Cooperative Diversity Based Multi-Carrier CDMA System with Decode and Forward Relays in Rayleigh Fading channels

Oruthota, Udesh; Rajatheva, Nandana

doi:10.1007/s11277-010-0133-2

Cited by 1 publication

(2 citation statements)

References 14 publications

(15 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…CDMA technique was introduced in relay systems in [60] [61] to take advantage of spread spectrum techniques. In [62], multicarrier CDMA decode-and-forward relay system performance was analyzed. The power allocation was analyzed in [63] for a CDMA based decode-and-forward relay system and cognitive relay networks are recently studied in different articles [64][65][66].…”

Section: Radio Systemmentioning

confidence: 99%

See 1 more Smart Citation

Throughput Analysis of Opportunistic Channel Access Techniques in Cognitive Radio Systems

Senthuran¹

2021

Preprint

View full text Add to dashboard Cite

In recent studies it was found out that previously allocated frequency spectrum is not fully utilized in all the wireless systems. Cognitive radio is the new concept to access this underutilized spectrum and, also a promising technology to cope with the ever increasing bandwidth demand for next generation wireless networks. Cognitive radio network can be classified into three different categories: interweave, underlay and overlay. In an interweave cognitive radio system, the unoccupied spectrum holes can be shared by cognitive users with minimal collision with primary users (spectrum owners) whereas in an underlay system, concurrent transmission is allowed with an interference threshold to the primary users. In an underlay system, cognitive users generally transmit at very low power. In an overlay system, cognitive users, similar to underlay cognitive radio systems, concurrently transmit with primary users but cognitive users may know the codewords of the primary transmitter. Hence, using that knowledge, cognitive transmitter may adopt different coding techniques to cancel/mitigate the interference at the primary receiver and/or it may assist the primary system by relaying primary user’s data. In this thesis, we improve the throughput/bit error rate performance of a cognitive radio system by effectively accessing the channels. Throughout the thesis we assume that cognitive user can sense only one channel at a time and we analyze the performance with perfect and imperfect sensing. First, we propose a novel opportunistic access scheme for cognitive radios in an interweave cognitive system, that considers the channel gain as well as the predicted idle channel probability (primary user occupancy: busy/idle). In contrast to previous work where a cognitive user vacates a channel only when that channel becomes busy, the proposed scheme requires the cognitive user to switch to the channel with the next highest idle probability if the current channel’s gain is below a certain threshold. We derive the threshold values that maximize the long term throughput for various primary user transition probabilities and cognitive user’s relative movement (Doppler spread). Then, we propose a three state Markov model to analyze the performance of a hybrid interweave-underlay system where the primary user’s occupancy states are hidden, but their activity statistics, ranges of transmission, and interference thresholds are known. The primary user is assumed to be in one of the three transmission modes as seen by the cognitive user: busy, concurrent and idle. We derive the transmission mode selection criteria (interweave/underlay) to improve the long term throughput of a cognitive user based on the primary user traffic characteristics and the achievable throughput ratio between the two modes of operation. Later, we incorporate the sensing error in our analysis where we study the optimal access strategy. Since the optimal policy requires the channel to be sensed in each time-slot, we propose and analyze a forward algorithm based cross-layer frame based sensing policy. Finally, we focus on the overlay cognitive radio system where cognitive relay nodes assist the primary transmission. As an initial study, we select a two-hop decode-and-forward orthogonal frequency and code division multiplexing based relay network. For this system, we propose adaptive channel allocation and, power allocation strategies and the bit error rate performance is numerically evaluated. This preliminary analysis can be extended to overlay cognitive systems.

show abstract

Section: Radio Systemmentioning

confidence: 99%

“…. , U K ) into another group as done in [62]. Further, it is assumed that there is an one-to-one mapping between two groups of users and they are paired (as partners) for cooperative relaying.…”

Section: Two-hop Overlay System Modelmentioning

confidence: 99%

Throughput Analysis of Opportunistic Channel Access Techniques in Cognitive Radio Systems

Senthuran¹

2021

Preprint

View full text Add to dashboard Cite

show abstract

Cooperative Diversity Based Multi-Carrier CDMA System with Decode and Forward Relays in Rayleigh Fading channels

Cited by 1 publication

References 14 publications

Throughput Analysis of Opportunistic Channel Access Techniques in Cognitive Radio Systems

Throughput Analysis of Opportunistic Channel Access Techniques in Cognitive Radio Systems

Contact Info

Product

Resources

About