Radio communication system and radio communication method

• US 20060250935A1
• Filed: 02/27/2004
• Published: 11/09/2006
• Est. Priority Date: 02/28/2003
• Status: Active Grant

• Current Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Original Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Inventors: Otsu, Toru, Hamamoto, Kozue, Yoshino, Hitoshi
• Granted Patent: US 7,889,632 B2
• Time in Patent Office: Days
• US Class Current: 370/203
• CPC Class Codes: H04L 25/0222 Estimation of channel variability, e.g. coherence bandwidth, coherence time, fading frequency
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0032 Distributed allocation, i.e. involving a plurality of allocating devices, each making partial allocation
• CPC Class Codes: H04L 5/0035 Resource allocation in a cooperative multipoint environment
• CPC Class Codes: H04L 5/0039 Frequency-contiguous, i.e. with no allocation of frequencies for one user or terminal between the frequencies allocated to another
• CPC Class Codes: H04L 5/0044 allocation of payload
• CPC Class Codes: H04L 5/0064 Rate requirement of the data, e.g. scalable bandwidth, data priority

Abstract

A radio communication system for carrying out communications between radio stations by modulating a plurality of signal sequences to be transmitted and received into at least one frequency channel assigned to each of a plurality of cells is formed by a channel mapping means for rearranging for each cell a plurality of frequency channels assigned with respect to each cell, and newly assigning particular frequency channels as a transmission and reception band of said signal sequences, and a bandwidth control means for controlling a bandwidth of said assigned frequency channel according to a propagation state of said assigned frequency channel.

Claims

1. A radio communication system for carrying out communications between radio stations by modulating a plurality of signal sequences to be transmitted and received into at least one frequency channel assigned to each of a plurality of cells, a radio communication system characterized by having

a channel mapping means for rearranging for each cell a plurality of frequency channels assigned with respect to each cell, and newly assigning particular frequency channels as a transmission and reception band of said signal sequences, and

a bandwidth control means for controlling a bandwidth of said assigned frequency channel according to a propagation state of said assigned frequency channel.

2. The radio communication system as described in claim 1, characterized in that

said channel mapping means is a means for carrying out communications between radio stations through the frequency channel assigned to each of a plurality of areas, and has

a channel mapping circuit for carrying out rearrangement of assignment of said frequency channels, and assigning particular continuous frequency channels of a system band for each of said areas, and

a converter for converting the frequency channels rearranged by said channel mapping circuit into sub-carriers by orthogonal multiplexing.

3. The radio communication system as described in claim 1, characterized in that

said bandwidth-control means is a means for converting information data sequences into a plurality of channels, and transmitting and receiving a signal sequence of each of these plurality of channels by a plurality of orthogonalized sub-carrier signals, and has

a fading estimation means for estimating a propagation route of said sub-carrier signals, and

a sub-carrier bandwidth control means for controlling a bandwidth of said sub-carrier signals to be transmitted and received, according to a fading information estimated by said fading estimation means.

4. A radio communication system for carrying out communications between radio stations through frequency channels assigned to each of a plurality of areas, a radio communication system characterized by having

a channel mapping circuit for carrying out rearrangement of assignment of said frequency channels, and assigning particular continuous frequency channels of a system band for each of said areas, and

a converter for converting the frequency channels rearranged by said channel mapping circuit into sub-carriers by orthogonal multiplexing.

5. The radio communication system as described in claim 4, characterized in that

it has a table memory device for storing a search table indicating a using state of frequency channels used in nearby areas, and

said channel mapping circuit acquires said search table and carries out a search of a vacant channel, and rearranges the frequency channels according to this search result and assigns continuous channels with respect to identical cell.

6. The radio communication system as described in claim 4, characterized by having a channel selection device for generating unused frequency channels by repeating rearrangement by said channel mapping circuit and the orthogonal multiplexing by said converter, and assigning new channels to generated unused frequency channels.

7. The radio communication system as described in claim 4, characterized in that

this radio communication system has a hierarchical cell structure formed by a macro-cell and micro-cells contained in this macro-cell, and in a case where these macro-cell and micro-cells use an identical frequency band, it has

means for shifting a partition which is a boundary between a frequency channel band of the macro-cell and a frequency channel band of the micro-cells, and

means for concentrating vacant channels before and after the partition by carrying out rearrangement of the frequency channels by searching vacant channels, using a shifted partition as a reference.

8. The radio communication system as described in claim 7, characterized in that said shifting of the partition is carried out by giving a priority level for each frequency channel according to a traffic state in said macro-cell and micro-cells, and rearranging the frequency channels according to this priority level.

9. The radio communication system as described in claim 4, characterized in that a transmission scheme used by this radio communication system is a scheme for spreading said information symbol in a plurality of time regions or frequency regions, according to a spread code assigned to a terminal of a receiving side, and making a rate of the spread code with respect to said information symbol rate variable.

10. In a signal transmission system for converting information data sequences into a plurality of channels, and transmitting and receiving a signal sequence of each of these plurality of channels by a plurality of orthogonalized sub-carrier signals, a radio communication system characterized by having

a fading estimation means for estimating a propagation route of said sub-carrier signals, and

a sub-carrier bandwidth control means for controlling a bandwidth of said sub-carrier signals to be transmitted and received, according to a fading information estimated by said fading estimation means.

