HK1134182A - Method and apparatus for flexible pilot pattern - Google Patents

Description

Method and apparatus for flexible pilot pattern

Cross Reference to Related Applications

The benefit of U.S. provisional patent application No.60/839,357 entitled "METHOD AND DAPPARATUS FOR FLEXIBLE PILOT PATTERN" filed on 21/8/2006, which is incorporated herein by reference in its entirety, is claimed in this application.

Technical Field

The following description relates generally to wireless communications, and more particularly to providing a mechanism with flexible pilot patterns in an Orthogonal Frequency Division Multiplexing (OFDM) system.

Background

Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. A typical wireless communication system may be a multiple-access system capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc.). Examples of the above-described multiple-access system may include a Code Division Multiple Access (CDMA) system, a Time Division Multiple Access (TDMA) system, a Frequency Division Multiple Access (FDMA) system, a 3GPP LTE system, an Orthogonal Frequency Division Multiplexing (OFDM), Localized Frequency Division Multiplexing (LFDM), an Orthogonal Frequency Division Multiple Access (OFDMA) system, and the like.

In a wireless communication system, a node B (or base station) may transmit data to a User Equipment (UE) on the downlink and/or receive data from the UE on the uplink. The downlink (or forward link) refers to the communication link from the node bs to the user equipment, and the uplink (or reverse link) refers to the communication link from the user equipment to the node bs. The node B may also send control information (e.g., allocation of system resources) to the user equipment. Similarly, the user equipment may send control information to the node B to support data transmission on the downlink, or for other purposes.

In prior art systems using multicast or broadcast transmission modes, a node B may transmit to a plurality of user equipments operating in the system. It would be feasible to operate a multicast or broadcast (point-to-multipoint) transmission as a Single Frequency Network (SFN) and take advantage of the higher enhanced data rates provided by the SFN transmission. SFN allows one or more neighboring cells to transmit the same content on one and the same subchannel on the downlink. However, SFN transmission may not be efficient if the entire portion of the bandwidth is used on the downlink when other non-data information needs to be transmitted as well.

Disclosure of Invention

The following presents a simplified summary of one or more embodiments in order to provide a basic understanding of such embodiments. This summary is not an extensive overview of all contemplated embodiments, and is intended to neither identify key or critical elements of all embodiments nor delineate the scope of any or all embodiments. Its sole purpose is to present some concepts of one or more embodiments in a simplified form as a prelude to the more detailed description that is presented later.

According to one aspect, a method for a wireless communication system, comprising: determining a time position in a subframe at which SFN transmission of data will occur; determining a first transmission mode and a second transmission mode for a reference signal, wherein the transmission modes indicate symbols and tones of a subframe for the reference signal; selecting a transmission mode to use between the first and second transmission modes for reference signals based on whether SFN data is to be transmitted in the subframe; and broadcasting information about the selected transmission mode before using the selected transmission mode.

According to one aspect, a method for a wireless communication system, comprising: determining a time position in a subframe at which SFN transmission of data will occur; determining a first transmission mode for transmitting a reference signal, wherein the first transmission mode comprises a position of a tone and a position of a symbol allocated for transmitting the reference signal in the subframe; broadcasting information about the first transmission mode prior to using the first transmission mode.

According to one aspect, a method for a wireless communication system, comprising: using a first transmission mode, wherein the first transmission mode comprises tones for transmitting a set of data in a Single Frequency Network (SFN) transmission scheme; using a second transmission mode, wherein the second transmission mode comprises tones for transmitting reference signals; and broadcasting information about the first and second transmission modes before using the first and second transmission modes.

According to one aspect, a method for a wireless communication system, comprising: receiving a time position in a subframe at which SFN transmission for data is to occur; and receiving information on the first transmission mode, wherein the information includes location information in time and frequency of at least one resource block for transmitting a set of data in a Single Frequency Network (SFN) transmission scheme.

According to one aspect, a method for a wireless communication system, comprising: receiving a time position in a subframe at which SFN transmission for data is to occur; and receiving information on the first transmission mode, wherein the information includes position information in time and frequency of at least one resource block for transmitting a reference signal.

To the accomplishment of the foregoing and related ends, the one or more embodiments comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative aspects of the one or more embodiments. These aspects are indicative, however, of but a few of the various ways in which the principles of various embodiments may be employed and the described embodiments are intended to include all such aspects and their equivalents.

Drawings

Fig. 1 illustrates a wireless communication system in accordance with various aspects set forth herein.

Fig. 2 depicts an example communications apparatus that can be employed in a wireless communication environment.

Fig. 3 shows a cell specific pilot transmission pattern.

Fig. 4 shows a transmission mode with SFN transmission.

Fig. 5 shows a transmission pattern with SFN transmission on each symbol of a subframe.

Fig. 6 shows a frame structure using various downlink transmissions.

Fig. 7 illustrates an example method for broadcasting an indication of a selected Downlink (DL) Transmission (TX) mode.

Fig. 8 illustrates an example method for receiving an indication of a selected Downlink (DL) Transmission (TX) mode.

Fig. 9 depicts an example access terminal capable of providing feedback to a communication network.

Fig. 10 illustrates an example base station that can be employed in conjunction with the wireless network environments disclosed herein.

Fig. 11 depicts an example system that can provide feedback to a wireless communication environment in accordance with one or more aspects.

Fig. 12 depicts an example system that can employ flexible transmission mode techniques in accordance with one or more aspects.

Fig. 13 depicts an example system that can employ flexible transmission mode techniques in accordance with one or more aspects.

Fig. 14 depicts an example system that can employ flexible transmission mode techniques in accordance with one or more aspects.

Fig. 15 depicts an example system that enables employing a flexible transmission mode technique in accordance with one or more aspects.

Detailed Description

Various aspects are described below in conjunction with the appended drawings, wherein like reference numerals are used to refer to like elements throughout. The following description is for the purpose of explanation and numerous specific details are set forth in order to provide a thorough understanding of one or more aspects. It may be evident that such aspect(s) may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing one or more aspects.

Additionally, various aspects of the disclosure are described below. It should be apparent that the teachings herein may be embodied in a wide variety of forms and that any specific structure and/or function disclosed herein is merely representative. As will be recognized by those of ordinary skill in the pertinent art based on the teachings herein, one aspect disclosed herein may be implemented independently of any other aspects, and two or more of the aspects may be combined in various ways. For example, an apparatus may be implemented and/or a method may be practiced using any of the aspects set forth herein. In addition, an apparatus may be implemented and/or a method may be practiced using other structure and/or functionality in addition to or other than one or more of the aspects set forth herein. As one example, many of the methods, devices, systems, and apparatuses described herein are described in the context of ad-hoc or unplanned/semi-planned configured wireless communications that provide for synchronized transmission and retransmission of SFN data. Those skilled in the art will appreciate that similar techniques can be applied to other communication environments.

