KR20050121136A - Method and device for uplink base station information transmission in ofdma systems - Google Patents

Method and device for uplink base station information transmission in ofdma systems Download PDF

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Publication number
KR20050121136A
KR20050121136A KR1020040046297A KR20040046297A KR20050121136A KR 20050121136 A KR20050121136 A KR 20050121136A KR 1020040046297 A KR1020040046297 A KR 1020040046297A KR 20040046297 A KR20040046297 A KR 20040046297A KR 20050121136 A KR20050121136 A KR 20050121136A
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South Korea
Prior art keywords
base station
optimal base
terminal
station information
optimal
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KR1020040046297A
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Korean (ko)
Inventor
변명광
전재호
맹승주
김정헌
장지호
이익범
주판유
조재원
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삼성전자주식회사
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Priority to KR1020040046297A priority Critical patent/KR20050121136A/en
Publication of KR20050121136A publication Critical patent/KR20050121136A/en

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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B7/00Radio transmission systems, i.e. using radiation field
    • H04B7/24Radio transmission systems, i.e. using radiation field for communication between two or more posts
    • H04B7/26Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
    • H04B7/2621Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile using frequency division multiple access [FDMA]
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00Arrangements affording multiple use of the transmission path
    • H04L5/003Arrangements for allocating sub-channels of the transmission path
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W24/00Supervisory, monitoring or testing arrangements
    • H04W24/02Arrangements for optimising operational condition
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W74/00Wireless channel access, e.g. scheduled or random access
    • H04W74/002Transmission of channel access control information
    • H04W74/004Transmission of channel access control information in the uplink, i.e. towards network

Abstract

The present invention provides a method for transmitting uplink optimal base station information in order to support fast cell switching for improved performance in an orthogonal frequency division multiple access system including a plurality of base stations wirelessly connected to a terminal. Assigning a predetermined number of uplink subchannels as physical channels for transmitting optimal base station information, and assigning a subchannel number and a codeword number to the terminal when the terminal is an active set, and the terminal is assigned to an active set Comparing the preamble signal strengths from the corresponding base stations to select an optimal base station, and when the terminal generates a data bit of the optimal base station information, received from the selected optimal base station for the optimal base station information Transmitting a codeword assigned through a subchannel, and the base stations Receiving a given code word of the sub-channel will be characterized in that it comprises the step of determining whether the selection by the best base station.

Description

Method and apparatus for optimal transmission and reception of uplink base station information in orthogonal frequency division multiple access system {METHOD AND DEVICE FOR UPLINK BASE STATION INFORMATION TRANSMISSION IN OFDMA SYSTEMS}

The present invention relates to a method and apparatus for transmitting control information in a mobile communication system, and more particularly, to a method for transmitting base station (or sector) information, which is fast feedback information, which is one of uplink control information in an orthogonal frequency division multiple access system. Relates to a device.

 Currently, mobile communication systems are evolving into the first generation of analog, the second generation of digital, and the third generation of high speed multimedia services of IMT-2000. The fourth generation mobile communication system can use a satellite network, a wireless LAN (LAN), the Internet network, etc. as one terminal. That is, all services such as voice, video, multimedia, internet data, voice mail, and instant message (IM) can be solved with one mobile terminal. The fourth generation mobile communication system aims at a transmission rate of 20Mbps for high speed multimedia services, and mainly uses orthogonal frequency division multiplexing such as orthogonal frequency division multiplexing (OFDM).

The OFDM scheme is a digital modulation scheme for multiplexing a plurality of orthogonal carrier signals. The OFDM scheme divides a single data stream into several low-speed streams and simultaneously transmits multiple subcarriers with low data rates.

In an orthogonal frequency division multiple access (OFDMA) system using the OFDM scheme, separate physical channels exist for transmitting uplink fast feedback information, which is one of uplink control information. The uplink high-speed feedback information includes an optimal base station or sector, a perfect signal-to-noise ratio (S / N), differential S / N per band, and high-speed multi-input multi-output (MIMO) feedback. , Mode selection feedback, and so on.

