June 2009
doc.: IEEE 802.19-09/xxxxr0
Logical Sector-based Resource Hopping Coexistence using Direct
Communication
Date: 2009-06-xx
Authors:
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Submission
Slide 1 Apurva N Mody (BAE Systems), Ranga Reddy (US Army)
June 2009
doc.: IEEE 802.19-09/xxxxr0
Abstract
•
This contribution discusses methods for resource allocation in situations that demand
coexistence
•
We propose Two Modes of operation – Normal mode and Co-existence Mode
•
We propose that a TVBD system will try and resolve the channel selection issues with
neighboring TVBD systems, first, based on what is known as spectrum etiquette in
802.22.
•
If channel selection does not get resolved using spectrum etiquette, then the TVBD
system will go into the Co-Existence Mode. Co-Existence Mode of operation is when
it is expected that a TVBD may interfere with other TVBDs in the area.
•
How the system resource is divided can be left up to future discussion. From the our
perspective, we propose sub-frame creation and sharing – concepts similar to the ones
discussed in IEEE 802.16h.
•
In the co-existence mode, the sub-frames are divided into zones. Clock-wise or anticlock-wise rotation policy is followed to achieve diversity and control message
passing.
•
Using sub-frame for resource allocation allows guaranteed QoS, delay and jitter
requirements in situations that demand co-existence – It can drive applications such
as VoIP and Gaming
•
We also suggest a couple of basic coexistence metrics
Submission
Slide 2 Apurva N Mody (BAE Systems), Ranga Reddy (US Army)
June 2009
doc.: IEEE 802.19-09/xxxxr0
Coexistence Is Necessary
Co-existence is necessary when:
TVBDB can not find any channels unoccupied by the protected users
(incumbents) after polling the
database, or advertisements
channel usage (e.g. spectrum
etiquette) of neighboring TVBDs.
Following cases are possible
• 4W TVBD tries to co-exist with a 4W
TVBD
• 4W TVBD tries to co-exist with a 100
mW TVBD
• 100mW TVBD tries to co-exist with a 4W
TVBD
• 100 mW TVBD tries to co-exist with a
100 mW TVBD
A
B
A
B
A B
Submission
Slide 3 Apurva N Mody (BAE Systems), Ranga Reddy (US Army)
June 2009
doc.: IEEE 802.19-09/xxxxr0
Simplified* Link Analysis from 1st Tier (4W) Neighbors (1/2)
•
•
•
•
•
•

•
PRxB = PTxA + GTxA – LTxA – LFS – LM + GRxB – LRxB
PRxB = Received Power at B
PTxA = Transmit power from A = 4W = 36 dBm
GTxA = Antenna Gain A = 0 dB
LTxA = Transmitter losses = 0 dB
Fc = Carrier frequency = 617 MHz -> Corresponding to the Channel 38
l = Wavelength = (3 x 108) / (617 x 106) = 0.48622 m
LFS = Free space loss = 20 * log10 (4p d/ l)
= 20 * log10 (4 p d / 0.48622)
= 117.79 dB, where d = Distance from B to A (30 km)
= 68.25 dB, where d = Distance from B to A (100 m)
•
LM = Miscellaneous losses = 0 dB
•
GRxB = Receiver (B) antenna gain = 0 dB
•
LRXB = Receiver losses at B = 0 dB
•
Based on the previous calculations,
– PRxB = -81.79 dBm for 30 km separation distance
– PRxB = -32.25 dBm for 100 m separation distance
* For detailed link analysis refer to [1] &
[2]N Mody (BAE Systems), Ranga Reddy (US Army)
Submission
Slide 4 Apurva
June 2009
doc.: IEEE 802.19-09/xxxxr0
Simplified* Link Analysis from 1st Tier (4W) Neighbors (2/2)
• Assuming the Noise Figure NF = 11 dB
• Noise Power (dBm) = PN = 10 * log10 (kTB/(1 x 10-3)) + 11 dB
= 10 * log10 (1.38 x 10-23 * 290 * 6 x 106 / (1 x 10-3)) + 11 dB = -95.19 dB
• SNRA->B = PRxB – Noise Power = PRxB + 95.19 dB
• The table below shows the SNR that is possible at a receiver who is separated
by a distance of 30km and 100m for 4W and 100mW transmitters
Tx Power (dBm)
Separation Distance (m)
SNR (dB)
36 dBm
30,000
13.4
36 dBm
100
62.94
20 dBm
30,000
-2.6
20dBm
100
46.94
Submission
* For detailed link analysis refer to [1] & [2]
Slide 5 Apurva N Mody (BAE Systems), Ranga Reddy (US Army)
June 2009
doc.: IEEE 802.19-09/xxxxr0
Co-existence Message Passing
Co-existence Message Passing for Various
Cases
• 4W TVBD tries to co-exist with a 4W
TVBD - Direct message passing between
BSs possible for
• 4W TVBD tries to co-exist with a 100
mW TVBD - Requires a relay station, e.
g. a CPE ‘a’ associated with BS A.
