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  • 2551.
    Zetterberg, Per
    et al.
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Ottersten, Björn
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Experiments Using an Antenna Array in a Mobile Communications Environment1994Ingår i: IEEE Seventh SP Workshop on Statistical Signal and Array Processing, 1994, s. 137-140Konferensbidrag (Refereegranskat)
    Abstract [en]

    The goal of this paper is to obtain knowledge about spatial characteristics of the mobile channel seen through an antenna array. Particular interest is paid to the effect of local scattering. i.e large number of rays in the vicinity of the mobile.

  • 2552.
    Zetterberg, Per
    et al.
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Ottersten, Björn
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    The Spectrum Efficiency of a Base Station Antenna Array System for Spatially Selective Transmission1995Ingår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 44, nr 3, s. 651-660Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper we investigate the spectrum efficiency gain using  ransmittingantenna arrays at the base stations of a mobile cellular  etwork. The proposedsystem estimates the angular positions of the mobiles from the received data, and allows multiple mobiles to be allocated to the same channel within a cell. This is possible by applying a transmit scheme which directs nulls against co-channel users within the cell. It is shown that multiple mobiles per cell is an efficient way of increasing capacity in comparison with reduced channel reuse distance and narrow beams (without directed nulls). The effect of the spatial spread angle of the locally scattered rays in the vicinity of the mobile is also investigated

  • 2553.
    Zetterberg, Per
    et al.
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Ottersten, Björn
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    The Spectrum Efficiency of a Base-Station Antenna Array System for Spatially Selective Transmission1994Ingår i: IEEE 44th Vehicular Technology Conference, IEEE , 1994, s. 1517-1521Konferensbidrag (Refereegranskat)
    Abstract [en]

    The goal of this paper is to estimate the gain, in terms of system capacity at a given outage probability, which can be obtained by applying antenna arrays in the base stations of a mobile cellular network. For this purpose apropagation model which incorporates the angular distribution of the rays in the vicinity of the mobile is postulated. Also included in the model is the interference from co-channel cells. With the aid of the model, aweight selection algorithm is derived. The proposed system is simulated with different numbers of mobiles per channel in each cell and different numbers of antenna elements in the arrays. Also varied is the cluster size. This is done to determine the optimal trade-off between reduced cluster size and multiple mobiles per channel in each cell. The results show that it is possible to increase capacity between two and twelve times depending on thenumber of antennas in the arrays and the spread of the local scattering.

  • 2554.
    Zetterström, Oskar
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Kolitsidas, Christos
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Jonsson, B. Lars G.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Glazunov, A. A.
    A 28-port MIMO Cube for Micro Base Station Applications2020Ingår i: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel multi-band, dual-polarized, 28-port multiple-input multiple-output (MIMO) cube is presented. The cube structure enables dense placement of the antennas, whilst still allowing for low correlation between the individual antenna ports. The total size of the cube is roughly 2×2×7 λ30, where λ0 is the wavelength at the lowest used frequency. The novelty of the design lies in the use of a combination of orthogonally polarized endfire and broadside radiating antenna elements. Full use of all facets of the cube is achieved without the need to sacrifice bottom or top facets for mounting. Therefore, full azimuthal coverage for communication in two orthogonal polarizations is readily achieved. The system operates in both cellular and Wi-Fi 2:4, 5:5 GHz bands, with a targeted |S11| below –10 dB. The MIMO performance of the system is evaluated in two environments: the Rich Isotropic Multipath environment and the Random Line-of-Sight environment. These two scenarios represent the edge environments of any real-life propagation scenario in terms of the directional distribution of outgoing or incoming waves at a MIMO transceiver. The intended application of the system is micro base stations and repeaters, with possible extension to massive MIMO.

  • 2555.
    Zhai, Kai
    et al.
    Southwest Jiaotong Univ, Prov Key Lab Informat Coding & Transmiss, Chengdu 610031, Sichuan, Peoples R China..
    Ma, Zheng
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Lei, Xianfu
    Southwest Jiaotong Univ, Prov Key Lab Informat Coding & Transmiss, Chengdu 610031, Sichuan, Peoples R China..
    Closed-formed distribution for the SINR of MMSE-detected MIMO systems and performance analysis2018Ingår i: AEU - International Journal of Electronics and Communications, ISSN 1434-8411, E-ISSN 1618-0399, Vol. 97, s. 16-24Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we investigate the error performance of multiple-input multiple-output (MIMO) wireless communications systems using minimum mean-square error (MMSE) detection. Particularly, a new closed-form statistical distribution for the output signal-to-interference-plus-noise ratio (SINR) of MMSE receiver is derived, for independent Rayleigh fading channels. The expression for the distribution of SINR is shown to be a linear combination of gamma distributions and polynomial of where xis the SINR. Base on the derived distribution for the SINR, closed-form and approximated expressions for the symbol error probability (SEP) of quadrature amplitude modulation (QAM) and phase shift keying (PSK) signaling are obtained, respectively. The derived SINR density and SEP are valid for arbitrary number of transmit and receive antennas. Furthermore, a reduced complexity approximation is introduced to obtain the SINR distribution and SEP performance of MMSE-Detected MIMO Systems with a large number of antennas. The provided simulation results confirm the validity of our theoretical analysis for both the SINR and SEP. All rights reserved.

  • 2556. Zhan, M.
    et al.
    Pang, Z.
    Dzung, D.
    Xiao, Ming
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Channel Coding for High Performance Wireless Control in Critical Applications: Survey and Analysis2018Ingår i: IEEE Access, E-ISSN 2169-3536, Vol. 6, s. 29648-29664Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Demanded by high-performance wireless (WirelessHP) networks for industrial control applications, channel coding should be used and optimized. However, the adopted coding schemes in modern wireless communication standards are not sufficient for WirelessHP applications, in terms of both low latency and high reliability. Starting from the essential characteristics of WirelessHP regarding channel coding, this paper gives a detailed analysis of currently used short packet coding schemes in industrial wireless sensor networks, including seven coding schemes and their possible variants. The metrics employed for evaluation are bit-error rate, packet error rate, and throughput. To find suitable coding schemes from a large number of options, we propose four principles to filter the most promising coding schemes. Based on overall comparison from the perspective of practical implementation, challenges of the available coding schemes are analyzed, and directions are recommended for future research. Some reflections on how to construct specially designed coding schemes for short packets to meet the high reliability and low-latency constraints of WirelessHP are also provided.

  • 2557.
    Zhan, Ming
    et al.
    KTH. Royal Inst Technol, Stockholm, Sweden.;ABB Corp Res Ctr, Vasteras, Sweden.;Southwest Univ, Coll Elect & Informat Engn, Chongqing, Peoples R China..
    Pang, Zhibo
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap. KTH, Stockholm, Sweden.;Tsinghua Univ, Beijing, Peoples R China.;Zhejiang Univ, Hangzhou, Zhejiang, Peoples R China.;Beijing Univ Posts & Telecommun, Beijing, Peoples R China..
    Xiao, Ming
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap. Royal Inst Technol, Commun Theory, Sch Elect Engn & Comp Sci, Stockholm, Sweden..
    Luvisotto, Michele
    ABB Corp Res Ctr, Vasteras, Sweden..
    Dzung, Dacfey
    ABB Corp Res, Ind & Util Commun, Baden, Switzerland..
    Wireless High-Performance Communications Improving Effectiveness and Creating Ultrahigh Reliability with Channel Coding2018Ingår i: IEEE Industrial Electronics Magazine, ISSN 1932-4529, E-ISSN 1941-0115, Vol. 12, nr 3, s. 32-37Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To meet a set of stringent requirements for wireless control in critical applications, the described wireless high-performance (WirelessHP) communication system represents a breakthrough regarding microsecondlevel latency, but the proof of ultrahigh reliability is still lacking. To this aim, we propose the incorporation of channel coding in its physical layer. Building on a customized protocol stack and a hardware demonstrator, we prove the effectiveness of channel coding and suggest further research in this area.

