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The third generation of mobile cellular systems are intended to unify the diverse systems we see today into a seamless radio infrastructure capable of offering a wide range of services in different radio environments, with the quality we
have come to expect from wire line communication networks. Since the mid-80's, studies on 3G systems have been carried out within the International Telecommunication Union (ITU), where it was called Future Public Land Mobile Telecommunication Systems (FPLMTS), lately renamed International Mobile Telecommunicatons-2000 (IMT-2000).
In Europe research and development on 3G technology, is commonly referred to as the Universal Mobile Telecommunication System (UMTS) and Mobile Broadband System (MBS), have been conducted under the European Community Research into Advanced Communications in Europe (RACE) and Advanced Communication Technologies and Services (ACTS) programs. With support from activities in Europe, the United States, Japan and developing countries, World Administrative Radio Conference (WARC) of ITU identified global bands 1885-2025Mhz and 2110-2200Mhz for IMT-2000 including 1980-2010Mhz and 2170-2200Mhz for the mobile satellite component. Key elements in the definition of 3G systems are the radio access system and Radio Transmission Technology (RTT). As a part of the standardization activities, a formal request by the ITU-Radio communication standardization sector (ITU-R) for submission of candidate RTTs for IMT-2000 has been distributed by the ITU. In response to this 10 proposals were submitted. Most of the proposals use CDMA or WCDMA as their multiple access technique. So in this seminar and presentation we are presenting the common features of WCDMA based 3G standards.
The primary focus of third generation architectures will be to attempt to seamlessly evolve second generation systems to provide high speed data services to support multimedia applications such as web browsing. The key word is "evolve" -
as the challenge to wireless equipment manufacturers is to provide existing customers, namely, service providers, with a migration path that simultaneously satisfies the requirements set forth by the International Telecommunications Union (ITU) for 3G wireless services while preserving customer investment in existing wireless
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THIRD GENERATION (3G) WIRELESS TECHNOLOGY
Third Generation (3G) mobile devices and services will transform wireless communications in to on-line, real-time connectivity. 3G wireless technology will allow an individual to have immediate access to location-specific services that offer information on demand. The first generation of mobile phones consisted of the analog models that emerged in the early 1980s. The second generation of digital mobile phones appeared about ten years later along with the first digital mobile networks. During the second generation, the mobile telecommunications industry experienced exponential growth both in terms of subscribers as well as new types of value-added services. Mobile phones are rapidly becoming the preferred means of personal communication, creating the world's largest consumer electronics industry.
The rapid and efficient deployment of new wireless data and Internet services has emerged as a critical priority for communications equipment manufacturers. Network components that enable wireless data services are fundamental to the next-generation network infrastructure. Wireless data services are expected to see the same explosive growth in demand that Internet services and wireless voice services have seen in recent years.
This white paper presents an overview of current technology trends in the wireless technology market, a historical overview of the evolving wireless technologies and an examination of how the communications industry plans to implement 3G wireless technology standards to address the growing demand for wireless multimedia services. We also show the differences between third generation wireless technology when compared to different wireless technologies.
3G Wireless Market Drivers:
Telecommunications service providers and network operators are embracing the recently adopted global third generation (3G) wireless standards in order to address emerging user demands and to provide new services. The concept of 3G wireless technology represents a shift from voice-centric services to multimedia-oriented (voice, data, video, fax) services. In addition, heavy demand for remote access to personalized data is fueling development of applications, such as the Wireless Application Protocol (WAP) and multimedia management, to complement the 3G protocols. Complementary standards, such as Bluetooth, will enable interoperability between a mobile terminal (phone, PDA etc.) and other electronic devices, such as a laptop/desktop and peripherals, providing added convenience to the consumer and allowing for the synchronization and uploading of information at all times. According to Lehman Brothers, approximately 50 percent of current voice services subscribers are expected to use wireless data services by 2007, instead of 25 percent as previously forecast1. Lehman Brothers further predicts that, within seven years, 18 percent of cellular revenues and 21 percent of PCS (personal communications services) revenue will come from wireless data services. Cellular subscriptions are forecast to exceed one billion by 20032, compared with the 306 million that was forecast at the end of 1998, representing a compound annual growth of 29 percent. Demand for voice services has traditionally been a market driver. However, today, demand for data services has emerged as an equally significant market driver. After many years of stasis, the telecommunications industry is undergoing revolutionary changes due to the impact of increased demand for data services on wireline and wireless networks. Up until recently, data
traffic over mobile networks remained low at around 2% due to the bandwidth limitations of the present second-generation (2G) wireless networks. Today, new technologies are quickly emerging that will optimize the transport of data services and offer higher bandwidth in a mobile environment. As a case in point, the increased use of the Internet as an acceptable source for information distribution and retrieval, in conjunction with the increased demand for global mobility has created a need for 3G wireless communications protocols.
The third generation of mobile communications will greatly enhance the implementation of sophisticated wireless applications. Users will be able to utilize personal, location-based wireless information and interactive services. Also, many companies and corporations are restructuring their business processes to be able to fully exploit the opportunities provided by the emerging new wireless data services. Many advanced wireless services are already available today, and the introduction of 3G wireless technologies will add to their ubiquity.
Generation First Wireless Technology:
The first generation of wireless mobile communications was based on analog signalling. Analog systems, implemented in North America, were known as Analog Mobile Phone Systems (AMPS), while systems implemented in Europe and the rest of the world were typically identified as a variation of Total Access Communication Systems (TACS). Analog systems were primarily based on circuit-switched technology and designed for voice, not data.
Second Generation Wireless Technology:
The second generation (2G) of the wireless mobile network was based on low-band digital data signalling. The most popular 2G wireless technology is known as Global Systems for Mobile Communications (GSM). GSM systems, first implemented in 1991, are now operating in about 140 countries and territories around the world. An estimated 248 million users now operate over GSM systems. GSM technology is a combination of Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA). The first GSM systems used a 25MHz frequency spectrum in the 900MHz band. FDMA is used to divide the available 25MHz of bandwidth into 124 carrier frequencies of 200kHz each. Each frequency is then divided using a TDMA scheme into eight timeslots. The use of separate timeslots for transmission and reception simplifies the electronics in the mobile units. Today, GSM systems operate in the 900MHz and 1.8 GHz bands throughout the world with the exception of the Americas where they operate in the 1.9 GHz band. In addition to GSM, a similar technology, called Personal Digital Communications (PDC), using TDMA-based technology, emerged in Japan. Since then, several other TDMA-based systems have been deployed worldwide and serve an estimated 89 million people worldwide. While GSM technology was developed in Europe, Code Division Multiple Access (CDMA) technology was developed in North America. CDMA uses spread spectrum technology to break up speech into small, digitized segments and encodes them to identify each call. CDMA systems have been implemented worldwide in about 30 countries and serve an estimated 44 million subscribers. While GSM and other TDMA-based systems have become the dominant 2G wireless technologies, CDMA technology is recognized as providing clearer voice quality with less background noise, fewer dropped calls, enhanced security, greater reliability and greater network capacity. The Second Generation (2G) wireless networks mentioned above are also mostly based on circuit-switched technology. 2G wireless networks are digital and expand the range of applications to more advanced voice services, such as Called Line Identification. 2G wireless technology can handle some data capabilities such as fax and short message service at the data rate of up to 9.6 kbps, but it is not suitable for web browsing and multimedia applications.