As used in this application, the terms "component," "system," and the like are intended to refer to a computer-related entity, either hardware, software in execution, firmware, middleware, microcode, and/or any combination thereof. For example, a component may be, but is not limited to being, a process running on a processor, an object, an executable, a thread of execution, a program, and/or a computer. One or more components can reside within a process and/or thread of execution and a component can be localized on one computer and/or distributed between two or more computers. Also, these components can execute from various computer readable media having various data structures stored thereon. For example, in accordance with a signal having one or more data packets (e.g., data from one component interacting with another component in a local system, distributed system, and/or across a network such as the Internet with other systems via the signal), the components may communicate by way of local and/or remote processes. Additionally, those skilled in the art will appreciate that the components of the systems described herein may be rearranged and/or additional components may be added to achieve the various aspects, goals, benefits, etc., described, without being limited to the precise configurations shown in a given figure.

In addition, various aspects described herein relate to a subscriber station. A subscriber station can also be called a system, a subscriber unit, mobile station, mobile, remote station, remote terminal, access terminal, user agent, a user device, or user equipment. A subscriber station may be a cellular telephone, a cordless telephone, a Session Initiation Protocol (SIP) phone, a Wireless Local Loop (WLL) station, a Personal Digital Assistant (PDA), a handheld device having wireless connection capability, or other processing device connected to a wireless modem or similar means that enables it to communicate wirelessly with the processing device.

In addition, various aspects or features described herein may be implemented as a method, apparatus, or article of manufacture using standard programming and/or engineering techniques. The term "article of manufacture" as used herein is intended to encompass a computer program accessible from any computer-readable device, carrier, or media. For example, computer-readable media can include but are not limited to magnetic storage devices (e.g., hard disk, floppy disk, magnetic strips), optical disks (e.g., Compact Disk (CD), Digital Versatile Disk (DVD), etc.), smart cards, and flash memory devices (e.g., card, stick, key drive, etc.). In addition, various storage media described herein can represent one or more devices and/or other machine-readable media for storing information. The term "machine-readable medium" can include, without being limited to, wireless channels and various other media capable of storing, containing, and/or carrying instruction(s) and/or data.

Additionally, the word "example" is used herein to mean an example, instance, or illustration. Any aspect or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, use of the word "example" is intended to introduce a concept in a particular manner. The term "or" as used in this application is intended to mean a non-exclusive "or" rather than an exclusive "or". That is, unless specified otherwise, or clear from context, "X employs A or B" is used to refer to any natural non-exclusive permutation, that is, "X employs A or B" satisfies any of the foregoing examples if X employs A, X to employ B, or X employs both A and B. In addition, the articles "a" and "an" as used in this application and the appended claims should generally be construed to mean "one or more" unless specified otherwise or clear from context to be directed to a singular form.

As used herein, the term to "infer" or "inference" refers generally to the process of reasoning about or inferring states of the system, environment, and/or user from a set of observations as captured via events and/or data. Inference can be employed to identify a specific context or action, or can generate a probability distribution over states, for example. The "inference" can be probabilistic-that is, the computation of a probability distribution over states of interest based on a consideration of data and events. "inference" can also refer to techniques employed for composing higher-level events from a set of events and/or data. "inference" results in the construction of new events or actions from a set of observed events and/or stored event data, whether or not the events are correlated in close temporal proximity, and whether the events and data come from one or several event and data sources.

The techniques described herein may be used in various wireless communication networks such as Code Division Multiple Access (CDMA) networks, Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, Orthogonal Frequency Division Multiple Access (OFDMA) networks, single carrier frequency division multiple access (SC-FDMA) networks, and so on. The terms "network" and "system" are often used interchangeably. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA), CDMA2000, and so on. UTRA includes wideband code division multiple access (W-CDMA) and Low Chip Rate (LCR). cdma2000 covers IS-2000, IS-95 and IS-856 standards. TDMA networks may implement wireless technologies such as global system for mobile communications (GSM). OFDMA networks may implement, for example, evolved UTRA (E-UTRA), IEEE 802.11, IEEE802.16, IEEE802.20, FlashEtc. wireless technologies. UTRA, E-UTRA and GSM are part of the Universal Mobile Telecommunications System (UMTS). Long Term Evolution (LTE) is an upcoming release of UMTS using E-UTRA. UTRA, E-UTRA, GSM, UMTS, and LTE are described in the literature of an organization entitled "third Generation partnership project" (3 GPP). Cdma2000 is described in the literature of the "third generation partnership project 2" (3GPP2) organization. These various wireless technologies and standards are well known in the art. For clarity, certain aspects are described below for LTE technology, and LTE terminology is used in many places in the following description.

Single carrier frequency division multiple access (SC-FDMA) uses single carrier modulation and frequency domain equalization techniques. SC-FDMA has similar performance and substantially the same overall complexity as OFDMA systems. The SC-FDMA signal has a low peak-to-average power ratio (PAPR) because of an inherent single carrier structure. SC-FDMA has attracted much attention, especially in uplink communications, where a lower PAPR greatly benefits mobile terminals in terms of transmit power efficiency. It is currently a working assumption for uplink multiple access schemes in 3GPP Long Term Evolution (LTE) or evolved UTRA.

Fig. 1 illustrates a wireless communication system 100 with multiple base stations 110 and multiple terminals 120, which may be employed, for example, in conjunction with one or more aspects. A base station is generally a fixed station that communicates with the terminals and may also be referred to as an access point, a node B, or some other terminology. Each base station 110 provides communication coverage for a particular geographic area, three geographic areas being illustrated, labeled 102a, 102b, and 102 c. The term "cell" can refer to a base station and/or its coverage area depending on the context in which it is used. To increase system capacity, the coverage area of a base station may be divided into multiple smaller areas (e.g., cell 102a in fig. 1 has three smaller areas 104a, 104b, and 104 c). Each smaller area may be served by a respective Base Transceiver Subsystem (BTS). The term "sector" can refer to a BTS and/or its coverage area depending on the context in which it is used. For a sectorized cell, the BTSs for all sectors of the cell are typically co-located within the base station for the cell. The transmission techniques described herein may be used for systems using sectorized cells as well as systems using unsectorized cells. For simplicity, the term "base station" in the following description generally refers to a fixed station that serves a sector as well as a fixed station that serves a cell.

Terminals 120 are typically distributed throughout the system, and each terminal may be fixed or mobile. A terminal may also be called a mobile station, user equipment, a user device, or some other terminology. The terminal may be a wireless device, a cellular telephone, a Personal Digital Assistant (PDA), a wireless modem card, or the like. Each terminal 120 may communicate with zero, one, or multiple base stations on the downlink and uplink at any given time. The downlink (or forward link) refers to the communication link from the base stations to the terminals, and the uplink (or reverse link) refers to the communication link from the terminals to the base stations.

For a centralized architecture, a system controller 130 couples to base stations 110 and provides coordination and control for base stations 110. For a distributed architecture, the base stations 110 may communicate with each other as needed. Data transmission on the forward link is from one access point to one access terminal, which transmits at or near the maximum data rate supported by the forward link and/or communication system. Other channels of the forward link (e.g., control channels) may be transmitted from multiple access points to an access terminal. Data communication on the reverse link may be from one access terminal to one or more access points.

