Orthogonal frequency division multiplexing communication system, multi-hop system, relay station, and spatially layered transmission mode

{
  "publication_number": "US2008247478A1",
  "country": "US",
  "kind": "A1",
  "title": "Orthogonal frequency division multiplexing communication system, multi-hop system, relay station, and spatially layered transmission mode",
  "abstract": "An apparatus and method for data transmission in an Orthogonal Frequency Division Multiplexing (OFDM) communication system are provided. An OFDM system includes a reference Relay Station (RS) and a cooperative relay station respectively for performing an Spatially Layered transmission Mode (SLM) process by modulating a phase and magnitude of a signal by using a predetermined modulation order suitable for the reference relay station to obtain a spatially-layered signal and for delivering the spatially-layered signal to a target Mobile Station (MS); a Base Station (BS) for selecting the reference relay station and the cooperative relay station among a plurality of relay stations; and an mobile station for detecting data through Maximum Likelihood (ML) detection in which a signal having the largest ML is detected by comparing the received spatially-layered signal with a signal which is converted through the SLM upon receiving the spatially-layered signal from the reference relay station and the cooperative relay station.",
  "claims": [
    "1. An Orthogonal Frequency Division Multiplexing (OFDM) system using a Spatially Layered transmission Mode (SLM), the system comprising: a reference relay station for performing an SLM process by modulating a phase and magnitude of a signal by using a predetermined modulation order suitable for the reference relay station to obtain a spatially-layered signal and for delivering the spatially-layered signal to a target mobile station; a cooperative relay station for performing the SLM process by modulating a phase and magnitude of a signal by using a predetermined modulation order suitable for the cooperative relay station to obtain a spatially-layered signal and for transmitting the spatially-layered signal to the target mobile station; a base station for selecting the reference relay station and the cooperative relay station among a plurality of relay stations and for transmitting data to the selected reference relay station and the cooperative relay station; and a mobile station for detecting data through Maximum Likelihood (ML) detection in which a signal having the largest ML is detected by comparing the received spatially-layered signal with a signal which is converted through the SLM after being subjected to a predetermined coding operation, upon receiving the spatially-layered signal from the reference relay station and the cooperative relay station.",
    "2. The OFDM system of claim 1, wherein, in order to select the reference relay station and the cooperative relay station, the base station generates a search request message for requesting location information of a neighbor mobile station and broadcasts the search request message to the relay stations, receives a search response message including the location information of the neighbor mobile station and average Channel Quality Information (CQI) with respect to the neighbor mobile station from the relay stations, and thus selects the reference relay station and the cooperative relay station by considering a distance from the target mobile station and the average CQI.",
    "3. The OFDM system of claim 2, wherein, when the search request message is received from the base station, the reference relay station and the cooperative relay station generate the search response message including the average CQI with respect to the neighbor mobile station and transmit the search response message to the base station.",
    "4. The OFDM system of claim 1, wherein the reference relay station performs the SLM process by modulating the phase and magnitude of the signal according to the equation: C SLM = 1 5  [s 1  α  (1 + θ)   s 2  α  (1 + θ)], where s1 and s2 are data received from the base station prior to modulation, θ=(1+√{square root over (5)})/2, and α=1+i(1−θ), where i is an imaginary unit.",
    "5. The OFDM system of claim 1, wherein the cooperative relay station performs the SLM process by modulating the phase and magnitude of the signal according to the equation: C SLM = 1 5  [s 2  γ  α _  (1 + θ _)   s 1  α _  (1 + θ _)], wherein s1 and s2 are data received from the base station prior to modulation, θ =(1+√{square root over (5)})/2, α =1+i(1− θ), and γ is an imaginary unit (i.e., i) representing a unit of imaginary number.",
    "6. The OFDM system of claim 1, wherein the mobile station performs the ML detection according to the equation: (s ^ 1 s ^ 2) = min ′ S 1 ′, S 2 ′  (Y - HC  (s 1 ′, s 2 ′)), where ŝ 1 and ŝ 2 are the detected signals having the largest ML, H is a fading channel matrix between mobile stations, Y is the spatially-layered signal received from the relay stations, and C(s 1 ′,s 2 ′) is a matrix of signals which are converted through the SLM after being subjected to the predetermined coding operation.",
