Broadband transmission providing variable rate with soft handover

IS 2 360 261 T3

DESCRIPTION

Variable rate broadcast with smooth transfer

Background

Field

The present disclosure relates generally to the field of wireless communications. More specifically, the embodiments disclosed herein relate to providing variable rate broadcast with soft handoff in wireless communications.

Background

Wireless communication systems have been widely developed to provide various types of communications (such as voice and data) to multiple users. Such systems may be based on code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), or multiple other access techniques. A wireless communication system can be designed to implement one or more standards, such as IS-95, cdma20000, IS-856, W-CDMA, TD-SCDMA, and other standards.

Broadcast and multicast services have been proposed to effectively transmit large amounts of data from a single point of origin to a group of users within wireless communication systems. Content appropriate for such point-to-multipoint services includes news, stock quotes, sporting events, movies, audio and video clips, and other multimedia data. As the demand for multimedia data transmission grows, the challenge of enhancing spectral efficiency and maximizing data transmission rates of broadcast / multicast services increases.

US 2003/0036384 describes a method and a system for handover in a broadcast communication system.

Document US 2003/0072312 describes the planning carried out for a switching network.

Brief description of the drawings

FIG. 1 illustrates an embodiment of a communication system;

FIGs. 2A to 2D illustrate an embodiment for implementing a soft handoff variable rate broadcast within a broadcast area of ​​a communication system;

FIG. 3 illustrates one embodiment of broadcast transmission timelines in the embodiment of FIG. 2D;

FIG. 4 illustrates a flow chart of a process, which can be used in one embodiment to implement variable rate broadcast with soft handoff;

FIG. 5 illustrates a flow chart of a process, which can be used in one embodiment to implement variable rate broadcast with soft handoff;

FIG. 6 illustrates a flow diagram of a process, which can be used in one embodiment to implement variable rate broadcast with soft handoff;

FIG. 7 illustrates a flow chart of a process, which can be used in one embodiment to implement variable rate broadcast with soft handoff;

FIG.8 shows a block diagram of an apparatus, in which some disclosed embodiments can be implemented; and FIG. 9 shows a block diagram of an apparatus, in which some disclosed embodiments can be implemented.

Detailed description

The embodiments disclosed herein relate to methods and systems for providing soft handoff variable rate broadcast services in communication systems.

IS 2 360 261 T3

A unicast communication described herein can generally refer to any one-to-one voice and / or data transmission from a single source to a single receiver. In a wireless communication system (eg, cellular), unicast communication may involve transmission from one or more transmitters (eg, in an access network) to a single receiver (eg, an access terminal). A broadcast / multicast communication (or service) described herein can generally refer to any point-to-multipoint data transmission from a single source to a group of users within a broadcast area, which may include one or more sectors (or cells).

For a given broadcast service, an access network can receive a flow of information from a content server and transmit the information over a designated channel to a group of users in a broadcast area. The content of a broadcast communication (referred to herein as "broadcast content") may be encapsulated in data packets (referred to herein as "broadcast packets"), as specified by the relevant protocols. (such as the Internet Protocol (IP)). Broadcast content may include (but is not limited to) text, audio, images, video, data files, software updates, and other information.

A broadcast / multicast service may have controlled access, for example, only users who subscribe to the service receive the desired broadcast content at their access terminals. Non-subscribing users do not have any access to the broadcast / multicast service. Such controlled access can be achieved by encrypting the transmission / broadcast content in a way that allows only subscribers to decrypt the broadcast content received, for example.

An access network controller (ANC) can refer to the portion of a communication system configured to interface with a core network (eg, a packet data network) and route data packets between access terminals. (AT) and the core network, perform various radio access and link maintenance actions (such as soft handover), control radio transmitters and receivers, etc. An ANC may include and / or implement the functions of a Base Station Controller (BSC), as found in a 2-way wireless network^to or 3^to generation. An ANC and one or more Access Points (APs) may constitute part of an Access Network (AN). An AP described herein may also be referred to as a base station transceiver system (BTS), an access network transceiver (ANT), a modem group transceiver (MPT), or a Node B (for example, in a W-CDMA type system), etc. A cell can refer to a coverage area served by an AP. A cell can also include one or more sectors. A diffusion area can include one or more cells.

An AT described herein can refer to various types of devices, including (but not limited to) a cordless phone, a cell phone, a laptop, a wireless communication personal computer (PC) card, an electronic diary ( PDA), an external or internal modem, etc. An AT can be any data device that communicates over a wireless channel or through a wired channel (for example, via coaxial or fiber optic cables). An AT can have several names, such as access unit, subscriber unit, mobile station, mobile device, mobile unit, mobile phone, mobile, remote station, remote terminal, remote unit, user device, user equipment, user device. manual clamping, etc. Different ATs can be incorporated into a system. ATs can be mobile or fixed and can be dispersed throughout a communication system. An AT can communicate with one or more APs over a forward link and / or a reverse link at any given time. Forward link (or downlink) refers to transmission from an AP to an AT. Reverse link (or uplink) refers to the transmission from the AT to the AP.

In a wireless communication system implementing a broadcast / multicast service, soft handoff can be used to increase the broadcast transmission rate. In soft handoff, identical transmissions from one or more APs can be received and combined in one AT, thereby enabling the AT to support a higher data transfer rate. Because a broadcast content is intended to be received by multiple users dispersed in a broadcast area, broadcast transmissions are typically identical between the various cells in the broadcast area. In some systems, broadcast transmissions may be in a CDMA format, and each subscribing AT may software combine transmissions from APs serving different APs, for example, using a Rake receiver and / or an equalized receiver. In other systems, the broadcast transmissions may be orthogonal frequency division multiplex (OFDM) format, and each subscriber AT may software combine transmissions from the APs serving the different cells, for example, using a demodulation scheme based on in the Fast Fourier Transform (FFT).

In practice, however, cells in a broadcast area may have different supported data rates. Consider, for example, a diffusion area that includes a dense urban network with a core of cells of limited capacity that are typically small in size, surrounded by a network

ES 2 360 261 T3 suburban with larger cells of limited coverage. Because the supported data transfer rate typically varies with the ratio of total received power (for example, from all cells involved in soft handover) to total interference power, the maximum bearable broadcast transmission rate for a small urban cell may be higher than that of a large suburban cell. To implement soft handoff within such a system, however, broadcast transmissions may have to be carried out at the lowest bearable rate between the various cells in the broadcast area, thus unduly limiting the spectral efficiency of the system.

There is therefore a need to improve spectral efficiency and to maximize the broadcast transmission rate of broadcast / multicast services.

To improve overall spectral efficiency, it would be desirable to operate broadcast transmissions at a variable rate relative to cell coverage. To maximize the broadcast transmission rate, it would be desirable to operate the broadcast transmissions in soft handoff. The embodiments disclosed herein relate to methods and systems for providing broadcast / multicast services at a variable transmission rate, while preserving smooth handoff, thereby enhancing overall spectral efficiency and maximizing transmission rate. broadcast transmission.

In one embodiment, a plurality of APs (eg, those serving various cells in a broadcast area) can transmit broadcast content according to a set of transmission rates. The set of transmission rates may include a plurality of differentiated data transmission rates, each associated with a transmission format (for example, specifying the number of transmission slots to transmit a data packet), configured to enable that the broadcast packets transmitted by the APs are incrementally combined (eg slot-by-slot at a subscriber AT). As an example, consider a set of transmission rates that includes three data transmission rates: R1 = R (for example, 1,843.2 kbps), R2 = R / 2 (for example, 921.6 kbps), and R3 = R / 3 (eg 614.4 kbps), eg associated with a 1-slot, 2-slot, and 3-slot transmission format respectively. The first slots of the broadcast transmissions at all three rates are identical and can be combined by software. The second slots of the broadcast transmissions at rate R2 and R3 are identical and can also be combined by software. Thus, to implement variable rate broadcast, the rate set may be configured in such a way as to enable an incremental combination, such as that described above. The rate set can also be configured to support soft handoff in the broadcast area, as will be described in more detail later.