Fig. 2 illustrates an ad-hoc or unplanned/semi-planned wireless communication environment 200 in accordance with various aspects. System 200 can comprise one or more base stations 202 in one or more sectors that receive, transmit, retransmit wireless communication signals to each other and/or to one or more mobile devices 204. As shown, each base station 202 can provide communication coverage for a particular geographic area, four geographic areas being illustrated, labeled 206a, 206b, 206c, and 206 d. Each base station 202 can comprise a transmitter chain and a receiver chain, each of which can in turn comprise a plurality of components associated with signal transmission and reception (e.g., processors, modulators, multiplexers, demodulators, demultiplexers, antennas, etc.), as will be appreciated by one skilled in the art. Mobile device 204 may be, for example, a cellular phone, a smart phone, a laptop, a handheld communication device, a handheld computing device, a satellite radio, a global positioning system, a PDA, and/or any other suitable device for communicating over wireless network 200. System 200 can be employed in conjunction with various aspects described herein in order to provide a flexible pilot pattern.

The techniques described herein may be used in various wireless communication systems, such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), frequencyDivision Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), and single carrier frequency division multiple access (SC-FDMA) systems. The terms "system" and "network" are often used interchangeably. A CDMA system may implement a radio technology such as Universal Terrestrial Radio Access (UTRA), CDMA2000, and so on. UTRA includes wideband code division multiple access (W-CDMA) and Low Chip Rate (LCR). cdma2000 covers IS-2000, IS-95 and IS-856 standards. TDMA systems may implement wireless technologies such as global system for mobile communications (GSM). OFDMA systems may implement, for example, evolved UTRA (E-UTRA), IEEE 802.11, IEEE802.16, IEEE802.20, FlashEtc. wireless technologies. These various wireless technologies and standards are well known in the art. UTRA, E-UTRA and GSM are part of the Universal Mobile Telecommunications System (UMTS). Long Term Evolution (LTE) is an upcoming release of UMTS using E-UTRA. UTRA, E-UTRA, GSM, UMTS, and LTE are described in the literature of an organization entitled "third Generation partnership project" (3 GPP). Cdma2000 is described in the literature of the "third generation partnership project 2" (3GPP2) organization. For clarity, certain ways of techniques for uplink transmission in LTE are described below, with 3GPP terminology used in many places in the following description.

LTE uses Orthogonal Frequency Division Multiplexing (OFDM) on the downlink and single carrier frequency division multiplexing (SC-FDM) on the uplink. OFDM and SC-FDM partition the system bandwidth into multiple (N) orthogonal subcarriers, also commonly referred to as tones (tones), bins (bins), etc., each of which may be modulated with data. Typically, modulation symbols are transmitted in the frequency domain with OFDM and in the time domain with SC-FDM. For LTE, the spacing between adjacent subcarriers may be fixed, and the total number of subcarriers (N) may depend on the system bandwidth. In one design, N may be 512 for a system bandwidth of 5MHz, 1024 for a system bandwidth of 10MHz, and 2048 for a system bandwidth of 20 MHz. In general, N may be any integer value.

The LTE downlink transmission scheme is divided by radio frames (e.g., 10 millisecond radio frames). Each frame includes a pattern (pattern) of frequencies (e.g., subcarriers) and time (e.g., OFDM symbols). The 10 ms radio frame is divided into a plurality of adjacent 0.5 ms subframes (also referred to as subframes or slots, used interchangeably hereinafter). Each subframe includes a plurality of resource blocks, where each resource block is comprised of one or more subcarriers and one or more OFDM symbols. One or more resource blocks may be used to transmit data, control information, pilot (also referred to as reference signals), or any combination thereof.

In order to achieve the most efficient use of SFN and cell-specific (e.g. unicast or multicast) schemes, different methods for multiplexing SFN and cell-specific pilot in downlink are described herein. One cell-specific pilot is sent with FDM and scrambled with one cell-specific scrambling code. Using FDM operation allows frequency reuse greater than 1 where pilot tones from a few neighboring cells do not collide with each other. This results in improved channel estimation, especially at the cell edge.

Fig. 3 shows a cell-specific pilot transmission pattern 300 according to an example, which is used for subframes for downlink transmission. According to an example, the cell-specific pilot pattern is used for a subframe of a radio frame consisting of a time period 360 and a frequency bandwidth 362. In the pilot pattern of this example, all tones of symbol 306 are allocated to transmitting pilot information. According to this example, up to six cells do not collide because their pilot transmissions are done using different tones in one symbol period. For example, pilot information for cell 0 is transmitted using tones 304, 320, and 332, pilot information for cell 1 is transmitted using tones 310, 322, and 334, pilot information for cell 2 is transmitted using tones 312, 324, and 336, pilot information for cell 3 is transmitted using tones 314, 326, and 338, pilot information for cell 4 is transmitted using tones 316, 328, and 340, and pilot information for cell 5 is transmitted using tones 318, 330, and 342. This pattern may repeat for several symbol periods, such as symbol periods 352 and 354. For the remaining tones in the subframe, the transmitter may send non-pilot information. In accordance with one aspect, cell 0 may transmit data or other information (e.g., non-pilot information) on the tones used by cells 1, 2, 3, 4, and 5 to transmit pilot. As a result, these pilot tones experience lower interference Power Spectral Density (PSD) and higher signal-to-noise ratio (SNR), which results in improved channel estimation. Depending on the system configuration, fewer or more cells may be designated as not colliding.

Fig. 4 illustrates a transmission pattern 400 with SFN transmission for a subframe for downlink transmission where cell-specific pilots are multiplexed with SFN data (e.g., data transmitted with an SFN transmission scheme) on the same subframe, according to an aspect. According to an example, the transmission mode is for a subframe of a radio frame consisting of a time period 460 and a frequency bandwidth 462. In this example mode, all tones of symbol 406 are allocated to transmit pilot information. In this example, six non-colliding cells are shown, and this is achieved by allocating a tone to each cell to transmit pilot information. For example, pilot information for cell 0 is transmitted using tones 404, 420, and 432, pilot information for cell 1 is transmitted using tones 410, 422, and 434, pilot information for cell 2 is transmitted using tones 412, 424, and 436, pilot information for cell 3 is transmitted using tones 414, 426, and 438, pilot information for cell 4 is transmitted using tones 416, 428, and 440, and pilot information for cell 5 is transmitted using tones 418, 430, and 442. The pattern may repeat for several symbol periods, such as symbol periods 452 and 454. The remaining tones are designated for SFN transmission (shown shaded in fig. 4). In an aspect, when SFN transmission and cell-specific transmission are multiplexed in the same subframe, frequency reuse may not be greater than 1 for cell-specific subframes where cells are not allowed to collide with each other due to the characteristics of SFN transmission. Then, in this example, cell 0 cannot transmit an SFN transmission on the tones used by cells 1, 2, 3, 4, and 5 to transmit pilot information. Thus, if pilots from different cells are not allowed to collide with each other, then non-pilot tones cannot be used for SFN data for a given cell. However, cell 0 may transmit other information such as control information, assignments, null tones (such that the frequency reuse pattern on the null tones and the frequency reuse pattern on the data tones are the same), or any non-pilot and non-SFN data. Then, the transmission mode of cell 0 may include: the transmission of pilot tones, e.g., tones 404, 420, and 432, repeated based on the number of cells designated to avoid collisions. The transmission mode may further include: non-pilot and non-SFN transmissions are performed on the tones used by other cells for pilot transmission, e.g., tones 410, 412, 414, 416, 418, 422, 424, 426, 428, 430, 434, 436, 438, 440, and 442. The remaining tones in the example subframe will be used for SFN transmission.

