WO2002087208A2

WO2002087208A2 - Modem relay system for dsl transmission

Info

Publication number: WO2002087208A2
Application number: PCT/CA2002/000562
Authority: WO
Inventors: Xiongjun Yu; Feng Wei
Original assignee: Gao Research & Consulting Ltd.
Priority date: 2001-04-23
Filing date: 2002-04-23
Publication date: 2002-10-31
Also published as: AU2002252887A1; WO2002087208A3

Abstract

A relay modem improves transmission in a communication network, where the transmission occurs between two modems. The relay modem comprises a relay client for communicating with a first of the modems, a relay server for communicating with a second of the modems, and a link coupling the relay client and the relay server for transmitting data in accordance with a predefined communication protocol, e.g. ATM. The relay modems separate the communication network into a plurality of sub-networks for increasing the transmission range for DSL lines. The relay modem works as a repeater for regenerating the signal.

Description

MODEM RELAY SYSTEM

0001 The present invention relates generally to a system and method for improving the performance between two modems, and specifically to the use of a relay modem for achieving the performance improvement.

BACKGROUND OF THE INVENTION

0002 Remote access and retrieval of data is becoming increasingly popular in data communication. The proliferation of the Internet, a global network of computers, has provided a vast network of information that is available to the general public. As the Internet grows and technology advances, this information is becoming increasingly voluminous and the details are become increasingly intricate. What used to comprise mainly text information has grown to include still and moving images as well as sound. The increase in the volume of information to be transferred has presented a need for an increase in Internet data transfer rates.

0003 In most industrialized countries, nearly every home has a telephone that allows instant voice and data communication. Networks allow almost instantaneous communication between computers, whether separated by a few feet or vast geographic distances. The Internet provides a variety of information that can be accessed from a telephone line virtually anywhere. Furthermore, wireless and cellular technology provides instant voice and data communication that is portable.

0004 As the need and desire to transfer information through a wide variety of networks increases, the burden on the networks increases. Given the need and interest in data communications, many techniques have been developed for compressing data bandwidth in communication systems in order to squeeze as much information through a bandwidth limited network as possible.

0005 A large portion of today's telecommunication traffic is carried over a public switched telephone network (PSTN). In order to achieve efficient implementation of Internet access, technology has been developed that takes advantage of the existing PSTN. 0006 Filters at the edge of the telephone network limit voice-grade bandwidth (also referred to as the "voice band") to approximately 3.3 kHz. Standard modems transmit data using the voice band and thus a top data rate of approximately 33.6 kbps for normal analog modems can be achieved. Newer modem technologies (also referred to as V.90 modems) transmit data over the voice band and can achieve a theoretical maximum of 56 kbps. However, while the theoretical maximum transfer rate for V.90 modems is 56 kbps, Federal Communications Commission (FCC) power regulations limit the maximum transfer rate to approximately 54 kbps.

0007 Generally V.90 technology attempts to increase the throughput by providing a digital connection between a service provider and the PSTN, rather than a traditional analog modem. Thus, a digital modem at the service provider digital encodes downstream data instead of modulating it, as do analog modems. This results in greater throughput downstream (from the service provider to the customer) but retains the traditional limitations on speed when sending data upstream (from the customer to the service provider).

0008 As described above, the V.90 technology is able to achieve high speed by implementing a digital modem at the service provider end. The use of a digital modem reduces the need for an analog-to-digital (A/D) converter. For an A/D converter, quantization noise is a major issue. Quantization noise occurs when an analog signal level does not coincide with a discrete digital level. Jf an analog waveform is being sampled at a point that does not exactly equal a digital discrete location then an approximation is made to the closest digital level. This approximation is referred to as quantization noise, which lowers the amount of information throughput. Thus, the lack of an A/D converter in V.90 technology allows for higher data transfer rates to be achieved.

0009 However, various line saving mechanisms are in place that do not allow the elimination of the A/D converter. An example of such a mechanism is a pair-gain system. Pair-gain systems are used to multiplex a plurality of voice-band signals over a signal connection, thus providing two or more telephone lines where only one physical line exists. This is often the case when a modem user wishes to have separate lines for telephone and modem use so the two can be used simultaneously. If two physical lines are not available, the pair-gain system is used. Additional analog to digital conversions are required to multiplex the signals on to a single line. This introduces a high noise floor in the digital sample that limits the downstream rate of transmission to approximately 26 kbps. Therefore, even if a customer is using a V.90, the downstream transmission rate is severely limited.

0010 Another technology that further increases the amount of information transferred over copper wire is Digital Subscriber Loops (DSL) technology. DSL technology takes advantage of an unused frequency spectrum above the voice-band for transmitting data. Although a variety of different DSL standards exist, the one that is currently most widely implemented is Asymmetric DSL (ADSL). It is estimated that ADSL will be able to provide a downstream data rate of approximately 6.144 megabits per second and an upstream data rate of approximately 640 kbps upstream. These data rates are estimated for loop lengths of approximately 18,000 feet (6.144M for 12000 feet, 2.408M for 16000 feet, and 1.544M for 18000 feet). It is estimated that approximately eighty percent of all telephone service subscribers are within 18,000 feet of a central office. At shorter lengths, ADSL speeds may increase. However, at longer lengths the service can degrade dramatically.

0011 Although DSL technology seems to hold great promise, several problems exist. One of these problems, as previously noted, is servicing loops that are longer than 18,000 feet. Such a distance may significantly reduce the quality of the transmission, resulting in lower transmission rate. Furthermore, as described with respect to the pair-gain system, implementation of the various DSL technologies, as well as wireless and other performance enhancing technologies, introduces the need for an A/D converter at the service provider end. As described, having only one conversion from analog to digital is essential for V.90 technology to achieve maximum downstream speeds. Thus, if a customer wishes to use a V.90 modem, but is connected to the PSTN via a DSL enabled network, it is likely that the V.90 modem would be limited to a maximum of 33.6 kbps for both the upstream and downstream directions.

0012 Thus, it is an object of the present invention to obviate or mitigate at least some of the above mentioned disadvantages. SUMMARY OF THE INVENTION

0013 In accordance with an aspect of the present invention, there is provided a relay modem for improving transmission in a communication network, where the transmission occurs between two modems. The relay modem comprises a relay client for communicating with a first of the modems, a relay server for communicating with a second of the modems, and a link coupling the relay client and the relay server for transmitting data in accordance with a predefined communication protocol. The relay modems separate the communication network into a plurality of sub-networks for improving the transmission.

BRIEF DESCRIPTION OF THE DRAWINGS

0014 Embodiments of the invention will now be described by way of example only with reference to the following drawings in which:

Figure 1 is a block diagram of a system implementing a relay modem;

Figure 2 is detailed block diagram of the system illustrated in Figure 1; Figure 3 is a flow diagram of a system illustrated in figure 1 ;

Figure 4 is a detailed block diagram of a relay client;

Figure 5 is a detailed block diagram of a relay server;

Figure 6 is a block diagram illustrating thresholds in a receive buffer;

Figure 7 is a block diagram of a DSL system implementing a relay modem; Figure 8a is a diagram of a protocol flow in a standard DSL system (prior art);

Figure 8b is a diagram of a protocol flow in a DSL system is accordance with an embodiment of the present invention;

Figure 9 is a block diagram illustrating the signal flow in bypass mode for the system illustrated in Figure 7; and

Figure 10 is block diagram illustrating the signal flow in relay mode for the system illustrated in Figure 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 0015 For convenience, like numerals in the description refer to like structures in the drawings. Referring to Figure 1, a block diagram of a system in accordance with an embodiment of the present invention is illustrated generally by numeral 100. The system 100 comprises a central office 102, a 2-wire/4-wire converter 104, relay module 106, a remote terminal 108, a subscriber modem 110, an analog-to-digital A/D converter 112, and a digital-to-analog D/A converter 114.

0016 The basic operation of the system is described as follows. A downstream signal is sampled at 8 KHz by the A/D converter, having 16-bit resolution, at the central office. A V.90 server modem is coupled with the client V.90 modem 110 by the relay module 106. The V.90 signal is sampled at 8KHz with a μ -law D/A converter at the remote terminal 108.

0017 During a V.90 modem call, the system demodulates the V.90 downstream signal during V.90 modem training and data mode using the detected demodulation parameters. When a V.90 modem call is not taking place, the system simply passes the data through. Further, the system cancels downstream echo to provide a high enough signal-to-noise ratio (SNR) in downstream signal. The system cancels upstream echo to provide high enough SNR in the upstream signal to drive the modem detection and monitoring. Standard echo cancellation algorithms are used.

0018 Referring to Figure 2, a more detailed block diagram of the system is illustrated generally by numeral 200. The system comprises a server 202, a relay modem 204, and a client 206. The server 202 includes at least one service provider 208 and at least one central office 210. The relay modem 204 includes a relay client 212 and a relay server 214. Each of the relay client and the relay server includes a codec 211 and a digital signal processor (DSP) 213 and 215. The client 206 includes a Central Terminal (CT) 216, a remote terminal 218, and a subscriber modem or telephone 220.

0019 The service providers 208 are coupled to the central offices 210, which are coupled to the relay client. The subscribers 220 are coupled to the remote terminal 218, which is coupled to the CT 216, which is coupled to the relay server 214. The relay server 214 and relay client 212 are coupled via a high-speed link and exchange data in accordance with a predefined flow control protocol. A serial port is used to exchange data between the two DSPs 213 and 215. A serial port is also used to couple each DSP 213 and 215 with a corresponding codec 211. The codec 211a associated with the DSP 213 of the relay client 212 further includes a direct access arrangement (DA A).

0020 Thus, it can be seen that the relay modem 204 effectively divides the system into two sub-systems. A first sub-system 222 includes the server 202 and the relay client 212. A second sub-system 224 includes the client 206 and the relay server 214. By creating two sub-systems, each sub-system includes only one data conversion between digital and analog. Therefore, the noise introduced into each sub-system is low enough to maintain V.90 data transfer rates.

0021 In the present embodiment, the relay client 212 is also referred to as an analog modem. This is true because it receives/transmits an analog signal from/to the server 202. Referring to Figure 4, a diagram for the relay client 212 is illustrated. The relay client includes a receiver 402, transmitter 404, modem processor 406, correction detector 412, transmit buffer 412, and receive buffer 414. Similarly, the relay server is referred to as a digital modem because it receives/transmits digital data from/to the client 206. Referring to Figure 5, a diagram for the relay server 214 is illustrated. The relay server includes a transmit buffer 502, a receive buffer 504, a correction transmitter 506, a modem processor 512, a pulse code modulator (PCM) input 514, and a PCM output 516.

0022 Flow control for data received by the relay client 212 is described as follows. There are two modes for the relay modem, each represented by a flag referred to as Detect_V90_Flag. For bypass mode, a V.90 transmission is not being made and the flag is set to 0. At the relay client, signals received from the server are received directly into the transmit buffer 412. A receive interrupt service of the serial port retrieves the signal from the transmit buffer and communicates it to the receive buffer 504 at the relay server. There the receive interrupt service of the serial port relay server retrieves the signal directly from the receive buffer 504 and transmits it to the client.

0023 Similarly, at the relay server, signals received from the client are received directly into the transmit buffer 502. A receive interrupt service of the serial port retrieves the signal from the transmit buffer and communicates it to the receive buffer 416 at the relay client. There the receive interrupt service of the serial port relay client retrieves the signal directly from the receive buffer 504 and transmits it to the server.

0024 While the system is in this mode, the relay client modem process 406 monitors the received signal from its associated coder/decoder (codec). Further, there is no need to perform flow control in this mode because a simple voice signal is transmitted at a slow rate that the system can transfer.

0025 When a customer using a V.90 modem uses it to connect to a service provider, the service provider answers the call by initially transmitting an ANSam signal. The

ANSam signal is specified by ITU standards as a 2100 Hz signal amplitude- modulated at 15 Hz, with periodic phase reversals. After ANSam has been transmitted for a predefined period, a call menu (CM) signal indicating the service provider modem's capabilities is transmitted. In response to the CM, the customer modem transmits a joint menu (JM) signal indicating the answer modem's capabilities.

0026 The relay client modem process 406 monitors for the ANSam signal as well as the CM signal. The CM signal indicates whether or not the service provider modem supports V.90. Further, the relay client modem process determines from either the CM or through data mode V.42 handshaking if the service provider supports V.42 for flow control. If the service provider modem supports V.90 and V.42, the relay client transmits a message to the relay server indicating that the service provider can support V.90. The relay server modem process monitors for the JM signal. The JM signal indicates whether or not the customer modem supports V.90. Further, the relay server modem process determines from either the JM or through data mode V.42 handshaking if the service provider supports V.42 for flow control. If the customer modem supports V.90 and V.42, the relay server transmits a message to the relay client indicating that the customer can support V.90. Once both the relay client and relay server have detected V.90 support, a transition is made into V.90 mode.

0027 In V.90 mode, the relay server receives signals from the customer modem and demodulates PCM signals to data. The data passes through V.42 for error correction and flow control to the relay client. The relay client passes the received data to V.42 for error correction and flow control, modulates the data to a PCM signal, and transmits the signal to the service provider modem. Similarly, in the other direction, the client server receives signals from the service provider modem and demodulates PCM signals to data. The data passes through V.42 for error correction and flow control to the relay server. The relay server passes the received data to V.42 for error correction and flow control, modulates the data to a PCM signal, and transmits the signal to the customer modem.

0028 While in V.90 mode, the relay client and relay server monitor received signals to determine a modem disconnect for switching back to bypass mode. Some of these signals include a V.42 disconnect command and a "clear down" signal. Further, conditions such as loss of carrier, handshaking failure, and retrain failure will also result in a return to bypass mode.

0029 Since the relay server and relay client communicate with the client and the server, respectively, in a standard manner, it is not necessary to describe this communication process in detail. The following describes the communication between the relay server and the relay client.

0030 Data is transmitted from a transmit buffer at the relay client to a receive buffer at the relay server and vice versa. The data transfer is performed in accordance with a series of predefined thresholds at the receive buffer. Referring to Figure 6, a block diagram of a receive buffer is illustrated generally by numeral 600. The receive buffer 600 of the present embodiment has two threshold levels, BUFFVACANT and BUFFFULL.

0031 If the number of elements in the receive buffer is below the threshold level indicated by BUFFVACANT, then the buffer is relatively empty. As a result, a handshaking command is issued for informing the transmit buffer to send data.

0032 Once the number of elements in the receive buffer rises above the threshold level indicated by BUFFVACANT, the buffer is approaching its maximum capacity. As a result a handshaking command is issued for informing the transmit buffer to stop transmitting data. The data transmission begins again when the number elements in the receive buffer falls below the threshold level indicated by BUFFVACANT.

0033 Protocols for managing the transfer of data between the relay server and the relay client will be apparent to a person skilled in the art. Numerous techniques exist for implementing a transfer between two, including those that are publicly available and those that are proprietary. The following protocol is provided only as an example of such a scheme.

0034 For every interrupt of the serial port, a 32-bit word is communicated between the relay server and relay client. The type of data contained in the word is indicated by the data contained in the highest 16 bits of the word, also referred to as the command header. The lowest 16 bits of the word carries data. In the present embodiment, there are three command headers that are used by the system. These command headers include COMMAND_OP, V90_PROTECT_CHX, and DIRECT PROTECT CHX.

0035 The command header COMMAND_OP indicates that the lower 16-bits of data is a V.90 mode starting or ending command. Furthermore, the command can operate on a predefined number of channels. The channel number is uniquely identified by the command. For example, for a two-channel system, the commands for indicating that V.90 has been detected at the relay client are CH0C V90STARTCOMMAND and CH1C_V90STARTCOMMAND, for the first and second channels respectively. The commands for indicating that V.90 has ended at the relay client are CH0C_V90ENDCOMMAND and CH1C_V90ENDCOMMAND, for the first and second channels respectively.

0036 Similarly, the relay server sends starting and ending commands to the relay client. Continuing the example for the two-channel system, the commands for indicating that V.90 has been detected at the relay server are CH0S_V90STARTCOMMAND and CH1S_V90STARTCOMMAND, for the first and second channels respectively. The commands for indicating that V.90 has ended at the relay server are CH0S_V90ENDCOMMAND and CHI S_V90ENDCOMMAND, for the first and second channels respectively. 0037 The command header V90_PROTECT_CHX indicates that the lower 16 bits of the word comprises data in V.90 mode. The "X" in the command header indicates for which channel the data contained in the lower 16 bits is destined. In V.90 mode, the low 16 bits can be either handshaking or V.90 data to be transferred. If the high 8 bits of the low 16-bit portion comprise a first predefined bit pattern, also referred to as the handshaking prefix, then the lower 8 bits are for handshaking. If the high 8 bits of the low 16-bit portion comprise a second predefined bit pattern, also referred to as the V.90 data prefix, then the lower 8 bits are for data transfer.

0038 The DIRECT J^>ROTECT_CHX indicates that the low 16 bits comprise data, but not in V.90 mode. Similarly to the case above, since there are two channels available and the low 16 bits comprise actual data, the command header indicates for which channel the data is destined.

0039 The following describes how data is processed at the relay client and relay server. Both the relay client and the relay server have their own transmit buffer, 412 and 502 respectively, and receive buffer, 416 and 504 respectively. The transmit and receive buffers facilitate flow control between the relay client and relay server.

0040 For every word that is transmitted between the relay client and relay server, the command headers are processed by the interrupt services of serial port directly and not taken from or put into the buffers. Then, depending on the command headers, the low 16 bits are processed accordingly.

0041 If the command header is COMMAND_OP, the low 16-bit commands, V90STARTCOMMAND or V90ENDCOMMAND are transmitted by placing the command into the transmit buffer and then transferring it from the buffer to the receiver. When received, the low 16-bit command, V90STARTCOMMAND or V90ENDCOMMAND, is processed directly and not inserted into the receive buffer.

0042 If the command header is V90_PROTECT_CHX, the data is transmitted by placing it into the transmit buffer and then transferring it from the transmit buffer to the receive buffer. For handshaking commands, both the handshaking prefix and the handshaking command are placed directly into the transmit buffer and then transferred. When the data is received, the handshaking command is processed and therefore need not be stored in the receive buffer.

0043 For V.90 data, the V.90 data prefix and V.90 data, retrieved from a digital terminal equipment reader DteRd, are placed in the transmit buffer. The V.90 data prefix and V.90 data are transferred from transmit buffer to the receive buffer. When received, the V.90 data is inserted into the receive buffer and then processed.

0044 If the command header is DIRECT_PROTECT_CHX, the data is transmitted by placing it directly into the transmit buffer and then transferring it from the buffer to the receiver. When the data is received, the low 16-bit data is placed directly into the receive buffer and then bypassed to the output.

0045 The following outlines some of the advantages of using such a modem relay system. The system allows downstream V.90 modem connection rates of up to 53 kbps, even through a pair-gain system. The system supports the target maximum downstream V.90 connection rate with a cable (26 AWG) between the switch line- card and central office terminal of about 500 feet. However, performance may decrease as the cable length increases. The system supports a target maximum V.90 downstream connection rate through N POTS channels simultaneously. Input and output 8 KHz μ-law and PCM data for DSL transmission is available for each POTS channel carrying V.90 modem for downstream and V.34 for upstream. Input and output 8 KHz linear data for the central office side for each POTS channel is available for carrying V.90 modem downstream and V.34 upstream. The system does not affect other types of traffic in the POTS channel, such as voice, facsimile, and other non-V.90 modem services. Lastly, the system provides a watchdog signal that avoids a lock-up state requiring human intervention to re-establish POTS service. The watchdog signal is transmitted to a monitoring station at regular intervals. Should the system reach a lock-up state, the watchdog signal is not transmitted, causing the monitoring station to reset the system.

0046 In an alternate embodiment, the modem relay can be applied to current DSL architectures in the form of a repeater. As previously described, ADSL technology works efficiently when the central office and the subscriber are within 18000 feet.

While this is often the case in large cities, it is not necessarily true especially in rural areas. Implementing the relay modem in a similar fashion to that described above results in two sub-systems.

0047 Referring to Figure 7, an ADSL system implementing a relay modem is illustrated generally by numeral 700. The central office is coupled to the remote terminal via a relay modem. Similarly to the previous example, the relay modem acts as a receiver to the central office modem and a transmitter to the customer modem. Thus a first sub-system comprises the central office and a client portion of the relay modem, referred to as the relay client. A second sub-system comprises a server portion of the relay modem, referred to as the relay server, and the subscriber modem.

0048 Referring to figure 8a, protocol flow in a DSL system is illustrated generally by numeral 800. The seven layers of the ISO seven-layer protocol model are illustrated as being present at the central office and at the subscriber. The central office transports data to a line card via a SONET network. The line card transfers the data at the ATM layer to the implemented DSL standard and transmits it along the standard copper wire. Referring to Figure 8b, protocol flow in a DSL system using the relay modem is illustrated generally by numeral 850. As illustrated, the relay modem uses the ATM level to transfer data between the relay client and the relay server, thus extending the service range of the DSL system.

0049 Each sub-system is capable of transmitting a distance of approximately 18000 ft. Thus, the effective range of system is essentially doubled to 36,000 ft.

Furthermore, it is not necessary to have the relay client and the relay server housed at the same physical location. Depending on the technology used to link the relay client and the relay server, the effective range can be extended even further. Using digital technology to link the relay client and relay server can result in virtually a limitless range extension.

0050 In yet an alternate embodiment, the previous two embodiments can be combined such that the relay modem acts both as a repeater for DSL and provides the ability to connect a V.90 modem to a DSL enabled telephone line. There are several modes for the relay system, indicated by the flags VB_Relay_Flag and BB_Relay_Flag. If the flag VB_Relay_Flag is set to 0 then the voice band signal is simply passed though. If the flag VB_Relay_Flag is set to 1 then the voice band signal is processed. If the flag BB_Relay_Flag is set to 0 then the broadband data signal is simply passed though. If the flag BB_Relay_Flag is set to 1 then the broadband signal is processed.

0051 In bypass mode, the flags VB_Relay_Flag and BB_Relay_Flag are both set to zero. For the voice band signal, as was the case in the first embodiment described, the signal arriving at the relay server from the client is simply transferred to the relay client and sent to the central office. Similarly, the signal arriving at the relay client from the central office is simply transferred to the relay server and sent to the client. The transfer occurs in a similar manner to that previously described. At the same time, both the relay server modem and relay client modem perform echo cancellation. Further, the relay client monitors the signal received from the service provider modem for detecting the ANSam tone and the CM signal, indicating the initialization of a V.90 modem. The relay server monitors the signal received from the customer modem for the JM signal, indicating the initialization of a V.90 modem.

0052 For the broadband signal, the relay client monitors signals from the service provider modem for detecting a DSL modem start. Specifically, the relay client looks for an R-Tones-Req signal, which specified in DSL standards. Since, there is neither V.90 detected in the voice-band nor DSL detected in the broadband, no flow control is implemented in this mode.

0053 In voice-band relay mode, the flag VB_Relay_Flag is equal to one. As described in the first embodiment, the relay server receives signals from the customer modem and demodulates PCM signals to data. The data passes through V.42 for error correction and flow control to the relay client. The relay client passes the received data to V.42 for error correction, modulates the data to a PCM signal, and transmits the signal to the service provider modem. Similarly, in the other direction, the client server receives signals from the service provider modem and demodulates PCM signals to data. The data passes through V.42 for error correction and flow control to the relay server. The relay server passes the received data to V.42 for error correction, modulates the data to a PCM signal, and transmits the signal to the customer modem. At the same time, the relay client and relay server monitor received signals to determine a modem disconnect for switching back to bypass mode. 0054 In broadband relay mode, the flag BB_Relay_Flag is equal to one. As described in the second embodiment, the relay server receives signals from customer modem, and demodulates the signals to data. The data flows through ATM/TC for flow control to the client relay. The client relay transfers data to ATM/TC, modulates the data to a signal, transmits the signal to the service provider modem. Similarly, in the other direction, the relay client receives signals from service provider modem, and demodulates the signals to data. The data flows through ATM/TC for flow control to the client server. The client server transfers data to ATM/TC, modulates the data to a signal, transmits the signal to the customer modem. At the same time, the relay client and relay server monitor received signals to determine a modem disconnect for switching back to bypass mode.

0055 In yet an alternate embodiment, the system can be applied to wireless connections. This is achieved by placing the relay server and relay client at opposite ends of the wireless channel. Thus, two land based, or wire linked, sub-systems are created, whereas the link between the relay server and relay client is wireless. Wireless protocols are implemented from transferring data between the transmit and receive buffers of the relay client and relay server, as will be appreciated by a person skilled in the art.

0056 In yet an alternate embodiment the system provides a V.34 fallback system. As described in the previous embodiments, the system from service provider to customer is separated into two sub-systems. While it is likely that the two subsystems will have similar transmission rates, it is highly unlikely that they will have the same transmission rates. Further, it is possible that the transmission rate differences between the two sub-systems can be significant. Reasons for transmission rate differences are well known in the art and include loop lengths, loop quality, connection quality, and the like.

0057 It is possible to take advantage of these differences to further enhance V.90 connection. Specifically, it is possible for a service provider modem and customer modem to both have V.90-enabled modems, but either or both are connected by a noisy loop. In such a case, the connection between the service provider modem and the customer modem would connect at V.90. However, if it is determined after the initial connection, that the rates cannot be maintained, the modems will either transmit at a reduced rate or attempt to retrain. If the modems attempt to retrain, they will determine that a V.90 connection is possible and try the connection again. This process may repeat for an extended period of time, which can be frustrating to the customer.

0058 Since there are effectively two sub-systems and the sub-systems can operate at different transmission rates, the noisy sub-system is reduced to transmit at a lower rate, such as V.34. The other sub-system can continue to transmit at V.90 transmission rates, with the difference in rates being managed by the flow control between the relay client and the relay server. While this does not provide an advantage in data throughput, it provides flexibility and reliability in the modem connection.

0059 In yet an alternate embodiment, the relay client and the relay server are implemented using general processors, rather DSPs. Further, it is possible that the relay client and the relay server are both contained in the same piece of software and thus the link between the components is a software link rather than a hardware link.

0060 While the above embodiments have been described with reference to specific embodiments, other implementations will become apparent to a person skilled in the art. For example, the relay modem is not limited to V.90 technology, but rather can be applied to other technologies that may also encounter difficulties when faced with a greater number of components than for which they where designed. Examples of other technologies include the upcoming V.92, V.44, and V.59 standards. The relay modem essentially separates the system into sub-systems so that each sub-system comprises no more than the maximum preferable number of limiting components.

0061 Furthermore, the technology used to link the relay client and the relay server will likely change with time to provide even greater loop lengths. Such technology can be used to further enhance the advantages of the present invention, as will be appreciated by a person skilled in the art.

0062 Although the invention has been described with reference to certain specific embodiments, various modifications thereof will be apparent to those skilled in the art without departing from the spirit and scope of the invention as outlined in the claims appended hereto.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A relay modem for improving transmission in a communication network, where said transmission occurs between two modems, said relay modem comprising: a) a relay client for communicating with a first of said modems; b) a relay server for communicating with a second of said modems; and c) a link coupling said relay client and said relay server for transmitting data in accordance with a predefined communication protocol, wherein said relay modems separate said communication network into a plurality of sub-networks for improving said transmission.

2. A relay modem as defined in claim 1, where said relay client comprises a client receive buffer and a client transmit buffer and said relay server comprises a server receive buffer and a server transmit buffer.

3. A relay modem as defined in claim 2, wherein said relay client transmits data from said client transmit buffer to said server receive buffer in accordance with a plurality of predefined thresholds at said server receive buffer.

4. A relay modem as defined in claim 2, wherein said relay server transmits data from said server transmit buffer to said client receive buffer in accordance with a plurality of predefined thresholds at said client receive buffer.

5. A relay modem as defined in claim 1, wherein said relay modem is bypassed until a predefined condition is met.

6. A relay modem as defined in claim 5, wherein once said predetermined condition is met, said relay client acts as a client modem to first modem and said relay server acts as a server modem to said second modem.

7. A relay modem as defined in claim 6, wherein said predefined condition is initialization of said first and second modems in a predefined protocol.

8. A relay modem as defined in claim 7, where said predefined protocol is V.90

9. A relay modem as defined in claim 7, wherein if a connection between said first modem and said relay client cannot be made at a predefined rate, said connection is made at a lower, fallback rate.

10. A relay modem as defined in claim 7, wherein if a connection between said second modem and said relay server cannot be made at a predefined rate, said connection is made at a lower, fallback rate.

11. A relay modem as defined in claim 1, wherein said relay client and said relay server are housed at separate locations.

12. A relay modem as defined in claim 1, wherein said relay client and said relay server are housed at the same locations.

13. A relay modem as defined in claim 12, wherein said relay client and said relay server are implemented using the same processor.

14. A relay modem as defined in claim 13, wherein said link is a software link.

15. A relay modem as defined in claim 14, wherein said link is a wireless link.

16. A relay modem as defined in claim 1, wherein said transmission between said first and second modems is a digital subscriber loop (DSL) transmission, said relay modem for increasing a distance between said modems while maintaining acceptable transmission rates.

17. A relay modem as defined in claim 16, wherein said distance between said first and second modem is doubled.

18. A relay modem as defined in claim 16, wherein said distance between said first and second modems is further increased by locating said relay client apart from said relay server by a specified distance, thereby providing an increased distance between said first and second modems in accordance with said specified distance.

19. A relay modem as defined in claim 18, where said link between said relay server and said relay client is digital.