1. Impact of IEEE 802.11n Operation On IEEE 802.15.4 Performance
November 2008
doc.: IEEE yy/xxxxr0
November 2008
Impact of IEEE n Operation On IEEE Performance
Date:
Authors:
Notice: This document has been prepared to assist IEEE 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.
Mukul Goyal, U Wisconsin Milwaukee
Mukul Goyal, U Wisconsin Milwaukee

2. November 2008
doc.: IEEE yy/xxxxr0
November 2008
Abstract
In this presentation, we evaluate the impact of IEEE n operation on IEEE performance via test bed experiments. The IEEE performance is measured in terms of packet loss rate and the latency for successfully delivered packets.
Mukul Goyal, U Wisconsin Milwaukee
Mukul Goyal, U Wisconsin Milwaukee

3. November 2008
IEEE : Overview
A MAC/PHY layer protocol for low power, low data rate (< 250 kbps) wireless sensor applications
Based on CSMA/CA
Mukul Goyal, U Wisconsin Milwaukee

4. The CSMA/CA algorithm in (unslotted) 802.15.4
November 2008
The CSMA/CA algorithm in (unslotted)
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
Mukul Goyal, U Wisconsin Milwaukee

5. The CSMA/CA algorithm in (unslotted) 802.15.4
November 2008
The CSMA/CA algorithm in (unslotted)
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
Mukul Goyal, U Wisconsin Milwaukee

6. Collisions and Retransmissions
November 2008
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.
Mukul Goyal, U Wisconsin Milwaukee

7. Packet Loss in IEEE 802.15.4 Channel access failure Collision failure
November 2008
Packet Loss in IEEE
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.
Mukul Goyal, U Wisconsin Milwaukee

8. Impact of IEEE 802.11n operation on IEEE 802.15.4 Performance
November 2008
Impact of IEEE n operation on IEEE Performance
IEEE 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 nodes due to the presence of an IEEE n network.
Mukul Goyal, U Wisconsin Milwaukee

9. Traffic in IEEE 802.15.4 Network
November 2008
Traffic in IEEE 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 network uses a 3 MHz wide channel centered at 2425 MHz (Channel 15)
Power level: 10dBm
Mukul Goyal, U Wisconsin Milwaukee

10. Traffic in IEEE 802.11n Network
November 2008
Traffic in IEEE n Network
An iperf client sends a UDP stream to an iperf server over an IEEE n network
Power level 17dBm
Packet size: 1470 bytes
Client generates traffic at rates 1, 2, 5, 10, 15, 20 Mbps.
Mukul Goyal, U Wisconsin Milwaukee

11. November 2008
IEEE n Channels Used
Scenario 1: Channel 1, 20 MHz wide, no overlap with IEEE channel
Scenario 2: Channel 6, 40 MHz wide (extends towards channel 11), no overlap with IEEE channel
Scenario 3: Channel 1, 40 MHz wide, extends into the channel used by IEEE network
Scenario 4: Channel 4, 20 MHz wide, overlaps the channel used by IEEE network
Mukul Goyal, U Wisconsin Milwaukee

12. Scenario 1: IEEE 802.11n on Channel 1, 20 MHz wide
November 2008
Scenario 1: IEEE n on Channel 1, 20 MHz wide
IEEE n
IEEE
2412 MHz
2425 MHz
22MHz
3MHz
Mukul Goyal, U Wisconsin Milwaukee

13. November 2008
Scenario 1: Impact of IEEE n Operation on IEEE Loss Rate
Mukul Goyal, U Wisconsin Milwaukee

14. Scenario 1: Impact of IEEE 802.11n Operation on IEEE 802.15.4 Latency
November 2008
Scenario 1: Impact of IEEE n Operation on IEEE Latency
Mukul Goyal, U Wisconsin Milwaukee

15. Scenario 2: IEEE 802.11n on Channel 6, 40 MHz wide
November 2008
Scenario 2: IEEE n on Channel 6, 40 MHz wide
IEEE n
IEEE
2425 MHz
2437 MHz
3MHz
44MHz
Mukul Goyal, U Wisconsin Milwaukee

16. November 2008
Scenario 2: Impact of IEEE n Operation on IEEE Loss Rate
Mukul Goyal, U Wisconsin Milwaukee

17. Scenario 2: Impact of IEEE 802.11n Operation on IEEE 802.15.4 Latency
November 2008
Scenario 2: Impact of IEEE n Operation on IEEE Latency
Mukul Goyal, U Wisconsin Milwaukee

18. Scenario 3: IEEE 802.11n on Channel 1, 40 MHz wide
November 2008
Scenario 3: IEEE n on Channel 1, 40 MHz wide
IEEE n
IEEE
2412 MHz
2425 MHz
3MHz
44MHz
Mukul Goyal, U Wisconsin Milwaukee

19. November 2008
Scenario 3: Impact of IEEE n Operation on IEEE Loss Rate
Mukul Goyal, U Wisconsin Milwaukee

20. Scenario 3: Impact of IEEE 802.11n Operation on IEEE 802.15.4 Latency
November 2008
Scenario 3: Impact of IEEE n Operation on IEEE Latency
Mukul Goyal, U Wisconsin Milwaukee

21. Scenario 4: IEEE 802.11n on Channel 4, 20 MHz wide
November 2008
Scenario 4: IEEE n on Channel 4, 20 MHz wide
IEEE n
IEEE
2425 MHz
2427 MHz
3MHz
22MHz
Mukul Goyal, U Wisconsin Milwaukee

22. November 2008
Scenario 4: Impact of IEEE n Operation on IEEE Loss Rate
Mukul Goyal, U Wisconsin Milwaukee

23. Scenario 4: Impact of IEEE 802.11n Operation on IEEE 802.15.4 Latency
November 2008
Scenario 4: Impact of IEEE n Operation on IEEE Latency
Mukul Goyal, U Wisconsin Milwaukee