WIRELESS UNIVERSAL SERIAL BUS

(WUSB)

ARKAPRAVA SADHU

CONTENTSIntroductionReasons for W-USBFeatures of W-USBTopologyProtocol StackPHY DesignMAC DesignSecurity DesignConclusion

INTRODUCTIONWireless USB is a short-range, high-

bandwidth wireless radio communication protocol.

It is based on the WiMedia Alliance's Ultra-Wide Band (UWB) common radio platform.

W-USB is defined as a bus, albeit logical and not physical, which can simultaneously connect a host with a number of peripherals.

INTRODUCTION

It has the capability of sending frames at 480 Mb/s at distances up to 3 metres and 110 Mb/s at up to 10 metres. 

The host divides the available bandwidth through a time-division multiple access (TDMA) strategy.

REASONS FOR WUSBWired Issues

◦Wires are restrictive◦Multiple Wires can be a hassle◦Wires slower than wireless solutions

Current Wireless Solutions Inadequate◦Bluetooth

Bandwidth of 3 Mbps not enough for higher demand applications (Video, HDTV, Monitor)

◦Wi-Fi Expensive Too much Power usage

FEATURES OF WUSB

Wireless version of USBMaximum speed of 480 MbpsHigh BandwidthLow Power UsageLow CostSmall Physical ImplementationsHigh level of securityBackward compatible with wired USB

devicesInteroperable across Consumer Electronics,

Mobile devices and Personal Computing Platforms.

TOPOLOGYWUSB supports a ‘hub-and-spoke’

topology. The relationships between devices

and host are called as clusters.Connections are point-to-point. WUSB host can connect to a

maximum of 127 wireless USB devices.

High spatial capacityDual Role Model

PROTOCOL STACK

PHY DESIGNThe PHY contains three functional

entities:◦Physical Medium Dependent functionality◦Convergence of radio devices.◦Layer management functionality.

Transmits a waveform from the output of an IFFT function to produce an OFDM symbol.

Coding of inputs to IFFT provides a range of data rates: 53.3, 80, 106.7, 160, 200, 320, 400 and 480 Mb/s.

PHY DESIGNIt operates in the frequency

range of 3.1 to 10.6 GHz.

This range is divided into 14 frequency bands, each 528 MHz wide.

PHY DESIGNThe figure shows a 3 band

hopping channel in Band Group 1.

FRAME STRUCTUREA PPDU consists of: Preamble,

Header and Payload.The Header is sent at a data rate

of 39.4 MbpsThe PSDU is sent at desired data

rate.PLCP

PreamblePLCP

HeaderPSDU Payload

MAC DESIGNDefines the Channel Access Control Also defines data transfer and

system management servicesOther features like:

◦Distributed Reservation Protocol (DRP)◦Prioritized Contention Access (PCA)

Power Saving MechanismsNon secure and secure,

authenticated frame exchange

SECURITY DESIGNSecurity needed due to crowded

environmentsThe payload contains a additional

20 bytes for security: Security header of12 bytes and Message Integrity Code of 8 bytes

Two major process: Association and Encryption

Association process is of two types: Cable model and Numeric model

SECURITY DESIGN

Cable Association Process:

SECURITY DESIGN

Numerical Association Process:

SECURITY DESIGNEncryption:

◦WUSB uses the AES-128 algorithm◦Devices are authorized to communicate

using the connection context◦During each session, the devices derive

‘session key’ (PTK)◦Wimedia devices do not encrypt the

PHY and MAC header information◦This allows devices to identify framing

and routing information for each packet.

FUTURE EXPECTATIONS

Transparency Market Research:

“Driven by the global trend towards the wireless connectivity, WUSB Devices will reach to 11.02 million units in volume sales by 2018”

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