Routing Protocols for Indoor Wireless Ad-Hoc Networks
—
A Cross-Layer Perspective
A Dissertation Submitted in Partial Fulfillment
of the Requirements for the Degree of Doctor of Philosophy in the Department of Computer and Decision Engineering of the
Faculty of Applied Sciences by
Jean-Michel Dricot
Universit´e Libre de Bruxelles
– 2007 –
Abstract
The all-over trend for an universal access and ubiquitous access to the Internet is driving a revolution in our societies. In order to support this era of nomadic applications, new flexible network architectures have emerged. They are referred to as“wireless ad-hoc networks.”
Since human-operated devices will more likely be used indoor, it leads to many issues related to the strength of the fading in this environment. Recently, it has been suggested that a possible interaction might exist between various parameters of the ad-hoc networks and, more precisely, between the propagation model and the routing protocol.
To address this question, we present in this dissertation a cross-layer perspective of the analysis of theseindoorad-hoc networks. Our reasoning is made of four stages. First, the cross-layer interactions are analyzed by the means of multivariate statistical techniques. Since a cross-layering between the physical layer and the routing protocol has been proven to be significant, we further investigate the possible development a physical layer-constrained rout- ing algorithm.
Second, fundamental equations governing the wireless telecommunications systems are developed in order to provide insightful informations on how a reliable routing strategy should be implemented in a strongly-faded environment. After that, and in order to allow a better spatial reuse, the routing protocol we propose is further enhanced by the adjonction of a power control algorithm. This last feature is extensively analyzed and a closed-form expression of the link probability of outage in presence of non-homogeneous transmission powers is given. Numerous simulations corroborate the applicability and the performance of the derived protocol. Also, we evaluate the gain, in terms of radio channel ressources, that has been achieved by the means of the power control algorithm.
Third, an architecture for the interconnection with a cellular network is investigated. A closed-form expression of the relaying stability of a node is given. This equation expresses the minimal requirement that a relaying node from the ad-hoc network must fullfil in order to bridge properly the connections to the base-station.
Finally, a real-life implementation is provided as a validation of the applicability of this novel ad-hoc routing protocol. It is concluded that, both from the performance and the spatial re-use point-of-views, it can be taken advantage from the cross-layering between the physi- cal and the routing layers to positively enhance the networking architectures deployed in an indoor environment.
Contents
1 Introduction 1
1.1 The Ad-Hoc Networking Paradigm . . . 1
1.2 Unicast Routing Techniques for Ad-Hoc Networks . . . 4
1.3 Motivations . . . 9
1.3.1 Indoor Wireless Personal Communications . . . 9
1.3.2 Cross-Layering in Wireless Networks . . . 11
1.4 Objectives of this Dissertation . . . 12
1.5 Dissertation Layout and Related Publications . . . 12
2 Modeling the Indoor Propagation 17 2.1 Introduction . . . 17
2.2 Propagation Mechanisms . . . 18
2.2.1 Maxwell’s equations . . . 18
2.2.2 Plane Waves Properties . . . 20
2.2.3 Polarization of the Plane Waves . . . 21
2.2.4 Reflection, Refraction, and Transmission . . . 22
2.2.5 Power of a Transmission . . . 24
2.3 Multipath Phenomena in Wireless Networks . . . 24
2.3.1 The Shadowing Effect . . . 25
2.3.2 Narrowband Fast Fading . . . 26
2.3.3 The Doppler Effect . . . 29
2.4 Stochastic Radio Channel Models . . . 31
2.5 A New Indoor Propagation Model for the NS-2 . . . 33
2.5.1 Motivation . . . 33
2.5.2 The Existing NS-2 Radio Propagation Model . . . 33
2.5.3 Computation of the Average Power of the Signal . . . 35
2.5.4 Simulation of the Fading in the Indoor Environment . . . 37
2.5.5 Experimental Calibration and Validation . . . 39
2.5.6 Considerations for the Implementation in the NS-2 Simulator . . . . 44
2.6 Concluding Remarks . . . 45 v
3 Evidences of the Cross-Layer Interactions in Wireless Networks 47
3.1 Introduction . . . 47
3.2 Sources of Cross-Layer Interaction . . . 48
3.3 Multivariate Analysis . . . 49
3.3.1 Background . . . 50
3.3.2 Characterizing the Interaction . . . 51
3.3.3 Power of the Test and Rejection . . . 53
3.3.4 Strength of the Relationship Between the Factors . . . 55
