TW515196B - Method and apparatus for supporting analog fax calls in a tandem configuration - Google Patents

Abstract

The present invention provides an apparatus and method for supporting analog fax calls between two wireless subscriber stations in a tandem configuration. The existence of a tandem configuration is detected, and a more efficient communication protocol is established between two base stations upon detection of the tandem configuration. A message generator in a first base station generates an identification message. If the identification message is received by a second base station, the second base station will be informed that the tandem configuration exists. A message generator in a second base station may then generate a return message, which when received by the first base station, will notify the first base station of the existence of the tandem configuration. To support the tandem configuration, full duplex communication may be established between the two base stations. Full duplex communication may be realized by incorporating an echo canceler in the base station, or by utilizing both BFSK channels of the V.21 fax system for communication. The tandem configuration may also be supported by advanced flag synchronization. Thus, after a message is transmitted from a first base station to a second base station, the second base station will immediately start sending preamble flags to the first base station. The first base station may then synchronize its receiver for immediate receipt of the return message from the second base station.

Description

515196 V. Description of the invention (1) Background of the invention I. Scope of the invention The invention relates to data (data) transmission. In particular, it relates to a device and method for analog fax support between two wireless subscriber stations (mobile phones) in a tandem (t a n d e m) configuration. I. Related technical description In a facsimile communication system, two facsimile machines usually transmit to each other via a standard public switched telephone network (PSTN) path. Digital communication systems or satellite lines can also be incorporated into this facsimile system to extend coverage and increase the mobility of these communication devices. An exemplary digital communication system that can be used in combination with a facsimile communication system is a terrestrial wireless system or a satellite communication system. In wireless mobile and wireless LAN circuits, a tandem configuration is established when a call is transmitted from a wireless U user to another wireless user via the PSTN. In this configuration, the base station usually does not know that it is communicating with another base station across the PSTN. Tandem configurations may be necessary for several reasons. The base station that is communicating with one user first may not know that the other user is also a wireless user. Therefore, the second base station must provide a link line to another user. The same two base stations need to be used because the two wireless users may not be in the same coverage area of either base station. In addition, for billing purposes, this call should be routed through PSTN (including the billing center). Although it is necessary for wireless users in Nexus 2, tandem configurations can degrade performance. For voice calls, the voice quality is deteriorated due to multiple codecs. Codecs are generated when the voice signal is sent from the user unit to the base station and sent to the receiver.

O: \ 55 \ 55424.ptd Page 7 V. Description of the invention (2) Base stations and user units with increased delay = this increase. For facsimile calls, the processing performance between two fax machines = base station is reduced due to errors. °, delay characteristics are ^ ~ standard PSTN path transmission path quality and delay are derived from thermal = and manageable. However, in the tandem configuration, the processing delay is the digital # processing and transmission delay. The extra multiplexing process is generated when the station combines with signals from many communication devices or it will become a long I, two transmission ## each. The final total delay will be through unannounced and unpredictable. Understanding delay-related = ϊ Γ knows the relevant processing can better understand the source of the delay and the facsimile communication system. For a standard Gr0uP group 3) Recommendation τ = 5, the timing and synchronization between fax machines is the same as " m 令 杜 彳 # 吉 # is the International Telecommunications Union): In the general switched telephone network, it is clear: I ,, (hereinafter referred to as the T.30 fax agreement, the magic first issue 1) ,. The T.30 fax protocol utilizes some modulation techniques for the transmission of forwarded information. In particular, the parameter negotiation and signal transmission between fax machines are used in "CCITT Recommendation V. 21CCCITT is the International Telephone and Telegraph Advisory Committee): 300 bps (bits per second) for general switched telephone network (GSTN) ) Two-way modem standard π (hereinafter referred to as V · 21 and one of the references of the present invention) to complete. Handshake establishes a suitable way for communication between facsimiles. For a T · 30 facsimile system, A V · 2 1 message is sent between a calling fax machine and a called fax machine when a call is established. A calling fax machine initiates a call by dialing the called fax machine and sending a call tone (CNG). The called fax machine detects the incoming call and sends back the called station identification tone (CED)

O: \ 55 \ 55424.ptd Page 8 515196 V. Description of the invention (3) On the calling fax machine. The called fax machine then sends its digital identification signal (D I S) to the calling fax machine to inform the calling fax machine of its capabilities (c a p a b i 1 i t y). When the D I S signal is detected, the calling fax machine sends a digital command signal (D C S) to inform the called fax machine of its ability to calculate the daytime usage. In addition to the above initial signals, other messages are also generated between the fax machines in the call. For example, sending signals, information messages, and termination messages are also typical fax calls. According to T. 3 0, whenever a fax machine sends a V · 2 1 message, it must first send out-a preamble with a length of one second. The previous sync signal contains a string of V. 2 1 flags. This flag is used to inform the receiver that a message will be sent and to enable the receiver to synchronize correctly so that the actual message can be properly received. Money ’Even if synchronization is required, the preamble delays the message by at least one second. Tandem configurations can further increase delays. Both the preamble and the message must be transmitted over the PSTN, and the additional processing delays associated with the transmission can cause unacceptable delays. In addition, this additional delay will cause the previous call to hang up. Delays due to tandem configurations can also cause message collisions. Message collision occurs when a message and a response signal are transmitted simultaneously. The T.30 fax protocol details the message sequence and format of messages such as CNG, CED, DIS and DCS messages. To address unfavorable access conditions, the T.30 agreement requires that unanswered messages from the source fax machine be repeated. The source fax machine can ask the calling or called fax machine. After the source & machine sends a message to the destination fax machine, the source fax machine expects a response from the destination fax machine within a certain period of time.

