WO2008136569A1

WO2008136569A1 - Method of signaling map in ofdma system

Info

Publication number: WO2008136569A1
Application number: PCT/KR2008/000163
Authority: WO
Inventors: Kwang-Jae Lim; Chul-Sik Yoon
Original assignee: Electronics And Telecommunications Research Institute
Priority date: 2007-05-08
Filing date: 2008-01-10
Publication date: 2008-11-13

Abstract

The present invention relates to a mobile application part (MAP) signaling method for transmitting a MAP to a user terminal from an orthogonal frequency division multiple access (OFDMA) system. In the MAP signaling method, a MAP heading for one or at least one MAP is generated, the MAP heading is transmitted, and the respective MAPs are transmitted by the MAP heading. Therefore, the amount of radio resources used to transmit the MAP may be reduced, and MAP information may be received by using the reduced number of receiving processes.

Description

Description METHOD OF SIGNALING MAP IN OFDMA SYSTEM

Technical Field

[1] The present invention relates to a mobile application part (MAP) signaling method in an orthogonal frequency division multiple access (OFDMA) system. More particularly, the present invention relates to a MAP signaling method for allocating radio resources to a mobile terminal and controlling a wireless link in an OFDMA system.

[2] This work was supported by the IT R&D program of MIC/IITA [2007-P 10-03, Development of WiBro Evolution Standards]. Background Art

[3] A transmitting apparatus in an orthogonal frequency division multiple access

(OFDMA) system performs subcarrier mapping for a symbol mapped signal by using orthogonality between subcarriers, adds a cyclic prefix to signals obtained by performing an inverse fast Fourier transform (IFFT), and transmits the signals through a transmitting antenna. In addition, a receiving apparatus in the OFDMA system eliminates the CP from the signal received through a receiving antenna, performs subcarrier demapping for signals obtained by performing a fast Fourier transform (FFT), performs detecting and decoding, and estimates a user signal.

[4] Standards for mobile communication of the OFDMA system are established in the

IEEE 802.16, and a MAP that is downlink transmitted for each frame is used to inform radio resources allocated to a mobile terminal or to transmit control information for wireless link control.

[5] FIG. 1 is a diagram representing an example of a downlink frame including a MAP in the OFDMA system. Here, the arrow on the vertical axis indicates an OFDMA symbol number, and the arrow on the horizontal axis indicates a subchannel logical number.

[6] As shown in FIG. 1, a first symbol in a downlink frame is used to transmit a preamble, and radio resources are formed by using slots.

[7] The first four slots after the preamble are used to transmit a frame control header

(FCH). In this case, the FCH informs a transmission method of a MAP transmitted after the FCH and a slot length of the MAP. In addition, the MAP allocates the radio resources in downlink and uplink frames, or the MAP includes information elements (IE) for wireless control.

[8] Further, each slot includes 48 data subcarriers, and MAP data bits are modulated and coded to the data subcarrier to be transmitted.

[9] FIG. 2 is a diagram representing subsequent slots used to transmit the FCH and the MAP. Here, an arrow of a horizontal axis indicates a logical slot number.

[10] As shown in FIG. 2, a transmission method and a length of the MAP are expressed as a logical slot in the FCH. In this case, the MAP is transmitted in a strong modulation and coding scheme so as to be received outside of the cell, and the MAP is usually 1/2 coded, quadrature phase shift keying (QPSK) modulated, and repeatedly transmitted six times.

[11] However, when control information for a user that is close to a base station is transmitted, a signal-to-interference-and-noise ratio (SINR) to the MAP of the user is relatively higher, and therefore a modulation and coding scheme having a higher frequency efficiency may be used.

[12] In addition, in the OFDMA system, to reduce the number of subchannels used to transmit the MAP, a sub-MAP transmission method for varying a modulation and coding scheme used to transmit the MAP according to user channel environments is used.

[13] FIG. 3 is a diagram representing an example of a downlink frame when a sub-MAP is used, and FIG. 4 is a diagram representing a FCH, a main MAP, and sub-MAPs in subsequent slots.

[14] As shown in FIG. 4, a sub-MAP pointer information element (IE) for informing transmission methods and MAP lengths of respective sub-MAPs is transmitted in the main MAP after the FCH, and the respective sub-MAPs defined by the sub-MAP pointer IE include control information for users.

[15] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. Disclosure of Invention Technical Problem

[16] As described above, the above sub-MAP transmission method has following problems.

