KR20020044575A - Wireless modem - Google Patents

Abstract

The present invention relates to a wireless modem system having two devices, each device capable of transmitting and receiving data through a plurality of RF channels, the data being supplied to the channels in order. In one embodiment, the first device is coupled to a computer and used to receive data from the computer. The first device encodes the data received from the computer and transmits the received data to the second device using a digital transmission form. The second device receives the data transmitted from the first device in the form of digital wireless transmission and further processes it in analog form for transmission over a wired telephone network.

Description

Wireless modem {WIRELESS MODEM}

Modems are widely used to enable electronic devices such as computers to communicate with each other. Typically, a modem connects a computer to a communications jack that can transmit and / or receive communications by wire or cable. However, physically connecting the modem to the jack limits the freedom of movement while using the device operated by the modem. As a solution, a wireless modem is designed to allow a user to send and / or receive communications from laptop computers and other electronic devices that are not physically connected to the jack, thereby allowing the computer to be located at any position of the computer relative to the jack. Can be used for communication. However, the conventional wireless modem has a major defect. Specifically, the integrity of the communication sent and / or received using the devices often fails. It is therefore an object of the present invention to provide a wireless modem with greater communication integrity.

TECHNICAL FIELD The present invention relates to wireless communications, and more particularly, to a wireless modem system that enables data processing remotely without physically connecting a computer to a telephone phone port. The system operates in a manner to protect the integrity of communications transmitted and / or received via the modem.

1 is a block diagram of an embodiment of a wireless modem system in accordance with the present invention.

2 is a flow chart of power up initialization for the device shown in FIG.

FIG. 3 is a flow diagram for a continuous execution loop RL that executes alignment bit monitoring and the receiving data buffer monitor receives at the device shown in FIG.

4 is a flow chart for transmitting data by the device shown in FIG.

5 is a flow chart for UART / modem interruption handled by the device shown in FIG.

6 is a flowchart for receiving data by the apparatus shown in FIG.

7 is a flow diagram of stopping a no packet received (NPR) channel tracking timer by the device shown in FIG.

8 is a schematic diagram of a main processor used in the apparatus shown in FIG. 1, including an SST (spread spectrum technique) processor and SRAM of the apparatus shown in FIG.

9 is a schematic diagram of a UART, LED indicator, and RS-232 interface used in the device shown in FIG.

10 is a schematic diagram of an RF transceiver used in the apparatus shown in FIG.

11 is a schematic diagram of a power supply used in the apparatus shown in FIG. 1;

12 and 13 are circuit diagrams of the device shown in FIG. 1.

The present invention provides a wireless modem system that protects communication integrity using digital spread spectrum operation to detect automatic RF signals to lock selected channels after a handshake process. In particular, the modem function of converting / demodulating data to / from a computer for transmission over an analog telephone line exists only in a remote wireless modem.

A wireless modem (WM) device, used in the wireless modem system described herein, also called a wireless modem jack (WMJ) or an RF link, is, for example, a 900 MHz ISM band (902-928 MHz). Will work). The wireless modem system includes, for example, one base apparatus 1000 and one wireless remote modem apparatus 1001 shown in FIG. These two devices can send and receive data / fax at the same time. The only difference is that a "modem" function (e.g., 18 ') and associated telephone processing (e.g., 20') are not needed in the base apparatus 1000, because the data is shown in FIG. This is because it is modulated / demodulated into an analog signal transmitted and received by the remote wireless device 1001 as shown.

The system is preferably designed based on Direct Sequence Spread Spectrum (DSSS) technology, which provides maximum security for transmitting data in the radio frequency spectrum, particularly in the 900 MHz range.

At this point, the maximum data rate for the WMJ will reach 115 Kbps (when over a radio frequency link), which is much faster than a regular hard-wired modem connection. The WMJ can be used to transmit / receive fax data as well as to deliver other forms of data as well as internet service access. All transmissions are done in the form of SST digital encryption.

Thus, the present invention enables the RF link to support data rates up to 115 Kbps while having error detection and correction capabilities. It is compatible with the V.90 / 56K flex modem standard, making it available for the services of many existing Internet service providers. The system provides automatic RF signal detection, as described later, and locks into the selected channel for the two devices (after the identified handshake process).

Since the base device 1000 is made of a serial port, the system can be used not only as a conventional modem to access a computer network via a telephone line, but also as a network connection shared by a remote printer between two PC terminals. have. The system can also support hyper terminal data transfer.

In addition, since the modulated signal is in digital form, the FCC can set the maximum transmit power to 1 watt instead of 100 kW in the analog modulation type. This would allow for a better transmission range, and would normally go up to the 300ft range (or more) in residential environmental conditions.

Nowadays, personal computers (PCs) and the Internet are widespread worldwide. Most consumers can access the Internet by normal connections through standard telephone jacks. Unfortunately, most residential homes have only one or two wall-jacks throughout the home. Therefore, most people have a problem when installing a PC away from a telephone outlet.

With WMJ, consumers can access the Internet, send and receive faxes, or transfer files between two PCs anywhere in the home, for example. The data (signal) will be in digital form with the signal encrypted. The radio frequency (RF) signal will be in the 900 MHz range, ie 902-928 MHz. The WMJ design is based on digital spread spectrum technology. Thus, the WMJ can transmit and receive signals over much greater distances (approximately 300 feet) than any 900 MHz signal transmitting signal in a constant analog modulation form. According to Part 15 of the FCC Rules, any device having a digital modulation form may have an RF output of 1 W compared to a device having an analog modulation form that may only have an output of 100 Hz.

See the block diagram of FIG. 1 for a base device RF link. The entire operation first describes a situation in which the RF link transmits data from a PC (not shown), and then describes a situation in which the RF link receives data from an RF link transmitter (not shown). Here again, the only difference between the base device 1000 and the remote device or extension device 1001 is the additional circuit 20 'which additionally establishes the modem function 18' on the remote device and interfaces to the RJ-11 jack and the telephone network. Note that) is installed. Therefore, in order to avoid duplication, the following description will focus on the base apparatus.

The DCE port 2 is coupled to a PC computer (not shown) and transmits the received serial digital data to the interface 4 which adjusts the voltage level of the bit to a standard value. The UART 6 converts the serial data into parallel data, and the processor 14 constructs a data packet having an alignment bit, a lead byte, a message byte, and a trailing byte. The data packet is then stored in the Tx buffer of the SRAM 8. The SST 10 examines the unused channel of the RF module 12, reads data from the Tx buffer of the SRAM 8, and provides the data to the channel of the RF module 12 in an iterative sequence. All operations are controlled by MCU 14, and LED indicator 16 displays various operating states.

When the RF link of FIG. 1 receives data from an external RF link, the SST scans the channel of the RF module 12, and the data received from the external link is Rx buffer (not shown) of the SRAM 8; Is delivered by the SST. Under the control of MCU 14, the data in the data packet is reconstructed and sent to UART 6, which converts parallel data into a serial bit string, which can be coupled to another PC. The voltage at the interface 4 is adjusted before being provided to the DCE port 2.

reset

Referring now to FIG. 2, the operation occurring in either the base device or the extension device when the power is turned on (block 22) is described. If the test of the device's SRAM 8 indicates that it is defective, no further operation occurs since the operation cannot be performed without the SRAM 8 operating correctly. In diamond type judgment block (hereinafter referred to as " decision block ") 26 it is determined whether something is coupled to the DCE port 2. As shown in Figure 1, if something (e.g. a PC) is coupled to the DEC port and the device is a base device BU, the modem 18 is ignored and the base device BU is the master slave. It must be set (block 28). The master bit of the DIPSW 1 shown in FIG. 8 is tested. When this switch is on (or set to the 'up' position), the corresponding master bit in the OPSTAT (operation status) register is set. Otherwise, the bit is cleared. Normally, the station apparatus EU is always set as the master device (the device which initiates the transmission) and the base device BU is set as the slave device (the device which is always in the following mode). Two BUs may be used for applications that do not require modem functionality. In such a case, one BU is set to 'master' and the other is set to 'slave'. If necessary, the BU (the serial port is selected) can be set as the master, and the other BU (the serial port is selected) or the station (EU) can be set as the slave.