The uplink high-speed feedback information is not a large amount in the overall communication service, but it is important for the operation of the communication system, so high reliability in transmission should be guaranteed. However, in order to reduce overhead ratio, it is common for a physical channel for transmitting uplink control information not to be allocated much frequency-timebase resources. Therefore, a different transmission method is required than channels in which many resources are allocated and a lot of information needs to be transmitted, such as a traffic channel.

In general, a method combining a binary channel code and a coherent modulation or a differential modulation is used to transmit uplink control information.

However, the transmission using the method using less frequency-timebase resources results in a higher probability of error, thereby lowering the stability of the communication system operation. In addition, when a large number of frequency-time base resources are used for transmitting uplink fast feedback information to increase stability, the overhead ratio is increased, thereby reducing the throughput of the communication system.

Meanwhile, in a cellular communication system using a conventional code division multiple access system, a fast cell switching method is used to improve performance. In this method, a terminal manages several base stations or several sectors as an active set, and a base station / sector having the best link performance (hereinafter, referred to as a base station) will be described. The Walsh Code is called Data Rate Control (DRC) cover. Then, downlink data is transmitted from the base station, thereby improving downlink performance. In particular, when the terminal is located at the cell boundary, the select diversity gain can be obtained. The concept of fast cell switching in such a CDMA communication system will be described with reference to the accompanying drawings.

1 is a diagram schematically illustrating fast cell switching in a code division multiple access system.

Referring to FIG. 1, the active set of the terminal 10 includes three base stations (or sectors) A, B, and C (21, 22, 23). In the CDMA communication system, the terminal 10 receives one Walsh code from each of base stations A, B, and C (21, 22, 23). Since the Walsh code length is 8 for 1X EV-DO, the possible Walsh code numbers are assigned 0 to 7 times. Therefore, in the example as shown in FIG. 1, the base station A 21 is numbered 1, the base station B 22 is 4, and the base station C 23 is assigned a Walsh code.

The terminal compares the signal (pilot) strength of the base stations received by the three base stations and informs the base station having the best link performance. If the signal from the base station C 23 is the strongest, as shown in FIG. 1, the Walsh code 3 is used as a DRC cover for uplink and transmitted. It should be noted, however, that Walsh code numbers given by the three base stations must be different. This is because the base station receiver divides users into long codes for user identification, and the optimal base station for each user is classified by Walsh code numbers.

In this CDMA method, many users (terminals) are distinguished by using a user-specific long code that is multiplied at the end of the digital transmitter, so that a signal sent by the terminal can be received by all base stations. The number of times of multiplying the long code for distinguishing a user may despread the Walsh code corresponding to the corresponding user to detect whether the user selects the optimal base station.

However, in the OFDMA communication method, each base station allocates frequency-time base resources to the terminals, and the terminal should transmit information only through the allocated resources. However, if all base stations allocate frequency-time base resources to all terminals applying fast cell switching, this causes a large overhead.

In addition, when the optimal base station is transmitted through an upper layer message rather than a physical channel, the cell switching speed is slowed down, thereby reducing the selection diversity gain and the scheduling performance.

Accordingly, an object of the present invention is to provide a method and apparatus for transmitting uplink optimal base station (or sector) information using a non-coherent modulation method in an orthogonal frequency division multiple access system.

Another object of the present invention is to provide a method and apparatus for efficiently transmitting optimal base station (or sector) information using less frequency-timebase resources to support fast cell switching in an orthogonal frequency division multiple access system. In providing.

In addition, another object of the present invention is to use a predetermined number of subchannels for each base station (or sector), assign a plurality of users to each subchannel, and classify each user by a code so as to optimize an uplink base station (or sector). The present invention provides a method and apparatus for transmitting information.

