Transcript IEEE C802.16m-08/882

Radio Resource Allocation for Multi-radio Coexistence
IEEE 802.16 Presentation Submission Template (Rev. 9)
Document Number:
IEEE C802.16m-08/882
Date Submitted:
2008-08-31
Source:
Feng Seng Chu
Graduate Institute of Communication Engineering
E-mail: [email protected]
Kwang Cheng Chen
Graduate Institute of Communication Engineering
E-mail: [email protected]
Neeli Prasad
Aalborg University
E-mail: [email protected]
Ramjee Prasad
Aalborg University
E-mail: [email protected]
Kanchei (Ken) Loa
Institute for Information Industry
E-mail: [email protected]
Venue:
IEEE 802.16 Interim, Session #57, Kobe, Japan
Purpose:
Propose radio resource allocation as collaborative and non-collaborative coexistence mechanism.
Notice:
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Necessity of Coexistence Mechanism
• Officially, according the LMSC P & P [1]
▫ For a wireless project to be authorized, the WG is
required to produce a Coexistence Assurance (CA)
document to be submitted with their draft unless
there is a compelling reason to omit this step.
• Furthermore, Section 8.3 in 802.16m SRD [2]
▫ Methods to avoid being the victim or source of
interference when co-deployed with legacy nonIEEE 802 (3GPP, CDMA2000, TD-SCDMA, etc.)
and IEEE 802-based systems (802.16, 802.15,
802.11, 802.22, etc) are required.
Necessity of Coexistence Mechanism (2)
• Technically, we need such mechanisms to achieve
reliable and quality communications by avoiding
interference among systems
▫ 1. operating in overlap/adjacent un-license bands.
▫ 2. as secondary in license bands.
• Please note, what we consider now is next
generation high-bandwidth-efficiency
wireless
technologies, only (MIMO) OFDMA based systems
is targeted.
What’s mechanism we consider?
• Since existing pure physical and MAC
approaches are neither effective nor scalable
with number of radios and number of vendors.
• From section 6.4 in 802.16m SRD [2]
▫ Resource management to support efficient
utilization of system resources and to reduce
interference are required.
• We consider radio resource allocation (RRA) as
our critical mechanism.
What’s the benefit?
• From many existing researches, RRA can largely
improve system capacity by dynamic allocating
OFDMA time slots and subcarriers among users.
• However, the significance of RRA for coexistence is
NOT only to transform this increased capacity to
system throughput or user data rate,
• but is to realize reliable communications and
guarantee quality service under such unsure
operating environments by this increased capacity.
What’s the benefit? (2)
• In additions, by adaptively utilizing system
resource, scalability and flexibility of 4G
requirements can be satisfied.
• Furthermore, such increased capacity can also
be used to
▫
▫
▫
▫
1. enlarge cell coverage.
2. Better support mobility.
3. keep as margin for backup.
4. ……
Different types of coexistence
• According to IEEE 802.15.2 [3]
▫ Collaborative and Non-collaborative
▫ Collocation and Non-collocation
• For us, collocation is not the point because the
RRA should be implemented at BS, we tend to
view the collocated standards in user terminal as
independent clients.
• In the following we propose RRA for
▫ 1. Non-collaborative coexistence.
▫ 2. Collaborative coexistence.
RRA for Non-collaborative scenario
• For systems operating in un-license band or as
secondary in license band, we at least need the
following three general functions.
▫ 1. Channel Identification.
▫ 2. Feedback.
▫ 3. Radio Resource Allocation.
• In this contribution we assume feedback channel
is perfect.
General System Operations
Feedback CSI of available sub-carriers
Channel Identification Algorithm
BS
MS
RRA Algorithm
Optimal or
Low-complexity
1. Identify available subcarrier
now by proposed composite
hypothesis test.
2. Estimate required CSI of
available subcarriers.
Data Traffic
3. Predict available subcarriers
and their CSI in next frame.
Channel Identification Example
• Generalized Likelihood Ratio test
Pp H1
  p is received power.
l p 
 , 
Pp H 0   H1 and H 0 represent availabili ty.
Radio resource allocation Example
c c
c c
User 1
c c
User 2
:un-available subcarrier
:available subcarrier
User 3
After collect above information from all user, the base station can allocate
available time slots and subcarriers of each user among all users.
Power is also considered in allocation.
Radio Resource Allocation Example
Power allocated to subcarrier k in time slot t
T  max
ωu ,t,k,p t,k
U
T
K
 ω
u 1 t 1 k 1
u,t,k
log 2 1  pt,k CNR
Channel to noise ratio
Subcarrier allocation index for user u, time slot t
and subcarrier k
Subject to
i  Total Power Constraint (ii) Non - negative Constraint
iii  Availabili
ty Constraint
iv  Fairness Constraint
Such a multi-variable non-linear optimization is hard to be solved.
A low-complexity but sub-optimal algorithm may be preferred.
Low-complexity Algorithm Example
• We can divide the optimal allocation into
▫ 1. time-frequency subcarrier allocation.
▫ 2.Power allocation.
Uniformly distribute power
T  max
ωu,t,k,p t,k
U
T
K
 ω
u,t,k
u 1 t 1 k 1
log 2 1  pt,k CNR 
Allocate
power among subcarriers
Allocate
subcarriers
T  max
ωu,t,k,p t,k
U
T
K
 ω
u 1 t 1 k 1
u,t,k
log 2 1  pt,k CNR 
By subcarriers allocation resulted in prior step.
Numerical Result (1)
System Capacity
14
Optimal
Low Complexity Algorithm, Step 1
Low Complexity Algorithm, Step 2
Low Complexity Algorithm, Step 3
Normalized Capacity
12
10
8
6
4
2
0
0
5
10
15
20
OSNR (dB)
25
30
35
40
Numerical Result (2)
System Capacity
16
Low Complexity Algorithm, Step 1
OFDM based FDMA
OFDMA-Subcarrier-Interleaved
14
Normalized Capacity
12
10
8
6
4
2
0
0
5
10
15
20
OSNR (dB)
25
30
35
40
Numerical Result (3)
System Capacity With/Without Fairness Normalization, (OSNR,P 11) = (20 dB,0.8)
9
8
Normalized Capacity
7
6
5
4
3
Low Complexity Step 1, Without Fairness Normalization
FDMA,
Without Fairness Normalization
Interleaved,
Without Fairness Normalization
Low Complexity Step 1, With Fairness Normalization
FDMA,
With Fairness Normalization
Interleaved,
With Fairness Normalization
2
1
0
0
0.1
0.2
0.3
0.4
0.5
Probability (P 00)
0.6
0.7
0.8
0.9
RRA for collaborative scenario
• Now there are information exchange among
coexisting systems, we can consider a more
aggressive scheme such as
▫ Cross-Three-Layer Radio Resource Allocation.
Fundamental Idea
Traditionally, frequency reuse are network layer issue and not
included in MAC-PHY RRA.
However, if the information exchange among BSs are possible,
dynamic allocate spectrum among cells become possible.
Actually, this scheme should be more considered when coexisting
BSs are collocated.
Problem Formulation
If we represent the total network capacity as CT ,
total capacity of each cell as Ci , and total capacity
of each system is Ci .
The maximizati on of network capacity by dynamic allocating
spectrum among cells can be formulated as
N
N
i
CT  max  Ci  max  Ci
Bi
i 1
Spectrum allocated to cell i
Bi
i 1  1
N : Number of cells.
X i : Numer of coexisting systems in cell i.
System Architecture
Problem Formulation (2)
• Furthermore, with different assumptions the
resulted capacity formulation of each systems
are different.
• For example, if we assume MIMO-OFDMA
systems, the system capacity can be
1
Ci 
TNT K i

