Coexistence of a Novel MAC Protocol for Wireless Ad hoc Networks and the IEEE 802.11

Jesús Alonso-Zárate, Elli Kartsakli, Luis Alonso, and Christos Verikoukis

May 2010, Cape Town, South Africa, ICC 2010

Coexistence of a Novel MAC Protocol for Wireless Ad hoc Networks and the IEEE 802.11

2/28ICC 2010 Cape Town, South Africa [email protected]

Outline

1) Introduction

2) 802.11 overview

3) DQMAN overview

4) Coexistence Methodology

5) Simulation Results

6) Conclusions


Outline

1) Introduction

2) 802.11 overview

3) DQMAN overview



6) Conclusions


Introduction

• Context: Wireless Local Area Networks (ad hoc)

• Focus: Medium Access Control protocols (MAC protocols)

• 1999: IEEE 802.11 and the Distributed Coordination Function (DCF)

• Since then letter soup (a,b,g,e,n, …), but few changes to MAC

• MAC very inefficient for high number of users or heavy data traffic

• Result: vast amount of new MAC protocols have been proposed


Introduction

• Problem and motivation:

1) Higher performance, at the cost of

2) Non-backwards compatibility

• Contribution:

1) Methodology for the coexistence of DQMAN and the DCF

2) Methodology can be applied to other MAC protocols.


Outline

1) Introduction

2) 802.11 overview

3) DQMAN overview



6) Conclusions


The IEEE 802.11: Overview

• DCF mandatory access method• Based on CSMA (listen-before-talk)• Collision Resolution Algorithm Binary Exponential Backoff (BEB)• Defines two modes of operation:

1) Basic access transmission of data + ACK

2) Collision Avoidance access adds a handshake RTS/CTS• Reduces the duration of collisions (long data packets)• Protection against hidden terminals


The IEEE 802.11: The BEB algorithm

• Slotted backoff

• Random backoff counter in the interval [0,CWi]

• CWmin minimum size of the contention window

• CWMAX maximum size of the contention window

• Backoff counter decreased by one unit after each slot if channel sensed idle, otherwise, the counter is frozen

min2 , .ii MAXCW min CW CW


The IEEE 802.11: Basic Access

DATA

ACK

Source

Destination

Others CW

NAV

DIFS SIFS DIFS

Time+

CW

• Clear Channel Assessment (CCA) Distributed Inter Frame Space (DIFS)• Short Inter Frame Space (SIFS) propagation, processing, turnaround delays• Virtual Carrier Sensing Network Allocation Vector (NAV)• Positive ACK (ACK timeout in case of error)


The IEEE 802.11: Collision Avoidance

DATA

ACK

Source

Destination

Others CW

DIFS

RTS

SIFS

CTS

SIFS

NAV RTS

NAV CTS

NAV DATA

DIFS

Time+

SIFS

• Inclusion of handshake:• RTS: Request to Send• CTS: Clear to Send


Outline

1) Introduction

2) 802.11 overview

3) DQMAN overview



6) Conclusions


DQMAN: Overview I

1) DQMAN extension of DQCA

2) DQCA requires a central coordination point

3) Approach in DQMAN:

1) Master-Slave,

2) Self-organizing,

3) Spontaneous,

4) Passive (no explicit clustering overhead),

5) Dynamic CLUSTERING.

4) Master, slave and idle stations.

5) Masters pretend to be temporary infrastructure for their local neighborhood

6) Clusters are temporary

M

S2

S1

S3S4

S6

S5

ID

ID

ID

Master Service Set (MSS)


DQMAN: Overview II

Time+

Station 3: SLAVE

Station 2: SLAVE

Station 1: SLAVE

Station 0: MASTER FBPFBP

Data from 1 to 3

ACK

Contention WindowSlaves with data to transmit select

a minislot at random where to send an Access Request Sequence (ARS)

Busy tones

Feedback information about the state of each of the access minislots. With this information, stations can execute the MAC protocol rules

in a distributed manner

SIFS Short Inter Frame Space

1 2 3


Outline

1) Introduction

2) 802.11 overview

3) DQMAN overview



6) Conclusions


Coexistence

• Assume that DQMAN stations are dual

• Default access: DCF of the IEEE 802.11 Standard

• Dual stations → special RTS → dual-RTS:

• If the destination is a DCF station, it responds with a CTS

• If the destination station is a dual station it can initiate a DQMAN phase by becoming master

• For the DQMAN phase, legacy stations should remain silent by properly updating the NAV with the FBP → dual-CTS


Coexistence

Format of regular RTS and CTS packets

Frame Control Duration Rx. Address Tx. Address CRC

Frame Control Duration Rx. Address CRC

RTS

CTS

Protocol Version

Type of frame (control)

Subtype:RTS or CTS

B0 B1 B15… B8 B9 …

B8: To APB9: From AP

16 Control Flags (1-bit)


Coexistence

Dual-RTS and Dual-CTS (FBP)



RTS

CTS

Protocol Version


Subtype:RTS or CTS

B0 B1 B15… B8 B9 …




Coexistence




RTS

CTS

Protocol Version


Subtype:RTS or CTS

B0 B1 B15… B8 B9 …




Coexistence




RTS

CTS

Protocol Version


Subtype:RTS or CTS

B0 B1 B15… B8 B9 …




Coexistence

Time+

d-Station 3: M

d-Station 2

Station 1

d-Station 0 RTSd

CTSd


Time+

d-Station 3: M

d-Station 2

Station 1

d-Station 0

DATA

RTSd

CTSd CTSd

DATA

CTSd

Backoff

Backoff

Backoff

NAV

Coexistence

A minimum DCF operation time is now performed to enable access to legacy stations

NAV


Outline

1) Introduction

2) 802.11 overview

3) DQMAN overview



6) Conclusions


Simulation Results

MTO

5 DQMAN dual stations + 5 legacy stations


Simulation Results



Simulation Results



Outline

1) Introduction

2) 802.11 overview

3) DQMAN overview



6) Conclusions


Conclusions

• Lots of MAC protocols with high performance for WLAN

• IEEE 802.11 is there Backwards compatibility is a must

• Coexistence methodology presented in this paper

• DQMAN with IEEE 802.11

• In simulation, it works!

• Can be extended to any other MAC protocol

• Next step: try a real testbed to see if it works.

Jesús Alonso-Zárate [email protected]

Questions?

Thanks for your kind attention!

http://www.cttc.es/

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Coexistence of a Novel MAC Protocol for Wireless Ad hoc Networks and the IEEE 802.11

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