Comparing Wireless Mesh Network

Mesh vs. Ad-Hoc Networks

 

  

Ad-Hoc Networks	WMN
Multihop	Multihop
Nodes are wireless,  possibly mobile	Nodes are wireless,    some mobile, some fixed
May rely on infrastructure	It relies on infrastructure
Most traffic is user-to-user	Most traffic is user-to-gateway

 

 

 

Mesh vs. Sensor Networks

 

Wireless Sensor Networks	WMN
Bandwidth is limited (tens of kbps)	Bandwidth is generous (>1Mbps)
In most applications, fixed nodes	Some nodes mobile, some fixed
Energy efficiency is an issue	Normally not energy limited
Resource constrained	Resources are not an issue
Most traffic is user-to-gateway	Most traffic is user-to-gateway

 

WLAN Coverage

 

	802.11	WMN
Wiring Costs	High	Low
Bandwidth	Very Good	Good
Number of APs	As needed	Twice as many
Cost of APs	Low	High

WRT54G- hardware hacking

The WRT54G has gained in popularity due to the fact that one can upgrade the unit with after market firmware. This is possible because the WRT54G runs Linux and uses other Open Source software in the box. As required by the GPL, Linksys has made available the source code and can be downloaded from the Internet. Hackers picked up this code and created new development branches that added features such as SSHD.

 

The “L” in the model number, WRT54GL, stands for Linux. The previous models of the WRT54G are also powered by Linux (version 1.0 to 4.0). The latest version of the Linksys WRT54G is version 5.0 and runs VxWorks. The move to VxWorks cut the memory footprint in half according to Mani Dhillon, senior manager of product marketing at Linksys. This claim appears to be based in fact because the Version 5.0 model only has 2MB of Flash and 8MB of SDRAM. “We still wanted to have a Linux SKU for the Linux audience,” said Dhillon, hence the WRT54GL.

 

 

Linksys WRT54GL Features

·        Linux Kernel 2.4

·        Based on the Broadcom BCM5352E SoC

·        Hardware design is the WRT54G Version 4.0

·        After market firmware upgrades

·        All-in-one Internet-sharing Router, 4-port Switch, and 54Mbps Wireless-G (802.11g) Access Point

·        Shares a single Internet connection and other resources with Ethernet wired and Wireless-G and -B devices

·        Push button setup feature makes wireless configuration secure and simple

·        High security: TKIP and AES encryption, wireless MAC address filtering, powerful SPI firewall

The Linksys Wireless-G Broadband Router is really three devices in one box. First, there’s the Wireless Access Point, which lets you connect to both a Wireless-G (802.11g at 54Mbps) and Wireless-B (802.11b at 11Mbps) devices to the network. There’s also a built-in 4-port full-duplex 10/100 Switch to connect your wired-Ethernet devices together. Connect four PCs directly, or attach more hubs and switches to create as big a network as you need. Finally, the Router function ties it all together and lets your whole network share a high-speed cable or DSL Internet connection.

 

 Basically the board of all WRT54G is same with the following main chips

1) WiFi router processor IC

2) WAN CHIP (Infineon ADM69961)

3) Diversity Chip

4) Flash Memory

5) RAM memory (HYNIX 72BUA)

 

 

 

 

 

 

 

 

 

 

 

Tomato……yummy!!!!

The ultimate firmware that we are presently using is tomato.(www.polarcloud.com/tomato)

This has all the features of a regular firmware minus the complex terminologies and does not give the ‘oh-mi-god-how-am-i-going-to-handle-this???’

The Tomato Firmware is a free HyperWRT + tofu based, linux core firmware for several wireless router, most notably the Linksys WRT54G (including the WRT54GL and WRT54GS),

The interface is quite simple and lucid and provides very easy control.User can select variegated hues from the colour list:tomato,pumpkin, cyan black etc. It just adds to the appeal of the interface and simplicity. The interactive bandwidth graphs and traffic monitoring software is added advantage. These tools also provide excellent wireless survey facilities.

Although one needs to install the SVG( scalable vector graphic) for the graphs and charts.Yet the firmware provides excellent user control and is quite transparent.

I am presently going ga-ga over the tomato and I have tested the wireless mesh network(IEEE 802.11s) for the voip and multimedia transmission and its working fine.

It’s ripe and yummy tomatoes for me!!!

Testing the firmware!!

Deploying the wireless mesh network has been a tough task. To start with we some how landed with the WRT54G series router, but our hard luck. They were version 7, with reduced NVRAM & flash memory. We just couldn’t load any firmware on to them whatever we tried.

Then we opted for WRT54GL which we got from hyderabad after getting turned down from Kolkata, Jaipur & mumbai. To begin with the elementary Linksys OPEN WRT firmware(www.openwrt.org), was a very crude one. We went for freifunk(www.freifunk.net).

But the firmware posed a constant problem and moreover its german literature did not solved the matters. Although the contact team of freifunk was very supportive yet we are working with freifunk.settled for another firmware.

 

VOIP over wireless mesh

Today trying to establish a wireless mesh network using Linksys WRT54GL router, and tomato software. We were able to establish the wireless mesh network.

     We tested the network for multimedia broadcasting and also for VOIP using windows netmeeting  and LAN voice chat. The voice quality was superb and crystal clear using netmeeting . Wheras using the LAN chat gave a good voice transmission but with jitters.  We also tried to establish VOIP communicatoion by connecting a Lenovo laptop to MP , but the vista did not supported netmeeting or either lan chat, and its inbuild network meeting space.

         Nevertheless we are now able to successfully deploy a wireless mesh network and VOIP communication and testing is going on in MATLAB background.

In Matlab we made a simple simulink model using audio from external device(ie microphone) and using UDP transmission.