JP2007074641A - Communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication system to improve a transfer efficiency of a USB packet in a communication. <P>SOLUTION: A radio USB master apparatus 18 and a radio USB slave apparatus 20 of a radio USB system 10 include a USB (Universal Serial Bus) 28, a USB-radio converting portion 30, a baseband portion 32 and a RF (Radio Frequency) portion 34 each. The USB converting portion 30 improves the transfer efficiency in a radio zone by including a transfer mode detection functioning portion 30a, a format conversion functioning portion 30b, a timing offset functioning portion 30c and a timing correction functioning portion 30d and improves the transfer efficiency of the USB packet. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a communication system. The communication system of the present invention particularly relates to communication by wireless USB (Universal Serial Bus).

  Conventional wireless communication systems include, for example, a TDD (Time Division Duplex) system and a CSMA (Carrier Sense Multiple Access) system. The former method uses the same frequency in a time-division manner and is widely used in mobile phones, PHS (Personal Handy Phone) and the like. The latter method is a method of sending data by looking at the communication status when communication is desired, and is used in a wireless local area network (LAN) or the like.

  Patent Document 1 describes a connection probability method, a communication method, a state change transmission method, a state change execution method, a wireless device, a wireless device, and a computer. Patent Document 1 employs a CSMA system based on a wireless LAN. In Patent Document 1, USB packet data is transferred as it is to wireless packet data. There are five in, out, setup, asynchronous in and asynchronous out transactions for USB transactions.

Japanese Patent No. 3045985

  When data transfer is performed using the CSMA method, that is, the current wireless LAN method as it is, as described in Patent Document 1, the following problems occur.

  It is required to add a synchronization signal for wireless communication to the head of the packet. This addition of information substantially reduces the amount of data to be transferred, resulting in a decrease in data transfer rate.

  In addition, when half-duplex communication is used, the communication speed is lowered because switching between wireless transmission and wireless reception is required. Such a communication speed substantially decreases even when the communication environment is bad. In this case, the decrease in communication speed is mainly caused by retransmission or by changing the transfer rate for communication.

  When installing a USB master device and a USB slave device between the host device and the device, connect the host personal computer (PC) and the USB master device (M) by wire, and connect the USB master device (M) and the USB slave device ( When wirelessly communicating (S) and connecting a USB slave device (S) and a device with priority, it is known that a predetermined time or more is required between the respective devices.

  For example, when sending data between PC and USB master device (M), SOF (Start Of Frame), waiting time, out transaction, waiting time, data sending, 2.7μsec, 1.33μsec, 2.7μsec, Requires 1.33 μsec and 45.3 μsec. USB device (M) sends 1.33 μsec to NAK (Non-ACKnowledge) to PC, USB master device (M) communicates with USB slave device (S) to DIFS (Distributed Inter-Frame Space) 9 μsec, It takes 16 μsec for the preamble and 144 μsec for the data. Next, the USB device (S) operates after a time of 120 μsec.

  The USB device (S) requires 2.7 μsec for ACK (ACKnowledge), 9 μsec for SIFS (Short Inter-Frame Space) for out-transaction to the device, 16 μsec for preamble, and 7 μsec for ACK. Next, the USB device (S) requires 1.33 μsec and 45.3 μsec for waiting time and data.

  The device takes 1.33 μsec to ACK the USB device (S). The USB device (S) uses 9 μsec for DIFS, 16 μsec for preamble, and 7 μsec for ACK for transmission of ACK_DATA, which is a response to data reception, to the USB device (M). Here, after a period of 120 μsec again, the operation starts. The USB device (M) outputs ACK, requiring 9 μsec for SIFS, 16 μsec for the preamble, and 7 μsec for ACK to the USB device (S).

  The host (PC) repeats the waiting time, out transaction, waiting time, and data at 1.33, 2.7, 1.33, and 45.3 μsec until an ACK is obtained from the USB device (M). After the ACK is received, the next processing starts after the time of 526.36 μsec or more has elapsed. Thus, it is required to construct an operation taking into account the time defined between the host and the device in advance.