Next Generation Mobile Networks:
Second Generation (2G+) Wireless Networks: As stated in a previous section, the virtual explosion of Internet usage has had a tremendous impact on the demand for advanced wireless data communication services. However, the effective data rate of 2G circuit-switched wireless systems is relatively slow -- too slow for today's Internet. As a result, GSM, PDC and other TDMA-based mobile system providers and carriers have developed 2G+ technology that is packet-based and increases the data communication speeds to as high as 384kbps. These 2G+ systems are based on the following technologies: High Speed Circuit-Switched Data (HSCSD), General Packet Radio Service (GPRS) and Enhanced Data Rates for Global Evolution (EDGE) technologies. HSCSD is one step towards 3G wideband mobile data networks. This circuit-switched technology improves the data rates up to 57.6kbps by introducing 14.4 kbps data coding and by aggregating 4 radio channels timeslots of 14.4 kbps. GPRS is an intermediate step that is designed to allow the GSM world to implement a full range of Internet services without waiting for the deployment of full-scale 3G wireless systems. GPRS technology is packet-based and designed to work in parallel with the 2G GSM, PDC and TDMA systems that are used for voice communications and for table look-up to obtain GPRS user profiles in the Location Register databases. GPRS uses a multiple of the 1 to 8 radio channel timeslots in the 200kHz-frequency band allocated for a carrier frequency to enable data speeds of up to 115kbps. The data is packetized and transported over Public Land Mobile Networks (PLMN) using an IP backbone so that mobile users can access services on the Internet, such as SMTP/POP-based e-mail, ftp and HTTP-based Web services. EDGE technology is a standard that has been specified to enhance the throughput per timeslot for both HSCSD and GPRS. The enhancement of HSCSD is called ECSD, whereas the enhancement of GPRS is called EGPRS. In ECSD, the maximum data rate will not increase from 64 kbps due to the restrictions in the A interface, but the data rate per timeslot will triple. Similarly, in EGPRS, the data rate per timeslot will triple and the peak throughput, including all eight timeslots in the radio interface, will exceed 384 kbps.
GPRS networks consist of an IP-based Public Mobile Land Network (PLMN), Base Station Services (BSS), Mobile handsets (MS), and Mobile Switching Centers (MSC) for circuit-switched network access and databases. The Serving GPRS Support Nodes (SGSN) and Gateway GPRS Support Nodes (GGSN) make up the PLMN. Roaming is accommodated through multiple PLMNs. SGSN and GGSN interface with the Home Location Register (HLR) to retrieve the mobile user's profiles to facilitate call completion. GGSN provides the connection to external Packet Data Network (PDN), e.g. an Internet backbone or an X.25 network. The BSS consists of Base Transceiver Stations and Base Station Controllers. The Base Transceiver Station (BTS) receives and transmits over the air interfaces (CDMA, TDMA), providing wireless voice and data connectivity to the mobile handsets. Base Station Controllers (BSC) route the data calls to the packet-switched PLMN over a Frame Relay (FR) link and the voice calls to the Mobile Switching Center (MSC). MSC switches the voice calls to circuit-switched PLMN network such as PSTN and ISDN. MSC accommodates the Visitor Location Register (VLR) to store the roaming subscriber information. The reverse process happens at the destination PLMN and the destination BSS. On the data side, the BSC routes the data calls to the SGSN, and then the data is switched to the external PDN through the GGSN or to another mobile subscriber.
Figure 1 shows a GPRS network.
The following is a brief description of each protocol layer in the GPRS network infrastructure: Sub-Network Dependent Convergence Protocol (SNDCP): protocol that maps a network level protocol, such as IP or X.25, to the underlying logical link control. SNDCP also provides other functions such as compression, segmentation and multiplexing of network-layer messages to a single virtual connection. Logical Link Control (LLC): a data link layer protocol for GPRS which functions similar to Link Access Protocol â€œ D (LAPD). This layer assures the reliable transfer of user data across a wireless network. Base Station System GPRS Protocol (BSSGP): processes routing and quality of service (QoS) information for the BSS. BSSGP uses the Frame Relay Q.922 core protocol as its transport mechanism. GPRS Tunnel Protocol (GTP): protocol that tunnels the protocol data units through the IP backbone by adding routing information. GTP operates on top of TCP/UDP over IP.
Figure 2 shows the protocols used in BTS, BSC, SGSN, GGSN, and mobile handsets:
GPRS Mobility Management (GMM/SM): protocol that operates in the signalling plane of GPRS, handles mobility issues such as roaming, authentication, selection of encryption algorithms and maintains PDP context. Network Service: protocol that manages the convergence sub-layer that operates between BSSGP and the Frame Relay Q.922 Core by mapping BSSGP's service requests to the appropriate Frame Relay services. BSSAP+: protocol that enables paging for voice connections from MSC via SGSN, thus optimizing paging for mobile subscribers. BSSAP+ is also responsible for location and routing updates as well as mobile station alerting. SCCP, MTP3, MTP2 are protocols used to support Mobile Application Part (MAP) and BSSAP+ in circuit switched PLMNs. Mobile Application Part (MAP): supports signaling between SGSN/GGSN and HLR/AuC/EIR.
Third Generation (3G) Wireless Networks:
3G wireless technology represents the convergence of various 2G wireless telecommunications systems into a single global system that includes both terrestrial and satellite components. One of the most important aspects of 3G wireless technology is its ability to unify existing cellular standards, such as CDMA, GSM, and TDMA, under one umbrella. The following three air interface modes accomplish this result: wideband CDMA, CDMA2000 and the Universal Wireless Communication (UWC-136) interfaces. Wideband CDMA (W-CDMA) is compatible with the current 2G GSM networks prevalent in Europe and parts of Asia. W-CDMA will require bandwidth of between 5Mhz and 10 Mhz, making it a suitable platform for higher capacity applications. It can be overlaid onto existing GSM, TDMA (IS-36) and IS95 networks. Subscribers are likely to access 3G wireless services initially via dual band terminal devices. W-CDMA networks will be used for high-capacity applications and 2G digital wireless systems will be used for voice calls. The second radio interface is CDMA2000 which is backward compatible with the second generation CDMA IS-95 standard predominantly used in US. The third radio interface, Universal Wireless Communications â€œ UWC-136, also called IS-136HS, was proposed by the TIA and designed to comply with ANSI-136, the North American TDMA standard. 3G wireless networks consist of a Radio Access Network (RAN) and a core network. The core network consists of a packet-switched domain, which includes 3G SGSNs and GSNs, which provide the same functionality that they provide in a GPRS system, and a circuit-switched domain, which includes 3G MSC for switching of voice calls. Charging for services and access is done through the Charging Gateway Function (CGF), which is also part of the core network. RAN functionality is independent from the core network functionality. The access network provides a core network technology independent access for mobile terminals to different types of core networks and network services. Either core network domain can access any appropriate RAN service; e.g. it should be possible to access a speech radio access bearer from the packet switched domain. The Radio Access Network consists of new network elements, known as Node B and Radio Network Controllers (RNCs). Node B is comparable to the Base Transceiver Station in 2G wireless networks. RNC replaces the Base Station Controller. It provides the radio resource management, handover control and support for the connections to circuit-switched and packet-switched domains. The interconnection of the network elements in RAN and between RAN and core network is over Iub, Iur and Iu interfaces based on ATM as a layer 2 switching technology. Data services run from the terminal device over IP, which in turn uses ATM as a reliable transport with QoS. Voice is embedded into ATM from the edge of the network (Node B) and is transported over ATM out of the RNC. The Iu interface is split into 2 parts: circuitswitched and packet-switched. The Iu interface is based on ATM with voice traffic embedded on virtual circuits using AAL2 technology and IP-over-ATM for data traffic using AAL5 technology. These traffic types are switched independently to either 3G SGSN for data or 3G MSC for voice.
The following is a brief description of each protocol layer in a 3G wireless network infrastructure:
Global Mobility Management (GMM): protocol that includes attach, detach, security, and routing area update functionality. Node B Application Part (NBAP): provides procedures for paging distribution, broadcast system information and management of dedicated and logical resources. Packet Data Convergence Protocol (PDCP): maps higher level characteristics onto the characteristics of the underlying radio-interface protocols. PDCP also provides protocol transparency for higher layer protocols
Figure 3 shows the 3G wireless network architecture.
Figure 4 shows protocols used in Node B, RNC and mobile handsets.
PDCP also provides protocol transparency for higher layer protocols. Radio Link Control (RLC): provides a logical link control over the radio interface. Medium Access Control (MAC): controls the access signaling (request and grant) procedures for the radio channel. Radio resource Control (RRC): manages the allocation and maintenance of radio communication paths.
