Lecture Series in Mobile Telecommunications and Networks (1583KB)

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From plain old Telephony to flawless mobile audio communication bandwidth extension module at the transmitter side will do the job. However, there is still much work to do and the listening tests have to be done on a broad basis. Perhaps I could just add a further comment to the last question. If we are moving towards UMTS LTE, and we are allowed to increase somewhat the bit rate, then the codecs will become more and more transparent to any kind of strange dialect. Andy Evans (Cable & Wireless EAUS): I just wondered how much interest there is in the standards forums in actually adopting these different codecs in future mobile standards – particularly LTE? Peter Vary: As far as I understand it – and I guess Mike can comment on that – one of the main reasons for the NGMN initiative is that there are too many standards and that the operators are surprised that there are the solutions A, B, C and D and you have to implement them all and then you will see on the market whether it is a good solution or not, and whether it is taken or not. The operators try to steer the standardisation and to settle all the critical issues, including the IPR method, before the standard is written. Michael Walker: I can add to that. One of the big costs in the business is that, because of the standardisation process, you often have multiple solutions for the same problem. All those solutions get implemented in the equipment and that is a waste of the resource. If we are going to see technologies like this, which could actually offer the user much more benefit, having multiple choices for basic functionality, then we have to resolve that problem. Dr Tim Moulsley (HJM Ltd): I am an independent consultant but formerly I was with Philips. Peter Vary: Yes, you were a colleague of mine. Tim Moulsley: Just picking up the point we are on now, which is looking at the standards for codecs, I wonder how the take-over of an all-IP network, both in fixed and in mobile, will affect this kind of debate. That would tend to push the codec to the application level, where there is much more flexibility about which codec standard you actually have, than if it is in as part of the wireless network or part of the telecoms network itself. Would you like to comment on that? Peter Vary: My impression is that voice-over IP is actually the driving force to introduce wideband in cellular. The point is that no one has the chance to listen to a phone in the shop. If you go to a shop to buy a telephone, you have no idea and you don’t think that it makes any sense to listen to the quality – because a phone has a certain quality and it is a phone. Now, however, we see some experienced users having voice-over IP communication. Voice-over IP can be significantly worse or sometimes much better. Many things are going on there. We have Skype and we have SIP telephones. We have the evolution of cordless telephones, the DECT telephones. They have now decided to implemented wideband the codec and you can buy DECT telephones which have two connections to networks – one traditional network, the telephone network, and one to the DSL router at your home. If you connect it to the DSL router, you have wideband speech with excellent quality. You have greater flexibility in voice-over IP and this will sort out which codecs will survive. There is also a debate between the mobile community and the IP community – that is, ITU on one side and 3GPP – as to whether we should use a universal codec in future in both fixed and wireless networks. There is some hope because they are talking to each other to get the same codec under a 3GPP number and under an ITU number. Some voice-over IP operators are already using AMR wideband. Professor Chris Guy (University of Reading): There is rather a chicken and egg situation here, because you have the operators and the handset manufacturers but who will jump first and implement it? One has to go before the other. Peter Vary: I try have tried to support this topic of wideband for many years, because I like it. I have been involved in many talks and contacts with manufacturers and operators. What you usually hear is that the manufacturers are saying that the operator does not require it, while the operator is saying that there are no terminals. I heard the same story just last week. I said to the operators that, if they introduced wideband, that would be some improvement compared to their competitors, and people would talk for longer. They would do more business if they had wideband codec. That is what The Royal Academy of Engineering 57
I said five years ago and what I hear now is that they are saying that they don’t like people talking that much because they have flat rates – so they should not talk at all. [Laughter] Andrew Poh (Qualcomm): I am speaking in my own personal capacity and I have three questions. The first is just for clarification on my part because I may have missed something. You mentioned the turbo error protection and the use of iterative source channel coding. Do you see this as something that you would use on the receiving side of the handset? You will probably incur some latency, going through the turbo error protection, as you go through a few iterations. Peter Vary: You can apply it to any standard transmission system. We have applied it just to plain GSM. You do not need to change the transmitter but you can do it just at the receiving end by additional processing and exchange of information between the channel decoder and the source decoder. However, if you study that in greater detail, you will discover that you can further