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Orthogonal Frequency Division Multiplexing (OFDM) is a potential transmission approach for high capacity communication systems. Despite the many advantages of OFDM, the major downside is the high peak-to-average power ratio (PAPR) which increases the system complexity, reduces the efficiency of the system, causes degradation in BER performance, and makes OFDM sensitive to nonlinear distortion in the transmission. Various methods have been proposed to deal with the PAPR problem, including the partial transmit sequence (PTS) that has attracted considerable attention. Hence, this paper presents a hybrid approach combining an enhanced PTS technique with Mu-Law companding. The PTS technique was enhanced through improving its sub-block partitioning scheme, where the enhanced partitioning scheme consolidated a conventional interleaved partitioning into an adjacent partitioning scheme. This incorporation of Mu-Law characteristic in time domain for PAPR reduction in OFDM essentially enhances the PAPR reduction performance, based on using numerical simulation results. Consequently, though the pseudorandom sub-block partition method obtains better PAPR reduction more than the other sub-block partition schemes (interleaved and adjacent) of ordinary PTS, it is quite difficult to be designed. The findings show that the enhanced PTS technique with Mu-Law companding, while maintaining low computational complexity, performs significantly better than the pseudorandom partitioning PTS on various types of modulation formats and subcarriers.

Orthogonal frequency division multiplexing (OFDM) is a promising modulation technique for transmitting large amounts of digital data through radio waves. One major drawback in OFDM communication is peak-to-average power ratio (PAPR). Mainly because of the nonlinearity of the high power amplifier, these results in high out-of-band radiation, inter-carrier interference, and bit error rate performance degradation. Partial transmit sequences (PTS), an attractive technique of PAPR reduction, provides significant PAPR reduction performance for (OFDM) signals. It essentially involves partitioning the OFDM data frame into disjoint subblocks. Adjacent partitioning (AP) scheme can be regarded as the best of the existing partitioning schemes when PAPR reduction performance and cost are considered together. In this paper, we study the impact of the size of PTS partitions on the performance through varying the size of the disjoint sub-blocks partition and comparing the PAPR reduction performance of three well known sub-block partitioning schemes namely Adjacent Partitioning (AP), Interleaved Partitioning (IP) and Pseudorandom Partitioning (PRP). Simulation results showed that performance of these PTS schemes largely depends on the chosen size of the partitions.Keywords-orthogonal frequency division multiplexing (OFDM), peak-to-average power ratio (PAPR), partial transmit sequences (PTS), sub-block partition scheme.

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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.