MXPA00007272A - System and method for providing ip/internet telephony - Google Patents

Abstract

A system and method are described providing a wireless interface to an Internet Protocol (IP)/Internet telephony system. A wireless connection via the unregulated 900 MHz cordless phone spectrum or other spectrum allocated for wireless communications provides an RF link between an IP connection device, a network interface box or set-top box, and one or more wirelss handsets. A processing/control element inthe network interface box runs the required IP protocols to establish and manage call set-up and teardown, translate the digital voice signal between IP and the local RF link protocol, and provide the RF base station function for the handset(s). Each handset would incorporate the other end of the RF link. The wireless interface to a telephone handset may be through a settop box that is tied into a cable network such as a hybrid coaxial cable network. A protocol such as the Internet Protocol may be used to maintain a digital connection into a cable network while using an RF link to transmit compressed voice/data information between a telephone device such as a telephone handset and an interface unit such as a settop box.

Description

SYSTEM AND METHOD TO PROVIDE TELEPHONY INTERNET / INTERNET PROTOCOL FIELD OF THE INVENTION The present invention generally relates to a system and method for providing Internet telephony. In particular, the present invention relates to a system and method for providing a wireless Internet telephone system over either a regular dial-up telephone or a cable network. BACKGROUND One of the main reasons of interest in offering Internet protocol (IP) / Internet telephony services is the price structures currently in place for the data service, and the voice service offered by the telephone operators. Long-distance voice service can be thought of as a "demand data" service, where the user pays a premium for instant access to a 64 Kbps channel (voice grade channel in the United States). Widely publicized, the promotional price for this service is in the order of $ 0.10 (United States dollars) one minute. In contrast, the data service offered by telephone operators, such as that offered by a Tl connection (24-voice quality data line, for a 1.544 Mbps connection) is priced at approximately $ 1000 / month (US dollars). United) which is $ 0.001 (United States dollars) one minute per voice line. In the very near future, cable operators will make extreme pressure to level data service rates for telephone operators, since the cable modem will allow cable operators to offer hundreds of Kbps of effective production for approximately $ 50 / month (United States dollars). The basic idea of IP / Internet voice telephony is to digitize the voice as one speaks on the telephone and send the digitized data as Internet protocol packets to the Internet. An Internet protocol voice device may be integrated within the Internet connection device such as a modem, a top box, or a computer. It can also be built as an independent product. The independent Internet protocol speech device, for example, can provide an Ethernet connector which can be connected to an Internet connection device and another local area network device. The Internet protocol speech device may also include interfaces to connect normal telephone sets. The quality of the speech heard through a normal telephone line requires a bandwidth of 64 Kbits / s. However, the most recent Internet connections have less bandwidth, such as a 28.8 Kbps modem, or 56 Kbps modem. Also, even if a fast-connect device is used, such as an ISDN, or cable modem , the Internet network itself is a shared medium and has limited bandwidth. Therefore, audio codec-decoders are usually integrated to compress the voice data. To ensure interoperability between Internet protocol voice devices of different vendors, the International Telecommunications Union (ITU) developed H.323 as the standard for telephony over the Internet protocol network. H.323 defines common procedures for call set-up, data compression, and data transport. In a general sense, it can be thought that the Internet protocol telephony provides a "virtual" point-to-point connection for voice services over the Internet. An Internet protocol voice device is basically a port to connect the regular telephone system to the Internet. The following example shows how it would be placed. A user in Indianapolis wants to call a friend in Paris. He picks up his telephone device Internet protocol voice device (or activates a virtual device on a computer screen for an "integrated" version) and hears the dial tone as a regular telephone dial tone. Then, dial your friend's phone number in Paris. The call travels over the Internet to a Switching Server provided by the Internet protocol telephony service provider. The switching server will connect the call to your friend's Internet protocol voice device and initiate the call. If your friend only has a regular phone, the switch server will connect the call to a port in Paris. The port in Paris initiates a call over the public switched telephone network (PSTN) to the local number in Paris. The cost to make telephone calls between Indianapolis and Paris using two Internet protocol voice devices is only the Internet access fee. If a party uses a regular telephone, the extra cost is only that of a local dial-up call. Depending on the Internet connection, there are at least two methods for making calls using an Internet protocol voice device: dial-up connections, and direct connections. With a dial-up connection, a user first calls an Internet Service Provider (ISP) on a regular dial-up line to establish an Internet connection. Then, you will use an Internet protocol voice device to dial the telephone number of the person you are calling. The present applicants recognize a problem with this approach which is that the receiver must be on the line waiting for the call. In this way, the sender first has to call the receiver using a regular telephone to make the appointment. With a direct connection, a user places a call using the Internet protocol voice device just as it does with the regular telephone. The direct connection indicates a permanent open channel to the Internet such as an ISDN, or a cable access device. For a dial-up connection call, a phone that has been called will not ring unless the Internet connection is already established for this phone. For a direct connection call, the phone will ring like a normal telephone. There are many advantages of telephony protocol Internet / Internet. One of these advantages is the reduced cost as described above. A lower bit-rate audio encoder-decoder integrated into the Internet protocol voice device allows voice calls over a 28.8 Kbps modem. For a small reduction in voice quality, the monthly telephone bill of a person will be greatly reduced. If the Internet Protocol voice device is used in conjunction with the cable modem, the private service network plus the high bandwidth of the cable modem will provide very good sound quality. Even if the voice quality provided by the Internet / Internet Protocol voice device is not convenient for all telephone communications, an Internet / Internet Protocol voice device may be useful as a second residential telephone line. Also, the H.323 standard supports several well-defined conference modes and, therefore, the Internet protocol voice device is capable of being used for conference calls from multiple points. A service marked by "Network" is advantageous for technical or customer support lines due, for example, to the fact that an Internet address of an Internet protocol voice device of a company can be integrated into the Web page of the company and customers can then call the company simply by clicking on that Internet address. The cost associated with toll-free numbers (numbers "800") will be reduced as a result. In addition, operators of cable television systems (MSO) have recently been interested in adding inexpensive telephone services using a hybrid hybrid coaxial network (HFC) combination of operators of cable television systems and the public Internet . Voice signals are converted into digital values and transported over networks using various established and proposed Internet protocols such as Internet Protocol (IP) packets. Reference DI (WO 97 29581 A) describes a transmission system which allows users to have a voice conversation via the Internet. DI uses the PSTN to con to an Internet service provider. The system described by DI includes transmitting a telephone call to the PSTN and a voice originating machinery that compresses the signal for transmission over the Internet. The signal is then transmitted over the Internet to a voice reception machinery. The voice reception machinery decompresses and demodulates the received signal and provides the signal to the PSTN (31). The PSTN compresses the signal into a format for transmission along it for reception by a receiving telephone. This system compresses and decompresses a signal in a convenient format for transmission through the PSTN. In addition, compression and decompression of the signal is done in the PSTN, remotely from the ends of the established communication channel. Thus, although this system eliminates most of the long distance charges associated with a voice call, there are still local charges associated with it and possibly long distance charges from the other side of the communications channel associated with contacting the Internet service provider. Reference D2 WO 98 11703 was published on March 19, 1998. However, there are also problems associated with existing Internet Protocol / Internet telephony systems. For example, the systems described above involve some combination of old simple telephone system of additional or revised cabling (POTS), additional or revised cable network cabling, or additional network interface boxes. In addition, any conion that replaces a public switched telephone network (PSTN) service (such as the reuse of existing simple old telephone system cabling within the home to replace PSTN services with telephone services) may be required. from HFC) to supply so-called "live line" services. Some of these options require professional installation that can be expensive, time consuming, and inconvenient for the user.

COMPENDIUM OF THE INVENTION The invention resides, in part, in the recognition of the aforementioned problems and, in part, in providing a system and method for solving these problems. In particular, the inventors recognize that the described problems are solved by providing a voice call over an Internet connection receiving a signal from a cable network. The signal represents Internet protocol data packets of the voice call and is modulated both in a first format and decompressed to match a cable network format. The signal is demodulated and decompressed. The signal is then compressed into a format of a domestic environment, modulated in a second format and transmitted wirelessly to a wireless device. The signal is then demodulated and decompressed in the wireless device. The inventors also provide a system that includes the elements necessary to carry out this method. One aspect of the present invention involves providing an Internet telephony system using a wireless connection such as via the unregulated 900 MHz wireless telephone spectrum or other spectrum allocated for wireless communications to provide a radio frequency link between a protocol connection device of the Internet, a network interface box or superior box; and one or more wireless devices. A processing / control element in the network interface box would execute the Internet protocols required to establish and manage call establishment and cutting (currently defined within the ITU-T H.323 standard), translate the signal from digital voice between the Internet protocol and the local radio frequency link protocol, and provide the function of the radiofrequency base station for the telephone device (s). Each telephone set would incorporate the other end of the radio frequency link, and analog to digital (A / D) and digital to analog (D / A) converter functions to convert the voice signal to and from digital packets, and potentially apply some compression algorithm to improve the utilization of bandwidth. In a telephone set design that does not incorporate sufficient processing power to perform the compression function, this function could potentially reside in the network interface box. Another aspect of the present invention involves a mechanism for establishing a wireless interface to a telephone device through an upper box that is tied into a cable network such as a hybrid coaxial cable network. Another aspect of the present invention involves using a standard protocol such as the Internet protocol to maintain a digital connection in a cable network at the same time that a radio frequency link is used to transmit compressed voice / data information between such a telephone device. as a telephone set and an interface unit such as a top case. Aspects of the present invention also involve providing eliminating the need for adding wiring, such as POTS cabling, to accommodate one or more telephone sets, or alternatively eliminating the need to add multiple cable dips and adapters such as POTS / HFC adapters. A wireless feature according to the aspect of the invention provides for coupling a network interface box to an existing cable outlet and adding telephone devices as required without installing additional outputs. In addition, aspects of the information provide multi-line Internet telephone calls without rewiring. Another aspect of the invention involves adding an analog trunk interface where an Internet protocol voice device can be connected to a PBX device to provide an Internet PBX. For example, a user could dial a prefix, such as "9" to make a regular outbound phone call, or call a different prefix, such as "8" to make a phone call over the Internet. According to another aspect of the present invention, an Internet protocol speech device or a superior box provides connect to internal equipment, such as a personal workstation computer, and the use of the computing power of external devices for provide additional features such as FAX service with Internet protocol or conferences with video.

BRIEF DESCRIPTION OF THE DRAWING The invention can be better understood by referring to the accompanying drawing in which: Figure 1 shows, in block diagram form, a system embodiment incorporating aspects of the invention; and Figures 2 through 7 show, in block diagram form, modalities of portions of the system shown in Figure 1.

Figure 8 is a flow diagram illustrating a method of operation in accordance with the principles of the present invention.

DETAILED DESCRIPTION In Figure 1, a system according to aspects of the invention comprises a PSTN network and a cable network coupled to a cable modem termination system. The PSTN network and / or the cable network provide alternative paths for coupling the displayed system to the Internet, for example, to an Internet service provider (ISP). The cable modem termination system is coupled to a port, such as a home environment, comprising a cable modem network interface and first and second codecs for coupling to a conventional wired telephone via a line interface unit of subscriber and / or to a wireless telephone unit via a radio frequency modem interface, respectively. The data transmission between the different units shown in Figure 1 is presented as follows. The data transmission between the PSTN and the cable modem termination system shown in Figure 1 (path 1 in Figure 1) can be presented in a 64 Kbps / voice line format or in a Ti or higher hierarchy. The data in the cable network (for example, path 2 between the cable network and the cable modem termination system in Figure 1, or path 2 between the cable modem termination system and the cable modem unit) Cable modem network interface in the port in Figure 1) can be carried out over TCP / IP compressed at various regimes or uncompressed linear at 64 Kbps / voice line. The transmission data between the cable modem network interface and the first encoder-decoder (path 3 in Figure 1) can be presented in linear PCM format at 64 Kbps / voice line. The data transmission between the cable modem network interface and the second encoder-decoder (path 4 in Figure 1) can be presented in linear format at 64 Kbps / voice line or compress at different rates. The data communication in the path 5 in Figure 1 (between the first encoder-decoder and the subscriber line interface unit) may be in compressed-extended format at 64 Kbps / voice line. The data communication via path 6 in Figure 1 (between the second encoder-decoder and the radio frequency modem interface) may be in linear format at 64 Kbps / voice line or in compressed format at various regimes. Data communicated to and from the subscriber line interface unit (path 7 in Figure 1) can be presented in analog format (for example, for a FJ11 connector) and data communicated to and from the radio frequency modem interface (trajectory 8 in Figure 1) can be presented in digital radiofrequency modulation format. In the modalities shown in Figures 2 and 3, the Internet protocol telephony compression algorithms, the call setup, and the wireless telephone adapter are incorporated into an Internet protocol connection device or a client server. An example of a modality of this device is a device known as a Network Computer (NC) which is a computer similar to a personal computer (PC) that is primarily intended to provide an interface with the Internet. That is, a network computer is primarily intended to provide computing power and sufficient features, for example, to connect to the Internet, run network browser software, and provide email capability. A wireless telephone adapter according to aspects of the invention would allow the convenience of calling from any room in a house without expensive rewiring. The phone would ring only when there is an incoming Internet protocol telephone call, and present a dial tone, etc. when used to place a call. Two exemplary embodiments of an Internet protocol connection device having a wireless telephone interface are shown in Figures 2 and 3. The system shown in Figure 2 utilizes an analog wireless telephone interface such as CT-1 (46 / 47 MHz). The system shown in Figure 3 uses a digital 900 MHz extended spectrum wireless telephone interface. The analog wireless Internet protocol voice device can provide a lower cost solution. However, a 900 MHz digital wireless Internet protocol voice device may be more advantageous in terms of voice quality and expandability. For example, a wireless telephone typically provides better voice quality due to the ability to cancel out noise from the digital system and a wireless Internet protocol voice device may have more than one telephone set. Also, an Internet protocol speech device such as that shown in Figure 2 and / or 3 can be used for data service when used in conjunction with wireless modem. The systems shown in Figures 2 and 3 may include a voice modem for compressing and decompressing voice data if the modem of the Internet protocol connection device is running at low speeds. Table 1 lists some popular standard speech decoder-decoder algorithms and their associated data regimes.

Table 1 Standard voice compression standards G.711 data rate 64 kbps G.723.1 5.3 / 6.3 kbps G.728 16 kbps G.729 8 kbps GSM 13.3 kbps Figure 2 shows a client server device that includes Internet protocol voice features which, for example, can be included in an Internet protocol voice adapter card included in the client server device. The Internet protocol speech feature includes a subsystem CT-1 comprising a radio frequency transmitter circuit Tx and a receiver circuit Rx, a programmable PLL synthesizer, a baseband processor (audio), and a microprocessor interface. The Tx and Rx components and the PPL synthesizer are used to modulate and demodulate radio frequency signals for transmission and reception of wireless telephone signals. A duplexer is used to separate the transmission and reception paths of radio frequency communications. As discussed above, an integrated PCM encoder-decoder with filters may be needed to provide A / D and D / A conversions and compression, as well as signal filtering and reception. The digital signal processing unit (DSP) can be, for example, an integrated circuit (IC) that implements the voice coder-decoder under the control of the central processing unit (CPU) which can be a microprocessor. The central processing unit provides central control of the wireless Internet protocol interface device shown in Figure 2. The central processing unit is connected to various components of the device via a data control bus. The central processing unit has an integrated memory for storing the required control codes, including the implementation of H.323 standards and the TCP / UDP / IP protocols. Figure 3 shows another exemplary Internet protocol connection device having a digital wireless telephone interface such as a 900 Mhz interface. A baseband device usually includes an extended spectrum modem, an audio machine (PCM, DTMF, etc.), a voice coder-decoder, and a microcontroller. The Tx and Rx components and the PLL synthesizer are used to modulate and demodulate radio frequency signals for the transmission and reception of wireless telephone signals to and from the wireless telephone handset. A duplexer is used to separate the transmission and reception paths of radio frequency communications. A DSP unit is used to implement the voice coder-decoder under the control of the central processing unit. The central processing unit, and central processor, provides the central control of the interface device of the wireless Internet protocol shown in Figure 3. The central processing unit is connected to various components of the device via a bus of the data control. The central processing unit has built-in memory to store the required control codes, including the implementation of H.323 standards and TCP / UDP / IP protocols. Another aspect of the present invention is a wireless Internet telephony system to be connected to a cable network. The architecture of the network according to the principles of the present invention is shown in Figure 4. In Figure 4, a cable interface network (100) comprises a cable modem termination in the physical layer having a channel bidirectional connected to the hybrid fiber coaxial network (105). The physical layer modulation scheme may comprise, for example, quadrature amplitude modulation (QAM). The transport mechanism may comprise TCP / IP. In order to establish the voice application over the cable modem, the network interface unit can extend a protocol such as H.323 over TCP / IP. This allows pointing, the establishment of calls and other functions. Voice data (the fax and analog modem are included in this paradigm) can be carried in a compressed or uncompressed format. For example, compressed-extended 64 Kbps voice data can be carried over the cable network immersed in TCP / IP packets. Alternatively, they can be compressed using one of many voice compression methods and carried over the cable network immersed in TCP / IP packets. Certain types of data can not be compressed (for example fax or analog modem) and need to be carried in a linear format. Figure 4 also represents a wireless interface (104) to a plurality of telephone devices or receiving devices (101, 102, 103 ...). The protocol between the base device (100) and the telephone sets can be completely proprietary or some standard interface. Additionally, the data or voice format (compressed in one of many possible or uncompressed algorithms) may be different in the radio frequency network compared to the format in which the voice is transported over the HFC network. The advantages associated with maintaining the same data format (for example, compression scheme) in the wired (wireless) and wireless network are: 1. Only a coding / decoding process is necessary which, in a domestic environment, can be carry out in the wireless telephone handset or in the mobile terminal (multiple transcoding processes usually result in degradation of the original source material); and 2. The base station (for example, in the house) is transparent to the data of the handset of the mobile terminal. An advantage associated with maintaining different data formats (for example compression scheme) in the wired (wire) and wireless network is that certain compressed formats are specifically adapted to be carried over certain transmission channels. Channel errors, depending on how they occur, can cause different degradation to the source material depending on the compression scheme used. Wired and wireless environments are very different in terms of channel characteristics. Therefore, the personalization of the coding scheme to adapt to the characteristics of the channels may have some benefits in the overall design of the system. Figure 5 shows other details of an exemplary embodiment of the cable top box (100) in Figure 4. The cable channel (91) carrying both downstream and upstream data is usually a multiplexed frequency division to allow channels simultaneous operations.

In addition, within a specific channel, due to the nature of the shared cable medium, multiple users can signal using a time division multiplexed access mechanism. The task is coordinated by the head end. The cable interface (40) is a network interface unit (NIU) comprising a modulator / demodulator pair and a processing unit for interpreting the input data stream and the messages. One of the transport mechanisms used is TCP / IP. The network interface unit receives data, demodulates, decodes and extracts the information pertaining to specific voice channels in this application. It is also responsible for maintaining signaling information with the external network (for example using the H.323 protocol stack or any other signaling stack commonly used in telephony). Additional features such as a caller ID, messaging, voice mail, etc. are features that are supported by the network interface unit. This is enabled by its interface with a caller identifier block (50), the external digital signal processor (10) with an immersed microprocessor (5) that coordinates the messaging task, and voice compression / decompression as necessary . The incoming messages are stored in compressed or uncompressed format in the message memory (60). Other system architectures can be used where messages are stored in message memory in yet another compressed format to increase the time over which messages can be stored in a given amount of available memory. This compression / decompression task can be carried out in the DSP unit 10. The code memory (70) contains the code for the DSP machinery. The radio-frequency wireless circuit (20) is responsible for communication with the "telephone sets or mobile units and the exchange of specific information destined for each device." In addition to the data exchange, the radio-frequency wireless circuit 20 is also responsible for exchanging signaling. and status information The system shown in Figure 5 includes a common bus (80) between the functional components for data exchange, but a generalized architecture need not be limited to the busbar structure shown in Figure 5. Additionally , the messaging information and the caller identification information are exchanged between 100 and the telephone devices of the mobile terminals through radio frequency / wireless circuits.Figure 6 shows an exemplary embodiment of the receiver / upper box 100 described above with with respect to Figure 4 and name unit 700 with respect to Figure 6. The transmission and reception signals in a cable network through the radio frequency connector (796) are kept isolated using a diplexer (795). The cable tuner (705) and the demodulator (710) converts the digitally modulated signal (for example QAM) into a composite digital bitstream that is delivered in a Medium Access Control block - MAC (720) which performs the task of separating information into logical transport streams. Additionally, the unit 720 is responsible for synchronizing with the cable head end in order to provide access control to the upper case to the common cable means for the return channel information. The burst modulator (740) and the power amplifier (730) create and send data in the return channel path back to the cable network. The chain of radio frequency processing to process the digital information from the cable network starts with the interface, or the input / output (I / O) unit (760) which can be implemented as a specific integrated circuit of the application (ASIC) and which is connected to a wireless phone processing unit (750), which can also be part of an ASIC or a separate ASIC, to create individual links with telephone sets or mobile receivers. The unit 750 is coupled with DRAM memory units 765 and ROM 770 to receive stored processing instructions and for temporary data storage during processing. The information destined for each individual telephone set or mobile receiver can be divided into time, modulated and sent over a radio frequency link through the radio frequency connector (797). Additional information streams processed by the MAC processing block (720) can be routed to an ethernet port (783) through an ethernet controller (781) or a universal serial bus (USB) port through a controller of universal series busbar (785) or an RS232 interface (791) through an RS232 (790) driver. The various functions shown in Figure 6 are connected to the busbar 721 for data communication and control information between the functions and between the functions and the central processing unit 786 which controls the operation of the function in the device. 700. Also coupled to the busbar 721 are the memory units 775 and 780 for storing control and data programs for the control unit for the central processing unit 786 and other functions in the device 700. The power for the unit 700 it is provided by a 792 power supply. Also, although many of the processing blocks shown in Figure 6 may optionally depend on the specific application or product, the system shown in Figure 6 illustrates the composite nature of the data that comes about. the cable system. The trajectory for voice channels is of particular interest with respect to the present invention. Figure 7 shows a block diagram of an implementation of a wireless telephone apparatus 101. The telephone apparatus 101 comprises a DSP unit 201 that includes a microprocessor 210, a loudspeaker, a headset, radio frequency circuits and a keyboard. The microprocessor 210 controls the various components of the wireless telephone apparatus 101 via a busbar of the system 202. The radio frequency circuits are connected to a radio frequency antenna to transmit and receive wireless radio frequency signals. A keypad 204 is used for a user to dial a telephone number and to control other functions of the cordless telephone. The DSP converts an analog signal into a digital signal to be transmitted over the radio frequency spectrum if a digital transmission system is used. The memory 203 stores the program codes to be executed by the microprocessor 210. Figure 8 shows a flow diagram illustrating a method of operation in accordance with the principles of the present invention. In step 802, a signal is received, for example, through the cable interface 40 of the unit 100. This signal is demodulated via the cable interface 40 in a signal demodulated in step 803. The unit can decide whether to compress or further decompresses this demodulated signal under the control of the DSP unit 10 as described above. The DSP causes this signal to be further modulated in step 805 by the radiofrequency / wireless circuits 20. This additional modulated signal is wirelessly transmitted to a wireless unit, for example, as shown in Figure 7. After receiving this signal Additional modulated on the wireless unit, the wireless unit demodulates this signal to complete the Internet protocol voice call. It will be understood that the embodiments and variations shown and described herein are illustrative only and that various modifications may be implemented by those skilled in the art without departing from the scope and spirit of the invention.

Claims (8)

1. CLAIMS l. A method for processing a voice call over an Internet comprising the steps of: receiving a signal from the cable network, the signal representing Internet protocol data packets of the voice call and both being modulated in a first format and compressed to match a cable network format; demodulate the modulated signal in the first format; decompress the signal; compress the signal in a format of a domestic environment; modulate the compressed signal in a second format; wirelessly transmit the compressed signal in the format of the domestic environment and modulate it in the second format to a wireless device; and demodulating and decompressing the signal in the wireless device.
2. 2. The method of claim 1, wherein the first format satisfies the H.323 standard.
3. 3. The method of claim 1, wherein the first format comprises a modulation scheme equal to the second format.
4. 4. The method of claim 1, wherein the first format comprises a modulation scheme different from the second format. A system for processing a voice call over the Internet, comprising: an element for receiving, demodulating and decompressing a signal representing Internet protocol data packets of the voice call, the signal being received from a network of cable, modulated in a first format and compressed in a cable network format; an element for modulating the signal in a second format and compressing the signal in a format of a domestic environment for wireless transmission of the modulated and compressed signal; and a wireless device that includes an element for demodulating and decompressing the signal to complete the voice call. 6. The system of claim 5, wherein the first format complies with the H.323 standard. The system of claim 5, wherein the first format comprises the same modulation scheme as the second format. The method of claim 1, wherein the first format comprises a modulation scheme different from the second format.