Cloud Processing and Edge Caching in HetNets: A Delivery Time Perspective

Size: px

Start display at page:

Download "Cloud Processing and Edge Caching in HetNets: A Delivery Time Perspective"

Augustine Robbins
5 years ago
Views:

Institute for Digital Communication Systems RUB, Bochum, Germany Joint CommNet2 &

1 Cloud Processing and Edge Caching in HetNets: A Delivery Time Perspective Aydin Sezgin Joint work with: Jaber Kakar, Soheil Gherekhloo and Zohaib Hassan Awan Institute for Digital Communication Systems RUB, Bochum, Germany Joint CommNet2 & icore Workshop 2017 A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 1

2 Contents RUB 1 Motivation 2 F-RAN System Model 3 Performance Metric: Delivery Time per Bit (DTB) 4 Main Result: Optimal Latency-Fronthaul-Cache Tradeoff 5 Conclusion A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 2

3 Introduction RUB Content delivery, e.g., video, is driving growth in wireless traffic Source: CISCO VNI Mobile, 2017 A. Sezgin Delivery Time in Cloud- and Cache-Aided HetNets 3

4 Introduction RUB Content delivery, e.g., video, is driving growth in wireless traffic Source: CISCO VNI Mobile, 2017 Solutions: Small cells In-network caching Centralized cloud processing A. Sezgin Delivery Time in Cloud- and Cache-Aided HetNets 3

5 RUB Introduction: Edge vs. Cloud-based Solutions cloud.png (PNG Image, pixels) server.jpg (JPEG Image, pixels) file:///h file:///home/kakarjyd/dropbox/conference_pap Cloud Fronthaul U2 enb Cache vs. U1 U2 enb U1 HeNB 1 of 1 15/05/1 HeNB enb: evolved NB HeNB: Home enb Cache-aided wireless network Cloud-aided wireless network 1 of 1 Edge caching: Storage of popular content at wireless edge nodes Reduces latency due to limited backhaul usage A. Sezgin (aydin.sezgin@rub.de) Centralization of baseband processing at the cloud Centralized interference management Delivery Time in Cloud- and Cache-Aided HetNets 4

6 RUB Fog Radio Access Network (F-RAN) F-RAN: Cloud- and cache-aided wireless network for content delivery cloud.png (PNG Image, pixels) server.jpg (JPEG Image, pixels) Cloud Fronthaul U2 enb U1 Cache 1 of 1 15/05/17 14:12 HeNB F-RAN Synergistic benefits of both networks 1 of 1 15/05/17 14:04 Goal: F-RAN latency-fronthaul-cache tradeoff A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 5

7 RUB System Model System parameters: cloud.png (PNG Image, pixels) File 1 File 1 File 2 U1 Placement phase: enb... File 2 µ File i... C F HeNB Wireless Links µ : fractional cache size, CF : fronthaul capacity U2 No inter-file coding Cloud and enb co-located Arbitrary number of files allowed A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 6

8 RUB System Model System parameters: µ : fractional cache size, CF : fronthaul capacity files.png (PNG Image, pixels) file:///home/kakarjyd/dropbox/conference_ C F HeNB cloud.png (PNG Image, pixels) files.png (PNG Image, pixels) µ Wireless Links Demands U1 enb files.png (PNG Image, pixels) file:///home/kakarjyd/dropbox/conference_ U2 Time Cloud and enb co-located Arbitrary number of files allowed A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 6

9 RUB System Model System parameters: µ : fractional cache size, CF : fronthaul capacity files.png (PNG Image, pixels) C F HeNB cloud.png (PNG Image, pixels) files.png (PNG Image, pixels) µ Wireless Links files.png (PNG Image, pixels) U1 Demands file:///home/kakarjyd/dropbox/conference_... enb files.png (PNG Image, pixels) file:///home/kakarjyd/dropbox/conference_ files.png (PNG Image, pixels) U2... Time Cloud and enb co-located Arbitrary number of files allowed A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 6

10 Delivery Phase - Time Consideration Serial vs. parallel transmission: Delivery time: T F Request 1 A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 7

11 Delivery Phase - Time Consideration Serial vs. parallel transmission: Delivery time: T F T E files.png (PNG Image, pixels) files.png (PNG Image, pixels) Request 1 File size A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 7

Delivery Phase - Time Consideration Serial vs. parallel transmission: Delivery time: T F T E files.png (PNG Image, 352 144 pixels) files.

