JP5376581B2 - IR-UWB transceiver - Google Patents

Description

  The present invention relates to an IR-UWB transmission / reception apparatus (transmission apparatus and reception apparatus) applied to an IR-UWB communication system that transmits and receives radio waves using IR-UWB (Ultra Wide Band) communication technology.

  In IR-UWB communication, a pulse signal having a very short time width of about 1 nanosecond is used, and information is transmitted without using a carrier wave by changing the position or phase on the time axis of the pulse signal. Since a pulse signal with a very short time width is used, the signal band occupied by the signal for IR-UWB communication is very wide as several GHz, but the modulation processing using the carrier wave itself becomes unnecessary, and the spectral power density is reduced. Can be reduced. For this reason, since it can be suppressed to a signal level of noise or less, it is not affected by other communication systems and various devices, and high data transmission characteristics are realized.

  In addition, in this IR-UWB communication, unlike a communication method using a carrier wave that transmits radio waves, it is possible to realize communication by transmitting very short pulses. It can be reduced, and it is possible to realize very high-speed communication by shortening the pulse signal transmission interval.

  Conventionally, as this IR-UWB communication system, for example, the technology disclosed in Patent Document 1 has been proposed.

JP 2007-300634 A

  By the way, an attempt to apply such an IR-UWB communication system to, for example, a body area network (BAN) has been recently made. In this BAN, an ultra-small wireless terminal is implanted into the human body or attached to the human body. Then, a receiving device is installed outside the human body. In such a case, the wireless terminal images the inside of the human body or senses various information in the body and transmits the acquired data to a receiving device outside the body. The receiving device receives such data and analyzes it to detect a human body abnormality.

  By the way, the power consumption of this wireless terminal requires at least the power required to operate a CPU (Central Processing Unit). Capacity etc. are mainly decided. However, when viewing via this wireless terminal, the battery of the device is consumed quickly. In particular, a device once embedded or mounted in the body is uneconomical and less practical if the battery is frequently replaced. For this reason, when the IR-UWB communication system is applied to the BAN, it is necessary to configure the wireless terminal to have a particularly low power consumption and a long battery period at the expense of some performance. In addition to this, when the IR-UWB communication system is applied to the BAN, there is a need for a system that transmits a signal with a low operation cycle.

  In addition to this, when applied to BAN, it is necessary to be configured to be non-interfering on the receiving device side with signals of other systems.

  However, in the conventional IR-UWB communication system, either improvement in feasibility or reduction in power consumption can be easily solved, but both cannot be realized simultaneously.

  Therefore, the present invention has been devised in view of the above-described problems, and its object is to achieve low power consumption and a long battery period required when applying an IR-UWB communication system to a BAN. Another object of the present invention is to provide an IR-UWB pulse signal generator capable of realizing an IR-UWB communication system that realizes a low operation period and is non-interfering on the receiving side.

  In order to solve the above-described problems, when the IR-UWB system is configured with complete digital specifications, it is possible to obtain high performance such as flexibility of the entire system and reduction of noise. However, when configured with such a digital specification, many technical problems required with a high sampling rate occur, and this has become a major barrier that must be overcome in order to actually realize the product.

  For this reason, in order to realize both performance as a device and low power consumption at the same time, the inventor described above by configuring both the IR-UWB pulse signal generator and the receiving device with an analog front end. We decided to solve the problem.

Ultra-low-power IR-UWB transceiver apparatus according to one aspect of the present invention (transmitter and a receiver) may generate the IR-UWB pulse train, ultra-low-power IR-UWB transceiver equipment for use in IR-UWB communication the Oite, and modulating means for modulating the input data bits to generate a sine wave signal, the oscillation signal generating means for oscillating according to the center frequency given by a look-up table, the trigger output signal from said modulating means And a superimposing unit that superimposes the triangular waveform generated based on the ring. The synthesized pulse waveform (oscillation output and triangular waveform) has a bandwidth of 500 MHz, and the center frequency varies within 14 subbands. The frequency hopping in the 14 subbands is performed by the constituent words of the MDS codeword in which different codewords are assigned to different devices , and the signal waveform x (t) is defined by the following equation (1):
Here, w (t): the basic pulse, T _s: the pulse repetition period, T: symbol time, a _n: the transmitted symbols in the n-th, l: device number assigned to the pulse signal generator, k: sub Is the band number, and f ^l _k in the equation (1) is derived from the following equation (2):
Here, f ₁ : first subband center frequency, BW: subband band, and MDS [l] [k] are codes or subband numbers read from the table. Examples of MDS codewords with q = 16 and q = 8 are shown in Tables 1 and 2. Note that frequency hopping is performed after transmitting a set of symbols.

