Wireless Versus Wired Networks

Wireless Versus Wired Networks
There are a number of fundamental differences between wired and wireless networks,
essentially all stemming from the inherent characteristic of wireless communications
(i.e., the replacement of fixed subscriber equipment connections by radio links). This
freedom from the wired “tether” provides enormous advantages for customers of
communications services but also introduces some new problems not encountered in
traditional wired networks.
Perhaps the most important characteristic of wireless networking is that a radio
link connecting the user’s device to a wired network infrastructure is inherently less
reliable than a fixed wired connection. This characteristic should be obvious and will be
familiar to users of cellular phones who have experienced signal breakup and dropped
connections on cellular phone calls. This inherent relative unreliability of radio links
leads to a need for considerably more complexity in the physical-layer design than is
required in traditional wired networks. Also, there is a need for connection management
techniques as part of the solution to the radio-link reliability problem.
Another important characteristic of wireless communications is the fundamental limitation
on the availability of frequency spectrum. For systems that operate in licensed
frequency bands (cellular telephone service is the primary example), each service
provider operates its network within a fixed band of frequencies, and means must
be provided to manage the sharing of allocated bandwidth among a large number of
users. Furthermore, as the service provider’s subscriber volume grows, there must be means for expanding the overall capacity of the service network in an efficient manner
to accommodate the growth in demand for service.
The bandwidth limitation problem also gives rise to the need for complexity in the
design of source coding techniques (speech coding in the case of voice service, and
other compression techniques in the case of multimedia transmission) so as to reduce
the amount of bandwidth needed for each user channel signal while maintaining a
prescribed level of signal quality as perceived by the user.
A very practical issue for users of mobile wireless devices is the necessary reliance
on batteries, with the need for periodic recharging. This issue has led to the clever
application of power management techniques in the design of mobile devices, so as to
extend talk time and recharging cycles.
The inherent advantage of wireless networking—mobility for the user—adds complexity
to the network design to manage changing the connection point to the fixed
network infrastructure, including changes over both small and large geographical areas.
This calls for greater complexity in registration and call routing techniques than are
needed in wired networks, and a need for the use of both permanent and temporary
addressing to support mobility.
Finally, the use of wireless transmission creates a vulnerability of the user’s communications
to eavesdropping and fraudulent intrusion into the network. Because of
these problems, considerable attention has been given to providing security and privacy
for wireless communications networks. Security provisions include such techniques as
authentication to prevent unauthorized access to networks. Privacy provisions include
the encryption of transmitted digital streams to prevent eavesdropping