Ben J. Wild

Detecting primary receivers for cognitive radio applications

In this paper we develop a framework for competition of future operators likely to operate in a mixed commons/property-rights regime under the regulation of a spectrum policy server (SPS). The operators dynamically compete for customers as well as portions of available spectrum. The operators are charged by the SPS for the amount of bandwidth they use in their services. Through demand responsive pricing, the operators try to come up with convincing service offers for the customers, while trying to maximize their profits. We first consider a single-user system as an illustrative example. We formulate the competition between the operators as a non-cooperative game and propose an SPS-based iterative bidding scheme that results in Nash equilibrium of the game. Numerical results suggest that, competition increases the users (customers) acceptance probability of the offered service, while reducing the profits achieved by the operators. It is also observed that as the cost of unit bandwidth increases relative to the cost of unit infrastructure (fixed cost), the operator with superior technology (higher fixed cost) becomes more competitive. We then extend the framework to a multiuser setting where the operators are competing for a number of users at once. We propose an SPS-based bandwidth allocation scheme in which the SPS optimally allocates bandwidth portions for each user-operator session to maximize its overall expected revenue resulting from the operator payments. Comparison of the performance of this scheme to one in which the bandwidth is equally shared between the user-operator pairs reveals that such an SPS-based scheme improves the user acceptance probabilities and the bandwidth utilization in multiuser systems

A Multi-Antenna Framework for Spectrum Reuse Based on Primary-Secondary Cooperation

This paper proposes a new framework for spectrum reuse. Existing architectures have centered on secondary users (cognitive radios) that can reliably sense primary users and opportunistically transmit, without directly interacting with the primary system. We present a paradigm in which the primary and secondary systems cooperate, to minimize interference to primary users and provide predictable access for secondary users. Because this architecture gives the primary system full control over spectrum sharing, it could be more favorable in the current economic and political environment. We illustrate a concrete instance of our framework by showing how secondary radios can reuse the entire uplink channel of a cellular network, with only modest changes to the primary infrastructure.

Layout decompression chip for maskless lithography

Future maskless lithography systems require data throughputs of the order of tens of terabits per second in order to have comparable performance to today’s mask-based lithography systems. This work presents an approach to overcome the throughput problem by compressing the layout data and decompressing it on the chip that interfaces to the writers. To achieve the required throughput, many decompression paths have to operate in parallel. The concept is demonstrated by designing an interface chip for layout decompression, consisting of a Huffman decoder and a Lempel-Ziv systolic decompressor. The 5.5mm x 2.5mm prototype chip, implemented in a 0.18μm, 1.8V CMOS process is fully functional at 100MHz dissipating 30mW per decompression row. By scaling the chip size up and implementing it in a 65nm technology, the decompressed data throughput required for writing 60 wafers per hour in 45nm technology is feasible.