Tropos introduces 802.11n into its outdoor wireless mesh

Tropos Networks has released a trio of new outdoor wireless mesh nodes, its first supporting the high-throughput 802.11n IEEE standard.

The new products are intended to double or triple node-to-node compared to the 6Mbps typical of the company's existing product. One of the new nodes is a two-radio device with a wide range of configuration options, including different antennas. Two others share a smaller form factor and integrated antennas.

A big target market for 11n nodes are aimed at outdoor municipal wireless deployments, which are seeing something of resurgence. Firetide Networks just announced high performance mesh nodes based on the same underlying multiple input, multiple output (MIMO) technology that's a key part of the 11n standard. But the new Firetide nodes, designed strictly as a broadband infrastructure, are not 802.11n certified.

Many municipalities instead of focusing on large-scale public wireless broadband nets are refocusing on extending their enterprise networks wirelessly to support public safety staff, video surveillance systems, and field workers. The high-throughput of 11n radios promises much better performance at any given range, and cleaner signals.

One challenge in using 11n in outdoor environments is that its multiple data streams, each linked to a send or receive antenna, benefit most from something that's actually a liability in conventional Wi-Fi radios: lots of surface and objects that reflect the radio signals. In 11n, this multi-path phenomenon is leveraged to boost throughput. But multipath is much less of an issue outdoors

The outdoor Tropos nodes exploit another 11n feature called maximal ratio combining (MRC), an algorithm that lets the mesh node adjust the differing phases and amplitudes of the signal it receives on each antenna from a sending client. In effect, it improves throughput on the uplink by enabling the node to better "hear" the client. Another benefit is increased coverage because of the clearer signal, according to Tom Ayers, Tropos president and CEO. Cisco makes use of MRC in its recently announced Aironet 1140 11n access point. 

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