Fast SC decoding overcomes the latency caused by the serial nature of the SC decoding by identifying new nodes in the upper levels of the SC decoding tree and implementing their fast parallel decoders. In this work, we first present a novel sequence repetition node corresponding to a particular class of bit sequences. Most existing special node types are special cases of the proposed sequence repetition node. Then, a fast parallel decoder is proposed for this class of node. To further speed up the decoding process of general nodes outside this class, a threshold-based hard-decision-aided scheme is introduced. The threshold value that guarantees a given error-correction performance in the proposed scheme is derived theoretically. Analysis and hardware implementation results on a polar code of length 1024 with code rates 1/4, 1/2, and 3/4 show that our proposed algorithm reduces the required clock cycles by up to 8%, and leads to a 10% improvement in the maximum operating frequency compared to state-of-the-art decoders without tangibly altering the error-correction performance. In addition, using the proposed threshold-based hard-decision-aided scheme, the decoding latency can be further reduced by 57% at Eb/N0= 5.0 dB.

This paper focuses on fast successive-cancellation (SC) decoding of polar codes. A threshold-based hard-decision-aided scheme is proposed to speed up the decoding process, especially when the communications channel has low noise. In addition, to eliminate the error-correction performance degradation caused by hard decisions, a backtracking strategy is introduced. Simulation results on a polar code of code length 1024 and rate 1/2 show that, with the help of the proposed scheme, the average decoding latency of existing fast SC decoding algorithms can be reduced by 53% at an Eb/N0 = 5.0 dB with negligible error-correction performance degradation.

This study proposes an enhanced list‐aided successive cancellation stack (ELSCS) decoding algorithm with adjustable decoding complexity. Also, a logarithmic likelihood ratio‐threshold based path extension scheme is designed to further reduce the memory consumption of stack decoding. Numerical simulation results show that without affecting the error correction performance, the proposed ELSCS decoding algorithm provides a flexible trade‐off between time complexity and computational complexity, while reducing storage space up to 70%. Based on the fact that most mobile devices operate in environments with stringent energy budget to support diverse applications, the proposed scheme is a promising candidate for meeting requirements of different applications while maintaining a low computational complexity and computing resource utilisation.

The development of 5G wireless networking is flourishing, introducing major paradigm shifts and key new technologies such as Radio- over-Fiber (RoF). A fundamental concept for achieving the 5G design objectives is dynamically allocating frequencies, sub-bands and wavelengths. While these allocation problems have been extensively studied in wireless and optical domains in isolation, the combination has received little attention so far. However, with the advances in software-defined radio access networking and RoF technologies, there is increasing need and scope for joint optimization across the two domains, in order to harness the full potential of these networks. Motivated by these observations, we introduce a model for jointly optimal sub-band and wavelength allocation in pico-cell networks where virtual access points (APs) transmit via remote radio heads (RRHs) connected through RoF technology. We specifically account for the optical network topology, which introduces a distinct set of constraints in both the optical and wireless domain. Since the resulting load balancing problem is NP-hard, we introduce a heuristic for obtaining a stabilizing allocation which provides all RRHs with sufficient spectrum capacity to deal with their load. Numerical experiments demonstrate that the heuristic provides near-optimal solutions.

Network densification has emerged as a powerful paradigm to boost spectral efficiency and accommodate the continual rise in demand for wireless capacity. The corresponding reduction in cell sizes also results however in greater spatial and temporal uncertainty and variation in traffic patterns and more extreme and unpredictable interference conditions. These features create unprecedented challenges for efficient allocation of spectral resources compared to conventional cellular networks. As a further challenge, the allocation of spectral resources needs to be jointly optimized with the assignment of wavelengths in the optical backhaul of Radio-over-Fiber (RoF) networks, which are increasingly used in dense deployments and indoor environments. Motivated by these issues, we develop online algorithms for joint radio frequency and optical wavelength assignment in RoF networks. The proposed algorithms rely on load measurements at the various access points, and involve configurable thresholds for triggering (re)assignment of spectral resources. We provide a detailed specification of a system implementation, and conduct extensive simulation experiments to examine the behaviour in various scenarios and assess the impact of key parameters. The results in particular demonstrate that the proposed algorithms are capable of maintaining adequate load levels for spatially heterogeneous and time-varying traffic conditions, while providing favourable throughput performance.

