@WILEY
`
`LTE for UMTS
`Evolution to
`LTE-Advanced
`
`SECOND EDITION
`
`--
`
`.. ~·· · -~··_..: : ~ -
`"-:..,_ -.. · : -. -
`
`! ~.~ . . 1(
`I~
`'
`.,- ~
`
`Samsung Ex. 1013
`
`

`

`LTE for UMTS
`Evolution to LTE-Advanced
`Second Edition
`
`Edited by
`
`Harri Holma and Antti Toskala
`Nokia Siemens Networks, Finland
`
`~WILEY
`
`A John Wiley and Sons, Ltd., Publication
`
`Samsung Ex. 1013
`
`

`

`This edition first published 2011
`© 2011 John Wiley & Sons, Ltd
`
`Registered office
`John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, United Kingdom
`
`For details of our global editorial offices, for customer services and for information about how to apply for
`permission to reuse the copyright material in this book please see our website at www.wiley.com.
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`
`All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in
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`
`Library of Congress Cataloging-in-Publication Data
`
`LTE for UMTS : Evolution to LTE-Advanced / edited by Harri Holma, Antti Toskala. - Second Edition.
`p. cm
`Includes bibliographical references and index.
`ISBN 978-0-470-66000-3 (hardback)
`I. Universal Mobile Telecommunications System. 2. Wireless communication systems - Standards. 3. Mobile
`communication systems - Standards. 4. Global system for mobile communications. 5. Long-Term Evolution
`(Telecommunications) I. Holma, Harri (Harri Kalevi), 1970-11. Toskala, Antti. ill. Title: Long Term Evolution for
`Universal Mobile Telecommunications Systems.
`TK5103.4883.L78 201 I
`621.3845' 6 - dc22
`
`2010050375
`
`A catalogue record for this book is available from the British Library.
`
`Print ISBN: 9780470660003 (H/B)
`ePDF ISBN: 9781119992950
`oBook ISBN: 9781119992943
`ePub ISBN: 9781119992936
`
`Typeset in 10/12 Times by Laserwords Private Limited, Chennai, India.
`
`Samsung Ex. 1013
`
`

`

`5 P
`
`hysical Layer
`
`Antti Toskala, Timo Lunttila, Esa Tiirola, Kari Hooli, Mieszko Chmiel
`and Juha Korhonen
`
`5.1 Introduction
`This chapter describes the physical layer of LTE, based on the use of OFDMA and
`SC-FDMA principles as covered in Chapter 4. The LTE physical layer is characterized by
`the design principle of not reserving dedicated resources for a single user; resource usage
`is based solely on dynamically allocated shared resources. This is analogous to resource
`usage in the internet, which is packet based without user-specific resource allocation.
`The physical layer of a radio access system has a key role of defining the resulting
`capacity and ends up being a focal point when comparing different systems in terms
`of expected performance. However, a competitive system requires an efficient protocol
`layer to ensure good performance all the way to the application layer and to the end
`user. The flat architecture adopted, covered in Chapter 3, also enables the dynamic nature
`of the radio interface as all radio resource control is located close to the radio in the
`base-station site. The 3GPP term for the base station used in rest of this chapter will be
`‘eNodeB’ (similar to the WCDMA BTS term, which is ‘Node B’, where ‘e’ stands for
`‘evolved’). This chapter first covers the physical channel structures and then introduces the
`channel coding and physical layer procedures. The chapter concludes with a description
`of physical layer measurements and device capabilities as well as with a brief look at
`physical layer parameter configuration aspects. In 3GPP specifications the physical layer
`was covered in the 36.2 series, with the four key physical layer specifications being [1–4].
`Many of the issues in this chapter apply to both FDD and TDD, but in some areas TDD
`receives special solutions due to the frame being divided between uplink and downlink.
`The resulting differences needed for a TDD implementation are covered in Chapter 15.
`
`5.2 Transport Channels and their Mapping
`to the Physical Channels
`By the nature of the design already discussed, the LTE contains only common transport
`channels; a dedicated transport channel (Dedicated Channel, DCH, as in WCDMA) does
`
`LTE for UMTS: Evolution to LTE-Advanced, Second Edition. Edited by Harri Holma and Antti Toskala.
`© 2011 John Wiley & Sons, Ltd. Published 2011 by John Wiley & Sons, Ltd. ISBN: 978-0-470-66000-3
`
`Samsung Ex. 1013
`
`

