India’s TSDSI candidate IMT 2020 RIT with Low Mobility Large Cell (LMLC) for rural coverage of 5G services

India’s telecom standards organization TSDSI has submitted its candidate Radio Interface Technology (RIT) to the IMT-2020 evaluation at the ITU-R WP 5D meeting #32 being held in Buzios, Brazil from 9 July 2019 to 17 July 2019.  TSDSI’s IMT 2020 submission is one of five candidate RIT proposals- see NOTE at bottom of this article for more information.

TSDSI’s RIT is described in document ITU-R WP5D-AR Contribution 770.  This RIT has been developed to address the rural requirements by enabling the implementation of  Low Mobility Large Cell (LMLC), particularly with emphasis on low-cost rural coverage of 5G wireless network services.  TSDSI believes that this RIT will also help to meet the rural requirements of other developing countries.  We agree!

TSDSI proposal on Low Mobility Large Cell (LMLC) configuration has been included as a mandatory test configuration under the Rural eMBB (enhanced Mobile BroadBand) test environment in IMT 2020 Technical Performance Requirements (TPR) in ITU-R with an enhanced Inter Sire Distance (ISD) of 6 km. Incorporation of LMLC in IMT2020 will help address the requirements of typical Indian rural settings and will be a key enabler for bridging the rural-urban divide with 5G rollouts.

–>The Indian administration (ITU member country) extends its support to the RIT of TSDSI and solicits the support of ITU Member States to support this proposal.

Indian wireless network operators, including Reliance Jio Infocomm Ltd, have expressed interest in LMLC.

Kiran Kumar Kuchi, a professor at IIT Hyderabad is building a 5G testbed there.  The system will exceed IMT 2020 5G performance requirements including Low Mobility Large Cell.

IIT Hyderabad 5G Testbed.   Photo courtesy of IIT Hyderabad.

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TSDSI’s baseline RIT (initial description template) is documented in ITU-R WP 5D Document 5D/980: Revision 2 to Document IMT-2020/7-E, submitted on 14 February 2019.  Several updates to TSDSI RIT included the updated characteristics template, initial link budget template, etc.  They are in Document 5D/1138: Attachment Part 1: 5D/1138!P1; Attachment Part 2: 5D/1138!P2; Attachment Part 3: 5D/1138!P3; Attachment Part 4: 5D/1138!P4)

Here are a few key excerpts from the TSDSI baseline RIT:

Describe details of the radio interface architecture and protocol stack such as: – Logical channels – Control channels – Traffic channels Transport channels and/or physical channels.

RAN/Radio Architectures: This RIT contains NR standalone architecture. The following paragraphs provide a high-level summary of radio interface protocols and channels.

Radio Protocols: The protocol stack for the user plane includes the following: SDAP, PDCP, RLC, MAC, and PHY sublayers (terminated in UE and gNB). On the Control plane, the following protocols are defined: – RRC, PDCP, RLC, MAC and PHY sublayers (terminated in UE and gNB); – NAS protocol (terminated in UE and AMF) For details on protocol services and functions, please refer to 3GPP specifications (e.g. [38.300]).

Radio Channels (Physical, Transport and Logical Channels):

  • The physical layer offers service to the MAC sublayer transport channels. The MAC sublayer offers service to the RLC sublayer logical channels.
  • The RLC sublayer offers service to the PDCP sublayer RLC channels.
  • The PDCP sublayer offers service to the SDAP and RRC sublayer radio bearers: data radio bearers (DRB) for user plane data and signalling radio bearers (SRB) for control plane data.
  • The SDAP sublayer offers 5GC QoS flows and DRBs mapping function.

The physical channels defined in the downlink are: – the Physical Downlink Shared Channel (PDSCH), – the Physical Downlink Control Channel (PDCCH), – the Physical Broadcast Channel (PBCH).