  • 2558.
    Zhan, Zhengquan
    et al.
    Southwest Jiaotong Univ, Key Lab Informat Coding & Transmiss, Chengdu 610031, Sichuan, Peoples R China..
    Ma, Zheng
    Southwest Jiaotong Univ, Key Lab Informat Coding & Transmiss, Chengdu 610031, Sichuan, Peoples R China..
    Xiao, Ming
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap. Royal Inst Technol, Sch Elect Engn, Dept Informat Sci & Engn, SE-10044 Stockholm, Sweden..
    Lei, Xianfu
    Southwest Jiaotong Univ, Inst Mobile Commun, Chengdu 610031, Sichuan, Peoples R China.;Southeast Univ, Natl Mobile Commun Res Lab, Nanjing 210096, Jiangsu, Peoples R China..
    Ding, Zhiguo
    Univ Lancaster, Sch Comp & Commun, Lancaster LA1 4YW, England..
    Fan, Pingzhi
    Southwest Jiaotong Univ, Key Lab Informat Coding & Transmiss, Chengdu 610031, Sichuan, Peoples R China..
    Fundamental Tradeoffs of Non-Orthogonal Multicast, Multicast, and Unicast in Ultra-Dense Networks2018Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 66, nr 8, s. 3555-3570Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ultra-dense networks (UDNs) are the promising technology for the fifth-generation wireless networks and beyond to significantly boost network capacity and improve network coverage by exploiting spatial spectrum reuse through the deployment of massive base stations (BSs). In this paper, the fundamental tradeoffs of non-orthogonal multicast, multicast, and unicast in the UDN are studied, to understand the impact of network densitification on them and provide some insights on UDN deployment. Non-orthogonal multicast with imperfect channel estimation and successive interference cancellation is also investigated. To evaluate the performance, a tractable model for performance analysis is developed by using stochastic geometry, and then the analytical expressions for downlink signal-to-interference-plus-noise ratio coverage probability, spectrum efficiency, area traffic capacity, and energy efficiency are derived. The numerical results together with the Monte Carlo simulations are also provided. The results demonstrate that non-orthogonal multicast can further improve the performance of multicast and achieve higher spectrum efficiency, area traffic capacity, and energy efficiency than unicast from the low-to-high BS density regions, but suffers from inferior performance to unicast in the very high BS density region. The results also show that the non-orthogonal multicast and multicast exhibit different performance trends from unicast.

  • 2559.
    Zhang, Bo
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Location Based Pre-caching and Network Coding in Smart Content Distribution2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Since the boom of the smart phones, there is a huge amount of applicationsthat deal with data located in the cloud. This fact can makethese applications unavailable when the network is inaccessible due tocoverage or congestion. A solution to these problems have been designedand developed for the Android OS in this master thesis. The approachis the application of location-based pre-caching, downloading the contentof an application before the user enters in the zone where the applicationmay use this content. Network coding has also been introduced in orderto reduce the amount of data sent over the wireless networks. A cachingscheme is introduced in binary network coding and applied to the problemof retransmission in wireless broadcast network. A binary network codingalgorithm is designed which could asymptotically approach the efficiency of linear network coding with a much lower decoding complexity. 

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  • 2560.
    Zhang, Charlie Jianzhong
    et al.
    Univ Wisconsin, Madison, WI 53706 USA..
    Ma, Jianglei
    Huawei Canada R Ctr, Markham, ON, Canada..
    Li, Geoffrey Ye
    Georgia Tech, Atlanta, GA 30332 USA..
    Kishiyama, Yoshihisa
    Hokkaido Univ, Sapporo, Hokkaido, Japan..
    Parkvall, Stefan
    KTH. Ericsson Res, Kista, Sweden.
    Liu, Guangyi
    China Mobile Res Inst, Wireless & Device Dept, Beijing, Peoples R China..
    Kim, Young-Han
    Univ Calif San Diego, Dept Elect & Comp Engn, La Jolla, CA 92093 USA..
    Key Technology for 5G New Radio2018Ingår i: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 56, nr 3, s. 10-11Artikel i tidskrift (Refereegranskat)
  • 2561. Zhang, D.
    et al.
    Ileri, Ömer
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Mandayam, N.
    Bandwidth exchange as an incentive for relaying2008Ingår i: CISS 2008, The 42nd Annual Conference on Information Sciences and Systems, 2008, s. 749-754Konferensbidrag (Refereegranskat)
    Abstract [en]

    Relay cooperation has been recognized as an important mechanism to enhance connectivity and throughput in multi-hop wireless networks, especially under varying channel conditions. One major problem of relay cooperation is that relaying always incurs energy and possibly delay costs. To a rational and selfish node these costs are worth incurring only if it receives at least comparable returns in the long term. In light of this, we propose a new incentive mechanism called bandwidth exchange (BE) where a node can delegate a portion of its bandwidth to another node in exchange for relay cooperation. In this paper we specifically study BE in the simple form of exchanging orthogonal frequency bands to provide incentives for relaying in a wireless network. Other forms of exchanging bandwidth such as delegation of time-slots or using spreading codes of different lengths are also possible. Using a Nash Bargaining framework, we explore the advantage of BE in both static and fading channels.

  • 2562.
    Zhang, Guoqiang
    KTH, Skolan för elektro- och systemteknik (EES), Ljud- och bildbehandling.
    Robust Multimedia Communications over Packet Networks2010Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Multimedia communications over packet networks, and in particular the voice over IP (VoIP) application, have become an integral part of society. However, the unreliable and heterogeneous nature of packet networks has led to a best-effort delivery of services. Delay, limitation of bandwidth, and packet-loss rate all affect the quality of service (QoS). In this thesis, we address two important network impairments in the design of robust multimedia communication systems: packet delay-variation and packet-loss.

    Paper A considers the mitigation of the effect of packet delay-variation for audio communications by introducing a buffer at the receiver side. A new adaptive playout scheduling approach is proposed to control the buffering length, or, equivalently, the packet playout deadlines, in response to varying network conditions. A Wiener process is used to model the fluctuation of the buffering length without any playout adjustment. The playout scheduling problem is then reformulated as a stochastic impulse control problem by taking the playout adjustment as the control signal. The proposed approach is shown to be the optimal solution to the new control problem. It is demonstrated experimentally that the proposed approach provides improved perceived conversional quality.

    Papers B, C and D address the packet-loss issue. Paper B focuses on the design of a low-complexity packet-loss concealment (PLC) method that is compatible with existing speech codecs for VoIP application. The new method is rigorously motivated based on the autoregressive (AR) speech model and the minimum mean squared error (MMSE) criterion. The effect of model estimation error on the prediction of the missing speech segment is also considered and an upper bound for the prediction error is derived. Both the theoretical and experimental results provide insight in the performance of the heuristically designed PLC methods. On the other hand, Paper C and D consider an active packet-loss-resilient coding scheme, namely multiple description coding (MDC). In general, MDC can be used for the transmission of any media data. Paper C derives a simple and accurate approximation of the rate-distortion lower bound of a particular multiple- description scenario and then demonstrates that the performance loss of some practical MD systems can be evaluated easily with the new approximation. Paper D studies the performance limit of a vector Gaussian multiple description scenario. An outer bound to the rate-distortion region is derived, and the outer bound is tight when the problem specializes to the scalar Gaussian case.

     

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  • 2563.
    Zhang, Guoqiang
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Ljud- och bildbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Kleijn, W. Bastiaan
    KTH, Skolan för elektro- och systemteknik (EES), Ljud- och bildbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Østergaard, Jan
    KTH, Skolan för elektro- och systemteknik (EES), Ljud- och bildbehandling.
    Bounding the Rate Region of Vector Gaussian Multiple Descriptions with Individual and Central Receivers2010Ingår i: Data Compression Conference Proceedings, 2010, s. 13-19Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this work, we study the rate region of the vector Gaussian multipledescription problem with individual and central quadratic distortion con-straints. In particular, we derive an outer bound to the rate region of theL-description problem. The bound is obtained by lower bounding a weightedsum rate for each supporting hyperplane of the rate region. The key ideais to introduce at most L-1 auxiliary random variables and further imposeupon the variables a Markov structure according to the ordering of the de-scription weights. This makes it possible to greatly simplify the derivationof the outer bound. In the scalar Gaussian case, the complete rate regionis fully characterized by showing that the outer bound is tight. In this case,the optimal weighted sum rate for each supporting hyperplane is obtained bysolving a single maximization problem. This contrasts with existing results,which require solving a min-max optimization problem.

  • 2564.
    Zhang, Guoqiang
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Lundin, Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Kleijn, W. Bastiaan
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Band control policy of playout scheduling for voice over IP2008Ingår i: Proceedings European Signal Processing Conference, 2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    We study adaptive-playout scheduling for VoIP using the framework of stochastic impulse control theory. A Wiener process is introduced to model the fluctuation of the buffer length in the absence of control. In this context, the control signal consists of length units that correspond to inserting or dropping a pitch cycle. We define an optimality criterion that has an adjustable trade-off between average buffing delay and average control length (the length of the pitch cycles added plus the length of the pitch cycles dropped). The clock-drift effect is treated in a unified manner within this framework. A band control policy is shown to be optimal. The algorithm does not require knowledge of the clock drift. It maintains the buffer length within a band region by imposing impulse control (inserted or dropped pitch cycles) whenever the bounds of the band are reached. Our experiments show that the proposed method outperforms a popular reference method.

  • 2565. Zhang, H.
    et al.
    Wang, S.
    Gong, Y.
    Liu, T.
    Xu, Tianhua
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Optik och Fotonik, OFO.
    Jia, D.
    Zhang, Y.
    A quantitative robustness evaluation model for optical fiber sensor networks2013Ingår i: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 31, nr 8, s. 1240-1246Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Optical fiber sensor networks (OFSNs) are facing the problem of a lack of systematic evaluation criteria to assess network performance. In this paper, a universal quantitative robustness evaluation model for OFSNs is proposed. The model defines robustness as the mathematical expectation of the monitoring coverage ratio, which has taken into account the performance under all possible network states and the probability of each state. This model is applied to four basic network topologies including line, ring, star and bus topologies, and their mathematical expressions of robustness are derived by analyzing all possible states in detail. Further simulation gives a quantitative comparison among these topologies, proving that the ring and star topologies are optimal for the monitoring of strip-shaped and square regions, respectively. Finally, two influencing factors, the attenuation coefficient and the threshold, are investigated for their impact on the robustness of the network.

  • 2566. Zhang, Haibo
    et al.
    Osterlind, Fredrik
    Soldati, Pablo
    Voigt, Thiemo
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Time-Optimal Convergecast With Separated Packet Copying: Scheduling Policies and Performance2015Ingår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 64, nr 2, s. 793-803Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Convergecast, in which packets originating from multiple sources are reported to a single sink, is a fundamental primitive for data collection in wireless sensor networks. This paper investigates the time-optimal link-scheduling problem for time-division multiple-access (TDMA)-based convergecast, aiming to minimize the amount of time required to complete convergecast. We observe that packet copying between the microcontroller and the radio transceiver in existing sensor platforms has a big impact on the packet forwarding delay, and we propose a novel model for convergecast in which packet copying is separated from packet transmission and reception. We establish tight lower bounds on the number of time slots required for convergecast in networks with line and tree routing topologies, and we present both centralized and distributed algorithms for constructing the time-optimal convergecast schedules. We evaluate our scheme in both simulations and experiments on hardware. The results show that our scheme can achieve a system throughput (defined as the number of data bits received by the sink per second) of 202.8 kb/s, which is 86.31% of the theoretical bound. In comparison with the traditional TDMA-based convergecast schemes, our scheme can achieve up to a 86.22% improvement on system throughput.

  • 2567.
    Zhang, Haibo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Soldati, Pablo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Optimal Link Scheduling and Channel Assignment for Convergecast in Linear Wireless HART Networks2009Ingår i: 2009 7TH INTERNATIONAL SYMPOSIUM ON MODELING AND OPTIMIZATION IN MOBILE, AD HOC, AND WIRELESS, NEW YORK: IEEE , 2009, s. 82-89Konferensbidrag (Refereegranskat)
    Abstract [en]

    Convergecast, in which data from a set of sources is routed toward one data sink, is a critical functionality for wireless networks deployed for industrial monitoring and control. We address the joint link scheduling and channel assignment problem for convergecast in networks operating according to the recent WirelessHART standard. For a linear network with N single-buffer devices, we demonstrate that the minimum time to complete convergecast is 2N - 1 time-slots, and that the minimum number of channels required for this operation is inverted right perpendicularN/2inverted left perpendicular. When the devices are allowed to buffer multiple packets, we prove that the optimal convergecast time remains the same while the number of required channels can be reduced to inverted right perpendicularN - root N-(N-1)/2inverted left perpendicular. For both cases, we present jointly time- and channel-optimal scheduling policies with complexity O(N-2). Numerical results demonstrate that our schemes are also efficient in terms of memory utilization.

  • 2568. Zhang, Haibo
    et al.
    Soldati, Pablo
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Performance Bounds and Latency-Optimal Scheduling for Convergecast in WirelessHART Networks2013Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 12, nr 6, s. 2688-2696Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Convergecast, in which data from a set of source devices is delivered to a single data sink, is a critical functionality in networks deployed for industrial monitoring and control. We address the latency-optimal link scheduling problem for convergecast in networks operating according to the recent WirelessHART standard. When there is no restriction on the number of channels, we present a latency-optimal scheduling policy in which each routing node is required to buffer at most one packet at any point in time. For networks with a limited number of channels, we first establish a lower bound on the number of channels for latency-optimal convergecast and a lower bound on latency for convergecast using a fixed number of channels, and then present a heuristic scheme for channel-constrained latency-optimal convergecast scheduling. Simulation results confirm that, at much modest computational cost, our heuristic scheme can construct convergecast schedules with latency close to that of the optimal schedules.

  • 2569. Zhang, L.
    et al.
    Tang, M.
    Feng, Z.
    Wang, R.
    Lin, Rin
    KTH, Skolan för informations- och kommunikationsteknik (ICT). School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, China.
    Xu, L.
    Wang, X.
    Zhou, C.
    Wu, J.
    Zhou, S.
    Deng, L.
    Fu, S.
    Liu, D.
    Shum, P.P.
    Low-cost in-band OSNR monitoring based on coherent hybrid in CO-OFDM system2015Ingår i: CLEO: Science and Innovations, CLEO-SI 2015, 2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    We proposed and demonstrated a cost-effective in-band optical signal to noise ratio (OSNR) monitoring technique based on coherent hybrid in 20Gb/s CO-OFDM system. Less than 0.5dB monitoring error is achieved with 400MHz balanced photodetector (PD).

