by R. K. Bloom

Wireless USB. Part 2

Wireless USB. Part 2

After writing the first introduction of a new wireless protocol Wireless

USB at the end of March 2005 the problem of surface

(User level) retelling of the opportunities and prospects for the use of technology as a whole seemed to me made. And indeed, the final specifications of the standard at that time was not yet, so that a detailed statement of the details for the “advanced” readers could especially not in a hurry.

The reality was much quicker my leisurely research WUSB.

In March 2005, there were two key events on the fate of the new standard: adopted draft specifications Wireless USB version 0.95, plus about the same time, the two main developer of technology alliances WiMedia Alliance and the MBOA-SIG announced the elimination of contradictions, and joint efforts in further developing WUSB .

After that, things were more than fast: in late May

  1. Online Wireless USB Developers Conference was declared the final version of Wireless USB 1.0, which finally eliminated the possibility of different interpretations of “raw” WUSB specifications and brought to the discharge ratified, “ready to eat” on a commercial scale standards. And I finally had the opportunity to
  2. finish the story without any dots.

So, today, along with the basic provisions of the specifications, Wireless USB 1.0, in

This material will be applied are set out prospects of implementing the standard. Having dealt

with the physics of the process and forms of implementation of Wireless USB, we will just have to wait

appearance of the first units of the new standard in the stores.

In addition, I would like to emphasize that, as part of this material is analyzed

only the basic principles of the technology and the basis of the implementation specifications, and on

business, like any industry-standard, Wireless USB 1.0 describes the set of

documents, normalizing all conceivable options, including passion,

as humidity and atmospheric pressure. In fact, quite the standard requirements

and made it hard to achieve full interoperability of numerous articles

companies, which, of course, with time to “stake out” a portion of a

this promising market.

In this study, the fundamental documents of the standard will be considered

all key aspects of the formation and transmission, and a little touch on the implementation of Wireless USB 1.0 in practice.

The mission of Wireless USB

List of wireless interfaces, performance, and very different purpose

are now so wide that one might legitimately ask: what

There have Wireless USB, which range in its “push” and

Does he need a really, whether it is a whim of producers?

In fact, a careful study of the capabilities of modern wireless

Technology you can see a decent gap: interfaces a lot, but there is no one

that would be “locked” specifically for the exchange of powerful streams of multimedia

content to close the distance, that is, something like a wired USB and FireWire.

Technologies such as Bluetooth (even in the most advanced version 2.0 with a maximum

bandwidth to 2.1 Mbit / s) and Zigbee can deal only with the transfer of stereo

headphones, neither of which share the video out of the question.

On the other hand, there is a pool of more productive interface Wi-Fi, capable of

ensure that traffic is already up to 54 Mbit / s, and in the future – up to 100 Mbit / s.

But here is not without flaws: the interfaces are still in the first “medium-”

and are aimed primarily at a distance of 100 meters. Of course, no one

prevent the use of them at close range 3 – 10 meters, however,

enters into force on another problem: the limited number of channels in conjunction

with a decent radius of action, sooner or later will have an effect, especially in

metropolitan areas. In addition, even the peak traffic 100 Mbit / s, which in the future promises

version of IEEE802.11n, can not be considered an adequate alternative to the current 480

Mbit / s with a wired USB 2.0.

Speculate about the possibility of alternatives in the form of trunk and “long range”

standards such as 3G/4G and WiMAX, and do something inappropriate in the first case because

that the cellular network is still not free, the second – the same as roast

eggs flamethrower, and in both cases is ridiculous to talk about the distances of 10 meters.

In other words, something like Wireless USB, sooner or later had to occur.

The next legitimate question: how to host a new and, judging by the performance

sufficient broadband interface, if the frequency bands, and now without it

over loaded? The only reasonable way – using svershirokopolosnoy

modulation (UWB, UltraWideBand) with a low spectral density of the signal. In other

words, the signal is a kind of “smeared” as a kind of white

noise on a wide range of frequencies. Using dedicated to UWB in the secondary

the basis of the frequency spectrum does not actually affect the performance of other funds

connection, since the peak level of radiation practically does not exceed that of the air

the noise level.

As shown in the slide above the recommended FCC (Federal Communications Commission Telecommunications USA) spectral density shall not exceed a certain level of -41.3 dBm / MHz.

For other countries this figure may vary slightly, although it can be

suggest that, ultimately, recommendations FCC will still standartoobrazuyuschimi.

The following is a comparative graph of the spectral density of the radiation limits

for some fairly common devices and interfaces.

Now its time to go into the details of the implementation of the basic foundations of Wireless

USB – Use of frequency bands, the physical PHY (Physical layer protocol)

and MAC (Media Access Control) level interface, its topology, on Software

and hardware support etc.

Topology of the Wireless USB

By analogy with wired USB, Wireless USB devices have their own address

received when connecting or credit. Each device Wireless USB

supports one or more channels for communication with the host.

Each device Wireless USB can operate as a MAC Layer device. Standard

  1. Wireless USB devices, describes the three categories, representing different degrees of
  2. implementation of the mechanism of MAC Layer, from avtosignalnogo “(self beaconing) type

to the complete lack of supporting it.

The basic elements of infrastructure are the WUSB Hub and radial

line. In this topology, the host controller initiates all communication between the

devices connected to it by allocating time slots and bandwidth

each connected device. This group is called a cluster. Described

compounds belong to the type of “point-point” and are carried out between WUSB-host

and WUSB-device.

WUSB-host with logically connected to it WUSB-devices (maximum -

127) forms an informal WUSB-cluster. Incidentally, the hubs in the definition

Wireless USB not as a class because of their complete lack of demand in the

this architecture. WUSB-clusters coexist in overlapping spatial

environment with minimal mutual interference, which allows to operate multiple

WUSB-clusters within the general area of ??the radio-emitting devices.

Describing the topology of the model will support dual-use, in which

the device can act as a limited host. Such a model

enables mobile devices to use the service, which provides

a central host (such as printers and display devices). In addition,

This model will allow the device to access data located outside the

cluster, which is currently connected to the device. For this device

should create a second cluster, acting as a host with disabilities.

As Wireless USB is backwards compatible with the wired version of USB, also appears

the ability to create transparent bridges to wired USB devices and host controllers,

that is, to organize the transfer of data between two clusters. The dual model

the use of Wireless USB, where the slave-device also has a limited

features a host controller, virtually on the run takes into account shortcomings of early

versions of wired USB, only resolved with the appearance of an additional protocol

USB 2.0 – USB-On-The-Go.

The final version features a host controller and client-side fine

illustrated slide listed below: