KR20100018296A - Method for acquiring information of reception signal strength and base station for providing thereof in wireless communication system - Google Patents

Abstract

PURPOSE: A method for obtaining RSSI(Received Signal Strength Indicator) information in a wireless communication system and a base station thereof are provided to predict an RSSI using given information, thereby removing a need of a separate wireless resource for the RSSI. CONSTITUTION: Uplink transmission power information and CQI(Channel Quality Information) are received from a mobile station(S210). A path loss value is calculated in consideration of the uplink transmission power information(S230). The RSSI of the mobile station is predicted from the path loss value and base station transmitting power(S240).

Description

Method for acquiring received signal strength information in a wireless communication system and a base station implementing the same

The present invention relates to a communication system, and more particularly, to a method in which a transmitter estimates a received signal strength of a receiver to obtain received signal strength information of the receiver and a base station implementing the same in a wireless communication system.

Wireless communication systems are being developed to provide various services such as broadcasting, multimedia video, and multimedia messages. In particular, in the next generation wireless communication system, active researches are being conducted to stably provide users with services of high quality of service (QoS: Quality of Service, hereinafter referred to as 'QoS'). Also, in the current generation wireless communication system, a wireless local area network (WLAN) system and a wireless metropolitan area network (WMAN) will be referred to as "WMAN". Researches are being actively conducted to support high-speed services in a form of guaranteeing mobility and QoS in a broadband wireless access (BWA) communication system such as a system. The representative communication system is Orthogonal Frequency Division Multiplexing (OFDM) or Orthogonal Frequency Division Multiple Access (OFDMA). Portable Internet system or Wi-Fi based on Institute of Electrical and Electronics Engineers (IEEE) 802.16 system WiMAX is the Worldwide Interoperability for Microwave Access system.

In addition, in a wireless communication system, multiple frequency (Frequency Assignment) is supported, and noise / interference of a specific region in a multi-FA environment is different for each FA due to path loss according to a carrier frequency. At this time, even if the carrier-to-interference noise ratio (CINR) is high in a specific area of a predetermined FA, the received signal strength (RSSI) is referred to as 'RSSI'. In case of low), a problem such as requiring a high level of power during uplink transmission may occur.To solve this problem, another FA with high CINR and RSSI is scanned to perform handover between FAs. Preference is given to performing. Therefore, in IEEE 802.16 system, RSSI as well as CINR is considered as a trigger condition.

However, in the current IEEE 802.16 system, the complex trigger condition for inter-FA handover considering the CINR and RSSI is not smoothly supported. If only the RSSI is smaller than a specific value, the FA scanning for inter-FA handover is simple. It supports triggering.

This problem is referred to as a base station (BS) that periodically receives CINR for downlink adaptive modulation and coding (AMC). If the BSI can be known, the BS can be solved by applying a complex trigger condition, but there is a problem that additional bandwidth for periodic RSSI reporting is required for the BS to recognize the RSSI.

Accordingly, there is a need for a solution to the problem that radio resources are required for periodic RSSI reporting to the BS.

Accordingly, an object of the present invention is to provide a method for acquiring signal reception strength information using given information in a wireless communication system and a base station implementing the same.

Another object of the present invention is to provide a method for acquiring signal reception strength information for handover / scanning under a complex trigger condition without delay in a wireless communication system and a base station implementing the same.

The method of the present invention for achieving the above objects comprises the steps of: receiving uplink transmit power information and channel quality information from a mobile station; Calculating a path loss value in consideration of the uplink transmission power information; And estimating a received signal strength indicator (RSSI) of the mobile station from the path loss value and the base station transmit power.

An apparatus of the present invention for achieving the above object, the calculation unit for calculating a path loss value using the uplink transmission power information received from the mobile station; And an estimator estimating a received signal strength indicator (RSSI) of the mobile station using the path loss value and the base station transmit power.

According to the present invention, by estimating a received signal strength using information given in a wireless communication system, a separate radio resource for the received signal strength is unnecessary, and accordingly, the radio resource can be efficiently utilized. In addition, by using the given information and the received signal strength, it is possible to smoothly support handover / scanning according to a complex trigger condition without delay.

