KR100808392B1 - Method for the communication of information and apparatus employing the method - Google Patents

Abstract

A method of transferring information units over a wireless digital communication link (30) between a transmitting station (20) and a receiving station (40) comprises transmitting first information units at a first energy level; Monitoring whether correct reception of the transmitted units is made; For first information units for which the monitoring does not indicate that an accurate reception has been made, transmitting second information units associated with the first information units at second energy levels, wherein the second information units are arranged in a first manner. Allowing said content of information units to be established, wherein said at least one of said associated second information units is connected to a series of first information unit transmissions with respective second information unit transmissions. When averaged across, the energy is transmitted at least partially selected to minimize the total transmitted energy. At least one second information units may be transmitted at an energy level below the energy level used for the transmission of the first information units. The second information units can be transmitted, at least in part, with duplicate content selected to minimize the total duplicate data content when averaged over a series of second information unit transmissions with each second information unit transmissions.

Information unit, information unit, receiver, redundancy

Description

Method for the communication of information and apparatus employing the method}

The present invention relates to the exchange of information over digital communication systems, in particular over wireless digital communication links of various qualities. Compared to wired links, larger quality changes are typically observed in wireless links, e.g., wireless links established in a cellular mobile radiotelephone system between mobile telephones and base stations. The invention may also be used in other fields, but more particularly relates to code division multiple access (CDMA) systems used in so-called third generation mobile communication systems such as universal mobile communication systems (UMTS).

Communication systems, including mobile communication systems and networks, are increasing the use of digital technology. Such networks require a wireless radio communication link to be established between the mobile terminal and the base station (or fixed terminal). Second and third generation mobile telephone systems exchange digital signals over a wireless radio communication link.

Digital systems can provide greater spectral efficiency of radio communication links than those provided by analog systems, and digital processing can often minimize the effects of interference.

In communication systems that rely on wireless links, such as mobile communication systems, the quality of these links can vary significantly. Many factors affect the quality of the link, and the system must be resistant to these random changes. In systems employing an analog link, the degradation in link quality establishes only a noisy but acceptable level of link. However, in a system employing a digital link, it is important that information transmitted over the link can be reliably recovered at the receiving end even when the link quality is poor. The incorrectness of the information received incorrectly depends on the application. For example, in the case of a digital cellular mobile radiotelephone system employing a wireless radio link, loss of information over the link and incorrect reception during a phone call can only result in temporary muting of sound. However, with the advent of mobile computing, mobile telephone cellular networks are increasingly used for the communication of data, in which situation no data loss is allowed.

To assist in the accurate communication of digital information through the media domain, various techniques are known, some of which fall within the scope of error detection and correction. One of these techniques is forward error correction (FEC), which involves encoding information prior to transmission in such a way that any errors that occur during communication can be identified and corrected upon receipt. Another technique employs an automatic repeat request (ARQ) error control scheme that involves retransmission of information that is either received incorrectly or is considered not received at all. There are various derivatives of the basic ARQ scheme, which are employed according to the probability of providing buffer space at the transmit / receive ends of the link and the requirements for efficiently utilizing the link. In fact, some ARQ schemes do not simply retransmit the same information. In the case of these structures, retransmission involves (re) transmitting only a portion of the information, or transmitting the appropriate FEC information or any combination thereof. Various ARQ schemes are well known to those skilled in the art, and it is equally well known that retransmission is initiated when there is no acknowledgment of whether the information was received correctly or incorrectly. This is in contrast to the situation where the exact request for retransmission is sent to the transmitter. When FEC and ARQ techniques are combined, they can provide robust error detection and correction mechanisms, and ARQ operations of certain implementations are only activated if the FEC fails to recover information. However, although wired twisted pair links are sensitive to noise and interference, both techniques will be more predictable and consistent as the quality of the link can be provided, for example, by coaxial cable. When it is most effective. In contrast, wireless radio communication links, such as those used between mobile terminals and fixed terminals, are for example mobile (where the terminal is moved), obstacles caused by buildings, geographic shape of the region, climatic conditions and Due to the distance of the radio link, there is a constantly changing link quality. The occurrence of interference can also affect link quality. In particularly poor conditions, ARQ techniques will generate multiple retransmissions, which can cause delays in data communication and an overall increase in system power consumption. For example, in the case where components of the system, such as mobile terminals, depend on battery power, this is not particularly desirable.

Radio link quality is degraded due to large signal fluctuations, for example, in the case of deep fade, various prior art remedies including methods for lowering the transmission rates and increasing the overall transmission power. It has been proposed to deal with reception failures.

In wireless systems such as UMTS, the main purpose of providing an ARQ scheme is to maximize throughput while minimizing the use of system radio frequency (RF) resources such as output and transmission periods. In addition, it is appropriate to minimize parameters such as interference caused for other users, end-to-end transmission delay, implementation complexity, and additional consumption of network transmission capacity. These are all long-standing problems.

Published international patent application WO-A-00 / 19634, filed under the name of Koninkli Philips Electronics N. V., uses transmission power used for previous (original) packet transmissions to which the transmission power level of retransmitted information packets corresponds. An ARQ scheme is disclosed that can be increased for a level. The motivation for doing this is to reduce the probability of unsuccessful reception of retransmitted information packets. This allows information packets to be initially transmitted at a lower power level in the case of an arrangement that does not take advantage from this structure, while maintaining overall the probability of a given packet reception failure. Because of this, it is also possible to reduce the total transmitted energy, ie the sum of the energies resulting from the first transmission and the predetermined retransmissions. In certain cases, this may mean a reduction in the interference caused to other users. This structure also reduces the probability that a large number of repetitive transmissions will occur, which constitutes a sub-optimal manner of communication for a number of reasons, including delays in information delivery.

While the above-described structure simultaneously seeks to regulate the interference caused to other users, while taking some way to provide an increase in the probability of accurate data reception upon retransmission, the object of the invention is, inter alia, a CDMA such as UMTS. With respect to systems, it is to improve this behavior.