  In addition, there is a case where a TDD system such as PHS is adopted and a USB packet is directly transferred to a PHS TDD wireless system. However, in this case, the synchronization signal is shortened, and the transmission time and the reception time are determined, so that it does not coincide with the USB transaction. As a result, the transfer rate in communication does not increase. Since the USB transaction is not fixed, it can be seen that it is not suitable for data transfer to a fixed transmission / reception such as TDD.

  An object of the present invention is to provide a communication system that can eliminate the drawbacks of the prior art and improve the transfer efficiency of USB packets in communication.

  In order to solve the above-described problems, the present invention provides a communication system that uses radio for a partial communication path between a host device on a host side and a device on a slave side. This system uses a time division multiplexing system for radio communication. It is characterized by using.

  According to the communication system of the present invention, it is possible to reduce the time used for the preamble and the synchronization time by using the time division multiplexing method for wireless communication, and the timing is fixed. A process for avoiding the collision becomes unnecessary, and the data transfer efficiency can be improved.

  Next, an embodiment of a communication system according to the present invention will be described in detail with reference to the accompanying drawings.

  In this embodiment, the communication system of the present invention is applied to the wireless USB system 10. The illustration and description of parts not directly related to the present invention are omitted. In the following description, the signal is indicated by the reference number of the connecting line in which it appears.

  As shown in FIG. 2, the wireless USB system 10 wirelessly communicates between the USB host 12 side and the USB slave 14 side. The USB host 12 side includes a host device 16 and a wireless USB master device 18. The USB slave 14 side includes a wireless USB slave device 20 and a device 22. The host device 16 functions as a USB host, like a personal computer, and has a function of controlling the connected lower device. The host device 16 is connected to the wireless USB master device 18. The wireless USB master device 18 is connected to the host device 16 via a wire 24 and communicates with the wireless USB slave device 20 via a wireless 26.

  As shown in FIG. 1, the wireless USB master device 18 and the wireless USB slave device 20 each include a USB 28, a USB-wireless conversion unit 30, a baseband unit 32, and an RF unit 34. The USB 28 has a function of connecting to the host device 16 or the device 22 and processing wired USB communication. When connecting to the host device 16, the USB 28 is connected to the host device 16 via the wire 24 as shown in FIG. 2. The USB 28 also exchanges USB data 36 with the USB-wireless conversion unit 30.

  The USB-wireless conversion unit 30 has functions of converting USB data 30 into wireless data using the TDD method, converting wireless data into USB data, wireless and baseband control, and USB 28 control functions. The USB-wireless conversion unit 30 transmits the wireless data 38 to the baseband unit 32 and receives the demodulated wireless data 38 from the baseband unit 32. The baseband unit 32 has a function of performing radio communication on the converted radio data 38 and a function of demodulating the modulated radio data 40.

  Further, constituent elements of the USB-wireless conversion unit 30 that are the features of the present invention will be described. The USB-wireless conversion unit 30 includes a transfer mode detection function unit 30a, a format conversion function unit 30b, a timing offset function unit 30c, and a timing correction function unit 30d. Each function may be configured by a circuit or may be realized by a program operation. The transfer mode detection function unit 30a has a function of detecting what mode the transfer mode of packets and data supplied to the USB-wireless conversion unit 30 is. As will be described later, the transfer mode includes out, in-transaction, asynchronous transfer mode, and the like. The format conversion function unit 30b has a function of converting into a USB / wireless slot format according to the supplied information. The relationship between the formats to be converted will be shown later. The timing offset function unit 30c has a function of offsetting the timing according to the transfer mode at the basic timing and shifting the timing to realize TDD communication. Thereby, for example, TDD communication can be realized only by providing an offset circuit for offsetting a timing circuit that realizes basic timing. When a plurality of wireless USB slave devices are arranged in the wireless USB system 10, the timing correction function unit 30d has a correction function for correcting the timing and corresponding to each slot of the wireless USB slave device. As described above, the USB-wireless conversion unit 30 is required to consider various functions when applying TDD, and cannot be realized simply by diverting the conventional technology.

  The baseband unit 32 transmits the modulated radio data 40 to the RF unit 34, and receives the modulated radio data 40 from the RF unit 34. The RF unit 34 has a function of actually performing wireless communication. The RF unit 34 converts the radio data 40 into a predetermined frequency, transmits the radio 26, and receives the radio 26 converted into the predetermined frequency. The wireless USB master device 18 and the wireless USB slave device 20 include an LSI (Large Semiconductor Integration) that implements the functions described above.

