lecture’l1’and’l2’ - aalborg...

Lecture L1 and L2

Network Coding: Paving the Way for a New Internet

The Telegraph System

•  Point to Point links •  Text oriented •  Paddington sta;on to West Drayton in 1839

The Telephone System

•  Voice oriented •  Star;ng in 1876 and onwards •  One line per communica;on partner •  Star architecture •  Later circuit switched

The Telephone System

The Internet

•  Paul Baran 1960s

Circuit switched to packet switched

Not Evolu;on, but Revolu;on

(Disintergra;on of curcuit)

The Internet

•  Mul;ple Service •  Packets do not have to

follow a given route and can change the route on the fly (delay!)

•  In prac;se single path communica;on

•  Not good for security •  Not exploi;ng full

poten;al of the network

Single Path vs Mul; Path

•  Comparison with the brain

•  Our brain uses mul; paths –  Reliability (Pain)

Access A

ccess •  Comparion with ants

•  Food retrival strategies

Cloudy Times

The Coded Internet

Packet switched to coded ...

•  Throughput •  Reliability •  Delay •  Security •  Complexity

•  Wireless meshed networks •  IoT/M2M/D2D

•  Storage and cloud services •  Content centric networks

Not Evolu;on, but Revolu;on

Compute and forward

(Disintergra;on of packet)

Samsung G

alaxy Tab 3 10.1 P5200 295.6 x 204 2560x1600

Samsung G

alaxy Tab 3 10.1 P5200 243.1 x 176.1 1280x800

Samsung G

alaxy Tab 3 8.0 209.8 x 123.8 1280x800

Samsung G

alaxy Tab 3 7.0 188 x 111.1 1024x600

Samsung G

alaxy Note II

N7100

151.1 x 80.5 720x1280

Samsung I9295 G

alaxy S4 Ac;ve

139.7 x 71.3 1080x1920

Samsung G

alaxy Ace 3

121.2 x 62.7 480x800

5G Challenges

•  More mesh topologies –  IoT/M2M/D2D –  mmWave network -‐> mul; path / frequent handover

•  Storage as integral part of the network –  Distributed edge caching

•  Minimal delay –  New access (not related to NC) –  Distributed access

•  Mul;path •  Distributed data

•  Security •  Massive heterogenity in devices and networks

15

NEW CHALLENGES!

SRC

DST

R1

R2

R3

R4

50%

50%

50%

50%

0%

0%

0%

0%

Inter flow network coding

XOR type of coding COPE

CATWOMAN ...

Intra flow network coding

RLNC type of coding MORE ...

What is Network Coding?

16

Network Coding: The Bucerfly

•  Two packets a and b should be conveyed to two des;na;ons

•  Capacity per link can handle one packet per ;me slot

•  Bocleneck in the middle

•  Either packet a or b will path the bocleneck

b

b

a

a

a b

a a b

a

a

17


•  Ahlswede et. al. In 2000 •  Linear combina;on of

packets •  Max-‐flow min-‐cut

theorem •  store and forward

replaced by computed and forward

b

b

a

a

a b

a+b

a+b a+b

a a b b

Ahlswede, Rudolf; N. Cai, Shuo-‐Yen Robert Li, and Raymond Wai-‐Ho Yeung (2000). "Network Informa;on Flow". IEEE TransacGons on InformaGon Theory, IT-‐46 46 (4): 1204–1216. 18

Network Coding: The Bucerfly XOR opera;on •  Bitwise opera;on •  Same bit value results in „0“

•  Different bit value results in „1“

0011

0011

0101

0101

0101 0011

0110

0110 0110

0101 0101 0011 0011

CODING

0101 XOR 0011

0110

DECODING

0101 XOR 0110

0011

DECODING

0011 XOR 0110

0101 19


•  Adding complexity at some nodes of the network

•  Adding overhead in order to know what was coded (encoding vector)

a

b

+

a+b EV

=

0101 10

0110 11

11 0110 11 0110

0101 10 0101 10

0101 10

0101 10

0011 01

0011 01

0011 01

0011 01 0011 01 20

Kirchhoff versus Network Coding

All engineers follow this principle!

Now we are alone ...!

21


Source: transmipng two informa;on en;;es

Receiver: receiving two

coded informa;on en;;es

22


23


24

SRC

DST

R1

R2

R3

R4

50%

50%

50%

50%

0%

0%

0%

0%

Inter flow network coding

XOR type of coding COPE

CATWOMAN ...

Intra flow network coding

RLNC type of coding MORE ...

What is Network Coding?

