WO2001050638A1

WO2001050638A1 - Apparatus and method for designating frame offset of supplemental channel in a cdma communication system

Info

Publication number: WO2001050638A1
Application number: PCT/KR2001/000007
Authority: WO
Inventors: Dae-Gyun Kim
Original assignee: Samsung Electronics Co., Ltd
Priority date: 2000-01-03
Filing date: 2001-01-03
Publication date: 2001-07-12
Also published as: AU2409901A; CN1363156A; JP2003519957A; AU757399B2; BR0103749A; CA2362420A1; EP1155516A1; RU2224374C2

Abstract

An apparatus for receiving data transmitted over fundamental channels having a predetermined frame offset for a plurality of mobile stations and supplemental channels assigned in association with the fundamental channels. In the apparatus, a timing generator receives a frame offset of the fundamental channel, a frame offset of the supplemental channel and a system time, outputs the system time delayed by the frame offset of the fundamental channel as a fundamental channel boundary signal, and outputs the system time delayed by the frame offset of the supplemental channel as a supplemental channel boundary signal. A first symbol combiner combines multi-path symbols transmitted over the fundamental channel. A second symbol combiner combines multi-path symbols transmitted over the supplemental channel. A first deinterleaver receives the symbols and the fundamental channel boundary signal from the first symbol combiner, and deinterleaves the symbols from the first symbol combiner in a frame unit determined by the fundamental channel boundary signal. A second deinterleaver receives the symbols and the supplemental channel boundary signal from the second symbol combiner, and deinterleaves the symbols from the second symbol combiner in a frame unit determined by the supplemental channel boundary signal.

Description

APPARATUS AND METHOD FOR DESIGNATING FRAME OFFSET

OF SUPPLEMENTAL CHANNEL

IN A CDMA COMMUNICATION SYSTEM

BACKGROUND OF THE INVENTION

1 _ Field of the Invention

The present invention relates generally to a communication apparatus and method for a CDMA mobile communication system, and m particular, to an apparatus and method for assigning a supplemental channel m a CDMA mobile communication system

2 Description of the Related Art In general, a CDMA (Code Division Multiple Access) mobile communication system assigns (or designates) different frame offsets to the users so as to distinguish the transmission frames to the respective users

In the conventional CDMA mobile communication system, one 20ms frame is equally divided into 16 1 25ms segments, to which different frame offsets are assigned according to the users A data frame is transmitted/received at a time point delayed by a frame offset assigned to the corresponding user on the basis of the system time

In a voice call, the frame offset contπbutes to dispersion of a load When many useis simultaneously intend to transmit data at a boundar> of the 2(Jms frame, there is a case where it is not possible to simultaneously process all the user frames In this case, the frame processing time is

ed in a channel card, a base station controller and a voice codec (or vocoder) This delay is a mam factor m quality deterioration of a voice service Therefore, the 20ms frame is equally divided into 16 segments, and then, the divided segments are uniformly distributed to the users so that the load should be naturally dispersed using the reference time delayed by the corresponding frame offset between the base station and the mobile station

Although the co entional CDMA mobile communication system has chiefly provided a voice service, a future CDMA mobile communication svstem will provide a high-speed data service as well as the voice service The future CDMA mobile communication system is normally called an IMT-2000 mobile communication system

The IMT-2000 mobile communication system can provide new sen ices such as a high- quality voice service, a mowng picture service, and an Internet search service

In the co entional voice service, loads are uniformly generated at regular intervals Therefore, m the voice service, the users uniformly dispersed

the frame offsets can process the voice data without delay However, the future CDMA mobile communication system, which chiefly provides a multimedia service, generates data which has different features from the existing voice data That is, the data having the different features may be packet data In many cases, the packet data is generated at a burst Therefore, the packet data has a feature that a large amount of data is generated at a short time, rather than a specific amount of data being consecutively generated

When a traffic having this feature is generated, the system assigns a supplemental channel (SCH) m addition to a fundamental channel (FCH) The newly added supplemental channel uses the same frame offset as the previously connected fundamental channel

When it is necessary for several users assigned the same frame offset to transmit a great amount of data at a high data rate, there may occur a state where the amount of the transmission data exceeds a traffic capacity in which the data can be transmitted at the corresponding frame offset without delay In this case, a call is set up using only an initial fundamental channel, and each user is assigned a unique frame offset for the initial fundamental channel

At this moment, several users may have the same frame offset As a result, there may occur a situation where the traffic exceeds a capacity of a link between a base station and a base station controller at a specific frame offset This will cause a delay in transmitting the data In a service of which quality is affected by the delay, such as the voice service using the fundamental channel, the delay of the data deteriorates the service quality.

On the other hand, the supplemental channel can be used in several methods In general, the CDMA mobile communication system assigns different supplemental channels to the respective users In this case, the future CDMA mobile communication system can assign a supplemental channel as a new traffic is generated m a state (or a traffic state) where a basic call is connected Here, the "traffic state" refers to a traffic channel-established state In this case, a service delay problem and a scheduling loss problem may occur because the supplemental channels are fixedly assigned to the users Furthermore, in the future high-speed communication system, several users may use a limited number of the supplemental channels on a time-division basis, rather than using the supplemental channels uniquely assigned to the users. However, this may cause a scheduling loss problem because the users have the different frame offsets.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a channel assignment apparatus and method for designating a frame offset upon receipt of a data transmission request in a traffic state, in a CDMA communication system.

It is another object of the present invention to provide an apparatus and method for assigning a supplemental channel by designating a frame offset of the supplemental channel upon receipt of a data transmission request in a traffic state in a CDMA communication system.

It is further another object of the present invention to provide an apparatus and method for designating new frame offset information such that a base station can assign a supplemental channel by designating a frame offset of the supplemental channel upon receipt of a data transmission request in a traffic state, in a CDMA communication system.

It is yet another object of the present invention to provide an apparatus and method in which a mobile station designates a frame offset of a supplemental channel by receiving the frame offset information from the base station upon receipt of a data transmission request in a traffic state in a CDMA communication system.

It is still another object of the present invention to provide an apparatus and method for assigning a new frame offset for a supplemental channel in a handoff state in a CDMA communication system.

It is still another object of the present invention to provide an apparatus and method for assigning a new frame offset for a supplemental channel when it is desired to hand off a supplemental channel in a handoff state, in a CDMA communication system.

