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Mollén, ChristopherORCID iD iconorcid.org/0000-0002-2093-5466
Publications (10 of 10) Show all publications
Van Chien, T., Mollén, C. & Björnson, E. (2019). Large-scale-fading decoding in cellular Massive MIMO systems with spatially correlated channels. IEEE Transactions on Communications, 67(4), 2746-2762
Open this publication in new window or tab >>Large-scale-fading decoding in cellular Massive MIMO systems with spatially correlated channels
2019 (English)In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 67, no 4, p. 2746-2762Article in journal (Refereed) Published
Abstract [en]

Massive multiple-input–multiple-output (MIMO) systems can suffer from coherent intercell interference due to the phenomenon of pilot contamination. This paper investigates a two-layer decoding method that mitigates both coherent and non-coherent interference in multi-cell Massive MIMO. To this end, each base station (BS) first estimates the channels to intra-cell users using either minimum mean-squared error (MMSE) or element-wise MMSE estimation based on uplink pilots. The estimates are used for local decoding on each BS followed by a second decoding layer where the BSs cooperate to mitigate inter-cell interference. An uplink achievable spectral efficiency (SE) expression is computed for arbitrary two-layer decoding schemes. A closed form expression is then obtained for correlated Rayleigh fading, maximum-ratio combining, and the proposed large-scale fading decoding (LSFD) in the second layer. We also formulate a sum SE maximization problem with both the data power and LSFD vectors as optimization variables. Since this is an NP-hard problem, we develop a low-complexity algorithm based on the weighted MMSE approach to obtain a local optimum. The numerical results show that both data power control and LSFD improve the sum SE performance over single-layer decoding multi-cell Massive MIMO systems.

Place, publisher, year, edition, pages
IEEE Communications Society, 2019
Keywords
Massive MIMO, Large-Scale Fading Decoding, Sum Spectral Efficiency Optimization, Channel Estimation
National Category
Communication Systems
Identifiers
urn:nbn:se:liu:diva-156657 (URN)10.1109/TCOMM.2018.2889090 (DOI)000465242700011 ()2-s2.0-85059010638 (Scopus ID)
Funder
ELLIIT - The Linköping‐Lund Initiative on IT and Mobile Communications
Note

Funding agencies: European Unions Horizon 2020 Research and Innovation Programme [641985]; ELLIIT; CENIIT

Available from: 2019-05-04 Created: 2019-05-04 Last updated: 2019-06-28Bibliographically approved
Van Chien, T., Mollén, C. & Björnson, E. (2019). Two-Layer Decoding in Cellular Massive MIMO Systems with Spatial Channel Correlation. In: : . Paper presented at IEEE International Conference on Communications (ICC), Shanghai, China, 20-24 May 2019.
Open this publication in new window or tab >>Two-Layer Decoding in Cellular Massive MIMO Systems with Spatial Channel Correlation
2019 (English)Conference paper, Published paper (Refereed)
Abstract [en]

This paper studies a two-layer decoding method that mitigates inter-cell interference in multi-cell Massive MIMO systems. In layer one, each base station (BS) estimates the channels to intra-cell users and uses the estimates for local decoding on each BS, followed by a second decoding layer where the BSs cooperate to mitigate inter-cell interference. An uplink achievable spectral efficiency (SE) expression is computed for arbitrary two-layer decoding schemes, while a closed-form expression is obtained for correlated Rayleigh fading channels, maximum-ratio combining (MRC), and large-scale fading decoding (LSFD) in the second layer. We formulate a non-convex sum SE maximization problem with both the data power and LSFD vectors as optimization variables and develop an algorithm based on the weighted MMSE (minimum mean square error) approach to obtain a stationary point with low computational complexity.

