MetroScale WiFi Networks Replacement for traditional Ethernet LANs Several Municipalities Portland OR Philadelphia PA San Francisco CA Thornton CA Rockville MA New Orleans LA Anaheim CA ID: 549479
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Slide1
Emerging Technologies in Wireless LANs
Metro-Scale Wi-Fi NetworksSlide2
Replacement for traditional
Ethernet LANs
Several MunicipalitiesPortland, ORPhiladelphia, PASan Francisco, CAThornton, CARockville, MANew Orleans, LAAnaheim, CABuilt-out Plan of the Network
IntroductionSlide3
Virtual Private Network (VPN) Technology
Network Security Mechanisms
802.11-based Device SupportQoS CapabilitiesAccess LevelsFreePremiumBusinessNetwork Operations Centers(NOC) & Authentication, Authorization and Accounting (AAA)
Network Use Cases & PerformanceSlide4
Access TierClient Connection Tier
802.11 b/g
Ad-hoc ModeInfrastructure ModeHandoff DelayOffering an AP for potential handoff.Continuously update routing information to the client device’s point of attachment.VoIP Latency Limit of 50ms
Multi-Tier Network DesignSlide5
Mesh TierPath Redundancy
Inefficiencies
Hidden Station PhenomenonCSMA/CA MAC Protocol at high capacityInjection TierExtends existing wired network at low cost.Connects Mesh Tier to Backhaul TierBackhaul Tier
Distribution TierSlide6
Aggregates user traffic and responsible for routing, subscriber-related administration functions.
Access Controller (AC) acts as the layer 3 router.
AAAOperates on a per-subscriber QoS policies.Network performance monitoring.Bottleneck PossibilitiesAccess ControllerBackhaul PoPNetwork Operations Center (NOC)Slide7
Design ProblemsCoverage, RF propagation, and interference require detailed site surveying.
AP placement dependant on scale and cost.
Must interoperate with existing 802.11 devices.AuthenticationEncryption802.11 b/g CompatibilityHandoff and Dynamic IP AddressingMulti-story buildings require AP cells that extend into the third dimension.
WiFi Tier DesignSlide8
Operate in Ad-Hoc Mode.Efficient Path Selection
It maximizes the throughput for the current flow as well as the aggregate throughput of the mesh.
It minimizes the delay and jitter imposed on packets of the current flow as well as other flows in the mesh.Throughput issuesHidden Station PhenomenonTransmission Range < Interference Range
Mesh Tier DesignSlide9
Connects wireless mesh network to a wired backhaul.Drastically reduces throughput.
1.544
MBps down to 3 Mbps (T1)Potentially a bottleneck.Opportunity for high cost.Injection Tier DesignSlide10
900 MHzPreferred in areas with high foliage.
Long Ranges and/or no LOS
Low Data Rates2.4 GHzCo-channel Interferencethe access tierthird-party 802.11 b/g devicesnon-802.11 interferers5 GHzPreferred when no subject to obstructions.
Frequency RangesSlide11
802.11r StandardAlternative for existing cellular networks
Needed capability of efficient handoffs.
Low signaling overhead, packet loss and latency.Principle ProblemsCustom protocols not on standard 802.11 devices.Non-standard software needed.RFC 2002 standards designed with low mobility in mind.Inefficient bandwidth usage.
Network-wide Seamless MobilitySlide12
Metro-Scale Wi-Fi Networks
Conclusion