| 1. |
- Almers, Peter, et al.
(författare)
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Measured capacity gain using waterfilling in frequency selective MIMO channels
- 2002
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Ingår i: The 13th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, 2002 , vol 1-5, Proceedings. - 0780375890 ; , s. 1347-1351
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Konferensbidrag (refereegranskat)abstract
- We analyze the channel capacity of multiple-input multiple-output (MIMO) systems in frequcncy selective channels, with channel knowledge at the transmitter side. An optimum transmission scheme uses Shannon's principle of waterfilling jointly in the frequency and the spatial domain. However, we show in this paper that the largest gain by using waterfilling resides in the spatial domain, and that the capacity gain from the frequency domain is very small for MIMO systems. We quantify the gain for a theoretical Rayleigh fading channel model and for microcellular channels as measured in an enclosed court-yard.
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| 2. |
- Dai, H, et al.
(författare)
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Downlink Capacity of Interference-Limited MIMO Systems
- 2002
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Ingår i: [Host publication title missing]. - 0780375890 ; , s. 849-853
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Konferensbidrag (refereegranskat)abstract
- In a paper by Dai and Molisch (see Proc. IEEE VTC 2002 Spring, Birmingham, AL, May 2002), space-time layered architectures (BLAST) and turbo coding/processing techniques, which are effective for single-link transmission, are combined with multiuser detection (MUD) methods for combating intercell interference. It is shown that, depending on the channel configuration, linear MMSE or successive interference cancellation (SIC) can be the preferable MUD method. Based on this fact, an adaptive scheme is developed. T/sup h/e downlink capacity of interference-limited multiple-input multiple-output (MIMO) cellular systems is investigated. It is found that the obtained MUD capacity is excellent in high to medium SIR scenario, but still deteriorates in strong interference environments, leaving ample room for possible improvement through other techniques. The performance of the proposed adaptive MUD scheme in a standard cellular environment, both in the non-line-of-sight (NLOS) and the line-of-sight (LOS) case, is simulated, and the advantages over the standard V-BLAST scheme are quantified.
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| 3. |
- Escudero-Pascual, Alberto, et al.
(författare)
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Role(s) of a proxy in location based services
- 2002
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Ingår i: 13TH IEEE INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, VOL 1-5, PROCEEDINGS. - : IEEE. - 0780375890 ; , s. 1252-1256
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Konferensbidrag (refereegranskat)abstract
- We examine a number of roles that a proxy server can play in location based services and how it can be used to provide protection of personal identifiable information. Location data, service requests, and privacy policies are encoded in XML by the mobile terminal and forwarded to a proxy server placed between the mobile terminal and the location based service(s). By a suitable architecture in the mobile terminal and in the proxy, we can hide the mobile device's network location, hide the identity of its user, and, in some cases, provide misleading physical location(s). We have applied our privacy model to location information obtained from a GPS receiver. The GPS-based method was chosen as being the only available method where the positioning calculation function (PCF) is fully under the user's control, since the position is calculated within the mobile terminal; other technologies rely on the network infrastructure, and hence some or all of the position data is outside the user's control. A proof of concept was implemented using Fastrax's iTrax02 small, ultra-low power consumption GPS receiver. We illustrate a number of different functions which can be provided by examining some scenarios.
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| 4. |
- Leanderson, Carl Fredrik, et al.
(författare)
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Joint source-channel list sequence decoding
- 2002
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Ingår i: 13th IEEE International Symposium on Personal Indoor and Mobile Radio Communications. PIMRC 2002. Proceedings (Cat. No.02TH8637). - 0780375890 ; , s. 951-955
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Konferensbidrag (refereegranskat)abstract
- We evaluate the performance of list sequence (LS) maximum a posteriori probability (MAP) decoding on the additive white Gaussian noise (AWGN) channel and the fully interleaved flat Rayleigh fading channel. In particular, we focus on the frame error rate (FER) of LS-MAP decoding with genie-assisted error detection. It is demonstrated that LS-MAP decoding yields significant performance improvements relative to single sequence MAP decoding on the AWGN channel as well as the fully interleaved flat Rayleigh fading channel. Furthermore, feedback convolutional codes have been observed to have the potential to yield improved FER performance with both single sequence MAP and IS-MAP decoding, compared to feedforward convolutional codes. Based on these performance improvements, we propose a joint source-channel IS decoding scheme. The scheme is based on the max-log list algorithm for simultaneous soft symbol and IS decoding of convolutional codes. In existing systems where a cyclic redundancy check for error mitigation is concatenated with a convolutional code for error correction, this scheme can be implemented in a fully backward compatible receiver
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| 5. |
- Stranne, André, et al.
(författare)
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Throughput of IEEE 802.11 FHSS networks in the presence of strongly interfering Bluetooth networks
- 2002
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Ingår i: 13th IEEE International Symposium on Personal Indoor and Mobile Radio Communications. PIMRC 2002. Proceedings (Cat. No.02TH8637). - 0780375890 ; , s. 161-165
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Konferensbidrag (refereegranskat)abstract
- The impact of interference from Bluetooth networks on the throughput of IEEE 802.11 FHSS networks is investigated. This is done by deriving an analytical approximation of the throughput of slow frequency-hopping systems. The derivation in itself provides valuable insights into the mechanisms of interference between systems employing the frequency-hopping technique. In deriving the approximation, it is assumed that packet collisions result in total loss of all information contained in the packets involved in the collisions, regardless of the distance between the networks. The results indicate that the Bluetooth networks may have a negative effect on the throughput of an IEEE 802.11 network using long packet types
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| 6. |
- Zander, Jens
(författare)
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Affordable Multiservice Wireless Networks - Research challenges for the next decade
- 2002
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Ingår i: 13TH IEEE INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, VOL 1-5, PROCEEDINGS - SAILING THE WAVES OF THE WIRELESS OCEANS. - New York : IEEE. - 0780375890 ; , s. 1-4
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Konferensbidrag (refereegranskat)abstract
- What the consumer of telecommunication services of tomorrow will expect to receive besides some vauge notion of "Wireless Internet" is not that clear. However to obtain a widespread demand for wireless services, they have to be widely available, simple to purchase and access. Affordability and adaptation to user requirements, rather than revolutionary higher performance, will be the key design features of future wireless access systems. In this paper we briefly analyze the key cost drivers and discuss some architectural concepts for affordable wireless infrastructures. Some research directions & challenges for the next decade are outlined.
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