KR101409092B1 - Method of reporting link quality in EGPRS2 system - Google Patents

Abstract

A method for reporting link quality for a wireless block using multiple modulation schemes is provided. The link quality reporting method includes measuring a link quality for a received radio block, reporting the link quality for the modulation scheme if there is a modulation scheme with the greatest number of radio blocks, And reporting link quality for a modulation scheme selected via a predetermined method when there are multiple schemes. According to the modulation scheme for the received radio block, the link quality is reported only for some modulation schemes, not all modulation schemes, thereby reducing the signaling overhead and minimizing the performance degradation of the link adaptation process.

Description

[0001] The present invention relates to a link quality reporting method for an EGPRS2 system,

The present invention relates to wireless communications, and more particularly to a method for reporting link quality for a wireless block using various modulation schemes.

Global System for Mobile communications (GSM) is a wireless technology developed as a system for standardizing wireless communication systems in Europe and is widely used around the world. General Packet Radio Service (GPRS) was introduced to provide packet switched data service in the circuit switched data service provided by GSM. EDGE (Enhanced Data Rate for GSM Evolution) uses 8-PSK (Phase Shift Keying) instead of GMSK (GMSK) used by GSM to increase data rate. EGPRS (Enhanced General Packet Radio Service) represents GPRS using EDGE.

A physical channel used for GPRS / EGPRS traffic is called a PDCH (Packet Data Channel). The PDCH includes a PCCCH used for a control signal required for initializing a packet transmission and a Packet Traffic Channel (PTCH) used for user data and dedicated signaling. A logical channel for user data is called PDTCH (Packet Data Traffic Channel), and a logical channel for dedicated signaling is called PACCH (Packet Associated Control Channel).

Recently, EGPRS2 has been developed to support a variety of modulation and coding schemes. While EGPRS supports only GMSK and 8-PSK, EGPRS2 additionally supports four modulation schemes of GMSK, 8-PSK, 16-Qaudrature Amplitude Modulation (16-QAM) and 32-QAM. EGPRS2 has two levels, EGPRS2-A and EGPRS2-B. EGPRS2-A supports GMSK, 8-PSK, 16-QAM and 32-QAM, and EGPRS2-B supports GMSK, QPSK, 16-QAM and 32-QAM. The modulation and coding scheme at each level in EGPRS2 is described in 3GPP TS 43.064 V7.6.0 (2007-08) "Technical Specification, GSM / EDGE Radio Access Network, General Packet Radio Service (GPRS) 2 (Release 7) "in Section 6.5.5.1.3.

Through various modulation and coding schemes, the EGPRS / EGPRS2 system provides multiple data rates. For example, data is transmitted at various data rates over the PDTCH. In the link adaptation process, the bit rate is adjusted based on the link quality. If the link quality is good, the data is transmitted at a high transmission rate. Conversely, if the link quality is poor, the data is transmitted at a low transmission rate. Transmitting data according to a modulation and coding scheme for a higher transmission rate than link quality can result in data loss. Link adaptation increases data throughput using the highest possible rate using a particular modulation and coding scheme at a given link quality.

For the link adaptation process, a mobile station needs to report link quality to a base station. In the EGPRS / EGPRS2 system, the link quality between the base station and the mobile station is expressed by BEP (Bit Error Probability). BEP is the expected value of the actual BER (Bit Error Rate) of the signal received by the mobile station over the wireless channel. BEP is measured by burst-by-burst. The base station selects the appropriate modulation and coding scheme according to the reported link quality. Link adaptation can be performed most effectively when the reported BEP estimates the most accurate BER. As additional modulation and coding schemes are used in EGPRS2, there is a need for a way to efficiently report link quality according to various modulation and coding schemes.

SUMMARY OF THE INVENTION The present invention provides a method for reporting link quality for some modulation schemes in an EGPRS2 system using multiple modulation schemes.

In an aspect, a method of reporting link quality for a wireless block using multiple modulation schemes is provided. The link quality reporting method includes measuring a link quality for a received radio block, reporting the link quality for the modulation scheme if there is a modulation scheme with the greatest number of radio blocks, And reporting link quality for a modulation scheme selected via a predetermined method when there are multiple schemes.