`

`84
`
`LTE for UMTS: Evolution to LTE-Advanced
`
`not exist. The transport channels are the ‘interface’ between the MAC layer and the
`physical layer. In each transport channel, the related physical layer processing is applied
`to the corresponding physical channels used to carry the transport channel in question. The
`physical layer is required to have the ability to provide dynamic resource assignment both
`in terms of data-rate variance and in terms of resource division between different users.
`This section presents the transport channels and their mapping to the physical channels.
`• The Broadcast Channel (BCH) is a downlink broadcast channel that is used to broad-
`cast the necessary system parameters to enable devices accessing the system. Such
`parameters include, for example, the cell’s bandwidth, the number of transmit antenna
`ports, the System Frame Number and PHICH-related configuration.
`• The Downlink Shared Channel (DL-SCH) carries the user data for point-to-point con-
`nections in the downlink direction. All the information (either user data or higher layer
`control information) intended for only one user or UE is transmitted on the DL-SCH,
`assuming the UE is already in the RRC_CONNECTED state. However, as in LTE, the
`role of BCH is mainly to inform the device of the scheduling of the system information.
`Control information intended for multiple devices is also carried on DL-SCH. In case
`data on DL-SCH are only intended for a single UE, then dynamic link adaptation and
`physical layer retransmissions can be used.
`• The Paging Channel (PCH) is used to carry paging information for the device in
`the downlink direction in order to move the device from the RRC_IDLE state to the
`RRC_CONNECTED state.
`• The Multicast Channel (MCH) is used to transfer multicast service content to the UEs
`in the downlink direction. 3GPP decided to provide full support in Release 9 (for
`shared carrier case).
`• The Uplink Shared Channel (UL-SCH) carries the user data as well as device-originated
`control information in the uplink direction in the RRC_CONNECTED state. As with
`the DL-SCH, dynamic link adaptation and retransmissions are available.
`• The Random Access Channel (RACH) is used in the uplink to respond to the paging
`message or to initiate the move from the RRC_CONNECTED state due to UE data
`transmission needs. There is no higher layer data or user data transmitted on RACH
`(as can be done with WCDMA) but it is used to enable UL-SCH transmission where,
`for example, actual connection set up with authentication and so forth will take place.
`
`In the uplink direction the UL-SCH is carried by the Physical Uplink Shared Channel
`(PUSCH). The RACH is carried by the Physical Random Access Channel (PRACH).
`Additional physical channels exist but these are used only for physical layer control
`information transfer as covered in section 5.6 on control information. Transport channel
`mapping is illustrated in Figure 5.1.
`In the downlink direction, the PCH is mapped to the Physical Downlink Shared Channel
`(PDSCH). The BCH is mapped to Physical Broadcast Channel (PBCH) but, as is shown
`
`MAC
`
`L1
`
`RACH
`
`l
`
`PRACH
`
`UL-SCH
`
`l
`
`PUSCH
`
`Figure 5.1 Mapping of the uplink transport channels to the physical channels
`
`Samsung Ex. 1013
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`

