2.5G/3G Mobile wireless systems in .NET Generation ANSI/AIM Code 128 in .NET 2.5G/3G Mobile wireless systems

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2.5G/3G Mobile wireless systems using vs .net toaccess code-128 with web,windows application USPS OneCode Solution Barcode mobile terminals with data c .NET Code 128A apability, as an example, requires introducing packet-based communications into the mobile wireless world. Second, packet communications has long been recognized as being a much more ef cient way of handling the disparate transmission requirements introduced by this newer world of multimedia traf c.

Data traf c can be bursty, meaning that the time between successive occurrences of data packets may be very long compared with the time to transmit the packets; there may be frequent transmission required of small volumes of traf c; nally, there may be occasional transmission of long les. (Think of the obvious Internet applications such as email transmission, sur ng the Web, downloading of les from a Web site, etc.) These variations in transmission requirements are vastly different than those seen in voice-based, circuit-switched traf c.

Packet transmission is more ef cient in handling bursty traf c than is circuit-switched transmission since multiple packets from various users may share transmission facilities as already noted, unlike circuit switching with its use of dedicated facilities. But to ensure ef cient use of the wireless resources such as frequency bandwidth, time slots, or codes in CDMA systems, transmission setup must be very fast and access times made very short. Connect times must be much less than those in the voice-based circuit-switched 2G cellular systems described in previous chapters.

Packet-switched data communication introduces signi cant differences in performance requirements for the user as well. We focused in 9 on such performance objectives as call blocking and handoff dropping probabilities. Packet-switched data transmission introduces a completely new set of user performance objectives, in addition to the two just mentioned.

These are described under the general rubric of quality of service or QoS. These objectives include, among others, packet priority level (different types of traf c may require different handling), probability of packet loss, packet delay transfer characteristics, and data throughput rates. We shall nd these packet-switching performance requirements and objectives recurring throughout our discussion in this chapter of 3G systems.

It was thought at rst that one worldwide 3G cellular network standard would be developed to which the three current 2G standards we have been discussing would converge. It turned out, as has so often been the case with the development of international standards, that agreement on one standard was not possible. Instead, a number of standards have been developed, with the hope that convergence will still be possible in the future.

In Sections 10.2 and 10.3 following, we describe three of the four 3G standards that have been developed, two based on CDMA technology, the other based on TDMA technology.

CDMA technology appears to be preferred for a number of reasons. It has the capability, as will be noted later in this chapter, of allocating bandwidth dynamically to different users. This is a desired attribute for packet-switched systems, enabling multimedia traf c, among other traf c types, to be supported.

Studies carried out worldwide have indicated as well that this type of technology results in higher-capacity cellular systems with the requisite bandwidths necessary to support higher bit rate multimedia traf c in addition to voice. The two CDMA standards, wideband CDMA or W-CDMA and cdma2000, are described in Section 10.2, after an introductory discussion of increased bit rate CDMA systems in general.

cdma2000 has been designed to be backwards compatible with IS-95. W-CDMA is considered to be an outgrowth of, and possible replacement for, GSM. The various countries and organizations worldwide currently deploying and supporting GSM developed the concept of Universal Mobile Telecommunication Services or UMTS as the.

Mobile Wireless Communications objective for the third-gene Code-128 for .NET ration replacement for GSM. The acronym UMTS is thus often considered synonymous with W-CDMA, and the W-CDMA standard is also referred to as the UMTS/IMT-2000 standard.

This standard was developed by the 3rd Generation Partnership Project, 3GPP. The cdma2000 standard was developed by a follow-on project, 3GPP2. These standards projects were created in 1998 and 1999, respectively, as a joint effort of standardization bodies in Europe, Japan, Korea, USA, and China.

The TDMA standard, also dubbed a 2.5/3G standard, is designed to provide a packetswitching capability for GSM as well as enhanced bit rates across the radio interface, while maintaining as much as possible the current characteristics of GSM, and allowing for compatibility in the transmission of voice, as well as other circuit-switched services. It thus represents a less far-reaching change than does W-CDMA.

The introduction of packet switching for data transmission over GSM networks does, however, require changes in the GSM wireless core network infrastructure, the resultant packet-switched core network standard being called GPRS (general packet radio service). The enhanced bit rates come from adopting a technique called EDGE (enhanced data rates for global evolution). The EDGE technique is being adopted for enhanced versions of IS-136 as well, with the expectation that there will be a future convergence of the two TDMA systems, GSM and IS-136.

Section 10.3 provides an overview of GPRS and EDGE. The concept of a layered architecture plays a signi cant role in the standardization of GPRS, as it does in all packet-switching networks.

We thus review this concept brie y and describe the layering adopted for GPRS in Section 10.3. Note that we indicated we would only be discussing two of the three CDMA standards in Section 10.

2. W-CDMA comes in two avors, a frequency-division duplex, FDD, version and a time-division duplex, TDD, version, to be used principally in indoor environments. Frequency-division duplexing is the technique used in all second-generation systems, with different frequency bands assigned to uplink and downlink transmission.

Time-division duplexing is a technique in which downlink and uplink transmission alternate in time in using the same frequency band. We shall be focusing on the FDD version in our discussion of W-CDMA. The cdma2000 system is designed to be backwards compatible with the circuit-switched IS-95, as noted above, yet is capable of handling much higher bit rate packet-switched data.

In the remaining two chapters we continue our focus on packet switching in wireless systems. In 11 following, we move away from speci c wireless network standards and discuss the problem of combining or multiplexing voice and packet-switched data over a common radio link in more general terms. This problem is generally referred to as the multi-access problem.

It is basically a resource allocation problem, that of allocating bandwidth most effectively to the different users, as well as to competing types of traf c such as voice, video, images, and les. It is often referred to as well as the scheduling problem. In the case of CDMA systems this corresponds to the appropriate allocation of time and codes; in TDMA systems, time slots in each frame represent the resource to be allocated.

Much work has been done in comparing different resource allocation strategies and we describe some of this work in both the CDMA and TDMA domains. An example of a resource allocation strategy that has been studied for cdma2000 appears here at the end of the next section, devoted to the various CDMA schemes proposed for third-generation systems..

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