Pulse or digital communications – Transmitters
Reexamination Certificate
1999-08-31
2003-12-02
Chin, Stephen (Department: 2634)
Pulse or digital communications
Transmitters
C704S215000
Reexamination Certificate
active
06658064
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Inventions
The present invention relates to a method for improving detectability of a data frame transmitting background noise information including a silence descriptor identifier and background noise parameters in a communication system in which the information to be transmitted is formed into data frames, said data frames are subjected to channel coding to form channel-coded frames, said channel-coded frames are interleaved to be transmitted in two or more data transmission frames, and information of two channel-coded frames is transmitted in each data transmission frame. The invention relates also to a communication system providing detectability of a data frame transmitting background noise information including a silence descriptor identifier and background noise parameters, the communication system comprising means for forming data frames of information to be transmitted, means for channel coding said data frames to form channel-coded data frames, means for interleaving said channel-coded data frames for transmission in two or more data transmission frames, wherein information of two channel-coded frames is arranged to be transmitted in each data transmission frame. The invention relates further to a mobile station providing improved detectability of a data frame transmitting background noise information including a silence descriptor identifier and background noise parameters, the mobile station comprising means for forming data frames of information to be transmitted, means for channel coding said data frames to form channel-coded data frames, means for interleaving said channel-coded data frames for transmission in two or more data transmission frames, wherein information of two channel-coded frames is arranged to be transmitted in each data transmission frame. The invention relates still further to a network element providing detectability of a data frame transmitting background noise information including a silence descriptor identifier and background noise parameters, the network element comprising means for forming data frames of information to be transmitted, means) for channel coding said data frames to form channel-coded data frames, means for interleaving said channel-coded data frames for transmission in two or more data transmission frames, wherein information of two channel-coded frames is arranged to be transmitted in each data transmission frame, means for deinterleaving received data transmission frames, means for channel decoding, and means for restoring information from channel-decoded data.
2. Brief Description of Related Developments
In data transmission in the form of data frames, the information to be transmitted is usually divided into data frames of fixed size. In addition to information, the data frames can contain header data and other data required in the transmission of the data frames. The data frames are transmitted from a sender to a receiver via a communication channel, which may comprise e.g. the radio channel or another wireless communication channel. The communication channel is subject to interference, such as ignition interference caused by electric equipment and in wireless data transmission, on the other hand, interference caused by other similar devices, such as radio transmitters. Another significant source of interference particularly in mobile transmitter/receiver devices is the fact that the signal to be received can enter the receiver via several routes of different lengths, wherein distortions are caused in the signal received. Consequently, for eliminating errors of transmission, data frames are usually equipped with error correction data or at least error detection data. One method to add error correction data is the use of so-called convolution codes, i.e. the information to be transmitted is encoded by using a suitable convolution code, wherein the convolution coded information is transmitted to the communication channel. At the receiving stage, a reverse operation is made to distinguish the transmitted information from the received data transmission flow. The error detecting data used is most usually parity checking data which is calculated from the information to be transmitted, or at least part of it. One such known parity checking method is the cyclic redundancy check (CRC). Thus, at the receiving end, the corresponding operation is made on the received information and the parity checking data generated at the receiving end is compared with the received parity checking data. If the data match, the receiving device interprets that the information was received correctly. If the calculated and received parity data do not match, a so-called BFI flag (bad frame indication) is set, to indicate to the receiving device that the received data frame was at least partly incorrect. After this, it is possible to request retransmission or an attempt can be made to interpret the incorrect frame e.g. by extrapolation or interpolation.
In current digital mobile communication systems, also speech is transmitted in the form of data frames. For example in the GSM mobile communication system (Global System for Mobile Communications), in the speech communication channel, most of the digital information generated from the audio signal is protected by error correction coding.
Furthermore, current digital mobile communication systems use a so-called discontinuous transmission, wherein the transmitter can be switched off for the time of pauses in speech. This reduces e.g. the power consumption and increases the usage time of the wireless communication device. Moreover, this discontinuous transmission reduces interference in other simultaneous data transmission connections. It is thus possible to improve the quality of the transmission. In practice, however, the transmission is not cut off for the time of the whole pause, but information is transmitted at intervals on background noise which is generated into audible noise in the receiver, corresponding substantially to the volume and frequency spectrum of noise detected at the transmission end. This generation of background noise is a further facility compared to muting the receiver completely for the time of pauses in speech. This background noise is typically transmitted in so-called silence descriptor frames SID at a lower bit rate than speech.
The frequency of transmitting these silence descriptor frames depends e.g. on the communication system used at the time. For example in the GSM mobile communication system according to prior art, speech coding takes place either at full rate (FR or enhanced full rate EFR) or at half rate (HR). During discontinuous transmission, only every 24th frame is transmitted in an FR channel (every 12th frame in an HR channel). All frames to be transmitted during discontinuous transmission are silence descriptor frames. In future mobile communication systems, it is possible to use e.g. adaptive multirate speech codecs (AMR). In silence descriptor frames of such systems, it is possible to transmit not only background noise but also information on the quality of the backward channel of the channel pair (uplink-downlink) used in the connection. For example, in communication between a mobile station and a network element such as a base transceiver station, the transmitting mobile station measures the quality of its receiving channel, i.e. the downlink of the base transceiver station, and transmits quality information in these silence descriptor frames to the base transceiver station. This quality information must be updated regularly to find out a possible need for change of the channel or the base transceiver station. For example in the AMR system, quality information must be transmitted more often than presently because of the change of the codec; consequently, quality information must also be transmitted as part of silence descriptor frames, which should therefore also be transmitted more often than presently.
In the decoder of the receiving device, such as a base transceiver station, the background noise is generate
Kapanen Pekka
Mikkola Hannu
Rotola-Pukkila Jani
Vainio Janne
Chin Stephen
Lugo David B.
Nokia Mobile Phones Limited
Perman & Green LLP
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