HK1084278B - Apparatus and method for tandem-free vocoder operation between non-compatible communication systems by extracting inter- or intrasystem tfo-information - Google Patents

Description

Apparatus and method for tandem-free vocoder operation between non-compatible communication systems by extracting intra-system or inter-system TFO information

Technical Field

The present invention relates to data communications, and more particularly to coordinating vocoder operations between non-compatible communication systems.

Background

The field of wireless communications has many applications including, for example, cordless telephones, paging, wireless local loops, Personal Digital Assistants (PDAs), internet telephony, and satellite communication systems. One particularly important application is the cellular telephone system of remote subscribers. As used herein, the term "cellular" system encompasses systems using cellular or Personal Communication Services (PCS) frequencies. Various air interfaces have been developed for such cellular telephone systems, such as Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), and Code Division Multiple Access (CDMA). In connection with this, various national and international standards have been established, such as Advanced Mobile Phone Service (AMPS), Global System for Mobile (GSM) and interim standard 95 (IS-95). IS-95 and its derivative standards IS-95A, IS-95B, ANSI J-STD-008 (generally referred to herein as IS-95) and proposed high data rate systems are promulgated by the Telecommunications Industry Association (TIA) and other well known standard entities.

Cellular telephone systems configured pursuant to the use of IS-95 employ CDMA signal processing techniques to provide efficient and robust cellular telephone service. Exemplary cellular telephone systems configured substantially in accordance with the use of the IS-95 standard are described in U.S. patent nos. 5,103,459 and 4,901,307, which are assigned to the assignee of the present invention and incorporated herein by reference. An exemplary system using CDMA techniques is the CDMA2000 ITU-R Radio Transmission Technology (RTT) candidate proposal (referred to herein as CDMA2000) issued by the TIA. The cdma200 standard IS set forth in the draft of IS-2000 and IS approved by the TIA. Another CDMA standard is the W-CDMA standard, as embodied in the third generation partnership project "3 GPP", with reference numbers 3G TS 25.211, 3G TS25.212, 3G TS 25.213, and 3G TS 25.214.

Each standard defines how various types of information are handled for transmission. In a typical communication system, an encoder generates a stream of information bits representing voice or data traffic. The bit stream is subdivided and grouped, concatenated with various control bits, and grouped into a suitable format for transmission. Voice and data traffic may be transmitted in various formats, such as frames, packets, and subpackets, according to an appropriate communication standard. For ease of explanation, the term "frame" will be used herein to describe the transmission format in which traffic is transmitted over the transmission medium. However, the term "frame" will also be used herein to describe the output of the speech coder. The meaning of a word depends on the context in which the word is used.

A speech encoder is a device that extracts parameters related to a model of human speech generation and then uses those parameters to compress the speech for transmission. A speech encoder generally comprises an encoder and a decoder. The speech encoder divides the incoming speech signal into blocks of time, or analysis frames. The encoder analyzes the incoming speech frame to extract certain relevant parameters and then quantizes the parameters into a binary representation. The binary representation is grouped into transmission frames and transmitted over a communication channel to a receiver with a decoder. The decoder processes the transport frames, dequantizes them to produce parameters, and re-synthesizes speech frames using the dequantized parameters. Speech coders are also referred to as voice coders, i.e., "vocoders," and these terms are used interchangeably herein.

The function of a speech encoder is to compress a digitized speech signal into a low bit rate signal by removing all natural redundancies inherent in speech. Digital compression is achieved by representing the speech frame with a set of parameters and employing quantization to represent the parameters with a set of bits. If the input speech frame has a plurality of bits N_iThe speech encoder generates an output frame having a plurality of bits N_oThen the compression factor achieved by the speech coder is C_r＝N_i/N_o. The challenge is to maintain high speech quality of the decoded speech while achieving the target compression factor. The performance of the speech coder depends on the implementation of the speech model, or the combination of the above-mentioned analysis and synthesis models, and on the number of frames N per frame_oThe case where the target bit rate of bits performs a parameter quantization process. Thus, the goal of the speech model is to use a small set of parameters per frame to obtain the essence of the speech signal, i.e., the target speech quality.

Different types of speech coders are employed in various existing wireless communication systems, often using quite different speech compression techniques. However, the transmission frame format and processing defined by one particular standard is likely to be different from that defined by other standards. For example, the CDMA standard supports the use of variable-rate vocoder frames in a spread spectrum environment, while the GSM standard supports the use of fixed-rate vocoder frames and multi-rate vocoder frames. Similarly, the Universal Mobile Telecommunications System (UMTS) standard also supports fixed-rate and multi-rate vocoders, but does not support variable-rate vocoders. For compatibility and interactivity between these incompatible communication systems, it is highly desirable to support variable-rate vocoder frames in GSM and UMTS systems, as well as support variable-rate vocoder frames in CDMA systems. An example of a variable rate vocoder is the Selectable Mode Vocoder (SMV), which is disclosed in US-893; one example of a multirate vocoder is the Adaptive Multirate (AMR) vocoder, which is described in "ETSI EN 301704 Digital Cellular Telecommunications System; (iii) Adaptive Multi-Rate (AMR) SpeechTranscoding (AMR Standard); while one example of a fixed-rate vocoder is the advanced full-rate vocoder, which is described in 3GPP TS 46.060: "Digital Cellular telecommunications system (Phase 2 +); published in Enhanced Full Rate (EFR) speed coding ".

