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We consider the downlink of a multiuser system with multiple antennas at the base station. Vector perturbation (VP) precoding is a promising variant of transmit-side channel inversion allowing the users to detect their data in a simple, noncooperative manner. VP precoding has so far been developed and analyzed under the assumptions that the transmitter has perfect channel state information (CSI) and...
Fourth Generation Networks will invariably adopt MIMO-OFDMA techniques, in order to cope with increased data rate demands and improved Quality of Service (QoS) requirements. OFDMA is a popular multiple access candidate, since it facilitates multi-user diversity by enabling two dimensional multiple access, in time and frequency domains. Random Beamforming enables exploitation of spatial multi-user...
Block diagonalization is a linear precoding technique which eliminates the multi-user interference at the transmitter side by creating parallel orthogonal single user links. In this technique, the transmit diversity order is fixed for each user and only power can be controlled to satisfy SINR requirements. This restricts the degrees of freedom available for resource allocation and limits the energy...
We propose a data precoded relay-assisted scheme, for a system cooperating with L relays, each one equipped with a single antenna. The use of relays is of significant interest to allow radio access in situations where either the direct path is not available or has poor quality. However because of the half duplex constraint at the relays, transmission of a data rate that would be possible using a modulation...
The mobile WiMAX standard (802.16e) uses multiple-input multiple-output (MIMO) limited feedback linear precoding to exploit the channel state information at the transmitter. Although the performance of limited feedback linear precoding in relation to traditional open-loop MIMO-OFDM has been extensively studied in the literature, these studies commonly assume perfect channel estimation at the receiver...
The focus of this paper is on the precoding and feedback strategies for a radio backhaul link between an access base station (ABS) and the hub base station (HBS) in the presence of mobile stations (MSs). In this paper it is assumed that the access and the backhaul links are simultaneous and use the same frequency band. Two feedback links are exploited at the ABS in order to optimize the communication...
Amplify-and-forward (AF) is one of the most common and simple approaches for transmitting information over a cooperative multi-input multi-output (MIMO) relay channel. It has recently been demonstrated that the spectral efficiency of AF scheme can be maximized by using the relay as a smart precoder. However, source node precoding has not been included in the overall maximization problem. In this paper,...
Amplify-and-forward (AF) is one of the most popular and simple approaches to transmit information over a cooperative multi-input multi-output (MIMO) relay channel. In this paper, we propose three novel power allocation methods for the downlink of cooperative multi-user MIMO AF system, which are designed to maximize the weighted sum-rate (WSR) of the cooperative system, by considering two different...
This paper addresses the problem of transmitting data to multiple mobile stations using a decode-and-forward strategy. Precoding vectors are used in relays to cancel out multiple access interference at the mobile stations. Statistical distribution of signal to noise ratio (SNR) is approximated by an expectation maximization algorithm. Based on this distribution, system performance is evaluated for...
In multiple-input multiple-output (MIMO) broadcast channel, the lattice-reduction-aided (LRA) precoder is the modified zero-forcing beamforming (ZFBF) scheme which perturbs data symbols to reduce the transmit power. In this paper, we propose the optimal user group selection (UGS) scheme for the LRA-precoder to maximize the sum-rate in MIMO broadcast systems. We derive the approximated sum-rate of...
The 3GPP (Third Generation Partnership Project) LTE (Long Term Evolution) and LTE-Advanced activities work toward the evolved UMTS (Universal Mobile Telecommunications System) Terrestrial Radio Access (E-UTRA), and the solution of IMT-Advanced (International Mobile Telecommunications) and systems beyond. The combination of OFDM (orthogonal frequency division multiplexing) and MIMO (multiple-input...
This paper proposes suboptimal precoding vector (PV) selection schemes combined with frequency domain scheduling when closed-loop MIMO precoding is adopted in the LTE (Long-Term Evolution)-Advanced uplink based on single carrier-frequency division multiple access (SC-FDMA) radio access. In the proposed schemes, frequency domain channel-dependent scheduling is performed based on a tentatively selected...
In this paper we analyze the sum rate of zero-forcing (ZF) precoding in MISO broadcast channels with limited feedback, transmit correlation and path loss. Our analysis assumes that the number of transmit antennas M and the number of users K are large, while their ratio remains bounded. By applying recent results from random matrix theory we derive a deterministic equivalent of the signal-to-interference...
One way of fully exploiting the channel capacity in multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems is to deploy precoding vectors derived from SVD to form parallel data pipes. Optimal precoding requires accurate channel state information for each OFDM subcarrier. This paper proposes a limited channel decomposition architecture by using an interpolation...
A multi-lattice-reduction aided (MLRA) vector precoding algorithm is proposed in this paper. Compared with traditional lattice-reduction-aided (LRA) method, the new method tries to find a set of candidates of perturbation vectors through reducing the formulated lattice to get subspaces of searching space. Within each subspace, a candidate vector is solved. Then the optimum vector is found in this...
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