  According to the present invention having the above-described configuration, it is possible to achieve non-interference on the receiving side while realizing low power consumption, a long battery period, and a low operation cycle required when the IR-UWB communication system is applied to BAN. IR-UWB communication system can be obtained.

It is a figure for demonstrating the whole structure of IR-UWB system to which this invention is applied. It is a block block diagram of a transmitter. It is another block block diagram of a transmitter. It is a block block diagram of a receiver. It is another block block diagram of a receiver. It is a figure which shows the example which simplified the structure of FIG.

  Hereinafter, an IR-UWB communication system that transmits and receives radio waves using an IR-UWB (Ultra Wide Band) communication technique will be described in detail with reference to the drawings.

  The IR-UWB communication system 1 to which the present invention is applied receives, for example, a plurality of transmission apparatuses 2 and a pulse train as radio waves transmitted from the transmission apparatus 2 as shown in FIG. And a receiving device 3 that obtains.

  In this IR-UWB communication system 1, as a body area network (BAN) in which the transmitter 2 is embedded (implanted) in, for example, the human body, or mounted on the human body, and the receiver 3 is disposed outside or on the human body. It may be configured. In such a case, the transmission device 2 images the inside of the human body or senses various information in the body, and transmits the acquired data to the reception device 3 outside the body. The receiving device 3 receives such data and analyzes it to detect abnormalities in the human body. The IR-UWB communication system 1 to which the present invention is applied is not limited to being applied to BAN, and may be used for any purpose.

  Further, both the transmission device 2 and the reception device 3 are configured by an analog front end.

  FIG. 2 shows a configuration example of the transmission device 2. The transmission apparatus 2 is sequentially connected from a PPM / DBPSK / OOK modulator 11, an IR-UWB pulse signal generator 12 connected to the PPM / DBPSK / OOK modulator 11, and an IR-UWB pulse signal generator 12. The band pass filter (BPF) 13, the power amplifier (PA) 14, the antenna 15, and the control unit 16 connected thereto are provided. The IR-UWB pulse signal generator 12 is further connected to an oscillator 21 and a waveform generator 23 to which an output signal from the PPM / DBPSK / OOK modulator 11 is supplied, and to the oscillator 21 and the waveform generator 23, and further to an output terminal. Is provided with a superimposing unit 22 connected to the BPF 13.

PPM / DBPSK / OOK modulator 11, the input data bits _{b n,} pulse position modulation (PPM: Pulse Position Modulation) or a differential phase modulation (DBPSK: Differential Phase Shift Keying) or, OOK (On-Off Keying ) Apply modulation. The modulation by the PPM / DBPS / OOKK modulator 11 is controlled by the control unit 16. The output signal output from the PPM / DBPSK / OOK modulator 11 is supplied to the oscillator 21 and the waveform generator 23.

The oscillator 21 is triggered by an output signal from the PPM / DBPSK / OOK modulator 11. The oscillator 21 is further supplied with a frequency signal f ^l _k from the control unit 16. When the output signal from the PPM / DBPSK / OOK modulator 11 is activated according to the center frequency f ¹ _k sent from the control unit 16, the oscillator 21 oscillates. This oscillation output is sent to the superposition unit 22 (mixer).

Waveform generator 23 produces a triangular waveform period T _p fed from the control unit 16. When generating this triangular waveform, it is based on triggering by an output signal output from the PPM / DBPSK / OOK modulator 11.

  The superimposition unit 22 receives a triangular waveform from the waveform generation unit 23. The superimposing unit 22 receives the oscillation output. The superimposing unit 22 generates an IR-UWB pulse train by superimposing a triangular waveform on the oscillation output.

  The BPF 13 filters each frequency component from the IR-UWB pulse train generated by the superposition unit 22. The PA 14 amplifies the signal filtered by the BPF 13. Further, the antenna 15 transmits the signal amplified in the PA 14 as a radio signal.

  With the above-described configuration, the transmission device 2 can transmit data using a so-called analog front end.

  FIG. 3 shows another configuration example of the transmission device 2. In FIG. 3, the same components and members as those in FIG. 2 described above are denoted by the same reference numerals, and the following description is omitted.

