KR20010016790A - Method for accepting a call in wireless asynchronous transfer mode - Google Patents

Abstract

PURPOSE: A method for controlling a call acceptance in a wireless asynchronous transfer mode(ATM) network is provided to predict a new area in which a handover progresses by using a record of a terminal handed over other area until now, and to measure an expectation value progressing in the predicted area, then to compare the amount of resources for being newly set up by using the measured expectation value, when a new terminal requests a real-time service to set up a call. CONSTITUTION: If a bandwidth change is requested(S1), an asynchronous transfer mode(ATM) wireless network decides whether the request is by a node intra hand-over(S2). If so, the ATM wireless network performs a node intra hand-over process(S5). If the request is not by the node intra hand-over, the ATM wireless network decides whether the request is by a service completion relating to a predetermined terminal(S7). If so, the ATM wireless network subtracts a bandwidth(Bn) guaranteed in the terminal from a bandwidth(Bk) guaranteed in a wireless transceiving device for managing a service completed-terminal, and resets the subtracted value as the bandwidth(Bk)(S9). The ATM wireless network rearranges bands relating to terminals according to information of the reset bandwidth(Bk)(S13). If the request is not by the service completion relating to the predetermined terminal, the ATM wireless network decides an acceptance of the requested band(Bn)(S11), and rearranges the bands relating to the terminals according to the accepted requested band(Bn)(S13). If the ATM wireless network is not capable of accepting the requested band(Bn), the ATM wireless network rejects a call request(S15).

Description

Call admission control method in wireless asynchronous transmission mode network {METHOD FOR ACCEPTING A CALL IN WIRELESS ASYNCHRONOUS TRANSFER MODE}

The present invention relates to a call admission control method in a wireless asynchronous transfer mode (ATM) network, and more particularly, to a method for controlling call admission using mobility information of a terminal currently in use.

According to the traffic management standard of the ATM forum, services in the B-ISDN network environment include Constant Bit Rate (CBR), Real Time-Variable Bit Rate (RT-VBR), and Non Real Time-Variable Bit (NRT-VBR). It is classified into service attributes such as Rate) and UBR (Unspecfied Bit Rate). These features distinguish between real-time processing services that allow some loss of data but are sensitive to propagation delays, and very sensitive to cell loss. In addition, due to the use of wireless, the mobile use of the terminal should be possible, and at this time, a handover process should be performed among a base station or a switch supporting mobility, which is a wireless and wired connection point. As a requirement for performing handover, it is important to maintain Quality of Service (QoS), which is defined in the ATM Forum.

In a wireless ATM environment, bandwidth is used for each terminal through call admission control. This will be described below with reference to the accompanying drawings.

The conventional wireless environment has a frame structure as shown in FIG. The uplink consists of random access channel slots and data transmission slots designated for call access and reservation requests, and each slot of the downlink is reserved for secondary slots and uplinks for acknowledgment of received data and reservation requests. It consists of a part for transmitting downlink data along with a subslot for notifying a result. Looking at the slot allocation process of the conventional method in more detail, as shown in Figure 2, it has a frame structure for notifying the slot allocation result through the downlink signal burst at regular intervals. Downlink signal bursts are inserted at regular intervals, and the information notified here includes uplink reservation results for the UE, a frame structure in the downlink, an acknowledgment for the RACH slot, and designation of various control channels.

When a packet is generated while the mobile station's buffer is empty, each terminal operates in a contention mode. At this time, the terminals perform a slot reservation request by random access or polling through the RACH slot on the uplink. The acknowledgment for this reservation request is performed in slots or signal burst periods in the downlink. When the reservation request is made by the random access method, since the yield is low, it is proposed to apply the polling method in consideration of the delay time and stability due to the collision. In the polling method, the reservation request priority of each terminal is calculated as shown in Equation 1, and the polling is performed in order of the highest priority.