According to a first aspect of the invention, there is provided a method of delivering information units over a wireless digital communication link between a transmitting station and a receiving station, the method comprising:

Transmitting first information units at a first energy level;

Monitoring whether accurate reception of transmitted units is made, and

Second energy levels associated with the first information units, allowing the content of the first information units to be established, for the first information units for which the monitoring does not indicate that correct reception has been made; Sending to,

At least one of the associated second information units is information transmitted at an energy level, selected to at least partially minimize the total transmitted energy when the series of first information unit transmissions with each second information unit transmissions are averaged A delivery method is provided.

At least one second information units may be transmitted at an energy level below the energy level used for the transmission of the first information units.

The method comprises a first received at the receiving station such that the received energy of the second information unit transmissions, or of each second information unit transmissions, complements the received energy of the first and any previous second information unit transmissions. Combining the first information units and associated second information units received at the receiving station, wherein the combining step increases the total energy of the combined received transmissions with each second information unit transmission event. To be performed.

Optionally, for a given first information unit transmission, the associated consecutive second information unit transmission events are performed with a gradual increase in transmission energy with respect to each other.

Optionally, the first and any associated successive second information unit transmission events are sent energy such that the total transmission energy obtained by combining the first and any second information unit transmission events increases substantially exponentially in value. Each is performed.

The first and any associated successive second information unit transmission events are each performed with transmission energy such that the total transmission energy obtained by combining the first and any second information unit transmission events conforms to Eq ^n-1 , where E is the transmission energy used for the first information unit transmission event, k is a constant, n is the individual information unit transmission event, n = 1 in the first information unit transmission event, and each successive second information unit N = 2, 3, 4,... , n. Optionally, k = 1.4.

For each second information unit transmission event, the second information units are transmitted at selected second energy levels based in part on the reception parameter target quality for each said second information unit. In this case, the target quality of the reception parameter for each second information unit can be calculated as a function of the actual quality of at least one previous target or reception parameter.

The target quality of the reception parameter for each second information unit can also be calculated as a function of the energy received due to the transmission of the information units.

The quality of the reception parameter may be a signal to interference (SIR) ratio.

The target quality of the reception parameter for the at least one second information units may be set such that the reception of less energy from the transmission of the at least one second information unit is caused than the energy received from the transmission of the first information unit.

For a given first information unit transmission, the associated consecutive second information unit transmission events can be set to yield a gradual increase in the received energy for each other.

Optionally, the first and any associated second information unit transmission events are received parameters that cause the total received energy obtained by combining the first and any second information unit transmission events to increase substantially substantially exponentially in value. Are each carried out with their target quality.

The first and any associated successive second information unit transmission events are each in target quality of reception parameters such that the total received energy obtained by combining the first and any second information unit transmission events conforms to equation Ek ^n-1 . Where E is the transmission energy used for the first information unit transmission event, k is a constant, n is the individual information unit transmission event, n = 1 in the first information unit transmission event, and each successive For the second information unit transmission event, n = 2, 3, 4,... , n. Optionally, k = 1.4.

The target quality of the reception parameter for the at least one second information units may be set to yield a lower actual quality of the reception parameter from the transmission of the at least one second information unit than the actual quality of the reception parameter of the first information unit. have.

For a given first information unit transmission, the target quality of the reception parameter for the associated consecutive second information unit transmission events can be set to yield a gradual increase in the actual quality of the reception parameter with respect to each other.

Optionally, the first and any associated consecutive second information unit transmission events result in a target quality of reception parameters that causes the total received parameter quality obtained by combining the first and any second information unit transmission events to increase substantially exponentially. Are performed respectively.

The first and any associated successive second information unit transmission events are converted into target quality of reception parameters such that the quality of the total received parameter obtained by combining the first and any second information unit transmission events conforms to Eq ^n-1 . Respectively, where E is the transmission energy used for the first information unit transmission event, k is a constant, n is the individual information unit transmission event, n = 1 in the first information unit transmission event, and each successive For the typical second information unit transmission event, n = 2, 3, 4,... , n. Optionally, k = 1.4.

The method analyzes an imbalance between the actual and target quality of the reception parameters of the received information unit transmissions, and if the quality of the reception parameter for the received information unit transmission is greater than the target quality of the reception parameter, transmission of the information unit. While reducing the information unit transmission information level, while increasing the information unit transmission power level during the transmission of the information unit if the quality of the reception parameter for the received information unit transmission is less than the target quality of the reception parameter. It includes.

The predetermined first information unit quality of the reception parameter, which can be preset, can be selected based on the target bit error rate or the block error rate of the information received at the receiving station by the first information units.

The communication link may be established by a facility operating in accordance with a communication protocol based on a universal mobile communication system (UMTS). The communication link may be established on at least one physical channel. Optionally, the receiving station transmits transmit power adjustment commands to the transmitting station in a Transmission Power Control (TCP) field carried on a control channel setup in the communication link. The transmit energy of the information units can be at least partly controlled by adjusting the scaling factor between the control and data channel transmit powers.                 

The target quality of the reception parameter for the first information units is selected to correspond to a defined probability of failed first information unit transmission and subsequent second information unit transmission.

An upper limit value may be applied to the transmission energy level of the first information units. An upper limit value may be applied to the transmission energy level of the second information units. In this case, the upper limit of the transmission energy level of the second transmission units may be different from the upper limit of the transmission energy level of the first information units.

According to a second aspect of the present invention, there is provided a digital wireless communication system.

At least one transmitter having means for transmitting first information units at a first power level,

At least one receiver having means for receiving the transmitted information units,

Monitoring means for monitoring whether accurate reception of the transmitted units is made,

The transmitting means transmits the second information units at second energy levels, for the first information units for which the monitoring does not indicate that the correct reception has been made, the second information units associated with the first information units, Allows the content of the first information units to be established, and also wherein at least one of the associated second information units is total transmit energy when the series of first information unit transmissions with each second information unit transmissions are averaged A digital wireless communication system is provided that is transmitted at an energy level selected to at least partially minimize it.

According to a third aspect of the present disclosure, a transmitting station for digital wireless transmission of traffic information is provided, and the transmitting station is

A transmitter for transmitting the first information units at a first energy level, and

Monitoring means for monitoring whether accurate reception of the transmitted units is made,

The transmitter transmits second information units associated with the first information units at second energy levels for first information units for which monitoring does not indicate that correct reception has been made, and wherein the second information units are configured for the first information units. Allows content of the first information units to be established, and further, at least one of the associated second information units determines the total transmission energy when the series of first information unit transmissions with each second information unit transmissions are averaged. Transmitted at an energy level selected to at least partially minimize.

According to a fourth aspect of the present invention, a receiver for use in a digital wireless communication system is provided, wherein the digital wireless communication system includes:

The digital wireless communication system includes at least one transmitter having means for transmitting first information units at a first power level, a receiver for receiving the transmitted information units, and monitoring whether correct reception of the transmitted units is achieved. Including monitoring means,

The transmitting means transmits the second information units associated with the first information units at second energy levels, for the first information units for which monitoring does not indicate that an accurate reception has been made, and the second information units have the Allows the content of the first information units to be established, and further, at least one of the associated second information units, total transmission energy when the series of first information unit transmissions with each second information unit transmissions are averaged. Is transmitted at an energy level selected to at least partially minimize it.

According to a fifth aspect of the invention, there is provided a method of delivering information units over a wireless digital communication link between a transmitting station and a receiving station, the method comprising:

Transmitting first information units having first redundancy content;

Monitoring whether accurate reception of transmitted units is made, and

Sending second information units associated with the first information units for the first information units for which the monitoring does not indicate that an accurate reception has been made, wherein the second information units are configured to establish the content of the first information units; Transmitting, allowing to be made;

At least one of the associated second information units is adapted to at least partially minimize data redundant content when the series of first information unit transmissions with each second information unit transmissions are averaged. There is provided a method of transmitting information that is carried with it.

The at least one second information units are transmitted with data duplicate content below the duplicate data content level used for the transmission of the first information units.

The method may further comprise combining first information units received at the receiving station and associated second information units received at the receiving station.

For a given first information unit transmission, the associated successive second information unit transmission events may be performed with a gradual increase in duplicate data content with respect to each other.

Optionally, said first and any associated second information unit transmission events have redundancy data content that causes the total redundancy data content obtained by combining the first and any second information unit transmission events to increase substantially exponentially. Each is performed.

The first and any associated second information unit transmission events may be performed with redundancy data content such that the amount of additional redundancy to be added to the NQJSwO transmission is given by Equations Bk ^n-1 -Bk ^n-2 , Where B is the total number of bits transmitted in the first transmission, n is the individual information unit transmission event, n = 1 in the first information unit transmission event, and for each successive second information unit transmission event, respectively. n = 2, 3, 4,... , n.

According to a sixth aspect of the present invention, there is provided a digital wireless communication system.

At least one transmitter having means for transmitting first information units having first redundant content;

At least one receiver having means for receiving the transmitted information units, and                 

10. A digital wireless communication system, comprising monitoring means for monitoring whether accurate reception of transmitted units is made;

The transmitting means transmits, to the first information units for which the monitoring does not indicate that the correct reception has been made, the second information units having second redundant content associated with the first information units, the second information units being Allows the content of the first information units to be established, and wherein at least one of the associated second information units is totally redundant when the series of first information unit transmissions with each second information unit transmissions are averaged A digital wireless communication system is provided that is transmitted with data redundancy content selected to at least partially minimize data content.

According to a seventh aspect of the present invention, there is provided a transmitting station for digital wireless transmission of traffic information, the transmitting station comprising:

A transmitter for transmitting first information units having first redundant content, and

Monitoring means for monitoring whether accurate reception of the transmitted units is made,

The transmitter transmits, for the first information units for which the monitoring does not indicate that the correct reception has been made, the second information units with second redundant content associated with the first information units, the second information units being Allows the content of the first information units to be established, and further, at least one of the associated second information units, total transmission redundancy when a series of first information unit transmissions with each second information unit transmissions are averaged It is sent with data redundancy content selected to at least partially minimize data content.

According to an eighth aspect of the present invention, there is provided a receiver for use in a digital wireless communication system, the receiver comprising:

The digital wireless communication system is configured to monitor at least one transmitter having means for transmitting first information units with first redundant content, a receiver for receiving the transmitted information units and for correct reception of the transmitted units. Means,

The transmitting means transmits, to the first information units for which the monitoring does not indicate that the correct reception has been made, the second information units having second redundant content associated with the first information units, the second information units being Allows the content of the first information units to be established, and further, at least one of the associated second information units is to be totally transmitted when a series of first information unit transmissions are averaged with each second information unit transmissions. It is transmitted with data duplicate content selected to at least partially minimize duplicate data content.

These and other aspects, as well as other optional features, are set forth in the appended claims, to which the reader will refer, which is incorporated herein by reference.

1 is a schematic diagram of a typical cellular mobile radio telephony communication system utilizing at least one wireless radio communication link.

2 is a schematic diagram of components in a transmitting station from the system of FIG.

FIG. 3 illustrates the operation of a conventionally known automatic repeat request (ARQ) error control structure.

4 illustrates the operation of an implementation of an error control structure using power control.

5 illustrates transmit power over time of an apparatus operating in accordance with the present invention.

The present invention will now be described by way of example with reference to the accompanying drawings.

With reference to FIG. 1, a communication system 1 in the form of a cellular mobile radio telephone system includes a switching center 10 connected to a public switched telephone network (PSTN) and other data networks, if necessary. The switching center is typically one of a plurality of switching centers, with a number of base stations 20 connected to each switching center. The main function of the base station 20 is to establish a radio link 30 with the terminal 40, such as a mobile telephone (or, in the case of UMTS, so-called user equipment (UE)), thereby remaining of the mobile terminal 40 and the system. It allows communication between parts. Each base station 20 may generally support a plurality of such links 30, and thus may support a plurality of mobile terminals 40. Although the base station 20 and the switching center 10 are shown as separate components, this is for illustrative purposes only and, as will be apparent to those skilled in the art, the switching center depending on how the system is implemented. And / or various functions may be performed by the base station. Base station 20 is sometimes referred to as a fixed terminal, and in some cases is meant to include components such as switching center 10 or at least these functional components associated with the switching center and other fixed infrastructure components. Can have. The base station 20 and the terminals 40 are provided with radio transmission and reception means for establishing the links 30, respectively. It is assumed that the radio link 30 is digital and may also use techniques such as time division multiple access (TDMA), frequency division multiple access (FDMA) or code division multiple access (CDMA).

