Mobile Networks (TDDD66)
Fall 2015
Examiner: Niklas Carlsson
niklas.carlsson@liu.se
www.ida.liu.se/~nikca/
Week 1
• WiFi speed: Home vs hotspot
WiFi speed: Home vs. hotspot
Channel 1
1
ChannelChannel
11
AP
AP
AP
AP
AP
Channel 1AP
Channel 6
Channel 6
• As you change location, you see different WiFi speed …
• There is a limited bandwidth spectrum ...
• Among other things, interference and channel selection affect the
efficiency of WiFi channel usage …
Week2
• One of the following two
– Radio energy usage
– Energy optimization: WiFi vs 3G/4G
Power
Radio energy usage: WiFi or LTE
…
p1
p0
p2,p3
p4
…
p0
?
• Phones etc. have limited batteries, with the radio consuming some
fraction of the total energy usage ...
• (Optimal) energy-delay tradeoff (e.g., delay-tolerant protocol using
PSM with multiple power levels)
• Power model (e.g., simple on-off or more complex)
• Impact of mobility (e.g., when driving your hybrid low-power car)
Energy optimization: WiFi vs 3G/4G
• Smartphones can typically use both WiFi and 3G/4G (each with
different characteristics) …
• Imagine that you are a developer and want to implement a protocol
that minimizes the energy usage associated with downloading a
large file, given access to both technologies and some download
time constraint …
• Impact and opportunities associated with mobility (e.g., when
driving your hybrid low-power car)
Week 3
• One of the following
– Power-aware routing
– Multi-path throughput optimization
Power-aware routing
?
?
• Reasonable per-node power model for information transmission
• (Optimal) energy-efficient path for a topology
• Distributed vs central routing decisions ...
Multi-path throughput optimization
?
?
• Reasonable per-node throughput model for information transmission
• (Optimal) multi-path throughput for a topology
• Distributed vs. central routing decisions ...
Week 4
• Tools and evaluation techniques
Tools and evaluation techniques
Experiments: e.g., using
dummynet (bandwidth,
delay, packet losses)
Simulations: e.g., using ns-3
(mobility, bandwidth, energy,
packet losses, protocols, …)
Analytic: e.g., using mathematical and
statistical tools that you know and/or can learn
• Method selection when evaluating the performance
– What, when, why ...?
– Tradeoffs …
vs …
Week 5
• Why I only get a small fraction of the
advertised 4G speed …
Why I only get a small fraction of
the advertised 4G speed …
RTT1, Pr(loss1)
RTT2, Pr(loss2)
• End-to-end arguments (complexity and end points), channel
interfaces, etc. …
• (Optimal) theoretic throughput
• Measured throughput
Week 6
• One of the following three
– Cache-size optimization and resource usage
– HTTP-based adaptive streaming
– Multicast using WiFi, LTE, or both
Cache-size optimization and resource usage
Proxy
Views (v)
Client
Example factors (miss cost and hit rates):
•
Cache size
•
Content type
•
Content size
•
Popularity
•
Locality
•
…
Rank (r)
HTTP-based adaptive streaming
Large
fraction of
Internet traffic
Client
1,4
1,3
1,2
1,1
2,4
2,3
2,2
2,1
3,4
3,3
3,2
3,1
4,4
4,3
4,2
4,1
5,4
5,3
5,2
5,1
Proxy
6,4
6,3
6,2
6,1
7,4
7,3
7,2
7,1
1,4
1,3
1,2
1,1
2,4
2,3
2,2
2,1
3,4
3,3
3,2
3,1
4,4
4,3
4,2
4,1
Client
5,4
5,3
5,2
5,1
6,4
6,3
6,2
6,1
7,4
7,3
7,2
7,1
Proxy
• Resource usage, cache hitrate, ...
16
Multicast using WiFi, LTE, or both
• The broadcast domain of wireless networking provide natural
opportunity for resource saving: Many users can obtain the
same message using a single transmission ...
– Live events: Super bowl, live soccer, Eurovision song contest
– Stored content: Highlights, news, ...
• E.g., where, when and how (do we best save bandwidth) ...
Week 7
• Select one scenario that you have not yet
considered (from week 2 or 6)