Wireless Pers Commun (2010) 53:253–267 DOI 10.1007/s11277-009-9682-7
Spectrum Efficiency Enhancement in Dynamic Space Coded Multiple Access (DSCMA) System Chee Kyun Ng · Nor Kamariah Noordin · Borhanuddin Mohd Ali · Sudhanshu Shekhar Jamuar · Mahamod Ismail
Published online: 10 March 2009 © Springer Science+Business Media, LLC. 2009
Abstract In cellular mobile communication systems using coded modulations, the spectrum efficiency of the system is related to the number of available codes. Recently, large area synchronous (LAS) CDMA codes, which exhibit a region called interference free window (IFW) within some delay-spread, have been accepted as one of fourth-generation (4G) wireless communication systems. However, the number of synthesized LAS codes is very low due to the low duty ratio of the sequence. In this paper, a dynamic space coded multiple access (DSCMA) scheme which utilizes the spatial diversity from smart antenna system is proposed to overcome the low spectrum efficiency in LAS CDMA system. In the DSCMA a modified version of LAS codes called LAS even ternary (LAS-ET) codes is proposed. These codes are used together with a novel algorithm called dynamic space code (DSC), which will decrease the code length so that the spectrum efficiency can be increased. By taking advantage of dynamic code reuse assignment in spatial diversity, the spectrum efficiency of the DSCMA can be further increased significantly.
C. K. Ng (B) · N. K. Noordin · B. M. Ali Department of Computer and Communication Systems Engineering, Universiti Putra Malaysia, Serdang, Malaysia e-mail:
[email protected];
[email protected] N. K. Noordin e-mail:
[email protected] B. M. Ali e-mail:
[email protected] S. S. Jamuar Department of Electrical and Electronic Engineering, Faculty of Engineering, Universiti Putra Malaysia, Serdang, Malaysia e-mail:
[email protected] M. Ismail Department of Electrical, Electronic and System Engineering, Faculty of Engineering, Universiti Kebangsaan Malaysia, Kuala Lumpur, Malaysia e-mail:
[email protected]
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Keywords Spectrum efficiency · LAS CDMA · IFW · Smart antenna · Code reuse · Duty ratio · Beamwidth
1 Introduction Radio spectrum is a limited resource for wireless technologies hence, the main thrust of fourth-generation (4G) wireless communication research is to enhance the spectrum efficiency of a system [1]. Recent third-generation (3G) systems are based on code division multiple access (CDMA) and enhanced by space division multiple access (SDMA). Both schemes are characterized as interference limited in non-uniform traffic environment with inter-symbol interference (ISI) as well as multiple access interference (MAI) [2]. In random access environment each user signal arrives at base station receiver with different delays in reverse link. The system performance is carried out in asynchronous manner [3]. Thus, traditional CDMA codes such as m-sequences, Gold codes, Kasami codes and Walsh codes exhibit non-zero correlation among their codes around some non-zero delay-spread region [4] while in SDMA, perfect spatial signatures cannot be obtained when user location are not situated at null directions of other users radiation pattern. There are several research initiatives to design CDMA codes that exhibit zero correlation within some delay-spread region. The attractive family of large area synchronized (LAS) CDMA codes have been introduced by Li [5] which is constituted by the combination of large area (LA) codes and loosely synchronous (LS) codes. The resultant LAS codes exhibit a zero correlation region called interference free window (IFW) within some delay-spread. Initially, Li [6] introduced LA codes to exhibit an IFW but its duty ratio is very low which is a major drawback for the code. To increase spectrum efficiency it is necessary to have higher duty ratio of a spreading sequence. Therefore, Li [5] merges its LA codes with LS codes to achieve a higher duty ratio. However, the consequences of the emerged LAS codes exhibit a small IFW and hard to be