Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04H—BROADCAST COMMUNICATION
  • H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
  • H04H20/20—Arrangements for broadcast or distribution of identical information via plural systems
  • H04H20/22—Arrangements for broadcast of identical information via plural broadcast systems
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03J—TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS
  • H03J1/00—Details of adjusting, driving, indicating, or mechanical control arrangements for resonant circuits in general
  • H03J1/0008—Details of adjusting, driving, indicating, or mechanical control arrangements for resonant circuits in general using a central processing unit, e.g. a microprocessor
  • H03J1/0058—Details of adjusting, driving, indicating, or mechanical control arrangements for resonant circuits in general using a central processing unit, e.g. a microprocessor provided with channel identification means
  • H03J1/0083—Details of adjusting, driving, indicating, or mechanical control arrangements for resonant circuits in general using a central processing unit, e.g. a microprocessor provided with channel identification means using two or more tuners
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B17/00—Monitoring; Testing
  • H04B17/20—Monitoring; Testing of receivers
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
  • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
  • H04B7/0802—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using antenna selection
  • H04B7/0817—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using antenna selection with multiple receivers and antenna path selection
  • H04B7/082—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using antenna selection with multiple receivers and antenna path selection selecting best antenna path
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
  • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
  • H04B7/0837—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using pre-detection combining
  • H04B7/0842—Weighted combining
  • H04B7/0848—Joint weighting
  • H04B7/0857—Joint weighting using maximum ratio combining techniques, e.g. signal-to- interference ratio [SIR], received signal strenght indication [RSS]
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/12—Frequency diversity
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04H—BROADCAST COMMUNICATION
  • H04H2201/00—Aspects of broadcast communication
  • H04H2201/10—Aspects of broadcast communication characterised by the type of broadcast system
  • H04H2201/20—Aspects of broadcast communication characterised by the type of broadcast system digital audio broadcasting [DAB]
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04H—BROADCAST COMMUNICATION
  • H04H2201/00—Aspects of broadcast communication
  • H04H2201/60—Aspects of broadcast communication characterised in that the receiver comprises more than one tuner

Definitions

• the present invention relates generally to a method and a device for change of reception frequency in a diversity radiofrequency receiver, especially mobile diversity radiofrequency receivers, in the intersection area between radio broadcasting regions with different broadcasting frequencies, especially in a diversity radiofrequency receiver for a digital audio/video broadcasting system (DAB/DVB) .
• DAB/DVB digital audio/video broadcasting system
• Diversity reception/combining is a well-known concept within the area of mobile telephony. Diversity reception is used to avoid the poor reception quality when a receiver and a transmitter mutually move in relation to each other, i.e. a stationary transmitter and a mobile receiver (for example a car radio) , a mobile transmitter (for example a mobile phone) and a stationary receiver (for example a base station), or a mobile transmitter and a mobile receiver.
• a stationary transmitter and a mobile receiver for example a car radio
• a mobile transmitter for example a mobile phone
• a stationary receiver for example a base station
• the use of spatial diversity which uses a plurality of antennas physically spaced apart one or more wavelengths, is based on the assumption that there is a high probability that not all antennas will be in a fading area at the same time.
• a receiver such as a mobile telephone, analog radio/TV receiver, or digital radio/TV receiver
• moves between different broadcasting areas/regions covered by transmitters of different frequencies then the receiver has to change reception frequency.
• a diversity receiver will only solve reception problems within a region/cell. The necessary change of reception frequency when moving between regions/cells of different frequencies will necessitate test receptions of alternative frequencies, unless a random trial method is used.
• Digital mobile telephony uses Time Division Multiplex Access (TDMA) and can thus use the time frames when there is no reception or transmission, for test receiving alternative frequencies.
• TDMA Time Division Multiplex Access
• Digital radio/TV broadcasting systems digital audio broadcasting (DAB) and digital video broadcasting (DVB) uses coded orthogonal frequency division multiplexing (COFDM) modulation.
• DAB and DVB was primarily intended as single frequency network (SFN) systems.
• SFN single frequency network
• COFDM modulation technique provides a robust method of information transfer and is very suitable for SFNs. But due to, for example, the interleaving and the decoding of the digital data stream, the digital data stream cannot be interrupted for a test reception of an alternative frequency to thereby implement an unnoticeable method of test receiving alternative frequencies.
• the DAB system broadcasts alternative frequencies of the current program so that a list of these can be maintained in the receiver in a manner comparable to that of the RDS system.
• the DAB receiver will, in accordance to the methods used previously in other systems, when the field strength of the received program falls below a preset threshold or according to a tendency of the field strength, interrupt the reception of the program and perform test receptions of the alternative frequencies in the list.
• the reception of the current program is unfortunately interrupted for a time interval, which can be considered annoying.
• a DAB receiver can arbitrarily choose one of the alternative frequencies on the list and perform a frequency change in between two information frames.
• An object of the invention is to define a method and a device which are able to test receive an alternative reception frequency for evaluation purposes in a diversity radiofrequency receiver, especially a mobile DAB or DVB diversity receiver, without interrupting the currently received program/information.
• test receptions of alternative frequencies are done by using momentarily not- needed reception paths/branches.
• the current program/information transfer is not interrupted at all during the test receptions.
• a subsequently determined frequency changeover can thereafter, with a high probability, be performed without any noticeable interruption.
• a method of test receiving an alternative reception frequency in a space/spatial diversity receiver comprising at least two receive paths.
• the method comprises a number of steps in the spatial diversity receiver.
• the third step of determining which receive path or paths should be removed from the diversity reception comprises the substep of determining which of the receive paths is a lowest quality receive path or paths and the substep of determining that at least one of the receive path or paths that are the determined lowest quality receive path or paths, should be the path or paths that should be removed from the diversity reception.
• the third step of determining which receive path or paths should be removed from the diversity reception can advantageously comprise the substep of determining which of the receive paths is a highest quality receive path or paths and the substep of determining that at least one of the receive path or paths that are different from the determined highest quality receive path or paths, should be the path or paths that should be removed from the diversity reception.
• the diversity reception can preferably be a selection diversity method or a maximum ratio combining diversity method.
• the second step of determining the quality of reception of the first signal further comprises the substep of determining a top quality tendency of the at least two receive paths and the substep of suspending further steps until the top quality tendency is equal or below a predetermined top value.
• the second step of determining the quality of reception of the first signal can also or either further comprise the substep of determining a top quality tendency of the at least two receive paths and the substep of suspending further steps until the top quality tendency is equal or above a predetermined minimum value.
• the second step of determining the quality of reception of the first signal can also or either further comprise the substep of determining a top quality of the at least two receive paths and the substep of determining a lowest quality of the at least two receive paths and the substep of suspending further steps until the difference between the top quality and the lowest quality is equal or greater than a predetermined value.
• the method can advantageously further comprise the steps of evaluating which is a best quality reception frequency: the quality of reception of the first signal having the first radio frequency, or the quality of reception of the alternative reception frequency, and of switching the reception frequency of the at least two receive paths to the best quality reception frequency.
• the step of switching the reception frequency of the at least two receive paths to the best quality reception frequency can preferably further comprise the substep of suspending the switching of the reception frequency until the best quality signal is properly synchronized in the diversity receiver.
• the method can further preferably comprise the steps of determining a list of alternative frequencies, and of systematically performing test receptions of the alternative frequencies on the determined list.
• the method preferably further comprises the steps of evaluating which of the quality of reception of the first signal and the quality of reception of the alternative reception frequencies on the determined list is a best quality reception frequency, and of switching the reception frequency of the at least two receive paths to the best quality reception frequency.
• the alternative frequencies on the determined list can systematically be test received at least once each before evaluating which of the quality of reception of the first signal and the quality of reception of the alternative reception frequencies on the determined list is a best quality reception frequency.
• the alternative frequencies on the determined list are systematically test received only once each before evaluating which of the quality of reception of the first signal and the quality of reception of the alternative reception frequencies on the determined list is a best quality reception frequency.
• the alternative frequencies on the determined list are systematically test received at least twice each before evaluating which of the quality of reception of the first signal and the quality of reception of the alternative reception frequencies on the determined list is a best quality reception frequency.
• the step of evaluating which of the quality of reception of the first signal and the quality of reception of the alternative reception frequencies on the determined list is a best quality reception frequency is preferably based on calculated tendency of the quality of reception of each alternative frequency on the determined list.
