Wireless USB

Certified Wireless USB, short CWUSB, is a radio-based extension of the universal serial bus standards and to ensure the safety and speed of wired transmission combined with the ease of wireless transmission.

CWUSB defined by the USB Implementers Forum. In parallel, there is a specification to WUSB of Cypress Semiconductors, which has nothing to do with the officially supported by the USB organization version.

Properties

CWUSB based on UWB (OFDM ) technology (see ECMA 368 ), which is defined by the WiMedia Alliance. The options provide transfer rates up to 480 Mbit / s. At a distance up to 3 meters, this corresponds to the data transfer rate of USB 2.0 At 10 meters, the maximum transfer rate is 110 Mbit / s

Transmission is done in the frequency range 3168-10560 MHz, which is divided into 14 bands with a bandwidth of 528 MHz. These bands are grouped into 5 band groups. The band groups 1 to 4 are 3 bands wide (Band Group 1: Volume 1 2 3 = 3168-4752 MHz band ... Group 4: Volume 10 11 12 = 7920-9504 MHz) band group 5, only 2 bands wide (Band group 5: Volume 13 14 = 9504-10560 MHz). The first devices are expected in the band group 1, wherein the frequency range is not currently enabled for this technology worldwide. In the EU, however, released 6000-8500 MHz for this technology from 2010, only the range of frequencies decision of the European Commission, which corresponds to the band group 3 ( Volume 7 8 9 = 6336-7920 MHz). In Germany this was done on 16 January 2008. At CeBIT 2008, first WUSB devices have been introduced by some manufacturers.

In a new revision, it is a band group 6 ( Volume 9 10 11 = 7392 ... 8976 MHz ) indicate that in the range of the band groups 3 and 4. These tapes are available worldwide without any restrictions. Mobile phones are likely to use the band group 3 or 6, as in the band group 1 caused mutual interference with UMTS / GSM / BT. In order for these devices would be incompatible with the first units shipped, the only support band group 1.

Roll

In CWUSB there is, as in USB also, a host that can handle up to 127 devices. The host determines at any time when a single device is allowed to send something. The host it uses the functions provided by a device available, for example, provides a mass storage device (MSC ) the host functions for read and write access to a memory.

CWUSB a device may be a simple device, a host, or a so-called dual- role device. A Dual Role Device can assume both the role of a host as well as a device.

Topology

The connection between the host and the terminal is a point-to- point connection. A network of a host and the connected devices are called clusters. Devices can only exchange data with the host, but not directly with other devices in the cluster.

Security

Before the first connecting a terminal to a host, the connection must be allowed and authorized. There are two methods:

• In association with user control, a common key is agreed without sending himself through the medium by means of a four-way handshake. For this, the host sends a random number H to the terminal, this responds with a random number D. Now, a common key is calculated with the aid of a CBC-MAC - way function of H, D, and the terminal addresses. Since this method is vulnerable to man-in -the -middle attack, the user must click the host display and the terminal display to verify that the numbers shown are the same. If this is the case, and the user confirms this, the compound is regarded as safe and can be used.
• In the out-of -band association by means of a wired USB connection, the wireless connection is authorized by some data is transferred ( Encryption Key, device identifier, host identifiers, Friendly Names, supported UWB bands, etc.). When CWUSB connection, no more entries are more then necessary. Alternatively, the key can also be displayed or printed at the terminal and are entered by the user on the host.

Authentication is required only once. When creating a connection, the data is always encrypted (AES -128 -CCM encryption), if the host has assigned to the USB terminal an address.

Migration of USB devices after CWUSB

Normal USB devices can be easily ported to the CWUSB technology by USB devices are connected to a Device Wire Adapter ( DWA) and a USB host to a host wire adapter ( HWA ). The USB device detects the PSA as a USB host and the host provides for the HWA as a terminal. One or more DWA are connected wirelessly to an HWA on CWUSB. Wired Adapter (WA) thus serve as a bridge between the wireless and wired technology.