KR100634212B1 - Method and apparatus for transmitting data based OFDM - Google Patents

Abstract

In the communication system, in particular, while enabling high-speed transmission of 1Gb / s in a short distance wirelessly, by adjusting the operation time of each part of the circuit according to the amount of data transmitted, the communication system and SoC (System-on-a- The present invention relates to an orthogonal division multiplexing data transmission method and apparatus capable of reducing power consumption of a chip.

In the orthogonal division multiplexing data transmission method according to the present invention, the method includes: forming a plurality of packets suitable for a transmission mode selected from data input to a transmitter, determining a transmission rate of the data; And determining that each of the plurality of packets is divided into a plurality of subpackets, and transmitting the divided subpackets, thereby reducing a power supply time of a transmitter when the subpackets are transmitted. It is done.

High-speed Wireless, Orthogonal Frequency Division Multiplexing (OFDM), Ultra-Wide Band (UWB), Transceiver, Wireless Personal Area Network (WPAN)

Description

Method and apparatus for orthogonal frequency division multiplexing data transmission

1 is a block diagram showing a transmission and reception system used in a conventional orthogonal frequency division multiplexing (OFDM) scheme.

2 is a block diagram showing the structure of a transmission and reception system according to an embodiment of the present invention.

3 is a graph showing a comparison between the transmission rate and the average power consumption when using a transmission and reception system according to the present invention and a conventional transmission and reception system.

4 is a view showing the relationship between the data rate and power consumption over time of the transmission and reception system in order to conceptually describe a method of reducing power consumption of the transmission and reception system according to the present invention.

5 is a flowchart illustrating a data transmission method using an orthogonal multiplexing method according to an embodiment of the present invention.

<Description of Symbols for Main Parts of Drawings>

           200: OFDM transmitter 202: packet construction unit

           204: packet division unit 206: OFDM modulation unit

           208: analog / RF section 210: fine state control section

           212: OFDM receiver 214: RF / digital part

           216: OFDM demodulator 218: Packet combiner

The present invention relates to an orthogonal multiplexing data transmission method and apparatus for reducing power consumption.

Next generation ultra high-speed wireless communication systems are being developed with the goal of realizing high-speed data transmission of 1Gb / s or more in the near field. The most prominent short-range high-speed wireless network technology is the next-generation wireless local area network (WLAN), which is being studied under the IEEE 802.11n standard, and the high-speed wireless personal area network under development with the IEEE 802.15.3a standard: WPAN) technology. Here, the next-generation wireless LAN (WLAN) is a technology for guaranteeing the actual data throughput (actual throughput) of 100Mb / s or more in the Media Access Control (MAC) layer.

In addition, the next-generation wireless LAN, Orthogonal Frequency Division Multiplexing (OFDM) in the physical layer (Physical Layer) in order to maintain backward compatibility with the existing IEEE 802.11a / g standard WLAN The method is basically used. In the orthogonal frequency division multiplexing scheme, the spectrums of sub-channels overlap each other while maintaining mutual orthogonality, so that spectral efficiency is good.

On the other hand, the signal transmission physical layer for the high-speed wireless personal area network (WPAN) is an ultra-wideband orthogonal frequency division multiplexing method with a baseband signal bandwidth of 528 MHz, and a spreading code multiplied by the DSSS (Direct-Sequence Spread Spectrum) As a method, the DS-UWB (Direct Sequence-Ultra WideBand) method, which converts a signal bandwidth into an ultra-wideband signal of 3 GHz or more and transmits it, has become a leading international standard technology. For a detailed description of each of the above methods, refer to the data of the IEEE 802.15.3a standardization working group.

1 is a block diagram illustrating a transmission and reception system according to a conventional orthogonal frequency division multiplexing (OFDM) scheme. Referring to FIG. 1, the OFDM transmitter 100 includes an OFDM modulator 100a for forming and OFDM modulating a packet from a payload data signal input through an upper application layer and a MAC layer, and digital-analog. After conversion to an analog signal through modulation is made of an analog / RF unit (100b) for transmitting an electromagnetic signal through the RF terminal and the antenna. In detail, the OFDM modulator 100a may include a scrambler 102 for converting input data, an encoder 104 for encoding the input data, and an error between adjacent bits. An interleaver 106, a mapper 108 for converting bitstream data into complex data on an IQ constellation, and a pilot inserter for adding a pilot signal necessary for channel estimation of an OFDM receiver. Pilot Insert (110), an Inverse Fast Fourier Transform (IFFT) unit 112 for transforming a frequency domain signal into a time domain signal by Fourier transform, an appropriate guard interval (GI) for coping with multipath fading, and It includes a guard interval and a cyclic guard interval inserting unit 114 for adding a cyclic protection interval (CP) signal.

