"3G and Beyond: The Convergence of Mobile Telephony and Computing" SFM-05: Moby University of Urbino Bertinoro, 28 April 2005 Matteo Magotti Vodafone Italy
Technology Evolution Data Transmission Technology Roadmap Max Trx Speed � Fast Internet 2,000 Kb/s UMTS UMTS � Heavy UMTS multimedia � Videotelephony 384 Kb/s EDGE EDGE EDGE 115 Kb/s � Enhanced Internet access GPRS GPRS GPRS � Telematic services � WAP HSCSD HSCSD HSCSD GSM GSM GSM 9.6 Kb/s 1999 2000 2001 2003 2002 2004 Bertinoro, 28-April 2005 Matteo Magotti 2
GPRS as Real “Data Wave” Enabler • Efficient data traffic management Real possibility Real possibility of new data of new data service offer service offer • Higher transmission speed Pricing well Pricing well • Volume and content-based billing fitted with new fitted with new data services (alongside time-based) data services Full usage Full usage support for support for • Continuous network connection data/info data/info services services Bertinoro, 28-April 2005 Matteo Magotti 3
Data applications best adapted to the GPRS GPRS Constraints Implications GPRS Constraints Implications GPRS Constraints Implications • Every time a “data object” is downloaded to a • A typical web page contains 30 “data objects” • Every time a “data object” is downloaded to a • A typical web page contains 30 “data objects” GPRS handset, the handset and the network which will be downloaded successively, with a GPRS handset, the handset and the network which will be downloaded successively, with a open a transfer session and allocate radio few seconds delay for each object (in addition open a transfer session and allocate radio few seconds delay for each object (in addition resources to the actual download time) resources to the actual download time) • Opening this transfer session takes some • GPRS is therefore well adapted for • Opening this transfer session takes some • GPRS is therefore well adapted for time, from half a second to a few seconds applications requiring few transfer sessions of time, from half a second to a few seconds applications requiring few transfer sessions of depending on the network configuration and rather large objects -e.g. email download depending on the network configuration and rather large objects -e.g. email download the load on the network the load on the network • For transactional applications, observed • For transactional applications, observed • Therefore, highly transactional applications performance might actually appear weaker • Therefore, highly transactional applications performance might actually appear weaker where many objects of small size are than with CSD where many objects of small size are than with CSD transferred create a few seconds of delay for transferred create a few seconds of delay for each object transferred each object transferred Bertinoro, 28-April 2005 Matteo Magotti 4
Why UMTS ? • Increased efficiency in the use of Long term Long term cost saving cost saving spectrum, bringing more capacity Customer Customer • Improved quality in service offer satisfaction and satisfaction and loyalty loyalty • More flexibility in offering New revenues New revenues from new from new current and new services services services Bertinoro, 28-April 2005 Matteo Magotti 5
Service Transmission Times: New business opportunities Transfer Time 2nd Generation Fixed 3rd Generation Service GSM - GPRS PSTN / ISDN UMTS Data Volume < 64 kbps 9,6 kbps 50 kbps 128 kbps 384 kbps 2 Mbps E-mail 8 s 1,7 s 1,6 s 1,2 s 0,5 s <0,5s 5 kbyte SMS with photogr. 8 s 1,7 s 1,6 s 1,2 s 0,5 s <0,5s 5 kbyte (JPEG 2000) Web page 4 s 20 s 4,5 s 2,4 s 0,8 s <0,5s 20 kbyte Document 25 s 2 min 35 s 12 s 4 s <1s 100 kbyte 3 min Audio CD 3 min --- 1) --- 1) 6,5 min 40 min 9 min 2 Mbyte MP3 10s Videoclip 15 s 2) 10 min 2,5 min 1,5 min 45 s 600 kbyte MPEG4 1) Optimal CD Quality Streaming = 128 kbps User acceptance 2) Videostreaming Bertinoro, 28-April 2005 Matteo Magotti 6
Mobile Networks Basic concepts Bertinoro, 28-April 2005 Matteo Magotti 7
The requirements for a wireless network Security Cost Mobility UMTS New Capacity services ETACS GSM What do we need to build Quality of a wireless network ? Coverage service Enhanced quality of service User equipments Bertinoro, 28-April 2005 Matteo Magotti 8
Radio channel access policy • Since different users have to share the same band, it is necessary to define an access policy with the aim of maximizing the number of served users and minimizing the bandwidth and power usage • An access policy has to be chosen and optimized according to the required system performance and to the operating scenarios of the provided service • The main access policies are: – FDMA (Frequency Division Multiple Access) – TDMA (Time Division Multiple Access) – CDMA (Code Division Multiple Access) Tx 1 Rx 1 Tx 2 Rx 2 Tx 3 radio channel Rx 3 Tx k Rx h Bertinoro, 28-April 2005 Matteo Magotti 9
TDMA • In TDMA systems the available radio resource is temporally divided in time slots , during which only one user at a time is allowed to access the channel • Time slots are periodically assigned to users, that cannot have a continuous access to the channel, but have to perform a buffer-and- burst policy user A frequency service bandwidth user B user C time slots time Bertinoro, 28-April 2005 Matteo Magotti 10
FDMA • In FDMA systems the available radio resource is divided in sub- bands that are assigned one per user for the whole duration of the user connection • This technology requires narrowband modulation methods and selective receive filters user A frequency service bandwidth user B user C single user channel time Bertinoro, 28-April 2005 Matteo Magotti 11
CDMA • In CDMA systems the whole available radio resource (both in the frequency and in the time domain) is shared by any user at the same time • The single user channel is identified by a code that is univocally assigned to the connected users code user A user B user C frequency time Bertinoro, 28-April 2005 Matteo Magotti 12
Duplexing • Telecommunications systems usually require data exchange both from mobile terminal to base station (uplink or reverse link) and from base station to mobile terminal (downlink or forward link) • Duplexing is the capability of a system to perform this operation for both links together • The main techniques for duplexing are: – FDD (Frequency Division Duplexing) uplink and downlink data exchange are performed in two different frequency bands – TDD (Time Division Duplexing) uplink and downlink data exchange are performed in the same frequency band, but in different time slots Bertinoro, 28-April 2005 Matteo Magotti 13
Cellular systems • Since a radio signal propagates into the space with an attenuation increasing with distance, the coverage area of a base station is spatially limited • Hence to provide a telecommunication service on wide areas, it is necessary to have different base stations (cells), that make a cellular system Good quality area Bad quality area Power Dist Bertinoro, 28-April 2005 Matteo Magotti 14
Standards: UMTS as our 3G choice • The target of a single 3G standard has vanished mainly for geopolitical reasons • UMTS has been specified by 3GPP, the regulatory forum which includes many national/continental regulators – FDD radio access network (W-CDMA: UMTS) and TDD radio access network (TD-CDMA) – Core network evolved from GSMGPRS system • Manifacturers, operators, scientific communities, regulation boards 3GPP founder members contributes to 3GPP Countries with UMTS Licensed Spectrum at 2.1 GHz Bertinoro, 28-April 2005 Matteo Magotti 15
W-CDMA multiple access • This approach does not attempt to allocate disjoint frequency or time resources to each user • The power transmitted by each user must be controlled to the minimum required to maintain a given signal-to-interference ratio for the required level of performance ( Power Control procedure) The ONU party: All the participants share the same resources (they speak at the same time), … it is possible to communicate with one of them, simply knowing his but, if the volume of everyone’s conversation is controlled … language (the channel key), that is different for any participant Bertinoro, 28-April 2005 Matteo Magotti 16
CDMA key paradigms Channel separation is achived by means of orthogonal codes Each carrier frequency can be shared by all the users ⇒ frequency reuse factor = 1 Soft degradation Users are interfered also by other users in their own cell and by users of adjacent cells GSM: reuse factor>1 UMTS: reuse factor=1 Transmitted power is strictly controlled to cause minimum amount of interference Bertinoro, 28-April 2005 Matteo Magotti 17
Soft handover W-CDMA system: all cells work on the same carrier frequency ⇒ the mobile terminal can be connected to more than one cell at the same time Consequences: SOFT HANDOVER : minimize the risk of call dropping when mobile users change cell MACRODIVERSITY : Better quality and reliability Active set = 2 Active set: Active set: set of cells to witch set of cells to witch a terminal is connected a terminal is connected at the same time at the same time Bertinoro, 28-April 2005 Matteo Magotti 18
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