A research group of the Department of Signal Theory and Telecommunications of the Universidad de Alcalá has developed demodulation procedures for broadband signal reception. The proposed approach implements a Wavelet OFDM receiver, based on modulated filter banks according to the Extended Lapped Transform. This modulation technique has been proposed in data transmission for broadband power line communications (PLC), and presents the following characteristics: a) a greater spectral separation between the subcarriers; b) more noise immunity, including narrow band interference impulsive. A block channel equalization is also incorporated in the frequency domain, which includes a parallel sine-modulated filter bank. This invention can be used in all those techniques with multicarrier modulation based on Wavelet OFDM in the transmitter.
The group looks for ICT companies to achieve manufacturing agreements and commercial agreements with technical assistance.
New and innovative aspects
-The present invention provides a receiver for Wavelet OFDM transmitter, recommended in broadband communications by the mains.
- Higher spectral separation and efficiency than windowed OFDM.
- It increases the robustness of the system, reducing the error probability.
- It improves the bit rate in noisy hostile environments, which results in transmission/reception of more information in the same time interval.
- It is more immune to narrow band interference.
Main advantages of its use
Use of the features provided by transmultiplexers based on ELT modulated filter banks, as increased spectral separation between the subcarriers, leading to more noise immunity, including narrow band interference of impulsive character.
The procedures described in this invention involve:
-Increased robustness of the system.
-Increased reliability in noisy channels.
This invention provides demodulation devices, and more generally signal receiving. The invention also relates to signal demodulation process as described below. Of course, the invention also concerns devices receiving signals carrying out the mentioned method.
The process of the invention is a receiver or bank of analysis which comes from a modulation scheme similar to the filter bank (in transmultiplexer configuration) called ELT (Extended Lapped Transform).
The receiver proposed in the invention (Figure 1) comprises a delay system of input signal and decimated (downsampling) of delayed signals (block 21). After this block, various branches may be coupled to each other through an overlap and add procedure. It also comprises a process of the resulting signals through a fast algorithm with matrix operations (blocks 12, 16, 17, 20, 15) of discrete transform type transformation of sine and/or cosine (blocks 13, 18) and polyphase filtering (block 11), the filters can be implemented with direct structures, or transposed, or lattices.
In the invention, this modulation scheme may include phase angle (phase angle [rad.] - Block 15), as detailed in Table 14.10-carrier frequencies that is included and can be found in the standard [IEE10]. In addition, another novelty of the invention is that the receiver includes an additional step obtained by sine-modulation of the prototype filter, in order to facilitate the process of equalization of the channel in the frequency domain.
The procedure proposed by the invention uses the features provided by transmultiplexers based on modulated filter banks ELT as, for example, increased spectral separation between subcarriers, leading to more noise immunity, including narrow band interference of impulsive character.
The receiver of the invention also comprises two channel equalization steps in the domain of FEQ-1 and FEQ-2 (blocks 14 and 19) frequency. In the same steps subcarrier signals obtained with discrete transforms the sine and/or cosine are processed (blocks 18 and 13) using a constant coefficient or system function which filter each signal.
[IEE10] IEEE Std 1901TM-2010, "IEEE Standard for Broadband over Power Line Networks: Medium Access Control and Physical Layer Specifications," Dec. 2010
Current development status
Developed, available for demonstration
Desired business relationship
The group seeks to achieve commercial agreements, cooperation or license agreements with companies in electronics, computers and telecommunications.