Cellular Technology Sections 6.4 & 6.7

Transcription

1 Overview Cellular Technology Sections 6. & 6.7 CSC 9 December, 0 Cellular architecture evolution Cellular telephony and internet terminology Mobility for cellular mobiles 6- Components of cellular architecture wired public different cellular s, operated by different providers = mobile switching center 6- Cellular Network Architecture First eneration, Voice only communication; FDMA Connect cellular voice users to the public phone Second eneration, &.5 Voice only expanded to voice + data SM: lobal System for Mobile Communication BTS: Base transceiver stations BSC: Base station controller } Base Station System : Mobile switching center Uses FDM/TDM (F bands) * (T slots) à supports F*T simultaneous calls Third eneration, Supports voice + data

2 (voice) architecture Circuit Base station system (BSS) BTS BSC ateway End-end resources allocated to and reserved for call between source & destination Dedicated resources: no sharing as in packet-switching Legend circuit-like (guaranteed) performance Base transceiver station (BTS) Base station controller (BSC) Circuit segment idle if not used by call (no sharing) Mobile () Commonly used in traditional s Mobile subscribers Cellular Network Architecture Core Network Connect radio access s to the public interoperating with the existing cellular voice and ADD cellular data functionality in parallel to this existing voice Circuit switched cellular voice Packet switched Smart phones running full TCP/IP stack (voice) architecture Base station system (BSS) BTS BSC Legend ateway Base transceiver station (BTS) Base station controller (BSC) Mobile () Mobile subscribers 6-8

3 (voice+data) architecture (voice+data) architecture radio controller ateway radio controller ateway Key insight: new cellular data operates in parallel (except at edge) with existing cellular voice v voice unchanged in core v data operates in parallel SSN SN Serving PRS Support Node (SSN) (eneral Packet Radio Service) ateway PRS Support Node (SN) radio interface radio access Universal Terrestrial Radio Access Network (UTRAN) SSN core eneral Packet Radio Service (PRS) Core Network SN public Fourth eneration, LTE: Long Term Evolution standard Simplified all-ip Both voice and data are carried in IP datagrams Avoid (rather than react to) congestion Network control plane is separate from the data plane Uses combination of TDM and FDM Each mobile node allocated one or more 0.5ms time slots in one or more of the channel frequencies WiFi Mobility via Indirect Routing addresses packets using address of mobile agent intercepts packets, forwards to foreign agent wide area foreign agent receives packets, forwards to mobile visited mobile replies directly to

4 Handling mobility in cellular s : of cellular provider you subscribe to (e.g., Sprint PCS, Verizon) location register (HLR): database in containing permanent cell phone #, information about current location (could be in another ) Leading digits in phone number globally identify the visited : in which mobile currently resides visitor location register (VLR): database with entry for each user currently in 6- SM: indirect routing to mobile consults HLR, gets roaming number of mobile in visited mobile user HLR Mobile VLR Mobile visited call routed to switched sets up nd leg of call to in visited in visited completes call through base station to mobile 6- SM: handoff with common SM: handoff with common old BSS VLR Mobile old routing new routing handoff goal: route call via new base station (without interruption) reasons for handoff: stronger signal to/from (continuing connectivity, less battery drain) load balance: free up channel in current BSS SM doesnt mandate why to perform handoff (policy), only how (mechanism) handoff initiated by old BSS old BSS VLR Mobile old BSS informs of impending handoff, provides list of + s. sets up path (allocates resources) to. allocates radio channel for use by mobile. signals, old BSS: ready 5. old BSS tells mobile: perform handoff to 6. mobile, signal to activate new channel 7. mobile signals via to : handoff complete. reroutes call 8 -old-bss resources released

5 SM: handoff between s SM: handoff between s Home anchor PSTN anchor : first visited during call call remains routed through anchor new s communicate with anchor as mobile moves about Home anchor PSTN anchor : first visited during call call remains routed through anchor new s communicate with anchor as mobile moves about before handoff after handoff Mobility: SM versus Mobile IP SM element Comment on SM element Mobile IP element Home system ateway Mobile, or. Home Location Register (HLR) Visited System Visited Mobile services. Visitor Location Record (VLR) Mobile Station Roaming Number (MSRN), or roaming number Network to which mobile user s permanent phone number belongs Home : point of contact to obtain routable address of mobile user. HLR: database in system containing permanent phone number, profile information, current location of mobile user, subscription information Network other than system where mobile user is currently residing Visited : responsible for setting up calls to/from mobile nodes in cells associated with. VLR: temporary database entry in visited system, containing subscription information for each visiting mobile user Routable address for call segment between and visited, visible to neither the mobile nor the. Home Home agent Visited Foreign agent Care-ofaddress 6-9 Summary enerations of cellular architecture Evolving from voice-only to voice + data is all-ip Mobility in cellular s similar to mobility in WiFi (80.) s 5