[17] Firstly, to receive a sub-MAP including control information for users, it is required to perform three steps including a step for receiving the FCH to obtain the transmission method and length information of the MAP, and a step for receiving the MAP to obtain the transmission method and length information of the sub-MAP, and a step for receiving the sub-MAP.

[18] Secondly, since the length information of the sub-MAP is designated by using slots, the number of subcarriers that are not actually used in the last slot among the slots used for the sub-MAP increases. [19] For example, when the sub-MAP is transmitted by using a 16 quadrature amplitude modulation (QAM) method and a 1/2 coding method, each slot may transmit data of 96 bits. In this case, when MAP data to be transmitted in the last slot are 12 bits, the remaining 84 bits are not used, and radio resources may be wasted. Technical Solution

[20] The present invention has been made in an effort to provide a mobile application part

(MAP) signaling method for allocating radio resources to a mobile terminal and controlling a wireless link in an orthogonal frequency division multiple access (OFDMA) system. In addition, the present invention has been made in an effort to provide a MAP signaling method for transmitting a MAP with less overhead, reducing the amount of radio resources used to transmit the MAP, and using the reduced number of receiving processes to receive MAP information in an OFDMA mobile communication system.

[21] According to an exemplary embodiment of the present invention, in a MAP signaling method for transmitting a MAP to a user terminal from an OFDMA system, a MAP heading for one or at least one MAP is generated, the MAP heading is transmitted, and the respective MAPs are transmitted by the MAP heading.

[22] In the MAP signaling method, when a part of a last slot among the slots of the MAP is not used, predetermined padding bits fill the part.

[23] Here, the MAP heading includes MAP transmission methods and MAP lengths of the respective MAPs. The respective MAP transmission methods are previously defined in the OFDMA system or determined by broadcasting information, and the respective MAP lengths are formed by using sub-slots that are smaller than reference slots used to transmit data.

[24] In addition, the MAP heading includes a number of MAPs transmitted in a current frame, numbers for the transmission method used to transmit the MAP, and a number of sub-slots used to transmit the MAPs. In this case, a size of all the MAPs is an integer number of times the sub-slot.

[25] When the MAP heading is transmitted, two slots are used to transmit the MAP heading, and the MAP heading informing the transmission methods and the sub-slot lengths of the respective MAPs is transmitted from the first slot of a downlink frame.

[26] When the respective MAPs are transmitted, the respective MAPs are transmitted by the MAP transmission method designated by the MAP heading in the sub-slots designated by the MAP heading, and the respective MAPs are transmitted by different transmission methods and different transmission powers.

[27] According to another exemplary embodiment of the present invention, in a MAP signaling method for receiving a MAP by a user terminal from an OFDMA system, a MAP heading is received from the OFDMA system, information on transmission methods of the respective MAPs and MAP lengths of the respective MAPs are obtained from previously defined numbers in the MAP heading, and control information is obtained from the respective MAPs designated by the MAP heading.

Advantageous Effects

[28] According to the exemplary embodiment of the present invention, since the MAP is transmitted with less overhead in the OFDMA system, the amount of radio resources used for the MAP transmission may be reduced, and the MAP information may be received by performing reduced receiving steps.

Brief Description of the Drawings [29] FIG. 1 is a diagram representing an example of a downlink frame including a mobile application part (MAP) in a conventional orthogonal frequency division multiple access (OFDMA) system.

[30] FIG. 2 is a diagram representing subsequent slots used to transmit a MAP in the conventional OFDMA system. [31] FIG. 3 is a diagram representing an example of a downlink frame when a sub-MAP is used in the conventional OFDMA system. [32] FIG. 4 is a diagram representing subsequent slots used to transmit a sub-MAP in the conventional OFDMA system. [33] FIG. 5 is a flowchart representing a MAP signaling method in an OFDMA system according to an exemplary embodiment of the present invention. [34] FIG. 6 is a diagram representing an example of a downlink frame including a MAP transmission method in the OFDMA system according to the exemplary embodiment of the present invention. [35] FIG. 7 is a diagram representing a MAP heading to subsequent sub-slots and MAP transmission in the OFDMA system according to the exemplary embodiment of the present invention. [36] FIG. 8 is a diagram representing a detailed configuration of a MAP heading in the

OFDMA system according to the exemplary embodiment of the present invention. [37] FIG. 9 is a diagram representing lengths of the respective MAPs by using sub-slots in the MAP heading of the OFDMA system according to the exemplary embodiment of the present invention.

