International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 2, Issue 3, March 2013
ISSN 2319 - 4847
Adaptive Power saving dynamic Radio Resource
Allocation in OFDMA Based Cellular Relay
Networks
D.Gurupandi1, M.Vadivel2
1
M.E Scholar, ETCE Dept., Sathyabama University, Chennai – 60 119, Tamilnadu, India.
2
Assistant Professor, ETCE Dept., Sathyabama University, Chennai-600 119, Tamilnadu, India.
ABSTRACT
In this paper, we are analyzing the performance of adaptive power saving resource allocation with frequency reuse method for
orthogonal frequency division multiple access (OFDMA) based cellular relay networks. An optimization problem is to minimize
the total transmitted power for the network and the other constraints such as relay and data rates of user. An optimization
solution can be obtained by allocating sub-channels with path loss, Rayleigh fading. We have proposed a dynamic resource
allocation algorithm for subcarrier allocation in the network by considering power saving and frequency reuse in the cellular
based relay transmissions. From the simulation results show that, we can conclude that the proposed dynamic resource
allocation algorithm can achieve minimized network power and low bit error rate (BER) with improved performance.
Keywords: OFDMA, BER, CRN, RAN
1. INTRODUCTION
OFDMA based cellular relay network plays a vital role in next generation wireless networks by increasing data rates
and coverage of larger area.OFDMA based radio resource allocation methods allocate different radio resources to
different users in the frequency domain as well as in the time domains. The overall performance of the wireless
networks can be improved by using relay networks. The performance includes wide coverage area, power saving, and
total throughput with minimum deployment cost. An orthogonal frequency-division multiple access (OFDMA)
combined with relay networks offers one of the powerful technique to enable high date rates for future wireless cellular
networks.
OFDMA based cellular relay networks has an ability to access multiple channels. It may transmit a processed version of
the signal to another subcarrier which is received from one subcarrier. We are proposed Adaptive dynamic radio
resource allocation algorithm [7] to achieve maximum sum rate capacity for an OFDMA based a multiple user multiple
cellular relay networks. To improve the power saving, we can dynamically allocate subcarriers, bit and power by
knowing the channel state information at the transmitter side of OFDMA system.
Spectral efficiency plays an important role in achieving high data rate in wireless cellular communication. Efficient
usage of power is important for wire communication as well as wireless communications.Radio resource management
schemes are mainly concentrating on maximizing the spectral efficiency of OFDMA systems rather than maximizing
total throughput of the system. In wireless Communication, it is important to minimize the total transmit power
consumption in RAN’s.Radio resource allocation in OFDMA based systems mainly depends on total transmit power
and data rate. So we are formulating the energy efficient resource allocation schemes with reduced complexity.OFDMA
plays an important role in future cellular relay networks. It also allows changing the spectral environments dynamically
by allocating unused spectrum to the secondary users. Spectrum utilization can also be improved by using OFDMA to
overcome the frequency selective fading. Efficient power allocation algorithms are necessary to optimize bit error rate,
transmission channel capacity, and transmit power in OFDMA based cellular relay [2] networks.
Our ultimate aim is to increase the channel capacity and power saving [1] efficiency of OFDMA based cellular relay
networks by limiting the interference introduced between cells. From The simulation results show that the proposed
dynamic resource allocation algorithm can achieve minimized network power and low bit error rate (BER) with
improved performance.
Volume 2, Issue 3, March 2013
Page 466
International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 2, Issue 3, March 2013
ISSN 2319 - 4847
2. SYSTEM MODEL
Relays play an important role in wireless communication particularly in cellular networks [6] to increase the coverage
area, reduce the total transmission power, enhance the rate sum capacity of a specific region with high traffic demands
and improve signal reception.
2.1. System Model of OFDMA based cellular relay networks
Figure 1. Block Diagram of OFDMA based cellular relay networks
In this paper, Figure 1 shows the block diagram of OFDMA based cellular relay networks for uplink as well as
downlink [8]. A central controller collects all the information from all the base stations (BS’s) and allocates resource
allocation according to channel state information(CSI).Base station collects information from the mobile
stations(MS’s).We can transfer the information either from MS to BS directly or from MS to BS via relay
station(RS)[5] and vice versa.
3. DESIGN METHODOLOGIES
Effective power allocation algorithms are needed in order to maximize the rate sum capacity of relay networks by
considering the two criteria channel state Information and bit error rate (BER).
