Lecture 1: Introduction CS 653, Spring 2014 CS 653, Spring 2014 - PowerPoint PPT Presentation

Lecture 1: Introduction CS 653, Spring 2014 CS 653, Spring 2014 MythiliVutukuru MythiliVutukuru

Topics for today  Course overview and logistics  Course overview and logistics  Revise basic concepts in networking – layering, protocols  Revise basic concepts in networking – layering, protocols  Challenges specific to mobile systems across various layers  Challenges specific to mobile systems across various layers  Examples of mobile systems: wireless LANs, cellular  Examples of mobile systems: wireless LANs, cellular systems,WiMAX, adhoc networks, sensor networks, RFID, systems,WiMAX, adhoc networks, sensor networks, RFID, Bluetooth, etc. Bluetooth, etc.

Networks, layers, protocols…  Network protocol – a standard mechanism by which two  Network protocol – a standard mechanism by which two entities can communicate entities can communicate  Layering – an abstraction by which a protocol can only worry  Layering – an abstraction by which a protocol can only worry about what it is supposed to, and abstract out the lower level about what it is supposed to, and abstract out the lower level details details  Examples on blackboard  Examples on blackboard  Walk through what happens at each layer when you open a web  Walk through what happens at each layer when you open a web page from your laptop overWiFi, and from your phone over 3G page from your laptop overWiFi, and from your phone over 3G  Each layers adds its own information in headers  Each layers adds its own information in headers (encapsulation), which its peer at the other end processes and (encapsulation), which its peer at the other end processes and removes (decapsulation) removes (decapsulation)

Common examples of mobile systems  Wireless LANs (802.11a/b/g/n)  Wireless LANs (802.11a/b/g/n)  Cellular systems (voice and data, 3G, 4G etc)  Cellular systems (voice and data, 3G, 4G etc)  Multihop adhoc networks  Multihop adhoc networks  RFID / NFC  RFID / NFC  Bluetooth  Bluetooth

Layers and challenges in mobile systems  Physical layer – deals with transmission of information over a  Physical layer – deals with transmission of information over a single hop single hop  Wireless physical layers use radio communication  Wireless physical layers use radio communication  Radio signal suffers losses as it travels through air (channel)  Radio signal suffers losses as it travels through air (channel)  Need to build a reliable link using unreliable signals  Need to build a reliable link using unreliable signals  Tradeoff between how much you can send and how many errors you  Tradeoff between how much you can send and how many errors you can tolerate can tolerate  Link layer / MAC – deals with coordinating multiple  Link layer / MAC – deals with coordinating multiple transmissions over a link transmissions over a link  Wireless is broadcast medium, need to share channel efficiently  Wireless is broadcast medium, need to share channel efficiently  Avoid interference between nodes, also enable channel reuse  Avoid interference between nodes, also enable channel reuse  Contention-based vs scheduling  Contention-based vs scheduling

Layers and challenges in mobile systems (2)  Network (IP) layer – handles routing  Network (IP) layer – handles routing  Need to handle mobility, changes in IP subnets  Need to handle mobility, changes in IP subnets  Multihop routing in multihop wireless networks  Multihop routing in multihop wireless networks  Transport (TCP/UDP) layer – handles end-to-end transport  Transport (TCP/UDP) layer – handles end-to-end transport of bytes of bytes  Need to handle mobility of end points  Need to handle mobility of end points  Wireless links add more losses, TCP is highly sensitive  Wireless links add more losses, TCP is highly sensitive  Application layer  Application layer  Applications must be able to handle disconnected operations  Applications must be able to handle disconnected operations

Challenges in mobile systems (across layers)  Energy conservation  Energy conservation  Localization and service discovery  Localization and service discovery  Security (wireless makes snooping easier)  Security (wireless makes snooping easier)  Adapt applications to new platforms (e.g., smartphones)  Adapt applications to new platforms (e.g., smartphones)

Overview of mobile systems: 802.11  Wireless LANs – access point (AP) bridges a wireless node  Wireless LANs – access point (AP) bridges a wireless node (client) to its IP gateway (client) to its IP gateway  Evolution: 802.11b (2.4 GHz, up to 11 Mbps)  802.11a  Evolution: 802.11b (2.4 GHz, up to 11 Mbps)  802.11a (5GHz, 54 Mbps)  802.11g (2.4GHz, 54 Mbps)  802.11n (5GHz, 54 Mbps)  802.11g (2.4GHz, 54 Mbps)  802.11n (higher rates due to new features like MIMO)  802.11ac and so (higher rates due to new features like MIMO)  802.11ac and so on on  Physical layer – provides lots of raw speed  Physical layer – provides lots of raw speed  MAC layer – nodes contend for access to medium, lots of spacing  MAC layer – nodes contend for access to medium, lots of spacing between frames, reduces the raw throughput provided by the between frames, reduces the raw throughput provided by the physical layer physical layer  We will learn about wireless LANs in great detail in this course  We will learn about wireless LANs in great detail in this course

Overview of mobile systems: cellular  Started for voice communication (1G – analog, 2G – digital voice)  Started for voice communication (1G – analog, 2G – digital voice)  Initially data was piggypacked over voice channels (2.5G)  Initially data was piggypacked over voice channels (2.5G)  Now, redesigned to have separate voice and data channels (3G and  Now, redesigned to have separate voice and data channels (3G and beyond) beyond)  Now, 4G (LTE) moving to flat, all-IP infrastructure  Now, 4G (LTE) moving to flat, all-IP infrastructure  Radio access network (wireless part) + core  all appear as one IP hop  Radio access network (wireless part) + core  all appear as one IP hop when accessing the internet from your phone. Convergence! when accessing the internet from your phone. Convergence!  Data tunnelled from phone to edge of the cellular network using various  Data tunnelled from phone to edge of the cellular network using various layers to protocols layers to protocols  Circuit switched (vs. packet switched in the internet) to provide better  Circuit switched (vs. packet switched in the internet) to provide better QoS QoS  Control plane (to set up signaling), management plane (billing), in  Control plane (to set up signaling), management plane (billing), in addition to data plane (for voice and data) addition to data plane (for voice and data)

Overview of mobile systems: Sensor networks, multihop adhoc networks  Many applications – military, environment, health, home  Many applications – military, environment, health, home automation, traffic management automation, traffic management  Design constraints – cheap, low power, scalable  Design constraints – cheap, low power, scalable communication, self-organizing communication, self-organizing  Physical layer – low cost design  Physical layer – low cost design  MAC – need to coordinate between many nodes  MAC – need to coordinate between many nodes  Network – discover routes efficiently  Network – discover routes efficiently  Transport – transfer information with low power and  Transport – transfer information with low power and memory memory  Requires rethink of many protocols  Requires rethink of many protocols

Overview of mobile systems: RFID, Bluetooth  Short range communications  Short range communications  Active (powered nodes like RFID reader) vs passive (tags with no  Active (powered nodes like RFID reader) vs passive (tags with no power source) power source)  Passive tags can be near field (small range of few cm, modulates  Passive tags can be near field (small range of few cm, modulates magnetic field) or far field (up to few metres, modulates and magnetic field) or far field (up to few metres, modulates and reflects radio signals) reflects radio signals)  Open issues – reading colocated tags, privacy  Open issues – reading colocated tags, privacy  RFID, Sensors  “Internet of things”  RFID, Sensors  “Internet of things”  Bluetooth  Bluetooth  All layers integrated and designed for low power and cost  All layers integrated and designed for low power and cost  Master and up to 7 slaves (“piconet”) communication  Master and up to 7 slaves (“piconet”) communication  We won’t go into much detail about exact protocols  We won’t go into much detail about exact protocols