  • 2570. Zhang, L.
    et al.
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Wu, G.
    Li, S.
    Liang, Y. -C
    Energy-efficient transmission with imperfect spectrum sensing in cognitive radio2016Ingår i: 2016 IEEE International Conference on Communications, ICC 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, s. 162-167, artikel-id 7510686Konferensbidrag (Refereegranskat)
    Abstract [en]

    We investigate the energy efficiency (EE) in cognitive radio networks, where cognitive users are allowed to access the licensed frequency band opportunistically, provided that the licensed band is vacant. In particular, we study the impact of imperfect spectrum sensing and formulate the EE maximization as a joint optimization problem of the spectrum sensing duration and the transmit power of the cognitive transmitter. Specially, we consider the constraints of both the collision probability between the primary and cognitive transmission and the outage probability of the cognitive transmission. Since the joint optimization problem of the sensing duration and the transmit power is hard to be solved directly, we decompose it into two sub-problems with the spectrum sensing duration and the transmit power as variables, respectively. Based on the analytical solvers of the two sub-problems, we propose an iterative-based algorithm to solve the joint optimization problem. Finally, numerical results are provided to validate the analysis and performance of our proposed algorithms.

  • 2571. Zhang, Lin
    et al.
    Liu, Jiaqi
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Teknisk informationsvetenskap.
    Wu, Gang
    Liang, Ying-Chang
    Li, Shaoqian
    Performance Analysis and Optimization in Downlink NOMA Systems With Cooperative Full-Duplex Relaying2017Ingår i: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 35, nr 10, s. 2398-2412Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study a downlink non-orthogonal multiple access system with cooperative full-duplex relaying, where the near user in terms of the base station (BS) is enabled to act as a full-duplex relay for the far user. In particular, we first derive the outage probability and ergodic sum rate with closed-form expressions when the power allocations at the BS and relay (or the near user) are fixed. Then, we analytically obtain the optimal power allocations with closed-form expressions at the BS and relay to minimize the outage probability. Furthermore, by taking the fairness between the near user and far user into account, we characterize the optimal power allocations with closed-form expressions at the BS and relay to maximize the minimum achievable rate of users. Simulation results validate the correctness of the theoretical analysis and demonstrate the advantages of the proposed algorithms over the state of the art.

  • 2572.
    Zhang, Lin
    et al.
    Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu, Sichuan, Peoples R China..
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES). Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu, Sichuan, Peoples R China.
    Liu, Jiaqi
    Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu, Sichuan, Peoples R China..
    Wu, Gang
    Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu, Sichuan, Peoples R China..
    Lin, Dengsheng
    Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu, Sichuan, Peoples R China..
    Li, Shaoqian
    Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu, Sichuan, Peoples R China..
    Outage Probability Analysis and Optimization in Downlink NOMA Systems with Cooperative Full-duplex Relaying2017Ingår i: 2017 IEEE 86th Vehicular Technology Conference (VTC-FALL), Institute of Electrical and Electronics Engineers (IEEE), 2017, Vol. 2017, s. 1-5Konferensbidrag (Refereegranskat)
    Abstract [en]

    We study a downlink non-orthogonal multiple access (NOMA) system with cooperative full-duplex relaying, where the near user in terms of the base station (BS) is enabled to act as a full-duplex relay for the far user. In particular, we first derive the outage probability with closed-form expressions when the power allocations at the BS and relay (or the near user) are fixed. Then, we analytically obtain the optimal power allocations with closed-form expressions at the BS and relay to minimize the outage probability. Numerical results validate the correctness of the theoretical analysis and demonstrate the advantages of the proposed algorithms over the state of arts.

  • 2573. Zhang, Lin
    et al.
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Wu, Gang
    Li, Shaoqian
    Efficient Scheduling and Power Allocation for D2D-Assisted Wireless Caching Networks2016Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 64, nr 6, s. 2438-2452Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study a one-hop device-to-device (D2D)-assisted wireless caching network, where popular files are randomly and independently cached in the memory of end users. Each user may obtain the requested files from its own memory without any transmission, or from a helper through a one-hop D2D transmission, or from the base station. We formulate a joint D2D link scheduling and power allocation problem to maximize the system throughput. However, the problem is non-convex, and obtaining an optimal solution is computationally hard. Alternatively, we decompose the problem into a D2D link-scheduling problem and an optimal power allocation problem. To solve the two subproblems, we first develop a D2D link-scheduling algorithm to select the largest number of D2D links satisfying both the signal to interference plus noise ratio and the transmit power constraints. Then, we develop an optimal power allocation algorithm to maximize the minimum transmission rate of the scheduled D2D links. Numerical results indicate that both the number of the scheduled D2D links and the system throughput can be improved simultaneously with the Zipf-distribution caching scheme, the proposed D2D link-scheduling algorithm, and the proposed optimal power allocation algorithm compared with the state of the arts.

  • 2574. Zhang, Lin
    et al.
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Wu, Gang
    Li, Shaoqian
    Liang, Ying-Chang
    Energy-Efficient Cognitive Transmission With Imperfect Spectrum Sensing2016Ingår i: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 34, nr 5, s. 1320-1335Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigate the energy efficiency (EE) in cognitive radio networks, where cognitive users are allowed to access a licensed frequency band opportunistically, provided that the licensed band is vacant. In particular, we study the impact of imperfect spectrum sensing and formulate the average EE maximization problem in fading channels as a joint optimization problem of the spectrum sensing duration and the transmit power of cognitive users. Meanwhile, we consider the constraints of both the collision probability between the primary and cognitive transmissions and the outage probability of cognitive transmissions. However, the joint optimization problem subject to the constraints is complicated and it is computationally hard to obtain the optimal solution. Alternatively, we develop two algorithms, i.e., a linear search algorithm and an iterative-based algorithm, with considerable complexity to solve the problem. Numerical results verify the correctness of both algorithms and show that the proposed algorithms can achieve the performance close to that of the exhaustive search algorithm and outperform the state of arts.

  • 2575.
    Zhang, Lu
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Datavetenskap, Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Udalcovs, Aleksejs
    Lin, Rui
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Datavetenskap, Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Ozolins, Oskars
    Pang, Xiaodan
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Datavetenskap, Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Gan, L.
    Schatz, Richard
    Djupsjöbacka, A.
    Mårtensson, J.
    Tang, M.
    Fu, S.
    Liu, D.
    Tong, W.
    Popov, Sergei
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Fotonik.
    Jacobsen, Gunnar
    Hu, W.
    Xiao, S.
    Chen, Jiajia
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Datavetenskap, Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Digital Radio-Over-Multicore-Fiber System with Self-Homodyne Coherent Detection and Entropy Coding for Mobile Fronthaul2018Ingår i: European Conference on Optical Communication, ECOC, Institute of Electrical and Electronics Engineers (IEEE), 2018, artikel-id 8535281Konferensbidrag (Refereegranskat)
    Abstract [en]

    We experimentally demonstrate a 28-Gbaud 16-QAM self-homodyne digital radio-over-33.6km-7-core-fiber system with entropy coding for mobile fronthaul, achieving error-free carrier aggregation of 330 100-MHz 4096-QAM 5G-new-radio channels and 921 100-MHz QPSK 5G-new-radio channels with CPRI-equivalent data rate up to 3.73-Tbit/s.

