Hussein Seleem

A Projected Parallel Interference Cancellation for Asynchronous Upstream OCDMA-PON

OCDMA is a promising candidate for next generation passive optical networks (NG-PON). OCDMA-PON can potentially provide all customers with a Gb/s-class BW upstream with inherent flexibility. Unfortunately OCDMA suffers from multiple access interference (MAI) and various detection noises. To mitigate MAI, we propose a novel parallel interference cancellation technique for incoherent DS-OCDMA that better exploits the non-negativity of the solution. The proposed PIC scheme incorporates this additional information into its structure. The proposed PIC detector is shown to outperform the conventional correlator detector, the decorrelator detector, the linear parallel interference Cancellation (LPIC) detector and even the linear minimum mean square error (LMMSE) detector.

Path loss channel models for 5G cellular communications in Riyadh city at 60 GHz

This paper presents propagation path loss channel models developed from real-field measurement campaigns that were conducted in indoor and outdoor Line-of-Site (LOS) propagation environments in Riyadh city, Saudi Arabia, using highly directional antennas at 60 GHz. The setup used in these measurements emulates the future fifth-generation (5G) cellular systems for both access and backhaul services, as well as for Machine-to-Machine (M2M) communications. We used our measurement data to develop the corresponding large-scale propagation path loss models at 60 GHz, using the log-distance and the floating intercept modeling approaches. It is shown that cellular radio links can be established in short-range distances up to 134 m indoors, and up to 77 m outdoors, when employing highly directional antennas at both the transmitter and receiver sides. It is also shown that path loss at 60 GHz in hot and sunny weather during the day, is higher than those obtained in cool and clear weather at night. This is partly due to solar radio noise effect arising from the intense solar radiation that characterizes summer afternoon in Riyadh city, which can cause a decrease in carrier-to-noise ratio at the input of receiving antennas. It is also partly due to the increase in thermal noise when electronics components in the measurement device become hot. The results presented here are thus very useful in 5G cellular design and infrastructure planning in the gulf region, where daytime temperature could reach 43° C or more.

Efficient interference cancellation detector for asynchronous upstream optical code division multiple access-passive optical network with mixed Poisson-Gaussian noise

Optical code division multiple access (OCDMA) is a promising candidate for next generation passive optical networks (NG-PON). OCDMA-PON can potentially provide all customers with a Gb/s-class BW upstream with inherent flexibility. Unfortunately OCDMA suffers from multiple access interference (MAI) and various detection noises. In this study, the authors consider developing efficient interference cancellation detection under mixed Poisson-Gaussian noise. The latter is more realistic than considering Gaussian or Poisson noise alone. The authors first start by developing a maximum likelihood framework of the detection process under Gaussian, Poisson and Poisson-Gaussian noises, respectively. Then, the authors develop the proposed interference cancellation detector for the Poisson-Gaussian noise case after deriving the conventional expectation-maximisation (EM) detector for the Poisson noise case. Finally, the authors simulate the proposed detector and compare it to the projected parallel interference cancellation, EM and other detectors to validate its superiority and enhanced performance.

Design tradeoffs of few-mode step index fiber for next generation mode division multiplexing optical networks

Next generation few mode fibers (FMF) promise to substantially increase the spectral efficiency of existing state-of-the-art optical communication networks by an order of magnitude [1]. In FMF, individual propagating modes are considered as independent optical communication channels that carry separate streams of data. The performance of these communication streams however, suffers from inter channel interference (ICI) that depends on the physical characteristics of the optical fiber. The ICI mainly results of two impairments, namely the mode coupling and the differential mode delay. It is known that step index (SI) FMF is the less expensive and the easiest to fabricate in addition to having a limited number of physical design parameters, i.e., step refractive index and core diameter. Our objective here is first to investigate the design trade-offs of SI-FMF and then identify the parameters intervals that minimize the inter channel interference by reducing: the mode coupling and the differential mode delay. Our numerical simulation identifies the desired design regions that minimize these impairments separately. Our analysis also illustrates the challenge to minimize both impairments simultaneously and get compromising design solutions.

Two-Stage Multiuser Access in 5G Cellular Using Massive MIMO and Beamforming

This paper explores the possibility of using multiuser massive MIMO and beamforming together as two-stage multiuser access methods in 5G cellular. Multi-carrier OFDM transmission as currently used in the 4G-LTE may be difficult to implement in 5G cellular because of the peculiarities of mmWave channels. Therefore, there is the need to analyze and propose suitable physical layer techniques suitable for 5G systems that are amenable to beamforming and/or massive MIMO. It turns out that both of these schemes are inherently multiuser access methods and can be used together in 5G cellular. Our results show that simple transmitter and receiver processing can be achieved when using the combined system. Moreover, the proposed approach will allow the system to accommodate more users at minor error rate degradation.

