02_Wireless_Chapter_7_v8.0.pdf

Chapter 7 Wireless and Mobile Networks A note on the use of these PowerPoint slides: We’re making these slides freely available to all (faculty, students, readers). They’re in PowerPoint form so you see the animations; and can add, modify, and delete slides (including this one) and slide content to...

Chapter 7 Wireless and Mobile Networks A note on the use of these PowerPoint slides: We’re making these slides freely available to all (faculty, students, readers). They’re in PowerPoint form so you see the animations; and can add, modify, and delete slides (including this one) and slide content to suit your needs. They obviously represent a lot of work on our part. In return for use, we only ask the following:  If you use these slides (e.g., in a class) that you mention their source (after all, we’d like people to use our book!)  If you post any slides on a www site, that you note that they are adapted from (or perhaps identical to) our slides, and note our copyright of this material. Computer Networking: A For a revision history, see the slide note for this page. Top-Down Approach Thanks and enjoy! JFK/KWR 8th edition All material copyright 1996-2020 Jim Kurose, Keith Ross J.F Kurose and K.W. Ross, All Rights Reserved 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 (1) 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 Wireless link characteristics (2)  SNR: signal-to-noise ratio 10-1 larger SNR – easier to extract signal 10-2 from noise (a “good thing”) 10-3  SNR versus BER tradeoffs BER 10-4 given physical layer: increase power -> 10-5 increase SNR->decrease BER 10-6 given SNR: choose physical layer that 10-7 meets BER requirement, giving 10 20 SNR(dB) 30 40 highest throughput QAM256 (8 Mbps) SNR may change with mobility: QAM16 (4 Mbps) dynamically adapt physical layer (modulation technique, rate) BPSK (1 Mbps) Wireless and Mobile Networks: 7- 14 Wireless link characteristics (3) Multiple wireless senders, receivers create additional problems (beyond multiple access): A B C C A’s signal C’s signal strength strength B A space Hidden terminal problem Signal attenuation:  B, A hear each other  B, A hear each other  B, C hear each other  B, C hear each other  A, C can not hear each other means A,  A, C can not hear each other C unaware of their interference at B interfering at B Wireless and Mobile Networks: 7- 15 Code Division Multiple Access (CDMA)  unique “code” assigned to each user; i.e., code set partitioning all users share same frequency, but each user has own “chipping” sequence (i.e., code) to encode data allows multiple users to “coexist” and transmit simultaneously with minimal interference (if codes are “orthogonal”)  encoding: inner product: (original data) X (chipping sequence)  decoding: summed inner-product: (encoded data) X (chipping sequence) Wireless and Mobile Networks: 7- 16 CDMA encode/decode channel output Zi,m Zi,m= di.cm data d0 = 1 1 1 1 1 1 1 1 1 d1 = -1 bits -1 -1 -1 -1 -1 -1 -1 -1 sender 1 1 1 1 1 1 1 1 slot 1 slot 0 code channel channel -1 -1 -1 -1 -1 -1 -1 -1 output output slot 1 slot 0 M Di = S Zi,m.cm m=1 M receiver received -1 -1 -1 1 -1 1 1 1 1 1 1 -1 1 -1 -1 -1 d0 = 1 input d1 = -1 1 1 1 1 1 1 1 1 slot 1 slot 0 code channel channel -1 -1 -1 -1 -1 -1 -1 -1 output output slot 1 slot 0 … but this isn’t really useful yet! Wireless and Mobile Networks: 7- 17 CDMA: two-sender interference channel sums together transmissions by sender Sender 1 1 and 2 Sender 2 using same code as sender 1, receiver recovers sender 1’s original data from summed channel data! … now that’s useful! Wireless and Mobile Networks: 7- 18 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: 6-19 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- 20 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- 21 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- 22 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- 23 IEEE 802.11: multiple access  avoid collisions: 2+ nodes transmitting at same time  802.11: CSMA - sense before transmitting don’t collide with detected ongoing transmission by another node  802.11: no collision detection! difficult to sense collisions: high transmitting signal, weak received signal due to fading can’t sense all collisions in any case: hidden terminal, fading goal: avoid collisions: CSMA/CollisionAvoidance A B C C A’s signal C’s signal B strength A strength space Wireless and