WO2006104371A1

WO2006104371A1 - Method and system for allocating adaptive modulation and coding subchannel for use in portable internet network

Info

Publication number: WO2006104371A1
Application number: PCT/KR2006/001223
Authority: WO
Inventors: Hongseo Ha; Daeyong Lim
Original assignee: Sk Telecom Co., Ltd.
Priority date: 2005-04-01
Filing date: 2006-04-03
Publication date: 2006-10-05
Also published as: KR100816441B1; KR20060105187A

Abstract

Disclosed is a system for allocating an AMC subchannel in a portable Internet network using a PSS which transmits an SINR value, which including: the PSS for accessing the portable Internet network by means of an OFDMA scheme and using a portable Internet service; an RAS for functioning as an AP of the PSS; an ACR for controlling multiple RASs; an HA for transmitting packets from an external packet data service server and an Internet; a data service server for transmitting various content data in a form of a packet; an AAA server for authenticating network access of the PSS; a NMS server for organizing a central monitoring system for equipments on a network, performing monitoring, planning, analysis, storing related data, and allowing the data to be immediately used if a situation requires; and an IP network for interconnecting the ACR, the HA, the AAA server and the NMS server.

Description

METHOD AND SYSTEM FOR ALLOCATING ADAPTIVE MODULATION AND CODING SUBCHANNEL FOR USE IN PORTABLE INTERNET NETWORK

Technical Field

The present invention relates to a method and a system for allocating an Adaptive Modulation and Coding (hereinafter, referred to as AMC) subchannel in a portable Internet network. More particularly, the present invention relates to a method and a system for allocating an AMC subchannel in a portable Internet network using a Personal Subscriber Station (hereinafter, referred to as PSS) which transmits a Signal to Interference and Noise Ratio (hereinafter, referred to as SINR) value, in which a Radio Access Station (hereinafter, referred to as RAS) allocates a channel in order to exchange data with a PSS, computes the number of Orthogonal Frequency Division Multiplex (hereinafter, referred to as OFDM) symbols required according to bands, compares the computed number of OFDM symbols with the number of symbols actually provided to the PSS, generates a list of user groups to which an AMC subchannel is to be redistributed, and efficiently redistributes the AMC subchannel to the PSS.

Background Art

With the rapid development of computer, electronic and communication technology, various wireless communication services using a wireless network have been provided. The most basic wireless communication service is a wireless voice communication service for providing voice communication to mobile communication terminal users in wireless manner, which has a characteristic of providing the service to the users regardless of time and place. Further, the wireless communication service supplements a voice communication service by providing a text message service. Recently, a wireless Internet service has emerged, which provides an Internet communication service to mobile communication terminal users through a wireless network.

With the development of mobile communication technology as described above, a service provided by a CDMA mobile communication system is being developed into a multimedia communication service for the transmission of data such as circuit and packet data, including a conventional voice service.

Recently, with the development of information communication, an International Mobile Telecommunication (hereinafter, referred to as IMT) -2000, e.g., a CDMA 2000 IX, 3X, EV-DO or a Wideband CDMA (WCDMA) , has been commercialized, which is the 3^rd mobile communication system and has been established as a standard by an International Telecommunication Union Recommendation (ITU-R) . The IMT- 2000 corresponds to a service capable of wireless Internet at a maximum transmission speed of 144 Kbps far faster than 14.4 Kbps or 56 Kbps, which is a data transmission speed supported by an Interim Standard (hereinafter, referred to as IS)-95A network or an IS-95B network, by means of an IS- 95C network evolved from the existing IS-95A network and IS- 95B network. In particular, an IMT-2000 service is used, so that the quality of an existing voice and Wireless Application Protocol (WAP) service can be improved and various multimedia services, e.g., Audio On Demand (AOD), Video On Demand (VOD), etc., can be provided at higher speed.

However, because the existing mobile communication system has a high base station installation cost, service charges for the wireless Internet are high. Further, because a mobile communication terminal has a small screen, available content is restricted. Therefore, there is a limitation in providing an ultra high-speed wireless Internet service.