Radio Access Network Application Protocol (RANAP): encapsulates higher layer signaling. Manages the signaling and GTP connections between RNC and 3G-SGSN, and signaling and circuit-switched connections between RNC and 3G MSC. Radio Network Service Application Part (RNSAP): provides the communication between RNCs. GPRS Tunnel Protocol (GTP): protocol that tunnels the protocol data units through the IP backbone by adding routing information. GTP operates on top of TCP/UDP over IP. Mobile Application Part (MAP): supports signaling between SGSN/GGSN and HLR/AuC/EIR. AAL2 Signaling (Q.2630.1, Q.2150.1, Q.2150.2, AAL2 SSSAR, and AAL2 CPS): protocols suite used to transfer voice over ATM backbone using ATM adaptation layer 2. Sigtran (SCTP, M3UA): protocols suite used to transfer SCN signaling protocols over IP network.
Evolution to 3G Wireless Technology:
Initial coverage Initially, 3G wireless technology will be deployed as "islands" in business areas where more capacity and advanced services are demanded. A complete evolution to 3G wireless technology is mandated by the end of 2000 in Japan (mostly due to capacity requirements) and by the end of 2001 in Europe. NTT DoCoMo is deploying 3G wireless services in Japan in the third quarter of 2000. In contrast, there is no similar mandate in North America and it is more likely thatcompetition will drive the deployment of 3G wireless technology in that region. For example, Nextel Communications has announced that it will be deploying 3G wireless services in North America during the fourth quarter of 2000. The implementation of 3G wireless systems raises several critical issues, such as the successful backward compatibility to air interfaces as well as to deployed infrastructures. Interworking with 2G and 2G+ Wireless Networks The existence of legacy networks in most regions of the world highlights the challenge that communications equipment manufacturers face when implementing next-generation wireless technology.Compatibility and interworking between the new 3G wireless systems and the old legacy networks must be achieved in order to ensure the acceptance of new 3G wireless technology by service providers and end-users.
The existing core technology used in mobile networks is based on traditional circuit-switched technology for delivery of voice services. However, this traditional technology is inefficient for the delivery of multimedia services. The core switches for next-generation of mobile networks will be based on packet-switched technology which is better suited for data and multimedia services. Second generation GSM networks consist of BTS, BSC, MSC/VLR and HLR/AuC/EIR network elements. The interfaces between BTS, BSC and MSC/VLR elements are circuit-switched PCM. GPRS technology adds a parallel packet-switched core network. The 2G+ network consists of BSC with packet interfaces to SGSN, GGSN, HLR/AuC/EIR. The interfaces between BSC and SGSN network elements are either Frame Relay and/or ATM so as to provide reliable transport with Quality of Service (QoS). 3G wireless technology introduces new Radio Access Network (RAN) consisting of Node B and RNC network elements. The 3G Core Network consists of the same entities as GSM and GPRS: 3G MSC/VLR, GMSC, HLR/AuC/EIR, 3G-SGSN, and GGSN. IP technology is used end-to-end for multimedia applications and ATM technology is used to provide reliable transport with QoS. 3G wireless solutions allow for the possibility of having an integrated network for circuit-switched and packet-switched services by utilizing ATM technology. The BSC may evolve into an RNC by using add-on cards or additional hardware that is co-located. The carrier frequency (5Mhz) and the bands (2.5 to 5Ghz) are different for 3G wireless technology compared to 2G/2G+ wireless technology. Evolution of BSC to RNC requires support for new protocols such as PDCP, RRC, RANAP, RNSAP and NBAP. Therefore, BTS' evolution into Node B may prove to be difficult and may represent significant capital expenditure on the part of network operators. MSC evolution depends on the selection of a fixed network to carry the requested services. If an ATM network is chosen, then ATM protocols will have to be supported in 3G MSC along with interworking between ATM and existing PSTN/ISDN networks. The evolution of SGSN and GGSN to 3G nodes is relatively easier. Enhancements to GTP protocol and support for new RANAP protocol are necessary to support 3G wireless systems. ATM protocols need to be incorporated to transport the services. The HLR databases evolve into 3G-HLR by adding 3G wireless user profiles. The VLR database must also be updated accordingly. The EIR database needs to change to accommodate new equipment that will be deployed for 3G wireless systems. Finally, global roaming requires compatibility to existing deployment and graceful fallback to an available level when requested services are not available in the region. Towards this end, the Operator Harmonization Group (OHG) is working closely with 3G Partnership Projects (3GPP and 3GPP2) to come up with global standards for 3G wireless protocols.
Comparison of 2G and 3G Mobile Networks:
As mentioned above, although there are many similarities between 2G and 3G wireless networks (and many of the 2G and 3G components are shared or connected through interworking functions), there are also many differences between the two technologies. Table 1 compares the differences between the core network, the radio portion and other areas of the two networks.
SLIMSOUISSI.ADVANCES RESEARCH.NOVATTEL WIRELESS INC.
CDMA DEVELOPMENT GROUP.WHITE PAPERS
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BACHELOR OF TECHNOLOGY
COCHIN UNIVERSITY OF SCIENCE AND TECHNOLOGY
Marconi's innovative perception of electromagnetic waves and the air interface in 1897 was the first milestone on the important road to shared use of the radio spectrum. But only after almost a century later did mobile wireless communication start to take off. Despite a series of disappointing false starts, communication world in the late 1980's was rapidly becoming more mobile for a much wider segment of communication users than ever before. With the advent of wireless technology, a transition from point-to-point communication toward person-to-person communication (i.e.; independent of position) has begun. Testimony to this is the rapidly increasing penetration of cellular phones all across the world. In anticipation of the growing consumer demands, the next generation of wireless systems endeavors to provide person-to-person communication of the circuit and packet multi media data.
The first generation cellular networks, which were based on analog technology with FM modulation, have been successfully deployed since the early and mid 1980's. A typical example of a first generation cellular telephone system (1G) is the Advanced Mobile Phone Services (AMPS). Second generation (2G) wireless systems employ digital modulation and advanced call-processing capabilities. In view of the processing complexity required for these digital systems, two offered advantages are the possibility of using spectrally efficient radio transmission schemes such as Time Division Multiple Access (TDMA) or Code Division Multiple Access (CDMA), in comparison to the analog Frequency Division Multiple Access (FDMA) schemes previously employed and the provision for implementation of a wide variety of integrated speech and data services such as paging and low data rate network access. Examples of 2G wireless systems include the Global System for Mobile communication (GSM), TDMA IS-54/IS-136 and Personal Digital Cellular (PDC).
Third Generation (3G) wireless systems will evolve from mature 2G networks with the aim of providing universal access and global roaming. More important these systems are expected to support multi dimensional (multi-information media, multi-transmission media, and multi-layered networks) high-speed wireless communication- an important milestone toward achieving the grand vision of ubiquitous personal communications. Introduction of wide band packet-data services for wireless Internet up to 2Mbps will be the main attribute of 3G system.
2) WHAT IS 3G ?
The third generation of mobile cellular systems are intended to unify the diverse systems we see today into a seamless radio infrastructure capable of offering a wide range of services in different radio environments, with the quality we have come to expect from wire line communication networks.
Since the mid-80's, studies on 3G systems have been carried out within the International Telecommunication Union (ITU), where it was called Future Public Land Mobile Telecommunication Systems (FPLMTS), lately renamed International Mobile Telecommunicatons-2000 (IMT-2000). In Europe research and development on 3G technology, is commonly referred to as the Universal Mobile Telecommunication System (UMTS) and Mobile Broadband System (MBS), have been conducted under the European Community Research into Advanced Communications in Europe (RACE) and Advanced Communication Technologies and Services (ACTS) programs. With support from activities in Europe, the United States, Japan and developing countries, World Administrative Radio Conference (WARC) of ITU identified global bands 1885-2025Mhz and 2110-2200Mhz for IMT-2000 including 1980-2010Mhz and 2170-2200Mhz for the mobile satellite component.
