LTE 1.1.pptx

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- 1 4G/5G cellular networks similarities to wired Internet  edge/core distinction, but both belong to same carrier  global cellular network: a network of networks  widespread use of protocols we’ve studied: HTTP, DNS, TCP, UDP, IP, NAT, separation of data/control planes, SDN, Ethernet, tunneling differences from wired Internet  different wireless link layer  mobility as a 1st class service  user “identity” (via SIM card)  business model: users subscribe to a cellular provider • strong notion of “home and Mobileon Networks: 7- 2 network” versus Wireless roaming Elements of 4G LTE architecture Mobile device:  smartphone, tablet, laptop, IoT, ... with 4G LTE radio  64-bit International Mobile Subscriber Identity (IMSI), stored on SIM (Subscriber Identity Module) card  LTE jargon: User Equipment (UE) Mobile device (UE) Base station (eNode-B) Mobility Manageme nt Entity (MME) Home Subscriber Service (HSS) to Internet PDN gateway (P-GW) … radio access network Serving Gateway (S-GW) all-IP Enhanced Packet Core (EPC) Wireless and Mobile Networks: 7- 3 Elements of 4G LTE architecture Base station:  at “edge” of carrier’s network  manages wireless radio resources, mobile devices in its coverage area (“cell”)  coordinates device authentication with other elements  similar to WiFi AP but: • active role in user mobility • coordinates with nearly base stations to Mobile device (UE) Base station (eNode-B) Mobility Manageme nt Entity (MME) Home Subscriber Service (HSS) to Internet PDN gateway (P-GW) … Serving Gateway (S-GW) Wireless and Mobile Networks: 7- 4 Elements of 4G LTE architecture Home Subscriber Service  stores info about mobile devices for which the HSS’s network is their “home network”  works with MME in device authentication Mobile device (UE) Base station (eNode-B) Mobility Manageme nt Entity (MME) Home Subscriber Service (HSS) to Internet PDN gateway (P-GW) … Serving Gateway (S-GW) Wireless and Mobile Networks: 7- 5 Elements of 4G LTE architecture Serving Gateway (SGW), PDN Gateway (P-GW)  lie on data path from mobile to/from Internet  P-GW • gateway to mobile cellular network • Looks like any other internet gateway router • provides NAT services  other routers: Mobile device (UE) Base station (eNode-B) Mobility Manageme nt Entity (MME) Home Subscriber Service (HSS) to Internet PDN gateway (P-GW) … Serving Gateway (S-GW) Wireless and Mobile Networks: 7- 6 Elements of 4G LTE architecture Mobility Management Entity Mobile device (UE)  device authentication (device-to-network, network-to-device) coordinated with mobile device home network  mobile management: HSS • device handover between cells • tracking/paging device location  path (tunneling) setup from mobile device to P-GW Base station (eNode-B) Mobility Manageme nt Entity (MME) Home Subscriber Service (HSS) to Internet PDN gateway (P-GW) … Serving Gateway (S-GW) Wireless and Mobile Networks: 7- 7 LTE: data plane control plane separation HSS base station base station MME P-GW S-GW S-GW IP tunnels P-GW control plane  new protocols for mobility management , security, authentication (later) data plane  new protocols at link, physical layers  extensive use of tunneling to facilitate mobility Wireless and Mobile Networks: 7- 8 Link LTE data plane protocol stack: first hop LTE link layer protocols: Application Transport IP IP Packet Data Convergence Radio Link Medium Access Packet Data Convergence Radio Link Medium Access Physical Physical base station  Packet Data Convergence: header compression, encryption  Radio Link Control (RLC) Protocol: fragmentation/reassembly, reliable data transfer  Medium Access: requesting, use of radio transmission slots S-GW P-GW data plane Wireless and Mobile Networks: 7- 9 Link LTE data plane protocol stack: first hop LTE radio access network: Application Transport IP IP Packet Data Convergence Radio Link Medium Access Packet Data Convergence Radio Link Medium Access Physical Physical base station  downstream channel: FDM, TDM within frequency channel (OFDM orthogonal frequency division multiplexing) • “orthogonal”: minimal interference between channels • 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 and Mobile Networks: 7- 10 standardized – up toWireless operator LTE data plane protocol stack: packet core tunneling: IP GTP-U UDP IP GTP-U UDP IP GTP-U UDP IP Packet Data Convergence Radio Link link link link Physical Physical Physical Medium Access Physical \ base station S-GW P-GW  mobile datagram encapsulated using GPRS Tunneling Protocol (GTP), sent inside UDP datagram to S-GW  S-GW re-tunnels datagrams to P-GW  supporting mobility: only tunneling endpoints change when mobile user Wireless and Mobile Networks: 7- 11 moves LTE data plane: associating with a BS 1 2 3 base station S-GW P-GW data plane BS broadcasts primary synch signal every 5 ms on all frequencies 1  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 BS getto info from multiple basepreference stations, multiple mobile selects which associate with (e.g., for home carrie 3 cellular networks more4 steps still needed to authenticate, establish state, set up data plane Wireless and Mobile Networks: 7- 12 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 reestablish association Wireless and Mobile Networks: 7- 13 Global cellular network: a network of IP networks home network HSS: Home Subscriber Server home mobile carrier network P-GW public Internet and … … in home network inter-carrier IPX P-GW visited mobile carrier network roaming in visited network … SIM card: global identify info in home network  identity & services info, while in home network and roaming all IP:  carriers interconnect with each other, and public internet at exchange points  legacy 2G, 3G: not all IP, handled otherwise Wireless and Mobile Networks: 7- 14 Mobility in 4G networks: major mobility tasks Mobility manage r Home Subscriber Server Home networ k MME 3 1 base station association: 1 2 base station S-GW P-GW 4 Internet P-GW Visited network  covered earlier  mobile provides IMSI – identifying itself, home network 2 control-plane configuration:  MME, home HSS establish control-plane Streamin state - mobile is in g server 3 data-plane configuration: network  MME configures visited forwarding tunnels for mobile  visited, home network establish tunnels 4 mobile handover: from home P-GW to mobile  mobile device changes its point of attachment to visited network Wireless and Mobile Networks: 7- 15 Configuring LTE control-plane elements Mobility manage r Home Subscriber Server Home networ k MME P-GW 2 P-GW S-GW base station 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- 16 Configuring data-plane tunnels for mobile • S-GW to BS tunnel: when mobile changes base stations, simply change endpoint IP address of tunnel • S-GW to home P-GW tunnel: implementation of indirect routing Mobility manage r Home Subscriber Server Home networ k MME base station S-GW P-GW Internet P-GW Visited network Streamin g server  tunneling via GTP (GPRS tunneling protocol): mobile’s datagram to streaming server encapsulated using GTP inside UDP, inside datagram Wireless and Mobile Networks: 7- 17 Handover between BSs in same cellular network 1 current (source) BS 3 selects target BS, sends 1 4 Handover Request 2 message to target BS 2 target BS pre-allocates radio time slots, responds with HR ACK target BS with info for mobile 3 source BS informs mobile of new BS  mobile can now send via new BS handover looks complete to mobile source BS data path before handover S-GW P-GW data path after handover MME 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- 18 Handover between BSs in same cellular network source BS S-GW 3 5 target BS informs MME 2 6 that it is new BS for P-GW 5 mobile 7  MME instructs S-GW to 5 change tunnel endpoint target BS MME to be (new) target BS 6 target BS ACKs back to source BS: handover complete, source BS can release resources 1 4 7 mobile’s datagrams now flow through new tunnel from target BS to S-GW Wireless and Mobile Networks: 7- 19 Mutual Authentication 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- 26

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