Mode for the Invention [38] In the following detailed description, only certain exemplary embodiments of the present invention have been shown and described, simply by way of illustration. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification.

[39] In addition, unless explicitly described to the contrary, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. The terms "unit", "module", and "block" used herein mean one unit that processes a specific function or operation, and may be implemented by hardware, software, or a combination thereof.

[40] A mobile application part (MAP) signaling method in an orthogonal frequency division multiple access (OFDMA) system according to an exemplary embodiment of the present invention will now be described with reference to FIG. 5 to FIG. 9.

[41] FIG. 5 is a flowchart representing the MAP signaling method in the OFDMA system according to the exemplary embodiment of the present invention, FIG. 6 is a diagram representing an example of a downlink frame including a MAP transmission method in the OFDMA system according to the exemplary embodiment of the present invention, FIG. 7 is a diagram representing a MAP heading to subsequent sub-slots and MAP transmission in the OFDMA system according to the exemplary embodiment of the present invention, FIG. 8 is a diagram representing a detailed configuration of the MAP heading in the OFDMA system according to the exemplary embodiment of the present invention, and FIG. 9 is a diagram representing lengths of the respective MAPs by using sub-slots in the MAP heading of the OFDMA system according to the exemplary embodiment of the present invention.

[42] In the MAP signaling method for transmitting the MAP including control information to a mobile terminal in the OFDMA system, MAP Heading information including a transmission method for one or more MAPs and subslot lengths of the respective MAPs is generated in step S501. In addition, the MAP transmission method is previously stored in the OFDMA system, or it is determined by broadcasting information.

[43] As shown in FIG. 8, the MAP Heading includes a MAP number N_MAP, a MAP transmission method number, a MAP sub-slot length, and a reserved field.

[44] The MAP number N_MAP is expressed as A bits, and designates the number of MAPs transmitted in a current frame. For example, when it is established to be A=2, the number of MAPs is shown as in Table 1. [Table 1 ]

[46] The MAP transmission method number is expressed as B bits, and indicates numbers allocated to the transmission methods used for MAP transmission. The transmission methods for the respective numbers are previously defined in the OFDMA system. A user terminal may acknowledge the transmission method of each MAP based on the previously defined number in the OFDMA system, and the transmission method of the MAP transmission method number may be defined by the broadcasting information. For example, when it is set to be B=2, a bit- width of a corresponding field is shown as in Table 2.

[47]

[Table 2]

[48] The MAP sub-slot length is expressed as C bits, and indicates the number of sub- slots used to transmit the respective MAPs. For example, when the MAP Heading is formed with 24 bits, the number of bits used in the MAP sub-slot length and the number of bits used for the reserved field are defined as shown in Table 3.

[49] [Table 3]

[50] Lengths of the respective MAPs are expressed with sub-slots that are smaller than a reference slot used for usual data transmission. For example, when the reference slot for the data transmission includes 48 data subcarriers, the sub-slot used to transmit the MAP includes 8 data subcarriers.

[51] In this case, one slot includes 6 sub-slots. When the MAP is transmitted by using the sub-slot, the number of subcarriers that are not actually used in the last sub-slot among the sub-slots used for the MAP may be reduced.

[52] The MAP Heading, as shown in FIG. 9, is transmitted by using two slots, and the transmission methods (MAP TF 0, MAP TF 1, MAP TF 3) of the respective MAPs and a sub-slot length of the MPA are informed by the MAP Heading.

[53] In this case, lengths of the respective MAPs and radio resources used by the MAP are determined based on the sub-slots. However, since the data transmission after the MAP is performed by using the slots, the size of all the MAPs is an integer number of times the slot. Accordingly, a part of the last slot among the slots of the MAP may not be used, and predetermined padding bits fill the part.

[54] Subsequently, the MAP Heading generated in step S501 is transmitted from a first slot after a preamble in a like manner of the OFDMA system in step S502. That is, the MAP Heading informing the transmission methods and the sub-slot lengths of the respective MAPs is transmitted from the first slot of a downlink frame.

[55] In addition, in the sub-slots designated by the MAP Heading generated in step S501, the MAP is transmitted by different transmission methods and different transmission powers in step S503. That is, the respective MAPs designated by the MAP Heading generated in step S501 may be transmitted by different transmission methods and different transmission powers.

