BUSINESS AND PROPERTY COURTS
INTELLECTUAL PROPERTY LIST (CHANCERY DIVISION)
Fetter Lane, London, EC4A 1NL
B e f o r e :
| KONINKLIJKE PHILIPS NV
|- and -
|(1) ASUSTEK COMPUTER INCORPORATION
(2) ASUSTEK (UK) LIMITED
(3) ASUS TECHNOLOGY PTE. LTD
(4) HTC CORPORATION
(5) HTC EUROPE CO. LTD
Thomas Hinchliffe QC and Joe Delaney (instructed by Taylor Wessing LLP) for the ASUS Defendants
and (instructed by Hogan Lovells International LLP) for the HTC Defendants
Hearing dates: 27, 30 April, 1-3, 9 May 2018
Crown Copyright ©
MR JUSTICE ARNOLD :
|Mobile telecommunication standards||20-68|
|Elements of a mobile telecommunications system||33-39|
|OSI seven-layer model||40-51|
|Multiple access schemes||55-56|
|Functions of the radio transmission chain||57-62|
|Repetition coding and channel coding||63-66|
|Error control strategies||67-78|
|Comparison of FEC and ARQ||76-77|
|Noise and interference||79-83|
|Signal transmission and detection||84-87|
|Modelling the effect of noise||87|
|Probability of error||88|
|Multipath (fast) fading||100-103|
|Power control techniques||104-109|
|UMTS Release 4||110-119|
|Development of HSDPA||120-126|
|The problem to which the Patent is addressed||127|
|Disclosure of the invention||134-136|
|Modes for carrying out the invention||137-145|
|The skilled person||148|
|Common general knowledge||152-174|
|Differential gain on channels and field||154|
|Differential powers on binary antipodal signalling||155|
|Power control of uplink channels in UMTS||156-157|
|TS 25.308 and TR 25.855||158-162|
|Soft handover in HSDPA||163-172|
|Agreed key points||173|
|Obviousness over Motorola 021||194-202|
|Difference between Motorola 021 and Claim 10||194|
|Obviousness over Shad||226-267|
|Difference between Shad and claim 10||226|
|The Dutch decision||266|
i) Document TSGR1/R2-12A010021 entitled "Control Channel Structure for High Speed DSCH (HS-DSCH)", a contribution submitted to the 3GPP TSG-RAN Working Group 1 and 2 ad hoc meeting in Sophia Antipolis, France on 5-6 April 2001 by Motorola ("Motorola 021");
ii) Document 3GPP2/TSG-C C50-20010709-024 entitled "Optimal Antipodal Signaling", a contribution submitted to the 3GPP2 TSG-C meeting in Montreal, Canada on 9-13 July 2001 by Faisal Shad and Brian Classon of Motorola ("Shad").
Mobile telecommunication standards
i) Radio Access Network (TSG-RAN);
ii) Core Network (TSG-CN);
iii) Service and System Aspects (TSG-SA);
iv) Terminals (TSG-T).
Elements of a mobile telecommunications system
OSI seven layer model
i) Layer 7, the Application Layer, which provides services to the user software applications (e.g. email delivery protocols and Hypertext Transfer Protocol (http));
ii) Layer 6, the Presentation Layer, performs translation and formatting of information received (which may include the functions of compression/decompression and/or encryption/decryption) to present to the application layer and provides an interface to the Session Layer;
iii) Layer 5, the Session Layer, which handles communications at a call level, initiating and terminating the communication between users;
iv) Layer 4, the Transport Layer, which provides communication of data between end users. End to end (i.e. terminal to terminal) error control forms part of this layer;
v) Layer 3, the Network Layer, which provides routing from where the data enters a network to where it leaves it;
vi) Layer 2, the Data Link Layer, which provides communication over an individual link within the network. Error control for the link is included in this layer; and
vii) Layer 1, the Physical Layer, which is concerned with the transmission of the data over the physical medium itself (i.e. protocols that specify how radio waves sent through the air represent data).
