LTE/Wifi coexistence (how to control number of back-off stages of LAA eNB)

[Joon 호]

Hello,

I want to fix the number of stages of LAA eNB,  so could anyone give me how to control LAA eNB's back-off stage?

also how to control CW of LAA eNB as well.

[Zoraze Ali]

Hi Joon, 

Have a look at lbt-access-manager.cc . 

Kind regards,

Zoraze 

[Joon 호]

Hi Zoraze,

Thanks for your comments. I looked into the file you mentioned and I found the variable that seems to be relevant as follows:

static ns3::GlobalValue g_cwUpdateRule ("cwUpdateRule",
                                         "Rule that will be used to update contention window of LAA node",
                                         ns3::EnumValue (LbtAccessManager::NACKS_80_PERCENT),
                                         ns3::MakeEnumChecker (ns3::LbtAccessManager::ALL_NACKS, "all",
                                                   ns3::LbtAccessManager::ANY_NACK, "any",
                                                   ns3::LbtAccessManager::NACKS_10_PERCENT, "nacks10",
                                                   ns3::LbtAccessManager::NACKS_80_PERCENT, "nacks80"));

Could you explain how to interpret the enum  (ALL_NACKS, ANY_NACK, NACKS_10_PERCENT, NACKS_80_PERCENT) ?

is there any  meaning of no contention window update ? because I am looking for the option of no back-off stage used in LAA.

Thanks in advance.

Regards,

Joon

2017년 8월 6일 일요일 오후 10시 58분 37초 UTC+9, Zoraze Ali 님의 말:

[Zoraze Ali]

Hi Joon, 

By standard, the contention window size (CWS) at eNB is updated, if Z=80% of HARQ feedbacks from the first subframe of the latest transmission burst are NACKs. So, if the attribute you found is configured to NACKS_80_PERCENT, it corresponds to the standard rule. Besides this rule, the attribute gives you three more option as follows, 

ALL_NACKS: Update CWS if all the feedbacks are NACKs

ANY_NACK: Update CWS if any of the feedback is NACK
NACKS_10_PERCENT, "nacks10": Update CWS if 10% of the feedbacks are NACKs

It maybe helpful for you to read this paper: https://www.researchgate.net/publication/301816703_Simulating_LTE_and_Wi-Fi_Coexistence_in_Unlicensed_Spectrum_with_ns-3

Could you please rephrase your following questions?

is there any  meaning of no contention window update ? 

because I am looking for the option of no back-off stage used in LAA.

Kind regards,

Zoraze

[Joon 호]

Hi Zoraze,
The paper you refer to is very useful to me and I realuze that backoff mechanism of LAA is based on HARQ feedbacks.

The meaning of my question , I assumed that LAA does not use backoff and if there are contensions, just reset backoff timer to initial value with initial contension window size. So I expected there is a way to disable updating contension window to next higher value. But there is not, instead, if I use ALL_NACKS option, this seems to be similar to what I want.

One more question for you, please show me how to change control mode between RTS/CTS and Basic scheme.

Best wishes,
Joon

[Zoraze Ali]

Hi Joon,

Well to stop LAA to update its contention window to next value, irrespective of any update rule, why not you just set the maxCW value to minimum(Just a thought). I assume you are asking about WiFi's RTS/CTS, have a look at the attributes of WifiRemoteStationManager,

https://www.nsnam.org/docs/release/3.26/doxygen/classns3_1_1_wifi_remote_station_manager.html

PS: Just to have quick answers you could also search the group first, e.g., just search for RTS/CTS

Kind regards,
Zoraze

[Joon 호]

Hi Zoraze,
Thanks a lot for helps.

Best regards
Joon

[Dorra Boughzala]

Hello Joon ,

For testing LAA with no backoff option , you need to use "  basic-lbt-access-manager " . In other words ,you just need to set you ChannelAccessManager as BasicLbt

Best regards ,

Dorra