`Physical Layer
`
`85
`
`MAC
`
`L1
`
`BCH
`
`PCH
`
`PBCH
`
`! -------- !
`
`DL-SCH
`
`PDSCH
`
`MCH
`
`!
`
`PMCH
`
`Figure 5.2 Mapping of the downlink transport channels to the physical channels
`
`in Chapter 6 for the mapping of logical channels to transport channels, only part of the
`broadcast parameters is on BCH while the actual System Information Blocks (SIBs) are
`then on DL-SCH. The DL-SCH is mapped to the PDSCH and MCH is mapped to Physical
`Multicast Channel, as shown in Figure 5.2.
`
`5.3 Modulation
`In the uplink direction, modulation is carried out through a more traditional QAM mod-
`ulator, as was explained in Chapter 4. The modulation methods available (for user data)
`are QPSK, 16QAM and 64QAM. The first two are available in all devices while support
`for 64QAM in the uplink direction is a UE capability, as covered in section 5.10. The
`different constellations are shown in Figure 5.3
`PRACH modulation is phase modulation as the sequences used are generated
`from Zadoff–Chu sequences with phase differences between different symbols of the
`sequences – see section 5.7 for further details. Depending on the sequence chosen, the
`resulting Peak-to-Average Ratio (PAR) or the more practical Cubic Metric (CM) value
`is somewhat above or below the QPSK value. In the uplink direction the signal cubic
`metric (CM) was discussed in Chapter 4 with SC-FDMA.
`The use of QPSK modulation allows good transmitter power efficiency when operating
`at full transmission power, as modulation determines the resulting CM (in case of SC-
`FDMA) and thus also the required device amplifier back-off. Devices will use lower
`maximum transmitter power when operating with 16QAM or 64QAM modulation. The
`actual Maximum Power Reduction (MPR) also depends on the bandwidth (number of
`physical resource blocks used) and in some cases frequency-band-specific Additional
`MPR (A-MPR) should be applied as instructed by the network to deal with specific
`emission limits in some regions and countries.
`In the downlink direction the modulation methods for user data are the same as in
`the uplink direction. In theory an OFDM system could use different modulation for
`
`QPSK
`2 bits/symbol
`
`•
`
`•
`
`•
`
`•
`
`16QAM
`4 bits/symbol
`
`• • • •
`• • • •
`• • • •
`• • • •
`
`64QAM
`6 bits/symbol
`
`••• • ••• •
`••• • ••• •
`••• • ••• •
`•••• • •••
`••• • ••• •
`••• • ••• •
`••• • ••• •
`••• • ••• •
`
`Figure 5.3 LTE modulation constellations
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`

`86
`
`LTE for UMTS: Evolution to LTE-Advanced
`
`each sub-carrier. But to have channel quality information (and signaling) with such a
`granularity would not be feasible due to the resulting excessive overhead. If modulation
`was sub-carrier specific, one would have too many bits both in the downlink for
`informing the receiver of parameters for each sub-carrier and in the uplink the CQI
`feedback that would be needed in order to achieve sub-carrier level granularity in the
`adaptation would be too detailed.
`Moreover, BPSK has been specified for control channels, which use either BPSK or
`QPSK for control information transmission. In a control channel, the modulation cannot
`be freely adapted because one needs to be able to receive it and a single signaling
`error must not prevent the detection of later control channel messages. This is similar
`to HSDPA/HSUPA where control channels have fixed parameterization to prevent error
`propagation due to frame-loss events. The exception is the uplink control data when
`multiplexed together with the user data. Here modulation for data and control is the
`same, even if 16QAM or 64QAM are utilized. This allows the multiplexing rules to be
`kept simpler.
`
`5.4 Uplink User Data Transmission
`The user data in the uplink direction is carried on the PUSCH. The PUSCH has the 10 ms
`frame structure and is based on the allocation of time and frequency domain resources
`with 1 ms and 180 kHz resolution. The resource allocation is coming from a scheduler
`located in the eNodeB, as illustrated in Figure 5.4. Thus there are no fixed resources for the
`devices; without prior signaling from the eNodeB only random access resources may be
`utilized. For this purpose the device needs to provide information for the uplink scheduler
`about its transmission needs (buffer status) as well as the available transmission power
`resources. This signaling is MAC layer signaling and is covered in detail in Chapter 6.
`The frame structure adopts the 0.5 ms slot structure and uses the two-slot (one sub-
`frame) allocation period. The shorter 0.5 ms allocation period (as initially planned in 3GPP
`to minimize the round trip time) would have been too signaling intensive, especially with
`
`UE 1 Transmitter
`
`~------- ~ - ~:=-~
`
`Uplink Control
`
`frequency
`
`eNodeB with scheduler
`Transmissions at
`eNodeB Receiver
`
`UE 2 Transmitter
`
`-
`
`frequency
`
`frequency
`
`Figure 5.4 Uplink resource allocation controlled by eNodeB scheduler
`
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`

