KR20070115522A - Modem in Mobile Communication System and Interface Method Therefor - Google Patents

Abstract

The present invention relates to an SDR-based baseband modem and an interface method for the same in a mobile communication system. The baseband modem of the present invention is a modem that supports a plurality of wireless standards based on software and is designated among the plurality of wireless standards. And a hardware block including a transmission / reception filter and a channel decoder reconfigured according to a standard, and a digital signal processor interworking with the hardware block and reconfiguring the hardware block by changing a predetermined system parameter according to the specified standard. . The interface method in the baseband modem includes a first process of confirming whether or not the data is transmitted from a channel decoder when a data to be decoded is generated by a digital signal processor that performs modulation and demodulation and channel estimation, and the digital signal processor prepares the data for transmission. And a second process of transmitting the data to the channel decoder when the data decoding is completed, and a third process of transmitting the decoded data after transmitting an interrupt signal to the digital signal processor when decoding of the data is completed in the channel decoder. It is characterized by.

When the SDR system is implemented using a DSP, the present invention efficiently shares the roles of hardware and software, thereby quickly coping with constantly changing standards, and has an effect of implementing a low power scheme and an efficient terminal modem. .

Description

MODEM IN MOBILE COMMUNICATION SYSTEM AND INTERFACING METHOD THEREOF}

1 illustrates a general modem structure in a terminal of a mobile communication system.

2 is a diagram illustrating a CC in an SDR terminal modem according to the present invention.

3 illustrates an SDR modem according to the present invention.

4 illustrates an SDR modem according to an embodiment of the present invention.

5A and 5B are signal flow diagrams illustrating an interface method in an SDR modem of the present invention.

The present invention relates to a modem in a mobile communication system, and more particularly, to an SDR-based baseband modem and an interface method therefor in a mobile communication system.

In recent years, mobile communication systems are not only second generation and third generation services, but also wireless and mobile in various ways such as wireless LAN, portable Internet, Bluetooth, Home Network, Ad-hoc Network, digital broadcasting, etc. Communication services provide a lot of convenience to users. However, the confusion of users due to the mixed heterogeneous standards and heterogeneous protocols is also a big problem. Furthermore, there is a demand for an environment in which a wide variety of services such as data, text, images, audio, and video as well as voice can be provided by a user's personal choice.

Recently, R & D and various standardization work for 4G mobile communication service are actively progressing. Here are some major issues. First is the convergence of services. In other words, the next-generation mobile communication system requires all-IP based core networks and ubiquitous access from anywhere with the goal of always being connected. Where possible, there is a need to implement seamless access and to achieve short range connectivity between advanced communication terminals. Second, the emergence of demand for reconfigurable networks and terminals. This will enable interoperability as well as a variety of interesting applications. Finally, customized services for individual users are required, which include content, price, and quality of service (QoS).

As described above, the terminal in the fourth generation mobile communication system should be provided with a modem applied for various protocols. Next, a modem of a terminal of a general mobile communication system will be described.

FIG. 1 is a diagram illustrating a general modem structure in a terminal of a mobile communication system, and illustrates an ASIC block transmitter.

Referring to FIG. 1, the microprocessor unit 10 functions to control the entire baseband processor 20 and the RF processor 30. The baseband processor 20 of the terminal stores the signal processing message generated by the microprocessor unit 10 in the buffer 21, and after channel encoding and interleaving data through the channel encoder 22, the modulator 23. And the coded signal through the filter 24 is modulated and filtered. In this manner, the transmission signal is converted into a baseband signal through band processing and converted into a digital signal through a digital to analog converter (DAC) 31. Thereafter, the converted digital signal is high frequency converted through the high frequency modulator 32 and the power amplifier 33 and transmitted through the duplexer 40 and the antenna 50.

The conventional terminal modem as described above is inflexible because it is based on the hardware of the ASIC type for low power.

That is, the conventional terminal modem is implemented in the form of ASIC, so it is necessary to redesign the hardware to adapt to various standards under development, and to meet the various standards for seamless roaming between standards. Each developed ASIC chip must be put into one terminal. However, in this case, since the ASIC chip is an expensive device composed of hardware, many problems such as low power, miniaturization, and low price are required. In addition, the need for new development of ASICs to support multiple standards from the outset is too much development time and cost.

