EP1864401A1 - A method for allocating downlink data streams in a distributed antenna system - Google Patents

A method for allocating downlink data streams in a distributed antenna system

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Publication number
EP1864401A1
EP1864401A1 EP06725459A EP06725459A EP1864401A1 EP 1864401 A1 EP1864401 A1 EP 1864401A1 EP 06725459 A EP06725459 A EP 06725459A EP 06725459 A EP06725459 A EP 06725459A EP 1864401 A1 EP1864401 A1 EP 1864401A1
Authority
EP
European Patent Office
Prior art keywords
data streams
mobile terminal
antenna system
remote units
distributed antenna
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP06725459A
Other languages
German (de)
French (fr)
Inventor
Guang Jie Li
Xin Chang
Hui Li
Egon Schulz
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens AG
Original Assignee
Siemens AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens AG filed Critical Siemens AG
Publication of EP1864401A1 publication Critical patent/EP1864401A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0002—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate
    • H04L1/0003—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate by switching between different modulation schemes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0009—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the channel coding
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/02—Arrangements for detecting or preventing errors in the information received by diversity reception
    • H04L1/06—Arrangements for detecting or preventing errors in the information received by diversity reception using space diversity
    • H04L1/0618—Space-time coding
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/0001—Arrangements for dividing the transmission path
    • H04L5/0014—Three-dimensional division
    • H04L5/0023—Time-frequency-space
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0044—Arrangements for allocating sub-channels of the transmission path allocation of payload
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0048—Allocation of pilot signals, i.e. of signals known to the receiver
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/08—Access point devices
    • H04W88/085—Access point devices with remote components

Definitions

  • the present invention relates to an method of optimizing the performance of a radio communication system, and more particularly, to a method for allocating downlink data streams in a distributed antenna system.
  • radio communication systems With the appearance and development of radio communication technology, radio communication systems have developed from analog systems to digital systems, and are now experiencing transition from the second generation to the third generation, i.e. transition from voice communication systems to data communication systems.
  • radio communication resources have always been a crucial factor of great importance optimizing the usage of limited radio communication resources and improving the frequency spectrum usage rate of radio communication resources has become a constant focal point for researchers in the field of communication.
  • MIMO Multiple Input and Multiple Output
  • multiple antenna units i.e. an antenna array
  • a spatial diversity gain is acquired or the transmission speed of radio signals is improved, as shown in Fig. 1.
  • spatial multiplex transmission and spatial diversity transmission are two main transmission schemes, wherein in the spatial multiplex transmission scheme, for example, the V-BLAST (Vertical Bell Laboratories Layered Space Time) scheme proposed by Bell Lab, multiple data streams of a radio signal are transmitted simultaneously through multiple antenna units with a spatial multiplex scheme, and thus the transmission speed of the radio signal can be improved significantly; and, in the spatial diversity transmission scheme, for example, using the STBC (Space Time Block Coded) scheme, multiple data streams of a radio signal are transmitted simultaneously through multiple antenna units with a space-time coding scheme, and thus a spatial diversity gain is acquired and the transmission performance of the radio signal is improved.
  • the gain in transmission speed or transmission performance of a radio signal that can be acquired will increase linearly with the increase in the number of antenna units.
  • a distributed antenna system is a special application form of MIMO radio transmission technology.
  • a distributed antenna system instead of using the concept of a traditional cell BS (Base Station) , provides multiple remote units in each cell, each remote unit including at least one antenna unit and at least one signal transceiving unit, wherein the signal transceiving unit is responsible for the conversion of a BB (Base Band) or IF (Intermediate Frequency) signal to a RF (Radio Frequency) signal or in reverse, and the antenna unit is responsible for transmitting and receiving the RF signal; the multiple remote units are further connected to a central unit which jointly processes radio signals from the multiple remote units; and, an area covered by multiple remote units pertaining to one central unit is called the service area of the distributed antenna system, as shown in Fig.2.
  • a mobile terminal is also provided with at least one antenna unit, and can simultaneously communicate with multiple remote units within the service area in which it is located, with the communication between the mobile terminal and the remote units being performed using MIMO radio transmission technology.
  • the mobile terminal can communicate with a remote terminal in its proximity, which greatly shortens the distances between the mobile terminal and remote units, thereby reducing the transmission power of both the mobile terminal and remote units as well as suppressing mutual interference within the radio communication system; furthermore, since the distance between the mobile terminal and remote units is shortened, when a radio signal is transmitted therebetween, there typically exists at least one line of sight (LOS) , which can further improve the transmission quality of the radio signal.
