10-06-2017, 06:59 AM
Integrated Fiber-Wireless (FiWi) Access Networks
Supporting Inter-ONU Communications
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Abstract
Integrated fiber-wireless (FiWi) access networks
provide a powerful platform to improve the throughput of
peer-to-peer communication by enabling traffic to be sent from
the source wireless client to an ingress optical network unit (ONU),
then to the egress ONU close to the destination wireless client, and
finally delivered to the destination wireless client.
INTRODUCTION
NOWADAYS, access can mainly be divided into wired
access and wireless access. Optical access which can
provide huge bandwidth is an attractive wired access approach
to meet the increasing bandwidth requirement, but it is costly
to achieve deep fiber penetration.
RELATED WORK AND PRELIMINARY KNOWLEDGE
Related Work on PON Architecture Design Supporting
Inter-ONU Communication: In conventional PON architectures,
it is generally assumed that there is little inter-ONU
traffic. Thus, inter-ONU communication is implemented by
sending the traffic from the source ONU to the OLT, which
then sends it back to the destination ONU [9]. This implementation,
however, suffers from optical to electronic to optical
(OEO) conversion delay and round-trip transmission delay.
To accommodate the emerging need for direct inter-ONU
communication, some PON architectures are developed to
support such communication. In [10], [11], inter-ONU communication
is conducted by broadcasting optical signals from
one ONU to all ONUs through star coupler (SC) which is
deployed at the remote node (RN). Such designs cause large
power loss and can only be applied to TDM PON. The authors
in [12] propose a WDM EPON architecture supporting direct
inter-ONU communication in which upstream transmission
and inter-ONU communication are alternately taken place, e.g.,
the transmission cycle is divided into two sub-cycles.
WAVELENGTH ASSIGNMENT IN WDM/TDM PON
In this section, we introduce how to assign ONUs to wavelengths
such that network throughput can be maximized. We
assume that upstream traffic and downstream traffic are symmetric.
For example, for a communication network, the resident
subscribers may request symmetric upstream bandwidth
and downstream bandwidth. Thus, we only need to consider the
wavelength assignment in one direction.
CONCLUSION
One of the challenging issues in FiWi access networks is how
to efficiently utilize the high bandwidth provided in the optical
subnetwork to improve the throughput of wireless subnetworks.
In this paper, we focus on the relevant issues in the optical
subnetwork in order to efficiently support peer-to-peer communication
among wireless clients in FiWi access networks.