Penalised and doubly-penalised parallel/successive interference cancellation multi-user detectors for asynchronous upstream optical code division multiple access passive optical network

Optical code division multiple access (OCDMA) is one of the emerging technologies for next generation passive optical networks that can offer customers a Gb/s-class experience in the upstream. However, OCDMA suffers from multiple access interference (MAI) that significantly reduces the capacity of the system. To mitigate MAI, three novel interference cancellation (IC) techniques have been proposed for incoherent direct sequence OCDMA systems that make use of some prior information to enhance their performance. Some of the IC structures exploit the non-negativity of the solution, while others exploit in addition to the non-negativity information the noise variance information. The proposed IC detectors outperform the conventional correlation receiver, the decorrelator detector, the linear parallel/successive interference cancellation detectors and even the linear minimum mean square error detector.

Hybrid Precoding-Beamforming Design With Hadamard RF Codebook for mmWave Large-Scale MIMO Systems

This paper proposes a hybrid structure for multi-stream large-scale multi-input multi-output (MIMO) beamforming systems, in single-user scenario, using a Hadamard radio frequency (RF) codebook with low-bit resolution phase shifters. We show that Hadamard transform can be used in RF beamsteering/beamcombining to achieve better performance in terms of average achievable spectral efficiency and low hardware cost using 1- or 2-b resolution APSs. In contrast, the state-of-the-art RF codebook designs available in the literature requires more than 7-b resolution to achieve the same performance as the proposed scheme, for large antenna arrays with up to 256 elements. The performance gains of the proposed RF codebook design is thoroughly investigated using MATLAB simulations for typical mmWave MIMO system, and the simulation results are closely verified by the analytical expressions.

Proposed Raised Cosine FMF for Dispersion Management in Next-Generation Optical Networks

Spatial mode-division multiplexing (MDM) that exploits the emerging few-mode fiber (FMF) technology is one potential candidate for next-generation petabyte optical communication links. In this paper, we focus on the design issues and specifications of the next-generation FMF that will better enable future MDM networks. These systems suffer from two main optical fiber impairments: intermodal coupling and dispersion. In this paper, we focus on the dispersion management issues through an FMF optical link. We first define two potential differential mode group delay (DMD) management strategies, namely, sawtooth and triangular. Moreover, we propose and investigate a novel parametric refractive index profile few-mode fiber, referred to as raised cosine (RC) function, which has been extensively used in digital communication pulse shaping. We investigate the achievable DMD for a wide range of the RC shape parameter and identify the design values of a two-mode FMF fiber. We then improve the RC profile by including additional shaping parameters. This enabled us to develop one four-mode fiber (4-FMF) and one six-mode fiber (6-FMF) having particularly attractive dispersion characteristics for three kinds of FMF applications: nz-, p-, and n-DMD.

Multiplicative PIC Detection for OCDMA Systems with Non-Negativity Constraints

Non-negativity constraints arise naturally in many applications such as medical and astronomical imaging. These constraints have been recently exploited in the optical communication field where a projected parallel interference cancelation detector has been developed within the context of cancelling multi-access interference in upstream on-off-keying optical code division multiple access passive optical networks; the latter possess the property that the transmitted data symbols are non-negative. The authors build upon these results and propose a new parallel interference cancellation structure with better features and improved performance. This detector is characterised by a multiplicative update equation and it exhibits a number of unique and desirable features such as stability and smooth convergence behaviour even for highly loaded systems. Up to our knowledge, this structure has not been proposed before either in optical or in wireless communication field. Simulation results are promising and further improvements are possible.

Experimental Demonstration for PAPR Reduction in OFDM System Using Partial-OSLM Technique

Orthogonal frequency division multiplexing (OFDM) modulation is proposed in 4G wireless communication systems, and is under consideration for the next generation 5G systems. This is due to the higher spectral efficiency (SE) and the better immunity to channel distortions. One of the shortcomings in OFDM is its high peak-to-average power ratio (PAPR). Several schemes have been proposed to reduce the PAPR in OFDM systems. This includes clipping, coding, and pre/post-distortion schemes with or without side information. In this paper, we experimentally demonstrate one of the most promising method, to mitigate the effect of PAPR, entitled the partial orthogonal selective mapping (POSLM). The experimental results show a comparable performance with respect to the simulation results in terms of PAPR reduction, power spectral density (PSD), and bit error rate (BER) metrics.