11. The radio communication system as described in claim 10, characterized by having a required number of sub-carriers control unit for calculating a required number of sub-carriers that can be assigned to a user, according to a sub-carrier bandwidth controlled by said sub-carrier bandwidth control means, and branching a number of said plurality of sub-carriers to be transmitted and received into the required number of sub-carriers.

12. The signal transmission system as described in claim 11, characterized in that said required number of sub-carriers control unit has a function for calculating a total bandwidth to be assigned to this user from a required information bit transmission speed of the user, and calculating the required number of sub-carriers from said total bandwidth and an optimum sub-carrier bandwidth information calculated by said sub-carrier bandwidth control unit.

13. The radio communication system as described in claim 10, characterized in that said fading estimation means generates a fading time variation information and a delay distortion information in a radio wave propagation path, according to a waveform of received signals, and estimates said propagation route according to these information.

14. The radio communication system as described in claim 10, characterized by having

a signal composition unit for transmitting the fading information estimated by said fading estimation means by multiplexing it with a user data information, and

a signal separation unit for separating said fading information from a received data matrix.

15. The radio communication system as described in claim 10, characterized by having

a means for detecting a sub-carrier bandwidth information according to said fading information,

a clock control means for calculating a clock frequency from the detected sub-carrier bandwidth information,

a means for converting a frequency generated by a clock oscillator into the clock frequency calculated by said clock control unit, and carrying out serial to parallel conversion at the clock frequency according to this sub-carrier frequency, and

a channel selection means for selecting a desired channel from a single or plurality of sub-carrier channels after an inverse discrete Fourier transform.

16. The radio communication system as described in claim 10, characterized in that a transmission scheme used by this signal transmission system is a scheme for spreading said information symbol in a plurality of time regions or frequency regions, according to a spread code assigned to a terminal of a receiving side, and making a rate of the spread code with respect to said information symbol rate variable.

17. A radio communication method for carrying out communications between radio stations by modulating a plurality of signal sequences to be transmitted and received into at least one frequency channel assigned to each of a plurality of cells, a radio communication method characterized by having

(a) a step for rearranging for each cell a plurality of frequency channels assigned with respect to each cell, and newly assigning particular frequency channels as a transmission and reception band of said signal sequences, and

(b) a step for controlling a bandwidth of said assigned frequency channel according to a propagation state of said assigned frequency channel.

18. The radio communication method characterized in that

said step (a) is a step for carrying out communications between radio stations through the frequency channel assigned to each of a plurality of areas, and has

(a1) a step for carrying out rearrangement of assignment of said frequency channels, and assigning particular continuous frequency channels of a system band for each of said areas, and

(a2) a step for converting the frequency channels rearranged by said channel mapping circuit into sub-carriers by orthogonal multiplexing.

19. The radio communication method characterized in that

said step (b) is a step for converting information data sequences into a plurality of channels, and transmitting and receiving a signal sequence of each of these plurality of channels by a plurality of orthogonalized sub-carrier signals, and has

(b1) a step for estimating a propagation route of said sub-carrier signals, and

(b2) a step for controlling a bandwidth of said sub-carrier signals to be transmitted and received, according to a fading information estimated by said step (b1).

20. A radio communication method for carrying out communications between radio stations through frequency channels assigned to each of a plurality of areas, a radio communication method characterized by having

(a1) a step for carrying out rearrangement of assignment of said frequency channels, and assigning particular continuous frequency channels of a system band for each of said areas, and

(a2) a step for converting the frequency channels rearranged by said channel mapping circuit into sub-carriers by orthogonal multiplexing.

21. The radio communication method as described in claim 20, characterized in that the rearrangement of channels by said step (a1) is carried out with respect to parallel output signal sequences of an identical symbol rate.

22. The radio communication method as described in claim 20, characterized in that the rearrangement of channels by said step (a1) is carried out with respect to parallel transmission baseband signal sequences corresponding to a plurality of users.

23. In a signal transmission method for converting information data sequences into a plurality of channels, and transmitting and receiving a signal sequence of each of these plurality of channels by a plurality of orthogonalized sub-carrier signals, a radio communication method characterized by having

(b1) a step for estimating a propagation route of said sub-carrier signals, and

(b2) a step for controlling a bandwidth of said sub-carrier signals to be transmitted and received, according to a fading information estimated by said step (b1).

24. The radio communication method as described in claim 23, characterized by making a setting regarding an optimum sub-carrier bandwidth, a required number of sub-carriers, and a guard interval according to said fading information, at a time of communication start.

25. The radio communication method as described in claim 23, characterized by making a setting of a guard interval length according to said fading information, periodically at a prescribed time interval determined in advance.

26. The radio communication method as described in claim 23, characterized by making a setting of a guard interval length according to said fading information, in a case where an optimum sub-carrier bandwidth, a required number of sub-carriers, a guard interval, or a signal error rate becomes less than or equal to a certain reference.