  In the configuration of FIG. 3, a CC (Convolutional code) unit 24, an interleaver 25, a symbol mapper formed by combining an accumulator and a PPM / DBPSK / OOK modulator, and an error correction unit 26 are further added as options. ing.

CC 24, the data input bit b _n, applies the convolution coding. The interleaver 25 performs random interleaving processing, and the symbol mapper unit 26 performs bit interleave coding modulation.

  FIG. 4 shows a configuration example of the receiving device 3. The receiving device 3 includes an antenna 31 for receiving a pulse signal based on IR-UWB communication from the transmitting device 2, a low noise amplifier (LNA) 32 connected to the antenna 31 for performing low noise amplification, and an LNA 32. The two BPFs 33a and 33b are connected to each other. The BPFs 33a and 33b are respectively mixed with mixer circuits 34a and 34b, mixer circuits 35a and 35b, integration circuits 36a and 36b, and a VGA (Variable Gain Amplifier) 37a. 37b and analog-digital converters (ADC) 38a, 38b are sequentially connected. Further, a local oscillator 41 is connected to the mixer circuits 34a and 34b, and a window control unit 43 is connected to the mixer circuits 35a and 35b. Further, a control unit 39 is connected to the local oscillator 41, the ADCs 38 a and 38 b, and the window control unit 43.

  The antenna 31 receives a pulse train as a radio wave transmitted from the transmission device 2, and converts this radio wave pulse train into a pulse train composed of an electrical signal.

  The LNA 33 amplifies the pulse train received by the antenna 31 with low noise. Since the pulse signal based on the IR-UWB system is weak below the signal level of the noise, it is impossible to distinguish the noise from the IR-UWB signal even if it is amplified by a normal amplifier. For this reason, by mounting the LNA 33, it becomes possible to selectively amplify only a desired pulse signal based on the IR-UWB system. The pulse train amplified with low noise by the LNA 33 is sent to the two connected BPFs 33a and 33b, and signals outside the predetermined band are removed. That is, in the process in which radio waves are transmitted from the transmission device 2 to the reception device 3, other signals may be superimposed, so that these signals are accurately removed by the BPFs 33a and 33b and the pulse signal again.

  The local oscillator 41 generates an in-phase signal (I signal) and a quadrature signal (Q signal) as a baseband reference signal under the control of the control unit 39. The local oscillator 41 outputs the generated I signal to the mixer circuit 34a and outputs the generated Q signal to the mixer circuit 34b. Further, the local transmitter 41 transmits a clock signal to the control unit 39. In the mixer circuits 34a and 34b, the I signal and the Q signal of the local oscillator 41 are input in the same phase as the received signal and simultaneously shifted in phase by 90 °. In the mixer circuits 34a and 34b, the BPFs 33a and 33b superimpose the received signal on the output of the oscillator.

  The mixer circuits 35a and 35b play a role of superimposing the outputs of the mixer circuits 34a and 34b on a predetermined triangular waveform (similar to a transmission device) transmitted from the window control unit 43. Further, the integrating circuits 36a and 36b integrate the signals supplied from the mixer circuits 35a and 35b, and output the integrated signals to the VGAs 37a and 37b.

  The VGAs 37a and 37b perform so-called automatic gain control by amplifying the baseband signals output from the integrating circuits 36a and 36b, respectively. The ADCs 38 a and 38 b perform analog-to-digital conversion on the signals output from the VGAs 37 a and 37 b, and output these to the control unit 39.

  In the configuration described above, the BPF 33, the mixer circuits 34 and 35, and the integrating circuit 36 serve as an analog correlator. That is, the receiving device 3 can receive data with a so-called analog front end.

  FIG. 5 shows another configuration example of the receiving device 3. In FIG. 5, the same components and members as those in FIG. 4 described above are denoted by the same reference numerals, and the following description is omitted.

In the configuration of FIG. 5, the switch 51 can control the time T _int (integration time). Switches 51 and 53 form a sample and hold circuit. The symbol time T can be controlled by the switch 52, and then the value held in the hold unit 53 is passed to the comparator. The comparator 55 compares the supplied signals with each other and outputs different values depending on the comparison result. DC offset and channel distortion are automatically normalized or compensated. The PPM / OOK demodulator 56 outputs data bits after performing pulse position or on / off demodulation.

