WO2008072928A1 - Method for constructing sub-carrier interference self-cancellation preamble - Google Patents

Method for constructing sub-carrier interference self-cancellation preamble Download PDF

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Publication number
WO2008072928A1
WO2008072928A1 PCT/KR2007/006542 KR2007006542W WO2008072928A1 WO 2008072928 A1 WO2008072928 A1 WO 2008072928A1 KR 2007006542 W KR2007006542 W KR 2007006542W WO 2008072928 A1 WO2008072928 A1 WO 2008072928A1
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WIPO (PCT)
Prior art keywords
sub
carriers
carrier
cell
data
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Application number
PCT/KR2007/006542
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French (fr)
Inventor
Zonchuang Liang
Jiacheng Wang
Chuan Zhong
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Samsung Electronics Co., Ltd.
Beijing Samsung Telecom R & D Center
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Application filed by Samsung Electronics Co., Ltd., Beijing Samsung Telecom R & D Center filed Critical Samsung Electronics Co., Ltd.
Publication of WO2008072928A1 publication Critical patent/WO2008072928A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2657—Carrier synchronisation

Definitions

  • This invention relates to information transmission field in Orthogonal Frequency Division Multiplexing (OFDM) / Orthogonal Frequency Division Multiplexing Access (OFDMA) systems, particularly relates to an OFDM or OFDMA systems in a multi-cell environment and when marginal cell users receive a number of neighborhood superimposed signals, the signals of each cell are separated to avoid interference from the neighbour cells.
  • OFDM Orthogonal Frequency Division Multiplexing
  • OFDMA Orthogonal Frequency Division Multiplexing Access
  • OFDM is a known communications technology that transmits information effectively in channels.
  • a number of parallel and low-speed-data transmission sub-carriers (sub-carrier frequency) are used to achieve high-data-rate communications.
  • the main point is to divide the channel transmission bandwidth into a number of sub-bands, transmit data information in a parallel way using orthogonal sub-carriers in each sub-band, and separate parallel transferred data information in a receiver by means of orthogonal characteristic between each sub-carrier.
  • OFDM technology has been successfully used in many communications systems.
  • DAB digital broadcasting
  • DVD digital television
  • OFDM technology as wireless transmission standard for air interface.
  • wireless LAN standard IEEE802.i l and wireless MAN standard IEEE802.16 also use OFDM technology.
  • OFDMA orthogonal frequency division multiple access
  • the OFDM system is very sensitive to frequency offset error.
  • the data transmitted on each sub-carrier which is supposed to be orthogonal will be affected by interference caused by other sub-carriers, especially when the mobile station receives signals coming from different base stations, different frequency deviation will make such inter-carrier interference issues more complex.
  • Preamble is used as an estimation guidance of each physical parameters. If a way of reducing the interference between sub-carriers is proposed, it will be very helpful to the estimation accuracy.
  • the technology usually used is time / frequency isolation for the various sub-guided cell preamble signals, or isolation by signal processing technique in a receiver and then a single-user handling for the separated signals. Appling the solution above will either reduce the resource utilization rate, or make a transmission and reception technology complex.
  • the object of this invention is to provide a method for constructing a sub-carrier interference self-cancellation preamble comprising steps of a) dividing sub-carriers in frequency domain into groups constructed by a number of adjacent sub-carriers; b) allocating the same data to two central symmetry sub-carriers which take a center of cell they belong to as symmetry center; c) combining two sub-carriers of central symmetry in group after a receiver extracts the data, and performing a subquent processing by using the result as the data of these two sub-carriers.
  • the invention is easy to realize, and can offset the inter-carrier interference caused by the frequency offset, and also has great compatibility with the existing high-technology.
  • Figure 1 is a structural diagram for Preamble
  • Figure 2 is a replicated double-symbol structure using the method accoridng to present invention.
  • This invention proposes a format of Preamble. Accoridng to present invention, the sub-carriers in frequency domain is divided into different groups, the symmetrical distribution strategy is used for sub-carriers in each cell in each group, and the same transmision data on each symmetrical sub-carrier is placed. In the receiver some changes in logicaloccur and if a certain condition is satisfied, it will offset the interference caused by frequency offset by itself.
  • the term cell mentioned includes a sector, a relay stations and so on. Their characteristic is that the receiver receives signals from different sources at the same time.
  • the invention is composed of two major parts, one is the method of constructing a Preamble in a transmitting side, including a sub-carrier allocation method and the corresponding code characteristics, and the other is the corresponding logic changes in the receiver.
  • the sub-carriers in frequency domain are divided into groups constructed by a number of adjacent sub-carriers, and the sub-carrier bandwidth occupied by each group should preferably not exceed coherent bandwidth.
  • the group center There may be odd-numbered and even-numbered sub-carriers, as shown in Figure 1.
  • the sub-carriers in frequency domain are divided into groups constructed by a number of adjacent sub-carriers, and then the sub-carriers in each group are divided further.
  • the carrier in the center is allocated to one cell, and then the two symmetry carriers are allocated to different cells in order by using the central carrier as symmetry point.
  • the two carriers in the center are allocated to one cell, and then the other symmetry carriers are allocated to different cells in order using these two carriers as symmetry points.
  • the following rules may be satisfied: the data transmitted on each symmetrical sub-carriers in each cell is the same.
  • the receiver needs to combine the receiving data at the symmetry location, and uses the result for the following processing.
  • the total number of sub-carriers is 2048.
  • each group consists of five consecutive sub-carriers, and a null carrier is inserted after the symbol for the purpose of isolation. The same operations continue in order until the sub-carriers are all allocated.
  • the left sub-carriers that don't have enough number to construct a group are set to the null carrier.
  • the total number of groups is H.
  • sub-carrier 1 and sub-carrier 5 in the group are allocated to cell 1 randomly, and value 1 or -1 are allocated to the two subcarriers randomly with the same requirement.
  • Sub-carrier 2 and sub-carrier 4 in the group are allocated to cell 2 randomly, and value 1 or - 1 are allocated to the two subcarriers randomly with the same requirement.
  • Sub-carrier 3 in the group is allocated to cell 3 randomly, and value 1 or - 1 is allocated to the sub-carrier randomly
  • the receiver After completing the corresponded time / frequency process, the receiver obtains frequency domain data of the two symbols.
  • the receiver combines the symmetric data in its own cell according to the allocation of sub-carriers inside cell.
  • YQi , Y c 2 h respectively means the data received from the first sub-carrier and its symmetric sub-carrier in cell c of the number h group. Then estimate the frequency offsets based on the following formula:
  • Y ] (H) and Y 2 (K) respectively means the symbol combined of the h th group in the first and the second symbol.