According to the modulation scheme for the received radio block, the link quality is reported only for some modulation schemes, not all modulation schemes, thereby reducing the signaling overhead and minimizing the performance degradation of the link adaptation process. Also, even when there are a plurality of different modulation schemes having the same number of received radio blocks, the modulation system to report link quality can be defined to improve the performance of the entire system.

1 is a block diagram illustrating a wireless communication system. This may be a wireless communication system supporting Enhanced General Packet Radio Service 2 (EGPRS2). Wireless communication systems are widely deployed to provide various communication services such as voice, packet data, and the like.

1, a mobile station (MS) 10 refers to a communication equipment carried by a user and includes a user equipment (UE), a user terminal (UT), a subscriber station (SS), a wireless device And so on.

A base station (BS) 20 includes a base transceiver station (BTS) 22 and a base station controller (BSC) 24. The BTS 22 communicates with the mobile station 10 in one cell area via a radio interface and performs functions such as synchronization with the mobile station 10. The BSC 24 interfaces at least one BTS 22 with a Mobile Switching Center (MSC) 30.

The MSC 30 connects a heterogeneous network such as a Public Switching Telephone Network (PSTN) 65 or a Public Land Mobile Network (PLMN) with the base station 20 through a gateway MSC 60. A Visitor Location Register (VLR) 40 stores temporary user data and includes information about roaming of all mobile stations 10 in the service area of the MSC 30. The Home Location Register (HLR) 50 includes information on all subscribers of the home network. A Serving GPRS Support Node (SGSN) 70 is responsible for mobility management of subscribers. The Gateway GPRS Support Node (GGSN) 80 routes the packet to the current location of the mobile station 10 and interfaces with an external packet data network such as a PDN (Public Data Network) 85.

The TFI (Temporary Block Flow) is a logical connection provided by two Medium Access Control (MAC) entities for supporting unidirectional transmission of RLC (Radio Link Control) Protocol Data Unit (PDU) onto a basic physical subchannel. TBF is not provided in packet idle mode. In the packet idle mode, no radio resources on the packet data physical channel are allocated to the mobile station. At least one TBF is provided in a packet transfer mode. In the packet transmission mode, radio resources on at least one or more packet data physical channels for transmission of packet data are allocated to the mobile station. A MAC-idle state refers to a MAC-control-entity to which no basic physical subchannel is assigned. A Temporary Flow Identity (TFI) is assigned to each TBF by the network. The mobile station assumes that the TFI value is unique among the concurrent TBFs in the same direction (uplink or downlink) on all Packet Data Channels (PDCH) common to the TBFs.

2 is a block diagram showing elements of a mobile station. The mobile station 50 includes a processor 51, a memory 52, an RF unit 53, a display unit 54, and a user interface unit 55 . The memory 52 is coupled to the processor 51 to store the mobile station driving system, applications and general files. The display unit 54 displays various information of the mobile station and can use well known elements such as a liquid crystal display (LCD) and an organic light emitting diode (OLED). The user interface unit 55 may be a combination of a well-known user interface such as a keypad or a touch screen. The RF unit 53 is connected to the processor to transmit and / or receive a radio signal.

The processor 51 measures and reports the link quality to radio blocks received through the RF unit 53. [

3 is a conceptual diagram showing a radio block.

Referring to FIG. 3, one frame in the EGPRS / EGPRS2 system is composed of eight time slots (TS0, TS1,..., TS7). The radio block consists of four consecutive time slots belonging to different frames. For example, the radio block may be configured by taking one first time slot (TS0) in four consecutive frames. Here, it is taken for the first time slot TS0, but it may take another time slot.

The average BEP MEAN_BEP for one radio block is obtained as follows.

Here, BEP _{burst i} is the BEP for the i-th burst. A burst refers to information carried in a time slot.

The coefficient of variation (BEP) CV_BEP for the radio block is obtained as follows.

The link quality is obtained by averaging the BEP for each radio block per channel and per modulation scheme. The reliability R _n of the quality parameters for each modulation scheme is defined as follows.

Where n is an iteration index that is incremented for each downlink radio block. e is a forgetting factor for individual filtering for each mobile station. e may be determined according to the BEP period transmitted from the base station. x _n represents the presence or absence of quality parameters for the n-th block for each modulation scheme. x _n has 0 or 1, respectively, depending on the presence or absence of the quality parameter.

Using the reliability, the mobile station obtains MEAN_BEP and CV_BEP corresponding to each time slot for radio blocks having a TFI belonging to the mobile station as follows.

