KR100800861B1 - Apparatus and method for performing handoff in a communication system - Google Patents

Abstract

The present invention includes a serving base station communicating using a first communication method, a neighbor base station using a second communication method different from the first communication method, and includes a terminal capable of communicating with the serving base station and the neighbor base station. For handoff in a communication system, the terminal is predetermined to determine whether to hand off at least one signal from the serving base station signal received from the serving base station and the neighbor base station signal received by the terminal from the neighbor base station; Compensation using the compensation value, and when only the serving base station signal is compensated, and comparing the compensated serving base station signal and the neighbor base station signal to determine whether the handoff of the terminal, and compensates only the neighbor base station signal, The serving base station signal and the compensated neighbor It is determined whether the terminal is handed off by comparing a station signal, and when the serving base station signal and the neighbor base station signal are compensated, the terminal is handed off by comparing the compensated serving base station signal with the compensated neighbor base station signal. Determine.

Handoff, Heterogeneous Communications, Heterogeneous Communications Systems, Offset, Scaling Factor

Description

Apparatus and method for handoff in a communication system {APPARATUS AND METHOD FOR PERFORMING HANDOFF IN A COMMUNICATION SYSTEM}

1 is a graph showing inter-cell pilot signal strength for handoff in a typical communication system;

2 is a diagram illustrating a pilot signal strength received by a terminal from base stations using different communication schemes;

3A to 3B are schematic views illustrating signal strength compensation of a base station received at a terminal using an offset according to an embodiment of the present invention;

4A to 4B are schematic diagrams illustrating signal strength compensation of a base station received at a terminal using a scaling factor and an offset according to another embodiment of the present invention;

5 is a flowchart schematically illustrating a handoff decision process according to an embodiment of the present invention;

6 is a system configuration diagram for performing a handoff operation between heterogeneous communication systems according to an embodiment of the present invention;

7 is a flowchart schematically illustrating a handoff operation process between heterogeneous communication systems according to an embodiment of the present invention;

8 is a flowchart schematically illustrating an operation process of a handoff controller according to an embodiment of the present invention;

9 is a system configuration diagram for performing a handoff operation between heterogeneous communication systems according to another embodiment of the present invention;

10 is a flowchart schematically illustrating a handoff operation process between heterogeneous communication systems according to another embodiment of the present invention;

11A and 11B are flowcharts schematically illustrating an operation of a terminal when performing handoff between heterogeneous communication systems according to another embodiment of the present invention.

The present invention relates to a communication system, and more particularly, to a handoff apparatus and method in a heterogeneous communication system having different communication schemes.

In the 4th Generation (hereinafter, referred to as '4G') communication system, active researches are provided to provide users with services having various speeds of quality (QoS). It's going on. In particular, broadband wireless access such as a wireless local area network (LAN) system and a wireless metropolitan area network (MAN) system Access, hereinafter referred to as 'BWA', has been actively studied to support high-speed services in a form of guaranteeing mobility and QoS in a communication system.

In addition, current communication systems such as 3rd generation (hereinafter referred to as '3G') communication systems and 3.5th generation (hereinafter referred to as '3.5G') communication systems are also evolving. New communication schemes are being proposed. Looking at this, High Speed Downlink Packet Access (hereinafter referred to as 'HSDPA'), Evolution-Data Only (EV-DO), Evolution-Data and Voice (EV-DV), Institute of IEEE Electrical and Electronics Engineers) Communication schemes such as 802.16, IEEE 802.11, and digital multimedia broadcasting (hereinafter referred to as 'DMB') have been proposed.

Therefore, the communication systems currently being developed may be an evolution of the various communication standards described above, or may be replaced with new innovative technologies to be a communication system to which a new communication scheme is applied. However, as the various communication schemes as described above appear, the next generation communication system will evolve into a heterogeneous communication system in which the various communication schemes as described above are mixed.

Meanwhile, in a communication system, the mobility of a mobile station (MS) should be taken into consideration, and handoff should be provided so that communication can be maintained smoothly regardless of the location of the mobile station.

1 is a graph showing inter-cell pilot signal strength for handoff in a general communication system.

Referring to FIG. 1, a general handoff will be described and an interim standard-95 (Code Division Multiple Access (CDMA)) scheme using a code division multiple access (CDMA) scheme will be described. Hereinafter, the communication system (hereinafter referred to as IS-95) (cdmaOne) will be described as an example.

It is assumed that a base station (BS) that currently provides a service to a terminal, that is, a serving base station (Serving BS) is a base station A. The terminal measures pilot signals currently received at the terminal, and the measured pilot signals are pilot signals of base stations A, B and C. The terminal measuring the pilot signal strength reports the measured pilot signal strength to the base station A at regular intervals.

The base station A receives the pilot signal strength from the terminal and determines whether the terminal is handed off. In this case, the pilot signal strength may be expressed in a dBm unit or a dB unit, and a received signal strength (RSS) reflecting the strength of the radio signal (hereinafter, referred to as 'RSS') or a signal-to-interference noise ratio (SINR) : Signal to Interference and Noise Ratio.

Accordingly, FIG. 1 illustrates a graph of the pilot signal strength received from a plurality of base stations, that is, base station A, base station B, and base station C, over time. The vertical axis of the graph means pilot signal strength, and the horizontal axis of the graph means time.

In the IS-95 communication system, base stations are classified and managed according to the pilot signal strength received by the terminal. An aggregate managed by the terminal is called a set.

There are two types of sets, and the terminal classifies the base stations into candidate sets and active sets. Among the base stations, a base station having a pilot signal strength greater than the first threshold value T_ADD is classified as an active set, and a base station having a value smaller than the second threshold value T_DROP is excluded from the active set.

1 illustrates a case where a terminal communicating with the base station A moves out of the service area of the base station A and moves to a service area of the base station B or the base station C and attempts to handoff. In this case, it is assumed that the handoff scheme is a soft handoff, and the active set of the terminal is assumed to be limited to two, for example.

The pilot signal strength of the base station A measured by the terminal decreases with time, and the pilot signal strengths of the base station B and the base station C gradually increase.

According to the handoff operation of the terminal according to time, first, since the terminal is in communication with the base station A before the 'a' time, the terminal is classified as a serving base station, and at the same time, the base station A is classified as an active set. At this time, both the pilot signal strengths of the base station B and the base station C have a value smaller than the threshold value T_ADD. Accordingly, the terminal classifies the base station B and the base station C into candidate sets.

Second, at the time 'a', the pilot signal strength of the base station B has a value greater than the first threshold value T_ADD. Therefore, the terminal classifies the base station B as an active set, and the terminal communicates with the base station B as well as the base station A. In addition, the base station C is classified into a candidate set.