In the above equation, c is a scaling factor, and r and τ _f each represent an average data rate of the corresponding UE and an elapsed time since the last transmission.

When such a reservation request is made, new parameters are newly displayed in the current buffer and the dynamic parameters such as the number of waiting packets and the remaining lifespan are transmitted together.Therefore, since there is not much information, one slot is divided into several sub-slots. Reduction measures are also proposed. In addition, it is proposed to control the transmission probability or increase or decrease the number of RACH slots according to the load of the reservation request terminal.

UEs in the reserved mode are notified of the band allocation result by the base station. The central base station is the connection-specific information such as the average and maximum data rates set when all mobile terminals access the call, the number of cells waiting in the buffer for each VC, the shortest remaining life, and the average of the cells in the largest buffer. Collect dynamic parameters such as remaining life. The dynamic parameter is generally included in the uplink packet and transmitted. The collected information is used to calculate priorities of cells to be transmitted, and every slot is allocated to a terminal having high priority. In this case, an example of calculating the priority of each terminal is shown in Equation 2.

Where a and b represent scaling factors and τ _r and Represents the remaining lifetime of the cell and the queue length in the buffer, respectively.

This bandwidth allocation method allocates additional required bandwidth without considering the current state. Therefore, when a mobile terminal operating in another area is handed over, there is a high possibility that the bandwidth for the handed over terminal is insufficient, and therefore, the handover is likely to be rejected.

As described above, in the conventional bandwidth allocation scheme, handover proceeds without any consideration for a case where a terminal using high-speed multimedia information is handed over due to local movement. Therefore, resources of a new region are available for handover. It is very likely that no extra resources remain when checking for availability. Therefore, there is a problem that real-time information in service can only be lost as much as the possibility of handover being rejected.

The present invention has been made to solve this problem, and an object of the present invention is to estimate a new area to be handed over using a record handed over to another area so far, and measure an expected value to proceed to the predicted area. In this state, when a new terminal requests a real-time service and wants to set up a call, the present invention provides a method of performing call admission control by comparing an amount of resources to be newly set using a measured expected value.

In order to achieve the above object, the present invention provides a call admission control method in an asynchronous transmission mode wireless network in which a plurality of radio transceivers are connected in an access point connected to an asynchronous transmission mode switch, and a bandwidth change is requested, Intra) determining whether the request by the handover; Performing handover processing in the access point jurisdiction, if it is caused by a handover in the access point jurisdiction; If it is not a request by handover in the access point jurisdiction, determining whether the bandwidth change request is caused by the termination of a service for a predetermined terminal; If the bandwidth change request is due to the termination of the service for a predetermined terminal, the bandwidth B _N allocated to the terminal is subtracted from the bandwidth B _K allocated to the radio transceiver for the terminal in which the service is terminated. Rearranging the bands for the terminals according to the bandwidth information after resetting to (B _K ); If the bandwidth is not requested by the service termination for a predetermined terminal,

(B _N is the requested bandwidth, B _max is the total available bandwidth, B _K is the bandwidth for the currently allocated real-time service, and EB _KO is the handover to reduce the allocated bandwidth by moving the terminal to another radio area. Expected expectations, Determining the acceptance of the request band (B _N ) by the expected value that is expected to be added by the terminal visit from the radio transceiver, and rearranging the bands for the terminals according to the acceptance band; If the request band of the terminal cannot be accepted, the step of rejecting the call request is configured to be sequentially performed for both the radio transceivers.

1 is a diagram illustrating a frame structure of a conventional protocol;

2 is a diagram illustrating a slot allocation process in a conventional wireless environment;

3 is a view showing a state of a network performing a call admission control method in a wireless asynchronous transmission mode network according to the present invention;

4 is a diagram showing a state of a table configured in an access point for performing a call admission control method in a wireless asynchronous transmission mode network according to the present invention;

5 is a diagram showing the state of another table configured in an access point for performing a call admission control method in a wireless asynchronous transmission mode network according to the present invention;

6 is a flowchart of a call admission control method in a wireless asynchronous transmission mode network according to the present invention;

7 is a flowchart illustrating an intra handover procedure in an access point in a call admission control method in a wireless asynchronous transmission mode network according to the present invention.

