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doc.: IEEE 802.11-02/138r0
Submission
March 2002
Yang Xiao and Jon Rosdahl , Micro LinearSlide 1
Throughput Analysis forIEEE 802.11a Higher Data
Rates
Yang Xiao and Jon Rosdahl
Micro L inear Co.
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doc.: IEEE 802.11-02/138r0
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March 2002
Yang Xiao and Jon Rosdahl , Micro LinearSlide 2
Agenda
Assumptions
Throughput Formulations
IEEE 802.11a parameters
Numerical Results
Improved Performance
AssumptionsNumerical Results
Conclusions
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doc.: IEEE 802.11-02/138r0
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March 2002
Yang Xiao and Jon Rosdahl , Micro LinearSlide 3
Assumptions
Data rates higher than 54Mbps have the
same set of overhead parameters as in IEEE
802.11a.
There are only two nodes in the BSS: one is
the sender and the other is the receiver.
The sender always has packets to send.
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March 2002
Yang Xiao and Jon Rosdahl , Micro LinearSlide 4
Throughput Formulations
ACKDSIFSDATADDIFSslot
DATA
TTTTTCW
LThroughput
__min
2
8
DBPS
DATASYMPHYHeambleDATAD
N
LCeilingTTTT
828*8616*_Pr_
DBPS
SYMPHYHeambleACKDN
CeilingTTTT14*8616
*_Pr_
delaynpropagatio:
symbolaoftimeontransmissi:
header,PHYoftimeontransmissi:
symbol,OFDMperbitsdata:
_
SYM
PHYH
DBPS
T
T
N
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doc.: IEEE 802.11-02/138r0
Submission
March 2002
Yang Xiao and Jon Rosdahl , Micro LinearSlide 5
IEEE 802.11a parameters
In numerical results:
(data rate, control rate) is (6,6), (9,6), (12, 12), (18, 12), (24, 24), (36, 24), (48, 24)or (54, 24) for IEEE 802.11a.
For data rates > 54Mps , both data rate and control rate are increased proportionally.
Table 1 Data Rates for the IEEE 802.11a
Data Rate (Mbps) Modulation NDBPS
6 BPSK 24
9 BPSK 36
12 QPSK 48
18 QPSK 72
24 16-QAM 96
36 16-QAM 144
48 64-QAM 192
54 64-QAM 216
,1,4,4,16
1023,,15,34,16,9
_Pr
maxmin
ssTsTsT
CWCWsTsTsT
SYMPHYHeamble
DIFSSIFSslot
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doc.: IEEE 802.11-02/138r0
Submission
March 2002
Yang Xiao and Jon Rosdahl , Micro LinearSlide 6
Throughputs for Higher Data Rates (HDR)
Data Rate Throughput
54Mbps 30.34Mbps
108Mbps 42.93Mbps
216Mbps 52.75Mbps
For 1500 bytes Payload
The throughput is quite
small compared to the datarate.
0 500 1000 15000
10
20
30
40
50
60
Packet Size (Bytes)
Throughput(Mbps)forhighe
rdatarates
6Mbps9Mbps12Mbps18Mbps24Mbps36Mbps48Mbps54Mbps72(=2*36)Mbps96(=2*48)Mbps108(=2*54)Mbps
144(=3*48)Mbps162(=3*54)Mbps192(=4*48)Mbps216(=4*54)Mbps
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doc.: IEEE 802.11-02/138r0
Submission
March 2002
Yang Xiao and Jon Rosdahl , Micro LinearSlide 7
Bandwidth Efficiency (BE) for HDR
Data Rate BE
6Mbps 89.8%
54Mbps 56.2%
108Mbps 39.75%
216Mbps 24.4%
For 1500 bytes Payload
BE is defined as thethroughput divided by thedata rate.
BE decreases as data rateincreases.0 500 1000 15000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
Packet Size (Bytes)
BandwidthEfficiencyforhighe
rdatarates
6Mbps9Mbps12Mbps18Mbps24Mbps36Mbps48Mbps54Mbps72(=2*36)Mbps96(=2*48)Mbps
108(=2*54)Mbps144(=3*48)Mbps162(=3*54)Mbps192(=4*48)Mbps216(=4*54)Mbps
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doc.: IEEE 802.11-02/138r0
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March 2002
Yang Xiao and Jon Rosdahl , Micro LinearSlide 8
Throughput Increases for doubling rates
Data Rate Increase
2*6Mbps 4.65Mbps
2*54Mbps 12.59Mbps
For 1500 bytes Payload
Increase as compared to theoriginal ones.
