Nokia Corporation

Nokia Mobile Phones Limited

Oy Nokia Ab

Nokia Technology Gmbh

Nokia Oy

Jukka A Henriksson

Jussi Vesma

Harri Juhani Pekonen

Pekka Talmola

Tommi Auranen

Miika Sakari Tupala

Visa Koivunen

Ari H H&auml;m&auml;l&auml;inen

Arto Tapio Palin

Jani Väre

Timo Laakso

Kimmo J Raivio

Vesa Valimaki

In a digital broadband broadcast transmitter, digital data is time interleaved for transmission, and the time interleaved digital data is transmitted in a digital broadband broadcast transmission towards a plurality of receivers. A cellular transmitter is operated in an apparatus. In the same apparatus, the digital broadband broadcast transmission transmitted by the digital broadband broadcast transmitter is received, and the received digital broadband broadcast transmission is time deinterleaved.

Interoperability of digital broadcasting and cellular communication systems

The invention is directed to efficient transfer of low bit rate services in a communication system. A synchronization symbol which has known characteristics may be included as a first symbol of digital broadcast frames. The synchronization symbol, which can be decoded without having to resort to trial and error methods, contains parameters for the rest of the signal. Low bit rate services are allocated to time slots following the pilot symbol used for synchronization allowing for fast access times with maximum power saving capabilities. A user terminal wakes up just before the synchronization symbol and received the data allocated for the low bit rate services. The user terminal may power off for the remaining time slots which are allocated for higher bit services to conserve power.

DVB low bit rate services

Systems and methods for receiving an OFDM preamble without knowledge of channel characteristics are provided. An OFDM preamble signal with frequency shifted cyclic extensions is received. Taken together the cyclic extensions form a frequency shifted version of the OFDM preamble signal. Frequency offsets and timing offsets are estimated and corrected in an efficient manner using a simple concatenation approach in the time domain, followed by a summation of the OFDM preamble signal and the concatenation after a transformation of the OFDM preamble and the concatenation into the frequency domain. Phase errors in the frequency domain are estimated and corrected after FFT transformations of the received signals. A valid preamble is detected and additional parameters for receiving subsequently transmitted OFDM symbols in a channel are extracted from the OFDM preamble. The methods are computationally efficient and robust. Receiver implementations for performing the methods in a DVB receiver are disclosed.

System and methods for receiving OFDM symbols having timing and frequency offsets

Embodiments are directed to first and second OFDM pilot symbols. The first and second pilot symbols may have first and second sets, respectively, of allowed, forbidden, and active carrier frequencies. The second sets of carrier frequencies may be formed by frequency shifting the respective first sets by a predetermined frequency, such as the frequency difference between adjacent carriers. An embodiment is directed to frequency translating part of a first received pilot symbol by one carrier interval in a first direction, frequency translating part of a second received pilot symbol by one carrier interval in a second direction that is opposite from the first direction, and forming a correlation by multiplying the frequency translated parts of the first and second pilot symbols by complex conjugates of parts of the pilot symbols upon which frequency translation has not been performed, and summing the multiplication results.

Orthogonal frequency division multiplexing synchronization

Aspects of the invention are directed to service and channel discovery in a digital broadcast network. A pilot synchronization symbol, which has known characteristics, is included as a first symbol of digital broadcast frames. The pilot symbol, which can be decoded without having to resort to trial and error methods, contains parameters for the rest of the signal. So, the rest of the signal can be decoded without trial and error methods after the pilot symbol (and any additional synchronization symbols) is decoded. Channels containing digital video broadcast services can be efficiently detected using the known part of the signal. If the fixed known part is not found from the examined signal, then the signal will be considered a non-digital-video-broadcast signal or an empty channel, and the receiver can promptly proceed to a next channel/frequency. In this way, detecting non-digital-video-broadcast and empty channels becomes relatively fast.

Digital broadcast service discovery correlation

The invention relates to a method for communicating digital data using an orthogonal frequency division multiplexing (OFDM) transmission system () including at least one transmitter () and receivers (). The method comprises selecting a mode of operation in a transmitter among at least one mode, each mode of operation being associated with a number of active carriers for payload data transmission, selecting a symbol interleaver in the transmitter from a set of symbol interleavers for symbol interleaving in said selected mode of operation, applying symbol interleaving in the transmitter on blocks of data units, mapping the interleaved data units onto the active carriers of said selected mode of operation, receiving the interleaved data units in the receiver, recognizing in the receiver the symbol interleaver used in the data transmission, selecting a de-interleaver in the receiver to correspond to the recognized symbol interleaver, and de-interleaving in the receiver the received data units using the selected de-interleaver.

Symbol interleaving

Method and system for tolerating impulsive burst noise in pilot based OFDM systems, especially using DVB-T standard. The method contains following steps: 1) recognition of the impulse position and possibly length in the time domain symbol, 2) blanking of those samples of the symbol where significant amount of impulse noise is present, 3) calculating the first estimate of the received signal from the blanked symbol, 4) using a prior information (guard band carriers, pilot carriers) an estimate of the blanked symbol is calculated using inverse FFT on the differences of the observed carrier values from the known values in the frequency domain, 5) correction values for the frequency domain carriers are derived taking the FFT of the restored time domain samples, 6) finally the corrected estimate of the received symbol is derived by summing the correction values of step 5 to the first estimate of carriers derived in step 3. The method allows correction of relatively long bursts of impulse noise with minor degradation. The method provides considerably reliable data reception in broadcast systems.

