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Outline

Outline. The KUL, imec and BelgiumPrevious workWork at BWRC. . 3. KUL and imec. Katholieke Universiteit Leuven Founded in 1425 (better than Lund Uni.!)> 4400 PhD and post-doc students 35 000 students (4500 international students)imec > 1600 staff170 PhD studentsSpin-off from KUL.

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Outline

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    1. Goal: to improve the performance of the interference channel in frequency-selective channels (OFDM system) Goal: to improve the performance of the interference channel in frequency-selective channels (OFDM system)

    2. Outline The KUL, imec and Belgium Previous work Work at BWRC 2

    3. Outline The KUL, imec and Belgium Previous work Work at BWRC 3

    4. KUL and imec Katholieke Universiteit Leuven Founded in 1425 (better than Lund Uni.!) > 4400 PhD and post-doc students 35 000 students (4500 international students) imec > 1600 staff 170 PhD students Spin-off from KUL 4

    5. Belgium 5 Population: 11M Dutch speaking 59% French speaking 40% German speaking 1%

    6. (some of the) research at imec imec wireless - Cognitive reconfigurable radios - Gbit/s radio @ mm wave (60 GHz) Nano-electronics: maintain performance at shrinking dimensions, new materials… Biomedical electronics: bio-sensing, diagnosis Energy technology: solar cells, harvesting energy Smart systems: reconfigurable radios, bio implants… 6

    7. Outline The KUL, imec and Belgium Previous work Work at BWRC 7

    8. 8 Mesh is a promising technology for 4G terminals Provide higher data rate (better link quality) Increase coverage (multi-hop transmissions) Improve power efficiency (network management) Enhance reliability (route alternative)

    9. 9 Mesh networks foreseen in main emerging IEEE standards 802.15.5 Mesh networking (Bluetooth, Zigbee) 802.11s Mesh networking (Wifi) 802.16e (Mobile WiMAX) Allow a set (up to 32) WLAN devices to communicate each other, Enable topology learning and dynamic path configuration.Allow a set (up to 32) WLAN devices to communicate each other, Enable topology learning and dynamic path configuration.

    10. Beamforming may improve the performance of wireless mesh networks 10

    11. 11 What is beamforming? The transmitter exploits some knowledge about the channel to shape the transmitted signal to the desired directions As a result, the performance can be increased, e.g., in terms of error rate, capacity… As a result, the performance can be increased (e.g. in terms of error rate, power consumption or throughput) In practice, most systems rely on partial CSI or codebook beamforming (e.g., 3GPP) As a result, the performance can be increased (e.g. in terms of error rate, power consumption or throughput) In practice, most systems rely on partial CSI or codebook beamforming (e.g., 3GPP)

    12. Non-cooperative beamforming Mitigate interference between users: increase frequency reuse factor 12

    13. Cooperative beamforming Increase channel quality towards a single (or possibly multiple) users 13

    14. Outline The KUL, imec and Belgium Previous work Work at BWRC 14

    15. Goal: study the impact of frequency offset in the cooperative scheme 15

    16. Source of errors in a multicarrier system 16

    17. Impact of carrier frequency offset (CFO) 17

    18. Channels (phase rotation) must be tracked 18

    19. Summary It is (very) challenging to compensate for the multiple frequency offsets at the receiver 1 - Fine synchronization necessary at the transmitters prior to transmissions 2 – Algorithms are needed to mitigate the effects of the frequency mismatch 19 In a single user scenario, the destination can mitigate the frequency offset (i.e, estimate the frequency offset and adjust its local oscillator accordingly) However this is not possible when multiple frequency offsets are present! In a single user scenario, the destination can mitigate the frequency offset (i.e, estimate the frequency offset and adjust its local oscillator accordingly) However this is not possible when multiple frequency offsets are present!

    20. 20

    21. Eusipco’09 21

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