The method for achieving the above object of the present invention, in the orthogonal frequency division multiple access system including a plurality of base stations wirelessly connected to the terminal to transmit the uplink optimal base station information to support high-speed cell switching for improved performance As a method for performing the above steps, the base stations allocate a predetermined number of uplink subchannels as physical channels for transmitting optimal base station information, and assign the subchannel number and the codeword number to the terminal when the base station is the active set. And comparing the preamble signal strength from base stations belonging to an active set by the terminal to select an optimal base station, and when the terminal generates a data bit of the optimal base station information, selecting the optimal base station from the selected optimal base station. Sub-channel granted through sub-channel granted for optimal base station information In that it comprises the step of determining whether the step of transmitting the word and the base stations by receiving a code word of the sub-channel assigned by the base station select the best characterized.

In addition, the apparatus for achieving the objects of the present invention, to transmit the uplink optimal base station information to support fast cell switching for improved performance in an orthogonal frequency division multiple access system including a plurality of base stations that are wirelessly connected to the terminal An apparatus for receiving a data bit of the uplink optimal base station information and outputting codewords corresponding to the data bits, and the orthogonal modulation of the symbols for the corresponding codeword of the input data bits of the subcarrier And a noncoherent modulator for outputting transmission symbols, and an inverse fast Fourier transformer for inverse fast Fourier transform transmission of the transmission signal consisting of the modulated transmission symbols and subcarrier bundles to which the pilot symbols are assigned.

In addition, another apparatus for achieving the object of the present invention, the uplink optimal base station information to support high-speed cell switching for improved performance in an orthogonal frequency division multiple access system including a plurality of base stations wirelessly connected to the terminal; An apparatus for receiving a signal comprising: a fast Fourier transformer for fast Fourier transforming a signal received from the terminal, and an absolute value square of a correlation value for a predetermined number of possible patterns for each of the subcarrier bundles of the fast Fourier transformed signal; And a noncoherent demodulator for performing quadrature phase demodulation by calculating a sum of squares of absolute values of correlation values of corresponding patterns with respect to response vector indices which are part of a channel quality indication code word on a time side. Check that you are selected as the best base station by comparing with the set threshold And a channel decoder.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

Preferred embodiments of the present invention to be described below will be described by applying to Orthogonal Frequency Division Multiplexing Access (hereinafter, referred to as OFDMA) system. In order to support fast cell switching, transmission of optimal base station (or sector, hereinafter, a base station) information, which is uplink fast feedback information, will be described using M-phase PSK modulation. First, a concept of fast cell switching in an OFDMA communication system will be described with reference to the accompanying drawings.

2 is a diagram schematically illustrating fast cell switching in an orthogonal frequency division multiple access system according to a preferred embodiment of the present invention.

Referring to FIG. 2, an active set of the terminal 110 includes base stations A, B, and C 121, 122, and 123. Each of the base stations A, B, and C (121, 122, 123) allocates a predetermined number of uplink subchannels as physical channels for transmitting optimal base stations. The base station is assigned a subchannel number and a codeword number to all base stations belonging to the active set.

The terminal 110 selects a base station having the best link performance by comparing the preamble signal strengths received from all base stations A, B, and C (121, 122, 123) belonging to the active set. Thereafter, the terminal 110 transmits the codeword of the number assigned through the subchannel received from the selected base station.

Each of the base stations A, B, and C (121, 122, 123) receives for each codeword of the subchannels allocated by the base stations A, B, and C, and determines whether the base station is selected as the optimal base station, and transmits downlink data if selected. . However, it should be noted that the codeword numbers given by the base station need not all be different. This is because the base station receiver divides each of the base stations 121, 122, and 123 into different subchannel structures, and the terminal 110 divides them by codeword numbers.

