BelAir Networks' BelAir200

Updated Software

I tested the BA200 with the company's latest software release, version 2.0. Enhancements include support for multiple SSIDs (Service Set Identifiers) and 802.1x authentication on the access radio; enhanced Spanning Tree Protocol support; improved backhaul security with TKIP (Temporal Key Integrity Protocol--formerly WEP2); and a comprehensive command line.Each BA200 can house up to three BRM (Backhaul Radio Modules), which are used to establish the mesh backhaul using multiple point-to-point links between neighboring BA200 nodes. I was pleasantly surprised to see the backhaul achieve a 15.4-Mbps data link throughput between two nodes about two miles apart and 24.9 Mbps when the nodes were a quarter-mile apart.

To test 2.0's RSTP (Rapid Spanning Tree Protocol) capabilities, I configured the nodes in a closed ring and set up IEEE 802.1w on the nodes to resolve redundant backhaul loops. When an active backhaul link was forced down, the network converged in about 17 seconds by changing a dormant backhaul link to an active state. The handshake exchange time for each of the three BPDUs (Bridge Protocol Data Unit) used between paired nodes is set to 5 seconds each.

Security in the Air

The BRM's support for mutual peer-to-peer authentication with TKIP using preshared WPA ensures that backhaul traffic traverses secure encrypted pipes. The Access Radio Module (ARM) supports dynamic WEP and WPA using the scalable 802.1x infrastructure with a backend authentication server. Version 2.0 extends traffic segmentation to the wireless network by supporting 16 simultaneous SSIDs, where users can associate with a specific wireless network based on their needs and identity credentials.With multiple SSIDs comes the need to support Multiple Spanning Tree, also new in version 2.0. I used the protocol on multiple VLANs to test VoIP (voice over IP) traffic when the backhaul link was fully loaded with bidirectional traffic on different VLANs. Although the nodes do not have QoS (quality of service) support, the MOS (Mean Opinion Score) of the voice calls on a loaded single VLAN mesh network maintained a 4.38 (5 is the highest) with a consistent one-way delay of 2 ms when tested with IxChariot, a high-quality communication channel.

Version 2.0 raises the BA200 to enterprise standards of reliability, scalability and high availability, while maintaining BelAir's competitive cost versus capacity and performance advantage. Although the BA200 can be characterized as an outdoor wireless product, its extensible backhaul infrastructure with multiple point-to-point mesh elements and a modular access layer make it a complete and plausible wireless AP for any location.

Frank Robinson is a systems associate at Syracuse University. Write to him at [email protected].

BelAir Networks has fashioned its product line around a patented cellular LAN architecture, which successfully integrates the modularity and long reach of cellular technologies with the open IP architecture and standards based Wi-Fi technology to deliver scalable wireless using multiple point-to-point mesh elements or nodes. The BA200 achieved throughput of about 25 Mbps on the 5-GHz backhaul and approximately 5 Mbps on the 2.4-GHz access point when tested with data traffic generated by IxChariot.

The BA200 is the only device I've come across that uses nonconventional IEEE 802.11a channels for its backhaul. The Backhaul Radio Module (BRM) can tune to frequencies that are offset by multiples of 5 MHz from the channel defined in the standard. I used AirMagnet Laptop Wireless LAN Analyzer to monitor the environment and couldn't detect any 5-GHz data transmission, but I noticed a consistent noise floor on the recommended 802.11a channel. The BRM also gives extraordinary distance on the backhaul, especially under in environments where line-of-site exists.The coverage offered by the Access Radio Module servicing clients through the 802.11b 2.4-GHz band is impressive, though it's important to note that increased coverage sometimes translates into lower per-user throughput in environments with moderate or high density. When I set up the BA200 to blast WiFi signals at 27 dBm into a 21-story building on the Syracuse University campus, the signal strength inside the building in areas facing the node supported a data rate of at least 1 Mbps to 2 Mbps across all the floors. Although this barely exceeds what we consider to be broadband connectivity, it's enough to support e-mail, Internet browsing and even limited voice over WLAN calls. BelAir engineers asserted that four radios surrounding the building could provide full inside coverage for less money than it would cost to install one or more APs on each floor in the building. BelAir claims it can support 256 simultaneous associations and up to 50 active users per node.

To test BelAir's claim to be the only solution capable of supporting VoIP, RFID, video and mobile data simultaneously, I set up the nodes in a star topology and loaded the backhaul with an aggregate throughput of 74.16 Mbps measured on the Ethernet port where the hub unit connected to our wired network. I was surprised to establish a VoIP call with a MOS value of 4.38 (highest score is 5). The MOS value dropped to 3.64 when there were two TCP flows in opposite direction on the same backhaul link, still an acceptable level to maintain an intelligent conversation.

The BelAir solution is engineered for harsh environments without the need to sacrifice flexibility or capacity. The system's support for Rapid Spanning Tree Protocol (802.1W) lets it self-heal without a central management controller. The platform is based on an embedded Linux platform that runs on each node facilitating classfull and classless routing, using OSPF, IGRP, RIP and static routes. This obviates dedicated network components to expand the wireless infrastructure.