January, 2006

Chun-Ting Chou, PhilipsSlide 1

doc.: IEEE 802.15-15-06-0018-00-003c

Submission

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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

Submission Title: [Medium Access Control (MAC) in Wireless PAN using Directional Antennas]Date Submitted: [16 January, 2006]Source: [Chun-Ting Chou, Alireza Seyedi and Richard Chen] Company [Philips]Address [345 Scarborough Rd, Briarcliff Manor, NY 10510]Voice:[914 945 6099], FAX: [914 945 6330], E-Mail:[chun-ting.chou@philips.com]

Re: [N/A]

Abstract: [Investigation of required MAC functionalities, given the introduction of directional antennas in 802.15.3c physical layer]

Purpose: [Discuss required MAC functionalities, given the introduction of directional antennas in 802.15.3c physical layer]

Notice: This document has been prepared to assist the IEEE P802.15. 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.Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15.

January, 2006

Chun-Ting Chou, PhilipsSlide 2

doc.: IEEE 802.15-15-06-0018-00-003c

Submission

Medium Access Control (MAC) in Wireless PAN using Directional

Antennas

Opportunities and challenges

January, 2006

Chun-Ting Chou, PhilipsSlide 3

doc.: IEEE 802.15-15-06-0018-00-003c

Submission

Outline

• Background

• Benefits of Directional Antennas

• Challenges at MAC layer

• Issues of existing IEEE 802.15.3 MAC

• Conclusions

January, 2006

Chun-Ting Chou, PhilipsSlide 4

doc.: IEEE 802.15-15-06-0018-00-003c

Submission

Background

• IEEE 802.15.3c Task Group is generating a high rate

mm wave (60GHz) alternate PHY for 802.15.3.

• High frequency results in high path-loss. Hence,

exploiting antenna gain is necessary.

• High frequency enables us to design small directional

antennas and/or antenna arrays.– What functionalities are necessary and/or beneficial for

a WPAN MAC with directional antennas.

– Is 802.15.3 MAC equipped to handle devices with

directional antennas?

January, 2006

Chun-Ting Chou, PhilipsSlide 5

doc.: IEEE 802.15-15-06-0018-00-003c

Submission

Benefits of Directional Antennas

January, 2006

Chun-Ting Chou, PhilipsSlide 6

doc.: IEEE 802.15-15-06-0018-00-003c

Submission

• Abstract model

• Advantages of directional antennas– Higher gains, longer transmission range– Directional transmission/reception: spatial

reuse

Omni. vs. Directional Antennas

TxRx

Tx

Rx

January, 2006

Chun-Ting Chou, PhilipsSlide 7

doc.: IEEE 802.15-15-06-0018-00-003c

Submission

Challenges at MAC Layer

January, 2006

Chun-Ting Chou, PhilipsSlide 8

doc.: IEEE 802.15-15-06-0018-00-003c

Submission

Challenge #1: Neighbor Discovery

• Different Tx/Rx antenna modes could be used at PHY layer

• Three types of neighbors– Omni-omni neighbors

– Directional-omni neighbors

– Directional-directional neighbors

January, 2006

Chun-Ting Chou, PhilipsSlide 9

doc.: IEEE 802.15-15-06-0018-00-003c

Submission

Challenge #1: Neighbors Discovery (conti.)

• Mechanisms for neighbor discovery – Discovery of omni-omni neighbors is trivial– New mechanisms are required for

discovery of directional-omni and directional-directional neighbors• Location/direction information makes it a lot

easier; otherwise,• Intelligent algorithms are needed

January, 2006

Chun-Ting Chou, PhilipsSlide 10

doc.: IEEE 802.15-15-06-0018-00-003c

Submission

Challenge #2: New Hidden-node Problems

• The Cause: Deafness– Asymmetry in Tx/Rx antenna gains

– Directional Transmission/Reception

CTSRTS

DATA

RTS

A B

A does not knowthe transmission

of B and vice versa

A

B does not know the

transmission between A and

Rx

Rx

Rx

Rx1

Rx2

B

B

Many other Cases !!

January, 2006

Chun-Ting Chou, PhilipsSlide 11

doc.: IEEE 802.15-15-06-0018-00-003c

Submission

Challenge #3: Spatial Reuse

• A by-product of directional transmission and reception

• Advantages: higher spectrum efficiency and user/system throughput (as high as 800% depending on the node density, antenna gain and types [1]-[3], very useful for compensating higher overheard due to high transmission rate)

A

B

Rx2

January, 2006

Chun-Ting Chou, PhilipsSlide 12

doc.: IEEE 802.15-15-06-0018-00-003c

Submission

Challenge #3: Spatial Reuse (conti.)

• A non-trivial problem– Hidden node problems (challenge #2)– Longer interference range

• Potential Solutions– Use directional network allocation vector

(D-NAV) in distributed networks

Rx2A RX1B RX2 B A Rx1

(a) Interference-free concurrent transmissions

(b) Interfering concurrent transmissions

January, 2006

Chun-Ting Chou, PhilipsSlide 13

doc.: IEEE 802.15-15-06-0018-00-003c

Submission

Challenge #3: Spatial Reuse (conti.)

– Use space-time scheduling in centralized networks

– Antenna gain/power control• without control

• with control

Rx2B Rx1A

directional-directional neighbors

Rx2B Rx1A

No interference

Receive interference

from B

Concurrent directional

transmission

January, 2006

Chun-Ting Chou, PhilipsSlide 14

doc.: IEEE 802.15-15-06-0018-00-003c

Submission

Issues of existing IEEE 802.15.3 MAC

January, 2006

Chun-Ting Chou, PhilipsSlide 15

doc.: IEEE 802.15-15-06-0018-00-003c

Submission

Existing IEEE 15.3 MAC

• Omni-omni neighbor is assumed

• Contention- and polling-based channel mechanism are both used

Superframe # m-1 Superframe # m+1

Channel time allocation periodBeacon

# m

Contention

access period

MCTA 1 MCTA 2 CTA 1 CTA 2 CTA n

Superframe # m

…

Piconet controller/devicesassociation via broadcasting beacons (neighbor discovery)

CSMA/CA medium access Control for control messages)

Scheduled transmission in channel time allocated by piconet controller

Challenge # 1 Challenge # 2 Challenges # 2 and 3

January, 2006

Chun-Ting Chou, PhilipsSlide 16

doc.: IEEE 802.15-15-06-0018-00-003c

Submission

Conclusions

• Directional antennas bring in new opportunities– Longer transmission range, higher

spectrum efficiency

• Challenges at MAC layer– Neighbor discovery, new hidden node

problems, spatial reuse and power control

• The next step?

January, 2006

Chun-Ting Chou, PhilipsSlide 17

doc.: IEEE 802.15-15-06-0018-00-003c

Submission

References

[1] R. Ramanathan and etc., “Ad Hoc Networking With Directional Antennas: A Complete System Solution,” IEEE Journal on Selected Areas in Communications, vol. 23, No. 3, Mar. 2005.

[2] R. Ramanathan, “On the Performance of Ad Hoc Networks with Beamforming Antennas”, ACM MobiHoc, 2001.

[3] R. Choudhury and etc., “Using Directional Antennas for Medium Access Control in Ad Hoc Networks,” ACM MOBICOM, 2002.

[4] L. Bao and etc., “Transmission Scheduling in Ad Hoc Networks with Directional Antennas,” ACM MOBICOM, 2002.

[5] T. Korakis and etc., “A MAC Protocol for Full Exploitation of Directional Antennas in Ad Hoc Wireless Networks,” ACM MobiHoc, 2003