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 obtains received signal strength information from a wireless communication system, for example, an IEEE (Institute of Electrical and Electronics Engineers) 802.16 system, which is a broadband wireless access (BWA) communication system. Suggest ways to do this. Here, in the embodiment of the present invention to be described later, orthogonal frequency division multiplexing (OFDM) orthogonal frequency division multiple access (OFDM) in the IEEE 802.16 system for convenience of description. Although an example of a communication system using an Orthogonal Frequency Division Multiple Access (OFDMA) scheme) is described as an example, it may be implemented in communication systems employing other schemes.

In addition, the present invention, the received signal strength information of a mobile station (MS: Mobile Station (hereinafter, referred to as "MS") that receives a communication service in a wireless communication system, referred to as a base station (BS) Proposes a method for obtaining. In an embodiment of the present invention to be described later, the BS will be referred to as a Receive Signal Strength Indicator (RSSI) received by the MS downlink (DL: DownLink, hereinafter referred to as 'DL'). Estimate). Here, the BS receives uplink (UL: Uplink, 'UL') transmission power information received from the MS, and estimates the RSSI from the UL transmission power information.

The BS performs scheduling and control on the MS using the estimated RSSI, feedback information, data related information, and the like. In more detail, the BS may include an estimated RSSI, noise and interference (hereinafter referred to as NI), and carrier to interference and noise ratio (CINR). Assigns a channel for transmitting / receiving data packet, control information, and feedback information for the MS using information on the data packet, and the like. MCS: Modulation and Coding Scheme (hereinafter referred to as 'MCS') level, and controls the handover (handover) according to the movement between the cells of the MS. Here, the handover supports complex trigger conditions for inter-FA handover considering the RSSI and CINR in, for example, a multiple frequency assignment environment.

In this case, as the BS estimates the RSSI from the UL transmission power information of the MS, a message for transmitting and receiving between the MS and the BS for the RSSI is unnecessary. An example of the message to be transmitted and received is a report request (REP-REQ: REP-REQ) / Report Response (REP-RSP: REP- RSP) for the RSSI report Message). Accordingly, the allocation of additional radio resources for the transmission and reception of the message (for example, the allocation of a dedicated channel) is unnecessary, and the overhead for the transmission and reception of the message is prevented. In addition, it is possible to stably provide a communication service by preventing a problem occurring when the message cannot be transmitted or received by performing scheduling and control of the MS normally. Next, a wireless communication system according to an exemplary embodiment of the present invention will be described in more detail with reference to FIG. 1.

1 is a view schematically showing the structure of a wireless communication system according to an embodiment of the present invention.

Referring to FIG. 1, a wireless communication system has a multi-cell structure, that is, a BS1 105 having a cell 1 (100), a cell 2 (130), and a cell 3 (160) and managing each of the cells (100, 130, 160). ), BS2 135, BS3 165, and MSs 110, 115, 120, 140, 170 present in the cells 100, 130, 160 and receiving communication services from the BSs 105, 135, 165. Here, the MSs 110, 115, 120, 140, and 170 have both mobility and fixedness, and all the MSs perform handover according to complex trigger conditions, in particular, the MS2 115 and the MS3 115 are the cell 1 100 and the cell. MS 130 exists in cell 2 (100), cell 1 (100) and cell 3 (160), and is likely to perform handover according to the complex trigger conditions. In addition, the transmission and reception of signals between the BSs 105, 135, 165 and the MSs 110, 115, 120, 140, and 170 in the cells 100, 130, and 160 will be described using the OFDM / OFDMA scheme. In the following description, for convenience of explanation, the description will be made based on the MS2 115 or the MS3 120, but the embodiment of the present invention may be equally applied to all MSs.

In addition, the wireless communication system supports multiple FAs for the cells 100, 130, and 160, for example, BS1 105 is assigned with FA1, FA2, and FA3, and BS2 135 is assigned with FA1 and FA2. In addition, the BS3 165 supports the use of FA1 and FA3. Accordingly, each of the cells 100, 130, and 160 becomes a multi-FA environment, and interference and noise in a specific area of each of the cells 100, 130, and 160 are different for each FA in this multi-FA environment. In addition, each FA may generate a different path loss according to a communication environment in a cell. In particular, when transmitting and receiving signals between the MS and the BS using the FA, signals may be transmitted or received by neighboring BSs or other MSs except the MS itself. Due to noise and interference, path loss may occur due to distance and obstacles in the cell.

