Flexible Spectrum and Power Allocation for OFDM Unlicensed Wireless Systems

Future generations of communication systems will benefit from cognitive radio technology, which significantly improves the efficient usage of the finite radio spectrum resource. In this paper we present a wireless unlicensed system that successfully coexists with the licensed systems in the same spe...

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Bibliographic Details
Published in:IEEE systems journal 2009-06, Vol.3 (2), p.254-264
Main Authors: Lacatus, C., Akopian, D., Yaddanapudi, P., Shadaram, M.
Format: Article
Language:English
Subjects:
Aggregates
Algorithms
Allocations
Cognitive radio
Constraint optimization
distributed algorithms
Dynamical systems
Dynamics
Frequency division multiplexing
Game theory
Interference
Licenses
Noise
OFDM modulation
Optimization
Orthogonal Frequency Division Multiplexing
Quality of service
Radio
Receivers
Resource management
spectrum sharing
Studies
Switches
System performance
unlicensed systems
Wireless networks
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Summary:Future generations of communication systems will benefit from cognitive radio technology, which significantly improves the efficient usage of the finite radio spectrum resource. In this paper we present a wireless unlicensed system that successfully coexists with the licensed systems in the same spectrum range. The proposed unlicensed system determines the level of signals and noise in each frequency band and properly adjusts the spectrum and power allocations subject to rate constraints. It employs orthogonal frequency-division multiplexing (OFDM) modulation and distributes each transmitted bit energy over all the bands using a novel concept of bit spectrum patterns. A distributed optimization problem is formulated as a dynamic selection of spectrum patterns and power allocations that are better suited to the available spectrum range without degrading the licensed system performance. Bit spectrum patterns are designed based on a normalized gradient approach and the transmission powers are minimized for a predefined quality of service (QoS). At the optimal equilibrium point, the receiver that employs a conventional correlation operation with the replica of the transmitted signal will have the same efficiency as the minimum mean-squared error (MMSE) receiver in the presence of noise and licensed systems. Additionally, the proposed approach maximizes the unlicensed system capacity for the optimal spectrum and power allocations. The performance of the proposed algorithm is verified through simulations.
ISSN:1932-8184
1937-9234
DOI:10.1109/JSYST.2009.2017391