| 1. |
- Coldrey, Mikael, 1972, et al.
(författare)
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Higher order MIMO outdoor-to-indoor measurements using repeaters
- 2010
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Ingår i: IEEE Vehicular Technology Conference. - 1550-2252. - 9781424425198
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper we present results from a outdoor- to-indoor MIMO measurement campaign where we study the effect of repeaters on singular values, spatial richness, capacity, and delay spread distributions. We present results from different repeater scenarios such as, e.g. different outdoor/indoor repeater deployments with single/dual polarized antennas. The measurements show that repeaters significantly enhance the received SNR while they increase the delay spread and decrease the spatial richness of the MIMO channel. However, the main conclusion is that a significant increase in channel capacity is attained when deploying repeaters mostly thanks to their ability to provide spatial multiplexing over the high-quality eigenmodes they may provide. The number of such eigenmodes is limited by the number of repeaters, deployment, and their antennas. © 2010 IEEE.
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| 2. |
- Ingason, Tryggvi, 1983, et al.
(författare)
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Impact of frequency selective channels on a line-of-sight MIMO microwave radio link
- 2010
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Ingår i: IEEE Vehicular Technology Conference. - 1550-2252. - 9781424425198
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Two line-of-sight (LoS) multiple-input multipleoutput (MIMO) systems for point-to-point microwave radio links are simulated and analyzed. Both 2×2 spatially-separated, singlepolarized and 4×4 spatially-separated, dual-polarized systems are considered in the presence of a frequency selective and time varying channel. Time dependence is introduced by moving the antennas during the simulation and thereby introducing the need for an adaptive space-time-equalizer (STE). Our results indicate that a time-varying frequency selective LoS MIMO channel puts higher requirements on the STE and introduces a higher SNR penalty compared to a single-input single-output (SISO) system. © 2010 IEEE.
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| 3. |
- Li, Jingya, 1986, et al.
(författare)
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A novel frequency reuse scheme for coordinated multi-point transmission.
- 2010
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Ingår i: IEEE Vehicular Technology Conference Spring, Taipei, Taiwan, May 2010. - 1550-2252. - 9781424425198 ; , s. 1-5
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Konferensbidrag (refereegranskat)abstract
- Coordinated Multi-Point (CoMP) transmission is considered in 3GPP LTE-Advanced as a key technique to improve the cell-edge performance. In order to support joint resource allocation among coordinate cells in CoMP systems, efficient frequency reuse schemes need to be designed. However, most of the existing frequency reuse schemes are not suitable for CoMP transmission due to not considering multi-cell joint transmission scenario in their frequency reuse rule. To solve this problem, a cooperative frequency reuse (CFR) scheme is proposed in this paper, which divides the cell-edge area of each cell into two types of zones, and defines a frequency reuse rule to support CoMP transmission for users in these zones. Compared with the conventional soft frequency reuse (SFR) scheme, simulation results demonstrate that the CFR scheme reduces the blocking probability by more than 50%, and improves the cell-edge throughput by 30~40%, with 5~9% additional cell-average throughput.
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| 4. |
- Makki, Behrooz, 1980, et al.
(författare)
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Efficient Channel Quality Feedback Signaling using Transform Coding and Bit Allocation
- 2010
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Ingår i: IEEE 71st Vehicular Technology Conference. - 1550-2252. - 9781424425198 ; 1
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Konferensbidrag (refereegranskat)abstract
- Recently, substantial attention has been paid to compressThe channel quality information feedback while preservingmost of its relevant information, as required for Adaptive Modulation and Coding (AMC). This paper compares the performance of some feedback lossy compression methods and, particularly, investigate the effect of bit allocation on their performance. Simulation results show that the Discrete Cosine Transform (DCT) approach, along with our proposed bit allocation method, leads to the best compression performance feedback.
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| 5. |
- Svensson, Tommy, 1970, et al.
(författare)
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On Power Amplifier Efficiency with Modulated Signals
- 2010
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Ingår i: Proc. IEEE Vehicular Technology Conference, VTC2010-Spring, 2010. - 1550-2252. - 9781424425198
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Konferensbidrag (refereegranskat)abstract
- We have investigated the performance in terms of overall efficiency and maximum output power of a real high power amplifier with various modulated signals, ranging from constant envelope signals to orthogonal frequency division multiplexing based signals having large envelope variations. We show that there are large differences on the overall amplifier efficiency as well as its maximum output power depending on the modulated signal and also on the operation mode. In particular, we show that for high overall efficiency it is important to operate the amplifier close to the maximum output power level as often as possible, and we show that this has consequences for the resource allocation in especially packet based multicarrier systems. We also show that the amplifier performance with various Single-Carrier Frequency Division Multiple Access signals is very similar, and that the peak-to-average-power ratio can be used to predict the overall efficiency for the traditional amplifier drive method. Finally, we show that with advanced, today infeasible, amplifier operation methods the overall amplifier efficiency depends less on the modulation scheme, thus motivating further research in that domain.