  • LOS line of sight
  • the distributed antenna system has inherited many advantages of MIMO radio transmission technology, such as high frequency spectrum efficiency, high transmission quality for the radio signal and so on, and can also adopt the link adaptation methods, such as, AMC (Adaptive Modulation and Coding) and power allocation, commonly used in MIMO radio transmission technology.
  • the distributed antenna system is not exactly the same as traditional applications of MIMO radio transmission technology.
  • data streams of a radio signal are transmitted only between a pair of antenna arrays, that is to say, they are limited in a point-to-point radio link, and no in-depth study has been undertaken on the method for allocating the data streams among multiple antenna arrays.
  • the data streams of the radio signal will be completely allocated to N antenna units of the remote unit nearest to the mobile terminal.
  • a mobile terminal in a distributed antenna system, can simultaneously communicate with multiple remote units within the service area in which it is located, that is to say, the mobile terminal can simultaneously establish multiple radio links with the multiple remote units, resulting in the problem of allocating data streams of a radio signal among multiple antenna arrays; and, when a radio signal is transmitted between the mobile terminal and the remote units, there typically exists at least one LOS, and propagation in the LOS will cause correlation of radio channels between different antenna units in the same antenna array, which will impair the transmission performance of the radio signal, thus it is also necessary to allocate the data streams of the radio signal among multiple remote units, which is a problem that cannot be solved by traditional applications of MIMO radio transmission technology.
  • An object of the present invention is to propose a method for allocating downlink data streams in a distributed antenna system, wherein in the downlink radio signal transmission from remote units to a mobile terminal the central unit of the service area in which the mobile terminal is located can allocate data streams of the radio signal among the remote units within its service area according to variations in the position of the mobile terminal and radio signal transmission environment.
  • the method further improves the transmission quality of the radio signal and optimizes the performance of the distributed antenna system.
  • the above object of the present invention is achieved by the following method: a method for allocating downlink data streams in a distributed antenna system, wherein in the downlink radio signal transmission from remote units to a mobile terminal, the central unit of the service area in which the mobile terminal is located allocates data streams of the radio signal among the remote units within its service area, according to the following steps: a) measuring the position in the service area in which the mobile terminal is located; b) measuring the correlation of the downlink radio signals transmitted to the mobile terminal from individual antenna units of all the remote units within the service area; c) the central unit determining the manner in which the data streams are allocated among the remote units based on the position of the mobile terminal and the measured value of the correlation of the downlink radio signals.
  • the central unit allocates corresponding pilot signals to the individual antenna units of all the remote units within its service area so that the pilot signals of the individual antenna units can be distinguished from each other; and, the mobile terminal measures its position and the correlation of the downlink radio signals by measuring large scale channel fading suffered by down pilot signals transmitted by the individual antenna units .
  • the central unit allocates corresponding pilot signals to the individual antenna units of all the remote units within its service area so that the pilot signals of the individual antenna units can be distinguished from each other; and, the mobile terminal measures large scale channel fading suffered by down pilot signals transmitted by the individual antenna units and reports to the central unit the measured values of the large scale channel fading, and then the central unit performs the measurement of the position of the mobile terminal and the correlation of the downlink radio signals.
  • the large scale channel fading comprises radio channel path loss and radio channel shadow fading.
  • the central unit adjusts the manner in which the data streams are allocated among the remote units periodically, based on the measured values .
  • the central unit allocates the data streams in combination with the link adaptation method of adaptive modulation and coding or power allocation, employing corresponding modulation and coding schemes on or allocating different transmission power for different downlink data streams.
  • the distributed antenna system employs an orthogonal frequency division multiple access or code division multiple access scheme.
  • the distributed antenna system employs a time division duplex or frequency division duplex scheme.
  • Fig.l illustrates a schematic of traditional applications of
  • Fig.2 illustrates a schematic of a distributed antenna system.
  • Fig.3 illustrates the first embodiment of the present invention.
  • Fig.4 illustrates the second embodiment of the present invention .
  • FIG.3 Two embodiments of the present invention are shown in Fig.3 and Fig.4, respectively.
  • radio links for transmitting a radio signal from remote units to a mobile terminal are called downlinks; and, radio links for transmitting a radio signal from a mobile terminal to remote units are called uplinks .