Key elements in the definition of 3G systems are the radio access system and Radio Transmission Technology (RTT). As a part of the standardization activities, a formal request by the ITU-Radio communication standardization sector (ITU-R) for submission of candidate RTTs for IMT-2000 has been distributed by the ITU. In response to this 10 proposals were submitted. Most of the proposals use CDMA or WCDMA as their multiple access technique. So in this seminar and presentation we are presenting the common features of WCDMA based 3G standards.
2.1) COMMON OBJECTIVES
Some major objectives envisioned for IMT-2000 and their key differences from the current 2G mobile systems can be briefly summarized as follows:
> Use of a common frequency band.
> Use of a small pocket terminal with worldwide roaming.
> Maximizing the commonality and optimization of radio interfaces for multiple operating environments, such as vehicular, pedestrian, office and Fixed Wireless Access (FWA) system.
> Significantly high transmission speed capability encompassing circuit and packet switched data with multimedia support.
> Support for both symmetric and asymmetric data transfer in all operating environments.
> Compatibility with wireless services, which currently exist.
Spectrum efficiency, quality and overall cost improvement as a result of utilization of advanced technologies such as DSP.
3) EVOLUTION TO 3G
The primary focus of third generation architectures will be to attempt to seamlessly evolve second generation systems to provide high speed data services to support multimedia applications such as web browsing. The key word is "evolve" -as the challenge to wireless equipment manufacturers is to provide existing customers, namely, service providers, with a migration path that simultaneously satisfies the requirements set forth by the International Telecommunications Union (ITU) for 3G wireless services while preserving customer investment in existing wireless infrastructure. The core of today's second generation networks provide the foundation on which third generation services -3G-are built. Next generation services will be delivered by a combination of existing and evolving digital equipments. The move to 3G is all about high-speed mobile data and IP traffic. That is why today's wireless networks will require grater band width and network capacity to support 3rd generation services.
Third Generation Systems
1G 2G 2.5G 3C
3.1) GSM EVOLUTION
GSM networks will enhance packet data services primarily in three phases. General Packet Radio Services (GPRS) refers to the first phase of GSM network architecture enhancements that allow mobiles to connect to IP or X.25 based networks.
The GSM/GPRS network architecture will further evolve to support Enhanced Data Rates for GSM Evolution (EDGE), which provides significant
improvements over GPRS. Finally, the ETSI/ARIB Wideband CDMA (WCDMA)
proposal provides a new air interface for GSM networks - supporting higher data rates that will meet or exceed UMTS/IMT-2000 specifications.
3.2) EVOLUTION OF IS-136
IS-136, sometimes referred to as North American TDMA (NA-TDMA), has a two- phase migration path as defined by UWC-136. In the first phase, referred to as 136+, significant enhancement will be made to allow for improved voice and data over the existing 30 kHz carrier, which uses 6 time slots per 40 ms frame. The second phase, referred to as 136 High Speed (136HS) will embrace the EDGE standard (at least in outdoor environments) in order to meet the requirements of UMTS/IMT-2000.
3.3) IS-95 EVOLUTION
IS-95, sometimes referred to as North American CDMA (NA-CDMA), has a two phase migration path: IS-95B and cdma2000. The key advantage of IS-95B and cdma2000 for existing CDMA operators is simple: preservation of capital investments. Both IS-95B and cdma2000 will provide a smooth migration path to IMT-2000 while maintaining backward compatibility with existing IS-95 infrastructure. In order to maintain backward compatibility, both IS-95B and cdma2000 will be based on synchronous base station operation and will therefore continue to rely on the GPS to maintain synchronicity. In addition, IS-95B and cdma2000 will continue to use 20 ms frames and perform closed loop power control on the reverse link at a rate of 800 times per second. Currently, IS-95 provides circuit-switched and packet-switched data at rates of 9.6 kbps or 14.4 kbps (depending on the speech coder) using a 1.25 MHz channel bandwidth and a chip rate of 1.2288 Mcps.
Evolution from 2G to 3G
Attribute Voice Data
Unit Of Communication Call/Circuit Session/P acket
Static Subscriber Data HLR Home Agent
Dynamic Subscriber D ata VLR Foreign Agent
M obility P aradi gm HandofT Rere gist ration*
Billing AMA/CDR Radius/D iameter
A c c ounting M o del Per M inute Per Byte
Billing Model Per M inute Fixed Rate
Traffic Delivery Guaranteed Best-Effort*
Delivery Timing Real-Time Not Guaranteed*
Latency 200msec 2+ Sec*
Wi de- Ar e a M obility Roam big Forwarding*
4) 3G STANDARDS
Third generation cellular telephony is on its way - not, unfortunately, as a single worldwide system, but as three incompatible ones. The main difference the three lies in their choice of radio interface technology. This fact is crucial for several reasons, since the f\radio interface determines not only the fundamental capacity of a mobile radio network, but also how it deals with such issues as interference, distortion, handing off calls from one base station to another as users move around etc.
In one way or the other, all three approaches provide for adaptive bandwidth on demand. Two of the systems use wideband code division multiple access (WCDMA) for the radio interface. The other uses a time division multiple access (TDMA) radio interface technique.
One of the most promising approaches to the new third generation is to
combine a wide band CDMA (W-CDMA) AIR INTERFACE with the fixed network
of the GSM. With WCDMA a users ' information bits are spread over an artificially broadened bandwidth. The job is done by multiplying them with pseudorandom bit stream several times as fast. The bits in the pseudorandom bit stream are referred to as chips, so the stream is known as chipping or spreading code. It increases the bit rate of the signal (and the amount of band width it occupies) by a ratio known as spreading factor, namely, the ratio of the chip rate to the original information rate.
The key device in any CDMA system is its correlation receivers, which stores exact copies of all the system's chipping codes. These codes are used by the receiver to multiply a received data stream, selecting the chipping code as was used in the transmitter. The devices also perform whatever mathematical functions required to restore the original user data. The result is that at the receiver output, the amplitude of the de-spread signal is increased by the spreading factor relative to the interfering signals. In the process, those interfering signals are diminished and add to the background noise level. This effect is called process gain.
CDMA the conversations occupy the same frequency band at the same time. But each interaction is multiplied by a different chipping code, and when the signals are de-spread, the only one that comes through intelligibly is the one whose code was used by the de-spreader. The others simply add to the background noise level, which ultimately limit the number of users that can share a channel.
For the system to work two factors are key. First only soft handovers may be employed, since with them mobile terminals can maintain simultaneous connections to different base stations as they move among them. Second transmitted power should be strictly controlled so that signals from all mobile terminals arrive at the base station with about the same strength, despite their differing distances from the base station.
Strict power control is maintained with real time power control channels. The control channels operate at power command rate between 800Hz and 1.5kHz. That is base station equipment measures the power received from each mobile unit as much as 1500 times a second and issues command to the mobile at that rate to raise or lower their output power.
Many users can be accommodated. The maximum WCDMA chip rate is 3.84Mcps (mega chips per second) and yields a modulated carrier of about 5Mhz wide. System operators can deploy multiple carriers, each of which occupies 5Mhz. More over in a WCDMA system, multiple end users can share each 5Mhz channel.
In addition to the above mentioned features a WCDMA system can support both fixed and variable data rate users in an adaptive manner. The system does this by continually changing the way it distributes the channel's band width among the users, adjusting the spreading factors of each of the users in every 10ms.
The community abiding by the Global System for Mobile communications extends itself into 3G under the general rubric of Universal Mobile Telecommunication Services (UMTS). Their radio interface uses WCDMA radio techniques and is called UMTS Terrestrial Radio Access (UTRA).
WCDMA has two forms, distinguished by how they separate the two directions of communication. Frequency Division Duplex (FDD) employs separate uplink and downlink frequency bands with a constant frequency offset between them. The other form Time Division Duplexing (TDD) puts the uplink and downlink in the same band, and then time-shares transmissions in each direction. This mode is useful for operators with spectrum restrictions.