Multiple access schemes
Functions of the radio transmission chain
Repetition coding and channel coding
Error control strategies
Noise and interference
Signal transmission and detection
UMTS Release 4
Development of HSDPA
The problem to which the Patent is addressed
"Since packet transmission is typically intermittent, discontinuous transmission (DTX) is normally employed so that nothing is transmitted by the MS unless a data packet has been received."
" A problem with such an ARQ scheme is that the consequences of errors in the ACK and NACK are significantly different. Normally the BS would re-transmit a packet if a NACK were received. If the BS receives a NACK when a ACK was sent, then the packet is re-transmitted anyway, which only wastes a little system resource. If a NACK is sent, but received as a ACK, then no re-transmission is made. Without special physical layer mechanisms, this situation can only be recovered from by using higher layer processes, which adds delay and is a significant waste of system resources. Hence, the cost of an error in a NACK is much more serious than the cost of an error in a ACK.
 In order to optimise system performance, it is desirable to control the relative probabilities of errors in decoding ACKs and NACKs. In one UMTS embodiment this is done by setting different detection thresholds at the BS, which requires the MS to transmit the ACK/NACK codeword with a specific power level (e.g. relative to uplink pilot power). This power level and the detection threshold can therefore be chosen to balance costs of ACK/NACK errors, interference generated by the MS, and battery power used by the MS. With DTX, the situation is a little more complex. However, the BS, as the source of the packet, is aware of when a ACK/NACK should be sent by the MS and it should therefore not normally be necessary to specifically detect the DTX state."
Disclosure of the invention
"By transmitting different acknowledgement signals at different power levels, the probability of the primary station correctly interpreting signals of different types can be manipulated to improve total system throughput and capacity. In one embodiment negative acknowledgements are transmitted at a higher power level than positive acknowledgements to increase the probability of the primary station retransmitting a data packet when necessary. In another embodiment an additional revert signal type is provided, which requests the primary station to retransmit a data packet initially transmitted prior to the current data packet and which was not correctly received. The revert signal may be identical to the negative acknowledgement signal but transmitted at a higher power level."
Modes for carrying out the invention
"As discussed briefly above, the consequences of errors in acknowledgements 204,206 received by the BS 100 are different. If an ACK 206 is received as a NACK 204, the respective packet 202 is retransmitted but the MS 110 can recognise this situation by the sequence number. However, if a NACK 204 is received as an ACK 206, the BS 100 continues with transmission of the next packet 202. The MS 110 can determine that this has happened, from the sequence number of the received packet 202. However, it cannot request the BS 100 to retransmit the packet 202 received in error without invoking higher layer procedures, thereby wasting significant resources."
" It is likely for most applications that DTX would be applied for most of the time, given the typically intermittent nature of packet data transmission. In addition, for a well configured system, NACKs 204 should be sent significantly less often than ACKs 206. Hence, in a system made in accordance with the present invention a NACK 204 is transmitted at a higher power level than an ACK 206. This power offset is advantageous because it reduces the error probability for the NACK 204 without increasing the power transmitted for the ACK 206. It is particularly advantageous if the probability of a MS 110 missing a packet is very small, so there is no need to consider optimum setting of BS detection thresholds to differentiate NACK from DTX. Hence, any given error performance targets could be achieved with minimum average power transmitted by the MS 110.
 It will be recognised that if a MS 110 is transmitting more NACKs 204 than ACKs 206, this proposed strategy would result in an increase in average uplink interference rather than the desired decrease. Therefore, in one embodiment of the present invention, the MS 110 is forbidden from applying the power offset unless it has previously positively acknowledged more than a certain proportion of packets (e.g. 50%). This prevents the power offset from causing an undue increase in uplink interference in poor downlink channel conditions."
