Tuyển tập các báo cáo nghiên cứu về hóa học được đăng trên tạp chí hóa hoc quốc tế đề tài : Two-dimensional downlink burst construction in IEEE networks | Lai and Chen EURASIP Journal on Wireless Communications and Networking 2011 2011 173 EURASIP Journal on . http content 2011 1 173 Wireless Communications and Networking a SpringerOpen Journal RESEARCH Open Access Two-dimensional downlink burst construction in IEEE networks Yuan-Cheng Lai and Yen-Hung Chen Abstract Several burst construction algorithms for orthogonal frequency division multiple access were proposed. However these algorithms did not meet the downlink burst characteristics specified in the IEEE standard. This article therefore proposes the best corner-oriented algorithm BCO . BCO not only complies with downlink burst characteristics but also considers the three issues to obtain high throughput as follows BCO maintains all free slots as a continuous area by constructing each burst in the corner of the available bandwidth area for minimizing external fragmentation BCO shrinks the burst area to minimize internal fragmentation if the requested bandwidth has been satisfied and for exploring the continuous subchannels with good channel quality BCO ensures that the burst adopts an optimal modulation coding scheme by selecting the excellent corner that can generate the maximal throughput. The simulation results indicate that BCO achieves 2-9 times the throughput achieved by the previous algorithms under a heavy load. Keywords burst construction downlink IEEE OFDMA 1. Introduction Because IEEE uses the technique of orthogonal frequency division multiple access OFDMA the bandwidth resources are represented by a two-dimensional area of slots in which the two dimensions are time in units of symbols and frequency in units of subchannels 1 . Therefore the bandwidth allocation in IEEE must consider the construction of a two-dimensional bandwidth area called a burst assigned to a connection. The subchannel diversity should be considered when constructing bursts. Subchannel diversity means that a connection .
