Doc.: IEEE 802.11-09/0782r0 Submission July 2009 Carlos Cordeiro, IntelSlide 1 Spatial Reuse and Interference Mitigation in 60 GHz Date: 2009-07-14 Authors:

July 2009

Carlos Cordeiro, Intel

Slide 1

doc.: IEEE 802.11-09/0782r0

Submission

Spatial Reuse and Interference Mitigation in 60 GHzDate: 2009-07-14

Authors:

Name Affiliations Address Phone Email

Carlos Cordeiro Intel Corp. OR, USA 503-712-9356 [email protected]

Sai Shankar Broadcom CA, USA [email protected]

Gal Basson Wilocity Israel [email protected]

Liwen Chu ST Micro CA, USA [email protected]

James Yee MediaTek Taiwan [email protected]

Yong Liu Marvell CA, USA [email protected]

Yongho Seok LGE S. Korea [email protected]

Minyoung Park Intel Corp. OR, USA [email protected]

Solomon Trainin Intel Corp. Israel [email protected]

Jason Trachewsky Broadcom CA, USA [email protected]

Chao-Chun Wang MediaTek Taiwan [email protected]

Christopher Hansen Broadcom CA, USA [email protected]

July 2009


Slide 2

doc.: IEEE 802.11-09/0782r0

Submission

Introduction and Goals

• As described in [2], channel access in 60GHz will use directional communication

• As a result, there is a big potential to exploit spatial reuse in 60GHz and increase the spectrum efficiency– This becomes even more important in those regulatory domains

with a single 60GHz channel (e.g., Australia)• On the flip side spatial reuse may also increase

interference, since a higher number of links will operate simultaneously and may interference with each other

• Therefore, in this presentation we:– Introduce spatial reuse and the potential it holds in 60GHz– Propose that TGad provides means for spatial reuse and

interference mitigation in 60GHz

July 2009


Slide 3

doc.: IEEE 802.11-09/0782r0

Submission

What is spatial reuse?

• Spatial (Frequency) Reuse = Two or more links sharing the same frequency channel in the same spatial vicinity at the same time

STA 3 STA 4

STA 2

STA 1

PCP

Spatial reusewithin one BSS/PBSS [1]

Example in the home

Spatial reuse across neighboring BSS/PBSS [1]

Example in the office

July 2009


Slide 4

doc.: IEEE 802.11-09/0782r0

Submission

Example usage models [3][4] which can take advantage of spatial reuse

• Wireless networking for small office (usage 2d in [3])

• Multi-media mesh backhaul (usage 4a in [3])– Hotspot, enterprise, small

Office or home, campus-wide deployments, municipal deployments

• Enterprise cubicle [4]

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The Enterprise Cubicle [4]

July 2009


Slide 5

doc.: IEEE 802.11-09/0782r0

Submission

Recap of [1]: the Personal BSS and high-density environments

• To support several key TGad usages [3] and cope with directional communication in 60GHz, the Personal BSS (PBSS) was introduced in [1]– PBSS is an extension of the IBSS

• PBSSs are logical and “unmanaged” networks– Not defined by physical proximity (e.g., as it is typical in a BSS),

and hence there can be multiple PBSSs in the same vicinity– Typically not managed by an authority with global information

(e.g., IT department)– Thus, PBSSs can lead to a highly dense environment

• Number of interfering links >> the number of available 60GHz channels (e.g., enterprise cubicle [4])

• Important TGad usages require a high spectrum efficiency and interference mitigation mechanisms

July 2009


Slide 6

doc.: IEEE 802.11-09/0782r0

Submission

Assessing the spatial reuse gain (1)

• Goal: compare the potential of spatialreuse with omni and directional communication

• Topology– Enterprise cubicle [4]– 9 cubicle office space, each office has

one randomly placed link• Simulation parameters

– Transmit power = 10 dBm– Square ant. array (random orientation)– No. of ant. elements = 1 (omni)

and 16 (directional)– NF=8 dB, implementation loss = 2dB– 5 reflectors/cube (2 dB reflection loss)– Penetration loss of partition wall = 3 dB*

• Methodology– Links are added to the office as long as the SINR of active links do not drop below a

prescribed SINR Threshold

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* This is based on internal channel measurements, which revealed that the penetration loss of a cubicle wall ranges from -3~-1 dB

July 2009


Slide 7

doc.: IEEE 802.11-09/0782r0

Submission

Assessing the spatial reuse gain (2)

• Spatial reuse through directional only communication can provide up to 5 times performance gain over omni communication

Spatial reuse gain

SINR Threshold = 20dB SINR Threshold = 10dB

Spatial reuse gain

July 2009


Slide 8

doc.: IEEE 802.11-09/0782r0

Submission

The Impact of Spatial Reuse on Interference

• Spatial reuse provides large gain, but may also lead to increased interference

• To evaluate this, we have setup a simple MAC simulator in OPNET– No “multiple access” (only 2 STAs per link and per

PBSS)