Furthermore, because Wireless Local Area Network (WLAN) technology shows radio wave interference, narrow service coverage, etc., there is a limitation in providing a public service. Accordingly, a High-speed Portable Internet (hereinafter, referred to as HPi) system has emerged, which can guarantee portability and mobility and an ultra highspeed wireless Internet service at a low cost. Portable Internet lies between a WLAN and a wireless Internet based on mobile communication, and provides a service having the advantages of the WLAN and the wireless Internet. That is, the portable Internet provides a service in which users access the Internet by means of a portable wireless terminal at high transmission speed in a stationary state or a medium/low speed movement state regardless of time and place, so that it is possible to obtain or use various information and content. In other words, the portable Internet corresponds to an Internet Protocol (IP) based wireless data system having an upload/download asynchronous transmission characteristic in which it provides low transmission speed as compared with the WLAN having an advantage in view of transmission speed, but it can ensure the mobility of a terminal, and it does not support high speed mobility of the wireless Internet having an advantage in view of mobility, but it can provide an Internet service at high transmission speed.

The portable Internet requires link adaptation in order to ensure a proper Carrier to Interference ratio (C/I) according to the position of a terminal, and its representative method is power control. However, since all users within a cell want to ensure the same transmission rate and quality of service only through power control due to limitation in maximum transmit power, the coverage is limited to the predetermined extent. In the case of a terminal located far from a base station, it is possible to allocate more power and ensure the same quality of service. In particular, in the case of an uplink, if power increases in a cell boundary, co-channel interference may occur in a neighbor cell using the same frequency. Therefore, it is necessary to perform power control in order to allocate minimum power necessary for ensuring quality of service.

Further, a method, which adaptively controls a transmission rate according to channel conditions, has been used for link adaptation in the portable Internet, instead of the power control. In general, a correlation function value among received signal amplitudes decreases as the speed of a terminal increases. However, when the speed of a terminal decreases, the correlation function value relatively_increases. For example, a Doppler frequency is 5 Hz, if a correlation value is maintained within 0.8 for 20 ms, it may be regarded that channel conditions do not change over a plurality of frames. Accordingly, it is possible to adaptively apply a proper level of modulation and channel coding scheme according to given channel conditions. This will be referred to as an Adaptive Modulation and Coding (AMC) scheme.

In the meantime, a packet data system such as portable Internet performs scheduling so that a user having good channel conditions can preferentially transmit data, thereby maximizing the total throughput of the system. Generally, in a method for allocating resources based on channel conditions, the resources are sequentially allocated according to the user priority determined by a scheduler. That is, the most proper band is allocated to a user having the highest priority, and then a proper band is sequentially allocated to a user having a subsequent priority when allocable resources exist. Since channel conditions of each user are theoretically independent, bands requested by each user are uniformly distributed throughout 24 bands, but there typically exists a specific band being commonly requested by multiple users. When a band requested by a user having a low priority corresponds to such a specific band, a proper band cannot be allocated to the user having the low priority because the specific band has been occupied by a user having a high priority. Therefore, it is impossible to accomplish efficient resource allocation. It is common that an AMC scheme is used in combination with such scheduling. However, it is necessary to provide a scheduling scheme for maximizing the throughput of a system and equity between users.

Disclosure of the Invention

Therefore, the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method and a system for allocating an AMC subchannel in a portable Internet network using a PSS which transmits an SINR value, in which an RAS allocates a channel in order to exchange data with a PSS, computes the number of OFDM symbols required according to bands, compares the computed number of OFDM symbols with the number of symbols actually provided to the PSS, generates a list of user groups to which an AMC subchannel is to be redistributed, and efficiently distributes the AMC subchannel to the PSS.

