Showing papers by "Abhijit Bhowmick published in 2014"

Throughput optimization with cooperative spectrum sensing in cognitive radio network

Abstract: In cognitive radio (CR) network spectrum sensing is an important issue. Cooperative spectrum sensing improves the detection probability. The accuracy in taking decision about the presence of primary user (PU) depends on sensing time and number of CR users involving in cooperation. A CR network can be efficient if it performs the detection process with minimum error probability and at the same time it maximizes its overall throughput. We have investigated the optimal number of CRs required in cooperation to minimize the total error. Throughput of the CR network has been investigated with respect to sensing time. The performance of the network has been investigated in terms of maximum throughput for optimal number of CR users.

Spectrum sensing with censoring of double threshold based cognitive radios in Rayleigh fading

Abstract: In this paper, the performance of cooperative spectrum sensing (CSS) with censoring of cognitive radios (CRs) has been evaluated using a simple majority logic fusion in presence of Rayleigh fading affecting both the sensing (S) and reporting (R) channels. Each CR senses the primary user (PU) using a double threshold based energy detection over the sensing channel. Censoring of CRs is done on the basis of the quality of Rayleigh faded R-channel. Typically two types of censoring such as rank-based and threshold-based censoring are considered to select the best CR based on the quality of the R-channels between CRs and a fusion center (FC). The performance of CSS, in terms of average missed detection, is evaluated in terms of relevant network parameters such as; (i) number of selected CRs, (ii) censoring thresholds, (iii) fail sensing probabilities, (iv) S and R-channel signal to noise ratios (SNRs) under both the perfect and imperfect channel estimation. The performance in terms of agility gain, normalized average number of transmitted bits for different number of CRs is also studied. Further the performance of double threshold based energy detection is compared with that of single threshold based energy detection. Our studies demonstrate that censoring with double threshold outperforms the censoring with single threshold.

Relay based cooperative spectrum sensing in cognitive radio network

Abstract: The cognitive nodes which are far away from primary user (PU) may not be able to detect the PU due to severe fading in channel. To improve the efficiency of spectrum sensing, we propose a co operative communication scheme based on cognitive relaying. Cognitive relay nodes sense the activity of PU and forward the received data to the Cognitive radio (CR) which is far a way from the PU. In this condition, the probability of detection increases, which in turn reduces the bit error rate (BER). Employment of an umber of relay nodes reduces the sensing time and increases the throughput of the system.

Multi-slot Spectrum Sensing in Fading Channels for a Cooperative Cognitive Radio Network

Abstract: The performance of cooperative spectrum sensing (CSS) with multi-slot sensing has been investigated. A number of cognitive radio (CR) enabled users sense the primary user (PU) spectrum in multiple sensing mini-slots and the decision of each slot is combined using OR rule to evaluate the local decision about PU. All the CRs send their local decisions over faded reporting channels (R-channel) to fusion centre (FC). FC takes the final decision about PU on the basis of majority logic fusion rule. The performance of spectrum sensing has been investigated in terms of detection probability and missed detection probability for different sensing parameters such as sensing threshold, number of mini-slots and sensing channel SNR (S-SNR) etc.

Power Control with Rank Based Censoring in Cognitive Radio Network

Abstract: The transmit power of secondary users (SUs) in an underlay cognitive radio network (CRN) needs to be controlled to limit the interference on primary users (PUs) The performance of spectrum sensing plays an important role in controlling the cognitive radio (CR) transmission power Co-operative spectrum sensing (CSS) improves the performance of spectrum sensing Incorporation of Rank-based censoring with CSS reduces the transmission overhead as well as improves the decision regarding the presence of primary user (PU) by eliminating the reporting channels whose SNR condition is bad The efficient spectrum sensing leads to control the secondary transmission power accurately In a co-existing network the controlled power from CR network minimize the interference to PU The maximum allowable transmission powers of CRs have also been investigated with respect to distance between PU receiver and CRs in a co-operative spectrum sensing framework The impact of reporting channel (R- channel) SNR on maximum allowable transmission power has been investigated