Joint Scheduling and Power Control for Wireless Ad Hoc Networks
Advisor: 王瑞騰Student: 黃軍翰
Introduction Infrastructure Wireless Networks
Wired Network
Access Point Access Point
Introduction Ad Hoc Wireless Networks
Abstract In this paper,we introduce a cross-layer design frame
work to the multiple access problem in contention-based wireless ad hoc networks.
The motivation for this study is twofold, limiting multiuser interference to increase single-hop
throughput and reducing power consumption to prolong battery life.
We focus on next neighbor transmissions where nodes are required to send information packets to their respective receivers subject to a constraint on the signal-to interference-and-noise ratio.
ASSUMPTIONS AND DEFINITIONS Consider a wireless ad hoc network consisting of n
nodes. Each node is supported by an omni-directional ante
nna. Each node knows the geographical location of all ot
her nodes Routing is not considered in this study.
The effect of users’ mobility is not considered in this study.
ASSUMPTIONS AND DEFINITIONS Assume that all nodes share the same frequency band,
and time is divided into equal size slots that are grouped into frames
The slot duration is assumed to be larger than the packet duration by an interval called a “guard band.”
In this study, we assume that the frame lengthis fixed throughout system operation.
Each node generates information packets of fixed length, destined to all other nodes, according to a Poisson distribution with aggregate rate λ packets/second.
ASSUMPTIONS AND DEFINITIONS We assume that each generated packet is
intended for a single neighbor only We assume a maximum power level, denoted
PMAX, that a node can use for transmission. assume that the transmission range of any
node is limited (typically circular) and beyond that range no interference
The power decay law is assumed to be inversely proportional to the fourth order of the distance between the transmitter and the receiver.
ASSUMPTIONS AND DEFINITIONS
We assume the existence of a separate feedback channel that enables receivers to send their SINR measurements to their respective transmitters in a contention-free manner
We assume the existence of a central controller responsible for executing the scheduling algorithms
Define the average slot throughout as the long-run average of the percentage of packets successfully received by single-hop neighbors in each time slot.
Algorithm Description The proposed algorithm determines the admissible set
of users that can safely transmit in the current slot without disrupting each other’s transmission. Accordingly, the objective is twofold
1. determine the set of users who can attempt transmission simultaneously in a given slot
2. specify the set of powers needed in order to satisfy SINR constraints at their respective receivers.
Algorithm Description Definition 1: In TDMA wireless ad hoc networks, a transmissio
n scenario is valid iff it satisfies the following three conditions.1. A node is not allowed to transmit and receive si
multaneously.2. A node cannot receive from more than one neig
hbor at the same time.3. A node receiving from a neighbor should be spa
tially separated from any other transmitter by at least a distance D.
5
4
3
2
1
6
7
i
j
k
x
dkx<dkj , D=dkx
5
4
3
2
1
6
7
dkx<dkj , D=dkx
i
j
k
x
Algorithm Description Definition 2: A transmission scenario involving
m links is admissible iff there is a set of transmission powers,pij≧0 ,which solves the following minimization problem:
s.t
minij
ijPm links
P
ijSINR ij links
DISTRIBUTED POWER CONTROL(TDMA Wireless Ad Hoc Networks)
max( 1) min , ( )( )i ii
P N P P NSINR N
Where
Pi power transmitted by node to its receiver
SINRi signal-to-interference-and-noise ratio at BS
N iteration number.
Algorithm DescriptionGiven a
transmission scenario in slot i
Is this scenario Valid?
Search for the optimum valid subset of users
Run the Distributed Power Control algorithm for this
valid scenario
Is the Valid scenario
Admissible
Nodes use the obtained set of powers to send
their packets
Go to next slot i = i+1
Search for the optimum
admissible subset of users
Scheduling Policies It is evident from the proposed algorithm that the
objective is to pack the maximum number of transmissions that can be successfully detected at their respective receivers in each slot.
The scheduling algorithm is responsible for solving two optimization problems, namely “valid scenario optimization” and “admissible scenario optimization”
Scheduling Policies valid scenario optimization
s.t.
INV:invalid transmission scenario admissible scenario optimization
s.t.
INA:vaild,yet inadmissable transmission scenario
max
SS
S INV
S is a valid scenario
max
Z
Z
ZZ
INA
is a admissible scenario
5
4
3
2
1
6
7
Node 1 2 3 4 5 6 7
7 7 2 3 6 7 4
Node 1 2 3 4 5 6 7
7 7 2 3 6 7 47 0 2 3 6 0 0
7 0 2 0 6 0 0
0 7 0 3 6 0 0
Node 1 2 3 4 5 6 7
7 7 2 3 6 7 4
7 0 2 0 6 0 0~3
0 7 0 3 6 0 0~3
0 0 2 0 6 0 4~3
7 0 0 3 6 0 0~3
0 0 2 0 6 0 4~3
0 0 2 0 0 7 0~2
0 0 2 0 6 0 4~3
5
4
3
2
1
6
7
Node 1 2 3 4 5 6 7
7 0 2 0 6 0 0
dkx<dkj
Node 1 2 3 4 5 6 7
7 0 0 0 0 0 0
5
4
3
2
1
6
7
Node 1 2 3 4 5 6 7
0 7 0 3 6 0 0
dkx<dkj
Node 1 2 3 4 5 6 7
0 7 0 0 0 0 0
5
4
3
2
1
6
7
Node 1 2 3 4 5 6 7
0 0 2 0 6 0 4
dkx<dkj
Node 1 2 3 4 5 6 7
0 0 0 0 6 0 4
Node 1 2 3 4 5 6 7
7 7 2 3 6 7 4
7 0 2 0 6 0 0~3
0 7 0 3 6 0 0~3
0 0 2 0 6 0 4~3
7 0 0 3 6 0 0~3
0 0 2 0 6 0 4~3
0 0 2 0 0 7 0~2
0 0 2 0 6 0 4~3
Node 1 2 3 4 5 6 7
7 7 2 3 6 7 4
7 0 0 0 0 0 0~1
0 7 0 0 0 0 0~1
0 0 0 0 6 0 4~2
7 0 0 0 0 0 0~1
0 0 0 0 6 0 4~2
0 0 2 0 0 0 0~1
0 0 0 0 6 0 4~2
5
4
3
2
1
6
7
Simulation Parameters
Number of nodes(n) 7
Slot Duration 2 msec
Frame Length 3 slots
Packet Inter-Arrival Time(1/λ) 6,7,..20 msec
SINR Threshold(β) 5
Noise Variance(σ2) 3.5
Maximum Power (Pmax) 100
Maximum Number of Iterations 30
Simulation
Simulation
Simulation
Simulation
Simulation
Simulation
Simulation
References [1] L. Williams, “Technology advances from small unit operations sit
uation awareness system development,” IEEE Personal Commun. Mag.pp. 30–33, Feb. 2001
[2] M. Mauve, J.Widmer, and H. Hartenstein, “A survey on position-based routing in mobile ad hoc networks,” IEEE Networks, pp. 30–39,Nov./Dec. 2001.
[3] Tamer Elbatt,Anthony Ephremides,”Joint Scheduling and Power Control for Wireless Ad Hoc Networks” IEEE Trans. Commun,vol.3no.1,January 2004
[4] S. Ulukus and R. Yates, “Stochastic power control for cellular radio systems,”IEEE Trans. Commun., vol. 46, pp. 784–798, June 1998.
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