U i
T
N T K i  Bi Δf


u 1 t 1
1
i ,
i , ,u ,t
i ,



log
1

SNR
p
 u ,t , ,k
 ,k
t , , k 
k 1
U i : Number of users in system.
u : user index
NT : Numer of Tx antenna in system .  : Antenna index
Problem Formulation (3)
• Apparently, the definition of SNR is direct relate
to the receiver structure and channel
assumption.
• We can formulate a cross-three-layer RRA by
prior description.
Numerical Result
Network Capacity
Normalized Network Capacity
15
Cross-Three-Layer
Cross-Two-Layer
Fixed Resource Allocation
10
5
0
0
5
10
15
20
SNR (dB)
25
30
35
40
Contributions
• We propose RRA as critical coexistence
mechanism.
• Algorithms for two different coexistence
scenarios are demonstrated.
• Both the algorithms can largely increase system
capacity from fixed resource allocation, we can
utilize this increased capacity to realize reliable
communication.
• Since resource are adaptive allocated, scalability
can be also satisfied.
Reference
[1] IEEE PROJECT 802 LMSC POLICIES AND PROCEDURES,
January, 2006. http://ieee802.org/policies-and-procedures.pdf.
[2] “Project 802.16m System Requirements Document (SRD),”
October, 2007. http://www.wirelessman.org/tgm/docs/80216m07_002r4.pdf.
[3] IEEE 802.15.2/D09, March 2003, http://myurl.com.tw/6gus.