  Returning to FIG. 1, when connecting to the device 22 in the wireless USB slave device 20, the USB 28 is connected to the device 22 via the wire 42. The device 22 is a device capable of USB connection, and includes, for example, a digital camera, a printer, a memory, and the like.

  Here, the types of USB packets handled in the wireless USB system 10 and the outline of the packets are simplified and shown in FIG. PID (Physical Interface Devices) types include token, data, handshake, and special types. In FIG. 3, italic letters mean that the USB version 2.0 is stipulated. In particular, in the case of a DATA0 / 1 packet, the maximum data size of this packet is determined by the size that defines the end point of the device, that is, the interface of the device.

  FIG. 4 shows the correspondence between the transfer mode and the transfer speed in the USB standard. Transfer modes include control transfer, bulk transfer, interrupt transfer, and asynchronous transfer. Among the transfer speeds, a high speed mode (HS) is excluded because it is not considered in this embodiment.

  In this embodiment, full speed and low speed are examined for each transfer mode. Low speed cannot be used in bulk transfer mode and asynchronous transfer mode. The items in FIG. 4 are provided with a size that can be transmitted and received and a size that can be set, and the range of transfer speeds that can be handled and the possible bytes or the range of the transfer speeds are indicated numerically in each speed column. The number of transactions per frame in the bulk transfer mode and the asynchronous transfer mode is represented by a reciprocal number.

  It defines the preconditions for operating under such USB standards. This precondition is merely an example, and a similar format other than this format may be used. The first condition is that the preamble of the wireless data time slot conforms to the PHS format. As a second condition, the wireless transfer rate is 4 Mbps. The third condition is that the frame format is 1 msec according to the USB standard. In addition, the connection condition is 1: 1 on the fourth condition. The USB-to-wireless conversion processing time or reverse conversion time is a processing sequence at the omitted logic level. Set the number of transfer data to 32 bytes.

  The USB packet format and the wireless slot format are as shown in FIG. The USB packet in SOF (Start Of Frame) of FIG. 5A is SYNC 8 bits, PID 8 bits, frame number 11 bits and CRC (Cyclic Redundancy Check) 5 bits, a total of 32 bits. For radio slots, R (Ramp time: ramp time for transient response) 4 bits, UW (synchronization word) 16 bits, channel number specification 2 bits, PID 8 bits, CRC 16 bits and G (Guard bit) 16 bits A total of 68 bits are supported.

  The USB packet in in, out, and setup in Fig. 5 (b) is SYNC 8 bits, PID 8 bits, ADDR (address information) 7 bits, ENDP (END Point information) 4 bits and CRC 16 bits, 32 bits in total. . In the case of a wireless slot, R 4 bits, PR (preamble) 6 bits, UW 8 bits, channel number specification 2 bits, PID 8 bits, ADDR 7 bits, ENDP 4 bits, CRC 16 bits and G 16 bits, 71 in total Bit corresponds.

  Further, the USB packet in the data of FIG. 5 (c) is SYNC 8 bits, PID 8 bits, data (DATA) 0 to 1023 bits and CRC 16 bits, 32 to 1055 bits in total. In the case of a wireless slot, R 4 bits, PR 6 bits, UW 8 bits, channel number designation 2 bits, PID 8 bits, data, CRC 16 bits and G 16 bits, 60 bits + data in total.

  Furthermore, the USB packet in the ACK of FIG. 5 (d) has 16 bits in total, 8 bits for SYNC and 8 bits for PID. In the case of a wireless slot, R 4 bits, PR 6 bits, UW 8 bits, channel number designation 2 bits, PID 8 bits, CRC 16 bits and G 16 bits, a total of 60 bits correspond.

  By using the TDD format for wireless communication, the wireless USB system 10 can shorten the preamble time and further improve the data transfer rate by shortening the synchronization time. Further, in the wireless USB system 10, if beacon information is deleted and transferred in wireless communication, transfer efficiency can be improved.