For example, the overlap region of cell 1 100 and cell 2 130 where MS2 115 is located has a greater interference at FA1 and FA2 than interference at FA3, and cell 1 (where MS3 120 is located). In the overlapping region of 100 and cell 3 160, when the interference in FA1 and FA3 is greater than the interference in FA2, the MS2 115 preferably transmits and receives a signal through FA3 than FA1 and FA2. The MS3 120 preferably transmits and receives a signal through FA2 rather than FA1 and FA3.

In this case, when the MS2 115 transmits and receives a signal through FA1 or FA2, the MS2 115 and BS1 105 of the MS2 115 perform handover between FAs to transmit and receive a signal. For inter-FA handover to the MS2 115, the BS1 105 triggers FA scanning / FA handover according to complex trigger conditions considering the CINR and RSSI of the MS2 115.

For example, the BS1 105 compares the CINR and the first threshold of the MS2 115, compares the RSSI and the second threshold of the MS2 115, and then compares the CINR with the CINR. If the complex trigger conditions considering the RSSI are satisfied, it triggers FA scanning / FA handover. In other words, if the RSSI is relatively small but the CINR is too large and the CINR is greater than the first threshold and the RSSI is greater than the second threshold, then FA scanning / FA handover is triggered, or if the CINR is greater than the first threshold or the RSSI is greater than the first threshold. If less than the second threshold triggers FA scanning / FA handover.

Here, the CINR of the MS2 115 is a channel received from the MS2 115 for DL adaptive modulation and coding (AMC) of the MS2 115. Obtained through quality information (CQI: Channel Quality Information, hereinafter referred to as 'CQI'). In other words, the BS1 105 receives the CQI from the MS2 115 to recognize the CINR of the MS2 115. The CQI is feedback information fed back from the MS2 115 and includes a CINR measured by the MS2 115 while transmitting and receiving a signal with the BS1 105.

In addition, the RSSI of the MS2 115 is obtained by the BS1 102 through UL transmission power information from the MS2 115. In other words, the BS1 105 receives UL transmission power information from the MS2 115 and estimates RSSI from the UL transmission power information to obtain RSSI information. Here, all MSs present in each cell periodically transmit the CQI and UL transmission power information to the BS, and the BS obtains the CINR through the CQI, and estimates the RSSI through the UL transmission power information to schedule and control the MS. To perform the FA scanning / FA handover trigger according to the above-described complex trigger conditions. Hereinafter, the RSSI estimation will be described in more detail.

In order to estimate the RSSI, a path loss is calculated using an UL power level determined by Equation 1 in an open loop power control scheme, and time division duplexing (TDD) is used. In this case, it is assumed that DL and UL are equivalent to each other.

In Equation 1, P denotes a transmission power level of the MS including a transmission antenna gain of the MS, and L denotes a path loss in the DL as an average current propagation path attenuation value estimated by the MS. Here, L includes the transmit antenna gain and the path loss of the MS and does not include the receive antenna gain of the BS. C / N means normalized C / N (target CINR) of modulation and forward error correction (FEC) rate for the current transmission, and R is modulation and The number of repetitions for the FEC rate, and NI means the average power level of noise and interference for each subcarrier estimated by the BS. Here, the NI does not include the receive antenna gain of the BS. In addition, the offset _MS is controlled at the MS with a correction value for the specific power offset of the MS and the initial value is zero. Offset _BS is controlled at the BS through a power control message with a correction for a specific power offset of the MS.

In this case, the BS, in Equation 1, has already recognized all parameters except L corresponding to the path loss of the DL, that is, the C / N, R, NI, Offset _MS , and Offset _BS , or the manual mode. In the open loop power control scheme, since the parameters are controlled by the BS, the BS can calculate a path loss through Equation 1. Here, the UL transmit power P of the MS is periodically reported and included in the transmit power information from the MS to calculate the headroom required for UL power control or AMC, e.g., the available power of the MS.

And, the BS BS transmission power, such as the effective isotropic radiated power of the BS in the DL: as that recognized the (EIRP hereinafter be referred to as Effective Isotropic Radiated Power, hereinafter _{'EIRP') (BS EIRP)} , the BS _EIRP and The RSSI is estimated or calculated through Equation 2 using the path loss L calculated through Equation 1.

