Shigeru Kuwano

Split-PHY processing architecture to realize base station coordination and transmission bandwidth reduction in mobile fronthaul

We propose a new RAN architecture splitting BS functions within PHY layer. It reduces mobile fronthaul transmission bandwidth by 90 % and achieves BS coordination performance with 0.5 dB SNR degradation compared to conventional C-RAN.

Performance evaluation of mobile front-haul employing ethernet- based TDM-PON with IQ data compression [Invited]

In this paper, we experimentally and numerically evaluate the performance of a common public radio interface (CPRI) over a time division multiplexed passive optical network (TDM-PON) system for accommodating densely deployed small cells in centralized-radio-accessnetwork- based future radio access. A prototype of the CPRI over TDM-PON is developed by using Ethernet-based TDM-PON. Experimental results showed that its synchronization accuracy and latency meet the requirements of a mobile front-haul using CPRI by the implemented delay jitter reduction and low-latency bandwidth allocation techniques. An in-phase and quadrature (IQ) data compression technique is also implemented on the system to enable a higher accommodation of remote radio heads. Experiments confirmed that the compression technique meets open radio equipment interface standards in terms of latency and signal quality degradation. Numerical results showed that the technique with a 0.45 compression ratio increases the number of supportable remote radio heads from 3 to 7 for a mobile front-haul with a 100 μs latency limitation.

Mobile front-haul employing ethernet-based TDM-PON system for small cells

We develop a mobile front-haul prototype based on TDM-PON (10G-EPON). The system can accommodate 3 CPRI option-3 links and 7 compressed CPRI option-3 links with reasonable latency under 100 μs.

Analysis of mobile fronthaul bandwidth and wireless transmission performance in split-PHY processing architecture.

We analyze the mobile fronthaul (MFH) bandwidth and the wireless transmission performance in the split-PHY processing (SPP) architecture, which redefines the functional split of centralized/cloud RAN (C-RAN) while preserving high wireless coordinated multi-point (CoMP) transmission/reception performance. The SPP architecture splits the base stations (BS) functions between wireless channel coding/decoding and wireless modulation/demodulation, and employs its own CoMP joint transmission and reception schemes. Simulation results show that the SPP architecture reduces the MFH bandwidth by up to 97% from conventional C-RAN while matching the wireless bit error rate (BER) performance of conventional C-RAN in uplink joint reception with only 2-dB signal to noise ratio (SNR) penalty.

Operator perspective on next-generation optical access for future radio access

Toward 5G mobile systems for 2020 and beyond, aggressive studies on radio access networks (RANs) are underway. In 5G systems, the role of the small cell based RAN is important to provide 10 Gb/s class broadband and flexible services, and optimization of the optical access network to accommodate small cells is also important. To efficiently deploy and operate small cells, cooperation between mobile and optical access networks is essential. For the fixed network operator side, TDM-PON based mobile backhaul and fronthaul are preferable for its cost effectiveness. In this article, radio access and optical access technologies are briefly introduced, and TDM-PON based optical access techniques for future radio access are described.

Dynamic IQ data compression using wireless resource allocation for mobile front-haul with TDM-PON [invited]

The time-division multiplexed-passive optical network (TDM-PON) architecture can efficiently accommodate densely deployed small cells in a centralized radio access network (C-RAN)-based future radio access (FRA). C-RAN is a type of mobile front-haul network, which connects multiple remote radio heads to a baseband unit pool by optical links. The required optical bandwidth in the mobile front-haul of FRA is very large, so it is necessary to efficiently use the optical bandwidth by using in-phase and quadrature-phase (IQ) data compression techniques. This paper proposes an IQ data compression technique that dynamically reduces the required optical bandwidth based on wireless resource allocation, and provides TDM-PON with statistical multiplexing gain. Simulation results showed the achievable compression ratio of the proposed IQ data compression technique. The feasibility of our technique was confirmed by experiments. The reduction in the average TDM-PON bandwidth was 50% when there were 60 mobile terminals, all of which required 0.18 Mbps bandwidth.

Uplink Joint Reception with LLR Forwarding for Optical Transmission Bandwidth Reduction in Mobile Fronthaul

We propose an uplink joint reception method for coordinated multi-point transmission and reception (CoMP) where the quantized log likelihood ratio (LLR) is forwarded by an optical interface different from the common public radio interface (CPRI), to suppress the explosive increase in the optical transmission bandwidth in the mobile fronthaul (MFH) of the centralized/cloud radio access network (C-RAN) and thus reduce the MFH optical transmission cost of future radio access. To exploit the proposed method, we focus on the split-PHY processing (SPP) architecture for MFH redefinition where the base station (BS) functions are split between modulation and channel coding functions within the PHY (Physical) layer. Numerical simulations of block error rate (BLER) performance confirm a signal to noise ratio (SNR) degradation due to the proposed method in the SPP architecture of less than 3 dB compared with the conventional C-RAN, and an SNR improvement compared to the performance without joint reception of more than 5 dB. Meanwhile, numerical calculations that assume future radio access show that the SPP architecture with the proposed method reduces MFH optical transmission bandwidth by at least 85 % compared to the conventional C-RAN. These results show that the SPP architecture with the proposed method will enable cost-effective MFH deployment.

System level performance of uplink transmission in split-PHY processing architecture with joint reception for future radio access

In this paper, the system level performance of uplink transmission in the split-PHY processing (SPP) architecture is evaluated. The SPP architecture splits the PHY functions of the base station so that some PHY functions are implemented on the remote radio head (RRH). Compared to the centralized radio access network (C-RAN) architecture with common public radio interface (CPRI), the SPP architecture significantly reduces the required optical bandwidth in the mobile front-haul. Moreover, by implementing the FEC processing in the baseband unit (BBU), joint reception can be realized in uplink transmissions by forwarding the quantized log likelihood ratio (LLR) from RRHs to the BBU. System level evaluations show that the SPP architecture improves the cell-edge user throughput by 116 % compared with the MAC-PHY split architecture without coordinated operations while reducing the required optical bandwidth by 92 % compared with the C-RAN architecture.

Mobile optical network for future radio access

As a future step of LTE-Advanced, future radio access based on large numbers of small cells of various types has been studied. Possible architectures and requirements of a mobile optical network that forms mobile fronthaul and mobile backhaul of the small cells, as well as some passive optical network (PON)-based technologies are provided.

Performance evaluation of mobile fronthaul optical bandwidth reduction and wireless transmission in Split-PHY processing architecture

The RAN architecture splitting BS functions within PHY layer is prototyped and evaluated to confirm its validity. Experiments show that mobile fronthaul optical bandwidth is reduced by 90% compared to conventional C-RAN maintaining wireless performance.