Introduction
The last time I looked at a pair of 5 GHz only 802.11n AP/Bridges was the WNHDE111 / WNHDEB111, over two years ago. Back then, they were one of the few ways to add 5 GHz 802.11n capability to your wireless LAN. But NETGEAR is finally bringing to market something I’ve often said would be needed to provide decent wireless 720p/1080p streaming—a product designed specifically for that purpose.
The WNHDB3004 3DHD Wireless Home Theater Networking Kit will list for $259.99 when it hits store and etail shelves around the middle of next month. It consists of two WNHD3004 Wireless-N HD Home Theater Adapters in a box complete with Ethernet cables and power wall warts. The adapters will also be sold individually for $149.99 each.
My image of an application-specific HD streaming product was actually more limited than what NETGEAR has come up with in the WNHDB3004. I had the products doing nothing more than HD streaming, i.e. they couldn’t be used as access points or general Wi-Fi bridges.
But what NETGEAR, with technology partner Quantenna Communications, has come up with, is actually more general purpose than what I imagined. NETGEAR has positioned the WNHDB3004 in its Home Theater offerings vs. its Wireless Range Extender / AP group. But the product can also be used as an 802.11a/n AP or bridge and will support regular ol’ wireless clients with data traffic. But what lies beneath its glossy black covers has a lot more going on than in a plain old 11n AP / bridge. I’ll get to that shortly, but first let’s take a quick look at the product.
A disclaimer to start. The product arrived in a plain brown box, which always makes me ask the vendor to clarify what was sent. NETGEAR said they sent part of a "pilot run" for a large service provider customer that was receiving the product in the plain box. I was assured that production units, which will start coming off the line at the end of this month, to hit retail in "early to mid November", will be "identical in hardware and software".
Figure 1 shows the controls, lights and ports on the front and rear panels of the WNHD3004, which are pretty straightforward and very similar to those on the WNHDE111. The front panel simply sports Power and Wireless Speed lights, the latter glowing red, yellow or green.
Figure 1: WNHD3004 Front and rear panels
According to the Installation Guide, which is currently the only documentation available besides the data sheet, green indicates that the WNHD3004 is operating at the "Best speed at which this device can operate". Yellow means "Good speed, capable of doing one to two HD streams" and red, "Not a good speed. You should move the bridge to get a better speed". This is similar to the scheme NETGEAR has adopted in its latest HomePlug AV adapters.
One the rear panel are Power, Auto / AP / Bridge mode switch and four switched ports, vs. the two on the WNHDE111. But, like the WNHDE111, the WNHD3004’s ports are 10/100, not Gigabit. But, never fear. Given the product’s throughput performance, this was a good choice.
The Inside
The WNHD3004’s design is quite different than your standard 802.11n AP / bridge. First, it’s based on Quantenna devices and second, it has four receive / transmit channels.
Since the FCC photos were fuzzy, I opened one up to ID the components. Figure 2 shows the top inside view, which differs from the FCC photo in that the main Quantenna SoC in the silver package doesn’t have a heatsink.
Figure 2: WNHD3004 inside top view
I expected to find the QHS600 as the main SoC, but instead found a Quantenna QT1018BH, which there is no mention of on Quantenna’s website. An Atheros AR8236 handles the four switched 10/100 Ethernet ports and there is 64 MB of RAM and 8 MB of flash to support the QT1018BH.
Figure 3: WNHD3004 inside bottom view
You can see these components more clearly, except for the Intel flash device on the bottom of the board, in Figure 4.
Figure 4: WNHD3004 top component detail
I didn’t want to risk disturbing the RF integrity by prying off the RF shield, so I turned to the FCC ID photos for a peek inside the can. Figure 5 shows a pretty clear close-up of the RF area. The two larger devices at the bottom of the photo are Quantenna QT1518Bs. But the four smaller devices at the top are way too small to make out their part numbers.
Figure 5: WNHD3004 RF section detail
As is NETGEAR’s practice, the WNHD3004 has etched-on-board antennas. Figure 6 shows a close-up of the top antenna area, where four antennae are clearly visible.
Figure 6: WNHD3004 top antenna detail
Figure 7 shows the bottom of the board, with what looks like ground plane running under the top antenna area. You can also see the heatsink plate that is coupled to the four tiny devices (most likely power amplifiers) on the top side of the board via thermal pads.
Figure 7: WNHD3004 bottom antenna detail
How It Works
I covered the basics of Quantenna’s "Full-11n" technology in 2010: The Year of HD Streaming Wirelessly? Part 2. So some of this will be going over covered ground. If you really want the gory tech details, check the videos linked in the article linked above and on Quantenna’s website and download the whitepaper from Quantenna (free, simple registration required).
Quantenna’s technology uses 4X4 MIMO (4 transmit, 4 receive), but with only two spatial streams. (This is abbreviated 4X4X2 in the NETGEAR and Quantenna literature.) They claim this technology produces "5x the coverage and 2x the throughput" of other 802.11n products.
But two spatial streams will support only a 300 Mbps maximum link (PHY) rate (with two bonded channels, i.e. 40 MHz channel bandwidth mode). And since two streams can be accomplished with 2X2 MIMO, why does Quantenna’s system incur the extra expense and complexity of 4X4 MIMO to get just two streams?
The complex answer essentially boils down to the fact that the more antennas used per stream, the higher the possible signal gain, so the higher the Signal To Noise Ratio (SNR). A high SNR yields higher effective (i.e. real) throughput with a lower bit or packed error rate (BER or PER). Figure 8 shows two spatial streams being multiplexed to four transmit antennas and recovered by four receive antennas.
Figure 8: 4×4 MIMO with multiplexing of two spatial streams
(courtesy Quantenna Communications)
BER/PER is particularly important, since most 802.11n implementations allow high BER/PER in order to achieve higher speed benchmarks in tests, which vendors have trained consumers to look for. But for reliable HD streaming, you need consistent throughput that is free of the second-long dropouts you get in most every other 802.11n system available today.
There is some pretty heavy-duty signal processing involved and Quantenna says its technology makes use of some of the techniques that are optional, but not commonly used in consumer 802.11n gear. Maximal Ratio Combining (MRC), for example, optimizes the received SNR by using all four antennas to recover two spatial streams.
Quantenna also makes heavy use of dynamic digital beamforming to increase gain. Beamforming works by having the MIMO receiver talk to its associated transmitter, telling it how to tweak the transmitted signal to compensate for the environment between them. Quantenna says that it obtains 12 to 25 dB of gain using this technique. Check this video if you’d like Dr. Rezvani, Quantenna’s Founder, President and Chairman, to give you a primer on dynamic beamforming.
A Peek At Performance
But most of you probably don’t care if NETGEAR’s box uses hamsters spinning on wheels inside, as long as it gets your HD stream from server to player. So what can you expect for your $260?
Quantenna says Full-11n "delivers up to four [emphasis mine] flawless high-definition (HD) video streams at more than 100 Mbps data rates, over 100 feet, and guarantees this performance nearly 100 percent of the time through near-zero packet error rate (PER) data transfers, regardless of signal impairments and dead zones that are typical in the home".
NETGEAR takes Quantennas claim of four streams and appears to double it (!) in the diagram shown in Figure 9, which appears on the product’s webpage and datasheet. But there were no actual throughput claims in any of NETGEAR’s marketing information, so I asked them what the product was designed to deliver.
Figure 9: VERY optimistic WNHD3004 connection diagram
Som Pal Choudhury, Director of Product Marketing, Consumer Networking, answered my query with the following:
Taking an average of MPEG2 1080p stream at 20 Mbps per stream… we can stream Multiple HD streams (Up to 3) inside a above average size single family home across multiple walls. As 3D streams implies double the bandwidth (one for each eye), you can do at least ONE if using 1080P MPEG2 taking 20 Mbps average.
So NETGEAR basically said the product can provide an average of ~ 60 Mbps throughput across multiple rooms.
And what about those eight devices connected via three WNHD3004s? Well, Som said they showed four devices per adapter because of its four Ethernet ports. But "Connects Up to Four Devices" (as noted in the diagram) is different than "Streams to up to four devices simultaneously", which is not what the diagram states. And since typically there is only one display device in a room, only one of the four devices will be active at a time.
Som also said they showed two rooms because, continuing with the one display per room model above and the claim of being able to support up to three 20 Mbps HD streams, they could support HD streaming to two rooms simultaneously.
My initial tests seem to support NETGEAR’s 60 Mbps claim, at least for same-room testing, but nowhere near Quantenna’s 100 Mbps. I set up the pair of WHD3004’s in my office about 10 feet apart with no other wireless traffic active. One WNHD3004 was connected to my LAN’s switch, the other to my Acer Aspire 1810T netbook. I let the WNHD3004s set themselves up, which they did without any intervention from me, right out of the box.
I then set up an IxChariot test, using three throughput.scr scripts with the test file size changed from 100,000 to 1,000,000 Bytes, using TCP/IP traffic and ran the test for the usual one minute.
Figure 10 shows the transmit results and Figure 11, the receive.
Figure 10: WNHD3004 Three TCP/IP Transmit streams – same room
Both directions produced >60 Mbps total throughput and >20 Mbps per stream, which validates NETGEAR’s claim in terms of maximum throughput. But remember, this is a stream over a 10 foot distance in the same room.
Figure 11: WNHD3004 Three TCP/IP Receive streams – same room
But I want you to notice how low the throughput variation is and that there was not one single throughput dropout during the one minute test. However, most HD video is longer than a minute. So I ran a one hour test (Figure 12) and was happy to see that it too, had no dropouts.
Figure 12: WNHD3004 Transmit and Receive – same room – 1 hour
So, at least for same-room operation, the WNHDB3004 kit seems to meet NETGEAR’s 60 Mbps design goal. The real test, however, will be how much of that throughput is lost as I test it in all six of my test locations. For those results, and the full review, you’ll have to check back in a few weeks.