4.1.1) TRANSITION FROM GSM TO 3G
The WCDMA physical layer includes variable bit rate transport channels required for bandwidth on demand user applications. These can multiplex several services onto a single connection between fixed infrastructure and a mobile terminal. Some of the physical channels do not carry transport signals, they do not carry user information of any kind. They serve the physical layer itself, and include such resources as some pilot channels (that assist in modulation recovery), a synchronization channel (that lets mobile terminals synchronize to the network, and an acquisition channel (that establishes the initial connections to the mobile terminals). WCDMA resembles all CDMA systems currently deployed in that it applies the spreading function in two phases. An initial channelization code spreading is followed by a scrambling code spreading. The initial channelization code spreading alone determines the occupied bandwidth of the radio signal. As for the scrambling code, it is used to distinguish different mobile terminals at the base station's receiver and to distinguish multiple cell sites in the mobile terminal's receiver.
The second-generation IS-95 CDMA systems uses a single pseudo noise code common to all base stations, but applied by each base station with different time offsets. WCDMA elaborates on this scheme to allow for multiple connections to a single mobile terminal as well as variable spreading factors at the channelization spreading stage. Low user data rates get lots of coding gain with high spreading ratios while high user data rates get less coding gain because of their lower spreading ratios. The spreading details differ in down link (base to mobile) and the up link (mobile to base) directions. In the downlink direction the channelization codes separate different users in a cell. In the uplink direction they separate different physical channels (parallel connections) in a single mobile. All the spreading occurs in 10 ms frames at a constant chip rate of 3.84 Mcps. WCDMA key features are:
Â¢ Wide band direct sequence CDMA, FDD and TDD support
Â¢ Support for 5, 10 or 20Mhz bandwidth
Â¢ QPSK modulation
Â¢ Closed loop power control
Â¢ Channel coding - convolutional
Â¢ Circuit or packet switched mode
4.2) cdma 2000
Sub-committee of TIA submitted a radio transmission technology called cdma 2000. This RTT protects investments in IS-95 equipments and systems. This is a multi carrier mode cdma. This is very similar to the frequency division multiplexing form of WCDMA. The chief differences from WCDMA are: 20 ms framing structure, instead of 10 ms and a slightly different spreading rate - 3.6864 Mcps which is exactly three times the IS-95 rate of 1.2288 Mcps. Multiple parallel connections can be established in up to three cdma carriers in what is called 3X operating mode.
The features of cdma-2000 can be summarized as follows:
Â¢ 1X and 3X 1.25Mhz channel
Â¢ MAC to support variable data rate
Â¢ Full support for packet and data services up to 2Mbps
Â¢ Voice over packet data
4.3) UWC-136 - The TDMA Mode
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In North America, the second-generation 2G services are already deployed in the part of the spectrum reserved for 3G. So such operators with limited spectrum cannot employ wide band CDMA as their RTT to provide 3G services. There fore, some TDMA based 3G standards have been adopted by such operators, which are collectively known as UWC-136.
One of the modes is almost identical to GSM packet radio scheme called Enhanced Data rate for GSM Evolution (EDGE). Packet radio techniques are coupled with adaptive modulation- Gaussian Minimum Shift Keying (GMSK) and 8-Phase Shift Keying (8-PSK)- to give EDGE all of the 3G features except for its 2Mbps data rate.
5) 3G DATA RATES
The International Telecommunication Union (ITU) has laid down some indicative minimum requirements for the data speeds that the INT - 2000 standards must support. These requirements are defined according to the degree of mobility involved when the 3G call is being made. As such the data rate that will be available over 3G will depend upon the environment the call is being made in:
Â¢ High Mobility: 144 kbps for rural outdoor mobile use. This data rate is available for environments in which the 3G user is travelling more than 120 kmph in outdoor environments.
Â¢ Full Mobility: 384 kbps for pedestrian users traveling less than 120 kmph in urban outdoor environments.
Â¢ Limited Mobility: At least 2mbps with low mobility (less than 10 kmph) in stationary indoor and short range outdoor environments.
Â¢ Satellite Environment: 3G is supposed to provide a minimum data rate of 9.6 kbps in this environment.
6) 3G NETWORK ARCHITECTURE
The 3G network architecture is very complex and is difficult to understand & represent. So network reference model is used which makes its representation simpler.
NETWORK REFERENCE MODEL (cdma2000/3gpp2)
Reference models are graphical tools used to visualize, structure, and describe certain complex subjects. A few such models are widely used in the 3GPP2 wireless recommendations. Figure 6.1 presents the network entities and associated reference points that comprise a wireless network. The network entities are represented by squares, triangles and rounded corner rectangles; the reference points are represented by circles.
The network reference model is a functional block diagram. A network entity represents a group of functions, not a physical device. Sometimes, for practical reasons, the functional network entity is a physical device. The Mobile Station (MS) is an excellent example.
A reference point is a conceptual point that divides two groups of functions. It is not necessarily a physical interface. A reference point only becomes a physical interface when the network entities on either side of it are contained in different physical devices.
The different components of the network are listed below:
AAA Authentication, Authorization, and Accounting
AC Authentication Center
BS Base Station
BSC Base Station Controller
BTS Base Transceiver System
CDCP Call Data Collection Point
CDGP Call Data Generation Point
CDIS Call Data Information Source
CDRP Call Data Rating Point
CF Collection Function
CSC Customer Service Center
DCE Data Circuit Equipment
DF Delivery Function
EIR Equipment Identity Register
HLR Home Location Register
IAP Intercept Access Point
IP Intelligent Peripheral
ISDN Integrated Services Digital Network
IWF Interworking Function
MC Message Center
MS Mobile Station
MSC Mobile Switching Center
MT Mobile Terminal
MWNE Managed Wireless Network Entity
NPDB Number Portability Database
OSF Operations System Function
OTAF Over-The-Air Service Provisioning Function
PDN Packet Data Network
PDSN Packet Data Serving Node
PSTN Public Switched Telephone Network
SCP Service Control Point SME Short Message Entity SN Service Node
TA Terminal Adapter TE Terminal Equipment UIM User Identity Module VLR Visitor Location Register WNE Wireless Network Entity
Authentication, Authorization and Accounting: The AAA is an entity that provides Internet Protocol functionality to support the functions of Authentication, Authorization, and Accounting. These IP functions are defined in Internet Engineering Task Force documents. The AAA interacts with the PDSN to perform AAA functions in support of the PDSN for requesting Mobile Stations. The AAA interacts with other AAA entities to perform AAA functions where the Home AAA is outside the serving mobile network.
Authentication Center (AC): The AC is an entity that manages the authentication information related to the MS. The AC may, or may not be located within, and be indistinguishable from an HLR. An AC may serve more than one HLR. Base Station (BS): A BS is an entity that provides the means for MSs to access network services using radio. It includes a BSC and a BTS.
Base Station Controller (BSC): The BSC is an entity that provides control and management for one or more BTSs. The BSC exchanges messages with both the BTS and the MSC. Traffic and signaling concerned with call control, mobility management, and MS management may pass transparently through the BSC. Base Transceiver System (BTS): The BTS is an entity that provides transmission capabilities across the U m reference
point. The BTS consists of radio devices, antenna and equipment. Call Data Collection Point (CDCP): The CDCP is the entity that collects the IS-124 format call detail information.
Call Data Generation Point (CDGP): The CDGP is an entity which provides call detail information to the CDCP in IS-124 format. This may be the entity which converts call detail information from a proprietary format into the IS-124 format. All information from the CDGP to the CDCP must be in IS-124 format.
Call Data Information Source (CDIS): The CDIS is an entity that can be the source of call detail information. This information may be in proprietary format. It is not required to be in IS-124 format.
Call Data Rating Point (CDRP): The CDRP is the entity that takes the unrated IS-124 format call detail information and
applies the applicable charge and tax related information. The charge and tax information is added using IS-124 format.
Collection Function (CF) - [Intercept]: The CF is an entity that is responsible for collecting intercepted communications for a lawfully authorized law enforcement agency.
