UCAN: A Unified Cellular and Ad-Hoc Network Architecture

1. UCAN: A Unified Cellular and Ad-Hoc Network Architecture Published by: Haiyun Luo, Ramachandran Ramjee, Prasun Sinha, Li (Erran) Li, Songwu Lu Rick Szcodronski ECE 256 February 12, 2008

2. A A Cellular vs. 802.11 Networks 1xEV-DO (HDR) 802.11b • Range = 250 m. • 1 - 11 Mbps • CSMA/CD • Range = 20 km. • 38.6 Kbps – 2.4 Mbps • CDMA / TDMA

3. Recall: Rate Control Rate = 10 B C E A D Rate = 20 Both 802.11 and HDR use Rate Control to transmit data

4. 38.6 Kbps 11 Mbps 2.4 Mbps 11 Mbps Motivation for UCAN B A

5. B R D Simple Test Layout HDR HDR 802.11b

6. Simple Test Results

7. UCAN Architecture • 3 Challenges Arise • Who is the best proxy? • What happens when route breaks? • Why should I forward your packets?

8. Proxy Application RTREQ RTREQ RTREQ Proxy Discovery • HDR Channel Rate Drops • D Sends Route Request Using 802.11 • RTREQ propagates using “Proxy Discovery” protocol • P sends proxy application to Base • Base updates proxy tables • Base routes packets for D via P P D 2.4 Mbps R R 38.6 Kbps

9. Greedy Proxy Discovery • Proxy Discovery Process • Periodic broadcast of HDR rate to neighbors • Client Unicasts RTREQ • Once TTL=0 or no better rate, proxy sends RTREQ to base • Advantages • Easy to implement • Low uplink overhead • Disadvantages • May not find best proxy! • High energy consumption

10. On-Demand Proxy Discovery • On-Demand Proxy Discovery • Broadcast RTREQ until TTL=0 • Send RTREQ to base if rate > previous • Clients/Base compare Seq_NO from previous entry • Advantages • Finds best proxy • Lower energy consumption • Disadvantages • High HDR uplink contention • Higher 802.11 congestion for large number of clients • 3 Challenges Arise • Who is the best proxy? • What happens when route breaks? • Why should I forward your packets?

11. Failure! Routing Failures • P,R,D are mobile and can break the relay path • R moves, P tells Base • Base clears proxy table • Base sends packets direct to D via HDR • D can re-initiate “proxy request” P R R D

12. Proxy Maintenance • Long Term Maintenance • P,R,D are mobile! • P piggybacks its rate on packets • D compares P’s rate to a threshold of its own • D requests new proxy • Short Term Maintenance • Base station can send packet to any client on D’s route • Increased Channel Diversity R=100 P R=60 R R R=30 D R=10

13. HDR Scheduling A DRC = 12 B DRC = 6 C DRC = 3 http://en.wikipedia.org/wiki/Evolution-Data_Optimized • Q: How do slots get scheduled fairly? • A: Proportional Fairness Scheduling D DRC = 1

14. Proportional Fairness Scheduling • 2 Goals • Maximize cell throughput • Maintain minimum individual Quality of Service • How can this extend to UCAN? • Proportional Fairness Scheduling • Tk(t) = Average Throughput • Rk(t) = Instantaneous Rate • Slot Winner = min{Tk(t)/Rk(t)} A DRC = 12 1 Slot C D DRC = 1 16 slots DRC = 3 4 Slots B DRC = 6 1 Slot A B C A B A D C B A Time

15. UCAN Scheduling • HDR uses proportional fairness scheduling • Maximize throughput, maintain minimum QoS • Client scheduled when downlink rate is high • UCAN Scheduling • Using Proxy’s Rk(t): unfair throughput gain • Using Destination’s Rk(t): distributed gain 1 2 A B No Relay R=2 R=1 1 2 A B* Relay w/ Prxy’s R R=2 R=2 A 1 2 3 R=2 B A A B* Relay w/ Dst’s R R=1 R=2 R=2 R=2 * Packets received using Proxy A

16. Secure Crediting • Why should I forward your packets? • Throughput gains for Active Clients • Wasted energy for Non-active Clients • Solution for Non-Active Clients • Award credits • Problem: Watch out for credit scam • Solution: Piggyback Message Authentication Code (MAC) in RTREQ

17. UCAN Performance Evaluation • HDR downlink degrades rapidly with distance • Average data rate = 600 Kpbs • Instantaneous Rate varies a lot in small time scale • Motivation for UCAN!

18. UCAN Performance Evaluation • Single Destination Client • Static destination = .8R • Mobile Relays • Variables • Relay Speed • Relay Density • UDP vs. TCP • Greedy vs. On-Demand P R R D

19. UCAN Throughput Evaluation • Throughput Trends • Gain over No-Relay stays constant with varying speed • Throughput Gain:On-Demand > Greedy • Gain over No-Relay increases with increased clients

20. UCAN HDR Uplink Evaluation On-Demand’s higher throughput comes at the price of increased HDR uplink overhead

21. UCAN Energy Evaluation • Energy Trends • Energy increases as clients increase • Energy increases as speed increases • Energy Comparison: Greedy > On-Demand

22. UCAN Multiple Client Evaluation • Multiple Client Setup • 80 Clients (5 Destination Clients) • ALL Clients are mobile • TTL = 1-4

23. UCAN Review • Questions • What is the energy comparison between Active UCAN Clients and Non-Active HDR Clients? • What happens when > 5 Clients are Active? • How will credits be implemented? • Can UCAN work across carriers (e.g. Verizon, Cingular, US Cellular)? • Can the HDR uplink support VOIP while using UCAN? • Promising Future • 310% Single User Gain • 60% Multiple User Gain • Always-on Internet (Indoors, Train, Car, etc.)

24. Questions or Comments?