Ultra-high reliability (UHR) is the main goal for the next IEEE wireless LAN standard 802.11bn, the future Wi-Fi 8. Coordination of multiple access points (APs) is a key feature of the new generation to ensure reliable operation and high performance. With the release of the first draft 802.11bn standard, a realistic evaluation of Wi-Fi 8 multi-AP coordination is possible. This paper presents performance simulations of 802.11bn multi-AP coordination with focus on coordinated beamforming (CoBF), where MIMO techniques are used to suppress interference between neighboring WLANs. The standard methods are compared with a novel optimized spatial nulling method, based on iterative phase optimization.

This study comprehensively examines the technical manifestation and planning process for a shared thermal energy network at a 75-hectare industrial area in Ingolstadt. Unlike traditional systems, this (5GDHC) network showcases a smart integration of energy flows across 70 buildings with a yearly heating demand of around 17 GWh and a yearly cooling demand of around 35 GWh. The network spans over 9,100 meters of piping with diameters up to 800 mm. With thermal power from various sources including 1.8 MW waste heat from a data centre and potential for 10 MW from the Danube River, the system epitomizes a dynamic balance of heating and cooling demands. The paper itself examines the planning process of the system and encompasses topics such as defining energy requirements and load profiles, assessing potential energy sources and sinks for enhanced system efficiency, and analysing pipe and network design. Through this investigation, the study provides valuable insights towards a methodology to facilitate the successful implementation of future industrial 5GDHC systems, furthering the cause of sustainable energy.

IEEE recently started to work on a new WLAN generation under the label ultra-high reliability (UHR). While Wi-Fi 7 focused on higher throughput, UHR aims for more reliable transmission. On the physical layer, this translates into rate-vs-range and latency improvements. Optimized multiuser (MU)-MIMO transmission is important to achieve these improvements. This paper proposes a new precoding method for uplink and downlink MU-MIMO, iterative phase optimization (IPO), and evaluates the performance in terms of rate-vs-range. IPO is shown to give near-optimal performance in typical use cases at a low computational complexity.

A suite of standards Recommendations has recently been developed in the ITU-T for a 50 Gb/s line rate passive optical network (PON) system. This 50G-PON system represents a significant leap in line rate from the 10 Gb/s systems being deployed today in fiber access applications. Achieving such a jump in performance necessitates an evolution in the underlying technologies. The 50G-PON system capitalizes on fundamental advances in the optical transceiver components working in conjunction with enhanced error correction and coding. It also introduces key innovations in activation procedures, contention-based operation, and expanded cryptographic features. With these improved capabilities, the 50G-PON system is ready to meet the new, and demanding, requirements of emerging services.

Increasing bandwidth requirements for home and business Internet connections as well as fiber links for 5G wireless drive the need for higher data rate passive optical networks (PON). PON is a cost-effective way to deploy fiber. A point-to-multipoint topology with passive optical splitters is used to connect many subscribers to one central node. The next development step in PON is 50 Gbit/s per wavelength, which requires improvements in error correction coding and receiver signal processing. This paper investigates digital equalization for PON with respect to performance with soft decision error correction decoding.

Capacity requirements of the fixed access network keep increasing towards multi-gigabit connections. For Hybrid Fiber Coaxial (HFC) networks, aggregated rates around 30 Gbit/s can be achieved by increasing the DOCSIS spectrum to 3 GHz, assuming a spectral efficiency around 10 bit/s/Hz. Replacement of spectrum limiting components such as passive taps in the HFC network is an efficient way to achieve these data rates, compared with the cost of fiber to the home (FTTH). Transmit amplifier distortion is a major issue in the extended spectrum in addition to the high spread of attenuation between low and high frequencies. Existing spectrum allocation strategies are no longer applicable. This work presents a new method of spectrum optimization for the coax channel up to 3 GHz, taking transmitter distortion into account in the optimization.

Capacity requirements of the fixed access network keep increasing towards multi-gigabit connections. For Hybrid Fiber Coaxial (HFC) networks, aggregated rates around 30 Gbit/s can be achieved by increasing the DOCSIS spectrum to 3GHz, assuming a spectral efficiency around 10 bit/s/Hz. Replacement of spectrum limiting components such as passive taps in the HFC network is an efficient way to achieve these data rates, compared with the cost of fiber to the home (FTTH). The fiber section of the network is capable of achieving capacities required to support 30 Gbit/s but it is a challenge to achieve 10 bit/s/Hz spectral efficiency on the coax link, especially at higher frequencies. This paper presents a new modulation and coding scheme (MCS) for DOCSIS that can achieve a 10% improvement in spectral efficiency over current DOCSIS MCS.

The articles in this special section addresses copper technologies and deployment practices beyond those currently available. Legacy copper infrastructure originally designed to provide voice services (twisted pair network) or television services (coaxial network) has performed vastly beyond specification and continues to deliver increased broadband speeds. Today’s mature technologies like vectored VDSL2 and G.fast for twisted pair and DOCSIS 3.1 for coaxial networks, are able to surpass present-day demand for broadband speeds in excess of several hundreds Mb/s per end user. The ability to off er gigabit speeds has been fueled by advances in digital signal processing and by a steady migration toward fiber rich access networks where only the last “mile” into the homes remains copper based (FTTx). We often get the question why the industry continues to consider copper access, while fiber is perceived as superior in terms of transmission properties.

