Coverage and Throughput Analyses for Multihop Relaying Networks

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Coverage and Throughput AnalysesofMobile Multi-hop Relaying NetworksP Udhay Prakash & Dr. D Sreenivasa Rao

JNTU [email protected], [email protected]

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Content for discussion Existing work

Single hop vs. multiple hop

SCN vs. MCN

IEEE 802.16j Networks

Mutihop cellular networks (MCN)

Mobile multi-hop relaying (MMR) Relay selection

Performance Analyses

Success rate

Route sustaining time

Connection sustaining time Connection duration-outage probability

Maximum gain(gmax)

Throughput gain

Concluding where single hop is better and where multihop is better

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Introduction Current deploymentssuffer from

Limited Spectrum

Low SINR at Cell edge

Coverage hole due to shadowing

Non-uniformly distributed traffic load

Unable to address users at cell boundaries, due to power constraints

Allocated 1-2 GHz frequency band is not that suiatble for nLOS

communication

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Introduction

Solution: Mobile Multi-hop relaying (MMR) basedaccess network.

Improved data throughput and coverage area with relaying in cellular

networks.

Relaying was alreadyused in non-cellular, adhoc networks.

This paper addresses relaying concept for the cellular networks.

Here, end user can choose to connect directly to a BS, or, a RS, to

establish a two-hop link using a relay.

Relay locations are modelled as realizations of a two-dimensional

Poisson process with random motion for analyses.

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Existing work Mobile radio channel Vary from LoS pathto complex path,severely obstructed by buildings, mountains, and foliage.

For multi-hop wireless network, a fundamental question is

to route over manyshorter hops (short-hop routing) or over a smaller number oflonger hops (long-hop routing).

In [4], it is shown that relaying is always not beneficial and the reasons why short hop routing is not as beneficial as it

seems to be.

In [6], the analysis reveals that multi-hop transmission performs very well in the power-limited regime but can become

inefficient in the bandwidth-limited regime without interference cancellation.

In [10], the optimal number of hops for a specified end-to-end spectral efficiency (throughput) was analysed for

evenly spaced linear networks.

In [7, 8], the relative advantages of one hop versus two hop routing were compared, where a deployed relay could provide

an improvement in spectral efficiency.

In the above literature,

Location of relays is either predeterminedor optimizedin the design phase.

This presentation focuses on the mobile relays , which was less studied the above literature.

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IEEE 802.16j networkIEEE 802.16 Broadband Wireless Access Working groupIEEE 802.16j supports relay mode operation

Use casesIncreased coverage

Extending the coverage range of a BS using multi-hop techniques

Addressing coverage hole problems (e.g., shadows of buildings).

Capacity enhancementUse of multiple links with greater efficiency, as opposed to single-hop links overpoor-quality channels.

Multi-hop communications, which can support spatial reuse [9].

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SCN vs. MCN Hop: The step from one router to the next, on the path of a packet on any communications

network.

SCN: Single-hop Cellular Network

MCN:Multihop cellular network

Infrastructure-based cellular networks with adhoc networking concept

SCN++

Fixed Base Stations + Adhoc networking

Enhancedcoverage, improved capacity and flexibility.

Mobile relays are not (yet) of practical interest except in some specific applications such as

professional radios for emergency response, police and security organizations.

Provides cellular systems with opportunity of peer-to-peer (mobile to mobile) communication as well as

communication relayed through other fixed and/or mobile terminals.

The increase in system throughput is the major advantage of MCN.

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SCN vs. MCN SCN

BSs must be reached by MSs in a single-hop.

Subcell in SCN-- area of a sub cell is the same as the area of a cell.

MCN

Cell radius is halfthe distance between two neighbouring BSs.

BSs need not always be reachable by MSs in a single hop.

sub cell in MCN-- area reachable in a single wireless hop by a BS or a MS

BS and MSs are not always reciprocally accessible in a single hop.

transmission range of BS and MSs can be reduced than that in SCNs.

accessible area by a BS or a MS is the area of a sub-cell.

