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The need for increased capacity was the great motivation for the advent of
American digital cellular technology. As demand for wireless services increased,
mainly in dense urban areas, the old analog standard, known as
AMPS (Advance Mobile Phone Service), proved inadequate to satisfy the demand.
Time Division Multiple Access technology, based on the EIA/TIA/IS-
54 specifications (later on enhanced and renamed EIA/TIA/IS-136) was the
first solution to the capacity problem of the old analog system. By offering
roughly a threefold increase in capacity by dividing each 30 kHz AMPS channel
into three time slots, this system was the first American response to the
European cellular second generation, the GSM.
This digital novelty, however, was not enough to soothe a number of service
providers, who argued that such a technology would not be adequate
for future growth in service. Other alternatives were then considered, and
a technical committee was formed to study and generate cellular standards
for wideband services. In the late 1980s and early 1990s, QUALCOMM, Inc.
of San Diego proposed a Code Division Multiple Access, CDMA, system
and together with Pacific Telesis demonstrated its operation. Extensive successful
field trials and network refinement led the Telecommunication
Industry Association (TIA) and the Electronic Industry Association (EIA) to
adoptQUALCOMMsystem as their interim standard, the “TIA/EIA/IS-95—
Mobile Station–Base Station Compatibility Standard for Dual-Mode Wideband
Spread Spectrum Cellular System.”
The TIA/EIA/IS-95 specifications establish that the system operate on a
dual-mode (analog and digital) basis, both modes within the same frequency
band. The dual-mode capability facilitates the transition from the analog environment
to a digital environment. Although compatible, analog and digital
systems are rather different. TIA/EIA/IS-95 supports a direct sequence spread spectrum technology
with 1.25 MHz band duplex channels. Therefore, an operating company
that chooses this CDMA technology must deactivate about 42 contiguous
30-kHz channels of its analog system. Coexistence of analog and digital systems
implies that dual-mode mobile stations are able to place and receive
calls in any system and, conversely, all systems are able to place and receive
calls from any mobile station. Handoff operations in such a scenario require
some attention. A mobile station may initiate a call in the CDMA system and,
while the call is still in progress, it may migrate to the analog system, if required.
The search for one or another system for the initial registration is not
specified by the standard and the exact action is dependent on the manufacturer.
In fact, the standard leaves a number of issues to be detailed by the
manufacturer. Those recommendations in the standard appearing with the
verbal forms “shall” and “shall not” identify the requirements from which
no deviation is permitted. Those with “should” and “should not” indicate
that several possibilities are permitted. There are still others with “may”
and “need not” and “can” and “cannot,” which are certainly much less restrictive.
Therefore, solutions may be implemented differently by different
manufacturers.
A number of innovations have been introduced in the CDMA system as
compared with earlier cellular systems. Soft handoff is certainly a great novelty.
In soft handoff, handoff from one base station to another occurs in a
smooth manner. In soft handoff, the mobile station keeps its radio link with
the original base station and establishes a connection with one or more base
stations. The excess connections are given up only when and if the new link
has sufficient quality. Another innovation introduced in the CDMA system is
the use of Global Positioning System (GPS) receivers at the base stations. GPSs
are utilized so that base stations be synchronized, a feature vital to the soft
handoff operation. Vocoders at variable rates are specified to accommodate
different voice activities aimed at controlling interference levels, thence increasing
system capacity. Sophisticated power control mechanisms are used
so that the full benefit of spread spectrum technique is realized.
The firstCDMAsystems were employed under the TIA/EIA/IS-95A speci-
fications. The A version of the specifications evolved to TIA/EIA/IS-95B, in
which new features related to higher data rate transmission, soft handoff
algorithms, and power control techniques have been introduced. The name
cdmaOne is then used to identify theCDMAtechnology operating with either
specification.
Features and Services
TIA/EIA/IS-95 specifications establish two types of features: voice features
and short message service features.
Voice Features
The following are the primary voice features.
Call Delivery (CD).CDallows the reception of a call while in a roaming
condition.
Call Forwarding Busy (CFB)/Call Forwarding Busy No Answer (CFNA)/
Call Forwarding Busy Unconditional (CFU). CFB, CFNA, and CFU
allow a called subscriber to have the system send incoming calls,
addressed to the called subscriber’s directory number, to another directory
number (forward-to number), or to the called subscriber’s
designated voice mailbox. This happens when the subscriber is engaged
in a call or service (for CFB active), or when the subscriber
does not respond to paging, does not answer the call within a specified
period after being alerted, or is otherwise inaccessible (CNFA
active). The inaccessibility may be characterized by the following: no
paging response, unknown subscriber’s location, inactive subscriber,
CD not active for a roaming subscriber, Do Not Disturb active, etc. If
CFU is active, calls are forwarded regardless of the condition of the
termination.
