WO2006059827A1

WO2006059827A1 - Methods for managing the band adaptive modulation and coding (band amc) in portable internet system

Info

Publication number: WO2006059827A1
Application number: PCT/KR2005/001796
Authority: WO
Inventors: Yong-Seouk Choi; June-Bae Seo; Nam-Hoon Park
Original assignee: Electronics And Telecommunications Research Institute; Samsung Electronics Co., Ltd.; Kt Corporation; Sk Telecom Co., Ltd.; Ktfreetel Co., Ltd.; Hanaro Telecom, Inc.
Priority date: 2004-11-30
Filing date: 2005-06-14
Publication date: 2006-06-08
Also published as: KR100684315B1; KR20060060221A

Abstract

The present invention relates to a band adaptive modulation and coding (Band AMC) management method for use in a portable Internet system. According to an embodiment of the present invention, the Band AMC method includes; a) a terminal transmitting a response message (REP-RSP) including a Band AMC allocation request to a base station; b) inserting sub¬ channel index information in a sub-channel mode field of a downlink/uplink MAP (DL/UL MAP) when the base station set the terminal to be operated in Band AMC mode; c) the terminal receiving a radio signal including sub-channel index information from the base station; and d) the terminal operating in the Band AMC mode with reference to sub-channel index. A mobile terminal operating in the Band AMC mode can change a previously allocated sub-channel, and mobile subscriber can communicate continuously in Band AMC mode. In addition, efficiency of the Band AMC management may be increased in the portable Internet system of IEEE 802.16 standard.

Description

METHODS FOR MANAGING THE BAND ADAPTIVE MODULATION AND CODING (BAND AMC) IN PORTABLE

INTERNET SYSTEM

Technical Field

[1] The present invention relates to a band adaptive modulation and coding (herein referred to as Band AMC) management method in a portable Internet system, and more particularly relates to a Band AMC management method which would allow a change of a previously allocated sub-channel while a mobile terminal is in a Band AMC operation.

Background Art

[2] An adaptive modulation and coding (herein referred to as AMC) scheme is a data transmission scheme for increasing efficiency of whole cells by determining a data channel modulation scheme and a coding scheme according to a channel condition between a base station and a mobile station.

[3] This AMC scheme includes a plurality of modulation schemes and a plurality of coding schemes, and provides a data channel signal modulation and coding by combining the modulation schemes and the coding schemes.

[4] Generally, each combination of the modulation schemes and coding schemes is called a modulation and coding scheme (herein referred to as MCS), and a plurality of MCSs from level 1 to level N can be defined, according to the number of the MCSs.

[5] The AMC scheme adaptively determines a level of the MCS according to a channel condition between the wirelessly connected mobile station and the base station, in order to increase the efficiency of the whole system.

[6] As prior art, Korean Patent Application No. 2003-9380 (filed in Feb. 14th 2003) discloses a "Frequency band modulation relaying apparatus for mobile communication".

[7] In the prior art, when using a mobile communication service (e.g., cellular, PCS, and IMT 2000), an apparatus inserts a frequency band modulator in a relay link transmission/receiving unit of a base station, and transmits wirelessly to a long distance shadow area, so that a frequency band may be used efficiently.

[8] In the prior art, since the whole cellular or PCS frequency band is modulated into a relatively far separated IMT-2000 frequency band and regenerates therein, it is possible for simultaneous calling to occur, thereby reducing congestion during calling. This may result in more subscribers being admitted.

[9] Another prior art document, Korean Patent Application No. 2002-66109 (filed Oct. 29th 2002) discloses a "Method for wireless data transmission speed changing process in mobile communication system."

[10] The prior art discloses a wireless data transmission speed changing and processing method for improving a data transmission performance of the mobile communication system by minimizing a data transmission holding time, when, in the mobile communication system, the data transmission speed is changed due to the variation of wireless channel condition between the mobile terminal and the base station.

[11] More particularly, according to such prior art, the data transmission speed may be changed into a high speed mode or a low speed mode according to a variation of the wireless channel condition. Accordingly, a suspension point of data transmission may differ and a suspension period for changing the data transmission speed may be minimized. Therefore, a data transmission performance of the mobile communication system may be improved, and an unnecessary waste of wireless resources may be minimized

[12] As another prior art, Korean Patent Application No. 2003-1732 (filed in Jan. 10th

2003) "Apparatus and method for data transmission speed control in mobile communication system" is disclosed.

[13] According to this prior art, in a mobile communication system, when transmitting data backward, a terminal manages a backward data transmission rate by applying a common bit for entire terminals and an additional bit for each terminal. Accordingly, in controlling the backward data transmission speed, the prior art provides advantages of increasing capacity and minimizing interference caused by a forward data transmission.

[14] A target service in the portable Internet system is allowing the Internet to be used freely while guaranteeing mobility without restriction of time and space. A conventional mobile communication network is mainly for voice, whereas the portable Internet system is mainly for data service.

[15] In the portable Internet system, data transmission speed is an important factor of the data service. Accordingly, there is an effort to develop solutions to increase a data transmission speed.

[16] In addition, efforts are underway to develop systems which overcome the limits of wireless resources.

[17] In the portable Internet, to increase the data transmission speed, a Band AMC method is used. According to the Band AMC method, a channel of good condition or bad condition is determined which refers to the condition of each sub-channel, and within the limit of the resource, the sub-channels are respectively allocated to each terminal.

[18] When such a Band AMC method is applied, a terminal having the resources including the channels in good condition is modulated to contain a higher capacity, and therefore a high speed data transmission becomes possible.

[19] In addition, according to the Band AMC method, an access terminal (herein referred to as AT) measures channel quality information (herein referred to as CQI), collects channel information of sub-channel being used, and based thereon, uses the band including the sub-channels that are determined to be in good condition. Therefore, the terminal is less influenced by the noise and interference of surroundings. Accordingly, the terminal to which the Band AMC is applied can increase a coding rate, and can transmit in at a relatively high speed.

[20] In a portable Internet based on IEEE 802.16, when the terminal is operating in diversity mode (diversity sub-channel scheme), which is a typical wireless state when a predetermined condition is satisfied, a terminal may be switched to the Band AMC mode.

[21] During initial operation, the terminal operates in the diversity mode. Then the access terminal (AT) measures CQI, and collects channel information of the subchannel currently being used. Thereafter, the condition of each sub-channel may be detected through the collected channel information, and a sub-channel of relatively good condition may be selected from the detected sub-channels.

[22] For Band AMC management in the portable Internet described above, when a terminal operating in the diversity mode shifts to the Band AMC mode, the base station is requested to select the sub-channels in the best condition.

[23] The base station transmits an acknowledgment message (herein referred to as Ack) allowing the above-noted request to the terminal according to a predetermined rule (e.g., a resource management rule), and then the terminal operates in Band AMC mode.

[24] More particularly, the terminal requests the base station which is an access point

(AP) to communicate through the sub-channel which is selected based on the CQI.

[25] The AP (base station) which received such a request informs the terminal whether the request will be allowed or not by considering an allocation of channel resources.

[26] When the base station allows the request for the Band AMC operation of the terminal, beginning with a frame thereafter, they communicate with each other only with the sub-channel selected based on the CQI.

[27] When the Band AMC method is adopted, the band including sub-channels of good quality is used for communication. The quality of the sub-channel is better than the quality of the sub-channels used in the diversity mode. Therefore, the communication performs strongly with the respect to the noise and the interference of neighbor cells. Moreover, a coding rate may be increased, so that the transmission speed may become higher. [28] Since the Band AMC is used in the portable Internet, a transmission speed may be increased compared to the conventional diversity sub-channel scheme. However, the terminal has mobility, and the condition of the sub-channel may change every moment. Accordingly, the terminal already operating in the Band AMC mode needs to change the sub-channel into a new one formed by the method of Band AMC.

[29] Therefore, the terminal includes the sub-channel which has improved in quality, and omits the sub-channel for which the quality has become worse according to subchannel information collected through the CQI. By this manner, the terminal reforms the sub-channels for the Band AMC.

[30] Then, the terminal needs to request a new Band AMC formed by the newly selected sub-channel to the base station, in order to communicate only through the reselected sub-channel.

[31] However, an appropriate operation for such a case is not described in the IEEE

802.16 standard that is currently a standard for the portable Internet.

[32] In other words, when the terminal which is already operating in Band AMC mode requests the change of the sub-channel, there are no means for transmitting a response for the request to the terminal.

[33] The information disclosed in this Background Art section is only for enhancement of understanding of the background art, and therefore, unless explicitly described to the contrary, it should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known in this country to a person of ordinary skill in the art. Disclosure of Invention

Technical Problem

[34] The present invention has been made in an effort to provide a band adaptive modulation and coding (Band AMC) management method in a portable Internet system. This method is advantageous because it allows a change of a previously allocated sub-channel while a mobile terminal is in a Band AMC operation in a portable Internet system.

[35] In a portable Internet based on IEEE 802.16, a terminal is operating in a diversity mode (diversity sub-channel scheme) which is a typical wireless state. After a predetermined condition is satisfied, a terminal begins to operate in a Band AMC mode. Technical Solution

[36] In an exemplary band adaptive modulation and coding management method for a terminal in a portable Internet system, according to an embodiment of the present invention, the method includes steps a), b), c), and d).

[37] In step a), the terminal transmits a response message (herein referred to as REP- RSP) including a Band AMC allocation request to a base station.

[38] In step b), sub-channel index information for a Band AMC is inserted in a subchannel mode field of a downlink/uplink MAP (herein referred to as DL/UL MAP) when the base station sets the terminal to be operated in Band AMC mode.

[39] In step c), the terminal receives a radio signal (herein referred to as RF) including sub-channel index information for the Band AMC from the base station.

[40] In step d), the terminal operates in the Band AMC mode with reference to subchannel index information of the DL/UL MAP.

[41] In another embodiment, the method further includes step e).

[42] In step e), the terminal confirms an acknowledgment of the base through subchannel index information of the DL/UL MAP when the terminal changes a previously allocated sub-channel while Band AMC operation.

[43] In a further embodiment, step d) further includes checking an accordance of subchannel indexes for the Band AMC between the base station and the terminal every frame through sub-channel index information of the DL/UL MAP.

[44] In another exemplary band adaptive modulation and coding management method according to an embodiment of the present invention, the method includes steps a), b), and c).

[45] In step a), the terminal in a Band AMC operation transmits a channel quality value and a sub-channel index for the Band AMC together with channel quality information (CQI) to be transmitted to a base station.

[46] In step b), the base station checks which sub-channel the channel quality value transmitted by the terminal through an uplink belongs to.

[47] In step c), the sub-channel indexes for the Band AMC between the base station and the terminal is accorded according to the checking result in step b).

[48] In another embodiment, the a) is performed in every frame.

[49] In a further exemplary band adaptive modulation and coding management method according to an embodiment of the present invention, the method includes steps a), b), and c).

[50] In step a), the terminal already in a Band AMC operation generates a Band AMC request message (herein referred to as BAMC-REQ) for the Band AMC management.

[51] In step b), the terminal requests the Band AMC at the base station by using the

Band AMC request message (BAMC-REQ).

[52] In the c), the base station transmits a Band AMC response message (herein referred to as BAMC-RSP) to the terminal as a response for the Band AMC request message (BAMC-REQ).

[53] In another embodiment, the Band AMC request message (BAMC-REQ) is a medium access control (herein referred to as MAC) management message exclusively for the Band AMC. [54] In a further embodiment, step a) further includes requesting the Band AMC by using the Band AMC request message (BAMC-REQ) when the terminal already in the

Band AMC mode needs to change the a sub-channel for the Band AMC. [55] In a still further embodiment, step c) further includes according the sub-channel indexes for the Band AMC between the base station and the terminal according to the

Band AMC response message (BAMC-RSP) transmitted by the base station. [56] In a still further embodiment, the Band AMC request message (BAMC-REQ) and the Band AMC response message (BAMC-RSP) are transmitted in a unicast transmission scheme.

Advantageous Effects

[57] According an embodiment of the present invention, the mobile terminal is able to change a previously allocated sub-channel to a new one even in the Band AMC operation, and accordingly the Band AMC mode operation can be continuously provided to a mobile subscriber. Additionally, in the portable Internet system of IEEE 802.16, an efficiency of the Band AMC management may be increased, and the problem which occurs during changing the sub-channel for the Band AMC may be solved even using the conventional standard. Brief Description of the Drawings

[58] FIG. 1 is a schematic diagram of a Band AMC management apparatus.

[59] FIG. 2 is a flowchart of a Band AMC operation.

[60] FIG. 3 is a flowchart of a Band AMC operation when a sub-channel mode and a sub-channel index in a DL/UL MAP is included according to an embodiment of the present invention.

[61] FIG. 4 is a flowchart of a Band AMC operation when a sub-channel index in channel quality information (CQI) is included according to an embodiment of the present invention.

[62] FIG. 5 is a flowchart of a Band AMC operation by a new medium access control

(MAC) message according to an embodiment of the present invention. Best Mode for Carrying Out the Invention

[63] In the following detailed description, exemplary embodiments of the present invention are shown and described, by way of illustration. As those skilled in the art would recognize, the described exemplary embodiments may be modified in various 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, rather than restrictive.

[64] In the drawings, illustrations of elements having no relation with the present invention are omitted in order to more clearly present the subject matter of the present invention. In the specification, the same or similar elements are denoted by the same reference numerals even though they are depicted in different drawings. An embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings.

[65] FIG. 1 is a schematic diagram of an apparatus for Band AMC management; the apparatus includes a RF processor 110, a modulator/demodulator 120, a channel quality information (CQI) processor 130, and a central controller 140.

[66] Referring to FIG. 1, the central controller 140 is a main control board controlling various functions of a terminal. The central controller 140 performs a function of general control for Band AMC of the terminal.

[67] The modulator/demodulator 120 modulates a signal and demodulates a received signal, and receives conditional information (e.g., coding rate) necessary for a modulation/demodulation in the Band AMC operation from the central controller 140.

[68] The modulator/demodulator 120 performs a modulation/demodulation based on conditional information.

[69] The RF processor 110 wirelessly transmits modulated data, or receives a radio signal transmitted from the base station and relays it to the modulator/demodulator 120.

[70] The CQI processor 130 measures and manages a carrier-to-interference-plus-noise ratio (herein referred to as CINR) based on the radio signal received by the RF processor 110, and relays the CINR information to the central controller 140. The central controller 140 manages the Band AMC based on the respective CINR of each sub-channel.

[71] According to an embodiment of the present invention, using the Band AMC management apparatus shown in FIG. 1, the Band AMC for according sub-channel indexes of the terminal and the base station can be managed by 1) inserting a subchannel mode and a sub-channel index in a DL/UL MAP, 2) inserting the sub-channel index in CQI, or 3) using an exclusive medium access control (MAC) management message for the Band AMC management.

[72] As to the scheme for inserting a sub-channel mode and a sub-channel index in the

DL/UL MAP, when a previously allocated sub-channel is changed based on subchannel index information in the DL/UL MAP of each frame during a Band AMC operation, an acknowledgment (Ack) of the base station may be checked through the sub-channel index information in the DL/UL MAP. Accordingly, both sub-channel indexes of the base station and the terminal for the Band AMC may always be matched to each other.

[73] As to the scheme for inserting the sub-channel index in CQI information, the terminal transmits the CQI including channel quality values for the Band AMC together with the sub-channel index to the base station, and the base station may recognize which sub-channel the transmitted CQI belongs to. Therefore both the subchannel indexes of the base station and the terminal for the Band AMC may always be matched to each other.

[74] As to the scheme for using an exclusive medium access control (MAC) management message for the Band AMC management, a dedicated message for the Band AMC is used instead of inserting information on the Band AMC in a conventional REP-RSP used for relaying channel information. Such a dedicated message may be transmitted not by a broadcasting scheme through the convention DL/UL MAP but by a unicasting scheme, so that resources may be saved. In addition, when the subchannel needs to be changed while maintaining the Band AMC operation in the terminal which is presently operated in the Band AMC mode, the exclusive MAC management message may be used, so that the both sub-channel indexes of the base station and the terminal for the Band AMC may be matched to each other.

[75] Therefore, according to an embodiment of the present invention, the sub-channels of good quality may be selected by checking the quality of sub-channels, and accordingly a data rate may be controlled, so that real-time variation of the data rate may be possible. Additionally, a real-time variation of the sub-channel may be possible by selecting the good-quality sub-channel to increase a coding rate, and the variation of a transmission speed is possible by changing the sub-channel.

[76] FIG. 2 is a flowchart of a Band AMC operation according to an embodiment of the present invention. Referring to the configuration of the apparatus for the Band AMC shown in FIG. 1, processes for the Band AMC will be hereinafter described in detail.

[77] Referring to FIG. 2, a terminal is operated in a diversity mode (i.e., a default mode) in step S201. In the beginning of operation, the terminal can only operate in the diversity mode because the terminal has not been informed of a condition of a subchannel.

[78] An uplink channel description (herein referred to as UCD) is received from the base station in step S202. In this step, the base station may transmit a MAC management message including system information (e.g., downlink map information (herein referred to as DL-MAP), uplink map information (herein referred to as UL-MAP), and downlink channel description/uplink channel description (herein referred to as DCD/ UCD signal) to the entire cell area by the broadcasting scheme, in order to relay system information of the portable Internet system to the terminals in the entire cell area.

[79] A field value related to the Band AMC is obtained from the UCD in step S203. In detail, the central controller 140 of the terminal, which has received the MAC management message including system information from the base station terminal, extracts information for the Band AMC from the MAC management message (in this case, from the UCD), and establishes the extracted information to be a reference for the Band AMC operation. Here, a threshold value and a timer value for a Band AMC allocation may be the reference for the Band AMC operation.

[80] The CQI processor of the terminal collects the respective CINR for each band in every frame in step S204. In detail, the central controller 140 controls the CQI processor 130 to start operating, and the CQI processor 130 measures then a signal intensity of a radio signal to be input to the RF processor 110, and calculates the CINR through a predetermined calculation process. Thereafter, the CQI processor 130 relays the measured and calculated CINR to the central controller 140.

[81] The respective CINR' s of twelve bands are compared with the allocation threshold value and the allocation timer value of the UCD in step S205. In other words, the central controller 140 checks correspondence between the relayed CINR and the reference for the Band AMC operation. Here, the threshold value and the timer value for the Band AMC allocation are used for checking the correspondence.

[82] The terminal determines whether the compared CINR accords with the reference for the Band AMC operation in step S206. The process returns to the step S203 when the CINR does not satisfy the reference for the Band AMC operation, whereas the terminal transmits the REP-RSP message to the base station in order to request a Band- AMC allocation in step S207 when the CINR satisfies the reference.

[83] In detail, when the CINR of the sub-channel is maintained to be greater than the threshold value for a while and the maintaining duration thereof is greater than the timer value, the sub-channel may be used for the Band AMC.

[84] The above-described process is operated every frame in the portable Internet system

(e.g., every 5 msec). When the number of sub-channels satisfying the reference becomes five or more than that, the terminal requests the Band AMC from the base station. Here, in requesting the Band AMC, the MAC management message, which is the response message (REP-RSP), is used. The REP-RSP message includes five subchannels for Band AMC and CQI thereof, and is transmitted to the base station.

[85] The modulator/demodulator of the terminal accesses a MAP decoding result, checks a sub-channel allocation result in step S208, and determines whether the allocation result satisfies a predetermined condition in step S209.

[86] When the predetermined condition is not satisfied, the Band- AMC is not allowed in step S210, the process then returns to the step S205, and the CINR is compared again. When the predetermined condition is satisfied, the B and- AMC mode is allowed and the terminal is operated therein in step S211, and returns to the step S208. In detail, the base station receiving the Band AMC request determines whether to allow while considering resource management. The result determined by the base station is included in DL/UL MAP included in the next frame. For example, the Band AMC request of the terminal is allowed when a sub-channel mode on the MAP is set to be the Band AMC, otherwise the request is denied when the sub-channel mode is continuously diversity mode.

[87] The terminal is continuously operated in the diversity mode when the request of the terminal is denied, otherwise a communication between the terminal and the base station is performed in the Band AMC mode when the request is allowed.

[88] Thus, in the Band AMC mode, signaling and traffic communication between the base station and the terminal is performed through the sub-channel allocated for the Band AMC. On and after the Band AMC operation, the terminal transmits CQI of the sub-channel to the base station during every frame, and the base station is informed of the state of the sub-channel during every frame through the CQI.

[89] On the other hand, in the portable Internet system, a terminal has mobility, and particularly needs to support a speed of at least 60 km/h. In such a mobile situation, surroundings of radio channels are changed greatly moment by moment, and accordingly, a radio channel state is changed every moment. As a result, such a variation of radio channel situation affects the terminal and the base station which are operated in the Band AMC mode.

[90] Referring to FIG. 1, the central controller 140 checks the sub-channel in the best condition with reference to the CQI relayed from the CQI processor 130 in every frame. When the previously allocated sub-channels are not of the best condition, the terminal requests a change of sub-channel to the base station through the REP-RSP message \ according to the above checking result.

[91] In this case, the base station requested to change sub-channels needs to reply to the terminal, but it is not impossible by the conventional method.

[92] In detail, according to the conventional method, the base station responds to the terminal through a sub-channel mode field on the DL/UL MAP. Here, when the Band AMC is allowed, the sub-channel mode field is changed from diversity to Band AMC, and when the sub-channel mode field is changed from diversity to Band AMC, the terminal operating in the diversity mode determines this change as an acknowledgment (Ack) for the Band AMC request. However, when the terminal has been already operating in the Band AMC mode, the response is received from the base station with the sub-channel mode field on DL/UL MAP already set to be Band AMC. Therefore, problems may occur when the response is determined as the acknowledgment (Ack).

[93] In addition, even when the base station does not receive the response message

(REP-RSP) for requesting a new allocation of the sub-channel of good quality, the communication is performed with the sub-channel mode on the DL/UL MAP continuously set to be the Band AMC mode including previous values. [94] When the terminal determines this as a response to the request for a new channel allocation, on and after the present frame, CQI to be transmitted to the base station by the CQI processor 130 will be the CQI of newly allocated sub-channel. Accordingly, the respective sub-channel indexes of the terminal and the base station may not be matched each other.

[95] Consequently, a discordance of the sub-channel indexes between the terminal and the base station may causes a mis-selection of the sub-channel, and the CQI transmitted by the terminal may become useless. In other words, in CQI transmitted by the terminal, a channel quality value is included therein, but channel index information indicating to which sub-channel the CQI belongs is not included therein.

[96] According to the portable Internet standard IEEE 802.16, the conventional method can be applied to the change from the diversity mode to Band AMC mode, but a process for changing the sub-channel in case of already operating in Band AMC mode is not defined therein, therefore the sub-channel index allocated for the Band AMC between the terminal and the base station may be discordant.

[97] Referring to FIG. 3 to FIG. 5, a Band AMC management method according to an embodiment of the present invention will be described. As shown in FIG. 3 to FIG. 5, broadly three types of Band AMC operation can be performed.

[98] FIG. 3 is a flowchart of a Band AMC operation in case of inserting a sub-channel mode and a sub-channel index in a DL/UL MAP according to an embodiment of the present invention.

[99] Referring to FIG. 3, a terminal 310 transmits the response message (REP-RSP) to a base station 320 in step S310, and the base station 320 transmits the DL/UL MAP to the terminal 310 in step S320. A Band AMC management (i.e., Band AMC operation) may be started with reference to the sub-channel mode field and sub-channel index of the DL/UL MAP in step S330. In other words, the Band AMC management is performed by inserting the sub-channel index information in the sub-channel mode field of the DL/UL MAP.

[100] By using this method, during the Band AMC operation, the terminal 310 may change the previously allocated sub-channel referring to sub-channel index information of the DL/UL MAP in every frame, and may confirm the acknowledgment (Ack) of the base station 320 through sub-channel index information of the DL/UL MAP. Therefore the sub-channel indexes for the Band AMC of the base station 320 and the terminal 310 can be accorded.

[101] FIG. 4 is a flowchart of a Band AMC operation in case of inserting a sub-channel index in channel quality information (CQI) according to an embodiment of the present invention.

[102] Referring to FIG. 4, a terminal 310 starts the Band AMC operation in step S410, and transmits the CQI during every frame in steps S421, S422, and S423. The CQI includes the channel quality value and the sub-channel index.

[103] In detail, the CQI to be transmitted to the base station 320 by the terminal 310 includes the channel quality value and the sub-channel index for the Band AMC together. By this manner, the base station 320 may be informed which sub-channel the CQI transmitted by terminal 310 belongs to, accordingly the sub-channel indexes for the Band AMC of the base station 320 and the terminal 310 can be accorded.

[104] FIG. 5 is a flowchart of a Band AMC operation for using a new medium access control (MAC) message according to an embodiment of the present invention.

[105] Referring to FIG. 5, a terminal 310 is already in the Band AMC operation in step

S510. The terminal 310 transmits a Band- AMC request message (BAMC-REQ) to the base station 320 in step S520. Afterward, when the sub-channel for the Band AMC is changed, the base station 320 transmits a Band- AMC response message (BAMC-RSP) to the terminal 310 in step S530.

[106] In detail, in the step S520, an exclusive MAC management message for the Band

AMC management is generated. The exclusive message for the Band AMC is used instead of inserting information about the Band AMC in the conventional response message (REP-RSP) used for relaying channel information.

[107] The terminal 310 requests the Band AMC to the base station 320 through the Band-

AMC request message (BAMC-REQ), and the base station 320 responds through the Band-AMC response message (BAMC-RSP). Such an exclusive message may be transmitted not by a broadcasting scheme through the convention DL/UL MAP, but by a unicasting scheme, so that resources may be saved. When the terminal 310 which is presently operating in the Band AMC mode needs to change the sub-channel while maintaining the Band AMC mode, it requests a change of the sub-channel through the Band AMC request message (BAMC-REQ) again, and receives the Band AMC response message (BAMC-RSP) for a response. Therefore, the sub-channel indexes for the Band AMC of the base station 320 and the terminal 310 can be accorded.

[108] Consequently, according to an embodiment of the present invention, in the conventional portable Internet standard IEEE 802.16, a problem which occurs while a mobile terminal is in the Band AMC operation may be solved. In detail, when the subchannel used for the Band AMC needs to be changed while maintaining the Band AMC mode, it may be accomplished by means of detecting each band, calculating a quality of each sub-channel, and selecting the sub-channel of good quality according thereto, a coding rate may be increased, a transmission speed may be also increased, and additionally a data transmission rate can be changed without a suspension of transmission in the case of changing transmission speed.

[109] According to an embodiment of the present invention, in the mobile portable Internet system, when the sub-channel mode is changed from the diversity mode to the Band AMC mode, a sub-channel index allocated for the Band AMC is changed moment by moment. In this case, the mobile terminal is able to change previously allocated sub-channel to a new one even when it is operating in the Band AMC mode, and accordingly the Band AMC mode operation can be continuously provided to a mobile subscriber. Additionally, in the portable Internet system of IEEE 802.16, the efficiency of the

Band AMC management may be increased, and the problem which occurs during changing the sub-channel for the Band AMC may be solved even in the conventional standard IEEE 802.16. 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

[1] A band adaptive modulation and coding management method for a terminal in a portable Internet system comprising; a) transmitting a response message (REP-RSP) from the terminal comprising a Band AMC allocation request to a base station; b) inserting sub-channel index information for a Band AMC in a sub-channel mode field of a downlink/uplink MAP (DL/UL MAP) when the base station sets the terminal to be operated in a Band AMC mode; c) receiving a radio frequency signal (RF) at the terminal comprising the subchannel index information for the Band AMC from the base station; and d) operating the terminal in the Band AMC mode with reference to the subchannel index information of the DL/UL MAP.

[2] The management method of claim 1, wherein the method further comprises, e) checking an acknowledgment of the base station through the sub-channel index information of the DL/UL MAP when the terminal changes a previously allocated sub-channel during a Band AMC operation.

[3] The management method of claim 1, wherein step d) further comprises, in every frame, checking an accordance of sub-channel indexes for the Band AMC between the base station and the terminal through the sub-channel index information of the DL/UL MAP.

[4] A band adaptive modulation and coding management method for a terminal in a portable Internet system comprising; a) transmitting from the terminal in a Band AMC operation a channel quality value and a sub-channel index for the Band AMC together with channel quality information (CQI) to a base station; b) checking with the base station which sub-channel the channel quality value transmitted by the terminal through an uplink belongs to; and c) according the sub-channel indexes for the Band AMC between the base station and the terminal according to the checking result in b).

[5] The management method of claim 4, wherein step a) is performed every frame.

[6] A band adaptive modulation and coding management method for a terminal in a portable Internet system comprising; a) generating at the terminal in a Band AMC operation, a Band AMC request message (BAMC-REQ) for the Band AMC management; b) requesting the Band AMC from the base station by using the Band AMC request message (BAMC-REQ); and c) transmitting a Band AMC response message (BAMC-RSP) from the base station to the terminal as a response for the Band AMC request message

(BAMC-REQ). [7] The management method of claim 6, wherein the Band AMC request message

(BAMC-REQ) is a medium access control (MAC) management message dedicated for the Band AMC. [8] The management method of claim 6, wherein step a) comprises requesting the

Band AMC by using the Band AMC request message (BAMC-REQ) when the terminal in the Band AMC mode needs to change the sub-channel for the Band

AMC. [9] The management method of claim 6, wherein, step c) comprises according the sub-channel indexes for the Band AMC between the base station and the terminal according to the Band AMC response message (BAMC-RSP) transmitted by the base station. [10] The management method of claim 6, wherein the Band AMC request message

(BAMC-REQ) and the Band AMC response message (BAMC-RSP) are transmitted in a unicast transmission scheme.