1. Title: Control channel allocation for femto-cells
Document Number: C802.16m-08/1350r1
Date Submitted: November 10, 2008
Source:
Mariana Goldhamer Voice:
ALVARION
21a HaBarzel Street, Tel Aviv, Israel
Venue:
Session #58, November, 2008
Base Document:
Purpose:
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2. Deployment problem 1 – high density of femto-BS creating interference to macro-MS
MS associated
with macro-BS

3. Deployment problem 2: blocking of the MS operating next to a femto-BS
The interference power at 1m distance is -15dBm
The receive power level is around -95dBm
Obvious MS receiver blocking
In the same channel
Also if the MS operates on the adjacent channel
The adjacent channel rejection is around 23dB
Femto-BS
25dBm eirp
MS associated
with macro-BS
1m,
40dB attenuation

4. Control channels operation
Macrocell operation
Using all the superframe; the interfered MS shall be protected at least at the superframe start to hear the control info
Preamble, FCH, MAPs
No femto-BS operation at the multi-frame start
No femto-BS operation in the OFDMA allocation for Reuse 1/3
Femto-cell operation
To be allowed only during certain frames or sub-frames
To use different control channel allocation from those used by the macro-cell

5. FFR in SDD – Clause 20.1 Separation in OFDMA domain
Macro cells to take the Reuse 1/3 partition
Femto-cells to use the Reuse 2/3 partition, but the actual reuse factor needs to be defined

6. Possible solution Frame 1 Superframe DL UL Reuse 1/3 Reuse 1/3 & 2/3
Dedicated resources for Cat. 1 Control Channels, DL and UL
Additional resources for Cat. 1 Control Channels, DL and UL
Frame 1
Superframe DL UL
Dedicated resources for Cat. 3 Control Channels, DL and UL
Additional resources for Cat. 3 Control Channels, DL and UL
Reuse 1/3
Reuse 1/3 & 2/3
Reuse 1
Frame 2
Frame 3
Frame 4

7. SDD Text Insert new clause 11.4.5:
Support for the Control Channels of femto cells in Frame Structure
802.16m systems shall support the staggering of Superframe start times, for allowing mobile stations in the vicinity of a femto-cell or a pico-cell to hear the control information from a faraway base station; the control information for femto-cells should be sent in the 2nd frame of the superframe.
The control channels of the femto cells shall use a different OFDMA partition from the partition used by the macro-cells. There is a need for multiple partitions.
An example of the Control Channel allocation, consistent with fig. 45, SDD clause 20.1 is presented in fig. xx. Controls channels for macro cells are placed in the Reuse 1/3 area of the first Frame within the superframe;
Control Channels for femto-cells are placed in the 2nd Frame of the Superframe, avoiding the Reuse 1/3 allocation reserved for macro cells.

8. Fig. xx Frame 1 Superframe DL UL Reuse 1/3 Reuse 1/3 & 2/3 Reuse 1
Dedicated resources for Cat. 1 Control Channels, DL and UL
Additional resources for Cat. 1 Control Channels, DL and UL
Frame 1
Superframe DL UL
Dedicated resources for Cat. 3 Control Channels, DL and UL
Additional resources for Cat. 3 Control Channels, DL and UL
Reuse 1/3
Reuse 1/3 & 2/3
Reuse 1
Frame 2
Frame 3
Frame 4