0 500 1000 15000
2
4
6
8
10
12
14
Packet Size (Bytes)
T
hroughputincrease(Mbps)fordoub
lingdatarates
12(=2*6)Mbps18(=2*9Mbps24(=2*12)Mbps36(=2*18)Mbps48(=2*24)Mbps72(=2*36)Mbps96(=2*48)Mbps108(=2*54)Mbps
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doc.: IEEE 802.11-02/138r0
Submission
March 2002
Yang Xiao and Jon Rosdahl , Micro LinearSlide 9
Throughput Increase (%) for doubling Rates
Data Rate Increase
2*54Mbps 41.5%
41.5% is far from
doubled, i.e. 100%
increase
For 1500 bytes Payload
0 500 1000 15000
10
20
30
40
50
60
70
80
90
Packet Size (Bytes)
Throughputincrease(%)fordoublingdatarates
12(=2*6)Mbps18(=2*9Mbps24(=2*12)Mbps36(=2*18)Mbps48(=2*24)Mbps72(=2*36)Mbps96(=2*48)Mbps108(=2*54)Mbps
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doc.: IEEE 802.11-02/138r0
Submission
March 2002
Yang Xiao and Jon Rosdahl , Micro LinearSlide 10
Throughput Increases (%)
for Tripling/Quadrupling Rates
Data Rate Increase (%)
144Mbps 68.4%
162Mbps 65.1%
192Mbps 86.2%
216Mbps 77%
The increased rates are farfrom tripling/Quadrupling,i.e. 200% or 300% increase.
For 1500 bytes Payload
0 500 1000 15000
10
20
30
40
50
60
70
80
90
Packet Size (Bytes)
Throughputincrease(%)fortripling/qu
adruplingdatarates
144(=3*48)Mbps162(=3*54)Mbps192(=4*48)Mbps216(=4*54)Mbps
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March 2002
Yang Xiao and Jon Rosdahl , Micro LinearSlide 11
Improved Performance: Assumptions
A specific method to reduce the overhead is
not proposed in the presentation.
Under the assumption that the overhead can
be reduced, the improved performance
follows.
In particular, assume that all the overheadscan be reduced by 10%, 30%, and 50%.
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March 2002
Yang Xiao and Jon Rosdahl , Micro LinearSlide 12
Throughputs for HDR with overheads reduced
For 1500 bytes PayloadData rate: 6Mbps
Overhead
Reduced
Throughput
0% 5.39Mbps
10% 5.44Mbps
30% 5.55Mbps
50% 5.66Mbps0 500 1000 15000
1
2
3
4
5
6
Packet Size (Bytes)
Throughput(Mbps)forhigh
erdatarates
6Mbps6Mbps with 10% overheads reduced6Mbps with 30% overheads reduced6Mbps with 50% overheads reduced
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doc.: IEEE 802.11-02/138r0
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March 2002
Yang Xiao and Jon Rosdahl , Micro LinearSlide 13
Throughputs for HDR with overheads reduced
For 1500 bytes Payload
Overhead
Reduced
Throughput
0% 30.34Mbps
10% 31.62Mbps
30% 34.52Mbps
50% 38.49Mbps
Data rate: 54Mbps
0 500 1000 15000
5
10
15
20
25
30
35
40
Packet Size (Bytes)
Throughput(Mbps)forhigherd
atarates
54Mbps
54Mbps with 10% overheads reduced54Mbps with 30% overheads reduced54Mbps with 50% overheads reduced
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doc.: IEEE 802.11-02/138r0
Submission
March 2002
Yang Xiao and Jon Rosdahl , Micro LinearSlide 14
Throughputs for HDR with overheads reduced
For 1500 bytes Payload
Data rate: 108Mbps
Overhead
Reduced
Throughput
0% 42.9Mbps
10% 45.5Mbps
30% 51.8Mbps
50% 60.1Mbps0 500 1000 1500
0
10
20
30
40
50
60
70
Packet Size (Bytes)
Throughput(Mbps)forhigherdatarates
108(=2*54)Mbps
108(=2*54)Mbps with 10% overheads reduced108(=2*54)Mbps with 30% overheads reduced108(=2*54)Mbps with 50% overheads reduced
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doc.: IEEE 802.11-02/138r0
