Joacim Olsson
Electronic Devices, Dept. of Electrical Engineering, Linköping University, Sweden \ Swedish Microelectronic Institute Acreo AB, Sweden
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Published in: GigaHertz 2003. Proceedings from the Seventh Symposium
Linköping Electronic Conference Proceedings 8:32, p.
Published: 2003-11-06
ISBN:
ISSN: 1650-3686 (print), 1650-3740 (online)
This work is related to the SoCTRix-project; where a multi-standard mobile transceiver is being designed as a demonstrator. This work focuses on the two standards 802.11a and WCDMA. The mobile terminal will have a high degree of integration and a large reuse of hardware at the same time as it will support standards very different from each other. The large difference between the two considered standards put different requirements on the receiver. The main focus of this work is to find the individually best architecture for the two standards and a way to combine them with little hardware overhead.
WCDMA uses code division multiple access (CDMA). WCDMA is a spread spectrum system that spreads the data with a direct sequence (DSSS) to a chip-rate of 3.84Mcps. By using different spreading rates from 2 to 256; it can accomplish varying data-rates from 12.2kbps to almost 2Mbps. The spread data is modulated with QPSK. Different users residing on the same frequency at the same time; are separated by different orthogonal codes. Duplex is accomplished by frequency division (FDD) where transmission and reception take place simultaneously at different frequencies. For details about WCDMA see [4].
802.11a uses an orthogonal frequency division multiplexing (OFDM)transmission scheme. It can be seen as information divided between a set of sub-carriers separated in frequency. The total bandwidth used is 16.6MHz. The information is modulated on to the sub-carriers with different schemes depending on the used data-rate. For the lowest rate the modulation scheme is QPSK ranging up to 64QAM for the highest data rate of 54Mbps. In 802.11a duplex is accomplished by time division (TDD) where transmission and reception takes place at different times at the same frequency. For details about 802.11a see [5].
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[4] ETSI TS 125 101 "UE Radio Transmission and Reception (FDD)"; v3.5.0 2000-12
[5] IEEE 802.11a - 1999 Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications High-speed Physical Layer in the 5 GHz Band
[6] S. Haykin. ”Digital Communications”; John Wiley & Sons Inc.; 1988; pp. 289.
