ePMP 1000 / 2000 / 3000 Performance questions

Hello all,

I had some questions and you might be interested in the same answers so I will ask them here.

as I become more interested in signals processing and such I wanted to know a few things about the ePMP system assuming we have a noise free channel and we have no retransmissions.

I would like to know how many frames per second the proccessing system is able to handle, i would also like to know if possible the symbol duration and what type of FEC is used i know we have numbers in the spec sheet but they do not tell us what method of forward error coding is being employed I know that we have some form of ARQ inplace also.

I guess what i would like to know is how the frames are constructed and the data is processed by the radios as they are received. at the other from a to z  also a flow chart of the process would be nice if possible.

Thanks

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@Spookiewrote:

Hello all,

I had some questions and you might be interested in the same answers so I will ask them here.

as I become more interested in signals processing and such I wanted to know a few things about the ePMP system assuming we have a noise free channel and we have no retransmissions.

I would like to know how many frames per second the proccessing system is able to handle, i would also like to know if possible the symbol duration and what type of FEC is used i know we have numbers in the spec sheet but they do not tell us what method of forward error coding is being employed I know that we have some form of ARQ inplace also.

I guess what i would like to know is how the frames are constructed and the data is processed by the radios as they are received. at the other from a to z  also a flow chart of the process would be nice if possible.

Thanks


these questions have been asked in the past, and most of them are answered in some of the original webinars. those can be re-watched in the webinar section.   

the specifics in the frame itself, cambiums always been hush about because they've done what no one else was able to do with these chips. I do know they chopped away a lot of the wifi overhead and extras that used to be there, and they organized the transmission almost completely different, but that's all I have.  

maybe a little more of the magic will get shared soon :)

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Hi, 

As Chris suggested, please feel free to checkout our webinar archive. There should be a few of them that will give you a nice overview of the custom technology behind ePMP. 

Some notes:

1. ePMP uses ARQ and not FEC

2. The frame is a TDD frame and can be configured as 5ms or 2.5ms in length. The frame contains the Tx portion and a Rx portion. Unlike WiFi, where there may be several gaps in the frame for timing advance to different subscribers, there is only a single gap for transition from TX <-> Rx to account for timing advance. This allows for efficient use of the frame. Some of the webinars may cover this. 

3. #2 applies when the AP is in TDD or TDD PTP mode and they allow frequency reuse via GPS sync. There is a third mode called ePTP mode and that is low latency non TDD mode of operation. You cannot sync in ePTP mode.

Sriram 

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Hi Sriram,

good day!
correct me if i'm wrong yet based on you;
1. ePMP uses ARQ and not FEC

yet on  the ePMP User Guide 3.5.1, it said that ePMP are using FEC.

see attached screenshots.

please enlighten me.

My apologies. That was a gross error on my part. ePMP uses ARQ and FEC. I don't know why I typed "not" in there. I need to proof read my posts before posting. 

Sri… so epmp is using a hybrid method of arq/fec error control?

Hi CWB, 

Not sure what you mean by hybrid. ARQ is used in addition to FEC on ePMP. 

Sriram

What I am referring to is called HARQ (Hybrid ARQ). It is a combination of FEC and ARQ. There are at least 2 protocols of HARQ that I am aware. Thought you may be using this for error correction.


@CWB wrote:
What I am referring to is called HARQ (Hybrid ARQ). It is a combination of FEC and ARQ. There are at least 2 protocols of HARQ that I am aware. Thought you may be using this for error correction.

Thanks for the clarification. No, ePMP does not use HARQ like in WiMAX. 

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