JP2003535489A - Wireless modem - Google Patents

Abstract

(57) [Summary] A wireless modem system including two devices capable of transmitting and receiving data sequentially supplied to channels via a plurality of RF channels. In one embodiment, the first device is used to connect to and receive data from a computer. The first device encodes received data from the computer and transmits the received data to the second device using a digital wireless transmission format. The second device receives data transmitted from the first device in a digital wireless transmission format and converts the data to an analog format for transmission over a wired telephone network.

Description

Detailed Description of the Invention

FIELD OF THE INVENTION The present invention relates to wireless communications, and more particularly to a wireless modem system that allows a computer to remotely process data without being physically coupled to a telephone horn port. . The system operates to protect the integrity of communication information sent and received via the wireless modem.

BACKGROUND OF THE INVENTION Modems are popular throughout the world to allow electronic devices such as computers to communicate with each other. Typically, modems connect a computer to a communications jack. Communication information is transmitted / received by a wire or a cable via a communication jack. However, the physical connection of the modem to the jack limits the freedom of movement while using the device enabled by the modem. Wireless modems, on the other hand, are designed to allow users to send and receive communication information from laptop computers and other electronic devices without physically connecting the computer to the jack, which allows it to The computer can be used because the communication is performed regardless of the location of the computer.

However, conventional wireless modems have serious drawbacks. In particular, the integrity of communication information transmitted and received using such devices is often compromised. for that reason,
The present invention seeks to provide a wireless modem with improved integrity of communication information.

SUMMARY According to the present invention, a wireless modem system uses a digital spread spectrum operation with automatic RF signal detection to lock on (continuously track) selected channels after a handshake process. Maintain communication integrity. In particular, the modem function of modulating and demodulating data to and from a computer for transmission over an analog telephone line is included only in remote wireless modems.

DETAILED DESCRIPTION OF THE INVENTION A wireless modem (W
M) devices, also referred to as wireless modem jacks (WMJ) or RF links, operate in the ISM band of 900 MHz (902-928 MHz), for example. The wireless modem system includes, for example, one base station 1000 and one wireless remote modem station 1001 as shown in FIG. Both stations can send and receive data / fax at the same time. The difference between both stations is that as shown in FIG. 1, the data is modulated and demodulated into an analog signal to be transmitted and received at the remote wireless station 1001 side so that the base station 1000 has a "modem" function (
For example, a modem 18 ') and an associated telephone function processing unit (eg, processing unit 20).
') And is not required.

The design of this system is preferably based on the direct spread spectrum (DSSS) method. Direct spread spectrum provides the highest security for data transmission over the radio frequency spectrum, especially in the 900 MHz range. At present, the maximum data transmission rate for WMJ reaches 115 Kbps (when using a radio frequency link), which is much faster than a regular hardwired modem connection. WMJ can be used for Internet service connections, sending and receiving fax data, or communicating other types of data. All transmission information is in SST digital encryption format.

The invention thus enables RF link support up to a data rate of 115 Kbps with error detection and correction. This is a V.2 that can be used with the services of many existing Internet service providers. Compatible with 90 / 56K flex modem standard. The system performs automatic RF signal detection and locks to the channel selected for both stations (after the confirmed handshake process), as described below.

Since the base station 1000 has a serial port, the system is not only used as a conventional modem for accessing a computer network via a telephone line, but also between two PC (personal computer) terminals. It can also be used for network connections for remote printer sharing. In that case, the system supports Hyper Terminal data transmission.

Furthermore, since the modulated signal is in digital form, the FCC allows a maximum transmit power of up to 1 W instead of 100 mW for the analog modulation type. This extends the transmission range, typically reaching 300 feet (3 x 30.48 m) or more under residential conditions.

In recent years, personal computers (PCs) and the Internet have become very popular all over the world. Most consumers access the Internet using a regular connection via a standard telephone jack. Unfortunately, for most homes,
Only one or two telephone wall jacks are installed. Therefore, setting up a PC away from the telephone wall jack is a problem for most people.

By using WMJ, consumers can access the internet, send and receive faxes, and transfer files between two PCs from anywhere in their home. The data (signal) is in digital format with signal encryption. Radio frequency (RF) signals fall in the 900 MHz range, or 902-928 MHz. The design of WMJ is based on the digital spread spectrum method. Thus, the WMJ is capable of transmitting and receiving signals over longer distances (about 300 feet) than 900 MHz devices that transmit signals in normal analog modulation format. Part 15 of the FCC rules permits any device that uses a digital modulation format to have an RF output power of 1W. In contrast, devices in analog modulation format only allow output powers of 100 mW.

