Method and system for reduction of decoding complexity in a communication system

Method and system for reducing decoding complexity in communication system

[0001] This application is a divisional application for an invention patent application with the application number 02823325. 5, the international filing date is October 8, 2002, and the invention title is "Methods and systems for reducing decoding complexity in communication systems" .

Technical field

[0002] The present invention relates to a communication system, and more particularly to a system and method for reducing decoding complexity in a communication system.

Background technique

[0003] Communication systems have been developed to allow the transmission of information signals from an originating station to physically different target stations. When an information signal is sent from the originating station on a communication channel, the information signal is first converted into a form suitable for effective transmission on the communication channel. The conversion (ie, modulation) of the information signal includes: changing the carrier parameters according to the information signal, and this change is carried out in such a way that the generated modulated carrier frequency spectrum is limited within the communication channel bandwidth. At the target station, the modulated carrier received on the communication channel replicates the original information signal. This duplication is generally achieved by using a process that is the reverse of the modulation process used by the originating station.

[0004] Modulation also facilitates multiple access to several signals on a common communication channel, that is, simultaneous transmission and/or reception. Multiple access communication systems usually include multiple subscriber units, which require intermittent services of relatively short duration, rather than continuous access to a common communication channel. Several multiple access technologies are known in the art, such as time division multiple access (TDMA), frequency division multiple access (FDMA), and amplitude modulation multiple access (AM). Another type of multiple access technology is the code division multiple access (CDMA) spread spectrum system, which complies with the TIA/EIA/IS-95 mobile station-base station compatibility standard (TIA/EIA/IS -95 Mobile Station-Base Station Compatibility Standard for Dual-Mode Wide-Band Spread Spectrum Cellular System)", hereinafter referred to as IS-95 standard. The use of CDMA technology in multiple access communication systems is disclosed in US Patent No. 4901307 and US Patent No. 5103459. The former is entitled "SPREAD SPECTRUM MULTIPLE-ACCESS COMMUNICATION SYSTEM USING SATELLITE OR TERRESTRIAL REPEATERS", the latter is entitled "SYSTEM AND METHOD FOR GENERATING WAVEFORMS IN A CDMA CELLULAR TELEPHONE SYSTEM", both of these patents are assigned to the assignee of the present invention.

[0005] Multiple access communication systems may be wireless or wired, and may transmit voice and/or data. An example of a communication system that can transmit both voice and data is a system that complies with the IS-95 standard, which specifies the transmission of voice and data on a communication channel. The method of sending data in a fixed-size coded channel frame is described in detail in US Patent No. 5,504,773. The patent is entitled^uMETHOD AND APPARATUS FOR THE FORMATTING OF DATA FOR TRANSMISSION" and is assigned to the assignee of the present invention. According to the IS-95 standard, data or voice is divided into several coded channel frames, these frames are 20 milliseconds wide, and the data rate is up to 14 . 4/Kbps_oOther examples of communication systems that can transmit both voice and data include communication systems that comply with the following standards: "3rd Generation Partnership Project (3GPP)", which is included in a set of documents, including document number 3G TS 25. 211, 3GTS 25. 212, 30 TS 25. 213 and 3G TS 25. 214 (W-CDMA standard); and the TR-45. 5 Physical Layer Standard for cdma2000 spread spectrum system (TR-45. 5 Physical Layer Standard for cdma2000 Spread Spectrum Systems) (IS-2000 standard).

[0006] An example of a data-only communication system is a high data rate (HDR) communication system, which complies with the TIA/EIA/IS-856 industry standard, which is hereinafter referred to as the IS-856 standard. The HDR system is based on the common pending application serial number 08/963386

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Open communication system, the application is entitled ^uMETHOD AND APPARATUS FOR HIGH RATE PACKET DATA TRANSMISSION, filed on November 3, 1997, is assigned to the assignee of the present invention. The HDR communication system defines a set of data rates, ranging from 38.4kbps to 2.4Mbps, at which the access point (AP) may send data to the subscriber station (access terminal, AT). Since APs are similar to base stations, the terms about cells and sectors are the same as those about voice systems.