implemented due to its complexity compared to the previous LA codes. It is necessary to increase spectrum efficiency without affecting the characteristics of the spreading sequences. In this paper, we introduce dynamic space coded multiple access (DSCMA) system by inserting CDMA codes into SDMA spatial diversity. A modified LAS codes called LAS even ternary (LAS-ET) codes with high duty ratio is used in this system. Higher spectrum efficiency can also be achieved by exploiting the dynamic code reuse assignment in fact the code is reusable in regions that are isolated spatially. Thus the number of traffic channels can be increased dramatically. Instead of inserting LS codes into LA codes to gain a higher duty ratio in LAS codes, the DSCMA system uses dynamic space code (DSC) algorithm to increase duty ratio of LAS-ET codes. Its duty ratio becomes adaptively increased when the beamwidth of smart antenna becomes narrower. The desired IFW size is reduced proportionately with the narrower beamwidth, and the sequence length can also be reduced. This paves a way for the system to increase its duty ratio. This modified LAS-ET codes are well organized and much easier to be synthesized compared to the original LAS codes. The narrower beam from smart antenna will drive all multipath signals to arrive within the exhibited IFW delay-spread duration. In such a manner, interference cancellation can also be realized from DSCMA system, which will directly increase the system capacity. This paper is organized as follows: In Sect. 2, the construction and properties of LAS CDMA codes are described. The DSC algorithm, which is used in DSCMA system together with LAS-ET codes and smart antenna, is presented in Sect. 3. Spectrum efficiency incease in LAS-ET codes is discussed in Sect. 4. The spectrum efficiency is further improved through
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Table 1 The arrangement of 16 LA(16,38,847) sequences
C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 C16
0
38
78
120
164
210
258
308
360
414
470
530
592
660
732
808
847
+ + + + + + + + + + + + + + + +
+ + + + − − − − + − + − − + + −
+ + + − − − − + − + − − + + − +
+ + − − − − + − + − − + + − + +
+ − − − − + − + − − + + − + + +
+ − − − + − + − − + + − + + + −
+ − − + − + − − + + − + + + − −
+ − + − + − − + + − + + + − − −
+ + − + − − + + − + + + − − − −
+ − + − − + + − + + + − − − − +
+ + − − + + − + + + − − − − + −
+ − − + + − + + + − − − − + − +
+ − + + − + + + − − − − + − + −
+ + + − + + + − − − − + − + − −
+ + − + + + − − − − + − + − − +
+ − + + + − − − − + − + − − + +
+ + + + + + + + + + + + + + + +
Fig. 1 LAS sequences construction method
dynamic code reuse assignment, which is discussed in Sect. 5. This paper is then concluded in Sect. 6.
2 Overview of LAS CDMA Codes The original LAS codes proposed by Li [5] are synthesized by seeding LS codes in LA codes to improve it spectrum efficiency. An N p LA codes are synthesized in such a manner that the N p non-zero ±1 pulses from m-sequences oriented are positioned as shown in Table 1. This arrangement forms a configuration of LA(N p , K 0 , L c ) where K 0 is the minimum number of zero padding in pulse interval of non-zero pulses which determine the size of IFW delay-spread in term of chips, while having a total code length of L c chips. The LS codes are then seeded into pulse intervals of LA codes as depicted in Fig. 1 to form LAS codes. Consequently, the resultant size of synthesized IFW from LAS codes becomes much smaller than the size of synthesized IFW from LA codes. This is a major drawback of LAS codes. In addition, the implementation of these LAS codes has become more complex. Figure 2 shows the cross-correlation property of LAS codes where here is a region where no cross-correlation side-lobes exist. This region around the origin is defined as interference free window (IFW). For an asynchronous CDMA system, if the delay spread of the multipath channel is within such IFW region, there is practically no ISI nor MAI.
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C. K. Ng et al.
