vtc 2004 spring, milan, italy complementing 3g cellular networks by multi hop capabilities of an...

VTC 2004 Spring, Milan, Italy

Complementing 3G Cellular Networks by Multi Hop Capabilities of an Enhanced

MAC Protocol for Wireless LAN

Frank H.P. Fitzek, Federico Bertocchi and Michele Zorzi

Department of Communications Technology, Aalborg UniversityNeils Jernes Vej 12, 9220 Aalborg Øst, Denmark, e-mail:

[email protected] of Ferrara, Via Saragat 1, I-44100 Ferrara, Italy, e-mail:

[fbertocchi|zorzi]@ing.unife.it

IEEE Semiannual Vehicular Technology ConferenceMay 17-19, 2004, Milan, Italy

2

Overview

3G/WLAN Coupling

Motivation

Architecture

Problem of IEEE802.11 MAC

IEEE802.11a introduction

New MAC Protocol

Simulation Scenario

Simulation Results

Conclusion


3

3G/WLAN Coupling

3G and WLAN (IEEE802.11) have disjunctive advantages3G backbone (services, billing, etc)3G coverageWLAN data rate (allows to create new services)

3GPP propose the 3G/WLAN coupling3G investments were incredible high and the installation of WLAN hotspots has to come at a minimum price.Multi hop networks are a viable option for installation of a network where it is missing/incomplete or as a complement to existing cellular systems.Coverage extension is attractive to reduce installation costs. In large WLAN hotspots ¾ of the total costs are caused by the fixed infrastructure.


4

Motivation for Multi Hop Networks from the cost perspective

Cum

mu

lati

ve c

ost

/retu

rn €

Time

Return of Investment

Cost without multi hop

Cost with multi hop


5

Possible Architecture for 3G/WLAN Coupling

Internet

CoreSGSN

GGSN

Chat MMS

IMSMBMS

application servers

ERAN

BTS

NodeB

UTRAN

BSC

RNC

Packet Data

Gateway

WT

WT

VAP

AP

SwitchVAP VAP VAP

AP

location Xlocation Y

location Z


6

Problems for multi-hop networks with standard IEEE802.11 WLAN

Many researchers report about the problem of IEEE802.11b in multi-hop networksReason: RTS /CTS exchange blocks ongoing communicationExample: Simple line communication

DC E FCTSCTSBRTSRTS

A


7

Problems for multi-hop networks with IEEE802.11 WLAN

Simple example shows the throughput degradation for multi-hop network operation (6 terminals are blocked while one packet is transmitted)Well documented and reported for IEEE802.11b even for more sophisticated network topologiesThe bandwidth is not use efficiently IEEE802.11a offers higher transmission rates, but the bandwidth inefficiency remains the sameThe problem resides in the MAC design


8

Data Rate versus Range IEEE802.11a


9

5GHz ISM Frequency Bands


10

Channel Structure IEEE802.11a


11

Possible Approaches For Spectrum Usage

Divide collision domain into smaller groups by assigning all different channels randomly– RANDOM APPROACH

reduce the RTS/CTS problemlow connectivity (N channels result in connectivity level of 1/N)routing over different channels is difficult

All terminals use the same channel - STATIC APPROACH

Inefficiency in the bandwidth usage (N channels result in a bandwidth efficiency of 1/N)higher connectivityStandard IEEE802.11

Communicate the usage of the assignment of the channels to all wireless nodes – DYNAMIC APPROACH

higher connectivitySolution need!!!


12

Proposed MAC Scheme

Use of a common signaling channelOnly for RTS/CTS exchange4 way handshake with probingData and ack on dedicated channel

Sender Receiver

signaling channel

dedicated channel

RTS1 CTS1 RTS2CTS2

probe data S2R ack

RTS1RTS2probe data S2RCTS1CTS2ack

NAVchannel

NAVchannel


13

Simulation Model and Metric

Simulation ModelFour different topologies Senario A/1R/1S/5SAssuming video services

Source: 24 “Friends” episodesVBR traffic peak/mean ~ 20Random length and starting phase

Randomly chosen sender and transmitterShortest path routing

MetricDelivery ratio of send and received packetsDelay of received packets including retransmissions and multi hop


14

Scenario A: Delivery


15

Scenario A: Delay


20

Scenario 5S: Delivery


21

Scenario 5S: Delay


22

Conclusion and Outlook

3G/WLAN coupling enables new services for the customerMulti Hop WLAN allows low cost installation of WLAN

Important in the initial phase

New proposed MAC protocol for Multi Hop yields high performance in terms of delivery ratio and delay even for real time video services.Small changes to the standard IEEE802.11 MAC protocol.Further improvements were already investigated.Future work should include TCP traffic.

VTC 2004 Spring, Milan, Italy

Thanks for your attention!

Q/[email protected]

[email protected]


24

Further Reading

F.H.P. Fitzek, P. Seeling, M. Reisslein, and M. Zorzi, "Visualisation Tool for Ad Hoc Networks - ViTAN", IEEE Network Magazine, software tools for networking, p. 9, Vol.17, No. 4, July/August 2003

F.H.P. Fitzek, D. Angelini, G. Mazzini, and M. Zorzi, "Design and Performance of an Enhanced IEEE802.11 MAC Protocol for Ad Hoc Networks" , In Proceedings IEEE VTC 2003, Wireless Communications: 3G and Beyond Symposium, October 6-9, 2003, Orlando, Florida, USA

F.H.P. Fitzek, G. Schulte, and M. Zorzi, "Connectivity, Multi Hop, and Upper Bound Capacity Calculation for Multi-Rate Terminals in Ad-Hoc Networks“, In Proceedings of Wireless World Research Forum 9, (WWRF9), July 1-2, 2003, Zürich, Switzerland

vtc 2004 spring, milan, italy complementing 3g cellular networks by multi hop capabilities of an...

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