[0007] In a multiple access communication system, communication between users is implemented through one or more base stations. The first user on one subscriber station transmits data to the second user on the second subscriber station by sending the data to the base station on the reverse link. The base station receives the data and can route the data to another base station. The data is sent to the second subscriber station on the forward link of the same base station or other base station. The forward link refers to the transmission from the base station to the subscriber station, and the reverse link refers to the transmission from the subscriber station to the base station. Likewise, communication can be implemented between a first user on a mobile subscriber station and a second user on a terrestrial wired station. The base station receives data from the user on the reverse link and routes the data to the second user through the public switched telephone network (PSTN). In many communication systems, such as IS-95.W-CDMA.IS-2000, the forward link and the reverse link are assigned to different frequencies.

[0008] The above-mentioned wireless communication service is an example of a point-to-point communication service. In contrast, broadcast services provide point-to-multipoint communication services. The basic model of the broadcasting system is a user broadcasting network served by one or more central stations. The central station sends information with certain content to users, such as news, movies, sports games, and so on. The subscriber station of each broadcast network user monitors a public broadcast forward link signal. Since the central station determines the content fixedly, users generally do not communicate back. Examples of commonly used broadcast service communication systems include TV broadcasting, radio broadcasting, and so on. Such communication systems are generally highly specialized communication systems. With recent developments in wireless cellular phone systems, attention has been paid to the existing infrastructure of a point-to-point cellular phone system that mainly uses point-to-point for broadcast services. (The term "cellular" system as used herein includes communication systems that use both cellular and PCS frequencies.)

[0009] Information signals to be exchanged between terminals in a communication system are usually organized into multiple packets. For the purposes of this specification, a packet is a set of bytes arranged in a specific format, including data (payload) and control elements. Control elements include, for example, pilot sequences and quality metrics. Quality metrics include, for example, cyclic redundancy check (CRC), parity bits, and other metric types known to those skilled in the art. The packet is then formatted according to the communication channel structure to fit a frame. Properly modulated frames are propagated between the originating terminal and the target terminal, which are affected by the characteristics of the communication channel, such as signal-to-noise ratio, fading, time difference, and other such characteristics. This characteristic affects the modulated signal differently in different communication channels. Therefore, compared with the transmission of a modulated signal on a wired communication channel (such as a coaxial cable or an optical cable), the transmission of a modulated signal on a wireless communication channel requires different considerations. In addition to selecting a modulation suitable for a specific communication channel, other methods for protecting information signals have also been designed. Such methods include, for example, encoding, symbol repetition, interleaving, and other methods known to those of ordinary skill in the art. However, these methods add overhead. Therefore, an engineering compromise must be made between the reliability of information signal delivery and the amount of overhead. Even with the protection of the information signal discussed above, the conditions of the communication channel may be degraded to the point where the target station cannot decode (erase) certain packets. When allowed to start from the target terminal In a data-only communication system where the sending terminal transmits feedback, one solution is to use the automatic repeat request (ARQ) from the target station to the originating station to retransmit undecoded packets. However, under certain conditions, ARQ can overload the communication system. Moreover, as discussed about the broadcast communication system, the subscriber will not pass back to the base station. Therefore, other means for information protection are expected.

[0010] The pending application with the serial number of 09/933912 discussed in detail the use of an external decoder in the broadcasting system. The application is entitled ^uMETHOD AND SYSTEM FOR UTILIZATION OF AN OUTER DECODER INBROADCAST

SERVICES COMMUNICATION SYSTEM" was submitted on August 20, 2001 and was assigned to the assignee of the present invention. As described in the pending application serial number 09/933912, the information bit stream to be sent is first The encoded stream is encoded by the external decoder, and then the encoded stream is encoded by the internal encoder. As shown in Fig. 1, the information bit stream 102 to be transmitted originates from a higher layer and is provided to the transmit buffer 104. The transmit buffer This is detailed in Figure 2. With reference to Figure 2, the bits fill the system part 204(1) of the transmit buffer 104 (of Figure 1) from left to right line by line. The system part 204(1) includes k lines of length L 208. Referring back to Fig. 1, once the system part 204(4) (of Fig. 2) is full, the external block encoder 106 is activated to encode the bits in the system part 204(1) (of Fig. 2) in the column direction. , To generate (nk) parity bits of additional rows 210 (of Fig. 2). The column-direction operation is performed column by column for binary outer coding, that is, m = Κ For non-binary coding, that is, m> 1, - Each m adjacent column in a row is regarded as an m-bit symbol. The external encoder reads the m-bit symbols of the k rows above to generate nk m-bit symbols, which fill the corresponding columns in these columns. Nk line below.