`Physical Layer
`
`87
`
`1 ms sub-frame
`
`0.5 ms slot
`
`0
`
`1
`
`…
`
`18
`
`19
`
`10 ms frame
`
`Figure 5.5 LTE FDD frame structure
`
`a large number of users. The 10 ms frame structure is illustrated in Figure 5.5. The frame
`structure is basically valid for both for FDD and TDD, but TDD mode has additional
`fields for the uplink/downlink transition point(s) in the frame as covered in Chapter 15.
`Within the 0.5 ms slot there are both reference symbols and user data symbols, in addi-
`tion to the signaling, which is covered later. The momentary user data rate thus varies as a
`function of uplink resource allocation depending on the allocated momentary bandwidth.
`The allocation bandwidth may be between 0 and 20 MHz in steps of 180 kHz. The allo-
`cation is continuous, as uplink transmission is FDMA modulated with only one symbol
`being transmitted at the time. The slot bandwidth adjustment between consecutive TTIs is
`illustrated in Figure 5.6, where doubling the data rate results in double bandwidth being
`used. The reference symbols always occupy the same space in the time domain and thus
`a higher data rate results in a corresponding increase for the reference symbol data rate.
`The cyclic prefix used in the uplink has two possible values depending on whether a
`short or extended cyclic prefix is applied. Other parameters stay unchanged and thus the
`0.5 ms slot can accommodate either six or seven symbols as indicated in Figure 5.7. The
`data payload is reduced if an extended cyclic prefix is used, but in reality it is not going
`to be used too frequently as, in the majority of cases, the performance benefit in having
`seven symbols is far greater than possible degradation from the inter-symbol interference
`due to channel delay that is longer than the cyclic prefix.
`The resulting instantaneous uplink data rate over a 1 ms sub-frame is a function of
`the modulation, the number of resource blocks allocated and the amount of control
`information overhead as well as the rate of channel coding applied. The instantaneous
`
`----
`
` …
`
`Bandwidth
`
`1 ms sub-frame
`
`Reference Symbols
`
`Symbol duration
`
`~ /
`d
`
`Double
`data rate
`
`Figure 5.6 Data rate between TTIs in the uplink direction
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`