National Category
Communication Systems
Identifiers
urn:nbn:se:liu:diva-156971 (URN)10.1109/ICC.2019.8761502 (DOI)9781538680889 (ISBN)9781538680896 (ISBN)
Conference
IEEE International Conference on Communications (ICC), Shanghai, China, 20-24 May 2019
Funder
ELLIIT - The Linköping‐Lund Initiative on IT and Mobile Communications
Available from: 2019-05-18 Created: 2019-05-18 Last updated: 2019-08-05Bibliographically approved
Mollén, C. (2017). High-End Performance with Low-End Hardware: Analysis of Massive MIMO Base Station Transceivers. (Doctoral dissertation). Linköping: Linköping University Electronic Press
Open this publication in new window or tab >>High-End Performance with Low-End Hardware: Analysis of Massive MIMO Base Station Transceivers
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Massive MIMO (multiple-input–multiple-output) is a multi-antenna technology for cellular wireless communication, where the base station uses a large number of individually controllable antennas to multiplex users spatially.  This technology can provide a high spectral efficiency.  One of its main challenges is the immense hardware complexity and cost of all the radio chains in the base station.  To make massive MIMO commercially viable, inexpensive, low-complexity hardware with low linearity has to be used, which inherently leads to more signal distortion.  This thesis investigates how the degenerated linearity of some of the main components—power amplifiers, analog-to-digital converters (ADCs) and low-noise amplifiers—affects the performance of the system, with respect to data rate, power consumption and out-of-band radiation. The main results are: Spatial processing can reduce PAR (peak-to-average ratio) of the transmit signals in the downlink to as low as 0B; this, however, does not necessarily reduce power consumption.  In environments with isotropic fading, one-bit ADCs lead to a reduction in effective signal-to-interference-and-noise ratio (SINR) of 4dB in the uplink and four-bit ADCs give a performance close to that of an unquantized system.  An analytical expression for the radiation pattern of the distortion from nonlinear power amplifiers is derived.  It shows how the distortion is beamformed to some extent, that its gain never is greater than that of the desired signal, and that the gain of the distortion is reduced with a higher number of served users and a higher number of channel taps.  Nonlinear low-noise amplifiers give rise to distortion that partly combines coherently and limits the possible SINR.  It is concluded that spatial processing with a large number of antennas reduces the impact of hardware distortion in most cases.  As long as proper attention is paid to the few sources of coherent distortion, the hardware complexity can be reduced in massive MIMO base stations to overcome the hardware challenge and make massive MIMO commercial reality.

Abstract [sv]

Massiv MIMO (eng: multiple-input–multiple-output) är en flerantennsteknologi för cellulär trådlös kommunikation, där basstationen använder ett stort antal individuellt styrbara antenner för att multiplexa användare i rummet.  Denna teknologi kan tillhandahålla en hög spektral effektivitet.  En av dess främsta utmaningar är den enorma hårdvarukomplexiteten och kostnaden hos basstationens alla radiokedjor.  För att massiv MIMO skall bli kommersiellt attraktivt, måste billiga, enkla hårdvarukomponenter med låg linjäritet användas, vilket oundvikligen leder till mer signaldistorsion.  Denna avhandling undersöker hur den försämrade linjäriteten hos några av huvudkomponenterna – effektförstärkare, analog-digital-omvandlare (AD-omvandlare) och lågbrusförstärkare – påverkar systemets prestanda, i termer av datatakt, effektförbrukning och utombandsstrålning.  Huvudresultaten är: Rumslig signalbehandling kan reducera sändsignalernas toppvärde i nerlänken ända ner till 0dB, vilket dock inte nödvändigtvis minskar effektförbrukningen.  I miljöer med isotrop fädning leder enbits-AD-omvandlare till 4dB lägre signal-till-interferens-och-brus-förhållande i upplänken, och fyrabits-AD-omvandlare ger en prestanda nära den ett system utan kvantisering kan uppnå.  Ett analytiskt uttryck för strålningsmönstret för distorsionen från icke-linjära effektförstärkare härleds.  Det visar hur distorsionen till viss del lobformas, att dess förstärkning aldrig är starkare än förstärkningen för den önskade signalen och att distorsionens förstärkning minskar med ett högre antal betjänade användare och ett högre antal kanaltappar.  Icke-linjära lågbrusförstärkare ger upphov distorsion som delvis kombinerar koherent och begränsar det möjliga signal-till-brus-och-interferens-förhållandet.  Slutsatsen är att rumslig signalbehandling med ett stort antal antenner reducerar hårdvarudistorsionens inverkan i de flesta fall.  Så länge som de få källorna till koherent distorsion ges tillbörlig uppmärksamhet, kan hårdvarukomplexiteten minskas i basstationer för massiv MIMO för att övervinna hårdvaruutmaningen och göra massiv MIMO kommersiell verklighet.