• 100mW TVBD tries to co-exist with a 4W
TVBD - Requires a relay station, e. g. a
CPE ‘a’ associated with BS A.
• 100 mW TVBD tries to co-exist with a
100 mW TVBD – Direct Messaging
Possible
A
B
a
A
B
Co-existence
message passing
using CBP – Worst
case situation may
require a relay node.
B to a and a to A
Given analysis on previous two slides, it is possible to
have TVBD decode some control channel information
that they directly communicate to each other to enable
coexistence
Submission
A B
Slide 6 Apurva N Mody (BAE Systems), Ranga Reddy (US Army)
June 2009
doc.: IEEE 802.19-09/xxxxr0
Entering Coexistence Mode
• In the Co-existence Mode Cell B requests
to share the channel with Cell A.
• Since TVBD A is the existing user of the
given channel, TVBD B requests channel
sharing with TVBD A using
• CO_EXISTENCE_REQ message using
CBP, backhaul or some other means.
• In response to the request from TVBD B,
TVBD A accepts or rejects to the
scheduling of a co-existence frame using
CO_EXISTENCE_RSP message.
• BS B then then sends
CO_EXISTENCE_ACK message to
acknowledge the receipt of the
CO_EXISTENCE_RSP message.
• TVBD A schedules CO-EXISTENCE
Frames in the subsequent super-frames.
Submission
Slide 7 Apurva N Mody (BAE Systems), Ranga Reddy (US Army)
June 2009
doc.: IEEE 802.19-09/xxxxr0
Coexistence Mode Operation
• TVBD Master devices divide their
area of operation into logical or
physical sectors
• Resources assigned to a sector can
represent a channel or portion of a
channel
• If interference from other users is
detected, then the coexistence
signaling mentioned earlier is used to
determine which resources can be
used in each zone
• Examples of methods for determining
which zone can use which resource
are:
– Contention
– Renting
• Then each TVBD then schedules its
users according to its own
MAC/PHY procedures. An example
is provided in the figure using subframes
Submission
Slide 8 Apurva N Mody (BAE Systems), Ranga Reddy (US Army)
June 2009
doc.: IEEE 802.19-09/xxxxr0
Co-Existence Mode Operation – Sub-frame Creation and Sharing for
Situations with More than Two Cells
• These figures illustrate how
resource allocation may be carried
our in situations which require coexistence between more than two
cells
Submission
Slide 9 Apurva N Mody (BAE Systems), Ranga Reddy (US Army)
June 2009
doc.: IEEE 802.19-09/xxxxr0
QoS Specifications for Various Category Types and Applications
* Information derived from – [3]
Submission
Slide 10 Apurva N Mody (BAE Systems), Ranga Reddy (US Army)
June 2009
doc.: IEEE 802.19-09/xxxxr0
QoS Specifications for Various Category Types and Applications
* Information derived from – [3]
Submission
Slide 11 Apurva N Mody (BAE Systems), Ranga Reddy (US Army)
September 2008
doc.: IEEE 802.19-09/xxxxr0
Advantages of Sub-frame Resource Allocation Over Inter-frame
Resource Allocation
• Sub-frame resource allocation can provide guaranteed QoS requirements
in situations that demand co-existence – It can drive applications such as
VoIP and Gaming
• Delay and jitter between successive transmissions can be guaranteed to
satisfy the QoS requirements –
• Note that VoIP packets in general are quite small – e.g. 20 - 150 bytes
• VoIP - Total Network (Source to Dest.) delay should be less than 150
ms which means that the Wireless Access Delay should be a few tens
of ms
• Delay Jitter < a few tens of mS)
• As an example: 802.16m – Super-Frame Duration = 20 ms is divided into
Four frames of 5 ms each, each frame is made up of 8 sub-frames
Submission
Slide 12
Apurva N. Mody, BAE Systems
June 2009
doc.: IEEE 802.19-09/xxxxr0
Resource Allocation in the Co-Existence Mode Sector Rotation for Diversity
and Information Exchange
•
•
TVBDs periodically rotate the channel/sub-channel assignments to sectors
This rotation periodicity and schedule is communicated between TVBDs during coexistence
signaling
• In the example above, TVBD A and B follow the zone rotation policy within the subsequent
frames in order to achieve diversity and create a periodic dedicated channel for information
exchange between the cells.
