• Heterogeneous is the characteristic of containing dissimilar
• A common use of this word in information technology is to
describe a product as able to contain or be part of a "heterogeneous
network," consisting of different manufacturers' products that can
• Heterogeneous networks are made possible by standards-
conforming hardware and software interfaces used in common by
different products, thus allowing them to communicate with each
• The Internet itself is an example of a heterogeneous network.
• Mobile experts define a HetNet as a network with
complex interoperation between macrocell, small
cell, and in some cases WiFi network elements used
together to provide a mosaic of coverage, with
handoff capability between network elements
HETNET is not a distinct network
• HETNET is not a distinct network by itself- it is a gradual
evolution of cellular topology.
• The term “heterogeneous” implies that various types of
networks like wifi, home and public
femtocells, picocells and microcells will be implemented in
different levels of network hierarchy but all of them will
eventually come together to form a larger network as a
• Cellular networks are formed with three main components:
Base stations (BSs), Mobile telephone switching offices
(MTSO) and mobile devices.
• A radio transceiver and controller is put on each base
station to provide radio communication to the mobile units
located in its cell
• A macrocell is a cell in a mobile phone network that provides
radio coverage served by a high power cellular base station
• The term macrocell is used to describe the widest range of cell
sizes. Macrocells are found in rural areas or along highways.
• The antennas for macrocells are mounted on ground-based masts,
rooftops and other existing structures, at a height that provides a
clear view over the surrounding buildings and terrain.
• Macrocell base stations have high power outputs .
• A picocell is a small cellular base station typically covering
a small area, such as in-building (offices, shopping malls,
train stations, stock exchanges, etc.), or more recently in-
• In cellular networks, picocells are typically used to extend
coverage to indoor areas where outdoor signals do not reach
well, or to add network capacity in areas with very dense
phone usage, such as train stations or stadiums.
• Picocells provide coverage and capacity in areas difficult or
expensive to reach using the more traditional macrocell
• HANDOVER ISSUE: Smooth handover between different
systems should be taken as a basic requirement. Multiple
authentications taken by various systems are annoyed.
• How to keep service continuity during handover across
different systems is an issue. Increased handovers due to
small cell sizes introduce a potential source of increased
Dropped Call Rate (DCR)