• the second step of determining the quality of reception of the first signal further comprises the substeps of determining a top quality tendency of the at least two receive paths, and of, if the top quality tendency is below a must change value, then determining if there is an alternative reception frequency which has recently been test received with an adequate quality, and of, if it is determined that there is no test received alternative reception frequency with an adequate quality, then performing one or more emergency test receptions of alternative reception frequencies at least until an alternative reception frequency with an adequate quality is found or the top quality tendency comes above the must change value.
• the aforementioned objects are achieved in accordance with the invention also by a device for test receiving an alternative reception frequency in a space/spatial diversity receiver.
• the diversity receiver comprising at least two receive paths receiving a first signal having a first radio frequency being a reception frequency in at least two of the at least two receive paths with a diversity reception.
• the device comprises a plurality of means arranged to carry out the invention.
• a first means arranged to determine a quality of reception of the first signal in the receive paths in question.
• a second means arranged to determine which receive path or paths should be removed from the diversity reception.
• a third means arranged to remove at least one of the determined receive path or paths from the diversity reception.
• a fourth means arranged to switch the reception frequency of at least one of the removed receive path or paths from the first radio frequency of the first signal to an alternative reception frequency, the alternative reception frequency being different from the first radio frequency of the first signal.
• a fifth means arranged to receive the alternative reception frequency by the at least one removed receive path or paths.
• a sixth means arranged to determine a quality of reception of the alternative reception frequency. Thereby a test reception of an alternative reception frequency is possible without interrupting the reception of the first signal having the first radio frequency.
• a stationary receiver might be located in an area which is an intersection of two or more broadcasting areas with different transmitter frequencies in such a way that under certain conditions, weather conditions for example, one reception frequency is better than the other (s), and under different conditions another reception frequency is superior.
• the invention can also advantageously be utilized in a single frequency network where a full coverage DAB/DVB network is not yet achieved and where analog FM or AM broadcasting is utilized to complement the DAB network and thereby provide complete coverage for regional and/or national programs.
• test receptions are performed on alternative FM or AM frequencies instead of on DAB/DVB frames and that the evaluation of the test receptions are adapted according to the type of test reception performed.
• Fig. 1 shows a block diagram of one DAB frame
• Fig. 2 shows a frequency coverage map
• Fig. 3 shows a block diagram of a diversity receiver according to the invention.
• Fig. 4 shows a flow chart of how at least one alternative reception frequency is measured and possibly changed to in a receiver according to one method of the invention.
• Figure 1 shows a block diagram of one DAB frame, which is merely provided for a deeper understanding of the DAB system in particular and to understand in general the principles of transmission coding systems, such as DVB, that cannot be interrupted.
• a DAB frame mainly comprises a synchronization channel 101, 102, a fast information channel (FIC) 103, and a main service channel
• the synchronization channel comprises a null symbol 101 and at least one phase reference symbol 102.
• the fast information channel (FIC) 103 is, for example, used for multiplex configuration information (MCI) and service information (SI) .
• the main service channel 104 carries the desired useful information, which can be a number of coded audio programs/channels, one or more digital information transfers, or a combination of these. Usually more than one program/channel or information transfer is coded into the main service channel.
• a DAB frame is configured to provide a robust way of transferring information, i.e. packets of digital information, from a transmitter to a receiver without any feedback through, for example, a back channel.
• a DAB frame is assembled in the following manner; Packets of digital information are coded, error protected, and then time interleaved. These are thereafter multiplexed into the main service channel 104 according to a predetermined, but changeable, service configuration.
• the multiplexer output is frequency interleaved and combined with multiplex control and service information which travel in the fast information channel 103 in order to avoid the time interleaving process.
• very rugged synchronization symbols 102 are added before applying orthogonal frequency division multiplexing (OFDM) and differential quadrature phase- shift keying (QPSK) modulation onto a large number of carriers to form the DAB signal.
• OFDM orthogonal frequency division multiplexing
• QPSK differential quadrature phase- shift keying
• the fast information channel 103 and the main service channel 104 cannot be interrupted for any substantial length of time without causing a substantial interruption of the received program/information before the interleaving is complete again.
• a frequency switch between a currently received frequency to an alternative frequency should not be preceded with interruptions of the currently received frequency for the purpose of test receiving alternative frequencies. If a diversity receiver knows which alternative frequency it should switch to when a currently received frequency deteriorates, then there is no need to perform test receptions of alternative frequencies for an evaluation of which alternative frequency the receiver should switch to. Unfortunately this is rarely or never the case. Therefore there is a need to test receive alternative frequencies, to thereby be able to evaluate which is a, for the moment, superior reception frequency.
