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Proportional Fair Power Allocation for Secondary Transmitters in the TV White Space

DOI: 10.1155/2013/272341

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The key bottleneck for secondary spectrum usage is the aggregate interference to the primary system receivers due to simultaneous secondary transmissions. Existing power allocation algorithms for multiple secondary transmitters in the TV white space either fail to protect the TV service in all cases or they allocate extremely low power levels to some of the transmitters. In this paper, we propose a power allocation algorithm that favors equally the secondary transmitters and it is able to protect the TV service in all cases. When the number of secondary transmitters is high, the computational complexity of the proposed algorithm becomes high too. We show how the algorithm could be modified to reduce its computational complexity at the cost of negligible performance loss. The modified algorithm could permit a spectrum allocation database to allocate near optimal transmit power levels to tens of thousands of secondary transmitters in real time. In addition, we describe how the modified algorithm could be applied to allow decentralized power allocation for mobile secondary transmitters. In that case, the proposed algorithm outperforms the existing algorithms because it allows reducing the communication signalling overhead between mobile secondary transmitters and the spectrum allocation database. 1. Introduction The main requirement for secondary spectrum usage is interference control. For single secondary transmitter, the power level maximizing the secondary transmission rate under primary system protection constraints has been derived in [1]. However, the bottleneck for secondary spectrum usage is the aggregate interference to the primary receivers due to simultaneous secondary transmissions. Allocating the power levels to multiple secondary transmitters has already drawn considerable interest for standardization bodies all over the world [2–4] and also for the academic research community. The SE43 working group in the Electronic Communications Committee (ECC) in Europe announced a power allocation rule for secondary operation in the TV white space (TVWS), hereafter referred to as the SE43 rule [2]. Initially, the SE43 rule allocates the maximum permitted transmit power level to each secondary transmitter. For 2–4 simultaneous transmissions the maximum transmit power is divided with the number of active transmitters. In that case, each transmitter generates an equal amount of interference at the TV system. For a larger number of simultaneous transmissions a safety protection margin should be utilized. It has been shown that the existing SE43 rule fails

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