Nonlinear precoding method for a digital broadcast channel

• US 20060198459A1
• Filed: 07/07/2004
• Published: 09/07/2006
• Est. Priority Date: 07/17/2003
• Status: Active Grant

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Fischer, Robert, Windpassinger, Christoph
• Granted Patent: US 8,130,854 B2
• Time in Patent Office: Days
• US Class Current: 375/267
• CPC Class Codes: H04L 1/0618 Space-time coding
• CPC Class Codes: H04L 2025/0342 QAM
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 25/4975 Correlative coding using Tomlinson precoding, Harashima precoding, Trellis precoding or GPRS

Abstract

Several subscriber signals are transmitted simultaneously and at the same frequency by a central transmitter to several decentralized receivers which do not cooperate with each other, by digital message transmission in a broadcast channel. A common transmission signal, which enables an error-free individual reception, should be generated with knowledge of all subscriber signals and of the current transmission conditions, by signal preprocessing methods on the transmission side. Known nonlinear precoding methods totally suppress the interference signals, so that the channel diversity cannot be used. In the claimed precoding method, the occurring interference signals are, on the contrary, taken into account. On the basis of a modulo arithmetic calculation, the transmission channel is not totally equalized, but virtually divided, so that the transmission of the subscriber signals is continued periodically; the signals are selected according to the minimal transmission power and pre-equalized, in a linear manner, and the residual interferences, still remaining between the subscriber signals, may assume special values from a preset set of values. The set of values is selected, so that the interference signals of the other subscribers are also merely reflected in the otherwise already existing periodic continuation and can be suppressed or used as required by a modulo decision, on the reception side.

Claims

1-3. -3. (canceled)

4. A nonlinear precoding method based on modulo arithmetic for the transmit-side preequalization of K user signals to be transmitted concurrently using a frequency in a digital broadcast channel with known transmission behavior set up between a central transmitting station and K decentralized, non-interconnected receiving stations, the user signals consisting of data symbols a_k with k from 1 to K from a signal constellation having M_k levels and a signal point spacing A_k with a periodic multiple representation of the undisturbedly transmitted data symbols a_k in data symbol intervals congruent for K receive-side modulo decision devices, a transmit-power-minimizing selection of representatives v_k from the range of values a_k+A_k·

M_k·

z_kk where z_kk are integers, and linear preequalization of the selected representatives v_k to form transmit signals x_k to be transmitted, comprising;

including interference symbols in the digital broadcast channel superimposed on the data symbols a_k and periodic multiple representation thereof due to cross-coupled user signals by an adapted periodic multiple representation, the interference symbols between the data symbol a_I with I from 1 to K and not equal to k and the data symbol a_k being assigned periodic representatives from a range of values A_k·

M_k·

z_Ik where z_Ik are integers; and

eliminating the interference symbols by the K receive-side modulo decision devices.

5. A nonlinear precoding method according to claim 4, wherein mathematically required transmission behavior of the broadcast channel is achieved by factorization of the channel matrix H, describing current transmission behavior and known prior to transmission, into a reduced channel matrix H_red to be preequalized and a residual interference matrix R, where H=R H_red, the residual interference matrix R assuming only 1 on the main diagonal and all other elements being row-wise integral multiples of the M_k levels of the signal constellation used and the reduced channel matrix H_red being obtained by factorization into a matrix F with orthogonal columns, a lower triangular matrix B and a permutation matrix P with the introduction of a receive-side scalar gain factor g according to P^TH_red=1/g B F⁻

1.

6. A nonlinear preceding method according to claim 5, wherein offset compensation is already carried out on the transmit signals x_k prior to transmission.

7. A nonlinear preceding method according to claim 4, wherein offset compensation is already carried out on the transmit signals x_k prior to transmission.