Motorola V2260 Instruction Manual download pdf (Page 16)

16 4/3/01

containing a cell site base station which

interfaces radiotelephone subscribers to the

switching system. Since there are no chan-

nels in CDMA, a user has a better chance of

completing a call. Also, now there is no hard

handoff between

cell sites since all sites operate on the same

frequency. This is called soft handoffs. In

this system, subscribers in cell A & D simul-

taneously operate in the same frequency. As

a user moves from cell site to cell site, the

base station monitors the signal strength of

the user. Based on this signal strength, the

base station decides which cell shall carry

the call. When a radiotelephone is in use well

within a cell, the signal strength received at

the cell site base station will be high. As the

phone is moved towards the edge of the cell,

its received signal strength decreases.

Signal strength information therefore

provides an indication of the subscriber’s

distance from a cell’s base station. This

change is handled automatically, and is com-

pletely transparent to the user. For example,

assume that a cellular tele-phone

initiates a call in cell A and then moves

across the system area through cells B and C

to cell D. As the phone moves into cell B, it

is instructed to change to a different fre-

quency that operates through the B cell

on that frequency. A similar change is per-

formed when the phone moves from cell B to

cell C and again

when the phone moves from cell C to cell D.

In this example, the radiotelephone has oper-

ated in four cell sites, through four cell sites,

and on the same spread spectrum without

interruptions in voice communica-

tions. As the radiotelephone leaves a cell, the

frequency on which the phone and base sta-

tion were operating is made available to

another subscriber in that cell. Since this

radiotelephone is dual mode, the

radiotelephone can operate in either a

CDMA system or Analog system.

Service Area

The area within which calls can be placed

and received is defined by the system oper-

ator.

(Because this is a radio system, there is no

exact boundary that can be drawn on a map.)

If the portable is outside the radio service

area, a No Svc (no service) message will

appear on the phone’s display, and calls

cannot be placed or received. If this happens

during a conversation, the call is lost. Places

where the ability to place or receive calls

would be lost are in totally enclosed areas,

such as underground parking garages, in

buildings without windows, and in elevators.

This situation would be indicated either by

the No Svc message illuminating, or by the

sound of either a fast busy signal or a high-

low siren signal when call placement is

attempted. General usage in buildings having

reason-able glass area is usually quite good.

However, it may be necessary to move closer

to a window to ensure reliable opera-tion.

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