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Muni-Fi Revisited

By Robert Syputa, Senior Analyst
Contact the author at robert@maravedis-bwa.com

The economics of muni-Fi (municipal Wi-Fi) has not changed: it has never been viable on its own.  Muni-fi has only been justifiable based on gaining a position to leverage other revenues (as mentioned in previous Maravedis reports and articles) and access to fiber optic and community support assets.

The mistake that many have made is in assuming that low cost Wi-Fi end user devices equates to a low-cost system.  This is like saying that since wood is cheaper than titanium and aluminum, it would be better to build jet aircraft with plywood.  Like the Spruce Goose, it just can't stay off the ground.  Cheap and pervasive Wi-Fi end user products provides a market with ease of entry but does not mean Wi-Fi is suited to be a cost effective and efficient wide area system.

802.11 is designed as a WLAN - wireless LOCAL area network.  The core mechanism of Wi-Fi is a “contention based network.”  That means that because it is used in unlicensed, public access (free) spectrum, every user is given the right to compete for equal access.  Each user contends for access, and that creates interference and sharing of bandwidth.  And Wi-Fi is not designed to be used among hundreds or thousands of users.  It has been extended within the standards and products such as those from Cisco, but is built upon the limitations of the WLAN-based standard.  WiMAX is built from the ground up to be a carrier class, managed access system and highly extensible network.  It has the ability to be built either simply or into an extremely complex mobile network and to evolve to become a “smart distributed wireless broadband network” that can configure itself within a flexible set of parameters to suit a variety or dynamic set of needs.

The case for Wi-Fi MESH breaks down in many ways:

1) Wi-Fi MESH is proprietary: there is neither a standard that governs how each vendor builds its version of MESH, nor any mechanism to have MESH gear certified beyond the normal link level Wi-Fi standards. And there is no interoperability between vendors.  That means there is little way to internationally scale Wi-Fi MESH similar to how Wi-Fi end products have scaled.
2) Wi-Fi MESH uses the contention-based MAC or a proprietary MAC that has to be built upon the contention-based mechanism and limited channelization scheme available in 802.11.  For each hop between nodes in a Wi-Fi MESH system, 1/2 of the capacity is lost.  Some vendors have reduced that through their use of proprietary MAC, which breaks the standard to deliver “only” 1/4-1/3 degradation with each hop.  But that still means that performance of Wi-Fi MESH is far less than optimal.
3) WiMAX MESH, on the other hand, can use segmented channels for back haul and hops.  These can be dynamically allocated according to changing demands on the network and changing channel conditions.  The performance of a WiMAX MESH degrades only by encoding overhead, which should be less than 20% in worst case.
4) WiMAX MESH can be built within the standard.  To do this properly will take setting up a system profile or super-set profile to provide conformance testing and compatibility.  But even without that, vendors must meet certification and compatibility requirements for their systems and devices and will be commercially compelled to work with other vendors to make the WiMAX MESH portion compatible across vendors.
5) WiMAX merchant chip vendors are getting involved to provide ICs that implement "smart distributed WBB networking" capabilities. These can implement WiMAX MESH, virtual base station aggregations, and other advances, while keeping compliance with the standard and WiMAX Forum profiles.  And because these are merchant chips, several vendors can more easily implement products that will work together.

The argument for Muni-Fi breaks down when cost/coverage is evaluated. Wi-Fi MESH gear is far more expensive than comparable coverage using WiMAX or WiMAX MESH.  The difference will be even greater as WiMAX develops into more easily configured and deployed smart distributed wireless broadband networks.

Wi-Fi can be an active part of a WiMAX/Wi-Fi hybrid network.  As Sprint-Clearwire and others roll out wide areas of WiMAX coverage, WiMAX combined with Wi-Fi can provide an immediate and effective way for large numbers of existing clients to gain access.  As a longer term solution, WiMAX to the end user makes both economic and ease-of-use sense.

For more information you can contact the author. robert@maravedis-bwa.com