![Page 1: Throughput Enhancement Through Dynamic Fragmentation in Wireless LANs](https://reader035.vdocument.in/reader035/viewer/2022070403/56813a02550346895da1c960/html5/thumbnails/1.jpg)
Throughput Enhancement Through Dynamic Fragmentation in Wireless LANsByung-Seo Kim, Yuguang Fang, Tan F. Wong, and Younggoo Kwon
IEEE Transactions on Vehicular TechnologyVol. 54, No. 4, July 2005
![Page 2: Throughput Enhancement Through Dynamic Fragmentation in Wireless LANs](https://reader035.vdocument.in/reader035/viewer/2022070403/56813a02550346895da1c960/html5/thumbnails/2.jpg)
Outline Introduction Proposed protocol
Fragmentation SchemeFragment burstNAV update
Performance evaluation Conclusion
![Page 3: Throughput Enhancement Through Dynamic Fragmentation in Wireless LANs](https://reader035.vdocument.in/reader035/viewer/2022070403/56813a02550346895da1c960/html5/thumbnails/3.jpg)
Introduction
Wireless communication link in a WLAN is time varying
Rate-adaptive MAC protocols have been proposed in the past for WLANsChannel conditionRTS/CTS handshake
![Page 4: Throughput Enhancement Through Dynamic Fragmentation in Wireless LANs](https://reader035.vdocument.in/reader035/viewer/2022070403/56813a02550346895da1c960/html5/thumbnails/4.jpg)
Introduction (cont.)
Receiver based rate determinationRTSCTS (selected rate information)DATA
Overhearing nodes update their NAV
ACK
![Page 5: Throughput Enhancement Through Dynamic Fragmentation in Wireless LANs](https://reader035.vdocument.in/reader035/viewer/2022070403/56813a02550346895da1c960/html5/thumbnails/5.jpg)
Introduction (cont.) Fragmentation in IEEE 802.11 MAC with r
ate adaption scheme
> aFragmentThreshold
AddPLCP Headerand Preamble
![Page 6: Throughput Enhancement Through Dynamic Fragmentation in Wireless LANs](https://reader035.vdocument.in/reader035/viewer/2022070403/56813a02550346895da1c960/html5/thumbnails/6.jpg)
Introduction (cont.)
These proposed protocols only allowed static size of fragmentsHigher overhead of transmitting each
fragmentChannel could not be used effectively
![Page 7: Throughput Enhancement Through Dynamic Fragmentation in Wireless LANs](https://reader035.vdocument.in/reader035/viewer/2022070403/56813a02550346895da1c960/html5/thumbnails/7.jpg)
Proposed protocol A dynamic fragmentation scheme to enhanc
e throughputDurations of all fragments, except the last one,
should be set the same in any data rateA Rate-Based fragmentation thresholding sche
me is employedA new fragment is generated only when the rate
is decided for the next fragment transmission Dynamic Fragmentation
![Page 8: Throughput Enhancement Through Dynamic Fragmentation in Wireless LANs](https://reader035.vdocument.in/reader035/viewer/2022070403/56813a02550346895da1c960/html5/thumbnails/8.jpg)
Fragmentation Scheme In order to generate fragments with the sa
me time duration, the different aFragmentationThresholds should be used in different data rate R
![Page 9: Throughput Enhancement Through Dynamic Fragmentation in Wireless LANs](https://reader035.vdocument.in/reader035/viewer/2022070403/56813a02550346895da1c960/html5/thumbnails/9.jpg)
Fragmentation Scheme (cont.)
The additional overhead of ThresholdB is
![Page 10: Throughput Enhancement Through Dynamic Fragmentation in Wireless LANs](https://reader035.vdocument.in/reader035/viewer/2022070403/56813a02550346895da1c960/html5/thumbnails/10.jpg)
Fragmentation Scheme (cont.)