The CFs typically include:
Â¢ the ability to receive and process call contents information for each intercept subject.
Â¢ the ability to receive information regarding each intercept subject (e.g., call associated or non-call associated) from the Delivery function and process it.
Customer Service Center (CSC): The CSC is an entity where service provider representatives receive telephone calls from customers wishing to subscribe to initial wireless service or request a change in the customer's existing service. The CSC interfaces proprietarily with the OTAF to perform network and MS related changes necessary to complete the service provisioning request.
Data Circuit Equipment (DCE): A termination that provides a non-ISDN user-network interface (e.g., ITU-T [CCITT] V series, ITU-T [CCITT] X series). Delivery Function (DF) - [Intercept]: The DF is an entity that is responsible for delivering intercepted communications to one or more collection functions. The DFs typically include:
Â¢ the ability to accept call contents for each intercept subject over one or more channels from each Access function.
Â¢ the ability to deliver call contents for each intercept subject over one or more channels to a Collection function as authorized for each law enforcement agency.
Â¢ the ability to accept information over one or more data channels and combine that information into a single data flow for each intercept subject.
Â¢ the ability to filter or select information on an intercept subject before delivery to a Collection function as authorized for a particular law enforcement agency.
Â¢ the optional ability to detect audio in-band DTMF digits for translation and delivery to a Collection function as authorized for a particular law enforcement agency.
Â¢ the ability to duplicate and deliver information on the intercept subject to one or more Collection functions as authorized for each law enforcement agency.
Â¢ the ability to provide security to restrict access.
Equipment Identity Register (EIR): The EIR is an entity that is the register to which user equipment identity may be assigned for record purposes. The nature, purpose, and utilization of this information is an area for further study. Home Location Register (HLR): The HLR is the location register to which a user identity is assigned for record purposes such as subscriber information (e.g. Electronic Serial Number (ESN), Mobile Directory Number (MDN), Profile Information, Current Location, Authorization Period).
Integrated Services Digital Network (ISDN): The ISDN is defined in accordance with the appropriate ANSI T1 Standards.
Intelligent Peripheral (IP): The IP is an entity that performs specialized resource functions such as playing announcements, collecting digits, performing speech-to-text or text-to-speech conversion, recording and storing voice messages, facsimile services, data services, etc.
Intercept Access Point (IAP): The IAP is an entity that provides access to the communications to, or from, the equipment, facilities, or services of an intercept subject.
Interworking Function (IWF): The IWF is an entity that provides information conversion for one or more WNEs. An IWF may have an interface to a single WNE providing conversion services. An IWF may augment an identified interface between two WNEs, providing conversion services to both WNEs.
Managed Wireless Network Entity (MWNE): A wireless Entity within the Collective Entity or any specific Network Entity having OS wireless management needs, including another OS.
Message Center (MC): The MC is an entity that stores and forwards short messages. The MC may also provide supplementary services for Short Message Service (SMS). Mobile Station (MS): A wireless terminal used by subscribers to access network services over a radio interface. MSs include portable units (e.g., hand-held units), units installed in vehicles, and somewhat paradoxically, fixed location MSs. The MS is the interface equipment used to terminate the radio path at the subscriber. Mobile Switching Center (MSC): The MSC switches MS originated or MS terminated traffic. An MSC is usually connected to at least one BS. It may connect to the other public networks (PSTN, ISDN, etc.), other MSCs in the same network, or MSCs in different networks. The MSC may store information to support these capabilities.
Mobile Terminal 0 (MT0): A self-contained data capable MS termination that does not support an external interface.
Mobile Terminal 1 (MT1): A MS termination that provides an ISDN user-network interface.
Mobile Terminal 2 (MT2): A MS termination that provides a non-ISDN user-network interface (e.g., ITU-T [CCITT] V series, ITU-T [CCITT] X series). Number Portability Database (NPDB): The NPDB is an entity which provides portability information for portable Directory Numbers.
Operations Systems Function (OSF): The OSF is defined by the Telecommunications Management Network (TMN) OSF. These functions include Element Management Layer (EML), Network Management Layer (NML), Service Management Layer (SML), and Business Management Layer (BML) functions spanning across all operations systems functions (e.g., Fault Management, Performance Management, Configuration management, accounting management and Security Management.
Over-The-Air Service Provisioning Function (OTAF): The OTAF is an entity that interfaces proprietarily to CSCs to support service provisioning activities. The OTAF interfaces with the MSC to send MS orders necessary to complete service provisioning requests.
Packet Data Serving Node (PDSN): The PDSN is an entity that provides Internet Protocol functionality to the mobile network. A PDSN establishes, maintains and terminates link layer sessions to the Mobile Station. A PDSN routes IP datagrams to the PDN. A PDSN may act as a Mobile IP Foreign Agent in the mobile network. A
PDSN may have interface to one or more Base Stations to provide the link layer session. A PDSN interacts with the AAA to provide IP authentication, authorization, and accounting support. A PDSN may interface to one or more IP networks either public or Intranet to provide IP network access.
Packet Data Network (PDN): A PDN, such as the Internet, provides a packet data transport mechanism between processing network entities capable of using such services.
Public Switched Telephone Network (PSTN): The PSTN is defined in accordance with the appropriate ANSI T1 Standards.
Service Control Point (SCP): The SCP is an entity that acts as a real-time database and transaction processing system that provides service control and service data functionality.
Service Node (SN): The SN is an entity that provides service control, service data, specialized resources and call control functions to support bearer-related services. Short Message Entity (SME): The SME is an entity that composes and decomposes short messages. A SME may, or may not be located within, and be indistinguishable from, an HLR, MC, VLR, MS, or MSC.
Terminal Adapter (TA): An entity that converts signaling and user data between a non-ISDN and an ISDN interface.
Terminal Adapter m (TAm): An entity that converts signaling and user data between a non-ISDN and an ISDN interface.
Terminal Equipment 1 (TE1): A data terminal that provides an ISDN user-network interface.
Terminal Equipment 2 (TE2): A data terminal that provides a non-ISDN user-network interface (e.g., ITU-T [CCITT] Vseries, ITU-T [CCITT] X series). User Identity Module (UIM): The UIM contains subscription information such as the NAM and may contain subscription feature information. The UIM can be integrated into any mobile terminal or it may be removable.
Visitor Location Register (VLR): The VLR is the location register other than the HLR used by an MSC to retrieve information for handling of calls to or from a visiting subscriber. The VLR may, or may not be located within, and be indistinguishable from an MSC. The VLR may serve more than one MSC. Wireless Network Entity (WNE): A Network Entity in the wireless Collective Entity
The U m reference point is the only reference point that is by definition a physical interface. The other reference points will be physical interfaces if network entities on either side them are contained in different physical devices. An interface exists when two Network Entities are interconnected through exactly one Reference Point. Reference Point A: the interface between the BSC and the MSC. Reference Point A I: the interface between the IP and the PSTN, plus the interface between the MSC and the PSTN, plus the interface between the SN and the PSTN. Reference Point A bis: the interface between the BSC and the BTS. Reference Point A ter: is the BS to BS interface. Reference Point Aquater: the interface between the PDSN and the BS. Reference Point B: the interface between the MSC and the VLR. Reference Point C: the interface between the MSC and the HLR. Reference Point D: the interface between the VLR and the HLR. Reference Point d: the interface between an IAP and the DF. Reference Point D 1: the interface between the OTAF and the VLR.
Reference Point D I: the interface between the IP & the ISDN, the IWF & the ISDN,
the interface between the MSC & the ISDN & the interface between the SN & ISDN.
Reference Point E: the interface between the MSC and the MSC.
Reference Point e: the interface between the CF and the DF.
Reference Point F: the interface between the MSC and the EIR.
Reference Point G: the interface between the VLR and the VLR.
Reference Point H the interface between the HLR and the AC.
Reference Point I: the interface between the CDIS and the CDGP. The operations
supported by this interface are described in IS-124.
Reference Point J: the interface between the CDGP and the CDCP. The operations supported by this interface are described in IS-124.
