Nihel Benzaoui

Optical Slot Switching Latency in Mobile Backhaul Networks

Next generation mobile networks such as LTE-Advanced will offer high data rates to users utilizing new radio access technologies. In addition, new applications as well as devices such as smartphones and tablets will result in a rapid mobile traffic growth. Consequently, a rapid increase of the load in the mobile backhaul segment is expected, resulting in turn into a substantial increase of the energy consumption. Moreover, by allowing the possibility of direct communications between base stations for instance to support interference cancellation mechanisms such as “CoMP” and expedite handovers, the traffic pattern turns into any-to-any node communication in the next generation mobile networks. In previous papers, we proposed an optical mobile backhaul network to transport the mobile user data in an energy-efficient fashion while supporting any-to-any traffic exchanges. In this paper, we evaluate, analytically and by simulation, the latency in such next-generation optical mobile backhaul networks for realistic scenarios. We also study the impact of the support of several classes of service.

Impact of the electronic architecture of optical slot switching nodes on latency in ring networks

Optical slot switching has formerly been proposed as a flexible solution for metropolitan ring networks to carry data traffic with a subwavelength switching granularity and with good energy efficiency, which is enabled by optical transparency. In this paper, we propose for the first time, to the best of our knowledge, several architectures for the electronic side of optical slot switching nodes to increase flexibility through the addition of electronic switches, working either at client packet granularity or at slot granularity. Such electronic switches can be located at either the transmitter side or receiver side, or at both sides of a node, thereby decreasing traffic latency, at the expense of increased node cost and/or energy consumption. This paper focuses on the latency aspect. We investigate the impact of a timer that can be used to upper bound the slot insertion time on the medium. We also propose a novel client packet queuing model in an optical slot switching ring and assess and compare the latency of these node architectures analytically and with simulations.

Transport mechanisms for mobility support in optical slot switching-based next-generation mobile backhaul networks

In order to implement the next-generation (e.g., LTE-A) mobile backhaul networking segment, an optical slot switching solution called packet optical add/drop multiplexer (POADM) was previously proposed. Optical slot switching is at the same time a high capacity, energy-efficient, and low-latency optical transport network technology that relies on the direct transmission of data from base station to base station without resorting to time-consuming electronic processing and energy-hungry optoelectronic conversions. Low latency is an important requirement of mobile backhaul networks for real-time traffic such as Coordinated MultiPoint (CoMP) and POADM was shown to be compatible with the strict latency requirement of CoMP-1 ms end-to-end-even for very high network loads of 80% and above. However, user mobility was not taken into account. The traffic of users moving from one cell to another cell during handovers should also meet this strict requirement. In this paper, we propose and evaluate several transport mechanisms to support User Element mobility at the optical layer in a next-generation mobile backhaul network implemented using our previously proposed optical slot switching technology. We show with simulations that with smart introduction of additional electronic processing for handover traffic only (traffic of user elements that have moved from one cell to another), very strict latency constraints (sub-ms) can be met even for the time-sensitive mobile traffic.

Optical Ethernet—Flexible Optical Metro Networks

Enhanced flexibility in optical transport networks is a key requirement to support dynamic traffic load in packet-based networks. Today, flexibility is achieved by packet switches linked by static point-to-point transport connections. Wide-stretched synchronization patterns, line coding schemes, and forward error correction (FEC) frames prohibit flexibility right at the transport layer. We introduce a new optical transport concept that combines packet aggregation with a multipoint-to-point line coding and FEC processing. This concept avoids the quadratic full mesh scalability problem of other aggregated switching technologies such as, e.g., wavelength switching. It combines the flexibility of a distributed Ethernet switch and the performance of a leading edge optical transport system.

Impact of tunability and blocking fabric on optical slot switching ring performance

Optical slot switching rings have been proposed as optical transport networks for segments subject to rapid traffic variations and latency restriction. In order to achieve any-to-any node communication over the ring, optical slot switching networks rely on fast wavelength tunable lasers. With the introduction of the coherent technology, fast wavelength tunability is now available at the receiver side. Additionally, optical slot switching nodes may use a slot blocker that can block any slot on any wavelength. In this paper we investigate the impact on the network performance of the optical part of the slot switching node, both in terms of location of the fast wavelength tunable element and of the presence of the slot blocker.

Transport Mechanisms for Mobility Support in Optical Slot Switching-Based Next-Generation Mobile Backhaul Networks

In order to implement the next-generation (e.g., LTE-A) mobile backhaul networking segment, an optical slot switching solution called packet optical add/drop multiplexer (POADM) was previously proposed. Optical slot switching is at the same time a high capacity, energy-efficient, and low-latency optical transport network technology that relies on the direct transmission of data from base station to base station without resorting to time-consuming electronic processing and energy-hungry optoelectronic conversions. Low latency is an important requirement of mobile backhaul networks for real-time traffic such as Coordinated MultiPoint (CoMP) and POADM was shown to be compatible with the strict latency requirement of CoMP—1 ms end-to-end—even for very high network loads of 80% and above. However, user mobility was not taken into account. The traffic of users moving from one cell to another cell during handovers should also meet this strict requirement. In this paper, we propose and evaluate several transport mechanisms to support User Element mobility at the optical layer in a next-generation mobile backhaul network implemented using our previously proposed optical slot switching technology. We show with simulations that with smart introduction of additional electronic processing for handover traffic only (traffic of user elements that have moved from one cell to another), very strict latency constraints (sub-ms) can be met even for the time-sensitive mobile traffic.

Performance analysis in a next generation optical mobile backhaul network

Next generation mobile networks will offer high data rates to users utilizing new radio access technologies. In addition, new applications as well as devices such as smartphones and tablets will result in a rapid mobile traffic growth. Consequently, a rapid increase of the load in the mobile backhaul segment is expected, resulting in turn into a substantial increase of the energy consumption. An optical mobile backhaul network is proposed as the suitable solution to transport the mobile user data in an energy efficient fashion while ensuring a low latency. We propose in this paper to evaluate, analytically and by simulation, the latency in such next generation optical mobile backhaul network for realistic scenarios. The impact of class of service handling is also quantified.

Optical slot switching latency in mobile backhaul networks

We show that an optical slot switching network fulfills the strict latency constraints of a next generation LTE advanced switching mobile backhaul network. The impact of class-of-service handling when aggregating client data into slots is also quantified.