The link quality obtained above is the link quality for the wireless block for one time slot per frame.

In an EGPRS / EGPRS2 system, a mobile station may be assigned multiple timeslots. Therefore, the average BEP and the dispersion coefficient BEP per modulation scheme are averaged over all allocated channels (time slots) as follows.

Where n is the iteration index at the reported time and j is the channel number. N is reset to 0 when entering the packet transmission mode or MAC sharing mode or selecting a new cell. When a new time slot is assigned to the downlink TBF, MEAN_BEP_TNn-1, CV_BEP_TNn-1, and Rn-1 are reset to zero.

The mobile station reports the total average BEP and the dispersion coefficient BEP (for example, GMSK_MEAN_BEP, GMSK_CV_BEP and / or 8PSK_MEAN_BEP, 8PSK_CV_BEP) calculated by Equations 6 and 7 for each modulation scheme. In addition, the mobile station can report the measured value (MEAN_BEP_TN, CV_BEP_TN) per time slot according to the demand of the network.

4 is a flowchart illustrating a link quality reporting method in accordance with an embodiment of the present invention.

Referring to FIG. 4, the network instructs a mobile station through a packet downlink assignment message (link quality report) (S210). The network transmits a radio block to the mobile station (S220). This is a packet transfer mode. The mobile station checks whether it is a radio block having an identifier belonging only to itself, for example, a TFI belonging to itself (S230). During the downlink TBF transmission, the mobile station measures the received signal quality, which is measured for the radio block of the designated mobile station. The mobile station confirms whether it is a radio block pointing to itself through the TFI. When the RLC / MAC data block is transmitted through the radio block, the mobile station can confirm the TFI through the RLC / MAC header because the RLC / MAC header always includes the TFI.

The mobile station that has confirmed the TFI measures link quality (S240). The mobile measures the link quality for the radio block containing the TFI assigned to it. The signal quality of each channel is measured by the mobile station in a burst-by-burst manner. The measure for link quality measurement may be a bit error probability (BEP). BEP includes MEAN_BEP and CV_BEP. BEP is measured for all possible modulation schemes. For example, suppose that the EGPRS2 system supports Gaussian Minimum Shift Keying (GMSK), 8-Phase Shift Keying (8-PSK), 16-QAM (16-Qaudrature Amplitude Modulation) and 32-QAM. The average BEP and the dispersion coefficient BEP are measured.

The mobile station reports the measured link quality to the modulation scheme to be reported to the network (S250). The mobile station can report the link quality through a Packet Associated Control Channel (PACCH). The mobile station may report the link quality (MEAN_BEP_TN and CV_BEP_TN) in time slot units or may report the average link quality (MEAN_BEP and CV_BEP) corresponding to a plurality of timeslots. The network can determine the modulation and coding scheme through the reported link quality and perform the link adaptation process.

EGPRS2 supports 16-QAM and 32-QAM in addition to GMSK and 8-PSK. EGPRS2 has two levels, EGPRS2-A and EGPRS2-B. EGPRS2-A supports GMSK, 8-PSK, 16-QAM and 32-QAM, and EGPRS2-B supports GMSK, QPSK, 16-QAM and 32-QAM. In EGPRS2 using various modulation schemes, if link quality can be reported for all modulation schemes, optimal link adaptation can be performed. However, link quality reporting for all modulation schemes may serve as a signaling overhead and may even lower the transmission rate. Therefore, it is necessary to efficiently transmit the link quality for the modulation scheme.

When the packet downlink message instructs the link quality report, the mobile station can report the link quality only for the most received modulation scheme since the previous link quality report. If there are two modulation schemes to report, the mobile station reports the link quality for the two modulation schemes in order of the most received modulation scheme. If there are three modulation schemes to report, the mobile station reports the link quality for the three modulation schemes in order of the most received modulation scheme. That is, it reports link quality only for some selected modulation schemes, not all modulation schemes, thereby avoiding overhead due to link quality reporting.

There is a problem in handling a plurality of different modulation schemes having the same number of received radio blocks. That is, when two types of modulation schemes to be reported and the types of reception radio blocks using the same modulation scheme are three or more (for example, GMSK, 16-QAM, 32-QAM) .