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  • 2576.
    Zhang, Lu
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Udalcovs, Aleksejs
    RISE Res Inst Sweden AB, Gothenburg, Sweden..
    Lin, Rui
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Ozolins, Oskars
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Fotonik.
    Pang, Xiaodan
    Infinera Metro HW R&D, Stockholm, Sweden..
    Gan, Lin
    HUST, Next Generat Internet Access Syst Not Engn Lab, Wuhan, Hubei, Peoples R China..
    Schatz, Richard
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Fotonik.
    Tang, Ming
    Huazhong Univ Sci & Technol, Wuhan, Hubei, Peoples R China..
    Fu, Songnian
    Huazhong Univ Sci & Technol, Wuhan, Hubei, Peoples R China..
    Liu, Deming
    Huazhong Univ Sci & Technol, Wuhan, Hubei, Peoples R China..
    Tong, Weijun
    Yangtze Opt Fibre & Cable Joint Stock Ltd Co, Speical Bussiness Unit, Wuhan, Hubei, Peoples R China..
    Popov, Sergei
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Fotonik.
    Jacobsen, Gunnar
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Fotonik.
    Hu, Weisheng
    Shanghai Jiao Tong Univ, Shanghai, Peoples R China..
    Xiao, Shilin
    Shanghai Jiao Tong Univ, Shanghai, Peoples R China..
    Chen, Jiajia
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Toward Terabit Digital Radio over Fiber Systems: Architecture and Key Technologies2019Ingår i: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 57, nr 4, s. 131-137Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To support massive deployment of broadband radio applications, such as 5G and high-definition videos for terrestrial televisions, large system capacity and high spectrum efficiency are highly demanded in radio over fiber (RoF) systems. In this article, we propose a terabit digital RoF system capable of providing high-speed transmission, where multicore fiber (MCF) is introduced for the access segment between the central unit and remote unit. Two key technologies that greatly enhance system capacity and spectrum efficiency, namely MCF enabled self-homodyne detection and compressed quantization, are demonstrated.

  • 2577.
    Zhang, Lu
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Van Kerrebrouck, Joris
    Univ Ghent, IMEC, IDLab, Dept Informat Technol, B-9000 Ghent, Belgium..
    Lin, Rui
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Pang, Xiaodan
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Udalcovs, Aleksejs
    RISE Acreo AB, NETLAB, SE-16425 Kista, Sweden..
    Ozolins, Oskars
    RISE Acreo AB, NETLAB, SE-16425 Kista, Sweden..
    Spiga, Silvia
    Tech Univ Munich, Walter Schottky Inst, D-85748 Garching, Germany..
    Amann, Markus-Christian
    Tech Univ Munich, Walter Schottky Inst, D-85748 Garching, Germany..
    Van Steenberge, Geert
    Univ Ghent, IMEC, Ctr Microsyst Technol, B-9052 Ghent, Belgium..
    Gan, Lin
    Huazhong Univ Sci & Technol, WNLO, Wuhan 430074, Hubei, Peoples R China..
    Tang, Ming
    Huazhong Univ Sci & Technol, WNLO, Wuhan 430074, Hubei, Peoples R China..
    Fu, Songnian
    Huazhong Univ Sci & Technol, WNLO, Wuhan 430074, Hubei, Peoples R China..
    Schatz, Richard
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Fotonik.
    Popov, Sergei
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Fotonik.
    Liu, Deming
    Huazhong Univ Sci & Technol, WNLO, Wuhan 430074, Hubei, Peoples R China..
    Tong, Weijun
    Yangtze Opt Fibre & Cable Co Ltd YOFC, Wuhan 430073, Hubei, Peoples R China..
    Xiao, Shilin
    Shanghai Jiao Tong Univ, State Key Lab Adv Opt Commun Syst & Networks, Shanghai 200240, Peoples R China..
    Torfs, Guy
    Univ Ghent, IMEC, IDLab, Dept Informat Technol, B-9000 Ghent, Belgium..
    Chen, Jiajia
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Bauwelinck, Johan
    Univ Ghent, IMEC, IDLab, Dept Informat Technol, B-9000 Ghent, Belgium..
    Yin, Xin
    Univ Ghent, IMEC, IDLab, Dept Informat Technol, B-9000 Ghent, Belgium..
    Nonlinearity Tolerant High-Speed DMT Transmission With 1.5-mu m Single-Mode VCSEL and Multi-Core Fibers for Optical Interconnects2019Ingår i: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 37, nr 2, s. 380-388Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We experimentally demonstrate the generation of 107-Gbit/s net-rate optical discrete multitone signal using a 1.5-mu m single-mode vertical cavity surface emitting laser (VCSEL) with modulation bandwidth of 22 GHz. Utilizing a nonlinearity-tolerant channel equalization algorithm for digital signal processing, total net-rates of 726.6-Gbit/s over 2.5-km dispersion-uncompensated 7-core fiber and 533.1-Gbit/s over 10-km dispersion-compensated 7-core fiber below 7% overhead hard-decision forward error correction limit have been experimentally achieved with a 1.5-mu m VCSEL-based intensity-modulation direct-detection system. The features of the 1.5-mu m single-mode VCSEL, 2.5-km/10km multi-core fibers, and fan-in/fan-out modules are presented. Besides, the Volterra series-based nonlinearity-tolerant channel equalization algorithm, which improves the signal-to-noise ratio with more than 5 dB, is mathematically described and experimentally validated. The results have demonstrated that 1.5-mu m single-mode VCSEL and multi-core-fiber-based transmission can be a promising candidate to solve the capacity challenges in short-reach optical interconnects.

  • 2578. Zhang, S.
    et al.
    Zhao, Kun
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Ying, Z.
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Body loss study of beamforming mode in LTE MIMO mobile terminals2015Ingår i: 2015 9th European Conference on Antennas and Propagation, EuCAP 2015, IEEE conference proceedings, 2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper mainly focuses on the investigation of the body loss of beamforming mode in LTE MIMO mobile terminals with CTIA user effects. The research of the body loss and radiation efficiency is carried out over different phase differences between two ports of each MIMO antenna. During studies, four kinds of typical LTE MIMO antennas are used, namely, collocated ground free (GF), parallel GF, parallel on ground (OG) and orthogonal OG MIMO antennas, under four mobile terminal lengths at low and high frequencies. Two kinds of CTIA user effects are included in the research. From the studies, the parallel GF MIMO antenna type exhibits the best beamforming performance in the four MIMO antenna types. In order to verify the simulations, envelope correlation coefficients of two MIMO antenna prototypes are measured. All the measured results agree well with the simulated.

  • 2579.
    Zhang, Shuai
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Alayón Glazunov, Andrés
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Ying, Zhinong
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Reduction of the envelope correlation coefficient with improved total efficiency for mobile LTE MIMO antenna arrays: Mutual scattering mode2013Ingår i: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 61, nr 6, s. 3280-3291Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A mutual scattering mode is introduced in this paper. Utilizing this mode, the correlation of a lossy long-term evolution (LTE) multiple-input and multiple-output (MIMO) antenna array can be reduced efficiently, even down to zero, by increasing the Q factors of the MIMO antenna elements. In practice, the Q factors can be straight forwardly tuned through different input impedance matching. The zero correlation occurs at a Q factor higher than that resulting from the conjugate input impedance matching. On one hand, if the inter-element distance is larger than a certain distance (what we denominate as the Critical Distance), the total efficiency can also be improved in addition to reducing the correlation. On the other hand, when the inter-element distance is less than the critical distance, a reference MIMO antenna with high correlation and high total efficiency is obtained. This antenna can well be proposed for over-the-air (OTA) measurement applications. The introduced scattering mode is investigated for dual monopoles on a large lossy ground plane and for various mobile terminal MIMO antenna designs. A wideband MIMO antenna, with multiple resonances, covering the band 746-870 MHz is proposed with the envelope correlation coefficient and total efficiency less than 0.5 and higher than 50% (-3 dB), respectively. Measurements and simulations agree well for all the fabricated prototypes. The envelope correlations and the multiplexing efficiencies of the prototypes are also investigated in propagation channels with Gaussian distributed angle of arrivals.

