1. C80216m-08/288r1 1 UL Control Channel Allocation Document Number: IEEE C80216m-08/288r1 Date Submitted: 2008-05-08 Source: Xiaoyi Wang, Yousuf Saifullah, Shashikant Maheshwari Voice:+8613511021252 Nokia Siemens NetworksE-mail: xiaoyi.wang@nsn.com Heping Li Dongjie, No.11 Beijing, China Venue: IEEE 802.16m-08/016r1: Call for Contributions on Project 802.16m System Description Document (SDD). Target topic: “Uplink Control Structures”. Base Contribution: N/A Purpose: Discussion and approval by TGm for the 802.16m SDD 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. C80216m-08/288r1 2 Motivations Current 16e UL control channel allocation is lack of flexibility and have a lot of overhead. The SRD requirements (IEEE 802.16m- 08/002r4) necessitate efficient control channel signaling design with capability of accommodating a large numbers of users

3. C80216m-08/288r1 3 Current fast-feedback allocation in 16e A “semi-dynamic” way of fast-feedback channel allocation is adopted in current.16 systems. –First, BS sends an index and an interval number to users (e.g. CQICH_alloc_IE). –BS dynamically allocates a fast-feedback region at every frame. –With the region information, SS locates its own fast-feedback channel by index. –SS uses fast-feedback at a certain interval (interval number) so that multi-user may reuse one fast-feedback channel. The index allocation is static since related signalling messages are designed to be transmitted once and the fast-feedback region is allocated dynamically. The 802.16e method is a simple way to allocate fast-feedback channels to users. However, it wastes some fast-feedback channels in the following cases: 1.When some CQICH indexes are de-allocated, Either messages like CQICH_alloc_IE are needed to re-adjust the index of some other users or there will be some empty gaps in fast-feedback region (some channels are not used). 2.Since some users may not need feedback at every frame, CQICH control IE also assign an periodicity to users which could be 1,2,4,8. However, this couldn’t guarantee a full occupation of the fast-feedback region. E.g. there are 5 users with interval of 8. Some feedback channels are wasted Besides, 802.16e method only provides a fixed density of fast-feedback usage to every user. It requires new allocation message whenever MS changes fast- feedback usage density

4. C80216m-08/288r1 4 Fast-feedback Channel Vacancy Problem For semi-dynamic Fast-feedback allocation method, since the index are assigned semi-statically. There might be some vacancy if some user stop using fast- feedback channel. In that case, BS might assign new index to other users to occupy that vacancy : “rearrange”. But such allocation requires signaling messages in DL.

5. C80216m-08/288r1 5 Simulation results Simulation Assumptions 1Ideal Wireless Channel 2Enough CQI Channels 3Enough signaling resource 4 Each SS in network has occupied no more than 1 CQI channel 5There are average 100 SSs using CQI channels 6On every CQI index change, signaling overhead is 2 slots 7Ration of different intervals(1:2:4:8): 1:3:3:3 OutputsDescription 1 Idle CQI channel num Average idle CQI channel num per frame 2Idle Ration Ration of idle CQI channel num to total utilized CQI channel num 3Adjust Times Average fast-feedback index allocatioin message num per frame 4Total OverheadAdjust times * 2 + Idle CQI channel Num A simulation has been done to estimate the overhead of using semi-dynamic allocation for UL feedback channels. Whenever the fast-feedback channel vacancy is more than threshold, BS will send index allocation messages to users to adjust fast-feedback channel occupation. Simulation results shows that for the best threshold value, there will be more than 4 slots wasted resource in every frame (DL singling overhead +UL fast-feedback vacancy). Considering UL resource is more valuable, the total overhead is more than that.

6. C80216m-08/288r1 6 Dynamic UL control channel allocation A dynamic method is developed for fast-feedback channel allocations. When BS detects sufficient gaps in the fast-feedback region because of de-allocation of some CQICH channels for some MSs. –BS transmits the bitmap in the UL-MAP to perform the shifting of CQICH channel used by active MS scheduled to transmit fast-feedback information in scheduled fast-feedback region. a compact fast-feedback occupation can be achieved. E.g. if the bit map is #1010, Where user 1 and user 3 are active while fast-feedback channel of user 2 and user 3 are de-allocated. In this case BS shall schedule a fast-feedback region with 2 channels. user with “bitmap index=1” should use fast-feedback channel 1 and user3 (index=3) should occupy fast-feedback channel=2, since user=2 has been de-allocated Since bitmap is multicast, users know which fast-feedback channel it should use.

7. C80216m-08/288r1 7 Advantages Proposed compact method of remapping the CQICH channel for MSs. No waste of any fast-feedback channels if some MS’s CQICH channels are de-allocated. Proposal can be dynamically used by BS to maximize the benefits. Proposed method is flexible to adjust the density of fast-feedback channel usage of every user whenever needed.

8. C80216m-08/288r1 8 Proposed Text to be included in SDD Insert the following text into section 10. 10.x Fast-feedback channel allocations –Each user are assigned with an index. –BS may broadcast the “CQICH Channel Remapping bitmap” to perform the shifting of CQICH channel used by MS scheduled to transmit fast-feedback information in the scheduled fast-feedback region. MS determines its current CQICH channel index by subtracting the number of Zero’s in the “CQICH Channel Remapping bitmap” before its allocated CQICH channel index.