  • the central unit of the service area in which the mobile terminal is located allocates data streams of the radio signal among the remote units within its service area, according to the following steps:
  • the central unit determining the manner in which the data streams are allocated among the remote units based on the position of the mobile terminal and the measured value of the correlation of the downlink radio signals.
  • the central unit can allocate corresponding pilot signals to individual antenna units of all the remote units within its service area so that the pilot signals of the individual antenna units can be distinguished from each other; and, the mobile terminal measures its position and the correlation of the downlink radio signals by measuring large scale channel fading suffered by down pilot signals transmitted by the individual antenna units, and reports to the central unit the measurement results of the position and correlation; in view of the limited computing ability of the mobile terminal, the mobile terminal can also report to the central unit the measured values of the large scale channel fading, and then the central unit performs the measurement of the position of the mobile terminal and the correlation of the downlink radio signals; and, the large scale channel fading comprises radio channel path loss and radio channel shadow fading.
  • the precise measurement of the position of the mobile terminal is not necessary, and nor is that of the instantaneous correlation of the downlink radio signals. Therefore, measuring the large scale channel fading can meet the requirements of measuring the position of the mobile terminal and the correlation of the downlink radio signals. According to the concept of the present invention, those skilled in the art can also implement the measurement of the position of the mobile terminal and the correlation of the downlink radio signals with other alternative measuring methods .
  • the central unit determines the manner in which the data streams are allocated among the remote units based on the position of the mobile terminal and the measured value of the correlation of the downlink radio signals. For example, when the correlation of the downlink radio signal is very high, it is supposed to avoid allocating multiple data streams of the radio signal to one of the remote units; and, when the mobile terminal is positioned in the middle of the multiple remote units, it is supposed to allocate the data streams of the radio signal to the multiple remote units as evenly as possible, so as to acquire a macro-diversity gain.
  • Fig.3 illustrates the first embodiment of the present invention.
  • the mobile terminal MT is positioned in the middle of four remote units RUl, RU2, RU3 and RU4, and the antenna array of the mobile terminal MT includes four antenna units; then, according to the method of the present invention, the downlink data streams Streaml, Stream2, Stream3 and Stream4 will be allocated to the four remote units RUl, RU2, RU3 and RU4, respectively.
  • the antenna array of each one of the remote units comprises four antenna units, and the number of the antenna units is larger than that of the data streams allocated thereto, i.e. four antenna units transmitting one data stream.
  • Fig.4 illustrates the second embodiment of the present invention, in which the mobile terminal MT is nearest to the remote unit RUl, while further from the other three remote units RU2, RU3 and RU4.
  • the data stream Streaml can be transmitted simultaneously through two antenna units of the remote unit RUl, and the data streams Stream2 and Stream3 can be transmitted, respectively, through the other two antenna units of the remote unit RUl, and the data stream Stream4 can be transmitted simultaneously through all twelve antenna units of remote units RU2, RU3 and RU4, and thus the transmission quality of the data streams is further improved.
  • the measurement of the position of the mobile terminal and the correlation of the downlink radio signals can be carried out periodically by the central unit, and the central unit adjusts the manner in which the data streams are allocated among the remote units periodically, based on the measured values, to adapt to the variations in the position of the mobile terminal and radio signal transmission environment.
  • the central unit can also perform the allocation of the data streams in combination with the link adaptation method of adaptive modulation and coding or power allocation used in traditional applications of MIMO radio transmission technology, employing corresponding modulation and coding schemes on or allocating different transmission power for different downlink data streams .
  • the method for allocating downlink data streams in a distributed antenna system according to the present invention has been described through the above two embodiments, but it is obvious for those skilled in the art that the distributed antenna system is not limited to the use of a particular multiple access scheme, for example, an orthogonal frequency division multiple access (OFDMA) or code division multiple access (CDMA) scheme can be used; and, the distributed antenna system is also not limited to the use of a particular duplex scheme, for example, a time division duplex (TDD) or frequency division duplex (FDD) scheme can be used.