  • 2580.
    Zhang, Shuai
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Lau, Buon Kiong
    Tan, Yi
    Ying, Zhinong
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Mutual Coupling Reduction of Two PIFAs With a T-Shape Slot Impedance Transformer for MIMO Mobile Terminals2012Ingår i: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 60, nr 3, s. 1521-1531Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An efficient technique is introduced to reduce mutual coupling between two closely spaced PIFAs for MIMO mobile terminals. The proposed mutual coupling reduction method is based on a T-shape slot impedance transformer and can be applied to both single-band and dual-band PIFAs. For the proposed single-band dual PIFAs, the 10 dB impedance bandwidth covers the 2.4 GHz WLAN band (2.4-2.48 GHz), and within the WLAN band an isolation of over 20 dB is achieved. Moreover, the dual-band version covers both the WLAN band and the WiMAX band of 3.4-3.6 GHz, with isolations of over 19.2 dB and 22.8 dB, respectively. The efficiency, gain and radiation patterns of the two-PIFA prototypes are verified in measurements. Due to very low pattern correlation and very good matching and isolation characteristics, the capacity performances are mainly limited by radiation efficiency. The single-band and dual-band PIFAs are also studied with respect to their locations on the ground plane. An eight-fold increase in the bandwidth of one PIFA is achieved, when the single-band PIFAs are positioned at one corner of the ground plane, with the bandwidth of the other PIFA and the good isolation unchanged.

  • 2581.
    Zhang, Shuai
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Ying, Zhinong
    Zhao, Kun
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Diagonal Antenna-Chassis Mode and Its Application for Wideband LTE MIMO Antennas in Mobile HandsetsArtikel i tidskrift (Övrigt vetenskapligt)
  • 2582.
    Zhang, Shuai
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Zetterberg, Per
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Printed MIMO antenna system of four closely-spaced elements with large bandwidth and high isolation2010Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 46, nr 15, s. 1052-1053Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A compact wideband printed MIMO antenna system (of four elements) with high isolation is presented. The proposed MIMO antenna system with an overall lateral size of only 0.43 lambda x 0.43 lambda can offer 22.8% bandwidth (1.63-2.05 GHz) and isolation of better than 24 dB. The measured gain is larger than 2.72 dBi over the whole band, and the calculated envelope correlation coefficient is better than 0.01. The radiation patterns and MIMO channel capacity are also measured.

  • 2583.
    Zhang, Shuai
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Zhao, Kun
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Ying, Zhinong
    Bolin, Thomas
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Body Loss and MIMO Performance Investigation of Different Mobil Terminal LTE MIMO Antenna Typer with User EffectsArtikel i tidskrift (Övrigt vetenskapligt)
  • 2584.
    Zhang, Shuai
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Zhao, Kun
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Ying, Zhinong
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Adaptive Quad-Element Multi-Wideband Antenna Array for User-Effective LTE MIMO Mobile Terminals2013Ingår i: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 61, nr 8, s. 4275-4283Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An LTE MIMO antenna array, which is adaptive to the effects of the user's body, is presented for mobile terminals. The bands of 750-960 MHz and 1700-2700 MHz are covered with a good efficiency in free space. Three kinds of user effects are studied, namely, "SAM head and PDA hand," "PDA hand," and "dual hands." The array is formed by selecting the best two elements out of four, with the two ports and grounding points of the other two elements open. The user effects on MIMO channel capacity are reduced through the adaptive selection of two optimal antenna elements. The total efficiency, envelope correlation coefficient, and multiplexing efficiency are presented for the three kinds of user effects. In the lower band, the decreased correlation due to the optimal selection improves the multiplexing efficiency. The underlying physical mechanisms and some general rules are discussed. The specific absorption rate (SAR) in the "SAM head and PDA hand" case is studied. Experiments for the three kinds of user effects are also carried out.

  • 2585.
    Zhang, Shuai
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Zhao, Kun
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Ying, Zhinong
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Diagonal Antenna-Chassis Mode for Wideband LTE MIMO Antenna Arrays in Mobile Handsets (Invited)2013Ingår i: 2013 International Workshop on Antenna Technology, iWAT 2013, IEEE , 2013, s. 407-410Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, the diagonal antenna-chassis mode is introduced to reduce the correlation between MTMO antenna elements. With this mode a wideband LTE MIMO antenna array is proposed, which can cover an impedance bandwidth of 747-960 MHz with an envelope correlation coefficient (ECC) less than 0.5 and an total efficiency better than -3 dB.

  • 2586.
    Zhang, Shuai
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Zhao, Kun
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Zhu, Bangguo
    Ying, Zhinong
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    MIMO Reference Antennas with Controllable Correlations and Total Efficiencies2014Ingår i: Progress In Electromagnetics Research, ISSN 1070-4698, E-ISSN 1559-8985, Vol. 145, s. 115-121Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    MIMO reference antennas are proposed for over the air (OTA) measurement applications. The reference antennas could get rid of feeding cable interference and control envelope correlation coefficients (ECC) continuously by only changing the length of an etched slot on a dual-feed PIFA. If only the ECC is investigated, the MIMO reference antenna is optimized to have a small variation of total efficiency from 70% to 50% when the ECC increases from 0.1 to 0.88. The prototypes are fabricated and measured in a scattered field chamber (SFC). Measurements agree well with the simulations. If the MIMO performance is studied, the MIMO reference antenna is proposed to own a large variation of total efficiencies from 90% to 47% while the ECC increases from 0 to 0.98. The bandwidth of the proposed reference antennas depend on the size of the antennas. This method is valid for all the frequencies.

  • 2587.
    Zhang, Xi
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Transceiver Design for Multiple Antenna Communication Systems with Imperfect Channel State Information2008Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    Wireless communication links with multiple antennas at both the transmitter and the receiver sides, so-called multiple-input-multiple-output (MIMO)systems, are attracting much interest since they can significantly increase the capacity of band-limited wireless channels to meet the requirements of the future high data rate wireless communications. The treatment of channel state information (CSI) is critical in the design of MIMO systems. Accurate CSI at the transmitter is often not possible or may require high feedback rates, especially in multi-user scenarios. Herein, we consider the robust design of linear transceivers with imperfect CSI either at the transmitter or at both sides of the link. The framework considers the design problem where the imperfect CSI consists of a channel mean and an channel covariance matrix or, equivalently, a channel estimate and an estimation error covariance matrix.

    For single-user systems, the proposed robust transceiver designs are based on a general cost function of the average mean square errors. Under different CSI conditions, our robust designs exhibit a similar structure to the transceiver designs for perfect CSI, but with a different equivalent channel and/or noise covariance matrix. Utilizing majorization theory, the robust linear transceiver design can be readily solved by convex optimization approaches in practice.

    For multi-user systems, we consider both the communication link from the users to the access point (up-link) as well as the reverse link from the access point to the users (down-link). For the up-link channel, it is possible to optimally design robust linear transceivers minimizing the average sum mean square errors of all the data streams for the users. Our robust linear transceivers are designed either by reformulating the optimization problem as a semidefinite program or by extending the design of a single-user system in an iterative manner. Under certain channel conditions, we show that the up-link design problem can even be solved partly in a distributed fashion.