In use, the quality of the link 30 established between the base station 20 and the terminal 40 varies greatly, and the system must be immune to link quality that changes from time to time. In the case where digital information is exchanged as in this embodiment, this may result in incorrect reception of digital information. Error correction techniques, such as forward error correction (FEC), can be used to recover accurate information from incorrectly received information. When the quality of the link 30 is degraded and other FEC techniques are unable to properly recover the correct information, in this case there is no alternative but to initiate additional transmissions on any incorrectly received information. Although an example may be to employ ARQ schemes as described above, these additional transmissions may take various forms. In each case, additional transmissions may be considered as the transmission of second information units associated in some manner with the first information units that have already been transmitted (failed), regardless of the selected scheme. Further, as described above, the additional transmissions (second information units) may include a straightforward retransmission of information, (re) transmission of only a portion of the information, transmission of appropriate FEC information, and enhanced FEC information. May involve the transfer of or any combination thereof. However, to illustrate the invention, by way of example only, the following detailed description relates to a conventional ARQ scheme in which the transmission of second information units actually constitutes repetitive transmission of (failed) first transmission units.

Retransmission of information occurs without user intervention and is therefore referred to as an automatic repeat request (ARQ). By way of example only, a typical ARQ scheme may be understood with reference to FIG. 3, which shows a frame sequence of a so-called selective RQ scheme ARQ implementation (when the frame is a unit of information conveyed over the data link 30 of this embodiment). ). This known scheme is described in detail in Fred Halsall's publication "Data Communications, Computer Networks and OSI", 2nd edition 126-127, published by Addison-Wesley Publishing Company. Although information often flows in both directions over a link, FIG. 3 shows the case where the information is transmitted from the transmitter S to the receiver R in the form of a number N of information frames I. Shows the situation. Each transmitted frame includes a unique identifier that enables the transmitter S and the receiver R to maintain separate frames. Both the transmitter and the receiver each have a buffer storage space C _S , C _R for recording the transmitted or received frames. By way of example, frame I (N), indicated as 101, is transmitted by transmitter S, which is written into buffer C _S. The frames are transmitted continuously, and the contents of C _S form a (temporary) retransmission list. The receiver R returns an acknowledgment ACK to S for each correctly received frame, and also records a list of correctly received frames in the buffer C _R. When the transmitter S receives an acknowledgment ACK that a particular frame has been correctly received from the receiver R, the transmitter S removes an entry corresponding to the received notification frame from the buffer C _S. Each I frame is coded to allow the receiver R to establish that each I frame is not corrupted. Various ways of doing this include the use of periodic redundancy check (CRC) error checking. Referring now to FIG. 3, it is assumed that frame I (n + 1), denoted 102, has been corrupted during transmission, which is shown by the cross line. This results in the reception notification of the other illustrated frames N, N + 2, N + 3, ... being normal while the reception notification for the I frame N + 1 does not exist. The transmitter S detects that the frame N + 1 has not been received, and the transmitter S retransmits the frame as shown at 103. Depending on the specific implementation of the ARQ scheme, subsequent retransmissions may be made until the correct reception of the frame is received.

If multiple retransmissions are made, this may cause problems for certain systems. First, multiple retransmissions can result in significant delays. The second problem arises in systems where large messages are transmitted that need to be divided into multiple frames. Since the frames must be reassembled in the correct order before the message is recovered, this requires using a large buffer storage space for temporary storage of received frames other than the sequence. This is illustrated in the above example in which the frame N + 1 is to be retransmitted after the frame N + 4. In order to recover the original message, the receiver R needs to buffer the received frames N + 2, N + 3 and N + 4 other than the sequence. Alternatively, or in addition to this buffering, the transmitter should buffer waiting frames for retransmission.

In data communication systems using a physical link such as a coaxial cable, inaccurate transfer of information is frequently caused by pseudo noise or data collisions, where simple retransmission of data is likely to succeed on the first attempt. However, in the case of a wireless communication link used between the mobile terminal 40 and the base station 20, incorrect transmission of information is frequently generated by a weak signal reaching the receiving end of the link. In addition, this signal strength may change constantly due to changing operating conditions, and in these situations, simple retransmission of incorrectly received information may not be satisfactory. In this case, information that needs to be retransmitted may be transmitted over the link 30 at a transmit power greater than the transmit power used to transmit the original information. This is illustrated in FIG. 4, which shows the same frame transmission sequence of FIG. 3 along the x-axis and transmit power on the y-axis. Frames are generally transmitted at power P ₁ and retransmission frames are transmitted at power P _R. This increases the probability that the repeated information will be successfully received upon retransmission, especially under conditions where the signal strength is weak or fading occurs. In addition, the increased probability of successful communication obtained at the first retransmission allows the buffer space for storing a list of frames or frames to be used at the transmitter and / or receiver to be smaller. The increased probability of successful communication obtained at the first retransmission may also result in a reduced delay in transmitting information, which is desirable when it involves real time information such as video or audio. In addition, an advantage can be obtained when transmitting other types of information for which a transmission delay exceeding a predetermined period is not allowed. Although different amplitudes may be selected to provide different relative powers, and this value does not limit the scope of the present invention, the power amplitude of the retransmitted frames (second information units) may be, for example, of the frames. It may be on the order of 3 dB higher than the power amplitudes used for the initial transmission (first information units).

2 shows the components of a transmitting station in base station 20 of telecommunication system 1. The transmitter 50 transmits units of information in frames with power determined by the control means 60. In this embodiment, the control means 60 responds to the monitoring means 70. As described above, the transmitter 50 outputs the retransmitted information at a transmit power higher than the transmit power originally used to transmit the information. Although the transmitter 50, the control means 60 and the monitoring means 70 are shown together as components of the transmitting station in the base station 20, this is not meant to be limiting. By way of example, the monitoring means may be arranged away from the transmitting station. In some cases, the monitoring means may be located at the receiving end of the wireless link.