  In the configuration of FIG. 6, the configuration of FIG. 5 described above is further simplified. The mixer circuit 34, the mixer circuit 35, the local oscillator 41, the window control unit 43, and the control unit 39 in FIG. Is omitted.

Next, the operation of the IR-UWB communication system 1 to which the present invention is applied will be described. In the IR-UWB system to which the present invention is applied, the input data bit b _n is first modulated by the PPM / DBPSK / OOK modulator 11.

  Next, the control unit 16 generates an IR-UWB signal. For the generation of the IR-UWB signal, a lookup table as shown in Table 2 described later is referred to. This table is stored in a memory or the like (not shown), and the control unit 16 can freely access and read the memory (not shown).

  In the table, code numbers are arranged in a matrix. The code number described in the table can be displayed by MDS [l] [k], for example. Here, l means a device number assigned to each pulse signal generator 12. K represents the number of each subband. In Table 2, l is assigned to the vertical axis and k is assigned to the horizontal axis.

  Table 2 is created by the code word of the MDS code for the Galois field GF (q).

The oscillator 21 reads the center frequency subband number from the table for the given device number 1 and the kth element of the table. Frequency hopping (k = 0, 1,..., Q in MDS [l] [k]) is performed after a predetermined set of symbols is transmitted. If the device number is “2” and the time slot to which the IR-UWB symbol to be generated belongs is “7”, the code number or subband number described in MDS [2] [7] Read “14”. Then, based on the read code number “14”, the center frequency signal f ^l _k is generated.

Next, the oscillator 21 oscillates another signal using the frequency signal f ^l _k sent from the control unit 16 in response to the output signal from the PPM / DBPSK / OOK modulator 11.

Here, the waveform x (t) of the frequency-modulated signal may be defined by the following equation (1) (PPM or OOK).
(1)

Here, w (t): the basic pulse, _{T s:} the pulse repetition period, T: symbol time, n: the transmitted symbols in the _n-th, a n: either the PPM or OOK symbol.

The center frequency for transmitting the IR-UWB waveform f ^l _k in the equation (1) is derived from the following equation (2).
(2)

Here, f ₁ : first subband center frequency, for example, 3432 MHz, BW: subband band, for example, 528 MHz, and MDS [l] [k] are codes or subband numbers read from the table in Table 2. MDS is an abbreviation for Maximum Distance Separable codes.

  The signal x (t) generated in the IR-UWB pulse signal generator 12 is sent to the BPF 13.

  In the waveform generation unit 23, a triangular waveform triggered by the output of the PPM / DBPSK / OOK modulator 11 is generated and supplied to the superposition unit 22. The superimposing unit 22 outputs the IR-UWB signal x (t).

  Thus, the IR-UWB communication system 1 to which the present invention is applied is a system capable of transmitting data by an analog front end. For this reason, it is possible to configure the battery with a considerably low power consumption and a long battery period. Therefore, it is suitable particularly when applied to BAN. Further, according to the present invention, it is possible to provide a system that sends a signal with a low operation cycle.

Furthermore, according to the present invention, as described above, the frequency signal f ^l _k is generated, and based on this, the modulation shown in the equation (1) is performed. The frequency signal f ^l _k is varied according to the device number and a certain time slot. For this reason, this IR-UWB communication system can be configured to be non-interfering with signals of other systems between the receiving apparatuses 3 that have received such signals.

Transmitter 2
ON-OFF signal notification is a modulation method that represents the best compromise when considering information theory, energy efficiency, system design and low risk of temperature rise for BAN.

When u _k is the k-th symbol, the ON-OFF signal notification has an input distribution u _k represented by Expression (1.1).
u _k = {1 with probability ξ, 0 with probability 1-ξ} (1.1)

Therefore, when u _k = 0, no signal (mass point at the starting point) is transmitted.

When u _k = 1, a pulse having an amplitude of √1 / ξ is transmitted, and the average power is constant with respect to the transmission probability ξ. As an example, the present invention uses an M-sequence PPM in which ξ = 1 / M and one pulse is transmitted per symbol. Therefore, the transmitted signal is obtained by the following equation (1.2).

... (1.2)
Where M is the number of time slots in the symbol period T. The PPM symbol is given as a _i ∈ A = {0, 1,..., M−1}. The pulse waveform g (t) to be transmitted has a finite platform within [0, Tp].

