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It is known that the accumulated contact data of all stations of multistatic sonar arrays cannot be handled by traditional VHF links. While other technologies like satellite communication systems could handle the amount of data, these systems are usually too costly in terms of money, weight, or power consumption to be deployed on sonar buoys. Therefore, we installed commercial off-the-shelf WLAN with...
In this paper, an antenna selection and power allocation algorithm is proposed based on user groups for distributed antenna systems. Users are departed into two groups according to their communication environments, one is inner-cell user, and another is cell-edge user. System level simulation plat is built for performance analysis, including cell total throughput, cell-edge user data rate and outage...
It is significantly important to reduce uplink energy consumption in order to prolong the battery lifetime of user equipment (UE). In this paper, an uplink energy-saving power control scheme is proposed based on Coordinated Multiple Points Reception (CoMP) in the heterogeneous cellular networks. The main idea of the proposed scheme is based on the tradeoff between the uplink transmission power and...
Millimeter wave (mmWave) communication is a promising candidate for future extremely high data rate, wireless networks. The main challenges of mmWave communications are deafness (misalignment between the beams of the transmitter and receiver) and blockage (severe attenuation due to obstacles). Due to deafness, prior to link establishment between a client and its access point, a time consuming alignment/beam...
With the ever increasing demand for mobile broadband service with very high bitrates to indoor users, there is large industry traction around different types of In Building Solutions (IBS) for Long Term Evolution (LTE). Multiple Input Multiple Output (MIMO) is a key feature in LTE enabling significantly improved user bitrates, and the indoor channel characteristics are also expected to be in favor...
Recently, LTE Release 12 and IEEE 802.11ac adopted 256-quadrature amplitude modulation (QAM) as a tool to accommodate high demand of data throughput in wireless systems. Furthermore, currently developing IEEE 802.11ax considers 1024-QAM to further increase the Wi-Fi throughput. In this paper, we propose low complexity schemes in soft detection of high order QAM symbols in multiple input multiple output...
Wireless local area networks (WLANs) are becoming denser and thus interference-limited due to heavy traffic from a number of adjacent access points (APs) and stations (STAs). We propose a novel interference management technique for overlapping basic service sets (OBSSs) in such WLANs, which intelligently applies an opportunistic interference alignment (OIA) concept to WLANs. Each BSS has an AP and...
Pilot reuse (PR) in each cell has been proposed to reduce the pilot overhead and improve the throughput of massive multiple-input multiple-output systems. Since PR can introduce interference into channel estimation, several pilot scheduling schemes have been developed to alleviate this problem. However, current schemes have high computational complexity. In this paper, we try to design a low-complexity...
The state of the art in measurement methods for the Multiple Input Multiple Output (MIMO) capable equipment are discussed in this paper. The principles of four anechoic chamber based candidates in standardization organizations are explained. Conventionally, most of these candidates would ask for 8 probes or more to perform test correctly. The idea of Selectively Distributing Probes Algorithm (SDPA)...
This paper presents a study on the performance of a dense urban small-cell densification, where the limitations and design challenges related to the wireless small-cell backhaul are considered. While most evaluations of the small-cell capability to increase the end-user experience do simply assume ideal backhaul, here a wireless and capacity-limited backhaul is introduced. The design methodology,...
This paper presents outdoor field experimental results showing the achievement of 3-Gbps throughput performance based on 400-MHz bandwidth transmission when applying carrier aggregation with 4 component carriers and 4-by-4 single-user multiple-in multiple-out multiplexing in the 15-GHz frequency band in the downlink of 5G cellular radio access. A new radio interface with time division duplexing and...
Cooperative multi-cell MIMO techniques are well known for their outstanding capability to mitigate inter-cell interference by allowing user data to be jointly processed by several interfering base stations for the improvement of the system performance. This paper proposes an iterative algorithm that designs the precoding matrix for cooperative multi-cell MIMO downlink communications. As the demand...
We consider the downlink of Cell-Free Massive MIMO systems, where a very large number of distributed access points (APs) simultaneously serve a much smaller number of users. Each AP uses local channel estimates obtained from received uplink pilots and applies conjugate beamforming to transmit data to the users. We derive a closed-form expression for the achievable rate. This expression enables us...
We consider a full-duplex decode-and-forward system, where the wirelessly powered relay employs the time-switching protocol to receive power from the source and then transmit information to the destination. It is assumed that the relay node is equipped with two sets of antennas to enable full-duplex communications. Three different interference mitigation schemes are studied, namely, 1) optimal 2)...
In this paper, the throughput performance of a hybrid Multiple-Input-Multiple-Output (MIMO) interweave/underlay Cognitive Radio (CR) system is examined on an analytical basis. Specifically, hybrid CR systems that switch between an interweave and an underlay transmission strategy, based upon spectrum sensing measurements, are investigated. For the first time the performance of such a hybrid CR system...
In the 5th generation cellular system, a large-scale cloud radio access network is one of the most promising structures for providing high quality-of-service to end users. This extended abstract presents the impact of interference on such a system. Based on stochastic geometry and probabilistic order notation, the scaling exponents of the guaranteed signal-to-interference-plus-noise ratio and the...
In this work, we argue against the common belief that millimeter-wave (mmwave) technology is not a viable option for building general purpose indoor WLANs due to the high directionality and susceptibility to blockage of 60GHz links. Our initial experiments, with commodity 802.11ad hardware, present a very encouraging picture, as far as range and blockage by commonly found materials in indoor WLAN...
Multiuser diversity and beamforming are two techniques that promise dramatically increased system throughput and spectral efficiency. In most systems it has however been considered infeasible to utilize spatial channel information, due to the increased feedback load.
In this work, we significantly increase the peak rate of the wideband CDMA spatio-temporal array-receiver (STAR) by enabling its operation with high-order modulations (HOM) up to 256QAM (i.e., peak rate of 768 Kb/s per spreading code with 32 spreading factor and 1/2 coding rate in 5 MHz). In order to allow an effective rate control for adaptive modulation and maximize throughput with the resulting...
This paper focuses on the Medium Access Control (MAC) layer design for an inevitable Hidden Terminal problem in Multi User Multiple Input Multiple Output (MU-MIMO) Wireless Local Area Networks (WLANs). Specifically, our MAC design is supported by the precoding vectors obtained by Zeroforcing technique which are used to address the Hidden Terminals. An efficient channel sounding process is used by...
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