Chapter 13 - Metro–Scale Wi–Fi Networks

Summary

In this chapter we present the requirements, architecture and design challenges for municipal wireless broadband access networks. We first provide an overview of the requirements and services anticipated for municipal Wi-Fi networks based on five recent municipal RFPs. Next, we present design guidelines for a layered network using access, mesh, injection and backhaul tiers to create a cost-effective municipal broadband network utilizing equipment conforming to the 802.11 family of standards in the mesh and access tiers. To illustrate the challenges involved in creating mesh networks we explore the costs and benefits of building single versus multi-radio mesh networks and of creating a network capable of supporting session-persistence roaming across a municipality. We provide design equations supported by measured data for multi-hop mesh networks using a single mesh radio configuration. Our roaming solution is designed to operate in the context of a routed mesh network and offers seamless integration with network access controllers, and in conjunction with dedicated network branch routers, session-persistent roaming within metro-scale Wi-Fi networks.

Introduction

Envisioned as a replacement for traditional Ethernet Local Area Networks in home and office environments, 802.11-based broadband access networks have seen an explosive growth in the public space over the last five years. Beginning with small scale hotspot deployments in high use public areas such as airports, cafes and businesses, cities have begun to embrace Wi-Fi technology as a catalyst for attracting customers and revitalizing downtown areas.