Mobile Networks: 7- 24 IEEE 802.11 MAC Protocol: CSMA/CA 802.11 sender sender receiver 1 if sense channel idle for DIFS then transmit entire frame (no CD) DIFS 2 if sense channel busy then start random backoff time timer counts down while channel idle data transmit when timer expires if no ACK, increase random backoff interval, repeat 2 SIFS 802.11 receiver ACK if frame received OK return ACK after SIFS (ACK needed due to hidden terminal problem) Wireless and Mobile Networks: 7- 25 Avoiding collisions (more) idea: sender “reserves” channel use for data frames using small reservation packets  sender first transmits small request-to-send (RTS) packet to BS using CSMA RTSs may still collide with each other (but they’re short)  BS broadcasts clear-to-send CTS in response to RTS  CTS heard by all nodes sender transmits data frame other stations defer transmissions Wireless and Mobile Networks: 7- 26 Collision Avoidance: RTS-CTS exchange A B AP reservation collision time DATA (A) defer Wireless and Mobile Networks: 7- 27 802.11 frame: addressing 2 2 6 6 6 2 6 0 - 2312 4 frame duration address address address seq address payload CRC control 1 2 3 control 4 Address 1: MAC address Address 4: used only in of wireless host or AP to ad hoc mode receive this frame Address 3: MAC address of Address 2: MAC address router interface to which AP of wireless host or AP is attached transmitting this frame Wireless and Mobile Networks: 7- 28 802.11 frame: addressing Internet H1 R1 802.3 Ethernet frame R1 MAC addr H2 MAC addr MAC dest addr MAC source addr AP MAC addr H1 MAC addr R1 MAC addr address 1 address 2 address 3 802.11 WiFi frame Wireless and Mobile Networks: 7- 29 802.11 frame: addressing duration of reserved frame sequence # (for reliable data transmission time (RTS/CTS) transfer) 2 2 6 6 6 2 6 0 - 2312 4 frame duration address address address seq address payload CRC control 1 2 3 control 4 2 2 4 1 1 1 1 1 1 1 1 protocol to from more power more type subtype retry WEP rsvd version AP AP frag mgt data frame type (RTS, CTS, ACK, data) Wireless and Mobile Networks: 7- 30 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- 31 802.11: advanced capabilities Rate adaptation  base station, mobile dynamically 10-1 10-2 change transmission rate (physical 10-3 layer modulation technique) as BER 10-4 mobile moves, SNR varies 10-5 10-6 10-7 1. SNR decreases, BER increase as node moves 10 20 30 40 away from base station SNR(dB) 2. When BER becomes too high, switch to lower QAM256 (8 Mbps) QAM16 (4 Mbps) transmission rate but with lower BER BPSK (1 Mbps) operating point Wireless and Mobile Networks: 7- 32 802.11: advanced capabilities power management  node-to-AP: “I am going to sleep until next beacon frame” AP knows not to transmit frames to this node node wakes up before next beacon frame  beacon frame: contains list of mobiles with AP-to-mobile frames waiting to be sent node will stay awake if AP-to-mobile frames to be sent; otherwise sleep again until next beacon frame Wireless and Mobile Networks: 7- 33 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- 34 Personal area networks: Bluetooth  TDM, 625 msec 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- 35 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: 6-36 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- 37 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- 38 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- 39  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- 40 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- 41 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 any other … Serving Gateway (S-GW) internet gateway router provides NAT services  other routers: extensive use of tunneling Wireless and Mobile Networks: 7- 42 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- 43 LTE: data plane control plane separation HSS control plane  new protocols for mobility management , security, base station MME P-GW authentication (later) S-GW data plane  new protocols at link, physical base station S-GW P-GW layers  extensive use of tunneling to IP tunnels facilitate mobility Wireless and Mobile Networks: 7- 44  LTE data plane protocol stack: first hop Application LTE link layer protocols: Transport  Packet Data Convergence: header IP IP compression, encryption Packet Data Convergence Packet Data Convergence  Radio Link Control (RLC) Protocol: Link Radio Link Radio Link