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From:	"Chris Smith (space DOT dandy AT icloud DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
MIME-version:	1.0 (1.0)
Subject:	Re: [geda-user] [OT] Wireless communication 101
Message-id:	<CDEC178F-5B26-4251-B4BB-83A985DC3F5E@icloud.com>
Date:	Thu, 24 Sep 2015 07:36:10 +0100
References:	<70C4A238-D361-4A6C-A81D-CBF019CADC4F AT icloud DOT com>
	<5601AE56 DOT 2050706 AT neurotica DOT com>
	<0958473E-0115-4C08-860F-EF92B84B7404 AT icloud DOT com>
	<56025516 DOT 3050403 AT ecosensory DOT com> <56030319 DOT 3070008 AT neurotica DOT com>
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> On 23 Sep 2015, at 20:52, Dave McGuire (mcguire AT neurotica DOT com) [via geda-user AT delorie DOT com] <geda-user AT delorie DOT com> wrote:
> 
> On 09/23/2015 03:30 AM, John Griessen wrote:
>>> What I'm looking for are any texts or references that discuss the
>>> principle of digital encoding for wireless transmission, which
>>> algorithms and strategies are used in what circumstances and why. As I
>>> said, I can't influence the RF part, only the ones and zeros that are
>>> encoded onto the carrier. I also can't change at this stage the
>>> simplex operation.
>> 
>> I don't have a reference, but I've heard that reed solomon encoding has
>> been used by nasa for telemetry
>> to get signals through under the noise.
> 
>  Reed-Solomon is a FEC (Forward Error Correction) algorithm that embeds
> enough error correction data in the bitstream to be able to fix some
> errors on the receiving end without retransmission.  It doesn't really
> do much for the noise floor.
> 
>  That said, though, it's an excellent suggestion.
> 
>  One other thing to do is bit-stuffing to maintain DC balance.  That's
> particularly important if the modulation is FM and the RX-side RF tuning
> is automatic.  A time-averaged DC value of 0 is very important in that case.

Yes, I'm already Manchester encoding the data and transmitting a significant amount of 0xAA preamble for the RX to lock on to.

Chris

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