According to one aspect of the present invention, there is provided a system for allocating an Adaptive Modulation and Coding (AMC) subchannel in a portable

Internet network using a Personal Subscriber Station (PSS) which transmits a Signal to Interference and Noise Ratio

(SINR) value, the system including: the PSS for accessing the portable Internet network by means of an Orthogonal Frequency Division Multiple Access (OFDMA) scheme and using a portable Internet service; a Radio Access Station (RAS) for functioning as an Access Point (AP) of the PSS in the portable Internet system; an Access Control Router (ACR) for controlling multiple RASs; an Home Agent (HA) for transmitting packets from an external packet data service server and an Internet; a data service server for transmitting various content data in a form of a packet; an Authentication, Authorization and Accounting (AAA) server for authenticating network access of the PSS; a Network Management System (NMS) server for organizing a central monitoring system for equipments on a network, performing monitoring, planning, analysis, storing related data, and allowing the data to be immediately used if a situation requires; and an IP network for interconnecting the ACR, the HA, the AAA server and the NMS server. According to another aspect of the present invention, there is provided a Radio Access Station (RAS) for allocating an Adaptive Modulation and Coding (AMC) subchannel in a portable Internet network using a Personal Subscriber Station (PSS) which transmits a Signal to Interference and Noise Ratio (SINR) value, the RAS including: a scheduler for determining a resource allocation sequence in which resources are allocated to the PSS; a resource allocator for mapping the resource allocation sequence to allocation bands based on the resource allocation sequence determined by the scheduler; and an OFDM transmitter for generating OFDM symbol signals and transmitting the OFDM symbol signals to an Access Control Router (ACR) or the PSS.

According to further another aspect of the present invention, there is provided a method for allocating an Adaptive Modulation and Coding (AMC) subchannel in a portable Internet network using a Personal Subscriber Station (PSS) which transmits a Signal to Interference and Noise Ratio (SINR) value, the method including the steps of: (a) allocating by a Radio Access Station (RAS) bands to the PSS in order to provide the PSS with data communication, and computing by the PSS SINR values of the allocated bands; (b) if the SINR values of bands selected by the PSS are computed, transmitting the SINR values to the RAS; (c) computing by the RAS N_sym_k' based on the SINR values received from the PSS; (d) computing by the RAS a total number N_total(k) of OFDM symbols, which is required for each band, by means of the computed N_sym_k' ; (e) defining by the RAS a number of OFDM symbols in a band having a largest N_total(k) as N_max; (f) determining by the RAS if the N_max is greater than a number N_band of OFDM symbols which can be actually used as an AMC subchannel; (G) when the N_max is less than the N_band, allocating by the RAS desired bands to all PSSs; (h) when the N_max is greater than the N_band, determining by the RAS if there exist collision bands which overlap with bands requested by multiple PSSs; (i) when the collision bands do not exist, releasing use of the AMC subchannel by the PSS using a band in which the N_max is greater than the N_band, and allocating the desired bands to said all PSSs within a provided OFDM symbol; (j) when the collision bands exist, arranging by the RAS the collision bands in a sequence in which a larger N_total(k) precedes a smaller N_total(k) , and defining a band having a maximum value of the N total(Ji) as k' ; (k) if it is assumed that each PSS is referred to as a PSS h, computing by the RAS a number N_sym_k', of allocation symbols according to bands of the PSS h, which is obtained when the band k' is allocated to the PSS h, computing a total number N_total(k') of OFDM symbols, which is required for each band, by means of the computed N_sym_k', , and setting a group of the PSS h; (1) if the group is set, redistributing by the RAS resources of the band k' to each PSS h, and computing the N_total(k) , N_max and N_sym_k', of each PSS h; (m) if the computation of the

, N_max and N_sym[, is terminated, selecting by the RAS a PSS h which minimizes the N_max, and redistributing the AMC subchannel; (n) if the redistribution of the AMC subchannel to PSS h is terminated, updating by the RAS a list of the collision bands; and (o) after the list of the collision bands is completely updated, determining by the RAS if the N_max is greater than the number N_band of OFDM symbols which can be actually used as the AMC subchannel.