Third, at time 'b', the base station C has a pilot signal strength greater than the first threshold value T_ADD. However, since the number of active sets is limited to two, the pilot signal strengths of the base station B and the base station C are compared. At this time, the pilot signal strength of the base station C has a smaller value than the pilot signal strength of the base station B. Accordingly, the base station C may be classified as an active set, but the base station C is classified as a candidate set.

를 출력한다. 상기 단말기는 상기 비교 결과

가 미리 정해된 설정 시간 동안 상기 기준값(T_COMP) 이상을 유지하는 경우 상기 기지국 B를 새로운 서빙 기지국으로 변경한다.Fourth, at the time 'c', the terminal compares the pilot signal strengths of the base station A and the base station B with each other, and as a result of the comparison,

Outputs The terminal is the comparison result

Maintains more than the reference value T_COMP for a predetermined set time, the base station B is changed to a new serving base station.

를 출력한다. 상기 단말기는 상기 비교결과

가 미리 정해진 설정 시간 동안 일정값(T_COMP) 이상을 유지하는 경우 상기 기지국 C를 액티브셋으로 변경한다. 따라서 상기 단말기는 상기 기지국 A를 후보셋으로 분류한다. 이때 상기 단말기는 기지국 A와 통신을 중지하고 상기 기지국 C와 통신한다. 만약 상기 액티브셋의 개수가 3개 이상인 경우에는 상기 단말기는 상기 기지국 A, 기지국 B, 기지국 C와 모두 통신할 수 있다.Fifth, the terminal compares the pilot signal strengths of the base station A and the base station C with each other at a 'd' time point, and as a result of the comparison,

Outputs The comparison result of the terminal

Maintains more than a predetermined value T_COMP for a predetermined set time, the base station C is changed to an active set. Accordingly, the terminal classifies the base station A into a candidate set. At this time, the terminal stops communicating with the base station A and communicates with the base station C. If the number of active sets is three or more, the terminal can communicate with all of the base station A, the base station B, and the base station C.

Sixth, when the base station A is an active set at the time 'e', the terminal classifies the base station A as a candidate set since the pilot signal strength of the base station A has a value smaller than the second threshold value T_DROP. do.

Hard handoff is similar to the soft handoff operation, and as in soft handoff, the base station becomes an active set and communicates with the terminal at the same time, but only performs preparation for handoff. Thus, in the case of the hard handoff, the base station communication of the terminal is performed through one base station. However, current communication systems will evolve into a heterogeneous communication system in which at least two different communication methods are mixed, rather than a single communication system using a single (one) communication method as described above. In such a heterogeneous communication system, the mobility of the terminal should be considered. In addition, a handoff for providing a seamless communication service according to the movement of the terminal should be considered.

FIG. 2 illustrates pilot signal strength received by a terminal from base stations using different communication schemes.

Referring to FIG. 2, a service area of base station A and a service area of base station B, that is, cell A 200 and cell B 250 are shown. Here, the base station A and the base station B are communication systems using different communication schemes.

In this case, when the terminal 201 supports both the communication schemes used by the base station A and the base station B, the terminal is located in the service area of the base station A and receives a service according to movement to the base station B service area. There may be a need to change this.

Currently, the base station A and the base station B use different communication schemes. Therefore, when measuring the pilot signal strength, as shown in FIG. 1, the pilot signal strength transmitted from each base station may not be constant as communication methods are different.

That is, when handoff is performed between heterogeneous communication systems as shown in FIG. 2, the minimum value of the pilot signal strength for communication with the base station A is referred to as 'min a', and the minimum value of the pilot signal strength for communication with the base station B is determined. In the case of 'min b', it is impossible to use an absolute pilot signal strength threshold for classifying a base station due to the difference between the two values. Furthermore, when the two base stations exceed the minimum values 'min a' and 'min b' for communication at the boundary area where cell A and cell B meet, the pilot signal strength for which base station signal is better for handoff determination Could not be compared. That is, handoff may not be performed by comparing the pilot signal strengths as shown in FIG. 1. It was also impossible to apply handoff parameters such as the first threshold value T_ADD, the second threshold value T_DROP, and the relative reference value T_COMP of FIG. 1.

As a result, there is a problem in that a heterogeneous communication system does not support proper handoff according to the movement of the terminal. Therefore, there is a need for a handoff room for providing a seamless communication service to a terminal in a heterogeneous communication system.

Accordingly, it is an object of the present invention to provide a handoff apparatus and method in a communication system.

Another object of the present invention is to provide a handoff apparatus and method for supporting the movement of a terminal in a heterogeneous communication system.

Another object of the present invention is to provide an apparatus and method for providing a seamless communication service to a terminal in a heterogeneous communication system.

It is still another object of the present invention to provide an apparatus and method for configuring a handoff controller in a heterogeneous communication system and performing a handoff through the handoff controller.

The method of the present invention for achieving the above objects; A communication system comprising a serving base station communicating using a first communication method, and a neighbor base station using a second communication method different from the first communication method, and including a terminal capable of communicating with the serving base station and the neighbor base station. The handoff method of claim 1, wherein the predetermined compensation is performed to determine whether to handoff at least one of a serving base station signal received by the terminal from the serving base station and a neighbor base station signal received by the terminal from the neighbor base station. Compensation using a value, and when only the serving base station signal is compensated, and comparing the compensated serving base station signal with the neighbor base station signal to determine whether the terminal handoff, and when only the neighbor base station signal is compensated, The serving base station signal and the compensated phosphorus Comparing a base station signal to determine whether the terminal is handed off, and when the serving base station signal and the neighboring base station signal are compensated, comparing the compensated serving base station signal and the compensated neighbor base station signal to determine whether the terminal is handed off Determine.

An apparatus of the present invention for achieving the above objects; And a serving base station communicating using a first communication method, and at least one neighboring base station using a second communication method different from the first communication method, and including a terminal capable of communicating with the serving base station and the neighboring base station. A handoff apparatus in a communication system, the handoff apparatus comprising: determining whether a signal strength of at least one of a serving base station signal received by the terminal from the serving base station and a neighbor base station signal received by the terminal from the neighbor base station; Compensating using a predetermined compensation value, and when only the serving base station signal is compensated, comparing the compensated serving base station signal with the neighbor base station signal to determine whether the terminal is handoff, and compensates only the neighbor base station signal If so, the serving base station signal The terminal compares the compensated neighbor base station signal to determine whether the terminal is handed off, and when the serving base station signal and the neighbor base station signal are compensated, the terminal compares the compensated serving base station signal with the compensated neighbor base station signal. And a handoff controller to determine whether to handoff.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in the following description, only parts necessary for understanding the operation according to the present invention will be described, and descriptions of other parts will be omitted so as not to distract from the gist of the present invention.

The present invention proposes a handoff apparatus and method in a communication system using at least two different communication schemes, that is, a heterogeneous communication system. In a communication system including transmitters using different communication methods, that is, base stations (BSs), the signal strengths received by a receiver, that is, a mobile station (MS), are measured, and the measured signal strengths are measured. The present invention proposes an apparatus and method for compensating to determine whether a terminal is handoff to determine a handoff, and to allow the terminal to handoff in response to the handoff decision.