• The zone rotation, or “hopping” may improve spectrum sensing by allowing the system to
sensing on channels that are not currently being used, thus allowing sensing to be
accomplished without interrupting system operation [5], [6], [7]
Submission
Slide 13 Apurva N Mody (BAE Systems), Ranga Reddy (US Army)
June 2009
doc.: IEEE 802.19-09/xxxxr0
Coexistence Metrics – Coexistence Resolution Timer
• Coexistence Resolution Timer – Time from when a TVBD system detects another
user, determines the type of system the other user is, decides upon a coexistence
action, and completes execution of that action
• What is the purpose of this metric?
• To allow objective analysis of how much time it takes to resolve a coexistence
situation. This is needed in order to fairly assess how various coexistence
methods perform when applied to the use cases and scenarios being developed
by the SG. Conventional wisdom would dictate that not all coexistence methods
are equal and therefore not applicable to all use cases/scenarios
Submission
Slide 14 Apurva N Mody (BAE Systems), Ranga Reddy (US Army)
June 2009
doc.: IEEE 802.19-09/xxxxr0
Coexistence Metrics – Spectrum Sensing Occupancy Percentage
• Spectrum Sensing Occupancy Percentage – Percentage of time or portion of
frame(s) within a reference operating period that a TVBD must dedicate to spectrum
sensing
• What is the purpose of this metric?
• Spectrum sensing to the signal levels as specified by the R&O requires
significant resources. The purpose of this metric is allow us to gauge how much
of the system capacity is dedicated for sensing in various coexistence scenarios
Submission
Slide 15 Apurva N Mody (BAE Systems), Ranga Reddy (US Army)
June 2009
doc.: IEEE 802.19-09/xxxxr0
Summary and Conclusions
•
This contribution discussed methods for resource allocation in situations that demanded
coexistence
•
We proposed Two Modes of operation – Normal mode and Co-existence Mode
•
We proposed that an TVBD system will try and resolve the channel selection issues with
neighboring WRAN systems, first, based on spectrum etiquette.
•
If channel selection does not get resolved using spectrum etiquette, then the TVBD system will go
into the Co-Existence Mode. Co-Existence Mode of operation is utilized when interference free
scheduling, dynamic resource renting / offering or contention is required for resource sharing
•
We proposed sub-frame creation and sharing – concepts similar to the ones discussed in IEEE
802.16h
•
In the co-existence mode, the sub-frames are divided into zones. Clock-wise or anti-clock-wise
rotation policy is followed to achieve diversity and control message passing.
•
Using sub-frame for resource allocation allows guaranteed QoS, delay and jitter requirements in
situations that demand co-existence – It can drive applications such as VoIP and Gaming
•
We also presented some ideas on new coexistence metrics to consider when evaluating various
coexistence metrics
Submission
Slide 16 Apurva N Mody (BAE Systems), Ranga Reddy (US Army)
June 2009
doc.: IEEE 802.19-09/xxxxr0
References
1.
2.
3.
4.
5.
6.
7.
Chounaird, Gerald, “WRAN Reference Model”, IEEE 802.22 WG Contribution, 22-
04-0002-17-0000-p802-22-intial-election-process.xls
Chouinard, Gerald, “Mutual Interference between 802.22 WRAN CPEs and
Portable Devices”, IEEE 802 TVWS ECSG Contribution, sg-whitespaces-090043-01-0000-mutual-interference, “Co-existence Capacity Allocation
Methods,”
White Paper: Mobile WiMAX Part I – Overview and Performance – WiMAX
Forum
http://www.opalsoft.net/qos/VoIP.htm
Hu, Wendong, et al., “Dynamic Frequency Hopping Communities for Efficient
IEEE 802.22 Operation”, IEEE Communications Magazine, May 2007
Hu, W. and Sofer, E., “IEEE 802.22 Wireless RAN Standard PHY and MAC
Proposal”, IEEE 802.22 WG Contribution, 22-05-0098-00-0000_STMRuncom_PHY-MAC_Outline
Hu, W. et al., “Dynamic Frequency Hopping Community”, IEEE 802.22 WG
Contribution, 22-06-0113-01-0000-dynamic-frequency-hopping-community
Submission
Slide 17 Apurva N Mody (BAE Systems), Ranga Reddy (US Army)