The scheme allows retransmitted data to be successfully communicated with an improved level of reliability, which can be utilized in applications where it is desirable for information to be successfully communicated by a first retransmission attempt. The transmit power levels for the first transmission attempt may be variable. As an example, it may be appropriate to select this initial transmit power level P ₁ so that a certain percentage of initial transmissions are likely to require retransmission (higher power level). The transmit power levels for the first transmission attempt affect the rate of retransmissions, thereby affecting the average transmit power level. Lowering the initial transmit power lowers the probability that the information will be successfully received. However, by using low transmit power, the power consumption of the transmitter is reduced. The transmit power for the first attempt may be a scheme used to control the average power consumption of the transmission circuit (which of course must consider transmission at higher power), and it is appropriate to maintain the minimum average power consumption. Obviously, certain applications are more resistant to the occurrence of retransmissions than others, and need to be balanced based on the relative importance of power savings versus the occurrence of retransmissions. Indeed, excessive retransmissions may result in greater average power consumption than selecting the initial transmission at a higher power level to reduce the number of retransmissions. The apparatus is primarily intended for use in the transmission of traffic, which may be, for example, user video, voice or file data, and the requirements for transmitting various types of traffic are known to those skilled in the art. The overall reduction in transmit power reduces power consumption. This is particularly suitable when consumable power sources such as batteries are used. In certain implementations, in view of power savings and / or transmission delay limitations, it may be appropriate to be given a limit of the number of retransmissions.

This power saving characteristic is also illustrated in FIG. 4. The information is first transmitted at a lower power P ₁ than the power P _K used for transmission and retransmission of the system, which does not take advantage of the method. As will be appreciated, the retransmitted information, in this case I frame N + 1, is retransmitted with a power P _R greater than P ₁ . In this case, P _R is not essential but is larger than P _K. Reduction of overall power consumption can provide a number of advantages in the case of battery powered installations, such as extended operating time, the use of smaller, lighter batteries, or the use of more economical battery technology.

At the receiver, the information actually received by each transmission and its associated retransmitted frames can be combined to improve the probability of correct reception of the message carried by that information. This combination may be done at the symbol level using the maximum ratio combination (although other combination techniques may be used). The maximum ratio combination is that the appropriate scaling factors are applied individually to each received frame of data in the combination, thus maximizing the overall signal to noise ratio (or signal to interference ratio) of the combined information. For a given piece of information communicated over a link, the total energy transmitted (ie, the energy obtained by the sum of the transmission energy of the first frame and the transmission energy of each associated subsequent retransmitted frame) and the exact reception of There is a relationship between probabilities. In cases where it is desirable to minimize interference to other users of the system, the total energy of the transmissions should be controlled with the goal of not collectively sending more energy than is needed to correctly receive the message. One way to achieve this is to select the initial transmit power based on path loss and estimation of noise and interference at the receiver. Then, if the first transmission fails, the total energy may be arranged to gradually increase in each subsequent retransmission. The information can then be correctly decoded when the actual total received energy is sufficient to achieve the required SNR (or SIR) at these ratios calculated for retransmissions combined with the initial transmission when combined as a whole. As an example, consider the case where the nth transmission is included, and the total energy up to is set to Ek ^n-1 , where E is the energy of the first transmission and k is a constant. If k is close to 1, then the total energy is increased in small steps until the SNR (or SIR) is sufficient for accurate reception. This means that the probability of sending too much energy is low. In practice, larger numbers of retransmissions are undesirable because of the signaling overhead required. Thus, the choice of k is a compromise between the number of retransmissions and the accuracy with which the required SNR can be reached, based on the knowledge of possible errors in the estimation of interference and path loss at the receiver. An appropriate choice of k may be 1.4, in which case the sequence of relative energies for the first few transmissions is about {1.0, 0.4, 0.6, 0.8, 1.2... … }to be.

The scheme may be in contrast to the prior art, where retransmissions are transmitted at the same power, so that the total energy after the nth transmission will be nE. This provides a larger step relative to the total energy between the first and second transmissions, after which the energy additions are gradually reduced.

To avoid confusion, the criteria for the terms signal-to-noise ratio and signal-to-interference ratio are used interchangeably, and one of these terms refers to the term, the other term, or both of these ratios. Note that it can be taken to mean a combination of all.                 

The energy of the retransmission can be conveniently defined according to the definition of the transmit power, but by way of example, by changing the modulation scheme or claiming GB0020597.1 (Application No. PHGB000115), filed August 21, 2000, Applicant filed Oct. 9, 2000, as described in Applicant's pending UK patent application GB0024698.3 (Applicant reference number PHGB000140) entitled "Method for Communication of Information and Apparatus Using the Method". Other methods may be used by the spreading factor of the CDMA scheme.

The above descriptions are mainly for a system in which some retransmitted information is substantially the same as the first information. However, other possibilities exist. As an example, the retransmission may include additional redundancy. In this case, it is possible to arrange such that the total amount of redundant information gradually increases by a given amount. This is equivalent to a gradual decrease in code rate. Thus, if the effective code rate after the nth transmission is Rk ^1-n , where R is the initial code rate, then the amount of additional redundancy to be added in the nth transmission is Bk ^n-1 -Bk ^n-2. Where B is the total number of bits transmitted in the first transmission. If the same amount of additional redundancy in each retransmission is equal to the number of bits in the first transmission, then the code rate in the nth transmission is R / n.

In some situations with fading channels and closed loop power control, it may be advantageous to consider parameters of the received signal energy instead of transmit power. More specifically, the target SIR is adjusted for each retransmission to provide an exponential increase in the total received energy according to a formula similar to that described above for the transmit energy, or the target SIR for each retransmission can be used to determine It can be adjusted to provide.

Another technique can be applied to systems that use simultaneous control and data channels. Closed loop power control and SIR targets can be applied to the control channel, and the transmit power for the data channel is determined by scaling from the transmit power of the control channel. In this situation, the scaling factor can be adjusted between each retransmission according to a formula similar to that described above. For example, if the scaling factor for the first transmission is S, then, the scaling factor for the nth retransmission may be given by Sk ^n-1 -Sk ^n-2 .

It is also possible, for example, to use a combination of these methods of adjusting the SIR target between retransmissions, as well as adjusting the scaling of transmit power between control and data channels.