<Explanation of symbols for main parts of drawing>

1: ATM switch AP1, AP2: access point

DT11-DT1k, DT21-DT2k: Radio Transceiver

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

3 is a schematic block diagram of a wireless ATM network in accordance with the present invention. As illustrated, a plurality of distributed transceivers DT11-DT1k and DT21-DT2k are connected to the ATM switch 1 through access points AP1-AP2. The radio transceivers DT11-DT1k and DT21-DT2k communicate with terminals MS in the jurisdiction. Although only two connection points AP1 and AP2 are connected to the ATM switch 1 in the drawing, it is easily understood by those skilled in the art that a plurality of connection points may be connected as necessary. Could be.

In the present invention having such a configuration, when the power of the terminal MT is turned on and registration is started, the area of the wireless transceiver (for example, DT11) to which the terminal MT mainly resides is set as a home region, and the wireless transceiver is set. The access point AP1 that manages the wireless transceiver DT11 by finding out which terminal MT belongs to the wireless cell area by the wireless transceiver DT11 through an identification signal (eg, a Beacon signal) from the DT11. In the memory. In addition, the bandwidth for the real-time service allocated to the terminal MT and the handover rate to other wireless transceiver devices DT12-DT1k and DT21-DT2k areas are recorded. The handover rate for any one terminal MT is the number of handovers performed for the number of connections (NC) from the first use of the terminal MT to the present time. ), And stores the past experience value in consideration of), and this value is managed only for the terminal MT designated as the main area of the radio transceivers DT11-DT1k and DT21-DT2k in the jurisdiction of the access points AP1 and AP2. , Is equal to equation (3).

Here, RH means the handover rate of the terminal, NC means the total number of access of the terminal and NH means the number of handover of the terminal.

On the other hand, the information on the terminal MS belonging to another access point AP1 or AP2 is only stored temporarily, and the handover rate RH in this case is designated as one.

In Equation 3, the NC may be fluidly operated such that the operator of the access point (AP, AP2) maintains only information within a month from the present time point for efficient use of the memory. In addition, the access points AP1 and AP2 record the visited area due to handover for each terminal MT, and manage the terminal MT as a candidate area to be handed over and exit as shown in FIG. 4 during call admission control. Is used to extract the expected value. Note 1 in FIG. 4, that is, DT _- MT1 means that the wireless transceiver DT1 becomes a home area and the identification number of the terminal MT becomes 1. In Note 2, UBW1 means the real-time bandwidth that DT _- MT1 is using.In Note 3, RH1 means the total rate that DT _- MT1 will hand over to another radio transmission area, and in Note 4, VR1 means DT _- MT1 Refers to the handover rate to candidate region 1, and VR2 in note 5 refers to the handover rate of DT _- MT1 to candidate region 2. Accordingly, the sum of the visiting ratios (VRs) to candidate regions for an arbitrary terminal MT is a handover rate (RH) to other wireless transceiver devices DT11-DT1k and DT21-DT2k. Equation 4 (for example, handover rate RH1 of terminal MS1) can be written as follows.

RH1 = VR11 + VR12 + .... + VR1n + VR21 + VR22 + .... + VR2k

In addition, at the access points AP1 and AP2, the bandwidth currently being used for the real-time service for each radio transceiver (DT11-DT1k, DT21-DT2k: denoted by D # in FIG. 5) as shown in FIG. 5, and other radio transceivers (DT11-DT1k, DT21-DT2k) stores the bandwidth expected to be added by handover from the area, and the value of the additional real time bandwidth determined by the combination of these values. First, the sum of the bandwidths currently used for the real-time service of each terminal MT stored in FIG. 4 becomes the bandwidth of any one wireless transceiver (eg, DT11), and for the real-time service in the wireless transceiver DT11. The bandwidth UBW in use can be written as Equation 5.