![Page 11: Throughput Enhancement Through Dynamic Fragmentation in Wireless LANs](https://reader035.vdocument.in/reader035/viewer/2022070403/56813a02550346895da1c960/html5/thumbnails/11.jpg)
Fragment Burst
CurrentRate (4)
NextRate (4)
Modified format of DSSSPLCP Header
![Page 12: Throughput Enhancement Through Dynamic Fragmentation in Wireless LANs](https://reader035.vdocument.in/reader035/viewer/2022070403/56813a02550346895da1c960/html5/thumbnails/12.jpg)
Fragment Burst (cont.)S R
RTS (base rate)
CTS (base rate)next rate is included
DATA is transmitted with selected rateIn aFragmentationThreshold size
ACK (selected rate)next rate is included
DATA is transmitted with selected rateIn aFragmentationThreshold size
˙˙˙
RTS
CTS
Fragment 1
ACK
Fragment 2 ˙˙˙
Next rate Next rate
![Page 13: Throughput Enhancement Through Dynamic Fragmentation in Wireless LANs](https://reader035.vdocument.in/reader035/viewer/2022070403/56813a02550346895da1c960/html5/thumbnails/13.jpg)
NAV update Because the durations of all the fragments
are the same, except the last fragmentMoreFragments = 1
NAV update
![Page 14: Throughput Enhancement Through Dynamic Fragmentation in Wireless LANs](https://reader035.vdocument.in/reader035/viewer/2022070403/56813a02550346895da1c960/html5/thumbnails/14.jpg)
Failure policy
When the transmission of a fragment failsThe size of the retransmitted fragment may not
be the same as before Channel condition may have changed
Sender only decreases the remaining MSDU size when receives the ACK from the receiver
![Page 15: Throughput Enhancement Through Dynamic Fragmentation in Wireless LANs](https://reader035.vdocument.in/reader035/viewer/2022070403/56813a02550346895da1c960/html5/thumbnails/15.jpg)
Performance Evaluation
Single-hop environment No hidden node
Transmission rage : 300 m Rate selection
![Page 16: Throughput Enhancement Through Dynamic Fragmentation in Wireless LANs](https://reader035.vdocument.in/reader035/viewer/2022070403/56813a02550346895da1c960/html5/thumbnails/16.jpg)
Performance Evaluation (cont.)
3 different configuration RFT-DF
Rate-based Dynamic
RFT-CF Rate-based Conventional
SFT-CF Single fragmentation threshold Conventional
![Page 17: Throughput Enhancement Through Dynamic Fragmentation in Wireless LANs](https://reader035.vdocument.in/reader035/viewer/2022070403/56813a02550346895da1c960/html5/thumbnails/17.jpg)
Throughput vs. number of nodes
4 m/s
![Page 18: Throughput Enhancement Through Dynamic Fragmentation in Wireless LANs](https://reader035.vdocument.in/reader035/viewer/2022070403/56813a02550346895da1c960/html5/thumbnails/18.jpg)
Packets per MSDU vs. number of nodesTime overhead vs. number of nodes
![Page 19: Throughput Enhancement Through Dynamic Fragmentation in Wireless LANs](https://reader035.vdocument.in/reader035/viewer/2022070403/56813a02550346895da1c960/html5/thumbnails/19.jpg)
PER vs. number of nodesMAC Service Time vs. number of nodes
![Page 20: Throughput Enhancement Through Dynamic Fragmentation in Wireless LANs](https://reader035.vdocument.in/reader035/viewer/2022070403/56813a02550346895da1c960/html5/thumbnails/20.jpg)
MSDU dropping rate vs. number of nodes
![Page 21: Throughput Enhancement Through Dynamic Fragmentation in Wireless LANs](https://reader035.vdocument.in/reader035/viewer/2022070403/56813a02550346895da1c960/html5/thumbnails/21.jpg)
Throughput vs. Node speed
40 nodes
![Page 22: Throughput Enhancement Through Dynamic Fragmentation in Wireless LANs](https://reader035.vdocument.in/reader035/viewer/2022070403/56813a02550346895da1c960/html5/thumbnails/22.jpg)
Throughput vs. Max. MSDU Size
4 m/s
40 nodes
![Page 23: Throughput Enhancement Through Dynamic Fragmentation in Wireless LANs](https://reader035.vdocument.in/reader035/viewer/2022070403/56813a02550346895da1c960/html5/thumbnails/23.jpg)
Throughput vs. Predictor Efficiency
4 m/s
40 nodes
![Page 24: Throughput Enhancement Through Dynamic Fragmentation in Wireless LANs](https://reader035.vdocument.in/reader035/viewer/2022070403/56813a02550346895da1c960/html5/thumbnails/24.jpg)
Conclusion
This paper proposes a new rate-adaptive MAC protocol with dynamic fragmentation
Nodes with good channels can transmit more data
Constant duration in physical layer simplifies the process of NAV update
Simulations show the throughput gain from the conventional scheme