439 results about "Symbol period" patented technology

The transmit diversity and symbol rate in a wireless mobile system are increased by allocating the complex symbols to be transmitted in accordance with a time-space slot format that incorporates non-orthogonal-based matrices, defined as matrices whose format is such that the product of the matrix and its Hermitian transpose is other than the identity matrix times a real number other than unity. The non-orthogonal-based matrices are indexed by antenna and by symbol period. Copies and complex conjugates (or negative complex conjugates) of the same symbol that are transmitted from different antennas are mutually separated into non-adjacent parts of the slot. Each non-orthogonal-based “space-time” matrix is composed of orthogonal-based matrices, i.e., matrices other than non-orthogonal-based matrices. Preferably, sequences of complex conjugates are time-reversed in the slot.

A diversity reception device includes a power combiner to combine electric powers of OFDM signals, each OFDM signal being received by a first antenna and second antenna, a switch to change connections between branched output-ports of the first and second antennas, in mid-stream of effective symbol periods, the effective symbol periods are assigned respectively in each of symbol periods of the OFDM signals, a receiver to demodulate the OFDM signals, a phase shifter to shift phases of the OFDM signals received by the second antenna, and an arithmetic and control processing circuit to calculate complex correlation coefficient between a guard interval, assigned in each of the symbol periods associated with the first antenna, and a copy-source interval, assigned in each of the symbol periods associated with the second antenna, and to determine rotation angle on the basis of the complex correlation coefficient.

In a wireless transmitter having a plurality of spatial streams differentiable at a receiver, wherein data is encoded and transmitted over a communication channel with pilot tones to provide the receiver with information about the effects of the communication channel and / or transmitter impairments and / or receiver impairments on the spatial streams transmitted, the benefits can be provided by identifying a plurality of symbol periods within which symbols representing some of the encoded data are to be transmitted, identifying pilot tone values for the plurality of symbol periods, wherein the identified pilot tone values are such that the receiver, when receiving at least some of the pilot tones having the identified pilot tone values, is provided with signals enabling the receiver to characterize the communication channel and / or transmitter impairments and / or receiver impairments to obtain transmit stream diversity gain, and transmitting the symbols and the pilot tones over the plurality of spatial streams for the plurality of symbol periods. In some embodiments, the pilot tones are orthogonal over space and time or over space and time and frequency, while in others they are semi-orthogonal. Pilot tone values might be of a constant amplitude and phase shifted, or might also have amplitude variations wherein at least two pilot tones are nonzero for spatial streams for a given symbol period.

Techniques for managing re-contention on a shared communication medium are disclosed. In order to facilitate re-contending for access to the communication medium, an access point may adjust one or more uplink transmission parameters associated with a triggering condition for invoking a contention timer. In addition or as an alternative, the access point may mute transmission on the communication medium during one or more symbol periods designated for transmission. In addition or as an alternative, the access point may configure a timing advance to create a re-contention gap.