Optical Wireless (OW) technologies deploying narrow multiwavelength light beams offer a promising alternative to traditional wireless indoor communications as they provide higher bandwidths and overcome the radio spectrum congestion typical of the 2.4 and 5GHz frequency bands. However, unlocking their full potential requires exploring novel control and management techniques. Specifically, there is a need for efficient and intelligent resource management and localization techniques that allot wavelengths and capacity to devices. In this paper we present a resource allocation model for one such indoor optical wireless approach, a Beam-steered Reconfigurable Optical-Wireless System for Energy-efficient communication (BROWSE). BROWSE aims to supply each user within a room with its own downstream infrared light beam with at least 10Gbps throughput, while providing a 60GHz radio channel upstream. Using Integer Linear Programming (ILP) techniques, we have designed and implemented a resource allocation model for the BROWSE OW downstream connection. The designed model optimises the trade-off between energy-consumption and throughput, while providing TDM capabilities to effectively serve densely deployed devices with a limited number of simultaneous available wavelengths. Through several test-scenarios we have assessed the model's performance, as well as its applicability to future ultra-high bandwidth video streaming applications.

Prioritization of flows in a home network based on traffic classification is still no guarantee that enough bandwidth will be available between a server and a client. Besides, such QoS technologies need to be supported by every device in the end-to-end path to be effective, which is relatively expensive for the owners of home networks. In any small-scale IP network (best-effort or QoS-enabled) it is therefore preferable to diagnose the network in real time, before admitting a new flow. In this paper we demonstrate a new method to probe the available bandwidth between a server and a client in an IP-based home network. The tool works with existing end-user devices, is non-intrusive, has a short measurement time, does not require pre-knowledge of the link layer network topology, and is accurate enough to make decisions about the admission of high-throughput high-quality streams such as for IPTV services.

Current QoS solutions for home networks are inspired by Internet technologies and typically based on traffic classification and prioritization. They are not well adopted because they need to be supported by every device in the end-to-end path to be effective. Besides, their use still does not guarantee that enough bandwidth will be available between a server and a client. It is therefore preferable to diagnose a home network in real time before admitting a new flow. We demonstrate a new method which probes the end-to-end path capacity as well as the available bandwidth in a small-scale IP network. Its distinguishing features are the applicability to networks consisting of legacy devices and any mixture of wired, wireless, and no-new-wires links, in combination with fast convergence, high accuracy, and non-intrusiveness.

Current QoS solutions for IP networks are usually based on traffic classification and need to be supported by every device in the end-to-end path to be effective. This is relatively expensive for home networks. Alternative techniques have been proposed that require end-user services to pragmatically adapt their properties to the actual condition of the network. For this, the condition of the network needs to be known in real time. In this article we demonstrate a new method to probe the path capacity between a server and a client in a home network or any other best-effort small-scale IP network. The tool requires adaptation of the server side only, is non-intrusive, has a short measurement time, does not require pre-knowledge of the link-layer network topology, and is accurate enough to make educated predictions about the admission of IPTV services and the like.

The increasing amount of bandwidth requirements and quality of service needs for the next-generation access networks has boosted extensive research in the fiber-optics communication field. In this light, passive optical networks (PONs) combined with optical code division multiple access (OCDMA), provide a potentially cost-effective solution to meet such bandwidth demands. This work proposes an optical transparent architecture which enables all-optical communication between the network nodes. The encoded data streams are multiplexed at a merging point which results in multiple user interference (MUI), thus significantly reducing the network throughput. The networking nodes are able to monitor and record user activity in the PON, and further register the (past) state of activity at the merging point. In this work, we study the coherence of state between the networking nodes and the merging point, for different packet size distributions, in order to predict an optimal transmission instant of each node's data packets. We note that the states are coherent depending on the packet size distribution.

Current service discovery protocols (SDP) hardly provide information on the actual availability of resources in the network or a mechanism for (device) resource reservation. When the resources cannot serve all multiple client requests at the same time, conflicts happen, often involving heavy and frequent reconfiguration traffic. This paper presents a generic resource reservation scheme. Its properties are derived from common SDP operations. We built a prototype, measured the extra overhead such a reservation manager introduces and simulated the gain in network scalability. The main conclusion is that our solution improves the scalability and the sustainability of the service access significantly, and at a minor cost.

