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broadband network


The convergence of voice, data and video onto a single network combined with large global consumer and corporate appetite for internetworking is leading to installation and upgrading of communication infrastructure worldwide.

The paper reviews recent trends in broadband infrastructure deployment and shows future possible directions. Network-ing integrated circuits (ICs), being the nuts and bolts of thisinfrastructure build-up, are continuously evolving leading tovery complex electronic devices. The main theme of thepaper is to link dramatic changes in Internet network withdemands placed on IC design, IC processes and device per-Fig. 1. Conceptual drawing of the broadband network.formance that are needed in order to continue fuelling thisinfrastructure growth.

The complexity of today’s global network infrastructure hasbeen primarily caused by the use of multiple etworks, and multiple protocols:

 Access networks { networks for both consumers
and corporate customers to provide data, video
and voice to all required locations using time-
domain multiplexing (TDM), synchronous opti-
cal network (SONET), and asynchronous transfer
mode (ATM) .
 LANs { local area networks that connect PCs, work-
stations, printers and other devices inside a building
or campus, traditionally using Ethernet (10 Mbit/s,
100 Mbit/s and 1 Gbit/s) connections.
 SANs { storage area networks that connect backend
storage disks via high-speed interfaces using primar-
ily ber channel (1 Gbit/s and 2 Gbit/s) protocols.
 MANs { metropolitan area networks that connect
data and voice trac at the city level typically us-
ing SONET rings (OC-48/OC-1921).
 WANs (core, backbone) { wide area networks which
connect multiple corporate locations or cities across
long distances. ATM, SONET and IP are used in the
core of the network .
Access. Access networks need to carry both voice and
data. Voice is carried using well-known circuit-switching
techniques. Data is carried using multiple di
erent tech-
nologies like TDM, integrated services digital network
(ISDN), ATM, plesio-synchronous digital hierarchy (PDH),
frame relay or digital subscriber loop (DSL). As data needs
to be merged with voice at some point in the network,
ATM is well suited for that purpose, being able to trans-
port reliably voice over SONET ( ber) or over DSL (copper
wire).

The access networks use di
erent media for data trans-
mission: copper twisted pair wires, coaxial cables, op-
tical bers or simply air in the case of wireless ac-
cess. Digital subscriber loop technology is becoming the
dominant technology for the transmission over the copper
wire, while cable modems are used for transmission over
the coaxial cable. As very small percentage of businesses
and households has a direct ber connection, ber to the
home (FTTH) technology cannot be e
ectively deployed.
Instead, ber to the curb (FTTC) is being considered due
to the progress in passive optical networks (PON) technol-
ogy which uses passive optical splitters to split the optical
signal from ber to copper wires.

Enterprise. Ethernet rules local area networks. This well
known technology has managed to evolve from 10 Mbit/s
to 100 Mbit/s (fast Ethernet) to 1 Gbit/s (gigabit Eth-
ernet), and now to 10 Gbit/s, in a backwards compat-
ible fashion. Ethernet architects are already discussing
40 and 100 Gbit/s versions of this technology although
practical implementations are probably years away. Due
its popularity and massive deployment in LANs, Ethernet
is cheap. As a result it threatens other protocols in areas
outside LAN. In particular, optical Ethernet (running Eth-
ernet over optical ber) might become popular in the fu-
ture in the access and metro networks shunning away ATM
and SONET.

Storage. Storage area networking is currently the fastest
growing segment of broadband deployment. While dis-
cussions continue on merits of network attached storage
(NAS) vs. storage area networks, both remain universally
deployed in large and very large corporations to store mas-
sive amounts of corporate data. Fiber channel is the dom-
inant protocol in SANs although iSCSI2 implementations
might threaten that dominant position in the future.
Metro. Current metropolitan infrastructure is primarily
based on SONET rings that carry ATM and IP traf-
c [3, 4]. Future services might use various other tech-
nologies, such as next-generation SONET, optical Eth-
ernet, multi-service dense wavelength division multi-
plexing (DWDM), or multi protocol Lambda switching
(MPLS) . It needs to be pointed out that the impor-
tant function of metropolitan area networks is also to col-
lect wireless data trac from third generation (3G) wireless
networks.

Core. Core networks require transmission over long distances, typically beyond 500 km, preferably beyond 5000 km. In traditional networks repeaters are used to re generate signals every 60{80 km . Long span without repeaters can be also accomplished using optical amplication enhanced by pulse shaping and error coding techniques. Optical signals can be restored using Raman or erbium doped ber ampli ers (EDFAs). Future optical techniques of ultra-long haul systems might use solitons, which, due to their unique properties, can travel in optical ber over very long distances. It is also anticipated that optical switching technology, probably based on MEMs structures, will replace electronic switching in the core of the network

Integrated circuits typically perform the following functions:

 Coding, modulation, and ampli cation of electrical
signals for transmission through physical medium
(optical ber, twisted pair copper wire, coaxial ca-
ble). Also in reverse direction: de-coding, de-
modulation and equalization for reception of elec-
trical signals. These devices are typically referred
to as physical medium devices (PMDs) and physi-
cal layer devices (PHYs), and are considered to be
Layer 1 devices in the OSI protocol stack. These
devices are either completely analog or mixed-signal
with signi cant analog content.

 Data formatting into frames or cells using prede-
ned protocols (ATM, Ethernet, ber channel, etc.).
These devices are typically referred to as framers or
mappers, and are considered to be Layer 2 devices.
These devices are providing digital processing and
the only analog/mixed-signal circuitry they require is
high-speed serial links used for chip-to-chip commu-
nication.

 Data-packet processing. Processing functions in-
clude protocol conversion, packet forwarding, polic-
ing, look-up, classi cation, encryption, and trac
management . These devices are typically
referred to as network processors, classi cation en-
gines or trac managers, and are considered to be
Layer 3 devices. Typically they are purely digital
devices that use highly parallel I/O interfaces.





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  1. Guru

    SONET – Synchronous Optical NETwork – a fiber-optic transmission system for high-speed digital traffic. SONET is an intelligent system that provides advanced network management and a standard optical interface, it uses a self healing ring architecture that is able to reroute traffic is a line goes down. Speeds range from 51 Mbps to several gigabits per second.






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