Abstract [zh]

蜂窩無線通訊領域中的大規模多天線技術以多個單獨可控的天線通過空間複用的方式服務多個用戶。如是可以大幅提高頻譜效率。實現此技術的主要難題在於基站所用射頻單元的極大複雜度及成本。爲使大規模多天線技術適用在商業系統中,需使用導致失真的低複雜度低成本的非線性硬件。本文探討若將一些主要部件——功放、模數轉換器、低噪聲放大器——的線性程度降低,系統性能是如何受到影響的,即系統的速率、功耗、帶外泄露等指標。主要的結果爲:空間信號處理可以降低下行信號的峯均比,直至0分貝;然而低峯均比不一定能夠降低功耗。用一比特模數轉換器使上行的信干噪比減少4分貝;用四比特模數轉換器可在各向同性衰落的環境裏實現接近無量化系統的性能。本文推導出非線性功放失真輻射方向的解析公式。該公式展示失真在某種程度上會被波束成形的;具體而言,失真的波束成形增益不大於有效信號的增益,波束成形增益會根據服務用戶數量和信道階數的增長而降低。非線性低噪聲放大器引起的失真,一部分會相干地合併,因此會限制信干噪比的增長。結論爲多天線的空間信號處理可以減少硬件失真的影響。只要適當地處理少數相干失真的來源,大規模多天線基站可以降低硬件複雜度,解決硬件難題,使大規模多天線技術成功地應用在商業系統中成爲現實。

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2017. p. 90
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1896
Keywords
Beamforming, distortion, massive MIMO, MIMO, nonlinear hardware, peak-to-average ratio
National Category
Signal Processing Telecommunications Communication Systems Other Electrical Engineering, Electronic Engineering, Information Engineering Computer Engineering
Identifiers
urn:nbn:se:liu:diva-143455 (URN)10.3384/diss-diva-143455 (DOI)9789176853887 (ISBN)
Public defence
2018-01-26, Ada Lovelace, B-huset, Campus Valla, Linköping, 13:15 (English)
Opponent
Supervisors
Available from: 2018-01-03 Created: 2017-12-08 Last updated: 2019-10-11Bibliographically approved
Mollén, C. (2016). On Massive MIMO Base Stations with Low-End Hardware. (Licentiate dissertation). Linköping: Linköping University Electronic Press
Open this publication in new window or tab >>On Massive MIMO Base Stations with Low-End Hardware
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Alternative title[sv]
Om massiv-MIMO-basstationer med enkel hårdvara
Abstract [en]

Massive MIMO (Multiple-Input Multiple-Output) base stations have proven, both in theory and in practice, to possess many of the qualities that future wireless communication systems will require.  They can provide equally high data rates throughout their coverage area and can concurrently serve multiple low-end handsets without requiring wider spectrum, denser base station deployment or significantly more power than current base stations.  The main challenge of massive MIMO is the immense hardware complexity and cost of the base station—each element in the large antenna array needs to be individually controllable and therefore requires its own radio chain.  To make massive MIMO commercially viable, the base station has to be built from inexpensive simple hardware.  In this thesis, it is investigated how the use of low-end power amplifiers and analog-to-digital converters (ADCs) affects the performance of massive MIMO.  In the study of the signal distortion from low-end amplifiers, it is shown that in-band distortion is negligible in massive MIMO and that out-of-band radiation is the limiting factor that decides what power efficiency the amplifiers can be operated at.  A precoder that produces transmit signals for the downlink with constant envelope in continuous time is presented to allow for highly power efficient low-end amplifiers.  Further, it is found that the out-of-band radiation is isotropic when the channel is frequency selective and when multiple users are served; and that it can be beamformed when the channel is frequency flat and when few users are served.  Since a massive MIMO base station radiates less power than today's base stations, isotropic out-of-band radiation means that low-end hardware with poorer linearity than required today can be used in massive MIMO.  It is also shown that using one-bit ADCs—the simplest and least power-hungry ADCs—at the base station only degrades the signal-to-interference-and-noise ratio of the system by approximately 4 dB when proper power allocation among users is done, which indicates that massive MIMO is resistant against coarse quantization and that low-end ADCs can be used.

