Showing papers by "Thomas L. Marzetta published in 2000"

Unitary space-time modulation for multiple-antenna communications in Rayleigh flat fading

Abstract: Motivated by information-theoretic considerations, we propose a signaling scheme, unitary space-time modulation, for multiple-antenna communication links. This modulation is ideally suited for Rayleigh fast-fading environments, since it does not require the receiver to know or learn the propagation coefficients. Unitary space-time modulation uses constellations of T/spl times/M space-time signals (/spl Phi//sub i/, l=1, ..., L), where T represents the coherence interval during which the fading is approximately constant, and M

Systematic design of unitary space-time constellations

Abstract: We propose a systematic method for creating constellations of unitary space-time signals for multiple-antenna communication links. Unitary space-time signals, which are orthonormal in time across the antennas, have been shown to be well-tailored to a Rayleigh fading channel where neither the transmitter nor the receiver knows the fading coefficients. The signals can achieve low probability of error by exploiting multiple-antenna diversity. Because the fading coefficients are not known, the criterion for creating and evaluating the constellation is nonstandard and differs markedly from the familiar maximum-Euclidean-distance norm. Our construction begins with the first signal in the constellation-an oblong complex-valued matrix whose columns are orthonormal-and systematically produces the remaining signals by successively rotating this signal in a high-dimensional complex space. This construction easily produces large constellations of high-dimensional signals. We demonstrate its efficacy through examples involving one, two, and three transmitter antennas.

Antenna array having reduced sensitivity to frequency-shift effects

Abstract: In a system for sending wireless communication signals on at least one downlink wavelength and receiving wireless communication signals on at least one uplink wavelength, there is a ratio r equal to the larger divided by the smaller of these wavelengths. The system comprises a receiver operative to receive signals imposed on a carrier having the uplink wavelength, a transmitter operative to transmit signals imposed on a carrier having the downlink wavelength, and an array of independent antenna elements. The array comprises a first and a second sub-array. One sub-array is electrically coupled to the transmitter, such that transmitted signals can be radiated from it, and the other sub-array is electrically coupled to the receiver, such that signals to be received can be extracted from it. The sub-arrays are geometrically similar to each other with a relative scale factor equal to the wavelength ratio r. The sub-arrays have at least one common antenna element.

Method of wireless communication using structured unitary space-time signal constellations

Abstract: A method is disclosed for generating unitary space-time signals for wireless communication using an array of M transmitting antennas. Each unitary space-time signal comprises T symbols. The method can be used to generate arbitrarily large signal constellations. The resulting unitary space-time signals have statistical properties that are favorable for reliable use in communication, and they can lead to very high data transmission rates. The disclosed method involves the mapping of binary strings of data to matrix products of the kind obtained by left-multiplying an initial T×M matrix by an ordered multiplicative sequence of exponentiated T×T unitary matrices, referred to as generator matrices. The result of each such multiplication is a unitary space-time signal matrix that may be transmitted. Each generator matrix corresponds to a single bit or a collection of bits of a binary string that is to be mapped. The value of the exponent of each generator matrix is determined by the pertinent bit or collection of bits.

Space-time autocoding: arbitrarily reliable communication in a single fading interval

Abstract: Prior treatments of space-time communications in Rayleigh flat fading generally assume that channel coding covers either one fading interval-in which case there is a nonzero "outage capacity"-or multiple fading intervals-in which case there is a nonzero Shannon capacity. However, we establish conditions under which channel codes span only one fading interval and yet are arbitrarily reliable. In short, space-time signals are their own channel codes. We call this phenomenon space-time autocoding, and the accompanying capacity the space-time autocapacity.

Cdma communication method

Abstract: PROBLEM TO BE SOLVED: To achieve diversity merits without receiving demerits so much by transmitting respective data symbol sets to the respective users of a user group by the form plural mutually different signal sequences which are the linear connection of spreading code sequences belonging to a corresponding code group. SOLUTION: An antenna 1 (25.1) transmits signals (1/21/2) (b1c1+b2c2) and the antenna 2 (25.2) transmits the signals (1/21/2) (b2c1-b1c2). In such a manner, while only two pieces of spreading codes are used, the two codes are used for a data symbol to the user (20.1) and also the two codes are used for the data symbol to the user (20.2) as well. Thus, at the time of using plural transmitter antennas, a system for sufficiently achieving the diversity merits without receiving the demerits in the number of the codes required to be allocated per user so much, is realized.

Antenna array free from large influence of frequency shift effect

Abstract: PROBLEM TO BE SOLVED: To obtain an antenna array used for communication of both up-link and down-link in a radio communication system like a cellular. SOLUTION: In a cellular base station including a receiver 95, a transmitter 100 m and a log period antenna array 105, an up-link (for reception) sub-array consists of antenna elements A2 to AM. The output of each of these elements is the input to the receiver 95. In this case, outputs are multiplied by weight coefficients W2 to WM on the outside of the receiver 95. A down-link (for transmission) sub-array consists of antenna elements A1 to AM-1. The transmitter 100 sends a modulated carrier signal to each element. Inputs of antenna elements A1 to AM-1 are multiplied by weight coefficients W'1 to W'M-1 on the outside of the transmitter 100. Thus, the log period antenna array 105 consisting of antenna elements A1 to AM is shared between transmission and reception.