O: \ 55 \ 55424.ptd Page 9 515196 V. Description of the invention (4) If no response signal is received within a certain time, the source fax machine will retransmit the message. This retransmission will not stop until a response signal is received from the destination fax machine or excessive attempts have been made. According to the T.30 facsimile agreement, the repetition period of the facsimile operation in the automatic mode is 3.0 seconds ± 0.45 seconds. This means that a fax machine that complies with the T. 30 fax agreement will not resend the message within 2.5 5 seconds of the previous message. Therefore, if such a fax receives a response signal within the shortest repetition period of 2.5 seconds, no collision will occur. But transmission delays in long communication paths can cause message collisions. In some cases, the source fax machine will send a message to the receiving fax machine, and the destination fax machine may not respond immediately due to transmission delay. This delay may be due to the extra time required for the base station to facsimile the wireless attack. Because the source fax machine did not receive the response signal in time, it will retransmit the message. The source fax machine will resend this message approximately every three seconds. At the same time, the destination fax machine may send a response signal. If the arrival time of the response signal from the destination fax machine is the same as the retransmission time of the source fax machine, a message collision situation will occur, and the response signal will not be received by the source fax machine. Collision of messages may cause the fax to abort the call. The possibility of excessively long delays and message collisions in a tandem configuration must be discussed for facsimile machines in networks that involve more than PSTN for stable operation. SUMMARY OF THE INVENTION The present invention is an apparatus and method for supporting analog facsimile calls between wireless subscriber mobile stations in a tandem configuration. Tandem configurations are created at every

O: \ 55 \ 55424.ptd Page 10 515196 Case No. 90104920 V. Description of the invention (5) The detection of the line user and the base connection, and the detection of the signal transmission connection configuration. The non-stand message is sent out and there is a tandem set in the facility which is the first to return the message facility s. The delay is detected. Road. Generally, the fax machine can establish industrial communications between the base stations can be borrowed. The base station is full dual Workers can also agree to transmit [transmission on Road 2 and let the amendments supplement 11λ when the base station connection must be processed by two base stations. A delay is caused by the two base stations via PSTN through wireless processing. This The invention facilitates the tandem setting and can establish a more efficient communication protocol between the two base stations by conducting a survey. It is clear that the message generator in a first base station generates a message that is identified as a base station. Non-standard equipment (NSF), which is usually familiar to advertising machine manufacturers, can be used for this purpose. If received by a second base station, it means that the second base station is notified of the storage. The second base station can then send a return message, and when it receives it, it will notify the first base station that the tandem settings are stored. It can be a non-standard equipment establishment (NS-S) message. During tandem configuration, a faster communication protocol will be established. In one embodiment, the two base stations can establish a full-duplex communication message. The fax machine operates in half-duplex mode and operates in half-duplex. Receive or transmit messages, but not both. Full-duplex communication on two bases will reduce latency in tandem configurations. Full duplex is achieved by a combination of an echo canceller and a base station modem. It can be built to receive incoming messages and send messages simultaneously. This is achieved by using alternative paths for reverse transmission. Although V. 2 1 dual channel is provided, the standard T. 30 V. 2 1 message is only available for communication > full duplex communication is available by having one base station on one channel and the second base station on the second channel The way of transmission is reached.

55424-911025.ptc Page 11 515196 V. Description of the Invention (6) In another embodiment, the delay can be reduced by providing advanced flag synchronization methods. Under the T. 30 protocol, a 1-second preamble is sent before each message is sent. The previous sync signal contained a series of V. 2 1 flags. According to the current procedure, after the message is sent from the first base station to a second base station, the second base station will forward the message to the fax machine and wait for a response from the fax machine. After the fax machine sends a reply message (after the preamble), the second base station then sends the reply message (after the preamble) to the first base station. The invention recognizes that tandem delay can be achieved by having the second base station transmit the preamble signal immediately after receiving the message, rather than having the second base station wait for a response signal from the facsimile machine. Therefore, if the second base station acknowledges the received message and confirms that it is waiting for a response signal, it immediately starts transmitting the V. 2 1 flag to the first base station. Although the reply message from the facsimile machine is not ready, a flag generator in the second base station will generate a flag signal transmitted via the second base station. When the message is ready, the reply message from the fax machine will be sent via the second base station. In this way, the first base station can begin to synchronize its V. 2 1 receiver early to reduce latency. In addition, the first base station will not repeatedly transmit its message as requested by T.30. Below T · 30, the message will be repeatedly transmitted until a response signal is received. The first base station reduces the possibility of collisions by eliminating the need to repeatedly send messages. Brief Description of the Drawings The present invention will make it easier to understand the features, capabilities, objectives, and advantages after cooperating with the drawings and the detailed descriptions provided below. The same reference code for each drawing indicates that the objects referred to are the same, of which:

O: \ 55 \ 55424.ptd Page 12 515196 V. Description of the invention (7) Figure 1 is a block diagram of a typical facsimile communication system; Figure 2 is a facsimile incorporating a wireless communication system in a tandem configuration Block diagram of a communication system; Figure 3 is a block diagram of a processing element in a base station to support facsimile calls in a tandem configuration, and Figure 4 is a diagram illustrating transmission between a fax machine and the base station for detection. Message flow chart for measuring tandem configuration; Figure 5 is a block diagram illustrating a processing element for establishing full-duplex communication using an echo canceller; Figure 6 is a block diagram illustrating full-duplex communication using two BFSK paths Figures; and-Figure 7 is a flowchart illustrating some of the steps involved in supporting advanced flag synchronization for tandem configurations. Detailed description of a suitable embodiment Figure 1 illustrates a typical facsimile communication system. In this facsimile communication system, a facsimile machine A 50 communicates with a facsimile machine B 52 through a public switched telephone network (PSTN) 54. The communication path connecting fax machine A 50 and fax machine B 52 to PSTN 54 is generally a standard RJ-11 interface. The characteristics and delays of RJ-11 and PSTN 54 are defined and explained in detail in the T.30 fax agreement. Wireless communication systems can be combined with facsimile communication systems. Fig. 2 illustrates an example of a facsimile system using wireless communication. In Figure 2, the fax machine 彳 n A 60 and the wireless subscriber unit A62 are generally through the RJ-11 interface. The wireless user unit A 6 2 can be like a fixed wireless terminal (F i X e d W i r e 1 e s s

