Mobility and cellular networks

Transcription

1 Mobility and cellular s Wireless WANs Cellular radio and PCS s Wireless data s Satellite links and s Mobility, etc.- 2 Cellular s First generation: initially debuted in Japan in 1979, analog transmission system Second generation (2G): introduced digital transmission, operational in G: offers enhancements to the data services on existing second-generation digital platforms Third generation (3G): digital, permit per-user and terminal mobility, broadband applications (voice, data, and multimedia streams) at higher data speeds 144Kbps to 384Kbps, up to 2Mbps Cellular s Mobile users use for a given time period channels (frequency pairs) to connect to base station Problem: interference from remote stations and users control channels fixed frequencies Mobility, etc.- 3 Mobility, etc.- 4

2 The concept of a cell The digital cellular architecture 1/ r Interference: reduced when cells are small ( ) Possibility of frequency reuse Size of cell: function of density of users and of demand, possibility of breaking large cells into smaller ones Need for hand-off 2 Cell 2 Cell 7 Cell 3 Cell 1 Cell 6 Cell 4 Cell 5 A seven-cell cluster Cell 2 Cell 2 Cell 7 Cell 3 Cell 7 Cell 3 Cell 1 Cell 1 Cell 6 Cell 4 Cell 6 Cell 4 Cell 5 Cell 5 Cell 2 Cell 7 Cell 3 Cell 1 Cell 6 Cell 4 Cell 5 frequency ruse variable size cells Cell 1 Cell 2 channels TDMA: time slots /frequency channel Mobility, etc.- 5 Mobility, etc.- 6 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

3 GPRS (2G+) Always-on data service, <115Kbps Packets sent over the 8 time slots of GSM More architectural components added to GSM the Gateway GPRS Service Node (GGSN) gateway between the GPRS and IP s, connect to other GPRS s to facilitate GPRS roaming the Serving GPRS Service Node (SGSN) The SGSN provides packet routing to and from the SGSN service area for all users in that service area, performs mobility management functions GSM evolution GSM new services, improved quality & performance, lower cost backward compatibility independent of UMTS standards GSM phase 2+ new services (ΙΝ services+) quality equal to fixed circuit switched data < 76.8 kbps efficient administration (routing, packet data) location services GSM/DECT interworking GPRS: wireless extension of Internet over GSM WWW, ftp,, low QoS, combines kbps voice ch. Mobility, etc.- 9 Mobility, etc G 3G (2) 3G is designed for high-speed multimedia data and voice Its goals include high-quality audio and video and advanced global roaming, which means being able to go anywhere and be automatically handed off to whatever wireless system is available (4G?) Objectives: improve throughput and QoS, voice quality, battery life, positionlocation services Coexistence with current infrastructures, including backward compatibility, ease of migration or overlay, interoperability and handoffs, the need for bandwidth on demand, improving authentication and encryption methodologies to support mobile commerce (m-commerce) 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

4 Universal Mobile Telecommunications Systems Goal: remove any distinctions between mobile and fixed ing supports the ITU's UPT concept: personal mobility across many different s, each user is issued a unique UPT number UMTS Forum: speedup processes, evolution regulatory framework, spectrum, standards the example of GSM UMTS: a whole system, not just technologies integrates existing technologies (GSM 2 ) proposes new ones global technology concept IP is pushed further into the Mobility, etc.- 13 The UMTS vision Personal communications in the 21 st century Universality low cost of new technologies open architectures Mobility personal mobility, smart cards, Virtual Home Environment, service mobility, personal service profile Telecommunications transparency of service access, seamless provisioning, satellite+terrestrial, Basic services interconnection, charging, security, management, performance Content and value-added services public, business to business, financial,... Mobility, etc.- 14 Code Division Multiple Access UMTS architecture Can we transmit on the same frequency and the same time? Yes, using CDMA: Frequency hopping: b, Bluetooth Direct Sequence CDMA: 3G user signals are spread up to a wideband by multiplication by a code power of user wideband signal must be above the rest of the signals in order to be successfully received at the receiver. power narrowband signal (i.e. voice call) power of one wideband signal -1 DS-CDMA New elements UMTS 99: RNC, Node B (WBTS) UMTS R4:MSC Server, Media Gateway (MGW) UMTS R5: all IP freq Mobility, etc.- 15 Mobility, etc.- 16

