Overcoming the Sensing-Throughput Tradeoff in Cognitive Radio Networks ICC 2010

Outline Introduction Novel cognitive radio system Throughput of the novel cognitive radio system under the energy detection scheme Simulation results Conclusions 2

Introduction Cognitive radio network that employs opportunistic spectrum access. In order to efficiently exploit the unused spectrum and effectively protect the quality of service of licensed networks. For this reason, a time slot has been allocated for spectrum sensing at the beginning of each frame in the systems proposed so far. During this slot, data transmission is prohibited, which results in the sensing throughput tradeoff problem. 3

Introduction(cont.) Propose a novel cognitive radio system that overcomes the sensing-throughput tradeoff by performing spectrum sensing and data transmission at the same time. Introduce a novel receiver and frame structure for cognitive radio and analytically prove that the proposed cognitive radio system exhibits improved throughput and sensing capabilities Maximizes both the sensing time and the throughput of the cognitive radio network. 4

Novel cognitive radio system Proposed cognitive radio system The secondary receiver decodes the signal from the secondary transmitter, strips it away from the received signal and uses the remaining signal for spectrum sensing. Novel cognitive radio receiver 5

Novel frame structure for cognitive radio Conventional frame structure Novel frame structure for cognitive radio 6

Opportunistic spectrum access scheme The throughput correctly detected to be idle throughput and the throughput of the cognitive radio network in this case is denoted by R 0 The throughput falsely detected to be idle : R 1 Average achievable throughput 7

Throughput of the novel cognitive radio system P (H 0 ) and P (H 1 ) denote the probability that the frequency band is idle and active respectively. The average throughput of the novel cognitive radio system. 8

Throughput of the novel cognitive radio system(cont.) Throughput is higher compared to the system that employs the conventional frame structure. 9

Energy detection scheme The energy detection is chosen here as a method of spectrum sensing The energy detection scheme is the most popular spectrum sensing technique in cognitive radio, because it exhibits low complexity, it is robust to unknown dispersed channels, fading and variation of the primary signal, and additionally it does not require any a priori knowledge of the primary signal under detection. 10

Energy detection scheme(cont.) The sensing time under the novel frame structure is equal to the frame duration T, Since the probability of false alarm is a decreasing function of the sensing time. < Finally, 11

Simulation Results Frame duration T is set to T = 100ms The probability that the frequency band is active is P(H 1 ) = 0.2 SNR from the secondary transmitter is SNR s = 20 dB Sampling frequency fs are assumed to be 6 MHz. 12

Simulation Results 13

Conclusions Introduced a novel receiver and frame structure and proved that the proposed cognitive radio system exhibits improved throughput and sensing capabilities, Compared to cognitive radio systems that dedicate a slot for spectrum sensing at the beginning of each frame, during which data transmission is prohibited. Proposed a novel cognitive radio system that performs spectrum sensing and data transmission at the same time. Simulation results were provided to validate our theoretical analysis. 14

15 每周一句  namely (also known as, in other words)  又名；即；換句話說  At the end of the frame, if the presence of primary users is detected, namely if the primary users started transmission after the initial spectrum sensing was performed, data transmission will be ceased to protect the primary users from harmful interference.