US007821913B2
`
`(12) United States Patent
`Malladi et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7,821,913 B2
`Oct. 26, 2010
`
`(54) METHOD AND APPARATUS FOR DATA AND
`PILOT STRUCTURES SUPPORTING
`EQUALIZATION
`(75) Inventors: Durga Prasad Malladi, San Diego, CA
`(US); Peter Gaal, San Diego, CA (US);
`Yongbin Wei, San Diego, CA (US)
`(73) Assignee: Qualcomm Incorporated, San Diego,
`CA (US)
`
`(*) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 1131 days.
`(21) Appl. No.: 11/388,535
`
`(22) Filed:
`(65)
`
`Mar 24, 2006
`Prior Publication Data
`US 2006/0221809 A1
`Oct. 5, 2006
`
`Related U.S. Application Data
`(60) Provisional application No. 60/666,333, filed on Mar.
`29, 2005.
`
`(51) Int. Cl.
`(2006.01)
`H4B 7/26
`(52) U.S. Cl. ....................................... 370/206; 370/350
`(58) Field of Classification Search ............... ... None
`See application file for complete search history.
`References Cited
`
`(56)
`
`U.S. PATENT DOCUMENTS
`6,304,611 B1 * 10/2001 Miyashita et al. ........... 375,260
`6,661,771 B1
`12/2003 Cupo et al.
`6,930,996 B2 * 8/2005 Rudolfetal. ............... 370/350
`6,993,068 B1
`1/2006 Isaksson et al.
`7,260,054 B2 * 8/2007 Olszewski .................. 370,208
`7,280,552 B2 10/2007 Isson
`
`7,411,894 B2 * 8/2008 Roet al. ..................... 370,203
`7,471,932 B2 * 12/2008 Wu et al. ...................... 455,91
`7,602,696 B2 * 10/2009 Rhodes ....................... 370,208
`
`WO
`
`FOREIGN PATENT DOCUMENTS
`2005/004428
`1, 2005
`
`OTHER PUBLICATIONS
`Tsumura et al. Design and Performance of Quasi-Synchronous
`Multi-Carrier CDMA System, IEEE, 5 pages, 2001.*
`3GPP TS 25.308 v5.2.0, High Speed Downlink Packet Access
`(HSDPA), 30 pages, 2002.*
`(Continued)
`Primary Examiner Frank Duong
`E" Agent, or Firm Rupit Patel; Larry J.
`OSKOW1UZ
`
`(57)
`
`ABSTRACT
`
`Techniques for transmitting data in a manner to facilitate
`equalization at a receiver are described. Guard intervals are
`appended to data blocks such that each data block has a guard
`interval at the beginning of the data block and a guard interval
`at the end of the data block. Each guard interval may be
`discontinuous transmission (DTX), a polyphase sequence, or
`Some other known sequence. Pilot is appended to each set of
`at least one data block. The data blocks, pilot, and guard
`intervals may be sent using various slot structures and are
`processed for transmission. The processing may include map
`ping the data blocks to at least one physical channel, chan
`nelizing the data blocks for each physical channel with a
`channelization code, combining all physical channels, and
`scrambling the combined data, pilot, and guard intervals with
`a scrambling code.
`
`26 Claims, 12 Drawing Sheets
`
`-1 Slot = 2560 Chips->
`500
`
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`
`
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`US 7821,913 B2
`Page 2
`
`OTHER PUBLICATIONS
`Yonghong Zeng et al. "Pilot Cyclic Prefixed Single Carrier Commu
`nication: Channel Estimation and Equalization.” IEEE Signal Pro
`cessing Letters IEEEUSA, Vol. 12, No. 1. Jan. 2005, pp. 56-59.
`Naofall Al-Dhahir et al. “A New Multicarrier Transceiver Based on
`the Discrete Cosine Transform.” IEEE Communications Society:
`Wireless Communications and Networking Conference, 2005 IEEE
`
`New Orleans, LA, USA Mar. 13-17, 2005, Piscataway, NJ, USA,
`IEEE, Mar. 13, 2005. pp. 45-50.
