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Signal-to-leakage-and-noise ratio (SLNR) is a promising criterion for linear precoder design in multiuser multiple-input multiple-output systems. In this paper, an expression of a precoder maximizing SLNR based on the generalized Rayleigh quotient theorem is derived for cellular networks. Compared with the conventional SLNR precoders, we consider the non-homogeneous average received signal-to-noise...
We consider the problem of transmit beamforming to multiple cochannel multicast groups. The conventional approach is to beamform a designated data stream to each group, while treating potential inter-group interference as noise at the receivers. In overloaded systems where the number of transmit antennas is insufficient to perform interference nulling, we show that inter-group interference dominates...
Cognitive radio is a promising approach that allows a secondary system to reuse radio resources assigned to a primary system. In a cognitive system, it is challenging to design a precoding scheme for the secondary system such that the sum rate of the secondary system is maximized while meeting interference constraints for the primary system. In this paper, we first formulate a sum rate maximization...
We present a new multiple-input-multiple-output (MIMO) transmission scheme for generic phase-shift-keying (PSK) modulations in the multi-user (MU) downlink channel, where Constant Envelope Precoding (CEP) is combined with concepts of interference exploitation. In the proposed approach, multi-user-interference (MUI) is treated as a resource for increasing the signal-to-interference-and-noise-ratio...
Interference Alignment (IA) is technique that, in a large sense, makes use of the increasing signal dimensions available in the system through MIMO and OFDM technologies in order to globally reduce the interference suffered by users in a network. In this paper, we address the problem of downlink cellular networks, the so-called interfering broadcast channels, where mobile users at cell edges may suffer...
Large scale multi-tier Heterogeneous Networks (HetNets) are expected to ensure a consistent quality of service (QoS) in 5G systems. Such networks consist of a macro base station (BS) equipped with a large number of antennas and a dense overlay of small cells. The small cells could be deployed within the same coverage of the macro-cell BS, thereby causing high levels of inter-cell interference. In...
This paper proposes a low-complexity precoding scheme for the downlink of single-cell two-user massive multi-input-multi-output (MIMO) systems, which can be seen as a combination of matched-filter (MF) precoding with extra user power adjustment. In this scheme, the base station (BS) antennas are grouped into two sets according to their channels, then each set has a main user to serve and a power coefficient...
Interference alignment (IA) is a promising interference management technique to efficiently improve the degrees of freedom and system capacity in a K-user interference network. The existence of the interference channel (IC) is the main reason why communication system is interference limited. However, in most cases, transmission performance of interference sub-channels has remarkable differences. Existing...
One of the main areas of research for the next generation of mobile communications (5G) is the concept of Massive MIMO, which implies using base stations that employ a considerably larger number of antennas than the classic MIMO systems (tens or even hundreds of antennas). The challenges become increasingly difficult when it comes to dealing with multiple mobile stations (MU-MIMO system) sharing the...
A novel generalized side-information cancelling precoder is proposed for the multiuser MIMO downlink systems over MIMO broadcast fading channels. The proposed transceiver involves the following stages. First, the minimum mean square error (MMSE) based channel inversion (MMSE-CI) technique is utilized to suppress multiuser broadcast interference. Next, using the generalized side-information cancellation...
This paper presents an inter-relay interference (IRI) cancellation scheme in amplify-and-forward (AF) cellular-type networks with successive downlink forwarding. In these half-duplex alternate relaying systems with two hops, the wireless medium in both hops is always utilized through the simultaneous transmissions of the base station (BS) and one of the relays which in turn causes IRI. In this work,...
This paper investigates the linear precoder design for cognitive multiple-access wiretap channel (CMAC-WT), where two secondary-user transmitters (STs) communicate with one secondary-user receiver (SR) in the presence of an eavesdropper and subject to interference threshold constraints at primary-user receivers (PRs). It designs linear precoders to maximize the ergodic secrecy sum rate for multiple-input...
In this paper, we analyze the spectral efficiency (SE) and energy efficiency (EE) of multi-user (MU) multiple-input and multiple-output (MIMO) in multi-cell downlink networks. We first analyze the achievable sum-rate, i.e., the SE, of MU-MIMO systems with maximal ratio transmission (MRT) and zero-forcing (ZF) precoders in downlink cellular networks. Different from the conventional analysis, we derive...
This paper aims to minimize the total transmit power consumption for Massive MIMO (multiple-input multiple-output) downlink cellular systems when each user is served by the optimized subset of the base stations (BSs). We derive a lower bound on the ergodic spectral efficiency (SE) for Rayleigh fading channels and maximum ratio transmission (MRT) when the BSs cooperate using non-coherent joint transmission...
We consider the physical layer security for the downlink system, where the confidential messages can be wiretapped by both the intended users (IUs) and the external eavesdroppers (EEs). Regularized channel inversion (RCI) precoding is adopted for multiuser communication because it can control the mutual information leakage among users. And, to enhance the secrecy performance, artificial noise (AN)...
As a promising downlink multiple access scheme for further cellular enhancements toward 5G, non- orthogonal multiple access (NOMA) improves both cell average and cell-edge user throughput compared to orthogonal multiple access (OMA). Our previous work showed that NOMA can improve system performance compared with OMA even when combined with multiple- input multiple-output (MIMO). However, for NOMA...
The fundamental problem in multi-cell two-way relaying is low uplink achievable rate due to the fact that the uplink signal transmitted by a user is significantly contaminated by the downlink signal transmitted simultaneously by the base station (BS) in the neighboring cell, which has much greater power than the power of the user uplink signal. In this paper, a novel relay precoding optimization scheme...
Massive MIMO is an energy efficient technique which utilizes frequency spectrum efficiently and provides secure and sturdy system. Therefore it is going to be backbone of future broadband network. Multi-cell Massive MIMO system reused orthogonal pilot sequence which results in pilot contamination. Pilot contamination causes poor channel estimation at the BS and degrades the performance of the system...
The N-continuous precoder for the suppression of OOB emission in OFDM systems that minimizes the EVM is introduced. We show that the minimum in-band interference due to the introduced precoding approach is 3 dB less than the inband interference of existing N-continuous precoders. Moreover, we introduce a novel practical block precoder that approaches the performance of the suggested optimal precoder...
The downlink performance of two-tier (macro/pico) multi-antenna cellular heterogeneous networks (HetNets) employing space division multiple access (SDMA) technique is analyzed in this paper. The number of users simultaneously served with SDMA by each BS in a resource block depends on user distribution, unlike previous studies which assume the number to be any arbitrary value. By exploiting the feasibility...
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