full auto rate mac protocol for wireless ad hoc networks z. li, a. das, a.k. gupta and s. nandi...
TRANSCRIPT
Full auto rate MAC protocol for wireless ad hoc networks
Z. Li, A. Das, A.K. Gupta and S. NandiSchool of Computer Engineering
Nanyang Technological University Singapore
IEE Proceedings-Communications, Vol. 152, No. 3, June 2005
Outlines
Introduction Motivation Modified Virtual Carrier Sensing (MVCS) Full Auto Rate (FAR) algorithm Analytical modeling Simulation Conclusion
Introduction
IEEE 802.11 standards provide high raw bandwidth and support multiple transmission rates
Several rate-adaptation algorithms had been proposed to improve the throughput Increase the utilization of bandwidthSuit the channel condition
Introduction (cont.)
However, these schemes considered the rate adaptation for the data frame only
The overhead of control frames which transmitted in the basic rate is considerable
Motivation
Motivation (cont.)
Motivation (cont.)
We could estimate the throughput by
Maximum throughput in IEEE 802.11b
Bandwidth utilization
Objective
In this paper, the protocol aims to transmit the control frames at an acceptable higher rate
MVCS
MVCS (cont.)
When a MAC frame did not correctly be received with a correct FCS value, EIFS shall be used
Since EIFS = SIFS + DIFS + Tx(ACK) EIFS is long enough for transmitting any control frame
at any rate RTS and ACK should be always transmitted at the hig
hest rate under the given channel conditions
MVCS (cont.)
If (Ldata / Rdata) < EIFSCTS should be transmitted at acceptable high
est rateThe higher data rate, the higher probability
Otherwise, CTS should be transmitted at the lowest basic rate
FAR
RTS
CTS
S
R
Data
ACK
SIFS SIFS SIFS
RTS CTS DATA ACK
Cached Cached or basic-rate
Piggy backed in CTS
Piggy backed in Data
Data length L/Chosen rate ACK/Chosen rate 0
CTS*Basic-rate Duration value Duration value Duration value
Tx Rate
Duration Field
Defer Time
Analytical modeling
Throughput : RBAR+MVCS vs. RBAR
Improvements of MVCS
Analytical modeling (cont.)
Throughput : FAR vs. RBAR+MVCS
FAR vs. RBAR+MVCS
Analytical modeling (cont.)
Throughput : FAR vs. RBAR
FAR vs. RBAR
Simulation
NS-2 Transmission range/Carrier sensing range
250m Mobility
Random way-point mobility modelPause time = 0Maximum speed = 5m/s
Single flow within single-hop2 nodes
200 * 200
Multiple flows within single-hop10 nodes200 * 200
Multiple flows within multi-hop20 nodes
1000 * 500
Conclusion
This paper proposed a new rate adaptation algorithm: FARTransmit all the frames at the highest rate
under the given channel conditions To ensure the correct operation of VCS,
MVCS is proposed
Conclusion (cont.)
Both analytical and simulation show that the FAR algorithm greatly improves the performance of IEEE 802.11
Routing protocol should be considered in the future work
Thank you !