Fig. 2 The IFW region from cross-correlation property of two LAS codes
3 DSC Algorithm with LAS-ET Codes The IFW region shown in Fig. 2 is rather small about 13 time shifts, and there is imperfect zero correlation at zero time shift. In order to achieve a perfect IFW including at the zero time shift, some modification is done to the original LA code to form LAS-ET codes. In this LAS-ET code, the pulse interval or zero paddings between two adjacent non-zero pulses is even in number. It is interesting to note that with this modification the sequence length of LAS-ET codes is shorter than original LA codes yielding from 847 chips to 818 chips. Hence, this modification increases the duty ratio of LAS-ET codes while the size of IFW is maintained. In DSCMA system, a narrower beam from smart antenna system is steered to a particular user. The beamwidth size is necessary to synchronize with the size of exhibited IFW from LAS-ET codes through DSC algorithm. This is to ensure that all the user signal components within the beam are driven into IFW such that all interferences are fully eliminated. This behaviour is described in Fig. 3a–e, when the distance between base station and mobile station is 10 km. With DSC algorithm, the required size of IFW can be adjusted to the size of the smart antenna beamwidth. Hence, the sequence length of LAS-ET codes can be further reduced to increase its duty ratio as the minimum number of zero padding in this sequence is further decreased. In this manner, the spectrum efficiency of spreading sequence can be further increased. In order to assure the high directivity narrow beam of smart antenna drops within the IFW delay-spread duration exhibited by proposed LAS-ET codes, the generated IFW delayspread duration must be larger than maximum excess delay, τmax of smart antenna narrow beam. Hence, by using DSC algorithm some adjustment in the construction of proposed LAS-ET codes, LAS − E T N p , K 0 , L c is done appropriately such that the IFW size will be larger than τmax for a given number of elements, Ne in a smart antenna system. For example, the 6.375◦ half-power beamwidth of 16 elements smart antenna which induces a maximum excess delay, τmax of 4.56 chips needs an IFW size of at least five chips delay-spread duration. Hence, the minimum pulse interval, K 0 in this LAS-ET code is taken as an even number of
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257
Fig. 3 The DSC algorithm showing the relationship between beamwidth and IFW. a Illustration of 25.5◦ beamwidth from four elements smart antenna with IFW region from correlation property of LASET (16,20,530) sequences. b Illustration of 12.75◦ beamwidth from eight elements smart antenna with IFW region from correlation property of LAS-ET (16,10,370) sequences. c Illustration of 6.375◦ beamwidth from 16 elements smart antenna with IFW region from correlation property of LAS-ET (16,6,306) sequences. d Illustration of 3.19◦ beamwidth from 32 elements smart antenna with IFW region from correlation property of LAS-ET (16,4,274) sequences. e Illustration of 1.59◦ beamwidth from 64 elements smart antenna with IFW region from correlation property of LAS-ET (16,2,242) sequences
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258
Fig. 3 continued
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C. K. Ng et al.
Spectrum Efficiency Enhancement
259
Fig. 3 continued
six. Thus, the sequence length, L c of proposed LAS-ET codes for N p = 16 and K 0 = 6 will become L c = 306, and the construction of this code yield LAS − E T (16, 6, 306). Table 2 shows the arrangement of the non-zero pulses in LAS-ET codes of K 0 = 20, 10, 6, 4, 2 for acquiring an IFW to accommodate the beamwidth synthesized from smart antenna with various numbers of elements, Ne = 4, 8, 16, 32, 64, respectively. Figure 3 shows how the main lobes of Ne = 4, 8, 16, 32, 64 smart antenna system totally dropped within the IFW delay-spread duration acquired from LAS-ET sequences of K 0 = 20, 10, 6, 4, 2, respectively. It is observed that the length of LAS-ET code is reduced when the required minimum pulse interval, K 0 is reduced. Therefore, the spectrum efficiency is increased when the sequence length of LAS-ET codes is decreased from 818 chips to 242 chips.
4 Spectrum Efficiency Increase in LAS-ET Codes The most important measure of a multiple access system is its spectrum efficiency, η which is defined by [6] η=
Nu R B
(1)
where Nu is the maximum number of users per sector or cell, B is the system bandwidth which is given as 1.25 MHz in CDMA system, and R is the average user data rate in bit per second. In a DSCMA system, when both R and B are fixed, spectrum efficiency is proportional to the number of available codes to accommodate Nu users.
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C. K. Ng et al.
