🚀 go-pugleaf

On Wed, 09 Jan 2008 01:00:41 GMT, John Navas
<spamfilter1@navasgroup.com> wrote in
<bj68o3dfun74fdtnueaf9p0drs48o2jnbn@4ax.com>:

>On Sun, 06 Jan 2008 17:48:35 GMT, DTC <me@nothingtoseehere.zzx> wrote in
><Tv8gj.28423$4V6.13287@newssvr14.news.prodigy.net>:
>
>>cross posted in alt.cellular.attws
>>to support Oxford's fantasy.
>>
>>http://tinyurl.com/ytrrgv
>>Startup Promises Free Wireless in San Francisco
>>
>>Meraki Networks Inc.
>>
>>[sniped]
>>San Francisco Mayor Gavin Newsom plans to help Meraki "publicize and 
>>grow the network without the bureaucracy and politics that challenged 
>>our last effort to bring free Wi-Fi to San Francisco," spokesman Nathan 
>>Ballard wrote in an e-mail. Newsom has been pushing for three years for 
>>citywide Wi-Fi.
>
>Ad hoc mesh network with no backbones.  Hugely wasteful of spectrum, dog
>slow under any sort of normal load, and probably unreliable as well.  So
>much for Newsom's fantasy.

<http://www.dailywireless.org/2004/06/28/ugly-truth-about-mesh-networks/>

   Ugly truths about mesh networks - they dont scale - for now.
   by Francis daCosta

   As founder and CTO of a Wireless Mesh networking company, I have
   pondered long and hard about whether or not I should submit this.

   The buzz on mesh networking certainly works in our favor. However,
   there is more hype than reality around mesh networking. Its time for
   a reality check on what mesh can and cannot do.

   First, Mesh networks are not a new concept. In some ways, the
   internet is a mesh network. And it works, despite its size - because
   it does not suffer from the limitations of conventional wireless mesh
   networks:

   1- Radio is a shared medium and forces everyone to stay silent while
   one person holds the stage. Wired networks, on the other hand, can
   and do hold multiple simultaneous conversations.

   2- In a single radio ad hoc mesh network, the best you can do is
   (1/2)^^n at each hop. So in a multi hop mesh network, the Max
   available bandwidth available to you degrades at the rate of 1/2,
   1/4, 1/8. By the time you are 4 hops away the max you can get is 1/16
   of the total available bandwidth.

   3- That does not sound too bad when you are putting together a
   wireless sensor network with limited bandwidth and latency
   considerations. It is DISASTROUS if you wish to provide the level of
   latency/throughput people are accustomed to with their wired
   networks. Consider the case of just 10 client stations at each node
   of a 4 hop mesh network. The clients at the last rung will receive
   -at best- 1/(16,0000) of the total bandwidth at the root.

   4- Why has this not been noticed as yet? Because first there are not
   a lot of mesh networks around and second, they have not been tested
   under high usage situations. Browsing and email don t count. Try
   video - where both latency and bandwidth matter - or VOIP where the
   bandwidth is a measly 64Kbps but where latency matters. Even in a
   simple 4 hop ad hoc mesh network with 10 clients, VOIP phones wont
   work well beyond the first or second hop the latency and jitter
   caused by CSMA/CA contention windows (how wireless systems avoid
   collisions) will be unbearable.

   Mesh networks are a great concept. But the challenge lies in managing
   the dynamics of mesh networks so users receive an acceptable level of
   performance in terms of both latency and throughput.

   Its time to focus on solving some real problems to make mesh networks
   scale and provide stable performance. 

-- 
Best regards,
John Navas     <http:/navasgroup.com>