Reference Point K: the interface between the CDGP and the CDRP. The operations supported by this interface are described in IS-124. Reference Point L: Reserved.
Reference Point M 1: the interface between the SME and the MC.
Reference Point M 2 the MC to MC interface.
Reference Point M 3: the SME to SME interface.
Reference Point N: the interface between the HLR and the MC.
Reference Point N 1: the interface between the HLR and the OTAF. Reference Point O1: the interface between an MWNE and the OSF. Reference Point O2: the interface between two Operations Systems Functions
Reference Point P I: the interface between the MSC, the IWF, the PDSN, the AAA, and the PDN. This reference point is also the interface between the PDSN and the
Reference Point Q: the interface between the MC and the MSC. Reference Point Q 1: the interface between the MSC and the OTAF. Reference Point R: the interface between the TA and the TE2.
Reference Point R m: the interface between the TE2 and the TA m plus the interface
between the TE2 and the MT2.
Reference Point R v: the interface between the DCE and the TE2.
Reference Point R x: the interface between the PPDN and the TE2.
Reference Point S: the interface between the ISDN and the TE1.
Reference Point S m: the interface between the TE1 and the MT1 plus the interface
between the TE1 and the TAm.
Reference Point T 1: the interface between the MSC and the SCP.
Reference Point T 2: the interface between the HLR and the SCP.
Reference Point T 3: the interface between the IP and the SCP.
Reference Point T 4: the interface between the HLR and the SN.
Reference Point T 5: the interface between the IP and the MSC.
Reference Point T 6: the interface between the MSC and the SN.
Reference Point T 7: the interface between the SCP and the SN.
Reference Point T 8: the interface between the SCP and the SCP.
Reference Point T 9: the interface between the HLR and the IP.
Reference Point U I: the interface between the integrated UIM and a MT.
Reference Point U m: the interface between the BS and the MS, which corresponds
to the air interface.
Reference Point U r: the interface between the Removable-UIM and a MT.
Reference Point V: the interface between the OTAF and the OTAF.
Reference Point W: the interface between the DCE and the PSTN.
Reference Point X: the interface between the CSC and the OTAF.
Reference Point Y: the interface between a Wireless Network Entity (WNE) & IWF.
Reference Point Z: the interface between the MSC and the NPDB.
7) 3G DUPLEX TECHNIQUES
3G standards employing WCDMA uses two types of duplexing techniques: Time Division Duplex (TDD) and Frequency Division Duplex (FDD).
Frequency Division Duplex
The frame structure in the FDD component is different in the uplink and downlink. In the uplink, the data and control channels are I/Q multiplexed, whereas in the downlink data and control channels are time multiplexed. The FDD component applies two-layered consisting of spreading codes and scrambling (long) codes. The I/Q multiplexed DPDCH and DPCCH in the uplink are quadrature phase shift keying (QPSK) modulated. Each channel is scrambled with a specific code for DPDCH and for DPCCH, and then scrambled with a mobile station specific scrambling code to distinguish different mobile stations. Each DPDCH is assigned its own channelization code.
On the downlink multiple codes are transmitted with possibly different spreading factors for the different DPCHs depending on the service. The data modulation is QPSK. Spreading is performed by channelization codes for each DPCH and a cell specific scrambling code to distinguish different cells. In the downlink the scrambling code is a cell specific 10ms (40960 chips) segment of a Gold code sequence. The FDD component supports both synchronous and asynchronous inter cell operation.
Time Division Duplex
The TDD component is based on TD-CDMA, which is a combination of TDMA and CDMA. Each time slot comprises several (maximum 16) orthogonal spreading codes. Different user rates are supported by code and/or time slot pooling. In the uplink the variable orthogonal spreading rate is also applied.
Due to the same carrier frequency in the uplink and downlink, a TDD system requires a frame synchronized network to control interference for coordinated operation.
8) WCDMA CHANNEL STRUTURE
The WCDMA channels can be classified as follows. A logical channel is defined by the type of information transferred. The logical channel types are:
> Control Channels (CCH) with logical broadcast control channel (L-BCCH), logical forward access channel (L-FACH), logical random access channel(L-RACH), and dedicated control channel(DCCH)
> Traffic channels (TCH) with dedicated traffic channel (DTCH) and user packet traffic channel (UPCH)
The physical layer offers information transfer services to the medium access control (MAC) and higher layers. The physical layer transport services are described by how and with what characteristics data are transferred over the radio interface. An adequate term for this is the transport channel. Transport channels can be generally classified into two types:
> Common channels with broadcast control channel (BCCH), paging channel (PCH), forward access channel (FACH), and random access
> Dedicated channels (DCH)
9) 3G PROTOCOLS
The protocol stack proposed for 3g wireless platform is shown below:
IP over WmATM WmATM with WAAL
WmATM cells are generated through the wireless ATM adaptation layer (WAAL). The DBA (Dynamic Bandwidth allocation) layer handles dynamic bandwidth allocation to increase the spectrum utilization. The wireless application protocol (WAP) is the de facto world standard for the presentation and delivery of wireless information. As per the International telecommunication union- radio communication standard sector (ITU-R) IOMT-2000 radio transmission technology adopts the CDMA and TDMA for the physical layer, which contain 16 time division duplex time slots and each slot can be composed of up to 64 CDMA codes for the 3g wireless systems.
Different services have various quality of service requirements as well as system parameters, so the bandwidth allocation should be dynamic and adaptive. This kind of MAC (Media access controller) can be implemented using DSP. 3G also supports Internet access through the mobile terminal, therefore it has to support
10) 3G HANDSET
The common trends in 3G terminals are:
> Bigger and better screen technology- screens will be color and must have considerably larger screen areas.
> Video and multimedia are central to the technology demonstration. So videoconference is an application that many of the concept terminals anticipate.
> Majority of 3G terminals include a miniature camera built into it.
10.1) HARDWARE REQUIREMENTS
Third generation handsets will demand new levels of performance from their RF sections. To meet the wider bandwidth, increased linearity and lower power requirements lead to high speed, low noise, bipolar integration technologies such as GaAs. One of the main challenges will be in the mixed signal area such as analog to digital converters and digital to analog converters that will have to operate at 10 mega samples per second. 3G products will be able to reduce the number and size of external passive devices used for filtering and coupling. Another difficulty is accommodating variable carrier bandwidth. So we move digitization of signals much closer to antenna enabling designers to use programmable DSPs to perform demodulation and decoding. It takes around 60 MIPS worth of DSP to support a typical GSM phone whereas a 3G EWCDMA phone will require 300 MIPS.
Real Time Operating System
LJ WCDMA Module
Digital Broadband Transceiver
Smart Antenna Array
Figure 10.1: An implementational framework of a 3G (tri-mode) phone with support
for global roaming
Users, operators & vendors want to improve the flexibility & capability of their wireless communication equipments by using software reconfigurable radio technology offers a potential of substantially improved operational capability at a lower cost. It also offers multi mode operations using the same hardware by simply changing the embedded software. This supports multi mode global roaming phones at an affordable price.
The main functional blocks in a 3G handset are the following :
1. A Smart Antenna Array: This antenna array is capable of controlling transmitted power according to the control information from the BTS. Most 3G systems employ a closed loop power control
2. Front End High Speed ADC & DAC: The third generation terminals make use of high speed ADC and DAC in the RF stage. This helps to use programmable DSP circuitry for up and down conversions, modulation-demodulation and coding-decoding functions.
3. A Microcontroller: This microcontroller controls the DSP operations and also helps in power management. In most of the 3G phone chipsets the microcontroller and the DSP are integrated into a single chip.
4. Colour LCD Display: As 3G system supports multimedia applications and mobile teleconferencing, a comparatively larger multi colour LCD display is necessary.