Various aspects, features, and embodiments are described in greater detail below.

FIG. 1 illustrates a schematic diagram of a communication system 100, in which various disclosed embodiments may be implemented. By way of example, system 100 may include a plurality of APs 110, such as APs 110a through 110c, each serving one cell (not explicitly shown in FIG. 1). Various AT 120s, including AT 120a through 120d, are dispersed in various cells throughout the system. Each AT 120 can communicate with one or more AP 110, for example, depending on whether the AT is active or not, and whether or not it is in soft handoff.

In system 100, an ANC 130 may be in communication with, and serve to provide coordination and control for, APs 110. For example, ANC 130 may be configured to control the routing of voice / data packets up to the AT 120 by means of the corresponding AP 110. The ANC 130 may also be in communication with a data network, for example, via a packet data serving serving node (PDSN) (neither of which is explicitly shown in FIG. 1). In some embodiments, the system 100 may be configured to support one or more wireless communication standards, for example, IS-95, cdma2000, IS-856, W-CDMA, TD-SCDMA. , other wireless communication standards, or a combination thereof.

System 100 may also be configured to implement a broadcast / multicast service, for example, in a broadcast area 140. For example, the ANC 130 may route broadcast content (e.g., received from the data network which may also include a content server) to APs 110, which may in turn transmit the broadcast content to the AT 120 within broadcast area 140.

In one embodiment, the broadcast / multicast service can be carried out at a variable rate with soft handoff. For example the ANC 130 may select a rate set that includes a plurality of discrete data rates, each associated with a transmission format, configured to enable broadcast transmissions to be incrementally combined (such as described above). The set of rates can be selected in relation to the data rates that are supported by the cells served by the APs 110 within the broadcast area 140, as well as the conditions to support soft handoff within

ES 2 360 261 T3 such cells, as described in greater detail below. The set of transmission rates may also be selected, in part, on the basis of the size of the broadcast content to be transmitted. The AN 130 can then instruct the APs 110 to transmit the broadcast content according to the selected rate set. The AT 120s in the broadcast area 140 may incrementally combine (eg, slot-by-slot) the broadcast packets received from the various AP 110s. For example, the AT 120b may incrementally combine the broadcast packets from APs 110a, 110b, for example, received via direct links 150, 152, respectively. The AT 120c can incrementally combine packets broadcast from APs 110b, 110c, for example, received via forward links 154, 156, respectively.

As described above, to implement variable rate broadcast with soft handoff, the data rate of the broadcast and the corresponding transmission format for a given cell need to be configured in such a way as to support the soft handoff to the cell, as well as to neighboring cells that reply to the cell for the soft handoff, as illustrated by the following examples. For illustrative and clarity reasons, the coverage of the soft handoff for a given cell (for example, one or more neighboring cells that support the cell in the soft handoff) extends to adjacent cells in the examples given below. continuation. Such coverages and examples should not be construed as limiting. The underlying procedures thus described can be applied to other situations where the soft transfer coverage extends beyond adjacent cells.

FIGs. 2A through 2D illustrate one embodiment of a broadcast area 200 in a communication system, including a plurality of cells. For illustrative and clarity reasons, the cells in these figures are shown to be uniform in shape and size. This should not be construed as limiting. In other embodiments, the cells can have varying sizes and shapes (and can be omni-directional or sectorized). Also for the sake of clarity and simplicity, the APs that serve, and the ATs scattered in, such cells are not explicitly shown in these figures.

Consider cell (s) A 210 illustrated in FIG. 2A. Cell A 210 can, for example, be part of a dense urban network, capable of supporting a higher data transfer rate. Suppose that cell A 210 is capable of supporting a data transfer rate of R, corresponding to a transmission format of n slots (n being an integer, eg, n = 1). To support soft handoff in cell A 210, neighboring cells (such as those illustrated with similar patterns) also need to be able to support the 1-slot transmission format.

FIG. 2B illustrates a group of B cells 220. Suppose that each B cell 220 is also capable of supporting the data transmission rate R and thus the 1-slot transmission format. To support soft handover in each B-cell 220, neighboring cells (such as those illustrated with similar patterns) also need to be able to support the 1-slot transmission format.

FIG. 2C illustrates a group of C 230 cells, which may, for example, be part of a large suburban network. Suppose that each C 230 cell is capable of supporting a data transfer rate of (n / m) R (where n and m are integers, for example n = 1, m = 3), corresponding to a transmission format of three grooves. To support soft handoff in each C 230 cell, neighboring cells (such as those illustrated with similar patterns) also need to be able to support the 3-slot transmission format.

In order to meet the requirements to support soft handover in all cells (for example, A 210 cell, B 220 cell, and C 230 cell), as described above, each B 220 cell needs to be able to supporting the 1-slot transmission format, as well as the 3-slot transmission format, to assist A-cell 210 and C-cells 230 in soft handoff. Because the data rates are such that the first slots of broadcast transmissions, in both the 1-slot and 3-slot transmission formats, are identical, each B 220 cell can be assigned the format of 3-slot drive, as shown in FIG. 2D (where B 220 cells are illustrated with patterns similar to those used for C 230 cells). In this way, the first slots of the broadcast transmissions in cell A 210 are identical and can be combined by software. Because the B cells 220 are able to support the 1-slot transmission format, the ATs in the B cells can successfully decode the broadcast packets after the first slot; the remaining two slots of the broadcast transmissions can serve to support soft handoff in C cells 230, as further illustrated in FIG. 3 referred to below.

FIG. 3 illustrates one embodiment of the broadcast transmissions timelines in the embodiment of FIG. 2D previously described. Legend 310 is used to indicate the pair of indices used to label each transmission slot. As illustrated in FIG. 3, for cell (s) A, transmission slots beyond the first slot can be used for unicast transmissions. Because B cells are capable of supporting the 1-slot transmission format, ATs in B cells can

ES 2 360 261 T3 successfully decoding packets broadcast after the first slot (as in cells A); the remaining two slots serve to support the incremental combination (for example, slot-by-slot) in C cells.

As illustrated in FIG. 2D and FIG. 3, B cells can act as "buffer" cells to effectively isolate two coverage areas (eg, A cell (s) and C cells) that support different data rates while maintaining the time smooth transfer. As illustrated above, such buffer cells may be able to support the data transfer rate of some neighboring cells (which have a higher data transfer rate with available support) but have the same data transfer rate assigned to them. transmission format than that of the other neighboring cells (having a lower data transfer rate with available support), thereby enabling neighboring cells to receive broadcast transmissions at different data rates, while preserving soft handoff (eg, enabling incremental combining such as previously described). Such a variable rate approach enhances overall spectral efficiency, minimizing the fraction of slots allocated for broadcast transmissions, while maximizing the broadcast data transfer rate while preserving smooth transfer. As shown in FIG. 3, without such a strategy, the broadcast transmissions to cells A would have to be in the 3-slot transmission format, and as a result, the transmission slots allocated for unicast transmissions would have to be used for broadcast transmissions as well, thereby limiting the overall spectral efficiency.

FIG. 4 illustrates a flow diagram of a process 400, which can be used in one embodiment to implement variable rate broadcast with soft handoff. Step 410 assigns a nominal rate to each cell, relative to the cell being in soft handoff with one or more neighboring cells (eg, within a given soft handoff coverage). The nominal transmission rate can, for example, take into consideration the soft handoff support that neighboring cells would provide. In some embodiments, the nominal data rates assigned to various cells in a broadcast area are configured to enable incremental combining, as described above. Step 420 identifies a minimum (or lowest) nominal rate assigned to each cell and neighboring cells with which it is in soft handoff (eg, the same neighboring cells considered in step 410). Step 430 assigns to each cell a broadcast data transfer rate equal to the minimum nominal rate thus identified.

FIG. 5 illustrates a flow diagram of a process 500, which may be used in one embodiment to implement variable rate broadcast with soft handoff. Step 510 selects a set of transmission rates, including a plurality of discrete data transmission rates, each associated with a transmission format. Step 520 instructs a plurality of APs to transmit broadcast content according to the set of transmission rates, the set of transmission rates being configured to allow the broadcast packets transmitted by the APs to be incrementally combined ( eg slot-to-slot on an AT). In some embodiments, the data rates and corresponding transmission formats in the rate set can be selected and assigned to the APs in relation to the bearable data rates of the cells served by the APs, as well as the constraints imposed by neighboring cells to support soft handover, as described above. The set of rates may also be selected, in part, based on the size of the broadcast content to be transmitted.

FIG. 6 illustrates a flow chart of a process 600, which may be used in one embodiment to implement variable rate broadcast with soft handoff. Step 610 assigns to a first AP n slots for transmitting broadcast content and (m - n) slots for unicast transmissions (m and n being integers and m> n). Step 620 assigns a second AP m slots to transmit the broadcast content. Step 630 assigns a third AP m slots to transmit the broadcast content. In one embodiment, the first AP may serve a first cell capable of supporting a data transfer rate of R. The second AP may serve a second cell adjacent to the first cell, which It is also capable of supporting the R data transfer rate. The third AP may serve a third cell adjacent to the second cell, which is capable of supporting a data transfer rate of (n / m) R, as described above.

FIG. 7 shows a flow diagram of a process 700, which may be used in one embodiment to implement variable rate broadcast with soft handoff. Step 710 sets a slot index i to zero. Step 720 selects a transmission slot and increases the slot index by 1 (i = i + 1). Step 730 determines if i <m, where m is the number of transmission slots allocated for broadcast transmissions. If the result of step 730 is "YES", step 740 follows and identifies the broadcast packets received from a plurality of APs in slot i. Step 750 below software combines the broadcast packets received in slot 1 (Note that, for broadcast transmissions in the format

IS 2 360 261 T3

CDMA, received signals may first undergo de-spreading, before being combined by software. For broadcast transmissions in OFDM format, the received signals can be directly combined by software). Process 700 then returns to step 720 and proceeds to the next transmission slot. If the result of step 730 is "NO", process 700 can, for example, continue to process unicast transmissions, as shown in step 760.

FIG. 8 shows a block diagram of an apparatus 800, which can be used to implement some disclosed embodiments (such as those described above). By way of example, apparatus 800 may include a rate set selection unit (or module) 810, configured to select a set of rates, including a plurality of discrete data rates, each associated with to a transmission format, and an instruction unit 820, configured to instruct a plurality of APs to transmit the broadcast content according to the set of transmission rates. The set of rates can be configured to enable the broadcast packets transmitted by the APs to be combined incrementally (as described above).

In some embodiments, the rate set selection unit 810 may, for example, be configured to carry out the process 400 illustrated in FIG. 4. The instruction unit 820 may, for example, be configured to carry out the process 600 illustrated in FIG. 6.

In apparatus 800, rate set selection unit 810 and instruction unit 820 may be coupled to a communication bus 830. A processing unit 840 and a memory unit 850 may also be coupled to the bus 830. The processing unit 840 may be configured to control and / or coordinate the operations of various units. The memory unit 850 can perform instructions to be executed by the processor 840.

In some embodiments, apparatus 800 may be implemented in an ANC (eg, ANC 130 illustrated in FIG. 1), a central controller for the network, or other network infrastructure means.

FIG. 9 shows a block diagram of an apparatus 900, which can be used to implement some disclosed embodiments (as described above). By way of example, apparatus 900 may include a receiving unit (or module) 910, configured to receive transmitted data packets from a plurality of APs, an identification unit 920 configured to identify broadcast packets in received data packets. and an incremental combining unit 930 configured to combine the identified broadcast packets incrementally (eg, slot-by-slot). In some embodiments, the receiving unit 910, the identification unit 920, and the incremental identification unit 930 may, for example, be configured to carry out the process 700 illustrated in FIG. 7.

In apparatus 900, receiving unit 910, identification unit 920, and incremental combining unit 930 may be coupled with a communication bus 940. A processing unit 950 and a memory unit 960 may also be coupled to the communication bus 940. The processing unit 950 can be configured to control and / or coordinate the operations of the various units. The memory unit 960 may carry out instructions to be executed by the processing unit 950.

In some embodiments, apparatus 900 may be implemented in an AT, or other data receiving medium.

The embodiments disclosed herein (such as those described above) provide some embodiments of variable rate broadcast services with soft handoff. There are other embodiments and implementations.

The various units / modules of FIGs. 8 and 9, and other embodiments, can be implemented in hardware, software, firmware, or a combination thereof. In a hardware implementation, the various units can be implemented within one or more application-specific integrated circuits (ASICs), digital signal processors (DSP), digital signal processing devices (DSPD), array of programmable gates on the field (FPGA), processors, microprocessors, controllers, microcontrollers, programmable logic devices (PLD), other electronic units, or any combination thereof. In a software implementation, various units can be implemented with modules (eg, procedures, functions, etc.), which execute the functions described herein. Software codes can be stored in a memory unit and executed by a processor (or a processing unit). The memory unit can be implemented within the processor or as external to the processor, in which case it can be communicatively coupled with the processor by various means known in the art.

The various disclosed embodiments can be implemented in a controller, AT, and other means.

ES 2 360 261 T3 to provide broadcast / multicast services. The embodiments disclosed herein may be applicable to a data processing system, a wireless communication system, a one-way broadcast system, and any other system desiring efficient transmission of information.

Those skilled in the art will readily understand that information and signals can be represented using any of a wide variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols and chips that can be mentioned throughout the above description can be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination of these elements.

Those skilled in the art will also appreciate that the various illustrative logic blocks, modules, circuits, and algorithm steps described in relation to the embodiments disclosed herein, can be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, the various illustrative components, blocks, modules, circuits, and stages have been described above in general terms of their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and design restrictions imposed on the global system. Those skilled in the art may implement the described functionality in various ways for each particular application, but such implementation decisions should not be construed as causing a departure from the scope of the present invention.

The various illustrative logic blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or realized 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 logic, or transistor, discrete hardware components, or any combination thereof, designed to perform the functions described herein. A general purpose processor can be a microprocessor but, alternatively, the processor can be any conventional processor, controller, microcontroller, or state machine. A processor can also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in combination with a DSP core, or any other such configuration.

The steps of a procedure or algorithm described in relation to the embodiments disclosed herein can be performed directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module can reside in a random access memory (RAM), a flash memory, a read-only memory (ROM), an electrically programmable ROM (EPROM), an electrically programmable erasable ROM (EEPROM), 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 with the processor such that the processor can read information from, and write information to, the storage medium. Alternatively, the storage medium can be integrated with the processor. The processor and storage medium can reside in an ASIC. The ASIC can reside in an AT. Alternatively, the processor and storage medium can reside as discrete components in an AT. The preceding description of the disclosed embodiments is provided to enable any person skilled in the art to practice or use the present invention. Various modifications to these embodiments will be immediately apparent to those skilled in the art. Thus, the present invention is not intended to be limited to the embodiments shown herein, but should be granted the widest scope in accordance with the claims.