Meanwhile, the analog / RF unit 100b includes a wave shaping unit 116 that combines the preamble signal and the OFDM symbol signal and selectively performs a filter function to reduce the spurious signal, and converts the digital data into an analog signal. Digital-to-analog converter (DAC) 118, the baseband analog (BBA) unit 120 to perform the filtering and amplification function for the analog signal, up-converting mixer array unit for converting the signal into an RF signal (RF Up-conversion Mixer Array) 122, an amplifier 124, an antenna 126, and a frequency synthesizer 128 for generating a frequency signal.

The OFDM receiver 130 includes an RF / digital unit 130a for amplifying and converting an electromagnetic wave signal received through an antenna into digital data, and an OFDM demodulator 130b for restoring data through OFDM demodulation. Specifically, the RF / digital unit 130a includes an amplifier 134 for amplifying a signal received from the antenna 132 and a down-converting mixer arrangement for converting an output signal of the amplifier into a baseband signal. Mixer Array (136), low pass filter 138 for performing a low pass filter function for the baseband analog signal, an analog / digital converter (ADC) 140 for converting an analog signal into a digital signal, the gain of the receiving end An automatic gain control unit (AGC) 142 for adjusting the digital signal processing to be suitable for digital signal processing, and a synchronous unit 144 for performing signal processing such as frame synchronization and symbol synchronization.

Meanwhile, the OFDM demodulator 130b performs Fourier transform on a guard interval and a cyclic guard interval remover 146 for removing a guard interval (GI) and a cyclic guard interval (CP) signal, and a time domain signal. Fast Fourier Transform (FFT) unit 148 converts a frequency domain signal into a frequency domain signal, and inserts it into an amplification or transmission path to correct distortion occurring during amplification or transmission of a signal, and has a function of synthesizing and uniformizing the characteristics thereof. A carrier phase and time tracking unit 152 connected to the equalizer 150, the FFT unit 148, and the equalizer 150 to track the phase and time of a carrier, and converts complex data back into bitstream data. A demapper 154, a deinterleaver 156, a decoder 158 for decoding data, and a descrambler 160 for removing scrambles are included.

However, when a baseband modem chip for data transmission rate 1Gb / s ultra-high speed wireless communication is implemented by using a transceiver used in the conventional orthogonal frequency division multiplexing (OFDM) method, the clock speed and the digital / The sampling clock speed of the analog converter 118, the analog / digital converter 140, and the bandwidth of the RF amplifiers 124 and 134 increase, resulting in a problem of increased power consumption.

Therefore, if there is no special consideration on power consumption, if the 1Mb / s-class low-speed transmission using the modem chip manufactured for 1Gb / s-class high-speed transmission consumes excessively more power than the data rate. It becomes inefficient. For example, when transmitting an audio signal using a chip manufactured in a wideband OFDM scheme suitable for 1Gb / s transmission, it consumes higher power than a chip optimized for low speed such as Bluetooth. In other words, in the conventional wireless communication system having a data rate of 100 Mb / s or less, the problem of managing power consumption according to the transmission rate, which is not seriously raised, becomes more important as the maximum data rate rises to 1Gb / s or more and power consumption increases. do.

At present, a technique for reducing power consumption includes a method of using a standby mode and a sleep mode to stop a chip operation and reduce power supply in an idle state in which no data is transmitted; A clock gating method (USP 6,609,209) that lowers or cuts off the clock speed supplied to the processor chip.

However, the technique using the electronic sleep mode has a problem in that it takes a considerable time to transition the entire transmission system from the active state to the dormant or standby state, or the reverse process.

It is also applicable to synchronous connection (SCO) or streaming applications where the required transmission rate is low, but the system must remain active during talk time or audio listening time, such as voice / audio signals. There is a problem that is difficult to do.