`International Search Report and Written Opinion—PCT/US2006/
`011668, International Search Authority—European Patent
`Office—Aug. 14, 2006.
`
`* cited by examiner
`
`
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`U.S. Patent
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`U.S. Patent
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`Sheet 4 of 12
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`US 7821,913 B2
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`Sheet 9 of 12
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`US 7821,913 B2
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`
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`US 7,821,913 B2
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`Sheet 11 of 12
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`US 7821,913 B2
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`U.S. Patent
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`Oct. 26, 2010
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`Sheet 12 of 12
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`US 7821,913 B2
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`
`
`1100
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`1200
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`Append guard intervals to data
`blockS Such that each data block
`has a guard interval at the beginning
`of the data block and a guard interval
`at the end of the data block
`
`Demultiplex received samples to
`obtain a first block of received
`samples for a known transmission
`and a Second block of received
`samples for a transmitted data block
`
`Append pilot to each set
`of at least one data block
`
`Derive a channel estimate based on
`the first block of received samples
`
`Process the data blocks, pilot,
`and guard intervals for transmission
`
`Perform equalization on the
`second block of received samples
`with the channel estimate
`
`FIG 11
`
`FIG, 12
`
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`US 7,821,913 B2
`
`1.
`METHOD AND APPARATUS FOR DATA AND
`PILOT STRUCTURES SUPPORTING
`EQUALIZATION
`
`I. CLAIM OF PRIORITY UNDER 35 U.S.C. S 119
`The present Application for Patent claims priority to Pro
`visional Application Ser. No. 60/666.333, entitled
`“METHOD ANDAPPARATUS FOR IMPROVEDEQUAL
`IZATION IN WIRELESS COMMUNICATIONS filed
`10
`Mar. 29, 2005, assigned to the assignee hereof, and expressly
`incorporated herein by reference.
`
`5
`
`BACKGROUND
`
`I. Field
`The present disclosure relates generally to communication,
`and more specifically to techniques for transmitting and
`receiving data in a wireless communication system.
`II. Background
`In a wireless communication system, a transmitter typi
`cally processes (e.g., encodes, interleaves, symbol maps,
`channelizes, and scrambles) traffic data to generate a
`sequence of chips. The transmitter then processes the chip
`sequence to generate a radio frequency (RF) signal and trans
`mits the RF signal via a wireless channel. The wireless chan
`nel distorts the transmitted RF signal with a channel response
`and further degrades the signal with noise and interference.
`A receiver receives the transmitted RF signal and processes
`the received RF signal to obtain samples. The receiver may
`perform equalization on the samples to obtain estimates of the
`chips sent by the transmitter. The receiver then processes
`(e.g., descrambles, dechannelizes, demodulates, deinter
`leaves, and decodes) the chip estimates to obtain decoded
`data. The equalization performed by the receiver typically has
`a large impact on the quality of the chip estimates as well as
`the reliability of the decoded data.
`There is therefore a need in the art for techniques to trans
`mit data in a manner to facilitate equalization at a receiver.
`
`15
`
`25
`
`30
`
`35
`
`SUMMARY
`
`40
`
`According to an embodiment of the invention, an apparatus
`is described which includes at least one processor and a
`memory. The processor(s) append guard intervals to data
`blocks such that each data block has a guard interval at the
`beginning of the data block and a guard interval at the end of
`the data block. Each guard interval may be discontinuous
`transmission (DTX), a polyphase sequence, or some other
`known sequence. The processor(s) then process the data
`blocks and the guard intervals for transmission.
`According to another embodiment, a method is provided in
`which guard intervals are appended to data blocks such that
`each data block has a guard interval at the beginning of the
`data block and a guard interval at the end of the data block.
`The data blocks and the guard intervals are then processed for
`transmission.
`According to yet another embodiment, an apparatus is
`described which includes means for appending guard inter
`vals to data blocks such that each data block has a guard
`interval at the beginning of the data block and a guard interval
`at the end of the data block, and means for processing the data
`blocks and the guard intervals for transmission.
`According to yet another embodiment, an apparatus is
`described which includes at least one processor and a
`memory. The processor(s) demultiplex received samples to
`obtain a first block of received samples for a known transmis
`
`45
`
`50
`
`55
`
`60
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`65
`
`2
`sion and a second block of received samples for a transmitted
`data block. Data blocks are transmitted such that each data
`block has a guard interval at the beginning of the data block
`and a guard interval at the end of the data block. The
`processor(s) then derive a channel estimate based on the first
`block of received samples and perform equalization on the
`second block of received samples with the channel estimate.
`According to yet another embodiment, a method is pro
`vided in which received samples are demultiplexed to obtain
`a first block of received samples for a known transmission and
`a second block of received samples for a transmitted data
`block, with data blocks being transmitted such that each data
`block has a guard interval at the beginning of the data block
`and a guard interval at the end of the data block. A channel
`estimate is derived based on the first block of received
`samples. Equalization is then performed on the second block
`of received samples with the channel estimate.
`According to yet another embodiment, an apparatus is
`described which includes means for demultiplexing received
`samples to obtain a first block of received samples for a
`known transmission and a second block of received samples
`for a transmitted data block, wherein data blocks are trans
`mitted Such that each data block has a guard interval at the
`beginning of the data block and a guard interval at the end of
`the data block. The apparatus further includes means for
`deriving a channel estimate based on the first block of
`received samples and means for performing equalization on
`the second block of received samples with the channel esti
`mate.
`Various aspects and embodiments of the invention are
`described in further detail below.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 shows a UMTS network.
`FIG. 2 shows an exemplary deployment of multiple carri
`CS.
`FIG. 3 shows a frame structure in W-CDMA.
`FIG. 4 shows a slot structure in W-CDMA Releases 5 and
`6.
`FIG. 5 shows a slot structure that supports equalization for
`the HS-PDSCHS.
`FIGS. 6A and 6B show additional slot structures that Sup
`port equalization.
`FIGS. 7A, 7B and 7C show additional slot structures for
`HSDPA
`FIG. 8 shows a block diagram of a transmitter and a
`receiver.
`FIGS. 9A and 9B show block diagrams of two embodi
`ments of a modulator.
`FIGS. 10A and 10B show block diagrams of two embodi
`ments of an equalizer.
`FIG. 11 shows a process for transmitting data and pilot.
`FIG. 12 shows a process for receiving data and pilot.
`
`DETAILED DESCRIPTION
`
`The word “exemplary' is used herein to mean “serving as
`an example, instance, or illustration. Any embodiment
`described herein as “exemplary' is not necessarily to be con
`Strued as preferred or advantageous over other embodiments.
`The techniques described herein may be used for various
`wireless communication systems such as Code Division Mul
`tiple Access (CDMA) systems, Time Division Multiple
`Access (TDMA) systems, and Frequency Division Multiple
`Access (FDMA) systems. The terms “system’’ and “network”
`are often used interchangeably. A CDMA network may
`
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`3
`implement a radio technology such as W-CDMA, cdma2000,
`and so on. cdma2000 covers IS-2000, IS-856 and IS-95 stan
`dards. ATDMA network may implement a radio technology
`such as Global System for Mobile Communications (GSM).
`These various radio technologies and standards are known in
`the art. W-CDMA and GSM are described in documents from
`an organization named "3rd Generation Partnership Project’
`(3GPP). cdma2000 is described in documents from an orga
`nization named "3rd Generation Partnership Project 2'
`(3GPP2). For clarity, the techniques are specifically
`described below for a UMTS network that utilizes W-CDMA,
`and UMTS terminology is used in much of the description
`below.
`FIG. 1 shows a UMTS network 100 with multiple Node Bs
`110 and multiple user equipments (UEs) 120. A Node B is
`generally a fixed station that communicates with the UEs and
`may also be referred to as a base station, an access point,
`and/or some other terminology. Each Node B 110 provides
`communication coverage for a particular geographic area
`102. UEs 120 are typically dispersed throughout the network,
`and each UE may be fixed or mobile. A UE may also be
`referred to as a mobile station, a user terminal, or some other
`terminology. A UE may be a cellular phone, a personal digital
`assistant (PDA), a wireless device, a handheld device, a wire
`less modem, and so on. The terms “UE' and “user are used
`interchangeably below. A UE may communicate with Zero,
`one, or multiple Node Bs on the downlink and/or uplinkatany
`given moment. The downlink (or forward link) refers to the
`communication link from the Node Bs to the UEs, and the
`uplink (or reverse link) refers to the communication link from
`the UEs to the Node Bs.A Radio Network Controller (RNC)
`130 couples to Node Bs 110 and provides coordination and
`control for the Node Bs.
`In W-CDMA, data to be transmitted to a UE is processed as
`one or more transport channels at a higher signaling layer. The
`transport channels may carry data for one or more services,
`e.g., voice, video, packet data, and so on. The transport chan
`nels are mapped to physical channels at a physical layer. The
`physical channels are channelized with different orthogonal
`variable spreading factor (OVSF) codes and are orthogonal to
`one another in code domain. The OVSF codes are also
`referred to as channelization codes.
`W-CDMA Release 5 and later supports High-Speed
`Downlink Packet Access (HSDPA), which is a set of channels
`and procedures that enables high-speed packet data transmis
`sion on the downlink. For HSDPA, data is processed in blocks
`that are multiplexed onto a High Speed Downlink Shared
`Channel (HS-DSCH), which is a transport channel. The HS
`DSCH may be mapped to one to more (up to 15) High Speed
`50
`Physical Downlink Shared Channels (HS-PDSCHs), which
`are physical channels. The HS-PDSCHs may carry data in a
`time and code division multiplexed (TDM/CDM) manner for
`multiple UEs. Control information for the HS-PDSCHs is
`sent on one or more Shared Control Channels for HS-DSCH
`(HS-SCCHs), which are physical channels. The control infor
`mation conveys various parameters used by the UEs to prop
`erly receive and process the HS-PDSCHs.
`UMTS network 100 may support one or more W-CDMA
`releases such as Release 99 (Rel-99), Release 5 (Rel-5),
`60
`Release 6 (Rel-6), and/or later releases. In the following
`description, Release X (Rel-X) is a release that is later than
`Release 6. Each release provides enhancements to prior
`releases.
`Release 5 introduces the following features:
`HSDPA for peak data rate of 14.4 megabits/second (Mbps)
`on the downlink,
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`4
`Space Time Transmit Diversity (STTD) and Closed Loop
`Transmit Diversity (CLTD) for downlink transmission
`from two antennas, and
`Transmission of dedicated pilot to specific UEs.
`Release 6 introduces the following features:
`Enhanced uplink with peak data rate of 4.1 Mbps,
`Mapping of DCCH to HS-DSCH to send signaling mes
`Sages, e.g., for handoff,
`Fractional Dedicated Physical Channel (F-DPCH) for
`sending transmit power command (TPC) and dedicated
`pilot to multiple UEs in a TDM manner, and
`Multimedia Broadcast Multicast Service (MBMS) for
`enhanced broadcast capability.
`Releases 5 and 6 are backward compatible with Release 99.
`Later releases may or may not be backward compatible with
`earlier releases.
`UMTS network 100 may operate on a single carrier or
`multiple carriers. Each carrier has a bandwidth of approxi
`mately 5 MHz and is centered at a specific frequency. Mul
`tiple carriers may be used to improve capacity.
`FIG. 2 shows an exemplary deployment 200 of multiple
`carriers. In general, any number of carriers may be deployed
`for multi-carrier W-CDMA (MC-WCDMA). In the embodi
`ment shown in FIG. 2, one carrier is designated as an anchor
`carrier that Supports Release 5. The remaining carriers are
`designated as auxiliary carriers. Each auxiliary carrier may
`support Release 5, Release 6, and/or Release X. The anchor
`carrier may carry common channels that Support system
`acquisition, access, paging, broadcast, and so on. These com
`mon channels may include the following:
`Synchronization Channel (SCH)—carry timing and infor
`mation for acquisition,
`Channel
`Physical
`Primary Common Control
`(P-CCPCH)—carry system and access parameters,
`Secondary CCPCH (S-CCPCH)—carry page messages
`and other UE directed signaling messages while the UE
`is in idle mode,
`Acquisition Indicator Channel (AICH)—carry responses
`for access probes,
`Page Indicator Channel (PICH)—carry paging indicators
`for page messages, and
`MBMS Indicator Channel (MICH)—carry indicators for
`MBMS messages.
`For the multi-carrier structure shown in FIG. 2, a UE may
`initially tune to the anchor carrier when first powered on. The
`UE may acquire system timing based on the SCH, decode the
`P-CCPCH to obtain system and access parameters, send
`access probes on a Physical Random Access Channel
`(PRACH), and wait for a response on the AICH. The UE may
`then perform registration and setup with the UMTS network
`and may thereafter enter a CELL DCH state. In the
`CELL DCH state, the UE is assigned a Dedicated Channel
`(DCH) and may send and/or receive data. The UE may remain
`on the anchor carrier to communicate with the network. The
`UE may also be handed off to an auxiliary carrier. The UE
`may receive and/or transmit data via multiple carriers to
`improve throughput.
`Each auxiliary carrier may or may not carry the common
`channels listed above. To reduce overhead, the network may
`send the common channels on only the anchor carrier. In this
`case, a UE may tune to the anchor carrier for system access as
`well as while in an Idle mode. The UE may be handed off to
`one or more auxiliary carriers in the CELL DCH state. The
`LE may make inter-frequency measurements and report the
`measurements to the network. The network may direct the UE
`to a suitable carrier based on the measurements.
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`US 7,821,913 B2
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`FIG. 3 shows a frame structure 300 in W-CDMA. The
`timeline for transmission on the downlink is divided into
`radio frames. Each radio frame is identified by a 12-bit system
`frame number (SFN) that is transmitted on a control channel.
`Each radio frame has a duration of 10 milliseconds (ms) and
`is further partitioned into 15 slots, which are labeled as slot 0
`through slot 14. Each slot includes 2560 chips and has a
`duration of 0.667 ms. Each chip has a duration of 260.42
`nanoseconds (ins) for a chip rate of 3.84 megachips/second
`(Mcps).
`Up to 15 HS-PDSCHs may be sent on each carrier for
`HSDPA. The HS-PDSCHS are sent in transmission time inter
`vals (TTIs), which are also called sub-frames. Each TTI spans
`three slots and has a duration of 2 ms. A new TTI for the
`HS-PDSCHs starts at the frame boundary. The HS-PDSCHs
`are assigned channelization codes with spreading factor of
`16. For the HS-PDSCHs, each slot spans 160 symbol periods,
`and each symbol period includes 16 chips. A data symbol may
`be sent in each symbol period and is channelized or spread
`with a 16-chip channelization code to generate 16 data chips
`that are sent in 16 chip periods. As used herein, a data symbol
`is a symbol for data, a pilot symbol is a symbol for pilot, a
`signaling symbol is a symbol for signaling, and a symbol is
`generally a complex value. A symbol may be a modulation
`symbol for a modulation scheme, e.g., M-PSK or M-QAM. A
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`pilot is a transmission that is known a priori by both a trans
`mitter and a receiver.
`FIG. 4 shows a slot structure 400 for some downlink physi
`cal channels in Releases 5 and 6. A slot structure may also be
`referred to as a slot format, a data and pilot structure, and so
`on. A Primary Common Pilot Channel (P-CPICH) carries 10
`pilot symbols per slot and is spread with channelization code
`Casco. In general, channelization code C is the k-th
`code of length K in the OVSF code tree, where K may be any
`power of two, e.g., 16, 128, or 256. The P-CCPCH carries 10
`signaling symbols per slot and is spread with channelization
`code Case. In Releases 5 and 6, up to 15 HS-PDSCHs may
`be sent for HSDPA using channelization codes Co.
