Method and apparatus for transmission framing in wireless communication system

[background] 35 U.S.C Priority claim based on Article 120 Priority of US Provisional Application No. 60,279,970, filed as 60 / 279,970, filed March 28, 2001, assigned to the assignee, and expressly incorporated herein by reference. Insist.

Reference to patent applications pending together The present invention relates to the following patent application at the United States Patent and Trademark Office.

"Methods for Security in Data Processing Systems" by Philip Hawks and others, having agent reference number 010497, filed at the same time as the present application, and transferred to the assignee, and expressly incorporated herein by reference. And equipment ", By Nikolai Leung, who has agent reference number 010439, is filed at the same time as this application, and is transferred to this assignee, and is expressly incorporated herein by reference, "Methods for Overhead Messaging in Wireless Communities and apparatus", "Out-of-band transmission of broadcast service options in wireless communication systems" by Nikolai Leung, who has agent reference number 010437, is filed at the same time as this application, and is transferred to this assignee, and is expressly incorporated herein by reference. Methods and equipment for ", Nikolai, having agent reference number 010438, filed at the same time as this application, and assigned to the assignee, and expressly incorporated herein by reference. "Methods and Devices for Broadcast Signaling in Wireless Communities" by Leung, By Raymond Hsu, who has agent reference number 010500, is filed at the same time as this application, and is transferred to this assignee, and is expressly incorporated herein by reference, "Methods for Header Compression in Wireless Communities and "Device", and "Methods for Data Transport in Wireless Communities," by Raymond Hsu, who has agent reference number 010499, is filed at the same time as the present application, and is transferred to the assignee, and is expressly incorporated herein by reference. And equipment ".

[Field] The present invention relates generally to wireless communication systems, and in particular methods and devices for message compression in preparation for transmission in wireless communication systems.

[background] There is an increasing demand for packetized data services in wireless communication systems. Since traditional wireless communication systems are designed for voice communication, they pose many challenges for expansion to support data services. Bandwidth maintenance is an overwhelming concern for most designers.

The transmission protocol and data preparation method used for two-way communication is that for one-way services such as broadcast service, two-way communication requires information that is not used in one-way transmission. It may not be optimal. As a result, there is a need for an efficient and accurate method for one-way transmission within wireless communication systems.

[Overview] The embodiments disclosed herein address the needs described above by providing a method for framing data packets in a data processing system.

In one aspect, the method of framing a packet in a wireless transmission system that supports broadcast transmission generates a portion of an Internet Protocol (IP) packet for transmission and a frame indicator on the portion of the IP packet. Add a start, apply the error detection mechanism to a part of the IP packet, prepare the frame for transmission with the start part of the frame indicator, the part of the IP packet, and the error detection mechanism, and the protocol. Includes sending the frame without information.

In another aspect, the communication signal transmitted by the carrier corresponds to the payload portion, the payload portion corresponding to at least a portion of the Internet Protocol (IP) packet of digital information, and identifies the state of the payload portion within the IP packet. It has an error detection part for confirming the start part of the frame part and the payload part.

In yet another aspect, a method for receiving a framed packet in a wireless transmission system that supports broadcast transmission is to receive a frame of packet transmission, where the frame is the start of the frame part, the payload part, And has an error detection part, where the frame has no protocol information, identifies the frame as the starting frame in packet transmission, uses the error detection part of the frame to identify the frame, and of the frame. Includes processing the payload part.

From yet another point of view, a computer program stored in a storage unit that can be read by a computer, where the computer program is for receiving framed packets in a wireless transmission system that supports broadcast transmission. Here, the computer program is the first combination of instructions for receiving a frame of packet transmission, where the frame has a start part, a payload part, and an error detection part of the frame part, where the frame is a protocol. A second combination of instructions to identify the frame as the starting frame in packet transmission, a third combination of instructions to identify the frame using the error detection part of the frame, and a frame Contains a fourth combination of instructions for processing the packet part.

<figref num="1">FIG. 1 is a diagram of a diffusion spectrum communication system that supports several users.</figref><figref num="2">Figure 2 is a block diagram of a communication system that supports broadcast transmission.</figref><figref num="3">Figure 3 is a model of the protocol stack corresponding to the broadcast service option in the wireless communication system.</figref><figref num="4">Figure 4 is a table of protocols applied to the layers of the protocol stack that support broadcast service options in wireless communication systems.</figref><figref num="5">FIG. 5 is a flow diagram for a message flow for a broadcast service in a wireless communication system topology.</figref><figref num="6">FIG. 6 is a broadcast stream in a wireless communication system.</figref><figref num="7">FIG. 7 is a header compression mapping in a wireless communication system.</figref><figref num="8">Figure 8 shows a periodic broadcast of header compression information.</figref><figref num="9">Figure 9 shows the header compression protocol.</figref><figref num="10">FIG. 10 shows a header compression protocol for a broadcast service in a wireless communication system.</figref><figref num="11">FIG. 11 is a flowchart regarding header compression for a broadcast service in a wireless communication system.</figref><figref num="12">FIG. 12 is a flow diagram relating to header compression for a broadcast service in a wireless communication system.</figref><figref num="13">Figure 13 shows an access network that supports broadcast transmission.</figref><figref num="14">Figure 14 shows an access network that supports broadcast transmission.</figref><figref num="15">Figure 15 illustrates the framing protocol.</figref><figref num="16">Figure 16 illustrates the framing protocol.</figref><figref num="17">Figure 17 illustrates the framing protocol.</figref>

[Detailed description] The term "typical" is used here in a limited way to mean "useful as an example, fact, or illustration." Any embodiment described herein as "typical" need not be construed as superior, desirable or advantageous over the other embodiments.