Regarding the base station RF link, refer to the block diagram of FIG. The general operation in the situation where the RF link first transmits data from the PC (not shown) and then the RF link receives data from the RF link transmitter (not shown) will be described. Here, the difference between the base station 1000 and the remote station or extension 1001 is that the modem function 18 'and an additional circuit 2 for connection to the RJ-11 jack to the telephone network.
Note that 0's are only embedded in the remote station. Therefore, in the following description, in order to avoid duplication, the emphasis is on the base station.

The DCE port 2 is connected to a PC computer (not shown) and passes the received serial digital data to the interface 4. Interface 4 adjusts the voltage level of the bit to a standard value. A UART (Universal Asynchronous Receiver / Transmitter) 6 converts the serial data into parallel data, and the processor 14 creates a data packet including alignment bits, read bits, message bytes, and trailing bits. The packet is held in the Tx (transmission) buffer of SRAM 8. SS
T10 searches for an unused channel in the RF module 12, reads data from the transmission buffer of the SRAM 8, and supplies the data to the channel of the RF module 12 in a repeating sequence. All operations are controlled by MCU14, LE
The D indicator 16 displays various operating conditions.

When the RF link of FIG. 1 receives data from the external RF link, the SST scans the channels of module 12 and the data received from the external RF link is SS.
It is transferred to the Rx (reception) buffer (not shown) of the SRAM 8 by T. M
Under the control of the CU 14, the data of the data packet is reconstructed and passed to the UART 6, where the parallel data is converted into a serial stream of bits, which are supplied to the DCE port 2, which can be connected to another PC. The voltage is adjusted by the interface 4 before the operation.

[Initialization] Referring to the flowchart of FIG. 2, when power is turned on in step 22,
The processing performed by the base station or the extension station will be described. If the station's SRAM 8 test reveals a SRAM failure, no further operation can be performed unless the SRAM 8 is properly operated. At decision step 26, it is determined if there is anything connected to DCE port 2. If something is connected, for example a PC is connected, and that PC is a base station BU, as shown in FIG. 1, then the modem 18 is ignored and the base station is shown in step 28. Set as master / slave. The master bit of the switch DIPSW1 shown in FIG. 8 is tested. When this switch is on (or set to the up position), the corresponding master bit in the operating status register OPSTAT is set. Otherwise, the bit is cleared. Normally, the extended station (EU) is always set as the master station (station that initiates transmission) and the base station (BU) is set as the slave station (station that is always in listening listening mode). For applications that do not require modem functionality, two base stations are used. In this case, one base station is set as the master and the other base station is set as the slave.
If necessary, the base station (with serial port selected) is set as the master,
The other base station (with serial port selected) or extension station is set as slave.

If the master setting has been made, as shown in decision step 30, the channels of the RF module 12 are scanned as shown in step 32. The master station monitors the RSSI (received signal strength indication signal) of the individual RF channels for 100 ms (milliseconds). All 10 RF channels (0-9) are examined.
The quietest channel is selected. The master station then monitors whether there is transmission activity on that channel. If not, the channel is selected for transmission. The MCU 14 timer is used as a channel scan timer handled by the chscan_to interrupt service routine.

After the channel selection, the packet not received timer is activated in step 34. This timer forces the link setup process to proceed when the timer expires. The process shown in FIG. 7 is continued. Then, in step 36, the appropriate registers of the Rx buffer and the HDx mode (transmit or receive operating mode) are set. At this point the station enters a run-time loop RL as shown in FIG.

If the station is not set as the master in decision step 30, that is, if it is set as the slave, the baud rate of the UART 6 is set in step 38, and the tracking timer is started in step 40. This function is performed by the slave station only and scans the RF channel of the master station. As an example, each channel is scanned for 20 milliseconds.

In decision step 26, if the DTR is not active, step 42.
Then, it is checked whether or not the modem 18 is incorporated. If so, the station is set as a slave, step 44 enables the modem Rx interrupt, indicating that no communication is planned with the modem, and proceeds to step 36. Slave enable UA if modem not integrated
The RTRx interrupt is set at step 46 and the routine returns to step 28.