In this way, each base station A, B, C (121, 122, 123) knows which user corresponds to the sub-channel number and codeword number given. For example, as shown in FIG. 2, the subchannel number (No. 0) assigned by the base station B 122 and the codeword number (No. 5) are assigned to the subchannel number 0 assigned by the base station C 123. (B) and the codeword number (5), the base stations B and C (122, 123) have different subchannel structures. Therefore, the terminal 110 does not receive the signal transmitted from the base station C 123 to the base station B 122 by mistake.

According to the above concept, a structure of a transmitter for a terminal for transmitting optimal base station information in an OFDMA system and a base station receiver for receiving the information will be described with reference to the accompanying drawings.

3 is a diagram schematically illustrating a transmitter structure of a terminal for uplink optimal base station information transmission in an orthogonal frequency division multiple access system according to a preferred embodiment of the present invention.

Referring to FIG. 3, the transmitter 200 includes a channel encoder (M-ary Channel Encoder) 210 for encoding an uplink optimal base station information data bit, and a noncoherent method for modulating the information data bit. A coherent modulator 220 and an inverse fast Fourier transform 230 which transmits a signal to be transmitted by an inverse fast Fourier transform (IFFT) is transmitted.

When a data bit of uplink fast feedback information to be sent is generated, the channel encoder 210 receives the information data bit and outputs a corresponding code word to the noncoherent modulator 220. Here, the channel encoder 210 may use an M-phase channel encoder using a binary channel encoder or an M-ary block code according to the input bit.

The noncoherent modulator 120 obtains a transmission symbol corresponding to the input codeword by using a noncoherent modulation scheme and outputs the transmitted symbol to the IFFT 130. Here, the noncoherent modulator 120 may use orthogonal modulation.

4 is a diagram illustrating a receiver structure of a base station for uplink optimal base station information transmission in an orthogonal frequency division multiple access system according to a preferred embodiment of the present invention.

Referring to FIG. 4, the receiver 300 performs a fast Fourier transform (FFT) 330 for fast Fourier transforming a received signal in a time domain to a received signal in a frequency domain, and demodulates a received signal in the frequency domain. A noncoherent demodulator 320 and a M-ary Channel Decoder 310 which decodes data bits of uplink optimal base station information from the demodulated received symbol are configured.

When the received signal is input, the FFT converter 330 performs a Fast Fourier Transform (FFT) to output the received symbol to the noncoherent demodulator 320.

The noncoherent demodulator 320 obtains a soft decision value of the received received symbol by using a noncoherent demodulation method and outputs it to the channel decoder 310.

The channel decoder 310 receives a soft decision value from the noncoherent demodulator 320 and determines which codeword should be determined that the transmitter 200 has transmitted, and outputs a corresponding data bit. . The channel decoder 210 may use a binary channel decoder or an M-phase channel decoder according to input bits. Although the terminal selects and transmits only one codeword, it should be noted that the base station receives the codewords transmitted by the various terminals in addition, and thus, it is necessary to determine whether to receive each codeword. In other words, the channel decoder does not select the most well-received codeword but selects whether or not all codewords are received or not.

A method for transmitting and receiving uplink control information in a transmitter and a receiver of a mobile terminal having such a structure will be described with reference to the accompanying drawings.

5 illustrates frequency-timebase resources allocated for information transmission in an orthogonal frequency division multiple access system according to a preferred embodiment of the present invention. Since M is 8, an 8-phase channel encoder is used. In the carrier bundle, the horizontal axis represents time (symbol) and the vertical axis represents frequency (subcarrier).

 Referring to FIG. 5, it can be seen that 6 times 3 × 3 subcarrier bundles are allocated on a frequency-time axis to transmit uplink base station information in uplink of an OFDMA communication system. This is a case where each base station uses one uplink subchannel for optimal base station transmission. The type of uplink subchannel consists of six 4x3 subcarrier bundles as well as six 3x3 subcarrier bundles. It should be noted that it is also applicable to cases. In addition, the same applies to the case of allocating two or more subchannels for optimal base station transmission, and in this case, the overhead ratio is increased, so that users in the base station can be distinguished by 8 users for each subchannel. Note that you can increase the number of users further.

