Chapter 7 Wireless and Mobile Networks PDF

Chapter 7 Wireless and Mobile Networks Computer Networking: A Top-Down Approach 8th edition Jim Kurose, Keith Ross Pearson, 2020 Wireless and Mobile Networks: context ▪ more wireless (mobile) phone subscriber...

Chapter 7 Wireless and Mobile Networks Computer Networking: A Top-Down Approach 8th edition Jim Kurose, Keith Ross Pearson, 2020 Wireless and Mobile Networks: context ▪ more wireless (mobile) phone subscribers than fixed (wired) phone subscribers (10-to-1 in 2019)! ▪ more mobile-broadband-connected devices than fixed-broadband- connected devices devices (5-1 in 2019)! 4G/5G cellular networks now embracing Internet protocol stack, including SDN ▪ two important (but different) challenges wireless: communication over wireless link mobility: handling the mobile user who changes point of attachment to network Wireless and Mobile Networks: 7-2 Chapter 7 outline ▪ Introduction Wireless Mobility ▪ Wireless Links and network ▪ Mobility management: principles characteristics ▪ Mobility management: practice ▪ WiFi: 802.11 wireless LANs 4G/5G networks ▪ Cellular networks: 4G and 5G Mobile IP ▪ Mobility: impact on higher-layer protocols Wireless and Mobile Networks: 7- 3 Elements of a wireless network wired network infrastructure Wireless and Mobile Networks: 7- 4 Elements of a wireless network wireless hosts ▪ laptop, smartphone, IoT ▪ run applications ▪ may be stationary (non-mobile) or mobile wired network wireless does not always mean mobility! infrastructure Wireless and Mobile Networks: 7- 5 Elements of a wireless network base station ▪ typically connected to wired network ▪ relay - responsible for sending packets between wired network and wireless wired network host(s) in its “area” infrastructure e.g., cell towers, 802.11 access points Wireless and Mobile Networks: 7- 6 Elements of a wireless network wireless link ▪ typically used to connect mobile(s) to base station, also used as backbone link ▪ multiple access protocol coordinates link access wired network ▪ various transmission rates and distances, infrastructure frequency bands Wireless and Mobile Networks: 7- 7 Characteristics of selected wireless links 14 Gbps 802.11ax 10 Gbps 5G 3.5 Gbps 802.11ac 802.11 af,ah 600 Mbps 802.11n 4G LTE 54 Mbps 802.11g 11 Mbps 802.11b 2 Mbps Bluetooth Indoor Outdoor Midrange Long range outdoor outdoor 10-30m 50-200m 200m-4Km 4Km-15Km Wireless and Mobile Networks: 7- 8 Elements of a wireless network infrastructure mode ▪ base station connects mobiles into wired network ▪ handoff: mobile changes base station wired network providing connection into wired infrastructure network Wireless and Mobile Networks: 7- 9 Elements of a wireless network ad hoc mode ▪ no base stations ▪ nodes can only transmit to other nodes within link coverage ▪ nodes organize themselves into a network: route among themselves Wireless and Mobile Networks: 7- 10 Wireless network taxonomy single hop multiple hops host connects to base host may have to relay infrastructure station (WiFi, cellular) through several wireless (e.g., APs) which connects to nodes to connect to larger larger Internet Internet: mesh net no base station, no no base station, no connection no connection to larger to larger Internet. May have infrastructure Internet (Bluetooth, ad to relay to reach other a given hoc nets) wireless node MANET, VANET Wireless and Mobile Networks: 7- 11 Chapter 7 outline ▪ Introduction Wireless Mobility ▪ Wireless links and network ▪ Mobility management: principles characteristics ▪ Mobility management: practice ▪ WiFi: 802.11 wireless LANs 4G/5G networks ▪ Cellular networks: 4G and 5G Mobile IP ▪ Mobility: impact on higher-layer protocols Link Layer: 6-12 Wireless link characteristics important differences from wired link …. ▪ decreased signal strength: radio signal attenuates as it propagates through matter (path loss) ▪ interference from other sources: wireless network frequencies (e.g., 2.4 GHz) shared by many devices (e.g., WiFi, cellular, motors): interference ▪ multipath propagation: radio signal reflects off objects ground, arriving at destination at slightly different times …. make communication across (even a point to point) wireless link much more “difficult” Wireless and Mobile Networks: 7- 13 Chapter 7 outline ▪ Introduction Wireless Mobility ▪ Wireless links and network ▪ Mobility management: principles characteristics ▪ Mobility management: practice ▪ WiFi: 802.11 wireless LANs 4G/5G networks ▪ Cellular networks: 4G and 5G Mobile IP ▪ Mobility: impact on higher-layer protocols Link Layer: 6-14 IEEE 802.11 Wireless LAN IEEE 802.11 Year Max data rate Range Frequency standard 802.11b 1999 11 Mbps 30 m 2.4 Ghz 802.11g 2003 54 Mbps 30m 2.4 Ghz 802.11n (WiFi 4) 2009 600 70m 2.4, 5 Ghz 802.11ac (WiFi 5) 2013 3.47Gpbs 70m 5 Ghz 802.11ax (WiFi 6) 2020 (exp.) 14 Gbps 70m 2.4, 5 Ghz 802.11af 2014 35 – 560 Mbps 1 Km unused TV bands (54-790 MHz) 802.11ah 2017 347Mbps 1 Km 900 Mhz ▪ all use CSMA/CA for multiple access, and have base-station and ad-hoc network versions Wireless and Mobile Networks: 7- 15 802.11 LAN architecture Internet ▪ wireless host communicates with base station base station = access point (AP) switch ▪ Basic Service Set (BSS) (aka “cell”) or router in infrastructure mode contains: wireless hosts BSS 1 access point (AP): base station ad hoc mode: hosts only BSS 2 Wireless and Mobile Networks: 7- 16 802.11: Channels, association ▪ spectrum divided into channels at different frequencies AP admin chooses frequency for AP interference possible: channel can be same as that chosen by neighboring AP! ▪ arriving host: must associate with an AP scans channels, listening for beacon frames containing AP’s name (SSID) and MAC address selects AP to associate with then may perform authentication [Chapter 8] BSS then typically run DHCP to get IP address in AP’s subnet Wireless and Mobile Networks: 7- 17 802.11: passive/active scanning BBS 1 BBS 2 BBS 1 BBS 2 1 1 1 AP 2 2 2 AP 2 AP 1 AP 1 2 3 3 4 H1 H1 passive scanning: active scanning: (1) beacon frames sent from APs (1) Probe Request frame broadcast from H1 (2) association Request frame sent: H1 (2) Probe Response frames sent from APs to selected AP (3) Association Request frame sent: H1 to (3) association Response frame sent selected AP from selected AP to H1 (4) Association Response frame sent from selected AP to H1 Wireless and Mobile Networks: 7- 18 802.11: mobility within same subnet ▪ H1 remains in same IP subnet: IP address can remain same ▪ switch: which AP is associated with H1? self-learning (Ch. 6): switch will see frame from H1 and “remember” which switch port can be used to reach H1 H1 BBS 2 BBS 1 Wireless and Mobile Networks: 7- 19 Personal area networks: Bluetooth ▪ less than 10 m diameter ▪ replacement for cables (mouse, C P keyboard, headphones) P M radius of coverage ▪ ad hoc: no infrastructure P C C ▪ 2.4-2.5 GHz ISM radio band, up to 3 P Mbps ▪ master controller / clients devices: M master device master polls clients, grants requests for C client device client transmissions P parked device (inactive) Wireless and Mobile Networks: 7- 20 Personal area networks: Bluetooth ▪ TDM, 625 sec sec. slot ▪ FDM: sender uses 79 frequency C P channels in known, pseudo-random P radius of M order slot-to-slot (spread spectrum) coverage other devices/equipment not in piconet only C P C P interfere in some slots ▪ parked mode: clients can “go to sleep” (park) and later wakeup (to preserve M master device battery) C client device ▪ bootstrapping: nodes self-assemble P parked device (inactive) (plug and play) into piconet Wireless and Mobile Networks: 7- 21 Chapter 7 outline ▪ Introduction Wireless Mobility ▪ Wireless links and network ▪ Mobility management: principles characteristics ▪ Mobility management: practice ▪ WiFi: 802.11 wireless LANs 4G/5G networks ▪ Cellular networks: 4G and 5G Mobile IP ▪ Mobility: impact on higher-layer protocols Link Layer: 6-22 4G/5G cellular networks ▪ the solution for wide-area mobile Internet ▪ widespread deployment/use: more mobile-broadband-connected devices than fixed- broadband-connected devices devices (5-1 in 2019)! 4G availability: 97% of time in Korea (90% in US) ▪ transmission rates up to 100’s Mbps ▪ technical standards: 3rd Generation Partnership Project (3GPP) wwww.3gpp.org 4G: Long-Term Evolution (LTE)standard Wireless and Mobile Networks: 7- 23 4G/5G cellular networks similarities to wired Internet differences from wired Internet ▪ edge/core distinction, but both ▪ different wireless link layer below to same carrier ▪ mobility as a 1st class service ▪ global cellular network: a ▪ user “identity” (via SIM card) network of networks ▪ business model: users ▪ widespread use of protocols subscribe to a cellular provider we’ve studied: HTTP, DNS, TCP, strong notion of “home network” UDP, IP, NAT, separation of versus roaming on visited nets data/control planes, SDN, global access, with authentication Ethernet, tunneling infrastructure, and inter-carrier ▪ interconnected to wired settlements Internet Wireless and Mobile Networks: 7- 24 Elements of 4G LTE architecture Mobile device: Mobility ▪ smartphone, tablet, laptop, Mobile device (UE) Management Entity (MME) Home Subscriber Service (HSS) Base station IoT,... with 4G LTE radio (eNode-B) ▪ 64-bit International Mobile to Internet Subscriber Identity (IMSI), stored on SIM (Subscriber PDN gateway (P-GW) Identity Module) card Serving Gateway (S-GW) … ▪ LTE jargon: User Equipment (UE) radio access network all-IP Enhanced Packet Core (EPC) Wireless and Mobile Networks: 7- 25  Elements of 4G LTE architecture Base station: ▪ at “edge” of carrier’s network ▪ manages wireless radio Mobile device Mobility Management Home Subscriber Service (HSS) resources, mobile devices in its (UE) Base station Entity (MME) coverage area (“cell”) (eNode-B) to ▪ coordinates device Internet authentication with other PDN gateway (P-GW) elements ▪ similar to WiFi AP but: … Serving Gateway (S-GW) active role in user mobility coordinates with nearly base stations to optimize radio use ▪ LTE jargon: eNode-B Wireless and Mobile Networks: 7- 26 Elements of 4G LTE architecture Home Subscriber Service ▪ stores info about mobile Mobility Management Home Subscriber devices for which the HSS’s Mobile device (UE) Entity (MME) Service (HSS) Base station network is their “home (eNode-B) network” to Internet ▪ works with MME in device PDN gateway (P-GW) authentication Serving Gateway (S-GW) … Wireless and Mobile Networks: 7- 27 Elements of 4G LTE architecture Serving Gateway (S-GW), PDN Gateway (P-GW) Mobility Management Home Subscriber ▪ lie on data path from mobile Mobile device Service (HSS) (UE) Entity (MME) Base station to/from Internet (eNode-B) to ▪ P-GW Internet gateway to mobile cellular PDN gateway (P-GW) network Looks like nay other … Serving Gateway (S-GW) internet gateway router provides NAT services ▪ other routers: extensive use of tunneling Wireless and Mobile Networks: 7- 28 Elements of 4G LTE architecture Mobility Management Entity Mobility Management Home Subscriber Mobile device Service (HSS) Entity (MME) ▪ device authentication (UE) Base station (eNode-B) (device-to-network, network- to to-device) coordinated with Internet mobile home network HSS PDN gateway (P-GW) ▪ mobile device management: Serving Gateway (S-GW) … device handover between cells tracking/paging device location ▪ path (tunneling) setup from mobile device to P-GW Wireless and Mobile Networks: 7- 29  Global cellular network: a network of IP networks home network HSS: Home Subscriber Server ▪ identify & services info, while in home network home mobile and roaming carrier network P-GW public Internet and inter-carrier IPX all IP: in home network ▪ carriers interconnect with each other, and public internet at exchange points P-GW SIM card: global visited mobile ▪ legacy 2G, 3G: not all IP, identify info in carrier network handled otherwise home network roaming in visited network Wireless and Mobile Networks: 7- 30 On to 5G! ▪ goal: 10x increase in peak bitrate, 10x decrease in latency, 100x increase in traffic capacity over 4G ▪ 5G NR (new radio): ▪ two frequency bands: FR1 (450 MHz–6 GHz) and FR2 (24 GHz–52 GHz): millimeter wave frequencies ▪ not backwards-compatible with 4G ▪ MIMO: multiple directional antennae ▪ millimeter wave frequencies: much higher data rates, but over shorter distances ▪ pico-cells: cells diameters: 10-100 m ▪ massive, dense deployment of new base stations required Wireless and Mobile Networks: 7- 31 Chapter 7 outline ▪ Introduction Wireless Mobility ▪ Wireless links and network ▪ Mobility management: principles characteristics ▪ Mobility management: practice ▪ WiFi: 802.11 wireless LANs 4G/5G networks ▪ Cellular networks: 4G and 5G Mobile IP ▪ Mobility: impact on higher-layer protocols Link Layer: 6-32 What is mobility? ▪ spectrum of mobility, from the network perspective: no mobility high mobility device moves device moves device moves device moves between within same AP in among APs in among multiple networks, but one provider one provider provider networks, powers down network network while maintaining while moving ongoing We’re interested in these! connections Wireless and Mobile Networks: 7- 33 Mobility approaches ▪ let network (routers) handle it: routers advertise well-known name, address (e.g., permanent 32- bit IP address), or number (e.g., cell #) of visiting mobile node via usual routing table exchange Internet routing could do this already with no changes! Routing tables indicate where each mobile located via longest prefix match! Wireless and Mobile Networks: 7- 34 Mobility approaches ▪ let network (routers) handle it: routers advertise well-known notname, address (e.g., permanent 32- bit IP address), or number (e.g., cell #) of visiting mobile node via scalable to billions of usual routing table exchange mobiles Internet routing could do this already with no changes! Routing tables indicate where each mobile located via longest prefix match! ▪ let end-systems handle it: functionality at the “edge” indirect routing: communication from correspondent to mobile goes through home network, then forwarded to remote mobile direct routing: correspondent gets foreign address of mobile, send directly to mobile Wireless and Mobile Networks: 7- 35 Contacting a mobile friend: I wonder where Alice moved to? Consider friend frequently changing locations, how do you find him/her? ▪ search all phone books? ▪ expect her to let you know where he/she is? ▪ call his/her parents? ▪ Facebook! The importance of having a “home”: ▪ a definitive source of information about you ▪ a place where people can find out where you are Wireless and Mobile Networks: 7- 36