CS 204 Wireless and Mobile Networks Lecture Notes PDF

SMU Classification: Restricted CS 204: Interconnection of Cyber Physical Systems Week 10: Wireless and Mobile Networks Link Layer: 7-1  SMU Classification: Restricted Checking in ▪Projects ok? ▪Individual assignment ok?...

SMU Classification: Restricted CS 204: Interconnection of Cyber Physical Systems Week 10: Wireless and Mobile Networks Link Layer: 7-1  SMU Classification: Restricted Checking in ▪Projects ok? ▪Individual assignment ok? ▪Will release past year exam ▪Class next week  hardware lab ▪Quiz before class starts  on this week’s content Wireless and Mobile Networks: 7- 2  SMU Classification: Restricted Recap: ARP protocol in action example: A wants to send datagram to B B’s MAC address not in A’s ARP table, so A uses ARP to find B’s MAC address C ARP table in A IP addr MAC addr TTL TTL A B 2 71-65-F7-2B-08-53 58-23-D7-FA-20-B0 137.196.7.23 137.196.7.14 2 B replies to A with ARP response, giving its MAC address D Link Layer: 6-3  SMU Classification: Restricted Recap: ARP protocol in action example: A wants to send datagram to B B’s MAC address not in A’s ARP table, so A uses ARP to find B’s MAC address C ARP table in A IP addr MAC addr TTL TTL 137.196. 58-23-D7-FA-20-B0 500 A B 7.14 71-65-F7-2B-08-53 58-23-D7-FA-20-B0 137.196.7.23 137.196.7.14 3 A receives B’s reply, adds B entry into its local ARP table D Link Layer: 6-4  SMU Classification: Restricted Recap: ARP protocol in action example: A wants to send datagram to B B’s MAC address not in A’s ARP table, so A uses ARP to find B’s MAC address C ARP table in A IP addr MAC addr TTL TTL A B 2 71-65-F7-2B-08-53 58-23-D7-FA-20-B0 137.196.7.23 137.196.7.14 2 B replies to A with ARP response, giving its MAC address D Link Layer: 6-5  SMU Classification: Restricted 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: 7-6  SMU Classification: Restricted Elements of a wireless network wired network infrastructure Wireless and Mobile Networks: 7- 7  SMU Classification: Restricted 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- 8  SMU Classification: Restricted 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- 9  SMU Classification: Restricted 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- 10  SMU Classification: Restricted Characteristics of selected wireless links 100 Gbps 802.11bn 46 Gbps 802.11be 11 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 Reference: https://en.wikipedia.org/wiki/Wi-Fi_7 Wireless and Mobile Networks: 7- 11  SMU Classification: Restricted Outline ▪ Introduction Wireless Mobility ▪ Wireless links and network ▪ Mobility management: principles characteristics ▪ Mobility management: practice ▪ Wi-Fi: 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- 15  SMU Classification: Restricted Wireless link characteristics: fading (attenuation) Wireless radio signal attenuates (loses power) as it propagates (free space “path loss”) Free space path loss ~ (fd)2 f: frequency d: distance higher frequency or larger free space longer distance path loss Wireless and Mobile Networks: 7- 16  SMU Classification: Restricted Wireless link characteristics: multipath multipath propagation: radio signal reflects off objects ground, built environment, arriving at destination at slightly different times reflected path line of sight reflected path (LOS) path Wireless and Mobile Networks: 7- 17  SMU Classification: Restricted Wireless link characteristics: multipath multipath propagation: radio signal reflects off objects ground, built environment, arriving at destination at slightly different times Coherence time: ▪ amount of time bit is present transmitted pulses in channel to be received time ▪ influences maximum possible received received multipath LOS pulse pulses received received multipath LOS pulse pulses transmission rate, since received coherence times can not pulse time overlap Tc: coherence time ▪ inversely proportional to frequency receiver velocity Wireless and Mobile Networks: 7- 18  SMU Classification: Restricted Wireless link characteristics: hidden terminals Hidden terminal problem Attenuation also causes “hidden terminals” C A B C B A C’s signal A’s signal strength strength ▪ B, A hear each other ▪ B, C hear each other space ▪ A, C can not hear each other means A, ▪ B, A hear each other C unaware of their interference at B ▪ B, C hear each other ▪ A, C can not hear each other interfering at B Wireless and Mobile Networks: 7- 20  SMU Classification: Restricted Outline ▪ Introduction Wireless ▪ Wireless links and network characteristics ▪ CDMA: code division multiple access ▪ Wi-Fi: 802.11 wireless LANs ▪ Bluetooth Class 22: 21  SMU Classification: Restricted 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- 22  SMU Classification: Restricted Outline ▪ Introduction Wireless Mobility ▪ Wireless links and network ▪ Mobility management: principles characteristics ▪ Mobility management: practice ▪ Wi-Fi: 802.11 wireless LANs 4G/5G networks ▪ Cellular networks: 4G and 5G Mobile IP ▪ Mobility: impact on higher-layer protocols Link Layer: 6-25  SMU Classification: Restricted IEEE 802.11 Wireless LAN (https://en.wikipedia.org/wiki/Wi-Fi_7) 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 (Wi-Fi 4) 2009 600 70m 2.4, 5 Ghz 802.11ac (Wi-Fi 5) 2013 3.47Gpbs 70m 5 Ghz 802.11af 2014 35 – 560 Mbps 1 Km unused TV bands (54-790 MHz) 802.11ah 2017 347Mbps 1 Km 900 Mhz 802.11ax (Wi-Fi 6) 2021 11 Gbps 70m 2.4, 5, 6 Ghz 802.11ax (Wi-Fi 7) 2024 (?) 46 Gbps 30m 2.4, 5, 6 Ghz 802.11ax (Wi-Fi 8) 2028 (?) 100 Gbps ? 