November 2008
doc.: IEEE 802.19-08/0030r1
Impact of IEEE 802.11n Operation On
IEEE 802.15.4 Performance
Date: 2008-11-02
Authors:
Name
Company
Address
Phone
email
Mukul Goyal
U Wisconsin
Milwaukee
1-414-2295001
mukul@uwm.edu
Yusuf Bashir
Johnson
Controls Inc.
3200 N Cramer St,
Milwaukee WI
53201
507 E Michigan St,
Milwaukee WI
53202
1-414-5268380
Yusuf.Bashir@jci.com
Notice: This document has been prepared to assist IEEE 802.19. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in
this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.
Submission
Slide 1
Mukul Goyal, U Wisconsin Milwaukee
November 2008
doc.: IEEE 802.19-08/0030r1
Abstract
In this presentation, we evaluate the impact of IEEE
802.11n operation on IEEE 802.15.4 performance via
test bed experiments. The IEEE 802.15.4 performance
is measured in terms of packet loss rate and the latency
for successfully delivered packets.
Submission
Slide 2
Mukul Goyal, U Wisconsin Milwaukee
November 2008
doc.: IEEE 802.19-08/0030r1
IEEE 802.15.4: Overview
• A MAC/PHY layer protocol for low power, low data
rate (< 250 kbps) wireless sensor applications
• Based on CSMA/CA
Submission
Slide 3
Mukul Goyal, U Wisconsin Milwaukee
November 2008
doc.: IEEE 802.19-08/0030r1
The CSMA/CA algorithm in (unslotted)
802.15.4
• The source node backoffs for a random number of slots
between 0 and (2^BE) – 1
– BE is Backoff Exponent
• After the backoff, the source node does the clear
channel assessment (CCA)
• If the channel is not idle (CCA Failure), the source node
increments BE and repeat the process up to 4 times
– The initial BE value is 3 and max BE value is 5
Submission
Slide 4
Mukul Goyal, U Wisconsin Milwaukee
November 2008
doc.: IEEE 802.19-08/0030r1
The CSMA/CA algorithm in (unslotted)
802.15.4
• If the CCA fails even after 4th retry, the source
node declares channel access failure (CAF) and
abandons the packet transmission
• If the CCA succeeds, the source node transmits
the packet.
• On receiving the packet, the destination
optionally sends an acknowledgement back
Submission
Slide 5
Mukul Goyal, U Wisconsin Milwaukee
November 2008
doc.: IEEE 802.19-08/0030r1
Collisions and Retransmissions
• If the packet or the ack suffers a collision, the
source node waits for a certain time duration
and then repeat the (backoff + transmission)
process up to 3 more times.
• If the ack is not received even after the 3rd
retry, the source node declares a collision
failure and abandons the packet.
Submission
Slide 6
Mukul Goyal, U Wisconsin Milwaukee
November 2008
doc.: IEEE 802.19-08/0030r1
Packet Loss in IEEE 802.15.4
• Channel access failure
– channel access failure occurs after 5 back-to-back CCA
failures during a try.
• Collision failure
– occurs after failure to receive the ack even after 4 tries.
• Note that a channel access failure causes
abandonment of packet transmission attempt
even if 4 tries have not been made.
Submission
Slide 7
Mukul Goyal, U Wisconsin Milwaukee
November 2008
doc.: IEEE 802.19-08/0030r1
Impact of IEEE 802.11n operation on IEEE
802.15.4 Performance
• IEEE 802.15.4 performance is measured in terms of the
packet loss rate and latency for successfully delivered
packets.
• In the following graphs, we plot the increase in average
loss rate/latency values for IEEE 802.15.4 nodes due to
the presence of an IEEE 802.11n network.
Submission
Slide 8
Mukul Goyal, U Wisconsin Milwaukee
November 2008
doc.: IEEE 802.19-08/0030r1
Traffic in IEEE 802.15.4 Network
• 15 nodes sending packets to the coordinator.
• The packet size is 112 bytes.
• Each node sends on average one packet per second
(poisson distributed) for 15 minutes
• IEEE 802.15.4 network uses a 3 MHz wide channel
centered at 2425 MHz (Channel 15)
• Power level: 10dBm
Submission
Slide 9
Mukul Goyal, U Wisconsin Milwaukee
November 2008
doc.: IEEE 802.19-08/0030r1
Traffic in IEEE 802.11n Network
• An iperf client sends a UDP stream to an iperf server
over an IEEE 802.11n network
• Power level 17dBm
• Packet size: 1470 bytes
• Client generates traffic at rates 1, 2, 5, 10, 15, 20 Mbps.
