Sanjib Kumar Deka

Constraint Based Cooperative Spectrum Sensing for Cognitive Radio Network

Cognitive Radio (CR) is a key technology that has been proposed to exploit the unused spectrum holes opportunistically. In CR communication, the issues of shadowing, multipath fading affect performance of spectrum sensing function that impacts the detection performance of secondary users (SUs). Cooperative Spectrum Sensing (CSS) has proven to be an emerging scheme which significantly improves spectrum sensing performance by utilizing spatial diversity of the SUs. This paper proposes a game theory based coalition model. The main contribution of this work is to consider the constraint during cooperation due to cost involved in reporting time and reporting energy. A formulation has been proposed to decide the optimal size of a coalition and a scheme for dynamic selection of coalition head. In the game, the condition to achieve the coalition stability is carried out. Simulation results have shown the efficacy of the proposed model that enhances the sensing performance significantly.

Distributed TDMA based MAC protocol for data dissemination in ad-hoc Cognitive Radio networks

Cognitive Radio (CR) seems to be a promising solution to radio spectrum overcrowding problem. Cognitive Radio Network (CRN) allows opportunistic uses of spectrum holes by enabling the coexistence of licensed (primary) users and unlicensed (secondary) users. Data dissemination in a CRN is very useful to propagate non-urgent messages in order to limit cost and complexity of the network. MAC protocols in existing legacy wireless networks do not support the coexistence of licensed and secondary users. This limits the productive utilization of spectrum holes by secondary users. In this paper, we propose a distributed TDMA based MAC protocol for data dissemination in multi-hop ad-hoc CRNs. Our protocol aims at not only ensuring highest message reachability but also avoiding collision among secondary users. It classifies the set of available channels based on both primary radio unoccupancy and number of cognitive radio neighbours having the channel in their available channel set. The secondary users prepare a TDMA schedule using a distributed approach. Secondary users select the best channel from the available channel set using a channel selection strategy. This increases data dissemination reliability in multi-hop ad-hoc CRNs. Simulation results show the efficacy of proposed method.

A Cross-Layer Based Location-Aware Forwarding Using Distributed TDMA MAC for Ad-Hoc Cognitive Radio Networks

Cognitive Radio has been the key technology for dynamic spectrum access in wireless networks. Cognitive Radio seems to be a promising solution to the radio spectrum overcrowding problem as well. Cognitive Radio Network allows opportunistic usage of the spectrum holes by enabling the coexistence of licensed (primary) users and unlicensed (secondary) users. The existing wireless legacy network protocols limit the productive utilization of spectrum holes by the secondary users. The contribution of this paper is a cross-layer based location-aware forwarding protocol, using a distributed TDMA MAC, for ad-hoc Cognitive Radio Networks. The distributed TDMA based MAC protocol constructs TDMA schedules by exchanging three rounds of control messages with collision avoidance among secondary users as a fundamental goal. Exchange of control messages takes place over a common control channel in a distributed fashion. The MAC protocol also uses the service of network layer, which classifies the available channels and selects the best ranked channel and passes this information to the MAC sub-layer for effective communication. The proposed location-aware forwarding protocol constructs request zone for making decisions regarding data packet forwarding with highest packet delivery ratio, by confining the flooding of packets, as a key objective. Simulation results show the efficacy of the proposed cross-layer scheme.

A General Framework for Spectrum Assignment in Cognitive Radio Networks

With its opportunistic nature to exploit the unused licensed bands, cognitive radio (CR) presents itself as an advancing technology that senses for spectrum holes and distributes them rightly among secondary users. This paper proposes a spectrum assignment approach for CR networks that looks to provide a proper sharing of the available channels such that spectrum utilization is improved. While incorporating a concurrent strategy for channel allocation, the model constraints to the allocation limitation stating that one channel can be allotted to only one user at a time, and also one secondary user can gain access to at most one channel at a time. Further, simulation results of the proposed model show its effectiveness in terms of spectrum utilization efficiency.

Spectrum Allocation in Cognitive Radio Networks—A Centralized Approach

Spectrum sharing is a key functionality of cognitive radio network (CRN) that features a fair distribution of vacant licensed channels among secondary users. This paper proposes a spectrum allocation scheme for CRN that takes into account different spectrum opportunities to be allocated to the secondary users while improving the spectrum utilization. A central entity is made responsible for deciding upon the channel assignment strategies. Moreover, channels are shared one after another in a sequential fashion such that a channel gets allotted to only one user at a time, and also a user can use at most one channel at a time. Simulation study reveals the performance improvement of the proposed scheme as compared to a random allocation strategy in terms of spectrum utilization efficiency.