UBW = UBW (1) + UBW (2) + ... + UBW (k)

Here, UBW (k) refers to a bandwidth being used by each terminal MT in the wireless transceiver DT11.

The expected value of the bandwidth to be added is equal to the sum of all values for which the desired radio transceivers DT11-DT1k and DT21-DT2k become candidate regions from the values of FIG. 4. That is, when obtaining the value of the bandwidth to be added in the wireless transceiver DT11, candidates from among the information as shown in FIG. The sum of all the visit rates at which the area becomes the wireless transceiver DT11. The expected value of the bandwidth to be deleted is equal to the value of FIG. 4 multiplied by UBW and RH. The additional real time bandwidth is calculated as shown in Equation 6 from the bandwidth to allow allocation when a new real time service is required.

That is, by considering the expected value to be handed over from another area during call admission control, it is possible to increase the probability of guaranteeing real-time service even if a handover occurs.

Several items are assumed to describe the call admission control method according to the present invention considering handover of real-time data service. In addition, the minimum unit transmission rate to each terminal MT is referred to as Bm, and one slot time is T (1 / Bm) and bandwidth allocated for real-time data transmission to the wireless transceivers DT12-DT1k and DT21-DT2k. (guaranteed bandwidth: GBW) the B _K, the terminal (MT) is prescribed by moving from the mobile transceiver (DT11-DT1k, DT21-DT2k of, e.g., D11) with the other wireless transceiver (e.g., DT12) region that is, the hand Overload occurs, as in accordance with the expected value which is expected to reduce the GBW were assigned to the mobile transceiver (D11) EB _KO, wireless transceiver (s DT11-DT1k, DT21-DT2k, e.g., D12) other wireless due to handover in a Expected value that GBW is expected to add by the visit of the terminal MT from the transmitting and receiving device D11 The new bandwidth guarantees a new bandwidth guarantee, the bandwidth B _N requires a change or addition, the bandwidth B _NH requires a change or addition by handover, and the maximum bandwidth of the wireless transceivers (DT11-DT1k, DT21-DT2k). Let B _max , the total available bandwidth of the access points AP1 and AP2 be B _O , and the total GBW set at the current access points AP1 and AP2 be B _C.

The change request of the real-time data service can be divided into two cases. One is a case where a new terminal MT requests a service, and the other is a mutual communication between the radio transceivers DT11-DT1k and DT21-DT2k by intra-AP handover in the access points AP1 and AP2. This is due to bandwidth exchange. In the case of requesting a new service, the service may be divided into two types, namely, the termination of the existing real-time service and the additional request for the real-time service.

As shown in the figure, it is determined whether a change of bandwidth for the real-time service is requested (S1), and if the change of bandwidth is requested, the process proceeds to step S3. In step S3, if it is determined that the request for bandwidth change is a request by intra-AP handover and is due to intra-jurisdiction handover, the process of FIG. 7 described below (intra-jurisdiction handover process) (S5). However, if the request is not due to intra-jurisdiction handover, the process proceeds to step S7 to determine whether the bandwidth change request is caused by the termination of the service for the predetermined terminal MT.

As a result of the determination in step S7, in the case of a bandwidth change request by the termination of the service for the predetermined terminal MT, the wireless transmission / reception apparatus DT12-that manages the terminal MT in which the current service is terminated, proceeds to step S9. The bandwidth B _N allocated to the terminal is subtracted from the bandwidth B _K allocated to DT1k and DT21-DT2k, and the subtracted value is reset to the bandwidth B _K. Then, the bands for the terminals MT are rearranged according to the bandwidth information (S13).

