135 research outputs found
Fast DGT Based Receivers for GFDM in Broadband Channels
Generalized frequency division multiplexing (GFDM) is a recent multicarrier
5G waveform candidate with flexibility of pulse shaping filters. However, the
flexibility of choosing a pulse shaping filter may result in inter carrier
interference (ICI) and inter symbol interference (ISI), which becomes more
severe in a broadband channel. In order to eliminate the ISI and ICI, based on
discrete Gabor transform (DGT), in this paper, a transmit GFDM signal is first
treated as an inverse DGT (IDGT), and then a frequency-domain DGT is formulated
to recover (as a receiver) the GFDM signal. Furthermore, to reduce the
complexity, a suboptimal frequency-domain DGT called local DGT (LDGT) is
developed. Some analyses are also given for the proposed DGT based receivers.Comment: 28 pages, 8 figure
Reduced Complexity Calculation of LMMSE Filter Coefficients for GFDM
A low-complexity algorithm for calculation of the LMMSE filter coefficients
for GFDM in a block-fading multipath environment is derived in this letter. The
simplification is based on the block circularity of the involved matrices. The
proposal reduces complexity from cubic to squared order. The proposed approach
can be generalized to other waveforms with circular pulse shaping.Comment: Submitted to IEEE Electronics Letter
Iterative Demodulation and Decoding for LDPC Coded Generalized Frequency Division Multiplexing
Currently, there is a standardization process underway to design the fifth generation
of wireless systems or 5G wireless systems. The ambitious targets set forth
for 5G wireless systems call for novel approaches in all layers of the network. At
the physical layer (PHY), Orthogonal Frequency Division Multiplexing (OFDM)
has become a de facto standard for wireless systems such as 4G cellular and IEEE
802.11 (Wi-Fi) systems. However, the large peak to average power ratio of OFDM
signals makes OFDM an unattractive candidate for some services envisioned in
5G systems, particularly in the uplink.
Recently, Generalized Frequency Division Multiplexing (GFDM), which is a
member of the non-orthogonal multiple access technologies has been proposed
as the modulation scheme for 5G wireless systems. GFDM has some advantages
over OFDM, such as looser requirements on synchronization, a lower PAPR requirement,as well as a lower out-of-band spectral leakage. However, in GFDM
the sub-channels are not orthogonal which results in inter-carrier interference and,
hence, an increased uncoded bit error rate. While iterative receivers have been
proposed for improving the bit error rate performance of uncoded GFDM, there
are very few works that have studied the performance of coded GFDM systems.
In this thesis, we investigate the performance of coded systems with GFDM. Using
earlier results on soft interference cancellation based turbo equalization and turbo
multi-user detection, we design an iterative receiver for GFDM with low density
parity check codes. We show that the receiver is able to successfully combat the
non-orthogonality of sub-channels in GFDM and provide performance similar to
that of coded OFDM systems at an increased receiver complexity
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