Systems and methods are described herein for communications bandwidth enhancement using Orthogonal Spatial Division Multiplexing (OSDM). For example, large sparse antenna arrays may be able to distinguish between signals emitted by multiple nearly collocated antennas, even if the signals have the same frequency, polarization, and coverage. Thus, the use of a large sparse antenna array may be able to resolve/isolate individual antennas on a single platform, allowing for OSDM, analogous to Orthogonal Frequency Divisional Multiplexing (OFDM). Using OSDM, multiple antennas on the same vehicle are able to reuse the same frequencies/polarizations without interference, thereby increasing spectrum availability while still providing the same transmitter power spectral density and total RF power emission.

A communication system includes a repetitive orthogonal frequency-division multiplexing (ROFDM) transmitter communicating with an ROFDM receiver. The ROFDM transmitter includes an ROFDM modulator, which includes a K-point Fast Fourier Transform receiving a block of time-domain data symbols and generating an initial orthogonal frequency-division multiplexing symbol. The initial orthogonal frequency-division multiplexing symbol is based on a block of frequency-domain data symbols corresponding to the block of time-domain data symbols. The initial orthogonal frequency-division multiplexing symbol includes an ending part. The ROFDM modulator includes an orthogonal frequency-division multiplexing symbol repeater generating a repetitive orthogonal frequency-division multiplexing symbol by repeatedly reproducing the initial orthogonal frequency-division multiplexing symbol. The modulator includes a cyclic prefix adder prepending a cyclic prefix to the repetitive orthogonal frequency-division multiplexing symbol to generate a baseband transmitted signal. The cyclic prefix includes the ending part of the initial orthogonal frequency-division multiplexing symbol. The ROFDM receiver includes an ROFDM demodulator.

Certain aspects of the present disclosure relate to communication systems, and more particularly, to single-carrier waveform generation for transmission. An exemplary method generally includes concatenating a first sequence of data samples with samples of a known sequence to generate a first series of samples, performing a discrete Fourier transform (DFT) on the first series of samples to generate a first series of frequency-domain samples, mapping the first series of frequency-domain samples and first zero values to first tones of a system bandwidth, performing an inverse discrete Fourier transform (IDFT) on the mapped first series of frequency-domain samples and the mapped first zero values to generate first time-domain samples of a first orthogonal frequency domain multiplexing (OFDM) symbol, and transmitting the first OFDM symbol as a single-carrier waveform in a first period.

A receiver circuit for separating a plurality of layers multiplexed in an orthogonal frequency domain multiplexed (OFDM) signal includes: a descrambling sub-circuit configured to descramble a plurality of signals received on non-adjacent subcarriers of the OFDM signal to generate a plurality of descrambled signals; an inverse fast Fourier transform sub-circuit configured to transform the descrambled signals from a frequency domain to a received signal including a plurality of samples in a time domain; and a layer separation sub-circuit configured to separate the layers multiplexed in the received signal by: defining a first time domain sampling window and a second time domain sampling window in accordance with a size of the inverse fast Fourier transform; extracting one or more first layers from the samples in the first time domain sampling window; and extracting one or more second layers from the samples in the second time domain sampling window.

Methods, systems, and devices are described for hierarchical communications and low latency support within a wireless communications system. An eNB and/or a UE may be configured to operate within the wireless communications system which is at least partially defined through a first layer with first layer transmissions having a first subframe type and a second layer with second layer transmissions having a second subframe type. The first subframe type may have a first round trip time (RTT) between transmission and acknowledgment of receipt of the transmission, and the second layer may have a second RTT that is less than the first RTT. Subframes of the first subframe type may be multiplexed with subframes of the second subframe type, such as through time division multiplexing. In some examples symbols of different duration may be multiplexed such that they different symbol durations coexist.

A transmitter comprises a first peak-to-average-power ratio (PAPR) suppression circuit and a second peak-to-average-power ratio (PAPR) suppression circuit. The first PAPR suppression circuit may receive a first sequence of time-domain symbols to be transmitted, alter the first sequence based on each of a plurality of symbol ordering and/or inversion descriptors to generate a corresponding plurality of second sequences of time-domain symbols, measure a PAPR corresponding to each of the second sequences, select one of the plurality of symbol ordering and/or inversion descriptors based on the measurement of PAPR, and convey the selected one of the symbol ordering and/or inversion descriptors to the second PAPR suppression circuit. The second PAPR suppression circuit may receive the first sequence of time-domain symbols to be transmitted, and alter the first sequence based on the selected one of the symbol ordering and/or inversion descriptors to generate a reordered and/or inverted symbol sequence.

According to one embodiment, a wireless communication device includes a transmitter configured to transmit a first frame including first information required for uplink multi-user transmission without receiving a transmission request for the first information; and a receiver configured to receive a second frame.

A method for a terminal transmitting a signal according to a resource allocation priority may comprise the steps of: when a sounding reference signal (SRS) symbol and a physical uplink control channel (PUCCH) symbol are configured so as to overlap, transmitting an SRS in a non-overlapping symbol; and dropping the transmission of the SRS in the overlapping symbol. The present invention can improve communication performance by being able to carry out transmission according to a resource allocation priority rule, when the SRS and PUCCH resource areas overlap.

Apparatuses, methods, and systems are disclosed for reference signal sequence determination. One apparatus includes a processor that determines an RS sequence for transmission. The RS sequence includes three symbols determined by the following equation: r.sub.u(n)=e.sup.j(n)/4. The RS sequence includes: a first RS sequence, wherein r.sub.u(n) is the first RS sequence, n=0 to 2, (0)=3, (1)=3, and (2)=1; or a second RS sequence, wherein r.sub.u(n) is the second RS sequence, n=0 to 2, (0)=3, (1)=1, and (2)=1. The apparatus also includes a transmitter that transmits the RS sequence on a time-frequency resource.

A receiver circuit for separating a plurality of layers multiplexed in an orthogonal frequency domain multiplexed (OFDM) signal includes: a descrambling sub-circuit configured to descramble a plurality of signals received on non-adjacent subcarriers of the OFDM signal to generate a plurality of descrambled signals; an inverse fast Fourier transform sub-circuit configured to transform the descrambled signals from a frequency domain to a received signal including a plurality of samples in a time domain; and a layer separation sub-circuit configured to separate the layers multiplexed in the received signal by: defining a first time domain sampling window and a second time domain sampling window in accordance with a size of the inverse fast Fourier transform; extracting one or more first layers from the samples in the first time domain sampling window; and extracting one or more second layers from the samples in the second time domain sampling window.