 In another embodiment of the present invention, the relative power levels of ACKs 206 and NACKs 204 are modified depending on the proportion of ACKs and NACKs sent. For example, this adaptation could be controlled by a time-weighted average of the proportion of ACKs 206 sent. The detection threshold at the BS 100 could [be] adapted in a similar way based on the proportion of ACKs 206 received. It is apparent that such processes would converge, even in the presence of errors.
 In another embodiment of the present invention, instead of being predetermined the ACK/NACK power offset (or maximum offset) could be signalled by the BS 100 depending on the type of service being conveyed to the MS 110 via the data packets 202. For example, in a real-time streaming service with strict timing constraints, a packet which is lost due to a wrongly-detected NACK 204 may simply be ignored by the application if there were not enough time even for a physical layer retransmission. However, for a data service where correct receipt of packets was essential, an ACK/NACK power offset could be signalled. The offset might also be useful in streaming services with slightly less strict timing requirements, where there was insufficient time for a higher-layer retransmission, but a NACK power offset would increase the chance of an erroneous packet being rectified by means of fast physical layer retransmission. It would therefore be beneficial to allow a different offset value to be signalled for each downlink transport channel."
"In one preferred embodiment, particularly suitable for UMTS HSDPA, the ACK/NACK power offset used by the MS 110, as well as the ACK power level would be determined by higher layer signalling from the network. Alternatively, the offset could be signalled using a single information bit, signifying 'no offset' (i.e. equal transmit power for ACK 206 and NACK 204) or 'use offset', signifying the use of a pre-determined value of power offset. More signalling bits could be used to indicate a larger range of values of offset."
As the skilled person would understand, "signalling from the network" would be relayed by the BS.
"In general, the power levels at which the ACK/NACK and/or REVERT commands are transmitted may be adjusted in order to achieve a required level of reliability. These power levels could be controlled by messages sent from the BS 100 to the MS 110. These could specify the power level relative to the pilot bits on the uplink dedicated control channel, or relative to the current power level for the channel quality metric. In the case of the dedicated control channels of one MS 110 being in soft handover with more than one BS 100 the power of the uplink dedicated control channel is not likely to be optimal for all the BSs 100 involved. Therefore, a different power level, preferably higher, may be used for sending the ACK/NACK and/or REVERT commands. This power difference could be fixed, or determined by a message from a BS 100. When the transmission of ACK/NACK and/or REVERT is directed to a particular BS 100, the power level may be further modified to take into account the quality of the radio channel for that transmission. For example, if the best radio link from the active set is being used, the power level may be lower than otherwise."
" A secondary station [i.e. MS] for use in a radio communication system
 having a communication channel for the transmission of data packets from a primary station [i.e. BS] to the secondary station,
 wherein receiving means are provided for receiving a data packet from the primary station
 and acknowledgement means are provided for transmitting a signal to the primary station to indicate the status of a received data packet,
 which signal is selected from a set of at least two available signal types,
 wherein the acknowledgement means is arranged to select the power level at which the signal is transmitted depending on its type
 and in dependence on an indication of the power level at which each type of signal is transmitted, the indication being signaled from the primary station to the secondary station."
The skilled person
Common general knowledge
Differential gain on channels and fields
Differential powers in binary antipodal signalling
Power control of uplink channels in UMTS
TS 25.308 and TR 25.855
Soft handover in HSDPA
"Q. The final topic on the common general knowledge, Mr. Edwards. We discussed on Friday the power control mechanism.
Q. And how that worked when a mobile was in soft handover; do you remember that?
Q. In that circumstance, in the UMTS circumstance, the mobiles power is set to the power of the base station that requires the least power?
Q. But the skilled person would obviously be aware in HSDPA that the data, the high speed data, is only from and to the single serving HSDPA base station?
Q. What that might mean is there might be fading on the channel between the mobile to a serving base station, but that would not be taken account of by ordinary power control, because the power control would be being controlled by a different base station?
"Q. The skilled person would recognise that was a problem that could happen?
A. The skilled person would recognise it as a question, and then based on some of the documents it did appear that the uplink signalling channel was quite robust. There are one or two pieces which no doubt you will come on to where it is discussed, but the general discussion was not around that point."
