Alloyant: High Performance Broadband Wireless Networks
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Header: Mobile and Fixed broadband wireless radio access systems

CDMA + OFDMA Hybrid Air Interface - (OCS-FDMA)

The StreamStar4 Air Interface is a hybrid design based on an optimal combination of CDMA and OFDMA - combining the best features of both technologies, and providing superior performance.


Like OFDMA, multiple access is done in the frequency domain by allocating different subcarriers to different users. This gives the airlink a natural time/frequency diversity of OFDMA which offers excellent multipath performance. Unlike traditional OFDMA however, the subcarriers are also code-spread with a pre-coding matrix like CDMA, providing a strong resistance to fading and inter-cell interference. The result is an air interface with a very high resource and spectral efficiency.


  • Compared to conventional OFDM/OFDMA, the Hybrid Air Interface has much better performance on signal fading especially for narrowband applications (voice), N=1 deployment, and dense deployments where multiple cells share frequencies.
  • The Hybrid Air Interface also outperforms pure CDMA/SCDMA on inter-code interference, which allows it to support high speed data rates, so both broadband and narrowband applications or any mix of both can be supported very efficiently.
  • The air interface implements adaptive modulation with QPSK, 8PSK, 16QAM and 64QAM schemes both on uplink and downlink, Reed-Solomon Forward Error Correction and automatic ARQ.
  • Dynamic Channel Allocation (DCA) is also an integral part of the air interface. The Base Station dynamically assigns channels based on real-time channel and interference conditions, and always assigns the best performing channels first, while the adaptive Nulling algorithm (Active Interference Cancellation) actively combats interference.

  • The Hybrid Air Interface is an ITU-R Radio Interface Standard.

  • The Hybrid Air Interface supports SDMA (Spatial Division Multiple Access) - vastly increasing the spectral efficiency.



Advanced Hybrid Radio Airlink combines CDMA and OFDMA

Hybrid Air Interface combines the advantages of CDMA and OFDMA (Click to enlarge)