On Mitigating the Broadcast Storm On Mitigating the Broadcast Storm Problem with Directional AntennasProblem with Directional Antennas

Sheng-Shih Wang

July 14, 2003

Chunyu Hu, Yifei Hong, and Jennifer HouDept. of Electrical and Computer Engineering, Dept. of Computer Science

University of Illinois at Urbana-Champaign

IEEE International Conference on Communications (ICC’03), vol. 1, pp. 104-110, 2003

July 14, 2003July 14, 2003 Sheng-Shih Wang2

OutlineOutline

Introduction Directional Broadcast Scheme Performance Evaluation Conclusions

July 14, 2003July 14, 2003 Sheng-Shih Wang3

Introduction Introduction --- Motivation & Objective & Solution--- Motivation & Objective & Solution

Motivation Broadcast storm problem

Too much redundant traffic Frequent contention Transmission collision

Objective Mitigates the Broadcast storm problem

Solution Directional antennas

July 14, 2003July 14, 2003 Sheng-Shih Wang4

Introduction Introduction --- Directional Broadcast Scheme--- Directional Broadcast Scheme

Advantage Increase the network capacity with spatial reuse Reduce the interference and contention Increase the number of on-going connections

Drawback Hardware cost

July 14, 2003July 14, 2003 Sheng-Shih Wang5

Introduction Introduction --- Network Model--- Network Model

For each node One transceiver 4 switched-beam directional antennas

For each directional antenna Span 90 degrees 4 antennas cover all the direction Two operating modes: active and passive

Only active antennas are used to transmit or receive

July 14, 2003July 14, 2003 Sheng-Shih Wang6

Introduction Introduction --- Network Model (cont.)--- Network Model (cont.)

Assumption The transmission range of both omni-directional and

directional antennas are the same MAC layer

control of each antenna’s mode learn the angle-of-arrival (AOA) and the strength of

incoming signal power All nodes use the same directional antenna patterns

July 14, 2003July 14, 2003 Sheng-Shih Wang7

Introduction Introduction --- Omni-directional Broadcast Scheme--- Omni-directional Broadcast Scheme

Idea On receipt of a broadcast packet, a node will forward

it to all its neighbors after the random delay timer expire

Advantage Maximize the number of nodes that broadcast

packets can reach Drawback

A significant amount of redundant traffic Serious interference/contention Collision

July 14, 2003July 14, 2003 Sheng-Shih Wang8

Directional Broadcast Scheme Directional Broadcast Scheme --- On/Off --- On/Off Directional Broadcast SchemeDirectional Broadcast Scheme

Idea Only forwards the packet in the directions other than

the incoming AOA Antenna mode setting

Passive The incoming antenna AOA The antenna AOA that the same packet is received

before the delay time expires Active

After the delay timer expires and the channel is sensed idle, only antennas that have not received the packet will be set to active and forward the packet

July 14, 2003July 14, 2003 Sheng-Shih Wang9

Directional Broadcast Scheme Directional Broadcast Scheme --- On/Off --- On/Off Directional Broadcast Scheme (cont.)Directional Broadcast Scheme (cont.)

July 14, 2003July 14, 2003 Sheng-Shih Wang10

Directional Broadcast Scheme Directional Broadcast Scheme --- Relay-Node---- Relay-Node-Based Directional Broadcast SchemeBased Directional Broadcast Scheme

Idea For each direction, only one relay node to forward

broadcast packets The relay node in a direction is the one-hop farthest

node

July 14, 2003July 14, 2003 Sheng-Shih Wang11

Directional Broadcast Scheme Directional Broadcast Scheme --- Relay-Node---- Relay-Node-Based Directional Broadcast Scheme (cont.)Based Directional Broadcast Scheme (cont.)

July 14, 2003July 14, 2003 Sheng-Shih Wang12

Directional Broadcast Scheme Directional Broadcast Scheme --- Location---- Location-Based Directional Broadcast SchemeBased Directional Broadcast Scheme

Idea The relay node should cover the largest extra area

that the broadcast packet has not received The delay is not uniform for all the directions

Larger extra area smaller delay The delay for each direction is proportional to the

extra coverage ratio The extra coverage ratio is the extra coverage over ¼ of

the circle area

July 14, 2003July 14, 2003 Sheng-Shih Wang13

Directional Broadcast Scheme Directional Broadcast Scheme --- Location---- Location-Based Directional Broadcast Scheme (cont.)Based Directional Broadcast Scheme (cont.)

July 14, 2003July 14, 2003 Sheng-Shih Wang14

Directional Broadcast Scheme Directional Broadcast Scheme --- Location---- Location-Based Directional Broadcast Scheme (cont.)Based Directional Broadcast Scheme (cont.)

Circle O(0,0): x2 + y2 = R2

0

III'2

0

II'1

0

I'0

CSBB'III'DSAA'II'SABI'

20

1 1 1

41

SS

r,SS

r,SS

r

SS,SS,SS

RS

Circle S(a,b): (x - a)2 + (y - b)2 = R2

July 14, 2003July 14, 2003 Sheng-Shih Wang15

Performance Evaluation Performance Evaluation --- Simulation Environment--- Simulation Environment

Simulator: QualNet 100 nodes are uniformly distributed in an area of

1500m 1500m Transmission range: 250m Transmission rate: 2 Mbps Simulation time: 300 sec Packet size: 118/118/134/122 bytes

July 14, 2003July 14, 2003 Sheng-Shih Wang16

Performance Evaluation Performance Evaluation --- Performance Metrics--- Performance Metrics

Coverage (# of nodes) The number of nodes that receive a broadcast

packet Latency (msec)

The time span from the instant a broadcast packet is sent till the instant all the nodes receive the packet

Redundancy (# of pkts / node) The total number of duplicate packets received by

nodes in a simulation run Collisions (per node)

The number of packets erroneously received because of collision

July 14, 2003July 14, 2003 Sheng-Shih Wang17

Performance Evaluation Performance Evaluation --- Simulation Result in --- Simulation Result in Static Wireless NetworksStatic Wireless Networks

Average Coverage(# of

nodes)

Latency(msec)

Redundancy(# of pkts/node)

Collision(per node)

Scheme 0 75.5 14.32 312.4 99.2

Scheme 1 87.7 14.38 200.5 53.6Scheme 2 79.8 11.04 63.9 78.2

Scheme 3 88.9 24.07 196.2 631) All three directional schemes outperform the omni-directional scheme2) Scheme 1 collision

Scheme 2 latency and redundancyScheme 3 coverage

3) Scheme 3 incurs the large latency one antenna, more carrier sense

July 14, 2003July 14, 2003 Sheng-Shih Wang18

Performance Evaluation Performance Evaluation --- Simulation Result for --- Simulation Result for MobilityMobility

The neighbor information is less reliable

(relay-node-based scheme)

July 14, 2003July 14, 2003 Sheng-Shih Wang19

ConclusionsConclusions

Proposed solutions On/Off Directional Broadcast Scheme

collision Relay-Node-Based Directional Broadcast Scheme

Latency, redundancy Location-Based Directional Broadcast Scheme

coverage Future work

Power management (sleep and awake periodically)