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From: Laron on 18 Mar 2010 03:59
Hi all,

How to achieve synchronization(carrier phase timing) in ofdm? did ofdm
need a pilot?
From: Tim Wescott on 18 Mar 2010 11:49
Laron wrote:
> Hi all,
>
> How to achieve synchronization(carrier phase timing) in ofdm? did ofdm
> need a pilot?

I haven't worked with any OFDM schemes, but I've reviewed some. While
in theory you could get away without using a pilot in OFDM, in practice
the OFDM protocols I see have pilot tones. Given the nature of OFDM,
dedicating a channel to a pilot tone eases the problem of synchronizing
the receiver considerably, while not wasting too much carrier power.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com
From: Laron on 18 Mar 2010 21:15
>Laron wrote:
>> Hi all,
>>
>> How to achieve synchronization(carrier phase timing) in ofdm? did
ofdm
>> need a pilot?
>
>I haven't worked with any OFDM schemes, but I've reviewed some. While
>in theory you could get away without using a pilot in OFDM, in practice
>the OFDM protocols I see have pilot tones. Given the nature of OFDM,
>dedicating a channel to a pilot tone eases the problem of synchronizing
>the receiver considerably, while not wasting too much carrier power.
>
It's easy to understand the synchronization in single carrier
implementation, however,with ofdm receiver, after downconvertion, the
process is first sampling then use fft to get indexes of time domain signal
at one time point? if so,then how to decide the sampling rate and how to
achieve synchronization after fft?

Just first time touching ofdm, is there any good reference for these detail
implementation?

Thanks a lot.
B. R.
Laron

From: Frank_os on 19 Mar 2010 14:04
Could you specify which OFDM system is interested for you? Wimax, LTE, IEEE
802.11 a/g, DVB? Each system has a unique design to implement the
synchronization.

Frank

>>Laron wrote:
>>> Hi all,
>>>
>>> How to achieve synchronization(carrier phase timing) in ofdm? did
>ofdm
>>> need a pilot?
>>
>>I haven't worked with any OFDM schemes, but I've reviewed some. While
>>in theory you could get away without using a pilot in OFDM, in practice
>>the OFDM protocols I see have pilot tones. Given the nature of OFDM,
>>dedicating a channel to a pilot tone eases the problem of synchronizing
>>the receiver considerably, while not wasting too much carrier power.
>>
>It's easy to understand the synchronization in single carrier
>implementation, however,with ofdm receiver, after downconvertion, the
>process is first sampling then use fft to get indexes of time domain
signal
>at one time point? if so,then how to decide the sampling rate and how to
>achieve synchronization after fft?
>
>Just first time touching ofdm, is there any good reference for these
detail
>implementation?
>
>Thanks a lot.
>B. R.
>Laron
>
>
From: John on 19 Mar 2010 17:34
On Mar 18, 9:15 pm, "Laron" <jason.piker(a)n_o_s_p_a_m.inbox.com> wrote:
> >Laron wrote:
> >> Hi all,
>
> >>     How to achieve synchronization(carrier phase timing) in ofdm? did
> ofdm
> >> need a pilot?
>
> >I haven't worked with any OFDM schemes, but I've reviewed some.  While
> >in theory you could get away without using a pilot in OFDM, in practice
> >the OFDM protocols I see have pilot tones.  Given the nature of OFDM,
> >dedicating a channel to a pilot tone eases the problem of synchronizing
> >the receiver considerably, while not wasting too much carrier power.
>
> It's easy to understand the synchronization in single carrier
> implementation, however,with ofdm receiver, after downconvertion, the
> process is first sampling then use fft to get indexes of time domain signal
> at one time point? if so,then how to decide the sampling rate and how to
> achieve synchronization after fft?
>
> Just first time touching ofdm, is there any good reference for these detail
> implementation?
>
> Thanks a lot.
> B. R.
> Laron

One thing you can do is differentially encode from one bin to the
next.

John
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