Hereinafter, since the terms handoff or handover are the same concept, the term handoff will be used. The term handover also refers to handoff.

To explain the present invention, first, a handoff determination method according to an embodiment of the present invention will be described. In order to determine the handoff, the present invention determines whether to handoff after compensating for a received signal of a base station using an offset or a scaling factor. Thus, the handoff decision will be described in detail below.

In the present invention, a handoff in a heterogeneous communication system is assumed. The heterogeneous communication system includes a base station using at least two different communication methods, and the terminal can support all communication methods used in the heterogeneous communication system. Assume that Accordingly, the terminal can support not only existing communication schemes but also all communication schemes used in next generation communication systems, and will be referred to as High Speed Downlink Packet Access (HSDPA). ), Evolution-Data Only (EV-DO), Evolution-Data and Voice (EV-DV), Institute of Electrical and Electronics Engineers (IEEE) 802.16, IEEE 802.11, Digital Multimedia Broadcasting (DMB) And at least two communication schemes.

The handoff determination may be performed in a handoff controller, and the handoff controller may be configured as a separate device or may be configured inside a base station or a terminal.

For the handoff determination, the handoff controller measures the signal strength received from the base stations from the terminal or receives the measured signal strength. If the terminal performs the function of the handoff controller, the terminal measures the signal strength received from the base stations and performs handoff using the measured signal strength. However, when the handoff controller is included in a device other than the terminal, the handoff controller receives the signal strength of the base station measured by the terminal and hands off using the received signal strength.

The signal received by the terminal may be a pilot signal or a preamble signal. In the measurement of the received signal strength, for example, the strength of the received signal may be measured by measuring the power value of the signal received by the terminal. The power value is determined by using Received Signal Strength (RSS) or Signal to Interference and Noise Ratio (SINR). It is possible to measure.

In general, the signal strength of the base station received by the terminal decreases as the distance from the base station increases. As such, when the signal strength is expressed in dB (m), modeling of the base station signal received by the terminal is possible. Here, the propagation path loss modeling the signal strength may be expressed by Equation 1 below.

는 송신 안테나의 이득,

은 수신 안테나의 이득,

는 중심 주파수에서의 파장,

는 송수신 장치 사이의 거리이다. 상기 단말기에 수신된 기지국의 신호 세기를 상기 수학식 1을 사용하여 모델링하는 경우 랜덤(random)한 성분인 로그-노멀 쉐도우잉(log-normal shadowing)으로 대표되는 롱-텀 페이딩(long-term fading)과 순간적인 숏-텀 페이딩(short-term fading)의 영향을 고려하지 않아도 된다. 상기 수학식 1을 사용하여 신호 세기를 모델링하는 경우에는 상기 도 2에서와 같은 그래프를 획득할 수 있다.Referring to Equation 1,

Is the gain of the transmitting antenna,

Is the gain of the receiving antenna,

Is the wavelength at the center frequency,

Is the distance between the transmitting and receiving devices. When modeling the signal strength of the base station received by the terminal using Equation 1, long-term fading represented by log-normal shadowing, which is a random component. ) And the effect of momentary short-term fading do not need to be considered. When modeling signal strength using Equation 1, a graph as shown in FIG. 2 may be obtained.

In addition, using Equation 1, the theoretical value of the RSS of the signal received from the terminal can be obtained, which follows Equation 2.

는 기지국 신호의 송신 전력(power) 값이다. 상기 송수신 안테나 이득, 중심 주파수, 셀 반경은 통신 네트워크 규격에 따라서 미리 결정되는 값들이다. 따라서 상기 단말기가 수신하는 신호의 RSS값은 실제로 상기 단말기와 상기 기지국 사이의 거리에 관한 함수가 된다. 이를 그래프로 나타내면, 상기 수학식 1의 경로손실의 식을 따르게 되어, 결국 상기 단말기와 상기 기지국 간의 거리에 관한 로그함수의 모양을 형성한다. 또한, 다른 파 일롯 신호 세기의 측정값인 SINR인 경우에도 무선 채널 상에서의 잡음값이 고려되기는 하나, 상기 RSS와 마찬가지로 상기 수학식 1에 나타난 경로 손실을 따른다. 따라서 상기 SINR의 경우에도 상기 단말기와 상기 기지국 간의 거리에 관한 로그함수의 모양을 형성한다.Referring to Equation 2,

Is the transmit power value of the base station signal. The transmit / receive antenna gain, center frequency, and cell radius are predetermined values according to a communication network standard. Therefore, the RSS value of the signal received by the terminal is actually a function of the distance between the terminal and the base station. When this is represented as a graph, the path loss of Equation 1 is followed, thereby forming a log function relating to the distance between the terminal and the base station. In addition, even in the case of SINR, which is a measurement value of another pilot signal strength, the noise value on the wireless channel is considered, but as in the RSS, it follows the path loss shown in Equation 1 above. Therefore, even in the SINR, a shape of a log function relating to the distance between the terminal and the base station is formed.

로 정의하면, 하기의 수학식 3과 같이 나타낼 수 있다.Therefore, assuming that the signal of the base station received by the terminal is a pilot signal, the unit of the pilot signal strength may be expressed in dB. And the signal strength

When defined as, it can be expressed as Equation 3 below.

Next, when handoff is performed in the heterogeneous communication system, it will be described that the signal strength is compensated to determine whether the signal strength of the base stations received by the terminal is handoff.

3A to 3B schematically illustrate compensating signal strength of a base station received by a terminal using an offset according to an embodiment of the present invention.

Referring to FIG. 3A, a cell of a base station A and a base station B using different communication schemes is shown, and cell A 300, which is a service area of base station A, and cell B 350, which is a service area of base station B. Is shown. In FIG. 3A, the terminal 301 moves from the cell A 300 to the cell B 350, and the signal strength received by the terminal 301 over time is shown.

As the location is changed, the terminal 301 may need to change the serving base station, that is, handoff. However, since the base station A and the base station B use different communication schemes, the handoff method used in the existing single communication system cannot be applied. Accordingly, the present invention compensates the signal strength received from the base station by using the offset to determine whether the terminal 301 is handed off.

3A illustrates whether handoff is performed by applying an offset to the signal strength of the base station B in order to determine the handoff between heterogeneous communication systems. The signal strengths of base station A using the first communication method and base station B using the second communication method are shown. In this case, the signal strength 311 is shown by compensating the signal strength of the base station B using the offset to compare the signal strength of each base station of the heterogeneous communication system.