Call Transfer (CT). CT enables the subscriber to transfer an in-progress
established call to a third party. The call to be transferred may be an
incoming or outgoing call.
CallWaiting(CW).CWprovides notification to a controlling subscriber
of an incoming call while the subscriber’s call is in the two-way state.
Subsequently, the controlling subscriber can either answer or ignore
the incoming call. If the controlling subscriber answers the second
call, it may alternate between the two calls.
Calling Number Identification Presentation (CNIP)/Calling Number Identification
Presentation Restriction (CNIR). CNIP provides and CNIR
restricts the number identification of the calling party to the called
subscriber. The termination network receives the calling number identification
(CNI) as part of the basic call setup. This CNI may include
one or two calling parties numbers (CPNs), a calling party
© 2002 by CRC Press LLC
subaddress (CPS), redirecting numbers (RNs), and a redirecting subaddress
(RS).
Conference Calling (CC). CC provides a subscriber with the ability to
conduct a multiconnection call, i.e., a simultaneous communication
between three or more parties (conferees). If any of the conferees to a
conference call disconnects, the remaining parties remain connected
until the controlling subscriber disconnects.
Do Not Disturb (DND). DND prevents a called subscriber from receiving
calls. When this feature is active, no incoming calls shall be
offered to the subscriber.DNDalso blocks other types of alerting, such
as the CFU abbreviated (or reminder) alerting and message waiting
notification alerting. DND makes the subscriber inaccessible for call
delivery.
Flexible Alerting (FA). FA causes a call to a pilot directory number to
branch the call into several legs to alert several termination addresses
simultaneously. The first leg to be answered is connected to the calling
party and the other call legs are abandoned.
Message Waiting Notification (MWN). MWN informs enrolled subscribers
when a voice message is available for retrieval. MWN may
use pip tone or alert pip tone to inform a subscriber of an unretrieved
voice message(s).
Mobile Access Hunting (MAH). MAH causes a call to a pilot directory
number to search a list of termination addresses for one that is idle
and able to be alerted, in a way that only one termination address is
alerted at a time.
Password Call Acceptance (PCA). PCA is a call-screening feature that
allows a subscriber to limit incoming calls to only those calling parties
who are able to provide a valid PCA password (i.e., a series of digits).
Preferred Language (PL). PL provides the subscriber with the ability to
specify the language for network services.
Priority Access and Channel Assignment (PACA). PACA allows a subscriber
to have priority access to voice or traffic channels on call origination
by queuing these subscribers’ originating calls when channels
are not available. The subscriber is assigned one of several priority
levels and the invocation ofPACAis determined to one of two options:
permanent, in which the feature is always available, and demand, in
which the feature is available only on request.
Remote Feature Control (RFC). RFC allows a calling party to call a
special RFC directory number to specify one or more feature
operations.
Selective Call Acceptance (SCA). SCA is a call-screening service that allows
a subscriber to receive calls only from parties whose CNPs are
in an SCA screening list of specified CNPs.
Subscriber PIN Access (SPINA). SPINA allows subscribers to control
whether their mobile station is allowed to access the network. This
feature may be used by subscribers to prevent unauthorized use of
their own mobile station or fraudulent use by a clone.
Subscriber PIN Intercept (SPINI). SPINI enables subscribers to restrict
outgoing calls originated from their mobile station. The subscriber
requires a SPINI PIN authorization code to originate calls meeting
specified criteria (e.g., international call type). SPINI PIN shall not be
required on unrestricted call types (e.g., emergency) and may not be
required for a list of frequently called numbers, regardless of their call
type.
Three-Way Calling (3WC). 3WC provides the subscriber with the ability
to add a third party to an established two-party call, so that all
three parties may communicate in a three-way call.
Voice Message Retrieval (VMR). VMR permits a subscriber to retrieve
messages from a voice message system (VMS).
Voice Privacy (VP). VP provides a degree of privacy for the subscriber
over the base station to mobile station (BS–MS) radio link.
Short Message Service Features
The following are the primary short message service features:
Short Message Delivery–Point-to-Point Bearer Service (SMD-PP). SMDPP
provides bearer service mechanisms for delivering a short message
as a packet of data between two service users, known as short message
entities (SMEs). The length of the bearer data may be up to 200
octets. Implementations and service providers may further restrict
this length. The SMD-PP service attempts to deliver a message to an
MS-based SME whenever the MS is registered even when the MS is
engaged in a voice or data call.
Cellular Paging Teleservice (CPT). CPT conveys short textual messages
(up to 63 characters) to an SME for display or storage.
Cellular Messaging Teleservice (CMT).CMTconveys and manages short
messages to an SME for display or storage. This teleservice should
coordinate the use of the display and arbitrate between conflicting
users or services. Each message includes attributes for management
of the messages received by the SME. | 
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