In addition, the existing ASIC-type terminal modem structure coexists with various standards, and it is difficult to flexibly cope with user's demand for multi-mode terminal. In particular, if the standard is still undecided, there are too many risks to implement ASICs with constantly changing specifications, and it is very difficult to properly respond to market demands because the standards have to be waited for to be completed. .

Accordingly, an object of the present invention is to provide a flexible baseband modem applicable to various types of systems in a mobile communication system and an interface method therein.

Another object of the present invention is to provide a baseband modem having high efficiency in a mobile communication system and an interface method therein.

It is another object of the present invention to provide a miracle band modem and an interface method within the modem, which are cost competitive in a mobile communication system.

Another object of the present invention is to provide a modem and an interface method for efficiently distributing the roles of software and hardware modem by using a high speed, low power DSP and a reconfigurable processor in a mobile communication system. .

According to an aspect of the present invention, there is provided a modem of a mobile terminal that supports a plurality of wireless standards based on software, comprising: a hardware block including a transmit / receive filter and a channel decoder reconfigured according to a specified standard among the plurality of wireless standards; And a digital signal processor interworking with the hardware block and reconfiguring the hardware block by changing a predetermined system parameter according to the specified standard.

The hardware block may include an analog core unit for converting transmission / reception signals into digital and analog signals, a filter unit for filtering a signal transmitted from the analog core, and a channel decoding for the signal transmitted from the digital signal processor. It includes a hardware accelerator.

The digital signal processor may perform demodulation and channel estimation on the received signal.

According to an aspect of the present invention, there is provided an interface method in a modem of a mobile terminal that supports a plurality of wireless standards based on software, and wherein the data is generated from a channel decoder when data is to be decoded by a digital signal processor that performs modulation and demodulation and channel estimation. A first step of confirming whether or not to transmit the data, a second step of transmitting the data to the channel decoder when the data is ready to be transmitted by the digital signal processor, and when the decoding of the data is completed by the channel decoder, And after transmitting the interrupt signal to the digital signal processor, transmitting the decoded data.

The first process may include checking a state of an input buffer of the channel decoder in the digital signal processor, and checking a transmission direction of the data in the digital signal processor.

DETAILED DESCRIPTION Hereinafter, detailed descriptions of preferred embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the same components in the figures represent the same numerals wherever possible. Specific details are set forth in the following description, which is provided to aid a more general understanding of the invention. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

In the present invention, a software defined radio (SDR) technology is used to satisfy a part required in the fourth generation mobile communication service in technical, service, and industrial aspects. The SDR technology is a wireless connection-based technology for integrating and accepting multiple wireless communication standards through a single transmission / reception system with only a modular software change without hardware modification based on advanced digital signal processing technology and high performance digital signal processing device.

Accordingly, the present invention proposes a reconfigurable SDR based terminal modem to implement a system applicable to a mobile communication system having various standards. In the following description, an SDR-based terminal modem for baseband processing will be referred to as an SDR modem. In order to implement the SDR modem in the present invention, some blocks, such as a filter and a channel decoder, which are simple, repetitive and have a large amount of computation, are implemented in hardware. That is, in order to efficiently implement the SDR-based terminal modem, a high performance, low power digital signal processor (DSP) and a flexible companion chip (Companion Chip: CC) are implemented. Here, CC refers to an SDR-based chip that can be reconfigured into a chip proposed in the present invention.

In the following description, the CC will be described first, and then a baseband modem having a structure in which the CC and the DSP are interworked will be described.

2 is a diagram illustrating a CC (200) used for an SDR-based terminal modem in accordance with the present invention.

Referring to FIG. 2, the CC 200 includes an analog core unit 210, a filter unit 220, and a hardware accelerator 230. The analog core unit 210 may include a converter for converting an analog signal into a digital signal (Analog to Digital Converter (ADC)), a converter for converting a digital signal into an analog signal (Digital to Analog Converter (DAC)) and the like. The filter unit 220 is a reconfigurable front end, and may include an interpolation filter, a decimation filter, and the like.

 The hardware accelerator 230 may also be a reconfigurable block, and may include a channel decoder.

As described above, the filter unit 220 and the hardware accelerator 230 of the CC 200 of the present invention may be designed such that each block can be reconfigured according to the system to flexibly implement a CDMA system, a WCDMA system, an OFDM system, and the like. Can be.

Next, an SDR modem using the CC 200 of the present invention will be described.

3 is a diagram illustrating a baseband modem 300 according to the present invention, and shows a structure in which the CC 200 and the DSP chip 240 are combined. Referring to FIG. 3, the baseband modem 300 of the present invention has a structure in which the baseband modem 300 operates as one communication modem in conjunction with the CC 200 and the DSP 310.

