Smart-Radio-Enabled Opportunistic Spectrum Utilization Xin Liu Computer Science Dept. University of California, Davis Netlabs Workshop, Davis, 2005

Netlabs Workshop 2005 Spectrum, Spectrum Spectrum is expensive and heavily regulated 3G spectrum auction in EU $35 billion in England, $46 billion in Germany Q: Is spectrum really that scarce and expensive?

Netlabs Workshop 2005 Spectrum Allocation

Netlabs Workshop 2005 Spectrum Occupancy Is Low Shared Spectrum’s measurements indicate low occupancy bands high occupancy bands Under 3GHz, over 62% of white space White space: more than 1MHz wide 10 minutes long FCC Spectrum Policy Task Force Report The limiting factor: spectrum access instead of physical scarcity of spectrum Due to legacy command-and-control regulation More flexible regulations needed

Netlabs Workshop 2005 Smart-Radio Technology The ability to Active negotiation/communication Passive sensing and decision making Adapt its transmission parameters Known as Software-defined radio, cognitive radio, programmable wireless, spectrum agile radio, brainy radio, etc.

Netlabs Workshop 2005 Spectrum Access Secondary market Interruptible leasing Real-time auction Non-interference based access Open access Non-interference based access Under-lay Spectrum access methods Listen-Before Talk Probe Geo-location/database

Netlabs Workshop 2005 Objectives Understand the impact and the properties of the white space Inherent properties How to capture it Share the white space dynamically and efficiently Develop algorithms and protocols

Netlabs Workshop 2005 Impact of White Space Understand the impact of opportunistic spectrum availability on secondary users. Performance metric: effective non- opportunistic bandwidth, temporal metric, fairness metric Impact of availability pattern & network topology Modeling

Netlabs Workshop 2005 System Model Objective: to capture both temporal and spatial correlation Prelim. model: Primary users (I,II,III,IV) Secondary users (1-5)

Netlabs Workshop 2005 Sensing-based Access Probe a channel (collaboratively) and decide whether or not to transmit Challenges: Capacity-interference tradeoff between primaries and secondaries Dynamic channel characteristics Sensing fidelity and collaborative sensing Cumulative interference of multiple secondary users Can compliment other approaches

Netlabs Workshop 2005 EscapeMAC Objective: to evacuate the channel when primary users come back Challenges: Low interference to primary users Maintain connectivity among secondary users Alarm other secondary users Approaches: Embedded signaling channel Hybrid ARQ

Netlabs Workshop 2005 Where do We Stand? History: a successful story, a $$$$$$ industry Current Rapid proliferation Policy evolution Future: More spectrum Advanced DSP and radio technologies Cool applications

Netlabs Workshop 2005