2.4, 5, 6 Ghz ▪ all use CSMA/CA for multiple access, and have base-station and ad-hoc network versions Wireless and Mobile Networks: 7- 26  SMU Classification: Restricted 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- 27  SMU Classification: Restricted 802.11: Channels ▪ 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! Example: 2.4 GHz Class 22: 28  SMU Classification: Restricted 802.11: Association ▪ 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 Class 22: 29  SMU Classification: Restricted 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- 31  SMU Classification: Restricted 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- 32  SMU Classification: Restricted 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- 33  SMU Classification: Restricted 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- 35  SMU Classification: Restricted 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 Wi-Fi frame Wireless and Mobile Networks: 7- 36  SMU Classification: Restricted 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- 39  SMU Classification: Restricted 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- 40  SMU Classification: Restricted Outline ▪ Introduction Wireless Mobility ▪ Wireless links and network ▪ Mobility management: principles characteristics ▪ Mobility management: practice ▪ Wi-Fi: 802.11 wireless LANs 4G/5G networks ▪ Cellular networks: 4G and 5G Mobile IP ▪ Mobility: impact on higher-layer protocols Link Layer: 6-45  SMU Classification: Restricted 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- 46  SMU Classification: Restricted 4G/5G cellular networks similarities to wired Internet differences from wired Internet ▪ edge/core distinction, but both ▪ different wireless link layer belong 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- 47  SMU Classification: Restricted 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- 48  SMU Classification: Restricted 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 Wi-Fi 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- 49  SMU Classification: Restricted Radio Access Network: 4G radio Mobile device (UE) Base station ▪ connects device (UE) to a base station (eNode-B) (eNode-B) multiple devices connected to each base station ▪ many different possible frequencies bands, multiple channels in each band popular bands: 600, 700, 850, 1500, 1700, 1900, 2100, 2600, 3500 MHz separate upstream and downstream channels ▪ sharing 4G radio channel among users: OFDM: Orthogonal Frequency Division Multiplexing combination of FDM, TDM ▪ 100’s Mbps possible per user/device Class 23: 50  SMU Classification: Restricted 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- 55  SMU Classification: Restricted 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- 56  SMU Classification: Restricted 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- 57  SMU Classification: Restricted 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- 61  SMU Classification: Restricted LTE mobiles: sleep modes ZZZZ... data plane as in Wi-Fi, 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- 62  SMU Classification: Restricted 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- 63  SMU Classification: Restricted On to 5G: motivation From Next Generation Mobile Networks (NGMS) alliance: 2020 white paper Hype/wishes need to be separated from reality or likely nearer-term reality Class 23: 64  SMU Classification: Restricted On to 5G: Radio ▪ 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 Class 23: 67  SMU Classification: Restricted Outline ▪ Introduction Wireless Mobility ▪ Wireless links and network ▪ Mobility management: principles characteristics ▪ Mobility management: practice ▪ Wi-Fi: 802.11 wireless LANs 4G/5G networks ▪ Cellular networks: 4G and 5G Mobile IP ▪ Mobility: impact on higher-layer protocols Link Layer: 6-73  SMU Classification: Restricted 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- 74  SMU Classification: Restricted Mobility challenge: content provider If a device moves from network datacenter network Verizon one network another: ▪ How will the public Internet “network” know to forward packets to the new network? client moves from Verizon to AT&T AT&T Wireless and Mobile Networks: 7- 75  SMU Classification: Restricted 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- 76  SMU Classification: Restricted 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- 77  SMU Classification: Restricted 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- 78  SMU Classification: Restricted 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- 79  SMU Classification: Restricted Outline ▪ Introduction Wireless Mobility ▪ Wireless links and network ▪ Mobility management: principles characteristics ▪ Mobility management: practice ▪ Wi-Fi: 802.11 wireless LANs 4G/5G networks ▪ Cellular networks: 4G and 5G Mobile IP ▪ Mobility: impact on higher-layer protocols Link Layer: 6-87  SMU Classification: Restricted Mobility in 4G networks: major mobility tasks Mobility 1 base station association: manager Home ▪ covered earlier 2 1 Subscriber 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- 88  SMU Classification: Restricted 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- 94  SMU Classification: Restricted Show and Tell ▪Wi-Fi Analyzer Tools Search on Android, OSX, iOS, Windows stores I use Wi-Fi Monitor on Android Heard spotter is good on OSX Wireless and Mobile Networks: 7- 95  SMU Classification: Restricted Summary Wireless ▪ Wireless Links and network characteristics ▪ Wi-Fi: 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- 96