The CC 200 is configured as a reconfigurable chip to implement an SDR-based communication modem, and is responsible for a simple repetitive and a large amount of computation. The DSP 310 is responsible for data processing in which a calculation formula is very complicated and frequently changes in a data processing method. In other words, by applying a CC that can be reconfigured for a simple iterative and a large amount of calculation, and processing a large amount of arithmetic and a large amount of calculation to the DSP 310 to support a variety of standards, it is possible to increase the flexibility and efficiency. For example, the CC implements a block such as a transmission / reception filter and a decoder, and the DSP may be responsible for modulation and channel estimation operations.

Here, the CC is implemented as a reconfigurable processor in the form of a reconfigurable filter and a channel decoder reconfigurable channel suitable for various standards only by changing a system parameter. Such a system parameter has a structure in which the configuration can be changed by setting the register value in the DSP.

Next, an example of actually applying a modem according to the present invention will be described with reference to FIG. 4.

As shown in Figure 4, the SDR modem 300 of the present invention can be applied to each as follows. The analog core part 210 of FIG. 3 is represented by the ADC 201 and the DAC 203, and the filter part 220 is a reconfigurable Rx filter 221 and a reconfigurable Tx filter. Can be divided by (223). The hardware accelerator 230 may be referred to as a reconfigurable channel decoder.

The data processing method of the mobile communication system will be described using the SDR modem 400 of FIG. Referring to FIG. 4, an I / Q signal received at an RF stage (not shown) is sampled and quantized by the ADC 201 and converted into a digital signal. The converted digital signal is input to the reception filter 221 and filtered by the reception filter defined in each standard, and transmits the filter output signal to the DSP 310. The DSP 310 performs a demodulation and channel estimation function according to a demodulation method used in a mobile communication system for the signal transmitted from the reception filter 221. The demodulated signal is again transmitted to the channel decoder 330 of the CC of the present invention for channel decoding. The channel decoder 330 decodes the transmitted signal and transmits the decoded data back to the DSP 310 to complete the reception process for all communication systems. This process can be applied to all mobile communication systems only by changing the DSP code. For example, when the DSP code for CDMA is downloaded, the DSP operates in the CDMA manner, and when the DSP code for GSM is downloaded, the DSP operates in the GSM manner. Thus, the DSP can be implemented just like the modem in the ASIC by replacing software. In this case, since the transmission method is performed in the inverse of the reception method, it will be omitted.

As described above, the SDR modem 400 according to the present invention implements a hardware block such as the filter 220 and the decoder 230 as a reconfigurable CC 200, and is responsible for processing complex calculations such as modulation and channel estimation. It is a structure for interlocking the DSP 310. Accordingly, an interface method between the CC 200 and the DSP 310 is required. This will be described with reference to FIGS. 5A and 5B.

5A and 5B are signal flow diagrams illustrating an interface method of the SDR modem according to the present invention, and show a case between the channel decoder 230 and the DSP 310. Here, the channel decoder 230 is assumed to be a convolutional turbo code (CTC), which is a channel decoder of a WiMax / WiBro system, and the DSP 310 has an ARM core (Advanced RISC Machine) embedded therein. It is assumed that the system has a Parallel Streaming Data (PSD) interface and a Multi-Port Memory Controller (MPMC) interface. The Parallel Streaming Data (PSD) interface is an interface through which 16 bits or more data bits are simultaneously transmitted according to a data clock. In the present invention, the PSD interface is mainly used for transferring a large amount of data between the CC 200 and the DSP 310, and in the case of reading / writing a register of the CC 200, It is suggested to mainly use the MPMC interface. However, depending on the amount and speed of data transmission, the MPMC interface can also be used as an interface for data transmission.

The WiMax / WiBro system has downlink map (DL MAP) data and download map burst (DL Burst) data indicating the map information in one frame. The signal processing result of 310 should be transmitted to the CC 310. Due to the characteristics of the WiMax / WiBro system, DL Map data occurs first, and DL Burst data occurs later. The transmission order for the DL Map and DL Burst data is shown in FIGS. 5A and 5B, respectively.