Brief Description of the Drawings

The foregoing and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:

FIG. 1 is a diagram illustrating the structure of an OFDMA frame in a portable Internet system according to a preferred embodiment of the present invention; FIG. 2 is a block diagram schematically illustrating the structure of a portable Internet system according to a preferred embodiment of the present invention;

FIG. 3 is a block diagram schematically illustrating the structure of a RAS according to a preferred embodiment of the present invention; and FIG. 4 is a flow diagram illustrating a method for allocating an AMC subchannel in a portable Internet network according to a preferred embodiment of the present invention.

Best Mode for Carrying Out the Invention

Reference will now be made in detail to the preferred embodiment of the present invention. In adding reference numerals to components of each drawing, it is noted that the same reference numerals are used to designate the same components even though the same components are shown in other drawings. In the following description of the present invention, a detailed description of known configurations and functions incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

FIG. 1 is a diagram illustrating the structure of an Orthogonal Frequency Division Multiple Access (hereinafter, referred to as OFDMA) frame in a portable Internet system according to a preferred embodiment of the present invention. A slot in a portable Internet standard is designated in a two dimensional space according to the number of symbols and the number of subcarriers on time and frequency domains, and the symbol is a minimum unit of allocation.

A slot is dependent on a scheme for actually forming a subchannel in an uplink 120 and a downlink 110. An allocation scheme of a subcarrier in a portable Internet may be classified as a scheme for collecting scattered subcarriers by a permutation to form a diversity subchannel 140 and a scheme for collecting physically consecutive subcarriers according to bands to form an AMC subchannel 150. A preamble 112 is allocated to the first symbol in the downlink 110, and the preamble 112 is used for frame synchronization and cell identification.

A Transmit/receive Transition Gap (hereinafter, referred to as TTG) 160 is interposed between the downlink 110 and the uplink 120, and a Receive/transmit/ Transition Gap (hereinafter, referred to as RTG) 170 is interposed between the end and beginning of a frame, so that it is possible to provide the maximum coverage of 1 km.

A frame of 5 ms includes 42 OFDM symbols, the TTG 160 and the RTG 170.

The transmission of the downlink 110 is accomplished in a sequence of one preamble symbol, a Frame Control Header (hereinafter, referred to as FCH) , a DL-MAP and a data symbol . Two symbols directly after the preamble 112 are always used as a Partial Usage Subchannel (hereinafter, referred to as PUSC) 130, and include a 24-bit FCH for transmitting frame configuration information.

A PUSC employs a concept of separating subchannels and allocating different subchannels according to sectors, instead of using all subchannels in one sector, which is contrary to a Full Usage Subchannel (FUSC) employing a concept of using all subchannels in one sector.

In the case of the uplink 120, the first three symbols are used in order to transmit control information such as ranging and channel guality indicators.

The downlink frame includes three types of subchannels, i.e. the PUSC 130, the diversity subchannel 140 and the AMC subchannel 150.

The uplink frame includes two types of subchannels, i.e. the diversity subchannel 140 and the AMC subchannel 150. The diversity subchannel 140 is scattered throughout the entire band to form a subcarrier, and changes its permutation by the symbol, so that it is possible to obtain diversity effect on a frequency domain. In the case of the diversity subchannel 140, one slot in the downlink 110 includes one subchannel and one OFDMA symbol, and one slot in the uplink 120 includes one subchannel and three OFDMA .symbols .

The AMC subchannel 150 is formed by collecting consecutive subcarriers according to the bands. Accordingly, bands having good channel conditions are selected and allocated, so that it is possible to pursue the maximization of band efficiency.

In the case of the AMC subchannel 150, one slot in the downlink 110 or the uplink 120 includes one subchannel and one OFDMA symbol.

The subchannel of the downlink 110 or the uplink 120 has a separate transmission interval including consecutive symbols, the PUSC 130 of the downlink 110 is defined throughout two symbols, and one PUSC 130 is comprised of four pilot subcarriers and 48 data subcarriers .