Method and system for receiving a multi-carrier signal

A receiverfor receiving a multi-carrier signal comprises detection means for detectingthe presence of impulse interference within the signal and identifying one or more samples of the signal affected by the impulse interference, means for selecting samples to be blanked, means for blanking the selected samples and meansfor estimating the blanked signal. The selected samples comprise those samples (lto l+k) identified as being affected by impulse interference and at least one of the following: a number of samples xpreceding the said identified samples (lto l+k) or a number of samples xfollowing the said identified samples (lto l+k). The blanking means may define the length of a blanking windowto have one of a plurality of different predetermined lengths, using the smallest of the predetermined lengths sufficient to encompass the selected samples.

Method and system for reducing noise in a multi-carrier signal

The present invention relates to receivers, and, more particularly, to improved diversity receivers. In some environments, such as those subject to multipath reflection or shadowing, some carriers may be received with low power. In these cases, diversity receivers may provide an improvement of around 3 dB to 6 dB, the latter figure referring to cases where the communication channel is under severe multipath fading and in mobile reception. A diversity receiver effectively comprises two or more separate receivers, or diversity branches, each with its own antenna. Each set of received carriers from each diversity branch is then combined. The present invention provides an improved method and apparatus for receiving multi-carrier signals.

Diversity receiver

The invention relates to a method and circuit arrangement for compensating for an interference component included in a signal in a digital transmission system such as a mobile communication system, radio system or television system. In the method according to the invention a decision error representing an interfering signal is classified using an adaptive method, and a table is drawn up of interference estimates corresponding to classified decision errors. So it is obtained on the basis of previous decision errors an interference estimate corresponding to the next signal sample and that estimate is subtracted from the signal sample before the current decision. The adaptive method is preferably a neural method such as a self-organizing map. With the method according to the invention it is possible to compensate for an interference component in a signal regardless of the interference source assuming that the interfering signal has internal correlation. If required, it is also possible to include in the method according to the invention equalization for delayed payload signal components.

Method and circuit arrangement for processing a signal containing interference

The invention relates to a method and arrangement for advantageously decoding and channel correcting a convolutionally encoded signal received over a transmission path. The signal comprises code words and the arrangement comprises a neural network comprising a set of neurons which comprise a set of inputs and an output. The received code words ( ) and at least some of the output signals ( ) of the neural network neurons are connected to the inputs of the neurons, and the neurons comprise means ( ) for multiplying at least some of the neuron inputs prior to combining means ( ). The arrangement also comprises means ( ) for estimating the transmission channel. Further, estimated channel data ( ) is connected to the inputs of the neurons and a predetermined neuron is arranged to give an estimate of the channel-corrected and decoded symbol in its output signal.

Method and arrangement for implementing convolutional decoding

The invention relates to a method and an arrangement for decoding a convolutionally encoded signal which comprises code words and the arrangement comprises a neural network which comprises a set of neurons comprising a set of inputs and an output. The received code words are applied to the inputs of the neurons, and the arrangement combines some of the inputs of the neuron in the neuron. In order to enable efficient decoding of the convolutional encoding, some of the output signals of the neural network neurons are fed back to the inputs of the neuron and the neuron multiplies at least some of the inputs of the neuron with one another before combining. The output signal of a predetermined neuron comprises an estimate of a decoded symbol.

The invention is related to a method and circuit arrangement for compensating for delayed components of a received transmission signal especially in a digital transmission system based on physical lines. The method and arrangement utilize a decision feedback equalizer, wherein the weighted sum of decisions based on earlier samples is subtracted from a sample. According to the invention, delayed components in the signal are measured in a measuring unit (11). The earlier decisions to be subtracted from a signal sample are selected from a predetermined group of consecutive decisions, and the strength of the delay component in the delay between each decision and the signal sample is used as a selection criterion. Advantageously, the equalizer according to the invention includes a selector (8) which connects some of the taps of the delay line (7) to multiplier units (9). By means of this method and arrangement it is possible to implement with a small number of multiplier units an equalizer capable of compensating for delayed components with long delays.

Method and circuit arrangement for compensating for delayed components

The invention is related to a method and circuit arrangement for processing a received signal in a variable symbol rate system, such as a digital television system. In the method and arrangement according to the system, a received signal is sampled at a fixed sampling frequency (f.sub.f) that is higher than the symbol frequency of any one of the received signals. The resulting sample sequence is converted to another sample sequence the sampling frequency of which equals the symbol frequency (f.sub.i) of the received signal or its integer multiple. Then the samples are filtered (8) and signal value decisions are made (9) for the filtered samples. Conversion of the sampling frequency is advantageously performed using a so-called modified Farrow-type fractional delay filter (6) which is controlled using a control signal proportional to the delay of each sample. Using the method and arrangement according to the invention it is possible to process received signals the symbol frequencies of which are arbitrary within set limits.

Growing community of inventors

Espoo, Finland

Jukka A Henriksson