Series of metal smartphones - and exposed antennas

I didn't see any mention of transmit diversity in those articles, and a quick Google came up empty. Can you point to some other articles or explanation of how the HTC, Nokia or iPhone utilizes transmit diversity?

I know HSPA, LTE, wifi, etc. can use 2 antennas for spatial multiplexing (MIMO) to achieve higher data rates, but that's different than transmit diversity. I don't think I have ever seen transmit diversity used in cellular. Receive diversity is used at the base station to reduce fading dips and improve signal. And in UMTS the phones there are rake receivers to combat multi-path, but again that receiving, not transmitting.

The only example of transmit diversity I can find in cellular networks is a somewhat recent trial by Qualcomm (2010). The benefit of it looks actually better than I expected, but usually when they trial this kind of stuff driving around in a van, it means any commercial implementation of it is several years away. I'd be really surprised if there are already 3 phones commercially available that support it

Very interesting to me, but I think it's a safe bet that most people don't get excited and buy phones based on antenna solutions Maybe metal housings tho...

 

Interesting, I'm aware receive (Rx) diversity has been used on the network side for a long time, either by 2 Rx antennas (space diversity) or more commonly by cross-polarized antennas within a single housing (polarization diversity). I wasn't really aware that phones were using diversity as well (are they using polarization diversity as well as space dicersity?). I found a Qualcomm research paper dated 2005 which explored Tx/Rx diversity in CDMA handsets:

The most recent commercial handset I found was a Palm Pre (2009) that had dual antennas. So I guess the dual antennas in cell-phones began commercially sometime in the late 2000's? In which case I'd say it's relatively "new", at least to someone like me who has been working with cellular since the late 1990's I guess it wasn't used much previously (ie: pre-2005) because of poor processing power of older phones, as well as trying to cram everything into a small device. But as components become smaller, and processing power increases, I can imagine Tx/Rx diversity in the phone itself is something handset mfgrs will explore more of and can probably have some good effects. The "intelligent switching" that Qualcomm described in 2005 and is in use today is just a beginning.

As for cell-phones with metal housings, that seems to be a relatively recent thing as well. The first aluminum-body phone I can find was the Nokia N8 released in 2010. It's also the first GSM/UMTS (ie: non-CDMA) phone I found that has dual antennas on it.



Normally the antennas are within the casing, and a metal housing would obviously interfere with that. On the Nokia N8, the top and bottom pieces, altho having a metallic-look, are actually plastic, and the antennas are encased there, allowing the phone to have a ~80% metal casing and still have internal antennas. The 2010 Motorola Devour also had a primarily aluminum housing, but had rubberized ends where antennas were located:




External antenna bands on phones with 100% metal casing, ala the iPhone, HTC One, Nokia Lumia, etc, obviously needs to be designed with a great deal of care, and have very good isolation, as hands touching exposed antennas can degrade the signal.

Altho I can agree a brushed-aluminum casing has a nice look and feel, I'm still "old-school" and prefer a rubberized exterior, mainly it's the non-slip properties.