    For the down-link channel, a system with one receive antenna per user is considered. A robust system design is obtained by reducing the feedback load from all users to allow only a few selected users to feed back accurate CSI to the access point. We study the properties of four typical user selection algorithms in conjunction with beamforming that guarantee certain signal-to-interference-plus-noise ratio (SINR) requirements under transmit power minimization. Specifically, we show

    that norm-based user selection is asymptotically optimal in the number of transmitter antennas and close-to-optimal in the number of users. Rooted in the practical significance of this result, a simpler down-link system design with reduced feedback requirements is proposed.

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  • 2588.
    Zhang, Xi
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Jorswieck, Eduard A.
    Communications Laboratory, Faculty of Electrical Engineering and Information Technology,Dresden University of Technology (TUD), Germany.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Paulraj, Arogyasvsami
    Information Systems Laboratory, Stanford University, US.
    On the Asymptotic Optimality of Opportunistic Norm-Based User Selection with Hard SINR Constraint2009Ingår i: EURASIP Journal on Advances in Signal Processing, ISSN 1687-6172, E-ISSN 1687-6180, ISSN 1687-6172Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recently, user selection algorithms in combination with linear precoding have been proposed that achieve the same scaling as the sum capacity of the MIMO broadcast channel. Robust opportunistic beamforming, which only requires partial channel state information for user selection, further reduces feedback requirements. In this work, we study the optimality of the opportunistic norm-based user selection system in conjunction with hard SINR requirements under max-min fair beamforming transmit power minimization. It is shown that opportunistic norm-based user selection is asymptotically optimal, as the number of transmit antennas goes to infinity when only two users are selected in high SNR regime. The asymptotic performance of opportunistic norm-based user selection is also studied when the number of users goes to infinity. When a limited number of transmit antennas and/or median range of users are available, only insignificant performance degradation is observed in simulations with an ideal channel model or based on measurement data.

  • 2589.
    Zhang, Xi
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Jorswieck, Eduard A.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Paulraj, Arogyaswami
    Information Systems Laboratory, Stanford University, USA.
    MSE based optimization of multiuser MIMO MAC with partial CSI2006Ingår i: 2006 Fortieth Asilomar Conference on Signals, Systems and Computers, 2006, s. 374-378Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper studies the optimal transmission design for multiple antenna multiple access channels with linear MMSE receiver at the base station and partial channel state information at the mobiles. The performance criterium for optimization is based on a Schur-concave function that works on the average individual MSEs of all users. The optimal beamforming matrix of each user corresponds to the eigenvector matrix of his channel correlation matrix. The remaining power allocation problem can be solved at reduced complexity. It is also direct to extend the results to Schur-convex functions. The results are illustrated by numerical simulations.

  • 2590.
    Zhang, Xi
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Jorswieck, Eduard A.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Paulraj, Arogyaswami
    Information Systems Laboratory, Stanford University, USA.
    User selection schemes in multiple antenna broadcast channels with guaranteed performance2007Ingår i: 2007 IEEE 8TH WORKSHOP ON SIGNAL PROCESSING ADVANCES IN WIRELESS COMMUNICATIONS, NEW YORK: IEEE , 2007, s. 1-5Konferensbidrag (Refereegranskat)
    Abstract [en]

    Recently, user selection algorithms in combination with linear precoding have been proposed that achieve the same scaling as the sum capacity of the MIMO BC. In this work, we study the properties of four user selection algorithms in conjunction with beamforming that guarantee certain SINR requirements under transmit power minimization. It is shown that for a large number of transmit antennas, the norm-based user selection performs close to the optimum. The results are illustrated by various numerical simulations.

  • 2591.
    Zhang, Xi
    et al.
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Ottersten, Björn
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Joint space-frequency optimization in multi user MIMO system2003Ingår i: PROCEEDINGS OF THE 3RD IEEE INTERNATIONAL SYMPOSIUM ON SIGNAL PROCESSING AND INFORMATION TECHNOLOGY, NEW YORK: IEEE , 2003, s. 170-173Konferensbidrag (Refereegranskat)
    Abstract [en]

    Herein, joint space-time multiplexing in a multi carrier multiple input multiple output (MIMO) system is considered. Previous results concerning spatial multiplexing optimization are used to address the joint problem of carrier assignment and choice of beamforming weights in a multi user MIMO system. For practical reasons, the joint optimization is divided into two parts: subcarrier assignment based on beamformer characteristics to adjust the carrier load, followed by beamforming optimization with subcarrier reassignment. The goal is to minimize total downlink transmit power while keeping fixed user data rates. The proposed multiplexing scheme is evaluated on a number of numerical examples.

  • 2592.
    Zhang, Xi
    et al.
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Ottersten, Björn
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Joint Space-Frequency Optimization in Multi User MIMO System2003Ingår i: IEEE International Symposium on Signal Processing and Information Technology, IEEE , 2003, s. 170-173Konferensbidrag (Refereegranskat)
    Abstract [en]

    Herein, joint space-time multiplexing in a multi carrier multiple input multiple output (MIMO) system is considered. Previous results concerning the spatial multiplexing optimization are used to address the joint problem of carrier assignment and choice of beamforming weights in a multi user MIMO system. For practical reasons, the joint optimization is divided into two parts: subcarrier assignment based on beamformer characteristics to adjust the carrier load, followed by beamforming optimization with subcarrier reassignment. The goal is to minimize total downlink transmit power while keeping the fixed user data rates. The proposed multiplexing scheme is evaluated on a number of numerical examples.

  • 2593.
    Zhang, Xi
    et al.
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Ottersten, Björn
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Power Allocation and Bit Loading for Spatial Multiplexing in MIMO Systems2003Ingår i: Proceedings IEEE International Conference on Acoustics, Speech, and Signal Processing, 2003, s. 53-56Konferensbidrag (Refereegranskat)
    Abstract [en]

    The power assignment problem is important for Multiple-Input-Multiple-Output (MIMO) systems to achieve high capacity. Although this problem is solved by well-known water filling algorithms, this does not provide an optimal solution if the system is constrained to a fixed raw bit error rate threshold and to discrete modulation orders. In this work an approximate approach, called QoS based WF, is proposed to solve the power assignment problem with such constrains. It is shown to outperform quantization of the conventional water filling solution and a well known bit loading algorithm (Chow’s algorithm) used in the Digital Subscriber Lines (DSL).

  • 2594.
    Zhang, Xi
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Palomar, Daniel P.
    Dept. of Electrical Engineering, Princeton University Princeton, NJ 08544, USA.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Robust design of linear MIMO transceiver for low SNR2005Ingår i: 2005 39th Asilomar Conference on Signals, Systems and Computers, Vols 1 and 2, NEW YORK: IEEE , 2005, s. 398-402Konferensbidrag (Refereegranskat)
    Abstract [en]

    In practical systems, the design of linear MIMO transceivers should be robust to partial or imperfect channel state information (CSI). This paper considers the case in which only the second-order statistics of the channel is known at the transmitter while the receiver has a perfect CSI. In such a case, it is possible to optimally design robust MIMO transceivers based on a general cost function covering several well known performance criteria. In particular, two families are considered in detail: Schur-convex and Schur-concave functions. Approximations are used in the low SNR regime to obtain simple optimization problems that can be readily solved. Numerical examples show substantial gains compared to other methods.