• FIG. 2 shows a frequency coverage map over four different broadcasting regions 211, 212, 213, 214, each region broadcasting with a different frequency.
• Each broadcasting region 211, 212, 213, 214 has at least one transmitter 221, 231, 222, 232, 242, 223, 224.
• a first broadcasting region 211 comprises two transmitters 221, 231, to be able to cover the whole first region 211.
• the two transmitters 221, 231, of the first region 211 transmit at the same frequency and thereby take advantage of a single frequency network (SFN) such as that of the DAB and DVB broadcasting systems.
• a second broadcasting region 212 comprises three transmitters 222, 232, 242, to cover the whole second region 212.
• the number of necessary transmitters can, for example, depend on the geography of the region or transmitter output power level.
• the first and second regions 211, 212 are single frequency networks on a small scale.
• These broadcasting regions 213, 214 can be of the DAB,
• the invention is not restricted to what type of broadcasting system a mobile receiver enters or a stationary receiver is in the vicinity of.
• the invention is however mainly directed toward the problems when the currently received program is transmitted from for example a DAB or DVB system since the invention deals with performing test receptions of alternative frequencies by a diversity receiver without interruption of the currently received program and thus for example the received DAB or DVB frames. It will be assumed in the following that all of the broadcasting regions 211, 212, 213, 214, are of the DAB or DVB type.
• the broadcasting regions 211, 213, (the first and third 211, 213) broadcast at least one common program/ information channel, the program being the one that our mobile receiver 290 is receiving when travelling along a road 200 that goes through the first and third broadcasting regions 211, 213, in our example.
• a diversity receiver would preferably change to an alternative frequency that transmits the same type of program that is currently received.
• the change to an alternative frequency is a bit more reluctant, i.e. the current frequency and therefore current program would be allowed to degrade a bit more before a change is performed than when the same program/information is available and a change back and forth can be performed without, for example, a listener noticing these changes.
• the DAB standard has provisions for not only broadcasting alternative frequencies that transmit the same program to the receiver, but also alternative frequencies that transmit the same type of program, i.e. news, pop music, jazz, sport etc.
• Test receptions of alternative frequencies is preferably done more or less continuously, but change to an alternative frequency will usually only be close at hand when a receiver is located in a region/intersection 219 between two or more broadcasting regions 211, 213, as is illustrated in figure 2.
• the recieved signal level will then be lower which gives an increased sensitivity to fading, which is at least in part compensated by a spatial diversity receiver.
• test receptions of alternative frequencies can either be performed more or less continuously or only when the reception level of the currently received frequency starts to deteriorate and for example an error bitrate rises.
• test receptions will preferably be performed at least when the mobile receiver 290 is on its way to enter a new broadcasting region 213.
• test receptions of alternative frequencies in a spatial diversity receiver are performed by one or more reception paths/branches that are not
• the alternative frequencies are not necessarily DAB or DVB transmissions and even if they are, it is not necessary for the invention that they are synchronized.
• an evaluation of the received signals is performed.
• a prediction as to the tendency, stronger and stronger or weaker and weaker, of the received signal can also possibly be done to support the determination as to what alternative frequency a change should be executed to and also when this should happen.
• the evaluation may comprise a determination of what type of signals are received, i.e. DAB, DVB, FM, or AM, so that an evaluation may take into account not only the received signal strength but also the received signal strength in view of the type of received signals.
• the method and device used for evaluation and prediction is outside the scope of this invention and within the capability of the man skilled in the art to implement and will therefore not be discussed any further herein .
• Figure 3 shows a block diagram of a diversity receiver according to the invention.
• the receiver according to the example only comprises two reception paths/branches, a first branch 301, 311, 321, 325, 331, 341 and a second branch 302, 312, 326, 322, 332, the minimum required by the invention, there is no upper limit to the number of reception branches used.
• the receiver according to figure 3 comprises two antennas 301, 302, which are suitably physically separated one or more wavelengths from each other. Mounted in a car, the antennas 301, 302 can suitably be placed in the vicinity of different corners of the car perimeter.
• Each branch then comprises a corresponding preamplifier and possible filter 311, 312, a local oscillator 321, 322, a mixer 325, 326 for a frequency shift to the baseband and possibly a filter 331, 332.
