Tuesday, February 21, 2012

No T1 Lines in Europe - The E-Carrier Hierarchy

Today I'll continue with a post on what I've been calling the legacy Public Switched Telephone Network (PSTN). In my last legacy post we covered T-4 and T-5 lines, today let's take a look at the European or “E” carrier system.

The European or “E” digital transmission format is slightly different than the North American T-carrier system format. With the E-Carrier system we are still taking individual voice call analog signals and converting to a digital signal by sampling the analog signal 8000 times per second and, after matching the instantaneous voltage sample level to one of 256 discrete levels, generating an 8 bit code for each sample. We are still dealing with the fundamental DS-0 building block of 64Kbps of digital bandwidth per single analog voice channel we used for the T-Carrier system. The differences between E-Carrier and T-Carrier deals with the number of channels and how these channels are used. Let’s start by looking at a European E-1 system and how it compares to a North American T-1 system.

The E-Carrier system starts by multiplexing 32 DS-0 channels together to form an E-1 circuit while the North American T-Carrier system multiplexes 24 DS-0 channels to form a T-1 circuit. 

The 32 DS-0 channels of an E-1 circuit combine from Channel 0 up to Channel 31. Channel 0 is used for framing (synchronization), channels 1-15 and 17-31 are used for individual DS-0 channels and Channel 16 is reserved and not used.
This system is also referred to as the “30 plus 2 system” because an E-1 signal consists of 30 DS-0 signals used for voice plus Channel 0, which is used for overhead and Channel 16 which is not used at all. In the European system, all synchronization (framing) is handled by Channel 0 so framing bits are not required on individual DS-0 channels.

We can calculate the signal rate for an E-1 circuit as follows:
E-2 through E-5 are carriers in increasing multiples of the E-1 format. We can look at a table showing DS data rates and how they correspond to the European E Carrier system.

In my next legacy PSTN post I'll cover the Synchronous Digital Hierarchy (SDH) system.

Thursday, February 16, 2012

Thank You Tim (2000-2012)

You were three when we got you. An amazingly trained bird dog with champion lineage. You knew all your spaniel verbal and whistle commands. Trained by the best and ready to go. Strong and powerful with an amazing nose - and - everyone’s best friend.

Never one to complain - you barked maybe 7 or 8 times your entire life. Never once growled or snapped. Always friendly to every person and dog you ever met. Respectful. Gentle. Easy to take care of. Always listened to me complain about things like work and when it snowed too much. We could tell you not to go someplace once and you knew - it was like you could read our minds. Always a buddy and a pal. Always there.

It was what I didn’t expect that you were the best at though. For the last nine years you helped Diane and I raise Eva and Gabby. You played with them, protected them, watched over them - sledding on the hill in back of the house in winter, surfing the waves on Cape Cod, playing ball. We’ll never forget how you loved watching and listening to them practice violin. Always there for them. And always on the lookout for all of us. I remember how you always stopped to smell flowers and how quickly you could get dirty after a bath. Loved the mud and loved to swim. You thought you were one of the kids and we did too. You were. Such a huge impact on all of our lives. 

You're gone but I see a lot of you in the two girls. Gabby was 11 and Eva 7 when you came home to us. You definitely had impact on shaping the type of person they have each become. I see parts of you in both of them, And that is all good.

Today was one of the hardest things I’ve ever had to do. The house is quiet without you. We miss you, we love you and we will remember you forever Tim.

Thank You Buddy.

Wednesday, February 15, 2012

Simulation and Modeling in Technology Education (SMTE) Project

This is a temporary tutorial video for the Knowledge and Skills Builder level 1 - the "Cave of Volume (shape volume and surface area) Challenge" in the Survival Master game for STEM learning.

You can follow along via the project website at http://gaming2learn.org/

Monday, February 13, 2012

DS-4 and DS-5 Lines

It's been a while since I've posted on what I've been calling the Legacy Public Switched Telephone Network (PSTN). My last related post was way back on December 15, 2011 titled What's a T3 Line? Today, Let's take a look at higher bit rate signals in the DS system.

DS-4 Signal
Back on December 15th, we said each DS-3 signal carries a bit rate of 44.736 Mbps. Six 44.736 Mbps digital DS-3 signals are multiplexed into one DS-4 signal. If we have six DS-3 signals per DS-4 signal and each DS-3 signal is 44.736 Mbps we can calculate:

Adding overhead consisting of timing and synchronization bits brings the DS-4 bit rate to 274.176 Mbps.

DS-4 Formation

DS-5 Signal
Each DS-4 signal carries a bit rate of 274.176 Mbps. Two 274.176 Mbps digital DS-4 signals are multiplexed into one DS-5 signal. If we have two DS-4 signals per DS-5 signal and each DS-4 signal is 274.176 Mbps we can calculate:

Adding overhead consisting of timing and synchronization bits brings the DS-5 bit rate to 560.16 Mbps.

DS-5 Formation

One DS-5 channel can carry 8064 voice channels.

We can look at a table showing these DS data rates and how they correspond to the North American T Carrier system.

Looking at the table it is easy to see that the DS-0 signal level is the foundation for the entire T Carrier hierarchy in North America. Notice one DS-1 line is the equivalent of 24 DS0 64 Kbps DS-0 voice channels. Also notice that one DS-2 line is the equivalent of 4 DS-1 lines or 96 DS-0 voice channels.

Copper wire pairs can be used to transmit at levels up to DS-2. At levels above DS-2 coaxial cable, fiber or microwaves must be used.

In my next Legacy PSTN post I'll cover the European (E) Carrier System.

Tuesday, February 7, 2012

A Little More Context With Location Based Social Networking

I'm a pretty private person. I'm very careful about the information I provide online. When I travel I try not to give any indication I'm out of town. If I've got things to post I usually wait until I'm back home to do it. I never give out when I'm taking vacation and I don't have my birthday posted on Facebook.

By now you've probably figured out I have not been a big user of location based social networking sites. That may be changing though. Here's a pretty cool video from foursquare.

Our First #4sqVid from foursquare on Vimeo.

So, what's this stuff really about? A recent post at The Social Media Marketing Blog says it's all about context. What's context? To me, its the circumstances that form the setting for an event. For example, the same words can have completely different meaning depending on the circumstances (location, audience, environment, etc). Context is also easy access to relevant content when a user needs it. It can be as simple as where to get the best cup of coffee or finding a place to eat nearby that serves really good fried clams (one of my biggest personal weaknesses).

Curating the most relevant subject knowledge, finding information that’s useful in real time. So simple and makes so much sense. It may be time to turn on my mobile device GPS radio and bring a little more context ( highly controlled of course :) into my life!

Monday, February 6, 2012

Podcast: The Need for Speed:802.11ac – 5th Generation Gigabit WiFi

Today, Mike Qaissaunee and I recorded an 18 minute and 40 second podcast titled The Need for Speed:802.11ac – 5th Generation Gigabit WiFi.

Rumors are that Apple is planning on incorporating support for the new faster 802.11ac Wi-Fi specification into products this year. In this podcast we discuss the 802.11ac and other wireless specs.
We discuss the following questions:
  • So, what’s the deal with this 802.11ac?
  • These 802 dot whatever standards - where do they come from?
  • So this 802.11ac is considered non-finalized. what does that mean?
  • I seem to get interference from things like wireless home phones. I know spectrum is involved.
  • So if I set my access point to run at 5GHz, will all my devices work? What do i need to understand to make it work?
  • What about range? You mentioned range limitations at 5 GHz.
  • Are there any ways to extend the range? I’ve heard about something called MIMO.
  • You mentioned 802.11a which is pretty old. Is the use of 5 GHz new?
  • When will we see 802.11ac products on the market?
  • What kinds of products from Apple? What are people saying?
  • What do you mean when you say potentially for the mobile devices?
Along with the Superbowl!

You can listen in the player here:

If you have iTunes installed you can listen to and subscribe to our podcasts by clicking here.

Wednesday, February 1, 2012

Facebook IPO - Huge Gain for California & Huge Loss for Massachusetts

[note: I live in Massachusetts and was originally going to title this "Why States Must Keep Their Startups" or something like that]

Lots of news about Facebook's Initial Public Offerring (IPO) with the company filing  papers this afternoon to raise at least $5 billion and begin to sell stock in the spring. Facebook has about 3,000 employees in Silicon Valley and with the IPO many will become millionaires. Good news all around - good for the employees, good for surrounding businesses that they frequent and really good for the entire state of California. More of this in a minute.

Most know that Facebook was started (and first incorporated as Thefacebook) by Mark Zuckerberg and some classmates when he was a student at Harvard in February 2004. Shortly after the company was started though, Zuckerberg moved it to Palo Alto, California. At the time I was on the Massachusetts Networking and Communications Council Board and I clearly remember members lamenting the loss.  Nobody knew how huge the company would eventually become but member guts were telling them it was going to be big.

California's Silicon Valley is a magnet for tech companies and they've done well over the years. As an example - in 2006 - Google went public, resulting in huge tax filings. To give you an idea how much money we're talking about - in 2006, sixteen (yes only 16 people!) high-level Google employees cashed in 9 million shares valued at $3.7 billion which meant they owed the state (again just 16 people) around $380 million in taxes. Resulting Google tax money was huge for the state allowing the Governator (Arnold Schwarzenegger) to spend big bucks on roads, schools, etc and help him get re-elected.

That Google IPO was massive in 2006 and Facebook's will be a lot bigger. On that first day in 2006 Google's market capitalization closed around $27 billion. Facebook's could be up to 4 times as large putting it over $100 billion. 

Simply put - we (Massachusetts) lost it. We had Facebook in our state and we lost it. We lost the employees, we lost their business and we lost the tax revenue. Am I oversimplifying - perhaps. Can't deny though - huge gain for California, huge loss for Massachusetts.