Table 2 The 16 non-zero pulse positions of LAS-ET codes (a) LAS-ET(16,20,530) sequences 0
20
42
66
92
120
150
182
216
252
290
330
372
416
462
510
C1
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
530 +
C2
+
+
+
+
−
−
−
−
+
−
+
−
−
+
+
−
+
C3
+
+
+
−
−
−
−
+
−
+
−
−
+
+
−
+
+ 370
(b) LAS-ET(16,10,370) sequences 0
10
22
36
52
70
90
112
136
162
190
220
252
286
322
360
C1
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
C2
+
+
+
+
−
−
−
−
+
−
+
−
−
+
+
−
+
C3
+
+
+
−
−
−
−
+
−
+
−
−
+
+
−
+
+ 306
(c) LAS-ET(16,6,306) sequences 0
6
14
24
36
50
66
84
104
126
150
176
204
234
266
300
C1
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
C2
+
+
+
+
−
−
−
+
−
+
−
−
+
+
−
+
C3
+
+
+
−
−
−
−
+
−
+
−
−
+
+
−
+
+ 274
(d) LAS-ET(16,4,274) sequences 0
4
10
18
28
40
54
70
88
108
130
154
180
208
238
270
C1
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
C2
+
+
+
+
−
−
−
−
+
−
+
−
−
+
+
−
+
C3
+
+
+
−
−
−
+
−
+
−
−
+
+
−
+
+ 242
(e) LAS-ET(16,2,242) sequences 0
2
6
12
20
30
42
56
72
90
110
132
156
182
210
240
C1
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
C2
+
+
+
+
−
−
−
−
+
−
+
−
−
+
+
−
+
C3
+
+
+
−
−
−
−
+
−
+
−
−
+
+
−
+
+
As mentioned earlier, initially, Li [6] introduced LA codes to exhibit an IFW but its duty ratio is very low which is a major drawback. To increase spectrum efficiency it is necessary to have higher duty ratio of a code. Therefore, Li [5] merges its LA codes with LS codes to achieve this higher duty ratio. However, the consequence of the emerged LAS codes exhibit a small IFW and hard to be implemented due to it complexity compared to the initial LA codes. In order to sustain the characteristics of LA sequence proposed in [6] without altering the size of IFW, a modified cods, LAS-ET is employed in DSCMA instead of LAS codes. The code’s duty ratio, D is defined by D=
Np L
(2)
where N p is the number of non-zero pulses in LAS-ET code, and L is the sequence length. Note that in a traditional CDMA code, where zero pulses do not exist, D is unity, hence the spectrum efficiency is proportional to the number of available codes to accommodate Nu users. Therefore, spectrum efficiency, η in DSCMA system is proportional to the code’s duty ratio, D and can be expressed as
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Spectrum Efficiency Enhancement
261
Table 3 The duty ratio improvement in LAS−ET sequence for various numbers of elements, Ne in smart antenna system Number of elements, Ne
Minimum pulse interval, K 0 (chip)
Length of code, L (chip)
Duty ratio, D
Percentage of improvement (%)
1
143
818
0.02
0
4
20
530
0.03
50
8
10
370
0.04
100
16
6
306
0.05
150
32
4
274
0.06
200
64
2
242
0.07
250
η=
Np R DR = B LB
(3)
The spectrum efficiency of proposed LAS-ET code is hence higher than Li’s original LA code. This is because the duty ratio of LAS − E T (16, 38, 818) is 0.0196, which is higher compared to duty ratio of 0.0189 in the original LA (16, 38, 847) code proposed in [6] thus, it results in a 3.7% spectrum efficiency increase. However, the duty ratio of LAS-ET sequence is still low compared to L A (16, 38, 714) sequence proposed in [7] which exhibits D = 0.0224. In DSCMA system, the length of LAS-ET code is reduced when the required minimum pulse interval, K 0 is reduced. This implies that in DSC algorithm the time of arrival (TOA) of narrower beam is shorter and the IFW size must be smaller such that the spectrum efficiency can be increased through the increase of code’s duty ratio. The duty ratio improvement in DSCMA system using DSC algorithm relative for a single element antenna system is shown in Table 3. It could be seen that when the beamwidth of smart antenna is reduced by increasing the number of elements, Ne the length of LAS-ET code, L c is reduced proportionately. For example, in the 64 elements of smart antenna system the length of code is reduced from 818 chips to 242 chips which is a 250% duty ratio improvement.
