doc.: IEEE 802.11-13/0720r1

Submission Slide 1

Date: 2013-07-16

Presenter:

Spatial Sharing Mechanism in 802.11aj (60GHz)

July 2013

Francois Chin

Name Company Address Phone email Francois Chin Po Shin

Institute for Infocomm Research (I2R) / CWPAN

1 Fusionopolis Way, #21-01 Connexis, Singapore

65-6408-2530

chinfrancois@i2r.a-star.edu.sg

doc.: IEEE 802.11-13/0720r1

Submission Slide 2

Author ListJuly 2013

Francois Chin

doc.: IEEE 802.11-13/0720r1

Submission

Background: 802.11ad Beamforming TXSS

• Beamforming training in 802.11ad : there are two phases for the beamforming training described in IEEE 802.11ad specification [1]: Sector level sweep (SLS) and Beam Refinement Protocol (BRP).

• SLS consists of TX sector sweep (TXSS) and RX sector sweep (RXSS)

Slide 3

PCP/AP

For the initial connection between two devices (Station (STA) and PBSS Control Point/Access Point (PCP/AP)), STA will receive with a quasi-omni-directional antenna while PCP sends a sequence of frames covering different TX sectors or vice versa.

STA

Figure 1. An example of TXSS

Source: IEEE 802.11ad

July 2013

Francois Chin

doc.: IEEE 802.11-13/0720r1

Submission

Background: 802.11ad Beamforming RXSS

Slide 4

Source: IEEE 802.11ad

• A device with a simple antenna may not have enough TX gain to reach a distant receiver that is using an omni-directional receiving antenna

• RX Sector Sweep may be employed by the device with the higher performance antenna system

• Allows a simple antenna device, like a handset, to connect at greater range

Simple Antenna Device

RX Sector Sweep is used to initiate beamforming on this link

After the beamforming training, STAs know their best sector ID for transmission /reception

Figure 2. An example of RXSS

July 2013

Francois Chin

doc.: IEEE 802.11-13/0720r1

Submission

Assume that beamforming training has been done: STAs know their best Sector ID for transmission

The existing spatial sharing mechanism in [1]:

• Spatial sharing can only be done in Service Period (SP), not Contention Based Access Period (CBAP)• Both existing SP and candidate SP need to perform measurement before usage• The mechanism is not very efficient. From PCP/AP’s perspective, it is a blind selection process.

Background: 802.11ad Spatial Sharing Mechanism

Slide 5

Figure 3. Example of spatial sharing assessment

July 2013

Francois Chin

doc.: IEEE 802.11-13/0720r1

Submission Slide 6

Proposed Method:

• A method to recommend an existing SP for spatial sharing with the new pair of devices with directional transmission

– Existing SP has one or more pairs of devices with directional transmission, all spatial sharing

Assumption:

• PCP/AP is updated with the beamforming training results between any two STAs, in terms of best selected sector IDs.

Proposed Spatial Sharing Selection Method

July 2013

Francois Chin

doc.: IEEE 802.11-13/0720r1

Submission

Assumption:• Each STA has 12 sectors with 30 degree transmission angel. • The beamforming training results are shown in Table 1 and 2 • PCP/AP has scheduled SP1 and SP2 for pair (A, B) and (C, D),

respectively. Purpose:• To recommend an initial SP for the candidate SP with pair (E,

F) from the existing SP set {SP1, SP2} for spatial sharing.

A B

C

D

1

3

11

7

5

9

8 1210

6 24

O

E 3

F7

Source device a Destination device b S(a, b)A B 1

A E 4A F 2B A 7B E 7B F 9E A 12E B 2E F 3F A 7F B 10F E 7

Table 1: Beamforming training results among {A, B, E, F}

Table 2: Beamforming training results among {C, D, E, F}

Source device a Destination device b S(a, b)

C D 10

C E 8

C F 12

D C 4

D E 5

D F 3

E C 4

E D 1

E F 3

F C 6

F D 9

F E 7

Slide 7

Example – Spatial Sharing in 802.11ad

Figure 4. An example of Spatial Sharing

July 2013

Francois Chin

doc.: IEEE 802.11-13/0720r1

Submission

• First, PCP/AP uses Table 1 to check whether SP1 is available for the candidate SP with pair (E, F).

• From Table 1, A and B choose Sector 1 and 7 (blue areas) to communicate with each other. E and F intend to use Sector 3 and 7, respectively.  

• Neither E nor F would be affected by A, because the beamforming results show that the Sector 4 and 2 would be the best sector for A to transmit to E and F, respectively, which are different with Sector 1.

• The sector number difference between two best sectors S(A, B) and S(A, E) , denoted by δA→B, E , is calculated as 3; Similarly, δA→B, F = 1.

Thus, A’s transmission has no interference to E and F.  

• However, if B is transmitting to A with Sector 7, E would be affected by B because the same

Sector 7 is selected for B to transmit to A and E. In this case, δB→A, E = 0. 

Therefore, the existing SP1 does Not satisfy with the condition of spatial sharing with the candidate SP with pair (E, F).

δ indicates the sector number difference between two best sectors S(a, b) and S(a, c) chosen by one source device a to two different destination devices b and c.