12 Delivery Phase - Time Consideration Serial vs. parallel transmission: Delivery time: T F T E files.png (PNG Image, pixels) files.png (PNG Image, pixels) Request 1 T P File size A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 7

13 Delivery Phase - Time Consideration Serial vs. parallel transmission: Delivery time: T F T F T E files.png (PNG Image, pixels) files.png (PNG Image, pixels) Request 1 T P Request 2 File size A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 7

Delivery Phase - Time Consideration Serial vs. parallel transmission: Delivery time: T F T E T E files.png (PNG Image, 352 144 pixels) T F files.png (PNG Image, 352 144 pixels) files.

14 Delivery Phase - Time Consideration Serial vs. parallel transmission: Delivery time: T F T E T E files.png (PNG Image, pixels) T F files.png (PNG Image, pixels) files.png (PNG Image, files.png (PNG pixels) Image, pixels) Request 1 T P Request 2 File size File size A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 7

15 Delivery Phase - Time Consideration Serial vs. parallel transmission: Delivery time: T F T E T E files.png (PNG Image, pixels) T F files.png (PNG Image, pixels) files.png (PNG Image, files.png (PNG pixels) Image, pixels) Request 1 T P File size T P Request 2 File size A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 7

16 Delivery Phase - Time Consideration Serial vs. parallel transmission: Delivery time: T F T E T E files.png (PNG Image, pixels) T F files.png (PNG Image, pixels)... files.png (PNG Image, files.png (PNG pixels) Image, pixels) Request 1 T P File size T P Request 2 File size A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 7

17 Bit-Pipe Model RUB Deterministic bit-pipe model [Avestimehr et al. 11] Example: Two-user broadcast channel (a) Gaussian case (b) Bit-pipe model y = h 1 x 1 + h 2 x 2 + z y = S q n1 x 1 S q n2 x 2 Real channels: 1 /2 log(snr i ) + n i Complex channels: log(snr i ) + n i A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 8

18 RUB Performance Metric: Delivery Time per Bit (DTB) Channels are modeled by bit-pipe model [Avestimehr et al. 11] Number of bit pipes: ndk and nf = dcf e nf HeNB cloud.png (PNG Image, pixels) files.png (PNG Image, pixels) µ nd1 U1 nd1 n = nd2 nd3 2 nd enb nd3 U2 Definition [Sengupta et al. 15] det (µ, nf, n) = max lim user s File size requests A. Sezgin (aydin.sezgin@rub.de) Delivery time File size Delivery Time in Cloud- and Cache-Aided HetNets 9

19 Main Result: Optimal DTB det Complete DTB characterization for serial and parallel transmission First, main result for serial case: DTB performance varies for distinct fronthaul regimes Low Intermediate High 0 n d2 max{nd2, n d3 } n F Class A ( High Fronthaul Threshold ) Enlarged Low High Class B ( Multiple Fronthaul Thresholds ) Low Intermediate High Class C ( Low Fronthaul Threshold ) Class D ( No Fronthaul Threshold ) Low Enlarged High Only Low For the sake of simplicity, let us consider a specific channel regime of Class A A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 10

20 Serial Transmission: Outline Optimal DTB Achievability BC DTB A 1 0 n F max{n d2, n d3 } n F > max{n d2, n d3 } Optimal DTB A 2 WL BN DTB B 1 0 µ (n) 1 µ Plot for Class A channel regime: n d1 + n d3 n d2 n d3 n d1 BC: Broadcast WL BN: Wireless bottleneck µ : µ needed such that wireless stage represents bottleneck A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 11