5 Spectrum Efficiency Further Improvement Through Dynamic Code Reuse Assignment In current mobile communication systems, the frequency reuse assignment in terms of number of cells is based on the minimum distance between two cells that the co-channel interference can be tolerated. In this paper, the code reuse assignment is based on the angle of arrival (AOA) of the mobile users. All the codes can be reused at every null generated from smart antenna. This concept is similar to that of SDMA system. Its spectrum efficiency is dependent on the number of null in the system. The null coverage is shown in Fig. 4. The length of arc, S due to null sector β ◦ is given by S = dβ
π 180
(4)
where d is the distance between base station and mobile user.
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Fig. 4 The null coverage make by β ◦
To realize the code reuse assignment, the location of the incoming mobile user is determined to check whether its AOA is within β = ±1◦ of the null directions of existing mobile user radiation pattern. If this requirement is met, the incoming mobile user will be assigned to the same code as the existing mobile user, otherwise a new successive code will be assigned. Hence a mobile user is considered to be static or in minimum mobility for a distance of 180 m if distance between mobile user and base station is 10 km for β = ±1◦ . Figure 5 shows how the spectrum efficiency improvement in SDMA system from Ne = 8 to Ne = 32. When both R and B are negligible, the spectrum efficiency, η in DSCMA system is given as η = Nc Nn
(5)
where Nc is the total available codes in the system. The code reuse factor, Nn is the number of nulls that a smart antenna can generate and it is given by Nn = Ne − 1
(6)
where Ne is the number of antenna elements. Equation 5 is a general equation for spectrum efficiency in the DSCMA system that takes advantage of dynamic code reuse assignment. The duty ratio, D in DSC algorithm can be increased by reducing the code length for higher number of elements in smart antenna. This is because the size of IFW decreases further when a narrower beam is assigned. Therefore, from Eq. 3 the spectrum efficiency, η in DSCMA system can be rewritten as
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Fig. 5 SDMA system for (a) Ne = 8 and (b) Ne = 32
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Table 4 System performance of DSCMA on LAS-ET codes for various number of elements, Ne in smart antenna system Number of elements, Ne
LAS-ET sequences configuration
Sequence length, L (chip)
Duty ratio, D
Spectrum efficiency, η
(a) With non-zero pulses, Np = 16 1
16,38,818
818
0.02
≈0
4
16,20,530
530
0.03
0.00017
8
16,10,370
370
0.04
0.0008
16
16,6,306
306
0.05
0.0025
32
16,4,274
274
0.06
0.0065
64
16,2,242
242
0.07
0.0169
(b) With non-zero pulses, Np = 32 1
32,38,2146
2146
0.015
≈0
4
32,20,1570
1570
0.02
0.000038
8
32,10,1250
1250
0.026
0.00014
16
32,6,1122
1122
0.029
0.00037
32
32,4,1058
1058
0.03
0.00083
64
32,2,994
994
0.032
0.00200
(c) With non-zero pulses, Np = 64 1
64,38,6338
6338
0.01
≈0
4
64,20,5186
5184
0.012
0.000007
8
64,10,4546
4546
0.014
0.000021
16
64,6,4290
4290
0.015
0.000051
32
64,4,4162
4162
0.015
0.00011
64
64,2,4034
4034
0.016
0.00024
η=
N p R Nn N p R(Ne − 1) D R Nn = = B LB LB
(7)
In DSCMA system, the duty ratio, D of the LAS-ET code is no longer unity, and its data rate, R is represented by R=
Rc L
(8)
where Rc is the sequence chip rate which is given as 1.2288 Mcps. So, η in DSCMA system is given as η=
N p Rc (Ne − 1) B L2
(9)
To analyze the spectrum efficiency improvement in DSCMA system, LAS-ET codes with non-zero pulses, N p of 16, 32 and 64 are occupied together with the smart antenna system with Ne = 4, 8, 16, 32 and 64 elements. The parameters B and Rc are fixed. Parameter L, sequence length is varied according to N p . This combination of parameters is listed in Table 4. From Eq. 9, the spectrum efficiency, η is calculated for each combination. The results of these combinations are shown in Table 4. In order to analyze the spectrum efficiency performance,
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Fig. 6 The spectrum efficiency improvement of DSCMA for non-zero pulses, N p = 16, 32 and 64 in LAS-ET sequence versus number of elements, Ne in smart antenna system