As indicated in decision block 30, once a master setup has been made, the channel of the RF module 12 is scanned (block 32). The master device monitors the RSSI (Receive Signal Strength Indicator) of the individual RF channel for 100 ms. All ten RF channels 0-9 are scanned. The most quiescent channel is then selected. Thereafter, the master device monitors for transmission activity on that channel. If there is no transmission operation, the channel is selected for transmission. The timer of the MCU 14 is used for the channel scan timer handled by chscan_ to interrupt the service routine.

After the channel is selected, the packet non-receive (NPR) timer is activated (block 34). This forces the entry into the link setup procedure when the timer expires. The procedure of FIG. 7 is then performed. In block 36, appropriate registers of the Rx buffer and HDx (transmit or receive mode of operation) are set. At this point, the device enters the runtime loop RL shown in FIG.

In decision block 30, if it is determined that the device is not a master and is a slave, then in block 38 the baud rate of the UART 6 will be set, and then in block 40 the tracking timer will be started. This function is performed only on the slave device and consists of scanning the RF channel of the master device. For example, each channel is scanned for 20 milliseconds.

At decision block 26, if the DTR is inactive, a check is made at block 42 to see if the modem 18 is installed. If a modem has been installed, the device is configured as a slave in block 44 and executes modem Rx abort to prevent communication with this modem, then proceeds to block 36. If no modem is installed, the slave enable UART Rx abort is set in block 46, and the routine returns to block 28.

Execution time loop

After the setup routine is performed in FIG. 2, the radio link enters the continuously running runtime loop shown in FIG. 3. In decision block 48, a query is made as to whether an alignment byte has been received. Since there is no alignment byte at the end of the data packet, the absence of that alignment byte means that the data packet was received. If the alignment byte has been received, the RBUF of the service routine enters a step of storing data in the Tx buffer or the Rx buffer of the SRAM 8. This small loop is repeated until no alignment byte is received. If there is no indication of the alignment byte in block 48, then in block 50 it is checked whether an RF link has been declared. Declaring an RF link means that the handshake is complete and the RF link is ready to send data. If not declared, the procedure goes back to the beginning of the loop. However, if an RF link is declared in block 50, then it is determined in block 52 as to whether there is any data in the Rx data buffer of the SRAM 8. If there is data, the data is sent to UART 6 or modem 18, depending on what kind of operation should occur (block 54). The device can only be used by the UART 6 or modem of the base device BU from the receiver buffer when the DTR is active (e.g., a PC is not ready to connect to the port) and the link is 'up'. Advance the data to (18). The modem function is relevant only to the BU. Write / read to / from UART 6 or the modem corresponds to write / read to / from FIFO buffer of UART 6 or modem. After sending the data, the procedure returns to the beginning of the loop.

send

The data transfer is performed as shown in FIG. 4 beginning at block 56. Initially, any data in the TX buffer of SRAM 8 is transferred. Next, a check is made at block 58 as to whether a retransmission bit has been received from block 118 (shown in FIG. 7) requesting repetitive transmission. If a retransmission bit has been received, a pointer in the TX buffer of the SRAM 8 is restored at block 60, and if no retransmission bit has been received, data is read from the Tx data buffer at block 62. The Tx buffer pointer is stored at block 64 and a data packet is made at UART 6 as indicated at block 66. Data is copied from the transmission buffer of the SRAM 8 to the data portion of the packet buffer (register of the MCU). The number of bytes of the data packet is 0 to 72. Packet envelope is added. The envelope includes a packet header byte, a link control byte, a packet length (counted from the header byte of the checksum to the last byte), and a channel number / unit, i.e. bytes.

In block 68 a 16-bit platformer checksum is calculated and added to the end of the last data byte. The transmitted packet is preceded by 15 preamble bytes (0x00) and two alignment bytes (0x80). Five trailing bytes (0xff) are added at the end of the packet transmission.

In block 70 it is checked whether the RF link is established by a manual switch as a master device. Once set by the manual switch, the NPR timer is started at block 72 and the procedure shown in FIG. 7 and described below is performed.