However, as a result of the determination in step S7, when the bandwidth request by the service termination for the predetermined terminal MT, that is, when a new real-time service is added, the allocation of the bandwidth (B _N ) of the added real-time service is It is determined in step S11 whether it is possible. That is, due to the handover in the difference between the total available bandwidth (B _max ) and the bandwidth (B _K ) for the currently allocated real-time service, the terminal (MT) moves to another area of the wireless transceiver (DT12-DT1k, DT21-DT2k). The difference between the expected value EB _KO expected to decrease by moving and the expected value expected to be added as the terminal MT visits from the radio transceivers DT12-DT1k and DT21-DT2k. When the smaller value of the difference is greater than the bandwidth B _N of the added real-time service (S11), the request band B _N of the visited terminal MT is allocated. That is, whether to accept the request band B _N of the terminal MT is set using Equation 7.

Result of executing the equation (7), the terminal (MT) in accordance with the band (B _N) of the terminal (MT) request bandwidth (B _N) there is a terminal (MT) to accept the process proceeds to step (S13) if one accepts the If the rearrangement of the bands is re-arranged, but the request band B _N of the terminal MT cannot be accepted, the call request is rejected (S15) and the process proceeds to step S17.

In step S17, it is determined whether the above-described process is performed for all the wireless transceivers DT11-DT1k and DT21-DT2k, and the above-described process is performed for all the wireless transceivers DT11-DT1k and DT21-DT2k. If not, other radio transceivers DT11-DT1k and DT21-DT2k that are not performed are set to perform the above-described process (S19).

However, when the above-described process is performed for all the wireless transceivers DT12-DT1n and DT21-DT2n, the process proceeds to step S20 and according to the newly allocated bandwidth information according to the process described above with reference to FIGS. 4 and 5. Update the table and finish the process.

Another request for a real-time data service change request is due to mutual bandwidth exchange between the radio transceivers DT11-DT1k and DT21-DT2k by handover within the jurisdiction of the access points AP1 and AP2. Fig. 7 shows the bandwidth handling procedure for real time service in this case. That is, FIG. 7 shows a new bandwidth processing procedure to be handed over.

As shown, the bandwidth MT (B _NH ) due to handover is caused by the terminal MT in the area of the radio transceiver (eg, DT11) with respect to the radio transceivers DT11-DT1k and DT21-DT2k (eg, DT12). ), The maximum bandwidth B _max of the radio transceiver DT12 is subtracted from the bandwidth B _{K + 1} allocated to the terminal DT12, and the subtracted value is subtracted from the terminal MT. It is determined whether the request bandwidth (B _NH ) or more (S21). That is, the radio transceiver DT12 determines whether there is room to accommodate the request bandwidth B _NH . As a result of the determination in step S21, if there is no room to accept, the flow advances to step S23 to reject the handover request. However, the receiving capacity are there to reset the allocated bandwidth (B _{K + 1)} requests bandwidth (B _NH) for adding the assigned bandwidth (B _{K + 1)} of the mobile transceiver (DT12) to the mobile transceiver (DT12) if (S25), the bandwidth B _NH of the terminal MT handed over to the bandwidth B _{K of} the radio transceiver DT11 is subtracted to reduce the bandwidth B _K of the radio transceiver DT11. Reset (S27).

Thereafter, in step S29, it is determined whether the above-described process is performed for all the wireless transceivers DT11-DT1k and DT21-DT2k, and the above-described process is performed for all the wireless transceivers DT11-DT1k and DT21-DT2k. If not performed, other wireless transceivers DT11-DT1k and DT21-DT2k that are not performed are set to perform the above-described process (S31).

However, when the above-described process is performed for all the wireless transceivers DT11-DT1k and DT21-DT2k, the process proceeds to step S21 in accordance with the newly allocated bandwidth information according to the above-described process of FIGS. 4 and 5. Update the table and finish the process.

