Comments on: BPSK on 433 MHz European ISM band

By: Ryan

Ryan — Tue, 04 Aug 2009 21:24:15 +0000

4QAM is not QPSK, they are similar in nature, but also slightly different. Many authors simply class them as one scheme which is wrong.

4QAM produces a slightly better result over an AWGN channel, but QPSK is more suitable for producing a resilient OFDM mapped signal.

utilising FEC, interleaving, etc will result in them producing almost identical BER vs SNR waterfall graphs. which you see in almost any referenced material.

A large number of satiellites use BPSK along with SDR to transmit images, etc. The work would be good for receiving data along those lines.

By: ReKlipz

ReKlipz — Tue, 04 Aug 2009 16:29:26 +0000

@qam: Probably because BPSK and QPSK are essentially 2-QAM and 4-QAM.

By: qam

qam — Tue, 04 Aug 2009 13:13:33 +0000

I wonder why he chose BPSK instead of something like QAM. QAM would’ve given him higher bitrates.

By: Ryan

Ryan — Tue, 04 Aug 2009 10:57:27 +0000

Nice build.
If he had utilised some form of forward error correction scheme you can obtain the same BER as BPSK with 4-QAM, which would increase the spectral efficiency and in turn increase the throughput.
Software Defined Radio (SDR) would be a nice platform to initially build and mess around with structures without building an application specific circuit, it would allow interleaving, FEC, puncturing, etc to be implemented easier.

By: Agent420

Agent420 — Tue, 04 Aug 2009 10:31:49 +0000

^ watership down !!!

great hack btw – i’ve never done any hifreq rf projects, but i have respect for those who can fab that kind of stuff.

By: jproach

jproach — Tue, 04 Aug 2009 06:40:37 +0000

concino: think of the rabbit2000 module as an arduino. But trust me when I say to avoid them like the plague.

By: az1324

az1324 — Tue, 04 Aug 2009 06:15:58 +0000

I was hoping for a nice open source 8-bit software-based modulation/demodulation implementation.

By: phil

phil — Tue, 04 Aug 2009 00:20:48 +0000

excellent hack

By: googfan

googfan — Tue, 04 Aug 2009 00:08:23 +0000

burp

By: concino

concino — Mon, 03 Aug 2009 23:56:39 +0000

Ok. I don’t get this hack at all. Besides there is no arduino :P