`88
`
`LTE for UMTS: Evolution to LTE-Advanced
`
`IIIIIIIHIIHII
`
`Symbol 66.68 μs
`
`5.21 μs
`
`Short cyclic prefix
`
`1 H H IOI H H ----------11 ~ - - ;~_ I
`~ ------Ir--I~ 1
`
`0.5 ms slot
`
`16.67 μs
`
`Extended cyclic prefix
`
`Figure 5.7 Uplink slot structure with short and extended cyclic prefix
`
`layer resources, is
`uplink peak data rate range, when calculated from the physical
`between 700 kbps and 86 Mbps There is no multi-antenna uplink transmission, specified
`in Release 8, because using more than one transmitter branch in a UE is not seen as
`particularly attractive from the cost and complexity perspective. The instantaneous data
`rate for one UE in the LTE depends on:
`• Modulation method applied, with 2, 4 or 6 bits per modulation symbol depending on
`the modulation order for QPSK, 16QAM and 64QAM respectively.
`• Bandwidth applied. The momentary bandwidth may, of course, vary between the min-
`imum allocation of 12 sub-carriers (one resource block of 180 kHz) and the system
`bandwidth, up to 1200 sub-carriers with 20 MHz bandwidth.
`• Channel coding rate applied.
`• The average data rate, then, also depends on the time domain resource allocation.
`The cell or sector-specific maximum total data throughput can be increased with
`the Virtual Multiple Input Multiple Output (V-MIMO). In V-MIMO the eNodeB will
`treat transmission from two different UEs (with single transmit antenna each) as one
`MIMO transmission and separate the data streams from each other based on the UE
`specific uplink reference symbol sequences. Thus V-MIMO does not contribute to
`the single user maximum data rate. The maximum data rates, taking into account the
`UE categories, are presented in section 5.10, while the maximum data rates for each
`bandwidth are covered in Chapter 13.
`The channel coding chosen for LTE user data was turbo coding. The encoder is parallel
`concatenated convolution coding (PCCC)-type turbo encoder, exactly the same as is
`being used in WCDMA/HSPA, as explained in [5]. The turbo interleaver was modified
`compared to that of WCDMA, to fit better LTE properties and slot structures and also
`to allow more flexibility for implementation in terms of parallel signal processing with
`increased data rates.
`The LTE also uses physical layer retransmission combination, often referred to as
`Hybrid Automatic Repeat Request (HARQ). In physical layer HARQ operations the
`receiver stores the packets with failed CRC checks and combines the received packet
`when a retransmission is received. Both soft combining, with identical retransmissions,
`and combining with incremental redundancy are facilitated.
`The channel coding chain for the uplink is shown in Figure 5.8, where the data and
`control information are separately coded and then mapped to separate symbols for trans-
`mission. As the control information has specific locations around the reference symbols,
`the physical layer control information is separately coded and placed in a predefined set
`of modulation symbols (but with the same modulation as data transmitted together). Thus
`
`Samsung Ex. 1013
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`

`Physical Layer
`
`89
`
`CRC Attachment
`
`Data
`
`Code Block
`Segmentation and
`CRC Attachment
`
`Channel Coding
`
`Rate Matching
`
`Code Block
`Concatenation
`
`Control
`
`Channel Coding
`
`Data and Control
`Multiplexing
`
`Channel
`Interleaver
`
`Figure 5.8 PUSCH channel coding chain
`
`the channel interleaver in Figure 5.8 does not refer to true joint interleaving between
`control and data.
`The data and control information are time multiplexed at the resource element level.
`Control is not evenly distributed but is intended to be either closest for the reference
`symbols in time domain or then filled in the top rows of Figure 5.9, depending on the
`type of control information, as covered in section 5.6. Data are modulated independently
`of control information, but modulation during the 1 ms TTI is the same.
`
`Modulation
`symbols for
`data
`
`Sub-carriers
`
`Modulation
`symbols for
`control
`
`Reference signals
`" ~-
`~ -
`
`Control information elements
`
`Resource elements
`
`,L----
`
`>-
`
`Resource Block
`
`Time domain
`signal generation
`
`_,)
`
`Reference signals
`
`\ 111 I 111
`
`~
`0.5 ms slot
`
`l l
`
`Control information elements
`(Only part of the resource elements)
`
`Figure 5.9 Multiplexing of uplink control and data
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`

