The rapid evaluation of data transmission in wireless communication technologies can show many problems. In the previous year's many routing protocols was developed, implemented, and evaluated for transmission of data in the Mobile ad hoc network (MANET), where it envisioned to be a useful technology in military communication systems and other areas. One of the routing protocols used in MANET is the hierarchical routing protocol that considered an energy efficient. Therefore, in this paper, a comprehensive study will be presented of the hierarchical routing protocol for MANET in order to expose new open issues to either improve the existing routing techniques or to develop new routing solutions for other researchers. The reviewed routing protocol is designed to support networks of a medium size, containing approximately between 150 to 250 nodes but less than 3,000 nodes. The reviewed design is intentionally simple to allow ease of implementation in comparison with other MANET protocols that provide similar functionality
Due to the spectacular growth of the wireless services and demands in recent years, Orthogonal Frequency Division Multiplexing (OFDM) is a latest and suiTable modulation scheme for commercial high-speed broadband wireless communication systems. OFDM is one of the main techniques proposed to be employed in 4th Generation Wireless Systems. One of the OFDM key parameters is a cyclic Prefix (CP). Cyclic prefix is a guard time length padded with every OFDM symbol to completely alleviate Inter-symbol Interference (ISI) and to preserve orthogonality among OFDM subcarriers as long as the guard time length is sufficiently greater than channel delay spread. This paper analyzes OFDM system and the effect of cyclic prefix and length of cyclic prefix on OFDM system. Besides, compare the performance of the system with and without cyclic prefix. The simulations were carried out over AWGN and Rayleigh fading channels, and the results have been compared with the theoretical ones.
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