A joint carrier frequency offset (CFO) and channel estimation technique is presented for burst mode OFDM systems. It employs the non-linear recursive least squares (NL-RLS) algorithm working in time domain and in decision directed mode.When compared with other techniques, this approach functions without the aid of pilot tones in the OFDM data symbols, maintains a reasonable complexity, and provides a superior performance, which is shown to be insensitive to decision errors even at low SNR.
-In this paper, we present a joint channel estimation and synchronization technique for burst-mode OFDM systems. The technique uses the non-linear recursive least squares algorithm (NL-RLS) to jointly estimate the channel impulse response (CIR), the carrier frequency offset (CFO), the sampling clock offset (SCO), and the timing offset, and to correct for each of these in the digital domain and without the use of a delay-locked loop (DLL). The need for pilot symbols in the payload data is eliminated by a decision-directed operation mode. The time-domain NL-RLS algorithm needs a small number of parameters to be estimated and can suppress the effect of decision feedback errors.Simulation results confirm its improved performance and relatively low variance.
The popularity of the smartphone and the resulting increase in the volume of wireless data traffic has created a large gap between bandwidth supply and demand. An attractive and less expensive solution to re-farming of spectrum is to maximize the use of under-utilized bands through spectrum sharing. Recent efforts in this area, that propose operation of wireless systems in shared spectrum, address the main challenge of how shared spectrum access systems can efficiently share and utilize spectrum resources. In this paper, we focus on the framework for multi-tier shared spectrum operation in wireless networks, where multiple entities -the Shared Spectrum Managers (SSMs) -dynamically acquire, manage and sell shared spectrum. We derive an auction based spectrum resource assignment algorithm which maximizes the overall system efficiency and provides incentives to the incumbents to make spectrum available for sharing. We demonstrate that the algorithm can be implemented in practice through messaging in which the SSM dynamically negotiates spectrum bidding and asking prices with the shared spectrum users. Simulations are performed under different scenarios and assumptions both to verify that the algorithm achieves the maximum utility value for shared spectrum systems, and to compare the outcome behavior under each scenario. Based on the observations, potential regulations that would need to be put in place in each scenario are discussed, and a set of future development areas are identified based on these observations.
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