fragmentation/reassembly, reliable data Medium Access Medium Access transfer Physical Physical  Medium Access: requesting, use of radio transmission slots data plane base station S-GW P-GW Wireless and Mobile Networks: 7- 45  LTE data plane protocol stack: first hop Application LTE radio access network: Transport  downstream channel: FDM, TDM within IP IP frequency channel (OFDM - orthogonal Packet Data Convergence Packet Data Convergence frequency division multiplexing) “orthogonal”: minimal interference Link Radio Link Radio Link Medium Access Medium Access between channels Physical Physical upstream: FDM, TDM similar to OFDM  each active mobile device allocated two or more 0.5 ms time slots over 12 frequencies scheduling algorithm not standardized – up base station to operator 100’s Mbps per device possible Wireless and Mobile Networks: 7- 46 LTE data plane protocol stack: packet core tunneling: GTP-U  mobile datagram GTP-U GTP-U UDP UDP UDP encapsulated using GPRS IP IP IP IP Tunneling Protocol (GTP), Packet Data Convergence sent inside UDP Radio Link link link link Medium Access datagram to S-GW Physical Physical Physical Physical  S-GW re-tunnels datagrams to P-GW  supporting mobility: only \ tunneling endpoints base station S-GW P-GW change when mobile user moves Wireless and Mobile Networks: 7- 47 LTE data plane: associating with a BS 1 2 3 data plane base station S-GW P-GW 1 BS broadcasts primary synch signal every 5 ms on all frequencies  BSs from multiple carriers may be broadcasting synch signals 2 mobile finds a primary synch signal, then locates 2nd synch signal on this freq.  mobile then finds info broadcast by BS: channel bandwidth, configurations; BS’s cellular carrier info  mobile may get info from multiple base stations, multiple cellular networks 3 mobile selects which BS to associate with (e.g., preference for home carrier) 4 more steps still needed to authenticate, establish state, set up data plane Wireless and Mobile Networks: 7- 48 LTE mobiles: sleep modes ZZZZ... data plane as in WiFi, Bluetooth: LTE mobile may put radio to “sleep” to conserve battery:  light sleep: after 100’s msec of inactivity  wake up periodically (100’s msec) to check for downstream transmissions  deep sleep: after 5-10 secs of inactivity  mobile may change cells while deep sleeping – need to re-establish association Wireless and Mobile Networks: 7- 49  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- 50 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- 51 5G is not one cohesive standard  Built on top of:  eMBB (Enhanced Mobile Broadband). Initial deployments of 5G NR have focused on eMBB, which provides for increased bandwidth for higher download and upload speeds, as well as a moderate reduction in latency when compared to 4G LTE. eMBB enables rich media applications, such as mobile augmented reality and virtual reality, as well as mobile 4K resolution and 360° video streaming.  URLLC (Ultra Reliable Low-Latency Communications). URLLC is targeted towards applications that are highly latency-sensitive, such as factory automation and autonomous driving. URLLC is targeting latencies of 1msec. As of this writing, technologies that enable URLLC are still being standardized.  mMTC (Massive Machine Type Communications). mMTC is a narrowband access type for sensing, metering, and monitoring applications. One priority for the design of 5G networks is to lower barriers for network connectivity for IoT devices. In addition to lowering latency, emerging technologies for 5G networks are focusing on reducing power requirements, making the use of IoT devices more pervasive than has been with 4G LTE. Wireless and Mobile Networks: 7- 52 5G and Millimeter Wave Frequencies  Because millimeter frequencies have much shorter range than 4G LTE frequencies, more base stations are required, which in turn increases the cell density.  Because 5G FR2 operates in a much larger frequency band (52 - 24 = 28 GHz) than 4G LTE (up to about 2 GHz), it has more available spectrum.  With regard to spectral efficiency, 5G uses MIMO-technology: multiple antennas at each base station. Rather than broadcasting signals in all directions, each MIMO antenna employs beam forming and directs the signal at the user. MIMO technology allows a base station to send to 10–20 users at the same time in the same frequency band. Wireless and Mobile Networks: 7- 53 5G Core Network  The 5G Core network is being redesigned to: Better integrate with the Internet and cloud-based services, and Include distributed servers and caches across the network to reduce latency  Designed for complete control and user-plane separation. The 5G Core consists purely of virtualized software-based network functions, to give operators the flexibility to meet the requirements of the different 5G applications.  