It is still another object of the present invention to provide an apparatus and method for assigning a supplemental channel by designating a new frame offset when it is desired to newly assign a supplemental channel in a handoff state, in a CDMA communication system. It is still another object of the present invention to

ιde an apparatus and method for designating new frame offset information such that a base station can assign or hand off a supplemental channel by designating a frame offset of the supplemental channel in a handoff state, m a CDMA communication system

It is still another object of the present invention to prov ide an apparatus and method m which a mobile station designates a frame offset of a supplemental channel by receiving the frame offset information from the base station in a handoff state m a CDMA communication system

To achieve the above and other objects, there is provided an apparatus for receiving data tiansmitted over fundamental channels having a predetermined frame offset for a plurality of mobile stations and supplemental channels assigned in association with the fundamental channels In the apparatus, a timing generator receives a frame offset of the fundamental channel, a frame offset of the supplemental channel and a system time, outputs the system time delayed by the frame offset of the fundamental channel as a fundamental channel boundary signal, and outputs the system time delayed by the frame offset of the supplemental channel as a supplemental channel boundary signal. A first symbol combiner combines multi-path symbols transmitted over the fundamental channel A second symbol combiner combines multi-path symbols transmitted over the supplemental channel A first deinterleav er receives the symbols and the fundamental channel boundary signal from the first symbol combiner, and deinterleaves the symbols from the first symbol combiner in a frame unit determined by the fundamental channel boundary signal A second deinterleaver receives the symbols and the supplemental channel boundary signal from the second

mbol combiner, and deinterleaves the symbols from the second symbol combiner in a frame unit determined by the supplemental channel boundary signal

Preferably, the timing generator comprises a first delay for receiving the frame offset of the fundamental channel and the system time, and delaying the system time by the frame offset of the fundamental channel to output the fundamental channel boundary signal; and a second delay for receiving the frame offset of the supplemental channel and the system time, and delaying the system time by the frame offset of the supplemental channel to output the supplemental channel boundary signal

Preferably, the frame offset of the fundamental channel is different from the frame offset of the supplemental channel Preferably, the frame offset of the supplemental channel is designated according to an amount of the transmission data for the respective frame offsets of the supplemental channels assigned m association w ith the fundamental channels

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will become moie apparent from the following detailed descπption when taken m conjunction with the accompany ing drawings m which FIG 1 is a flow diagram illustrating a general procedure for assigning a supplemental channel in a CDMA communication system,

FIG 2 is a flow chart illustrating a procedure added to designate a frame offset of a supplemental channel w hile assigning a supplemental channel m a CDMA communication system according to an embodiment of the present ιn\ ention, FIG 3 is a diagram illustrating a field definition of an extended supplemental channel assignment message (ESCAM) to which the frame offset-related fields for the supplemental channel are new ly added,

FIG 4 is a block diagram illustrating a demodulator for a receiver m a CDMA communication system, FIG 5 is a block diagram illustrating a combiner m the demodulator m a CDMA communication system according to an embodiment of the present inv ention,

FIG 6 is a block diagram illustrating a timing generator m the combiner of FIG

5,

FIG 7 is a flow diagram illustrating a call setup procedure m a CDMA communication svstem,

FIG 8 is a flow chart illustrating a procedure added to designate a frame offset of the supplemental channel m a service negotiation process in a CDMA communication system according to an embodiment of the present invention,

FIG 9 is a flow diagram illustrating a handoff procedure m a CDMA communication system according to an embodiment of the present invention,

FIG 10 is a flow chart illustrating a procedure for designating a frame offset of a supplemental channel during a handoff in a CDMA communication system according to an embodiment of the present invention, and

FIG 1 1 is a diagram illustrating a field definition of an extended supplemental channel assignment message or a universal handoff direction message, to which a non- negotiation service configLiration record field is added according to an embodiment of the present invention DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of the present invention will be descπbed herein below with reference to the accompanying drawings In the following description, well-known functions or constructions are not described in detail since they would obscure the invention m unnecessary detail

The present invention is to be applied to a futuie CDMA mobile communication system Therefore, although the present invention will be descπbed herein with reference to the American CDMA-2000 system, it is also possible to apply the invention to the

European UMTS system

The present

ention proposes an apparatus and method for additional assigning of a supplemental channel for data transmission, upon receipt of a high-speed data transmission request in a traffic state (oi a traffic channel-established state) between the base station and the mobile station a CDMA mobile communication system More specifically, the apparatus and method properly designates a fiame offset of the supplemental channel according to an amount of transmission/reception data for the respective frame offsets To this end, a CDMA communication system according to an embodiment of the present invention additionally assigns a supplemental channel upon receipt of a high-speed data transmission request in the traffic state between the base station and the mobile station At this point, a frame offset of the sLipplemental channel is properly established according to an amount of the transmission/reception data for the respective frame offsets presently in use In this case, the supplemental channel can be designated (oi assigned) the diffeient frame offset from the name offset of the presently used fundamental channel Alternatively, the supplemental channel can be designated the same frame offset as the frame offset of the fundamental channel When the fundamental channel and the supplemental channel are designated the different frame offsets, several users assigned the same frame offset can simultaneously transmit data at a high data rate The base station then sends information for designating a new frame offset to the mobile station through an extended SLipplemental channel assignment message Upon receipt of the frame offset information from the base station, the mobile station additionally designates a frame offset for the supplemental channel m addition to a frame offset for the fundamental channel, thereby making it possible to operate the different frame offsets in the ftindamental channel and the supplemental channel

FIG 1 shows a general procedure for assigning a supplemental channel m a CDMA communication system Specifically, FIG 1 shows a message exchange procedure between modules m the mobile station and modules m the base station

Referring to FIG 1, the mobile station includes a service option for driving an application service, a message processor SIG for processing a channel estabhshment- related control message, and a resource controller (RC) for managing and controlling base station resources A stiucture of the base station is similar to the structure of the mobile station That is, the base station also includes a service option for driving an application service, a message processor SIG for processing a channel establishment-related control message, and a resouice controller (RC) for managing and controlling logical and physical resources of the mobile station

Now, a procedure for assigning a supplemental channel will be descπbed with reference to FIG 1 When the mobile station has user data to transmit, the service option checks a size (oi amoLint) of the data and determines whether it is necessary to assign a supplemental channel If it is determined that it is necessary to assign a supplemental channel, the service option sends a supplemental channel assignment request signal Data_Tx_SCH Req to the resource controller (RC) in step 110 The resource controller then sends a supplemental channel assignment approval signal SCH_Assιgn Req to the message processor SIG in step 120 The message processor SIG sends a supplemental channel request message (SCRM) to the base station in step 130

When the base station receives the supplemental channel request message transmitted from the mobile station, the message processor SIG in the base station inquires of the resource controller (RC) in the base station whether it is possible to assign the supplemental channel requested by the mobile station, m step 140 (SCH_Assιgn Ind)