On the other hand, the clock gating technique is suitable for a computer or a digital processor, but there is a problem that it is not sufficient to apply to a wireless transmission system including a plurality of analog and RF circuits that operate independently of the clock signal.

In addition, unlike computer, clock and timing information is very important and communication system is designed by selecting clocks optimized for communication standard at the stage of chip development. Changes to the specification are required. Accordingly, there is a need for a broadband low power technology capable of efficiently transmitting low-speed streaming data in a broadband transmission system capable of 1Gb / s ultra high speed wireless communication.

Accordingly, an object of the present invention is to enable high-speed 1Gb / s transmission at short distances, while reducing the operation time in low data rate applications such as voice / audio transmission. The present invention provides an orthogonal multiplexing data transmission method and apparatus that can reduce power consumption of a communication system and a system-on-a-chip (SoC) by adjusting the operation time of the system.

According to an aspect of the present invention, an orthogonal division multiplexing data transmission method is provided. The method may include forming a plurality of packets suitable for a transmission mode selected from data input to a transmitter, determining a transmission rate of the data, and when the determination result is a low transmission rate, the plurality of packets. And dividing each into a plurality of subpackets, and transmitting the divided subpackets, and reducing a power supply time of a transmitter when the subpackets are transmitted. If it is determined that the transmission rate is high, the packet is transmitted without division. The low transmission rate is characterized in that the transmission rate is less than 10Mb / s. The transmitting of the divided subpackets may include reducing a power supply time of the transmitter from a transmission end point of each divided subpacket to a transmission start point of a next subpacket.

According to another feature of the present invention, an orthogonal multiplexing data transmission apparatus is provided. The transmitting device includes: packet constructing means for forming and storing a plurality of packets suitable for a transmission mode selected from payload data generated in an upper application layer and a MAC layer; Packet dividing means for dividing each of the plurality of packets into a plurality of subpackets when the transmission rate of the stored packet is determined to be a low transmission rate; Modulation means for quadrature frequency division modulation of the packet or subpacket; Analog / RF means for converting and modulating the modulated signal into an analog signal; And fine state control means for reducing the power supply time of the modulation means and the analog / RF means during transmission of the subpacket.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the following detailed description is provided for illustrative purposes only and should not be construed as limiting the inventive concept to any particular physical configuration.

2 is a block diagram showing the structure of a transmission and reception system according to an embodiment of the present invention. Referring to FIG. 2, the transmitter 200 of the transmission / reception system includes a packet constitution unit 202, a packet division unit 204, an OFDM modulator 206, an analog / RF unit 208, and a fine state control unit 210. ).

The packet constitution unit 202 is a part of a physical layer service access point (PHY-SAP) connecting a physical layer and a higher layer, and in one embodiment, a media access control (MAC), which is a higher layer. Header, Header Check Sequence (HCS), Tail Bits, Error Check Units (FCS), and Pad Bits according to control parameters It adds back and forth to form a packet and stores it. In another embodiment, the packet constructing unit 202 may also perform a function of collecting a plurality of payload data to form a packet of a larger size.

The packet dividing unit 204 determines the transmission rate of the packet to be transmitted, and divides the packet formed by the packet constitution unit 202 into sub-packets of shorter length when it is determined that the transmission rate is low. Perform. In one embodiment, the criterion for determining the low transmission rate is when the transmission rate is less than 10 Mb / s.

Next, the OFDM modulator 206 performs OFDM modulation on the payload data of the packet. Specifically, the OFDM modulator 206 functions as a scrambler, a convolutional coding or a turbo coding, a low density parity check (LDPC) coding for converting a payload data portion of a packet. Forward Error Correction (FEC) Encoder to perform the error, an interleaver to reduce errors between adjacent bits, and convert the bitstream data into complex data on the IQ constellation. Quadrature Amplitude Modulation (N-QAM) mapper, Pilot Insertion for adding pilot signals necessary for channel estimation of OFDM receivers, and Inverse Fast Fourier (IFFT) for converting frequency-domain signals into time-domain signals by Fourier transform Transform unit, protection zone and cyclic protection to add appropriate guard interval (GI) and cyclic prefix (CP) signals to cope with multipath fading A preamble generator, a preamble generator, and a preamble signal and an OFDM symbol signal for generating signals necessary for core signal processing such as an interval inserter, frame synchronization of a receiver, symbol synchronization, channel estimation, and offset compensation. Wave shaping is included to selectively filter to combine and reduce the spurious signal.

