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PUSC (Partially Used Subcarriers (for WiMAX))

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Partially Used Subcarriers (PUSC) is a subcarrier allocation scheme used in WiMAX (Worldwide Interoperability for Microwave Access) systems. WiMAX is a wireless communication technology that provides high-speed broadband access over long distances.

In WiMAX, the available spectrum is divided into subcarriers, which are narrowband channels used to transmit data. PUSC is one of the subcarrier allocation methods used in the downlink direction, where the base station communicates with multiple subscriber stations.

The PUSC scheme is designed to mitigate the effects of multipath fading and interference in wireless channels. It achieves this by allocating different subcarriers to different users, which helps in improving the overall system performance and maintaining the quality of service.

Here are the key features and components of the PUSC scheme:

  1. Subcarrier Allocation: PUSC divides the available spectrum into groups of subcarriers known as subchannels. Each subchannel consists of multiple subcarriers. The subcarriers within a subchannel are distributed across the frequency range to minimize the impact of frequency-selective fading.
  2. Subchannel Configuration: The subchannels in PUSC are configured with different patterns known as Subchannelization Types (ST). Each ST defines the specific arrangement of subcarriers within a subchannel. The choice of ST depends on factors such as channel conditions, interference levels, and system capacity requirements.
  3. Allocation Flexibility: PUSC offers flexibility in subchannel allocation to accommodate different user requirements and channel conditions. It allows for dynamic adaptation of subchannelization patterns based on the changing environment.
  4. Frequency Diversity: PUSC exploits frequency diversity by allocating different subcarriers to a user across multiple subchannels. This helps in reducing the impact of frequency-selective fading and improving the overall link reliability.
  5. Interference Mitigation: PUSC employs frequency and time-domain interleaving techniques to mitigate the effects of interference. By spreading the subcarriers across the frequency range and applying interleaving, it minimizes the impact of narrowband interference and improves the system's robustness.
  6. Channel Estimation: PUSC requires accurate channel estimation at the receiver to properly demodulate the received signal. Various pilot signals are transmitted periodically to estimate the channel conditions and adapt the transmission parameters accordingly.

Overall, PUSC is an effective subcarrier allocation scheme used in WiMAX systems to enhance system performance, mitigate fading and interference effects, and provide reliable communication over long distances. It offers flexibility, adaptability, and robustness in allocating subcarriers to different users based on their specific channel conditions and quality of service requirements.