O: \ 55 \ 55424.ptd Page 13 515196 V. Description of the invention (8) T r r m i n a 1, F W T) wireless telephone or other wireless user equipment. Wireless subscribers, including mobile phones and FWTs, are often referred to as Wireless Access Subscriber Units (WASU). The communication between the user unit A 62 and the base station A 64 communicates via a wireless communication channel: This wireless channel can be a ground wireless link (1 ink) or a satellite link. In a wireless system, signals can be modulated according to formats such as code division multiple access (CDMA), channel division access (TDMA), or frequency division multiple access (FDMA). = The CDMA modulation format is used in the examples given. The relevant description can be found in the US patent ^ U 9 U 2 I, f is " spread spectrum multi-subsidiary system using satellite or ground amplifier ", this The text is the research object of the present invention and is used for the present invention. In order to achieve the objective of the present invention, the base station A 64 receives a signal from a wireless user eV, a certain frequency, a frequency, a frequency, and a frequency, and adjusts it, and will Data is sent to the PSTN unit A 6t I choose the future 1 PSTN 66 messages are forwarded to the wireless user body can be connected to a place ^ quasi ^ 1 "1 line or any similar transmission medium J base 66 and J platform B The communication of 68 is through% of the T1 / E1 line, so the wireless user unit B 7 ° is located in the hive where there is no ground. M: B, 2 = wireless user unit B 7 0 The communication is through the home unit β 7 The wireless communication path of the 0 i transmission straight or Hesheng link. The wireless connection. The real machine B 7 2 is generally connected via the RJ-1 1 interface due to the wireless use $ w, A ... ^ The user's early position A 6 2 and Handling between base stations a 6 4; base

515196 V. Description of the invention (9) The communication between base station A 6 4 and base station B 6 8 is via PSTN 6 6; and the processing between wireless subscriber unit B 70 and base station B 68 will introduce errors and delays. Degraded performance. The present invention is concerned with reducing these errors. The configuration shown in Figure 2 is the so-called tandem configuration. In a tandem configuration, wireless processing and transmission delays can cause performance degradation. In addition, a facsimile communication protocol between base stations connected via the PSTN may cause a delay. The invention uses this information to detect a tandem call to establish a faster communication protocol between base stations. In a more suitable embodiment, the base station detects a tandem configuration using the processing element shown in FIG. 3. The base station uses the same frequency band to detect the tandem configuration. Co-band messaging refers to the transmission of information and messages related to facsimile calls directly, as opposed to out-of-band messaging, which involves indirect transmission of data and information about facsimile calls. Referring to FIG. 3, the message processors 80a and 80b know the existence of the tandem configuration by using the same-frequency signaling method. As mentioned above, some messages are transmitted between the calling and called fax machines when a fax call is established. The calling fax machine sends a CNG message to the called fax machine that responds with a CED message. The called fax machine sends a D I S message to the calling fax machine to identify its capabilities. In addition to D I S, the called fax machine can also set up a non-standard equipment (NSF) message to the calling fax machine (before sending out D I S). NSF is a T. 30 message used by a facsimile machine to reveal details of non-standard equipment to the manufacturer. If the calling fax machine recognizes the NSF, it can respond with a non-standard device setup (NSS) message. If the calling fax machine does not recognize N S F, it will send a DC message. N S F and N S S messages are generally used to identify and transmit non-standard information between two fax machines of the same manufacturer for the benefit of

O: \ 55 \ 55424.ptd Page 15 515196 V. Description of the invention (ίο) Material treatment. When you know that you are a fax machine from the same manufacturer, you can take advantage of special features. The present invention does not use NSF and NSS to identify non-standard equipment, but determines the existence of a tandem configuration by identifying these messages that are available to the base station. Comparing Figure 3 with Figure 2, the detection of the tandem configuration can use the fax machine A 6 0 as the calling fax machine, the base station A 6 as the calling base station, and the fax machine as the called fax machine. Explain B 7 2 and base station B 6 8 as the called base station. Fax machine A 60 initiates a call by sending a CNG message to fax machine B 72. Fax machine B 72 responds by sending a CED message to fax machine A 60. The messages are transmitted through wireless subscriber units 62 and 70, base stations 64 and 68, and PSTN 66. Fax machine B 72 then sends a D IS message, and it can also send a selective NSF message at the same time. Generally, a selective NS message is sent before a DS message. These messages are transmitted wirelessly by the wireless subscriber unit B 70 and received by the base station B 68. Base station B 68 sends a special NSF message to base station A 6 4 via PSTN 66 after the DIS message. After base station A 6 4 receives a special message, it will recognize that it is talking to a base station and knows that a tandem situation exists. Base station A 6 4 then sends a special N SS message instead of DC message to notify base station B 6 8 of the tandem situation. If there is no tandem configuration, the called base station will still send a special NSF through the PSTN. At the other end of the PSTN, however, are standard fax machines rather than calling base stations. In this case, the standard fax machine will not recognize that this special NSF is from the base station and will not respond with a special NSS. Take

