Developing Practical Wireless Applications

Wide-area and Personal-area Communications 23

Chapter 3

wireless-enabled products, and Developing Practical Wireless Applications explores in some

detail the existing and emerging new wireless technologies, coupled with the myriad of

applications that occupy and impress upon our personal and working environments.

In the following sections we appraise the generations of more established wireless

technologies and it will naturally provide a complete picture of the historical genera-

tion of wide- and personal-area, whilst molding a comparable impression of the over-

lap created between them. It is becoming more evident that manufacturers integrate

new wireless technology into cellular phones, notebooks and so on, resulting in the

overlap of wide-area and personal-area communications (see Figure 3.4). It is this

overlap that bestows the mobility and freedom characteristics of our personal and

working environments.

Generations of Wireless Technology

Undoubtedly, many of us have witnessed the emergence of generations of wide-area

technologies each depicting the advancement of applications and digital capability.

Regularly we read in the technology news, the relentless press releases announcing

faster and better applications that now rely on 3G technology (more about this later).

Perhaps the label of old seems somewhat inappropriate, as the more established gen-

erations of the wide-area era are growing at a phenomenal rate. The depiction of

wide-area communications helps us understand clearly where the respective technol-

ogies lie within the realm of personal-area emerging technologies, as we have concep-

tualized in Figure 3.5 (data rate vs. distance).

First Generation (1G)

First generation (or 1G) cellular telecommunications were only capable of supporting

voice traffic. What’s more, they were very susceptible to interference and offered no

security (eavesdroppers with basic radio equipment could listen in on conversations).

It has been reported that data traffic could occur, although “ideal” network conditions

were required, perhaps something similar to, the wind blowing in your hair and the sun

shinning on your face! 1G was introduced in the early 1980s and was based upon an

analog system comprising Frequency Modulation (FM), Frequency Division Duplex

(FDD) and Frequency Division Multiple Access (FDMA). Combining these primary

methods of radio transmission and reception, several variants of the first cellular tech-

nologies emerged to include the Advanced Mobile Phone Standard (AMPS), Total Access

Communication System (TACS) and the Nordic Mobile Telephony (NMT); these variants

24 Developing Practical Wireless Applications

were widely based in North America, Japan and Europe and became the most popular

and first commercially available cellular systems.

Understanding how FDMA works

FDMA offers a radio spectrum that is divided into channels, where typically each

channel is 30kHz; there is also a separate control channel, which is used to manage

and coordinate voice channel assignment. The reference to a channel within the

FDMA rationale is in fact two 30kHz channels: one for each direction, known as

uplink (or reverse channel) and downlink (or forward channel). This two-way strategy

is known as FDD and typically you will come across 1G technology being referred to

as FDMA/FDD. FDMA/FDD is a narrowband telecommunications system, which

implies that the available spectrum is divided into narrow radio channels, along with

a channel separator that is used to separate the uplink and downlink communication

pathway (primarily to reduce the likelihood of interference). When a cellular phone

initiates a call, a frequency channel is reserved for the duration of that call; frequency

modulation is then used to modulate voice data within the reserved frequency band.

Figure 3.5

The conceptual

presentation of

data rates versus

distance

illustrating the

placement of wide-

and personal-area

wireless

technologies.