Abstract

A method for constructing a sub-carrier interference self-cancellation preamblecomprising steps of dividing sub-carriers in frequency domain into groups constructed by a number of adjacent sub-carriers; allocate the same data to two central symmetry sub-carriers which take a center of cell they belong to as symmetry center; combining two sub-carriers of central symmetry in group after a receiver extracts the data, and performing a subquent processing by using the result as the data of these two sub-carriers. The invention is easy to realize, and can offset the inter-carrier interference caused by the frequency offset, and also has great compatibility with the existing high-technology.

Description

METHOD FOR CONSTRUCTING SUB-CARRIER INTERFERENCE SELF-CANCELLATION PREAMBLE
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to information transmission field in Orthogonal Frequency Division Multiplexing (OFDM) / Orthogonal Frequency Division Multiplexing Access (OFDMA) systems, particularly relates to an OFDM or OFDMA systems in a multi-cell environment and when marginal cell users receive a number of neighborhood superimposed signals, the signals of each cell are separated to avoid interference from the neighbour cells.
2. Description of the Related Art
For the purpose of clear description,the description only regards to cells in the following. In fact, similar to situation for the cell, the invention may also apply to situation for sectors.
OFDM is a known communications technology that transmits information effectively in channels. A number of parallel and low-speed-data transmission sub-carriers (sub-carrier frequency) are used to achieve high-data-rate communications. The main point is to divide the channel transmission bandwidth into a number of sub-bands, transmit data information in a parallel way using orthogonal sub-carriers in each sub-band, and separate parallel transferred data information in a receiver by means of orthogonal characteristic between each sub-carrier.
OFDM technology has been successfully used in many communications systems. For example, digital broadcasting (DAB) and digital television (DVB) developed by the European Telecommunication Standardization Organization use OFDM technology as wireless transmission standard for air interface. In addition, wireless LAN standard IEEE802.i l and wireless MAN standard IEEE802.16 also use OFDM technology.
With the development of communications business, and continual emergence of new business demands, OFDMA technology is widely used gradually. OFDMA is based on OFDM technology, and can distribute different business in different sub-channels formed 2OO6ioi65892.6by allocating different resources in time-frequency resources, in order to get greater flexibility.
However, the OFDM system is very sensitive to frequency offset error. When the frequency offset error occurs, the data transmitted on each sub-carrier which is supposed to be orthogonal will be affected by interference caused by other sub-carriers, especially when the mobile station receives signals coming from different base stations, different frequency deviation will make such inter-carrier interference issues more complex.
Preamble is used as an estimation guidance of each physical parameters. If a way of reducing the interference between sub-carriers is proposed, it will be very helpful to the estimation accuracy.
At present, the technology usually used is time / frequency isolation for the various sub-guided cell preamble signals, or isolation by signal processing technique in a receiver and then a single-user handling for the separated signals. Appling the solution above will either reduce the resource utilization rate, or make a transmission and reception technology complex.
SUMMARY OF THE INVENTION
The object of this invention is to provide a method for constructing a sub-carrier interference self-cancellation preamble comprising steps of a) dividing sub-carriers in frequency domain into groups constructed by a number of adjacent sub-carriers; b) allocating the same data to two central symmetry sub-carriers which take a center of cell they belong to as symmetry center; c) combining two sub-carriers of central symmetry in group after a receiver extracts the data, and performing a subquent processing by using the result as the data of these two sub-carriers.
The invention is easy to realize, and can offset the inter-carrier interference caused by the frequency offset, and also has great compatibility with the existing high-technology.
BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a structural diagram for Preamble;
Figure 2 is a replicated double-symbol structure using the method accoridng to present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS This invention proposes a format of Preamble. Accoridng to present invention, the sub-carriers in frequency domain is divided into different groups, the symmetrical distribution strategy is used for sub-carriers in each cell in each group, and the same transmision data on each symmetrical sub-carrier is placed. In the receiver some changes in logicaloccur and if a certain condition is satisfied, it will offset the interference caused by frequency offset by itself. In this invention, the term cell mentioned includes a sector, a relay stations and so on. Their characteristic is that the receiver receives signals from different sources at the same time.
The invention is composed of two major parts, one is the method of constructing a Preamble in a transmitting side, including a sub-carrier allocation method and the corresponding code characteristics, and the other is the corresponding logic changes in the receiver.
At first, the sub-carriers in frequency domain are divided into groups constructed by a number of adjacent sub-carriers, and the sub-carrier bandwidth occupied by each group should preferably not exceed coherent bandwidth. When allocating sub-carriers to each cell, it is required to occupy sub-carriers by using the group center as symmetry point. There may be odd-numbered and even-numbered sub-carriers, as shown in Figure 1. The sub-carriers in frequency domain are divided into groups constructed by a number of adjacent sub-carriers, and then the sub-carriers in each group are divided further. When there are odd-numbered carriers, the carrier in the center is allocated to one cell, and then the two symmetry carriers are allocated to different cells in order by using the central carrier as symmetry point. When there are even-numbered carriers in each group, the two carriers in the center are allocated to one cell, and then the other symmetry carriers are allocated to different cells in order using these two carriers as symmetry points. When determining the data transmited on the preamble, the following rules may be satisfied: the data transmitted on each symmetrical sub-carriers in each cell is the same.
The receiver needs to combine the receiving data at the symmetry location, and uses the result for the following processing.
In this way, when the signals from different cells have frequency offsets, the interference caused by frequency offsets will be cancelled partly.
Here, a double-symbol structure used to detect offset is taken as an example to explain it. It proves that the accuracy of final detected offset results has been improved through the method introduced in this article. The total number of sub-carriers is 2048. In a first symbol, each group consists of five consecutive sub-carriers, and a null carrier is inserted after the symbol for the purpose of isolation. The same operations continue in order until the sub-carriers are all allocated. The left sub-carriers that don't have enough number to construct a group are set to the null carrier. The total number of groups is H.
[1 , 2, 3 , 4, 5] , 6, [7, 8, 9, 10, 11] , 12, ....
In such a way for allocating the odd-numbered sub-carriers within a group, sub-carrier 1 and sub-carrier 5 in the group are allocated to cell 1 randomly, and value 1 or -1 are allocated to the two subcarriers randomly with the same requirement. Sub-carrier 2 and sub-carrier 4 in the group are allocated to cell 2 randomly, and value 1 or - 1 are allocated to the two subcarriers randomly with the same requirement. Sub-carrier 3 in the group is allocated to cell 3 randomly, and value 1 or - 1 is allocated to the sub-carrier randomly
This way for allocating is known by the receiver.
The second symbol is a copy of the first symbol. The results are shown in Figure 2.
After completing the corresponded time / frequency process, the receiver obtains frequency domain data of the two symbols. The receiver combines the symmetric data in its own cell according to the allocation of sub-carriers inside cell.
YQi) =
Figure imgf000006_0001
, Yc 2 h respectively means the data received from the first sub-carrier and its symmetric sub-carrier in cell c of the number h group. Then estimate the frequency offsets based on the following formula:
Figure imgf000006_0002
where Y] (H) and Y2 (K) respectively means the symbol combined of the hth group in the first and the second symbol.