Thus what the witness was saying was that it was known that there might be an issue, but it was not generally thought to be a problem.
i) R1-01-0571, a contribution by Ericsson to TSG-RAN WG1 meeting 20 in Busan, Korea on 21-25 May 2001. This notes at page 2 that "the Hybrid-ARQ signalling may need to be transmitted with a different power, compared to the other DPCCH fields, as the required power for the Hybrid-ARQ signalling may depend on e.g. whether the UE is in soft handover or not" and argues for an approach that "allows for simple independent power setting for DPCCH and uplink Hybrid-ARQ signalling. As already mentioned, the required received energy per Hybrid-ARQ 'acknowledgement' may vary significantly between a soft-handover and a non-soft handover situation." Mr Edwards accepted that this was recognising that the power of the ACK/NACK signalling might need to be separately controlled in the soft handover situation because the serving HSDPA BS might not be the one that was doing the power control.
ii) R2-01-1177, a contribution by Nokia to TSG-RAN WG2 meeting 21 in Busan, Korea on 21-25 May 2001. This proposes various "HSPA related signalling parameters in downlink", one of which is described on the fourth page as follows:
"Power offset for uplink control channel
This will inform to the UE what kind of power offset it should use in uplink, when sending e.g. ACK during soft handover. NodeB could estimate the SIR from uplink, and calculate the needed power offset in uplink, in order to make sure that ack can be decoded reliably."
Mr Edwards accepted that this set out the problem and the proposed solution.
iii) R1-01-0874, a contribution by Samsung to TSG-RAN WG1 meeting 21 in Turin, Italy on 27-31 August 2001. This begins by listing the downlink-signalling parameters discussed in TR 25.855, one of which is "Power offset for uplink control channel". It goes on to say on the eighth page:
"2.8 Power offset for uplink control channel
When UE is in soft handover region, the uplink power level can be inappropriate. Therefore, power offset for uplink control channel is needed. Example proposals on the number of bits required for signalling UL power offset are shown in Table 10. … This information does not need to be sent before HS-PDSCH and it should be received by UE only before the ACK/NACK will be sent. … "
Mr Edwards accepted that what Samsung was doing in this paper was "gathering together what everyone was talking about in the standardisation meetings and reflecting that back".
"9.1.7 Power offset for uplink control channel
This informs the UE what kind of power offset it should use in the uplink, when sending e.g. ACK during soft handover. Node B could estimate the SIR from the uplink, and calculate the needed power offset in the uplink, in order to make sure that an ACK can be decoded reliably. This information may be sent at a much lower rate than the other parameters described in this section."
Agreed key points
i) The cost of a false ACK is more significant than the cost of a false NACK.
ii) Signals sent at higher powers are more reliably detected at the BS, but the use of more power may increase interference between signals in a CDMA system. The probability of a receiver correctly interpreting a signal can be manipulated by varying the power at which the signal is sent, and increasing interference at a BS would decrease the total system capacity. This can be thought of as "Shout louder if you want to be more sure you will be heard".
iii) Reducing interference at the BS is beneficial in that it makes it easier for the BS to receive signals from the MSs it is serving.
iv) In conventional modulation, the further away the received voltage of a signal from the decision threshold, the lower the probability of error.
v) As discussed above, the generally accepted method of power control for uplink channels was for the BS to control the MS.
vi) The way fast fading was dealt with in CDMA was by closed loop power control. This worked by the BS monitoring the uplink signal from the MS and comparing it to a target SNR, which was related to the number of errors (the higher the SNR, the lower the errors, and vice-versa).
vii) At the Priority Date a new uplink control channel for HSDPA was proposed and specified in TS 25.308.
viii) It had been decided that the HARQ protocol for HSDPA would use a Multi-Channel SAW process, which was asynchronous on the downlink and synchronous on the uplink. The acceptable error rates for the ACK and NACK messages in HSDPA had not been agreed at the Priority Date, however.
ix) It was known that in UMTS Release 4 the closed loop power control mechanism ensured that a MS in soft handover with two or more BSs transmitted sufficient power to communicate with at least one BS (i.e. the BS(s) with the best uplink channel quality).
x) It was known from UMTS Release 4 that uplink power levels could be set by the BS relative to the uplink power of the pilot bits sent on the DPCCH.
xi) The skilled person would not be concerned by the possibility of errors due to DTX in the context of ACK/NACK signalling in HSDPA.