That is, if there is only available bandwidth of the new wireless transceiver devices DT11-DT1k and DT21-DT2k to be handed over, the bandwidth of the new area is added, the bandwidth of the existing area is removed, and the contents of FIGS. 4 and 5 are updated. And proceed to the next. Therefore, in the bandwidth adjustment by the handover process, since the call is set up in consideration of the handover in the call admission control process, the connection establishment can be performed immediately to reduce the rejection state of the handover due to the lack of resources (BW) to the minimum. have.

That is, in the present invention, if a record of the movement of the terminal is kept and a new call is required, the mobility of the terminal operating in the area to which the bandwidth required for the real-time service is greater than the currently available bandwidth and the call is to be established By estimating the outgoing bandwidth, and estimating the real-time bandwidth of the terminal to enter from another area, the new call is set up only when the bandwidth of the state considering the expected value is greater than the desired bandwidth. The city can guarantee the service as much as possible.

As such, in the present invention, the possibility of maintaining the existing bandwidth intact in handover is increased, which is advantageous in providing a real-time service among services using wireless ATM.

Claims (4)

A call admission control method in an asynchronous transmission mode wireless network in which a plurality of radio transceivers are connected in an access point connected to an asynchronous transmission mode switch, Determining a request for a change of bandwidth, and requesting a request by an intra handover (Intra) handover; Performing handover processing in the access point jurisdiction, if it is caused by a handover in the access point jurisdiction; If it is not a request by handover in the access point jurisdiction, determining whether the bandwidth change request is caused by the termination of a service for a predetermined terminal; If the bandwidth change request is due to the termination of the service for a predetermined terminal, the bandwidth B _N allocated to the terminal is subtracted from the bandwidth B _K allocated to the radio transceiver for the terminal in which the service is terminated. Rearranging the bands for the terminals according to the bandwidth information after resetting to (B _K ); If the bandwidth is not requested by the service termination for a predetermined terminal, (B _N is the requested bandwidth, B _max is the total available bandwidth, B _K is the bandwidth for the currently allocated real-time service, and EB _KO is the handover to reduce the allocated bandwidth by moving the terminal to another radio area. Expected expectations, Determining the acceptance of the request band (B _N ) by the expected value that is expected to be added by the terminal visit from the radio transceiver, and rearranging the bands for the terminals according to the acceptance band; If the request band of the terminal cannot accept the call admission control method in a wireless asynchronous transmission mode network to perform the step of rejecting the call request to all of the radio transceiver sequentially. The handover process of claim 1, wherein The maximum bandwidth (B _max ) of the radio transceiver for which the handover is requested is subtracted by the bandwidth (B _{K + 1} ) allocated to the terminal to be handed over, and whether the subtracted value is greater than or equal to the requested bandwidth (B _NH ) of the terminal. Judging; Rejecting the handover request if the subtraction value is less than or equal to the requested bandwidth; If the subtraction value is greater than or equal to the requested bandwidth, the requested bandwidth B _NH is added to the allocated bandwidth B _{K + 1} of the radio transceiver for which the handover is requested, and the allocated bandwidth B _{K +} of the radio transceiver for which the handover is requested. ₁ ) The previous area of the terminal requesting the handover by resetting and subtracting the bandwidth used (B _NH ) of the terminal to be handed over from the allocated bandwidth (B _K ) of the radio transceiver having the previous area of the terminal requesting the handover. A method for controlling call admission in a wireless asynchronous transmission mode network in which the step of resetting the allocated bandwidth (B _K ) of a wireless transceiver having jurisdiction over all wireless transceivers is performed sequentially. 3. The method of claim 2, wherein the total available bandwidth (B _max ), the bandwidth for the currently allocated real-time service (B _K ), and the handover are expected to reduce the allocated bandwidth by moving the terminal to another radio region. Expected value (EB _KO ), the expected value that is expected to be added as the terminal visits from the radio ( ) Is a call admission control method in a wireless asynchronous transmission mode network stored in a table in the access point. 4. The method of claim 3, wherein when request bands for the terminals are set, the contents of the table in the access point are updated according to the set request bands.