Claims

WHAT IS CLAIMED IS:
1. A method for constructing a sub-carrier interference self-cancellation preamblecomprising steps of a) dividing sub-carriers in frequency domain into groups constructed by a number of adjacent sub-carriers; b) allocating the same data to two central symmetry sub-carriers which take a center of cell they belong to as symmetry center; c) combining two sub-carriers of central symmetry in group after a receiver extracts the data, and performing a subquent processing by using the result as the data of these two sub-carriers.
2. The method according to Claim 1, the step a) further comprising: if there are odd-numbered carriers, allocating a carrier in center to one cell, and then allocating two carriers of central symmetry to different cells in order.
3. The method according to Claim 1, the step a) further comprising: if there are even-numbered carriers, allocating two carriers in center to different cells, and then allocating two carriers of central symmetry to different cells in order.
4. The method according to Claim 1, wherein a sub-carrier bandwidth occupied by each group does not exceed a coherent bandwidth.
5. The method according to Claim 1, the step b) furhter comprising: placing sub-carriers which are not in their own cell into null carriers.
PCT/KR2007/006542 2006-12-14 2007-12-14 Method for constructing sub-carrier interference self-cancellation preamble WO2008072928A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CN2006101658926A CN101202727B (en) 2006-12-14 2006-12-14 Method for constructing sub carrier wave interference self-counteract guide symbol
CN200610165892.6 2006-12-14

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CN102045287A (en) 2009-10-19 2011-05-04 北京三星通信技术研究有限公司 Method for mapping and de-mapping data, transmitting device and receiving device
CN102594765A (en) * 2012-03-23 2012-07-18 清华大学深圳研究生院 Base-band symbol mapping and demapping methods for onboard orthogonal frequency division multiplexing (OFDM) communication system

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