Abstract [sv]

Massiv-MIMO-basstationer (eng: Multiple-Input Multiple-Output) har visats, både i teori och praktik, besitta många av de egenskaper som framtida trådlösa kommunikationssystem kommer att behöva.  De kan tillhandahålla enhetligt höga datatakter i hela täckningsområdet och simultant betjäna flera enkla mobilenheter utan att använda bredare spektrum, tätare basstationsplacering eller betydligt mer effekt än dagens basstationer.  Huvudutmaningen med massiv MIMO är basstationens enorma hårdvarukomplexitet och -kostnad – varje element i den stora gruppantennen skall kunna kontrolleras individuellt och kräver sålunda sin egen radiokedja.  För att massiv MIMO skall bli kommersiellt attraktiv, måste basstationen byggas av billig, enkel hårdvara.  I denna avhandling undersöks hur enkla effektförstärkare och analog-till-digital-omvandlare (AD-omvandlare) påverkar massiv-MIMO-systemets prestanda.  I studien av signaldistorsionen från enkla förstärkare visas det att inband-distorsionen är försumbar i massiv MIMO och att utombandsstrålningen är den begränsande faktorn som bestämmer vid vilken verkningsgrad förstärkarna kan arbeta.  En förkodare som åstadkommer nerlänks-sändsignaler som har konstant envelopp i kontinuerlig tid presenteras för att möjliggöra användandet av enkla förstärkare med hög verkningsgrad.  Vidare konstateras det att utombandsstrålningen är isotrop när kanalen är frekvensselektiv och när flera användare betjänas; och att den kan lobformas när kanalen är frekvensflat och när få användare betjänas.  Eftersom en massiv-MIMO-basstation utstrålar mindre effekt än dagens basstationer, betyder isotrop utombandsstrålning att enkel hårdvara med sämre linearitet än vad som krävs idag kan användas i massiv MIMO.  Det visas även att användandet av enbits-AD-omvandlare – de enklaste och mest strömsnåla AD-omvandlarna – i basstationen endast minskar signal-till-interferens-och-brus-förhållandet med 4 dB när tillbörlig effektallokering mellan användarna utförs, vilket indikerar att massiv MIMO är motståndskraftig mot grov kvantisering och att enkla AD-omvandlare kan användas.

Abstract [zh]

大規模多輸入多輸出基站,無論從理論上或實際上,皆已經證明具有許多未來無線通訊系統所需的特質。比如:在其整個覆蓋區域均一地提供高數據傳輸速率、在同一時間頻率資源上服務多個簡單的終端設備,而無需佔用更多頻譜資源或更密集地部署基站,亦無需提高基站的功耗。實現大規模多入多出系统的主要挑戰在於硬件複雜度及基站成本——大規模天線陣列中的每一個天線元必須單獨可控,因此需要其自身的射頻鏈路。爲使大規模多入多出基站有商業吸引力,基站必須以簡單低成本的硬件來建造。本論文探討簡單的功率放大器與模擬數字轉換器對大規模多入多出性能的影響。對低端功放信號失真的研究表明,帶內失真對大規模多入多出的性能影響幾乎可以忽略,而帶外泄露是限制功放效率的決定因素。爲使用高功率效率低端功放,本文提出能產生具有恆定包絡連續時間信號的預編碼。本文指出,在頻率選擇性衰落信道上服務多個用戶時,帶外泄露呈現各向同性;而在平坦衰落信道上服務少數用戶時,帶外泄露可呈現波束賦形。由於大規模多入多出基站比現用基站輻射較少功率,帶外泄露各向同性意味著大規模多入多出基站可使用低端硬件,其線性要求不比現有基站的高。另外表明,如果進行合理的多用戶功率分配,基站使用單比特模擬數字轉換器——最簡單低耗的轉換器——僅使系統的信干噪比降低約4分貝。以此可見,大規模多入多出系統對非精確量比較穩定,低端模擬數字轉換器可於此類系統中使用。