Fig. 5 illustrates a Downlink (DL) Transmission (TX) pattern 500 (also referred to as an SFN + CS transmission pattern) in which the cell-specific pilot is multiplexed with SFN data (e.g., data transmitted using an SFN transmission scheme) on the same subframe, according to another aspect. According to an example, the transmission mode is for a subframe of a radio frame consisting of a time period 560 and a frequency bandwidth 562. According to one aspect, all cells in the system are required to use designated tones for pilot transmission (shown as unicast), null tones, or any combination thereof. According to the transmission mode of this example, the resource blocks defined at subcarriers 504, 520, and 532 and symbols 506, 552, and 554 are used by all cells in the system for pilot information transmission. According to another aspect, pilot tones may be assigned using one transmission mode (not shown), the assigned pilot tones not colliding with pilot tones used by other cells. The remaining tones are allocated to the SFN transmission scheme for delivering the content to the user equipment. Thus, the pilots of each cell allow for collision and SFN transmission on a larger set of tones.

For a flexible pilot pattern scheme, the tones designated for pilot transmission may be adjacent in frequency, time, or any combination thereof. Then, in one aspect, all pilot tones that one SFN + CS transmission mode has are adjacent in frequency. In another aspect, all pilot tones with one SFN + CS transmission mode are adjacent in time. In yet another aspect, one SFN + CS transmission mode has all tones designated for cell-specific pilot transmission adjacent in frequency and grouped at the top of the frequency bandwidth of the subframe, e.g., all pilot transmission tones are adjacent at 570 of symbols 506, 552 and 554. In another aspect, one SFN + CS transmission mode has all tones designated for cell-specific pilot transmission adjacent in frequency and grouped in the middle of the frequency bandwidth of the subframe, e.g., all pilot transmission tones are adjacent at 572 of symbols 506, 552, and 554. In another aspect, one SFN + CS transmission mode has all tones designated for cell-specific pilot transmission adjacent in frequency and grouped at the bottom of the frequency bandwidth of the subframe, e.g., all pilot transmission tones are adjacent at 574 of symbols 506, 552 and 554. It should be noted that, depending on the system, not all cells may repeat pilot transmission in frequency and time. Thus, for example, one cell may transmit pilots only on the tones specified by subcarriers 504 of symbols 506, 552, and 554, or only on subcarriers 504, 520, and 532 of symbol period 552.

Fig. 6 shows a frame structure 600 that uses the downlink transmission mode described above during system operation. According to one aspect, cell-specific pilots are transmitted using one or more patterns selected from a set of downlink transmission patterns. For example, in time period 602, four subframes 604, 606, 608, and 610 are transmitted. In an aspect, for subframe 604, the system may select a first mode (e.g., cell-specific reuse greater than 1, as described in fig. 3) or a second mode (e.g., cell-specific + SFN and all variants of this mode, as described in fig. 5). For the 606, 608, and 610 subframes, the system may use the first or second mode. Thus, in a sub-frame without SFN transmission, the cell specific pilot pattern corresponds to a frequency reuse greater than 1, and in other sub-frames, the pattern corresponds to a frequency reuse equal to 1.

Each cell includes a mechanism for selecting a downlink transmission mode based on all conditions of the system, data rate requirements, transfer rates necessary for certain content, etc. The SFN + CS transmission mode may be used periodically. In this case, the allocation of subframes selected to use the SFN + CS transmission mode is periodically broadcast in each cell. Once a downlink transmission mode is selected, all cells in the system will broadcast (e.g., signal using a broadcast channel) information about the selected downlink transmission mode. This can be done by sending an indicator (one or more bits) and subframe to the user equipment when the downlink transmission mode is to be used by the cell. The downlink transmission mode may be valid for only one subframe, where the indicator must be re-signaled or broadcast before using the selected downlink transmission mode. Optionally, one or more subframes may be allocated to use the selected downlink transmission mode. In this case, information about the allocated subframes that will use, for example, the SFN + CS transmission mode will be broadcast by the cell to the user equipment.

In an aspect, the downlink transmission mode described above may be identified with an identifier. To reduce overhead, only the transmission mode identifier and the specified subframe number are broadcast to the user equipment. The user equipment can then retrieve from memory the correct processing method associated with the transmission mode and use that method to process the received transmission for the specified subframe.

Referring to fig. 7-8, methodologies relating to a mechanism that uses and broadcasts an indication of an SFN + CS transmission mode that is allocated as a downlink transmission for one subframe. While, for purposes of simplicity of explanation, the methodology is shown and described as a series of acts, it is to be understood and appreciated that the methodology is not limited by the order of acts, as some acts may, in accordance with the claimed subject matter, occur in different orders and/or concurrently with other acts from that shown and described herein. For example, those skilled in the art will understand and appreciate that a methodology could alternatively be represented as a series of interrelated states or events, such as in a state diagram. Moreover, not all illustrated acts may be required to implement a methodology in accordance with the claimed subject matter.

With particular reference to fig. 7, an example methodology 700 is described that enables broadcasting an indication of a selected downlink transmission mode in a wireless communication system according to an aspect. The methodology 700 can enable transmitting an indication from a cell (e.g., an enhanced node base station, eNode B, Access Point (AP), base station, or the like) to one or more terminal devices (e.g., user equipment, UE, AT, or the like) in a wireless communication network. The method begins at 702 by determining whether it is time to use SFN transmission for downlink transmission. In one aspect, a cell periodically determines whether SFN transmission is needed to transmit content at an enhanced data rate or whether a request is received from the system to begin using SFN transmission. In one aspect, a cell receives an indication from a system to perform SFN transmission and a time location in a subframe where SFN transmission of data should occur. If it is determined that SFN transmission is required, the method performs blocks 704, 706 and 708. Otherwise, at block 720, the method continues with using a default transmission mode, such as the first mode described in fig. 3. At block 704, the cell determines an SFN transmission mode from one or more transmission modes, each of which indicates symbols and tones in a subframe for a reference signal (e.g., pilot data) and for transmitting data using an SFN transmission scheme. Once the transmission mode is selected, the cell allocates the selected mode for the designated subframe. Depending on the system, the method selects one SFN transmission mode from a list of several SFN transmission modes available. For example, the SFN + CS transmission mode described in fig. 5 above, or a variation of this mode (e.g., a mode with aggregated or staggered pilot tones based on frequency and/or time). After selecting one transmission mode, the method proceeds to block 706. At 706, the cell broadcasts the selected downlink transmission mode information and a designated subframe that is valid for all user equipments served by the cell. The method may pre-broadcast the indication and allow all user equipments to receive the indication before using the selected downlink transmission mode, according to system requirements. The indication may be a predetermined transmission mode identifier or more detailed information about the selected transmission mode. At block 708, the method transmits data (e.g., content) using a downlink transmission mode selected for the designated subframe.

Referring to fig. 8, an example methodology 800 is described that receives an indication of a selected downlink transmission mode in a wireless communication system in accordance with an aspect. The methodology 800 can enable receiving an indication from a cell (e.g., an enhanced node base station, eNode B, Access Point (AP), base station, or similar device) in a wireless communication network. In accordance with one aspect, at block 802, the method receives an indication on the forward link to process a specified subframe using a specified SFN transmission mode (e.g., SFN + CS transmission mode). At block 804, the method begins processing the received transmission based on the SFN transmission mode specified for the specified subframe.

