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When fast and accurate channel state information (CSI) at the transmitter is available, opportunistic power control (OPC) is an attractive alternative to signal-to-interference-and-noise ratio (SINR) target following approaches, because it maximizes throughput by taking advantage of fast channel variations. On the other hand, in multiple-input multiple-output (MIMO) systems, open loop schemes such...
In this paper we propose a novel multicarrier (MC) architecture to address the energy saving problem in WLAN applications. We refer to this scheme as hybrid filtered multitone (H-FMT). Depending on the channel condition, H-FMT wisely switches between Filtered Multitone Modulation (FMT) with orthogonal pulses and adaptive orthogonal frequency division multiplexing (A-OFDM). We show that H-FMT provides...
Performance of next generation OFDM/OFDMA based Distributed Cellular Network (ODCN) where no cooperation based interference management schemes are used, is dependent on four major factors: 1) spectrum reuse factor, 2) number of sectors per site, 3) number of relay station per site and 4) modulation and coding efficiency achievable through link adaptation. The combined effect of these factors on the...
In this paper we propose a novel hybrid multicarrier architecture for wireless LAN (WLAN) applications. We refer to this architecture as hybrid filtered multitone (HFMT). Depending on the experienced channel condition, H-FMT switches between short orthogonal FMT (SO-FMT) modulation, and adaptive orthogonal frequency division multiplexing (A-OFDM). Extensive numerical results show that H-FMT could...
Multi-carrier modulation and especially CP-OFDM is widely used nowadays in several radio communications. However, FBMC is a potential alternative to CP-OFDM since it does not require cyclic prefix, and thus, it has a higher spectral efficiency. One of the characteristics of FBMC is that the received data are accompanied by a two dimensional inter-symbol interference term (2D ISI), which complicates...
FBMC transmission system was proposed as an alternative approach to OFDM system since it has a higher spectral efficiency. One of the characteristics of FBMC is that the demodulated transmitted symbols are accompanied by interference terms caused by the neighboring transmitted data in time and frequency domain. The presence of this interference is an issue for the Maximum Likelihood (ML) implementation...
Being sensitive to carrier frequency offset (CFO) is known to be one of the main drawbacks of multicarrier systems. In this paper, the effects of CFO on a filter bank based multicarrier system (FBMC) in a multipath fading channel are discussed, where an ideal root-raised cosine (RRC) filter with roll-off factor 1 is used as the prototype filter which enables analytical derivations of the interference...
In modern wireless communication systems, scheduling and resource allocation are two closely related tasks of the medium access control (MAC) and physical (PHY) layers respectively. In this paper, we present a separate yet interactive design of the two functional modules, where the scheduler prioritizes data packets from different service flows according to their traffic characteristics and feedback...
In this paper we present a new adaptive fractional frequency reuse scheme (AFFR) for multi-cell OFDMA based IEEE 802.16e network. The adaptive fractional frequency reuse (AFFR) scheme is managed by the access service network gateway (ASN-GW) which coordinate a set of BSs (one cluster). To make better usage of radio resources; we assume that the cell area is virtually divided into two different zones:...
In this paper, we investigate the energy consumption of a wireless cognitive radio (CR) network, where each node is equipped with CR and the network is an OFDMA system operating on time slots. In particular, we investigate the energy consumption efficiency in CR network using a joint adaptive modulation and power allocation algorithm. We also investigate the optimum network area for green communication.
This paper studies the computation of postprocessing signal-to-interference plus noise ratio (SINR) for maximum likelihood detector (MLD) in multiple-input and multiple output (MIMO)-orthogonal frequency division multiplexing (OFDM) spatial multiplexing systems. We derive an effective post-MLD SINR for each spatial stream, which is computed as post minimum mean-squared error (MMSE) SINR plus gain...
A unique frequency reuse scheme by means of cell sectorization is proposed in this paper that reuses effectively a given frequency resource in a cellular environment. The key concept is to find a scheme that controls interferences among neighboring cells in a systematic manner while achieving high frequency reuse factor. Based on, user distribution in a cell, two problems are investigated. First,...
In IEEE 802.16e OFDMA system, the system capacity for accommodating VoIP traffic with small-sized PDUs is severely reduced due to a large amount of signalling overhead. In order to mitigate this problem, the IEEE 802.16 maintenance group has recently proposed a persistent allocation scheme to increase the voice over IP (VoIP) system capacity. However, it is difficult to use the conventional modulation...
To improve the spectrum utilization, more and more attention was paid to OFDM based opportunistic spectrum access (OSA) systems in recent years. In this paper, to enable coexistence between a secondary user and a primary user, a novel method called EAIC was proposed for spectral sculpting of OFDM signal effectively. In EAIC, however, the cancellation signals cause self-interferences to OFDM data tones...
The carrier frequency offset (CFO) could destroy the orthogonality of OFDM subcarriers and induce the inter-carrier interference (ICI) spread. However, the generalized multi-carrier (GMC) system reflects different interference characters in the presence of CFO. In this paper, we exactly analyze the CFO effect on GMC, which multiplexes several single band single carrier based frequency division multiple...
Although orthogonal frequency division multiplexing (OFDM) communication systems that use inverse discrete Fourier (IDFT) for multicarrier modulation and discrete Fourier transform (DFT) for demodulation are dominantly adopted in the current broadband standards, there have been some reports in recent years that discuss the shortcomings of OFDM in highly mobile and/or multiple access environments....
This paper presents statistical properties and the impact of out-of-band emission in Orthogonal Frequency Division Multiplexing (OFDM) and in Discrete Fourier Transform Spread OFDM (DFT-SOFDM) on the link performance. The analysis on the power spectrum density shows that if the signal distortion by a nonlinear power amplifier is not considered, OFDM has the same average power spectrum density as DFT-SOFDM...
We propose a design method for multicarrier systems based on the achievable rate. We focus on pulse-shaped OFDM, adopted by the HomePlug AV system, and filtered multitone modulation (FMT). For a given sub-channel pulse shape, the number of tones and the interpolation factor can be determined by maximizing a design metric based on the achievable rate. Numerical results and comparisons are reported...
OFDM/DMT has been proposed as a suitable modulation for power-line communications (PLC). Meanwhile, another modulation, named OFDM/OQAM, was presented to be also an alternative to OFDM. Further, the HS-OQAM system was proposed particularly for the baseband communications such as PLC. This paper gives a theoretical expression of the inter-symbol interference (ISI) plus inter-carrier interference (ICI)...
To enable coexistence between an OFDM based opportunistic spectrum access system and a primary user, we proposed two novel methods called EAIC (Extended Active Interference Cancellation) and EAIC-H (EAIC-Hybrid) for spectral sculpting of OFDM signal. In EAIC and EAIC-H, cancellation signals are added to OFDM signal to cancel interference in target spectrum band caused by data tones, so that interference...
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