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The digital telecommunication department of a Greek university has developed a method for improving the performance of wireless communication systems by combining signals that arrive to a diversity receiver. The university holds a European patent and is looking for companies in the telecommunication sector to license the patent and apply the technology.
It is known that multichannel receivers followed by certain diversity combining techniques can significantly improve the performance of wireless communication systems. To combine signals from two different antennas, a maximal ratio combiner (MRC) is used, in order to maximize the signal to noise ratio (SNR). Nevertheless, the optimum performance of MRC is achieved at the expense of the high hardware complexity. To overcome this drawback, various sub-optimum diversity receivers with lower complexity have been proposed. The most important among them is the equal-gain combiner (EGC), which adds all the received signals at each branch. The EGC receiver has a major disadvantage however when operating over wireless channels with unequal gains at each path, e.g. in multipath channels. Under such conditions, the EGC results in a so-called “combining loss”, meaning that combining more signals does not necessarily enhance performance, especially for high bit error rates (BERs). The reason is that weak branches contribute more to increasing noise.
The present invention aims at minimizing the combining loss of EGC receivers and minimizing the bit error rate (BER). The digital communication department of the Greek university proposes a method for combining signals received by a diversity receiver comprising of at least two branches, with the signals transmitting symbols through a multi-paths channel. It comprises of combining the signals after their processing in individual branches and demodulation and detection of the transmitted symbols. Such a method does not require the continuous estimation of the instantaneous channel gains at each branch, which is thus avoided and thus reduces the need for expensive hardware. It nevertheless allows good combining results, significantly better than EGC receivers, even when operating over wireless channels with unequal gains at each path, and even more so than with five branches.
The received signals at each diversity branch are not equally weighted as in conventional EGC receivers. According to the proposed methodology, the received signals from each branch are co-phased and weighted by specific coefficients.
The diversity received proposed in this invention, is specially designed. It comprises at least two branches for receiving signals, where the signals transmit symbols through a multipath channel. It also comprises a combining device for the signals after their processing in individual branches and a demodulation device for the demodulation and detection of the transmitted symbols.
The university holds a European patent for this technology and is interested in licensing the patent to a company dealing with wireless devices and receivers for a variety of applications.
The diversity receiver used in this invention is specially designed so as to be simpler and cheaper than the maximal ratio combiners (MRCs) which are conventionally used, since it avoids the expense of the high hardware complexity and gives significantly better results than an equal-gain combiner (EGC) receiver. In particular it minimizes the combining loss.
Furthermore, the synchronization device is comprised of components which estimate the time delay induced by the channel for each received signal, related to the transmission time of the transmission signal, and counters the possible delay accordingly for each received signal. Thus, it allows a better quality of synchronization.
Compared to conventional EGC receivers, the received signals at each diversity branch are not equally weighted.
Expertise: manufacturing of wireless devices and receivers for a variety of applications.
Activities to be performed: license the patent and adopt the technology for wireless devices and receivers.