| 1. |
- Bengtsson, Erik L., et al.
(författare)
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A Simulation Framework for Multiple-Antenna Terminals in 5G Massive MIMO Systems
- 2017
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Ingår i: IEEE Access. - 2169-3536. ; 5, s. 26819-26831
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Tidskriftsartikel (refereegranskat)abstract
- The recent interest in massive MIMO has spurred intensive work on massive MIMO channel modeling in contemporary literature. However, current models fail to take the characteristics of terminal antennas into account. There is no massive MIMO channel model available that can be used for evaluation of the influence of different antenna characteristics at the terminal side. In this paper, we provide a simulation framework that fills this gap. We evaluate the framework with antennas integrated into Sony Xperia handsets operating at 3.7 GHz as this spectrum is identified for the 5G new radio standard by 3GPP. The simulation results are compared with measured terminal performance when communicating with the Lund University’s massive MIMO testbed under the same loading conditions. Expressions are derived for comparison of the gain obtained from different diversity schemes computed from measured far-field antenna patterns. We conclude that the simulation framework yields results close to the measured ones and that the framework can be used for antenna evaluation for terminals in a practical precoded massive MIMO system.
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| 2. |
- Bengtsson, Erik L, et al.
(författare)
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Transmission schemes for Multiple Antenna Terminals in Real Massive MIMO systems
- 2016
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Ingår i: 2016 IEEE Global Communications Conference (GLOBECOM). - 9781509013296 - 9781509013289
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Konferensbidrag (refereegranskat)abstract
- In massive MIMO performance evaluations it is often assumed that the terminal has a single antenna. The combination of multiple antennas in a terminal and massive MIMO precoding at the base station side can further improve overall system performance. We present measurement results for multi antenna terminals operating in different transmission schemes and how they perform under varying loading conditions. Gain expressions are derived that enable easy comparison between the transmission schemes. The evaluation is performed on realistic antennas integrated into Sony Xperia handsets tuned to 3.7~GHz and operated together with the Lund University massive MIMO (LuMaMi) test bed. It is concluded that the approach used in today's mobile systems, where up link and down link are addressed independently, will not provide the best performance. The performance can be improved by the selection of transmission schemes optimized for massive MIMO.
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| 3. |
- Bourdoux, Andre, et al.
(författare)
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D1.2 MaMi Channel Characteristics: Measurement Results
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This deliverable presents channel measurement results for the scenariosOpen exhibition and Crowded auditiorium. The measurement procedureand equipment are described. Massive MIMO (MaMi) channel characteristicsand key parameters are extracted and used in an extended COST 2100channel model for MaMi. The initial validation performed shows that themodel is capable of reproducing the statistics in terms of temporal behaviorof the user separability, singular value spread, capacity and sum-rate anddirectional characteristics. The model can be used for system and link levelMaMi simulations.
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| 4. |
- Dahman, Ghassan, et al.
(författare)
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On the probability of non-shared multipath clusters in cellular networks
- 2015
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Ingår i: IEEE Wireless Communications Letters. - 2162-2345. ; :99
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Tidskriftsartikel (refereegranskat)abstract
- In Space Division Multiple Access (SDMA) systems, users are separated based on their positions. The base-station (BS) signals typically reach the users through multipath clusters. The goal of this work is to find the probability that a randomly selected user will receive the signal from the BS via at least one nonshared (by any other user) multipath cluster. This probability, referred to as PSuccess, provides (under some conditions) the limit of the probability that the BS is able to communicate successfully with a randomly selected user using SDMA without causing significant interference to other users. In order to find PSuccess, we first derive a model describing the probability distribution function (pdf) of the non-overlapping area of a set of circles, that have the same radius and are spatially distributed according to a Poisson distribution. Then, the proposed model for this pdf is used to express PSuccess as a function of the user’s intensity and the clusters’ intensity. Simulations, using the COST 2100 model, for outdoor and indoor scenarios, are used to validate the derived expression for PSuccess with a very good agreement, where the maximum error was 0:04.
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| 5. |
- Flordelis, Jose, et al.
(författare)
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Exploiting antenna correlation in measured massive MIMO channels
- 2016
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Ingår i: 2016 IEEE 27th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications, PIMRC 2016. - 9781509032549
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Konferensbidrag (refereegranskat)abstract
- We investigate antenna correlation of an M-antenna massive multiple-input multiple-output (MIMO) setup with the purpose of obtaining a low-rank representation of the instantaneous massive MIMO channel. Low-rank representation bases using short-term and long-term antenna correlation statistics are defined, and their performance is evaluated with data sets obtained from channel measurements in both indoor and outdoor environments at 2.6 GHz. Our results indicate that the short-term bases can capture a larger amount of the channel energy compared to the long-term ones, but they have a limited timespan, one coherence time or less. On the other hand, the long-term bases are stable over time-spans of a few seconds. Hence, they can be obtained relatively easily. We also investigate a rank-p vector-scalar LMMSE channel estimator that exploits antenna correlation. Our results show that the investigated estimator can achieve a performance similar to that of full-rank LMMSE at a (2p + 1)/M times lower cost. The investigated estimator may be used in conjunction with estimators that exploit correlation in the frequency and time domains or, alternatively, in situations in which these estimators cannot be used, e.g., when pilot separation is larger than the channel coherence bandwidth or time.
