Green Deployment Strategy of Different Generation Mobile Networks Based on Spectrum Analysis Anwesha Mukherjee, Priti Deb, Debashis De Department of Computer Science & Engineering, West Bengal University of Technology, BF-142, Sector-I, Salt Lake, Kolkata-700064, West Bengal, India.
[email protected] Abstract— Mobile devices have become an essential part of our daily life. Different types of cellular networks exist for providing service to the mobile users. GSM is the first mobile communication system which raises the popularity of mobile services. After GSM, other kinds of wireless communication systems come into the scenario such as WCDMA, LTE etc. Each of these systems has their own pros and cons. In this paper we have performed a comparative signal analysis between these popular networks considering noise effect, bandwidth, and power using vector signal generator to draw a conclusion on their effective deployment in different scenarios. The power transmission by the base stations in an area covered by GSM, WCDMA and LTE network based on user density is determined and compared with the same using only GSM network. Simulation results present that using proposed deployment scenario 10.22-17.5% reduction in power transmission is achieved and hence it is referred as a green network.
wireless networks as well as computer, consumer electronics, communication technology, and several other convergences that is capable of providing 100 Mbps and 1 Gbps respectively in outdoor and indoor environments with end-to-end Quality of Service (QoS) and high security, offering any kind of services anytime, anywhere, at affordable cost and billing. To provide 4G services Long Term Evaluation (LTE) network is developed [6-7]. With the development of LTE network femtocell is introduced. Femtocell is a low power base station having small coverage area [8-11]. Now the suitability of these networks to provide good QoS depends on the user traffic. For example, in case of remote area 4G services are not required at all whereas they mostly fit to the urban area. TABLE I presents a comparison between these technologies. TABLE I.
Keywords— GSM; WCDMA; LTE; Noise; VSG; Power
I.
INTRODUCTION
Global System for Mobile Communications (GSM) is the basic wireless communication network which gives birth of digital mobile communication i.e. second generation (2G) mobile communication. GSM is available in all over 219 countries. GSM standard has replaced the first generation (1G) analog cellular networks, and introduced a digital, circuitswitched network. This includes data communications, first by circuit-switched transport, and then packet data transport via General Packet Radio Services (GPRS) and Enhanced Data Rates for GSM Evolution or EGPRS (EDGE). Instead of the essence of digital communication, 2G technology has several constraints such as weaker digital signal, angular decay curve, and reduced range of sound [1-2]. To overcome these difficulties and to enhance the data transmission rate Wideband Code Division Multiple Access (WCDMA) is introduced as third generation (3G) cellular network. Although 3G networks allow a wider radio spectrum for faster data transmission, multimedia services and larger network capacity but several disadvantages are there like poor battery life of mobile devices, problems in handover, overweight handsets etc. To overcome these difficulties and to support high speed multimedia data transfer, HDTV content and high speed internet access, fourth generation (4G) cellular network comes [3-5]. The 4G is a fully IP-based integrated systems and network of networks achieved after the convergence of wired and
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COMPARISON BETWEEN GSM, WCDMA AND LTE NETWORK
Features Starting Time Driven Technique Bandwidth Radio Frequency Cellular Coverage Generation Service Type
Core Networks
GSM 1992 Digital signal Processing 9.6-14.4Kbps 9001800MHz Medium area 2G Voice, SMS, Mono-media data, Person-toperson Telecom networks
Network Standard WCDMA LTE 2002 2010-2012 Intelligent signal Processing 2-5Mbps 1GHz
Intelligent software Auto configuration 10-20Mbps 2GHz
Small area
Very small area
3G Voice, Some multimedia data, Person-tomachine Telecom networks, Some IP networks
4G Multimedia data, Machine-tomachine All-IP networks
In this paper we have compared these three systems using vector signal generator (VSG) and spectrum analyzer [12]. VSG is used to generate the spectrum. The generated spectra are analyzed with respect to different parameters like power level, noise, bandwidth etc. Based on these measurements a comparative study is performed between GSM, WCDMA and LTE spectrum. We have used Agilent EXG Vector Signal Generator N5172B and EXA Signal Analyzer 9010A present in the wireless laboratory of West Bengal University of
Technology. Fig. 1 presents the image of VSG in our laboratory.
bandwidth over which two signals can be separated. VBW filters noise. The centre frequency is set to 935.1991 MHz as observed from Fig.2.(a). From Fig.2.(a) it is observed that in case of GSM spectrum the RBW and VBW both are 5.6 KHz and signal power level is approximately -20.6 to -70.6 dBm. Fig.2. (b) presents the IQ spectrum of GSM. In Fig. 2.(b) the upper half of the GSM spectrum presents the trace of the GSM signal and its average in the frequency domain. The lower half of the GSM spectrum in Fig. 2. (b) shows the traces of the I and Q of the input GSM signal.
Fig.1. Agilent Vector signal generator and signal analyzer used in our experiment
The contributions of this paper are: • The spectra of these technologies are presented using signal generator. • The noise levels in case of these three networks are presented using spectrum analyzer. • Based on the experimental analysis a comparative study is performed. • Based on the comparative study, an effective deployment strategy of these networks according to their features is presented with the power transmission model. This paper is organized as: section II presents the spectrum analysis using VSG; Usage of GSM, WCDMA and LTE network based on user density is discussed in section III with final conclusion in section IV. II.
(a)
SPECTRUM ANALYSIS USING VSG
The technical method of decomposing a complex signal into smaller segments is referred as spectrum analysis. Spectrum analysis can be done on the entire signal or on the small segments which are known as frame. Fourier analysis is a popular mathematical method used in spectrum analysis. To preset the amplitude and phase of each frequency component a two-dimensional vector is used which is a complex number. It consists of two parts: a) magnitude which presents the amplitude and b) phase. In signal processing squared amplitude is considered where the resulting plot is a power spectrum. The complex spectrum is measured based on the Fast Fourier Transform. In complex spectrum I and Q signal waveforms are presented where I denotes the phase and Q denotes the quadrature. The complex spectrum of the IQ analyzer presents the complex components of the same signal without making any changes to the settings or measurements. A. GSM, WCDMA and LTE Spectram GSM spectrum obtained using VSG is presented in Fig.2.(a) with the resolution bandwidth (RBW) and video bandwidth (VBW) with sweep and span. RBW is the minimum
(b) Fig.2. (a) GSM spectrum observed from VSG, (b) GSM spectrum obtained using IQ analyzer
Fig.3.(a) presents the WCDMA spectrum with RBW and VBW with sweep and span. The centre frequency is set to 999.989 MHz as shown in Fig.3.(a). In case of WCDMA spectrum the RBW and VBW both are 20 KHz and signal power level is approximately -20.6 to -101 dBm as presented in Fig.3. (a). The IQ spectrum of WCDMA is presented in Fig.3. (b). In Fig.3.(b) the upper half of the WCDMA spectrum presents the trace of the WCDMA signal and its average in the frequency domain. The lower half of the
WCDMA spectrum in Fig.3.(b) shows the traces of the I and Q of the input WCDMA signal.
(a)
(a)
(b) Fig.4. (a) LTE spectrum observed from VSG, (b) LTE spectrum obtained using IQ analyzer
B. Noise Level in GSM, WCDMA and LTE Network Fig.5 presents the noise level in GSM spectrum. It is observed that the noise level in GSM is -51.70 dB/Hz. (b) Fig.3. (a) WCDMA spectrum observed from VSG, (b) WCDMA spectrum obtained using IQ analyzer
Fig.4.(a) presents the LTE spectrum with RBW and VBW with sweep and span. The centre frequency is set to 2.001091 GHz as observed from Fig.4.(a). In case of LTE spectrum the RBW and VBW both are 180 KHz and signal power level is -18 to -98 dBm as presented in Fig.4. (a). Fig.4. (b) presents the IQ spectrum of LTE. In Fig.4.(b) the upper half of the LTE spectrum presents the trace of the LTE signal and its average in the frequency domain. The lower half of the LTE spectrum in Fig.4.(b) shows the traces of the I and Q of the input LTE signal. Fig.5. Noise level in GSM spectrum observed from VSG
Fig.6 presents that the noise level in WCDMA spectrum is -83.47dB/Hz which is less than that of the GSM spectrum. Hence it is demonstrated that using WCDMA noise level can be reduced and thus signal-to-noise ratio can be improved.
From TABLE II it is observed that the RBW and VBW both are maximum in case of LTE network whereas in GSM these values are minimum. As per the results the noise level of LTE is minimum which indicates that using LTE better signaling can be provided to the user. This in turn can avoid the probability of call drop due to poor signal strength. The power level in case of WCDMA is minimum which means using WCDMA radiation can be reduced. Radiation in LTE network is also low but greater than WCDMA. Hence with respect to the service quality as per signal level as well as bandwidth LTE is the optimum one whereas if low radiation is desired WCDMA is the better option. III.
EFFECTIVE DEPLOYMENT STRATEGY OF GSM, WCDMA AND LTE NETWORKS
A. Proposed Deployment Strategy In the previous section we have discussed on three communication networks based on our experimental observation. These networks can be properly used with respect to the user density in an area as follows: • Consider a geographical region where cellular network has to be deployed. • The region contains rural, urban and suburban area as shown in Fig.8.
Fig.6. Noise level in WCDMA spectrum observed from VSG
Fig.7. Noise level in LTE spectrum observed from VSG
Fig.7 presents the noise level in case of LTE spectrum and it is -105dB which is lesser than both GSM and WCDMA. Thus LTE provides enhanced signal-to-noise ratio. C. Comparative Analysis between GSM, WCDMA and LTE TABLE II presents the frequency, RBW, VBW, noise level and power in case of GSM, WCDMA and LTE spectrum based on the observations from Fig. 2 to Fig. 7. These figures present the original results obtained by us using VSG in the wireless laboratory of our institution West Bengal University of Technology. TABLE II.
Parameters Frequency RBW VBW Noise level Power
COMPARISON BETWEEN GSM, WCDMA AND LTE SPECTRUM
GSM 935.1991 MHz (935 MHz approx.) 5.6 KHz 5.6 KHz -51.70 dB/Hz -20.6 to -70.6 dBm
Network Standard WCDMA 999.989 MHz (1 GHz approx.) 20 KHz 20 KHz -83.47 dB/Hz -20.6 to -101 dBm
LTE 2.001091 GHz (2 GHz approx.) 180 KHz 180 KHz -105dB/Hz -18 to -98 dBm
Fig.8. Effective deployment of different generation mobile networks
•
In rural area the user traffic is very low. Thus providing 3G or 4G service in such region can results unnecessary wastage of resources. Hence in such area GSM can be used to provide 2G network services. • Suburban area contains moderate amount of traffic. The users may require voice and data services. Hence in such case WCDMA can be used to provide 3G network services. • In case of urban area the traffic is high. So the required amount of bandwidth is also high. As LTE provides high bandwidth with low noise level, then LTE is a better choice for urban region to provide 4G network services. As rural area is covered by GSM network due to low user density i.e. probably low amount of traffic, macrocells and microcells are deployed there as shown in Fig.9. Sub-urban area is covered by WCDMA network due to medium user density i.e. probably moderate amount of traffic. Hence
macrocells, microcells and picocells are allocated there as presented in Fig.9. Urban area is covered by LTE network due to high user density i.e. probably high user traffic. Thus macrocells, microcells, picocells, and femtocells are allocated in that region as demonstrated in Fig.9.
The transmission power of a PBS is given by [7],
Ptp =
Prp (4π )2 R p2 L
(3)
GtpGr λ 2
The transmission power of a FBS is given by [7],
Ptf =
(4π Prf )
(4)
(3 3 / 2)QGtf
where Q is the normalized radiation pattern in the direction (θ,Φ) i.e. equals to unity in the direction of maximum radiation. If the total area (x) is covered by macrocells and microcells, the total power transmission in that area is given as,
Ptot = ∑ Ptm + ∑ Ptmi Nm
Fig.9. Cell allocation in different types of mobile network based on geographical region and user density
B. Power Transmission Model Parameters used in the power transmission model are presented in TABLE III. TABLE III. Parameter Prm Prmi Prp Prf Gtm Gtmi Gtp Gtf Gr Rm Rmi Rp Rf L λ
PARAMETERS USED IN POWER TRANSMISSION MODEL Definition Minimum received power by a mobile station (MS) inside a macrocell base station (MBS) Minimum received power by a MS inside a microcell a base station (MiBS) Minimum received power by a MS inside a picocell base station (PBS) Minimum received power by a MS inside a femtocell base station (FBS) MBS antenna gain MiBS antenna gain PBS antenna gain FBS antenna gain MS antenna gain Macrocell radius (1-10km) Microcell radius (200m-1km) Picocell radius (50-200m) Femtocell radius (10-20m) System loss Wavelength of the carrier wave
The transmission power of a MBS is given by [7],
Ptm =
Prm (4π )2 Rm2 L GtmGr λ 2
2 Prmi (4π ) 2 Rmi L 2 GtmiGr λ
where Nm and Nmi are the number of macrocells and microcells respectively covering the area x. Hence using only macrocells and microcells as in GSM network, power transmission in the network is determined using equation (5). According to our suggestive deployment scheme instead of covering the total area by macrocells and microcells like GSM network, base station allocation takes place depending on user density; the rural area is covered by GSM network i.e. macrocells and microcells are used, the suburban area is covered by WCDMA network i.e. macrocells, microcells, and picocells are used, the urban area is covered by LTE network i.e. macrocells, microcells, picocells and femtocells are used. Let the total area is divided into three parts: a, b, and c, covered by GSM, WCDMA and LTE network respectively. Therefore, a+b+c=x and a
