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EXISTING SYSTEM

PROPOSED SYSTEM

EXISTING CONCEPT

Cognitive radio technology has recently emerged as an aspirant solution for the problem of spectrum scarcity.  

Unlike the traditional static command-and-control approach, it provides a more dynamic means for spectrum management and utilization. more specifically, cognitive radio protocols such as those in ieee 802.22 allow the cognitive users, alternatively called secondary users (sus), to dynamically share the underutilized frequency bands with primary users (pus) both in time and space under various forms of primary quality-of-service (qos) protections.

PROPOSED CONCEPT

      It also investigates multiuser diversity gains for the distributed cognitive uplink by deriving tight sum-rate capacity scaling laws under the optimum distributed power control mechanisms.

       In the centralized uplink, the secondary base-station (SBS) is primarily responsible for the power control task. That is, it first acquires global knowledge of direct (from SUs to the SBS) and interference (from SUs to PUs) channel gains via a feedback mechanism, and then exploits this knowledge to obtain the optimum transmission power level for each SU by respecting primary QoS requirements. Finally, the allocated transmission power levels are broadcasted to SUs by the SBS at each fading block.

ALGORITHM / TECHNIQUE

     Centralized band manager or perfect instantaneous CSI feedback between primary and secondary networks.

ALGORITHM / TECHNIQUE

    Optimum Power Control And Throughput Scaling In (DTPIL) Networks

DRAWBACKS

Ø  Performance of the capacity (throughput)         is low.

Ø  Sensitivity to noise.

ADVANTAGES

      Performance of the capacity (throughput)  rate is high

     Noise  is less