Heterogeneous Wireless Access in Large Mesh Networks Haiping Liu, Xin Liu, Chen-Nee Chuah, Prasant Mohapatra University of California, Davis IEEE MASS 2008

Outline Introduction Related Work Theoretical Study Proposed Method Evaluation Conclusion

Introduction The Major obstacles of large Wi-Fi mesh network  Multihop transmission The performance of multihop transmission decreases quickly as the number of hops increases  Link quality Depending on specific topologies and failure probabilities, the proportion of island nodes may not be negligible.  Distributed In large mesh networks, centralized MAC-layer schemes, global link transmission scheduling, or synchronization are not practical.

Introduction These problems cause:  Low Capacity  Limited system performance  Uncertainty of mesh topologies  Wireless link quality

Introduction The Major obstacles of large WiMAX mesh network  Spatial-reuse Although the large cover age of WiMAX reduces the number of wireless hops in the network, it cannot support good spatial-reuse of spectrum.  Expensive WiMAX devices have much higher power consumption and are much more expensive than Wi-Fi devices.  Deployment Wi-Fi devices have been widely deployed, and there fore it is beneficial to integrate WiMAX networks with existing Wi-Fi network.

Architecture Customer terminal mesh node WiMAX base station (WMBS) portal

Related Work WiMAX-only mesh network  Cannot fully reuse bandwidth and disregards the widely deployed Wi-Fi device Wi-Fi/WiMAX  Few of them analyze the major drawbacks of Wi-Fi or WiMAX-only mesh networks, offer theoretical proof of the heterogeneous architecture and publish corresponding solution.

Goal The paper propose an integrated Wi-Fi / WiMAX architecture that exploits the advantages of both technologies. The primary objective of this paper is to facilitate a good cooperation of the last two kinds of connections and improve the overall system performance

Theoretical Study – Notation γ Maximum utilization in the heterogeneous network

Theoretical Study – Formulation

Theoretical Study – Environment Set Environment Set Node equips with both Wi-Fi and WiMAX devices Link Capacity Wi-Fi54Mbps WiMAX70Mbps Coverage Wi-Fibetween any two neighboring Wi-Fi nodes WiMAXwhole network

Theoretical Study – Solution and Analysis

Protocol Design Although it is shown that a heterogeneous network is a good solution through the theoretical study, it is necessary to design a protocol that can achieve the gain in practice and deal with challenges that are not captured by the idealized model. We propose a threshold-based protocol and an optimization algorithm

Assumptions WiMAX utilized the scheduled MAC scheme. In Wi-Fi networks, nodes utilize IEEE MAC instead of the scheduled MAC as in theoretical study. The WMBSs do not try to control the routing or scheduling inside the Wi-Fi network.

Proposed Protocol – LABHW TH = 10 Cong a = 5 < 10 = TH WMBS Node a Cong a = 15 > 10 = TH Request Collect Requests from all nodes and run the algorithm. RejectAccept/ Traffic = 15 Receive and forward Traffic Reclaim BW Update and Broadcast TH

LABHW Algorithm – Notification

LABHW Algorithm – Formulation WMBS Node iNode j

Evaluation – Environment Set Environment Set node equip with both Wi-Fi and WiMAX devices link capacity Wi-Fi54Mbps WiMAX70Mbps coverage Wi-Fibetween any two neighboring Wi-Fi nodes WiMAXwhole network Simulator Qualnet 4.0

Evaluation

Conclusion This paper proposes a heterogeneous network architecture, consisting of Wi-Fi and WiMAX. To solve the major problems and improve the performance of multihop Wi-Fi mesh networks of large size. Based on the insights from the theoretical study, we design a practical protocol.

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