  Next, FIG. 6 shows the transfer time for one transaction in this embodiment. The number of USB bits and the number of wireless bits each represent the total number of bits in the format. In particular, the data size is 512 bits for both USB and wireless bits. In addition, the USB section transfer time is 2.7 μsec for SOF, in, out, and setup transactions, 45.3 μsec for data transactions, and 1.33 μsec for ACK and USB wait times. The transfer time of the radio section is different. That is, 17 μsec for SOF, 17.75 μsec for in, out and setup transactions, 142 μsec for data transactions, 15 μsec for ACK transactions, and 120 μsec for RF switching time. This format is an example.

  Here, a case where the above-described setting is applied to each transaction will be described. Along with the slot structure of the TDD method in the out transaction, the length and width reflecting the required time and data are shown. Further, since the communication state is compared with the USB packet, a communication state in which there is no error in the packet communication by USB is assumed. This communication state is assumed in the same way for each subsequent transaction. Fig. 7 (a) shows a USB out transaction in which SOF, out (OUT) packets and data are transferred sequentially from the host device 16 to the wireless USB host device 18 at predetermined time intervals, and the USB data is converted into wireless data. It shows until. It also shows the returned ACK packet. That is, data between the host device 16 and the wireless USB host device 18 in FIG. 2 is shown in a time series. In FIG. 7B, the wireless data between the wireless USB master device 18 and the wireless USB slave device 20 after this conversion transmits SOF, out packet, and data without leaving an interval. Since this wireless data is not spaced, it takes time to transfer each wireless data. For this reason, each region in FIG. 7 (b) is represented with a long length and a wide width. Further, FIG. 7 (c) shows the transfer between the wireless USB slave device 20 and the device 22. Transfer here returns to USB standard and transfers. Therefore, it has the same length as the SOF, out, and data packet shown in FIG. 7 (a). However, in this transfer, the time interval from SOF to OUT is opened in response to a request to widen the transfer time, as will be described later. The ACKs in FIGS. 7 (a), (b), and (c) are similarly expressed in consideration of the transfer time.

  FIG. 8 shows a data communication procedure by TDD in the out transaction. When data is transferred from the host device 16 to the device 22, an SOF packet indicating the head of the frame is output with a transfer time of 2.7 μsec. The host device 16 outputs SOF periodically. This period is 1 msec in the USB standard. Although not shown, the wireless USB master device 18 transfers the SOF to the wireless USB slave device 20 with a transfer time of 17 μsec after a waiting time of 1.33 μsec has elapsed since this transfer.

  The host device 16 outputs an out packet (OUT) 44 to the wireless USB master device 18 with a transfer time of 2.7 μsec. Although not shown, in parallel with this output, the wireless USB slave device 20 transfers the SOF to the device 22 with a transfer time of 2.7 μsec. Thereafter, after the standby time of 1.33 μsec has elapsed, the wireless USB master device 18 transfers the out packet 46 converted to TDD wireless data in conformity with the format of the out transaction to the wireless USB slave device 20 over a transfer time of 17.75 μsec. The transmission timing of the out packet 46 is transmitted in a periodic slot corresponding to the SOF after receiving the USB SOF. The wireless USB slave device 20 transfers the out packet 48 to the device 22 with a transfer time of 2.7 μsec. After this transfer, the wireless USB slave device 20 waits for 1.33 μsec until the data packet 54 is transmitted.

  Next, following the SOF packet and the out packet, the host device 16 transfers the data packet (DATA) 50 to the wireless USB master device 18 over a transfer time of 45.3 μsec. The wireless USB master device 18 transfers the data (DATA) 52 to the wireless USB slave device 20 with a transfer time of 143 μsec. The transmission timing of the data (DATA) 52 is also transmitted to the wireless USB slave device 22 in the next slot to which the OUT 46 is transferred after receiving the USB data packet 50, though not shown. Further, the wireless USB master device 18 sends a NAK packet to the host device 16 over a transfer time of 1.33 μsec.

  Although the wireless USB slave device 22 is almost the same as the transmission timing of FIG. 8, actually, after the data 52 is received, the out packet 48 is transmitted, and after a waiting time of 1.33 μsec, the transfer time is 45.3 μsec. The data packet (DATA) 54 is transferred to the device 22 in accordance with the USB standard. The host device 16 repeatedly outputs out and data packets at predetermined time intervals until receiving an ACK (OUT 56 and DATA 58). In response to receiving the data packet 54, the device 22 transfers the ACK packet 60 to the wireless USB slave device 20 over a transfer time of 1.33 μsec.

