Wireless-optical Access Network Research Articles

Energy Efficiency In Optical-Wireless Access Network Using Dynamic Bandwidth Allocation

High capacity networks are needed for enormous quantity of internet traffic, which is driven by both the exponential growth of the number of people using the internet and the ongoing introduction of new high-bandwidth requiring applications. Combining optical and wireless technologies is a new and promising access network solution. The energy efficiency of telecommunication networks is therefore attracting increasing attention today than in the past. This study is aimed at evaluating energy efficiency of optical-wireless access network which combines Passive Optical Network (PON) and Long Term Evolution - Advanced (LTE-A) networks into one. The network was designed using Optimum Network Engineering Tool (OPNET) modeler software. Traffic was generated using inbuilt tools provided in the OPNET modeler software. Dynamic Bandwidth Allocation (DBA) algorithm was applied on the network and simulation was carried out using the simulation tool provided by OPNET to evaluate the effect of the DBA algorithm on the energy consumption and efficiency in the network. The findings showed energy utilization of 430 watt-second when DBA algorithm was applied on the access network as against 700 watt-second when it was not activated. This shows a 38.6% energy conservation. It was concluded that with the application of energy saving techniques to combined optical-wireless access network, substantial energy could be conserved even in the presence of heavy traffic without compromising the quality of service of the access network.

Photonics-Assisted Millimeter-Wave Communication System Based on Low-Bit Gaussian Mixture Model Adaptive Vector Quantization

The quantization technique with a low-bit resolution can significantly reduce the cost and power consumption of analog-to-digital converter (ADC). It will play an important role in energy conservation and cost reduction for the incoming B5G millimeter-wave (MMW) communication systems. In this paper, we propose and demonstrated experimentally a low-bit Gaussian mixture model (GMM) based non-uniform adaptive vector quantization (AVQ) scheme for the low-cost intensity modulated envelope detection photonics-assisted 28 GHz MMW communication system for the first time. The principles of GMM-based one-dimensional adaptive scalar quantization (ASQ) and multi-dimensional AVQ are first introduced, and then are used to realize the low-bit non-uniform adaptive quantization for reducing the ADC bit resolution of MMW receiver. Furthermore, the performance of traditional uniform quantization, the present <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</i> -means and proposed GMM-based non-uniform ASQ/AVQ schemes are evaluated and compared in detail. Utilizing the proposed GMM-based AVQ scheme, the ADC quantization resolution in our MMW receiver can be reduced from 5 bits of the traditional uniform quantization to as low as 2 bits, without noticeable performance penalty. Moreover, as compared with the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</i> -means-based quantization scheme, the MMW receiver enabled by GMM-based ASQ/AVQ scheme can save about half of the quantization time under similar performance. This is mainly because the clustering based on probability converges faster than the Euclidean distance, which significantly reduces the number of iterations required. Therefore, the GMM-based AVQ scheme is a promising solution to realize high performance ADCs with low-bit resolution for future MMW-enabled optical fiber wireless access networks.

Wavelength &amp; mm-Wave Flexible Converged Optical Fronthaul With a Low Noise Si-Based Integrated Dual Laser Source

A widely tunable hybrid InP-Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> dual laser module (DLM) with low linewidth and relative intensity noise (RIN) is used to develop a wavelength and frequency flexible optical fronthaul system for high-capacity wireless networks. The wavelength flexible (over C-band) delivery of 5G signals over an analog radio-over-fiber (A-RoF) system, incorporating wireless transmission at 60 GHz is demonstrated. A phase noise (PN) and frequency offset (FO) cancelling receiver is used to overcome phase/frequency noise from the DLM due to thermal fluctuations, and this reduces the received (error vector magnitude) EVM to as low as 5%. Using the same DLM we demonstrate the mm-wave frequency flexible (over sub-V-band) delivery of 5G and WiGig signals over a simplified converged fronthaul link. The experimental results show excellent performance with bit error ratio (BER) values as low as 8.46×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> and 1.11×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> , and lowest EVMs of 2.4% and 6.1%, achieved for sub-V-band 5G and WiGig signals, respectively. In addition to highlighting the high flexibility of the DLM, this work also presents an approach to deploy this source in future optical-wireless access networks paving way for beyond 5G and 6G technologies.

