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As the convergence of wireless technology and as the Internet continues at an escalating pace, the new potential created by third-generation (3G) and fourth-generation (4G) technologies seems to be endless. Current TDMA operators are preparing for the revolution, they must develop their networks to take advantage of mobile multimedia applications and the eventual shift to an all-Internet Protocol (IP) architecture. GPRS and Enhanced GPRS (EGPRS) evolution enables the operators to do so. However, soon after GPRSs initial integration, some operators will begin the next step in the evolution process to Enhanced Data Rates for Global Evolution (EDGE). With EDGE, Existing TDMA networks can host a variety of new applications, including: Online e-mail, Access to the World Wide Web, Enhanced Short Messages Services (SMSs), Wireless imaging with instant photo or graphics, Video services and more. At the same time, some operators will skip the step to EDGE and go directly to Universal Mobile Telecommunications Systems (UMTSs), or what we consider to be a 3G technology.
Packet networks provide a seamless and immediate connection to the Internet or corporate intranet, enabling access to existing Internet applications, such as e-mail and Web browsing, without dialing into an Internet Service Provider (ISP). The advantage of a packet-based approach is that it uses the medium only as long as data is being sent or received. Multiple users can share the same radio channel very efficiently. In contrast, with current circuit-switched connections, users have dedicated connections during their entire call, even if they are not sending data. Many applications have idle periods during a session. With packet data, users will only pay for the amount of data they actually communicate, and not the idle time. In fact, with GPRS, users could be "virtually" connected for hours at a time and only pay small connect charges. Although packet-based communications works well with all types of communications, it is especially well suited for frequent transmission of small amounts of data. Packet is equally well suited for large batch operations and other applications involving large file transfers. However, when using large file transfers, the cost can become very expensive compared to circuit-switched data transmissions. GPRS supports the IP as well as the X.25 protocol. IP support is increasingly more important as companies look to the Internet as a way for their remote workers to access corporate intranets. This is true when using a Virtual Private Network (VPN). UMTS is a European Telecommunications Standards Institute (ETSI) term for a 3G mobile telecommunications service. Over recent years, mobile telephony evolutions have become known as the following categories:
Enhanced General Packet Radio Service (EGPRS) EGPRS offers eight additional coding schemes. The lower layers of the user data plane, which has been specifically designed for GPRS operation, is reflected in the protocol stack, comprising the physical, Radio Link Control/Medium Access Control (RLC/MAC), and Logical Link Control (LLC) layers. Although the LLC layer can be used without modifications when EDGE functionality is integrated into the model, it is necessary to modify the RLC/MAC layer to support features such as efficient multiplexing and link adaptation. The basic modifications needed for EDGE consider the form of the data blocks that are being transferred across the radio interface. For EGPRS, several combinations of interleaving and coding have been proposed, whereas in the current GPRS proposals, the interleaving depth is set to four bursts. Link adaptation offers mechanisms for choosing the best modulation and coding alternative for the current radio link. In GPRS, only the coding scheme can be altered between two consecutive LLC frames; however, with EGPRS, a refined link adaptation concept can be utilized that enables both coding and modulation schemes to be charged to suit the given radio link. In addition, link adaptation should enable seamless switching between the two modulation schemes. It is commonly assumed that each link is able to choose the modulation and coding combination that achieves the highest throughput for that particular link quality. Enhanced Data Rates for GSM Evolution (EDGE) Beyond GPRS, EDGE takes the cellular community one step closer to UMTS. It provides higher data rates than GPRS and introduces a new modulation scheme called s-PSK. The TDMA community also adopted EDGE for their migration to UMTS. The data rates allocated for EDGE start at 384 Kbps and above as a second stage to GPRS. EDGE uses a combination of Frequency Division Multiple Access (FDMA) and TDMA as the multiple access control methods and actually uses them at the MAC layer of the OSI model. The channel separations are the same as GSM and GPRS. The number of TDMA slots on each carrier is the same (eight) as the GSM and GPRS architecture. When a mobile station wants to transmit its data, it can request and use one to eight time slots per TDMA frame. Connectivity is handled via a packet-switched data network such as IP and X.25. These can be public data networks or private data networks. The rollout of high-bandwidth wireless transport technology faces many possibilities. The International Telecommunications Union-Radio communications Standardization Sector (ITU-R) has actually established five different standards that fall into the category of 3G/UMTS.
EDGE is a proposed modification to the modulation scheme utilized by GSM. EDGE is a new modulation scheme that is bandwidth efficient. The technology defines a new physical layer: 8-PSK modulation, thi new modulation scheme enables each pulse to carry 3 bits of information. This idea will drastically increase the bit rates available to end users for the purpose of data transfer. The expectation is that the enhanced modulation techniques will make it possible to maintain a good quality link by automatically adapting to the radio interference conditions and thereby provide the highest possible rate. Therefore, EDGE has the potential to increase the data rate of existing GSM systems by a factor of three. Wherever possible, EDGE adopts the GSM standards so as to minimize the changes required by manufacturers and operators who want to support this new technology. A study carried out by ETSI on EDGE proposes that it will be able to support both transparent and non-transparent circuit-switched services, in addition to the packet-based GPRS. These three new services will be called: * ECSD-T- Enhanced Circuit-Switched Data-Transparent. * ECSD-NT- Enhanced Circuit-Switched Data-Non-Transparent. * EGPRS-Enhanced GPRS.
UMTS will deliver voice, graphics, video and other broadband information directly to the user, regardless of location, network or terminal. These personal communication services will provide terminal and service mobility on fixed and mobile networks, taking advantage of the convergence of existing and future fixed and mobile networks and the potential synergies that can be derived from such convergence. The key benefits that UMTS promises include improvements in quality and security, incorporating broadband and networked multimedia services, flexibility in service creation, and ubiquitous service portability. Networked multimedia can be defined to include services such as: Pay-TV, video and audio on-demand, interactive entertainment, educational and information services and communication services such as video-telephony and fast, large file transfer. UMTS will enter the market at a time when fixed mobile integration is becoming a reality; the telecommunications, computer, and media industries have converged on IP as a shared standard; and data accounts for a significant proportion of the traffic carried by mobile networks. UMTS requirements include: small, low-cost packet terminals, worldwide roaming, a single system for residential, office, cellular, and satellite environments and high-speed data. The UMTS systems will support data rates of up to 2 Mbps and new multimedia applications over a new, wideband air interface based on CDMA techniques. Services will be supported by a wide range of terminals customized to the requirements of voice, data, and multimedia services. UMTS will encompass more than just cellular systems, devloping from GSM and embracing fixed networks and other wireless and wire access technologies. Services will be globally available, delivered over the mobile, satellite, or fixed networks that provide the best accessibility for the consumer's specific location. The current vision of most operators is that UMTS will exist as "islands of coverage" with data services supported by GPRS in areas of lower traffic density. If data demand is sufficient, it may be economical to upgrade such areas to EDGE, rather than deploy W-CDMA. Despite the apparent attractions of deploying EDGE as an incremental solution, operators will need to deploy UMTS, as only W-CDMA can support the high traffic densities encountered in the core of mature networks. The initial release of the EDGE standard is aimed at increasing the capacity and speed of GPRS data services. The second phase of the EDGE standard will support packet voice using VoIP techniques.
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Last updated: 02-06-2003.
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