The analog / RF unit 208 converts an analog signal through digital-analog modulation and transmits an electromagnetic signal through an RF terminal and an antenna. Specifically, the analog / RF unit 208 includes a digital / analog converter (DAC) for converting digital data into an analog signal, and a baseband analog (BBA) unit for filtering and amplifying a baseband analog signal. RF up-conversion mixer array for converting baseband signals to RF signals, high frequency wideband amplifier, wideband antenna, and multi-frequency synthesizer for generating multi-tone frequency signals over wideband -Frequency Synthesizer).

On the other hand, the present invention aims to fabricate a semiconductor chip in which all of the major components of the analog / RF unit 208 except for the broadband antenna among the main components are integrated in the form of a single chip. That is, each element is composed of a low voltage complementary metal oxide semiconductor (CMOS) or SiGe device, which is suitable for integration into a single chip using a highly integrated semiconductor technology.

The micro state controller 210 controls the active states of the components of the OFDM modulator 206 and the analog / RF unit 208 according to the data rate, and particularly when the data rate is low, It serves to reduce.

The OFDM receiver 212 includes an RF / digital unit 214 for amplifying and converting an electromagnetic wave signal received through an antenna into digital data, and an OFDM demodulator 216 and a packet for restoring a data packet through OFDM demodulation. Combination unit 218 is included.

The RF / digital unit 214 and the OFDM demodulator 216 are blocks corresponding to the RF / digital unit 130a and the OFDM demodulator 130b of the conventional system shown in FIG. 1, and their functions and details configuring the same. Since the elements are also known elements as shown in Fig. 1, detailed description thereof will be omitted.

When the data packet recovered by the OFDM demodulator 216 is a subpacket, the packet combiner 218 combines them to form a packet suitable for the selected transmission mode and outputs the packet.

3 is a graph showing a comparison between the transmission rate and the average power consumption when using a transmission and reception system according to the present invention and a conventional transmission and reception system.

3 (a) is a graph showing the relationship between the transmission rate and the average power consumption when the transmission and reception system according to the present invention is used, and the transmission and reception system shows that the transmission rate and the average power consumption maintain a directly proportional relationship. That is, when the transmission rate is small, the average power consumption is also consumed less. When the transmission rate is large, the average power consumption is also increased proportionally.

On the other hand, referring to the graph showing the relationship between the transmission rate and the average power consumption when using the conventional transmission and reception system shown in Figure 3 (b), it can be seen that almost constant power consumption regardless of the transmission rate. .

That is, in the conventional OFDM-based wideband transmission / reception system as shown in FIG. 1, the digital / analog converter (DAC) 118, the analog / digital converter (ADC) 140, and the RF amplification unit, which consume the most power, are used. 124, 134, the operation of the IFFT unit 112, FFT unit 148 is almost constant regardless of the data rate, so even if the rate is low, the power consumption reduction effect of the entire system is not significant.

Therefore, the present invention enables high-speed 1Gb / s transmission at short distances, while reducing the operation time in applications with low data rates such as voice / audio transmission. By adjusting the time, the power consumption of the communication system and SoC chip can be reduced.

In addition, the present invention enables low power consumption even in a high-speed wireless personal area network (WPAN) having a 1Gb / s payload data transmission performance and a low transmission rate streaming mode.

4 is a view illustrating a relationship between data rate and power consumption according to time of the transmission / reception system in order to conceptually describe a method of reducing power consumption during data transmission according to the present invention. FIG. A graph showing power consumption when transmitting data to a transceiver is a graph showing Bluetooth as an example, and FIG. 4 (b) is a graph showing power consumption when transmitting data to a broadband transceiver according to the present invention.

