| 1. |
- Gunnarsson, Fredrik, et al.
(författare)
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Post-processing of drive test measurements using spatial filtering
- 2004
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Ingår i: IEEE Vehicular Technology Conference (VTC) Proceedings. - : IEEE. - 1550-2252. ; 1, s. 79-83
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Tidskriftsartikel (refereegranskat)abstract
- Drive tests are important means to evaluate critical properties of a wireless network in operation. The network coverage is vital, and therefore, the received power of pilot signals from the base stations are monitored to estimate the spatial distributions and variations of the power gain. With uniform time-sampling and a varying velocity, the typical temporal filter fails to extract the interesting information. In this paper we apply convolutional spatial filtering, both causal and non-causal, to resolve the problem. Relations to spatial data analysis methods are also commented upon. Simulations indicate significant improvements.
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| 2. |
- Tufvesson, Fredrik, et al.
(författare)
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Ultra-wideband communication using hybrid matched filter correlation receivers
- 2004
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Ingår i: IEEE Vehicular Technology Conference. - 1550-2252. ; 59:3, s. 1290-1294
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Konferensbidrag (refereegranskat)abstract
- For ultra-wideband (UWB) communication, Rake receivers using matched filter detection show the best performance but they are complex to realize due to the inherent channel estimation problem and combining problem. Transmitted reference schemes, on the other hand, allow for a less complex receiver structure that is able to combine the energy from different multipath components without channel estimation. These schemes, however, show a performance loss due to non-linear operations on noise terms (generation of noise-noise crossterms) when forming the decision variable. This paper describes a receiver structure for UWB communication capable of capturing the energy from different paths without the need for channel estimation. The proposed hybrid matched filter correlation receivers reduce the performance loss, due to the noise-times-noise term.
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| 3. |
- van de Beek, Jaap, et al.
(författare)
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Benefits of modulation diversity in turbo-coded OFDM systems
- 2004
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Ingår i: IEEE Vehicular Technology Conference (VTC) Proceedings. - 1550-2252. ; 59:2, s. 929-933
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we show that the use of modulation diversity provides gains to punctured, turbo-coded OFDM systems. For an OFDM transmission scenario based on the downlink of the 3GPP standard for mobile communications, we show that the order-2 modulation diversity observed for the raw bit-error rate transfers to the block-error rate in a number of investigated channel environments. We demonstrate gains of up to 2.5 dB depending on the puncturing rate of the scheme and the particular channel characteristics. Alternatively, for schemes with higher puncturing rates, 2 or 3 turbo decoder iterations suffice to achieve the same performance as achieved by 8 decoder iterations in a regular transmission.
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| 4. |
- Wyne, Shurjeel, et al.
(författare)
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Outdoor to indoor office MIMO measurements at 5.2 GHz
- 2004
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Ingår i: IEEE Vehicular Technology Conference. - 1550-2252. - 0780385217 ; 1, s. 101-105
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Konferensbidrag (refereegranskat)abstract
- This paper presents the results of one of the first measurement campaigns for the double-directional characterization of outdoor to indoor wireless propagation channels. Such channels play a vital role for cellular systems with multiple antenna elements at transmitter and receiver, i.e. multiple-input multiple-output (MIMO) systems. Measurements were performed at 5.2 GHz between 53 different receiver locations in an office building, and three "base station" positions on a nearby rooftop. In the paper we present results for angular-delay profiles, RMS angular spread, and other statistical parameters characterizing delay and angular dispersion.
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| 5. |
- Zander, Roland, et al.
(författare)
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A rate-based bandwidth borrowing and reservation scheme for cellular networks
- 2004
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Ingår i: IEEE Vehicular Technology Conference. - 1550-2252. ; 60:2, s. 1123-1128
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Konferensbidrag (refereegranskat)abstract
- In the third generation cellular networks and beyond, a wide variety of different services are/will be provided by the operators. Out of QoS reasons, it is preferable to give higher priority to certain connection types. These include calls carrying delay-sensitive services and already ongoing calls. In this paper, a prioritization method combining bandwidth borrowing and reservation, called BBR, is introduced. BBR monitors the rate-adaptiveness of the ongoing calls in a cell. Simultaneously, advanced movement predictions are applied to estimate the arrival rate to each cell. If it is determined that the use of bandwidth borrowing (temporarily reducing the data rate of other calls in the same cell) is not sufficient to support the high priority calls that are expected to arrive, a portion of the assigned bandwidth to the cell is exclusively reserved for these calls to prevent call dropping. The scheme enables the operator to increase the average user satisfaction in the network. This is achieved by defining appropriate penalty functions for blocking, dropping and bandwidth reduction of a call.
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| 6. |
- Zander, Roland, et al.
(författare)
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A zone-based bandwidth reservation scheme for UMTS
- 2004
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Ingår i: IEEE Vehicular Technology Conference. - 1550-2252. ; 59:4, s. 1993-1998
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Konferensbidrag (refereegranskat)abstract
- It is out of QoS reasons advisable for cellular operators to give higher priority to already ongoing connections than new call attempts. This can be achieved by having bandwidth in each cell exclusively reserved for these calls. Herein, a method for dynamically determining the size of the reserved bandwidth in UMTS networks, called Zone-based Reservation Scheme (ZRS), is introduced. For this purpose, ZRS applies advanced subscriber movement predictions. The prediction accuracy is improved by grouping the calls according to previous movement patterns and speed, where data are collected separately for each group. To handle the soft capacity property of UMTS, ZRS considers both intra- and intercellular movements. This is achieved by dividing the cell areas into zones and tracking every cell zone ID alteration for all ongoing calls. ZRS can be implemented together with most call admission control schemes.
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