Referring to FIG. 3B, unlike FIG. 3B, the signal strength of the base station A is compensated for, unlike the signal strength of the base station B in FIG. 3A. For convenience of description, the same contents as those described with reference to FIG. 3A will be referred to FIG. 3A and will be omitted below. Accordingly, FIG. 3B illustrates that, unlike FIG. 3A, after the offset is applied to the signal strength of the base station A in order to determine whether to handoff between heterogeneous communication systems, the handoff is determined. The signal strengths of base station A using the first communication method and base station B using the second communication method are shown. In this case, the signal strength 321 is shown by compensating the signal strength of the base station A using an offset to compare the signal strength of each base station of the heterogeneous communication system.

As described above, it is possible to determine whether the terminal 301 is handed off using the signal strengths 311 and 321 compensated as shown in FIGS. 3A and 3B.

,

,

,

는 모두 상수값을 가지며, 상기 수학식 3은 송수신 장치의 거리값인 'd'의 값에 따라 결정된다. 따라서 상기 단말기(301)에 수신되는 상기 신호 세기 그래프의 기울기는 변화하지 않으며, 상기 도 3a와 상기 도 3b에 나타난 바와 같이 로그함수의 형태가 된다. 따라서 각 신호 세기의 상대적인 크기의 차이만을 보상하기 위한 수학식 4는 하기에 나타나있다.In general, when the center frequency is determined in one system,

,

,

,

Have a constant value, and Equation 3 is determined according to the value of 'd', which is a distance value of the transceiver. Therefore, the slope of the signal strength graph received by the terminal 301 does not change, and as shown in FIGS. 3A and 3B, the log function is in the form of a log function. Therefore, Equation 4 for compensating only the difference in the relative magnitude of each signal strength is shown below.

는 특정 기지국으로부터 단말기(301)가 수신한 신호 세기(예를 들어, 파일롯 신호 세기)를 나타내고, 상기

는 상기 신호 세기 보상을 위해서 상기

에 더해주는 오프셋을 나타낸다. 따라서 상기

는 보상된 특정 기지국의 신호 세기를 나타낸다.Referring to Equation 4,

Denotes the signal strength (for example, pilot signal strength) received by the terminal 301 from a specific base station.

For the signal strength compensation

Represents an offset added to. Thus above

Denotes the signal strength of the particular base station compensated.

The specific base station of FIG. 3A is the base station B, and the specific base station of FIG. 3B is base station A. Although FIG. 3A and FIG. 3B compensate only one base station signal strength, respectively, the signal strength of the base station A and the signal strength of the base station B may be compensated by using Equation 4, and then handoff may be determined.

Accordingly, FIGS. 3A and 3B compensate signal strengths of base stations B and A, respectively, and determine whether to handoff between heterogeneous communication systems using the compensated signal strengths 311 and 321. Using the compensated signal strength, it is possible to perform a handoff using a method for determining whether a handoff was used in a single communication system.

On the other hand, the offset is applied to the signal strength of the base station to perform the signal compensation, and has a real value. The offset compensates for signal strength of base stations using different communication schemes, thereby enabling handoff determination between base stations using different communication schemes. Accordingly, the offset may be determined using a difference value between the reference signal strength set for signal strength compensation between base stations using different communication schemes and the signal strength of the base station to be compensated. In this case, as shown in FIG. 3A and FIG. 3B, the reference signal strength may set a signal strength of a serving base station or a neighboring base station as a reference signal strength, and a preset reference signal strength may be set as the reference signal strength. . In addition, the offset may be determined using a measured value through a handoff simulation or an actual experiment. The offset is an element that can be set differently according to each communication method to determine whether the terminal is handoff, and can be determined using the parameters shown in Equation (1).

4A to 4B schematically illustrate compensating for signal strength of a base station received at a terminal by using a scaling factor and an offset according to another embodiment of the present invention.

Referring to FIG. 4A, cells of base station A and base station B using different communication schemes are shown, and cell A 400, which is a service area of base station A, and cell B 450, which is a service area of base station B. Is shown. In FIG. 4A, the terminal 401 moves from the cell A 400 to the cell B 450, and the signal strength received by the terminal 401 over time is shown.

The terminal 401 may need to change a serving base station, that is, handoff, as the location changes. However, since the base station A and the base station B use different communication schemes, the handoff method used in the existing single communication system cannot be applied. Therefore, the present invention compensates the signal strength received from the base station by using a scaling factor and an offset to determine whether the terminal 401 is handed off.

The signal strengths of base station A using the first communication method and base station B using the second communication method are shown. In this case, the signal strength 411 is shown by compensating the signal strength of the base station B using a scaling factor and an offset to compare the signal strength of each base station of the heterogeneous communication system.

As the location is changed, the terminal 401 may need to perform a handoff to change a base station receiving a service, that is, a serving base station. However, since the base station A and the base station B use different communication schemes, the handoff method used in the existing single communication system cannot be applied. Therefore, the present invention compensates the signal strength received from the base station by using a scaling factor and an offset to determine whether the terminal 401 is handed off.

Referring to FIG. 4B, unlike FIG. 4B, the signal strength of the base station A is compensated in contrast to the signal strength of the base station B in FIG. 4A. For convenience of description, the same contents as those described with reference to FIG. 4A will be described with reference to FIG. 4A and will be omitted below. In FIG. 4B, unlike FIG. 4A, in order to determine whether to handoff between heterogeneous communication systems, a scaling factor and an offset are applied to the signal strength of the base station A to determine whether the handoff is performed. The signal strengths of base station A using the first communication method and base station B using the second communication method are shown. In this case, the signal strength 421 of the base station A, which compensates the signal strength of the base station A by using an offset for comparing the signal strength of each base station of the heterogeneous communication system, is shown.

As such, it is possible to determine whether the terminal 401 is handed off using the signal strengths 411 and 421 of the base station compensated as shown in FIGS. 4A and 4B.

The scaling factor of FIGS. 4A and 4B is a factor for changing the slope of the signal strength of each base station signal. That is, the scaling factor is a factor that is determined according to the ratio of the reference signal strength and the base station signal strength to compensate. Accordingly, the scaling factor may be determined according to a ratio of the reference signal strength set for signal strength compensation between base stations using different communication schemes and the signal strength of the base station to be compensated. In this case, as shown in FIGS. 4A and 4B, the reference signal strength may set a signal strength of a serving base station or an adjacent base station as a reference signal strength, and a preset reference signal strength may be set as the reference signal strength. . In addition, the scaling factor may determine the offset using the measured value through the handoff simulation or the actual experiment. The scaling factor is an element that can be set differently according to each communication scheme for handoff determination of the terminal, and can be determined using the parameters shown in Equation (1).

Therefore, determining whether the handoff is performed by simultaneously using the scaling factor and the offset for each signal strength is shown in Equation 5 below.