Referring to Figure 4 (a), the Bluetooth data transmission rate is up to 1Mb / s, but the transmission rate is very low compared to the communication system or IEEE 802.11a / b / g wireless LAN according to the present invention, such as voice calls It is a kind of communication protocol standard designed for low speed and low power communication. In general, the transmission rate required for a voice call is considerably lower than 64kb / s, but the two communication devices, the master device and the slave device, are always active during the call. state (Synchronous Connection-Oriented) link.

For example, in the related art, during the time t1 when the first low power slave device DEV1LP transmits a synchronous connection (SCO) packet signal in a time division duplex (TDD) scheme, the entire transmitting end of the first low power slave device is always present. It consumes low power within about 20mW while remaining active. If the conventional method used in the conventional Bluetooth is applied to a high-speed broadband OFDM transmission and reception system, the basic power consumed by the broadband OFDM transmission and reception system is several hundred mW or more, so it is inefficient to keep active for the packet transmission time t1. to be.

In the conventional broadband OFDM transmission scheme for high-speed wireless personal area network (IEEE 802.15.3a), although the packet for supporting the streaming mode is defined, the length of a PLCP preamble including a packet synchronization sequence, a frame synchronization, and a channel estimation sequence Reaches 5.625 us, and the packet overhead due to the preamble is high.

In general, the time occupied by payload data in one packet is estimated by Equation 1 below.

       T_data = T_sym * R_data / (N_DBPS * R_packet)

      In Equation 1, T_sym denotes an interval of one OFDM symbol, R_data denotes a required data rate, N_DBPS denotes a number of data bits per OFDM symbol, and R_packet denotes a number of packets transmitted per second (packet rate).

In general, if the packet size is larger than a certain size, the packet error rate (PER) increases, which causes a significant performance degradation due to retransmission. Therefore, in the conventional high-speed wireless personal area network technology based on the OFDM method, one packet payload is used. The data size is limited to a maximum of 4095 bytes. Therefore, the packet transmission rate considering the payload size and the coding rate is estimated as shown in Equation 2 below.

       R_packet = R_data / (N_payload * R_coding)

      In Equation 2, N_payload denotes the number of payload bits in the packet, and R_coding denotes a forward error correction coding rate. For example, to transmit 1Mb / s-class streaming data in QPSK modulated 55Mb / s mode based on the conventional high speed wireless personal area network standard,

      T_data = 312.5ns / symbol * 1Mb / s / (17bit / symbol * 100 packet / s)

             = 184 us / packet

It consumes power while remaining active for a period of time.

The packet preamble, PHY header, MAC header, header check sequence (HCS), tail bits (Tail Bits), error check unit (FCS), pad bits (Pad Bits), etc. It should be active for about 190us per hour. (See IEEE 802.15.3a documentation)

Meanwhile, referring to FIG. 4 (b), the broadband transceiver according to the present invention transmits data using a 16-QAM modulated 1Gb / s-class high speed communication mode. In this case, when Equation 2 is applied,

       T_data = 312.5ns / symbol * 1Mb / s / (300bit / symbol * 100 packet / s)

              = 10.4 us / packet

It is only necessary to maintain the operation state for a very short time (tH1), so even if 16-QAM OFDM consumes about twice as much power due to the operating state of the transmitter as compared to QPSK, the average time during packet transmission Power consumption can be reduced by 184us / (10.4us * 2) = 8.8 times. That is, according to the present invention, it is possible to achieve the effect of dramatically reducing the power consumption by reducing the time of the operating state.

5 is a flowchart illustrating a data transmission method using an orthogonal division multiplexing method according to an embodiment of the present invention. Referring to FIG. 5, first, a device (DEV) including a wideband OFDM transmission / reception chip starts operation, and an initial connection between a pico-net coordinator (PNC) and a device (DEV) is performed. WPAN) and WLAN.

After the initial connection is made, packets suitable for the OFDM scheme are formed from the streaming data to be transmitted (S500). In one embodiment, the packets are formed to conform to the 1 Gb / s mode of the 16QAM OFDM scheme. Next, it is determined whether the required data rate of the streaming data to be transmitted is less than 10Mb / s (S502). As a result of the determination, when the required data rate of the streaming data to be transmitted is low as less than 10Mb / s, and the transmission distance is short, the payload data portion of the packet may be reconstructed into a plurality of smaller parts to reduce overhead such as a preamble. The packet is divided into sub-packets (S504). In one embodiment, the short transmission distance is typically less than 3m.