3.4 Methodology . . . 55
3.4.1 Mobility Model . . . 56
3.4.2 Traffic Model . . . 59
3.4.3 Propagation Model . . . 60
3.4.4 Performance Metrics . . . 60
3.5 Preliminary Investigation of the Possible Cross-Layering . . . 61
3.5.1 One-way Interactions . . . 61
3.5.2 Two-way Interactions . . . 64
3.5.3 Higher-level Interactions . . . 66
3.6 Cross-Layer Interaction between the Physical Layer and the Routing Protocol 66 3.6.1 Introduction and Methodology . . . 66
3.6.2 Analysis and Interpretation . . . 67
3.7 Multivariate Analysis of the Indoor Scenario . . . 73
3.7.1 Introduction and Analysis . . . 73
3.7.2 Preliminary Conclusions . . . 75
3.8 Concluding Remarks . . . 80
4 A Physical Layer-Constrained Approach for Indoor Wireless Networks 83 4.1 Introduction . . . 83
4.2 Preliminaries . . . 84
4.2.1 Topology and Movement Considerations . . . 84
4.2.2 Traffic modeling . . . 85
4.3 Physical-Constrained Routing . . . 86
4.3.1 Bit Error Rate at the End of a Multi-hop Route . . . 87
4.3.2 Bit Error Rate at the End of a Multi-hop Route – Scenarios with Strong LOS Communications . . . 88
4.3.3 Bit Error Rate at the End of a Multi-hop Route – Scenarios with Faded Communications . . . 89
4.3.4 Physical Layer-Constrained Routing Algorithm . . . 90
4.4 MAC-Level Power Control . . . 95
4.4.1 Advocacy for an Interoperability between the Power Control and Routing Process . . . 95 4.4.2 Probability of Collision in Presence of Inhomogeneous Transmit Power 98
4.4.3 Discussion . . . 102
4.5 Probability of Outage on a Single Link . . . 105
4.5.1 Impact of Carrier Sensing . . . 105
4.5.2 Evaluation of the Probability of Outage . . . 106
4.5.3 Application to theAODVϕProtocol . . . 110
4.5.4 Complete Derivation of the Probability of Outage . . . 114
4.5.5 Probability of Outage Along a Route . . . 115
4.5.6 Interpretation and Impact on Routing Approach . . . 116
4.6 Spatio-Temporal Locking . . . 122
4.6.1 Surface ratio locked for a one-hop transmission . . . 122
4.6.2 Time Required for a Transmission . . . 124
4.6.3 Effect of Traffic Density . . . 125
4.6.4 Spatio-Temporal Locking . . . 125
4.6.5 Interpretation and Use of Space×Time Metric . . . 126
4.6.6 Requirements for Successful Spatio-Temporal Re-use . . . 128
4.6.7 Theoretical Limit for the Gain trough Power Control . . . 133
4.7 A Dual Approach toAODVϕ . . . 134
4.7.1 Motivation . . . 134
4.7.2 Preliminary Developments . . . 135
4.7.3 Implementation of the Rewarding Scheme inAODVπ . . . 136
4.8 Concluding Remarks . . . 139
5 Performance Analysis of Physical-Layer Constrained Routing 141 5.1 Introduction . . . 141
5.2 Performance Metrics . . . 142
5.3 Performance of theAODVϕRouting Protocol . . . 143
5.3.1 Amount of Collisions due to Power Control Adjustment . . . 143
5.3.2 Scalability . . . 146
5.3.3 Impact of Initial Energy . . . 147
5.3.4 Impact of Nodes Mobility . . . 148
5.3.5 Spatio-Temporal Volume . . . 148
5.4 Performance of theAODVπRouting Protocol . . . 151
5.4.1 Scalability . . . 151
5.4.2 Impact of Initial Energy . . . 151
5.4.3 Impact of Nodes Mobility . . . 154
5.5 Concluding Remarks . . . 154
6 Hybridation between Cellular and Indoor Ad-Hoc Wireless Systems 157 6.1 Introduction . . . 157
6.2 Propagation Models . . . 159
6.3 Opportunities for a Hybrid Architecture . . . 160
6.4 Architecture Design for the Interconnection with Cellular Systems . . . 162
6.4.1 Network Entities . . . 164
6.4.2 Ad-hoc Wireless Network Portion . . . 164
6.4.3 UMTS Portion . . . 165
6.4.4 Data Packets Forwarding Scheme . . . 165
6.4.5 Charging and Billing . . . 166
6.5 Protocol Description . . . 166
6.5.1 The Associativity Between a NodeB and a Gateway . . . 166
6.5.2 Gateway Selection Algorithm . . . 170
6.6 Performance Analysis of theiAODVϕArchitecture . . . 172
6.6.1 Performance Metrics . . . 172
6.6.2 Impact of the Number of Simultaneous Connections . . . 174
6.6.3 Impact of the Traffic Load . . . 175
6.6.4 Indoorvs.Outdoor Deployment . . . 176
6.7 Concluding Remarks . . . 178
7 System Services for the Support of theAODVϕRouting Protocol 180 7.1 Introduction . . . 180
7.2 Technology Opportunities . . . 181
7.2.1 The Linux Wireless Extensions . . . 182
7.2.2 The NetFilters Tools . . . 182
7.3 Requirements . . . 184
7.4 Architecture . . . 185
7.5 TheAODVϕimplementation . . . 186
7.5.1 Functionalities of the System Services . . . 187
7.5.2 Data Structures . . . 190
7.5.3 Daemon-to-Kernel Communication . . . 192
7.6 Performance Analysis . . . 193
7.6.1 Network Model . . . 193
7.6.2 Scenarios . . . 194
7.6.3 Discussion . . . 195
7.7 Concluding Remarks . . . 197
8 Final Remarks 200
References 205
