1. Low Rate Enabler Date: 2011-03-13 Authors: March 2011 Month Year
doc.: IEEE yy/xxxxr0
March 2011
Low Rate Enabler
Date:
Authors:
Rahul Tandra, Qualcomm Inc.
John Doe, Some Company

2. Month Year
doc.: IEEE yy/xxxxr0
March 2011
Abstract
According to the latest FCC TVWS regulations [1], every Mode II device must have the ability to perform geo-location with a 50 m accuracy. This geo-location requirement is very difficult to meet in indoor environments. Existing indoor geo-location technologies are very expensive and hence may not be suitable for low-cost access points (APs).
In this presentation we propose a solution to circumvent the indoor geo-location problem. We propose the idea of a Low Rate Enabler which serves as a Mode II device and provides enablement to all mode I devices (APs and STAs) in a wide region (office buildings, malls or apartment complexes). The key idea is that a single device equipped with a standard GPS receiver, which can be located near a window or on a rooftop, can provide enablement for all other TVWS devices in wide area.
Rahul Tandra, Qualcomm Inc.
John Doe, Some Company

3. Problem description FCC regulations [1]
March 2011
Problem description
FCC regulations [1]
All Mode II devices must have Geo-location with a 50 m accuracy
Meeting the geo-location requirement in indoor environments is extremely challenging
Building high sensitivity GPS is very expensive (massive correlators) [2]
Network assisted GPS requires the APs to have a cellular radio [3]
APs placed next to a window, or outdoors can meet geo-location requirement through existing GPS technology
Not a good location from a coverage standpoint, especially in enterprise scenarios
Rahul Tandra, Qualcomm Inc.

4. Proposed solution: Low Rate Enabler
March 2011
Proposed solution: Low Rate Enabler
Low Rate
Enabler
Mode I AP
Mode I
STA
Design a special Mode II device (can work as a Wi-Fi AP), called a Low Rate Enabler (LRE) that is placed near a window, or on the roof
Low Rate enabler has a GPS receiver
One or two low rate enablers can provide enablement for the entire building
Good for enterprise solutions, malls, apartment complexes or other large indoor facilities
Regular APs and STAs (mode I devices) may now be placed anywhere in the building
Do not require GPS receiver
Receive enablement and CVS through the low rate enabler
Rahul Tandra, Qualcomm Inc.

5. Low rate enabler requirements
Month Year
doc.: IEEE yy/xxxxr0
March 2011
Low rate enabler requirements
High-level design
Portable device
Statistically more channels available for portable devices than fixed devices
Low-complexity
PHY design
Have a low data rate PHY to provide wide coverage (e.g. building)
Initial enablement and periodic CVS for all mode I devices across a large area
MAC design
Medium access protocol for TVWS such that it can coexist with other networks
Should be able to share medium with other shorter range networks
Rahul Tandra, Qualcomm Inc.
John Doe, Some Company

6. Low-rate PHY design Low Rate PHY requirements
March 2011
Low-rate PHY design
Low Rate PHY requirements
Long communication range, to enable all devices in a wide area
Low-rate transmission to extend range
Two possible design choices to enable low rate modes
IEEE DSSS based PHY
Original 1 Mb/s DSSS PHY scaled to 5 MHz gives 250 kb/s PHY
Possible to modify 20 MHz DSSS designs for 250 kb/s which would scale to 62.5 kb/s is useful to extend range further
OFDM based PHY
Lowest rate with current PHY design (clocking down by 4) for 5 MHz operation is 1.5 Mbps
Can lower data rates by repetition coding based ideas
Rahul Tandra, Qualcomm Inc.