    "7. A data transmission method of a base station in an Orthogonal Frequency Division Multiplexing (OFDM) system using a Spatially Layered transmission Mode (SLM), the method comprising: when there is data to be transmitted, generating a search request message for requesting location information of a neighbor mobile station and Channel Quality Information (CQI) and broadcasting the search request message to a plurality of relay stations; receiving the search response message including the location information of the neighbor mobile station and the CQI from the relay stations; selecting at least two relay stations neighboring to a target mobile station and having good channel quality by using the received search response message; and transmitting the data to the selected relay stations.",
    "8. The data transmission method of claim 7, wherein, in the selecting two relay stations, the relay station closest in distance to the target mobile station and having the best channel quality is selected as a reference relay station, and the relay station second closest to the target mobile station and having the second best channel quality as a cooperative relay station.",
    "9. A method for a Spatially Layered transmission Mode (SLM) of a relay station in an Orthogonal Frequency Division Multiplexing (OFDM) system, the method comprising: upon receiving a search request message from a base station, requesting neighbor mobile stations to send location information; receiving the location information from the neighbor mobile stations, checking average Channel Quality Information (CQI) and thus generating a search response message including the location information and the average CQI, and transmitting the search response message to the base station; when the relay station is selected a reference relay station or a cooperative relay station by the base station, receiving data to be transmitted to a target mobile station from the base station; performing an SLM process by modulating the received data into a signal having a predetermined phase and magnitude suitable for the reference relay station or the cooperative relay station selected by the base station; and transmitting the spatially-layered data to the target mobile station.",
    "10. The method of claim 9, wherein, in the SLM process, when the relay station is selected as the reference relay station, the phase and magnitude of the signal is modulated according to the equation: C SLM = 1 5  [s 1  α  (1 + θ)   s 2  α  (1 + θ)], where s 1 and s 2 are data received from the base station prior to modulation, θ=(1+√{square root over (5)})/2, and α=1+i(1−θ), where i is an imaginary unit.",
    "11. The method of claim 9, wherein, in the SLM process, when the relay station is selected as the reference relay station, the phase and magnitude of the signal is modulated according to the equation: C SLM = 1 5  [s 2  γ  α _  (1 + θ _)   s 1  α _  (1 + θ _)], wherein s 1 and s 2 are data received from the base station prior to modulation, θ =(1+√{square root over (5)})/2, α =1+i(1− θ), and γ is an imaginary unit (i.e., i) representing a unit of imaginary number.",
    "12. A method of receiving a spatially-layered signal in a mobile station of an Orthogonal Frequency Division Multiplexing (OFDM) system, the method comprising: when location information is requested from a relay station, transmitting the location information to the relay station; receiving the spatially-layered signal, whose phase and magnitude are modulated, from a reference relay station and a cooperative relay station; and detecting data transmitted from a base station through Maximum Likelihood (ML) detection in which a signal having the largest ML is detected by comparing the received spatially-layered signal with a signal which is converted through a Spatially Layered transmission Mode (SLM) after being subjected to a predetermined coding operation.",
    "13. The method of claim 12, wherein the ML detection is performed according to the equation: (s ^ 1 s ^ 2) = min ′ S 1 ′, S 2 ′  (Y - HC  (s 1 ′, s 2 ′)) where ŝ 1 and ŝ 2 are the detected signals having the largest ML, H is a fading channel matrix between mobile stations, Y is the spatially-layered signal received from the relay stations, and C(s 1 ′,s 2 ′) is a matrix of signals which are converted through the SLM after being subjected to a predetermined coding operation.",
    "14. A data transmission method in an Orthogonal Frequency Division Multiplexing (OFDM) system using a Spatially Layered transmission Mode (SLM), the method comprising: generating a search request message for requesting location information of a neighbor mobile station; receiving a search response message from one or more relay stations; selecting a reference relay station and a cooperative relay station from among the one or more relay stations; and transmitting data to the reference relay station and the cooperative relay station.",
    "15. The data transmission method of claim 14, wherein the reference relay station and the cooperative relay station are selected according to a distance from a corresponding mobile station and a channel quality.",
