NEC Looks at the Future of Certified Wireless USB

Certified Wireless USB is out the door, at least for the specifications and reference design. But there are perceptions that the new standard is just a cable-free version of USB. NEC Senior Engineering Manager Masami Katagiri discussed in this article that Certified Wireless USB can create new product categories that aren't feasible with USB 2.0. In addition, he also talked about how getting rid of mini-B connector can also make the device sleeker. Of course, you would need an electromagnetic system to recharge the built-in battery. Read on to find out more the new possibilities.

The USB 2.0 standard was developed to fill market demands for high-speed, high-bandwidth applications, particularly in the networking and storage area. The first key area for USB was the PC peripheral market, starting with host and hub solutions, and moving on to keyboards, mouse devices and video products such as USB video capture and TV tuner devices. Additional products, including modem, Ethernet equipment and speakers, helped to round out the USB market, although they did not constitute a significant market segment.

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Includes:
USB-IF Chairman's WUSB Overview
John Koon's WUSB Retail Analysis
NXP's View on Future of WUSB
NEC's Look at WUSB Opportunities
Lecroy's Guide to Certified WUSB Testing

Wireless USB
Developed by the Wireless USB Promoter Group, Certified Wireless USB, or Wireless USB (Wireless USB), is one of the leading UWB technology protocols. One key advantage of this technology is its compatibility with current USB 2.0 devices. There already is widespread adoption of USB technology in peripheral devices, so implementing Wireless USB as the wireless version of those current devices is a good starting point, as this transition doesn't require a drastic change to the existing device. Instead, wireless technology can be added through the use of a device wire adapter (DWA) such as NEC Electronics' µPD720180 device, the industry's first dedicated DWA controller.

The DWA is a hub device with wireless capability on its upstream port and USB 2.0 capability on the downstream port. By cutting two USB interface signals to the USB "B" connector, and placing and connecting the DWA chip on the board, designers can use the DWA to bridge the Wireless USB and USB 2.0 protocols. Using the DWA in the system eliminates the need for changes in USB 2.0 hardware, firmware or even drivers. The devices can be used "as is," facilitating a smooth transition from wired to wireless. This easy transition opens the door for the development of USB devices and usage models for cable replacement, wireless PC docking, multiple host sharing, and wireless-to-wireless and wireless-only, each with their own design challenges (Figure 1).

Cable Replacement for Hubs
Except for the wireless upstream port, the wireless hub is very similar to the USB 2.0 hub, featuring nearly identical usage models and sharing the same device hardware, firmware and drivers. The wireless hub is an ideal solution when there are multiple USB devices in a room and they are all connected to the USB 2.0 hub. By replacing the existing USB 2.0 hub, users can go completely wireless. In addition, as with current USB hubs, multiple Certified Wireless hubs can be used to connect one wireless host. (Figure 2).

Cable Replacement for Mass Storage Devices
Mass storage devices, including hard disk drives (HDDs) and flash drives, also are ideal for use with Wireless USB. Hard disk sizes and power consumption are both shrinking, while flash drive capacities are increasing, putting pressure on HDDs in the memory card area. While HDDs will have both wired and wireless methods of communicating with PCs, their key value in this market will be true mobility.

Cable Replacement for Network Adapters
Internet connection speeds are now matching genuine Ethernet speeds of five years ago. WiFi has been a key driver in increasing Internet usage worldwide, but only recently have Internet connection speeds caught up with the speed of WiFi. Today, Internet connection speeds actually are going beyond WiFi in some parts of the world. While IEEE is being challenged to implement 802.11n, with its expected throughput of 100 Mbps, Wireless USB defines connection speeds of 480 Mbps and has an expected throughput of 300 Mbps, much faster than any Internet connection service available for end users. Wireless gigabit Ethernet adapters also should emerge as a ground-breaking product of the future.

Cable Replacement for Digital Still Cameras
A recent trend for digital still cameras (DSCs) is wireless transfer. Some DSC vendors already have equipped cameras with a WiFi interface; however, managing the TCP/IP setting is still a challenge for consumers. Switching from WiFi to Wireless USB simplifies the setup process significantly, without changing the usage model or compromising picture file transfer speeds, and is completed in a matter of seconds. By using an electromagnetic system instead of a docking station to charge the camera battery, DSC users are able to go completely wireless for true mobility.

New Usage Models
Wireless PC Docking Stations A new approach to building a PC docking station is to combine all of the required USB interface cables (PS/2, LAN, memory card slot, parallel, serial, and so forth) in a wireless hub. A video graphics array (VGA) cable still would be required, but by integrating a USB 2.0-to-VGA interface cable into the wireless hub, users can create the perfect wireless PC docking station (Figure 3).