`

`90
`
`LTE for UMTS: Evolution to LTE-Advanced
`
`5.5 Downlink User Data Transmission
`The user data rate in the downlink direction is carried on the Physical Downlink Shared
`Channel (PDSCH). The same 1 ms resource allocation is valid in the downlink direction
`as well and the sub-carriers are allocated in resource units of 12 sub-carriers, resulting
`in 180 kHz allocation units (physical resource blocks, PRBs). In the case of PDSCH,
`however, the multiple access is OFDMA, so each sub-carrier is transmitted as a parallel
`15 kHz sub-carrier and thus the user data rate is dependent on the number of allocated sub-
`carriers (or resource blocks in practice) for a given user. The eNodeB does the resource
`allocation based on the Channel Quality Indicator (CQI) from the terminal. As with the
`uplink, the resources are allocated both in the time and the frequency domain, as illustrated
`in Figure 5.10.
`The Physical Downlink Control Channel (PDCCH) informs the device about which
`resource blocks are allocated to it dynamically with 1 ms allocation granularity. The
`PDSCH data occupy between three and seven symbols per 0.5 ms slot depending on the
`allocation for PDCCH and depending on whether a short or extended cyclic prefix is
`used. Within the 1 ms sub-frame, only the first 0.5 ms slot contains PDCCH; the second
`0.5 ms slot is purely for data (for PDSCH). For an extended cyclic prefix, six symbols
`are accommodated in the 0.5 ms slot, while a short cyclic prefix can fit seven symbols,
`as shown in Figure 5.11. The example in Figure 5.11 assumes three symbols for PDCCH
`but that can vary between one and three. With the smallest bandwidth of 1.4 MHz, the
`number of PDCCH symbols varies between two and four to enable sufficient signaling
`capacity and enough bits to allow good enough channel coding for range-critical cases.
`In addition to the control symbols for PDCCH, space from the user data is reduced
`due to the reference signals, synchronization signals and broadcast data. As discussed
`in Chapter 4, due to the channel estimation it is beneficial when the reference symbols
`are distributed evenly in the time and frequency domains. This reduces the overhead
`needed, but requires some rules to be defined so that receiver and transmitter understand
`the resource mapping in similar manner. From the total resource allocation space over
`
`CQI with Frequency
`Domain Info
`
`k T X
`
`D o w n li n
`
`Frequency
`
`…
`
`UE 1
`
`TTI n + 1
`
`TTI n
`
`…
`
`UE 2 Data
`
`UE 1 Data
`
`CQI
`
`UE 2
`
`UE 1 Data
`
`UE 2 Data
`
`Figure 5.10 Downlink resource allocation at eNodeB
`
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`

`Physical Layer
`
`91
`
`10 ms Radio Frame
`
`1 ms Downlink Sub-frame
`
`0
`
`1
`
`2
`
`3
`
`17
`
`18
`
`19
`
`…
`
`Control Symbols Data Symbols
`
`Data Symbols
`
`Sub-
`carriers
`
`1st 0.5 ms Slot
`
`2nd 0.5 ms Slot
`
`Figure 5.11 Downlink slot structure for bandwidths above 1.4 MHz
`
`Reference
`Signals
`
`PDCCH
`
`PDSCH
`
`Sub-carriers
`
`Figure 5.12 Example of downlink resource sharing between PDCCH and PDSCH
`
`Symbols
`
`the whole carrier one needs to account for common channels, such as the Physical
`Broadcast Channel, which consume their own resource space. Figure 5.12 presents an
`example of PDCCH and PDSCH resource allocation.
`The channel coding for user data in the downlink direction was also 1/3 mother rate
`turbo coding, as in the uplink direction. The maximum code block size for turbo coding is
`limited to 6144 bits to reduce the processing burden; higher allocations are then segmented
`to multiple code blocks. Higher block sizes would not add anything to performance as
`the turbo encoder performance improvement effect for big block sizes is saturated much
`earlier. In addition to turbo coding, the downlink uses physical layer HARQ with the same
`combining methods as in the uplink direction. The device categories reflect the amount
`
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`

