Are two antenna connections required for DC-HSDPA?

[ginggs]

Newer modems like the K4505 (aka Huawei E1820), K4605 (aka Huawei E372) and Huawei E367 have two antennae on the modem, but only one external antenna connector. The external antenna connector seems to switch out one of the modem's antennae, the primary antenna in the case of the E372 and E367 and the secondary antenna in the case of the E1820.

Sometime in early December 2011, the negotiated QoS values returned by my modem from my closest Vodacom tower changed from 16000/8640 to 21000/5760 on an E1820 and 42000/5760 on a K4605. I hoped that this meant my tower had been upgraded to 42Mbps DC-HSDPA, but to date have not seen a speed test result above 21Mbps, which I think would be clear evidence thereof.

Having had some success using a Wilkinson power divider (or splitter) with an E1820 on Cell-C's network, I wondered whether this could be used to improve speeds by presenting a strong signal at both the modem's external antenna connector and the unswitched antenna on the modem using an inductive coupler.

I have an existing LPDA-A0044 antenna aimed at my closest Vodacom tower, Poynting Direct loaned me a SPLT-A0014 2-way splitter and ADPT-026 inductive coupler, which I connected together with a CAB-038 pigtail to a K4605 modem.

Test results:

Antenna Connection	Ping (ms)	Download (Mbps)	Upload (Mbps)	Cell ID	RSSI (dBm)	Link
CAB-038	78	13.7	1.55	64351	-55	1
CAB-038	91	7.06	1.49	64351	-55	1
CAB-038	88	10.27	1.44	64351	-55	1
CAB-038 & ADPT-026	96	17.78	1.45	64356	-59	1
CAB-038 & ADPT-026	90	12.63	1.70	63256	-59	1
CAB-038 & ADPT-026	73	12.23	1.43	64356	-59	1
CAB-038	92	14.85	1.63	64351	-55	1
CAB-038	89	14.02	1.42	64351	-55	1
CAB-038	89	12	1.57	64351	-55	1
CAB-038 & ADPT-026	95	13.4	1.63	64351	-61	1
CAB-038 & ADPT-026	79	13.24	1.53	64351	-61	1
CAB-038 & ADPT-026	87	13.89	1.45	64351	-61	1

Averages:

Antenna Connection	Ping (ms)	Download (Mbps)	Upload (Mbps)
CAB-038	88	11.98	1.52
CAB-038 & ADPT-026	87	13.86	1.53

I was disappointed by the results, I was really hoping to see the speeds almost doubling.
Perhaps this is just means my tower has not yet been upgraded.

I also noticed my upload speeds were half the speed they had been previously.
Shortly before I got those results, I had a Vodacom technician at my house investigating an unrelated problem. While doing speed tests, he commented that my upload results were poor and that he would have the site reset, this made a noticeable difference, but seems to have been short lived.

[T-Man]

Hi ginggs

Well put together, links to the speedtest, links to previous posts and references to the equipments used.

In short - this is a excellent post. We can all learn from this.

[sajunky]

I was disappointed by the results, I was really hoping to see the speeds almost doubling.

In HSPA+ Release 8 speeds are doubling not because of using two antennas. These two antennas are used for the same purpose as in R7 (for receive diversity).

Speed doubling is achieved from single antenna by assigning two adjacent 5MHz bands (giving one 10MHz band), it is processed by the same receivers and single equaliser.

It is why splitter didn't bring expected doubling speed. By definition it shoudn't. When dropping out extraordinary samples (17.78 and 7.06) difference is negligible.

Averages:
Antenna Connection Ping (ms) Download (Mbps)
CAB-038 12.97
both 13.08

Question whether Vodacom activated R8 or merely updated QoS values remains unanswered. Some anwsers can be found when comparing results with E367. However K4606 can be still faster on 21Mbps network due to the Type 3i receivers.

When tested E1820 with splitter it is completely different story. With pigtail (no splitter) your transmitted signal is weak, bouncing many times before reaching tower. It is why using splitter helps, as it directs your transmitted power to the external antenna. In K4606 external antenna connector is properly implemented, splitter is not going to help.

[ginggs]

Newer modems like the Huawei E398 / Vodafone K5005 and Huawei E3276 have two external antenna connectors.

[nuyork]

I've noticed this on the LTE modems as well. Is this for MIMO support? Does that mean one would need to connect two seperate Poynting yagi antenna's to the device? Or can one get a connector to join the two connections into one to connect to a single yagi antenna?

From what I understand DC (dual carrier) is different to MIMO.