Gwillerm Froc

Multi-Band OFDM Transmission at 100 Gbps With Sub-Band Optical Switching

In this paper, we present an original work on sub-wavelength optical switching performed over a coherent multi-band orthogonal frequency-division multiplexing (MB-OFDM) super-channel operating at 100 Gbps. After having demonstrated that dual-polarization MB-OFDM (DP-MB-OFDM) is as efficient as single-carrier dual-polarization quaternary phase shift keying (DP-QPSK) technology to transport 100 Gbps data-rate over a 10 × 100-km G.652 fiber-based transmission line, we show that optical add-drop of OFDM sub-bands as narrow as 8 GHz inside a 100 Gbps DP-MB-OFDM signal constituted of four sub-bands is feasible in the middle of this 1000-km transmission line. The flexible optical add-drop multiplexer (FOADM) implemented here is constituted by the association of an ultra-narrow pass-band and stop-band optical filter. The design and realization of such ultra-selective optical filters is presented, while the impact of their physical features over the quality of transmission is discussed. To prove that several add-drop multiplexers can be cascaded, our FOADM is introduced into a G.652 fiber-based recirculating loop and the impact of the cumulated filtering transfer function as well as the crosstalk inside the OADM are investigated. A typical use case for the introduction of such FOADM into long-haul transport networks is given, and the capital expenditure (CAPEX) cost advantage for the multi-layer transport networks is highlighted. By the proof of concept delivered here, combination of super-channel and sub-wavelength optical switching pushes network flexibility far away of what is today proposed by system vendors, opening new horizons for an optimized use of multi-layer transport networks.

Design and performance of wireless data gathering networks based on unicast random walk routing

Wireless environment monitoring applications with significantly relaxed quality-of-service constraints are emerging. Hence, the possibility to use rough low knowledge routing in sensor networks to reduce hardware resource and software complexity is questionable. Moreover, low knowledge handling allows better genericity, which is of interest, for instance, for basic operation enabling system set-up. In this framework, this paper revisits stateless unicast random walk routing in wireless sensor networks. Based on random walk theory, original closed-form expressions of the delay, the power consumption and related spatial behaviors are provided according to the scale of the system. Basic properties of such a random routing are discussed. Exploiting its properties, data gathering schemes that fulfill the requirements of the application with rather good energy efficiency are then identified.

On the Data Delivery Delay taken by Random Walks in Wireless Sensor Networks

In recent years, the use of random walk techniques in wireless sensor networks has attracted considerable interest among numerous research efforts. The popularity of this approach is attributed to the natural properties of random walks such as locality, simplicity, low-overhead and inherent robustness. However, throughout the variety of research works that assess the effectiveness of random walk techniques, most results are derived from a qualitative view or by means of simulations. Furthermore, when analytical tools are used, the obtained results often provide bounds on various performance metrics of interest, which may have little consequences for practical applications. Instead, our goal in this paper is to quantify the effectiveness of such techniques based on the derivation of closed-form expressions.In particular, we focus on the delay taken for the random walk to deliver messages from sensor to sink nodes and study its statistics through closed-form derivations.

Resource allocation and wireless scheduling scheme for a HiperLAN/2 system

In this paper, a dynamic resource allocation scheme for a wireless local area network system is presented. It aims at enforcing the Quality of Service requirements of the applications that are carried on the wireless link even when errors occur on it. The allocation takes benefit from the coexistence of connections that have different QoS tolerances so that, when facing errors, the bandwidth allocated to the more tolerant connections could be reduced and attributed to the connection with more stringent QoS requirements to perform retransmissions. For that purpose, two classes of Quality of Service are considered that are related to Constant Bit Rate traffics and best-effort traffics. The scheduling framework is then based on a hierarchical rate-based fair queuing algorithm and is extended in order to cope with error. To illustrate its operation, the proposed scheme is applied to the ETSI HiperLAN/2 WLAN. Some simulation results are reported and show the impact of the scheduling principles on best-effort traffics such as TCP applications and its actual benefits for CBR traffic. The efficiency of the proposed mechanism is evaluated using measurement of delays and throughputs at Data Link Layer level. The aim of this paper is not so much to prove the fairness of this mechanism but rather its ability to guarantee negotiated services required by heterogeneous applications.

Algorithm for ad-hoc piconet topology initialization

This paper deals with piconet topology issues in IEEE802.15.3 high rate wireless personal area network standard. These issues preventing two devices to establish a connection come from the coexistence of two conflicting concepts: ad-hoc networking and centralized coordination. An algorithm for the initialization of the topology of the piconet is proposed. This algorithm leads to a probability higher than 95% of connection success in the whole power emission range defined by the standard.

Mitigation of PDL in coherent optical communications: How close to the fundamental limit?

Considering coherent optical transmissions with PDL disturbance, we evaluate how far from the fundamental limit (based on the outage probability) are conventional coding schemes using Polarization-Time codes and/or LDPC codes.

100 Gbps Multi-Band OFDM Transmission over 1000 km of G.652 Fibre and a Cascade of Five Sub-Wavelength OADMs

We study here the impact of sub-wavelength optical filtering on 100 Gbps coherent multi-band OFDM transmission system. Error-free transmission is achieved after 1000 km of uncompensated G.652 fibre line and a cascade of five optical add-drop multiplexers.

Influence of guard band on channel capacity for optical transmission systems

We analyze the influence in non-dispersive and dispersive fiber of guard band between WDM channels on the data rate limit given by the information-theoretic Shannon capacity concept when nonlinear Kerr effect occurs.