Runtime Loop In FIG. 2, after the setup routine is complete, the wireless link enters the continuously operating runtime loop shown in FIG. In decision step 48,
A query is made as to whether the alignment byte has been received. If there is no alignment byte at the end of the data packet, it means that the data packet has been received. If an alignment byte is received, service routine RBUF
_In, the data is held in the Tx buffer or Rx buffer of the SRAM 8. This short loop repeats until no alignment bytes are received. In step 48, when there is no alignment bite, in step 50,
Check to see if the RF link has been declared, ie the handshake is complete, so that the RF link is ready to send data. If the RF link is not declared, there is no need to proceed, so the process returns to the beginning of the loop.
If the RF link was declared in step 50, in step 52 SRAM8
It is determined whether or not there is data in the Rx data buffer. If data is present, it is sent in step 54 to the UART 6 or to the modem 18, depending on what type of operation is being performed. The station
If both DTRs are active, transfer data from the receive buffer to UART 6 or modem 18 dedicated to the base station and the link goes up. The modem function is relevant only to base stations. Writing / reading to / from the UART6 or modem corresponds to writing / reading to / from the FIFO buffer of the UART6 or modem. After the data has been sent, processing returns to the top of the loop.

[Transmission] Data transmission is performed as shown in FIG. 4, and starts from step 56. First, the data in the Tx buffer of the SRAM 8 is transmitted. First, step 58
At, it is checked if a retransmission bit requesting a retransmission has been received from step 118 shown in FIG. SRA if the retransmission bit is set
The pointer in the M8 Tx buffer is returned at step 60, and if not set, the data is read from the Tx data buffer at step 62. T
The x buffer pointer is saved in step 64 and the data packet is saved in step 6
As shown by 6, it is created by UART6. The data is copied from the transmission buffer of the SRAM 8 to the data portion of the packet buffer (register of MCU).
The number of bytes in the data packet is 0 (nil) to 72. A packet envelope is added. The envelope includes a packet header byte, a link control byte, a packet length (counting from the header byte to the last byte of the checksum), and a channel number / station identification byte.

In step 68, the routine calculates a 16-bit Fletcher checksum and appends it to the end of the last data byte. The transmitted packet is preceded by a 15-byte preamble byte (0x00) and a 2-byte alignment byte (0x80). 5 bytes trailing byte (0xff)
Is added at the end of the packet transmission.

In step 70, it is checked whether the RF link has been set as a master station by a manual switch. If set as the master station, the packet not received timer is started at step 72, followed by the process shown in FIG. 7 below.

FIG. 5 is a flow chart showing the steps of the UART / modem interrupt handling service 102. The data is read from the UART 6 or modem Rx FIFO in step 104. When the buffer is empty, at step 106 T
Writing to the x data buffer is performed, and in step 108, the process returns to the start step 56 of the transmission process of FIG.

[Reception] Referring to FIG. 6, the routine RBUF_IN starts at step 74 and 2
Monitor consecutive alignment bytes (0x80). These bytes may not be properly aligned. The station reads and aligns the next 7 bytes in the packet (6-78). When the packet length exceeds 6 (never exceeds 78)
, The station reads the remaining bytes from the SST and stores them in the packet buffer (register of MCU). If a header byte is received at decision step 76, the data is read from the SST's Rx FIFO into SRAM 8 at step 78. In decision step 80, the validity of the data packet is checked. At decision step 82, the data is checked to see if the address of the data is the address of the receiving RF link. To prepare the master and slave stations for transmission, it is a program function in MCV8 of both stations to check if the packet has link up or link down set. As a result, capture of transmission information in the vicinity is prevented. The link is
A light is signaled when the RF link is ready to receive, declared at step 84 and a check is made at step 86 to see if the master / slave switch is set to the slave side. If it is set on the slave side, the user sets the baud rate by switch combination or software in step 88. Normally, the baud rate is set to the maximum value. The packet not received timer starts at step 90 (see FIG. 7) and at step 92 a link setup packet is set up in the MCU 14 to request more data from the buffer. If it is determined at decision step 86 that it is the master station, the data is transmitted at step 87,
Proceed to the run-time loop in FIG.

Referring again to the decision step 82, the case where the link setup packet is not received will be described. In step 94, if the data packets are received in sequence, the data packets are written to the Rx data buffer of SRAM 8 and proceed to step 100. If a negative determination is made at decision steps 76, 80 and 94, processing returns to the run-time loop of FIG.

FIG. 7 is an explanatory diagram of a packet unreceived / channel tracking timer interrupt handling routine for both the master and the slave. If the two data links are up as determined at decision step 100, ie, there is a handshake between the data links, then the timeout counter is read at step 112. The timeout counter starts counting when an interruption of transmission occurs. As each data packet is sent, the timeout counter starts running and the clock is set back to 0 when the last byte of the message, the trailer byte, has passed. Therefore, in decision step 114,
When the counter is non-zero, it indicates that the data packet has not been completely transmitted, in which case the retransmission bit is sent back to the transmitter. This retransmitted bit is the retransmitted bit that appears in decision step 58 of FIG. 4 to explain the transmission. After returning the retransmission bit, the process returns to decision step 110.