As of this writing, many 5G standards have yet to be finalized.  Final goals of 5G network: To become a pervasive broadband wireless service; To successfully compete with WiFi for indoor wireless service; To become a critical component of factory automation and the autonomous vehicle infrastructure. Wireless and Mobile Networks: 7- 54 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: 6-55 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- 56 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- 57 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- 58 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- 59  Home network, visited network: 4G/5G Home home network: Subscriber Server  (paid) service plan with cellular provider, e.g., home mobile carrier network P-GW Verizon, Orange public Internet  home network HSS stores and inter-carrier IPX identify & services info in home network visited network:  any network other than P-GW your home network SIM card: global visited mobile identify info carrier network  service agreement with including home other networks: to provide network roaming in visited network access to visiting mobile Wireless and Mobile Networks: 7- 60  Home network, visited network: ISP/WiFi ISP/WiFi: no notion of global “home” authentication  credentials from ISP (e.g., access server username, password) stored on device or with user public  ISPs may have national, Internet attach international presence  different networks: different credentials some exceptions (e.g., authentication eduroam) access server architectures exist (mobile IP) for 4G-like mobility, but attach not used Wireless and Mobile Networks: 7- 61 Home network, visited network: generic Home Network Visited Network e.g.,: 128.119/16 e.g.,: 79.129/16 Permanent IP: Home NAT IP: 128.119.40.186 Subscriber 10.0.0.99 IMSI Server IMSI Mobility 78:4f:43:98:d9:27 manager 78:4f:43:98:d9:27 Mobility Visited manager Home network network Home gateway gateway gateway public or private Internet Correspondent Wireless and Mobile Networks: 7- 62 Registration: home needs to know where you are! Home Network Visited Network e.g.,: 128.119/16 e.g.,: 79.129/16 1 mobile associates Permanent IP: Home 128.119.40.186 Subscriber 2 NAT IP: 10.0.0.99 with visited IMSI Server Mobility 78:4f:43:98:d9:27 IMSI 78:4f:43:98:d9:27 manager mobility manager Mobility Home Visited visited mobility manager network network Home gateway gateway manager registers gateway public or private mobile’s location Internet with home HSS end result:  visited mobility manager knows about mobile  home HSS knows location of mobile Wireless and Mobile Networks: 7- 63  Mobility with indirect routing Home Network Visited Network e.g.,: 128.119/16 e.g.,: 79.129/16 Permanent IP: Home NAT IP: 128.119.40.186 Subscriber 10.0.0.99 3 IMSI Server IMSI Mobility 78:4f:43:98:d9:27 manager 78:4f:43:98:d9:27 visited gateway router 2 Mobility Visited forwards to mobile manager Home 4a network network Home gateway gateway gateway home gateway receives public or private Internet datagram, forwards (tunnels) 1 4b visited gateway router forwards to remote gateway reply to correspondent via home correspondent uses home network (4a) or directly (4b) address as datagram Correspondent destination address Wireless and Mobile Networks: 7- 64 Mobility with indirect routing: comments  triangle routing: inefficient when correspondent and mobile are in same network  mobile moves among visited networks: transparent to correspondent! registers in new visited network new visited network registers with home HSS datagrams continue to be forwarded from home network to mobile in new network on-going (e.g., TCP) connections between correspondent and mobile can be maintained! Wireless and Mobile Networks: 7- 65 Mobility with direct routing Home Network Visited Network e.g.,: 128.119/16 e.g.,: 79.129/16 Permanent IP: Home NAT IP: 128.119.40.186 Subscriber 10.0.0.99 4 IMSI Server IMSI Mobility 78:4f:43:98:d9:27 manager 78:4f:43:98:d9:27 visited gateway router Mobility Visited