14.18.7 Incremental Redundancy Performance

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

An EGPRS capable MS shall, under the conditions stated in the table below, achieve a long-term throughput of 20 kbps per time slot (see NOTE) measured between LLC and RLC/MAC layer.

Propagation conditions

Static, input level –97.0 dBm

Modulation and Coding Scheme


Acknowledgements polling period

32 RLC data blocks

Roundtrip time

120 ms

Number of timeslots

Maximum capability of the MS

Transmit window size

Maximum for the MS timeslot capability

NOTE: This corresponds to an equivalent block error rate of approximately 0.66 using the prescribed MCS-9.

3GPP TS 05.05, subclause 6.7 (3GPP 45.005, subclause 6.7). Test purpose

To verify that the EGPRS MS can operate in Incremental Redundancy RLC mode for a sufficiently long time and that it achieves a long-term throughput of 20 kbps per timeslot, measured between LLC and RLC/MAC layer, under the conditions defined in conformance requirement. 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 preceded with random payload data according to the Incremental Redundancy RLC mode procedures using MCS-9. 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 next partial bitmap irrespective of the polling period.

If the MS is setting the MS OUT OF MEMORY BIT to 1 in the EGPRS Packet Downlink ACK/NACK message the SS should take care that only NACKED RLC data blocks are retransmitted with MCS 9 and if the MS sets again the MS OUT OF MEMORY BIT to 0 the SS can continue transmitting also new data with MCS 9.

Initial conditions

The SS establishes a downlink EGPRS 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 MCS-9 as the Modulation and Coding Scheme and the maximum RLC downlink window size the number of used time slots allows for the data transfer. The SS commands the MS to use maximum transmit power in the uplink, decreases the transmit power to –96 dBm in the downlink and preserves the fading conditions as static. The power control parameter ALPHA (α) is set to 0.


a) Using MSC-9 with Puncturing Scheme 1 (PS1), the SS continues the EGPRS TBF in the downlink by transmitting RLC data blocks with valid Block Sequence Numbers (BSN) within the RLC downlink window of maximum size according to MS’s multislot class, and polls the MS for acknowledgements after every polling period of 32 RLC data blocks.

b) The SS updates it’s associated acknowledge state array V(B) according to the ack/nack bitmap in the EGPRS 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 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.

  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 duration from the beginning of the transmission of RLC data blocks to reaching the stop condition, then the average throughput per timeslot is (x · 592 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 20kbps on low, mid and high ARFCN range.