When Priority Resolution Goes Way Too Far: An Experimental - PowerPoint PPT Presentation

When Priority Resolution Goes Way Too Far: An Experimental Evaluation in PLC Networks Cristina Cano and David Malone 09/06/2015

2/9 Motivation In-house Power Line Communications Standards: Homeplug/Homeplug AV/IEEE 1901 Qualcomm Atheros reports 100 M PLC devices shipped Research efforts focused on the physical layer PLC MAC is relatively unexplored MAC like IEEE 802.11, but: Deferral counter Strict priority resolution scheme Negotiated tone map Large aggregated frames

3/9 Priority Resolution Definition of 4 CAs CA3/CA2 and CA1/CA0 share W i (BO) and M i (DC) values Strict prioritisation through Priority Resolution Slots (PRS) RIFS CIFS FRAME FRAME ... ACK PRS0 PRS1 BACKOFF TRANSMISSION TRANSMISSION t But, only present after successful transmissions!

4/9 Testbed Setup Devices Zyxel PLA4215 PLC adapters with INT7400 chipset Connected via an UPS unit Attached to the Gigabit Ethernet port of Soekris boxes Tools: Iperf : Generate traffic/measure per-second throughput Faifa Count channel accesses (Jain’s Fairness Index) Spectrum Analyser Get more insight on the transmissions on the channel

5/9 PRS?

6/9 Lower Priority Starvation Two saturated stations in different CAs. How strict is the prioritisation? 250 200 CA3 av. 179.3564 Frequency 150 min. 0 max. 203.0952 100 50 0 0 20 40 60 80 100 120 140 160 180 200 S CA3 [Mbits/s] 2500 2000 CA2 av. 1.2075 Frequency 1500 min. 0 max. 181.5979 1000 500 0 0 20 40 60 80 100 120 140 160 180 200 S CA2 [Mbits/s]

7/9 Higher Priority Contention 3 CA3 Stations. What???!!! 1000 CA3 Frequency av. 58.4822 500 min. 0 max. 197.1211 0 0 20 40 60 80 100 120 140 160 180 200 S CA3 [Mbits/s] 1000 CA3 Frequency av. 44.3043 500 min. 0 max. 200.4139 0 0 20 40 60 80 100 120 140 160 180 200 S CA3 [Mbits/s] 1000 CA3 Frequency av. 48.2669 500 min. 0 max. 199.2262 0 0 20 40 60 80 100 120 140 160 180 200 S CA3 [Mbits/s]

8/9 Higher Priority Contention Oscillatory Behaviour! 200 180 160 140 Throughput [Mbits/s] 120 100 80 60 40 20 0 0 50 100 150 200 250 300 t Tone map information is sent at CA2!

9/9 Conclusions Outcomes Lower-CA traffic Suffers from starvation High variability (aggregation and buffer management) Higher-CA flows Oscillatory behaviour Some plausible solutions Reserved priority for control messages Police/Shape higher classes Limit variability of aggregation JSAC Issue on PLC in Networking Ecosystem: Submission 1 July 2015.