Routing strategies and buffer management in delay tolerant networks

The Delay Tolerant Networks (DTN) is an intermittently connected network that enables communication among wireless nodes in the heterogeneous environments where end-to-end connectivity between nodes does not exist.These networks are characterized by a long delay, asymmetric data rate and low data rate.DTN uses store and forward mechanism to transmit messages from the source node to destination node.Routing in DTN is challenging because of frequent and long duration periods of disconnectivity.Therefore, the selection of routing protocol in DTN depends on the application environment in which it is used. This study presents a comprehensive survey on DTN and brief outlines of popular routing protocols in DTN.This paper also highlights the buffer management technologies that are used in DTN.Where an efficient buffer management scheme is required to choose at each step which of the messages should be transmitted in case of limited bandwidth and which of the messages should be dropped when the buffer is full.Regardless of which routing algorithms used

Survey and comparison of operating concept for routing protocols in DTN

Delay Tolerant Network (DTN) are promising techniques to enable data transmission in challenging scenarios where sophisticated infrastructure is not available and the end-to-end path does not exist at the moment of data transmission.These networks are characterized by a long delay, intermittent connectivity and high error rates.Furthermore, the dynamic topology of the network may change randomly.Therefore, routing is one of the most crucial issues that affect the performance of DTN in terms of data delivery, latency and using resources if node mobility is considered.The routing design in DTN raises many challenges to the networks.Therefore, the problem of how to route a packet from one node to another in DTN is of the essence. This paper puts forward a rigorous survey of various routing protocols as well as performs a comparison of diverse routing strategies regarding significant issues in DTN

Boosted PTS Method with Mu-Law Companding Techniques for PAPR Reduction in OFDM Systems

This paper proposes an enhanced PAPR reduction technique which combines an enhanced PTS method with Mu-Law companding. The enhanced PTS method improves performances in both the partitioning and phase rotation steps. Enhancement in partitioning is achieved through a judicious incorporation of AP-PTS scheme into the IP-PTS. As for phase rotation, an optimal set of rotation vectors is derived based on the correlation properties of candidate signals. The PAPR reduction of this enhanced PTS method is further improved by annexing Mu-Law companding at the end of the enhanced PTS. This application of Mu-Law characteristic in the time domain of OFDM signal significantly improves the PAPR reduction capability of the approach. Simulation results show that the PAPR performance of the enhanced PTS method with Mu-Law companding technique on various scenarios with different modulation schemes is better than that of the PRP-PTS. This approach can be considered as a very attractive candidate for achieving a significant reduction of PAPR, while maintaining a low computational complexity

EFFICIENT PAPR REDUCTION OF OFDM SIGNAL USING PTS TECHNIQUE WITH HYBRID PARTITIONING METHOD

ABSTRACT The high peak-to-average power ratio (PAPR) is one of the major problems of orthogonal frequency division multiplexing (OFDM) systems in wireless transmission. Therefore, partial transmit sequence (PTS), a promising scheme that can provide good PAPR reduction performance, has been proposed for OFDM transmission to eliminate distortion. The PTS method divides the input data block into disjoint sub-blocks, computes Inverse Fourier Transform of the subblocks, rotates the sub-blocks with appropriate phase factors and combines them to form the transmitted signal. This paper presents an enhanced PTS approach that combines two PTS partitioning schemes (adjacent and interleaved) to effectively reduce the PAPR of the OFDM systems. The influence of the proposed approach on performance is investigated by varying the size of the disjoint sub-blocks. The PAPR reduction performance of the proposed PTS method is compared with two well known sub-blocks partitioning schemes, namely, Adjacent Partitioning (AP), Interleaved Partitioning (IP). The various computer simulation results for the various sub-blocks confirmed that the proposed method provides better PAPR reduction performance compared with AP and IP partitioning based PTS scheme. In addition, these PTS schemes largely depend on the chosen size of the partitions

Efficient PAPR reduction of OFDM signal using PTS technique with hybrid partitioning method

The high peak-to-average power ratio (PAPR) is one of the major problems of orthogonal frequency division multiplexing (OFDM) systems in wireless transmission.Therefore, partial transmit sequence (PTS), a promising scheme that can provide good PAPR reduction performance, has been proposed for OFDM transmission to eliminate distortion. The PTS method divides the input data block into disjoint sub-blocks, computes Inverse Fourier Transform of the subblocks, rotates the sub-blocks with appropriate phase factors and combines them to form the transmitted signal.This paper presents an enhanced PTS approach that combines two PTS partitioning schemes (adjacent and interleaved) to effectively reduce the PAPR of the OFDM systems. The influence of the proposed approach on performance is investigated by varying the size of the disjoint sub-blocks.The PAPR reduction performance of the proposed PTS method is compared with two well known sub-blocks partitioning schemes, namely, Adjacent Partitioning (AP), Interleaved Partitioning (IP).The various computer simulation results for the various sub-blocks confirmed that the proposed method provides better PAPR reduction performance compared with AP and IP partitioning based PTS scheme. In addition, these PTS schemes largely depend on the chosen size of the partitions