14.18.7b Incremental Redundancy Performance in EC-GSM-IoT Configuration

3GPP51.010-1Mobile Station (MS) conformance specificationPart 1: Conformance specificationTS

14.18.7b.1 Definition

In Incremental Redundancy RLC mode, soft information from multiple, differently punctured versions of an RLC data block may be used when decoding the RLC data block. This significantly increases the link performance.

14.18.7b.2 Conformance requirement

An EC-GSM-IoT MS shall under the conditions stated in table below achieve the long-term throughput per time slot, measured between LLC and RLC/MAC layer as shown in table below.

The throughput requirements are dependent on the MS support level:

– In case the MS supports only GMSK, i.e. MCS 1-4, the requirements for ‘EC-GSM-IoT Only GMSK supported’ and ‘EC-GSM-IoT, MCS-1/16’ apply.

– In case the MS supports GMSK and 8-PSK, i.e. MCS 1-9, the requirements for ‘EC-GSM-IoT 8-PSK supported’ and ‘EC-GSM-IoT, MCS-1/16’ apply.

Table 14.18-1: Incremental redundancy – conditions

MS support level	EGPRS	EGPRS2	EC-GSM-IoT, 8-PSK supported	EC-GSM-IoT, Only GMSK supported
Required throughput [kbps / timeslot]	20,0	33,0	[20,0]	[6,0]
Propagation conditions	Static	Static	Static	Static
Input level [dBm]	-97,0	-94,0	-97,0	[-111,0]
Modulation and Coding Scheme	MCS-9	DAS-12	MCS-9	MCS-4
Acknowledgements polling period [RLC data blocks]	32	32	8	8
Roundtrip time [ms]	120	120	120	120
Number of timeslots	Maximum capability of the MS	Maximum capability of the MS	Maximum capability of the MS	Maximum capability of the MS
Transmit window size	Maximum for the MS timeslot capability	Maximum for the MS timeslot capability	16	16

3GPP 45.005, subclause 6.7, table 6.7-1.

14.18.7b.3 Test purpose

To verify that the EC-GSM-IoT capable MS can operate in Incremental Redundancy RLC mode for a sufficiently long time and that it achieves a long-term throughput of tbd kbps per timeslot, measured between LLC and RLC/MAC layer, under the conditions defined in conformance requirement.

14.18.7b.4 Method of test

The SS establishes a downlink TBF in Incremental Redundancy RLC mode, beginning on a Mid ARFCN Range, under the conditions defined in the conformance requirement. The downlink data transfer is proceeded with random payload data according to the Incremental Redundancy RLC mode procedures using MCS-4 or MCS-9, depending on MS capability, see table 14.18-1 The throughput between LLC and RLC/MAC layer is determined by the SS on the basis of the amount of successfully delivered LLC data, i.e. the amount of data bits in acknowledged RLC data blocks in the correct order without gaps representing LLC or higher layer data. The long-term throughput is determined until at least 6000 RLC data blocks have been send from RLC/MAC layer to the LLC layer within the MS. The test is repeated in Low and High ARFCN range.

If the END_OF_WINDOW bit in the ack/nack message is not set, the SS shall poll the MS for the first partial bitmap irrespective of the polling period.

If the MS is setting the MS OUT OF MEMORY BIT to 1 in the EC Packet Downlink ACK/NACK message the SS should take care that only NACKED RLC data blocks are retransmitted with MCS-1 and if the MS sets again the MS OUT OF MEMORY BIT to 0 the SS can continue transmitting also new data with MCS-1

Initial conditions

The SS establishes a downlink TBF in Incremental Redundancy RLC mode according to the generic procedures defined in sect. 50, on a Mid ARFCN Range. For the TBF, the SS allocates the maximum number of timeslots according to the multislot capability of the MS under test, applies the applicable Modulation and Coding Scheme according to MS capability, see table 14.18-1. The SS commands the MS to use maximum transmit power in the uplink, decreases the transmit power to tbd dBm in the downlink and preserves the fading conditions as static. The power control parameter ALPHA (α) is set to 0.

Specific PICS statements:

Procedure

a) Using the applicable MCS according to MS capability, see table 14.18-1, with Puncturing Scheme 1 (PS1), the SS continues the TBF in the downlink by transmitting RLC data blocks with valid Block Sequence Numbers (BSN) within the RLC downlink window, and polls the MS for acknowledgements after every polling period of 8 RLC data blocks.

b) The SS updates its associated acknowledge state array V(B) according to the ack/nack bitmap in the EC Downlink Ack/Nack message transmitted by the MS as a response to polling and shifts the RLC downlink window accordingly.

c) While continuing the transmission of further RLC data blocks with PS1, the SS retransmits, after a delay that corresponds to a round trip time of 120ms, all unacknowledged RLC data blocks with PS2 starting from the oldest unacknowledged RLC blocks.

d) The SS repeats the steps a) to c). For retransmissions of RLC data blocks using MCS-9 that have already been retransmitted with PS2, the SS applies PS3 for such blocks and further again PS1 and PS2 in cyclic manner if necessary. For retransmissions of RLC data blocks using MCS-4 that have already been retransmitted with PS2 the SS applies PS1, and then PS2 in a cyclic manner if necessary.

1. Steps a) to d) are repeated until at least 6000 RLC data blocks are transmitted from RLC to LLC layer within the MS, but never more then 18000 RLC data blocks from SS to MS.

NOTE: If the MS needs more than 18000 RLC data blocks received to send 6000 RLC blocks up to the LLC layer it will never fulfil the conformance requirements.

1. The SS calculates the data throughput per time slot between RLC/MAC and LLC layers on the basis of successfully transmitted LLC-data during steps a) to e). For this the lower end of the RLC downlink window can be used to measure the progress of the transmission in terms of amount of data passed on to the LLC.

If n is the number of timeslots, x the position of the lower end of the RLC downlink window, and t is the active time duration of allocated radio blocks carrying RLC data blocks before reaching the stop condition, then the average throughput per timeslot is:

– For MCS-4: (x · 352 bit)/(n·t).

g) Steps a) to f) are repeated at Low and High ARFCN ranges.

Test requirements

The long-term throughput per time slot as a result of step f) of the test procedure shall equal or exceed 6 kbps on low, mid and high ARFCN range.