these results are plotted. Henceforth, the spectrum efficiency in DSCMA system for various parameter combinations is shown in Fig. 6. Figure 6 shows that the spectrum efficiency in DSCMA system increases proportional to the number of elements in smart antenna system. This is because there are many nulls available when the number of antenna elements increases and at the same time the beamwidth of smart antenna becomes narrower so that the required size of IFW can be reduced. Therefore, the code length of LAS-ET spreading sequence decreases to increase its duty ratio. As a result, the spectrum efficiency of DSCMA increases. The spectrum efficiency in DSCMA system refers to how efficient the number of codes in LAS-ET codes can be synthesized. Hence, it is directly related to the duty ratio of the spreading sequence. It could be seen that the small number of non-zero pulses in LAS-ET code gives higher spectrum efficiency in DSCMA system. It shows that the increase in N p in order to increase the number of available codes does not necessarily increase its spectrum efficiency because the duty ratio decreases when N p increases while maintaining its dedicated IFW size. This is due to the additional zero paddings in the LAS-ET code which causes the code length to become longer. Therefore, spectrum efficiency in DSCMA system can only be increased by the code reuse assignment as the number of elements is increased in smart antenna system, not through the increase in the number of available codes in LAS-ET codes. Similarly, the code reuse assignment can be applied in multiple cell scenario to increase its spectrum efficiency. The base station of incoming mobile user must check whether its AOA is located at the null directions of the existing mobile user in neighbouring sectors n such a way that every beam with the same sequence will stay orthogonal with each other. It will mitigate co-channel interference between neighbouring cells by means of spatial signature. Therefore this spatial signature based dynamic code reuse assignment will overcome the constraints of available orthogonal codes arising from the increasing number of users.
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6 Conclusions This paper shows that the spectrum efficiency in DSCMA system can be enhanced by using smart antenna with dynamic code reuse assignment. Spectrum efficiency increases when more antenna elements are deployed in a smart antenna system. The modified LAS-ET sequence reduces code lengths so that the duty ratio increases. The code duty ratio is further increased when the length of LAS-ET sequence is reduced by using DSC algorithm. However, the increase in the number of non-zero pulses in LAS-ET sequence in order to increase the number of codes may not increase the spectrum efficiency. Nevertheless, this method can take advantage of dynamic code reuse assignment in DSCMA system to increase spectrum efficiency.
References 1. Lu, W. W. (2003). 4G mobile research in Asia. IEEE Communications Magazine, 41(3),104–106, March 2003. 2. Yu, J., Yao, Y. D., & Zhang, J. (2004). Reverse-link capacity of power-controlled CDMA systems with beamforming. IEEE Transactions on Vehicular Technology, 53(5),1423–1433, September 2004. 3. Sirbu, M., & Koivunen, V. (2002). Channel estimation and tracking in asynchronous uplink DS/CDMA using multiple antenna. Fourteenth international conference on digital signal (DSP 2002) Processing, Vol. 2 (pp. 635–638), July 1–3, 2002. 4. Wei, H., Yang, L., & Hanzo, L. (2005). Interference-free broadband single and multicarrier DS-CDMA. IEEE Communications Magazine, 43(2), 68–73, Feburary 2005. 5. Li, D. (2003). The Perspectives of Large Area Synchronous CDMA Technology for the Fourth-Generation Mobile Radio. IEEE Communications Magazine, 41(3),114–118, March 2003. 6. Li, D. (1999). A high spectrum efficient multiple access code. Fifth Asia-Pacific Conference on Communications and Fourth Optoelectronics and Communications Conference (APCC/OECC ‘99), Vol. 1, (pp. 598–605), October 18–22, 1999. 7. Choi, B. J., & Hanzo, L. (2002). On the design of LAS spreading codes. IEEE 56th vehicular technology conference (VTC 2002-fall) proceedings, Vol. 4, (pp. 2172–2176), September 24–28, 2002.