  • the method of the present invention is applicable to the distributed antenna system using a multiple access or duplex scheme.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

A method for allocating downlink data streams in a distributed antenna system, wherein in the downlink radio signal transmission from remote units to a mobile terminal, the central unit of the service area in which the mobile terminal is located allocates data streams of the radio signal among the remote units within its service area, according to the following steps: firstly, measuring the position in the service area in which the mobile terminal is located; secondly, measuring the correlation of the downlink radio signals transmitted to the mobile terminal from individual antenna units of all the remote units within the service area; lastly, the central unit determining the manner in which the data streams are allocated among the remote units based on the position of the mobile terminal and the measured value of the correlation of the downlink radio signals. The method of the present invention can allocate data streams of a radio signal among remote units in a service area according to the variations in the position of the mobile terminal and radio signal transmission environment, and compared with traditional applications of MIMO radio transmission technology, the method further improves the transmission quality of radio signals and optimizes the performance of distributed antenna systems.

Description

A method for allocating downlink data streams in a distributed antenna system
Technical field
The present invention relates to an method of optimizing the performance of a radio communication system, and more particularly, to a method for allocating downlink data streams in a distributed antenna system.
Technical background
With the appearance and development of radio communication technology, radio communication systems have developed from analog systems to digital systems, and are now experiencing transition from the second generation to the third generation, i.e. transition from voice communication systems to data communication systems. During the development of radio communication technology, radio communication resources have always been a crucial factor of great importance optimizing the usage of limited radio communication resources and improving the frequency spectrum usage rate of radio communication resources has become a constant focal point for researchers in the field of communication.
At present, MIMO (Multiple Input and Multiple Output) radio transmission technology is attracting increasing attention and having increasing application because of its high frequency spectrum usage rate. In MIMO radio transmission technology, multiple antenna units, i.e. an antenna array, are provided for the transmit end and receive end of radio signals, respectively, so as to utilize spatial resources available during the radio transmission, and thus a spatial diversity gain is acquired or the transmission speed of radio signals is improved, as shown in Fig. 1. In MIMO radio transmission technology, spatial multiplex transmission and spatial diversity transmission are two main transmission schemes, wherein in the spatial multiplex transmission scheme, for example, the V-BLAST (Vertical Bell Laboratories Layered Space Time) scheme proposed by Bell Lab, multiple data streams of a radio signal are transmitted simultaneously through multiple antenna units with a spatial multiplex scheme, and thus the transmission speed of the radio signal can be improved significantly; and, in the spatial diversity transmission scheme, for example, using the STBC (Space Time Block Coded) scheme, multiple data streams of a radio signal are transmitted simultaneously through multiple antenna units with a space-time coding scheme, and thus a spatial diversity gain is acquired and the transmission performance of the radio signal is improved. Theoretically, in MIMO radio transmission technology, the gain in transmission speed or transmission performance of a radio signal that can be acquired will increase linearly with the increase in the number of antenna units.
A distributed antenna system is a special application form of MIMO radio transmission technology. Different from traditional cell structured radio communication systems, a distributed antenna system, instead of using the concept of a traditional cell BS (Base Station) , provides multiple remote units in each cell, each remote unit including at least one antenna unit and at least one signal transceiving unit, wherein the signal transceiving unit is responsible for the conversion of a BB (Base Band) or IF (Intermediate Frequency) signal to a RF (Radio Frequency) signal or in reverse, and the antenna unit is responsible for transmitting and receiving the RF signal; the multiple remote units are further connected to a central unit which jointly processes radio signals from the multiple remote units; and, an area covered by multiple remote units pertaining to one central unit is called the service area of the distributed antenna system, as shown in Fig.2. In the distributed antenna system, a mobile terminal is also provided with at least one antenna unit, and can simultaneously communicate with multiple remote units within the service area in which it is located, with the communication between the mobile terminal and the remote units being performed using MIMO radio transmission technology. By providing multiple remote units in different places within the service area, the mobile terminal can communicate with a remote terminal in its proximity, which greatly shortens the distances between the mobile terminal and remote units, thereby reducing the transmission power of both the mobile terminal and remote units as well as suppressing mutual interference within the radio communication system; furthermore, since the distance between the mobile terminal and remote units is shortened, when a radio signal is transmitted therebetween, there typically exists at least one line of sight (LOS) , which can further improve the transmission quality of the radio signal.
