MaximumPC 2007 09

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Any requests? What hardware—new or old—would you like to see go under

Maximum PC’s autopsy knife? Email your suggestions to [email protected].

Hardware Autopsy

r&dBREAKING DOWN TECH —PRESENT AND FUTURE

White Paper: Mesh Networking

Draft N Wi-Fi Adapter

The battle to establish an IEEE 802.11n standard for wireless networking is finally drawing

to a close. Now that the Wi-Fi Alliance is certifying interoperability among Draft N products,

we thought it was time to peel one open.

Any requests? What hardware—new or old—would you like to see go under

Maximum PC’s autopsy knife? Email your suggestions to [email protected].

connection. Members of the Roofnet team

recently formed a startup venture, Meraki

Networks, to commercialize this concept.

Meraki markets indoor and outdoor repeaters

that enable entire neighborhoods to share a

single broadband connection. The company

offers a solar-powered outdoor repeater, which

is particularly appropriate for emerging mar-

kets where electricity is scarce or unreliable.

Earthlink is in the midst of deploying a

commercial Wi-Fi mesh network in the city of

Philadelphia. Its project is designed to create

a massive network covering 135 square miles

and will offer qualifying low-income households

broadband Internet access at discounted rates

of just $10 per month. Other subscribers will

pay $20 per month. No-cost access is offered

in Philadelphia city parks.

The automobile industry is getting in on

the mesh-networking act, too. European auto-

makers such as Audi, BMW, DaimlerChrysler,

and Volkswagen have formed the Car 2 Car

Communication Consortium to explore using

mesh-networking concepts to facilitate inter-

vehicle communication. The idea is to adapt

the 802.11 protocol to enable two or more

vehicles to form an ad hoc network as soon as

they are within range of each other. Every car

would function as a router, passing along mes-

sages regarding weather and traffi c conditions.

Each car relays what it knows about current

road conditions to the car closest to it, so if an

accident or congestion occurs, this information

can bounce down the highway to unaffected

drivers who can then take a different route to

avoid the problem.

HUMANITARIAN APPLICATIONS

The One Laptop Per Child project, which is

working to fabricate a $100 laptop computer

that can be distributed to children in develop-

ing nations, has tapped mesh networking as

its solution for inexpensive Internet access in

underserved markets.

Members of OLPC believe that building

schools and training teachers is the slow-

est way to educate children in the rural areas

of developing nations. It would be far more

effi cient, they say, to help children educate

themselves and each other by providing them

with access to simple technology and the

Internet. The current design for the group’s

XO laptop includes a Wi-Fi module (based on

the 802.11b/g standard) that can operate as a

mesh point even when the computer’s primary

CPU is shut off. The mesh routing protocol is

based on the 802.11s standard being devel-

oped by the IEEE’s 802.11 Task Group S.

Mesh networks are decentralized, self-

healing, highly adaptive, and supremely

resilient. Is it any wonder they’re now

becoming pervasive?

65

MAC AND BASEBAND

CONTROLLER

The BCM4321 forms one

half of Broadcom’s Intensi-fi

chipset, which Linksys uses

as the basis of its WPC300N

Wi-Fi adapter. This chip is

a media-access (MAC) and

baseband controller for draft

802.11n devices.

DUAL-BAND RADIO

The BCM2055 is the other half of

the Intensi-fi chipset. It’s a dual-

band, single-chip radio capable

of managing simultaneous data

streams on both the 2.4GHz and

5GHz frequency bands.

POWER AMPLIFIERS

These two SiGe SE2528L

chips are power amplifiers

for the radio. A secondary

plate shields one power

amp to prevent the devices

from interfering with each

other.

RF SHIELD

The radio and the

two power amps

are encased in a

metal can to pre-

vent RF leakage.

ANTENNAS

All 802.11 Draft N products

are based on the MIMO con-

cept (multiple inputs/multiple

outputs) and use multiple

antennas for broadcasting and

receiving multiple streams of

data simultaneously.

SEPTEMBER 2007 MAXIMUMPC