uu.seUppsala University Publications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Channel Estimation and Prediction for 5G Applications
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Accurate channel state information (CSI) is important for many candidate techniques of future wireless communication systems. However, acquiring CSI can sometimes be difficult, especially if the user equipment is mobile in which case the future channel realisations must be estimated/predicted. In realistic settings the predictability of radio channels is limited due to measurement noise, limited model orders and since the fading statistics must be modelled based on a set of limited and noisy training data.

In this thesis, the limits of predictability for the radio channel are investigated. Results show that the predictability is limited primarily due to limitations in the training data, while the model order provides a second order limitation effect and the measurement noise comes in as a third order effect.

Then, a Kalman-based linear filter is studied for potential 5G technologies:

Coherent coordinated multipoint joint transmission, where channel predictions and the covariance matrix of the prediction error are used to design a robust linear precoder, evaluated in a three base station system. Results show that prediction improves the CSI for the pedestrian users such that system delays of 10 ms are acceptable. The use of the covariance matrix is important for difficult user groups, but of less importance with a simple user grouping system proposed.

Massive multiple-input multiple-output (MIMO) in frequency division duplex (FDD) systems were a reduced, suboptimal, Kalman filter is suggested to estimate channels based on non-orthogonal pilots. By introducing a fixed grid of beams, the system generates sparsity in the channel vectors seen by each user, which then estimates its most relevant channels based on unique pilot codes for each beam. Results show that there is a 5 dB loss compared to orthogonal pilots.

Downlink time division duplex (TDD) channels are estimated based on uplink pilots. By using a predictor antenna, which scouts the channel in advance, the desired downlink channel can be estimated using pilot-based estimates of the channels before and after it (in space). Results indicate that, with the help of Kalman smoothing, predictor antennas can enable accurate CSI for TDD downlinks at vehicular velocities of 80 km/h.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. , p. 116
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1642
Keywords [en]
Channel estimation, Channel prediction, Channel smoothing, Linear estimation, Kalman filter, Massive MIMO, Coordinated Multipoint transmission, Robust precoding, Predictor antennas, Limits of predictability, Long range predictions
National Category
Signal Processing Telecommunications
Research subject
Electrical Engineering with specialization in Signal Processing
Identifiers
URN: urn:nbn:se:uu:diva-344270ISBN: 978-91-513-0263-8 (print)OAI: oai:DiVA.org:uu-344270DiVA, id: diva2:1188360
Public defence
2018-04-27, Häggsalen, Å10132, Lägerhyddsvägen 1, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2018-04-05 Created: 2018-03-07 Last updated: 2018-04-24
List of papers
1. Kalman predictions for multipoint OFDM downlink channels
Open this publication in new window or tab >>Kalman predictions for multipoint OFDM downlink channels
2014 (English)Report (Other academic)
National Category
Engineering and Technology
Research subject
Electrical Engineering with specialization in Signal Processing
Identifiers
urn:nbn:se:uu:diva-235010 (URN)
Available from: 2014-10-28 Created: 2014-10-28 Last updated: 2018-03-07
2. Design and measurement based evaluations of coherent JT CoMP: A study of precoding, user grouping and resource allocation using predicted CSI
Open this publication in new window or tab >>Design and measurement based evaluations of coherent JT CoMP: A study of precoding, user grouping and resource allocation using predicted CSI
2014 (English)In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499Article in journal (Refereed) Published
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-235014 (URN)DOI:10.1186/1687-1499-2014-100 (DOI)
Available from: 2014-10-28 Created: 2014-10-28 Last updated: 2018-11-08
3. Robust linear precoder for coordinated multipoint joint transmission under limited backhaul with imperfect CSI
Open this publication in new window or tab >>Robust linear precoder for coordinated multipoint joint transmission under limited backhaul with imperfect CSI
2014 (English)In: 2014 11TH INTERNATIONAL SYMPOSIUM ON WIRELESS COMMUNICATIONS SYSTEMS (ISWCS), 2014, p. 138-143Conference paper, Published paper (Refereed)
Abstract [en]