Now, the basic concept of using different transmit power for repetitive transmissions has been described, and the operation according to the invention can be controlled by the use of closed loop power control. In a system with closed loop power control such as UMTS when operating in frequency division duplex (FDD) mode, the transmit power for retransmissions is based on at least one parameter indicative of the quality of the transmissions received at the receiving end of the link. It is proposed that it should be controlled. One such parameter is the signal-to-interference (SIR) ratio. The transmit power can be adjusted as needed so that the required SIR ratio ('target' SIR ratio) is achieved in the transmissions detected by the receiver. In order to cause a change in transmit power for repeat transmissions for the original transmissions, it is possible to raise or lower the target SIR ratio at the receiver for certain retransmissions relative to the target SIR set at the receiver for the original transmissions. This change in the target SIR setting can be made under the control of the physical layer or by explicit signaling between the mobile terminal and the fixed terminal. One procedure already exists for setting the target SIR, which is the current version of the UMTS specification 3G TS25.43v3.2.0 "UTRAN lub interface NBAP signaling" which references the techniques herein 8.2 Defined in Chapter 17.

In a system such as UMTS, the transmit power levels of the information carried on the control and data channels may be different. Thus, data retransmissions can also be effectively adjusted by varying the ratio of transmit power between the data information of the data channel and the pilot information of the control channel. In addition, the received condition of pilot information sent as part of the control information may be used in power control operations.

In the case of UMTS uplink (UL), a closed loop power control procedure is used for the uplink dedicated channel (DCH). This procedure is described in the current version of the UMTS specification 3GTS25.214v3.3.0 "Physical Lamination Procedures (FDD)" section 5.1.2, whose description is referred to herein. This procedure can be further subdivided into two processes operating in parallel: outer loop power control and inner loop power control.

Outer loop power control for the uplink operates within the base station (BS) and is responsible for setting the target SIR of transmissions as it is received at the BS from each UE. This goal is set on an individual basis for each UE according to the required block error rate (BLER) of the decoded data received from the UE. In general, where the error rate of the received, decoded data needs to be low, then the SIR of the received undecoded transmissions needs to be relatively high. In applications where a higher error rate of decoded data is allowed, it may be acceptable to receive transmissions with lower SIR. The required BLER depends on the particular service involved, and thus can be higher for data services than for voice services, for example. Outer loop power control adjusts the SIR target until the required BLER is achieved. SIR is calculated by the reception of known pilot information.

The inner loop power control mechanism cancels the fading of the radio channel and controls the transmitted power of the UE to meet the SIR target at the BS set by the outer loop.

If the inner loop power control fails to adequately cancel the fades in the channel, the BLER increases, and the outer loop power control increases the SIR target, so that the average received SIR from the UE is increased.

The BS compares this target with the SIR received from the UE once every time slot (0.666 ms). If the received SIR is greater than the target SIR, the BS sends a TCP (“Transmission Power Control”) command “0” to the UE via the downlink dedicated control channel. This command instructs the transmitter to reduce the transmit power. If the received SIR is below the target, the BS sends a TPC command “1” to the UE.

In the case of the UMTS downlink, inner and outer loop power control operates on dedicated channels in a manner similar to the uplink.                 

Additional information on the uplink and downlink power control systems used in UMTS is presented at the 3G 2000 “Mobile Communication Technology” International Conference, March 27-29, 2000, in London, UK, which is referenced therein. , Titled "Power Control in 99th Edition UMTS (MPJ Baker, Tj Moulsley IEEE 3G2000 Mobile Communication Rechnologies Conference 27th-29th March 2000 (London))".

In the particular arrangement proposed here, a DSCH (downlink shared channel) can be used to transmit packet data on the downlink. A pair of DCHs (dedicated channels) are used on the uplink and downlink to support functions such as signaling and power control. If the packet is misreceived by the UE, then the target SIR at the UE used by the downlink power control loop may be changed. The new SIR has the effect of requesting the UE that the network (via closed loop internal power control) should transmit at different powers. This new target is applied until the packet is correctly received, and at the correct reception, the target SIR can be restored to its original value.

This operation is illustrated in FIG. 5 showing the SIR on the y-axis versus the time on the x-axis. Solid line 150 represents the received SIR value. For the first transmission of information units, the target SIR is set to the value A. The actual received SIR value may change from time to time (for a number of reasons already described above). In order to compensate for these frequently changing, closed loop power control is used, so that the receiver sends transmit power “raise” or power “fall” TCP commands to the transmitter, so that the received SIR is the target SIR value (A). Will be adjusted to

Now, assuming that the reception of the first transmission units has failed, the receiver sends this indicator to the transmitter, which is negatively received according to the type of ARQ scheme used, as is known to those skilled in the art. It may be in the form of a lack of a notification command (NACK) or a positive receive notification command (ACK). Consider an example of a scheme in which received first information units are discarded when they are misreceived. Now, the receiver also raises the target SIR to a value B higher than the target SIR value A. This is indicated at 151 in FIG. 5. The SIR value of the received transmissions is less than the target SIR B, which causes the receiver to send power “raise” commands to the transmitter, which are sent until a new target SIR B is reached. This is shown at 152 in FIG. The higher target SIR B is maintained until it communicates to the receiver the data for which retransmission failed successfully. Upon receipt of the correct reception of the information units, the receiver sets the target SIR to a lower value A, as shown at 153. Since the SIR value of the received transmission is now higher than the target SIR, the receiver sends a power “fall” command to the transmitter, which is sent until the actual SIR value of the received signals reaches the target SIR A. This is shown at 154 in FIG.

The same principle can be used for uplink communications. Changes in the SIR target may be commanded or requested by the transmitting station.

If additional packets are transmitted before the misreceived ones are retransmitted, the operation becomes more complicated and requires the use of buffers and a means of correctly storing the received packets of data. One way to simplify the operation is to fix or regulate the delay of certain retransmissions, so that the target SIR can be raised at the correct time (or near exact time).

The first information units are not discarded, but are combined with some retransmitted information, where the desired quality target can be the SIR of this combination. Suitable combination techniques are already known, and for example, this can be done symbol-by-symbol or bit-by-bit using soft decision information. Thus, the required SIR target can be reached at lower power for retransmissions than the first transmission. In this case, the energy of the retransmitted information only needs to be sufficient to fill the deviation between the SIR of the received first transmission and the SIR target of the correct reception.