System optimization consistent with broadcast services is desirable in wireless communication systems to maintain an important resource, the available bandwidth. Efficient use of available bandwidth has a strong impact on the characteristics and breadth of the system. Towards that end, various techniques have been applied to reduce the size of the transmitted overhead information in addition to the data or content information, as well as to reduce the size of the transmitted data. .. For example, in digital transmission, data is transmitted within a frame. A frame can be a packet portion of data, a data message portion, or a contiguous frame within a stream of information such as an audio and / or video stream. Attached to each frame of data (and each packet or message) is a header that contains processing information that allows the receiver to understand the information contained within the frame. This header information is considered to be overhead, that is, processing information transmitted together with the information content. The information content is referred to as the payload. While each individual header is typically much smaller than a given payload, the cumulative effect of sending the header has a strong impact on the available bandwidth.

A typical embodiment of a wireless communication system uses a framing method that reduces the size of a frame while satisfying the accuracy and transmission requirements of the system. A typical embodiment supports a one-way broadcast service. Broadcast services provide video and / or audio streams to multiple users. Subscribers to the broadcast service "tune" to the channel chosen to access the broadcast transmission. Due to the wide bandwidth requirements for high-speed transmission of video broadcasts, it is desirable to reduce the size of any overhead combined with such broadcast transmission.

The following discussion develops a typical example by first generally providing a diffusion spectrum radio communication system. Next, a broadcast service will be introduced. Here, the service is referred to as a High Speed Broadcast Service (HSBS). And the discussion involves channel allocation in typical embodiments. A subscription model is given there, including options for paid bookings, free bookings, and combined booking planning, similar to those currently available for television transmission. The details of accessing the broadcast service are detailed there, given the use of service options to define the details of a given transmission. Message flow in a broadcast system is discussed with respect to the topology of the system or backbone element. Finally, the header compression used in typical embodiments is discussed.

Typical examples are given as examples throughout this discussion, however, it should be noted that alternative examples can be combined with various perspectives without departing from the scope of the invention. .. In particular, the present invention is applicable to data processing systems, wireless communication systems, one-way broadcast systems, and any other system that desires efficient transmission of information.

<u style="single">Wireless communication system</u> A typical embodiment uses a diffusion spectrum radio communication system that supports broadcast services. Wireless communication systems have been widely deployed to provide voice, data, and various other forms of communication. These systems can be based on code division multiple access (CDMA), time division multiple access (TDMA), or some other modulation technique. CDMA systems offer certain advantages, including increased system capacity over other types of systems.

The system is referred to herein as "TIA / EIA / IS-95-B Mobile Station, Base Station Compatibility Standard for Dual Mode Broadband Spread Spectrum Cellular Systems", referred to herein as 3GPP. Document numbers 3G TS25.211, 3G TS25.212, 3G TS25.213, and 3G TS25., Provided by the Association named 3G Partnership Project and referred to here as the W-CDMA standard. Standards embodied in a series of documents, including 214, 3G TS25.302, standards provided by the association named "3rd Generation Partnership Project 2", referred to here as 3GPP2, and here as cdma2000 standards. It can be designed to support one or more standards referenced, such as TR-45.5, formerly known as IS-2000MC. The standards cited above are explicitly incorporated therein by this result reference.

Each standard clearly defines the processing of data for transmission from base station to mobile and vice versa. As a typical example, the following discussion considers a diffusion spectrum communication system that is consistent with the CDMA200 standard for protocols. Alternative examples can be combined with other standards. In still other embodiments, the compression methods disclosed herein can be applied to other formats of data processing systems.

FIG. 1 is valid as an example for communication system 100, which supports several users and is capable of implementing at least some aspects and examples of the present invention. Both algorithmic and method variants can be used to schedule transmissions in System 100. System 100 provides communication to cell numbers 102A to 102G, each of which is serviced by the corresponding base stations 104A to 104G. In a typical embodiment, some of the base stations 104 have a plurality of receiving antennas, and others have only one receiving antenna. Similarly, some of the base stations 104 have multiple transmitting antennas, and others have only one transmitting antenna. There are no restrictions on the combination of the transmitting antenna and the receiving antenna. As a result, for base station 104, having multiple transmitting antennas and only one receiving antenna, or having multiple receiving antennas and only one transmitting antenna, or both having only one or more transmitting and It is possible to have a receiving antenna.

The terminal 106 in the coverage area can be fixed (ie stationary) or mobile. As shown in FIG. 1, the various terminals 106 are distributed throughout the system. Each terminal 106 is designed for, for example, whether soft handoff is being used or not at any given moment, or for the terminal to receive multiple transmissions (simultaneously or continuously) from multiple base stations. It then communicates with at least one and perhaps more base stations 104 on the downlink and uplink, depending on whether it is activated or not. Soft handoffs in CDMA communication systems are well known in the industry and have been transferred to the transferor of the present invention, a US patent entitled "Methods and Systems for Providing Soft Handoffs in CDMA Cellular Telephone Systems". It is described in detail in 5,101,501.

The downlink refers to the transmission from the base station to the terminal, and the uplink refers to the transmission from the terminal to the base station. In a typical embodiment, some of the terminals 106 have a plurality of receiving antennas, and others have only one receiving antenna. In FIG. 1, base station 104A transmits data to terminals 106A and 106J on the downlink, base station 104B transmits data to terminals 106B and 106J, base station 104C transmits data to terminals 106C, and so on. ..

The increasing demand for wireless data transmission and the expansion of available services through wireless communication technologies have led to the development of special data services. One such service is referred to as High Data Rate (HDR). A typical HDR service is proposed in the "EIA / TIA-IS856cdma2000 High Rate Packet Data Air Interface Standard" referred to as the "HDR Standard". HDR services are generally overlays on voice communication systems that provide an efficient way to send packets of data in wireless communication systems. As the total amount of data transmitted and the number of transmissions increase, the finite bandwidth available for wireless transmission becomes an important resource. As a result, there is a need for an efficient and correct way to schedule transmission in communication systems that optimize the use of available bandwidth. In a typical embodiment, the system 100 shown in FIG. 1 is consistent with a CDMA format system having HDR service.

<u style="single">High Speed Broadcast System (HSBS)</u> FIG. 2 shows the wireless communication system 200. Here, the video and audio information is given to the Packeted Data Services Network (PDSN) 202. Video and audio information can be from television broadcast programming or radio transmission. The information is given as packetized data such as in an IP packet. PDSN202 processes IP packets for distribution within the access network (AN). As shown, AN is defined as part of a system that includes BS204 in communication with multiple MS206s. PDSN202 is bound to BS204. For the HSBS service, the BS204 receives a stream of information from the PDSN202 and feeds the information on the selected channel to the subscribers in the system 200.

Within a given sector there are several routes through which the HSBS broadcast service can be deployed. Factors required in designing a system include, but are not limited to, the number of HSBS sessions supported, the number of frequency allocations, and the number of broadcast physical channels supported.

HSBS is a stream of information given on an air interface in a wireless communication system. The "HSBS channel" is attributed to only one logical HSBS broadcast session as defined by the broadcast content. It should be noted that the content of a given HSBS channel can change over time, for example, 7am news, 8am weather, 9am movies, and so on. Time-based appointments are similar to just one television channel. The "broadcast channel" is attributed to only one forward link physical channel, the given Walsh code that carries the broadcast traffic. Broadcast channel, BCH corresponds to only one CDM channel.

One broadcast channel can carry one or more HSBS channels. In this case, the HSBS channel will be multiplexed in a time division multiplexing (TDM) fashion within a single broadcast channel. In one embodiment, one HSBS channel is provided on one or more broadcast channels within a sector. In other embodiments, one HSBS channel is provided at different frequencies to serve subscribers at these frequencies.

According to a typical embodiment, the system 100 shown in FIG. 1 supports a high speed multimedia broadcast service referred to as a high speed broadcast service (HSBS). The broadcast capability of the service is intended to provide programming at a data rate sufficient to support video and audio communications. As an example, HSBS applications can include video streaming of movies, sporting events, etc. The HSBS service is a packet data service based on the Internet Protocol (IP).

According to a typical embodiment, the service provider is referred to as a content server (CS). Here, CS advertises the effectiveness of such a high-speed broadcast service to system users. Any user who wishes to receive HSBS services can subscribe to CS. There, the subscriber can scan the broadcast service schedule in various ways that can be given by CS. For example, broadcast content includes advertisements, Short Management System (SMS) messages, Wireless Application Protocol (WAP), and / or some other methods that are generally consistent and convenient for mobile wireless communications. It is possible to be notified through. Mobile users are referred to as mobile stations (MS). Base station (BS; Base) Station) transmits parameters related to HSBS on channels selected for control and information, and / or in overhead messages or non-payload messages, such as those transmitted at frequency. The payload is related to the information content of the transmission. Here, for a broadcast session, the payload is a broadcast content, that is, a video program or the like. When a broadcast service subscriber wishes to receive a broadcast session, a particular scheduled broadcast program, the MS reads overhead messages and learns the proper sequence. The MS then tunes to the frequency including the HSBS channel and receives the broadcast service content.

The channel structure of a typical example is consistent there with the cdma2000 standard, where Forward Supplemental Channels (F-SCHs) support data transmission. One embodiment is a number of Forward Fundamental Channels (F-FCH) or Forward Dedicated Control Channels (F-DCCH) to achieve higher data rate requirements for data services. Control Channel) is bundled. A typical example utilizes F-SCH as the basis for F-BSCH supporting a payload of 64 kbps (exclusive RTP overhead). F-BSCH can also be partially modified to support other payload rates, for example by subdividing the 64kbps payload rate into lower rate substreams.

One embodiment can also support group calls on several different routes. For example, by using the current unicast channel, that is, one forward link channel per MS with no sharing for F-FCH (or F-DCCH) for both forward and reverse links. .. In other examples, F-SCH (shared by group members in the same sector) and F-DCCH (most times, no frames other than the forward power control subchannel) and vice versa on the forward link. R-DCCH on the directional link is used. In other examples, high-rate F-BSCH on the forward link and access channel on the reverse link (or enhanced access channel / reverse common control channel combination) are used.

A typical embodiment of F-BSCH, which has a high data rate, may use a very large portion of the base station's forward link power to provide adequate coverage. HSBC's physical layer design is therefore focused on improving efficiency within the broadcast environment.