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| 6. |
- Tahmasebi Toyserkani, Arash, 1978, et al.
(författare)
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A Complexity Adjustable Scheduling Algorithm for Throughput Maximization in Clusterized TDMA Networks
- 2010
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Ingår i: IEEE Vehicular Technology Conference. - 1550-2252. - 9781424425198
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Konferensbidrag (refereegranskat)abstract
- We consider clustered wireless networks, wheretransceivers in a cluster use a time-slotted mechanism (TDMA) to access a wireless channel that is shared among several clusters.Earlier work has demonstrated that a significant increase innetwork throughput can be achieved if all the schedules areoptimized jointly. However, a drawback of this approach is the prohibitive level of computational complexity is required when a network with a large number of clusters and time-slots is to be scheduled. In this paper, we propose a modification to our previously proposed algorithm which allows for the complexityto be adjusted to the available processing power, provided some minimum processing power is available. This is achieved by carefully reducing the number of interfering clusters considered when scheduling a cluster. In addition, we propose and evaluatetwo heuristic methods of discarding the less significant clusters.While the optimality of the obtained schedule is not proven, our results demonstrate that large gains are consistently attainable.
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| 7. |
- Wilhelmsson, Leif, et al.
(författare)
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Performance analysis of sign-based pre-FFT synchronization in OFDM systems
- 2010
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Ingår i: IEEE Vehicular Technology Conference. - 1550-2252. - 9781424425198
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Konferensbidrag (refereegranskat)abstract
- This paper treats the feasibility to use only the sign bit of the in-phase and quadrature components when estimating time and frequency in OFDM systems. Using only the sign bit is shown to result in a frequency dependent bias, which can be easily compensated. The approach is evaluated for LTE and DVB-H, where the estimation is performed using the cyclic prefix, and for WLAN 802.11g, where the estimation is done using the short training field (STF). The performance is compared to a floating point implementation, and it is also compared to what is believed to be reasonable requirements for initial time and frequency estimation.
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| 8. |
- Alegria, Juan Vidal, et al.
(författare)
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Decentralized equalizer construction for large intelligent surfaces
- 2019
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Ingår i: 2019 IEEE 90th Vehicular Technology Conference, VTC 2019 Fall - Proceedings. - 1550-2252. - 9781728112206 ; 2019-September
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Konferensbidrag (refereegranskat)abstract
- In this paper we present fully decentralized methods for calculating an approximate zero- forzing (ZF) equalizer in a large intelligent surface (LIS). A LIS is intended for wireless communication and facilitates unprecedented MU- MIMO performance, far superior to that of Massive MIMO. Antenna modules in the grid connect to their neighbors to exchange messages of information needed for interference cancellation in a fully- decentralized fashion, making the system scalable. By a careful design of how the messages are routed, we show that the proposed method is able to cancel inter-user interference sufficiently well without any centralized coordination, opening the door for the realization of this type of structures.
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| 9. |
- Almers, Peter, et al.
(författare)
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Effect of random walk phase noise on MIMO measurements
- 2005
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Ingår i: [Host publication title missing]. - 1550-2252. ; 61:1, s. 141-145
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Konferensbidrag (refereegranskat)abstract
- In this paper we study the influence of phase noise from free-running local oscillators on SAGE signal parameter estimation. Phase noise is here modeled as a random-walk process. We present phase noise estimates from our LUND RUSK MIMO channel sounder, and draw conclusions on requirements on local oscillators' phase noise in terms of the Allan variance. We investigate an error propagation effect in SAGE, and finally, we present random-walk phase noise effect on channel capacity.
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| 10. |
- Ang, Lay-Hong, et al.
(författare)
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Modification of SOVA-based Algorithms for Efficient Hardware Implementation
- 2010
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Ingår i: IEEE 71st Vehicular Technology Conference (VTC 2010-Spring), 2010. - 1550-2252. ; , s. 1-5
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Konferensbidrag (refereegranskat)abstract
- In this paper, a modified soft-output Viterbi algorithm (SOVA) is presented to enable efficient hardware implementation. The forward-only processing of the SOVA has an inherent lower latency than forward-backward algorithms such as BCJR and its offspring, which are commonly used in iterative decoders. Thus, SOVA-based architectures require less parallelization and therefore hardware for the same data throughput. A simplification is proposed to the Battail rule ( BR) SOVA to approximate the concurrent path reliability values with the corresponding metric differences. This simplified BR-SOVA (SB-SOVA) performs close to max-log-MAP. Furthermore, a novel hybrid decoding architecture is proposed that combines the simplicity of the original Hagenauer rule and the performance-preserving properties of the SB-SOVA to trade implementation complexity for decoding performance. The hybrid approach is evaluated with practical link-level simulations of the downlink data channel in LTE Rel-8.
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