  Since the number of transmission data is known in the data transfer of each of the host device 16, the wireless USB master device 18, the wireless USB slave device 20, and the device 22, for example, in anticipation of the end of the transfer of the data packet 50, the OUT (OUT) 46 When the transmission starts, the transfer time is effectively used. Here, as an example, the same can be considered in other transfer modes, that is, out, in and asynchronous transfer modes.

  Although not appearing in FIG. 8, the wireless USB slave device 20 switches RF (radio frequency). For RF switching, as shown in FIG. 6, the time is 120 μsec. When switching is performed in the transfer time zone (1.33 + 45.3 + 1.33) μsec with the device 22 after the data is transferred, the RF switching time is 120− (1.33 + 45.3 + 1.33) = 72.04 μsec.

  The wireless USB slave device 20 transfers the ACK 62 to the wireless USB master device 18 over a transfer time of 15 μsec. The wireless USB system 10 has a waiting time of 1.33 μsec. As described above, the host device 16 transfers the out packet 64 with a transfer time of 2.7 μsec. The host device 16 transfers the data packet 66 after the waiting time of 1.33 μsec has elapsed. The wireless USB master device 18 transfers the ACK packet 68 to the host device 16 with a transfer time of 1.33 μsec.

  In this way, after the end of the transaction, considering slot repetition, RF switching occurs again. In this case, when the ACK packet 68 is successfully transferred to the host device 16 at the fastest speed, the ACK transfer time to the host device 16 is 1.33 μsec (1). Assuming transfer of an out transaction from the next host device 16, (1.33 + 2.7 + 1.33 + 45.3) = 50.66 μsec (2).

  However, since the transfer time of 17.75 μsec is required to transfer the out-packet wirelessly during this time (2), the margin for switching is 50.66-17.75 = 32.91 μsec. In view of these requirements, if the allowance time is excluded, the switching time is 120− (1.33 + 32.91) = 85.76 μsec. This switching time will allow more time if the host transfer for normal ACK delivery in the previous transaction is delayed. In addition, by adopting the time slot method, it is desirable to allocate 500 μsec to one transaction as a result of time measurement. Furthermore, when the transfer data is a transfer other than 64 bytes, it can be changed to a slot that matches the slot format that matches the data size. The slot format in the radio section is simply shown in FIG. However, (3) shows transfer from the wireless USB slave device 20.

  Next, the TDD method in in-transaction is shown. Along with the slot structure of the TDD scheme in the in-transaction, the time and the length reflecting the required time and data are given as in FIG. Fig. 10 (a) shows a sequence of USB in-transactions in which SOF and IN (IN) packets are transferred sequentially from the host device 16 to the wireless USB host device 18 at predetermined time intervals, and the IN packets are converted into wireless data. And returned data and ACK transmission. In FIG. 10 (b), the wireless data between the wireless USB master device 20 and the wireless USB slave device 22 after the conversion is converted into SOF and in-packet and transmitted without a gap. Each region in FIG. 10 (b) is expressed with a longer length and a wider width. Further, FIG. 10 (c) shows the transfer between the wireless USB slave device 20 and the device 22. The transfer here returns to the USB standard, and the SOF and in-packet are transferred to the device 22. It is represented by the same length as the SOF and in-packet shown in FIG.

  The device 22 transfers the data packet and the ACK packet to the wireless USB slave device 20 in consideration of the transfer time in the order of FIG. 10 (c), (b) and (a). The wireless USB slave device 20 converts the data packet and the ACK packet output thereafter to wireless data, and transfers it to the wireless USB master device 18. The wireless USB master device 18 outputs a USB standard data packet or ACK packet to the host device 16.

  The sequential in-transaction will be described with reference to FIG. Although this sequential also considers the transfer time of FIG. 6, in the description of the sequential of FIG. 11, only transmission / reception of commands will be described. SOF is omitted. The host device 16 transfers the in-packet 70 to the wireless USB master device 18. The wireless USB master device 18 converts the in-packet 70 into wireless data, and transfers the in-data 72 to the wireless USB slave device 20. The wireless USB slave device 20 converts the in-data 72 into an in-packet 74 of USB standard and outputs the in-packet 74 to the device 22. Since the wireless USB master device 18 has not received the requested data, it outputs a NAK packet 76 to the host device 16. The host device 16 outputs the in-packet 78 again. Between the host device 16 and the wireless USB master device 18, in-packets and NAK packets are repeatedly output until wireless data is received from the wireless USB slave device 20 and data packets are output (IN 78, NAK 80 And IN 82).