`92
`
`LTE for UMTS: Evolution to LTE-Advanced
`
`DL-SCH data
`
`Transport Block
`CRC Attachment
`
`Code block
`Segmentation and
`
`CRC Attachment
`
`Turbo
`Encoding
`
`
`Rate Matching
`
`Code Block
`
`Concatenation
`
`Figure 5.13 DL-SCH channel encoding chain
`
`of soft memory available for retransmission combining. The downlink encoding chain is
`illustrated in Figure 5.13. There is no multiplexing to same physical layer resources with
`PDCCH as they have their own resources during the 1 ms sub-frame.
`Once the data have been encoded, the code words are provided onwards for scrambling
`and modulation functionality. Scrambling in the physical layer should not be confused
`with the ciphering functionality; it is simply intended to avoid a wrong device successfully
`decoding the data if the resource allocation happens to be identical between cells. The
`modulation mapper applies the desired modulation (QPSK, 16QAM or 64QAM) and then
`symbols are fed for the layer mapping and precoding. Where there are multiple transmit
`antennas (two or four) the data are divided into the same number of different streams
`and then mapped to the correct resource elements available for PDSCH. Then the actual
`OFDMA signal is generated, as shown in Figure 5.14 with an example of two antenna
`transmissions. If there is only a single transmit antenna available then obviously the layer
`mapping and precoding functionalities do not have a role in signal transmission.
`The downlink resulting instantaneous data rate depends on:
`• Modulation – the same methods being possible as in the uplink direction.
`• The allocated number of sub-carriers. In the 1.4 MHz case the overhead is the largest
`due to the common channels and synchronization signals. Note that in the downlink the
`resource blocks are not necessary having continuous allocation in frequency domain.
`The range of allocation is the same as in the uplink direction from 12 sub-carriers
`(180 kHz) up to the system bandwidth with 1200 sub-carriers.
`• Channel encoding rate.
`• Number of transmit antennas (independent streams) with MIMO operation.
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`

