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New channel estimation technique is proposed for multiband orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB) systems. Several steps have been carried out to achieve this purpose. In first step, refined least square (LS) channel estimation is found out by using subspace-based narrowband interference (NBI) estimation method with prilimonary LS channel. In second step, low rank...
In this paper, we consider a system based on Orthogonal Frequency Division Multiple Access (OFDMA) and investigate the benefits of combining the Satisfaction Oriented Resource Allocation (SORA) algorithm, which aims at maximizing the number of satisfied users in a system, and Orthogonal Random Beamforming (ORB), which provides spatial multiplexing gains and has low computacional complexity, low signaling...
In this paper we focus on the subcarrier allocation for the uplink OFDMA based cooperative relay networks. Multiple cells were considered, each composed of a single base station (destination), multiple amplify and forward (AF) relay stations and multiple subscriber stations (sources). The effects of inter-cell interference (ICI) have been considered to optimize the subcarrier allocation with low complexity...
In this paper, the issue of carrier frequency offset compensation in orthogonal frequency division multiple access (OFDMA) uplink system is investigated. To mitigate the effect of the multiple access interference (MAI) caused by the carrier frequency offset (CFO) of different users, a new iterative compensation algorithm is proposed. However, this scheme has unaffordable complexity. To tackle this...
In communication systems that use orthogonal frequency-division multiplexing and multiple transmit and receive antennas, beamforming (BF) is conventionally carried out on a subcarrier basis. The computational requirements are high as dedicated discrete Fourier transform (DFT) processors are needed for each antenna. Considerable complexity reductions can be achieved by symbol-wise BF, which performs...
Dynamic spectrum access has recently attracted interest for better utilisation of reserved frequency bands. Quality of service issues have to be addressed in these systems in the presence of multipath fading. This is especially the case when the number of users in the secondary system grow. Multi-user resource scheduling is critical to mitigate the issue. In this work, we consider scheduling for dynamic...
This paper addresses resource allocation for weighted sum throughput maximization (WSTM) in OFDMA multi-cellular networks. The WSTM problem is a trade-off between maximizing the sum data rate, and balancing the users' queue lengths. It may therefore be seen as a cross-layer resource allocation objective suited for Best Effort users. A graph-based subcarrier allocation for WSTM, deduced from the pairwise...
In this paper, a low complexity ordered successive interference cancellation (OSIC) equalizer based on minimum-mean squared error (MMSE) criterion is proposed for suppressing intercarrier interference (ICI) caused by time-selective channels in OFDM systems. The proposed scheme exploits a low complexity MMSE equalizer and a partial MMSE-OSIC equalizer appropriately, according to symbol selection algorithm...
This paper evaluates the ultra low complexity non-eigen decomposition (NED) algorithm for adaptive interference mitigation. Current blind beamforming algorithms require computational complexity too high for many target applications. NED does not rely on the eignenvalues and eigenvectors used by conventional algorithms and requires significantly less computations, with a total computational load of...
In orthogonal frequency division multiplexing (OFDM) systems, time- and frequency-selective (or doubly-selective) fading leads to the loss of subcarrier orthogonality and the occurrence of inter-carrier interference (ICI), which increases an irreducible error floor in proportional to the normalized Doppler frequency offset. Channel estimation (CE) in rapidly time-varying multi-path scenarios is critical...
Orthogonal frequency division multiplexing (OFDM) is the modulation scheme of choice for digital video broadcasting-handheld (DVB-H), which is required to operate under high mobility conditions resulting in significant Inter-carrier Interference (ICI). To mitigate ICI, several cancellation schemes have been proposed but they require reliable channel information at the receiver which is quite challenging...
Some communication applications, like multimedia, deliver data of different importance classes allowing unequal error protection (UEP) levels. In this paper, a multiple-input multiple-output (MIMO) system using orthogonal frequency division multiplexing (OFDM) is considered with a new UEP bit-loading algorithm based on the non-UEP algorithm by Chow, Cioffi, and Bingham. In the proposed bit-loading...
Orthogonal frequency division multiplexing (OFDM) is the modulation scheme of choice for digital video broadcasting-handheld (DVB-H) which is required to operate under high mobility conditions resulting in significant Inter-Carrier Interference (ICI). Under these conditions, the conventional one-tap per subcarrier channel estimation and equalization is suboptimal since it does not account for ICI...
This paper addresses adaptive channel estimation for time-varying mobile wireless channels with nonstationary statistics. We presents a reduced complexity adaptive channel estimator based on a set membership filtering approach known as the Optimal Bounding Ellipsoid (OBE) algorithm. To exploit time and frequency domain correlation properties of the channel in an efficient low-complexity way, we allow...
Ultra-wideband (UWB) systems possess several distinct features such as very high data rate, large multipath or frequency diversity and improved ranging precision while requiring low-power low-complexity transceivers. Among the different modulation schemes, differential PSK is an attractive option because it does not require channel estimation, and hence reduces implementation complexity. This paper...
The next generation of wireless networks (4G) will use OFDMA (Orthogonal Frequency Division Multiple Access) in the reverse link. In OFDMA, the reverse link resources assigned to a user are called tiles each of which consists of a subset of consecutive subcarriers. Since at most one user is assigned to each of these tiles then reverse link transmissions within a sector are orthogonal. However, the...
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