1. Inter Working Signal (IWS) for Femtocells Detection Document Number: IEEE C80216m-09/1124 Date Submitted: 2009-04-30 Source: Jaehee Cho, Youngbo Cho, Jonghyung Kwon, Email: Jaehee1.cho@samsung.comJaehee1.cho@samsung.com Jumi Lee Samsung Electronics Venue:IEEE Session #61 Base Contributions: Re: IEEE 802.16m-08/003r8 Purpose: Discussion and Approval Notice: This document does not represent the agreed views of the IEEE 802.16 Working Group or any of its subgroups. It represents only the views of the participants listed in the “Source(s)” field above. It is offered as a basis for discussion. It is not binding on the contributor(s), who reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.16. Patent Policy: The contributor is familiar with the IEEE-SA Patent Policy and Procedures: and.http://standards.ieee.org/guides/bylaws/sect6-7.html#6http://standards.ieee.org/guides/opman/sect6.html#6.3 Further information is located at and.http://standards.ieee.org/board/pat/pat-material.htmlhttp://standards.ieee.org/board/pat

2. 2 Motivation Due to inter-FA scanning, chance of breaking of real time service will increase in Femto deployment – Scanning duration will break real time service In M-WiMAX, scanning duration is typically 10 frames (50 ms) – Scanning will occur due to omni-presence of femto BS In M-WiMAX, scanning occurs only in coverage edge There are some concerns to IWS such as additional IOT, DoS problem, etc. – However, the proplems are inevitable and our solution is presented in this slides.

3. 3 Additional IOT for Femto We can easily find additional IOT items for femto BS/MS – CSG operation ID acquisition, CSG access control – Hand in for femto without help of NBR list – Low duty mode of femto BS The increment of IOT test case is very limited – For IOT test purpose, IWS can be considered as a P-SFH It does not have much variants – DL/UL PHY will have much variation due to partition/subbands

4. 4 DoS Problem There are two scenarios in femto deployment – Scenario 1 Assumption: Femto and Macro BS shall operate in different FAs Certification on femto BS – Certification will not guarantee femto BS not to cause any DoS problem when femto BS transmits in macro FA DoS from IWS – Cheep femto BS can Tx IWS in macro FA and it may cause DoS – Scenario 2 Assumption: Femto and Macro BS can operate in same FAs – It allows femto and macro BS will operate in the separate FAs Certification on femto BS – Certification shall guarantee femto BS not to cause any DoS problem when femto BS transmits in macro FA DoS from IWS – The certification of IWS is just one of certification for the case femto and macro BS operate in the same FA – The certification will guarantee no additional DoS due to IWS Evaluation of scenario 1 and 2 – Assumption of scenario 1 is not feasible Femto forum, Mobile WiMAX assume and etc. assume same FA operation Conclusions – IWS will not cause any additional DoS problem

5. 5 Femto BS synchronization in TDD mode 1/2 Unsynchronized Femto BS will create blocking area near Femto BS – DL macro signal will be interfered by UL Femto MS Tx UL Femto MS ’ s Tx will create blocking area – 10 meters from building wall where femto is installed is blocking area The least interference level in the 10m blocking area is -55dBm (EMD based) RX signal strength of 50% of macro MSs is less than -67dBm (EMD based) SNR of 50% of macro MSs is less than -12dB due to non-synchronization 10m from building wall means that streets in Manhattan Model are blocking areas Distance from wall 5 m10 m The Interference Level at blocking area >-50 dBm>-55 dBm Various EMD indoor model with additional wall loss (~20dB) Femto MS is located 1 meter away from building walll Femto MS Tx at 23dBm

6. 6 Femto BS synchronization in TDD mode 2/2 Samsung suggests not to allow un-synch Femto BS to transmit – At least, Femto BS coverage overlaps with neighbor BSs ’ Coverage In case C, only network entry after FA search will happen. – IWS nor snooping is needed The BS ’ s identification of case C is necessary to determine ordinary DL/UL. – There is no reason to identify case C for IWS Tx because IWS will not be used in the case – Rather, one needs to find how to identify case C to allow such un-synch femto to Tx signal (A) Coverage overlaps & Synchronized (B) Coverage overlaps & Non-Synchronized Not allowed (C) Coverage Not overlaps & Non-Synchronized But allowed

7. 7 Differentiating case B and case C Basically, it is not the scope of IWS – Breaking real time service is not problem in B/C Our solution – MS report can help macro/femto BS to differentiate B and C Case B: When a MS detects both macro/femto BS at a time Case C: When a MS detects only femto BS and cannot detect macro BS at a time – Operation If a MS connected to macro BS detects asynch femto BS, the MS sends a report femtocell’s information (BS ID, timing offset, etc) to the macro BS If new femto BS is reported, the macro BS update neighbor list and force femto BS to turn off. – Such report is already assumed for HO parameter optimization or coverage hole compensation

8. 8 Conclusions Adopt IWS as solution to frequent inter-FA scanning – IWS will be distinctive feature in 16m spec. – IWS will be applied only for femto BSs with synchronization Isolated Femto BS does not need IWS – In this case, AMS have to operate inter-FA scanning Overlapped but non-synch BS shall not transmit anything – Otherwise, it will cause serious interference – Assuming the same FA operation of femto/macro, DoS argument does not stand anymore – Additional IOT except IWS for femto BS is inevitable The amount of additional IOT is very limited