는 특정 기지국으로부터 단말기(401)가 수신한 신호 세기를 나타내고, 상기

는 특정 기지국의 신호 세기 보상을 위해서

와 곱해지는 스케일링 팩터를 나타내며, 상기

는 상기 신호 세기 보상을 위해서 상기

에 더해주는 오프셋을 나타낸다. 따라서 상기

는 보상된 특정 기지국의 신호 세기를 나타낸다.Referring to Equation 5,

Denotes the signal strength received by the terminal 401 from a specific base station,

To compensate for the signal strength of a specific base station

A scaling factor that is multiplied by

For the signal strength compensation

Represents an offset added to. Thus above

Denotes the signal strength of the particular base station compensated.

The specific base station of FIG. 4A is base station A, and the specific base station of FIG. 4B is base station B. Although FIG. 4A and FIG. 4B compensate only one base station signal strength, respectively, the signal strength and base station of base station A are After the signal strength of B is all compensated using Equation 5, whether or not the handoff may be determined.

Thus, FIGS. 4A and 4B compensate signal strengths of base stations B and A, respectively, and determine whether to handoff between heterogeneous communication systems using the compensated signal strengths 411 and 421. Using the compensated signal strength, it is possible to perform a handoff using a method for determining whether a handoff was used in a single communication system.

에 비례하며, 이러한 경우에는 상기 신호 세기의 그래프의 기울기는 변화하지 않는다. 그러므로 오프셋을 사용하여 핸드오프 여부를 결정할 수 있으며, 이를 상기 도 3a와 상기 도 3b에 나타내었다.In general, as shown in Equation 1 of the path loss.

In this case, the slope of the graph of the signal strength does not change. Therefore, the offset can be used to determine whether the handoff, which is shown in Figures 3a and 3b.

에 비례하지 않고,

에 비례할 수 있다. 또한 상기 n값이 변경되는 경우에는 상기 신호 세기의 그래프의 기울기까지 변화한다. 그러므로 상기 오프셋뿐만 아니라 기울기까지도 고려한 스케일링 팩터를 추가로 사용하여 핸드오프 여부를 결정할 수 있으며, 이를 상기 도 4a와 상기 도 4b에 나타내었다.However, the path loss equation is as shown in Equation 1 above.

Not proportional to

Can be proportional to In addition, when the value of n is changed, it is changed up to the slope of the graph of the signal strength. Therefore, it is possible to determine whether to hand off by additionally using a scaling factor considering not only the offset but also the slope, as shown in FIGS. 4A and 4B.

3A to 4B illustrate the handoff from the base station using the first communication method to the base station using the second communication method according to the movement of the terminal, but other than the first communication method and the second communication method. Even when communication systems using another communication method of C are mixed, it is possible to use the above method to determine whether to hand off.

As described above, when a terminal performs handoff in a heterogeneous communication system, the terminal compensates the signals received from each base station by using one reference signal strength. In this case, the reference signal strength may use a preset reference signal strength, a signal strength of the serving base station (eg, base station A), a signal strength of an adjacent base station (eg, base station B), and the like.

The handoff determination is performed by a handoff controller, the handoff controller being first included in the terminal to determine whether the terminal is the handoff, and secondly, the handoff controller is a base station or a base station. It is included in the controller to determine whether the handoff. Thirdly, the handoff controller may be configured as a separate device to determine whether to handoff.

5 is a flowchart schematically illustrating a handoff decision process according to an embodiment of the present invention.

Referring to FIG. 5, in step 501, the handoff controller measures the received signal strength and proceeds to step 503. The operation of the handoff controller of step 501 is a case where the handoff controller is included in the terminal, and thus it is possible to directly measure a signal received from the base station to the terminal. If the handoff controller is not included in the terminal, base station signal strength measurement information received by the terminal must be received from the terminal.

In step 503, the handoff controller selects a base station to compensate for signal strength to determine a handoff, and proceeds to step 505. It is possible to select one or more base stations to compensate for the signal strength, and it is possible to perform signal strength compensation of all base stations. In this case, the compensation of the signal strength applies a scaling factor or offset to the signal strength. The scaling factor and offset allow handoff determination by compensating signal strength of each base station of a communication system using a different communication scheme.

In step 505, the handoff controller determines whether the signal strength is compensated according to the determination of the base station to compensate the signal strength. If it is determined that the base station to compensate for the signal strength is not selected and the signal strength does not need to be compensated, the process proceeds to step 515. In this case, all of the base stations to determine whether the handoff is the base station using the same communication scheme. Therefore, since the base station using the same communication scheme does not have to compensate for the signal strength of the base station received by the terminal for handoff determination, it is possible to perform handoff using the existing handoff determination scheme. However, if the base station to compensate for the signal strength is selected as the determination result, the signal strength should be compensated and the process proceeds to step 507.

In step 507, the handoff controller determines whether to apply a scaling factor to a signal strength of a base station to compensate for the signal strength. If the scaling factor is not applied, the process proceeds to step 511. However, if the scaling factor is applied as the determination result, the process proceeds to step 509. The scaling factor makes it possible to change the slope of the graph of the signal strength of the base station received at the terminal.

In step 509, the handoff controller applies a scaling factor to the signal strength of the corresponding base station and proceeds to step 511.

In step 511, the handoff controller determines whether to apply an offset to the signal strength of the base station to compensate for the signal strength. If it is determined that the offset is not applied, the process proceeds to step 515. However, if the offset is applied to the determination result, the process proceeds to step 513. The offset makes it possible to change the magnitude of the signal strength of the base station received at the terminal. The scaling factor and the offset value may be real numbers including all positive values, negative values, and zero.

In step 515, the handoff controller has an advantage that it is possible to determine the handoff of the terminal using the signals received from the neighbor base station of the terminal.

5 illustrates the operation of the handoff controller according to the handoff decision. Then, the handoff according to the position of the handoff controller will be described in detail below.

<First Embodiment>

6 is a system configuration diagram for performing a handoff operation between heterogeneous communication systems according to an embodiment of the present invention.

Before describing FIG. 6, the handoff controller according to the embodiment of the present invention is implemented as an internal or external base station (for example, a handoff controller, a separate handoff control device, etc.) regardless of the same communication method or different communication methods. Available). Thus, the handoff controller is a functional block implemented in hardware or software. In addition, the characteristic of the handoff controller is that the scaling factor and offset proposed by the present invention are stored according to each system and used for handoff decision.

Referring to FIG. 6, the base station A 620 is connected to the A communication system network using the A communication method, and the base station B 640 is connected to the B communication system network using the B communication method. In addition, it is assumed that the terminal 600 communicates with the base station A 620 which is the current serving base station. Here, the base station A 620 and the base station B 640 may be replaced by a router.

In addition, the handoff controller 660 stores the scaling factor or offset in a memory for handoff determination according to an embodiment of the present invention. Alternatively, the scaling factor and offset may be received through the terminal. The handoff controller 660 receives the signal strength of each base station measured by the terminal 600 at a predetermined time interval through the serving base station of the terminal, that is, the base station A 620.

