cant advantages as lower operational expenditures, trans- ... wireless access architectures. ... focus on the convergence of optical and wireless access archi-.
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SERIES EDITORIAL
OPTICAL FIBER-WIRELESS ACCESS NETWORKS: ARCHITECTURES AND PERFORMANCE IMPROVEMENTS
Osman S. Gebizlioglu
T
Hideo Kuwahara
he global telecommunications industry continues its transformation in network architectures and services. In the past 10 years, we have seen major shifts in technology innovations from optical transport to last-mile access networks. While synchronous optical network/synchronous digital hierarchy (SONET/SDH) was the center of attention for service providers and their suppliers in the 1980–1995 timeframe, we have witnessed the growth of wavelength-division multiplexing (WDM) to meet bandwidth growth fueled by fiber to the x (FTTx) video and internet service demand starting at about 1995. During the last decade, passive optical networks (PONs) emerged as the most promising access network as the major technology and cost barriers to optical fiber deployment started to come down. Global PON deployments have been based on two major standards: International Telecommunication Union — Telecommunication Standardization Sector (ITU-T) G.984 Gigabit PON (GPON) and IEEE 802.3ah Ethernet PON (EPON). For service providers, PONs offer such significant advantages as lower operational expenditures, transparency to data rate and signal format, and upgradability with new technologies that may involve bimodal optical Ffiberwireless access architectures. In recognition of the worldwide focus on the convergence of optical and wireless access architectures, we have chosen to present current perspectives on this convergence in this Optical Communications Series (OCS) issue. In this issue, we have selected four contributions that address technologies which promise to provide performance improvements in next-generation PONs (NG-PONs), perspectives on providing power over optical links in emerging networks, advances in optical wireless (OW), also known as free space optical (FSO) communications, as a promising complementary technology for radio frequency (RF), and a novel optical fiber-wireless (FiWi) backhaul network architecture that integrates next-generation WLAN-based wireless mesh network (WMN) and EPON technologies. In the first contribution, Kerim Fouli, Martin Maier, and Muriel Medard discuss network coding (NC) technology, which involves bit- or packet-level coding operations to improve throughput, simplify routing, and provide robustness against transmission errors and failures in various packet networks. After their introduction of NC’s basic principles, they review its applicability to NG-PONs, and provide illustrations
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Vijay Jain
John Spencer
and demonstrations of network throughput gains in NCenabled Wi-Fi-based mesh networks. In the second contribution, Salah Al-Chalabi presents a discussion on powering communications networks by optical power over optical fiber links. The proposed approach is focused on the use of interferometer-based optical communications systems to lower power consumption in the network depending on the system power usage in the quiescent, call, and ringing states, and call and ringing durations. It is also noted that PON networks built on current GPON and EPON standards cannot be powered remotely over fiber and must use battery backup, offering limited availability. In the third contribution, Hany Elgala, Raed Mesleh, and Harald Haas present a review of recent advances in OW communications systems with an emphasis on indoor deployment scenarios. They cover duplex transmission, multiple access, medium access control (MAC) protocols, and link capacity improvements. The vision for the next (fourth) generation (4G) wireless communication systems includes the peak download speed at 100 Mb/s for high-mobility communication and 1 Gb/s for low-mobility communication. Moreover, 4G systems are not expected to be based on a single access technology; rather, these systems will encompass a number of different complementary access technologies. It is now widely considered that OW is the essential technology for short-range communication links, (i.e. lowmobility indoor applications) with high data rate throughputs. OW technology offers several benefits including unregulated terahertz bandwidth, license-free operation, and low-cost front-ends. In the fourth contribution, Navid Ghazisaidi and Martin Maier present a novel FiWi backhaul network architecture integrating next-generation wireless local area network (WLAN)-based wireless mesh network (WMN) and EPON. They examine advanced hierarchical aggregation techniques by a combination of analysis, simulation and experimentation to demonstrate improvements in FiWi network throughputdelay performance for telephony, video, and data traffic. Frame aggregation has been considered as a major MAC enhancement technique for next-generation WLANs to offer a significantly increased throughput of 100 Mb/s or higher at the MAC service access point. We thank all OCS authors for their contributions, and invite manuscript submissions on all current and emerging topics in optical communications.
IEEE Communications Magazine • September 2011