In addition to the mechanism of setting the target SIR described above, and in addition to causing a change in transmit power only depending on inner loop power control, an initial power change is applied at the start of retransmissions, so that the new target SIR is more It may also be possible to reach quickly. This is shown at 155 in FIG. 5, which shows that the new SIR value B is reached more quickly due to fewer inner loop power control cycles to reach the required SIR.

The principles described above can also be applied to communications performed using other channels of the UMTS system, using appropriate modifications as needed, as will be apparent to those skilled in the art.

The invention can be implemented in terms of the requirements of a particular application. In applications that can tolerate occasional transmission errors, based on the fact that successful transmission is likely to occur during repeated transmissions, power consumption can be significantly reduced by significantly reducing the quality of the reception parameters (eg, SIR target) or the initial transmission power. It may be possible to greatly reduce. In applications where power savings need to be balanced against the avoidance of unnecessary retransmissions, the initial transmit power is not reduced to the same range.

Although the present invention has been described with reference to mobile cellular radio telephone systems and so-called third generation mobile communication systems, other applications include other cordless telephone systems, wireless LANs (e.g., hyperlans) and the like. .

Changes to the basic scheme include increasing the quality of the reception parameter (eg, SIR target) or retransmission power only after the first or multiple initial retransmission attempts have failed, thus providing a greater range of power consumption reduction. do.

Another variant of the basic scheme is to provide a gradual power increase for information that is retransmitted more than once. As an example, the target SIR may be incrementally increased until the information is successfully received. This reduces the probability that unsuccessfully transmitted information will be further delayed as a result of multiple retransmissions. In the general case, there may be a preset sequence of SIR values according to the number of retransmissions. In some cases, it may be desirable to limit the maximum allowed number of retransmission attempts for a given initial transmission.

It is also desirable to apply a restriction on the transmit power of certain retransmissions, which may be the same as or different than the predetermined maximum power regulation applied to the first transmission.                 

The invention can be used in conjunction with the concept of transmitting second transmission units on a carrier modulated with a modulation scheme different from the modulation scheme used to transmit the first transmission units, which was filed on August 21, 2000. Dated Oct. 9, 2000, in the name of Koninclique Philips Electronics NV, entitled "Method for Communication of Information and Apparatus Using the Method" claiming GB0020597.1 (Applicant Zombie No. PHGB000115) as a priority. It is the subject of the applicant's pending UK patent application GB0024698.3 (applicant reference number PHGB000140). These applications may also relate to changing the spreading factor applied to the transmitted data and to using a different communication link bandwidth between the first and second information unit transmissions.

The invention discloses, as a priority, GB0020599.7, filed Aug. 21, 2000 (Application No. PHGB000113), entitled "Method for Communication of Information and Apparatus Using the Method". Similar to the subject of the pending applicant's pending UK patent application GB0024699.1 (Applicant reference number PHGB000139) filed Oct. 9, 2000 in the name of Electronics NV, the concept of transmitting second transmission units at a higher power level. It can be used in conjunction with.

Although the present invention provides direct advantages with respect to reliable communication of information and reduction of power consumption, other indirect advantages can be obtained through the correct implementation of the present invention. Lower initial (and therefore average) transmit power may cause a reduction in interference with other transmissions. This example in a cellular system can be observed as a reduction in the overall shared channel interface (and a possible reduction in other types of interference) since the duration of high power transmissions is relatively short. This can result in lower interference for other users.

Although the present invention has been described with reference to known ARQ schemes, it is not intended to represent any limitation. As described, the present invention is primarily contemplated as a particular ARQ scheme when the information is general digital data organized into frames or packets. In this case, the invention is complemented by additional transmissions at power levels different from the power used to transmit the original packets or data frames, or packets deemed to have been communicated unsuccessfully, or It can be considered as an automatic repeat request error control scheme aimed at achieving a quality of a reception parameter (e.g. SIR ratio) that is larger than that generated for transmission of the original packets or data frames. In addition, the present invention is coordinated with techniques in which the first and subsequent transmissions or retransmissions can be combined to recover information. In these techniques, it may be appropriate to use some type of averaging, which in this case also provides more "weight" to information received at higher quality of the received parameters or transmitted at higher power. It is appropriate to. Although the present invention is best used over a wireless radio link, in addition, although the problem of power consumption is typically less important than in wireless communication links, in principle, other media, such as coaxial cable, twisted pair It may be implemented in systems using a link such as those. In addition, although the present invention has been described with reference to examples using transmission between fixed and portable terminals, those skilled in the art will clearly appreciate that the present invention is not limited to this application. That is, the present invention can be used to convey information in either or both directions over a communication link, regardless of whether the transmitting and / or receiving stations are fixed or mobile. Those skilled in the art will also clearly appreciate that in a two-way communication system, the transmitting station may be combined with the receiving station.

By reading this specification, skilled artisans will be apparent to other variations. Such variations may involve other features already known in the design, manufacture, and use of systems and apparatus, which may be used in place of or in addition to the features already described herein.

Claims (25)