[0011] The external encoder includes, for example, the system's Reed-Solomon (RS) encoder. Referring back to FIG. 1, the content of the transmission buffer 104 is then provided to the physical layer 108. At the physical layer 108, individual frames are coded by an internal encoder (not shown) to produce coded frames. The structure of the internal decoder is known to those of ordinary skill in the art. The system rows and parity columns of the buffer can be interleaved during transmission to reduce the chance of erasing a large number of system rows when the total number of erasures of the inner code exceeds the error correction capability of the outer code. The frame is further processed according to the selected modulation scheme, which includes cdma2000, WCDMA, UMTS, and other modulation schemes known to those of ordinary skill in the art. The processed frame is then sent on the communication channel 110.

[0012] The transmitted frame is received at the target station and provided to the physical layer 112. At the physical layer 112, individual frames are demodulated and provided to an internal decoder (not shown). The internal decoder decodes each frame, and if the decoding is successful, it outputs the correctly decoded frame; otherwise, if the decoding is unsuccessful, an erasure is announced. The success or failure of decoding must be determined with high accuracy, for example, by including a long (for example, 16-bit) cyclic redundancy check (CRC) in the frame after the outer encoding and before the inner encoding. The included CRC obtained from the decoded frame is compared with the CRC calculated from the bits of the decoded frame, and if the two CRCs are the same, the decoding is declared successful.

[0013] If the internal decoder cannot decode the frame, the decoder declares an erasure and provides an indication to the external block decoder 116 indicating that the frame is lost. This process continues until the same number of parity frames as the erased system frames are correctly received and delivered to the parity portion 114(2) of the receive buffer 114. The receiver stops the reception of any remaining frames and activates an external decoder (not shown) to restore the erased system frames. The restored system frame is passed to the upper layer.

[0014] It is well known in the art that as the value of the number of rows in the sending buffer 104 increases, the computational complexity of decoding/error correction also increases. Since the computational complexity of decoding/error correction affects the hardware complexity and power consumption at the receiving terminal, there is a need for such a method and system in the art.

Summary of the invention

[0015] The embodiments disclosed herein solve the above-mentioned needs by providing a method and a system that executes the method by: encoding the systematic bits in each of the multiple buffers with an external code; The contents of the multiple buffers are multiplexed; and the multiplexed content is encoded with internal coding to provide a set of frames.

[0016] In another aspect of the present invention, the received frame is decoded by the internal decoder; the correctly decoded frame

It is demultiplexed into multiple buffers; the contents of each buffer are further processed. If the system part of the buffer has been decoded correctly, the processing includes providing the content of the system part to higher layers. Or, if it is determined that the decoding of the buffer content by the external decoder restores the system part, the external decoder is activated, and the restored content of the system part and the correctly received content are provided to a higher layer.

Description of the drawings

[0017] FIG. 1 illustrates the physical layer processing of the prior art;

[0018] FIG. 2 illustrates a transmit buffer;

[0019] FIG. 3 illustrates physical layer processing according to an embodiment of the present invention;

[0020]Dingyi

[0021] The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment described herein as "exemplary" need not be construed as more preferred or advantageous than other embodiments.

[0022] The term "point-to-point" is used herein to mean communication between two subscriber stations on a dedicated communication channel.

[0023] The term "broadcast communication" or "point-to-multipoint communication" as used herein means a type of communication in which multiple subscriber stations receive communication from one source.

[0024] The term "packet" is used here to mean a group of bits arranged in a specific format, including data (load) and control elements. The control elements include, for example, the leader sequence, quality metrics, and other elements known to those skilled in the art. Quality metrics include, for example, cyclic redundancy check (CRC), parity bits, and other metrics known to those skilled in the art.

[0025] The term "access network" is used here to mean a base station (BS) and a collection of one or more base station controllers. The access network transmits data packets between multiple subscriber stations. The access network can also be connected to other networks outside the access network, such as an enterprise intranet or the Internet, and can transmit data packets between each access terminal and this external network.

[0026] The term "base station" is used here to mean the hardware with which the subscriber station communicates. A cell refers to a hardware or geographic coverage area, depending on the environment in which the term is used. The sector is a part of the cell. Since the sector has the attributes of a cell, the principles described here about the cell can also be easily extended to the sector.