"It is desirable to use BPSK coherent detection for transmitting the ACK bit on the uplink so that a 10-5 false alarm rate with approximately 0.99 probability of detection can be maintained."
i) the ACK bit signals an ACK or NACK depending on its value;
ii) the reference to a "10-5 false alarm rate", means a probability of 0.00001 of the BS interpreting a transmitted NACK as an ACK i.e. a 1 in 100,000 chance of there being a false ACK; and
iii) the reference to "0.99 probability of detection" means a 99 in 100 chance of the BS correctly interpreting a transmitted ACK as an ACK i.e. a 1 in 100 chance of there being a false NACK.
"The ACK/NACK bits are sent using BPSK modulation i.e. if the HS-DSCH packet is decoded correctly an ACK bit (+1) is transmitted and if it is decoded in error a NACK bit (-1) is transmitted. With the proposed slot format the ACK bits are repetition coded 20 or 30 times. A separate gain control may be used for ACK bits so that those bits can be decoded with high probability (0.97-0.98) and with low probability of false alarm (1e-05) at Node-B. The ROC for optimal coherent BPSK demodulation given 1 path and a single receive antenna in AWGN in Figure 2."
"7.79 The reference to 'gain control' could mean changing the gain on the bit irrespective of the information it carries (ACK or NACK) or it could mean changing the gain on the ACK bit relative to the NACK bit. I believe the skilled team would probably have understood that the authors of the paper meant the former. There is the mention of ACK 'bits' as opposed to the ACK bit and NACK bit and there is no discussion elsewhere in the paper about altering the relative gain on the ACK and NACK bits.
7.89 I believe that the skilled team would probably understand Motorola to be suggesting [applying the same power gain to both the ACK and NACK signals, but biasing the detector by moving the decision threshold], although it is not clear. …"
"6.6 … On balance I think that the skilled team would understand that in Motorola the different target error rates for false ACKs and false NACKs have been achieved by biasing the detector (as I said at Paragraphs 7.89 and 7.92 of my First Report), most likely in conjunction with an additional separate gain to the ACK/NACK bits (see my Paragraphs 6.4 to 6.5 above). …
6.16 At Paragraph 375, Mr Edwards makes the point that Motorola only refers to a single gain for the ACK bits field. Whilst I believe that this is how the skilled team would interpret the gain control described in Motorola, as I have explained in my First Report and above, the skilled team would be aware that the asymmetric error rates set out in Motorola could be obtained either by applying an equal gain to the ACK field bits and biasing the detector, or by applying unequal gains to the two signals. The two were obvious technical alternatives."
Obviousness over Motorola 021
"In this contribution the transmit gains for an antipodal signaling scheme in which the transmit probabilities are known a priori is jointly optimized with the receiver hard decision device threshold value in order to obtain the required error probabilities for a minimum bit SNR. This type of signaling for example applies to the Hybrid ARQ acknowledgement channel in which the average frame error rate is known to the transmitter, and certain false acknowledgement and false negative acknowledgement probabilities are prescribed by the upper layers."