21 Serial Transmission: Outline Optimal DTB Achievability BC DTB A 1 0 n F max{n d2, n d3 } n F > max{n d2, n d3 } A 1 : T F = 0, T E = 1 Optimal DTB WL BN DTB A 2 B 1 0 µ (n) 1 µ Plot for Class A channel regime: n d1 + n d3 n d2 n d3 n d1 BC: Broadcast WL BN: Wireless bottleneck µ : µ needed such that wireless stage represents bottleneck A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 11

22 Serial Transmission: Outline Optimal DTB Achievability BC DTB A 1 0 n F max{n d2, n d3 } n F > max{n d2, n d3 } A 1 : T F = 0, T E = 1 B 1 : T F = 0, T E = 1 Optimal DTB WL BN DTB A 2 B 1 0 µ (n) 1 µ Plot for Class A channel regime: n d1 + n d3 n d2 n d3 n d1 BC: Broadcast WL BN: Wireless bottleneck µ : µ needed such that wireless stage represents bottleneck A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 11

23 Serial Transmission: Outline Optimal DTB Achievability BC DTB A 1 0 n F max{n d2, n d3 } n F > max{n d2, n d3 } A 1 : T F = 0, T E = 1 B 1 : T F = 0, T E = 1 Optimal DTB WL BN DTB A 2 B 1 0 µ (n) 1 µ Plot for Class A channel regime: n d1 + n d3 n d2 n d3 n d1 BC: Broadcast WL BN: Wireless bottleneck A 2 : T F > 0, T E = 1 µ : µ needed such that wireless stage represents bottleneck A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 11

Serial Transmission: Details on DTB Achievability at B 1 Common, private and interference neutralizing information n IN = v IN u IN B 1 : T F = 0, T E = 1 L max rate params.

24 Serial Transmission: Details on DTB Achievability at B 1 Common, private and interference neutralizing information n IN = v IN u IN B 1 : T F = 0, T E = 1 L max rate params. min{r U1, R U2 } s.t. Cache capacity constraint Reliability constraints rate params 0 det = T E L = WL BN DTB U 1 U 2 A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 12

25 Example Serial Transmission: DTB Achievability at B 1 Cache-only scheme requiring common, private and interference neutralizing information Example: n d1 = 2, n d2 = 5, n d3 = 4, µ (n) = 1 /3 Lower bound: 1 /3 cu/bit A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 13

26 Serial Transmission: Details on DTB Achievability at A 2 Fronthaul-edge transmission scheme Send µ (n) L bits over fronthaul link + then apply wireless transmission scheme of B 1 T F = µ (n) L BC DTB n F, T E = DTB B 1 A 1 0 n F max{n d2, n d3 } n F > max{n d2, n d3 } Optimal DTB A 2 µ (n) nf B 1 WL BN DTB 0 µ (n) 1 µ Plot for Class A channel regime: n d1 + n d3 n d2 n d3 n d1 A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 14

27 What happens for Parallel Transmission? n F,max (n): n F needed such that wireless stage represents bottleneck Fronthauling always useful if n F n F,max (n) When n F = n F,max (n), A 1 = B 1 Always n F,max (n) n d1 no congestion at HeNB Optimal DTB WL BN DTB A 1 0 n F < n F,max (n) n F n F,max (n) ( ) 2 A 1 = 0, nf +max{nd2,nd3} B 1 0 µ P (n, n) F2 µ P (n, n) 1 F1 µ Plot for Class A channel regime: n d1 + n d3 n d2 n d3 n d1 A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 15

28 Serial vs. Parallel Transmission: An Example Example: n d1 = 2, n d2 = 5, n d3 = 6, n F = 1 Lower bound: 1 /4 cu/bit Serial: µ = 1 /2, L = 4 Parallel: µ P = 1 /4, L = 4, n F,max = 2 Separability in HeNB s delivery content: µ (n) L = µ P (n F, n) L +n F A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 16

29 Synergy: Cloud and Edge Processing BC DTB A 1 0 n F max{n d2, n d3} n F > max{n d2, n d3} 0 n F < n F,max(n) n F n F,max(n) Optimal DTB A 2 Optimal DTB A 1 ( ) A1 = 0, 2 nf +max{nd2,nd3} WL BN DTB B 1 WL BN DTB B 1 0 µ (n) 1 µ 0 µ P (nf2, n) µ P (nf1, n) 1 µ Serial transmission Parallel transmission Synergy for µ (0, µ ) if n F > max{n d2, n d3 } µ (0, µ P ] if n F < n F,max A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 17