FIG. 5 shows a flow diagram illustrating the steps of UART / modem abort handling service 102 to read data from either UART 6 or modem Rx FIFO at block 104. Until then, the buffer is empty, and writing is made to the Tx data buffer in block 106, and then returned to transfer initiation block 56 in FIG.

reception

Referring to FIG. 6 beginning at block 74, the routine monitors two consecutive alignment bytes (0x80). These bytes may not be properly aligned. The device reads and sorts the next 7 bytes of data in packets 6-78. If the packet length exceeds 6 (but less than 78), the device reads the remaining bytes from the SST and stores them in a packet buffer (a register in the MCU). When the header byte is received (decision block 76), as indicated in block 78, data is read from the SST Rx FIFO of the SRAM 8. In decision block 80 the validity of the data packet is checked. Decision block 82 checks the data to see if the address is the address of the receiving RF link. This is a program function of the MCV8 of the two devices for checking whether the link up or link down of the packet is set in order to prepare the transmission master device and the slave device. This function is forbidden to pick up adjacent transmissions. The link is declared at block 84 with light indicating that the RF link is ready to receive, and a check is made at block 86 to see if the master / slave switch is set to the slave position. If set to the slave position, the user can set the baud rate at block 88 via a combination of switches or software. In general, the bow rate is set to maximum. The NPR timer is started at block 90 (see FIG. 7), and at block 92, a link setup packet is set in the MCU 14 to request more data from the buffer. If it is determined in decision block 86 that it is the master, then data is transmitted in block 87 and enters the runtime loop of FIG.

In decision block 82, indicate that no link setup packet is received, and if the data packets are received in order in block 94, the data packets are written to the Rx data buffer of the SRAM 8 and sent to block 100. . If the determination result from any of the decision blocks 76, 80, and 94 is NO, the procedure returns to the execution time loop of FIG.

7 illustrates an NPR / channel tracking timer abort handling routine for a master and a slave. If the two data links are " up " as determined in decision block 110, ie there is a handshake between them, then the time out counter is read in block 112. The time out counter starts counting when it stops transmitting. When each data packet is sent, the timeout counter starts executing, and when the last or trailing byte of the message passes, the clock is set back to '0'. Thus, if the counter is not '0' at decision block 114, it means that the data packet was not completely transmitted, in which case the retransmission bit is sent back to the transmitter. This is the reset bit mentioned in decision block 58 of FIG. 4 describing the transfer. After doing this, the procedure returns to decision block 110.

The time out counter is maintained and used by the master device and the slave device to declare link down. The value of the counter is different for the master and slave devices. That is, 10 and 1 for the master and slave devices, respectively. In addition, the value of the No-packet received (NPR) timer is different for the master and slave devices. That is, 50 ms and 1000 ms for the master and slave devices, respectively.

In the master device, if no valid data packet is received from the slave device within 50 ms after sending the data packet, the master device retransmits the data packet. Ten consecutive terminations of the NPR timer declare a link down and the master device re-enters the channel scan process. The counter is reloaded each time a valid data packet is received. The value of the NPR should be sufficient to cope with the longest data packet. The data packet length varies from 6 to 78 bytes except for the preamble, alignment, and back bits.

Since the slave device is always in following mode, i.e. cannot initiate data packet transmission, only one NPR termination is sufficient to declare the link down. The value of the NPR is selected to cover the total time that the master device attempts to receive a response from the slave device by retransmitting a data packet, i.e. 10 x 50 ms. After declaring a link down, the slave device becomes " plays dead " for another 1000 ms in order for the master device to declare a link down and start link setup again. Note that the mechanism is not used during the link setup process. This is because the master device will continue to send link setup unless there is a response from the slave device.

However, if it is indicated in decision block 114 that the timeout counter is again '0', this means the end of the transmission to the master device and the slave device, but it is determined whether the master and slave device are master or slave. It will stay in handshake mode until it is determined by. If so, the SST 10 scans the channel at block 117 as indicated at blocks 32 and 34 of FIG.

