KTH ROYAL INSTITUTEOF TECHNOLOGY

Lifetime-Aware Scheduling and Power Control for MTC in LTE Networks

Amin Azari and Guowang Miao

KTH Royal Institute of Technology

VTC Conference 2015, UK

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Contents:

• Introduction• System model and problem formulation• Proposed solutions• Performance evaluation• Conclusion

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Introduction

Future wireless access (5G) • Key challenges:

• Traffic growth: volume and number• Spectral & energy efficiency

M2M communications: • Communications without human intervention.

• Large number of short-lived sessions• low-payload• Diverse characteristics and QoS requirements

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Problem formulation

• Massive concurrent access requests• Collisions, idle-listening, and energy wasting.

• Forming local area networks:• Issue: How?

– EE cluster-forming & feasible regions [3] ,[4]– Cluster-size and CH selection [VTC]– Communication protocols [5]– Scheduling for CHs [VTC]

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System model: Basics

• Single Cell with one BS in the center

• Machine nodes: • Massive number, battery-driven

– long battery lifetime is desired

• Communications to the BS [1], [2]:• SC-FDMA

– Each subcarrier to at most one user,– Adjacent-subcarriers to a user,– Tx power on all assigned subcarriers the same.

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System model: Lifetime Metric Definition:

Static energy consumption

Reliable transmission: circuit + transmission

energy

Length of duty cycleLifetime at time Remaining energy

• Network lifetime: First Energy Drain (FED)

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P1: How should clusters be formed?

Optimal cluster size

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P1: How should clusters be formed?

• Cluster-size (g) optimization problem:

where,

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E in the CH mode

E in the CM mode

duty cycleRemaining E

cluster lifetime

Probability of being CH

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P1:How should clusters be formed? (cont.)

• is a strictly concave function of g• Using convex optimization tools, can be found.

• BS broadcasts to machine nodes• Each node will be a CH with probability .• Otherwise, attaches to the closest CH.

• How to prevent energy-drain in CHs?• How to prevent low-energy nodes to be the CH?

• Optimal CH selection

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Further improve

P2: Cluster-head selection schemes

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P2: Cluster-head selection schemes

• Centralized Cluster-head Selection Scheme:– maximize the minimum individual lifetime

– where– Current CH finds the next one.

• Distributed Cluster-forming Scheme:– Deviating from based on the :

– More details inside the paper.

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𝑝∗= 1𝑔∗

[𝐸 𝑖(𝑡 0) ]𝜇𝐷𝑖/𝑇 𝑖

𝐄𝑖 {[𝐸𝑖 (𝑡0)]𝜇𝐷𝑖 /𝑇 𝑖 }

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P2: Cluster-head selection schemes (cont.)

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reference random-resel proposed-(\mu=1)proposed-(\mu=3) optimal1

1.5

2

2.5

3

Life

time

Fac

tor

Lifetime Factor

Cluster lifetime evaluation for different cluster-forming schemes

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Even further improve

P3: Scheduling and power control for CHs

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P3: Scheduling and power control for CHs

• RBs are dedicated to the CHs.• RA among CHs?• Optimal transmit power for a given ?

• Then, find:• number of assigned RBs to CH ;• : modulation index.

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P3: Scheduling (heuristic solution)

• Optimization problem for joint scheduling and the power control:

• A heuristic solution to this non-convex is Algorithm 1 in the paper.• Complexity analysis and merits

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P3: Scheduling (Low-complexity Solution)

• The transmit energy-per-subcarrier the same for all nodes.• Tx power is controlled by .• The lifetime is a concave function of .

• Using linear relaxation, the NP-hard integer scheduling problem transforms to a related linear convex optimization problem.• Solvable in polynomial time,• Lower complexity

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Simulation Results• Model: uplink of a single cell,

• multi-user 3GPP LTE network in which, 2.7 MHz bandwidth is allocated to 10 CHs.

• Benchmarks:• Equal resource allocation (ERA)• Throughput-aware RA.

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-10 -5 0 5 10 15 200.8

1.3

1.8

2.2

SNRtarget

in dB

Life

time

Fa

cto

r

-10 -5 0 5 10 15 20

2

4

6

x 105

Life

time

(

duty

cyc

le)

Optimal LT-awareSubopt. LT-awareEqual RAThroughput-awareEqual RA (abs. value)

FED Network lifetime evaluation for different scheduling schemes

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Conclusion

• Key requirement for enabling M2M communication over cellular networks:• Providing energy efficiency,

• How?• Clustering prolongs the network lifetime.• Further improve: Optimal cluster-size and CH selection .• Even further: Lifetime-aware scheduling and power control

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References:

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1) H. Myung, J. Lim, and D. Goodman, “Single carrier FDMA for uplink wireless transmission,” IEEE Vehicular Technology Magazine,, vol. 1, no. 3, pp. 30–38, Sept. 2006.

2) 3GPP TS 36.213, “Evolved universal terrestrial radio access (EUTRA); physical layer procedures.” Tech. Rep., (Release 10).

3) P. Zhang and G. Miao, “Energy-Efficient Clustering Design for M2M Communications,” in 2nd IEEE Global Conference on Signal and Information Processing, 2014.

4) A. Azari and G. Miao, “-MAC: Energy Efficient Medium Access For Massive M2M Communications,” has been submitted to the JSAC, 2015.

5) A. Azari and G. Miao, “Energy efficient MAC for cellular-based M2M communications,” in 2nd IEEE Global Conference on Signal and Information Processing, 2014.

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Thanks for your participation.

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Question and Answer