As a special application form of MIMO radio transmission technology, the distributed antenna system has inherited many advantages of MIMO radio transmission technology, such as high frequency spectrum efficiency, high transmission quality for the radio signal and so on, and can also adopt the link adaptation methods, such as, AMC (Adaptive Modulation and Coding) and power allocation, commonly used in MIMO radio transmission technology. However, the distributed antenna system is not exactly the same as traditional applications of MIMO radio transmission technology. As shown in Fig.l, in traditional applications of MIMO radio transmission technology, data streams of a radio signal are transmitted only between a pair of antenna arrays, that is to say, they are limited in a point-to-point radio link, and no in-depth study has been undertaken on the method for allocating the data streams among multiple antenna arrays. For example, if there are M antenna units provided in the antenna array of each of the remote units and N antenna units provided in the antenna array of the mobile terminal, and usually M is not less than N, then in traditional applications of MIMO radio transmission technology, the data streams of the radio signal will be completely allocated to N antenna units of the remote unit nearest to the mobile terminal. However, as described above, in a distributed antenna system, a mobile terminal can simultaneously communicate with multiple remote units within the service area in which it is located, that is to say, the mobile terminal can simultaneously establish multiple radio links with the multiple remote units, resulting in the problem of allocating data streams of a radio signal among multiple antenna arrays; and, when a radio signal is transmitted between the mobile terminal and the remote units, there typically exists at least one LOS, and propagation in the LOS will cause correlation of radio channels between different antenna units in the same antenna array, which will impair the transmission performance of the radio signal, thus it is also necessary to allocate the data streams of the radio signal among multiple remote units, which is a problem that cannot be solved by traditional applications of MIMO radio transmission technology.
Summary of the invention
An object of the present invention is to propose a method for allocating downlink data streams in a distributed antenna system, wherein in the downlink radio signal transmission from remote units to a mobile terminal the central unit of the service area in which the mobile terminal is located can allocate data streams of the radio signal among the remote units within its service area according to variations in the position of the mobile terminal and radio signal transmission environment. Compared with traditional applications of MIMO radio transmission technology, the method further improves the transmission quality of the radio signal and optimizes the performance of the distributed antenna system. The above object of the present invention is achieved by the following method: a method for allocating downlink data streams in a distributed antenna system, wherein in the downlink radio signal transmission from remote units to a mobile terminal, the central unit of the service area in which the mobile terminal is located allocates data streams of the radio signal among the remote units within its service area, according to the following steps: a) measuring the position in the service area in which the mobile terminal is located; b) measuring the correlation of the downlink radio signals transmitted to the mobile terminal from individual antenna units of all the remote units within the service area; c) the central unit determining the manner in which the data streams are allocated among the remote units based on the position of the mobile terminal and the measured value of the correlation of the downlink radio signals.
In one aspect of the present invention, the central unit allocates corresponding pilot signals to the individual antenna units of all the remote units within its service area so that the pilot signals of the individual antenna units can be distinguished from each other; and, the mobile terminal measures its position and the correlation of the downlink radio signals by measuring large scale channel fading suffered by down pilot signals transmitted by the individual antenna units .
In one aspect of the present invention, the central unit allocates corresponding pilot signals to the individual antenna units of all the remote units within its service area so that the pilot signals of the individual antenna units can be distinguished from each other; and, the mobile terminal measures large scale channel fading suffered by down pilot signals transmitted by the individual antenna units and reports to the central unit the measured values of the large scale channel fading, and then the central unit performs the measurement of the position of the mobile terminal and the correlation of the downlink radio signals.
In one aspect of the present invention, the large scale channel fading comprises radio channel path loss and radio channel shadow fading.
In one aspect of the present invention, during the movement of the mobile terminal, the measurement of the position of the mobile terminal and the correlation of the downlink radio signals is performed periodically, and the central unit adjusts the manner in which the data streams are allocated among the remote units periodically, based on the measured values .
In one aspect of the present invention, the central unit allocates the data streams in combination with the link adaptation method of adaptive modulation and coding or power allocation, employing corresponding modulation and coding schemes on or allocating different transmission power for different downlink data streams.
In one aspect of the present invention, the distributed antenna system employs an orthogonal frequency division multiple access or code division multiple access scheme.
In one aspect of the present invention, the distributed antenna system employs a time division duplex or frequency division duplex scheme.
Brief description of the drawings
The objects and features of the present invention will be described in detail by embodiments, which are illustrative but not limitative, with reference being made to the accompanying drawings . Fig.l illustrates a schematic of traditional applications of
MIMO radio transmission technology.
Fig.2 illustrates a schematic of a distributed antenna system.
Fig.3 illustrates the first embodiment of the present invention.
Fig.4 illustrates the second embodiment of the present invention .
Detailed description of the embodiments
Two embodiments of the present invention are shown in Fig.3 and Fig.4, respectively.