Multi Wings Chaotic Encryption Scheme for PAM-DMT-Based Optical Access Network

In this paper, we propose a novel 3-dimension multi wings chaotic encryption scheme for PAM-DMT-based optical wireless access network. In our proposed scheme, one dimension (x) is used for XOR operation, one dimension (y) is used for confusion of PAM signal's amplitude and one dimension (z) is use for DMT subcarrier scrambling. We experimentally demonstrate the 3-dimension multi wings chaotic encryption scheme in PAM4-DMT optical access network. The experimental results show that our proposed scheme can effectively enhance physical-layer transmission security and simultaneously improve transmission performance. What is more, the proposed scheme has good scalability. It can be extended to high order PAM-DMT system and can use more wings to enlarge the key space. To verify the effectiveness of the scheme for practical application, encrypted transmission of a digital image in 60 km SMMF is demonstrated.

Indoor optical wireless access networks—recent progress [Invited

Optical wireless access networks have seen rapid progress. With beam-steering capability, optical wireless communications can deliver very high capacity, support user mobility with indoor localization supported directly at the optical layer, be resilient against the blocking of beams by exploiting spatial diversity at the optical layer, and guarantee low-latency links with modified protocols and network architectures. This paper presents a review of recent progress in achieving functions of communication, localization, resiliency, and dynamic networking using optical-layer techniques.

Digital-Analog Hybrid Optical Access Integrating 56-Gbps PAM-4 Signal and 5G mmWave Signal by Spectral Null Filling

A bandwidth-efficient and low-cost spectral-null-filling scheme simultaneously delivering a 56-Gbps 4-level pulse amplitude modulation (PAM-4) digital signal and a 10 × 400-MHz analog radio frequency (RF) signal on a single wavelength is demonstrated for high-capacity wired and wireless optical access networks. The data rate of the PAM-4 signal is consistent with the next-generation passive optical network (PON), and the PAM-4 signal inherently provides a spectral null at 28 GHz, which can be filled with the RF signal exactly at the 5G-specified millimeter wave (mmW) band. Since pulse shaping is not essential in this hybrid transmission system, a low-cost 2-bit digital-to-analog converter (DAC) is adopted for the PAM-4 signal generation. Volterra nonlinear equalizer is adopted to effectively eliminate the analog-to-digital crosstalk without reserving a frequency gap in between. The digital-analog hybrid signal is simultaneously transmitted over a 25-km standard single-mode fiber in telecom C-band and the impact of chromatic dispersion on the number of supported mmW bands is analyzed. In addition, three types of hybrid transmitters are experimentally demonstrated, among which the first-time proposed IQ-modulator-based hybrid transmitter shows the best performance.

DEC TDMA: A delay controlled and energy efficient clustered TDMA mechanism for FiWi access network

Integration of passive optical network and wireless access network is referred as FiWi access network. It provides larger bandwidth and flexibility for end users to improve last mile performance. With rapid growth in internet traffic and expansion in ICT, reduction in delay and efficient energy utilization have become major concerns in FiWi network. There has been lot of work done on delay and energy efficiency separately for optical back end and wireless front end to provide desired QoS. But this paper presents a cooperative mechanism namely DEC TDMA which is based on the concept of clustered TDMA. In DEC TDMA cooperation between front end and back end is achieved by providing synchronization using time stamping. Analytical expressions are also derived for energy efficiency, cycle time and delay for proposed and existing methods. Results found that proposed mechanism reduces delay very significantly specially at heavy load. It also provides better energy efficiency for large number of ONUs. Moreover DEC TDMA exhibits better delay performance due to implementation of dynamic bandwidth allocation while providing data slots in TDMA. Therefore proposed mechanism offers delay and energy efficient solution for large sized FiWi access network demanding high bandwidth applications in heavy load conditions.

Can Fine-Grained Functional Split Benefit to the Converged Optical-Wireless Access Networks in 5G and Beyond?

