Re: [802.3_EPOC] Study Group Questions
刚才的邮件不知道为什么被过滤掉了我单独发一次试试。
十分遗憾，我参加不了。能否简单介绍一下频率分割和放大节距（关系到电缆是否需要重新开口）是否改变？我听到一种说法：上行没有变只是下行扩展到3GHz，不知是否确切？如果如此，那么EPOC应用还需要改造同轴网。如果这一次改造只按照博通目前设计的下行5G、上行1G，扩展到1.7GHz，那么三年以后主流应用可能会扩展到双向10G，到那时再改造一次？如果电缆需要重新开口（这是很不好的），那实际上还要重新敷设电缆，因为原有开口位置的余留电缆要改变到新开口处，如果开口增加过多，余留可能会无法满足，这些工程因素考虑起来，人工也不少。再考虑到放大器的耗电、维护，我感觉，即使在北美，也不如一次改造成N+0合算。
在N+0的情况下，FDD应用依然不如TDD灵活，因为设备生产之后频率分割点就确定了，不可能随时改变。而TDD在任何地方都一样，没有分割问题，随便哪一段空闲频谱都可以用。至于MAC层改动的问题，我昨天已经说过，在静态分配上下行带宽的前提下，跟FDD没有本质区别。我这么说不是否定FDD，只是希望充分看到TDD的优势，能够既支持FDD,又支持TDD。这样不是分割市场，而是扩大市场。
姚永
----- Original Message -----
From: Eugene.Dai@xxxxxxx
To: yy0412@xxxxxxxxx ; wuguangsheng@xxxxxxxxxx
Sent: Friday, January 06, 2012 6:16 AM
Subject: RE: 咨询Cox 3GHz HFC网络情况
Are you coming to the IEEE 802.3 interim meeting this month? If so we can discuss there.
Thanks,
Eugene
----- Original Message -----
From: "Matthew Schmitt" <m.schmitt@xxxxxxxxxxxxx>
To: <STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>
Sent: Wednesday, January 04, 2012 6:46 AM
Subject: Re: [802.3_EPOC] Study Group Questions
> Alex,
>
> In response to your comment below to me...
>
> I'm not sure I agree that a TDD system inherently provides more spectral
> flexibility than an FDD system in a passive coax environment. Depending
> on the PHY layer, you can do quite a bit of steering regardless of FDD vs.
> TDD. I will agree that a TDD solution can provide advantages in terms of
> the relative allocation of bandwidth to upstream vs. downstream operation,
> although only with a MAC designed to support such features.
>
> That said, I'm more than open to being proven wrong, and so I will
> definitely look forward to your presentation to highlight why you believe
> TDD had advantages over FDD.
>
> BTW, I also tend to agree with others on this thread that it's MUCH
> preferred if we can develop a single solution. Without that, you end up
> with a fragmented market, and it's much harder to achieve the same
> economies of scale that you could have with a single, unified solution.
> If it's simply not possible to come up with a single unified solution, so
> be it; but I think that should be our goal if at all possible.
>
> Thanks.
>
> Matt
>
>
>
> On 12/15/11 7:48 PM, "Liu, Alex" <alexliu@xxxxxxxxxxxxxxxx> wrote:
>
>>Ed,
>>
>>Let me reiterate some of the finer points of my previous missive: (1) TDD
>>systems have a wide footprint in China in part due to their spectral
>>convenience, (2) TDD should be an optional profile in addition to and not
>>in place of FDD. I do believe that market enthusiasm for, and acceptance
>>of, this standard and its ensuing products should be our guiding
>>principle, and not doctrinal orthodoxy within a standards framework. If
>>things weren't so, Ethernet would have never abandoned CSMA/CD for
>>first-mile applications.
>>
>>More specifically, it is clear that an FDD RF system that directly maps
>>to the dedicated wavelengths in fiber and thus the EPON protocol is most
>>appropriate for the N. American MSO environment. I would like to raise
>>the possibility that this is not necessarily true for China. Passive
>>cable plant coupled with haphazard spectrum planning makes for an
>>inviting TDD target. There are then the orthodoxies emanating from the
>>Chinese side. If we are serious about targeting the China market, I
>>suggest we consider SARFT's input.
>>
>>@Matt: TDD's ability to operate in unpaired spectrum makes "lively"
>>spectrum plans possible in China. Perhaps this is improperly termed
>>"coexistence with" and is better called "steering around" existing TV and
>>data systems. This additional degree of freedom may perhaps be attractive
>>to N. American operators as well.
>>
>>@Mark: we *are* working toward a single standard. Transparent EPON
>>protocol operation over coax is the goal and FDD RF operation should be
>>the mandatory supported mode. Employing the modern PHY proposals being
>>developed in an optional TDD mode should not detract from this stated
>>goal. LTE offers an instructive precedent.
>>
>>Alex
>>
>
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