Wireless WANs Mobility and cellular networks Mobility and cellular networks � Cellular radio and PCS networks � Wireless data networks � Satellite links and networks Mobility, etc.- 2 Basic concepts and directions in telecommunications C. Courcoubetis Cellular networks Cellular networks � First generation: initially debuted in Japan in � Mobile users use for a given time period channels 1979, analog transmission system (frequency pairs) to connect to base station � Second generation (2G): introduced digital � Problem: interference from remote stations and transmission, operational in 1992 users � 2.5G: offers enhancements to the data services on existing second-generation digital platforms � Third generation (3G): digital, permit per-user frequencies and terminal mobility, broadband applications control channels (voice, data, and multimedia streams) at higher data speeds 144Kbps to 384Kbps, up to 2Mbps fixed network Mobility, etc.- 3 Mobility, etc.- 4 Basic concepts and directions in telecommunications C. Courcoubetis Basic concepts and directions in telecommunications C. Courcoubetis
The concept of a cell The digital cellular architecture � Interference: reduced when cells are small ( ) 2 1 r / Cell 2 � Possibility of frequency reuse Cell 3 Cell 7 Cell 2 Cell 2 Cell 3 Cell 1 Cell 7 � Size of cell: function of density of users and of Cell 3 Cell 7 Cell 4 Cell 6 Cell 1 Cell 5 demand, possibility of breaking large cells into Cell 6 Cell 4 Cell 1 Cell 5 Cell 2 smaller ones Cell 4 Cell 6 Cell 3 Cell 7 Cell 1 variable size Cell 5 � Need for hand-off Cell 4 cells Cell 6 A seven-cell cluster Cell 5 frequency ruse Cell 1 Cell 2 TDMA: time slots /frequency channel channels Mobility, etc.- 5 Mobility, etc.- 6 Basic concepts and directions in telecommunications C. Courcoubetis Basic concepts and directions in telecommunications C. Courcoubetis The digital cellular architecture (2) GSM (2G) � GSM supports 124 channel pairs with a 200KHz spacing to prevent channel interference � TDM with 8 slots: eight callers per channel � Basic GSM: data rates 9.6Kbps � International roaming with a single invoice, SIM card security, SMS Mobility, etc.- 7 Mobility, etc.- 8 Basic concepts and directions in telecommunications C. Courcoubetis Basic concepts and directions in telecommunications C. Courcoubetis
GPRS (2G+) GSM evolution � GSM � Always-on data service, <115Kbps – new services, improved quality & performance, lower cost � Packets sent over the 8 time slots of GSM – backward compatibility – independent of UMTS standards � More architectural components added to GSM � GSM phase 2+ – the Gateway GPRS Service Node (GGSN) – new services ( ΙΝ services+) � gateway between the GPRS network and IP networks, – quality equal to fixed network connect to other GPRS networks to facilitate GPRS – circuit switched data < 76.8 kbps roaming – efficient administration (routing, packet data) – location services – the Serving GPRS Service Node (SGSN) – GSM/DECT interworking � The SGSN provides packet routing to and from the – GPRS: wireless extension of Internet over GSM network SGSN service area for all users in that service area, � WWW, ftp,…, low QoS , combines 1-8 14kbps voice ch. performs mobility management functions Mobility, etc.- 9 Mobility, etc.- 10 Basic concepts and directions in telecommunications C. Courcoubetis Basic concepts and directions in telecommunications C. Courcoubetis 3G 3G (2) � 3G is designed for high-speed multimedia data and � Objectives: voice – improve throughput and QoS, voice quality, battery life, position- location services � Its goals include high-quality audio and video and – Coexistence with current infrastructures, including backward advanced global roaming, which means being able compatibility, ease of migration or overlay, interoperability and handoffs, the need for bandwidth on demand, improving to go anywhere and be automatically handed off to authentication and encryption methodologies to support mobile commerce (m-commerce) whatever wireless system is available (4G?) – Supporting higher bandwidths over greater allocations (that is, 5MHz to 20MHz) � UMTS is considered the proposed 3G standard towards the IMT2000 Mobility, etc.- 11 Mobility, etc.- 12 Basic concepts and directions in telecommunications C. Courcoubetis Basic concepts and directions in telecommunications C. Courcoubetis