The centralized radio access network (C-RAN) is an effective architecture to promote CAPEX/OPEX reduction and cell cooperation derived from its centralized baseband processing. However, there is a contradiction between centralization gain and transport resource saving, which hinders the vision of a resource-efficient and cost-effective RAN deployment. Advanced RAN architectures with functional splits are then introduced to cope with this challenge. Distinguished with other studies, we are intended to investigate whether a fine-grained functional split architecture could benefit to the RAN evolution, and how it impacts on the converged optical-wireless access networks. To this end, we establish a quantitative model to analyze the performance of this architecture. With the fine-grained split, baseband unit (BBU) is divided into a set of fine-grained units (FU) to be placed in desired processing pools (PP) as a service chain. To analyze the placement performance, we propose a mixed-integer linear programming model (MILP) considering the PP selection, routing, wavelength and bandwidth assignment, as well as latency control to minimize the number of PPs, bandwidth, latency, and functions deployment cost. We compare its performance with other two coarse-grained split architectures, i.e., SBBU (adopt low-PHY split like BBU in 4G) and recently emerged DU-CU in both small-scale and large-scale network scenarios. Our analyses provide insights into the modeling and design of efficient converged optical-wireless access networks in 5G and beyond.

Last mile mobile hybrid optical wireless access network routing enhancement

This study focuses on mobile ad hoc networks (MANETs) that support Internet routing protocol imposing stringent resource consumption constraints of Quality of service (QoS). The mobile Internet causes the ongoing issue of inefficient use of the MANET resources due to its random nature of wireless environments. In this paper, the new improved architecture of the last mile mobile hybrid optical-wireless access network (adLMMHOWAN) is proposed and designed to tackle the arised issues. The proposed design is based on a unified wireless-wired network solution required the deployment of MANET-based wireless fidelity (WiFi) technology at the wireless front-end and wavelengths division multiplexing passive optical network (WDM PON) at the optical backhaul. The critical performance metrics such as network capacity and energy consumption based on modified AODVUU routing protocol using OMNeT++ software is analyzed with 2 scenarios, namely the number of nodes and mobility speed. This mode of communication results in better QoS network capacity of 47.07% improvement, with 26.85% reduction of lower energy resource consumption for mobile wireless front-end over passive optical network backhaul architecture when compared with the existing work of oRiq scheme that focus on improvement in MANETs.

Potential Sites Searching for ONUs in FiWi Network

Fiber Wireless (FiWi) access network is the incorporation of optical access network and wireless access network. ONU Placement is important issue in FiWi, since it relates to the network performance and cost of the network. The present research work finding the potential sites of ONUs in the network with the help of proposed algorithm. In this, Firstly ONUs are put in the center part of the grids in network. Further the positions of ONUs are optimized with Whale optimization algorithm followed by minimizing of the ONUs. Hence proposed work gives potential sites for ONUs. Simulation result demonstrates and proves the utility of the present paper.

Bandwidth reusability by handoff management for new ONUs in passive optical networks

Abstract Optical-wireless access networks constitute a very alluring answer to meet the consistently expanding bandwidth requirements of end-clients, offering critical advantages, pervasive scope in the wireless area and immense bandwidth in the optical space. Meeting optical and wireless systems administration innovations, with Passive Optical Networks (PONs) and 4G wireless models; which involves real difficulties such as Dynamic Bandwidth Allocation (DBA) requirement, high frame loss, fairness, increasing data rates of optical networks [1] and selection of an adequate portion of the available spectrum to satisfy the requested capacity [2]. Looking into these problems we have proposed a method which is capable of increasing the capacity with the increase in load. In this specific situation, outlining effective and reasonable bandwidth requirements broadcasting with Quality of Service (QoS) support is a difficult assignment because of the dependence of asset allotment procedure to both optical and wireless areas. This work uses reuse partitioning approach to govern the bandwidth allocation by distributing the optical area into group and sub group with different radii. The reconciling guard bandwidths alleviate the sizeable quantity of increase within the new Optical Network Unit (ONU) interference because of guard bandwidths. The performance of the planned theme is conferred in terms of interference chance, upstream dropping chance shows improvement of 0.14 and bandwidth utilization with improvement of 0.211 by value and 2.2686 × 10 3 in terms of latency improvement. Simulation results show that the planned theme will cut back the interference moreover a dropping considerably in extremely blown up group.

Power Consumption Modeling and Analysis of Integrated Optical-Wireless Access Network

The integration of optical and wireless technologies at access networks are considered as a future solution which provide both high bandwidth and high mobility in an efficient way. GPON is a suitable candidate for optical backhaul due to the combination of higher data rates, greater split ratio and support for triple play services hence it offers maximum flexibility and cost advantages. On the other hand, recent developments of new radio access technologies and introduction of femtocell base stations provide the potential of offering broadband services and applications to everyone and everywhere. However, the power consumption of this network demands a particular attention because access networks are the largest contributor the network related electricity consumption. Therefore, in this paper we evaluate the power consumption of integrated optical-wireless access network which is based on independent ONU-BS architecture. We proposed a power consumption model for such network and the assessment has been done under different simulation scenarios. The constructed model will provide insight of the energy performance of the integrated access network so that in the network design process, focus can be done to the most energy saving strategies.

