2.4 Ghz Transceiver IC with > 10 Mbps - Page 1
Forum section: electronics / rf-microwave

author: rfspezi
author_rank: Regular Contributor
timestamp: February 24, 2020, 01:34:52 pm
content: I am in search of a transceiver IC (or modul) that supports at least 10 Mbps in the 2,4 GHz band.It should be low level accessable so that i got full control over the chip-parameters, the protocol and the timings.The fastest i found so far are the ones from Nordic supporting 2 Mbps.Does anybody know a suitable product?

author: rfspezi
author_rank: Regular Contributor
timestamp: February 24, 2020, 02:48:50 pm
content: I thought in SDR aswell but it's not practical and too expensive.It's really interresting, that there are absolutely no OFDM transceiver ICs available for proprietary usage.

author: rfspezi
author_rank: Regular Contributor
timestamp: February 25, 2020, 07:58:25 am
content: Quote from: blueskull on February 24, 2020, 03:00:11 pmReally, getting even a single "Bit" of information about the SDR part from Espressif is totally unrealistic and by the way not a solution for me.I noticed, that using OFDM means increased latency by default und thus is no option.So what i am still in search of is a solution using FSKn modulation or similar.

author: OwO
author_rank: Super Contributor
timestamp: February 25, 2020, 08:33:25 am
content: I'm pretty sure the ESP32 has the wifi MAC and packet logic baked in to the hardware, if not that then the OFDM FFT module and carrier/symbol timing recovery. What I am sure is that the software never sees the I/Q data.BPSK at 20Mb/s is trivial to do, but any reflections and your bits are all smeared and you receive garbage even with high SNR. OFDM is used in everything these days for a reason.

author: tszaboo
author_rank: Super Contributor
timestamp: February 25, 2020, 08:46:56 am
content: The reason you dont find FSK 10 Mbps ICs, because you are not supposed to do that. If you still manage to do it, probably your equipment will violate out-of-band emissions, that are mandated by FCC, RED, and other regulations.

author: rfspezi
author_rank: Regular Contributor
timestamp: February 25, 2020, 03:04:15 pm
content: Quote from: NANDBlog on February 25, 2020, 08:46:56 amWhy shouldn't 83,5 MHz (2,400-2,4835 GHz) bandwidth be enough to handle a 10 Mbps MSK modulated signal?

author: rfspezi
author_rank: Regular Contributor
timestamp: February 25, 2020, 03:52:18 pm
content: Quote from: blueskull on February 25, 2020, 03:16:27 pmI am not planing to do so, i just wanted to point out that even a 10 Mbps using MSK or GFSK does by far not occupy 83,5 MHz.QuoteThat's definately true, but i thought the more experienced people in here could give some constructive advice.QuoteOfcourse not.QuoteAlmost... TX power is less than -20 dBm

author: OwO
author_rank: Super Contributor
timestamp: February 25, 2020, 05:53:35 pm
content: Actually it's the opposite - the regulations (in the US) say you can't concentrate all your power in a narrow bandwidth, but that if you spread it over a certain minimum bandwidth you are allowed higher transmit power (30dBm or 1W). There's nothing that says you can't spread it over the entire 2.4GHz band, and in fact if you do there is little potential for interference. Something like 20dBm spread over 100MHz of bandwidth won't even be noticed by your neighbors because walls block the signal well and their own wifi signal will overpower it, but in your own room you may notice some range degradation. This is assuming you actually spread it properly; something like frequency hopping with a slow hop rate WILL jam wifi. OFDM and DSSS are fair game I recall but double check the latest regulations.

author: tszaboo
author_rank: Super Contributor
timestamp: February 25, 2020, 09:34:14 pm
content: Quote from: rfspezi on February 25, 2020, 03:04:15 pmBut you are not supposed to do that. Its the law.Just connect two "n" modules with Wifi direct and get some 70 mbit/sec on a a 20 MHz band and call it a day.

author: rfspezi
author_rank: Regular Contributor
timestamp: February 26, 2020, 07:04:36 am
content: Quote from: NANDBlog on February 25, 2020, 09:34:14 pmSo what is the maximum allowed bandwith in my case (-20 dBm and GFSK)?As mentioned before, OFDM is no solution in my case since it introduces too much latency.[EDIT:]Just found this module here which claims to provide up to 8 Mbps?https://www.vishay.com/company/press/releases/2006/060908trm/en

author: scatha
author_rank: Regular Contributor
timestamp: February 26, 2020, 07:14:44 am
content: Quote from: rfspezi on February 26, 2020, 07:04:36 amWhat's your definition of 'too much latency'?

author: rfspezi
author_rank: Regular Contributor
timestamp: February 26, 2020, 07:33:36 am
content: Quote from: scatha on February 26, 2020, 07:14:44 amThe communication-cycle time should be below 4 us (32 bit total - incl. preamble).Using standard 802.11n, the preamble alone needs 16us plus 4us for signaling before payload starts.

author: OwO
author_rank: Super Contributor
timestamp: February 26, 2020, 07:36:09 am
content: There is no "maximum bandwidth" except you may not leak outside the ISM band boundary. There is, however, a minimum bandwidth which is set by the maximum power spectral density limit (it varies by band and by country, go look up the relevant regulations for your location). At -20dBm and >=1MHz I wouldn't worry about it. OFDM doesn't necessarily mean high latency - if this is for short distances (no long echoes to deal with) a 16-subcarrier OFDM will give you 16 symbols of latency and still divide the channel into ~1MHz chunks which you can assume to be coherent.