In a distributed antenna system, radio links for transmitting a radio signal from remote units to a mobile terminal are called downlinks; and, radio links for transmitting a radio signal from a mobile terminal to remote units are called uplinks .
According to the method of the present invention, in the downlink radio signal transmission from remote units to a mobile terminal, the central unit of the service area in which the mobile terminal is located allocates data streams of the radio signal among the remote units within its service area, according to the following steps:
A. measuring the position in the service area in which the mobile terminal is located;
B. measuring the correlation of the downlink radio signals transmitted to the mobile terminal from individual antenna units of all the remote units within the service area;
C. the central unit determining the manner in which the data streams are allocated among the remote units based on the position of the mobile terminal and the measured value of the correlation of the downlink radio signals.
Wherein, during the measurement of steps A and B, the central unit can allocate corresponding pilot signals to individual antenna units of all the remote units within its service area so that the pilot signals of the individual antenna units can be distinguished from each other; and, the mobile terminal measures its position and the correlation of the downlink radio signals by measuring large scale channel fading suffered by down pilot signals transmitted by the individual antenna units, and reports to the central unit the measurement results of the position and correlation; in view of the limited computing ability of the mobile terminal, the mobile terminal can also report to the central unit the measured values of the large scale channel fading, and then the central unit performs the measurement of the position of the mobile terminal and the correlation of the downlink radio signals; and, the large scale channel fading comprises radio channel path loss and radio channel shadow fading. During the allocation of the radio signal data streams, the precise measurement of the position of the mobile terminal is not necessary, and nor is that of the instantaneous correlation of the downlink radio signals. Therefore, measuring the large scale channel fading can meet the requirements of measuring the position of the mobile terminal and the correlation of the downlink radio signals. According to the concept of the present invention, those skilled in the art can also implement the measurement of the position of the mobile terminal and the correlation of the downlink radio signals with other alternative measuring methods .
Furthermore, according to step C of the method of the present invention, the central unit determines the manner in which the data streams are allocated among the remote units based on the position of the mobile terminal and the measured value of the correlation of the downlink radio signals. For example, when the correlation of the downlink radio signal is very high, it is supposed to avoid allocating multiple data streams of the radio signal to one of the remote units; and, when the mobile terminal is positioned in the middle of the multiple remote units, it is supposed to allocate the data streams of the radio signal to the multiple remote units as evenly as possible, so as to acquire a macro-diversity gain. Fig.3 illustrates the first embodiment of the present invention. As shown in Fig.3, the mobile terminal MT is positioned in the middle of four remote units RUl, RU2, RU3 and RU4, and the antenna array of the mobile terminal MT includes four antenna units; then, according to the method of the present invention, the downlink data streams Streaml, Stream2, Stream3 and Stream4 will be allocated to the four remote units RUl, RU2, RU3 and RU4, respectively. In the first embodiment, the antenna array of each one of the remote units comprises four antenna units, and the number of the antenna units is larger than that of the data streams allocated thereto, i.e. four antenna units transmitting one data stream. In this case, the same data stream can be transmitted simultaneously through four antenna units, or the transmission power of the same data stream is weighted, respectively, based on the large scale channel fading experienced by the downlink data stream from the four antenna units. Then the data stream is transmitted through the four antenna units, and thus the transmission quality of the data stream can be further improved. Fig.4 illustrates the second embodiment of the present invention, in which the mobile terminal MT is nearest to the remote unit RUl, while further from the other three remote units RU2, RU3 and RU4. Due to the presence of LOS for transmission of the radio signal between the remote unit RUl and the mobile terminal MT, there is correlation between the downlink radio signals from the four antenna units of the remote unit RUl, so the downlink data streams Streaml, Stream2 and Stream3 are allocated to the remote unit RUl, while the downlink data stream Stream4 is allocated to the other three remote units RU2, RU3 and RU4. Likewise, since the number of the antenna units in the antenna array of remote units is larger than that of the data streams allocated thereto, the data stream Streaml can be transmitted simultaneously through two antenna units of the remote unit RUl, and the data streams Stream2 and Stream3 can be transmitted, respectively, through the other two antenna units of the remote unit RUl, and the data stream Stream4 can be transmitted simultaneously through all twelve antenna units of remote units RU2, RU3 and RU4, and thus the transmission quality of the data streams is further improved.