    "16. A relay method for data transmission in a mobile station of an Orthogonal Frequency Division Multiplexing (OFDM) system using a Spatially Layered transmission Mode (SLM), the method comprising: after receiving a search request message for requesting location information of a neighbor mobile station from a base station, requesting the neighbor mobile station to send the location information; after receiving the location information from the neighbor mobile station, generating a search response message and transmitting the search response message to the base station; and when a relay station is selected as a reference relay station or a cooperative relay station by the base station, transmitting data received from the base station to a corresponding mobile station according to the SLM.",
    "17. The relay method of claim 16, wherein, when the relay station is selected as the reference relay station, the phase and magnitude of the signal is spatially layered by modulating according to the equation: C SLM = 1 5  [s 1  α  (1 + θ)   s 2  α  (1 + θ)], where s 1 and s 2 are data received from the base station prior to modulation, θ=(1+{square root over (5)})/2, and α=1+i(1−θ), where i is an imaginary unit.",
    "18. The relay method of claim 16, wherein, when the relay station is selected as the reference relay station, the phase and magnitude of the signal is spatially layered by modulating according to the equation: C SLM = 1 5  [s 2  γ  α _  (1 + θ _)   s 1  α _  (1 + θ _)], wherein s 1 and s 2 are data received from the base station prior to modulation, θ =(1+√{square root over (5)})/2, α =1+i(1− θ), and γ is an imaginary unit (i.e., i) representing a unit of imaginary number.",
    "19. A method of receiving data in an Orthogonal Frequency Division multiplexing (OFDM) system using a Spatially Layered transmission Mode (SLM), the method comprising: receiving a spatially-layered signal from a reference relay station and a cooperative relay station; and detecting data through Maximum Likelihood (ML) detection in which a signal having the largest ML is detected by comparing the spatially-layered signal with a signal which is converted through the SLM after being subjected to a predetermined coding operation.",
    "20. A relay station for data transmission in an Orthogonal Frequency Division Multiplexing (OFDM) system using a Spatially Layered transmission Mode (SLM), the Relay Station comprising: a transmitter for receiving a search request message to request location information of a neighbor mobile station from a base station and then requesting the neighbor mobile station to send the location information, for receiving the location information from the neighbor mobile station and then generating a search request message, and for transmitting the search response message to the base station; and a spatial layering converter for transmitting data received from the base station to a corresponding mobile station according to the SLM when the relay station is selected as a reference relay station or a cooperative relay station by the base station.",
    "21. The relay station of claim 20, wherein, when the relay station is selected as the reference relay station, the spatial layering converter performs an SLM process by modulating the phase and magnitude of the signal according to the equation: C SLM = 1 5  [s 1  α  (1 + θ)   s 2  α  (1 + θ)], where s 1 and s 2 are data received from the base station prior to modulation, θ=(1+√{square root over (5)})/2 and α=1+i(1−θ), where i is an imaginary unit.",
    "22. The relay station of claim 20, wherein, when the relay station is selected as the reference relay station, the spatial layering converter performs the SLM process by modulating the phase and magnitude of the signal according to the equation: C SLM = 1 5  [s 2  γ  α _  (1 + θ _)   s 1  α _  (1 + θ _)], where s 1 and s 2 are data received from the base station prior to modulation, θ =(1+√{square root over (5)})/2, α =1+i(1− θ), and γ is an imaginary unit (i.e., i) representing a unit of imaginary number.",
    "23. A mobile station of an Orthogonal Frequency Division Multiplexing (OFDM) system, comprising: means for receiving the spatially-layered signal from a reference relay station and a cooperative relay station; and means for detecting data from a base station through Maximum Likelihood (ML) detection in which a signal having the largest ML is detected by comparing the received spatially-layered signal with a signal which is converted through a Spatially Layered transmission Mode (SLM)."
  ],
  "cpc": [
    "H04L 5/0007",
    "H04B 7/155",
    "H04B 7/15528",
    "H04L 1/0026",
    "H04L 2001/0097",
    "H04L 25/03057",
    "H04L 25/03178"
  ],
  "assignees": [
    "SAMSUNG ELECTRONICS CO LTD",
    "IND ACADEMIC COOP"
  ],
  "filing_date": "2008-04-03",
  "publication_date": "2008-10-09",
  "priority_date": "2007-04-03",
  "application_number": "US-8065008-A",
  "family_id": "39826872",
  "citations": [
    "US2005141593A1",
    "US2006276212A1",
    "US2007070953A1",
    "US2008014884A1",
    "US2008123574A1",
    "US2009047898A1",
    "US2009061767A1",
    "US2011090832A1",
    "US7606182B2",
    "US7944985B2",
    "WO2006106692A1"
  ]
}