`Physical Layer
`
`93
`
`DL-SCH data from channel encoding
`
`Scrambling
`
`Modulation
`Mapper
`
`Layer Mapping &
`Precoding
`
`Resource Element
`Mapper
`
`OFDM Signal
`
`
`Generation
`
`Antennas
`
`Figure 5.14 Downlink signal generation
`
`The instantaneous downlink peak data rate (assuming all resources to a single user
`and counting only the physical layer resources available) ranges between 0.7 Mbps and
`170 Mbps; 300 Mbps or higher could be expected using 4 × 4 antenna MIMO operation.
`There is no limit on the smallest data rate, and should the smallest allocation unit (one
`resource block) be too high then padding could be applied (in higher layers). Section 5.10
`presents the maximum data rates taking the UE categories into account. The possible data
`rates for different bandwidth/coding/modulation combinations are presented in Chapter 10.
`
`5.6 Uplink Physical Layer Signaling Transmission
`Uplink L1/L2 control signaling is divided into two classes in the LTE system:
`• Control signaling in the absence of UL data, which takes place on the PUCCH (Physical
`Uplink Control Channel).
`• Control signaling in the presence of UL data, which takes place on PUSCH (Physical
`Uplink Shared Channel).
`
`The simultaneous transmission of PUCCH and PUSCH is not allowed due to single
`carrier limitations. This means that separate control resources are defined for cases with
`and without UL data. Parallel transmission in the frequency domain (bad for the transmitter
`envelope) or pure time division (bad for control channel coverage) was considered as a
`possible alternative. The selected approach maximizes the link budget for PUCCH and
`maintains single carrier properties on the transmitted signal.
`PUCCH is a shared frequency/time resource reserved exclusively for UEs transmitting
`only L1/L2 control signals. It has been optimized for a large number of simultaneous UEs
`with a relatively small number of control signaling bits per UE.
`PUSCH carries the UL L1/L2 control signals in cases when the UE has been scheduled
`for data transmission. PUSCH is capable of transmitting control signals and supporting a
`large range of signaling sizes. Data and different control fields such as ACK/NACK and
`CQI are separated by means of TDM by mapping them into separate modulation symbols
`prior to the DFT. Different coding rates for control are achieved by occupying different
`number of symbols for each control field.
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`
`There are two types of uplink L1 and L2 control-signaling information as discussed
`in [6]:
`• data-associated signaling (for example, transport format and HARQ information), which
`is associated with uplink data transmission; and
`• non-data-associated signaling (ACK/NACK due to downlink transmissions, downlink
`CQI, and scheduling requests for uplink transmission).
`
`It has been decided there is no data-associated control signaling in LTE UL. Fur-
`thermore, it is assumed that eNodeB is not required to perform blind transport format
`detection. This means that UE just obeys the UL scheduling grant with no freedom in
`transport format selection. Furthermore, there is a new data indicator (1 bit) included in
`the UL grant together with implicit information about the redundancy version [7]. This
`guarantees, that the eNodeB always has exact information about the UL transport format.
`
`5.6.1 Physical Uplink Control Channel, PUCCH
`From a single UE perspective, PUCCH consists of a frequency resource of one resource
`block (12 sub-carriers) and a time resource of one sub-frame. To handle coverage-limited
`situations, transmission of ACK/NACK spans the full 1 ms sub-frame. To support extreme
`coverage-limited cases it has been agreed that ACK/NACK repetition is supported in LTE
`UL. Slot-based frequency hopping on the band edges symmetrically over the center fre-
`quency is always used on PUCCH, as shown in Figure 5.15. Frequency hopping provides
`the necessary frequency diversity needed for delay-critical control signaling.
`Different UEs are separated on PUCCH by means of Frequency Division Multiplexing
`(FDM) and Code Division Multiplexing (CDM). FDM is used only between the resource
`blocks whereas code division multiplexing is used inside the PUCCH resource block.
`There are two ways to realize CDM inside the PUCCH resource block:
`• by means of cyclic shifts of a CAZAC1 sequence;
`• by means of blockwise spreading with orthogonal cover sequences.
`
`system
`bandwidth
`
`Resource block
`
`PUCCH
`
`slot
`
`Figure 5.15 PUCCH resource
`
`1 The applied sequences are not true CAZAC but computer searched Zero-Autocorrelation (ZAC) sequences. The
`same sequences are applied as reference signals with bandwidth allocation of one resource block.
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`
`The main issue with CDM is the well-known near-far problem. Orthogonality properties
`of the considered CDM techniques were carefully studied during the Work Item phase of
`LTE standardization. We note that:
`• channel delay spread limits the orthogonality between cyclically shifted CAZAC
`sequences;
`• channel Doppler spread limits the orthogonality between blockwise spread sequences.
`Orthogonality properties are optimized by means of staggered and configurable chan-
`nelization arrangement (see more details in section 5.6.2.1), proper configuration of block
`spreading and a versatile randomization arrangement including optimized hopping patterns
`used for the control channel resources and the applied CAZAC sequences.
`
`5.6.1.1 Sequence Modulation
`
`Control signaling on PUCCH is based on sequence modulation. Cyclically shifted CAZAC
`sequences take care of CDM and convey control information. Figure 5.16 shows a block
`diagram of the sequence modulator configured to transmit periodic CQI on PUCCH. On
`the PUCCH application CAZAC sequences of length 12 symbols (1 RB) are BPSK or
`QPSK modulated thus carrying one or two information bits per sequence. Different UEs
`can be multiplexed into the given frequency/time resource by allocating different cyclic
`shifts of the CAZAC sequence for them. There are six parallel channels available per RB,
`assuming that every second cyclic shift is in use.
`
`5.6.1.2 Block-wise Spreading
`
`Block-wise spreading increases the multiplexing capacity of PUCCH by a factor of the
`spreading factor (SF) used. The principle of block-wise spreading is shown in Figure 5.17,
`
`Control
`signalling
`bits
`
`CAZAC
`CODES
`with UE
`specific
`cyclic
`shift
`
`Phase
`modulator
`
`Sequence modulator
`
`Sub-
`carrier
`mapping
`
`IFFT
`
`CP
`
`modulated CQI
`sequence
`
`1 1
`
`CQI
`
`1 1
`
`RS
`
`1 1
`
`CQI
`
`1 1
`
`CQI
`
`1 1
`
`CQI
`
`1 1
`
`RS
`
`CQI
`
`1 1
`
`Figure 5.16 Block diagram of CAZAC sequence modulation applied for CQI
`
`slot
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`
`Sequence
`modulator
`
`modulated A/N sequence
`
`w0
`
`w1
`
`w2
`
`w3
`
`11
`
`A/N
`
`11
`
`A/N
`
`11
`
`RS
`
`11
`
`RS
`
`11
`
`RS
`
`11
`
`A/N
`
`11
`
`A/N
`
`Figure 5.17 Principle of block spreading applied for ACK/NACK, sp