Henning Paul

Impact of Modulator Bias on the OSNR Requirement of Direct-Detection Optical OFDM

In optical orthogonal frequency-division multiplexing (OFDM) with direct detection, modulator bias voltage has a significant impact on receiver sensitivity. It is a compromise between control of carrier power and nonlinear distortion of the OFDM signal. In this letter, sensitivity improvement due to reduction of carrier power is treated analytically. Its range of validity is examined by simulation. The impact of nonlinearity is identified as the difference in sensitivity between a linear and a nonlinear model.

Benefits and challenges of virtualization in 5G radio access networks

Future 5G deployments will embrace a multitude of novel technologies that will significantly change the air interface, system architecture, and service delivery platforms. However, compared to previous migrations to next-generation technologies, this time the implementation of mobile networks will receive particular attention. The virtualization of network functionality, the application of open, standardized, and inter-operable software, as well as the use of commodity hardware, will transform mobile-network technology. In this article we focus on the benefits, challenges, and limitations that accompany virtualization in 5G radio access networks (RANs). Within the context of virtualized RAN, we consider its implementation requirements and analyze its cost. We also outline the impact on standardization, which will continue to involve 3GPP but will engage new players whose inclusion in the discussion encourages novel implementation concepts.

Implementation and analysis of forward error correction decoding for Cloud-RAN systems

In future 5G mobile networks, radio access network functions will be virtualized and implemented on centralized cloud platforms. In principle, this allows for more advanced algorithms of joint processing and offers the ability to balance the computational load. However, the shift of functionality on a cloud-platform also imposes challenges on the design of the applied algorithms. In this paper, we analyse the implementation of forward error correction decoding algorithms on general purpose hardware, which draws the main computational burden of signal processing in the uplink. Although the protocol stack introduces strict timing requirements we demonstrate by numerical results the feasibility of such implementation.

Bit and power loading for optical IM/DD transmission

Orthogonal Frequency Division Multiplexing (OFDM) is an established technique for equalization of the dispersion-dominated fiber-optical channel. The dispersive nature of the optical channel results in a frequency selective equivalent channel if double sideband (DSB) intensity modulation (IM) and direct detection (DD) is employed. In order to maintain the allpass nature of the physical channel, sideband suppression using optical filters has to be applied. We will show that by use of bit and power loading, this optical filter can be rendered unnecessary.

Linearisation of Transmitter and Receiver Nonlinearities in Optical OFDM Transmission

In this paper, linearisation of transmitter and receiver nonlinearities of an optical Intensity Modulation/Direct Detection system using digital signal processing is presented and analysed. The system performance is estimated on basis of the signal-to-interference-and-noise ratio. Furthermore, the bit error performance of a linearised system is compared to a non-linearised one.