O: \ 55 \ 55424.ptd Page 16 515196 V. Description of the invention (for the 10th generation, the standard fax machine will use the capabilities provided in the standard D] [S message to select this barking parameter. In the embodiment, the base stations 64 and 68 use the message processors 8 0a and 8 Ob shown in FIG. 3 to process special NSF and special NSS messages. At the base station B 6 8 and the transceiver 8 2 b, reception has been performed by fax ]) I s message sent by the machine β 7 2. In addition, the transceiver 8 2b may or may not receive NS messages from the fax " machine B 7 2 ". In any case, when the controller 8 4 b confirms that it has received a d 1 s message, it will cause the message generator 8 6 b to generate a special nsf message. The controller 8 4b then causes the transceiver 8 2b to simultaneously transmit the D S message and the special N S F message generated by the Δ interest generator 8 6 b. Special n s F and D I S messages are transmitted to base station A 6 4 via PST N 6 6. — On base station A 64, transceiver 82a receives special NSF and DIS messages. When recognizing a special NSF message, the controller 84a will be informed of the existence of a tandem configuration and can generate a speed communication protocol between the base stations. The controller 84a causes the transceiver 82a to transmit the D IS message to the facsimile machine 60. The facsimile machine A 60 then responds with a DCS message, and this message is sent to the transceiver 82a through the wireless subscriber unit A 62. The controller 84a generator 86a uses the information in the DCS message to generate a suitable special message. The controller 84a also commands the transceiver 82a to transmit the special PSTN 66 to the base station B 68. The heart is exposed on base station B 68, and the transceiver 82b receives this special NSS signal and when it recognizes the special NSS message, the controller 84b will be notified of the existence = knee f configuration and can generate an intervening base Faster communication protocol between stations. = $, 8 4b will also direct the message generator 86b from the special NSS%

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515196 V. Description of the invention (12) DCS information and generate a related DCS message. The controller 84b then sends the command transceiver 82b to the fax machine B 72 via the wireless subscriber unit 70. The operation of the flag generators 88a and 88b will be explained later. It should be understood that various processing blocks of the message processors 80a and 80b shown in FIG. 3 may be configured in a digital signal processor (DSP) or an application specific integrated circuit (AS I C). The functional description of the present invention will enable people with ordinary skills to perform the present invention in a DSP or "10" without formal experimentation. In the embodiment just mentioned, the last name is used to identify non-standard equipment. Because of this, NSF and special NSS messages are not non-standard equipment functionality. JF messages can be used to identify tandem configurations. These messages can be designed to be unavailable at the same time. The alternative is- Detection of drum connection conditions and non-standard settings f In one embodiment,

Special NSF and NSS messages that still do two functions with reference to Figures 3 and 2 also send NSF f fans in addition to DIS messages. If the fax machine B 72 will generate a special NSF breath during transmission to the base station B 6 8, then the base station B 6 8 8 6 b generates a fax containing: from the controller 8 4 b will make the message generator The original NSF message in. The special 'B 72' is concentrated on the special NSF message platform A 6 4. When the NsF hand of base station A sends base station b 6 8 to base controller 84a, it will be able to identify the sink and 64 receivers owe a special NSF message. The manufacturer code and other special The generator 8 6 a can be customized in the condensed message followed by special information & manufacturer parameters. The base station a 6 4's message sender 8 2 a extracts the concentrated SF information from the removed message,%, and f, and receives the facsimile machine A 60 as an NSF message. need

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515196 V. Description of the invention (13) Note that the extracted message is the original NSF message sent by fax machine B 72.

II If the facsimile machine A 6 0 recognizes the NS message, it can respond with the NS message forwarded to the base station A 6 4 via the wireless subscriber unit A 6 2. The message generator 8 6 a of the base station A 6 4 will condense the N S S message into a special n S S message, and the special N S S message will be sent to the base station B 6 8. When a special NS message is received, the controller 8 4 b of the base station B 6 8 will recognize that a tandem configuration exists. In addition, the message generator 8 6 b of the base station B 6 8 will extract the concentrated NS message, and the transceiver 8 2 b forwards this message to the fax machine B 7 2 through the wireless subscriber unit B 7 0. The wireless subscriber unit B 70 receives the NS message and can identify the specific manufacturer parameters in the message. This makes use of non-standard equipment. It should be noted that the taken out NS message is the original NSS message sent by the fax machine A60. In another embodiment, the ability to detect tandem conditions and identify non-standard equipment is supported by transmitting a new message other than the original NS or NS message. Therefore, after the transceiver 8 2 b of the wireless subscriber unit B 6 8 receives the NSF message sent by the fax machine B 72, the message generator of the base station B 68 will generate a new N SF message containing the original NSF message followed by it. A special N sF message. The special NSF message will serve to inform base station A 6 4 of the existence of the connection. The original NSF message, but not the new NSF message, is transmitted to Facsimile A 60. If facsimile machine A 60 recognizes a special NSF message, it can respond with an NSS message that is forwarded to base station A 64. The base station A.64's message generator 8 6 a will then generate a special NS message. This message contains a

O: \ 55 \ 55424.ptd Page 19 515196 V. Description of the invention (14) The original NSS message follows the new NSS message. Special NSS messages are transmitted to base station B 6 8. When a new NSS message has been received in the special message, the controller 84b of the base station B 68 recognizes that a tandem condition exists. Furthermore, the original NSS message is transmitted to fax machine B 72, and fax machine B 72 recognizes the specific manufacturer parameters in the original NSS message. In this way, the functionality of non-standard equipment is preserved while special NS F and special NS messages are also used to identify the presence of tandem conditions.

