This paper investigates the adaptive subcarrier and bit allocation algorithm for OFDMA systems. To minimize overall transmitted power, we propose a novel adaptive subcarrier and bit allocation algorithm based on channel state information (CSI) and quality state information (QSI). A suboptimal approach that separately performs subcarrier allocation and bit loading is proposed. It is shown that a...

In this paper, a bit-loading algorithm for DMT (Discrete MultiTone) broadband indoor power line communications is proposed. In noisy channels with high attenuation values, most of the carriers remain empty after the application of conventional strategies. This is due to the limitation in the power spectral density (PSD) mask for the transmitted signal imposed by regulations. Under these circums...

The main goal of next generation wireless systems is to provide multimedia communication with spectrally efficient communication. Most of the up-to-date systems have been standardised to use OFDM modulation which prevents inter-symbol interference and make use of parallel subcarriers. The large number of subcarriers helps to avoid the effects of fast fading by distributing channel coded informa...

A novel method to improve the performance of frequency band is cognitive radio that was introduced in 1999. Due a lot advantages OFDM, adaptive OFDM method, this technique used (CR) systems, widely. In transmission rate and power subcarriers are allocated based on channel variations system performance. This paper investigates resource allocation CR systems transmit data. The aim maximize achiev...

the chitosan nanoparticles used widely as a drug delivery systems recently. in the present study the echis carinataus snake venom loaded chitosan nanoparticles were prepared based on ionic gelation of tripolyphosphate and chitosan. the nanoparticles physicochemical characteristics, stability and biological activity of encapsulated venom were studied. the particles were spherical in shape and th...

A new mismatch insensitive 1.5-bit multiplying digital–analogue converter (MDAC) is proposed. This circuit samples the input in closed-loop form using the opamp in non-inverting configuration; hence, only the parasitic input capacitance loads the previous stage. This technique uses a fully-differential four-input OTA instead of two single-ended two-input OTAs to further improve power consumptio...

Advanced forward error correcting (FEC) and modulation scheme basing on low-density parity-check codes (LDPC) and adaptive bit loading (ABL) procedure is investigated for WLAN physical layer (PHY) of IEEE 802.11a standard. The main intention of the present paper is to study influence of the advanced PHY algorithms on the WLAN throughput under the realistic deployment conditions, for which a har...

This paper proposes a new algorithm of adaptive subcarrier allocation and bit loading for simultaneous voice and data transmission in multiuser OFDM systems. The algorithm dynamically assigns the number of subcarriers and bits/per symbol on each subcarrier for each user in a single cell. To cope with the stringent delay requirement of voice service, the subcarriers with low channel gains are as...