If it is possible to assign the supplemental channel, the resource controller informs the service option, an application service layer of the base station, that a data transmission request has been receiv ed from the mobile station, in step 150 Upon receipt of the data transmission request, the service option, which is the application service layer, performs several data reception processes

In step 160, the service option of the base station performs an operation m response to the data transmission request The operation of the step 160 can be separately described for one case where the data tiansmission request is originated by the mobile station and anothei case where the data transmission request is originated by the base station When the data transmission request is oπgmated from the mobile station, the base station sends the resource controller a ready-to-receive signal Data_Rx_SCH.Res, m step 160 In the case where the data has previously been transmitted/received over the fundamental channel, it is not necessary to send the ready-to-receive signal to the resource controller On the contrary w hen the data transmission request is ongmated by the base station, the base station sends the resource controller a forward supplemental channel assignment request signal Data_T\_SCH Req m step 160

Upon receipt of the ready-to-receive signal Data_Rx_SCH Res or the data channel assignment l equest signal Data_T\_SCH Req from the service option, the resource controller determines whether it is possible to assign a reverse or forward supplemental channel In this process, the embodiment of the present invention adds a procedure for re-designatmg a requested frame offset The added procedure includes a process for establishing a new frame offset having a low er load out of the parameters required m assigning the supplemental channel This procedure will be descπbed later in detail with reference to FIG 2 Thereafter, in step 170, the resource controller sends the message processor a message SCH_Assιgn Res indicating whether to approve the reverse or forward supplemental channel If assignment of the supplemental channel for transmitting data is approved, the message processor SIG sends an extended supplemental channel assignment message (ESCAM) to the mobile station in step 180

Upon receipt of the extended SLipplemental channel assignment message transmitted from the base station, the message process SIG in the mobile station sends a control signal SCH_Assιgn Conf to the resource controller in step 190 At this moment, the resource controller assigns a transmission channel or a reception channel of the corresponding SLipplemental channel Finally, after completing assignment of the supplemental channel, the resource controller sends to the service option, which is the application sen ice layei of the mobile station, a data transmit receive possibility conformation message Data_Tx_SCH conf or Data_Rx_SCH Conf m step 195 After performing the above procedure, the base station and the mobile station exchange a data traffic over the additionally assigned supplemental channel

FIG 2 shows a procedure for assigning a frame offset for a supplemental channel according to an embodiment of the present invention, performed in the supplemental channel assignment process of FIG 1 In FIG 2, operations of steps 210-250 correspond to the operations of steps 140-170 in FIG 1 are performed by the base station Further, operations of steps 260-295 correspond to the operations of steps 180- 195 m FIG 1 are performed by the mobile station The procedure for assigning the frame offset for the supplemental channel by the base station is performed through the steps 140-180 of FIG 1, and the procedure for assigning the frame offset for the supplemental channel by the mobile station is performed through the steps 110, 120, 130, 190 and 195 of FIG 1 If a supplemental channel request message (SCRM) is receiv ed from the mobile station or a supplemental channel assignment message is receiv ed from the application service layer of the base station as the application service layer has traffic data to transmit, the resource controller checks the present capacity of the base station in step 220 to determine whether the physical/logical resources are available, to thereby decide whether it is possible to assign the additional reverse or fonvaid supplemental channel If assignment of the supplemental channel is not permissible, the resource controller proceeds to step 230 where the resource controller transmits the data traffic over the previously connected fundamental channel (FCH) or a dedicated control channel (DCCH), or awaits a next command vv hile delaying transmission of the data traffic

Othenvise, if assignment of the supplemental channel is permissible m step 220 or a supplemental channel request message (SCRM) is received from the mobile station, the resoLirce controller proceeds to step 240 where the resource controller designates a frame offset available for the supplemental channel, provides this information to the message processor, and further, provides information about the frame offset for the supplemental channel to the physical layer The physical layer then sets this value as an exclusive frame offset for processing the supplemental channel Here, for the frame offset of the supplemental channel established for data transmission, a proper frame offset can be designated according to the amount of the transmission/ reception data for the respective frame offsets The frame offset can be set to be different from the frame offset of the fundamental channel Alternatively, the frame offset can be set to be identical to the frame offset of the fundamental channel Here, the frame offset of the supplemental channel can be eithei pre iously set or generated by the base station through a separate operation In the frame offset designation process, the lesource controller should set a proper frame offset value such that the loads are properly dispersed to transmit the data without delay Thereafter, in step 250, the resource controller generates an extended supplemental channel assignment message (ESCAM) to which the frame offset-related fields for the supplemental channel are added, and sends the generated extended supplemental channel assignment message to the mobile station

Upon receipt of the extended supplemental channel assignment message from the base station, the message processor in the mobile station analyzes the received extended supplemental channel assignment message and provides the analyzed results to the resource controller in the mobile station, m step 260 In this process, the message processor sends to the resource controller the information about whether the frame offset for the supplemental channel is designated, and its corresponding value, together with other supplemental channel parameters Upon receipt of the analy zed results from the message processor, the resource controller determines in step 270 whether the frame offset of the supplemental channel is designated or not If the frame offset of the SLipplemental channel is designated, the resource controller sets a frame offset for the supplemental channel according to the value m step 280 After setting the frame offset for the supplemental channel, or if the frame offset of the supplemental channel is not designated, the resource controllei sends to the physical layer new frame offset information together with a SLipplemental channel assignment signal, in step 290 Upon receipt of the supplemental channel-related signal from the resource controller, the physical layer assigns a supplemental channel and additionally sets a frame offset for the supplemental channel so as to enable data transmission/reception When the reverse or forward supplemental channel is established between the base station and the mobile station m the abo e method, the data traffic is transmitted to the application service m step 295

In the embodiment of the present invention, the base station includes a step (a) in which the resource controller of the base station detenmnes whether the supplemental channel is available, a step (b) in which if the supplemental channel is available, the resource controller determines a frame offset to be exclusively used for the supplemental channel, a step (c) in which the resource controller creates the extended supplemental channel assignment message shown m FIG 3 to transmit the frame offset information to the mobile station, and a step (d) in which the resource controller designates the frame offset assigned by the physical layer to the supplemental channel Here, m the step (d), the resource controller should set a proper value such that the loads should be properly dispersed to transmit the data without delay

In addition, the mobile station includes a step (a) foi detecting a frame offset for the supplemental channel the process of analyzing the extended SLipplemental channel assignment message and providing the detected frame offset information to the resource controller, a step (b) m which the resoLirce controller provides the set value to the physical channel, and a step (c) m which the physical layer newly sets the frame offset duπng assignment of the supplemental channel

FIG 3 shows a structure of an extended supplemental channel assignment message (ESCAM) to which the frame offset-related fields for the supplemental channel are newly added