Referring now to FIG. 4 and referring to FIG. 2, the flowchart shown illustrates a message flow that is used to determine the presence of a tandem configuration. The message was sent to fax A

60 (calling fax machine), wireless subscriber unit A 6 2, base station A 6 4, base station B 6 8, wireless subscriber unit B 7 2 and fax machine B 7 2 (called fax-machine). A CNG message is transmitted from facsimile machine A 60 to facsimile machine B 72 via wireless subscriber unit A 6 2, base station A 6 4, base station B 6 8 and wireless subscriber unit B 70. In response, a CED message will be transmitted from fax machine B 72 to fax machine A 60 through wireless subscriber unit B 70, base station B 68, base station A 64, and wireless subscriber unit A 62. Fax machine B 72 also sends a DIS message, and may or may not send an NSF message. The optional NSF message is shown in Figure 4 as the n (NSF) n character. Selective N SF and D I S messages are received at base station B 6 8. The D I S message is transmitted to base station A 64. In addition, a special NS message is sent to base station A 64 regardless of whether the NSF message is received at base station B 68. This special NSF message can be combined with the original NSF message sent from fax machine B 72. A special NSF message will notify base station A 64 that a tandem situation exists0

O: \ 55 \ 55424.ptd Page 20 515196 V. Description of the invention (15) After the base station A 6 4 received the special NSF and DIS messages, the fake original NSF messages were combined into the special NSF messages Will be removed. The retrieved NSF message and D I S message are then sent to the fax machine A 60 through the wireless subscriber unit a 62. If the original NSF message is not combined in a special NSF message ’, only the D I S message will be sent to the fax machine A 60 through the wireless subscriber unit a 6 2.

In response to the DIS message, the fax machine A 60 will send a DCS or NSS message (characters marked " NSS / DCS in Figure 4). If a DCS message instead of an NSS message is transmitted from the fax machine A 60 to the base station a 64, then the base station A 64 will combine this poor information into a special NSS message and send this special message to base station B. 68 on. This special NSS message will tell base station B 68 that there is a connection. When the base station B 6 8 receives this special NS message, it will take out the combined DCS information and send the relevant DCS message to the special machine B%. If the NSS message is sent from the fax machine a 60, the base station a 64 will also send a special NSS message to the base station b 68. This special like message can be here and there. Combined with original NSS information. A special NSS message informs the straight-through machine B 68 = Tandem condition exists. When base station B 68 receives this special message, it will retrieve the original NSS information and send the retrieved Nss message to fax machine B 7 2. Although the above mentioned use of NSF and NSS messages to detect tandem conditions, those who understand the technology should be able to agree that similar characteristics can also be used for tandem situations. Other embodiments may use special tones to indicate tandem conditions. For example, base station B 6 8 can send a special tone that does not interfere with standard V.21 signals. Base station A 64 will use 21 solutions

515196 V. Description of the invention (16) The detector operated in parallel by the modulator to detect this special tone and identify the connection condition accordingly. Once a tandem call is detected, the two base stations can establish a more efficient communication protocol. For example, the base station can communicate more effectively by establishing a full-duplex link. In general, when a fax machine is operating in half-duplex mode, the messages in it can only be sent or received at any given moment, but not both. Therefore, the fax machines must take turns before sending messages to each other. Although this is a simple and early agreement, it is relatively slow because it usually involves waiting for a clear channel. By establishing full-duplex communication, messages can be transmitted between base stations without waiting, and delays due to tandem settings can be reduced. In one embodiment, full-duplex communication can be achieved using an echo-canceller in the base station. This is similar to how a full-duplex modem operates. See Figure 5 for how to use the echo canceller to perform full-duplex communication. In Figure 5, the echo cancellation system is included in base station A64. It is important to know that base station B 68 also includes a similar echo cancellation system. Referring now to FIG. 5 and referring to FIG. 2, a message from the wireless subscriber unit A 6 2 is received on the transceiver 8 2 a and sent to the message controller 9 2 a. The message controller 92a forwards this message to the V. 21 modulator 94a. The modulator 94a modulates the message according to the V. 21 standard to be transmitted to the base station B 6 8 through P ST N 6 6. The modulated message is also sent to an echo canceller 96a. Because PSTN 66 is not a perfect path, the signal from the V. 21 modulator 96a is transmitted through the echo path 9 8 a, and the echo of the signal may be sent back to the base station A 6 4. If the signal is also sent from the base station B 68, the echo will be added to the signal from the base station B 68 at the adder 100a to generate a composite signal. Close

O: \ 55 \ 55424.ptd Page 22 515196 V. Description of the invention (17) The signal was received at base station A 6 4. It should be understood that the echo path 9 8 a and the adder 1 0 0 a are not internal components of the communication system but artificial traces in the system and are only for convenience of understanding. The synthesized signal received at the base station A 6 4 is sent to an echo canceller and an adder. The echo canceller 9 6 a subtracts the echo of the V. 2 1 signal from the synthesized signal. Using adaptive filtering and wave technology, the echo canceller will generate an estimated value of the echo and send the estimated value to the adder 10 2 a. At the adder 10 2a, the echo estimate is taken from the received signal so as to be able to provide an echo canceled signal. Exemplary types of echo cancellers can be found in US Patent No. 5,307,405, which is called π network echo canceller π. This article is one of the research objects of this invention and is the subject of this article. reference. – The echo cancellation signal is transmitted to a V. 21 demodulator 104a. The V. 21 demodulation / transformer 1 0 4 a demodulates the echo cancellation signal into data bits, and the demodulated signal is sent to the message controller 9 2 a. The message controller 9 2 a sends the signal out of the transceiver 8 2 a, and the transceiver 8 2 a sends the signal to the wireless subscriber unit A 6 2. With the echo canceller incorporated in base station A 64, the V. 21 modulator can send a signal when it is received by the V. 21 demodulator 104a. It is not possible to achieve full duplex without echo cancellation 9 6a because the signal echo from the V. 21 modulator 94a destroys the signal received by the V. 21 demodulator 104a '. By combining the echo canceller 9 6 a, the signal echo transmitted from the V. 2 1 modulator 9 4 a will be cancelled, allowing the V. 2 1 demodulator 1 0 4 a to receive the signal from the base station B. 6 8 signal without distortion of the echo. The echo canceller of base station B 6 8 operates in a similar manner. Therefore, base station A 6 4 and base station B 6 8 can transmit messages to each other at the same time without a message collision to reduce the message delay.