Sharing the Device Among Multiple Hosts
Another good candidate for Wireless USB devices is the printer. The challenge is that wireless printers are already used or shared among multiple users, and those users expect that Wireless USB printers can be shared as well. However, since Wireless USB shares the same topology as USB, it's strictly a one-to-one connection from host to device, and there is no notion of "sharing." This can be a big problem, but one that can be resolved by following the standard.

Wireless USB defines the association process, which is required for secure communication between the host and device. After the association process, a connection context (CC) is exchanged and stored on each side - in the printer as well as the host. If there are multiple hosts and this association process is repeated, the device will usually overwrite the CC so that only one CC remains, because the standard only allows the device to have one active CC at any given moment.

However, it is also true that the standard doesn't inhibit the device from having multiple CCs for multiple hosts, as long as there is only one active CC per device. If there are multiple hosts that want to communicate with the device, the device must select the appropriate CC. This switching mechanism is implementation-dependent and a good point of differentiation.

Wireless to Wireless
This approach features devices that transfer data from wireless to wireless, such as wireless TV tuners and wireless WiFi adapters. Given today's digital broadcasting environment, the digital tuner adapter will soon be required to support digital cables and satellites. Unlike terrestrial broadcasting, cable and satellite feeds require in-house installation to change the point of reception. Using a wireless tuner allows users to change viewing locations without requiring a new feed to be installed. This can be achieved with WiFi technology as well. However, Wireless USB supports greater bandwidth and better quality of service (QoS) systems.

Wireless USB WiFi adapters are another wireless-to-wireless option. The term may sound a little strange - if you have WiFi in the laptop PC, you don't need Wireless USB. However, WiFi reception is sensitive to the reception point, so to ensure the best use, the receiver must be mobile in the room. A WiFi-to- WiFi bridge is available, but it cannot achieve the full bandwidth. For Wireless USB technology, the data connection speed at the maximum distance of 10 meters is 110 Mbps, which goes beyond the best speed of most of the current WiFi adapters.

Wireless Video & Audio Devices
Digital video is one type of application that is well suited for the transition to a wireless-only device, particularly for features that do not need cables, like a Wireless USB speaker. For example, satellite speakers are usually several meters away from the host. Wired speakers are connected with speaker cords that are often hidden on the floor or underneath the carpet. With wireless speakers, the main concern is the AC power source, which is usually on a nearby wall, so there are no worries about accidentally kicking the codes.

Other targeted wireless-only devices include applications that do not have the space for a B or mini-B connector. One example is the extremely portable hard drive with battery, where the device's small size, light weight and large capacity make it difficult to include a B or mini-B connector. This type of hard drive is very popular because it allows users to upload or download the data to and from the host without removing the device from the pocket or the bag. Another example is the sleek digital camera, which does not have enough thickness to have a mini-B.

Wireless Docks
There is also the possibility of a "docking station" for the digital camera and portable music and/or video player. This would feature a data connection to the PC and charging capability without exception. The data connection portion can be achieved through Wireless USB technology to make the docking station location-free as long as an AC outlet is nearby. By combining this with an electromagnetic energy propagation device to charge the device, users can make the docking station truly "connector free."

Wireless Gigabit Ethernet
Aggressive UWB PHY vendors have already started talking about the demands for higher bit rates, and some say the speed may reach the gigabits per second (Gbps) order in a few years. This would create a number of exciting new opportunities in the device area, such as a very fast interface like Gigabit Ethernet (GbE), which supports data transfer rates up to 1 Gbps. Speed has been the main stumbling block for widespread adoption of this technology. However, with a Wireless USB + PHY enhancement, designers will be able to resolve that issue, paving the way for native GbE speeds to be carried out on wireless.

Express Card and Monitor Cable Replacements
If the demand goes beyond 1 Gbps, some other very unusual devices will come onto the scene, such as the Express Card wireless extension interface chip, which features PCI Express and a Wireless USB interface on-chip. This enables most PCI Express device to go wireless without sacrificing speed or performance. Looking further out, we may see wireless video cable that delivers a raw video data stream to the PC display, big-screen TV and ultra-portable remote display with keyboard/mouse or tablet for desktop PC - with no compression required.

Conclusion
There is a perception that Wireless USB is just a cable-free version of USB. However, as has been discussed, Wireless USB technology can be implemented to develop a range of devices, from cable-replacement products to wireless-towireless devices to wireless-only devices. With the significant benefits of wireless technology, Wireless USB promises a new generation of variety and convenience for the USB world. And with the advancements in wireless technology and the increasing consumer demand for smaller, lighter devices, Wireless USB has the potential to offer true mobility for consumers.