30 Special Case: Lower Bound for n F = 0 Distinct files requested S: HeNB cached content x T E 1 function of S Decodability of W 1 and/or W 2 for distinct information subsets Decoded File(s) W 1 W 2 {W 1, W 2} Required Information Subset y T E 1 {S, S q n d2 x T E y T E 2 2 } {y T E 1, y T E 2 } {S, S q max{n d2,n d3 } x T E 2 } 5 lower bounds A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 18

31 Conclusion RUB Complete characterization of latency-fronthaul-cache tradeoff for 2-user F-RAN Synergestic benefits of cloud and edge processing is exploited in F-RAN For further details: Kakar et al., Fundamental Limits on Delivery Time in Cloud- and Cache-Aided Heterogeneous Networks A. Sezgin Delivery Time in Cloud- and Cache-Aided HetNets 19

32 Thank you for your attention. A. Sezgin Delivery Time in Cloud- and Cache-Aided HetNets 20

33 Related Works RUB 2017: Kakar et al., Fundamental Limits on Latency in Cloudand Cache-Aided HetNets 2017: Kakar et al., Fundamental Limits on Latency in Transceiver Cache-Aided HetNets 2016: Azimi et al., Fundamental Limits on Latency in Small-Cell Caching Systems: An Information-Theoretic Analysis 2016: Tandon et al., Cloud-Aided Wireless Networks with Edge Caching: Fundamental Latency Trade-Offs in Fog Radio Access Networks 2015: Sengupta et al., Cache Aided Wireless Networks: Tradeoffs between Storage and Latency 2015: Maddah-Ali et al., Cache-Aided Interference Channels 2011: Avestimehr et al., Wireless Network Information Flow: A Deterministic Approach A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 21

34 RUB Serial Transmission: Optimal DTB nd1 nf HeNB µ cloud.png (PNG Image, pixels) nd U1 ( 0LB (n) 2 = max 1 1,, nd3 max{nd1,nd2 } 2 max{nd1 +nd3,nd2 } ( files.png (PNG Image, pixels) 00LB (n) = max nd3 enb U2 0LB (n), ) ) 1 nd3 nd2 Optimal DTB n o 2 µ max 1 µ, max{n, 0LB (n) for nf nd2 n,n } d2 d2 d3 ( 1 µ ) nd2 00 max nf + 1 nf LB (n), for n n max{n, n } F d2 d2 d3 2 µ, 0LB (n)?det (µ, nf, n) = max{n d2,nd3 } 2 µ + 1 max{nd2,nd3 } 0 (n), LB nf nf max for nf 1 µ + 1 nd2 0 (n), 0 (n) LB LB n n max{n, n } 1 of 1 15/05/17 18:52 F A. Sezgin (aydin.sezgin@rub.de) F d2 Delivery Time in Cloud- and Cache-Aided HetNets d3 22

35 RUB Parallel Transmission: Optimal DTB nd1 nf HeNB µ cloud.png (PNG Image, pixels) files.png (PNG Image, pixels) nd U1 2 ( 0LB (n) = max nd3 enb 1 1,, nd3 max{nd1,nd2 } 2 max{nd1 +nd3,nd2 } ) U2 Optimal DTB?det (µ, nf, n) = max 1 of 1 n o 1 µ 2 µ,, 0LB (n) nf + nd2 nf + max{nd2, nd3 } 15/05/17 18:52 A. Sezgin (aydin.sezgin@rub.de) Delivery Time in Cloud- and Cache-Aided HetNets 23

Storage-Latency Trade-off in Cache-Aided Fog Radio Access Networks

Storage-Latency Trade-off in Cache-Aided Fog Radio Access Networks Joan S. Pujol Roig Imperial College London jp5215@imperial.ac.uk Filippo Tosato Toshiba Research Europe filippo.tosato@toshiba-trel.com