SFN and OFDM

6 08 2009

July 28th, 2008 questions and answers in my Advanced RF/Wireless Techniques class.

1. What is SFN?

SFN, or Single Frequency Network, is a broadcast network where several transmitters simultaneously send the same signal over the same frequency channel.

2. Why does OFDM enable SFN technique?

OFDM, or Orthogonal Frequency Division Multiplexing, which is used in wideband digital broadcasting, enables SFN technique in order to have efficient utilization of the radio spectrum, allowing a higher number of radio and TV programs in comparison to traditional multi-frequency network (MFN) transmission. An SFN may also increase the coverage area and decrease the outage probability in comparison to an MFN, since the total received signal strength may increase to positions midway between the transmitters.

SFN considerably improves the utilization of frequency bands and channels as well as energy balance of digital transmitters. The signal coverage of a certain area can be provided by a number of transmitters, transmitting the multiplex of digital television or radio signals in the identical frequency channel. Their partial signal contributions in the reception point not only do not interfere, under certain circumstances then even improve the reception.

3. What are the benefits of broadcasting using SFN?

The benefits of broadcasting using SFN are:

  • Improvement in the utilization of frequency bands and channels in the available spectrum,
  • Improved coverage area, and
  • Decreased outage probability.

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This is definitely just a random post.


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Categories : School, Tech, Wireless

Using Linux

27 03 2009

(This post is a modified version of a Multiply blog post I wrote on February 10th, 2008.)

During the 2008 winter term, I was taking up a Unix/Linux course (COMP 1156) at George Brown College – Casa Loma campus. Here’s a little knowledge I’d like to share about what I learned in my first class.

A little history about Linux:Linux

  • Linux is a modern, free operating system based on UNIX standards.
  • First developed as a small but self-contained kernel in 1991 by Linus Torvalds, with the major design goal of UNIX compatibility.
  • Its history has been one of collaboration by many users from all around the world, corresponding almost exclusively over the internet.
  • It has been designed to run efficiently and reliably on common PC hardware, but also runs on a variety of other platforms.
  • The core Linux operating system kernel is entirely original, but it can run much existing free UNIX software, resulting in an entire UNIX-compatible operating system free from proprietary code.

Using Linux as your operating system actually has many advantages:

  • Risk reduction
  • Meeting business needs
  • Stability and security
  • Different hardware platforms
  • Ease of customization
  • Ease of obtaining support
  • Cost reduction

Risk reduction means that using open source software (OSS) products offer you the opportunity to change and maintain the source code. Even if the market and consumer needs would change frequently, you don’t really have to worry much about changing software. This would surely result in reduced costs in administration and upgrades. If you used closed source software, on the other hand, then you would be gaining some burden in the financial aspect.

Red Hat Linux

Red Hat Linux

Linux is a system that meets a lot of business needs because it has different software available for different uses. It is also more stable and secure compared to closed source OS like Windows, since bugs and security loopholes can be identified and fixed more quickly. Fact is there’s actually lesser viruses in Linux compared to Windows.

There are also quite a number of different hardware platforms on which Linux can run, e.g. Intel, Macintosh, Itanium, Mainframe, Cirrus Logic, SPARC, and others. Linux is also easily customizable wherein you can compile the kernel needed to support only what is needed.

Linux documentation, newsgroups, and user groups contribute to the ease of obtaining support, whenever you would have a problem. Here are some helpful sites:

The Linux Documentation Project

Red Hat Linux Manuals

cpqlinux.com – This site seems to have disappeared already now though.

I like programming and scripting but haven’t had the chance to do so lately. Sometimes I wish I took Computer Engineering instead of Electronics & Communications Engineering, but we’ll save that as another story for another day.


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Categories : Linux, School, Tech

How Schools Could Use Social Media

27 03 2009

This topic idea is taken from Chris Brogan’s 100 Blog Topics I Hope YOU Write About (No.12).

When I was in university, social media wasn’t being really used that much. I mean, yes, students use them for personal use, like Friendster, Multiply, YouTube and instant messaging, but for the school itself, they didn’t really utilize it that much. That was in 2002 to 2007.

Students and TeacherRight now, social media is everywhere. Businesses, organizations, academic institutions, and just about everyone else uses social media. If you don’t use it, I’d say you are way behind with the times. The community and the world constantly changes. Lots of new things are being developed and it is always good to know what these are so you will be able to know if you could use it as you continuously try to improve yourself and your organization.

Let me talk about how I think schools could use social media. Firstly, I think the most important thing is that a school should have a website. With a website, its students, alumni, faculty will have easy access to general information including student registration, events and important announcements.

However, just having a website is not enough. I have noticed that there are those who are satisfied with having the same content on their website for months, maybe even years. It is important that the school’s website content be regularly updated. Setting a regular schedule weekly or monthly, if not daily, would probably be sufficient. At least one event does happen every month after all, right?

NetworkA Wikipedia page would be helpful as well. In addition to a website, I’d say an online forum will be a great addition. This will be a great venue for students to speak out their concerns to the administration, the student government, the student clubs, or any other relevant groups or purpose.

Speaking of a venue for students, faculty, and administration to connect and interact, a Facebook group would be great, too. Many students are already on it; all it needs is a common place in it where they could all gather.

Another idea is the use of video-streaming or even just regular online video. According to Mary O’Malley, executive producer of University of New South Wales’ YouTube channel, “YouTube iconThis is a vehicle for communicating research and selected teaching material and is part of an overall strategy of publishing content where it can be most easily accessed.”

Richard Buckland, a computer science lecturer at UNSW, has used YouTube as his classroom allowing students to earn college credit. This strategy may work for some schools, while some it may not. It all depends on every situation the school faces.

One last thing, email is also important. Sending out newsletters or regular communications through email would also be a good idea for schools to implement. With this, students will be informed directly even if they do not use all the other social media.

I’m definitely not an expert in social media, but I just wanted to share my thoughts on this and I am always open to more ideas.


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Categories : School, Social Media, Tech