The ITU-T project G.mgfast defines the MGFAST technology providing aggregate bit rates of up to 10 Gb/s over twisted pair and coaxial wiring. The first volume of the Recommendation is to be completed in January 2020. Multi-gigabitper- second access to the customer premises is achieved by substantial expansion of frequency spectrum, advanced coding, and use of full-duplex transmission. In addition, MGFAST can provide sub-millisecond latency, enhanced support of multiple quality of service grades, and point-to-multipoint operation.

Achieving high data rates on low quality twisted pair cables under certain power and complexity constraints requires optimized physical layer transmission. This chapter discusses signal transmission in G.fast with the focus on precoding and spectrum optimization in downstream direction. The power constraints to be considered for wireline transmission are different than a sum-power constraint that is mostly used in literature, requiring a more general optimization framework. A realistic estimation of the achievable data rates under the conditions of an implementable G.fast transceiver is provided.

It can be observed that the achievable rate region of a G.fast DSL system is no longer rectangular, as it is the case for vectored VDSL systems, due to stronger crosstalk couplings at high frequencies. Therefore, alternative operating points that are not optimal in a sum-rate sense may be utilized to adapt the system performance to the users' actual demands. To this end, we propose a new precoding scheme based on defining a subset of prioritized users, where we optimize the sum-rate of the prioritized users under a minimum rate guarantee for the remaining users. We present a solution based on Lagrangian duality theory and propose a well-performing one-step heuristic solution. By means of simulations, we show that significant rate gains for the prioritized users can be obtained by the proposed precoding scheme.

G.fast uses time division duplexing (TDD) rather than frequency division duplexing, as it was used in previous DSL systems, to allow a more energy efficient analog and mixed-signal design. Besides the TDD scheme, G.fast introduces a method called “Discontinuous Operation” (DO) to further reduce the transmit and receive time within a frame, depending on the current data traffic. The main reason to introduce DO is power consumption, but it can also be used to increase data rates.

In future, Internet access speeds beyond 1 Gbit/s will be required, which is mainly provided by fiber connections in the fixed access network. A high-performance copper-based transmission technology can enable fiber to the building and fiber to the home installations in a cost-effective copper/fiber hybrid network. ITU has started a project for multi-gigabit copper access (MGfast), as a successor of the G.fast technology with the goal to provide symmetric services with 10 Gbit/s aggregated rate for each subscriber. Besides the use of higher bandwidth up to 424 MHz or 848 MHz, full duplex transmission with echo cancellation is another major improvement in MGfast. Line bonding and frequency bonding allow the use of the same physical layer architecture for different media types. This paper discusses network topologies for the hybrid network and technology options for copper transmission to achieve the desired rate and reach.

To satisfy the increasing demands for higher bandwidth, the fixed broadband access network is continuously improved. Twisted pair copper-based Internet access is still the dominant fixed access technology. The most recent development step on the copper access network is the G.fast technology, which aims to provide Gbit/s services for each subscriber in a fiber to the distribution point (FTTdp) topology. The main challenges are the use of high frequencies up to 212 MHz on low quality copper wires, which requires to operate on high crosstalk channels and the strict power consumption targets which result from the FTTdp topology.

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Twisted pair cables used in the access network were not built for the frequencies up to 212 MHz used by G.fast. With increasing frequency, the simplified modeling approach used for VDSL2 does no longer give accurate results because the behavior of twisted pair cables changes. This chapter presents measurement data of twisted pair cables at G.fast frequencies and introduces a MIMO cable binder model for the copper access network in the fiber to the distribution point topology.

Digital subscriber line technologies such as G.fast face strong crosstalk between different twisted pair copper wires on higher frequencies. With crosstalk cancellation and interference management techniques, the performance is optimized with respect to high crosstalk. Maximum sum-rate is a widely used objective for groups of multiple subscribers, but does not reflect the subscriber demands and may lead to a high spread of data rates. This paper presents an approach to utilize weighted sum-rate optimization to improve data rates for a subset of subscribers with higher demand, resulting in a longer reach for a certain data rate while using free resources from other subscribers. Results for linear and non-linear zero-forcing precoding as well as a gradient approach for linear MMSE precoding are investigated.

Previous work on precoding for G.fast systems focused on linear and non-linear precoding techniques to maximize the overall throughput. It has been shown that the existing algorithms almost achieve the sum capacity. However, the rate region does no longer feature a rectangular shape as for VDSL systems, that motivates the utilization of operating points suboptimal w.r.t. sum rate to meet the individual users demands. In these points, the gap between existing zero-forcing techniques and the corresponding weighted sum capacity is significantly larger. Therefore, we propose to improve the linear zero-forcing precoding by employing generalized inverses, for which we present methods that enable us to cope with the large system size of G.fast systems. Our simulations show that our proposed precoding scheme outperforms linear ZF solutions based on the Moore-Penrose pseudoinverse significantly in scenarios with greatly varying user demands.