Fig. 9 depicts an example access terminal 900 that can provide feedback to a communication network in accordance with one or more aspects. Access terminal 900 includes a receiver 902 (e.g., an antenna), where receiver 902 receives a signal and performs a particular operation (e.g., filters, amplifies, downconverts, etc.) the received signal. In particular, receiver 902 can also receive a service schedule defining services allocated in one or more blocks of a transmission allocation period, an associated schedule associating downlink resource blocks with uplink resource blocks for providing feedback information as described herein, and the like. Receiver 902 can comprise a demodulator 904, where demodulator 904 can demodulate received symbols and provide them to a processor 906 for evaluation. Processor 906 can be a processor dedicated to analyzing information received by receiver 902 and/or generating information for transmission by a transmitter 916. Further, processor 906 can be a processor that controls one or more components of access terminal 900, and/or a processor that analyzes information received by receiver 902, generates information for transmission by transmitter 916, and controls one or more components of access terminal 900. Further, as described herein, processor 906 can execute instructions to interpret a correlation between uplink and downlink resources received by receiver 902, identify non-received downlink blocks, or generate a feedback message (e.g., a bitmap) to signal the non-received blocks, or analyze a hash function to determine an appropriate uplink resource of a plurality of uplink resources.

Access terminal 900 can additionally comprise memory 908 that is operatively coupled to processor 906 and that can store data to be transmitted, received, or the like. Memory 908 can store information associated with downlink resource scheduling for evaluating the aforementioned protocols, as well as for identifying an unreceived portion of a transmission, determining an undecipherable transmission, sending a feedback message to an access point, and so forth.

It will be appreciated that the data store (e.g., memory 908) described herein can be either volatile memory or nonvolatile memory, or can include both volatile and nonvolatile memory. By way of illustration, and not limitation, nonvolatile memory can include Read Only Memory (ROM), Programmable Read Only Memory (PROM), Electrically Programmable Read Only Memory (EPROM), Electrically Erasable Programmable Read Only Memory (EEPROM), or flash memory. Volatile memory can include Random Access Memory (RAM), which acts as external cache memory. By way of illustration and not limitation, random access memory RAM has many available forms such as Synchronous Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), Synchronous Dynamic Random Access Memory (SDRAM), double-rate synchronous dynamic random access memory (DDR SDRAM), Enhanced Synchronous Dynamic Random Access Memory (ESDRAM), synchlink dynamic random access memory (SLDRAM), and Direct Rambus RAM (DRRAM). The memory 908 of the subject systems and methods is intended to comprise, without being limited to, these and any other suitable types of memory.

Receiver 902 is further operatively coupled to a multiple antenna 910 that can receive scheduled correlations between one or more additional blocks of downlink transmission resources and one block of uplink transmission resources (e.g., to cause multiple Negative Acknowledgement (NACK) or positive Acknowledgement (ACK) messages to be provided in one bitmap response). The multiplexing processor 906 may include a multi-bit bitmap within a feedback message providing an ACK or NACK message indicating whether each of the first downlink block and one or more additional downlink blocks are received or not received on a separate uplink resource. Additionally, calculation processor 912 can receive a feedback probability function that limits the probability of providing a feedback message by access terminal 900 if a block of downlink transmission resources or data associated therewith is not received, as described herein. In particular, the above probability function may be used to reduce interference if multiple devices are reporting missing data simultaneously.

Access terminal 900 further comprises a modulator 914 and a transmitter 916, where transmitter 916 transmits signals to a base station, access point, another access terminal, remote agent, etc. Although the signal generator 910 and the indicator evaluator 912 are depicted as being separate from the processor 906, it can be appreciated that the signal generator 910 and the indicator evaluator 912 can be part of the processor 906 or part of multiple processors (not shown).

Fig. 10 illustrates a system 1000 that can provide feedback regarding lost transmission data for an LTE network. System 1000 includes a base station 1002 (e.g., access point, etc.) having a receiver 1010 that receives signals from one or more mobile devices 1004 via a plurality of receive antennas 1006 and a transmitter 1022 that transmits data to one or more mobile devices 1004 via a transmit antenna 1008. Receiver 1010 can receive information from receive antennas 1006 and can further comprise a signal receiver (not shown) that receives feedback data related to packets that were not received or could not be interpreted. In addition, receiver 1010 is operatively associated with a demodulator 1012 that demodulates received information. A processor 1014 coupled to a memory 1016 analyzes the demodulated symbols, the memory 1016 storing: information relating to the correlation of uplink and downlink resources, providing dynamic and/or static correlation from a network, as well as data to be transmitted or received from the mobile device 1004 (or a disparate base station (not shown)), and/or any other suitable information relating to performing the various operations and functions set forth herein.

The processor 1014 is further coupled to an association processor 1018, the association processor 1018 being capable of scheduling a correlation between a block of downlink transmission resources and a block of uplink transmission resources for a multicast or broadcast service during the allocation. Additionally, association processor 1018 can further schedule a correlation between one or more additional blocks of uplink transmission resources and the block of downlink transmission resources to enable receipt of a plurality of feedback messages for the downlink resource. As a result, the relative number of feedback messages related to the downlink resource may be determined. In addition, association processor 1018 can schedule a correlation between a plurality of blocks of downlink transmission resources and one uplink transmission resource for multicast or broadcast traffic, and as such, a single bitmap included in the feedback message can indicate ACK or NACK information for the plurality of blocks of downlink transmission resources.

The association processor 1018 may be coupled to a calculation processor 1020, the calculation processor 1020 generating a probability factor that may limit the likelihood that the terminal device provides the feedback message. The base station 1002 can use the probability factor to reduce feedback interference from multiple terminal devices. In addition, the calculation processor 1020 may generate a hash function transmitted by the base station 1002 that is capable of indicating to each of the plurality of terminal devices a particular uplink transmission resource to use when submitting the feedback message. The indication of the hash function may be based at least in part on an access category of each terminal device, a hash of each terminal identification, an identification of a service used by each terminal device, or block specific information, or a combination thereof.

Further, the calculation processor 1020 may be coupled to an ordering processor 1021, which is capable of determining a number of received feedback messages related to a downlink transmission resource block. For example, if one block of downlink transmission resources is correlated with multiple uplink transmission resources (e.g., the correlation is scheduled by association processor 1018 described above), base station 1002 can receive two or more feedback messages for the downlink resources. The ordering processor 1021 can thus identify what feedback message corresponds to the downlink block, which can indicate a retransmission priority for the downlink block. Further, the ordering processor 1021 can select between retransmitting multiple blocks of downlink transmission resources based at least in part on the number of feedback messages received in relation to each block of downlink transmission resources.

Referring now to fig. 11, on a downlink, at access point 1105, a Transmit (TX) data processor 1110 receives, formats, codes, interleaves, and modulates (or symbol maps) traffic data and provides modulation symbols ("data symbols"). A symbol modulator 1115 receives and processes the data symbols and pilot symbols and provides a stream of symbols. A symbol modulator 1115 multiplexes data and pilot symbols and provides them to a transmitter unit (TMTR) 1120. Each transmitted symbol may be a data symbol, a pilot symbol, or a signal with a value of zero. The pilot symbols may be sent continuously in each symbol period. The pilot symbols may be Frequency Division Multiplexed (FDM), Orthogonal Frequency Division Multiplexed (OFDM), Time Division Multiplexed (TDM), Frequency Division Multiplexed (FDM), or Code Division Multiplexed (CDM).