7. Super Long Range (SLR) PHY
March 2011
Super Long Range (SLR) PHY
Propose a 62.5 kb/s SLR PHY to provide sufficient coverage for the LRE
See MAPL calculations in Appendix B
Based on the DSSS PHY Design
Step 1: Down-clock the 1 Mb/s b DSSS PHY by four
Effective data rate of 250 kb/s
Step 2: Every bit in the down-clocked packet is repeated by 4 to give a 6 dB gain
Provides data rate of 62.5 kb/s
Same 11-chip Barker sequence as in
Differential BPSK modulation
Rahul Tandra, Qualcomm Inc.

8. March 2011
SLR PHY: Frame format
SYNC sequence: Alternating 0,1 ‘s with a bit-level repetition of 4
Provide enough SLR symbol transitions such that the SLR detector can estimate the symbol boundary
SFD, SIGNAL, SERVICE, LENGTH, and CRC fields remain unchanged
Bit level repetition by 4 to give 6 dB link budget SNR gain
Rahul Tandra, Qualcomm Inc.

9. Low Rate Enabler Operation
March 2011
Low Rate Enabler Operation
Low rate enabler provides enablement on a single (base) channel
Low rate enabler visits the APs/STAs on their channels to provide CVS
Quieting on each channel during their scheduled CVS
Quieting on the base channel during enablement beacon (if it is a shared channel)
Rahul Tandra, Qualcomm Inc.

10. MAC design Advertizes enablement beacon CVS message
March 2011
MAC design
Advertizes enablement beacon
All mode I devices must listen to this beacon (in Ch A) to get enabled
Unicast message exchange between the TVWS enabler and each mode I device (FCC mandated enablement process)
Additional information elements can be exchanged during the initial enablement process
List of previously enabled channels (Ch A, Ch B, Ch C)
Period of the CVS message for each channel
CVS message
Enabler periodically hops across all the currently used channels (Ch A, Ch B, Ch C) to transmit CVS information for previously enabled APs and STAs
The CVS message can be sent through public action frames
Ensure power-save STAs receive CVS message
Mode I APs need to wake up power-save STAs to receive CVS message
Protect low rate enabler’s CVS/Enablement beacon from collisions
Rahul Tandra, Qualcomm Inc.

11. Protecting low rate enabler transmissions
March 2011
Protecting low rate enabler transmissions
Low rate enabler may share the medium with other APs and STAs for
Enablement beacon (only in the case when the base channel is shared)
Transmitting periodic CVS message
Scheduling quiet-times:
Low rate enabler transmissions can be heard by all APs and STAs in a wide area (low rate packets)
Low rate enabler cannot hear the transmissions from APs and STAs which are far away (higher rate packets)
Low rate enabler cannot rely on CSMA to avoid collisions
APs must schedule quiet times to protect the TVWS transmissions from collisions
Rahul Tandra, Qualcomm Inc.

12. Scheduling Quiet Times
March 2011
Scheduling Quiet Times
TVWS enabler
APs wake the STAs using the DTIM message described in the previous slide
APs know the approximate time to the next CVS or Enablement beacon
APs send a CTS to Self message with duration field set to cover the CVS/Enablement beacon
A CF End message can be used to reset the NAV field at the STAs if the duration setting in the CTS to self message was too long
Rahul Tandra, Qualcomm Inc.

13. DTIM messaging for power save STAs
March 2011
DTIM messaging for power save STAs
Low rate enabler sends CVS periodically
The period of the CVS is known to the Mode I APs
AP detects a CVS and sends DTIM to wake up all STAs
Chooses the TIM message nearest to the next CVS to send a DTIM
All the TIMs preceding this DTIM will contains the arrival time of this DTIM message
Broadcast bit in DTIM turned ON
STAs receive the next CVS signal from the enabler
STAs stay on till the next DTIM
Rahul Tandra, Qualcomm Inc.

14. Standards change MAC PHY Description of low-rate enabler
March 2011
Standards change
MAC
Description of low-rate enabler
Some additional information elements
Operating channel of the low rate enabler
Operating channel of other Mode I APs
CVS schedule
PHY
Low-rate DSSS PHY
Rahul Tandra, Qualcomm Inc.