The timeout counter is maintained and used by both master and slave stations to declare a link down. The value of the counter differs between the master station and the slave station. For example, the value of the counter of the master station is 10 and the value of the counter of the slave station is 1. Further, the value of the packet not received (NPR) timer is different between the master station and the slave station and is 50 ms for the master station.
1000 ms for the slave station.

The master station retransmits the data packet if a valid data packet cannot be received from the slave station within 50 ms after the data packet is transmitted. If the packet not received timer expires 10 times in a row, the link down state is declared and the master station redoes the channel scanning process. The counter is reloaded each time a valid data packet is received. The value of the packet not-received timer needs to be large enough to handle the longest data packet. The data packet length is 6 to 78 bytes, excluding preamble bits, alignment bits and trailing bits.

Since the slave station is always in the listening (listening) mode, that is, it does not start the transmission of the data packet, only one expiration of the packet non-reception timer is required to declare the link down. . The value of the packet not-received timer is selected to cover the total time, for example 10 × 50 ms, that the master station will try to receive a response from the slave station by retransmitting the data packet. After declaring link down, slave station, master station declares link down,
An additional 1000 ms to ensure that the link setup is re-initialized
Stay dormant during. Note that this mechanism is not used during the link setup process. This is because the master station continuously sends the link setup unless it receives a response from the slave station.

However, if it is found in the decision step 114 that the timeout counter has returned to 0, the master station and the slave station have finished transmission, but the master station and the slave station decide in the decision step 116 that RF It stays in handshake mode until it is determined whether the link is master or slave. If the RF link is the master, the SST 10 will:
The channels are scanned in step 117.

On the other hand, if it is determined in decision step 116 that the RF link is not the master, and therefore the slave, the master asks in step 126 to declare link down. That is, the master and slave stations are asked to declare the end of transmission, but the master and slave stations still maintain the handshake mode. In step 128, available channels are detected. These channels are used in the DSS mode in step 124, where the tracking timer is started to send data in sequence to the available channels.

In the decision step 110, it is determined that the link between the RF stations is not properly established, that is, it is determined that the link is not in the up state, and the decision step 1
If it is determined at 20 that it is not the master station, that is, if it is a slave station, then at step 122, the available channels are detected as in step 125. If in step 120 it is determined to be the master station, the data packet is transmitted in step 126 and the packet not received timer is started in step 128.

In describing the block diagrams of FIGS. 8-13, it should be noted that the particular microchips specified are merely illustrative of the devices that can be used. Microchips are designated by U, numbers and initials.

FIG. 8 is a block diagram of a main processor whose MCU 140 is U4. The test pattern for SRAM 8, U6, as shown in step 24 of FIG. 2, and the response from SRAM U6 are conveyed by data path 130. A switch 132 for providing RF link identification information, baud rate, and master and slave station distinction is connected to a pin 138 of the MCU, U4, via a buffer 134 and a data path 136. The oscillator 138 RFs to the SST chip 141 which connects to the GFSK transceiver 142 of FIG.
The GFSK transceiver 142 supplies the signal to the antenna 145 of FIG.
Providing RF channels. Those skilled in the art can implement the present invention based on the matters shown in the drawings and the detailed description, and therefore, description of all connections will not be given.

FIG. 9 illustrates UART6, designated as U10, and RS-2 at number 146.
It is a block diagram showing 32 interface processing part 4. DCE communication port 2 is
The LED, shown at 148 and indicating a number of operating conditions, is shown at 150.

FIG. 11 shows a power supply 152 for use with a base station as shown in FIG.
FIG. 7 is a diagram showing a power supply 154 for an expansion unit.

12 and 13 are block diagrams of a modem 18 that enables the expansion unit to communicate with the Internet. The modem 18 includes U18 and is provided with a jack 154 for connecting a telephone line.

Various modifications to the embodiments of the invention, as well as alternative embodiments, will be apparent to those skilled in the art from the foregoing description. Therefore, the foregoing description is merely exemplary and is intended to teach those skilled in the art the best mode of carrying out the invention. The details of the embodiments may be changed without departing from the spirit of the invention, and all modifications that come within the scope of the claimed subject matter are contemplated.