In the extended supplemental channel assignment message as shown in FIG 3, the fields for assigning the frame offset for the supplemental channel include a REV_SCH_FRAME_OFFSET NCL field indicating whether to newly designate a frame offset during assignment of the reverse supplemental channel, and a REV_SCH_FRAME_OFFSET field for actually designating a new frame offset. The fields further include FOR_SCH_FRAME_OFFSET_INCL and

FOR_SCH_FRAME_OFFSET fields indicating whether the frame offset is designated during assignment of the fonvard supplemental channel and the designated value, respectively. In the existing system, the supplemental channel is also assigned the same value as the frame offset designated during assignment of the fundamental channel of the dedicated control channel. However, in the embodiment of the present invention, the

REV_SCH_FRAME_OFFSET and FOR_SCH_FRAME_OFFSET field values are designated such that one of 16 frame offsets should be designated within 20ms during assignment of the supplemental channel, thereby making it possible to designate the frame offsets in a unit of 1.25ms.

FIG. 4 shows a demodulator for a receiver in a CDMA communication system.

Referring to FIG. 4, reference numeral 400 indicates an antenna of the mobile station for receiving various input signals. Reference numeral 410 indicates correlators for separating the multi-path signals received through the antenna 400. Reference numeral

420 indicates a combiner for combining the separated multi-path signals into one signal. The combined signal output from the combiner 420 is applied to deinterleavers 430, and the output signals of the deinterleavers 430 provided to decoders 440. The combiner 420 provides a frame boundary indication signal to the deinterleavers 430 through a control line 450 in addition to the combined symbols.

In operation, the correlators 410 detect correlation values of the associated multi- path signals, and the combiner 420 combines the correlation values output from the correlators 410. Further, the combiner 420 generates a signal for distinguishing a frame at a frame boundary. In the embodiment of the present invention, since the frame offset value of the fundamental channel is set to be different from frame offset value of the supplemental channel, the combiner 420 generates the frame boundary signals of the fundamental channel and the supplemental channel at the different time points. The detailed description of the frame boLindary signals will be made with reference to FIG. 5.

The deinterleavers 430 receive the frame boundary signals from the combiner 420 through the control line 450, and deinterleave the symbols output from the combiner 420 in a frame unit. Here, the frame boundary signals output through the control line 450 mclude an FCH/DCCH frame boundary signal and an SCH frame botindary signal The decoders 440 decode the sv mbols output from the demtei leav ers 430 to create decoded data

FIG 5 shows a detailed structure of the combmei 420 of FIG 4

Referring to FIG 5 the combiner 420 includes a timing generator 540, a first symbol combiner 550 for combining FCH/DCCH symbols and a second svmbol combiner 555 for combining SCH symbols The timing generator 540 receiving a system time, sets frame boundanes generates corresponding frame boundary signals at the set frame boLindaπes, and prov ides the generated frame boundary signals to first and second demterleav eis 431 and 435 Since the embodiment of the present mv ention sets the frame offset of the supplemental channel at the point where the supplemental channel is assigned, the fundamental channel and the supplemental channel can use the different frame offsets Therefoie, the timing generator 540 generates a first frame boundary signal for FCH/DCCH through a control line 565 and a second frame boundary signal for SCH through a contiol line 560, depending on the system time, the FCH/DCCH frame offset value and the SCH frame offset value That is, when it is intended to additionally assign a supplemental channel to transmit data, the timing generator 540 properly sets a frame offset of the supplemental channel such that the supplemental channel should have the different frame offset from the frame offset of the presently assigned fundamental channel in the traffic state The FCH DCCH frame offset value and the SCH frame offset value are received with the channel assignment message transmitted from the base station The FCH/DCCH frame offset v alue is transmitted with a fundamental channel assignment message, and the SCH frame offset v alue is transmitted w ith a supplemental channel assignment message The channel assignment messages are prov ided to a message processor 510, and the channel assignment messages processed by the message processor 510 are provided to a l esource controller 520 The resource controller 520 outputs a set frame offset value for the fundamental channel (FCH DCCH) and a set frame offset value for the supplemental channel (SCH) The frame offset values for the fundamental channel and the supplemental channel are provided to the timing generator 540

The fust symbol combiner 550 combines the multi-path symbols on the fundamental channel/dedicated control channel (FCH DCCH), and the second symbol combiner 555 combines the multi-path symbols on the SLipplemental channel (SCH) The first deinterleaver 431 deinterleaves the combined symbol output from the first symbol combiner 550 in a frame unit m response to the first frame boundary signal on the control line 565, and the second deinterleav er 435 deinterleaves the combined symbol output from the second symbol combiner 555 m a frame unit response to the second frame boundary signal on the control line 560

FIG 6 show s a detailed diagram of the timing generator 540 of FIG 5 The timing generator 540 includes tw o delays 620 and 630 to generate frame boundary signals using the system time 530 and the frame offsets 610 and 640 The frame offsets 610 and 640 include the frame offset 610 for the fundamental channel (FCH/DCCH) and the frame offset 640 for the supplemental channel (SCH) The frame offsets 610 and 640 are provided from the resource controller 520 shown m FIG 5 The delay 620 delays the system time 530 by the frame offset 610 set by the resourced controller 520 That is, the delay 620 delays the system time 530 by the FCH/DCCH frame offset 610 provided from the resource controller 520 and outputs the FCH DCCH frame boundary signal 565 The delay 630 delays the system time 530 by the frame offset 640 set by the resourced controller 520 That is, the delay 630 delays the system time 530 by the SCH frame offset 640 provided from the resource controller 520 and outputs the SCH frame boundary signal 560 As descπbed abov e, m the embodiment of the present invention, the timing generator 540 includes the tw o additional delays 620 and 630 so that the fundamental channel and the SLipplemental channel have the different frame offsets The delays 620 and 630 perform delay operations using their unique frame offsets 610 and 640, respectively. That is, the embodiment of the present invention additionally includes the delay for the supplemental channel in order to designate the frame offset assigned for the supplemental channel

FIG 7 shows a general call setup procedure in a CDMA communication system Specifically, FIG 7 sho s a message exchange procedure between modules the mobile station and modules the base station

Referring to FIG 7, the mobile station includes a message processor SIG for processing a channel establishment-related control message and a resource controller (RC) for managing and controlling base station resources A structure of the base station is similar to the structure of the mobile station That is, the base station also includes a message processor SIG for processing a channel establishment-related control message and a resource controller (RC) for managing and controlling logical and physical resources of the mobile station

