basic for wimax study

1. Basics for WI-MAX Binoy Tomy NexGTech Wireless R & D [email_address] +91 9952170483

3. To understand how OFDM and OFDMA work, lets start with its "mother" namely FDM (Frequency Division Multiplexing).

5. Each group is named a sub-channel.

6. The sub-carriers that form a sub-channel need not be adjacent.

7. In the downlink, a sub-channel may be intended for different receivers. In the uplink, a transmitter may be assigned one or more sub-channels.

9. Using sub-channelization, within the same time slot a Mobile WiMAX Base Station (BS) can allocate more transmit power to user devices (SSs) with lower SNR (Signal-to-Noise Ratio), and less power to user devices with higher SNR.

11. This power-saving feature is particularly useful for battery-powered user devices, the likely case in Mobile WiMAX.

13. A copy of last part of the OFDM symbol is prepended to the T.Xed symbols and removed at the receiver

15. Pilot subcarriers for various estimation and synchronization purposes.

16. Null subcarriers for no transmission at all, used for guard bands and DC carriers. Type of OFDMA Subcarrier

18. Can adjust modulation and coding for each carriers

19. Better spectral efficiency

20. Low complexity modulation that can easily be implemented using IFFT/FFT

22. Scales the FFT size.

23. Smaller FFT size is given to lower bandwidth channels, while larger FFT size to wider channels.

24. OFDMA mode used in IEEE 802.16e.

25. Bandwidth : 1.25 MHz to 20 MHz.

26. Vary the number of subcarriers and control transmission rates and the number of individual users simultaneously.

28. Number of Subcarrier scales with Bandwidth.

29. Based on the concept of Subchannel, the smallest unit of Bandwidth allocation is fixed and independent of Bandwidth.

30. Capacity of each individual subchannel remains constant.

33. PARAMETERS