[0027] The term "subscriber station" is used here to mean the hardware with which the access network communicates. The subscriber station can be mobile or stationary. The subscriber station may be any data device that communicates through a wireless channel or through a wired channel, for example, using optical fiber or coaxial cable. The subscriber station can also be any of many device types, including but not limited to: PC card, micro flash memory, external or internal modem, or wireless or wired telephone. A subscriber station in the process of establishing an active traffic channel connection with a base station is said to be in a connection setup state. A subscriber station that has established an active traffic channel connection with the base station is said to be in a traffic state.

[0028] The term "physical channel" is used here to mean a communication route on which modulation characteristics and codes are used to describe signal propagation.

[0029] The term "logical channel" is used here to mean a communication route within the protocol layer of a base station or a subscriber station.

[0030] The term "communication channel/link" is used here to mean a physical channel or a logical channel according to the context.

[0031] The term "reverse channel/link" is used herein to mean a communication channel/link through which a subscriber station sends a signal to a base station.

[0032] The term "forward channel/link" is used here to mean a communication channel through which a base station sends a signal to a subscriber station

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/link.

[0033] The term "soft handover" is used here to mean a subscriber station and communication between two or more sectors, where each sector belongs to a different cell. The reverse link communication is received by both sectors, and the forward link communication is implemented on the forward links of two or more sectors at the same time.

[0034] The term "softer handover" is used here to mean a subscriber station and communication between two or more sectors, where each sector belongs to the same cell. The reverse link communication is received by both sectors, and the forward link communication is implemented simultaneously on one of the forward links of two or more sectors.

[0035] The term "erasing" is used here to mean failure to recognize a message.

[0036] The term "dedicated channel" is used herein to mean a channel modulated by information specific to an individual subscriber station.

[0037] The term "common channel" is used here to mean a channel modulated by information shared among all subscriber stations.

[0038] The term "physical layer" is specifically used here to refer to the part of the communication protocol responsible for the reception of transmission data between the originating terminal and the target terminal. The physical layer corresponds to layer 1 in the International Standards Organization model of open systems interconnection.

[0039] The term "higher layer" is specifically used here to mean that part of the communication protocol between the originating terminal and the target terminal that is higher than the physical layer. The higher layers correspond to layers 2 to 7 in the International Standards Organization model of open systems interconnection.

[0040]

[0041] According to an embodiment of the present invention, as shown in FIG. 3, the information bit stream 302 to be transmitted originating from a higher layer is demultiplexed and provided to the transmission buffer 304(i). These bits fill the system portion 306(1) of the transmit buffer 304(1) line by line from left to right. The system part 306(1) includes k lines of length L. In an embodiment, the length of the buffer is consistent with the length of the radio frame without overhead (such as the CRC to help the internal decoder and the tail bits of the internal encoder). Once the system portion 306(1) of the transmit buffer 304(1) is full, the process is repeated for the remaining transmit buffers 302(2)-304(p). Once the system part 306(i) of the transmission buffer 304(i) is full, the external block encoder 310(i) is activated to encode the bits in the system part 306(i) in the column direction to generate another (nk) The parity bit of the row 308(i). This column-direction operation is performed column by column for the unary outer code (ie m=1). For non-binary coding, that is, m>1-every m adjacent columns in a row are regarded as an m-bit symbol. The external encoder reads the m-bit symbols of the upper k rows to generate nk m-bit symbols, which fill the lower nk rows of these columns.

[0042] In another embodiment, the length L of the buffer is equal to the number of bits of a radio frame without overhead divided by m, where m is the size of the external encoder encoding. In this embodiment, the first m rows of the transmit buffer 304(i) are transmitted in the first radio frame, and the second m rows of bits are transmitted in the second radio frame, until all the buffers are transmitted. Once the system portion 306(1) of the transmit buffer 304(1) is full, the process is repeated for the remaining transmit buffers 304(2)-304(ρ). Once the system part 306(i) of the transmission buffer 304(i) is full, the external block encoder 310(i) is activated to encode the bits in the system part 304(i) in the column direction to generate another m(nk ) The parity bits of the row 308(i). This column-direction operation is performed column by column for the binary external code (ie m = 1). For non-binary codes (ie, m> 1), each m row of a column forms an m-bit symbol. The external encoder reads the k symbols of the upper km row in the column to generate (nk) m-bit symbols, which fill the m(nk) rows below the column.

