Electronic Design

Do You Need Wireless Video Transmission For Your HDTV? Maybe, Sort Of…

Amimon’s WHDI standard and SiBEAM’s Wireless HD standard are making a push for wireless HD video

It has been possible to send HD video over wireless links for consumer electronic equipment connectivity for a long time. Wi-Fi and WiMedia UWB solutions have been around a few years, but both rely on compression techniques to bring the data load down into a range that the wireless data speeds can handle. But compressing and then decompressing video always leaves it just a bit less definitive than before compression.

The Holy Grail in video transmission has always been to transmit uncompressed video and retain all of the definition possible. An HDMI cable does just that. Up until now, wireless links have lacked the data rate capability to handle uncompressed video at a typical rate of 1.5 Gbits/s or more depending on the HD format.

Two wireless technologies have emerged to handle this chore between the HD set, the cable or satellite box, the DVD/Blu-ray recorder, and other HD devices. These are the WHDI standard by Amimon and WirelessHD standard by SiBEAM.

Amimon and WHDI

Amimon has a second-generation chipset that implements the Wireless Home Digital Interface (WHDI) standard. It operates in the 5.8-GHz unlicensed band and can achieve a data rate of 3 Gbits/s in a 40-MHz wide channel. That speed is obtained by using a four-transceiver by five-transceiver MIMO system and OFDM. A dynamic frequency selection (DFS) technique keeps the Amimon devices from being stepped on by 802.11a or 802.11n transmissions on the same frequency.

Amimon also uses a unique coding technique where the most critical visual bits are maximally protected while other less important pieces get less protection. The system will handle the 1080p HD format at 60 Hz with ease. Maximum range in a multi-room environment and through walls is about 100 feet, which is good enough for most home installations. The standard has a latency of less than one millisecond and supports the Hollywood-approved HDCP 2.0 copy protection scheme.

The new Amimon chips, the AMN 2120 and AMN2220, match up with the AMN3110 transmitter chip and the AMN3210 receiver chip, respectively. They are designed to be embedded in consumer devices such as TV sets and STBs but will also find their way into game consoles, PCs, dongles, and other accessories. The chipset is programmable to allow upgrades as the WHDI standard is revised and updated. The chips also interface directly with the video I/Os of other circuits, eliminating the need for codecs, memory buffers, or controls.

Amimon’s first-generation chipsets were previously embedded in a number of commercial HD TV sets and other products from the likes of Sony, Mitsubishi, and Gefen. The new chipsets, which are available now, are expected to further expand that adoption.

SiBEAM and WirelessHD

The other wireless video transmission technology is the WirelessHD standard. It is implemented with a chipset and module made by SiBEAM. This technology uses the unlicensed 60-GHz band. With lots of bandwidth to play with (7 GHz), it is relatively easy to achieve data rates of up to 4 Gbits/s. The WirelessHD standard uses OFDM and transmits uncompressed 1080p/60 Hz over a range of up to 10 meters.

To mitigate the effects of direct line-of-sight transmissions of 60-GHz signals as well as their tendency to travel over multiple reflective paths, SiBEAM has created a unique adjustable beamforming smart antenna system that adjusts itself to beam interruptions and changes in orientation or other conditions in a family room. The 36-dipole phased array is so tiny at 60 GHz that it is easy to integrate on a chip along with its control circuitry. The chips are made with common CMOS.

The SiBEAM chips and modules are already showing up in some consumer gear from Panasonic and LG. Look for more adoptions as this technology takes off. Agilent Technologies’ CTS-1000 automated test system and software for WirelessHD products is designed specifically to comply with the standards in order to achieve certification.

Incidentally, technology similar to that used with the WirelessHD standard is a candidate for the forthcoming 1-Gbits/s IEEE 802.11ad wireless standard. Furthermore, a new organization supporting 60-GHz wireless called the Wireless Gigabit Alliance or WiGig is working on a standard for consumer wireless as well as PC connectivity.

Which is best?

I have not witnessed a demo of either of these technologies but they obviously both work well because of their adoptions. As usual, the consumer has to deal with multiple standards. I would guess that both technologies are somewhat “challenged” by their power consumption and the short range fraught with multipath corruptions. There’s no doubt that additional work will solve those problems in time. In any case, both technologies get the job done. I am just happy we can transmit uncompressed video by radio. Who would have thought?

But what percentage of consumers with HDTV sets really needs this product? Why isn’t a cable good enough? I have only one HDMI cable connection that could be done by wireless, but it is only 5 feet long. It seems like a stretch to use a complex wireless system for a small area. Maybe that’s just me. But I can see that some homes with multiple boxes and sets would love the ease and freedom of wireless interconnects, especially if the wireless is embedded. Now what we need is a way for all of those potentially incompatible boxes to talk to one another.

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