5. Signal Processing Circuitry: This will be a DSP processor which will handle digital audio decoding, video streaming, voice compression, channel coding, modem, equalization, encryption, echo cancellation, speech recognition, noise suppression security encryption and decryption, for mobile commerce and more to add new functionality to digital wireless phones (The world's lowest power DSP, the new TMS320C55xâ€žÂ¢ announced February 22, 2000, is the processor of choice for the next-generation digital wireless phones and a whole new generation of wireless Internet appliances)
10.2) SOFTWARE REQUIREMENTS[/b]
As the 3G phones use programmable hardware an embedded operating system is used in addition to this to handle user interface of the phone a Java Virtual Machine is used.
11) 3G-QUALITY OF SERVICE
First and second-generation cellular systems provided their circuit switched resources to subscribers with a fixed quality of services (QoS). Networks in the latest generation, on the other hand, will assign default QoS profiles to users and their applications. A subscriber's application negotiates a suitable QoS profile with the network which allots its resources according to the default profile or with some alternative profile, depending on the load on the network, the propagation conditions and QoS profiles authorized by user's subscription.
At the subscriber level, four kinds of traffic can be distinguished: conversational, streaming, interactive and background.
Conversational traffic is the most familiar type of traffic. Fairly tolerant of errors, conversational and videoconferencing traffic have different throughput requirements, but they demand a constant and rather short end-to-end delay.
Streaming traffic applies to applications that can start processing the traffic for presentation to the user before the whole file is transmitted to the subscriber. It can work within a small range of delays and throughput delays.
Interactive traffic is used by online applications, in which a subscriber is allowed to interact with a server of some kind: Web browsing, e-commerce, games and location-based services. Interactive traffic can work acceptably over an intermediate range of delays and throughput rates.
Finally, background traffic is very tolerant of delays, works within a wide range of throughput rates, but is relatively intolerant of errors. These include applications such as e-mail, short messaging services and file downloads. Background traffic is the most naturally compatible with packet data networks.
12) 3G APPLICATIONS
There are several applications that will be enabled by the broadband wireless communication channels that will come with 3G. These applications include:
Audio or video over the Internet is downloaded (transferred, stored and played) or streamed (played as it is being send but not stored). The different compression algorithms such as MP3 can be used. With 3G, MP3 files will be downloadable over the air directly to the phone via a dedicated server. The large computational power available in the 3G phones helps the decoding of MP3 formats.
VOICE OVER INTERNET PROTOCOL
Another audio application for 3G is Voice over IP (VoIP) - the ability to route telephone calls over the Internet to provide voice telephone service at local call rates to anywhere in the world. With the higher data rates supported by 3G, VoIP will be available on mobile phones.
Still images such as photographs, pictures, letters, postcards, greeting cards, presentations and static web pages can be send and received over mobile networks just as they are across an IP based network.
Sending moving images in a mobile environment has several vertical market applications including monitoring parking lots or building sites for intruders or thieves, sending images of a patient from an ambulance to a hospital, mobile video conferencing applications etc.
VIRTUAL HOME ENVIRONMENT (VHE)
A Universal Mobile Telecommunications Services (UMTS) service that is often mentioned in the vendor's brochures is so called Virtual Home Environment, a service that simply lets customers have seamless access with a common look and feel to their services from home, office or on the move in any city as if they were at home. VHE is there fore aimed at roamers, a small subset of mobile phone users. VHE could also allow some other useful services by placing their Universal Identity Module into any terminal and those terminals could be other than mobile devices (if smart cards are more widely supported than they are today).
Electronic agents are supposed to play an important role for mobile working in the future - as agents are dispatched to carry out searches and tasks on the Internet and report back to their owners. This is an efficient way to get things done on the move. Electronic agents are defined as " mobile programs that go to places in the network to carry out their owner's instructions". Agents are self-contained programs that roam communication networks, delivering and receiving messages or looking for information or services. Certainly, 3G terminals will give their owners much more control over their lives than today's mobile phones. They will be e-assistance, e-secretaries, e-advisors, e-administrators etc. This kind of control is what home automation applications anticipate.
In the 21st century, software will increasingly be downloaded electronically from the Internet rather than purchased as boxed products in stores. This is like file transfer applications that involve downloading the software itself. We might, for example need WinZip or adobe acrobat to read a file and can download that over the 3G network to a 3G terminal. Additionally Application Service Provision (ASP) market in which software platforms and server software is being hosted by third parties and accessed by client software mimics this thin client world in which the bandwidth is high enough for applications and files to be retrieved from the Internet on the fly whenever they are needed.
Data Service Characteristics
Figure 12.1: Different 3G applications and corresponding data rates
13) 3G DRAWBACKS
The main draw back of 3G is its high cost. Considering a typical example, to set up 3G trial network infrastructure The Nippon Telephone and Telegraph had to invest 18$ billion in 1999. Also a 3G phone may cost 1000$+.
The second disadvantage is shorter battery life of 3G phones when compared to 2G mobile phones. This is because 3G phones have a comparatively larger display screen and the increased power consumption of modern high speed DSP processors used in 3G phones.
The most important disadvantage of 3G services is the lack of an internationally uniformed standard. The third generation cellular telephony is on its way, not as a single worldwide system but as three incompatible ones. This will make the global roaming difficult. For global roaming we have to use multimode phones, which can operate in different radio interface standards and this will result in costlier handsets.
14) VISIONS OF THE FUTURE
3G is capable of providing very high data rate in different radio environments. It can provide dream multimedia services. At present there is no hope of a wireless communication technology, which can perform better than 3G. It is expected that the trends should last into a Fourth Generation (4G) of even better spectrum efficiencies, higher radio carrier frequencies, even higher user data rates, and a blizzard of new non voice applications plus the terminals to support them.
A wireless terminal that is your gateway to the world of voice data, video and multimedia communications sounds possible sooner. The year is 2005, your traveling in the passenger seat of your work-colleague's car with a laptop computer in front of you, you sip a cup of coffee while you write a short report on the meeting you attended that day. Suddenly, you hear the tone that tells you there's an incoming videoconference call. You click on the screen icon, the computer screen changes and you see your assistant's face. The two of you have a brief conversation. Then she tells you about a new intranet site that could b useful for your next customer meeting. So without interrupting the conversation, you take a look at the website, and your assistant guides you to the most interesting pages. A few minutes later, your sales department calls and sends you the technical specifications and pricing information that you need for your next meeting. At the same time you send your completed report to the eight people who need copies. Meanwhile, a memo from one of your co-directors arrives on your computer. It's about an important item on your own company, broadcast on that morning's TV news report. A clip of the TV item is attached to the e-mail, so you watch it. This is not science fiction, it a preview of everyday communication services that will be a commercial reality within the next few years. So called "third generation" wireless services (also referred to as "3G services") will significantly expand the range of options available to users and allow communications, information and entertainment services to be delivered via wireless terminals. The exciting thing is that the foundation for these services has already been laid down - in a shape of today's digital mobile phone networks. All that is needed to support these advanced multimedia services is to expand the information capacity, or "bandwidth" of the radio communications technology.
A tremendous growth of mobile subscribers is expected, with nearly 1.8 billion in the year 2010 with a dominant base in Asia. GSM is the mobile radio standard with the highest penetration world wide. Mobile multimedia will increase after the year 2000 to about 60% of the traffic in the year 2010. Therefore third generation systems have to support a wide range of services from voice to low data rate up to high data rate circuit switched and packet oriented services. In addition a high grade of asymmetry for data application is expected. With this wireless break through, unified IP network including wireless and wireline provides a generic information transmission platform for value added personal Internet services and multidimensional wireless communication services.
In this seminar and presentation we briefly surveyed the evolution 3G wireless systems from 2G and 2.5G technologies. Similarities and key differences between the various 3G proposals submitted to ITU-R are reviewed. IN order to have a common standard for RTT, it is imperative to carry out harmonization in an international level. With the recent technological breakthroughs in digital signal processing, RF and battery technologies as well as developments in modern VLSI chip designs, the dream of ubiquitous communication between any one, any where, at any time is becoming a reality. To cut it short, we can say that the wireless information super highway is converging to 3G and during the coming decade we will see how 3G will make the other wireless communication methods obsolete.
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