The physical channels defined in the uplink are: – the Physical Random Access Channel (PRACH), – the Physical Uplink Shared Channel (PUSCH), – and the Physical Uplink Control Channel (PUCCH). In addition to the physical channels above, PHY layer signals are defined, which can be reference signals, primary and secondary synchronization signals.

The following transport channels, and their mapping to PHY channels, are defined:

Uplink: – Uplink Shared Channel (UL-SCH), mapped to PUSCH – Random Access Channel (RACH), mapped to PRACH

Downlink: – Downlink Shared Channel (DL-SCH), mapped to PDSCH – Broadcast channel (BCH), mapped to PBCH – Paging channel (PCH), mapped to (TBD)

Logical channels are classified into two groups: Control Channels and Traffic Channels.

Control channels: – Broadcast Control Channel (BCCH): a downlink channel for broadcasting system control information. – Paging Control Channel (PCCH): a downlink channel that transfers paging information and system information change notifications. – Common Control Channel (CCCH): channel for transmitting control information between UEs and network. – Dedicated Control Channel (DCCH): a point-to-point bi-directional channel that transmits dedicated control information between a UE and the network.

Traffic channels: Dedicated Traffic Channel (DTCH), which can exist in both UL and DL. In Downlink, the following connections between logical channels and transport channels exist: – BCCH can be mapped to BCH, or DL-SCH; – PCCH can be mapped to PCH; – CCCH, DCCH, DTCH can be mapped to DL-SCH;

In Uplink, the following connections between logical channels and transport channels exist: – CCCH, DCCH, DTCH can be mapped to UL-SCH.

Enhancements:

1. Method to improve broadcast and paging control channel efficiency over access elements.

2. Reduce the impact of congestion in the data path and control path to improve overall efficiency in the network. Other aspects – NR QoS architecture The QoS architecture in NG-RAN (connected to 5GC), can be summarized as follows: For each UE, 5GC establishes one or more PDU Sessions. For each UE, the NG-RAN establishes one or more Data Radio Bearers (DRB) per PDU Session. The NG-RAN maps packets belonging to different PDU sessions to different DRBs. Hence, the NG-RAN establishes at least one default DRB for each PDU Session. NAS level packet filters in the UE and in the 5GC associate UL and DL packets with QoS Flows. AS-level mapping rules in the UE and in the NG-RAN associate UL and DL QoS Flows with DRBs – Carrier Aggregation (CA) In case of CA, the multi-carrier nature of the physical layer is only exposed to the MAC layer for which one HARQ entity is required per serving cell. – Dual Connectivity (DC) In DC, the radio protocol architecture that a radio bearer uses depends on how the radio bearer is setup.

Four bearer types (information carrying channels) exist: MCG bearer, MCG split bearer, SCG bearer and SCG split bearer.

The following terminology/definitions apply:

– Master gNB: in dual connectivity, the gNB which terminates at least NG-C.

– Secondary gNB: in dual connectivity, the gNB that is providing additional radio resources for the UE but is not the Master node.

– Master Cell Group (MCG): in dual connectivity, a group of serving cells associated with the MgNB

– Secondary Cell Group (SCG): in dual connectivity, a group of serving cells associated with the SgNB

– MCG bearer: in dual connectivity, a bearer whose radio protocols are only located in the MCG.

– MCG split bearer: in dual connectivity, a bearer whose radio protocols are split at the MgNB and belong to both MCG and SCG.

– SCG bearer: in dual connectivity, a bearer whose radio protocols are only located in the SCG.

– SCG split bearer: in dual connectivity, a bearer whose radio protocols are split at the SgNB and belong to both SCG and MCG.

In case of DC, the UE is configured with two MAC entities: one MAC entity for the MCG and one MAC entity for the SCG. For a split bearer, UE is configured over which link (or both) the UE transmits UL PDCP PDUs. On the link which is not responsible for UL PDCP PDUs transmission, the RLC layer only transmits corresponding ARQ feedback for the downlink data.

