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In this paper, we propose a spatial multi-user physical layer network coding (SM-PNC) scheme by jointly utilizing PNC and beamforming techniques in a multi-user one relay communication system. The relay is equipped with multiple antennas and each user node is only equipped with a single antenna. The two way relay transmission consists of two phases. In multiple access phase, the summation and difference...
In this paper, we develop a novel joint transmit and receive design for multiuser MIMO (MU-MIMO) systems. The proposed scheme exploits the channel temporal correlation and incorporates the matched filter (MF) combining vector into the beamforming design. Considering the beamforming is optimized with the outdated channel state information (CSI) feedback, we design the beamformer by maximizing the conditional...
This paper presents indoor experimental results on an implemented real-time downlink multiuser multiple-input multiple-output (DL-MU-MIMO) transceiver for next generation wireless LAN systems. In the transceiver, channel state information (CSI) is estimated at each station (STA) and fed back to an access point (AP) on a real-time basis. At the AP, transmit beamforming weight for DL-MU-MIMO transmission...
In this paper, a resource allocation problem for downlink multiple input-single output orthogonal frequency division multiple access (MISO-OFDMA) systems is investigated. The problem is defined as maximizing the minimum user rate with the constraints of total power and bit error rate (BER). Since it is difficult to obtain the optimal solution to this problem, a suboptimal but efficient solution is...
In the 3rd generation partnership project (3GPP) long term evolution (LTE) time division duplex (TDD) systems, base stations use uplink sounding reference signals (SRSs) to estimate downlink channel state information (CSI) for downlink beamforming transmissions. Because SRSs sent by up to 8 users are multiplexed on the same time-frequency resources, there exist mutual interferences among these SRSs...
We considers the beamforming assisted multiple-antenna receiver for space-division multiple-access based multiuser systems that employ high-throughput quadrature amplitude modulation (QAM) signalling. The bit error ratio (BER) expression as the function of the beamformer's weight vector is derived, and the minimum BER (MBER) beamforming receiver is then obtained as the solution of the resulting optimisation...
In this paper, we investigate efficient beamforming schemes for downlink broadcast channels of MIMO systems. Optimal solution to this problem is known to be infeasible due to the prohibitive complexity and recent research focuses on suboptimal approaches with reduced complexity. We first present a progressive beamforming method that maximizes the net gain in sum throughput for newly added users and...
We consider an overlay mode of an orthogonal frequency division multiple access (OFDMA) based cellular system using orthogonal beamforming to provide broadband wireless access for rural users. In overlay mode, since the signals transmitted to rural users should not interfere with mobile users of higher priority in the OFDMA-based cellular system, the beamforming vectors to rural users have to be orthogonal...
In the previous works on multiple-input multiple-output (MIMO) interference channels, it is usually assumed that the transmit power is fixed and only MIMO beamforming is applied to mitigate interference. In this paper, we design the transmit powers and beamforming vectors jointly for each transmit-receive pairs (links) to maximize the energy efficiency in MIMO interference channels. Centralized and...
Transmission of signals using multiple antennas can significantly improve the energy efficiency of a wireless network, and the proper alignment of the transmitted signals' phases at the receiver is one of the key factors so this efficiency improvement can be realized. In a time-varying channel, due to the relative motion between the transmitters and the receiver, the development of a scheme that guarantees...
In this paper we consider the coexistence of a single-input single-output (SISO) primary link with a multiple-input single-output (MISO) secondary user pair that has non-causal knowledge of the primary message. We study an achievable rate region that exploits this knowledge by combining selfless relaying to maintain the rate supported by the primary link with dirty paper coding to pre-cancel the interference...
In this paper, we study adaptive transmission mode switching between statistical and instantaneous channel state information (CSI) aided single-user (SU) and multiuser (MU) precoding for a two-user downlink system, where two transmit antennas are equipped at the base station and each mobile user has one receive antenna. In the case where only statistical CSI (SCSI) is available at the transmitter,...
In transmit beamforming multi-antenna systems, the representative quantized channel direction information (CDI) may become outdated due to the feedback delay. Grassmannian predictive coding (GPC) has been shown as an effective method to overcome this problem. However, the existing GPC algorithm is still of practical concern as the quantization resolution may not be ensured at relatively low feedback...
When the joint processing technique is applied in the coordinated multipoint (CoMP) transmission downlink, the user data for each mobile station (MS) needs to be distributed among multiple base stations (BSs), which incurs the exchange of user data via the backhaul. In order to alleviate the requirement on the backhaul capacity, we propose to minimize the exchange of user data among the BSs, subject...
In this paper, we first study the Decode-and-Forward strategy for secrecy in a single-relay network. We propose a suboptimal Decode-and-Forward with Zero Forcing (DF/ZF) strategy for which we obtain the optimal power control policy. Next, we consider the multiple relay problem. We propose three different strategies based on DF/ZF. The first strategy is a single-hop strategy in which all the relays...
In this paper, two novel approaches to filter-and-forward beamforming (FF-BF) in an underlay based relay-assisted cognitive network with frequency-selective channels are proposed. In our scheme, secondary users are allowed to transmit through multiple relays simultaneously with primary users over the same spectrum. Such a network suffers from both inter-symbol interference (ISI) and bidirectional...
The problem of distributed coordination in multi-cell wireless network has been concerned in the research community recently due to its ability to enhance intended signal and mitigate interference in the system. In the previous research, the design of beamforming weights at transmitter has been addressed from the perspective of egoism and altruism concepts considering the tradeoff between egoistic...
Coordinated multi-point transmission (CoMP) has been widely recognized as a promising technique for improving spectral efficiency in future cellular systems. However, it may require high-capacity backhaul links, which can increase expense. In this paper, we study the cooperative transmission method with limited-capacity backhaul. Downlink CoMP transmission requires the exchange of information between...
This study addresses the resource allocation problem for multi-user MIMO systems with consideration of real-time services. Specifically, we focused on the delay constraints modeling in this paper, since it is a fundamental QoS requirement for all real-time services. To simultaneously meet the delay constraints of all users, we first modeled this resource allocation problem with specific delay restrictions...
Coordinated beamforming in multipoint MIMO networks has been introduced to increase the overall capacity of wireless networks. In coordinated beamforming, the channel state information between the different MIMO access points/base stations in one hand, and the mobile stations on the other hand, needs to be shared among the MIMO nodes. A “backhaul” between different MIMO access points is used to transfer...
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