Recently, orthogonal frequency division multiple access (OFDMA) where different subcarriers are allocated to different users, has attracted very much attention and has been adopted for the uplink of several standards. Although OFDMA provides robustness against multipath fading channels, it is highly sensitive to carrier frequency offset (CFO) between transmitter and the receiver. OFDMA systems experience different carrier frequency offsets due to different users which destroys the orthogonality of the subcarriers. To compensate for the effect of multiple CFOs, we propose a CFO compensation technique applicable to interleaved and block interleaved carrier assignment schemes utilizing the special block circulant property of the interference matrix. In contrast to the other sophisticated CFO compensation algorithms, the proposed linear decorrelating detector (LDD) does not need any iteration. Thereby, the computational complexity of the detector will be dramatically reduced which reduces the processing time and consequently enables higher data rates. This technique does not only have lower computational complexity but also has more robust performance in comparison with the current solutions.
What Problem Does it Solve/Advantages
Since the current synchronization techniques for the CFO compensation are based on iterative algorithms where they generate the MAI terms and subtract them from the received signal in an iterative fashion, they suffer from their very high computational complexity and also they cannot completely eliminate the MAI even in high signal to noise ratios (SNRs). On the other hand, LS based compensators can completely retrieve the orthogonality of the subcarriers. This technology uses the block circulant property of the interference matrix in LS based solution to reduce the computational complexity of the system and consequently diminishes the processing time while removing the MAI completely even without computing the interference matrix itself. It also can be easily extended to MMSE solution for the case of low SNRs.
- The invention can be applied for the uplink of any multiuser system using OFDMA based technologies for the uplink in order to retrieve the orthogonality of the subcarriers and detect the transmitted signals.
- Cellular systems of the fourth generation (4G) have been optimized to provide high data rates and reliable coverage to mobile users. Cellular systems of the next generation will face more diverse application requirements: the demand for higher data rates exceeds 4G capabilities; battery-driven communication sensors need ultra-low power consumption; and control applications require very short response times. We envision a unified physical layer waveform, referred to as generalized frequency division multiplexing (GFDM), to address these requirements. This technology contributes to the following areas: 1) the means for engineering the waveform's spectral properties; 2) analytical analysis of symbol error performance over different channel models; 3) concepts for MIMO-GFDM to achieve diversity; 4) preamble-based synchronization that preserves the excellent spectral properties of the waveform; 5) bit error rate performance for channel coded GFDM transmission using iterative receivers; 6) relevant application scenarios and suitable GFDM parameterizations; and 7) GFDM proof-of-concept and implementation aspects of the prototype using hardware platforms available today. In summary, the flexible nature of GFDM makes this waveform a suitable candidate for future 5G networks.
Technology and Patent Status
This technology is available for license/collaboration.
Researcher: Prof Arman Farhang