15. Concluding remarks Low rate enabler solves the indoor GPS problem
March 2011
Concluding remarks
Low rate enabler solves the indoor GPS problem
Low rate enabler provides enablement and CVS for many APs and STAs
Other APs no longer need GPS. When there are multiple APs (e.g. enterprise scenario) which significantly reduces deployment complexity
Low rate enabler can reduce the search time for discovery since the LRE can tell new STAs which channels/bandwidths are available in the area
Minimal changes needed to the af MAC
Additional information elements
CTS to self message to schedule quiet-times for CVS transmissions
Reuse existing DTIM messaging for power save nodes
Low rate PHY
Low complexity DSSS PHY based on simple modification of original 1 Mb/s DSSS PHY
Rahul Tandra, Qualcomm Inc.

16. March 2011
References
Federal Communication Commission, Second Memorandum Opinion and Order In the Matter of Unlicensed Operation in the TV Broadcast Bands, Additional Spectrum for Unlicensed Devices Below 900 MHz and in the 3 GHz Band, Document , September 23, 2010
S. Schon and O. Bielenberg, On the capability of high sensitivity GPS for precise indoor positioning, Firth Workshop on Positioning, Navigation and Communication, March 2008
F. van Diggelen, Indoor GPS theory & implementation, IEEE Position Location and Navigation Symposium, August 2002
Rahul Tandra, Qualcomm Inc.

17. Annex - A FCC Regulations
March 2011
Annex - A FCC Regulations
Qualcomm Incorporated

18. Enablement Requirements based on FCC Regulations
March 2011
Enablement Requirements based on FCC Regulations
Category
Requirement
Startup
Mode I device shall transmit to Fixed/Mode II device to request enablement.
To initiate contact Mode I device may only transmit on channel used by Fixed/Mode II or channel indicated is available by Fixed/Mode II device.
When requesting enablement the Mode I device shall send its FCC ID.
The enablement request shall be sent in a secure manner
Enablement
Fixed/Mode II must provide Mode I FCC ID to database for verification
After verification the Fixed/Mode II sends white space map (WSM) and method of decoding contact verification signal (CVS) to Mode I
CVS
The Fixed/Mode II device shall broadcast a CVS at least every 60 seconds
The Mode I device must receive a CVS every 60 seconds from the Fixed/Mode II device that enabled it originally, or contact the Fixed/Mode II device.
If Mode I does not receive CVS or can not contact Fixed/Mode II it must cease transmission
Power Loss
Mode I must contact Fixed/Mode II. Mode II must contact database.
Qualcomm Incorporated

19. FCC Regulations on Enablement
March 2011
FCC Regulations on Enablement
FCC Regulations
Low Rate Enabler Architecture
A Mode I personal/portable TVBD may only transmit upon receiving a list of available channels from a fixed or Mode II TVBD that has contacted a database and verified that the FCC identifier (FCC ID) of the Mode I device is valid
The Mode I APs and STAs must first contact the Mode II low-rate enabler before transmitting
Meets FCC Rule
The list of channels provided to the Mode I device must be the same as the list of channels that are available to the fixed or Mode II device, except that a Mode I device may operate only on channels that are permissible for its use under §
Low-rate enabler, Mode I APs, and Mode I STAs are all portable and operate on the same set of channels
A fixed device may also obtain from a database a separate list of available channels that includes adjacent channels that would be available to a Mode I personal/portable device and provide that list to the Mode I device
Since Low-rate enabler is portable this does not apply. If it was Fixed this would still work
Qualcomm Incorporated

