Wireless Universal Serial Bus
Christopher Hanudel
Outline
Wired Universal Serial Bus (USB) Overview of Wireless USB (wUSB)
History/Vision Features
How wUSB Works
Design Security
Issues/Limitations Current Implementations Future/Conclusion
Wired USB
Overview
Plug/Play standard for peripheral devices Standardized by the USB Implementers Forum Host/Slave Connection
Technical Details
PC (host) manages all transfers; peripherals (slave) just responds Supports 127 slaves per host Four wire connection
Physical Connection
Two wires for power (+5 and GND) Two wires (twisted pair) for synchronous serial data
Computer supplies power (up to 500 mA)
Wired USB
Technical Details (Cont.)
Data Rates
Low Speed: 1.5 Mbps (Keyboards, mice, etc.) Full Speed: 12 Mbps (USB1.1 max speed) Hi-Speed: 480 Mbps (USB2.0 max speed)
Reasons For Wireless USB
Wired 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) Expensive Too much power usage for mobile devices
WiFi
Data Rate Comparisons
Wireless USB Overview
Overview
Has evolved as companies figured out standards Based on Ultra-Wideband (UWB) RF technology UWB is a technology for transmitting data over a large bandwidth (>500 MHz)
History of Ultra-Wideband (UWB)
Late 1800s: Started with Spark Gap radio for transmitting Morse Code 1924: Spark Gap forbidden due to disruptive nature to narrowband carrier radios 1960s 1999s: Better test equipment promoted research of UWB for radar and communications
Wireless USB Overview
History of Ultra-Wideband (cont.)
April 2002: FCC issued UWB Regulations 2002: Two standards emerge
Permitted marketing and operation of new products Limited power and freq range
Orthogonal Frequency Division Multiplexing (OFDM) UWB
Direct Sequence (DS) UWB
WiMedia Alliance & Intel UWB Forum & Freescale
2006: DS-UWB loses support & OFDM-UWB wins
2007: Products begin to hit the market
Freescale left UWB Forum; became quiet Many companies dropped Freescale chips Freescale trying proprietary Cable-Free USB
Wireless USB Overview
Goals of Intel OFDM-UWB Wireless USB Standard
Wireless version of USB; same features, speeds Interoperable across three major platforms
High bandwidth to support demanding data transfer (High Definition, Monitors) Mobile friendly
Consumer Electronic devices (digital video/audio) Mobile devices (cellular phones, PDA) Personal Computing (laptop, PC, printer, peripherals)
High level of security Next gen Wireless Personal Area Network (WPAN)
Low power usage Inexpensive costs Small physical implementation
Wireless USB Vision
Wireless USB Vision
Wireless USB Physical Design
Features of UWB
Speed/Range
Scaleable speeds up over 1 Gbps Currently 480 Mbps at 3 m; 110 Mbps at 10 m Divided into 14 bands; 5 groups
Frequency: 3.1 GHz to 10.6 GHz
Each band is 528 MHz wide OFDM symbols are interleaved across all bands Provides protection against multi-path / interference
Wireless USB Physical Design
Features of UWB (cont.)
Frequency: 3.1 GHz to 10.6 GHz (cont.)
Band Groups 1 & 2: Longer range apps Bands Groups 3 & 4: Shorter range apps Bands can be turned off to accommodate for conflicts or for regulations
Wireless USB Physical Design
Features of UWB (cont.)
Power
Power is limited due to usage of wide spectrum Low power for mobile devices and minimum interference Max output to -41.3 dBm/MHz
Wireless USB Security Design
Overview
Strongly stressed in wUSB specification and outlined in its own requirements document Security needed due to crowded environments Two major components: Association and Encryption Overview
Association
Device must first associate with the host in a one-time event Accomplished via wired verification or numeric association
Wireless USB Security Design
Association (cont.)
Wired Verification
Cable is attached between devices Exchanges a unique 384-bit identifier known as the connection context Devices associate wirelessly User must enter a hex code manually
Numeric Association
Wireless USB Security Design
Encryption
Data encrypted with the AES 128 algorithm During each session devices derive a session key based on connection context Wireless data is encrypted using session key Does not encrypt PHY and MAC headers
Wireless USB Connection Design
Host/Slave Connection
Similar to wired USB (127 devices; host is PC) Each host forms a cluster Clusters can coexist with minimum interference
Power Management
Sleep/Listen/Wake used to conserve power Tx/Rx power management
Wireless USB Issues/Problems
Interference Issues
Potential conflict to devices on same frequencies Detect and Avoid
Wisairs solution to detect other frequencies Switches to frequencies not being used
Conflict issues are more of a concern for wireless USB devices being overpowered Cable-Free USB (Freescale) USB-Implementers Forum (Intel, HP, Microsoft)
Competing Standards
Product Comparison
Wireless USB Implementations
Belkin Cable Free Hub
Released Dec, 2006 Dongle attaches to PC Retail price of $199.00 Speeds up to 480 Mbps
Wireless USB Implementations
GeFen HMDI Extender
Coming soon Based on WiMedia Alliance specification Retail price of $699.00 Range of 20 meters; data rates up to 480 Mbps Frequency band: 3.1 - 4.8 GHz Resolution support : 480i, 480p, 720p, and 1080i
Wireless USB Implementations
Seagate Wireless USB Hard Drive
Coming soon 2.5 inches wide Speeds up to 480 Mbps
Future of Wireless USB
Early 2007
Initial devices being produced Expect wUSB being built into laptops, PCs, multimedia devices Visiongain research firm predicts increase of wUSB by 400 percent
Late 2007
2008
2009-2010
Wide scale interoperability?
Concluding Thoughts
Appears well designed; good support Slow start of products
Will it really catch on? More products need to be developed
Promises a lot; will it deliver? Security is very important
Questions?
