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Systems Issues in Wireless Networks

Systems Issues in Wireless Networks. Henning Schulzrinne Columbia University NSF wireless workshop – July 2003. Overview. Applications Autoconfiguration Evolution Hybrid networks Non-data applications New wireless models? New types of networks?. What makes wireless networks different?.

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Systems Issues in Wireless Networks

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  1. Systems Issues in Wireless Networks Henning Schulzrinne Columbia University NSF wireless workshop – July 2003

  2. Overview • Applications • Autoconfiguration • Evolution • Hybrid networks • Non-data applications • New wireless models? • New types of networks?

  3. What makes wireless networks different? • Network probabilistic throughout • wired generally hides this at lowest layer • Node and link availability • Identifier collisions • Packet loss • Link bandwidth availability

  4. Applications • Transition from general-purpose networks to niche networks • Need honesty in scoping (cf. active networks) • What are different types of networks good for (and what not)? • Applications for ad-hoc and sensor networks • Beyond the (dubious) emergency and military applications • Clusters of vehicles • Short-term ad-hoc networks • Beer glasses waiting to be filled

  5. Autoconfiguration & Discovery • With open spectrum, how to find • Available network services  can’t just scan 3 GHz of bandwidth • Might be hundreds of ad-hoc and infrastructure networks • Available services that take my credentials • That offer best/cheapest/… service • Geographic service discovery • Ad-hoc and disconnected network services • How to automatically deploy networks • In simulations, they just magically connect… • Not much usable development • LDAP doesn’t scale (administratively) • SLP has severe functionality limitations (no hierarchy) • UDDI, etc. too narrow • Zero-conf too low level and not suitable for all networks

  6. Evolution • Implicit assumption: natural evolution • from specialized to general • from circuit to packets • from ATM to IP • from large to small cells • from single network access to global AAA with roaming • However, even IP networks can look rather crufty: • GPRS Russian-doll stack • WAP & 3G “walled garden” bias • Longer lifetime of networks • analog wireless may not disappear for a decade+ • Specialization and large-enough eco system niches • restricted applications simplify security (DOS), billing, lower cost • Stuck with glueing together 30 years of wireless technology at the application layer? • very little research on evolution, co-existence and gateway models • economics, security and technical issues

  7. Non-data applications • Almost exclusive research focus on data (and multimedia) applications • higher bandwidth, general-purpose networks • Other wireless applications: • location sensing (GPS, location beacons) • awareness of other people and resources • remote control (garage door opener…) • Layer on top of general-purpose networks or construct special-purpose networks?

  8. Hybrid networks • Not just vertical hand-off • Software-defined radios: use diverse networks at (almost) the same time • e.g., high-speed ad hoc network + low bandwidth WWAN • separate control and data channels?

  9. New wireless models • Have we explored the architecture space? • infrastructure access • ad-hoc as infrastructure “funnel” • ad-hoc networks • intermittent-connectivity networks • Do things change with highly directional networks that are no longer broadcast?

  10. New types of networks • Roughly now have tools for ubiquitous and high-bandwidth data delivery • But still far too expensive for many applications • BlueTooth USB: $50 – requires “real” processor • only useful for very small groups, not clusters of O(100) • New sets of applications for wide area, very low bandwidth, ultra low complexity devices • many applications only need 1 bit/hour (light switch, thermostat) • many sensor applications (toothbrush, scale, toaster, traffic light controlled by bus, …) • 802.15 status? • Parasitic networks?

  11. Protocol design challenges • Wireless starting to reach up the stack – cross-layer design, but need to be precise • Applications and transport have only limited repertoire of actions: send packet, drop packet, delay packet, fragment packet • Currently, usually don’t even know outgoing/incoming interface for a socket (and its current bandwidth) • Trade-off error rate vs. bit rate more explicit in wireless • not just binary  another example of probabilistic network behavior • Examples: • packet loss  • wait (fade) • reduce rate (congestion) • retransmit (but probably better delegated down) • Unequal error protection (UEP) • Delivery of errored PDU to application • application needs control • may need stronger e2e checksum if done inadvertently

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