To provide adequate support for video services, the system design takes into account the required base station power for the various methods for transmitting channels, as well as the supported video quality. One aspect of the design is the subjective trade-off between the perceived video quality around the effective range and that close to the cell site. The effective error correction code rate increases as the payload rate decreases, and the given level of base station transmit power provides a better effective range around the cell. For mobile stations located closer to the base station, channel reception will remain error-free, and video quality will be degraded due to the degraded source rate. This similar trade-off also applies to other non-video applications that F-BSCH can support. The reduced payload rate supported by the channel increases the scope at the expense of reduced download speeds for these applications. The goal is to balance the relative importance vs. coverage between video quality and data throughput. The form chosen seeks an optimized form for a particular application, and a good compromise among all possibilities.

Payload rate for F-BSCH is an important design parameter. The following assumptions can be used when designing a system that supports broadcast transmission according to typical examples. (1) The target payload rate is 64 kbps. And it gives adoptable video quality for SKT. (2) For streaming video services, the payload rate is assumed to include 12 8-bit bytes per packet overhead of RTP packets. (3) The average overhead for all layers between the RTP and physical layers is approximately the sum of 64 8-bit bytes per packet and 8 bits per F-SCH frame overhead used by the MUXPDU header.

In a typical embodiment, the maximum rate supported for non-video broadcast services is 64 kbps. However, many other possible payload rates below 64 kbps are also achievable.

<u style="single">Reserved model</u> There are several possible booking / revenue models for HSBS services, including free access, controlled access, and partially controlled access. No reservation is required to receive the service for free access. The BS broadcasts the content without encryption, and the mobile of interest can receive the content. Revenues for service providers can be generated through advertisements that can also be sent within the broadcast channel. For example, a movie clip that is about to appear can be sent because the studio will pay the service provider for it.

For controlled access, the MS user makes a reservation for the service and pays the corresponding fee to receive the broadcast service. Users who have not made a reservation will not be able to receive the HSBS service. Controlled access can be achieved by encrypting the HSBS transmission / content so that only the reserved user can decrypt the content. It may use an over-the-air encryption key exchange procedure. This method provides strong security and prevents theft of services.

The hybrid access scheme, referred to as partially controlled access, provides the HSBS service as a service based on encrypted reservations, along with intermittent unencrypted ad transmission. These advertisements may be intended to facilitate bookings for encrypted HSBS services. The appointment of these unencrypted parts could be communicated to MS through external means.

<u style="single">HSBS service option</u> HSBS service options are defined by (1) the protocol stack, (2) the options in the protocol stack, and (3) the procedure for establishing and synchronizing services. A protocol stack according to a typical example is shown in Figures 3 and 4. As shown in Figure 3, the protocol stack is specific for mission-critical facility elements, namely MS, BS, PDSN and CS in typical examples.

Continuing with FIG. 3, for the MS application layer, the protocol defines an audio codec and a visual codec as well as any visual profile. In addition, the protocol defines the RTP payload format when the Radio Transport Protocol (RTP) is used. For the MS transport layer, the protocol defines a User Datagram Protocol (UDP) port. The security layer of MS is defined by the protocol. Here the security parameters are given via the out-of-band channel when security is first combined with CS. The network layer defines IP header compression parameters.

<u style="single">Message flow</u> FIG. 5 shows a typical example call flow for a given system topology. The system includes MS, BS, PDSN, and CS as shown on the horizontal axis. The vertical axis represents time. The user, or MS, is a subscriber to the HSBS service. At time t1, MS and CS negotiate reservation security for the broadcast service. The arrangement includes the exchange and maintenance of encryption keys and the like used to receive broadcast content on the broadcast channel. The user establishes a security tie-up with CS for receiving cryptographic information. The cryptographic information may include a broadcast access key (BAK) or key combination from CS. According to a typical embodiment, CS is during the packet data session. Cryptographic information is given on a dedicated channel by PPP, WAP, or other out-of-band method.

At time t2, the MS tunes to the broadcast channel and begins receiving packets. At this point, the MS is unable to process the received packet because the IP / ESP header is compressed by ROHC and the MS decompressor is not initialized. The PDSN gives header compression information at time t3 (detailed below). From the ROHC packet header, the MS detects and retrieves ROHC initialization and update (IR) packets that are periodically sent from the PDSN to the broadcast channel. ROHC The IR packet is used to allow the MS to decompress the IP / ESP header of the received packet and initialize the state of the decompressor in the MS. The MS can then process the IP / ESP header of the received packet, but the MS also processes the ESP payload because the payload is encrypted with the short term key (SK) in CS. Request information to do so. SK operates in the same way as BAK, where SK is decoded at the receiver using BAK. CS further gives updated key information, that is, encrypted information such as the current SK at time t4. It should be noted that the CS periodically gives this information to the MS to ensure the ongoing security of the broadcast. At time t5, the MS receives the broadcast content from the CS. It should be noted that alternative embodiments can incorporate alternative compression and decompression methods that provide efficient transmission of header information. It should be noted that further alternative embodiments can implement various security schemes to protect the broadcast content. Yet an alternative embodiment can also provide an insecure broadcast service. MS uses encrypted information such as SK to decrypt and display the broadcast content.

<u style="single">compression</u> According to a typical embodiment, the broadcast content is transmitted on a dedicated broadcast channel. The transport layer provides cryptographic overhead for carrying the broadcast content in IP packets. The system supports data compression and especially header compression. The decision to compress the data depends on the average throughput required (including transport / cryptographic overhead, data link layer overhead, and physical layer overhead) and the user perception of broadcast quality. Carrying larger broadcast content within each IP packet reduces overhead and thus broadcast channel bandwidth. In contrast, compression increases the packet error rate (PER), which affects user perception. This is due to the transmission of each long IP packet over multiple physical layer frames, and is associated with an increase in the frame error rate (FER) as a result. If the carrier decides to use smaller IP packets to improve broadcast quality, the carrier can opt for header compression to reduce the transport and cryptographic overhead of the IP packets.

The RTP / UDP / IP protocol is used to transport broadcast content from CS to MS, and the content is protected by the Encapsulation Security Payload (ESP) in transport mode. Transport overhead is RTP / UDP / IP header, and 40 bytes per IP packet data. Cryptographic overhead is in the form of ESP headers, initialization vectors (IV), and ESP trailers. The ESP header and IV are inserted between the IP header and the UDP header. The ESP header contains the security parameter index (SPI) (4 bytes) and the sequence number (4 bytes). The length of the IV is specific to which cryptographic algorithm is used. For the AES cipher algorithm, the IV length is 16 bytes. The ESP trailer is prepended to the UDP datagram and contains the padding, the next header (1 byte), and the padding length (1 byte). The cipher block size of the AES algorithm is 16 bytes, so the padding size ranges from 0 to 15 bytes. The ceiling function of the average padding size is 8 bytes. For a single IP packet, the total transport and cryptographic overhead, not including the PDSN to MS data link layer overhead, ranges from 66 to 81 bytes with an average of 74 bytes.

Header compression, such as Robust Header Compression (ROHC), can be used to reduce the SPI fields of IP and ESP headers from 24 bytes to 2 bytes. The sequence number in the ESP header is not compressed because it is used to order the compressed packets. IV is not compressed because it changes randomly for each packet. UDP / RTP headers and ESP trailers cannot be compressed because they are encrypted. As a result, if ROHC is used to compress IP / ESP headers, the average overhead due to transport and cryptography is reduced from 74 bytes per IP packet to 52 bytes.

According to a typical embodiment, header compression such as robust header compression (ROHC) is applied to avoid transmission of decompression errors. As shown in Figure 7, the header information is compressed from 24 bytes down to 2 bytes. Header 500 includes IP header 502 and SPI portion 504. The compression algorithm results in a 2 byte result after compression. There, some form of arrangement provides unidirectional transmission of compressed information, as opposed to traditional header compression required between MS and PDSN or other backbone elements. The MS needs to request compressed information, that is, sufficient header compression parameters for decompression of the information received by the MS. Rather, the PDSN provides compression information periodically as shown in FIG. The PDSN disperses the compressed information in the broadcast content and gives it on the broadcast channel. The preparation of control information in the data stream is referred to as "in-band" as no isolation channel is required. As shown, the broadcast stream 600 includes broadcast content portion 604 and decompression information or compression information 602. Decompression information is T_{DECOMPRESSION}Given with a period of. An alternative embodiment can provide decompression information at the time of the occurrence of a preset event rather than cyclically. Since the MS does not require decompression information, the PDSN supplies the information frequently to prevent delays in accessing the broadcast content. In other words, the PDSN should provide information frequently so that the MS can access the broadcast at any time without having to wait for decompression information.

It should be noted that ROHC can be operated in unidirectional mode, where packets are sent from the compressor to the decompressor in only one direction. As a result, in this mode, the return route from the decompressor to the compressor is not available here or allows ROHC to be used on undesired links. The decompressor state is initialized before the MS can decompress the packets received from the broadcast channel. Initialization &amp; Refresh (IR) packets are used for this purpose. There are two alternatives for ROHC initialization.

The subscriber "tunes" to the broadcast channel and waits for ROHC IR packets to be periodically sent by the ROHC compressor in the PDSN. Frequent ROHC IR packets may be needed by the MS to begin decompressing the received packets immediately. Frequent ROHC IR packets may use a great deal of bandwidth within the broadcast channel. The IR packet is about 30 bytes for the IP / ESP compression profile. If the IR packet is sent once every 250 milliseconds, the process consumes about 1 kbps within the broadcast channel. Consuming IR packets on the air will further delay MS getting ROHC initialization.

If the decompression progresses out of sync due to packet loss, residual errors in the received compressed header, or failure, the resulting decompression error is decompression. May be communicated until is resynchronized or reinitialized. ROHC-compressed headers include a Cyclic Redundant Check (CRC) planned across all headers prior to compression. This CRC allows decompression (in the case of packet loss and residual errors) to perform a local context repair that results in a synchronous context. When decompression recovers from malfunction, periodic IR packets efficiently reinitialize the decompression process.

<u style="single">Data link layer</u> Data link layer framing protocols or transport layer protocols are applied between PDSN and MS to accurately describe packets received from broadcast channels. With reference to Figure 3, the information within the transport layer identified as the LINK LAYER is given between PDSN and MS. This framing information is generated in PDSN and given to MS via BS. The PDSN receives the IP stream from CS and frames the IP stream according to a preset framing protocol. As shown in a typical example, PDSN is a High-Level Data Link (HDLC). Apply the framing protocol version of Control). HDLC, defined in the ISO standard, corresponds to Layer 2 in the International Organization for Standardization (ISO) 7-Layered Architecture, where Layer 2 is referred to as the data link layer. The HDLC protocol works to provide error-free movement of data between network nodes. To this end, the HDLC layer is designed to ensure the integrity of the data passed to the next layer. In other words, the framing protocol operates to regenerate the received data exactly as it was originally transmitted, without error, without loss of information, and in the correct order.