One important reason for facilitating compatibility and interactivity between non-compatible systems is to enable the use of wideband vocoders between non-compatible systems. A "wideband" vocoder is a vocoder that encodes speech in the 7000Hz frequency range. In conventional landline telephone systems, the bandwidth of the transmission medium and the terminals is limited to 4000Hz, so voice is typically transmitted in a narrow band of 300Hz to 3400Hz, while control and signaling overhead is carried outside this range.

Given the physical constraints of landline telephone systems, signal propagation within cellular telephone systems is implemented with these same narrow-band frequency constraints so that calls originating from a cellular subscriber unit can be sent to the landline unit. However, cellular telephone systems are able to transmit signals over a wide frequency range because there are no physical limitations in cellular systems that require a narrow frequency range. An exemplary standard for generating signals with a wide frequency range is published in document G.722 ITU-T entitled "7 kHz Audio-Coding with 64 kBits/s" in 1989. Thus, wideband copies of the variable-rate and multi-rate vocoders referenced above were developed. Wideband copies provide a sound advantage over narrowband vocoders.

When switching broadband signals between two broadband terminals operating in a cellular system, additional processing and constraints must be utilized, since the broadband signals are "large" for the narrowband transmission channels. Currently, the maximum data capacity of the Public Switched Telephone Network (PSTN) is 64 kbps. For a narrow band signal 8000 samples/sec must be obtained in order to reconstruct the original signal accurately. Standard Pulse Code Modulation (PCM) sample data is represented by 8-bit symbols. By using 8-bit symbols, the maximum data capacity of the PSTN connection can be achieved while minimizing the quantization error (8000 samples/sec × 8 bits/sample 64000 bps). However, for wideband signals, 16000 samples/sec must be obtained in order to accurately reconstruct the original signal. Therefore, the wideband signal is too "large" for the narrowband transmission channel.

Problems arising from the physical constraints of a 64kbps PSTN connection can be avoided by implementing a tandem-free operation between infrastructure entities within the network. Tandem free operation refers to bypassing vocoders within infrastructure entities in the network. When tandem-free operation is implemented, a wideband signal from one terminal in a network may be transmitted over the PSTN to another terminal in the same network by using punctured 8-bit PCM symbols, where the vocoder output bits are punctured into PCM symbols.

In order to achieve tandem-free operation, the vocoders at the transmitting and receiving ends must be compatible. This is not a problem when broadband signals are exchanged between terminals within the same communication network. Copending U.S. patent application (attorney docket No. 010004) "COMMUNICATIONS USING wireless terminal" (now U.S. patent publication No. 2002-. However, there is a problem when it is desired to exchange broadband signals between terminals of non-compatible networks.

For example, in multiple access systems such as CDMA, a variable rate vocoder is implemented. An example of a variable rate vocoder is a wideband selectable mode vocoder (WB-SMV). However, in multiple access systems such as GSM, fixed-rate or multi-rate vocoders are implemented. An example of a multi-rate vocoder is the wideband adaptive multi-rate vocoder (AMR-WB). Although vocoder types differ structurally and functionally, it should be noted that common general terms are shared among vocoder types. For example, a "mode" in an AMR-WB vocoder refers to a vocoder frame having a fixed data rate. However, the "mode" in the WB-SMV vocoder refers to the average data rate achieved by mixing different frame types. The meaning of a word should be derived from the context in which the word is used. To minimize confusion resulting from the use of such common shared terminology among multiple classes of vocoders, the embodiments described below will use WB-SMV vocoder configurations and terminology to refer to variable-rate vocoders, while AMR-WB vocoder configurations and terminology to refer to fixed-rate and multi-rate vocoders, rather than narrowband versions. It should be understood, however, that the configuration details may be extended to accommodate other vocoders without undue experimentation. The technical specification of the AMR-WB frame structure is specified in document 3GPP TS 26.201 V5.0.0 (2001-03). The technical specification of the WB-SMV frame structure has not yet been released.

Thus, the embodiments described below are used to coordinate the transmission of wideband signals between different vocoders of non-compatible systems, such that the voice advantage of the wideband vocoder is not sacrificed when transmitting between non-compatible systems.