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2016. p. 53
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1756
Keywords
massive MIMO, hardware, ADC, power amplifier, out-of-band radiation, peak-to-average ratio
National Category
Communication Systems
Identifiers
urn:nbn:se:liu:diva-130516 (URN)10.3384/lic.diva-130516 (DOI)9789176857076 (ISBN)
Presentation
2016-09-02, Algortimen, Hus B, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2016-08-23 Created: 2016-08-11 Last updated: 2017-03-22Bibliographically approved
Mollén, C., Choi, J., Larsson, E. G. & Heath, R. W. (2016). One-Bit ADCs in Wideband Massive MIMO Systems with OFDM Transmission. In: 2016 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH AND SIGNAL PROCESSING PROCEEDINGS: . Paper presented at ICASSP 2016, The 41st IEEE International Conference on Acoustics, Speech, and Signal Processing, 20-25 March, Shanghai, China (pp. 3386-3390). Institute of Electrical and Electronics Engineers (IEEE)
Open this publication in new window or tab >>One-Bit ADCs in Wideband Massive MIMO Systems with OFDM Transmission
2016 (English)In: 2016 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH AND SIGNAL PROCESSING PROCEEDINGS, Institute of Electrical and Electronics Engineers (IEEE), 2016, p. 3386-3390Conference paper, Published paper (Refereed)
Abstract [en]

We investigate the performance of wideband massive MIMO base stations that use one-bit ADCs for quantizing the uplink signal. Ourmain result is to show that the many taps of the frequency-selective channel make linear combiners asymptotically consistent and the quantization noise additive and Gaussian, which simplifies signal processing and enables the straightforward use of OFDM . We also find that single-carrier systems and OFDM systems are affected in the same way by one-bit quantizers in wideband systems because the distribution of the quantization noise becomes the same in both systems as the number of channel taps grows.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2016
Series
International Conference on Acoustics Speech and Signal Processing ICASSP, ISSN 1520-6149
National Category
Communication Systems
Identifiers
urn:nbn:se:liu:diva-124241 (URN)10.1109/ICASSP.2016.7472305 (DOI)000388373403105 ()978-1-4799-9988-0 (ISBN)
Conference
ICASSP 2016, The 41st IEEE International Conference on Acoustics, Speech, and Signal Processing, 20-25 March, Shanghai, China
Available from: 2016-01-24 Created: 2016-01-24 Last updated: 2017-01-11Bibliographically approved
Mollén, C., Gustavsson, U., Eriksson, T. & Larsson, E. G. (2016). Out-of-Band Radiation Measure for MIMO Arrays with Beamformed Transmission. In: 2016 IEEE International Conference on Communications (ICC): . Paper presented at 2016 IEEE International Conference on Communications (ICC), 22-27 May 2016, Kuala Lumpur, Malaysia (pp. 1-6). IEEE
Open this publication in new window or tab >>Out-of-Band Radiation Measure for MIMO Arrays with Beamformed Transmission
2016 (English)In: 2016 IEEE International Conference on Communications (ICC), IEEE , 2016, p. 1-6Conference paper, Published paper (Refereed)
Abstract [en]

The spatial characteristics of the out-of-band radiation that a multiuser MIMO system emits, due to its power amplifiers (modeled by a polynomial model) being nonlinear, are studied by deriving an analytical expression for the continuous-time cross-correlation of the transmit signals.  It is shown that, at any spatial point and on any frequency, the received power averaged over many channel realizations from a MIMO base station is the same as from a SISO base station when the two radiate the same amount of power.  For a specific channel realization however, the received power can deviate from this average.  We show that the deviations from the average are small in a MIMO system with multiple users and that the deviations can be significant with only one user.  Using an ergodicity argument, we conclude that out-of-band radiation is less of a problem in massive MIMO, where precoding and array gain let us reduce the total radiated power compared to SISO systems.  The requirements on spectral regrowth can therefore be relaxed in MIMO systems without causing more total out-of-band radiation.