In addition, by using the RSSI calculated through Equation 2, the BS may perform scheduling and control for the MS. In particular, as described above, the BS may use the RSSI in a complex trigger condition for inter-FA handover or FA scanning. Can be. Here, the BS acquires and recognizes the above-described parameters, that is, C / N, R, NI, Offset _MS , and Offset _BS through information received from the upper end, neighbor BSs, and _MS , and recognizes the BS _EIRP. The BS _EIRP is recognized as determined by the BS itself by BS's own system information, such as transmit power, transmit antenna gain, and loss in the BS. In addition, the BS performs scheduling and control for the MS in consideration of RSSI and parameters, BS _EIRP , and the like, and includes downlink including control information for transmitting and receiving data packets, for example, the aforementioned parameters and transmission power level. Downlink channel descriptor (DCD) and MAP information are transmitted to the MS, and the UL transmit power information including the UL transmit power P of the MS as described above. The CQI including the CINR is reported.

Here, although not shown, the BS receives UL transmission power information and CQI which are periodically reported from the MS, and thus the UL transmission power P and the aforementioned parameters C / N, R, NI, Offset _MS , and Offset. _BS and recognizes and calculates a path loss (L) using the UL transmission power (P) and the parameters (C / N, R, NI, Offset _MS , and Offset _BS ), and the path loss Estimation unit for estimating RSSI using (L) and BS transmit power (BS _EIRP ), and performing scheduling and control using the RSSI and parameters (C / N, R, NI, Offset _MS , and Offset _BS ) It includes a decision unit to determine to. In this case, the determiner determines to perform a handover according to a combined trigger condition for channel allocation, MCS level and transmission power control and inter-FA handover or FA scanning using RSSI. Next, an operation process of acquiring received signal strength information in the wireless communication system according to an exemplary embodiment of the present invention will be described in detail with reference to FIG. 2.

2 is a diagram schematically illustrating a process of acquiring received signal strength information of a BS in a wireless communication system according to an embodiment of the present invention.

Referring to FIG. 2, in step S210, UL transmission power information and CQI are received from an MS existing in a cell. Here, the UL transmission power information includes the UL transmission power level determined by the MS, and the CQI includes the CINR measured by the MS. Then, in step S220, the UE determines the CINR measured by the MS through the CQI, the UL transmission power level determined by the MS through the UL transmission power information, and the previously recognized parameters as described above, that is, the equation Check the C / N, R, NI, Offset _MS , and Offset _BS described in 1. In operation S230, the path loss of the MS is calculated through Equation 1 by using the UL transmission power level of the MS and the parameters already recognized.

Next, by using the calculated path loss and BS transmit power (BS _EIRP ) in step S240 to estimate the RSSI of the MS through the equation (2) to obtain the received signal strength information of the MS in the DL. Then, scheduling and control may be performed using the identified CINR, RSSI, and parameters. For example, the channel of the MS may be allocated, the MCS level may be determined, and the transmission power level may be determined. Can be performed.

On the other hand, in the detailed description of the present invention has been described with respect to specific embodiments, various modifications are possible without departing from the scope of the 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.

1 schematically illustrates the structure of a wireless communication system in accordance with an embodiment of the present invention;

2 is a diagram schematically illustrating a process of acquiring received signal strength information of a BS in a wireless communication system according to an embodiment of the present invention.

Claims (5)

A method of obtaining received signal strength information in a wireless communication system using an open loop power control method, Receiving uplink transmit power information and channel quality information from a mobile station; Calculating a path loss value in consideration of the uplink transmission power information; And Estimating a received signal strength indicator (RSSI) of the mobile station from the path loss value and the base station transmit power. The method of claim 1, The calculating of the path loss value may be performed by further considering a carrier / noise ratio (C / N), noise and interference (NI), repetition, and offset parameters. A method of obtaining received signal strength information. In a wireless communication system using an open loop power control method, A calculator configured to calculate a path loss value using uplink transmission power information received from the mobile station; And And an estimator for estimating a received signal strength indicator (RSSI) of the mobile station using the path loss value and the base station transmit power. The method of claim 3, The calculation unit may further calculate the path loss value using a carrier / noise ratio (C / N), noise and interference (NI), repetition, and offset parameters. Base station. The method according to claim 3 or 4, And a determining unit which determines a handover of the mobile station by using the received signal strength and channel quality information.

Images