Coordinated Multipoint (COMP) transmission provides high theoretic gains in spectral efficiency, in particular with coherent linear Joint Transmission (JT) to multiple users. However, this requires high backhaul capacity. If the backhaul requirement cannot be met by the system, then CoNIP gains decrease as the linear precoder matrix must be adjusted to include zeros. To minimize the loss of CoMP gains, all elements in the precoder should be adjusted as zeros are added to the precoder. We here propose a low complexity method for adjusting a precoder matrix when some elements are required to be zero, with respect to a robust MSE criterion. This is done by introducing penalties on specific precoder matrix elements. This generalized MSE criterion can then be used as a low complexity tool for optimizing e.g. with respect to sum-rate. Results show that this does indeed provide a better solution than if zeros are added separately. It is especially beneficial for cell edge users, i.e. for the same users that can gain the most from JT CoNIP.

National Category
Engineering and Technology
Research subject
Electrical Engineering with specialization in Signal Processing
Identifiers
urn:nbn:se:uu:diva-235007 (URN)000363906500027 ()978-1-4799-5863-4 (ISBN)
Conference
International Symposium on Wireless Communication Systems ISWCS, Barcelona, Spanien, 25-29 Augusti
Available from: 2014-10-28 Created: 2014-10-28 Last updated: 2018-03-07Bibliographically approved
4. Joint reference signal design and Kalman/Wiener channel estimation for FDD massive MIMO. Extended Report Version.
Open this publication in new window or tab >>Joint reference signal design and Kalman/Wiener channel estimation for FDD massive MIMO. Extended Report Version.
2017 (English)Report (Other academic)
Place, publisher, year, edition, pages
Uppsala: Signals and Systems, Uppsala University, 2017
Series
Report r1701
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-330705 (URN)
Available from: 2017-10-03 Created: 2017-10-03 Last updated: 2018-03-07
5. Kalman smoothing for irregular pilot patterns; A case study for predictor antennas in TDD systems
Open this publication in new window or tab >>Kalman smoothing for irregular pilot patterns; A case study for predictor antennas in TDD systems
(English)Manuscript (preprint) (Other academic)
Abstract [en]

For future large-scale multi-antenna systems, channel orthogonal downlink pilots are not feasible due to extensive overhead requirements. Instead, channel reciprocity can be utilized in time division duplex (TDD) systems so that the downlink channel estimates can be based on pilots transmitted during the uplink. User mobility affects the reciprocity and makes the channel state information outdated for high velocities and/or long downlink subframe durations. Channel extrapolation, e.g. through Kalman prediction, can reduce the problem but is also limited by high velocities and long downlink subframes. An alternative solution has been proposed where channel predictions are made with the help of an extra antenna, e.g. on the roof of a car, so called predictor antenna, with the primary objective to measure the channel at a position that is later encountered by the rearward antenna(s). The predictor antenna is not directly limited by high velocities and allows the channel in the downlinks to be interpolated rather than extrapolated. One remaining challenge here is to obtain a good interpolation of the uplink channel estimate, since a sequence of uplink reference signals (pilots) will be interrupted by downlink subframes. We here evaluate a Kalman smoothing estimate of the downlink channels and compare it to a cubic spline interpolation. These results are compared to results where uplink channels are estimated through Kalman filters and predictors. Results are based on measured channels and show that with Kalman smoothing, predictor antennas can enable accurate channel estimates for a longer downlink period at vehicular velocities.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-344267 (URN)
Available from: 2018-03-06 Created: 2018-03-06 Last updated: 2018-03-07

Open Access in DiVA

fulltext(1934 kB)591 downloads
File information
File name FULLTEXT01.pdfFile size 1934 kBChecksum SHA-512
3dee3f65e231788218c402b1bc267d03b33d197e40fd4e3ecf4e8cd67c92acb8ba9b8ea43e2b31d092b630fd12b8c6f56829cfe9df0f08a1e9cdbe67886ae193
Type fulltextMimetype application/pdf
Buy this publication >>

Authority records BETA

Apelfröjd, Rikke

Search in DiVA

By author/editor
Apelfröjd, Rikke
By organisation
Signals and Systems Group
Signal ProcessingTelecommunications

Search outside of DiVA

GoogleGoogle Scholar
Total: 591 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 1495 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf