HK1074318A

HK1074318A - Method and system for hard handoff in a broadcast communication system

Info

Publication number: HK1074318A
Application number: HK05106670.9A
Authority: HK
Inventors: N．K．N．伦
Original assignee: 高通股份有限公司
Priority date: 2001-10-24
Filing date: 2002-10-23
Publication date: 2005-11-04

Description

Method and system for handoff in a broadcast communication system

Background

FIELD

The present invention relates to broadcast communications, also known as point-to-multipoint communications, in wireless communication systems, and more particularly to systems and methods for hard handoff in such broadcast communication systems.

Background

Communication systems have been developed to allow transmission of information signals from an origination station to a physically different destination station. When an information signal is transmitted from an origination station over a communication channel, the information signal is first converted into a form suitable for efficient transmission over the communication channel. The conversion (i.e., modulation) of the information signal includes: the carrier parameter is varied in accordance with the information signal in such a way that the resulting modulated carrier spectrum is confined within the communication channel bandwidth. At the destination station, the original information signal is replicated from the modulated carrier wave received over the communication channel. Such replication is typically accomplished by using a process that is the inverse of the modulation process employed by the origination station.

Modulation also facilitates multiple access, i.e., simultaneous transmission and/or reception, of several signals on a common communication channel. Multiple-access communication systems typically include a plurality of subscriber units that require intermittent service of relatively short duration rather than continuous access to a common communication channel. Several multiple access techniques are known in the art, such as Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), amplitude modulation multiple Access (AM). Another type of multiple access technique IS Code Division Multiple Access (CDMA) Spread Spectrum systems that conform to the TIA/EIA/IS-95 Mobile Station-Base Station Compatibility Standard for dual-Mode wideband Spread Spectrum Cellular systems (TIA/EIA/IS-95 Mobile Station-Base Station Compatibility Standard for dual-Mode Wide-Band Spread Spectrum Cellular System), hereinafter referred to as the IS-95 Standard. The use of CDMA techniques IN MULTIPLE ACCESS communication SYSTEMs is disclosed IN U.S. patent No. 4901307 entitled "forward speech MULTIPLE-ACCESS communication SYSTEM USING SATELLITE positioning SYSTEM OR TERRESTRIAL REPEATERS" and U.S. patent No. 5103459, both of which are assigned to the assignee of the present invention.

Multiple-access communication systems may be wireless or wired and may communicate voice and/or data. An example of a communication system capable of communicating both voice and data IS a system that conforms to the IS-95 standard, which specifies transmitting voice and data over a communication channel. A METHOD OF transmitting data in a fixed size coded channel frame is described in detail in U.S. Pat. No. 5504773, entitled "METHOD AND APPARATUS FOR THE FORMATION OF DATAFOR TRANSMISSION", assigned to THE assignee OF THE present invention. According to the IS-95 standard, data or speech IS divided into encoded channel frames that are 20 milliseconds wide, with data rates as high as 14.4 Kbps. Other examples of communication systems capable of communicating both voice and data include communication systems that comply with the following standards: "third generation partnership project (3 GPP)" which is contained within a set of documents including document numbers 3G TS 25.211, 3GTS 25.212, 3G TS 25.213 and 3G TS 25.214(W-CDMA standard); and "TR-45.5 Physical Layer Standard for cdma2000Spread Spectrum Systems" (IS-2000 Standard) for cdma2000Spread Spectrum Systems ".

An example of a data-only communication system IS a High Data Rate (HDR) communication system that conforms to the TIA/EIA/IS-856 industry standard, hereinafter referred to as the IS-856 standard. The HDR system is based on the communication system disclosed in co-pending application serial No. 08/963386, entitled "METHOD AND APPARATUS FOR HIGH RATEPACKET DATA TRANSMISSION", filed at 11/3/1997 AND assigned to the assignee of the present invention. HDR communication systems define a set of data rates, ranging from 38.4kbps to 2.4Mbps, AT which an Access Point (AP) may transmit data to a subscriber station (access terminal, AT). Since APs are similar to base stations, the terminology with respect to cells and sectors is the same as with respect to voice systems.

In a multiple access communication system, communication between users is conducted through one or more base stations. A first user on one subscriber station communicates data to a second user on a second subscriber station by transmitting the data on a reverse link to a base station. A base station receives data and may route the data to another base station. Data is sent on the forward link of the same base station, or other base stations, to the second subscriber station. The forward link refers to transmission from a base station to a subscriber station, and the reverse link refers to transmission from a subscriber station to a base station. Likewise, communication may be conducted between a first user on a mobile subscriber station and a second user on a landline station. The base station receives data from the subscriber on the reverse link and routes the data to a second subscriber through the Public Switched Telephone Network (PSTN). In many communication systems, such as IS-95, W-CDMA, IS-2000, the forward link and reverse link are assigned different frequencies.

The above-described wireless communication service is an example of a point-to-point communication service. In contrast, a broadcast service provides a point-to-multipoint communication service. The basic model of a broadcast system consists of a network of broadcast subscribers served by one or more central stations which transmit information with specific content, such as news, movies, sports events, etc., to the subscribers. Subscriber stations of each broadcast network user monitor a common broadcast forward link signal. Since the central station fixedly determines the content, the user generally does not return a communication. Examples of common uses of broadcast service communication systems are TV broadcasting, radio broadcasting, and the like. Such communication systems are typically highly proprietary configured communication systems. With the recent development of wireless cellular telephone systems, the existing infrastructure that primarily uses point-to-point cellular telephone systems for broadcast services has become a focus of attention. (the term "cellular" system as used herein includes communication systems using both cellular and PCS frequencies.)

When a subscriber station moves outside the boundaries of the base station with which the subscriber station is currently communicating, it is desirable to maintain a communication link by diverting the call to a different subscriber station. Methods and SYSTEMs for providing communication with a subscriber station through more than one base station during a SOFT handoff procedure are disclosed IN U.S. patent No. 5267261 entitled MOBILE ASSISTED SOFT HAND-OFF IN a CDMA cellular TELEPHONE SYSTEM, assigned to the assignee of the present invention. METHODs AND systems FOR providing softer handoffs are described in detail in U.S. patent No. 5933787 entitled "METHOD AND APPARATUS FOR PERFORCING AND-OFFBETWEEN SECTORS OF A COMMON BASE STATION", assigned to the assignee OF the present invention. By using these methods, the communication between subscriber stations is not disturbed by a possible handover from the originating base station to the subsequent base station. Such a handoff may be considered a "soft" handoff because communication with a subsequent base station is established before communication with the originating base station is terminated. When a subscriber unit communicates with two base stations, the subscriber unit combines the signals received from the respective base stations in the same manner as the multipath signals from the common base station.

Although the above-described handoff method of the point-to-point communication system may be applied to a broadcasting system, the handoff based on the exchange of the base station-subscriber station signaling messages may cause a high signaling load in the broadcasting system. The high signaling load is caused by a large number of subscribers monitoring a common broadcast forward channel. Also, as described in the above-referenced patents nos. 5267261 and 2933787, transmissions received simultaneously by the subscriber station during handoff are synchronized at the transmitting base station. Since the broadcast transmission is directed to many subscriber stations, the base station cannot synchronize the transmission for each subscriber station for which a handoff is desired. In light of the above, there is a need in the art for a system and method for performing handoff in such a broadcast communication system.

SUMMARY

Embodiments disclosed herein address the above stated needs by providing a method, and a system for performing the method, for: detecting a need for a handoff at a physical layer; notifying higher layers of said detected need for handoff; and initiating resynchronization in accordance with the notification.

In another aspect of the invention, the initiation of resynchronization is effected upon receipt of the notification by determining parameters for: processing a second broadcast channel transmitted from a second terminal; terminating processing of a first broadcast channel transmitted from a first terminal; and starting processing the second broadcast channel in accordance with the determined parameters.

In yet another aspect of the present invention, the processed output of the first broadcast channel is synchronized with the processed output of the second broadcast channel before terminating the processing of the first broadcast channel.

In yet another aspect of the present invention, the above need is addressed by providing a method, and a system for performing the method, for: processing a broadcast session on a first broadcast channel transmitted from a first terminal according to a first set of parameters; performing a handover to a second broadcast channel transmitted from a second terminal; and processing the broadcast session on the second broadcast channel in accordance with the first set of parameters if the handoff period is less than the lifetime of the broadcast session.

In yet another aspect of the invention, the second set of parameters is obtained from the first broadcast channel or from the second broadcast channel.

Brief Description of Drawings

FIG. 1 illustrates a conceptual block diagram of a high speed broadcast service communication system;

fig. 2 illustrates the concept of a soft handoff group in a broadcast communication system;

FIG. 3 illustrates resynchronization in accordance with one embodiment;

FIG. 4 illustrates broadcast stream realignment according to an embodiment;

FIG. 5 illustrates broadcast stream realignment when a new broadcast stream is advanced relative to an old broadcast stream;

FIG. 6 illustrates broadcast stream realignment when a new broadcast stream is delayed relative to an old broadcast stream;

FIG. 7 illustrates a protocol data unit in accordance with one embodiment; and

fig. 8 illustrates resynchronization in accordance with another embodiment.

Detailed Description

Definition of

The word "exemplary" is used herein to mean "serving as an example, instance, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

The term "point-to-point communication" is used herein to mean communication between two subscriber stations over a dedicated communication channel.

The term "broadcast communication" or "point-to-multipoint communication" is used herein to mean a communication in which multiple subscriber stations receive communications from one source.

The term "packet" is used herein to mean a set of bits, including data (payload) and control elements, arranged into a particular format. Control elements include, for example, a preamble, a quality metric, 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.

The term "access network" is used herein to mean a Base Station (BS) and a set of one or more base station controllers. An access network transports data packets between multiple subscriber stations. The access network may also be connected to other networks outside the access network, such as a corporate intranet or the internet, and may transport data packets between individual access terminals and such outside networks.

The term "base station" is used herein to mean the hardware with which a subscriber station communicates. A cell refers to either hardware or a geographic coverage area, depending on the environment in which the term is used. A sector is a portion of a cell. Since a sector has the properties of a cell, the principles described herein with respect to a cell are also easily extended to a sector.

The term "subscriber station" is used herein to mean the hardware with which an access network communicates. A subscriber station may be mobile or stationary. A subscriber station may be any data device that communicates through a wireless channel or through a wired channel, for example using fiber optic or coaxial cables. A subscriber station may also be any of a number of device types, including but not limited to: PC card, micro flash, external or internal modem, or wireless or wireline phone. A subscriber station that is 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 a base station is said to be in a traffic state.

The term "physical channel" is used herein to mean a communication route over which signals propagate using modulation characteristics and coding.

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

The term "communication channel/link" is used herein to mean a physical channel or a logical channel in accordance with the context.

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

The term "forward channel/link" is used herein to mean a communication channel/link through which a base station sends signals to a subscriber station.

The term "hard handoff" is used herein to mean the communication between a subscriber station and a first sector to a second sector by ending the communication between the subscriber station and the first sector before starting the communication between the subscriber station and the second sector.

The term "soft handoff" is used herein to mean communication between a subscriber station and two or more sectors, where each sector belongs to a different cell. Reverse link communications are received by both sectors and forward link communications are simultaneously effectuated upon the forward links of the two or more sectors.

The term "softer handoff" is used herein to mean a communication between a subscriber station and two or more sectors, where the sectors belong to the same cell. Reverse link communications are received by both sectors and forward link communications are simultaneously effectuated upon one of the forward links of the two or more sectors.

The term "erasure" is used herein to mean a failure to identify a message.

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

The term "common channel" is used herein to mean a channel modulated by information shared among all subscriber stations.

Description of the invention

As already discussed, the basic model of a broadcast system consists of a user broadcast network served by one or more central stations, which transmit information with specific content, such as news, movies, sports events, etc., to the user. Subscriber stations of each broadcast network user monitor a common broadcast forward link signal. Fig. 1 illustrates a conceptual block diagram of a communication system 100 capable of performing High Speed Broadcast Services (HSBS) in accordance with an embodiment of the present invention.

Broadcast content originates at a Content Server (CS) 102. The content server may be located within a carrier network (not shown) or outside the Internet (IP) 104. The content is delivered in packets to a Broadcast Packet Data Serving Node (BPDSN) 106. The term BPSDN is used because although the BPSDN may be physically co-located with or identical to a conventional PDSN (not shown), the BPSDN may be logically different from a conventional PDSN. The BPDSN 106 delivers the packet to a Packet Control Function (PCF)108 according to the packet's destination. The PCF is a control entity controlling the functions of the base station 11O of the HSBS as if the base station controller were used for regular voice and data services. To illustrate the connection of the high-level concept of HSBS to the physical access network, fig. 1 shows a PCF that is physically co-located or even identical, but logically different, to a Base Station Controller (BSC). Those of ordinary skill in the art will appreciate that this is for illustrative purposes only. The BSC/PCF 108 provides the packets to the base station 110.

Communication system 100 enables High Speed Broadcast Services (HSBS) by introducing a forward broadcast shared channel (F-BSCH)112, which forward broadcast shared channel 112 can have a high data rate transmitted from base station 110 that can be received by a large number of subscriber stations 114. The term "forward broadcast shared channel" is used herein to mean a single forward link physical channel that carries broadcast traffic. A single F-BSCH may carry one or more HSBS channels multiplexed in TDM fashion within the single F-BSCH. The term "HSBS channel" is used herein to mean a single logical HSBS broadcast session defined by the broadcast content of the session. Each session is defined by broadcast content that may change over time; such as 7 am-news, 8 am-weather, 9 am-movies, and so forth.

Since the HSBS channels are multiplexed onto the F-BSCH physical channels as described above and there are various possibilities how to implement the HSBS channels in the F-BSCH channels, the subscriber station needs to know which HSBS channel is implemented on which F-BSCH. This information is specified by a logical to physical mapping. The physical to logical mapping of BROADCAST services is disclosed in co-pending U.S. patent application serial No. 09/933978 entitled "a METHOD and SYSTEM FOR SIGNALING IN BROADCAST COMMUNICATION SYSTEM", filed on 20/8/2001 and assigned to the assignee of the present invention. Also, the forward broadcast shared channel includes various combinations of upper layer protocols based on the type of content delivered. Therefore, the subscriber station also requires information about these upper layer protocols for interpretation of the broadcast transmission.

The different options for per rank HSBS service are referred to as HSBS service options. In general, HSBS service options are defined by the protocol stack, options in the protocol stack, and procedures for establishing and synchronizing services. The HSBS service option may be provided to the subscriber station via an out-of-band method, i.e., transmission via a separate channel other than the broadcast channel by the HSBS service option. Alternatively, the HSBS service option may be provided to the subscriber station via an in-band method, wherein the HSBS service option is multiplexed with the information content of the HSBS channel. The HSBS service option description may use protocols known to those of ordinary skill in the art. One such protocol description of the application layer and the transport layer includes the Session Description Protocol (SDP). The session description protocol is a format defined for conveying sufficient information to recover or participate in a multimedia or other broadcast type session. In one example, SDP is specified in RFC 2327 entitled "SDP: SessionDescription Protocol ", published by m.handley and v.jacobson at 4 months 1998, incorporated herein by reference. A detailed description FOR providing protocol options is disclosed in co-pending U.S. patent application Ser. No. 09/933914 entitled "METHOD AND APPATUS FOR BROADCAST SIGNALINGIN A WIRELESS COMMUNICATION SYSTEM" filed on 8/20/2001 AND assigned to the assignee of the present invention.

Hard handoff on common broadcast forward link

Soft and softer handoff is desirable in the overlapping coverage areas of different sectors in order to improve the performance of the common broadcast forward link. A METHOD and SYSTEM FOR providing communication with a subscriber station through more than one base station during a soft HANDOFF procedure is disclosed IN co-pending U.S. patent application serial No. 09/933607 entitled "METHOD AND SYSTEM FOR a hand off IN a BROADCAST communication SYSTEM," filed on 20/8/2001, assigned to the assignee of the present invention.

Although soft and softer handoff methods are desirable because the subscriber station does not experience a discontinuity in the transmitted information, such methods are not always available for use in broadcast communication systems. Subscriber stations may only transmit for synchronizationPerforming soft combination; thus, a subscriber station may perform soft and softer handoff only between base stations belonging to the same Soft Handoff (SHO) group. As used herein, a SHO group means a group in which all base stations transmit simultaneously and synchronously on a common broadcast forward link. FIG. 2 illustrates two SHOs, one including a BS₁、BS₂And BS₃And the other one including a BS₄、BS₅、BS₆And BS₇. Thus, if the subscriber station crosses a boundary from the coverage area of SHO group 1202 to the coverage area of SHO group 2204, a hard handoff is required.

When a subscriber station is in two unsynchronized cells/sectors (e.g., BS)₂And BS₄) When performing hard handoff between, the BS₂May be relative to the BS₄Is advanced or delayed. Also, the broadcast session and service options may change because the handoff from one broadcast stream to another requires some time. To prevent subscriber stations from being directed to a BS₄The subscriber station needs to perform a resynchronization procedure when such a hard handoff occurs. The term "resynchronization" as used herein means a process necessary to provide the output of the post-handoff broadcast service content to the user. During the resynchronization procedure after the hard handoff, the decoding and outputting of the broadcast service content is interrupted. This interruption is annoying to the user and should be eliminated, or at least minimized.

According to known handoff methods, such as those described in the above-mentioned U.S. application nos. 5267261 and 5933787, the need for handoff is detected by layer 1 of the International Standards Organization (ISO) open system interconnection (0SI) layering model, and the handoff is supported by layer 3 of the OSI. These layers are referred to below as lower layers. The layers above layer 3 of the OSI (hereinafter referred to as higher layers) are not notified or involved in the handover. According to an embodiment of the present invention, when a subscriber station determines a need for a handoff at a lower layer (e.g., the physical layer), the higher layer is notified of the upcoming handoff. Upon receiving the notification, the higher layer initiates the resynchronization method.

Fig. 3 illustrates resynchronization in accordance with one embodiment. The method starts at step 3200 and continues to step 3202.

In step 3202, the need for a hard handoff is tested. If the test is positive, the method continues to step 3204, otherwise, the method continues to step 3210.

In step 3204, a subscriber station receiving a broadcast session on a broadcast channel (old broadcast stream) transmitted from a first terminal obtains the broadcast session on a broadcast channel (new broadcast stream) transmitted from a second terminal, obtains the new broadcast stream, and searches the new broadcast stream for service option information, such as a header compression protocol and a decompression status, and a Session Description Protocol (SDP) when all contents of the old broadcast stream are simultaneously decoded. The subscriber station does not extend significant processing power because the subscriber station does not have to decode the session content of the new broadcast stream. Once the subscriber station identifies the service option information, the method continues to step 3206.

In step 3206, the subscriber station decodes the identified service option information, thus obtaining parameters necessary for processing the new broadcast stream. The method continues to step 3208.

In step 3208, the subscriber station ends the handoff by ending decoding and outputting the old broadcast stream. The method continues to step 3210.

In step 3210, the subscriber station decodes and outputs the received broadcast stream using the latest parameters.

As described above, the old broadcast stream and the new broadcast stream are not synchronized, which may cause discontinuity of output information. Also, a time interval between the end of decoding and outputting of the old broadcast stream and the start of decoding and outputting of the new broadcast stream may cause discontinuity of output information. To minimize or prevent such discontinuities, in another embodiment, the subscriber station also determines the timing of the old and new broadcast streams and uses this information to realign the output of the information content.

Fig. 4 illustrates realignment according to an embodiment. The method begins at step 4300 and continues to step 4302.

In step 4302, upon detecting the need for a handoff, the subscriber station acquires a new broadcast stream, identifies and decodes service option information of the new broadcast stream. The method of step 4302 may include steps 3204 and 3206 of fig. 3. The method continues to step 4304.

In step 4304, the subscriber station also decodes the timing information of the new broadcast stream. The timing information may be obtained, for example, from a time stamp of the broadcast stream information content. Alternatively, the timing information may be obtained from a sequence number of the broadcast stream information element. The method continues to step 4306.

In step 4306, the subscriber station determines whether the broadcast streams are synchronized. If the broadcast streams are synchronized, the method continues to step 4308; otherwise, the method continues to step 4310.

In step 4308, the subscriber station starts decoding a new broadcast stream, and when the subscriber station is ready to output the decoded new broadcast stream, the subscriber station ends the handoff by ending decoding and outputting the old broadcast stream and starting decoding and outputting the new broadcast stream. The method returns to step 4302.

In step 4310, the subscriber station determines the relative timing of the old broadcast stream and the new broadcast stream. Further realignment depends on the relative timing of the broadcast streams. After realigning the broadcast streams, the subscriber station ends the handoff and the method returns to step 4302.

Fig. 5 illustrates a case where a new broadcast stream is advanced with respect to an old broadcast stream. At time t₀Here, the subscriber station is decoding the information content of the old broadcast stream 5402 and outputting the decoded information content 5404. Meanwhile, the subscriber station decodes the information content of the new broadcast stream 5406 and determines the timing indicated by the sequence number of the new broadcast stream 5406 unit. At time t₁Here, the subscriber station starts accumulating the units of the new broadcast stream 5406 into the buffer 5408. At time t₂Stored in buffer 5408The first unit has the same sequence number (5) as the unit of the old broadcast stream 5402 to be output. Thus, the subscriber station starts outputting cells from the buffer 5408 and suspends decoding and reception of the old broadcast stream 5404. To eliminate the delay between the contents of the buffer 5408 and the units received and decoded from the new broadcast stream 5406, the subscriber station outputs the buffered units at a faster rate than the units are received. At time t₃Where there are no more cells in the buffer 5408, the new broadcast stream 5406 cells (17) are aligned with the expected cells (17) at output 5404, thus the subscriber station suspends cell buffering and provides the cells directly to the output.

Fig. 6 illustrates a case where a new broadcast stream is delayed with respect to an old broadcast stream. At time t₀Here, the subscriber station is decoding the information content of the old broadcast stream 6502 and outputting the decoded information content 6504. At the same time, the subscriber station decodes the information content of the new broadcast stream 6506 and determines the timing indicated by the sequence number of the new broadcast stream 6506 unit. At time t₁Here, the subscriber station starts accumulating the units of the old broadcast stream 6502 into the buffer 6508 and outputs the units from the buffer 6508 at a slower speed than the speed at which the units from the new broadcast stream 6506 are received. At time t₂Here, the last unit stored in the buffer 6508 has the same sequence number as the unit of the new broadcast stream 6506 to be output (13). Thus, the subscriber station stops outputting units from the buffer 6508, suspends decoding and reception of the old broadcast stream 6502, and starts outputting units from the new broadcast stream 6506.

Typically, both content streams have the same protocol options. The only time the protocol options are different before and after the handoff is the time the subscriber station performs the handoff when the session changes. In another embodiment, the subscriber station takes advantage of the fact that the old broadcast stream may contain information about the next session.

As described in the above-mentioned copending U.S. application No. 09/933914, a Session Description Protocol (SDP) describing broadcast sessions may be sent as a Protocol Data Unit (PDU) that includes a number of predefined fields as shown in fig. 7. The length of the fields is given according to an embodiment, but may vary according to the design goals and constraints of a given system. The PDU field is described as follows:

CONTROL identifies the format of the PDU and indicates whether the fields NEXT _ SDP _ ID, INCL _ SDP _ DESC _ ID, and INCL _ SDP _ DESC are included within the PDU.

CURRENT _ SDP _ ID identifies the currently active SDP description, i.e., the description currently used for encoding and processing the broadcast session content.

CURRENT _ SDP _ LIFE represents the time when the CURRENT SDP is valid.

The NEXT _ SDP _ ID identifies the SDP of the NEXT session. The ID may be used to retrieve the SDP for the next session before the next session starts.

The INCL _ SDP _ DESC _ ID identifies the SDP that may be included in the PDU. The SDP may be the current description, the SDP for the next session, or the SDP for any future session. Sending the SDP for future sessions enables the subscriber station to store the SDP for viewing future content without retrieving the SDP directly from a server.

INCL _ SDP _ DESC, SDP of a specific session. Sending the SDP prevents the subscriber station from having to retrieve the SDP description separately from the content server. However, SDP requires high bandwidth, and it is recommended that the INCL _ SDP _ DESC be sent only before and after session parameter changes (i.e. at the boundary between two sessions).

The embodiment using a time indication that the current broadcast session is valid starts at step 8600 and proceeds to step 8602.

In step 8602, the subscriber station processes the old broadcast stream, decodes the service option information and determines a value of a session duration, and whether the service option information includes a protocol parameter of a next session. The method continues to step 8604.

In step 8604, the subscriber station compares the value of the session duration to the handoff time. If the value of the session duration is greater than the handoff time, the method continues to step 8606, otherwise the method continues to step 8608.

In step 8606, the subscriber station performs a handover, acquires a new flow, and starts processing the new broadcast flow with the current service option information. The method returns to step 8602.

In step 8608, the subscriber station proceeds according to whether the service option information determined in step 8602 includes protocol parameters for the next session. If the service option information includes protocol parameters for the next session, the method continues to step 8610; otherwise, the method continues to step 8612.

In step 8610, the subscriber station performs a handoff, acquires a new flow, and begins processing the new broadcast flow with the protocol parameters for the next session.

In step 8612, the subscriber station performs a handoff, obtains a new stream, identifies and decodes the service option information, and decodes the new broadcast stream with the protocol parameters obtained from the service option information. The method continues to step 8602.

Those skilled in the art will appreciate that although the flow diagrams are drawn in an order that facilitates understanding, in actual implementations some steps may be implemented in parallel. Moreover, unless otherwise indicated, the method steps may be interchanged without departing from the scope of the invention. Moreover, although signaling of service options is described in terms of in-band signaling, this is for illustration purposes only, and the use of out-of-band signaling is within the spirit and scope of the present invention.

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, 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. The skilled person will recognize the interactivity of the hardware and software in these cases and how best to implement the described functionality for each particular application. 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 subscriber unit. 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 the use of the inventive faculty. 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.

A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the patent and trademark office patent file or records, but otherwise reserves all copyright rights whatsoever.

Claims

1. A method for resynchronization in a communication system, the method comprising:

detecting a need for a handoff at a physical layer; and

higher layers are notified about the detected need for handoff.

2. The method of claim 1, further comprising:

determining parameters for processing a second broadcast channel transmitted from a second terminal;

terminating processing of a first broadcast channel transmitted from a first terminal; and

processing of the second broadcast channel is started in accordance with the determined parameters.

3. The method of claim 2, further comprising:

adjusting an output of the processed first broadcast channel transmitted from the first terminal in response to the start of the second broadcast channel processing.

4. The method of claim 3, wherein the adjusting the output comprises:

the rate at which the processed first broadcast channel is output is reduced.

5. The method of claim 3, wherein the adjusting the output comprises:

the rate of outputting the processed first broadcast channel is increased.

6. The method of claim 2, wherein the terminating the processing of the first broadcast channel comprises:

after the first broadcast channel and the second broadcast channel are synchronized, the process of the first broadcast channel is terminated.

7. The method of claim 6, wherein the synchronizing the first broadcast channel and the second broadcast channel comprises:

a common timestamp in the first broadcast channel and the second broadcast channel is identified.

8. The method of claim 6, wherein the synchronizing the first broadcast channel and the second broadcast channel comprises:

a common sequence number in the first and second transport streams is identified.

9. A method for resynchronization in a communication system, the method comprising:

processing a first broadcast channel transmitted from a first terminal;

determining a parameter for processing a second broadcast channel transmitted from a second terminal;

terminating the processing of the first broadcast channel; and

10. The method of claim 9, further comprising:

adjusting an output of the processed first broadcast channel in response to a start of the second broadcast channel processing.

11. The method of claim 10, wherein the adjusting the output comprises:

the rate at which the processed first broadcast channel is output is reduced.

12. The method of claim 10, wherein the adjusting the output comprises:

the rate of outputting the processed first broadcast channel is increased.

13. The method of claim 9, wherein the terminating the processing of the first broadcast channel comprises:

14. The method of claim 13, wherein the synchronizing the first broadcast channel and the second broadcast channel comprises:

15. The method of claim 13, wherein the synchronizing the first broadcast channel and the second broadcast channel comprises:

a common sequence number in the first broadcast channel and the second broadcast channel is identified.

16. The method of claim 9, further comprising:

detecting a need for a handoff at a physical layer;

higher layers are notified about the detected need for handoff.

17. A method for resynchronization in a communication system, the method comprising:

processing a broadcast session on a first broadcast channel transmitted from a first terminal according to a first set of parameters;

performing a handover to a second broadcast channel transmitted from a second terminal; and

if the handoff period is less than the broadcast session duration, the broadcast session on the second broadcast channel is processed according to the first set of parameters.

18. The method of claim 17, further comprising:

if the handoff period is greater than the broadcast session duration, the broadcast session on the second broadcast channel is processed according to the second set of parameters.

19. The method of claim 17, wherein processing the broadcast session on the second broadcast channel in accordance with the second set of parameters comprises:

a second set of parameters is obtained from the first broadcast channel.

20. The method of claim 17, wherein processing the broadcast session on the second broadcast channel in accordance with the second set of parameters comprises:

a second set of parameters is obtained from a second broadcast channel.

21. The method of claim 17, further comprising:

detecting a need for a handoff at a physical layer; and

higher layers are notified about the detected need for handoff.

22. An apparatus for resynchronization in a communication system, the apparatus comprising:

means for detecting a need for handoff at a physical layer; and

means for notifying higher layers of the detected need for handoff.