"The objective of this contribution is to obtain the optimal power allocations to an antipodal signaling scheme such that the required performance is achieved with a minimum bit SNR. This is done by applying unequal gains to the transmit voltages of the two possible signals. At the receiver, the threshold of the hard decision device is biased so that the required error rate is achieved for each of the two types of errors."
i) "s1" is an ACK signal, and "s2" is a NACK signal.
ii) The probability "p" is the probability of transmitting "s1" (i.e. an ACK) and the probability "1-p" is the probability of transmitting "s2" (i.e. a NACK). In other words, the probability of the MS transmitting either an ACK or NACK is 1. This is related to the quality of the downlink channel (amongst other things).
iii) "k" is the gain to be applied to the power of the ACK signals and "l" is the gain to be applied to the power of the NACK signals. These affect the voltage at which each type of signal is sent by the MS: the higher the gain, the higher the voltage (which depends on the square root of the transmit power, or the square root of the applied gain k or l).
iv) "z" is the decision threshold in the receiver. If a received signal is higher than z, it is assumed to be an ACK, otherwise it is assumed to be a NACK. Thus moving z to the left decreases the probability of false NACKs, but increases the probability of false ACKs.
v) "pfack" is the probability of a false ACK.
vi) "pfnack" is the probability of a false NACK.
"The goal is to minimize the bit SNR γb, defined by Equation 1, subject to the constraint that the false ACK probability remain below pfack-req and that the false NACK probability be below pfnack-req."
"From the table it can be seen that the required γb is minimal when p is either very small or very large. In these cases a large voltage is applied to the less likely signal, and hence the distance between the signal points is relatively large for a small γb as defined by Equation 1. It is also interesting that the decision threshold z tends to be biased in the direction of the ACK bit that is assigned a positive voltage when pfack_req << pfnack_req. This minimizes the chance of a false ACK at the expense of a higher probability of a false NACK. Finally, the optimal detector outperforms the MAP detector by approximately 2 dB for the selected parameters."
"Due to the fading channel and power control, the actual EbNt requirement and optimal values of z, k, and l may be quite different from the values reported in Table 1. One possible approach for obtaining the correct values for z, k, and l in the context of the Reverse Acknowledgement Indicator Subchannel of 1XTREME is as follows. The ratio of k to l can be determined by the measured FER on the Forward Shared Channel. The mobile keeps track of pfack and pfnack. It can gather these statistics based on the number of duplicate and missing frames that are observed. If either pfack or pfnack are too high, the values of k and l are scaled up by a constant. If both pfack and pfnack are too low, then k and l are scaled down by a constant. The value of z can be initialized based on a Gaussian channel assumption. Then it can be adjusted based on feedback from the mobile."
Obviousness over Shad
"Q. I am not sure suggesting the skilled person would not read on, what I am putting to you is the skilled person is not going to be interested in implementing 1XTREME; I suggest to you he is interested in taking the concepts of Shad and considering how he can implement them in HSDPA?
A. Yes, and I think they would look at this and see relevance, potential relevance, to the HSDPA ACK/NACK channel, and they would read his implementation and try and follow it."
On the other hand, it can be seen from this that Mr Edwards did not accept that implementation in the context of HSDPA would in itself lead the skilled person to do anything different to what Shad taught. Nor did Mr Gould's evidence go quite that far.
"The Skilled Person would first need to contemplate the abandonment of the error statistics gathered by the MS, which are essential to Shad. Second, the Skilled Person would need to hit upon the idea of approximating ACK/NACK error statistics with SNR. Third, the Skilled Person would need to envisage replacing Shad's table with a table calculated on a different basis. Fourth, the Skilled Person would need to keep going, envisaging multiple tables for different channel conditions and geographies. Fifth, the Skilled Person would need to hit upon the idea of repeating this process still further for different error targets, corresponding to different data services. Finally, the Skilled Person would need to envisage switching between look-up tables for different channel conditions, such as different levels of uncompensated fading, based on measurement of the uplink, while also monitoring the uplink as a proxy for the target error rates."
"In [Shad], a R-ACKCH approach where the ACK and NAK responses are transmitted with different powers was presented for discussion. We believe this increases the mobile station complexity with an insignificant, if any, performance improvement. So we recommend that the baseline approach using the same power levels for ACK and NAK responses be retained."