Different health signals to be monitored are located in the analog domain. However, since the digital domain is much more tolerant of noise and interference, information transmission occurs in the digital domain. Such an analog signal provided from the sensor is converted to a digital signal by a low complexity ADC. Therefore, the bit group is mapped onto the M = 2 ^b PPM symbol. Since the decimal value corresponding to the bit group is a PPM symbol, this mapping rule is very simple. Therefore, the PPM symbol indicates the slot number in which the pulse waveform is transmitted. Thus, a low duty cycle, low power signal is generated for transmission.

  The transmitter consumes significantly less energy than the receiver, but in an IR-UWB system, the transmitted signal must satisfy the spectral mask given by the control body. Since BAN requires a moderate data transfer rate, it is not necessary to form a short pulse whose bandwidth covers the GHz band. Furthermore, since there is a problem of coexistence of other wireless systems operating in other IR-UWB systems and IR-UWB bands, in order to reduce interference with or from other systems, the operating band and transmission bandwidth should be reduced. Flexible changes are recommended.

  Since the maximum data transfer rate for each radio link is 10 Mbps, a minimum IR-UWB transmission bandwidth of 500 MHz is sufficient. Therefore, following the MB-OFDM frequency plan concept, a multi-band IR-UWB system having a bandwidth of 500 MHz has been proposed.

  This frequency band can be changed depending on the coexistence with other systems. On the other hand, it is clear that the synthesis of short pulse shapes with controllable bandwidth and center frequency is difficult to introduce in practice. Therefore, a gated oscillator is used as another practical method for generating short pulses. The reason is the flexibility and ease of introduction of IC technology. Of course, the oscillator is a common building block in the integrated circuit.

  In particular, the gate oscillator can be triggered so that its duty cycle and frequency are easily changed, and short pulses are generated whose bandwidth and center frequency are easily changed as well. The shape of the pulse waveform is not important per se. This is because, in order to have a simple and low power consumption receiver structure, energy detection in a specific time slot (ON-OFF signal notification) is considered in the receiver.

  Two methods have been proposed for triggering the gate oscillator. One way is to charge and discharge a capacitor (similar to a trigonometric function), and the other way is to program the oscillator to continue for half the sine period. The trigger function is obtained by the following equations (1.3a) and (1.3b).

・ ・ ・ ・ ・ ・ ・ (1.3a)
・ ・ ・ ・ ・ ・ ・ (1.3b)

  Here, Tp is a trigger function period. Such a trigger function is combined with a gate oscillator and acts as a baseband pulse that generates a short pulse whose bandwidth and center frequency can be easily changed. Furthermore, as described above, these functions can be achieved with current IC technology without a digital front end. Such a trigger function and a gate oscillator output can be obtained by the following equation (1.4).

・ ・ ・ ・ ・ ・ ・ (1.4)
Here, f _q (n) is the center frequency of the i-th subband obtained by the permutation function i = q (n) according to an arbitrary frequency plan. An unmodulated transmission signal is obtained by the following equation (1.5).

・ ・ ・ ・ ・ ・ ・ (1.5)
Here, Nb is the number of subbands in an arbitrary frequency plan, and T ≧ Tp. Both trigger functions have double sided bandwidth given by Bb = 4 / Tp. Therefore, as an example, if the IR-UWB subband bandwidth is set to 500 MHz, Tp = 8 nsec. Here, a plan of 14 subbands of W-Media Alliance is acquired as in the following equation.

... (1.6)

  As described above, the frequency sub-index i = q (n) is obtained by the frequency plan. Such a frequency plan may be provided by a time-frequency code. This therefore provides a better way to deal with frequency diversity, interference reduction and coexistence with other systems in the IR-UWB band.

The number of symbols in the signal design alphabet is M = 2b. Here, b is the number of bits of information for each symbol. In the present invention, two cases were tested. That is, there are two cases where M = 2 or b = 1 and M = 4 or b = 2. For data transfer rate, R _b = 1 Mbps is selected, which is sufficient for medical applications. The symbol time is obtained by the following equation (2.1).

・ ・ ・ ・ ・ ・ ・ (2.1)
The slot time is obtained by equation (2.2).
・ ・ ・ ・ ・ ・ ・ (2.2)

When the pulse width is T _p = 8 nsec, the system has a very low duty cycle.