Referring to FIG. 5A, an interface method for DL MAP is described. First, when DL Map data is generated in the DSP 310 as in step 500, a direct memory for data transmission to the channel decoder 230 of the CC 200 is described. Set the access (Transmitter Direct Memory Access: Tx DMA). Thereafter, the DSP 310 reads a register value indicating whether the input buffer of the channel decoder 230 is empty from the CC 200 in step 501. If the input buffer of the channel decoder 230 is empty, the DSP 310 writes a value to a register for setting the direction of the PSD interface in step 502. In addition, the register value is written to inform the channel decoder 230 for the block size of the data to be transmitted as in step 503. Thereafter, the DSP 310 transmits a start command CTC_START_CMD for data transmission to the CC 200 in step 504.

Upon receiving the start command, the CC 200 transmits a PSD clock (Enable) signal to the DSP 310 in step 505. Then, the DSP 310 transmits the data to be decoded in step 506 to the channel decoder buffer in the CC 200. When the DL MAP data is transmitted completely, the DSP 310 sets up a receive DMA (Rx DMA) to receive the DL MAP decoding result, and changes the direction of the PSD from the CC 200 to the DSP 310.

After receiving the DL MAP data, the channel decoder 230 transmits the PSD clock enable through the PSD interface as in steps 509 and 510, and then decodes the decoded data. 310). When the decoded DL Map data is transmitted to the DSP 310, the CC 200 informs the DSP 310 by using an external interrupter in step 511. Upon receiving the interrupt, the DSP 310 transmits the DL Map data decoded in step 512 to the MAP decoder processed by the DSP 310, and changes the Tx DMA setting and the direction of the PSD.

Next, an interface method related to DL burst data will be described with reference to FIG. 5B. Referring to FIG. 5B, if there is DL Burst data as in step 513, the DSP 310 inputs the buffer of the channel decoder 230 through the register value CTC_RDY transmitted from the CC 200 in step 514. Check to see if it is empty. Then, the DSP 310 writes the register value TR_BLK_NUM for the block size of the data to be transmitted in step 515, and then, in step 516, the start command CTC_START_CMD for data transmission to the CC 200. Get off. Upon receiving the start command, the CC 200 transmits a PSD clock enable to the DSP 310 in step 517. Upon receiving the PSD clock enable, the DSP 310 transmits DL burst data to the channel decoder 230 in the CC 200 in step 518. Thereafter, the channel decoder 230 performs a decoding operation of the DL burst data in step 519.

Due to the data structure of the WiMax / WiBro system, the decoded DL burst data is transmitted to the LMAC. For example, if the LMAC is implemented as another reconfigurable processor in the CC 200, the decoded DL burst data is transmitted to the LMAC block inside the CC 200 and the data is transmitted to the LMAC block. The interrupt will inform the LMAC. The data sent to the LMAC is processed by LMAC and finally stored in external memory by the ARM through the MPMC interface.

Thereafter, if DL Burst data is generated in the DSP 310, steps 514 to 518 may be repeatedly performed.

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 determined not only by the scope of the following claims, but also by the equivalents of the claims.

Therefore, when the SDR system is implemented using a DSP, the present invention efficiently divides the roles of hardware and software, thereby rapidly coping with constantly changing standards, and has an effect of implementing a low power scheme and an efficient terminal modem. have.

Claims (5)

In the modem of a mobile terminal that supports a plurality of wireless standards based on software, A hardware block including a transmit / receive filter and a channel decoder reconfigured according to a specified standard among the plurality of wireless standards; And a digital signal processor interworking with the hardware block and reconfiguring the hardware block by changing a predetermined system parameter according to the specified standard. The method of claim 1, wherein the hardware block, An analog core unit for converting transmission / reception signals into digital and analog signals, A filter unit for filtering the signal transmitted from the analog core; And a hardware accelerator for performing channel decoding on the signal transmitted from the digital signal processor. The method of claim 1, wherein the digital signal processing unit, And demodulating and performing channel estimation on the received signal. An interface method in a modem of a mobile terminal supporting a plurality of wireless standards based on software, A first step of confirming whether or not the data is transmitted from a channel decoder when data to be channel decoded is generated by a digital signal processor performing modulation and demodulation and channel estimation; A second process of transmitting the data to the channel decoder when the digital signal processor is ready to transmit the data; And a third step of transmitting the decoded data after transmitting the interrupt signal to the digital signal processing unit when the decoding of the data is completed in the channel decoder. The method of claim 4, wherein the first process comprises: Checking a state of an input buffer of the channel decoder by the digital signal processor; And confirming the transmission direction of the data in the digital signal processor.

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