Emerging Technologies in Wireless LANs

Replacement for traditional Ethernet LANs Several Municipalities Portland, OR Philadelphia, PA San Francisco, CA Thornton, CA Rockville, MA New Orleans, LA Anaheim, CA Built-out Plan of the Network

Virtual Private Network (VPN) Technology Network Security Mechanisms based Device Support QoS Capabilities Access Levels Free Premium Business Network Operations Centers(NOC) & Authentication, Authorization and Accounting (AAA)

Access Tier Client Connection Tier b/g Ad-hoc Mode Infrastructure Mode Handoff Delay 1. Offering an AP for potential handoff. 2. Continuously update routing information to the client device’s point of attachment. VoIP Latency Limit of 50ms

Mesh Tier Path Redundancy Inefficiencies Hidden Station Phenomenon CSMA/CA MAC Protocol at high capacity Injection Tier Extends existing wired network at low cost. Connects Mesh Tier to Backhaul Tier Backhaul Tier

Aggregates user traffic and responsible for routing, subscriber-related administration functions. Access Controller (AC) acts as the layer 3 router. AAA Operates on a per-subscriber QoS policies. Network performance monitoring. Bottleneck Possibilities Access Controller Backhaul PoP

Design Problems Coverage, RF propagation, and interference require detailed site surveying. AP placement dependant on scale and cost. Must interoperate with existing devices. Authentication Encryption b/g Compatibility Handoff and Dynamic IP Addressing Multi-story buildings require AP cells that extend into the third dimension.

Operate in Ad-Hoc Mode. Efficient Path Selection 1. It maximizes the throughput for the current flow as well as the aggregate throughput of the mesh. 2. It minimizes the delay and jitter imposed on packets of the current flow as well as other flows in the mesh. Throughput issues Hidden Station Phenomenon Transmission Range < Interference Range

Connects wireless mesh network to a wired backhaul. Drastically reduces throughput MBps down to 3 Mbps (T1) Potentially a bottleneck. Opportunity for high cost.

900 MHz Preferred in areas with high foliage. Long Ranges and/or no LOS Low Data Rates 2.4 GHz Co-channel Interference the access tier third-party b/g devices non interferers 5 GHz Preferred when no subject to obstructions.

802.11r Standard Alternative for existing cellular networks Needed capability of efficient handoffs. Low signaling overhead, packet loss and latency. Principle Problems Custom protocols not on standard devices. Non-standard software needed. RFC 2002 standards designed with low mobility in mind. Inefficient bandwidth usage.

Conclusion