Re: [802.3_EPOC] Study Group Questions
是只适应一部分市场好还是适应所有市场好？
FDD技术实现比较简单，但频谱规划很困难，特别是针对全球，很难统一。这和DOCSIS不同——一个下行信道只需要8MHz及以下频谱，如果采用FDD方式，应该按照10GEPOC规划，否则后续升级无法后向兼容，而10G系统频谱很难规划；对于邻信道干扰，在EPOC系统也和DOCSIS完全不同——DOCSIS是多信道应用，FDD有很大好处，但EPOC是单信道应用（很难找到满足多信道的频谱）。4G就是同时支持TDD和FDD的。FDD比较容易支持有源中继，但考虑到频谱规划的难度和改造的投资，我很怀疑是否值得——与其改造同轴网，还不如光纤延伸，取消放大器。
姚永
----- 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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