On the other hand, if it is determined in block 116 that the RF link is a slave rather than a master, then in block 126 the master is instructed to declare the link down, i.e. to declare transmission termination for the master device and the slave device, The master and slave devices remain in handshake mode. In block 128, the available channels are found. These channels are used in DSS mode at block 124 where a tracking timer is started to send data in order on the available channels.

If it is determined in decision block 110 that the link between the RF devices is not set up correctly, that is, it is determined that the link is not up, and in decision block 120 that it is not a master device but a slave, then in block 122 the same method as in block 124 Examine the available channels. If the decision block 120 indicates that it is the master device, then a data packet is sent in block 126 and the NPR timer is started in block 128.

In describing the schematic diagrams of FIGS. 8 to 13, it should be understood that the specific microchip designated only represents one example that is available. The chips are denoted by their "U" number and acronyms.

8 is a schematic diagram of a main processor in which MCU 140 is U ₄ . As in block 24 of FIG. 2, the pattern for testing the SRAM 8, ie U ₆ , and the response of the SRAM, ie U ₆ , is carried by the data path 130. A switch that provides the RF link identification, the baud rate, and the result of the determination as to whether the device is a master or a slave is indicated by reference numeral 132, and through the buffer 134 and the data path 136 the MCU (U _4). ) Pins 136. The oscillator 138 provides RF to the GFSK transceiver 142 of FIG. 10 via the SST chip 141 and the leads 144 and provides ten RF channels to the antenna 145 of FIG. As those skilled in the art will know how to implement the present invention, not all connections will be described herein.

9 is a schematic diagram showing UART 6 as U ₁₀ and RS-232 interface processing 4 as 146. The DCE com port 2 is indicated by the reference numeral "148", and the LEDs indicating the various operating states are indicated by the reference numeral "150".

FIG. 11 is a schematic diagram showing a power source 152 and an extension device power source 154 used for the base apparatus as shown in FIG.

12 and 13 are schematic diagrams of a modem 18 that allows an extension device to communicate with the Internet. The modem consists of U ₁₈ and U ₁₈ and has a jack 154 for coupling to a telephone line.

Those skilled in the art will understand that other embodiments of the present invention may be made or modified variously based on the above description. Therefore, this description is for illustrative purposes only, and to teach those skilled in the art how best to carry out the invention. The details of the above embodiments can be changed without departing from the spirit of the invention, and exclusive use of all modifications covered by the appended claims is assured.

Claims (7)

A first device and a second device, The first device, Means for coupling to and receiving data from the computer, Means for encoding the received data and transmitting the received data using a digital wireless transmission form, And said second device comprises means for receiving data transmitted from said first device in said digital transmission form and processing said transmitted data in analog form for transmission over a wireline telephone network. The wireless modem system of claim 1, wherein the received data is transmitted to the second device using the digital radio transmission form on a selected one of the available channels. The wireless modem system of claim 1, wherein the second device further comprises a modem for further processing the received transmission data in analog form. 4. The wireless modem system of claim 3 wherein the modem receives and demodulates an analog signal from the wireline network. A first device and a second device, wherein the first and second devices, respectively, A port for receiving serial data, Signal conversion means coupled to the port for converting serial data provided on one side of the port into parallel data; With a transmitter buffer, Receiver buffer, Control means for generating a data packet from data generated from the signal conversion means; Means for coupling the data packet to the transmitter buffer; A transceiver having a plurality of channels, Means for providing data in the transmitter buffer to a selected channel of the transceiver in a repeating sequence; Means for storing a data packet received by the transceiver in the receiver buffer, And said control means forwards the data packet of said receiver buffer to said signal conversion means. 6. The apparatus of claim 5, further comprising means for scanning channels of the transceiver to identify a clear channel, The channels are used as the selected channel. 5. The apparatus of claim 4, further comprising: manual control means for selectively setting an address of the apparatus in each of the first and second apparatuses; Manual control means for setting an address of another RF device in each of the first and second devices; Means for writing the address of the device and the address of the other device in the first and second devices into transmitter buffers of the first and second devices; Means for comparing the received address of the other device with a known address of the other RF device in response to receiving its own address at the first and second devices; Means for performing further communication if the compared address is the same.