RU2439796C2 - Pseudo-random sequence mapping in wireless communication - Google Patents

Abstract

FIELD: information technology.

SUBSTANCE: systems and methodologies are described, which facilitate scrambling of downlink reference signals utilising a pseudo-random sequence (PRS) corresponding to a primary synchronisation code (PSC) and secondary synchronisation code (SSC) combination. Use of the combination allows for orthogonal sequencing to be removed from the scrambling. This can be beneficial, for example, where resources required for the orthogonalisation of the reference signal outweigh the benefit of utilising the orthogonal sequences. In such scenarios, selective scrambling can be utilised such that the orthogonal sequence or instead the PSC/SSC combination can be provided to efficiently use advantages of both mechanisms in the given scenarios.

EFFECT: increased noise immunity.

45 cl, 11 dwg

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to provisional US patent application Serial No. 60 / 942,201, entitled "A METHOD AND APPARATUS FOR PSEUDO-RANDOM SEQUENCE (PRS) MAPPING FOR LTE", which was filed June 5, 2007, and provisional patent application serial No. 60/945,073, entitled "METHOD AND APPARATUS FOR PSEUDO-RANDOM SEQUENCE (PRS) MAPPING FOR LTE", which was filed June 19, 2007. All contents of the above applications are incorporated herein by reference.

Technical field

The following description generally relates to wireless communications, and more specifically to pseudo-random sequence conversion for physical layer communication channels.

State of the art

Wireless communication systems are widely used to provide various types of communication content, such as, for example, speech, data, and so on. Typical wireless communication systems may be multiple access systems capable of supporting the exchange of information with several users by sharing available system resources (eg, bandwidth, transmit power, ...). Examples of such multiple access systems may include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access systems channels (OFDMA) and similar. Moreover, systems can meet specifications such as Third Generation Partnership Project (3GPP), 3GPP Long-Term Development System (LTE), Ultra Mobile Broadband (UMB), etc.

Typically, multiple access wireless communication systems can simultaneously support the exchange of information for multiple mobile devices. Each mobile device can communicate with one or more base stations via transmissions on the forward and reverse links. A forward communication line (or downlink) refers to a communication line from base stations to mobile devices, and a reverse communication line (or uplink) refers to a communication line from mobile devices to base stations. Moreover, communication between mobile devices and base stations can be established using single-input and single-output (SISO) systems, multi-input and single-output (MISO) systems, multi-input and multi-output (MIMO) systems, and so on. In addition, mobile devices can communicate with other mobile devices (and / or base stations with other base stations) in peer-to-peer wireless network configurations.

MIMO systems typically employ multiple (N _T ) transmit antennas and multiple (N _R ) receive antennas for data transmission. Antennas can relate to both base stations and mobile devices in one example, allowing bidirectional communication between devices on a wireless network. Transmissions across multiple antennas are sometimes scrambled to allow independent communication from a number of cells over the antennas. Previously, this was achieved using a pseudo-random signal, which is random over a number of cells, and orthogonal sequences (OS) of complex numbers used to orthogonalize the reference signals from different sectors in the same base station. However, when communicating with an extended cyclic prefix (CP) (for example, to take into account long-range echoes in some environments), it is assumed that communication channels become more selective in frequency, resulting in a significant loss of orthogonality of orthogonal sequences at the receiver.

SUMMARY OF THE INVENTION

The following is a simplified summary of one or more embodiments in order to provide a basic understanding of such embodiments. This entity is not a comprehensive general presentation of all intended embodiments and is not intended to identify key or important elements of all embodiments or to outline the scope of any or all embodiments. Its sole purpose is to present some ideas of one or more embodiments in a simplified form as a prelude to the more detailed description that is presented later.

In accordance with one or more embodiments and their corresponding disclosure, various features are described with respect to facilitating providing scrambling for wireless communication for a number of cells without using an orthogonal sequence (OS) or at least for some communication subframes based on at least in part, their cyclic prefix (CP). In one example, scrambling can be implemented using a pair of synchronization codes containing a primary synchronization code (PSC), which can have variable values for reuse, unlike traditional PSC, and a secondary synchronization code (SSC), which is converted into a pseudo-random signal. The PSC / SSC combination identifies the cell and is directly converted to the sequence used to scramble the transmission of information from the cell.

In accordance with related features, a method for interpreting a downlink reference signal in a wireless communication network is provided. The method may comprise receiving a scrambled downlink reference signal from the transmitter and determining a pseudo-random sequence based at least in part on the received primary and secondary synchronization codes. The method may also include descrambling a portion of the subframes of the downlink reference signal in accordance with a pseudo-random sequence and a determined cyclic prefix length for one or more of the subframes.

Another feature relates to a wireless device. A wireless communication device may include at least one processor configured to determine a cyclic prefix length for one or more subframes of a downlink reference signal and select descrambling based at least in part on the cyclic prefix length. A wireless communication device may also include a storage device coupled to at least one processor.

Another feature relates to a wireless communication device that receives and interprets reference signals downlink. The wireless communication device may comprise means for receiving a scrambled downlink reference signal from the transmitter and means for associating a pseudo-random sequence with at least a primary and secondary synchronization code in the downlink reference signal. The wireless communication device may further include means for descrambling a portion of the downlink reference signal in accordance with a pseudo-random sequence.

Another feature relates to a computer program product, which may include a computer-readable medium including code that instructs at least one computer to receive a scrambled downlink reference signal from a transmitter. The computer-readable medium may also comprise a code instructing the at least one computer to determine a pseudo-random sequence using at least a primary and secondary synchronization code. In addition, the computer-readable medium may comprise a code instructing the at least one computer to descramble a portion of the downlink reference signal in accordance with a pseudo-random sequence and a determined cyclic prefix length for one or more of the subframe portion.

In accordance with an additional feature, a method for transmitting a downlink reference signal in a wireless communication network is provided. The method includes generating a downlink reference signal comprising primary and secondary synchronization codes. The method further includes scrambling the downlink reference signal based at least in part on a pseudorandom sequence corresponding to the combination of the primary and secondary synchronization codes, and transmitting the scrambled downlink reference signal.

Another feature relates to a wireless device. The wireless communication device may include at least one processor configured to obtain a pseudo-random sequence related to the selected combination of the primary and secondary synchronization code, and scramble the downlink reference signal using a pseudo-random sequence. A wireless communication device may also include a storage device coupled to at least one processor.

Another feature relates to a wireless communications apparatus for scrambling downlink reference signals in a wireless communications network. The wireless communication device may include means for generating a downlink reference signal comprising primary and secondary synchronization codes. The wireless communication device may further include means for scrambling the downlink reference signal based at least in part on a pseudo-random sequence corresponding to a combination of primary and secondary synchronization codes.

Another feature relates to a computer program product, which may have a computer-readable medium including a code instructing at least one computer to generate a downlink reference signal containing primary and secondary synchronization codes. In addition, the computer-readable medium may comprise a code instructing at least one computer to scramble the downlink reference signal based at least in part on a pseudo-random sequence corresponding to a combination of primary and secondary synchronization codes.

To the accomplishment of the foregoing and related ends, 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 explanatory features of one or more embodiments. These features, however, indicate only some of the various ways in which the principles of various embodiments can be used, and the described embodiments are intended to include all such features and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

1 is an illustration of a wireless communication system in accordance with various features set forth herein.

2 is an illustration of an example communication device for use in a wireless communication environment.

FIG. 3 is an illustration of an example wireless communication system that transmits scrambled downlink reference signals.

4 is an illustration of an example methodology that facilitates transmitting scrambled downlink reference signals.

5 is an illustration of an example methodology that facilitates the interpretation of scrambled downlink reference signals.

6 is an illustration of an example methodology that facilitates the interpretation of reference signals based on cyclic prefixes.

7 is an illustration of an example mobile device that facilitates the interpretation of scrambled reference signals.

8 is an illustration of an example system that facilitates transmitting downlink reference signals.

FIG. 9 is an illustration of an example wireless network environment that can be used in conjunction with various systems and methods described herein.

10 is an illustration of an example system that descrambles scrambled reference signals.

11 is an illustration of an example system that scrambles downlink reference signals.

DETAILED DESCRIPTION

Various embodiments are now described with reference to the drawings, in which the same reference numbers are used to refer to the same elements throughout the description. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. However, it may be obvious that such embodiment (s) can 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 embodiments.

When used in this application, the terms "component", "module", "system", etc. are intended to refer to an object associated with the use of a computer, any of the hardware, firmware, a combination of hardware and software, software or software during execution. For example, a component may be, but is not limited to, a process running on a processor, a processor, an object, an executable, a thread of execution, a program, and / or a computer. By way of illustration, both an application running on a computing device and a computing device can be a component. One or more components may be in the process and / or thread of execution, and the component may be located on one computer and / or distributed between two or more computers. In addition, these components can be executed from various computer-readable media having various data structures recorded thereon. Components can communicate through local and / or remote processes, for example, in accordance with a signal having one or more data packets (for example, data from one component communicating with another component in a local system, distributed system and / or over a network, such like the Internet, with other systems through a signal).

In addition, various embodiments are described herein with reference to a mobile device. A mobile device may also be called a system, subscriber module, subscriber station, mobile station, mobile, remote station, remote terminal, access terminal, user terminal, terminal, wireless device, user agent, user device, or user equipment (UE). The mobile device may be a cellular telephone, a cordless telephone, a Session Initiation Protocol (SIP) telephone, a wireless local area communications system (WLL) station, a personal digital assistant (PDA), a wireless handheld device, a computing device or other processing device, connected to a wireless modem. In addition, various embodiments are described herein with reference to a base station. A base station can be used to communicate with a mobile device (s) and can also be called an access point, Node B, an advanced Node B (eNode B or eNB), a base transceiver station (BTS), or some other terminology.

In addition, various features or features described herein may be implemented as a method, device, or product using standard software and / or technical techniques. The term "product" when used in this document is intended to include a computer program accessible from any computer-readable device, carrier or media. For example, computer-readable media may include, but are not limited to, magnetic storage devices (e.g., hard disk, floppy disk, magnetic tapes, etc.), optical disks (e.g., compact disc (CD), digital versatile disk ( DVD), etc.), smart cards and flash memory devices (e.g. EPROM, memory card, removable flash memory device, etc.). Moreover, the various storage media described herein may represent one or more devices and / or other computer-readable media for storing information. The term “computer-readable medium” may include, but is not limited to, wireless channels and various other media capable of storing, containing and / or moving commands (commands) and / or data.

The techniques described in this document can be used for various wireless communication systems, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal multiple access frequency division multiplexing (OFDMA), single-carrier frequency domain multiplexing (SC-FDM) and other 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, etc. UTRA includes Broadband CDMA (W-CDMA) and other varieties of CDMA. CDMA2000 covers IS-2000, IS-95, and IS-856 standards. A TDMA system may implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA system may implement a radio technology such as Enhanced UTRA (E-UTRA), Ultra-Wideband Mobile Communications (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of the Universal Mobile Telecommunications System (UMTS). 3GPP Long Term Evolution (LTE) System is the upcoming release of UMTS that uses E-UTRA, which uses OFDMA on the downlink and SC-FDMA on the uplink. UTRA, E-UTRA, UMTS, LTE, and GSM are described in documents from an organization called the Third Generation Partnership Project (3GPP). CDMA2000 and UMB are described in documents from an organization called the Second Third Generation Partnership Project (3GPP2).

Turning now to FIG. 1, a wireless communication system 100 is illustrated in accordance with various embodiments presented herein. System 100 includes a base station 102, which may include several groups of antennas. For example, one antenna group may include antennas 104 and 106, another group may include antennas 108 and 110, and an additional group may include antennas 112 and 114. Two antennas are illustrated for each antenna group; however, more or fewer antennas may be used for each group. Base station 102 may further include a transmitter circuit and a receiver circuit, each of which, in turn, may contain multiple components associated with signal transmission and reception (e.g., processors, modulators, multiplexers, demodulators, demultiplexers, antennas, etc. ), which will be clear to a person skilled in the art.

Base station 102 may communicate with one or more mobile devices, such as mobile device 116 and mobile device 122; however, it should be appreciated that base station 102 can communicate with virtually any number of mobile devices similar to mobile devices 116 and 122. Mobile devices 116 and 122 can be, for example, cell phones, smartphones, laptop computers, handheld communication devices, handheld devices computing devices, satellite radio stations, global positioning systems, PDAs and / or any other suitable device for communicating in a wireless communication system 100. As shown, mobile device 116 communicates with antennas 112 and 114, where antennas 112 and 114 transmit information to mobile device 116 on forward link 118 and receive information from mobile device 116 on reverse link 120. In addition, mobile device 122 communicates with antennas 104 and 106, where antennas 104 and 106 transmit information to mobile device 122 on forward link 124 and receive information from mobile device 122 on reverse link 126. In a frequency duplex diversity (FDD) system, the forward link 118 may use, for example, a different frequency band than that used by the reverse link 120, and the forward link 124 may use a different frequency band than that used by the reverse link 126. In addition, in a time division duplex (TDD) system, forward link 118 and reverse link 120 may use a common frequency band, and forward link 124 and reverse link 126 may use a common frequency band.

Each group of antennas and / or the area in which they are intended for communication can be called a sector of the base station 102. For example, groups of antennas can be designed to communicate with mobile devices in the sector of the areas covered by the base station 102. When communicating directly to the communication lines 118 and 124, the transmitting antennas of the base station 102 can use beamforming to improve the signal-to-noise ratio of the direct communication lines 118 and 124 for mobile devices 116 and 122. Also, although the base station 102 and Using beamforming for transmission to mobile devices 116 and 122, scattered randomly in the associated area, mobile devices in neighboring cells may be less interference than a base station transmitting all its mobile devices through one antenna. In addition, mobile devices 116 and 122 can communicate directly with each other using peer-to-peer or special technology, which is depicted.

According to an example, the system 100 may be a communication system with many inputs and many outputs (MIMO). Additionally, system 100 can use virtually any type of duplex technique to separate communication channels (e.g., forward link, reverse link, ...) such as FDD, TDD, and the like. In addition, one or more multiplexing schemes (eg, OFDM) can be used to modulate several signals on a number of frequency subcarriers forming one or more communication channels. In one example, a channel transmitter, such as a base station 102 and / or mobile devices 116 and 122, may further transmit a pilot or reference signal to help synchronize communication with another device or in channel estimation. For example, a downlink reference signal (RS) transmitted from a sector in base station 102 may depend on one or more synchronization codes. In the example, the RS may have a duration equal to the number of subframes (for example, 10 subframes), and the synchronization codes may be in one or more subframes (subframes 0 and 5 in one example).

According to an example, the used synchronization codes can uniquely determine the pseudo-random sequence (PRS) used to scramble the RS. In one example, RS is scrambled by performing an XOR operation with PRS. As mentioned, previous systems used the orthogonal sequence together with PRS to provide cell-specific scrambling uniquely tied to cell identity; however, it is contemplated that transmissions having an extended cyclic prefix (CP) result in greater channel selectivity, which begins to gradually reduce orthogonality in orthogonal sequences at the receiver (e.g., mobile devices 116 and / or 122). The subject matter described in this document uses a secondary synchronization code (SSC), which is converted to PRS together with a primary synchronization code (PSC), not only for the traditional determination of the boundary of the time interval, but also as a dynamic repetition factor for PRS, so that scramble RS according to some PRS. The combination of PSC / SSC can also serve to identify the RS transmitter (for example, a particular sector in the base station 102, mobile devices 116 and 122, or a related transmitting cell). Thus, instead of applying PRS and an orthogonal sequence, only PRS based on the PSC / SSC combination is applied. Since the number of PSCs can be almost the same as the number of orthogonal sequences previously, the subject matter described herein provides almost the same number of combinations that were available using the orthogonal sequence. However, it should be taken into account that in subframes having a normal CP (or CP below a predetermined threshold value), where orthogonal signals can provide significant gains, such signals can still be used along with PRS to provide cell-specific scrambling, uniquely tied to cell identity.

Turning to FIG. 2, a communication device 200 for use in a wireless communication environment is illustrated. The communication device 200 may be a sector of a base station or part thereof, a mobile device or part thereof, or virtually any communication device that receives data transmitted in a wireless communication environment. The communication device 200 may include a reference signal determining unit 202 that generates an RS for broadcasting to one or more completely different communication devices, a scrambler 204 that scrambles the RS in accordance with one or more synchronization codes, and a transmitter 206 that transmits the scrambled RS .

According to an example, the communication device 200 may transmit a downlink RS, which may be used by the receiver to determine transmission information from the communication device 200. In one example, the reference signal determining unit 202 may create an RS that can be used to identify or synchronize with communication device 200 and / or the like. Synchronization codes may contain PSC and SSC related to cell-specific scrambling used for RS transmission. The SSC can uniquely determine the corresponding PRS, and the PSC can uniquely determine the repetition factor for the PRS. Thus, the available amount of PRS can be almost equal to the product of available PSC and available SSC.

The PSC and SSC used by the communication device 200 may refer to the PRS used by the scrambler 204 to scramble the RS. It can also serve to identify communication device 200 with respect to surrounding transmitting devices. In the LTE example, 3GPP 170 SSCs can correspond to 170 PRSs, which the scrambler 204 can use to scramble the RS. Moreover, 3 PSCs can provide a repetition factor for PRS representation 510, which can be used to scramble the RS and uniquely identify the communication device 200 or its cell with respect to communication devices receiving the RS. A scrambled RS can be transmitted to one or more of these devices by using a transmitter 206. It should be noted that the above example can reduce the use of orthogonal sequences in RS scrambling, where, for example, subframes with extended or longer CPs are used (for example, where subject to far echo -signals, etc.).

However, orthogonalization of RS can be advantageous when orthogonality can be maintained, which is assumed using the usual length of CP. Thus, where extended CPs are used (e.g., CPs having a length exceeding a predetermined threshold value), the aforementioned PSC / SSC combination may determine the PRS used by the scrambler 204 from the RS. It is not necessary where the CP does not exceed a threshold value or has a normal length, the used PRS may refer to a single SSC, and the signal may be orthogonalized in accordance with a conventional orthogonal sequence. In the LTE example, 3GPP 170 SSCs can correspond to 170 PRSs, which the scrambler 204 can use to scramble the RS. Moreover, 3 orthogonal sequences can be available for RS orthogonalization to represent 510 combinations of the orthogonal sequence and PRS, which can be used to scramble the RS and uniquely identify the communication device 200 or its cell.

Referring now to FIG. 3, a wireless communication system 300 is illustrated that transmits a downlink RS scrambled with a cell identifier. System 300 includes a base station sector 302 that communicates with a mobile device 304 (and / or any number of completely different mobile devices (not shown)). Base station sector 302 may transmit information to mobile device 304 over a forward link or downlink channel; furthermore, base station sector 302 may receive information from mobile device 304 over a reverse link or uplink channel. In addition, system 300 may be a MIMO system. Also, the components and functionality shown and described below in the base station sector 302 may be present in one example in the mobile device 304, and vice versa with the same success; the configuration shown excludes these components for ease of explanation.

The base station sector 302 includes a reference signal determining unit 306 that can generate an RS for transmission to the mobile device 304, where the RS may contain information for interpreting signals transmitted from the base station sector 302, a scrambler 308 that can scramble the RS using PRS identifying the source and transmitter 310, which can transmit the scrambled RS. As described, the PRS may correspond to an SSC and / or a PSC / SSC pair stored in the RS. For example, PRS may correspond to SSC, where conventional CP subframes are used in conjunction with the orthogonal sequence to orthogonalize RS, and PRS may correspond to a PSC / SSC pair where extended CP subframes are used, as described previously.

Mobile device 304 includes a receiver 312 that can receive the transmitted signals, a reference signal detector 314 that can detect the signals as RS, and a descrambler 316 that can descramble the RS in accordance with the information received therein. In one example, the receiver 312 may receive one or more reference signals, and the reference detector 314 may determine that the signal is RS and extract synchronization information from one or more subframes in the RS. The descrambler 316 may descramble the reference signal to find additional information in accordance with the extracted information.

In one example, the reference signal determining unit 306 may create an RS as previously described, and the scrambler 308 may scramble an RS as previously described using a PRS corresponding to the PSC / SSC combination. RS can optionally store PSC and SSC. Subsequently, transmitter 310 may transmit the RS to one or more mobile devices, such as mobile device 304, to provide synchronization / identity information to sector 302 of the base station to communicate with it. An RS may be received by a receiver 312 of the mobile device 304 and detected as an RS by a reference signal detector 314. The reference signal detector 314 can detect the signal by at least partially determining its PSC and / or SSC (for example, based on subframe 0 in RS). After determining the PSC / SSC combination, the reference detector 314 may recognize the PRS used to scramble the RS, and the descrambler 316 may descramble the RS in accordance with the PRS.

As described, in working with extended CP, the traditional step of the orthogonal sequence in scrambling can become dangerous. Thus, using only PRS when expanding the number of available PRSs to provide almost the same amount as PRS / orthogonal sequence combinations provides similar flexibility to identify base station sector 302 without additional orthogonalization steps. However, as mentioned, the use of an orthogonal sequence can provide a gain in working with a regular CP; accordingly, in this case, an orthogonal sequence can be used along with the combination of PSC / SSC in subframes with extended CP in one example.

In this example, the mobile device 304 can receive the RS through the receiver 312, and the reference signal detector 314 can determine whether the subframe 0 of the RS was sent in the extended or conventional CP subframe. If the extended CP is detected in subframe 0, then the reference signal detector 314 may determine that orthogonal ordering has not been used in RS scrambling for a given subframe. Thus, PRS was created from a unique transformation from the PSC / SSC combination, and only PRS was used to scramble the RS. On the other hand, if a conventional CP is detected in subframe 0, then the reference signal detector 314 can determine that orthogonal ordering has been used in RS scrambling for a given subframe. Thus, PRS was created from the conversion of a single SSC and was used to scramble the RS together with the orthogonal sequence. Descrambler 316 may use this information in RS descrambling.

Moreover, in this example, if the reference signal detector 314 detects an extended CP in subframe 0, then an extended CP in one example may be assumed for the remainder of the subframes. Therefore, the extracted PSC / SSC combination can be used by descrambler 316 to descramble the remaining subframes. However, if the reference signal detector 314 detects a conventional CP in subframe 0, then the physical broadcast channel (PBCH), which is usually found in subframe 0, or the dynamic broadcast channel (DBCH) may indicate which subframes use the enhanced CP and which use regular CP. Where the remaining subframes use conventional CP, the SSC may correlate with the PRS used to scramble the corresponding subframes, and the reference signal detector 314 may allow the use of an orthogonal sequence in these subframes; where the remaining subframes use the enhanced CP, the PSC / SSC combination may correlate with the PRS used to scramble the corresponding subframe, and orthogonal ordering has not been used. It should be appreciated that where subframe 0 uses the enhanced CP, the dynamic BCH may further indicate subframes having the regular and advanced CP, so that the above distinction can be used with respect to the remaining subframes. Moreover, it should be appreciated that the PSC / SSC combination in one example can be used in all subframes, regardless of the length of the CP.

Referring to FIGS. 4-6, methodologies related to scrambling downlink reference signals in accordance with primary and secondary synchronization codes are illustrated. Although in order to simplify the explanations of the methodologies are shown and described as a sequence of actions, it must be understood and taken into account that the methodologies are not limited to the order of actions, since some actions in accordance with one or more options for implementation can be performed in other orders and / or simultaneously with other actions, in Unlike those shown and described in this document. For example, those skilled in the art will understand and appreciate that, as an alternative, a methodology could be represented as a sequence of interrelated states or events, such as in a state diagram. In addition, not all illustrated acts may be necessary to implement a methodology in accordance with one or more embodiments.

Turning to FIG. 4, a methodology 400 is shown that facilitates the generation and transmission of a scrambled downlink RS. At step 402, a downlink RS is generated containing information related to the RS transmitter. For example, the information may include synchronization codes, data in the primary broadcast channel, and / or the like. At 404, a unique PRS may be determined that corresponds to the primary and secondary synchronization code used by the RS transmitter. Code combination can be displayed directly in PRS; accordingly, other transmitters in the vicinity can also transmit RSs using completely different PRSs that help distinguish between RSs. Also in this regard, the PRS may allow the RS receiver to identify the transmitter.

At step 406, the downlink reference signal is scrambled using PRS. In one example, this can be accomplished through an XOR operation between RS and PRS. At 408, a scrambled downlink RS is transmitted. Thus, RS scrambling can be performed without using an orthogonal sequence, while preserving a number of possible scrambling, where the number of available PSCs coincides with previously available orthogonal sequences. This may be advantageous in subframes having an enhanced CP, as described, where the benefits of orthogonal ordering may be lost due to the assumed high frequency selectivity of the channel.

Turning to FIG. 5, a methodology 500 is illustrated that facilitates descrambling of reference signals based at least in part on synchronization codes. At 502, a downlink RS is received; in one example, it may come from a transmitter, communication with which is necessary. At 504, the primary and secondary synchronization codes in the RS part are determined. Codes can be extracted from specific time-frequency locations in certain subframes, for example, subframes 0 and 5. At step 506, the PRS is determined based at least in part on the primary and secondary synchronization codes; it can also be partially based on the duration of CP, as described previously. For example, the codes may correlate with the PRS used to scramble the RS before transmission, and at step 508 the PRS may be used to descramble the RS. In one example, the secondary synchronization code may relate directly to PRS, while the primary synchronization code is the repetition factor for PRS, or vice versa.

Turning to FIG. 6, illustrated is a methodology 600 that facilitates descrambling RS downlink based at least in part on the size of the cyclic prefix associated with one or more frames or subframes in the RS. At 602, a downlink RS containing one or more subframes is received. The method starts with subframe 0 as the current subframe. At 604, the CP length of the current subframe is estimated. If the CP is extended (for example, having a length greater than a predetermined threshold value), then the previously extracted PSC / SSC combination can be used to determine the PRS for RS descrambling. It will be appreciated that at 606, the PSC / SSC combination may be retrieved using virtually any of the methods described herein. At 608, it can be determined if there is a next subframe in the RS. If this is the case, then it can be assumed that the remaining subframes also have an extended prefix, and accordingly, at step 610, since subframe 0 has an extended CP, the next subframe may become the current subframe and likewise evaluated at 606 until there are no more subframes. When there are no more subframes, the method continues to block 612, where RS is interpreted.

If it is determined in step 604 that subframe 0 does not have an extended CP, then in step 614, the previously extracted SSC can be used to determine the directly correlated PRS in order to descramble the subframe with the same orthogonal sequence. In this regard, for an unexpanded or conventional CP, the orthogonal sequence was used by the scrambler in the transmitter. However, in this case, it cannot be assumed that the remaining subframes have unexpanded CP; accordingly, if the next subframes remain in step 608, since subframe 0 does not have an extended CP in step 610, the method returns to step 604 to evaluate the CP of the next subframe. However, if there are no subframes, then at step 612, the RS is interpreted. Therefore, the method may permit the use of orthogonal sequences in conventional CP subframes to preserve their benefits, while eliminating orthogonal ordering from the extended CP subframes, as described herein, where the benefits of orthogonal ordering may be disrupted by the assumed frequency selectivity of the channel.

You will need to take into account that, in accordance with one or more of the features described in this document, conclusions can be made regarding the definition of PSC or SSC for given transmitters as described. As used herein, the term “infer” or “inference” generally refers to the process of reasoning or inferring states of a system, environment, and / or user from a collection of observations that are recorded through events and / or data. Inference can be used to identify a particular context or action, or, for example, can form a probability distribution by state. The conclusion can be probabilistic - that is, by calculating the probability distribution over states of interest based on a consideration of data and events. The conclusion may also relate to the techniques used to compose high-level events from a combination of events and / or data. This conclusion leads to the construction of new events or actions from the totality of the observed events and / or stored event data, regardless of whether the events are correlated in the immediate temporal proximity, and whether events and data come from one or more sources of events and data.

According to an example, one or more of the above methods may include obtaining conclusions regarding the determination of the PSC / SSC combination, the associated PRS, the transmitter identity based on the PSC / SSC combination, the orthogonal sequence used in subframes with conventional CP, length cyclic prefix for one or more subframes, etc.

7 is an illustration of a mobile device 700 that facilitates descrambling received downlink RSs. Mobile device 700 includes a receiver 702 that receives a signal, for example, from a receiving antenna (not shown), performs typical actions on the received signal (e.g., filters, amplifies, downconverts, etc.) and digitizes the converted signal to obtain samples. Receiver 702 may include a demodulator 704 that can demodulate received symbols and provide them to a processor 706 for channel estimation. The processor 706 may be a processor for analyzing information received by the receiver 702 and / or generating information for transmission by the transmitter 716, a processor that controls one or more components of the mobile device 700, and / or a processor that analyzes the information received by the receiver 702 , generates information for transmission by the transmitter 716, and controls one or more components of the mobile device 700.

Mobile device 700 may further comprise a storage device 708 that is operatively connected to a processor 706 and which can store data to be transmitted, received data, information related to available channels, data associated with the analyzed signal and / or interference power, information related to a dedicated channel, power, speed or the like, and any other suitable information for channel estimation and channel communication. Storage device 708 may further store protocols and / or algorithms associated with channel estimation and / or utilization (eg, performance based, capacity based, etc.).

It will be appreciated that the data storage described in this document (e.g., storage device 708) can be either volatile storage device or non-volatile storage device, or can include both volatile and non-volatile storage device. By way of illustration, and not limitation, non-volatile memory may include read only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable PROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM), which acts as an external cache. By way of illustration, and not limitation, RAM is available in many forms, such as synchronous RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double-bit rate SDRAM (DDR SDRAM), advanced SDRAM (ESDRAM), DRAM with synchronous communication channel (SLDRAM) and RAM with direct access from Rambus (DRRAM). A storage device 708 of the discussed systems and methods is intended to comprise (without being limited) these and any other suitable types of storage devices.

The processor 706 and / or receiver 702 may further be operatively coupled to a reference signal detector 710, which determines whether the received signal is a downlink reference signal. In addition, the reference signal detector 710 can determine the PRS used by the transmitter to scramble the RS before transmission. In one example, this may be based, at least in part, on the extracted PSC / SSC combination provided in the RS that is associated with the given PRS. In addition, this combination can be used to identify the RS transmitter. In another example where the cyclic prefix is common, the reference signal detector 710 can equally well determine the orthogonal sequence used to scramble the RS. Using this information, descrambler 712 can descramble RS.

According to an example, the reference signal detector 710 can determine the cyclic prefix length of one or more RS subframes and determine whether to descramble using PRS relating to the PSC / SSC combination or PRS relating to SSC together with the orthogonal sequence. As described, the former can be used in extended CP subframes, since orthogonality would probably be lost if frequency selectivity is due to enhanced CP, while the latter can be used for subframes having conventional CP. Alternatively, the combination of PSC / SSC can be displayed in PRS in almost all cases. The mobile device 700, moreover, contains a modulator 714 and a transmitter 716, which respectively modulate and transmit the signal, for example, to a base station, another mobile device, etc. Although depicted as separate from the processor 706, it should be understood that the reference signal detector 710, descrambler 712, demodulator 704 and / or modulator 714 may be part of a processor 706 or multiple processors (not shown).

8 is an illustration of a system 800 that facilitates forming and scrambling a downlink RS for transmission thereof. System 800 comprises a base station 802 (eg, an access point, ...) with a receiver 810 that receives signal (s) from one or more mobile devices 804 through multiple receiving antennas 806, and a transmitter 824 that transmits to one or more mobile devices 804 via transmit antenna 808. Receiver 810 can receive information from receive antennas 806 and is operatively coupled to a demodulator 812 that demodulates received information. The demodulated symbols are analyzed by a processor 814, which may be similar to the processor described above with respect to FIG. 7, and which is coupled to a memory 816 that stores information related to estimating a signal level (e.g., pilot signal) and / or interference level , data that must be transmitted or received from mobile device (s) 804 (or a completely different base station (not shown)), and / or any other suitable information related to the performance of various actions and functions, is outlined ennyh in this document. A processor 814 is further coupled to a reference signal generator 818 that creates an RS, which can be used to determine synchronization, identity, and / or other information about the base station 802, and a scrambler 820 that can scramble the RS.

According to an example, the reference signal driver 818 may generate an RS containing primary and secondary synchronization codes. The codes can uniquely identify the base station 802 and can also directly correspond to one of a number of PRSs. Scrambler 820 can scramble RS using PRS (for example, through an XOR operation). In subframes having a regular CP, PRS may refer to SSC, and the orthogonal sequence in one example may further be used to scramble the RS. The scrambled RS can be transmitted to one or more mobile devices 804 from the transmitter 824. In addition, although depicted as separate from the processor 814, it should be understood that the reference signal driver 818, scrambler 820, demodulator 812 and / or modulator 822 may be part of processor 814 or multiple processors (not shown).

9 shows an example of a wireless communication system 900. Wireless communication system 900 depicts one base station 910 and one mobile device 950 for short. However, it will be appreciated that system 900 may include more than one base station and / or more than one mobile device, where additional base stations and / or mobile devices may be substantially the same or different from the example of base station 910 and mobile device 950 described below. In addition, it should be understood that the base station 910 and / or mobile device 950 can use the systems (FIGS. 1-3 and 7-8) and / or methods (FIGS. 4-6) described herein to facilitate wireless communication between them.

At base station 910, traffic data for a number of data streams is provided from a data source 912 to a transmit (TX) data processor 914. According to an example, each data stream may be transmitted on a respective antenna. Transmission data processor 914 formats, codes, and interleaves the traffic data stream based on the particular coding scheme selected for that data stream to provide encoded data.

The coded data for each data stream may be multiplexed with pilot data using orthogonal frequency division multiplexing (OFDM) techniques. Additionally or alternatively, the pilot symbols may be frequency division multiplexed (FDM), time division multiplexed (TDM) or code division multiplexed (CDM). Pilot data is typically a known data pattern that is processed in a known manner and can be used on mobile device 950 to estimate channel performance. Multiplexed pilot signals and encoded data for each data stream can be modulated (e.g., symbol-wise) based on a particular modulation scheme (e.g., on-off phase shift keying (BPSK), quadrature phase shift keying (QPSK), M-position phase shift keying (M-PSK ), M-Position Quadrature Amplitude Modulation (M-QAM), etc.) selected for this data stream to provide modulation symbols. The data rate, coding, and modulation for each data stream may be determined by instructions executed or provided by processor 930.

Modulation symbols for data streams may be provided to a MIMO transmission processor 920, which may further process modulation symbols (eg, for OFDM). The MIMO transmit processor 920 then provides N _T modulation symbol streams to N _T transmitters 922a through 922t (TMTR). In various embodiments, the MIMO transmission processor 920 applies beamforming weights to the symbols from the data streams and to the antenna from which the symbol is transmitted.

Each transmitter 922 receives and processes a respective symbol stream to provide one or more analog signals, and further processes (e.g., amplifies, filters, and upconverts) the analog signals to provide a modulated signal suitable for transmission over the MIMO channel. Next, N _T modulated signals from transmitters 922a through 922t are transmitted from N _T antennas 924a through 924t, respectively.

At mobile device 950, the transmitted modulated signals are received by N _R antennas 952a through 952r, and the received signal from each antenna 952 is provided to a respective receiver 954a through 954r (RCVR). Each receiver 954 processes (eg, filters, amplifies, and downconverts) a respective signal, digitizes the processed signal to provide samples, and further processes the samples to provide a corresponding “received” symbol stream.

A received data processor 960 can receive and process N _R received symbol streams from N _R receivers 954 based on a specific receiver processing technique to provide N _T “detected” symbol streams. Received data processor 960 can demodulate, eliminate interleaving, and decode each detected symbol stream to recover traffic data for the data stream. The processing by the received data processor 960 is complementary to that performed by the MIMO transmission processor 920 and the transmitted data processor 914 at the base station 910.

The processor 970 may periodically determine which precoding matrix to use, as discussed above. Further, processor 970 may compose a reverse link message comprising a matrix index portion and a rank value portion.

The reverse link message may contain various types of information regarding the communication link and / or the received data stream. The reverse link message may be processed by the transmitted data processor 938, which also receives traffic data for a number of data streams from the data source 936, modulated by a modulator 980, processed by transmitters 954a-954r, and transmitted back to the base station 910.

At base station 910, modulated signals from mobile device 950 are received by antennas 924, processed by receivers 922, demodulated by demodulator 940, and processed by received data processor 942 to retrieve the reverse link message transmitted by mobile device 950. Next, processor 930 can process the extracted message to determine which precoding matrix to use to determine the beam formation weights.

Processors 930 and 970 can direct (e.g., monitor, coordinate, manage, etc.) operation at base station 910 and mobile device 950, respectively. Corresponding processors 930 and 970 may be associated with memory devices 932 and 972 that store program codes and data. Processors 930 and 970 can also perform calculations to derive frequency and impulse response estimates for the uplink and downlink, respectively.

You must understand that the embodiments described in this document can be implemented in hardware, software (software), firmware, middleware, microcode, or any combination thereof. For hardware implementation, the processing modules can be implemented in one or more specialized integrated circuits (ASIC), digital signal processors (DSP), digital signal processing devices (DSPD), programmable logic devices (PLD), user programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, other electronic units designed to perform the functions described in this document, or in combination thereof.

When embodiments are implemented in software, firmware, middleware or microcode, program code or code segments, they may be stored on a computer-readable medium, such as a storage component. A code segment can be a procedure, function, subroutine, program, procedure, subroutine, module, software package, class, or any combination of instructions, data structures, or program statements. A code segment may be associated with another code segment or a hardware circuit by transmitting and / or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. can be forwarded, redirected or transmitted using any suitable means, including memory sharing, message forwarding, relay transmission, network transmission, etc.

For a software implementation, the techniques described in this document can be implemented using modules (eg, procedures, functions, and so on) that perform the functions described in this document. Software codes may be stored in memory devices and executed by processors. The storage device may be implemented inside the processor or outside the processor, in which case it may be communicatively connected to the processor through various means that are known in the art.

With reference to FIG. 10, illustrated is a system 1000 that descrambles the received downlink RSs in accordance with the PRS. For example, system 1000 may reside at least in part in a base station, mobile device, etc. You need to understand that the system 1000 is presented as including functional blocks, which can be functional blocks that represent functions implemented by a processor, software, or a combination thereof (e.g., firmware). System 1000 includes a logical grouping 1002 of electrical components that can act in conjunction. For example, logical grouping 1002 may include an electrical component 1004 for receiving a scrambled downlink RS. For example, the RS may be received from the transmitter and may contain synchronization information and / or identifying information about the transmitter, for example, unique synchronization codes that can be selected from an available set of codes. Additionally, the logical grouping 1002 may comprise an electrical component 1006 for associating a PRS with at least a primary and secondary synchronization code in a downlink RS. For example, unique synchronization codes may correspond to PRS; the uniqueness property can help in identifying the RS transmitter. In addition, the logical grouping 1002 may include an electrical component 1008 for descrambling the downlink RS portion in accordance with the PRS. RS can subsequently be optionally interpreted to extract other information. Moreover, system 1000 may include a storage device 1010 that stores instructions for performing functions associated with electrical components 1004, 1006, and 1008. It will be appreciated that one or more electrical components 1004, 1006, and 1008 may exist within memory 1010 , although shown as external to the storage device 1010.

Turning to FIG. 11, illustrated is a system 1100 that creates and scrambles RSs for transmission over a wireless communications network. System 1100 may reside, for example, in a base station, mobile device, etc. As depicted, system 1100 includes function blocks that may represent functions implemented by a processor, software, or a combination thereof (eg, firmware). System 1100 includes a logical grouping 1102 of electrical components that facilitate the formation and scrambling of RS. Logical grouping 1102 may include an electrical component 1104 for generating a downlink RS containing primary and secondary synchronization codes. Such information not only allows the receiver to identify the information transmitter, but also obtain synchronization information with the transmitter for subsequent communication. Moreover, such information may indicate which PRS is used to scramble the RS before transmission. Furthermore, logical grouping 1102 may include an electrical component 1106 for scrambling a downlink RS based at least in part on a PRS corresponding to a combination of primary and secondary synchronization codes. Thus, there may be a set of PRS used by the transmitter directly converted to a combination of synchronization codes. In this regard, depending on the number of conversions, the PRS / synchronization code, the chances of a similar PRS used by a completely different transmitter, which can cause interference, decrease with increasing number of conversions. After scrambling, the RS can be transmitted or broadcast to various receivers. Moreover, system 1100 may include a storage device 1108 that stores instructions for performing functions associated with electrical components 1104 and 1106. It will be appreciated that electrical components 1104 and 1106 may exist inside storage device 1108, although shown as external relative to the storage device 1108.

What is described above includes examples of one or more embodiments. Of course, it is not possible to describe every possible combination of components or methodologies in order to describe the aforementioned embodiments, however, one of ordinary skill in the art may recognize that many additional combinations and permutations of various embodiments are acceptable. Accordingly, the described embodiments are intended to cover all such changes, modifications and variations that fall within the spirit and scope of the appended claims. In addition, in the case where the term “includes” is used either in the detailed description or in the claims, such a term is intended to be inclusive, in a sense similar to the term “comprising”, since “comprising” is interpreted when used as a transition words in the claims.

Claims (45)

1. A method of receiving a reference signal downlink in a wireless communication network, comprising stages in which:
receiving a scrambled downlink reference signal;
determining a pseudo-random sequence based, at least in part, on the received primary and secondary synchronization codes; and
descramble the portion of the subframes of the downlink reference signal in accordance with the pseudo-random sequence and the determined cyclic prefix length for one or more of the portion of the subframes. 2. The method according to claim 1, in which the primary and secondary synchronization codes are received in a completely different signal from the transmitter. 3. The method of claim 1, wherein the step of descrambling is performed on a subframe with a cyclic prefix length above a predetermined threshold value. 4. The method of claim 1, further comprising descrambling a portion of the subframes of the downlink reference signal having a cyclic prefix length less than a predetermined threshold value based at least in part on a pseudorandom sequence corresponding to a secondary synchronization code and an orthogonal sequence. 5. The method of claim 1, further comprising evaluating a first subframe to determine a cyclic prefix length for the first subframe and possible cyclic prefix lengths for the remaining subframes. 6. The method of claim 5, wherein the dynamic broadcast channel in the subframe provides cyclic prefix lengths of the remaining subframes. 7. The method of claim 1, further comprising identifying the transmitter based at least in part on the primary and secondary synchronization codes. 8. The method according to claim 1, further comprising the step of extracting the primary and secondary synchronization codes from the downlink reference signal. 9. A wireless communications device for descrambling a downlink reference signal, comprising:
at least one processor configured to determine the length of the cyclic prefix of one or more subframes of the downlink reference signal, selecting descrambling based at least in part on the length of the cyclic prefix and descrambling the downlink reference signal according to the selected descrambling; and
a storage device connected to at least one processor. 10. The wireless communications apparatus of claim 9, wherein the cyclic prefix length of one or more subframes exceeds a predetermined threshold, and descrambling is performed using a pseudo-random sequence determined from a combination of the primary and secondary synchronization codes in the reference signal. 11. The wireless communications apparatus of claim 10, wherein the combination of the primary and secondary synchronization code identifies the reference signal transmitter. 12. The wireless communications apparatus of claim 9, wherein the cyclic prefix length of one or more subframes is below a predetermined threshold, and descrambling is performed using a pseudo-random sequence determined from the secondary synchronization code in the reference signal and a specific orthogonal sequence. 13. The wireless communications apparatus of claim 9, wherein the one or more subframes are a first subframe of a reference signal. 14. The wireless communications apparatus of claim 13, wherein the cyclic prefix of the first subframe is of a normal length, and at least one processor is further configured to determine cyclic prefix lengths for the remaining subframes by estimating a dynamic broadcast channel in a downlink reference signal . 15. The wireless communications apparatus of claim 13, wherein the cyclic prefix of the first subframe is an extended length cyclic prefix, and at least one processor is further configured to determine remaining subframes having increased cyclic prefix lengths. 16. A wireless communication device for receiving reference signals downlink, comprising:
means for receiving a scrambled downlink reference signal;
means for associating a pseudo-random sequence with at least a primary and secondary synchronization code in a downlink reference signal; and
means for descrambling a portion of the downlink reference signal in accordance with a pseudo-random sequence. 17. The wireless communications apparatus of claim 16, further comprising means for determining a cyclic prefix length for one or more subframes of a portion of the downlink reference signal. 18. The wireless communications apparatus of claim 17, wherein the descrambling is performed on at least one subframe with a cyclic prefix length above a predetermined threshold. 19. The wireless communications apparatus of claim 17, further comprising means for descrambling at least one subframe having a cyclic prefix length less than a predetermined threshold value based at least in part on a pseudorandom sequence corresponding to a secondary synchronization code and an orthogonal sequence. 20. The wireless communications apparatus of claim 17, further comprising means for evaluating the first subframe to determine a cyclic prefix length for the first subframe and possible cyclic prefix lengths for the remaining subframes. 21. The wireless communications apparatus of claim 20, wherein the dynamic broadcast channel in the subframe provides cyclic prefix lengths of the remaining subframes. 22. The wireless communications apparatus of claim 16, further comprising means for identifying the transmitter based at least in part on the primary and secondary synchronization codes. 23. The wireless communications apparatus of claim 16, further comprising means for extracting primary and secondary synchronization codes from the downlink reference signal. 24. A machine-readable medium containing codes stored on it, which when executed by a computer, instructs the computer to perform a method of receiving a downlink reference signal in a wireless communication network, the codes comprising:
code directing at least one computer to receive a scrambled downlink reference signal;
a code directing at least one computer to determine a pseudo-random sequence using at least a primary and secondary synchronization code; and
a code that instructs at least one computer to descramble a portion of the downlink reference signal in accordance with a pseudo-random sequence and a determined cyclic prefix length for one or more of the subframe portion. 25. The computer-readable medium of claim 24, further comprising a code instructing the at least one computer to determine a cyclic prefix length for one or more subframes of a portion of the downlink reference signal. 26. A method for transmitting a downlink reference signal in a wireless communication network, comprising the steps of:
forming a reference signal downlink containing primary and secondary synchronization codes;
scrambling the downlink reference signal based at least in part on a pseudo-random sequence corresponding to a combination of primary and secondary synchronization codes; and
transmit the scrambled downlink reference signal. 27. The method of claim 26, wherein the step of scrambling is performed on the part of the subframes of the downlink reference signal having a cyclic prefix length above a predetermined threshold value. 28. The method according to item 27, further comprising stages, in which:
scrambling a portion of the subframes of the reference signal having a cyclic prefix length less than or equal to a threshold value based at least in part on a pseudo-random sequence corresponding to a secondary synchronization code; and
apply the orthogonal sequence to the scrambled subframes of the reference signal having a cyclic prefix length less than or equal to a threshold value. 29. The method according to p, in which the pseudo-random sequence corresponds to the secondary synchronization code, and the primary synchronization code is the repetition factor for the pseudo-random sequence. 30. The method according to p, in which the combination of the primary and secondary synchronization code identifies the transmitter of the reference signal. 31. A wireless communication device for scrambling a reference signal downlink, comprising:
at least one processor configured to obtain a pseudo-random sequence related to the selected combination of the primary and secondary synchronization codes, and scramble the downlink reference signal using a pseudo-random sequence; and
a storage device connected to at least one processor. 32. The wireless communications apparatus of claim 31, wherein the at least one processor is further configured to transmit a scrambled downlink reference signal. 33. The wireless communications apparatus of claim 31, wherein the at least one processor scrambles a portion of the subframes of the downlink reference signal having a cyclic prefix length above a predetermined threshold. 34. The wireless communications apparatus of claim 33, wherein the at least one processor is further configured to:
scrambling a completely different part of the subframes of the reference signal having a cyclic prefix length less than a threshold value based at least in part on a completely different pseudo-random sequence corresponding to a secondary synchronization code; and
applying the orthogonal sequence to the unequal part of the subframes. 35. The wireless communications apparatus of claim 31, wherein the pseudo-random sequence corresponds to a secondary synchronization code, and the primary synchronization code is a repetition factor for the pseudo-random sequence. 36. The wireless communications apparatus of claim 31, wherein the combination of the primary and secondary synchronization code identifies the wireless communications apparatus. 37. A wireless communication device for scrambling reference signals downlink in a wireless communication network, comprising:
means for generating a downlink reference signal comprising primary and secondary synchronization codes; and
means for scrambling the downlink reference signal based at least in part on a pseudo-random sequence corresponding to a combination of primary and secondary synchronization codes. 38. The wireless communications apparatus of claim 37, further comprising means for transmitting the scrambled downlink reference signal. 39. The wireless communications apparatus of claim 37, wherein scrambling is performed on a portion of the subframes of the downlink reference signal having a cyclic prefix length above a predetermined threshold. 40. The wireless communications apparatus of claim 39, further comprising:
means for scrambling a portion of the subframes of the reference signal having a cyclic prefix length less than a threshold value based at least in part on a pseudo-random sequence corresponding to a secondary synchronization code; and
means for applying the orthogonal sequence to the scrambled subframes of the reference signal having a cyclic prefix length less than a threshold value. 41. The wireless communications apparatus of claim 37, wherein the pseudo-random sequence corresponds to a secondary synchronization code, and the primary synchronization code is a repetition factor for the pseudo-random sequence. 42. The wireless communications apparatus of claim 37, wherein the combination of the primary and secondary synchronization code identifies the reference signal transmitter. 43. A computer-readable medium containing codes stored on it which, when executed by a computer, instruct the computer to perform a method of transmitting a downlink reference signal in a wireless communication network, the codes comprising
a code directing at least one computer to generate a downlink reference signal comprising primary and secondary synchronization codes; and
a code directing at least one computer to scramble the downlink reference signal based at least in part on a pseudo-random sequence corresponding to a combination of primary and secondary synchronization codes. 44. The computer-readable medium of claim 43, further comprising a code instructing the at least one computer to transmit the scrambled downlink reference signal. 45. The computer-readable medium of claim 43, wherein scrambling is performed on a portion of the subframes of the downlink reference signal having a cyclic prefix length above a predetermined threshold value.

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