`through Cels. The HS-PDSCHs used in Releases 5 and 6
`are referred to herein as Rel-5 HS-PDSCHS. Each Rel-5
`HS-PDSCH carries up to 160 data symbols per slot and is
`spread with a different 16-chip channelization code. In
`Release 6, an F-DPCH may be sent using a 256-chip chan
`nelization code C.2s, which may be selected by a Node B
`and signaled to the UEs. The F-DPCH may carry up to 10
`symbols for TPC and/or dedicated pilot for specific UEs.
`It is desirable to perform equalization at a UE to achieve
`good performance. Equalization is particularly important at
`high data rates, such as the data rates envisaged in multi
`carrier HSDPA (MC-HSDPA). In general, equalization may
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`be performed in the time domain or the frequency domain. A
`time-domain equalizer with a large number of taps may be
`used to achieve good performance. Time-domain equaliza
`tion may be complex since the taps are derived jointly and a
`large matrix inversion may be required. A frequency-domain
`equalizer with a large number of coefficients may also be used
`to achieve good performance. However, frequency-domain
`equalization may be simpler since the coefficients may be
`derived separately for each frequency tone orbin. Hence, it is
`desirable to have slot structures that Support frequency-do
`main equalization.
`To facilitate frequency-domain equalization at a receiver, a
`transmitter may insert guard intervals between data blocks
`prior to transmission. The guard interval at the beginning of a
`data block is referred to as a prefix, and the guard interval at
`the end of the data block is referred to as a suffix. The prefix
`should be equal to the suffix for each data block. This cyclic
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`property converts a linear convolution with a wireless channel
`to a circular convolution, if the prefix and suffix are suffi
`ciently long. The cyclic property combats inter-symbol inter
`ferences (ISI) and allows the receiver to perform a fast Fourier
`transform (FFT) on each received data block to obtain fre
`quency-domain symbols. The receiver may then perform
`equalization on these symbols in the frequency domain, as
`described below.
`FIG. 5 shows an embodiment of a slot structure 500 that
`supports equalization for the HS-PDSCHs and is backward
`compatible with Releases 5 and 6. In this embodiment, the
`P-CPICH may be sent with channelization code Cisco and
`the P-CCPCH may be sent with channelization code Case,
`as described above for FIG. 4.
`Up to 15 new HS-PDSCHs may be sent for HSDPA using
`channelization codes Co., through Colis. These new
`HS-PDSCHS are referred to herein as Rel-X HS-PDSCHS. In
`the embodiment shown in FIG. 5, a slot for a Rel-X HS
`PDSCH includes aguard field 512, a TDM pilot (P) field 514,
`a guard field 516, a first data field 518, a guard field 520, and
`a second data field 522. Each guard field provides a guard
`interval between two transmissions, e.g., between two data
`blocks or between a data block and pilot. In the embodiment
`shown in FIG. 5, each guard field is DTX, which comprises
`Zero signal values that are essentially not transmitted. Pilot
`field 514 carries pilot symbols that may be used for channel
`estimation. Each of data fields 518 and 522 may carry a data
`block that may include any number of data symbols.
`In general, each field of the Rel-X HS-PDSCHS may have
`any suitably selected duration. Each guard field may be used
`as a prefix for one data block and/or as a suffix for another data
`block. The duration of each guard field may be selected to be
`equal to or longer than an effective delay spread, which is the
`Sum of the channel delay spread and the time extent of a
`Root-Raised-Cosine (RRC) autocorrelation. The channel
`delay spread is the expected difference between the earliest
`and latest arriving signal paths at a receiver. The RRC auto
`correlation is the correlation between an RRC pulse shaping
`filter at a transmitter and a matched filter at a receiver. A
`sufficiently long guard field reduces ISI.
`Multiple Rel-5 and/or Rel-X HS-PDSCHs may be sent
`simultaneously using different channelization codes. In this
`case, each field of the Rel-X HS-PDSCHs may be selected to
`be an integer multiple of the channelization code length for
`the HS-PDSCHs, or 16L, where L21. This constraint main
`tains orthogonality among the HS-PDSCHs being sent simul
`taneously. In a specific embodiment, each guard field spans
`48 chips, the pilot field spans 80 chips, the first data field
`spans 2000 chips, and the second data field spans 336 chips.