A method of delivering information in units over a wireless digital communication link between a transmitting station and a receiving station, the method comprising: Transmitting the first information units at a first energy level, Monitoring whether correct reception of the transmitted units is made, and For first information units for which the monitoring does not indicate that correct reception has been made, transmitting second information units associated with the first information units at second energy levels, wherein the second information units comprise the first information unit; The transmitting step of allowing content of one information units to be established, At least one of the associated second information units is transmitted at an energy level selected to at least partially minimize the total transmitted energy when the series of first information unit transmissions with each second information unit transmissions are averaged, For a given first information unit transmission, the associated successive second information unit transmission events are performed with a gradual increase in transmission energy with respect to each other. The method of claim 1, At least one of said second information units is transmitted at an energy level below an energy level used for transmission of said first information units. The method according to claim 1 or 2, First information received at the receiving station such that the received energy of the second information unit transmissions or each second information unit transmissions complements the received energy of the first and any previous second information unit transmissions. Combining the units with associated second information units received at the receiving station, The combining step is performed such that the total energy of the combined received transmissions increases with each second information unit transmission event. The method according to claim 1 or 2, The first and any associated second consecutive information unit transmission events are each performed with transmission energy such that the total transmission energy obtained by combining the first and any second information unit transmission events is substantially exponentially increased in value. Information delivery method to do. The method according to claim 1 or 2, The first and any associated second consecutive information unit transmission events are each performed with transmission energy such that the total transmission energy obtained by combining the first and any second information unit transmission events is substantially in Eq ^n-1 . In line with Where E is the transmission energy used for the first information unit transmission event, k is a constant, n is an individual information unit transmission event, n = 1 in the case of the first information unit transmission event, and each successive N = 2, 3, 4,... For the second information unit transmission event. , n, information delivery method. The method of claim 5, Information delivery method, wherein k = 1.4. The method according to claim 1 or 2, For each second information unit transmission event, the second information units are transmitted at second energy levels partially selected based on a target quality of a reception parameter for each second information unit. The method of claim 7, wherein The target quality of the reception parameter for each second information unit is calculated as a function of at least one previous target or actual quality of the reception parameter. The method of claim 8, The target quality of the reception parameter for each second information unit is also calculated as a function of the energy received due to the transmission of the information units. The method of claim 7, wherein Analyze the difference between the actual and target quality of the received parameters of the received information unit transmissions, and if the quality of the received parameter for the received information unit transmission is better than the target quality of the received parameter, the transmission of the information unit Increase the information unit transmit power level during the transmission of the information unit if the quality of the reception parameter for the received information unit transmission is less than the target quality of the reception parameter. Further comprising the step of making the information transfer. The method according to claim 1 or 2, Wherein the communication link is established by a facility operating in accordance with a communication protocol based on a Universal Mobile Telecommunication System (UMTS). The method of claim 11, And the receiving station forwards transmit power adjustment commands to the transmitting station in a transmit power control (TPC) field carried on a control channel set up in a communication link. The method of claim 7, wherein The target quality of the reception parameter for the first information units is selected to correspond to a defined probability of failed first information units transmission and successive second information units transmission. A transmitting station for digital wireless transmission of traffic information to a receiver, A transmitter for transmitting the first information units at a first energy level, and Monitoring means for monitoring whether the correct reception of the transmitted units is made, The transmitter transmits, at first energy units, second information units associated with the first information units to second energy levels, for the first information units for which the monitoring means does not indicate that correct reception has been made. Allow the content of the first information units to be established, Further, at least one of the associated second information units is transmitted at an energy level selected to at least partially minimize the total transmitted energy when the series of first information unit transmissions with each second information unit transmissions are averaged. , For a given first information unit transmission, the associated successive second information unit transmission events are transmitted at an energy level, which is performed with a gradual increase in transmit energy with respect to each other. At least one transmitter as claimed in claim 14, At least one receiver having means for receiving transmitted information units and monitoring means for monitoring whether an accurate reception of the transmitted units has been made A receiver for use in a digital wireless communication system comprising at least one transmitter having means for transmitting first information units at a first power level, the receiver comprising: means for receiving the transmitted information units; In the receiver having monitoring means for monitoring whether the correct reception of the transmitted units is made, The means for transmitting transmits the second information units associated with the first information units at second energy levels, for the first information units for which the monitoring does not indicate that an accurate reception has been made, and wherein the second information Units allow the content of the first information units to be established, Further, at least one of the associated second information units is transmitted at an energy level selected to at least partially minimize the total transmitted energy when the series of first information unit transmissions with each second information unit transmissions are averaged. , For a given first information unit transmission, the associated consecutive second information unit transmission events are performed with progressively increasing transmission energy with respect to each other. A method of transferring information of units via a wireless digital communication link between a transmitting station and a receiving station, the method comprising: Transmitting first information units having first redundancy content; Monitoring whether correct reception of the transmitted units is made, and Sending second information units with second redundant content, associated with the first information units, for the first information units for which the monitoring does not indicate that an accurate reception has been made, wherein the second information units are assigned to the first information units. The transmitting step of allowing content of one information units to be established, At least one of the associated second information units is transmitted with data duplicate content selected to at least partially minimize total duplicate data content when the series of first information unit transmissions with each second information unit transmissions are averaged; , For a given first information unit transmission, the associated successive second information unit transmission events are performed with progressively increasing duplicate data content with respect to each other. The method of claim 17, At least one of the second information units is transmitted with data redundant content below the level of duplicate data content used in the transmission of the first information units. The method of claim 17 or 18, Combining the first information units received at the receiving station with the associated second information units received at the receiving station. The method of claim 17 or 18, For a given first information unit transmission, the associated successive second information unit transmission events are performed with progressively increasing duplicate data content with respect to each other. A transmitting station for digital wireless transmission of traffic information to a receiver, A transmitter for transmitting first information units having first redundant content, and Monitoring means for monitoring whether accurate reception of the transmitted units is made, The transmitter transmits, to the first information units for which the monitoring means does not indicate that the correct reception has been made, the second information units having second redundant content associated with the first information units, and the second information. Units allow the content of the first information units to be established, In addition, at least one of the associated second information units has data redundancy content selected to at least partially minimize total duplicate data content when a series of first information unit transmissions with each second information unit transmissions are averaged Sent, For a given first information unit transmission, the associated consecutive second information unit transmission events are performed with progressively increasing duplicate data content with respect to each other. At least one transmitter as claimed in claim 21, and At least one receiver having means for receiving transmitted information units and monitoring means for monitoring whether an accurate reception of the transmitted units has been made. A receiver for use in a digital wireless communication system comprising at least one transmitter having means for transmitting first information units having first redundant content, comprising: means for receiving the transmitted information units; And monitoring means for monitoring whether accurate reception of the transmitted units is made; The means for transmitting transmits the second information units with second redundant content, associated with the first information units, to the first information units for which the monitoring does not indicate that correct reception has been made, and wherein the second Information units allow the content of the first information units to be established, In addition, at least one of the associated second information units is data redundant content selected to at least partially minimize the total transmitted duplicate data content when a series of first information unit transmissions with each second information unit transmissions are averaged. Is sent with For a given first information unit transmission, the associated consecutive second information unit transmission events are performed with progressively increasing duplicate data content with respect to each other. delete delete

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