For more details on (3GPP “5G”) NR Radio Protocol architecture and channels, refer to: [38.300], [38.401], [38.201], [37.340] What is the bit rate required for transmitting feedback information? The information will be provided in later update.

Channel access: Describe in detail how RIT/SRIT accomplishes initial channel access, (e.g. contention or non-contention based).

Initial channel access is typically accomplished via the “random access procedure” (assuming no dedicated/scheduled resources are allocated). The random access procedure can be contention based (e.g. at initial connection from idle mode) or non-contention based (e.g. during Handover to a new cell). Random access resources and parameters are configured by the network and signaled to the UE (via broadcast or dedicated signaling). Contention based random access procedure encompasses the transmission of a random access preamble by the UE (subject to possible contention with other UEs), followed by a random access response (RAR) in DL (including allocating specific radio resources for the uplink transmission). Afterwards, the UE transmits the initial UL message (e.g. RRC connection Request) using the allocated resources, and wait for a contention resolution message in DL (to confirming access to that UE). The UE could perform multiple attempts until it is successful in accessing the channel or until a timer (supervising the procedure) elapses. Non-contention based random access procedure foresees the assignment of a dedicated random access resource/preamble to a UE (e.g. part of an HO command). This avoids the contention resolution phase, i.e. only the random access preamble and random access response messages are needed to get channel access.

From a L1 perspective, a random access preamble is transmitted (UL) in a PRACH, random access response (DL) in a PDSCH, UL transmission in a PUSCH, and contention resolution message (DL) in a PDSCH.

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NOTES:

 

1.    TSDSI’s RIT is one of five proposals for the IMT 2020 RIT/SRIT.

The other four are from: 3GPP,  South Korea, China, and ETSI/DECT Forum.  All but the latter are based on 3GPP “5G NR.”

  • The Candidate RIT/SRIT submission from China, as acknowledged in IMT-2020/5, is technically identical to the 5G NR RIT submitted from 3GPP as acknowledged in IMT-2020/3.
  • The candidate RIT/SRIT submission from South Korea, as acknowledged in IMT-2020/4, is technically identical to the 5G NR RIT submitted from 3GPP as acknowledged in IMT-2020/3.

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2.   3GPP release 16:

As we have stated numerous times, 3GPP’s final IMT 2020 RIT/SRIT submission to ITU-R  WP 5D will be largely based on 3GPP release 16 (with perhaps some elements of release 15 also included).  From the 3GPP website 

Release 16 will meet the ITU IMT-2020 submission requirements and the time-plan as outlined in RP-172101.

Some Background on 3GPP Release 16:

Here is the active status of 3GPP release 16 project.

The 3GPP release 16 completion date has been delayed by at least 3 months (1Q 2020) with no new completion date specified at this time.

3. DECT Forum/ETSI submission for IMT 2020 SRIT:

From a July 1, 2019 contribution to ITU-R WP5D Brazil meeting:

DECT Forum would like to announce its support and endorsement for the IMT-2020 contribution from ETSI for an SRIT candidate for inclusion in IMT-2020.   The proposed SRIT consists of two component RITs:
DECT-2020 NR RIT
3GPP 5G CANDIDATE FOR INCLUSION IN IMT-2020: SUBMISSION 2 FOR IMT-2020 (RIT)

DECT Forum confirms its continuation as a proponent of this IMT-2020 proposal.

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References:

India delays 5G trials; Advocates “the Indian Way” within ITU-R WP 5D for IMT 2020

ATIS endorses 3GPP IMT 2020 RIT submission to ITU-R WP 5D; sees no need for separate LMLC India national option

3GPP Workshop: IMT 2020 Submission to ITU-R WP5D and Timelines for 5G Standards Completion

TSDSI and the 5G IA signed a Memorandum of Understanding to foster collaboration on Research, Standards, Regulations and Policies

ITU-R Proposal: Report on IMT-2020 for remote sparsely populated areas providing high data rate coverage

 

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