The diversity subchannel 140 of the downlink 110 is comprised of 48 subcarriers selected from available effective subcarriers in one symbol.

A basic allocation unit constituting the diversity subchannel 140 of the uplink 120 may use either a tile 142, which is formed by -collecting three adjacent subcarriers in three consecutive symbol intervals, or a tile 142 (including four pilot subcarriers) formed by collecting four adjacent subcarriers in three consecutive symbol intervals. The diversity subchannel 140 of the uplink 120 is comprised of six tiles 142, and each of the tiles 142 is dispersed throughout the entire frequency band.

A basic unit constituting the AMC subchannel 150 of the downlink 110 and the uplink 120 is a bin 152. The bin 152 is comprised of nine adjacent subcarriers in the same symbol. The AMC subchannel interval of the downlink 110 and the uplink 120 has a plurality of bands, and four bins 152 exist in one band.

The AMC subchannel 150 of the downlink 110 and the uplink 120 is comprised of six adjacent bins 152 existing in the same band. Herein, the pilot subcarrier has a position determined according to the positions of the bin 152 and the symbol .

An FCH is allocated to a subchannel in the first symbol next to the preamble 112 of each frame after the RTG 170. The FCH is an area for transmitting a downlink frame prefix. The downlink frame prefix transmits information relating to the current frame, including the length of a subsequent DL-MAP message, repetitive coding and channel coding schemes applied to a DL-MAP, etc. The downlink frame prefix is comprised of 24 bits, and the 24 bits are repeated to form a 48-bit FEC block. The downlink frame prefix is transmitted after passing through

QPSK modulation and coding (R=l/2) and is repeatedly transmitted four times. FIG. 2 is a block diagram schematically illustrating the structure of the portable Internet system according to the preferred embodiment of the present invention.

In the portable Internet system according to the present invention, the AMC subchannel allocation system includes a PSS 200, an RAS 210, an Access Control Router

(hereinafter, referred to as ACR) 220, a Home Agent (hereinafter, referred to as HA) 230, an Authentication, Authorization and Accounting (hereinafter, referred to as AAA) server 240, an IP network 250, the Internet 260, a data service server 270, a Network Management System (hereinafter, referred to as NMS) server 280, etc.

The PSS 200 represents a mobile communication terminal for accessing the portable Internet network by means of an OFDMA scheme and using a portable Internet service. The PSS 200 has a low power Radio Frequency (RF) /Intermediate Frequency (IF) module, and performs a Media Access control (MAC) frame variable control function according to service characteristics and radio wave conditions, a handoff function, a multicast service reception function, an interworking function with other networks, a user authentication and encryption function, etc. Further, the PSS 200 selects a band in order to transmit and receive data through the portable Internet network, measures an SINR value of the selected band, and transmits the measured SINR to the RAS 210. The RAS 210 corresponds to an Access Point (AP) of the portable Internet system, and functions as a data repeater for transmitting data, which are received from the ACR 220, to the PSS 200 in a wireless manner, or transmitting data, which are received from the PSS 200, to the ACR 220. Further, the RAS 210 performs a radio resource management and control function, a handoff support function, a downlink multicast function, accounting, a statistical information generation and notification function, and an authentication and security function. Furthermore, the RAS 210 is an apparatus for receiving an SINR value from the PSS 200. The ACR 220 accommodates multiple RASs 210, and performs a handoff control function among the RASs 210, an IP routing and handoff management function, a function for providing an accounting server with an accounting service, an IP multicast function, a resource management and control function, an authentication and security function, etc.

The HA 230 performs routing for transmitting packets from an external packet data service server including the Internet 260. The AAA server 240 interworks with the RAS 210, performs accounting for packet data used by the PSS 200, and authenticates access from the PSS 200.

The IP network 250 interconnects the ACR 220, the HA 230, the AAA server 240, the NMS server 280, a downlink/uplink ratio setup server, etc., receives packet data from the external packet data service server including the Internet 260 and a data service server for providing various contents, and transmits the received data to the ACR 220.