MSs can directly communicate with each other provided that they are mutually reachable and belonging to the same

cell.

perform multi-hop routing.

when destination MS is in a different cell from that of the source MS, then the Relay Station forwards the packets to its

own BS, which in turn, forwards to the destined MS via its BS.

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MMR MMR-Mobile multihop relaying

Concept of relaying user data and possibly control information between an MMR-BS

and MS through one or more relay stations (RS).

Mobilebecause both RS & MS are mobile. Relaying

To enhance coverage, range, and throughput and possibly capacity of an MMR-BS

To enable very low power devices to participate in the network.

Multipath routing between the MMR-BS and an MS to communicate user data and/or

control/management information, to improve communications reliability.

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Relay selection Relay Selection effects hop delay and the complexity involved. Assumed variables are

dij(t)distance between mobile iand mobile jat time t. Index 0 denotes the BS.

di0(t) & dj0(t)distances between mobile iand BS, & mobile jand BS respectively at time instant t.

rtransmission range for any mobile.

Clearly, d00(t)=0 for all t.

M= { 1,2,..N }set of mobiles and N= { 0,1,2,, N}set of nodes including the BS (i=0).

R(t)Nset of relay nodes at time slot t.

A(t) Mset of active nodes. i.e, the nodes that are not acting as relays.

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Relay selection Node i A(t) selects relay ki as Ki = argminjFi(t){dij + (1-)dj0} for all i A(t)

where 0 1 is a weighting parameter

Fi(t)

set of feasible relays for mobile i. Fi(t) ={ j/j R(t); dij< r; dj0 di0}

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Performance Analyses- Simulation consideration

Simulations were performed in MATLAB 7.12.

End user is fixed at coordinates (l,0) and Mobile relay is at coordinates (r,

)

Since BS coverage has been normalized, l>1 corresponds to out-of-coverage users,

l 1 implies the end user is within the coverage area.

M/M/ queuing model is used to capture relay mobility

Ldistance between BS and end user

r

distance between BS and mobile relay

- angle between BS and mobile relay with end user

1and 2SNRs of BS and mobile relay respectively

path loss exponent

Naverage no. of usable relays in cell coverage area

N=, with relay density Assuming N = 20 to represent a low density cell

N = 100 to represent a high density cell for numerical evaluation.

Average relay speed is normalized to the cell diameter

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Performance Analyses

Simulation Environment with respective Nodes coordinate positions.

20 nodes (node may be MS, BS or a relay) forming a network, with every nodesconnected to its nearby nodes, is created.

The relay movement is randomized in distance and direction.

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Success rate For r = 10, = 35, and SNR of BS and

relay is 1= 2= 3dBwith= 3,

Simulations for l= 1.05, 1.10, 1.15 and

1.20, for out of coverage end user.

As feasible region shrinks with

increasing l, chance of locating a relay

within the feasible region also declines.

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Success rate Impact of SNRs 1 and 2 on two-hop

routing success probability is depictedhere for an end user 10% away fromthe BS coverage area l = 1.1 andconsidering 1= 2 dB, 3 dB, 4 dB and 5dB.

For two hop relaying to be useful, therelay SNR at unit distance 2 should becloser to that of the BS, 1, as 1increases.

Even with 1= 2, higher SNRs reduceprobability of feasible relays.

Two-hop relaying is less favourable inhigh SNR regions for line networks.

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Route sustaining time Once the route (path) is established,

its sustainability is analysed, eitherwith or without re-routing.

Assuming that handoffs betweenrelays are allowed and they must bein time.

Here l = 1, 1.05, 1.1, 1.15, and 1.2,with pedestrian speed as 2 andvehicular speed as 10, with = 3 and1= 2= 3 dB.

Average route sustaining time ismuch longer than average burst

duration in IEEE 802.16j networkarchitecture, even when the mobilerelay travels at a vehicular speed.

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Connection sustaining time For user to BS distances l =1.1

Tn connection sustaining time,averaged over all time instants for nfeasible relays.

route sustaining time >> connection

sustaining time due to possibility of new relays entering

the feasible region as current feasiblerelays leave.

So, allowing mobile relay hand-off is aneffective method to extend connection

time.

