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EXISTING SYSTEM

PROPOSED SYSTEM

EXISTING CONCEPT

Rapid growths of wireless communications and conventional fixed spectrum allocation policy have led to the problem of spectrum scarcity. However, according to a survey of spectrum utilization in the licensed spectrum is not used efficiently in both temporal and geographical dimensions. Cognitive radio (CR) which is one of the most promising technologies for the future radio spectrum management, improves spectrum utilization by using these underutilized parts of the spectrum. In CR networks, the secondary users are allowed to communicate, provided that the interferences caused to the primary receivers (PRs) are below a given threshold, called interference temperature limit.

The nonlinear behavior of the PA, leads to spectral regrowth of its output signal, and as a result, the adjacent channel interference (ACI).

PROPOSED CONCEPT

        The ACI power is a nonlinear increasing function of the PA input power. Therefore, for the power allocation in CR networks by noting the interference temperature limits, it is important to consider the PA nonlinear behavior of the CR transmitter and the resulting ACI power.

         The optimal power allocation that minimizes the average bit error rate in a non-CR scenario, subject to the average and peak transmission power constraints, is analyzed in An axiomatic framework for autonomous power control by individual users in CR network is developed in aiming opportunism and admissibility to secondary users, but the transmit power is considered to be unbounded. In and for the linear PA, the optimal power allocation and outage probability in a spectrum sharing scenario are obtained under upper transmit power limit as well as average and peak interference power constraints at each PR.

ALGORITHM / TECHNIQUE DEFINITION

  Fixed spectrum allocation policy.

Ø  The licensed spectrum is not used efficiently in both temporal and geographical dimensions.

ALGORITHM / TECHNIQUE DEFINITION

  Adjacent channel interference.

  Power Allocation with Average ACI Constraints.

DRAWBACKS

The spectrum allocation is low.

Sensitivity to noise

ADVANTAGES

The spectrum allocation is high

  Less sensitivity to noise