Now, the call setup procedure will be descπbed w ith reference to FIG 7 When the mobile station has user data to transmit, the resource controller sends a call setup request signal Call_Setup Req to the message processoi SIG in step 710 The message processor SIG then sends an origination message (or call setup request message) to the base station in step 712

Upon receipt of the origination message transmitted from the mobile station, the message processor SIG in the base station inquires of the lesource controller m the base station whether it is possible to setup the call requested by the mobile station, m step 714 (CalljSetup Ind) If it is possible to settip the call, the resource controller sends a channel assignment approv al signal Call_Setup Res to the message processor SIG m step 716 The message processor SIG then sends an extended channel assignment message for approving assignment of the requested channel to the mobile station m step 718

Upon leceipt of the extended channel assignment message from the base station, the message piocess SIG in the mobile station sends a call setup confirmation signal Call_Setup Conf to the lesoLii ce controller in step 720 theieby completing establishment of the fonvard and reverse fundamental channel/dedicated control channel

After completing establishment of the fundamental channel between the base station and the mobile station in the above process, the mobile station and the base station perform a service negotiation piocess m step 722 If the base station and the mobile station come to an agreement on a service configuration iecord m the service negotiation process, the message piocessor SIG of the base station sends the agreed record value with a service connect message to the mobile station step 724 Further, the service connect message also includes a non-negotiation service configuration record The non- negotiation serv ice configuration record is registered m a non-negotiation service configuration record field assigned to the sen'ice connect message In this process, the resource controller of the base station designates a frame offset of the supplemental channel to be used until a renegotiation is made later w ith the mobile station, and registers the designated frame offset value m the non-negotiation service configLiration record field In step 726, the message processor SIG of the mobile station sends to the resource controller a Call_Setup Conf signal indicating that the frame offset of the supplemental channel has been set In addition the message processor of the mobile station sends a service connect completion message to the base station in step 728, thereby completing the call setup procedure

The non-negotiation sen ice configuration recoid can be transmitted with the service connect message or a univ ersal handoff direction message, not only when a call is initially setup, but also when a new service is connected oi a service configuration is changed, or w hen a handoff is performed Therefore, the embodiment can newly designate the frame offset of the supplemental channel m a state other than the call setup state

FIG 8 shows a detailed procedure for setting a frame offset of the supplemental channel, performed m the resoLirce controller, shown m FIG 7 More specifically, FIG 8 shows a procedure for designating a frame offset for the supplemental channel duπng a call setup process or a new service connect process according to an embodiment of the present invention That is, FIG 8 shows a procedure for setting a frame offset for the supplemental channel during a call setup process or a new service connect process according to an embodiment of the present invention

In FIG 8, operations of steps 810-818 are performed by the base station (BS), and operations of steps 820-828 are performed by the mobile station (MS) Further the procedure for assigning the frame offset for the supplemental channel performed bv the base station m steps 810-818 corresponds to a procedure performed m the sen ice negotiation process of step 722 of FIG 7 Further, the procedure for assigning the frame offset for the supplemental channel performed by the mobile station m steps 820-828 corresponds to a procedure performed after the mobile station receives the sen'ice connect message from the base station m step 724

Upon receipt of a call setup request message or a new service request message from the mobile station, the base station determines whether it is possible to assign the reverse or fonvard supplemental channel When determined to perform an initial call setup, additional traffic transmission or service connection, the base station sends a channel assignment message steps 810 and 812 Thereafter, a traffic channel is established or a new senπce is additionally connected between the base station and the mobile station At this moment, the base station negotiates information for the call setup or the new service connection with the mobile station

After completing the service negotiation in step 812, the base station determines the non-negotiation service configuration record constituting the service connect message to be transmitted to the mobile station, in step 814 That is, the base station sets the non- negotiation service configuration record to be added to the service connect message m step 814 At this point, the base station determines through the resource controller whether to newly designate a frame offset of the supplemental channel added m the present invention If it is determined to designate a new frame offset to the supplemental channel in step 814, the base station determines a proper frame offset taking into consideration the setup call, the traffic feature of the newly connected sen ice and the base station resources The frame offset of the supplemental channel can be set to be either identical to or different from the frame offset of the fundamental channel Here, the frame offset of the supplemental channel can be either previously set or generated by the base station through a separate operation In the frame offset designation process, the resource controller should set a proper frame offset value such that the loads are properly dispersed to transmit the data without delay Such determined frame offset of the supplemental channel is prov ided to the message processor SIG and registered m the non- negotiation sen ice configLiration record field The above operation of determining the frame offset of the SLipplemental channel and registering the determined frame offset of the SLipplemental channel in the non-negotiation service configLiration record field is performed in step 816 The legistered frame offset for the SLipplemental channel is set as a frame offset value of the supplemental channel to be assigned later Meanwhile, in step 818, the message processor SIG of the base station sends the sen ice connect message including the set negotiation serv ice configLiration recoid and non-negotiation service configuration l ecord to the mobile station

If the base station sends the service connect message for the call setup or the new service connection, the message processor SIG of the mobile station receives the service connect message in step 820 Upon receipt of the service connect message, the message processor SIG analyzes the received service connect message and prov ides the analyzed results to the resource controller of the mobile station, m step 822 That is, m step 822, the message processor SIG analy zes the non-negotiation sen ce configuration record as well as the other service configLiration record (negotiation service configuration record) Further, step 822, the message processor SIG sends the analyzed results of the non- negotiation sen ice configui ation record, I e , information about whether the frame offset of the SLipplemental channel is designated, and the set frame offset v alue to the resource controller

Upon receipt of the analyzed results, the resource controller determines m step 824 whether the frame offset of the supplemental channel is registered in the non- negotiation seivice configLiration record field If it is determined that the frame offset of the supplemental channel is registered in the non-negotiation service configuration record field, the message processoi SIG proceeds to step 826, and otherwise, proceeds to step 828. In step 826, the resource controllei assigns the frame offset for the supplemental channel, prov ided from the message piocessor SIG, to the corresponding supplemental channel, or stores the provided frame offset to use it when it is necessary to assign the supplemental channel oi use it m response to a supplemental channel request message (SCRM) from the mobile station Finally, step 828, the mobile station sends a service corrnect completion message, to thereby end the frame offset setting process

As stated abo e, hen the base station needs to assign a supplemental channel after registering the frame offset of the supplemental channel or has received the supplemental channel request message (SCRM) from the mobile station, the base station can use the registered frame offset

As described abov e, the embodiment of the present inv ention designates an exclusive frame offset for the SLipplemental channel, being different from the frame offset of the fundamental channel, to assign the supplemental channel, thereby making it possible to the scheduling loss which may caused by an excess of the link capacity