• the diversity receiver also comprises a diversity combiner 360, which determines if an output signal 390 should be derived from only one reception branch and in that case which branch, or if the output signal 390 should be derived from some sort of combining of the received signals from two or more branches.
• the diversity combiner 360 makes use of a quality checker 350 when combining the received signals from the attached branches.
• the quality checker 350 can for example determine the received signal strength, bit error rate, and/or tendencies for use as a quality base.
• At least one branch comprises a switch 341 which removes a branch in question and directs the signal of the branch to a quality checker, preferably being the quality checker 350 of the receiver.
• each branch of the receiver comprises a corresponding switch 341, 342 such that any branch can be disconnected from the diversity reception and instead be connected to a quality checker for evaluation of alternatively received frequencies in the disconnected branches.
• a switch 341 there is a cost and space saving, with the disadvantage of only being able to test receive alternative frequencies in one branch.
• the quality checker 350 will determine when the quality of the currently received signals from a currently received reception frequency has deteriorated to such a degree that there is a need to change reception frequency, and thus a need to determine to which alternative frequency a change should be made, by means of test receptions. In certain embodiments or modes of the invention test receptions are performed at regular or irregular intervals instead of waiting for an acute need. When it has been determined that a test reception of an alternative frequency should be made, then it is determined which reception branch that is not momentarily needed for a proper reception of the currently received signals of the current reception frequency. Preferably the quality checker 350 is used to determine which branch is not momentarily needed, i.e.
• Fading can in principle be divided into two basic types, a first type which is dependent on the relative movement between a transmitter and a receiver and a second type which is dependent on the spatial relationship between the transmitter and the receiver which brings in geographical and atmospherical conditions.
• the first type of fading is periodically varying and is dependent on factors such as the relative speed between receiver and transmitter and used frequency.
• the periods can be measured and will give a possibility to predict length of availability of a path/branch for test receptions and also when this will occur. Unfortunately the periods become shorter and shorter (i.e.
• the second type of fading is unpredictable and will vary even if receiver and transmitter are not moving relative each other.
• the second type of fading is more difficult to predict, but it is possible during favorable conditions. According to the invention it is possible to interupt a test reception and return one or more used paths for reception of the original reception frequency if the fading takes an unexpected negative turn, i.e. the reception quality deteriorates, on the path or paths used for receiving the current reception frequency.
• the determination of which branch (or branches in a spatial diversity reception system with more than two branches) that is not needed can be based on which branch
• the first branch 301, 311, 321, 325, 331 is determined not needed then it is removed/disconnected from the diversity combiner 360 by a switch 341 of the branch in question.
• the diversity combiner 360 will then only receive signals from the second branch 302, 312, 326, 322, 332.
• the local oscillator 321 of the first branch is then changed so that an alternative frequency is received.
• the received signals of the alternative frequency are directed to a quality checker, preferably the quality checker 350 so that the quality of the alternative frequency can be measured.
• a plurality of alternative frequencies can be test received by simply adjusting the local oscillator 321 of the first branch, or the first branch is returned to receiving the current signal of the current reception frequency and a new evaluation/determination of which path is not needed is made.
• Fig. 4 shows a flow chart of how at least one alternative reception frequency is test received, measured and possibly changed to in a receiver according to one method of the invention.
• a current frequency is received by the different paths/branches of a diversity receiver.
• a quality determination step 420 the quality of reception of the currently received frequency is determined. The quality determination can, for example, be based on measured field strength, number of bit errors, or tendencies, i.e. is the situation getting worse or better.
• a measured field strength or for example an error bitrate of the currently received frequency is either compared to a fixed threshold value or used in a prediction computation with which a tendency is computed and thereafter compared with model tendencies.
• Model tendencies can be either computated from knowledge of for example fading behaviour, such as described above, and/or from previous measurements, a car receiver which travels the same route day after day. If the field strength is above the fixed threshold or does not show a weakening tendency, then the procedure returns to the receive state 410.
• the procedure proceeds to a second optional step 433, or if there is no optional step 433 directly to a third step 440 which will be described in full below.
• the procedure can also possibly be suspended if the received quality is below a threshold, below which it is determined that all or most paths/branches are needed to ensure that the reception is not interrupted.
• the first optional step 431 is optional, the method according to the invention, as described below, can be performed continuously, initiated by another program, or initiated on demand by other methods/devices than by the method which has been described in relation to the first optional step 431.