A typical example applies a version of HDLC framing that applies a subset of the parameters defined in HDLC. FIG. 9 shows an example of HDLS framing. Here, frame 700 contains multiple fields, as defined by the HDLC protocol outlined in RFC1662. Field 702 defines the display of the start of FLAG or frame. FLAG has a selected bit length and is defined by a preset bit pattern. HDLC is convenient to apply because HDLC is a commonly available standardized protocol. One drawback of the full HDLC framing protocol is the processing time required to generate frames at the transmitter and to retrieve frames at the receiver.

In particular, the HDLC protocol is considered processor-intensive, as additional processing is used to ensure that the payload does not contain a sequence of bits similar to FLAG. On the transmitter, if a FLAG sequence of bits is detected in the payload, an escape character is inserted in the payload to identify that FLAG is part of the payload and does not indicate the start of a frame. To. The process of adding escape characters is referred to as "escaping" 0x7E and 0x7D hexadecimal patterns in the frame payload. An alternative method referred to as an efficient framing protocol, which is less process-intensive than HDLC-like framing, is described below. Figure 9 shows the option to use HDLC framing to transport PPP frames. For HSBS operation, HDLC-like framing overhead can be reduced by eliminating fields that are not needed or make little sense for one-way broadcasts, and / or give little information. It is possible. As mentioned above, FLAG is a preset sequence of bits that marks the beginning of an HDLC frame. A typical embodiment incorporates the start of FLAG or other frame indicator 802, as shown in format 800 of FIG. The frame termination, in contrast to the format of FIG. 9, is not shown with overhead information in typical embodiments. Format 700 addresses and control fields have static values and are not included in format 800.

Continuing in FIG. 10, all packets are the same on the broadcast channel because the purpose of protocol field 708 (FIG. 9) is to identify payload formats such as LCP control packets, ROHC packets, IP packets, etc. As it belongs to the format, this discriminator is not needed for broadcast operation. For example, if ROHC compression is used for packet transmission, all packets in the broadcast channel are treated as ROHC packets. The format of ROHC packets, such as IR packets, compressed packets, etc., is identified by the packet format field in the ROHC packet header. As a result, the protocol field is not included in format 800. In addition, format 800 includes error detection field 806 after payload 804. Error detection field 806 provides information to the receiver to allow the receiver to detect errors in the received payload. A typical example incorporates a frame checksum (FCS) that can be defined as null, 16-bit, or 32-bit. It is recommended to use 16-bit FCS, as HDLC frames may span multiple physical layer frames in the broadcast channel.

The octet stuffing procedure defined in RFC1662 also applies to typical embodiments. Here, after the FCS calculation, the HDLC transmitter in the PDSN inspects each byte in the HDLC frame (excluding flags) for the 0x7E and 0x7D patterns. Patterns 0x7E will be encoded as 0x7D and 0x5E. The pattern 0x7D will then be encoded as 0x7D and 0x5D. The HDLC transmitter will not encode any other pattern. This means that the Async-Control-Character-Map (ACCM) is set to all zeros, as defined in RFC1662.

HDLC framing overhead is the sum of 3 bytes and octet stuffing overhead. Assuming the byte pattern is evenly distributed, the average octet stuffing overhead is 1 byte per 128 bytes of HDLC frame. For example, if the payload is 256 bytes, the HDLC framing overhead averages 5 bytes.

FIG. 11 is a flow diagram of the framing method 900 performed in the transmitter. The transmitter determines the payload portion of the packetized data in step 902 and forms a broadcast frame by generating a start of flag (SOF). The transmitter then checks for frames for any SOF sequence contained within payload 904. If the SOF sequence is found in the payload, the transmitter adds an escape character in step 912. Otherwise, the transmitter adds SOF to the payload in step 906 and gives it to the error detection mechanism in step 908. The frame is transmitted in step 910. The transmitted frame has the format 800 of FIG. Alternative embodiments can implement other fields within the framing format. And it is possible to incorporate any form of classifier to put the SOF sequence in the payload.

FIG. 12 is a flow diagram relating to the deframing method 920 performed on the receiver. The process begins with the reception of the broadcast frame in step 922. The receiver identifies the SOF in step 924 and checks the escape character in the payload in the decision diamond 926. If an escape character or other SOF sequence identifier is found in the payload, the receiver removes the escape character in step 932. Otherwise, the receiver performs error detection in step 928 and processes the frame in step 930.

An alternative example is octet-based HDLC-like frameless framing used in an attempt to avoid processor-intensive operation using octet stuffing (referred to as escaping). Incorporate the protocol. Instead, this alternative uses a packet-based framing layer that is less device-intensive and is referred to here as the "efficient framing protocol." FIG. 15 shows the process and protocol 2000 for forming framing layer packets 2016 from IP layer packets 2002, full layer packets, and packing layer packets. Framing layer processing 2000 packs variable length packets received from higher layers such as the IP layer into fixed length packets 2016, and the resulting framing layer packets 2016 are combined into lower layers or physical layers (not shown). ). The framing layer allows the receiver to determine the higher layer packet boundaries and verify the integrity of the higher layer packets.

As shown, process 2000 includes several process sublayers, including a full layer and a packing layer. The full layer forms the full layer payload portion 2006 from the IP layer packet 2002 and adds trailer 2008. In one embodiment, the full layer payload portion 2006 includes an IP layer packet 2002. However, alternative embodiments include a portion of IP Layer Packet 2002 or multiple IP Layer Packets 2002, or any combination thereof. Trailer 2008 can be an integrity detection mechanism.

The integrity layer adds an integrity detection field, or trailer 2008, to each IP layer packet 2002, that is, packets received from layers above the IP layer in this case. The full layer then passes the resulting full layer packets 2006, 2008 to a lower layer, which in this case is the packing layer. Packets are further processed to form framing layer packets 2016 and transmitted through the physical layer. At the receiver, packets are received via the physical layer and fed to higher layers. The integrity layer at the receiver processes the integrity detection mechanism or trailer, which allows the receiver to verify the integrity of packets received from lower layers before they are passed to the higher layers. To do. The full layer format is shown in Figure 16 and discussed below.

Continuing in FIG. 15, the full layer passes full layer packets 2006, 2008 to the packing layer for the formation of packing layer packets. The packing layer forms a packet having at least one packing header or pack header 2010, at least one packing payload or pack payload 2012, and pad 2014. The examples shown include multiple pack payloads 2012, each with a combined pack header 2010. Alternative embodiments can incorporate any number of pack payloads 2012 and pack headers 2010. From the packing layer, process 2000 then generates framing layer packets 2016 in preparation for the physical layer (not shown).

The packing layer packs variable-length packets received from higher layers (eg, full layers) into fixed-length packing layer packets 2016, and the resulting packing layer packets 2016 are lower layers (eg, physical layers). Pass to. The packing layer allows the receiver to determine higher layer packet boundaries.

FIG. 16 shows format 2050 for full layer packets (2006, 2008 in FIG. 15). As shown, format 2050 contains two parts, a payload field 2052 and a frame detection sequence (FCS) field 2054. Payload portion 2052 is a variable length field containing exactly one higher layer packet octet. FCS Potion 2056 is a 32-bit field containing the FCS for the payload. FCS is a 32-bit CRC calculated over the payload field. Alternative embodiments can implement other error detection mechanisms.

FIG. 17 shows the packing layer packet format 2060 according to one embodiment. Format 2060 is four fields, continuations, lengths, payloads, and pads. The continuation field 2062 and the length field 2064 form the header part. The continuation field 2062 is a 1-bit field indicating whether the corresponding payload field 2066 is the start or continuation of a higher layer packet. An alternative embodiment can implement any bit number that makes sense with respect to payload field 2066. In the embodiment shown in FIG. 17, when the continuation field is set, the corresponding payload field is the continuation of the higher layer packet. Otherwise, the later payload field is the start of a higher layer packet. In this way, each pack payload 2012 (FIG. 15) can include a full IP layer packet 2002 (or full layer payload 2006), a portion of the IP layer packet 2006, and a plurality of IP layer packets 2002. According to an alternative embodiment, the continuation field 2062 is not included in the packing layer format 2060. Again, if the previous framing layer packet is discarded before it reaches the framing layer of the receiver, the receiver can use full layer processing to determine the start or continuation state of the full layer packet. Is. However, such an embodiment puts an additional processing load on the complete layer and extends the integrity detection process. It should also be noted that in one embodiment, the continuation field 2062 is only one bit, where the importance of the bits corresponds to the polarity of the bits. Alternative embodiments can have alternative polarities, or, as mentioned above, bit combinations can be implemented to provide additional information such as sequence numbers.

Continuing in FIG. 17, the header position further includes the length field 2064. In one embodiment, the length field 2064 indicates the number of octets from the first octet in the corresponding payload field 2066 to the last octet in the layer packet above the next payload field. It is a 15-bit field. Payload field 2066 is a variable length field containing octets from one full layer packet 2006, 2008 (Fig. 15). The number of octets in payload field 2066 is less than the length of the octet or the number of octets from the beginning of payload field 2006 to the end of packing layer packet 2016. Pad field 2068 is a variable length field that contains enough bits to maintain the size of the packing layer packet 2016, up to the size of the lower layer payload supported by the physical layer. The composition of Padfield 2068 reflects a preset recognizable pattern, such as an all-zero octet. The transmitter replenishes Padfield 2068, which has been received and ignored or discarded by the receiver.

<u style="single">Access network</u> A typical access network topology for System 1000 is shown in Figure 13 with CS1002, PDSN1004, and two PCFs, PCF1 1006 and PCF2 1008. FIG. 13 contains datagrams defining transmissions from each backbone element shown in System 1000. As shown, the CS1002 prepares an IP packet of information and sends the packet in at least one frame with a payload and inner header H1. The inner header has source and destination information, where the source identifies the CS1002 and the destination identifies the reserved group. The CS1002 sends frames to the PDSN1004, which maps destination reservation groups to individual subscribers within a set of active users.

The PDSN1004 determines the number of individual users in the active set within the destination reservation group and copies the frames received from the CS1002 for each of these users. PDSN1004 determines the PCF corresponding to each user in the reservation group. The PDSN1004 then adds an outer header H2 to each of the prepared frames. Here H2 identifies the PCF. The PDSN1004 then sends the frame to the PCF. Transmission from PDSN1004 includes the original payload, header H1, and header H2. As shown, PDSN 1004 sends N transmission frames to PCF1 1006 and M transmission frames to PCF2 1008. N transmission frames correspond to N users in the reservation group served via PCF1 1006, and M transmission groups correspond to M users in the reservation group served via PCF2 1008. To do. In this scenario, PDSN1004 copies frames received any number of times for transmission to the corresponding subscribers.

FIG. 14 shows a typical embodiment of system 1020 with CS1022 communicating with PCF1 1026 and PCF2 1028 via PDSN1024. As shown, the CS1022 prepares an IP packet of information and sends the packet to at least one frame with a payload and inner header H1. The inner header has source and destination information, where the source identifies the CS1022 and the destination identifies the reserved group. CS1022 sends the frame to PDSN1024. Here PDSN1024 adds an outer header H2, where H2 ships the frame to at least one PCF. PDSN1024 then sends the frame to the PCF. Transmission from PDSN1024 includes the original payload, header H1, and header H2. As shown, PDSN1024 sends one transmission frame to PCF1 1026 and one transmission frame to PCF2 1028. The PCF1 1026 sends one transmission frame to N users in the reservation group. PCF2 The 1028 sends one transmission frame to M users in the reservation group.

According to a typical embodiment, the broadcast CS sends an IP packet containing encrypted broadcast content to a multicast group identified by a class D multicast IP address. This address is used in the destination address field of the IP packet. The given PDSN1024 participates in the multicast delivery of these packets. After header compression, PDSN1024 puts each packet in an HDLC frame for transmission. HDLC frames are encapsulated by generic routing encapsulation (GRE) packets. The key field in the GRE packet header is the broadcast bearer Use a special value to indicate connection). The GRE packet is appended with a 20-byte IP packet header with a source address field identifying the IP address of PDSN1024, and the destination address field uses a class D multicast IP address. It is recommended that this multicast IP address be different from the one used by Broadcast CS. System 1020 forms at least one multicast shipping table for each PCF and PDSN. Packets delivered within the broadcast connection are given sequentially. In a typical example, the GRE sequencing property is enabled. Copying of IP multicast packets is performed within a multicast-capable router.

In a typical example, each PCF is further attached to a BSC (not shown). The BSC given here is capable of copying packets and sending them to other BSCs. BSC chaining provides better soft handoff characteristics. The fixed BSC provides better soft handoff characteristics. The fixed BSC copies the transmission frame and sends it to its adjacent BSC with the same time-stamp. Timestamp information is important for soft handoff operation because mobile stations receive transmission frames from different BSCs.

Skilled people in the industry will understand that information and signals can be represented using any variation of different methods and techniques. For example, data, commands, commands, information, signals, bits, symbols, and chips that may have been referenced through the above description are voltages, currents, electromagnetic waves, magnetic fields or particles, light fields or particles, or any of these. It can be represented by a combination.

Skilled people will also find that the various exemplary logic blocks, modules, circuits, and algorithm steps described in connection with the examples disclosed herein are electronic hardware, computer software, or a combination of both. Will appreciate what can be achieved as. To articulate this compatibility of hardware and software, various exemplary components, blocks, modules, circuits, and steps have been more commonly shown above in their functional representation. There is. Whether such a function is realized as hardware or software depends on the specific application and design constraints imposed on the entire system. A skilled technician can implement the described functions in different ways for each particular application. However, such a realization decision should not be construed as a cause of deviation from the scope of the invention.

The various exemplary logic blocks, modules, and circuits described in connection with the embodiments disclosed herein are general purpose processors, digital signal processors (DSPs), and application specific integrated circuits. (ASIC; Application Specific Integrated Circuit), Field Programmable Gate Array (FPGA) Array), or any other programmable logic device, individual gate or transistor logic, individual hardware components, or any combination of these designed to perform the functions described herein. Is possible. The general purpose processing device may be a micro processing device, but instead the processing device may be any conventional processing device, controller, micro controller, or state machine. The processing equipment may also be a combination of computing devices, such as a combination of DSP and microprocessing equipment, multiple microprocessing equipment, one or more microprocessing equipment associated with a DSP core, or any other such array. It can be realized.

The steps or algorithms of the methods described with respect to the embodiments disclosed herein may be embodied directly in hardware, in software modules executed by a processor, or in a combination of the two. It is possible. The software module can be placed in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, resistors, hard disks, removable disks, CD-ROMs, or any other form of recording medium known in the art. It is possible to get rid of. A typical recording medium is coupled with a processing device such that the processing device can read information from the recording medium and write the information to the recording medium. Instead, the recording medium can be integrated into the processing apparatus. Processing equipment and recording media may be located in the ASIC. The ASIC may be placed inside the user terminal. Instead, the processor and recording medium may be placed in the user terminal as separate components.

The above description of the disclosed examples is provided to allow anyone skilled in the art to create or use the present invention. Various variations on these examples will be readily apparent to skilled people in the industry. And the general principles defined therein can be applied to other embodiments without departing from the spirit or scope of the invention. The present invention is therefore not intended to be limited to the examples presented herein, but should be consistent with the broadest scope consistent with the principles and novel features disclosed herein.