5 UMTS architecture Convergence of technologies BS BS Circuit core SGSN GGSN Packet core SGSN GGSN IP Packet core PSTN IP PSTN IMS (IP) IP Initial implementation R5 and beyond IMS Combine elements from 2G: GSM, IP, ATM GPRS (GSM phase 2+, point-to-point-multi-point connectionless, connection-oriented, IP service, tunneling), WAP ATM TCP (wireless case, new proposals: link-layer forward error corrections, end-to-end Selective ACKs, splitconnection, Snoop protocol), QoS enhancements mobility management (MIPv6++) addressing issues The purpose is service continuation regardless of user s place and client capabilities. Mobility, etc.- 17 Mobility, etc.- 18 Next Generation Networks IMS - IP Multimedia Subsystem Transition from single-service s to multi-service s In NGN service intelligence is decoupled from transmission Offers converged services: fixed telephony, mobile telephony, broadband Internet, leased lines, Traffic from various access s types is aggregated: fixed (ISDN, FTTx), mobile (PLMN), wireless (802.1x), Core is IP-based Supports QoS (G/MPLS) Content Access Access Servers Communcation Control IP Core Network Access Access Clients Access Access Content Mobility, etc GPP (3rd Generation Partnership Project) is working on IMS 3G Release 5 A commercial step towards NGN Enables services that are independent from access technologies Based on Internet protocols 4G? 3 layer architecture Transport (ing fabric & gateways) Control (signaling elements) Services (back end systems & content) Mobility, etc.- 20

6 IMS and mobility IMS Main Components SIP is the protocol used for session management Users have a public SIP address (identifier) user@sipprovider.com Mobility is enabled through proxy servers and registrars Proxy servers process/forward requests from users and other proxies A registrar stores information about users (IP address of user s terminal or current proxy server) Home provider has control on services received from roaming user, as he participates in authentication and performs authorization, accounting in order to bill A 4G-provider is expected to be a 3G provider that can interoperate with other 3G providers during the provision of a single service Call Session Control Function (CSCF): Set of entities for managing user sessions Proxy CSCF: UE s first point of contact (can be either on the visited or home ) Interrogating CSCF: a type of proxy for incoming SIP requests from other s Serving CSCF: session controller assigned to subscriber (always on the home ) Home Subscriber Server (HSS): a database with subscriber information Registration example 200 OK REG P-CSCF 200 OK REG 200 OK REG S-CSCF Visited Home Mobility, etc.- 21 Mobility, etc.- 22 Example of a session between 2 roaming users in IMS BT Fusion B s home User A A s visited GPRS S-CSCF P-CSCF Required on registration, optional on session establish SIP voice packets Required on registration, optional on session establish A s home S-CSCF Optional GPRS P-CSCF B s visited User B The first commercially available service bringing Fixed-Mobile Convergence (since fall 2005) BT decides the most appropriate access for delivering services, based on subscriber s location 3 choices in case of telephony services: POTS, VoIP, Mobile Combines functionality of a mobile phone with reliability of fixed telephony and/or lower charges (especially for VoIP) Vodafone is the associated mobile operator Mobility, etc.- 23 Mobility, etc.- 24

7 BT Fusion User owns a special access point and a dual-mode handset User is assigned only one identifying number (from BT) Calls routed to fixed-line within range of Bluetooth access point (WiFi in future) VoIP if quality is acceptable, POTS otherwise Out of range calls routed to cellular BT has full control (not the user)! Convergent Handset Cellular Cell site PSTN Link PSTN Content strategies A walled garden is a mechanism for a provider to restrict the user experience by confining the user to a specific region/space as defined by the provider more profit for the provider traditional strategy of cable operators & cellular providers An open access portal model allows the user unrestricted access to whatever content is available. based on the End-to-end principle of Internet operators charge purely on traffic (bit pushers) Bluetooth or WiFi Fusion Access Point OR NTE ADSL NTE Broadband Link VoIP Gateway Mobility, etc.- 25 Mobility, etc.- 26