  In order to relax the average power with respect to the pulse width Tp, such power is expanded with respect to the spreading sequence of the period Nc. Furthermore, it is possible to provide multipath diversity that improves the BER. The short spread sequence does not extend the symbol time, but has two problems of increasing the pulse width (a kind of PRF) within the slot time. Conventionally, the spreading sequence is a binary or ternary sequence, but since the receiver is suitable for detecting non-interference energy, neither spreading sequence can be used as autocorrelation or cross-correlation. Since the output of the non-interference energy detection stage is in an on state (a state in which a pulse exists) or an off state (a state in which no pulse exists), a special unipolar spreading sequence whose component is 0 or 1 is required. It becomes. Fortunately, these series have been studied with optical CDMA stem (OCDMA). In particular, the present invention uses codeword (7,3,1) or c = {1101000}. Therefore, the transmission period for each pulse is extended to 48 nsec.

The low power transceiver design modulation method directly affects the bandwidth efficiency R / B of the system and the minimum achievable energy per bit (E _b / N ₀ ) for a BER target value of 10 ⁻³ . In practical systems aimed at low energy consumption, the modulation methods used, such as BPSK, 2FSK, OOK, etc. are the most common modulation methods. These modulation methods represent a compromise between energy efficiency and design simplicity. Of course, from a system structure perspective, it may not be sufficient to select a low (E _b / N ₀ ) modulation method. That is, even if (E _b / N ₀ ) is low, the capacity of the entire system may still be insufficient. Of course, this is the case if the power required for the generation, modulation and demodulation of information signals is equal to or greater than the power required for transmission of such information signals.

  The key conditions for BAN applications are long battery life, small form factor and short reach.

  Therefore, it is particularly important to select a modulation method that requires less power for implementation and has sufficient overall system capability.

The ideal modulation method does not require a complex and high power circuit, maximizes the link margin and capacity for an arbitrary signal power, and minimizes the target BER E _b / N ₀ .

  Choosing incoherent modulation reduces link margins, but saves considerable energy because incoherent communication reduces circuit and structural complexity.

  On the other hand, in particular, in the BAN PHY solution, the energy required to transmit one bit of information represented by the following equation (3.1) must be minimized.

・ ・ ・ ・ ・ ・ ・ (3.1)
Therefore, minimizing the energy per bit for the transceiver means reducing the power consumption to generate and detect multiple bits of information and on / off times. At the system level, this means actively reducing the duty cycle of wireless operation.

  In other words, IR-UWB signal design and transceiver structure design for practical BAN applications achieve a reliable communication link with the lowest possible power (or bit-by-bit energy in equation (3.1)). To implement. Obviously the ability is sacrificed.

  Therefore, an IR-UWB transceiver with ON-OFF signal notification and non-interference detection is preferred in terms of energy efficiency and implementation. In particular, IR-UWB has its own low duty cycle and is more attractive due to transceiver energy savings.

  Furthermore, the non-interfering structure is applied to the transceiver, so the pulse shape is secondary. Of course, simple energy detection is only concerned with energy collection in pulse transmission. Therefore, the pulse generator need only generate a pulse waveform having as little power as possible regardless of the pulse waveform itself.

  In order to alleviate the peak power limit value with the control spectrum mask, a short spreading sequence is introduced in the present invention. That is, the power limit value between the pulse widths extends within the spreading sequence period. Furthermore, the detection capability is enhanced by multipath diversity.

  Average power consumption depends mainly on good power management and energy efficiency protocols, but the structure and circuit design of the transceiver determines the instantaneous power consumption.

  In particular, for the IR-UWB system, several system structures have been proposed. Early methods are based on analog systems. More recently, a structure based on a digital structure has been proposed in consideration of signal processing flexibility and noise recovery. The conventional wireless structure performs more operations in the digital domain and consumes less power. However, this is not always correct in an IR-UWB system. Of course, the high sampling rate required by the wireless front end generates high power consumption by the ADC / DAC and a pulse match filter of the receiver. Furthermore, the ADC / DAC of about 20 GHz necessary to cover the IR-UWB band cannot be achieved with the current technology.

  The state-of-the-art in IR-UWB radio architectures is to use a parallel structure (channelized ADC), down-conversion before ADC, and sub-sampling to determine the sampling rate in one or both ADC / DAC and match filter banks. It is considered whether to reduce it. The above adjustment is an attempt to reduce the sampling rate, but always remains in the digital domain. Furthermore, current solutions based on IEEE 802.15.4a and Wi-Media standards are quite complex and high power consumption for BAN requirements.

  Therefore, the proposal is aimed at achieving short-term compliance with low power consumption (long battery life) and small form factor (integration in small devices). This is achieved by the following steps.