• The Antenna/RF model of this simulator is the same as in [5]– The simulator implements the partition-based path loss

model [6]

July 2009


Slide 9

doc.: IEEE 802.11-09/0782r0

Submission

Simulation parameters

• PHY: – Antennas:

• PCP [1]: 36 antenna elements• STA: 16 antenna elements

– TX_Power: 10dBm output power – PHY_Rate (fixed, no real time link-adaptation)

• PHY rate of 3.8 Gbps used for directed data transmission• PHY rate of 0.9Gbps used for directed control transmissions• Beacon is transmitted with an effective rate of 2.5Mbps

• MAC: 16msec beacon interval• Traffic: each PBSS has one flow which sends

data at 751 Mbps CBR traffic rate

July 2009


Slide 10

doc.: IEEE 802.11-09/0782r0

Submission

Example: Spatial Reuse (1)

PBSS 2 PBSS 1

PBSS 1 PBSS 2

CBR Traffic Load

751 Mbps 751 Mbps

Packet Drop 0% 0%

Application Throughput

751 Mbps 751 Mbps

•The two PBSSs can achieve spatial reuse with good throughput and no packet drop

Transmissions on top of each other:allowing spatial reuse

CBR=Constant Bit Rate

time

PBSS 1 “on” times


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1m

July 2009


Slide 11

doc.: IEEE 802.11-09/0782r0

Submission

PBSS 2 PBSS 1

STA in PBSS 2 moved

to a different location

•PBSS 1 suffers significant throughput degradation due to interference from PBSS 2

• Also leads to higher power consumption and latency

Example: Interference impact (2)

Transmissions on top of each other:causing interference

PBSS 1 PBSS 2

CBR Traffic Load 751 Mbps 751 Mbps

Packet Drop before re-transmission

59% 0%

Packet Drop after re-transmission

33% 0%


504 Mbps 751 Mbps

time



1m

1m1m

July 2009


Slide 12

doc.: IEEE 802.11-09/0782r0

Submission

How to mitigate the interference impact? Some options

• Several mechanisms are possible to mitigate interference such as channel switching and power control

• In addition, there are options which are access scheme dependent. For example:– Random access inherently adapts to the available bandwidth (there

are challenges to this in 60GHz though [2])– For scheduled access, re-scheduling on the basis of interference

may be used

• Or a combination of an access scheme dependent option with power control and/or channel switching

July 2009


Slide 13

doc.: IEEE 802.11-09/0782r0

Submission

PBSS 2 PBSS 1

• STAs in PBSS 1 detect the interference and re-schedule their links

• This helps the performance of PBSS 1 to recover

• If security is not a concern, PBSS 1 and PBSS 2 could also be merged

Example: Interference mitigation in scheduled access

Time-sharing the channel

PBSS 1 PBSS 2

CBR Traffic Load 751 Mbps 751 Mbps

Packet Drop

Before re-transmission

4% 0%

Packet Drop

After re-transmission

3% 0%


730 Mbps 751 Mbps

time

PBSS 1 “on” times (after re-scheduling)

PBSS 2 “on” times (after re-scheduling)

1m1m1m

July 2009


Slide 14

doc.: IEEE 802.11-09/0782r0

Submission

Conclusions

• Directionality makes spatial reuse a natural characteristic in the 60GHz band

• TGad should define means to enable interference mitigation and exploit spatial reuse in order to:– Take advantage of directionality in 60GHz– Satisfy the needs of important usage models (e.g., high-

density scenarios such as enterprise cubicle)– Better utilize the limited number of channels available in

the 60GHz spectrum– Substantially increase network capacity

July 2009


Slide 15

doc.: IEEE 802.11-09/0782r0

Submission

References

[1] C. Cordeiro et al., 802.11-09/0391r0[2] S. Shankar et al., 802.11-09/0572r0[3] A. Myles and R. de Vegt, 802.11-07/2988r3[4] E. Perahia, 802.11-09/296r6[5] M. Park et al., 802.11-09/559r0[6] C. R. Anderson and T. S. Rappaport, “In-

Building Wideband Partition Loss Measurements at 2.5 and 60 GHz,” IEEE Trans. on Wireless Comm., Vol. 3, No. 3, May 2004, pp922-928.

July 2009


Slide 16

doc.: IEEE 802.11-09/0782r0

Submission

Backup

July 2009


Slide 17

doc.: IEEE 802.11-09/0782r0

Submission

Assessing the spatial reuse gain in terms of aggregate throughput

• PHY rate=4Gbps for SINR ≥ 20 dB

• PHY rate=2Gbps for 10 dB ≤ SINR < 20dB

• PHY rate=6Gbps for SINR ≥ 20 dB

• PHY rate=2Gbps for 10 dB ≤ SINR < 20dB

Documents

Doc.: IEEE 802.11-09/0782r0 Submission July 2009 Carlos Cordeiro, IntelSlide 1 Spatial Reuse and Interference Mitigation in 60 GHz Date: 2009-07-14 Authors: