Monday, December 19, 2011

Facebook Friends and Frenemies Report - Why We Add and Remove

There's a new Facebook research report from Nielsen McKinsey's NM Incite titled Friends & Frenemies: Why We Add and Remove Facebook Friends that's pretty interesting. The report looks at the factors that help Facebook users decide whether they want to add someone as a friend or remove an existing person the their friend list. Here's a few details:

  • Knowing someone in real life is the top reason cited for friend-ing someone (82%)
  • Offensive comments are the main reason someone gets the boot (55%)
Additional report details suggests that real world interactions drive online friendships. Meanwhile, sales-oriented and depressing comments help drive friend removals. Facebook etiquette also plays a role, with updating too often, too little or having too many friends a consideration for some Facebook users.

Regarding gender, the report research indicates that men are more likely to use social media for careers/networking and dating – while women use social media for a creative outlet, to get coupons/promos or to give positive feedback. More men add friends based on business networks or physical attractiveness and women are more likely to friend based on knowing someone in real life or remove them due to offensive comments.

Here's an interesting infographic from the report.

Thursday, December 15, 2011

What's a T3 Line?

In my last post I described what a T1, also called a DS-1, line was. Most of us have also heard the "T3 Line" term used. Let's take a look at what a T3 or DS-3 line is.

DS-2 Signal
Before we can describe a DS-3 line, let's first take a look at a DS-2. In that last post we figured out how each DS-1 signal (T1 line or circuit) carries a bit rate of 1.544 Mbps. Four 1.544 Mbps digital DS-1 signals are multiplexed into one DS-2 signal. If we have 4 DS-1 signals per DS-2 signal and each DS-1 signal is 1.544 Mbps we can calculate:

Adding overhead consisting of timing and synchronization bits brings the DS-2 bit rate to 6.312 Mbps.

DS-2 Formation

DS-3 Signal
Each DS-2 signal carries a bit rate of 6.312 Mbps. Seven 6.312 Mbps digital DS-2 signals are multiplexed into one DS-3 signal. If we have 7 DS-2 signals per DS-3 signal and each DS-2 signal is 6.312 Mbps we can calculate:
Adding overhead consisting of timing and synchronization bits brings the DS-3 bit rate to 44.736 Mbps.
And..... 44.736 Mbps.... that's a T-3 line!

Tuesday, December 6, 2011

T1 Lines - What They Are

Most of us have heard about "T1" lines. We know they are some kind of (expensive) communications line you can get from one of the telephone companies. It turns out T1's are part of the Digital Signal (DS) Level System. 

Back in August, I wrote a post titled More on CODECs: Quantization + Sampling Rate = A PCM Wave. In that post I described how a piece of an analog signal is quantized and companded and then given an 8 bit binary code in a process referred to as encoding. From that post, we know to convert an analog signal to a digital signal the analog signal is sampled 8000 times per second and, after matching the instantaneous voltage sample level to one of 256 discrete levels, an 8 bit code is generated for each sample. If we multiply the sample rate by the bit code we get:

(8000 samples/second)(8 bits/sample) = 64,000 bits per second (bps)

So we can say a single analog voice channel, after conversion from analog to digital, requires 64Kbps of digital bandwidth. This 64Kbps is referred to as Digital Signal Level 0 (DS-0) and is the basic building block or channel for the existing digitally multiplexed T carrier system in the United States and the digital E carrier system used in Europe. 

Voice calls are digitally multiplexed using either time division multiplexing or statistical time division multiplexing. Calls are grouped in a way similar to frequency division multiplexing. Let’s look at how this is done.

Digroups or DS-1 signals
Individual analog voice call channels converted to digital and require a bit rate of 64 Kbps each. 24 64 Kbps digital voice channels are multiplexed into digroups or DS-1 signals. If we have 24 DS-0 signals per DS-1 signal and each channel is 64 Kbps we can calculate:

Adding overhead consisting of timing and synchronization bits brings the DS-1 bit rate to 1.544 Mbps - that's a T1!
DS-1 Formation

DS-1 Overhead
We’ve described the process of encoding where an analog signal is sampled 8000 times per second, quantized into one of 256 discrete signal levels, companded it is then given an 8 bit binary code. After a single analog signal sample has been encoded it is multiplexed, with 24 other encoded 8 bit sample signals. This generates a 192 bit (8 bits/sample signal × 24 sample signals) sequence for the 24 sample signals. A process called framing then adds one framing bit to create a 193 bit frame.
DS-1 With Overhead

The framing bits are used to keep the receiving device in synch with the frames it is receiving. Every twelve frames are grouped into a masterframe, also referred to as a superframe. Included within each masterframe is a twelve bit frame pattern from the 12 grouped 193 bit frames This twelve bit frame pattern carries a bit pattern of 000110111001 and repeats itself with each masterframe.


This masterframe bit pattern is used for synchronization.

Remember each channel is sampled 8000 times per second so a single frame represents one eight-thousandth of 24 individual channels or telephone calls. We can also say that, in one second a DS-1 signal transmits 8000 193 bit frames. We can use these numbers to calculate the true DS-1 bit rate which includes both data and overhead (framing) bits:
Each DS-1 signal carries a bit rate of 1.544 Mbps and.... that's a T1!

Friday, December 2, 2011

Carrier IQ - are You Being Tracked?

Last month, security researcher Trevor Eckhart published a report accusing CarrierIQ of installing malware on more than 140 million devices worldwide. Eckhart also published a video showing CIQ's software secretly running in the background and monitoring a variety of handset activity on an HTC device including key presses, browsing history, SMS logs, and location data. If you have not seen it, here's Part 2 of Trevor's video: 

Yesterday Senator Al Franken from Minnesota "reached out" to AT&T, HTC, Samsung, and Sprint Nextel after they acknowledged their use of Carrier IQ’s diagnostic software to request that they explain (within the next 12 days) what they do with the information they receive from the software.
Also yesterday, Carrier IQ released a statement saying:

We measure and summarize performance of the device to assist Operators in delivering better service. While a few individuals have identified that there is a great deal of information available to the Carrier IQ software inside the handset, our software does not record, store or transmit the contents of SMS messages, email, photographs, audio or video. For example, we understand whether an SMS was sent accurately, but do not record or transmit the content of the SMS. We know which applications are draining your battery, but do not capture the screen.
In addition, the following updates have been posted by The Huffington Post:
Grant Paul, a well-known iPhone hacker who goes by the screenname "chpwn",wrote on his blog that Apple has included Carrier IQ on the iPhone, but the software's default is disabled.  
Want to find out if your phone is secretly tracking you? Check out our comprehensive list of the devices and carriers known to use Carrier IQ.