6 illustrates output codewords of a channel encoder according to a preferred embodiment of the present invention.

In FIG. 6, the 8-phase channel encoder sets the minimum Hamming distance between codewords to be maximum for a given number and length of codewords. In this case, the minimum hamming distance, which is a factor mainly affecting the codeword error probability performance, is 6. That is, in the eight possible code words, for example, the sign word "0", the pattern of the code words A0, A1, A2, A3, A4, A5 for the subcarrier bundle is "000000". In the case of the code word " 7 ", the patterns of A0, A1, A2, A3, A4, and A5 become "777777", and the Hamming distance between the two codewords is 6. The channel encoder is not limited to one example as shown in FIG. 6 and may be replaced with any encoder having a minimum hamming distance of six. For example, it may be replaced by an encoder having eight codewords of "012345", "123456", "234567", "345670", "456701", "567012", "670123", and "701234".

The noncoherent modulator uses an orthogonal modulation method. Orthogonal vectors to be used for such orthogonal modulation are as shown in FIG. 7 and can be obtained as Equation 1 below.

In Equation 1, P0, P1, P2, and P3 are QPSK modulation symbols. The eight subcarriers at the edge of the 3x3 subcarrier bundle transmit symbols as shown in FIG. One subcarrier of the rest transmits a pilot symbol. Here, the pilot symbol can be arbitrarily set. The values of the transmitted symbols are set as orthogonal vectors corresponding to the corresponding vector index.

Given the optimal base station information data to be transmitted, the transmitter determines the code words A0, A1, A2, A3, A4, A5 by applying Equation 2 above. Here, information data, i.e., symbol values corresponding to vector index 0 are set to P0, P1, P2, P3, P0, P1, P2, and P3, and symbol values corresponding to vector index 4 are set to P0, P0, It can be seen that P0, P0, P0, P0, P0, and P0 are set, and symbol values corresponding to the vector index 7 are set to P0, P2, P2, P0, P2, P0, P0, and P2.

Upon receiving the transmission signal transmitted from the transmitter, the receiver converts the received signal through a fast Fourier transformer. The receiver then computes the absolute square of the correlation value for eight possible orthogonal vectors for each of the three 3 x 3 subcarrier bundles in the noncoherent demodulator. Then, for each of the eight possible codewords in the M-Phase channel decoder, calculate the sum of the squares of the absolute values of the correlation values of the corresponding patterns, and compare these values with the appropriate threshold values, If it is large, it is determined that this codeword has been transmitted. If it is less than the threshold, it is determined that this codeword has not been transmitted.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, the present invention efficiently utilizes a predetermined number of subchannels for each base station or sector, allocates multiple users to each subchannel, and divides the users into codes, thereby efficiently identifying uplink optimal base station or sector information. It can transmit and support fast cell switching using less frequency-timebase resources. Accordingly, the reliability of information transmission is improved, thereby increasing the capacity of the cellular system or enabling stable system operation.

1 is a schematic diagram illustrating fast cell switching in a code division multiple access system;

2 is a diagram schematically illustrating fast cell switching in an orthogonal frequency division multiple access system according to a preferred embodiment of the present invention;

3 is a diagram illustrating a transmitter structure of a terminal for uplink optimal base station (or sector) information transmission in an orthogonal frequency division multiple access system according to an embodiment of the present invention;

4 is a diagram illustrating a receiver structure of a base station for uplink optimal base station (or sector) information transmission in an orthogonal frequency division multiple access system according to an embodiment of the present invention;

5 illustrates frequency-timebase resources allocated for information transmission in an orthogonal frequency division multiple access system according to a preferred embodiment of the present invention;

6 illustrates output codewords of a channel encoder according to a preferred embodiment of the present invention;

7 shows orthogonal vectors to be used for modulation in accordance with a preferred embodiment of the present invention.

