SFN and OFDM
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.
—–
This is definitely just a random post.
Antenna Selection
In choosing an antenna you want to use for transmission or extending a wireless network range, there are several things you need to determine. I found this list of questions somewhere on the internet (which I copied down when I was trying to decide on an antenna for purchase, but forgot to take note of the source) that will help in the antenna selection process:
- What is the operating frequency range of the system?
- How much gain is required?
- What kind of radiation pattern is desired?
- What is the maximum allowable VSWR?
- What polarization is required?
- What type of connector interface is required?
- How much power will the antenna have to handle?
- Where will the antenna be mounted?
- Is a radome required?
- What is the lifetime of the antenna?
Yup, that’s it.
Photo Credit: michaelstyne
Custom Building a PC
When you want a powerful PC, one that is able to do multiple heavy tasks, it is probably a good idea if you custom build your own, since you could make it more powerful and at the same time cheaper than those ready-to-use PCs. Okay, I understand that not all people are that tech-savvy to be building their own PC, but if you somehow like taking risks, maybe you could try doing it, but of course it would help if you had a tech-savvy friend around.
The last PC I built had the following components, which are great for heavy-duty video making and graphic design:
- Case: Antec Three Hundred ATX
- Motherboard: Gigabyte UltraDurable 3 (GA-MA78GM-US2H)
- Processor: Intel Core i7 920 CPU (2.93 GHz & 2.66 GHz Quadcore)
- Heat Sink Fan: Scythe Zipang SCZP-1000 CPU HSF
- Memory: Corsair DDR3 6GB Kit Core i7 compatible
- Hard Drive: WD Velociraptor 300GB HDD
- Video Card: ASUS ATI Radeon HD 4770 PCI-E
- Power Supply: PC Power & Cooling 610W PSU
And of course, monitor(s), keyboard, and optical mouse are additional things you must have. Be sure your monitors have DVI input. I liked having to use two 24-inch monitors. If you have to use two monitors, you would also need to install the correct drivers so you would be able to use the two as one big screen, and not two separate screens.
Now if for some reason you needed to have two PCs, you would also need a KVM (Keyboard/Video/Mouse) switch, plus additional cables. This would allow you to switch from one PC to another and view it on the same two screens.
There are resources on the internet which you could utilize as you build your own PC, so refer to them if you ever decide to build one of your own.
Photo Credit: NightRP Star
Pomegranate Phone
Phones these days include features such as email, internet browsing, camera, video, music player, and GPS among others. Have you ever thought of the possibility of the phone having other features such as the following:
- Projector
- Global Voice Translator
- Coffee Brewer
- Shaver
- Harmonica
Well then, check out the amazing Pomegranate Phone! [http://pomegranatephone.com]
Too good to be true, eh? 🙂 Turns out, it’s only like a promo thing for Nova Scotia [read: non-existent] which you’ll realize when you click on the Release Date link. Very creative, I must say!
It’s pretty cool that companies can interact with the consumers using the web 2.0 tools used in social media, get feedback directly from them, and be able to respond back more promptly, especially when there are issues that need urgent attention. It can be painful to read what the people say sometimes, especially when people can be really harsh online, but it is really helpful.
From my observation, print ads, broadcast ads, and website ads are not enough, especially if you are a major corporation and are one of the major players in the industry. I am actually surprised that some companies haven’t fully utilized the web 2.0 tools that are so popular and are most useful right now. Think about it – if it is so popular, then the consumers that you so want to keep and/or acquire might be there. They might be talking about your brand, and they might have some major influence to other consumers as well. For instance, a discussion starts in a blog, people comment on the blog post, and these in turn might inspire others to start posts on other sites in relation to the topic/discussion. Are you there to see it and able to learn and do something about it?
Here’s an idea. Once you’ve identified the key influencers and evangelists (e.g. bloggers with a large audience), you need to contact them and establish good relations with them. You can then try to ask them to start a blog contest for example and your business can sponsor the prizes. The topic for example can be something like: Write a blog post about Company X’s product on how it has brought a major impact to the community. Or something better.