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Clearwire Corporation (CLWRD) Message Board

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  • sunnybeach73 sunnybeach73 Dec 28, 2012 12:20 PM Flag

    Nearly Blind - TD-LTE Vision Restored

    Do you really know why SC-FDMA uses less power and why it has been set up only with a single carrier channel?

    The SC-FDMA does not require continuous power source feeding because in an OFDMA (downlink) it requires a continuous power source due to multiple transmissions simultaneously through MIMO and this phenomenon worsen significantly when it’s 4x4 because it requires to interact with the network to eliminate the tear-down/set-up time thereby becomes a power drain to the battery.

    Secondly, SC-FDMA has been set up as a single carrier channel because how much of an 'upload' does a mobile user do therefore your point about range extension is worthless unless you are transmitting video out of your smartphone/tablet all the time rather than watching (down-streaming) video like normal subscriber does. The reason SC-FDMA is not used in FDD-LTE is because of its symmetrical channel setup on both directions (UL/DL), thereby requires OFDMA on both.

    Do you really understand what you are talking about? Perhaps you should stop your non-sense, amateur!

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    • Hey Bozo, SC-FDMA re-orders the TX bits across carriers to maintain low peak-to-average ratio of TX (uplink) signal.
      Lower PAR allows reduced PA bias levels (you know the old AC load line) or increase in TX power without degrading the ACP (adjacent channel power) performance.
      I was designing PAs while you were still suckling mommies teets.

      Despite its name, Single Carrier Frequency Division Multiple Access (SC-FDMA) also transmits data over the air interface in many sub-carriers but adds an additional processing step. Instead of putting 4 bits together as in the OFDM example to form the signal for one sub-carrier, the additional processing block in SC-FDMA spreads the information of each bit over all the sub-carriers. This is done as follows: Again, a number of bits (e.g. 4 representing a 16 QAM modulation) are grouped together. In OFDM, these groups of bits would have been the input of the IDFT. In SC-FDMA, however, these bits are now piped into a Fast Fourier Transformation (FFT) function first. The output of the process is the basis for the creation of the sub-carriers for the following IFFT.

      Summary of the difference between OFDM and SC-FDMA:

      OFDM takes groups of input bits (0's and 1's) to assemble the sub-carriers which are then processed by the IDFT to get a time signal. SC-FDMA in contrast first runs an FFT over the groups of input bits to spread them over all sub-carriers and then uses the result for the IDFT which creates the time signal. This is why SC-FDMA is sometimes also referred to as FFT spread OFDM.

      While SC-FDMA adds additional complexity at both the transmitter and receiver side, the 3GPP standardization body has nevertheless decided for it as treating signal this way reduces the Peak to Average Power Ratio (PAPR). This is important to lower the power consumption of mobile devices.

      What TD-LTE brings to 2.6 GHz is a BIG DEAL. Don't let any of the clowns on this blog tell you otherwise.

      $8+ or NO on Buyout !!!

      • 4 Replies to indano
      • A plagiarizing pumper that knows squat yet still pretending signifies a person with no integrity. I have noticed you've been busy doing your 'cut and paste' from a published article while rearranging the order so you won't get caught which means you’re just an amateur that have no technical understanding. Aren't you even a bit embarrassed of getting caught plagerizling?

        “SC-FDMA spreads the information of each bit over all the sub-carriers. This is done as follows: Again, a number of bits (e.g. 4 representing a 16 QAM modulation) are grouped together. Thus, instead of detecting the bits on many different sub-carriers, only a single detector is used on a single carrier.

        Summary of the difference between OFDM and SC-FDMA:

        OFDM takes groups of input bits (0's and 1's) to assemble the sub-carriers which are then processed by the IDFT to get a time signal. SC-FDMA in contrast first runs an FFT over the groups of input bits to spread them over all sub-carriers and then uses the result for the IDFT which creates the time signal. This is why SC-FDMA is sometimes also referred to as FFT spread OFDM.

        While SC-FDMA adds additional complexity at both the transmitter and receiver side, the 3GPP standardization body has nevertheless decided for it as treating signal this way reduces the Peak to Average Power Ratio (PAPR). This is important to lower the power consumption of mobile devices.”

        (change DOT to’.’)

        mobilesocietyDOTtypepadDOTcom/mobile_life/2007/05/index.html

      • Great work Indano - you rock!. Ignore Mfers like sunnybeach and trep who don't know squat when it comes to deep technical stuff. You really need to send this stuff to the lawyers / agencies that matter. GL and keep up the good work.

        Sentiment: Strong Buy

      • Indiano, committing literary theft, that's what Webster calls plagiarize!

        At least have the decency to paraphrase them instead of copying word by word of someone else's achievement and pretending to be yours. Sunny is right, you are a thief!

        Shame! Shame!

      • LOL! You are repeating a history leasson.. which means what?

        Tell everyone what that means to Clearwire in real terms as a business and investment given their and investor's circumstances. This conversation about SC-FDMA was of consequence in decisions to use LTE vs. WiMAX. Even them, the major advantages of SC-FDMA are to spread power across spectrum... a form of spread-spectrum technology that uses the frequency domain.

        "SC-FDMA system use different orthogonal frequencies (subcarriers) to transmit information symbols. However, they transmit the subcarriers sequentially, rather than in parallel."

        SC-FDMA uses the same functional blocks as OFDMA but, as noted, preorders transmission across carriers in order to spread power to achieve lower PAPR, peak to average power ratio that reduces power consumption and increases amplifier efficiencies.

        "Single carrier frequency division multiple access (SC-FDMA) which utilizes single carrier
        modulation at the transmitter and frequency domain equalization at the receiver is a technique
        that has similar performance and essentially the same overall structure as those of an OFDMA
        system. "

        This conversation is academic and is only for going business concerns, not businesses that are in the process of being scrubbed with the remaining issue being how much scraps will be left on the table... whether the current offer will be accepted or increased. It is good for you to take an interest in this as it will be important to Sprint-Softbank and other going concerns moving forward. However, this type of conversation had become meaningless a couple years ago. As pointed out, it is part of the LTE tech and all competitors can benefit from it to compete with other viable competitors. Clearwire stopped being a self-sustained company in a real sense over three years ago. It has become so clear to everyone that they no longer are able to survive that their only option is to acquiesce to being taken out of their misery.. as a public company that is...

        The King is dead, long live the king!The technology is just starting, Clearwire is dead one way or the other.

 

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