WCDMA: =>Mobile Phone Glossary(2)

Thursday, July 31, 2008

=>Mobile Phone Glossary(2)

CLDC J2ME Connected Limited Device Configuration. The CLDC serves the market consisting of personal, mobile, connected information devices. This configuration includes some new classes designed specifically to fit the needs of small-footprint devices. Communicator A generic name for information centric mobile phones. In effect a fully featured personal digital assistant and mobile phone in one unit. The Nokia 9210 Communicator is an example of such a Symbian OS phone. Content Provider A company that provides services to mobile phone users or network operators. These services could be shopping, web surfing, chat rooms, playing games, accessing data such as music and books through a server. Crystal Code-name for a half VGA reference design for Symbian OS.

D-AMPS

Digital AMPS (Digital-Advanced Mobile Phone Service) is the digital wireless standard widely used throughout the Americas, Asia Pacific and other areas. D-AMPS uses digital TDMA on the one hand, and is required to be compatible with installed AMPS base station networks on the other. D-AMPS operates on the 800 and 1900 MHz bands.

DCS 1800

Digital Communications System: another name for GSM working on a radio frequency of 1800 MHz. Also known as GSM1800 or PCN, this digital network operates in Europe and Asia Pacific. Digital A way of encoding information. On digital networks, data doesn't need to go though the extra step of being converted to an analog signal, voice is sampled and coded in a way similar to how it is recorded on a CD. Digital networks are fast replacing analog ones as they offer improved sound quality, secure transmission and can handle data directly as well as voice. Digital networks include mobile systems GSM, D-AMPS, CDMA, TDMA and UMTS. Dual band Dual band mobile phones can work on networks that operate on different frequency bands. This is useful if you move between areas covered by different networks. Some networks operate on two bands, for instance GSM-1800 in town centers and GSM-900 in the rest of the country.
Dual mode Dual mode mobile phones have more than one air interface and hence can work on more than one network. One example is phones that operate on both digital and analog networks. They are quite useful if you want the advantages of a digital phone, but regularly visit areas where analog is the only service available.

EDGE

Enhanced Data Rates for GSM Evolution. An enhanced modulation technique designed to increase network capacity and data rates in GSM networks. EDGE should provide data rates up to 384 Kbps. EDGE will let operators without a 3G license to compete with 3G networks offering similar data services. EDGE is not expected before 2001 at the earliest.
EPOC Deprecated term. Refer to Symbian OS.

E-TACS

Extended Total Access Communications System: a 1G mobile phone network developed in the UK and available in Europe and Asia.
FCT Fixed Cellular Terminal - also known as : GSM Gateway, GSM Modem, GSM Router, Mobile Gateway, channel bank, GSM channel Bank, ISDN GSM Gateway, analogue GSM gateway.

Fixed Cellular Terminal Mobile

Device that allows fixed telephony devices such as PBX Telephone Systems to connect directly to the GSM Mobile Phone Network - This may be to allow PBX users to call colleages on their mobiles free of charge, or call other mobile users at reduced rates (depending upon available tariffs) - or for use in remote offices where no fixed line services are available (eg building site / remote monitoring post) - for landline substitution then Fixed Cellular Terminals are available that can provide voice, fax and data over the GSM network such as the Ericsson F251m .

History of spread spectrum and CDMA

This brief historical explanation begins with a look at Spread Spectrum (SS)
principles, since they are fundamental to the multiple access principle known as
CDMA.
The frequency bandwidth needed to transmit a given amount of information is directly
related to the information rate – the amount of information transmitted per unit of
time. The term “bandwidth” is now often used interchangeably with “bit rate” so this
appears intuitively clear to most people.
SS techniques are methods by which more frequency bandwidth is deliberately used
than motivated by the actual information rate (spectrum spreading). On one hand,
this implies a certain waste of valuable frequency spectrum; but on the other hand,
these techniques have advantages such as increasing the resistance to interference,
jamming and interception.

Technologies in WCDMA

In this section we describe some of the important innovations that constitute the WCDMA standard, developed in response to the challenging 3G requirements placed on it. We also include descriptions of how the technologies differ from those used in the IS-95 family of standards. In particular we discuss functions related to the air interface, which is the interface between the mobile device and the network.

Asynchronous network operation
Several of the requirements for WCDMA did not exist in legacy standards, including IS-95. One such requirement is asynchronous network operation. Early on, one of the fundamental technical principles shared by the Japanese and European WCDMA concepts (including CoDiT) was asynchronous operation; that is, the base stations should not have to be synchronized to each other. This was an opposite requirement to that of the IS-95 (and later Cdma2000) standard, which relies on GPS (Global Positioning System) for its proper operation. The UMTS requirement for an asynchronous system was fundamentally important because it led to a standalone and easily deployable system attractive to operators around the world. But it also gave rise to several new technological challenges for WCDMA, including cell search and handover, described below.

Cell search
Before engaging in any kind of communication with the network, a mobile device must first synchronize to the signals sent from base stations. Mobile devices need to find out which base station code to look for and then synchronize to it. Searching for all possible base station codes at all possible times is an arduous task that could potentially affect the time from power-on to placing a call. Being asynchronous, WCDMA could not employ the principle adopted in the IS-95/Cdma2000 standards, where a common base station code with unique GPS time-shifts was used throughout the system. Clearly there was a need for innovation in this area. The early Japanese version of WCDMA included a structure based on dual synchronization channels, but it was generally considered too complex. Extensive research was conducted to find an information encoding principle that would minimize the cell search time while still keeping the complexity of the search at a negligible level. Solutions were progressively proposed to the standard and soon the goals had been achieved [13]. One of the early major technical challenges of asynchronous CDMA-based 3G had been overcome.

Soft handover
In most older mobile systems, the mobile devices are connected to one base station at a time and handover is the process of seamlessly shifting a mobile device’s connection from one base station to another. In “soft handover” however, mobile devices communicate the same information through two or more base stations simultaneously (see Figure 7). In practice, soft handover is a prerequisite for any high-capacity DS-CDMA-based system operating with the same carrier frequency in neighboring cells. As early as 1988, Jan Uddenfeldt et al., of Ericsson, pioneered the fundamental principles of soft handover in some of Ericsson’s early patents in the digital cellular field [14].

Compressed mode

Already from the beginning, virtually all WCDMA mobile devices were expected to bedual-mode (to support GSM) as the initial WCDMA coverage would probably not beas wide as that of GSM. Therefore, handover of ongoing connections betweenWCDMA and GSM was crucial for a smooth early rollout of WCDMA4. For a securehandover from WCDMA to GSM, the mobile device needs to perform signalmonitoring on potential GSM target base stations in the area, even during an activecall on the WCDMA system. The problem is to find time for this, because the mobiledevice is “busy all the time” with sending and receiving on a given WCDMA carrierfrequency. A technology denoted “Compressed Mode,” originally developed in CoDiT[9, 16], was adopted in WCDMA to solve this problem.

WCDMA

Thursday, July 31, 2008

=>Mobile Phone Glossary(2)

Blog Archive

My Blog List

About Me

History of spread spectrum and CDMA

Early spread spectrum and CDMA development

Technologies in WCDMA

Compressed mode

Counter