On the other hand a handoff may occur while data is transmitted over the supplemental channel assigned according to the embodiment of the present invention Therefore, the handoff is possible when an exclusive frame offset for the supplemental channel is different from the frame offset of the fundamental channel, as provided m the present invention In the context of the present invention, consideration is thus given to a case where it is not possible to support a frame offset value for the presently Lised SLipplemental channel, because a target base station uses a frame offset value for the existing supplemental channel when the handoff occurs In this situation, it is not possible to continuously provide the service

Theiefore, in an embodiment of the present inv ention, when a supplemental channel is handed off oi ne ly assigned in a handoff state betw een the base station and the mobile station of the CDMA communication system, a source base station measLires loads of the respectiv e frame offsets for a target base station, to designate or reset a mutually proper frame offset for the SLipplemental channel To this end, m the CDMA communication system according to an embodiment of the present invention, the frame offset for the supplemental channel is designated as a frame offset value different from the frame offset of the presently used fundamental channel or different from a predetermined frame offset a handoff state between the base station and the mobile station The base station then sends to the mobile station new frame offset designation information with a universal handoff direction message Upon receipt of frame offset information from the base station, the mobile station can additionally designate a frame offset for the supplemental channel in addition to the frame offset for the fundamental channel, or can operate a frame offset value different fiom the previously designated frame offset foi the supplemental channel Novv, a detailed description of a handoff procedure w ill be made with reference to the accompanying drawings, to bring a better understanding of the present invention

FIG 9 shows a general handoff procedure m a CDMA communication system Specifically, FIG 9 shows a message exchange procedure between modules of the mobile station and module of the base station

Referring to FIG 9, the mobile station includes a message processor SIG for processing a channel establishment-related control message and a resource controller (RC) for managing and conti ollmg base station resources The base station also includes a message processor SIG for piocessmg a channel establishment-related control message and a resource control lei (RC) for managing and controlling logical and physical resources of the mobile station Here, the base station includes a source base station presently in sen ice and a target base station to which the mobile station is to be handed off

Now, the handoff pi ocedure w ill be descπbed with reference to FIG 9 Upon detecting a pilot channel having a new pseudo-noise (PN) value, the resource controller of the mobile station reports measured pilot strength to the message processor SIG and commands the message processor SIG to send a new pilot strength measurement message or extended pilot strength measurement message, m step 1 110 Upon receipt of this command, the message processor SIG sends a pilot strength measurement message to the base station in step 1 120

Upon l eceipt of the pi lot sti ength measurement message transmitted from the mobile station, the message processor SIG in the source base station determines in step 1130 whether to add the mobile station to a new active set based on the pilot strength measurement value provided to the resource controller of the source base station from the mobile station If it is determined to add the mobile station to the active set, the resource controller of the source base station inquires of the resource controller of the target base station whether it is possible to assign a handoff resource to the resource controller of the target base station, in step 1 140 (Handoff Req) One of the factors for determining whether it is possible to assign the resouice may include supplemental channel-related contents If the taiget base station can accept the handoff the resource controller of the target base station sends a handoff acceptance response Handoff Conf to the resource controller of the source base station, in step 1150

Upon receipt of the handoff acceptance response Handoff Conf from the target base station, the source base station sends a universal handoff direction message including the new active set to the mobile station m step 1160 Here, if the target base station approves the handoff. the source base station forms a new physical channel. However, an actual part for generating the message is a message processor SIG of the source base station, and the generated message is transmitted to the mobile station using physical layers of the source and target base stations, not shown in FIG 1 1 Such generated and transmitted universal handoff direction message includes supplemental channel-related information when a SLipplemental channel is newly assigned or handed off

When determining in step 1140 whether it is possible to perform the handoff, the resource controller of the taiget base station examines whether it is possible to hand off the reverse or fonv ard supplemental channel. In this process, the frame offset re- designation proceduie is added during a handoff according to an embodiment of the present invention The re-designation procedure is a procedure included the Handoff Req and Handoff Conf messages, and a frame offset part must be added to a supplemental channel-related factor m the Handoff.Req message transmitted to the target base station If the target base station accepts the same frame offset as the frame offset of the supplemental channel presently in service, it is possible to soft-handoff the supplemental channel without re-designation of the frame offset However, when the service (or source) base station does not operate with the same frame offset as presently used one, the target base station negotiates an acceptable frame offset for the supplemental channel with the source base station, so that the source and target base stations newly designate the same frame offset, thereby performing a hard handoff The added procedure is a procedure for setting a new frame offset This procedure will be described m detail w ith rcfei ence to FIG 10

In step 1 170. the message processor SIG of the mobile station sends a control signal Handoff.Req to the resource controller of the mobile station, and assigns a transmission channel or a reception channel of the corresponding fundamental channel and the supplemental channel After completing assignment of the resource necessary for the handoff, the resource controller informs the service option which is an application sen/ice layer of the mobile station, that it is possible to transmit/receive data, in step 1180 (Handoff Conf) Finally, in step 1190, the message generator SIG sends a handoff completion message to indicate completion of the handoff procedure Here, the handoff completion message is processed by the message processor of the source base station

After completion of the above procedure, the base station and the mobile station exchange the data traffic w ith the handoff-related base station through the fundamental or supplemental channel FIG 10 shows a procedure for assigning a frame offset for the supplemental channel according to an embodiment of the present inv ention, performed duπng the handoff procedure of FIG 9 In FIG 10, operations of steps 1210-1224 correspond to the operations of steps 1130-1 150 m FIG 9 and are performed by the source and target base stations Further, operations of steps 1226- 1236 correspond to the operations of steps 1170-1 190 m FIG 9 and are performed by the mobile station The procedure for assigning the frame offset foi the supplemental channel by the source and target base stations is performed through the steps 1 140-1 150 of FIG 9, and the procedui e for assigning the frame offset for the supplemental channel by the mobile station is performed through the steps 1 170 and 1 180 of FIG 9

When the mobile station sends a pilot strength measurement message (PSMM) m step 1210, the resource controller of the source base station determines m step 1212 whether to add a pilot having the new ly added PN value to the activ e set, depending on the pilot strength If it is determined not to add the pilot to the activ e set, the resource controller proceeds to step 1214 to av oid performing the handoff However, if it is determined to add the pilot to the active set, the resource controller determines in step 1216 whethei the supplemental channel and other resources are presently assigned If the supplemental channel is not assigned, the resource conti oiler hands off only the fundamental channel or the dedicated control channel m step 1220 Otherwise, when the supplemental channel is assigned in step 1216, the resouice controller proceeds to step 1218 and determines whether it is possible to hand off the SLipplemental channel At this point, it is necessary to inquire of not only the source base station but also the target base station w hethei it is possible to assign the handoff resource foi the supplemental channel