O: \ 55 \ 55424.ptd Page 23 515196 V. Description of the invention (18) In another embodiment, full-duplex communication is achieved by using the alternative path reverse transmission method. The V. 21 fax protocol has provided two Binay frequency shift keying (BFSK) paths, Path 1 and Path 2. For each channel, the transmitter uses one frequency representing '0' for the binary and the other frequency representing '1' for the binary. Although two channels 1 standard T. 30 V. 21 messages are provided on channel 2, channel 1 is not used. Both channels can be used simultaneously as long as the receiver is properly tuned to the correct frequency. _ In an example case, two base stations (base station A 6 4 and base station B 6 8 in FIG. 2) begin to communicate on the conventional V. 2 1 channel and channel 2. When the called base station receives the NSS, it will recognize that a tandem situation exists. In addition, it will interpret the NSS message as the calling base station can receive on the channel. The called base station then sends a message on the channel and receives the incoming message on channel 2. The calling base station operates in reverse. Fig. 6 illustrates a situation in which the calling base station (base station A 6 4) and the called base station (base station B 6 8) use both channel 1 and channel 2 to communicate. Because the transmission of messages on different channels is not disturbed by this, the base station can send messages without waiting and thus reduce the delay of the tandem configuration. When detecting the presence of a tandem configuration, the two base stations can be synchronized to reduce latency. As discussed above, the T.30 protocol requires a 1-second preamble before the actual signal is transmitted. The preamble contains a string of V. 21 flags. The V. 21 flag is a byte with the value of Ox7E. When the flag is received, the receiving fax machine is notified that a message will follow, and the receiving fax machine is notified that a message will follow, and synchronization starts.

O: \ 55 \ 55424.ptd Page 24 515196 V. Description of Invention (19) The message can be received properly. The problem with preambles is that they delay the message. Actual message data will be at least 1 second slower. The other delay comes from wireless processing and transmission in the tandem configuration. In addition, collisions are likely to occur. If the transmitting base station does not receive a response signal from the receiving base station within 3 seconds, the transmitting base station will resend the message every 3 seconds. At the same time, the receiving base station may be responding. Because the fax machine operates in half-duplex mode, collisions can occur.

The invention can reduce the delay caused by the tandem configuration and can reduce the possibility of collision caused by the delay. Referring back to FIG. 3 and referring to FIG. 2, the base station can perform advanced flag synchronization to resolve delay and collision issues. If it has been found that there is a tandem configuration. Suppose also that fax machine A 6 0 is sending a message to fax machine B 7 2. This message is sent from fax machine A 60 to base station A 6 4 and base station A 6 4 will later send this message to base station B 6 8. The message is transmitted via PSTN 66. After the base station B 68 receives this message, if the controller 8 4 b recognizes this message and knows that the base station A 6 4 is waiting for a response, the controller 84b will cause the flag generator 88b to start generating the V. 21 flag immediately. . The controller 84b also causes the transceiver 82b to immediately begin transmitting these V. 21 flags to the base station A 64. Base station B 6 8 has not received actual responses from fax machine B 7 2 but has started transmitting these flags. # Sending a flag immediately after receiving a message serves two purposes. First, base station A 6 4 was informed that base station B 6 8 had correctly received the final message, so base station A 6 4 should not resend this message as requested by T. 30 and thus avoid a potential collision situation . Secondly, base station A 6 4 can start the alignment as soon as the flag is received.

: O: \ 55 \ 55424.ptd Page 25 515196 V. Description of the invention (20) The V. 2 1 receiver is synchronized, which can greatly reduce the delay. Base station A 6 4 should also not have excessive interruption flags as required by the standard T. 30 fax agreement. Now when base station B 6 8 has received a response from fax machine B 7 2, base station B 7 2 can send a message to base station A 6 4 without causing a 1 second flag delay. Base station B 68 can immediately send a response signal because it knows that base station A 64 is waiting for this response and base station A 6 4 has synchronized its receiver. Referring now to FIG. 7, a flowchart illustrating some of the processing steps performed by base station B 6 8 after receiving a message is illustrated. Step B illustrated in FIG. 7 is performed by the base station B 6 8 processing element described with reference to FIG. 3.

It should be noted that the flag generator 8 8 a of the base station A 6 4 performs the same function as the flag generator of the base station B 6 8. So when the message is received in the transceiver 8 2 a, if the controller 8 4 a confirms the message and determines that the base station B 6 8 is waiting for a response, the controller 8 4 a will immediately start the flag generator 8 8 a Generates a V. 2 1 flag. The controller 8 4 a also causes the transceiver 8 2 a to immediately start sending these V. 21 flags to the base station B 68. By sending these flags away immediately. The invention can reduce the delay and the possibility of collision caused by the tandem configuration.