TMTR 1120 receives and converts the stream of symbols into one or more analog signals and further conditions (e.g., amplifies, filters, and frequency upconverts) the analog signals to generate a downlink signal suitable for transmission over the wireless channel. The downlink signal is then transmitted through an antenna 1125 to the terminals. At terminal 1130, an antenna 1135 receives the downlink signal and provides a received signal to a receiver unit (RCVR) 1140. Receiver unit 1140 conditions (e.g., filters, amplifies, and frequency downconverts) the received signal and digitizes the conditioned signal to obtain samples. A symbol demodulator 1145 demodulates and provides received pilot symbols to a processor 1150 for channel estimation. Symbol demodulator 1145 further receives a frequency response estimate for the downlink from processor 1150, performs data demodulation on the received data symbols to obtain data symbol estimates (which are estimates of the transmitted data symbols), and provides the data symbol estimates to a receive data processor 1155, which receives data processor 1155 to demodulate (e.g., symbol demap), deinterleave, and decode the data symbol estimates to recover the transmitted traffic data. The processing by symbol demodulator 1145 and rx data processor 1155 is complementary to the processing by symbol modulator 1115 and tx data processor 1110, respectively, at access point 1105.

On the uplink, a transmit data processor 1160 processes traffic data and provides data symbols. A symbol modulator 1165 receives and multiplexes the data symbols with pilot symbols, performs modulation, and provides a stream of symbols. A transmitter unit 1170 then receives and processes the stream of symbols to generate an uplink signal, which is transmitted by the antenna 1135 to the access point 1105.

At access point 1105, the uplink signal from terminal 1130 is received by the antenna 1125 and processed by a receive unit 1175 to obtain samples. A symbol demodulator 1180 then processes the samples and provides received pilot symbols and data symbol estimates for the uplink. A rx data processor 1185 processes the data symbol estimates to recover the traffic data transmitted by terminal 1130. A processor 1190 performs channel estimation for each active terminal transmitting on the uplink. Multiple terminals may transmit pilot concurrently on the uplink on their respective assigned sets of pilot subbands, which may be interlaced.

Processors 1190 and 1150 direct (e.g., control, coordinate, manage, etc.) operation at access point 1105 and terminal 1130, respectively. Processors 1190 and 1150 can be associated with memory units (not shown) that store program codes and data, respectively. Processors 1190 and 1150 can also perform computations to obtain frequency response estimates and impulse response estimates for the uplink and downlink, respectively.

For a multiple-access system (e.g., FDMA, OFDMA, CDMA, TDMA, etc.), multiple terminals may transmit simultaneously on the uplink. For such systems, the pilot subbands may be shared among different terminals. The channel estimation techniques may be used for cases where the pilot subbands for each terminal span the entire operating band (possibly except for the band edges). Such a pilot subband structure is required to obtain frequency diversity for each terminal. The techniques described herein may be implemented in various ways. For example, these techniques may be implemented in hardware, software, or a combination thereof. For a hardware implementation, which may be digital, analog, or both digital and analog, the processing units used for channel estimation may be implemented within one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof. For software, implementation can be through modules (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in memory unit and executed by the processors 1190 and 1150.

It is to be understood that the specific embodiments described herein may be implemented in hardware, software, firmware, middleware, microcode, or any combination thereof. For a hardware implementation, the processing units may be implemented within one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof.

When the embodiments are implemented in software, firmware, middleware or microcode, program code or code segments, they may be stored in a machine-readable medium, such as a storage component. A code segment may be represented as a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and/or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted using any suitable means including memory sharing, message passing, token passing, network transmission, etc.

For a software implementation, the techniques described herein may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in memory units and executed by processors. The memory unit may be implemented within or external to the processor, in which case it can be communicatively coupled to the processor via various means as is known in the art.

Referring now to fig. 12, illustrated is a system 1200 that enables utilizing flexible transmission modes in wireless communications. The system 1200 may include: a module 1202 for determining a temporal location in a subframe at which SFN transmission of data will occur; a module 1204 for determining a first transmission mode and a second transmission mode for a reference signal; the block 1206: means for selecting a transmission mode to use between a first transmission mode and a second transmission mode for a reference signal based on whether SFN data is to be transmitted in the subframe; means 1208 for broadcasting information about the selected transmission mode before using the transmission mode. The module 1202-1208 may be a processor or any electronic device and may be coupled to a storage module 1210.

Referring now to fig. 13, illustrated is a system 1300 that enables employing flexible transmission modes in wireless communications. The system 1300 may include: a module 1302 for determining a temporal location in a subframe at which SFN transmission of data is to occur; a module 1304 for determining a first transmission mode and a second transmission mode for a reference signal; means 1306 for broadcasting information about the selected transmission mode before using the transmission mode. Module 1302, 1306 may be a processor or any electronic device and may be coupled to storage module 1308.

Referring now to fig. 14, illustrated is a system 1400 that enables employing flexible transmission modes in wireless communications 1400. The system 1400 may include: a module 1402 for using a first transmission mode, wherein the first transmission mode comprises tones for transmitting a set of data in accordance with a Single Frequency Network (SFN) transmission scheme; a module 1404 for using a second transmission mode, wherein the second transmission mode includes tones for transmitting reference signals; a module 1406 for broadcasting information about the selected transmission mode before using the transmission mode. Module 1402, 1406 may be a processor or any electronic device and may be coupled to storage module 1408.

Referring now to fig. 15, illustrated is a system 1500 that enables flexible transmission modes to be utilized in wireless communications. The system 1500 may include: a module 1502 for receiving a time position in a subframe at which SFN transmission of data is to occur; a module 1504 for receiving information regarding a first transmission mode, wherein the information includes location information in time and frequency of at least one resource block for transmitting a set of data in accordance with a Single Frequency Network (SFN) transmission scheme. The module 1502 and 1504 may be a processor or any electronic device and may be coupled to a storage module 1506.

What has been described above includes examples of one or more aspects. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the aforementioned aspects, but one of ordinary skill in the art may recognize that many further combinations and permutations of various aspects are possible. Accordingly, the described aspects are intended to embrace all such alterations, modifications and variations that fall within the scope of the appended claims. Furthermore, to the extent that the term "includes" is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term "comprising" as "comprising" is interpreted when employed as a transitional word in a claim.

Claims (77)

1. A method for wireless communication, comprising:

determining a time position in a subframe at which SFN transmission of data will occur;

determining a first transmission mode and a second transmission mode for a reference signal, wherein the transmission modes indicate symbols and tones of a subframe for the reference signal;

selecting a transmission mode to use between the first and second transmission modes for reference signals based on whether SFN data is to be transmitted in the subframe; and

broadcasting information about the selected transmission mode before using the selected transmission mode.

2. The method of claim 1, further comprising:

a time position in a subframe where SFN transmission for data will occur and information on the first and second transmission modes for a reference signal are received.

3. The method of claim 1, further comprising:

broadcasting information about the first and second transmission modes of the reference signal prior to using the first and second transmission modes of the reference signal.

4. The method of claim 1, further comprising:

a third transmission mode for transmitting SFN data is determined, wherein the third transmission mode comprises a position of a tone in a subframe allocated to transmit data using the SFN transmission scheme.

5. The method of claim 4, wherein broadcasting information about the third transmission mode comprises:

transmitting location information in time and frequency of one or more resource blocks in the subframe for transmitting data using the SFN transmission scheme.

6. The method of claim 1, further comprising:

selecting a second transmission mode for the reference signal if SFN data is not to be transmitted in the subframe.

7. The method of claim 1, wherein determining the first transmission mode and the second transmission mode comprises:

parameters for the first transmission mode and the second transmission mode are received.

8. The method of claim 1, wherein broadcasting the information comprises:

transmitting location information in time and frequency of a resource block for SFN transmission in the subframe and a time location in the subframe allocated for the SFN transmission.

9. The method of claim 4, wherein broadcasting the information comprises:

the time position in the subframe that is allocated for the SFN transmission is transmitted.

10. The method of claim 1, wherein determining the first transmission mode comprises:

parameters of the first transmission mode are received.

11. The method of claim 1, wherein determining the first transmission mode comprises:

the first transmission mode is selected from a set of transmission modes.

12. The method of claim 11, wherein selecting the first transmission mode comprises:

each symbol in the selected subframe contains a first transmission mode of data tones for SFN transmission.

13. The method of claim 11, wherein selecting the pattern having one or more tones for pilot comprises:

the pattern is selected where the tones used for pilot are not adjacent.

14. The method of claim 11, wherein selecting the pattern having one or more tones for pilot comprises:

the pattern of adjacent tones for the pilot is selected.

15. The method of claim 1, further comprising:

an indication is received indicating that SFN transmission for the data is performed.

16. The method of claim 3, wherein determining the second transmission mode comprises:

a second transmission mode is selected having tones on each symbol of the subframe allocated to transmit data in accordance with the SFN transmission scheme.

17. A method for wireless communication, comprising:

determining a time position in a subframe at which SFN transmission of data will occur;

determining a first transmission mode for transmitting a reference signal, wherein the first transmission mode comprises a position of a tone and a position of a symbol allocated for transmitting the reference signal in the subframe;

broadcasting information about the first transmission mode prior to using the first transmission mode.

18. The method of claim 17, further comprising:

a time position in the subframe where SFN transmission of data will occur and information on the first transmission mode are received.

19. The method of claim 17, further comprising:

an SFN transmission mode for transmitting SFN data is determined, wherein the SFN transmission mode includes a location of a tone in the subframe that is allocated to transmit data using an SFN transmission scheme.

20. The method of claim 19, further comprising:

information about the SFN transmission mode is broadcasted before the SFN transmission mode is used.

21. The method of claim 20, wherein broadcasting the information regarding the SFN transmission mode comprises:

transmitting location information in time and frequency of one or more resource blocks in the subframe for transmitting the SFN transmission data.

22. A method for wireless communication, comprising:

using a first transmission mode, wherein the first transmission mode comprises tones for transmitting a set of data in a Single Frequency Network (SFN) transmission scheme;

using a second transmission mode, wherein the second transmission mode comprises tones for transmitting reference signals; and

information about the first and second transmission modes is broadcast prior to using the first and second transmission modes.

23. The method of claim 22, further comprising:

a time position in a subframe where SFN transmission of data will occur and information on the first transmission mode are received.

24. The method of claim 22, further comprising:

a subframe in which the first transmission mode is to be used is specified.

25. The method of claim 24, wherein using the first transmission mode comprises:

a first transmission mode is selected from one or more transmission modes.

26. The method of claim 22, wherein using the first transmission mode comprises:

a first transmission mode is selected having tones allocated on each symbol of a subframe for transmitting data in accordance with the SFN transmission scheme.

27. A method for wireless communication, comprising:

receiving a time position in a subframe at which SFN transmission for data is to occur; and

information is received regarding a first transmission mode, wherein the information includes location information in time and frequency of at least one resource block for transmitting a set of data in a Single Frequency Network (SFN) transmission scheme.

28. The method of claim 27, wherein receiving comprises:

position information in time and frequency of at least one resource block for transmitting a reference signal is received.

29. The method of claim 27, further comprising:

the resource block is processed based on the first transmission mode.

30. The method of claim 29, wherein processing comprises:

it is determined whether the current subframe contains data transmitted using the SFN transmission scheme.

31. The method of claim 27, further comprising:

an indication indicating use of a first transmission mode is received.

32. A method for wireless communication, comprising:

receiving a time position in a subframe at which SFN transmission for data is to occur; and

information on a first transmission mode is received, wherein the information includes position information in time and frequency of at least one resource block for transmitting a reference signal.

33. The method of claim 32, further comprising:

an indication indicating use of a first transmission mode is received.

34. The method of claim 32, wherein processing comprises:

it is determined whether the current subframe contains data transmitted using the SFN transmission scheme.

35. The method of claim 34, further comprising:

an indication indicating use of a first transmission mode is received.

36. An apparatus for wireless communication, comprising:

means for determining a time position in a subframe at which SFN transmission of data will occur;

means for determining a first transmission mode and a second transmission mode for a reference signal, wherein the transmission modes indicate symbols and tones of a subframe for the reference signal;

means for selecting a transmission mode to use between the first transmission mode and a second transmission mode for reference signals based on whether SFN data is to be transmitted in the subframe; and

means for broadcasting information about the selected transmission mode prior to using the selected transmission mode.

37. The apparatus of claim 36, further comprising:

the apparatus includes means for receiving a time location in a subframe where SFN transmission of data will occur and information regarding the first and second transmission modes for a reference signal.

38. The apparatus of claim 36, further comprising:

means for broadcasting information about the first and second transmission modes of the reference signal prior to using the first and second transmission modes of the reference signal.

39. The apparatus of claim 36, further comprising:

the apparatus can include means for determining a third transmission mode for transmitting SFN data, where the third transmission mode includes a position of a tone in a subframe allocated to transmit data using the SFN transmission scheme.

40. The apparatus of claim 4, wherein the means for broadcasting information about the third transmission mode comprises:

means for transmitting location information in time and frequency of one or more resource blocks in the subframe for transmitting data using an SFN transmission scheme.

41. The apparatus of claim 36, further comprising:

means for selecting a second transmission mode for the reference signal if SFN data is not to be transmitted in the subframe.

42. The apparatus of claim 36, the means for determining the first transmission mode and the second transmission mode comprising:

a module that receives parameters of the first transmission mode and the second transmission mode.

43. The apparatus of claim 36, wherein the means for broadcasting the information comprises:

means for transmitting location information in time and frequency of resource blocks for SFN transmission in the subframe and a time location allocated for the SFN transmission in the subframe.

44. The apparatus of claim 39, wherein the means for broadcasting the information comprises:

means for transmitting the time position allocated for the SFN transmission in the subframe.

45. The apparatus of claim 36, wherein the means for determining the first transmission mode comprises:

a module that receives parameters of the first transmission mode.

46. The apparatus of claim 36, wherein the means for determining the first transmission mode comprises:

a module for selecting the first transmission mode from a set of transmission modes.

47. The apparatus of claim 46, wherein the means for selecting the first transmission mode comprises:

the apparatus can include means for selecting a first transmission mode for each symbol in a subframe that includes data tones for SFN transmission.

48. The apparatus of claim 46, wherein the means for selecting the pattern of one or more pilot tones comprises:

a module that selects a mode in which the pilot tones are not adjacent.

49. The apparatus of claim 46, wherein the means for selecting the pattern of one or more pilot tones comprises:

a module that selects a pattern adjacent to the pilot tone.

50. The apparatus of claim 36, further comprising:

means for receiving an indication indicating that SFN transmission for data is performed.

51. The apparatus of claim 38, wherein the means for determining the second transmission mode comprises:

means for selecting a second transmission mode having tones allocated for transmitting data in accordance with the SFN transmission scheme on each symbol of the subframe.

52. An apparatus for wireless communication, comprising:

means for determining a time position in a subframe at which SFN transmission of data will occur;

means for determining a first transmission mode for transmitting a reference signal, wherein the first transmission mode comprises a position of a tone and a position of a symbol allocated for transmitting the reference signal in the subframe;

a module that broadcasts information about the first transmission mode prior to using the first transmission mode.

53. The apparatus of claim 52, further comprising:

a module that receives a time position in the subframe at which SFN transmission of data will occur and information regarding the first transmission mode.

54. The apparatus of claim 52, further comprising:

the apparatus can include means for determining an SFN transmission mode for transmitting SFN data, wherein the SFN transmission mode includes a location of a tone in the subframe that is allocated to transmit data using an SFN transmission scheme.

55. The apparatus of claim 54, further comprising:

means for broadcasting information regarding the SFN transmission mode prior to using the SFN transmission mode.

56. The apparatus of claim 55, wherein the means for broadcasting information regarding the SFN transmission mode comprises:

means for transmitting location information in time and frequency of one or more resource blocks in the subframe for transmitting the SFN transmission data.

57. An apparatus for wireless communication, comprising:

means for using a first transmission mode, wherein the first transmission mode comprises tones for transmitting a set of data in a Single Frequency Network (SFN) transmission scheme;

means for using a second transmission mode, wherein the second transmission mode includes tones for transmitting reference signals; and

a module that broadcasts information about the first and second transmission modes prior to using the first and second transmission modes.

58. The apparatus of claim 57, further comprising:

a module that receives a time position in a subframe at which SFN transmission of data will occur and information regarding the first transmission mode.

59. The apparatus of claim 57, further comprising:

a module that specifies a subframe that will use the first transmission mode.

60. The apparatus of claim 59, wherein the means for using the first transmission mode comprises:

a module that selects a first transmission mode from one or more transmission modes.

61. The apparatus of claim 59, wherein the means for using the first transmission mode comprises:

the apparatus generally includes means for selecting a first transmission mode having tones allocated on each symbol of a subframe for transmitting data in accordance with an SFN transmission scheme.

62. An apparatus for wireless communication, comprising:

means for receiving a time location in a subframe at which SFN transmission of data is to occur; and

the apparatus includes means for receiving information regarding a first transmission mode, wherein the information includes location information in time and frequency of at least one resource block for transmitting a set of data in a Single Frequency Network (SFN) transmission scheme.

63. The apparatus of claim 62, wherein the means for receiving comprises:

means for receiving location information in time and frequency of at least one resource block used to transmit a reference signal.

64. The apparatus of claim 62, further comprising:

means for processing the resource block based on the first transmission mode.

65. The apparatus of claim 64, wherein the means for processing comprises:

means for determining whether a current subframe contains data transmitted using an SFN transmission scheme.

66. The apparatus of claim 62, further comprising:

a module that receives an indication indicating that a first transmission mode is used.

67. An apparatus for wireless communication, comprising:

means for receiving a time location in a subframe at which SFN transmission of data is to occur; and

the apparatus includes means for receiving information regarding a first transmission mode, wherein the information includes location information in time and frequency of at least one resource block used to transmit a reference signal.

68. The apparatus of claim 67, further comprising:

a module that receives an indication indicating that a first transmission mode is used.

69. The apparatus of claim 67, wherein the means for processing comprises:

means for determining whether a current subframe contains data transmitted using an SFN transmission scheme.

70. The apparatus of claim 69, further comprising:

a module that receives an indication indicating that a first transmission mode is used.

71. A computer program product, comprising:

a computer-readable medium comprising:

code for causing at least one computer to determine a temporal location in a subframe at which SFN transmission of data will occur;

code for causing at least one computer to determine a first transmission mode and a second transmission mode for a reference signal, wherein the transmission modes indicate symbols and tones of a subframe for the reference signal;

code for causing at least one computer to select a transmission mode to use between the first transmission mode and a second transmission mode for reference signals based on whether SFN data is to be transmitted in the subframe; and

code that causes the at least one computer to broadcast information about the selected transmission mode prior to using the selected transmission mode.

72. A computer program product, comprising:

a computer-readable medium comprising:

code for causing at least one computer to determine a temporal location in a subframe at which SFN transmission of data will occur;

code for causing at least one computer to determine a first transmission mode for transmitting reference signals, wherein the first transmission mode comprises locations of tones and symbols in the subframe allocated for transmitting reference signals;

code that causes at least one computer to broadcast information about the first transmission mode prior to using the first transmission mode.

73. A computer program product, comprising:

a computer-readable medium comprising:

code for causing at least one computer to receive a time position in a subframe at which SFN transmission of data will occur; and

code for causing at least one computer to receive information regarding a first transmission mode, wherein the information comprises location information in time and frequency of at least one resource block for transmitting a set of data in a Single Frequency Network (SFN) transmission scheme.

74. An apparatus for wireless communication, comprising:

at least one processor configured to:

determining a time position in a subframe at which SFN transmission of data will occur;

determining a first transmission mode and a second transmission mode for a reference signal, wherein the transmission modes indicate symbols and tones of a subframe for the reference signal;

selecting a transmission mode to use between the first and second transmission modes for reference signals based on whether SFN data is to be transmitted in the subframe; and

broadcasting information about the selected transmission mode before using the selected transmission mode.

75. An apparatus for wireless communication, comprising:

at least one processor configured to:

determining a time position in a subframe at which SFN transmission of data will occur;

determining a first transmission mode for transmitting a reference signal, wherein the first transmission mode comprises a position of a tone and a position of a symbol allocated for transmitting the reference signal in the subframe;

broadcasting information about the first transmission mode prior to using the first transmission mode.

76. An apparatus for wireless communication, comprising:

at least one processor configured to:

receiving a time position in a subframe at which SFN transmission for data is to occur; and

information is received regarding a first transmission mode, wherein the information includes location information in time and frequency of at least one resource block for transmitting a set of data in a Single Frequency Network (SFN) transmission scheme.

77. A method for wireless communication, comprising:

determining a time position in a subframe at which SFN transmission of data will occur;

determining a first transmission mode for transmitting a reference signal, wherein the first transmission mode includes positions of tones and symbols allocated for transmitting the reference signal and for null tones in the subframe;

broadcasting information about the first transmission mode prior to using the first transmission mode.