  • 2595.
    Zhang, Xi
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Palomar, Daniel P.
    Dept. of Electronic and Computer Engineering, Hong Kong University of Science and Technology, Kowloon, Hong Kong.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Robust MAC MIMO transceiver design with partial CSIT and CSIR2007Ingår i: CONFERENCE RECORD OF THE FORTY-FIRST ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS & COMPUTERS, VOLS 1-5, NEW YORK: IEEE , 2007, s. 324-328Konferensbidrag (Refereegranskat)
    Abstract [en]

    In practical wireless systems, the design of linear MIMO transceivers should be robust to imperfect channel state information (CSI), especially in multiuser systems where accurate CSI is difficult to obtain. This paper considers the case in which the CSI is perturbed at both sides of the link. In such a case, it is possible to optimally design robust MIMO transceivers to minimize the average sum MSE of all the data streams and the users. For systems with a sum power constraint, our robust design can be shown to be a convex SDP problem; for systems with individual power constraints, our robust design is based on an underlying SDP problem.

  • 2596.
    Zhang, Xi
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Svedman, Patrick
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Lundin, Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Zetterberg, Per
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Implementation of a smart antenna multiuser algorithm on a DSP-based wireless MIMO test-bed2005Ingår i: IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC, 2005, Vol. 1, s. 126-130Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper describes the implementation and performance of three communication schemes on a DSP-based MIMO test-bed. A multicell scenario with two basestations and two users in the same room is evaluated. Eigenbeamforming with and without interference pre-whitening at both transmitter and receiver is compared with SISO multicell communication. Experimental results show that the gain from using interference pre-whitening is significant. The BER performance of beamforming without intercell interference suppression is only marginally better than single antenna communication. The paper also presents the implementation of synchronization, equalization, frequency offset estimation and decision directed beamforming mismatch compensation.

  • 2597.
    Zhang, Xu
    et al.
    University of Bedfordshire.
    Zhou, DiBin
    University of Bedfordshire.
    Xiao, Zhu
    University of Bedfordshire.
    Liu, Enjie
    University of Bedfordshire.
    Zhang, Jie
    University of Bedfordshire.
    Alayon Glazunov, Andres
    University of Bedfordshire.
    Dynamic Group PCI Assignment Scheme2011Ingår i: The Seventh International Conference on Wireless and Mobile Communications (ICWMC 2011), 2011, s. 101-106Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Physical Cell Identity (PCI) is used to identify femtocell in LTE femtocell as the physical layer identity. Due to the fact that a) the PCIs are normally allocated without planning; and b) the limitation of the number of PCI, the cross-tier PCI confusion problem has arisen. The current solution in 3GPP Release 9 is to use Cell Global Identity (CGI) associated with PCI to solve this problem of confusion. However, using CGI has many serious drawbacks. Especially CGI might cause the inbound-handover is failure. In order to mitigate the CGI problem, this research proposes a dynamic PCI assignment scheme of DG-PCI in the macrocell and femtocell environment. The proposed scheme is tested by using system-level simulation. The simulations showed that the approach offers an optimal PCI distribution between macrocell and femtocell. The test showed that the CGI problem can be solved, and hence increase the successful rate of inbound-handover.

  • 2598. Zhang, Zhengquan
    et al.
    Ma, Zheng
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Karagiannidis, George K.
    Ding, Zhiguo
    Fan, Pingzhi
    Two-Timeslot Two-Way Full-Duplex Relaying for 5G Wireless Communication Networks2016Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 64, nr 7, s. 2873-2887Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We propose a novel two-timeslot two-way full-duplex (FD) relaying scheme, in which the access link and the backhaul link are divided in the time domain, and we study the average end-to-end rate and the outage performance. According to the user equipment capability and services, we investigate two scenarios: three-node I-and four-node Y-relaying channels. Among various relaying protocols, the well-known amplify-and-forward and decode-and-forward are considered. Closed-form expressions for the average end-to-end rate and the outage probability, under the effect of residual self-interference and inter-user interference, are presented. The results show that the proposed two-timeslot two-way FD relaying scheme can achieve higher rate and better outage performance than the half-duplex one, when residual self-interference is below a certain level. Therefore, this relaying scheme presents a reasonable tradeoff between performance and complexity, and so, it could be efficiently used in the fifth-generation wireless networks.

  • 2599. Zhang, Zhengquan
    et al.
    Ma, Zheng
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Teknisk informationsvetenskap.
    Liu, Gang
    Fan, Pingzhi
    Modeling and Analysis of Non-Orthogonal MBMS Transmission in Heterogeneous Networks2017Ingår i: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 35, nr 10, s. 2221-2237Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Multimedia broadcast/multicast service (MBMS) transmission, which distributes the media content to multiple users on the same radio resources by using point-to-multipoint communications, is a highly spectrum efficient mechanism for multimedia communications. In this paper, we study the application of power domain non-orthogonal transmission to MBMS enhancements in a K-tier heterogeneous network, in order to satisfy the ever-increasing demands for emerging applications and performance requirements. Then, we present non-orthogonal multi-rate MBMS transmission (NOMRMT) and non-orthogonal multi-service MBMS transmission schemes and investigate their performance by using stochastic geometry. A tractable mode is developed to analyze the performance of asynchronous and synchronous non-orthogonal MBMS transmission. Based on this model, analytical expressions for the signal-to-interference-plusnoise ratio coverage probability, average number of served users, and sum rate are derived. The results demonstrate that non-orthogonal MBMS transmission can achieve better performance than the orthogonal one, while synchronous non-orthogonal MBMS transmission is superior to the asynchronous one.

  • 2600.
    Zhang, Zhengquan
    et al.
    Southwest Jiaotong Univ, Chengdu, Sichuan, Peoples R China..
    Xiao, Yue
    Southwest Jiaotong Univ, Chengdu, Sichuan, Peoples R China..
    Ma, Zheng
    Southwest Jiaotong Univ, Sch Informat Sci & Technol, Chengdu, Sichuan, Peoples R China..
    Xiao, Ming
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Ding, Zhiguo
    Univ Manchester, Commun, Manchester, Lancs, England..
    Lei, Xianfu
    Southwest Jiaotong Univ, Sch Informat Sci & Technol, Chengdu, Sichuan, Peoples R China..
    Karagiannidis, George K.
    Aristotle Univ Thessaloniki, Elect & Comp Engn Dept, Thessaloniki, Greece.;Aristotle Univ Thessaloniki, Digital Telecommun Syst & Networks Lab, Thessaloniki, Greece..
    Fan, Pingzhi
    Southwest Jiaotong Univ, Chengdu, Sichuan, Peoples R China..
    6G WIRELESS NETWORKS Vision, Requirements, Architecture, and Key Technologies2019Ingår i: IEEE Vehicular Technology Magazine, ISSN 1556-6072, E-ISSN 1556-6080, Vol. 14, nr 3, s. 28-41Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A key enabler for the intelligent information society of 2030, 6G networks are expected to provide performance superior to 5G and satisfy emerging services and applications. In this article, we present our vision of what 6G will be and describe usage scenarios and requirements for multi-terabyte per second (Tb/s) and intelligent 6G networks. We present a large-dimensional and autonomous network architecture that integrates space, air, ground, and underwater networks to provide ubiquitous and unlimited wireless connectivity. We also discuss artificial intelligence (AI) and machine learning [1], [2] for autonomous networks and innovative air-interface design. Finally, we identify several promising technologies for the 6G ecosystem, including terahertz (THz) communications, very-large-scale antenna arrays [i.e., supermassive (SM) multiple-input, multiple-output (MIMO)], large intelligent surfaces (LISs) and holographic beamforming (HBF), orbital angular momentum (OAM) multiplexing, laser and visible-light communications (VLC), blockchain-based spectrum sharing, quantum communications and computing, molecular communications, and the Internet of Nano-Things.

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