Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
  • H04L1/0056—Systems characterized by the type of code used
  • H04L1/0061—Error detection codes
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
  • H04L1/0045—Arrangements at the receiver end
  • H04L1/0046—Code rate detection or code type detection
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L1/20—Arrangements for detecting or preventing errors in the information received using signal quality detector

Definitions

• the present invention relates to a method and apparatus for estimating the transport format, i.e. the start and stop of data, of a transport channel.
• TFCI Transport Format Combination Indication
• TFC Transport Format Combination
• BTFD Blind Transport Format Detection
• CRC cyclic redundancy check
• a device for receiving blind transport format data and estimating the transport format of the data includes a soft decision magnitude/power monitor for monitoring the magnitude or power of soft decisions in the data over time; and a power or magnitude change detector for detecting changes in the magnitude of the monitored soft decisions, the position of detected changes representing characteristics of the transport format, or representing high probabilities of representing characteristics of the transport format.
• the blind transport format data includes a cyclic redundancy check (CRC).
• this invention can lead to faster identification of the transport format without having to do all Viterbi trace backs followed by CRC checks.
• the position of the power/magnitude changes indicate which CRC positions to check first. This also has the advantage of requiring less power consumption thereby extending battery life, or allowing the use of a smaller capacity battery for comparable battery life.
• a method of estimating the transport format of received blind transport format data which comprises monitoring the magnitude (power) of soft decisions in the data over time; and detecting changes in the magnitude of the monitored soft decisions, the position of detected changes representing characteristics of the transport format or representing high probabilities of representing characteristics of the transport format.
• the bar at the top indicates the single channel of a frame within which three transport channels are multiplexed.
• the single channel is divided by time into three time periods each of which is filled or part-filled by data from one of the multiple transport channels.
• the periods will be of the same size or duration.
• the periods are defined at the beginning and end in Figure 1 with a bold vertical line so the first period begins at the far left of Figure 1 and ends just before the second cyclic redundancy check (CRC) word.
• CRC cyclic redundancy check
• the data within a period might not fill that period. For example, in the first time period, ,the data fills most of the period, leaving about one sixth of the period at the end empty.
• At least one of the transport channel data must have a cyclic redundancy check (CRC) word appended to it.
• CRC cyclic redundancy check
• the position of the CRC word identifies the end of the transport channel since it is located at the end of the channel data.
• the data from the first transport channel has a CRC word at the end of the data, but before the end of the time period.
• the CRC word appears at the beginning of the time period.
• the CRC word appears before the end. In the period of time between the CRC word and the end of the time period, no data is transmitted.
• Data from the transport channels is received in the form of soft decisions.
• the use of soft decisions signifies probabilities of data bits being +1 or -1 instead of l's and O'S.
• the signal for a particular bit might be +0.82 which represents a high probability of that bit being +1.
• a bit value of -0.71 shows a high probability of the bit being -1.
• the probabilities will be high, and so the power associated with these signals will also be high, as is shown in the graph in Figure 1 during the period indicated "inferred TF for TrCH 0".
• the power is also high during the transmission of the second (CRC) word at the end of the second time period.
• the power is high during transmission of the data and CRC word associated with the third transmission channel (TrCH 2).
• DTX bits are transmitted at zero power and hence should be received at a lower power level, as can be seen from Figure 1.
• the position of the end of each transport channel can be identified or at least narrowed down. Identifying a drop in power will not necessarily indicate the exact transport format length, but will identify a number of likely positions for the ends of transport format lengths. Of course, the beginning of transport format lengths are always known because they are fixed.
• the detection of jumps in the power is not difficult to achieve.
• the power is measured and monitored, and can be fed into an edge detector.
• the edge detector can work in any one of a number of ways. It could detect jumps in the power of greater than a certain size, or could be arranged to identify when the power crosses a pre-set threshold value, where the threshold value is located between the normal power value during transmission of data, and the normal power value of the DTX soft decisions during the time in a period between the transmission of the CRC word and the end of the period.
• the speed at which blind transport format detection takes place is significantly increased by use of this invention either by immediately identifying the transport formats from the jumps in power, or by prioritising which transport format to decode by identifying the most likely positions of the ends of periods or by prioritising which CRC word to check first if the channel decoding was used to encode the data for error correction purposes.
• This invention applies to any system that relies on blind transport format detection where the multiplexed data is positioned in fixed positioned periods, such as in the 3 G UMTS specification or GSM specification, thereby correctly demultiplexing the received data.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Detection And Prevention Of Errors In Transmission (AREA)
• Error Detection And Correction (AREA)

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Citations (3)

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• 2001
  • 2001-10-09 GB GB0124238A patent/GB2380909A/en not_active Withdrawn
• 2002
  • 2002-10-09 EP EP02765105A patent/EP1435147A1/en not_active Withdrawn
  • 2002-10-09 CN CN 02819450 patent/CN1561599A/zh active Pending
  • 2002-10-09 WO PCT/GB2002/004557 patent/WO2003032559A1/en not_active Application Discontinuation

Patent Citations (3)

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