WinlabMadwifi → Pipeline MAC paper Discussion
Cooperative Scheduling Via Pipelining in 802.11 Wireless Networks
Ramana Rao Kompella, Sriram Ramabhadran, Ishwar Ramani, Alex C. Snoeren
University of California, San Diego
- Per packet Micro-scheduling need firmware/hardware(MAC) upgrade
- Macro-scheduling could be done in multiple packet basis periodically, e.g 10ms.
- Cooperative scheduling extensions can be supported using a new layer on top of the existing MAC layer.
Features of Scheme
- each node conducts "global scheduling" based on "load information" of all other nodes.
- the global scheduling determines a TDMA-like slot/bandwidth allocation
- 3 stages, 2 ½ pipelining:
- Estimation — load exchange — scheduling
- equivalent to predict — signaling — access
- "load excange" phase overlapping with "estimation"
- First cycle's scheduling overlap with second cycle's "load exchange" phase
- Kernel code modification
Figure 1: 802.11 extension layer architecture
Figure 2:2.5-stage pipeline architecture. Each pipeline stage is equal in duration, but estimation stage and load exchange stage for a given cycle overlap with each other.
using 2 nodes and 1 AP, configure 1 node to have twice bandwidth as another node (interferer/competitor). All use NETGEAR cards (Atheros-chip).
- a solution for IEEE 802.11 Wireless LAN, not a solution for multi-hop
- no solution for signalling loss, wrong scheduling automatically fades out in next cycle.
- rely on AP's beacon to sync all nodes.
- very simple experiment scenario and incomplete results.
- Is a kernel patch a good approach? The kernel & driver are difficult to develop. As long as the software can be stablized, it is a feasible approach.
- 10ms scheduling resolution, good enough? No. Schedule too many packets in a batch. It's better to use HW timer, a 64-bit timing counter in Atheros chip.