Chapter 6. Wireless and Mobile Networks. IEEE : personal area network : WiMAX: downlink, uplink scheduling

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Cornelius Allison
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1 Chapter 6 Wireless and Networks Part II IEEE : personal area less than 10 m diameter replacement for cables (mouse, keyboard, headphones) ad hoc: no infrastructure master/slaves: slaves request permission to send (to master) master grants requests : evolved from Bluetooth specification i GHz radio band in TDM manner with time slots of 625 microsec., 79 channels up to 721 kbps, 3 Mbps (v.2), 24 Mbps (v.3) (Bluetooth) th) piconet S M S Up to 8 active devices (255 parked devices) P M P S P Master device radius of coverage S Slave device P Parked device (inactive) P (Worldwide Interoperability for Microwave Access) : WiMAX like & cellular: base station model transmissions to/from base station by hosts with omnidirectional antenna base station-to-base station backhaul with point-to-point antenna unlike : range ~ 6 miles (9.654 km) ( city rather than coffee shop ) ~14 Mbps 1 ไมล = ก โลเมตร point-to-point point-to-multipoint : WiMAX: downlink, uplink scheduling transmission frame down-link subframe: base station to node uplink subframe: node to base station Inform SS of physical layer properties (modulation scheme, coding and error-correction parameters) that will be used for transmitting subsequent bursts of packets with in frame eam. pre DL- UL- DL DL DL Initial request SS #1 SS #2 SS #k MAP MAP burst 1 burst 2 burst n maint. conn. downlink subframe uplink subframe base station tells nodes who will get to receive (DL map) and who will get to send (UL map), and when WiMAX standard provide mechanism for scheduling, but not scheduling algorithm

2 Time Tme Dvson Division Duplexing (TDD) General Downlink Frame Structuret Downlink Interval Usage Code (DIUC) indicates burst profile General Uplink Frame Structure Chapter 6 outline Uplink Interval Usage Code (UIUC) indicates burst profile 6.1 Introduction Mobility 6.5 Principles: Wireless addressing and routing 6.2 Wireless links, to mobile users characteristics 6.6 IP CDMA 6.7 Handling mobility in 6.3 IEEE cellular l s wireless LANs ( wi-fi ) 6.8 Mobility and higher- 6.4 Cellular Internet layer protocols Access architecture 6.9 Summary standards (e.g., GSM)

3 Components of cellular architecture cell covers geographical region Base station (BS) analogous to AP users attach to through h BS Air-interface: physical and link layer protocol between mobile and BS connects cells to net manages call setup (more later!) handles mobility (more later!) Public Switched Telephone Network (PSTN) Center Center Public telephone, and Internet Cellular s: the first hop Two techniques for sharing mobile-to-bs radio spectrum combined FDMA/TDMA: divide spectrum in frequency channels, divide each channel into time slots CDMA: Code Division Multiple Access frequency bands time slots wired Cellular standards: brief survey 2G systems: voice channels IS-136 TDMA: (digital AMPS) combined FDMA/TDMA (north america) GSM (Global System for communications): combined FDMA/TDMA most widely deployed IS-95 CDMA: Code Division Multiple Access IS : Interim Standard GSM Don t drown in a bowl of alphabet soup: use this for reference only Cellular standards: brief survey 2.5 G systems: voice and data channels for those who can t wait for 3G service: 2G extensions general packet radio service (GPRS) evolved from GSM data sent on multiple channels (if available) Data rates kbps enhanced data rates for global evolution (EDGE) also evolved from GSM, using enhanced modulation data rates up to 384K CDMA-2000 (phase 1) data rates up to 144K evolved from IS-95

