UL Control Information Classification • Control and signaling for network access • i.e. access probing • Control and signaling for synchronization • i.e. ranging • Control and signaling for traffic • UL HARQ ACK signaling • CQI report • CSI signaling • BW request • Upper layer control signaling • HO, RRC state control, measurement report, and so on
Uplink Physical Control Channel • UL physical control channel in subframe includes: • Non-synchronized ranging channel • Synchronized ranging channel • HARQ ACK channel • Feedback channel • CQI/Precoding feedback channel • Sounding channel
Logical Resource Structure • UL physical control channel and data in same subframe are multiplexed in a FDM fashion in order to guarantee uplink coverage since the maximal transmitting power of MS is limited. • In logical view, control resource is assigned firstly, then diversity data resource and localized data resource are assigned.
Non-synchronized Ranging Channel • Non-synchronized ranging channel carries network entry and handover probing without fully uplink synchronization • Non-synchronized ranging channel should occupy small BW and long time, the time length is whole sub-frame and the BW size is FFS. • long CP equal to maximal RTD plus the maximal delay spread should be employed in the non-synchronized ranging channel, the whole non-synchronized ranging channel should be regarded as a single long OFDM symbol so that the power can be easily collected. And the guard time after the non-synchronized ranging channel should be equal to the maximal RTD. • To minimize the inter-carrier interference, we prefer that each non-synchronized ranging channel should occupy the localized sub-carriers, when more than one non-synchronized ranging channel is configured in one sub-frame, all those non-synchronized ranging channels should be physically continuous in frequency domain.
Synchronized Ranging Channel • Synchronized ranging channel carries probing from MSs achieving fully uplink synchronization. • The synchronized ranging channel uses the same OFDM symbol structure with the traffic channel. • To achieve the frequency diversity, the synchronized ranging channel occupies the distributed sub-carriers. • The synchronized ranging channel size in time domain is the whole sub-frame so that more power can be collected but inter-cell interference is limited.
HARQ ACK Channel • UL HARQ ACK channel carries the acknowledgement for DL data transmission. • UL HARQ ACK resource is configured by BS, which indicates the number of maximal affordable UL HARQ ACK channels. • MS determines index of HARQ ACK channel in an implicit mapping way to save assignment overhead. • Diversity resource is suitable for such mapping way since control resource for HARQ ACK channel can’t be scheduled near optimal according to corresponsive channel condition.
Multiplexing Scheme • Two common multiplexing schemes are considered: FDM and CDM. • Orthogonal sequence based scheme is benefit for inter-cell interference mitigation due to power smoothing over subcarriers of control resource. • In addition, orthogonal sequence based scheme provides flexibility to carry different number of HARQ ACK channels. • Orthogonal sequence based scheme is preferred for uplink HARQ ACK transmission. HARQ ACK groups are multiplexed in FDM, and ACK channels in one group are multiplexed in CDM.
Transmission Scheme • If MCW is set for downlink transmission, more than one ACK signal is needed. • Considering complexity, at most 4 codewords are supported. Two HARQ ACK channels are assigned when MCW is employed on downlink transmission. • Modulation scheme of uplink HARQ ACK signal is given in following table
Resource Mapping Scheme (I) • All uplink HARQ ACK resource is divided into several ACK Groups, each of which carries 4 HARQ ACK channels. FFS if more than 4 HARQ ACK channels can be supported per ACK Group. • The resource of ACK Group consists of 12 subcarriers over 6 OFDM symbols. The resource is divided into 6 non-adjacent tiles, which consists of 2 contiguous subcarriers by 6 OFDM symbols. • Orthogonal sequence maps to the tile and replicate 6 times. • Pilot sequence maps to 4 pilot subcarriers in OFDM symbol 2 and 5 of one tile. Data sequence maps to remaining 8 subcarriers in same tile. An illustration is given in next slide.
Feedback Channel • The uplink feedback channel contains Uplink CQI/Precoding channel and Uplink Sounding channel. • Uplink CQI/Precoding channel provides channel quality indicator (CQI) and the feedback information for spatial precoding of downlink channel. • Uplink Sounding channel provides uplink channel information and additional downlink channel information, which is used for uplink and downlink scheduling, AMC and timing, etc. • With different antenna modes and channel conditions, the CQI report modes are different. • Both Periodic CQI reporting and trigger-based CQI reporting is supported. Four types of CQI report are supported, e.g. wideband CQI report, sub-band CQI report, MCW CQI report and PMI report. More types of CQI report might be included in further study.