20. FCC Regulations on Enablement
March 2011
FCC Regulations on Enablement
FCC Regulations
Low Rate Enabler Architecture
A fixed or Mode II device may provide a Mode I device with a list of available channels only after it contacts its database, provides the database the FCC Identifier (FCC ID) of the Mode I device requesting available channels, and receives verification that the FCC ID is valid for operation
The Mode I APs and STAs must transmit their FCC ID to the low-rate enabler before they are sent the list of channels
Meets the FCC Rule
To initiate contact with a fixed or Mode II device, a Mode I device may transmit on an available channel used by the fixed or Mode II TVBD or on a channel the fixed or Mode II TVBD indicates is available for use by a Mode I device on a signal seeking such contacts
The Mode I APs and STAs transmit initially on the base channel of the low-rate enabler, to request enablement
Qualcomm Incorporated

21. FCC Regulations on Enablement
March 2011
FCC Regulations on Enablement
FCC Regulations
Low Rate Enabler Architecture
At least once every 60 seconds, except when in sleep mode, i.e., a mode in which the device is inactive but is not powered-down, a Mode I device must either receive a contact verification signal from the Mode II or fixed device that provided its current list of available channels or contact a Mode II or fixed device to re-verify/re-establish channel availability
The Low-rate enabler visits the operating channels of the Mode I APs and STAs and send them the CVS signal
Meets the FCC Rule
A Mode I device must cease operation immediately if it does not receive a contact verification signal or is not able to re-establish a list of available channels through contact with a fixed or Mode II device on this schedule. In addition, a Mode II device must re-check/reestablish contact with a fixed or Mode II device to obtain a list of available channels if they lose power. Collaterally, if a Mode II device loses power and obtains a new channel list, it must signal all Mode I devices it is serving to acquire new channel list.
Mode I APs and STAs must re-contact the low-rate enabler if they do not receive the CVS signal
If low-rate enabler looses power it must send new CVS with new Map ID to indicate a new Map is available
Qualcomm Incorporated

22. FCC Regulations on Enablement
March 2011
FCC Regulations on Enablement
FCC Regulations
Low Rate Enabler Architecture
Communications between a Mode I device and a fixed or Mode II device for purposes of obtaining a list of available channels shall employ secure methods that ensure against corruption or unauthorized modification of the data
Map is sent securely
Meets the FCC Rule
When a Mode I device makes a request to a fixed or Mode II device for a list of available channels the receiving device shall check with TV bands database that the Mode I device has a valid FCC Identified before providing a list of available channels
Low-rate enabler send the FCC ID of the Mode I device to the TVWS database
Contact verification signals transmitted for Mode I devices are to be encoded with encryption to secure the identity of the transmitting device
CVS signal is sent securely
Qualcomm Incorporated

23. FCC Regulations on Enablement
March 2011
FCC Regulations on Enablement
FCC Regulations
Low Rate Enabler Architecture
Mode I devices using contact verification signals shall accept as valid for authorization only the signals of the device from which they obtained their list of available channels
Mode I APs and STAs only accept CVS signals from the low-rate enabler that provided the Map
Meets the FCC Rule
Qualcomm Incorporated

24. Annex - B Pathloss calculations
March 2011
Annex - B Pathloss calculations
Qualcomm Incorporated

25. Pathloss and range calculations
March 2011
Pathloss and range calculations
Pathloss calculation
PL = PTX – SNRRX – N0
Numerical parameter & notation:
Noise figure = 8 dB
Bandwidth = 5 MHz
Transmit power , PTX= 16 dBm
Carrier frequency: 650 MHz
Dw --- separation between two walls
floor(d/Dw) --- average number of walls
n --- number of floors separating transmitter and receiver
Floor loss ~ 18 dB, wall loss ~ 5 dB
PHY
Data rate
(Mbps)
Minimum SNR
(dB)
MAPL
(dBm)
Range in meters
(IEEE D-NLOS model)
(3GPP indoor prop. model)
0 dB
Shadowing margin
10 dB
Dw=6,n=0
Dw=4,n=0
Dw=4,n=1
OFDM PHY
1.5
12.5
102.5 92 48 49 36 24
DSSS PHY
0.250 7
108
133 69 54 40 28
Low-rate DSSS
0.0625 1
114
197
102 60 44 32
Rahul Tandra, Qualcomm Inc.