presentation - dynamic tuning of rts threshold
TRANSCRIPT
CMPUT 640Resource Allocation In Networks
Final Project Presentation
TopicDynamic Tuning of RTS Threshold in IEEE802.11 based on
Packet Distribution of Network
Presented ByMohammad Saiful Islam
Student # 1270123
Outline
IEEE 802.11 IEEE 802.11 MAC A Balanced Intermix Previous Work Relatively Small Dynamic RTS Threshold Calculation Simulation Discussion
IEEE 802.11
Standard for Medium Access Control (MAC) & Physical Layer in wireless LAN
Ad-Hoc (DCF) & Infrastructure (PCF) Mode in MAC layer
Distributed Co-ordination Function (DCF)○ Basic & RTS/CTS based scheme
Basic Scheme○ Physical Carrier Sensing○ DATA – ACK○ Hidden Node Problem
IEEE 802.11 MAC Request to send (RTS)/Clear to send (CTS)
○ RTS - CTS - DATA - ACK○ Virtual Carrier Sensing○ Solves Hidden & Exposed Node Problems○ Problems [1]
— Virtual Jamming— Inhibiting non-interfering parallel transmission— False blocking
RTS Threshold (RT) value decides which scheme to use for each packet
Packet size >= RT → use RTS/CTS scheme else use Basic scheme
A Balanced Intermix Continue with both schemes in a balanced way Small packets => Low collision probability => Basic
scheme Large packets => High collison probability =>
RTS/CTS scheme
So smaller η% with Basic & larger (1-η)% with RTS/CTS
Problems with fixed RT○ Packet size can not be predicted before○ All packets may be smaller than the value○ Opposite can be also true
Previous Works
Author Basis of Tuning Assumptions
Shaohu et al. [2] Minimizing average time spent in successful and unsuccessful transmission
Homogenous traffic, negligible channel noise, no hidden node problem, static nodes
Liu et al. [3] Minimizing time overhead of packet transmission
No hidden node problem, static nodes
Zhang et al. [4] Minimizing time between two successful transmissions
Single-hop network, no hiddennode problem, fixed number ofnodes, static nodes
Mjidi et al. [5] Packet Delivery Ratio Static nodes
Huei-Jiun et al. [6] Use ”Waiting for CTS timeout” asthreshold
Ideal channel, linear network, static nodes
Ahsan et al. [7] Exploiting packet distribution toensure certain amount of packetsuse Basic Scheme
Static Nodes
Relatively Small Proposal
○ Use Basic scheme for relatively small sized packets and RTS/CTS scheme for relatively large packets
○ Set RT dynamically so that η% packet is lower than this value
Implementation○ Node has generated or received packet of size
○ Increase frequency count for that size
○ Do this in each interval of size δ○ After the end of each interval
— Adjust RT based on frequency count of the previous interval
— Reset frequency counter
sif i
Dynamic RTS Threshold Calculation
α is the memory factor
is the greatest probability less than or equal to η
is the packet size at
is the least probability greater than η
is the packet size at
RT current=[P s−P r∗C s−P s
C r−Pr]
RT average=[∗RT prev1−∗RT current ]
Pr
P s
C rC s
C r
Pr
Pi=Pr {Ssi}=∑j=1
i
f j
∑k=1
n
f k
Queuing Analysis
The average arrival rate is 13.58 packet/s with a confidence interval of 0.000327.
The average throughput is 13.024 with a confidence interval of 0.00028.
Simulation
NS-3 Simulator
Area 1000 * 1000 unit
Random Walk 2d Mobility Model
○ Speed 0.1 m/s
○ Nodes change direction in every 50 sec IEEE 802.11b in Ad-Hoc mode
Multi-hop network
1 source – destination pair for each 10 nodes
○ Source generates UDP packets
○ Packet inter arrival time and size exponentially distributed Routing Protocol – AODV and Static
Simulation Cont...
Independent variables
○ η = 0 to 100 in step of 10
○ Number of nodes 30, 50, 70
○ Packet Generation Rate 1, 2, 3 packet/sec Performance Metric
○ System Throughput
○ Total bytes received in all destination application layer
References
[1] Ashikur Rahman and Pawel Gburzynski. Hidden problems with the hidden node problem. In 23rd Biennial Symposium on Communications- QBSC 2006, pages 270–273, 2006.
[2] Shiqi Wu-Wei Guo Shaohu Yan, Yongning Zhuo. Adaptive RTS threshold for maximum networkthroughput in IEEE 802.11 DCF. volume 5284, pages 332–343, 2004.
[3] Bai long Xiao Fei Huang Jun Liu, Wei Guo. RTSthreshold adjustment algorithm for IEEE 802.11 DCF.In 6th International Conference on ITS Telecommunications, pages 654–658, 2006.
[4] Liang Zhang and Yantai Shu. Rts threshold self-tuning algorithm based on delay analysis on 802.11 dcf. volume 1, pages 627 – 630, sep. 2005.
[5] Naoki Nakamura Kazuhide Koide Atushi Takeda Norio Shiratori Mostafa Mjidi, Debasish Chakraborty. Anew dynamic scheme for effcient RTS threshold handling in wireless networks. In 22nd International Conference on Advanced Information Networking and Applications, pages 734–740, 2008.
Reference cont...
[6] Yen-Cheng Kuan Huei-Jiun Ju, Izhak Rubin. An adaptive RTS/CTS control mechanism for IEEE 802.11 MAC protocol. Vehicular Technology Conference, 2003. VTC 2003-Spring. The 57th IEEE Semiannual, 2:1469– 1473, 2003
[7] S.M.R. Ahsan, M.S. Islam, N. Hassan, and A. Rahman. Exploiting packet distribution for tuning rtsthreshold in ieee 802.11. pages 369 –372, may. 2010.