The handoff controller 660 uses the signal strength measured by the terminal 600 and, in a heterogeneous communication system, determines the handoff of the terminal 600 by compensating for the signal strength. In this case, the handoff controller 660 compensates for the signal strength by using the scaling factor or offset to determine the handoff of the terminal 600.

When the terminal 600 changes a service access point to a target base station, that is, base station B 640, the handoff controller 660 performs an operation of handing off from the base station A 620 to the base station B 640. To control.

The handoff controller 660 may be located between communication systems using different communication schemes for handoff in a heterogeneous communication system, and may be located inside a base station controller controlling each base station, and inside each base station. And may be located between the wireless network and the base station. The handoff controller may be implemented in various ways depending on the implementation. For example, the handoff controller may be included in a base station controller or each base station, and its function may be implemented in the base station controller or each base station.

7 is a flowchart schematically illustrating a handoff operation process between heterogeneous communication systems according to an embodiment of the present invention.

Referring to FIG. 7, a message transmission and reception procedure for handoff between the terminal 600, the base station A 620, the base station B 640, and the handoff controller 660 is illustrated.

The terminal 600 performs voice and data communication with the base station A 620, which is a serving base station (step 701). The terminal 600 receives a signal transmitted from the base station A 620 and the base station B 640, for example, a pilot signal. Accordingly, the terminal 600 receives a pilot signal transmitted from the base station A 620 (step 703). The terminal receives a pilot signal transmitted from the base station B 640 (step 705).

The terminal 600 measures the pilot signal strength received from each base station (step 707). In this case, the terminal 600 receives a signal of each base station at intervals of a predetermined period and measures it.

If the serving base station communicating with the terminal 600 is the base station A 620, the terminal 600 transmits the signal measurement result to the base station A 620 (step 709). The base station A 620 transmits a signal measurement result to the handoff controller 660 (step 711).

The handoff controller 660 compensates the measurement values according to the signal strength of each base station using the scaling factor or offset using the signal strength measurement result measured by the terminal 600 (step 713). In operation 715, a handoff of the terminal 600 is determined. The handoff decision of the handoff controller 660 has been described with reference to FIG. 5.

When the handoff controller 660 determines, as base station B 640, a target base station to hand off according to the handoff decision, the base station A 620 notifies the base station B 640 of the handoff. In step 717, the processor transmits the message to the processor.

The handoff controller 660 transmits a handoff message to the base station B 640 informing that the terminal 600 is to hand off to the base station B 640 (step 719).

The base station A 620 notifies the terminal 600 that the terminal 600 should handoff to the base station B 640 (step 721).

The terminal 600 performs a handoff from the serving base station, that is, the base station A 620, to the target base station, that is, the base station B 640 (step 723). When the terminal 600 successfully performs the handoff, the terminal 600 notifies the base station A 620 that the handoff is completed (step 725).

Upon receipt of the handoff completion report of the terminal 600, the base station A 620 reports the handoff completion to the handoff controller (step 727). Recognizing the completion of the handoff, the base station A 620 terminates voice and data communication with the terminal 600 (step 729).

In FIG. 6, the terminal 600 notifies the handoff controller 660 of the handoff completion report through the base station A 620. However, the base station A 620 may also notify the handoff controller 660 of the handoff completion report through the base station B 640.

8 is a flowchart schematically illustrating an operation process of a handoff controller according to an exemplary embodiment of the present invention.

Referring to FIG. 8, in step 801, the handoff controller receives signal strengths, that is, signal strengths of respective base stations measured by the terminal, and proceeds to step 803.

In step 803, the handoff controller compensates for the pilot signal strength to determine the handoff of the terminal and proceeds to step 805.

Compensation of the pilot signal strength uses an offset or scaling factor as described with reference to FIG. 5. The handoff controller determines a reference signal strength for signal strength compensation and selects a base station to compensate for the signal strength according to the determined reference signal strength. For example, when the determined reference signal strength is the signal strength of the base station A, the base station B is determined as the base station to compensate for the signal strength, and when the determined reference signal strength is the signal strength of the base station B, the base station A is the signal strength. Determine as the base station to compensate. In addition, when the determined reference signal strength is a preset reference signal, both base stations A and B are selected as base stations to compensate for the signal strength.

In step 805, the handoff controller determines the handoff of the terminal by comparing the compensated signal strength, that is, the pilot signal, and comparing the pilot signal, and proceeds to step 807. It is possible to determine the handoff even in a heterogeneous communication system by comparing the pilot signal strength compensated in step 803.

In step 807, the handoff controller determines whether the terminal is to be handed off according to the handoff decision. If it is determined that the handoff controller does not handoff the terminal, the controller proceeds to step 801. However, if it is determined that the handoff controller causes the terminal to handoff, the process proceeds to step 809.

In step 809, the handoff controller notifies the serving base station of the handoff of the terminal and the target base station to which the terminal is to be handed off, and proceeds to step 811. The target base station is determined by the handoff controller to compensate for the pilot signal strength of the base station and in accordance with the pilot signal strength compensation.

In step 811, the handoff controller checks whether the handoff is completed. If it is determined that the handoff complete message is not received from the serving base station or the target base station, the process proceeds to step 809. However, when the handoff complete message indicating that the handoff is completed is confirmed, the handoff process is terminated.

Herein, the handoff operation procedure constituting the handoff controller has been described as an example, and handoff is possible in a heterogeneous communication system by determining whether to handoff by compensating for base station signal strength received by a terminal between base stations using different communication schemes. Has the advantage.

The above-described handoff controller may be configured as, for example, a base station controller, a base station, or a separate device, and determines a handoff by compensating pilot signal strengths of respective base stations received by the terminal, and determines the handoff. To control the handoff operation.

Second Embodiment

9 is a system configuration diagram for performing a handoff operation between heterogeneous communication systems according to another embodiment of the present invention.

Before referring to FIG. 9, the above-described handoff controller is built in the terminal or implemented in software through the terminal, and scaling factor for compensating the difference value of the signal strength for each base station according to each communication method. It stores the and offsets and uses them to determine the handoff.

Referring to FIG. 9, base station A 920 is connected to A communication system network using A communication method, and base station B 940 is connected to B communication system network using B communication method. C 960 is connected to a C communication system network using the C communication scheme. In addition, it is assumed that the terminal 900 communicates with the base station A 920 which is the current serving base station.

The terminal 900 receives a signal from each of the base stations 920, 940, and 960 and measures the signals at predetermined time intervals. In this case, the terminal 900 determines the reference signal strength so that the signals can be compared, and compensates the signal strengths of the base stations 920, 940, 960 with the determined signal strength, and then determines whether to handoff.

Currently, the serving base station of the terminal 900 is the base station A 920, and the terminal 900 determines the target base station as the base station B 940 through the pilot signal strength compensation received from the base stations, and the base station B ( Assume that handoff to 940, the operation described above with reference to Figure 10 will be described in detail below.