[0043] In an embodiment, the external encoder 310(i) includes a system of Reed-Solomon (RS) encoders. The content of the transmission buffer 304(i) is then provided to the multiplexer 312. The multiplexer 312 circulates through the transmission buffers 304(1)-304(ρ), and after the bit block containing a predetermined number of bits has been transmitted from the previous buffer 304(il), selects the subsequent transmission buffer 304 (i) ο In one embodiment, the predetermined number of bits in a block is equal to L. This strategy intends to evenly distribute the data corruption caused by the disturbance of the physical channel 316 among the buffers 304(i). However, the ability

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Those of ordinary skill in the field will understand that other multiplexing strategies can also be applied equivalently and can be used without departing from the spirit or scope of the present invention. The multiplexed bit block is provided to the physical layer 314 of the originating terminal. At the physical layer 314, additional overhead bits (e.g., CRC check) are added to each bit block, and the resulting structure is encoded by an internal encoder (not shown), which produces an encoded frame. The structure of the external and internal encoders and multiplexers can be as shown in FIG. 3. These frames are further processed according to the selected modulation scheme. In one embodiment, the processing is performed in accordance with the IS-2000 standard. The processed frames are sent on the general communication channel 316 in conjunction with the general rules.

[0044] The transmitted frame is received at the target station (not shown) and provided to the physical layer 318 at the target station. At the physical layer 318, individual frames are demodulated and provided to an internal decoder (not shown). In an embodiment, the internal decoder decodes each frame, and if the decoding is successful, it outputs the correctly decoded frame; otherwise, if the decoding is unsuccessful, an erasure is announced. The success or failure of decoding must be determined with high accuracy. In an embodiment, as described above, accuracy is achieved by including a long (eg, 16-bit) cyclic redundancy check (CRC) in the frame after the outer encoding and before the inner encoding. However, those of ordinary skill in the art recognize that other mechanisms for frame quality indication can be used. The included CRC obtained from the decoded frame is compared with the CRC calculated from the bits of the decoded frame, and if the two CRCs are the same, the decoding is declared successful. The further processing at the physical layer is carried out according to the result of the decision of the internal decoder.

[0045] The correctly decoded frames are provided to the demultiplexer 320, which distributes the correctly decoded frames in the middle of the receiving buffer 322(i), using a method opposite to that used for multiplexing. If the internal decoder of the specific receiving buffer 322(i) correctly decodes all the system k frames, the system part 324(i) of the receiving buffer 322(i) is provided to the higher layer.

[0046] If the internal decoder cannot decode the frame, the decoder declares an erasure and provides an indication to the demultiplexer 324 indicating that the frame is lost. The demultiplexer 324 provides the information to the external block decoder 328(i) communicatively coupled with the receiving buffer 322(i), and the frame belongs to the receiving buffer 322(i). This process continues until enough system frames and correctly received parity frames are accumulated in the system part 324(i) and parity part 326(i) of the receiving buffer 322(i), or until the receiving buffer 322(i) ) Is full. Then an external decoder (not shown) is activated to recover the erased system frame. The restored system frame is provided to higher layers.

[0047] If the total number of correctly received frames in the receiving buffer 322(i) is less than k, according to an embodiment, the external decoder is not activated because there is no guarantee that the decoding will succeed. The correctly received system frame and the identification of the missing bits are provided to the higher layer together. In another embodiment, the receiver uses decoded bits from the internal decoder (indicated as unreliable by a failed CRC check) to recover the bits for the system bits. According to an embodiment, the receiver decodes the unreliable bits from the internal decoder and finds the most probable codeword. In another embodiment, the receiver uses the signal quality metric of the erased frames in the buffer to select the sufficiently erroneously received frame with the highest signal-to-noise ratio to form an auxiliary buffer with k rows. Then, the receiver performs bit flipping (every time at each column, changing the bit value 0 to bit value 1, and vice versa), and checks whether bit flipping occurs in the codeword. In one embodiment, bit flip is performed on the least reliable bit first, and then the remaining bits are flipped in order of increasing bit reliability. Bit reliability can be determined according to internal decoding metrics, such as the signal-to-noise and interference ratio during the frame, the Yamamoto-like metric, the re-encoded symbol error rate, the re-encoded energy metric, and those of ordinary skill in the art. Other metrics, or a combination of metrics. If the codeword is not found, then continue bit flipping for all remaining columns of all unreliable rows. If the codeword is not found, continue In bit reversal, the number of bits flipped increases (that is, changes 2 bits at a time, then 3 bits, until the maximum number of bits), until the codeword is found or all combinations are exhausted. In another embodiment, the CRC from the unreliable row is used to check the overall success of the decoding in this case. Only when the CRC of all rows is the same, the frame is provided to the higher layer; otherwise, only the

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The self-reliable bits are provided to higher layers.