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| 6. |
- Flordelis, Jose, et al.
(författare)
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Spatial Separation of Closely-Spaced Users in Measured Massive Multi-User MIMO Channels
- 2015
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Ingår i: 2015 IEEE International Conference on Communications (ICC). ; , s. 1441-1446
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Konferensbidrag (refereegranskat)abstract
- Fully-synchronous measurements of a massive multi-user multiple-input multiple-output (MU-MIMO) radio propagation channel are presented. We evaluate the ability of a massive MIMO system to spatially separate users located close to each other in line-of-sight (LOS) propagation conditions. The system consists of a base-station (BS) antenna array equipped with 64 dual-polarized antenna elements (128 ports) arranged in a cylindrical configuration, and eight single-antenna users. The users are confined to a five-meter diameter circle and move randomly at pedestrian speeds. The BS antenna array is located on top of a 20 m tall building and has LOS to the users. We examine user separability by studying singular value spread of the MU-MIMO channel matrix for several subsets of BS antenna array ports, along with sum-rate capacity and achievable sum-rates with both zero-forcing and matched-filtering linear precoders. We also analyze the performance of the user with the lowest rate. Finally, a comparison between the performance offered by the massive MIMO system and that of a conventional MU-MIMO system is provided. To the best of our knowledge, this is the first report of fully-synchronous dynamic measurements of a massive MIMO system. Our investigation shows that even users located close to each other in LOS propagation conditions can be spatially separated in a massive MIMO system.
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| 7. |
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| 8. |
- Gao, Xiang, et al.
(författare)
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Extension of the COST 2100 channel model for massive MIMO
- 2015
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Massive MIMO has been shown, both in theory and through experiments, to offer very promising properties. These include the possibility to decrease output power by at least an order of magnitude while still achieving large gains in spectral efficiency, as compared to today’s access schemes. To efficiently design communication algorithms and evaluate massive MIMO schemes, channel models that capture important massive MIMO channel characteristics are needed. We pursue this by extending a well-known cluster-based MIMO channel model - the COST 2100 model. In the paper, we suggest a model extension for massive MIMO, and we discuss main concepts, parameters and implementation issues. The modeling work is based on measurement data from a measurement campaign in the 2.6 GHz frequency range using a physically-large array with 128 elements.
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| 9. |
- Gao, Xiang, et al.
(författare)
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Massive MIMO performance evaluation based on measured propagation data
- 2015
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Ingår i: IEEE Transactions on Wireless Communications. - 1536-1276. ; 14:7, s. 3899-3911
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Tidskriftsartikel (refereegranskat)abstract
- Massive MIMO, also known as very-large MIMO or large-scale antenna systems, is a new technique that potentially can offer large network capacities in multi-user scenarios. With a massive MIMO system, we consider the case where a base station equipped with a large number of antenna elements simultaneously serves multiple single-antenna users in the same time-frequency resource. So far, investigations are mostly based on theoretical channels with independent and identically distributed (i.i.d.) complex Gaussian coefficients, i.e., i.i.d. Rayleigh channels. Here, we investigate how massive MIMO performs in channels measured in real propagation environments. Channel measurements were performed at 2.6 GHz using a virtual uniform linear array (ULA) which has a physically large aperture, and a practical uniform cylindrical array (UCA) which is more compact in size, both having 128 antenna ports. Based on measurement data, we illustrate channel behavior of massive MIMO in three representative propagation conditions, and evaluate the corresponding performance. The investigation shows that the measured channels, for both array types, allow us to achieve performance close to that in i.i.d. Rayleigh channels. It is concluded that in real propagation environments we have characteristics that can allow for efficient use of massive MIMO, i.e., the theoretical advantages of this new technology can also be harvested in real channels.
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| 10. |
- Karlsson, Fredrik, et al.
(författare)
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Sensor Fused Indoor Positioning Using Dual Band WiFi Signal Measurements
- 2015
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Ingår i: 2015 European Control Conference (ECC). - 9783952426937 ; , s. 1669-1672
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Konferensbidrag (refereegranskat)abstract
- In this paper, signal strengths from known WiFi access points are used together with a particle filter to perform indoor navigation. It is shown that more information is obtained by using signals of both 2.4 and 5.0 GHz, compared to using only one frequency. Thus, using both frequencies provides a more accurate positioning. The second contribution is an algorithm where WiFi measurements are combined with pedestrian dead reckoning (PDR), which is based on step counting using an accelerometer and hypotheses of the heading using a gyroscope. This was found to provide further accuracy compared to more conventional methods.
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