The 60-GHz band offers ample, license-free bandwidth. In the US, the range from 57 to 64 GHz is available, while in Japan, 59 to 66 GHz are available. With seven gigahertz of bandwidth, there are many high data rate applications one can envision, as depicted below.
Wireless Personal Area Networks
60 GHz is ideally suited for personal area network (PAN) applications. A 60-GHz link could be used to replace various cables used today in the office or home, including gigabit Ethernet (1000Mbps), USB 2.0 (480Mbps), or IEEE 1394 (~800Mbps). Currently, the data rates of these connections have precluded wireless links, since they require so much bandwidth. While other standards are evolving to address this market (802.11n and UWB), 60-GHz is another viable candidate. The intended range of wireless PANs is ten meters or less, which covers the size of most offices, medium-size conference rooms, and rooms in the home.
Wireless PANs could interconnect various electronic devices, including laptops, cameras, PDAs, and monitors. Applications include wireless display, wireless docking station, and wireless streaming of data from one device to the other.
Streaming data from one device to another is an application which benefits from the high data rates achievable at 60GHz. For example, a digital camera with one gigabyte of memory (2^33 bits) will take ~159 seconds to download its contents over a 54 Mbps WiFi connection, but ~13.5 seconds to download over a 630Mbps 60-GHz connection (this calculation blissfully ignores all of the overhead required in a wireless link—hand-shaking and the like).
Wireless HDMI
The High-Definition Multimedia Interface (HDMI) is evolving to be the standard interface for high-definition TVs. This cable provides both video and audio information. Depending on the resolution of the display, the data rates required for an uncompressed HDMI signal can be substantial. The key advantage of 60-GHz is the ability to provide wireless, secure, and uncompressed high-definition video distribution.
Wireless allows the display to be located far from the information source (DVD player, cable box, etc.). This obviates the need for bulky wires from the “picture-frame” display on the wall to the DVD player in the cabinet.
Security is provided at 60-GHz due to the atmospheric and material properties at this frequency. Over long ranges, there is significant signal loss due to oxygen absorption. There is also significant attenuation through walls. These two facts prevent the HDTV signal from leaking into adjacent rooms and residences. This is a definite benefit when it comes to content providers, who desire to limit distribution of the content to whoever paid for it.
Uncompressed signaling retains the image quality on the link, which is of particular concern if “lossy” compression was being considered. Additionally, avoiding compression avoids the need to pay royalties for the compression algorithm.
The data rates for HDMI depend on the resolution of the display and the use of interlacing or progressive scan. For example, 1080i (the “i” stands for interlaced), with a resolution of 1920x1080, and a frame rate of 25 fps, requires ~2.1 Gbps. This can be calculated by multiplying the number of pixels per frame by the frame rate to get the pixel rate. This number is then multiplied by the number of bits per pixel, which we’ll estimate at 40 (Three 10-bit words for the three colors, and one 10-bit word for audio and vertical/horizontal synch. Refer to the HDMI standard for more precise information). Shifting to 1080p progressive-scan doubles the data rate, as the frame rate doubles. A resolution of 720p would require ~1.8Gbps, and yields similar image quality to 1080i.
Point-to-Point 60-GHz Links
Point-to-point links are used today for telecommunications backhauls. They employ high-gain antennas to increase the range of the link. The 60-GHz band is being used in the marketplace today for such links, and the chips are implemented in III-V technologies. Silicon offers the promise to reduce the cost of these systems, though the bulk of the system cost is still installation fees requiring someone to install the equipment on top of a pole, for example.
One drawback of 60-GHz is the oxygen absorption (~10dB/km at sea level) which begins to play a role at ranges greater than 100m. Additionally, rainfall adds additional attenuation (another ~5dB/km for region K at rain rate of 12mm/hr). High-gain antennas certainly help to overcome these atmospheric effects.