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[Author] Ramjee PRASAD(3hit)

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  • Weighted OFDM for Wireless Multipath Channels

    Homayoun NIKOOKAR  Ramjee PRASAD  

     
    PAPER

      Vol:
    E83-B No:8
      Page(s):
    1864-1872

    In this paper the novel method of "weighted OFDM" is addressed. Different types of weighting factors (including Rectangular, Bartlett, Gaussian, Raised cosine, Half-sin and Shanon) are considered. The impact of weighting of OFDM on the peak-to-average power ratio (PAPR) is investigated by means of simulation and is compared for the above mentioned weighting factors. Results show that by weighting of the OFDM signal the PAPR reduces. Bit error performance of weighted multicarrier transmission over a multipath channel is also investigated. Results indicate that there is a trade off between PAPR reduction and bit error performance degradation by weighting.

  • European Research towards Future Wireless Communications

    Flemming Bjerge FREDERIKSEN  Ramjee PRASAD  Gert F. PEDERSEN  Istvan Z. KOVACS  

     
    INVITED PAPER

      Vol:
    E88-B No:6
      Page(s):
    2259-2267

    This paper presents an overview of four on-going European research projects in the field of mobile and wireless communications leading to the next generations of wireless communications. The projects started in 2004. They investigate requirements and definition of access technology, network architecture, antennas and propagation, security, services, applications and socio-economic impact.

  • Capacity Analysis of a Cellular Direct Sequence Code Division Multiple Access System with Imperfect Power Control

    Ramjee PRASAD  Michel G. JANSEN  Adriaan KEGEL  

     
    PAPER

      Vol:
    E76-B No:8
      Page(s):
    894-905

    The capacity of a cellular direct sequence code division multiple access system is investigated in situations with and without power control for both the reverse link (from mobile to base station) and the forward link (from base station to mobile). The capacity is defined as the number of simultaneous users per cell with a prespecified performance. A theoretical analysis of the effect of imperfect power control on the reverse link capacity is presented using an analytical model. To investigate the reverse link capacity without any form of power control, a general spatial user distribution is developed which is very suitable for analytical study of any multiple access system with the near-far effect problem. The performance of the reverse link of a CDMA system is also evaluated considering the users located in surrounding cells. Finally, the forward link capacity is studied considering multiple cells. Two possible forward power control schemes, namely carrier-to-interference ratio driven and distance driven systems, are discussed.