`
`ZTE Corporation and ZTE (USA) Inc.
`
`
`
`Inv. No. 337-TA-868
`
`RX-3141
`
`TSG-RAN Working Group 1 #21
`Torino, Italy, Aug. 27-31 2001
`
`R1-01-0972
`
`Source:
`
`|nterDigital Comm. Corp.
`
`Title:
`
`Simplified Illustration of the performance benefit of UE dependent CRC
`
`Document for: Discussion
`
`Introduction
`
`Several companies have proposed or supported the use of the UE dependent CRC for
`HSDPA downlink signaling, in which the CRC is combined with the UE ID, and only the UE-
`dependent ID is transmitted over the air. Some members of the Working Group have been
`concerned that the technique has only imagined benefits.
`
`This paper provides a quantitative illustration of the benefits of implict UE ID. Since the
`purpose is to be illustrative the analysis uses simplified assumptions.
`
`The analysis will show that, for a given allocation of bits for the combined functions of UE ID
`and CRC, the UE dependent CRC provides better detection of errors for the case where the
`erroneous block is intended for the receiving UE.
`
`Assumptions
`To facilitate the discussion assume three alternative concepts, each using the same number
`of bits, e.g. 16,
`to support the combined UE ID and CRC.
`
`1) UE ID length = CRC length: 16 bits; UE dependent CRC
`2) UE ID length = CRC length = 8 bits; both are transmitted
`3) UE ID length =16 bits; no CRC
`
`Note that concepts (1) and (3) support more UE IDs than concept (2).
`
`Assume that the probability of bit error, given that the block is in error, = p, independent from
`bit to bit.
`
`Note that 0.5 2 p 2 0
`
`Erroneous Cases
`There are two cases of interest:
`
`a) The transmission is not intended for the UE
`b) The transmission is intended for the UE
`
`Analysis of the cases
`Case (a), the transmission is not intended for the UE
`
`NK868|TCO15906877
`
`ZTE Corporation and ZTE (USA) Inc.
`Exhibit 1032-00001
`
`
`
`(2), and (3), the probability of false acceptance of the CRC (given that the
`For concepts (1) ,
`burst is in error)= 1/216
`
`Each bit received has equal probability (i.e. 1/2) of matching the expected value.
`
`Case (b), the transmission is intended for the UE
`Given that the block is received in error,
`
`For concept (1), the probability of acceptance = 1/216
`For concept (2),
`the probability of acceptance = (1-p)8/28
`For concept (3), the probability of acceptance = (1—p)16
`
`The performance of the three options is shown in figure 1. If the bit error probability = 0.5 for
`each of the bits of a failed block, then all concepts are equal in performance. As long as an
`incorrectly processed block has more correct bits than incorrect bits, then the UE dependent
`CRC has better error detection performance.
`
`Concept 3
`no CRC
`16 bit UEID
`
`ncept2
`' UEI D+8bit
`(‘pr
`
`concept 1
`UE specific CRC
`
`0.4
`0.3
`0.2
`Probability of bit error (given block error)
`
`Wox:
`5o.C’uu
`
`<'
`
`6E
`
`‘
`EN.o
`Ea.
`
`Figure 1 Probability of false acceptance versus conditional bit error probability for an
`erroneous block intended for the receiving UE
`
`N K868|TCO15906878
`
`ZTE Corporation and ZTE (USA) Inc.
`Exhibit 1032-00002
`
`
`
`Conclusion
`
`Assuming the same number of bits is allocated for the combined functions of UE ID and
`CRC:
`
`o The benefit of the UE specific CRC is in its improved protection in rejecting errors in
`blocks addressed to the receiving UE.
`
`o
`
`In regard to protection against accepting blocks intended for other UEs, all of the
`approaches are equivilent.
`
`N K868|TCO15906879
`
`ZTE Corporation and ZTE (USA) Inc.
`Exhibit 1032-00003