improve if you modify the transmitter but it is a matter of the environment in which you apply it. If we were starting to think about a new radio standard, then we would say that you should not use Gray coding, for example, index mapping at the transmitter, but there are better solutions. We can improve the existing system. Andrew Poh: Is that applicable for real time volume, since there will be some latency if you go to - ? Peter Vary: There are two sources of latency. One is the interleaver and we have it there, and it is sufficiently large. The second is some latency due to processing but, in any case, you have to do the processing before the next packet arrives and so you have to increase the processing speed. The turbo decoding as such, therefore, will not increase the latency. Andrew Poh: My second question follows on from the question asked earlier. There was the question about the use of AMR wideband and I guess this has been debated in the mobile community for quite some time. The operators will always argue that no one is really willing to pay any extra for it and so they have been dragging their heels, and we have seen that happening. They always say that it will be this year, but it never happens. With the introduction or standardisation of AMR wideband and 3GPP, it is taking an awfully long time. Companies like Skype, as we know, have this week introduced a new wideband speech codec. Is it possible that doing that on a packet-switch network, using perhaps a Windows mobile phone and just downloading the codec, would be quicker than getting the industry together to introduce AMR wideband over a circuit switched connection? Peter Vary: Yes, that is what we hear. There is a consensus that if we have UMTS LTE it will be packet transmission and then there will be greater flexibility and more convergence with the internet world. However, we should be careful here because latency is an issue, the headers are an issue, and the frequency/economy is an issue, as is the energy efficiency. If you require short latency, the packets are short but you have the header and you could discover that you double the number of bits you have to transmit and therefore you need to improve protocols, header compression and techniques like that – at least on the air interface, and then you go into the fixed network. I am pretty sure that the future will be IP. Andrew Poh: My third question is something which you perhaps touched upon in your very excellent presentation: 3GPP works like something like distributed speech recognition. Obviously, they also debated whether to use something for speech communication or whether to go for a totally different codec which is optimised for machine recognition, a speech recognition type of thing. Would you be able to comment on the use of a codec for speech recognition? Peter Vary: The idea is to do the speech recognition task not in the mobile but to have in the mobile just the feature extraction: you don’t transmit the speech, but you extract the features. You save computational power in the mobile and you have a very powerful processor in the fixed network. The idea is not that bad, but I am not sure. I am not sure about speech recognition at all. We have been hearing for years that there will be a breakthrough within the next one, two or three years. As the quality is hopefully increasing in the network, if you have wideband coding, the question is why should we do the parameter extraction in the mobile and the recognition task in the central switching office? If we check the bit rates for a codec like the AMR codec, you will see that roughly 50 per cent of the bit rate is for the parameters of the vocal tract and the model, and this is exactly the information you need for speech recognition. You will not save that much in terms of bit rate. I know that there is standardisation and that there are some very nice, interesting research topics, but I do not really see that as the future of speech recognition. I don’t know. 58 The Royal Academy of Engineering
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Lecture Series in Mobile Telecommun
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Foreword This compilation brings to
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From wireless networks to sensor ne
Page 7 and 8: From wireless networks to sensor ne
Page 9 and 10: As far as the routing of packets is
Page 11 and 12: easons. In the internet, one never
Page 13 and 14: Implementation with laser pointers,
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Page 19 and 20: Questions & Answers Mike Walker: Th
Page 21 and 22: Human beings will also evolve and w
Page 23 and 24: Welcome and introduction Professor
Page 25 and 26: ComReg Collection - Start 16/Apr/20
Page 27 and 28: evidence that people give in favour
Page 29 and 30: chunks of spectrum where you are in
Page 31 and 32: As an aside, I was reading a few of
Page 33 and 34: Of course, it is not just one mask,
Page 35 and 36: I apologise for hopping between top
Page 37 and 38: Questions & Answers Michael Walker:
Page 39 and 40: Nobody - believe you me, it came ou
Page 41 and 42: The second aspect of my comment is
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Page 45 and 46: From plain old Telephony to flawles
Page 47 and 48: From plain old Telephony to flawles
Page 49 and 50: You can see that there is much room
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Page 53 and 54: Bandwidth extension with hidden sid
Page 55 and 56: 4 Vision: ambience audio communicat
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Lecture Series in Mobile Telecommunications and Networks (1583KB)

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