[Brief description of drawings]

[Figure 1]   1 is a block diagram of one embodiment of a wireless modem system according to the present invention.

[Fig. 2]   3 is a flowchart of a power-on initialization process for the device shown in FIG. 1.

FIG. 3 is a flow chart of a continuous run-time loop RL that monitors alignment bits and a receive data buffer in the apparatus shown in FIG.

[Figure 4]   6 is a flowchart of a data transmission process by the device shown in FIG. 1.

5 is a flow chart of UART / modem interrupt handling by the apparatus shown in FIG.

[Figure 6]   6 is a flowchart of a data reception process by the device shown in FIG. 1.

FIG. 7 is a flowchart of packet unreceived channel tracking timer interrupt processing by the device shown in FIG.

FIG. 8A is a SST (Spread Spectrum Technology) processor and S for the device shown in FIG.
FIG. 2 is a block diagram of a main processor including a RAM and used in the device shown in FIG. 1.

FIG. 8B is a SST (Spread Spectrum Technology) processor and S for the device shown in FIG.
FIG. 2 is a block diagram of a main processor including a RAM and used in the device shown in FIG. 1.

9 is a UART, an LED indicator and an RS used in the device shown in FIG.
It is a block diagram of a 232C interface.

[Figure 10]   2 is a block diagram of an RF transceiver used in the apparatus shown in FIG. 1. FIG.

FIG. 11   FIG. 2 is a configuration diagram of a power supply used in the device shown in FIG. 1.

[Fig. 12]   2 is a circuit diagram of the device shown in FIG. 1. FIG.

[Fig. 13]   2 is a circuit diagram of the device shown in FIG. 1. FIG.

─────────────────────────────────────────────────── ─── Continued front page    (81) Designated countries EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, I T, LU, MC, NL, PT, SE), OA (BF, BJ , CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, K E, LS, MW, MZ, SD, SL, SZ, TZ, UG , ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AG, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, BZ, C A, CH, CN, CR, CU, CZ, DE, DK, DM , DZ, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS, JP, K E, KG, KP, KR, KZ, LC, LK, LR, LS , LT, LU, LV, MA, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, S D, SE, SG, SI, SK, SL, TJ, TM, TR , TT, TZ, UA, UG, US, UZ, VN, YU, ZA, ZW (72) Inventor Pranthip, Dongchai             Bangkok, Thailand 10240 Sapan Sun               Ramkamaen 118 Puruxa chart               15 99/209 F-term (reference) 5K034 AA05 EE03 FF01 FF05 HH62                       KK27

Claims (7)

[Claims] 1. A first device and a second device, wherein the first device is connected to a computer, receives the data from the computer, encodes the received data, and digitally receives the received data. Means for transmitting using a wireless transmission format, wherein the second device receives the data transmitted in the digital wireless transmission format from the first device and transmits the analog data via a wired telephone network. A wireless modem system comprising means for processing into a format. 2. The wireless modem system of claim 1, wherein the received data is transmitted to the second device using a digital wireless transmission format on a selected one of the available channels. 3. The wireless modem system of claim 1, wherein the second device comprises a modem that further processes the transmitted and received data into an analog format. 4. The wireless modem system of claim 3, wherein the modem receives and demodulates analog signals from a wireline telephone network. 5. A wireless modem system having a first device and a second device, wherein each of the first device and the second device has a port for receiving serial data and one side. Signal conversion means for converting serial data supplied from the device into parallel data supplied to the port, a transmission buffer, a reception buffer, and control means for creating a data packet from the data obtained by the signal conversion means. Means for supplying the data packet to the transmission buffer, a transceiver having a plurality of channels, means for supplying the data in the transmission buffer to a selected channel of the transceiver in an iterative order, the transceiver Storing the data packet received by the receiving buffer in the receiving buffer; A wireless modem system adapted to transfer data packets to the signal converting means. 6. The method of claim 5, further comprising means for scanning channels of the transceiver to identify free channels used as the selected channel.
The described wireless modem system. 7. A means that is separately provided in the first device and the second device and that is manually controlled to selectively set an address of the own device, the first device and the second device. Means separately provided for each of the devices and manually controlled to selectively set the address of another RF device; and the address of the own device and the other provided for the first device and the second device. Means for writing the address of this device in the transmission buffer of its own device, and the address of the other device that is provided in the first device and the second device and responds to the reception of the unique address of the own device. 6. The method according to claim 5, further comprising: means for comparing with the known address for another RF device; and means for performing further communication if the address of the compared other device matches the known address. Wireless modem system.