[56] In this case, in step S503, in the sub-slots designated by the MAP Heading generated in step S501, the respective MAPs are transmitted by the MAP transmission method designated by the MAP Heading. In addition, the lengths of the respective MAPs designated by the MAP Heading are previously established by the sub-slots that are smaller than the reference slot used for data burst signaling. That is, the sub-slot designated by the MAP Heading generated in step S501 is previously established by the sub-carrier that is an integer number of times smaller than the reference slot for the data burst signaling.

[57] In addition, in the MAP signaling method of the OFDMA system according to the exemplary embodiment of the present invention, when a user terminal receives MAP information from the OFDMA system, the MAP Heading is firstly received from the OFDMA system to obtain information on the transmission methods and MAP lengths of the respective MAPs, and control information is obtained from the respective MAPs designated by the received MAP Heading.

[58] That is, the MAP signaling method for receiving the MAP information by a mobile terminal from the OFDMA system according to the exemplary embodiment of the present invention includes a step for obtaining the information on the transmission methods and the MAP lengths of the respective MAPs, and a step for obtaining the control information from the respective MAPs.

[59] In addition, in the MAP signaling method of the OFDMA system according to the exemplary embodiment of the present invention, various MAP transmission methods may be performed when one MAP is transmitted, or when a plurality of MAPs are transmitted by the same transmission method or different transmission powers.

[60] As described, according to the exemplary embodiment of the present invention, in a method for transmitting the MAP including the control information to the mobile terminal in the OFDMA system, the MAP Heading informing the transmission methods and the sub-slot lengths of the respective MAPs are transmitted from the first slot of the downlink frame, and the respective MAPs are transmitted by the MAP transmission method designated by the MAP Heading in the sub-slots designated by the MAP Heading. Further, according to the exemplary embodiment of the present invention, the mobile terminal receives the MAP information from the OFDMA system to obtain the transmission methods and the MAP lengths of the respective MAPs, and obtains the control information from the respective MAPs.

[61] The exemplary embodiment of the present invention that has been described above may be implemented by not only an apparatus and a method but also a program capable of realizing a function corresponding to the structure according to the exemplary embodiment of the present invention and a recording medium having the program recorded therein. It can be understood by those skilled in the art that the implementation can be easily made from the above-described exemplary embodiment of the present invention.

[62] While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

[I] A mobile application part (MAP) signaling method for transmitting a MAP to a user terminal from an orthogonal frequency division multiple access (OFDMA) system, the MAP signaling method comprising: generating a MAP heading for one or at least one MAP and transmitting the

MAP heading; and transmitting the respective MAPs by the MAP heading.

[2] The MAP signaling method of claim 1, wherein the MAP heading comprises

MAP transmission methods and MAP lengths of the respective MAPs.

[3] The MAP signaling method of claim 2, wherein the respective MAP transmission methods are previously defined in the OFDMA system or determined by broadcasting information.

[4] The MAP signaling method of claim 2, wherein the respective MAP lengths are formed by using sub-slots that are smaller than reference slots used to transmit data.

[5] The MAP signaling method of claim 1, wherein the MAP heading comprises a number of MAPs transmitted in a current frame, numbers for the transmission method used to transmit the MAP, and a number of sub-slots used to transmit the MAPs.

[6] The MAP signaling method of claim 5, wherein a size of all the MAPs is an integer number of times the sub-slot.

[7] The MAP signaling method of claim 1, wherein, when a part of a last slot among the slots of the MAP is not used, predetermined padding bits fill the part.

[8] The MAP signaling method of claim 1, wherein, in the transmitting of the MAP heading, two slots are used to transmit the MAP heading.

[9] The MAP signaling method of claim 1, wherein, in the transmitting of the MAP heading, the MAP heading informing the transmission methods and the sub-slot lengths of the respective MAPs is transmitted from the first slot of a downlink frame.

[10] The MAP signaling method of claim 9, wherein, in the transmitting the respective MAPs, the respective MAPs are transmitted by the MAP transmission method designated by the MAP heading in the sub-slots designated by the MAP heading.

[I I] The MAP signaling method of claim 1, wherein, in the transmitting of the respective MAPs, the respective MAPs are transmitted by different transmission methods and different transmission powers.

[12] A mobile application part (MAP) signaling method for receiving a MAP by a user terminal from an orthogonal frequency division multiple access (OFDMA) system, the MAP signaling method comprising: receiving a MAP heading from the OFDMA system; obtaining information on transmission methods of the respective MAPs and

MAP lengths of the respective MAPs from previously defined numbers in the

MAP heading; and obtaining control information from the respective MAPs designated by the MAP heading.