Fronthaul evolution: From CPRI to Ethernet

It is proposed that using Ethernet in the fronthaul, between base station baseband unit (BBU) pools and remote radio heads (RRHs), can bring a number of advantages, from use of lower-cost equipment, shared use of infrastructure with fixed access networks, to obtaining statistical multiplexing and optimised performance through probe-based monitoring and software-defined networking. However, a number of challenges exist: ultra-high-bit-rate requirements from the transport of increased bandwidth radio streams for multiple antennas in future mobile networks, and low latency and jitter to meet delay requirements and the demands of joint processing. A new fronthaul functional division is proposed which can alleviate the most demanding bit-rate requirements by transport of baseband signals instead of sampled radio waveforms, and enable statistical multiplexing gains. Delay and synchronisation issues remain to be solved

A Flexible, Ethernet Fronthaul for 5th Generation Mobile and Beyond

Using Ethernet in the fronthaul can deliver the statistical multiplexing gains offered by the new functional splits proposed for the radio access network, but latency and delay variations are challenges that must be overcome

Somatic Mutation of the Cd95 Gene in Human B Cells as a Side-Effect of the Germinal Center Reaction

Somatic hypermutation specifically modifies rearranged immunoglobulin (Ig) genes in germinal center (GC) B cells. However, the bcl-6 gene can also acquire somatic mutations during the GC reaction, indicating that certain non-Ig genes can be targeted by the somatic hypermutation machinery. The CD95 gene, implicated in negative selection of B lymphocytes in GCs, is specifically expressed by GC B cells and was recently identified as a tumor suppressor gene being frequently mutated in (post) GC B cell lymphomas. In this study, the 5′ region (5′R) and/or the last exon coding for the death domain (DD) of the CD95 gene were investigated in naive, GC, and memory B cells from seven healthy donors. About 15% of GC and memory, but not naive, B cells carried mutations within the 5′R (mutation frequency 2.5 × 10−4 per basepair). Mutations within the DD were very rare but could be efficiently selected by inducing CD95-mediated apoptosis: in 22 apoptosis-resistant cells, 12 DD mutations were found. These results indicate that human B cells can acquire somatic mutations of the CD95 gene during the GC reaction, which potentially confers apoptosis resistance and may counteract negative selection through the CD95 pathway

Software-defined open architecture for front- and backhaul in 5G mobile networks

New software-defined open network concepts are proposed in this paper to enable an efficient implementation of front- and backhaul solutions for future 5G mobile networks. Main requirements for 5G front- and backhaul are derived and then related to the open network architecture enabling multiple operators to share the same physical infrastructure. The value of software-defined networking (SDN) is particularly outlined therefore. For the use of SDN in the fronthaul, CPRI over Ethernet (CoE) is proposed as a new transport protocol. In the backhaul, distributed security can be implemented using SDN where direct links are confined inside the access domain, as opposed to the current centralized security solution including also the transport domain. In this way, low latency can be realized e.g. for machine-type communications. As the benefits for fixed-mobile convergence are evident, SDN should be enabled increasingly in the access domain. © 2014 IEEE

Analog vs. Next-Generation Digital Fronthaul: How to Minimize Optical Bandwidth Utilization

In this paper we investigate two promising approaches to reduce the optical bandwidth utilization in the mobile fronthaul of next-generation cloud radio access networks. We analyze and compare the performance of an analog radioover-fiber and a new digital fronthaul in a chromatic dispersionlimited scenario. The former uses several analog channels, generated by up- and down-converting of baseband signals, and the latter utilizes simple OOK NRZ for the transmission to the remote radio head. Both principles are applied to a custom millimeter-wave system, consisting of several analog channels with baseband bandwidths as expected for 5G. The performance of both concepts at transmission rates of up to 100 Gb/s and 100 km of fiber is evaluated. We will show that both approaches are suitable for transmission distances typical for fronthaul and discuss their advantages and disadvantages. Furthermore, an optimized bandwidth concept for the analog radio-over-fiber system is presented, which enables transmission distances on the scale of metro networks

Special Issue on Light Communications: Latest Advances and Prospects

The wireless information carrier shift from the radio frequencies to optical frequencies has been studied in increasing detail since the invention of the laser in the 1960s. With the advent of optical fiber communications and their global use, we have seen a growing interest in the field of optical wireless communications (OWC) for front- and back-haul access networks and beyond as part of fifth-generation (5G) wireless networks. OWC has found niche applications in a wide range of systems, from short-range indoor to long-range outdoor and very long deep space and inter-satellite links. New components, such as visible light-emitting sources, image sensors, advanced signal processing techniques, multi-input multi-output, and machine learning are pushing the OWC technology into new application areas such as vehicular communications, smart environments, medical, manufacturing, etc., as part of 5G wireless networks and the emerging 6G networks and beyond.This Special Issue was put together with the goal of bringing together the latest research and development in wireless light communications. A total of 53 submissions were received, and 24 were selected for publication in this Special Issue. The published works present novel results mainly on outdoor and indoor applications of light communications, while a few papers also address broader areas. We briefly present these works in the following sections

Experimental Investigation of New Fronthaul Concepts for 5G

The evolution to a centralized radio access network (C-RAN), where multiple base band units (BBU) are co-located to jointly serve multiple remote radio heads (RRH), results in a more efficient use of radio resources [1]. Nevertheless, it also imposes more stringent requirements on the transport network connecting the BBU pool to the RRHs, also known as fronthaul. Especially the increasing demand for higher data rates in the fronthaul challenges current solutions based on protocols like the widespread common public radio interface (CPRI). In this paper, we investigate two promising approaches to reduce the optical bandwidth utilization in the mobile fronthaul of next-generation cloud radio access networks. We experimentally analyze and compare the performance of an analog radio-over-fronthaul and a new digital fronthaul. The analog system consists of four pi/4-shift DQPSK modulated sub-channels with a data rate of 2.5 Gbit/s each and originates from a custom millimeter-wave system. The digital fronthaul approach utilizes On-Off-Keying (OOK) and is based on 10 Gigabit Ethernet. Kurzfassun