`This embodiment allows the receiver to perform a 2048-point
`FFT for the data block sent in data field 518 and a 512-point
`FFT for the data block sent in data field 522. In this embodi
`ment, the overhead for the TDM pilot and the guard intervals
`is 8.75%. The fields of the Rel-X HS-PDSCHs may also have
`other durations.
`In an embodiment, the data fields of each Rel-X HS-PD
`SCH are channelized with the channelization code for that
`HS-PDSCH. In an embodiment, the TDM pilot of each Rel-X
`HS-PDSCH is sent with channelization code Casco. In this
`embodiment, the same TDM pilot is sent on all Rel-X HS
`PDSCHs as well as the P-CPICH, which reduces interference
`on the TDM pilot and allows a receiver to derive a more
`accurate channel estimate. The TDM pilot may be any
`sequence having good temporal and spectral characteristics,
`e.g., a polyphase sequence described below.
`The Rel-X HS-PDSCH slot structure shown in FIG. 5 has
`various desirable features. First, a prefix and a suffix are
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`provided for each data block, which allows a receiver to
`perform accurate frequency domain processing for each data
`block. In particular, guard field 516 is the prefix and guard
`field 520 is the Suffix for the data block sent in data field 518.
`Guard field 520 is also the prefix for the data block sent in data
`field 522, and guard field 516 in the next slot is the suffix for
`this data block. Thus, guard fields 516 and 520 are each
`efficiently used as a prefix for one data block and as a suffix
`for another data block. Guard field 512 isolates the TDM pilot
`sent in pilot field 514 from the data block sent in data field 522
`of a preceding slot.
`Guard filed 512 creates a cyclic structure for the pilot sent
`in field 514. This cyclic structure enables frequency domain
`processing of the pilot for channel estimation purposes inde
`pendent of the processing mode for the data sent in field 522.
`In one use of the pilot, channel estimation is achieved before
`equalization by processing pilot field 514. To enable this use,
`guard field 512 should have a length comparable to that of
`guard fields 516 and 520. In another use of the pilot, a residual
`channel estimate may be obtained by processing pilot field
`514 after equalization. The residual channel includes the
`compound effects of the wireless channel and the equalizer.
`Since the residual channel typically has a shorter delay spread
`than the wireless channel itself, to enable this use, guard field
`512 may be of shorter length than guard fields 516 and 520. In
`the exemplary embodiment shown in FIG. 5, guard field 512
`is of the same length as guard fields 516 and 520 and hence
`supports both uses of pilot field 514.
`The use of DTX for the guard fields preserves the cyclic
`property for each data block in the presence of scrambling. In
`W-CDMA, a Node B channelizes the data for each physical
`channel with the assigned channelization code, sums the
`channelized data for all physical channels, and Scrambles the
`Summed data with a scrambling code to generate output
`chips. If the prefix and Suffix for a given data block are equal
`but non-zero, then the scrambling would result in the prefix
`being different from the suffix because the portion of the
`scrambling code applied to the prefix is likely not equal to the
`portion of the scrambling code applied to the suffix. A
`receiver performs equalization first, followed by descram
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`bling. Thus, if the prefix and suffix are non-zero, then the
`scrambling would destroy the cyclic property for the data
`block since the prefix is no longer equal to the suffix when the
`equalization is performed, which would then degrade perfor
`mance. The use of DTX for the prefix and suffix preserves the
`cyclic property at the time of equalization, which is desirable.
`Since all of the physical channels are combined and then
`scrambled, it is desirable to have no transmissions from other
`physical channels during the guard intervals in the Rel-X
`HS-PDSCHs. For the F-DPCH, DTX may be sent in the first
`and ninth symbol periods that overlap the guard intervals of
`the Rel-X HS-PDSCHs, as shown in FIG. 5. TPC and dedi
`cated pilot for up to four UEs may be sent in a TDM manner
`on the F-DPCH in the remaining eight symbol periods, as
`shown in FIG. 5. The F-DPCH is orthogonal to the Rel-X
`HS-PDSCHs during most of the data portions because of the
`code division multiplexing.
`A Node B may support both Rel-5/6 users as well as Rel-X
`users. R