In one embodiment, link quality is reported for two modulation schemes with a high order modulation scheme. For example, if the mobile stations are GMSK, 16-QAM, and 32-QAM with the same number of radio blocks as the most received, the mobile station can use 16-QAM and 32- Report quality.

In another embodiment, the link quality for two modulation schemes with lower order modulation schemes is reported. For example, if the different modulation schemes with the same number of radio blocks that the mobile station receives the most are GMSK, 16-QAM, and 32-QAM, the mobile station reports link quality for GMSK and 16-QAM.

In another embodiment, the link quality is reported for a modulation scheme with a smaller average BEP. For example, if GMSK, 16-QAM, and 32-QAM are the different modulation schemes with the same number of radio blocks, the GMSK_MEAN_BEP is 0.001, 16QAM_MEAN_BEP is 0.003, and 32QAM_MEAN_BEP is 0.005. Lt; / RTI >

In another embodiment, the link quality is reported for a modulation scheme with a larger average BEP. For example, if GMSK, 16-QAM, and 32-QAM are the different modulation schemes with the same number of received radio blocks, and GMSK_MEAN_BEP is 0.001, 16QAM_MEAN_BEP is 0.003, and 32QAM_MEAN_BEP is 0.005, - Report link quality to QAM.

When there are a plurality of different modulation schemes having the same number of received radio blocks, the modulation scheme for reporting the link quality can be selected by various other methods. The method of selecting the modulation scheme may be preset in the mobile station, or the network may inform the mobile station.

According to the modulation scheme for the received radio block, the link quality is reported only for some modulation schemes, not all modulation schemes, thereby reducing the signaling overhead and minimizing the performance degradation of the link adaptation process. Also, even when there are a plurality of different modulation schemes having the same number of received radio blocks, the modulation system to report link quality can be defined to improve the performance of the entire system.

The present invention may be implemented in hardware, software, or a combination thereof. (DSP), a programmable logic device (PLD), a field programmable gate array (FPGA), a processor, a controller, a microprocessor, and the like, which are designed to perform the above- , Other electronic units, or a combination thereof. In software implementation, it may be implemented as a module that performs the above-described functions. The software may be stored in a memory unit and executed by a processor. The memory unit or processor may employ various means well known to those skilled in the art.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. It will be understood that various modifications and changes may be made without departing from the spirit and scope of the invention. Accordingly, modifications of the embodiments of the present invention will not depart from the scope of the present invention.

1 is a block diagram illustrating a wireless communication system.

2 is a block diagram showing elements of a mobile station.

3 is a conceptual diagram showing a radio block.

4 is a flowchart illustrating a link quality reporting method in accordance with an embodiment of the present invention.

Claims (6)

A link quality reporting method for reporting link quality for a wireless block using a plurality of modulation schemes, Determining a modulation scheme and a link quality parameter for each time slot of the mobile station; Determine the number of each modulation scheme used by each mobile station in each of the time slots allocated for the reporting period; If a plurality of used modulation schemes having the same number are determined, selecting one of the plurality of used modulation schemes based on at least one of a modulation order and an error rate; And The mobile station reporting link quality parameters for the selected modulation scheme to the network, Wherein the plurality of used modulation schemes is a modulation scheme in which the mobile station is associated with the largest number of radio blocks received per time slot during the reporting period. The link quality reporting method of claim 1, wherein the selected modulation scheme is selected to have the highest modulation order among the plurality of used modulation schemes. 2. The method of claim 1, wherein the selected modulation scheme is selected to have the lowest modulation order among the plurality of used modulation schemes. The link quality reporting method of claim 1, wherein the selected modulation scheme is selected to have the smallest average BEP (Bit Error Probability) among the plurality of used modulation schemes. 2. The method of claim 1, wherein the selected modulation scheme is selected to have the largest average BEP among the plurality of used modulation schemes. A mobile station reporting link quality for a radio block using a plurality of modulation schemes, Determine each modulation scheme assigned and a link quality parameter for each time slot; Determine the number of each modulation scheme used in each time slot assigned during the reporting period; If a plurality of used modulation schemes having the same number are determined, selecting one of the plurality of used modulation schemes based on at least one of a modulation order and an error rate; And And a link quality parameter for the selected modulation scheme to the network, Wherein the plurality of used modulation schemes is a modulation scheme in which the mobile station is associated with the largest number of radio blocks received per time slot during the reporting period.

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