10 is a flowchart schematically illustrating a handoff operation process between heterogeneous communication systems according to another exemplary embodiment of the present invention.

Referring to FIG. 10, a message transmission and reception procedure for handoff between a terminal 900, a base station A 920, a base station B 940, and a base station C 960 is illustrated.

The terminal 900 is communicating with the base station A 920 serving as a serving base station, and receives neighbor base station information from the serving base station A (step 801). The terminal 900 stores information of neighbor base stations, for example, the base station B 940 and the base station C 960 in the terminal (step 903). Next, the terminal receives a pilot signal as a signal of a serving base station and neighboring base stations, that is, the base station A 920, the base station B 940, and the base station C 960 (steps 1005, 1007, Step 1009).

Upon receiving the pilot signal, the terminal 900 periodically tracks and stores forward synchronization information of neighboring base stations (step 1011). The terminal 900 measures the strength of the received pilot signal and compensates for the measured pilot signal strength (step 1013). The compensation of the pilot signal strength of the terminal 900 determines a reference signal for pilot signal compensation and determines a base station to compensate for the signal strength according to the reference signal determination. The terminal compensates the pilot signal strength of the base station to compensate. The terminal 900 may compensate for the pilot signal strength by using the scaling factor or offset as described with reference to FIG. 5. The terminal 900 makes a handoff decision of the terminal 900. If the determined target base station to be handed off is the base station B 920, the base station A 900 is notified of the handoff to the base station B 920 (step 1019).

In addition, the terminal 900 is allocated an interval without data transmission from the base station A 920 so that the terminal 900 synchronizes forward and reverse synchronization with the base station B 940. The terminal 900 is allocated a section without data transmission for handoff determination.

In addition, the terminal 900 synchronizes forward and backward synchronization with a target base station, that is, the base station B 940 in a section in which there is no data transmission with the serving base station. Here, the forward sync is quickly adjusted using the forward sync information stored in the terminal 900 (step 1021). The terminal 900 adjusts backward synchronization through a random access process, and performs random access to the base station B 940 using neighboring base station information stored by the terminal (step 1023). ).

The base station B 940 transmits a response message for the random access of the terminal 900 (step 1025). The terminal 900 completes synchronization adjustment with the base station B 940 through the above-described procedure of synchronizing the forward and reverse synchronization (step 1027).

When the synchronization adjustment is completed, the terminal 900 requests a handoff to the base station B 940 (step 1029). The base station B 940 notifies the terminal 900 of the handoff permission according to the handoff request of the terminal 900 (step 1031).

After receiving the handoff grant message, the terminal 900 sends a radio resource release request to the serving base station A 920 (step 1033). The base station A 920 releases radio resources in response to the radio resource release request of the terminal (1035).

The terminal 900 and the base station B 940 perform parameter adjustment, authentication, encryption, etc. according to link performance in step 1037. Thus, if the terminal 900 can communicate with the base station B 740, the terminal 900 performs a handoff to the base station B 940 and completes the handoff (step 1039).

In response to the handoff, the terminal 900 must release radio resources allocated to the terminal 900 in order to terminate communication with the base station A 920 serving as the serving base station. There may be various processes for releasing radio resources according to this.

The terminal 900 and the base station A 920 perform radio resource release in steps 1033 and 1035, but may be performed after the handoff is completed after step 1039.

11A and 11B are flowcharts schematically illustrating an operation process of a terminal when performing handoff between heterogeneous communication systems according to another exemplary embodiment of the present invention.

Referring to FIG. 11A, in step 1101, the terminal receives information of a neighbor base station from a serving base station providing a service to the terminal, and proceeds to step 1103. In step 1103, the terminal stores the information of the neighbor base stations received from the serving base station and proceeds to step 1105.

In step 1105, the terminal receives a pilot signal as an example of a signal of neighboring base stations and proceeds to step 1107. In this case, the signal received by the terminal includes both the signals of the serving base station and the adjacent base station.

In step 1107, the terminal stores forward synchronization information of neighboring base stations at intervals of a predetermined period and proceeds to step 1109. The periodic sync information may be periodically stored as the pilot signal is periodically received. In step 1109, the terminal measures forward synchronization information at predetermined intervals by neighboring base stations and proceeds to step 1111.

In step 1111, the terminal compensates the pilot signal to be comparable to each other using the pilot signal strength measurement values of the respective base stations. Compensation of the pilot signal may be compensated using the above-described scaling factor and offset.

Herein, if the reference signal strength for the pilot signal compensation is assumed to be the signal strength of the base station A, the signals of the base station B and the base station C are compensated, and if the reference signal strength is the signal strength of the base station B, Compensating the signal of the base station C, assuming that the reference signal strength is the signal strength of the base station C, and compensates the signals of the base station A and the base station B, assuming that the reference signal strength is a predetermined reference signal strength, base station A, Compensate for signals from both base stations B and C. At this time, when compensating the pilot signal, the scaling factor and the offset are used to compensate.

In step 1113, the terminal compares the pilot signals of the compensated base stations with each other. If the handoff of the terminal is necessary as a result of the comparison, the terminal determines the handoff of the terminal and proceeds to step 1115. At this time, the terminal determines the target base station to which the terminal is to hand off.

In step 1115, the terminal determines whether to handoff. If the terminal does not handoff as a result of the determination, step 1105 is performed. However, if the terminal handoffs, it proceeds to step 1117.

Referring to FIG. 11B, in step 1117, the terminal notifies the serving base station of the target base station to be handed off, that is, the base station B, handoff to the handoff, and proceeds to step 1119.

In step 1119, the terminal adjusts forward synchronization and reverse synchronization with the target base station and proceeds to step 1121.

In step 1121, when the synchronization adjustment is completed in step 1119, the terminal requests a handoff to the target base station and proceeds to step 1123.

In step 1123, the terminal determines whether a handoff grant message corresponding to the handoff request has been received from the target base station. If the terminal does not receive the handoff grant message, the terminal proceeds to step 1105. However, if the terminal receives the handoff grant message as a result of the check, step 1125 is performed.

In step 1125, the terminal transmits a radio resource release request message to the serving base station and proceeds to step 1127. In step 1127, the terminal performs a procedure of adjusting parameter values, authentication, encryption, etc. for communication with the target base station to be handed off, and proceeds to step 1129.

In step 1129, the terminal completes the handoff when it is possible to handoff with the base station.

As described above, unlike the first embodiment, since the handoff is performed in the terminal, the handoff controller in the first embodiment may be regarded as implemented in the terminal.