  The device 22 outputs the data packet 84 to the wireless USB slave device 20. The wireless USB slave device 20 converts the data packet 84 into wireless data 86 and outputs the wireless data 86 to the wireless USB master device 18. The wireless USB master device 18 outputs a data packet 88 to the host device 16. Further, the device 22 outputs the ACK packet 90 to the wireless USB slave device 20 after transmitting the data packet 84. The wireless USB slave device 20 converts the ACK packet 90 into wireless data, that is, ACK data 92, and outputs the wireless data 92 to the wireless USB master device 18. The wireless USB master device 18 outputs an ACK packet 94 to the host device 16.

  Next, transfer will be described by paying attention to TDD between the wireless USB master device 18 and the wireless USB slave device 20. FIG. As with in-transactions, the transfer time can be increased as in in-transactions. The transfer slot in FIG. 12 is the same as the transfer slot in FIG. 9 and is the same with the timing shifted by one. Therefore, the USB-wireless conversion unit 30 is provided with one timing circuit. The offset in timing is used as an offset. The wireless USB system 10 can be configured with an in-transaction slot format simply by shifting the offset. Therefore, the USB-wireless conversion unit 30 does not require a new complicated timing circuit.

  Next, the TDD method in an asynchronous transaction is shown. Out and in in this case are the same as those except for ACK in FIGS. 7 and 10, respectively. The illustration is omitted to avoid complication.

  In the out sequence in the asynchronous transaction, the host device 16 transfers the out token packet 96 to the wireless USB master device 18. The wireless USB master device 18 converts the out packet 96 into wireless data, and transmits the converted wireless data and out data 98 to the wireless USB slave device 20. The wireless USB slave device 20 converts the out data 98 into a USB standard out packet 100 and transfers the out packet 100 to the device 22.

  The host device 16 transfers the data packet 102 to the wireless USB master device 18 following the out token. Here, since the transfer size of the data size is known, it is possible to change the transfer size based on the 1-slot time information of the slot format for the transfer data.

  The wireless USB master device 18 converts the data packet 102 into wireless data, and transmits the converted wireless data and data 104 to the wireless USB slave device 20. The wireless USB slave device 20 converts the received data 104 into a USB standard data packet 106 and transfers the data packet 106 to the device 22.

  Between the wireless USB master device 18 and the wireless USB slave device 20, as shown in FIG. 14 (a), (1), (2), (1), (2), (1), ( It can be seen that 2) is transferred to the slave side.

  In addition, in the case of this asynchronous out, ACK in the radio section is unnecessary compared with CSMA transfer, and thus the effect of transfer efficiency is greatly improved. However, since it is not possible to confirm the existence of the slave by this alone, it is possible to cope with it by inserting a control slot for confirmation once in one place or several frames of the frame. As a countermeasure circuit, a basic timing circuit is applied as an example, and the normal frame is (1), (2), (1), (2), (1), (2) ... To insert the confirmation frame, as shown in Fig. 14 (b), the last slot (2), (3), (1), (2), (3), (1) ... It is only necessary to add a few circuit timing correctors by correcting the timing circuit.

  Further, the host device 16 transfers the in token packet 108 to the wireless USB master device 18 in the sequential of IN in the asynchronous transaction. The wireless USB master device 18 converts the in-packet 108 into wireless data, and transmits the converted wireless data and in-data 110 to the wireless USB slave device 20. The wireless USB slave device 20 converts the in-data 110 into the USB standard in-packet 112 and transfers the in-packet 112 to the device 22.

  The host device 16 transfers the in token 114 to the wireless USB master device 18 following the in token. On the other hand, the device 22 transfers the requested data to the wireless USB slave device 20 as a data packet 116. The wireless USB slave device 20 converts the supplied data packet 116 into wireless data 118 and transfers the wireless data 118 to the wireless USB master device 18. The wireless USB slave device 20 transfers the in-packet 120 to the device 22.