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March 2002
Yang Xiao and Jon Rosdahl , Micro LinearSlide 15
Bandwidth Efficiency with overheads reduced
For 1500 bytes Payload
Data rate: 6Mbps
Overhead
Reduced
Bandwidth
Efficiency
0% 89.79%
10% 90.60%
30% 92.44%
50% 94.53%0 500 1000 1500
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Packet Size (Bytes)
BandwidthEfficiencyforhigherdatarates
6Mbps6Mbps with 10% overheads reduced6Mbps with 30% overheads reduced6Mbps with 50% overheads reduced
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doc.: IEEE 802.11-02/138r0
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March 2002
Yang Xiao and Jon Rosdahl , Micro LinearSlide 16
Bandwidth Efficiency with overheads reduced
For 1500 bytes Payload
Data rate: 54Mbps
Overhead
Reduced
Bandwidth
Efficiency
0% 56.19%
10% 58.55%
30% 63.92%
50% 71.28%0 500 1000 1500
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Packet Size (Bytes)
BandwidthEfficiencyforhigherd
atarates
54Mbps
54Mbps with 10% overheads reduced54Mbps with 30% overheads reduced54Mbps with 50% overheads reduced
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doc.: IEEE 802.11-02/138r0
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March 2002
Yang Xiao and Jon Rosdahl , Micro LinearSlide 17
Bandwidth Efficiency with overheads reduced
For 1500 bytes Payload
Data rate: 108Mbps
Overhead
Reduced
Bandwidth
Efficiency
0% 39.8%
10% 42.2%
30% 48.0%
50% 55.6%0 500 1000 1500
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Packet Size (Bytes)
BandwidthEfficiencyforhigher
datarates
108(=2*54)Mbps108(=2*54)Mbps with 10% overheads reduced108(=2*54)Mbps with 30% overheads reduced108(=2*54)Mbps with 50% overheads reduced
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doc.: IEEE 802.11-02/138r0
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March 2002
Yang Xiao and Jon Rosdahl , Micro LinearSlide 18
Throughput Increase with overheads reduced
For 1500 bytes Payload
Doubled Rate: 12 (=2*6)Mbps
Overhead
ReducedThroughput
Increase
0% 4.65Mbps
10%
4.82Mbps30% 5.14Mbps
50% 5.52Mbps0 500 1000 1500
0
1
2
3
4
5
6
Packet Size (Bytes), Note: assume that the original is not reduced
Throughputincrease(Mbps)fordoubleddatarates
12(=2*6)Mbps12(=2*6)Mbps with 10% overheads reduced12(=2*6)Mbps with 30% overheads reduced12(=2*6)Mbps with 50% overheads reduced
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doc.: IEEE 802.11-02/138r0
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March 2002
Yang Xiao and Jon Rosdahl , Micro LinearSlide 19
Throughput Increase with overheads reduced
For 1500 bytes Payload
Doubled Rate:108(=2*54)Mbps
Overhead
ReducedThroughput
Increase
0% 12.59Mbps
10%
15.19Mbps30% 21.46Mbps
50% 29.73Mbps0 500 1000 15000
5
10
15
20
25
30
Packet Size (Bytes), Note: assume that the original is not reduced
Throughputincrease(Mbps)fordo
ubleddatarates
108(=2*54)Mbps
108(=2*54)Mbps with 10% overheads reduced108(=2*54)Mbps with 30% overheads reduced108(=2*54)Mbps with 50% overheads reduced
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March 2002
Yang Xiao and Jon Rosdahl , Micro LinearSlide 20
Conclusions
Higher Data Rates with IEEE 802.11a
compatibility should be pursued.
Effective throughput can be increased byreducing overhead.
How to achieve the Higher Data Rates and
reduce the overhead are open issues