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In this paper, we report on a mobile broadband wireless access (MBWA) system field trial with Fast Low-latency Access with Seamless Handoff Orthogonal Frequency Division Multiplexing (FLASH-OFDM), which was carried out at Sendai city in Japan. This paper describes coverage estimates of an uplink 16 quadrature amplitude modulation (QAM) signal under the condition of constant terminal output power when...
For Mobile WiMAX, data rate and throughput figures are often presented in literature. However, the used calculation methods and the influence of the packet size on the data rate are often unclear. Therefore, we develop a new method in order to obtain more precise data rate figures at the MAC (Medium Access Control) layer. In this paper the common physical data rate and MAC data rate calculation method...
The challenge of our work is to enhance the effec- tiveness of Channel Quality Indicator (CQI)reporting schemes in multi-user OFDMA-based communication systems. Based on information theory, we propose a novel CQI reporting scheme that exploits instantaneous mutual information at the User Equipment (UE) in order to choose the best Physical Resource Blocks (PRBs) / CQI pairs to be fed back. While predicting...
This paper presents a two-step downlink resource allocation algorithm for multicarrier based cognitive radio systems. The algorithm allocates the subcarriers to the users in the first step. In the second step, the power is allocated to these subcarriers in order to maximize the downlink capacity of the system without causing excessive interference to the primary user. The performance of the proposed...
WiMAX (IEEE 802.16) has emerged as a promising radio access technology for providing high speed broadband connectivity to subscribers over large geographic regions. New enhancements allow deployments of relay stations (RSs) that can extend the coverage of the base station (BS), increase cell capacity, or both. In this paper, we focus on deploying RSs for the purpose of coverage extension. We propose...
Inter-cell interference (ICI) is always a big obstacle to attain wide area coverage and high spectral efficiency in cellular systems. In this work we make a study of two well-known frequency reuse approaches, namely the Soft Frequency Reuse (SFR) scheme and the Incremental Frequency Reuse (IFR) scheme. Both of them aim to mitigate excessive ICI among neighboring cells. Based on a discussion of their...
Cognitive relaying is a recent communication paradigm that increases network coverage and improves spectral efficiency by allowing unlicensed (secondary) users to concurrently operate with licensed (primary) users. The major contribution of this paper is in proposing a bit allocation algorithm to be used in a cognitive relay network. The dynamic spectrum access in an OFDM-based cognitive relay network...
To mitigate inter-cell interference (ICI) and achieve higher spectrum efficiency, fractional frequency reuse (FFR) has been widely adopted by the next generation wireless systems, wherein different frequency reuse factors are applied to cell center and cell edge zones. In such conventional FFR, a contiguous radio spectrum is partitioned in a fixed fashion across all cells for edge and cell center...
The problem of resource allocation in multiuser OFDM system is a combinatorial optimization problem, difficult to solve in polynomial time. For the sake of reducing complexity, it can be solved either by relaxing constraints and making use of linear algorithms or by metaheuristic methods. In this paper, ant colony optimization, a typical algorithm of metaheuristic methods, is applied to solve the...
Chunk-based resource allocation can effectively reduce the complexity of resource allocation in multiuser orthogonal frequency division multiplexing (OFDM) systems by grouping a number of neighboring subcarriers into a chunk and being carried out chunk by chunk. To ensure the bit error rate (BER) constraint within a chunk, an adaptive BER-based chunk allocation scheme is proposed and analyzed in this...
The impact of channel estimation error is investigated for Spectrally Modulated, Spectrally Encoded (SMSE) waveform designs in a coexistent environment containing multiple 802.11 Primary User (PU) systems. As previously demonstrated, the SMSE waveform design process can exploit statistical knowledge of PU spectral and temporal behavior to maximize SMSE system throughput (bits/second). This can be...
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