Place, publisher, year, edition, pages
IEEE, 2016
Series
IEEE International Conference on Communications, ISSN 1550-3607
National Category
Communication Systems
Identifiers
urn:nbn:se:liu:diva-130513 (URN)10.1109/ICC.2016.7511629 (DOI)000390993205153 ()9781479966646 (ISBN)
Conference
2016 IEEE International Conference on Communications (ICC), 22-27 May 2016, Kuala Lumpur, Malaysia
Funder
EU, FP7, Seventh Framework Programme, ICT-619086Swedish Research Council
Available from: 2016-08-11 Created: 2016-08-11 Last updated: 2017-01-29Bibliographically approved
Mollén, C., Larsson, E. G., Choi, J. & Heath, R. W. (2016). Performance of Linear Receivers for Wideband Massive MIMO with One-Bit ADCs. In: : . Paper presented at WSA 2016 - 20th International ITG Workshop on Smart Antennas 03/09/2016 - 03/11/2016 at München, Deutschland (pp. 7).
Open this publication in new window or tab >>Performance of Linear Receivers for Wideband Massive MIMO with One-Bit ADCs
2016 (English)Conference paper, Published paper (Refereed)
Abstract [en]

The power consumption of analog-to-digital converters (ADCs) grows linearly in the number of antennas in massive MIMO base stations. To reduce power consumption, one-bit ADCs can be used. It is believed that the nonlinear distortion of onebit ADCs makes channel estimation and symbol equalization in such systems computationally complex and resource demanding. In this paper, it is shown that low-complexity linear channel estimation and symbol equalization are feasible in massive MIMO with one-bit ADCs when the number of channel taps is large. The effective SINR of the received symbol estimates of a maximum-ratio combiner with estimated channel state information is 4 dB lower in a system with one-bit ADCs than in an equivalent unquantized system.

National Category
Communication Systems
Identifiers
urn:nbn:se:liu:diva-130515 (URN)
Conference
WSA 2016 - 20th International ITG Workshop on Smart Antennas 03/09/2016 - 03/11/2016 at München, Deutschland
Available from: 2016-08-11 Created: 2016-08-11 Last updated: 2016-08-31
Mollén, C., Larsson, E. G. & Eriksson, T. (2016). Waveforms for the Massive MIMO Downlink: Amplifier Efficiency, Distortion and Performance. IEEE Transactions on Communications, 46(12), 5050-5063
Open this publication in new window or tab >>Waveforms for the Massive MIMO Downlink: Amplifier Efficiency, Distortion and Performance
2016 (English)In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 46, no 12, p. 5050-5063Article in journal (Refereed) Published
Abstract [en]

In massive multiple-input multiple-output (MIMO), most precoders result in downlink signals that suffer from high peak-to-average ratio (PAR), independently of modulation order and whether single-carrier or orthogonal frequency-division multiplexing (OFDM) transmission is used. The high PAR lowers the power efficiency of the base-station amplifiers. To increase the power efficiency, low-PAR precoders have been proposed. In this paper, we compare different transmission methods for massive MIMO in terms of the power consumed by the amplifiers. It is found that: 1) OFDM and single-carrier transmission have the same performance over a hardened massive MIMO channel and 2) when the higher amplifier power efficiency of low-PAR precoding is taken into account, conventional and low-PAR precoders lead to approximately the same power consumption. Since downlink signals with low PAR allow for simpler and cheaper hardware, than signals with high PAR, therefore, the results suggest that low-PAR precoding with either single-carrier or OFDM transmission should be used in a massive MIMO base station.