4 Cellular standards: brief survey 3G systems: voice/data Universal Telecommunications Service (UMTS) data service: High Speed Uplink/Downlink k packet Access (HSDPA/HSUPA): 3 Mbps CDMA-2000: CDMA in TDMA slots data service: 1xEvlution Data Optimized (1xEVDO) up to 14 Mbps เป เปาหมายดานความเรวในการรบสงขอม ล าหมายด านความเร วในการร บส งข อมล 144 kbps ขณะใช โทรศ พท ม อถ อในยานพาหนะท ก าล งเคล อนท ด วย ความเร ว 384 kbps ขณะเด นหร ออย ในพ นท เขตเม อง 2 Mbps ขณะอย ก บท หร ออย ภายในอาคาร CDMA2000 RTT= Radio Telephone Technology 1xRTT = 1.25 MHz 3xRTT = 3.75 MHz WCDMA.. more (and more interesting) cellular topics due to mobility (stay tuned for details) Time-Division Synchronous CDMA (TD-SCDMA) Chapter 6 outline 6.1 Introduction Mobility 6.5 Principles: Wireless addressing and routing 6.2 Wireless links, to mobile users characteristics 6.6 IP CDMA 6.7 Handling mobility in 6.3 IEEE cellular l s wireless LANs ( wi-fi ) 6.8 Mobility and higher- 6.4 Cellular Internet layer protocols Access architecture 6.9 Summary standards (e.g., GSM) What is mobility? moblty? spectrum of mobility, from the perspective: p no mobility mobile wireless user, using same access point mobile user, connecting/ disconnecting from using DHCP. high hgh moblty mobility mobile user, passing through multiple access point while maintaining ongoing connections (like cell phone)

5 Mobility: Vocabulary Mobility: more vocabulary Home : permanent home of mobile (e.g., /24) Home agent: entity that will perform mobility functions on behalf of mobile, when mobile is remote Permanent address: remains constant (e.g., ) Care-of-Address: address in visited. (e.g., 79, ) Visited : in which mobile currently resides (e.g., /24) Permanent address: address in home, can always be used to reach mobile e.g., Correspondent: wants to communicate with mobile Foreign agent: entity in visited that performs mobility functions on behalf of mobile. How do you contact a mobile friend: Mobility: approaches Consider friend frequently changing addresses, how do you find her? search all phone books? call her parents? expect her to let you know where he/she is? I wonder where Alice moved to? Let routing handle it: routers advertise permanent address of mobile-nodes-in-residence via usual routing table exchange. routing tables indicate where each mobile located no changes to end-systems Let end-systems handle it: indirect routing: communication from to mobile goes through home agent, then forwarded d to remote direct routing: gets foreign address of mobile, sends directly to mobile

6 Mobility: approaches Let routing handle it: routers advertise permanent address of mobile-nodes-in-residence not via usual routing table exchange. scalable to millions of routing tables indicate mobiles where each mobile located no changes to end-systems let end-systems handle it: indirect routing: communication from to mobile goes through home agent, then forwarded d to remote direct routing: gets foreign address of mobile, sends directly to mobile Mobility: registration home 2 foreign agent contacts home agent home: this mobile is resident in my End result: Foreign agent knows about mobile Home agent knows location of mobile visited 1 mobile contacts foreign agent on entering visited Mobility via Indirect Routing Indirect Routing: comments home addresses packets using home address of mobile home agent intercepts packets, forwards to foreign agent 1 2 foreign agent receives packets, forwards to mobile 4 3 visited mobile replies directly to uses two addresses: permanent address: used by (hence mobile location is transparent to ) care-of-address: used by home agent to forward datagrams to mobile foreign agent functions may be done by mobile itself triangle routing: -home-mobile inefficient when, mobile are in same

7 Indirect Routing: moving between s suppose mobile user moves to another registers with new foreign agent new foreign agent registers with home agent home agent update care-of-address for mobile packets continue to be forwarded to mobile (but with new care-of-address) mobility, changing foreign s transparent: on going connections can be maintained! Mobility via Direct Routing forwards to foreign agent foreign agent receives packets, forwards to mobile Home 4 requests, receives foreign address of mobile Visited mobile replies directly to Mobility via Direct Routing: comments overcome triangle routing problem non-transparent to : must get care-of-address from home agent what if mobile changes visited? Accommodating mobility with direct routing anchor foreign agent: FA in first visited data always routed first to anchor FA when mobile moves: new FA arranges to have data forwarded from old FA (chaining) 1 agent anchor foreign agent new foreign agent foreign net visited at session start 2 new foreign

8 Chapter 6 outline 6.1 Introduction Mobility 6.5 Principles: Wireless addressing and routing 6.2 Wireless links, to mobile users characteristics 6.6 IP CDMA 6.7 Handling mobility in 6.3 IEEE cellular l s wireless LANs ( wi-fi ) 6.8 Mobility and higher- 6.4 Cellular Internet layer protocols Access architecture 6.9 Summary standards (e.g., GSM) IP RFC 3344 has many features we ve seen: home agents, foreign agents, foreign-agent registration, care-of-addresses, encapsulation (packet-within-a-packet) three components to standard: d indirect routing of datagrams agent discovery registration with home agent IP: indirect routing IP: agent discovery packet sent by home agent to foreign agent: a packet within a packet dest: dest: Permanent address: dest: packet sent by foreign-agent-to-mobile packet dest: Care-of address: agent advertisement: foreign/home agents advertise service by broadcasting ICMP messages (typefield = 9) Route advertisement H,F bits: home and/or foreign agent R bit: registration required B Foreign Agent busy M Min. Encapsulation G GRE Encapsulation V การบ บอ ดเฮดเดอร แบบ Van Jacobson GRE : Generic Routing Encapsulation type = 9 code = 0 checksum h k router address type = 16 length sequence # RBHFMGV registration lifetime reserved bits 0 or more care-ofaddresses standard ICMP fields mobility agent advertisement extension

9 IP: registration example Components of cellular architecture home agent foreign agent HA: COA: registration req. COA: HA: MA: Lifetime: 9999 identification: 714 encapsulation format. ICMP agent adv. COA: registration req. COA: HA: MA: Lifetime: 9999 identification:714. visited : /24 agent MA: recall: wired public telephone registration ti reply time HA: MA: Lifetime: 4999 Identification: 714 encapsulation format. registration reply HA: MA: Lifetime: 4999 Identification: 714. different cellular s, operated by different providers Handling mobility in cellular s GSM: indirect routing to mobile Home : of cellular provider you subscribe to (e.g., Sprint PCS, Verizon) Home Location Register (HLR): database in home containing permanent cell phone #, profile information (services, preferences, billing), information about current location (could be in another ) Visited : in which mobile currently resides Visitor it Location Register (VLR): database with entry for each user currently in could be home home consults HLR, gets roaming number of mobile in visited mobile user HLR 2 home home Center VLR Center 4 visited 3 PSTN 1 call routed to home Public switched telephone home sets up 2 nd leg of call to in visited in visited completes call through base station to mobile

10 GSM: handoff with common GSM: handoff with common old BSS VLR Center old routing new routing new BSS Handoff goal: route call via new base station (without interruption) reasons for handoff: stronger signal to/from new BSS (continuing connectivity, less battery drain) load balance: free up channel in current BSS GSM doesn t mandate why to perform handoff (policy), only how (mechanism) handoff initiated by old BSS old BSS VLR Center new BSS 1. old BSS informs of impending handoff, provides list of 1 + new BSSs 2. sets up path (allocates resources) to new BSS 3. new BSS allocates radio channel for use by mobile 4. new BSS signals, old BSS: ready 5. old BSS tells mobile: perform handoff to new BSS 6. mobile, new BSS signal to activate new channel 7. mobile signals via new BSS to : handoff complete. reroutes call 8 -old-bss resources released GSM: handoff between s GSM: handoff between s home Home anchor PSTN (a) before handoff Anchor : first visited during call call remains routed through anchor new s add on to end of chain as mobile moves to new IS-41 allows optional path minimization step to shorten multi- chain home Home anchor PSTN (b) after handoff Anchor : first visited during cal call remains routed through anchor new s add on to end of chain as mobile moves to new IS-41 allows optional path minimization step to shorten multi- chain IS-41 standard for mobility management is similar to GSM

11 Mobility: GSM versus IP GSM element Comment on GSM element IP element Home system Gateway Center, or home. Home Location Register (HLR) Visited System Visited services Center. Visitor Location Record (VLR) 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 home system containing permanent phone number, profile information, current location of mobile user, subscription information Network other than home 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 telephone call segment between home and visited, visible to neither the mobile nor the. Home Home agent Visited Foreign agent Care-ofaddress Wireless, mobility: impact on higher layer protocols logically, impact should be minimal best effort service model remains unchanged TCP and UDP can (and do) run over wireless, mobile but performance-wise: packet loss/delay due to bit-errors (discarded packets, delays for link-layer retransmissions), and handoff TCP interprets loss as congestion, will decrease congestion window un-necessarilynecessarily delay impairments for real-time traffic limited bandwidth of wireless links Chapter 6 Summary Wireless wireless links: capacity, distance channel impairments CDMA IEEE ( wi-fi ) CSMA/CA reflects wireless channel characteristics cellular access architecture standards (e.g., GSM, CDMA-2000, UMTS) Mobility principles: addressing, routing to mobile users home, visited s direct, indirect routing care-of-addresses case studies mobile IP mobility in GSM impact on higher-layer h protocols

CSC 4900 Computer Networks: Mobility

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