Author Biographies Chee Kyun Ng was born on the 13th January 1975 in Kuala Lumpur, Malaysia. He received his Bachelor of Engineering and Master of Science degrees majoring in Computer & Communication Systems from Universiti Putra Malaysia, Serdang, Selangor, Malaysia, in the years of 1999 and 2002 respectively. Presently, the author has completed his Ph.D. programme majoring in Communications and Network Engineering at the same university. He is currently undertaking his research on wireless multiple access schemes and smart antenna system. His research interests include mobile and satellite communications, digital signal processing, wireless networking and network security. Along the period of his Ph.D. programme, he received a scholarship award from the government of Malaysia under the National Science Fellowship (NSF) scheme.
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267 Nor Kamariah Noordin received her B.Sc. in Electrical Engineering majoring in Telecommunications from University of Alabama, USA, in 1987. She became a tutor at the Department of Computer and Electronics Engineering, Universiti Putra Malaysia, and pursued her Masters Degree at Universiti Teknologi Malaysia and Ph.D. at Universiti Putra Malaysia. She then became a lecturer in 1991 at the same department where she was later appointed as the Head from year 2000 to 2002. She is currently the Deputy Dean (Academic, Student Affairs and Alumni) of the Faculty. During her more than 15 years at the department she has been actively involved in teaching, research and administrative activities. She has supervised a number of undergraduate students as well as postgraduate students in the area of wireless communications, which led to receiving some national and UPM research awards. Her research work also led her to publish more than 100 papers in journals and in conferences.
Borhanuddin Mohd Ali obtained his B.Sc. (Hons) Electrical and Electronics Engineering from Loughborough University in 1979; M.Sc. and Ph.D. from University of Wales, UK, in 1981 and 1985, respectively. He became a lecturer at the Faculty of Engineering UPM in 1985, made a Professor in 2002, and Director of Institute of Multimedia and Software, 2001–2006. In 1997 he co founded the national networking testbed project code named Teman, and became Chairman of the MYREN Research Community in 2002, the successor to Teman. His research interest is in Wireless Communications and Networks where he publishes over 80 journal and 200 conference papers. He is a Senior Member of IEEE and a member of IET and a Chartered Engineer, and the present ComSoc Chapter Chair. He is presently on a 2-year secondment term with Mimos as a Principal Researcher, heading the Wireless Networks and Protocol Research Lab.
Sudhanshu Shekhar Jamuar received his M.Tech and Ph.D. in Electrical Engineering from Indian Institute of Technology, Kanpur, India in 1970 and 1977 respectively. He worked as Research Assistant, Senior Research Fellow and Senior Research Assistant from 1969 to 1975 at IIT Kanpur. During 1975–76, he was with Hindustan Aeronautics Ltd., Lucknow. Subsequently he joined the Lasers and Spectroscopy Group in the Physics Department at IIT Kanpur, where he was involved in the design of various types of Laser Systems. He joined as Lecturer Electrical Engineering Department at Indian Institute of Technology Delhi in 1977, where he became Assistant Professor in 1980. He was attached to Bath College of Further Education, Bath (UK), Aalborg University, Aalborg (Denmark) during 1987 and 2000. He was a Professor in the Department of Electrical Engineering at IIT Delhi from 1991 to 2003. He was with University Putra Malaysia during 1996–97 in the Faculty of Engineering. Presently he is Professor in the Electrical and Electronic Engineering Department in the Faculty of Engineering, University Putra Malaysia (Malaysia) since 2001. He has about 40 papers in the International Journals and has attended several International Conferences and presented papers. He is senior member of IEEE and Fellow of Institution of Electronics and Telecommunications Engineering (India). He is presently the Chapter Chair for IEEE CAS Chapter in Malaysia. He is one of DLP speakers for the term 2008–2009 for the IEEE Circuits and System Society.
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