  Short pulse generation and detection is performed in the analog domain. Since there is no need for high power consumption by the ADC / DAC, the implementation covers the entire IR-UWB band, and the disadvantages associated with the work can be compensated by a relatively short reach communication link. Since this detection is non-interfering energy detection and the pulse waveform is secondary, the pulse generator is achieved with as little power as possible.

Similar to the W-Media method, the IR-UWB band is divided into 14 subbands of 535.711 MHz each. In the present invention, it is proposed to use IR-UWB having a transmission bandwidth of 535.711 MHz. This is because the application in the medical field requires a low data transfer rate, and an IFFTFFT circuit is not necessary in addition to high power consumption. With a low duty cycle for low data rates, ON-OFF signal notification can be efficiently achieved with IR-UWB having a transmission bandwidth of 535.711 MHz. Since IR-UWB is a secondary service, it is necessary to coexist with the primary service in the IR-UWB band and in the vicinity of the IR-UWB band (spurious emission). Therefore, in addition to improving robustness against interference from primary services and other IR-UWB systems by introducing a time-frequency code for 14 subbands or one subband set, frequency A simple method that coexists as IR-UWB signal hopping in the domain is provided. These time-frequency codes are generated in advance and stored in the memory. These codes are based on the longest distance divisible code for Galois field GF (q) with the property that constituent words are repeated up to twice over the codeword. However, the constituent words of many code words are not repeated.
This assigns codewords to devices or piconets with different low interference probabilities.

Receiver (especially FIGS. 5 and 6)
This is a simplified non-interfering energy detection match filter. This filter collects the received energy over the integration period for each slot in the symbol time and stores it in the sample and hold circuit. After the symbol time has elapsed, such energy values are provided to the comparator for DC offset compensation and path distortion normalization as described above. Finally, the PPM demodulator selects one bit or multiple bits corresponding to the output of the comparator. Also, this method does not require an external RFPPL or ADC. Clearly, while providing performance degradation compared to non-interfering energy detection match filters, it provides the best compromise for power consumption in IR-UWB receivers for BAN.

  The radio link associated with QoS is divided into three cases. That is, in the case of a short-range communication link (apparatus close to the coordinator), an energy detection method can be used. Since the communication link is located farther away or the QoS is reduced, the receiver can internally switch to the non-interfering energy detection match filter mode. If QoS further decreases, any channel coded modulation method can be switched as well. The aim is to provide the best compromise between the functions and power consumption required to actually implement an IR-UWB for BAN fully integrated on a chip with long battery life.

Multiband Longest Distance Dividable (MDS) Code The time-frequency code for the multiband method is achieved by the longest distance divisible codeword (MDS) component. The MDS code is a linear code for GF (q), n is the code length, k indicates the number of information symbols, d is the minimum code distance, and GF (q) is a Galois field having q elements. Represents. (Note that q = _pm, _p is a prime number, and m is an integer.) If the code length is set to n = q, the MDS codeword includes n elements over GF (q). It is defined in a form in which a set (GF (q)) k having k elements extending over GF (q) is mapped onto a set (GF (q)) n. Therefore, a = [a ₀ , a ₁ ,..., A _k−1 ] is k information symbol (aj ∈ GF (q)), and the polynomial expression is obtained by the following equation (5.1).

... (5.1)
However, in the present invention, z is used so as not to be confused with x used in the polynomial expression of the elements of GF (q). qk different polynomials (codewords) can be generated.

Let (β ₀ , β ₁ ,..., β _q-1 ) be eight elements of GF (q) arranged in an arbitrary order. In this case, the most common arrangement in the calculation is (β ₀ = 0, β ₁ = 1, β = α, ..., β _j = α ^j-2 , ..., β _q-1 = α ^{q -2} = α ^-1 ). Here, α is a basic element of GF (q). However, for convenience of explanation, in the present invention, the original notation is continuously placed on paper. Therefore, the MDS codeword maps information symbols onto n elements (p (β ₀ ), p (β ₁ ),..., P (β _q-1 )) over GF (q). To be acquired. The element of GF (q) is obtained by the equation (5.2).

... (5.2)
Here, i = 0, 1,..., Q−1, and the rule is β ⁰ ₀ = 1. Accordingly, q ^k different n elements are generated by the following mapping.