Place, publisher, year, edition, pages
IEEE, 2016
National Category
Communication Systems
Identifiers
urn:nbn:se:liu:diva-130514 (URN)10.1109/TCOMM.2016.2557781 (DOI)000391694500013 ()
Funder
EU, FP7, Seventh Framework Programme, ICT-619086Swedish Research CouncilELLIIT - The Linköping‐Lund Initiative on IT and Mobile Communications
Note

Funding agencies: European Union [ICT-619086]; Swedish Research Council (Vetenskapsradet); ELLIIT

Available from: 2016-08-11 Created: 2016-08-11 Last updated: 2018-01-03
Mollén, C. & Larsson, E. G. (2015). Multiuser MIMO Precoding with Per-Antenna Continuous-Time Constant-Envelope Constraints. In: 2015 IEEE 16th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC): . Paper presented at SPAWC 2015 The 16th IEEE International Workshop on Signal Processing Advances in Wireless Communications, June 28 – July 1, 2015, Stockholm, Sweden (pp. 261-265). Institute of Electrical and Electronics Engineers (IEEE)
Open this publication in new window or tab >>Multiuser MIMO Precoding with Per-Antenna Continuous-Time Constant-Envelope Constraints
2015 (English)In: 2015 IEEE 16th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), Institute of Electrical and Electronics Engineers (IEEE), 2015, p. 261-265Conference paper, Published paper (Refereed)
Abstract [en]

A transmission scheme for the multiuser MIMO downlink, where the transmit signal from each antenna has constant envelope and a limited bandwidth, is proposed in order to enable the use of highly efficient, nonlinear amplifiers at the base station. To evaluate its performance, an achievable rate is derived and the necessary transmit power of the proposed scheme is computed for a system with 40 antennas that serves 4 users at data rates around 1 bpcu. For this system and 40% excess 30 dB-bandwidth, approximately 3 dB more transmit power is required to achieve the same sum-rate as without the constantenvelope constraints.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2015
Series
IEEE International Workshop on Signal Processing Advances in Wireless Communications, ISSN 2325-3789
National Category
Communication Systems
Identifiers
urn:nbn:se:liu:diva-120251 (URN)10.1109/SPAWC.2015.7227040 (DOI)000380547100053 ()978-1-4799-1931-4 (ISBN)
Conference
SPAWC 2015 The 16th IEEE International Workshop on Signal Processing Advances in Wireless Communications, June 28 – July 1, 2015, Stockholm, Sweden
Available from: 2015-07-20 Created: 2015-07-20 Last updated: 2018-01-03Bibliographically approved
Mollén, C., Larsson, E. G. & Eriksson, T. (2014). On the Impact of PA-Induced In-Band Distortion in Massive MIMO. In: Proceedings of European Wireless 2014: . Paper presented at 20th European Wireless Conference, 14-16 May 2014, Barcelona, Spain (pp. 201-206). Berlin, Offenbach, Germany: VDE Verlag GmbH
Open this publication in new window or tab >>On the Impact of PA-Induced In-Band Distortion in Massive MIMO
2014 (English)In: Proceedings of European Wireless 2014, Berlin, Offenbach, Germany: VDE Verlag GmbH, 2014, p. 201-206Conference paper, Published paper (Refereed)
Abstract [en]

Conventional downlink signals in massive MIMO suffer from high PAR, which requires the power amplifiers of the base station to be backed off to avoid signal distortion, which lowers power efficiency. To improve efficiency, there are precoding schemes that produce signals with low PAR. To compare different precoding schemes, this article estimates their power consumptions through simulations, in which in-band distortion and amplifier efficiency effects are taken into consideration. It is found that, when only in-band distortion and the data rate requirement determine the back-off, the inband distortion is negligible and the power amplifiers can be operated at peak efficiency. It also turns out that low-PAR and conventional, high-PAR, precoding schemes consume approximately the same amount of power when the out-of-band part of the distortion is disregarded.

Place, publisher, year, edition, pages
Berlin, Offenbach, Germany: VDE Verlag GmbH, 2014
Keywords
massive MIMO; multiuser precoding, crest-factor reduction, low-PAR precoding, massiv MIMO, fleranvändarförkodning, toppvärdesreducering, lågtoppvärdesförkodning
National Category
Communication Systems
Identifiers
urn:nbn:se:liu:diva-112395 (URN)978-3-8007-3621-8 (ISBN)
Conference
20th European Wireless Conference, 14-16 May 2014, Barcelona, Spain
Available from: 2014-11-25 Created: 2014-11-25 Last updated: 2016-08-31Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-2093-5466

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