For many, because of its influence in both everyday life and business, fourth-generation (4G) wireless communication has a distinguished place, where coupling orthogonal frequency-division multiplexing (OFDM) and multiple input, multiple output (MIMO) is one of its cornerstones. Low-density parity-check (LDPC) coding, which supports parallel encoding and light decoding, is understandably deployed for the MIMO antenna platform. To reduce the required memory and processing time, this important paper proposes, and analytically discusses, a new architecture.
The paper starts with an illustrative abstract. In the introduction, the authors emphasize the efficiency of OFDM-MIMO conjunction to gain high data-rate transmission over frequency-selective broadband channels. In the proposal, to gain higher speed data transmission and promote the operation of conventional single-codeword layered space-time-frequency (LSTF), multiple-codeword encoder transmission LSTF is featured: the data stream is divided into Nt (number of transmission antennas) sub-streams, a distribution function dispatches the sub-streams in the sub-carriers (transmission antennas) at different time intervals, and all the diversities (three degrees of freedom) can be utilized more effectively. The proposed architecture is explained schematically with a complete description of its components. Therein, the distribution function and detector components are studied in more detail. The properties of using a list sphere with LDPC are considered. The authors also demonstrate channel estimation mechanisms using time multiplexed pilot channels, the supremacy of list sphere detection over maximum likelihood, and LDPC encoding implementation with a simulation sample.
The simulation results have merit. They analytically discuss the influence of all the system’s effective components and parameters: number of receive and transmit antennas, carrier frequency, bandwidth, number of sub-carriers, spacing, inverse fast Fourier transform (IFFT) points, OFDM symbols in a packet, guard interval, and many more important factors. Average performance, regular and random distribution functions, the effect of perfect or imperfect channel estimation, codeword length, the footprint of pilot channel energy percentage in one packet, the efficacy of average signal-to-noise ratio of every receive antenna, the impact of delayed spread of the root mean square, the influence of frequency diversity on performance, the impact of fading correlation on antennas, and the effect of Doppler frequency shift are considered and detailed pictorially.
More than a decade has passed since its publication, yet it is still considered a seminal paper. An influential and well-structured contribution to the field. In addition to its worthy technical aspects, it can also be used as a good example for researchers and students composing their own works.