WCDMA: =>Mobile Phone Glossary(4)

Thursday, July 31, 2008

=>Mobile Phone Glossary(4)

J2ME

Java 2 Platform, Micro Edition (J2ME): The edition of the Java platform that is targeted at small, standalone or connectable consumer and embedded devices. The J2ME technology consists of a virtual machine and a set of APIs suitable for tailored runtime environments for these devices. The J2ME technology has two primary kinds of components – configurations and profiles. JavaPhone A Java API specification controlling contacts, power management, call control, and phonebook management, intended specifically for the programmability requirements of mobile phones.

JTAPI The Java Telephony API is an extensible API that offers an interface to all call control services (from those needed in a consumer device up to those of call centers). JTAPI is part of the JavaPhone API. Kernel Core of an operating system, a kernel manages the machine's hardware resources (including the processor and the memory), and provides and controls the way any other software component can access these resources. The kernel runs with a higher privilege than other programs (so-called user-mode programs). The power and robustness of an OS's kernel play a major role in shaping overall system design and reliability.

MExE

Mobile Station Application Execution Environment (GSM 02.57): a framework to ensure a predictable environment for third-party applications in GSM or UMTS handsets (ie the Mobile Station). MExE does this by defining different technology requirements called "classmarks". MExE classmark 1 is based on WAP, classmark 2 on PersonalJava and JavaPhone, and classmark 3 on J2ME CLDC and MIDP. Other classmarks may be defined in the future. MExE specifies additional requirements for all classmarks, for instance a security environment, capability and content negotiation, a user profile, user interface personalization, management of services and virtual home environment. A handset can support any number of classmarks.

MIDP

Mobile Information Device Profile. Set of Java APIs that is generally implemented on the Connected Limited Device Configuration (CLDC). It provides a basic J2ME application runtime environment targeted at mobile information devices, such as mobile phones and two-way pagers. The MIDP specification addresses issues such as user interface, persistent storage, networking, and application model. Network operator Company with a license to provide wireless telephony services.

NMT

Nordic Mobile Telephone. One of the earliest 1G cellular network developed jointly in Denmark, Finland, Iceland, Norway and Sweden. Originally operated in the 450 MHz band. Later the 900 MHz was used as well. OBEX Object Exchange: a set of high-level protocols allowing objects such as vCard contact information and vCalendar schedule entries to be exchanged using either IrDA (IrOBEX) or Bluetooth. Symbian OS implements IrOBEX for exchange of vCards, for example between a Nokia 9210 Communicator and an Ericsson R380 Smartphone, and vCalendar.

Operating System: historically, the minimal set of software needed to manage a device's hardware capability and share it between application programs. Practically, "OS" is now used to mean all software including kernel, device drivers, comms, graphics, data management, GUI framework, system shell application, and utility applications. This would define Windows, Palm OS and MacOS as operating systems. Symbian provides an operating system – Symbian OS – tailored for data-enabled mobile phones.

OPL A BASIC-like programming language, for rapid application development, used on Symbian OS. Packet-switching Technique whereby the information (voice or data) to be sent is broken up into packets, of at most a few KB each, which are then routed by the network between different destinations based on addressing data within each packet. Use of network resources is optimized, as the resources are needed only during the handling of each packet. This is an ideal model for ad hoc data communication, and works well also for voice, video and other streamed data. Mobile phones with packet-switched communication appear to be "always connected" to the data network, whereas in the case of circuit-switched connections, setup time takes around 30 seconds to connect from a mobile phone to an ISP. Use of packet-switched network can be charged according to the volume of data transferred and not to any notion of time spent online. PCN Personal Communications Network: another name for GSM 1800 (it is also known as DCS 1800). It is used in Europe and Asia Pacific.

PCS

Personal Communications Service: an American generic term for a mass-market mobile phone service, emphasizing personal communication, independent of the technology used to provide it. PCS includes such digital cellular technologies as GSM 1900, CDMA and TDMA IS-136.

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(4)

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History of spread spectrum and CDMA

Early spread spectrum and CDMA development

Technologies in WCDMA

Compressed mode

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