The above explanation of the preferred embodiment enables anyone skilled in the art to utilize the present invention. Various modifications to these embodiments are very easy for those skilled in the art, and the general principles described herein can be applied to other embodiments without using the apparatus of the present invention. Therefore, the present invention is not limited to the embodiments shown herein, and is encompassed to the broadest scope which is part of the present invention as long as it is consistent with these principles and the novel properties disclosed herein.

O: \ 55 \ 55424.ptd page 26 515196 _ case number 90104920 β 1 year! ^ MonthyT a_correction diagram brief description of component symbol descriptions 50 fax machine A 52 fax machine B 54 public switched telephone network (PSTN) 60 fax machine A 62 i-line subscriber unit A 64 base station A 66 PSTN 68 base station B 70 wireless subscriber single SB 72 fax machine B 80a, 80b message processor 82a, 82b transceiver 84a, 84b controller 86a, 86b message generator 92a message controller 94a V. 2 1 modulator 96a echo canceller 9 8 8 echo path 100a adder 102a adder 104a V. 2 1 demodulator

55424-911025.ptc Page 27

Claims (1)

515196 _ Case No. 90104920 ^ Year 7 < Day Amendment_ VI. Patent Application Scope 1. A device for detecting the tandem configuration in a facsimile communication system in a base station, comprising: a transceiver for receiving incoming messages; A controller for analyzing the incoming message to produce a decision to determine whether a tandem situation exists; and a message generator for generating an outgoing message according to the decision. 2. The device according to the scope of patent application, wherein the decision indicates that the incoming message is generated from another base station, representing the existence of a tandem situation, and wherein the outgoing message includes a transmission to the other base station In order to inform the other base station of the existence of the message. 3. For the device in the scope of patent application, the incoming message includes a non-standard equipment (NSF) message, and the outgoing message includes a non-standard equipment establishment (NSS) message. 4. The device according to item 1 of the scope of patent application, wherein the decision indicates that the incoming message contains a digital identification signal (DIS) transmitted by a facsimile machine, and wherein the outgoing message contains non-discriminatory messages other than the DIS message. A standard equipment (NSF) message is sent to another base station, and the NSF message is used to notify another base station that the outgoing message originates from a base station. 5. The device according to the scope of patent application, wherein the decision indicates that the incoming message contains an original non-standard equipment (NSF) message sent by a facsimile machine, and wherein the outgoing message contains a condensed original NSF The message is a special NSF message, the outgoing message is used for transmission to another base station. 6. The device according to item 1 of the scope of patent application, wherein the decision indicates the development O: \ 55 \ 55424-911025.ptc Page 28 515196 _Case No. 90104920_Qiao (year (P steam / Yue __) VI. Patent application scope The message contains a non-standard device (NSF) transmitted by a fax machine And the outgoing message contains a special NSF message containing a new NSF message followed by the original NSF message, and the outgoing message is used to transmit to another base station. 7. If the scope of patent application is the first Item, where the decision indicates that the incoming message contains a digital command signal (DC S) sent by a facsimile machine, and wherein the outgoing message contains a non-standard device setup (NSS) message for transmission to another Base station, the N SS message informs another base station that the outgoing message is from a base station. 8. For the device in the scope of patent application, the incoming message contains an original non-standard device sent by a facsimile machine. Create (N SS) message, and the outgoing message contains a special message condensing the original NSS message, and the outgoing message is used to transmit to another base station. The device of scope 1, wherein the incoming message includes a non-standard equipment establishment (NSS) message sent by a fax machine, and the outgoing message includes a new NSS message containing the original NSS message following Special NSS message, the outgoing message is used to send to another base station. 1 0. —A device used in a base station to detect the tandem configuration in the facsimile communication system, including: Means; means for analyzing the incoming message to generate a decision that determines the existence of a tandem situation; and means for generating an outgoing message in accordance with the decision. O: \ 55 \ 55424-911025.ptc page 29 515196 _ case number 90104920 amended on 7th of July _ VI. Patent application scope 1 1. For the device with patent scope item 10, where the decision indicates that The incoming message comes from another base station, indicating that there is a tandem situation, and the outgoing message is used to send to another base station to notify the other base station that a tandem situation exists. 12. The device according to item 11 of the scope of patent application, wherein the incoming message includes a non-standard equipment (NS F) message, and the outgoing message includes a non-standard equipment establishment (NS) message. 1 3. A method for determining the existence of a tandem configuration in a facsimile communication system in a base station, including the following steps: receiving an incoming message; analyzing the incoming message to generate a decision that determines the existence of a tandem situation; and An outgoing message is generated based on the decision. 14. The method according to item 13 of the scope of patent application, wherein the analysis step will generate a decision indicating that the incoming message is from another base station, representing the existence of a tandem situation, and the generation step will generate An outgoing message is used to transmit to the other base station to notify the other base station that a tandem condition exists. 15. The method according to item 14 of the scope of patent application, wherein the incoming message includes a non-standard equipment (NSF) message, and the outgoing message includes a non-standard equipment establishment (NSS) message. 16. —A device in the base station to support full-duplex communication with another base station. The startup of this device depends on whether a tandem configuration exists in the fax communication system, including: O: \ 55 \ 55424-911025.ptc page 30 515196 _ case number 90104920 ^ year ρ month / day correction_ VI. Patent application scope A modulator is used to receive the first signal from the wireless user unit and to be used in accordance with a predetermined The modulation format modulates the first signal to generate a modulated signal for transmission to the other base station; an echo canceller is used to receive the modulated signal, and is used to receive a second signal containing another signal from another base station And a composite signal of the echo of the modulation signal, used to determine an estimated value of the echo in accordance with the modulated signal, and used to extract the estimated value of the echo from the modulated signal to generate an echo cancellation A signal; and a demodulator for receiving the echo cancellation signal and demodulating the echo cancellation signal according to a predetermined demodulation format to generate a demodulation signal_ for transmitting to the wireless subscriber unit. 1 7. The device according to item 16 of the scope of patent application, wherein the modulator is a V. 2 1 modulator and the demodulator is a V. 2 1 demodulator. 