In addition, the handoff method proposed in the present invention can compare the signal strengths of two or more base stations for handoff, and compensate each base station signal strength received by the terminal using a predetermined reference signal strength. . In this case, the signal compensation is performed using the scaling factor and the offset to determine whether to perform a handoff.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, the present invention provides a handoff of a terminal in a heterogeneous communication system by determining whether to handoff by compensating for base station signal strengths received by the terminal during handoff in a communication system using different communication methods, that is, a heterogeneous communication system. Has the advantage that it is possible. Therefore, it is advantageous to ensure seamless data transmission and reception according to handoff of a terminal even in a heterogeneous communication system.

Claims (29)

A communication system comprising a serving base station communicating using a first communication method, and a neighbor base station using a second communication method different from the first communication method, and including a terminal capable of communicating with the serving base station and the neighbor base station. In the handoff method, Compensating by the terminal using a predetermined compensation value to determine whether to handoff at least one of a serving base station signal received from the serving base station and a neighbor base station signal received by the terminal from the neighbor base station; and, When only the serving base station signal is compensated, the compensated serving base station signal and the neighbor base station signal are compared to determine whether the terminal is handed off, and when only the neighbor base station signal is compensated, the serving base station signal and the compensated neighbor Comparing a base station signal to determine whether the terminal is handed off, and when the serving base station signal and the neighboring base station signal are compensated, comparing the compensated serving base station signal and the compensated neighbor base station signal to determine whether the terminal is handed off Handoff method comprising the step of determining. The method of claim 1, And the serving base station signal and the neighbor base station signal are at least one of a pilot signal and a preamble signal. The method of claim 1, The determining of the handoff may further include determining whether the handoff is performed using the signal strengths of the serving base station signal and the neighboring base station signal, wherein the signal strength is used to determine the power value of the signal received by the terminal. Handoff method characterized in that the generated by measuring. The method of claim 3, wherein Wherein the power value is one of a received signal strength value and a signal to noise ratio value. The method of claim 1, Compensating at least one of the serving base station signal and the adjacent base station signal by using a compensation value, Determining a reference signal for signal compensation; Selecting at least one base station from among the serving base station and the adjacent base station as a signal compensation base station according to the determined reference signal; And compensating for receiving a signal from the selected base station to the terminal using the compensation value to determine whether to handoff the signal. The method of claim 5, wherein And the reference signal strength is one of a predetermined signal, a signal of the serving base station, and a signal of the neighboring base station. The method of claim 5, wherein And the compensation value comprises at least one of an offset and a scaling factor used for signal compensation of the selected base station. The method of claim 7, wherein And the offset is determined using a difference value between the reference signal and a base station signal to be compensated for. The method of claim 7, wherein Compensating the selected base station signal, Compensating the selected base station signal using the following equation.

Is the compensated signal,

Is a specific base station signal received by the terminal,

Is an offset for specific base station signal compensation. The method of claim 7, wherein And the offset is determined using the following equations according to path loss.

Is the gain of the transmitting antenna,

Is the gain of the receiving antenna,

Is the wavelength at the center frequency and d is the distance between the transmitting and receiving devices. The method of claim 7, wherein The scaling factor is determined according to the ratio of the reference signal and the base station signal to compensate. The method of claim 7, wherein Compensating the selected base station signal, Compensating the selected base station signal using the following equation.

Is the compensated signal,

Is a specific base station signal received by the terminal,

Is a scaling factor for specific base station signal compensation. The method of claim 7, wherein The scaling factor value is determined using the following equations according to the path loss.

Is the gain of the transmitting antenna,

Is the gain of the receiving antenna,

Is the wavelength at the center frequency and d is the distance between the transmitting and receiving devices. The method of claim 7, wherein Compensating the selected base station signal; Compensating the selected base station signal using the following equation.

remind

Is the compensated signal,

Is a specific base station signal received by the terminal,

Is a scaling factor for specific base station signal compensation,

Is an offset for specific base station signal compensation. And a serving base station communicating using a first communication method, and at least one neighboring base station using a second communication method different from the first communication method, and including a terminal capable of communicating with the serving base station and the neighboring base station. A handoff device in a communication system, Compensation using a predetermined compensation value to determine whether the terminal hands off the signal strength of at least one of the serving base station signal received from the serving base station and the neighbor base station signal received by the terminal from the neighbor base station. When only the serving base station signal is compensated, the compensated serving base station signal and the neighbor base station signal are compared to determine whether the terminal is handed off, and when only the neighbor base station signal is compensated, the serving base station signal and the compensation The terminal determines whether the terminal is handed off by comparing the neighboring base station signals, and when the serving base station signal and the neighboring base station signal are compensated, the compensated serving base station signal is compared with the compensated neighbor base station signal. To determine whether off A handoff device comprising a handoff controller. The method of claim 15, And the serving base station signal and the neighbor base station signal are at least one of a pilot signal and a preamble signal. The method of claim 15, The handoff controller may determine whether to handoff using the signal strengths of the serving base station signal and the adjacent base station signal, and the signal strength is generated by measuring a power value of a signal received by the terminal. Handover device characterized in that. The method of claim 15, Wherein the power value is one of a received signal strength value and a signal to noise ratio value. The method of claim 15, The handoff controller determines a reference signal for signal compensation, selects at least one of the serving base station and the neighboring base station as a signal compensation base station according to the determined reference signal, and then uses the selected base station using the compensation value. Handoff device, characterized in that for compensating to be able to determine whether the handoff signal received from the terminal. The method of claim 19, And wherein the reference signal strength is one of a predetermined signal, a signal of the serving base station, and a signal of the neighboring base station. The method of claim 19, And the compensation value comprises at least one of an offset and a scaling factor used for signal compensation of the selected base station. The method of claim 21, And the offset is determined using a difference value between the reference signal and a base station signal to be compensated for. The method of claim 21, And the handoff controller compensates for the selected base station signal using the following equation.

Is the compensated signal,

Is a specific base station signal received by the terminal,

Is an offset for specific base station signal compensation. The method of claim 21, Wherein the offset is determined using the following equations according to path loss.

Is the gain of the transmitting antenna,

Is the gain of the receiving antenna,

Is the wavelength at the center frequency and d is the distance between the transmitting and receiving devices. The method of claim 21, The scaling factor is determined according to the ratio of the reference signal and the base station signal to compensate. The method of claim 21, And the handoff controller compensates for the signal strength by using the following equation.

Is the compensated signal,

Is a specific base station signal received by the terminal,

Is a scaling factor for specific base station signal compensation. The method of claim 21, The scaling factor value is determined using the following equations according to the path loss.

Is the gain of the transmitting antenna,

Is the gain of the receiving antenna,

Is the wavelength at the center frequency and d is the distance between the transmitting and receiving devices. The method of claim 21, And handing off the selected base station signal using the following equation.

remind

Is the compensated signal,

Is a specific base station signal received by the terminal,

Is a scaling factor for specific base station signal compensation,

Is an offset for specific base station signal compensation. The method of claim 15, The handoff controller is included in at least one of a base station controller, a base station, a terminal of a communication system.

Images