  Further, the wireless USB master device 18 converts the received wireless data 118 into a USB standard data packet 122 and transfers the data packet 122 to the host device 16. On the other hand, the device 22 transfers the data packet 124 to the wireless USB slave device 20 in response to the received in-packet 120. In response to receiving the data packet 122, the host device 16 sends an ACK packet 126 to the wireless USB master device 18.

  The wireless USB slave device 20 again converts the data packet 124 into wireless data 128 and transmits it to the wireless USB master device 18. The wireless USB master device 18 converts the received wireless data 128 into a data packet 130 and transfers it to the host device 16.

  By the way, by adopting such a method as a whole, first, when transferring SOF data in a USB frame, beacon information necessary for packet transfer can be assigned to a slot including SOF information. Second, when there are a plurality of slaves, it is easy to assign the repeated slot format part to another slave as shown in FIG. 14 (c). At this time, it is necessary to consider the collision avoidance circuit and timing in packet transfer, but the timing is already fixed in the time slot method, so the timing for collision avoidance is changed even if there are multiple slaves. It is easy to assign the slot format of one transaction to another slave. At this time, there is an advantage that the transfer capability of the wireless USB master device is not lowered.

  When operated as described above, the transfer rate can be improved by using the TDD format instead of returning ACK for one data transfer as in packet communication. In addition, it is possible to shorten the synchronization preamble and the like, and it is possible to secure a time available for the entire data transfer.

  Further, the slot timing can be changed only by providing an offset in each transfer mode, and the increase in circuit scale can be limited. And even when there are multiple slaves, the time slot is fixed by using the TDD method, so it is possible to avoid collisions and eliminate the need for system configuration considerations for collision avoidance. The circuit can be easily simplified.

It is a block diagram which shows the schematic structure of each of the wireless USB master and slave device to which the communication system of the present invention is applied. 1 is a block diagram showing a schematic configuration of a wireless USB system to which a communication system of the present invention is applied. It is a figure which shows the kind of USB packet used in the wireless USB system of FIG. 2, and its outline. It is a figure which shows the transfer mode and transfer speed of USB specification used in the wireless USB system of FIG. It is a figure which shows the format of the USB packet and wireless slot which are used in the wireless USB system of FIG. It is a figure which shows the bit number and transfer time in 1 transaction used in the wireless USB system of FIG. It is a figure which shows each transfer based on data, transfer time, and a specification. 3 is a sequential chart of an out transaction in the wireless USB system of FIG. It is a figure explaining the communication by TDD between a wireless USB master apparatus and a wireless USB slave apparatus among the out transactions of FIG. It is a figure which shows each transfer based on data, transfer time, and a specification. 3 is a sequential chart of an out transaction in the wireless USB system of FIG. FIG. 12 is a diagram illustrating communication by TDD between a wireless USB master device and a wireless USB slave device in the in-transaction of FIG. 3 is a sequential chart of asynchronous transfer out in the wireless USB system of FIG. 2. FIG. 14 is a diagram illustrating communication by TDD between a wireless USB master device and a wireless USB slave device in the case of transfer, confirmation frames, and a plurality of slaves in the asynchronous transfer of FIG. 3 is a sequential chart in the asynchronous transfer in in the wireless USB system of FIG. 2.

Explanation of symbols

10 Wireless USB system
16 Host device
18 Wireless USB master device
20 Wireless USB slave device
22 devices
28 USB
30 USB-to-wireless converter
32 Baseband section
34 RF section

Claims (4)

  A communication system that uses radio for a partial communication path between a host device on a host side and a device on a slave side, wherein the system uses a time division multiplexing system for radio communication. The system according to claim 1, wherein the system includes a wireless master device on a master side and a wireless slave device on a slave side,
The wireless master device and the wireless slave device further include a mode detection function for detecting a packet transfer mode handled in the USB (Universal Serial Bus) standard,
A communication system comprising: a change function for changing the packet to a time slot format in the time division multiplexing method for use in wireless communication and conversely changing the changed time slot to the packet format.   3. The communication system according to claim 1, wherein the wireless master device and the wireless slave device further include an offset function for shifting the timing of the time slot by an offset.   4. The system according to claim 1, wherein the wireless master device includes an allocation correction function that corrects the correspondence of the time slots according to the number of the wireless slave devices existing on the slave side. A communication system.

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