Slide 8

A B

C

D

1

3

11

7

5

9

8 1210

6 24

O

E 3

F7

Procedure of Initial Recommendation (1/2)

Figure 4. An example of Spatial Sharing

July 2013

Francois Chin

doc.: IEEE 802.11-13/0720r1

Submission

• Second, PCP/AP uses Table 2 to check whether SP2 is available for the candidate SP with pair (E, F). Thus, we have

δC→D, E = 2 δC→D, F = 2 δD→C, E = 1 δD→C, F = 1 δE→F, C = 1 δE→F, D = 2 δF→E, C = 1 δF→E, D = 2

• Since the minimum value of the above δ’s is larger than 0, the existing SP2 can be recommended as an initial SP for the candidate SP with pair (E, F).

Slide 9

Procedure of Initial Recommendation (2/2)

A B

C

D

1

3

11

7

5

9

8 1210

6 24

O

E 3

F7

Finally, PCP/AP responds to E-F pair with the best initial recommendation of SP2.

Figure 4. An example of Spatial Sharing

July 2013

Francois Chin

doc.: IEEE 802.11-13/0720r1

Submission

The Condition for Spatial Sharing

• Spatial sharing condition: As long as any source STA involved in an existing SP does not employ the same transmit sector with the one that it employs to communicate with any other STA involved in a candidate SP, and vice versa, the PCP/AP may schedule this existing SP and the candidate SP time-overlapping with each other for spatial sharing.

• Furthermore, if a pair of existing SP and candidate SP satisfies the above condition, the larger the sector number difference δ, between any two of transmit sectors employed by a source STA to communicate with its destination STA and with any other STA involved in the other SP, the better chance to implement spatial sharing and interference mitigation among them.

• Therefore, the parameter δ is considered as the criteria of the selection for the best initial slot that can be scheduled slot or contention based slot.

Slide 10

July 2013

Francois Chin

doc.: IEEE 802.11-13/0720r1

Submission

The Flow Chart of Proposed Method

Slide 11

Start

End

Y

N

Y

NPCP/AP checks the next existing SPe

for a candidate SPc with transmission pair (i, j) and set δ*e = 0;

For each scheduled transmission pair (x, y) in this SPe

Does any of the following cases occur between the intended transmission pair (i,j) and (x, y) ?S(x, i) == S(x, y) || S(x, j) == S(x, y) ||S(y, i) == S (y, x) || S(y, j) == S(y, x) ||S(i, x) == S(i, j) || S(i, y) == S(i, j) ||S(j, x) == S(j, i) || S(j, y) == S(j, i)

Calculate the values of δIf δ < δ*e δ*e = δ;

Finish the traverse of the existing SP set {SPe}?

Add SPe into initial recommendation set {SPe} with δ*e

Finish the traverse of the scheduled transmission set {x, y}e in this SPe?

Y

Search the best initial recommendation from {SPK} with the selection criteria of the largest δ*e

N

Figure 5. Flow chart of the proposed method for IEEE 802.11aj network

July 2013

Francois Chin

doc.: IEEE 802.11-13/0720r1

Submission

Benefits of Proposed Spatial Sharing Selection Method

• Accurate allocation of spatial sharing among pair of devices;

• Avoids unnecessary operation of measuring and report feedback among those pair of devices that may cause interference with each other if they transmit concurrently;

• Fast allocation of spatial sharing among pair of devices;

• Power saving of the resource allocation for the spatial sharing as it can significantly reduce the number of pair of devices that can be used for measuring and report feedback

Slide 12

July 2013

Francois Chin

doc.: IEEE 802.11-13/0720r1

Submission

Modifications to 802.11ad

• PCP/AP will be informed and updated of the results of the beamforming training among non-PCP/non-AP STAs.

• At the last step of beamforming phase, non-PCP/non-AP initiator (responder) shall notify PCP/AP through a SSW-Report frame which contains an SSW Report field indicating Source AID, Destination AID, Sector Select, DMG Antenna Select, SNR Report, etc.

The Source AID field identifies the transmitter that is the intended initiator (responder) of beamforming. The Source AID field identifies the receiver that is the intended responder (initiator) of beamforming.

Slide 13

Figure 6. SSW-Report frame format and Initiator (Responder) Link Report field

July 2013

Francois Chin

doc.: IEEE 802.11-13/0720r1

Submission

Conclusions

• Proposed a method to recommend an existing SP for spatial sharing with the new pair of devices with directional transmission

– based on the priori information of beamforming training results among devices

– Existing SP has one or more pairs of devices with directional transmission, all spatial sharing

• Proposed SSW-report frame format for non-PCP/non-AP STAs to report the results of the beamforming training, in terms of best sector IDs, to PCP/AP

Slide 14

July 2013

Francois Chin

doc.: IEEE 802.11-13/0720r1

Submission

Reference

[1] IEEE P802.11adTM-2012 Standard “Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications – Amendment 3: Enhancements for Very High Throughput in the 60 GHz band,” December 2012.

Slide 15

July 2013

Francois Chin

doc.: IEEE 802.11-13/0720r1

Submission Slide 16

Thank YOU

July 2013

Francois Chin