23. The apparatus of claim 22, further comprising:

means for determining a parameter for processing a second broadcast channel transmitted from a second terminal;

means for terminating processing of a first broadcast channel transmitted from a first terminal;

means for starting processing the second broadcast channel in accordance with said determined parameters.

24. The apparatus of claim 23, further comprising:

25. The apparatus of claim 24, wherein the means for adjusting the output comprises:

means for reducing a rate of outputting the processed first broadcast channel.

26. The apparatus of claim 24, wherein the means for adjusting the output comprises:

means for increasing a rate of outputting the processed first broadcast channel.

27. The apparatus of claim 23, wherein the means for terminating processing of the first broadcast channel comprises:

means for terminating processing of the first broadcast channel after synchronizing the first broadcast channel and the second broadcast channel.

28. The apparatus of claim 27, wherein the synchronizing the first broadcast channel and the second broadcast channel comprises:

29. The apparatus of claim 27, wherein the synchronizing the first broadcast channel and the second broadcast channel comprises:

30. An apparatus for resynchronization in a communication system, the apparatus comprising:

means for processing a first broadcast channel transmitted from a first terminal;

means for terminating processing of the first broadcast channel; and

means for starting processing of the second broadcast channel in accordance with the determined parameters.

31. The apparatus of claim 30, further comprising:

means for adjusting the output of the processed first broadcast channel in response to the start of the second broadcast channel processing.

32. The apparatus of claim 31, wherein the means for adjusting the output comprises:

means for reducing a rate of outputting the processed first broadcast channel.

33. The apparatus of claim 31, wherein the means for adjusting the output comprises:

34. The apparatus of claim 30, wherein the means for terminating the processing of the first broadcast channel comprises:

means for terminating the processing of the first broadcast channel after synchronizing the first broadcast channel and the second broadcast channel.

35. The apparatus of claim 34, wherein the synchronizing the first broadcast channel and the second broadcast channel comprises:

36. The apparatus of claim 34, wherein the synchronizing the first broadcast channel and the second broadcast channel comprises:

37. The apparatus of claim 30, further comprising:

means for detecting a need for handoff at a physical layer; and

means for notifying higher layers of said detected need for handoff.

38. An apparatus for resynchronization in a communication system, the apparatus comprising:

means for processing a broadcast session on a first broadcast channel transmitted from a first terminal in accordance with a first set of parameters;

means for performing a handover to a second broadcast channel transmitted from a second terminal; and

means for processing the broadcast session on the second broadcast channel in accordance with the first set of parameters if the handoff period is less than the broadcast session duration.

39. The apparatus of claim 38, further comprising:

means for processing the broadcast session on the second broadcast channel in accordance with the second set of parameters if the handoff period is greater than the broadcast session duration.

40. The apparatus of claim 38, wherein the means for processing the broadcast session on the second broadcast channel in accordance with the second set of parameters comprises:

means for obtaining a second set of parameters from the first broadcast channel.

41. The apparatus of claim 38, wherein the means for processing the broadcast session on the second broadcast channel in accordance with the second set of parameters comprises:

means for obtaining a second set of parameters from a second broadcast channel.

42. The apparatus of claim 38, further comprising:

means for detecting a need for handoff at a physical layer; and

means for notifying higher layers of said detected need for handoff.

43. An apparatus for providing multi-layered content, comprising:

a memory; and

an apparatus communicatively coupled to a memory and capable of performing digital signal processing, comprising:

detecting a need for a handoff at a physical layer; and

higher layers are notified about the detected need for handoff.

44. The apparatus of claim 43, the device communicatively coupled with a memory and capable of performing digital signal processing further comprising: and starting resynchronization according to the notification.

45. The apparatus of claim 44, wherein the initiating resynchronization comprises:

parameters for processing a second broadcast channel transmitted from a second terminal are determined.

processing of the second broadcast channel is commenced in accordance with the determined parameters.

46. An apparatus for providing multi-layered content, comprising:

a memory; and

a device communicatively coupled to the memory and capable of performing digital signal processing, the processing comprising:

processing a first broadcast channel transmitted from a first terminal;

terminating processing of the first broadcast channel; and

47. An apparatus for providing multi-layered content, comprising:

a memory; and

processing a broadcast session on a first broadcast channel originating from a first terminal in accordance with a first set of parameters;