• the second optional step 433 determines a list of alternative frequencies that can be suitable to test receive.
• the list might consist of only one alternative frequency or a plurality.
• the currently received frequency can preferably be included in the list.
• the list might be assembled from all or selected frequencies from those included in the information received by the currently received, for example DAB or DVB, transmissions, preprogrammed frequencies, one or more random frequencies generated, for example, from a random generator, all or selected frequencies in the neighborhood of the currently received frequency, or all or selected frequencies in the frequency range of the receiver or a combination of any of these possibilities.
• one or more branches are removed from use for reception of the currently received frequency, i.e. this or these branches are not to be used for diversity reception, but for reception of alternative reception frequencies.
• the method for removing one or more branches can be determined in different manners in dependence on the specific embodiment of the invention.
• the branch or branches that are determined to have the currently received frequency' s worst reception quality can be the one or ones that are removed. In other embodiments it can be the one or more branches that are removed that is/are not or do not belong the group of branches that are determined to have the currently received frequency's highest quality reception.
• a fourth step 450 At least one branch of the removed branch or branches have their reception frequency switched to an alternative reception frequency.
• the alternative reception frequency is received in a fifth step.
• the quality of the received alternative frequency is determined.
• the quality determination can, for example, be based on measured field strength, number of bit errors, or tendencies, i.e. is the situation getting worse or better.
• the procedure according to the method according to the invention can then optionally comprise a third optional step 481.
• the third optional step 481 will determine if there are more alternative frequencies to measure/test receive. If, for example, there is a list of alternative reception frequencies to measure, then preferably all of them should be measured at least once, maybe even more times to thereby be able to calculate reception tendencies. If all alternative frequencies have been measured then the procedure will optionally continue with a 483 fourth optional step. On the other hand, if it is determined that more alternative frequencies should be measured, then the procedure can, for example either continue the fourth step 450, or to the first step 410, with or without returning the removed branch or branches to the current frequency, for starting the procedure from the top.
• the fourth optional step 483 it is determined if an alternative frequency is better than the currently received frequency. Basically a comparison of the results from the second step 420 and the sixth step 470 is made, i.e. the quality of the received frequency is compared with the quality of alternative frequency or frequencies. If the currently received frequency is determined as having a better quality, i.e. being the most preferable, then the procedure preferably either exits from the procedure or returns to the top with the first step 410 to start the procedure over again. On the other hand, if it is determined that an alternative frequency is of a better quality then the procedure preferably continues with possibly a fifth optional step 485 and a sixth optional step 487.
• the fifth optional step 485 suspends further processing until the alternative frequency it has been determined has a better quality, has been properly synchronized.
• the procedure continues with the sixth optional step 487, which switches reception of preferably all the reception branches to the alternative frequency. Thereafter the procedure exists or returns to the top of the procedure and starts over again with the first step 410.
• the present invention can be put into apparatus-form either as pure hardware, as pure software or as a combination of hardware and software. If the method according to the invention is realized in the form of software, it can be completely independent or it can be one part of a larger program.
• the software can suitably be located in a general-purpose computer or in a dedicated computer.
• the invention can basically be described as a device and a method which provide test receptions of alternative reception frequencies to thereby enable a change of reception frequency in a spatial diversity receiver without interrupting reception of the currently received frequency.
• FIG 1 A first figure.
• first optional step - is it necessary to measure alternative frequencies; 433 second optional step - determine list of alternative frequencies; 440 third step - remove one or more branches;
• fourth step - switch frequency of removed branch (s) 460 fifth step - removed branch (s) receive alternative frequency; 470 sixth step - determine quality of received alternative frequency; 481 third optional step - are there more alternative frequencies to measure; 483 fourth optional step - is an alternative frequency better than currently received frequency, signal; 485 fifth optional step - synchronize alternative frequency, signal; 487 sixth optional step - switch reception to alternative frequency;

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• Microelectronics & Electronic Packaging (AREA)
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• 1999
  • 1999-12-29 SE SE9904842A patent/SE515967C2/sv not_active IP Right Cessation
• 2000
  • 2000-11-14 WO PCT/SE2000/002224 patent/WO2001050648A1/en not_active Application Discontinuation
  • 2000-11-14 AU AU14287/01A patent/AU1428701A/en not_active Abandoned
  • 2000-11-14 EP EP00976524A patent/EP1247362A1/en not_active Withdrawn

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