Claims (7)

  1. A method for transmitting uplink optimal base station information to support fast cell switching for improved performance in an orthogonal frequency division multiple access system including a plurality of base stations wirelessly connected to a terminal, the method comprising:
    Assigning a predetermined number of uplink subchannels to a physical channel for transmitting optimal base station information by the base stations and assigning a subchannel number and a codeword number to the terminal when the base station is an active set;
    Selecting, by the terminal, an optimal base station by comparing preamble signal strengths from base stations belonging to an active set;
    When the terminal generates a data bit of the optimal base station information, transmitting a codeword granted through the subchannel received for the optimal base station information from the selected optimal base station;
    And receiving a codeword of the subchannels assigned by the base stations to determine whether the base station is selected as an optimal base station.
  2. The method of claim 1, wherein the transmitting of the codeword comprises:
    Receiving data bits of the uplink optimal base station information and outputting codewords corresponding to the data bits;
    Outputting the transmission symbols of the subcarrier by performing orthogonal modulation on symbols of the corresponding code word of the input data bit;
    And performing inverse fast Fourier transform on a transmission signal consisting of the modulated transmit symbols and the subcarrier bundles to which the pilot symbols are assigned.
  3. The method of claim 1, wherein the receiving of the codeword of the subchannel and determining whether the optimal base station is selected is performed.
    A fast Fourier transform for fast Fourier transforming the signal received from the terminal;
    Performing quadrature phase demodulation by calculating a square of an absolute value of a correlation value for a predetermined number of possible patterns for each of the subcarrier bundles of the fast Fourier transformed signal;
    For response vector indices that are part of the channel quality indication code word on the temporal side, the sum of the squares of the absolute values of the correlation values of the corresponding pattern is respectively calculated, and the calculated values are compared with the preset thresholds to select the optimal base station. Determining whether the process is complete.
  4. The method of claim 3,
    The confirmation of whether the optimal base station is selected is determined according to the determination that the codeword for the data bit of the optimal base station information is received when the calculated values are larger than the threshold.
  5. An apparatus for transmitting uplink optimal base station information to support fast cell switching for improved performance in an orthogonal frequency division multiple access system including a plurality of base stations wirelessly connected to a terminal, the apparatus comprising:
    A channel encoder for receiving data bits of the uplink optimal base station information and outputting codewords corresponding to the data bits;
    A noncoherent modulator configured to orthogonally modulate symbols of a corresponding code word of the input data bit to output transmission symbols of a subcarrier;
    And an inverse fast Fourier transformer for transmitting an inverse fast Fourier transform of a transmission signal consisting of the modulated transmit symbols and subcarrier bundles to which the pilot symbols are assigned.
  6. An apparatus for receiving uplink optimal base station information to support fast cell switching for improved performance in an orthogonal frequency division multiple access system including a plurality of base stations wirelessly connected to a terminal, the apparatus comprising:
    A fast Fourier transformer for fast Fourier transforming the signal received from the terminal;
    A noncoherent demodulator for quadrature phase demodulating a square of an absolute value of a correlation value for a predetermined number of possible patterns for each of the subcarrier bundles of the fast Fourier transformed signal;
    For response vector indices that are part of the channel quality indication code word on the temporal side, the sum of the squares of the absolute values of the correlation values of the corresponding pattern is respectively calculated, and the calculated values are compared with the preset thresholds to select the optimal base station. And a channel decoder for checking whether a signal is received.
  7. The method of claim 6, wherein the channel decoder,
     And if the calculated values are greater than the threshold, determining whether the optimal base station has been selected as determined to have received a codeword for the data bits of the optimal base station information.
KR1020040046297A 2004-06-21 2004-06-21 Method and device for uplink base station information transmission in ofdma systems KR20050121136A (en)

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