Disclosure of Invention

Methods and apparatus are presented herein to enable tandem-free operation between incompatible systems. In one aspect, an apparatus is presented for coordinating operation between a first vocoder of a first communication system and a second vocoder of a second communication system, wherein the first communication system is incompatible with the second communication system, the apparatus comprising: a first extraction element for extracting Tandem Free Operation (TFO) information from a received intra-system TFO frame; a second extraction element for extracting TFO information from the received intersystem TFO frame; and a selection element communicatively coupled to the first extraction element and the second extraction element, wherein the selection element is configured to select either of the extraction elements based on whether the received frame is an intra-system TFO frame or an inter-system TFO frame.

In another aspect, a method is presented for coordinating a tandem-free operation feature of a first communication system with a tandem-free operation feature of a second communication system, wherein the first communication system is incompatible with the second communication system, the method comprising: determining, at a first infrastructure entity of a first communication system, an extraction capability of a second infrastructure entity of a second communication system; selecting a proper Tandem Free Operation (TFO) frame format; encapsulating a vocoder frame into a TFO frame using the appropriate TFO frame format; sending the TFO frame to a second infrastructure entity; receiving the TFO frame at a second infrastructure entity; determining the source type of the TFO frame; and extracting the content of the TFO frame according to the source type of the TFO frame.

In another aspect, an apparatus for coordinating a tandem free operation feature of a first communication system with a tandem free operation feature of a second communication system, wherein the first communication system is incompatible with the second communication system, the apparatus comprising: means for determining, at a first infrastructure entity of a first communication system, an extraction capability of a second infrastructure entity of a second communication system; means for selecting an appropriate Tandem Free Operation (TFO) frame format and encapsulating a vocoder frame into a TFO frame using the appropriate TFO frame format; means for transmitting the TFO frame to a second infrastructure entity; means for receiving a TFO frame at a second infrastructure entity; and means for determining a source type of the TFO frame and extracting the content of the TFO frame according to the source type of the TFO frame.

In yet another aspect, an apparatus is presented for coordinating operation between a first vocoder of a first communication system and a second vocoder of a second communication system, wherein the first communication system is incompatible with the second communication system, the apparatus comprising: at least one memory element; and at least one processing element configured to implement a set of instructions held in the at least one memory element, the set of instructions to: extracting Tandem Free Operation (TFO) information from the received intra-system TFO frame using a first table; and extracting TFO information from the received intersystem TFO frame using a second table, wherein the intrasystem TFO frame and the intersystem TFO frame have the same fields, but the first table and the second table have different bit definitions.

Drawings

Fig. 1 is a schematic diagram of a communication system supporting multiple users.

Fig. 2 is a block diagram of the encoding and decoding functions performed by various vocoders located within the communication device of fig. 1.

Fig. 3 is a block diagram of a general arrangement for intra-system vocoder bypass in system 1 and system 2.

Fig. 4 is a hardware block diagram for generating an intra-system TFO frame and receiving an intra-system/inter-system TFO frame.

Fig. 5 is a hardware block diagram for generating intra-system/inter-system TFO frames and receiving intra-system TFO frames.

Fig. 6 is a hardware block diagram for generating and receiving intra-system/inter-system TFO frames at an originating system and receiving inter-system TFO frames at a target system.

Fig. 7 is a block diagram of another hardware configuration for generating and receiving intra-system/inter-system TFO frames.

Fig. 8A and 8B are flow diagrams illustrating coordinated TFO operations between communication systems.

Detailed Description

As shown in fig. 1, a wireless communication network 10 generally includes a plurality of remote stations (also referred to as subscriber units or mobile stations or user equipment) 12a-12d, a plurality of base stations (also referred to as Base Transceiver Stations (BTSs) or node bs) 14a-14c, a Base Station Controller (BSC) (also referred to as a radio network controller or packet control function 16), a Mobile Switching Center (MSC) or switch 18, a Packet Data Serving Node (PDSN) or interworking function (IWF)20, a Public Switched Telephone Network (PSTN)22 (typically a telephone company), and an Internet Protocol (IP) network 24 (typically the internet). For simplicity, four remote stations 12a-12d, three base stations 14a-14c, one BSC 16, one MSC18, and one PDSN20 are shown. Those skilled in the art will appreciate that there may be any number of remote stations 12, base stations 14, BSCs 16, MSCs 18, and PDSNs 20.

In one embodiment, the wireless communication network 10 is a packet data service network. The remote stations 12a-12d may be any of a number of different types of wireless communication device such as a portable phone, a cellular phone connected to a notebook computer running an IP-based Web browser application, a cellular phone with an associated hands-free car kit, a Personal Digital Assistant (PDA) running an IP-based Web browser application, a wireless communication module incorporated within a portable computer, or a fixed location communication module such as found in a wireless local loop or meter reading system. In the most general embodiment, the remote station may be any type of communication unit.

The remote stations 12a-12d may be advantageously configured to execute one or more wireless packet data protocols, such as the protocols described in the EIA/TIA/IS-707 standard. In a particular embodiment, the remote stations 12a-12d generate IP packets directed to the IP network 24 and encapsulate the IP packets into frames using a Point-to-Point protocol (PPP).

In one embodiment, the IP network 24 is coupled to the PDSN20, the PDSN20 is coupled to the MSC18, the MSC is coupled to the BSC 16 and the PSTN 22, and the BSC 16 is coupled to the base stations 14a-14c by wireline configured for voice and/or data packet transmission according to any of several known protocols, including, for example, E1, T1, Asynchronous Transfer Mode (ATM), Internet Protocol (IP), Point-to-Point protocol (PPP), frame Relay, high bit Rate digital subscriber line (HDSL), Asymmetric Digital Subscriber Line (ADSL), or other common digital subscriber line equipment and services (xDSL). In another embodiment, the BSC 16 is coupled directly to the PDSN20, and the MSC18 is not coupled to the PDSN 20.

During normal operation of the wireless communication network 10, the base stations 14a-14c receive and demodulate sets of reverse link signals from various remote stations 12a-12d involved in telephone calls, Web browsing, or other data communications. As used herein, the "reverse link" refers to transmissions directed from a remote station to a base station. Each reverse link signal received by a given base station 14a-14c is processed at that base station 14a-14 c. Each base station 14a-14c may communicate with a plurality of remote stations 12a-12d by modulating and transmitting sets of forward link signals to the remote stations 12a-12 d. As used herein, the "forward link" refers to transmissions directed from a base station to a remote station. For example, as shown in FIG. 1, the base station 14a communicates with first and second remote stations 12a, 12b simultaneously, and the base station 14c communicates with third and fourth remote stations 12c, 12d simultaneously. The resulting packets are forwarded to the BSC 16, which provides call resource allocation and mobility management functions including soft handoff of a call for a particular remote station 12a-12d from one base station 14a-14c to another base station 14a-14 c. For example, the remote station 12c communicates with two base stations 14b, 14c simultaneously. Eventually, when the remote station 12c moves far enough away from one of the base stations 14c, the call will be handed off to the other base station 14 b. In a W-CDMA system, which is classified as a UMTS system, the terms of the components of the wireless communication system are different but the functions are the same. For example, a base station is referred to as a Radio Network Controller (RNC) operating in a UMTS terrestrial radio access network (U-TRAN). The forward link is called the "downlink" and the reverse link is called the "uplink.

If the transmission is a conventional telephone call, the BSC 16 will route the received data to the MSC18, which provides additional routing services for interfacing with the PSTN 22. If the transmission is a packet-based transmission, such as a data call directed to the IP network 24, the MSC18 will route the data packet to the PDSN20, which will send the packet to the IP network 24. Alternatively, the BSC 16 may route the packets directly to the PDSN20, which sends the packets to the IP network 24.

Fig. 2 is a block diagram of the encoding and decoding functions performed by various vocoders located within the communication devices of the wireless communication system of fig. 1. Remote station or terminal 12a is a communication device that includes a vocoder 201 having an encoding portion 202 and a decoding portion 203. The analog speech is received by the remote terminal 12a and encoded into packetized data by the encoding portion 202. The packetized data is transmitted to the base station 14 a. The decoding portion 213 of the vocoder 211 converts the packetized data into a standard pulse code modulated signal (PCM) for transmission over the PSTN (not shown). The PCM signal is sent over the PSTN to the target base station 14b, which target base station 14b alerts the target remote terminal 12 c. The encoding portion 222 of the vocoder 221 at the target base station 14b encodes the PCM signal into packetized data for transmission to the remote terminal 12 c. The decoding portion 233 of the vocoder 231 at the remote terminal 12c decodes the packetized data and forms synthesized speech.

The above process is also used to transmit signals from the remote terminal 12c to the remote terminal 12a through the encoder 232, decoder 223 and encoder 212. The use of multiple vocoders as shown in fig. 2 is referred to as "tandem vocoding. Degradation of a speech signal occurs due to multiple encoding and decoding functions performed on the speech signal. The concatenated vocoders may be bypassed if the vocoder at the originating terminal has the same configuration as the vocoder at the target site. Details of the implementation of vocoder Bypass are described in U.S. patent No. 5,956,673, entitled "Detection and Bypass of tandem coding Using Detection Codes," assigned to the assignee of the present invention and incorporated herein by reference. In particular, a pseudo-random detection code may be embedded in the PCM output so that a receiving vocoder programmed with the correct service option can detect the code, thereby concluding that the originator is using a similar vocoder. If the vocoders of the remote terminals are the same, the decoder of the target remote terminal may decode the encoded speech produced by the originating remote terminal. However, if the vocoders are not identical, bypass of concatenated vocoders cannot be achieved in the prior art.

The embodiments described herein are used to coordinate the operation of different vocoders, thereby enabling tandem-free operation, i.e., vocoder bypass, between non-compatible systems. As used herein, a non-compatible system may be considered a system that uses a different access technology than the originating system. For example, CDMA-based systems and TDMA-based systems are considered to be incompatible systems herein. In general, the embodiments are directed to transmitting variable-rate and multi-rate vocoder frame content in a format that is accessible by both the infrastructure entities of the originating and terminating systems.

It should be noted first that Tandem Free Operation (TFO) is essential in order to achieve the full voice advantage of wideband code generation between two terminals. The wideband signal requires a data capacity of 128kbps (16000 samples/sec × 8 bits/sample), while the narrowband transmission channel provides only a capacity of 64 kbps. To overcome this problem, certain "in-path" devices of the infrastructure entity, such as echo cancellers and the like, should be disabled, while the encoder at the transmitting infrastructure entity should generate an impure PCM signal. In particular, an originating terminal encodes a wideband input signal into vocoder frames and transmits the vocoder frames to the originating infrastructure entity. The originating infrastructure entity decodes the received vocoder frame and generates PCM symbols based on the decoded signal. The originating infrastructure entity then punctures the received vocoder frame bits into the resulting stream of PCM symbols. In other words, the generated PCM symbol stream is altered by the inclusion of vocoder frame bits.

Conventionally, a PCM symbol is 8 bits long. In one approach, the stream of PCM symbols is altered by replacing the two least significant bits of the PCM symbols with the two bits of the received vocoder frame. At the target infrastructure entity, the two least significant bits are extracted and used to reconstruct the vocoder frame. The other 6 bits of the PCM symbol are discarded or these bits are saved when the tandem free connection fails.

At the target infrastructure entity, the reconstructed vocoder frame is transmitted directly to the target terminal. The procedures and apparatus required to transmit a vocoder frame from a non-compliant infrastructure entity to a non-compliant target terminal are described in co-pending U.S. patent application (attorney docket No. 020742, now U.S. patent application publication No. 2004-0081195) and co-pending U.S. patent application (attorney docket No.). In the above-mentioned U.S. patent application, vocoder frames are transferred between vocoders of non-compatible systems by reformatting the vocoder frames at the infrastructure entity, as opposed to converting the vocoder frames. The details of the reformatting are not discussed herein.

Embodiments described herein relate to processes and apparatus for puncturing PCM symbols with vocoder frame bits at an originating infrastructure entity and processes and apparatus for extracting vocoder frame bits from the punctured PCM symbols at a target infrastructure entity. The setup process for establishing the tandem free operation is not the subject of the present application.

In one embodiment, a vocoder frame is repackaged into a special TFO frame that is punctured into PCM symbols. In one aspect of this embodiment, new tables are created that redefine the control bits of the already existing transport channel frames in order to generate the special TFO frame. In another embodiment, the decoding subsystem of the non-compliant party is implemented within an infrastructure entity such that the received transport channel frames are checked for non-compliant vocoder frame content and routed to the appropriate decoding subsystem.

In a first embodiment, an infrastructure entity within the originating infrastructure entity receives a vocoder frame and generates a TFO frame. The hardware performing this task is generally referred to herein as a TFO frame generator and may comprise any suitably configured processing entity. Similarly, software may be implemented to perform the functions of the TFO frame generator. The following shows a general TFO frame structure output from the TFO frame generator.

TFO frame structure

Bit octet	1	2	3	4	5	6	7	8
									0	System identifier bits, data bits and control bits
1
	2
...
	...
39

In the above example, the TFO frame consists of 40 octets with 320 bits. The data bits and control bits in the received vocoder frame are strategically embedded in the TFO frame structure. A particular bit position corresponds to a particular function. For example, the bit positions in the first octet may be reserved for system identifiers, the bit positions in the second third octet are reserved for data only, i.e., the bits of the vocoder, and the bits in the last third octet may be reserved for control bits from the originating infrastructure entity to the target infrastructure entity. Thus, each bit position has a defined meaning. 320 bits are sufficient to transmit one vocoder frame. For example, for a20 ms analysis frame, the wideband vocoder outputs 267 bits. Thus, one TFO frame may correspond to one vocoder frame.

After generating the TFO frame or while the TFO frame is being generated, an infrastructure entity within the originating infrastructure entity decodes the received vocoder frame into speech and generates PCM symbols with the decoded speech. Since the originating infrastructure entity would need bits in the PCM symbols to transmit the TFO frame, the PCM waveform should use 2⁶Cryptographic representation of stages, not 2⁸A codebook of stages. Therefore, the quantization error increases. The infrastructure entity then starts to attach the generated TFO frame to the generated PCM symbols. Alternatively, the infrastructure entity may keep a larger PCM codebook, simply "truncating" the PCM symbols at least once at some specified locations. In either case, the PCM symbols are likely to be sent in 20ms TFO transmission frames, since each 20ms frame can transmit 160 symbols, which is sufficient to transmit 320 TFO frame bits.

The purpose of generating a PCM signal from decoded vocoder frames is not due to any technical constraints but rather due to legal constraints. The transmission of PCM signals is only necessary in order to comply with the consortium directives requiring access to communication between parties by appropriate law enforcement authorities.

At the target infrastructure entity, the altered PCM symbols are received and the bits of the TFO frame are extracted. The extraction may be performed by any hardware suitably configured to perform the extraction function. Alternatively, software may be implemented by the processing entity and the memory to perform the extraction function. For purposes of illustration, the hardware/software will be referred to herein as a TFO frame extractor. Note that the target infrastructure entity is aware of the presence of TFO bits through the call setup process, which is the subject of the above-mentioned co-pending U.S. patent application. The TFO frame extractor may be further configured to reconstruct the TFO frame from the extracted bits. The bits of the vocoder frame are extracted from the reconstructed TFO frame and rearranged into a vocoder frame. Likewise, the extraction of vocoder bits may be performed by any hardware/software suitably configured to perform the extraction function. For purposes of illustration, an alternative to hardware or software would be referred to as a vocoder frame extractor. The vocoder frame is then further reformatted for transmission to the target terminal. It is noted that the functions of the TFO frame extractor and the vocoder frame extractor may be combined in a single functional entity, if desired.

In the above embodiment, the TFO frame generator is configured to generate two different types of TFO frames according to the source of the vocoder frame. If the source of the vocoder frame is a variable rate vocoder and the target terminal is in a GSM or UMTS system, or if the source of the vocoder frame is a multi-rate vocoder and the target terminal is in a CDMA system, special control bits are inserted into the TFO frame depending on the source type. Thus, the decoder at the target infrastructure entity should be configured to correctly interpret the control bits within a given TFO frame. Decoder configuration details are given below in connection with the hardware configuration.

A TFO frame may be viewed as a table in which specific bit positions convey information about system parameters. For example, bit positions in one location would identify an operating mode for the originating vocoder, bit positions in another location would identify the vocoder type, and bit positions in yet another location would identify the codebook used by the vocoder. This understanding of TFO frames is consistent with the interpretation of typical transport frames. However, there is an important difference because the control bits of these TFO frames are not interpreted in the same way as the regular transmission frames.

The embodiments are directed to variations at the infrastructure entity of a non-compatible system, and in particular to the transmit and receive subsystems at the infrastructure entity. The described embodiments contemplate flexible transmit and receive subsystems that can alternate between conventional transmission frame formats and TFO frame formats of intersystem wideband vocoder frame bits. Furthermore, the generation and extraction of TFO frames with wideband vocoder frame bits may be simplified by appropriating existing tables for the TFO frame format of intra-system vocoder frame bits.

TFO frame generator and extractor

To implement the ideas and concepts described herein, the sending and receiver subsystems at the originating and terminating infrastructure entities must be properly configured. In order to perform vocoder bypass within the system, each infrastructure entity within the network should have a TFO frame generator capable of generating TFO frames and a TFO frame extractor capable of processing received TFO frames. (the vocoder frame extractor is not included in the following example for illustrative purposes only.) fig. 3 illustrates a common arrangement of vocoder bypass within the system.

The infrastructure entities 300a, 300b of the system 1 are each configured with a TFO frame generator G₁And a TFO frame extractor E₁For performing vocoder bypass within the system. The infrastructure entities 310a, 310b of system 2 are each configured with a TFO frame generator G₂And a TFO frame extractor E₂For performing vocoder bypass within the system. The following embodiments are directed to changing existing tables for implementing intra-system TFO within each system. However, in order to perform intersystem vocoder bypass, infrastructure entities in different communication systems should include at least one of the configurations shown in fig. 4 to 7.

Fig. 4 is a block diagram illustrating an embodiment in which hardware for generating intra-system TRO frames and hardware for receiving intra-system and inter-system TFO frames are implemented at all infrastructure entities of a non-compatible system. In this embodiment, each infrastructure entity 400a, 400b in system 1 includes an intra-system TFO frame generator G₁An intra-system TFO frame extractor E₁And TFO frame extractor E of system 2₂System 2 is not compatible with system 1. Each infrastructure entity 410a, 410b in System 2 includes an intra-System TFO frame Generator G₂An intra-system TFO frame extractor E₂And TFO frame extractor E of system 1₁。

According to this embodiment, each infrastructure entity is equipped with a TFO frame extractor of another system. The intra-system TFO frame extractor need not be changed. To select an extractor appropriate for the TFO frame content (i.e., either intra-system vocoder frame bits or inter-system vocoder frame bits), a switching entity should be cooperatively coupled to the different TFO frame extractors. Any hardware or software configuration for selecting between extractors may be implemented. Note that each extractor will use a different table to determine the interpretation of the bits at a particular location within the TFO frame. An alternative embodiment may therefore be a single extractor implemented with two tables, wherein a selection element determines which table the extractor uses depending on the source type of the received TFO frame. This alternative embodiment may be implemented for any of the embodiments described below.

Fig. 5 is a block diagram illustrating an embodiment in which hardware for generating intra-system and inter-system TFO frames and hardware for receiving intra-system TFO frames are implemented at all infrastructure entities of a non-compatible system. In this embodiment, each infrastructure entity 500a, 500b in system 1 includes an intra-system TFO frame generator G₁An intra-system TFO frame extractor E₁' and TFO frame generator G of System 2₂', system 2 is not compatible with system 1. Each infrastructure entity 510a, 510b in System 2 includes an intra-System TFO frame Generator G₂An intra-system TFO frame extractor E₂An intersystem TFO frame extractor E₂' and TFO frame generator G of System 1₁’。

As used herein, the subscript indicates that the extractor or generator has been modified in order to receive vocoder frames from a vocoder of another system. For example, if system 1 is a CDMA system and system 2 is a GSM system, then TFO frame generator G₂May be configured to receive a multi-rate vocoder frame. However, direct substitution of G in CDMA systems₂Cause problems because of G₂Are not configured to receive variable rate vocoder frames. Therefore, it is necessary to handle G₂Modified as G₂The latter can receive variable rate vocoder frames and still generate TFO frame formats suitable for GSM.

The modification may take the form of an alternative table in which additional identification codes are created, different CRC polynomials are used, and discontinuous/continuous (DTX/CTX) transmission indicators are disabled. (DTX/CTX is a feature of multi-rate vocoders that is not found in variable-rate vocoders.) the substituted table redefines the function of bits at specific locations of the TFO frame. For example, bits representing the AMR-WB mode can be placed in a frame table modified based on the WB-SMVTFO frame table. As described above, the TFO frame format for WB-SMV bypass within the system has been defined. There are no bit positions specified for the AMR-WB mode bits in the WB-SMV TFO frame format within the system. In this embodiment, the functionality of specific bit positions in the WB-SMV TFO frame table is redefined so that AMR-WB mode bits can be transmitted at these bit positions and vice versa.

For example, bit position 2 in the third octet may be interpreted as a data bit according to a given table of the intra-system WB-SMV TFO frame. However, if a WB-SMV intra-system TFO frame is to be used as an inter-system TFO frame for an AMR-WB target site, the infrastructure entity in the CDMA system may use an alternative AMR-WB table that defines bit position 2 in the third octet as a control bit. Thus, the infrastructure entity may have hardware and/or software that already has possession of the existing intra-system frame format for functionality in the external system.

If TFO frame generator G₂' modified from G₂Then the receiver subsystem at system 2 needs to be able to read G correctly₂' generated TFO frame. The receiver at system 2 also needs to be able to read intra-system TFO frames.

Note that this embodiment enables the infrastructure entity to receive intra-system TFO frames and slightly modified intra-system TFO frames. The infrastructure entity need not receive intra-system TFO frames of another system, which may have a completely incompatible format.

Fig. 6 is a block diagram illustrating an embodiment, where hardware for generating and receiving inter-system and intra-system TFO frames is present at the originating system,hardware is present at the terminating system for generating intra-system TFO frames and receiving inter-system TFO frames. In this embodiment, each infrastructure entity 600a, 600b in system 1 includes an intra-system TFO frame generator G₁An intra-system TFO frame extractor E₁TFO frame generator G of system 2₂' and TFO frame extractor E of System 2₂. Each infrastructure entity 610a, 610b in System 2 includes an intra-System TFO frame Generator G₂And an intra-system TFO frame extractor E₂’。

Fig. 7 is a block diagram illustrating an embodiment in which hardware for generating intra-system TFO frames and receiving inter-system TFO frames is implemented at an originating system and hardware for generating and receiving intra-system and inter-system TFO frames is present at a terminating system. In this embodiment, each infrastructure entity 700a, 700b in system 1 includes an intra-system TFO frame generator G₁And an intra-system TFO frame extractor E₁'. Each infrastructure entity 710a, 710b in System 2 includes an intra-System TFO frame Generator G₂An intra-system TFO frame extractor E₂TFO frame generator G of system 1₁' and TFO frame extractor E of System 1₁。

Fig. 8A and 8B are flowcharts describing the method of the above embodiment. Fig. 8A depicts the generation of TFO frames at the originating system and fig. 8B depicts the extraction of TFO frames at the target system.

At step 800 of fig. 8A, it is determined that broadband communication should be initiated between a terminal of a first communication system and a target terminal of a non-compatible communication system.

At step 802, the TFO frame generator of the first system determines the extraction capabilities of the second system.

Based on the decision at step 802, the TFO frame generator selects an appropriate TFO frame format at step 804 for transmitting vocoder bits from the terminal of the first communication system to the target terminal.

At step 806, the intersystem TFO frame is transmitted to an infrastructure entity of the second communication system, wherein the infrastructure entity supports the target terminal.

At step 810 of fig. 8B, the infrastructure entity of the second communication system begins receiving TFO frames that are punctured into PCM streams. At step 812, the infrastructure entity determines the source type of the TFO frame. If the source type is the type of intra-system TFO frame, flow proceeds to step 820. If the source type is the type of inter-system TFO frame, flow proceeds to step 830.

At step 820, the infrastructure entity proceeds to extract TFO frame bits from the truncated PCM stream and determines the contents of the TFO frame according to intra-system specifications.

At step 830, the infrastructure entity proceeds to extract TFO frame bits from the punctured PCM stream and determines the contents of the TFO frame based on intra-system TFO parameters of the first communication system.

The decision made at step 812 is based on the system being configured with a plurality of extraction elements, each configured with intra-system TFO parameters of the external system. It should be noted that step 812 and step 830 need not be implemented if the first communication system incorporates the intra-system TFO parameters of the second communication system and is capable of transmitting TFO frames of the second communication system.

For clarity, various aspects, embodiments, and features of the present invention have been described for particular implementations of W-CDMA systems and CDMA2000 systems. However, other fixed rate, multi-rate, and variable rate systems and standards may be advantageously implemented or employed to support the embodiments described herein.

Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

The implementation or execution of the various illustrative logical blocks, modules, and algorithm steps described in connection with the embodiments described herein may be implemented or performed with: a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.

The previous description of the preferred embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (8)

1. An apparatus for coordinating operation between a first vocoder of a first communication system and a second vocoder of a second communication system, wherein the first communication system is incompatible with the second communication system, the apparatus comprising:

a first extraction element, configured to extract TFO information from a received in-system tandem free operation TFO frame;

a second extraction element for extracting TFO information from the received intersystem TFO frame; and

a selection element communicatively coupled to the first extraction element and the second extraction element, wherein the selection element is to select either of the extraction elements based on whether the received frame is an intra-system TFO frame or an inter-system TFO frame.

2. The apparatus of claim 1, further comprising:

a first generator for generating an intra-system TFO frame for transmission; and

a second generator for generating an intersystem TFO frame for transmission.

3. The apparatus of claim 1, wherein the first extraction element is further configured to extract a vocoder frame from a received intra-system TFO frame.

4. The apparatus of claim 1, wherein the second extraction element is further configured to extract a vocoder frame from the received inter-system TFO frame.

5. The apparatus of claim 2, wherein the second generator generates an intersystem TFO frame by occupying an intersystem TFO frame.

6. A method for coordinating a tandem free operation characteristic of a first communication system with a tandem free operation characteristic of a second communication system, wherein the first communication system is incompatible with the second communication system, the method comprising:

determining, at a first infrastructure entity of a first communication system, an extraction capability of a second infrastructure entity of a second communication system;

selecting a proper tandem free operation TFO frame format;

encapsulating a vocoder frame into a TFO frame using the appropriate TFO frame format;

transmitting the TFO frame to a second infrastructure entity;

receiving the TFO frame at the second infrastructure entity;

determining the source type of the TFO frame;

and extracting the content of the TFO frame according to the source type of the TFO frame.

7. Apparatus for coordinating a tandem free operation characteristic of a first communication system with a tandem free operation characteristic of a second communication system, wherein the first communication system is incompatible with the second communication system, the apparatus comprising:

means for determining, at a first infrastructure entity of a first communication system, an extraction capability of a second infrastructure entity of a second communication system;

means for selecting an appropriate tandem free operation TFO frame format and encapsulating a vocoder frame into a TFO frame using the appropriate TFO frame format;

means for transmitting the TFO frame to a second infrastructure entity;

means for receiving the TFO frame at the second infrastructure entity; and

means for determining a source type of the TFO frame and extracting content of the TFO frame according to the source type of the TFO frame.

8. An apparatus for coordinating operation between a first vocoder of a first communication system and a second vocoder of a second communication system, wherein the first communication system is incompatible with the second communication system, the apparatus comprising:

at least one memory element; and

at least one processing element configured to implement a set of instructions held in the at least one memory element, the set of instructions to:

extracting TFO information from the received tandem free operation TFO frame in the system by using a first table; and

the TFO information is extracted from the received intersystem TFO frame using a second table, wherein the intrasystem TFO frame has the same fields as the intersystem TFO frame, but the first table and the second table have different bit definitions.