R2-061038
`
`3GPP TSG-RAN WG2 meeting #52
`27-31 March 2006
`Athens, Greece
`
`Agenda item:
`Joint03.7
`Source:
`Qualcomm Europe
`Title:
`LTE Physical Layer Model
`Document for: Discussion, Decision
`
`1. Introduction
`In the following contribution we present our physical layer model for LTE. In section 2 we present the different logical,
`transport and physical channels and in section 3 we present the mapping for both the downlink and the uplink.
`
`2. Logical-Transport-Physical Channels
`
`2.1.Definitions
`
`2.1.1.Logical Channel
`A logical channel identifies the data coming from a single RLC entity and carries the QoS information relevant to its
`transmission over the air. The logical channel originates in the AGW and terminates in the eNode B (where it is mapped
`onto a transport channel). Effectively this definition collapses the WCDMA logical and transport channels into one
`entity. The attributes of the logical channel are the following:
`
`
`
`Priority
`
` QoS attributes
`o Maximum bit rate
`o Guaranteed bit rate
`o Discard Timer
`o
`SDU parameters (maximum SDU size, residual SDU error ratio…)
`o Traffic description
`
`2.1.2.Transport Channel
`Although the transport channel would not carry QoS information in LTE (since QoS is conveyed in the logical channel)
`there is still a need to describe how and with what characteristics data is transferred over the radio interface. The
`attributes for transport channels are the following:
`
` Use of HARQ.
`
` Use of link adaptation by modifying modulation, coding and transmit power.
`
` Type of bit rate (static, semi-static or dynamic).
`
` Type of resource allocation (static, semi-static or dynamic).
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`2.1.3.Physical Channel
`A Physical Channel is identified by the following attributes:
`
` A Carrier Frequency
`
` A Frequency allocation: set of tones providing the frequency boundaries of the allocation
`
` A Time allocation: set of symbols providing time boundaries of allocation
`
` A Scrambling code
`
` A Virtual Antenna Identity in case of MIMO MCW
`
`2.2.List of Channels
`
`2.2.1.Logical Channels
`Logical Control Channels
`
`
`
` Broadcast Control Channel (BCCH)
`o DL channel for broadcasting system control information.
`Paging Control Channel (PCCH)
`o DL channel that transfers paging information
`o Used when E-UTRAN does not know the location cell of the UE
` Multicast Control Channel (MCCH)
`o
`
`Point-to-multipoint DL channel used for transmitting MBMS scheduling and control information for
`one or several MTCHs
`o After establishing RRC connection this channel is only used by UEs that receive MBMS.
` Dedicated Control Channel (DCCH)
`o
`Point-to-point bi-directional channel that transmits dedicated control information
`o Used by UEs having an RRC connection
`Logical Traffic Channels
`
` Dedicated Traffic Channel (DTCH)
`o
` Multicast Traffic Channel (MTCH)
`o
`
`Point-to-point bi-directional channel, dedicated to one UE, for the transfer of user information
`
`Point-to-multipoint DL channel for transmitting traffic data. Data from only one application may be
`carried in one MTCH.
`
`2.2.2.Transport Channels
`In Table 1 we summarize the transport channel attributes of each transport channels.
`
`Transport
`Channel
`
`Use of
`HARQ
`
`Use of Link
`adaptation
`
`Data rate
`(static/semi-
`static/Dynamic)
`
`Resource
`allocation
`(static/semi-
`static/Dynamic)
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`BCH
`
`MCH
`
`DL-SDCH
`
`UL-SDCH
`
`No
`
`No
`
`Yes
`
`Yes
`
`No
`
`No
`
`Yes
`
`Yes
`
`Fixed
`
`Static
`
`Semi-static
`
`Semi-static
`
`Dynamic
`
`Dynamic
`
`Dynamic
`
`Dynamic
`
`Table 1: Transport Channel attributes
`In this table the RACH is not listed as a transport channel. Indeed, since the RACH is considered to carry only very
`limited signalling information and no data, it can be viewed as a physical layer channel only.
`
`Similarly the PCH is not listed as a transport channel. In this case we view the attributes of the DL-SDCH to be
`sufficiently flexible to also cover the needs of the transport of paging messages.
`
`2.2.3.Physical Channels
`Downlink Physical Channels
`
` Common Pilot Channel (CPICH)
`o Broadband pilot channel uniformly spanning all the system bandwidth [3]. This allows channel
`estimation for coherent demodulation of other physical channels and assists in handoff operation.
`
`
`
`It is scrambled by the cell specific scrambling code.
`
`o
`Synchronization Channel (SCH)
`o
`
`Physical channel that allows the initial system acquisition (DL timing acquisition and cell scrambling
`code determination). The SCH is transmitted over the entire cell in the superframe preambles [3].
`o The SCH is TDM’d within the superframe preamble with the CCCH. The exact number of OFDM
`symbols in the superframe preamble dedicated to the SCH is FFS.
`
`
`
` Common Control Channel (CCCH)
`o CCCH provides all the system and cell specific control information and the paging indications. A list
`of control information has been provided in section 2.3 of [1].
`o The CCCH is TDM’d within the superframe preamble with the SCH (the superframe has been
`introduced in [1]). The exact number of OFDM symbols in the superframe preamble dedicated to the
`CCCH is FFS.
`o Messages in the CCCH span a multiple number of superframe preambles.
`o
`It is scrambled by the cell specific scrambling code.
`Shared DL Control Channel (SDCCH)
`o Channel providing the control information associated with the Shared Data Channel (SDCH). The list
`of control information has been provided in section 2.4 of [1].
`o This channel may be multicast (to the target UE and the UE(s) whose resources are being de-
`allocated) and is scrambled by the cell specific scrambling.
`o The SDCCH is transmitted every subframe over FFS OFDM symbols.
` Multicast Physical Data Channel (MPDCH)
`o This channel carries the MBMS Transport Channel (MCH).
` MPCCH:
`o Carries the logical ID as described in [2].
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`
`
`Shared UL Assignment Channel (SUACH)
`o Channel providing the control information associated with the UL-SDCH. The list of control
`information has been provided in section 2.5 of [1].
`o This channel may be multicast (to the target UE and the UE(s) whose resources are being de-
`allocated) and is scrambled by the cell specific scrambling.
`o The SUACH is transmitted every subframe over FFS OFDM symbols
` Acknowledgement Channel (ACKCH)
`o
`o
`
`Physical channel carrying the L1 acknowledgement for UL-SDCH transmissions.
`
`It is transmitted at a power level to reach the target UE and is scrambled by the cell specific
`scrambling
`o A mapping exists from the UL data channel resource allocation to the DL ACKCH physical allocation
` DL Physical Shared Data Channel (DL-PSDCH)
`o Carries the DL-SDCH transport channel
`o
`It is scrambled by the cell specific scrambling
`o The DL-PSDCH is transmitted every subframe. The occupied bandwidth for different target UEs is
`controlled at the scheduler to be consistent with the corresponding UE Rx bandwidth capability
`
` UL Power Control Channel (UPCCH)
`o Carries a single bit (Up/Down) for UL transmit power adjustment
`o The command is used by the UE to adjust its PSD and power to reach a particular degree of reliability
`on the reception of UL physical channels.
`
`o
`
`It is transmitted at a power level to reach the target UE and is scrambled by the cell specific
`scrambling
`
`
`
`It need not be transmitted at every subframe, leading to a power control rate smaller than 2000 Hz
`
`o
`Paging Indicator Channel (PICH)
`o
`Indicators for paging
`o Transmitted over the superframe preamble
`o
`It directs paged UEs to listen to SDCCH for the paging message.
` Load Indicator Channel (LICH)
`o Carries a load indication associated with the transmitting cell. The combined use of this load indicator
`(across different cells) may be viewed as a way to coordinate interference levels.
`
`o
`It is transmitted over the entire cell and is scrambled by the cell specific scrambling
`o The LICH need not be transmitted at every subframe.
`Uplink Physical Channels. These channels have already been presented in [4].
`
`
`
`Physical Random Access Channel (PRACH)
`o Enables initial system access and L1 synchronization
`o
`Implies UL resource request
`o No explicit message part
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`Preamble contains an indication of DL radio conditions and very limited scheduling information
`
`Physical channel carrying the L1 acknowledgement for DL-SDCH
`
`Predefined mapping of DL data resource allocation to UL ACK physical allocation
`
`o
` Channel Quality Indicator Channel (CQICH)
`o Contains DL channel quality information for the selected set of virtual antennas
` Acknowledgement Channel (ACKCH)
`o
`o
` Antenna Subset Indicator Channel (ASICH)
`o Used for MIMO and SDMA feedback information
`Shared Request Channel (SREQCH)
`o Enables fast allocation of UL resources to UEs that are time and frequency synchronized
`o Contains Scheduling information (buffer information, priority, power headroom, UE MAC ID)
`o The UL resource request may also be done in-band over the UL-PSDCH
` UL Physical Shared Data Channel (UL-PSDCH)
`o Carries the UL-SDCH transport channel
`o Uses the resources and the format indicated by the associated SUACH
` Broadband Pilot Channel (BPICH)
`o Transmitted together with SREQCH
`o
`Provides UL reference signal
`o BPICH is uniformly spaced in frequency and spans the entire system bandwidth
`
`
`
`3. Channel Mapping
`In the following figures, we present the mapping between the logical, transport and physical channels. The arrows
`between channels only indicate an association (it does not indicate the direction of data flow).
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`Logica
`lchannel
`s
`
`Transpor
`tchannel
`s
`
`PHY
`channels
`
`Logica
`lchannel
`s
`
`Transpor
`tchannel
`s
`
`PHY
`channels
`
`3.1.Downlink
`
`BCCH
`
`PCCH
`
`DCCH
`
`DTCH
`
`MCCH
`
`MTCH
`
`BCH
`
`DL-SDCH
`
`MCH
`
`CCCH
`
`SCH
`
`CPICH
`
`ACKCH
`
`DL-PSDCH
`
`MPDCH MPCCH
`
`PICH
`
`LICH
`
`SUACH
`
`SDCCH
`
`UPCCH
`
`3.2.Uplink
`
`DCCH
`
`DTCH
`
`UL-SDCH
`
`PRACH
`
`SREQCH
`
`ACKCH
`
`UL-PSDCH
`
`UPCCH
`
`BPICH
`
`CQICH
`
`ASICH
`
`4. References
`[1] R1-060461 DL PHY channels - Overall structure. Qualcomm Europe.
`
`[2] R2-060993 E-MBMS Structure. Qualcomm Europe.
`
`[3] R1-060465 Principles of Acquisition. Qualcomm Europe.
`
`[4] R1-060477 UL PHY Channels – Overall structure. Qualcomm Europe.
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