[0048] In order to improve the reliability of decoding, in another embodiment, demodulation and internal decoding are performed on more than k correctly received frames in the buffer. According to yet another embodiment, demodulation and internal decoding are performed for all frames in the buffer. In the above two embodiments, external decoding is performed on the k (or km) rows with the highest quality. The quality can be determined according to internal decoding metrics, such as the signal-to-noise and interference ratio during the frame, the Yamamoto-like metric, the re-encoded symbol error rate, the re-encoded energy metric, and others known to those of ordinary skill in the art. Measures, or combinations of measures. The use of quality metrics for quality estimation is disclosed in detail in the following U.S. patents: U.S. Patent No. 5,751,725, entitled METHOD AND APPARATUS FOR DETERMINING THE RATE OF RECEIVED DATA IN A VARIABLE RATE COMMUNICATIONS SYSTEM", and U.S. Patent No. 5,774,496, entitled^uMETHOD AND APPARATUS FOR DETERMINING DATA RATE OF TRANSMITTED VARIABLE RATE DATA IN A COMMUNICATIONS RECEIVER, both of these patents are assigned to the assignee of the present invention.

[0049] Those skilled in the art will understand that the number of transmit buffers 304 and receive buffers 322 is a trade-off between processing overhead and the amount of potential data loss. A small value of k makes more transmit/receive buffers and increase processing overhead. On the other hand, a large value of k causes fewer transmit/receive buffers to increase the size of the transmit buffer, which causes a large amount of data to be discarded if the contents of the transmit buffer cannot be restored due to more than (nk) line erasure. Piece. The large transmit buffer size also increases the memory requirements at the target terminal.

[0050] Those skilled in the art can understand that information and signals can be represented by any of a variety of different technologies and processes. For example, the data, instructions, commands, information, signals, bits, symbols, and chips that may be involved in the above description can be represented by voltage, current, electromagnetic waves, magnetic fields or their particles, light fields or their particles, or any combination of them. .

[0051] Those skilled in the art can further understand that the various illustrative logical blocks, modules, and algorithm steps described in conjunction with the embodiments disclosed herein can be implemented as electronic hardware, computer software, or a combination of both. In order to clearly illustrate the interchangeability between hardware and software, various illustrative components, block diagrams, modules, circuits, and steps are generally described in accordance with their functionality. Whether these functionalities are implemented as hardware or software depends on the specific application and design adopted by the entire system. The skilled person can recognize the interactivity of hardware and software in these situations, and how to best implement the functions of each specific application. Technicians may implement the functions in different ways for each specific application, but this implementation decision should not be construed as causing a departure from the scope of the present invention.

[0052] The various illustrative logic blocks, modules, and algorithm steps described in conjunction with the embodiments described herein can be implemented or executed by: general-purpose processors, digital signal processors (DSP), and application-specific integrated circuits (ASIC). , Field Programmable Gate Array (FPGA) or other programmable logic devices, 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. The processor may also be implemented by a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration.

[0053] The steps of the method or algorithm described in conjunction with the embodiments disclosed herein may be directly included in hardware, in a software module executed by a processor, or in both. The software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, removable disk>CD-ROM or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from the storage medium or write information to the storage medium. Alternatively, the storage medium can be integrated with the processor. The processor and storage medium may reside in the ASIC. The ASIC may reside in the subscriber unit. Alternatively, the processor and storage media may reside as discrete components

In the user terminal.

[0054] The above description of the preferred embodiments enables those skilled in the art to make or use the present invention. Various modifications of these embodiments are obvious to those skilled in the art, and the general principles defined here can be applied to other embodiments without using creative ability. Therefore, the present invention is not limited to the embodiments shown here, but should conform to the broadest scope consistent with the principles and novel features disclosed herein.

[0055] A part of the disclosure of the application document contains copyrighted material. The copyright owner has no objection to fax copying of this application document or application disclosure. It appears in the patent documents or records of the United States Patent and Trademark Office, but all copyrights are still reserved in any case.

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