| 1. |
- Bayer, Nico, et al.
(författare)
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VoIP service performance optimization in pre-IEEE 802.11s Wireless Mesh Networks
- 2008
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Ingår i: Proceedings of the IEEE International Conference on Circuits andSystems for Communications (ICCSC) 2008. - : IEEE conference proceedings. - 9781424417070 ; , s. 75-79
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Konferensbidrag (refereegranskat)abstract
- 802.11-based wireless mesh networks are seen as a means for providing last mile connections to next generation networks. Due to the low deployment cost and the mature technology used, they are scalable, easy to implement and robust. With an increasing coverage of wireless networks, VoIP becomes a cheaper alternative for traditional and cellular telephony. In this paper, we carry out a feasibility study of VoIP in a dual radio mesh environment. Heading towards 802.11s, we present the design of a mesh testbed and methodology for performing the measurements. Additionally, we address the problem that small voice packets introduce a high overhead leading to a low voice capacity of 802.11 based mesh networks. In order to alleviate this problem and increase the voice capacity, a novel packet aggregation mechanism is presented and evaluated using the ns-2 simulator.
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| 2. |
- Rodriguez, Saul, et al.
(författare)
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A Novel BiST and Calibration Technique for CMOS Down-Converters
- 2008
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Ingår i: Circuits and Systems for Communications, 2008. ICCSC 2008. 4th IEEE International Conference on. - 9781424417070 ; , s. 828-832
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Konferensbidrag (refereegranskat)abstract
- This paper presents a new digital calibration methodology that allows CMOS Gilbert cell down-converters to meet their block specifications under large process, temperature and power supply variations. The calibration method consists of a novel built-in self test for direct conversion receivers that is able to measure the gain, and the second and third order intermodulation products of the mixer. A random optimizer algorithm based on a least square error function provides digital control of the biasing circuit and the loads of the mixer. The gain and IIP3 are calibrated by regulating the current of the input differential pair and by switching the loads. IIP2 calibration is achieved by using a novel technique that consists of offset voltages cancellation in the switching pairs. The technique is validated by calibrating a 0.18um CMOS mixer in several corner conditions.
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| 3. |
- Wu, Di, 1979-, et al.
(författare)
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A Programmable Lattice-Reduction Aided Detector for MIMO-OFDMA
- 2008
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Ingår i: 4th IEEE International Conference on Circuits and Systems, ICCSC,2008. - : IEEE. - 9781424417087 - 9781424417070 ; , s. 293-297
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Konferensbidrag (refereegranskat)abstract
- This paper presents the first programmable Lattice- Reduction Aided (LRA) symbol detector for Multiple-Input Multiple-Output (MIMO) and Orthogonal Frequency Division Multiple Access (OFDMA). The detector proposed is implemented using 65 nm ASIC technologies. Owing to the programmability, the detector can be dynamically switched between linear (e.g. MMSE) and lattice-reduction aided (e.g. LRA-MMSE) detectors by simply running another software subroutine. Therefore, it allows a good trade-off between performance and computational latency to be achieved under various scenarios. Along with the hardware, two algorithm simplifications (SCNT-LR and SOT-LR) are proposed for finding subcarriers with ill- conditioned channel matrices. And in the end, interpolated LR (I- LR) is proposed to further reduce the computational complexity for real-time implementations.
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