Universal Mobile Telecommunications Systems The UMTS vision � Personal communications in the 21 st century � Goal: remove any distinctions between mobile and fixed networking � Universality – supports the ITU's UPT concept: personal mobility across – low cost of new technologies many different networks, each user is issued a unique – open architectures UPT number � Mobility � UMTS Forum: speedup processes, evolution – personal mobility, smart cards, Virtual Home Environment, service mobility, personal service profile – regulatory framework, spectrum, standards Telecommunications � – the example of GSM – transparency of service access, seamless provisioning, � UMTS: a whole system, not just technologies satellite+terrestrial,… – integrates existing technologies (GSM 2…) � Basic services – proposes new ones – interconnection, charging, security, management, performance – global technology concept � Content and value-added services – IP is pushed further into the network – public, business to business, financial, ... Mobility, etc.- 13 Mobility, etc.- 14 Basic concepts and directions in telecommunications C. Courcoubetis Basic concepts and directions in telecommunications C. Courcoubetis Code Division Multiple Access UMTS architecture Can we transmit on the same frequency and the same time? Yes, � � New elements using CDMA: – UMTS 99: – Frequency hopping: 802.11b, Bluetooth RNC, Node B – Direct Sequence CDMA: 3G � user signals are spread up to a wideband by multiplication by a code (WBTS) � power of user wideband signal must be above the rest of the signals in – UMTS order to be successfully received at the receiver. R4:MSC Server, narrowband signal Media (i.e. voice call) DS-CDMA power Gateway 1 (MGW) power of one -1 wideband signal – UMTS R5: all IP network -1 1 -1 -1 1 -1 1 1 -1 1 -1 -1 1 -1 1 1 -1 1 -1 -1 1 -1 1 1 1 -1 1 1 -1 1 -1 -1 freq Mobility, etc.- 15 Mobility, etc.- 16 Basic concepts and directions in telecommunications C. Courcoubetis Basic concepts and directions in telecommunications C. Courcoubetis
UMTS architecture Convergence of technologies � Combine elements from 2G: GSM, IP, ATM Initial implementation Circuit core PSTN – GPRS (GSM phase 2+, point-to-point-multi-point BS connectionless, connection-oriented, IP service, tunneling), WAP IP SGSN GGSN – ATM Packet core – TCP (wireless case, new proposals: link-layer forward error corrections, end-to-end Selective ACKs, split- PSTN R5 and beyond connection, Snoop protocol), QoS enhancements – mobility management (MIPv6++) BS SGSN GGSN IMS (IP) IMS – addressing issues IP Packet core � The purpose is service continuation regardless of IP user’s place and client capabilities. Mobility, etc.- 17 Mobility, etc.- 18 Basic concepts and directions in telecommunications C. Courcoubetis Basic concepts and directions in telecommunications C. Courcoubetis Next Generation Networks IMS - IP Multimedia Subsystem � 3GPP (3rd Generation Transition from single-service � Partnership Project) is networks to multi-service working on IMS networks Content Content Servers – 3G Release 5 In NGN service intelligence is � decoupled from network – A commercial step towards Communcation Control transmission NGN Offers converged services: fixed – Enables services that are � IP Core Network telephony, mobile telephony, independent from access broadband Internet, leased network technologies lines, … Access Access – Based on Internet protocols Access Access Traffic from various access Access � Access – 4G? networks types is aggregated: � 3 layer architecture fixed (ISDN, FTTx), mobile (PLMN), wireless (802.1x), … – Transport (networking fabric & gateways) Clients Core network is IP-based � – Control (signaling elements) Supports QoS (G/MPLS) � – Services (back end systems & content) Mobility, etc.- 19 Mobility, etc.- 20 Basic concepts and directions in telecommunications C. Courcoubetis Basic concepts and directions in telecommunications C. Courcoubetis
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