With the advent of opening up 60 GHz Radio with 5 GHz of available spectrum, many bandwidth-hungry applications can be supported. The immediate concern, however, is the constraint on the line-of-sight transmission as well as the short transmission range of signals. As a result, in an indoor network, a mobile user might experience frequent breaks or losses of connection when one moves from one cell to another. To mitigate this problem, the Extended Cell (EC) architecture is proposed. In this paper, a dynamic Extended Cell formation algorithm is proposed based on the actual floor plan and the traffic situation under the network. Moreover, by applying this dynamic EC formation algorithm, we show that the call blocking probability is reduced. The dynamic EC formation also eases the deployment and maintenance cost due to its adaptability to the changing environment.

The current service- and device discovery protocols are not platform- and network independent Therefore, proxy servers will be needed to extend the range of IP-based discovery protocols to non-IP domains. We developed an architecture of a proxy that enables UPnP devices and services to be discovered on the Bluetooth network and vice versa, and allows Bluetooth devices and UPnP control points to access and utilize services located on devices in the other network. We managed to keep all functionality needed for effective proxying running on a single device, e.g. the mobile phone or the Residential Gateway. © 2007 IEEE.

In this paper, theoretical results are presented on the modular construction of orthogonal tree and cascade encoders/decoders of any size for truly asynchronous and cost-efficient spectral amplitude encoded OCDMA on a passive optical network. Three modular building blocks are proposed and described in detail. The tree structure is introduced that enables parallel code processing with a single device. The orthogonality of the code set is evaluated whereafter a revised construction method is proposed. Analysis and simulation confirm that a tree constructed via this method is orthogonal.

This paper addresses the issues of designing an infrastructure to support seamless in-building communication at the 60 GHz band. Recently, the 60 GHz band has received much attention due to its 5 GHz of available spectrum. However, the propagation of signals in this band is strongly hindered by attenuation and line-of-sight requirements. The situation gets worse in the in-building environment where signal propagation is obstructed by physical objects such as walls, furniture etc. In this paper, we present a novel radio over fiber (RoF) architecture that is cost-effective and is able to deliver high data-rate of the order of gigabits. To ensure a seamless communication environment at the 60 GHz band, we propose the concept of extended cells (EC) in order to create sufficient overlap areas. Finally, we illustrate the effectiveness of the proposed architecture by simulating an in-building network at the 60 GHz band employing the RoF and EC concepts

After conquering the core and metropolitan networks, fiber is now penetrating into the access domain. Its low loss and huge bandwidth enable the delivery of any current and foreseeable set of broadband services, and also make it a nice match to the wireless link to the end user. Cost effectiveness is a key issue, and will be decisive for the network topology choices. Point-to-point may be the most cost-effective for short-reach access, whereas point-to-multipoint may be the most interesting at medium- to long-reach access, or when line terminations in the local exchange become a key issue. A number of optical techniques being deployed for shared-fiber multiple access are discussed, based on time slot multiplexing, frequency slot multiplexing, code division multiplexing, and wavelength multiplexing, including their application in fiber to the home/fiber to the premises (FTTH/FTTP) networks for fast data transfer (asynchronous transfer mode (ATM) or Ethernet based) and for broadband service distribution (such as CATV). In the research laboratories, techniques aiming at next-generation optical access are being studied, such as wavelength routing for flexible capacity allocation and easily adaptable hosting of services and service providers, and radio-over-fiber techniques creating a powerful symbiosis of the fiber world and the wireless world by enabling centralized radio signal processing

A review is given of the statistics of modal noise and of the expressions for the signal-to-noise ratio for the cases of a monochromatic and a nonmonochromatic light source including the effects of source frequency fluctuations. Using the results, a quantitative analysis is made of how modal noise degrades the bit-error-rate performance of a digital transmission link with multimode fiber. Plots of the bit-error rate versus the received optical power show the characteristic asymptotic behavior (BER floor); expressions are derived for the asymptotic BER. The power penalty due to modal noise can be considerably reduced by suitable system modifications, e.g., by optimization of the decision threshold setting or by application of a low coherent light source such as an LED or a laser diode operating with several spectral emission lines of low coherence and low partition noise.