During the allocation of the data streams, with the movement of the mobile terminal, the measurement of the position of the mobile terminal and the correlation of the downlink radio signals can be carried out periodically by the central unit, and the central unit adjusts the manner in which the data streams are allocated among the remote units periodically, based on the measured values, to adapt to the variations in the position of the mobile terminal and radio signal transmission environment. At the same time, the central unit can also perform the allocation of the data streams in combination with the link adaptation method of adaptive modulation and coding or power allocation used in traditional applications of MIMO radio transmission technology, employing corresponding modulation and coding schemes on or allocating different transmission power for different downlink data streams .
The method for allocating downlink data streams in a distributed antenna system according to the present invention has been described through the above two embodiments, but it is obvious for those skilled in the art that the distributed antenna system is not limited to the use of a particular multiple access scheme, for example, an orthogonal frequency division multiple access (OFDMA) or code division multiple access (CDMA) scheme can be used; and, the distributed antenna system is also not limited to the use of a particular duplex scheme, for example, a time division duplex (TDD) or frequency division duplex (FDD) scheme can be used. The method of the present invention is applicable to the distributed antenna system using a multiple access or duplex scheme.

Claims

1. A method for allocating downlink data streams in a distributed antenna system, characterized in that in the downlink radio signal transmission from remote units to a mobile terminal, the central unit of the service area in which the mobile terminal is located allocates data streams of the radio signal among the remote units within its service area, according to the following steps:
1) measuring the position in the service area in which the mobile terminal is located;
2) measuring the correlation of the downlink radio signals transmitted to the mobile terminal from individual antenna units of all the remote units within the service area;
3) the central unit determining the manner in which the data streams are allocated among the remote units based on the position of the mobile terminal and the measured value of the correlation of the downlink radio signals.
2. The method for allocating downlink data streams in a distributed antenna system as claimed in claim 1, characterized in that the central unit allocates corresponding pilot signals to the individual antenna units of all the remote units within its service area so that the pilot signals of the individual antenna units can be distinguished from each other; and, the mobile terminal measures its position and the correlation of the downlink radio signals by measuring large scale channel fading suffered by down pilot signals transmitted by the individual antenna units.
3. The method for allocating downlink data streams in a distributed antenna system as claimed in claim 1, characterized in that the central unit allocates corresponding pilot signals to the individual antenna units of all the remote units within its service area so that the pilot signals of the individual antenna units can be distinguished from each other; and, the mobile terminal measures large scale channel fading suffered by down pilot signals transmitted by the individual antenna units and reports to the central unit the measured values of the large scale channel fading, and then the central unit performs the measurement of the position of the mobile terminal and the correlation of the downlink radio signals .
4. The method for allocating downlink data streams in a distributed antenna system as claimed in claim 2 or 3, characterized in that the large scale channel fading comprises radio channel path loss and radio channel shadow fading.
5. The method for allocating downlink data streams in a distributed antenna system as claimed in claim 1, characterized in that during the movement of the mobile terminal, the measurement of the position of the mobile terminal and the correlation of the downlink radio signals is performed periodically, and the central unit adjusts the manner in which the data streams are allocated among the remote units periodically, based on the measured values .
6. The method for allocating downlink data streams in a distributed antenna system as claimed in claim 1 or 5, characterized in that the central unit allocates the data streams in combination with the link adaptation method of adaptive modulation and coding, employing corresponding modulation and coding schemes on different downlink data streams .
7. The method for allocating downlink data streams in a distributed antenna system as claimed in claim 1 or 5, characterized in that the central unit allocates the data streams in combination with the link adaptation method of power allocation, allocating different transmission power for different downlink data streams.
8. The method for allocating downlink data streams in a distributed antenna system as claimed in claim 1 or 5, characterized in that the distributed antenna system employs an orthogonal frequency division multiple access or code division multiple access scheme.
9. The method for allocating downlink data streams in a distributed antenna system as claimed in claim 1 or 5, characterized in that the distributed antenna system employs a time division duplex or frequency division duplex scheme.
EP06725459A 2005-03-31 2006-03-31 A method for allocating downlink data streams in a distributed antenna system Withdrawn EP1864401A1 (en)

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CN 200510059760 CN1841960B (en) 2005-03-31 2005-03-31 Downlink chain circuit data stream distribution method in distributed antenna system
PCT/EP2006/061211 WO2006103283A1 (en) 2005-03-31 2006-03-31 A method for allocating downlink data streams in a distributed antenna system

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