Network Coding in WiFi Networks

•  Core contribu;on by Kap et. al. „XOR in the Air“ applying XOR coding to WiFi enabled meshed networks

26

Topology

•  Two way relay (Alice and Bob)

•  Chain

•  X-‐ Topology

•  Cross

•  Cross with Overhearing

27

Alice and Bob

A B R

28

Alice and Bob: Forwarding

A B R

29


A B R

30


A B R

31


A B R

4 ;me slots for exchange

32

Alice and Bob: Network Coding

A B R

33


A B R

34


A B R

3 ;me slots for exchange 33% improvement

35


A B R

What do you need to make it happen? Talk to your neighbor (3min)

36


A B R

What do you need to make it happen? •  Memory: buffer sent packets for decoding

•  Delay packets at R to promote coding 37

Alice and Bob

w/o NC with NC

Gain = 33% 38

X Topology with Overhearing

C A

B D

R

39


C A

B D

R A

40


C A

B D

R

A

41


C A

B D

R C

42


C A

B D

R

C

43


C A

B D

R A

A

44


C A

B D

R

C

CA

A

45


C A

B D

R

C

CA

A

&

46


C A

B D

R C

&

A

CA &

&

47


C A

B D

R C

C

A

A

&

Gain = 33% 48

Cross Topology with Overhearing

C

A

B

D R

Overhearing the ac;vi;es of the neighboring node

49

Cross Topology with Overhearing 1/5

C

A

B

D R A

AA

50


C

A

B

D R A

B

AA

BB

51


C

A

B

D R A

B

C

A

B

AA

BB

C

C

52


C

A

B

D R A

B

C

A

B

AA

BB

C

C

D

D

D

53


C

A

B

D R A

B

C

A

B

AA

BB

C

C

D

D

D

&

&&

&

54


C

A

B

D R AA

BB

C

C

D

D

&

&&

&

A

B

DC

55

C

A

B

D D C

B

A


R AA

BB

C

C

D

D

&

&&

&

A

B

DC

Gain = 60% 56

Cross Topology with Overhearing Problems

C

A

B

D R

57

MODEL FOR ALICE AND BOB (SYMMETRIC TRAFFIC) WITH MEDIUM ACCESS

58

Assump;on

•  Alice and Bob have no direct connec;on •  Same amount of traffic is generated by Alice and Bob

•  Medium Access Control (MAC) is based on IEEE802.11, i.e. CSMA/CA

A R B

59

Throughput Model A & B

Load 1: w/o NC the relay sends twice as much as Alice and Bob. No impact on the throughput.

15% 15% 30%

60

Throughput Model

Load 2: w/o NC the relay sends twice as much as Alice and Bob and channel capacity is reached. S;ll no impact on the throughput.

25% 25% 50%

61

Throughput Model

Load 3: w/o NC Alice and Bob are „stealing“ the capacity from the relay. 802.11 fairness destroys the performance of the system.

29% 29% 42%

62

Throughput Model

Load 3: w/o NC Alice and Bob are „stealing“ the capacity from the relay. 802.11 fairness destroys the performance of the system.

33% 33% 33%

63

Throughput Model

Load 1: w NC the relay sends the same amount of data as Alice or Bob.

15% 15% 15%

64

Throughput Model

Load 2: w NC channel capacity is NOT reached

25% 25% 25%

65

Throughput Model

Load 3: w NC Alice, Bob and the relay live in perfect harmony, each of the en;;es requests one third of the capacity

29% 29% 29%

66

Throughput Model

Load 4: w NC Alice, Bob and the relay live in perfect harmony now the channel capacity is reach and therefore the throughput remains constant.

33% 33% 33%

67

R

A

B

C

D

r

s

i

i

i

r

i

s

i

i

r

i

i

s

i

r

i

i

i

s

s

r

i

i

i

s

i

r

i

i

s

i

i

r

i

s

i

i

i

r

R

A

B

C

D

r

s

i

i

i

r

i

s

i

i

r

i

i

s

i

r

i

i

i

s

s

r

i

i

i

pure re

laying

Cross Forwarding

•  Whatever goes into the relay has to be forwarded.

•  What to do if there is not enough capacity?