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Connection sustaining time For user to BS distances l =1.2

For vehicular speed and pedestrianspeed users

When relay density is high, average

connection sustaining time for l= 1.1is very long on the order of days, depending on

maximum time.

connection success rate approachingone as the relay densityincreases.

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Connection duration-outage probability Probability that two-hop connection fails to

meet connection duration requirement due to

depletion of feasible mobile relays.

Exponentially distributed with mean given by

the x-axis value,

Mobile relays are distributed with poisson

point process such that there are an average N

= 20 relays in the cell.

Mobile relays are assumed to move atpedestrian speed, with = 3.

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Maximum gain(gmax)

For = 4 with 1= 3 dB, 2= 1 dB, 2 dBand 3 dB and for = 3 with 1= 3 dB, 2= 1 dB, 2 dB

and 3 dB. Gmax can be determined by searching

for the optimum relay position.

Graph depicts how Gmax varies withuser distance l. Assumin has a big impact on Gmax. Gmax increases with increasing l, as end

users close to BS already enjoy a highthroughput.

So, multi-hop is less favourable in thehigh spectral efficiency regime.

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Throughput gain For = 3 , and end user is

located at cell boundary.

With the upper bound Gmax,simulation results show how

random relay placement affects

the throughput gain.

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Throughput gain For = 4, and end user is located at

cell boundary.

With increasing relay density,

probability that relaying achieves a

gain close to Gmax increases.

And, the average throughput gain

approaches Gmax.

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Conclusions

Concluding where single hop is better and where multihop is better. For the two-hop links,

success rate is inversely proportional to the coverage distance.

two hop networks are unfavourable in high SNR regions for line networks.

Average route sustaining time is much longer than the average burst duration.

Connection sustaining time is directly proportional to the relay density and inversely

proportional to the relay speed.

With increasing relay density, the achievable throughput reaches the maximum gain level.

For an out of-coverage end-user, mobile relays offer substantial coverage extension benefits.

With randomly placed moderate number of mobile relays, significant average throughput gains

can be obtained for end users near cell boundaries.

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Future Scope Above presented work can be extended for

different SNR values.

Power consumption and security aspects of relay

supported cellular networks can be analysed.

Alternative techniques for delay reduction such

as decreasing packet size can be analysed.

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References1) Y. D. Lin and Y. C. Hsu, Multi-hop cellular: A new architecture for wireless communication, in

IEEE INFOCOM '2000, 2000, pp. 12731282.

2) Andrea Goldsmith, Wireless Communications, Cambridge University Press, 2005.

3) Halim Yanikomeroglu, Cellular Multi-hop Communications: infrastructure Based Relay Network

Architecture for 4G Systems, Queen's University 22nd Biennial Symposium on Communications

(QBSC'04), Kingston, Ontario, Canada, 1st June 2004.

4) M. Haenggi and D. Puccinelli, Routing in adhoc networks: a case for long hops, IEEE

Commun. Mag., vol. 43, pp. 93-101, Oct. 2005.

5) A. Florea and H. Yanikomeroglu, On the Optimal number of hops in infrastructure-based fixed

relay networks, in Proc. IEEE Globecom, St. Louis, MO, Nov. 2005.

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References6) M. Sikora, J.N. Laneman, M. Haenggi, D.J. Costello Jr., and T. E. Fuja, Bandwidth and Power

efficient routing in linear wireless networks, IEEE Transactions on Inf. Theory, Vol.52, pp. 2624-

2633, June 2006.

7) S. V. Maiya, Spectral efficiency and its relation torouting strategies in simple communication

networks, Master's thesis, University of Notre Dame, Notre Dame, 2007.

8) S.V. Maiya and T.E. Fuja, One hop vs two hop routing in simple networks with fading: an outage

probability analysis addressing spectral efficiency, in Proc. Wireless Communication Networks

Conference (WCNC 2008), Las Vegas, Mar. 2008.

9) Vaskengenc, Seanmurphy, Yangju and Johnmurphy, IEEE 802.16j Relay-based Wireless Access

Networks: An Overview, IEEE Wireless Communications, October 2008.

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Documents

Coverage and Throughput Analyses for Multihop Relaying Networks