Interference is the other side of the reliability coin, and this is a concern, particularly for devices operating in the 2.4-GHz band. WLAN systems, cordless phones and myriad other low-cost radio devices can affect a fixed-wireless system. Again, these problems can often be managed by using alternate radio channels or through antenna polarization, but there's always the risk of DoS (denial of service) attacks being mounted using inexpensive, easy-to-conceal radios and antennas. In fairness, motivated criminals can mount DoS attacks on most information systems, so in that sense, wireless isn't unique. Nonetheless, an increasing number of organizations are choosing to implement their fixed-wireless systems in the 5-GHz bands, where more channels are available and the risk of interference is lower.
Some of the reliability risk of point-to-point systems is associated with these systems' dependence on LoS (line of sight) communications. If LoS is broken, the link will go down. Syracuse University, one of our Real-World Labs® partners, recently experienced just such an outage when a crane being used to construct a new parking garage was parked directly between two buildings connected via wireless. Those situations can be dicey to manage, so as with any mission-critical system, put contingency plans in place before you dive in.
wireless technology is evolving rapidly, and technical breakthroughs that enhance performance and reliability are likely. Much of the innovation that is occurring in the WLAN space is bleeding over into both multipoint and point-to-point fixed wireless. For example, use of new 5-GHz WLAN chipsets will likely spawn a clutch of low-cost, high-performance fixed wireless systems. Significant progress is also being made to deliver more sophisticated mesh topologies that improve overall system reliability. In addition, the requirements that LoS be available between antennas is likely to be relaxed with the release of near-LoS and, eventually, non-LoS systems. These developments are particularly important for the evolution of multipoint fixed wireless but will likely expand the possibilities for point-to-point systems as well.
Dave Molta is a Network Computing senior technology editor. He is also an assistant professor in the School of Information Studies and director of the Center for Emerging Network Technologies at Syracuse University in New York. Write to him at [email protected].
We can see the personal ad now: "Sick of sexy mobile technologies taking your money then leaving you vulnerable? Tired of T3 leased lines that squeeze your budget dry? Consider hooking up with a cheap and available fixed wireless link. You won't be disappointed."