What the heck is on that guyz roof?

I often see the strangest antennas strapped to someone's chimney or poking out of someone's trunk of the car. Usually it belongs to someone who's a ham radio enthusiast, or buddy searching for extra terrestrials or simply someone grabbing HDTV off the air. I've always been fascinated by the symmetry or the mathematical basis behind the aesthetic design, and "what does that antenna do?"

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I came across a Log Periodic Antenna design, while looking up the Blonder-Tongue Doctrine in US patent law oddly enough; the case set a precedent. Sometimes LPA is referred to as Isabel (in honor of one of the creators) at the University of Illinois.  The repeating nature also gives it a fractal design. The design parameters are simplified into four design criteria

1) Upper and lower operating frequencies set the shortest and longest dipole length
2) Number of elements
3) Apex angle of antennae
4) Each successive element is a scaled-down length of its immediate predecessor down the array.
5) The scaling factor τ (tau) derived from a log function.

The longest dipole is 1/4 wavelength of the lowest frequency; the shortest dipole is 1/4 wavelength of the highest frequency. The geometry diagram shows only the top half of the antenna; the bottom half is a mirror image of it. I don't understand why they have to make it a pyramidal design for aesthetics. They must do this to achieve a symetrical RF footprint instead for two lobe pairs instead of just a single side.  This article explains in detail how the formulas are used and the magic math involved.

I found an online calculator for the LPA design parameters but I just find it creepy that the page displays your IP address and makes snide comments about the browser you're using. Other than that, it's very accurate, I matched the numbers I punched in with a real Kathrein-Scala dual band wireless antenna spec sheet.

Cross Polarization

The LPA can be quite small to cover a fairly broad radiation footprint with a reasonable power gain. What's neat is only a part of the array is active at a given frequency. Therefore the antenna can cover a wide frequency band without the need of a switching system. This is good for television reception or as advertised, dual band wireless applications.

To the untrained eye, the Log Periodic Antenna could be confused as a Yagi or have many similarities but I'd say that the LPA is more triangular while a yagi is more rectangular.

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Miss Canada answers Ubiquitous Broadband Internet Access

At every beauty pageant they always ask the bikini-clad candidate, what is your wish for mankind. Everyone always says the noble standard answer, "World peace" and the crowds cheer. However if I were ever the Miss Canada candidate, I would have to make my answer, free broadband Internet access in Africa.

I cannot claim this idea as my own but it starts with an obscure agreement between the government of the Province of British Columbia and a major Canadian telco Telus Corporation signed in July 29, 2011.  BC is in a business agreement with Telus, for a transfer of $10.00 Canadian (if I read that right), to provide access to all residents in BC access to broadband Internet and telecommunications services to have access to the social benefits of connectivity for economic initiatives, access to government services, electronic health and
education services. Contract in pdf here.

The 109 page document signed by the Minister of Citizen's Services and Open Government outlines lots of provisions including askingTelus
- to facilitate last mile connectivity
- expand cellular coverage in rural areas
- maintain Central Office live status if no other ISP is available
- to provide carrier service to the CO for a small ISP
- set a fair wholesale pricing list
- to not compete with eligible ISPs to provide the retail broadband services to end users, except where Telus already has cellular coverage (EVDO, HSPA, LTE) and DSL

The agreement seems to support fair market prices for the consumer and a non competition period of three years, and seems to leave it up to Telus to build the infrastructure, the way I understand it. Sound like a pretty sweet deal for all!

I read a recent article on CNN that poverty in the USA was linked to lack of access to basic telecommunications and Internet because job searching opportunities and even access to higher education and everything these days were most accessible to folks with Internet access, and the have nots were hurting even more with lack of it. We'll see how this reaches out the more rural communities and people living off the grid. Imagine what it could do for a developing nation! Access to information and the capability to communicate and collaborate with other humans.

In my search for the road to world peace, I came across the most inspiring article on CNN by Hamadoun Touré who writes the best case scenario for how mobile broadband could save Africa and help them reach Millennium Development Goals. The UN Millennium Development Goals are best summarized in three categories of education, health, and the environment, and the author sees mobile broadband  playing a key role in each. Alright, he takes the crown from Miss Canada's idea.

"If you combat disease, you also reduce child mortality; if you give every child a primary education, you promote gender equality. It is because these goals are interlinked that broadband is so important."
http://edition.cnn.com/2012/02/27/opinion/technology-toure-africa-mobile/index.html?iref=allsearch

The government priority or foreign aid should be geared at building the infrastructure to support the broadband network or even mobile public transport vehicles equipped with low-cost wifi repeaters.

Here are examples of the Smartphone usage helping local businesses
1) Regular weather updates for the farmer on his Smartphone to plan his planting and seeding schedules
2) GPS geolocation capability for precision farming and optimizing fertilizer and pesticide usage
3) Online access to employment and training in Kenya
4) A young entrepreneur who developed an app for children to improve literacy, numeracy and general knowledge and the platform to delivery the wifi Internet access by public transport vehicles

As long as the kids don't spend too much time playing Angry Birds, here's to saving Africa one smartphone at a time.

Ask Siri to Sing Happy Birthday

At a friend's birthday party dinner this evening in a very fancy Italian restaurant as we all finished dinner and everyone somehow felt it was appropriate to whip out that iPhone and start texting the buddies at the other long end of the table, the guy beside me suggested let's play Ask Siri!

I don't have an iPhone, I don't even own a cell phone really. I'm very curious who is Suri (I didn't even know how to spell it). The "Industry Canada RF Bandwidth Allocation Committee member" rolls her eyes and says,  you folks are wasting bandwidth! I suppose this is true, asking age old questions like why did the chicken cross the road, what is the meaning of life, who's your daddy, and How big is the Pacific Ocean? (that's a good one) Siri gives the answers in Liters with extra information about the comparative volume, 51% of the all the earth's oceans. I'm hooked.  I ask, What is Pippa Middleton wearing? Siri displays button to perform a website for that.  I'm giggling too much at the idea of asking a computer for answers. I get one of the guyz to ask, what are you wearing Siri? But I miss the answer because it's just too funny.

We're at a birthday party so buddy asks, Siri would you sing happy birthday to my friend please?
Siri answers, Daisy, daisy, give me your answer do.

It wasn't quite the answer I was searching for. People keep texting each other or playing Angry Birds, but I desire an explanation! The Cisco guy at the end of the table explains that it is a cultural reference to the IBM computer that became the first computer to sing Daisy Bell.

In the late 1950's  a computer sung a song for the first time. Here is a nice clip from  YouTube.
Daisy, daisy, give me your answer do.
I'm half crazy all for the love of you.
It won't be a stylish marriage -
I can't afford a carriage,
But you'd look sweet on the seat
Of a bicycle built for two.

This is quite a cute response. I guess it's an AI joke that's preprogrammed in, but it's still very cute. Well here are some other questions to ask Siri though personally I think people should really talk to their friends at a party and not play with their phones too much. Tweet tweet.

Where does TV come from?

I had the same discussion with my child the other day, and I managed to explain about digital off the air and rabbit ear antennas, and the converter; plus since we're still old school, the good old CRT TV.

Now I'm contemplating the absurdity yet logic of a friend's post, "watching youtube on tv through HDMI to playbook wifi controlled by Blackberry Bold using bluetooth" That's impressive.

Cisco ICND1 Flashcard: Wireless LAN Implementation and Security

The Wireless Access notes for the CCNA Exam in short form.
The topic of Wireless LAN is covered in the ICND1 Exam

Connecting to a Wireless Network

This is how it happens at Starbucks, MacDonald's, the hotel offering free wireless internet, or your own home.  Wireless Access Points send out beacons announcing the SSID, data rates and other information.  The client's laptop wifi network card scans all channels while listening for beacons and responses from the AP. Then the client will associate to the AP with the strongest signal.  Client repeats the scan if the signal becomes slow to associate to another AP while roaming.  During the association phase, SSID, MAC address, and security settings are sent from the client to AP, and verified by the AP.  The basic service area is the physical area of RF coverage provided by the AP.

Wireless access is a half duplex CSMA/ CA (Carrier Sense Multiple Access - Collision Avoidance) half-duplex type of signal that uses RTS (ready to send) and CTS (clear to send) protocols. Yes I know it is wierd to place the acronym ahead of the definition at first use.   For every packet sent, an RTS/CTS and acknowledgment must be received.

About the RF Wireless Signal
While setting up the Access Point, the following parameters are configured. Basic IP address (static or DHCP), subnet mask, default gateway; the wireless protocol being used could be 802.11a, b, g, n; channel adjustments namely channel 1, 6, 11 and a power adjustment.  Security parameters include SSID which identifies the network, authentication scheme (WPA, WPA2 PSK) and the encryption method (TKIP, AES).

IBSS - Independent Basic Service Set Identifier, users connected in ad hoc mode without an AP
BSSID - Mac Address of the RF Interface Card

SSID - Net Admin configured network identified that is broadcast, sent in the clear

The frequencies of the unlicensed bands are:

900 MHz
2.4 GHz used by the 802.11b and g, using DSSS. Max data rate of 11 Mbps (for 802.11g when using DSS) Other rates possible 1,2, 5.

5 GHz used by 802.11a, using OFDM data rate of 6, 9, 12, 18, 24, 36, 48 Mbps to 54 Mbps, 12 non-overlapping frequency channels. When 802.11g operates on OFDM the max data rate of 54 Mbps can be achieved.

The FCC has released three unlicensed bands for public use: 900MHz, 2.4GHz, and 5.7GHz. The 900MHz and 2.4GHz bands are referred to as the Industrial, Scientific, and Medical (ISM) bands, and the 5-GHz band is known as the Unlicensed National Information Infrastructure (UNII) band.

802.11a operating in the 5GHz radio band, makes it immune to interference from devices operating in the 2.4GHz band, like microwave ovens, cordless phones, and Bluetooth devices.
Quiz: Which two 802.11 standards have the highest data rate?
802.11a and 802.11g both up to 54 Mbps

Quiz: Which standards are most widely used today?
 802.11b/g being the most widely used wireless network found today.  802.11b operates in the 2.4GHz unlicensed radio band, delivers a maximum data rate of 11Mbps

Facts to consider: This is the sort of thought process in an exam question, the 802.11g standard delivers the same 54Mbps maximum data rate as 802.11a but runs in the 2.4GHz range—the same as 802.11b

Data rates for Indoor and Outdoor ranges.
802.11g  400m  140m
802.11b  40m    140m
802.11a  35m    100m
802.11n  70m    250m

Modulation
802.11a and 802.11g uses OFDM
802.11b uses Direct Sequence Spread Spectrum (DSSS)
though 802.11g is DSSS/ OFDM

IEEE 802.11 was the first, original standardized WLAN at 1 and 2Mbps, running in the 2.4GHz

802.11n the New Wireless Standard
802.11n supports more channels using spatial division multiplex and more transmittes to reach a higher data rate of 600Mbps.  It also uses OFDM (I need more info) and is backward compatible with 802.11a,b,g

802.11b
It is more accessible, has a higher CCK and data rate.  There are 14 channels each 22MHz wide with a 5MHz separation. To completely avoid overlapping, the signalling requires a 5-channel separation; therefore only Channels 1, 6, and 11 are in use.

Wifi Equipment

Access points, wireless controllers, wireless LAN client adapters, security and management servers, wireless management devices, wireless integrated switches and routers—even antennas and accessories

Key Players in Wifi
The Wifi Alliance is a non government, no profit, industry trade organization that promotes interoperability between wifi product manufacturers, and promotes wireless growth. As for securing wireles networks, the evolution of encryption algorithms have come a long way.

The IEEE writes out the technical standards or Engineering specs, publishes technical documentation or journals.

ITU-R is the international union that regulates RF usage bands including wireless.

Quiz: Who created WPA?
Answer: WPA was created by the Wifi Alliance based on the IEEE 802.11i standard

Quiz: What is a rogue access point? An unsecured AP that has been placed on the WLAN.

WIFI Encryption
Common standards dealing with wireless client authentication, coding something from plaintext into ciphertext.

• WEP is a bit outdated and too easy to break, very basic and static.
• Cisco adds CKIP and MIC to protect keys.
• Enhancements are TKIP MIC (Per Packet Keying Message Integrity Check)
• TKIP 802.1x EAP
• WPA uses TKIP/ MIC Encryption
• 802.11i/ WPA2 is the strongest level of WLAN security
• WPA2 includes a AES counter with CBC-MAC Protocol (AES-CCMP)
• Enhancement to TKIP is AES 128 bit, 192 bit, and 256 bit.
• LEAP uses TCP handshake like EAP-TLS and Radius

How is the client authenticated in IEEE 802.1x?
The AP encapsulates any 802.1x traffic that is bound for the authentication server and sends it to the server

Modes of Operation

Ad Hoc Mode
IBSS - Client directly connects to the server peer to peer, no access point.
Infrastructure Mode
BSS - clients connect to each other through a network resource. The BSSID is the MAC address of the RF interface card; B for basic.
ESS - Two or more BSS are connected by a common distibution system. E for extended. SSID is the wireless network advertised, user configured.


More than one BSS will form an ESS, that means when a group of BSS (or many AP's) in the WLAN have the same SSID, the client can be mobile and authenticate with the various AP's in the same BSS.

WPA

Enterprise mode

used for Business, Education, Government and a term for products tested to be interoperable for authentication in PSK + IEEE 802.1x EAP

Personal mode

for SOHO, home, personal and interoperable in PSK mode of operation only

Issues with Roaming

• Consider the range of combined calls form an extended service area
• Allow 10-15% overlap to allow users to roam without losing RF connection
• Configure three access points with the same SSID so user can roam wirelesly without dropping connectivity
• Allow the range of 15-20% overlap for wireless voice

Solution for Roaming

• Shift the data rate while moving: 11 Mbps, 5.5 Mbps, 2 Mbps
• The higher data rate requires stronger signals at the receiver; a lower data rate, the range is longer
• The clients want the highest data rate
• If there are transmission errors, reduce the data rate 

Connecting the AP to a LAN switch, which cable would you use? Just a straight through, much like a regulare PC.

Wireless Zero Configuration 
Three basic wireless access point parameters: SSID, authentication, RF channel with optional power. Microsoft has a feature that does all this automatically. Though most Wireless NIC vendors have their own software GUI as well.

Cisco’s Wireless Control System (WCS) actually requires zero configuration. This means the AP will automatically configure itself based on the controller’s information, check for channel overlap and interference and move to a  non-overlapping channel; lower its transmitting level to limit interference called by Cisco as "auto RF controls."

I found a really good reference for the Wireless LAN topic. I'd hazard to say that I found nuggets of information that I had missed on the exam from my notes! Lookup the Cisco Tests blog.