Submission
Slide 10
Mukul Goyal, U Wisconsin Milwaukee
November 2008
doc.: IEEE 802.19-08/0030r1
IEEE 802.11n Channels Used
• Scenario 1: Channel 1, 20 MHz wide, no overlap with
IEEE 802.15.4 channel
• Scenario 2: Channel 6, 40 MHz wide (extends towards
channel 11), no overlap with IEEE 802.15.4 channel
• Scenario 3: Channel 1, 40 MHz wide, extends into the
channel used by IEEE 802.15.4 network
• Scenario 4: Channel 4, 20 MHz wide, overlaps the
channel used by IEEE 802.15.4 network
Submission
Slide 11
Mukul Goyal, U Wisconsin Milwaukee
November 2008
doc.: IEEE 802.19-08/0030r1
Scenario 1: IEEE 802.11n on Channel 1, 20
MHz wide
IEEE 802.11n
IEEE 802.15.4
2412 MHz
2425 MHz
22MHz
Submission
3MHz
Slide 12
Mukul Goyal, U Wisconsin Milwaukee
November 2008
doc.: IEEE 802.19-08/0030r1
Scenario 1: Impact of IEEE 802.11n Operation
on IEEE 802.15.4 Loss Rate
0.003
Increase in Loss Rate
0.0025
0.002
0.0015
0.001
0.0005
0
1
Submission
2
5
10
15
IEEE 802.11n Traffic Load (Mbps)
Slide 13
20
Mukul Goyal, U Wisconsin Milwaukee
November 2008
doc.: IEEE 802.19-08/0030r1
Scenario 1: Impact of IEEE 802.11n Operation
on IEEE 802.15.4 Latency
2
Increase in Latency (ms)
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
1
Submission
2
5
10
15
IEEE 802.11n Traffic Load (Mbps)
Slide 14
20
Mukul Goyal, U Wisconsin Milwaukee
November 2008
doc.: IEEE 802.19-08/0030r1
Scenario 2: IEEE 802.11n on Channel 6, 40
MHz wide
IEEE 802.11n
IEEE 802.15.4
2425 MHz
3MHz
Submission
2437 MHz
44MHz
Slide 15
Mukul Goyal, U Wisconsin Milwaukee
November 2008
doc.: IEEE 802.19-08/0030r1
Scenario 2: Impact of IEEE 802.11n Operation
on IEEE 802.15.4 Loss Rate
0.007
Increase in Loss Rate
0.006
0.005
0.004
0.003
0.002
0.001
0
1
Submission
2
5
10
15
IEEE 802.11n Traffic Load (Mbps)
Slide 16
20
Mukul Goyal, U Wisconsin Milwaukee
November 2008
doc.: IEEE 802.19-08/0030r1
Scenario 2: Impact of IEEE 802.11n Operation
on IEEE 802.15.4 Latency
Increase in Latency (ms)
2.5
2
1.5
1
0.5
0
1
Submission
2
5
10
15
IEEE 802.11n Traffic Load (Mbps)
Slide 17
20
Mukul Goyal, U Wisconsin Milwaukee
November 2008
doc.: IEEE 802.19-08/0030r1
Scenario 3: IEEE 802.11n on Channel 1, 40
MHz wide
IEEE 802.11n
IEEE 802.15.4
2412 MHz 2425 MHz
3MHz
44MHz
Submission
Slide 18
Mukul Goyal, U Wisconsin Milwaukee
November 2008
doc.: IEEE 802.19-08/0030r1
Scenario 3: Impact of IEEE 802.11n Operation
on IEEE 802.15.4 Loss Rate
0.03
Increase in Loss Rate
0.025
0.02
0.015
0.01
0.005
0
1
Submission
2
5
10
15
IEEE 802.11n Traffic Load (Mbps)
Slide 19
20
Mukul Goyal, U Wisconsin Milwaukee
November 2008
doc.: IEEE 802.19-08/0030r1
Scenario 3: Impact of IEEE 802.11n Operation
on IEEE 802.15.4 Latency
7
Increase in Latency (ms)
6
5
4
3
2
1
0
1
Submission
2
5
10
IEEE 802.11n Traffic Load (Mbps)
Slide 20
15
20
Mukul Goyal, U Wisconsin Milwaukee
November 2008
doc.: IEEE 802.19-08/0030r1
Scenario 4: IEEE 802.11n on Channel 4, 20
MHz wide
IEEE 802.11n
IEEE 802.15.4
2425 MHz 2427 MHz
3MHz
22MHz
Submission
Slide 21
Mukul Goyal, U Wisconsin Milwaukee
November 2008
doc.: IEEE 802.19-08/0030r1
Scenario 4: Impact of IEEE 802.11n Operation
on IEEE 802.15.4 Loss Rate
0.4
Increase in Loss Rate
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
1
Submission
2
5
10
15
IEEE 802.11n Traffic Load (Mbps)
Slide 22
20
Mukul Goyal, U Wisconsin Milwaukee
November 2008
doc.: IEEE 802.19-08/0030r1
Scenario 4: Impact of IEEE 802.11n Operation
on IEEE 802.15.4 Latency
100
Increase in Latency (ms)
90
80
70
60
50
40
30
20
10
0
1
Submission
2
5
10
15
IEEE 802.11n Traffic Load (Mbps)
Slide 23
20
Mukul Goyal, U Wisconsin Milwaukee