Relay based systems uses the radio resources channel, power, and subcarrier [3] [4] to improve the performance like
total throughput and less bit error rate. Power can be minimized by reducing the total transmit power for a given sum
data rate.
We can write the optimization problem by mathematically
Data rate Rk can be related by using
b k ,n
and
k ,n is given by
K
N
 b
k ,n
k,n
(1)
k 1 n 1
Where
N - Total number of subcarriers
K - Total number of radio links
b k ,n = number of bits allocated for link k in the subcarrier n
k ,n = subcarrier assignment indicator
Volume 2, Issue 3, March 2013
Page 467
International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 2, Issue 3, March 2013
ISSN 2319 - 4847
k ,n ={0,1}
4. PROPOSED ALGORITHM
The proposed algorithm for Power allocation is compared with existing algorithms how close they come to the optimum
allocation.
4.1. Proposed Optimal Power Allocation
After assigning subchannels to the users by using subcarrier allocation algorithm, we can allocate the power according
to channel state information from all the users to achieve maximum transmission capacity to all the users by allowing
the less interference introduced into users. Transmit power may vary according to data rate for the number of users.
The optimal transmission power allocated for link k in the subcarrier n is can be expressed as
P k ,n 
p rr
b
k ,n

(2)
h
2
k ,n
Where
p rr  b k ,n
h k ,n
 = Required power to receive the number of bits allocated for link k in the subcarrier n
= Channel gain for user k in the subcarrier n
5. RESULTS AND DISCUSSIONS
The performance of proposed algorithm can be shown in the simulation results by using MATLAB 7.9.The simulation
parameters are Total number of subcarriers N=256, Total number of Base stations =5, Total number of Relay stations
=30, Total number of Mobile stations in each cell =30, BER=1x10 - 1.25, Bandwidth B= 10 MHz, AWGN=-198
dBm/Hz, Total number of channel realizations K=1200.
5.1. Simulation Results
Figure 2. Total transmit power Vs Cumulative Distribution Function
Figure 2 shows the simulation result of total transmit power versus cumulative distribution function.
Figure 3. Eb/No Vs BER
Figure 3 shows the simulation result of Eb/No versus bit error rate(BER).
Volume 2, Issue 3, March 2013
Page 468
International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 2, Issue 3, March 2013
ISSN 2319 - 4847
Figure 4. Data rate Vs Power difference between algorithms 2 & 4
Figure 4 shows the simulation result of data rate versus power difference between algorithm 2 & 4.
6. CONCLUSION
From the simulation results show that, we can conclude that, the proposed dynamic resource allocation algorithm can
achieve minimized network power and low bit error rate (BER) with improved performance and also achieve a good
tradeoff between total transmit power and cumulative distribution function, data rate and power difference between
algorithms.
REFERENCES
[1] Jingon Joung and Sumei Sun, “A Simple Network Power Saving Resource Allocation Method for OFDMA
Cellular Networks with Multiple Relays”, IEEE,pp. 2504-2507,2011
[2] Mohamed Salem, Abdulkareem Adinoyi, Halim Yanikomeroglu, and David Falconer, “Opportunities and
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[3] Gautam Kulkarni, Sachin Adlakha, and Mani Srivastava, “Subcarrier Allocation and Bit Loading Algorithms for
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2005
[4] Christian Muller, Anja Klein, Frank Wegner, Martin Kuipers and Bernhard Raaf, “Dynamic Subcarrier, Bit and
Power Allocation in OFDMA-Based Relay Networks”, Proc. of 12th International OFDM-Workshop, Hamburg,
Germany, Aug. 2007.
[5] M. Kaneko, P. Popovski, “Adaptive resource allocation in cellular OFDMA system with multiple relay stations,” in
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[6] O. Oyman, “OFDM2A: A centralized resource allocation policy for cellular Multi-hop networks,” The 40th
Asilomar Conference on Signals, Systems and Computers, pp. 656–660, Oct. and Nov. 2006.
[7] Muller C, Klein A, Wegner F, Kuipers M, Raaf B. “Dynamic Subcarrier, Bit and Power allocation in OFDMAbased Relay networks”, Proceedings of 12th International OFDM Workshop, Berlin, Germany, 2007.
[8] N. Ksairi, P. Bianchi, P. Ciblat, W. Hachem, “Resource Allocation for Downlink Cellular OFDMA Systems—Part
II: Practical Algorithms and Optimal Reuse Factor,” IEEE Trans. On Signal Processing, vol. 58, no.2, pp. 735749, Feb. 2010.
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