Analysis of Next-Generation Multiuser Hybrid Optical Wireless Access Network (HOWAN) with Different Technologies; A Review

Today’s rapid speed internet demand has become high to satisfy the request of higher data rate and expensive transmission capacity another communication system required. Optical fiber is used to fulfill these demands. Optical communication is needed for higher speed data transmission. In optical fiber communication, multi carrier modulation (MCM) gives more attention instead of single carrier modulation (SCM). Orthogonal Frequency Division Multiplexing (OFDM) is a very attractive multiplexing and modulation technique that is used for both wireless and wired communication system. Advantages of optical orthogonal system are spectrum efficiency and channel robustness. Optical Orthogonal Frequency Division Multiplexing (OFDM), without complex Equalization can easily adjust to severe channel condition. This paper provides an overview of beginnings, different technologies and latest development of Next Generation of Passive Optical Network Keywords: Orthogonal Frequency Division Multiplexing (OFDM); Coherent receiving; Optical heterodyne; Passive Optical Network; Radio over Fiber (ROF); XG-PON; Multicast.

DIANA: A Machine Learning Mechanism for Adjusting the TDD Uplink-Downlink Configuration in XG-PON-LTE Systems

Modern broadband hybrid optical-wireless access networks have gained the attention of academia and industry due to their strategic advantages (cost-efficiency, huge bandwidth, flexibility, and mobility). At the same time, the proliferation of Software Defined Networking (SDN) enables the efficient reconfiguration of the underlying network components dynamically using SDN controllers. Hence, effective traffic-aware schemes are feasible in dynamically determining suitable configuration parameters for advancing the network performance. To this end, a novel machine learning mechanism is proposed for an SDN-enabled hybrid optical-wireless network. The proposed architecture consists of a 10-gigabit-capable passive optical network (XG-PON) in the network backhaul and multiple Long Term Evolution (LTE) radio access networks in the fronthaul. The proposed mechanism receives traffic-aware knowledge from the SDN controllers and applies an adjustment on the uplink-downlink configuration in the LTE radio communication. This traffic-aware mechanism is capable of determining the most suitable configuration based on the traffic dynamics in the whole hybrid network. The introduced scheme is evaluated in a realistic environment using real traffic traces such as Voice over IP (VoIP), real-time video, and streaming video. According to the obtained numerical results, the proposed mechanism offers significant improvements in the network performance in terms of latency and jitter.

Design and development of a portable bit-error rate tester with low cost for any rate between 10 Mb/s and 11.3 Gb/s

The bit-error rate (BER) is an important specification for characterizing the reliability of a communication network link. Aiming at the passive optical access network and wireless broadband access network with the multi-rate levels and the high cost of operation and maintenance, a low cost and portable bit-error rate tester (BERT) with both optical and electrical ports, and operational rates between 10Mb/s and 11.3Gb/s, is designed and developed in this paper, which consists of a pseudo random binary sequence (PRBS) generator, an error detector (ED), a microcontroller unit (MCU) and a small form-factor pluggable optical transceiver. The test results reveals the generated PRBS has the characteristics of high stability and low jitter and the error counter is accurate for a variety of communication protocols.

New Perspectives on Future Smart FiWi Networks: Scalability, Reliability, and Energy Efficiency

Fiber-Wireless (FiWi) network, as an integration of optical fiber network and wireless access network, has attracted intensive research interest and enjoyed significant growth in its applications over the last two decades. Besides bringing great opportunities for the development of FiWi networks, the new applications and techniques, like the emerging Internet of Things (IoT), raise unprecedented challenges in different aspects of FiWi integration. Based on such observation, we provide in this paper a comprehensive survey of recent progress and ongoing research works in the aspects of network architecture, QoS provisioning, scalability improving, reliability enhancing, energy saving, as well as standardization activities and case studies. Furthermore, new trends and challenging issues on future smart FiWi networks are identified and discussed in details.

Optical wireless network convergence in support of energy-efficient mobile cloud services

Mobile computation offloading has been identified as a key-enabling technology to overcome the inherent processing power and storage constraints of mobile end devices. To satisfy the low-latency requirements of content-rich mobile applications, existing mobile cloud computing solutions allow mobile devices to access the required resources by accessing a nearby resource-rich cloudlet, suffering increased capital and operational expenditures. To address this issue, in this paper, we propose an infrastructure and architectural approach based on the orchestrated planning and operation of optical data center networks and wireless access networks. To this end, a novel formulation based on a multi-objective nonlinear programming model is presented that considers energy-efficient virtual infrastructure planning over the converged wireless, optical network interconnecting DCs with mobile devices, taking a holistic view of the infrastructure. Our modelling results identify trends and trade-offs relating to end-to-end service delay, mobility, resource requirements and energy consumption levels of the infrastructure across the various technology domains.

Polar-Based OFDM and SC-FDE Links Toward Energy-Efficient Gbps Transmission Under IM-DD Optical System Constraints [Invited

Recent studies have investigated the use of orthogonal frequency division multiplexing (OFDM) and single carrier frequency-domain equalization (SC-FDE) for gigabyte per second (Gpbs) short-range optical wired and wireless access networks based on direct intensitymodulation with direct detection (IM-DD). OFDM systems have an inherent high peak-to-average power ratio (PAPR). SC-FDE systems have lower PAPR and thus outperform comparable OFDM systems in terms of bit-error performance under various practical considerations, mainly the limited dynamic range of operation at the transmitter. In RF-based OFDM and SC-FDE systems, the output signal is bipolar, complex, and cannot be transmitted in IM-DD systems. Therefore, several power efficient schemes, however spectrally inefficient, have been proposed to make positive OFDM and SC-FDE signals, e.g., asymmetrically clipped optical OFDM (ACO-OFDM) and repetition and clipping optical SCFDE (RCO-SCFDE). To increase the data rate, novel OFDM and SC-FDE signal formats, called polar OFDM (P-OFDM) and polar SC-FDE (P-SC-FDE), based on a polar representation of complex symbols, are proposed. The proposed format offers twice as much spectral efficiency as state-of-the art unipolar OFDM and SC-FDE formats. Moreover, using a power allocation approach on the time-domain positive samples, the PAPR is further reduced, and the numerical evaluation of the bit-error performance under optical source power and dynamic range constraints demonstrates superior results toward Gpbs transmission.

Wired and wireless convergent extended-reach optical access network using direct-detection of all-optical OFDM super-channel signal

We propose and demonstrate the feasibility of using all-optical orthogonal frequency division multiplexing (AO-OFDM) for the convergent optical wired and wireless access networks. AO-OFDM relies on all-optically generated orthogonal subcarriers; hence, high data rate (> 100 Gb/s) can be easily achieved without hitting the speed limit of electronic digital-to-analog and analog-to-digital converters (DAC/ADC). A proof-of-concept convergent access network using AO-OFDM super-channel (SC) is demonstrated supporting 40 - 100 Gb/s wired and gigabit/s 100 GHz millimeter-wave (MMW) ROF transmissions.

Delay analysis of converged optical‐wireless networks with quality of service support

The convergence of two popular access technologies, namely Worldwide interoperability for Microwave Access (WiMAX) and passive optical network (PON) is a promising access solution that combines the mobility feature of WiMAX and the ample bandwidth of PONs. In such a converged optical-wireless access network, the provision of quality of service (QoS) support is a challenging issue, mainly because of the different bandwidth allocation mechanisms of the two access technologies. Since the considered convergence seems to be dominant, it deserves assiduous analysis and evaluation. In this study, the authors investigate the delay performance of a converged optical-wireless network that provides QoS support by considering multiple service-classes with different priorities. In the wireless domain, the IEEE 802.16 standard is applied, whereas in the optical domain a wavelength division multiplexing ethernet PON provides connectivity to both wired and wireless users. The authors present an analytical framework for the calculation of the average end-to-end packet delay of each service-class, by developing two queuing models for each domain of the converged network. The end-to-end delay is calculated as the sum of the queuing delay in both domains, and the transmission and propagation delay in the optical domain. The accuracy of the proposed analysis has been verified by simulation and found to be quite satisfactory.