forwards to mobile manager network Home gateway gateway 2 public or private 3 Internet correspondent contacts 1 home HSS, gets mobile’s Correspondent visited network addresses datagram to visited network Correspondent address Wireless and Mobile Networks: 7- 66 Mobility with direct routing: comments  overcomes triangle routing inefficiencies  non-transparent to correspondent: correspondent must get care-of- address from home agent  what if mobile changes visited network? can be handled, but with additional complexity Wireless and Mobile Networks: 7- 67 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: 6-68 Mobility in 4G networks: major mobility tasks Mobility 1 base station association: manager Home  covered earlier Subscriber 2 1 Server MME  mobile provides IMSI – Home 3 base station identifying itself, home network network P-GW S-GW 4 2 control-plane configuration: Internet  MME, home HSS establish P-GW Visited network control-plane state - mobile is in visited network Streaming server 3 data-plane configuration:  MME configures forwarding tunnels for mobile  visited, home network establish tunnels from 4 mobile handover: home P-GW to mobile  mobile device changes its point of attachment to visited network Wireless and Mobile Networks: 7- 69 Configuring LTE control-plane elements Mobility manager Home Subscriber MME 2 Server Home base station network P-GW P-GW S-GW Visited network  Mobile communicates with local MME via BS control-plane channel  MME uses mobile’s IMSI info to contact mobile’s home HSS retrieve authentication, encryption, network service information home HHS knows mobile now resident in visited network  BS, mobile select parameters for BS-mobile data-plane radio channel Wireless and Mobile Networks: 7- 70 Configuring data-plane tunnels for mobile Mobility  S-GW to BS tunnel: when Home manager Subscriber mobile changes base Server MME stations, simply change Home network P-GW S-GW base station endpoint IP address of tunnel Internet P-GW Visited network  S-GW to home P-GW tunnel: implementation of Streaming server indirect routing  tunneling via GTP (GPRS tunneling protocol): mobile’s datagram to streaming server encapsulated using GTP inside UDP, inside datagram Wireless and Mobile Networks: 7- 71 Handover between BSs in same cellular network data path before handover source BS 1 current (source) BS selects S-GW 3 target BS, sends Handover 1 4 Request message to target BS 2 P-GW 2 target BS pre-allocates radio data path after time slots, responds with HR handover MME target BS ACK with info for mobile 3 source BS informs mobile of new BS  mobile can now send via new BS - handover looks complete to mobile 4 source BS stops sending datagrams to mobile, instead forwards to new BS (who forwards to mobile over radio channel) Wireless and Mobile Networks: 7- 72 Handover between BSs in same cellular network source BS S-GW 3 1 4 5 target BS informs MME that it is 2 6 P-GW new BS for mobile 5 7  MME instructs S-GW to 5 change tunnel endpoint to be MME target BS (new) target BS 6 target BS ACKs back to source BS: handover complete, source BS can release resources 7 mobile’s datagrams now flow through new tunnel from target BS to S-GW Wireless and Mobile Networks: 7- 73 Mobile IP  mobile IP architecture standardized ~20 years ago [RFC 5944] long before ubiquitous smartphones, 4G support for Internet protocols did not see wide deployment/use perhaps WiFi for Internet, and 2G/3G phones for voice were “good enough” at the time  mobile IP architecture: indirect routing to node (via home network) using tunnels mobile IP home agent: combined roles of 4G HSS and home P-GW mobile IP foreign agent: combined roles of 4G MME and S-GW protocols for agent discovery in visited network, registration of visited location in home network via ICMP extensions Wireless and Mobile Networks: 7- 74 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 handover loss TCP interprets loss as congestion, will decrease congestion window un- necessarily delay impairments for real-time traffic bandwidth a scare resource for wireless links Wireless and Mobile Networks: 7- 75 Chapter 7 summary Wireless  Wireless Links and network characteristics  WiFi: 802.11 wireless LANs  Cellular networks: 4G and 5G Mobility  Mobility management: principles  Mobility management: practice 4G/5G networks Mobile IP  Mobility: impact on higher-layer protocols Wireless and Mobile Networks: 7- 76