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331 results about "Word error rate" patented technology

Word error rate (WER) is a common metric of the performance of a speech recognition or machine translation system. The general difficulty of measuring performance lies in the fact that the recognized word sequence can have a different length from the reference word sequence (supposedly the correct one). The WER is derived from the Levenshtein distance, working at the word level instead of the phoneme level.

Adaptive postfilter

The invention relates to the coding of speech at a variable bit rate, whereby the bit rates can vary from frame to frame, and more specifically to the methods and filters used for improving the quality of the decoded speech. In the solution according to the invention the weighting factors of the postfilter are not adapted on the basis of the momentary bit rate or the bit rate used in the coding of each frame, but the weighting factors are adapted according to the average bit rate calculated on the basis of a predetermined length of time. In addition to this, the weighting factors of the postfilter are also adjusted on the basis of whether the frame in question contains a voiced speech signal, an unvoiced speech signal or background noise. At frames containing an unvoiced speech signal or background noise, postfiltering is weakened so as to avoid the distortion of the signal tone because the postfiltering is adapted to a voiced signal. The weighting factors of the postfilter can also be adapted on the basis of the error rate or other parameter describing the quality of the signal or the data transfer channel. For example, postfiltering can conveniently be adjusted so that when the channel error rate and the amount of coding error increase, postfiltering is increased, whereby the effect of data transfer errors on the decoded speech signal is reduced and the tolerance of the system with regard to data transfer errors increases.
Owner:NOKIA MOBILE PHONES LTD +1

Powerline data communication

Data communication between two devices (11, 12) over the public powerline network (13) uses a multi carrier technology wherein a communication channel is divided into a plurality of subchannels by frequency division multiplexing. A partial power as part of the total transmission power and a partial rate as a fraction of the total data rate are assigned to each subchannel as follows:Initially, the same partial power is assigned to each subchannel and the S / N ratio of each subchannel is obtained. Starting with the subchannel of the lowest S / N ratio and proceeding to that of the highest S / N ratio, the following steps are performed for each subchannel:Firstly, the partial rate is assigned in accordance with the respective S / N ratio such as to result in a predetermined transmission error rate. The assigned partial rate is then quantised to an integral value. If the quantising corresponds to a rounding down, the initially assigned partial power is reduced such that the transmission error rate remains the same as before quantisation. Further, the partial power of other subchannels with higher S / N ratio is increased such that the sum of all partial powers remains constant. Eventually, the increased S / N ratio resulting from increasing the partial power for these subchannels is calculated so that, when the present steps are conducted for them, an optimum partial rate can be assigned to them.This method maximises the total data rate of the entire communication channel while the error rate of each subchannel and the sum of all partial powers remain constant.
Owner:POLYTRAX INFORMATION TECH

Method of modulating variable pulse amplitude position and improving error rate for visible light communication system

The invention discloses a method of modulating a variable pulse amplitude position and improving an error rate for a visible light communication system, belonging to the field of visible light wireless communication technologies. According to the method, modulation of the variable pulse amplitude position is utilized in a modulation module of a signal transmitting end, a modulation method is multi-system modulation capable of combining pulse amplitude position modulation and pulse width modulation, transmission of communication data is guaranteed while a system dimming function is provided, improvement of the communication quality mainly includes that the transmission rate can be improved under the condition of the same symbol rates, the advantages of high multi-system modulation bandwidth efficiency and high pulse position modulation power efficiency are combined, the spectral efficiency can be effectively improved, and compared with the other multi-system modulation manner, the complexity is lower. In order to further improve the error rate of the visible light communication system, the method utilizes a channel balancer based on a feed-forward back propagation multilayer perceptron on a receiving end, so that the error rate is effectively improved, and the communication quality is further improved.
Owner:CHONGQING UNIV OF POSTS & TELECOMM

Self-adaptive transmission method of large-scale MIMO downlink

The invention provides a self-adaptive transmission method of a large-scale MIMO downlink. The self-adaptive transmission method of the large-scale MIMO downlink comprises the following steps: firstly, utilizing a stronger correlation of a large-scale MIMO spatial channel to transform the spatial channel into a beam domain through a DFT transformation; in the beam domain, utilizing a maximum system and rate as a criterion to select uses communicate simultaneously, and assigning an optimal transmission beam for each user, thereby determining a transport layer number and a pre-coding matrix for each user; then, by taking inter-user interferences into consideration, calculating a MMSE balanced posterior signal to interference plus noise ratio on each resource element of each transport layer for each user; and then, acquiring an equivalent signal to interference plus noise ratio for each user by an equivalent signal to noise ratio mapping; finally, on the premise that a word error rate of the transmission is ensured, by each client, to be lower than a given value, determining and feeding back a channel quality indicator of each codon, aiming at maximizing the system throughput. By the self-adaptive transmission method of the large-scale MIMO downlink, the reliability of a large-scale MIMO wireless transmission is increased; and an excellent system spectral efficiency is acquired while the system word error rate is ensured to be lower than the given value.
Owner:SOUTHEAST UNIV
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