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shah_jiii
Joined: 12 Apr 2007
Posts: 6
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 13 Apr 2007 10:42 how WiMAX changes its modulation technique |
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| need help on the ability of WiMAX to change its modulation technique as distance from BS increases
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ricksidd
Joined: 23 Feb 2006
Posts: 158
Helped: 4
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| 13 Apr 2007 18:36 Re: how WiMAX changes its modulation technique |
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WiMAX system adjust the signal modulation and coding scheme on the basis of Signal to Noise ratio (SINR) condition of the radio link. When the radio link quality is high the highest modulation sceme and light coding is used giving the system more capacity. During a signal fade or long signal path the wiMAX system can shift to a lower order modulation sceme with heavier coding to maintain the connection quality and link stability.
So we have SNR = 22 dB the modulation is 64 QAM
SNR= 16 dB modulation 16 QAM
SNR= 9 dB modulation QPSK and
SNR = 6 dB modulation BPSK
-Sidd
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yasiranwar86
Joined: 12 Mar 2007
Posts: 21
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| 19 Apr 2007 19:23 how WiMAX changes its modulation technique |
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| sir can u give some more detail or link or some article related to modulation techniques
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ricksidd
Joined: 23 Feb 2006
Posts: 158
Helped: 4
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| 20 Apr 2007 18:26 Re: how WiMAX changes its modulation technique |
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The IEEE 802.16 standard speaks about this also
you can find various papers in this forum itself.......
Try to search for Adaptive Modulation for the conceptual understanding.
-Sidd
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darock
Joined: 04 Mar 2007
Posts: 57
Helped: 16
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| 21 Apr 2007 22:58 Re: how WiMAX changes its modulation technique |
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One question: How does the base station mesaure the SNR..
just by measuring its received power?
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ricksidd
Joined: 23 Feb 2006
Posts: 158
Helped: 4
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| 22 Apr 2007 13:59 Re: how WiMAX changes its modulation technique |
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Yes, for uplink SNR the Base station calculates SNR by received power while for downlink the subscriber station calculates and sends the requirement of its particular suitable burst profile....
Typical calculation can be --------
If Pr is received power in dBm then.
SNR(dB) = Pr(dBm) – No(dBm)
Where No (dBm) is the noise power in dBm, Assume, the carrier bandwidth is B, the receiver noise figure is F, the spectral efficiency is rb/B and the coding gain Gc
Then the SNR for coded modulation with data rate rb can be obtained by
SNR (dB)= 10 log[(Pr/No)x(rb/B)] -Gc
Where No (dBm) = -174(dBm) + 10 log B + F (dB)
Where Gc is normally considered as 5dB.
-Sidd
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ekh_81
Joined: 25 Oct 2005
Posts: 15
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| 22 Apr 2007 23:01 how WiMAX changes its modulation technique |
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thank you ricksidd, could you give us any book or website containing informations about the calculation of SNR of WiMax
Many thanx
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admoon
Joined: 01 Jul 2008
Posts: 34
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| 14 Aug 2008 17:40 how WiMAX changes its modulation technique |
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can you give me matlab code for how to change code rate and modulation scheme?
thanks
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bhq
Joined: 11 Jun 2008
Posts: 81
Helped: 7
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| 21 Aug 2008 13:44 Re: how WiMAX changes its modulation technique |
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| Actually WiMax uses the technique of OFDM in which we have the Orthogonal frequencies to modulate oure data. Thats changes the technique of modulation in WiMAx
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marshalzhu
Joined: 12 Aug 2005
Posts: 5
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| 03 Sep 2008 8:38 how WiMAX changes its modulation technique |
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| bit loading decrease 1 per 3dB
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bilal_rajput
Joined: 08 Sep 2008
Posts: 2
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| 09 Sep 2008 15:15 how WiMAX changes its modulation technique |
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is there any way to do a project on WiMAX but also in hardware related? n if posible, how much would it cost?
regards.
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iransatforum
Joined: 04 May 2004
Posts: 165
Helped: 9
Location: Sorrow-Land
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| 18 Nov 2008 12:04 Re: how WiMAX changes its modulation technique |
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| ekh_81 wrote: |
thank you ricksidd, could you give us any book or website containing informations about the calculation of SNR of WiMax
Many thanx |
h**p://www.esnips.com/doc/22406aa7-a327-4bbf-b3a4-f8e08fb71f0a/John.Wiley..Sons.WiMAX-Technology.for.Broadband.Wireless.Access.2007
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satish_mahankali
Joined: 09 Jun 2008
Posts: 4
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| 25 Nov 2008 7:53 Re: how WiMAX changes its modulation technique |
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As far as I know the wimax std species mandatory modulation techniques as Qpsk(1/2,3/4) 16 QAM ,64qQAM ..
BS station species the modulation we are using which is the same for the whole frame.
suppose if u have a frame with 30 symbol duration the modulation scheme remains the same for all the symbols
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medaziz
Joined: 13 Dec 2006
Posts: 43
Helped: 1
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| 25 Nov 2008 12:10 Re: how WiMAX changes its modulation technique |
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Hi
If you have a frame with 30 symbols duration i think that the modulation scheme remains the same for all the symbols because logically and if we examine the OSI Model , frame will take delimitor in second layer (link)whereas the modulation will be in physical layer.
Added after 46 seconds:
Hi
If you have a frame with 30 symbols duration i think that the modulation scheme remains the same for all the symbols because logically and if we examine the OSI Model , frame will take delimitor in second layer (link)whereas the modulation will be in physical layer.
Added after 1 hours 47 minutes:
Hi
If you have a frame with 30 symbols duration i think that the modulation scheme remains the same for all the symbols because logically and if we examine the OSI Model , frame will take delimitor in second layer (link)whereas the modulation will be in physical layer.
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