If it is not possible to hand off the SLipplemental channel, the lesource controller hands off only the fundamental channel or the dedicated control channel in step 1220 Othenvise, if it is possible to hand off the supplemental channel, it is necessary to search the frame offset having the lower load in both the source and target base stations

Therefore, in step 1222, the resource controllers of the source and target base stations designate a frame offset foi the supplemental channel, inform the message processoi SIG of the designated frame offset, and also, inform the phv sical layers of the source and taiget base stations of the fr ame offset for the coπ espondmg supplemental channel Here, i f the target base station accepts the same frame offset as the frame offset of the supplemental channel presently in service, it is not necessarv to re-designate the frame offset Howevei , if the target base station does not opei ate w ith the same frame offset, the target base station negotiates an acceptable frame offset for the supplemental channel with the source base station, so that the source and target base stations newly designate the same frame offset The physical layer then sets this v alue as an exclusive frame offset value for the supplemental channel Hei e, the frame offset of the SLipplemental channel established for data transmission can properly be designated according to an amount (or load) of the transmission/reception data for the respective frame offsets The frame offset of the supplemental channel can be set to be either identical to or different from the frame offset of the fundamental channel Here, the frame offset value is properly determined such that the loads of the service base station and the target base station, vv Inch designated the frame offset, are properly dispersed to transmit the data without delay Thereafter, m step 1224, the resource controller of the source base station directs the univ ersal handoff direction message (UHDM) to be created, to which frame offset-related fields for the supplemental channel are added Upon receipt of the direction, the message controller SIG of the source base station generates the corresponding message and sends the generated message to the mobile station through the physical layers of the source base station and the target base station

Upon receipt of the univ ersal handoff direction message from the base station, the message processor SIG of the mobile station analyzes the received universal handoff direction message and provides the analyzed results to the source controller of the mobile station, m step 1226 After completing the analysis, the resource controller determines m step 1228 whether the supplemental channel is included, based on analyzed results If the supplemental channel is included, the message processor SIG sends to the resource controller information about w hether the frame offset for the supplemental channel is set, and the offset v alue, together with other supplemental channel parameters The resource controllei then l eceiv cs the analyzed results by the message processor SIG and determines in step 1230 w hether the frame offset of the supplemental channel is designated or not If the frame offset of the supplemental channel is designated, the resource controller sets the corresponding frame offset value for the SLipplemental channel and sends to the physical layer the new frame offset value together with the supplemental channel assignment signal, m step 1232 Upon receipt of the supplemental channel-related signal from the resource controller, the physical layer assigns the supplemental channel and additionally sets a frame offset value for the supplemental channel to enable data transmission/reception When the fonvard/reverse supplemental channel is established between the base station and the mobile station as stated above, the resource controller performs a handoff on the established supplemental channel in step 1234 However, if it is determined in step 1228 that the supplemental channel is not included, the resource controller performs a handoff on the fundamental channel/dedicated control channel in step 1236 Meanwhile, after completion of the handoff, the resource controller sends a handoff completion message (HCM) m step 1238, and thereafter, the data traffic of the application senice is transmitted

In the embodiment of the present invention, the base station includes a step (a) m which the resource controllei of the base station determines whethei it is possible to set the supplemental channel, a step (b) m which if it is determined to set the supplemental channel, the resource controller checks a frame offset SCH_frame_offset to be exclusively used for the SLipplemental channel, a step (c) which the resource controller adds the frame offset to the SLipplemental channel assignment message to make a message shown FIG 11 , in order to send the frame offset to the mobile station, and a step (d) m which the resource controllei designates the frame offset value designated by the physical layer to the assigned supplemental channel Here, m the step (d), the resource controller should set a proper value such that the loads should be propeily dispersed to transmit the data without delay

In addition, the mobile station includes a step (a) for detecting a frame offset for the supplemental channel in the process of analyzing the extended supplemental channel assignment message and providing the detected frame offset information to the resource controller, a step (b) in which the resource controller provides the set value to the physical channel, and a step (c) in which the physical layer newly sets the frame offset dunng assignment of the supplemental channel

FIG 1 1 shows a sti ucture of an extended supplemental channel assignment message or a universal handoff direction message, to which a non-negotiation service configui ation lecoid field is added according to an embodiment of the present invention

In the extended supplemental channel assignment message or the universal handoff direction message as shown in FIG 1 1 , the non-negotiation service configuration record field includes a REV_SCH_ID field indicating an identification (ID) of a channel assigned the mobile station during assignment of the reverse supplemental channel, a

REV_SCH_FRAME_OFFSET_INCL field indicating whether to newly designate a frame offset during assignment of the reverse supplemental channel, and a REV_SCH_FRAME_OFFSET field foi actually designating a new frame offset The non- negotiation seiv ice configui ation l ecoi d field further includes a FOR_SCH_ID field indicating an identification (ID) of a channel assigned the mobile station duπng assignment of the fonvard supplemental channel, and

FOR_SCH_FRAME_OFFSET_INCL and FOR_SCH_FRAME_OFFSET fields indicating whether the frame offset is designated during assignment of the fonvard supplemental channel and the designated value, respectively In the existing system, every channel is assigned the same value as the initially assigned frame offset ev en m the handoff state However, in the embodiment of the present invention, the REλ'_SCH_FRAME_OFFSET and FOR_SCH_FRAME_OFFSET field values are designated such that one of 16 frame offsets should be designated w ithin 20ms during assignment of the supplemental channel, thereby making it possible to designate the frame offsets m a unit of 1 25ms The physical layer designates the frame offset of the SLipplemental channel through the above message Conventionally, the physical channel registers the frame offset value of the supplemental channel m the REV_SCH_FRAME_OFFSET, and FOR_SCH_FRAME_OFFSET fields, and this value is changed in a unit of 20ms to a REVjVIULTI_FRAME_OFFSET or FOR_MULTI_FRAME_OFFSET field value according to the multi-frame size of the supplemental channel designated m the service configuration record determined dunng service negotiation In the embodiment of the present invention, the record value is changed m a unit of 1 25ms m order to change the frame offset value every 1 25ms dunng assignment of the supplemental channel

As described above, the present invention is applied to a case where the future CDMA communication system assigns a SLipplemental channel when data traffic is generated in a traffic state where a basic call is connected By providing the novel apparatus and method for designating a new frame offset for the supplemental channel to fixedly assign the supplemental channel to the user, it is possible to reduce the transmission delay and the scheduling loss, which may be caused by traffic concentration on a specific frame offset because the traffic has the burst property in the data sen'ice

While the invention has been shown and described with reference to a certain preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims

Claims

WHAT IS CLAIMED IS:

1 A method tor transmitting, in a base station, spread data obtained by spreading data of a plurality of users w ith orthogonal codes assigned to the respective users in frames on a plurahtv of supplemental channels, the method compnsmg the step of trasmittmg the spieaci data of different users ovei the supplemental channels, m different frames hav ing a frame offset time determined according to an amount of data on the respective supplemental channels

2 The method as claimed m claim 1 , wherein the supplemental channels are assigned in association w ith prev iously assigned fundamental channels

3 The method as claimed in claim 1 , whei ein the supplemental channels are reverse SLipplemental channels

4 The method as claimed claim 1 , wherein the supplemental channels are fonvard supplemental channels

5 A method for assigning a supplemental channel corresponding to one of a plurality of assigned fundamental channels using the same frame offset at a request for assigning a supplemental channel coπespondmg to one of the fundamental channels, the method comprising the step of. designating a frame offset of the supplemental channel to be different from frame offsets of the assigned supplemental channels according to an amotint of data transmitted ov ei supplemental channels assigned m association w ith the fundamental channels using the same frame offset

6 The method as claimed in claim 5, wherein the supplemental channel assignment request is a supplemental channel request message from a mobile station in which the fundamental channel is previously assigned

7 The method as claimed in claim 6, whei ein the supplemental channels are reveise supplemental channels

8 The method as claimed in claim 5, wherein the supplemental channel assignment request is generated depending on data to be ti ansmitted to a mobile station m which the fundamental channel is prev lously assigned 9 The method as claimed in claim 8, wherein the supplemental channels are fonvard supplemental channels

10 A method for assigning a supplemental channel corresponding to a plurality of fundamental channels having a predetermined frame offset, assigned in association with a plurality of mobile stations, the method comprising the steps of upon leceipt of a lequest for assigning a supplemental channel corresponding to the fundamental channels, detecting an amount of transmission data for respective frame offsets of the supplemental channels presently assigned in association with the fundamental channels, and designating a frame offset of the assignment-requested supplemental channel according to the detected amount of the transmission data foi the respectiv e frames offsets

1 1 The method as claimed in claim 10, w hei ein the supplemental channel assignment request is a supplemental channel request message from a mobile station m which the fundamental channel is previously assigned

12 The method as claimed in claim 11 , wherein the supplemental channels are reverse supplemental channels

13 The method as claimed in claim 10, wherein the supplemental channel assignment request is generated depending on data to be ti ansmitted to a mobile station m which the fundamental channel is previously assigned

14 The method as claimed in claim 13, wheiein the supplemental channels are fonvard supplemental channels

15 A method for assigning a supplemental channel corresponding to a plurality of fundamental channels having a predetermined frame offset, assigned in association with a plurality ot mobile stations, the method comprising the steps of upon receipt of a request for assigning a supplemental channel corresponding to the fundamental channels, detecting an amount of transmission data for respective frame offsets of the supplemental channels presently assigned in association w ith the fundamental channels, designating a frame offset of the assignment-requested supplemental channel accoi dmg to the detected amount of the transmission data for the respective frames offsets, and sending the designated frame offset with an extended SLipplemental channel assignment message, and upon receipt of the extended supplemental channel assignment message, assigning a supplemental channel having the designated frame offset, if the received extended supplemental channel assignment message has the designated frame offset of the supplemental channel

16 The method as claimed in claim 15, whei em the supplemental channel assignment request is a supplemental channel request message from a mobile station which the fundamental channel is previously assigned

1 7 The method as claimed m claim 16, wheiem the supplemental channels are reverse supplemental channels

I S The method as claimed in claim 15, w herein the supplemental channel assignment request is generated depending on data to be transmitted to a mobile station m which the fundamental channel is previously assigned

19 The method as claimed m claim 18, whei em the supplemental channels are forward supplemental channels

20 A method for performing a handoff, from a source base station to a target base station, on a mobile station to which a plurality of fundamental channels having a predetermined frame offset and a supplemental channel corresponding to the fundamental channels are assigned, the method comprising the steps of upon receipt of a handoff request for the mobile station, the source base station sending to the taiget base station fr ame offset information of the fundamental channel and the supplemental channel assigned to the mobile station, to determine whether the supplemental channel is acceptable, performing a soft handoff on the mobile station using the frame offset of the supplemental channel, if the frame offset of the supplemental channel is acceptable by the target base station, and designating a frame offset different from the frame offset of the supplemental channel through a negotiation between the target base station and the source base station and performing a hard handoff on the mobile station using the designated frame offset of the supplemental channel, i f the frame offset of the supplemental channel is not acceptable by the target base station

21 The method as claimed in claim 20, w hei em the handoff request is generated depending on a power level of a pilot signal that the source base station has receiv ed from the mobile station

22 The method as claimed m claim 20, wherein whether the supplemental channel is acceptable is determined on whether the target base station can transmit data using the frame offset of the supplemental channel

23 An apparatus for receiv ing data transmitted over fundamental channels having a predetermined frame offset for a plurality of mobile stations and supplemental channels assigned in association w ith the fundamental channels, the apparatus comprising a timing generator for receiving a frame offset of the fundamental channel, a frame offset of the supplemental channel and a system time, outputtmg the sy stem time delayed by the frame offset of the fundamental channel as a fundamental channel boundary signal, and outputtmg the sy stem time delayed by the frame offset of the SLipplemental channel as a supplemental channel boundary signal, a first symbol combiner for combining multi-path symbols transmitted ov er the fundamental channel, a second symbol combiner for combining multi-path symbols transmitted over the supplemental channel, a first deinterlea er for receiv ing the symbols and the fundamental channel boLindarv signal from the first symbol combiner, and deinterleavmg the symbols from the first symbol combiner in a frame unit determined by the fundamental channel boundary signal, and a second deinterleaver for receiving the symbols and the supplemental channel boundary signal from the second symbol combiner, and deinterleavmg the symbols from the second symbol combiner in a frame unit determined by the supplemental channel boundary signal

24 The apparatus as claimed in claim 23, wherein the timing generator comprises a first delay for receiving the frame offset of the fundamental channel and the system time, and delaying the system time by the frame offset of the fundamental channel to output the fundamental channel boundary signal, and a second delay for receiving the frame offset of the supplemental channel and the system time, and delaying the system time by the frame offset of the supplemental channel to output the supplemental channel boundary signal

25 The apparatus as claimed m claim 23, wherein the frame offset of the fundamental channel is different from the frame offset of the supplemental channel

26 The apparatus as claimed in claim 23, w herein the frame offset of the supplemental channel is designated according to an amount of the transmission data for the respective frame offsets of the supplemental channels assigned in association with the fundamental channels