What is mobile offloading?
Shift traffic away from cellular network
Why do we want to implement mobile offloading?
Mobile networks are congested and crowded.
Mobile links are:
- shared and licensed spectrum (expensive and crowded)
- Constrained backhaul (bottleneck)
- Dedicated packet core & internet peering
What benefits does offloading offer for operator and user?
Operator:
- reduce capacity demands on core network infrastructure and wireless spectrum
- active control via data plans with data usage caps
- prevent poor qos due to congestion
User:
- reduce access cost
- increase network access performance
- lower power use
What are key issues and questions for mobile offloading?
- Offloading w/o breaking app connections (client involvement? Sophisticated infrastructure?)
- When to offload? Who decides - device or operator?
- What to offload? Which apps are suitable
- To which network? Cost, Capacity, Availability?
- Energy implications - 1 vs 2 interfaces
Name and explain shortly the 5 basic concepts of offloading?
- Independent AN: no operator ctrl, device controlled
- independent or coop AN: route via inet to home operator to allow operator ctrl
- Operator ctrl’ed AN: operator ctrls offloading (wifi -> operator network)
- Relay via peer: LTE D2D, wifi direct: operator/peer ctrl’ed, both to same base station
- time shifting (for delay tolerant): wait until wifi, opportunistic content dissemination
AN = access network
Explain the role of mobility for mobile offloading
Mobility as problem solved by these systems:
- network attachment point change
- existing flows might be disrupted
Mobility as enabler of solutions:
- human mobility has long pause times in a small set of locations
- mobility brings devices into contact w/ multiple networks: opportunities for data offloading
- mobility enables content distribution: store-and-carry forward
Name some technical aspects of mobile offloading
- Discovering networks
- Predicting future availability
- Choosing networks
- Authentication
- Making or maintaining connections (handover)
- Duration of WLAN access
Distinguish 3 offloading initiators
Network-initiated:
- centralized offloading
- network-operator makes the decision
- uses comprehensive knowledge about load situation (availability of WLANs)
User-initiated:
- Decentralized decision
- User decides when to offload
- Possible also for which applications
Special case: Device-initiated:
- Switching to known WLANs whenever available
- Application controls in th Emobile device setting to limit cell usage
Explain the basic concept of I-WLAN
Offloading to 3GPP network and WLAN
- Loggin into WLAN w/ cellular provider creds
- Access to home mobile network services
- RADIUS auth
- Radius -> Home mobile networks
- IPSec tunnel from mobile device to home mobile network
Explain the basic concept of GAN
Generic Access Network: Access to home mobile network via arbitrary IP network
- Access to home network services
- Seamless service continuity
- Treat external WLAN is mobile network BS
- Add GAN controller to home network, analogous to Radio Network Controller (multi BS controller)
- Connect via IPsec to GANC
Name some issues with offloading
Complex landscape of many operators and WLAN hotspot providers -> vertical handover procedures are non-trivial
WLAN subject to broader wireless interface -> not necessarily predictable what wlan can offer
What is mobile computational offloading and why do want to do this?
Offload computation to external device.
- mobile device rely on finite energy sources (but transmission has overhead too)
- mobile devices have less computation power
- computation is cheaper on static resources
- data might already reside in cloud
Which 2 targets can be used for offloading?
- Infrastructure (cloud, edge)
- Other mobile devices (peers)
Which degrees of offloading can be distinguished?
- Mobile app only on device
- Mobile app on device (data stored externally, app interacts w/ backend)
- Mobile app features a frontend on mobile (data stored externally, input/output from/to backend)
- Mobile app is just ui (data, app & presentation logic in cloud)
What is cyber foraging? What are issues with it?
Offloading computation to device nearby (e.g. laptop) which might communicate with other services online
- How to discover?
- How to establish trust?
- What kind of trust?
- How to load balance/administer/quick-start surrogates?
- Scale? additional Infrastructure?
What is a cloudlet?
Virtualized resources in the one-hop environment
Name two central issues w/ offloading to peers
Motivation: Why should they compute sth for you?
Reliability: Would a node get back the results?
What do we need to develop and execute apps in comp offloading to peers?
- decompose service into components of computation
- Instantiate set of components in env
- Tie I/O together