The NMS server 280 organizes a central monitoring system for equipments on a network, performs monitoring, planning, analysis, etc., stores related data, and allows the data to be immediately used if the situation requires. FIG. 3 is a block diagram schematically illustrating the structure of the RAS for allocating an AMC subchannel in the portable Internet network using the PSS for transmitting an SINR value according to the preferred embodiment of the present invention.

First, a scheduler 310 determines a resource allocation sequence, in which resources are allocated to the PSS 200, by means of the SINR value, which is transmitted from the PSS 200, and code packet size information, receives packet data from the PSS 200, and transmits the received packet data to an OFDM transmitter 330.

A resource allocator 320 receives the resource allocation sequence from the scheduler 310, maps the received resource allocation sequence to a predetermined band so that resources can be sequentially allocated to each PSS 200, and transmits band information obtained as a result of the mapping to the OFDM transmitter 330.

If the band information having the mapped resource allocation sequence is received from the resource allocator 320, the OFDM transmitter 330 arranges packet data, which are received through the scheduler 310, in the sequence mapped to the band, generates OFDM symbol signals, and transmits the OFDM symbol signals to the ACR 220 or the PSS 200. FIG. 4 is a flow diagram illustrating a method for allocating an AMC subchannel in the portable Internet network using the PSS for transmitting an SINR value according to the preferred embodiment of the present invention.

First, if the RAS 210 allocates bands to the PSS 200 in order to provide the PSS 200 with data communication, the PSS 200 selects four or five bands having good band conditions from the bands allocated by the RAS 210, and simultaneously computes SINR values of the selected bands (S400) . Then, the PSS 200 transmits the SINR values, which are obtained as a result of the computation, to the RAS 210 (402) .

The RAS 210 computes the number N_sym_k' of OFDM symbols, which is necessary when an k^th band is used for an i^th PSS 202, by means of the code packet size N_EP(i) of data to be transmitted to the i^th PSS 202, and an SINR value SINR (k) of the k^th band, which is selected by the i^th PSS 202, based on the SINR values received from the PSS 200 (S404) .

The RAS 210 computes the total number N_total(k) of OFDM symbols, which is required for each band, by means of equation 1 based on the computed number N_sym_k' of OFDM symbols (S406) .

Equation 1

M N_total(k) = ∑ N_sym_k' In equation 1, M represents the number of the PSSs 200 using the AMC subchannel.

The RAS 210 defines the number of OFDM symbols in a band having the largest N total(Jc) as N_max (S408).

The RAS 210 determines if the N_max is greater than the number N_band of OFDM symbols which can be actually used as the AMC subchannel (S410) .

When the N_max is less than the N_band, the RAS 210 allocates desired bands to all PSSs 200 within a provided OFDM symbol (S412) .

However, when the N_max is greater than the N_band, the RAS 210 determines if there exist collision bands which overlap with bands requested by multiple PSSs 200 (S414) . When the collision bands do not exist, the RAS 210 releases the use of an AMC subchannel by a PSS using a band in which the N_max is greater than the N_band, and allocates the desired bands to all PSSs 200 within the provided OFDM symbol (S416) . However, when the collision bands exist, the RAS 210 arranges the collision bands in a sequence in which a larger N_total(k) precedes a smaller N_total(k) , and defines a band having the maximum value of the N_total(k) as k' (S418) .

In a case in which it is assumed that each PSS 200 is referred to as a PSS h, the RAS 210 computes the number

N_sym_k', of allocation symbols according to bands of the PSS h, which is obtained when the band k/ is allocated to the PSS h, computes the total number N_total(k') of OFDM symbols, which is required for each band, by means of the N_sym_k', , and sets a group A of the PSS h, which satisfies the following expression (S420) .

Equation 2

N _ total (Jc' ) - N _ symbol*, ≤ N _ band wherein, k'= max N _ total (k) kecollisionband

If the group is set, the RAS 210 redistributes the resources of the band k' to each PSS h, and computes the N_total(h) , N_max and N_sym_k', of each PSS h (S422) .