... (5.3)
Note that a lookup table for different MDS codewords is obtained by assigning k-tuples aj εGF (q) and then mapping equation (5.3). Therefore, the i-th element of the l-th code word is obtained by the following equations (5.4) and (5.5).

... (5.4)
... (5.5)

  The advantage of this unique MDS code structure is that the number of components repeated along the codeword is limited to two. Therefore, the probability of interference is reduced by assigning codewords for each device for multiband frequency hopping (time-frequency code).

  In the present example, two MDS code structures are provided. That is, n = q = 16 and n = q = 8 evaluated for (a0, a1) or k = 2 in GF (16) and GF (8), respectively. Note that the MDS codeword is simply calculated using a binary representation of βi. Table 1 shows the first eight MDS codewords (8, 2). (For convenience of explanation, the symbol β is not shown.) A constituent element of a certain code word represents a frequency band in which one symbol or a plurality of symbols are transmitted. In this case, the hopping is limited to within 8 subbands.

  This is a kind of simple scenario when the lower IR-UWB subband is discarded due to coexistence with, for example, MB-OFDM, IEEE 802.15.4a, Wi-Max and FWS. Table 2 shows the first four MDS codewords (16,2). In this case, it is conceivable to hop in all 14 subbands.

  The multiband transmission signal is obtained by the following equations (5.6) and (5.7).

... (5.6)
・ ・ ・ ・ ・ ・ ・ (5.7)
Here, when the MDS code is (16, 2), f ₁ = 3432 MHz, BW = 528 MHz, and k = k Mod 14. Frequency band hopping can be performed after a set of transmitted symbols, but frequency band hopping occurs at every symbol time k = n.

DESCRIPTION OF SYMBOLS 1 Communication system 2 Transmitter 3 Receiver 11 PPM / DBPSK modulator 12 IR-UWB pulse signal generator 13 Band pass filter (BPF)
14 Power amplifier (PA)
15, 31 Antenna 16 Control unit 21 Oscillator 22 Superimposition unit 23 Waveform generation unit 32 Low noise amplifier (LNA)
33 BPF
34, 35 Mixer circuit 36 Integration circuit 37 VGA
38 AD converter (ADC)
39 Control Unit 41 Local Oscillator 43 Window Control Unit

Claims (4)

In an ultra-low power IR-UWB transmission / reception device (transmission device and reception device) that generates an IR-UWB pulse train and is used for IR-UWB communication,
Modulation means for modulating the input data bits;
An oscillation signal generating means for generating a sine wave signal and oscillating according to the center frequency given by the lookup table;
A triangular waveform generated based on the triggering of the output signal from the modulation means is superimposed, and a composite pulse waveform (oscillation output and triangle) having a bandwidth of 500 MHz and a center frequency changing within 14 subbands. Superimposing means for obtaining a waveform),
The frequency hopping within these 14 subbands is performed by the constituent words of the MDS codeword, where different codewords are assigned to different devices ,
The waveform x (t) of the signal is defined by the following equation (1):
Here, w (t): the basic pulse, T _s: the pulse repetition period, T: symbol time, a _n: the transmitted symbols in the n-th, l: device number assigned to the pulse signal generator, k: sub The number of the band,
F ^l _k in the equation (1) is derived from the following equation (2):
Here, f _{1 is} the first subband center frequency, BW is the subband band, and MDS [l] [k] is the code or subband number read from the table . A CC section that performs convolution coding of the input data bits;
An interleaver that performs a predetermined interleaving process;
The IR-UWB transmission / reception apparatus according to claim 1, further comprising a symbol mapper formed by combining an accumulator and a PPM / DBPSK / OOK modulator that performs bit interleave code modulation. 1 SL and placing the IR-UWB transceiver apparatus according to claim, a transmission device and a transmission means for transmitting the IR-UWB pulse train output from said superimposing means as a radio wave,
An IR-UWB communication system, comprising: a receiving device that receives an IR-UWB pulse train transmitted as a radio wave from the transmitting device and acquires information contained therein. Claim 1 Symbol placement of IR-UWB pulse train pulse signal receptor for receiving from IR-UWB transceiver - a a,
Demodulation means for demodulating the received IR-UWB pulse train;
A superimposing unit that superimposes a predetermined waveform transmitted from the window control unit of the signal demodulated by the demodulating unit;
Analog-digital conversion (ADC) means for ADC conversion of the output signal from the superimposing means;
An information acquisition means for acquiring information from the digital signal ADC-converted by the ADC conversion means.