Used in the UK for DAB ie digital radio. I heard that it had been dumped for car radios because it doesn't work due to multipath. Any truth in this? My contact was with Ford Radio. They stuck with FM instead and gave up on digital.
OFDM
Started by ●January 24, 2014
Reply by ●January 24, 20142014-01-24
gyansorova@gmail.com writes:> Used in the UK for DAB ie digital radio. I heard that it had been > dumped for car radios because it doesn't work due to multipath. Any > truth in this? My contact was with Ford Radio. They stuck with FM > instead and gave up on digital.Does multipath act differently in the UK than the US? -- Randy Yates Digital Signal Labs http://www.digitalsignallabs.com
Reply by ●January 24, 20142014-01-24
On Fri, 24 Jan 2014 13:20:17 -0800 (PST), gyansorova@gmail.com wrote:>Used in the UK for DAB ie digital radio. I heard that it had been dumped for car radios because it doesn't work due to multipath. Any truth in this? My contact was with Ford Radio. They stuck with FM instead and gave up on digital.OFDM is very robust in multipath, but everything has its limits. For most signals as the bandwidth increases it gets harder to deal with dynamic multipath, especially highly mobile multipath. Plus, you need to determine what "doesn't work" means in your context. Analog FM radio has a lot of advantages, including robustness, simplicity, low cost, and power efficiency. I hope it stays around for a long time. Eric Jacobsen Anchor Hill Communications http://www.anchorhill.com
Reply by ●January 24, 20142014-01-24
On Saturday, January 25, 2014 10:54:19 AM UTC+13, Randy Yates wrote:> gyansorova@gmail.com writes: > > > > > Used in the UK for DAB ie digital radio. I heard that it had been > > > dumped for car radios because it doesn't work due to multipath. Any > > > truth in this? My contact was with Ford Radio. They stuck with FM > > > instead and gave up on digital. > > > > Does multipath act differently in the UK than the US? > > -- > > Randy Yates > > Digital Signal Labs > > http://www.digitalsignallabs.comI wasn't sure if they had OFDM in the US. The UK were probably first because the BBC adopted a long time ago. Ford radios were designed in Detroit but I think the UK branch is now bust. They found OFDM to be useless in a car.
Reply by ●January 24, 20142014-01-24
On Friday, January 24, 2014 8:01:56 PM UTC-5, gyans...@gmail.com wrote:> On Saturday, January 25, 2014 10:54:19 AM UTC+13, Randy Yates wrote: > > > gyansorova@gmail.com writes: > > > > > > > > > > > > > Used in the UK for DAB ie digital radio. I heard that it had been > > > > > > > dumped for car radios because it doesn't work due to multipath. Any > > > > > > > truth in this? My contact was with Ford Radio. They stuck with FM > > > > > > > instead and gave up on digital. > > > > > > > > > > > > Does multipath act differently in the UK than the US? > > > > > > -- > > > > > > Randy Yates > > > > > > Digital Signal Labs > > > > > > http://www.digitalsignallabs.com > > > > I wasn't sure if they had OFDM in the US. The UK were probably first because the BBC adopted a long time ago. Ford radios were designed in Detroit but I think the UK branch is now bust. They found OFDM to be useless in a car.One of the AM digital audio systems in the US has a cool backward compatibility feature. The OFDM data is modulated in quadrature to the analog. So envelope detectors still pick up the analog program. Not widely deployed but I think its pretty cool. John
Reply by ●January 25, 20142014-01-25
Resistance to multi path is supposed to be one of the main advantages of OFDM. It really doesn't have much else going for it. Mark
Reply by ●January 25, 20142014-01-25
On Fri, 24 Jan 2014 21:11:59 -0800 (PST), makolber@yahoo.com wrote:>Resistance to multi path is supposed to be one of the main advantages of OFDM. >It really doesn't have much else going for it. >Mark^^^^ That. Eric Jacobsen Anchor Hill Communications http://www.anchorhill.com
Reply by ●January 25, 20142014-01-25
Am 24.01.2014 22:20, schrieb gyansorova@gmail.com:> Used in the UK for DAB ie digital radio. I heard that it had been dumped for car radios because it doesn't work due to multipath.That does not sound right. Well, if you're driving in a car with your receiver, you'll also experience a "Doppler spread" due to multipath. Maybe the DAB OFDM symbol rate is too low so that the whole thing is not that robust w.r.t. Doppler spreads. But for a given Doppler spread and temporal spreading there is an optimal choice of OFDM symbol rate and guard interval that maximizes the troughput. So, I don't see why OFDM itself should be an issue. LTE uses OFDM and is designed to be able to deal with mobile phones moving at up to 300km/h (about 186 mph) as far as I know. Cheers! SG
Reply by ●January 25, 20142014-01-25
On Friday, January 24, 2014 3:54:19 PM UTC-6, Randy Yates asked:> > Does multipath act differently in the UK than the US?Of course it does; since they drive on the left in the UK, the multipath interference comes from a different direction and can be quite different from the multipath encountered in the US and Europe (different path losses, different delays, etc.)
Reply by ●January 25, 20142014-01-25
On Saturday, January 25, 2014 12:11:59 AM UTC-5, mako...@yahoo.com wrote:> Resistance to multi path is supposed to be one of the main advantages of OFDM. > > It really doesn't have much else going for it. > > MarkWhether OFDM is more resistant to multipath compared to other spread spectrum techniques is debatable. What's clear is OFDM can greatly simplify the equalizer compared to an otherwise comparable single carrier system. Another thing OFDM has going for it is scalability in subcarrier space. This can be used for, among other things, more optimal allocation of spectrum in multiuser systems. The biggest knock on it may be the demanding RF PA linearity requirement in low power (portable) applications.