18. The device according to item 16 of the patent application scope, wherein the first signal and the demodulated signal belong to a code division multiple access (CDMA) format. 19. A device used in a base station to support full-duplex communication with another base station. The startup of the device depends on whether a tandem configuration exists in the facsimile communication system and includes: a modulator device for wireless communication The user unit receives the first signal and is used to de-transform the first signal according to a predetermined modulation format to generate a modulation signal that can be transmitted to another base station; an echo canceller device is used to receive the modulation signal and Receiving a composite signal containing a second signal from the other base station and an echo of the modulated signal, for determining an estimated value of the echo according to the modulated signal, O: \ 55 \ 55424-911025.ptc page 31 515196 _ case number 90104920 month / day amendment_ VI. Patent application scope and the estimated value used to extract the echo from the composite signal to generate an echo cancellation A signal; and a demodulator device for receiving the echo cancellation signal and for demodulating the echo cancellation signal according to a predetermined demodulation format to generate a demodulated signal that can be transmitted to the wireless subscriber unit. 20. The device according to item 19 of the patent application scope, wherein the modulator device includes a V. 2 1 modulator and the demodulator device includes a V. 2 1 demodulator. 2 1. The device according to item 19 of the scope of patent application, wherein the first signal and the demodulated signal belong to a code division multiple access (CDMA) format. 2 2. — A method for improving communication using a base station in a facsimile communication system, including the following steps: deciding that a tandem configuration exists in the base station; and establishing a connection between the base station and another when determining that the tandem configuration exists. Full-duplex communication between a base station. 2. The method according to item 22 of the scope of patent application, further comprising the following steps: receiving a first signal from a wireless subscriber unit at the base station; modulating the first signal according to a predetermined format to generate a A modulation signal that can be transmitted to the other base station; receive a composite signal containing a second signal from the other, base station and an echo of the modulation signal; determine one according to the modulation signal An estimated value of the echo; taking the estimated value of the echo from the composite signal to generate an echo cancellation O: \ 55 \ 55424-911025.ptc Page 32 515196 _ Case No. 90104920 Amended on β / Y / Y_ Sixth, apply for a patent to divide the signal; and demodulate the echo cancellation signal according to a predetermined demodulation format To generate a demodulated signal that can be transmitted to the wireless subscriber unit. 2 4 · The method according to item 23 of the scope of patent application, wherein the step of modulating the first signal is modulated according to a V. 2 1 modulation format. 25. The method according to item 23 of the scope of patent application, wherein the step of demodulation is demodulation of the echo cancellation signal according to a V. 2 1 demodulation format. 26. The method according to item 23 of the scope of patent application, wherein the first signal and the demodulated signal belong to a code division multiple access (CDMA) format. 2 7. The method according to item 22 of the scope of patent application, wherein the step of establishing full-duplex communication includes the steps of: modulating an outgoing signal according to a first predetermined binary frequency key shift format; The modulated outgoing signal is transmitted to the other base station on one path, and an incoming signal modulated according to a second predetermined binary frequency key shift format is received on a second path. 2 8. The method of claim 27 in the scope of patent application, wherein the first path and the second path are V. 21 communication paths. 29. A device in a base station for establishing synchronization with advanced flags of another base station, the device will wait for activation when determining the tandem configuration exists in a facsimile communication system, including: a transceiver for receiving An incoming message from the other base station; O: \ 55 \ 55424-91i025.ptc Page 33 515196 _ Case No. 90104920 minutes F_P < __ VI. Patent application scope A controller analyzes the incoming message to determine whether another base station is waiting for the A response message of the incoming message; a flag generator for generating a preamble signal including a series of flags so as to immediately transmit the synchronization signal to another base station when the controller determines that the other base station is waiting for a response message; And a message generator is used to generate a response message that can be sent to another base station. 30. The device according to item 29 of the patent application scope, wherein each of the flags belongs to the V. 2 1 flag. 31. The device according to item 30 of the patent application scope, wherein the V. 2 1 flag is a byte with a value of 0 X 7 E. 3 2. As for the device in the scope of patent application No. 29, the flag is intended to inform another base station that the response message will follow, and the other base station should start synchronizing its receiver to prepare Receive the response message. 3 3. A method for improving communication in a facsimile communication system by using a base station, including the following steps: determining the existence of a tandem configuration at the base station; and establishing an advanced connection with another base station when determining the existence of the tandem configuration Flags are synchronized. 34. The method of claim 33, wherein the step of establishing advanced flag synchronization includes the following steps: receiving an incoming message from another base station; analyzing the incoming message to determine the other base Whether the station is waiting for a response message to the incoming message; O: \ 55 \ 55424-911025.ptc Page 34 515196 Amendment No. 90104920, " month β VI. Patent Application Scope In this analysis step, it is determined that the other base station is waiting for a response message to generate an include The preamble of the flag can be immediately transmitted to another base station; and a response message can be transmitted to the other base station. 35. The method of claim 34, wherein each of the flags is a V. 21 flag. 36. The method according to item 35 of the patent application scope, wherein the V. 2 1 flag is a byte with a value of 0 X 7 E. 37. The method of claim 33, wherein the flag is used to notify the other base station that the response message will follow, and the other base station should start synchronizing its receiver to Ready to receive the response message. O: \ 55 \ 55424-911025.ptc Page 35