68

r

R

A

B

C

D

r

s

i

i

i

r

i

s

i

i

r

i

i

s

i

r

i

i

i

s

s

r

r

i

i

s

i

i

r

R

A

B

C

D

r

s

i

i

i

r

i

s

i

i

r

i

i

s

i

r

i

i

i

s

s

r

r

i

i

NC w/o overhearing

XOR Network Coding

•  Each out node sends to the relay •  And for each pair the relay sends out one coded packet

69

R

A

B

C

D

r

s

i

r

r

r

i

s

r

r

r

r

r

s

i

r

r

r

i

s

s

r

r

r

r NC with overhe

aring

XOR Network Coding with overhearing

•  Each outer node sends a packet to the relay •  Each outer node will overhear two packets from neighboring nodes

•  Relay sends out one full coded packet 70

Throughput

R

A

B

C

D

R

A

B

C

D

R

A

B

C

D

R

A

B

C

D

R

A

B

C

D

71

REAL WORLD: ERROR PRONE WIRELESS LINKS

72

CATWOMAN (2011)

•  Mul;hop network based on BATMAN rou;ng (dras RFC)

•  Implementa;on of network coding on real WiFi access points

•  Mul; hop

•  Part of Linux Kernel 3.10

73

CATWOMAN Testbed

74

CATWOMAN Testbed

75

Network Coding in WiFi Networks Theory CATWOMAN Testbed

•  AAU and MIT collabora;on •  Two way relay •  Inter flow NC needs synchronous flows

A R B

76

CATWOMAN Results

77

Comparison: Energy Per Bit

78

The Cross (MAC) Hardware •  16bit PIC24 microprocessor •  nRF905 transceiver (433 MHz, 50

kbps)

Sosware •  MAC-‐Protocol: A CSMA/CA design •  Network Coding: A simple XOR

design [COPE06]

Capability •  Easy access to the sosware •  Full control of both HW and SW

79

CROSS Measurement Expected

80

Reliable Mul;cast

81

Reliable Mul;cast: Mo;va;on

•  Wireless has the advantage of inherent broadcast

•  Wireless is error prone

•  Coding versus Retransmissions

•  N = number of packets

•  J = number of users

82

Simple Broadcast

Ini;al Phase N=1000 ; J=10

Recover

Recover 1

Recover

Recover 2

Recover

Ini;al Phase N=1000 ; J=1000

Recover

Recover 1

Recover

Recover 2

Recover

Recover 3

Recover

83

In wireless networks –  Broadcast advantage –  Genera;on of packets (three in this case) –  Packet erasures (losses)

p1 p2 p3

p1

p3

p2 p3

p1 p2

p1+ p2 + p3

p1+ p2 + p3

p1+ p2 + p3

Index Coding

p1

p2

p3

p1+ p2 + p3

84

Index Coding

9 13 27 31 45

Ʃ3 Ʃ3 Ʃ1 Ʃ2 Ʃ2 Ʃ2 Ʃ1

1 2 7 3 4 5 6

8 9 14 10 11 12 13

15 16 21 17 18 19 20

22 23 28 24 25 26 27

29 30 35 31 32 33 34

36 37 42 38 39 40 41

43 44 49 45 46 47 48

1 2 7 3 4 5 6

8 9 14 10 11 12 13

15 16 21 17 18 19 20

22 23 28 24 25 26 27

29 30 35 31 32 33 34

36 37 42 38 39 40 41

43 44 49 45 46 47 48

1 2 7 3 4 5 6

8 9 14 10 11 12 13

15 16 21 17 18 19 20

22 23 28 24 25 26 27

29 30 35 31 32 33 34

36 37 42 38 39 40 41

43 44 49 45 46 47 48

1 7 41 21 25 29 33

19 36

And then ?

85

Index Coding

Recover I

Recover

R2

Recover

R3 R4

Recover I

Recover

R2

Ini;al Phase N=1000 ;J=1000

Recover

Ini;al Phase N=1000 ;J=10

Recover

86

COPE ON N810 (2008)

•  XOR coding on N810 (linux device by NOKIA)

•  Remote setup –  Predefined set –  Random set

•  Constantly exchanging recep;on updates (who needs what)

•  Overall goal is to let all devices have all informa;on

•  Enriching teaching ac;vi;es

Results: N810 Disjoint StarWng Phase: (no duplicates on beginning)

Random StarWng phase: (duplicates are possible)

PROTOCOLS MATTER!

Network Coding: The Bucerfly++

a

a

a

c

a b c

c

c

c

b

c a

a+b

b+c

a+c

a+b+c ? ? ?

a

b

b

89

Network Coding: The Bucerfly++

a

a

a

c

a b c

c

c

c

b

c a

a+b

b+c

a+c

a+b+c ? ? ?

a

b

b

What did you send? What did you send?

What should we send?

What did you send? What did you send?

What did you recveive? What did you recveive?

90

Inter Flow Network Coding

Pro

•  No delay •  Low complexity •  Easy integra;on with

commercial solu;ons

•  Some ideas are used in ANALOG network coding

Cons

•  Planning and book keeping needed

•  Certain traffic characterisitcs are beneficial in mesh networks

•  Symmetric traffic allows for more coding poten;al

91

lecture’l1’and’l2’ - aalborg...

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