Next, the subpacket is transmitted while reducing the power supply of the baseband modulator and the analog / RF unit from the end of transmission of each divided subpacket to the start of transmission of the next subpacket (S506).

Next, in step 508, it is determined whether all one transmission frame is finished, and when the transmission packet frame is over, switch to the reception mode (S516), and if the transmission frame is not over, enter step 506, and enter the The subpacket transmission is repeated until the frame transmission is completed.

On the other hand, as a result of the determination in step 502, if the required data rate of the streaming data to be transmitted is 10Mb / s or more, similarly to the conventional method, the packet is activated by activating the OFDM transmitter and the RF transmitter of the physical layer.

That is, the 1Qb / s mode packet of the 16QAM OFDM scheme, which is not divided, is transmitted (S510), and it is determined whether all of one transmission frame is finished (S512). If it is not finished (S514), it repeats until all the one frame transmission is finished, and then switches to the reception mode (S516).

By this operation, the transmission / reception system according to the present invention has a number of data bits per OFDM symbol of 300 bits or more, and the OFDM sampling frequency is higher than 500 MHz, thereby enabling high-speed 1Gb / s-class wireless transmission. In addition, in applications with low data rates such as voice and audio transmission, the operation time of each part of the circuit may be adjusted according to the amount of data transmitted, such as reducing the operation time, thereby reducing power consumption of the communication system and the SoC chip.

The present invention has been described above with reference to the preferred embodiments, which are merely examples and are not intended to limit the present invention, and those skilled in the art to which the present invention pertains do not depart from the essential characteristics of the present invention. It will be appreciated that various modifications and applications are not possible that are not illustrated above.

For example, each component specifically shown in the embodiment of the present invention can be modified. And differences relating to such modifications and applications will have to be construed as being included in the scope of the invention defined in the appended claims.

The present invention enables a 1Gb / s high-speed transmission in a short distance wirelessly, while reducing the operation time in a low data rate application such as voice / audio transmission. By adjusting, power consumption of the communication system and system-on-a-chip (SoC) can be reduced. In addition, the present invention enables low power consumption even in a high-speed wireless personal area network (WPAN) having a 1Gb / s payload data transmission performance and a low transmission rate streaming mode.

Claims (9)

Forming a plurality of packets suitable for a transmission mode selected from data input to the transmitter; Determining a transmission rate of the data; Dividing each of the plurality of packets into a plurality of subpackets when it is determined that the transmission rate is low; And transmitting the divided subpackets, and reducing a power supply time of the transmitter during transmission of the subpackets. The method of claim 1, And if it is determined that the transmission rate is high, transmitting the packet without segmentation. The method of claim 1, The low data rate data transmission method of orthogonal multiplexing, characterized in that the transmission rate is less than 10Mb / s. The method of claim 1, The packet is a quadrature multiplexed data transmission method, characterized in that the packet is formed suitable for the 1Gb / s transmission mode of 16QAM OFDM. The method of claim 1, The transmitting of the divided subpackets is characterized in that the power supply time of the transmitter is reduced from the end of transmission of each divided subpacket to the start of transmission of the next subpacket. Packet constructing means for forming and storing a plurality of packets suitable for a selected transmission mode from payload data generated in an upper application layer and a MAC layer; Packet dividing means for dividing each of the plurality of packets into a plurality of subpackets when the transmission rate of the stored packet is determined to be a low transmission rate; Modulation means for quadrature frequency division modulation of the packet or subpacket; Analog / RF means for converting and modulating the modulated signal into an analog signal; And Fine state control means for reducing the power supply time of the modulation means and the analog / RF means during transmission of the subpacket Orthogonal frequency division scheme data transmission apparatus comprising a. The method of claim 6, The micro-state control means reduces the power supply time of the orthogonal frequency division modulation means and the analog / RF means from the transmission end point of each divided subpacket to the transmission start point of the next subpacket. Type data transmission device. The method of claim 6, And a packet formed by the packet constituting means is transmitted without segmentation when it is determined that the packet segmentation means has a high transmission rate. The method of claim 6, And the packet dividing means adds a preamble to the divided subpackets to generate subpackets having a predetermined interval.

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