Utility Aware Cooperative Spectrum Sensing Using Coalitional Game Theory

Cooperative spectrum sensing (CSS) emerges as an efficient technique for cognitive radio overcoming the issues of independent sensing. In this work, a distributed cooperative spectrum sensing scheme using non-transferable coalitional game model has been proposed for cognitive radio networks (CRNs) which contributes to improve the opportunity detection and throughput. To determine the cooperative decision, a novel algorithm for selecting a fusion center is also proposed. The performance evaluation of the proposed CSS scheme is carried out through simulation study.

Coalitional Game Theory based Cooperative Spectrum Sensing in CRNs

Spectrum sensing is a key functionality of Cognitive Radio to detect the availability of Primary User (PU) in a licensed band. However, the local sensing performance of Cognitive Radio users is adversely affected by the issues like multi-path fading, shadowing, and receiver uncertainty problem. These issues can be addressed by Cooperative Spectrum Sensing (CSS). In this work, we have proposed a distributed Cooperative Spectrum Sensing scheme using Coalitional Game theoretic model for Cognitive Radio Networks which contributes to improve the sensing performance in terms of detection probability. The utility function of the game is formulated considering the trade-off between gain and cost during coalition formation. It is also proved that the proposed game model has a non-transferable utility amongst the players and the algorithm terminates in finite time with formation of stable coalitions. A simulation study has been carried out to evaluate the performance of the proposed scheme.

Opportunity prediction at MAC-layer sensing for ad-hoc cognitive radio networks

Knowledge of channel usage pattern of primary users (PUs) helps in predicting future channel availability which can reduce MAC-layer sensing overhead in cognitive radio networks. In this work, two important issues of MAC-layer sensing have been investigated for underlay mode cognitive radio networks. These are - (a) estimation and modeling of licensed channel usage pattern of PUs, while tolerating interference from secondary users (SUs), and (b) usage of learnt channel usage patterns for discovery of opportunities by the SUs. Accordingly, a Hidden Markov Model (HMM) based channel usage pattern of PUs is proposed for use by the SUs to predict the spectrum opportunity. The proposed model uses estimated interference power constraint (IPC) in determining the interference due to presence of SUs to protect the PUs from harmful interference. A formulation deriving the availability metric (AM) for licensed channels is developed which helps in selecting the best channel by an SU for its transmission needs. Experimental results show that the trained HMMs can be used for predicting future channel availability, provided the same IPC condition prevails for a certain period. It is also observed that the AM of the channel sequences generated by the trained HMMs is effective in selecting a suitable channel for transmission. Furthermore, a distributed medium access control protocol for data dissemination (DMDD) in underlay mode CRNs is proposed which utilizes the proposed channel usage model. Simulation based results have shown the effectiveness of the proposed channel usage model.

A Capacity Constraint Distributed Data Dissemination Protocol for Ad Hoc Cognitive Radio Networks

Cognitive radio (CR) has emerged as a proven technique to overcome the spectrum scarcity problem in wireless communication. Data dissemination in CR networks (CRNs) is an important activity for successful deployment of CRN. In the presence of challenges like (i) opportunity detection and (ii) requirement for strict primary user (PU) protection, modeling a technique for efficient data dissemination in CRNs is an interesting problem. Motivated with this problem, in this paper we propose a capacity rate constraint distributed data dissemination protocol (DDDP), which includes a weighted channel selection strategy and a technique to prepare distributed data dissemination schedule based on adopting a neighbor discovery method for a multi-hop ad hoc CRN. The simulation results demonstrate the efficacy of the proposed model in terms of improving packet delivery ratio, minimizing interference to the primary user (PU), and reducing the number of redundant messages in the network, which eventually improves the channel utilization.

Allocation and access mechanisms for spectrum sharing in CRNs - a brief review

Radio spectrum perceives the need for a new paradigm considering its ineffectual use. With such an incentive, Cognitive Radio (CR) paved its way to exploit unused frequency bands in an opportunistic fashion. CR extends different functionalities for its dynamic behavior amongst which spectrum sharing holds a significant place. This paper reviews the state-of-art proposals on the subject of spectrum sharing in CRN and presents an overview on the attributes of allocation and access mechanisms. Finally, it highlights some of the challenging issues for future research in this area.