An Introduction to Wireless Technology, Second Edition

7.3 PCN and PCS

The first step toward ubiquitous wireless communications will be the Personal

Communications Network (PCN) or Personal Communications System (PCS).

These networks are designed to provide access to a cellular communications

service in locations where people live and work. They are digital cellular

networks tailored for the urban and suburban environment, with good in-building

coverage and highly portable devices. PCN/PCS networks are not designed for

people traveling long distances or for vehicle installations, although the devices

may be used in vehicles and may have adapters and connections to improve

their in-vehicle usability. The networks will use microcells, which in an urban

environment would cover an area of approximately one city block. They are

designed to supplement, or even in some cases replace the existing wired

telephone network.

PCN/PCS networks will be used for wireless data communications in new

families of computing devices known as Personal Communicating Assistants

(PCAs) or communicating Personal Digital Assistants (PDAs). These devices will

provide various levels of functionality including Personal Information

Management (PIM), E-mail, fax mail, and access to information services. The

devices may be pen-based or have keyboards, and may or may not have voice

capabilities. An example of the use of such a device would be to book a

meeting. An entry for a meeting in the diary function of a PCA would generate a

wireless message to all the attendees with compatible PCAs which could check

for a free slot in their diaries and book a mutually acceptable time. Attendees

who did not have compatible devices would be alerted to the meeting by means

of a fax message or E-mail message. Diary management functions could reside

in the PCA itself or in a host system. The key advantage is that a user will have

only one diary and entries from any source will mean that it is automatically

updated. This system only works satisfactorily using wireless technology. Any

wired connection would have to rely on the user making a connection so that his

host system can provide an update or be updated.

7.4 Global Communications

It is possible to use the telephone network to speak to anyone from almost

anywhere in the world. In the last few years it has become accepted that it is

possible to pick up a phone and dial directly to a subscriber almost anywhere.

The same applies to data communications with a number of global networks

available to provide interconnections for data users. The IBM Global Network

(IGN) allows data users in many countries to connect to services and computing

resource across the world.

Terrestrial long distance radio communication is limited to a few applications.

For example:

•

Ship to shore outside coastal waters

•

Short wave amateur radio

•

Remote telemetry

•

Communications to remote communities (Australian Outback)

•

Communications for scientific expeditions and military applications

These applications all use relatively low-frequency carriers to allow long

distance propagation of radio waves. Low-frequency communications, however,

136 An Introduction to Wireless Technology