobile broadband (eMBB) in 5G, we propose an orthogonal chirp division multiplexing modulation in MMW fiber-wireless integrated systems. By adjusting the sparsity in chirp assignment, we can dynamically and digitally switch between eMBB and URLLC, to serve different traffic patterns and requirements. Without significantly additional complexity in system architecture and DSP, we experimentally demonstrate better reliability to interferences and noises without losing the eMBB data rate or performance.