Title: XORS IN THE AIR: PRACTICAL WIRELESS NETWORK CODING
1XORS IN THE AIR PRACTICAL WIRELESS NETWORK CODING
- Athours
- Sachin Katti Hariharan Rahul Wenjun Hu?
Dina Katabi Muriel Medard Jon Crowcroft? - MIT CSAIL ?Univ. of Cambridge
SIGCOMM06
2OUTLINE
- Motivation
- Methodology - COPE
- Opportunistic Coding
- Understanding COPSs gains
- Coding MAC gain
- Experimental Results
- Pros and Cons
3MOTIVATION
- This paper proposes COPE, a new architecture for
wireless mesh networks - In addition to forwarding packets, routers code
packets from different sources to increase the
information content of each transmission - COPE is run as a bundle layer between MAC layer
and network layer - This paper implements COPE on WiFi 802.11
4MOTIVATION
5MOTIVATION
- P1 01001 P2 10011
- gt P3 P1 xor P2 11010
- Alice P3 xor P1 10011 P2
- Bob P3 xor P2 01001 P1
6METHODOLOGY - OPPORTUNISTIC CODING
7METHODOLOGY - UNDERSTANDING COPSS GAINS
- (a) transmissions 4
- (b) transmissions 3
- gt Coding gain 4/3 1.33
8METHODOLOGY - CODING MAC GAIN
- Assuming all nodes continuously have traffic to
send - Because it tries to be fair, the MAC divides the
bandwidth equally between the 3 contending nodes
Alice, Bob, and the router.
1.5K
3K
3K
1.5K
9METHODOLOGY - CODING MAC GAIN
- Assuming all nodes continuously have traffic to
send - Because it tries to be fair, the MAC divides the
bandwidth equally between the 3 contending nodes
Alice, Bob, and the router.
1.5K
Received by Alice and Bob 3K
1.5K
1.5K
1.5K
10METHODOLOGY - CODING MAC GAIN
Received by Alice and Bob 6K
3K
3K
3K
11METHODOLOGY - GAIN
- Theoretical gains for a few basic topologies
Chain topology
X topology
Cross topology
Wheel topology
12EXPERIMENTAL RESULTS TEST BED
20 nodes locations for two floor of the testbed
13EXPERIMENTAL RESULTS - COPE IN GADGET TOPOLOGIES
TCP gain in the Alice-and-Bob topology
UDP gain in the Alice-and-Bob topology
14EXPERIMENTAL RESULTS - COPE IN GADGET TOPOLOGIES
TCP gain in the X-topology
UDP gain in the X-topology
15EXPERIMENTAL RESULTS - COPE IN GADGET TOPOLOGIES
TCP gain in the cross topology
UDP gain in the cross topology
16EXPERIMENTAL RESULTS TESTBED
- COPE provides 38 increase in TCP goodput when
the testbed topology does not contain hidden
terminals
17EXPERIMENTAL RESULTS TESTBED
- COPE can provide a several-fold (3-4x) increase
in the throughput of wireless Ad hoc networks.
Results are for UDP flows with randomly picked
source-destination pairs, Poisson arrivals, and
heavytail size distribution.
18PROS
- COPE provides enhancement of throughput without
too much extra coding overhead - COPE can not only apply on WiFi, but also other
MAC protocols, such as WiMax, sensor networks. - COPE doesnt optimize power usage
CONS
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