If the RAS 210 completes the computation of the N_total(k) , N_max and N_sym_k', , the RAS 210 selects a PSS h which minimizes the N_max, and redistributes the AMC subchannel (S424) .

If the redistribution of the AMC subchannel to PSS h is terminated, the RAS 210 updates a list of the collision bands (S426) . After the list of the collision bands is completely updated, the RAS 210 determines if the N_max is greater than the number N_band of OFDM symbols which can be actually used as the AMC subchannel (S428) .

While this invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiment and the drawings, but, on the contrary, it is intended to cover various modifications and variations within the spirit and scope of the appended claims.

Industrial Applicability

In the case of a portable Internet system employing an AMC, since a transmission rate changes due to channel conditions according to the positions of a user, equity among users cannot be ensured. According to the present invention as described above, the number of OFDM symbols for AMC subchannel intervals is reduced through resource redistribution, so that the number of diversity subchannel users increases and the amount of occupation data according to bands is similarly distributed. Consequently, it is possible to efficiently use resources and increase the total throughput of the system.

Claims

1. A system for allocating an Adaptive Modulation and

Coding (AMC) subchannel in a portable Internet network using a Personal Subscriber Station (PSS) which transmits a Signal to Interference and Noise Ratio (SINR) value, the system comprising: the PSS for accessing the portable Internet network by means of an Orthogonal Frequency Division Multiple Access (OFDMA) scheme and using a portable Internet service; a Radio Access Station (RAS) for functioning as an Access Point (AP) of the PSS in the portable Internet system; an Access Control Router (ACR) for controlling multiple RASs; an Home Agent (HA) for transmitting packets from an external packet data service server and an Internet; a data service server for transmitting various content data in a form of a packet; an Authentication, Authorization and Accounting (AAA) server for authenticating network access of the PSS; a Network Management System (NMS) server for organizing a central monitoring system for equipments on a network, performing monitoring, planning, analysis, storing related data, and allowing the data to be immediately used if a situation requires; and an IP network for interconnecting the ACR, the HA, the AAA server and the NMS server.

2. The system as claimed in claim 1, wherein the PSS selects a band in order to transmit and receive data through the portable Internet network, measures the SINR value of the selected band, and transmits the measured SINR to the RAS.

3. The system as claimed in claim 1, wherein the RAS functions as a data repeater for transmitting data, which are received from the ACR, to the PSS in a wireless manner, or transmitting data, which are received from the PSS, to the ACR, performs a radio resource management and control function, a handoff support function, a downlink multicast function, accounting, a statistical information generation and notification function, and an authentication and security function, and receives the SINR value from the PSS.

4. The system as claimed in claim 1, wherein the ACR performs a handoff control function among the RASs, an IP routing and handoff management function, a function for providing an accounting server with an accounting service, an IP multicast function, a resource management and control function, and an authentication and security function.

5. A Radio Access Station (RAS) for allocating an Adaptive Modulation and Coding (AMC) subchannel in a portable Internet network using a Personal Subscriber Station (PSS) which transmits a Signal to Interference and Noise Ratio (SINR) value, the RAS comprising: a scheduler for determining a resource allocation sequence in which resources are allocated to the PSS; a resource allocator for mapping the resource allocation sequence to allocation bands based on the resource allocation sequence determined by the scheduler; and an OFDM transmitter for generating OFDM symbol signals and transmitting the OFDM symbol signals to an Access Control Router (ACR) or the PSS.

6. The RAS as claimed in claim 5, wherein the scheduler determines the resource allocation sequence by means of the SINR value, which is transmitted from the PSS, and code packet size information.

7. The RAS as claimed in claim 5, wherein the resource allocator receives the resource allocation sequence from the scheduler, maps the received resource allocation sequence to a predetermined band so that resources can be sequentially allocated to each PSS, and transmits band information obtained as a result of the mapping to the OFDM transmitter.

