| 1. |
- Chen, Lei, et al.
(författare)
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Generalized Frequency Reuse Schemes for OFDMA Networks: Optimization and Comparison
- 2010
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Ingår i: IEEE 71st Vehicular Technology Conference (VTC 2010-Spring), 2010. - Piscataway, NJ, USA : IEEE. - 9781424425181 - 9781424425198
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Konferensbidrag (refereegranskat)abstract
- Frequency reuse is a key concept for interference mitigation and thereby enhancing cell-edge performance in OFDMA networks. Two representative strategies are Fractional Frequency Reuse (FFR) and Soft Frequency Reuse (SFR). Both divide a cell into a center zone and an edge zone, and differentiate their levels of frequency reuse. Previous work on FFR and SFR has focused on networks of relatively small size with standard hexagon-shaped cells. And dividing the cell edge frequency band into three parts has been a common practice so far. However, for real-life networks, this is inadequate because of the irregular cell layout. We consider generalized FFR and SFR schemes, where the number of sub-bands is not restricted to three, and for SFR the power ratio is variable. To find optimal sub- band allocation for the generalized schemes, we present an approach based on large-scale optimization to deal with networks with irregular cell layout. The optimization process allows us to analyze the impact of the number of sub-bands and the SFR power ratio on cell-edge performance, and thereby compare the reuse schemes. We conduct experiments on large networks with realistic radio propagations and present a thorough numerical comparison.
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| 2. |
- 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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| 3. |
- Botella Mascarell, Carmen, 1979, et al.
(författare)
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On the performance of joint processing schemes over the cluster area
- 2010
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Ingår i: IEEE Vehicular Technology Conference Spring, Taipei, Taiwan, May 2010. - 1550-2252. - 9781424425181 ; 2010-January, s. 1-5
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Konferensbidrag (refereegranskat)abstract
- In this paper, three joint processing schemes for the downlink are characterized and compared within a cluster of base stations. The motivation of this study is to analyze the performance of these schemes over the cluster area, as a first step towards designing an adaptive joint processing scheme supporting dynamic usage scenarios. Each one of the analyzed schemes, the centralized, partial and distributed joint processing approaches, requires a different amount of available channel knowledge at the transmitter side, inter-base information exchange and feedback from the users. In addition, these schemes show varying capabilities to serve the users depending on their location in the cluster area. Therefore, in a real scenario, an adaptive joint processing scheme encompassing the three schemes could be used by the cluster of base stations. Simulation results show that, assuming coherent transmission, the centralized joint processing scheme outperforms with 25% the partial joint processing scheme and with 50% the distributed joint processing approach in the cell edge when a backhaul-load weighted average sum-rate per cell metric is taken into account.
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| 4. |
- 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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| 5. |
- Kolmonen, Veli-Matti, et al.
(författare)
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A dual-link capacity analysis of measured time-variant radio indoor channels
- 2010
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Ingår i: 2010 IEEE 71st Vehicular Technology Conference. - 9781424425181
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Konferensbidrag (refereegranskat)abstract
- There has been extensive research about single link multiple-input multiple-output (MIMO) channels, both simulated and measured, but only few studies have targeted multilink analysis with measured channel data. Hence, in this paper, we analyze the influence of spatial separation of user terminals and the human shadowing effect on the MIMO capacity and to the signal to interference ratio (SIR) in a time-variant dual-link scenario. The paper analyses the dual-link channel capacity based on simulations as well as measurements conducted using dynamic dual-link dual-polarized wideband MIMO channel sounder in an indoor office environment, and compare the results to the singlelink capacity. Here the analysis is restricted to 4 x 4 MIMO links. The following conclusions have been obtained from the analyses: 1) Compared to the single link case, the dual-link channel capacity is more affected by the SIR than the spatial separation of the users. 2) The human shadowing introduced variations of SIR up to ±10 dB, causing large fluctuations in the dual-link capacity.
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| 6. |
- 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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| 7. |
- Lungaro, Pietro, et al.
(författare)
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Predictive and Context-based Multimedia Content Delivery inFuture Cellular Networks
- 2010
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Ingår i: 2010 IEEE 71ST VEHICULAR TECHNOLOGY CONFERENCE. - 9781424425198
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Konferensbidrag (refereegranskat)abstract
- A context aware model for the delivery of contentin mobile networks is presented and studied through simulation.The proposed model is based on predictive knowledge of mobileuser behavior related to consumption of content on smartterminals. Content prediction is here exploited to change the timeand the location of content delivery, opportunistically utilizing theinstantaneously available excess of resources in the network. Thisis anticipated both to increase network utilization and to enhanceuser perceived service quality. However, since the accuracy of thecontext information, and associated content predictions, mighthave a significant impact on performances, our investigationshave been accounting for different content prediction capabilitiesas well as for various degrees of similarity in users’ contentrequests. The obtained results show that substantial gains bothin terms of wireless network efficiency and improved user serviceperception can be achieved, as compared to classical contentdelivery methods, for a number of realistic scenarios.
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| 8. |
- 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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| 9. |
- Modarres Razavi, Sara, 1981-, et al.
(författare)
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Exploiting Tracking Area List for Improving Signaling Overhead in LTE
- 2010
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Ingår i: Proceedings of IEEE 71st Vehicular Technology Conference (VTC 2010-Spring). - : IEEE. - 9781424425181 ; , s. 1-5
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Konferensbidrag (refereegranskat)abstract
- Reducing the overhead required for tracing mobile devices is one of the major aspects in the study of mobility management of a cellular network. The Long Term Evolution (LTE) systems give a more flexible configuration of Tracking Area (TA) design by means of Tracking Area List (TAL). Being a novel concept, TAL goes beyond the capability of the conventional TA approach. Although TAL is expected to be able to reduce the overall signaling overhead by overcoming a couple of major limitations of the conventional TA concept, how to apply TAL in large scale networks, remains unexplored. In this paper, we present a novel approach for allocating and assigning TA lists. The approach does not require any data other than what is needed for conventional TA design. We present numerical results to illustrate the approach for a realistic network of Lisbon city. The experiments demonstrate the ability of TAL in reducing the signaling overhead compared to the conventional TA concept.
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| 10. |
- Sjödin, Tomas, et al.
(författare)
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Two-slot channel estimation for analog network coding based on OFDM in a frequency-selective fading channel
- 2010
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Ingår i: IEEE Vehicular Technology Conference. - : IEEE. - 9781424425181 ; , s. 1-5
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Konferensbidrag (refereegranskat)abstract
- Recently, broadband analog network coding (ANC) was introduced to utilize high-data rate transmission over the wireless - frequency selective fading - channel. However, ANC requires the knowledge of channel state information (CSI) for self-information removal and coherent signal detection. In this paper, we propose a two-slot pilot-assisted CE for bi-directional broadband ANC. In the first slot, two users transmit their respective pilots to the relay, where the users' pilot signals are designed to avoid the interference and consequently, allow the relay to estimate the CSIs from both users. During the second slot the relay broadcast its pilot signal to both users that estimate the corresponding CSIs. It was shown by computer simulation that, even with imperfect CSI, the BER performance of broadband ANC gives a satisfactory performance for a low and moderate mobile terminal speed in a frequency-selective fading channel.
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