Transmission period and resource allocation of certain CQI modes is instructed by specific signal from BS. An illustrated example is given in following figure Detailed format of CQI report is instructed by BS. The resource between CQI channel and ACK channel may be shared, and the detailed design is FFS. CQI Resource Allocation Mode
CQI/Precoding Control Message Format • Wideband CQI is used by MSs scheduled on distributed channels, such as high speed MSs, persistently scheduled MSs and MSs in active state but with no data to receive, for fast access to radio resources. When MCW is enabled, CQI message format "A" carry channel quality in the basic layer. • When MSs experience slow mobility and frequency selective scheduling is employed, MSs are typically instructed to use the CQI message format "B". CQI/Precoding control message format "A" CQI/Precoding control message format "B"
CQI/Precoding Control Message Format • When MSs experience slow mobility and good channel conditions, MSs may be instructed to use the CQI message format "C". • Format "D" may include Precoding Matrix Indices for SU-MIMO, and/or multiple Precoding Vector Indices in the case of MU-MIMO. CQI/Precoding control message format "C" CQI/Precoding control message format "D"
Size of CQI Message Fields • The choice of Npmi and Npvi and depends on the number of transmit antennas employed in the BS and codebook design. • Sub-band CQI report size is depended on RBG size, number of RBG and system BW. For different bandwidth modes the value of M and Nlabelmay be different.
Other Considerations • Trigger for switching between different CQI modes • In-band signaling • Share wideband CQI resource • RACH channel • The detailed design is FFS • Coding and modulation scheme is under investigation to save overhead, for an instance, avoiding CRC by erasure decoding • The CQI report can have different format indicated by a type field within same size of control resource. It is FFS.
CQI Resource Mapping • The basic unit of CQI resource is CQI control tile, which consists of 6 subcarriers over 6 OFDM symbols. • CQI control tile can be 2 distributed elements (3*6) or 1 localized element(6*6). • Different CQI report mode occupies one or more CQI control tiles to support different size CQI report. For an instance, sub-band CQI can occupy 2 CQI control tiles. • CQI resources allocation is indicated by BS. • Wideband CQI report is mapped on periodic resource by persistent assignment. Other CQI reports may be multiplexed in a CDM fashion. FFS if a smaller size CQI control tile can be supported.
Uplink Sounding Channel • Uplink sounding channel provides uplink channel information and additional downlink channel information, which is used for uplink and downlink scheduling, AMC and timing, etc. • Sounding transmission period depend on the mobility of MS and system load.
Sounding Channel ResourceMapping and Multiplexing • Option 1: Sounding channel is mapped to one OFDM symbol of every sub-frame. • Option 2: Sounding channel is distributed to all OFDM symbol of every sub-frame. • Sounding signal is transmitted on the uplink resource except uplink control channel • Sounding segment contains multiple sounding channels and every sounding channel may contain multiple sounding sub-channels • every sounding sub-channel occupies narrowband resource and the multiplexing between sub-channels is CDM/FDM • Independent sequence for every sub-channel • To mitigate destruction of pilot sequences orthogonality due to frequency selective fading • a MS may use one or several sounding sub-channel • the transmission bandwidth used by MS depend on the power limitation and requirement of MS
Text Proposal Insert the following text in SDD Chapter 11 (Physical Layer): 11.x UL Control Structure 11.x.1 UL Control Information 11.x.1.1 UL control information classification Control information carried on uplink includes: Control and signaling for network access; Control and signaling for uplink synchronization; Control and signaling for traffic; Upper layer control signaling. 11.x.1.2 Mapping of UL control information
Text Proposal 11.x.2 UL Physical Control Channel 11.x.2.1 Non-synchronized ranging channel Non-synchronized ranging channel carries network entry and handover probing without fully uplink synchronization. Non-synchronized ranging channel occupies localized sub-carriers. Long CP equal to maximal RTD plus maximal delay spread and guard time after non-synchronized ranging channel is equal to maximal RTD. 11.x.2.2 Synchronized ranging channel Synchronized ranging channel carries probing from MSs achieving fully uplink synchronization. The synchronized ranging channel uses the same OFDM symbol structure with the traffic channel and occupies distributed sub-carriers.
Text Proposal 11.x.2.3 HARQ ACK channel HARQ ACK channels are divided into groups multiplexed in FDM. In each HARQ ACK group, HARQ ACK signaling is mapping to the orthogonal sequence and carried on the same time-frequency resource of group. 11.x.2.4 Feedback channel Feedback channel contains Uplink CQI/Precoding channel and Uplink Sounding channel. Multiple types of CQI report are supported, such as wideband CQI report, sub-band CQI report, MCW CQI report, PMI report and so on. The mode, timing, resource assignment of CQI report are instructed by specific signal from BS. 11.x.3 Transmission of Control Channel