8. The RAS as claimed in claim 5, wherein, if band information, to which the resource allocation sequence has been mapped, is received from the resource allocator, the OFDM transmitter arranges packet data in a sequence mapped to the band, and generates the OFDM symbol signals, the packet data being received through the scheduler.

9. A method for allocating an Adaptive Modulation and Coding (AMC) subchannel in a portable Internet network using a Personal Subscriber Station (PSS) which transmits a Signal to Interference and Noise Ratio (SINR) value, the method comprising the steps of: (a) allocating by a Radio Access Station (RAS) bands to the PSS in order to provide the PSS with data communication, and computing by the PSS SINR values of the allocated bands;

(b) if the SINR values of bands selected by the PSS are computed, transmitting the SINR values to the RAS;

(c) computing by the RAS N_sym_k' based on the SINR values received from the PSS;

(d) computing by the RAS a total number N_total(k) of OFDM symbols, which is required for each band, by means of the computed N_syrri_k ;

(e) defining by the RAS a number of OFDM symbols in a band having a largest N_total(k) as N_max;

(f) determining by the RAS if the N_max is greater than a number N_band of OFDM symbols which can be actually used as an AMC subchannel; (G) when the N_max is less than the N_band, allocating by the RAS desired bands to all PSSs;

(h) when the N_max is greater than the N_band, determining by the RAS if there exist collision bands which overlap with bands requested by multiple PSSs; (i) when the collision bands do not exist, releasing use of the AMC subchannel by the PSS using a band in which the N_max is greater than the N_band, and allocating the desired bands to said all PSSs within a provided OFDM symbol; (j) when the collision bands exist, arranging by the RAS the collision bands in a sequence in which a larger N_total(k) precedes a smaller N_total(k) , and defining a band having a maximum value of the N_total(k) as k' ;

(k) if it is assumed that each PSS is referred to as a PSS h, computing by the RAS a number N_sym_k', of allocation symbols according to bands of the PSS h, which is obtained when the band k' is allocated to the PSS h, computing a total number N_total(k') of OFDM symbols, which is required for each band, by means of the computed N_sym_k', , and setting a group of the PSS h;

(1) if the group is set, redistributing by the RAS resources of the band k' to each PSS h, and computing the N_total(k) , N_max and N_sym_k', of each PSS h;

(m) if the computation of the N_total(k) , N_max and N_sym_k', is terminated, selecting by the RAS a PSS h which minimizes the N_max, and redistributing the AMC subchannel;

(n) if the redistribution of the AMC subchannel to PSS h is terminated, updating by the RAS a list of the collision bands; and

(o) after the list of the collision bands is completely updated, determining by the RAS if the N_max is greater than the number N_band of OFDM symbols which can be actually used as the AMC subchannel.

10. The method as claimed in claim 9, wherein, in step (a), the PSS selects four or five bands having proper band conditions from the bands allocated by the RAS, and simultaneously computes the SINR values of the selected bands .

11. The method as claimed in claim 9, wherein, in step (c) , the RAS computes the number N_sym_k' of OFDM symbols, which is necessary when an k^th band is used for an i^th PSS, by means of a code packet size N_EP(i) of data to be transmitted to the i^th PSS.

12. The method as claimed in claim 9, wherein, in step (d) , the N total (k) is computed by an equation

M

N _ totalik) = ^] N _ sym_k' .

13. The method as claimed in claim 12, wherein, in the

M equation N_total(k) = ∑ N_sym_k' , M represents a number of the

PSSs using the AMC subchannel.

14. The method as claimed in claim 9, wherein, in step (h) , when the N_max is greater than the N_band, the RAS allows the PSS to use the AMC subchannel.

15. The method as claimed in claim 9, wherein, in step (k), the RAS sets the group of the PSS h, which satisfies an expression N_total(k')- N_symbol_k ^h, ≤N_band .

16. The method as claimed in claim 15, wherein, in the expression N_total(k')- N_symbol_k, < N_band , k' satisfies

max N _ total (k) . k≡collisionb and