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The conventional polyphase architecture for linear-phase finite impulse response (FIR) filter loses its coefficient symmetry property due to the inefficient arrangement of the filter coefficients among its subfilters. Although, existing polyphase structures can avail the benefits of coefficient symmetry property, at the cost of versatility and complex subfilters arrangement of the conventional polyphase structure. To address these issues, in this paper, we first present the mathematical expressions for inherent characteristics of the conventional polyphase structure. Thereafter, we use these expressions to develop a generalized mathematical framework which exploits coefficient symmetry by retaining the direct use of conventional FIR filter coefficients. Further, the transfer function expressions for the proposed Type-1/ transposed Type-1 polyphase structures using coefficient symmetry are derived. The proposed structures can reduce the requirement of multiplier units in polyphase FIR filters by half. We also demonstrate the decimator design using the proposed Type-1 polyphase structure and the interpolator design using the proposed transposed Type-1 polyphase structure. Moreover, the phase and magnitude characteristics of the proposed Type-1/transposed Type-1 polyphase structures are presented. It is revealed via numerical examples that all subfilters of the proposed symmetric polyphase structure possess linear-phase characteristics. INDEX TERMS Coefficient symmetry, frequency response, polyphase FIR structures, pre/post processing, sampling rate conversion.

This paper investigates the joint impact of nodes' mobility and imperfect channel estimates on the secrecy performance of an underlay cognitive radio vehicular network over Nakagami-m fading channels. Specifically, the secondary network consists of a single-antenna source vehicle, an ND-antenna destination vehicle, and an NE-antenna passive eavesdropper vehicle, whereas the primary network comprises of a singleantenna primary receiver vehicle. The time selective fading links arise due to nodes' mobility are modeled via first-order autoregressive process, and the channel state information is estimated using linear minimum mean square error estimation method. Moreover, the transmit power of secondary source is constrained by both the interference threshold of the primary receiver and the maximum transmit power of secondary network. Under such a realistic scenario, we derive the analytical closed-form secrecy outage probability (SOP) and ergodic secrecy capacity expressions. Furthermore, we present asymptotic SOP analysis to obtain key insights into the system's secrecy diversity order. We also report several practical cases of interest to reveal valuable information about the system's secrecy behavior. Moreover, we illustrate the impacts of system/channel parameters, nodes' mobility, imperfect channel estimates, interference temperature limit, and the maximum available source power. Finally, the simulation studies corroborate our derived analytical findings.

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